Inhibition and induction of human cytochrome P450 enzymes: current status

REVIEW ARTICLE

Inhibition and induction of human cytochrome P450 enzymes:current status

Olavi Pelkonen Æ Miia Turpeinen Æ Jukka Hakkola ÆPaavo Honkakoski Æ Janne Hukkanen Æ Hannu Raunio

Received: 23 May 2008 / Accepted: 16 June 2008 / Published online: 11 July 2008

� Springer-Verlag 2008

Abstract Variability of drug metabolism, especially that

of the most important phase I enzymes or cytochrome P450

(CYP) enzymes, is an important complicating factor in

many areas of pharmacology and toxicology, in drug

development, preclinical toxicity studies, clinical trials,

drug therapy, environmental exposures and risk assess-

ment. These frequently enormous consequences in mind,

predictive and pre-emptying measures have been a top

priority in both pharmacology and toxicology. This means

the development of predictive in vitro approaches. The

sound prediction is always based on the firm background of

basic research on the phenomena of inhibition and induc-

tion and their underlying mechanisms; consequently the

description of these aspects is the purpose of this review.

We cover both inhibition and induction of CYP enzymes,

always keeping in mind the basic mechanisms on which to

build predictive and preventive in vitro approaches. Just

because validation is an essential part of any in vitro–in

vivo extrapolation scenario, we cover also necessary in

vivo research and findings in order to provide a proper

view to justify in vitro approaches and observations.

Keywords Cytochrome P450 (CYP) � Inhibition �Induction

Introduction

Activities of cytochrome P450 (CYP) enzymes are affected

by numerous genetic, endogenous host, and environmental

factors, making drug metabolism exceedingly variable and

even individualistic. This variability has important reper-

cussions to drug development, clinical drug therapy and in

general to sensitivity to chemicals foreign to the body, i.e.

xenobiotics. Among environmental factors, compounds

causing inhibition and induction are amongst the most

important ones, or at least the most researched.

Inhibition of CYP enzymes by other drugs or chemicals

has received considerable attention since cimetidine was

shown to affect drug metabolism in both animals and

humans (Puurunen and Pelkonen 1979; Rendic et al. 1979).

Mechanistic insights, predictive in vitro assays and mod-

eling and validation of in vitro–in vivo extrapolation have

revolutionized this part of drug development. However,

inhibitory interactions in the metabolism of compounds

other than pharmaceuticals have been less well developed

O. Pelkonen (&) � M. Turpeinen � J. Hakkola

Department of Pharmacology and Toxicology,

Institute of Biomedicine, University of Oulu,

PO Box 5000 (Aapistie 5 B), 90014 Oulu, Finland

e-mail: [email protected]

M. Turpeinen

Dr. Margarete Fischer-Bosch Institute of Clinical Pharmacology,

Stuttgart, Germany

e-mail: [email protected]

M. Turpeinen

Department of Clinical Pharmacology, University of Tubingen,

Tubingen, Germany

P. Honkakoski

Department of Pharmaceutics, University of Kuopio,

Kuopio, Finland

J. Hukkanen

Department of Internal Medicine, Oulu University Hospital,

Oulu, Finland

H. Raunio

Department of Pharmacology and Toxicology,

University of Kuopio, Kuopio, Finland

123

Arch Toxicol (2008) 82:667–715

DOI 10.1007/s00204-008-0332-8

and the significance of chemical–drug or chemical–chem-

ical interactions is still not very well understood.

Although the role of Ah receptor in the induction of aryl

hydrocarbon hydroxylase was elucidated already more than

20 years ago, it was only after the unraveling of the role of

pregnane X receptor (PXR) and constitutive androstane

receptor (CAR) in more general P450 induction phenom-

ena that the research field experienced almost logarithmic

growth. With the advent of several other nuclear receptors,

their crosstalk in regulating CYP induction and pleiotypic

responses after the exposure of the organism to nuclear

receptor ligands, we have started to understand the com-

plex interwoven regulatory networks, which link drug

metabolism with the regulation of many facets of inter-

mediary metabolism, such as bile acids, lipids, glucose and

so on.

In this review we present an updated view on the scope

and significance of both inhibition and induction of CYP

enzymes, especially in humans, but taking examples also

from animal studies. We have tried to cover pertinent lit-

erature until March 2008, but the earlier literature, which

was covered in our earlier review article (Pelkonen et al.

1998), will be mentioned only sporadically. It is impossi-

ble to cover all the literature on CYP inhibition and

induction published during the last 10 years, so we have to

apologize for any omission of significant references and

authors.

CYP enzymes in human tissues

In February 2008, the CYP superfamily consisted of more

than 7,000 named sequences in animals, plants, bacteria

and fungi (http://drnelson.utmem.edu/CytochromeP450.

html). The human genome has 57 CYP genes, and the

function for most of the corresponding enzymes is known

at least to some degree. Fifteen individual CYP enzymes in

families 1, 2 and 3 metabolize xenobiotics, including the

majority of small molecule drugs currently in use. A typ-

ical feature of these CYPs is broad and overlapping

substrate specificity (Guengerich et al. 2005). Other CYPs

with much narrower substrate specificity are devoted

mainly to the metabolism of endogenous substrates, such as

sterols, fatty acids, eicosanoids, and vitamins. It has

become evident that expression patterns of many individual

CYPs in different tissues and cell types of an organ have

important physiological roles (Seliskar and Rozman 2007).

Cytochrome P450 enzymes are found in practically all

tissues, with highest abundance and largest number of

individual CYP forms present in the liver. CYPs reside also

in the intestine, lung, kidney, brain, adrenal gland, gonads,

heart, nasal and tracheal mucosa, and skin. In human liver

CYP enzymes comprise approximately 2% of total

microsomal protein (0.3–0.6 nmol of total CYP per mg of

microsomal protein). The content of drug-metabolizing

CYPs is much lower in other tissues (Table 1). While

extrahepatic metabolism may have clinically significant

local effects, systemic metabolic clearance of drugs occurs

in the liver with a significant contribution by the gut wall in

special cases.

Metabolism is the main route of clearance for approxi-

mately 70% of currently used drugs. Ten individual CYP

forms in the adult human liver carry out virtually the whole

CYP-mediated metabolism. CYP3A4 is the highest abun-

dance form and it metabolizes the greatest number of drugs

and a very large number of other xenobiotics. A minority of

Caucasian people have relatively high amount of CYP3A5

in the liver, and CYP3A7 is a fetal enzyme. Also CYP2D6,

although of much lower abundance, mediates the metabo-

lism of numerous drugs. Together CYP2B6, CYP2C9,

CYP2C19, CYP2D6 and CYP3A4 are responsible for more

than 90% of known oxidative drug metabolism reactions

(Wienkers and Heath 2005; Guengerich 2008). Figure 1

illustrates the relative abundance of individual CYP forms

in the liver, and lists some examples of substrates, inhibitors

and inducers. The CYP enzymes are well known for their

capacity to metabolize a vast number of structurally diverse

xenobiotics. Several reviews (e.g. Rendic 2002; Guengerich

et al. 2005; Liu et al. 2007; Brown et al. 2008; Hrycay and

Bandiera 2008) and Internet sites (e.g. http://medicine.

iupui.edu/flockhart) contain exhaustive lists of xenobiotics

that are CYP substrates.

The genes encoding CYP enzymes are highly poly-

morphic (http://www.cypalleles.ki.se). Numerous studies

have established that several variant alleles of individual

CYP genes encode functionally deficient enzymes, the

prime example being CYP2D6. When challenged with a

CYP2D6 substrate drug, e.g. dextromethorphan, individu-

als with a deficient enzyme phenotype [poor metabolizers

(PMs)] may experience adverse effects due to excessive

serum concentrations of the drug. On the other hand,

individuals with multiple copies of the CYP2D6 gene

Table 1 Total CYP content in selected human tissues (Hrycay and

Bandiera 2008)

Tissue CYP content

(nmol/mg microsomal protein)

Liver 0.30–0.60

Adrenal 0.23–0.54

Small intestine 0.03–0.21

Brain 0.10

Kidney 0.03

Lung 0.01

Testis 0.01

668 Arch Toxicol (2008) 82:667–715

123

http://drnelson.utmem.edu/CytochromeP450.html

http://drnelson.utmem.edu/CytochromeP450.html

http://medicine.iupui.edu/flockhart

http://medicine.iupui.edu/flockhart

http://www.cypalleles.ki.se

(ultrarapid metabolizers) will have insufficient clinical

response since the drug is eliminated during first-pass

metabolism (Kirchheiner et al. 2005). Thus, genotyping

patients for CYP2D6 and other drug-metabolizing genes

before implementing drug therapy would be advantageous.

Nevertheless, implementing this type of genetic informa-

tion into practice is a daunting task with several obstacles

to overcome before individualized drug therapy is a reality

(Nebert et al. 2008).

Most drugs cleared by the CYP system are metabolized

through several CYP forms. As a general rule, drugs that

are metabolized by a single CYP form are more susceptible

to drug interactions than drugs metabolized by multiple

forms. For investigational purposes, an ideal marker

(probe) drug should be metabolized by a single CYP form.

The FDA has issued a draft guidance on drug interaction

studies (Huang et al. 2007). In this guidance, examples are

given on substrates, inhibitors and inducers that can be

used in clinical drug interaction studies (Table 2).

Inhibition of CYP enzymes

Inhibition of CYP enzymes is the most common cause of

harmful drug–drug interactions and has led to the removal

of several drugs from the market during the past years

(Friedman et al. 1999; Lasser et al. 2002). Inhibition can

lead to increased bioavailability of the parent compound

normally subject to extensive first-pass elimination or to

decreased elimination of compounds dependent on

metabolism for systemic clearance. If a drug is metabolized

mainly via single pathway, inhibition may result in

increased steady-state concentration and accumulation

ratio and non-linear kinetics as a consequence of the sat-

uration of enzymatic processes. Especially with prodrugs,

inhibition may result in a decrease in the amount of the

active drug form. Thus, inhibition of CYPs may lead to the

toxicity or lack of efficacy of a drug.

The type of CYP inhibition can be either irreversible

(mechanism-based inhibition) or reversible. The distinction

is relative and can be hard to determine if the inhibitor

binds tightly to the enzyme and is released slowly (Wien-

kers and Heath 2005). Irreversible inhibition requires

biotransformation of the inhibitor, while reversible inhibi-

tion can take place directly, without metabolism.

Reversible inhibition is the most common type of enzyme

inhibition and can be further divided into competitive, non-

competitive, uncompetitive, and mixed-type inhibition (Lin

and Lu 1998; Hollenberg 2002; Madan et al. 2002).

Mechanism-based inhibition

Mechanism-based inhibition can occur via the formation of

metabolite intermediate complexes or via the strong,

covalent binding of reactive intermediates to the protein or

heme of the CYP. The most important phenomenon of

mechanism-based inhibition is the time-, concentration-,

and NADPH-dependent enzyme inactivation (Halpert

1995; Lin and Lu 1998). Mechanism-based inhibition is

terminated by enzyme resynthesis and is therefore usually

long-lasting (Halpert 1995; Ito et al. 1998; Kent et al.

2001). In some cases, the metabolic product inactivates the

INDUCERS

2D6<5%

2B6<5%

2C19<5%

2C8~5%

2A6~10%

1A2>10%

2C9>15%

2E1~15%

3A4/5/7>35%

Sparteine

BufuralolPaclitaxel

RepaglinideNicotine

Coumarin

Tolbutamide

S-Warfarin

Phenytoin

Midazolam

Erythromycin

Cyclosporine

Testosterone

Simvastatin

Chlorzoxazone

Acetaminophen

EthanolCaffeine

Phenacetin

BupropionEfavirenz

Omeprazole

S-Mephenytoin

Quinidine

MontelukastMethoxsalen

Tranylcypromine

Sulfafenazole

Fluconazole

Ketoconazole

Itraconazole

Pyridine

Disulfiram

Furafylline

Fluvoxamine

Fluconazole

ThioTEPA

Rifampicin Phenob. Phenob.

Rifampicin

Carbamazepine

Dexamethasone

Ethanol

Isoniazid

TCDD

Smoking

Omeprazole

Phenob.

Rifampicin

nk Phenob.

Rifampicin

Phenob.

Rifampicin

INDUCERS

2D6<5%

2B6<5%

2C19<5%

2C8~5%

2A6~10%

1A2>10%

2C9>15%

2E1~15%

3A4/5/7>35%

Sparteine

BufuralolPaclitaxel

RepaglinideNicotine

Coumarin

Tolbutamide

S-Warfarin

Phenytoin

Midazolam

Erythromycin

Cyclosporine

Testosterone

Simvastatin

Chlorzoxazone

Acetaminophen

EthanolCaffeine

Phenacetin

BupropionEfavirenz

Omeprazole

S-Mephenytoin

Quinidine

MontelukastMethoxsalen

Tranylcypromine

Sulfafenazole

Fluconazole

Ketoconazole

Itraconazole

Pyridine

Disulfiram

Furafylline

Fluvoxamine

Fluconazole

ThioTEPA

Rifampicin Phenob. Phenob.

Rifampicin

Carbamazepine

Dexamethasone

Ethanol

Isoniazid

TCDD

Smoking

Omeprazole

Phenob.

Rifampicin

nk Phenob.

Rifampicin

Phenob.

Rifampicin

SUBSTRATES

INHIBITORS

Fig. 1 Relative abundance of individual CYP forms in the liver and some examples of substrates, inhibitors and inducers. CYPs with clinically

significant genetic polymorphism in gray. Phenob. phenobarbital, TCDD 2,3,7,8-tetrachlorodibenzo-p-dioxin, nk not known

Arch Toxicol (2008) 82:667–715 669

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https://www.researchgate.net/publication/6544103_FDA_Guidance_Page._Draft_Guidance_for_Industry_Drug_Interaction_StudiesStudy_Design_Data_Analysis_and_Implications_for_Dosing_and_Labeling?el=1_x_8&enrichId=rgreq-2150677c-4eae-4a61-9dbd-a651e97c1092&enrichSource=Y292ZXJQYWdlOzUyMzQ3NTM7QVM6MjExNTg1NTUwMjk1MDQ3QDE0Mjc0NTczMzQ2NTk=

enzyme completely (suicide inhibition). Classical mecha-

nism-based inhibitors include the CYP1A2 inhibitor

furafylline (Sesardic et al. 1990; Kunze and Trager 1993)

and the CYP3A4-inhibitor gestodene (Guengerich 1990;

Back et al. 1991).

Reversible inhibition

Reversible inhibition occurs as a result of competition at

the active site of the enzyme and probably involves only

the first step of the P450 catalytic cycle. Binding to the

enzyme takes place usually with weak bonds, which are

both formed and broken down easily. Consequently,

reversible inhibitors act rapidly, but do not permanently

destroy the enzyme (Lin and Lu 1998; Hollenberg 2002;

Madan et al. 2002).

In competitive inhibition, competition between the

substrate and inhibitor to bind to the same position on the

active site of the enzyme takes place. In the noncompetitive

mode of inhibition, the active binding site of the substrate

and inhibitor is different from each other. In the case of

uncompetitive inhibition, the inhibitor binds to the

enzyme–substrate complex, but not to the free enzyme

entity. In practice, mixed-type inhibition displaying ele-

ments of both competitive and noncompetitive inhibition

are frequently observed (Madan et al. 2002).

Inhibition of individual CYP enzymes: examples

of substrates and inhibitors

Many individual members of CYP families exhibit distinct,

but often overlapping, selectivity towards certain substrates

and inhibitors. The most commonly used probe substrates

and diagnostic inhibitors for each CYP form are collected

in respective tables and discussed briefly below. The Km

and Ki values are collected from the appropriate in vitro

studies.

CYP1 family

CYP1A2 is the only hepatic member of the CYP1 family.

CYP1A1 and CYP1B1 are the other enzymes in this

family, of which CYP1A1 is the major human extrahepatic

CYP form (Ding and Kaminsky 2003). The hepatic

expression of CYP1B1 is insubstantial, but otherwise it is

known to be expressed in almost every other tissue (Sutter

et al. 1994; Shimada et al. 1996a, b). All members of this

family are regulated by the AhR-receptor (see ‘‘Induction

of CYP enzymes: mechanisms’’). Besides detoxification,

the CYP1 family members are often responsible for met-

abolic activation of polycyclic aromatic hydrocarbons

(PAHs) and aromatic amines and thus they have been

linked to chemical carcinogenesis (Boobis et al. 1994; Io-

annides and Lewis 2004).

CYP1A2

Initially the expression of CYP1A2 was thought to be

limited only to the liver, but recent studies have shown that

it is expressed along with CYP1A1 in the lung (Wei et al.

2002; Liu et al. 2003). Over 20 single nucleotide poly-

morphisms (SNPs) within CYP1A2 have been reported,

though most of them have been found to be very rare

(Nakajima et al. 1994; Sachse et al. 1999). Despite

extensive interindividual variation in CYP1A2 activity and

systematic sequencing efforts, no predictive CYP1A2

polymorphisms have been reported (Ingelman-Sundberg

et al. 2007). However, recent twin studies have suggested a

strong role of genetic factors in CYP1A2 function (Ras-

mussen et al. 2002).

Substrates and inhibitors of CYP1A2

CYP1A2 is a major enzyme in the metabolism of a number

of important chemicals, which typically belong structurally

to the group of planar polyaromatic amides and amines

Table 2 Examples of in vivo substrate, inhibitor, and inducer for CYP enzymes recommended for study (oral administration) (Huang et al.

2007)

Enzyme Substrate Inhibitor Inducer

CYP1A2 Theophylline, caffeine Fluvoxamine Smokers versus non-smokers

CYP2B6 Efavirenz Rifampicin

CYP2C8 Repaglinide, rosiglitazone Gemfibrozil Rifampicin

CYP2C9 Warfarin, tolbutamide Fluconazole, amiodarone Rifampicin

CYP2C19 Omeprazole, other prazoles Omeprazole, fluvoxamine Rifampicin

CYP2D6 Desipramine, dextrometorphan, atomoxetine Paroxetine, quinidine, fluoxetine

CYP2E1 Chlorzoxazone Disulfiram Ethanol

CYP3A4/5 Midazolam, buspirone, felodipine, etc. Atazanavir, clarithromycin, itraconazole, etc. Rifampicin, carbamazepine

670 Arch Toxicol (2008) 82:667–715

123

(Lewis 2004). Ethoxyresorufin, caffeine, phenacetin, the-

ophylline, clozapine, melatonin, and tizanidine are

biotransformed predominantly by this CYP form (Table 3).

Caffeine clearance has been regarded as ‘the golden stan-

dard’ for in vivo phenotyping purposes due to the

predominating role of CYP1A2 in the overall metabolism

of caffeine and the excellent tolerability of this probe

substrate (Faber et al. 2005). Recently, also oral melatonin

has been suggested as a suitable marker for CYP1A2

phenotyping (Hartter et al. 2001; Faber et al. 2005). For in

vitro purposes, especially phenacetin, but also ethoxyres-

orufin are recommended, whereas the xanthines caffeine

and theophylline are not so favored due to the low turnover

of these compound in vitro (Tucker et al. 2001; Bjornsson

et al. 2003).

Potent inhibitors of CYP1A2 include furafylline, flu-

voxamine, ciprofloxacin, and rofecoxib. Also oral hormone

replacement therapy and oral contraceptives have been

shown to significantly inhibit CYP1A2-mediated metabo-

lism (Laine et al. 1999; Pollock et al. 1999). Furafylline, a

methylxanthine analog, is a selective and potent mecha-

nism-based inhibitor of several CYP1A2-mediated

reactions and is widely employed in in vitro studies.

However, it is not available for in vivo use, since it has

severe interactions with caffeine (Tarrus et al. 1987). For in

vivo study purposes, selective serotonin reuptake inhibitor

fluvoxamine and fluoroquinolone antibiotic ciprofloxacin

are usually applied.

CYP2 family

The human CYP2 family is very diverse and comprises a

number of important drug-metabolizing CYPs. Members of

this family do not share any common regulation patterns

and their substrate specificities and tissue expression vary

substantially. CYP2B6, CYP2D6, and CYP2E1 are the

only functional enzymes in their subfamilies, whereas

CYP2A contains two, and CYP2C four functional mem-

bers. The clinically most important CYP polymorphisms

are found within the CYP2 family (i.e. CYP2C9, CYP2C19,

and CYP2D6).

CYP2A6

At the quantitative level, CYP2A6 is a minor component

among hepatic CYPs (Rostami-Hodjegan and Tucker

2007). Several variant CYP2A6 alleles with distinct fre-

quencies between ethnic populations have been

characterized. Some of these alleles have been associated

with altered nicotine pharmacokinetics and furthermore to

differing smoking habits in variant genotype populations

(London et al. 1999; Raunio et al. 2001). Relatively large

variability in the enzyme activity between individuals has

been described, with a fair proportion of Japanese known to

lack the functional protein completely (Shimada et al.

1996b; Pelkonen et al. 2000).


Substrates of CYP2A6 are usually structurally small and

planar molecules (Lewis 2004). CYP2A6 has a predomi-

nant role in the overall metabolism of nicotine and its

metabolite cotinine (Hukkanen et al. 2005). The 7-

hydroxylation of coumarin is known to be solely catalyzed

by CYP2A6 and therefore coumarin has been traditionally

employed as the prototypical model substrate for this

enzyme (Pelkonen et al. 2000) (Table 4). In addition to

pharmaceuticals, bioactivation of some toxicologically

significant substances such as aflatoxin B1 and nitrosoam-

ines are known to be mediated at least to some extent via

CYP2A6 (Pelkonen et al. 2000; Raunio et al. 2001).

A number of potent inhibitors with variable selectivity

against CYP2A6 have been characterized. The most used

in vitro inhibitors include tranylcypromine and methoxsa-

len (8-methoxypsoralen).

CYP2B6

Initially CYP2B6 was regarded as a minor hepatic CYP in

humans, essentially expressed only in a few livers and with

minor significance in the overall xenobiotic metabolism.

This view has changed over the very last few years and

currently CYP2B6 belongs to a set of important hepatic

drug-metabolizing CYPs (Turpeinen et al. 2006). An

extensive interindividual variability in the expression of

CYP2B6 has been reported, mainly due to genetic factors,

and CYP2B6 has been estimated to represent approxi-

mately 1–10% of the total hepatic CYP pool (Rostami-

Hodjegan and Tucker 2007; Zanger et al. 2007).

Substrates and inhibitors of CYP2B6

The list of CYP2B6 substrates has increased drastically in

the past few years (Turpeinen et al. 2006). CYP2B6 usually

metabolizes non-planar, neutral, or weakly basic molecules

with one or two hydrogen bond acceptors (HBAs) (Lewis

2004). For the metabolic pathway and kinetics of bupro-

pion, cyclophosphamide, ifosfamide, efavirenz, ketamine,

and propofol, CYP2B6 is of considerable importance

(Table 5). In addition to pharmaceuticals, CYP2B6 appears

to both detoxify and bioactivate a number of procarcino-

gens (Code et al. 1997; Smith et al. 2003a). Bupropion has

been suggested as a good model substrate both for in vitro

and in vivo studies. It is extensively metabolized in human

liver, resulting in low levels of the parent compound in

plasma. The major metabolite, pharmacologically active

Arch Toxicol (2008) 82:667–715 671

123

Table 3 Substrates and inhibitors of CYP1A2 enzyme

Drug Reaction Km in HLMs (lM) Specificity near Km References

Substrates

Caffeinea 3N-demethylation 200–500 High Campbell et al. (1987)

Butler et al. (1989)

Tassaneeyakul et al. (1992)

Phenacetinb O-de-ethylation 10–50 lM High Distlerath et al. (1985)

Sesardic et al. (1988)

Brosen et al. (1993)

Tassaneeyakul et al. (1993a)

Ethoxyresorufinb O-de-ethylation 0.11–0.23 Moderate (CYP1A1) Burke et al. (1985)

Tassaneeyakul et al. (1993a)

Bourrie et al. (1996)

Tacrineb 1-Hydroxylation 2.8–16 High Hooper et al. (1994)

Spaldin et al. (1995)

Becquemont et al. (1998)

Theophyllineb N-demethylation 280–1230 High Campbell et al. (1987)

Sarkar and Jackson (1994)

Tjia et al. (1996)

Melatonin 6-Hydroxylation 6 Moderate (CYP1A1, 2C19) Facciola et al. (2001)

Hartter et al. (2001)

Ma et al. 2005

Riluzole N-hydroxylation 30 High Sanderink et al. (1997)

Tizanidine Oxidative metabolism nk Highc Granfors et al. (2004)

Zolmitriptan N-demethylation High Wild et al. (1999)

Ropivacaine 3-Hydroxylation 16 High Oda et al. (1995)

Ekstrom and Gunnarsson (1996)

Flutamide 2-Hydroxylation 18* High Shet et al. (1997)

Rochat et al. (2001)

Frovatriptan Oxidative and reductive

metabolism

nk Highc Buchan et al. (2002)

Balbisi (2006)

Lidocaine 3-Hydroxylation

N-de-ethylation

975–6,395

228–270

High Wang et al. (2000a)

Orlando et al. (2004)

Ropinirole N-depropylation

Hydroxylation

5–518–87 Moderate (CYP3A4) Bloomer et al. (1997)

Mirtazapine 8-Hydroxylation 92–194 Moderate (CYP2D6, 2C9, 3A4) Stormer et al. (2000)

Clozapine N-demethylation 120 Moderate (3A4, 2C) Bertilsson et al. (1994)

Fang et al. (1998)

Tugnait et al. (1999)

Olesen and Linnet (2001)

Drug Mode of inhibition Ki in HLMs (lM) CYP selectivity and

other CYPs inhibited

References

Inhibitors

Fyrafylline Mechanism-based 0.6–0.7 High Sesardic et al. (1990)

Kunze and

Trager (1993)

Clarke et al. (1994a, b)

672 Arch Toxicol (2008) 82:667–715

123

hydroxybupropion, is formed selectively by CYP2B6

(Turpeinen et al. 2006).

Potent inhibitors of CYP2B6 include thienopyridine

derivatives clopidogrel and ticlopidine and the anticancer

agent thioTEPA, which is a very selective inhibitor of this

particular CYP.

CYP2C8

Like in the case of CYP2B6, the importance of CYP2C8

for drug metabolism has been elucidated quite recently

(Totah and Rettie 2005). Also a number of functional

CYP2C8 polymorphisms have been published during

recent years (Dai et al. 2001; Niemi et al. 2003a). Some

SNPs or their combinations in the CYP2C8 gene have been

associated with certain disease states or adverse drug

reactions, but more studies about the importance of

CYP2C8 polymorphisms and also the general role of this

enzyme in drug metabolism are still needed.

Substrates and inhibitors of CYP2C8

Drugs metabolized by CYP2C8 do not share any common

structure or chemical pattern. There seems to be some

overlapping especially with CYP2C9 and CYP3A4

substrates. Drugs with major importance of CYP2C8

include amodiaquine, paclitaxel, cerivastatin, and several

oral antidiabetics such as repaglinide, pioglitazone, and

rosiglitazone (Table 6). Paclitaxel 6a-hydroxylation has

been regarded as the typical index of CYP2C8 activity, but

partly due to the high costs of authentic chemical standards

and unsuitability for in vivo use, other probe substrates

have also gained interest. Recently, the N-deethylation of

the antimalarial amodiaquine was demonstrated as a good

model substrate for CYP2C8 with high affinity and turn-

over rate. So far the applicability of glitazones as model

substrates has been restricted by difficulties in obtaining

metabolite standards.

Known CYP2C8 inhibitors include quercetin, which has

been used for several years for in vitro purposes, and leu-

kotriene receptor antagonists montelukast and zafirlukast.

Although montelukast and zafirlukast are potent inhibitors

of CYP2C8 in vitro, they both are highly bound to plasma

proteins ([99%) resulting in very low free fraction in

humans. Thus these two drugs are not suitable for in vivo

inhibition purposes (Jaakkola et al. 2006a; Kim et al.

2007). The lipid-lowering drug gemfibrozil inhibits

CYP2C8 potently in vivo via its phase II metabolite,

gemfibrozil 1-O-b-glucuronide. Besides CYP2C8, gemfi-

brozil inhibits the organic anion-transporting polypeptide-2

Table 3 continued



References

Fluvoxamine Competitive 0.12–0.24 Moderate (CYP2B6, 2C9, 2C19, 2D6) Brosen et al. (1993)

Rasmussen et al. (1995)

Hartter et al. (2001)

Turpeinen et al. (2005a)

a-Naphthoflavone Competitive 0.01 Moderate (CYP1A1) Tassaneeyakul et al. (1993a)

Tsyrlov et al. (1993)

Ciprofloxacin Competitive 90–290 High McLellan et al. (1996)

Fuhr et al. (1990)

Rofecoxib Mechanism-based 4.8 High? Bachmann et al. (2003)

Karjalainen et al. (2006)

Backman et al. (2006a, b)

Mexiletine Competitive 4.3–8.3 Moderate (CYP1A1) Ogiso et al. (1995)

Konishi et al. (1999)

Propafenone Competitive 21d nk Kobayashi et al. 1998

Enoxacin Competitive 65–170 High Fuhr et al. (1990)

Valero et al. (1991)

nk not knowna Preferred in vivo probe substrateb Preferred in vitro probe substratec Contribution of CYP1A2 to the overall metabolismd Km from cDNA expressed CYP1A2

Arch Toxicol (2008) 82:667–715 673

123

(OATP2)-transporter, which should be noted when evalu-

ating its in vivo effects (Shitara et al. 2004; Schneck et al.

2004).

CYP2C9

CYP2C9 is the predominant CYP2C form with high

abundance among hepatic CYPs (Rostami-Hodjegan and

Tucker 2007). It is polymorphically expressed, and the

importance of the SNPs within CYP2C9 gene is empha-

sized especially with S-warfarin, which uses CYP2C9 as a

major metabolic pathway and possesses a narrow thera-

peutic window with a potentially fatal side-effect profile

(Aithal et al. 1999; Daly and King 2003; Kirchheiner and

Brockmoller 2005).


Besides S-warfarin, CYP2C9 catalyses the metabolism of a

number of other clinically relevant drugs such as fluoxe-

tine, fluvastatin, losartan, and several non-steroidal

anti-inflammatory agents, as well as the classical probe

substrate tolbutamide (Table 7). Tolbutamide methylhydr-

oxylation and diclofenac 40-hydroxylation are both

validated for CYP2C9 marker reactions both in vitro and

in vivo.

Among the recognized inhibitors of CYP2C9 are ami-

odarone, and fluconazole, which both are suitable for in

vivo use, but are relatively unselective. For in vitro pur-

poses, sulphaphenazole is traditionally employed, because

of very high potency and selectivity.

CYP2C19

Drugs metabolized via CYP2C19 are usually amides or

weak bases with two HBAs (Lewis 2004). Compared to

CYP2D6 (see later), polymorphisms of the CYP2C19 gene

represent a smaller proportion and perhaps have less clin-

ical significance in Caucasians, but in Orientals the

frequency of CYP2C19 PMs has been characterized to be

up to 20% of the population (Bertilsson 1995; Ingelman-

Sundberg et al. 2007).

Table 4 Substrates and inhibitors of CYP2A6 enzyme


Substrates

Nicotinea N-10-oxidation 65–95 High Cashman et al. (1992)

Nakajima et al. (1996a, b)

Messina et al. (1997)

Coumarinb 7-Hydroxylation 0.2–2.4 High Pelkonen et al. (1985)

Pearce et al. (1992)

Li et al. (1997)

Walsky and Obach (2004)

Cotinine 30-Hydroxylation 235 High Nakajima et al. (1996b)

Pilocarpine 3-Hydroxylation 1.5 High Endo et al. (2007)

SM-12502 S-oxidation 21 High Nunoya et al. (1996)

Drug Mode of inhibition Ki in HLMs (lM) CYP selectivity and other CYPs inhibited References

Inhibitors

Tranylcypromine Competitive 0.08–0.2 Moderate (CYP2E1) Draper et al. (1997)

Taavitsainen et al. (2001)

Zhang et al. (2001a, b)

Methoxsalen Mechanism-based 0.2–0.8 Moderate (CYP1A2) Maenpaa et al. (1994)

Draper et al. (1997)

Koenigs et al. (1997)

Tryptamine Competitive 0.2 Poor (CYP1A2) Draper et al. (1997)

Higashi et al. (2007a, b)

Pilocarpine Competitive 1 High? Kinonen et al. (1995)

Koenigs et al. (1997)

a Preferred in vivo probe substrateb Preferred in vitro probe substrate? Probably high

674 Arch Toxicol (2008) 82:667–715

123


CYP2C19 participates in the metabolism of many com-

monly used pharmaceuticals, e.g. diazepam, citalopram,

amitriptyline, mephenytoin, proguanil, and phenytoin.

The metabolism of most of the proton pump inhibitors

(omeprazole, esomeprazole, lansoprazole and pantopraz-

ole) is mediated mainly by CYP2C19. Classical marker

reactions for this enzyme include S-mephenytoin

40-hydroxylation and omeprazole 5-hydroxylation

(Table 8).

No selective drug inhibitors for CYP2C19 have been

found yet, but at least omeprazole, ticlopidine, nootkatone,

and fluconazole—all with some affinity towards other

CYPs, too—have been employed for this purpose.

CYP2D6

Since the characterization of the interindividual differences

in the oxidation of debrisoquine and sparteine in the late

1970s, CYP2D6 has become the most studied CYP with

respect to pharmacogenetics. The genetic polymorphism

Table 5 Substrates and inhibitors of CYP2B6 enzyme


Substrates

Bupropiona,b Hydroxylation 89–130 High Faucette et al. (2000)

Hesse et al. (2000)

Turpeinen et al. (2005a)

Efavirenz 8-Hydroxylation 17–23 Moderate (CYP1A2, 3A4) Ward et al. (2003)

Cyclophosphamide 4-Hydroxylation 2,000 Moderate (CYP2C9, 2C19, 3A4) Roy et al. (1999a)

Huang et al. (2000)

Ifosfamide N-dechloro-ethylation 1,900 Moderate (CYP2C9, 2C19, 3A4) Roy et al. (1999a, b)

Huang et al. 2000

Piclamilast (RP 73401) Hydroxylation 8–26 High Stevens et al. (1997)

S-mephobarbital N-demethylation 236–276 High Kobayashi et al. (1999)

Pethidine (meperidine) N-demethylation 45 Moderate (CYP3A4) Ramırez et al. (2004)

Propofol Hydroxylation 8–10 Moderate (CYP2C9) Court et al. (2001)

Oda et al. (2001)

Ketamine N-demethylation 24–48 Moderate (CYP2C9, 3A4) Yanagihara et al. (2001)

Hijazi and Boulieu (2002)

Nicotine N-demethylation 619 Moderate (CYP2A6) Yamanaka et al. (2005)

Artemisinin nk nk Moderate (CYP3A4)c Svensson and Ashton (1999)


Inhibitors

ThioTEPA Mechanism-based 2.8–3.8 High Rae et al. (2002)

Harleton et al. (2004)

Turpeinen et al. (2004)

Richter et al. (2005

Ticlopidine Mechanism-based 0.2–0.8 Moderate (CYP1A2, 2C19, 2D6) Richter et al. (2004)


Turpeinen et al. (2005a, b)

Clopidogrel Mechanism-based 1.1 Moderate (CYP2C19, 2C9) Richter et al. (2004)

Turpeinen et al. (2005b)

17-a-Ethynylestradiol Mechanism-based 0.8 Moderate (CYP1A2) Kent et al. (2002)

Palovaara et al. (2003)

a Preferred in vivo probe substrateb Preferred in vitro probe substratec Contribution of CYP2B6 to the overall metabolism

Arch Toxicol (2008) 82:667–715 675

123

within the CYP2D6 gene causes wide and clinically

important variability in CYP2D6 enzyme activity (Ei-

chelbaum et al. 2006; Ingelman-Sundberg et al. 2007).

Ultimate examples of the polymorphism of the CYP2D6

gene include the PMs lacking the functional enzyme, and

the ultra-rapid metabolizers (UMs) having duplications or

multiplications of the gene. Approximately 7 and 5.5% of

Caucasians have been genotyped for CYP2D6 PMs and

UMs, respectively (Zanger et al. 2004; Ingelman-Sundberg

et al. 2007). Wide variability between ethnic groups with

respect to CYP2D6 phenotype exists; for instance, the PM

phenotype is practically absent in Oriental populations and

the UM phenotype is very frequent in certain Arabian and

Eastern African populations (Ingelman-Sundberg et al.

2007). CYP2D6 belongs to the set of most relevant target

genes where genotype/phenotype testing has been

suggested as a useful tool in dosing and monitoring in

clinical practice (Dahl 2002; Kirchheiner et al. 2005; Ei-

chelbaum et al. 2006).

Substrates and inhibitors of CYP2D6

CYP2D6 contributes to the metabolism of dextromethor-

phan, debrisoquine, and bufuralol, which all have been

used as model substrates for this enzyme. Since debrisoq-

uine is no longer available for in vivo studies, also newer

substances like atomoxetine have been introduced for

phenotyping purposes. The metabolism of several b-adre-

noceptor antagonists like metoprolol and propranolol,

several important antidepressants such as fluoxetine and

paroxetine, and atypical antipsychotics like risperidone and

aripiprazole is mediated predominantly via CYP2D6

Table 6 Substrates and inhibitors of CYP2C8 enzyme


Substrates

Repaglinidea Oxidation 24 Moderate (CYP3A4) Bidstrup et al. (2003)

Kajosaari et al. (2005)

Rosiglitazonea p-Hydroxylation

N-demethylation

4–8

12–20

Moderate (CYP2C9) Baldwin et al. (1999)

Paclitaxelb 6a-Hydroxylation 2.5–19 High Desai et al. (1998)

Cresteil et al. (1994)

Ohyama et al. (2000)

Li et al. (2003)

Amodiaquineb N-de-ethylation 1.9–3.4 High Li et al. (2002)

Li et al. (2003)


Amiodarone N-de-ethylation 19–38 Poor (CYP1A2, 2C19, 3A4) Soyama et al. (2002)


Tazarotenic acid Sulfoxidation 25 High Attar et al. (2003)

Chloroquine N-de-ethylation 210–444 Moderate (CYP3A4) Projean et al. (2003)

Kim et al. (2003a, b)


Inhibitors

Montelukast Competitive 0.009–0.15 Moderate (CYP2C9, 3A4) Walsky et al. (2005a, b)

Quercetin Competitive 1.1–1.6 Poor (CYP1A2, 2E1, 3A4) Li et al. (2002)


Walsky et al. (2005b)

Trimethoprim Competitive 29–32 High Wen et al. (2002)

Hruska et al. (2005)

Gemfibrozil (glucuronide) Mechanism-based 52–75 High Wang et al. (2002)

Kajosaari et al. (2005)

Ogilvie et al. (2006)

a Preferred in vivo probe substrateb Preferred in vitro probe substrate

676 Arch Toxicol (2008) 82:667–715

123

(Table 9). On structural basis, the common characteristic

for CYP2D6 substrates seems to be, that they are mostly

basic molecules with protonatable nitrogen atom 4–7 A

from the site of metabolism (Lewis 2004).

CYP2D6 is inhibited potently by a variety of different

drugs, of which a large proportion belongs also to the list of

CYP2D6 substrates. Traditionally an antiarrhythmic drug

quinidine has been utilized as a highly selective and very

efficient CYP2D6 inhibitor for metabolism studies. Inci-

dentally, quinidine is not a substrate of CYP2D6.

CYP2E1

Although CYP2E1 is one of the most abundant hepatic

CYPs, only a few pharmaceuticals are metabolized via this

enzyme. However, from the toxicological perspective, the

role of CYP2E1 is without dispute. CYP2E1 has been

studied extensively due to its central role in the metabolism

of ethanol (Kessova and Cederbaum 2003; Lieber 2004), in

the bioactivation of several industrial solvents (Raucy et al.

1993), as an activator of chemical carcinogenesis, and as a



Substrates

Tolbutamidea,b Hydroxylation 60–580 High Relling et al. (1990)

Veronese et al. (1991)


Yuan et al. (2002)

Diclofenacb 4-Hydroxylation 2–22 High Leemann et al. (1993)

Li et al. (2003)


Kumar et al. (2006)

S-warfarinb 7-Hydroxylation 3–4 High Kunze et al. (1996)

Kumar et al. (2006)

Phenytoin 40-Hydroxylation 12–117 Moderate (CYP2C19) Veronese et al. (1991)

Doecke et al. (1991)

Giancarlo et al. (2001)

Losartan Oxidation (E-3174) 4–20 Moderate (CYP3A4) Stearns et al. (1995)

Yasar et al. (2001)

Ibuprofen 2-Hydroxylation

3-Hydroxylation

13–19629–200 Moderate (CYP2C8) Hamman et al. (1997)

Carlile et al. (1999)

Naproxen O-demethylation 92–160 Moderate (CYP1A2) Rodrigues et al. (1996)

Miners et al. (1996)

Tracy et al. (1997)

Flurbiprofen 40-Hydroxylation 6–42 High Tracy et al. (1996)

Yamazaki et al. (1998)

Indomethacin O-demethylation 35 Moderate (CYP2C19) Nakajima et al. (1998)


Inhibitors

Sulphaphenazole Competitive 0.3 High Back et al. (1988)


Baldwin et al. (1995)

Fluconazole Mixed type 7–8 Poor (CYP2C19, 3A4) Back et al. (1988)

Kunze et al. (1996)

Amiodarone Non-competitive 95 Poor (CYP2D6, 3A4) Heimark et al. (1992)



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123

producer of free radicals causing tissue injury (Caro and

Cederbaum 2004; Gonzalez 2005). CYP2E1 is also linked

to acetaminophen-related hepatotoxicity (Rumack 2004).

Although a number of SNPs within the CYP2E1 gene have

been described, no polymorphisms leading to a loss of

function have been reported (Gonzalez 2005).

Substrates and inhibitors of CYP2E1

The substrates of CYP2E1 usually consist of hydrophobic

and low molecular weight compounds (Lewis 2004). For

modeling purposes, chlorzoxazone is probably the most

widely used, but also the metabolism of acetaminophen,

enflurane, and halothane seems to be mediated to some

extent by CYP2E1 (Table 10). It is noteworthy that several

substrates of CYP2E1 (e.g. ethanol, acetone and pyrazole)

act as inducing agents of this enzyme.

Inhibitors of CYP2E1 include pyridine and disulfiram,

the latter being utilized in clinical practice as a treatment of

alcohol dependence.

CYP3 family

The human CYP3 family represents about 30% of the total

hepatic P450 content and is considered to be the most

important CYP subfamily in the biotransformation of

drugs. This family contains one subfamily including three

functional proteins: CYP3A4, CYP3A5, and CYP3A7, and

one pseudoprotein, CYP3A34 (Ingelman-Sundberg 2005).

These enzymes have overlapping catalytic specificities and

their tissue expression patterns differ.

CYP3A5 is a minor polymorphic CYP form in human

liver (Westlind-Johnsson et al. 2003), but in extrahepatic

tissues it is consistently expressed in kidney, lung, colon,

and esophagus (Ding and Kaminsky 2003; Burk and Woj-

nowski 2004). Despite a few exceptions, the substrate and

inhibitor specificity of CYP3A5 seems to be highly similar

to CYP3A4, albeit the catalytic capability might be some-

what lower (Wrighton et al. 1990; Williams et al. 2002).

CYP3A7 is mainly expressed in embryonic, fetal, and

newborn livers, where it is the predominant CYP form



Substrates

Omeprazolea,b 5-Hydroxylation 6–10 High Andersson et al. (1993)

Chiba et al. (1993)

Abelo et al. (2000)

S-mephenytoina,b 40-Hydroxylation 23–169 High Chiba et al. (1993)

Coller et al. (1999)



Lansoprazole 5-Hydroxylation 15–17 Moderate (CYP3A4) Pearce et al. (1996)

Kim et al. (2003a, b)

Diazepam N-demethylation 120 Moderate (CYP3A4) Andersson et al. (1994)

Yasumori et al. (1994)

Proguanil Oxidation (cycloguanil) 35–380 Moderate (CYP3A4) Coller et al. (1999)

Birkett et al. (1994)

Funck-Brentano et al. (1997)


Inhibitors

Omeprazole Competitive 2–3 Moderate (CYP2C9, 3A4) Chiba et al. (1993)

Ko et al. (1997)

Funck-Brentano et al. (1997)

Ticlopidine Mechanism-based 1.2 Poor (CYP2B6, 1A2, 2D6) Ko et al. (2000)

Ha-Duong et al. (2001)


Nootkatone nk 0.5 Poor (CYP2A6) Tassaneeyakul et al. (2000)


678 Arch Toxicol (2008) 82:667–715

123

(Kitada and Kamataki 1994; Hakkola et al. 2001), whereas in

the adult liver, CYP3A7 seems to be a minor form (Schuetz

et al. 1994). CYP3A7 has an important role during the fetal

period in the hydroxylation of several endogenous sub-

stances like retinoic acid and steroid hormones, and therefore

it has relevance to normal embryonal development (de Wildt

et al. 1999; Hines and McCarver 2002). In drug metabolism,

the role of CYP3A7 is not yet clear.

CYP3A4

CYP3A4 is the sixth most abundant enzyme in human liver

at the mRNA level and constitutes the major CYP form in

the liver and the small intestine (Kivisto et al. 1996; von

Richter et al. 2004; Paine et al. 2006; Rostami-Hodjegan

and Tucker 2007). CYP3A4 has a pivotal role in xenobiotic

metabolism, and it has been estimated to be involved in the

Table 9 Substrates and inhibitors of CYP2D6 enzyme


Substrates

Dextromethorphana,b O-demethylation 2.8–22 High Broly et al. (1989)


Schmider et al. (1997)


Bufuralolb 10-Hydroxylation 3–30 High Ohyama et al. (2000)

Yuan et al. (2002)

Debrisoquinea 4-Hydroxylation 130 High Kahn et al. (1982)

Boobis et al. (1983)

Distlerath et al. (1985)

Codeine O-demethylation 149 High Dayer et al. (1988)

Mortimer et al. (1990)

Desipramine 2-Hydroxylation 10–15 High von Moltke et al. (1998a)

Atomoxetine 4-Hydroxylation 2.2–2.3 High Ring et al. (2002)

Thioridazine 2-Sulfoxidation (mesoridazine) 62c Moderate (CYP2C19, 3A4) Wojcikowski et al. (2006)


Inhibitors

Quinidine Competitive 0.018–0.06 Good Broly et al. (1989)

Otton et al. (1984)

Otton et al. (1988)

Abdel-Rahman et al. (1999)

Terbinafine Competitive 0.028–0.044 Good Abdel-Rahman et al. (1999)

Vickers et al. (1999)

Paroxetine Competitive 0.15 Moderate (CYP2C9, 2C19) Crewe et al. (1992)

Kobayashi et al. (1995)


Fluoxetine Competitive 0.6 Moderate (CYP2C9, 2C19) Crewe et al. (1992)



Norfluoxetine Competitive 0.43 Moderate (CYP2C9, 2C19) Crewe et al. (1992)



Sertraline Competitive 0.7 Moderate (CYP2C9, 2C19) Crewe et al. (1992)



a Preferred in vivo probe substrateb Preferred in vitro probe substratec Km from cDNA expressed CYP2D6

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123

metabolism of approximately 50% of the drugs in clinical

use. The active site of CYP3A4 is very large and flexible

allowing multiple small molecules to be present simulta-

neously in the active site. The substrate binding is

principally based on hydrophobicity with some steric

interactions. A concept where multiple conformations of

the enzyme can exist both in the presence and absence of

substrate has been proposed (Ekins et al. 2003; Scott and

Halpert 2005). The kinetic interaction between CYP3A4

and its substrates is often atypical, making the prediction

and modeling of CYP3A4-mediated drug–drug interactions

troublesome (Ekins et al. 2003; Houston and Galetin 2005).


The known substrates of CYP3A4 vary widely in size and

structure. Among the substrates of CYP3A4 are several

clinically important drugs, e.g. cyclosporine A, erythro-

mycin, nifedipine, felodipine, midazolam, triazolam,

simvastatin, atorvastatin, and quinidine (Table 11), as well

as several endogenous agents including testosterone, pro-

gesterone, androstenedione, and bile acid (Waxman et al.

1991; Patki et al. 2003). Consequently, altered CYP3A4

activity can lead to notable drug–drug interactions and

adverse effects. Bioactivation of some procarcinogens such

as aflatoxin B1 (Aoyama et al. 1990) and PAHs (Hecht

1999) are also mediated partially via CYP3A4.

A relatively low degree of substrate selectivity makes

CYP3A4 susceptible to inhibition by different chemicals.

Inhibitors of CYP3A4 cover a broad variety of structurally

unrelated substances. The most well established and clin-

ically the most relevant inhibitors include certain azole

antifungal agents (ketoconazole and itraconazole), antimi-

crobials (clarithromycin, erythromycin and ritonavir),

antihypertensives (verapamil and diltiazem) and several

herbal and food constituents, e.g. grapefruit juice and

bergamottin (He and Edeki 2004; Fujita 2004). It is note-

worthy that IC50 values for CYP3A4 inhibitors are highly

substrate-dependent, and the use of multiple probe sub-

strates for inhibition studies is thus recommended

Table 10 Substrates and inhibitors of CYP2E1 enzyme

Drug Reaction Km in HLMs (lM) Specificity nearKm References

Substrates

Chlorzoxazonea,b 6-Hydroxylation 39–157 High Ono et al. (1995)

Yuan et al. (2002)


p-Nitrophenol 3-Hydroxylation 30 High Tassaneeyakul et al. (1993b)

Koop and Coon (1986)

Aniline 4-Hydroxylation 6–24 High Koop and Coon (1986)


Lauric acid 11-Hydroxylation 130 Moderate (CYP4A) Clarke et al. (1994a, b)

Amet et al. (1995)



References

Inhibitors

Pyridine Not known 0.4 Highc Hargreaves et al. (1994)

Disulfiram Mechanism-based Not known Moderate (CYP2A6) Brady et al. (1991a)

Guengerich et al. (1991)

Kharasch et al. (1998)

Diethyldithio-carbamate Mechanism-based 10–34 Poor (CYP1A2, 2A6, 2B6,

2C8, 3A4)

Guengerich et al. (1991)

Chang et al. 1994

Clomethiazole Noncompetitive 12 ? Hu et al. (1994)

Gebhardt et al. (1997)

Diallylsulfide Mechanism-based 150–188 ? Brady et al. (1991b)

Amet et al. (1995)

a Preferred in vivo probe substrateb Preferred in vitro probe substratec Also an inducer of CYP2E1? Not known

680 Arch Toxicol (2008) 82:667–715

123

Table 11 Substrates and inhibitors of CYP3A4/5 enzyme


Substrates

Midazolama,b 10-Hydroxylation 1–14 High Von Moltke et al. (1996)

Li et al. (2002)


Yuan et al. (2002)

Testosteroneb 6b-hydroxylation 33–94 High Ohyama et al. (2000)

Yuan et al. (2002)

Patki et al. (2003)


Felodipinea Dehydrogenation 2.8–6.9 High Baarnhielm et al. (1986)


Eriksson et al. (1991)

Erythromycina N-demethylation 33–88 High Yamazaki et al. (1996)

Wang et al. (1997)

Nifedipine Oxidation 5–47 High Bourrie et al. (1996)

Patki et al. (2003)

Triazolama 4-Hydroxylation 238–304 High Von Moltke et al. (1996b)

Patki et al. (2003)

Simvastatina Oxidative metabolism 13–59 Moderate (CYP2C8) Prueksaritanont et al. (1997, 2003)

Atorvastatina Hydroxylation 1.5–30 High Kearney et al. (1993)

Jacobsen et al. (2000)

Alprazolam 10-Hydroxylation 63–441 High Von Moltke et al. (1993)

Gorski et al. (1999)

Allqvist et al. (2007)

Cyclosporin A Oxidative metabolism nk High Kronbach et al. (1988)

Christians et al. (1991)

Back and Tjia (1991)

Buspirone Hydroxylation

N-oxidation

4–1134 High Zhu et al. (2005)

Alfentanil N-dealkylation 23 High Lavrijsen et al. (1988)

Tateishi et al. (1996)

Klees et al. (2005)

Quinidine 3-Hydroxylation 30–59 High Guengerich et al. (1986)

Otton et al. (1988)

Nielsen et al. (1999)

Allqvist et al. (2007)

Lovastatin Oxidative metabolism 7–10 High Wang et al. (1991)

Jacobsen et al. (1999)

Eletriptan N-demethylation nk Moderate (CYP2D6) Evans et al. (2003)

Sildenafil N-demethylation 39–129 Moderate (CYP2C9) Warrington et al. (2000)

Hyland et al. (2001)

Vincristine Oxidative metabolism 14–20c High Yao et al. (2000)

Dennison et al. (2006)

Tacrolimus 13-O-demethylation 0.21c High Kamdem et al. (2005)

Dai et al. (2006)


Inhibitors

Ketoconazole Competitive 0.0037–0.028 Moderate (CYP2C, 1A2, 2D6) Back and Tjia (1991)

Baldwin et al. (1995)

von Moltke et al. (1996a)

Patki et al. (2003)


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123

(Kenworthy et al. 1999; Wang et al. 2000b; Galetin et al.

2003). The detailed characteristics of several CYP3A4

substrates and inhibitors are summarized recently in a

review by Liu et al. (2007).

Inhibition: in vitro–in vivo extrapolation

Inhibitory potency in vitro-inhibition of clearance

Based on the requirements of the authorities, new drugs

need to be tested with respect to their potential to cause

drug–drug interactions (EMEA 1997, U.S. FDA 1997).

These estimations rely primarily on projected in vivo

concentrations of compounds and on estimates of their

inhibitory constants obtained from in vitro studies.

The degree of inhibition depends also on the inhibition

pattern when the substrate concentration is high. How-

ever, when the substrate concentration [S] � Km—which

is the most usual case in clinical use—the degree of

inhibition (R) can be expressed by the following equation

independent of the inhibition pattern, except in the case of

the uncompetitive inhibition (Tucker 1992; Ito et al.

1998):

R ¼ 1

1þ ½I�=Ki

When [S] C Km, the degree of the inhibition can be

estimated from the following assuming competitive

inhibition (Tucker 1992; Ito et al. 1998):

R ¼ ðKm þ ½S�Þ½Kmð1þ ½I�=KiÞ þ S�

In the case of competitive inhibition, it is possible to

calculate the inhibition constants on the basis of

experimentally determined IC50 values using the

Tornheim equation (Tornheim 1994):

Ki ¼½I�

ðV0=V � 1Þð1þ ½S�=KmÞ

A recent study by Obach et al. (2006) involving a variety of

drugs attempted to estimate the utility of in vitro data for

Table 11 continued


Itraconazole Competitive 0.013–0.27 High Back and Tjia (1991)

von Moltke et al. (1996b)

Isoherranen et al. (2004)

Niwa et al. (2005)

Troleandomycin Mechanism-based 0.26c High Newton et al. (1995)

Yamazaki and Shimada (1998)

Soars et al. (2006)

Verapamil Mechanism-based 2.3–2.9 High Yeo and Yeo (2001)

Wang et al. (2005)

Indinavir Competitive 0.17–0.5 High Chiba et al. (1996)

Eagling et al. (1997)

Saquinavir Mechanism-based 0.65–2.99 High Ernest et al. (2005)

Eagling et al. (1997)

Diltiazem Mechanism-based 2.2–5.0 High Yeo and Yeo (2001)

Clarithromycin Mechanism-based 5.5–10 High Ito et al. (2003)

Pinto et al. (2005)

Galetin et al. (2006)

Gestodene Mechanism-based 46 High Guengerich (1990)

Back et al. (1991)

Ritonavir Mechanism-based 0.019–0.17 Moderate (CYP2C9) Eagling et al. (1997)

Koudriakova et al. (1998)

Ernest et al. (2005)

Nelfinavir Competitive 1–4.8 Moderate (CYP2D6) Lillibridge et al. (1998)

Ernest et al. (2005)

nk not knowna Preferred in vivo probe substrateb Preferred in vitro probe substratec Km or Ki from cDNA expressed CYP3A4 and CYP3A5

682 Arch Toxicol (2008) 82:667–715

123

prediction of drug–drug interactions in clinical situations.

They concluded that in vitro inhibition data could be reli-

ably used for predictions for at least CYP1A2, CYP2C9,

CYP2C19, and CYP2D6, while for CYP3A4, the effects of

both hepatic and intestinal metabolism should be consid-

ered. Other factors affecting in vivo–in vitro extrapolation

will be discussed below.

Factors affecting in vitro–in vivo extrapolation

As presented above, affinity and CYP specificity for an

inhibitor can be studied in vitro and further, the potential of

a compound to cause interactions can be revealed. How-

ever, this does not necessarily mean that the compound

would cause clinically significant drug–drug interactions.

For such interactions to take place in vivo, two prerequi-

sites have to be fulfilled: first, the concentration of the

substrate in the in vivo situation should be high enough for

the inhibition to occur in clinical situation, and second, the

therapeutic index of the drug should be narrow, so that the

change caused by the inhibitor would be manifested in

adverse effects (Pelkonen et al. 1998, 2005). Semiquanti-

tative classifications for the extrapolation purposes have

been constructed such as that of Bjornsson et al. (2003)

based to the ratio of Cmax over Ki predicting the clinical

relevance of the interaction in the case of competitive

inhibition (Bjornsson et al. 2003).

However, free inhibitor concentrations at the site of

action (adjacent to the enzyme) are in most cases unknown

in in vivo situations. Based on the hypothesis that only an

unbound fraction of a drug is capable of diffusing into

hepatic tissue, predictions are made assuming that unbound

inhibitor concentrations in plasma and hepatic tissue are

equal (Ito et al. 1998; von Moltke et al. 1998b). For very

lipophilic compounds, this assumption is known to be

false; despite an extensive binding to plasma proteins, their

hepatic concentrations are multiple to their plasma values

(Chou et al. 1993; von Moltke et al. 1998b; Schmider et al.

1999; Cook et al. 2004). A recent analysis by Ito et al.

(2004) suggested that total inhibitor concentrations with in

vitro Ki values would probably be the most useful approach

for the categorization of CYP inhibitors.

Although the expression of CYPs is centered in the liver,

several other barrier tissues such as intestinal mucosa,

lungs, and skin contain metabolic enzymes on a smaller

scale and contribute to xenobiotic biotransformation

(Kapitulnik and Strobel 1999; Ding and Kaminsky 2003).

Knowing that the systemic bioavailability depends both on

the dose absorbed and the fraction surviving from hepatic

and extrahepatic metabolism, it should be noted that espe-

cially intestinal metabolism may affect in vitro–in vivo

extrapolations (Wu et al. 1995; Hall et al. 1999; Kivisto

et al. 2004). However, often the amount of extrahepatic

metabolism is not known and consequently, estimations

concerning the in vivo situation may be misleading.

The role of transporters, especially P-glycoprotein (P-gp)

and human organic anion-transporting polypeptides

(OATPs), has been recognized as a major contributor to

drug–drug interactions. P-gp is known to possess a signifi-

cant substrate overlap with the CYP3A family: drug

substrates for both CYP3A4 and P-gp include cyclosporin

A, verapamil, quinidine, erythromycin, and HIV-1 protease

inhibitors (Wacher et al. 1995; Kim et al. 1999). Among

drug substrates of OATPs are, e.g fexofenadine (Cvetkovic

et al. 1999; Dresser et al. 2002) and pravastatin (Hsiang

et al. 1999; Nishizato et al. 2003). Nevertheless, estimations

concerning the net effect of transporters on interactions are

very uncertain and have been so far poorly taken into

account in in vitro–in vivo extrapolation calculations.

Finally, when estimating clinical significance of the

interaction, one should take into account that results

obtained from in vitro test systems are highly dependent on

several technical aspects including the microsomal protein

amount, incubation time, and initial velocity conditions

used in the test system. The best predictive value is usually

obtained when the substrate concentration used is within

the linear part of the time and protein concentration

dependence curve for the metabolite formation (Maenpaa

et al. 1998; Lin and Lu 1998; Yuan et al. 1999). It is

supposed, with some restrictions, that the values obtained

from inappropriate experimental settings would lead to the

greatest extrapolation error with compounds of intermedi-

ate inhibitory potency (Ghanbari et al. 2006).

Induction of CYP enzymes: mechanisms

Transcriptional regulation by ligand-activated

transcription factors

Induction of CYP enzymes by exogenous compounds is

mediated to major extent by group of ligand-activated

transcription factors. These intracellular receptors involve

aryl hydrocarbon receptor (AhR) that belongs structurally

to the class of basic-helix-loop-helix (bHLH)-Per-Arnt-Sim

(PAS) proteins and nuclear receptors pregnane X receptor

(PXR, NR1I2) and constitutive androstane receptor (CAR,

NR1I3). Together these receptors are able to sense a great

variety of xenobiotics and consequently regulate numerous

phase I and phase II drug-metabolizing enzymes and drug

transporters in order to adjust the organism to the

requirements of the chemical environment. In addition to

these well-established xenosensors some other nuclear

receptors such as estrogen receptor (ER) a and glucocor-

ticoid receptor (GR) may be involved in some induction

phenomena (Higashi et al. 2007a, b; Hukkanen et al. 2003).

Arch Toxicol (2008) 82:667–715 683

123

AhR

AhR is expressed widely in human tissues with highest

expression in placenta, lung, heart, pancreas and liver

(Dolwick et al. 1993). AhR typically accepts hydropho-

bic, planar compounds such as classical AhR activator

2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) as ligands.

However, numerous molecular structures and both

xenobiotics and endogenous compounds have been

described to be ligands for AhR (recently reviewed by

Nguyen and Bradfield 2008). The major classes of

xenobiotic ligands include halogenated dioxins, poly-

chlorinated biphenyls and PAHs. Furthermore, some

dietary compounds can activate AhR. Indole-3-carbinol

present in cruciferous plants appears to, perhaps through

active derivates produced in gastrointestinal track, be

able to activate AhR function (Bjeldanes et al. 1991).

Also several endogenous compounds are AhR agonists;

however, it remains to be shown if any of these thus far

identified compounds represent true endogenous ligands

(Nguyen and Bradfield 2008).

In the absence of a ligand, AhR is located in cytosolic

compartment in complex with chaperone proteins Hsp90,

ARA9 (also known as XAP2 or AIP) and p23 (Carlson and

Perdew 2002). Binding of an agonist launches a confor-

mational change that allows nuclear localization signal to

interact with nuclear import machinery. In the nucleus AhR

dimerizes with another bHLH-PAS protein AhR nuclear

translocator (ARNT) thus forming the actual DNA-binding

complex. The AhR/ARNT heterodimer interacts with

XRE-binding elements with consensus core sequence 50-TNGCGTG-30. The DNA bound AhR/ARNT complex then

activates transcription through recruitment of complex of

multiple coactivators including CBP/p300, SRC-1, NCOA-

2 and Mediator (Kawajiri and Fujii-Kuriyama 2007). The

coactivators in turn modulate the chromatin structure and

interact with the general transcription factors to allow

activation of transcription.

AhR primary regulates expression of genes in CYP

family 1, i.e. CYP1A1, CYP1A2 and CYP1B1. However,

also some CYP2 family members are AhR target genes

(Rivera et al. 2002; Arpiainen et al. 2005) (see Table 12).

Our understanding on molecular details of AhR function is

mainly based on extensive study of CYP1A1 induction

mechanism (for a review see Ma 2001). CYP1A1 is induced

extremely powerfully by AhR ligands while effect on most

other AhR target genes is less pronounced. This may be

due to multiple XRE sites in the CYP1A1 50 flanking region

(Kress et al. 1998). Furthermore, the low constitutive

expression of CYP1A1 may emphasize the magnitude of

induction. Ligand-activated AhR induces expression of

AhR repressor (AhRR), which is able to dimerize with

ARNT and bind XRE, but in contrast to AhR, represses

transcription (Mimura et al. 1999). This may represent a

negative feedback loop.

PXR

Discovery of mouse and subsequently human PXR at the

end of 1990s represented a major breakthrough in under-

standing the molecular mechanisms of many clinically

significant induction phenomena (Kliewer et al. 1998;

Lehmann et al. 1998; Blumberg et al. 1998; Bertilsson

et al. 1998). Human PXR ligands (recently reviewed by

Chang and Waxman 2006) include many therapeutic drugs,

such as rifampicin, known to induce drug metabolism. PXR

has large and flexible ligand-binding pocket which enables

binding of numerous compounds of varying size and

structure (Watkins et al. 2001). There are, however, major

differences in PXR ligand preferences between species

because of poorly conserved ligand-binding domain (Leh-

mann et al. 1998; Blumberg et al. 1998). Thus rifampicin is

a good agonist for human PXR, but poorly activates mouse

PXR. The opposite is true for mouse PXR agonist preg-

nenolone-16a-carbonitrile. These sharp differences in PXR

ligand preferences affect and limit extrapolation of results

from experimental animals to humans. PXR ligands

include also endogenous compounds such as some bile

acids (Staudinger et al. 2001; Xie et al. 2001).

Tissue distribution of PXR is quite narrow. In human,

the main sites of PXR expression are liver and small

intestine while limited expression can be detected in kidney

and lung (Miki et al. 2005). This expression profile is in

good agreement with the putative role as an environmental

xenosensor and coincides with that of a major target gene

CYP3A4. PXR protein level is regulated by microRNA,

which in turn affects CYP3A4 expression level (Takagi

et al. 2008). There has been some controversy about sub-

cellular localization of unliganded PXR. While Koyano

et al. (2004) reported constant nuclear localization of PXR

regardless of the presence or absence of agonist some other

recent studies have suggested cytoplasmic localization and

nuclear transport after ligand binding (Kawana et al. 2003;

Squires et al. 2004). Ligand bound PXR forms heterodimer

with another nuclear receptor RXR. This heterodimer is

able to bind several distinct DNA elements including both

direct and everted repeats of sequence AGGTCA and its’

variants. A number of different coregulators including

SRC-1, p300 and PGC-1 have been reported to interact

with PXR (Orans et al. 2005). Interestingly, in addition to

ligand, also tissue and target gene promoter appear to affect

PXR coactivator interactions (Masuyama et al. 2005).

PXR target genes include members in subfamilies

CYP2A, CYP2B, CYP2C and CYP3A (see Table 13).

Especially regulation of CYP3A4 by PXR has been studied

extensively [for reviews see Burk and Wojnowski (2004)

684 Arch Toxicol (2008) 82:667–715

123

and Plant (2007)]. Initially PXR was found to interact with

ER6 motif present in the proximal promoter of the

CYP3A4 gene (Lehmann et al. 1998). Subsequently

Goodwin et al. 1999 identified a so-called XREM (xeno-

biotic-response enhancer module) in the distal CYP3A4

promoter -7784/-7672 that was found to play a major role

in CYP3A4 induction by PXR ligands. The XREM con-

tains several nuclear receptor-binding elements of which a

DR3 element is of major importance. Both the DR3 ele-

ment in the XREM and the ER6 element in the proximal

promoter are needed for the maximal induction by PXR.

Recently an additional PXR-binding element was identi-

fied in the far upstream region -11400/-10500 (Liu et al.

2008). Similar to XREM also this far module seem to act

in collaboration with the proximal promoter. Hepatocyte

nuclear factor 4 a (HNF4a) has been shown to augment

PXR mediated induction of CYP3A4 (Tirona et al. 2003).

However, there is some controversy if HNF4a DNA

binding is necessary. Tirona et al. (2003) reported that

HNF4-binding element in the XREM is needed for

enhancement of PXR function by HNF4a. On the other

hand, Li and Chiang (2006) suggested that rifampicin-

activated PXR interacts with HNF4a through protein–

protein interaction independently from HNF4a DNA

binding. Regulation of CYP3A4 by PXR has been sche-

matically presented in Fig. 2. Small heterodimeric partner

(SHP) is able to interact with PXR and repress its tran-

scriptional activity (Ourlin et al. 2003). Rifampicin-

activated PXR downregulates SHP transcription (Li and

Chiang 2006), which may enable maximal induction of

PXR target genes such as CYP3A4.

Constitutive androstane receptor

Constitutive androstane receptor is the closest relative of

PXR and is present only in mammals suggesting that CAR

arose from a duplication of an ancestral PXR gene (Resc-

hly and Krasowski 2006). CAR expression is limited to

human liver and kidney and very low in other tissues

(Nishimura et al. 2004). The special feature of CAR is

constitutive activity, i.e. transactivation in the absence of a

ligand. This is because of the unusual structure of the CAR

ligand-binding domain in which the AF-2 (helix 12) is

stabilized to the active confirmation (Xu et al. 2004; Suino

et al. 2004; Shan et al. 2004). Therefore activators of CAR

involve both direct ligand-dependent and ligand-indepen-

dent mechanisms. Similar to PXR also CAR ligands

display species specificity (for review see Chang and

Waxman 2006). Well-established agonists for mouse and

human CAR are 1,4-bis[2-(3,5-dichloropyridyloxy)]ben-

zene (TCPOBOP) and 6-(4-chlorophenyl)imidazo[2,1-

b][1,3]thiazole-5-carbalehyde O-[3,4dichlorobenzyl)oxime

(CITCO), respectively (Chang and Waxman 2006). CAR

constitutive activity can be inhibited with inverse agonist

such as androstanol for mouse CAR (Forman et al. 1998).

In the absence of an activator CAR is retained in the

cytosol in a complex with cytoplasmic CAR retention

protein (CCRP) and Hsp90 (Kobayashi et al. 2003). Phe-

nobarbital is a classical inducer of drug-metabolizing

enzymes and CAR was shown to mediate phenobarbital

induction of mouse Cyp2b10 gene (Honkakoski et al.

1998a). However, phenobarbital is not a direct ligand for

CAR (Moore et al. 2000). Instead phenobarbital induces

nuclear translocation of CAR by a mechanism involving 30

amino acid leucine-rich region in the C-terminus of CAR

(Zelko et al. 2001) and subsequently ligand independent

transactivation. The detailed mechanisms of phenobarbital

induction and CAR translocation are still unclear. Phos-

phorylation events appear to be important. Upon

phenobarbital induction cytosolic CAR complex recruits

protein phosphatase 2A (Yoshinari et al. 2003). Further-

more, extracellular signal-regulated kinase affects CAR

subcellular location (Koike et al. 2007). Phenobarbital also

activates AMP-activated protein kinase, which has been

suggested to be necessary for phenobarbital induction

(Rencurel et al. 2006). In nucleus CAR heterodimerizes

with RXR and binds to DNA-binding elements, of which

many are shared with PXR. Several coactivators including

SRC-1, PGC-1 and GRIP1 have already been shown to

interact with CAR (Timsit and Negishi 2007).

Classical CAR targets include the CYP2B family

members, in humans CYP2B6 (Honkakoski and Negishi

1997; Sueyoshi et al. 1999). CYP2B genes contain 51 bp

phenobarbital responsive enhancer module (PBREM) in

their regulatory regions that constitutes of two DR4 type

Fig. 2 Schematic model of CYP3A4 regulation by ligand activated

PXR. Both ER6 sequence at the proximal promoter -170/-153 (P-

ER6) and XREM sequence at the distal 50 flanking region -7784/-

7672 bind PXR and are necessary for maximal induction. Recently a

novel ER-6 type PXR binding element was identified in the far

module (F-MOD) -11400/-10500 that also appears to coordinate

CYP3A4 induction together with the proximal ER-6 site. HNF4ainteracts with PXR and augments PXR mediated induction. PXR

recruits a number of coactivators which consequently modify

chromatin structure and engage the transcription initiation complex

Arch Toxicol (2008) 82:667–715 685

123

nuclear receptor-binding sites binding CAR/RXR hetero-

dimer and nuclear factor I (NFI) site in between

(Honkakoski et al. 1998b). NFI site is needed for the full

activity of the PBREM (Kim et al. 2001). Mouse PBREM

favors CAR over PXR while human PBREM is less

selective (Makinen et al. 2002). This may explain induction

of human CYP2B6 by typical PXR ligands such as rifam-

picin (Goodwin et al. 2001). In addition to CYP2B

subfamily, CAR regulates members in the CYP2C and

CYP3A families (see Table 13). Also CYP1A2 and

CYP2A6 are modestly induced by phenobarbital in human

hepatocytes but direct involvement of CAR is still to be

shown (Donato et al. 2000; Madan et al. 2003).

Crosstalk of xenosensing receptors

Detailed investigation of signaling mechanism involving

xenosensing receptors has revealed extensive crosstalk

with each other as well as with number of other factors (for

recent review see Pascussi et al. 2008). The levels of

crosstalk involve sharing of ligands, sharing of DNA-

binding elements, receptor–receptor interactions, interac-

tion with common coactivators and secondary regulation of

the regulators. For example CAR and PXR share some

ligands and DNA-binding elements. Furthermore, increas-

ing evidence shows that all AhR, CAR and PXR participate

in regulation of also many other important cellular func-

tions besides regulation of metabolism and transport of

xenobiotics. For example, PXR has been found to interact

with several important transcription factors inducing

HNF4a, FOXA2, FOXO1, CREB and to modify via them

glucose and lipid metabolism (Li and Chiang 2005; Kod-

ama et al. 2004, 2007; Nakamura et al. 2007). This

emerging area of research should help us in the future to

understand complex responses to xenobiotics.

Post-transcriptional induction

Significant post-transcriptional regulation has been shown

only for few CYPs. CYP2E1 appears to be the only CYP

regulated mainly at the post-translational level by xenobi-

otics such as ethanol, acetone, pyrazole and isoniazid

(Song et al. 1989; Carroccio et al. 1994). CYP2E1 protein

has short half life which is significantly increased by

CYP2E1 inducing compounds. In rat liver CYP2E1 protein

is degraded in two phases with half-lives of 7 and 37 h.

However, after 10-day acetone treatment the fast degra-

dation phase was abolished (Song et al. 1989). This

stabilization may involve inhibition of proteosomal deg-

radation pathway (Cederbaum 2006).

Regulation of mRNA stability has been found to medi-

ate induction by xenobiotics in a few cases. Most

extensively has been studied regulation of mouse CYP2A5

by pyrazole which involves binding of heterogeneous

nuclear ribonucleoprotein A1 to the 30-untranslated region

of the CYP2A5 mRNA (Raffalli-Mathieu et al. 2002).

Similar mechanism was reported to regulate also human

CYP2A6 (Christian et al. 2004).

Experimental tools to study induction

Here, we present the current status of methods that have

been developed and used to predict and detect induction in

humans or in human-derived preparations. The methods

involve either assaying various outcomes of agonist bind-

ing to the receptors that govern induction of CYP enzymes,

or direct detection of induced CYP mRNAs and/or activi-

ties. The relative benefits and drawbacks of these methods

are compared in Table 12.

In silico methods

The ability of a chemical to bind the cognate receptor

responsible for CYP induction can be computationally

estimated, and the evolving status of in silico models for

AhR, CAR and PXR has been reviewed (Lewis et al. 2002;

Ekins et al. 2002; Jacobs 2004; Poso and Honkakoski 2006;

Schuster et al. 2006; Vedani et al. 2006). In silico screening

can be performed in two fundamental ways. Briefly, in

ligand-based methods (e.g. QSAR and pharmacophore

models), molecular descriptors extracted from a set of

known receptor ligands will provide rules that will classify

other chemicals as potential CYP inducers via receptor-

mediated mechanisms. The number and breadth of chem-

ical structures used for model building and the use of

separate validation sets are critical for the applicability and

predictivity of the models. In the protein-based approach,

candidate ligands are docked into the 3D structure or a

homology model of the receptor, and evaluation of the

binding fitness by various scoring functions will identify

the chemicals with highest potential for receptor binding

and CYP induction. Combinations of protein- and ligand-

based methods have been also reported (e.g. Schuster and

Langer 2005; Lemaire et al. 2007). In homology models,

inappropriate template structures will lead to erroneous

binding cavities for the modeled receptor (e.g. Xiao et al.

2002; Jacobs 2004), inability to distinguish between ago-

nistic and antagonistic binding (Schuster and Langer 2005),

and naturally, problems in prediction as noted elsewhere

(Schuster et al. 2006; Windshugel et al. 2007). The

dynamic flexibility of the receptor protein has been mostly

omitted in the dockings although it is important for nuclear

receptor function. Only recently, modeling employing

induced fit (Sherman et al. 2006; Nabuurs et al. 2007; Repo

et al., submitted) or with molecular dynamics simulations

686 Arch Toxicol (2008) 82:667–715

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(Poso and Honkakoski 2006) has been done with nuclear

receptors.

For AhR, comprehensive QSAR models covering sev-

eral classes of polyhalogenated and polycyclic

hydrocarbons have been constructed (e.g. Waller and Mc-

Kinney 1992; Mekenyan et al. 1996). A later homology

model yielded a quite robust model with cross-validation

coefficient (q2) of 0.58 or greater (Lo Piparo et al. 2006). In

these studies, p–p stacking interactions, planarity of the

compounds, and electronegative features of the ligand

seem to determine high AhR-binding affinity. Quantum

mechanical calculations that incorporate dispersion inter-

actions and electrophilicity have successfully explained

AhR binding and/or EROD inducibility to a level of 70%

or above (Arulmozhiraja and Morita 2004; Gu et al. 2007).

Due to the lack of 3D AhR structure, direct docking studies

have not been done.

Only few purely ligand-based PXR studies have been

conducted (Ekins and Erickson 2002; Jacobs 2004), in

which PXR ligands seem to have one HBA and four

hydrophobic regions (HPR) and models can classify

ligands as either potent or weak PXR agonists. A machine-

learning system based on structures of 128 PXR activators

and 77 non-activators could correctly predict approxi-

mately four out of five PXR agonists (Ung et al. 2007).

Combined approaches utilizing key residues within the five

3D PXR LBD structures (Poso and Honkakoski 2006; Xue

et al. 2007) suggest the presence of one or two HBAs and

three to five HPRs in PXR activators (Schuster and Langer

2005; Ekins et al. 2007; Lemaire et al. 2007). These ligand

characteristics roughly correspond with the key features of

the PXR LBD with Gln285 and His407 acting as hydrogen

bond donors and several residues contributing to hydro-

phobic interactions.

There is only one pharmacophore model and one QSAR

model on inhibition for the mouse CAR (Ekins et al. 2002;

Jyrkkarinne et al. 2003). The studies published on human

CAR deal with detailed homology modeling and molecular

dynamics simulations (Jyrkkarinne et al. 2005; Windshugel

et al. 2007). Hydrophobic features of the ligand and

interactions with the key LBD residues including Phe161

appear to be critical for CAR activation. On-going studies

in our laboratory have identified a novel 3D-QSAR model

and shown that virtual screening can be used to identify

Table 12 Comparison of methods to assess receptor-mediated induction

Method Advantages Disadvantages

In silico models Relatively good prediction for AhR ligands

within chemical classes

Virtual screening for thousands of

compounds possible

No X-ray structure of AhR available

Binding versus activation not yet clear for

PXR and CAR

Cell-free assays High capacity

Rather inexpensive assays

Use of mechanism-based assays to enhance

specificity

False positives for several binding assays

Reporter assays Receptor-mediated activation is a relevant

endpoint

Medium-to-high capacity

Species differences can be studied easily

No information of extent of target gene

activation

Other mechanisms not accounted for

Continuous cell lines Induction of CYP1A1 readily detected

CYP3A4 only in some cell lines

CAR not present in most cell lines

Many CYPs and other proteins not regulated

properly

Primary hepatocytes Target gene activation

Direct measurement of metabolism possible

Best model of in vivo situation

Variability in response

Poor availability and quality

Loss of functions over time

Liver slices Target gene activation

Direct measurement of metabolism

Instrumentation cost, time

Less validated data

Permeability and heterogeneity issues

Humanized animal models Responses humanized in vivo -like

information

Availability

Modulation by other murine factors

In vivo studies Relevant human in vivo information obtained Human subjects needed cost, time

Focus only on CYP3A4

Results depend on the probe drug used

Arch Toxicol (2008) 82:667–715 687

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novel CAR agonists (Jyrkkarinne et al., submitted; Kubl-

beck et al., submitted).

Cell-free assays

These in vitro assays fall into two different categories. The

first category includes assays where the suspected inducer

competes with a high-affinity radiolabeled ligand (such as

[3H]TCDD for AhR, [3H]clotrimazole for CAR, and

[3H]SR12183 for PXR) for receptor binding in an extract or

a purified receptor preparation, and the amount of bound

label is quantified by standard separation techniques

(Roberts et al. 1990) or by scintillation proximity assays

which have a higher throughput (Moore et al. 2000; Jones

et al. 2000). However, it seems that ligand binding to PXR

is not a very good measure of PXR activation or CYP3A4

induction (Zhu et al. 2004), and due to the high basal

activity of CAR, inverse agonists cannot be distinguished

from agonists with the radiolabel-binding assay (Poso and

Honkakoski 2006).

The assays in the second category utilize a part of the

signaling pathway to detect the activated, agonist-bound

receptor. For example, ligand-elicited formation of AhR/

ARNT complexes on dioxin-responsive DNA elements has

been detected initially by gel electrophoresis (Seidel et al.

2000) and later by more rapid PCR, fluorescence or ELISA

techniques (Sun et al. 2004; Fukuda et al. 2004; You et al.

2006). However, the DNA-binding assay is reported to give

more false positive results than the cell-based AhR reporter

assay (Seidel et al. 2000), and the gel-based assay for

ligand-dependent DNA/receptor complexes for CAR and

PXR has a narrow linear range (Makinen et al. 2002). A

better choice is to measure ligand-dependent association of

CAR and PXR with NR-interacting peptides from a co-

activator such SRC-1 by gel electrophoresis (Frank et al.

2004) or more easily with fluorescent resonance energy

transfer techniques (Moore et al. 2000; Maglich et al.

2003). In the latter case, other detection systems such as

fluorescently labeled microbeads or chemiluminiscence

could be adapted to increase assay sensitivity or throughput

(Rouleau et al. 2003; Iannone et al. 2001).

Cell-based reporter assays

The chemically activated luciferase expression (CALUX)

assay has been used to detect AhR-activating chemicals

(Murk et al. 1996; Whyte et al. 2004). The CALUX is a

very sensitive method, surpassing the sensitivity of the

CYP1A-mediated EROD assay. The CALUX system is

based on the stable transfection of a luciferase reporter,

driven by TCDD-responsive gene promoters or DNA ele-

ments, into hepatoma cells that express a functional AhR

such as rat H4IIE (Long et al. 2003), mouse H1L1.1c2

(Seidel et al. 2000) or human HepG2 cells (Yueh et al.

2005) Therefore, cell line- and species-dependent factors

can affect the results as noted by Long et al. (2003). To

streamline the detection system, green fluorescent protein

(GFP) has been utilized as a simple and inexpensive

reporter for AhR (Nagy et al. 2002).

Because PXR and CAR are not expressed at significant

levels in most continuous cell lines, most activation assays

have relied on transient transfection of CAR/PXR cDNA

and an appropriate responsive reporter plasmid into the

cells, followed by chemical treatment and reporter assays.

In many cases, full-length CAR and PXR receptors control

the expression of natural CYP3A4 or CYP2B6 gene pro-

moters or PXR/CAR-responsive derivatives thereof (Ogg

et al. 1999; Goodwin et al. 1999; Sueyoshi et al. 1999; El-

Sankary et al. 2001; Moore et al. 2002; Makinen et al.

2002). To avoid competition by endogenous NRs for the

response elements and to utilize one common reporter

construct, the mammalian 1-hybrid system has been

employed. Here, the yeast GAL4 DBD/NR LBD construct

drives the ligand-dependent expression of a GAL4-

responsive luciferase reporter (Makinen et al. 2002; Vig-

nati et al. 2004; Jyrkkarinne et al. 2005). Such systems

have been useful in delineating, e.g. species differences in

CAR and PXR ligand responses (Moore et al. 2002;

Makinen et al. 2002; Vignati et al. 2004). PXR- and CAR-

responsive double-stable cell lines have been developed in

order to streamline the procedure and to reduce variability

from the transient transfection step (Trubetskoy et al. 2005;

Lemaire et al. 2007).

However, the use for different promoter and reporter

constructs, different cell lines with variable coactivator and

corepressor contents, varying culture conditions and the

lack of validation gives rise to widely different responses

even with the established PXR ligands (Stanley et al.

2006). For examples, the activation by 10 lM rifampicin

has been reported to vary from fourfold to more than 50-

fold, depending on the assay set-up (e.g. Goodwin et al.

1999; El-Sankary et al. 2001; van Giersbergen et al.

2002a), and contradictory results for CAR modulators such

as clotrimazole have been reported (Moore et al. 2000;

Jyrkkarinne et al. 2005; Faucette et al. 2007). Nevertheless,

due to the high throughput of the assay, transient trans-

fection techniques have already been used to assess human

PXR activation for hundreds of chemicals (Luo et al. 2002;

Zhu et al. 2004; Persson et al. 2006; Sinz et al. 2006). This

method seems acceptable for rapid screening of potential

CYP inducers although their actual influence on the met-

abolic CYP activity cannot be predicted in this way (Luo

et al. 2004). The high constitutive activity of CAR gives

problems for detection of its ligands. For example, Moore

et al. (2002) could not detect any CAR agonists in their

assay in CV1 cells, and agonist responses have often been

688 Arch Toxicol (2008) 82:667–715

123

modest (Kobayashi et al. 2005; Stanley et al. 2006). Such

problems have been circumvented by addition of CAR

inverse agonists in the assay medium (Makinen et al. 2003;

Jyrkkarinne et al., submitted) or by using a CAR splice

variant with attenuated basal activity (Faucette et al. 2007).

Both modifications introduce uncertainties about actual

EC50 values or ligand specificities, respectively. In our

experience, careful selection of the host cell line is essen-

tial for a robust CAR activation assay (Jyrkkarinne et al.

2005; Kublbeck et al., submitted).

Continuous, immortalized and stem cell lines

Many human cell lines express AhR and its partner ARNT

and therefore, increases in CYP1A1-mediated activities

can be detected with the traditional EROD assay, with

novel P450-Glo substrates or by measurement of CYP1A1

mRNA with quantitative RT-PCR methods (e.g. Behnisch

et al. 2001; Westerink and Schoonen, 2007). Even then,

different sources of the same cell line vary in the enzyme

profile, requiring careful characterization (Hewitt and He-

witt 2004). It is notable, however, that in these cells

CYP1A1 is induced while the preferred form in primary

hepatocytes or in liver is CYP1A2 (Zhang et al. 2006). In

contrast, the basal levels of other major CYP mRNAs

(1A2, 2B6, 2Cs, 2D6, 3A4), CYP-mediated activities and

their induction responses are generally very low in HepG2

or other hepatoma cells (Rodrıguez-Antona et al. 2002;

Donato et al. 2008) although the presence of PXR and the

response of CYP3A4 mRNA to rifampicin has often been

demonstrated (e.g. Sumida et al. 2000; Gomez-Lechon

et al. 2001; Westerink and Schoonen 2007; Martin et al.

2008).

More substantial induction of CYP3A4 mRNA and/or

activities and the presence of functional PXR has been

reported in other cell lines of hepatic origin such as FLC-5

(Iwahori et al. 2003), Huh7 (Wang et al. 2006) and HC-04

(Lim et al. 2007). The same is true for some intestinal cell

lines such as LS180 and LS174 but not for Caco-2 cells

commonly used as a permeability model (Pfrunder et al.

2003; Hartley et al. 2006) in which CYP3A4 is up-regu-

lated by the vitamin-D receptor (Schmiedlin-Ren et al.

1997). As far as we know, functional CAR is absent or at

very low levels in all these cell lines. However, it seems

possible to up regulate CAR, PXR and/or CYP expression

to some extent by optimizing culture conditions (Korjamo

et al. 2005; Osabe et al. 2008; Martin et al. 2008), by

encapsulating cells in alginate (Elkayam et al. 2006) or by

selective culture techniques (Rencurel et al. 2005). Most

hepatomas that have been immortalized by, e.g. transfec-

tion of cell cycle inhibitors or telomerase or by other means

appear to express some CYP enzymes. However, their

utility for metabolism or induction studies is limited

(Vermeir et al. 2005). One exception is the SV40-immor-

talized Fa2N-4 cell line (Hariparsad et al. 2008) which

seems to reproduce PXR-dependent induction rather well.

However, Fa2N-4 cells were unresponsive to CAR agonists

indicating a similar lack of CAR expression as in other

continuous cell lines.

A novel cell line HepaRG, derived spontaneously from a

human hepatocellular carcinoma, has recently been intro-

duced (Gripon et al. 2002). At high seeding density and

after differentiation with 2% DMSO, HepaRG cells express

the major CYPs and their regulators including CAR at or

near the levels found in freshly isolated hepatocytes (An-

inat et al. 2006). The extent of CYP mRNA induction in

HepaRG varies according to the culture conditions, but

often reaching values obtained with human hepatocytes

(Aninat et al. 2006; Kanebratt and Andersson 2008). The

long-term stability of HepaRG cultures as compared to

primary hepatocytes makes these cells an attractive alter-

native for prolonged in vitro toxicity studies (Josse et al.

2008).

Many human stem cell lines display hepatocyte markers

upon differentiation in culture and they have been antici-

pated to provide better in vitro cell models. However, in

most cases, these cell lines have very low expression of

CYP mRNAs, proteins or activities (Cai et al. 2007; Ek

et al. 2007; Agarwal et al. 2008, Campard et al. 2008) with

substantial expression of only CYP1A2 and CYP3A4/7 (Ek

et al. 2007). Further work in the development, culture and

differentiation of stem cells is thus warranted.

Fresh, cryopreserved and fetal primary hepatocytes

The golden standard and requirement by the authorities for

induction studies are cultured primary human hepatocytes,

which express all the relevant metabolic enzymes, trans-

porters and their regulators. Their properties and

difficulties in their procurement, variable quality, differ-

ences in genetics and prior exposure to inducers of donors

and problems related to the time-dependent decreases in

enzyme and transporter activity have been excellently

reviewed (Lecluyse 2001; Gomez-Lechon et al. 2003;

Parkinson et al. 2004; Hewitt et al. 2007a). The current

status of how induction studies are and should be con-

ducted has also been reviewed (Hewitt et al. 2007b, c).

Briefly, hepatocytes from several donors are preincubated

for 24–48 h in a (sandwich-type) monolayer in the presence

of low concentrations of dexamethasone to allow stabil-

ization of CYP expression. Cells are then exposed to

increasing concentrations of inducing agents and estab-

lished inducers for 3–4 days before measurement of CYP

marker activities. It should be noted that the induction of

CYP mRNA precedes and often exceeds that of enzyme

activity, and therefore, mRNA levels are often quantified

Arch Toxicol (2008) 82:667–715 689

123

after 24 h of treatment. The assessment of induction at both

mRNA and CYP activity levels will help identify inducing

agents (e.g. ritonavir and troleandomycin) that also inhibit

CYP activities, and the simultaneous measurement of

cytotoxicity only adds to the versatility of the hepatocyte

culture system (Kostrubsky et al. 1999; Luo et al. 2002;

Madan et al. 2003). Induction of phase II transferases and

transporters can also be seen (Soars et al. 2004; Sahi et al.

2003).

Cryopreserved hepatocytes have been plagued by the

low and unpredictable extent of cell attachment after

seeding and lower CYP activities than in fresh hepatocytes,

rendering them questionable for induction studies (Li et al.

1999; Hengstler et al. 2000). Technical improvements have

led to the wider acceptance of cryopreserved hepatocytes

for CYP induction studies despite the fact that basal levels

of some CYP activities are quite low (Garcia et al. 2003;

Roymans et al. 2005; Hewitt et al. 2007b).

Fetal hepatocytes are able to proliferate in culture, but

this advantage is offset by the fact that the profile and

regulation of CYPs and other metabolizing enzymes do not

match the adult situation due to, e.g. low expression of

several transferases, high levels of CYP3A7 and marginal

PXR-dependent induction (McCarver and Hines 2002;

Matsunaga et al. 2004; Maruyama et al. 2007).

Liver slices

Because all cellular systems described above lack proper

3D contacts between hepatic cells, precision-cut liver slices

have been used to investigate drug metabolism and clear-

ance in different species (Lerche-Langrand and Toutain

2000). Despite the loss of CYP activities in prolonged

culture, recent studies have shown that induction of the

major CYP mRNAs can be detected in human liver slices

(Martin et al. 2003; Persson et al. 2006). These data indi-

cate that both AhR-, PXR- and CAR-dependent induction

can be mimicked in slices although the extent of induction

is often lower than in primary hepatocytes (Martin et al.

2003; Edwards et al. 2003). This is most likely due to poor

permeability of the inducing compounds within the slice

fragment. Variability in responses can also complicate the

use of liver slices.

Animal models for human CYP induction

Investigations in an in vivo system would provide better

estimation of clearance, pharmacokinetic/pharmacody-

namic and toxicological consequences of enzyme

induction. Due to species differences in the ligand/sub-

strate/product specificities of the receptors and CYP

enzymes, in vivo studies in laboratory animals are not

predictive for human CYP induction. A classical example

is the selectivity difference between humans and rodents

for induction of CYP3A enzymes by rifampicin and

pregnenolone 16a-carbonitrile, respectively, which is due

to variation at key ligand-binding pocket residues in the

corresponding PXR forms (Stanley et al. 2006). Geneti-

cally modified mice carrying the human AhR (Moriguchi

et al. 2003), PXR (Xie et al. 2000; Ma et al. 2007) or CAR

(Huang et al. 2003) in lieu of the murine receptor have

been created. These humanized mice are useful for studies

of in vivo-like responses to human inducers. Their wider

use may be compromised by the presence of other mouse

proteins that are relevant for compound permeability,

metabolism and potential species differences in the

receptor’s target gene repertoire. To overcome such prob-

lems and to provide a renewable source of human

hepatocytes, immunodeficient mice in which transplanted

human hepatocytes can colonize the liver have been

developed (Tateno et al. 2004). In these chimeric mice, at

least the profile and inducibility of CYP3A4 and CYP1A2

seems to be similar to those in human hepatocytes (Ni-

shimura et al. 2005; Emoto et al. 2008; Katoh et al. 2008).

A recent study reported a more advanced mouse strain

(Azuma et al. 2007) that harbors transplanted human

hepatocytes in which a broad array of CYPs, other enzymes

and transporters and CAR and PXR are expressed at or

near normal levels. More studies on the applicability of

these mice for toxicological research are imminent.

In vivo studies

The focus of human in vivo induction studies has been on

the CYP3A4 enzyme and its reaction products from either

endogenous or exogenous substances. The increases in

urinary excretion of 6b-hydroxycortisol, typically less than

twofold by PB but up to sevenfold by rifampicin, have been

widely used to reflect changes in the CYP3A4 activity

(Galteau and Shamsa 2003). Hydroxylated metabolites of

bile acids, produced by CYP3A4, can be quantified in the

urine of test subjects (Furster and Wikvall 1999; Bodin

et al. 2005), and plasma levels of 4b-hydroxycholesterol

have been reported to reflect CYP3A4 activity and to be

significantly elevated by several CAR/PXR activators

(Bodin et al. 2001; Diczfalusy et al. 2008). For other CYPs,

similar endogenous biomarkers have not yet been identi-

fied. Of the earliest exogenous test substances, the

erythromycin breath test measures [14C]CO2 in the exhaled

air formed by CYP3A4-mediated N-demethylation of

intravenously administered radiolabeled erythromycin

(Watkins et al. 1989; McCune et al. 2000). The safety

issues, together with relative insensitivity and tediousness

of the assay, limit its use mainly to clinical studies. The

changes in pharmacokinetic parameters or metabolic ratios

of specific probe substrates such as midazolam (CYP3A4),

690 Arch Toxicol (2008) 82:667–715

123

caffeine (CYP1A2) and others (see ‘‘Induction of CYP

enzymes in humans in vivo’’) have been detected after

pretreatment with inducers, although the extent of induc-

tion is highly dependent on the selectivity of metabolism

and disposition of the test substrate (Gurley et al. 2002;

Niemi et al. 2003a, b; Faber et al. 2005; Hukkanen et al.

2005; Loboz et al., 2006). Identifying better CYP form-

specific probe substances and the use of cocktail protocols

could provide a wider test battery for human in vivo

induction studies.

Induction of CYP enzymes in humans in vivo

The two preceding sections show that there is consider-

able understanding of basic mechanisms of induction as

well as a variety of tools and experimental setups to study

induction in silico, in vitro and in vivo. It is equally

evident from the above sections that despite the consid-

erably increased knowledge about induction in human,

humanized, or human-derived or mimicking systems,

there is a notable gap between experimental studies and

clinical observations. Consequently, in the following

sections and Table 13 we will present a systematic survey

of the inducers of the specific CYP enzymes in vivo in

humans. Studies with experimental animals and human

cell lines including human primary hepatocytes, which

have demonstrated many other in vitro inducers, are not

included here. In addition, established in vivo inducers

(such as clotrimazole, troglitazone and moricizine), that

are no longer in systemic clinical use and are without

current toxicological interest, are not reviewed here due to

space constraints.

CYP1 family

Although the induction of both CYP1A1 and CYP1B1

enzymes by various inducers are classic examples of CYP

induction, human in vivo induction of CYP1A1 and

CYP1B1 has been difficult to study due to their very low

hepatic levels when compared to CYP1A2 (Chang et al.

2003). Since these three enzymes have overlapping sub-

strate specificities and their induction share regulatory

features with each other as discussed previously, the

induction seen in phenotyping studies usually reflects the

induction of CYP1A2 in liver. Only when gene and

enzyme-specific methods are applied at tissue level can it

be construed that CYP1A1 and CYP1B1 are induced. With

such methods, smoking has been shown to induce CYP1A1

and CYP1B1 in tissues such as lung, liver (only mRNA is

detected) and placenta (Chang et al. 2003; Hakkola et al.

1998; Hukkanen et al. 2002; Huuskonen et al. 2008). Also,

topical coal tar and ultraviolet-B radiation treatments

induce CYP1A1 and CYP1B1 in skin (Katiyar et al. 2000;

Smith et al. 2006). Furthermore, CYP1B1 is induced in

peripheral leukocytes of waste incinerator workers, coke

oven workers and smokers (Hanaoka et al. 2002; Hu et al.

2006; Lampe et al. 2004; van Leeuwen et al. 2007). The

induction of CYP1A1 mRNA and CYP1A protein by

omeprazole occurs in duodenum (Buchthal et al. 1995;

McDonnell et al. 1992). Duodenal CYP1A1 mRNA and

protein are also induced by charbroiled meat containing

diet (Fontana et al. 1999).

The induction of CYP1A2 in vivo has been widely

studied. AhR ligands such as indole-3-carbinole (in cru-

ciferous vegetables), PAHs (in tobacco smoke, charbroiled

meat and coffee) and TCDD induce CYP1A2-associated

activities in humans (Djordjevic et al. 2008; Faber et al.

2005; Landi et al. 1999; Reed et al. 2005). Topically

applied coal tar induced CYP1A2 mRNA in skin (Smith

et al. 2006). The activity of CYP1A2 enzyme as assessed

by theophylline, clozapine, tizanidine, ropivacaine or caf-

feine pharmacokinetics is induced by pharmaceuticals such

as omeprazole (Ma and Lu 2007), rifampicin (Backman

et al. 2006a, b), phenytoin (Miller et al. 1984; Wietholtz

et al. 1989), carbamazepine (Parker et al. 1998), pheno-

barbital (Landay et al. 1978), pentobarbital (Dahlqvist et al.

1989), secobarbital (Paladino et al. 1983), sulfinpyrazole

(Birkett et al. 1983) and ritonavir (Hsu et al. 1998; Yeh

et al. 2006).

CYP2A6

CYP2A6 has recently been shown to be under the regula-

tion of ERa (Higashi et al. 2007a, b). This is reflected in the

increased CYP2A6-mediated nicotine and cotinine metab-

olism in oral contraceptive users (Benowitz et al. 2006;

Berlin et al. 2007). Subjects taking combination oral con-

traceptives and estrogen-only contraceptives had

accelerated nicotine metabolism, whereas progesterone-

only contraceptives did not affect nicotine metabolism

(Benowitz et al. 2006). The induction of CYP2A6 by

estrogens is supported by the findings that female gender

and pregnancy induce nicotine metabolism (Benowitz et al.

2006; Berlin et al. 2007; Dempsey et al. 2002). Also,

CYP2A6 protein is induced in the glandular cells of the

endometrium in the proliferative phase when compared to

the secretory phase (Higashi et al. 2007a, b). There is some

evidence for the induction of CYP2A6 in vivo by pheno-

barbital and other anticonvulsant drugs. Coumarin

phenotyping shows increased metabolism in epileptic

patients treated with carbamazepine, phenobarbital, and/or

phenytoin (Sotaniemi et al. 1995). Two-day treatment with

phenobarbital prior to a liver biopsy resulted in induction

of metabolism of nicotine to cotinine in hepatocytes

(Kyerematen et al. 1990). Liver microsomes from

Arch Toxicol (2008) 82:667–715 691

123

Table 13 Induction of CYP enzymes in humans in vivo by xenobiotics

Enzyme Inducer Receptor involved References

CYP1A1 PAHsa AhR Chang et al. (2003)

Fontana et al. (1999)

Hakkola et al. (1998)

Hukkanen et al. (2002)

McDonnell et al. (1992)

Smith et al. (2006)

Omeprazole AhR

CYP1A2 PAHsb AhR Backman et al. (2006a, b)

Birkett et al. (1983)

Dahlqvist et al. (1989)

Djordjevic et al. (2008)

Faber et al. (2005)

Hsu et al. (1998)

Landay et al. (1978)

Landi et al. (1999)

Ma and Lu (2007)

Miller et al. (1984)

Paladino et al. (1983)

Parker et al. (1998)

Reed et al. (2005)

Smith et al. (2006)

Wietholtz et al. (1989)

Yeh et al. (2006)

Indole-3-carbinolc AhR

TCDD AhR

Omeprazole AhR

Rifampicin PXR

Ritonavir PXR

Sulfinpyrazone PXR

Carbamazepine CAR

Barbiturates (phenobarbital, etc.) CAR/PXR

Phenytoin CAR/PXR

CYP1B1 PAHsd AhR Chang et al. (2003)

Hakkola et al. (1998)

Hanaoka et al. (2002)

Hu et al. (2006)

Hukkanen et al. (2002)

Huuskonen et al. (2008)

Smith et al. (2006)

van Leeuwen et al. (2007)

CYP2A6 Ethinyl estradiol ERa Asimus et al. (2008)

Benowitz et al. (2006)

Berlin et al. (2007)

Cashman et al. (1992)

Kyerematen et al. (1990)

Sotaniemi et al. (1995)

Yamano et al. (1990)

Phenobarbital CAR/PXR

Artemisinin CAR/PXR

CYP2B6 Rifampicin PXR Sustiva (2007) (efavirenz)

Elsherbiny et al. (2008)

Jao et al. (1972)

Ketter et al. (1995)

Kharasch et al. (2008)

Loboz et al. (2006)

Lopez-Cortes et al. (2002)

Saussele et al. (2007)

Simonsson et al. (2003)

Slattery et al. (1996)

Ritonavir PXR

Carbamazepine CAR

Phenobarbital CAR/PXR

Phenytoin CAR/PXR

Artemisinin antimalarialse PXR/CAR

Metamizole Not known

692 Arch Toxicol (2008) 82:667–715

123

Table 13 continued


CYP2C8 Rifampicin PXR Bidstrup et al. (2004)

Jaakkola et al. (2006a, b)

Niemi et al. (2000, 2004)

Park et al. (2004)

CYP2C9 Rifampicin PXR Depre et al. (2005)

Dickinson et al. (1985)

Goldberg et al. (1996)

Herman et al. (2006)

Jiang et al. (2006, 2004)

Kay et al. (1985)

Lim et al. (2004)

Miners and Birkett (1998)

Niemi et al. (2001)

O’Reilly (1974)

O’Reilly et al. (1980)

Orme and Breckenridge (1976)

Shadle et al. (2004)

van Giersbergen et al. (2002a, b)

Weber et al. (1999)

Williamson et al. (1998)

Yeh et al. (2006)

Yoshida et al. (1993)

Zilly et al. (1975)

Aprepitant PXR

Bosentan PXR

Ritonavir (with lopinavir) PXR

St. John’s wort PXR

Carbamazepine CAR


Phenytoin? CAR/PXR

CYP2C19 Rifampicin PXR Asimus et al. (2007)

Desta et al. (2002)

Elsherbiny et al. (2008)

Heinemeyer et al. (1987)

Mihara et al. (1999)

Richter et al. (1980)

Svensson et al. (1998)

Wang et al. (2004a, b)

Yeh et al. (2006)

Ritonavir (with lopinavir) PXR


Artemisinin antimalarialsf PXR/CAR


CYP2E1 Ethanol Stabilization Benowitz et al. (2003)

Chien et al. (1997)

Girre et al. (1994)

Gurley et al. (2002, 2005)

Lucas et al. (1995)

Oneta et al. (2002)

O’Shea et al. (1997)

Perrot et al. (1989)

Takahashi et al. (1993)

Tsutsumi et al. (1989)

Zand et al. (1993)

Isoniazid Stabilization

Smoking Stabilization?

St. John’s wort Not known

CYP2S1 PAHsg AhR Smith et al. (2003a, b)

Thum et al. (2006)Topical all-trans retinoid acid RXR?

Arch Toxicol (2008) 82:667–715 693

123

phenobarbital-treated patients have higher amounts of

CYP2A6 protein than microsomes from untreated patients

(Cashman et al. 1992; Yamano et al. 1990). A recent study

showed that artemisinin (antimalarial) administration

affected significantly the pharmacokinetics of both nicotine

and coumarin suggesting induction of CYP2A6 (Asimus

et al. 2008).

CYP2B6

Although induction of CYP2B enzymes by phenobarbital

is the archetypal example of enzyme induction in exper-

imental animals, the induction of human CYP2B6 in vivo

is less well characterized. However, the induction of

CYP2B6 has been shown to occur with several drugs as

evidenced by the changes in the pharmacokinetics of

bupropion by rifampicin, ritonavir and carbamazepine

(Ketter et al. 1995; Kharasch et al. 2008; Loboz et al.

2006), efavirenz by rifampicin and carbamazepine (Sus-

tiva (efavirenz); Lopez-Cortes et al. 2002), S-mephenytoin

(N-demethylation) by several artemisinin antimalarials

(Elsherbiny et al. 2008; Simonsson et al. 2003) and

cyclophosphamide by phenytoin and phenobarbital (Jao

et al. 1972; Slattery et al. 1996). Carbamazepine use has

been associated with high hepatic CYP2B6 protein con-

tent and enzymatic activity in two carbamazepine-exposed

liver samples when compared to 85 non-exposed liver

samples (Desta et al. 2007). Additionally, metamizole was

Table 13 continued


CYP3A4 Rifampicin PXR Anglicheau et al. (2003)

Asimus et al. (2007)

Barditch-Crovo et al. (1999)

Dailly et al. (2006)

Darwish et al. (2008)

Dingemanse and van Giersbergen (2004)

Fellay et al. (2005)

Justesen et al. (2003)

Kashuba et al. (2005)

Kuypers et al. (2004)

Luo et al. (2004)

McCune et al. (2000)

Mildvan et al. (2002)

Mouly et al. (2002)

Perucca et al. (1988)

Robertson et al. (2002)

Shadle et al. (2004)

Solas et al. (2004)

Staiger et al. (1983)

van Duijnhoven et al. (2003)

Watkins et al. (1989)

Wing et al. (1985)

Rifabutin PXR

Amprenavir PXR

Aprepitant PXR

Bosentan PXR

Ritonavir PXR


Sulfinpyrazone PXR

Topiramate PXR

Carbamazepine CAR

Efavirenz CAR

Nevirapine CAR


Phenytoin CAR/PXR

Dexamethasone PXR/GR

Methylprednisolone PXR/GR

Prednisolone PXR/GR

Artemisinin antimalarialsh PXR/CAR

Metamizole Not known

Modafinil Not known

CYP3A5 Rifampicin PXR Burk et al. (2004)

Smith et al. (2006)Topical clobetasol 17-propionate GR

PAH polycyclic aromatic hydrocarbona Smoking, charbroiled meat, topical coal tarb Smoking, topical coal tar, charbroiled meat, coffeec Cruciferous vegetablesd Smoking, topical coal tar, work in coke ovens and waste incineratorse Artemisinin, artemether, arteether, dihydroartemisinin, artesunatef Artemisinin, artemether, arteetherg Smoking?, topical coal tarh Artemisinin, artemether, dihydroartemisinin

694 Arch Toxicol (2008) 82:667–715

123

recently shown to induce CYP2B6 protein and activity in

human liver in vivo (Saussele et al. 2007).

CYP2C8

Studies with pioglitazone, rosiglitazone and repaglinide as

substrates show induction in CYP2C8 activity by rifam-

picin (Bidstrup et al. 2004; Jaakkola et al. 2006a, b; Niemi

et al. 2000, 2004; Park et al. 2004). Rifampicin also

induces CYP2C8 protein in jejunal enterocytes in vivo

(Glaeser et al. 2005). Paclitaxel has been used as a

CYP2C8 probe (Rodriguez-Antona et al. 2007) and pac-

litaxel metabolism is induced in patients treated with

phenytoin, carbamazepine or phenobarbital (Chang et al.

1998; Fetell et al. 1997). However, it seems that these

antiepileptics preferentially induce the minor CYP3A4-

mediated pathway (Chang et al. 1998; Cresteil et al. 1994).

CYP2C9

The induction of CYP2C9 activity has been shown with

rifampicin (Kay et al. 1985; Niemi et al. 2001; O’Reilly

1974; Williamson et al. 1998; Zilly et al. 1975), pheno-

barbital (Goldberg et al. 1996; Orme and Breckenridge

1976; Udall 1975), pentobarbital (Yoshida et al. 1993),

secobarbital (O’Reilly et al. 1980; Udall 1975), carbam-

azepine (Herman et al. 2006), St. John’s wort (Jiang et al.

2006; Jiang et al. 2004), ritonavir (in combination with

lopinavir)(Lim et al. 2004; Yeh et al. 2006), aprepitant

(Depre et al. 2005; Shadle et al. 2004) and bosentan (van

Giersbergen et al. 2002b; Weber et al. 1999) when studied

with warfarin, losartan, phenytoin, tolbutamide or gliben-

clamide pharmacokinetics (reviewed in (Miners and

Birkett 1998). Rifampicin also induces CYP2C9 protein in

jejunal enterocytes (Glaeser et al. 2005). There is some

evidence concerning the inducing effect of phenytoin on

CYP2C9 but good quality studies on the subject are lacking

(Dickinson et al. 1985; Levine and Sheppard 1984).

CYP2C19

CYP2C19 activity measured using S-mephenytoin, ome-

prazole or hexobarbital as probes is induced by rifampicin

(reviewed in Desta et al. 2002), phenobarbital (Richter

et al. 1980), pentobarbital (Heinemeyer et al. 1987), St.

John’s wort (Wang et al. 2004a, b), ritonavir (in combi-

nation with lopinavir) (Yeh et al. 2006) and artemisinin

antimalarials (artemisinin, artemether, arteether) (Asimus

et al. 2007; Elsherbiny et al. 2008; Mihara et al. 1999;

Svensson et al. 1998). Phenobarbital treatment induces

CYP2C19 protein and activity in liver in vivo (Lecamwa-

sam et al. 1975; Perrot et al. 1989).

CYP2E1

As discussed above, both transcriptional and posttran-

scriptional mechanisms influence the induction of CYP2E1

with stabilization of mRNA and protein having major

significance in contrast to many other CYP forms

(reviewed in Lieber 1999). Only a few human in vivo

CYP2E1 inducers are known. The characteristic inducer is

ethanol as shown with increased CYP2E1 mRNA and

protein in liver biopsies and as increased chlorzoxazone

hydroxylation after ethanol administration and in alcohol-

ics (Girre et al. 1994; Lucas et al. 1995; Oneta et al. 2002;

Perrot et al. 1989; Takahashi et al. 1993; Tsutsumi et al.

1989). In addition, CYP2E1 mRNA and protein are

induced in peripheral blood lymphocytes in alcoholics and

correlate with chlorzoxazone clearance in vivo (Raucy

et al. 1999; Raucy et al. 1997). Also the full-term placentas

of heavily drinking mothers express increased levels of

CYP2E1 protein (Rasheed et al. 1997). CYP2E1-related

activities are induced by isoniazid and smoking (Benowitz

et al. 2003; Chien et al. 1997; Mazze et al. 1982; O’Shea

et al. 1997; Zand et al. 1993). The induction of CYP2E1

protein in the brain of the smoking alcoholics when com-

pared to nonalcoholic nonsmokers has been proposed

(Howard et al. 2003). A relatively long-term administration

(28 days) of St. John’s wort induces chlorzoxazone

hydroxylation (Gurley et al. 2002, 2005). Several patho-

logic conditions such as diabetes, nonalcoholic

steatohepatitis and obesity have been associated with the

increased levels of CYP2E1 (reviewed in Lieber 2004).

CYP2S1

The AhR-regulated CYP2S1 enzyme has been implicated

in the chemical carcinogenesis (Saarikoski et al. 2005).

CYP2S1 is induced by coal tar, ultraviolet radiation and

all-trans retinoid acid in skin (Smith et al. 2003b).

Smoking may induce CYP2S1 in bronchoalveolar macro-

phages but not in pulmonary bronchi or placenta

(Huuskonen et al. 2008; Thum et al. 2006).

CYP3A4

A multitude of compounds induce CYP3A4. Since the

literature on human CYP3A4 induction is vast and rapidly

expanding, we refer the reader to a recent review (Luo

et al. 2004) and aim to complement its list of inducers with

latest findings and to fill in certain omissions. As reviewed

comprehensively by Luo and coauthors, there is convincing

evidence for the induction of CYP3A4 activities in vivo by

carbamazepine, phenobarbital, phenytoin, rifampicin,

ritonavir, St. John’s wort and topiramate, as well as

Arch Toxicol (2008) 82:667–715 695

123

troglitazone (withdrawn due to hepatotoxicity) (Luo et al.

2004).

In addition to rifampicin, another rifamycin antibiotic

rifabutin induces CYP3A4 activities (Barditch-Crovo

et al. 1999; Perucca et al. 1988). Other PXR ligands with

proven in vivo CYP3A4 inducing properties include

bosentan (Dingemanse and van Giersbergen 2004), sul-

finpyrazone (Staiger et al. 1983; Wing et al. 1985) and

artemisinin antimalarials (Asimus et al. 2007). Aprepitant,

which is predicted to be a PXR ligand based on in silico

methods (Ekins et al. 2006), induces CYP3A4 slightly as

studied with midazolam as a probe (Shadle et al. 2004).

Modafinil and its R-enantiomer armodafinil induce

CYP3A4 based on their effects on triazolam, midazolam

and ethinyl estradiol pharmacokinetics (Darwish et al.

2008; Robertson et al. 2002). Besides ritonavir, antiret-

rovirals such as efavirenz (Fellay et al. 2005; Mouly et al.

2002), nevirapine (Dailly et al. 2006; Mildvan et al. 2002;

Solas et al. 2004) and amprenavir (Justesen et al. 2003;

Kashuba et al. 2005) induce CYP3A4-related activies.

Metamizole was recently shown to induce CYP3A4 pro-

tein and activity in human liver in vivo (Saussele et al.

2007). Several corticosteroids such as dexamethasone

(McCune et al. 2000; Watkins et al. 1989), methylpred-

nisolone (Kuypers et al. 2004), prednisolone (van

Duijnhoven et al. 2003) and prednisone (Anglicheau et al.

2003) induce CYP3A4 activities. However, smaller doses

of corticosteroids do not seem to induce CYP3A4 (Vil-

likka et al. 1998, 2001).

CYP3A5

The study of CYP3A5 induction in vivo has been ham-

pered by the overlapping substrate and inducer

specificities with CYP3A4, and lower hepatic expression

levels when compared to CYP3A4. Thus, the induction of

CYP3A-specific activities is usually construed as a sign of

CYP3A4 induction. In analogy to CYP1A1 and CYP1B1

in relation to CYP1A2, only when gene and enzyme-

specific methods are applied at tissue level can it be

ascertained if CYP3A5 is induced in vivo. There is only

limited evidence of the CYP3A5 induction in vivo. Rif-

ampicin administration induced duodenal CYP3A5

mRNA in three of eight subjects with some indication of

the effect of CYP3A5 genotype (Burk et al. 2004). Phe-

nobarbital did not induce hepatic CYP3A5 protein in

phenobarbital-treated children (Busi and Cresteil 2005). A

recent study on the induction of CYP enzymes in skin

biopsies showed a significant induction of CYP3A5

mRNA by topical administration of the glucocorticoid

clobetasol 17-propionate (Smith et al. 2006). To the best

of our knowledge, there is no evidence of the induction of

CYP3A7 by xenobiotics in vivo.

Clinical and toxicological consequences of enzyme

induction

As discussed above, the scope of compounds capable of

inducing CYP enzymes in humans is extensive. The clin-

ical and toxicological significance of CYP induction

depends on several factors. These include inducer-specific

aspects such as the potency of the inducer, the dose and the

concentration of the inducer needed for the induction to

occur, the duration of the exposure needed for the induc-

tion to happen, the metabolic properties of the inducer, the

length of the exposure to the inducer, the duration of the

induction once the inducer is withdrawn, the route of the

exposure (e.g. orally, topically or by inhalation), and the

anatomical location of the CYP enzymes induced (e.g.

intestine, skin or lung). Some inducers are also inhibitors of

the same CYP enzyme they induce further complicating the

situation. Especially many of the antiretrovirals with

CYP3A4 inducing properties are potent CYP3A4 inhibitors

as well (Antoniou and Tseng 2005). Significant induction

of CYP3A4 by a potent inducer such as rifampicin may not

have clinical consequences if used short term in the setting

where no comedication is metabolized by CYP3A4.

On the other hand, if the duration of rifampicin treat-

ment is prolonged, complications, such as drug-induced

osteomalacia via the CYP3A4-mediated catabolism of

vitamin-D (1,25-(OH)2-D3) (Zhou et al. 2006), may arise

even without co-medications. The properties of the come-

dications are important factors predicting the consequences

of induction; the risk of significant interactions is increased

if concurrently administered drugs have low therapeutic

indexes or high first-pass metabolism, or the induced CYP

is the major pathway of their metabolism (Park et al. 1996).

For example, the AUC of oral midazolam (a drug with high

first-pass metabolism and CYP3A4-mediated metabolism)

is reduced by 96% if given after rifampicin induction when

compared to AUC in noninduced state (Backman et al.

1996).

Another multitude of factors affecting the consequences

of the inducers are the host-specific aspects such as genetic

variations in the transporters of the inducer, in the enzymes

metabolizing the inducer and in the receptors mediating the

induction and in the CYP genes themselves as well as

diseases, nutritional status, gender and age of the host. All

these factors lead to marked interindividual variability in

the induction of CYP enzymes (Tang et al. 2005). In

general, the lower the baseline enzymatic activity, the

higher the induction achieved with inducers (McCune et al.

2000; Vesell and Page 1969) unless the low baseline

activity is caused by CYP null alleles or other genetic

factors.

The most obvious characteristic affecting the impor-

tance of a specific inducer is the magnitude of the

696 Arch Toxicol (2008) 82:667–715

123

induction; inducer may cause a detectable induction of a

certain CYP enzyme in the controlled setting of a phar-

macokinetic study but if the magnitude of the induction is

minor, it might not have any discernible ramifications in

clinical setting. Nevertheless, the interplay between the

patient’s genetic makeup, the dose of the inducer and the

comedications often complicates the issue. As an example,

omeprazole, an established inducer of CYP1A2, is usually

considered not to have any significant inducing effect at the

dose of 40 mg per day used clinically. However, the same

dose is effective in inducing CYP1A2 in patients who are

PMs of omeprazole (mediated by CYP2C19) and further-

more, a higher dose of 120 mg is sufficient to cause

induction also in extensive metabolizers (Ma and Lu 2007).

Although not yet studied, this type of scenario might also

transpire if a potent CYP2C19 inhibitor like fluconazole

was administered together with omeprazole. Another

example of the interplay between genetic makeup of the

host and the induction potential is the induction of CYP2E1

by isoniazid, which is only seen in patients with slow N-

acetylation status (a major pathway of isoniazid metabo-

lism) leading to higher isoniazid concentrations (O’Shea

et al. 1997).

Generally, for drugs that are active in their parent form,

induction may increase the drug’s elimination and decrease

its pharmacological effect. A well-established case is the

use of CYP3A4 inducers such as St. John’s wort together

with cyclosporine in organ transplant patients leading to

reduced cyclosporine concentrations and organ rejection

(Zhou et al. 2004). Other well-known examples are the

increased risk of pregnancy with oral contraceptives when

combined with enzyme inducing antiepileptics or rifam-

picin, and the problems encountered with warfarin

anticoagulation when inducers are started (reduction in

anticoagulant activity) or when inducers are withdrawn

(increased risk of hemorrhages) (Perucca 2006; Zhang

et al. 2007). For prodrugs, compounds that require meta-

bolic activation and whose effects are produced by the

active metabolites, enhanced pharmacodynamic effects

may be expected. Thus, there is some evidence for the

enhanced antiplatelet activity of prodrug clopidogrel with

CYP3A4 inducers such as rifampicin and St. John’s wort

(Lau and Gurbel 2006). In addition, induction may lead to

increased toxicity if the increased metabolism of the parent

compound is accompanied by the increase in exposure to a

toxic metabolite. For example, anecdotal evidence links the

CYP2E1 induction by ethanol to the increased risk of

carbon tetrachloride toxicity in a setting of accidental

occupational exposure to carbon tetrachloride of fire

extinguishing liquids (Manno et al. 1996).

As is well known, CYP1 family of enzymes is of

importance due to their toxicological significance in the

activation of several procarcinogens to more mutagenic

forms. This is reflected in the finding that the expression

levels of pulmonary CYP1A1 mRNA and protein correlate

positively with the aromatic/hydrophobic DNA adduct

levels in human lung tissue (Cheng et al. 2000; Mollerup

et al. 1999). However, the latest paradigm concerning the

CYP1A enzymes based on studies in CYP1 knockout

mouse lines emphasizes the beneficial effects of these

enzymes in protection against chemical carcinogenesis in

intact organisms (Ma and Lu 2007; Nebert and Dalton

2006). This kind of hypothesis may explain the finding that

phenobarbital treatment has been associated with decreased

amounts of the aromatic amine-hemoglobin adducts in

smoking epileptics (Wallin et al. 1995). The detailed pic-

ture of the significance of the carcinogen-metabolizing

CYP enzymes in general and their induction specifically is

yet to emerge.

Research needs and future trends

Inhibition and drug–drug interactions

Despite some deficiencies and uncertainties in in vitro

inhibition screens (see ‘‘Inhibition: in vitro–in vivo

extrapolation’’), they are used widely in drug industry (and

also increasingly in food and chemical industries) and there

seems to be a general consensus that their performance is

relatively good. Drug regulatory agencies have provided

guidances in the hope of harmonizing the approaches to

screen drugs by in vitro and in vivo investigations. Har-

monization is intimately linked with the standardization of

CYP probe substrates, inhibitors and inducers and with the

development of classification systems to improve the risk

communication to all concerned stakeholders (Bjornsson

et al. 2003).

Despite promising results of in vitro inhibition screens,

there are still some areas which need further development.

One is the relatively narrow focusing on CYP enzymes.

Admittedly they are of primary importance for drug and

chemical metabolism, but there are a huge number of other

drug-metabolizing enzymes, which may be of importance

for individual drugs and chemicals and which are not

covered by current screening systems. This area certainly

needs much further work in the future. A partial solution to

this problem may be a use of substrate loss assays in a cell

(hepatocyte)-based assays for inhibition screens, because

such a system should be able to take into consideration the

totality of enzymes metabolizing a particular drug or a

chemical.

In silico tools are also available for predicting substrates

and inhibitors of CYP enzymes as well as ligands of AhR,

PXR, and CAR, but their prediction power needs to

improve before they can be routinely used in drug

Arch Toxicol (2008) 82:667–715 697

123

metabolism or safety evaluation. Another important ques-

tion concerns extrapolation models; the precision of

prediction is dependent on what kind of model is selected.

The application of some physiologically based pharmaco-

kinetic models, such as Simcyp or PK-Sim (see Pelkonen

et al. 2008), seem capable of providing a fairly reliable

projection to the in vivo situation. Modeling and simula-

tion, however, always brings forth the necessity of

validation, which is a primary concern from the application

point of view of any in silico (or in vitro, for that matter)

approach.

Induction

Looking back at the phenomenal development of nuclear

receptor field, one cannot help thinking that their role

should be more or less completely defined in the near

future. On the other hand, increasing number of tran-

scription factors, coactivators, corepressors, their

interwoven roles and cross-talk between various regulatory

pathways are making the regulatory studies very complex

and we expect that new factors and concepts will emerge to

better understand the regulation of induction phenomenon.

Actually it seems that ‘induction’ as understood until now

is only a small part of regulatory devices to keep homeo-

stasis and adjust the organism to a changing chemical and

biological internal milieu and environment. However, it

may be difficult to predict these developments at least to

what extent they affect drug development, toxicological

risk assessment and clinical drug therapy.

In our opinion, three major fields will emerge within

development of experimental tools. First, receptor-based

reporter assays will become a widely used system to pre-

dict CYP induction although their validation with primary

hepatocytes will be needed. Second, further research on

renewable cell lines is warranted to provide an unlimited

source of hepatocyte-mimicking cells for metabolism,

induction and toxicity studies. Third, improved in silico

algorithms will be needed that can help distinguish true

receptor agonists from large sets of chemicals. No doubt,

these developments, if fulfilled, will help enormously

especially drug development, but also chemical risk

assessment.

The development of hepatocyte-mimicking cells will

also help the targeting of in vivo induction studies.

Currently there is a large gap between a profusion of

compounds suggested to be inducers on the basis of

current in vitro tools and reliable in vivo induction data

in humans. Another problem in characterizing induction

in vivo (and partially in vitro cellular systems) is the

outdated terminology (Smith et al. 2007). The response

should be characterized by both potency (e.g. EC50 or

ED50) and maximal response in a given system to be

able to compare various compounds and their effects at

the cellular or organism levels. This would help also

judge about whether the induction by a given compound

would cause clinically relevant consequences (Smith

2000).

Acknowledgments The authors wish to thank the following sources

for support to their research: The Academy of Finland, the Finnish

Funding Agency for Technological Research and Innovation (TE-

KES), The EU COST Programme (COST B15 and COST B25).

References

Abdel-Rahman SM, Marcucci K, Boge T et al (1999) Potent

inhibition of cytochrome P-450 2D6-mediated dextromethor-

phan O-demethylation by terbinafine. Drug Metab Dispos

27:770–775

Abelo A, Andersson TB, Antonsson M et al (2000) Stereoselective

metabolism of omeprazole by human cytochrome P450

enzymes. Drug Metab Dispos 28:966–972

Agarwal S, Holton KL, Lanza R (2008) Efficient differentiation of

functional hepatocytes from human embryonic stem cells. Stem

Cells. doi:10.1634/stemcells.2007-1102

Aithal GP, Day CP, Kesteven PJ et al (1999) Association of

polymorphisms in the cytochrome P450 CYP2C9 with warfarin

dose requirement and risk of bleeding complications. Lancet

27:717–719

Allqvist A, Miura J, Bertilsson L et al (2007) Inhibition of CYP3A4

and CYP3A5 catalyzed metabolism of alprazolam and quinine

by ketoconazole as racemate and four different enantiomers. Eur

J Clin Pharmacol 63:173–179

Amet Y, Berthou F, Baird S et al (1995) Validation of the (omega-1)-

hydroxylation of lauric acid as an in vitro substrate probe for

human liver CYP2E1. Biochem Pharmacol 50:1775–1782

Andersson T, Miners JO, Veronese ME et al (1993) Identification of

human liver cytochrome P450 isoforms mediating omeprazole

metabolism. Br J Clin Pharmacol 36:521–530

Andersson T, Miners JO, Veronese ME et al (1994) Diazepam

metabolism by human liver microsomes is mediated by both S-

mephenytoin hydroxylase and CYP3A isoforms. Br J Clin

Pharmacol 38:131–137

Anglicheau D, Flamant M, Schlageter MH et al (2003) Pharmaco-

kinetic interaction between corticosteroids and tacrolimus after

renal transplantation. Nephrol Dial Transplant 18:2409–2414

Aninat C, Piton A, Glaise D et al (2006) Expression of cytochromes

P450, conjugating enzymes and nuclear receptors in human

hepatoma HepaRG cells. Drug Metab Dispos 34:75–83

Antoniou T, Tseng AL (2005) Interactions between antiretrovirals

and antineoplastic drug therapy. Clin Pharmacokinet 44:111–145

Aoyama T, Yamano S, Guzelian PS et al (1990) Five of 12 forms of

vaccinia virus-expressed human hepatic cytochrome P450 met-

abolically activate aflatoxin B1. Proc Natl Acad Sci USA

87:4790–4793

Arpiainen S, Raffalli-Mathieu F, Lang MA et al (2005) Regulation of

the Cyp2a5 gene involves an aryl hydrocarbon receptor-depen-

dent pathway. Mol Pharmacol 67:1325–1333

Arulmozhiraja S, Morita M (2004) Structure-activity relationships for

the toxicity of polychlorinated dibenzofurans: approach through

density functional theory-based descriptors. Chem Res Toxicol

17:348–356

Asimus S, Elsherbiny D, Hai TN et al (2007) Artemisinin antimal-

arials moderately affect cytochrome P450 enzyme activity in

healthy subjects. Fundam Clin Pharmacol 21:307–316

698 Arch Toxicol (2008) 82:667–715

123

http://dx.doi.org/10.1634/stemcells.2007-1102

Asimus S, Hai TN, Van Huong N et al (2008) Artemisinin and

CYP2A6 activity in healthy subjects. Eur J Clin Pharmacol

64:283–292

Attar M, Dong D, Ling KH et al (2003) Cytochrome P450 2C8 and

flavin-containing monooxygenases are involved in the metabolism

of tazarotenic acid in humans. Drug Metab Dispos 31:476–481

Azuma H, Paulk N, Ranade A et al (2007) Robust expansion of

human hepatocytes in Fah-/-/Rag2-/-/Il2rg-/- mice. Nat Biotech-

nol 25:903–910

Baarnhielm C, Backman A, Hoffmann KJ et al (1986) Biotransfor-

mation of felodipine in liver microsomes from rat, dog, and man.

Drug Metab Dispos 14:613–618

Bachmann K, White D, Jauregui L et al (2003) An evaluation of the

dose-dependent inhibition of CYP1A2 by rofecoxib using

theophylline as a CYP1A2 probe. J Clin Pharmacol 43:1082–

1090

Back DJ, Houlgrave R, Tjia JF et al (1991) Effect of the progestogens,

gestodene, 3-keto desogestrel, levonorgestrel, norethisterone and

norgestimate on the oxidation of ethinyloestradiol and other

substrates by human liver microsomes. J Steroid Biochem Mol

Biol 38:219–225

Back DJ, Tjia JF, Karbwang J et al (1988) In vitro inhibition studies

of tolbutamide hydroxylase activity of human liver microsomes

by azoles, sulphonamides and quinolines. Br J Clin Pharmacol

26:23–29

Back DJ, Tjia JF (1991) Comparative effects of the antimycotic drugs

ketoconazole, fluconazole, itraconazole and terbinafine on the

metabolism of cyclosporin by human liver microsomes. Br J Clin


Backman JT, Olkkola KT, Neuvonen PJ (1996) Rifampin drastically

reduces plasma concentrations and effects of oral midazolam.

Clin Pharmacol Ther 59:7–13

Backman JT, Granfors MT, Neuvonen PJ (2006a) Rifampicin is only

a weak inducer of CYP1A2-mediated presystemic and systemic

metabolism: studies with tizanidine and caffeine. Eur J Clin


Backman JT, Karjalainen MJ, Neuvonen M et al (2006b) Rofecoxib is

a potent inhibitor of cytochrome P450 1A2: studies with

tizanidine and caffeine in healthy subjects. Br J Clin Pharmacol

62:345–357

Balbisi EA (2006) Frovatriptan: a review of pharmacology, pharma-

cokinetics and clinical potential in the treatment of menstrual

migraine. Ther Clin Risk Manag 2:303–308

Baldwin SJ, Bloomer JC, Smith GJ et al (1995) Ketoconazole and

sulphaphenazole as the respective selective inhibitors of P4503A

and 2C9. Xenobiotica 25:261–270

Baldwin SJ, Clarke SE, Chenery RJ (1999) Characterization of the

cytochrome P450 enzymes involved in the in vitro metabolism

of rosiglitazone. Br J Clin Pharmacol 48:424–432

Barditch-Crovo P, Trapnell CB, Ette E et al (1999) The effects of

rifampin and rifabutin on the pharmacokinetics and pharmaco-

dynamics of a combination oral contraceptive. Clin Pharmacol

Ther 65:428–438

Becquemont L, Le Bot MA, Riche C et al (1998) Use of

heterologously expressed human cytochrome P450 1A2 to

predict tacrine–fluvoxamine drug interaction in man. Pharmaco-

genetics 8:101–108

Behnisch PA, Hosoe K, Sakai S (2001) Bioanalytical screening

methods for dioxins and dioxin-like compounds a review of

bioassay/biomarker technology. Environ Int 27:413–439

Benowitz NL, Peng M, Jacob P 3rd (2003) Effects of cigarette

smoking and carbon monoxide on chlorzoxazone and caffeine

metabolism. Clin Pharmacol Ther 74:468–474

Benowitz NL, Lessov-Schlaggar CN, Swan GE et al (2006) Female

sex and oral contraceptive use accelerate nicotine metabolism.


Berlin I, Gasior MJ, Moolchan ET (2007) Sex-based and hormonal

contraception effects on the metabolism of nicotine among

adolescent tobacco-dependent smokers. Nicotine Tob Res

9:493–498

Bertilsson G, Heidrich J, Svensson K et al (1998) Identification of a

human nuclear receptor defines a new signaling pathway for

CYP3A induction. Proc Natl Acad Sci USA 95:12208–12213

Bertilsson L, Carrillo JA, Dahl ML et al (1994) Clozapine disposition

covaries with CYP1A2 activity determined by a caffeine test. Br


Bertilsson L (1995) Geographical/interracial differences in polymor-

phic drug oxidation. Current state of knowledge of cytochromes

P450 (CYP) 2D6 and 2C19. Clin Pharmacokinet 29:192–209

Bidstrup TB, Bjørnsdottir I, Sidelmann UG et al (2003) CYP2C8 and

CYP3A4 are the principal enzymes involved in the human in

vitro biotransformation of the insulin secretagogue repaglinide.

Br J Clin Pharmacol 56:305–314

Bidstrup TB, Stilling N, Damkier P et al (2004) Rifampicin seems to

act as both an inducer and an inhibitor of the metabolism of

repaglinide. Eur J Clin Pharmacol 60:109–114

Birkett DJ, Miners JO, Attwood J (1983) Evidence for a dual action of

sulphinpyrazone on drug metabolism in man: theophylline-

sulphinpyrazone interaction. Br J Clin Pharmacol 15:567–569

Birkett DJ, Rees D, Andersson T et al (1994) In vitro proguanil

activation to cycloguanil by human liver microsomes is mediated

by CYP3A isoforms as well as by S-mephenytoin hydroxylase.


Bjeldanes LF, Kim JY, Grose KR et al (1991) Aromatic hydrocarbon

responsiveness-receptor agonists generated from indole-3-carbi-

nol in vitro and in vivo: comparisons with 2,3,7,8-

tetrachlorodibenzo-p-dioxin. Proc Natl Acad Sci USA

88:9543–9547

Bjornsson TD, Callaghan JT, Einolf HJ et al (2003) The conduct of in

vitro and in vivo drug–drug interaction studies: a Pharmaceutical

Research and Manufacturers of America (PhRMA) perspective.


Bloomer JC, Clarke SE, Chenery RJ (1997) In vitro identification of

the P450 enzymes responsible for the metabolism of ropinirole.


Blumberg B, Sabbagh W Jr, Juguilon H et al (1998) SXR, a novel

steroid and xenobiotic-sensing nuclear receptor. Genes Dev

12:3195–3205

Bodin K, Bretillon L, Aden Y et al (2001) Antiepileptic drugs

increase plasma levels of 4b-hydroxycholesterol in humans:

evidence for involvement of cytochrome P450 3A4. J Biol Chem

276:38685–38689

Bodin K, Lindbom U, Diczfalusy U (2005) Novel pathways of bile

acid metabolism involving CYP3A4. Biochim Biophys Acta

1687:84–93

Boobis AR, Murray S, Kahn GC et al (1983) Substrate specificity of

the form of cytochrome P-450 catalyzing the 4-hydroxylation of

debrisoquine in man. Mol Pharmacol 23:474–481

Boobis AR, Lynch AM, Murray S et al (1994) CYP1A2-catalyzed

conversion of dietary heterocyclic amines to their proximate

carcinogens is their major route of metabolism in humans.

Cancer Res 54:89–94

Bourrie M, Meunier V, Berger Y et al (1996) Cytochrome P450

isoform inhibitors as a tool for the investigation of metabolic

reactions catalyzed by human liver microsomes. J Pharmacol

Exp Ther 277:321–332

Brady JF, Xiao F, Wang MH et al (1991a) Effects of disulfiram on

hepatic P450IIE1, other microsomal enzymes, and hepatotoxic-

ity in rats. Toxicol Appl Pharmacol 108:366–373

Brady JF, Ishizaki H, Fukuto JM et al (1991b) Inhibition of

cytochrome P-450 2E1 by diallyl sulfide and its metabolites.

Chem Res Toxicol 4:642–647

Arch Toxicol (2008) 82:667–715 699

123

Broly F, Libersa C, Lhermitte M et al (1989) Effect of quinidine on

the dextromethorphan O-demethylase activity of microsomal

fractions from human liver. Br J Clin Pharmacol 28:29–36

Brosen K, Skjelbo E, Rasmussen BB et al (1993) Fluvoxamine is a

potent inhibitor of cytochrome P4501A2. Biochem Pharmacol

45:1211–1214

Brown CM, Reisfeld B, Mayeno AN (2008) Cytochromes P450: a

structure-based summary of biotransformations using represen-

tative substrates. Drug Metab Rev 40:1–100

Buchan P, Wade A, Ward C et al (2002) Frovatriptan: a review of

drug–drug interactions. Headache 42(suppl 2):S63–S73

Buchthal J, Grund KE, Buchmann A et al (1995) Induction of

cytochrome P4501A by smoking or omeprazole in comparison

with UDP-glucuronosyltransferase in biopsies of human duode-

nal mucosa. Eur J Clin Pharmacol 47:431–435

Burk O, Koch I, Raucy J et al (2004) The induction of cytochrome

P450 3A5 (CYP3A5) in the human liver and intestine is

mediated by the xenobiotic sensors pregnane X receptor (PXR)

and constitutively activated receptor (CAR). J Biol Chem

279:38379–38385

Burk O, Wojnowski L (2004) Cytochrome P450 3A and their

regulation. Naunyn Schmiedebergs Arch Pharmacol 369:105–

124

Burke MD, Thompson S, Elcombe CR et al (1985) Ethoxy-, pentoxy-

and benzyloxyphenoxazones and homologues: a series of

substrates to distinguish between different induced cytochromes

P-450. Biochem Pharmacol 34:3337–3345

Busi F, Cresteil T (2005) CYP3A5 mRNA degradation by nonsense-

mediated mRNA decay. Mol Pharmacol 68:808–815

Butler MA, Iwasaki M, Guengerich FP et al (1989) Human

cytochrome P-450PA (P-450IA2), the phenacetin O-deethylase,

is primarily responsible for the hepatic 3-demethylation of

caffeine and N-oxidation of carcinogenic arylamines. Proc Natl

Acad Sci USA 86:7696–7700

Cai J, Zhao Y, Liu Y et al (2007) Directed differentiation of human

embryonic stem cells into functional hepatic cells. Hepatology

45:1229–1239

Campard D, Lysy PA, Najimi M et al (2008) Native umbilical cord

matrix stem cells express hepatic markers and differentiate into

hepatocyte-like cells. Gastroenterology 134:833–848

Campbell ME, Grant DM, Inaba T et al (1987) Biotransformation of

caffeine, paraxanthine, theophylline, and theobromine by poly-

cyclic aromatic hydrocarbon-inducible cytochrome(s) P-450 in

human liver microsomes. Drug Metab Dispos 15:237–249

Carlile DJ, Hakooz N, Bayliss MK et al (1999) Microsomal prediction

of in vivo clearance of CYP2C9 substrates in humans. Br J Clin


Carlson DB, Perdew GH (2002) A dynamic role for the Ah receptor in

cell signaling? Insights from a diverse group of Ah receptor

interacting proteins. J Biochem Mol Toxicol 16:317–325

Caro AA, Cederbaum AI (2004) Oxidative stress, toxicology, and

pharmacology of CYP2E1. Annu Rev Pharmacol Toxicol 44:27–

42

Carroccio A, Wu D, Cederbaum AI (1994) Ethanol increases

content and activity of human cytochrome P4502E1 in a

transduced HepG2 cell line. Biochem Biophys Res Commun

203:727–733

Cashman JR, Park SB, Yang ZC et al (1992) Metabolism of nicotine

by human liver microsomes: stereoselective formation of trans-

nicotine N0-oxide. Chem Res Toxicol 5:639–646

Cederbaum AI (2006) CYP2E1—biochemical and toxicological

aspects and role in alcohol-induced liver injury. Mt Sinai J

Med 73:657–672

Chang SM, Kuhn JG, Rizzo J et al (1998) Phase I study of paclitaxel

in patients with recurrent malignant glioma: a North American

Brain Tumor Consortium report. J Clin Oncol 16:2188–2194

Chang TK, Gonzalez FJ, Waxman DJ (1994) Evaluation of triacetyl-

oleandomycin, alpha-naphthoflavone and diethyldithiocarbamate

as selective chemical probes for inhibition of human cyto-

chromes P450. Arch Biochem Biophys 311:437–442

Chang TK, Chen J, Pillay V et al (2003) Real-time polymerase chain

reaction analysis of CYP1B1 gene expression in human liver.

Toxicol Sci 71:11–19

Chang TK, Waxman DJ (2006) Synthetic drugs and natural products

as modulators of constitutive androstane receptor (CAR) and

pregnane X receptor (PXR). Drug Metab Rev 38:51–73

Cheng YW, Chen CY, Lin P et al (2000) DNA adduct level in lung

tissue may act as a risk biomarker of lung cancer. Eur J Cancer

36:1381–1388

Chiba K, Kobayashi K, Manabe K et al (1993) Oxidative metabolism

of omeprazole in human liver microsomes: cosegregation with S-

mephenytoin 4’-hydroxylation. J Pharmacol Exp Ther 266:52–59

Chiba M, Hensleigh M, Nishime JA et al (1996) Role of cytochrome

P450 3A4 in human metabolism of MK-639, a potent human

immunodeficiency virus protease inhibitor. Drug Metab Dispos

24:307–314

Chien JY, Peter RM, Nolan CM et al (1997) Influence of polymorphic

N-acetyltransferase phenotype on the inhibition and induction of

acetaminophen bioactivation with long-term isoniazid. Clin

Pharmacol Ther 61:24–34

Chou CH, Evans AM, Fornasini G et al (1993) Relationship between

lipophilicity and hepatic dispersion and distribution for a

homologous series of barbiturates in the isolated perfused in

situ rat liver. Drug Metab Dispos 21:933–938

Christian K, Lang M, Maurel P et al (2004) Interaction of

heterogeneous nuclear ribonucleoprotein A1 with cytochrome

P450 2A6 mRNA: implications for post-transcriptional regula-

tion of the CYP2A6 gene. Mol Pharmacol 65:1405–1414

Christians U, Strohmeyer S, Kownatzki R et al (1991) Investigations

on the metabolic pathways of cyclosporine: II. Elucidation of the

metabolic pathways in vitro by human liver microsomes.

Xenobiotica 21:1199–1210

Clarke SE, Ayrton AD, Chenery RJ (1994a) Characterization of the

inhibition of P4501A2 by furafylline. Xenobiotica 24:517–526

Clarke SE, Baldwin SJ, Bloomer JC et al (1994b) Lauric acid as a

model substrate for the simultaneous determination of cyto-

chrome P450 2E1 and 4A in hepatic microsomes. Chem Res

Toxicol 7:836–842

Code EL, Crespi CL, Penman BW et al (1997) Human cytochrome

P4502B6: interindividual hepatic expression, substrate specific-

ity, and role in procarcinogen activation. Drug Metab Dispos

25:985–993

Coller JK, Somogyi AA, Bochner F (1999) Comparison of (S)-

mephenytoin and proguanil oxidation in vitro: contribution of

several CYP isoforms. Br J Clin Pharmacol 48:158–167

Cook CS, Berry LM, Burton E (2004) Prediction of in vivo drug

interactions with eplerenone in man from in vitro metabolic

inhibition data. Xenobiotica 34:215–228

Court MH, Duan SX, Hesse LM et al (2001) Cytochrome P-450 2B6

is responsible for interindividual variability of propofol hydrox-

ylation by human liver microsomes. Anesthesiology 94:110–119

Cresteil T, Monsarrat B, Alvinerie P et al (1994) Taxol metabolism by

human liver microsomes: identification of cytochrome P450

isozymes involved in its biotransformation. Cancer Res 54:386–

392

Crewe HK, Lennard MS, Tucker GT et al (1992) The effect of

selective serotonin re-uptake inhibitors on cytochrome P4502D6

(CYP2D6) activity in human liver microsomes. Br J Clin


Cvetkovic M, Leake B, Fromm MF et al (1999) OATP and P-

glycoprotein transporters mediate the cellular uptake and excre-

tion of fexofenadine. Drug Metab Dispos 27:866–871

700 Arch Toxicol (2008) 82:667–715

123

Dahl ML (2002) Cytochrome p450 phenotyping/genotyping in

patients receiving antipsychotics: useful aid to prescribing? Clin

Pharmacokinet 41:453–470

Dahlqvist R, Steiner E, Koike Y et al (1989) Induction of theophylline

metabolism by pentobarbital. Ther Drug Monit 11:408–410

Dai D, Zeldin DC, Blaisdell JA et al (2001) Polymorphisms in human

CYP2C8 decrease metabolism of the anticancer drug paclitaxel

and arachidonic acid. Pharmacogenetics 11:597–607

Dai Y, Hebert MF, Isoherranen N et al (2006) Effect of CYP3A5

polymorphism on tacrolimus metabolic clearance in vitro. Drug

Metab Dispos 34:836–847

Dailly E, Tribut O, Tattevin P et al (2006) Influence of tenofovir,

nevirapine and efavirenz on ritonavir-boosted atazanavir phar-

macokinetics in HIV-infected patients. Eur J Clin Pharmacol

62:523–526

Daly AK, King BP (2003) Pharmacogenetics of oral anticoagulants.

Pharmacogenetics 13:247–252

Darwish M, Kirby M, Robertson P Jr et al (2008) Interaction profile of

armodafinil with medications metabolized by cytochrome P450

enzymes 1A2, 3A4 and 2C19 in healthy subjects. Clin Pharma-

cokinet 47:61–74

Dayer P, Desmeules J, Leemann T et al (1988) Bioactivation of the

narcotic drug codeine in human liver is mediated by the

polymorphic monooxygenase catalyzing debrisoquine 4-hydrox-

ylation (cytochrome P-450 dbl/bufI). Biochem Biophys Res

Commun 152:411–416

de Wildt SN, Kearns GL, Leeder JS, van den Anker JN (1999)

Cytochrome P450 3A: ontogeny and drug disposition. Clin


Dempsey D, Jacob P 3rd, Benowitz NL (2002) Accelerated metab-

olism of nicotine and cotinine in pregnant smokers. J Pharmacol

Exp Ther 301:594–598

Dennison JB, Kulanthaivel P, Barbuch RJ et al (2006) Selective

metabolism of vincristine in vitro by CYP3A5. Drug Metab

Dispos 34:1317–1327

Depre M, Van Hecken A, Oeyen M et al (2005) Effect of aprepitant

on the pharmacokinetics and pharmacodynamics of warfarin.

Eur J Clin Pharmacol 61:341–346

Desai PB, Duan JZ, Zhu YW et al (1998) Human liver microsomal

metabolism of paclitaxel and drug interactions. Eur J Drug

Metab Pharmacokinet 23:417–424

Desta Z, Zhao X, Shin JG et al (2002) Clinical significance of the

cytochrome P450 2C19 genetic polymorphism. Clin Pharmaco-

kinet 41:913–958

Desta Z, Saussele T, Ward B et al (2007) Impact of CYP2B6

polymorphism on hepatic efavirenz metabolism in vitro. Phar-

macogenomics 8:547–558

Dickinson RG, Hooper WD, Patterson M et al (1985) Extent of

urinary excretion of p-hydroxyphenytoin in healthy subjects

given phenytoin. Ther Drug Monit 7:283–289

Diczfalusy U, Miura J, Roh HK et al (2008) 4Beta-hydroxycholes-

terol is a new endogenous CYP3A marker: relationship to

CYP3A5 genotype, quinine 3-hydroxylation and sex in Koreans,

Swedes and Tanzanians. Pharmacogenet Genomics 18:201–208

Ding X, Kaminsky LS (2003) Human extrahepatic cytochromes P450:

function in xenobiotic metabolism and tissue-selective chemical

toxicity in the respiratory and gastrointestinal tracts. Annu Rev

Pharmacol Toxicol 43:149–173

Dingemanse J, van Giersbergen PL (2004) Clinical pharmacology of

bosentan, a dual endothelin receptor antagonist. Clin Pharmaco-

kinet 43:1089–1115

Distlerath LM, Reilly PE, Martin MV et al (1985) Purification and

characterization of the human liver cytochromes P-450 involved

in debrisoquine 4-hydroxylation and phenacetin O-deethylation,

two prototypes for genetic polymorphism in oxidative drug

metabolism. J Biol Chem 260:9057–9067

Djordjevic N, Ghotbi R, Bertilsson L et al (2008) Induction of

CYP1A2 by heavy coffee consumption in Serbs and Swedes. Eur


Doecke CJ, Veronese ME, Pond SM et al (1991) Relationship

between phenytoin and tolbutamide hydroxylations in human

liver microsomes. Br J Clin Pharmacol 31:125–130

Dolwick KM, Schmidt JV, Carver LA et al (1993) Cloning and

expression of a human Ah receptor cDNA. Mol Pharmacol

44:911–917

Donato MT, Viitala P, Rodriguez-Antona C et al (2000) CYP2A5/

CYP2A6 expression in mouse and human hepatocytes treated

with various in vivo inducers. Drug Metab Dispos 28:1321–1326

Donato MT, Lahoz A, Castell JV et al (2008) Cell lines: a tool for in

vitro drug metabolism studies. Curr Drug Metab 9:1–11

Draper AJ, Madan A, Parkinson A (1997) Inhibition of coumarin 7-

hydroxylase activity in human liver microsomes. Arch Biochem

Biophys 341:47–61

Dresser GK, Bailey DG, Leake BF et al (2002) Fruit juices inhibit

organic anion transporting polypeptide-mediated drug uptake to

decrease the oral availability of fexofenadine. Clin Pharmacol

Ther 71:11–20

Eagling VA, Back DJ, Barry MG (1997) Differential inhibition of

cytochrome P450 isoforms by the protease inhibitors, ritonavir,

saquinavir and indinavir. Br J Clin Pharmacol 44:190–194

Edwards RJ, Price RJ, Watts PS et al (2003) Induction of cytochrome

P450 enzymes in cultured precision-cut human liver slices. Drug


Eichelbaum M, Ingelman-Sundberg M, Evans WE (2006) Pharmac-

ogenomics and individualized drug therapy. Annu Rev Med

57:119–137

Ek M, Soderdahl T, Kuppers-Munther B et al (2007) Expression of

drug metabolizing enzymes in hepatocyte-like cells derived from

human embryonic stem cells. Biochem Pharmacol 74:496–503

Ekins S, Erickson JA (2002) A pharmacophore for human pregnane X

receptor ligands. Drug Metab Dispos 30:96–99

Ekins S, Mirny L, Schuetz EG (2002) A ligand-based approach to

understanding selectivity of nuclear hormone receptors PXR,

CAR, FXR, LXRalpha, and LXRbeta. Pharm Res 19:1788–1800

Ekins S, Stresser DM, Williams JA (2003) In vitro and pharmaco-

phore insights into CYP3A enzymes. Trends Pharmacol Sci

24:161–166

Ekins S, Andreyev S, Ryabov A et al (2006) A combined approach to

drug metabolism and toxicity assessment. Drug Metab Dispos

34:495–503

Ekins S, Chang C, Mani S et al (2007) Human pregnane X receptor

antagonists and agonists define molecular requirements for

different binding sites. Mol Pharmacol 72:592–603

Ekstrom G, Gunnarsson UB (1996) Ropivacaine, a new amide-type

local anesthetic agent, is metabolized by cytochromes P450 1A

and 3A in human liver microsomes. Drug Metab Dispos 24:955–

961

Elkayam T, Amitay-Shaprut S, Dvir-Ginzberg M et al (2006)

Enhancing the drug metabolism activities of C3A—a human

hepatocyte cell line—by tissue engineering within alginate

scaffolds. Tissue Eng 12:1357–1368

El-Sankary W, Gibson GG, Ayrton A et al (2001) Use of a reporter

gene assay to predict and rank the potency and efficacy of

CYP3A4 inducers. Drug Metab Dispos 29:1499–1504

Elsherbiny DA, Asimus SA, Karlsson MO et al (2008) A model based

assessment of the CYP2B6 and CYP2C19 inductive properties

by artemisinin antimalarials: implications for combination

regimens. J Pharmacokinet Pharmacodyn. doi:10.1007/s10928-

008-9084-6

Emoto C, Yamato Y, Sato Y et al (2008) Non-invasive method to

detect induction of CYP3A4 in chimeric mice with a humanized

liver. Xenobiotica 38:239–248

Arch Toxicol (2008) 82:667–715 701

123

http://dx.doi.org/10.1007/s10928-008-9084-6

http://dx.doi.org/10.1007/s10928-008-9084-6

Endo T, Ban M, Hirata K et al (2007) Involvement of CYP2A6 in the

formation of a novel metabolite, 3-hydroxypilocarpine, from

pilocarpine in human liver microsomes. Drug Metab Dispos

35:476–483

Eriksson UG, Lundahl J, Baarnhielm C et al (1991) Stereoselective

metabolism of felodipine in liver microsomes from rat, dog, and

human. Drug Metab Dispos 19:889–894

Ernest CS 2nd, Hall SD, Jones DR (2005) Mechanism-based

inactivation of CYP3A by HIV protease inhibitors. J Pharmacol

Exp Ther 312:583–591

Evans DC, O’Connor D, Lake BG et al (2003) Eletriptan metabolism

by human hepatic CYP450 enzymes and transport by human P-

glycoprotein. Drug Metab Dispos 31:861–869

Faber MS, Jetter A, Fuhr U (2005) Assessment of CYP1A2 activity in

clinical practice: why, how, and when? Basic Clin Pharmacol

Toxicol 97:125–134

Facciola G, Hidestrand M, von Bahr C et al (2001) Cytochrome P450

isoforms involved in melatonin metabolism in human liver

microsomes. Eur J Clin Pharmacol 56:881–888

Fang J, Coutts RT, McKenna KF et al (1998) Elucidation of

individual cytochrome P450 enzymes involved in the metabo-

lism of clozapine. Naunyn Schmiedebergs Arch Pharmacol

358:592–599

Faucette SR, Hawke RL, Lecluyse EL et al (2000) Validation of

bupropion hydroxylation as a selective marker of human

cytochrome P450 2B6 catalytic activity. Drug Metab Dispos

28:1222–1230

Faucette SR, Zhang TC, Moore R et al (2007) Relative activation of

human pregnane X receptor versus constitutive androstane

receptor defines distinct classes of CYP2B6 and CYP3A4

inducers. J Pharmacol Exp Ther 320:72–80

Fellay J, Marzolini C, Decosterd L et al (2005) Variations of CYP3A

activity induced by antiretroviral treatment in HIV-1 infected

patients. Eur J Clin Pharmacol 60:865–873

Fetell MR, Grossman SA, Fisher JD et al (1997) Preirradiation

paclitaxel in glioblastoma multiforme: efficacy, pharmacology,

and drug interactions. New approaches to brain tumor therapy

central nervous system consortium. J Clin Oncol 15:3121–3128

Fontana RJ, Lown KS, Paine MF et al (1999) Effects of a chargrilled

meat diet on expression of CYP3A, CYP1A, and P-glycoprotein

levels in healthy volunteers. Gastroenterology 117:89–98

Forman BM, Tzameli I, Choi HS et al (1998) Androstane metabolites

bind to and deactivate the nuclear receptor CAR-beta. Nature

395:612–615

Frank C, Molnar F, Matilainen M et al (2004) Agonist-dependent and

agonist-independent transactivations of the human constitutive

androstane receptor are modulated by specific amino acid pairs. J

Biol Chem 279:33558–33566

Friedman MA, Woodcock J, Lumpkin MM et al (1999) The safety of

newly approved medicines: do recent market removals mean

there is a problem? JAMA 281:1728–1734

Fuhr U, Wolff T, Harder S et al (1990) Quinolone inhibition of

cytochrome P-450-dependent caffeine metabolism in human

liver microsomes. Drug Metab Dispos 18:1005–1010

Fujita K (2004) Food–drug interactions via human cytochrome P450

3A (CYP3A). Drug Metabol Drug Interact 20:195–217

Fukuda I, Nishiumi S, Yabushita Y et al (2004) A new southwestern

chemistry-based ELISA for detection of aryl hydrocarbon

receptor transformation: application to the screening of its

receptor agonists and antagonists. J Immunol Methods 287:187–

201

Funck-Brentano C, Becquemont L, Lenevu A et al (1997) Inhibition

by omeprazole of proguanil metabolism: mechanism of the

interaction in vitro and prediction of in vivo results from the in

vitro experiments. J Pharmacol Exp Ther 280:730–738

Furster C, Wikvall K (1999) Identification of CYP3A4 as the major

enzyme responsible for 25-hydroxylation of 5b-cholestane-3a,

7a, 12a-triol in human liver microsomes. Biochim Biophys Acta

1437:46–52

Galetin A, Clarke SE, Houston JB (2003) Multisite kinetic analysis of

interactions between prototypical CYP3A4 subgroup substrates:

midazolam, testosterone, and nifedipine. Drug Metab Dispos

31:1108–1116

Galetin A, Burt H, Gibbons L et al (2006) Prediction of time-

dependent CYP3A4 drug–drug interactions: impact of enzyme

degradation, parallel elimination pathways, and intestinal inhi-

bition. Drug Metab Dispos 34:166–175

Galteau MM, Shamsa F (2003) Urinary 6b-hydroxycortisol: a

validated test for evaluating drug induction or drug inhibition

mediated through CYP3A in humans and in animals. Eur J Clin


Garcia M, Rager J, Wang Q et al (2003) Cryopreserved human

hepatocytes as alternative in vitro model for cytochrome P450

induction studies. In Vitro Cell Dev Biol Anim 39:283–287

Gebhardt AC, Lucas D, Menez JF et al (1997) Chlormethiazole

inhibition of cytochrome P450 2E1 as assessed by chlorzoxazone

hydroxylation in humans. Hepatology 26:957–961

Ghanbari F, Rowland-Yeo K, Bloomer JC et al (2006) A critical

evaluation of the experimental design of studies of mechanism

based enzyme inhibition, with implications for in vitro–in vivo

extrapolation. Curr Drug Metab 7:315–334

Giancarlo GM, Venkatakrishnan K, Granda BW et al (2001) Relative

contributions of CYP2C9 and 2C19 to phenytoin 4-hydroxyl-

ation in vitro: inhibition by sulfaphenazole, omeprazole, and

ticlopidine. Eur J Clin Pharmacol 57:31–36

Girre C, Lucas D, Hispard E et al (1994) Assessment of cytochrome

P4502E1 induction in alcoholic patients by chlorzoxazone

pharmacokinetics. Biochem Pharmacol 47:1503–1508

Glaeser H, Drescher S, Eichelbaum M et al (2005) Influence of

rifampicin on the expression and function of human intestinal

cytochrome P450 enzymes. Br J Clin Pharmacol 59:199–206

Goldberg MR, Lo MW, Deutsch PJ et al (1996) Phenobarbital

minimally alters plasma concentrations of losartan and its active

metabolite E-3174. Clin Pharmacol Ther 59:268–274

Gomez-Lechon MJ, Donato T, Jover R et al (2001) Expression and

induction of a large set of drug-metabolizing enzymes by the

highly differentiated human hepatoma cell line BC2. Eur J

Biochem 268(5):1448–1459

Gomez-Lechon MJ, Donato MT, Castell JV et al (2003) Human

hepatocytes as a tool for studying toxicity and drug metabolism.

Curr Drug Metab 4:292–312

Gonzalez FJ (2005) Role of cytochromes P450 in chemical toxicity

and oxidative stress: studies with CYP2E1. Mutat Res 569:101–

110

Goodwin B, Hodgson E, Liddle C (1999) The orphan human

pregnane X receptor mediates the transcriptional activation of

CYP3A4 by rifampicin through a distal enhancer module. Mol


Goodwin B, Moore LB, Stoltz CM et al (2001) Regulation of the

human CYP2B6 gene by the nuclear pregnane X receptor. Mol


Gorski JC, Jones DR, Hamman MA et al (1999) Biotransformation of

alprazolam by members of the human cytochrome P4503A

subfamily. Xenobiotica 29:931–944

Granfors MT, Backman JT, Laitila J et al (2004) Tizanidine is mainly

metabolized by cytochrome p450 1A2 in vitro. Br J Clin


Gripon P, Rumin S, Urban S et al (2002) Infection of a human

hepatoma cell line by hepatitis B virus. Proc Natl Acad Sci USA

99:15655–15660

702 Arch Toxicol (2008) 82:667–715

123

Gu CG, Jiang X, Ju XH et al (2007) DFT study on the structure-

toxicity relationship of dioxin compounds using PLS analysis.

SAR QSAR Environ Res 18:603–619

Guengerich FP, Muller-Enoch D, Blair IA (1986) Oxidation of

quinidine by human liver cytochrome P-450. Mol Pharmacol

30:287–295

Guengerich FP (1990) Mechanism-based inactivation of human liver

microsomal cytochrome P-450 IIIA4 by gestodene. Chem Res

Toxicol 3:363–371

Guengerich FP, Kim DH, Iwasaki M (1991) Role of human

cytochrome P-450 IIE1 in the oxidation of many low molecular

weight cancer suspects. Chem Res Toxicol 4:168–179

Guengerich FP, Wu Z, Bartleson CJ (2005) Function of human

cytochrome P450s: characterisation of the orphans. Biochem

Biophys Res Commun 338:465–469

Guengerich FP (2008) Cytochrome p450 and chemical toxicology.

Chem Res Toxicol 21:70–83

Gurley BJ, Gardner SF, Hubbard MA et al (2002) Cytochrome P450

phenotypic ratios for predicting herb–drug interactions in

humans. Clin Pharmacol Ther 72:276–287

Gurley BJ, Gardner SF, Hubbard MA et al (2005) Clinical assessment

of effects of botanical supplementation on cytochrome P450

phenotypes in the elderly: St John’s wort, garlic oil, Panax

ginseng and Ginkgo biloba. Drugs Aging 22:525–539

Ha-Duong NT, Dijols S, Macherey AC et al (2001) Ticlopidine as a

selective mechanism-based inhibitor of human cytochrome P450

2C19. Biochemistry 40:12112–12122

Hakkola J, Pelkonen O, Pasanen M et al (1998) Xenobiotic-metabo-

lizing cytochrome P450 enzymes in the human feto-placental unit:

role in intrauterine toxicity. Crit Rev Toxicol 28:35–72

Hakkola J, Raunio H, Purkunen R et al (2001) Cytochrome P450 3A

expression in the human fetal liver: evidence that CYP3A5 is

expressed in only a limited number of fetal livers. Biol Neonate

80:193–201

Hall SD, Thummel KE, Watkins PB et al (1999) Molecular and

physical mechanisms of first-pass extraction. Drug Metab Dispos

27:161–166

Halpert JR (1995) Structural basis of selective cytochrome P450

inhibition. Annu Rev Pharmacol Toxicol 35:29–53

Hamman MA, Thompson GA, Hall SD (1997) Regioselective and

stereoselective metabolism of ibuprofen by human cytochrome

P450 2C. Biochem Pharmacol 54:33–41

Hanaoka T, Yamano Y, Pan G et al (2002) Cytochrome P450 1B1

mRNA levels in peripheral blood cells and exposure to

polycyclic aromatic hydrocarbons in Chinese coke oven work-

ers. Sci Total Environ 296:27–33

Hargreaves MB, Jones BC, Smith DA et al (1994) Inhibition of p-

nitrophenol hydroxylase in rat liver microsomes by small

aromatic and heterocyclic molecules. Drug Metab Dispos

22:806–810

Hariparsad N, Carr BA, Evers R et al (2008) Comparison of

immortalized Fa2N-4 cells and human hepatocytes as in vitro

models for cytochrome P450 induction. Drug Metab Dispos. doi:

10.1124/dmd.108.020677

Harleton E, Webster M, Bumpus NN et al (2004) Metabolism of N,

N0, N00-triethylenethiophosphoramide by CYP2B1 and CYP2B6

results in the inactivation of both isoforms by two distinct

mechanisms. J Pharmacol Exp Ther 310:1011–1019

Hartley DP, Dai X, Yabut J et al (2006) Identification of potential

pharmacological and toxicological targets differentiating struc-

tural analogs by a combination of transcriptional profiling and

promoter analysis in LS-180 and Caco-2 adenocarcinoma cell

lines. Pharmacogenet Genomics 16:579–599

Hartter S, Wang X, Weigmann H et al (2001) Differential effects of

fluvoxamine and other antidepressants on the biotransformation

of melatonin. J Clin Psychopharmacol 21:167–174

He N, Edeki T (2004) The inhibitory effects of herbal components on

CYP2C9 and CYP3A4 catalytic activities in human liver

microsomes. Am J Ther 11:206–212

Hecht SS (1999) DNA adduct formation from tobacco-specific N-

nitrosamines. Mutat Res 424:127–142

Heimark LD, Wienkers L, Kunze K et al (1992) The mechanism of

the interaction between amiodarone and warfarin in humans.


Heinemeyer G, Gramm HJ, Simgen W et al (1987) Kinetics of

hexobarbital and dipyrone in critical care patients receiving

high-dose pentobarbital. Eur J Clin Pharmacol 32:273–277

Hengstler JG, Utesch D, Steinberg P et al (2000) Cryopreserved

primary hepatocytes as a constantly available in vitro model for

the evaluation of human and animal drug metabolism and

enzyme induction. Drug Metab Rev 32:81–118

Herman D, Locatelli I, Grabnar I et al (2006) The influence of co-

treatment with carbamazepine, amiodarone and statins on

warfarin metabolism and maintenance dose. Eur J Clin Pharma-

col 62:291–296

Hesse LM, Venkatakrishnan K, Court MH et al (2000) CYP2B6

mediates the in vitro hydroxylation of bupropion: potential drug

interactions with other antidepressants. Drug Metab Dispos

28:1176–1183

Hewitt NJ, Hewitt P (2004) Phase I and II enzyme characterization of

two sources of HepG2 cell lines. Xenobiotica 34:243–256

Hewitt NJ, Lechon MJ, Houston JB et al (2007a) Primary hepato-

cytes: current understanding of the regulation of metabolic

enzymes and transporter proteins, and pharmaceutical practice

for the use of hepatocytes in metabolism, enzyme induction,

transporter, clearance, and hepatotoxicity studies. Drug Metab

Rev 39:159–234

Hewitt NJ, de Kanter R, LeCluyse E (2007b) Induction of drug

metabolizing enzymes: a survey of in vitro methodologies and

interpretations used in the pharmaceutical industry—do they

comply with FDA recommendations? Chem Biol Interact

168:51–65

Hewitt NJ, Lecluyse EL, Ferguson SS (2007c) Induction of hepatic

cytochrome P450 enzymes: methods, mechanisms, recommen-

dations, and in vitro–in vivo correlations. Xenobiotica 37:1196–

1224

Higashi E, Fukami T, Itoh M et al (2007a) Human CYP2A6 is

induced by estrogen via estrogen receptor. Drug Metab Dispos

35:1935–1941

Higashi E, Nakajima M, Katoh M et al (2007b) Inhibitory effects of

neurotransmitters and steroids on human CYP2A6. Drug Metab

Dispos 35:508–514

Hijazi Y, Boulieu R (2002) Contribution of CYP3A4, CYP2B6, and

CYP2C9 isoforms to N-demethylation of ketamine in human

liver microsomes. Drug Metab Dispos 30:853–858

Hines RN, McCarver DG (2002) The ontogeny of human drug-

metabolizing enzymes: phase I oxidative enzymes. J Pharmacol

Exp Ther 300:355–360

Hollenberg PF (2002) Characteristics and common properties of

inhibitors, inducers, and activators of CYP enzymes. Drug

Metab Rev 34:17–35

Honkakoski P, Negishi M (1997) Characterization of a phenobarbital-

responsive enhancer module in mouse P450 Cyp2b10 gene. J

Biol Chem 272:14943–14949

Honkakoski P, Moore R, Washburn KA et al (1998a) Activation by

diverse xenochemicals of the 51-base pair phenobarbital-respon-

sive enhancer module in the CYP2B10 gene. Mol Pharmacol

53:597–601

Honkakoski P, Zelko I, Sueyoshi T et al (1998b) The nuclear orphan

receptor CAR-retinoid X receptor heterodimer activates the

phenobarbital-responsive enhancer module of the CYP2B gene.

Mol Cell Biol 18:5652–5658

Arch Toxicol (2008) 82:667–715 703

123

http://dx.doi.org/10.1124/dmd.108.020677

Hooper WD, Pool WF, Woolf TF et al (1994) Stereoselective

hydroxylation of tacrine in rats and humans. Drug Metab Dispos

22:719–724

Houston JB, Galetin A (2005) Modelling atypical CYP3A4 kinetics:

principles and pragmatism. Arch Biochem Biophys 433:351–360

Howard LA, Miksys S, Hoffmann E et al (2003) Brain CYP2E1 is

induced by nicotine and ethanol in rat and is higher in smokers

and alcoholics. Br J Pharmacol 138:1376–1386

Hruska MW, Amico JA, Langaee TY et al (2005) The effect of

trimethoprim on CYP2C8 mediated rosiglitazone metabolism in

human liver microsomes and healthy subjects. Br J Clin


Hrycay EG, Bandiera SM (2008) Cytochrome P450 Enzymes. In: Gad

SC (ed) Preclinical development handbook. ADME and bio-

pharmaceutical properties. Wiley, New York

Hsiang B, Zhu Y, Wang Z et al (1999) A novel human hepatic organic

anion transporting polypeptide (OATP2). Identification of a

liver-specific human organic anion transporting polypeptide and

identification of rat and human hydroxymethylglutaryl-CoA

reductase inhibitor transporters. J Biol Chem 274:37161–37168

Hsu A, Granneman GR, Bertz RJ (1998) Ritonavir: clinical pharma-

cokinetics and interactions with other anti-HIV agents. Clin


Hu Y, Mishin V, Johansson I et al (1994) Chlormethiazole as an

efficient inhibitor of cytochrome P450 2E1 expression in rat

liver. J Pharmacol Exp Ther 269:1286–1291

Hu SW, Chen CC, Kuo CY et al (2006) Increased cytochrome

P4501B1 gene expression in peripheral leukocytes of municipal

waste incinerator workers. Toxicol Lett 160:112–120

Huang Z, Roy P, Waxman DJ (2000) Role of human liver microsomal

CYP3A4 and CYP2B6 in catalyzing N dechloroethylation of

cyclophosphamide and ifosfamide. Biochem Pharmacol 59:961–

972

Huang W, Zhang J, Chua SS et al (2003) Induction of bilirubin

clearance by the constitutive androstane receptor (CAR). Proc

Natl Acad Sci USA 100:4156–4161

Huang SM, Temple R, Throckmorton DC et al (2007) Drug

interaction studies: study design, data analysis, and implications

for dosing and labeling. Clin Pharmacol Ther 81:298–304

Hukkanen J, Pelkonen O, Hakkola J et al (2002) Expression and

regulation of xenobiotic-metabolizing cytochrome P450 (CYP)

enzymes in human lung. Crit Rev Toxicol 32:391–411

Hukkanen J, Vaisanen T, Lassila A et al (2003) Regulation of

CYP3A5 by glucocorticoids and cigarette smoke in human lung-

derived cells. J Pharmacol Exp Ther 304:745–752

Hukkanen J, Jacob P 3rd, Benowitz NL (2005) Metabolism and

disposition kinetics of nicotine. Pharmacol Rev 57:79–115

Huuskonen P, Storvik M, Reinisalo M et al (2008) Microarray

analysis of the global alterations in the gene expression in the

placentas from cigarette-smoking mothers. Clin Pharmacol Ther

83:542–550

Hyland R, Roe EG, Jones BC, Smith DA (2001) Identification of the

cytochrome P450 enzymes involved in the N-demethylation of

sildenafil. Br J Clin Pharmacol 51:239–248

Iannone MA, Consler TG, Pearce KH et al (2001) Multiplexed

molecular interactions of nuclear receptors using fluorescent

microspheres. Cytometry 44:326–337

Ingelman-Sundberg M (2005) The human genome project and novel

aspects of cytochrome P450 research. Toxicol Appl Pharmacol

207(suppl 2):52–56

Ingelman-Sundberg M, Sim SC, Gomez A et al (2007) Influence of

cytochrome P450 polymorphisms on drug therapies: pharmaco-

genetic, pharmacoepigenetic and clinical aspects. Pharmacol

Ther 116:496–526

Ioannides C, Lewis DF (2004) Cytochromes P450 in the bioactivation

of chemicals. Curr Top Med Chem 4:1767–1788

Isoherranen N, Kunze KL, Allen KE et al (2004) Role of itraconazole

metabolites in CYP3A4 inhibition. Drug Metab Dispos 32:1121–

1131

Ito K, Iwatsubo T, Kanamitsu S et al (1998) Prediction of

pharmacokinetic alterations caused by drug–drug interactions:

metabolic interaction in the liver. Pharmacol Rev 50:387–412

Ito K, Ogihara K, Kanamitsu S et al (2003) Prediction of the in vivo

interaction between midazolam and macrolides based on in vitro

studies using human liver microsomes. Drug Metab Dispos

31:945–954

Ito K, Brown HS, Houston JB (2004) Database analyses for the

prediction of in vivo drug–drug interactions from in vitro data.


Iwahori T, Matsuura T, Maehashi H et al (2003) CYP3A4 inducible

model for in vitro analysis of human drug metabolism using a

bioartificial liver. Hepatology 37:665–673

Jaakkola T, Backman JT, Neuvonen M et al (2006a) Montelukast and

zafirlukast do not affect the pharmacokinetics of the CYP2C8

substrate pioglitazone. Eur J Clin Pharmacol 62(7):503–509

Jaakkola T, Backman JT, Neuvonen M et al (2006b) Effect of

rifampicin on the pharmacokinetics of pioglitazone. Br J Clin


Jacobs MN (2004) In silico tools to aid risk assessment of endocrine

disrupting chemicals. Toxicology 205:43–53

Jacobsen W, Kirchner G, Hallensleben K et al (1999) Comparison of

cytochrome P-450-dependent metabolism and drug interactions of

the 3-hydroxy-3-methylglutaryl-CoA reductase inhibitors lova-

statin and pravastatin in the liver. Drug Metab Dispos 27:173–179

Jacobsen W, Kuhn B, Soldner A et al (2000) Lactonization is the

critical first step in the disposition of the 3-hydroxy-3-methyl-

glutaryl-CoA reductase inhibitor atorvastatin. Drug Metab

Dispos 28:1369–1378

Jao JY, Jusko WJ, Cohen JL (1972) Phenobarbital effects on

cyclophosphamide pharmacokinetics in man. Cancer Res

32:2761–2764

Jiang X, Williams KM, Liauw WS et al (2004) Effect of St John’s

wort and ginseng on the pharmacokinetics and pharmacody-

namics of warfarin in healthy subjects. Br J Clin Pharmacol

57:592–599

Jiang X, Blair EY, McLachlan AJ (2006) Investigation of the effects

of herbal medicines on warfarin response in healthy subjects: a

population pharmacokinetic-pharmacodynamic modeling

approach. J Clin Pharmacol 46:1370–1378

Jones SA, Moore LB, Shenk JL et al (2000) The pregnane X receptor:

a promiscuous xenobiotic receptor that has diverged during

evolution. Mol Endocrinol 14:27–39

Josse R, Aninat C, Glaise D et al (2008) Long-term functional

stability of human HepaRG hepatocytes and use for chronic

toxicity and genotoxicity studies. Drug Metab Dispos. doi:

10.1124/dmd.107.019901

Justesen US, Klitgaard NA, Brosen K et al (2003) Pharmacokinetic

interaction between amprenavir and delavirdine after multiple-

dose administration in healthy volunteers. Br J Clin Pharmacol

55:100–106

Jyrkkarinne J, Makinen J, Gynther J et al (2003) Molecular

determinants of steroid inhibition for the mouse constitutive

androstane receptor. J Med Chem 46:4687–4695

Jyrkkarinne J, Windshugel B, Makinen J et al (2005) Amino acids

important for ligand specificity of the human constitutive

androstane receptor. J Biol Chem 280:5960–5971

Kahn GC, Boobis AR, Murray S et al (1982) Assay and character-

isation of debrisoquine 4-hydroxylase activity of microsomal

fractions of human liver. Br J Clin Pharmacol 13:637–645

Kajosaari LI, Laitila J, Neuvonen PJ et al (2005) Metabolism of

repaglinide by CYP2C8 and CYP3A4 in vitro: effect of fibrates

and rifampicin. Basic Clin Pharmacol Toxicol 97:249–256

704 Arch Toxicol (2008) 82:667–715

123

http://dx.doi.org/10.1124/dmd.107.019901

Kamdem LK, Streit F, Zanger UM et al (2005) Contribution of

CYP3A5 to the in vitro hepatic clearance of tacrolimus. Clin

Chem 51:1374–1381

Kanebratt KP, Andersson TB (2008) HepaRG cells as an in vitro

model for evaluation of cytochrome P450 induction in humans.


Kapitulnik J, Strobel HW (1999) Extrahepatic drug metabolizing

enzymes. J Biochem Mol Toxicol 13:227–230

Karjalainen MJ, Neuvonen PJ, Backman JT (2006) Rofecoxib is a

potent, metabolism-dependent inhibitor of CYP1A2: implica-

tions for in vitro prediction of drug interactions. Drug Metab

Dispos 34:2091–2096

Kashuba AD, Tierney C, Downey GF et al (2005) Combining

fosamprenavir with lopinavir/ritonavir substantially reduces

amprenavir and lopinavir exposure: ACTG protocol A5143

results. Aids 19:145–152

Katiyar SK, Matsui MS, Mukhtar H (2000) Ultraviolet-B exposure of

human skin induces cytochromes P450 1A1 and 1B1. J Invest

Dermatol 114:328–333

Katoh M, Tateno C, Yoshizato K et al (2008) Chimeric mice with

humanized liver. Toxicology 246:9–17

Kawajiri K, Fujii-Kuriyama Y (2007) Cytochrome P450 gene

regulation and physiological functions mediated by the aryl

hydrocarbon receptor. Arch Biochem Biophys 464:207–212

Kawana K, Ikuta T, Kobayashi Y et al (2003) Molecular mechanism

of nuclear translocation of an orphan nuclear receptor, SXR. Mol


Kay L, Kampmann JP, Svendsen TL et al (1985) Influence of

rifampicin and isoniazid on the kinetics of phenytoin. Br J Clin


Kearney AS, Crawford LF, Mehta SC et al (1993) The interconver-

sion kinetics, equilibrium, and solubilities of the lactone and

hydroxyacid forms of the HMG-CoA reductase inhibitor, CI-

981. Pharm Res 10:1461–1465

Kent UM, Juschyshyn MI, Hollenberg PF (2001) Mechanism-based

inactivators as probes of cytochrome P450 structure and

function. Curr Drug Metab 2:215–243

Kent UM, Mills DE, Rajnarayanan RV et al (2002) Effect of 17-

alpha-ethynylestradiol on activities of cytochrome P450 2B

(P450 2B) enzymes: characterization of inactivation of P450s

2B1 and 2B6 and identification of metabolites. J Pharmacol Exp

Ther 300:549–558

Kenworthy KE, Bloomer JC, Clarke SE et al (1999) CYP3A4 drug

interactions: correlation of 10 in vitro probe substrates. Br J Clin


Kessova I, Cederbaum AI (2003) CYP2E1: biochemistry, toxicology,

regulation and function in ethanol-induced liver injury. Curr Mol

Med 3:509–518

Ketter TA, Jenkins JB, Schroeder DH et al (1995) Carbamazepine but

not valproate induces bupropion metabolism. J Clin Psycho-

pharmacol 15:327–333

Kharasch ED, Hankins DC, Baxter PJ et al (1998) Single-dose

disulfiram does not inhibit CYP2A6 activity. Clin Pharmacol

Ther 64:39–45

Kharasch ED, Mitchell D, Coles R et al (2008) Rapid clinical induction

of hepatic cytochrome P4502B6 (CYP2B6) activity by ritonavir.

Antimicrob Agents Chemother. doi:10.1128/AAC.01600-07

Kim RB, Wandel C, Leake B et al (1999) Interrelationship between

substrates and inhibitors of human CYP3A and P-glycoprotein.

Pharm Res 16:408–414

Kim J, Min G, Kemper B (2001) Chromatin assembly enhances

binding to the CYP2B1 phenobarbital-responsive unit (PBRU)

of nuclear factor-1, which binds simultaneously with constitutive

androstane receptor (CAR)/retinoid X receptor (RXR) and

enhances CAR/RXR-mediated activation of the PBRU. J Biol

Chem 276:7559–7567

Kim KA, Park JY, Lee JS et al (2003a) Cytochrome P450 2C8 and

CYP3A4/5 are involved in chloroquine metabolism in human

liver microsomes. Arch Pharm Res 26:631–637

Kim KA, Kim MJ, Park JY et al (2003b) Stereoselective metabolism

of lansoprazole by human liver cytochrome P450 enzymes. Drug


Kim KA, Park PW, Kim KR et al (2007) Effect of multiple doses of

montelukast on the pharmacokinetics of rosiglitazone, a

CYP2C8 substrate, in humans. Br J Clin Pharmacol 63:339–345

Kinonen T, Pasanen M, Gynther J et al (1995) Competitive inhibition

of coumarin 7-hydroxylation by pilocarpine and its interaction

with mouse CYP 2A5 and human CYP 2A6. Br J Pharmacol

116:2625–2630

Kirchheiner J, Brockmoller J (2005) Clinical consequences of

cytochrome P450 2C9 polymorphisms. Clin Pharmacol Ther

77:1–16

Kirchheiner J, Fuhr U, Brockmoller J (2005) Pharmacogenetics-based

therapeutic recommendations—ready for clinical practice? Nat

Rev Drug Discov 4:639–647

Kitada M, Kamataki T (1994) Cytochrome P450 in human fetal liver:

significance and fetal-specific expression. Drug Metab Rev

26:305–323

Kivisto KT, Bookjans G, Fromm MF et al (1996) Expression of

CYP3A4, CYP3A5 and CYP3A7 in human duodenal tissue. Br J

Clin Pharmacol 42:387–389

Kivisto KT, Niemi M, Fromm MF (2004) Functional interaction of

intestinal CYP3A4 and P-glycoprotein. Fundam Clin Pharmacol

18:621–626

Klees TM, Sheffels P, Dale O et al (2005) Metabolism of alfentanil by

cytochrome p4503a (cyp3a) enzymes. Drug Metab Dispos

33:303–311

Kliewer SA, Moore JT, Wade L et al (1998) An orphan nuclear

receptor activated by pregnanes defines a novel steroid signaling

pathway. Cell 92:73–82

Ko JW, Sukhova N, Thacker D et al (1997) Evaluation of omeprazole

and lansoprazole as inhibitors of cytochrome P450 isoforms.


Ko JW, Desta Z, Soukhova NV et al (2000) In vitro inhibition of the

cytochrome P450 (CYP450) system by the antiplatelet drug

ticlopidine: potent effect on CYP2C19 and CYP2D6. Br J Clin


Kobayashi K, Yamamoto T, Chiba K et al (1995) The effects of

selective serotonin reuptake inhibitors and their metabolites on

S-mephenytoin 40-hydroxylase activity in human liver micro-

somes. Br J Clin Pharmacol 40:481–485

Kobayashi K, Nakajima M, Chiba K et al (1998) Inhibitory effects of

antiarrhythmic drugs on phenacetin O-deethylation catalysed by

human CYP1A2. Br J Clin Pharmacol 45:361–368

Kobayashi K, Abe S, Nakajima M et al (1999) Role of human

CYP2B6 in S-mephobarbital N-demethylation. Drug Metab

Dispos 27:1429–1433

Kobayashi K, Sueyoshi T, Inoue K et al (2003) Cytoplasmic

accumulation of the nuclear receptor CAR by a tetratricopeptide

repeat protein in HepG2 cells. Mol Pharmacol 64:1069–1075

Kobayashi K, Yamanaka Y, Iwazaki N et al (2005) Identification of

HMG-CoA reductase inhibitors as activators for human, mouse

and rat constitutive androstane receptor. Drug Metab Dispos

33:924–929

Kodama S, Koike C, Negishi M et al (2004) Nuclear receptors CAR

and PXR cross talk with FOXO1 to regulate genes that encode

drug-metabolizing and gluconeogenic enzymes. Mol Cell Biol

24:7931–7940

Kodama S, Moore R, Yamamoto Y et al (2007) Human nuclear

pregnane X receptor cross-talk with CREB to repress cAMP

activation of the glucose-6-phosphatase gene. Biochem J

407:373–381

Arch Toxicol (2008) 82:667–715 705

123

http://dx.doi.org/10.1128/AAC.01600-07

Koenigs LL, Peter RM, Thompson SJ et al (1997) Mechanism-based

inactivation of human liver cytochrome P450 2A6 by 8-

methoxypsoralen. Drug Metab Dispos 25:1407–1415

Koike C, Moore R, Negishi M (2007) Extracellular signal-regulated

kinase is an endogenous signal retaining the nuclear constitutive

active/androstane receptor (CAR) in the cytoplasm of mouse

primary hepatocytes. Mol Pharmacol 71:1217–1221

Konishi H, Morita K, Minouchi T et al (1999) Preferential inhibition

of CYP1A enzymes in hepatic microsomes by mexiletine. Eur J

Drug Metab Pharmacokinet 24:149–153

Koop DR, Coon MJ (1986) (1986) Ethanol oxidation and toxicity:

role of alcohol P-450 oxygenase. Alcohol Clin Exp Res 10(suppl

6):44S–49S

Korjamo T, Honkakoski P, Toppinen MR et al (2005) Absorption

properties and P-glycoprotein activity of modified Caco-2 cell

lines. Eur J Pharm Sci 26:266–279

Kostrubsky VE, Ramachandran V, Venkataramanan R et al (1999)

The use of human hepatocyte cultures to study the induction of

cytochrome P-450. Drug Metab Dispos 27:887–894

Koudriakova T, Iatsimirskaia E, Utkin I et al (1998) Metabolism of

the human immunodeficiency virus protease inhibitors indinavir

and ritonavir by human intestinal microsomes and expressed

cytochrome P4503A4/3A5: mechanism-based inactivation of

cytochrome P4503A by ritonavir. Drug Metab Dispos 26:552–

561

Koyano S, Kurose K, Saito Y et al (2004) Functional characterization

of four naturally occurring variants of human pregnane X

receptor (PXR): one variant causes dramatic loss of both DNA

binding activity and the transactivation of the CYP3A4 pro-

moter/enhancer region. Drug Metab Dispos 32:149–154

Kress S, Reichert J, Schwarz M (1998) Functional analysis of the

human cytochrome P4501A1 (CYP1A1) gene enhancer. Eur J

Biochem 258:803–812

Kronbach T, Fischer V, Meyer UA (1988) Cyclosporine metabolism

in human liver: identification of a cytochrome P-450III gene

family as the major cyclosporine-metabolizing enzyme explains

interactions of cyclosporine with other drugs. Clin Pharmacol

Ther 43:630–635

Kumar V, Rock DA, Warren CJ et al (2006) Enzyme source effects

on CYP2C9 kinetics and inhibition. Drug Metab Dispos

34:1903–1908

Kunze KL, Trager WF (1993) Isoform-selective mechanism-based

inhibition of human cytochrome P450 1A2 by furafylline. Chem

Res Toxicol 6:649–656

Kunze KL, Wienkers LC, Thummel KE et al (1996) Warfarin-

fluconazole. I. Inhibition of the human cytochrome P450-

dependent metabolism of warfarin by fluconazole: in vitro

studies. Drug Metab Dispos 24:414–421

Kuypers DR, Claes K, Evenepoel P et al (2004) Time-related clinical

determinants of long-term tacrolimus pharmacokinetics in com-

bination therapy with mycophenolic acid and corticosteroids: a

prospective study in one hundred de novo renal transplant

recipients. Clin Pharmacokinet 43:741–762

Kyerematen GA, Morgan M, Warner G et al (1990) Metabolism of

nicotine by hepatocytes. Biochem Pharmacol 40:1747–1756

Laine K, Palovaara S, Tapanainen P et al (1999) Plasma tacrine

concentrations are significantly increased by concomitant hor-

mone replacement therapy. Clin Pharmacol Ther 66:602–608

Lampe JW, Stepaniants SB, Mao M et al (2004) Signatures of

environmental exposures using peripheral leukocyte gene

expression: tobacco smoke. Cancer Epidemiol Biomarkers Prev

13:445–453

Landay RA, Gonzalez MA, Taylor JC (1978) Effect of phenobarbital

on theophylline disposition. J Allergy Clin Immunol 62:27–29

Landi MT, Sinha R, Lang NP et al (1999) Human cytochrome

P4501A2. IARC Sci Publ 173–195

Lasser KE, Allen PD, Woolhandler SJ et al (2002) Timing of new

black box warnings and withdrawals for prescription medica-

tions. JAMA 287:2215–2220

Lau WC, Gurbel PA (2006) Antiplatelet drug resistance and drug–

drug interactions: Role of cytochrome P450 3A4. Pharm Res

23:2691–2708

Lavrijsen KL, Van Houdt JM, Van Dyck DM et al (1988) Is the

metabolism of alfentanil subject to debrisoquine polymorphism?

A study using human liver microsomes. Anesthesiology 69:535–

540

Lecamwasam DS, Franklin C, Turner P (1975) Effect of phenobar-

bitone on hepatic drug-metabolizing enzymes and urinary D-

glucaric acid excretion in man. Br J Clin Pharmacol 2:257–262

LeCluyse EL (2001) Human hepatocyte culture systems for the in

vitro evaluation of cytochrome P450 expression and regulation.

Eur J Pharm Sci 13:343–368

Leemann T, Transon C, Dayer P (1993) Cytochrome P450 TB

(CYP2C): a major monooxygenase catalyzing diclofenac 40-hydroxylation in human liver. Life Sci 52:29–34

Lehmann JM, McKee DD, Watson MA et al (1998) The human

orphan nuclear receptor PXR is activated by compounds that

regulate CYP3A4 gene expression and cause drug interactions. J

Clin Invest 102:1016–1023

Lemaire G, Benod C, Nahoum V et al (2007) Discovery of a highly

active ligand of human pregnane X receptor: a case study from

pharmacophore modeling and virtual screening to ‘‘in vivo’’

biological activity. Mol Pharmacol 72(3):572–851

Lerche-Langrand C, Toutain HJ (2000) Precision-cut liver slices:

characteristics and use for in vitro pharmaco-toxicology. Tox-

icology 153:221–253

Levine M, Sheppard I (1984) Biphasic interaction of phenytoin with

warfarin. Clin Pharm 3:200–203

Lewis DF, Jacobs MN, Dickins M et al (2002) Quantitative structure–

activity relationships for inducers of cytochromes P450 and

nuclear receptor ligands involved in P450 regulation within the

CYP1, CYP2, CYP3 and CYP4 families. Toxicology 176:51–57

Lewis DF (2004) 57 Varieties: the human cytochromes P450.

Pharmacogenomics 5:305–318

Li AP, Gorycki PD, Hengstler JG et al (1999) Present status of the

application of cryopreserved hepatocytes in the evaluation of

xenobiotics: consensus of an international expert panel. Chem

Biol Interact 121:117–123

Li T, Chiang JY (2005) Mechanism of rifampicin and pregnane X

receptor inhibition of human cholesterol 7 alpha-hydroxylase

gene transcription. Am J Physiol Gastrointest Liver Physiol

288:G74–G84

Li T, Chiang JY (2006) Rifampicin induction of CYP3A4 requires

pregnane X receptor cross talk with hepatocyte nuclear factor

4alpha and coactivators, and suppression of small heterodimer

partner gene expression. Drug Metab Dispos 34:756–764

Li Y, Li NY, Sellers EM (1997) Comparison of CYP2A6 catalytic

activity on coumarin 7-hydroxylation in human and monkey

liver microsomes. Eur J Drug Metab Pharmacokinet 22:295–

304

Li XQ, Bjorkman A, Andersson TB et al (2002) Amodiaquine

clearance and its metabolism to N-desethylamodiaquine is

mediated by CYP2C8: a new high affinity and turnover

enzyme-specific probe substrate. J Pharmacol Exp Ther

300:399–407

Li XQ, Bjorkman A, Andersson TB et al (2003) Identification of

human cytochrome P(450)s that metabolise anti-parasitic drugs

and predictions of in vivo drug hepatic clearance from in vitro

data. Eur J Clin Pharmacol 59:429–442

Lieber CS (1999) Microsomal ethanol-oxidizing system (MEOS): the

first 30 years (1968–1998)—a review. Alcohol Clin Exp Res

23:991–1007

706 Arch Toxicol (2008) 82:667–715

123

Lieber CS (2004) The discovery of the microsomal ethanol oxidizing

system and its physiologic and pathologic role. Drug Metab Rev

36:511–529

Lillibridge JH, Liang BH, Kerr BM et al (1998) Characterization of

the selectivity and mechanism of human cytochrome P450

inhibition by the human immunodeficiency virus-protease

inhibitor nelfinavir mesylate. Drug Metab Dispos 26:609–616

Lim ML, Min SS, Eron JJ et al (2004) Coadministration of lopinavir/

ritonavir and phenytoin results in two-way drug interaction

through cytochrome P-450 induction. J Acquir Immune Defic

Syndr 36:1034–1040

Lim PL, Tan W, Latchoumycandane C et al (2007) Molecular and

functional characterization of drug-metabolizing enzymes and

transporter expression in the novel spontaneously immortalized

human hepatocyte line HC-04. Toxicol In Vitro 21:1390–1401

Lin JH, Lu AY (1998) Inhibition and induction of cytochrome P450

and the clinical implications. Clin Pharmacokinet 35:361–390

Liu C, Russell RM, Wang XD (2003) Exposing ferrets to cigarette

smoke and a pharmacological dose of beta-carotene supplemen-

tation enhance in vitro retinoic acid catabolism in lungs via

induction of cytochrome P450 enzymes. J Nutr 133:173–179

Liu YT, Hao HP, Liu CX et al (2007) Drugs as CYP3A probes,

inducers, and inhibitors. Drug Metab Rev 39:699–721

Liu FJ, Song X, Yang D et al (2008) The far and distal enhancers in

the CYP3A4 gene co-ordinate the proximal promoter in

responding similarly to the pregnane X receptor but differen-

tially to hepatocyte nuclear factor-4a. Biochem J 409:243–250

Lo Piparo E, Koehler K et al (2006) Virtual screening for aryl

hydrocarbon receptor binding prediction. J Med Chem 49:5702–

5709

Loboz KK, Gross AS, Williams KM et al (2006) Cytochrome P450

2B6 activity as measured by bupropion hydroxylation: effect of

induction by rifampin and ethnicity. Clin Pharmacol Ther 80:75–

84

London SJ, Idle JR, Daly AK et al (1999) Genetic variation of

CYP2A6, smoking, and risk of cancer. Lancet 353:898–899

Long M, Laier P, Vinggaard AM et al (2003) Effects of currently used

pesticides in the AhR-CALUX assay: comparison between the

human TV101L and the rat H4IIE cell line. Toxicology 194:77–93

Lopez-Cortes LF, Ruiz-Valderas R, Viciana P et al (2002) Pharma-

cokinetic interactions between efavirenz and rifampicin in HIV-

infected patients with tuberculosis. Clin Pharmacokinet 41:681–

690

Lucas D, Menez C, Girre C et al (1995) Decrease in cytochrome

P4502E1 as assessed by the rate of chlorzoxazone hydroxylation

in alcoholics during the withdrawal phase. Alcohol Clin Exp Res

19:362–366

Luo G, Cunningham M, Kim S et al (2002) CYP3A4 induction by

drugs: correlation between a pregnane X receptor reporter gene

assay and CYP3A4 expression in human hepatocytes. Drug


Luo G, Guenthner T, Gan LS et al (2004) CYP3A4 induction by

xenobiotics: biochemistry, experimental methods and impact on

drug discovery and development. Curr Drug Metab 5:483–505

Ma Q (2001) Induction of CYP1A1. The AhR/DRE paradigm:

transcription, receptor regulation, and expanding biological

roles. Curr Drug Metab 2:149–164

Ma Q, Lu AY (2007) CYP1A induction and human risk assessment:

an evolving tale of in vitro and in vivo studies. Drug Metab

Dispos 35:1009–1016

Ma X, Idle JR, Krausz KW et al (2005) Metabolism of melatonin by

human cytochromes p450. Drug Metab Dispos 33:489–494

Ma X, Shah Y, Cheung C et al (2007) The PREgnane X receptor

gene-humanized mouse: a model for investigating drug–drug

interactions mediated by cytochromes P450 3A. Drug Metab

Dispos 35:194–200

Madan A, Usuki E, Burton LA et al (2002) In vitro approaches for

studying the inhibition of drug-metabolizing enzymes responsi-

ble for the metabolism of drugs. In: Rodrigues AD (ed) Drug–

drug interactions: from basic pharmacokinetic concepts to

marketing issues. Marcel-Dekker, London

Madan A, Graham RA, Carroll KM et al (2003) Effects of prototypical

microsomal enzyme inducers on cytochrome P450 expression in

cultured human hepatocytes. Drug Metab Dispos 31:421–431

Maenpaa J, Juvonen R, Raunio H et al (1994) Metabolic interactions

of methoxsalen and coumarin in humans and mice. Biochem

Pharmacol 48(7):1363–1369

Maenpaa J, Hall SD, Ring BJ et al (1998) Human cytochrome P450 3A

(CYP3A) mediated midazolam metabolism: the effect of assay

conditions and regioselective stimulation by alpha-naphthoflav-

one, terfenadine and testosterone. Pharmacogenetics 8:137–155

Maglich JM, Parks DJ, Moore LB et al (2003) Identification of a

novel human constitutive androstane receptor (CAR) agonist and

its use in the identification of CAR target genes. J Biol Chem

278(19):17277–17283

Makinen J, Frank C, Jyrkkarinne J et al (2002) Modulation of mouse

and human phenobarbital-responsive enhancer module by

nuclear receptors. Mol Pharmacol 62(2):366–378

Makinen J, Reinisalo M, Niemi K et al (2003) Dual action of

oestrogens on the mouse constitutive androstane receptor.

Biochem J 376:465–472

Manno M, Rezzadore M, Grossi M et al (1996) Potentiation of

occupational carbon tetrachloride toxicity by ethanol abuse.

Hum Exp Toxicol 15:294–300

Martin H, Sarsat JP, de Waziers I et al (2003) Induction of

cytochrome P450 2B6 and 3A4 expression by phenobarbital

and cyclophosphamide in cultured human liver slices. Pharm Res

20:557–568

Martin P, Riley R, Back DJ et al (2008) Comparison of the induction

profile for drug disposition proteins by typical nuclear receptor

activators in human hepatic and intestinal cells. Br J Pharmacol

153(4):805–819

Maruyama M, Matsunaga T, Harada E et al (2007) Comparison of

basal gene expression and induction of CYP3As in HepG2 and

human fetal liver cells. Biol Pharm Bull 30(11):2091–2097

Masuyama H, Suwaki N, Tateishi Y et al (2005) The pregnane X

receptor regulates gene expression in a ligand- and promoter-

selective fashion. Mol Endocrinol 19:1170–1180

Matsunaga T, Maruyama M, Harada E et al (2004) Expression and

induction of CYP3As in human fetal hepatocytes. Biochem

Biophys Res Commun 318(2):428–434

Mazze RI, Woodruff RE, Heerdt ME (1982) Isoniazid-induced

enflurane defluorination in humans. Anesthesiology 57:5–8

McCarver DG, Hines RN (2002) The ontogeny of human drug-

metabolizing enzymes: phase II conjugation enzymes and

regulatory mechanisms. J Pharmacol Exp Ther 300:361–366

McCune JS, Hawke RL, LeCluyse EL et al (2000) In vivo and in vitro

induction of human cytochrome P4503A4 by dexamethasone.


McDonnell WM, Scheiman JM, Traber PG (1992) Induction of

cytochrome P450IA genes (CYP1A) by omeprazole in the

human alimentary tract. Gastroenterology 103:1509–1516

McLellan RA, Drobitch RK, Monshouwer M et al (1996) Fluoro-

quinolone antibiotics inhibit cytochrome P450-mediated

microsomal drug metabolism in rat and human. Drug Metab

Dispos 24:1134–1138

Mekenyan OG, Veith GD, Call DJ et al (1996) A QSAR evaluation of

Ah receptor binding of halogenated aromatic xenobiotics.

Environ Health Perspect 104:1302–1310

Messina ES, Tyndale RF, Sellers EM (1997) A major role for

CYP2A6 in nicotine C-oxidation by human liver microsomes. J

Pharmacol Exp Ther 282:1608–1614

Arch Toxicol (2008) 82:667–715 707

123

Mihara K, Svensson US, Tybring G et al (1999) Stereospecific

analysis of omeprazole supports artemisinin as a potent inducer

of CYP2C19. Fundam Clin Pharmacol 13:671–675

Miki Y, Suzuki T, Tazawa C et al (2005) Steroid and xenobiotic

receptor (SXR), cytochrome P450 3A4 and multidrug resistance

gene 1 in human adult and fetal tissues. Mol Cell Endocrinol

231:75–85

Mildvan D, Yarrish R, Marshak A et al (2002) Pharmacokinetic

interaction between nevirapine and ethinyl estradiol/norethin-

drone when administered concurrently to HIV-infected women. J

Acquir Immune Defic Syndr 29:471–477

Miller M, Cosgriff J, Kwong T et al (1984) Influence of phenytoin on

theophylline clearance. Clin Pharmacol Ther 35:666–669

Mimura J, Ema M, Sogawa K et al (1999) Identification of a novel

mechanism of regulation of Ah (dioxin) receptor function. Genes

Dev 13:20–25

Miners JO, Coulter S, Tukey RH et al (1996) Cytochromes P450,

1A2, and 2C9 are responsible for the human hepatic O-

demethylation of R- and S-naproxen. Biochem Pharmacol

51:1003–1008

Miners JO, Birkett DJ (1998) Cytochrome P4502C9: an enzyme of

major importance in human drug metabolism. Br J Clin


Mollerup S, Ryberg D, Hewer A et al (1999) Sex differences in lung

CYP1A1 expression and DNA adduct levels among lung cancer

patients. Cancer Res 59:3317–3320

Moore LB, Parks DJ, Jones SA et al (2000) Orphan nuclear receptors

constitutive androstane receptor and pregnane X receptor share

xenobiotic and steroid ligands. J Biol Chem 275:15122–15127

Moore LB, Maglich JM, McKee DD et al (2002) Pregnane X receptor

(PXR), constitutive androstane receptor (CAR), and benzoate X

receptor (BXR) define three pharmacologically distinct classes

of nuclear receptors. Mol Endocrinol 16:977–986

Moriguchi T, Motohashi H, Hosoya T et al (2003) Distinct response

to dioxin in an arylhydrocarbon receptor (AHR)-humanized

mouse. Proc Natl Acad Sci USA 100:5652–5657

Mortimer O, Persson K, Ladona MG et al (1990) Polymorphic

formation of morphine from codeine in poor and extensive

metabolizers of dextromethorphan: relationship to the presence

of immunoidentified cytochrome P-450IID1. Clin Pharmacol

Ther 47:27–35

Mouly S, Lown KS, Kornhauser D et al (2002) Hepatic but not

intestinal CYP3A4 displays dose-dependent induction by efavi-

renz in humans. Clin Pharmacol Ther 72:1–9

Murk AJ, Legler J, Denison MS et al (1996) Chemical-activated

luciferase gene expression (CALUX): a novel in vitro bioassay

for Ah receptor active compounds in sediments and pore water.

Fundam Appl Toxicol 33:149–160

Nabuurs SB, Wagener M, de Vlieg J (2007) A flexible approach to

induced fit docking. J Med Chem 50:6507–6518

Nagy SR, Sanborn JR, Hammock BD et al (2002) Development of a

green fluorescent protein-based cell bioassay for the rapid and

inexpensive detection and characterization of Ah receptor

agonists. Toxicol Sci 65:200–210

Nakajima M, Yokoi T, Mizutani M et al (1994) Phenotyping of

CYP1A2 in Japanese population by analysis of caffeine urinary

metabolites: absence of mutation prescribing the phenotype in

the CYP1A2 gene. Cancer Epidemiol Biomarkers Prev 3:413–

421

Nakajima M, Yamamoto T, Nunoya K et al (1996a) Role of human

cytochrome P4502A6 in C-oxidation of nicotine. Drug Metab

Dispos 24:1212–1217

Nakajima M, Yamamoto T, Nunoya K et al (1996b) Characterization

of CYP2A6 involved in 30-hydroxylation of cotinine in human

liver microsomes. J Pharmacol Exp Ther 277:1010–1015

Nakajima M, Inoue T, Shimada N et al (1998) Cytochrome P450 2C9

catalyzes indomethacin O-demethylation in human liver micro-

somes. Drug Metab Dispos 26:261–266

Nakamura K, Moore R, Negishi M et al (2007) Nucar pregnane X

receptor cross-talk with FoxA2 to mediate drug-induced regu-

lation of lipid metabolism in fasting mouse liver. J Biol Chem

282:9768–9776

Nebert DW, Dalton TP (2006) The role of cytochrome P450 enzymes

in endogenous signalling pathways and environmental carcino-

genesis. Nat Rev Cancer 6:947–960

Nebert DW, Zhang G, Vesell ES (2008) From human genetics and

genomics to pharmacogenetics and pharmacogenomics: past

lessons, future directions. Drug Metab Rev 40:187–224

Nelson DR, Zeldin DC, Hoffman SM et al (2004) Comparison of

cytochrome P450 (CYP) genes from the mouse and human

genomes, including nomenclature recommendations for genes,

pseudogenes and alternative-splice variants. Pharmacogenetics

14:1–18

Newton DJ, Wang RW, Lu AY (1995) Cytochrome P450 inhibitors.

Evaluation of specificities in the in vitrometabolism of thera-

peutic agents by human liver microsomes. Drug Metab Dispos

23:154–158

Nguyen LP, Bradfield CA (2008) The search for endogenous

activators of the aryl hydrocarbon receptor. Chem Res Toxicol

21:102–116

Nielsen TL, Rasmussen BB, Flinois JP et al (1999) In vitro

metabolism of quinidine: the (3S)-3-hydroxylation of quinidine

is a specific marker reaction for cytochrome P-4503A4 activity

in human liver microsomes. J Pharmacol Exp Ther 289:31–37

Niemi M, Backman JT, Neuvonen M et al (2000) Rifampin decreases

the plasma concentrations and effects of repaglinide. Clin


Niemi M, Backman JT, Neuvonen M et al (2001) Effects of rifampin

on the pharmacokinetics and pharmacodynamics of glyburide

and glipizide. Clin Pharmacol Ther 69:400–406

Niemi M, Leathart JB, Neuvonen M et al (2003a) Polymorphism in

CYP2C8 is associated with reduced plasma concentrations of

repaglinide. Clin Pharmacol Ther 74:380–387

Niemi M, Backman JT, Fromm MF et al (2003b) Pharmacokinetic

interactions with rifampicin: clinical relevance. Clin Pharmaco-

kinet 42:819–850

Niemi M, Backman JT, Neuvonen PJ (2004) Effects of trimethoprim

and rifampin on the pharmacokinetics of the cytochrome P450

2C8 substrate rosiglitazone. Clin Pharmacol Ther 76:239–249

Nishimura M, Naito S, Yokoi T (2004) Tissue-specific mRNA

expression profiles of human nuclear receptor subfamilies. Drug

Metab Pharmacokinet 19:135–149

Nishimura M, Yoshitsugu H, Yokoi T et al (2005) Evaluation of

mRNA expression of human drug-metabolizing enzymes and

transporters in chimeric mouse with humanized liver. Xenobio-

tica 35:877–890

Nishizato Y, Ieiri I, Suzuki H et al (2003) Polymorphisms of

OATP-C (SLC21A6) and OAT3 (SLC22A8) genes: conse-

quences for pravastatin pharmacokinetics. Clin Pharmacol Ther

73:554–565

Niwa T, Shiraga T, Takagi A (2005) Effect of antifungal drugs on

cytochrome P450 (CYP) 2C9, CYP2C19, and CYP3A4 activities

in human liver microsomes. Biol Pharm Bull 28:1805–1808

Nunoya K, Yokoi Y, Kimura K et al (1996) (+)-cis-3, 5-Dimethyl-2-

(3-pyridyl) thiazolidin-4-one hydrochloride (SM-12502) as a

novel substrate for cytochrome P450 2A6 in human liver

microsomes. J Pharmacol Exp Ther 277:768–774

Obach RS, Walsky RL, Venkatakrishnan K et al (2006) The utility of

in vitro cytochrome P450 inhibition data in the prediction of

drug–drug interactions. J Pharmacol Exp Ther 316:336–348

708 Arch Toxicol (2008) 82:667–715

123

Oda Y, Furuichi K, Tanaka K et al (1995) Metabolism of a new local

anesthetic, ropivacaine, by human hepatic cytochrome P450.

Anesthesiology 82:214–220

Oda Y, Hamaoka N, Hiroi T et al (2001) Involvement of human liver

cytochrome P4502B6 in the metabolism of propofol. Br J Clin


Ogg MS, Williams JM, Tarbit M et al (1999) A reporter gene assay to

assess the molecular mechanisms of xenobiotic-dependent

induction of the human CYP3A4 gene in vitro. Xenobiotica

29:269–279

Ogilvie BW, Zhang D, Li W et al (2006) Glucuronidation converts

gemfibrozil to a potent, metabolism-dependent inhibitor of

CYP2C8: implications for drug–drug interactions. Drug Metab

Dispos 34:191–197

Ogiso T, Iwaki M, Uno S (1995) Inhibition kinetics of theophylline

metabolism by mexiletine and its metabolites. Biol Pharm Bull

18:75–81

Ohyama K, Nakajima M, Nakamura S et al (2000) A significant role

of human cytochrome P450 2C8 in amiodarone N-deethylation:

an approach to predict the contribution with relative activity

factor. Drug Metab Dispos 28:1303–1310

Olesen OV, Linnet K (2001) Contributions of five human cytochrome

P450 isoforms to the N-demethylation of clozapine in vitro at

low and high concentrations. J Clin Pharmacol 41:823–832

Oneta CM, Lieber CS, Li J et al (2002) Dynamics of cytochrome

P4502E1 activity in man: induction by ethanol and disappear-

ance during withdrawal phase. J Hepatol 36:47–52

Ono S, Hatanaka T, Hotta H et al (1995) Chlorzoxazone is

metabolized by human CYP1A2 as well as by human CYP2E1.

Pharmacogenetics 5:143–150

Orans J, Teotico DG, Redinbo MR (2005) The nuclear xenobiotic

receptor pregnane X receptor: recent insights and new chal-

lenges. Mol Endocrinol 19:2891–2900

O’Reilly RA (1974) Interaction of sodium warfarin and rifampin.

Studies in man. Ann Intern Med 81:337–340

O’Reilly RA, Trager WF, Motley CH et al (1980) Interaction of

secobarbital with warfarin pseudoracemates. Clin Pharmacol

Ther 28:187–195

Orlando R, Piccoli P, De Martin S et al (2004) Cytochrome P450 1A2

is a major determinant of lidocaine metabolism in vivo: effects

of liver function. Clin Pharmacol Ther 75:80–88

Orme M, Breckenridge A (1976) Enantiomers of warfarin and

phenobarbital. N Engl J Med 295:1482–1483

Osabe M, Sugatani J, Takemura A et al (2008) Expression of CAR in

SW480 and HepG2 cells during G1 is associated with cell

proliferation. Biochem Biophys Res Commun 369:1027–1033

O’Shea D, Kim RB, Wilkinson GR (1997) Modulation of CYP2E1

activity by isoniazid in rapid and slow N-acetylators. Br J Clin


Otton SV, Inaba T, Kalow W (1984) Competitive inhibition of

sparteine oxidation in human liver by beta-adrenoceptor antag-

onists and other cardiovascular drugs. Life Sci 34:73–80

Otton SV, Brinn RU, Gram LF (1988) In vitro evidence against the

oxidation of quinidine by the sparteine/debrisoquine monooxy-

genase of human liver. Drug Metab Dispos 16:15–17

Ourlin JC, Lasserre F, Pineau T et al (2003) The small heterodimer

partner interacts with the pregnane X receptor and represses its

transcriptional activity. Mol Endocrinol 17:1693–1703

Paine MF, Hart HL, Ludington SS et al (2006) The human intestinal

cytochrome P450 ‘‘pie’’. Drug Metab Dispos 34:880–886

Paladino JA, Blumer NA, Maddox RR (1983) Effect of secobarbital

on theophylline clearance. Ther Drug Monit 5:135–139

Palovaara S, Pelkonen O, Uusitalo J et al (2003) Inhibition of

cytochrome P450 2B6 activity by hormone replacement therapy

and oral contraceptive as measured by bupropion hydroxylation.


Park BK, Kitteringham NR, Pirmohamed M et al (1996) Relevance of

induction of human drug-metabolizing enzymes: pharmacolog-

ical and toxicological implications. Br J Clin Pharmacol 41:477–

491

Park JY, Kim KA, Kang MH et al (2004) Effect of rifampin on the

pharmacokinetics of rosiglitazone in healthy subjects. Clin


Parker AC, Pritchard P, Preston T et al (1998) Induction of CYP1A2

activity by carbamazepine in children using the caffeine breath

test. Br J Clin Pharmacol 45:176–178

Parkinson A, Mudra DR, Johnson C et al (2004) The effects of gender,

age, ethnicity, and liver cirrhosis on cytochrome P450 enzyme

activity in human liver microsomes and inducibility in cultured

human hepatocytes. Toxicol Appl Pharmacol 199:193–209

Pascussi JM, Gerbal-Chaloin S, Duret C et al (2008) The tangle of

nuclear receptors that controls xenobiotic metabolism and

transport: crosstalk and consequences. Annu Rev Pharmacol

Toxicol 48:1–32

Patki KC, Von Moltke LL, Greenblatt DJ (2003) In vitro metabolism

of midazolam, triazolam, nifedipine, and testosterone by human

liver microsomes and recombinant cytochromes p450: role of

cyp3a4 and cyp3a5. Drug Metab Dispos 31:938–944

Pearce R, Greenway D, Parkinson A (1992) Species differences and

interindividual variation in liver microsomal cytochrome P450

2A enzymes: effects on coumarin, dicumarol, and testosterone

oxidation. Arch Biochem Biophys 298:211–225

Pearce RE, Rodrigues AD, Goldstein JA et al (1996) Identification of

the human P450 enzymes involved in lansoprazole metabolism. J

Pharmacol Exp Ther 277:805–816

Pelkonen O, Sotaniemi EA, Ahokas JT (1985) Coumarin 7-hydrox-

ylase activity in human liver microsomes. Properties of the

enzyme and interspecies comparisons. Br J Clin Pharmacol

19:59–66

Pelkonen O, Maenpaa J, Taavitsainen P et al (1998) Inhibition andinduction of human cytochrome P450 (CYP) enzymes. Xeno-

biotica 28:1203–1253

Pelkonen O, Rautio A, Raunio H et al (2000) CYP2A6: a human

coumarin 7-hydroxylase. Toxicology 144:139–147

Pelkonen O, Turpeinen M, Uusitalo J et al (2005) Prediction of drug

metabolism and interactions on the basis of in vitro investiga-

tions. Basic Clin Pharmacol Toxicol 96:167–175

Pelkonen O, Kapitulnik J, Gundert-Remy U et al (2008) Local

kinetics and dynamics of xenobiotics. Crit Rev Toxicol, in press

Perrot N, Nalpas B, Yang CS et al (1989) Modulation of cytochrome

P450 isozymes in human liver, by ethanol and drug intake. Eur J

Clin Invest 19:549–555

Persson KP, Ekehed S, Otter C et al (2006) Evaluation of human liver

slices and reporter gene assays as systems for predicting the

cytochrome P450 induction potential of drugs in vivo in humans.

Pharm Res 23:56–69

Perucca E (2006) Clinically relevant drug interactions with antiep-

ileptic drugs. Br J Clin Pharmacol 61:246–255

Perucca E, Grimaldi R, Frigo GM et al (1988) Comparative effects of

rifabutin and rifampicin on hepatic microsomal enzyme activity

in normal subjects. Eur J Clin Pharmacol 34:595–599

Pfrunder A, Gutmann H, Beglinger C et al (2003) Gene expression of

CYP3A4, ABC-transporters (MDR1 and MRP1-MRP5) and

hPXR in three different human colon carcinoma cell lines. J

Pharm Pharmacol 55:59–66

Pinto AG, Wang YH, Chalasani N et al (2005) Inhibition of human

intestinal wall metabolism by macrolide antibiotics: effect of

clarithromycin on cytochrome P450 3A4/5 activity and expres-

sion. Clin Pharmacol Ther 77:178–188

Plant N (2007) The human cytochrome P450 sub-family: transcrip-

tional regulation, inter-individual variation and interaction

networks. Biochim Biophys Acta 1770:478–488

Arch Toxicol (2008) 82:667–715 709

123

Pollock BG, Wylie M, Stack JA et al (1999) Inhibition of caffeine

metabolism by estrogen replacement therapy in postmenopausal

women. J Clin Pharmacol 39:936–940

Poso A, Honkakoski P (2006) Ligand recognition by drug-activated

nuclear receptors PXR and CAR: structural, site-directed muta-

genesis and molecular modeling studies. Mini Rev Med Chem

6:937–947

Projean D, Baune B, Farinotti R et al (2003) In vitro metabolism of

chloroquine: identification of CYP2C8, CYP3A4, and CYP2D6

as the main isoforms catalyzing N-desethylchloroquine forma-

tion. Drug Metab Dispos 31:748–754

Prueksaritanont T, Gorham LM, Ma B et al (1997) In vitro

metabolism of simvastatin in humans [SBT]identification of

metabolizing enzymes and effect of the drug on hepatic P450s.


Prueksaritanont T, Ma B, Yu N (2003) The human hepatic

metabolism of simvastatin hydroxy acid is mediated primarily

by CYP3A, and not CYP2D6. Br J Clin Pharmacol 56:120–124

Puurunen J, Pelkonen O (1979) Cimetidine inhibits microsomal drug

metabolism in the rat. Eur J Pharmacol 55:335–336

Rae JM, Soukhova NV, Flockhart DA et al (2002) Triethylenethio-

phosphoramide is a specific inhibitor of cytochrome P450 2B6:

implications for cyclophosphamide metabolism. Drug Metab

Dispos 30:525–530

Raffalli-Mathieu F, Glisovic T, Ben-David Y et al (2002) Heteroge-

neous nuclear ribonucleoprotein A1 and regulation of the

xenobiotic-inducible gene Cyp2a5. Mol Pharmacol 61:795–799

Ramırez J, Innocenti F, Schuetz EG et al (2004) CYP2B6, CYP3A4,

and CYP2C19 are responsible for the in vitro N-demethylation of

meperidine in human liver microsomes. Drug Metab Dispos

32:930–936

Rasheed A, Hines RN, McCarver-May DG (1997) Variation in

induction of human placental CYP2E1: possible role in suscep-

tibility to fetal alcohol syndrome? Toxicol Appl Pharmacol

144:396–400

Rasmussen BB, Maenpaa J, Pelkonen O et al (1995) Selective

serotonin reuptake inhibitors and theophylline metabolism in

human liver microsomes: potent inhibition by fluvoxamine. Br J


Rasmussen BB, Brix TH, Kyvik KO et al (2002) The interindividual

differences in the 3-demethylation of caffeine alias CYP1A2 is

determined by both genetic and environmental factors. Pharma-

cogenetics 12:473–478

Raucy JL, Kraner JC, Lasker JM (1993) Bioactivation of halogenated

hydrocarbons by cytochrome P4502E1. Crit Rev Toxicol 23:1–20

Raucy JL, Schultz ED, Wester MR et al (1997) Human lymphocyte

cytochrome P450 2E1, a putative marker for alcohol-mediated

changes in hepatic chlorzoxazone activity. Drug Metab Dispos

25:1429–1435

Raucy JL, Schultz ED, Kearins MC et al (1999) CYP2E1 expression

in human lymphocytes from various ethnic populations. Alcohol

Clin Exp Res 23:1868–1874

Raunio H, Rautio A, Gullsten H et al (2001) Polymorphisms of

CYP2A6 and its practical consequences. Br J Clin Pharmacol

52:357–363

Reed GA, Peterson KS, Smith HJ et al (2005) A phase I study of

indole-3-carbinol in women: tolerability and effects. Cancer

Epidemiol Biomarkers Prev 14:1953–1960

Relling MV, Aoyama T, Gonzalez FJ et al (1990) Tolbutamide and

mephenytoin hydroxylation by human cytochrome P450s in the

CYP2C subfamily. J Pharmacol Exp Ther 252:442–447

Rencurel F, Foretz M, Kaufmann MR et al (2006) Stimulation of

AMP-activated protein kinase is essential for the induction of

drug metabolizing enzymes by phenobarbital in human and

mouse liver. Mol Pharmacol 70:1925–1934

Rencurel F, Stenhouse A, Hawley SA et al (2005) AMP-activated

protein kinase mediates phenobarbital induction of CYP2B gene

expression in hepatocytes and a newly derived human hepatoma

cell line. J Biol Chem 280:4367–4373

Rendic S, Sunjic V, Toso R et al (1979) Interaction of cimetidine with

liver microsomes. Xenobiotica 9:555–564

Rendic S (2002) Summary of information on human CYP enzymes:

human P450 metabolism data. Drug Metab Rev 34:83–448

Reschly EJ, Krasowski MD (2006) Evolution and function of the

NR1I nuclear hormone receptor subfamily (VDR, PXR, and

CAR) with respect to metabolism of xenobiotics and endogenous

compounds. Curr Drug Metab 7:349–365

Richter E, Breimer DD, Zilly W (1980) Disposition of hexobarbital in

intra- and extrahepatic cholestasis in man and the influence of

drug metabolism-inducing agents. Eur J Clin Pharmacol 17:197–

202

Richter T, Murdter TE, Heinkele G et al (2004) Potent mechanism-

based inhibition of human CYP2B6 by clopidogrel and ticlopi-

dine. J Pharmacol Exp Ther 308:189–197

Richter T, Schwab M, Eichelbaum M et al (2005) Inhibition of human

CYP2B6 by N, N0, N00-triethylenethiophosphoramide is irrevers-

ible and mechanism-based. Biochem Pharmacol 69:517–524

Ring BJ, Gillespie JS, Eckstein JA et al (2002) Identification of the

human cytochromes P450 responsible for atomoxetine metabo-

lism. Drug Metab Dispos 30:319–323

Rivera SP, Saarikoski ST, Hankinson O (2002) Identification of a

novel dioxin-inducible cytochrome P450. Mol Pharmacol

61:255–259

Roberts EA, Johnson KC, Harper PA et al (1990) Characterization of

the Ah receptor mediating aryl hydrocarbon hydroxylase induc-

tion in the human liver cell line Hep G2. Arch Biochem Biophys

276:442–450

Robertson P Jr, Hellriegel ET, Arora S et al (2002) Effect of modafinil

on the pharmacokinetics of ethinyl estradiol and triazolam in

healthy volunteers. Clin Pharmacol Ther 71:46–56

Rochat B, Morsman JM, Murray GI et al (2001) Human CYP1B1 and

anticancer agent metabolism: mechanism for tumor-specific drug

inactivation? J Pharmacol Exp Ther 296:537–541

Rodrigues AD, Kukulka MJ, Roberts EM et al (1996) [O-methyl

14C]naproxen O-demethylase activity in human liver micro-

somes: evidence for the involvement of cytochrome P4501A2

and P4502C9/10. Drug Metab Dispos 24:126–136

Rodrıguez-Antona C, Donato MT, Boobis A et al (2002) Cytochrome

P450 expression in human hepatocytes and hepatoma cell lines:

molecular mechanisms that determine lower expression in

cultured cells. Xenobiotica 32:505–520

Rodriguez-Antona C, Niemi M, Backman JT et al (2007) Character-

ization of novel CYP2C8 haplotypes and their contribution to

paclitaxel and repaglinide metabolism. Pharmacogenomics J.

doi:10.1038/sj.tpj.6500482

Rostami-Hodjegan A, Tucker GT (2007) Simulation and prediction of

in vivo drug metabolism in human populations from in vitro

data. Nat Rev Drug Discov 6:140–148

Rouleau N, Turcotte S, Mondou MH et al (2003) Development of a

versatile platform for nuclear receptor screening using Alpha-

Screen. J Biomol Screen 8:191–197

Roy P, Yu LJ, Crespi CL et al (1999a) Development of a substrate-

activity based approach to identify the major human liver P-450

catalysts of cyclophosphamide and ifosfamide activation based

on cDNA-expressed activities and liver microsomal P-450

profiles. Drug Metab Dispos 7:655–666

Roy P, Tretyakov O, Wright J et al (1999b) Stereoselective

metabolism of ifosfamide by human P-450s 3A4 and 2B6.

Favorable metabolic properties of R-enantiomer. Drug Metab

Dispos 7:1309–1318

710 Arch Toxicol (2008) 82:667–715

123

http://dx.doi.org/10.1038/sj.tpj.6500482

Roymans D, Annaert P, Van Houdt J et al (2005) Expression and

induction potential of cytochromes P450 in human cryopre-

served hepatocytes. Drug Metab Dispos 33:1004–1016

Rumack BH (2004) Acetaminophen misconceptions. Hepatology

40:10–15

Saarikoski ST, Rivera SP, Hankinson O et al (2005) CYP2S1: a short

review. Toxicol Appl Pharmacol 207:62–69

Sachse C, Brockmoller J, Bauer S et al (1999) Functional significance

of a C ? A polymorphism in intron 1 of the cytochrome P450

CYP1A2 gene tested with caffeine. Br J Clin Pharmacol 47:445–

449

Sahi J, Milad MA, Zheng X et al (2003) Avasimibe induces CYP3A4

and multiple drug resistance protein 1 gene expression through

activation of the pregnane X receptor. J Pharmacol Exp Ther

306:1027–1034

Sanderink GJ, Bournique B, Stevens J et al (1997) Involvement of

human CYP1A isoenzymes in the metabolism and drug interac-

tions of riluzole in vitro. J Pharmacol Exp Ther 282:1465–1472

Sarkar MA, Jackson BJ (1994) Theophylline N-demethylations as

probes for P4501A1 and P4501A2. Drug Metab Dispos 22:827–

834

Saussele T, Burk O, Blievernicht JK et al (2007) Selective induction

of human hepatic cytochromes P450 2B6 and 3A4 by metam-

izole. Clin Pharmacol Ther 82:265–274

Schmider J, Greenblatt DJ, Fogelman SM et al (1997) Metabolism of

dextromethorphan in vitro: involvement of cytochromes P450

2D6 and 3A3/4, with a possible role of 2E1. Biopharm Drug

Dispos 18:227–240

Schmider J, von Moltke LL, Shader RI et al (1999) Extrapolating in

vitro data on drug metabolism to in vivo pharmacokinetics:

evaluation of the pharmacokinetic interaction between amitrip-

tyline and fluoxetine. Drug Metab Rev 31:545–560

Schmiedlin-Ren P, Thummel KE, Fisher JM et al (1997) Expression

of enzymatically active CYP3A4 by Caco-2 cells grown on

extracellular matrix-coated permeable supports in the presence

of 1a, 25-dihydroxyvitamin D3. Mol Pharmacol 51:741–754

Schneck DW, Birmingham BK, Zalikowski JA et al (2004) The effect

of gemfibrozil on the pharmacokinetics of rosuvastatin. Clin


Schuetz JD, Beach DL, Guzelian PS (1994) Selective expression of

cytochrome P450 CYP3A mRNAs in embryonic and adult

human liver. Pharmacogenetics 4:11–20

Schuster D, Langer T (2005) The identification of ligand features

essential for PXR activation by pharmacophore modeling. J

Chem Inf Model 45:431–439

Schuster D, Steindl TM, Langer T (2006) Predicting drug metabolism

induction in silico. Curr Top Med Chem 6:1627–1640

Scott EE, Halpert JR (2005) Structures of cytochrome P450 3A4.

Trends Biochem Sci 30:5–7

Seidel SD, Li V, Winter GM et al (2000) Ah receptor-based chemical

screening bioassays: application and limitations for the detection

of Ah receptor agonists. Toxicol Sci 55:107–115

Seliskar M, Rozman D (2007) Mammalian cytochromes P450—

importance of tissue specificity. Biochim Biophys Acta

1770:458–466

Sesardic D, Boobis AR, Edwards RJ et al (1988) A form of

cytochrome P450 in man, orthologous to form d in the rat,

catalyses the O-deethylation of phenacetin and is inducible by

cigarette smoking. Br J Clin Pharmacol 26:363–372

Sesardic D, Pasanen M, Pelkonen O et al (1990) Differential expression

and regulation of members of the cytochrome P450IA gene

subfamily in human tissues. Carcinogenesis 11:1183–1188

Shadle CR, Lee Y, Majumdar AK et al (2004) Evaluation of potential

inductive effects of aprepitant on cytochrome P450 3A4 and 2C9

activity. J Clin Pharmacol 44:215–223

Shan L, Vincent J, Brunzelle JS et al (2004) Structure of the murine

constitutive androstane receptor complexed to androstenol: a

molecular basis for inverse agonism. Mol Cell 16:907–917

Sherman W, Day T, Jacobson MP et al (2006) Novel procedure for

modeling ligand/receptor induced fit effects. J Med Chem

49:534–553

Shet MS, McPhaul M, Fisher CW et al (1997) Metabolism of the

antiandrogenic drug (Flutamide) by human CYP1A2. Drug


Shimada T, Hayes CL, Yamazaki H et al (1996a) Activation of

chemically diverse procarcinogens by human cytochrome P-450

1B1. Cancer Res 56:2979–2984

Shimada T, Yamazaki H, Guengerich FP (1996b) Ethnic-related

differences in coumarin 7-hydroxylation activities catalyzed by

cytochrome P4502A6 in liver microsomes of Japanese and

Caucasian populations. Xenobiotica 26:395–403

Shitara Y, Hirano M, Sato H et al (2004) Gemfibrozil and its

glucuronide inhibit the organic anion transporting polypeptide 2

(OATP2/OATP1B1:SLC21A6)-mediated hepatic uptake and

CYP2C8-mediated metabolism of cerivastatin: analysis of the

mechanism of the clinically relevant drug–drug interaction

between cerivastatin and gemfibrozil. J Pharmacol Exp Ther

311:228–236

Simonsson US, Jansson B, Hai TN et al (2003) Artemisinin

autoinduction is caused by involvement of cytochrome P450

2B6 but not 2C9. Clin Pharmacol Ther 74:32–43

Sinz M, Kim S, Zhu Z et al (2006) Evaluation of 170 xenobiotics as

transactivators of human pregnane X receptor (hPXR) and

correlation to known CYP3A4 drug interactions. Curr Drug

Metab 7:375–388

Slattery JT, Kalhorn TF, McDonald GB et al (1996) Conditioning

regimen-dependent disposition of cyclophosphamide and hy-

droxycyclophosphamide in human marrow transplantation

patients. J Clin Oncol 14:1484–1494

Smith DA (2000) Induction and drug development. Eur J Pharm Sci

11:185–189

Smith GB, Bend JR, Bedard LL et al (2003a) Biotransformation of 4-

(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) in periph-

eral human lung microsomes. Drug Metab Dispos 31:1134–1141

Smith G, Wolf CR, Deeni YY et al (2003b) Cutaneous expression of

cytochrome P450 CYP2S1: individuality in regulation by

therapeutic agents for psoriasis and other skin diseases. Lancet

361:1336–1343

Smith G, Ibbotson SH, Comrie MM et al (2006) Regulation of

cutaneous drug-metabolizing enzymes and cytoprotective gene

expression by topical drugs in human skin in vivo. Br J Dermatol

155:275–281

Smith DA, Dickins M, Fahmi OA et al (2007) The time to move

cytochrome p450 induction into mainstream pharmacology is

long overdue. Drug Metab Dispos 35:697–698

Soars MG, Petullo DM, Eckstein JA et al (2004) An assessment of

UDP-glucuronosyltransferase induction using primary human

hepatocytes. Drug Metab Dispos 32:140–148

Soars MG, Grime K, Riley RJ (2006) Comparative analysis of

substrate and inhibitor interactions with CYP3A4 and CYP3A5.

Xenobiotica 36:287–299

Solas C, Poizot-Martin I, Drogoul MP et al (2004) Therapeutic drug

monitoring of lopinavir/ritonavir given alone or with a non-

nucleoside reverse transcriptase inhibitor. Br J Clin Pharmacol

57:436–440

Song BJ, Veech RL, Park SS et al (1989) Induction of rat hepatic N-

nitrosodimethylamine demethylase by acetone is due to protein

stabilization. J Biol Chem 264:3568–3572

Sotaniemi EA, Rautio A, Backstrom M et al (1995) CYP3A4 and

CYP2A6 activities marked by the metabolism of lignocaine and

Arch Toxicol (2008) 82:667–715 711

123

coumarin in patients with liver and kidney diseases and epileptic

patients. Br J Clin Pharmacol 39:71–76

Soyama A, Hanioka N, Saito Y et al (2002) Amiodarone N-

deethylation by CYP2C8 and its variants, CYP2C8*3 and

CYP2C8 P404A. Pharmacol Toxicol 91:174–178

Spaldin V, Madden S, Adams DA et al (1995) Determination of

human hepatic cytochrome P4501A2 activity in vitro use of

tacrine as an isoenzyme-specific probe. Drug Metab Dispos

23:929–934

Squires EJ, Sueyoshi T, Negishi M (2004) Cytoplasmic localization

of pregnane X receptor and ligand-dependent nuclear transloca-

tion in mouse liver. J Biol Chem 279: 49307–49314

Staiger C, Schlicht F, Walter E et al (1983) Effect of single and

multiple doses of sulphinpyrazone on antipyrine metabolism and

urinary excretion of 6-beta-hydroxycortisol. Eur J Clin Pharma-

col 25:797–801

Stanley LA, Horsburgh BC, Ross J et al (2006) PXR and CAR:

nuclear receptors which play a pivotal role in drug disposition

and chemical toxicity. Drug Metab Rev 38:515–597

Staudinger JL, Goodwin B, Jones SA et al (2001) The nuclear

receptor PXR is a lithocholic acid sensor that protects against

liver toxicity. Proc Natl Acad Sci USA 98:3369–3374

Stearns RA, Chakravarty PK, Chen R et al (1995) Biotransformation

of losartan to its active carboxylic acid metabolite in human liver

microsomes. Role of cytochrome P4502C and 3A subfamily

members. Drug Metab Dispos 23:207–215

Stevens JC, White RB, Hsu SH et al (1997) Human liver CYP2B6-

catalyzed hydroxylation of RP 73401. J Pharmacol Exp Ther

282:1389–1395

Stormer E, von Moltke LL, Shader RI et al (2000) Metabolism of the

antidepressant mirtazapine in vitro: contribution of cytochromes

P-450 1A2, 2D6, and 3A4. Drug Metab Dispos 28:1168–1175

Sueyoshi T, Kawamoto T, Zelko I et al (1999) The repressed nuclear

receptor CAR responds to phenobarbital in activating the human

CYP2B6 gene. J Biol Chem 274:6043–6046

Suino K, Peng L, Reynolds R et al (2004) The nuclear xenobiotic

receptor CAR: structural determinants of constitutive activation

and heterodimerization. Mol Cell 16:893–905

Sumida A, Fukuen S, Yamamoto I et al (2000) Quantitative analysis

of constitutive and inducible CYPs mRNA expression in the

HepG2 cell line using reverse transcription-competitive PCR.

Biochem Biophys Res Commun 267:756–760

Sun X, Li F, Wang YJ et al (2004) Development of an exonuclease

protection mediated PCR bioassay for sensitive detection of Ah

receptor agonists. Toxicol Sci 80:49–53

Sustiva (2007) Electronic Medicines compendium (eMC). Available

at http://emc.medicines.org.uk. Accessed 5 April 2008

Sutter TR, Tang YM, Hayes CL et al (1994) Complete cDNA

sequence of a human dioxin-inducible mRNA identifies a new

gene subfamily of cytochrome P450 that maps to chromosome 2.

J Biol Chem 269:13092–13099

Svensson US, Ashton M, Trinh NH et al (1998) Artemisinin induces

omeprazole metabolism in human beings. Clin Pharmacol Ther

64:160–167

Svensson US, Ashton M (1999) Identification of the human

cytochrome P450 enzymes involved in the in vitro metabolism

of artemisinin. Br J Clin Pharmacol 48:528–535

Taavitsainen P, Juvonen R, Pelkonen O (2001) In vitro inhibition of

cytochrome P450 enzymes in human liver microsomes by a

potent CYP2A6 inhibitor, trans–2-phenylcyclopropylamine

(tranylcypromine), and its nonamine analog, cyclopropylben-

zene. Drug Metab Dispos 29:217–222

Takagi S, Nakajima M, Mohri T et al (2008) Post-transcriptional

Regulation of Human Pregnane X Receptor by Micro-RNA

Affects the Expression of Cytochrome P450 3A4. J Biol Chem

283:9674–9680

Takahashi T, Lasker JM, Rosman AS et al (1993) Induction of

cytochrome P-4502E1 in the human liver by ethanol is caused by

a corresponding increase in encoding messenger RNA. Hepa-

tology 17:236–245

Tang C, Lin JH, Lu AY (2005) Metabolism-based drug–drug

interactions: what determines individual variability in cyto-

chrome P450 induction? Drug Metab Dispos 33:603–613

Tarrus E, Cami J, Roberts DJ et al (1987) Accumulation of caffeine in

healthy volunteers treated with furafylline. Br J Clin Pharmacol

23:9–18

Tassaneeyakul W, Mohamed Z, Birkett DJ et al (1992) Caffeine as a

probe for human cytochromes P450: validation using cDNA-

expression, immunoinhibition and microsomal kinetic and

inhibitor techniques. Pharmacogenetics 2:173–183

Tassaneeyakul W, Birkett DJ, Veronese ME et al (1993a) Specificity

of substrate and inhibitor probes for human cytochromes P450

1A1 and 1A2. J Pharmacol Exp Ther 265:401–407

Tassaneeyakul W, Veronese ME, Birkett DJ et al (1993b) Validation

of 4-nitrophenol as an in vitro substrate probe for human liver

CYP2E1 using cDNA expression and microsomal kinetic

techniques. Biochem Pharmacol 46:1975–1981

Tassaneeyakul W, Guo LQ, Fukuda K et al (2000) Inhibition

selectivity of grapefruit juice components on human cyto-

chromes P450. Arch Biochem Biophys 378:356–363

Tateishi T, Krivoruk Y, Ueng YF et al (1996) Identification of human

liver cytochrome P-450 3A4 as the enzyme responsible for

fentanyl and sufentanil N-dealkylation. Anesth Analg 82:167–

172

Tateno C, Yoshizane Y, Saito N et al (2004) Near completely

humanized liver in mice shows human-type metabolic responses

to drugs. Am J Pathol 165:901–912

Thum T, Erpenbeck VJ, Moeller J et al (2006) Expression of

xenobiotic metabolizing enzymes in different lung compart-

ments of smokers and nonsmokers. Environ Health Perspect

114:1655–1661

Timsit YE, Negishi M (2007) CAR and PXR: the xenobiotic-sensing

receptors. Steroids 72:231–246

Tirona RG, Lee W, Leake BF et al (2003) The orphan nuclear

receptor HNF4alpha determines PXR- and CAR-mediated

xenobiotic induction of CYP3A4. Nat Med 9:220–224

Tjia JF, Colbert J, Back DJ (1996) Theophylline metabolism in

human liver microsomes: inhibition studies. J Pharmacol Exp

Ther 276:912–917

Tornheim K (1994) Kinetic applications using high substrate and

competitive inhibitor concentrations to determine Ki or Km.Anal Biochem 221:53–56

Totah RA, Rettie AE (2005) Cytochrome P450 2C8: substrates,

inhibitors, pharmacogenetics, and clinical relevance. Clin Phar-

macol Ther 77:341–352

Tracy TS, Marra C, Wrighton SA et al (1996) Studies of flurbiprofen

40-hydroxylation. Additional evidence suggesting the sole

involvement of cytochrome P450 2C9. Biochem Pharmacol

52:1305–1309

Tracy TS, Marra C, Wrighton SA et al (1997) Involvement of

multiple cytochrome P450 isoforms in naproxen O-demethyla-

tion. Eur J Clin Pharmacol 52:293–298

Trubetskoy O, Marks B, Zielinski T et al (2005) A simultaneous

assessment of CYP3A4 metabolism and induction in the DPX-2

cell line. AAPS J 7:E6–E13

Tsutsumi M, Lasker JM, Shimizu M et al (1989) The intralobular

distribution of ethanol-inducible P450IIE1 in rat and human

liver. Hepatology 10:437–446

Tsyrlov IB, Goldfarb IS, Gelboin HV (1993) Enzyme-kinetic and

immunochemical characteristics of mouse cDNA-expressed,

microsomal, and purified CYP1A1 and CYP1A2. Arch Biochem

Biophys 307:259–266

712 Arch Toxicol (2008) 82:667–715

123

http://emc.medicines.org.uk

Tucker GT (1992) The rational selection of drug interaction studies:

implications of recent advances in drug metabolism. Int J Clin

Pharmacol Ther Toxicol 30:550–553

Tucker GT, Houston JB, Huang SM (2001) Optimizing drug

development: strategies to assess drug metabolism/transporter

interaction potential–towards a consensus. Br J Clin Pharmacol

52:107–117

Tugnait M, Hawes EM, McKay G et al (1999) Characterization of the

human hepatic cytochromes P450 involved in the in vitro

oxidation of clozapine. Chem Biol Interact 118:171–189

Turpeinen M, Nieminen R, Juntunen T et al (2004) Selective

inhibition of CYP2B6-catalyzed bupropion hydroxylation in

human liver microsomes in vitro. Drug Metab Dispos 32:626–

631

Turpeinen M, Uusitalo J, Jalonen J et al (2005a) Multiple P450

substrates in a single run: rapid and comprehensive in vitro

interaction assay. Eur J Pharm Sci 24:123–132

Turpeinen M, Tolonen A, Uusitalo J et al (2005b) Effect of

clopidogrel and ticlopidine on cytochrome P450 2B6 activity

as measured by bupropion hydroxylation. Clin Pharmacol Ther

77:553–559

Turpeinen M, Raunio H, Pelkonen O (2006) The functional role of

CYP2B6 in human drug metabolism: substrates and inhibitors in

vitro, in vivo and in silico. Curr Drug Metab 7:705–714

Udall JA (1975) Clinical implications of warfarin interactions with

five sedatives. Am J Cardiol 35:67–71

Ung CY, Li H, Yap CW et al (2007) In silico prediction of pregnane

X receptor activators by machine learning approaches. Mol


Valero F, de la Torre R, Segura J (1991) Selective in-vitro inhibition

of hepatic oxidative metabolism by quinolones: 7-ethoxyresoru-

fin and caffeine as model substrates. J Pharm Pharmacol 43:17–

21

van Duijnhoven EM, Boots JM, Christiaans MH et al (2003) Increase

in tacrolimus trough levels after steroid withdrawal. Transpl Int

16:721–725

van Giersbergen PL, Gnerre C, Treiber A et al (2002a) Bosentan, a

dual endothelin receptor antagonist, activates the pregnane X

nuclear receptor. Eur J Pharmacol 450:115–121

van Giersbergen PL, Treiber A, Clozel M et al (2002b) In vivo and in

vitro studies exploring the pharmacokinetic interaction between

bosentan, a dual endothelin receptor antagonist, and glyburide.


van Leeuwen DM, van Agen E, Gottschalk RW et al (2007) Cigarette

smoke-induced differential gene expression in blood cells from

monozygotic twin pairs. Carcinogenesis 28:691–697

Vedani A, Dobler M, Lill MA (2006) The challenge of predicting drug

toxicity in silico. Basic Clin Pharmacol Toxicol 99:195–208

Vermeir M, Annaert P, Mamidi RN et al (2005) Cell-based models to

study hepatic drug metabolism and enzyme induction in humans.

Expert Opin Drug Metab Toxicol 1:75–90

Veronese ME, Mackenzie PI, Doecke CJ et al (1991) Tolbutamide

and phenytoin hydroxylations by cDNA-expressed human liver

cytochrome P4502C9. Biochem Biophys Res Commun

175:1112–1118

Vesell ES, Page JG (1969) Genetic control of the phenobarbital-

induced shortening of plasma antipyrine half-lives in man. J Clin

Invest 48:2202–2209

Vickers AE, Sinclair JR, Zollinger M et al (1999) Multiple

cytochrome P-450s involved in the metabolism of terbinafine

suggest a limited potential for drug–drug interactions. Drug


Vignati LA, Bogni A, Grossi P et al (2004) A human and mouse

pregnane X receptor reporter gene assay in combination with

cytotoxicity measurements as a tool to evaluate species-specific

CYP3A induction. Toxicology 199:23–33

Villikka K, Kivisto KT, Neuvonen PJ (1998) The effect of

dexamethasone on the pharmacokinetics of triazolam. Pharmacol

Toxicol 83:135–138

Villikka K, Varis T, Backman JT et al (2001) Effect of methylpred-

nisolone on CYP3A4-mediated drug metabolism in vivo. Eur J


von Moltke LL, Greenblatt DJ, Harmatz JS et al (1993) Alprazolam

metabolism in vitro: studies of human, monkey, mouse, and rat

liver microsomes. Pharmacology 47:268–276

von Moltke LL, Greenblatt DJ, Schmider J et al (1996a) Midazolam

hydroxylation by human liver microsomes in vitro: inhibition by

fluoxetine, norfluoxetine, and by azole antifungal agents. J Clin


von Moltke LL, Greenblatt DJ, Harmatz JS et al (1996b) Triazolam

biotransformation by human liver microsomes in vitro: effects of

metabolic inhibitors and clinical confirmation of a predicted

interaction with ketoconazole. J Pharmacol Exp Ther 276:370–379

von Moltke LL, Greenblatt DJ, Duan SX et al (1998a) Inhibition of

desipramine hydroxylation (Cytochrome P450–2D6) in vitro by

quinidine and by viral protease inhibitors: relation to drug

interactions in vivo. J Pharm Sci 87:1184–1189

von Moltke LL, Greenblatt DJ, Schmider J et al (1998b) In vitro

approaches to predicting drug interactions in vivo. Biochem


von Richter O, Burk O, Fromm MF et al (2004) Cytochrome P450

3A4 and P-glycoprotein expression in human small intestinal

enterocytes and hepatocytes: a comparative analysis in paired

tissue specimens. Clin Pharmacol Ther 75:172–183

Wacher VJ, Wu CY, Benet LZ (1995) Overlapping substrate

specificities and tissue distribution of cytochrome P450 3A and

P-glycoprotein: implications for drug delivery and activity in

cancer chemotherapy. Mol Carcinog 13:129–134

Waller CL, McKinney JD (1992) Comparative molecular field

analysis of polyhalogenated dibenzo-p-dioxins, dibenzofurans,

and biphenyls. J Med Chem 35:3660–3666

Wallin H, Skipper PL, Tannenbaum SR et al (1995) Altered aromatic

amine metabolism in epileptic patients treated with phenobar-

bital. Cancer Epidemiol Biomarkers Prev 4:771–773

Walsky RL, Obach RS (2004) Validated assays for human cyto-

chrome P450 activities. Drug Metab Dispos 32:647–660

Walsky RL, Gaman EA, Obach RS (2005a) Examination of 209 drugs

for inhibition of cytochrome P450 2C8. J Clin Pharmacol 45:68–78

Walsky RL, Obach RS, Gaman EA et al (2005b) Selective inhibition

of human cytochrome P4502C8 by montelukast. Drug Metab

Dispos 33:413–418

Wang RW, Kari PH, Lu AY et al (1991) Biotransformation of

lovastatin. IV. Identification of cytochrome P450 3A proteins as

the major enzymes responsible for the oxidative metabolism of

lovastatin in rat and human liver microsomes. Arch Biochem

Biophys 290:355–361

Wang RW, Newton DJ, Scheri TD et al (1997) Human cytochrome

P450 3A4-catalyzed testosterone 6 beta-hydroxylation and

erythromycin N-demethylation. Competition during catalysis.


Wang JS, Backman JT, Taavitsainen P et al (2000a) Involvement of

CYP1A2 and CYP3A4 in lidocaine N-deethylation and 3-

hydroxylation in humans. Drug Metab Dispos 28:959–965

Wang RW, Newton DJ, Liu N et al (2000b) Human cytochrome P-

450 3A4: in vitro drug–drug interaction patterns are substrate-

dependent. Drug Metab Dispos 28:360–366

Wang JS, Neuvonen M, Wen X et al (2002) Gemfibrozil inhibits

CYP2C8-mediated cerivastatin metabolism in human liver

microsomes. Drug Metab Dispos 30:1352–1356

Wang LS, Zhou G, Zhu B et al (2004a) St John’s wort induces both

cytochrome P450 3A4-catalyzed sulfoxidation and 2C19-

Arch Toxicol (2008) 82:667–715 713

123

dependent hydroxylation of omeprazole. Clin Pharmacol Ther

75:191–197

Wang LS, Zhu B, Abd El-Aty AM et al (2004b) The influence of St

John’s Wort on CYP2C19 activity with respect to genotype. J


Wang YH, Jones DR, Hall SD (2005) Differential mechanism-based

inhibition of CYP3A4 and CYP3A5 by verapamil. Drug Metab

Dispos 33:664–671

Wang K, Mendy AJ, Dai G et al (2006) Retinoids activate the RXR/

SXR-mediated pathway and induce the endogenous CYP3A4

activity in Huh7 human hepatoma cells. Toxicol Sci 92:51–60

Ward BA, Gorski JC, Jones DR et al (2003) The cytochrome P450

2B6 (CYP2B6) is the main catalyst of efavirenz primary and

secondary metabolism: implication for HIV/AIDS therapy and

utility of efavirenz as a substrate marker of CYP2B6 catalytic

activity. J Pharmacol Exp Ther 306:287–300

Warrington JS, Shader RI, von Moltke LL et al (2000) In vitro

biotransformation of sildenafil (Viagra): identification of human

cytochromes and potential drug interactions. Drug Metab Dispos

28:392–397

Watkins PB, Murray SA, Winkelman LG et al (1989) Erythromycin

breath test as an assay of glucocorticoid-inducible liver cyto-

chromes P-450. Studies in rats and patients. J Clin Invest

83:688–697

Watkins RE, Wisely GB, Moore LB et al (2001) The human nuclear

xenobiotic receptor PXR: structural determinants of directed

promiscuity. Science 292:2329–2333

Waxman DJ, Lapenson DP, Aoyama T et al (1991) Steroid hormone

hydroxylase specificities of eleven cDNA-expressed human

cytochrome P450s. Arch Biochem Biophys 290:160–166

Weber C, Banken L, Birnboeck H et al (1999) Effect of the

endothelin-receptor antagonist bosentan on the pharmacokinetics

and pharmacodynamics of warfarin. J Clin Pharmacol 39:847–

854

Wei C, Caccavale RJ, Weyand EH et al (2002) Induction of CYP1A1

and CYP1A2 expressions by prototypic and atypical inducers in

the human lung. Cancer Lett 178:25–36

Wen X, Wang JS, Backman JT et al (2002) Trimethoprim and

sulfamethoxazole are selective inhibitors of CYP2C8 and

CYP2C9, respectively. Drug Metab Dispos 30:631–635

Westerink WM, Schoonen WG (2007) Cytochrome P450 enzyme

levels in HepG2 cells and cryopreserved primary human

hepatocytes and their induction in HepG2 cells. Toxicol In

Vitro 21:1581–1591

Westlind-Johnsson A, Malmebo S, Johansson A et al (2003)

Comparative analysis of CYP3A expression in human liver

suggests only a minor role for CYP3A5 in drug metabolism.


Whyte JJ, Schmitt CJ, Tillitt DE (2004) The H4IIE cell bioassay as an

indicator of dioxin-like chemicals in wildlife and the environ-

ment. Crit Rev Toxicol 34:1–83

Wienkers LC, Heath TG (2005) Predicting in vivo drug interactions

from in vitro drug discovery data. Nat Rev Drug Discov 4:825–

833

Wietholtz H, Zysset T, Kreiten K et al (1989) Effect of phenytoin,

carbamazepine, and valproic acid on caffeine metabolism. Eur J


Wild MJ, McKillop D, Butters CJ (1999) Determination of the human

cytochrome P450 isoforms involved in the metabolism of

zolmitriptan. Xenobiotica 29:847–857

Williamson KM, Patterson JH, McQueen RH et al (1998) Effects of

erythromycin or rifampin on losartan pharmacokinetics in

healthy volunteers. Clin Pharmacol Ther 63:316–323

Williams JA, Ring BJ, Cantrell VE et al (2002) Comparative

metabolic capabilities of CYP3A4, CYP3A5, and CYP3A7.


Windshugel B, Jyrkkarinne J, Vanamo J et al (2007) Comparison of

homology models and X-ray structures of the nuclear receptor

CAR: assessing the structural basis of constitutive activity. J Mol

Graph Model 25:644–657

Wing LM, Miners JO, Lillywhite KJ (1985) Verapamil disposition—

effects of sulphinpyrazone and cimetidine. Br J Clin Pharmacol

19:385–391

Wojcikowski J, Maurel P, Daniel W (2006) Characterization of

human cytochrome p450 enzymes involved in the metabolism of

the piperidine-type phenothiazine neuroleptic thioridazine. Drug


Wrighton SA, Brian WR, Sari MA et al (1990) Studies on the

expression and metabolic capabilities of human liver cytochrome

P450IIIA5 (HLp3). Mol Pharmacol 38:207–213

Wu CY, Benet LZ, Hebert MF et al (1995) Differentiation of

absorption and first-pass gut and hepatic metabolism in humans:

studies with cyclosporine. Clin Pharmacol Ther 58:492–497

Xiao L, Cui X, Madison V et al (2002) Insights from a three-

dimensional model into ligand binding to constitutive active

receptor. Drug Metab Dispos 30:951–956

Xie W, Barwick JL, Downes M et al (2000) Humanized xenobiotic

response in mice expressing nuclear receptor SXR. Nature

406:435–439

Xie W, Radominska-Pandya A, Shi Y et al (2001) An essential role

for nuclear receptors SXR/PXR in detoxification of cholestatic

bile acids. Proc Natl Acad Sci USA 98:3375–3380

Xu RX, Lambert MH, Wisely BB et al (2004) A structural basis for

constitutive activity in the human CAR/RXRalpha heterodimer.

Mol Cell 16:919–928

Xue Y, Moore LB, Orans J, Peng L, Bencharit S, Kliewer SA,

Redinbo MR (2007) Crystal structure of the pregnane X

receptor-estradiol complex provides insights into endobiotic

recognition. Mol Endocrinol 21:1028–1038

Yamanaka H, Nakajima M, Fukami T et al (2005) CYP2A6 and

CYP2B6 are involved in nornicotine formation from nicotine in

humans: interindividual differences in these contributions. Drug


Yamano S, Tatsuno J, Gonzalez FJ (1990) The CYP2A3 gene product

catalyzes coumarin 7-hydroxylation in human liver microsomes.

Biochemistry 29:1322–1329

Yamazaki H, Hiroki S, Urano T et al (1996) Effects of roxithromycin,

erythromycin and troleandomycin on their N-demethylation by

rat and human cytochrome P450 enzymes. Xenobiotica

26:1143–1153

Yamazaki H, Inoue K, Chiba K et al (1998) Comparative studies on

the catalytic roles of cytochrome P450 2C9 and its Cys- and Leu-

variants in the oxidation of warfarin, flurbiprofen, and diclofenac

by human liver microsomes. Biochem Pharmacol 56:243–251

Yamazaki H, Shimada T (1998) Comparative studies of in vitroinhibition of cytochrome P450 3A4-dependent testosterone

6beta-hydroxylation by roxithromycin and its metabolites,

troleandomycin, and erythromycin. Drug Metab Dispos

26:1053–1057

Yanagihara Y, Kariya S, Ohtani M et al (2001) Involvement of

CYP2B6 in n-demethylation of ketamine in human liver

microsomes. Drug Metab Dispos 29:887–890

Yao D, Ding S, Burchell B et al (2000) Detoxication of vinca

alkaloids by human P450 CYP3A4-mediated metabolism:

implications for the development of drug resistance. J Pharmacol

Exp Ther 294:387–395

Yasar U, Tybring G, Hidestrand M et al (2001) Role of CYP2C9

polymorphism in losartan oxidation. Drug Metab Dispos

29:1051–1056

Yasumori T, Li QH, Yamazoe Y et al (1994) Lack of low Km

diazepam N-demethylase in livers of poor metabolizers for S-

mephenytoin 40-hydroxylation. Pharmacogenetics 4:323–331

714 Arch Toxicol (2008) 82:667–715

123

Yeh RF, Gaver VE, Patterson KB et al (2006) Lopinavir/ritonavir

induces the hepatic activity of cytochrome P450 enzymes

CYP2C9, CYP2C19, and CYP1A2 but inhibits the hepatic and

intestinal activity of CYP3A as measured by a phenotyping drug

cocktail in healthy volunteers. J Acquir Immune Defic Syndr

42:52–60

Yeo KR, Yeo WW (2001) Inhibitory effects of verapamil and

diltiazem on simvastatin metabolism in human liver microsomes.


Yoshida N, Oda Y, Nishi S et al (1993) Effect of barbiturate

therapy on phenytoin pharmacokinetics. Crit Care Med

21:1514–1522

Yoshinari K, Kobayashi K, Moore R et al (2003) Identification of the

nuclear receptor CAR:HSP90 complex in mouse liver and

recruitment of protein phosphatase 2A in response to phenobar-

bital. FEBS Lett 548:17–20

You F, Zhou YF, Zhang XE et al (2006) Cell-free bioassay for

measurement of dioxins based on fluorescence enhancement of

fluorescein isothiocyanate-labeled DNA probe. Anal Chem

78:7138–7144

Yuan R, Parmelee T, Balian JD et al (1999) In vitro metabolic

interaction studies: experience of the Food and Drug Adminis-

tration. Clin Pharmacol Ther 66:9–15

Yuan R, Madani S, Wei XX et al (2002) Evaluation of cytochrome

P450 probe substrates commonly used by the pharmaceutical

industry to study in vitro drug interactions. Drug Metab Dispos

30:1311–1319

Yueh MF, Kawahara M, Raucy J (2005) Cell-based high-throughput

bioassays to assess induction and inhibition of CYP1A enzymes.

Toxicol In Vitro 19:275–287

Zand R, Nelson SD, Slattery JT et al (1993) Inhibition and induction

of cytochrome P4502E1-catalyzed oxidation by isoniazid in

humans. Clin Pharmacol Ther 54:142–149

Zanger UM, Raimundo S, Eichelbaum M (2004) Cytochrome P450

2D6: overview and update on pharmacology, genetics, biochem-

istry. Naunyn Schmiedebergs Arch Pharmacol 369:23–37

Zanger UM, Klein K, Saussele T et al (2007) Polymorphic CYP2B6:

molecular mechanisms and emerging clinical significance.

Pharmacogenomics 8:743–759

Zelko I, Sueyoshi T, Kawamoto T et al (2001) The peptide near the C

terminus regulates receptor CAR nuclear translocation induced

by xenochemicals in mouse liver. Mol Cell Biol 21:2838–2846

Zhang L, Fitzloff JF, Engel LC et al (2001a) Species difference in

stereoselective involvement of CYP3A in the mono-N-dealky-

lation of disopyramide. Xenobiotica 31:73–83

Zhang W, Kilicarslan T, Tyndale RF et al (2001b) Evaluation of

methoxsalen, tranylcypromine, and tryptamine as specific and

selective CYP2A6 inhibitors in vitro. Drug Metab Dispos

29:897–902

Zhang ZY, Pelletier RD, Wong YN et al (2006) Preferential

inducibility of CYP1A1 and CYP1A2 by TCDD: differential

regulation in primary human hepatocytes versus transformed

human cells. Biochem Biophys Res Commun 34:399–407

Zhang H, Cui D, Wang B et al (2007) Pharmacokinetic drug

interactions involving 17alpha-ethinylestradiol: a new look at an

old drug. Clin Pharmacokinet 46:133–157

Zhou S, Chan E, Pan SQ et al (2004) Pharmacokinetic interactions of

drugs with St John’s wort. J Psychopharmacol 18:262–276

Zhou C, Assem M, Tay JC et al (2006) Steroid and xenobiotic

receptor and vitamin D receptor crosstalk mediates CYP24

expression and drug-induced osteomalacia. J Clin Invest

116:1703–1712

Zhu Z, Kim S, Chen T et al (2004) Correlation of high-throughput

pregnane X receptor (PXR) transactivation and binding assays. J

Biomol Screen 9:533–540

Zhu M, Zhao W, Jimenez H et al (2005) Cytochrome P450 3A-

mediated metabolism of buspirone in human liver microsomes.


Zilly W, Breimer DD, Richter E (1975) Induction of drug metabolism

in man after rifampicin treatment measured by increased

hexobarbital and tolbutamide clearance. Eur J Clin Pharmacol

9:219–227

Arch Toxicol (2008) 82:667–715 715

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Inhibition and induction of human cytochrome P450 enzymes: current status