Porphyrins II

David Hart

Dec 13, 2006

HEME

CH3-

BonkovskyASH Education BookDecember 2005

Hentze, Muckenthaler & AndrewsCell, Vol 117, 285-297, April 30, 2004

Hepcidin

Lecture Outline

• Heme function

• Heme synthesis and regulation

• Iron metabolism

• Porphyrias

• Heme degradation

Disorders of Heme Synthesis

• X-linked Sideroblastic Anemia

• Lead Poisoning

• Iron Deficiency Anemia

• The Porphyrias

Porphyrias

• Inherited defects in heme synthesis– Accumulation and excretion of porphyrins– Pattern depends on which enzyme affected– Decreased heme synthesis derepresses hepatic ALAS

• Most are Autosomal Dominant • Erythropoietic, Hepatic or Mixed• Acute and Chronic

– Acute: Neurovisceral attacks

• Porphyrin accumulation: Photosensitivity– Formation of reactive oxygen species– Damage tissues, Release lysosomal enzymes

FuseliThree WitchesTate

Gillray 1791Weird Sisters

Tate

Very Rare Recessive Porphyria

Lead Poisoning

ALA-D Porphyria

X-linked Sideroblastic Anemia


AcuteHepatic

PBG and ALA (Neurotoxic)Accumulate in Urine

PBG in Urine: Diagnostic ScreenNeurovisceral Attacks

No Photosensitivity with AIP

Hydroxymethylbilane Synthase

Lead Poisoning



ALA-D Porphyria

Acute PorphyriasClinically indistinguishable (Locus Heterogeneity)

PBG in Urine: Diagnostic Screen• Agents which induce cytochrome P450

– Drugs, Alcohol, Hormones• Precipitated by fasting, treated with glucose • After puberty; more in women• Begin with minor behavioral changes• Proceeds to autonomic and sensomotoric

neuropathy; Convulsions• Pain: Back, Extremities, Abdomen• Hypertension and Tachycardia• Arrhythmias; cardiac arrest

AcuteHepatic

Erythropoietic

RECESSIVEPorphyrin accumulation: PhotosensitivityPorphyrins are Fluorescent compoundsFormation of reactive oxygen species,

Activate Complement

Lead Poisoning


ALA-D Porphyria



Clin Med2005:5

Dr. Meyer-Betz1912

GM Murphy, Dermatologic Therapy, March 2003

CEP

CEPNEJM9/7/2006

mccaskey4.home.mindspring.com

Erythropoietic

AcuteHepatic

Chronic

Lead Poisoning


ALA-D Porphyria



Porphyria Cutanea Tarda (PCT)

• Most common Porphyria– 80% sporadic

• Hepatic and Erythropoietic• Photosensitivity• Uroporphyrin accumulates in Urine

– Red-Brown in natural light

• Clinical expression in 4th - 5th decade• Decrease in UROD activity by Iron-dependent mechanism

– Alcohol, viruses, drugs, hormones– HFE Hemochromatosis

• Venesection, Chloroquine

Autosomal Dominant PCT (Hepatoerythropoietic Porphyria)

• Hepatic UROD activity < 50% during symptoms

• Additional decrease from reversible inactivation

• C282Y HFE causes earlier onset

PCT; www.Utah.edu

Erythropoietic

AcuteHepatic

AcuteHepatic

Photosensitivity(Unlike AIP)

Lead Poisoning


Chronic

ALA-D Porphyria



medlib.med.utah.edu

NormalLiver

www.med.niigata-u.ac.j

Granular, Dark Reddish BrownSurface of Liver in Hemochromatosis

Lecha, Herrero, Ozalla, Dermatologic Therapy, March 2003

HepaticPorphyria

AcuteHepatic

Erythropoietic

AcuteHepatic

AcuteHepatic

Photosensitivity

Lead Poisoning


Chronic

ALA-D Porphyria



Hair AnalysisLancetJuly 2005

Lancet July 23-29, 2005

• King George III (1738-1820)• Likely diagnosis of Variegate Porphyria

– Proposed 1969 based on family tree

• Lock of hair showed high lead– Widespread use in his era

• Extremely high levels of arsenic– Likely secondary to medications

LancetJuly 2005

Color of Urine“Alicante Wine”

http://www.aw-bc.com/mathews/GH/HEME.GIF

Introduction of Fe2+ into PPIXOccurs spontaneously, but

Enhanced by FERROCHELATASEAn enzyme which is inhibited by LEAD

http://www.photodermatologie.de

AcuteHepatic

AcuteHepatic

Erythropoietic

AcuteHepatic

Erythropoietic

Photosensitivity

Lead Poisoning


Chronic

ALA-D Porphyria



Erythropoietic Protoporphyria

• Presentation in early childhood• Burning, stinging pain with sunlight• Subsequent skin changes• Expression requires low-expression allele

in trans– 10% of population of France and UK– IVS3-48 alternative splice acceptor– With AD mutation FECH 35% of normal– Homozygosity does not cause disease

• Beta carotene: free radical scavenger

www.immunochemistry.com


EPP


EPP

www.goa-world.ne

AcuteHepatic

AcuteHepatic

Erythropoietic

AcuteHepatic

Erythropoietic

Photosensitivity

Lead Poisoning

No PhotosensitivityWith Lead

Lead Poisoning


Chronic



ALA-D Porphyria

http://www.photodermatologie.de

AcuteHepatic

AcuteHepatic

Erythropoietic

AcuteHepatic

Erythropoietic

Photosensitivity

Iron Deficiency

“Free” ErythrocytePPIX accumulatesin Lead Poisoning and Iron Deficiency

Lead Poisoning


Chronic



ALA-D Porphyria

Porphyrias: Genetics / Epigenetics

• 5 out of 7 are Low-penetrance Autosomal Dominant

• Most mutations are restricted to one family

• Rare Homozygotes very severe• No dominant negative mutants described• 50% residual activity is normally sufficient

Molecular basis of “low penetrance”

• Genotype/phenotype correlations

• Increased demand– Fasting (low Glucose)– Cell, August 26, 2005

• Low expression allele in trans

• Iron / HFE hemochromatosis can directly inhibit enzymes

• Other epigenetic phenomena

Treatment

• Medical Support during acute attacks• Treatment for pain and vomiting• Glucose infusion until Hemin available• Intravenous Hemin

– Decreases synthesis of ALAS

• Avoid Sunlight -carotene, a free-radical scavenger• Chronic transfusion for Erythropoietic

Degradation of Heme

• At end of their 120 day lifespan, red blood cells are taken up and degraded by the reticuloendothelial (RE) system (liver and spleen)

• 85% heme for degradation from RBC• 15% immature RBC, cytochromes

from extraerythroid tissues

N

NH N

HNH3C-

H3C-

-CH=CH2

-CH3

CH2

CH2

COOH

CH2

CH2

COOH

CH3

Fe2+

CH=CH2HEME

N

NH N

HNH3C-

H3C-

-CH=CH2

-CH3

CH2

CH2

COOH

CH2

CH2

COOH

CH3

Fe2+

CH=CH2

MACROPHAGEtakes up HEME

Heme Oxygenaseis Inducible by a variety of agents

Inhibited by TinProtoporphyrin

N

NH N

HNH3C-

H3C-

-CH=CH2

-CH3

CH2

CH2

COOH

CH2

CH2

COOH

CH3CH=CH2MACROPHAGEHemeOxygenase

Step 1NADPH O2

Fe3+

OH

N

NH N

HNH3C-

H3C-

-CH=CH2

-CH3

CH2

CH2

COOH

CH2

CH2

COOH

CH3CH=CH2MACROPHAGEHemeOxygenase

Step 2Fe3+ COReleased

O O

BILIVERDIN

HO also has Cytoprotectiveeffects

J Cell Mol Med 2006

NH

CH

VM

N CH

PM

NH

CH

MP

NH

O

VM

O

BILIVERDIN

NH

CH

VM

N CH

PM

NH

CH

MP

NH

O

VM

O

NH

CH

VM

NH

CH2

PM

NH

CH

MP

NH

O

VM

O

BILIVERDIN

BILIVERDIN REDUCTASE+ NADPH

BILIRUBIN

BILIRUBIN ALBUMINLow AlbuminAnionic Drugs:SalicylatesSulfonamides

BILIRUBIN ALBUMIN

Unbound BilirubinCan enter CNSCause Kernicterus in Neonate

Bilirubin Released from Macrophage, binds to Albumin in the Plasma

BILIRUBIN ALBUMIN

LIVER BILIRUBIN LIGANDIN

CONJUGATION with2 MoleculesGlucuronic Acid fromUDP-glucuronic acid

BilirubinGlucuronyltransferase

Bilirubin Diglucuronide BILEActiveTransport

BILIRUBIN: Unconjugated (Indirect)

LIVER

CONJUGATIONBilirubinGlucuronyltransferase

Bilirubin Diglucuronide:Conjugated (Direct) Bilirubin

VAN DEN BERGH COLORMETRIC REACTIONTOTAL BILIRUBIN: Soluble in Methanol

Less Soluble in Aqueous Solution, reacts more slowly

More Soluble, reacts more quickly

GALL

BLADDER

Ac

tiveT

ran

sp

ort

Bilirubin Diglucuronide

LIVER


UROBILINOGEN STERCOBILIN

KID

NE

YB

ILE

INTESTINAL BACTERIA

UrobilinogenUrobili

nogen

Enterohepatic

Circulation

UROBILIN

Bilirubin

GALL

BLADDER

Ac

tiveT

ran

sp

ort

BilirubinDiglucuronide

LIVER



KID

NE

YB

ILE

INTESTINAL BACTERIA

UrobilinogenUrobili

nogen

Enterohepatic

Circulation

UROBILIN

BILIRUBINHEMOLYSIS: Unconjugated(Indirect) Hyperbilirubinemia

GALL

BLADDER

Ac

tiveT

ran

sp

ort

Bilirubin DG

LIVER



KID

NE

YB

ILE

INTESTINAL BACTERIA

UrobilinogenUrobili

nogen

Enterohepatic

Circulation

UROBILIN

BILIRUBIN

NEONATAL JAUNDICE: Unconjugated Hyperbilirubinemia

www.mtwthailand.org

home.hawaii.rr.com

GALL

BLADDER

Ac

tiveT

ran

sp

ort


LIVER

KID

NE

YB

ILE

INTESTINAL BACTERIA

UROBILIN

Bilirubin OBSTRUCTIVE JAUNDICEDirect (Conjugated) Bilirubin

GALL

BLADDER

Ac

tive

Tra

ns

po

rt

Bilirubin DG

LIVER



KID

NE

YB

ILE

INTESTINAL BACTERIA

Urobilinogen Dark Urine

BILIRUBIN

HEPATOCELLULAR JAUNDICE: Unconjugated Hyperbilirubinemia

ENTEROHEPATIC

CIRCULATION

www.privivka.ru

Carotenemia

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Porphyrins II