M.C. Currás-CollazoDept. of Cell Biology & Neuroscience University of California, Riverside

The indoor flame retardants PBDEs disrupt cardiovascular and osmotic regulation: role of central nitric oxide and vasopressin

From: Kodavanti & Curras-Collazo, Frontiers in Neuroendocrinol. 2010

Persistent organic pollutants share a similar halogenated biphenyl structure

Biphenyl = diphenylTwo aromatic rings

Polyhalogenated: 209 possible congeners

PCBs used as heat exchangers/dielectrics, plasticizers

PBDEs used as indoor flame retardants

Chemical structure similar to thyroid and vasopressin hormones

www.eurofinsus.com/Services/Polybrominated%20Diphenyl%20Ether%20.html?gclid=CKCs8oS-6KQCFQoEbAodGhfb0w; M. J. La Guardia et al, 2006. Environ. Sci. Technol., 2006, 40, 6247–6254; http://www.doh.wa.gov/ehp/oehas/pbde/pbdeuse.htm

Why use flame retardants? To help prevent fire-related deaths (600) and injuries (47,000 in children)

PBDEs are blended into plastics and foams (constitute up to 30% of product); when exposed to flame and high heat, they release bromines that rob the air of the oxygen needed to start a fire.

Uses of industrial PBDE mixtures:PentaBDE (DE-60F, DE-61, DE-62, and DE-71): polyurethane foam (mattresses, seat cushions) OctaBDE (DE-79): high-impact plastics (fax, computers, cars, phones, kitchen appliances) DecaBDE (DE 83R and Saytex 102E): carpet and draperies, television sets, computers, cable insulation, adhesives (most widely used)

US is the world's largest producer and consumer of PBDEs. 95% of global pentaBDE and 44% of decaBDEs are used in the Americas.

The most abundant PBDE congeners in wildlife and humans are BDE-47 (tetra-) and 99 (penta-BDE).

Lower brominated PBDEs are the most toxic to thyroid, reproductive system and brain.

There are no product labels that list PBDEs and retailers generally are not aware which products contain PBDEs.

Inhalation of indoor dust (house,

office, car, airplane)

Breastmilk Occupation

Maternal transfer to fetus

Hand-to-mouth transfer

Diet (esp., fish)

salmon, ground beef, butter,

and cheese

Human Exposure to PBDE

http://www.agreenspan.org/mainsite/index.php?option=com_easygallery&act=photos&cid=29&Itemid=50; www.delta.dfg.ca.gov; http://www.doh.wa.gov/ehp/oehas/pbde/pbdehumanhealth.htm

Recent human studies on PBDEs

Highest PBDE levels in children reported in Chihuahua (Mexico), South China and Managua (Nicaragua) that work in waste sites or live in industrialized sites (Leung et al, 2010; Pérez-Maldonado et al., 2009; Athanasiadou et al., 2008).

In low-income California households the estimated daily non-dietary intake for PBDE 47 and 99 exceeded the US EPA recommended chronic reference dose for up to 5 children combined (Rose et al, 2010; Quiros-Alcala et al, 2011).

Maternal serum PBDE levels have been positively associated with lower scores on measures of intelligence and attention (Herbstman et al, 2010; Roze et al, 2009). Those with highest PBDEs in umbilical cord blood at birth showed lower scores on tests of mental and physical development between the ages 1-6. At 4 years, verbal and full IQ scores were reduced by as much as 5.5-8.0 points.

Women with higher blood levels of PBDEs took longer to become pregnant (Harley et al, 2010).

Children are at Special Risk: lactational transfer and ingestion of PBDEs

Body burdens (ng/g lipid wt):Adult (> 16 yr): 18 + 5 Children (0-4 yr): 73 + 7

Daily Intake of PBDE (ng/kg b.w.):Adults – 7.7 Toddlers- 49.9

Daily Intake of PBDE near e-waste site (ng/kg b.w.):

6 mo-old breastfed infants -2,240

US EPA recommended chronic reference dose for penta-BDE = 2,000 ng/kg/day

Total PCB Total PBDE

Toxi

cant

Lev

els

in B

reas

t Milk

(ng/

g lw

) n=4

0

0

20

40

60

80

100

120

140

160

She et al., (2007) Chemosphere 67: S307-S317

Lorber, M. (2007) J Expo Sci Environ Epidemiol.Toms, L.M., et al (2008) Environ Sci Technol. 42(19):7510-5.Leung et al, 2010 Environ Sci Poll Res. 17(7): 1300-1313.

Breast milk PBDEs in first–time mothersof Pacific Northwest and Canada

Concerns about PBDEs

Toxicology Findings:• Neurodevelopmental toxicity• Thyroid effects• Endocrine disruption• Some supporting human epidemiology

Exposure:• Primary exposure seems to be through house dust• Higher exposures for young children• Measured in human breast milk• Body burdens in U.S. much higher than in other countries• Debromination of decaBDEs

www.cartage.org.l

Objectives

• To determine the potential for neuroendocrine disruption by PBDEs

• To evaluate the effects of PBDEs on osmoregulation and cardiovascular reactivity to stress

PVN

SON

3V

OT

VP-NP antibody gift from Dr. Gloria Hoffman, University of Maryland, Baltimore, MD

Magnocellular neuroendocrine cell (MNC) system

2 locations:SON - supraopticPVN - paraventricular

2 populations:OxytocinVasopressin (VP)

From: Neuroscience: Exploring the Brain, Eds. Bear et al, Williams and Wilkins, New York, 1996.

MNCs are part of the hypothalamo-neurohypophysial system (HNS)

VP

VP

Stimuli:HyperosmolalityHypovolemia

Detectors:Osmoreceptors in forebrain

Effectors: Magnocellular neuroendocrine cells (MNCs)

Correctional mechanism:Water retention(kidney), vaso-constriction(blood vessels)

Somatodendritic (central VP release)

VPRVP

glu

G

MNC

Central VP binds to VP autoreceptors (VPR) to control firing rate, axonal VP output into blood and osmoregulation.

Modified from Dr. S. Qiu

Dual release of VP from MNCs may have autoregulatory function

SO

N V

P (p

g/m

l/ug)

0

1

2

3

4

5

6

b

normosmotic dehydrated

a

a

- PCB PCB in vitro(20 µM)

bb

acute exposure in vitro

*

1. Micro-dissection of SON

4. VP enzyme-linked immunoassay

2. Maintain tissue viable:Oxygenated and warm Microwells

3. In vitro testing –10 min collection

From: Coburn, Gillard and Curras-Collazo, 2005

CG Coburn, MC Curras-Collazo and PRS Kodavanti, Tox. Sci., 2007

In Vitro PCBs or PBDEs abolish stimulated release of central VP

PCBPBDE

*

0

2

4

6

8

10

12

14

**

#SO

N VP

Rele

ase

(pg

/ µg

prot

ein)

Normal Hyperosmotic control ----------------------------------------------------------------- Control DE-71 Aroclor 1254 ----------------------- ---------------------- 17.6 µg/ml 5.8 µg/ml 10 µg/ml 3.3 µg/ml30 µM 10 µM 30 µM 10 µM

3-5 hrs in vivo

Non-invasive monitoring of BP, HR

DE-71 dosing of dams (GD 6-PND 21) via Cheeto™ treats or oral gavage; 1.7 (low dose) or 30mg/kg/d (high dose)

3.5 M NaCl ip (6 ml/kg)

(Hyper)

0.15 M NaCl, ip

(Normal)

Acute osmotic challenge

Measure plasma osmolality

Sacrifice

Perinatal Exposure to DE-71

Plasma VP

Pregnant Dams14-18 months

Stabilization of BP after 3 weeks of acclimation

From: Shah et al, Toxicology and Applied Pharmacology (accepted)

Perinatal PBDE exposure alters blood pressure responses

From: Shah et al, Toxicology and Applied Pharmacology (accepted)

Perinatal exposure to DE-71 alters osmoregulation

From: Shah et al, Toxicology and Applied Pharmacology (accepted)

NORMAL HYPER

45 Minutes 3 Hour 45 Minutes 3 Hour

Oil 300.3± 2.1 (n=4) 301.2 ± 2.0 (n=4) 343.2 ± 8.8 (n=8)** 343.1 ± 6.9 (n=8)

PBDE Low

345.0 ± 10.7 (n=4)** 362.0 ± 12.1 (n=4)

PBDE High

325.1 ± 11.4 (n=4)* 358.3 ± 12.4 (n=4)#

PBDE All

335.1+8.2 (n=8)** 360.2+8.1 (n=8)╪

Plasma hyperosmolality is not due to insufficient VP release

From: Shah et al, Toxicology and Applied Pharmacology (accepted)

Summary & Conclusions• Acute in vitro application of PCBs or PBDEs interferes

with osmotic-stimulated central vasopressin release.

• Like PCBs, ingestion of PBDEs may disrupt stimulated plasma VP levels by reducing central VP signals.

• Perinatal exposure to the PBDE mixture DE-71 disrupts osmoregulation and increases cardiovascular reactivity to stress in late adulthood.

• Collectively, these results suggest that PCBs and PBDEs act as disruptors of neuroendocrine function, osmoregulation and cardiovascular function.

• The underlying mechanisms may include reduced thyroid status and/or vasopressin receptor density during development and/or renal toxicity.

AcknowledgementsUCR:Postdocs:Dr. E.R. Gillard

Graduate Students:Dr. Cary CoburnSamuel Mucios-Ramirez

Undergraduate Students:Borin HouChad CheethamAbena Watson-SiriboeAshini ShahRebecca WhitleyMark GaertnerAnoush Shahdizadeh Anna Carrera

Collaborators:Dr. M. Leon-Olea et al, Instituto Nacional de Psiquiatria, Mexico City, MexicoDr. P. Kodavanti, U.S. Environmental Protection Agency

ewg.org/pbdefree

• Some major manufacturers have publicly committed to eliminate all BFRs from their products world-wide in response to restrictions on toxic chemicals in electronic products sold in Europe and several U.S. states:

Acer, Apple, Eizo Nanao, LG Electronics, Lenovo, Matsushita, Microsoft, Nokia, Phillips, Samsung, Sharp, Sony-Ericsson, Toshiba.

• Some are phasing out decaPBDEs but not all BFRs: Canon, Daikin, Intel, IBM, HP, Minolta, Mitsubishi, Motorola, NEC, Nokia, Xerox.

Become an informed and selective consumer

• Blockade of central VP receptors elevate plasma VP levels ( ).• Hyperosmotic stimulation upregulate NOS in MNCs (Villar et al, 1994; Nylen et al,

2001).• NOS inhibitors exaggerate plasma VP and deplete pituitary VP content (Kadowaki

et al, 1994; Liu et al, 1998; Lutz-Bucher &Koch, 1994).

Like central VP, nitric oxide (NO) act as brake on pituitary VP release

Since PCBs block NO production (Sharma & Kodavanti, 2002)

Then….PCBs and similar compounds should reduce central VP and exaggerate plasma VP levels

Central NO leads to central VP• Hyperosmolality stimulates NO production and local release of NO within

the SON (Gillard et al, 2007).• Stimulated local VP release depends on central NO production (Gillard et

al, 2007).

Central Vasopressin System

Cardiovascular RegulationThermoregulationLearning & Memory Social & Reproductive BehaviorsReproductive FunctionAnxiety & Stress Responses

From: Kodavanti & Curras-Collazo, Frontiers in Neuroendocrinol. 2010

From: D. Axelrad, US EPA

From: D. Axelrad, US EPA

• In response to restrictions on toxic chemicals in electronic products sold in Europe and several U.S. states major some major manufacturers have publicly committed to eliminate all BFRs from their products world-wide: Acer, Apple, Eizo Nanao, LG Electronics, Lenovo, Matsushita, Microsoft, Nokia, Phillips, Samsung, Sharp, Sony-Ericsson, Toshiba.

• Some are phasing out decaPBDEs but not all BFRs: Canon, Daikin, Intel, IBM, HP, Minolta, Mitsubishi, Motorola, NEC, Nokia, Xerox.

Postnatal Day0 10 20 30 40 50 60

Seru

m T

hyro

xine

(ng/

ml)

0

10

20

30

40

50

60

70

Control 1.7 mg/kg/day 10.2 mg/kg/day 30.6 mg/kg/day

Male

Postnatal Day0 10 20 30 40 50 60

Seru

m T

hyro

xine

(ng/

ml)

0

10

20

30

40

50

60

70

Control 1.7 mg/kg/day 10.2 mg/kg/day 30.6 mg/kg/day

Female

***

**

*

**

*

**

Perinatal Exposure to the Industrial PBDE Mixture (DE-71)

Induces Transient Hypothyroidism

Kodavanti et al, 2010

Control 1.7 mg/kg 10.2 mg/kg 30.6 mg/kg

Tota

l Ser

um T

hyro

xine

(T4)

, ng/

ml

0

10

20

30

40

50

*

*

*

*

Industrial use of PBDEs as indoor flame retardants –mostly penta, octa and deca mixtures

Furniture & Automobile Upholstery (polyurethane) Foam

Electrical Appliances & Circuitry: computers, TVs,electrical appliances.

Plastics

Carpet Padding, Back Coatings for Draperies

Mattresses, foam items for infants and kids, toys

Building materials