NMS Labs Dinner Presentation by Dr. Andrea Gore 5-27-10

Bisphenol A and other suspected estrogenic endocrine disruptors
1
Andrea C. Gore Ph.D., University of Texas at Austin

2
Environmental Endocrine-Disrupting Chemicals (EDCs)
Compounds in the environment that interfere with, block, or mimic effects of natural hormones.
Plastics (BPA), Plasticizers (phthalates)
Industry (PCBs, dioxins)
Pesticides, fungicides (DDT, methoxychlor, vinclozolin)
Pharmaceuticals (DES, EE)
Phytoestrogens (soy, alfalfa)
Heavy metals

3
Estrogenic EDCs
BPA
PCBs
Pesticides (methoxychlor)
Phytoestrogens (?)
Heavy metals

4
Estrogenic EDCs
Mechanisms of action:
Nuclear hormone receptors – ERa, ERb
Membrane receptors – GPER (GPR30)
Steroidogenic enzymes (p450 aromatase)
Steroid metabolizing enzymes – steroid sulfatase
Neurotransmitter receptors

EDCs –Brain & Behavior
5
Estrogenic EDCs
Peripheral hormones,
Reproductive function, Behaviors
“Fetal/developmental basis
of adult disease”

6
Bisphenol A (BPA) – background
Monomer used to manufacture polycarbonate plastics, food liners, dental sealants.
Used in high volume: >6 billion lbs annually.
Heat causes hydrolysis and leaching.
H3C
C3H
HO
OH
Richter et al., Reprod. Toxicol. 24: 199-224 (2007)

7
Bisphenol A (BPA) – mechanisms of action
Estrogen receptor agonist/antagonist – up-regulation of Esr1, Esr2
Androgen receptor antagonist
Thyroid hormone receptor antagonist
AhR, RARa, RXRa are up-regulated by BPA
Enzyme activity
Epigenetic modifications (DNA methylation)
ER agonist effects are best-studied.

8
Bisphenol A (BPA) – low doses
Generally used to refer to “environmentally” or “ecologically” relevant.
LOAEL EPA reference dose = 50 mg/kg/day
However: Is there really a LOAEL?

9
Bisphenol A (BPA) – humans
Measurable in serum, urine, amiotic fluid, placenta, umbilical cord blood, and human blood.
Serum levels estimated from 0.2 to 20 ng/ml.
Amniotic fluid levels measured at 8.3 ng/ml.
Breast milk: mean 0.61 ng/ml.
Urine: Numerous studies show detectable BPA.
Assays include GC-MS, HPLC, ELISA, with sensitivity from 0.01 to 0.5 ng/ml.
Vandenberg et al., Reprod. Toxicol. 24: 139-177 (2007)

10
Bisphenol A (BPA) – other important considerations
Gestational/early postnatal exposures and long delay until the manifestation of a dysfunction.
Multiple mechanisms make prediction of outcomes difficult.
Likelihood of mixtures of EDC exposures.
Individual differences in genes and factors regulating gene expression.

11
Bisphenol A (BPA) – the brain
Increased aggressive behavior
Increased motor activity
Increased pain sensitivity
Impaired learning & memory
Decreased maternal behavior
Impairments in sexual behavior
Impaired neural plasticity – rodents & non-human primates
Hypothalamus and brain sexual differentiation are disrupted

12
Bisphenol A (BPA) – other endocrine targets
Mammary gland
Prostate
Ovary (oocytes)/ Testes (sperm)
Uterus and vagina/ epididymis & seminal vesicles
Adipocytes
Thyroid
Anti-androgen
Newbold, Reprod. Toxicol. 23: 290-296 (2007)

13
Polychlorinated Biphenyls (PCBs)
Estrogenic EDC
Persist & bioaccumulate
Adult exposure- contaminated food
Developmental exposure- placental and lactational transfer
Developmental PCB exposure- neurological/ reproductive deficits
Aroclor 1221: PCB used in our lab

14
PCB effects on P1
Treatment
Vehicle (DMSO)
E2 (50 µg)
A1221 (1 mg/kg)
Birth
E0
E16
E18
P0
♂
♂
♀
♀
P1
P60
Puberty
Exposure during the critical period of brain sexual differentiation

15
ERα Expression in the mPOA (P1)
Female
DMSO
A1221
Male
DMSO
A1221
Sarah Dickerson, PhD dissertation (unpub.)

16
Apoptosis in the mPOA (P1)
DAPI
TUNEL
DAPI + TUNEL
Apoptosis is lower in females than males.
PCBs cause increased apoptosis in females – making them more “male-like.”

17
PCB effects in adulthood
Injections
Vehicle (DMSO)
E2 (50 µg)
A1221 (1 mg/kg)
Birth
E0
E16
E18
P0
♂
♂
♀
♀
P1
P60
Puberty
Postnatal development, Reproductive cycles,
Hypothalamic protein/gene expression, Behavior

Developmental effects
Eye opening: Advanced in females (PCB).
Pubertal timing: Advanced in females (EB, PCB), delayed in males (EB, PCB).
Estrous cyclicity: Prolonged cycles in EB (46%), PCB (33%).
18

19
Hypothalamic control of reproduction
EDCs

ERα cells in AVPV (P60)
Female
Male
DMSO
A1221
DMSO
A1221
ERa is greater in the AVPV of females than males.
PCBs cause ERa to decrease in the AVPV of females – making them more “male-like.”
20

21
Kisspeptin in AVPV (P60)
Female
Male
DMSO
A1221
DMSO
A1221
Kisspeptin is greater in the AVPV of females than males.
PCBs cause kisspeptin to decrease in the AVPV of females – making them more “male-like.”

22
GnRH-Fos co-expression (P60) in females
The co-expression of Fos in GnRH neurons is significantly suppressed in PCB females.
2X
20X
40X
100X

23
Paced mating behavior in females
Reproductive success is the ultimate biological outcome.
Reproductive success is enhanced when the female controls the pace of the mating.
A paced mating paradigm enables dissection of female-typical behaviors.
RM Steinberg et al. (2007) Horm Behav 51: 364-372.

Summary
Exposure to estrogenic EDCs during fetal development has long-term consequences on the molecular and cellular processes controlling reproduction.
EDCs are associated with the masculinization of the hypothalamus of females.
Puberty and reproductive physiology are perturbed, and reproductive behaviors are compromised.
24

Implications
I propose that fetal exposures to EDCs reprogram the hypothalamus, and that this programming permanently compromises reproductive success.
I also believe that these effects may be transmitted to future generations through molecular epigenetic changes.
25

26
Acknowledgments
Funding:
NIH RC1 ES018139
NIH R21 ES12272
PhRMA
UT-Austin Fellowships
Sarah Dickerson
Deena Walker

http://www.nmslab.com	62
http://www.nmslabs.com	41
http://nmslabs.com	5
http://216.128.30.159	1

NMS Labs Dinner Presentation by Dr. Andrea Gore 5-27-10

by nmslabs on Dec 16, 2010

Accessibility

Categories

Tags

Upload Details

Usage Rights

4 Embeds 109

Statistics

NMS Labs Dinner Presentation by Dr. Andrea Gore 5-27-10 — Presentation Transcript