Female Reproductive Toxicology
1 ENV 310 2017 R Loch-Caruso The Inside Story
Fallopian/uterine tubes
Ovary
Uterus Cervix Vagina
2 Female Reproductive Tract Differentiation
Anterior ends of paramesonephric ducts form uterine fallopian tubes Posterior ends of paramesonephric ducts fuse to form uterine corpus (body)
3 ENVIRON 310 2017 Differentiation of Internal Reproductive Tract
Immature urogenital tract of human embryo at 8 weeks gestation
4 ENVIRON 310 2017 Female Reproductive Tract Differentiation
Chromosomal Gonadal Phenotypic Sex Sex Sex
Primordial gonads Lack of testicular hormones allows No Y chromosome differentiate into ovaries in absence of Y female tract to chromosome gene differentiate & causes products male tract to die
5 5 Ovarian toxicants can disrupt:
Oocyte production Sex steroid hormone production Estrogen Progesterone Androgens Ovary of adult
6 ENV 310 2017 R Loch-Caruso Follicles Ovarian Follicles
Ovary
Oogenesis takes place in ovarian follicles Single oocyte per follicle Follicular cells surround each oocyte Synthesize estrogen, progesterone & androgen
7 ENV 310 2017 R Loch-Caruso Oogenesis: Production of Female Germ Cells
Oogonium 46 Primary oocyte 46 46 Before birth Secondary oocyte Before each & 1st polar body ovulation 23 23
Fertilized ovum After & polar bodies 23 23 23 23 fertilization
8 ENV 310 2017 R Loch-Caruso Rita Loch-Caruso Oogenesis is Disrupted by DNA Damage
DNA damage is dangerous to cells that attempt to divide with a damaged DNA template Oogenesis undergo cell division in a narrow time frame in cycle DNA damage causes oocyte cell death leading to decreased fertility DNA repair Female gametes retain DNA repair capability throughout oogenesis
9 ENV 310 2017 R Loch-Caruso Some toxicants deplete oocytes by inducing apoptosis
4-Vinylcyclohexene Used in rubber production Is metabolized to a DNA damaging epoxide metabolite Selectively depletes germ Ovary showing different stages of cells in ovaries by apoptosis follicle development
10 ENV 310 2017 R Loch-Caruso 2-Bromopropane (2-BP) Alternative to Korean electronics workers chlorofluorocarbons as metal (1995) cleaning fluid 17 of 25 female workers had ovarian dysfunction & amenorrhea Only 2/17 affected females regained normal ovarian function within 2 years of cessation of exposure Mutagenic in bacteria DNA damage in rat Leydig cells 6 of 8 male workers had oligospermia or azospermia
11 ENV 310 2017 R Loch-Caruso DNA Damage may Cause Premature Reproductive Senescence
Cigarette smoking in women ≥ 2 packs/day decreases age of onset of menopause 1 pack/day Cigarette smoke contains Nonsmoker polycyclic aromatic hydrocarbons (PAHs) PAHs are metabolized to DNA damaging metabolites in the
ovary http://healthline99.com/ PAHs deplete germ cells in Age (years) female rodents who then show premature senescence
12 ENV 310 2017 R Loch-Caruso Human Chromosomes
13 ENV 310 2017 R Loch-Caruso Chromosome Segregation
Meiosis Animation
14 ENV 310 2017 R Loch-Caruso Heteroploidy: Error of Chromosome Number Aneuploidy Gain or loss of single chromosome Trisomy is most common Causes of heteroploidy Microtubule disruptors Failure of chromosomes to disengage after synapsis during meiosis Some cancer chemotherapy drugs are microtubule disruptors Colchicine Taxol Vinblastine From: Medical Embryology 502, Gametogenesis, University of Michigan
15 ENV 310 2017 R Loch-Caruso Aneuploidy is associated with spontaneous abortion
Aneuploidy accounts for the majority of pregnancy loss Inversely related to gestation age at time of spontaneous abortion Most aneuploidy arises during gametogenesis Microtubule disruption The fungicide carbendazim is a microtubule / spindle poison and increases pregnancy loss in female mated hamsters exposed just prior to fertilization.
16 ENV 310 2017 R Loch-Caruso Hypothalamic-Pituitary-Ovarian Axis Hypothalamus The pituitary “master gland” secretes hormones that regulate ovarian hormone synthesis Pituitary Release of pituitary hormones is dependent on neuronal (brain) input to the hypothalamus & on feedback from circulating ovarian hormones Hormones The hypothalamic-pituitary-ovarian Ovary axis developmental program is established early in life and is sex- Hormones specific
Target Cell 17 EHS 602 Rita Loch-Caruso Sexual Differentiation of Brain Testosterone is metabolized by the brain to estrogen In rodents: Estrogen induces a “masculine” brain during embryonic development Females exposed prenatally to synthetic estrogens or testosterone develop abnormal brain functions due to “masculinization” sites.sinauer.com The extent to which this occurs in humans is controversial α-Fetoprotein avidly binds endogenous estrogens and limits estrogen bioavailability to fetal tissues
18 ENVIRON 310 2017 Disruption of the Hypothalamic-Pituitary-Gonadal Axis Developmental Program
Males have testosterone estrogenic stimulation of developing brain masculinized brain pattern Male pattern is characterized by tonic pattern of pituitary gonadotropin secretion that is refractory to estrogen stimulation In females, bisphenol A & methoxyclor exposure during critical period disrupts hormone cycling in adulthood Thought to be mediated by estrogenic activity of the toxicants
19 ENVIRON 310 2017 Hypothalamic-Pituitary-Ovarian Axis
Hypothalamus
Pituitary
LH + FSH +
Progesterone - Estrogen +
Ovary
20 ENV 310 2017 R Loch-Caruso Women’s Reproductive Cycles
Hormonal (estrogen, progesterone, LH & FSH) Ovarian follicular Vaginal Uterine Menstrual
21 Orchestration of Women’s Reproductive Cycles
22 http://www.soc.ucsb.edu/sexinfo/article/the-menstrual-cycle Hypothalamic-Pituitary-Ovarian Axis
Hypothalamus
Pituitary
Lindane
DEHP Progesterone - Estrogen + Chromium-6
Ovary
23 ENV 310 2017 R Loch-Caruso Disruption of Hormone Synthesis Lindane (insecticide and pharmaceutical agent) Acts on the rat pituitary gland → inhibits release of a pituitary hormone necessary for ovulation → blocks ovulation Diethylhexyl phthalate (DEHP) (plasticizer) Inhibits expression of gene for an enzyme needed to synthesize estrogen in the ovary Low estrogen → prevents pituitary from releasing LH, the hormone needed for ovulation → blocks ovulation → decreases fertility Chromium-6 Associated with menstrual abnormalities in exposed women Evidence for oxidative stress mechanism in rat: generates reactive oxygen species within gonads → decreases estradiol and progesterone in blood. Antioxidants prevent adverse reproductive effects in rat
24 ENV 310 2017 R Loch-Caruso Puberty Onset
25 ENV 310 2017 R Loch-Caruso PBBs in Michigan
In Michigan (1973), the fire retardant FireMaster was accidently added to livestock feed instead of the nutritional supplement NutriMaster Contaminated animal and dairy products were distributed & consumed throughout Michigan A registry of exposed individuals was established
26 ENV 310 2017 R Loch-Caruso Polybrominated Biphenyls (PBBs) & Puberty
Daughters of women exposed to PBBs were evaluated for puberty onset Breastfed girls exposed to high levels of PBB in utero (≤7 ppb) had an earlier onset of puberty
HM Blanck et al., Epidemiology 11:641– 647, 2000 27 ENV 310 2017 R Loch-Caruso Breast
Main function Milk production Potential problems Reduced number of lobes (stunted development) Precocious breast development (thelarche) Poor lactation postpartum
28 ENV 310 2017 R Loch-Caruso Toxicology of the Breast
Rats exposed to TCDD on gestation day 15 had abnormal mammary gland development Reduced primary branches Decreased epithelial elongation Fewer alveolar buds and lateral branches Persisted into adulthood
SE Fenton et al., Toxicol Sci 67(1):63-74, 2002
29 ENV 310 2017 R Loch-Caruso Preterm Birth
Preterm birth is the birth of a live infant between 20 and 37 completed weeks of gestation
Last day of Limit of Preterm menstruation viability (37 weeks)
20 0 40 Gestation Length (weeks)
30 ENV 310 2017 R Loch-Caruso DDT Many studies found an associations between DDT exposure and preterm birth Environmentally persistent insecticide Continues to be applied worldwide for malarial control of mosquitoes © 2001, Smithsonian Institution Press. Possible mechanism: increased http://www.smithsonianlegacies.si.edu/ intracellular calcium in uterine muscle --> increasing uterine contractions
31 ENV 310 2017 R Loch-Caruso Air Pollution & Preterm Birth
Women are at increased risk http://www.fotosearch.com/ of delivering preterm if they: Live near sources of air pollution (roads, industries, shipyards) Are exposed to environmental tobacco smoke
Mechanism not clear http://www.demographia.com/db-fuji.htm
http://www.publichealthgrey 32 ENV 310 2017 R Loch-Caruso bruce.on.ca/ Toxicant Activation of Parturition Pathways
Loch-Caruso Lab
Some toxicants have been shown to increase reactive oxygen species (ROS) production in placenta and its membranes and thereby stimulate release of cell signaling molecules known to stimulate labor Brominated flame retardant chemicals Phthalate metabolite MEHP Trichloroethylene (TCE) metabolite DCVC
33 ENV 310 2017 R Loch-Caruso Listeria Infection Listeria monocytogenes bacterial infection during pregnancy causes preterm birth & spontaneous abortion Colonizes placenta and causes placental degeneration About 2,500 people in the US become ill from listeria every year 20% die from the disease Pregnant women are about 20 times more likely than other healthy adults to get ill from listeria The immune system is suppressed during pregnancy About a third of reported cases occur in pregnant women
34 ENV 310 2017 R Loch-Caruso Listeria is a Common Food Contaminant Pregnant women are advised to avoid: Raw (unpasteurized) milk Foods that contain unpasteurized milk Premade ham salad, chicken salad, egg salad, tuna salad, seafood salad, and bean sprouts Pregnant women are advised to avoid soft cheeses unless labeled as made with pasteurized milk e.g., brie, Camembert, feta, blue-veined cheeses, Mexican-style cheeses such as "queso blanco fresco" Pregnant women are advised to avoid hot dogs, luncheon meats & deli meats unless reheated to http://images.google.com/ steaming hot
35 ENV 310 2017 R Loch-Caruso Pregnancy Alters Susceptibility to Toxicants
Increased absorption of inhaled toxicants Pregnant women have an increased respiratory rate & tidal volume Increased sensitivity to respiratory irritants & allergens
36 ENV 310 2017 R Loch-Caruso Breast Milk Contamination
Alcohol distributes to milk in 1:1 ratio with mother’s blood Lipophilic chemicals concentrate in milk because of high fat DDT, polychlorinated biphenyls (PCBs), carbon tetrachloride Benefits of breast feeding demonstrated despite contamination with PCBs and dioxin
37 ENV 310 2017 R Loch-Caruso Important Concepts
Why and how DNA damage can affect fertility Endocrine disruption mechanism examples Michigan PBB contamination & effects on puberty Listeria infection during pregnancy Possible mechanism examples of toxicant-related preterm birth How pregnancy alters susceptibility to toxicants
38 ENV 310 2017 R Loch-Caruso Alexander Tsiaras: Conception to birth – visualized
39 ENV 310 2017 R Loch-Caruso