Effects of Bisphenol A and Methoxychlor on Xenopus laevis Embryos

Primordial germ cells (PGCs) are a population of cells that will ultimately differentiate into the organism’s sex cells. Their distinctiveness from somatic cells stems from the maintenance of pluripotency much longer than the surrounding differentiating cells. The toxins bisphenol-A (BPA) and methoxychlor (MXC) have been shown to have adverse effects on the reproductive systems of various animal models. Here, we use model organism Xenopus laevis to probe the fate of primordial germs cells in the developing Xenopus embryo in response to the presence of these toxicants. We show that BPA affects the total PGC population at the tailbud stage when the embryos are exposed at the 32-cell stage. Conversely, MXC did not exhibit an effect on the final PGC count. However, exposure to MXC does result in somatic malformation such as, decrease in tailbud melanocytes, a malformed gut, and early onset muscle movements.Ope

Gambling with Gametes: A Tale of Two Toxins

Primordial germ cells (PGCs) are a population of cells that will ultimately differentiate into the organism’s sex cells. Their distinctiveness from somatic cells stems from the maintenance of pluripotency much longer than the surrounding differentiating cells. The toxins bisphenol-A (BPA) and methoxychlor (MXC) have been shown to have adverse effects on the reproductive systems of various animal models. Here, we use model organism Xenopus laevis to probe the fate of primordial germs cells in the developing Xenopus embryo in response to the presence of these toxicants. We show that BPA affects the total PGC population at the tailbud stage when the embryos are exposed at the 32-cell stage. Conversely, MXC did not exhibit an effect on the final PGC count. However, exposure to MXC does result in somatic malformation such as, decrease in tailbud melanocytes, a malformed gut, and early onset muscle movements.Ope

PPARγ Loss Leads to Reduced Fertility

The peroxisome proliferation-activated receptor gamma (PPARγ) is expressed in many cell types including mammary epithelium, ovary, macrophages, and B- and T-cells. PPARγ has an anti-proliferative effect in pre-adipocytes and mammary epithelial cells, and treatment with its ligands reduced the progression of carcinogen-induced mammary tumors in mice. Because PPARγ-null mice die in utero it has not been possible to study its role in development and tumorigenesis in vivo. To investigate whether PPARγ is required for the establishment and physiology of different cell types, a cell-specific deletion of the gene was carried out in mice using the Cre-loxP recombination system. We deleted the PPARγ gene in mammary epithelium using WAP-Cre transgenic mice and in epithelial cells, B- and T-cells, and ovary cells using MMTV-Cre mice. The presence of PPARγ was not required for functional development of the mammary gland during pregnancy and for the establishment of B- and T-cells. In addition, no increase in mammary tumors was observed. However, loss of the PPARγ gene in oocytes and granulosa cells resulted in impaired fertility. These mice have normal populations of follicles, they ovulate and develop corpora lutea. Although progesterone levels are decreased and implantation rates are reduced, the exact cause of the impaired fertility remains to be determined

Urinary Bisphenol A Concentrations and Implantation Failure among Women Undergoing in Vitro Fertilization

Background: Bisphenol A (BPA) is a synthetic chemical widely used in the production of polycarbonate plastic and epoxy resins found in numerous consumer products. In experimental animals, BPA increases embryo implantation failure and reduces litter size. Objective: We evaluated the association of urinary BPA concentrations with implantation failure among women undergoing in vitro fertilization (IVF). Methods: We used online solid phase extraction–high performance liquid chromatography–isotope dilution tandem mass spectrometry to measure urinary BPA concentrations in 137 women in a prospective cohort study among women undergoing IVF at the Massachusetts General Hospital Fertility Center in Boston, Massachusetts. We used logistic regression to evaluate the association of cycle-specific urinary BPA concentrations with implantation failure, accounting for correlation among multiple IVF cycles in the same woman using generalized estimating equations. Implantation failure was defined as a negative serum β-human chorionic gonadotropin test (β-hCG < 6 IU/L) 17 days after egg retrieval. Results: Among 137 women undergoing 180 IVF cycles, urinary BPA concentrations had a geometric mean (SD) of 1.53 (2.22) µg/L. Overall, 42% (n = 75) of the IVF cycles resulted in implantation failure. In adjusted models, there was an increased odds of implantation failure with higher quartiles of urinary BPA concentrations {odds ratio (OR) 1.02 [95% confidence interval (CI): 0.35, 2.95}, 1.60 (95% CI: 0.70, 3.78), and 2.11 (95% CI: 0.84, 5.31) for quartiles 2, 3, and 4, respectively, compared with the lowest quartile (p-trend = 0.06). Conclusion: There was a positive linear dose–response association between BPA urinary concentrations and implantation failure

Free Fatty Acids Rewire Cancer Metabolism in Obesity-Associated Breast Cancer via Estrogen Receptor and mTOR Signaling

Obesity is a risk factor for postmenopausal estrogen receptor alpha (ERα)-positive (ER+) breast cancer. Molecular mechanisms underlying factors from plasma that contribute to this risk and how these mechanisms affect ERα signaling have yet to be elucidated. To identify such mechanisms, we performed whole metabolite and protein profiling in plasma samples from women at high risk for breast cancer, which led us to focus on factors that were differentially present in plasma of obese versus nonobese postmenopausal women. These studies, combined with in vitro assays, identified free fatty acids (FFA) as circulating plasma factors that correlated with increased proliferation and aggressiveness in ER+ breast cancer cells. FFAs activated both the ERα and mTOR pathways and rewired metabolism in breast cancer cells. Pathway preferential estrogen-1 (PaPE-1), which targets ERα and mTOR signaling, was able to block changes induced by FFA and was more effective in the presence of FFA. Collectively, these data suggest a role for obesity-associated gene and metabolic rewiring in providing new targetable vulnerabilities for ER+ breast cancer in postmenopausal women. Furthermore, they provide a basis for preclinical and clinical trials where the impact of agents that target ERα and mTOR signaling cross-talk would be tested to prevent ER+ breast cancers in obese postmenopausal women

The mechanism of action of 4-vinylcyclohexene diepoxide in the induction of ovarian toxicity.

Exposure of females to environmental chemicals can disrupt reproductive function by altering the normal functions of the oviducts, uterus, cervix, hypothalamus, anterior pituitary, or ovary. Compounds that directly affect the ovary can have a profound impact on fertility. Chemicals which destroy oocytes contained in primordial follicles cause early menopause and permanent infertility because only a finite number of these oocytes is contained within the ovary at birth and cannot be replaced. 4-vinylcyclohexene diepoxide (VCD) is one compound that has been shown to destroy oocytes contained in primordial follicles in rats and mice. The purpose of this dissertation was to determine: (1) the contribution of ovarian metabolism to VCD-induced oocyte depletion, (2) whether age is an important factor in the ability of VCD to disrupt reproduction, (3) the initial follicular and cellular target for destruction of oocytes by VCD, and (4) a possible mechanism by which VCD induces ovotoxicity. Data from this dissertation have shown that ovarian metabolism contributes to VCD-induced ovotoxicity because small pre-antral follicles (those follicles which are susceptible to VCD) were shown to have a reduced capacity to detoxify VCD compared to nontarget tissues such as large pre-antral follicles and hepatocytes. It has also been shown that age may not be an important factor in the ability of VCD to destroy oocytes because VCD destroyed oocytes to an equal extent in adult and immature rats. Age, however, was a factor in the ability of VCD to disrupt cyclicity and uterine function since reduced cyclicity and uterine weights were observed in adult, but not immature rats. Additionally, these studies have shown that the initial follicular target for VCD is the primordial follicle, 7-15 days of daily dosing are required to observe oocyte destruction, and VCD modulates secretion of a factor by granulosa cells that may lead to destruction of oocytes via inhibition of protein synthesis. Collectively, these studies have enhanced our understanding of factors which contribute to destruction of oocytes in small pre-antral follicles. Additionally, these studies have provided information regarding interactions of granulosa cells and oocytes contained in those follicles

Role of microRNA in Endocrine Disruptor-Induced Immunomodulation of Metabolic Health

The prevalence of poor metabolic health is growing exponentially worldwide. This condition is associated with complex comorbidities that lead to a compromised quality of life. One of the contributing factors recently gaining attention is exposure to environmental chemicals, such as endocrine-disrupting chemicals (EDCs). Considerable evidence suggests that EDCs can alter the endocrine system through immunomodulation. More concerning, EDC exposure during the fetal development stage has prominent adverse effects later in life, which may pass on to subsequent generations. Although the mechanism of action for this phenomenon is mostly unexplored, recent reports implicate that non-coding RNAs, such as microRNAs (miRs), may play a vital role in this scenario. MiRs are significant contributors in post-transcriptional regulation of gene expression. Studies demonstrating the immunomodulation of EDCs via miRs in metabolic health or towards the Developmental Origins of Health and Disease (DOHaD) Hypothesis are still deficient. The aim of the current review was to focus on studies that demonstrate the impact of EDCs primarily on innate immunity and the potential role of miRs in metabolic health

Organizational and activational effects of estrogenic endocrine disrupting chemicals Efeitos de organização e ativação dos desreguladores estrogênicos

Endocrine disruption is a hypothesis of common mode of action that may define a set of structurally varied chemicals, both natural and synthetic. Their common mode of action may suggest that they produce or contribute to similar toxic effects, although this has been difficult to demonstrate. Insights from developmental biology suggest that development of hormone sensitive systems, such as the brain and the genitourinary tract, may be particularly sensitive to EDCs. Because these systems are both organized and later activated by hormones, the brain and vagina may be valuable model systems to study the toxicity of EDCs in females and to elucidate mechanisms whereby early exposures appear to affect long term function.A desregulação endócrina é uma hipótese de um modo de ação comum capaz de definir um conjunto de substâncias químicas estruturalmente variadas, tanto naturais quanto sintéticas. O modo de ação comum pode sugerir que produzam ou contribuam para efeitos tóxicos semelhantes, embora tal hipótese tenha sido difícil de demonstrar. Evidências provenientes da biologia do desenvolvimento sugerem que o desenvolvimento de sistemas sensíveis aos hormônios, tais como o cérebro e o trato genito-urinário, podem ser particularmente sensíveis aos desreguladores endócrinos. Uma vez que tais sistemas são organizados, e depois ativados, por hormônios, o cérebro e a vagina podem representar modelos importantes para estudar a toxicidade dos desreguladores endócrinos e para elucidar os mecanismos pelos quais parecem afetar a função a longo prazo

Methoxychlor and Estradiol Induce Oxidative Stress DNA Damage in the Mouse Ovarian Surface Epithelium

Estrogenic compounds such as 17β-estradiol (E2) and methoxychlor (MXC) induce oxidative stress damage in breast cells and mouse ovarian follicles, respectively. However, little is known about whether estrogenic compounds cause oxidative stress in the ovarian surface epithelium (OSE). Thus, this work tested the hypothesis that E2 and MXC cause oxidative stress in the OSE. To test this hypothesis, we employed an improved mouse tissue culture assay in which OSE cells were treated with hydrogen peroxide (H2O2; positive control), MXC, or E2 ± the anti-oxidant vitamin E, or progesterone. The cells then were subjected to a novel direct immunofluorescent assay in which cells in the microtiter plate were reacted with antibodies that detect oxidative damage to DNA (8-hydroxy-2′-deoxyguanosine). The signal was identified with a tyramide Alexa Fluor fluorescent probe and quantified by microfluorimetry. Correction for cellularity was carried out for each well with a fluorescent DNA dye system (CyQuant) at a different wavelength. After 24 h, the mean Alexa Fluor CyQuant ratio was 11.3 ± 0.9 for controls, 132 ± 15 for H2O2 treated positive control cells (p ≤ 0.01 from control), 105 ± 6.6 for E2 treated cells (p ≤ 0.01 from control), and 64 ± 5.1 for MXC-treated cells (p ≤ 0.01 from control). After 72 h, the mean ratio was 121 ± 10.6 for controls, 391 ± 23 for H2O2 treated cells (p ≤ 0.01 from control), 200 ± 15 for E2 treated cells (p ≤ 0.03), and 228 ± 21 for MXC-treated cells (p ≤ 0.01). Further, vitamin E, but not progesterone, protected OSE cells from E2- and MXC-induced oxidative damage. This study demonstrates the feasibility of direct immunofluorescent quantitation of DNA adducts in cell cultures without DNA extraction. Moreover, these data indicate that E2 and MXC produce oxidative DNA damage in the OSE, and that this damage is prevented by the anti-oxidant vitamin E