Developmental exposure to Bisphenol a impairs the uterine response to ovarian steroids in the adult

Toxicological Impact of Bisphenol A on Females' Reproductive System: Review Based on Experimental and Epidemiological Studies

The study encompassing research papers documented in the last two decades pertaining to the possible influence of bisphenol A (BPA) on the fertility of females are appraised with emphasis on the influence of BPA in reproductive organs (uterus and ovaries) and pregnancy outcomes including discussion on the reproductive process (implantation, estrous cycle, hormone secretion); outcomes reveal a connection amongst BPA and female infertility. Ovary, uterus, and its shape as well as function can alter a person's ability to become pregnant by influencing the hypothalamus-pituitary axis in the ovarian model. Additionally, implantation and the estrous cycle may be affected by BPA. However, more research is warranted to comprehend the underlying action mechanisms and to promptly identify any imminent reproductive harm.

Uterine histopathology and steroid metabolism in a polycystic ovary syndrome rat model

The aim of this study was to investigate uterine lesions, uterine endocrine status and expression of genes involved in uterine differentiation in a rat model of polycystic ovary syndrome (PCOS). The possible involvement of the androgen receptor (AR) was also investigated. PCOS rats showed an increased incidence of uterine epithelial and glandular lesions and elevated serum testosterone level, which was not detected in uterine tissue. Uterine 17β-estradiol, estrone and progesterone were detected in 100%, 75% and 50% of the animals, respectively. This was associated with a decrease in Star and an increase in Hsd17b2, Srd5a1 and Cyp19a1, suggesting that uterine steroids are not synthesized de novo in PCOS and that alterations in these enzymes may explain the absence of testosterone and low progesterone. In addition, ESR2 decreased and AR increased, suggesting possible steroid receptor crosstalk. Genes associated with uterine differentiation, PTEN and WNT5a, also showed reduced expression. PCOS rats treated with flutamide, an AR antagonist, were similar to PCOS rats in terms of uterine lesions, serum steroid levels, ESR2, PTEN and WNT5a expression. However, testosterone, AR and aromatase levels were similar to control rats, with decreased expression of ESR1 and HOXA10, suggesting that these expressions are AR dependent. Our results suggest that the primary cause of the observed uterine lesions in the PCOS rat model is the altered endocrine status and consequently changes in genes related to uterine differentiation.

Exposure to endocrine disrupting chemicals (bisphenols, parabens, and triclosan) and their associations with preterm birth in humans

Preterm birth in humans (PTB), defined as birth prior to 37 weeks of gestation, is one of the most important causes of neonatal morbidity and mortality and is associated with adverse health outcomes later in life. Attributed to many different etiological factors, estimated 15.1 million or 11.1% of births each year are preterm, which is more than 1 per 10 livebirths globally. Environmental pollution is a well-established risk factor that could influence the pathogenesis of PTB. Increasing evidence has shown an association between maternal exposure to endocrine disrupting chemicals (EDCs) and PTB. This scoping review aims to summarize current research on the association between EDC exposure and PTB in humans. Database PubMed was used to identify articles discussing the effect of selected EDCs, namely bisphenol A, bisphenol S, bisphenol F, parabens, and triclosan, found in plastics, cosmetics and other personal care products, on PTB occurrence. Regardless of some inconsistences in the findings across studies, the reviewed studies suggest a potential association between involuntary exposure to reviewed EDCs and the risk of PTB. However, further studies are needed to delineate exact correlations and mechanisms through which EDC exposure causes PTB so that efficient preventative measures could be implemented. Until then, health care providers should inform women about possible EDC exposure thus empowering them to make healthy choices and at the same time decrease the EDC negative effects.

Endocrine-disrupting compounds and their impact on human placental function: evidence from placenta organ-on-chip studies

The effects of endocrine-disrupting compounds (EDCs) on the placenta, a critical gestational organ for xenobiotic protection, are well reported; however, models to determine the role of EDCs in placental disruption are limited. An advanced 2nd-trimester human placenta organ-on-chip model (2TPLA-OOC) was developed and validated, with six representative cells of the maternal and the fetal interface interconnected with microchannels. Various EDCs (150 ng mL-1 each of bisphenol A, bisphenol S, and polybrominated diphenyl ethers-47 and -99) were gradually propagated across the chip for 72 hours, and their various effects were determined. Cigarette smoke extract (CSE), an environmental risk factor, was used as a positive control. EDCs produced overall oxidative stress in the placental/decidual cells, induced cell-specific endocrine effects, caused limited (<10%) apoptosis/necrosis in trophoblasts and mesenchymal cells, induced localized inflammation but an overall anti-inflammatory shift, did not change immune cell migration from stroma to decidua, and did not affect placental nutrient transport. Overall, (1) the humanized 2TPLA-OOC recreated the placental organ and generated data distinct from the trophoblast and other cells studied in isolation, and (2) at doses associated with adverse pregnancies, EDCs produced limited and localized insults, and the whole organ compensated for the exposure.

Medicinal Mushroom Leucocalocybe mongolica Imai Extracts Improve Mammary Gland Differentiation in Lactating Rats via Regulating Protein Expression

Leucocalocybe mongolica is a known medicinal mushroom in China. It possesses many biological activities. This study investigated the effect of L. mongolica petroleum ether and water extracts (200, 500, and 1,000 mg/kg BW) on mammary gland differentiation during lactation. However, prolactin, growth hormone, progesterone, and estrogen levels were determined in serum by ELISA assay. Immunofluorescence, western blot, and real-time PCR were utilized to evaluate the expression levels of β-casein, α-Lactalbumin, prolactin receptor, progesterone receptor, and STAT-5a. The immunohistochemistry staining was used to detect the presence of steroid receptors. The results showed that petroleum ether and water extracts increased milk yield and milk content of calcium, total fat, total carbohydrate, and total protein. Prolactin and growth hormone levels were significantly upregulated in all treated groups compared with the control group. In contrast, progesterone and estrogen were downregulated. The high doses of petroleum ether and water extracts increased the expression levels of β-Cas, α-Lactalb, PRLR, PR, and STAT-5a. The observation of histological sections showed that the extracts induced higher mammary gland differentiation than the control group. This study is the first to use mushrooms as nutritional supplements to improve milk production and mammary gland differentiation during lactation.

Actions of Bisphenol A on Different Feto-Maternal Compartments Contributing to Preterm Birth

Preterm birth remains to be one of the most prevalent obstetric complications worldwide. Since there are multiple etiological factors associated with this disease process, an integrative literature search in PubMed and Scopus databases on possible mechanism of action and effect of bisphenols on exposure on human or animal placental samples in preterm birth was conducted. From 2332 articles on initial literature search, 63 studies were included for full data extraction. Altogether, several pathways were shown to be possibly affected by bisphenols, leading to dysregulations in structural and endocrine foundation in the placenta, potential induction of senescence and failure of decidualization in the decidua, and possible propagation of inflammation in the fetal membranes. Combined, these actions may eventually counteract bisphenol-induced relaxation of the myometrium and promote contractility alongside fetal membrane weakening. In totality, these individual impairments in gestation-critical processes may lead to failure of maintenance of pregnancy, and thus effecting preterm birth.

HOXA10 Regulates the Synthesis of Cholesterol in Endometrial Stromal Cells

BACKGROUND

The expression of homeobox A10 (HOXA10) in endometrial stromal cells is regulated by steroid hormones, especially by estrogen. As a precursor molecule of estrogen, abnormal cholesterol metabolism is significantly positively correlated with endometriosis. The purpose of this study was to explore the regulation of HOXA10 on cholesterol synthesis in endometrial stromal cells.

METHOD

mRNA expression data of eutopic endometrial stromal cell (ESC) and ovarian endometriotic cysts stromal cell (OESC) were download from the Gene Expression Omnibus (GEO) databases. Overexpression and silence of HOXA10 were conducted in cultured ESC and subjected to mRNA sequencing. The differentially expressed genes (DEGs) were selected by analyzing the sequencing data. Weighted gene co-expression network analysis (WGCNA) was applied to identify the key genes associated with HOXA10. The methylation rate of HOXA10 CpGs and the correlation between HOXA10 expression and the methylation in eutopic endometrial tissue (EU) and ovarian cyst (OC) were analyzed.

RESULTS

HOXA10 in ESC was significantly higher expressed than that in OESC. Six key genes (HMGCR, MSMO1, ACAT2, HMGCS1, EBP, and SQLE), which were regulated by HOXA10, were identified from the salmon4 module by WGCNA. All these key genes were enriched in cholesterol synthesis. Moreover, the expression of HOXA10 was negatively related to its CpGs methylation rate.

CONCLUSION

In this study, six key genes that were regulated by HOXA10 were selected, and all of them were enriched in cholesterol synthesis. This finding provided a new insight into the metabolic mechanism of cholesterol in ESC. It also provided a potential treatment strategy for cholesterol metabolism maladjustment in patients with ovarian endometriosis.

Endocrine-Disrupting Chemicals and Vitamin D Deficiency in the Pathogenesis of Uterine Fibroids

Uterine fibroids (UFs) are the most prevalent gynecologic neoplasm, affecting 70-80% of women over their lifespan. Although UFs are benign they can become life-threatening and require invasive surgeries such as myomectomy and hysterectomy. Notwithstanding the significant negative influence UFs have on female reproductive health, very little is known about early events that initiate tumor development. Several risk factors for UFs have been identified including vitamin D deficiency, inflammation, DNA repair deficiency, and environmental exposures to endocrine-disrupting chemicals (EDCs). EDCs have come under scrutiny recently due to their role in UF development. Epidemiologic studies have found an association between increased risk for early UF diagnosis and in utero EDC exposure. Environmental exposure to EDCs during uterine development increases UF incidence in a UF animal model. Notably, several studies demonstrated that abnormal myometrial stem cells (MMSCs) are the cell origin for UFs development. Our recent studies demonstrated that early-life EDC exposure reprogrammed the MMSCs toward a pro-fibroid landscape and altered the DNA repair and inflammation pathways. Notably, Vitamin D3 (VITD3) as a natural compound shrank the UF growth concomitantly with the reversion of several abnormal biological pathways and ameliorated the developmental exposure-induced DNA damage and pro-inflammation pathway in primed MMSCs. This review highlights and emphasizes the importance of multiple pathway interactions in the context of hypovitaminosis D at the MMSCs level and provides proof-of-concept information that can help develop a safe, long-term, durable, and non-surgical therapeutic option for UFs.

Effects of Endocrine-Disrupting Chemicals on Endometrial Receptivity and Embryo Implantation: A Systematic Review of 34 Mouse Model Studies

Several available studies have already analyzed the systemic effects of endocrine-disrupting chemicals (EDCs) on fertile woman and neonatal outcomes, but little is still known in humans about the precise mechanisms of interference of these compounds with the endometrial receptivity. There is consistent evidence that continuous and prolonged exposure to EDCs is a risk factor for reduced fertility and fecundity in women. Preliminary studies on mammalian models provide robust evidence about this issue and could help gynecologists worldwide to prevent long term injury caused by EDCs on human fertility. In this systematic review, we aimed to systematically summarize all available data about EDC effects on blastocyst endometrial implantation. We performed a systematic review using PubMed^®/MEDLINE^® to summarize all in vivo studies, carried out on mice models, analyzing the molecular consequences of the prolonged exposure of EDC on the implantation process. 34 studies carried out on mouse models were included. Primary effects of EDC were a reduction of the number of implantation sites and pregnancy rates, particularly after BPA and phthalate exposure. Furthermore, the endometrial expression of estrogen (ER) and progesterone receptors (PR), as well as their activation pathways, is compromised after EDC exposure. Finally, the expression of the primary endometrial markers of receptivity (such as MUC1, HOXA10, Inn and E-cadherin) after EDC contact was analyzed. In conclusion EDC deeply affect blastocyst implantation in mouse model. Several players of the implantation mechanism are strongly influenced by the exposure to different categories of EDC.

Evaluation of the effects of low nanomolar bisphenol A-like compounds' levels on early human embryonic development and lipid metabolism with human embryonic stem cell in vitro differentiation models

The widely used chemical bisphenol A (BPA) has been associated with several health effects. In recent years, many derivatives were developed to replace BPA although without thorough toxicological evaluation. Here, we employed a human embryoid body (EB)-based in vitro global differentiation and hepatic specification models, followed by RNA-seq analyses, to comprehensively study the potential developmental toxicity of six BPA replacements (BPS, BPF, BPZ, BPB, BPE, and BPAF), as compared to BPA. We found that those bisphenols may disrupt lineage commitment and lipid metabolism during early embryonic development. These effects mostly manifested via the dysregulation of HOX and APO family genes. Moreover, among the seven bisphenols analyzed, BPE seemed to have the mildest effects.

Evaluation of Development of the Rat Uterus as a Toxicity Biomarker

The developing uterus is highly sensitive to a brief exposure to different substances, in particular those with endocrine-disrupting activity. Thus, exposure to environmental, nutritional, chemical, and other xenobiotic factors affecting signaling events during critical organizational periods can alter the normal course of uterine development with lasting consequences. In this chapter, we provide an experimental protocol to evaluate the development of the rat uterus as a toxicity biomarker at two different developmental time points: (1) the neonatal period, on postnatal day (PND) 8, and (2) the prepubertal period, on PND21. In this experimental approach, we propose to assess: (1) uterine morphology and cytodifferentiation, (2) uterine cell proliferation, and (3) the expression of proteins involved in uterine organogenetic differentiation. All these morphological and molecular markers are useful tools to determine the consequences of exposure to toxicants with the potential to disrupt the uterine development.

The distribution of some homeobox proteins in the bovine placenta during gestation

Homeobox proteins are transcription factors known to be involved in the molecular basics of body model formation and transformation. Some homeobox proteins are known to play critical roles in the control of the extraembryonic development of the placenta during gestation and in the regulation of uterine and placental physiology in adults. The gravid uteruses and placentas of 27 Holsteins cows, obtained from private slaughterhouses, were used in this study. The tissues were assigned to three groups as belonging to the first, second and third timesters of gestation, based on the fetal ages determined. Subsequently, the tissues were subjected to immunohistochemical staining using antibodies specific to the proteins investigated in the study. The evaluation of the immunohistochemical findings obtained in this study, demonstrated the presence of trimester-dependent varying intensities of immunoreactions in the uterus and placenta. Immunoreactivity was observed particularly in the luminal and glandular epithelial cells of the uterus, as well as in stromal and some endothelial cells. Furthermore, immunoreactivity for the proteins HOXA10, HOXB6, HOXC6 and Dlx-5 was determined in the smooth muscle cells. Moreover, immunoreactivity was also detected in the maternal epithelium and fetal trophoblasts found in the structure of the placenta. The results suggest that the homeobox proteins investigated may have critical roles in the regulation of endometrial functions in cows, and the proliferation and differentiation of endometrial and placental cells. It is concluded that these proteins may have physiological roles in the formation and development of the placenta, as well as in the maintenance of pregnancy.

Effects of agricultural pesticides on the reproductive system of aquatic wildlife species, with crocodilians as sentinel species

Agricultural pesticides represent a significant class of endocrine-disrupting chemicals (EDCs) to which non-target organisms around the world are constantly exposed. Laboratory studies have found strong evidence showing the endocrine-disruptive potential of these pesticides at environmentally relevant exposure levels. Since the field of endocrine disruption continues to grow in richness and complexity, this review aims to provide an update on the effects of two agricultural pesticides that act as EDCs: atrazine and endosulfan. We will focus mainly on the effects on crocodilians due to their worldwide occurrence in tropical and sub-tropical wetland ecosystems and their ecological and physiological features, which render them vulnerable to exposure to pesticides with endocrine-disrupting action at all life stages. The results here reviewed provide important insights into the effects of hormonally active agricultural pesticides at cellular, tissue, and organ levels in the reproductive system of crocodiles. A better understanding of the effects of exposure to environmentally relevant doses of EDCs on the reproductive system of crocodilians will contribute to protect and improve the health of both wildlife species and humans.

Androgen receptor and uterine histoarchitecture in a PCOS rat model

Polycystic ovary syndrome (PCOS) is associated with hyperandrogenemia and uterine abnormalities. Our aim was to investigate the uterine effects of PCOS that are mediated through the androgen receptor (AR). After weaning, female rats were treated with sesame oil (Control), dehydroepiandrosterone (DHEA), or DHEA + flutamide (FLU, an AR antagonist) for 20 consecutive days. On postnatal day 41, serum, ovarian and uterine tissues were collected. DHEA and DHEA + FLU rats showed increased testosterone levels. DHEA rats showed increased epithelial height, glandular density, subepithelial stroma and myometrial thickness, associated with decreased nuclei density. These rats also showed increased uterine water content, with decreased aquaporin (AQP) 3, 7 and 8 expression in the uterine epithelium and increased AQP8 expression in the myometrium. DHEA rats also showed decreased uterine collagen remodeling, decreased cell proliferation in the subepithelial stroma, and increased apoptosis in the luminal and glandular epithelium and in the myometrium. They also showed an increase in insulin-like growth factor-1 and a decrease in phosphatidylinositol-3,4,5-trisphosphate 3-phosphatase. The uterine stroma of DHEA rats showed no changes in progesterone receptor or estrogen receptor alpha (ERα) and increased AR expression. DHEA + FLU rats showed a smaller increase in the myometrial thickness, an increase in the uterine water content without AQP8 induction and a smaller decrease in collagen remodeling. These rats also showed no apoptosis induction and decreased proliferation in the myometrium, decreased ERα in the subepithelial stroma and myometrium and no modifications in AR. Our results demonstrate that the uterine cell turnover and collagen remodeling in DHEA rats are regulated through AR, directly or indirectly associated with ERα expression.

Neonatal exposure to a glyphosate-based herbicide alters the uterine differentiation of prepubertal ewe lambs

The exposure to endocrine-disrupting compounds (EDCs), such as glyphosate-based herbicides (GBHs), during early life might alter female fertility. The aim of the present study was to evaluate the effects of neonatal exposure to a GBH on sheep uterine development. To achieve this, Friesian ewe lambs were exposed to GBH (2 mg/kg of body weight/day; n = 12) or vehicle (controls; n = 10) through s.c. injections, from postnatal day (PND) 1 to PND14; on PND45, the uteri were obtained to evaluate histomorphological and molecular parameters. Morphological parameters were determined by picrosirius-hematoxylin staining. Protein expression of Ki67 (as a cell proliferation marker), p27, and molecules involved in uterine organogenetic differentiation was measured by immunohistochemistry. We also determined the mRNA expression of the IGF molecular pathway by RT-PCR. Although histomorphology was not modified, the uteri of GBH-exposed ewe lambs showed lower cell proliferation, together with higher p27 protein expression. In addition, the uteri of GBH-exposed ewe lambs showed increased gene expression of insulin-like growth factor binding protein 3 (IGFBP-3), decreased expression of ERα in the luminal (LE) and glandular (GE) epithelia and in the subepithelial stroma (SS), and lower PR expression in the LE but higher in the GE and SS. In addition, GBH treatment decreased the uterine expression of Wnt5a in the GE, of Wnt7a in the SS, of β-catenin in the LE and GE, of Hoxa10 in the SS, and of Foxa2 in the GE as compared with controls. In conclusion, neonatal exposure to GBH decreased cell proliferation and altered the expression of molecules that control proliferation and development in the uterus. All these changes might have adverse consequences on uterine differentiation and functionality, affecting the female reproductive health of sheep. GBH may be responsible for uterine subfertility, acting as an EDC.

Neonatal exposure to environment-relevant levels of tributyltin leads to uterine dysplasia in rats

Endocrine-disrupting chemicals (EDCs) are natural/synthetic compounds that mimic or inhibit the biological actions of endogenous hormones. Studies have revealed that environmental estrogen, such as bisphenol A (BPA), causes developmental defects in the uterus. Tributyltin (TBT) is a typical environmental androgen. In this study, we aimed to explore the effect and mechanism of TBT on uterine development. Neonatal female rats were exposed to TBT (10 and 100 ng/kg bw) from postnatal days 1 to 16. BPA (50 μg/kg bw) was used as a positive control. Neonatal exposure to environmental concentrations of TBT resulted in pathological changes in the uterus, including thickening of the uterine luminal epithelium, a low density of glands, endometrial inflammation and fibrosis. Further, TBT affected the Wnt signaling pathway, which might mediate developmental disorders of the endometrial epithelial cells and glands in the uterus. TBT exposure also activated the NF-κB signaling pathway, which triggered inflammation. Moreover, TBT exposure upregulated the TGF-β/Smads signaling pathway, possibly leading to endometrial fibrosis. In summary, our results demonstrate that neonatal exposure to an environment-relevant level of TBT leads to uterine dysplasia and provide potential molecular mechanisms. Our study is helpful for clarifying the effects of environmental androgens on the female reproduction system.

Acute uterine effects and long-term reproductive alterations in postnatally exposed female rats to a mixture of commercial formulations of endosulfan and glyphosate

Endosulfan and glyphosate are widely used pesticides and have been associated to reproductive disorders. We examine the acute and long-term effects of postnatal exposure to commercial formulations of endosulfan (EF), glyphosate (glyphosate-based herbicide, GBH) and a mixture of both pesticides (MIX). After birth, female pups of Wistar rats received saline solution (CONTROL), EF (600 μg/kg of b.w/day), GBH (2 mg/kg of b.w/day) or a mixture (at the same doses) from postnatal day (PND) 1 to PND7. The uterine histology and expression of Hoxa10, estrogen (ERα) and progesterone (PR) receptors were evaluated on PND8. Reproductive performance was evaluated on gestational day 19. GBH and MIX rats showed an increment of 1) the incidence of luminal epithelial hyperplasia, 2) PR and Hoxa10 expression. EF modified ERα and Hoxa10 expression. During adulthood, MIX and GBH rats showed higher post-implantation losses while EF alone produced an increase of pre-implantation losses. We showed that the co-administration of both pesticides produced acute uterine effects and long-term deleterious reproductive effects that were similar to those induced by GBH alone. We consider important to highlight the necessity to evaluate the commercial pesticide mixture as a more representative model of human exposure to a high number of pesticides.

Effect of neonatal exposure to endosulfan on myometrial adaptation during early pregnancy and labor in rats

Proper myometrial adaptation during gestation is crucial for embryo implantation, pregnancy maintenance and parturition. Previously, we reported that neonatal exposure to endosulfan alters uterine development and induces implantation failures. The present work investigates the effects of endosulfan exposure on myometrial differentiation at the pre-implantation period, and myometrial activation during labor. Newborn female rats were s.c. injected with corn oil (vehicle) or 600 μg/kg/day of endosulfan (Endo600) on postnatal days (PND) 1, 3, 5 and 7. On PND90, the rats were mated to evaluate: i) the myometrial differentiation on gestational day 5 (GD5, pre-implantation period), by assessment myometrial histomorphology, smooth muscle cells (SMCs) proliferation, and expression of proteins involved in myometrial adaptation for embryo implantation (steroid receptors, Wnt7a and Hoxa10); ii) the timing of parturition and myometrial activation during labor by determining the uterine expression of contraction-associated genes (oxytocin receptor, OTXR; prostaglandin F₂α receptor, PTGFR and connexin-43, Cx-43). Endosulfan decreased the thickness of both myometrial layers, with a concomitant decrease in the collagen remodeling. Blood vessels relative area in the interstitial connective tissue between muscle layers was also decreased. Endo600 group showed lower myometrial proliferation in association with a downregulation of Wnt7a and Hoxa10. Although in all females labor occurred on GD23, the exposure to endosulfan altered the timing of parturition, by inducing advancement in the initiation of labor. This alteration was associated with an increased uterine expression of OTXR, PTGFR and Cx-43. In conclusion, neonatal exposure to endosulfan produced long-term effects affecting myometrial adaptation during early pregnancy and labor. These alterations could be associated with the aberrant effects of endosulfan on the implantation process and the timing of parturition.

The impact of sensory and motor enrichment on the epigenetic control of steroidogenic-related genes in rat hippocampus

In the present study, we analyzed the effects of a short-term environmental enrichment on the mRNA expression and DNA methylation of steroidogenic enzymes in the hippocampus. Thus, young adult (80-day-old) and middle-aged (350-day-old) Wistar female rats were exposed to sensory (SE) or motor (ME) enrichment during 10 days and compared to animals housed under standard conditions. SE was provided by an assortment of objects that included plastic tubes and toys; for ME, rodent wheels were provided. In young adult animals, SE and ME increased the mRNA expression of cytochrome P450 17α-hydroxylase/c17,20-lyase, steroid 5α-reductase type 1 (5αR-1) and 3α-hydroxysteroid dehydrogenase and decreased the methylation levels of 5αR-1 gene. In middle-aged rats, ME and SE upregulated the gene expression of aldosterone synthase and decreased the methylation state of its promoter. These results propose that SE and ME differentially regulate the transcription of neurosteroidogenic enzymes through epigenetic mechanisms in young and aged rats.

Glyphosate-based herbicide enhances the uterine sensitivity to estradiol in rats

In a previous work, we detected that postnatal exposure to a glyphosate-based herbicide (GBH) alters uterine development in prepubertal rats causing endometrial hyperplasia and increasing cell proliferation. Our goal was to determine whether exposure to low dose of a GBH during postnatal development might enhance the sensitivity of the uterus to an estrogenic treatment. Female Wistar pups were subcutaneously injected with saline solution (control) or GBH using the reference dose (2 mg/kg/day, EPA) on postnatal days (PND) 1, 3, 5 and 7. At weaning (PND21), female rats were bilaterally ovariectomized and treated with silastic capsules containing 17β-estradiol (E2, 1 mg/mL) until they were 2 months of age. On PND60, uterine samples were removed and processed for histology, immunohistochemistry and mRNA extraction to evaluate: (i) uterine morphology, (ii) uterine cell proliferation by the detection of Ki67, (iii) the expression of the estrogen receptors alpha (ESR1) and beta (ESR2) and (iv) the expression of WNT7A and CTNNB1. GBH-exposed animals showed increased luminal epithelial height and stromal nuclei density. The luminal and glandular epithelium were markedly hyperplastic in 43% of GBH-exposed animals. GBH exposure caused an increase in E2-induced cell proliferation in association with an induction of both ESR1 and ESR2. GBH treatment decreased membranous and cytoplasmic expression of CTNNB1 in luminal and glandular epithelial cells and increased WNT7A expression in the luminal epithelium. These results suggest that early postnatal exposure to a GBH enhances the sensitivity of the rat uterus to estradiol and induces histomorphological and molecular changes associated with uterine hyperplasia.

Bisphenol A accelerates meiotic progression in embryonic chickens via the estrogen receptor β signaling pathway

Bisphenol A (BPA) as an endocrine-disrupting chemical with weak estrogenic activity affects formation of primordial follicles. This study aimed to identify the potential effects and molecular mechanisms of BPA on meiosis and primordial follicle formation in chickens. The results suggest that the cortical layer was thickened and the number of germ cells that entered into meiosis was increased in BPA-treated ovaries. The percentage of γH2AX-positive cells increased significantly. In addition, up-regulated mRNA expression of meiotic genes, including stimulated by retinoic acid gene 8 (Stra8), disrupted meiotic cDNA 1 homologue (Dmc1) and synaptonemal complex protein 3 (Scp3) were observed in BPA-treated ovaries. Therefore, progression to meiosis prophase I was accelerated by exposure to BPA. Furthermore, the results demonstrated that injection of BPA resulted in hypomethylation of Dazl (Deleted in A Zoospermia-Like gene) and Stra8 and up-regulation mRNA expression of Dazl and Stra8 during meiotic onset. Finally, the relationship between estrogen receptor (ER) expression and BPA-induced meiosis was revealed using an in vitro ovarian culture system. BPA enhanced ERβ expression at the levels of mRNA and protein, while BPA exerted no significant effect on ERα and membrane-bound estrogen receptor (GPR30) expression. The inducing effects of BPA on meiosis were blocked by ER inhibitor. Collectively, these results demonstrate the dynamic ovarian response to BPA exposure, which indicate that BPA affects the formation of primordial follicles by promoting meiotic progression of oocytes via hypomethylation of Dazl and Stra8 and ERβ signaling pathways.

Bisphenol A disrupts the temporal pattern of histofunctional changes in the female reproductive tract of Caiman latirostris

Recently, we have described the ontogeny of histofunctional differentiation changes in the oviduct of Caiman latirostris. The expression of estrogen receptor alpha and progesterone receptor shows that the caiman oviduct could be a target of the action of xenoestrogens such as the widely environmentally present Bisphenol A (BPA), early in life. The aims of this study were: to complement oviduct characterization by establishing the ontogenetic changes in androgen receptor (AR) expression and assessing the effects of early postnatal exposure to 17-β-estradiol (E2) or BPA on the histofunctional features of the oviduct. AR was expressed in all the stages studied. The spatial pattern of AR immunostaining changed from neonatal to juvenile caimans. In the luminal epithelium, changes were at the subcellular level, from cytoplasmic to nuclear. In the subepithelium, although both cytoplasmic and nuclear AR expression was observed, changes were mainly at tissue level, from the subepithelial compartment to the outer muscular layer. The oviduct was highly sensitive to E2 and BPA at the early postnatal developmental stage. E2- and BPA-exposed caimans showed increased luminal epithelial height and higher proliferative activity. Changes in histomorphological features (measured by a scoring system), steroid hormone receptors, collagen remodeling and muscle-associated proteins suggest a precocious oviduct histofunctional differentiation in E2- and BPA-exposed caimans. The modification of the temporal pattern of oviductal biomarkers suggests that organizational changes could impair C. latirostris reproductive health later in life. The alterations in the caiman female reproductive tract exposed to BPA highlight the importance of preserving aquatic environments from plastic pollution.

Effect of bisphenol A on reproductive processes: A review of in vitro, in vivo and epidemiological studies

As bisphenol A (BPA) is characterized by a pronounced influence on human hormonal regulation, particular attention has been aimed at understanding its role in reproductive processes in males and females, as well as on fetal development. Owing to the increasing number of alarming reports on the negative consequences of the presence of BPA in human surroundings, more and more studies are being undertaken to clarify the negative effects of BPA on human reproductive processes. The aim of this work was to collect and summarize data on the influence of BPA exposure on reproductive health. Based on an analysis of selected publications it was stated that there is strong proof confirming that BPA is an ovarian, uterine and prostate toxicant at a level below the lowest observed adverse effect level (50 mg kg^-1 bodyweight) as well as a level below the proposed safe level (4 μg kg^-1 bodyweight). It seems there is also reliable evidence in relation to the negative effect of BPA on sperm quality and motility. Limited evidence also pertains to the case of the potential of BPA to affect polycystic ovary syndrome occurrence. Although in epidemiological studies this disease was common, in studies on animal models such results were still not confirmed. No unambiguous results of epidemiological studies and with animal models were obtained in relation to the evaluation of associations between BPA and implantation failure in women, evaluation of associations between BPA and sexual dysfunction in men, and impact of BPA on birth rate, birth weight and length of gestation. Copyright © 2017 John Wiley & Sons, Ltd.

Neonatal exposure to a glyphosate based herbicide alters the development of the rat uterus

Glyphosate-based herbicides (GBHs) are extensively used to control weeds on both cropland and non-cropland areas. No reports are available regarding the effects of GBHs exposure on uterine development. We evaluated if neonatal exposure to a GBH affects uterine morphology, proliferation and expression of proteins that regulate uterine organogenetic differentiation in rats. Female Wistar pups received saline solution (control, C) or a commercial formulation of glyphosate (GBH, 2mg/kg) by sc injection every 48h from postnatal day (PND) 1 to PND7. Rats were sacrificed on PND8 (neonatal period) and PND21 (prepubertal period) to evaluate acute and short-term effects, respectively. The uterine morphology was evaluated in hematoxylin and eosin stained sections. The epithelial and stromal immunophenotypes were established by assessing the expression of luminal epithelial protein (cytokeratin 8; CK8), basal epithelial proteins (p63 and pan cytokeratin CK1, 5, 10 and 14); and vimentin by immunohistochemistry (IHC). To investigate changes on proteins that regulate uterine organogenetic differentiation we evaluated the expression of estrogen receptor alpha (ERα), progesterone receptor (PR), Hoxa10 and Wnt7a by IHC. The GBH-exposed uteri showed morphological changes, characterized by an increase in the incidence of luminal epithelial hyperplasia (LEH) and an increase in the stromal and myometrial thickness. The epithelial cells showed a positive immunostaining for CK8, while the stromal cells for vimentin. GBH treatment increased cell proliferation in the luminal and stromal compartment on PND8, without changes on PND21. GBH treatment also altered the expression of proteins involved in uterine organogenetic differentiation. PR and Hoxa10 were deregulated both immediately and two weeks after the exposure. ERα was induced in the stromal compartment on PND8, and was downregulated in the luminal epithelial cells of gyphosate-exposed animals on PND21. GBH treatment also increased the expression of Wnt7a in the stromal and glandular epithelial cells on PND21. Neonatal exposure to GBH disrupts the postnatal uterine development at the neonatal and prepubertal period. All these changes may alter the functional differentiation of the uterus, affecting the female fertility and/or promoting the development of neoplasias.

Effects of neonatal exposure to a glyphosate-based herbicide on female rat reproduction

In this study, we investigated whether neonatal exposure to a glyphosate-based herbicide (GBH) alters the reproductive performance and the molecular mechanisms involved in the decidualization process in adult rats. Newborn female rats received vehicle or 2 mg/kg/day of a GBH on postnatal days (PND) 1, 3, 5 and 7. On PND90, the rats were mated to evaluate (i) the reproductive performance on gestational day (GD) 19 and (ii) the ovarian steroid levels, uterine morphology, endometrial cell proliferation, apoptosis and cell cycle regulators, and endocrine pathways that regulate uterine decidualization (steroid receptors/COUP-TFII/Bmp2/Hoxa10) at the implantation sites (IS) on GD9. The GBH-exposed group showed a significant increase in the number of resorption sites on GD19, associated with an altered decidualization response. In fact, on GD9, the GBH-treated rats showed morphological changes at the IS, associated with a decreased expression of estrogen and progesterone receptors, a downregulation of COUP-TFII (Nr2f2) and Bmp2 mRNA and an increased expression of HOXA10 and the proliferation marker Ki67(Mki67) at the IS. We concluded that alterations in endometrial decidualization might be the mechanism of GBH-induced post-implantation embryo loss.

Postnatal development and histofunctional differentiation of the oviduct in the broad-snouted caiman (Caiman latirostris)

Caiman latirostris is a South American crocodilian species characterized as a sentinel of the presence of endocrine-disrupting compounds (EDCs). Evaluating developmental events in hormone-dependent organs, such as the oviduct, is crucial to understand physiological postnatal development, to identify putative periods of exposure sensitive to EDCs, and/or to identify biomarkers useful to evaluate the effects of EDC exposure. In this study, we describe the histomorphological features of C. latirostris oviducts by establishing the ontogeny of changes at cellular, tissue and molecular levels from the neonatal to the pre-pubertal juvenile stages. Since the histological diagnosis of the adenogenic oviduct lies on a group of features, here we defined a histofunctional score system and a cut-off value to distinguish between preadenogenic and adenogenic oviducts. Our results showed that the maturation of the C. latirostris oviduct is completed postnatally and characterized by changes that mimic the pattern of histological modifications described for the mammalian uterus. Ontogenic changes in the oviductal epithelium parallel changes at subepithelial level, and include collagen remodeling and characteristic spatial-temporal patterns of α-actin and desmin. The expression pattern of estrogen receptor alpha and progesterone receptor evidenced that, even at early postnatal developmental stages, the oviduct of C. latirostris is a target organ of endogenous and environmental hormones. Besides, oviductal adenogenesis seems to be an estrogen-dependent process. Results presented here provide not only insights into the histophysiological aspect of caiman female reproductive ducts but also new tools to better characterize caimans as sentinels of endocrine disruption.

Chronic exposure to bisphenol a impairs progesterone receptor-mediated signaling in the uterus during early pregnancy

Environmental and occupational exposure to endocrine disrupting chemicals (EDCs) is a major threat to female reproductive health. Bisphenol A (BPA), an environmental toxicant that is commonly found in polycarbonate plastics and epoxy resins, has received much attention due to its estrogenic activity and high risk of chronic exposure in human. Whereas BPA has been linked to infertility and recurrent miscarriage in women, the impact of its exposure on uterine function during early pregnancy remains unclear. In a recent publication in Endocrinology, we demonstrated that prolonged exposure to an environmental relevant dose of BPA disrupts progesterone receptor-regulated uterine functions, thus affecting uterine receptivity for embryo implantation and decidua morphogenesis, two critical events for establishment and maintenance of early pregnancy. In particular we reported a marked impairment of progesterone receptor (PGR) expression and its downstream effector HAND2 in the uterine stromal cells in response to chronic BPA exposure. In an earlier study we have shown that HAND2 controls embryo implantation by repressing fibroblast growth factor (FGF) expression and the MAP kinase signaling pathway, thus inhibiting epithelial proliferation. Interestingly we observed that downregulation of PGR and HAND2 expression in uterine stroma upon BPA exposure was associated with an enhanced activation of FGFR and MAPK signaling, aberrant proliferation, and lack of uterine receptivity in the epithelium. In addition, the proliferation and differentiation of endometrial stromal cells to decidual cells, an event critical for the maintenance of early pregnancy, was severely compromised in response to BPA. This research highlight will provide an overview of our findings and discuss the potential mechanisms by which chronic BPA impairs PGR-HAND2 pathway and adversely affects implantation and the establishment of pregnancy.

Evidence for bisphenol A-induced female infertility: a review (2007-2016)

We summarized the scientific literature published from 2007 to 2016 on the potential effects of bisphenol A (BPA) on female fertility. We focused on overall fertility outcomes (e.g., ability to become pregnant, number of offspring), organs that are important for female reproduction (i.e., oviduct, uterus, ovary, hypothalamus, and pituitary), and reproductive-related processes (i.e., estrous cyclicity, implantation, and hormonal secretion). The reviewed literature indicates that BPA may be associated with infertility in women. Potential explanations for this association can be generated from experimental studies. Specifically, BPA may alter overall female reproductive capacity by affecting the morphology and function of the oviduct, uterus, ovary, and hypothalamus-pituitary-ovarian axis in animal models. In addition, BPA may disrupt estrous cyclicity and implantation. Nevertheless, further studies are needed to better understand the exact mechanisms of action and to detect potential reproductive toxicity at earlier stages.

A deregulated expression of estrogen-target genes is associated with an altered response to estradiol in aged rats perinatally exposed to bisphenol A

Here we assessed the effects of perinatal exposure to bisphenol A (BPA) on the uterine response to 17β-estradiol (E2) in aged rats. Pregnant rats were orally exposed to 0.5 or 50 μg BPA/kg/day from gestational day 9 until weaning. On postnatal day (PND) 360, the rats were ovariectomized and treated with E2 for three months. The uterine tissue of BPA50 and BPA0.5 rats showed increased density of glands with squamous metaplasia (GSM) and glands with daughter glands respectively. Wnt7a expression was lower in GSM of BPA50 rats than in controls. The expression of estrogen receptor 1 (ESR1) and its 5'- untranslated exons ESR1-O and ESR1-OT was lower in BPA50 rats. Both doses of BPA modified the expression of coactivator proteins and epigenetic regulatory enzymes. Thus, perinatal BPA-exposed rats showed different glandular abnormalities associated with deregulated expression of E2-target genes. Different mechanisms would be involved depending on the BPA dose administered.

Chronic Exposure to Bisphenol A Affects Uterine Function During Early Pregnancy in Mice

Environmental and occupational exposure to bisphenol A (BPA), a chemical widely used in polycarbonate plastics and epoxy resins, has received much attention in female reproductive health due to its widespread toxic effects. Although BPA has been linked to infertility and recurrent miscarriage in women, the impact of its exposure on uterine function during early pregnancy remains unclear. In this study, we addressed the effect of prolonged exposure to an environmental relevant dose of BPA on embryo implantation and establishment of pregnancy. Our studies revealed that treatment of mice with BPA led to improper endometrial epithelial and stromal functions thus affecting embryo implantation and establishment of pregnancy. Upon further analyses, we found that the expression of progesterone receptor (PGR) and its downstream target gene, HAND2 (heart and neural crest derivatives expressed 2), was markedly suppressed in BPA-exposed uterine tissues. Previous studies have shown that HAND2 controls embryo implantation by repressing fibroblast growth factor and the MAPK signaling pathways and inhibiting epithelial proliferation. Interestingly, we observed that down-regulation of PGR and HAND2 expression in uterine stroma upon BPA exposure was associated with enhanced activation of fibroblast growth factor and MAPK signaling in the epithelium, thus contributing to aberrant proliferation and lack of uterine receptivity. Further, the differentiation of endometrial stromal cells to decidual cells, an event critical for the establishment and maintenance of pregnancy, was severely compromised in response to BPA. In summary, our studies revealed that chronic exposure to BPA impairs PGR-HAND2 pathway and adversely affects implantation and the establishment of pregnancy.

Ovarian dysfunctions in adult female rat offspring born to mothers perinatally exposed to low doses of bisphenol A

The study of oral exposure to the environmental estrogen bisphenol A (BPA) during the perinatal period and its effects on ovarian functionality in adulthood has generated special interest. Thus, our objective was to investigate ovarian folliculogenesis and steroidogenesis in adult female rat offspring born to mothers exposed to low doses of BPA (BPA50: 50μg/kgday; BPA0.5: 0.5μg/kgday) by the oral route during gestation and breastfeeding. Ovaries from both BPA-treated groups showed reduced primordial follicle recruitment and a greater number of corpora lutea, indicating an increased number of ovulated oocytes, coupled with higher levels of mRNA expression of 3β-hydroxysteroid dehydrogenase and serum progesterone. BPA50-treated animals had lower expression of androgen receptor (AR) at different stages of the growing follicle population. BPA0.5-treated rats evidenced an imbalance of AR expression between primordial/primary follicles, with higher mRNA-follicle-stimulating hormone receptor expression. These results add to the growing evidence that folliculogenesis and steroidogenesis are targets of BPA within the ovary.

Effects of Endocrine-disrupting Chemicals on Female Reproductive Health

Endocrine-disrupting chemicals (EDCs) are increasingly prevalent in the environment and the evidence demonstrates that they affect reproductive health, has been accumulating for the last few decades. In this review of recent literature, we present evidence of the effects of estrogen-mimicking EDCs on female reproductive health especially the ovaries and uteri. As representative EDCs, data from studies with a pharmaceutical estrogen, diethylstilbestrol (DES), an organochlorine pesticide methoxychlor (MXC), a phytoestrogen (genistein), and a chemical used in plastics, bisphenol a (BPA) have been presented. We also discuss the effects of a commonly found plasticizer in the environment, a phthalate (DEHP), even though it is not a typical estrogenic EDC. Collectively, these studies show that exposures during fetal and neonatal periods cause developmental reprogramming leading to adult reproductive disease. Puberty, estrous cyclicity, ovarian follicular development, and uterine functions are all affected by exposure to these EDCs. Evidence that epigenetic modifications are involved in the progression to adult disease is also presented.

EDC-2: The Endocrine Society's Second Scientific Statement on Endocrine-Disrupting Chemicals

The Endocrine Society's first Scientific Statement in 2009 provided a wake-up call to the scientific community about how environmental endocrine-disrupting chemicals (EDCs) affect health and disease. Five years later, a substantially larger body of literature has solidified our understanding of plausible mechanisms underlying EDC actions and how exposures in animals and humans-especially during development-may lay the foundations for disease later in life. At this point in history, we have much stronger knowledge about how EDCs alter gene-environment interactions via physiological, cellular, molecular, and epigenetic changes, thereby producing effects in exposed individuals as well as their descendants. Causal links between exposure and manifestation of disease are substantiated by experimental animal models and are consistent with correlative epidemiological data in humans. There are several caveats because differences in how experimental animal work is conducted can lead to difficulties in drawing broad conclusions, and we must continue to be cautious about inferring causality in humans. In this second Scientific Statement, we reviewed the literature on a subset of topics for which the translational evidence is strongest: 1) obesity and diabetes; 2) female reproduction; 3) male reproduction; 4) hormone-sensitive cancers in females; 5) prostate; 6) thyroid; and 7) neurodevelopment and neuroendocrine systems. Our inclusion criteria for studies were those conducted predominantly in the past 5 years deemed to be of high quality based on appropriate negative and positive control groups or populations, adequate sample size and experimental design, and mammalian animal studies with exposure levels in a range that was relevant to humans. We also focused on studies using the developmental origins of health and disease model. No report was excluded based on a positive or negative effect of the EDC exposure. The bulk of the results across the board strengthen the evidence for endocrine health-related actions of EDCs. Based on this much more complete understanding of the endocrine principles by which EDCs act, including nonmonotonic dose-responses, low-dose effects, and developmental vulnerability, these findings can be much better translated to human health. Armed with this information, researchers, physicians, and other healthcare providers can guide regulators and policymakers as they make responsible decisions.

Early programing of uterine tissue by bisphenol A: Critical evaluation of evidence from animal exposure studies

Exposure to Bisphenol A (BPA) during the critical window of uterine development has been proposed to program the uterus for increased disease susceptibility based on well-documented effects of the potent xenoestrogen diethylstilbestrol. To investigate this proposal, we reviewed 37 studies of prenatal and/or perinatal BPA exposure in animal models and evaluated evidence for: molecular signatures of early BPA exposure; the development of adverse uterine health effects; and epigenetic changes linked to long-term dysregulation of uterine gene expression and health effects. We found substantial evidence for adult uterine effects of early BPA exposure. In contrast, experimental support for epigenetic actions of early BPA exposure is very limited, and largely consists of effects on Hoxa gene DNA methylation. Critical knowledge gaps were identified, including the need to fully characterize short-term and long-term uterine gene responses, interactions with estrogens and other endogenous hormones, and any long-lasting epigenetic signatures that impact adult disease.

Bisphenol A modulates receptivity and secretory function of human decidual cells: an in vitro study

The human endometrium is a fertility-determining tissue and a target of steroid hormones' action. Endocrine disruptors (EDs) can exert adverse effects on the physiological function of the decidua at the maternal-fetal interface. We examined the potential effects of an ED, bisphenol A (BPA), on endometrial maturation/decidualization, receptivity, and secretion of decidual factors (biomarkers). In vitro decidualized, endometrial stromal cells from six hysterectomy specimens were treated with 1  pM-1  μM of BPA, for 24  h and assessed for cell viability and proliferation. Three non-toxic concentrations of BPA (1  μM, 1  nM, and 1  pM) were selected to study its influence on secretion of cell decidualization biomarkers (IGF-binding protein and decidual prolactin (dPRL)), macrophage migration inhibitory factor (MIF) secretion, and hormone receptors' expression (estrogen receptors (ERα and ERβ); progesterone receptors (PRA and PRB); and human chorionic gonadotropin (hCG)/LH receptor (LH-R)). The results showed a decrease in cell viability (P<0.001) in response to BPA at the level of 1  mM. At the non-toxic concentrations used, BPA perturbed the expression of ERα, ERβ, PRA, PRB, and hCG/LH-R (P<0.05). Furthermore, 1  μM of BPA reduced the mRNA transcription of dPRL (P<0.05). Secretion of MIF was stimulated by all BPA treatments, the lowest concentration (1  pM) being the most effective (P<0.001). The multi-targeted disruption of BPA on decidual cells, at concentrations commonly detected in the human population, raises great concern about the possible consequences of exposure to BPA on the function of decidua and thus its potential deleterious effect on pregnancy.

Nuclear receptors in transgenerational epigenetic inheritance

Nuclear Receptors are ligand-activated transcription factors that translate information about the lipid environment into specific genetic programs, a property that renders them good candidates to be mediators of rapid adaptation changes of a species. Lipid-based morphogens, endocrine hormones, fatty acids and xenobiotics might act through this class of transcription factors making them regulators able to fine-tune physiological processes. Here we review the basic concepts and current knowledge on the process whereby small molecules act through nuclear receptors and contribute to transgenerational changes. Several molecules shown to cause transgenerational changes like phthalates, BPA, nicotine, tributylin bind and activate nuclear receptors like ERs, androgen receptors, glucocorticoid receptors or PPARγ. A specific subset of observations involving nuclear receptors has focused on the effects of environmental stress or maternal behaviour on the development of transgenerational traits. While these effects do not involve environmental ligands, they change the expression levels of Estrogen and glucocorticoid receptors of the second generation and consequently initiate an altered genetic program in the second generation. In this review we summarize the available literature about the role of nuclear receptors in transgenerational inheritance.

Neonatal exposure to xenoestrogens impairs the ovarian response to gonadotropin treatment in lambs

Bisphenol A (BPA) and diethylstilbestrol (DES) are xenoestrogens, which have been associated with altered effects on reproduction. We hypothesized that neonatal xenoestrogen exposure affects the ovarian functionality in lambs. Thus, we evaluated the ovarian response to exogenous ovine FSH (oFSH) administered from postnatal day 30 (PND30) to PND32 in female lambs previously exposed to low doses of DES or BPA (BPA50: 50 μg/kg per day, BPA0.5: 0.5 μg/kg per day) from PND1 to PND14. We determined: i) follicular growth, ii) circulating levels of 17β-estradiol (E2), iii) steroid receptors (estrogen receptor alpha, estrogen receptor beta, and androgen receptor (AR)) and atresia, and iv) mRNA expression levels of the ovarian bone morphogenetic protein (BMPs) system (BMP6, BMP15, BMPR1B, and GDF9) and FSH receptor (FSHR). Lambs neonatally exposed to DES or BPA showed an impaired ovarian response to oFSH with a lower number of follicles ≥2 mm in diameter together with a lower number of atretic follicles and no increase in E2 serum levels in response to oFSH treatment. In addition, AR induction by oFSH was disrupted in granulosa and theca cells of lambs exposed to DES or BPA. An increase in GDF9 mRNA expression levels was observed in oFSH-primed lambs previously treated with DES or BPA50. In contrast, a decrease in BMPR1B was observed in BPA0.5-postnatally exposed lambs. The modifications in AR, GDF9, and BMPR1B may be associated with the altered ovarian function due to neonatal xenoestrogen exposure in response to an exogenous gonadotropin stimulus. These alterations may be the pathophysiological basis of subfertility syndrome in adulthood.

Developmental exposure to bisphenol A alters the differentiation and functional response of the adult rat uterus to estrogen treatment

We assessed the long-term effect of perinatal exposure to bisphenol A (BPA) on the rat uterus and the uterine response to estrogen (E2) replacement therapy. BPA (0.5 or 50μg/kg/day) was administered in the drinking water from gestational day 9 until weaning. We studied the uterus of female offspring on postnatal day (PND) 90 and 360, and the uterine E2 response on PND460 (PND460-E2). On PND90, BPA-exposed rats showed altered glandular proliferation and α-actin expression. On PND360, BPA exposure increased the incidence of abnormalities in the luminal and glandular epithelium. On PND460-E2, the multiplicity of glands with squamous metaplasia increased in BPA50 while the incidence of glands with daughter glands increased in BPA0.5. The expression of steroid receptors, p63 and IGF-I was modified in BPA-exposed rats on PND460-E2. The long-lasting effects of perinatal exposure to BPA included induction of abnormalities in uterine tissue and altered response to E2 replacement therapy.

Neonatal exposure to low doses of endosulfan induces implantation failure and disrupts uterine functional differentiation at the pre-implantation period in rats

We investigated whether neonatal exposure to low doses of endosulfan affects fertility and uterine functional differentiation at pre-implantation in rats. Newborn female rats received the vehicle, 0.2 µg/kg/d of diethylstilbestrol (DES), 6 µg/kg/d of endosulfan (Endo6) or 600 µg/kg/d of endosulfan (Endo600) on postnatal days (PND) 1, 3, 5, and 7. On PND90, the rats were mated to evaluate their reproductive performance on gestational day (GD) 19 and their ovarian steroid serum levels, endometrial proliferation and implantation-associated proteins on GD5. DES and endosulfan decreased the pregnancy rate and the number of implantation sites. On GD5, DES and endosulfan did not change the serum levels of 17β-estradiol (E2) and progesterone (P); the endometrial proliferation decreased, which was associated with silencing of Hoxa10 in the Endo600-treated rats. Both doses of endosulfan increased the progesterone receptor (PR) expression, whereas the higher dose led additionally to an increase in estrogen receptor alpha (ERα). In the Endo600-treated rats, the down-regulation of Hoxa10 was associated with a deregulation of the steroid receptor coregulators. Alterations in endometrial proliferation and the endocrine pathway of Hoxa10/steroid receptors/coregulators might be the mechanism of endosulfan-induced implantation failure.

Early-life Exposure to Endocrine Disrupting Chemicals and Later-life Health Outcomes: An Epigenetic Bridge?

A growing body of evidence demonstrates that adverse events early in development, and particularly during intrauterine life, may program risks for diseases in adult life. Increasing evidence has been accumulated indicating the important role of epigenetic regulation including DNA methylation, histone modifications and miRNAs in developmental programming. Among the environmental factors which play an important role in programming of chronic pathologies, the endocrine-disrupting chemicals (EDCs) that have estrogenic, anti-estrogenic, and anti-androgenic activity are of specific concern because the developing organism is extremely sensitive to perturbation by substances with hormone-like activity. Among EDCs, there are many substances that are constantly present in the modern human environment or are in widespread use, including dioxin and dioxin-like compounds, phthalates, agricultural pesticides, polychlorinated biphenyls, industrial solvents, pharmaceuticals, and heavy metals. Apart from their common endocrine active properties, several EDCs have been shown to disrupt developmental epigenomic programming. The purpose of this review is to provide a summary of recent research findings which indicate that exposure to EDCs during in-utero and/or neonatal development can cause long-term health outcomes via mechanisms of epigenetic memory.

Egr1 is rapidly and transiently induced by estrogen and bisphenol A via activation of nuclear estrogen receptor-dependent ERK1/2 pathway in the uterus

Coordinate actions of ovarian estrogen (E2) and progesterone (P4) via their own receptors are critical for establishing uterine receptivity for embryo implantation in the uterus. E2 regulates expression of an array of genes to mediate its major actions on heterogeneous uterine cell types. Here we have investigated regulatory mechanism(s) of E2 and bisphenol A (BPA), an endocrine disruptor with potent estrogenic activity on expression of early growth response 1 (Egr1), a zinc finger transcription factor that regulates cell growth, differentiation and apoptosis in the uterus. Egr1 was rapidly and transiently induced by E2 and BPA mainly in stromal cells via nuclear estrogen receptor (ER)-ERK1/2 pathway. ICI 182,780, an ER antagonist, effectively inhibited their actions on EGR1 expression following ERK1/2 phosphorylation. Administration of pharmacological inhibitors for ERK1/2, but not AKT significantly blocked EGR1 expression induced by E2 and BPA. P4 effectively dampened action(s) of E2 and BPA on Egr1 expression via nuclear progesterone receptor. Its antagonistic effects were partially interfered with RU486 pretreatment. Interestingly, EGR1 is specifically induced in stromal cells surrounding implanting blastocyst. Collectively, our results show that through nuclear ER-dependent ERK1/2 phosphorylation, not only E2 but also endocrine disruptors with estrogenic activity such as BPA rapidly and transiently induce Egr1 which may be important for embryo implantation and decidualization in mouse uterus.

GnRH analogues may increase endometrial Hoxa10 promoter methylation and affect endometrial receptivity

The present study aimed to investigate whether gonadotropin-releasing hormone analogues (GnRH-as), including GnRH agonists and antagonists, affect endometrial homeobox (Hox) a10 DNA methylation during the implantation window in mice. GnRH analogue mouse models were used and were treated with either human menopausal gonadotropin (HMG) and a GnRH agonist or HMG and a GnRH antagonist. Uterus samples were collected 48 h after GnRH analogue treatment or ovulation. Bisulfite sequencing polymerase chain reaction (PCR), quantitative-PCR and western blot analysis were performed to assess Hoxa10 and integrin β3 expression. Scanning electron microscope analyses were conducted to analyze pinopode development. Compared with the natural cycle control mice, mice in the GnRH analogue groups were found to exhibit increased levels of methylation at the Hoxa10 promoter, decreased Hoxa10 mRNA and protein expression and disrupted pinopode development. These findings suggest that GnRH-as may be associated with altered Hoxa10 DNA methylation, thus GnRH-as may affect uterine Hoxa10 expression and endometrial receptivity.

Bisphenol a and reproductive health: update of experimental and human evidence, 2007-2013

BACKGROUND

In 2007, an expert panel reviewed associations between bisphenol A (BPA) exposure and reproductive health outcomes. Since then, new studies have been conducted on the impact of BPA on reproduction.

OBJECTIVE

In this review, we summarize data obtained since 2007, focusing on a) findings from human and animal studies, b) the effects of BPA on a variety of reproductive end points, and c) mechanisms of BPA action.

METHODS

We reviewed the literature published from 2007 to 2013 using a PubMed search based on keywords related to BPA and male and female reproduction.

DISCUSSION

Because BPA has been reported to affect the onset of meiosis in both animal and in vitro models, interfere with germ cell nest breakdown in animal models, accelerate follicle transition in several animal species, alter steroidogenesis in multiple animal models and women, and reduce oocyte quality in animal models and women undergoing in vitro fertilization (IVF), we consider it an ovarian toxicant. In addition, strong evidence suggests that BPA is a uterine toxicant because it impaired uterine endometrial proliferation, decreased uterine receptivity, and increased implantation failure in animal models. BPA exposure may be associated with adverse birth outcomes, hyperandrogenism, sexual dysfunction, and impaired implantation in humans, but additional studies are required to confirm these associations. Studies also suggest that BPA may be a testicular toxicant in animal models, but the data in humans are equivocal. Finally, insufficient evidence exists regarding effects of BPA on the oviduct, the placenta, and pubertal development.

CONCLUSION

Based on reports that BPA impacts female reproduction and has the potential to affect male reproductive systems in humans and animals, we conclude that BPA is a reproductive toxicant.

Bisphenol A alters β-hCG and MIF release by human placenta: an in vitro study to understand the role of endometrial cells

A proper fetomaternal immune-endocrine cross-talk in pregnancy is fundamental for reproductive success. This might be unbalanced by exposure to environmental chemicals, such as bisphenol A (BPA). As fetoplacental contamination with BPA originates from the maternal compartment, this study investigated the role of the endometrium in BPA effects on the placenta. To this end, in vitro decidualized stromal cells were exposed to BPA 1 nM, and their conditioned medium (diluted 1 : 2) was used on chorionic villous explants from human placenta. Parallel cultures of placental explants were directly exposed to 0.5 nM BPA while, control cultures were exposed to the vehicle (EtOH 0.1%). After 24–48 h, culture medium from BPA-treated and control cultures was assayed for concentration of hormone human Chorionic Gonadotropin (β-hCG) and cytokine Macrophage Migration Inhibitory Factor (MIF). The results showed that direct exposure to BPA stimulated the release of both MIF and β-hCG. These effects were abolished/diminished in placental cultures exposed to endometrial cell-conditioned medium. GM-MS analysis revealed that endometrial cells retain BPA, thus reducing the availability of this chemical for the placenta. The data obtained highlight the importance of in vitro models including the maternal component in reproducing the effects of environmental chemicals on human fetus/placenta.