PCBs exert an estrogenic effect through repression of the Wnt7a signaling pathway in the female reproductive tract

The effect of folic acid supplementation and folate deficiency on embryo implantation

Implantation is a critical stage of pregnancy, which occurs in a short period of interaction between the receptive endometrium and the embryo. Folic acid (FA) is a synthetic derivative of folate and is recommended as a pre-conceptional supplement. However, the impact of different doses of FA supplementation and folate deficiency during the early stages of pregnancy requires further investigation. The aim of this study was to investigate the possible effects of FA supplementation and folate deficiency on expression of Estrogen Receptor Alpha (ER-α), Vascular Endothelial Growth Factor-A (VEGFA), and Integrin alpha V and beta3 (Integrin αVβ3). A total of 32, 6-8-week old Wistar albino rats were divided into four groups of control, folate-deficiency, low-dose, and high-dose FA supplement groups. After five weeks of FA supplementation and folate deficiency model formation, mated rats were sacrificed on the 5th gestational day (GD), and implantation sites were collected. The expression of ER- α, VEGFA, and Integrin αVβ3 in the implantation sites were examined with immunohistochemistry and real-time PCR. The results revealed that the mRNA levels of ESR1, VEGFA, and Integrin αV and β3 were significantly increased in the high-dose FA group and significantly decreased in the folate deficiency group compared to the control group (p < 0.05). Based on these results, it can be concluded that FA supplementation before pregnancy has positive effects on the maintenance of pregnancy, and folate deficiency may lead to implantation disorders.

Advances in polychlorinated biphenyls-induced female reproductive toxicity

Polychlorinated biphenyls (PCBs) are a class of endocrine-disrupting chemicals (EDCs) widely present in the environment. PCBs have been of concern due to their anti/estrogen-like effects, which make them more toxic to the female reproductive system. However, there is still a lack of systematic reviews on the reproductive toxicity of PCBs in females, so the adverse effects and mechanisms of PCBs on the female reproductive system were summarized in this paper. Our findings showed that PCBs are positively associated with lower pregnancy rate, hormone disruption, miscarriage and various reproductive diseases in women. In animal experiments, PCBs can damage the structure and function of the ovaries, uterus and oviducts. Also, PCBs could produce epigenetic effects and be transferred to the offspring through the maternal placenta, causing development retardation, malformation and death of embryos, and damage to organs of multiple generations. Furthermore, the mechanisms of PCBs-induced female reproductive toxicity mainly include receptor-mediated hormone disorders, oxidative stress, apoptosis, autophagy, and epigenetic modifications. Finally, we also present some directions for future research on the reproductive toxicity of PCBs. This detailed information provided a valuable reference for fully understanding the reproductive toxicity of PCBs.

Polychlorinated biphenyl (PCB) exposure in adult female mice can influence bladder contractility

Lower urinary tract symptoms (LUTS) greatly reduce quality of life. While LUTS etiology is not completely understood, it is plausible that environmental contaminants could play a role. Polychlorinated biphenyls (PCBs), are a group of persistent environmental toxicants frequently documented in animal and human tissues. PCBs are capable of influencing voiding function in mouse offspring exposed developmentally, however whether PCB exposure during adulthood can also influence voiding dynamics is unknown. Therefore, the purpose of this study was to determine whether PCB exposure in adult female mice can impact voiding function. As part of a larger study to generate developmentally exposed offspring, adult female C57Bl/6J mice were dosed orally with the MARBLES PCB mixture (0.1, 1, or 6 mg/kg/day) or vehicle control beginning two weeks before mating and throughout gestation and lactation (9 weeks). Adult dosed female dams then underwent void spot assay, uroflowmetry, and anesthetized cystometry to assess voiding function. Bladder contractility was assessed in ex vivo bladder bath assays, and bladders were collected for morphology and histology assessments. While voiding behavior endpoints were minimally impacted, alterations to bladder contractility dynamics were more pronounced. Adult female mice dosed with 1 mg/kg/d PCB showed an increase in urine spots 2-3 cm2 in size, increased bladder contractility in response to electrical field stimulation, and decreased bladder wall thickness compared to vehicle control. PCBs also altered contractile response to cholinergic agonist in a dose-dependent manner. Overall, these results indicate that exposure to PCBs in adult female mice is sufficient to produce changes in bladder physiology. These results also highlight the critical role of timing of exposure in influencing voiding function.

Environmental toxicants, brown adipose tissue, and potential links to obesity and metabolic disease

Rates of human obesity, type 2 diabetes, and non-alcoholic fatty liver disease (NAFLD) have risen faster than anticipated and cannot solely be explained by excessive caloric intake or physical inactivity. Importantly, this effect is also observed in many other domesticated and non-domesticated mammals, which has led to the hypothesis that synthetic environmental pollutants may be contributing to disease development. While the impact of these chemicals on appetite and adipogenesis has been extensively studied, their potential role in reducing energy expenditure is less studied. An important component of whole-body energy expenditure is adaptive and diet-induced thermogenesis in human brown adipose tissue (BAT). This review summarizes recent evidence that environmental pollutants such as the pesticide chlorpyrifos inhibit BAT function, diet-induced thermogenesis and the potential signaling pathways mediating these effects. Lastly, we discuss the importance of housing experimental mice at thermoneutrality, rather than room temperature, to maximize the translation of findings to humans.

Disruption of developmental programming with long-term consequences after exposure to a glyphosate-based herbicide in a rat model

Glyphosate-based herbicides (GBHs) have been associated with endocrine disrupting effects on reproductive organs. We examined whether postnatal exposure to GBH affects developmental programming of the uterus with long-term consequences. Female Wistar pups received vehicle (control) or GBH (2 mg of glyphosate/kg/day) from postnatal day (PND) 1 to PND7, where the developing uterus is highly sensitive to endocrine disruption. Short-, mid- and long-term effects were evaluated on PND8, PND120 and PND600, respectively. GBH induced hyperplasia and epigenetic alterations in the uterus of neonatal females (PND8). DNA hypermethylation, enrichment of H3K9me3 and reductions of H3K27me3 at regulatory regions of the morphoregulatory gene Hoxa10 resulted in gene downregulation. In young adult females (PND120), GBH increased 17β-estradiol (E2) and decreased progesterone (P4) serum levels, altering estrous cyclicity. Aged females (PND600) exposed to GBH developed leiomyoma and pre-neoplastic glandular lesions in the uterus. Vaginal rhabdomyosarcoma and intrahepatic bile duct adenoma were also observed. In conclusion, neonatal exposure to GBH altered the expression and induced hypermethylation of the Hoxa10 gene in uterine tissue at early life, and increased E2/P4 ratio serum level at middle-age. We propose that epigenetic reprogramming of Hoxa10 in association with hormonal imbalance could be among the possible mechanisms underlying the long-term adverse effects detected in GBH-exposed rats.

Neonatal Exposure to BPA, BDE-99, and PCB Produces Persistent Changes in Hepatic Transcriptome Associated With Gut Dysbiosis in Adult Mouse Livers

Recent evidence suggests that complex diseases can result from early life exposure to environmental toxicants. Polybrominated diphenyl ethers (PBDEs), and polychlorinated biphenyls (PCBs) are persistent organic pollutants (POPs) and remain a continuing risk to human health despite being banned from production. Developmental BPA exposure mediated-adult onset of liver cancer via epigenetic reprogramming mechanisms has been identified. Here, we investigated whether the gut microbiome and liver can be persistently reprogrammed following neonatal exposure to POPs, and the associations between microbial biomarkers and disease-prone changes in the hepatic transcriptome in adulthood, compared with BPA. C57BL/6 male and female mouse pups were orally administered vehicle, BPA, BDE-99 (a breast milk-enriched PBDE congener), or the Fox River PCB mixture (PCBs), once daily for three consecutive days (postnatal days [PND] 2-4). Tissues were collected at PND5 and PND60. Among the three chemicals investigated, early life exposure to BDE-99 produced the most prominent developmental reprogramming of the gut-liver axis, including hepatic inflammatory and cancer-prone signatures. In adulthood, neonatal BDE-99 exposure resulted in a persistent increase in Akkermansia muciniphila throughout the intestine, accompanied by increased hepatic levels of acetate and succinate, the known products of A. muciniphila. In males, this was positively associated with permissive epigenetic marks H3K4me1 and H3K27, which were enriched in loci near liver cancer-related genes that were dysregulated following neonatal exposure to BDE-99. Our findings provide novel insights that early life exposure to POPs can have a life-long impact on disease risk, which may partly be regulated by the gut microbiome.

Biotreatment potential of co-contaminants hexavalent chromium and polychlorinated biphenyls in industrial wastewater: Individual and simultaneous prospects

Co-existence of polychlorinated biphenyls (PCBs) and hexavalent chromium (Cr(VI)) in the environment due to effluent from industries has aggravated the pollution problem. Both contaminants can alter chemical interactions, processes and impair enzymatic activities in the ecosystem that results in negative impacts on aquatic and terrestrial life. Previously, research has been performed for the fate and transfer of these contaminants individually, but simultaneous removal approaches have not received much attention. Cr(VI) exists in a highly toxic form in the environment once released, whereas location of chlorine atoms in the ring determines PCBs toxicity. Lower chlorinated compounds are easily degradable whereas as high chlorinated compounds require sequential strategy for transformation. Microorganisms can develop different mechanism to detoxify both pollutants. However, occurrence of multiple contaminants in single system can alter the bioremediation efficiency of bacteria. Use of metal resistance bacterial for the degradation of organic compounds has been widely used bioaugmentation strategy. Along with that use of sorbents/bio sorbents, biosurfactants and phytoremediation approaches have already been well reported. Bioremediation strategy with dual potential to detoxify the Cr(VI) and PCBs would be a probable option for simultaneous biotreatment. Application of bioreactors and biofilms covered organic particles can be utilized as efficient bioaugmentation approach. In this review, biotreatment systems and bacterial oxidative and reductive enzymes/processes are explained and possible biotransformation pathway has been purposed for bioremediation of co-contaminated waters.

Exposure to xenoestrogens alters the expression of key morphoregulatory proteins of oviduct adenogenesis in the broad-snouted caiman (Caiman latirostris)

Endocrine disrupting compounds (EDCs) are contaminants ubiquitously found in the environment, which pose a potential threat to aquatic and wetland ecosystems. Caiman latirostris, a crocodilian species that inhabits South American wetlands, is highly sensitive to EDC exposure. Previously, we reported that early postnatal exposure to EDCs such as Bisphenol A (BPA) and 17β-Estradiol (E₂) alters C. latirostris oviduct differentiation. The aim of this work was to elucidate the molecular mechanisms behind this alteration. To accomplish this, we established the ontogenic changes in histological features and the expression of Wnt-7a, Wnt-5a, β-catenin, FoxA2, desmin, and alpha smooth muscle actin (α-SMA) in the oviduct of C. latirostris. Then, we evaluated the effects of BPA and E₂ exposure on these histological features and protein expressions. Our results showed that during the postnatal differentiation of the oviduct the presence of histological features related to adenogenesis is associated with the levels of expression of FoxA2, β-catenin, Wnt-5a and Wnt-7a. Early postnatal exposure to BPA and E₂ decreased the presence of histological features related to adenogenesis and altered the levels of expression of FoxA2, β-catenin, Wnt-5a and Wnt-7a, as well as the desmin/α-SMA ratio. These findings suggest that altered levels of Wnt-7a, Wnt-5a, β-catenin and FoxA2 could play a role in the BPA and E₂-induced alteration in oviduct differentiation in C. latirostris. Thus, impaired adenogenesis and, probably, impaired reproduction in wildlife naturally exposed to BPA and other estrogenic agonists cannot be completely ruled out.

Release and toxicity of bisphenol-A (BPA) contained in orthodontic adhesives: A systematic review

OBJECTIVE

The objectives of this systematic review of the literature are to search for BPA release from biomaterials used in orthodontics and to highlight their possible impact on human health.

MATERIALS AND METHODS

Using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) model, digital and manual searches were conducted in February 2020 in the database of CENTRAL, MEDLINE and EMBASE. Thirteen parameters relating to the release and biological effects of BPA were identified and analysed.

RESULTS

Thirty-one non-randomized clinical trials were included. In general, the level of evidence was low, and the risk of bias ranged from moderate to high. Furthermore, although at different concentrations, most of in vitro and in vivo studies found BPA release from orthodontic adhesives. The lack of standardized protocols and the clinical and methodological heterogeneity of the studies prevented a valid interpretation of the actual results. Concerning the possible toxicity of BPA, no conclusive scientific evidence could be drawn, but it seems that orthodontic biomaterials containing BPA have potential adverse biological effects in humans.

DISCUSSION AND CONCLUSION

Until we have solid evidence from clinical trials, clinicians should consider that orthodontic adhesives containing BPA have potential short- and long-term adverse biological effects in humans. Careful consideration should therefore be given to bonding, polymerization and debonding protocols in orthodontics.

Hydroxylated polychlorinated biphenyls (OH-PCBs) exert strong inhibitory effects towards human carboxylesterases (CESs)

Polychlorinated biphenyls (PCBs) have been reported to pose a severe risk towards human health, and hydroxylated polychlorinated biphenyls (OH-PCBs) were potential substances basis for PCBs' toxicity. This study aims to determine the inhibition of OH-PCBs towards human carboxylesterases (CESs), including CES1 and CES2. For phenotypic analysis of CES1 and CES2 activity, we used the hydrolysis metabolism of 2-(2-benzoyl3-methoxyphenyl) benzothiazole (BMBT) and fluorescein diacetate (FD) catalyzed by human liver microsomes (HLMs) as the probe reactions. Preliminary inhibition screening showed that the inhibition potential of OH-PCBs towards CES1 and CES2 increased with the increased numbers of chlorine atoms in OH-PCBs. Both 2'-OH-PCB61 and 2'-OH-PCB65 showed concentration-dependent inhibition towards both CES1 and CES2. Lineweaver-Burk plots showed that 2'-OH-PCB61 and 2'-OH-PCB65 exerted non-competitive inhibition towards CES1 and competitive inhibition towards CES2. The inhibition kinetics parameters (Ki) were 6.8 μM and 7.0 μM for 2'-OH-PCB61 and 2'-OH-PCB65 towards CES1, respectively. The inhibition kinetics parameters (Ki) were 1.4 μM and 1.0 μM for 2'-OH-PCB61 and 2'-OH-PCB65 towards CES2, respectively. In silico docking methods elucidate the contribution of hydrogen bonds and hydrophobic contacts towards the binding of 2'-OH-PCB61 and 2'-OH-PCB65 with CES1 and CES2. All these results will provide a new perspective for elucidation of toxicity mechanism of PCBs and OH-PCBs.

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.

BPA and its analogues (BPS and BPF) modify the expression of genes involved in the endocrine pathway and apoptosis and a multi drug resistance gene of the aquatic midge Chironomus riparius (Diptera)

Many countries are limiting the use of bisphenol A (BPA) because evidence shows it is dangerous to human health and wildlife. For the manufacturing of polycarbonate plastics, bisphenol S (BPS) and bisphenol F (BPF) are proposed as safer alternatives. They have already been released into the aquatic environment without previously available information about their potential adverse effects. In this study, we compared the effects of BPA, BPS and BPF exposure to the expression profile of genes involved in the endocrine pathway (EcR and E74), ecdysone metabolism (Cyp18a1 and Shadow), apoptosis (DRONC) and the multidrug resistance-associated protein 1 gene (MRP1) in the midge, Chironomus riparius (Diptera). The three toxicants increased Shadow expression, which is involved in ecdysone synthesis, but only BPF significantly altered Cyp18a1, which is implicated in ecdysone degradation. BPS and BPF modified EcR and E74 expression; BPF upregulated the effector caspase DRONC. Furthermore, BPA significantly increased MRP1 expression. This study provides insights into the action of bisphenols at the molecular level and highlights the potential risks of BPS and BPF as BPA alternatives.

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.

Stop eating plastic, molecular signaling of bisphenol A in breast cancer

Breast cancer is the second most common fatal cancer in women. Developing a breast cancer is a multi-factorial and hormonal-dependent process, which may be triggered by many risk factors. An endocrine disrupting substance known as bisphenol A (BPA), that is used greatly in the manufacture of plastic products, was suggested as a possible risk factor for developing breast cancer. BPA has a strong binding affinity to non-classical membrane estrogen receptors like estrogen-related and G protein-coupled (GPER) receptors. Based on animal and in vitro studies, results showed a link between BPA exposure and increased incidence of breast cancer. BPA has the ability to alter multiple molecular pathways in cells namely, G protein-coupled receptor (GPER) pathway, estrogen-related receptor gamma (ERRγ) pathway, HOXB9 (homeobox-containing gene) pathway, bone morphogenetic protein 2 (BMP2) and (BMP4), immunoregulatory cytokine disturbance in the mammary gland, EGFR-STAT3 pathway, FOXA1 in ER-breast cancer cells, enhancer of zeste homolog 2 (EZH2), and epigenetic changes. Thus, the aforementioned alterations cause undesired gene stimulation or repression that increase risk of developing breast cancer. So, restricting exposure to BPA should be considered to aid in lowering the risk of developing breast cancer.

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.

The Effect of Bisphenol A on Puberty: A Critical Review of the Medical Literature

Many scientific studies have revealed a trend towards an earlier onset of puberty and have disclosed an increasing number of children that display precocious puberty. As an explanation, some authors have considered the global socio-economic improvement across different populations, and other authors have considered the action of endocrine disrupting chemicals (EDCs). Among these, bisphenol A (BPA), an aromatic compound largely used worldwide as a precursor of some plastics and chemical additives, is well known for its molecular oestrogen-like and obesogenic actions. We reviewed the medical literature of the previous 20 years that examined associations between BPA exposure and the age of puberty in humans, considering only those referring to clinical or epidemiological data. Of 19 studies, only 7 showed a correlation between BPA and puberty. In particular, the possible disruptive role of BPA on puberty may be seen in those with central precocious puberty or isolated premature breast development aged 2 months to 4 years old, even if the mechanism is undefined. Some studies also found a close relationship between urinary BPA, body weight, and early puberty, which can be explained by the obesogenic effect of BPA itself. The currently available data do not allow establishment of a clear role for BPA in pubertal development because of the conflicting results among all clinical and epidemiological studies examined. Further research is needed to fully understand the potential role of exposure to EDCs and their adverse endocrine health outcomes.

Chlorinated biphenyls effect on estrogen-related receptor expression, steroid secretion, mitochondria ultrastructure but not on mitochondrial membrane potential in Leydig cells

To characterize polychlorinated biphenyls (PCBs) action on Leydig cells, PCBs congeners, low-chlorinated (delor 103; d103) and high-chlorinated ones (delor 106; d106) were selected. The cells were treated according to PCBs dose (d103 or d106 0.2 ng/ml in low doses:, or 2 ng/ml in high doses) and type (d103 + d106 in low doses or 103 + 106 in high doses). After 24 h treatment with PCBs, a distinct increase in estrogen-related receptors (ERRs type α, β and γ) expression was revealed. However, the dose- and type-dependent PCBs effect was mostly exerted on ERRα expression. A similar increase in ERRs expression was demonstrated by estradiol but not testosterone, which was without an effect on ERRs. PCBs caused no decrease in the membrane potential status of Leydig cells (either in dose or type schedule) but had severe effects on the mitochondria number and structure. Moreover, PCBs markedly increased calcium (Ca2+) concentration and sex steroid secretion (both androgens and estrogens were elevated). These findings suggest a similar estrogenic action of PCBs congeners (d103 and d106) on Leydig cell function. We report dose- and type-specific effects of PCBs only on Leydig cell ERRs expression. Both delors showed common effects on the mitochondria ultrastructural and functional status. Based on our results, ERRα seems to be the most sensitive to hormonal modulation. The increases in Ca2+ and sex steroid secretion may be due to the activation of ERRs by PCBs binding and/or direct effect of PCBs on ERRs mRNA/protein expression. Nevertheless, to confirm the existence of possible relationships between ERRs signaling (including PCBs as ligands) and mitochondria function in Leydig cells, further intensive studies are needed.

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.

Persistent organic pollutants (POPs) in human follicular fluid and in vitro fertilization outcomes, a pilot study

Persistent organic pollutants (POPs) are ubiquitously distributed among the U.S. population and adversely impact human reproduction. These compounds have been detected in human ovarian follicular fluid (FF), where they directly contact a developing oocyte. As a pilot investigation, we measured 43 polychlorinated biphenyl (PCB) congeners, p,p'-dichlorodiphenyltrichloroethane (DDT), and its persistent metabolite p,p'-dichlorodiphenyldichloroethylene (DDE) in residual FF collected from 32 women undergoing in vitro fertilization (IVF). We identified significant inverse associations between higher levels of PCB congeners and indicators of ovarian reserve (e.g., antral follicle count), follicular response to administered gonadotropins (e.g., peak estradiol, number of oocytes retrieved, endometrial thickness), intermediate IVF endpoints (e.g., oocyte fertilization and embryo quality), and clinical IVF outcomes (e.g., embryo implantation and live birth), after adjusting for body mass index, cigarette smoking, race, and age. Our results suggest that ongoing exposure to POPs impacts IVF and merit confirmation in a larger and more definitive future study.

Endosulfan affects uterine development and functional differentiation by disrupting Wnt7a and β-catenin expression in rats

Neonatal exposure to a low dose of endosulfan may disrupt the expression of Wnt7a and β-catenin during uterine development leading to the failure of uterine functional differentiation during implantation. New-born female Wistar rats were treated with vehicle, endosulfan (600 μg/kg/d, E600) or diethylstilbestrol (0.2 μg/kg/d, DES) on postnatal days (PNDs) 1, 3, 5 and 7. Subsequently, uterine histomorphology and the protein expression of Wnt7a and β-catenin were evaluated on PND8, PND21 and gestational day (GD) 5 (pre-implantation period). In the E600 rats, Wnt7a and β-catenin protein expression was increased in the epithelium on PND8, and Wnt7a expression was decreased in the endometrial glands on PND21. On GD5, the number of uterine glands was decreased in the E600-and DES-treated rats. In addition, Wnt7a expression was decreased in all uterine compartments, and β-catenin expression was increased in the luminal and glandular epithelia of the E600-and DES-treated rats. Disruption of Wnt7a and β-catenin uterine expression in the prepubertal and adult females altered the uterine preparation for embryo implantation, which could be associated with the subfertility triggered by endosulfan.

Methodological issues in human studies of endocrine disrupting chemicals

Possible harm from endocrine disrupting chemicals (EDCs) in humans is speculated based on two types of evidence; 1) increasing trends of suspected diseases in ecological studies of populations and 2) findings from traditional epidemiological studies of individuals. However, ecological findings are not regarded as direct human evidence of the relation between EDCs and disease, while the evidence among epidemiological studies of individuals is often inconsistent. Thus, a criticism is that linking EDCs and health in human is naively presumed without solid evidence. However, human studies of EDCs are methodologically complex and understanding methodological issues will help to interpret findings from existing human studies and to properly design optimal human studies. The key issues are low reliability of exposure assessment of EDCs with short half-lives, EDC mixtures, possibility of non-monotonic dose-response relationships, non-existence of an unexposed group, difficulties in measuring exposure during critical periods, and interactions with established risk factors. Furthermore, EDC mixtures may affect human health through other mechanisms than traditional endocrine disruption, for example glutathione depletion or mitochondrial dysfunction. Given this complexity, the most plausible scenario in humans is that exposure to EDC mixtures leads to increasing risk of related diseases at the ecological level, but inconsistent associations would be expected in traditional epidemiological studies. Although epidemiologists have long relied on Bradford Hill's criteria to objectively evaluate whether associations observed in epidemiology can be interpreted as causal, there are challenges to use these criteria for EDCs, particularly concerning consistency across studies and the findings of linear dose-response relationships. At the individual level, compared to EDCs with short half-lives, epidemiological studies of EDCs with long half-lives among populations with a relatively low exposure dose range of exposure can likely produce relatively more reliable results, because the measurement of EDCs with long half-lives likely represents typical long-term exposure and populations with exposure in the low range of doses are likely to have a reference group closer to non-exposure.

Endocrine disrupting chemicals (EDCs) and female cancer: Informing the patients

Breast and uterine cancer are the most frequent female gender related neoplasms whose growth is mostly estrogen dependent. Therefore, any EDC exhibiting estrogenic effects may increase the risk of these two malignancies. This review focuses on the potential role of EDCs with estrogenic potential on the risk of breast and uterine neoplasms but also points to the possible role of the exposure to EDCs in the pathogenesis of ovarian and cervical cancer. It also underlines the necessity of informing the public about the presence of EDCs in common consumer products, their detrimental health effects and methods of reducing the exposure risk.

Integrated Bioinformatics, Environmental Epidemiologic and Genomic Approaches to Identify Environmental and Molecular Links between Endometriosis and Breast Cancer

We present a combined environmental epidemiologic, genomic, and bioinformatics approach to identify: exposure of environmental chemicals with estrogenic activity; epidemiologic association between endocrine disrupting chemical (EDC) and health effects, such as, breast cancer or endometriosis; and gene-EDC interactions and disease associations. Human exposure measurement and modeling confirmed estrogenic activity of three selected class of environmental chemicals, polychlorinated biphenyls (PCBs), bisphenols (BPs), and phthalates. Meta-analysis showed that PCBs exposure, not Bisphenol A (BPA) and phthalates, increased the summary odds ratio for breast cancer and endometriosis. Bioinformatics analysis of gene-EDC interactions and disease associations identified several hundred genes that were altered by exposure to PCBs, phthalate or BPA. EDCs-modified genes in breast neoplasms and endometriosis are part of steroid hormone signaling and inflammation pathways. All three EDCs–PCB 153, phthalates, and BPA influenced five common genes—CYP19A1, EGFR, ESR2, FOS, and IGF1—in breast cancer as well as in endometriosis. These genes are environmentally and estrogen responsive, altered in human breast and uterine tumors and endometriosis lesions, and part of Mitogen Activated Protein Kinase (MAPK) signaling pathways in cancer. Our findings suggest that breast cancer and endometriosis share some common environmental and molecular risk factors.

Array-based detection of persistent organic pollutants via cyclodextrin promoted energy transfer

We report herein the selective array-based detection of 30 persistent organic pollutants via cyclodextrin-promoted energy transfer. The use of three fluorophores enabled the development of an array that classified 30 analytes with 100% accuracy and identified unknown analytes with 96% accuracy, as well as identifying 92% of analytes in urine.

Metabolism and metabolites of polychlorinated biphenyls

Abstract The metabolism of polychlorinated biphenyls (PCBs) is complex and has an impact on toxicity, and thereby on the assessment of PCB risks. A large number of reactive and stable metabolites are formed in the processes of biotransformation in biota in general, and in humans in particular. The aim of this document is to provide an overview of PCB metabolism, and to identify the metabolites of concern and their occurrence. Emphasis is given to mammalian metabolism of PCBs and their hydroxyl, methylsulfonyl, and sulfated metabolites, especially those that persist in human blood. Potential intracellular targets and health risks are also discussed.

Bisphenol-A exposure alters memory consolidation and hippocampal CA1 spine formation through Wnt signaling in vivo and in vitro

Based on Wnt signaling pathway, this study aims to further mechanistically understand memory alteration after BPA exposure.

In utero exposure to mixtures of xenoestrogens and child neuropsychological development

BACKGROUND

To date, no epidemiological studies have explored the impact and persistence of in utero exposure to mixtures of xenoestrogens on the developing brain. We aimed to assess whether the cumulative effect of xenoestrogens in the placenta is associated with altered infant neuropsychological functioning at two and at four years of age, and if associations differ among boys and girls.

METHODS

Cumulative prenatal exposure to xenoestrogens was quantified in the placenta using the biomarker Total Effective Xenoestrogen Burden (TEXB-alpha) in 489 participants from the INMA (Childhood and the Environment) Project. TEXB-alpha was split in tertiles to test its association with the mental and psychomotor scores of the Bayley Scales of Infant Development (BSID) at 1-2 years of age, and with the McCarthy Scales of Children׳s Abilities (MSCA) general cognitive index and motor scale assessed at 4-5 years of age. Interactions with sex were investigated.

RESULTS

After adjustment for potential confounders, no association was observed between TEXB-alpha and mental scores at 1-2 years of age. We found a significant interactions with sex for the association between TEXB-alpha and infant psychomotor development (interaction p-value=0.029). Boys in the third tertile of exposure scored on average 5.2 points less than those in the first tertile on tests of motor development at 1-2 years of age (p-value=0.052), while no associations were observed in girls. However, this association disappeared in children at 4-5 years of age and no association between TEXB-alpha and children׳s cognition was found.

CONCLUSIONS

Our results suggest that boys' early motor development might be more vulnerable to prenatal exposure to mixtures of xenoestrogens, but associations do not persist in preschool children.

Chlorinated persistent organic pollutants, obesity, and type 2 diabetes

Persistent organic pollutants (POPs) are lipophilic compounds that travel with lipids and accumulate mainly in adipose tissue. Recent human evidence links low-dose POPs to an increased risk of type 2 diabetes (T2D). Because humans are contaminated by POP mixtures and POPs possibly have nonmonotonic dose-response relations with T2D, critical methodological issues arise in evaluating human findings. This review summarizes epidemiological results on chlorinated POPs and T2D, and relevant experimental evidence. It also discusses how features of POPs can affect inferences in humans. The evidence as a whole suggests that, rather than a few individual POPs, background exposure to POP mixtures-including organochlorine pesticides and polychlorinated biphenyls-can increase T2D risk in humans. Inconsistent statistical significance for individual POPs may arise due to distributional differences in POP mixtures among populations. Differences in the observed shape of the dose-response curves among human studies may reflect an inverted U-shaped association secondary to mitochondrial dysfunction or endocrine disruption. Finally, we examine the relationship between POPs and obesity. There is evidence in animal studies that low-dose POP mixtures are obesogenic. However, relationships between POPs and obesity in humans have been inconsistent. Adipose tissue plays a dual role of promoting T2D and providing a relatively safe place to store POPs. Large prospective studies with serial measurements of a broad range of POPs, adiposity, and clinically relevant biomarkers are needed to disentangle the interrelationships among POPs, obesity, and the development of T2D. Also needed are laboratory experiments that more closely mimic real-world POP doses, mixtures, and exposure duration in humans.

Chlorinated persistent organic pollutants, obesity, and type 2 diabetes

Persistent organic pollutants (POPs) are lipophilic compounds that travel with lipids and accumulate mainly in adipose tissue. Recent human evidence links low-dose POPs to an increased risk of type 2 diabetes (T2D). Because humans are contaminated by POP mixtures and POPs possibly have nonmonotonic dose-response relations with T2D, critical methodological issues arise in evaluating human findings. This review summarizes epidemiological results on chlorinated POPs and T2D, and relevant experimental evidence. It also discusses how features of POPs can affect inferences in humans. The evidence as a whole suggests that, rather than a few individual POPs, background exposure to POP mixtures-including organochlorine pesticides and polychlorinated biphenyls-can increase T2D risk in humans. Inconsistent statistical significance for individual POPs may arise due to distributional differences in POP mixtures among populations. Differences in the observed shape of the dose-response curves among human studies may reflect an inverted U-shaped association secondary to mitochondrial dysfunction or endocrine disruption. Finally, we examine the relationship between POPs and obesity. There is evidence in animal studies that low-dose POP mixtures are obesogenic. However, relationships between POPs and obesity in humans have been inconsistent. Adipose tissue plays a dual role of promoting T2D and providing a relatively safe place to store POPs. Large prospective studies with serial measurements of a broad range of POPs, adiposity, and clinically relevant biomarkers are needed to disentangle the interrelationships among POPs, obesity, and the development of T2D. Also needed are laboratory experiments that more closely mimic real-world POP doses, mixtures, and exposure duration in humans.

In silico predictive studies of mAHR congener binding using homology modelling and molecular docking

The aryl hydrocarbon receptor (AHR) is one of the principal xenobiotic, nuclear receptor that is responsible for the early events involved in the transcription of a complex set of genes comprising the CYP450 gene family. In the present computational study, homology modelling and molecular docking were carried out with the objective of predicting the relationship between the binding efficiency and the lipophilicity of different polychlorinated biphenyl (PCB) congeners and the AHR in silico. Homology model of the murine AHR was constructed by several automated servers and assessed by PROCHECK, ERRAT, VERIFY3D and WHAT IF. The resulting model of the AHR by MODWEB was used to carry out molecular docking of 36 PCB congeners using PatchDock server. The lipophilicity of the congeners was predicted using the XLOGP3 tool. The results suggest that the lipophilicity influences binding energy scores and is positively correlated with the same. Score and Log P were correlated with r = +0.506 at p = 0.01 level. In addition, the number of chlorine (Cl) atoms and Log P were highly correlated with r = +0.900 at p = 0.01 level. The number of Cl atoms and scores also showed a moderate positive correlation of r = +0.481 at p = 0.01 level. To the best of our knowledge, this is the first study employing PatchDock in the docking of AHR to the environmentally deleterious congeners and attempting to correlate structural features of the AHR with its biochemical properties with regards to PCBs. The result of this study are consistent with those of other computational studies reported in the previous literature that suggests that a combination of docking, scoring and ranking organic pollutants could be a possible predictive tool for investigating ligand-mediated toxicity, for their subsequent validation using wet lab-based studies.

Endocrine-disrupting chemicals and public health protection: a statement of principles from The Endocrine Society

An endocrine-disrupting chemical (EDC) is an exogenous chemical, or mixture of chemicals, that can interfere with any aspect of hormone action. The potential for deleterious effects of EDC must be considered relative to the regulation of hormone synthesis, secretion, and actions and the variability in regulation of these events across the life cycle. The developmental age at which EDC exposures occur is a critical consideration in understanding their effects. Because endocrine systems exhibit tissue-, cell-, and receptor-specific actions during the life cycle, EDC can produce complex, mosaic effects. This complexity causes difficulty when a static approach to toxicity through endocrine mechanisms driven by rigid guidelines is used to identify EDC and manage risk to human and wildlife populations. We propose that principles taken from fundamental endocrinology be employed to identify EDC and manage their risk to exposed populations. We emphasize the importance of developmental stage and, in particular, the realization that exposure to a presumptive "safe" dose of chemical may impact a life stage when there is normally no endogenous hormone exposure, thereby underscoring the potential for very low-dose EDC exposures to have potent and irreversible effects. Finally, with regard to the current program designed to detect putative EDC, namely, the Endocrine Disruptor Screening Program, we offer recommendations for strengthening this program through the incorporation of basic endocrine principles to promote further understanding of complex EDC effects, especially due to developmental exposures.

Common classification schemes for PCB congeners and the gene expression of CYP17, CYP19, ESR1 and ESR2

BACKGROUND

Reliable techniques to measure polychlorinated biphenyl (PCB) congeners make the clearer definition of their effects on human health possible. Given that PCBs are classified as endocrine disrupters, we sought to explore the expression of some key genes involved in sex steroid metabolism.

OBJECTIVES

To examine common classification schemes of PCB congeners and determine whether exposure to groups classified by mechanism of action alter the gene expression (GE) of CYP17, CYP19, and ESR1 and ESR2.

METHODS

GE and exposure to various classifications of lipid-adjusted PCB congeners were examined in 139 daughters of the Michigan Fisheaters' Cohort. Using mixed models analyses and adjusting for age, menopausal status, and current use of oral contraceptives and hormone replacement therapy, GE data were regressed on exposure to PCB congener groupings based on mechanism of action.

RESULTS

Three novel findings are elucidated: first, that up-regulation of CYP19 expression is associated with exposure to PCB groupings containing dioxin-like, potentially anti-estrogenic, immunotoxic congeners, including PCB IUPAC #74, #105, #118, #138, #156, #157, #158, #167, and #170 from this cohort. Second, that exposure to similar congeners (PCB IUPAC #105, #156, #157, #158, and #167 in this cohort) but using a classification based solely on hormonal mechanisms of action is associated with increased expression of ESR2. Third, that increased expression of CYP17 is of borderline significance when associated with exposure to PCB IUPAC #118, #138, and #156.

CONCLUSIONS

These findings are both counter-intuitive and intriguing. Rather than exhibiting anti-estrogenic effects alone, they suggest that these congeners up-regulate the major enzyme involved in estrogen synthesis and tend to confirm previous findings of links between AhR and ER signaling pathways. Replication of these findings, expansion of the number of genes examined, exploration of mixtures of environmental chemicals, and subsequent study of health outcomes in a larger cohort are future priorities.

Variants of the WNT7A gene in Chinese patients with müllerian duct abnormalities

OBJECTIVE

To search for WNT7A gene mutations in a cohort of 191 Chinese Han patients with müllerian duct abnormalities (MDAs).

DESIGN

Phenotypic and mutational study.

SETTING

University hospital.

PATIENT(S)

A total of 191 Chinese Han patients with MDAs and 192 healthy control individuals.

INTERVENTION(S)

Genomic DNA extracted from blood samples, all coding regions amplified by polymerase chain reaction (PCR) then directly sequenced to screen variants.

MAIN OUTCOME MEASURE(S)

Not applicable.

RESULT(S)

The sequence analysis revealed one novel synonymous variant and three known single-nucleotide polymorphisms (SNPs).

CONCLUSION(S)

The results indicate that mutations in the coding sequence of WNT7A are not responsible for müllerian duct abnormalities in the Chinese population.

Maternal exposure to polychlorinated biphenyls and the secondary sex ratio: an occupational cohort study

BACKGROUND

Though commercial production of polychlorinated biphenyls was banned in the United States in 1977, exposure continues due to their environmental persistence. Several studies have examined the association between environmental polychlorinated biphenyl exposure and modulations of the secondary sex ratio, with conflicting results.

OBJECTIVE

Our objective was to evaluate the association between maternal preconceptional occupational polychlorinated biphenyl exposure and the secondary sex ratio.

METHODS

We examined primipara singleton births of 2595 women, who worked in three capacitor plants at least one year during the period polychlorinated biphenyls were used. Cumulative estimated maternal occupational polychlorinated biphenyl exposure at the time of the infant's conception was calculated from plant-specific job-exposure matrices. A logistic regression analysis was used to evaluate the association between maternal polychlorinated biphenyl exposure and male sex at birth (yes/no).

RESULTS

Maternal body mass index at age 20, smoking status, and race did not vary between those occupationally exposed and those unexposed before the child's conception. Polychlorinated biphenyl-exposed mothers were, however, more likely to have used oral contraceptives and to have been older at the birth of their first child than non-occupationally exposed women. Among 1506 infants liveborn to polychlorinated biphenyl-exposed primiparous women, 49.8% were male; compared to 49.9% among those not exposed (n = 1089). Multivariate analyses controlling for mother's age and year of birth found no significant association between the odds of a male birth and mother's cumulative estimated polychlorinated biphenyl exposure to time of conception.

CONCLUSIONS

Based on these data, we find no evidence of altered sex ratio among children born to primiparous polychlorinated biphenyl-exposed female workers.

Induction of oxidative stress and cytotoxicity by PCB126 in JEG-3 human choriocarcinoma cells

The compound 3,3',4,4',5-pentachlorobiphenyl (PCB126) exists in various environmental media, which may have adverse effects on human health. In the present study, induction of the oxidative stress and cytotoxicity by PCB126 were investigated in the human choriocarcinoma cell line JEG-3 cells. Both the reactive oxygen species (ROS) generation and lipid peroxidation production of malondialdehyde (MDA) were obviously increased. Whereas the activity of antioxidant enzymes (superoxide dismutase [SOD] and catalase [CAT]) and glutathione (GSH) content were declined with dose-dependent manners. Furthermore, the result of the cytotoxicity assay showed a clear, dose-dependent growth inhibition effect of PCB126 in JEG-3 cells. Our present results revealed that PCB126 exhibited significant oxidative stress and cytotoxicity in human trophoblast. Given the widespread use of PCBs, a more comprehensive understanding of the significance of reproductive toxicity of PBCs is imperative for improving risk assessment and regulation of these chemicals.

Endocrine disruptors in female reproductive tract development and carcinogenesis

Growing concerns over endocrine disrupting chemicals (EDCs) and their effects on human fetal development and adult health have promoted research into the underlying molecular mechanisms of endocrine disruption. Gene targeting technology has allowed insight into the genetic pathways governing reproductive tract development and how exposure to EDCs during a critical developmental window can alter reproductive tract development, potentially forming the basis for adult diseases. This review primarily uses diethylstilbestrol (DES) as a model agent for EDCs and discusses the recent progress elucidating how DES and other EDCs affect murine female reproductive tract development and cancer at the molecular level.

Non-canonical Wnt signaling regulates cell polarity in female reproductive tract development via van gogh-like 2

Wnt signaling effectors direct the development and adult remodeling of the female reproductive tract (FRT); however, the role of non-canonical Wnt signaling has not been explored in this tissue. The non-canonical Wnt signaling protein van gogh-like 2 is mutated in loop-tail (Lp) mutant mice (Vangl2(Lp)), which display defects in multiple tissues. We find that Vangl2(Lp) mutant uterine epithelium displays altered cell polarity, concommitant with changes in cytoskeletal actin and scribble (scribbled, Scrb1) localization. The postnatal mutant phenotype is an exacerbation of that seen at birth, exhibiting more smooth muscle and reduced stromal mesenchyme. These data suggest that early changes in cell polarity have lasting consequences for FRT development. Furthermore, Vangl2 is required to restrict Scrb1 protein to the basolateral epithelial membrane in the neonatal uterus, and an accumulation of fibrillar-like structures observed by electron microscopy in Vangl2(Lp) mutant epithelium suggests that mislocalization of Scrb1 in mutants alters the composition of the apical face of the epithelium. Heterozygous and homozygous Vangl2(Lp) mutant postnatal tissues exhibit similar phenotypes and polarity defects and display a 50% reduction in Wnt7a levels, suggesting that the Vangl2(Lp) mutation acts dominantly in the FRT. These studies demonstrate that the establishment and maintenance of cell polarity through non-canonical Wnt signaling are required for FRT development.

Bisphenol-A and the great divide: a review of controversies in the field of endocrine disruption

In 1991, a group of 21 scientists gathered at the Wingspread Conference Center to discuss evidence of developmental alterations observed in wildlife populations after chemical exposures. There, the term "endocrine disruptor" was agreed upon to describe a class of chemicals including those that act as agonists and antagonists of the estrogen receptors (ERs), androgen receptor, thyroid hormone receptor, and others. This definition has since evolved, and the field has grown to encompass hundreds of chemicals. Despite significant advances in the study of endocrine disruptors, several controversies have sprung up and continue, including the debate over the existence of nonmonotonic dose response curves, the mechanisms of low-dose effects, and the importance of considering critical periods of exposure in experimental design. One chemical found ubiquitously in our environment, bisphenol-A (BPA), has received a tremendous amount of attention from research scientists, government panels, and the popular press. In this review, we have covered the above-mentioned controversies plus six additional issues that have divided scientists in the field of BPA research, namely: 1) mechanisms of BPA action; 2) levels of human exposure; 3) routes of human exposure; 4) pharmacokinetic models of BPA metabolism; 5) effects of BPA on exposed animals; and 6) links between BPA and cancer. Understanding these topics is essential for educating the public and medical professionals about potential risks associated with developmental exposure to BPA and other endocrine disruptors, the design of rigorously researched programs using both epidemiological and animal studies, and ultimately the development of a sound public health policy.

Bioelectronome. Integrated Approach to Receptor Chemistry, Radicals, Electrochemistry, Cell Signaling, and Physiological Effects Based on Electron Transfer

Bioelectronome refers to the host of electron transfer (ET) reactions that occur in living systems. This review presents an integrated approach to receptor chemistry based on electron transfer, radicals, electrochemistry, cell signaling, and end result. First, receptor activity is addressed from the unifying standpoint of redox transformations in which various receptors are discussed. After a listing of receptor-binding modes, receptor chemistry is treated with focus on generation of reactive oxygen species (ROS), activation by ROS, and subsequent cell signaling involving ROS. A general electrostatic mechanism is proposed for receptor-ligand action with supporting evidence. Cell-signaling processes appear to entail electron transfer, ROS, redox chains, and relays. The widespread involvement of phosphate from phosphorylation may be rationalized electrostatically by analogy with DNA phosphate. Extensive evidence supports important participation of ET functionalities in the mechanism of drugs and toxins. The integrated approach is applied to the main ET classes, namely, quinones, metal complexes, iminium species, and aromatic nitro compounds.

Possible effects of environmental nitrates and toxic organochlorines on human thyroid in highly polluted areas in Slovakia

Heavy environmental pollution resulting from uncontrolled industrial and agricultural activities has occurred in several areas of Slovakia. So far, field surveys focused mainly on the thyroid have been conducted in one area polluted by nitrates and in a large area polluted mainly by organochlorinated toxicants. In children from the high nitrate area (HNA, n = 324) significantly higher thyroid volume (ThV) by ultrasound was found compared with age-matched children from surrounding areas with low nitrate (LNA, n = 764). In blood samples of 324 children from the HNA and of 100 children from the LNA no difference between areas was found in the level of total thyroxine (T4) and free triiodothyronine (T3). However, positive thyroid peroxidase antibodies (TPOAb) were found in 7/324 (2.2%) and thyrotropin (TSH) levels > 4.0 mIU/L in 13/324 (4.0%) of children from the HNA area, while no positive values were obtained in the LNA. In the area heavily polluted by an organochlorine (OC) cocktail consisting of polychlorinated biphenyls (PCBs), 2,2'-bis(4-chlorophenyl)-1,1-dichloroethylene (p,p'-DDE), hexachlorobenzene (HCB), and dioxins and furans (polluted area) and in the background pollution area (background area) a total of 2046 adults were examined. In polluted area very high blood levels of OCs were found as well as increased ThV and prevalence of thyroid hypoechogenicity by ultrasound. For the evaluation of data the level of PCBs was used as a marker of all OCs. Increasing PCB levels were significantly associated with the increase of free T4 (p < 0.001) and total T3 (p < 0.05) in blood, while slight but not significant negative association of PCBs was observed with the level of TSH. In both women and men the prevalence of TPOAb was significantly higher in polluted area. Although the absolute TPOAb prevalence in both areas was higher in women than that in men, the increase in polluted vs. background area was more striking in men. From these data it appears that the effects of environmental pollution on the thyroid cannot be neglected.

Does breast cancer start in the womb?

Perturbations in the foetal environment predispose individuals to diseases that become apparent in adulthood. These findings prompted researchers to hypothesize that foetal exposure to environmental oestrogens may play a role in the increased incidence of breast cancer observed in European and US populations over the last 50 years. There is widespread human exposure to bisphenol A, an oestrogenic compound that leaches from dental materials and consumer products. In CD-1 mice, perinatal exposure to environmentally relevant bisphenol A levels induced alterations of the mammary gland architecture. Bisphenol A increased the number of terminal end buds at puberty and terminal ends at 6 months of age and increased ductal lateral branching at 4 months of age. Exposed mice also showed an enhanced sensitivity to oestradiol when ovariectomized prior to puberty. All these parameters are associated in human beings with an increased risk for developing breast cancer. To assess whether bisphenol A induces mammary gland neoplasia, we chose a rat model because it more closely mimics the human disease than mouse models. Examination of the mammary glands of Wistar/Furth rats during early adulthood revealed that gestational exposure to bisphenol A induced the development of pre-neoplastic lesions and carcinoma in situ in the absence of any additional treatment aimed at increasing tumour development. Emerging epidemiological data reveal an increased incidence of breast cancer in women exposed to diethylstilboestrol during gestation. Hence, both animal experiments and epidemiological data strengthen the hypothesis that foetal exposure to xenooestrogens may be an underlying cause of the increased incidence of breast cancer observed over the last 50 years.

Reduced embryonic survival in rainbow trout resulting from paternal exposure to the environmental estrogen 17alpha-ethynylestradiol during late sexual maturation

Exposure of fishes to environmental estrogens is known to affect sexual development and spawning, but little information exists regarding effects on gametes. This study evaluated embryonic survival of offspring from male rainbow trout (Oncorhynchus mykiss) exposed to 17alpha-ethynylestradiol (EE(2)) using an in vitro fertilization protocol. Males were exposed at either 1800 or 6700 degree days ( degrees d) (i.e. 161 or 587 days post-fertilization (dpf)) to test for effects on testes linked to reproductive ontogeny. At 1800 degrees d, fish were beginning testicular differentiation and were exposed to 109 ng EE(2)/l for 21 days. At 6700 degrees d, fish have testes containing spermatocytes and spermatids and were exposed for 56 days to either 0.8, 8.3, or 65 ng EE(2)/l. Semen was collected at full sexual maturity in each group and used to fertilize eggs pooled from several non-exposed females. Significant decreases in embryonic survival were observed only with the 6700 degrees d exposure. In 0.8 and 8.3 ng EE(2)/l treatments, embryo survival was significantly reduced at 19 dpf when compared with the control. In contrast, an immediate decrease in embryonic survival at 0.5 dpf was observed in the 65 ng EE(2)/l treatment. Blood samples collected at spawning from 6700 degrees d exposed males revealed a significant decrease in 11-ketotestosterone and a significant increase in luteinizing hormone levels for the 65 ng EE(2)/l treatment when compared with the other treatment groups. Results indicate that sexually maturing male rainbow trout are susceptible to EE(2) exposure with these fish exhibiting two possible mechanisms of reduced embryonic survival through sperm varying dependant on EE(2) exposure concentrations experienced.

Thyroid ultrasound volume, structure and function after long-term high exposure of large population to polychlorinated biphenyls, pesticides and dioxin

We examined 2,046 adults (834 males and 1,212 females aged 20-75 years) from polluted district in East Slovakia (POLL) and two neighboring upstream and upwind located districts of background pollution (BCGR). By ultrasound we estimated the thyroid volume (ThV), hypoechogenicity (HYE), nodules and cysts. Serum levels of thyrotropin (TSH), thyroperoxidase antibodies (TPOab) and thyroglobulin were estimated by electrochemiluminiscent assay and these of 15 PCB congeners, p,p'-DDE, p,p'-DDT, hexachlorobenzene (HCB) and hexachlorocyclohexane by high-resolution gas chromatography. In 320 subjects also selected hydroxylated and methylsulfonated PCB metabolites, polychlorinated dibenzo-dioxins (PCDDs), -furans (PCDFs), five dioxin-like coplanar and eight mono-ortho PCB congeners were estimated. Urinary iodine was measured by automatic microplate method. Reciprocal positive association was found between three major POPs (PCBs, DDE and HCB), the levels of these and also PCDDs plus PCDFs in polluted area being considerably higher than in background pollution area. ThV in groups of males and females from POLL with high PCBs level was significantly higher (p<0.001 by t-test) then in age and sex matched groups from BCGR with low PCBs level. In 1,048 males and females aged <60 years with serum PCBs level >1,000 ng g(-1) lipid (median=1,756 ng g(-1)) a significant effect of age on ThV was found (p<0.01 by ANOVA), while in 921 respective subjects with PCBs level <1,000 ng g(-1) (median=661 ng g(-1)) it was not. These findings supported the view on the additional effect of PCBs on ThV other than that of age. Since the urinary iodine in both districts showed optimal range, any interfering effect of unsatisfactory iodine intake on ThV may be excluded. The frequency of autoimmune thyroiditis signs such as HYE, increased serum level of TPOab and TSH resulting in subclinical or overt thyroid hypofunction was positively associated with sex, age and organochlorine levels. The increase of such frequency in males with POPs levels was much more abrupt than that in females. No considerable differences in the frequency of thyroid nodules as related to PCBs level were found.