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

Maternal Exposure to Phthalates and Nanoplastics, Isolated or Combined: Impacts on Placental Structure, Development, and Antioxidant Defense as a Trigger for Maternal-Fetal Adversities

The placenta is an essential maternal-fetal organ for the healthy development of the fetus, linking maternal and fetal circulations. Endocrine disrupting chemicals (EDCs), such as phthalates derived from plastic residues, may impair offspring development and increase the risk of metabolic disorders. Plastics also degrade into microplastics (MPs) and nanoplastics (NPs), which can cross the placenta, carrying EDCs and impacting fetal development. The objective of this study was to investigate whether gestational exposure to a phthalate mixture (PM) and NPs interferes with the maternal-fetal interface, altering female reproductive efficiency and placental morphophysiology. Pregnant SD rats were divided into 6 groups: CTR(control; vehicle), T1(20μg/kg/day-PM), T2(200mg/kg/day-PM), T3(1mg/kg/day NPs-100nm), T4(20μg/kg/dayPM+1mg/kg/day-NPs-100nm), and T5(200mg/kg/day-PM+1mg/kg/day-NPs-100 nm). Treatment was administered orally from gestational day 5 (GD5) to GD20. At GD20, 5-8 rats from each group were anesthetized and underwent laparotomy, and blood, ovaries, uterus, and placentas were analyzed. There was an increase in pre-implantation loss in T3, T4 and T5 groups, a reduction in placental weight, and an increase in placental efficiency in male offspring in T3 group. An increase in the number of fetuses small for gestational age was observed in T3 and T5 vs. C. Furthermore, the treatment caused an increase in the expression of targets related to trophoblast cell differentiation in T5, and growth factors related to angiogenesis in the placenta in T3 and T4 groups. There was a decrease in TBARS, SOD, and GSTpi levels in T2, while CAT increased in T3, suggesting that these pollutants modulate placental gene expression and energy metabolism.

Propylparaben negatively impacts IN VITRO preimplantation mouse embryo development

Parabens are chemicals widely used in personal care products and food as antimicrobial preservatives. They exhibit potential estrogenic activity by binding to estrogen receptors 1 and 2, classifying them as endocrine-disrupting chemicals. Given the substantial daily exposure of women to parabens, it is crucial to investigate their effects on the female reproductive system. Previous studies in mouse models have shown that paraben exposure impacts ovarian development, resulting in an increase in cystic follicles and a decrease in corpora lutea. However, the effects of parabens on embryo development have not been extensively studied. This study aimed to determine the impact of propylparaben exposure on preimplantation embryo development in vitro. We tested the effects of 0 (0.075 % DMSO), 0.5 μg/mL, 5.0 μg/mL, 10 μg/mL, and 15 μg/mL propylparaben on rate of development of mouse zygotes to hatched blastocyst stage, quantified the number of inner cell mass (ICM) and trophectoderm (TE) cells in hatched blastocysts, and the distribution of cytoskeletal F-actin. The percentage of hatched blastocysts was significantly decreased at 0.5 μg/mL and 10 μg/mL compared to controls. Propylparaben treatment did not alter TE cell numbers. However, treatment with 0.5 or 15 μg/mL significantly decreased the number of ICM cells compared to controls. Additionally, the intensity of phalloidin fluorescence staining for F-actin was significantly reduced at 10 μg/mL and 15 μg/mL propylparaben. In summary, our findings show that propylparaben exposure disrupts ICM formation, impacts the cytoskeletal filamentous actin (F-actin) network, and alters the rate of hatched blastocyst development in preimplantation mouse embryos.

Uterine Microbiota and Bisphenols: Novel Influencers in Reproductive Health

Infertility affects 8-12% of couples worldwide, and 30-75% of preclinical pregnancy losses are due to a failure during the implantation process. Exposure to endocrine disruptors, like bisphenols, among others, has been associated with the increase in infertility observed in the past decades. An increase in infertility has correlated with exposure to endocrine disruptors like bisphenols. The uterus harbors its own microbiota, and changes in this microbiota have been linked to several gynecological conditions, including reproductive failure. There are no studies on the effects of bisphenols on the uterine-microbiota composition, but some inferences can be gleaned by looking at the gut. Bisphenols can alter the gut microbiota, and the molecular mechanism by which gut microbiota regulates intestinal permeability involves Toll-like receptors (TLRs) and tight junction (TJ) proteins. TJs participate in embryo implantation in the uterus, but bisphenol exposure disrupts the expression and localization of TJ proteins. The aim of this review is to summarize the current knowledge on the microbiota of the female reproductive tract (FRT), its association with different reproductive diseases-particularly reproductive failure-the effects of bisphenols on microbiota composition and reproductive health, and the molecular mechanisms regulating uterine-microbiota interactions crucial for embryo implantation. This review also highlights existing knowledge gaps and outlines research needs for future risk assessments regarding the effects of bisphenols on reproduction.

IMPACT OF REAL-LIFE ENVIRONMENTAL EXPOSURES ON REPRODUCTION: Phthalates disrupt female reproductive health: a call for enhanced investigation into mixtures

In brief

Exposure to phthalates, known endocrine-disrupting chemicals (EDCs), is ubiquitous, but the effects on women's reproductive health are largely unknown. This review summarizes the literature investigating associations between phthalate exposures and clinical reproductive outcomes and reproductive disease states in women, and it emphasizes the need to investigate the effects of phthalate mixtures on women's reproductive health.

Abstract

Daily exposure to a mixture of phthalates is unavoidable in humans and poses a risk to reproductive health because they are known EDCs. Specific to female reproductive health, the literature has linked phthalate exposure to impairments in ovarian function, uterine function, pregnancy outcomes and endocrine signaling in the hypothalamic-pituitary-ovarian axis. However, limitations of these studies are that they primarily focus on single-phthalate exposures in animal models. Thus, the effects of real-life exposures to mixtures of phthalates and the clinical and translational impacts on reproductive function in women are largely unknown. This review summarizes the recent literature specifically investigating associations between phthalate mixture exposures and clinical reproductive outcomes and reproductive disease states in women. Because these studies are scarce, they are supplemented with the literature utilizing single-phthalate analyses in women and mechanistic basic science studies using phthalate mixture exposures. Main findings from the literature suggest that elevated phthalate exposure is associated with altered menstrual cyclicity, altered pubertal timing, disrupted ovarian folliculogenesis and steroidogenesis, ovarian disorders including primary ovarian insufficiency and polycystic ovary syndrome, uterine disorders including endometriosis and leiomyomas, poor in vitro fertilization outcomes and poor pregnancy outcomes. There is an urgent need to better incorporate phthalate mixtures in epidemiology (mixture analyses) and basic science (direct exposures) study designs. Furthermore, as exposure to multiple phthalates is ubiquitous, elucidating the mechanism of phthalate mixture toxicities is paramount for improving women's reproductive health.

Biochanin a modulates steroidogenesis and cellular metabolism in human granulosa cells through TAS2Rs activation: a spotlight on ovarian function

BACKGROUND

Endocrine-disrupting chemicals (EDCs) interfere with the endocrine system and negatively impact reproductive health. Biochanin A (BCA), an isoflavone with anti-inflammatory and estrogen-like properties, has been identified as one such EDC. This study investigates the effects of BCA on transcription, metabolism, and hormone regulation in primary human granulosa cells (GCs), with a specific focus on the activation of bitter taste receptors (TAS2Rs).

METHODS

Primary human GCs from 60 participants were treated with 10 µM BCA, and selective antagonists were used to block TAS2R activation. The study assessed the expression of TAS2R14 and TAS2R43, and analyzed the impact on StAR and CYP17A1 gene expression. Intracellular calcium levels, lipid droplet size, and mitochondrial network complexity were measured to evaluate cellular metabolism and energy dynamics.

RESULTS

BCA treatment significantly upregulated TAS2R14 and TAS2R43 expression, leading to a 70% increase in StAR mRNA levels and a twofold increase in CYP17A1 expression (p < 0.05). These effects were reversed by TAS2R antagonists. Additionally, BCA treatment decreased intracellular Ca2+ levels (p < 0.01) and reduced lipid droplet size (p < 0.001), both of which were counteracted by antagonists. Enhanced mitochondrial network complexity (p < 0.001) was also observed, suggesting increased mitochondrial fusion and improved cellular energy dynamics.

CONCLUSION

The findings indicate that BCA modulates transcriptional and metabolic processes in GCs through the activation of TAS2Rs, highlighting their role in endocrine regulation. The statistically significant results emphasize the relevance of further exploring the effects of EDCs like BCA on reproductive health. Collaborative research efforts are essential to address and mitigate the adverse impacts of EDCs on fertility.

Endocrine disruptor chemicals exposure and female fertility declining: from pathophysiology to epigenetic risks

Over the last decades, human infertility has become a major concern in public health, with severe societal and health consequences. Growing evidence shows that endocrine disruptors chemicals (EDCs) have been considered as risk factors of infertility. Their presence in our everyday life has become ubiquitous because of their universal use in food and beverage containers, personal care products, cosmetics, phytosanitary products. Exposure to these products has an impact on human reproductive health. Recent studies suggest that women are more exposed to EDCs than men due to higher chemical products use. The aim of this review is to understand the possible link between reproductive disorders and EDCs such as phthalates, bisphenol, dioxins, and pesticides. In women, the loss of endocrine balance leads to altered oocyte maturation, competency, anovulation and uterine disorders, endometriosis, premature ovarian insufficiency (POI) or embryonic defect and decreases the in vitro fertilization outcomes. In this review, we consider EDCs effects on the women's reproductive system, embryogenesis, with a focus on associated reproductive pathologies.

Modified Hongteng Baijiang decoction enema improves sequelae of pelvic inflammatory disease by regulating the LIF/JAK2/STAT3 pathway and gut microbiota

OBJECTIVE

The sequelae of pelvic inflammatory disease (SPID) are major causes of secondary infertility. Modified Hongteng Baijiang decoction (MHTBD) has produced positive results in the treatment of patients with chronic pelvic inflammatory disease; however, its role in SPID remains elusive. Therefore, this study clarified the role of MHTBD in SPID pathogenesis.

METHODS

The main components in MHTBD were analyzed by using liquid chromatography‒mass spectrometry (LC/MS). An SPID rat model was established, and the rats were treated with different doses of MHTBD (0.504 g of raw drug/kg, 1.008 g of raw drug/kg, and 2.016 g of raw drug/kg). Endometrial pinopodes were observed via scanning electron microscopy, endometrial thickness and inflammatory cell infiltration were assessed via HE staining, and the expression of estrogen receptor (ER), progesterone receptor (PR), integrin β3 (ITGB3), and CD31 in the endometrium was detected by using immunohistochemistry. Western blot analysis was used to detect the protein expression of LIF, JAK2, p-JAK2, STAT3, and p-STAT3 in the endometrium. Moreover, the changes in the gut microbiota were analyzed via 16S rRNA sequencing.

RESULTS

MHTBD improved endometrial receptivity, attenuated endometrial pathologic damage, reduced inflammatory cell infiltration, decreased ER and PR expression in the endometrium, and promoted the expression of LIF, p-JAK2, and p-STAT3 in the endometrium (p < .05) in SPID rats. Additionally, MHTBD treatment affected the composition of the gut microbiota in SPID rats. Furthermore, MHTBD attenuated endometrial receptivity and pathological damage in SPID rats by promoting the LIF/JAK2/STAT3 pathway.

CONCLUSION

MHTBD attenuates SPID in rats by promoting the LIF/JAK2/STAT3 pathway and improving the composition of the gut microbiota. MHTBD may be a valuable drug for SPID therapy.

Bisphenol A triggers apoptosis in mouse pre-antral follicle granulosa cells via oxidative stress

BACKGROUND

Bisphenol A (BPA), an endocrine disrupting chemical with weak estrogenic and anti-androgenic activity, is widely present in various environmental media and organisms. It has certain reproductive toxicity and can cause a variety of female reproductive system diseases. Although BPA-stimulated apoptosis of granulosa cells has been widely elaborated, the effect of BPA on mouse pre-antral follicle granulosa cells (mpGCs) has not been well elucidated.

RESULTS

In this study, the results of live-dead cell staining showed that high concentrations of BPA severely impaired mpGCs growth viability and affected the cell cycle transition of mpGCs. We confirmed that BPA promotes the production of reactive oxygen species (ROS) and facilitates oxidative stress in mpGCs. In addition, immunofluorescence, transmission electron microscopy, and flow cytometry experiments demonstrated that BPA treatment for mpGCs resulted in apoptotic features, such as rounding, cytoplasmic crinkling, and mitochondrial damage. This was accompanied by a large production of ROS and apoptosis-inducing factor (AIF) translocation from the mitochondria to the nucleus. RNA-seq data showed that several apoptosis-related pathways were enriched in the high concentration BPA-treated group compared with the normal group, such as the p53 pathway, MAPK pathway, etc. CONCLUSIONS: These results suggest that cells undergo oxidative stress effects and apoptosis after BPA treatment for mpGCs, which affects normal follicle development. The potential mechanism of BPA-induced female reproductive toxicity was elucidated, while providing a research basis for the prevention and treatment of female reproductive diseases.

Endocrine disruptors: Unravelling the link between chemical exposure and Women's reproductive health

An Endocrine Disrupting Chemical (EDC) is any compound that disrupts the function of the endocrine system in humans and is ubiquitous in the environment either as a result of natural events or through anthropogenic activities. Bisphenol A, phthalates, parabens, pesticides, triclosan, polychlorinated biphenyls, and heavy metals, which are frequently found in the pharmaceutical, cosmetic, and packaging sectors, are some of the major sources of EDC pollutants. EDCs have been identified to have a deteriorating effect on the female reproductive system, as evidenced by the increasing number of reproductive disorders such as endometriosis, uterine fibroids, polycystic ovary syndrome, premature ovarian failure, menstrual irregularity, menarche, and infertility. Studying EDCs in relation to women's health is essential for understanding the complex interactions between environmental factors and health outcomes. It enables the development of strategies to mitigate risks, protect reproductive and overall health, and inform public policy decisions to safeguard women's well-being. Healthcare professionals must know the possible dangers of EDC exposure and ask about environmental exposures while evaluating patients. This may result in more precise diagnosis and personalized treatment regimens. This review summarises the existing understanding of prevalent EDCs that impact women's health and involvement in female reproductive dysfunction and underscores the need for more research. Further insights on potential mechanisms of action of EDCs on female has been emphasized in the article. We also discuss the role of nutritional intervention in reducing the effect of EDCs on women's reproductive health. EDC pollution can be further reduced by adhering to strict regulations prohibiting the release of estrogenic substances into the environment.

Reversing Uteropathies Including Cancer-Like Changes in Mice by Transplanting Mesenchymal Stromal Cells or XAR Treatment

Pluripotent, very small embryonic-like stem cells (VSELs) and tissue-committed 'progenitors' termed endometrial stem cells (EnSCs) are reported in mouse uterus. They express gonadal and gonadotropin hormone receptors and thus are vulnerable to early-life endocrine insults. Neonatal exposure of mouse pups to endocrine disruption cause stem/progenitor cells to undergo epigenetic changes, excessive self-renewal, and blocked differentiation that results in various uteropathies including non-receptive endometrium, hyperplasia, endometriosis, adenomyosis, and cancer-like changes in adult life. Present study investigated reversal of these uteropathies, by normalizing functions of VSELs and EnSCs. Two strategies were evaluated including (i) transplanting mesenchymal stromal cells (provide paracrine support) on D60 or (ii) oral administration of XAR (epigenetic regulator) daily from days 60-100 and effects were studied later in 100 days old mice. Results show normalization of stem/progenitor cells (Oct-4, Oct-4A, Sox-2, Nanog) and Wnt signalling (Wnt-4, β-catenin, Axin-2) specific transcripts. Flow cytometry results showed reduced numbers of 2-6 µm, LIN-CD45-SCA-1 + VSELs. Hyperplasia (Ki67) of epithelial (Pax-8, Foxa-2) and myometrial (α-Sma, Tgf-β) cells was reduced, adenogenesis (differentiation of glands) was restored, endometrial receptivity and differentiation (LIF, c-KIT, SOX-9, NUMB) and stromal cells niche (CD90, VIMENTIN, Pdgfra, Vimentin) were improved, cancer stem cells markers (OCT-4, CD166) were reduced while tumor suppressor genes (PTEN, P53) and epigenetic regulators (Ezh-2, Sirt-1) were increased. To conclude, normalizing VSELs/EnSCs to manage uteropathies provides a novel basis for initiating clinical studies. The study falls under the umbrella of United Nations Sustainable Development Goal 3 to ensure healthy lives and well-being for all of all ages.

Heavy Metals in Follicular Fluid Affect the Ultrastructure of the Human Mature Cumulus-Oocyte Complex

It is known that exposure to heavy metal such as lead (Pb) and cadmium (Cd) has several adverse effects, particularly on the human reproductive system. Pb and Cd have been associated with infertility in both men and women. In pregnant women, they have been associated with spontaneous abortion, preterm birth, and impairment of the development of the fetus. Since these heavy metals come from both natural and anthropogenic activities and their harmful effects have been observed even at low levels of exposure, exposure to them remains a public health issue, especially for the reproductive system. Given this, the present study aimed to investigate the potential reproductive effects of Pb and Cd levels in the follicular fluid (FF) of infertile women and non-smokers exposed to heavy metals for professional reasons or as a result of living in rural areas near landfills and waste disposal areas in order to correlate the intrafollicular presence of these metals with possible alterations in the ultrastructure of human cumulus-oocyte complexes (COCs), which are probably responsible for infertility. Blood and FF metals were measured using atomic absorption spectrometry. COCs corresponding to each FF analyzed were subjected to ultrastructural analyses using transmission electron microscopy. We demonstrated for the first time that intrafollicular levels of Pb (0.66 µg/dL-0.85 µg/dL) and Cd (0.26 µg/L-0.41 µg/L) could be associated with morphological alterations of both the oocyte and cumulus cells' (CCs) ultrastructure. Since blood Cd levels (0.54 µg/L-1.87 µg/L) were above the current reference values established by the guidelines of the Agency for Toxic Substances and Disease Registry (ATSDR) and the Environmental Protection Agency (EPA) (0.4 µg/L), whereas blood Pb levels (1.28 µg/dL-3.98 µg/dL) were below the ATSDR reference values (≤5 µg/dL), we believe that these alterations could be due especially to Cd, even if we cannot exclude a possible additional effect of Pb. Our results highlighted that oocytes were affected in maturation and quality, whereas CCs showed scarcely active steroidogenic elements. Regressing CCs, with cytoplasmic alterations, were also numerous. According to Cd's endocrine-disrupting activity, the poor steroidogenic activity of CCs might correlate with delayed oocyte cytoplasmic maturation. So, we conclude that levels of heavy metals in the blood and the FF might negatively affect fertilization, embryo development, and pregnancy, compromising oocyte competence in fertilization both directly and indirectly, impairing CC steroidogenic activity, and inducing CC apoptosis.

Effects of polycyclic aromatic hydrocarbons (PAHs) on pregnancy, placenta, and placental trophoblasts

Polycyclic aromatic hydrocarbons (PAHs) are a group of persistent organic pollutants that are carcinogenic, mutagenic, endocrine-toxic, and immunotoxic. PAHs can be found in maternal and fetal blood and in the placenta during pregnancy. They may thus affect placental and fetal development. Therefore, the exposure levels and toxic effects of PAHs in the placenta deserve further study and discussion. This review aims to summarize current knowledge on the effects of PAHs and their metabolites on pregnancy and birth outcomes and on placental trophoblast cells. A growing number of epidemiological studies detected PAH-DNA adducts as well as the 16 high-priority PAHs in the human placenta and showed that placental PAH exposure is associated with adverse fetal outcomes. Trophoblasts are important cells in the placenta and are involved in placental development and function. In vitro studies have shown that exposure to either PAH mixtures, benzo(a)pyrene (BaP) or BaP metabolite benzo(a)pyrene-7,8-dihydrodiol-9,10-epoxide (BPDE) affected trophoblast cell viability, differentiation, migration, and invasion through various signaling pathways. Furthermore, similar effects of BPDE on trophoblast cells could also be observed in BaP-treated mouse models and were related to miscarriage. Although the current data show that PAHs may affect placental trophoblast cells and pregnancy outcomes, further studies (population studies, in vitro studies, and animal studies) are necessary to show the specific effects of different PAHs on placental trophoblasts and pregnancy outcomes.

The effects of endocrine-disrupting chemicals on ovarian- and ovulation-related fertility outcomes

Exposure to endocrine-disrupting chemicals (EDCs) is unavoidable, which represents a public health concern given the ability of EDCs to target the ovary. However, there is a large gap in the knowledge about the impact of EDCs on ovarian function, including the process of ovulation. Defects in ovulation are the leading cause of infertility in women, and EDC exposures are contributing to the prevalence of infertility. Thus, investigating the effects of EDCs on the ovary and ovulation is an emerging area for research and is the focus of this review. The effects of EDCs on gametogenesis, uterine function, embryonic development, and other aspects of fertility are not addressed to focus on ovarian- and ovulation-related fertility issues. Herein, findings from epidemiological and basic science studies are summarized for several EDCs, including phthalates, bisphenols, per- and poly-fluoroalkyl substances, flame retardants, parabens, and triclosan. Epidemiological literature suggests that exposure is associated with impaired fecundity and in vitro fertilization outcomes (decreased egg yield, pregnancies, and births), while basic science literature reports altered ovarian follicle and corpora lutea numbers, altered hormone levels, and impaired ovulatory processes. Future directions include identification of the mechanisms by which EDCs disrupt ovulation leading to infertility, especially in women.

Molecular consequences of the exposure to toxic substances for the endocrine system of females

Endocrine-disrupting chemicals (EDCs) are common in the environment and in everyday products such as cosmetics, plastic food packaging, and medicines. These substances are toxic in small doses (even in the order of micrograms) and enter the body through the skin, digestive or respiratory system. Numerous studies confirm the negative impact of EDCs on living organisms. They disrupt endocrine functions, contributing to the development of neoplastic and neurological diseases, as well as problems with the circulatory system and reproduction. EDCs affect humans and animals by modulating epigenetic processes that can lead to disturbances in gene expression or failure and even death. They also affect steroid hormones by binding to their receptors as well as interfering with synthesis and secretion of hormones. Prenatal exposure may be related to the impact of EDCs on offspring, resulting in effects of these substances on the ovaries and leading to the reduction of fertility through disturbances in the function of steroid receptors or problems with steroidogenesis and gametogenesis. Current literature indicates the need to continue research on the effects of EDCs on the female reproductive system. The aim of this review was to identify the effects of endocrine-disrupting chemicals on the female reproductive system and their genetic effects based on recent literature.

Endocrine Disruptors and Endometrial Cancer: Molecular Mechanisms of Action and Clinical Implications, a Systematic Review

It has been widely demonstrated that endocrine disruptors play a central role in various physiopathological processes of human health. In the literature, various carcinogenic processes have been associated with endocrine disruptors. A review of the molecular mechanisms underlying the interaction between endocrine disruptors and the endometrial cancer has been poorly developed. A systematic review was performed using PubMed^®/MEDLINE. A total of 25 in vivo and in vitro works were selected. Numerous endocrine disruptors were analyzed. The most relevant results showed how Bisphenol A (BPA) interacts with the carcinogenesis process on several levels. It has been demonstrated how BPA can interact with hormonal receptors and with different transcription proliferative and antiproliferative factors. Furthermore, the effect of Polycyclic aromatic hydrocarbons on Aryl hydrocarbon receptors was investigated, and the role of flame retardants in promoting proliferation and metastasis was confirmed. The results obtained demonstrate how the mechanisms of action of endocrine disruptors are manifold in the pathophysiology of endometrial cancer, acting on different levels of the cancerogenesis process.

OUP accepted manuscript

Over the past half-century, the world has witnessed a steep decline in fertility rates in virtually every country on Earth. This universal decline in fertility is being driven by increasing prosperity largely through the mediation of social factors, the most powerful of which are the education of women and an accompanying shift in life’s purpose away from procreation. In addition, it is clear that environmental and lifestyle factors are also having a profound impact on our reproductive competence particularly in the male where increasing prosperity is associated with a significant rise in the incidence of testicular cancer and a secular decline in semen quality and testosterone levels. On a different timescale, we should also recognize that the increased prosperity associated with the demographic transition greatly reduces the selection pressure on high fertility genes by lowering the rates of infant and childhood mortality. The retention of poor fertility genes within the human population is also being exacerbated by the increased uptake of ART. It is arguable that all of these elements are colluding to drive our species into an infertility trap. If we are to avoid the latter, it will be important to recognize the factors contributing to this phenomenon and adopt the social, political, environmental and lifestyle changes needed to bring this situation under control.

Systematic Review Methodologies and Endocrine Disrupting Chemicals: Improving Evaluations of the Plastic Monomer Bisphenol A

BACKGROUND

Endocrine disrupting chemicals (EDCs) are found in plastics, personal care products, household items, and other consumer goods. Risk assessments are intended to characterize a chemical's hazards, identify the doses at which adverse outcomes are observed, quantify exposure levels, and then compare these doses to determine the likelihood of risk in a given population. There are many problems with risk assessments for EDCs, allowing people to be exposed to levels that are later associated with serious health outcomes in epidemiology studies.

OBJECTIVE

In this review, we examine issues that affect the evaluation of EDCs in risk assessments (e.g., use of insensitive rodent strains and absence of disease-oriented outcomes in hazard assessments; inadequate exposure assessments). We then review one well-studied chemical, Bisphenol A (BPA; CAS #80-05-7) an EDC found in plastics, food packaging, and other consumer products. More than one hundred epidemiology studies suggest associations between BPA exposures and adverse health outcomes in environmentally exposed human populations.

FINDINGS

We present support for the use of systematic review methodologies in the evaluation of BPA and other EDCs. Systematic reviews would allow studies to be evaluated for their reliability and risk of bias. They would also allow all data to be used in risk assessments, which is a requirement for some regulatory agencies.

CONCLUSION

Systematic review methodologies can be used to improve evaluations of BPA and other EDCs. Their use could help to restore faith in risk assessments and ensure that all data are utilized in decision-making. Regulatory agencies are urged to conduct transparent, well-documented and proper systematic reviews for BPA and other EDCs.

Endocrine Disruption of the Follicle-Stimulating Hormone Receptor Signaling During the Human Antral Follicle Growth

An increasing number of pollutants with endocrine disrupting potential are accumulating in the environment, increasing the exposure risk for humans. Several of them are known or suspected to interfere with endocrine signals, impairing reproductive functions. Follicle-stimulating hormone (FSH) is a glycoprotein playing an essential role in supporting antral follicle maturation and may be a target of disrupting chemicals (EDs) likely impacting female fertility. EDs may interfere with FSH-mediated signals at different levels, since they may modulate the mRNA or protein levels of both the hormone and its receptor (FSHR), perturb the functioning of partner membrane molecules, modify intracellular signal transduction pathways and gene expression. In vitro studies and animal models provided results helpful to understand ED modes of action and suggest that they could effectively play a role as molecules interfering with the female reproductive system. However, most of these data are potentially subjected to experimental limitations and need to be confirmed by long-term observations in human.