Environmental toxicology of bisphenol A: Mechanistic insights and clinical implications on the neuroendocrine system

Bisphenol A (BPA) is a widely used environmental estrogen found in a variety of products, including food packaging, canned goods, baby bottle soothers, reusable cups, medical devices, tableware, dental sealants, and other consumer goods. This substance has been found to have detrimental effects on both the environment and human health, particularly on the reproductive, immune, embryonic development, nervous, endocrine, and respiratory systems. This paper aims to provide a comprehensive review of the effects of BPA on the neuroendocrine system, with a primary focus on its impact on the brain, neurons, oligodendrocytes, neural stem cell proliferation, DNA damage, and behavioral development. Additionally, the review explores the clinical implications of BPA, specifically examining its role in the onset and progression of various diseases associated with the neuroendocrine metabolic system. By delving into the mechanistic analysis and clinical implications, this review aims to serve as a valuable resource for studying the impacts of BPA exposure on organisms.

Association between Urinary BPA Substitutes and Precocious Puberty among Girls: A Single-Exposure and Mixed Exposure Approach from a Chinese Case-Control Study

There is an argument that BPA substitutes may have the same or more deleterious health effects as BPA due to their structural similarity. This study explored the association between urinary BPA substitutes and precocious puberty among girls by including 120 girls with precocious puberty (cases) aged 2-10 years enrolled at Nanjing Children's Hospital Department of Endocrinology in China between April 2021 to September 2021 and 145 healthy girls (controls) recruited from a primary school. Logistic regression was used to evaluate the effect of single exposures, and Bayesian kernel machine regression (BKMR) and quantile-based g-computation were used for the mixed effect. In the multivariate logistic regression, BPS (bisphenol S), TBBPA (tetrabromobisphenol A), and BPFL (bisphenol-FL) were significantly associated with increased risk of precocious puberty (odds ratio (OR) = 1.75, 95% confidence interval (CI): 1.13, 2.76, p = 0.014), (OR = 1.46, CI: 1.06, 2.05; p = 0.023), and (OR = 1.47, CI: 1.01, 2.18; p = 0.047), respectively. The BMKR and quantile-based g-computation models revealed consistent associations for single exposures and there was insufficient evidence for the associations of the mixed exposure of bisphenols with precocious puberty. In conclusion, BPA substitutes such as BPS, TBBPA, and BPFL may be associated with an increased risk of precocious puberty in girls.

Modulation of fetoplacental growth, development and reproductive function by endocrine disrupters

Maternal endocrine homeostasis is vital to a successful pregnancy, regulated by several hormones such as human chorionic gonadotropin, estrogen, leptin, glucocorticoid, insulin, prostaglandin, and others. Endocrine stress during pregnancy can modulate nutrient availability from mother to fetus, alter fetoplacental growth and reproductive functions. Endocrine disrupters such as bisphenols (BPs) and phthalates are exposed in our daily life's highest volume. Therefore, they are extensively scrutinized for their effects on metabolism, steroidogenesis, insulin signaling, and inflammation involving obesity, diabetes, and the reproductive system. BPs have their structural similarity to 17-β estradiol and their ability to bind as an agonist or antagonist to estrogen receptors to elicit an adverse response to the function of the endocrine and reproductive system. While adults can negate the adverse effects of these endocrine-disrupting chemicals (EDCs), fetuses do not equip themselves with enzymatic machinery to catabolize their conjugates. Therefore, EDC exposure makes the fetoplacental developmental window vulnerable to programming in utero. On the one hand prenatal BPs and phthalates exposure can impair the structure and function of the ovary and uterus, resulting in placental vascular defects, inappropriate placental expression of angiogenic growth factors due to altered hypothalamic response, expression of nutrient transporters, and epigenetic changes associated with maternal endocrine stress. On the other, their exposure during pregnancy can affect the offspring's metabolic, endocrine and reproductive functions by altering fetoplacental programming. This review highlights the latest development in maternal metabolic and endocrine modulations from exposure to estrogenic mimic chemicals on subcellular and transgenerational changes in placental development and its effects on fetal growth, size, and metabolic & reproductive functions.

An Overview of the Health Effects of Bisphenol A from a One Health Perspective

Bisphenol A (BPA) is a chemical compound, considered as an "emerging pollutant", that appears ubiquitously, contaminating the environment and food. It is an endocrine disruptor, found in a multitude of consumer products, as it is a constituent of polycarbonate used in the manufacture of plastics and epoxy resins. Many studies have evaluated the effects of BPA, using a wide range of doses and animal models. In this work, we carried out a review of relevant research related to the effects of BPA on health, through studies performed at different doses, in different animal models, and in human monitoring studies. Numerous effects of BPA on health have been described; in different animal species, it has been reported that it interferes with fertility in both females and males and causes alterations in their offspring, as well as being associated with an increase in hormone-dependent pathologies. Similarly, exposure to BPA has been related to other diseases of great relevance in public health such as obesity, hypertension, diabetes, or neurodevelopmental disorders. Its ubiquity and nonmonotonic behavior, triggering effects at exposure levels considered "safe", make it especially relevant when both animal and human populations are constantly and inadvertently exposed to this compound. Its effects at low exposure levels make it essential to establish safe exposure levels, and research into the effects of BPA must continue and be focused from a "One Health" perspective to take into account all the factors that could intervene in the development of a disease in any exposed organism.

Prenatal bisphenol S exposure induces hepatic lipid deposition in male mice offspring through downregulation of adipose-derived exosomal miR-29a-3p

The increased usage of bisphenol S (BPS) results in wide distribution in pregnant women. In this study, pregnant mice were given multiple-dose BPS during gestation. Results showed that prenatal BPS exposure (50 μg/kg/day) induced increased weight gain, dyslipidemia, higher liver triglyceride (TG), adipocyte hypertrophy, and hepatic lipid deposition in male offspring. Exosomes play important roles in regulating lipid metabolism. Here, serum exosomes and adipose miRNA sequencing of male offspring indicated a remarkable decrease in miR-29a-3p expression. To clarify whether adipocyte-derived exosomes mediate hepatic lipid deposition, exosomes were extracted from BPS-treated adipocytes and co-cultured with hepatocytes. These exosomes could be taken up by hepatocytes and promoted lipid deposition, and notably, exosomal miR-29a-3p was downregulated. Furthermore, miR-29a-3p knockdown in adipocyte-derived exosomes promoted hepatocyte lipid deposition, whereas overexpression led to the opposite effect. Also, the role of miR-29a-3p was demonstrated in hepatocytes by overexpressing or knocking it down. Subsequent studies have shown that miR-29a-3p can promote lipid deposition by directly targeting Col4a1. Taken together, prenatal BPS exposure could lead to lower miR-29a-3p yield in adipocyte-derived exosomes and decrease miR-29a-3p content transported to hepatocytes, which further negatively regulate Col4a1 and promote hepatic lipid deposition. Our findings provided clues to maternal environmental exposure-induced liver metabolic diseases.

Prenatal BPA exposure disrupts male reproductive functions by interfering with DNA methylation and GDNF expression in the testes of male offspring rats

BPA is a ubiquitous environmental endocrine-disrupting chemical, and maternal exposure to BPA is associated with impaired male reproductive functions; however, the mechanisms remain to be elucidated. Glial cell line-derived neurotrophic factor (GDNF) plays an important role in maintaining normal spermatogenesis and fertility. However, the effect of prenatal BPA exposure on GDNF expression and its mechanism in the testis has not been reported. In this study, pregnant Sprague-Dawley rats were respectively exposed to 0, 0.05, 0.5, 5, and 50 mg/kg/day BPA via oral gavage from gestational day (GD) 5 to GD 19, with 6 pregnant rats in each group. ELISA, histochemistry, real-time PCR, western blot, and methylation-specific PCR (MSP) were used to detect the sex hormone levels, testicular histopathology, mRNA and protein expression of DNA methyltransferases (DNMTs) and GDNF, and the promoter methylation of Gdnf in the testes of male offspring at postnatal day (PND) 21 and PND 56. Prenatal BPA exposure increased body weight; decreased sperm counts and serum levels of testosterone (T), follicle-stimulating hormone (FSH), and luteinizing hormone (LH); and induced testicular histological damage, which indicated the damage of male reproductive function. Prenatal BPA exposure also upregulated Dnmt1 in 5 mg/kg group and Dnmt3b in 0.5 mg/kg group, but down-regulated Dnmt1 in 50 mg/kg group at PND 21. At PND 56, Dnmt1 was significantly increased in 0.05 mg/kg group but decreased in 0.5, 5, and 50 mg/kg groups, Dnmt3a was decreased, and Dnmt3b was markedly increased in 0.05 and 0.5 mg/kg groups but decreased in 5 and 50 mg/kg groups. The mRNA and protein expression levels of Gdnf were decreased markedly in 0.5 and 50 mg/kg groups at PND 21. And the methylation level of Gdnf promoter was significantly increased in 0.5 mg/kg group, but decreased in 5 and 50 mg/kg groups at PND 21. In conclusion, our study indicates that prenatal BPA exposure disrupts male reproductive functions, interferes with the expression of DNMTs, and decreases Gdnf expression in the testes of male offspring. Gdnf expression may be regulated by DNA methylation; however, the detailed mechanism needs to be further investigated.

Chromatin modifiers: A new class of pollutants with potential epigenetic effects revealed by in vitro assays and transcriptomic analyses

A great variety of endocrine-disrupting chemicals (EDCs) have been used extensively and become widespread in the environment nowadays. Limited mammalian studies have shown that certain EDCs may target chromosome and epigenome of the germline, leading to adverse effects in subsequent generations, despite these progenies having never been exposed to the EDC before. However, the underlying mechanisms of chromosomal changes induced by these pollutants remain poorly known. Using the human ovarian granulosa tumor cell line COV434 as a model, we investigated and compared the transcriptomic changes induced by nine EDCs with diverse chemical structures (i.e. BDE-47, BPA, BP-3, DEHP, DHP, EE2, TCS, TDCPP and NP), to inquire if there is any common epigenetic modification associated with reproductive functions induced by these EDCs. Our results showed that COV434 cells were more responsive to BP-3, NP, DEHP and EE2, and more importantly, these four EDCs altered the expression of gene clusters related to DNA damage response, cell cycle, proliferation, and chromatin remodeling, which can potentially lead to epigenetic modifications and transgenerational inheritance. Furthermore, dysregulation of similar gene clusters was common in DEHP and NP treatments. Bioinformatics analysis further revealed that BP-3 disturbed signaling pathways associated with reproductive functions, whereas alterations in telomere-related pathways were highlighted upon EE2 exposure. Overall, this study highlighted chromatin modifications caused by a class of chemicals which that may potentially lead to epigenetic changes and transgenerational reproductive impairments.

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.

Prenatal exposure to a low dose of BPS causes sex-dependent alterations to vascular endothelial function in adult offspring

Background: Bisphenol S (BPS) is among the most commonly used substitutes for Bisphenol A (BPA), an endocrine disrupting chemical used as a plasticizer in the manufacture of polycarbonate plastics and epoxy resins. Bisphenols interfere with estrogen receptor (ER) signaling, which modulates vascular function through stimulation of nitric oxide (NO) production via endothelial nitric oxide synthase (eNOS). BPS can cross into the placenta and accumulates in the fetal compartment to a greater extent than BPA, potentially interfering with key developmental events. Little is known regarding the developmental impact of exposure to BPA substitutes, particularly with respect to the vasculature.

Objective: To determine if prenatal BPS exposure influences vascular health in adulthood.

Methods: At the time of mating, female C57BL/6 dams were administered BPS (250 nM) or vehicle control in the drinking water, and exposure continued during lactation. At 12-week of age, mesenteric arteries were excised from male and female offspring and assessed for responses to an endothelium-dependent (acetylcholine, ACh) and endothelium-independent (sodium nitroprusside, SNP) vasodilator. Endothelium-dependent dilation was measured in the presence or absence of L-NAME, an eNOS inhibitor. To further explore the role of NO and ER signaling, wire myography was used to assess ACh responses in aortic rings after acute exposure to BPS in the presence or absence of L-NAME or an ER antagonist.

Results: Increased ACh dilation and increased sensitivity to Phe were observed in microvessels from BPS-exposed females, while no changes were observed in male offspring. Differences in ACh-induced dilation between control or BPS-exposed females were eliminated with L-NAME. Increased dilatory responses to ACh after acute BPS exposure were observed in aortic rings from female mice only, and differences were eliminated with inhibition of eNOS or inhibition of ER.

Conclusion: Prenatal BPS exposure leads to persistent changes in endothelium-dependent vascular function in a sex-specific manner that appears to be modulated by interaction of BPS with ER signaling.

Exposure to either Bisphenol A or S Represents a Risk for Crucial Behaviors for Pup Survival, Such as Spontaneous Maternal Behavior in Mice

INTRODUCTION

Maternal behavior depends on a multitude of factors, including environmental ones, such as Endocrine Disrupting Chemicals (EDCs), which are increasingly attracting attention. Bisphenol A (BPA), an EDC present in plastic, is known to exert negative effects on maternal behavior. Bisphenol S (BPS), a BPA substitute, seems to share some endocrine disrupting properties. In this study, we focused on the analysis of the effects of low-dose (i.e., 4 µg/kg body weight/day, EFSA TDI for BPA) BPA or BPS exposure throughout pregnancy and lactation in mice.

METHODS

We administered adult C57BL/6 J females orally BPA, BPS, or vehicle from mating to offspring weaning. We assessed the number of pups at birth, the sex ratio, and the percentage of dead pups in each litter, and during the first postnatal week, we observed spontaneous maternal behavior. At the weaning of the pups, we sacrificed the dams and analyzed the oxytocin system, known to be involved in the control of maternal care, in the hypothalamic magnocellular nuclei.

RESULTS

At birth, pups from BPA-treated dams tended to have a lower male-to-female ratio compared to controls, while the opposite was observed among BPS-treated dams' litters. During the first postnatal week, offspring mortality impacted differentially in the BPA and BPS litters, with more female dead pups among the BPA litters, while more male dead pups in the BPS litters, sharpening the difference in the sex ratio. BPA- and BPS-treated dams spent significantly less time in pup-related behaviors than controls. Oxytocin immunoreactivity in the paraventricular and supraoptic nuclei was increased only in the BPA-treated dams.

DISCUSSION/CONCLUSIONS

Alterations in maternal care, along with the treatment itself, may affect, later in life, the offspring's physiology and behavior. Exposure to BPs during sensitive developmental periods represents a risk for both dams and offspring, even at low environmentally relevant doses, through the functional alteration of neural circuits controlling fundamental behaviors for pup survival, such as maternal behaviors.

Effects of BPA substitutes on the prenatal and cardiovascular systems

Bisphenol A (BPA) is a ubiquitous chemical compound constantly being released into the environment, making it one of the most persistent endocrine-disrupting chemical (EDC) in nature. This EDC has already been associated with developing various pathologies, such as diabetes, obesity, and cardiovascular, renal, and behavioral complications, among others. Therefore, over the years, BPA has been replaced, gradually, by its analog compounds. However, these compounds are structurally similar to BPA, so, in recent years, questions have been raised concerning their safety for human health. Numerous investigations have been performed to determine the effects BPA substitutes may cause, particularly during pregnancy and prenatal life. On the other hand, studies investigating the association of these compounds with the development of cardiovascular diseases (CVD) have been developed. In this sense, this review summarizes the existing literature on the transgenerational transfer of BPA substitutes and the consequent effects on maternal and offspring health following prenatal exposure. In addition, these compounds' effects on the cardiovascular system and the susceptibility to develop CVD will be presented. Therefore, this review aims to highlight the need to investigate further the safety and benefits, or hazards, associated with replacing BPA with its analogs.

Transgenerational effects of parental bisphenol S exposure on zebrafish (Danio rerio) reproduction

Bisphenol S (BPS) is extensively used for production of polycarbonates and other commodities, and is often detected in environment and biota. Parental BPS exposure has been reported to interfere with reproductive development of offspring, but limited information is available on its multigenerational reproductive toxicity. In our present study, zebrafish (Danio rerio) were exposed to BPS (1 and 100 μg/L) from 3 hpf to 120 dpf, and the effects on reproduction, sex steroid hormones, DNA methylation levels and gene transcription involved in steroidogenesis and DNA methylation were investigated in unexposed F1-2 offspring. The results showed that 100 μg/L BPS exposure increased DNA methylation in F1 testes, and 1 μg/L BPS led to DNA methylation in F2 ovaries. The increased DNA methylation levels led to decreased expression of steroidogenic enzymes, including cyp11a, cyp17 and 3βhsd, which might be a main reason for the elevated plasma 17β-estradiol and decreased testosterone levels. In addition, sex ratio indicated a female dominance trend, and reproductive capacity of male fish was severely impaired. Overall, these findings suggest that parental BPS exposure impairs reproductive development of unexposed offspring via DNA methylation and BPS-induced epigenetic modification inheritance has a long-term effect on the fitness and sustainability of fish populations.

Early programming of reproductive health and fertility: novel neuroendocrine mechanisms and implications in reproductive medicine

BACKGROUND

According to the Developmental Origins of Health and Disease (DOHaD) hypothesis, environmental changes taking place during early maturational periods may alter normal development and predispose to the occurrence of diverse pathologies later in life. Indeed, adverse conditions during these critical developmental windows of high plasticity have been reported to alter the offspring developmental trajectory, causing permanent functional and structural perturbations that in the long term may enhance disease susceptibility. However, while solid evidence has documented that fluctuations in environmental factors, ranging from nutrient availability to chemicals, in early developmental stages (including the peri-conceptional period) have discernible programming effects that increase vulnerability to develop metabolic perturbations, the impact and eventual mechanisms involved, of such developmental alterations on the reproductive phenotype of offspring have received less attention.

OBJECTIVE AND RATIONALE

This review will summarize recent advances in basic and clinical research that support the concept of DOHaD in the context of the impact of nutritional and hormonal perturbations, occurring during the periconceptional, fetal and early postnatal stages, on different aspects of reproductive function in both sexes. Special emphasis will be given to the effects of early nutritional stress on the timing of puberty and adult gonadotropic function, and to address the underlying neuroendocrine pathways, with particular attention to involvement of the Kiss1 system in these reproductive perturbations. The implications of such phenomena in terms of reproductive medicine will also be considered.

SEARCH METHODS

A comprehensive MEDLINE search, using PubMed as main interface, of research articles and reviews, published mainly between 2006 and 2021, has been carried out. Search was implemented using multiple terms, focusing on clinical and preclinical data from DOHaD studies, addressing periconceptional, gestational and perinatal programming of reproduction. Selected studies addressing early programming of metabolic function have also been considered, when relevant.

OUTCOMES

A solid body of evidence, from clinical and preclinical studies, has documented the impact of nutritional and hormonal fluctuations during the periconceptional, prenatal and early postnatal periods on pubertal maturation, as well as adult gonadotropic function and fertility. Furthermore, exposure to environmental chemicals, such as bisphenol A, and maternal stress has been shown to negatively influence pubertal development and gonadotropic function in adulthood. The underlying neuroendocrine pathways and mechanisms involved have been also addressed, mainly by preclinical studies, which have identified an, as yet incomplete, array of molecular and neurohormonal effectors. These include, prominently, epigenetic regulatory mechanisms and the hypothalamic Kiss1 system, which likely contribute to the generation of reproductive alterations in conditions of early nutritional and/or metabolic stress. In addition to the Kiss1 system, other major hypothalamic regulators of GnRH neurosecretion, such as γ-aminobutyric acid and glutamate, may be targets of developmental programming.

WIDER IMPLICATIONS

This review addresses an underdeveloped area of reproductive biology and medicine that may help to improve our understanding of human reproductive disorders and stresses the importance, and eventual pathogenic impact, of early determinants of puberty, adult reproductive function and fertility.

Regulatory and academic studies to derive reference values for human health: The case of bisphenol S

The close structural analogy of bisphenol (BP) S with BPA, a recognized endocrine-disrupting chemical and a substance of very high concern in the European Union, highlights the need to assess the extent of similarities between the two compounds and carefully scrutinize BPS potential toxicity for human health. This analysis aimed to investigate human health toxicity data regarding BPS, to find a point of departure for the derivation of human guidance values. A systematic and transparent methodology was applied to determine whether European or international reference values have been established for BPS. In the absence of such values, the scientific literature on human health effects was evaluated by focusing on human epidemiological and animal experimental studies. The results were analyzed by target organ/system: male and female reproduction, mammary gland, neurobehavior, and metabolism/obesity. Academic experimental studies were analyzed and compared to regulatory data including subchronic studies and an extended one-generation and reproduction study. In contrast to the regulatory studies, which were performed at dose levels in the mg/kg bw/day range, the academic dataset on specific target organs or systems showed adverse effects for BPS at much lower doses (0.5-10 μg/kg bw/day). A large disparity between the lowest-observed-adverse-effect levels (LOAELs) derived from regulatory and academic studies was observed for BPS, as for BPA. Toxicokinetic data on BPS from animal and human studies were also analyzed and showed a 100-fold higher oral bioavailability compared to BPA in a pig model. The similarities and differences between the two bisphenols, in particular the higher bioavailability of BPS in its active (non-conjugated) form and its potential impact on human health, are discussed. Based on the available experimental data, and for a better human protection, we propose to derive human reference values for exposure to BPS from the N(L)OAELs determined in academic studies.

Associations between urinary bisphenol A and its analogues and semen quality: A cross-sectional study among Chinese men from an infertility clinic

Human studies on association between bisphenol A (BPA) exposure and semen quality, mostly based on single urinary measurement, are inconsistent. There is limited human evidence on BPA analogues such as bisphenol F (BPF) and bisphenol S (BPS), and little is known on potential effects of bisphenol mixtures. We aimed to explore whether individual or mixtures of BPA, BPS and BPF assessed in repeated urinary measurements were associated with semen quality among 984 Chinese men from an infertility clinic. We found that higher BPA exposure was associated with increased odds ratios (ORs) of having below-reference sperm concentration, total sperm count, progressive motility and total motility (all P for trends < 0.05). Higher BPS exposure was associated with increased ORs of having below-reference progressive motility and total motility (both P for trends = 0.02); the ORs comparing extreme quartiles were 1.62 (95% CI: 1.07, 2.43) and 1.57 (95% CI: 1.06, 2.33), respectively. Elevated risks for each outcome were also observed when bisphenol mixtures were at ≥ 55th percentiles. For semen quality parameters modeled as continuous outcomes, inverse associations with individual BPA and BPS and bisphenol mixtures were still estimated. Our results suggested that higher exposure to individual BPA and BPS and bisphenol mixtures were associated with impaired semen quality.

Combinational exposure to Bisphenol A and a high-fat diet causes trans-generational Malfunction of the female reproductive system in mice

Bisphenol A (BPA) is a common endocrine disruptor and a high-fat diet (HFD) also affects fertility. However, little is known about the long-term consequences of simultaneous exposure to BPA and a HFD on reproductive health. Herein, we assessed the effects of maternal exposure to BPA in combination with a HFD on reproductive function in subsequent generations of female mice and evaluated its effects on the hypothalamic-pituitary-gonadal axis. We found that the combination of maternal exposure to BPA and a HFD led to increased urine BPA levels, precocious puberty, altered estrous cyclicity, decreased follicle numbers, and altered hypothalamic Kiss1 methylation status in F1 and F2 mice. Therefore, we demonstrated that maternal exposure to BPA in combination with a HFD exerts a trans-generational effect on female reproduction.

Immunohistochemical expression of aromatase cyp19a1a and cyp19a1b in the ovary and brain of zebrafish (Danio rerio) exposed to different concentrations of bisphenol A

Bisphenol A (BPA) is used to produce plastic and plastic derived products in multitude of daily utensils, being one of the industrial compounds most widely used. This endocrine disrupting chemical (EDCs) is a well-known environmental pollutant released into the aquatic environment from industrial wastewater, sewage sludge or landfill leachate. Aromatases are considered potential targets of EDCs with characteristics that make them suitable biomarkers of exposure to their effects. The main objective of our study was to evaluate the expression of cyp19a aromatase as a toxicological endpoint after BPA exposure through the identification and assessment of alterations of the main cells responsible for cyp19a1a and cyp19a1b expression in the zebrafish ovary and brain using different concentrations of BPA in water. Immunohistochemistry was used to analyze the expression of these enzymes in female zebrafish exposed and not exposed to different concentrations of BPA (1, 10, 100 and 1000 μg / L) in water (n = 6/group) for 14 days. The results obtained in this study showed that the cyp19a aromatase system, involved in the synthesis of steroid compounds, is specially located in distinct oocyte stages in the ovary (cyp19a1a) and in radial glial cells of the brain (cyp19a1b). An overexpression of these aromatases was observed after BPA exposure in zebrafish, peaking from a concentration of 10 µg/L and showing to be good biomarkers of exposure to identify the early effects of low BPA concentrations. To our knowledge, this study is the first to localize and quantify the expression of cyp19a1a and cyp19a1b in the cells of brain and ovary after fish exposure to different BPA concentrations in water.

BPA's transgenerational disturbance to transcription of ovarian steroidogenic genes in rare minnow Gobiocypris rarus via DNA and histone methylation

As a well-known estrogenic endocrine disruptor, bisphenol A (BPA) is of utmost concern since it is reported with harmful effects on animal reproduction. However, the adverse effects on progeny after parental BPA exposure are largely unknown in fishes. To investigate the epigenetic effects of BPA on progeny gonadal development, parental rare minnow (Gobiocypris rarus) were exposed to BPA (15 μg L^-1) for two months, then were purged in clean water for one, two or three months, respectively. From the second month, parents were mated once a month and the offspring were reared to 5 months old. Results showed that parental BPA exposure inhibited the ovary development of the offspring by reducing the number of mature oocytes while the transcripts of steroidogenic genes (cyp11a1, cyp17a1, cyp19a1a and star) were significantly affected. And the negative effects of parental BPA exposure on the offspring were reversible. The DNA methylation and histone trimethylation levels (H3K9me3 and H3K27me3) together with the expression of dnmts (dnmt1, dnmt5 and dnmt7) and histone methyltransferase genes (setdb1, setdb2 and ezh2) were significantly altered in the ovaries of the 5-month old offsprings. BPA interfered the expression of steroidogenic genes by altering histone recruitment in star (H3K4me3 and H3K9me3), in cyp11a1 and cyp17a1 (H3K9me3 and H3K27me3), as well as in cyp19a1a (H3K4me3, H3K9me3 and H3K27me3). In addition, altering of DNA methylation at CpG site caused by BPA exposure involved in the regulation of star, cyp17a1 and cyp19a1a expression. These results suggest that BPA transgenerationally imposes detriment to reproduction and the epigenetic changes in DNA methylation and histone trimethylation might account for steroidogenic genes expression.

The effects of plasticizers on the ovary

Endocrine disrupting chemicals pose a threat to health and reproduction. Plasticizers such as phthalates and bisphenols are particularly problematic because they are present in many consumer products and exposure can begin in utero and continue throughout the lifetime of the individual. Evidence suggests that these chemicals can have ancestral and transgenerational effects, making them a huge public health concern for the reproductive health of current and future generations. Studies performed in rodents or using rodent- or human-derived tissues have been critical for understanding the toxic effects of plasticizers on the ovary and their mechanisms of action. This review addresses current in vitro and rodent-based in vivo studies investigating the effects of bisphenols and phthalates on ovarian health, female reproduction, and correlations between human exposure and reproductive pathologies.

Independent and combined effects of Bisphenol A and Diethylhexyl Phthalate on gestational outcomes and offspring development in Sprague-Dawley rats

Bisphenol A (BPA) and Diethylhexyl Phthalate (DEHP) are well-studied endocrine disrupting chemicals (EDCs), however, the effects of mixtures of these EDCs are not. To assess the consequences of prenatal exposure to a mixture of these EDCs, dams were orally administered either saline (control), BPA (5 μg/kg BW/day), high dose DEHP (HD-D; 7.5 mg/kg BW/day), or a combination of BPA with HD-D in experiment 1; saline, BPA (5 μg/kg BW/day), low-dose DEHP (LD-D; 5 μg/kg BW/day) or a combination of BPA with LD-D in experiment 2. Gestational weights, number of abortions, litter size and weights, number of live births and stillbirths were recorded. Morphometric measures were obtained at birth and body weight, food and water intake were monitored weekly from postnatal weeks 3-12. Offspring were sacrificed at 16-24 weeks of age and organ weights were measured. The abortion rate of dams exposed to HD-D and the mixtures, BPA + LD-D and BPA + HD-D were higher at 9, 14 and 27% respectively. Prenatal exposure to BPA or HD-D significantly decreased relative thymus weights in male but not female offspring. Apoptotic cells were detected in thymus sections of both male and female offspring prenatally exposed to DEHP. Relative heart weights increased in BPA + HD-D exposed male offspring compared to the other groups. The results indicate that a mixture of BPA and DEHP, produced a pronounced effect on pregnancy outcomes. Male offspring appear to be more susceptible to the programming effects of these EDCs or their mixture suggesting a need to reconsider the possible additive, antagonistic or synergistic effects of EDC mixtures.

Endocrine disrupting chemicals and reproductive disorders in women, men, and animal models

This chapter covers the known effects of endocrine disrupting chemicals (EDCs) on reproductive disorders. The EDCs represented are highly studied, including plasticizers (bisphenols and phthalates), chemicals in personal care products (parabens), persistent environmental contaminants (polychlorinated biphenyls), and chemicals in pesticides or herbicides. Both female and male reproductive disorders are reviewed in the chapter. Female disorders include infertility/subfertility, irregular reproductive cycles, early menopause, premature ovarian insufficiency, polycystic ovarian syndrome, endometriosis, and uterine fibroids. Male disorders include infertility/subfertility, cryptorchidism, and hypospadias. Findings from both human and animal studies are represented.

Maternal Bisphenol S exposure affects the reproductive capacity of F1 and F2 offspring in mice

Bisphenol S (BPS) is an endocrine disruptor which is widely used in commercial plastic products. Previous studies have shown that exposure to BPS has toxic effects on various aspects of mammalian, but there are few reports about reproductive toxicity. In order to investigate the effects of maternal BPS exposure on the reproductive of F1 and F2 female mice, the pregnant mice were orally administered with different dosages of BPS only once every day from 12.5 to 15.5 days post-coitus (dpc). The results showed that maternal BPS exposure to 2 μg per kg of body weight per day (2 μg/kg) and 10 μg/kg accelerated the meiotic prophase I (MPI) of F1 female mice and the expression of the genes related to meiotic were increased. Further studies showed that maternal BPS exposure resulted in a significant increase in the percentage of oocytes enclosed in primordial follicles in the 3 days post-partum (3 dpp) ovaries of F1 female mice. And at the time of 21 days post-partum (21 dpp) in F1 female mice, the number of antral follicles were significantly lower compare to controls. In the study of five-week female mice of F1, we found that BPS disturbed the folliculogenesis, and the maturation rates and fertilization rates of oocytes were significantly decreased. Of note, maternal BPS exposure disrupted H3K4 and H3K9 tri-methylation levels in F1 ovaries. Maternal BPS exposure only affected the cyst breakdown in F2 female mice. Taken together, our results suggest that, maternal BPS exposure impaired the process of meiosis and oogenesis of F1 and F2 offspring, resulting in abnormal follicular development and serious damage to the reproduction.

A comprehensive review of the neurobehavioral effects of bisphenol S and the mechanisms of action: New insights from in vitro and in vivo models

The normal brain development and function are delicately driven by an ever-changing milieu of steroid hormones arising from fetal, placental, and maternal origins. This reliance on the neuroendocrine system sets the stage for the exquisite sensitivity of the central nervous system to the adverse effects of endocrine-disrupting chemicals (EDCs). Bisphenol A (BPA) is one of the most common EDCs which has been a particular focus of environmental concern for decades due to its widespread nature and formidable threat to human and animal health. The heightened regulatory actions and the scientific and public concern over the adverse health effects of BPA have led to its replacement with a suite of structurally similar but less known alternative chemicals. Bisphenol S (BPS) is the main substitute for BPA that is increasingly being used in a wide array of consumer and industrial products. Although it was considered to be a safe BPA alternative, mounting evidence points to the deleterious effects of BPS on a wide range of neuroendocrine functions in animals. In addition to its reproductive toxicity, recent experimental efforts indicate that BPS has a considerable potential to induce neurotoxicity and behavioral dysfunction. This review analyzes the current state of knowledge regarding the neurobehavioral effects of BPS and discusses its potential mode of actions on several aspects of the neuroendocrine system. We summarize the role of certain hormones and their signaling pathways in the regulation of brain and behavior and discuss how BPS induces neurotoxicity through interactions with these pathways. Finally, we review potential links between BPS exposure and aberrant neurobehavioral functions in animals and identify key knowledge gaps and hypotheses for future research.

Maternal and paternal preconception exposure to phenols and preterm birth

BACKGROUND

Phenol exposure during pregnancy has been associated with preterm birth, but the potential effect of preconception exposure in either parent is unknown. There is a growing body of evidence to suggest that the preconception period is a critical window of vulnerability for adverse pregnancy outcomes.

OBJECTIVE

We examined whether maternal and paternal preconception urinary concentrations of select phenols were associated with the risk of preterm birth among couples attending fertility care.

METHODS

The analysis included 417 female and 229 male participants of the Environment and Reproductive Health (EARTH) Study who gave birth to 418 singleton infants between 2005 and 2018 and for whom we had phenol biomarkers quantified in at least one urine sample collected before conception. Mothers and fathers provided an average of 4 and 3 urine samples during the preconception period, respectively. We calculated the geometric mean of bisphenol A (BPA), bisphenol S (BPS), benzophenone-3, triclosan, and the molar sum of parabens (ΣParabens) urinary concentrations to estimate each participant's preconception exposure. Risk ratios (RRs) of preterm birth (live birth before 37 completed weeks' gestation) were estimated using modified Poisson regression models adjusted for covariates.

RESULTS

The mean (SD) gestational age among singletons was 39.3 (1.7) weeks with 8% born preterm. A natural log-unit increase in maternal preconception BPA (RR 1.94; 95% CI: 1.20, 3.14) and BPS (RR 2.42; 95% CI: 1.01, 5.77) concentration was associated with an increased risk of preterm birth. These associations remained after further adjustment for maternal prenatal and paternal preconception biomarker concentrations. Paternal preconception ΣParabens concentrations showed a possible elevated risk of preterm birth (RR 1.36; 95% CI: 0.94, 1.96). No consistent pattern of association was observed for benzophenone-3 or triclosan biomarkers in either parent.

DISCUSSION

Maternal preconception urinary BPA and BPS concentrations, as well as paternal preconception urinary parabens concentrations were prospectively associated with a higher risk of preterm birth. Subfertile couples' exposure to select phenols during the preconception period may be an unrecognized risk factor for adverse pregnancy outcomes.

Occurrence and Maternal Transfer of Multiple Bisphenols, Including an Emerging Derivative with Unexpectedly High Concentrations, in the Human Maternal-Fetal-Placental Unit

In this study, a set of 15 bisphenols (BPs) and one emerging derivative (4-hydroxyphenyl 4-isoprooxyphenylsulfone, BPSIP) were analyzed in 60 pairs of maternal plasma, cord plasma, and placenta samples from pregnant women in South China. A total of 4 of the 15 target BPs, i.e., BPA, bisphenol S (BPS), bisphenol AF (BPAF), and bisphenol E (BPE), were frequently detected in the three human biological matrixes. The derivative BPSIP was identified in all maternal plasma samples at unexpectedly high levels, second only to BPA. The concentrations of bisphenols in maternal plasma were slightly higher than in cord plasma for BPA, BPS, and BPE but much higher for BPSIP and much lower for BPAF, indicating that the five frequently detected bisphenols have different placental transfer behaviors. The placental transfer efficiencies (PTEs) of BPA, BPS, and BPE were similar, which were significantly higher than the PTE of BPSIP. The PTE of BPAF was much higher than other BPs, indicating its strong maternal transfer and high fetal accumulation. The PTEs of bisphenols were structure-dependent, and passive diffusion was suggested as the potential mechanism of placental transfer. Significant concentration correlations of the five major bisphenols between maternal plasma and cord plasma were observed (p < 0.05). Meanwhile, significant associations of BPAF concentrations in maternal/cord plasma with some maternal characteristics and adverse birth outcomes were also identified (p < 0.05).

The dark side of the breastfeeding: In the light of endocrine disruptors

Breastfeeding plays an essential role in the healthy development of a newborn, but human milk is obviously compromised by pollutants from our environment. The main contaminants of human milk with endocrine-disrupting compound (EDCs) have raised concern for public and environmental health. Bisphenol A (BPA), which can leach from plastics, are among the most well-studied. Since EDs are known to cross the mammary gland barrier and BPA may accumulate in the neonate, “BPA-free” products have been introduced to the market. However, recent studies have shown that alternative bisphenols (e.g. BPS, BPF) can be detected in breast milk, have ED activities and may have developmental effects similar to BPA.