Exposure of preimplantation embryos to low-dose bisphenol A impairs testes development and suppresses histone acetylation of StAR promoter to reduce production of testosterone in mice

Environmental toxins and reproductive health: unraveling the effects on Sertoli cells and the blood-testis barrier in animals†

Environmental pollution is an inevitable ecological issue accompanying the process of socialization, with increasing attention to its impacts on individual organisms and ecological chains. The reproductive system, responsible for transmitting genetic material in animals, is one of the most sensitive systems to environmental toxins. Research reveals that Sertoli cells are the primary target cells for the action of environmental toxins. Different environmental toxins mostly affect the blood-testis barrier and lead to male reproductive disorders by disrupting Sertoli cells. Therefore, this article provides an in-depth exploration of the toxic mechanisms of various types of environmental toxins on the male testes. It reveals the dynamic processes of tight junctions in the blood-testis barrier affected by environmental toxins and their specific roles in the reconstruction process.

Mechanistic Insights into Bisphenol A-Mediated Male Infertility: Potential Role of Panax Ginseng Extract

Male infertility is identified by the inability of a man to successfully impregnate his fertile female partner, even following a year of regular unprotected sexual intercourse. About half of all infertility cases are attributed to what is known as "male factor" infertility. The escalating prevalence of male infertility in the contemporary era across the globe can be largely attributed to environmental pollution, which is the common etiological factor due to the ubiquitous presence of the environmental contaminants. Bisphenol A is recognized as an endocrine-disrupting chemical that has adverse effects on both male and female reproductive systems. On the other hand, numerous studies have demonstrated that Panax ginseng possessed the potential to improve male infertility parameters; promote spermatogenesis, recover the quality and motility of sperm and enhance testicular functions as it acted as a natural androgen supplement. The objective of this review is to offer a summary of the findings obtained from the current research data on the insult of bisphenol A (BPA) on male infertility and its supposed mode of action, as well as shed light on the potent ameliorative role of Panax ginseng extract, with a special focus on the mechanism behind its action. This review delivers a clear understanding of BPA mechanism of action on male infertility and the presumed risks deriving from its exposure. Also, this review provides evidence for the functional role of Panax ginseng extract in restoring male fertility.

Prenatal dexamethasone exposure impairs rat blood-testis barrier function and sperm quality in adult offspring via GR/KDM1B/FSTL3/TGFβ signaling

Both epidemiological and animal studies suggest that adverse environment during pregnancy can change the offspring development programming, but it is difficult to achieve prenatal early warning. In this study we investigated the impact of prenatal dexamethasone exposure (PDE) on sperm quality and function of blood-testis barrier (BTB) in adult offspring and the underlying mechanisms. Pregnant rats were injected with dexamethasone (0.1, 0.2 and 0.4 mg·kg-1·d-1, s.c.) from GD9 to GD20. After weaning (PW4), the pups were fed with lab chow. At PW12 and PW28, the male offspring were euthanized to collect blood and testes samples. We showed that PDE significantly decreased sperm quality (including quantity and motility) in male offspring, which was associated with impaired BTB and decreased CX43/E-cadherin expression in the testis. We demonstrated that PDE induced morphological abnormalities of fetal testicle and Sertoli cell development originated from intrauterine. By tracing to fetal testicular Sertoli cells, we found that PDE dose-dependently increased expression of histone lysine demethylases (KDM1B), decreasing histone 3 lysine 9 dimethylation (H3K9me2) levels of follistatin-like-3 (FSTL3) promoter region and increased FSTL3 expression, and inhibited TGFβ signaling and CX43/E-cadherin expression in offspring before and after birth. These results were validated in TM4 Sertoli cells following dexamethasone treatment. Meanwhile, the H3K9me2 levels of FSTL3 promoter in maternal peripheral blood mononuclear cell (PBMC) and placenta were decreased and its expression increased, which was positively correlated with the changes in offspring testis. Based on analysis of human samples, we found that the H3K9me2 levels of FSTL3 promoter in maternal blood PBMC and placenta were positively correlated with fetal blood testosterone levels after prenatal dexamethasone exposure. We conclude that PDE can reduce sperm quality in adult offspring rats, which is related to the damage of testis BTB via epigenetic modification and change of FSTL3 expression in Sertoli cells. The H3K9me2 levels of the FSTL3 promoter and its expression in the maternal blood PBMC can be used as a prenatal warning marker for fetal testicular dysplasia.

Syringin alleviates bisphenol A-induced spermatogenic defects and testicular injury by suppressing oxidative stress and inflammation in male zebrafish

Syringin (SRG) is a bioactive principle possessing extensive activities including scavenging of free radicals, inhibition of apoptosis, and anti-inflammatory properties. However, its effects on spermatogenic defects and testicular injury as well as the underlying mechanisms are still unclear. This study aims to investigate the protective effect of SRG on testis damage in zebrafish and explore its potential molecular events. Zebrafish testicular injury was induced by exposure to bisphenol A (BPA) (3000 μg/L) for two weeks. Fish were treated with intraperitoneal injection of SRG at different doses (5 and 50 mg/kg bodyweight) for two more weeks under BPA induction. Subsequently, the testis and sperm were collected for morphological, histological, biochemical and gene expression examination. It was found that the administration of SRG resulted in a significant protection from BPA-caused impact on sperm concentration, morphology, motility, fertility rate, testosterone level, spermatogenic dysfunction and resulted in increased apoptotic and reactive oxygen species' levels. Furthermore, testicular transcriptional profiling alterations revealed that the regulation of inflammatory response and oxidative stress were generally enriched in differentially expressed genes (DEGs) after SRG treatment. Additionally, it was identified that SRG prevented BPA-induced zebrafish testis injury through upregulation of fn1a, krt17, fabp10a, serpina1l and ctss2. These results indicate that SRG alleviated spermatogenic defects and testicular injury by suppressing oxidative stress and inflammation in male zebrafish.

Bisphenol A Exposure Interferes with Reproductive Hormones and Decreases Sperm Counts: A Systematic Review and Meta-Analysis of Epidemiological Studies

Bisphenol A (BPA), an acknowledged endocrine disrupter, is easily exposed to humans via food packaging and container. However, a consensus has not been reached on the extent to which BPA exposure affects the reproductive system. We therefore conducted this systematic review and meta-analysis to elucidate the relationship between BPA exposure and male reproduction-related indicators. Up to October 2023, a comprehensive search was carried out in the PubMed, Embase, Cochrane and Web of Science, and 18 studies were ultimately included. β coefficients from multivariate linear regression analyses were pooled using a random effects model. The results showed that the urinary BPA concentration was negatively correlated with the sperm concentration (β coefficient = -0.03; 95% CI: -0.06 to -0.01; I2 = 0.0%, p = 0.003) and total sperm count (β coefficient = -0.05; 95% CI: -0.08 to -0.02; I2 = 0.0%, p < 0.001). In addition, BPA concentrations were associated with increased sex hormone-binding globulin (SHBG) levels, increased estradiol (E2) levels, and reduced biologically active androgen levels. However, the relationship between an increased risk of below-reference sperm quality and BPA exposure was not robust. This systematic review revealed that BPA exposure disrupts reproductive hormones, reduces sperm counts and may ultimately adversely affect male reproduction.

Redox mechanisms of environmental toxicants on male reproductive function

Humans and wildlife, including domesticated animals, are exposed to a myriad of environmental contaminants that are derived from various human activities, including agricultural, household, cosmetic, pharmaceutical, and industrial products. Excessive exposure to pesticides, heavy metals, and phthalates consequently causes the overproduction of reactive oxygen species. The equilibrium between reactive oxygen species and the antioxidant system is preserved to maintain cellular redox homeostasis. Mitochondria play a key role in cellular function and cell survival. Mitochondria are vulnerable to damage that can be provoked by environmental exposures. Once the mitochondrial metabolism is damaged, it interferes with energy metabolism and eventually causes the overproduction of free radicals. Furthermore, it also perceives inflammation signals to generate an inflammatory response, which is involved in pathophysiological mechanisms. A depleted antioxidant system provokes oxidative stress that triggers inflammation and regulates epigenetic function and apoptotic events. Apart from that, these chemicals influence steroidogenesis, deteriorate sperm quality, and damage male reproductive organs. It is strongly believed that redox signaling molecules are the key regulators that mediate reproductive toxicity. This review article aims to spotlight the redox toxicology of environmental chemicals on male reproduction function and its fertility prognosis. Furthermore, we shed light on the influence of redox signaling and metabolism in modulating the response of environmental toxins to reproductive function. Additionally, we emphasize the supporting evidence from diverse cellular and animal studies.

Rapamycin protects Sertoli cells against BPA-induced autophagy disorders

Bisphenol A (BPA) is a well-known environmental contaminant that can negatively impact reproductive function. Disruption of autophagy is implicated in BPA-induced cell injury, the specific molecular mechanisms through which BPA affects autophagy in Sertoli cells are still unknown. In the present study, TM4 cells were exposed to various doses of BPA (10, 100, and 200 μM), and the results indicated that BPA exposure led to the accumulation of autophagosomes, this change was accompanied by increased expression of p-mTOR and decreased expression of Atg12, a protein involved in regulating autophagy initiation. Additionally, BPA exposure upregulated the expression levels of p62, a protein involved in autophagic degradation. The inhibition of autophagy initiation and autophagic degradation contributes to the accumulation of autophagosomes. Further studies showed that BPA exposure didn't affect the expression of the lysosome protein LAMP1; however, decreased cytoplasmic retention of acridine orange in TM4 cells may explain the disruption of autophagy. The role of rapamycin and chloroquine (CQ), an autophagy inhibitor that impairs lysosomal degradation also confirmed the effect of BPA on autophagy regulation. Specifically, rapamycin can protect Sertoli cells against BPA-induced cell injury by promoting autophagy. These findings contribute to our understanding of the mechanisms underlying reproductive toxicity caused by BPA.

The State of Research and Weight of Evidence on the Epigenetic Effects of Bisphenol A

Bisphenol A (BPA) is a high-production-volume chemical with numerous industrial and consumer applications. BPA is extensively used in the manufacture of polycarbonate plastics and epoxy resins. The widespread utilities of BPA include its use as internal coating for food and beverage cans, bottles, and food-packaging materials, and as a building block for countless goods of common use. BPA can be released into the environment and enter the human body at any stage during its production, or in the process of manufacture, use, or disposal of materials made from this chemical. While the general population is predominantly exposed to BPA through contaminated food and drinking water, non-dietary exposures through the respiratory system, integumentary system, and vertical transmission, as well as other routes of exposure, also exist. BPA is often classified as an endocrine-disrupting chemical as it can act as a xenoestrogen. Exposure to BPA has been associated with developmental, reproductive, cardiovascular, neurological, metabolic, or immune effects, as well as oncogenic effects. BPA can disrupt the synthesis or clearance of hormones by binding and interfering with biological receptors. BPA can also interact with key transcription factors to modulate regulation of gene expression. Over the past 17 years, an epigenetic mechanism of action for BPA has emerged. This article summarizes the current state of research on the epigenetic effects of BPA by analyzing the findings from various studies in model systems and human populations. It evaluates the weight of evidence on the ability of BPA to alter the epigenome, while also discussing the direction of future research.

Molecular cloning and characterization of Sirt1 and its role in the follicle of juvenile Chinese soft-shelled turtle (Pelodiscus sinensis)

Sirt1 is a member of the Sirtuins family that regulates ovarian senescence, follicular development, and oocyte maturation in vertebrates. To understand its role in the ovary of Pelodiscus sinensis, we cloned the full-length cDNA of Ps-Sirt1 and characterized its potential function by intraperitoneally injecting agonist (resveratrol) and antagonist (EX527) in the female juvenile turtle. The full-length cDNA of Ps-Sirt1 was 2106 bp, comprising 203 bp 5'UTR, a 226 bp 3'UTR, and a 1677 bp ORF encoding 558 amino acids. The calculated molecular weight of predicted protein was 63 kDa, and the isoelectric point was 4.65. The predicted protein comprised a conserved Sir2 domain. Amino acid sequence alignment and phylogenetic analyses showed that Ps-Sirt1 was most closely related to turtles, and distantly related to fish. Expression pattern analysis showed Ps-Sirt1 was highest expressed in ovary, followed by testis, liver, heart, and brain. In the ovarian differentiation processes, Sirt1 showed significantly higher expression at embryonic stage 15 and 21. In the testis differentiation process, Sirt1 expression was downregulated at embryonic stages 15-19. Activated and inactivated Sirt1 decreased the number of primordial follicles in juvenile turtles. Bcl2, Bax, mTOR, and rpS6 expressions were up-regulated, whereas GnRH, Fshb, p50, and p65 were down-regulated after agonist treatment. The inaction of Sirt1 with antagonist up-regulated GnRH, Fshb, p65, p53, Foxo3a, Bcl2, Bax, mTOR, and rpS6, but down-regulated p50. In summary, Sirt1 might be involved in the ovarian follicle development of P. sinensis.

BPA disrupted the testis testosterone levels by interfering ER enrichments within StAR 5' flanking region in rare minnow Gobiocypris rarus

Bisphenol A (BPA) is a widely used endocrine disruptor, which has attracted much attention due to its harmful effects on male reproduction. To investigate the interference of BPA on steroid synthesis in males, male rare minnows (Gobiocypris rarus) were exposed to 15 μg L^-1 BPA for 7, 14 and 21 d. Meanwhile, a positive control group was performed with 25 ng L^-1 17α-ethynyl estradiol (EE2). Results showed that BPA exposure induced lower testosterone (T) levels, while affecting the transcripts of steroidogenic gene StAR. Moreover, BPA induced abnormal germ cells proliferation in the testis in rare minnow. Transcriptome analysis showed that 354 transcripts significantly differentially expressed after BPA exposure for 14 d, several of them were enriched in the signaling pathways of cell cycle process, PPAR signaling pathway, the steroid synthesis pathway and estrogen signaling pathway. BPA significantly increased estrogen receptor (ER) levels and induced abnormal protein levels of PPARγ. BPA disrupted the StAR expression by interfering ER enrichments within StAR 5' flanking region. Additionally, our study also revealed that BPA and EE2 might have different mechanisms for interfering with steroid hormone levels and germ cells proliferation in the testis.

Effects of gestational exposure to bisphenol A on the hepatic transcriptome and lipidome of rat dams: Intergenerational comparison of effects in the offspring

Our previous studies demonstrated that prenatal bisphenol A (BPA) exposure affected the hepatic transcriptome and lipidome in rat offspring in a sex- and age-dependent manner. In this study, we investigated the effects of gestational exposure to BPA on the rat dams, after weaning period, and compared them with those of their offspring. Our results showed alterations in hepatic transcriptome related to insulin signaling, circadian rhythm, and infectious disease pathways in BPA-treated dams even 4 weeks after the exposure, whereas slight modifications on the lipid profile were found. Alterations in lipid and transcriptome profiles were more prominent in the prenatally BPA-exposed offspring at postnatal day (PND) 1 and 21 than those in the dams, suggesting that in utero exposure to BPA is more serious than exposure in the adulthood. Cryptochrome-1 (Cry1) and peroxisome proliferator-activated receptor delta (Ppard) were commonly altered in both dams and offspring. Nevertheless, the results of DIABLO (Data Integration Analysis for Biomarker discovery using Latent cOmponents), showed that multi-omics data successfully distinguished the exposed dams from the corresponding controls and their offspring with a high level of accuracy. The accuracy rates in BPA50 models (including control and 50 μg BPA/kg bw/day exposed groups) were smaller than those in BPA5000 models (control and 5000 μg BPA/kg bw/day exposed groups), suggesting dose-dependent severity in BPA effects. Palmitic acid and genes related to circadian rhythm, insulin responses, and lipid metabolism (e.g., 1-acylglycerol-3-phosphate O-acyltransferase 2 (Agpat2), B-cell CLL/lymphoma 10 (Bcl10), Cry1, Harvey rat sarcoma virus oncogene (Hras), and NLR family member X1 (Nlrx1)) were identified through DIABLO models as novel biomarkers of effects of BPA across two generations.

The Bisphenols Found in the Ejaculate of Men Does Not Pass through the Testes

Exposure to bisphenols is related to negative effects on male reproduction. The bisphenols exposure is associated with several modes of action including negative impact on the blood–testis barrier (BTB) in testes or direct effect on spermatozoa. Bisphenols have been detected in human seminal plasma, but the possible mechanism of seminal transfer of bisphenols is not clear. Some authors consider the transfer through the blood–testis barrier to be crucial. Therefore, in this work, we compared normozoospermic men and men after vasectomy who have interrupted vas deferens and their ejaculate does not contain testicular products. We measured the concentration of bisphenol A (BPA), bisphenol S (BPS) and bisphenol F (BPF) in the urine and seminal plasma of these men using liquid chromatography tandem mass spectrometry (LC/MSMS). We found that the ratio of urinary and seminal plasma content of bisphenols did not differ in normozoospermic men or men after vasectomy. From the obtained data, it can be concluded that the pathways of transport of bisphenols into seminal plasma are not primarily through the testicular tissue, but this pathway is applied similarly to other routes of transmission by a corresponding ejaculate volume ratio. To a much greater extent than through testicular tissue, bisphenols enter the seminal plasma mainly as part of the secretions of the accessory glands.

Prenatal dexamethasone exposure programs the decreased testosterone synthesis in offspring rats by low level of endogenous glucocorticoids

Prenatal dexamethasone exposure (PDE) can decrease maternal endogenous glucocorticoid level and induce testicular dysplasia in male offspring rats. In this study we investigated low level endogenous glucocorticoid-mediated testicular dysplasia in PDE offspring and elucidated the intrauterine epigenetic programming mechanisms. Pregnant rats were injected with dexamethasone (0.2 mg·kg^-1·d^-1, sc) on gestational day (GD) 9-20. The offspring rat blood and testis were collected after euthanasia on GD20, postnatal week (PW) 12 or PW28. We showed that PDE induced abnormal morphology of testis and significantly decreased the expression of testosterone synthesis-related genes as well as testosterone production before and after birth. Meanwhile, serum corticosterone, the expression and histone 3 lysine 14 acetylation (H3K14ac) of testicular insulin-like growth factor 1 (IGF1) were significantly decreased. After the pregnant rats were subjected to chronic stress for 2 weeks (PW10-12), serum corticosterone level was increased in the adult PDE offspring, and the above-mentioned other indicators were also improved. Cultured Leydig cells (TM3) were treated with corticosterone (62.5-500 nM) in vitro. We showed that corticosterone concentration-dependently inhibited glucocorticoid receptor α (GRα) and miR-124-3p expression, increased histone deacetylase 5 (HDAC5) expression, and decreased IGF1 H3K14ac level and the expression of IGF1/steroidogenic acute regulatory protein (StAR), suggesting that corticosterone at lower than physiological level (<500 nM) inhibited testosterone synthesis by reducing H3K14ac and the expression level of IGF1 through GRα/miR-124-3p/HDAC5 pathway. In conclusion, PDE can cause persistent inhibition of testosterone synthesis before and after birth in the offspring rats by low level of endogenous glucocorticoids.

The hazardous threat of Bisphenol A: Toxicity, detection and remediation

Bisphenol A (or BPA) is a toxic endocrine disrupting chemical that is released into the environment through modern manufacturing practices. BPA can disrupt the production, function and activity of endogenous hormones causing irregularity in the hypothalamus-pituitary-gonadal glands and also the pituitary-adrenal function. BPA has immuno-suppression activity and can downregulate T cells and antioxidant genes. The genotoxicity and cytotoxicity of BPA is paramount and therefore, there is an immediate need to properly detect and remediate its influence. In this review, we discuss the toxic effects of BPA on different metabolic systems in the human body, followed by its mechanism of action. Various novel detection techniques (LC-MS, GC-MS, capillary electrophoresis, immunoassay and sensors) involving a pretreatment step (liquid-liquid microextraction and molecularly imprinted solid-phase extraction) have also been detailed. Mechanisms of various remediation strategies, including biodegradation using native enzymes, membrane separation processes, photocatalytic oxidation, use of nanosorbents and thermal degradation has been detailed. An overview of the global regulations pertaining to BPA has been presented. More investigations are required on the efficiency of integrated remediation technologies rather than standalone methods for BPA removal. The effect of processing operations on BPA in food matrices is also warranted to restrict its transport into food products.

Prenatal exposure to phenols and benzophenones in relation to markers of male reproductive function in adulthood

INTRODUCTION

Environmental exposure during fetal life may disrupt testicular development. In humans, a limited number of studies have investigated whether these adverse effects persist into adulthood. Using data from a prospective, population-based birth cohort study, The Copenhagen Mother-Child cohort, the objective was to assess if there is an association between fetal exposure to selected phenols and benzophenones and markers of testicular function in adult men.

METHODS

Pregnant women were recruited in 1997-2001. Their sons were examined clinically at 18-20 years of age, with focus on adult markers of reproductive function (anogenital distance (AGD), semen quality and reproductive hormones). In total, 101 18-20-year-old men were included, whose mothers during pregnancy had a serum sample drawn and analyzed for bisphenol A (BPA) and seven other simple phenols, as well as six benzophenones. To investigate the association between chemical levels (in tertiles, T1-T3) in relation to markers of reproductive function, univariate and multiple linear regression analyses were performed.

RESULTS

In fully adjusted analyses, increased levels of luteinizing hormone (LH) were observed with higher fetal exposure to BPA (percentage difference (95%CI)) (T2: 12% (-8%,36%) and T3: 33% (10%,62%), compared to T1) and benzophenone-3 (BP-3) (T2: 21% (-2%,49%), T3: 18% (-4%,45%)), while no clear association was seen to total testosterone (TT). Higher levels of BPA and BP-3 were associated with a lower TT/LH ratio, although only significant for BPA (p-trend=0.01). No associations were seen to AGD or markers of semen quality.

CONCLUSION

In conclusion, high exposure to BPA and BP-3 was associated with a compensated reduced Leydig cell function but no other changes in markers of reproductive health. As maternal levels of BPA and BP-3 were not correlated, separate effects may be at play. Larger studies on long-term reproductive consequences of prenatal exposures are warranted to validate our findings.

Bisphenol A and its effects on the systemic organs of children

For the past two decades, growing research has been pointing to multiple repercussions of bisphenol A (BPA) exposure to human health. BPA is a synthetic oestrogen which primarily targets the endocrine system; however, the compound also disturbs other systemic organ functions, in which the magnitude of impacts in those other systems is as comparable to those in the endocrine system. To date, the discoveries on the association between BPA and health outcomes mainly came from animal and in vitro studies, with limited human studies which emphasised on children's health. In this comprehensive review, we summarised studies on human, in vivo and in vitro models to understand the consequences of pre-, post- and perinatal BPA exposure on the perinatal, children and adult health, encompassing cardiovascular, neurodevelopmental, endocrine and reproductive effects.Conclusion: Evidence from in vitro and animal studies may provide further support and better understanding on the correlation between environmental BPA exposure and its detrimental effects in humans and child development, despite the difficulties to draw direct causal relations of BPA effects on the pathophysiology of the diseases/syndromes in children, due to differences in body system complexity between children and adults, as well as between animal and in vitro models and humans. What is known: • Very limited reviews are available on how BPA adversely affects children's health. • Previous papers mainly covered two systems in children. What is new: • Comprehensive review on the detrimental effects of BPA on children health outcomes, including expectations on adult health outcomes following perinatal BPA exposure, as well as covering a small part of BPA alternatives. • Essentially, BPA exposure during pregnancy has huge impacts on the foetus in which it may cause changes in foetal epigenetic programming, resulting in disease onsets during childhood as well as adulthood.

Chronic low-level perfluorooctane sulfonate (PFOS) exposure promotes testicular steroidogenesis through enhanced histone acetylation

Perfluorooctane sulfonate (PFOS), an artificial perfluorinated compound, has been associated with male reproductive disorders. Histone modifications are important epigenetic mediators; however, the impact of PFOS exposure on testicular steroidogenesis through histone modification regulations remains to be elucidated. In this study, we examined the roles of histone modifications in regulating steroid hormone production in male rats chronically exposed to low-level PFOS. The results indicate that PFOS exposure significantly up-regulated the expressions of StAR, CYP11A1 and 3β-HSD, while CYP17A1 and 17β-HSD were down-regulated, thus contributing to the elevated progesterone and testosterone levels. Furthermore, PFOS significantly increased the histones H3K9me2, H3K9ac and H3K18ac while reduced H3K9me3 in rat testis. It is known that histone modifications are closely involved in gene transcription. Therefore, to investigate the association between histone modifications and steroidogenic gene regulation, the levels of these histone marks were further measured in steroidogenic gene promoter regions by ChIP. It was found that H3K18ac was augmented in Cyp11a1 promoter, and H3K9ac was increased in Hsd3b after PFOS exposure, which is proposed to result in the activation of CYP11A1 and 3β-HSD, respectively. To sum up, chronic low-level PFOS exposure activated key steroidogenic gene expression through enhancing histone acetylation (H3K9ac and H3K18ac), ultimately stimulating steroid hormone biosynthesis in rat testis.

Bisphenol A and male murine reproductive system: finding a link between plasticizer and compromised health

The global burden of male infertility is rising at an alarming rate affecting the lives of millions in terms of physical, emotional and societal perspectives. Among several existing endocrine disrupting chemicals, bisphenol A (BPA) has been reported by many to inflict male reproductive toxicity in different experimental models, especially in mice. This review article critically discusses the overall reproductive toxicity of BPA with a special note to its ubiquitous existence, contamination route, effects on the reproductive system and toxicity mechanisms in male mice. Disturbed redox status in germ cells and spermatozoa plays a pivotal role in BPA induced male reproductive toxicity. In this context, the involvement of mitochondria and endoplasmic reticulum is also of grave importance. Induction of caspase-dependent apoptosis is the extreme consequence that leads to deterioration of cellular parameters. Besides the oxidative cellular and histoarchitectural damages, perturbed endocrine regulation, subsequent impaired hormonal and cellular genesis program, epigenetic alterations and inflammation cumulatively reflect poor sperm quality leading to compromised reproduction. Moreover, several key issues have also been highlighted that, if addressed, will strengthen our understanding of BPA mediated male reproductive toxicity.

Adult Male Rats Show Resilience to Adolescent Bisphenol A Effects on Hormonal and Behavioral Responses While Co-Exposure With Hop Extracts Supports Synergistic Actions

The adolescence period, marked by sexual and brain maturation, has shown sensitivity to various environmental disruptors. Exposure to the xenoestrogen bisphenol A (BPA) is known to alter physiological and behavioral responses although its role at this critical period remains largely unknown. Recent research further suggests biochemical and genomic effects of BPA to be mitigated by various natural compounds, while effects on behavior have not been examined. This study aimed to characterize (1) the effects of dietary BPA during adolescence on endogenous corticosterone (CORT) secretion, emotional behavior, and testosterone (T) in adulthood, and (2) the impact of combined exposure to BPA with hop extracts (Hop), a phytoestrogen with anxiolytic properties. To do so, four groups of male Wistar rats [postnatal day (PND) 28] were administered corn oil (control), BPA (40 mg/kg), hops (40 mg/kg), or BPA-hops by oral gavage for 21 days (PND 28–48). Blood droplets collected on PND 28, 48, and 71 served to measure CORT and T changes. As adults, rats were tested in the elevated plus maze (EPM), the social interaction test, and the forced swim test. Our findings demonstrated elevated anxiety and a trend toward depressive-like behaviors in BPA- compared to hops-exposed rats. However, BPA intake had no impact on basal CORT levels, or adulthood T secretion and sociability. Of note, BPA's anxiogenic effect manifested through decreased EPM open arm entries was abolished by hops co-supplementation. Together, our observations suggest the adolescence period to be less sensitive to deleterious effects of BPA than what has been reported upon gestational and perinatal exposure.

Endocrine disrupting chemicals (EDCs) and sex steroid receptors

Sex-steroid receptors (SSRs) are essential mediators of estrogen, progestin, and androgen signaling that are critical in vast aspects of human development and multi-organ homeostasis. Dysregulation of SSR function has been implicated in numerous pathologies including cancers, obesity, Type II diabetes mellitus, neuroendocrine disorders, cardiovascular disease, hyperlipidemia, male and female infertility, and other reproductive disorders. Endocrine disrupting chemicals (EDCs) modulate SSR function in a wide variety of cell and tissues. There exists strong experimental, clinical, and epidemiological evidence that engagement of EDCs with SSRs may disrupt endogenous hormone signaling leading to physiological abnormalities that may manifest in disease. In this chapter, we discuss the molecular mechanisms by which EDCs interact with estrogen, progestin, and androgen receptors and alter SSR functions in target cells. In addition, the pathological consequences of disruption of SSR action in reproductive and other organs by EDCs is described with an emphasis on underlying mechanisms of receptors dysfunction.

Environmental pollutants exposure and male reproductive toxicity: The role of epigenetic modifications

Male fertility rates have shown a progressive decrease in recent decades. There is a growing concern about the male reproductive dysfunction caused by environmental pollutants exposure, however the underlying molecular mechanisms are still not well understood. Epigenetic modifications play a key role in the biological responses to external stressors. Therefore, this review discusses the roles of epigenetic modifications in male reproductive toxicity induced by environmental pollutants, with a particular emphasis on DNA methylation, histone modifications and miRNAs. The available literature proposed that environmental pollutants can directly or cause oxidative stress and DNA damage to induce a variety of epigenetic changes, which lead to gene dysregulation, mitochondrial dysfunction and consequent male reproductive toxicity. However, future studies focusing on more kinds of epigenetic modifications and their crosstalk as well as epidemiological data are still required to fill in the current research gaps. In addition, the intrinsic links between pollutants-mediated epigenetic regulations and male reproduction-related physiological responses deserve to be further explored.

Multisystemic alterations in humans induced by bisphenol A and phthalates: Experimental, epidemiological and clinical studies reveal the need to change health policies

A vast amount of evidence indicates that bisphenol A (BPA) and phthalates are widely distributed in the environment since these compounds are mass-produced for the manufacture of plastics and plasticizers. These compounds belong to a large group of substances termed endocrine-disrupting chemicals (EDC). It is well known that humans and living organisms are unavoidably and unintentionally exposed to BPA and phthalates from food packaging materials and many other everyday products. BPA and phthalates exert their effect by interfering with hormone synthesis, bioavailability, and action, thereby altering cellular proliferation and differentiation, tissue development, and the regulation of several physiological processes. In fact, these EDC can alter fetal programming at an epigenetic level, which can be transgenerational transmitted and may be involved in the development of various chronic pathologies later in the adulthood, including metabolic, reproductive and degenerative diseases, and certain types of cancer. In this review, we describe the most recent proposed mechanisms of action of these EDC and offer a compelling selection of experimental, epidemiological and clinical studies, which show evidence of how exposure to these pollutants affects our health during development, and their association with a wide range of reproductive, metabolic and neurological diseases, as well as hormone-related cancers. We stress the importance of concern in the general population and the urgent need for the medical health care system to closely monitor EDC levels in the population due to unavoidable and involuntary exposure to these pollutants and their impact on human health.

Fighting Bisphenol A-Induced Male Infertility: The Power of Antioxidants

Bisphenol A (BPA), a well-known endocrine disruptor present in epoxy resins and polycarbonate plastics, negatively disturbs the male reproductive system affecting male fertility. In vivo studies showed that BPA exposure has deleterious effects on spermatogenesis by disturbing the hypothalamic–pituitary–gonadal axis and inducing oxidative stress in testis. This compound seems to disrupt hormone signalling even at low concentrations, modifying the levels of inhibin B, oestradiol, and testosterone. The adverse effects on seminal parameters are mainly supported by studies based on urinary BPA concentration, showing a negative association between BPA levels and sperm concentration, motility, and sperm DNA damage. Recent studies explored potential approaches to treat or prevent BPA-induced testicular toxicity and male infertility. Since the effect of BPA on testicular cells and spermatozoa is associated with an increased production of reactive oxygen species, most of the pharmacological approaches are based on the use of natural or synthetic antioxidants. In this review, we briefly describe the effects of BPA on male reproductive health and discuss the use of antioxidants to prevent or revert the BPA-induced toxicity and infertility in men.

Bisphenol A Deranges the Endocannabinoid System of Primary Sertoli Cells with an Impact on Inhibin B Production

Bisphenol A (BPA) is an endocrine disruptor that negatively affects spermatogenesis, a process where Sertoli cells play a central role. Thus, in the present study we sought to ascertain whether BPA could modulate the endocannabinoid (eCB) system in exposed mouse primary Sertoli cells. Under our experimental conditions, BPA turned out to be cytotoxic to Sertoli cells with an half-maximal inhibitory concentration (IC₅₀) of ~6.0 µM. Exposure to a non-cytotoxic dose of BPA (i.e., 0.5 μM for 48 h) increased the expression levels of specific components of the eCB system, namely: type-1 cannabinoid (CB₁) receptor and diacylglycerol lipase-α (DAGL-α), at mRNA level, type-2 cannabinoid (CB₂) receptor, transient receptor potential vanilloid 1 (TRPV1) receptors, and DAGL-β, at protein level. Interestingly, BPA also increased the production of inhibin B, but not that of transferrin, and blockade of either CB₂ receptor or TRPV1 receptor further enhanced the BPA effect. Altogether, our study provides unprecedented evidence that BPA deranges the eCB system of Sertoli cells towards CB₂- and TRPV1-dependent signal transduction, both receptors being engaged in modulating BPA effects on inhibin B production. These findings add CB₂ and TRPV1 receptors, and hence the eCB signaling, to the other molecular targets of BPA already known in mammalian cells.

Vitamin K in Vertebrates' Reproduction: Further Puzzling Pieces of Evidence from Teleost Fish Species

Vitamin K (VK) is a fat-soluble vitamin that vertebrates have to acquire from the diet, since they are not able to de novo synthesize it. VK has been historically known to be required for the control of blood coagulation, and more recently, bone development and homeostasis. Our understanding of the VK metabolism and the VK-related molecular pathways has been also increased, and the two main VK-related pathways-the pregnane X receptor (PXR) transactivation and the co-factor role on the γ-glutamyl carboxylation of the VK dependent proteins-have been thoroughly investigated during the last decades. Although several studies evidenced how VK may have a broader VK biological function than previously thought, including the reproduction, little is known about the specific molecular pathways. In vertebrates, sex differentiation and gametogenesis are tightly regulated processes through a highly complex molecular, cellular and tissue crosstalk. Here, VK metabolism and related pathways, as well as how gametogenesis might be impacted by VK nutritional status, will be reviewed. Critical knowledge gaps and future perspectives on how the different VK-related pathways come into play on vertebrate's reproduction will be identified and proposed. The present review will pave the research progress to warrant a successful reproductive status through VK nutritional interventions as well as towards the establishment of reliable biomarkers for determining proper nutritional VK status in vertebrates.

Effects of BPA on zebrafish gonads: Focus on the endocannabinoid system

Bisphenol A (BPA), a monomer used for polycarbonate manufacture, has been widely reported as an endocrine-disrupting chemical (EDC). Among other alterations, BPA induces reproductive dysfunctionalities. Changes in the endocannabinoid system (ECS) have been recently shown to be associated with reproductive disorders. The ECS is a lipid-based signaling system (cannabinoid receptors, endocannabinoids and enzymatic machinery) involved in several physiological functions. The main goal of the present study was to assess the effects of two environmental concentrations of BPA (10 and 20 μg/L) on the ECS in 1-year old zebrafish gonads. In males, BPA increased the gonadosomatic index (GSI) and altered testicular levels of endocannabinoids as well as reduced the testicular area occupied by spermatogonia. In male liver, exposure to 20 μg/L BPA significantly increased vitellogenin (vtg) transcript levels. In female zebrafish, BPA altered ovarian endocannabinoid levels, elevated hepatic vtg mRNA levels as well as increased the percentage of vitellogenic oocytes in the ovaries. In conclusion, exposure to two environmentally relevant concentrations of BPA altered the ECS and consequently, gonadal function in both male and female zebrafish.

Bisphenol A-associated alterations in DNA and histone methylation affects semen quality in rare minnow Gobiocypris rarus

Bisphenol A (BPA), a well-known estrogenic endocrine disruptor, is ubiquitously present in the environment, possessing the potential to interfere with the reproductive endocrine system in male mammals. However, there are limited studies on the reproductive toxicity in male aquatic animals associated with epigenetic modifications. In order to evaluate the potential effects of BPA on reproduction and better understand the underlying mechanism, adult male rare minnow (Gobiocypris rarus) were exposed to 15 μg L^-1 BPA over a period of 63 d. Results showed that BPA induced congestion of blood vessels and infiltration of inflammatory cells after 21 d exposure, and decreased sperm fertilization after 63 d exposure. The genome DNA methylation levels were significantly increased throughout the treatment, and a strong positive stain were found in the spermatocyte, spermatid and sperm. The H3K4me3 level in all types of germ cell were increased by 21 d exposure while decreased following 63 d exposure. The positive stain of H3K9me3 was decreased in sperms while increased in spermatids by 21 d exposure. In addition, the H3K9me3 level was significantly increased after 63 d exposure, and a strong positive stain were found in spermatocytes, spermatids, and sperms. Our result also revealed that the transcripts of DNA methyltransferase genes (dnmt1 and dnmt3-8) and histone methyltransferase genes (mll2-5, setdb1-2 and ezh2) were also markedly changed under BPA exposure for 21-63 d. These findings indicated that BPA had toxicity in male reproductive, and DNA/histone methylation might play a vital role in the regulation of BPA-triggered the decreased of sperm quality.

Environmental contaminants and male infertility: Effects and mechanisms

The escalating prevalence of male infertility and decreasing trend in sperm quality have been correlated with rapid industrialisation and the associated discharge of an excess of synthetic substances into the environment. Humans are inevitably exposed to these ubiquitously distributed environmental contaminants, which possess the ability to intervene with the growth and function of male reproductive organs. Several epidemiological reports have correlated the blood and seminal levels of environmental contaminants with poor sperm quality. Numerous in vivo and in vitro studies have been conducted to investigate the effect of various environmental contaminants on spermatogenesis, steroidogenesis, Sertoli cells, blood-testis barrier, epididymis and sperm functions. The reported reprotoxic effects include alterations in the spermatogenic cycle, increased germ cell apoptosis, inhibition of steroidogenesis, decreased Leydig cell viability, impairment of Sertoli cell structure and function, altered expression of steroid receptors, increased permeability of blood-testis barrier, induction of peroxidative and epigenetic alterations in spermatozoa resulting in poor sperm quality and function. In light of recent scientific reports, this review discusses the effects of environmental contaminants on the male reproductive function and the possible mechanisms of action.

The effects of pubertal exposure to bisphenol-A on social behavior in male mice

Puberty is a crucial developmental period for structural modifications of brain and activation of the neural circuits underlying sex differences in social behavior. It is possible that pubertal exposure to bisphenol-A (BPA), a common EED with a weak estrogenic activity, influences social behavior. After being exposed to BPA at 0.04, 0.4, 4 mg kg^-1 for 18 days, the 7-week-old male mice were tested with social play and three-chamber. The results showed that pubertal BPA exposure decreased social play between adolescent males and sociability of adolescent males. Further, pubertal BPA exposure reduced sociability and inhibited social novel preferences of adult males. BPA inhibited social interactions with opposite sex but improved socio-sexual exploration and the low-intensity mating behavior (mounting) with same sex in adult males. In residential-intruder test, BPA-exposed adult males showed a decrease in aggressiveness and an enhancement in prosocial behavior with intruder. Western blot analysis showed that BPA (especially at 4 mg/kg/d) down-regulated the levels of AR in the amygdala and the striatum but up-regulated the levels of DR1 and DAT proteins in the striatum of adult males. BPA at 4 mg kg^-1 decreased the levels of T in the serum and the brain. These results suggest that pubertal BPA exposure affects social play and sociability of adolescent males and even results in long-term effects on social behavior of adult males. BPA-induced down-regulations of the levels of AR in the amygdala and the striatum and up-regulation of the levels of DR1 and DAT in the striatum may be involved.

Bisphenols and Male Reproductive Health: From Toxicological Models to Therapeutic Hypotheses

Bisphenols, and in particular bisphenol A (BPA), have been widely used for the production of plastic manufacts in the last 50 years. Currently, BPA is present in a variety of daily use polycarbonate plastics and epoxy resins, and dietary ingestion is considered the main route of human exposure. Accordingly, BPA is the chemical pollutant with the widest exposure in humans, involving nearly 90% of general population, according to recent studies. Concerns about BPA effects on human health date back to 1930s, when severe impact on male sexual development was suggested. Now, the acknowledged biological effects of BPA are various. In regard to human fertility, BPA has been shown to disrupt hormone signaling even at low concentrations. Results from human epidemiological studies have reported BPA interference with follicle stimulating hormone, inhibin B, estradiol, testosterone levels, and sexual function in male subjects. Moreover, recent studies have reported an association between BPA levels and reduced sperm concentration, motility, normal morphology, sperm DNA damage, and altered epigenetic pattern, resulting in trans-generational legacy of BPA effects. In this review, the recognized effects of BPA on male reproductive health are described, from the most recent issues on experimental models to epidemiological data. In addition, the very recent interest about the use of nutraceutical remedies to counteract BPA effects are discussed.

The Impact of Prenatal Exposure to Bisphenol A on Male Reproductive Function

Bisphenol A (BPA) is a recognized xenoestrogen, in that it possesses oestrogenic and anti-androgenic properties. These endocrine-disrupting effects of BPA at the estrogen receptor (ER) occur despite the very low affinity of BPA for the ERβ, which is 10,000 times lower than that of 17-β estradiol, and despite the European regulatory authorities stating that BPA is safe, at usual exposure concentrations, the use of BPA in baby drink bottles was banned in 2011. There exists conflicting evidence from human epidemiological studies as to its influence on adult male reproductive function, although animal data is more convincing. This mini-review will report on the limited epidemiological data from human studies relating early life exposure to BPA on adult male reproductive function. A long term follow-up study from Western Australia using a birth cohort, the Raine Study, demonstrated no adverse associations of antenatal exposure to BPA, and potentially a positive association with antenatal BPA exposure with sperm concentration and motility at 20 years of age, although recent scientific reports suggest traditional measures of BPA exposure may underestimate exposure levels, which makes data interpretation potentially flawed.

Bisphenol A-Induced Epigenetic Changes and Its Effects on the Male Reproductive System

Bisphenol A (BPA) is a widespread chemical agent which can exert detrimental effects on the male reproductive system. Exposure to BPA has been shown to induce several epigenetic modifications in both animal and human cells. Specifically, BPA could not only modify the methylation pattern of multiple genes encoding proteins related to reproductive physiology but also directly influence the genes responsible for DNA methylation. BPA effects include hormonal alterations, microscopic and macroscopic alteration of male reproductive organs, and inheritable epigenetic changes involving human reproduction. BPA exposure was also linked to prostate cancer. This review aims to show the current scenario of BPA-induced epigenetic changes and its effects on the male reproductive system. Possible strategies to counter the toxic effect of BPA were also addressed.

Reduced testicular steroidogenesis in rat offspring by prenatal nicotine exposure: Epigenetic programming and heritability via nAChR/HDAC4

Prenatal nicotine exposure (PNE) may lead to offspring's testicular dysplasia. Here, we confirmed the intergenerational effect of PNE on testosterone synthetic function and explored its epigenetic programming mechanism. Pregnant Wistar rats were injected subcutaneously with nicotine (2 mg/kg.d) from gestational day 9-20. Some dams were anesthetized to obtain fetal rats, the rest were allowed to spontaneous labor to generate F1 and F2 generation. In utero, PNE impaired testicular development and testosterone production. Meanwhile, the expression of steroidogenic acute regulatory protein (StAR) and 3β-hydroxysteroid dehydrogenase (3β-HSD) were decreased both in F1 and F2 generations. Furthermore, PNE enhanced the expression of fetal testicular nicotinic acetylcholine receptors (nAChRs) and histone deacetylase 4 (HDAC4), while obviously weakened histone 3 lysine 9 acetylation (H3K9ac) level of StAR/3β-HSD promoter from GD20 to postnatal week 12 and even in F2 generation. In vitro, nicotine increased nAChRs and HDAC4 expression, and decreased the StAR/3β-HSD H3K9ac level and expression, as well as the testosterone production in Leydig cells. Antagonism of nAChRs and inhibition of HDAC4 reversed the aforementioned changes. In conclusion, PNE programmed testicular low steroidogenesis and its heritability in male offspring rats. The underlying mechanism was associated to the low-level programming of StAR/3β-HSD H3K9ac via nAChR/HDAC4.

The adverse health effects of bisphenol A and related toxicity mechanisms

Bisphenol A (BPA) is an industrial component commonly used in synthesis of polycarbonate plastics, epoxy resin and other polymer materials. Due to its mass productions and widespread applications, the presence of BPA is ubiquitous in the environment. BPA can enter the body via different ways such as digestive tract, respiratory tract and dermal tract. As an endocrine disruptor, BPA has estrogen-like and anti-androgen effects causing damages to different tissues and organs, including reproductive system, immune system and neuroendocrine system, etc. Recently, it has been shown that BPA could induce carcinogenesis and mutagenesis in animal models. Here, the underlying mechanisms of BPA-induced multi-organ toxicity were well summarized, involving the receptor pathways, disruption of neuroendocrine system, inhibition of enzymes, modulation of immune and inflammatory responses, as well as genotoxic and epigenetic mechanisms. The aim of this review is to compile the available current research data regarding BPA and provide an overview of the current status of BPA exposure and relevant health effects covering reproductive, developmental, metabolic, immuno, respiratory, hepatic and renal toxicity and carcinogenesis of BPA. This review provides comprehensive data of BPA toxicity on human health and related mechanisms. We also identify any missing data which should be addressed by further studies.

Comparative study of environmental pollutants bisphenol A and bisphenol S on sexual differentiation of anteroventral periventricular nucleus and spermatogenesis

BACKGROUND

Bisphenol A is well known endocrine-disrupting chemical while Bisphenol S was considered a safe alternative. The present study aims to examine the comparative effects of xenobiotic bisphenol-A (BPA) and its substitute bisphenol-S (BPS) on spermatogenesis and development of sexually dimorphic nucleus population of dopaminergic neurons in the anteroventral periventricular nucleus (AVPV) of the hypothalamus in male pups.

METHODS

Sprague Dawley rat's pups were administered subcutaneously at the neonatal stage from postnatal day PND1 to PND 27. Thirty animals were divided into six experimental groups (6 animals/group). The first group served as control and was provided with normal olive oil. The four groups were treated with 2 μg/kg and 200 μg/kg of BPA and BPS, respectively. The sixth group was given with 50 μg/kg of estradiol dissolved in olive oil as a standard to find the development of dopaminergic tyrosine hydroxylase neurons in AVPV regions. Histological analysis for testicular tissues and immunohistochemistry for brain tissues was performed.

RESULTS

The results revealed adverse histopathological changes in testis after administration of different doses of BPA and BPS. These degenerative changes were marked by highly significant (p < 0.001) decrease in tubular and luminal diameters of seminiferous tubule and epithelial height among bisphenols treated groups as compared to control. Furthermore, significantly increased (p < 0.001) TH-ir cell bodies in the AVPV region of the brain with 200 μg/kg dose of BPA and BPS was evident.

CONCLUSION

It is concluded that exposure of BPA and BPS during a critical developmental period can structural impairments in testes and affects sexual differentiation of a dimorphic dopaminergic population of AVPV region of hypothalamus in the male brain.

Male exposure to bisphenol a impairs spermatogenesis and triggers histone hyperacetylation in zebrafish testes

Bisphenol A (BPA) is an endocrine disruptor whose ubiquitous presence in the environment has been related with impairment of male reproduction. BPA can cause both transcriptomic and epigenetic changes during spermatogenesis. To evaluate the potential effects of male exposure to BPA, adult zebrafish males were exposed during spermatogenesis to doses of 100 and 2000 μg/L, which were reported in contaminated water bodies and higher than those allowed for human consumption. Fertilization capacity and survival at hatching were analysed after mating with untreated females. Spermatogenic progress was analysed through a morphometrical study of testes and apoptosis was evaluated by TUNEL assay. Testicular gene expression was evaluated by RT-qPCR and epigenetics by using ELISA and immunocytochemistry. In vitro studies were performed to investigate the role of Gper. Chromatin fragmentation and the presence of transcripts were also evaluated in ejaculated sperm. Results on testes from males treated with the highest dose showed a significant decrease in spermatocytes, an increase in apoptosis, a downregulation of ccnb1 and sycp3, all of which point to an alteration of spermatogenesis and to meiotic arrest and an upregulation of gper1 and esrrga receptors. Additionally, BPA at 2000 μg/L caused missregulation of epigenetic remodelling enzymes transcripts in testes and promoted DNA hypermethylation and H3K27me3 demethylation. BPA also triggered an increase in histone acetyltransferase activity, which led to hyperacetylation of histones (H3K9ac, H3K14ac, H4K12ac). In vitro reversion of histone acetylation changes using a specific GPER antagonist, G-36, suggested this receptor as mediator of histone hyperacetylation. Males treated with the lower dose only showed an increase in some histone acetylation marks (H3K14ac, H4K12ac) but their progeny displayed very limited survival at hatching, revealing the deleterious effects of unbalanced paternal epigenetic information. Furthermore, the highest dose of BPA led to chromatin fragmentation, promoting direct reproductive effects, which are incompatible with embryo development.

Corticosterone rather than ethanol epigenetic programmed testicular dysplasia caused by prenatal ethanol exposure in male offspring rats

Prenatal ethanol exposure (PEE) could affect offspring's testicular development. This study aimed to illuminate its intrauterine origin and the programming mechanism caused by PEE. Pregnant Wistar rats were given ethanol (4 g/kg.d) by gavage administration during gestational days (GD) 9-20. Serum samples and testes of male offspring rats were collected on GD20, postnatal week (PW) 6, and PW12. We found that PEE induced testicular morphological abnormality, low serum testosterone levels, expressive suppression of 3β-hydroxysteroid dehydrogenase (3β-HSD), and low acetylation levels of histone 3 lysine 14 (H3K14ac) of 3β-HSD before and after birth. In utero, when fetal rats were overexposed to corticosterone by PEE, the expression levels of testicular glucocorticoid receptor (GR) and histone deacetylase 2 (HDAC2) were increased, while that of steroidogenic factor 1 (SF1) was decreased. In vitro, corticosterone (rather than ethanol) at 500 to 2,000 nM concentration decreased testosterone production and 3β-HSD expression in a concentration-dependent manner. Moreover, corticosterone downregulated SF1 and upregulated HDAC2 via activating GR, accompanied by a low H3K14ac level of 3β-HSD; SF1 overexpression could reverse the increased HDAC2 expression, and knockdown of HDAC2 could partially reverse the inhibitory effects of corticosterone on H3K14ac level and 3β-HSD expression but not on SF1 expression. Taken together, PEE caused testicular dysplasia in male offspring rats, which was associated with corticosterone-induced low-functional programming of 3β-HSD through the GR/SF1/HDAC2/H3K14ac pathway. This study provides new academic perspectives to illuminate the theory of 'Developmental Origins of Health and Disease.'

"Bisphenol a: an emerging threat to male fertility"

BACKGROUND

Among the factors causing male infertility, one of the most debated is the exposure to environmental contaminants. Recently, the chemical compound Bisphenol A (BPA) has drawn attention from the reproductive science community, due to its ubiquitous presence in day-to-day life. Its toxic action appears to mainly affect the male reproductive system, directly impacting male fertility. MAIN: The purpose of this review is to investigate current research data on BPA, providing an overview of the findings obtained from studies in animal and human models, as well as on its supposed mechanisms of action.

CONCLUSION

A clear understanding of BPA action mechanisms, as well as the presumed risks deriving from its exposure, is becoming crucial to preserve male fertility. The development and validation of methodologies to detect BPA toxic effects on reproductive organs can provide greater awareness of the potential threat that this chemical represents.

Decreased H3K9ac level of StAR mediated testicular dysplasia induced by prenatal dexamethasone exposure in male offspring rats

Prenatal dexamethasone exposure (PDE) could induce testicular developmental toxicity in adults. The present study aims to confirm its intrauterine origination, and to explore its potential intrauterine programming mechanism. The pregnant rats were respectively injected subcutaneously with 0.2 and 0.8 mg/kg d dexamethasone during gestational days (GD) 9 to 20. The testes and serum of offspring rats were collected on GD20 and postnatal week (PW) 12. In vivo, PDE significantly induced the abnormal testicular morphology in offspring from GD20 to PW12. Moreover, the serum and intratesticular testosterone levels and the expression of testicular steroidogenic acute regulatory protein (StAR) were reduced by PDE. The expression levels of glucocorticoid receptor (GR) and histone deacetylase 7 (HDAC7) were increased in fetal testes. Furthermore, the histone 3 lysine 9 acetylation (H3K9ac) level in the StAR promoter was decreased by PDE from GD20 to PW12. In vitro, mouse Leydig tumour cell line (MLTC-1) cells were treated with dexamethasone (20, 100 and 500 nM), and the testosterone production and StAR expression were reduced. Moreover, dexamethasone increased the expression of HDAC7 by activating GR, which decreased the H3K9ac level in the StAR promoter. Taken together, PDE caused testicular dysplasia before and after birth in male offspring rats, and its mechanism was related to the low-expressional programming of StAR mediated by decreasing H3K9ac level.

Mice exposed to bisphenol A exhibit depressive-like behavior with neurotransmitter and neuroactive steroid dysfunction

Fetal exposure to endocrine disrupting chemicals (EDCs) has been associated with adverse neurobehavioral outcomes across the lifespan and can persist across multiple generations of offspring. However, the underlying mechanisms driving these changes are not well understood. We investigated the molecular perturbations associated with EDC-induced behavioral changes in first (F1) and second (F2) filial generations, using the model EDC bisphenol A (BPA). C57BL/6J dams were exposed to BPA from preconception until lactation through the diet at doses (10 μg/kg bw/d-lower dose or 10 mg/kg bw/d-upper dose) representative of human exposure levels. As adults, F1 male offspring exhibited increased depressive-like behavior, measured by the forced swim test, while females were unaffected. These behavioral changes were limited to the F1 generation and were not associated with altered maternal care. Transcriptome analysis by RNA-sequencing in F1 control and upper dose BPA-exposed adult male hippocampus revealed neurotransmitter systems as major pathways disrupted by developmental BPA exposure. High performance liquid chromatography demonstrated a male-specific reduction in hippocampal serotonin. Administration of the selective serotonin reuptake inhibitor fluoxetine (20 mg/kg bw) rescued the depressive-like phenotype in males exposed to lower, but not upper, dose BPA, suggesting distinct mechanisms of action for each exposure dose. Finally, high resolution mass spectrometry revealed reduced circulating levels of the neuroactive steroid dehydroepiandrosterone in BPA-exposed males, suggesting another potential mechanism underlying the depressive-like phenotype. Thus, behavioral changes associated with early life BPA exposure may be mediated by sex-specific disruptions in the serotonergic system and/or sex steroid biogenesis in male offspring.

Effects of perinatal exposure to bisphenol A on the intraprostatic levels of aromatase and 5α-reductase isozymes in juvenile rats

The impact of bisphenol A (BPA) on the prostate gland has taken center stage, with a special focus placed on understanding how BPA affects prostate physiopathology. In this study, we evaluated the ability of lower doses of BPA to induce alterations in 5α-R isozymes and aromatase, in the prostate of juvenile rats exposed during developmental stage. Gestating Wistar rats were treated s.c with either vehicle or BPA (2.4 and 10 μg/kg b.w./day) from gestational day 12 to parturition. Then, male pups were s.c treated from postnatal day 1 through day 21, when they were euthanized and qRT-PCR, western blot and hormone levels determination were performed. We found that BPA at dose of 2.4 and 10 μg/kg b.w./day significantly decreased the mRNA and protein levels of 5α-R2. However, neither 5α-R1 nor 5α-R3 was affected by this exposure. BPA at dose of 10 μg/kg b.w./day significantly increased the mRNA and protein levels of aromatase. BPA also decreased plasma levels of both testosterone and dihydrotestosterone and increased estradiol. These data lend support that low-dose BPA during fetal and neonatal prostate development interfere with in situ estrogen and androgen production in the prostate gland of juvenile rats through the enzymes aromatase and 5α-Reductase.

Chronic exposure to low dose of bisphenol A impacts on the first round of spermatogenesis via SIRT1 modulation

Spermatogenesis depends on endocrine, autocrine and paracrine communications along the hypothalamus-pituitary-gonad axis. Bisphenol A (BPA), an estrogen-mimic endocrine disrupting chemical, is an environmental contaminant used to manufacture polycarbonate plastics and epoxy resins with toxic effects for male reproduction. Here we investigated whether the chronic exposure to low BPA doses affects spermatogenesis through the modulation of SIRT1, a NAD+-dependent deacetylase involved in the progression of spermatogenesis, with outcomes on apoptosis, oxidative stress, metabolism and energy homeostasis. BPA exposure via placenta first, and lactation and drinking water later, affected the body weight gain in male offspring at 45 postnatal days and the first round of spermatogenesis, with impairment of blood testis barrier, reactive oxygen species production, DNA damage and decreased expression of SIRT1. The analysis of SIRT1 downstream molecular pathways revealed the increase of acetyl-p53Lys370, γH2AX foci, the decrease of oxidative stress defenses and the higher apoptotic rate in the testis of treated animals, with partial rescue at sex maturation. In conclusion, SIRT1 pathways disruption after BPA exposure can have serious consequences on the first round of spermatogenesis.

The Impact of Traditional Food and Lifestyle Behavior on Epigenetic Burden of Chronic Disease

Noncommunicable chronic diseases (NCCDs) are the leading causes of morbidity and mortality globally. The mismatch between present day diets and ancestral genome is suggested to contribute to the NCCDs burden, which is promoted by traditional risk factors like unhealthy diets, physical inactivity, alcohol and tobacco. However, epigenetic evidence now suggests that cumulatively inherited epigenetic modifications may have made humans more prone to the effects of present day lifestyle factors. Perinatal starvation was widespread in the 19th century. This together with more recent events like increasing consumption of western and low fiber diets, smoking, harmful use of alcohol, physical inactivity, and environmental pollutants may have programed the human epigenome for higher NCCDs risk. In this review, on the basis of available epigenetic data it is hypothesized that transgenerational effects of lifestyle factors may be contributing to the current global burden of NCCDs. Thus, there is a need to reconsider prevention strategies so that the subsequent generations will not have to pay for our sins and those of our ancestors.

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

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

Bisphenol A in culture media and plastic consumables used for ART

STUDY QUESTION

Do the embryo culture media and plastic materials used during assisted reproductive technology (ART) laboratory procedures expose embryos to bisphenol A (BPA)?

SUMMARY ANSWER

BPA was not detected in embryo culture media or protein supplements at concentrations above those encountered in normal patient serum and follicular fluids.

WHAT IS KNOWN ALREADY

BPA is strongly suspected of altering the epigenome during mammalian development. Medical devices have been shown to be a source of BPA exposure in adult and neonatal intensive care units.

STUDY DESIGN, SIZE, DURATION

An analytical study of ART culture media and plastic labware products was performed under conditions close to routine practice and if BPA was detected, tests were carried out under more stringent conditions.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Two single-step embryo culture media, two sequential media and three different protein supplements [a purified human serum albumin (HSA), a synthetic serum substitute, and a recombinant HSA] were tested for BPA. Thirty-three different plastic consumables, used from oocyte collection through to embryo transfer, were tested for their ability to leach BPA into their surrounding environment.BPA concentrations were measured according to a previously described liquid chromatography/mass spectrometry method. This method is linear over the calibration range from 0.5 to 100 ng/ml using a linear model weighted by 1/X² and validated in terms of selectivity, linearity, repeatability, reproducibility and limit of quantification (0.5 ng/ml).

MAIN RESULTS AND THE ROLE OF CHANCE

Neither the culture media nor the protein supplements were shown to contain detectable levels of BPA. None of the plastic materials leached BPA into the surrounding medium at levels higher than the upper limit detected previously in serum and follicular fluids in women (about 2 ng/ml). However, the plastic of the three tested strippers used for oocyte denudation/embryo handling did contain BPA. Two of these strippers are made with polycarbonate, a plastic whose synthesis is known to require BPA.

LIMITATIONS, REASONS FOR CAUTION

This study is limited to the ART media and materials tested here and using a BPA assay with a limit of quantification at 0.5 ng/ml. A minimum volume was required for testing, and one type of plastic labware could not be tested in conditions identical to those in routine use.

WIDER IMPLICATIONS OF THE FINDINGS

Although we demonstrated that some plastic materials used in ART contain BPA, under routine conditions none appear capable of leaching BPA at levels higher than those from maternal internal exposure. However, BPA is strongly suspected of altering the epigenome. Since important epigenetic modifications occur in the early embryonic stage, it is questionable whether plastics that contain BPA, polycarbonate in particular, should be used in the manufacture of plastic consumables for ART procedures.

STUDY FUNDING/COMPETING INTERESTS

This work was supported by a grant from the Agence de Biomédecine (AOR 2012) and by a grant from the French Ministry of Health (Clinical Research Hospital Program 2012; no.12-018-0560). The authors declared no competing interest.