Bisphenol A Exposure and Sperm ACHE Hydroxymethylation in Men

Adverse effects of bisphenol A and its analogues on male fertility: An epigenetic perspective

In recent years, there has been growing concern about the adverse effects of endocrine disrupting chemicals (EDCs) on male fertility. Epigenetic modification is critical for male germline development, and has been suggested as a potential mechanism for impaired fertility induced by EDCs. Bisphenol A (BPA) has been recognized as a typical EDC. BPA and its analogues, which are still widely used in various consumer products, have garnered increasing attention due to their reproductive toxicity and the potential to induce epigenetic alteration. This literature review provides an overview of studies investigating the adverse effects of bisphenol exposures on epigenetic modifications and male fertility. Existing studies provide evidence that exposure to bisphenols can lead to adverse effects on male fertility, including declined semen quality, altered reproductive hormone levels, and adverse reproductive outcomes. Epigenetic patterns, including DNA methylation, histone modification, and non-coding RNA expression, can be altered by bisphenol exposures. Transgenerational effects, which influence the fertility and epigenetic patterns of unexposed generations, have also been identified. However, the magnitude and direction of certain outcomes varied across different studies. Investigations into the dynamics of histopathological and epigenetic alterations associated with bisphenol exposures during developmental stages can enhance the understanding of the epigenetic effects of bisphenols, the implication of epigenetic alteration on male fertility, and the health of successive generation.

The adverse role of endocrine disrupting chemicals in the reproductive system

Reproductive system diseases pose prominent threats to human physical and mental well-being. Besides being influenced by genetic material regulation and changes in lifestyle, the occurrence of these diseases is closely connected to exposure to harmful substances in the environment. Endocrine disrupting chemicals (EDCs), characterized by hormone-like effects, have a wide range of influences on the reproductive system. EDCs are ubiquitous in the natural environment and are present in a wide range of industrial and everyday products. Currently, thousands of chemicals have been reported to exhibit endocrine effects, and this number is likely to increase as the testing for potential EDCs has not been consistently required, and obtaining data has been limited, partly due to the long latency of many diseases. The ability to avoid exposure to EDCs, especially those of artificially synthesized origin, is increasingly challenging. While EDCs can be divided into persistent and non-persistent depending on their degree of degradation, due to the recent uptick in research studies in this area, we have chosen to focus on the research pertaining to the detrimental effects on reproductive health of exposure to several EDCs that are widely encountered in daily life over the past six years, specifically bisphenol A (BPA), phthalates (PAEs), polychlorinated biphenyls (PCBs), parabens, pesticides, heavy metals, and so on. By focusing on the impact of EDCs on the hypothalamic-pituitary-gonadal (HPG) axis, which leads to the occurrence and development of reproductive system diseases, this review aims to provide new insights into the molecular mechanisms of EDCs' damage to human health and to encourage further in-depth research to clarify the potentially harmful effects of EDC exposure through various other mechanisms. Ultimately, it offers a scientific basis to enhance EDCs risk management, an endeavor of significant scientific and societal importance for safeguarding reproductive health.

The Effects of Bisphenol A on Human Male Infertility: A Review of Current Epidemiological Studies

Endocrine disruptor chemicals (EDCs) can have a harmful effect on the human body's endocrine system and thus adversely affect the development, reproduction, neurological, cardiovascular, and immune systems and metabolism in humans and wildlife. According to the World Health Organization, EDCs are mostly man-made and found ubiquitously in our daily lives, notably in pesticides, metals, and additives or contaminants in food and personal care products. Human exposure occurs through ingestion, inhalation, and dermal contact. Bisphenol A (BPA) is a proven EDC capable of mimicking or blocking receptors and altering hormone concentrations and metabolism. Although consumed in low doses, it can stimulate cellular responses and affect the body's functions. In humans, exposure to BPA has been correlated with the onset or development of several diseases. This literature review aimed to verify the effects of BPA on human male infertility using the most recently published literature. Thus, this review allowed us to conclude that this compound seems to have harmful effects on human male fertility, causing changes in hormonal and semen characteristics. However, these conclusions lack more robust and reproducible scientific studies. Even so, and since male infertility prevalence is increasing, preventive measures must be taken to ensure male fertility.

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.

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.

Abnormal histone replacement following BPA exposure affects spermatogenesis and fertility sequentially

Bisphenol A (BPA) is an endocrine-disrupting chemical widely distributed in the environment. Its exposure has been linked to male infertility in animals and humans due to its ability to induce epigenetic modification. Despite extensive research confirming the impact of BPA on epigenetic regulation, fundamental concerns about how BPA causes epigenetic changes and the underlying mechanism of BPA on the male reproductive system remain unresolved. Therefore, we sought to investigate the effects of BPA on epigenetic regulation and the histone-to-protamine (PRM) transition, which is fundamental process for male fertility in testes and spermatozoa by exposing male mice to BPA for 6 weeks while giving the mice in the control group corn oil by oral gavage. Our results demonstrated that the mRNA levels of the histone family and PRMs were significantly altered by BPA exposure in testes and spermatozoa. Subsequently, core histone proteins, the PRM1/PRM2 ratio, directly linked to male fertility, and transition proteins were significantly reduced. Furthermore, we discovered that BPA significantly caused abnormal histone-to-protamine replacement during spermiogenesis by increased histone variants-related to histone-to-PRM transition. The levels of histone H3 modification in the testes and DNA methylation in spermatozoa were significantly increased. Consequently, sperm concentration/motility/hyperactivation, fertilization, and early embryonic development were adversely affected as a consequence of altered signaling proteins following BPA exposure. To our knowledge, this is the first study to indicate that BPA exposure influences the histone-to-PRM transition via altering epigenetic modification and eventually causing reduced male fertility.

Association of occupations with decreased semen quality in eastern China: a cross-sectional study of 12 301 semen donors

OBJECTIVES

This study aims to examine the association between occupational factors and semen quality in semen donors in eastern China.

METHODS

We recruited 12 301 semen donors from 2006 to 2020 as the studying population. A self-designed questionnaire was applied for collecting lifestyle and work style information. Semen samples were analysed according to WHO guidelines. A crude and adjusted linear regression model was used to analyse the association between occupational factors and semen quality.

RESULTS

College students accounted for 36.2% of all semen donors. The majority (81.3%) of semen donors were between 18 year and 30 years. Soldiers or the police had the highest semen volume (the median value=3.8 mL), however, they had the lowest sperm concentration (53.6×10⁶/ml) and sperm motility (45.5%). Workers in finance or insurance had an elevated risk of low semen volume, sperm concentration and total sperm count (OR=1.43, 1.57 and 1.98, respectively). Unemployed men had a high risk of low sperm concentration and low total sperm count (OR=1.84 and 1.58, respectively). Working in the information technology industry had a deleterious effect on the progressive motility of sperm (OR=1.27, 95% CI 1.03 to 1.57).

CONCLUSION

Our study indicated that sedentary work style and intensive sports in certain professions might be associated with decreased semen quality. We reported evidence of becoming unemployed on the damage to semen quality. Hence, we advocate a healthy work style to improve semen quality in eastern China.

From Oxidative Stress to Male Infertility: Review of the Associations of Endocrine-Disrupting Chemicals (Bisphenols, Phthalates, and Parabens) with Human Semen Quality

Exposure to endocrine-disrupting chemicals (EDCs) may result in oxidative stress and endocrine system disturbance, which can have an impact on human reproduction and development. In male reproductive health, EDCs have been related to impaired reproductive function and male infertility, altered fetal development, and testicular germ-cell, prostate, and breast cancers. We conducted an electronic search using PubMed on endocrine disruptors related to oxidative stress and male infertility, and evaluated their association with endocrine-disrupting chemicals (bisphenols, phthalates, and parabens) in 25 articles. Higher levels of urinary bisphenols showed correlation with impaired semen quality and increased DNA damage. Considering phthalates and their metabolites, all studies found a positive association between urinary levels of phthalates and at least one semen parameter indicative of low semen quality; some studies also revealed sperm DNA damage. The studies on parabens less often revealed correlation of urinary parabens concentrations with a decrease in sperm count, as well as motility and DNA damage. Moreover, EDCs can elevate ROS production and lipid peroxidation, increase apoptosis, induce epigenetic modifications, and change the Y:X sperm chromosome ratio and sperm protein composition. Our review revealed detrimental effects of EDCs on semen quality and sperm DNA integrity-especially in BPA and phthalates, but also in parabens.

Effects of bisphenol A and estradiol in adult rat testis after prepubertal and pubertal exposure

Over the past few decades, male fertility has been decreasing worldwide. Many studies attribute this outcome to endocrine disruptors exposure such as bisphenol A (BPA), which is a chemical compound used in plastics synthesis and exhibiting estrogenic activity. In order to assess how the window of exposure modulates the effects of BPA on the testis, prepubertal (15 dpp to 30 dpp) and pubertal (60 dpp to 75 dpp) male Sprague-Dawley rats were exposed to BPA (50 µg/kg bw/day), 17-β-estradiol (E2) (20 µg/kg bw/day) as a positive control, or to a combination of these compounds. For both periods of exposure, the rats were sacrificed and their testes were collected at 75 dpp. The histological analysis and the quantification of the gene expression of testis cell markers by RT-qPCR confirmed the complete spermatogenesis in all groups for both periods of exposure. However, our results suggest a deleterious effect of BPA on the blood-testis barrier in adults after pubertal exposure as BPA and BPA+E2 treatments induced a decrease in caveolin-1 and connexin-43 gene expression; which are proteins of the junctional complexes. As none of these effects were found after a prepubertal exposure, these results suggested the reversibility of BPA's effects. Caution must be taken when transposing this finding to humans and further studies are needed in this regard. However, from a regulatory perspective, this study emphasizes the importance of taking into account different periods of exposure, as they present different sensitivities to BPA exposure.

Lipidomic biomarkers: Potential mediators of associations between urinary bisphenol A exposure and colorectal cancer

Previous research reported associations between bisphenol A (BPA) exposure and some malignant tumor incidences, yet the underlying mechanism remains largely uncertain. This investigation was aimed to explore the association of BPA exposure burden with colorectal cancer (CRC) and the role of tumor tissue lipid metabolism in the associations between BPA and CRC using lipidomic approach. Urinary BPA levels in CRC cases were significantly higher than those in controls (P value < 0.05). BPA was positively correlated with all three serum CRC biomarkers, with an estimated odds ratio (OR) of 4.45 (95% confidence interval (95% CI): [1.31, 15.14]) between the highest and lowest tertiles of exposure. Lipidomic screening of tumor samples suggested significant perturbation in the glycerophospholipid metabolism pathway, of which phosphatidylcholine (PC 34:0), phosphatidylcholine (PC 37:1), phosphatidylethanolamine (PE 34:2), triacylglycerol (TG 56:4) demonstrated mediation contribution of 21.9%, 18.7%, 18.4% and 27.39%, respectively, in the association between BPA exposure and CRC. Our work provides novel findings that cancer tissue metabolites may be playing vital mediating roles in the associations between BPA exposure burden and CRC risk. These findings contribute to better understanding of the etiology of CRC induced by environmental stressors.

Global trend of clinical biomarkers of health and disease during the period (1913–2021): systematic review and bibliometric analysis

Background

The literature review provides a concise and detailed description of the available and published data on the investigated research problem. The study summarizes findings over the last 100 years regarding clinical biomarkers during health and disease. Research expanded to present the range of enzyme acetylcholinesterase in human blood utilizing diverse methodology during the 1949–2021 year.

Main body

Data analysis includes program SPSS v23.0, frequency, percentage, numbers and graphical presentation of results. Information from the papers gathers in Microsoft Excel 2007 and contains information: study type, journal, publisher, year of publication, continent, the health status of respondents, biomarkers, number and age of participants, types of samples, methodology, goals and conclusions. Data collection includes electronic databases, the National Center for Biotechnology Information and Google Scholar, with several inclusion criteria: (1) anthropometry (2) urine (3) blood in the healthy and diseased population parameters during different physiological states of the organism. The initial number of collected and analyzed papers is 1900. The final analysis included 982 studies out of 1454 selected papers. After the selection process, 67.53% remains useful. The range of enzyme acetylcholinesterase included 107 publications.

Conclusion

The number of published scientific papers has been increasing over the years. Little practical information in scientific and clinical practice exists. There is an urgent need for concise highlighting of literature key arguments and ideas. Results apply to a specialized area of research.

Bisphenol A Induces Accelerated Cell Aging in Murine Endothelium

Bisphenol A (BPA) is a widespread endocrine disruptor affecting many organs and systems. Previous work in our laboratory demonstrated that BPA could induce death due to necroptosis in murine aortic endothelial cells (MAECs). This work aims to evaluate the possible involvement of BPA-induced senescence mechanisms in endothelial cells. The β-Gal assays showed interesting differences in cell senescence at relatively low doses (100 nM and 5 µM). Western blots confirmed that proteins involved in senescence mechanisms, p16 and p21, were overexpressed in the presence of BPA. In addition, the UPR (unfolding protein response) system, which is part of the senescent phenotype, was also explored by Western blot and qPCR, confirming the involvement of the PERK-ATF4-CHOP pathway (related to pathological processes). The endothelium of mice treated with BPA showed an evident increase in the expression of the proteins p16, p21, and CHOP, confirming the results observed in cells. Our results demonstrate that oxidative stress induced by BPA leads to UPR activation and senescence since pretreatment with N-acetylcysteine (NAC) in BPA-treated cells reduced the percentage of senescent cells prevented the overexpression of proteins related to BPA-induced senescence and reduced the activation of the UPR system. The results suggest that BPA participates actively in accelerated cell aging mechanisms, affecting the vascular endothelium and promoting cardiovascular diseases.

Genome-wide association and genomic prediction for scrotal circumference in Hereford and Braford bulls

Scrotal circumference (SC) is widely used as a selection criterion for bulls in breeding programs, since it is easily assessed and correlated with several desirable reproductive traits. The objectives of this study were: to perform a genome-wide association study (GWAS) to identify genomic regions associated with SC adjusted for age (SCa) and for both age and weight (SCaw); to select Tag SNPs from GWAS to construct low-density panel for genomic prediction; and to compare the prediction accuracy of the SC through different methods for Braford and Hereford bulls from the same genetic breeding program. Data of SC from 18,172 bulls (30.4 ± 3.7 cm) and of genotypes from 131 sires and 3,545 animals were used. From GWAS, the top 1% of 1-Mb windows were observed on chromosome (BTA) 2, 20, 7, 8, 15, 3, 16, 27, 6 and 8 for SCa and on BTA 8, 15, 16, 21, 19, 2, 6, 5 and 10 for SCaw, representing 17.4% and 18.8% of the additive genetic variance of SCa and SCaw, respectively. The MeSH analysis was able to translate genomic information providing biological meanings of more specific gene functions related to the SCa and SCaw. The genomic enhancement methods, especially single step GBLUP, that combined phenotype and pedigree data with direct genomic values generated gains in accuracy in relation to pedigree BLUP, suggesting that genomic predictions should be applied to improve genetic gain and to narrow the generation interval compared to traditional methods. The proposed Tag-SNP panels may be useful for lower-cost commercial genomic prediction applications in the future, when the number of bulls in the reference population increases for SC in Hereford and Braford breeds.

The role of epigenetics in the reproductive toxicity of environmental endocrine disruptors

Environmental endocrine disruptors (EEDs) seriously endanger human health by interfering with the normal function of reproductive systems. In males, EEDs can affect sperm formation and semen quality as well spermatogenesis, ultimately reducing fertility. In females, EEDs can affect uterine development and the expression levels of reproduction-related genes, ultimately reducing female fertility and the normal development of the fetus. There are a large number of putative mechanisms by which EEDs can induce reproductive toxicity, and many studies have shown the involvement of epigenetics. In this review, we summarize the role of DNA methylation, noncoding RNAs, genomic imprinting, chromatin remodeling and histone modification in the reproductive toxicity of EEDs.

Environmental Epigenetics and Genome Flexibility: Focus on 5-Hydroxymethylcytosine

Convincing evidence accumulated over the last decades demonstrates the crucial role of epigenetic modifications for mammalian genome regulation and its flexibility. DNA methylation and demethylation is a key mechanism of genome programming and reprogramming. During ontogenesis, the DNA methylome undergoes both programmed changes and those induced by environmental and endogenous factors. The former enable accurate activation of developmental programs; the latter drive epigenetic responses to factors that directly or indirectly affect epigenetic biochemistry leading to alterations in genome regulation and mediating organism response to environmental transformations. Adverse environmental exposure can induce aberrant DNA methylation changes conducive to genetic dysfunction and, eventually, various pathologies. In recent years, evidence was derived that apart from 5-methylcytosine, the DNA methylation/demethylation cycle includes three other oxidative derivatives of cytosine-5-hydroxymethylcytosine (5hmC), 5-formylcytosine, and 5-carboxylcytosine. 5hmC is a predominantly stable form and serves as both an intermediate product of active DNA demethylation and an essential hallmark of epigenetic gene regulation. This makes 5hmC a potential contributor to epigenetically mediated responses to environmental factors. In this state-of-the-art review, we consolidate the latest findings on environmentally induced adverse effects on 5hmC patterns in mammalian genomes. Types of environmental exposure under consideration include hypnotic drugs and medicines (i.e., phenobarbital, diethylstilbestrol, cocaine, methamphetamine, ethanol, dimethyl sulfoxide), as well as anthropogenic pollutants (i.e., heavy metals, particulate air pollution, bisphenol A, hydroquinone, and pentachlorophenol metabolites). We put a special focus on the discussion of molecular mechanisms underlying environmentally induced alterations in DNA hydroxymethylation patterns and their impact on genetic dysfunction. We conclude that DNA hydroxymethylation is a sensitive biosensor for many harmful environmental factors each of which specifically targets 5hmC in different organs, cell types, and DNA sequences and induces its changes through a specific metabolic pathway. The associated transcriptional changes suggest that environmentally induced 5hmC alterations play a role in epigenetically mediated genome flexibility. We believe that knowledge accumulated in this review together with further studies will provide a solid basis for new approaches to epigenetic therapy and chemoprevention of environmentally induced epigenetic toxicity involving 5hmC patterns.

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.

Bisphenols as a Legacy Pollutant, and Their Effects on Organ Vulnerability

Bisphenols are widely used in the synthesis of polycarbonate plastics, epoxy resins, and thermal paper, which are used in manufacturing items of daily use. Packaged foods and drinks are the main sources of exposure to bisphenols. These chemicals affect humans and animals by disrupting the estrogen, androgen, progesterone, thyroid, and aryl hydrocarbon receptor functions. Bisphenols exert numerous harmful effects because of their interaction with receptors, reactive oxygen species (ROS) formation, lipid peroxidation, mitochondrial dysfunction, and cell signal alterations. Both cohort and case-control studies have determined an association between bisphenol exposure and increased risk of cardiovascular diseases, neurological disorders, reproductive abnormalities, obesity, and diabetes. Prenatal exposure to bisphenols results in developmental disorders in animals. These chemicals also affect the immune cells and play a significant role in initiating the inflammatory response. Exposure to bisphenols exhibit age, gender, and dose-dependent effects. Even at low concentrations, bisphenols exert toxicity, and hence deserve a critical assessment of their uses. Since bisphenols have a global influence on human health, the need to discover the underlying pathways involved in all disease conditions is essential. Furthermore, it is important to promote the use of alternatives for bisphenols, thereby restricting their uses.