Effects of Low-Dose Bisphenol A on DNA Damage and Proliferation of Breast Cells: The Role of c-Myc

Bisphenol A drives nuclear factor-kappa B signaling activation and enhanced motility in non-transformed breast cells

Bisphenol A (BPA) is a chemical compound found in a wide range of everyday consumer products, resulting in human exposure. BPA has been described as an endocrine disruptor, affecting different systems of the human body. Notably, nanomolar levels of BPA have been detected in human matrices, including plasma and milk. BPA exposure has been associated with the development of breast cancer, and the increase in breast cancer incidence prompted us to investigate the effects of BPA in MCF10A, a model of non-transformed mammary epithelium. Cells were treated with 10 nM BPA for 24 h to capture early molecular alterations preceding phenotypic transitions. Comprehensive transcriptomic analyses were conducted to identify differentially expressed genes and enriched signaling pathways. Subsequent validations included assessment of cytokine release, protein expression, immunofluorescence for subcellular localization of Nuclear Factor-Kappa B (NF-κB), and evaluation of actin cytoskeletal organization. Transcriptome analysis revealed enrichment in interleukin signaling and activation of the NF-κB pathway following BPA exposure. Functional assays demonstrated that BPA treatment enhanced cell motility, accompanied by increased phosphorylation of NF-κB. Inhibition of NF-κB effectively mitigated BPA-induced effects, including augmented cell motility, nuclear translocation of NF-κB, and cytoskeletal rearrangements. Notably, inhibition of the Mitogen-Activated Protein Kinase (MAPK) pathway, and to a lesser extent of the AKT pathway, counteracted BPA-induced NF-κB activation and the associated increase in cell motility. In conclusion, we show that nanomolar concentration of BPA induces significant changes in the molecular setting and behaviour of non-tranformed breast cells, activating NF-κB signalling that in turn controls inflammation, cell cycle, proliferation and cell motility. Our findings indicate that nanomolar concentrations of BPA can induce significant molecular and behavioral changes in non-transformed breast epithelial cells. These results contribute to a deeper understanding of how environmental pollutants like BPA may perturb breast epithelial cell function and potentially contribute to carcinogenesis.

Evaluation of effects of bisphenol analogs AF, S, and F on viability, proliferation, production of selected cancer-related factors, and expression of selected transcripts in Caov-3 human ovarian epithelial cell line

Bisphenol A (BPA) has been a substantial additive in plastics until the reports on its adverse effects have led to its restrictions and replacement. Monitoring studies document the increasing occurrence of bisphenol analogs, however, data on their effects and risks is still insufficient. Based on the indications that BPA might contribute to ovarian cancer pathogenesis, we examined effects of the analogs AF (BPAF), S (BPS) and F (BPF) (10-9-10-4 M) on the Caov-3 epithelial cancer cells, including the impact on cell viability, proliferation, oxidative stress, and production and expression of several factors and genes related to ovarian cancer. At environmentally relevant doses, bisphenols did not exert significant effects. At the highest concentration, BPAF caused varied alterations, including decreased cell viability and proliferation, caspase activation, down-regulation of PCNA and BIRC5, elevation of IL8, VEGFA, MYC, PTGS2 and ABCB1 expressions. Only BPA (10-4 M) increased IL-6, IL-8 and VEGFA output by the Caov-3 cells. Each bisphenol induced generation of reactive oxygen species and decreased superoxide dismutase activity at the highest concentration. Although the effects were observed only in the supraphysiological doses, the results indicate that certain bisphenol analogs might affect several ovarian cancer cell characteristics and merit further investigation.

Novel insights into the role of bisphenol A (BPA) in genomic instability

Bisphenol A (BPA) is a phenolic chemical that has been used for over 50 years in the manufacturing of polycarbonate and polyvinyl chloride plastics, and it is one of the highest volume chemicals produced worldwide. Because BPA can bind to and activate estrogen receptors, studies have mainly focused on the effect of BPA in disrupting the human endocrine and reproductive systems. However, BPA also plays a role in promoting genomic instability and has been associated with initiating carcinogenesis. For example, it has been recently shown that exposure to BPA promotes the formation of single stranded DNA gaps, which may be associated with increased genomic instability. In this review, we outline the mechanisms by which BPA works to promote genomic instability including chromosomal instability, DNA adduct formation, ROS production, and estrogen receptor (ER) activation. Moreover, we define the ways in which BPA promotes both carcinogenesis and resistance to chemotherapy, and we provide critical insights into future directions and outstanding questions in the field.

Bisphenol A and bisphenol AF co-exposure induced apoptosis of human ovarian granulosa cells via mitochondrial dysfunction

Bisphenol A (BPA) is a synthetic chemical primarily utilized in the manufacturing of polycarbonate plastics and epoxy resins that are present in various consumer products. While the BPA impacts on female reproductive toxicity have been widely investigated, very little is currently identified about the mixed toxicity of BPA and bisphenol AF (BPAF), another common BPA derivative that is used in many industrial applications. In this study, we assessed the effect of co-exposure of BPA (30 and 50 μM) and BPAF (3 and 5 μM) on mitochondrial dysfunction in human granulosa cells (KGN cells) for 24 h. Our results exhibited that high-concentration bisphenol individual or their mixture exposure of KGN cells induced significant mitochondrial dysfunction by reducing mitochondrial mass, reducing ATP production, and damaging the mitochondrial respiratory chain. In addition, we found that the combination of BPA and BPAF significantly induced mitochondrial stress by increasing calcium levels and the production of ROS in mitochondria. Mitochondrial stress induced by BPA and BPAF was determined to be a mechanism that promoted cell apoptosis after pretreating the cells with the mitochondrial-targeted antioxidant and the calcium chelator. Our results provide novel evidence of the cytotoxicity of mixtures of different bisphenol compounds.

Application of the Key Characteristics of Carcinogens to Bisphenol A

The ten key characteristics (KCs) of carcinogens are based on characteristics of known human carcinogens and encompass many types of endpoints. We propose that an objective review of the large amount of cancer mechanistic evidence for the chemical bisphenol A (BPA) can be achieved through use of these KCs. A search on metabolic and mechanistic data relevant to the carcinogenicity of BPA was conducted and web-based software tools were used to screen and organize the results. We applied the KCs to systematically identify, organize, and summarize mechanistic information for BPA, and to bring relevant carcinogenic mechanisms into focus. For some KCs with very large data sets, we utilized reviews focused on specific endpoints. Over 3000 studies for BPA from various data streams (exposed humans, animals, in vitro and cell-free systems) were identified. Mechanistic data relevant to each of the ten KCs were identified, with receptor-mediated effects, epigenetic alterations, oxidative stress, and cell proliferation being especially data rich. Reactive and bioactive metabolites are also associated with a number of KCs. This review demonstrates how the KCs can be applied to evaluate mechanistic data, especially for data-rich chemicals. While individual entities may have different approaches for the incorporation of mechanistic data in cancer hazard identification, the KCs provide a practical framework for conducting an objective examination of the available mechanistic data without a priori assumptions on mode of action. This analysis of the mechanistic data available for BPA suggests multiple and inter-connected mechanisms through which this chemical can act.

Transcriptomic Integration Analyses Uncover Common Bisphenol A Effects Across Species and Tissues Primarily Mediated by Disruption of JUN/FOS, EGFR, ER, PPARG, and P53 Pathways

Bisphenol A (BPA) is a common endocrine disruptor widely used in the production of electronic, sports, and medical equipment, as well as consumer products like milk bottles, dental sealants, and thermal paper. Despite its widespread use, current assessments of BPA exposure risks remain limited due to the lack of comprehensive cross-species comparative analyses. To address this gap, we conducted a study aimed at identifying genes and fundamental molecular processes consistently affected by BPA in various species and tissues, employing an effective data integration method and bioinformatic analyses. Our findings revealed that exposure to BPA led to significant changes in processes like lipid metabolism, proliferation, and apoptosis in the tissues/cells of mammals, fish, and nematodes. These processes were found to be commonly affected in adipose, liver, mammary, uterus, testes, and ovary tissues. Additionally, through an in-depth analysis of signaling pathways influenced by BPA in different species and tissues, we observed that the JUN/FOS, EGFR, ER, PPARG, and P53 pathways, along with their downstream key transcription factors and kinases, were all impacted by BPA. Our study provides compelling evidence that BPA indeed induces similar toxic effects across different species and tissues. Furthermore, our investigation sheds light on the underlying molecular mechanisms responsible for these toxic effects. By uncovering these mechanisms, we gain valuable insights into the potential health implications associated with BPA exposure, highlighting the importance of comprehensive assessments and awareness of this widespread endocrine disruptor.

Worldwide risk assessment of phthalates and bisphenol A in humans: The need for updating guidelines

Phthalates and bisphenol A (BPA) are compounds widely used as raw materials in the production of plastics, making them ubiquitous in our daily lives. This results in widespread human exposure and human health hazards. Although efforts have been conducted to evaluate the risk of these compounds in diverse regions around the world, data scattering may mask important trends that could be useful for updating current guidelines and regulations. This study offers a comprehensive global assessment of human exposure levels to these chemicals, considering dietary and nondietary ingestion, and evaluates the associated risk. Overall, the exposure daily intake (EDI) values of phthalates and BPA reported worldwide ranged from 1.11 × 10-7 to 3 700 µg kg bw-1 d-1 and from 3.00 × 10-5 to 6.56 µg kg bw-1 d-1, respectively. Nevertheless, the dose-additive effect of phthalates has been shown to increase the EDI up to 5 100 µg kg bw-1 d-1, representing a high risk in terms of noncarcinogenic (HQ) and carcinogenic (CR) effects. The worldwide HQ values of phthalates and BPA ranged from 2.25 × 10-7 to 3.66 and from 2.74 × 10-7 to 9.72 × 10-2, respectively. Meanwhile, a significant number of studies exhibit high CR values for benzyl butyl phthalate (BBP) and di(2-ethylhexyl) phthalate (DEHP). Moreover, DEHP has shown the highest maximum mean CR values for humans in numerous studies, up to 179-fold higher than BBP. Despite mounting evidence of the harmful effects of these chemicals at low-dose exposure on animals and humans, most regulations have not been updated. Thus, this article emphasizes the need for updating guidelines and public policies considering compelling evidence for the adverse effects of low-dose exposure, and it cautions against the use of alternative plasticizers as substitutes for phthalates and BPA because of the significant gaps in their safety.

Evaluation of biotechnological processing through solid-state fermentation of oilseed cakes on extracts bioactive potential

Oilseed cakes (OC) are natural sources of lignocellulosic biomass, produced every year in large amounts. In addition to their main applications as animal feed, plant or soil fertilizer, and compost, they present enormous potential for being used in biotechnological processes for the obtainment and extraction of valuable bioactive compounds. This work evaluated the effect of solid-state fermentation on the bioactive properties of extracts obtained from the bioprocessing of OC and evaluated the effect of solvents on the recovery of compounds with higher bioactive potential. A general decrease of EC50 values was observed for fermented extracts obtained using a mixture of water/methanol (1:1) as extraction solvent. A decrease in the minimum inhibitory concentration was observed for fermented water extracts compared to non-fermented. Additionally, growth inhibition of Listeria monocytogenes was observed when using aqueous methanolic fermented extracts. These extracts also exhibited a higher percentage of growth reduction against phytopathogenic fungi, and some extracts exhibited increased protection against genotoxic agents such as camptothecin and bisphenol A. It was demonstrated that bioprocessing of OC through SSF is an effective approach to obtaining valuable compounds with bioactive properties for use in the food, pharmaceutical or cosmetic industries.

An integrated automatic lab-in-syringe sol-gel coated foam microextraction platform as a front-end to high performance liquid chromatography for the migration studies of bisphenol A

The proof-of-concept of an integrated automatic foam microextraction lab-in-syringe (FME-LIS) platform coupled to high performance liquid chromatography is presented. Three different sol-gel coated foams were synthesized, characterized, and conveniently packed inside the glass barrel of the LIS syringe pump, as an alternative approach for sample preparation, preconcentration and separation. The proposed system efficiently combines the inherent benefits of lab-in-syringe technique, the good features of sol-gel sorbents, the versatile nature of foams/sponges, as well as the advantages of automatic systems. Bisphenol A (BPA) was used as model analyte, due to the increasing concern for the migration of this compound from household containers. The main parameters that affect the extraction performance of the system were optimized and the proposed method was validated. The limit of detection for BPA were 0.5 and 2.9 μg L^-1, for a sample volume of 50 mL and 10 mL, respectively. The intra-day precision was <4.7% and the inter-day precision was <5.1% in all cases. The performance of the proposed methodology was evaluated for the migration studies of BPA using different food simulants, as well as for the analysis of drinking water. Good method applicability was observed based on the relative recovery studies (93-103%).

High-content analysis of testicular toxicity of BPA and its selected analogs in mouse spermatogonial, Sertoli cells, and Leydig cells revealed BPAF induced unique multinucleation phenotype associated with the increased DNA synthesis

Bisphenol A is an endocrine disruptor that has been shown to have testicular toxicity in animal models. Its structural analog, including bisphenol S (BPS), bisphenol AF (BPAF), and tetrabromobisphenol A (TBBPA) have been introduced to the market as BPA alternatives. Previously, we developed high-content analysis (HCA) assays and applied machine learning to compare the testicular toxicity of BPA and its analogs in spermatogonial cells and testicular cell co-culture models. There are diverse cell populations in the testis to support spermatogenesis, but their cell type-specific toxicities are still not clear. The purpose of this study is to examine the selective toxicity of BPA, BPS), BPAF, and TBBPA on these testicular cells, including Sertoli cells, Leydig cells, and spermatogonia cells. We developed a high-content image-based single-cell analysis and measured a broad spectrum of adverse endpoints related to the development of reproductive toxicology, including cell number, nuclear morphology, DNA synthesis, cell cycle progression, early DNA damage response, cytoskeleton structure, DNA methylation status, and autophagy. We introduced an HCA index and spectrum to reveal multiple HCA parameters and observed distinct toxicity profiling of BPA and its analogs among three testicular types. The HCA spectrum shows the dynamic, chemical-specific, dose-dependent changes of each HCA parameter. Each chemical displayed a unique dose-dependent profile within each type of cell. All three types of cells showed the highest response to BPAF at 10 μM across all endpoints measured. BPAF targeted spermatogonial cell (C18) more significantly at 5 μM. BPS more likely targeted Sertoli cell (TM4) and Leydig cell (TM3) and less at spermatogonia cells. TBBPA targeted spermatogonia, Sertoli cells, and less at TM3 cells. BPA is mainly targeted at TM4, followed by TM3 cells, and less at spermatogonial cells. Most importantly, we observed that BPAF induced a dose-dependent increase in spermatogonia cells, not in Sertoli and Leydig cells. In summary, our current HCA assays revealed the cell-type-specific toxicities of BPA and its analogs in different testicular cells. Multinucleation induced by BPAF, along with increased DNA damage and synthesis at low doses, could possibly have a profound long-term effect on reproductive systems.

Toxicity overview of endocrine disrupting chemicals interacting in vitro with the oestrogen receptor

The oestrogen receptor (ER) from the nuclear receptor family is involved in different physiological processes, which can be affected by multiple xenobiotics. Some of these compounds, such as bisphenols, pesticides, and phthalates, are widespread as consequence of human activities and are commonly present also in human organism. Xenobiotics able to interact with ER and trigger a hormone-like response, are known as endocrine disruptors. In this review, we aim to summarize the available knowledge on products derived from human industrial activity and other xenobiotics reported to interact with ER. ER-disrupting chemicals behave differently towards oestrogen-dependent cell lines than endogenous oestradiol. In low concentrations, they stimulate proliferation, whereas at higher concentrations, are toxic to cells. In addition, most of the knowledge on the topic is based on individual compound testing, and only a few studies assess xenobiotic combinations, which better resemble real circumstances. Confirmation from in vivo models is lacking also.

Re-evaluation of the risks to public health related to the presence of bisphenol A (BPA) in foodstuffs

In 2015, EFSA established a temporary tolerable daily intake (t-TDI) for BPA of 4 μg/kg body weight (bw) per day. In 2016, the European Commission mandated EFSA to re-evaluate the risks to public health from the presence of BPA in foodstuffs and to establish a tolerable daily intake (TDI). For this re-evaluation, a pre-established protocol was used that had undergone public consultation. The CEP Panel concluded that it is Unlikely to Very Unlikely that BPA presents a genotoxic hazard through a direct mechanism. Taking into consideration the evidence from animal data and support from human observational studies, the immune system was identified as most sensitive to BPA exposure. An effect on Th17 cells in mice was identified as the critical effect; these cells are pivotal in cellular immune mechanisms and involved in the development of inflammatory conditions, including autoimmunity and lung inflammation. A reference point (RP) of 8.2 ng/kg bw per day, expressed as human equivalent dose, was identified for the critical effect. Uncertainty analysis assessed a probability of 57-73% that the lowest estimated Benchmark Dose (BMD) for other health effects was below the RP based on Th17 cells. In view of this, the CEP Panel judged that an additional uncertainty factor (UF) of 2 was needed for establishing the TDI. Applying an overall UF of 50 to the RP, a TDI of 0.2 ng BPA/kg bw per day was established. Comparison of this TDI with the dietary exposure estimates from the 2015 EFSA opinion showed that both the mean and the 95th percentile dietary exposures in all age groups exceeded the TDI by two to three orders of magnitude. Even considering the uncertainty in the exposure assessment, the exceedance being so large, the CEP Panel concluded that there is a health concern from dietary BPA exposure.

Lysosome-related exosome secretion mediated by miR-26b / Rab31 pathway was associated with the proliferation and migration of MCF-7 cells treated with BPA

Bisphenol A (BPA), one of the typical environmental endocrine disruptors (EEDs), can promote the proliferation and migration of cancer cells, but the mechanism of which remains largely unclear. Exosome secretion plays an important role in the stress response of cells to environmental stimuli. This study was designed to explore whether exosome secretion was involved in the toxic effect of BPA on the proliferation and migration of MCF-7 cells, and the related mechanism. Our data shows that the IC₅₀ value of MCF-7 exposure to BPA was about 65.82 µM. The exposure of MCF-7 to 10 µM BPA resulted in a decreased miR-26b expression and the activation of miR-26b/Rab-31 pathway, consequently, the number and activity of lysosomes decreased, the secretion of exosomes increased, cell proliferation and migration were enhanced obviously. Interestingly, miR-26b mimic up-regulated the number and activity of lysosomes via miR-26b/miR-31 pathway, exosome secretion was down-regulated, cell proliferation and migration decreased. Further, when GW4869 was used to directly inhibit the exosome secretion of MCF-7 treated with BPA, their proliferation and migration were down-regulated. Herein, we concluded that the stimulating effect of BPA on the proliferation and migration of MCF-7 cells was associated with the lysosome - related exosome secretion via miR-26b / Rab31 pathway.

In vitro and in silico assessment of GPER-dependent neurocytotoxicity of emerging bisphenols

To rapidly assess the toxicity of bisphenols (BPs) via the activation of G protein-coupled estrogen receptor (GPER), eight BPs action on GPER were evaluated by molecular docking and molecular dynamics (MD) simulation and then confirmed with IMR-32 cells. The target BPs significantly promoted the production of reactive oxygen species (ROS), reduced cell viability, activated the expression of apoptosis-related proteins and increased the apoptosis rate of IMR-32 cells. Intracellular Ca²⁺ level increased significantly after the treatments with bisphenol A (BPA), bisphenol E (BPE), bisphenol C (BPC) and bisphenol AP (BPAP), suggesting the activation of GPER. Moreover, the stable binding conformations between GPER and BPA, BPE, BPC and BPAP and their dynamic changes of GPER-BPs via MD simulation also suggest that these BPs may activate GPER. The interaction between bisphenol G/bisphenol P/bisphenol PH and GPER are weak, which is consistent with their low GPER activity in vitro. Notably, after the pretreatment of GPER antagonist, Ca²⁺ accumulation and ROS production induced by BPA, BPE, BPC and BPAP in IMR-32 cells were attenuated. Overall, MD simulation and in vitro results mutually verified the activation of GPER by BPs, and MD simulation can rapidly evaluate the neurocytotoxicity of BPs.

Adverse (geno)toxic effects of bisphenol A and its analogues in hepatic 3D cell model

Bisphenol A (BPA) is one of the most widely used and versatile chemical compounds in polymer additives and epoxy resins for manufacturing a range of products for human applications. It is known as endocrine disruptor, however, there is growing evidence that it is genotoxic. Because of its adverse effects, the European Union has restricted its use to protect human health and the environment. As a result, the industry has begun developing BPA analogues, but there are not yet sufficient toxicity data to claim that they are safe. We investigated the adverse toxic effects of BPA and its analogues (BPS, BPAP, BPAF, BPFL, and BPC) with emphasis on their cytotoxic and genotoxic activities after short (24-h) and prolonged (96-h) exposure in in vitro hepatic three-dimensional cell model developed from HepG2 cells. The results showed that BPFL and BPC (formed by an additional ring system) were the most cytotoxic analogues that affected cell viability, spheroid surface area and morphology, cell proliferation, and apoptotic cell death. BPA, BPAP, and BPAF induced DNA double-strand break formation (γH2AX assay), whereas BPAF and BPC increased the percentage of p-H3-positive cells, indicating their aneugenic activity. All BPs induced DNA single-strand break formation (comet assay), with BPAP (≥0.1 μM) being the most effective and BPA and BPC the least effective (≥1 μM) under conditions applied. The results indicate that not all of the analogues studied are safer alternatives to BPA and thus more in-depth research is urgently needed to adequately evaluate the risks of BPA analogues and assess their safety for humans.

Genome-wide distribution of histone trimethylation reveals a global impact of bisphenol A on telomeric binding proteins and histone acetyltransferase factors: a pilot study with human and in vitro data

OBJECTIVE

To assess the genetic and epigenetic effects promoted by Bisphenol A (BPA) exposure in adolescent males from the Spanish INMA-Granada birth cohort, and in human cells.

METHODS

DNA methylation was analysed using MEDIP. Repeat number variation in genomic DNA was evaluated, along with the analysis of H3K4me3 by using chromatin immunoprecipitation followed by high-throughput sequencing (ChIP-seq). Analyses were performed with material extracted from whole blood of the adolescents, complemented by in vitro assessments of human (HeLa) cells exposed to 10 nM BPA, specifically, immunofluorescence evaluation of protein levels, gene expression analysis and ChIP‒qPCR analysis.

RESULTS

Adolescents in the high urinary BPA levels group presented a higher level of Satellite A (SATA) repetitive region copy numbers compared to those in the low BPA group and a tendency towards increase in telomere length. We also observed decreased DNA methylation at the promoters of the imprinted genes H19, KCNQ1, and IGF2; at LINE1 retroelements; and at the ARID2, EGFR and ESRRA and TERT genes. Genome-wide sequencing revealed increased H3K4me3 occupancy at the promoters of genes encoding histone acetyltransferases, telomeric DNA binding factors and DNA repair genes. Results were supported in HeLa cells exposed to 10 nM BPA in vitro. In accordance with the data obtained in blood samples, we observed higher H3K4me3 occupancy and lower DNA methylation at some specific targets in HeLa cells. In exposed cells, changes in the expression of genes encoding DNA repair factors (ATM, ARID2, TRP53) were observed, and increased expression of several genes encoding telomeric DNA binding factors (SMG7, TERT, TEN1, UPF1, ZBTB48) were also found. Furthermore, an increase in ESR1/ERa was observed in the nuclei of HeLa cells along with increased binding of ESR1 to KAT5, KMT2E and TERF2IP promoters and decreased ESR1 binding at the RARA promoter. The DNA damage marker p53/TP53 was also increased.

CONCLUSION

In this pilot study, genome-wide analysis of histone trimethylation in adolescent males exposed to BPA revealed a global impact on the expression of genes encoding telomeric binding proteins and histone acetyltransferase factors with similar results in HeLa cells. Nevertheless, larger studies should confirm our findings.

Impact of Bisphenol A on Structure and Function of Mitochondria: A Critical Review

Bisphenol A (BPA) is an industrial chemical used extensively to manufacture polycarbonate plastics and epoxy resins. Because of its estrogen-mimicking properties, BPA acts as an endocrine-disrupting chemical. It has gained attention due to its high chances of daily and constant human exposure, bioaccumulation, and the ability to cause cellular toxicities and diseases at extremely low doses. Several elegant studies have shown that BPA can exert cellular toxicities by interfering with the structure and function of mitochondria, leading to mitochondrial dysfunction. Exposure to BPA results in oxidative stress and alterations in mitochondrial DNA (mtDNA), mitochondrial biogenesis, bioenergetics, mitochondrial membrane potential (MMP) decline, mitophagy, and apoptosis. Accumulation of reactive oxygen species (ROS) in conjunction with oxidative damage may be responsible for causing BPA-mediated cellular toxicity. Thus, several reports have suggested using antioxidant treatment to mitigate the toxicological effects of BPA. The present literature review emphasizes the adverse effects of BPA on mitochondria, with a comprehensive note on the molecular aspects of the structural and functional alterations in mitochondria in response to BPA exposure. The review also confers the possible approaches to alleviate BPA-mediated oxidative damage and the existing knowledge gaps in this emerging area of research.

Bisphenol A and 2,3,7,8-tetrachlorodibenzo-p-dioxin at non-cytotoxic doses alter the differentiation potential and cell function of rat adipose-stem cells

The possibility of chemical contamination is an important issue to consider when designing a cell therapy strategy. Both bisphenol A (BPA) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) are among the most environmentally relevant endocrine disrupting chemicals (EDCs, compounds with a high affinity for adipose tissue) recently studied. Adipose-derived stem cells (ASCs) are mesenchymal stromal cells (MSCs) obtained from adipose tissue widely used in regenerative medicine to prevent and treat diseases in several tissues and organs. Although the experimental use of tissue-engineered constructs requires careful analysis for approval and implantation, there has been a recent increase in the number of approved clinical trials for this promising strategy. This study aimed to evaluate cell viability, apoptosis, DNA damage, and the adipogenic or osteogenic differentiation potential of rat adipose-derived stem cells (rASCs) exposed to previously established non-cytotoxic doses of BPA and TCDD in vitro. Results demonstrated that 10 μM of BPA and 10 nM of TCDD were able to significantly reduce cell viability, while all exposure levels resulted in DNA damage, although did not increase the apoptosis rate. According to the analysis of adipogenic differentiation, 1 μM of BPA induced the significant formation of oil droplets, suggesting an increased adipocyte differentiation, while both 10 μM of BPA and 10 nM of TCDD decreased adipocyte differentiation. Osteogenic differentiation did not differ among the treatments. As such, BPA and TCDD in the concentrations tested can modify important processes in rASCs such as cell viability, adipogenic differentiation, and DNA damage. Together, these findings prove that EDCs play an important role as contaminants, putatively interfering in cell differentiation and thus impairing the therapeutic use of ASCs.

Natural Products in Mitigation of Bisphenol A Toxicity: Future Therapeutic Use

Bisphenol A (BPA) is a ubiquitous environmental toxin with deleterious endocrine-disrupting effects. It is widely used in producing epoxy resins, polycarbonate plastics, and polyvinyl chloride plastics. Human beings are regularly exposed to BPA through inhalation, ingestion, and topical absorption routes. The prevalence of BPA exposure has considerably increased over the past decades. Previous research studies have found a plethora of evidence of BPA’s harmful effects. Interestingly, even at a lower concentration, this industrial product was found to be harmful at cellular and tissue levels, affecting various body functions. A noble and possible treatment could be made plausible by using natural products (NPs). In this review, we highlight existing experimental evidence of NPs against BPA exposure-induced adverse effects, which involve the body’s reproductive, neurological, hepatic, renal, cardiovascular, and endocrine systems. The review also focuses on the targeted signaling pathways of NPs involved in BPA-induced toxicity. Although potential molecular mechanisms underlying BPA-induced toxicity have been investigated, there is currently no specific targeted treatment for BPA-induced toxicity. Hence, natural products could be considered for future therapeutic use against adverse and harmful effects of BPA exposure.

Genotoxic potential of bisphenol A: A review

Bisphenol A (BPA), as a major component of some plastic products, is abundant environmental pollutant. Due to its ability to bind to several types of estrogen receptors, it can trigger multiple cellular responses, which can contribute to various manifestations at the organism level. The most studied effect of BPA is endocrine disruption, but recently its prooxidative potential has been confirmed. BPA ability to induce oxidative stress through increased ROS production, altered activity of antioxidant enzymes, or accumulation of oxidation products of biomacromolecules is observed in a wide range of organisms - estrogen receptor-positive and -negative. Subsequently, increased intracellular oxidation can lead to DNA damage induction, represented by oxidative damage, single- and double-strand DNA breaks. Importantly, BPA shows several mechanisms of action and can trigger adverse effects on all organisms inhabiting a wide variety of ecosystem types. Therefore, the main aim of this review is to summarize the genotoxic effects of BPA on organisms across all taxa.

Bisphenols induce human genomic damage and modulate HERVs/env expression

Bisphenol A (BPA), a recognized endocrine-disrupting chemical, is used in the production of epoxy and polycarbonate resins. Since human exposure to BPA has been associated with increased cancer susceptibility, the market has shifted to products often labeled as "BPA free" containing BPA analogs such as bisphenol F (BPF) and bisphenol S (BPS). However, the European legislation on BPF and BPS is still unclear. This study analyzed the effects of BPA, BPF, and BPS exposure on human peripheral blood mononuclear cells by using in vitro micronucleus assay. Furthermore, it investigated the impact of bisphenols exposure on human endogenous retroviruses (HERVs) expression, which is implicated with the pathogenesis of several human diseases. The micronucleus assay revealed a significant genotoxic effect in peripheral blood cells after exposure to BPA and BPF at concentrations of 0.1, 0.05, and 0.025 μg/ml, and to BPS at 0.1 and 0.05 μg/ml. In addition, BPA exposure seems to upregulate the expression of HERVs, while a downregulation was observed after BPF and BPS treatments. Overall, our data showed the toxic effect of BPA and its analogs on circulating cells in the blood and demonstrated that they could modulate the HERVs expression.

DNA damage, serum metabolomic alteration and carcinogenic risk associated with low-level air pollution

Outdoor air pollution has been classified as carcinogenic to humans (Group 1) for lung cancer, but the underlying mechanism and key toxic components remain incompletely understood. Since DNA damage and metabolite alterations are associated with cancer progression, exploring potential mechanisms linking air pollution and cancer might be meaningful. In this study, a real-time ambient air exposure system was established to simulate the real-world environment of adult male SD rats in Beijing from June 13th, 2018, to October 8th, 2018. 8-OHdG in the urine, γ-H2AX in the lungs and mtDNA copy number in the peripheral blood were analyzed to explore DNA damage at different levels. Serum non-targeted metabolomics analysis was performed. Pair-wise spearman was used to explore the correlation between DNA damage biomarkers and serum differential metabolites. Carcinogenic risks of heavy metals and PAHs via inhalation were assessed according to US EPA guidelines. Results showed that PM_2.5 and O₃ were the major air pollutants in the exposure group and not detected in the control group. Compared with control group, higher levels of 8-OHdG, mtDNA copy number, γ-H2AX and PCNA-positive nuclei cells were observed in the exposure group. Histopathological evaluation suggested ambient air induced alveolar wall thickening and inflammatory cell infiltration in lungs. Perturbed metabolic pathways identified included glycolysis/gluconeogenesis metabolism, purine and pyrimidine metabolism, etc. γ-H2AX was positively correlated with serum ADP, 3-phospho-D-glyceroyl phosphate and N-acetyl-D-glucosamine. The BaPeq was 0.120 ng/m³. Risks of Cr(VI), As, V, BaP, BaA and BbF were above 1 × 10^-6. We concluded that low-level air pollution was associated with DNA damage and serum metabolomic alterations in rats. Cr(VI) and BaP were identified as key carcinogenic components in PM_2.5. Our results provided experimental evidence for hazard identification and risk assessment of low-level air pollution.

Bisphenol A drives di(2-ethylhexyl) phthalate promoting thyroid tumorigenesis via regulating HDAC6/PTEN and c-MYC signaling

Bisphenol A (BPA) and di-(2-ethylhcxyl) phthalate (DEHP) are exist widespread in the environment and produce adverse effect to human as environmental disruptors (EDCs). Epidemiological studies have found that the exposure of DEHP and BPA could increase the susceptibility to thyroid diseases including thyroid cancer and benign thyroid nodules. Due to the existence of multiple pollutants in our daily life, the mixed toxic effects of exposure and their interrelationships may distinguish from the exposure to a single chemical, so it is of great significance to explore the mixed toxic effect of DEHP and BPA co-exposure. Thyroid, as one of the target organs of EDCs, is prone to tumor occurrence, however, whether the mixture of BPA and DEHP will affect the occurrence of thyroid cancer is still obscure. We aim to investigate the effect of single or combined exposure to BPA and DEHP on the occurrence of thyroid cancer. An animal model of exposure to BPA and DEHP was firstly established to evaluate their effect on DMD-induced thyroid cancer. Additionally, human thyroid cancer cells BCPAP and thyroid cells Nthy-ori3-1 were used to further clarify some possible mechanisms of BPA and MEHP, the main metabolite of DEHP. Consequently, we found that BPA alone could increase the incidence of thyroid tumors in female rats compared with DEHP, and DEHP enhanced the effect of BPA on cancer promotion. BPA alone and in combination with DEHP mainly induced the expression of HDAC6, inhibited tumor suppressor gene PTEN upregulated the expression of oncogene c-MYC, and eventually elevate the susceptibility to thyroid tumors. Mechanistically, BPA alone and in combination with MEHP could significantly induce the proliferation of BCPAP cells depending on HDAC6, which could modulate H3K9ac to inhibit PTEN, activate AKT signaling pathway, and simultaneously upregulate the expression of c-MYC. Interestingly, we found that BPA alone and in combination with MEHP could significantly induce the proliferation of Nthy-ori3-1 cells independent on HDAC6 via activating ERK signaling pathway. Taken together, these findings not only provide new evidence of the promoting effect of BPA and DEHP on thyroid cancer but also discusses some possible mechanisms underlying these effects.

Urinary bisphenol A and its interaction with CYP17A1 rs743572 are associated with breast cancer risk

OBJECTIVE

Bisphenol A (BPA), a common endocrine disrupter, can be activated by cytochrome P450 (CYP) metabolizing enzymes and might influence the development of breast cancer (BC). We hypothesized that BPA could interact with CYP genes, synergistically contributing to the BC risk.

METHODS

Urinary BPA was measured in a total of 302 newly diagnosed BC patients and 302 healthy controls by ultra-high performance liquid chromatography-high resolution mass spectrometry. A set of seven CYP gene polymorphisms was genotyped by using the Sequenom MassARRAY system. A multivariate logistic regression model was used to assess the associations of BPA and BPA-SNP interaction with BC risk.

RESULTS

BC patients had a higher urinary BPA concentration than healthy individuals (P < 0.001). Each 1-unit increase in log-transformed urinary BPA was associated with a 54 % increased BC risk [95 % confidence interval (CI), 1.34-1.77, P < 0.001]. Individuals with the CYP19A1 rs1902580 GA + AA genotype showed a significantly higher BC risk than those with the GG genotype (OR = 1.45, 95 % CI, 1.01-2.09, P < 0.05). A significant BPA-CYP17A1 rs743572 interaction was found to be associated with a higher risk of BC (P_interaction = 0.020). Compared with low-BPA individuals carrying CYP17A1 rs743572 GG genotypes, high-BPA individuals with the GA + AA genotype had a higher BC risk, with an odds ratio of 2.49 (95 % CI, 1.52-4.13, P < 0.05).

CONCLUSIONS

The positive association of BPA exposure with BC risk might be modified by CYP17A1 rs743572, providing evidence for the interaction effect of environment-genes on the etiology of BC.

Bisphenol A-induced DNA damages promote to lymphoma progression in human lymphoblastoid cells through aberrant CTNNB1 signaling pathway

Lymphoma is a group of blood cancers that develop from the immune system, and one of the main risk factors is associated with exposure to environmental chemicals. Bisphenol A (BPA) is a common chemical used in the manufacture of materials in polycarbonate and epoxy plastic products and can interfere with the immune system. BPA is considered to possibly induce lymphoma development by affecting the immune system, but its potential mechanisms have not been well established. This study performed a gene-network analysis of microarray data sets in human lymphoma tissues as well as in human cells with BPA exposure to explore module genes and construct the potential pathway for lymphomagenesis in response to BPA. This study provided evidence that BPA exposure resulted in disrupted cell cycle and DNA damage by activating CTNNB1, the initiator of the aberrant constructed CTNNB1-NFKB1-AR-IGF1-TWIST1 pathway, which may potentially lead to lymphomagenesis.

Molecular mechanisms of mammary gland remodeling: A review of the homeostatic versus bisphenol a disrupted microenvironment

Mammary gland (MG) undergoes critical points of structural changes throughout a woman's life. During the perinatal and pubertal stages, MG develops through growth and differentiation to establish a pre-mature feature. If pregnancy and lactation occur, the epithelial compartment branches and differentiates to create a specialized structure for milk secretion and nurturing of the newborn. However, the ultimate MG modification consists of a regression process aiming to reestablish the smaller and less energy demanding structure until another production cycle happens. The unraveling of these fascinating physiologic cycles has helped the scientific community elucidate aspects of molecular regulation of proliferative and apoptotic events and remodeling of the stromal compartment. However, greater understanding of the hormonal pathways involved in MG developmental stages led to concern that endocrine disruptors such as bisphenol A (BPA), may influence these specific development/involution stages, called "windows of susceptibility". Since it is used in the manufacture of polycarbonate plastics and epoxy resins, BPA is a ubiquitous chemical present in human everyday life, exerting an estrogenic effect. Thus, descriptions of its deleterious effects on the MG, especially in terms of serum hormone concentrations, hormonal receptor expression, molecular pathways, and epigenetic alterations, have been widely published. Therefore, allied to a didactic description of the main physiological mechanisms involved in different critical points of MG development, the current review provides a summary of key mechanisms by which the endocrine disruptor BPA impacts MG homeostasis at different windows of susceptibility, causing short- and long-term effects.

Molecular mechanism study of BPAF-induced proliferation of ERα-negative SKBR-3 human breast cancer cells in vitro/in vivo

Bisphenol AF (BPAF) is a known estrogen disruptor of the ERα pathway. The aim of the present study was to characterize the proliferation effects of BPAF on ERα-negative SKBR-3 breast cancer cells with mechanistic insights. BPAF at low concentrations (0.001-0.1 μM) significantly induced the proliferation of SKBR-3 cells. In a SKBR-3 tumor model in BALB/c nude mice, BPAF at 100 mg/kg body weight/day also significantly promoted the growth of SKBR-3 tumors. Low concentrations of BPAF markedly increased the expression of G protein-coupled estrogen receptor (GPER1), c-Myc, CyclinD1 and c-Fos proteins, and enhanced phosphorylation of extracellular signal-regulated kinase (Erk) and protein kinase B (Akt) in SKBR-3 cells. Further, BPAF significantly upregulated mRNA levels of related target genes in SKBR-3 cells and SKBR-3 tumor tissues in nude mice. The GPER1 inhibitor G15 and phosphatidylinositide 3-kinase (PI3K) inhibitor wortmannin (WM) inhibited phosphorylation of Erk and Akt. The specific signal inhibitors also markedly decreased the expression of target genes and weakened the cell proliferation induced by low-concentration BPAF. The findings showed that GPER1 could independently regulate BPAF-induced proliferation of SKBR-3 cells without requiring ERα. These results provide mechanistic insights into the effects of BPAF regarding ERα-negative human breast cancer development.

Insight into the mechanism of tetrachlorobisphenol A (TCBPA)-induced proliferation of breast cancer cells by GPER-mediated signaling pathways

Tetrachlorobisphenol A (TCBPA), a chlorinated derivative of bisphenol A, is an endocrine disruptor based on interaction with nuclear estrogen receptor alpha (ERα). However, there is only limited data on the mechanisms through which TCBPA-associated estrogenic activity is related to the membrane G protein-coupled estrogen receptor (GPER) pathway. In this study, three human breast cancer cell lines-MCF-7, SKBR3, and MDA-MB-231 cells were used to evaluate whether, as well as how, TCBPA at concentration range of 0.001-50 μM affect cell proliferation. The role of GPER signaling in TCBPA-induced cell proliferation was studied by analyzing the protein expression and mRNA levels of relevant signal targets. The results showed that low concentrations of TCBPA significantly induced the proliferation of MCF-7, SKBR3, and MDA-MB-231 cells, with MCF-7 cells being the most sensitive to TCBPA exposure. Low-concentration TCBPA also upregulated the expression of GPER, CyclinD1, c-Myc, and c-Fos proteins, as well as increased the phosphorylation of extracellular signal-regulated-kinase 1/2 (Erk1/2) and protein kinase B (Akt). Additionally, the mRNA levels of genes associated with estrogen signaling pathways also increased upon exposure to TCBPA. However, the phosphorylation of Erk1/2 and Akt decreased when the cells were treated with GPER inhibitor G15 and phosphatidylinositide 3-kinase (PI3K) inhibitor wortmannin (WM) prior to TCBPA exposure. Besides, the increased proliferation of breast cancer cells induced by TCBPA were also inhibited. In ERα-positive MCF-7 cells, TCBPA also upregulated ERα expression, and ERα was found to interact with GPER-mediated signaling. The results indicate that GPER activates the PI3K/Akt and Erk1/2 signal cascades to drive the cell proliferation observed for low concentrations of TCBPA. The presented results suggest a new mechanism by which TCBPA exerts estrogenic action in breast cancer cells, namely, GPER signaling in an ERα-independent manner, and also highlights the potential risks to human health of the usage of TCBPA.

The proliferation effects of fluoxetine and amitriptyline on human breast cancer cells and the underlying molecular mechanisms

Some studies have suggested possible estrogen actions for antidepressants such as fluoxetine. However, the specific molecular mechanisms remain unclear. In this study, the molecular mechanism of fluoxetine-induced the proliferation of breast cancer SKBR3 and MCF-7 cells was evaluated by detecting ERα and GPR30-mediated ERK and PI3K/AKT signals. We found that low concentrations of fluoxetine upregulated the expression of GPR30, ERα, CyclinD1, and C-MYC proteins, as well as elevated the phosphorylation of ERK and AKT. The phosphorylation of ERK and AKT decreased when the cells were pretreated with ERα inhibitor ICI, GPR30 inhibitor G15, and PI3K inhibitor WM prior to fluoxetine exposure. The addition of these inhibitors also attenuated the fluoxetine-induced cell proliferation. These findings indicated that fluoxetine activated the PI3K/AKT and ERK signaling cascades via GPR30 to derive the cell proliferation. It suggests that fluoxetine has the potential to exert estrogen actions via GPR30.

A comprehensive review on the carcinogenic potential of bisphenol A: clues and evidence

Bisphenol A [BPA; (CH3)2C(C6H4OH)2] is a synthetic chemical used as a precursor material for the manufacturing of plastics and resins. It gained attention due to its high chances of human exposure and predisposing individuals at extremely low doses to diseases, including cancer. It enters the human body via oral, inhaled, and dermal routes as leach-out products. BPA may be anticipated as a probable human carcinogen. Studies using in vitro cell lines, rodent models, and epidemiological analysis have convincingly shown the increasing susceptibility to cancer at doses below the oral reference dose set by the Environmental Protection Agency for BPA. Furthermore, BPA exerts its toxicological effects at the genetic and epigenetic levels, influencing various cell signaling pathways. The present review summarizes the available data on BPA and its potential impact on cancer and its clinical outcome.

Bisphenol A promotes stress granule assembly and modulates the integrated stress response

Bisphenol-A (BPA) is a ubiquitous precursor of polycarbonate plastics that is found in the blood and serum of >92% of Americans. While BPA has been well documented to act as a weak estrogen receptor (ER) agonist, its effects on cellular stress are unclear. Here, we demonstrate that high-dose BPA causes stress granules (SGs) in human cells. A common estrogen derivative, β-estradiol, does not trigger SGs, indicating the mechanism of SG induction is not via the ER pathway. We also tested other structurally related environmental contaminants including the common BPA substitutes BPS and BPF, the industrial chemical 4-nonylphenol (4-NP) and structurally related compounds 4-EP and 4-VP, as well as the pesticide 2,4-dichlorophenoxyacetic acid (2,4-D). The variable results from these related compounds suggest that structural homology is not a reliable predictor of the capacity of a compound to cause SGs. Also, we demonstrate that BPA acts primarily through the PERK pathway to generate canonical SGs. Finally, we show that chronic exposure to a low physiologically relevant dose of BPA suppresses SG assembly upon subsequent acute stress. Interestingly, this SG inhibition does not affect phosphorylation of eIF2α or translation inhibition, thus uncoupling the physical assembly of SGs from translational control. Our work identifies additional effects of BPA beyond endocrine disruption that may have consequences for human health.

Summary: Physiologically-relevant doses of the plasticizing agent BPA inhibit stress granule formation in response to a secondary acute stress, indicating BPA may affect the way human cells cope with cellular stress.

A comprehensive study on bisphenol A degradation by newly isolated strains Acinetobacter sp. K1MN and Pseudomonas sp. BG12

Bisphenol A (BPA) is an endocrine disrupting chemical. Its extensive use has led to the wide occurrence of BPA in various environmental ecosystems, at levels that may cause negative effects to the ecosystem and public health. Although there are many bacteria able to BPA utilization, only a few of them have a strong capacity for its biodegradation. Therefore, it is important to search for new bacteria strains, investigate their BPA biodegradation ability and potential effect of pH and other organic compounds on the process. These tasks have become the object of the present study. The results of our research show that for the newly isolated strains Acinetobacter sp. K1MN and Pseudomonas sp. BG12 after 15 days, with an initial BPA concentration of 100 mg L^− 1, the highest BPA removal was achieved at pH 8, while sodium glutamate as a biostimulant best accelerated BPA degradation. Kinetic data for BPA biodegradation by both strains best fitted the Monod model. The specific degradation rate and the half saturation constant were estimated respectively as 8.75 mg L^− 1 day^− 1 and 111.27 mg L^− 1 for Acinetobacter sp. K1MN, and 8.6 mg L^− 1 day^− 1 and 135.79 mg L^− 1 for Pseudomonas sp. BG12. The half-maximal effective concentration (EC₅₀) of BPA for Acinetobacter sp. K1MN was 120 mg L^− 1 and for Pseudomonas sp. BG12 it was 123 mg L^− 1. The toxicity bioassay (Microtox test) showed that elimination of BPA by both strains is accompanied by reduction of its toxic effect. The ability of tested strains to degrade BPA combined with their high resistance to this xenobiotic indicates that Acinetobacter sp. K1MN and Pseudomonas sp. BG12 are potential tools for BPA removal during wastewater treatment plant.

White rot fungi can be a promising tool for removal of bisphenol A, bisphenol S, and nonylphenol from wastewater

Endocrine-disrupting chemicals (EDC) are a wide group of chemicals that interfere with the endocrine system. Their similarity to natural steroid hormones makes them able to attach to hormone receptors, thereby causing unfavorable health effects. Among EDC, bisphenol A (BPA), bisphenol S (BPS), and nonylphenol (NP) seem to be particularly harmful. As the industry is experiencing rapid expansion, BPA, BPS, and NP are being produced in growing amounts, generating considerable environmental pollution. White rot fungi (WRF) are an economical, ecologically friendly, and socially acceptable way to remove EDC contamination from ecosystems. WRF secrete extracellular ligninolytic enzymes such as laccase, manganese peroxidase, lignin peroxidase, and versatile peroxidase, involved in lignin deterioration. Owing to the broad substrate specificity of these enzymes, they are able to remove numerous xenobiotics, including EDC. Therefore, WRF seem to be a promising tool in the abovementioned EDC elimination during wastewater treatment processes. Here, we review WRF application for this EDC removal from wastewater and indicate several strengths and limitations of such methods.

Role of DNA damage and repair mechanisms in uterine fibroid/leiomyomas: a review

There has been a significant annual increase in the number of cases of uterine leiomyomas or fibroids (UF) among women of all races and ages across the world. A fortune is usually spent by the healthcare sector for fibroid-related treatments and management. Molecular studies have established the higher mutational heterogeneity in UF as compared to normal myometrial cells. The contribution of DNA damage and defects in repair responses further increases the mutational burden on the cells. This in turn leads to genetic instability, associated with cancer risk and other adverse reproductive health outcomes. Such and many more growing bodies of literature have highlighted the genetic/molecular, biochemical and clinical aspects of UF; none the less there appear to be a lacuna bridging the bench to bed gap in addressing and preventing this disease. Presented here is an exhaustive review of not only the molecular mechanisms underlying the predisposition to the disease but also possible strategies to effectively diagnose, prevent, manage, and treat this disease.

Bisphenol-A exposure during pregnancy alters pancreatic β-cell division and mass in male mice offspring: A role for ERβ

Bisphenol-A (BPA) is a widespread endocrine disrupting chemical that constitutes a risk factor for type 2 diabetes mellitus (T2DM). Data from animal and human studies have demonstrated that early exposure to BPA results in adverse metabolic outcomes in adult life. In the present work, we exposed pregnant heterozygous estrogen receptor β (ERβ) knock out (BERKO) mice to 10 μg/kg/day BPA, during days 9-16 of pregnancy, and measured β-cell mass and proliferation in wildtype (WT) and BERKO male offspring at postnatal day 30. We observed increased pancreatic β-cell proliferation and mass in WT, yet no effect was produced in BERKO mice. Dispersed islet cells in primary culture treated with 1 nM BPA showed an enhanced pancreatic β-cell replication rate, which was blunted in pancreatic β-cells from BERKO mice and mimicked by the selective ERβ agonist WAY200070. This increased β-cell proliferation was found in male adult as well as in neonate pancreatic β-cells, suggesting that BPA directly impacts β-cell division at earliest stages of life. These findings strongly indicate that BPA during pregnancy upregulates pancreatic β-cell division and mass in an ERβ-dependent manner. Thus, other natural or artificial chemicals may use this ERβ-mediated pathway to promote similar effects.

Impacts of bisphenol A analogues on zebrafish post-embryonic brain

Bisphenol A (BPA) is a widely studied and well-recognised endocrine-disrupting chemical, and one of the current issues is its safe replacement by various analogues. Using larva zebrafish as a model, the present study reveals that moderate and chronic exposure to BPA analogues such as bisphenol S, bisphenol F and bisphenol AF may also affect vertebrate neurodevelopment and locomotor activity. Several parameters of embryo-larval development were investigated, such as mortality, hatching, number of mitotically active cell, as defined by 5-bromo-2'-deoxyuridine incorporation and proliferative cell nuclear antigen labelling, aromatase B protein expression in radial glial cell and locomotor activity. Our results show that exposure to several bisphenol analogues induced an acceleration of embryo hatching rate. At the level of the developing brain, a strong up-regulation of the oestrogen-sensitive Aromatase B was also detected in the hypothalamic region. This up-regulation was not associated with effects on the numbers of mitotically active progenitors nor differentiated neurones in the preoptic area and in the nuclear recessus posterior of the hypothalamus zebrafish larvae. Furthermore, using a high-throughput video tracking system to monitor locomotor activity in zebrafish larvae, we show that some bisphenol analogues, such as bisphenol AF, significantly reduced locomotor activity following 6 days of exposure. Taken together, our study provides evidence that BPA analogues can also affect the neurobehavioural development of zebrafish.

Organic extract of indoor dust induces estrogen-like effects in human breast cancer cells

Indoor dust often contains organic contaminants, which adversely impacts human health. In this study, the organic contaminants in the indoor dust from commercial offices and residential houses in Nanjing, China were extracted and their effects on human breast cancer cells (MCF-7) were investigated. Both dust extracts promoted proliferation of MCF-7 cells at ≤24 μg/100 μL, with cell viability being decreased with increasing dust concentrations. Based on LC₅₀, house dust was less toxic than office dust. At 8 μg/100 μL, both extracts caused more MCF-7 cells into active cycling (G2/M + S) and increased intracellular Ca²⁺ influx, with house dust inducing stronger effects than office dust. Further, the expression of estrogen-responsive genes for TFF1 and EGR3 was enhanced by 3-9 and 4-9 folds, while the expression of cell cycle regulatory genes for cyclin D was enhanced by 2-5 folds. The results suggested that organic dust extract influenced cell viability, altered cell cycle, increased intracellular Ca²⁺ levels, and activated cell cycle regulatory and estrogen-responsive gene expressions, with house dust showing lower cytotoxicity but higher estrogenic potential on MCF-7 cells. The results indicate the importance of reducing organic contaminants in indoor dust to mitigate their adverse impacts on human health.

Endocrine disruptors from the environment affecting breast cancer

Evaluation of carcinogenic substances from the environment is a challenge for scientists. Recently, a novel approach based on 10 key characteristics of human carcinogens classified by the International Agency for Research on Cancer (IARC) has emerged. Carcinogenesis depends on different mechanisms and factors, including genetic, infectious (bacteria, viruses) and environmental (chemicals) factors. Endocrine disruptors are exogenous chemicals that can interfere and impair the function of the endocrine system due to their interaction with estrogen receptors or their estrogen signaling pathways inducing adverse effects in the normal mammary development, originating cancer. They are heterogeneous chemicals and include numerous synthetic substances used worldwide in agriculture, industry and consumer products. The most common are plasticizers, such as bisphenol A (BPA), pesticides, such as dichlorodiphenyltrichloroethane, and polychlorinated biphenyls (PCBs). Xenoestrogens appear to serve an important role in the increased incidence of breast cancer in the United States and numerous other countries. Several studies have demonstrated the role of organochlorine xenoestrogens in breast cancer. Therefore, the overall cumulative exposure of women to estrogens results in an increased risk for this type of cancer. Factors like lifestyle and diet also serve a role in the increased incidence of this disease. The aim of the present study was to analyze these chemical compounds based on the key characteristics given by the IARC, with a special focus on breast cancer, to establish whether these compounds are carcinogens, and to create a model for future analysis of other endocrine disruptors.

Discrepant dose responses of bisphenol A on oxidative stress and DNA methylation in grass carp ovary cells

Bisphenol A (BPA), is a common contaminant in diverse environmental compartments and its endocrine disruptive effect on living organisms has been widely reported. Further works are still required to facilitate the research on cytotoxicity and genotoxicity. In the present study, grass carp ovary (GCO) cells were used to investigate cellular oxidative stress and genomic DNA methylation under BPA exposure. Results showed that BPA exposure for 48 h arrested cell proliferation and viability. The oxidative stress was distinctly enhanced with increased reactive oxygen species (ROS), malondialdehyde level, and oxidation of reduced glutathione (GSH) in 30 μM BPA group. Furthermore, the global 5-methylcytosine (5 mC) level was elevated and showed inverted U-shaped responses to the BPA doses. Besides, one-carbon metabolism and de novo GSH synthesis were disrupted at 30 μM BPA. Current data suggested that low dose of BPA exposure could exhibit hormesis in recycling circular biosynthesis of GSH and scavenging ROS to create a relatively reductive intracellular environment, and up-regulate transcripts of methyltransferases that increased the 5 mC level in GCO cells. While high dose of BPA distinctly induced oxidative stress, elevated de novo GSH synthesis, and then attenuated transmethylation activity and decreased 5 mC level. Current study highlighted the discrepant dose responses of BPA in fish ovary cells that facilitated the understanding of pleiotropic consequences in organisms.

Oxidative Stress and BPA Toxicity: An Antioxidant Approach for Male and Female Reproductive Dysfunction

Bisphenol A (BPA) is a non-persistent anthropic and environmentally ubiquitous compound widely employed and detected in many consumer products and food items; thus, human exposure is prolonged. Over the last ten years, many studies have examined the underlying molecular mechanisms of BPA toxicity and revealed links among BPA-induced oxidative stress, male and female reproductive defects, and human disease. Because of its hormone-like feature, BPA shows tissue effects on specific hormone receptors in target cells, triggering noxious cellular responses associated with oxidative stress and inflammation. As a metabolic and endocrine disruptor, BPA impairs redox homeostasis via the increase of oxidative mediators and the reduction of antioxidant enzymes, causing mitochondrial dysfunction, alteration in cell signaling pathways, and induction of apoptosis. This review aims to examine the scenery of the current BPA literature on understanding how the induction of oxidative stress can be considered the "fil rouge" of BPA's toxic mechanisms of action with pleiotropic outcomes on reproduction. Here, we focus on the protective effects of five classes of antioxidants-vitamins and co-factors, natural products (herbals and phytochemicals), melatonin, selenium, and methyl donors (used alone or in combination)-that have been found useful to counteract BPA toxicity in male and female reproductive functions.

Effect of bisphenols on telomerase expression and activity in breast cancer cell lines

Bisphenol A (BPA), a monomer of polycarbonates and resins, was shown to induce the expression of telomerase enzyme which has been associated with breast cancer development and progression. However, the effects of BPA analogues, bisphenol F (BPF) and bisphenol S (BPS) on telomere-linked pathway have not been evaluated. Herein, MCF-7 (estrogen receptor (ER)-positive) and MDA-MB-231 (ER-negative) cells were treated with BPA, BPF and BPS ± estrogen receptor inhibitor (ERI), for 24 and/or 48 h. RNA expression and enzymatic activity of telomerase were measured using reverse transcription quantitative polymerase chain reaction (RT-qPCR) and telomeric repeat amplification protocol (TRAP); respectively. Relative telomere length (RTL) was also measured using quantitative PCR. After 24 h, the three bisphenols resulted in a 2-3 folds increase in expression and activity of telomerase in MCF-7 but not in MDA-MB-231 cells, and this increase was prevented upon co-treatment with ERI. The observed increase in the expression and activity of telomerase after 24 h of treatment with bisphenols was associated with differential and modest ER-dependent lengthening in RTL at 48 h. Our results show that telomerase potentially mediates the effects of the three bisphenols in ER-positive breast carcinoma. Hence, further investigation is warranted to elucidate the telomerase-linked pathways that could underlie bisphenol-related effects.

Integration of proteomics and metabolomics reveals promotion of proliferation by exposure of bisphenol S in human breast epithelial MCF-10A cells

Bisphenol S (BPS) has been reported to have similar estrogenic effects as bisphenol A (BPA). Considering the endocrine disrupting effects of BPS, in this study, we investigated the effects of BPS exposure on normal human breast epithelial cell line MCF-10A by using mass spectrometry (MS)-based metabolomics and quantitative proteomics. We found that exposure to BPS for 24 h altered the proliferation of MCF-10A cells in a hormetic manner with the highest proliferation rate at the dosage of 1 μM. A total of 200 proteins were identified to be significantly changed by 1 μM of BPS exposure. The upregulation of epidermal growth factor receptor (EGFR) and Ras/mTOR-related proteins implied that EGFR-mediated pathways were involved in BPS-induced proliferation of MCF-10A cells. In addition, several proliferation-related protein markers were found to be elevated, such as MKI67 and CDH1, further indicating the promotion of proliferation by low dose of BPS exposure. Besides, 35 endogenous metabolites were found to be significantly changed. The joint pathway analysis of the altered metabolites and proteins suggested changes in pathways of tricarboxylic acid (TCA) cycle, purine metabolism, pyruvate metabolism and lipid metabolism, which were involved in sustaining cell proliferation and cellular signal transduction. Taken together, this study provides insights into the effects and the potential mechanisms of BPS on estrogen receptor α-negative normal breast cell line MCF-10A, broadening our knowledge about the risk of using BPS as the alternative of BPA.

Determination of bisphenol A in barreled drinking water by a SPE-LC-MS method

A quantitative method was established to determine the well-known endocrine disruptor bisphenol A (BPA) in barreled drinking water. Samples were pretreated by solid phase extraction (SPE), and then analyzed by liquid chromatography-mass spectrometry (LC-MS). Working standard solutions were obtained by pretreatment of a series of aqueous standard solutions over the concentration range of 122.9-1190.7 ng L^-1. The linear calibration curve was Y = 69.4X + 2206.2 with the correlation coefficient (R²) of 0.9929. The average recoveries from spiked samples were more than 91.6%. The relative standard deviations (n = 6) were less than 9.6%. The method allowed the detection of 7.0 ng L^-1 BPA in barreled drinking water. Typical barreled drinking water products in the market were detected. As results, thirty-five of fifty-two commercial samples were found to contain BPA with a maximum concentration of 898.7 ng L^-1. The occurrence of BPA in barreled drinking water may be due to the pollution of raw water, the inefficiency of purification processes and the migration of BPA from barrels. The daily exposure of adults to BPA through drinking barreled drinking water is far below the current human tolerable daily intake (TDI) set by European Food Safety Authority (EFSA).

High-Content Image-Based Single-Cell Phenotypic Analysis for the Testicular Toxicity Prediction Induced by Bisphenol A and Its Analogs Bisphenol S, Bisphenol AF, and Tetrabromobisphenol A in a Three-Dimensional Testicular Cell Co-culture Model

Emerging data indicate that structural analogs of bisphenol A (BPA) such as bisphenol S (BPS), tetrabromobisphenol A (TBBPA), and bisphenol AF (BPAF) have been introduced into the market as substitutes for BPA. Our previous study compared in vitro testicular toxicity using murine C18-4 spermatogonial cells and found that BPAF and TBBPA exhibited higher spermatogonial toxicities as compared with BPA and BPS. Recently, we developed a novel in vitro three-dimensional (3D) testicular cell co-culture model, enabling the classification of reproductive toxic substances. In this study, we applied the testicular cell co-culture model and employed a high-content image (HCA)-based single-cell analysis to further compare the testicular toxicities of BPA and its analogs. We also developed a machine learning (ML)-based HCA pipeline to examine the complex phenotypic changes associated with testicular toxicities. We found dose- and time-dependent changes in a wide spectrum of adverse endpoints, including nuclear morphology, DNA synthesis, DNA damage, and cytoskeletal structure in a single-cell-based analysis. The co-cultured testicular cells were more sensitive than the C18 spermatogonial cells in response to BPA and its analogs. Unlike conventional population-averaged assays, single-cell-based assays not only showed the levels of the averaged population, but also revealed changes in the sub-population. Machine learning-based phenotypic analysis revealed that treatment of BPA and its analogs resulted in the loss of spatial cytoskeletal structure, and an accumulation of M phase cells in a dose- and time-dependent manner. Furthermore, treatment of BPAF-induced multinucleated cells, which were associated with altered DNA damage response and impaired cellular F-actin filaments. Overall, we demonstrated a new and effective means to evaluate multiple toxic endpoints in the testicular co-culture model through the combination of ML and high-content image-based single-cell analysis. This approach provided an in-depth analysis of the multi-dimensional HCA data and provided an unbiased quantitative analysis of the phenotypes of interest.

Role of TET Dioxygenases and DNA Hydroxymethylation in Bisphenols-Stimulated Proliferation of Breast Cancer Cells

BACKGROUND

Bisphenol A (BPA), a ubiquitous environmental endocrine disruptor targeting estrogen receptors (ERs), has been implicated in the promotion of breast cancer. Perinatal exposure of BPA could induce longitudinal alteration of DNA hydroxymethylation in imprinted loci of mouse blood cells. To date, no data has been reported on the effects of BPA on DNA hydroxymethylation in breast cells. Therefore, we asked whether BPA can induce DNA hydroxymethylation change in human breast cells. Given that dysregulated epigenetic DNA hydroxymethylation is observed in various cancers, we wondered how DNA hydroxymethylation modulates cancer development, and specifically, whether and how BPA and its analogs promote breast cancer development via DNA hydroxymethylation.

OBJECTIVES

We aimed to explore the interplay of the estrogenic activity of bisphenols at environmental exposure dose levels with TET dioxygenase-catalyzed DNA hydroxymethylation and to elucidate their roles in the proliferation of ER+ breast cancer cells as stimulated by environmentally relevant bisphenols.

METHODS

Human MCF-7 and T47D cell lines were used as ER-dependent breast cell proliferation models, and the human MDA-MB-231 cell line was used as an ER-independent breast cell model. These cells were treated with BPA or bisphenol S (BPS) to examine BPA/BPS-related proliferation. Ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) and enzyme-linked immunosorbent assays (ELISAs) were used to detect DNA hydroxymethylation. Crispr/Cas9 and RNA interference technologies, quantitative polymerase chain reaction (qPCR), and Western blot analyses were used to evaluate the expression and function of genes. Co-immunoprecipitation (Co-IP), bisulfite sequencing-PCR (BSP), and chromatin immunoprecipitation-qPCR (ChIP-qPCR) were used to identify the interactions of target proteins.

RESULTS

We measured higher proliferation in ER+ breast cancer cells treated with BPA or its replacement, BPS, accompanied by an ERα-dependent decrease in genomic DNA hydroxymethylation. The results of our overexpression, knockout, knockdown, and inhibition experiments suggested that TET2-catalyzed DNA hydroxymethylation played a suppressive role in BPA/BPS-stimulated cell proliferation. On the other hand, we observed that TET2 was negatively regulated by the activation of ERα (dimerized and phosphorylated), which was also induced by BPA/BPS binding. Instead of a direct interaction between TET2 and ERα, data of our Co-IP, BSP, and ChIP-qPCR experiments indicated that the activated ERα increased the DNA methyltransferase (DNMT)-mediated promoter methylation of TET2, leading to an inhibition of the TET2 expression and DNA hydroxymethylation.

CONCLUSIONS

We identified a new feedback circuit of ERα activation-DNMT-TET2-DNA hydroxymethylation in ER+ breast cancer cells and uncovered a pivotal role of TET2-mediated DNA hydroxymethylation in modulating BPA/BPS-stimulated proliferation. Moreover, to our knowledge, we for the first time established a linkage among chemical exposure, DNA hydroxymethylation, and tumor-associated proliferation. These findings further clarify the estrogenic activity of BPA/BPS and its profound implications for the regulation of epigenetic DNA hydroxymethylation and cell proliferation. https://doi.org/10.1289/EHP5862.

Wnt pathway: A mechanism worth considering in endocrine disrupting chemical action

Endocrine disrupting chemicals (EDCs) are defined as exogenous substances that can alter the development and functioning of the endocrine system. The Wnt signaling pathway is an evolutionarily conserved pathway consisting of proteins that transmit cell-to-cell receptors through cell surface receptors, regulating important aspects of cell migration, polarity, neural formation, and organogenesis, which determines the fate of the cell during embryonic development. Although the effects of EDCs have been studied in terms of many molecular mechanisms; because of its critical role in embryogenesis, the Wnt pathway is of special interest in EDC exposure. This review provides information about the effects of EDC exposure on the Wnt/β-catenin pathway focusing on studies on bisphenol A, di-(2-ethylhexyl) phthalate, diethylstilbestrol, cadmium, and 2,3,7,8-tetrachlorodibenzo-p-dioxin.

Bisphenol A-induced apoptosis, oxidative stress and DNA damage in cultured rhesus monkey embryo renal epithelial Marc-145 cells

Bisphenol A (BPA) is widely used in the production of epoxy resins and polycarbonate plastics. Under harsh situations, these plastics likely desorb BPA, which then can seep into the environment. Various concentrations of BPA have been detected in most biological fluid. However, there is paucity of information on the detrimental effects of BPA and its subsequent cellular events in chronic kidney disease (CKD). Hence, in this in vitro study, we aimed to investigate the effects of BPA on renal epithelial cell activation, apoptosis, and DNA damage. Rhesus monkey embryo renal epithelial Marc-145 cells were exposed to 0, 10^-1, 10^-2, 10^-3, 10^-4, 10^-5, and 10^-6 M of BPA. Alterations in intracellular apoptosis, oxidative stress, and DNA damage were evaluated. The results showed that BPA decreased cell viability, superoxide dismutase (SOD) activity and glutathione (GSH) level, with concomitant increases in apoptosis related indices, lactate dehydrogenase (LDH) activity, reactive oxygen species (ROS) generation, thiobarbituric acid reactive substances (TBARS) content, and the rate of comet Marc-145 cells with a dose-dependent manner. The data indicated that increased oxidative stress, apoptosis and DNA damage in epithelial Marc-145 cells might play a pivotal role in the mechanism of BPA-induced nephrotoxicity.