Molecular analysis of the apoptotic effects of BPA in acute myeloid leukemia cells

Exploring novel insights into the molecular mechanisms underlying Bisphenol A-induced toxicity: A persistent threat to human health

Bisphenol A (BPA) is a ubiquitous industrial chemical used in the production of polycarbonate plastics and epoxy resins, found in numerous consumer products. Despite its widespread use, its potential adverse health effects have raised significant concerns. This review explores the molecular mechanisms and evidence-based literature underlying BPA-induced toxicities and its implications for human health. BPA is an endocrine-disrupting chemical (EDC) which exhibits carcinogenic properties by influencing various receptors, such as ER, AhR, PPARs, LXRs, and RARs. It induces oxidative stress and contributes to cellular dysfunction, inflammation, and DNA damage, ultimately leading to various toxicities including but not limited to reproductive, cardiotoxicity, neurotoxicity, and endocrine toxicity. Moreover, BPA can modify DNA methylation patterns, histone modifications, and non-coding RNA expression, leading to epigenetic changes and contribute to carcinogenesis. Overall, understanding molecular mechanisms of BPA-induced toxicity is crucial for developing effective strategies and policies to mitigate its adverse effects on human health.

Computational Construction of Toxicant Signaling Networks

Humans and animals are regularly exposed to compounds that may have adverse effects on health. The Toxicity Forecaster (ToxCast) program was developed to use high throughput screening assays to quickly screen chemicals by measuring their effects on many biological end points. Many of these assays test for effects on cellular receptors and transcription factors (TFs), under the assumption that a toxicant may perturb normal signaling pathways in the cell. We hypothesized that we could reconstruct the intermediate proteins in these pathways that may be directly or indirectly affected by the toxicant, potentially revealing important physiological processes not yet tested for many chemicals. We integrate data from ToxCast with a human protein interactome to build toxicant signaling networks that contain physical and signaling protein interactions that may be affected as a result of toxicant exposure. To build these networks, we developed the EdgeLinker algorithm, which efficiently finds short paths in the interactome that connect the receptors to TFs for each toxicant. We performed multiple evaluations and found evidence suggesting that these signaling networks capture biologically relevant effects of toxicants. To aid in dissemination and interpretation, interactive visualizations of these networks are available at http://graphspace.org.

Effects of bone marrow-derived mesenchymal stem cells exposed to endocrine-disrupting chemicals on the differentiation of umbilical cord blood hematopoietic stem cells

Endocrine-disrupting chemicals (EDCs), a class of peripheral toxic substances, can cause many environmental and clinical side effects, particularly on the human body's endocrine system. Bisphenol A (BPA) and diethylhexyl phthalate (DEHP) are two well-known EDCs in the medicine industry. However, there are no comprehensive studies on their effects on hematopoiesis. Hence, this study aimed to investigate the effect of these two aforementioned substances on the clonogenic capacity of umbilical cord blood hematopoietic stem cells (CB-HSCs). The HSCs which express CD34 + were isolated from umbilical cord blood by the magnetic-activated cell sorting (MACS) system. To investigate the effects of different optimized concentrations of BPA and DEHP, CB-CD34⁺ HSCs were exposed to EDCs in semisolid medium. For evaluation of coexposures, CB-CD34⁺ HSCs were cocultured with bone marrow-derived mesenchymal stem cells (BM-MSCs) in the presence of BPA and DEHP. Finally, the number and types of colonies were evaluated after 14 days. Statistical analysis was performed by GraphPad Prism through ANOVA. CB-HSC treated by BPA and DEHP showed a lower absolute colony count than the control group (P < 0.05). Decrease in clonogenic potential of HSCs was more significant in coculture condition by MSCs. In particular, there was a significant decrease in the BFU-E colonies in comedicated-derived fractions (P < 0.0001). In the presence of EDCs such as BPA and DEHP, the patterns of differentiation in CD34⁺ CB-HSCs changed from suppressed erythroid differentiation toward stimulated myelogenesis pathways.

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.

Potential role of CFTR in bisphenol A-induced malignant transformation of prostate cells via mitochondrial apoptosis

Bisphenol A (BPA) is an environmental endocrine disruptor and a risk factor for prostate cancer. The cystic fibrosis transmembrane conductance regulator (CFTR) is proposed to be a prostate cancer suppressor in some recent researches. However, the potential role and mechanism of CFTR in BPA-induced prostate cancer cells has not been well identified. In this study, BPA decreased the viability of human normal prostate RWPE-1 cells detected with a CCK-8 kit. The capacity of the cell line on soft agar colony formation, wound healing, and transwell invasion indicated malignant transformation induced by BPA. Western blot analysis demonstrated that the levels of CFTR and Bcl-2 decreased, whereas Bax level increased, and ELISA detection showed a decreased ATP level in BPA-exposed cells. Cell apoptosis was analyzed with Annexin V-FITC Detection Kit by flow cytometry. However, no significant difference was observed in cell viability and apoptosis rates compared to normal RWPE-1 cells. Our research revealed a potential role of CFTR in BPA-induced malignant transformation via mitochondrial apoptosis of normal prostate cells.

Bisphenol A and Male Fertility: Myths and Realities

Bisphenol A (BPA) represents the main chemical monomer of epoxy resins and polycarbonate plastics. The environmental presence of BPA is widespread, and it can easily be absorbed by the human body through dietary and transdermal routes, so that more than 90% of the population in western countries display detectable BPA levels in the urine. As BPA is qualified as an endocrine disruptor, growing concern is rising for possible harmful effects on human health. This review critically discusses the available literature dealing with the possible impact of BPA on male fertility. In rodent models, the in vivo exposure to BPA negatively interfered with the regulation of spermatogenesis throughout the hypothalamic-pituitary-gonadal axis. Furthermore, in in vitro studies, BPA promoted mitochondrial dysfunction and oxidative/apoptotic damages in spermatozoa from different species, including humans. To date, the claimed clinical adverse effects on male fertility are largely based on the results from studies assessing the relationship between urinary BPA concentration and conventional semen parameters. These studies, however, produced controversial evidence due to heterogeneity in the extent of BPA exposure, type of population, and enrollment setting. Moreover, the cause-effect relationship cannot be established due to the cross-sectional design of the studies as well as the large spontaneous between- and within-subject variability of semen parameters. The best evidence of an adverse effect of BPA on male fertility would be provided by prospective studies on clinically relevant endpoints, including natural or medically assisted pregnancies among men either with different exposure degrees (occupational/environmental) or with different clinical conditions (fertile/subfertile).

Benzyl butyl phthalate (BBP) triggers the malignancy of acute myeloid leukemia cells via upregulation of PDK4

Acute Myeloid Leukemia (AML) is a cancer of hematopoietic stem cells with a rapid progression. Recent studies indicated that endocrine disruptor chemicals (EDCs) are potential risk factors for AML progression. Our present data showed that an industrial endocrine disrupting chemical, Benzyl butyl phthalate (BBP), can promote the proliferation of AML cells and decrease their sensitivity to daunorubicin (DNR) and cytarabine (Ara-C) treatments. Further, BBP can increase the glucose consumption, lactate generation, and ATP levels of AML cells. Among the measured glycolysis-related genes, BBP can increase the expression of pyruvate dehydrogenase lipoamide kinase isozyme 4 (PDK4), a mitochondrial protein that regulates the tricarboxylic acid cycle (TCA) cycle. The inhibitor of PDK4 or its specific siRNA can attenuate BBP-induced cell proliferation and ATP generation, which suggested the essential roles of PDK4 in BBP-induced glycolysis and proliferation. Further, BBP can increase the mRNA stability of PDK4, while had no effect on its transcription and protein stability. miR-15b-5p can bind with the 3'UTR of PDK4 to decrease its mRNA stability, while BBP can decrease the expression of miR-15b-5p in AML cells. Collectively, our data showed that BBP can trigger the malignancy of AML cells via regulation of miR-15b-5p/PDK4 signals.

Ameliorative effect of Silybin on bisphenol A induced oxidative stress, cell proliferation and steroid hormones oxidation in HepG2 cell cultures

Bisphenol A (BPA) and silybin are considered xenoestrogens and could interfere with the action of endogenous hormones. It was demonstrated a higher level of BPA in plasma of nonalcoholic steatohepatitis (NASH) patients, compared to those with steatosis (NAFL). We investigated the effect of BPA and silybin, alone or in combination, on proliferation, oxidative stress and steroid metabolism in HepG2 grown in high glucose concentration medium (H-HepG2). Cell viability was assessed by adding 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT). TBARS were quantified by spectrophotometry. The effect of BPA, silybin and their combination on the expression of phosphorilized extracellular signal-regulated kinase (ERK), ERK and Caspase 3 was determined by Western blot analysis. The identifications of lipids and steroid hormones was performed by mass spectrometry. BPA elicited in H-HepG2 oxidative stress and steroid hormones oxidation leading to the formation of metabolite with estrogenic and genotoxic potentials. Silybin ameliorates the harmful BPA-induced effect decreasing glucose uptake and lipid peroxidation. Moreover silybin activates the synthesis of vitamin D3 metabolites and prevent the steroid hormones oxidation. BPA could be considered as an important risk factor in worsening and progression of NAFLD. At the same time silybin could be a valid support to counteract these effects in NASH patients.

A mini review of bisphenol A (BPA) effects on cancer-related cellular signaling pathways

Bisphenol A (BPA) is a plasticizer used widely in many industrial products and is now well established as an endocrine-disrupting chemical (EDC). BPA readily leaches out from these products into the environment and into foodstuffs (from packaging materials) and human exposure can be considerable. Many studies have shown that BPA exposure is associated with a range of chronic human health conditions, including diabetes, cardiovascular disorders, polycystic ovarian disease, hepatotoxicity, and various types of cancer. BPA exerts its effects through deregulating cell signaling pathways associated with cell growth, proliferation, migration, invasion, and apoptosis. Previous studies on the molecular mechanisms of BPA have illustrated a variety of pathways impaired at very low exposure concentrations and that stimulate cellular responses relating to tumorigenesis both in cancer onset and progression. In this mini review, the recent advancements made through in vitro analyses are reported on for the effect of BPA on various cellular signaling pathways focusing on the signaling pathways that play a major role in carcinogenesis.

DNA damaging and apoptotic potentials of Bisphenol A and Bisphenol S in human bronchial epithelial cells

DNA damage caused by environmental agents often lead to many chronic diseases, including cancer. The present study aimed to understand the relative toxicity possessed by Bisphenol A (BPA) and Bisphenol S (BPS) on human bronchial epithelial cells (BEAS-2B). The cells were exposed to either BPA or BPS and evaluated for its cytotoxicity, reactive oxygen species (ROS), DNA fragmentation, phosphorylated histone protein (γ-H2AX) and DNA tail damage levels. Further, we also studied DNA damage response (DDR) and caspase-3 mechanisms, to evaluate its mechanism of cell death processes. Exposure with 200 μM of BPA, significantly (p < 0.05) induces caspase-3-mediated cell death by inducing cytotoxicity, ROS, and DNA fragmentation. Higher levels of γ-H2AX and DNA tail damage indicated BPA's DNA damaging potential through an ATM/ATR/Chk1/p53-dependent pathway in BEAS-2B cells. Overall, in vitro data exhibited moderate toxicity for BPS in comparison with BPA suggesting the need for a thorough clinical investigation over its safety profile.

Bisphenol A induces cell cycle arrest in primary and prostate cancer cells through EGFR/ERK/p53 signaling pathway activation

Bisphenol A (BPA) belongs to the class of chemicals known as endocrine disruptors and has been also involved in the pathogenesis and progression of endocrine related cancer such as breast and prostate cancers. Here, we have investigated the effect of BPA in human prostate cancer LNCaP cells and in human non-transformed epithelial prostate EPN cells. Our data showed that BPA induces the down regulation of cyclin D1 expression and the upregulation of the cell cycle inhibitors p21 and p27, leading to cell cycle arrest. Interestingly, we found that the BPA anti-proliferative response depends on a strong and rapid activation of epidermal growth factor receptor (EGFR), which stimulates ERK-dependent pathway. This, in turn, induces expression of p53 and its phosphorylation on residue Ser15, which is responsible for cell cycle arrest. EGFR activation occurs upon a cross talk with androgen (AR) and estradiol receptor-β (ERβ) which are known to bind BPA.

Altogether, these findings show a novel signaling pathway in which EGFR activation plays a key role on BPA-induced cell cycle inhibition through a pathway involving AR and ERβ/EGFR complexes, ERK and p53. Our results provide new insights for understanding the molecular mechanisms in human prostate cancer. On the other, they could allow the development of new compounds that may be used to overcome human prostate cancer resistance to endocrine therapy in promising target therapeutic approaches.

Adverse effects of bisphenol A (BPA) on the dopamine system in two distinct cell models and corpus striatum of the Sprague-Dawley rat

The aim of this study was to examine the effects of bisphenol A (BPA) on the brain dopamine (DA) system utilizing both in vitro models (GH3 cells, a rat pituitary cell line, and SH-SY5Y cells, a human neuroblastoma cell line) and an animal model such as Sprague-Dawley (SD) rats. First, cellular DA uptake was measured 2 or 8 h following BPA exposure (0.1-400 μM) in SH-SY5Y cells, where a significant increase in DA uptake was noted. BPA exerted no marked effect on dopamine active transporter levels in GH3 cells exposed for 8 or 24 h. However, SH-SY5Y cells displayed an increase in dopamine transporter (DAT) levels following 24 h of exposure to BPA. In contrast to DAT levels, BPA exposure produced no marked effect on DA D1 receptor levels in SH-SY5Y cells, yet a significant decrease in GH3 cells following both 8- and 24-h exposure periods was noted, suggesting that BPA exerts differential effects dependent upon cell type. BPA produced no significant effects on prolactin levels at 2 h, but a marked fall occurred at 24 h of exposure in GH3 cells. Finally, to examine the influence of dietary developmental exposure to BPA on brain DA levels in F1 offspring, SD rats were exposed to BPA (0.5-20 mg/kg) through maternal transfer and/or diet and striatal DA levels were measured on postnatal day (PND) 60 using high-performance liquid chromatography (HPLC). Data demonstrated that chronic exposure to BPA did not significantly alter striatal DA levels in the SD rat.

Bisphenol A accelerates toxic amyloid formation of human islet amyloid polypeptide: a possible link between bisphenol A exposure and type 2 diabetes

Bisphenol A (BPA) is a chemical compound widely used in manufacturing plastic products. Recent epidemiological studies suggest BPA exposure is positively associated with the incidence of type 2 diabetes mellitus (T2DM), however the mechanisms underlying this link remain unclear. Human islet amyloid polypeptide (hIAPP) is a hormone synthesized and secreted by the pancreatic β-cells. Misfolding of hIAPP into toxic oligomers and mature fibrils can disrupt cell membrane and lead to β-cell death, which is regarded as one of the causative factors of T2DM. To test whether there are any connections between BPA exposure and hIAPP misfolding, we investigated the effects of BPA on hIAPP aggregation using thioflavin-T based fluorescence, transmission electronic microscopy, circular dichroism, dynamic light scattering, size-exclusion chromatography, fluorescence-dye leakage assay in an artificial micelle system and the generation of reactive oxygen species in INS-1 cells. We demonstrated that BPA not only dose-dependently promotes the aggregation of hIAPP and enhances the membrane disruption effects of hIAPP, but also promotes the extent of hIAPP aggregation related oxidative stress. Taken together, our results suggest that BPA exposure increased T2DM risk may involve the exacerbated toxic aggregation of hIAPP.

Low dose bisphenol A impairs spermatogenesis by suppressing reproductive hormone production and promoting germ cell apoptosis in adult rats

Bisphenol A (BPA), an estrogenic chemical, has been shown to reduce sperm count; however, the underlying mechanisms remain unknown. Herein, we show that oral administration of BPA (2 µg/kg) for consecutive 14 days in adult rats (BPA rats) significantly reduced the sperm count and the number of germ cells compared to controls. The serum levels of testosterone and follicle-stimulating hormone (FSH), as well as the level of GnRH mRNA in BPA rats were lower than those of control rats. Testosterone treatment could partially rescue the reduction of germ cells in BPA rats. Notably, the number of apoptotic germ cells was significantly increased in BPA rats, which was insensitive to testosterone. Furthermore, the levels of Fas, FasL and caspase-3 mRNA in the testicle of BPA rats were increased in comparison with controls. These results indicate that exposure to a low dose of BPA impairs spermatogenesis through decreasing reproductive hormones and activating the Fas/FasL signaling pathway.

Activation of the mTOR pathway by low levels of xenoestrogens in breast epithelial cells from high-risk women

Breast cancer is an estrogen-driven disease. Consequently, hormone replacement therapy correlates with disease incidence. However, increasing male breast cancer rates over the past three decades implicate additional sources of estrogenic exposure including wide spread estrogen-mimicking chemicals or xenoestrogens (XEs), such as bisphenol-A (BPA). By exposing renewable, human, high-risk donor breast epithelial cells (HRBECs) to BPA at concentrations that are detectable in human blood, placenta and milk, we previously identified gene expression profile changes associated with activation of mammalian target of rapamycin (mTOR) pathway genesets likely to trigger prosurvival changes in human breast cells. We now provide functional validation of mTOR activation using pairwise comparisons of 16 independent HRBEC samples with and without BPA exposure. We demonstrate induction of key genes and proteins in the PI3K-mTOR pathway--AKT1, RPS6 and 4EBP1 and a concurrent reduction in the tumor suppressor, phosphatase and tensin homolog gene protein. Altered regulation of mTOR pathway proteins in BPA-treated HRBECs led to marked resistance to rapamycin, the defining mTOR inhibitor. Moreover, HRBECs pretreated with BPA, or the XE, methylparaben (MP), surmounted antiestrogenic effects of tamoxifen showing dose-dependent apoptosis evasion and induction of cell cycling. Overall, XEs, when tested in benign breast cells from multiple human subjects, consistently initiated specific functional changes of the kind that are attributed to malignant onset in breast tissue. Our observations demonstrate the feasibility of studying renewable human samples as surrogates and reinforce the concern that BPA and MP, at low concentrations detected in humans, can have adverse health consequences.

Pre-natal exposure of mice to bisphenol A elicits an endometriosis-like phenotype in female offspring

Endometriosis is a chronic gynecological disease characterized by the growth of endometrial tissue outside the uterine cavity. Exposure to endocrine disruptors during critical period of development causes long-lasting effects, being the genital system one of the targets. This study describes the effects on female genital system caused by developmental exposure to the endocrine-disrupting chemical bisphenol A (BPA) during pre- and peri-natal development in mice. To this end, timed pregnant Balb-C mice were treated from day 1 of gestation to 7 days after delivery with BPA (100, or 1000 microg/kg/day). After delivery, pups were held for 3 months; then, pelvic organs were analyzed in their entirety and livers of both pups and moms were studied for the presence of BPA. We found in the adipose tissue surrounding the genital tracts of a consistent number of treated animals, endometriosis-like structure with the presence of both glands and stroma and expressing both estrogen receptor and HOXA-10. Moreover, cystic ovaries, adenomatous hyperplasia with cystic endometrial hyperplasia and atypical hyperplasia were significantly more frequent in treated animals respect to the controls. Finally, BPA was found in the livers of exposed moms and female offspring. In conclusion, we describe for the first time an endometriosis-like phenotype in mice, elicited by pre-natal exposition to BPA. This observation may induce to thoroughly reconsider the pathogenesis and treatment of endometriosis, considering the high incidence of endometriosis and the problems caused by associated infertility.