Low-dose Bisphenol A Research Articles

Long-term exposure to environmentally relevant Bisphenol-A levels affects growth, swimming, condition factor, sex ratio and histology of juvenile zebrafish

Bisphenol A (BPA) is an environmental estrogen which perturbs hormone signaling pathways adversely affecting aquatic organisms. To evaluate the impact of developmental exposure to long term yet environmentally relevant low doses of BPA, wild-type juvenile zebrafish of 35 days post fertilization were treated with BPA (1 and 10 µg/L), treatment control (0.5% v/v methanol) and control for 60 days. Both BPA treatments led to significantly increased morality overtime. Length increment and specific growth rates became significantly high in BPA exposed zebrafish overtime. Obesogenic property of BPA was not evident with longexposure to low BPA doses. A significantly high and BPA dose-dependent female-biased sex ratios were observed following the juvenile exposure. Significantly low swimming speed was recorded in the fish of both BPA-treated tanks than that of control. Condition factor was significantly low in BPA exposed fish indicating the poor-wellness. There were numerous histopathological alterations of gonads, liver and kidney indicating impacts of juvenile exposure in zebrafish. Altered growth, swimming, mortality, feminization and histopathological changes in zebrafish induced by BPA indicate the risks associated with developmental exposures. The findings call for more comprehensive studies to comprehend the ecological risks imposed by low concentrations of environmental estrogens in urban aquatic ecosystems.

The Possible Protective Effect of Taurine on Bisphenol Induced Structural Changes on the Cerebral Cortex of Rats: Histological and Immunohistochemical Study.

Bisphenol A (BPA) is a chemical compound that has been used in many industries, such as paints and dental sealants. Taurine is a semi-essential amino acid with antioxidant, anti-inflammatory, and anti-apoptotic actions. This study aimed to evaluate the possible protective effect of taurine on BPA-induced structural changes in the cerebral cortex of rats using histological and immunohistochemical methods. 35 Wistar rats (180-200 gm) were divided into control: 10 rats; Group I: 5 rats received corn oil (0.5 mL/day); Group II (Bisphenol low dose; BPAL): 5 rats received a low dose of BPA (25 mg/kg/three times/week); Group III (Bisphenol high dose; BPAH): 5 rats received a high dose of BPA (100 mg/kg/three times/week; Group IV: (BPAL + taurine): 5 rats received taurine 100 mg/kg/day and BPAL (25 mg/kg/three times/week); Group V: (BPAH + taurine): 5 rats received taurine 100 mg/kg/day and BPH (100 mg/kg/ three times/week). BPAL& BPAH groups showed significant dose-dependent histological changes of the neuropil, pyramidal, and neuroglial cells at H&E stained sections, significantly increased GFAP, caspase- 3 immunohistochemical reaction with cells positive for Ki67 with many mitotic figures. BPAL + taurine and BPAH + taurine groups showed amelioration of the previously mentioned results. Taurine ameliorated the structural changes induced by BPA in the cerebral cortex of rats.

Prenatal low-dose Bisphenol A exposure impacts cortical development via cAMP-PKA-CREB pathway in offspring.

Bisphenol A (BPA) is a widely used plasticizer known to cause various disorders. Despite a global reduction in the use of BPA-containing products, prenatal exposure to low-dose BPA, even those below established safety limits, has been linked to neurological and behavioral deficits in childhood. The precise mechanisms underlying these effects remain unclear. In the present study, we observed a significant increase in the number of cortical neurons in offspring born to dams exposed to low-dose BPA during pregnancy. We also found that this prenatal exposure to low-dose BPA led to increased proliferation but reduced migration of cortical neurons. Transcriptomic analysis via RNA sequencing revealed an aberrant activation of the cAMP-PKA-CREB pathway in offspring exposed to BPA. The use of H89, a selective PKA inhibitor, effectively rescued the deficits in both proliferation and migration of cortical neurons. Furthermore, offspring from dams exposed to low-dose BPA exhibited manic-like behaviors, including hyperactivity, anti-depressant-like responses, and reduced anxiety. While H89 normalized hyperactivity, it didn't affect the other behavioral changes. These results suggest that the overactivation of PKA plays a causative role in BPA-induced changes in neuronal development. Our data also indicate that manic-like behaviors induced by prenatal low-dose BPA exposure may be influenced by both altered neuronal development and abnormal PKA signaling in adulthood.

Prenatal Exposure to Bisphenol A and/or Diethylhexyl Phthalate Impacts Brain Monoamine Levels in Rat Offspring.

This study examines the sex-specific effects of gestational exposure (days 6-21) to endocrine-disrupting chemicals such as bisphenol A (BPA), diethylhexyl phthalate (DEHP), or their combination on brain monoamine levels that play an important role in regulating behavior. Pregnant Sprague-Dawley rats were orally administered saline, low doses (5 µg/kg BW/day) of BPA or DEHP, and their combination or a high dose (7.5 mg/kg BW/day) of DEHP alone or in combination with BPA during pregnancy. The offspring were subjected to a behavioral test and sacrificed in adulthood, and the brains were analyzed for neurotransmitter levels. In the paraventricular nucleus, there was a marked reduction in dopamine levels (p < 0.01) in male offspring from the BPA, DEHP, and B + D (HD) groups, which correlated well with their shock probe defensive burying times. Neurotransmitter changes in all brain regions examined were significant in female offspring, with DEHP (HD) females being affected the most, followed by the B + D groups. BPA and/or DEHP (LD) increased monoamine turnover in a region-specific manner in male offspring (p < 0.05). Overall, prenatal exposure to BPA, DEHP, or their combination alters monoamine levels in a brain region-specific, sex-specific, and dose-dependent manner, which could have implications for their behavioral and neuroendocrine effects.

Gestational bisphenol A exposure alters energy homeostasis and adult hypothalamic neurogenesis in female mice

Regulation of physiological homeostasis, including energy balance, is thought to be modified by low levels of adult neurogenesis in the hypothalamus. Hormones such as oestradiol can influence both embryonic and adult hypothalamic neurogenic programs, demonstrating a sensitivity of hypothalamic neural progenitor cells to endogenous hormones. Previously we showed that gestational exposure to environmental levels of the xenoestrogen bisphenol A (BPA) changed neural progenitor cell behaviors in the embryo; however, we did not examine if these changes were permanent to affect adult neurogenesis. Here we investigated whether adult neuro- and/or gliogenesis were altered in mice prenatally exposed to BPA and placed on a high-fat diet challenge. Gestationally exposed adult female mice on a standard diet gained less weight than non-BPA controls, whereas gestationally exposed BPA females on a high-fat diet gained more weight than controls. Males exposed to gestational BPA showed no differences in weight gain relative to control males. Concomitantly, adult neurogenesis was increased in the VMH, DMH, and PVN of adult female mice exposed to BPA on standard diet, suggesting that disrupted adult neurogenesis might perturb normal energy balance regulation in females. These results add to growing evidence that low-dose BPA exposure in utero causes changes to adult hypothalamic function.

The Olfactory Receptor Olfr25 Mediates Sperm Dysfunction Induced by Low-Dose Bisphenol A through the CatSper-Ca2+ Signaling Pathway.

Bisphenol A (BPA), a typical endocrine disruptor, is known to have various adverse effects on the male reproductive system. However, the toxic effects and mechanisms of low-dose BPA have not yet been fully explored. In this study, male Kunming mice were orally administered low-dose BPA (0.03, 0.3 and 3 mg/kg/d) for ten consecutive weeks. Pathological sections of testicular tissue showed no significant morphological differences after BPA exposure. An analysis of the functional parameters of sperm revealed that exposure to low-dose BPA significantly decreased sperm motility, chemotaxis, and the acrosome reaction. An in vitro BPA exposure model combined with an omics data analysis showed that the olfactory receptor-related pathway was significantly enriched after BPA treatment. Subsequent experiments verified the reduced mRNA level of a novel olfactory receptor gene, Olfr25, in vivo and in vitro exposure models. Meanwhile, exposure to low-dose BPA reduced the intracellular calcium ion concentration and the mRNA levels of pore-forming subunits of the CatSper channel in sperm. Importantly, the knockdown of Olfr25 inhibited calcium ion levels and CatSper subunit expression in GC-2 cells. Olfr25 overexpression attenuated the BPA-induced downregulation of CatSper subunit expression in GC-2 cells. These findings indicate that Olfr25 might participate in low-dose BPA-induced sperm dysfunction by affecting the CatSper-Ca2+ signaling pathway. This study reveals a new mechanism underlying the effects of low-dose BPA on sperm function and provides a reference for assessing the safety of low-dose BPA exposure.

Distinct epigenetic modulation of differentially expressed genes in the adult mouse brain following prenatal exposure to low-dose bisphenol A.

Bisphenol A (BPA) is a common component in the manufacture of daily plastic consumer goods. Recent studies have suggested that prenatal exposure to BPA can increase the susceptibility of offspring to mental illness, although the underlying mechanisms remain unclear. In this study, we performed transcriptomic and epigenomic profiling in the adult mouse brain following prenatal exposure to low-dose BPA. We observed a sex-specific transcriptional dysregulation in the cortex, with more significant differentially expressed genes was observed in adult cortex from male offspring. Moreover, the upregulated genes primarily influenced neuronal functions, while the downregulated genes were significantly associated with energy metabolism pathways. More evidence supporting impaired mitochondrial function included a decreased ATP level and a reduced number of mitochondria in the cortical neuron of the BPA group. We further investigated the higher-order chromatin regulatory patterns of DEGs by incorporating published Hi-C data. Interestingly, we found that upregulated genes exhibited more distal interactions with multiple enhancers, while downregulated genes displayed relatively short-range interactions among adjacent genes. Our data further revealed decreased H3K9me3 signal on the distal enhancers of upregulated genes, whereas increased DNA methylation and H3K27me3 signals on the promoters of downregulated genes. In summary, our study provides compelling evidence for the potential health risks associated with prenatal exposure to BPA, and uncovers sex-specific transcriptional changes with a complex interplay of multiple epigenetic mechanisms.

Prenatal exposure to low-dose bisphenol A disrupts hippocampal DNA methylation and demethylation in male rat offspring.

Earlier research has demonstrated that developmental exposure to bisphenol A (BPA) has persistent impacts on both adult brain growth and actions. It has been suggested that BPA might obstruct the methylation coding of the genes in the brain. In this study, the methylation changes in the hippocampus tissue of male rat pups were examined following prenatal BPA exposure. Pregnant Sprague-Dawley rats were treated with either vehicle (tocopherol-stripped corn oil) or BPA (4, 40, or 400μg/kg·body weight/day) throughout the entire duration of gestation and lactation. At 3weeks of age, the male rat offspring were euthanized, and the hippocampus were dissected out for analysis. The expression levels of DNA methyltransferases (DNMT1, DNMT3A, and DNMT3B) and DNA demethylases (TET1, Gadd45a, Gadd45b, and Apobec1) were analyzed in the hippocampus by means of quantitative real-time polymerase chain reaction and Western blotting, respectively. The results showed that prenatal exposure to BPA upregulated the expression of enzymes associated with DNA methylation and demethylation processes in the hippocampus of male rat offspring. These findings suggest that prenatal exposure to a low dose of BPA could potentially disrupt the balance of methylation and demethylation in the hippocampus, thereby perturbing epigenetic modifications. This may represent a neurotoxicity mechanism of BPA.

Low-dose BPA-induced neuronal energy metabolism dysfunction and apoptosis mediated by PINK1/parkin mitophagy pathway in juvenile rats

Bisphenol A (BPA) is related to neurological disorders involving mitochondrial dysfunction, while the mechanism remains elusive. Therefore, we explored it through in vitro and in vivo experiments. In vitro, hippocampal neurons derived from neonatal rats of different genders were exposed to 1–100 nM and 100 μM BPA, autophagy activator Rapa and inhibitor 3-MA for 7 d. The results suggested that even nanomolar BPA (1–100 nM) disturbed Ca2+ homeostasis and damaged the integrity of mitochondrial cristae in neurons (p < 0.05). Furthermore, BPA increased the number of autophagic lysosomes, LC3II/LC3I ratio, and p62 expression, and decreased parkin expression (p < 0.05), suggesting that the entry of damaged mitochondria into autophagic pathway was prompted, while the autophagic degradation pathway was blocked. This further disrupts neuronal energy metabolism and promotes neuronal apoptosis. However, Rapa attenuated the adverse effects caused by BPA, while 3-MA exacerbated these reactions. In vivo, exposure of juvenile rats to 0.5, 50, 5000 μg/kg‧bw/day BPA during PND 7–21 markedly impaired the structure of hippocampal mitochondria, increased the number of autophagosomes, the rate of neuronal apoptosis, and the expression levels of pro-apoptotic proteins Cyt C, Bax, Bak1, and Caspase3, and decreased the expression of anti-apoptotic protein Bcl2 (p < 0.05). Particularly, male rats are more sensitive to low-dose BPA than females. Overall, environmental-doses BPA can induce the imbalance of energy metabolism in hippocampal neurons via PINK1/parkin mitophagy, thereby inducing their apoptosis. Importantly, this study provides a theoretical basis for attenuating BPA-related neurological diseases.

Toxicity of low dose bisphenols in human iPSC-derived cardiomyocytes and human cardiac organoids – Impact on contractile function and hypertrophy

Bisphenol A (BPA) and its analogs are common environmental chemicals with various adverse health impacts, including cardiac toxicity. In this study, we examined the long term effect of low dose BPA and three common BPA analogs, bisphenol S (BPS), bisphenol F (BPF), and bisphenol AF (BPAF), in human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) based models. HiPSC-CMs and human cardiac organoids were exposed to these chemicals for 4–5 or 20 days. 1 nM BPA, BPS, and BPAF, but not BPF, resulted in suppressed myocyte contractility, retarded contraction kinetics, and aberrant Ca2+ transients in hiPSC-CMs. In cardiac organoids, BPAF and BPA, but not the other bisphenols, resulted in suppressed contraction and Ca2+ transients, and aberrant contraction kinetics. The order of toxicities was BPAF > BPA>∼BPS > BPF and the toxicities of BPAF and BPA were more pronounced under longer exposure. The impact of BPAF on myocyte contraction and Ca2+ handling was mediated by reduction of sarcoplasmic reticulum Ca2+ load and inhibition of L-type Ca2+ channel involving alternation of Ca2+ handling proteins. Impaired myocyte Ca2+ handling plays a key role in cardiac pathophysiology and is a characteristic of cardiac hypertrophy; therefore we examined the potential pro-hypertrophic cardiotoxicity of these bisphenols. Four to five day exposure to BPAF did not cause hypertrophy in normal hiPSC-CMs, but significantly exacerbated the hypertrophic phenotype in myocytes with existing hypertrophy induced by endothelin-1, characterized by increased cell size and elevated expression of the hypertrophic marker proBNP. This pro-hypertrophic cardiotoxicity was also occurred in cardiac organoids, with BPAF having the strongest toxicity, followed by BPA. Our findings demonstrate that long term exposures to BPA and some of its analogs cause contractile dysfunction and abnormal Ca2+ handling, and have potential pro-hypertrophic cardiotoxicity in human heart cells/tissues, and suggest that some bisphenol chemicals may be a risk factor for cardiac hypertrophy in human hearts.

Maternal oral exposure to low-dose BPA accelerates the onset of puberty by promoting prepubertal Kiss1 expression in the AVPV nucleus of female offspring

As the incidence of precocious puberty has risen in recent years and the age at puberty onset is younger, children may be at increased risk for health consequences associated with the early onset of puberty. Bisphenol A (BPA) is recognized as an endocrine disruptor chemical that is reported to induce precocious puberty. The effect of BPA exposure modes, times, and doses (especially low dose) were controversial. In the present study, we evaluated the potential effects of maternal exposure to low-dose BPA on the hypothalamus, particularly on the arcuate (ARC) nucleus and anteroventral periventricular (AVPV) nucleus during peri-puberty in offspring of BPA-treated rats. Pregnant rats were exposed to corn oil vehicle, 0.05 mg·kg−1·day−1 BPA, or 5 mg·kg−1·day−1 from gestation day 1 (GD1) to postnatal day 21 (PND21) by daily gavage. Body weight (BW), vaginal opening (VO), ovarian follicular luteinization, and relevant hormone concentrations were measured; hypothalamic Kiss1 and GnRH1 levels by western immunoblot analysis were also assessed as indices of puberty onset. During or after exposure, low-dose BPA restricted BW after birth (at PND1 and PND5), and subsequently accelerated puberty onset by promoting the expression of prepubertal Kiss1 and GnRH1 in the AVPV nucleus on PND30, leading to advanced VO, an elevation in LH and FSH concentrations (on PND30). We also noted increased BW on PND30 and PND35. Maternal oral exposure to low-dose BPA altered the BW curve during the neonatal and peripubertal periods, and subsequently accelerated puberty onset by promoting prepubertal Kiss1 expression in the AVPV nucleus.

Bisphenol A (BPA) exposure aggravates hepatic oxidative stress and inflammatory response under hypertensive milieu – Impact of low dose on hepatocytes and influence of MAPK and ER stress pathways

Human exposure to the hazardous chemical, Bisphenol A (BPA), is almost ubiquitous. Due to the prevalence of hypertension (CVD risk factor) in the aged human population, it is necessary to explore its adverse effect in hypertensive subjects. The current study exposed the Nω-nitro-l-arginine methyl ester (L-NAME) induced hypertensive Wistar rats to human exposure relevant low dose of BPA (50 μg/kg) for 30 days period. The liver biochemical parameters, histopathology, immunohistochemistry, gene expression (RT-qPCR), trace elements (ICP-MS), primary rat hepatocytes cell culture and metabolomic (1H NMR) assessments were performed. Results illustrate that BPA exposure potentiates/aggravates hypertension induced tissue abnormalities (hepatic fibrosis), oxidative stress, ACE activity, malfunction of the antioxidant system, lipid abnormalities and inflammatory factor (TNF-α and IL-6) expression. Also, in cells, BPA increased ROS generation, mitochondrial dysfunction and lipid peroxidation without any impact on cytotoxicity and caspase 3 and 9 activation. Notably, BPA exposure modulate lipid metabolism (cholesterol and fatty acid) in primary hepatocytes. Finally, the influence of ERK1/2, p38MAPK, ER stress and oxidative stress during relatively high dose of BPA elicited cytotoxicity was observed. Therefore, a precise hazardous risk investigation of BPA exposure in hypertensive populations is highly recommended.

Reproductive toxicity of bisphenol A, at environmentally relevant concentrations, on ovarian redox balance, maturational response, and intra-oocyte signalling events in Labeo bata

Bisphenol A (BPA) is a widely used plastic monomer that potentially interferes with ovarian neuroendocrine, endocrine, and autocrine/paracrine factors, causing reproductive dysfunction. However, the influence of BPA on redox balance, estrogen receptor (ER) expression vis-à-vis meiotic cell cycle progression, and intra-oocyte signalling events has not been extensively investigated. The present study examines the impact of BPA on reproductive toxicity in female Labeo bata (Order Cypriniformes, Family Cyprinidae), a freshwater teleost preferred as a food fish in the Indian subcontinent. Our results show that while ovarian weight (gonadosomatic index, GSI) and dynamics of follicular growth undergo pronounced changes during the annual reproductive cycle, chronic BPA exposure at environmentally relevant concentrations promotes follicular atresia concomitant with reduced GSI during the spawning phase, the highest response being observed due to low-dose (0.1 μg/L, 0.438 nM) BPA exposure in vivo. Furthermore, BPA perturbation of ovarian StAR expression and ERα/ERβ homeostasis corroborates with elevated oxidative stress in BPA-treated ovary, FG follicles, and follicular cells. A sharp increase in ROS accumulation and nitric oxide (NO) levels in BPA-treated full-grown (FG) follicles coupled with loss of redox balance, elevated follicular cell death, and activation of apoptotic markers (caspase -8, -9, -3, Bax) indicate poor oocyte health and reproductive toxicity. Importantly, maturational steroid (MIS, 17,20β-P)-induced cyclin B-p34cdc2 activation and elevated GVBD (germinal vesicle breakdown) response require protein kinase A (PKA) inhibition and participation of Mos/MAPK- and cdc25-mediated signalling events. While the adenylate cyclase activator forskolin (FK) abrogates, priming with a PKA inhibitor (H89) promotes the meiotic G2-M1 transition, confirming the role of PKA in meiotic cell cycle progression in this species. Furthermore, the negative influence of BPA priming on 17,20β-P-induced oocyte maturation involves elevated PKAc phosphorylation (activation) and significant alteration in Mos/MAPK signalling, indicating derailed meiotic maturational competence and disrupted oocyte quality.

Impact of bisphenol A on cell viability and inflammatory cytokine production in human cervical epithelial cells.

An intact cervix is a barrier that prevents pathogenic bacteria from invading the uterine and amniotic cavity during pregnancy. Its disruption is associated with ascending infection and adverse pregnancy outcomes. This study analyzed the effects of bisphenol A (BPA), a chemical used in plastics manufacturing, on cell death and inflammation in cervical epithelial cells. Ectocervical epithelial (ecto) and endocervical epithelial (endo) cells were treated with 100ng/mL and 300ng/mL of BPA for 48h. The cells were subjected to flow cytometry using annexin V and propidium iodide to determine apoptosis and necrosis, cell cycle analysis, and ELISA to determine the levels of inflammatory cytokines (IL-6, IL-8, and IL-10). Low-dose and high-dose BPA significantly increased the live ecto cell population dose-dependently. BPA did not have any noticeable effect on cell cycle progression in either cell type. BPA treatment also decreased the apoptotic ecto and endo cell population dose-dependently. Lastly, high dose BPA significantly increased IL-6 in ecto and endo cells. However, IL-8 and IL-10 were not affected by BPA treatments. Chemical exposure damage to the cervix can lead to adverse pregnancy outcomes. Our study showed that the BPA concentrations reported in pregnant subjects do not induce cervical cell toxicity . The decrease in apoptosis and increase in live cells may be a compensatory mechanism to preserve the integrity of the cervical epithelial layer.

Exposure to low dose of Bisphenol A (BPA) intensifies kidney oxidative stress, inflammatory factors expression and modulates Angiotensin II signaling under hypertensive milieu.

Humans are constantly exposed to low concentrations of ubiquitous environmental pollutant, Bisphenol A (BPA). Due to the prevalence of hypertension (one of the major risk factors of cardiovascular disease [CVD]) in the population, it is necessary to explore the adverse effect of BPA under hypertension associated pathogenic milieu. The current study exposed the Nω-nitro-l-arginine methyl ester (L-NAME) induced hypertensive Wistar rats to low dose BPA (50 μg/kg) for 30 days period. In tissue samples immunohistochemistry, real-time quantitative polymerase chain reaction and enzymatic assays were conducted. Moreover, studies on primary kidney cell culture were employed to explore the impact of low dose of BPA exposure at nanomolar level (20-80 nM range) on renal cells through various fluorescence assays. The observed results illustrate that BPA exposure potentiates/aggravates hypertension induced tissue abnormalities (renal fibrosis), oxidative stress (ROS generation), elevated angiotensin-converting enzyme activity, malfunction of the antioxidant and tricarboxylic acid cycle enzymes, tissue lipid abnormalities and inflammatory factor expression (both messenger RNA and protein level of TNF-α and IL-6). Further, in vitro exposure of nM levels of BPA to primary kidney cells modulates oxidative stress (both superoxide and total ROS), mitochondrial physiology (reduced mitochondrial transmembrane potential-∆ψm) and lipid peroxidation in a dose dependent manner. In addition, angiotensin II induced ROS generation was aggravated further by BPA during coexposure in kidney cells. Therefore, during risk assessment, a precise investigation on BPA exposure in hypertensive (CVD vulnerable) populations is highly suggested.

Low-dose Bisphenol A exposure alters the functionality and cellular environment in a human cardiomyocyte model

Early embryonic development represents a sensitive time-window during which the foetus might be vulnerable to the exposure of environmental contaminants, potentially leading to heart diseases also later in life. Bisphenol A (BPA), a synthetic chemical widely used in plastics manufacturing, has been associated with heart developmental defects, even in low concentrations. This study aims to investigate the effects of environmentally relevant doses of BPA on developing cardiomyocytes using a human induced pluripotent stem cell (hiPSC)-derived model. Firstly, a 2D in vitro differentiation system to obtain cardiomyocytes from hiPSCs (hiPSC-CMs) have been established and characterised to provide a suitable model for the early stages of cardiac development. Then, the effects of a repeated BPA exposure, starting from the undifferentiated stage throughout the differentiation process, were evaluated. The chemical significantly decreased the beat rate of hiPSC-CMs, extending the contraction and relaxation time in a dose-dependent manner. Quantitative proteomics analysis revealed a high abundance of basement membrane (BM) components (e.g., COL4A1, COL4A2, LAMC1, NID2) and a significant increase in TNNC1 and SERBP1 proteins in hiPSC-CMs treated with BPA. Network analysis of proteomics data supported altered extracellular matrix remodelling and provided a disease-gene association with well-known pathological conditions of the heart. Furthermore, upon hypoxia-reoxygenation challenge, hiPSC-CMs treated with BPA showed higher rate of apoptotic events. Taken together, our results revealed that a long-term treatment, even with low doses of BPA, interferes with hiPSC-CMs functionality and alters the surrounding cellular environment, providing new insights about diseases that might arise upon the toxin exposure. Our study contributes to the current understanding of BPA effects on developing human foetal cardiomyocytes, in correlation with human clinical observations and animal studies, and it provides a suitable model for New Approach Methodologies (NAMs) for environmental chemical hazard and risk assessment.

Bisphenol-A exposure alters liver, kidney, and pancreatic Klotho expression by HSP60-activated mTOR/autophagy pathway in male albino rats.

The effect of bisphenol-A (BPA) on Klotho protein (aging-suppressing protein) expression in different body organs has not been sufficiently addressed by literature studies. The study investigated the impact of BPA on Klotho expression in multiple organs including the liver, kidney, and pancreas and suggested the involved molecular pathways. Twenty-seven male Wistar albino rats were divided into 3 equal groups: control, low-dose BPA (4.5 µg/L), and high-dose BPA (8 µg/L) groups in drinking water for 45 consecutive days. Liver, kidney, and pancreatic specimens were prepared for a gene study of Klotho, HSP60, mTOR, and ULK1 mRNA expressions. Also, the tissue specimens were measured for malondialdehyde (MDA), superoxide dismutase (SOD), and nitric oxide (NO) levels. Paraffin-embedded sections were also prepared and subjected to Hematoxylin and Eosin (H&E) staining and immunohistochemical detection of Klotho and HSP60. The results revealed an alteration in the MDA, SOD, NO tissue levels, disturbed gene expression profile, and apoptotic changes in the histological findings of the examined organs which were obvious (p < 0.05) in the high-dose group. The anti-aging Klotho gene/protein expression was reduced (p < 0.05) more in the high-dose BPA group than in the low dose. In contrast, HSP60 gene/protein expression was significantly increased (p < 0.05) more in the high dose. It was concluded that BPA exposure contributed to cell stress and markedly reduced Klotho protein expression in liver, kidney, and pancreatic tissues, possibly by modulation of the HSP60-activated mTOR/autophagy signaling.

Curcumin protects against bisphenol A-induced hepatic steatosis by inhibiting cholesterol absorption and synthesis inCD-1 mice.

Curcumin is a polyphenol extracted from the rhizome of turmeric, and our previous research showed that curcumin inhibited cholesterol absorption and had cholesterol-lowering effect. Bisphenol A (BPA), a common plasticizer, is widely used in the manufacture of food packaging and is associated with non-alcoholic fatty liver disease (NAFLD). We hypothesized that curcumin could protect against BPA-induced hepatic steatosis by inhibiting cholesterol absorption and synthesis. Male CD-1 mice fed BPA-contaminated diet with or without curcumin for 24 weeks were used to test our hypothesis. We found that chronic low-dose BPA exposure significantly increased the levels of serum triglyceride (TG), total cholesterol (TC), and low-density lipoprotein cholesterol and the contents of liver TG and TC, resulting in liver fat accumulation and hepatic steatosis while curcumin supplementation could alleviate BPA-induced dyslipidemia and hepatic steatosis. Moreover, the anti-steatosis and cholesterol-lowering effects of curcumin against BPA coincided with a significant reduction in intestinal cholesterol absorption and liver cholesterol synthesis, which was modulated by suppressing the expression of sterol regulatory element-binding protein-2 (SREBP-2), Niemann-Pick C1-like 1 (NPC1L1), and 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGCR) in the small intestine and liver. In addition, the expression levels of liver lipogenic genes such as liver X receptor alpha (LXRα), SREBP-1c, acetyl-CoA carboxylase 1 (ACC1), and ACC2 were also markedly down-regulated by curcumin. Overall, our findings indicated that curcumin inhibited BPA-induced intestinal cholesterol absorption and liver cholesterol synthesis by suppressing SREBP-2, NPC1L1, and HMGCR expression, subsequently reducing liver cholesterol accumulation and fat synthesis, thereby preventing hepatic steatosis and NAFLD.

Bisphenol A induced hepatic steatosis by disturbing bile acid metabolism and FXR/TGR5 signaling pathways via remodeling the gut microbiota in CD-1 mice

Dysregulation of gut microbiota-mediated bile acid (BA) metabolism plays an important role in the pathogenesis of hepatic steatosis and nonalcoholic fatty liver disease (NAFLD). Our previous studies found that bisphenol A (BPA) exposure induced hepatic steatosis and gut microbiota dysbiosis. However, whether the gut microbiota-dependent BA metabolism alterations were involved in BPA-induced hepatic steatosis remains unclear. Therefore, we explored the gut microbiota-related metabolic mechanisms of hepatic steatosis induced by BPA. Male CD-1 mice were exposed to low-dose BPA (50 μg/kg/day) for 6 months. Fecal microbiota transplantation (FMT) and broad-spectrum antibiotic cocktail (ABX) treatment were further adopted to test the role of gut microbiota in the adverse effects of BPA. We found that BPA induced hepatic steatosis in mice. Additionally, 16S rRNA gene sequencing showed that BPA reduced the relative abundance of Bacteroides, Parabacteroides and Akkermansia, which are associated with BA metabolism. Metabolomic analyses demonstrated that BPA significantly altered the ratio of conjugated to unconjugated BAs and increased the total level of taurine-α/β-muricholic acid while decreasing the level of chenodeoxycholic acid, thus inhibiting the activation of special receptors, including farnesoid X receptor (FXR) and Takeda G protein-coupled receptor 5 (TGR5), in the ileum and liver. The inhibition of FXR reduced short heterodimer partner and subsequently induced cholesterol 7α-hydroxylase and sterol regulatory element-binding protein-1c expression, which is related to hepatic BA synthesis and lipogenesis, eventually leading to liver cholestasis and steatosis. Furthermore, we found that mice that received FMT from BPA-exposed mice developed hepatic steatosis, and the influences of BPA on hepatic steatosis and FXR/TGR5 signaling pathways could be eliminated by ABX treatment, confirming the role of gut microbiota in BPA effects. Collectively, our study illustrates that suppressed microbiota-BA-FXR/TGR signaling pathways may be a potential mechanism for hepatic steatosis induced by BPA, providing a new target for the prevention of BPA-induced NAFLD.

Proarrhythmic toxicity of low dose bisphenol A and its analogs in human iPSC-derived cardiomyocytes and human cardiac organoids through delay of cardiac repolarization

Bisphenol A (BPA) and its analogs are common environmental chemicals with many potential adverse health effects. The impact of environmentally relevant low dose BPA on human heart, including cardiac electrical properties, is not understood. Perturbation of cardiac electrical properties is a key arrhythmogenic mechanism. In particular, delay of cardiac repolarization can cause ectopic excitation of cardiomyocytes and malignant arrhythmia. This can occur as a result of genetic mutations (i.e., long QT (LQT) syndrome), or cardiotoxicity of drugs and environmental chemicals. To define the impact of low dose BPA on electrical properties of cardiomyocytes in a human-relevant model system, we examined the rapid effects of 1 nM BPA in human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) using patch-clamp and confocal fluorescence imaging. Acute exposure to BPA delayed repolarization and prolonged action potential duration (APD) in hiPSC-CMs through inhibition of the hERG K+ channel. In nodal-like hiPSC-CMs, BPA acutely increased pacing rate through stimulation of the If pacemaker channel. Existing arrhythmia susceptibility determines the response of hiPSC-CMs to BPA. BPA resulted in modest APD prolongation but no ectopic excitation in baseline condition, while rapidly promoted aberrant excitations and tachycardia-like events in myocytes that had drug-simulated LQT phenotype. In hiPSC-CM-based human cardiac organoids, the effects of BPA on APD and aberrant excitation were shared by its analog chemicals, which are often used in “BPA-free” products, with bisphenol AF having the largest effects. Our results reveal that BPA and its analogs have repolarization delay-associated pro-arrhythmic toxicity in human cardiomyocytes, particularly in myocytes that are prone to arrhythmias. The toxicity of these chemicals depends on existing pathophysiological conditions of the heart, and may be particularly pronounced in susceptible individuals. An individualized approach is needed in risk assessment and protection.