Effects of single or combined exposure to bisphenol A and mono(2-ethylhexyl)phthalate on oxidant/antioxidant status, endoplasmic reticulum stress, and apoptosis in HepG2 cell line

Consensus on the key characteristics of metabolism disruptors

Metabolism-disrupting agents (MDAs) are chemical, infectious or physical agents that increase the risk of metabolic disorders. Examples include pharmaceuticals, such as antidepressants, and environmental agents, such as bisphenol A. Various types of studies can provide evidence to identify MDAs, yet a systematic method is needed to integrate these data to help to identify such hazards. Inspired by work to improve hazard identification of carcinogens using key characteristics (KCs), we developed 12 KCs of MDAs based on our knowledge of processes underlying metabolic diseases and the effects of their causal agents: (1) alters function of the endocrine pancreas; (2) impairs function of adipose tissue; (3) alters nervous system control of metabolic function; (4) promotes insulin resistance; (5) disrupts metabolic signalling pathways; (6) alters development and fate of metabolic cell types; (7) alters energy homeostasis; (8) causes inappropriate nutrient handling and partitioning; (9) promotes chronic inflammation and immune dysregulation in metabolic tissues; (10) disrupts gastrointestinal tract function; (11) induces cellular stress pathways; and (12) disrupts circadian rhythms. In this Consensus Statement, we present the logic that revealed the KCs of MDAs and highlight evidence that supports the identification of KCs. We use chemical, infectious and physical agents as examples to illustrate how the KCs can be used to organize and use mechanistic data to help to identify MDAs.

Enhanced endoplasmic reticulum stress signaling disrupts porcine sertoli cell function in response to Bisphenol A exposure

Bisphenol A (BPA), a pervasive substance in our daily lives and livestock excreta, poses significant threats due to its infiltration into foods and water sources. BPA has adverse impacts on male reproductive function, particularly affecting the critical Sertoli (ST) cells that play a pivotal role in the process of spermatogonia differentiating into spermatozoa. In this study, we examined the prevalence of BPA within the pig industry and delved into the impact of BPA exposure on the motility of boar sperm, the function of pig ST cells, as well as the underlying molecular mechanisms involved. This study revealed spatial disparities in the global distribution of BPA and its analogue contamination, utilizing data compiled from 130 comprehensive studies. The average concentration of BPA found in pig feed ranges from 9.7 to 47.9 μg/kg, while in serum, it averages between 55.1 and 75.6 ng/L. The BPA concentration in feed exhibits a negative correlation with sperm viability and the percentage of progressive motile spermatozoa. Exposure to BPA reduced sperm motility in boar and ST cell activity at both 6 and 24 h. The transcriptome analysis revealed that, compared to untreated control cells, endoplasmic reticulum stress (ERS)-related genes were upregulated in ST cells exposed to BPA at 6 and 24 h. This activation of ERS in ST cells was mediated by receptor protein kinase RNA-like endoplasmic reticulum kinase (PERK), inositol-requiring protein-1α (IRE1α), and activating transcription factor 6 (ATF6). Additionally, BPA exposure triggered oxidative stress and a proinflammatory response mediated by the transcription factor NF-κB, accompanied by an increase in downstream proinflammatory cytokines. BPA exposure also led to apoptosis in ST cells and upregulated the expression levels of pro-apoptosis proteins. However, inhibiting ERS activity with 4-PBA attenuated the BPA-induced inflammatory response and apoptosis in ST cells. Our findings suggest that BPA induced apoptosis and inflammatory response in porcine ST cells through persistent activation of ERS, thereby compromising the normal function of these cells.

Mixtures of phthalates disrupt expression of genes related to lipid metabolism and peroxisome proliferator-activated receptor signaling in mouse granulosa cells

Phthalates are a class of known endocrine-disrupting chemicals that are found in common everyday products. Several studies associate phthalate exposure with detrimental effects on ovarian function, including growth and development of the follicle and production of steroid hormones. We hypothesized that dysregulation of the ovary by phthalates may be mediated by phthalate toxicity towards granulosa cells, a major cell type in ovarian follicles responsible for key steps of hormone production and nourishing the developing oocyte. To test the hypothesis that phthalates target granulosa cells, we harvested granulosa cells from adult CD-1 mouse ovaries and cultured them for 96 h in vehicle control, a phthalate mixture, or a phthalate metabolite mixture (0.1 to 100 μg/ml). After culture, we measured metabolism of the phthalate mixture into monoester metabolites by the granulosa cells, finding that granulosa cells do not significantly contribute to ovarian metabolism of phthalates. Immunohistochemistry of phthalate metabolizing enzymes in whole ovaries confirmed that these enzymes are not strongly expressed in granulosa cells of antral follicles and that ovarian metabolism of phthalates likely occurs primarily in the stroma. RNA sequencing of treated granulosa cells identified 407 differentially expressed genes, with overrepresentation of genes from lipid metabolic processes, cholesterol metabolism, and peroxisome proliferator-activated receptor (PPAR) signaling pathways. Expression of significantly differentially expressed genes related to these pathways was confirmed using qPCR. Our results agree with previous findings that phthalates and phthalate metabolites have different effects on the ovary, but both interfere with PPAR signaling in granulosa cells.

Tetra methyl bisphenol F: another potential obesogen

BACKGROUND/OBJECTIVES

Obesity and its associated metabolic diseases are increasing globally. Sedentary lifestyle, high caloric diet, and genetic predisposition are known to contribute to the onset of obesity. It is increasingly recognized that exposure to environmental chemicals such as Bisphenol A (BPA) may also play a significant role. BPA has been correlated with an array of adverse health effects, including obesity and metabolic disorders. Due to public concern, manufacturers are replacing BPA with structural analogues for which there is limited toxicological data. The objective of this study was to assess the effects of these BPA analogues on adipogenesis.

METHODS

The adipogenic effects of Tetra Methyl Bisphenol F (TMBPF), Bisphenol F (BPF), Bisphenol AP (BPAP), and fluorine-9-bisphenol (BHPF) were evaluated in murine 3T3-L1 cells. The cells were treated with BPA and its analogues at concentrations from 0.01 µM to 20 µM, throughout differentiation, in the absence of Dexamethasone (Dex). Lipid accumulation, mRNA and protein levels of adipogenic markers was assessed.

RESULTS

We found that TMBPF, BPF and BPA increased 3T3-L1 lipid accumulation and the expression levels of adipogenic markers lipoprotein lipase (Lpl), fatty acid binding protein 4 (Fabp4) and perilipin (Plin) (1-20 µM; p < 0.05), whereas BHPF and BPAP had no effect in this model. Further, TMBPF induced adipogenesis to a greater extent than all the other chemicals including BPA (1-20 µM; p < 0.05). The effect mediated by TMBPF on expression levels of Fabp4, but not Plin, is likely mediated via peroxisome proliferator-activated receptor (PPAR) γ activation.

CONCLUSIONS

Of the BPA analogues tested, BPF was most similar to BPA in its effects, while TMBPF was most adipogenic. In addition, TMBPF is likely a PPARγ agonist, it is likely an obesogenic chemical and may be a metabolic disruptor.

Obesogens: a unifying theory for the global rise in obesity

Despite varied treatment, mitigation, and prevention efforts, the global prevalence and severity of obesity continue to worsen. Here we propose a combined model of obesity, a unifying paradigm that links four general models: the energy balance model (EBM), based on calories as the driver of weight gain; the carbohydrate-insulin model (CIM), based on insulin as a driver of energy storage; the oxidation-reduction model (REDOX), based on reactive oxygen species (ROS) as a driver of altered metabolic signaling; and the obesogens model (OBS), which proposes that environmental chemicals interfere with hormonal signaling leading to adiposity. We propose a combined OBS/REDOX model in which environmental chemicals (in air, food, food packaging, and household products) generate false autocrine and endocrine metabolic signals, including ROS, that subvert standard regulatory energy mechanisms, increase basal and stimulated insulin secretion, disrupt energy efficiency, and influence appetite and energy expenditure leading to weight gain. This combined model incorporates the data supporting the EBM and CIM models, thus creating one integrated model that covers significant aspects of all the mechanisms potentially contributing to the obesity pandemic. Importantly, the OBS/REDOX model provides a rationale and approach for future preventative efforts based on environmental chemical exposure reduction.

Potential impacts of bisphenols on prostate cells: An overview of cytotoxicity, proliferation, oxidative stress, apoptosis, and ER-stress response activation

This study aimed to evaluate the toxic effects of Bisphenol A (BPA), Bisphenol F (BPF) and Bisphenol S (BPS) on PNT1A and PC-3 cells, focusing on their effects on endoplasmic reticulum (ER) stress and related pathways. PNT1A and PC-3 were treated with BPA, BPF and BPS at concentrations of 0.1, 1 and 10 μM for 48 h cytotoxicity, BrdU cell proliferation, ROS generation, apoptosis detection, gene expression analysis and Western blot analysis were performed. BPA induced proliferation and late apoptosis in PNT1A cells, whereas it induced both late apoptosis and early apoptosis in PC-3 cells. BPF and BPS induced late apoptosis in PC-3 cells. Increased ROS levels were observed in PNT1A cells exposed to 1-10 μM BPA. BPA, BPF and BPS increased the expression levels of ER stress-related genes in PNT1A cells. Furthermore, exposure to BPA increased the expression of ER stress-related CHOP/DDIT3 protein in PNT1A cells. These findings highlight the potential health risks associated with BPA, BPF and BPS exposure and emphasize the importance of investigating the underlying mechanisms by which these chemicals may affect human health. Further research is required to comprehensively understand the role of ER stress pathways in cellular responses to these substances.

Prenatal exposures to phthalates and bisphenols in relation to oxidative stress: single pollutant and mixtures analyses

Prenatal exposures to phthalates and bisphenols have been shown to be linked with adverse birth outcomes. Oxidative stress (OS) is considered a potential mechanism. The objective of this study was to explore the individual and mixtures of prenatal exposures to phthalates and bisphenols in associations with OS biomarkers. We measured eight phthalate metabolites and three bisphenols in the urine samples from 105 pregnant women in Wuhan, China. Urinary 8-hydroxydeoxyguanosine (8-OHdG), 8-isoprostaglandin F2α (8-isoPGF2α), and 4-hydroxy-2-nonenal-mercapturic acid (HNE-MA) were determined as OS biomarkers. The OS biomarkers in associations with the individual chemicals were estimated by linear regression models and restricted cubic spline (RCS) models, and their associations with the chemical mixtures were explored by quantile g-computation (qg-comp) models. In single-pollutant analyses, five phthalate metabolites including monomethyl phthalate (MMP), monoethyl phthalate (MEP), mono-(2-ethylhexyl) phthalate (MEHP), (2-ethyl-5-hydroxyhexyl) phthalate (MEHHP), and mono (2-ethyl-5-oxohexyl) phthalate (MEOHP) were positively associated with urinary 8-OHdG levels (all FDR-adjusted P = 0.06). These associations were further confirmed by the RCS models and were linear (P for overall association ≤ 0.05 and P for non-linear association > 0.05). In mixture analyses, qg-comp models showed that a one-quartile increase in the chemical mixtures of phthalate metabolites and bisphenols was positively associated with urinary levels of 8-OHdG and 8-isoPGF2α, and bisphenol A (BPA) and bisphenol F (BPF) were the most contributing chemicals, respectively. Prenatal exposures to individual phthalates and mixtures of phthalates and bisphenols were associated with higher OS levels.

The role of angiotensin I-converting enzyme gene polymorphism and global DNA methylation in the negative associations between urine di-(2-ethylhexyl) phthalate metabolites and serum adiponectin in a young Taiwanese population

BACKGROUND

Adiponectin is a key protein produced in adipose tissue, with crucial involvement in multiple metabolic processes. Di-(2-ethylhexyl) phthalate (DEHP), one of the phthalate compounds used as a plasticizer, has been shown to decrease adiponectin levels in vitro and in vivo studies. However, the role of angiotensin I-converting enzyme (ACE) gene polymorphism and epigenetic changes in the relationship between DEHP exposure and adiponectin levels is not well understood.

METHODS

This study examined the correlation between urine levels of DEHP metabolite, epigenetic marker 5mdC/dG, ACE gene phenotypes, and adiponectin levels in a sample of 699 individuals aged 12-30 from Taiwan.

RESULTS

Results showed a positive relationship between mono-2-ethylhexyl phthalate (MEHP) and 5mdC/dG, and a negative association between both MEHP and 5mdC/dG with adiponectin. The study found that the inverse relationship between MEHP and adiponectin was stronger when levels of 5mdC/dG were above the median. This was supported by differential unstandardized regression coefficients (- 0.095 vs. - 0.049, P value for interaction = 0.038)). Subgroup analysis also showed a negative correlation between MEHP and adiponectin in individuals with the I/I ACE genotype, but not in those with other genotypes, although the P value for interaction was borderline significant (0.06). The structural equation model analysis indicated that MEHP has a direct inverse effect on adiponectin and an indirect effect via 5mdC/dG.

CONCLUSIONS

In this young Taiwanese population, our findings suggest that urine MEHP levels are negatively correlated with serum adiponectin levels, and epigenetic modifications may play a role in this association. Further study is needed to validate these results and determine causality.

Protective Effects of Selenium Nanoparticles against Bisphenol A-Induced Toxicity in Porcine Intestinal Epithelial Cells

Bisphenol A (BPA) is widely used to harden plastics and polycarbonates and causes serious toxic effects in multiple organs, including the intestines. Selenium, as an essential nutrient element for humans and animals, exhibits a predominant effect in various physiological processes. Selenium nanoparticles have attracted more and more attention due to their outstanding biological activity and biosafety. We prepared chitosan-coated selenium nanoparticles (SeNPs) and further compared the protective effects, and investigated the underlying mechanism of SeNPs and inorganic selenium (Na₂SeO₃) on BPA-induced toxicity in porcine intestinal epithelial cells (IPEC-J2). The particle size, zeta potential, and microstructure of SeNPs were detected by using a nano-selenium particle size meter and a transmission electron microscope. IPEC-J2 cells were exposed to BPA alone or simultaneously exposed to BPA and SeNPs or Na₂SeO₃. The CCK8 assay was performed to screen the optimal concentration of BPA exposure and the optimal concentration of SeNPs and Na₂SeO₃ treatment. The apoptosis rate was detected by flow cytometry. Real-time PCR and Western blot methods were used to analyze the mRNA and protein expression of factors related to tight junctions, apoptosis, inflammatory responses and endoplasmic reticulum stress. Increased death and morphological damage were observed after BPA exposure, and these increases were attenuated by SeNPs and Na₂SeO₃ treatment. BPA exposure disturbed the tight junction function involved with decreased expression of tight junction protein Zonula occludens 1 (ZO-1), occludin, and claudin-1 proteins. Proinflammatory response mediated by the transcription factor nuclear factor-k-gene binding (NF-κB), such as elevated levels of interleukin-1β(IL-1β), interleukin-6 (IL-6), interferon-γ (IFN-γ), interleukin-17 (IL-17), and tumor necrosis factor-α (TNF-α) expression was induced at 6 and 24 h after BPA exposure. BPA exposure also disturbed the oxidant/antioxidant status and led to oxidative stress. IPEC-J2 cell apoptosis was induced by BPA exposure, as indicated by increased BCL-2-associated X protein (Bax), caspase 3, caspase 8, and caspase 9 expression and decreased B-cell lymphoma-2 (Bcl-2) and Bcl-xl expression. BPA exposure activated the endoplasmic reticulum stress (ERS) mediated by the receptor protein kinase receptor-like endoplasmic reticulum kinase (PERK), Inositol requiring enzyme 1 (IRE1α), and activating transcription factor 6 (ATF6). We found that treatment with SeNPs and Na₂SeO₃ can alleviate the intestinal damage caused by BPA. SeNPs were superior to Na₂SeO₃ and counteracted BPA-induced tight junction function injury, proinflammatory response, oxidative stress, apoptosis, and ERS stress. Our findings suggest that SeNPs protect intestinal epithelial cells from BPA-induced damage, partly through inhibiting ER stress activation and subsequently attenuating proinflammatory responses and oxidative stress and suppressing apoptosis, thus enhancing the intestinal epithelial barrier function. Our data indicate that selenium nanoparticles may represent an effective and reliable tool for preventing BPA toxicity in animals and humans.

Endocrine-Disrupting Chemicals and Disease Endpoints

Endocrine-disrupting chemicals (EDCs) have significant impacts on biological systems, and have been shown to interfere with physiological systems, especially by disrupting the hormone balance. During the last few decades, EDCs have been shown to affect reproductive, neurological, and metabolic development and function and even stimulate tumor growth. EDC exposure during development can disrupt normal development patterns and alter susceptibility to disease. Many chemicals have endocrine-disrupting properties, including bisphenol A, organochlorines, polybrominated flame retardants, alkylphenols, and phthalates. These compounds have gradually been elucidated as risk factors for many diseases, such as reproductive, neural, and metabolic diseases and cancers. Endocrine disruption has been spread to wildlife and species that are connected to the food chains. Dietary uptake represents an important source of EDC exposure. Although EDCs represent a significant public health concern, the relationship and specific mechanism between EDCs and diseases remain unclear. This review focuses on the disease-EDC relationship and the disease endpoints associated with endocrine disruption for a better understanding of the relationship between EDCs-disease and elucidates the development of new prevention/treatment opportunities and screening methods.