Physiologically Based Pharmacokinetic (PBPK) Modeling of the Bisphenols BPA, BPS, BPF, and BPAF with New Experimental Metabolic Parameters: Comparing the Pharmacokinetic Behavior of BPA with Its Substitutes

Development and application of the physiologically-based toxicokinetic (PBTK) model for ochratoxin A (OTA) in rats and humans

Ochratoxin A (OTA) is a common fungal toxin frequently detected in food and human plasma samples. Currently, the physiologically based toxicokinetic (PBTK) model plays an active role in dose translation and can improve and enhance the risk assessment of toxins. In this study, the PBTK model of OTA in rats and humans was established based on knowledge of OTA-specific absorption, distribution, metabolism, and excretion (ADME) in order to better explain the disposition of OTA in humans and the discrepancies with other species. The models were calibrated and optimized using the available kinetic and toxicokinetic (TK) data, and independent test datasets were used for model evaluation. Subsequently, sensitivity analyses and population simulations were performed to characterize the extent to which variations in physiological and specific chemical parameters affected the model output. Finally, the constructed models were used for dose extrapolation of OTA, including the rat-to-human dose adjustment factor (DAF) and the human exposure conversion factor (ECF). The results showed that the unbound fraction (Fup) of OTA in plasma of rat and human was 0.02-0.04% and 0.13-4.21%, respectively. In vitro experiments, the maximum enzyme velocity (Vmax) and Michaelis-Menten constant (Km) of OTA in rat and human liver microsomes were 3.86 and 78.17 μg/g min-1, 0.46 and 4.108 μg/mL, respectively. The predicted results of the model were in good agreement with the observed data, and the models in rats and humans were verified. The PBTK model derived a DAF of 0.1081 between rats and humans, whereas the ECF was 2.03. The established PBTK model can be used to estimate short- or long-term OTA exposure levels in rats and humans, with the capacity for dose translation of OTA to provide the underlying data for risk assessment of OTA.

Long-term Bisphenol S exposure induced gut microbiota dysbiosis, obesity, hepatic lipid accumulation, intestinal lesions and dyslipidemia in mice

Bisphenol S (BPS) is a commonly detected chemical raw material in water, which poses significant threats to both the ecological environment and human health. Despite being recognized as a typical endocrine disruptor and a substitute for Bisphenol A, the toxicological effects of BPS remain nonnegligible. In order to comprehensively understand the health impacts of BPS, a long-term (154 days) exposure experiment was conducted on mice, during which the physiological indicators of the liver, intestine, and blood were observed. The findings revealed that exposure to BPS resulted in dysbiosis of the gut microbiota, obesity, hepatic lipid accumulation, intestinal lesions, and dyslipidemia. Furthermore, there exists a significant correlation between gut microbiota and indicators of host health. Consequently, the identification of specific gut microbiota can be considered as potential biomarkers for the evaluation of risk associated with BPS. This study will effectively address the deficiency in toxicological data pertaining to BPS. The novel BPS data obtained from this research can serve as a valuable reference for professionals in the field.

Urinary concentrations of bisphenol A and its alternatives: Potential predictors of and associations with antral follicle count among women from an infertility clinic in Northern China

BACKGROUND

Experimental studies have suggested exposure to bisphenol A (BPA) and its alternatives, such as bisphenol F (BPF) and bisphenol S (BPS), may exert adverse effects on ovarian reserve, but human evidence is limited. Moreover, the potential predictors of exposure to bisphenols among women seeking infertility treatment have not been reported.

OBJECTIVE

To explore whether individual or mixture of BPA, BPF, and BPS were related to antral follicle count (AFC), and further identify the predictors of exposure to bisphenols among women seeking assisted reproductive treatment.

METHODS

A total of 111 women from a reproductive center in Shenyang, China were enrolled in this study from September 2020 to February 2021. The concentrations of urinary BPA, BPF, and BPS were measured using ultra-high-performance liquid chromatography-triple quadruple mass spectrometry (UHPLC-MS/MS). AFC was measured by two infertility physicians through transvaginal ultrasonography on the 2-5 days of a natural cycle. Demographic characteristics, dietary habits, and lifestyles were obtained by questionnaires. The associations between individual and mixture of urinary bisphenols concentrations (BPA, BPF, and BPS) and AFC were assessed by the Poisson regression models and the quantile-based g-computation (QGC) model, respectively. The potential predictors of exposure to bisphenols were identified by the multivariate linear regression models.

RESULTS

After adjusting for confounders, elevated urinary concentrations of BPA, BPF and BPS were associated with reduced AFC (β = -0.016; 95%CI: -0.025, -0.006 in BPA; β = -0.017; 95%CI: -0.029, -0.004 in BPF; β = -0.128; 95%CI: -0.197, -0.060 in BPS). A quantile increase in the bisphenols mixture was negatively associated with AFC (β = -0.101; 95%CI: -0.173, -0.030). Intake of fried food had higher urinary concentrations of BPF, BPS, and total bisphenols (∑BPs) than women who did not eat, and age was related to increased urinary BPF concentrations.

CONCLUSION

Our findings indicated that exposure to individual BPA, BPF, BPS and bisphenol mixtures were associated with impaired ovarian reserve. Furthermore, the intake of fried food, as identified in this study, could serve as an important bisphenols exposure route for reproductive-aged women.

Evaluation of exposure to multiple organic pollutants in riparian communities of the Brazilian Amazon: Screening levels and potential health risks

Organic pollutants are widely distributed in the environment. Due to their physical and chemical characteristics, they tend to be biomagnified in food chains, mainly in aquatic organisms. Therefore, food consumption is a significant route of lifelong exposure. Although the Amazon River basin contains the highest freshwater biodiversity on Earth, there is scarce literature focusing on the levels of organic pollutants in the local population. The present study was aimed at assessing the levels of several environmental pollutants (polycyclic aromatic hydrocarbons, bisphenols, parabens, and benzophenones) in urine samples from riverside communities along the Tapajós and Amazon Rivers in the Brazilian Amazon region. The results show a 100 % detection of naphthalene metabolites (namely, 1-hydroxy-naphthalene (1OH-NAP), 2-hydroxy-naphthalene (2OH-NAP)), with the highest levels belonging to benzylparaben (BzP) (17.3 ng/mL). Gender-specific analysis revealed that women had significantly higher levels of certain PAH metabolites (i.e., 1OH-NAP and 2-hydroxy-fluorene (2OH-FLU)) than men. In turn, most of the evaluated compounds were higher in urine samples from people living near the Amazon River, which presents increased traffic of boats and ships than the Tapajós River. On the other hand, the human health risk assessment suggested that all communities are at risk of suffering non-carcinogenic effects from exposure to PAHs. At the same time, they are also at risk of carcinogenic effects from exposure to benzo[a]pyrene metabolites. Thus, further studies are needed in order to evaluate the potential health effects of exposure to a mixture of these organic pollutants and other contaminants present in the area, such as mercury.

Alternatives Exert Higher Health Risks than Bisphenol A on Indo-Pacific Humpback Dolphins

The detrimental effects of bisphenol (BP) exposure are a concern for vulnerable species, Indo-Pacific humpback dolphins (Sousa chinensis). To investigate the characteristics of BP profiles and their adverse impact on humpback dolphins, we assessed the concentrations of six BPs, including bisphenol A (BPA), bisphenol S (BPS), bisphenol F (BPF), bisphenol AF (BPAF), bisphenol B (BPB), and bisphenol P (BPP) in blubber (n = 26) and kidney (n = 12) of humpback dolphins stranded in the Pearl River Estuary, China. BPS accounted for the largest proportion of the total bisphenols (∑BPs) in blubber (55%) and kidney (69%). The concentration of ∑BP in blubber was significantly higher than that in the kidney and liver. The EC50 values of five BPA alternatives were lower than those of BPA in humpback dolphin skin fibroblasts (ScSF) and human skin fibroblasts (HSF). ScSF was more sensitive to BPS, BPAF, BPB, and BPP than HSF. The enrichment pathway of BPA was found to be associated with inflammation and immune dysregulation, while BPP and BPS demonstrated a preference for genotoxicity. BPA, BPP, and BPS, which had risk quotients (RQs) > 1, were found to contribute to subhealth and chronic disease in humpback dolphins. According to the EC50-based risk assessment, BPS poses a higher health risk than BPA for humpback dolphins. This study successfully evaluated the risks of bisphenols in rare and endangered cetacean cell lines using a noninvasive method. More in vivo and in field observations are necessary to know whether the BPA alternatives are likely to be regrettable substitutions.

Urinary concentrations of environmental phenol among pregnant women in the Japan Environment and Children's Study

Humans are exposed to various bisphenols, alkylphenols and nitrophenols through dietary intake, food packaging and container materials, indoor and outdoor air/dust. This study aimed to evaluate exposure of Japanese pregnant women to environmental phenols by measuring target compounds in urine samples. From a cohort of the Japan Environment and Children's Study, 4577 pregnant women were selected. Bisphenol A (BPA), bisphenol S (BPS), bisphenol F (BPF), bisphenol AF (BPAF), para-nitrophenol (PNP), 3-methyl-4-nitrophenol (PNMC), branched 4-nonylphenol (4-NP), linear 4-nonylphenol and 4-tert-octylphenol (4-t-OP) were analysed using a high-performance liquid chromatograph coupled to a triple-quadrupole mass spectrometer. The urinary metabolite data were combined with a questionnaire to examine the determinants of phenol exposure by machine learning. The estimated daily intake (EDI) and hazard quotient (HQ) of BPA were calculated. PNP (68.2%) and BPA (71.5%) had the highest detection frequencies, with median concentrations of 0.76 and 0.46 μg/g creatinine, respectively. PNMC, BPS, BPF and 4-NP were determined in 24.9%, 11.9%, 1.3% and 0.4% of samples, respectively, whereas BPAF (0.02%) and 4-t-OP (0.02%) were only determined in a few samples. The PNP concentrations measured in this study were comparable with those reported in previous studies, whereas the BPA concentrations were lower than those reported previously worldwide. The EDI of BPA was 0.014 μg/kg body weight/day. Compared with the tolerable daily intake set by the German Federal Institute for Risk Assessment, the median (95th percentile) HQ was 0.044 (0.2). This indicates that the observed levels of BPA exposure pose a negligible health risk to Japanese pregnant women. Determinants of bisphenol and nitrophenol exposure could not be identified by analysing the questionnaire solely, suggesting that biological measurement is necessary to assess exposure of pregnant women to bisphenols and nitrophenols. This is the first study to report environmental phenol exposure of Japanese pregnant women on a nationwide scale.

Exploring Route-Specific Pharmacokinetics of PFAS in Mice by Coupling in Vivo Tests and Physiologically Based Toxicokinetic Models

BACKGROUND

Oral ingestion, inhalation, and skin contact are important exposure routes for humans to uptake per- and polyfluoroalkyl substances (PFAS). However, nasal and dermal exposure to PFAS remains unclear, and accurately predicting internal body burden of PFAS in humans via multiple exposure pathways is urgently required.

OBJECTIVES

We aimed to develop multiple physiologically based toxicokinetic (PBTK) models to unveil the route-specific pharmacokinetics and bioavailability of PFAS via respective oral, nasal, and dermal exposure pathways using a mouse model and sought to predict the internal concentrations in various tissues through multiple exposure routes and extrapolate it to humans.

METHODS

Mice were administered the mixed solution of perfluorohexane sulfonate, perfluorooctane sulfonate, and perfluorooctanoic acid through oral, nasal, and dermal exposure separately or jointly. The time-dependent concentrations of PFAS in plasma and tissues were determined to calibrate and validate the individual and combined PBTK models, which were applied in single- and repeated-dose scenarios.

RESULTS

The developed route-specific PBTK models successfully simulated the tissue concentrations of PFAS in mice following single or joint exposure routes as well as long-term repeated dose scenarios. The time to peak concentration of PFAS in plasma via dermal exposure was much longer (34.1-83.0 h) than that via nasal exposure (0.960 h). The bioavailability of PFAS via oral exposure was the highest (73.2%-98.0%), followed by nasal (33.9%-66.8%) and dermal exposure (4.59%-7.80%). This model was extrapolated to predict internal levels in human under real environment.

DISCUSSION

Based on these data, we predict the following: PFAS were absorbed quickly via nasal exposure, whereas a distinct hysteresis effect was observed for dermal exposure. Almost all the PFAS to which mice were exposed via gastrointestinal route were absorbed into plasma, which exhibited the highest bioavailability. Exhalation clearance greatly depressed the bioavailability of PFAS via nasal exposure, whereas the lowest bioavailability in dermal exposure was because of the interception of PFAS within the skin layers. https://doi.org/10.1289/EHP11969.

The intestinal microbiota as mediators between dietary contaminants and host health

The gut microbiota sit at an important interface between the host and the environment, and are exposed to a multitude of nutritive and non-nutritive substances. These microbiota are critical to maintaining host health, but their supportive roles may be compromised in response to endogenous compounds. Numerous non-nutritive substances are introduced through contaminated foods, with three common groups of contaminants being bisphenols, phthalates, and mycotoxins. The former contaminants are commonly introduced through food and/or beverages packaged in plastic, while mycotoxins contaminate various crops used to feed livestock and humans alike. Each group of contaminants have been shown to shift microbial communities following exposure; however, specific patterns in microbial responses have yet to be identified, and little is known about the capacity of the microbiota to metabolize these contaminants. This review characterizes the state of existing research related to gut microbial responses to and biotransformation of bisphenols, phthalates, and mycotoxins. Collectively, we highlight the need to identify consistent, contaminant-specific responses in microbial shifts, whether these community alterations are a result of contaminant effects on the host or microbiota directly, and to identify the extent of contaminant biotransformation by microbiota, including if these transformations occur in physiologically relevant contexts.

In vitro to in vivo extrapolation for predicting human equivalent dose of phenolic endocrine disrupting chemicals: PBTK model development, biological pathways, outcomes and performance

In vitro to in vivo (IVIVE) leverages in vitro high-throughput biological responses to predict the corresponding in vivo exposures and further estimate the human safe dose. However, for phenolic endocrine disrupting chemicals (EDCs) linked with complicated biological pathways and adverse outcomes (AO), such as bisphenol A (BPA) and 4-nonylphenol (4-NP), plausible estimation of human equivalent doses (HED) by IVIVE approaches considering various biological pathways and endpoints is still challenging. To explore the capabilities and limitations of IVIVE, this study conducted physiologically based toxicokinetic (PBTK)-IVIVE approaches to derive pathway-specific HEDs using BPA and 4-NP as examples. In vitro HEDs of BPA and 4-NP varied in different adverse outcomes, pathways, and testing endpoints and ranged from 0.0013 to 1.0986 mg/kg bw/day and 0.0551 to 1.7483 mg/kg bw/day, respectively. In vitro HEDs associated with reproductive AOs initiated by PPARα activation and ER agonism were the most sensitive. Model verification suggested the potential of using effective in vitro data to determine reasonable approximation of in vivo HEDs for the same AO (fold differences of most AOs ranged in 0.14-2.74 and better predictions for apical endpoints). Furthermore, system-specific parameters of cardiac output and its fraction, body weight, as well as chemical-specific parameters of partition coefficient and liver metabolic were most sensitive for the PBTK simulations. The results indicated that the application of fit for-purpose PBTK-IVIVE approach could provide credible pathway-specific HEDs and contribute to high throughput prioritization of chemicals in a more realistic scenario.

Profile, Tissue Distribution, and Time Trend of Bisphenol Plastic Additives in Freshwater Wildlife of the Pearl River Ecosystem, China

Plastic-related contaminants in the environment have attracted increasing attention, with plastic pollution becoming a serious issue globally. The present study investigated the potential bioaccumulation and biotransfer of bisphenol (BP) compounds that are widely added in various products such as plastics and other products in a freshwater ecosystem, China. Among commonly applied 14 BP analogues, bisphenol A (BPA), bisphenol F (BPF), and bisphenol S (BPS) were predominant, representing 64%-100% of the total concentrations of BPs (ΣBPs) in freshwater wildlife. Both the concentrations and analogue profiles in the fish showed seasonal differences and species dependence. Higher BP concentrations were observed in fish collected during the dry season than the wet season. Higher percentages of non-BPA analogues (e.g., BPS and BPF) were observed in fish collected during the wet season. Pelagic species accumulated notably higher levels of BPs than midwater and bottom species. The liver generally contained the highest ΣBPs, followed successively by the swim bladder, belly fat, and dorsal muscle. The analogue profile also showed some differences among tissues, varying by species and season. Lower ΣBPs but higher percentages of non-BPA analogues were observed in female than male common carp. Time trends of the BPA concentration in fish varied by species, probably related to habitats and diets of the fish. Habitats, feeding behaviors, and trophic transfer may have significant impacts on exposure of wildlife to BPs in natural ecosystems. The BPs did not demonstrate strong potential for bioaccumulation. More research is warranted about metabolism and transgenerational transfer of BPs in wildlife to fully reveal the bioaccumulation and consequently ecological risks of these chemicals in the environment. Environ Toxicol Chem 2023;42:2130-2142. © 2023 SETAC.

Vitamin E (α-Tocopherol) Does Not Ameliorate the Toxic Effect of Bisphenol S on the Metabolic Analytes and Pancreas Histoarchitecture of Diabetic Rats

This study investigated whether the coadministration of vitamin E (VitE) diminishes the harmful effects provoked by plasticizer bisphenol S (BPS) in the serum metabolites related to hepatic and renal metabolism, as well as the endocrine pancreatic function in diabetic male Wistar rats. Rats were divided into five groups (n = 5-6); the first group was healthy rats (Ctrl group). The other four groups were diabetic rats induced with 45 mg/kg bw of streptozotocin: Ctrl-D (diabetic control); VitE-D (100 mg/kg bw/d of VitE); BPS-D (100 mg/kg bw/d of BPS); The animals from the VitE + BPS-D group were administered 100 mg/kg bw/d of VitE + 100 mg/kg bw/d of BPS. All compounds were administered orally for 30 days. Body weight, biochemical assays, urinalysis, glucose tolerance test, pancreas histopathology, proximate chemical analysis in feces, and the activity of antioxidants in rat serum were assessed. The coadministration of VitE + BPS produced weight losses, increases in 14 serum analytes, and degeneration in the pancreas. Therefore, the VitE + BPS coadministration did not have a protective effect versus the harmful impact of BPS or the diabetic metabolic state; on the contrary, it partially aggravated the damage produced by the BPS. VitE is likely to have an additive effect on the toxicity of BPS.

Environmentally relevant doses of endocrine disrupting chemicals affect male fertility by interfering with sertoli cell glucose metabolism in mice

The growing global deterioration in several aspects of human health has been partly attributed to hazardous effects of endocrine-disrupting chemicals (EDCs) exposure. Therefore, experts and government regulatory agencies have consistently advocated for studies on the combined effects of EDCs that model human exposure to multiple environmental chemicals in real life. Here, we investigated how low concentrations of bisphenol A (BPA), and phthalates compounds affect the Sertoli cell glucose uptake/lactate production in the testis and male fertility. An EDC mixture containing a detected amount of each chemical compound in humans, called daily exposure (DE), and DE increased in magnitude by 25 (DE25), 250 (DE250), and 2500 (DE2500), and corn oil (control) were administered for six weeks to male mice. We found that DE activated estrogen receptor beta (Erβ) and glucose-regulated protein 78 (Grp 78) and disrupted the estradiol (E2) balance. In addition, DE25, DE250, and DE2500 doses of the EDC mixture via binding with Sertoli cells' estrogen receptors (ERs) inhibited the glucose uptake and lactate production processes by downregulating glucose transporters (GLUTs) and glycolytic enzymes. As a result, endoplasmic reticulum stress (ERS), marked by unfolded protein response (UPR) activation, was induced. The accompanying upregulation of activating transcription factor 4 (ATF4), inositol requiring enzyme-1 (IRE1), C/EBP homologous protein (CHOP), and mitogen-activated protein kinase (MAPK) signaling promoted antioxidant depletion, testicular cell apoptosis, abnormal regulation of the blood-testis barrier, and decreased sperm count. Therefore, these findings suggest that human and wildlife exposure to multiple environmental chemicals can produce a wide range of reproductive health complications in male mammals.

New Evidence on BPA's Role in Adipose Tissue Development of Proinflammatory Processes and Its Relationship with Obesity

Bisphenol A (BPA) is a xenobiotic with endocrine disruptor properties which interacts with various receptors, eliciting a cellular response. In the plastic industry, BPA is widely used in the production of polycarbonate and epoxy-phenolic resins to provide elastic properties. It can be found in the lining of canned foods, certain plastic containers, thermal printing papers, composite dental fillings, and medical devices, among other things. Therefore, it is a compound that, directly or indirectly, is in daily contact with the human organism. BPA is postulated to be a factor responsible for the global epidemic of obesity and non-communicable chronic diseases, belonging to the obesogenic and diabetogenic group of compounds. Hence, this endocrine disruptor may be responsible for the development of metabolic disorders, promoting in fat cells an increase in proinflammatory pathways and upregulating the expression and release of certain cytokines, such as IL6, IL1β, and TNFα. These, in turn, at a systemic and local level, are associated with a chronic low-grade inflammatory state, which allows the perpetuation of the typical physiological complications of obesity.

Development of human dermal PBPK models for the bisphenols BPA, BPS, BPF, and BPAF with parallel-layered skin compartment: Basing on dermal administration studies in humans

Risk assessment of human exposure to bisphenols (BPs) including bisphenol A, S, F and AF (BPA, BPS, BPF and BPAF) have suggested that except for ingestion, health risk resulting from dermal contact is not negligible. However, the absorption kinetics of BPA substitutes in humans following dermal exposure have been poorly studied. This study aimed to address the knowledge gap in physiologically based pharmacokinetic (PBPK) modeling of BPA and its high-concerned substitutes (BPS, BPF and BPAF) following dermal administration. Parallel-layered skin compartmental model for dermal absorption of BPs was for the first time proposed and human dermal administration studies were conducted to determine dermal bio-accessibility of BPS from thermal paper (TP) (n = 4), BPF (n = 4) and BPAF (n = 5) from personal care products (PCPs). Further, pharmacokinetics of BPS and its metabolites following human handling TP were investigated and the dermal PBPK models for BPA and BPS were validated using the available human biomonitoring data. Overall, 28.03 % ± 13.76 % of BPS in TP was transferred to fingers followed by absorption of 96.17 % ± 2.78 % of that. The dermal bio-accessibilities of BPs in PCPs were 31.65 % ± 2.90 % for BPF and 12.49 % ± 1.66 % for BPAF. Monte Carlo analysis indicated that 90 % of the predicted variability fell within one order of magnitude, which suggested that the developed PBPK models had medium uncertainty. Global sensitivity analysis revealed that the model uncertainty is mainly attributed to the variabilities of dermal absorption parameters. Compared with the previous models for BPs, the developed dermal PBPK models were capable of more accurate predictions of the internal dose metric in target organs following human dermal exposure to BPs via TP and PCPs routes. These results suggested that the developed human dermal PBPK models would provide an alternative tool for assessing the risk of human exposure to BPs through dermal absorption.

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.

Importance of relative binding of bisphenol A and bisphenol S to plasma proteins for predicting their in vivo potencies

Many studies suggest that the potential impact of bisphenol S (BPS) as an endocrine disruptor is comparable to that of bisphenol A (BPA). However, in vitro-to-in vivo and from animal to human extrapolations require knowledge of the plasma free fraction of the active endocrine compounds. The present study aimed to characterise BPA and BPS binding to plasma proteins both in humans and different animal species. The plasma protein binding of BPA and BPS was assessed by equilibrium dialysis in plasma from adult female mice, rats, monkeys, early and late pregnant women as well as paired cord blood, early and late pregnant sheep and foetal sheep. The fraction of free BPA was independent of plasma concentrations and ranged between 4% and 7% in adults. This fraction was 2 to 3.5 times lower than that of BPS in all species except sheep, ranging from 3% to 20%. Plasma binding of BPA and BPS was not affected by the stage of pregnancy, BPA and BPS free fractions representing about 4% and 9% during early and late human pregnancy, respectively. These fractions were lower than the free fractions of BPA (7%) and BPS (12%) in cord blood. Our results suggest that similarly to BPA, BPS is extensively bound to proteins, mainly albumin. The higher fraction of free BPS compared to BPA may have implications for human exposure assessment since BPS free plasma concentrations are expected to be 2 to 3.5 times higher than that of BPA for similar plasma concentration.

Human biomonitoring guidance values (HBM-GVs) for priority substances under the HBM4EU initiative - New values derivation for deltamethrin and cyfluthrin and overall results

The European Initiative HBM4EU aimed to further establish human biomonitoring across Europe as an important tool for determining population exposure to chemicals and as part of health-related risk assessments, thus making it applicable for policy advice. Not only should analytical methods and survey design be harmonized and quality assured, but also the evaluation of human biomonitoring data. For the health-related interpretation of the data within HBM4EU, a strategy for deriving health-based human biomonitoring guidance values (HBM-GVs) for both the general population and workers was agreed on. On this basis, HBM-GVs for exposure biomarkers of 1,2-cyclohexane dicarboxylic acid diisononyl ester (DINCH), phthalates (diethyl hexyl phthalate (DEHP), di-n-butyl phthalate (DnBP), diisobutyl phthalate (DiBP), butyl benzyl phthalate (BBzP), and bis-(2-propylheptyl) phthalate (DPHP)), bisphenols A and S, pyrethroids (deltamethrin and cyfluthrin), solvents (1-methyl-2-pyrrolidone (NMP), 1-ethylpyrrolidin-2-one (NEP), N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAC)), the heavy metal cadmium and the mycotoxin deoxynivalenol (DON) were developed and assigned a level of confidence. The approach to HBM-GV derivations, results, and limitations in data interpretation with special focus on the pyrethroids are presented in this paper.

The Role of "Physiologically Based Pharmacokinetic Model (PBPK)" New Approach Methodology (NAM) in Pharmaceuticals and Environmental Chemical Risk Assessment

Physiologically Based Pharmacokinetic (PBPK) models are mechanistic tools generally employed in the pharmaceutical industry and environmental health risk assessment. These models are recognized by regulatory authorities for predicting organ concentration-time profiles, pharmacokinetics and daily intake dose of xenobiotics. The extension of PBPK models to capture sensitive populations such as pediatric, geriatric, pregnant females, fetus, etc., and diseased populations such as those with renal impairment, liver cirrhosis, etc., is a must. However, the current modelling practices and existing models are not mature enough to confidently predict the risk in these populations. A multidisciplinary collaboration between clinicians, experimental and modeler scientist is vital to improve the physiology and calculation of biochemical parameters for integrating knowledge and refining existing PBPK models. Specific PBPK covering compartments such as cerebrospinal fluid and the hippocampus are required to gain mechanistic understanding about xenobiotic disposition in these sub-parts. The PBPK model assists in building quantitative adverse outcome pathways (qAOPs) for several endpoints such as developmental neurotoxicity (DNT), hepatotoxicity and cardiotoxicity. Machine learning algorithms can predict physicochemical parameters required to develop in silico models where experimental data are unavailable. Integrating machine learning with PBPK carries the potential to revolutionize the field of drug discovery and development and environmental risk. Overall, this review tried to summarize the recent developments in the in-silico models, building of qAOPs and use of machine learning for improving existing models, along with a regulatory perspective. This review can act as a guide for toxicologists who wish to build their careers in kinetic modeling.

Physiologically based modelling of dermal absorption and kinetics of consumer-relevant chemicals: A case study with exposure to bisphenol A from thermal paper

Bisphenol A (BPA) is one of the best studied industrial chemicals in terms of exposure, toxicity, and toxicokinetics. This renders it an ideal candidate to exploit the recent advancements in physiologically based pharmacokinetic (PBPK) modelling to support risk assessment of BPA specifically, and of other consumer-relevant hazardous chemicals in general. Using the exposure from thermal paper as a case scenario, this study employed the multi-phase multi-layer mechanistic dermal absorption (MPML MechDermA) model available in the Simcyp® Simulator to simulate the dermal toxicokinetics of BPA at local and systemic levels. Sensitivity analysis helped to identify physicochemical and physiological factors influencing the systemic exposure to BPA. The iterative modelling process was as follows: (i) development of compound files for BPA and its conjugates, (ii) setting-up of a PBPK model for intravenous administration, (iii) extension for oral administration, and (iv) extension for exposure via skin (i.e., hand) contact. A toxicokinetic study involving hand contact to BPA-containing paper was used for model refinement. Cumulative urinary excretion of total BPA had to be employed for dose reconstruction. PBPK model performance was verified using the observed serum BPA concentrations. The predicted distribution across the skin compartments revealed a depot of BPA in the stratum corneum (SC). These findings shed light on the role of the SC to act as temporary reservoir for lipophilic chemicals prior to systemic absorption, which inter alia is relevant for the interpretation of human biomonitoring data and for establishing the relationship between external and internal measures of exposure.

Evaluation of toxicological effects of bisphenol S with an in vitro human bone marrow mesenchymal stem cell: Implications for bone health

As the use of bisphenol A (BPA) has been restricted in consumer products, bisphenol S (BPS) is one major alternative to BPA for various materials, leading to growing concerns about its health risks in human beings. However, little is known about the toxic effects of BPS on bone health. We employed human bone marrow mesenchymal stem cells (hBMSCs) for the in vitro assessment of BPS on cell proliferation, differentiation, and self-renewal. Our study revealed that BPS at concentrations of 10^-10-10^-7 M increased cell viability but induced the morphological changes of hBMSCs. Moreover, BPS decreased ROS generation and increased Nrf2 expression. Furthermore, BPS not only activated ERα/β expression but also increased β-catenin expression and induced the replicative senescence of hBMSCs. Furthermore, we found that the upregulation of β-catenin induced by BPS was mediated, in part, by ER signaling. Overall, our results suggested BPS exposure caused the homeostatic imbalance of hBMSCs.

Comparison of toxicokinetic properties of eleven analogues of Bisphenol A in pig after intravenous and oral administrations

Due to the restrictions of its use, Bisphenol A (BPA) has been replaced by many structurally related bisphenols (BPs) in consumer products. The endocrine disrupting potential similar to that of BPA has been described for several bisphenols, there is therefore an urgent need of toxicokinetic (TK) data for these emerging BPs in order to evaluate if their internal exposure could increase the risk of endocrine disruption. We investigated TK behaviors of eleven BPA substitutes (BPS, BPAF, BPB, BPF, BPM, BPZ, 3-3BPA, BP4-4, BPAP, BPP, and BPFL) by intravenous and oral administrations of mixtures of them to piglets and serial collection of blood over 72 h and urine over 24 h, to evaluate their disposition. Data were analyzed using nonlinear mixed-effects modeling and a comparison was made with TK predicted by the generic model HTTK package. The low urinary excretion of some BPs, in particular BPM, BPP and BPFL, is an important aspect to consider in predicting human exposure based on urine biomonitoring. Despite their structural similarities, for the same oral dose, all BPA analogues investigated showed a higher systemic exposure (area under the plasma concentration-time curve (AUC) of the unconjugated Bisphenol) than BPA (2 to 4 fold for 3-3BPA, BPAF, BPB and BPZ, 7-20 fold for BP4-4, BPAP, BPP, BPFL, BPF and BPM and 150 fold for BPS) due mainly to a considerable variation of oral bioavailability (proportion of BP administered by oral route that attains the systemic circulation unchanged). Given similarities in the digestive tract between pigs and humans, our TK data suggest that replacing BPA with some of its alternatives, particularly BPS, will likely lead to higher internal exposure to potential endocrine disruptive compounds. These findings are crucial for evaluating the risk of human exposure to these emerging BPs.

Association between urinary bisphenol analogue concentrations and lung cancer in adults: A case-control study

Elevated urinary bisphenol A (BPA) concentrations have been associated with lung cancer in humans. However, toxicological studies demonstrated that the proliferation of lung cancer cells was inhibited by BPA exposure. Therefore, it is still necessary to determine whether exposure to BPA and other bisphenol analogues (BPs) is associated with lung cancer in humans. In this study, 226 lung cancer patients and 243 controls were randomly recruited. Concentrations of three BPs in human urine were quantified and their relationships with the risk of human lung cancer were evaluated. BPA (mean 1.03 ng/mL, 0.87 μg/g Cre) was the predominant BP in human urine, followed by bisphenol S (BPS) (0.72 ng/mL, 0.53 μg/g Cre) and bisphenol F (0.32 ng/mL, 0.37 μg/g Cre). Significant correlations between creatinine-corrected urinary BPA concentrations and the lung cancer risk (odds ratio (OR) _adjusted = 1.28, 95% confidence interval (CI): 1.17, 1.40; P_trend = 0.04) were found using logistical regression analysis. Creatinine-corrected urinary concentrations of BPS in participants showed significant correlations with lung cancer (OR_adjusted = 1.23, 95% CI: 1.04, 1.59; P_trend = 0.01) in the adjusted model. In the stratification analysis, the significant correlation between urinary creatinine-corrected concentrations of BPA and the risk of lung cancer still observed in male participants (OR = 1.36, 95% CI: 1.09, 1.62, p = 0.040). This study demonstrates that elevated human exposure to BPA and BPS may be associated with the increased lung cancer risk.

Unravelling sex-specific BPA toxicokinetics in children using a pediatric PBPK model

Bisphenol A (BPA) is a widely known endocrine disruptor (ED) found in many children's products such as toys, feeding utensils, and teething rings. Recent epidemiology association studies have shown postnatal BPA exposure resulted in developing various diseases such as diabetes, obesity, and neurodegeneration, etc., later in their lives. However, little is known about its sex-specific metabolism and consequently internal exposure. The aim of this study was to develop a sex-specific pediatric physiologically based pharmacokinetic model (PBPK) for BPA to compare their toxicokinetic differences. First, the published adult PBPK model was re-validated, and then this model was extended by interpolation to incorporate pediatric sex specific physiological and biochemical parameters. We used both the classical body weight and ontogeny-based scaling approach to interpolate the metabolic process. Then, the pharmacokinetic attributes of the models using the two-scaling approach mentioned above were compared with adult model. Further, a sex-specific PBPK model with an ontogeny scaling approach was preferred to evaluate the pharmacokinetic differences. Moreover, this model was used to reconstruct the BPA exposure from two cohorts (Helix and PBAT Cohort) from 7 EU countries. The half-life of BPA was found to be almost the same in boys and girls at the same exposure levels. Our model estimated BPA children's exposure to be about 1500 times higher than the tolerable daily intake (TDI) recently set by European Food Safety Authority (EFSA) i.e., 0.04 ng/kg BW/day. The model demonstrated feasibility of extending the adult PBPK to sex-specific pediatric, thus investigate a gender-specific health risk assessment.

Distribution profiles of bisphenols in school supplies and implications for human exposure

Bisphenol compounds (BPs) are usually applied in the production of school supplies, however, little is known on the occurrence of BPs in school supplies. In this study, 15 BPs were detected in 121 samples of school supplies collected from commercial market. Among all compounds studied, BPA, BPF, and BPS were the dominant compounds in school supplies with the detection frequency of 93.15 %, 85.62 % and 82.53 %, respectively, and at median concentrations of 161, 23.64 and 14.11 ng g^-1 dw. The total concentrations of BPs varied among types of school supplies in the following order: paper (median: 1347 ng g^-1 dw) > fabric (521.4 ng g^-1 dw) > plastic (472.7 ng g^-1 dw) > rubber (352.4 ng g^-1 dw). Risk assessment of BPs in school supplies was evaluated by the estimated daily intake (EDI) via dermal absorption, and the median EDIs of ∑15 BPs were 156.78 ng d^-1 (11.27-37,042.37 ng d^-1) and 432.75 ng d^-1 (32.44-91,624.22 ng d^-1) for general and occupational people, respectively.

Physiologically-based toxicokinetic modeling of human dermal exposure to diethyl phthalate: Application to health risk assessment

Diethyl phthalate (DEP) has been most frequently detected in personal care products (PCPs) as a solvent followed by indoor air as one of the semi-volatile organic compounds (SVOCs). Human exposure to DEP predominantly occurs via dermal uptake. However, the available physiologically based toxicokinetics (PBTK) models are developed in rats for risk assessment of DEP exposure resulting from the oral than dermal pathway. To address this issue, DEP in simulated PCPs was dermally administrated to five adult volunteers at real population levels. Following the construction of a dermal absorption model for DEP, the dermal PBTK modeling of DEP involving PCPs and air-to-skin exposure routes in humans was developed for the first time. The data of monoethyl phthalate (MEP) in serum or urine obtained from published human studies and this study were applied to calibrate and validate the developed dermal PBTK model. Monte Carlo simulation was used to evaluate model uncertainty. The dermal absorption fraction of DEP was obtained to be 56.2% for PCPs exposure and 100% for air-to-skin exposure, respectively. Approximate 24.9% of DEP in exposed skin became absorbed into systemic circulation. Model predictions were generally within 2-fold of the observed MEP levels in human serum or urine. Uncertainty analysis showed 90% of the predicted variability (P₉₅/P₅) fell within less than one order of magnitude. Assuming human intake of 5 mg/kg bw per day, the predicted serum area under the curve at steady state of DEP from the dermal route was 1.7 (PCPs) and 2.4 (air) times of those from the peroral route, respectively. It suggested that dermal exposure to DEP would pose greater risk to human health compared with oral exposure. The application of the developed dermal PBTK model provides a valuable insight into health risk assessment of DEP in humans.

Last piece in the puzzle of bisphenols BPA, BPS and BPF metabolism: Kinetics of the in vitro sulfation reaction

Bisphenols are endocrine-disrupting chemicals ubiquitously present in the environment, with the consequent exposure to humans. In humans, bisphenols are metabolized to glucuronide and sulfate conjugates. Recent studies indicate that sulfation represents an important bisphenol metabolic pathway for the most vulnerable humans, such as the growing fetus. Our aim was to evaluate sulfation kinetics of commonly detected bisphenols in biological samples: bisphenol A (BPA), bisphenol S (BPS), and bisphenol F (BPF). Furthermore, we evaluated estrogenic agonist potencies and long-term stability of these bisphenol sulfates. BPS and BPF sulfates were prepared by chemical synthesis. Sulfation kinetics of the selected bisphenols were tested in pooled human liver cytosol, as a source for soluble phase II enzymes, including liver sulfotransferases, with quantification by LC-MS/MS. A validated transactivation assay using the hERα-Hela 9903 cell line was used to determine estrogenic agonist potencies. Moreover, BPA, BPS, and BPF sulfate stabilities were examined under various conditions and during storage. In vitro sulfation of BPA and BPS followed Michaelis-Menten kinetics; BPF sulfation followed a substrate inhibition model. Sulfation rates were comparable for these bisphenols, although their K_M values indicated some large differences in affinities. BPA and BPS sulfates are not hERα agonists. The bisphenol sulfates can be considered stable for at least 2 days under these tested media conditions. These data indicate that bisphenol sulfation is an important route in their biotransformation. Compared to glucuronidation, these bisphenols show slower sulfation rates but similar K_M values. BPA and BPS metabolic biotransformation by sulfation provides their detoxification as they are without estrogenic activities.

Hepatic consequences of a mixture of endocrine-disrupting chemicals in male mice

The global epidemic of metabolic syndrome has been partially linked to ubiquitous exposure to endocrine-disrupting chemicals (EDCs). Although the impacts of exposure to single EDCs have been thoroughly studied, the consequences of simultaneous uncontrolled exposure to multiple EDCs require further investigations. Therefore, in this study, we evaluated how exposure to mixtures containing bisphenol A and seven phthalates impacts liver functions and metabolic homeostasis. Male mice were gavaged with either EDCs at four different dose combinations or corn oil (control) for six weeks. The results showed that exposure to EDCs at the human daily exposure limit had a negligible impact on liver function. However, EDC at ≥ 25 orders of magnitude of human-relevant doses had detrimental impacts on overall liver function, leading to metabolic abnormalities, steatohepatitis, and hepatic fibrosis via the activation of both genomic and non-genomic pathways. The metabolic phenotype was linked to alterations in key genes involved in hepatic lipid and glucose metabolism. In contrast, alterations in cytokine expression, oxidative stress, and apoptosis impacted steatohepatitis and fibrosis. Because EDC exposure does not occur independently, the findings of the combined effects of exposure to multiple EDCs have significant relevance for public health.

Combined exposures to bisphenols, polychlorinated dioxins, paracetamol, and phthalates as drivers of deteriorating semen quality

BACKGROUND

Semen quality in men continues to decline in Western countries, but the contours of the issue remain obscure, in relation to contributing chemicals.

OBJECTIVES

To obtain more clarity about the chemicals that drive the deterioration of semen quality, we conducted a mixture risk assessment based on European exposures.

METHODS

We included chemicals capable of affecting semen quality after prenatal exposures, among them androgen receptor antagonists, substances that disrupt prostaglandin signalling, suppress testosterone synthesis, inhibit steroidogenic enzymes or activate the aryl hydrocarbon receptor. We employed the Hazard Index approach (HI), based on risk quotients of exposures in Europe and reference doses for reductions in semen quality. By summing up the risk quotients of the 29 chemicals included in the assessment we examined fold-exceedances of "acceptable" mixture exposures relative to an index value of 1. For bisphenols A, F, S, phthalates DEHP, DnBP, BBzP, DiNP, n-butyl paraben and paracetamol we relied on biomonitoring studies in which these 9 chemicals were measured together in the same subjects. This allowed us to construct personalised Hazard Indices.

RESULTS

Highly exposed subjects experienced combined exposures to the 9 chemicals that exceeded the index value of 1 by more than 100-fold; the median was a 17-fold exceedance. Accounting for median background exposures to the remaining 20 chemicals added a Hazard Index of 1.39. Bisphenol A made the largest contribution to the HI, followed by polychlorinated dioxins, bisphenols S and F and DEHP. Eliminating bisphenol A alone would still leave unacceptably high mixture risks. Paracetamol is also a driver of mixture risks among subjects using the drug.

CONCLUSIONS

Tolerable exposures to substances associated with deteriorations of semen quality are exceeded by a large margin. Bisphenols, polychlorinated dioxins, phthalates and analgesics drive these risks. Dedicated efforts towards lowering exposures to these substances are necessary to mitigate risks.

The Bisphenols Found in the Ejaculate of Men Does Not Pass through the Testes

Exposure to bisphenols is related to negative effects on male reproduction. The bisphenols exposure is associated with several modes of action including negative impact on the blood–testis barrier (BTB) in testes or direct effect on spermatozoa. Bisphenols have been detected in human seminal plasma, but the possible mechanism of seminal transfer of bisphenols is not clear. Some authors consider the transfer through the blood–testis barrier to be crucial. Therefore, in this work, we compared normozoospermic men and men after vasectomy who have interrupted vas deferens and their ejaculate does not contain testicular products. We measured the concentration of bisphenol A (BPA), bisphenol S (BPS) and bisphenol F (BPF) in the urine and seminal plasma of these men using liquid chromatography tandem mass spectrometry (LC/MSMS). We found that the ratio of urinary and seminal plasma content of bisphenols did not differ in normozoospermic men or men after vasectomy. From the obtained data, it can be concluded that the pathways of transport of bisphenols into seminal plasma are not primarily through the testicular tissue, but this pathway is applied similarly to other routes of transmission by a corresponding ejaculate volume ratio. To a much greater extent than through testicular tissue, bisphenols enter the seminal plasma mainly as part of the secretions of the accessory glands.

The toxicokinetics of bisphenol A and its metabolites in fish elucidated by a PBTK model

Bisphenol A (BPA) is a chemical of major concern due to its endocrine disrupting function, high production volume, and persistence in the aquatic environment. Consequently, organisms such as fish are subject to chronic exposure to BPA. However, physiologically-based toxicokinetic (PBTK) models, which are valuable tools to improve the understanding of a chemical's fate in an organism, have never been specifically adapted to model BPA toxicokinetics (TK) in fish. In our work, an existing PBTK developed for four different fish species was modified to model BPA ADME processes (absorption, distribution, metabolization and excretion). The metabolization of BPA into BPA-monoglucuronide (BPA gluc) and BPA-monosulfate (BPA sulf) and their TK in various organs was taking into account in the model. Experiments were performed to generate BPA TK data in a model species commonly used in ecotoxicology, the stickleback. The model structure had to include two sites of metabolization to simulate BPA TK accurately in stickleback organs. Thus, the fish liver may not be the only site of the metabolization of BPA: plasma or gills could also play a role in BPA metabolization. The PBTK model predictive performance evaluated on literature data in zebrafish and rainbow trout concurs with this conclusion. Finally, a calibration mixing data from the three species was compared to the calibration on stickleback data only.

Transcriptomics analysis and benchmark concentration estimating-based in vitro test with IOSE80 cells to unveil the mode of action for female reproductive toxicity of bisphenol A at human-relevant levels

Bisphenol A (BPA) is of great concern in public health, of which female reproductive toxicity is one major adverse health effect with the unclear mode of action (MOA) yet. Based on the principle of Toxicity Testing in the 21st Century, the purpose of this study is to explore the MOA for female reproductive toxicity using human normal ovarian epithelial cells IOSE80 at 28-day human-relevant-level exposure. A physiological based pharmacokinetic model was used to select the administration concentrations according to the BPA levels in female gonads at human actual exposure scenario. Enrichment KEGG pathways interrupted by BPA consisted of RNA transport, ribosome biogenesis in eukaryotes, cell cycle, cellular senescence, progesterone-mediated oocyte maturation, and oocyte meiosis. Increased relative mRNA and protein expressions of ERK and CDKN3, and proportion of S phase, as well as decreased proportion of G0/G1 phase were observed with increasing BPA concentrations, which could be partially inhibited by ERK inhibitor U0126. Among all the benchmark concentration lower confidence limits, mRNA expression of MAPK3 served as the lowest. In conclusion, the MOA of BPA induced female reproductive toxicity at human-relevant levels may include: key event (KE)1-ERK activation, KE2-increased expression of CDKN3, and KE3-cell cycle arrest. However, more in vivo studies may be needed to complete the MOA.

Bisphenol A correlates with fewer retrieved oocytes in women with tubal factor infertility

PURPOSE

Serum and urinary bisphenol A (BPA) concentrations have been associated negatively with the number of retrieved oocytes after in vitro fertilization (IVF). The impact of BPA upon women with polycystic ovary syndrome (PCOS) and women with tubal factor infertility (TFI), following IVF, was investigated. To this purpose, associations among serum and urinary and follicular fluid (FF) BPA concentrations and the number of retrieved and fertilized oocytes and comparisons between pregnancy rates were evaluated.

METHODS

This was a cross-sectional study conducted at a university-affiliated assisted conception unit between January and November 2019, including 93 women of reproductive age (PCOS: 45; TFI: 48) following IVF. Unconjugated FF and serum BPA concentrations and total urinary BPA concentration were measured using a novel gas chromatography-mass spectrometry method. The number of retrieved and fertilized oocytes and pregnancy rate were documented and evaluated.

RESULTS

The number of oocytes retrieved from PCOS women was greater than that of 21 TFI women, independently of BMI. Lower FF BPA concentrations were found in all PCOS women and in overweight/obese PCOS compared to TFI women (0.50, 0.38, and 1.13 ng/mL, respectively). In TFI women, FF BPA concentrations correlated negatively with the number of retrieved oocytes. Serum and FF and urinary BPA concentrations did not significantly affect the number of fertilized oocytes and pregnancy rate in both groups.

CONCLUSION

FF BPA concentrations were lower in all PCOS women and in overweight/obese PCOS than in TFI women. In TFI women, FF BPA concentrations correlated negatively with retrieved oocytes. Confirmation of these findings might lead to moderation of use of BPA-containing products by women undergoing IVF.

Human Biomonitoring Guidance Values (HBM-GVs) for Bisphenol S and Assessment of the Risk Due to the Exposure to Bisphenols A and S, in Europe

Within the European Joint Programme HBM4EU, Human Biomonitoring Guidance Values (HBM-GVs) were derived for several prioritised substances. In this paper, the derivation of HBM-GVs for the general population (HBM-GVGenPop) and workers (HBM-GVworker) referring to bisphenol S (BPS) is presented. For the general population, this resulted in an estimation of the total urinary concentration of BPS of 1.0 µg/L assuming a 24 h continuous exposure to BPS. For workers, the modelling was refined in order to reflect continuous exposure during the working day, leading to a total urinary concentration of BPS of 3.0 µg/L. The usefulness for risk assessment of the HBM-GVs derived for BPS and bisphenol A (BPA) is illustrated. Risk Characterisation Ratios (RCRs) were calculated leading to a clear difference between risk assessments performed for both bisphenols, with a very low RCR regarding exposure to BPA., contrary to that obtained for BPS. This may be due to the endocrine mediated endpoints selected to derive the HBM-GVs for BPS, whereas the values calculated for BPA are based on the temporary Tolerable Daily Intake (t-TDI) from EFSA set in 2015. A comparison with the revised TDI recently opened for comments by EFSA is also discussed. Regarding the occupational field, results indicate that the risk from occupational exposure to both bisphenols cannot be disregarded.

Regulatory and academic studies to derive reference values for human health: The case of bisphenol S

The close structural analogy of bisphenol (BP) S with BPA, a recognized endocrine-disrupting chemical and a substance of very high concern in the European Union, highlights the need to assess the extent of similarities between the two compounds and carefully scrutinize BPS potential toxicity for human health. This analysis aimed to investigate human health toxicity data regarding BPS, to find a point of departure for the derivation of human guidance values. A systematic and transparent methodology was applied to determine whether European or international reference values have been established for BPS. In the absence of such values, the scientific literature on human health effects was evaluated by focusing on human epidemiological and animal experimental studies. The results were analyzed by target organ/system: male and female reproduction, mammary gland, neurobehavior, and metabolism/obesity. Academic experimental studies were analyzed and compared to regulatory data including subchronic studies and an extended one-generation and reproduction study. In contrast to the regulatory studies, which were performed at dose levels in the mg/kg bw/day range, the academic dataset on specific target organs or systems showed adverse effects for BPS at much lower doses (0.5-10 μg/kg bw/day). A large disparity between the lowest-observed-adverse-effect levels (LOAELs) derived from regulatory and academic studies was observed for BPS, as for BPA. Toxicokinetic data on BPS from animal and human studies were also analyzed and showed a 100-fold higher oral bioavailability compared to BPA in a pig model. The similarities and differences between the two bisphenols, in particular the higher bioavailability of BPS in its active (non-conjugated) form and its potential impact on human health, are discussed. Based on the available experimental data, and for a better human protection, we propose to derive human reference values for exposure to BPS from the N(L)OAELs determined in academic studies.

Enzymatic probe sonication for quick extraction of total bisphenols from animal-derived foods: Applicability to occurrence and exposure assessment

A high demand exists in bisphenols (BPs) screening studies for quick, reliable and straightforward analytical methods that generate data faster and simultaneously. Herein, we describe a combination of enzymatic probe sonication (EPS) and ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) for quick extraction and simultaneous quantification of eight important BPs in animal-derived foods. Results obtained demonstrated that the ultrasonic probe power could not only enhance the enzymatic hydrolysis efficiency, but also accelerate the liquid-liquid extraction procedure. Under optimized EPS parameters, one sample could be exhaustively extracted within 120 s, as compared with 12 h needed for the conventional enzymatic extraction which is more suitable for high-throughput analysis. The method was successfully applied to analyze residual BPs in animal-derived foods collected from Beijing, China. Widespread occurrence of BPA, BPS, BPF, BPAF, BPP, and BPB were found, with detection frequencies of 65.2%, 42.4%, 33.7%, 29.4%, 28.3%, and 27.2%, respectively. The highest total concentration levels of BPs (sum of the eight BPs analyzed, ΣBPs) were found in chicken liver (mean 12.2 μg/kg), followed by swine liver (6.37 μg/kg), bovine muscle (3.24 μg/kg), egg (2.03 μg/kg), sheep muscle (2.03 μg/kg), chicken muscle (1.45 μg/kg), swine muscle (1.42 μg/kg), and milk (1.17 μg/kg). The estimated daily intake (EDI) of BPs, based on the mean and 95th percentile concentrations and daily food consumptions, was estimated to be 5.687 ng/kg bw/d and 22.71 ng/kg bw/d, respectively. The human health risk assessment in this work suggests that currently BPs do not pose significant risks to the consumers because the hazard index (HI) was <1.

Overview of the Mechanisms of Action of Selected Bisphenols and Perfluoroalkyl Chemicals on the Male Reproductive Axes

Male fertility has been deteriorating worldwide for considerable time, with the greatest deterioration recorded mainly in the United States, Europe countries, and Australia. That is, especially in countries where an abundance of chemicals called endocrine disruptors has repeatedly been reported, both in the environment and in human matrices. Human exposure to persistent and non-persistent chemicals is ubiquitous and associated with endocrine-disrupting effects. This group of endocrine disrupting chemicals (EDC) can act as agonists or antagonists of hormone receptors and can thus significantly affect a number of physiological processes. It can even negatively affect human reproduction with an impact on the development of gonads and gametogenesis, fertilization, and the subsequent development of embryos. The negative effects of endocrine disruptors on sperm gametogenesis and male fertility in general have been investigated and repeatedly demonstrated in experimental and epidemiological studies. Male reproduction is affected by endocrine disruptors via their effect on testicular development, impact on estrogen and androgen receptors, potential epigenetic effect, production of reactive oxygen species or direct effect on spermatozoa and other cells of testicular tissue. Emerging scientific evidence suggests that the increasing incidence of male infertility is associated with the exposure to persistent and non-persistent endocrine-disrupting chemicals such as bisphenols and perfluoroalkyl chemicals (PFAS). These chemicals may impact men’s fertility through various mechanisms. This study provides an overview of the mechanisms of action common to persistent (PFAS) and nonpersistent (bisphenols) EDC on male fertility.

A fast and direct determination of bisphenol S in thermal paper samples using paper spray ionization mass spectrometry

Concerns about human health regarding the large use of bisphenol A in thermal papers have led to its replacement by bisphenol S. Analyses of bisphenols require several sample pretreatment steps, which are laborious, expensive, and time-consuming. A paper spray ionization mass spectrometry (PSI-MS) was developed to detect and quantify bisphenol S in three different brands of thermal papers commercially available. Parameters such as paper size, and paper position relative to the mass spectrometer inlet were evaluated. The analyses were performed in selected ion monitoring mode on a linear ion trap mass spectrometer. The developed method presented absolute recovery values ranging from 92.2 to 109.04%, accuracy values from -1.2 to 9.0%, and inter assay precision from 1.8 to 5.6% and enabled LOD as low as 5 ng g^-1. The concentration of bisphenol S in all of the three brands of BPA-free thermal papers evaluated ranged from 1.36 to 6.77 μg g^-1, and the concentrarion of BPA ranged from 6.56 to 16.4 μg g^-1 in all samples of thermal paper evaluated. The PSI-MS method described here was comparable to the conventional ones, such as liquid chromatography coupled with mass spectrometry and gas chromatography coupled with mass spectrometry described in the literature. The present study proved to be practical, fast, and efficient for the direct determination of bisphenol S in thermal papers. Furthermore, the methodology here described showed to be a promising alternative to replace the classical methods for determination of bisphenol S, due to its simplicity, and no needing of any sample pretreatment.

Individual and combined effects of BPA, BPS and BPAF on the cardiomyocyte differentiation of embryonic stem cells

Exposure to many kinds of bisphenols (BPs) is common, and the effects of BP mixtures may differ from those of individual BPs. Therefore, evaluating combined exposure effects is necessary. Our study evaluated the individual and combined exposure effects of bisphenol A (BPA), bisphenol S (BPS) and bisphenol AF (BPAF) on embryonic development using an embryonic stem cell test (EST) and a concentration additive (CA) model at relatively high doses to uncover the interaction model of the three BPs. Environmentally relevant concentrations were then used to evaluate the possible effects of the individual and combined BPs at actual human exposure levels. Exposure to relatively high-dose BPA, BPS and BPAF inhibited embryonic stem cell differentiation into cardiomyocytes and exhibited weak embryo toxicity. Individually, BPA, BPS and BPAF inhibited endoderm, mesoderm and ectoderm marker expression but enhanced pluripotency marker expression. Combined exposure to BPs had an additive effect on cardiomyocyte differentiation and embryonic stem cell proliferation based on the CA model. Environmentally relevant individual or combined BP doses (10 ng/ml individual BPA, BPS and BPAF doses or 1 ng/ml and 10 ng/ml BP mixture doses) failed to cause oxidative stress, DNA damage or apoptosis changes in stem cell differentiation. The cardiomyocyte differentiation ratio also did not change significantly. Individual and combined exposure to environmentally relevant BP doses led to a significant increase in collagen expression. BPAF and the combination of BPs increased the type 1 collagen level, while the combination also increased the type 3 collagen level, which may be related to p38 pathway activation. The p38 pathway inhibitor SB203580 inhibited the increase in collagen during cardiomyocyte differentiation caused by low-dose BPs. These results suggest that relatively high-dose BPs in combination have an additive effect on cardiomyocyte differentiation. Low-dose BPs individually and in combination may affect cardiomyocyte collagen through the p38 pathway.

Human biomonitoring initiative (HBM4EU): Human biomonitoring guidance values (HBM-GVs) derived for bisphenol A

The "European Human Biomonitoring Initiative" (HBM4EU) derives human biomonitoring guidance values (HBM-GVs) for the general population (HBM-GV_GenPop) and/or for occupationally exposed adults (HBM-GV_Worker) for several priority substances and substance groups as identified by policy makers, scientists and stakeholders at EU and national level, including bisphenol A (BPA). Human exposure to BPA is widespread and of particular concern because of its known endocrine-disrupting properties. Unlike the conjugated forms of BPA circulating in the body, free BPA is known to interact with the nuclear estrogen receptors. Because free BPA is considered to be more toxicologically active than the conjugated forms (e.g. BPA-glucuronide (BPA-G) and BPA-sulfate (BPA-S)), its measurement in blood provides the superior surrogate of the biologically effective dose. However, considering the difficulty of implementing blood sampling in large HBM cohorts, as well as the current analytical capacities complying with the quality assurance (QA)/quality control (QC) schemes, total BPA in urine (i.e. the sum of free and conjugated forms of BPA measured after an hydrolysis of phase II metabolites) was retained as the relevant exposure biomarker for BPA. HBM-GV_GenPop for total BPA in urine of 230 µg/L and 135 µg/L for adults and children, respectively, were developed on the basis of toxicological data. To derive these values, the concentrations of urinary total BPA consistent with a steady-state exposure to the temporary Tolerable Daily Intake (t-TDI) of 4 µg/kg bw/day set in 2015 by the European Food Safety Authority (EFSA) were estimated. The BPA human physiologically-based pharmacokinetic (PBPK) model developed by Karrer et al. (2018) was used, assuming an oral exposure to BPA at the t-TDI level averaged over 24 h. Dermal uptake of BPA is suspected to contribute substantially to the total BPA body burden, which in comparison with the oral route, is generating a higher ratio of free BPA to total BPA in blood. Therefore, an alternative approach for calculating the HBM-GV_GenPop according to the estimated relative contributions of both the oral and dermal routes to the global BPA exposure is also discussed. Regarding BPA exposure at the workplace, the steady-state concentration of urinary total BPA was estimated after a dermal uptake of BPA that would generate the same concentration of free BPA in plasma (considered as the bioactive form) as would a 24 h-averaged intake to the European Chemicals Agency (ECHA)'s oral DNEL of 8 µg BPA/kg bw/day set for workers. The predicted concentration of urinary total BPA at steady-state is equivalent to, or exceeds the 95th percentile of total BPA in urine measured in different European HBM studies conducted in the general population. Thus, no HBM-GV_Worker was proposed, as the high background level of BPA coming from environmental exposure - mostly through food intake - is making the discrimination with the occupational exposure to BPA difficult.

A Systematic Review of Bisphenol A from Dietary and Non-Dietary Sources during Pregnancy and Its Possible Connection with Fetal Growth Restriction: Investigating Its Potential Effects and the Window of Fetal Vulnerability

Bisphenol A (BPA), a ubiquitous endocrine-disrupting chemical (EDC), is increasingly hypothesized to be a factor contributing to changes in fetal growth velocity. BPA exposure may be environmental, occupational, and/or dietary, with canned foods and plastic bottles contributing significantly. Our systematic review aims to evaluate the current literature and to investigate the role of BPA in abnormal fetal growth patterns. A search was conducted in the PubMed and Cochrane databases. A total of 25 articles met the eligibility criteria and were included in this systematic review. Eleven of them failed to show a clear relationship between BPA and abnormal fetal growth. The majority of the remaining studies (9/14) found an inverse association of BPA with indicators of fetal growth, whereas three studies suggested increased fetal growth, and two studies produced contradictory findings. Of note, both of the studies that collected a sample (amniotic fluid) directly reflecting BPA concentration in the fetus during the first half of pregnancy revealed an inverse association with birth weight. In conclusion, there is mounting evidence that combined exposure to BPA from dietary and non-dietary sources during pregnancy may contribute to abnormal fetal growth; a tendency towards fetal growth restriction was shown, especially when exposure occurs during the first half.

Metabolic pathways, alterations in miRNAs expression and effects of genetic polymorphisms of bisphenol a analogues: A systematic review

Bisphenol A (BPA) is one of the most common endocrine disruptors found in the environment and its harmful health effects in humans and wildlife have been extensively reported One of the main aims of this review was to examine the metabolic pathways of BPA and BPA substitutes and the endocrine disrupting properties of their metabolites. According to the available literature, phase I and phase II metabolic reactions play an important role in the detoxification process of bisphenols (BPs), but their metabolism can also lead to the formation of highly reactive metabolites. The second part of this work addresses the associations between exposure to BPA and its analogues with the alterations in miRNAs expression and the effects of single nucleotide polymorphisms (SNPs). Available scientific evidence shows that BPs can dysregulate the expression of several miRNAs, and in turn, these miRNAs could be considered as epigenetic biomarkers to prevent the development of a variety of BP-mediated diseases. Interestingly, genetic polymorphisms are able to modify the relationship of BPA exposure with the risk of adverse health effects, suggesting that interindividual genetic differences modulate the susceptibility to the effects of environmental contaminants.

Investigating the glucuronidation and sulfation pathways contribution and disposition kinetics of Bisphenol S and its metabolites using LC-MS/MS-based nonenzymatic hydrolysis method

Despite showing serious health consequences and widespread exposure, the toxicokinetic information required to evaluate the health risks of BPS is insufficient. Thus, we aim to describe the comprehensive toxicokinetics of BPS and its glucuronide (BPS-G) and sulfate (BPS-S) metabolites in rats. Simultaneous quantification of BPS and its metabolites (authentic standards) was accomplished using UPLC-MS/MS method. BPS displayed rapid absorption, extensive metabolism and fast elimination after oral administration. Following intravenous administration, BPS exhibited CL (8.8 L/h/kg) higher than the rat hepatic blood flow rate suggesting the likelihood of extrahepatic clearance. The CL value differed from those reported previously (sheep and piglets) and the probable reason could be attributed to dose- and/or interspecies differences. BPS was extensively metabolized and excreted primarily through urine as BPS-G (∼56%). BPS and BPS-S exhibited a high protein binding capacity in comparison to BPS-G. In in vitro metabolic stability study, BPS was predominantly metabolized through glucuronidation. The predicted in vivo hepatic clearance of BPS suggested it to be a high and intermediate clearance chemical in rats and humans, respectively. The significant interspecies difference observed in the clearance of BPS between rats and humans indicated that toxicokinetics of BPS should be considered for health risk assessment in humans.

The interference effects of bisphenol A on the synthesis of steroid hormones in human ovarian granulosa cells

Numerous studies have shown that endocrine-disrupting chemicals are one of the important pathogenic factors in women with polycystic ovary syndrome. Our previous study has revealed that bisphenol A (BPA) can cause steroid hormone imbalance, polycystic ovary, and estrus cycle disorder. In this study, we aimed to explore the effect of BPA, a typical environmental estrogen, on the synthesis of steroid hormones in human ovarian granulosa KGN cells. Exposure of KGN cells to BPA (0.5, 5, 50, and 500 μg/L) resulted in the decrease of progesterone (P), estradiol (E2), and the ratio of estradiol to testosterone (E2/T). BPA affected the expression of genes related to steroid hormone synthesis in KGN cells, including the decreased expression of the steroidogenic acute regulatory protein, ferredoxin, and ferredoxin reductase genes during progesterone synthesis; upregulating the expression of cytochrome p450 oxidoreductase gene associated with E2 and T synthesis; and the downregulated cytochrome P450 family 1 subfamily A member 1 and cytochrome P450 family 1 subfamily B member 1 in E2 degradation. BPA also reduced the expression of stimulatory G proteins (GS) in follicle-stimulating hormone receptor (FSHR)/GS/adenylate cyclase (AC) signaling pathway. In summary, our research has demonstrated that environment-relevant level of BPA exposure leads to steroid hormone synthesis disorder in human ovarian granulosa cells, which might cause the reduction of gene expression in hormone synthesis and the suppression of the FSHR/GS/AC signaling pathway.

Physiologically-based pharmacokinetic modeling to support bioequivalence and approval of generic products: A case for diclofenac sodium topical gel, 1

Establishing bioequivalence (BE) for dermatological drug products by conducting comparative clinical end point studies can be costly and the studies may not be sufficiently sensitive to detect certain formulation differences. Quantitative methods and modeling, such as physiologically‐based pharmacokinetic (PBPK) modeling, can support alternative BE approaches with reduced or no human testing. To enable PBPK modeling for regulatory decision making, models should be sufficiently verified and validated (V&V) for the intended purpose. This report illustrates the US Food and Drug Administration (FDA) approval of a generic diclofenac sodium topical gel that was based on a totality of evidence, including qualitative and quantitative sameness and physical and structural similarity to the reference product, an in vivo BE study with PK end points, and, more importantly, for the purposes of this report, a virtual BE assessment leveraging dermal PBPK modeling and simulation instead of a comparative clinical end point study in patients. The modeling approach characterized the relationship between systemic (plasma) and local (skin and synovial fluid) diclofenac exposure and demonstrated BE between the generic and reference products at the presumed site of action. Based on the fit‐for‐purpose modeling principle, the V&V process involved assessing observed data of diclofenac concentrations in skin tissues and plasma, and the overall performance of the modeling platform for relevant products. Using this case as an example, this report provides current scientific considerations on good practices for model V&V and the establishment of BE for dermatological drug products when leveraging PBPK modeling and simulation for regulatory decision making.

Influence of experimental parameters on in vitro human skin permeation of Bisphenol A

Bisphenol A (BPA) in vitro skin permeation studies have shown inconsistent results, which could be due to experimental conditions. We studied the impact of in vitro parameters on BPA skin permeation using flow-through diffusion cells with ex-vivo human skin (12 donors, 3-12 replicates). We varied skin status (viable or frozen skin) and thickness (200, 400, 800 μm), BPA concentrations (18, 250 mg/l) and vehicle volumes (10, 100 and 1000 μl/cm²). These conditions led to a wide range of BPA absorption (2%-24% after 24 h exposure), peak permeation rates (J = 0.02-1.31 μg/cm²/h), and permeability coefficients (K_p = 1.6-5.2 × 10^-3 cm/h). This is the first time steady state conditions were reached for BPA aqueous solutions in vitro (1000 μl/cm² applied at concentration 250 mg/l). A reduction of the skin thickness from 800 and 400 μm to 200 μm led to a 3-fold increase of J (P < 0.05). A reduction of the vehicle volume from 1000 to 100 led to a 2-fold decrease in J (P > 0.05). Previously frozen skin led to a 3-fold increase in J compared to viable skin (P < 0.001). We found that results from published studies were consistent when adjusting J according to experimental parameters. We propose appropriate J values for different exposure scenarios to calculate BPA internal exposures for use in risk assessment.

Pregnancy-specific physiologically-based toxicokinetic models for bisphenol A and bisphenol S

Predictions from physiologically based toxicokinetic (PBTK) models can help inform human health risk assessment for potentially toxic chemicals in the environment. Bisphenol S (BPS) is the second most abundant bisphenol detected in humans in the United States, after bisphenol A (BPA). We have recently demonstrated that BPS, much like BPA, can cross the placental barrier and disrupt placental function. Differences in physicochemical properties, toxicokinetics, and exposure outcomes between BPA and other bisphenols prevent direct extrapolation of existing BPA PBTK models to BPS. The current study aimed to develop pregnancy-specific PBTK (p-PBTK) models for BPA and BPS, using a common p-PBTK model structure. Novel paired maternal and fetal pregnancy data sets for total, unconjugated, and conjugated BPA and BPS plasma concentrations from three independent studies in pregnant sheep were used for model calibration. The nine-compartment (maternal blood, liver, kidney, fat, placenta and rest of body, and fetal liver, blood and rest of body) models simulated maternal and fetal experimental data for both BPA and BPS within one standard deviation for the majority of the experimental data points, highlighting the robustness of both models. Simulations were run to examine fetal exposure following daily maternal exposure to BPA or BPS at their tolerable daily intake dose over a two-week period. These predictive simulations show fetal accumulation of both bisphenols over time. Interestingly, the steady-state approximation following this dosing strategy achieved a fetal concentration of unconjugated BPA to levels observed in cord blood from human biomonitoring studies. These models advance our understanding of bisphenolic compound toxicokinetics during pregnancy and may be used as a quantitative comparison tool in future p-PBTK models for related chemicals.

Multigenerational study of the obesogen effects of bisphenol S after a perinatal exposure in C57BL6/J mice fed a high fat diet

BACKGROUND

Bisphenol S is an endocrine disruptor exhibiting metabolic disturbances, especially following perinatal exposures. To date, no data are available on the obesogen effects of BPS in a mutligenerational issue.

OBJECTIVES

We investigated obesogen effects of BPS in a multigenerational study by focusing on body weight, adipose tissue and plasma parameters in male and female mice.

METHODS

Pregnant C57BL6/J mice were exposed to BPS (1.5 μg/kg bw/day ie a human equivalent dose of 0.12 μg/kg bw/day) by drinking water from gestational day 0 to post natal day 21. All offsprings were fed with a high fat diet during 15 weeks. Body weight was monitored weekly and fat mass was measured before euthanasia. At euthanasia, blood glucose, insuline, triglyceride, cholesterol and no esterified fatty acid plasma levels were determined and gene expressions in visceral adipose tissue were assessed. F1 males and females were mated to obtain the F2 generation. Likewise, the F2 mice were cross-bred to obtain F3. The same analyses were performed.

RESULTS

In F1 BPS induced an overweight in male mice associated to lipolysis gene expressions upregulation. In F1 females, dyslipidemia was observed. In F2, BPS exposure was associated to an increase in body weight, fat and VAT masses in males and females. Several plasma parameters were increased but with a sex related pattern (blood glucose, triglycerides and cholesterol in males and NEFA in females). We observed a down-regulation in mRNA expression of gene involved in lipogenesis and in lipolysis for females but only in the lipogenesis for males. In F3, a decrease in VAT mass and an upregulation of lipogenesis gene expression occurred only in females.

CONCLUSIONS

BPS perinatal exposure induced sex-dependent obesogen multigenerational effects, the F2 generation being the most impacted. Transgenerational disturbances persisted only in females.

Cumulative health risks for bisphenols using the maximum cumulative ratio among Chinese pregnant women

Bisphenol A and its alternatives are frequently detected in environmental and human samples, but studies associated with the pattern of combined health hazards from the exposure to the bisphenol mixtures are lacking, particularly for pregnant women. Here, we recruited 941 pregnant women with a full set of urine samples in the three trimesters collected under a cohort study project in Wuhan, China, between 2014 and 2015. We measured the concentrations of 8 bisphenols in 2823 urine samples, and calculated the average concentrations of bisphenols, which were detected in over 50% of samples, once during each trimester of pregnancy. We calculated the maximum cumulative ratio (MCR) on basis of estimated daily intake (EDI), hazard quotient (HQ), hazard index (HI) of three major bisphenols, including bisphenol A (BPA), bisphenol F (BPF), and bisphenol S (BPS), to find which one or mixtures drive risks. Participants were categorized into four groups according to their maximum HQ, HI and MCR values. We found negative relationships between log(MCR-1) and log(HI) with the slope (-0.6431). Percentage of HQ of BPA in HI ranged from 37.1% (<25th percentiles of HI) to 75.5% (>95th percentiles of HI) indicating the upward trend of dominance by BPA at increasing HI ranges. The cumulative health risks of bisphenol exposures largely originated from the health hazards of BPA and BPS, particularly BPA. The intervention for regulation on the production and application of BPA and its alternatives are urgent, and China should consider national regulation on these chemicals based on its risk to human health.

Hepatic transcriptome and DNA methylation patterns following perinatal and chronic BPS exposure in male mice

Background

Bisphenol S (BPS) is a common bisphenol A (BPA) substitute, since BPA is virtually banned worldwide. However, BPS and BPA have both endocrine disrupting properties. Their effects appear mostly in adulthood following perinatal exposures. The objective of the present study was to investigate the impact of perinatal and chronic exposure to BPS at the low dose of 1.5 μg/kg body weight/day on the transcriptome and methylome of the liver in 23 weeks-old C57BL6/J male mice.

Results

This multi-omic study highlights a major impact of BPS on gene expression (374 significant deregulated genes) and Gene Set Enrichment Analysis show an enrichment focused on several biological pathways related to metabolic liver regulation. BPS exposure also induces a hypomethylation in 58.5% of the differentially methylated regions (DMR). Systematic connections were not found between gene expression and methylation profile excepted for 18 genes, including 4 genes involved in lipid metabolism pathways (Fasn, Hmgcr, Elovl6, Lpin1), which were downregulated and featured differentially methylated CpGs in their exons or introns.

Conclusions

This descriptive study shows an impact of BPS on biological pathways mainly related to an integrative disruption of metabolism (energy metabolism, detoxification, protein and steroid metabolism) and, like most high-throughput studies, contributes to the identification of potential exposure biomarkers.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-020-07294-3.