Bisphenol A (BPA) alternatives are increasingly used in the manufacture of industrial and consumer products, following regulatory restrictions on BPA. However, insufficient safety data on these substitutes raise concern as regards potential regrettable substitutions. Under the EU Partnership for the Assessment of Risks from Chemicals (PARC), Work Package 5 (WP5) addresses this challenge by applying a human-relevant tiered hazard assessment strategy grounded on OECD test guidelines as first tier and expanding the battery to include NAMs (New Approach Methodologies). Eight BPA alternatives were prioritized for studies addressing key toxicological endpoints, namely, endocrine disruption (ED), developmental neurotoxicity (DNT), immunotoxicity, genotoxicity and carcinogenicity and metabolic fate examination (detoxification vs. potential bioactivation), to enable early identification of biological activity and support cross-endpoint prioritization. This manuscript describes the structure and implementation of the testing framework. This integrated testing strategy proposes a structured approach to identify substances of potential concern, guide targeted higher-tier studies, and support regulatory prioritization. PARC WP5 framework is testing whether coordinated NAM-based methods may contribute to next-generation risk assessment and help prevent regrettable substitutions among BPA alternatives for rapid regulatory adoption. Detailed experimental results will be reported separately upon completion of the project.

Metabolism disrupting chemicals (MDCs) are a class of endocrine disrupting substances that promote metabolic changes leading to metabolic disorders in humans. Central to assessing their adverse effects is the need to better understand their modes of action (MoA). Cytochrome P450 (CYP) enzymes play a major role in xenobiotic metabolism, but also catalyse many endogenous metabolic reactions. Therefore, modulation of CYP functionality may impact homeostasis, contributing to adverse outcomes. At the functional level, alteration of the activity of human CYPs by MDCs largely remains unexplored. In this study we investigated the capability of six candidate MDCs, bisphenol A (BPA), perfluorooctanoic acid (PFOA), tributyltin (TBT), dichlorodiphenyldichloroethylene (p,p'-DDE), triclosan (TCS) and triphenylphosphate (TPP) to induce CYP1A2, CYP2B6 and CYP3A4 activities in the human hepatic HepaRG cell line. The CYP induction test method previously validated for pharmaceuticals was optimised and selected MDCs were tested in the context of the European Horizon 2020 GOLIATH project. Induction was revealed using a cocktail of CYP-selective probe substrates, followed by probe metabolite quantification by mass spectrometry. All MDCs except TCS induced CYP activities. PFOA, TBT, p,p'-DDE and TPP induced CYP1A2, TPP being the most potent inducer. BPA, PFOA, TBT and TPP induced CYP2B6, PFOA being the most potent inducer. BPA, PFOA, TBT, p,p'-DDE and TPP all induced CYP3A4, p,p'-DDE and BPA being the most potent inducers. These results highlight the capability of candidate MDCs to induce key CYP activities in a human relevant hepatic model, paving the way for a better understanding of MDCs mechanisms of action.

Perfluorooctanoic acid (PFOA) is a persistent organic pollutant recognised for its environmental presence and bioaccumulation, despite regulatory restrictions under the Stockholm Convention. While systemic effects of PFOA have been studied extensively, its interaction with the first biological barrier encountered after oral exposure, the gastrointestinal barrier, remains poorly characterised. In this study, we evaluated the fate, uptake and effects of PFOA in human intestinal cell culture models after acute (24 h) and repeated (11-day) exposures. Using radiolabelled PFOA profiling, we found that PFOA was not metabolised by Caco-2 cells nor by HT29-MTX mucus-producing cells, in monocultures or in co-culture. Mass balance studies revealed higher basolateral passage of PFOA in Caco-2 monocultures compared to Caco-2/HT29-MTX co-cultures, suggesting that the mucus in the co-culture may trap PFOA and limit its passage. These observations led us to conduct further toxicological evaluations in the Caco-2 monoculture model. Acute exposure, while having no effect on cell viability, increased cellular ATP at highest exposure concentration. Repeated exposure led to a progressive concentration-dependent decrease in trans-epithelial electrical resistance, indicating a compromised barrier function. This effect was not linked to changes in tight junction gene expression, but rather attributed to cell death. High-resolution chemical imaging revealed intracellular accumulation of PFOA in Caco-2 cell cytosol after repeated exposure. These findings highlight the potential of repeated exposure to PFOA, even at low concentrations, to impair intestinal barrier integrity, which may have implications for systemic absorption and toxicity.

Identification of Endocrine-Disrupting Chemicals (EDCs) in a regulatory context requires a high level of evidence. However, lines of evidence (e.g. human, in vivo, in vitro or in silico) are heterogeneous and incomplete for quantifying evidence of the adverse effects and mechanisms involved. To date, for the regulatory appraisal of metabolism-disrupting chemicals (MDCs), no harmonised guidance to assess the weight of evidence has been developed at the EU or international level. To explore how to develop this, we applied a formal Expert Knowledge Elicitation (EKE) approach within the European GOLIATH project. EKE captures expert judgment in a quantitative manner and provides an estimate of uncertainty of the final opinion. As a proof of principle, we selected one suspected MDC -triphenyl phosphate (TPP) - based on its related adverse endpoints (obesity/adipogenicity) relevant to metabolic disruption and a putative Molecular Initiating Event (MIE): activation of peroxisome proliferator activated receptor gamma (PPARγ). We conducted a systematic literature review and assessed the quality of the lines of evidence with two independent groups of experts within GOLIATH, with the objective of categorising the metabolic disruption properties of TPP, by applying an EKE approach. Having followed the entire process separately, both groups arrived at the same conclusion, designating TPP as a “suspected MDC” with an overall quantitative agreement exceeding 85%, indicating robust reproducibility. The EKE method provides to be an important way to bring together scientists with diverse expertise and is recommended for future work in this area.

Bisphenol A (BPA), a synthetic chemical widely used in the production of polycarbonate plastic and epoxy resins, has been associated with a variety of adverse effects in humans including metabolic, immunological, reproductive, and neurodevelopmental effects, raising concern about its health impact. In the EU, it has been classified as toxic to reproduction and as an endocrine disruptor and was thus included in the candidate list of substances of very high concern (SVHC). On this basis, its use has been banned or restricted in some products. As a consequence, industries turned to bisphenol alternatives, such as bisphenol S (BPS) and bisphenol F (BPF), which are now found in various consumer products, as well as in human matrices at a global scale. However, due to their toxicity, these two bisphenols are in the process of being regulated. Other BPA alternatives, whose potential toxicity remains largely unknown due to a knowledge gap, have also started to be used in manufacturing processes. The gradual restriction of the use of BPA underscores the importance of understanding the potential risks associated with its alternatives to avoid regrettable substitutions. This review aims to summarize the current knowledge on the potential hazards related to BPA alternatives prioritized by European Regulatory Agencies based on their regulatory relevance and selected to be studied under the European Partnership for the Assessment of Risks from Chemicals (PARC): BPE, BPAP, BPP, BPZ, BPS-MAE, and TCBPA. The focus is on data related to toxicokinetic, endocrine disruption, immunotoxicity, developmental neurotoxicity, and genotoxicity/carcinogenicity, which were considered the most relevant endpoints to assess the hazard related to those substances. The goal here is to identify the data gaps in BPA alternatives toxicology and hence formulate the future directions that will be taken in the frame of the PARC project, which seeks also to enhance chemical risk assessment methodologies using new approach methodologies (NAMs).

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.

Tyrosine kinase inhibitors pazopanib and sunitinib are both used to treat advanced renal cell carcinoma but expose patients to an increased risk of hepatotoxicity. We have previously identified two aldehyde derivatives for pazopanib and sunitinib (P-CHO and S-CHO, respectively) in liver microsomes. In this study, we aimed to decipher their role in hepatotoxicity by treating HepG2 and HepaRG hepatic cell lines with these derivatives and evaluating cell viability, mitochondrial dysfunction, and oxidative stress accumulation. Additionally, plasma concentrations of P-CHO were assessed in a cohort of patients treated with pazopanib. Results showed that S-CHO slightly decreased the viability of HepG2, but to a lesser extent than sunitinib, and affected the maximal respiratory capacity of the mitochondrial chain. P-CHO decreased viability and ATP production in HepG2. Traces of P-CHO were detected in the plasma of patients treated with pazopanib. Overall, these results showed that P-CHO and S-CHO affect hepatocyte integrity and could be involved in the pazopanib and sunitinib hepatotoxicity.

Fetal brain development depends on maternofetal thyroid function. In rodents and sheep, perinatal BPA exposure is associated with maternal and/or fetal thyroid disruption and alterations in central nervous system development as demonstrated by metabolic modulations in the encephala of mice. We hypothesized that a gestational exposure to a low dose of BPA affects maternofetal thyroid function and fetal brain development in a region-specific manner. Pregnant ewes, a relevant model for human thyroid and brain development, were exposed to BPA (5 mu g/kg bw/d, sc). The thyroid status of ewes during gestation and term fetuses at delivery was monitored. Fetal brain development was assessed by metabolic fingerprints at birth in 10 areas followed by metabolic network-based analysis. BPA treatment was associated with a significant time-dependent decrease in maternal TT4 serum concentrations. For 8 fetal brain regions, statistical models allowed discriminating BPA-treated from control lambs. Metabolic network computational analysis revealed that prenatal exposure to BPA modulated several metabolic pathways, in particular excitatory and inhibitory amino-acid, cholinergic, energy and lipid homeostasis pathways. These pathways might contribute to BPA-related neurobehavioral and cognitive disorders. Discrimination was particularly clear for the dorsal hippocampus, the cerebellar vermis, the dorsal hypothalamus, the caudate nucleus and the lateral part of the frontal cortex. Compared with previous results in rodents, the use of a larger animal model allowed to examine specific brain areas, and generate evidence of the distinct region-specific effects of fetal BPA exposure on the brain metabolome. These modifications occur concomitantly to subtle maternal thyroid function alteration. The functional link between such moderate thyroid changes and fetal brain metabolomic fingerprints remains to be determined as well as the potential implication of other modes of action triggered by BPA such as estrogenic ones. Our results pave the ways for new scientific strategies aiming at linking environmental endocrine disruption and altered neurodevelopment.

The functional understanding of metabolic changes requires both a significant investigation into metabolic pathways, as enabled by global metabolomics and lipidomics approaches, and the comprehensive and accurate exploration of specific key pathways. To answer this pivotal challenge, we propose an optimized approach, which combines an efficient sample preparation, aiming to reduce the variability, with a biphasic extraction method, where both the aqueous and organic phases of the same sample are used for mass spectrometry analyses. We demonstrated that this double extraction protocol allows working with one single sample without decreasing the metabolome and lipidome coverage. It enables the targeted analysis of 40 polar metabolites and 82 lipids, together with the absolute quantification of 32 polar metabolites, providing comprehensive coverage and quantitative measurement of the metabolites involved in central carbon energy pathways. With this method, we evidenced modulations of several lipids, amino acids, and energy metabolites in HepaRG cells exposed to fenofibrate, a model hepatic toxicant, and metabolic modulator. This new protocol is particularly relevant for experiments involving limited amounts of biological material and for functional metabolic explorations and is thus of particular interest for studies aiming to decipher the effects and modes of action of metabolic disrupting compounds.

Metabolomics has found numerous applications in the study of liver metabolism in health and disease. Metabolomics studies can be conducted in a variety of biological matrices ranging from easily accessible biofluids such as urine, blood or feces, to organs, tissues or even cells. Sample collection and storage are critical steps for which standard operating procedures must be followed. Inappropriate sample collection or storage can indeed result in high variability, interferences with instrumentation or degradation of metabolites. In this review, we will first highlight important general factors that should be considered when planning sample collection in the study design of metabolomic studies, such as nutritional status and circadian rhythm. Then, we will discuss in more detail the specific procedures that have been described for optimal pre-analytical handling of the most commonly used matrices (urine, blood, feces, tissues and cells).

The authors wish to make the following comment to the paper [...]

Being able to explore the metabolism of broad metabolizing cells is of critical importance in many research fields. This article presents an original modeling solution combining metabolic network and omics data to identify modulated metabolic pathways and changes in metabolic functions occurring during differentiation of a human hepatic cell line (HepaRG). Our results confirm the activation of hepato-specific functionalities and newly evidence modulation of other metabolic pathways, which could not be evidenced from transcriptomic data alone. Our method takes advantage of the network structure to detect changes in metabolic pathways that do not have gene annotations and exploits flux analyses techniques to identify activated metabolic functions. Compared to the usual cell-specific metabolic network reconstruction approaches, it limits false predictions by considering several possible network configurations to represent one phenotype rather than one arbitrarily selected network. Our approach significantly enhances the comprehensive and functional assessment of cell metabolism, opening further perspectives to investigate metabolic shifts occurring within various biological contexts.

The model xeno-estrogen bisphenol A (BPA) has been extensively studied over the past two decades, contributing to major advances in the field of endocrine disrupting chemicals research. Besides its well documented adverse effects on reproduction and development observed in rodents, latest studies strongly suggest that BPA disrupts several endogenous metabolic pathways, with suspected steatogenic and obesogenic effects. BPA's adverse effects on reproduction are attributed to its ability to activate estrogen receptors (ERs), but its effects on metabolism and its mechanism(s) of action at low doses are so far only marginally understood. Metabolomics based approaches are increasingly used in toxicology to investigate the biological changes induced by model toxicants and chemical mixtures, to identify markers of toxicity and biological effects. In this study, we used proton nuclear magnetic resonance (1H-NMR) based untargeted metabolite profiling, followed by multivariate statistics and computational analysis of metabolic networks to examine the metabolic modulation induced in human hepatic cells (HepG2) by an exposure to low and very low doses of BPA (10-6M, 10-9M, and 10-12M), vs. the female reference hormone 17β-estradiol (E2, 10-9M, 10-12M, and 10-15M). Metabolomic analysis combined to metabolic network reconstruction highlighted different mechanisms at lower doses of exposure. At the highest dose, our results evidence that BPA shares with E2 the capability to modulate several major metabolic routes that ensure cellular functions and detoxification processes, although the effects of the model xeno-estrogen and of the natural hormone can still be distinguished.

Luminescent lanthanide coordination polymers [H2NMe2]3[Ln(DPA)3] (Ln = Eu, Tb, Sm, Dy; [H2NMe2]+ = dimethyl amino cation; H2DPA = 2,6-dipicolinic acid) are synthesized, whose multi-color can be tuned and even white color luminescence can be integrated. Besides, the fluorescent sensing property of the [H2NMe2]3[Tb(DPA)3] system is checked, which shows selective fluorescent quenching effect for Fe3 +.

An increasing body of literature suggests that perinatal exposure to low doses of bisphenol A (BPA) has lasting effects on brain development and/or behavior in rodents (1, 2). Concerns about the occurrence of similar effects in humans are based on the parallel increase of neurobehavioral conditions in humans that appear in rodents exposed to BPA (3), and on epidemiological studies (4). In their recent article, Franssen et al (5) demonstrated opposite dose-dependent effects of BPA on the neuroendocrine maturation of female rats exposed during early life from postnatal day (PND)1 to PND15. In animals exposed to a 0.025g BPA/kg bw (body weight)/d dose, neuroendocrine maturation related to puberty was found to be delayed, with opposite effects observed in animals exposed to a 5000g BPA/kg bw/d dose. Modulation of inhibitory -aminobutiric acid (GABA)ergic neurotransmission was found to be associated with the delayed maturation of GnRH secretion through increased GABAergic tone for the 0.025g BPA/kg bw/d dose; opposite effects were observed for the higher dose. These new findings prompted us to reexamine in more detail our results obtained for male mice exposed to very low doses of BPA from gestational day 8 to PND16 (maternal exposure to 0-, 0.025-, 0.25-, or 25g BPA/kg bw/d) (6). In this 2013 study, we used untargeted H-nuclear magnetic resonance (NMR) metabolomics to explore the metabolites present in a set of tissues, including male brains at PND21. All brain metabolites were included in a partial least square-discriminant analysis model, which demonstrated extremely significant differences between the 4 groups. GABA was one of the major metabolites responsible for intergroup differences. To better understand the mechanisms by which BPA disrupts brain development, we reanalyzed our raw data from 2013 with the purpose of 1) challenging the hypotheses by Franssen et al, and 2) seeking additional hypotheses that could explain the disruption of GABAergic pathways. We addressed the former by means of a 2 by 2 group comparison and the latter by analyzing the genome-scale metabolic net-

Several human and fish bioassays have been designed to characterize the toxicity and the estrogenic activity of chemicals. However, their biotransformation capability (bioactivation/detoxification processes) is rarely reported, although this can influence the estrogenic potency of test compounds. The fate of two estrogenic chemicals, the UV filter benzophenone-2 (BP2) and the bisphenol A substitute bisphenol S (BPS) was deciphered in eight human and zebrafish in vitro cell models, encompassing hepatic and mammary cellular contexts. BP2 and BPS were metabolized into a variety of gluco- and sulfo-conjugated metabolites. Similar patterns of BP2 and BPS biotransformation were observed among zebrafish models (primary hepatocytes, ZFL and ZELH-zfER cell lines). Interestingly, metabolic patterns in zebrafish models and in the human hepatic cell line HepaRG shared many similarities, while biotransformation rates in cell lines widely used for estrogenicity testing (MELN and T47D-KBLuc) were quantitatively low and qualitatively different. This study provides new data on the comparative metabolism of BP2 and BPS in human and fish cellular models that will help characterize their metabolic capabilities, and underlines the relevance of using in vitro zebrafish-based bioassays when screening for endocrine disrupting chemicals.

Along with the well-established effects on fertility and fecundity, perinatal exposure to endocrine disrupting chemicals, and notably to xeno-estrogens, is strongly suspected of modulating general metabolism. The metabolism of a perinatally exposed individual may be durably altered leading to a higher susceptibility of developing metabolic disorders such as obesity and diabetes; however, experimental designs involving the long term study of these dynamic changes in the metabolome raise novel challenges. 1H-NMR-based metabolomics was applied to study the effects of bisphenol-A (BPA, 0; 0.25; 2.5, 25 and 250 μg/kg BW/day) in rats exposed perinatally. Serum and liver samples of exposed animals were analyzed on days 21, 50, 90, 140 and 200 in order to explore whether maternal exposure to BPA alters metabolism. Partial Least Squares-Discriminant Analysis (PLS-DA) was independently applied to each time point, demonstrating a significant pair-wise discrimination for liver as well as serum samples at all time-points, and highlighting unequivocal metabolic shifts in rats perinatally exposed to BPA, including those exposed to lower doses. In BPA exposed animals, metabolism of glucose, lactate and fatty acids was modified over time. To further explore dynamic variation, ANOVA-Simultaneous Component Analysis (A-SCA) was used to separate data into blocks corresponding to the different sources of variation (Time, Dose and Time*Dose interaction). A-SCA enabled the demonstration of a dynamic, time/age dependent shift of serum metabolome throughout the rats’ lifetimes. Variables responsible for the discrimination between groups clearly indicate that BPA modulates energy metabolism, and suggest alterations of neurotransmitter signaling, the latter finding being compatible with the neurodevelopmental effect of this xenoestrogen. In conclusion, long lasting metabolic effects of BPA could be characterized over 200 days, despite physiological (and thus metabolic) changes connected with sexual maturation and aging.