Differential influences of the BPA, BPS and BPF on in vitro IL-17 secretion by mouse and human T cells

International audienceThe endocrine disruptor and food contaminant bisphenol A (BPA) is frequently present in consumer plastics and can produce several adverse health effects participating in the development of inflammatory and autoimmune diseases. Regulatory restrictions have been established to prevent risks for human health, leading to the substitution of BPA by structural analogues, such as bisphenol S (BPS) and F (BPF). In this study, we aimed at comparing the in vitro impact of these bisphenols from 0.05 to 50,000 nM on Th17 differentiation, frequency and function in mouse systemic and intestinal immune T cells and in human blood T cells. This study reports the ability of these bisphenols, at low and environmentally relevant concentration, i.e, 0.05 nM, to increase significantly IL-17 production in mouse T cells but not in human T lymphocytes. The use of an aryl hydrocarbon receptor (AhR) specific inhibitor demonstrated its involvement in this bisphenol-induced IL-17 production. We also observed an increased IL-17 secretion by BPS and BPF, and not by BPA, in mouse naive T cells undergoing in vitro Th17 differentiation. In total, this study emphasizes the link between bisphenol exposures and the susceptibility to develop immune diseases, questioning thus the rational of their use to replace BPA

Cell resistance to the cytolethal distending toxin involves an association of DNA repair mechanisms

The Cytolethal Distending Toxin (CDT), produced by many bacteria, has been associated with various diseases including cancer. CDT induces DNA double-strand breaks (DSBs), leading to cell death or mutagenesis if misrepaired. At low doses of CDT, other DNA lesions precede replication-dependent DSB formation, implying that non-DSB repair mechanisms may contribute to CDT cell resistance. To address this question, we developed a proliferation assay using human cell lines specifically depleted in each of the main DNA repair pathways. Here, we validate the involvement of the two major DSB repair mechanisms, Homologous Recombination and Non Homologous End Joining, in the management of CDT-induced lesions. We show that impairment of single-strand break repair (SSBR), but not nucleotide excision repair, sensitizes cells to CDT, and we explore the interplay of SSBR with the DSB repair mechanisms. Finally, we document the role of the replicative stress response and demonstrate the involvement of the Fanconi Anemia repair pathway in response to CDT. In conclusion, our work indicates that cellular survival to CDT-induced DNA damage involves different repair pathways, in particular SSBR. This reinforces a model where CDT-related genotoxicity primarily involves SSBs rather than DSBs, underlining the importance of cell proliferation during CDT intoxication and pathogenicity

Validating intestinal effects of food-grade titanium dioxide using a murine gut organoid model as alternative to in vivo models

International audienceBackground: Nanoparticles (NPs) found in the human diet mainly originate from inorganic food additives, often used quantum satis in common foodstuff, which raises public health concerns due to daily exposure. The whitener and opacifying agent titanium dioxide (TiO2, E171 in EU) is one of the most studied nanomaterial, evoking inflammatory responses and precancerous lesions in the rodent intestine. Investigating the potential hazards of chronic oral exposure to NPs is often time-consuming and requires animal models, specific spaces and skills. However, recent technical advances in stem cells and threedimensional cultures allowed the use of organoids as an alternative model to in vivo experiments. Herein we used murine intestinal organoids to characterize intestinal impacts of food-grade TiO2 in comparison to already reported in vivo data, and to validate organoids as a reliable model for studying the effects of foodborne NPs in the gut.Methods: Three different wild-type C57bl/6 mice were used for small intestine collection. Intestinal crypts were purified, dissociated, and cells were cultured for organoid growth. After 4 passages, organoids were dissociated and seeded as a 2.5D culture, then exposed to 0.1, 1, 10 or 100µg/ml of E171 for 24h. Supernatants were collected, and cytotoxicity assessed by LDH release quantification. Total RNA was extracted from samples and analyzed for cell proliferation and differentiation, genotoxicity, antimicrobial peptides, permeability, oxidative stress, Toll Like Receptors (TLR), NFκB, cytokine and chemokine gene expressions by qPCR. Cell apoptosis was also evaluated by cleaved Caspase-3 quantification using immunofluorescence.Results: Gut organoids exposed to E171 showed a dose-dependent up-regulation of the cell proliferation marker Mki67 together with increased protein expression of cleaved-Caspase-3, suggesting epithelium renewal or restructuring. This occurred in parallel to a decreased expression of the enterocyte differentiation markers Alpi and Krt20 as well as up-regulation of the neuroendocrine marker Chga. Moreover, food-grade E171 decreased gene expression of antimicrobial peptides (Lyz, Reg3b, S100a8) and tight junction proteins (F11r, Tjp1, Ocln, Cldn7, Cldn15), suggesting altered epithelial secretion and permeability. We also showed that the TLR4-NFκB pathway was negatively impacted in a dose-dependent manner, while oxidative stress, cytokine and chemokine gene expressions remained unaltered. Although E171 exposure was not cytotoxic, TiO2 increased expression of gadd45a at low dose (i.e. 1µg/ml), suggesting DNA damage.Conclusions: Taking together, a 24h-exposure of murine intestinal organoids to food-grade TiO2 impacts epithelial barrier integrity (cell proliferation and differentiation, gut permeability, genotoxic effect) and antimicrobial defenses as reported in vivo in rodent models, hence validating the use of intestinal organoids for toxicological studies of foodborne NPs

Gut dysbiosis and impairment of immune system homeostasis in perinatally-exposed mice to Bisphenol A precede obese phenotype development

Abstract Epidemiology evidenced the Bisphenol A (BPA), a chemical found in daily consumer products, as an environmental contributor to obesity and type II diabetes (T2D) in Humans. However, the BPA-mediated effects supporting these metabolic disorders are still unknown. Knowing that obesity and T2D are associated with low-grade inflammation and gut dysbiosis, we performed a longitudinal study in mice to determine the sequential adverse effects of BPA on immune system and intestinal microbiota that could contribute to the development of metabolic disorders. We observed that perinatal exposure to BPA (50 µg/kg body weight/day) induced intestinal and systemic immune imbalances at PND45, through a decrease of Th1/Th17 cell frequencies in the lamina propria concomitant to an increase of splenic Th1/Th17 immune responses. These early effects are associated with an altered glucose sensitivity, a defect of IgA secretion into faeces and a fall of faecal bifidobacteria relative to control mice. Such BPA-mediated events precede infiltration of pro-inflammatory M1 macrophages in gonadal white adipose tissue appearing with ageing, together with a decreased insulin sensitivity and an increased weight gain. Our findings provide a better understanding of the sequential events provoked by perinatal exposure to BPA that could support metabolic disorder development in later life