A 60-days oral exposure to the food-grade silicon dioxide blocks oral tolerance induction in the gut and exacerbates gluten immunopathology in amouse model of celiac disease

International audience

إنجليزي. The gut immune system is daily exposed to inorganic particles used as food additives or processing aids in the food industry, such as silicon dioxide (SiO2), acommon anticaking agent in manufacturing powdered foods (milk, infant formulae, instant soups), ingredients (spices, salt, flours) and supplements. Inmucosal surfaces like the gut, a state of unresponsiveness to non-self antigens, called oral tolerance (OT), is established to prevent sensitivities, such as foodallergies (peanuts, seafood) and autoimmune conditions driven by gluten proteins, namely, celiac disease (CeD). Here we investigated whether long-term oralexposure to food-grade (fg) SiO2 alters the intestinal immune response involved in OT, and the consequences in a model of gluten sensitivity. Wild type mice(C57BL/6) were daily treated for 60 days with fg-SiO2 (10mg/kg body weight/day) in water suspension (gastric gavage) or incorporated into food pellets (solidmatrix). Controls received only water. The gut immune response and OT induction to a food antigen model (ovalbumin, OVA) were evaluated, and intestinalimmune cell populations analysed by flow cytometry. In addition, non-obese diabetic (NOD) mice expressing the CeD susceptibility gene DQ8 and exposed tofg-SiO2 were sensitized to gluten. Development of small intestinal immunopathology was assessed at sacrifice. Chronic oral exposure to fg-SiO2 at humandietary levels, triggers low-grade intestinal inflammation evidenced by increased production of the pro-inflammatory cytokines IFN-γ, and decreasedproduction of the anti-inflammatory cytokines IL-10 and TGF-β, key mediators of OT. After OT induction to OVA, fg-SiO2 exposure decreased the frequency ofIL-10 and TGF-β producing T cells, leading to breakdown of OT and mucosal inflammation. fg-SiO2 exposure through gastric gavage, but not through foodpellets, decreased the frequency of CD103+ dendritic cells. Using water as fg-SiO2 vehicle, gluten immunopathology was worsened in NOD/DQ8 mice,characterized by decreased villus-to-crypt ratios, increased CD3+ IELs counts, and an enhanced Th1 inflammatory response. These data collectively show thatchronic, daily oral exposure to food-grade SiO2 particles blocked the establishment of OT in the gut, inducing intestinal inflammation worsening thedevelopment of gluten sensitivity in a mouse model of CeD. This raises the hypothesis that chronic exposure to SiO2 through the diet could act asenvironmental trigger of loss of tolerance in genetically susceptible people and lead to onset of food sensitivities. Our results should encourageepidemiological research on potential adverse effects related to the chronic intake of food additive SiO2 in particular, its association with food allergies andautoimmune conditions, such as celiac disease.