An Escherichia coli strain with extra catalase activity protects against murine colitis by scavenging hydrogen peroxide and regulating regulatory t cell/interleukin-17 pathways

Background Inflammatory bowel disease (IBD) is a chronic inflammatory disease of the gastrointestinal tract whose occurrence is attributed to various factors, including genetic factors, immune response, microbial changes, and oxidative stress. Microbial-targeted therapy has emerged as an alternative to immunosuppressive therapy for IBD. Methods The effects of an atypical commensal Escherichia coli strain harboring an additional catalase gene (compared to typical E. coli strain) on dextran sulfate sodium (DSS)-induced colitis were explored in mice. Results The atypical E. coli (atEc) significantly restored body weight, reduced disease activity score, and improved histological scores in mice with colitis. Hydrogen peroxide levels in colitis mice were noticeably decreased when the mice were administered atEc. The proinflammatory cytokine levels were decreased and regulatory T cell numbers were increased after the administration of atEc. The abundance of Firmicutes was significantly recovered, while that of Proteobacteria decreased in atEc -treated mice compared with that in vehicle-treated wild-type mice. To investigate the role of interleukin (IL)-17A in mediating the anti-inflammatory effects of the atEc, IL-17A‒knockout mice were orally administered atEc. Clinical and immune responses and microbial composition were significantly reduced in IL-17A‒knockout mice compared with those in wild-type mice. Conclusions atEc ameliorates colonic inflammation by controlling hydrogen peroxide levels, immune responses (including regulatory T cells and IL-17A), and microbial composition. atEc could be a novel candidate of probiotic for IBD treatment.