Mingming Sun

Abstract T-cells are crucial in maintanence of intestinal homeostasis, however, it is still unclear how microbiota metabolites regulate T-effector cells. Here we show gut microbiota-derived short-chain fatty acids (SCFAs) promote microbiota antigen-specific Th1 cell IL-10 production, mediated by G-protein coupled receptors 43 (GPR43). Microbiota antigen-specific Gpr43 −/− CBir1 transgenic (Tg) Th1 cells, specific for microbiota antigen CBir1 flagellin, induce more severe colitis compared with wide type (WT) CBir1 Tg Th1 cells in Rag −/− recipient mice. Treatment with SCFAs limits colitis induction by promoting IL-10 production, and administration of anti-IL-10R antibody promotes colitis development. Mechanistically, SCFAs activate Th1 cell STAT3 and mTOR, and consequently upregulate transcription factor B lymphocyte-induced maturation protein 1 (Blimp-1), which mediates SCFA-induction of IL-10. SCFA-treated Blimp1 −/− Th1 cells produce less IL-10 and induce more severe colitis compared to SCFA-treated WT Th1 cells. Our studies, thus, provide insight into how microbiota metabolites regulate Th1 cell functions to maintain intestinal homeostasis.

BACKGROUND: How the gut microbiota regulates intestinal homeostasis is not completely clear. Gut microbiota metabolite short-chain fatty acids (SCFAs) have been reported to regulate T-cell differentiation. However, the mechanisms underlying SCFA regulation of T-cell differentiation and function remain to be investigated. METHODS: CBir1, an immunodominant microbiota antigen, transgenic T cells were treated with butyrate under various T-cell polarization conditions to investigate butyrate regulation of T-cell differentiation and the mechanism involved. Transfer of butyrate-treated CBir T cells into Rag1-/- mice was performed to study the in vivo role of such T cells in inducing colitis. RESULTS: Although butyrate promoted Th1 cell development by promoting IFN-γ and T-bet expression, it inhibited Th17 cell development by suppressing IL-17, Rorα, and Rorγt expression. Interestingly, butyrate upregulated IL-10 production in T cells both under Th1 and Th17 cell conditions. Furthermore, butyrate induced T-cell B-lymphocyte-induced maturation protein 1 (Blimp1) expression, and deficiency of Blimp1 in T cells impaired the butyrate upregulation of IL-10 production, indicating that butyrate promotes T-cell IL-10 production at least partially through Blimp1. Rag1-/- mice transferred with butyrate-treated T cells demonstrated less severe colitis, compared with transfer of untreated T cells, and administration of anti-IL-10R antibody exacerbated colitis development in Rag-/- mice that had received butyrate-treated T cells. Mechanistically, the effects of butyrate on the development of Th1 cells was through inhibition of histone deacetylase but was independent of GPR43. CONCLUSIONS: These data indicate that butyrate controls the capacity of T cells in the induction of colitis by differentially regulating Th1 and Th17 cell differentiation and promoting IL-10 production, providing insights into butyrate as a potential therapeutic for the treatment of inflammatory bowel disease.