Aryl hydrocarbon receptor-mediated induction of the microRNA-132/212 cluster promotes interleukin-17-producing T-helper cell differentiation.

Aryl hydrocarbon receptor (AHR) plays critical roles in various autoimmune diseases such as multiple sclerosis by controlling in-terleukin- 17 (IL-17)-producing T-helper (T(H)17) and regulatory T cells. Although various transcription factors and cytokines have been identified as key participants in TH17 generation, the role of microRNAs in this process is poorly understood. In this study, we found that expression of the microRNA (miR)-132/212 cluster is up-regulated by AHR activation under T(H)17-inducing, but not regulatory T-inducing conditions. Deficiency of the miR-132/212 cluster prevented the enhancement of T(H)17 differentiation by AHR activation. We also identified B-cell lymphoma 6, a negative regulator of T(H)17 differentiation, as a potential target of the miR-212. Finally, we investigated the roles of the miR-132/212 cluster in experimental autoimmune encephalomyelitis, a murine model of multiple sclerosis. Mice deficient in the miR-132/212 cluster exhibited significantly higher resistance to the development of experimental autoimmune encephalomyelitis and lower frequencies of both T(H)1 and T(H)17 cells in draining lymph nodes. Our findings reveal a unique mechanism of AHR-dependent T(H)17 differentiation that depends on the miR-132/212 cluster

The aryl hydrocarbon receptor/microRNA-212/132 axis in T cells regulates IL-10 production to maintain intestinal homeostasis.

Aryl hydrocarbon receptor (Ahr), a transcription factor, plays a critical role in autoimmune inflammation of the intestine. In addition, microRNAs (miRNAs), small non-coding oligonucleotides, mediate pathogenesis of inflammatory bowel diseases (IBD). However, the precise mechanism and interactions of these molecules in IBD pathogenesis have not yet been investigated. We analyzed the role of Ahr and Ahr-regulated miRNAs in colonic inflammation. Our results show that deficiency of Ahr in intestinal epithelial cells in mice exacerbated inflammation in dextran sodium sulfate-induced colitis. Deletion of Ahr in T cells attenuated colitis, which was manifested by suppressed T-h 17 cell infiltration into the lamina propria. Candidate miRNA analysis showed that induction of colitis elevated expression of the miR-212/132 cluster in the colon of wild-type mice, whereas in Ahr(-/-) mice, expression was clearly lower. Furthermore, miR-212/132(-/-) mice were highly resistant to colitis and had reduced levels of T-h 17 cells and elevated levels of IL-10-producing CD4(+) cells. In vitro analyses revealed that induction of type 1 regulatory T (Tr1) cells was significantly elevated in miR-212/132(-/-) T cells with increased c-Maf expression. Our findings emphasize the vital role of Ahr in intestinal homeostasis and suggest that inhibition of miR-212/132 represents a viable therapeutic strategy for treating colitis