HIF-2α-dependent induction of miR-29a restrains TH1 activity during T cell dependent colitis.

Metabolic imbalance leading to inflammatory hypoxia and stabilization of hypoxia-inducible transcription factors (HIFs) is a hallmark of inflammatory bowel diseases. We hypothesize that HIF could be stabilized in CD4⁺ T cells during intestinal inflammation and alter the functional responses of T cells via regulation of microRNAs. Our assays reveal markedly increased T cell-intrinsic hypoxia and stabilization of HIF protein during experimental colitis. microRNA screen in primary CD4⁺ T cells points us towards miR-29a and our subsequent studies identify a selective role for HIF-2α in CD4-cell-intrinsic induction of miR-29a during hypoxia. Mice with T cell-intrinsic HIF-2α deletion display elevated T-bet (target of miR-29a) levels and exacerbated intestinal inflammation. Mice with miR-29a deficiency in T cells show enhanced intestinal inflammation. T cell-intrinsic overexpression of HIF-2α or delivery of miR-29a mimetic dampen T_H1-driven colitis. In this work, we show a previously unrecognized function for hypoxia-dependent induction of miR-29a in attenuating T_H1-mediated inflammation. Inflammatory intestinal lesions are often hypoxic, which results in the stabilization and activation of hypoxia-inducible-factors (HIF). Here authors show that in a mouse model of colitis, HIF-2α is specifically stabilized in CD4+ type 1T helper (T_H1) cells, leading to the upregulation of miR-29a expression and suppression of T_H1 cell function, which pathway is potentially targetable for therapeutic purposes. [ABSTRACT FROM AUTHOR]