Vitamin D/vitamin D receptor (VDR) signaling is reported to have a protective effect on the onset or progression of inflammatory bowel diseases (IBD) and hypoxia-inducible factor 1α (HIF-1α) activation is demonstrated to be closely associated with chemical-induced colitis. However, the association between vitamin D/VDR signaling and HIF-1α on IBD development remains a mystery. Here, we showed that HIF-1α expression was largely increased in the colonic epithelial cells of diseased tissues from ulcerative colitis (UC) patients. Consistently, HIF-1α activation was also improved in colonic epithelial cells upon TNFα treatment in a NF-κB pathway-dependent manner. HIF-1α inhibitors treatments ameliorated 2,4,6-trinitrobenzenesulfonic acid (TNBS)- or dextran sulfate sodium (DSS)-induced colitis in animal models. In cell or colitis animal models, vitamin D/VDR signaling suppressed HIF-1α overexpression in colonic epithelial cells via regulating NF-κB pathway, resulting in the inhibition of IFNγ and IL-1β overproductions in these cells. Collectively, these data suggest that vitamin D/VDR signaling relieves colitis development in animal models, at least in part, by suppressing HIF-1α expression in colonic epithelial cells.

The nuclear N6‐methyladenosine (m6A) reader YT521‐B homology‐domain‐containing protein 1 (YTHDC1) is required to maintain embryonic stem cell identity. However, little is known about its biological functions in intestinal‐resident macrophages and inflammatory bowel disease (IBD). Herein, it is demonstrated that macrophage‐specific depletion or insufficiency of YTHDC1 accelerates IBD development in animal models. On the molecular basis, YTHDC1 reduction in IBD‐derived macrophages is attributed to Zinc finger protein 36 (ZFP36)‐induced mRNA degradation. Importantly, transcriptome profiling and mechanistic assays unveil that YTHDC1 in macrophages regulates Ras homolog family member H (RHOH) to suppress inflammatory responses and fine‐tunes NME nucleoside diphosphate kinase 1 (NME1) to enhance the integrity of colonic epithelial barrier, respectively. Collectively, this study identifies YTHDC1 as an important factor for the resolution of inflammatory responses and restoration of colonic epithelial barrier in the setting of IBD.