MicroRNA‐146b improves intestinal injury in mouse colitis by activating nuclear factor‐κB and improving epithelial barrier function

The precise role of microRNAs in inflammatory disease is not clear. The present study investigated the effect of microRNA (miR-146b) with respect to improving intestinal inflammation.The microRNA profile in interleukin-10 deficient mice was examined using microRNA arrays and miR-146b was selected for the subsequent experiments. The expression vectors containing either the whole sequence of miR-146b or small interfering RNA for miR-146b were intraperitoneally administered to the dextran sodium sulfate (DSS)-induced colitis mouse. The expression levels of inflammation-related mediators were examined by the reverse transcriptase-polymerase chain reaction and western blotting analysis. Intestinal barrier function was evaluated by an ex vivo mannitol flux study.The overexpression of miR-146b activated the NF-κB pathway, improved epithelial barrier function, relieved intestinal inflammation in the DSS-induced colitis mice, and improved the survival rate of mice with lethal colitis. Furthermore, this amelioration of intestinal inflammation by miR-146b was negated by the inhibitor for the NF-κB pathway. The overexpression of miR-146b decreased the expression of siah2, which has a target sequence for miR-146b, and promoted the ubiquitination of TRAF proteins. This suggests that the up-regulation of NF-κB by miR-146b was mediated by inhibition of the ubiquitination of TRAF proteins upstream of NF-κB.miR-146b improves intestinal inflammation by up-regulating NF-κB as a result of the decreased expression of siah2, which ubiquitinates TRAF proteins. Modulation of the miR-146b expression is a potentially useful therapy for the treatment of intestinal inflammation via activation of the NF-κB pathway.