miR‑146a‑5p negatively regulates the IL‑1β‑stimulated inflammatory response via downregulation of the IRAK1/TRAF6 signaling pathway in human intestinal epithelial cells

The primary pathophysiological alteration caused by inflammatory bowel disease (IBD) is prolonged, excessive inflammatory response to stimulation factors, which leads to intestinal mucosal lesions. microRNA (miR)-146a-5p is broadly activated in the mucosal immune response. At present, the biogenesis, function and role of miR-146a-5p in intestinal epithelial cells (IECs) during the pathogenesis of IBD remain elusive. The human colon cancer epithelial Caco-2 cell line was cultured with 10 ng/ml recombinant human IL-1β for 3 h to establish an in vitro IECs inflammatory model. Relative levels of miR-146a-5p and inflammatory factors (IL-6, IL-1β, TNF-α and IP-10) were measured by reverse transcription-quantitative PCR (RT-qPCR) and western blotting. Transfection of miR-146a-5p mimic or inhibitor into Caco-2 cells was performed to identify the influence of miR-146a-5p on Caco-2 cell inflammatory factors expression. The targeting relationship between miR-146a-5p and interleukin 1 receptor associated kinase 1 (IRAK1)/tumor necrosis factor receptor-associated factor 6 (TRAF6) was predicted by TargetScan 8.0. The present study demonstrated that miR-146a-5p and inflammatory factors (IL-6, IL-1β, TNF-α and IP-10) were upregulated in a dose- and time-dependent manner in IL-1β-stimulated Caco-2 cells. Moreover, upregulation of miR-146a-5p negatively regulated the expression of inflammatory factors, but the downregulation of miR-146a-5p increased their expression. The results of the present study demonstrated that miR-146a-5p decreased the expression of the inflammatory factors through targeted downregulation of IRAK1/TRAF6. These results suggest that miR-146a-5p negatively regulates the IL-1β-stimulated inflammatory response via downregulation of the IRAK1/TRAF6 signaling pathway in human IECs. Therefore, miR-146a-5p may act as an important diagnostic biomarker and treatment target of IBD.