Abstract
Although aberrant microRNA (miRNA) expression has frequently been observed in inflammatory bowel disease (IBD), its biological functions and targets remain largely unknown. Present study found that miR-19b was significantly downregulated in active Crohn's disease (CD). Using bioinformatics analysis, suppressor of cytokine signalling 3 (SOCS3), a physiological regulator of innate and adaptive immunity that controls several immuno-inflammatory diseases, was predicted to be a potential target of miR-19b. An inverse correlation between miR-19b and SOCS3 protein levels, but not mRNA, was identified in active-CD intestinal tissue samples. By overexpressing or knocking down miR-19b in Caco2 cells and HT29 cells, it was experimentally validated that miR-19b is a direct regulator of SOCS3. Using a luciferase reporter assay, it was confirmed that miR-19b directly recognizes the 3'-untranslated region (3'-UTR) of SOCS3. Furthermore, overexpression of miR-19b decreased SOCS3 expression, leading to increased production of macrophage-inflammatory protein-3α (MIP-3α) in Caco2 cells. In contrast, knockdown of miR-19b increased SOCS3 and decreased MIP-3α. Finally, intracolonically delivered miR-19b decreased the severity of colitis induced with 2,4,6-trinitrobenzene sulphonic acid (TNBS). Taken together, our findings suggest that miR-19b suppresses the inflammatory response by inhibiting SOCS3 to modulate chemokine production in intestinal epithelial cells (IECs) and thereby prevents the pathogenesis of CD.