MicroRNA-424 May Regulate Transcripts Involved in the Pathogenesis of Inflammatory Bowel Disease (IBD)

Recently we showed by massive sequencing analysis of ileal biopsies that increased expression of multiple microRNAs (miRs) occurs in ulcerative colitis patients after total proctocolectomy and pouch surgery, specifically in those developing pouchitis and Crohn's-like disease of the pouch (CLDP). Thus, we hypothesized that miRs may have a role in down-regulation of mRNA in IBD. Based on our in silico data mir-424 was selected to define the interaction with its potential targets solute carrier family 6 member 4 (SLC6A4) and solute carrier family 36 member 1 (SLC36A1) and the mechanisms modifying miRs expression in intestinal inflammation. The expression of miR-424 significantly increased (3.3 fold, p<0.001), while SLC6A4 mRNA expression significantly decreased (5.8 fold, p<0.01) and that of SLC36A1 was lower in ileal biopsies of CLDP patients compared to normal controls. Primary to mature miR-424 expression ratios were higher in the normal pouch compared to pouchitis (4 fold increase). Similarly, intestinal epithelial cell lines (HCT-116) stimulated with inflammatory cytokines expressed 4-fold more miR-424 (p<0.05) and less SLC6A4 (2.8 fold decrease, p<0.05) and SLC36A1 (1.3 fold, p<0.01) compared to no treatment. Transfection of miR-424 mimic into HCT-116 cells resulted in a decrease in SLC6A4 and SLC36A1 expression (1.3 fold, p<0.05) whereas transfection of miR-424 inhibitor resulted in an increase in SLC6A4 and SLC36A1 expression (2 fold, p<0.01 and 1.3 fold, p<0.05, respectively). miR-424 expression correlates with intestinal inflammation and it modifies its target transcripts. Thus miR-424 behaviour may model the role of miRs in regulating intestinal inflammation in IBD.