MicroRNA-155Is Involved In The Pathogenesis Of Ulcerative Colitis By Targeting FOXO3a

BackgroundUlcerative colitis (UC) is a chronic and relapsing condition of the intestinalinflammation.The precise pathogenesis of UC remains unknown, butepidemiologic and genome-wide linkage studies confirmed that UC was acomplex polygenic and multifactorial disease, and these dysregulated genes couldinfluence the development of the disease via certain signaling pathways. Althoughdysregulation in the intestinal epithelial cell has been widely reported in UC, themolecular basis and pathophysiology of UC are incompletely understood.MicroRNAs (miRNAs) are small (18-24-nucleotide), noncoding RNAs thatposttranscriptionally modulate the expression of multiple target genes. MiRNAsbind to complementary sequences in the3'untranslated region (UTR) of specifictarget mRNAs and can prevent protein synthesis. MiRNAs are believed to play acrucial role in the regulation of many biological processes, such as cellularproliferation, differentiation and apoptosis. These studies may lead to new insightsinto UC pathogenesis as well as biomarkers for disease activity and therapeuticresponse.AimsThe purpose of the present study was to identify miRNAs induced in theinflamed colonic mucosa of patients with active UC and evaluate the role ofmiRNA and its target gene in the molecular mechanisms underlying thepathophysiology of UC, with the aim of better elucidating the mechanisms of UCand laying a foundation for formulating novel UC therapeutic strategies.Methods1. Previous miRNA microarray was analyzed and after literature review, we chose miR-155to have further investigation.Realtime RT-PCR was carriedout for validation of miRNA microarray results.2. Predicted the potential gene targets of miRNA-155by Targetscan andmiRanda software. Western blot were used to examine the expression of thetarget gene FOXO3a in UC and healthy control tissues. Constructed apGL3-REPORT plasmids for the FOXO33'UTR and mutant, the effect ofmiR-155on FOXO3a was evaluated by luciferase reporter gene assay andwestern blot.3. The effect of FOXO3a-siRNA and miR-155on IL-8protein level in theTNF-α treated HT29cells were detected by ELISA.Results1. Analyze the previous miRNA microarray, miR-155which expression wassignificantly up-regulated in UC tissues compared with healthy control tissuesand confirmed the result by subsequent qRT-PCR.2. Through bioinformatics analysis and screened the target genes of miR-155,FOXO3a was identified as a putative miR-155target gene by usingbioinformatics prediction, luciferase array and western blot.3. The expression of miR-155was increased in TNF-α treated HT29cells andFOXO3a protein level was decreased which were time-dependent. ELISAresults showed that down-regulated expression of FOXO3a by siRNA andmiR-155mimics increased IL-8level in the TNF-α treated HT29cells.ConclusionsWe report the altered miR-155expression pattern in UC, investigate thepotential role of miR-155in the pathogenesis of UC, and demonstrate thatFOXO3a is a target gene of miR-155. Our data demonstrate an important rolefor miR-155in the molecular basis and pathophysiology of UC and suggest itspotential application in UC therapy.