microRNA-15 Activates NF-κB Pathway via Down Regulating Expression of Adenosine A2 Receptor in Ulcerative Colitis.

BACKGROUND/AIMS: The role of miR-15 in ulcerative colitis (UC) is unclear. In this study, we found that miR-15 downregulated the expression of adenosine A2a receptor (A2aAR) in the colonic tissues of patients with UC and in HT-29 human colonic epithelial cells.

METHODS: The study population comprised patients with UC (n=23), irritable bowel syndrome (IBS, n=22), and healthy subjects (n = 20). The levels of miR-15, A2aAR, and protein in colon tissue biopsies were determined by real-time quantitative reverse transcription polymerase chain reaction, immunofluorescence staining, and Western blotting. The TargetScan prediction algorithm was used to identify the miR-15 binding site in the 3'-UTR of A2aAR. To assess the effects of miR-15 on A2aAR levels, HT-29 cells were transfected with miR-15 mimics.

RESULTS: Relative to expression in healthy subjects, A2aAR expression was decreased in UC patients and was similar in IBS patients. MiR-15 levels were higher in UC patients than in IBS patients or healthy subjects. A2aAR was the target of miR-15 in HT-29 cells, which downregulated A2aAR mRNA levels. MiR-15 mimics induced nuclear translocation of NF-κB p65 and upregulated the expression of IL-8 and IFN-γ in colonic epithelial cells; these effects were reversed by an miR-15 inhibitor. A2aAR knockdown confirmed that miR-15 activated the NF-κB cascade.

CONCLUSION: Our data suggest that miR-15 modulates inflammatory and immune responses by suppressing the expression of A2aAR and regulating the NF-κB cascade.