The role of the miR-21-5p-mediated inflammatory pathway in ulcerative colitis

Ulcerative colitis (UC), a major type of inflammatory bowel disease, is also a chronic non-specific intestinal inflammation condition of unknown etiology. The pathogenesis of UC is closely associated with immune abnormalities, inflammatory damage and genetics. The present study aimed to explore the effects of microRNA (miR)-21-5p on the interleukin-6 (IL-6) receptor (IL6R)/signal transducer and activator of transcription (STAT3) signal pathway in UC, in order to identify a highly effective treatment for UC. A total of 45 patients with UC and 45 healthy controls were recruited for the present study. The expression levels of miR-21-5p and STAT3 in the sera of patients with UC and healthy controls were determined by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). A UC rat model was established using dextran sulfate sodium. Following lipopolysaccharide (LPS) treatment, RAW264.7 cells were transfected with a miR-21-5p inhibitor. The levels of morphological damage and apoptosis of the colonic mucosal epithelial tissue were investigated using hematoxylin and eosin staining and a TUNEL staining assay, and then the colon macroscopic damage index and disease activity index were measured in rats. Western blot analysis was used to detect the protein expression levels of IL6R, STAT3, intracellular adhesion molecule 1 (ICAM-1), NF-κB, cleaved caspase-3, cleaved caspase-9 and Fas ligand (FasL). RT-qPCR detected the mRNA expression levels of miR-21-5p, IL6R, STAT3, ICAM-1, NF-κB, caspase-3, caspase-9 and FasL. An ELISA was performed to measure the levels of inflammatory cytokines. The viability and apoptosis levels of RAW264.7 cells were examined using MTT and flow cytometry assays. Additionally, STAT3 was investigated as a direct target of miR-21-5p in RAW264.7 cells using a dual-luciferase reporter assay. The results of the present study demonstrated that inflammation and apoptotic markers were revealed to be significantly downregulated following transfection with miR-21-5p inhibitors in RAW264.7 cells induced by LPS, and that cell viability was increased. Furthermore, STAT3 was confirmed to be a target of miR-21-5p in RAW264.7 cells. Collectively, these data demonstrated that miR-21-5p inhibition mediated the IL-6/STAT3 pathway in UC rats to decrease the levels of inflammation and apoptosis in RAW264.7 cells, and suggested that miR-21-5p may be an important therapy target in human UC.