MicroRNA-155 inhibitor ameliorates collagen-induced arthritis by modulating the phenotype of pro-inflammatory macrophages in a mouse model

Background: The present study aims to investigate the roles of microRNA-155 in collagen-induced arthritis (CIA) and its underlying mechanisms. Methods: CIA mouse model was established and miR155 inhibitor was intravenously injected. In in vitro studies, bone marrow-derived macrophages (BMDMs) were induced into M1 macrophages followed by the treatment of miR155 inhibitor. Quantitative reverse transcription PCR (RT-qPCR) was applied to determine the mRNA expressions. Flow cytometry was applied to determine the frequency of M1 or M2 macrophages. Western blotting was determined to detect protein expressions. Enzyme-linked immunosorbent assay (ELISA) was applied to determine the levels of inflammatory cytokines and anti-collagen antibody. Results: The levels of miR155 were increased in macrophages from rheumatoid arthritis (RA) patients and M1 macrophages. The treatment of miR155 inhibitor decreased inflammatory cytokines in M1 macrophages. Besides, treatment of miR155 inhibitors promoted the differentiation of M0 macrophages into M2 macrophages. In vivo studies demonstrated that the treatment of miR155 inhibitors ameliorated the RA symptoms by decreasing inflammatory cytokines in the CIA mouse model. Treatment of miR155 also resulted in a decrease of M1 macrophage biomarker and an increase of M2 macrophage biomarker. Conclusion: microRNA-155 inhibitor ameliorates RA symptoms in part by regulating macrophage phenotypes.