Inhibition of microRNA-448 suppresses CD4+ T cell inflammatory activation via up-regulating suppressor of cytokine signaling 5 in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease. MicroRNA-448 (miR-448) has a pro-inflammatory effect in various inflammation-related diseases and is up-regulated in serum of patients with SLE. However, the role of miR-448 in SLE development remains elusive. In our study, we found high expression of miR-448 in peripheral blood mononuclear cells (PBMCs) of SLE patients, and miR-448 level was positively associated with disease severity. Besides, miR-448 level was up-regulated during the growth of MRL/lpr mice. To investigate the function of miR-448 in SLE, we subjected 8-week MRL/lpr mice to injection of lentivirus (LV)-mediated anti-miR-448. Inhibition of miR-448 reduced serum IgG and anti-dsDNA IgG contents, 24 h urine protein and blood urea nitrogen (BUN) levels, increased complement C3 concentration, and ameliorated splenomegaly and lymphadenectasis in MRL/lpr mice. MiR-448 inhibition alleviated renal inflammatory infiltration and glycogen deposition. Moreover, miR-448 inhibition promoted Treg cell activation and inhibited Th17 cell proportion in naïve CD4+ T cells from spleens, along with elevated interleukin (IL)-10 and reduced IL-17A levels. In vitro, miR-448 inhibition diminished CD4+ T cell polarization toward Th17 cells under Th17-polarizing conditions. Further, luciferase reporter assay revealed that miR-448 binds to the 3'UTR of suppressor of cytokine signaling 5 (SOCS5). SOCS5 expression was down-regulated in the spleens of MRL/lpr mice and induced Th17 cells. SOCS5 deficiency partially reversed the role of miR-448 in Th17 differentiation and IL-17A expression in SLE. Taken together, inhibition of miR-448 impedes Th17 cell activation and tissue damages via targeting SOCS5 in SLE.