LncRNA CASC2 alleviates renal interstitial inflammation and fibrosis through MEF2C downregulation-induced hinderance of M1 macrophage polarization

Abstract

Introduction: LncRNA CASC2 alleviates the progression of diabetic nephropathy by inhibiting inflammation and fibrosis. This study investigated how CASC2 impacts renal interstitial fibrosis (RIF) through regulating M1-macrophage (M1) polarization. Method: Nine-week-old mice underwent unilateral ureteral obstruction (UUO) establishment. Macrophages were induced towards M1 polarization using lipopolysaccharides (LPS) in vitro and cocultured with fibroblasts to examine how M1 polarization influences RIF. lncecell predicted that CASC2 interacted with myocyte enhancer factor 2 C (MEF2C), which was validated by dual-luciferase reporter assay. CASC2/MEF2C overexpression was achieved by LV-CASC2 injection in vivo, or CASC2 and MEF2C transfection in vitro. Renal injury was evaluated through biochemical analysis and hematoxylin-eosin/masson staining. Macrophage infiltration and M1 polarization in the kidney and/or macrophages were detected by immunofluorescence, flow cytometry and/or qRT-PCR. Expressions of CASC2, MEF2C and markers related to inflammation/M1/fibrosis in the kidney/macrophages/fibroblasts were analyzed by qRT-PCR, FISH, ELISA and/or western blot. Result: In the kidneys of mice, CASC2 was downregulated and macrophage infiltration was promoted time-dependently from day 3 to 14 post-UUO induction; CASC2 overexpression alleviated renal histological abnormalities, hindered macrophage infiltration and M1 polarization, downregulated renal function markers Scr and Bun, and inflammation/M1/fibrosis-related makers and offset UUO-related MEF2C upregulation. LncRNA CASC2 overexpression inhibited fibroblast fibrosis and M1 polarization in cocultured fibroblasts with LPS-activated macrophages. Also, CASC2 bound to MEF2C and inhibited its expression in LPS-activated macrophages. Furthermore, MEF2C reversed the inhibitory effects of lncRNA CASC2 overexpression. Conclusion: CASC2 alleviates RIF by inhibiting M1 polarization through directly downregulating MEF2C expression. CASC2 might represent a promising value of future investigations on treatment for RIF.