Circ_0000491 Promotes Apoptosis, Inflammation, Oxidative Stress, and Fibrosis in High Glucose-Induced Mesangial Cells by Regulating miR-455-3p/Hmgb1 Axis

Background: Diabetic nephropathy (DN) is a severe microvascular complication of diabetes. Recently, many circular RNAs can exert crucial roles in DN progression. This study intended to explore the role and mechanism of circ_0000491 in DN. Methods: The DN mouse model was constructed by streptozotocin injection, and the DN cell model was established using high glucose (HG) treatment in mouse mesangial cells (SV40-MES13). The expression of circ_0000491 and microRNA-455-3p (miR-455-3p) was detected by quantitative real-time polymerase chain reaction. Cell apoptosis was evaluated by flow cytometry. The expression levels of high-mobility group box 1 (Hmgb1) protein, apoptosis-related proteins, and fibrosis-related proteins were examined by the Western blot assay. The release of inflammatory cytokines was assessed by enzyme-linked immunosorbent assay. The oxidative stress factors were analyzed by corresponding kits. The predicted interaction between miR-455-3p and circ_0000491 or Hmgb1 was verified by dual-luciferase reporter assay and RNA immunoprecipitation assay. Results: Circ_0000491 was overexpressed in the DN mouse model and HG-induced SV40-MES13 cells. Knockdown of circ_0000491 weakened HG-induced apoptosis, inflammation, oxidative stress, and fibrosis in SV40-MES13 cells. miR-455-3p was a direct target of circ_0000491, and miR-455-3p inhibition could reverse the role of circ_0000491 silencing in HG-induced SV40-MES13 cells. Moreover, Hmgb1 was a target gene of miR-455-3p, and miR-455-3p played a protective role against HG-induced cell injury by targeting Hmgb1. In addition, circ_0000491 regulated Hmgb1 expression by sponging miR-455-3p. Conclusion: Circ_0000491 knockdown inhibited HG-induced apoptosis, inflammation, oxidative stress, and fibrosis in SV40-MES13 cells by regulating miR-455-3p/Hmgb1 axis.