LncRNA CASC2 regulates high glucose-induced proliferation, extracellular matrix accumulation and oxidative stress of human mesangial cells via miR-133b/FOXP1 axis

Diabetic nephropathy (DN) is one of the primary complications of diabetes. Long non-coding RNA cancer susceptibility candidate 2 (CASC2) has been established to function in DN, while its role in high glucose (HG)-induced human mesangial cells (HMCs) remains limited.The expression level of CASC2 and miR-133b was detected by quantitative real-time polymerase chain reaction (qRT-PCR). Cell proliferation was assessed using cell counting kit-8 (CCK-8) assay. Extracellular matrix (ECM) accumulation was monitored through the expression levels of collagen IV (Col IV) and fibronectin (FN) using qRT-PCR and western blot analyses. Oxidative stress was observed through the expression of NADPH oxidase2 (NOX2) and the activity of malondialdehyde (MDA) and superoxide dismutase (SOD) using western blot or corresponding detection kit. The expression of forkhead box P1 (FOXP1) at mRNA and protein levels was determined by qRT-PCR and Western blot, respectively. The relationship between miR-133b and CASC2 or FOXP1 was predicted by online bioinformatics tools and verified by dual-luciferase reporter assay or RNA pull-down.The expression of CASC2 was reduced in serum from DN patients and HG-induced HMCs. CASC2 upregulation inhibited HG-induced HMCs proliferation, ECM accumulation and oxidative stress. MiR-133b was a target of CASC2 with a high level in serum from DN patients and HG-induced HMCs, and its enrichment reversed the effects of CASC2 upregulation. Besides, FOXP1 was a target of miR-133b with a low level in HG-induced HMCs, and its knockdown abolished the impacts of CASC2 upregulation.CASC2 upregulation suppressed HG-induced proliferation, ECM accumulation and oxidative stress of HMCs through miR-133b /FOXP1 regulatory axis, suggesting that CASC2 was a novel biomarker for DN treatment.