Inhibition of miR-34a reduces podocyte apoptosis by targeting Bcl-2 and autophagy

Abstract

BACKGROUND: Podocyte apoptosis is a key event in the pathogenesis of diabetic nephropathy. MiR-34a has been reported to be involved in cell proliferation and apoptosis, but its potential roles in podocytes under the diabetic condition remains unknown. METHODS: Type 2 diabetic nephropathy was established by uninephrectomy (Unx) in nine-week-old db/db mice. In cultured immortalized human podocytes, miR-34a was overexpressed or knocked down by transfection with miR-34a precursor (pre-34a) or inhibitor (anti-34a), respectively. Podocytes were exposed to glycated human serum albumin (AGEs) and then examined for the expression of apoptosis and autophagy markers. The expression of miR-34a in mouse renal cortex and cultured podocytes were determined by quantitative PCR (Q-PCR) using specific Taqman miRNA assay. RESULTS: Compared with control group, Unx db/db mice(n=7) showed significantly higher expression level of miR-34a in renal cortex. In cultured human podocytes, exposure to AGEs also markedly increased miR-34a expression. The anti-apoptosis genes Bcl-2 and survivin, podocyte cytoskeleton molecule synaptopodin, tight junction protein ZO-1, as well as autophagy marker LC3-II, were all reduced after AGE treatment. Moreover, inhibition of miR-34a by transfection with anti-34a in podocytes prevented AGE-induced apoptosis by rescue of Bcl-2 and LC3-II expression. CONCLUSIONS: Our data demonstrated that miR-34a is involved in podocyte injury under diabetic conditions. Inhibition of miR-34a in podocytes attenuates apoptosis induced by AGEs via enhancing expression of Bcl-2 and regulating autophagy. These results indicate that targeting miR-34a might be a potential therapeutic strategy for diabetic nephropathy. This study is supported by the National Basic Research Program of China 973 program no. 2012CB517600 (no. 2012CB517606), Small Project Funding (project code 201309176123)