Objective To investigate the effect of microRNA-381-3p (miR-381-3p) targeting SRY related HMG box-9 (Sox9) on high glucose (HG)-induced renal tubular epithelial HK-2 cells apoptosis.

Methods The renal tubular epithelial HK-2 cells were cultured in vitro, and divided into control group, HG group, HG+miR-NC group (transfected with miR-NC), HG+miR-381-3p mimics group (transfected with miR-381-3p mimics), HG+si-NC group (transfected with si-NC), HG+si-Sox9 group (transfected with si-Sox9), HG+miR-381-3p mimics+pcDNA group (co-transfected with miR-381-3p mimics and pcDNA) and HG+miR-381-3p mimics+pcDNA-Sox9 group (co-transfected with miR-381-3p mimics and pcDNA-Sox9).Except the control group, the cells in other groups were treated with 30 mmol/L glucose.The expression of miR-381-3p and Sox9 at mRNA level in HK-2 cells was detected by real-time fluorescent quantitative PCR, the apoptosis was detected by flow cytometry, the protein expressions of Sox9, B lymphoma-2 related protein (Bax) and B lymphoma-2 (Bcl-2) in HK-2 cells were detected by Western blotting, and the targeting relationship between miR-381-3p and Sox9 was verified by the dual luciferase reporter gene experiment.

Results Compared with the control group, the apoptosis rate, the mRNA and protein expression levels of Bax in HG group were increased, and the expression of miR-381-3p and Bcl-2 at mRNA and protein levels were decreased, which had significant statistical difference (P < 0.05).The targetscan database predicted that miR-381-3p had a binding site with the 3′UTR region of Sox9 mRNA.When overexpression of miR-381-3p or inhibition of Sox9 expression, the apoptosis rate, the mRNA and protein expression levels of Bax and Sox9 were significantly reduced (P < 0.05), and the mRNA and protein expression level of Bcl-2 was significantly increased (P < 0.05).Overexpression of miR-381-3p or inhibition of Sox9 expression decreased the apoptosis rate, mRNA and protein expression levels of Bax and Sox9, and increased the mRNA and protein expression levels of Bcl-2, the difference was statistically significant (P < 0.05).

Conclusions MiR-381-3p is low-expressed in HG-induced renal tubular epithelial cells, overexpression of miR-381-3p can reduce HG-induced renal tubular epithelial cell apoptosis by targeted inhibition of Sox9 expression.