Effects of 1,25-dihydroxyvitamin D3 on high glucose-induced expression of uncoupling protein 2 and oxidative stress in human renal tubular epithelial cells

Abstract

[Summary] The HK-2 cells with different culture media were divided into normal glucose group (NG group,5.5 mmol/L D-glucose) ; high glucose group (HG group,30 mmol/L D-glucose) ; mannitol group (MG group,5.5mmol/L D-glucose+24.5 mmol/L mannitol) ; 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] groups (V1-V3 group)which were exposed to medium containing 30 mmol/L D-glucose and different concentrations of 1,25-(OH)2D3 ;Nethyl-cysteim control group (NAC group,30 mmoL/L D-glucose + 1.0 mmol/L N-Nethyl-cysteim) ; and ethanol control group(SG group,30 mmol/L D-glucose+6.86 × 10-2 mol/L ethanol).The level of intracellular reactive oxygen species,mitochondrial membrane potential,activity of total-superoxide dismutase (T-SOD),level of malondialdehyde,expression of UCP2 mRNA and protein in HK-2 cells were detected.Compared with NG group,the mitochondrial membrane potential significantly decreased in HG group (P＜0.01),and the mitochondrial membrane potential in V group was lower than that in HG group(P＜0.01).The activity ofT-SOD in HG group was significantly lower than that in NG group(P＜0.01),while its level of malondialdehyde was significantly higher than that in NG group(P＜0.01).Compared with HG group,the activity of T-SOD in V groups was significantly increased (P＜0.05)and the level of malondialdehyde in these groups significantly decreased (P＜0.01).The mRNA expression of UCP2 in HG group was increased significantly in comparison with NG group (P ＜ 0.05) and the expression in V groups was significantly decreased in comparison with HG group (P＜0.01).The results suggest that 1,25-(OH)2D3 could reduce the mitochondrial membrane potential,the production of reactive oxygen species,and regulate the expression of UCP2 in order to suppress the oxidative stress induced by high glucose. Key words: Diabetic nephropathy; 1,25-dihydroxyvitamin D3; Human renal tubular epithelial cells; Uncoupling protein 2 ; Oxidative stress