Effects of 1, 25-(OH)2D3 on the expression of vitamin D receptor and angiotensin II in human proximal tubular epithelial cells induced by high glucose

Objective To investigate the effects of active vitamin D3 on the expression of vitamin D receptor(VDR)and angiotensin Ⅱ in the human proximal tubular epithelial cells HK-2 induced by high glucose. Methods Cultured HK-2 cells were divided into the following five groups: (1)control group (5.5 mmol/L glucose), (2)mannitol group (5.5 mmol/L glucose + 19.5 mmol/L mannitol), (3)high glucose group (25.0 mmol/L glucose), (4)high glucose + 1, 25-(OH)2D3 group (25.0 mmol/L glucose + 1, 25-(OH)2D3, for 1.0×10-6, 1.0×10-7, 1.0×10-8 mol/L respectively), (5)high glucose + 1, 25-(OH)2D3+ siRNA VDR group(25.0 mmol/L glucose + 1, 25-(OH)2D3, 10-6 mol/ L + siRNA VDR) . The expression of VDR mRNA and protein were detected by real-time quantitative PCR and western blot, respectively. Dual luciferase reporter gene assay was used to detect VDR gene transcription activity. Radioimmunoassay was used to examine the expression of angiotensin Ⅱ. Significance between different groups was compared by one-way analysis of variance. The q-test was used to evaluate the differences in means between groups. P<0.05 were considered to be statistically significant. Results Compared with the control group, the mRNA, protein expression and gene transcription activity of VDR in the high glucose group were lower(1.34±0.22 vs 2.47±0.31, 0.51±0.06 vs 1.14±0.13, 0.51±0.21 vs 1.42±0.28, all P 0.05). Conclusion Angiotensin Ⅱ could be reversely regulated by 1, 25-(OH)2D3 in the human proximal tubular epithelial cells induced by high glucose via a VDR-mediated mechanism. The finding could be of particular value in the prevention of diabetic nephropathy. Key words: Active vitamin D3; High glucose; Tubular epithelial cells; Receptor; Angiotensin Ⅱ