It has previously been reported that 1,25-(OH)2D3 inhibits high glucose-induced epithelial-to-mesenchymal transition (EMT) in HK-2 cells. However, the mechanism of this renoprotective action remains unclear. Elocalcitol (BXL-628), a vitamin D analog, has been suggested to be effective on the RhoA/Rho associated protein kinase (ROCK) pathway, which serves a crucial role in high glucose-induced EMT. The aim of the present study was to investigate the effect of 1,25-(OH)2D3 and its analogue BXL-628 on high glucose-induced activation of the RhoA/ROCK pathway in human renal proximal tubular cells. HK-2 cells were co-treated with high glucose and either 1,25-(OH)2D3 or BXL-628. The RhoA expression levels and ROCK activity of the membrane were assessed via western blot analysis or immunofluorescence. α-smooth muscle actin (α-SMA) and epithelial (E)-cadherin were detected using western blotting and reverse transcription-quantitative polymerase chain reaction (RT-qPCR), whereas collagen I and fibronectin levels were measured by ELISA and RT-qPCR. The results demonstrated that 1,25-(OH)2D3 and BXL-628 both significantly downregulated the expression of active RhoA and ROCK activity induced by high glucose (P<0.05). Furthermore, the expressions of α-SMA, collagen I, and fibronectin were significantly downregulated at both protein and mRNA (P<0.05) levels, whereas the expression of E-cadherin was significantly increased (P<0.05) by 1,25-(OH)2D3 or BXL-628 treatment. In conclusion, the vitamin D receptor agonist 1,25-(OH)2D3 and its analogue BXL-628 were both able to attenuate high glucose-induced EMT and extracellular matrix accumulation of HK-2 cells by suppressing the RhoA/ROCK signaling pathway in vitro.
Keywords: 1,25-(OH)2D3; RhoA/Rho associated protein kinase pathway; diabetic nephropathy; elocalcitol; epithelial-mesenchymal transition.