Role of SARA in renal tubular epithelial to mesenchymal transition in diabetic nephropathy and its associated mechanism / 中华肾脏病杂志

ABSTRACT

Objective To determine the effect of smad anchor for receptor activation (SARA) on renal tubular epithelial to mesenchymal transtion (EMT) induced by high glucose and to investigate the associated mechanism.Methods HK-2 cells were exposed to high glucose (30 mmol/L).HK-2 cells were transfected with the plasmids of wild-type SARA [SARA (WT)] or SARA mutant [SARA with SBD deletion,called SARA (dSBD)] and then was stimulated by high glucose.The gene expression was assayed by real-time PCR and the protein expression was detected by Western blotting.Results During the process of high glucose-induced EMT of HK-2 cells,the gene and protein expression of SARA were down-regulated.The expression of TGF-β1 and Smad3 increased after stimulation of high glucose in HK-2.However,the Smad2 mRNA expression increased while its protein expression was down-regulated in a time-dependent manner.Smad2 and Smad3 were activated by high glucose stimulation and Smad3 kept activation for longer time than Smad2.Compared with high glucose group,over-expression of SARA by transfection of SARA (WT) up-regulated the expression of zona occludens(ZO)1 and down-regulated the expression of vimentin (P＜0.05).However,SARA (dSBD) had no such effects on above expressions.The Smad2 protein expression increased along with the over-expression of SARA.Meanwhile,over-expression of SARA prolonged the activation time of Smad2 and shortened the activation time of Smad3.Conclusions TGF-β1 signaling is activated and SARA expression is down-regulated during the process of high glucose-induced EMT in HK-2 cells.Over-expression of SARA can inhibit the EMT via increase of Smad2 protein expression and longer activation time of Smad2.