Abstract:

ABSTRACT   Objective: To determine the effect of smad anchor for receptor activation (SARA) on the development of high glucose induced extracellular matrix (ECM) accumulation in human renal tubular epithelial cells. Methodology: In the study, HK-2 cells were exposed to high glucose (30mM D-glucose). Furthmore, 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 levels were assayed by Realtime PCR and the protein expression levels were detected by Western-blot. Results: High glucose resulted in ECM accumulation in HK-2 cells. The expression of TGF-β1 and Smad3 was increased after stimulation of high glucose in HK-2. However, the mRNA expression of Smad2 was increased while its protein expression was downregulated in a time dependent manner. Smad2 and Smad3 were activated by glucose stimulation and Smad3 kept activation for a longer time than Smad2. Meanwhile, the gene and protein expression of SARA was decreased. Compared with high glucose group, overexpression of SARA can down-regulate the expression of FN and ColⅠ. However, SARA (dSBD) had no significant effect on their expression.   Conclusion: TGF-β signaling was activated and SARA expression was downregulated during the process of high glucose induced ECM accumulation in HK-2 cells. Overexpression of SARA could inhibit the ECM accumulation and this effect depended on the SBD domain of SARA.

Key words: HK-2  , high glucose  , ECM  , SARA