Objective       To address whether glycogen synthase kinase-3 beta （GSK3β）plays direct roles in renal fibrosis based on our previous study that expression of GSK3β is substantially increased in transplanted human kidney with chronic allograft nephropathy and valproate markedly ameliorates renal fibrosis in rats with unilateral urethral obstruction.       Methods       A standard in vitro model of interstitial fibrosis

cultured human tubular epithelial (HK-2) cells treated with TGF-β1

was examined in our experiments. A selective GSK3β inhibitor

LiCl was used to suppress the activity of GSK3β. The eukaryotic expression vectors encoding  HA-tagged wild type (WT-GSK3β-HA/pcDNA3.1)

uninhibitable mutant GSK3β (S9A-GSK3β-HA/pcDNA3.1) and kinase dead mutant GSK3β (K85

86A-GSK3β-HA/pcDNA3.1) were transfected in HK-2 cells respectively.       Results       LiCl increased the phosphorylation of GSK3β， and suppressed both the basal and TGF-β1 induced fibronectin （FN） expression in HK-2 cells. When transfected with expression vector encoding wild type GSK3β or an mutant GSK3β S9A， HK-2 cells displayed increased FN expression； whereas decreased FN expression was observed when transfected vector encoding GSK3β K85A，K86A. To further analyze the possible pathway that GSK3β regulated fibrosis，it was found that in LiCl treated HK-2 cells，phosphorylation of Smad3 was suppressed. While there was no change observed for the phosphorylation level of Smad2.       Conclusion       In summary，our results suggest that TGF-β/Smad3 pathway can be regulated by GSK3β

and therefore GSK3β plays pro-fibrogenic activity in renal tubular epithelial cells.