ABSTRACT
Objective To investigate the effect of Sirt1 gene knockout on chronic kidney disease induced by 5/6 nephrectomy in mice and vascular endothelial growth factor (VEGF)/fetal liver kinase-1 (Flk-1) signaling pathway.Methods Twenty four male Sirt1 +/+ and Sirt1 +/-mice wererandomly divided into four groups:Sirt1+/+ mice with sham-operation (WT-Sham,n=6),Sirt1+/-mice with sham-operation (KO-Sham,n=6),Sirt1 +/+ mice with 5/6 nephrectomy (WT-Nx,n=6) and Sirt1 +/-mice with 5/6 nephrectomy (KO-Nx,n=6).Proteinuria was determined by urine collection from 8:00 to 8:00 the next day at 20 weeks.Serum creatinine (Scr),urea nitrogen (BUN) and the renal pathological changes were measured after 20 weeks.Expressions of Sirt1,collagen Ⅰ and transforming growth factor β(TGF-β) were used to analyze the changes of renal fibrosis by immunohistochemistry staining.Real-time PCR and Western blotting were used to measure the mRNA and protein expressions of Sirt1,fibronectin,collagen Ⅰ,VEGF and Flk-1 in kidney.Results Sirt1 expressed in glomernlar endothelial cells,podocytes,mesangial cells and renal tubular epithelial cells in Sirt1 +/+ mice,while Sirt1 expression intensity was significantly reduced in Sirt1 +/-mice.Compared with the WT-Sham group,WT-Nx group had increased proteinuria,BUN,Scr,glomernlar sclerosis index and tubulointerstitial fibrosis index at 12 weeks after operation (all P ＜ 0.01),and KO-Nx group had exacerbated the above up-regulations (all P ＜ 0.01).Compared with those in WT-Sham group,the expressions of fibronectin,collagen Ⅰ and TGF-β were up-regulated in WT-Nx group (all P ＜ 0.01),and were significantly augmented in KO-Nx group (all P ＜ 0.01).Compared with those in WT-Sham group,renal mRNA and protein expressions of VEGF and Flk-1 were decreased in WT-Nx group,and KO-Nx group aggravated their down-regulation (all P ＜ 0.01).Conclusions Sirt1 gene knockout can increase proteinuria and Scr,and aggravate renal pathology and renal fibrosis in 5/6 nephrectomized mice,which is associated with the inhibition of VEGF/Flk-1 signaling pathway.It is suggested that Sirt1 may be a potential therapeutic target of chronic kidney disease.