Protective Effects Of Salvianolic Acid B On Renal Fibrosis In Diabetic Rats And Potential Mechanisms Implicated

Objective:To investigate the effect of Salvianolic acid B?Sal B?on renal fibrosis in diabetic rats and the potential mechanisms implicated.Methods:1.Animal experiment:Diabetes in SD rats was induced by high sugar high fat diet combined with intraperitoneal injection of streptozotocin?STZ,40 mg/kg?.Diabetic rats were allocated randomly to model group,high dose of Sal B group?160mg/kg?and low dose of SalB group?80 mg/kg?.Rats in Sal B groups were administered intragastrically with corresponding dose of Sal B for six weeks,while those in the control and model group were given distilled water of the same volume.At the end of experiment,the levels of fasting blood glucose?FBG?,triglycerides?TG?,total cholesterol?TC?,serum creatinine?SCr?,urine microalbumin?UAlb?,albumin?ALB?,total protein?TP?,nitric oxide?NO?,serum malondialdehyde?MAD?,total antioxidant capacity?TAC?and superoxide dismutase?SOD?were determined with commercially available kits.Moreover,basic nephridial tissue histopathological changes and nephridial tissue collagen fibres changes were observed by HE staining and Masson staining respectively.Renal contents of type I and type III collagen were determined by ELISA.The protein levels of TGF-?1,p-Smad2,Smad7 and p-p38MAPK were evaluated by Western blot analysis.2.Cell experiments:HGMCs were randomly divided into control group,high glucose group and high dose,medium dose and low dose of Sal B groups.Cells except those in control group were exposed to high glucose?33.3 mmol/L?for 72 h,while those in Sal B groups were co-incubated with indicated concentrations of Sal B.Protein levels of?smooth muscle actin??-SMA?,transforming growth factor?₁?TGF-?₁?and phosphorylated protein levels of Smad2 and p38 mitogen-activated protein kinase?p38MAPK?were determined by western blot analysis.Protein levels of?smooth muscle actin??-SMA?was also determined by immunocytochemical method.Contents of Col I,Col III,FN and LN were analysed by ELISA.Results:1.Animal experiments:?1?Sal B improved the weight of diabetic rats?P<0.01 or P<0.05?and reduced the fasting blood glucose?FBG?of diabetic rats?P<0.01 or P<0.05?.?2?Sal B significantly reduced the level of serum triglycerides and cholesterol in diabetic rats?P<0.01 or P<0.05?.?3?Sal B significantly decresed the content of blood urea nitrogen?BUN?,urine trace albumin?UAlb?,serum creatinine?SCr?and increased the content of serum albumin,total protein?TP?of diabetic rats?P<0.01 or P<0.05?.?4?Sal B significantly decreased the content of the serum malondialdehyde?MDA?and nitric oxide?NO??P<0.01 or P<0.05?,increased the content of superoxide dismutase?SOD?activity and total antioxidant capacity?TAC?of diabetic rats?P<0.01 or P<0.05?.?5?Sal B significantly improved kidney pathological damage of diabetes rats?P<0.01 or P<0.05?,reduced the content of the collagen in kidney tissue?P<0.01 or P<0.05?.?6?Sal B down-regulated the expression of the TGF-?1,phosphorylated Smad2 and phosphorylated p38MAPK protein?P<0.01 or P<0.05?,up-regulated the expression of Smad7 in kidney tissue?P<0.01 or P<0.05?.2.Cell experiment:Exposure to high glucose markedly increased the expression of?-SMA,TGF-?₁,Col I,Col III,FN and LN proteins in HGMCs?P<0.01 or P<0.05?.The levels of Smad2 and p38MAPK protein phosphorylation were significantly increased as well?P<0.01 or P<0.05?.Co-incubation with Sal B evidently decreased the expression of?-SMA,TGF-?₁,Col I,Col III,FN and LN proteins induced by high glucose?P<0.01 or P<0.05?.The levels of phosphorylated Smad2 and p38MAPK protein were also reduced noticeably?P<0.01 or P<0.05?.Conclusion:1.Sal B is capable of ameliorating renal fibrosis in diabetic rats,which might be related to its antioxidant property and regulation of TGF-?1/Smad and TGF-?1/p38MAPK signaling pathways.2.Sal B significantly suppressed high glucose induced phenotypic transition and ECM secretion in HGMCs,which might be attributed to inhibition of TGF-?₁/Smad signaling pathway and p38MAPK activation.