Astragaloside Ⅳ Improves Vascular Endothelial Dysfunction By Inhibiting The TLR4/NF-κB Signaling Pathway

The aim of this study was to investigate the protective effect and mechanism of As-Ⅳ on vascular endothelial dysfunction in STZ induced SD diabetic rats.Methods In vivo,a single intraperitoneal injection of streptozotocin(STZ,65 mg/kg)was used to establish diabetic model.Rat tail vein blood glucose level above 16.7 mmol/L were regarded as a criterion for successful establishment of diabetic model.After successful establishment of a diabetic rat model,As-Ⅳ(40 and 80 mg/kg/d)was orally administered to rats for 8 weeks.The rats were randomly divided into four groups: Normal,Diabetic group,As-Ⅳ 40 mg/kg group,and As-Ⅳ 80 mg/kg group.In vitro,human umbilical vein endothelial cells(HUVECs)were treated with high glucose(33 m M glucose)in the presence or absence of As-Ⅳ,BAY 11-7082(NF-κB p65 inhibitor),TAK-242(TLR4 inhibitor)and L-NAME(NO synthesis inhibitor)+ As-Ⅳ.Endothelial function in isolated aortic rings was examined;serum interleukin-6(IL-6)and tumor necrosis factor-α(TNF-α)were tested by ELISA.The expression of nuclear Factor-κB p65(NF-κB p65)in aortic tissue was detected by immunohistochemistry.Plasma nitric oxide(NO)was measured by the nitrate reductase method.The expressions of endothelial nitric oxide synthase(e NOS),intercellular adhesion molecule-1(ICAM-1),vascular cell adhesion molecule-1(VCAM-1)and toll-like receptor 4(TLR4)in aortic tissue were determined by western blot.Results The results showed that As-Ⅳ significantly improved aortic endothelial function;increased e NOS expression and NO production;and decreased the content of IL-6 and TNF-α and the expressions of VCAM-1,ICAM-1,TLR4,and nuclear NF-κB p65 in vitro and in vivo.In addition,the above mentioned effects of As-Ⅳ on human umbilical vein endothelial cells(HUVECs)were similar to that of TAK-242(TLR4 inhibitor)and Bay 11-7082(NF-κB p65 inhibitor).Furthermore,L-NAME(NO synthesis inhibitor)partially abolished the effect of As-Ⅳ.Conclusions As-Ⅳ has a protective effect on vascular endothelial dysfunction induced by hyperglycemia,which may be mediated partly through TLR4/NF-κB signaling pathway.These findings provide a theoretical basis for further study of As-Ⅳ in the treatment of diabetes-related endothelial dysfunction.