Xiaokening stimulates endothelial nitric oxide release in diabetic rats

Abstract

Introduction: Diabetes mellitus induces microangiopathic changes that lead to endothelial dysfunction. This study investigated the effect of Xiaokening, a type of Chinese compound medicine, on the mesenteric arteriolar endothelial cell function of diabetic rats and its underlying mechanism.

Methods: Diabetes mellitus was induced in rat models via intraperitoneal injection of 60 mg/kg streptozotocin and observed over three weeks. Mesenteric arterioles, which were isolated in a cannulated and pressurised state, were incubated with intravascular injections of 1, 3 or 5 g/L Xiaokening for 24, 48 or 72 hours. The effects of Xiaokening on the release of nitric oxide (NO) on the mesenteric arterioles were detected under shear stress of 1, 10 and 20 dyn/cm(2). Biochemical methods were used to determine the activities of superoxide dismutase (SOD) and xanthine oxidase (XO). The expressions of endothelial NO synthase (eNOS), SOD and XO in the mesenteric arterioles were assessed using Western blot.

Results: Compared to normal rat arterioles, less NO was released in the mesenteric arterioles of diabetic rats. Xiaokening was found to have a concentration- and time-dependent effect on NO release; when the shear stress was increased, there was a gradual increase in the release of NO. Compared to normal arterioles, the expression of eNOS in the mesenteric arterioles of diabetic rats was lower. Incubation with Xiaokening increased SOD activity and expression, and decreased XO activity and expression in the mesenteric arterioles of the diabetic rats.

Conclusion: Xiaokening was able to significantly increase NO release and improve the endothelial function of mesenteric arterioles through antioxidative mechanisms.

Keywords: Xiaokening; diabetes mellitus; endothelial cells; nitric oxide.

Fig. 1

Bar graphs show the effect of Xiaokening on shear stress (1, 10 and 20 dyn/cm²). There was an increase in the induced perfusate nitrite among the isolated mesenteric arterioles of the streptozotocin (STZ)-induced diabetic rats after 24, 48 and 72 hours of Xiaokening treatment. Data shown as mean ± standard error, n = 6 per group. *p < 0.05 vs. control group; †p < 0.05 vs. STZ-induced diabetic group.

Fig. 2

Representative Western blot shows endothelial nitric oxide synthase (eNOS) protein from the isolated mesenteric arterioles of rats from the control group and the streptozotocin (STZ)-induced diabetic group, with and without treatment with 5 g/L Xiaokening for 72 hours. Data is normalised by means of densitometric ratios of eNOS and β-actin, and shown as mean ± standard error, n = 3 per group. *p < 0.05 vs. control group; †p < 0.05 vs. STZ-induced diabetic group.

Fig. 3

Bar graph shows that 5 g/L of Xiaokening treatment for 72 hours inhibits the increase of O₂^- in the isolated mesenteric arterioles of streptozotocin (STZ)-induced diabetic rats. Data is shown as mean ± standard error, n = 6 per group. *p < 0.05 vs. control group; †p < 0.05 vs. STZ-induced diabetic group. eNOS: endothelial nitric oxide synthase

Fig. 4

Bar graphs show the changes in xanthine oxidase (XO) and manganese-superoxide dismutase (Mn-SOD) expression and activity before and after treatment with 5 g/L Xiaokening for 72 hours. Data is shown as mean ± standard error, n = 6 per group (in a & b), n = 3 per group (in c & d). *p < 0.05 vs. control group; †p < 0.05 vs. streptozotocin (STZ)-induced diabetic group.