Xiaokening stimulates endothelial nitric oxide release in diabetic rats

Abstract

INTRODUCTIONDiabetes mellitus is a group of metabolic diseases that is characterised by high blood sugar levels. This occurs either because the body does not produce enough insulin or because cells do not respond to the insulin that is produced. In the past few decades, many studies have shown a clear worldwide increase in the incidence of both type 1 and type 2 diabetes mellitus.(1) Without proper treatment, diabetes mellitus can cause many long-term complications, including cardiovascular disease, chronic renal failure, blindness and nerve damage. Microangiopathy, which is caused by vascular endothelial cell injury and dysfunction, is a fundamental process in diabetes mellitus complications.(2-4) Drug interventions are needed to treat these microvascular complications.Reactive oxygen species (ROS) play a crucial role in the pathogenesis of some diseases (e.g. cancer, cardiovascular disease, diabetes mellitus and infl ammation).(5) The effect of the increased production of free radicals in diabetes mellitus is devastating and well documented.(6-8) Streptozotocin (STZ)-induced diabetic rats are one of the animal models for type 1 diabetes mellitus.(9) In type 1 diabetes mellitus, destruction of the β-cells of the islets of Langerhans causes degranulation or reduction of insulin secretion, but not the total absence of insulin in blood.(10) The cytotoxic action of STZ is associated with the generation of ROS, which causes oxidative tissue damage.(11) There is considerable evidence of the role of altered antioxidant defences (including both nonenzymatic and enzymatic antioxidant systems) and free radicals in the aetiology of diabetes mellitus. (12,13) Many studies have reported that the use of traditional Chinese medicines not only helps to lower serum glucose, but also helps to inhibit the development of diabetic complications. ( 14,15) Our previous research, which was conducted on umbilical vein endothelial cells (ECV-304), found that Xiaokening effectively reduces cellular injury and proliferation inhibition resulting from high glucose serum levels. (16,17) In other words, Xiaokening was found to have protective effects for endothelial cells and the ability to improve cell propagation. These fi ndings indicate that Xiaokening has a positive effect on endothelial cells in vitro. However, there is little information on the effect of Xiaokening on endothelial cells within vessels. As the effect of Xiaokening on diabetic arterioles has not been reported, the aim of the present study was to explore its effect on the mesenteric arteriolar endothelial cell function of diabetic rats and the underlying mechanism. METHODSSTZ and 2,3-diaminonaphthalene (DAN) were purchased from Sigma Chemical Company, MO, USA. The STZ was dissolved in a solution of cold citrate buffer (0.1 M, pH 4.5). The DAN was dissolved in methanol. The STZ and DAN solutions used in the present study were freshly dissolved and shielded from light. Antibody for endothelial nitric oxide synthase (eNOS) was purchased from Santa Cruz Biotechnology, TX, USA....