Inhibition of glucose-induced vascular endothelial growth factor expression by Salvia miltiorrhiza hydrophilic extract in human microvascular endothelial cells: Evidence for mitochondrial oxidative stress

Aim of study: Diabetes mellitus is frequently combined with vascular diseases, which are associated with the expression of vascular endothelial growth factor (VEGF). An approach that can reverse the induction of VEGF by hyperglycemia may potentially benefit the outcome of diabetic patients. Therefore, in the present study, we investigated the effect of Salvia miltiorrhiza (S. miltiorrhiza) hydrophilic extract on the expression of VEGF induced by high concentration of glucose. Materials and methods: Vector of VEGF promoter luc was transiently transfected into HMEC-1 cells, and luciferase activity was measured to determine the promoter activity. In order to investigate the mechanism of Salvia miltiorrhiza hydrophilic extract, mitochondrial uncoupling protein 2(UCP2) was knockdown by using UCP2 siRNA. The expression of VEGF was obtained by using quantitative RT-PCR and dot blot. The level of reactive oxygen species (ROS) was expressed by the level of 2',7'-dichlorfluorescein. Results: Exposure of HMEC-1 cells to 30mM glucose resulted in a significant increase in the expression of VEGF mRNA (5.7 fold at 3 mM glucose, P < 0.005), and an increase of ROS formation (2.4 fold at 3 mM glucose, P < 0.005). These effects were completely antagonized by an inhibitor of electron transport chain complex II, thenoyltrifluoroacetone (TFFA) and an uncoupler of oxidative phosphorylation, carbonylcyanide-m-chlorophenylhydrazone (CCCP). Addition of Salvia miltiorrhiza hydrophilic extract (10 mu g/ml) led to a significant decrease of VEGF mRNA and ROS formation in 30 mM glucose condition. Interestingly, knockdown of mitochondrial UCP-2 by UCP-2 siRNA abolished the reduction of VEGF expression and ROS formation by Salvia miltiorrhiza hydrophilic extract. Conclusions: These findings indicated that Salvia miltiorrhiza hydrophilic extract effectively reversed induction of VEGF expression by high glucose via ameliorating mitochondrial oxidative stress. Salvia miltiorrhiza hydrophilic extract can potentially be an effective antioxidant therapy for the treatment of diabetic chronic vascular complication. (C) 2011 Elsevier Ireland Ltd. All rights reserved.