Objectives Intermittent high glucose, one general and important phenomenon existed in patients with diabetes, has greater effect than sustained high glucose on development of diabetic cardiovascular complications, in which endothelial dysfunction caused by oxidative stress is regarded as the initiation of these pathophysiology. However, at present, no data are available neither on the degree of endothelial oxidative DNA damage caused by intermittent high glucose nor on the potential protective role of antioxidants. Ginkgo biloba extract (EGb) 761, an antioxidant herbal medicine, has commonly been used as a therapeutic agent for cardiovascular and neurological disorders. The aim of this study was to investigate oxidative DNA damage of endothelial cells under the pro-atherosclerotic stressor intermittent high glucose and the potential protective role of EGb761 in vitro.
Methods Human umbilical vein endothelial cells (HUVECs) were cultured in intermittent high glucose with or without EGb 761 (25-100 μg/ml) for 72 h. Subsequently, reactive oxygen species (ROS) generation, 8-hydroxy-2’-deoxyguanosine (8-OHdG) concentration, intracellular total antioxidant capacity (TAC), and oxidative DNA damage detected by comet assay were performed.
Results Intermittent high glucose increased ROS generation, 8-OHdG content and oxidative DNA damage (comet%) by about 2.4-, 4.3- and 3.0-fold compared to HUVECs under normal glucose exposure respectively (all P < 0.01). While compared with those in normal glucose conditions, TAC contents were significantly decreased in HUVECs cultured in intermittent high glucose (3.63 1.17 U/ml vs 10.4 ± 1.21 U/ml, P < 0.01), which were negatively correlated to both 8-OHdG content (r =-0.776, P = 0.003,) and comet% (r =-0.741, P = 0.006). These high glucose-induced phenomena could be suppressed by EGb 761 (25-100 μg/ml) in a dose-dependent manner (from 2.58 ± 0.18 to 1.33 ± 0.17, P < 0.001 for ROS, from 51.0 ± 4.05 ng/ml to 19.4 ± 2.48 ng/ml, P < 0.01 for 8-OHdG, from 22.1 ± 4.47% to 13.0 ± 2.39%, P < 0.01 for comet%, from 5.33 ± 1.39 U/ml to 8.5 ± 1.11 U/ml, P < 0.01 for TAC).
Conclusions Our results indicate the presence of significant oxidative DNA damage in HUVECs exposed to intermittent high glucose. EGb 761 can remarkably alleviate oxidative damage caused by intermittent high glucose, which may provide a novel approach for endothelial protection in the presence of intermittent high glucose.