Prevention of reactive oxygen species-induced oxidative stress in human microvascular endothelial cells by green tea polyphenol.

The potential protective roles played by green tea polyphenol (GTP) against the injurious effects of reactive oxygen species in human microvascular endothelial cells (HUMVECs) were investigated. Oxidative stress was induced in cultured HUMVECs, either by adding 10 mM H2O2 or by the action of 10 U/l xanthine oxidase (XO) in the presence of xanthine (250 microM). Both treatments produced a significant reduction (to 68% and 71%, respectively) in HUMVEC viability, as assessed by fluorescence double staining method followed by flow cytometric analysis. On the microscopic observations, the morphological changes and necrotic detachment were appreciably induced by both treatments. The H2O2-induced alterations were completely prevented by pre-incubating the ECs with 10 microg/ml GTP for 1 h. When the oxidative stress was induced by XO, the cell viability and morphology were also significantly maintained at the same GTP concentration. These results demonstrate that GTP can act as a biological antioxidant in a cell culture experimental model and prevent oxidative stress-induced cytotoxicity in ECs.