Catechin-rich green tea extract modulates the oxidative status of human retinal pigment epithelial cells

摘要

Oxidative damages to the retinal pigment epithelium (RPE) have been suggested to play a key role in the pathogenesis of age related macular degeneration (AMD). Our purpose was to evaluate the effects of a catechin rich green tea extract Polyphenon E against induced oxidative stress in cultured human RPE cells. Cell viability (MTT assay) and level of intracellular reactive oxygen species (ROS) generated after treatments with Polyphenon E +/- hydrogen peroxide were measured. The activities of superoxid dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) as well as the gluthatione GSH concentration were determined. Polyphenon E has no cytotoxic effect up to concentrations of 200 microgram/ml in culture media and showed a protective effect against hydrogen peroxide induced toxicity. Administration of the catechin-rich extract induced an increase of SOD activity in normal and oxidative stress conditions and an increase of catalase only in induced oxidative stress condition. Polyphenon E determined a decrease of glutathione peroxidase activity and of glutathione level. However, the significant inhibition of intracellular ROS generation supports the hypothesis that catechin can contribute to antioxidant defense by direct scavenge of ROS in RPE cells.