A polysaccharide from green tea (Camellia sinensis L.) protects human retinal endothelial cells against hydrogen peroxide-induced oxidative injury and apoptosis

Oxidative damage of retinal pigment epithelium (RPE) cells is involved in the pathogenesis age related macular degeneration (AMD). The purpose of this study was to evaluate the potential protective effect of a purified green tea polysaccharide (GTWP) against hydrogen peroxide (H2O2) induced oxidative stress and apoptosis in human retinal pigment epithelial cells (ARPE-19 cells). Human ARPE-19 cells were treated with 1 h of 500 μM H2O2 before incubation with GTWP for 24 h. Pretreatment of GTWP decreased H2O2-induced cell death and cell apoptosis, and efficiently suppressed the intracellular ROS production and malondialdehyde (MDA) generation induced by H2O2 treatment. Moreover, a loss of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and glutathione (GSH) activities were restored to normal level in H2O2-induced ARPE-19 cells upon GTWP (100 μg/ml) exposure. Also, the tendency of increased protein expression of Bax and cleaved-caspsae-3, as well as decrease of Bcl-2 protein in ARPE-19 cells challenged with H2O2 was changed to individual opposite way, thus inhibiting the apoptotic cell death. Our results demonstrated that GTWP protected RPE cells against oxidative injury through activation of anti-apoptotic and endogenous antioxidant enzymes signaling pathway, suggesting GTWP has attractive therapeutic potential to AMD.