Abstract
Purpose: :
Oxidative stress is recognized as an important factor in the pathogenesis of age-related macular degeneration (ARMD). It could play a role in the degeneration of retinal pigment epithelium (RPE). The aim of this work was to evaluate the protective effect of green tea polyphenol epigallocatechin gallate (EGCG) against oxidative stress in cultured RPE cells.
Methods: :
Primary cultures of RPE cells were established from Long-Evans newborn rats. RPE cells were incubated with EGCG (5, 10, 25 and 50 µM) for 24 hours and were treated with hydrogen peroxide (H2O2, 0.6 mM) for 1-2 hours to induce oxidative stress. 1) Cell viability was measured using 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay. 2) Apoptosis was quantified by flow cytometry using propidium iodide (PI).
Results: :
1) The percentage of viable RPE cells was significantly lower in cultures treated with H2O2 0.6 mM than in control cultures. Pretreatment of RPE cultures with EGCG reduced H2O2-induced cell death in a dose dependent manner. EGCG at 50 µM significantly reduced cell mortality due to the treatment with H2O2. 2) The proportion of PI positive cells increased significantly in cultures treated with H2O2 0.6 mM compared to control cultures. EGCG at 50 µM significantly reduced apoptosis of RPE cells induced by the treatment with H2O2.
Conclusions: :
EGCG is able to protect RPE cells from H2O2-induced oxidative stress and to reduce apoptosis induced by oxidative stress. This suggests potential protective effect of EGCG against retinal diseases associated with oxidative stress including ARMD.
Keywords: retinal pigment epithelium • apoptosis/cell death • antioxidants