Hydrogen peroxide stimulates apoptosis in cultured human retinal pigment epithelial cells

Purpose. To determine whether hydrogen peroxide (H2O2), a physiological mediator of oxidative stress induces apoptosis in retinal pigment epithelial (RPE) cells. Methods. To demonstrate that oxidatively stressed retinal pigment epithelial cells undergo apoptosis consequential to mitochondrial dysfunction, biochemical parameters of apoptosis were determined in cultured cells after treatment with 50-200 muM H2O2 for different times Caspase-3 protease activity was determined from hydrolysis of DEVD-rho -nitroanilide. Expression of the anti-apoptotic protein, bcl-2 and the pro-apoptotic proteins p53 and p21 were analyzed by western blotting. Results. Caspase-3 activity significantly increased in cells exposed to H2O2 Also, the expression of bcl-2 in cells treated with 200 muM H2O2 was diminished whereas expression of p53 and p21(waf-1) was increased compared to the controls. Conclusions. Exposure of retinal pigment epithelial cells to concentrations of H2O2 that cause in vitro mitochondrial DNA damage also promotes apoptosis.