Bcl-2 overexpression increases survival in human retinal pigment epithelial cells exposed to H2O2

The integrity of the retinal pigment epithelium, especially that of the macula is essential for the preservation of vision into old age. The chronic exposure to sunlight and peroxidized lipids from phagocytized photoreceptor outer segments imposes a high level of oxidative stress on the retinal tissues, which increases with age as antioxidant protection declines and therefore could accelerate apoptosis. Bcl-2 known to facilitate mitochondrial DNA repair and cellular survival in other tissues was overexpressed in a single clone of human retinal pigment epithelium cells after stable transfection with human bcl-2 in pSFV-neoexpression factor. Near confluent cells (2nd-4th generation permanently bcl-2 transfected) were protected from mitochondrial dysfunction after exposure to H2O2 up to 150 mum. With 200 pm H2O2, function in transfected cells declined by only 25 % control activity as determined by MTT reduction assays, compared to wild type and vector only transfected cells expressing normal bcl-2 levels. Similarly the bcl-2-transfected cells were more resistant to mitochondrial DNA damage after H2O2 treatment than the other groups and suffered 50 % less damage after exposure to 200 mum H2O2, as assayed by quantitative polymerase chain reaction assays. These data suggest that bcl-2 overexpression protects human RPE cells from mitochondrial respiratory dysfuction, mitochondrial DNA damage and promotes cellular survival in response to oxidative stress induced by H2O2. (C) 2002 Elsevier Science Ltd.