Oxidative damage of retinal pigment epithelial cells and age-related macular degeneration

Damage to the retinal pigment epithelial (RPE) cells is an early and crucial event in the molecular pathways leading to clinically relevant age‐related macular degeneration (AMD) changes. Oxidative stress, the major environmental risk factor for atrophic AMD, causes RPE injury that results in a chronic inflammatory response, drusen formation, and RPE atrophy. RPE degeneration ultimately leads to a progressive irreversible degeneration of photoreceptors. In vitro studies show that oxidant‐treated RPE cells undergo apoptosis, a possible mechanism by which RPE cells are lost during the early phase of atrophic AMD. The main target of oxidative injury appears to be mitochondria, an organelle known to accumulate genomic damage during aging. Addition of GSH, the most abundant intracellular thiol antioxidant, protects RPE cells from oxidant‐induced apoptosis. Similar protection occurs with dietary enzyme inducers that increase GSH synthesis. In addition, enhancing survival signaling preserves RPE cells under oxidative stress. These results indicate that therapeutic or nutritional intervention to enhance the antioxidant capacity and survival signaling of RPE may provide an effective way to prevent or treat AMD. This review describes major molecular and cellular events leading to RPE death, and presents currently used and new experimental, forthcoming therapeutic strategies. Drug Dev Res 68:213–225, 2007. © 2007 Wiley‐Liss, Inc.