Antioxidant enzymes in the macular retinal pigment epithelium of eyes withneovascular age-related macular degeneration

PURPOSE: To test the hypothesis that neovascular age-related macular degene ration is related to oxidative stress involving the macular retinal pigment epithelium, This study investigated, as a function of age, levels of enzym es-that defend tissues against oxidative stress in the macular retinal pigm ent epithelium of human eyes with this disease, METHODS: Surgical specimens of macular choroidal neovascular membranes from eyes with age related macular degeneration and the macular regions of whol e donor eyes with neovascular age-related macular degeneration or without e vident ocular disease were studied by quantitative electron microscopic imm unocytochemistry with colloidal gold-labeled second antibodies. Relative le vels in retinal pigment epithelium cell cytoplasm and lysosomes were determ ined of five enzymes believed to protect cells from oxidative stress, as we ll as levels of the retinal pigment epithelium marker cytoplasmic retinalde hyde-binding protein, for comparison with the enzymes, RESULTS: Copper, zinc superoxide dismutase immunoreactivity increased and c atalase immunoreactivity decreased with age in cytoplasm and lysosomes from macular retinal pigment epithelium cells of normal eyes and eyes with age- related macular degeneration. Cytoplasmic retinaldehyde-binding protein imm unoreactivity showed no significant relationship to age or the presence of neovascular age-related macular degeneration. Glutathione peroxidase immuno reactivity was absent from human retinal pigment epithelium cells. Both hem e oxygenase-1 and heme oxygenase-2 had highly significantly greater immunor eactivity in retinal pigment epithelium cell lysosomes than in cytoplasm, d iffering from the much greater cytoplasmic immunoreactivity of the other pr oteins studied. This immunoreactivity decreased with age, particularly in t he lysosomes of retinal pigment epithelium cells from eyes with neovascular age related macular degeneration, These decreases were of border line sign ificance (P = .067 for heme oxygenase-1; P = .12 for heme oxygenase-2) when eyes with age-related macular degeneration were compared with normal eyes by multivariable logistic regression, CONCLUSIONS: The high heme oxygenase-1 and heme oxygenase-2 lysosomal antig en levels in macular retinal pigment epithelium cells of eyes with neovascu lar age-related macular degeneration suggest that oxidative stress causes a pathologic upregulation of these enzymes, Increased lysosomal disposal may indicate that the reparative functions of: these enzymes are accompanied b y deleterious effects, necessitating their rapid removal from the cell. The much higher heme oxygenase-1 and heme oxygenase-2 antigen levels in macula r retinal pigment epithelium cells from younger individuals suggest that pr otective mechanisms against oxidation and, hence, presumably to the develop ment of age-related macular degeneration, decrease with age, (Am J Ophthalm ol 1999;127:694-709. (C) 1999 by Elsevier Science Inc. All rights reserved. ).