Retinal pigment epithelium pigment granules stimulate the photo-oxidation of unsaturated fatty acids

• Published in: Free radical biology & medicine Vol. 26; no. 11; pp. 1436 - 1446
• Main Authors: Dontsov, Alexander E., Glickman, Randolph D., Ostrovsky, Mikhail A.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01-06-1999
• Subjects: Animals; Cattle; Cytoplasmic Granules - metabolism; Fatty Acids, Unsaturated - metabolism; Free radicals; Humans; Light; Linoleic Acid - metabolism; Lipofuscin; Lipofuscin - metabolism; Melanin; Melanins - metabolism; Melanolipofuscin; Melanosomes - drug effects; Melanosomes - metabolism; Oxidative Stress - physiology; Photochemistry; Photooxidative stress; Photosensitizing Agents - pharmacology; Pigment Epithelium of Eye - metabolism; Pigment Epithelium of Eye - ultrastructure; Polyunsaturated fatty acids; Retinal degeneration; Retinal pigment epithelium; Free radicals; Polyunsaturated fatty acids; PUFA; MLF; MS; RPE; TBARS; Lipofuscin; Retinal pigment epithelium; Melanolipofuscin; LA; Retinal degeneration; LF; DHA; Melanin; Photooxidative stress
• ISSN: 0891-5849; 1873-4596
• DOI: 10.1016/S0891-5849(99)00003-9

The cellular pigments of the retinal pigment epithelium (RPE) have been shown to catalyze free radical activity, especially when illuminated with visible or ultraviolet light. This activity is sufficient to cause photooxidation of several major cellular components. The present investigation determined the relative ability of melanin, lipofuscin, and melanolipofuscin granules isolated from human and bovine eyes to oxidize polyunsaturated fatty acids, specifically linoleic and docosahexaenoic acids. The dark reactivity as well as the light-stimulated reactions were determined. The production of hydroperoxide derivatives of the linoleic and docosahexaenoic acids were determined by NADPH oxidation coupled to the activity of glutathione peroxidase, and also by production of thiobarbituric acid reactive substances. All RPE pigment granules stimulated fatty acid oxidation when irradiated with short wavelength (<550 nm) visible light, with the melanosomes exhibiting the greatest light-induced activity. Only lipofuscin granules, however, caused peroxidation of fatty acids in the dark. These findings provide additional support for the role of RPE pigments in “blue light toxicity” as well as indicating that accumulation of lipofuscin may contribute to increased photooxidation in the aging RPE.