Abstract
The retina and, in particular, retinal pigment epithelial cells are unusual for being encumbered by exposure to visible light, while being oxygen-rich, and also amassing photoreactive molecules. These fluorophores (bisretinoids) are generated as a byproduct of the activity of vitamin A aldehyde—the chromophore necessary for vision. Bisretinoids form in photoreceptor cells due to random reactions of two molecules of vitamin A aldehyde with phosphatidylethanolamine; bisretinoids are subsequently transferred to retinal pigment epithelial (RPE) cells, where they accumulate in the lysosomal compartment with age. Bisretinoids can generate reactive oxygen species by both energy and electron transfer, and they become photo-oxidized and photolyzed in the process. While these fluorescent molecules are accrued by RPE cells of all healthy eyes, they are also implicated in retinal disease.
Highlights
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Once peroxyl radicals are generated through multiple steps, the peroxyl radicals cause the formation of aldehyde-bearing end products of lipid peroxidation, such as HNE (4-hydroxynonenal) and MDA
In studies of age-related macular degeneration (AMD) cohorts [67], it was found that qAF in patients with soft and cuticular drusen were within the 95% confidence intervals of qAF values in age-similar healthy eyes. qAF levels were below the 95% confidence intervals in patients with reticular pseudodrusen
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. OH is highly reactive toward most organic molecules Photosensitizers, both natural and synthetic, are molecules that can be activated by specific wavelengths of light, because they exhibit the conjugated double-bond systems that are necessary for intersystem crossing to the triplet-excited state, wherein the spin of the excited electron is reversed such that it is parallel to a ground-state electron. A photosensitizer may transfer one electron to oxygen to produce a superoxide anion (O2 − ) The latter can be converted to hydrogen peroxide (H2 O2 ) by superoxide dismutase [4], with H2 O2 forming the highly reactive hydroxyl radical ( OH) in the presence of iron (Fenton reaction). Byproduct of the activity of vitamin A aldehyde—the chromophore necessary for vision
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