The human macula, the specialized region of the retina responsible for high resolution visual acuity, selectively accumulates two xanthophy11 carotenoids derived from the diet, lutein and zeaxanthin. Several recent epidemiological studies have demonstrated a strong inverse correlation between dietary intake of lutein and zeaxanthin and the risk of progression Age-Related Macular Degeneration (AMD) the leading cause of blindness among the elderly in the United States. It is thought that the macular carotenoids protect against least-induced damage to the retina by filtering out damaging wavelengths of light and by acting as antioxidants. The biochemical mechanisms that mediate the selective uptake, concentration, and stabilization of the macular carotenoids are unknown. In lower animals, such as lobsters and cyanobacteria, specialized carotenoid-binding proteins perform these tasks. It is hypothesized that comparable carotenoid-binding proteins may have a similar role in the human macula. A major goal of this project is to understand the biochemical processes responsible for the specific deposition of lutein and zeaxanthin the macula, with special emphasis on the search for potential carotenoid-binding proteins. This project will also investigate the properties of carotenoid- protein and carotenoid-lipid interactions through quantitative binding studies and various spectroscopic methods, including resonance Raman spectroscopy, in model systems and in intact retinal tissue. The experiments of this proposal may provide new insights into the biochemical basis of the specific uptake lutein and zeaxanthin into the macula. Derangements of the mechanisms of uptake and stabilization of the macular carotenoids could have profound impact on the progression of AMD and inherited retinal dystrophies. Anticipated interventional clinical studies may be able to take advantage of the specific uptake systems to increase the level of macular carotenoid pigment and perhaps retard or prevent the progressive blindness produced by these diseases.
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