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A.R. Wielgus, F.B. Lih, K.B. Tomer, C.F. Chignell, J.E. Roberts; Blue Light Induces A2E Oxidation in Rat Eyes . Invest. Ophthalmol. Vis. Sci. 2006;47(13):1533.
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Blue light induced retinal injury has been associated with age–related macular degeneration. A2E is a blue light absorbing retinal chromophore that increases with age. Our previous studies have determined that A2E has little phototoxicity, however the oxidation products of A2E can contribute to retinal photodamage. Thus, we examined the potential phototoxic effect of blue light exposure in rat eyes and its relationship to A2E and oxidized A2E.
Albino rats were dark adapted for 24 hours. Control rats (N=10) remained in the dark while the experimental ones (N=10) were exposed to blue light (220 ftc) for 6 hours. Rats were sacrificed immediately following light treatment. The eyes were enucleated under dim red light and frozen in liquid nitrogen. Isolated retinas were homogenized in the Folch extraction mixture and then in chloroform. Dry extracts were reconstituted and divided for determination of organic soluble compounds. Esters of fatty acids were determined by GC–MS, A2E and other chromophores using HPLC, and A2E oxidation products by LC–MS.
Blue light exposure of rat eyes does not significantly change fatty acids composition of the retina. A2E concentration (normalized to fatty acids content) in blue light exposed animals was found to be lower than A2E concentration in rats housed under normal light conditions. The concentration of the isomer of A2E, iso–A2E, was also lower in blue light exposure than under normal light conditions. On the other hand, the amount of A2E oxidized forms was higher in the animals exposed to blue light.
It appears that blue light exposure promotes the oxidation of A2E and iso–A2E to A2E epoxides in the rat eyes. As these A2E oxides are toxic to retinal tissue, this may partially explain blue light induced retinal injury. These studies suggest that similar phototoxic effects may also take place in human eyes; however suitable research in that area is required.
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