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L.S. Barsalou, R.M. Darrow, D.T. Organisciak; Time–Dependent and Intense Light–Induced Changes in Retinal Gene Expression . Invest. Ophthalmol. Vis. Sci. 2004;45(13):683.
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Purpose: To determine changes in retinal gene expression in rats exposed to intense visible light at times when the retina is more or less susceptible to light induced damage. Methods: Weanling male Sprague–Dawley rats were reared in dim cyclic light for 12 hours per day. At P60, rats were dark adapted for 16 hours before exposure to intense light beginning at 0100, 0900 or 1700. For each time point, retinas were excised from 3 separate groups of three animals, either exposed to light or not. Gene profiles were obtained from Affymetrix Rat 230A Genechips® and used as a guide for real time PCR studies. Using this approach we confirmed the expression of 29 genes of interest. Individual comparisons for genes in light exposed samples were made to gene expression profiles in unexposed rat retinal samples taken at the start and end of the light exposure period. Results: Intense light treatment resulted in changes in a large number of retinal genes, prominent among which were all classes of crystallins. Gamma crystallins were found to be differentially expressed during the day and night and to be induced particularly by intense light at 0900 and at 1700. Expected increases in GFAP, a Muller cell specific gene and Hemeoxygenase, an indicator of oxidative stress, were also found upon light exposure. A suprisingly large induction of Monocyte–Chemoattrant Protein–1, indicative of an inflammatory response, was found when rats were exposed to light at 0100. Conclusions: Retinal light damage susceptibility varies based on the time of day that the intense light exposure occurs. Light–induced changes in crystallin gene expression correlate with the period of reduced light damage susceptibility during the day. Light treatment during the night results in an apparent inflammatory response which also correlates with the retinas’ increased susceptibility to light damage.
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