Study on Molecular Mechanism and Therapy of Light-induce Retinal Damage

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PURPOSE. To examine our hypothesis that glutathione peroxidase (GPX) is induced at different time points after retinal light exposure and localizes in different retinal cells.METHODS. The rats were kept cyclic light for 2 weeks before the experiments. The animals were maintained in 12-hour cycles of light and dark before and after exposure to intense white fluorescent light for as long as 24 hours and then returned to cyclic light. GPX expression was measured by immunohisto-cytochemistry, Western, and Northern blots. Light-induced retinal damage was determined by the outer nuclear layer (ONL) thickness relative to the total retinal thickness.RESULTS. GPX labeling was not seen in the photoreceptor inner segments and slight labeling was observed in the photoreceptor outer segments or the retinal pigment epithelial (RPE) cells in the normal retina kept in cyclic light. In retinal specimens maintained in light for 12 and 24 hours GPX labeling was induced in the photoreceptor outer segments … More and RPE cells. High GPX expression in the retinal pigment, epithelium was sustained until day 7 after challenge. In contrast, GPX expression in the photoreceptor outer segments decreased on day 1 and disappeared on days 3 and 7 after exposure. Intense GPX labeling was seen from the internal limiting membrane to fan lion cell layer. GPX labeling was constantly localized in both high-intensity white light and cyclic conditions, suggesting no induction of GPX in those areas. In addition, GPX labeling was apparent at the posterior retinal pole but not at the peripheral retina. We observe marked upregulation of GPX mRNA in rats kept in high-intensity white light. One, 3 and 7 days after exposure to high-intensity white light, there was a significant difference (P<0.0001) between the control and experimental groups in the ratio of the outer nuclear layer thickness to the entire retina.CONCLUSIONS. GPX was Induced at different time points after exposure to high-intensity white light and localized in different retinal cells. Changes in GPX expression after light exposure may, be related to the difference in light-damage susceptibility of the retina. Less