Abstract
Abstract: :
Purpose: Photic injury induces photoreceptor apoptosis, but the mechanism of apoptosis is incompletely understood. Oxidants are most likely involved, as anti-oxidants can ameliorate photic damage. Our goals are to increase understanding of the stress response to photic injury and the mechanism of apoptosis by studying the gene expression profile of oxidative-stress and apoptosis genes in mouse and rat retinas after photic injury. Methods: Retinas were dissected from two month old rodents immediately after the animals were exposed to cool white fluorescent light for 6 hours with an intensity sufficient to induce TUNEL positive photoreceptors. Retinas were studied either 6hr or 18hr following onset of photic injury to detect both early and later changes in gene expression. Microarray analysis with the MG-U74Av2 or RG-U34A chips was performed following the manufacturer's protocols (Affymetrix). RT-PCR was used to confirm the expressional alteration in some of the genes identified from the above microarray analysis experiments. Results: No change occurred in housekeeping genes including GAPDH. As expected, an early increase in c-fos was detected. In addition, up-regulation of several genes of interest, including junB, and glutathione synthetase was detected. There was no significant change in the expression of a subset of the oxidative stress related genes, including superoxide dismutase, glutathione peroxidase, and nitric oxide synthetase. Conclusions: The absence of change in housekeeping gene expression and elevation in c-fos expression confirm the accuracy of gene expression detection in this system. Upregulation of immediate early gene junB may function in either stress protection or initiation of apoptosis. Upregulation of glutathione synthetase is likely to serve as a protective mechanism against photo-oxidative stress.
Keywords: 517 photoreceptors • 417 gene/expression • 316 animal model