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Majda Hadziahmetovic, Usha Kumar, Ying Song, Steven Grieco, Yafeng Li, Delu Song, Joshua L. Dunaief; Microarray Analysis Following Murine Retinal Light Damage Reveals Changes in Iron Regulatory Genes, Complement, and Antioxidant Genes in the Neural Retina and Isolated RPE. Invest. Ophthalmol. Vis. Sci. 2012;53(14):2563.
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Light damage is an established model of retinal degeneration. The purpose of our study was to investigate light damage induced transcript changes within the neurosensory retina (NSR) and isolated RPE cells. Similar studies have been conducted previously, but usually limited to the NSR and only a portion of the genome. Herein we were able to query most of the genome in not just the neural retina but also isolated RPE cells.
Mice (n = 4), were exposed to 10,000 lux cool white fluorescent light for 18 hours. The control group (n = 4) was kept on a regular 12-hour light-dark cycle. Mice were sacrificed 4 hours after photic injury. NSR and isolated RPE were collected, and RNA was isolated. DNA microarray hybridization was conducted as described in the Affymetrix GeneChip Expression Analysis Technical Manual. Microarray analysis was performed using probe intensity data derived from the Mouse Gene 1.0 ST Array. For the genes of interest, confirmation of gene expression was done using quantitative real-time PCR. Immunofluorescence assessed protein levels and localization.
Sixteen iron regulatory genes were significantly changed in the light exposed NSR and 20 genes in the RPE. Several of these gene expression changes could cause an iron-overloaded state. For example, the iron importer transferrin receptor was upregulated in both light exposed NSR and RPE. Consistent with this, there was stronger transferrin receptor immunoreactivity in the light exposed retinas. In the oxidative-stress category, we identified 4 genes significantly changed in the light exposed NSR and 6 genes in the RPE. In the complement category, there were 5 genes in both the NSR and RPE that were significantly changed.
We introduce the concept of a photo-oxidative stress induced vicious cycle of increased iron uptake followed by iron-exacerbated oxidative stress. Our findings provide further insight into pathways by which excessive light exposure may promote dangerous spiral of retinal oxidative stress.
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