Microarray analysis of murine retinal light damage reveals changes in iron regulatory, complement, and antioxidant...

The purpose of this study was to investigate light damage-induced transcript changes within neurosensory retina (NSR) and isolated retinal pigment epithelium (RPE). Similar studies have been conducted previously, but were usually limited to the NSR and only a portion of the transcriptome. Herein most of the transcriptome, not just in the NSR but also in isolated RPE, was queried.

Mice were exposed to 10,000 lux cool white fluorescent light for 18 hours and euthanized 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.

Numerous iron regulatory genes were significantly changed in the light-exposed NSR and RPE. Several of these gene expression changes favored an iron-overloaded state. For example, the 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. Significant changes in gene expression following light damage were also observed in oxidative stress and complement system genes.

The concept of a photooxidative stress-induced vicious cycle of increased iron uptake leading to further oxidative stress was introduced.