Comparison of DNA methylation, together with mRNA levels, revealed significant differences between AMD versus normal retinas. The evidence presented suggests that GSTM1 and GSTM5 undergo epigenetic repression in AMD RPE/choroid, which may increase susceptibility to oxidative stress in AMD retinas.

Dexras1, a small G-protein localized predominantly to the brain, is transcriptionally upregulated by the synthetic glucocorticoid dexamethasone. It has close homology to the Ras subfamily, but differs in that Dexras1 contains an extended 7 kDa C-terminal tail. Previous studies in our laboratory showed that NMDA receptor activation, via NO and Dexras1, physiologically stimulates DMT1, the major iron importer. A membrane permeable iron chelator substantially reduces NMDA-excitotoxicity suggesting that Dexras1-mediated iron influx plays a crucial role in NMDA/NO-mediated cell death. We here report that iron influx is elicited by nitric oxide but not by other pro-apoptotic stimuli such as H2O2 or staurosporine. Deletion of Dexras1 in mice attenuates NO-mediated cell death in dissociated primary cortical neurons and retinal ganglion cells in vivo. Thus Dexras1 appears to mediate NMDA-elicited neurotoxicity via NO and iron influx.

These data provide proof of principle that the oral iron chelator DFP can protect the retina against diverse insults. Further testing of DFP in additional animal retinal degeneration models at a range of doses is warranted.