Rapid Changes in Retinal Oxidative Protein Modifications Induced by Blue Light

Abstract

Abstract: : Purpose: To better understand the molecular mechanisms of retinal light damage, we have monitored oxidative protein modifications in mouse retina after in vivo exposure to intense blue light. Methods: Dark adapted mice were exposed to blue light of 408 +/– 10 nm at 30 mW/cm² for 5 min then sacrificed immediately or sacrificed after 1 h or 4 h following light treatment. Retinas were isolated, immediately washed with antioxidant–containing buffer and flash frozen at –80ºC until analysis. Lipids were extracted with chloroform/methanol and proteins were solubilized with SDS. Western analyses for oxidative protein modifications were performed with antibodies to carboxyethylpyrrole (CEP) and nitrotyrosine (nY). Results: Blue light exposure induced CEP modifications and nitration of protein tyrosine in mouse retina compared with control animals maintained in the dark. CEP adducts result from oxidation of docosahexaenoate–containing lipids and nY is generated from reactive nitrogen oxide species. These oxidative protein modifications were more abundant in retina from mice sacrificed immediately after light exposure. Animals sacrificed 1h or 4h after light treatment exhibited intermediate or control levels of CEP and nY immunoreactivities. Conclusions: Intense blue light generates CEP and nY modifications in rodent retina, as does green light in the range of 490 – 580 nm (2003 ARVO abstract 5129). Formation of blue light induced oxidative protein modifications in mouse retina was rapid as was the appearance of retinal lesions (2003 ARVO abstract 5132). Notably, adduct degradation and/or repair also appears to be rapid under the conditions employed. It remains to be seen whether CEP, nY and other oxidative products can initiate the apoptotic death cascade seen after blue light exposure.

Keywords: proteomics • oxidation/oxidative or free radical damage • protein modifications–post translational