ABSTRACT
Objective:To investigate the expression of endoplasmic reticulum stress proteins in photoreceptor apoptosis in light-induced retinal degeneration. Methods: Exposure to excessive levels of light induced photoreceptor apoptosis and had been previously used as a model for the study of retinal degeneration. Photoreceptor apoptosis was detected by terminal dUTP transferase nick end labeling (TUNEL). The protein expression levels of ER stress sensors including glucose-regulated protein-78 (GRP78/BiP), caspase-12, phospho-eukaryotic initiation factor 2? (eIF2?) and phospho-double-stranded RNA-activated protein kinase-like endoplasmic reticulum kinase (PERK) were examined by immuno-fluorescence and Western blot analysis. Results: Following light exposure, the protein expression levels of GRP78/BiP, caspase-12, phospho-eIF2? and phospho-PERK were up-regulated in a time dependent manner. The up-regulation of these proteins coincided with or preceded the photoreceptor apoptosis. At the peak of their expression, they were mainly located in the photoreceptor inner segments and/or outer nuclear layers (ONL). Conclusion: Activation of endoplasmic reticulum stress proteins appears to play an important role in light-induced retinal degeneration. Therefore endoplasmic reticulum stress modulators could become a strong candidate for a therapeutic agent in treatment of these diseases.