Endoplasmic reticulum stress in the pathogenesis of age-related macular degeneration

Age-related macular degeneration(ARMD)is a main cause of irreversible visual impairment in the elderly. The major pathological features are drusen formation, macular pigment disorder, geographic atrophy and abnormal neovascularization. Retinal pigment epithelium(RPE)function is impaired in ARMD. Endoplasmic reticulum(ER)is an organelle in eukaryotes responsible for protein synthesis, modification, integration and quality control. ER also participates in the maintenance of calcium homeostasis and lipid biosynthesis. Stimuli from the external and internal environment may trigger ER stress and therefore activate the intracellular signal transduction pathway-the unfolded protein response(UPR), to restore cell homeostasis. However, prolonged ER stress may lead to apoptosis. The pathogenesis of ARMD has not been fully elucidated, nevertheless, compelling evidence demonstrates that ER stress is involved. In this article, we summarize recent advances in UPR pathways, as well as the role of ER stress in the physiological function of RPE and in the pathogenesis of ARMD.