BioProject

Age-related macular degeneration (AMD), the leading cause of blindness among the elderly, is without effective treatment for early, dry disease. More...

Age-related macular degeneration (AMD), the leading cause of blindness among the elderly, is without effective treatment for early, dry disease. Retinal pigment epithelial (RPE) cell degeneration is a cardinal feature of dry AMD. Given the reliance of photoreceptors on the RPE for maintaining health and vision, rejuvenating dysfunctional RPE is a logical treatment strategy. Here, the interplay between two cytoprotective pathways, Pink1 mediated mitophagy and the Nrf2 stress-response, was studied in human AMD tissue samples, RPE cells, and relevant mouse models. Pink1 immunolabeling was decreased in the RPE of early AMD eyes. The RPE from Pink1-/- mice and Pink1 deficient cultured human RPE cells displayed impaired mitophagy, decreased aerobic respiration, and increased mitochondrial reactive oxygen species (ROS) generation, and coincidently, developed morphological, molecular, and functional features of epithelial-mesenchymal transition (EMT). This change was triggered by novel retrograde mitochondrial to nuclear signaling that was initiated by mitochondrial ROS, which activated Nrf2 to induce TXNRD1, PI3K/AKT, and canonical EMT transcription factors Zeb1 and Snail. Nrf2 signaling was pivotal since its deficiency prevented EMT and increased cell death. A dendrimer containing N-acetyl cysteine that is tropic for the RPE and contains the mitochondrial targeting ligand Triphenyl phosphinium abrogates EMT in human RPE cells in vitro and in Pink1-/- mice. This study describes a novel interdependency of mitophagy and the Nrf2 antioxidant response in determining cell fate and introduces an RPE and mitochondrial specific ROS reducing dendrimer that can rescue RPE cells in EMT, a change recognized in early AMD. Less...