title: Dysfunctional autophagy in RPE, a contributing factor in age-related macular degeneration.
abstract: Age-related macular degeneration (AMD) is a devastating neurodegenerative disease and a major cause of blindness in the developed world. Owing to its complexity and the lack of an adequate human model that recapitulates key aspects of the disease, the molecular mechanisms of AMD pathogenesis remain poorly understood. Here we show that cultured human retinal pigment epithelium (RPE) from AMD donors (AMD RPE) are functionally impaired and exhibit distinct phenotypes compared with RPE cultured from normal donors (normal RPE). Accumulation of lipid droplets and glycogen granules, disintegration of mitochondria, and an increase in autophagosomes were observed in AMD RPE cultures. Compared with normal RPE, AMD RPE exhibit increased susceptibility to oxidative stress, produce higher levels of reactive oxygen species (ROS) under stress conditions, and showed reduced mitochondrial activity. Measurement of the ratio of LC3-II/ LC3-I, revealed impaired autophagy in AMD RPE as compared with normal RPE. Autophagic flux was also reduced in AMD RPE as compared with normal RPE, as shown by inability of AMD RPE to downregulate p62 levels during starvation. Impaired autophagic pathways were further shown by analyzing late autophagic vesicles; immunostaining with lysosome-associated membrane protein 1 (LAMP-1) antibody revealed enlarged and annular LAMP-1-positive organelles in AMD RPE as opposed to smaller discrete puncta observed in normal RPE. Our study provides insights into AMD cellular and molecular mechanisms, proposes dysfunctional autophagy as an underlying mechanism contributing to the pathophysiology of the disease, and opens up new avenues for development of novel treatment strategies.
authors.affiliation: Department of Ophthalmology, Georgetown University Medical Center, Washington, DC, USA.|Department of Neurology, Georgetown University Medical Center, Washington, DC, USA.|Department of Biochemistry and Molecular & Cellular Biology, Georgetown University Medical Center, Washington, DC, USA.
authors.forename: Nady
authors.initials: N
authors.lastname: Golestaneh
authors.affiliation: Department of Ophthalmology, Georgetown University Medical Center, Washington, DC, USA.
authors.forename: Yi
authors.initials: Y
authors.lastname: Chu
authors.affiliation: Department of Ophthalmology, Georgetown University Medical Center, Washington, DC, USA.
authors.forename: Yang-Yu
authors.initials: YY
authors.lastname: Xiao
authors.affiliation: Department of Ophthalmology, Georgetown University Medical Center, Washington, DC, USA.
authors.forename: Gianna L
authors.initials: GL
authors.lastname: Stoleru
authors.affiliation: Department of Human Science, Georgetown University, Washington, DC, USA.
authors.forename: Alexander C
authors.initials: AC
authors.lastname: Theos
mesh_terms: D000071182:Autophagosomes / Q000378:metabolism / Q000473:pathology; D002478:Cells, Cultured; D006003:Glycogen / Q000378:metabolism; D006801:Humans; D066292:Lipid Droplets / Q000378:metabolism / Q000473:pathology; D051907:Lysosomal Membrane Proteins / Q000096:biosynthesis / Q000235:genetics*; D008268:Macular Degeneration / Q000378:metabolism* / Q000473:pathology; D008928:Mitochondria / Q000378:metabolism* / Q000473:pathology; D018384:Oxidative Stress / Q000235:genetics; D017382:Reactive Oxygen Species / Q000378:metabolism; D055213:Retinal Pigment Epithelium / Q000254:growth & development / Q000378:metabolism* / Q000473:pathology; D052118:Lysosomal-Associated Membrane Protein 1
chemical_list: D006003:Glycogen; D051907:Lysosomal Membrane Proteins; D017382:Reactive Oxygen Species; C489116:LAMP1 protein, human; D052118:Lysosomal-Associated Membrane Protein 1