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  • Title: The lipofuscin fluorophore A2E mediates blue light-induced damage to retinal pigmented epithelial cells.
    Author: Sparrow JR, Nakanishi K, Parish CA.
    Journal: Invest Ophthalmol Vis Sci; 2000 Jun; 41(7):1981-9. PubMed ID: 10845625.
    Abstract:
    PURPOSE: To determine whether the lipofuscin fluorophore A2E participates in blue light-induced damage to retinal pigmented epithelial (RPE) cells. METHODS: Human RPE cells (ARPE-19) accumulated A2E from 10, 50, and 100 microM concentrations in media, the levels of internalized A2E ranging from less than 5 to 64 ng/10(5) cells, as assayed by quantitative high-performance liquid chromatography (HPLC). Restricted zones (0.5-mm diameter spots) of confluent cultures were subsequently exposed to 480 +/- 20-nm (blue) or 545 +/- 1-nm (green) light for 15 to 60 seconds. Phototoxicity was quantified at various periods after exposure by fluorescence staining of the nuclei of membrane-compromised cells, by TdT-dUTP terminal nick-end labeling (TUNEL) of apoptotic cells and by Annexin V labeling for phosphatidylserine exposure. RESULTS: Nonviable cells were located in blue light- exposed zones of A2E-containing RPE cells, whereas cells situated outside the illuminated areas remained viable. As shown by fluorescence labeling of the nuclei of membrane-damaged cells and by the presence of TUNEL-positive cells, the numbers of nonviable cells increased with exposure duration and as a function of the concentration of A2E used to load the cells before illumination. The numbers of blue light-induced TUNEL-positive cells also increased in advance of the increase in labeling of membrane-compromised cells, a finding that, together with Annexin V labeling, indicates an apoptotic form of cell death. Conversely, blue light- exposed RPE cells that did not contain A2E remained viable. In addition, illumination with green light resulted in the appearance of substantially fewer nonviable cells. CONCLUSIONS: These studies implicate A2E as an initiator of blue light-induced apoptosis of RPE cells.
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