title: Sub-lethal photodynamic damage to ARPE-19 cells transiently inhibits their phagocytic activity.
abstract: Efficient phagocytosis of photoreceptor outer segments (POS) membranes by retinal pigment epithelium (RPE) plays a key role in biological renewal of these highly peroxidizable structures. Here, we tested whether photodynamic treatment, mediated by merocyanine 540 (MC 540), rose Bengal or a zinc-substituted chlorophyllide inhibited phagocytic activity of ARPE-19 cells in vitro. Specific phagocytosis of fluorescein-5-isothiocyanate-labeled POS isolated from cow retinas and nonspecific phagocytosis of fluorescent polystyrene beads were measured by flow cytometry. Photodynamic treatment, mediated by all three photosensitizers with sub-threshold doses, induced significant inhibition of the cell-specific phagocytosis. The nonspecific phagocytosis was inhibited by photodynamic treatment mediated only by MC 540. The inhibition of phagocytosis was a reversible phenomenon and after 24 h, the photodynamically treated cells exhibited phagocytic activity that was comparable with that of untreated cells. This study provides proof of principle that sub-threshold photodynamic treatment of ARPE-19 cells with appropriate photosensitizers is a convenient experimental approach for in vitro study of the effects of oxidative stress on specific phagocytic activity of RPE cells. We postulate that oxidative damage to key components of the cell phagocytic machinery may be responsible for severe impairment of its activity, which can lead to retinal degeneration.
authors.affiliation: Department of Biophysics, Jagiellonian University, Krakow, Poland.
authors.forename: Magdalena
authors.initials: M
authors.lastname: Olchawa
authors.forename: Grzegorz
authors.initials: G
authors.lastname: Szewczyk
authors.forename: Mariusz
authors.initials: M
authors.lastname: Zareba
authors.forename: Anna
authors.initials: A
authors.lastname: Piłat
authors.forename: Małgorzata
authors.initials: M
authors.lastname: Bzowska
authors.forename: Tomasz
authors.initials: T
authors.lastname: Mikołajczyk
authors.forename: Tadeusz
authors.initials: T
authors.lastname: Sarna
mesh_terms: D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D002735:Chlorophyllides / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D006801:Humans; D010084:Oxidation-Reduction; D018384:Oxidative Stress / Q000187:drug effects; D010587:Phagocytosis / Q000187:drug effects*; D010778:Photochemotherapy / Q000009:adverse effects*; D017319:Photosensitizing Agents / Q000494:pharmacology*; D011744:Pyrimidinones / Q000494:pharmacology; D012395:Rose Bengal / Q000494:pharmacology; D014018:Tissue Distribution
chemical_list: D002735:Chlorophyllides; D017319:Photosensitizing Agents; D011744:Pyrimidinones; D012395:Rose Bengal; C003954:merocyanine dye; C007020:chlorophyllin