title: Hydroxyl radicals cause fluctuation in intracellular ferrous ion levels upon light exposure during photoreceptor cell death.
abstract: Iron accumulation is a potential pathogenic event often seen in age-related macular degeneration (AMD) patients. In this study, we focused on the relationship between AMD pathology and concentrations of ferrous ion, which is a highly reactive oxygen generator in biological systems. Murine cone-cells-derived 661 W cells were exposed to white fluorescence light at 2500 lx for 1, 3, 6, or 12 h. Levels of ferrous ions, reactive oxygen species (ROS), and hydroxyl radicals were detected by RhoNox-1, a novel fluorescent probe for the selective detection of ferrous ion, 5-(and-6)-chloromethyl-2',7'-dichlorodihydrofluorescein diacetate, acetyl ester (CM-H2DCFDA), and 3'-p-(aminophenyl) fluorescein, respectively. Reduced glutathione, total iron levels and photoreceptor cell death were also measured. Two genes related to iron metabolism, transferrin receptor 1 (TfR1) and H ferritin (HFt), were quantified by RT-PCR. The effects of ferrous ion on cell death and hydroxyl radical production were determined by treatment with a ferrous ion chelating agent, 2,2'-bipyridyl. We found that the ferrous ion level decreased with light exposure in the short time frame, whereas it was upregulated during a 6-h light exposure. Total iron, ROS, cell death rate, and expression of TfR and HFt genes were significantly increased in a time-dependent manner in 661 W cells exposed to light. Chelation with 2,2'-bipyridyl reduced the level of hydroxyl radicals and protected against light-induced cell death. These results suggest that light exposure decreases ferrous ion levels and enhances iron uptake in photoreceptor cells. Ferrous ion may be involved in light-induced photoreceptor cell death through production of hydroxyl radicals.
authors.affiliation: Molecular Pharmacology, Department of Biofunctional Evaluation, Gifu Pharmaceutical University, 1-25-4 Daigaku-nishi, Gifu 501-1196, Japan.
authors.forename: Tomoyo
authors.initials: T
authors.lastname: Imamura
authors.affiliation: Pharmaceutical and Medicinal Chemistry, Department of Organic and Medicinal Chemistry, Gifu Pharmaceutical University, 1-25-4 Daigaku-nishi, Gifu 501-1196, Japan.
authors.forename: Tasuku
authors.initials: T
authors.lastname: Hirayama
authors.affiliation: Molecular Pharmacology, Department of Biofunctional Evaluation, Gifu Pharmaceutical University, 1-25-4 Daigaku-nishi, Gifu 501-1196, Japan.
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Tsuruma
authors.affiliation: Molecular Pharmacology, Department of Biofunctional Evaluation, Gifu Pharmaceutical University, 1-25-4 Daigaku-nishi, Gifu 501-1196, Japan.
authors.forename: Masamitsu
authors.initials: M
authors.lastname: Shimazawa
authors.affiliation: Pharmaceutical and Medicinal Chemistry, Department of Organic and Medicinal Chemistry, Gifu Pharmaceutical University, 1-25-4 Daigaku-nishi, Gifu 501-1196, Japan.
authors.forename: Hideko
authors.initials: H
authors.lastname: Nagasawa
authors.affiliation: Molecular Pharmacology, Department of Biofunctional Evaluation, Gifu Pharmaceutical University, 1-25-4 Daigaku-nishi, Gifu 501-1196, Japan. Electronic address: hidehara@gifu-pu.ac.jp.
authors.forename: Hideaki
authors.initials: H
authors.lastname: Hara
mesh_terms: D000818:Animals; D016923:Cell Death / Q000528:radiation effects*; D004195:Disease Models, Animal; D017665:Hydroxyl Radical / Q000494:pharmacology*; D006912:Hydroxyquinolines / Q000378:metabolism*; D007424:Intracellular Fluid / Q000737:chemistry; D051379:Mice; D020419:Photoreceptor Cells, Vertebrate / Q000378:metabolism* / Q000473:pathology / Q000528:radiation effects; D012313:RNA / Q000235:genetics*; D017382:Reactive Oxygen Species / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D012162:Retinal Degeneration / Q000235:genetics / Q000378:metabolism* / Q000473:pathology
chemical_list: D006912:Hydroxyquinolines; D017382:Reactive Oxygen Species; D017665:Hydroxyl Radical; D012313:RNA; C002833:8-hydroxy-7-iodo-5-quinolinesulfonic acid
keywords: Age-related macular degeneration; Ferrous; Hydroxyl radical; Iron; Light-induced retinal damage