title: 9,10-Phenanthraquinone in diesel exhaust particles downregulates Cu,Zn-SOD and HO-1 in human pulmonary epithelial cells: intracellular iron scavenger 1,10-phenanthroline affords protection against apoptosis.
abstract: 9,10-Phenanthraquinone (PQ), a major quinone contained in diesel exhaust particles and atmospheric PM(2.5), undergoes one-electron reduction by flavin enzymes such as NADPH-cytochrome P450 reductase, leading to production of reactive oxygen species in vitro. We have detected an ESR signal for superoxide (O(2)(-)) and hydroxyl radicals ((.)OH) by the spin trap method when PQ was mixed with P450 reductase, NADPH, and iron(III). When we examined the effects of PQ on A549 human pulmonary epithelial cells, PQ induced apoptosis with a LC(50) of approximately 7 microM. Formation of protein carbonyls was also detected in cells after treatment with PQ, suggesting that PQ induces oxidative damage. Iron chelators such as 1,10-phenanthroline (OP), desferrioxamine mesylate, and deferiprone respectively afforded protection against the toxic effects of PQ. Furthermore, treatment of A549 cells with 10-20 microM PQ for 12 h specifically down-regulated protein levels of Cu,Zn-superoxide dismutase (Cu,Zn-SOD) and heme oxygenase-1 (HO-1) by more than 50%. Pretreatment of cells with OP (10 microM) markedly reduced the down-regulation of Cu,Zn-SOD and HO-1 and protein carbonyl formation in response to PQ. The inhibitor of Cu,Zn-SOD, diethyldithiocarbamate, enhanced the toxic effects of 5 microM PQ. The present findings suggest that PQ causes iron-mediated oxidative damage that is exacerbated by the concomitant down-regulation of Cu,Zn-SOD.
authors.affiliation: Majors of Medical Sciences, Graduate School of Comprehensive Human Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8575, Japan.
authors.forename: Rika
authors.initials: R
authors.lastname: Sugimoto
authors.forename: Yoshito
authors.initials: Y
authors.lastname: Kumagai
authors.forename: Yumi
authors.initials: Y
authors.lastname: Nakai
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Ishii
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D004050:Ditiocarb / Q000494:pharmacology; D004578:Electron Spin Resonance Spectroscopy; D004847:Epithelial Cells / Q000187:drug effects*; D016166:Free Radical Scavengers / Q000737:chemistry / Q000494:pharmacology*; D005609:Free Radicals / Q000737:chemistry; D006419:Heme Oxygenase (Decyclizing) / Q000187:drug effects* / Q000378:metabolism; D051547:Heme Oxygenase-1; D006801:Humans; D007502:Iron Chelating Agents / Q000737:chemistry / Q000494:pharmacology*; D008565:Membrane Proteins; D010616:Phenanthrenes / Q000037:antagonists & inhibitors / Q000633:toxicity*; D010618:Phenanthrolines / Q000494:pharmacology; D011650:Pulmonary Alveoli / Q000166:cytology; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D013482:Superoxide Dismutase / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D001335:Vehicle Emissions / Q000633:toxicity
chemical_list: D016166:Free Radical Scavengers; D005609:Free Radicals; D007502:Iron Chelating Agents; D008565:Membrane Proteins; D010616:Phenanthrenes; D010618:Phenanthrolines; D012333:RNA, Messenger; D017382:Reactive Oxygen Species; D001335:Vehicle Emissions; C005399:9,10-phenanthrenequinone; D003577:Cytochrome P-450 Enzyme System; D004050:Ditiocarb; C496541:HMOX1 protein, human; D006419:Heme Oxygenase (Decyclizing); D051547:Heme Oxygenase-1; D013482:Superoxide Dismutase; C025205:1,10-phenanthroline