title: Mitochondria-targeted Ogg1 and aconitase-2 prevent oxidant-induced mitochondrial DNA damage in alveolar epithelial cells.
abstract: Mitochondria-targeted human 8-oxoguanine DNA glycosylase (mt-hOgg1) and aconitase-2 (Aco-2) each reduce oxidant-induced alveolar epithelial cell (AEC) apoptosis, but it is unclear whether protection occurs by preventing AEC mitochondrial DNA (mtDNA) damage. Using quantitative PCR-based measurements of mitochondrial and nuclear DNA damage, mtDNA damage was preferentially noted in AEC after exposure to oxidative stress (e.g. amosite asbestos (5-25 μg/cm(2)) or H2O2 (100-250 μM)) for 24 h. Overexpression of wild-type mt-hOgg1 or mt-long α/β 317-323 hOgg1 mutant incapable of DNA repair (mt-hOgg1-Mut) each blocked A549 cell oxidant-induced mtDNA damage, mitochondrial p53 translocation, and intrinsic apoptosis as assessed by DNA fragmentation and cleaved caspase-9. In contrast, compared with controls, knockdown of Ogg1 (using Ogg1 shRNA in A549 cells or primary alveolar type 2 cells from ogg1(-/-) mice) augmented mtDNA lesions and intrinsic apoptosis at base line, and these effects were increased further after exposure to oxidative stress. Notably, overexpression of Aco-2 reduced oxidant-induced mtDNA lesions, mitochondrial p53 translocation, and apoptosis, whereas siRNA for Aco-2 (siAco-2) enhanced mtDNA damage, mitochondrial p53 translocation, and apoptosis. Finally, siAco-2 attenuated the protective effects of mt-hOgg1-Mut but not wild-type mt-hOgg1 against oxidant-induced mtDNA damage and apoptosis. Collectively, these data demonstrate a novel role for mt-hOgg1 and Aco-2 in preserving AEC mtDNA integrity, thereby preventing oxidant-induced mitochondrial dysfunction, p53 mitochondrial translocation, and intrinsic apoptosis. Furthermore, mt-hOgg1 chaperoning of Aco-2 in preventing oxidant-mediated mtDNA damage and apoptosis may afford an innovative target for the molecular events underlying oxidant-induced toxicity.
authors.affiliation: From the Department of Medicine, Division of Pulmonary and Critical Care Medicine, Jesse Brown Veterans Affairs Medical Center and Northwestern University Feinberg School of Medicine, Chicago, Illinois 60611.
authors.forename: Seok-Jo
authors.initials: SJ
authors.lastname: Kim
authors.forename: Paul
authors.initials: P
authors.lastname: Cheresh
authors.forename: David
authors.initials: D
authors.lastname: Williams
authors.forename: Yuan
authors.initials: Y
authors.lastname: Cheng
authors.forename: Karen
authors.initials: K
authors.lastname: Ridge
authors.forename: Paul T
authors.initials: PT
authors.lastname: Schumacker
authors.forename: Sigmund
authors.initials: S
authors.lastname: Weitzman
authors.forename: Vilhelm A
authors.initials: VA
authors.lastname: Bohr
authors.forename: David W
authors.initials: DW
authors.lastname: Kamp
mesh_terms: D000154:Aconitate Hydratase / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D017639:Asbestos, Amosite / Q000633:toxicity; D045744:Cell Line, Tumor; D004249:DNA Damage; D045647:DNA Glycosylases / Q000235:genetics / Q000378:metabolism*; D004272:DNA, Mitochondrial / Q000235:genetics / Q000378:metabolism*; D004847:Epithelial Cells / Q000201:enzymology* / Q000473:pathology; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D008928:Mitochondria / Q000201:enzymology* / Q000235:genetics / Q000473:pathology; D009154:Mutation; D016877:Oxidants / Q000009:adverse effects / Q000494:pharmacology*; D018384:Oxidative Stress / Q000187:drug effects*; D011650:Pulmonary Alveoli / Q000201:enzymology* / Q000473:pathology; D051381:Rats; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism
chemical_list: D004272:DNA, Mitochondrial; D016877:Oxidants; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; D017639:Asbestos, Amosite; D045647:DNA Glycosylases; C483741:OGG1 protein, rat; C485990:Ogg1 protein, mouse; C479058:oxoguanine glycosylase 1, human; C476079:ACO2 protein, human; D000154:Aconitate Hydratase; C543483:aconitase 2, mouse
keywords: DNA Damage; DNA Repair; Epithelial Cell; Fibrosis; Lung Fibrosis; Mitochondrial Aconitase; Mitochondrial DNA Damage; Mitochondrial hOgg1; Oxidative Stress