Mitochondria-targeted Ogg1 and aconitase-2 prevent oxidant-induced mitochondrial DNA damage in alveolar epithelial cells

J Biol Chem. 2014 Feb 28;289(9):6165-76. doi: 10.1074/jbc.M113.515130. Epub 2014 Jan 15.


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.

Keywords: DNA Damage; DNA Repair; Epithelial Cell; Fibrosis; Lung Fibrosis; Mitochondrial Aconitase; Mitochondrial DNA Damage; Mitochondrial hOgg1; Oxidative Stress.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Aconitate Hydratase / genetics
  • Aconitate Hydratase / metabolism*
  • Animals
  • Apoptosis / drug effects
  • Asbestos, Amosite / toxicity
  • Cell Line, Tumor
  • DNA Damage*
  • DNA Glycosylases / genetics
  • DNA Glycosylases / metabolism*
  • DNA, Mitochondrial / genetics
  • DNA, Mitochondrial / metabolism*
  • Epithelial Cells / enzymology*
  • Epithelial Cells / pathology
  • Humans
  • Mice
  • Mice, Knockout
  • Mitochondria / enzymology*
  • Mitochondria / genetics
  • Mitochondria / pathology
  • Mutation
  • Oxidants / adverse effects
  • Oxidants / pharmacology*
  • Oxidative Stress / drug effects*
  • Pulmonary Alveoli / enzymology*
  • Pulmonary Alveoli / pathology
  • Rats
  • Tumor Suppressor Protein p53 / genetics
  • Tumor Suppressor Protein p53 / metabolism


  • DNA, Mitochondrial
  • Oxidants
  • TP53 protein, human
  • Tumor Suppressor Protein p53
  • Asbestos, Amosite
  • DNA Glycosylases
  • OGG1 protein, rat
  • Ogg1 protein, mouse
  • oxoguanine glycosylase 1, human
  • ACO2 protein, human
  • Aconitate Hydratase
  • aconitase 2, mouse