title: The role of mitochondrial glutathione in DNA base oxidation.
abstract: The objective of this study was to elucidate the role of mitochondrial GSH in the reactions leading to mitochondrial DNA oxidative damage in terms of 8-hydroxy-desoxyguanosine (8-HOdG) accumulation. With this purpose, tightly coupled mitochondria depleted of matrix GSH were used and the effects of H2O2 (generated during the oxidation of substrates) on 8-HOdG levels were investigated. Mitochondrial integrity, assessed by O2 uptake, respiratory control and P/O ratios, was conserved upon depletion of GSH up to 95%. The rates of H2O2 production linked to the oxidation of endogenous substrates by control and GSH-depleted mitochondria were similar. Succinate (in the absence or presence of antimycin A) enhanced the rate H2O2 production to a similar extent in both control and GSH-depleted mitochondria. These rates of H2O2 production accounted for 1.5-2.5% of the rate of O2 uptake. The levels of 8-HOdG in GSH-depleted mitochondria were 35-50% lower than those in control mitochondria, when measured at different H2O2 production rates. Conversely, in experiments carried out with calf thymus DNA with different Cu/Fe content, GSH increased 1.4-2.4-fold the accumulation of 8-HOdG. These values were further enhanced (44-50%) by superoxide dismutase and decreased by catalase. The lower levels of 8-HOdG in GSH-depleted mitochondria and the higher levels in GSH-supplemented calf thymus DNA suggest a role for the non-protein thiol in the reactions leading to mtDNA oxidative damage. These findings are interpreted in terms of the redox transitions involving O2, GSH, and metal catalysts bound to DNA. A mechanism is proposed by which GSH plays a critical role in the reduction of DNA-Cu complexes and decays by free radical pathways kinetically regulated by superoxide dismutase.
authors.affiliation: Department of Molecular Pharmacology and Toxicology, School of Pharmacy, University of Southern California, Los Angeles 90033, USA.
authors.forename: C
authors.initials: C
authors.lastname: Giulivi
authors.forename: E
authors.initials: E
authors.lastname: Cadenas
mesh_terms: D000080242:8-Hydroxy-2'-Deoxyguanosine; D000818:Animals; D002417:Cattle; D003300:Copper / Q000378:metabolism; D004249:DNA Damage; D004272:DNA, Mitochondrial / Q000737:chemistry* / Q000378:metabolism*; D003849:Deoxyguanosine / Q000031:analogs & derivatives / Q000378:metabolism; D005609:Free Radicals / Q000378:metabolism; D005978:Glutathione / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000378:metabolism; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D008928:Mitochondria / Q000378:metabolism*; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D051381:Rats; D017208:Rats, Wistar; D017382:Reactive Oxygen Species / Q000378:metabolism; D013438:Sulfhydryl Compounds / Q000378:metabolism
chemical_list: D004272:DNA, Mitochondrial; D005609:Free Radicals; D017382:Reactive Oxygen Species; D013438:Sulfhydryl Compounds; D003300:Copper; D000080242:8-Hydroxy-2'-Deoxyguanosine; D006861:Hydrogen Peroxide; D003849:Deoxyguanosine; D005978:Glutathione