title: Testing the vicious cycle theory of mitochondrial ROS production: effects of H2O2 and cumene hydroperoxide treatment on heart mitochondria.
abstract: Vicious cycle theories of aging and oxidative stress propose that ROS produced by the mitochondrial electron transport chain damage the mitochondria leading exponentially to more ROS production and mitochondrial damage. Although this theory is widely discussed in the field of research on aging and oxidative stress, there is little supporting data. Therefore, in order to help clarify to what extent the vicious cycle theory of aging is correct, we have exposed mitochondria in vitro to different concentrations of hydrogen peroxide or cumene-hydroperoxide (0, 30, 100 and 500 muM). We have found that 30 muM hydrogen peroxide (or higher concentrations) inhibit oxygen consumption in state 3 and increase ROS production with pyruvate/malate but not with succinate as substrate, indicating that these effects occur specifically at complex I. Similar levels of cumene-OOH inhibit state 3 respiration with both kinds of substrates, and increase ROS production in both state 4 and state 3 with pyruvate/malate and with succinate. The effects of cumene-OOH on ROS generation are due to action of the peroxide in the complex III or in the complex III plus complex I ROS generators. In all cases, the increase in ROS production occurred at a threshold level of peroxide exposure without further exponential increase in ROS generation. These results are consistent with the idea that ROS production can contribute to increase oxidative stress in old animals, but the results do not fit with a vicious cycle theory in which peroxide generation leads exponentially to more and more ROS production with age.
authors.affiliation: Department of Animal Physiology-II, Faculty of Biology, Complutense University, Madrid, 28040, Spain.
authors.forename: Alberto
authors.initials: A
authors.lastname: Sanz
authors.forename: Pilar
authors.initials: P
authors.lastname: Caro
authors.forename: José
authors.initials: J
authors.lastname: Gómez
authors.forename: Gustavo
authors.initials: G
authors.lastname: Barja
mesh_terms: D000818:Animals; D001555:Benzene Derivatives / Q000494:pharmacology*; D016922:Cellular Senescence; D042967:Electron Transport Complex I / Q000502:physiology; D014450:Electron Transport Complex III / Q000502:physiology; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D066298:In Vitro Techniques; D008293:Malates / Q000378:metabolism; D008297:Male; D008929:Mitochondria, Heart / Q000187:drug effects / Q000502:physiology*; D008954:Models, Biological; D010101:Oxygen Consumption; D010507:Periodicity; D019289:Pyruvic Acid / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D017382:Reactive Oxygen Species / Q000378:metabolism*; D019802:Succinic Acid / Q000378:metabolism
chemical_list: D001555:Benzene Derivatives; D008293:Malates; D017382:Reactive Oxygen Species; C030298:malic acid; D019289:Pyruvic Acid; D019802:Succinic Acid; D006861:Hydrogen Peroxide; D042967:Electron Transport Complex I; D014450:Electron Transport Complex III; C007164:cumene hydroperoxide