title: Low hydrogen peroxide production in mitochondria of the long-lived Arctica islandica: underlying mechanisms for slow aging.
abstract: The observation of an inverse relationship between lifespan and mitochondrial H₂O₂ production rate would represent strong evidence for the disputed oxidative stress theory of aging. Studies on this subject using invertebrates are surprisingly lacking, despite their significance in both taxonomic richness and biomass. Bivalve mollusks represent an interesting taxonomic group to challenge this relationship. They are exposed to environmental constraints such as microbial H₂S, anoxia/reoxygenation, and temperature variations known to elicit oxidative stress. Their mitochondrial electron transport system is also connected to an alternative oxidase that might improve their ability to modulate reactive oxygen species (ROS) yield. Here, we compared H₂O₂ production rates in isolated mantle mitochondria between the longest-living metazoan--the bivalve Arctica islandica--and two taxonomically related species of comparable size. In an attempt to test mechanisms previously proposed to account for a reduction of ROS production in long-lived species, we compared oxygen consumption of isolated mitochondria and enzymatic activity of different complexes of the electron transport system in the two species with the greatest difference in longevity. We found that A. islandica mitochondria produced significantly less H₂O₂ than those of the two short-lived species in nearly all conditions of mitochondrial respiration tested, including forward, reverse, and convergent electron flow. Alternative oxidase activity does not seem to explain these differences. However, our data suggest that reduced complex I and III activity can contribute to the lower ROS production of A. islandica mitochondria, in accordance with previous studies. We further propose that a lower complex II activity could also be involved.
authors.affiliation: Biology Department, Université du Québec à Rimouski, 300, allée des Ursulines, CP 3300, succ. A, Rimouski, QC, Canada, G5L 3A1. dmunro70@hotmail.com
authors.forename: Daniel
authors.initials: D
authors.lastname: Munro
authors.forename: Nicolas
authors.initials: N
authors.lastname: Pichaud
authors.forename: Frédérique
authors.initials: F
authors.lastname: Paquin
authors.forename: Vincent
authors.initials: V
authors.lastname: Kemeid
authors.forename: Pierre U
authors.initials: PU
authors.lastname: Blier
mesh_terms: D000818:Animals; D019069:Cell Respiration; D004579:Electron Transport; D004789:Enzyme Activation; D006861:Hydrogen Peroxide / Q000378:metabolism*; D008136:Longevity / Q000502:physiology*; D008928:Mitochondria / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000378:metabolism; D049892:Mya / Q000378:metabolism* / Q000502:physiology; D010088:Oxidoreductases / Q000378:metabolism; D010101:Oxygen Consumption; D010940:Plant Proteins / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D049890:Spisula / Q000378:metabolism* / Q000502:physiology; D013997:Time Factors; D000099188:Alternative Oxidase
chemical_list: D006861:Hydrogen Peroxide; D024101:Mitochondrial Proteins; D010088:Oxidoreductases; D010940:Plant Proteins; D017382:Reactive Oxygen Species; D000099188:Alternative Oxidase
keywords: Arctica islandica; alternative oxidase; complex I; complex II; mitochondria; reactive oxygen species