title: Nitrite-nitric oxide control of mitochondrial respiration at the frontier of anoxia.
abstract: Actively respiring animal and plant tissues experience hypoxia because of mitochondrial O(2) consumption. Controlling oxygen balance is a critical issue that involves in mammals hypoxia-inducible factor (HIF) mediated transcriptional regulation, cytochrome oxidase (COX) subunit adjustment and nitric oxide (NO) as a mediator in vasodilatation and oxygen homeostasis. In plants, NO, mainly derived from nitrite, is also an important signalling molecule. We describe here a mechanism by which mitochondrial respiration is adjusted to prevent a tissue to reach anoxia. During pea seed germination, the internal atmosphere was strongly hypoxic due to very active mitochondrial respiration. There was no sign of fermentation, suggesting a down-regulation of O(2) consumption near anoxia. Mitochondria were found to finely regulate their surrounding O(2) level through a nitrite-dependent NO production, which was ascertained using electron paramagnetic resonance (EPR) spin trapping of NO within membranes. At low O(2), nitrite is reduced into NO, likely at complex III, and in turn reversibly inhibits COX, provoking a rise to a higher steady state level of oxygen. Since NO can be re-oxidized into nitrite chemically or by COX, a nitrite-NO pool is maintained, preventing mitochondrial anoxia. Such an evolutionarily conserved mechanism should have an important role for oxygen homeostasis in tissues undergoing hypoxia.
authors.affiliation: UMR 1191 Physiologie Moléculaire des Semences, Université d'Angers/INH/INRA, Angers, France.
authors.forename: Abdelilah
authors.initials: A
authors.lastname: Benamar
authors.forename: Hardy
authors.initials: H
authors.lastname: Rolletschek
authors.forename: Ljudmilla
authors.initials: L
authors.lastname: Borisjuk
authors.forename: Marie-Hélène
authors.initials: MH
authors.lastname: Avelange-Macherel
authors.forename: Gilles
authors.initials: G
authors.lastname: Curien
authors.forename: H Ahmed
authors.initials: HA
authors.lastname: Mostefai
authors.forename: Ramaroson
authors.initials: R
authors.lastname: Andriantsitohaina
authors.forename: David
authors.initials: D
authors.lastname: Macherel
mesh_terms: D000818:Animals; D019069:Cell Respiration / Q000502:physiology*; D004578:Electron Spin Resonance Spectroscopy; D000860:Hypoxia; D008928:Mitochondria / Q000378:metabolism*; D009569:Nitric Oxide / Q000737:chemistry / Q000378:metabolism*; D009573:Nitrites / Q000737:chemistry / Q000378:metabolism*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism; D018532:Pisum sativum / Q000033:anatomy & histology / Q000737:chemistry / Q000378:metabolism; D010944:Plants / Q000378:metabolism; D012639:Seeds / Q000737:chemistry / Q000378:metabolism
chemical_list: D009573:Nitrites; D009569:Nitric Oxide; D010100:Oxygen