title: Complex I dysfunction and tolerance to nitroglycerin: an approach based on mitochondrial-targeted antioxidants.
abstract: Nitroglycerin (GTN) tolerance was induced in vivo (rats) and in vitro (rat and human vessels). Electrochemical detection revealed that the incubation dose of GTN (5x10(-6) mol/L) did not release NO or modify O(2) consumption when administered acutely. However, development of tolerance produced a decrease in both mitochondrial O(2) consumption and the K(m) for O(2) in animal and human vessels and endothelial cells in a noncompetitive action. GTN tolerance has been associated with impairment of GTN biotransformation through inhibition of aldehyde dehydrogenase (ALDH)-2, and with uncoupling of mitochondrial respiration. Feeding rats with mitochondrial-targeted antioxidants (mitoquinone [MQ]) and in vitro coincubation with MQ (10(-6) mol/L) or glutathione (GSH) ester (10(-4) mol/L) prevented tolerance and the effects of GTN on mitochondrial respiration and ALDH-2 activity. Biotransformation of GTN requires functionally active mitochondria and induces reactive oxygen species production and oxidative stress within this organelle, as it is inhibited by mitochondrial-targeted antioxidants and is absent in HUVECrho(0) cells. Experiments analyzing complex I-dependent respiration demonstrate that its inhibition by GTN is prevented by mitochondrial-targeted antioxidants. Furthermore, in presence of succinate (10x10(-3) mol/L), a complex II electron donor added to bypass complex I-dependent respiration, GTN-treated cells exhibited O(2) consumption rates similar to those of controls, thus suggesting that complex I was affected by GTN. We propose that, following prolonged treatment with GTN in addition to ALDH-2, complex I is a target for mitochondrially generated reactive oxygen species. Our data also suggest a role for mitochondrial-targeted antioxidants as therapeutic tools in the control of the tolerance that accompanies chronic nitrate use.
authors.affiliation: Departamento de Farmacologia, Facultad de Medicina, Universitat de Valencia, Spain.
authors.forename: Juan V
authors.initials: JV
authors.lastname: Esplugues
authors.forename: Milagros
authors.initials: M
authors.lastname: Rocha
authors.forename: Cristina
authors.initials: C
authors.lastname: Nuñez
authors.forename: Irene
authors.initials: I
authors.lastname: Bosca
authors.forename: Sales
authors.initials: S
authors.lastname: Ibiza
authors.forename: Jose R
authors.initials: JR
authors.lastname: Herance
authors.forename: Angel
authors.initials: A
authors.lastname: Ortega
authors.forename: Juan M
authors.initials: JM
authors.lastname: Serrador
authors.forename: Pilar
authors.initials: P
authors.lastname: D'Ocon
authors.forename: Victor M
authors.initials: VM
authors.lastname: Victor
mesh_terms: D000444:Aldehyde Dehydrogenase / Q000378:metabolism; D000071396:Aldehyde Dehydrogenase, Mitochondrial; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology*; D006152:Cyclic GMP / Q000096:biosynthesis; D004305:Dose-Response Relationship, Drug; D004361:Drug Tolerance; D042967:Electron Transport Complex I / Q000378:metabolism*; D042783:Endothelial Cells; D005978:Glutathione / Q000378:metabolism / Q000494:pharmacology*; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D008928:Mitochondria / Q000187:drug effects* / Q000201:enzymology* / Q000502:physiology; D024101:Mitochondrial Proteins / Q000378:metabolism; D009119:Muscle Contraction / Q000187:drug effects; D009126:Muscle Relaxation / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000201:enzymology; D005996:Nitroglycerin / Q000494:pharmacology*; D009943:Organophosphorus Compounds / Q000494:pharmacology*; D018384:Oxidative Stress; D010101:Oxygen Consumption / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000378:metabolism; D014451:Ubiquinone / Q000494:pharmacology* / Q000031:analogs & derivatives; D014665:Vasodilator Agents / Q000494:pharmacology*
chemical_list: D000975:Antioxidants; D024101:Mitochondrial Proteins; D009943:Organophosphorus Compounds; D017382:Reactive Oxygen Species; D014665:Vasodilator Agents; D014451:Ubiquinone; C429014:mitoquinone; C096127:ALDH2 protein, human; D000444:Aldehyde Dehydrogenase; D000071396:Aldehyde Dehydrogenase, Mitochondrial; C505112:Aldh2 protein, rat; D042967:Electron Transport Complex I; D005996:Nitroglycerin; D005978:Glutathione; D006152:Cyclic GMP