Complex I Dysfunction and Tolerance to Nitroglycerin: An Approach Based on Mitochondrial-Targeted Antioxidants

• Published in: Circulation research 2006-11, Vol.99 (10), p.1067-1075
• Main Authors: Esplugues, Juan V, Rocha, Milagros, Nuñez, Cristina, Bosca, Irene, Ibiza, Sales, Herance, Jose R, Ortega, Angel, Serrador, Juan M, DʼOcon, Pilar, Victor, Victor M
• Format: Article
• Language: English
• Subjects: Aldehyde Dehydrogenase - metabolism; Aldehyde Dehydrogenase, Mitochondrial; Animals; Antioxidants - pharmacology; Biological and medical sciences; Cyclic GMP - biosynthesis; Dose-Response Relationship, Drug; Drug Tolerance; Electron Transport Complex I - metabolism; Endothelial Cells; Fundamental and applied biological sciences. Psychology; Glutathione - metabolism; Glutathione - pharmacology; Humans; In Vitro Techniques; Male; Mitochondria - drug effects; Mitochondria - enzymology; Mitochondria - physiology; Mitochondrial Proteins - metabolism; Muscle Contraction - drug effects; Muscle Relaxation - drug effects; Muscle, Smooth, Vascular - enzymology; Nitroglycerin - pharmacology; Organophosphorus Compounds - pharmacology; Oxidative Stress; Oxygen Consumption - drug effects; Rats; Rats, Sprague-Dawley; Reactive Oxygen Species - metabolism; Ubiquinone - pharmacology; Vasodilator Agents - pharmacology; Vertebrates: cardiovascular system
• ISSN: 0009-7330; 1524-4571
• DOI: 10.1161/01.RES.0000250430.62775.99

Nitroglycerin (GTN) tolerance was induced in vivo (rats) and in vitro (rat and human vessels). Electrochemical detection revealed that the incubation dose of GTN (5×10 mol/L) did not release NO or modify O2 consumption when administered acutely. However, development of tolerance produced a decrease in both mitochondrial O2 consumption and the Km for O2 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 mol/L) or glutathione (GSH) ester (10 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 HUVECρ cells. Experiments analyzing complex I–dependent respiration demonstrate that its inhibition by GTN is prevented by mitochondrial-targeted antioxidants. Furthermore, in presence of succinate (10×10 mol/L), a complex II electron donor added to bypass complex I–dependent respiration, GTN-treated cells exhibited O2 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.