6533b857fe1ef96bd12b3b1c

RESEARCH PRODUCT

Complex I dysfunction and tolerance to nitroglycerin: an approach based on mitochondrial-targeted antioxidants.

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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 −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 HUVECρ 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 (10×10 −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.