title: Role of reduced lipoic acid in the redox regulation of mitochondrial aldehyde dehydrogenase (ALDH-2) activity. Implications for mitochondrial oxidative stress and nitrate tolerance.
abstract: Chronic therapy with nitroglycerin results in a rapid development of nitrate tolerance, which is associated with an increased production of reactive oxygen species. We have recently shown that mitochondria are an important source of nitroglycerin-induced oxidants and that the nitroglycerin-bioactivating mitochondrial aldehyde dehydrogenase is oxidatively inactivated in the setting of tolerance. Here we investigated the effect of various oxidants on aldehyde dehydrogenase activity and its restoration by dihydrolipoic acid. In vivo tolerance in Wistar rats was induced by infusion of nitroglycerin (6.6 microg/kg/min, 4 days). Vascular reactivity was measured by isometric tension studies of isolated aortic rings in response to nitroglycerin. Chronic nitroglycerin infusion lead to impaired vascular responses to nitroglycerin and decreased dehydrogenase activity, which was corrected by dihydrolipoic acid co-incubation. Superoxide, peroxynitrite, and nitroglycerin itself were highly efficient in inhibiting mitochondrial and yeast aldehyde dehydrogenase activity, which was restored by dithiol compounds such as dihydrolipoic acid and dithiothreitol. Hydrogen peroxide and nitric oxide were rather insensitive inhibitors. Our observations indicate that mitochondrial oxidative stress (especially superoxide and peroxynitrite) in response to organic nitrate treatment may inactivate aldehyde dehydrogenase thereby leading to nitrate tolerance. Glutathionylation obviously amplifies oxidative inactivation of the enzyme providing another regulatory pathway. Furthermore, the present data demonstrate that the mitochondrial dithiol compound dihydrolipoic acid restores mitochondrial aldehyde dehydrogenase activity via reduction of a disulfide at the active site and thereby improves nitrate tolerance.
authors.affiliation: Department of Cardiology, 2nd Medical Clinic, Johannes Gutenberg University, University Hospital Mainz, 55101 Mainz, Germany.
authors.forename: Philip
authors.initials: P
authors.lastname: Wenzel
authors.forename: Ulrich
authors.initials: U
authors.lastname: Hink
authors.forename: Matthias
authors.initials: M
authors.lastname: Oelze
authors.forename: Swaantje
authors.initials: S
authors.lastname: Schuppan
authors.forename: Karin
authors.initials: K
authors.lastname: Schaeuble
authors.forename: Stefan
authors.initials: S
authors.lastname: Schildknecht
authors.forename: Kwok K
authors.initials: KK
authors.lastname: Ho
authors.forename: Henry
authors.initials: H
authors.lastname: Weiner
authors.forename: Markus
authors.initials: M
authors.lastname: Bachschmid
authors.forename: Thomas
authors.initials: T
authors.lastname: Münzel
authors.forename: Andreas
authors.initials: A
authors.lastname: Daiber
mesh_terms: D000444:Aldehyde Dehydrogenase / Q000737:chemistry / Q000502:physiology*; D000071396:Aldehyde Dehydrogenase, Mitochondrial; D000818:Animals; D005978:Glutathione / Q000737:chemistry / Q000378:metabolism; D020128:Inhibitory Concentration 50; D008297:Male; D008928:Mitochondria / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000737:chemistry / Q000502:physiology*; D008954:Models, Biological; D009206:Myocardium / Q000378:metabolism; D009566:Nitrates / Q000737:chemistry*; D016877:Oxidants / Q000737:chemistry / Q000378:metabolism; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D051381:Rats; D017208:Rats, Wistar; D008063:Thioctic Acid / Q000737:chemistry*
chemical_list: D024101:Mitochondrial Proteins; D009566:Nitrates; D016877:Oxidants; D008063:Thioctic Acid; D000444:Aldehyde Dehydrogenase; D000071396:Aldehyde Dehydrogenase, Mitochondrial; C505112:Aldh2 protein, rat; D005978:Glutathione