Hydralazine is a powerful inhibitor of peroxynitrite formation as a possible explanation for its beneficial effects on prognosis in patients with congestive heart failure.
The hemodynamic and anti-ischemic effects of nitroglycerin (GTN) are rapidly blunted as a result of the development of nitrate tolerance. Hydralazine has been shown to prevent tolerance in experimental and clinical studies, all of which may be at least in part secondary to antioxidant properties of this compound. The antioxidant effects of hydralazine were tested in cell free systems, cultured smooth muscle cells, isolated mitochondria, and isolated vessels. Inhibitory effects on the formation of superoxide and/or peroxynitrite formation were tested using lucigenin and L-012 enhanced chemiluminescence as well as DHE-fluorescence. The peroxynitrite scavenging properties were also assessed by inhibition of nitration of phenol. Prevention of impairment of NO downstream signaling and GTN bioactivation was determined by measurement of P-VASP (surrogate parameter for the activity of the cGMP-dependent kinase-I, cGK-I) and mitochondrial aldehyde dehydrogenase (ALDH-2) activity. Hydralazine dose-dependently decreased the chemiluminescence signal induced by peroxynitrite from SIN-1 and by superoxide from HX/XO in a cell free system, by superoxide in smooth muscle cells and mitochondria acutely challenged with GTN. Moreover, hydralazine inhibited the peroxynitrite-mediated nitration of phenols as well as proteins in smooth muscle cells in a dose-dependent fashion. Finally, hydralazine normalized impaired cGK-I activity as well as impaired vascular ALDH-2 activity. Our results indicate that hydralazine is a highly potent radical scavenger. Thus, the combination with isosorbide dinitrate (ISDN) will favorably influence the nitroso-redox balance in the cardiovascular system in patients with congestive heart failure and may explain at least in part the improvement of prognosis in patients with chronic congestive heart failure.
Daiber
Andreas
A
Klinikum der Johannes Gutenberg-Universität, II. Medizinische Klinik und Poliklinik, Labor für Molekulare Kardiologie, 55101 Mainz, Germany. andreas.daiber@bioredox.com
Oelze
Matthias
M
Coldewey
Meike
M
Kaiser
K
K
Huth
C
C
Schildknecht
S
S
Bachschmid
M
M
Nazirisadeh
Y
Y
Ullrich
V
V
Mülsch
A
A
Münzel
T
T
Tsilimingas
N
N
D000444:Aldehyde Dehydrogenase / Q000037:antagonists & inhibitors; D000071396:Aldehyde Dehydrogenase, Mitochondrial; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology* / Q000627:therapeutic use; D015815:Cell Adhesion Molecules / Q000096:biosynthesis; D004361:Drug Tolerance / Q000502:physiology; D016166:Free Radical Scavengers / Q000494:pharmacology; D006333:Heart Failure / Q000188:drug therapy*; D006801:Humans; D006830:Hydralazine / Q000494:pharmacology* / Q000627:therapeutic use; D008297:Male; D008840:Microfilament Proteins / Q000096:biosynthesis; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D024101:Mitochondrial Proteins / Q000037:antagonists & inhibitors; D005996:Nitroglycerin / Q000494:pharmacology; D018384:Oxidative Stress / Q000187:drug effects; D030421:Peroxynitrous Acid / Q000037:antagonists & inhibitors* / Q000096:biosynthesis*; D010750:Phosphoproteins / Q000096:biosynthesis; D011379:Prognosis; D051381:Rats; D017208:Rats, Wistar; D026361:Reactive Nitrogen Species / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D000098662:Vasodilator-Stimulated Phosphoprotein
D000975:Antioxidants; D015815:Cell Adhesion Molecules; D016166:Free Radical Scavengers; D008840:Microfilament Proteins; D024101:Mitochondrial Proteins; D010750:Phosphoproteins; D026361:Reactive Nitrogen Species; D017382:Reactive Oxygen Species; D000098662:Vasodilator-Stimulated Phosphoprotein; D030421:Peroxynitrous Acid; D006830:Hydralazine; D000444:Aldehyde Dehydrogenase; D000071396:Aldehyde Dehydrogenase, Mitochondrial; C505112:Aldh2 protein, rat; D005996:Nitroglycerin