Number of nitrate groups determines reactivity and potency of organic nitrates: a proof of concept study in ALDH-2-/- mice.
OBJECTIVE
Mitochondrial aldehyde dehydrogenase (ALDH-2) has been shown to provide a pathway for bioactivation of organic nitrates and to be prone to desensitization in response to highly potent, but not to less potent, nitrates. We therefore sought to support the hypothesis that bioactivation by ALDH-2 critically depends on the number of nitrate groups within the nitrovasodilator.


METHODS
Nitrates with one (PEMN), two (PEDN; GDN), three (PETriN; glyceryl trinitrate, GTN) and four (pentaerithrityl tetranitrate, PETN) nitrate groups were investigated. Vasodilatory potency was measured in isometric tension studies using isolated aortic segments of wild type (WT) and ALDH-2-/- mice. Activity of the cGMP-dependent kinase-I (reflected by levels of phosphorylated VAsodilator Stimulated Phosphoprotein, P-VASP) was quantified by Western blot analysis, mitochondrial dehydrogenase activity by HPLC. Following incubation of isolated mitochondria with PETN, PETriN-chromophore and PEDN, metabolites were quantified using chemiluminescence nitrogen detection and mass spectrometry.


RESULTS
Compared to WT, vasorelaxation in response to PETN, PETriN and GTN was attenuated about 10fold in ALDH-2-/- mice, identical to WT vessels preincubated with inhibitors of ALDH-2. Reduced vasodilator potency correlated with reduced P-VASP formation and diminished biotransformation of the tetranitrate- and trinitrate-compounds. None of these findings were observed for PEDN, GDN and PEMN.


CONCLUSIONS
Our results support the crucial role of ALDH-2 in bioactivating highly reactive nitrates like GTN, PETN and PETriN. ALDH-2-mediated relaxation by organic nitrates therefore depends mainly on the number of nitrate groups. Less potent nitrates like PEDN, GDN and PEMN are apparently biotransformed by other pathways.
Wenzel
P
P
II. Medizinische Klinik der Johannes-Gutenberg-Universität Mainz, Mainz, Germany.
Hink
U
U
Oelze
M
M
Seeling
A
A
Isse
T
T
Bruns
K
K
Steinhoff
L
L
Brandt
M
M
Kleschyov
A L
AL
Schulz
E
E
Lange
K
K
Weiner
H
H
Lehmann
J
J
Lackner
K J
KJ
Kawamoto
T
T
Münzel
T
T
Daiber
A
A
D000444:Aldehyde Dehydrogenase / Q000235:genetics*; D000071396:Aldehyde Dehydrogenase, Mitochondrial; D000818:Animals; D015153:Blotting, Western; D015815:Cell Adhesion Molecules / Q000378:metabolism; D017869:Cyclic GMP-Dependent Protein Kinases / Q000378:metabolism; D007537:Isometric Contraction / Q000187:drug effects; D049449:Luminescence; D013058:Mass Spectrometry; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008840:Microfilament Proteins / Q000378:metabolism; D008931:Mitochondria, Muscle / Q000201:enzymology; D009566:Nitrates / Q000737:chemistry* / Q000494:pharmacology*; D005996:Nitroglycerin / Q000031:analogs & derivatives / Q000494:pharmacology; D009599:Nitroprusside / Q000494:pharmacology; D010069:Oxadiazoles / Q000494:pharmacology; D010417:Pentaerythritol Tetranitrate / Q000494:pharmacology; D010750:Phosphoproteins / Q000378:metabolism; D011810:Quinoxalines / Q000494:pharmacology; D013329:Structure-Activity Relationship; D014665:Vasodilator Agents / Q000494:pharmacology; D000098662:Vasodilator-Stimulated Phosphoprotein
C095284:1H-(1,2,4)oxadiazolo(4,3-a)quinoxalin-1-one; D015815:Cell Adhesion Molecules; D008840:Microfilament Proteins; D009566:Nitrates; D010069:Oxadiazoles; D010750:Phosphoproteins; D011810:Quinoxalines; D014665:Vasodilator Agents; D000098662:Vasodilator-Stimulated Phosphoprotein; D010417:Pentaerythritol Tetranitrate; D009599:Nitroprusside; C014509:dinitroglycerol; C515029:ALDH2 protein, mouse; D000444:Aldehyde Dehydrogenase; D000071396:Aldehyde Dehydrogenase, Mitochondrial; D017869:Cyclic GMP-Dependent Protein Kinases; D005996:Nitroglycerin