Vascular bioactivation of nitroglycerin is catalyzed by cytosolic aldehyde dehydrogenase-2.
BACKGROUND
According to general view, aldehyde dehydrogenase-2 (ALDH2) catalyzes the high-affinity pathway of vascular nitroglycerin (GTN) bioactivation in smooth muscle mitochondria. Despite having wide implications to GTN pharmacology and raising many questions that are still unresolved, mitochondrial bioactivation of GTN in blood vessels is still lacking experimental support.


OBJECTIVE
In the present study, we investigated whether bioactivation of GTN is affected by the subcellular localization of ALDH2 using immortalized ALDH2-deficient aortic smooth muscle cells and mouse aortas with selective overexpression of the enzyme in either cytosol or mitochondria.


RESULTS
Quantitative Western blotting revealed that ALDH2 is mainly cytosolic in mouse aorta and human coronary arteries, with only approximately 15% (mouse) and approximately 5% (human) of the enzyme being localized in mitochondria. Infection of ALDH2-deficient aortic smooth muscle cells or isolated aortas with adenovirus containing ALDH2 cDNA with or without the mitochondrial signal peptide sequence led to selective expression of the protein in mitochondria and cytosol, respectively. Cytosolic overexpression of ALDH2 restored GTN-induced relaxation and GTN denitration to wild-type levels, whereas overexpression in mitochondria (6-fold vs wild-type) had no effect on relaxation. Overexpression of ALDH2 in the cytosol of ALDH2-deficient aortic smooth muscle cells led to a significant increase in GTN denitration and cyclic GMP accumulation, whereas mitochondrial overexpression had no effect.


CONCLUSIONS
The data indicate that vascular bioactivation of GTN is catalyzed by cytosolic ALDH2. Mitochondrial GTN metabolism may contribute to oxidative stress-related adverse effects of nitrate therapy and the development of nitrate tolerance.
Department of Pharmacology and Toxicology, Karl-Franzens Universität Graz, Austria.
Matteo
M
Beretta
Gerald
G
Wölkart
Michaela
M
Schernthaner
Martina
M
Griesberger
Regina
R
Neubauer
Kurt
K
Schmidt
Michael
M
Sacherer
Frank R
FR
Heinzel
Sepp D
SD
Kohlwein
Bernd
B
Mayer
D000256:Adenoviridae / Q000235:genetics; D000444:Aldehyde Dehydrogenase / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D000071396:Aldehyde Dehydrogenase, Mitochondrial; D000818:Animals; D001011:Aorta / Q000166:cytology / Q000378:metabolism*; D001711:Biotransformation; D002460:Cell Line; D003600:Cytosol / Q000378:metabolism*; D004247:DNA / Q000235:genetics; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D008931:Mitochondria, Muscle / Q000378:metabolism*; D023421:Models, Animal; D005996:Nitroglycerin / Q000378:metabolism* / Q000494:pharmacology; D018384:Oxidative Stress / Q000187:drug effects / Q000502:physiology; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology; D014665:Vasodilator Agents / Q000378:metabolism* / Q000494:pharmacology
D014665:Vasodilator Agents; D004247:DNA; C515029:ALDH2 protein, mouse; D000444:Aldehyde Dehydrogenase; D000071396:Aldehyde Dehydrogenase, Mitochondrial; D005996:Nitroglycerin