Received for publication May 12, 2004.
Revised July 15, 2004.
Accepted for publication August 24, 2004.

Oxidative Stress and Mitochondrial Aldehyde Dehydrogenase Activity: A Comparison of Pentaerythrityl Tetranitrate (PETN) with Other Organic Nitrates

Abstract

Mitochondrial aldehyde dehydrogenase (ALDH-2) was recently identified to be essential for bio-activation of glyceryl trinitrate (GTN). We now assessed whether other organic nitrates are bio-activated by a similar mechanism. The ALDH-2 inhibitor benomyl reduced the vasodilator potency, but not the efficacy, of GTN, pentaerythrityl tetranitrate (PETN) and pentaerythrityl trinitrate in phenylephrine-constricted rat aorta, whereas vasodilator responses to isosorbide dinitrate, isosorbide-5-mononitrate, pentaerythrityl dinitrate, pentaerythrityl mononitrate and the endothelium-dependent vasodilator acetylcholine were not affected. Similarly, benomyl decreased GTN and PETN-elicited phosphorylation of the cGMP-activated protein kinase substrate vasodilator-activated phosphoprotein (VASP), but not that elicited by other nitrates. The vasodilator potency of organic nitrates correlated with their potency to inhibit ALDH-2 dehydrogenase activity in mitochondria from rat heart, and to increase mitochondrial superoxide formation, as detected by chemiluminescence. In contrast, mitochondrial ALDH-2 esterase activity was not affected by PETN and its metabolites, whereas it was inhibited by benomyl, GTN applied in vitro and in vivo, and some sulfhydryl-oxidants. The bio-activation related metabolism of GTN to glyceryl-1,2-dinitrate by isolated RAW-macrophages was reduced by the ALDH-2 inhibitors benomyl and daidzin, as well as by GTN concentrations > 1 µM. We conclude that mitochondrial ALDH-2, specifically its esterase activity, is required for bio-activation of the organic nitrates with high vasodilator potency, such as GTN and PETN, but not for the less potent nitrates. Interestingly, ALDH-2 esterase activity was inhibited by GTN only, not by the other nitrates tested. This difference might explain why GTN elicits mitochondrial superoxide formation and nitrate tolerance with the highest potency.

Key words: Guanylyl cyclase, Nitric oxide, cGMP, Oxidative stress/antioxidants