Nitric oxide exposure inhibits endothelial NOS activity but not gene expression: a role for superoxide

Department of Pediatrics, University of California, San Francisco, California 94143-0106 Recent studies have characterized a rebound pulmonary vasoconstriction with abrupt withdrawal of inhaled nitric oxide (NO) during therapy for pulmonary hypertension, suggesting that inhaled NO may downregulate b...

Full description

Saved in:
Bibliographic Details
Published inAmerican journal of physiology. Lung cellular and molecular physiology Vol. 274; no. 5; pp. 833 - L841
Main Authors Sheehy, A. Macduff, Burson, Michael A, Black, Stephen M
Format Journal Article
LanguageEnglish
Published United States 01.05.1998
Subjects
Online AccessGet full text

Cover

Loading…
More Information
Summary:Department of Pediatrics, University of California, San Francisco, California 94143-0106 Recent studies have characterized a rebound pulmonary vasoconstriction with abrupt withdrawal of inhaled nitric oxide (NO) during therapy for pulmonary hypertension, suggesting that inhaled NO may downregulate basal NO production. However, the exact mechanism of this rebound pulmonary hypertension remains unclear. The objectives of these studies were to determine the effect of NO exposure on endothelial NO synthase (eNOS) gene expression, enzyme activity, and posttranslational modification in cultured pulmonary arterial endothelial cells. Sodium nitroprusside (SNP) treatment had no effect on eNOS mRNA or protein levels but did produce a significant decrease in enzyme activity. Furthermore, although SNP treatment induced protein kinase C (PKC)-dependent eNOS phosphorylation, blockade of PKC activity did not protect against the effects of SNP. When the xanthine oxidase inhibitor allopurinol or the superoxide scavenger 4,5-dihydroxy-1-benzene-disulfonic acid were coincubated with SNP, the inhibitory effects on eNOS activity could be partially alleviated. Also, the levels of superoxide were found to be elevated 4.5-fold when cultured pulmonary arterial endothelial cells were exposed to the NO donor spermine/NO. This suggests that NO can stimulate xanthine oxidase to cause an increase in cellular superoxide generation. A reaction between NO and superoxide would produce peroxynitrite, which could then react with the eNOS protein, resulting in enzyme inactivation. This mechanism may explain, at least in part, how NO produces NOS inhibition in vivo and may delineate, in part, the mechanism of rebound pulmonary hypertension after withdrawal of inhaled NO. enzyme inhibition; protein; phosphorylation; nitric oxide synthase
ISSN:1040-0605
0002-9513
1522-1504
DOI:10.1152/ajplung.1998.274.5.l833