Administration of SIN-1 induces guinea pig airway hyperresponsiveness through inactivation of airway neutral endopeptidase.
BACKGROUND
Peroxynitrite plays an important role in the pathogenesis of airway inflammation. We have already found that peroxynitrite may contribute to decreased beta(2)-adrenoceptor responses in airway smooth muscle. However, it is not known whether peroxynitrite can alter neutral endopeptidase (EC 3.4.24.11; NEP) activity in the airways. This study was designed to determine whether peroxynitrite induces airway hyperresponsiveness to substance P (SP) and endothelin-1 (ET-1) through the inactivation of airway NEP.


METHODS
We examined whether the administration of S-morpholinosydnonimine (SIN-1), a compound that releases peroxynitrite, increased bronchoconstrictor responses to SP and ET-1 in anesthetized guinea pigs. In addition, we assayed NEP activity in the airways of SIN-1-exposed guinea pigs.


RESULTS
Though SIN-1 (10(-7) M) alone had no effect on pulmonary resistance, pretreatment with SIN-1 significantly enhanced SP- and ET-1-induced bronchoconstriction. Pretreatment with phosphoramidon, an NEP inhibitor, also enhanced SP- and ET-1-induced bronchoconstriction. However, simultaneous administration of phosphoramidon and SIN-1 had no additive effect on SP- and ET-1-induced bronchoconstriction. Peroxynitrite formation by SIN-1 was completely inhibited by N-acetylcysteine (NAC) and glutathione (GSH) in vitro, and pretreatment with NAC and GSH significantly reversed the potentiation by SIN-1 of SP-induced bronchoconstriction. In addition, the NEP activity of the trachea after SIN-1 exposure was significantly reduced compared to the level in control guinea pigs (solvent for SIN-1: 30.0+/-4.2 fmol.min(-1).mg tissue(-1); 10(-7) M SIN-1; 15.5+/-4.5 fmol.min(-1).mg tissue(-1), p<0.05).


CONCLUSIONS
These findings suggest that peroxynitrite induces airway hyperresponsiveness to SP and ET-1 through the inactivation of airway NEP, and that peroxynitrite is an important mediator of the alterations in airway functions.
Kanazawa
H
H
The First Department of Internal Medicine, Osaka City University Medical School, Osaka, Japan.
Hirata
K
K
Yoshikawa
J
J
D000818:Animals; D016535:Bronchial Hyperreactivity / Q000139:chemically induced*; D016084:Bronchoconstriction / Q000187:drug effects; D019332:Endothelin-1 / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D006020:Glycopeptides / Q000494:pharmacology; D006168:Guinea Pigs; D008297:Male; D008981:Molsidomine / Q000008:administration & dosage / Q000031:analogs & derivatives*; D015260:Neprilysin / Q000378:metabolism*; D009566:Nitrates / Q000494:pharmacology; D016877:Oxidants / Q000494:pharmacology; D011480:Protease Inhibitors / Q000494:pharmacology; D012137:Respiratory System / Q000201:enzymology; D013373:Substance P / Q000494:pharmacology; D014132:Trachea / Q000201:enzymology; D014665:Vasodilator Agents / Q000008:administration & dosage
D019332:Endothelin-1; D006020:Glycopeptides; D009566:Nitrates; D016877:Oxidants; D011480:Protease Inhibitors; D014665:Vasodilator Agents; C039642:peroxynitric acid; D013373:Substance P; C002385:linsidomine; D008981:Molsidomine; D015260:Neprilysin; C008890:phosphoramidon