Abstract
Nitric oxide and other reactive oxygen species generated by nitric-oxide synthases (NOS) modulate, among several other cellular responses, the production of eicosanoids and platelet aggregation. The roles of specific NOS in these two phenomena remain to be determined. Thus, the present study assessed whether inducible NOS (iNOS) and endothelial NOS (eNOS) modulate in a similar manner the production of eicosanoids and platelet aggregation. Mice knocked out for eNOS (eNOS–/–) or iNOS (iNOS–/–) and their wild-type (WT) congeners were used to analyze agonist-induced increases in plasma levels of eicosanoids as well as inhibition of platelet aggregation ex vivo. Systemically administered endothelin-1 (ET-1) triggered an increase in plasma levels of 6-keto prostaglandin F1α (6-keto PGF1α) in WT and eNOS–/– but not in iNOS–/– mice. ET-1 (0.01–1 nmol/kg) also induced a dose-dependent inhibition of platelet aggregation in WT and eNOS–/– but not in iNOS–/– mice. Another agonist, bradykinin (10 nmol/kg), triggered the release of 6-keto PGF1α and inhibited platelet aggregation in all strains of mice studied. In addition, ADP-induced platelet aggregation in vitro was similarly reduced by iloprost (100 nM) in iNOS–/– mice and WT congeners. In another series of experiments, ET-1 (0.1 nmol/kg) significantly increased 8-isoprostane plasma levels in WT but not in iNOS–/– mice. Finally, a 3-week treatment with anti-oxidants inhibited the capacity of ET-1 to significantly increase plasma 6-keto PGF1α in WT mice. We show for the first time that iNOS is involved in the control of ET-1-induced prostacyclin release and related inhibition of platelet aggregation in the murine model.
Footnotes
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This work was supported by Canadian Institutes for Health Research Grant MOP-57764. P.D.-J. and A.J.dB.-F. are National and Senior Scholars of the Fonds de la Recherche en Santé du Québec (FRSQ), respectively. E.C. is in receipt of a FRSQ Studentship.
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Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
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doi:10.1124/jpet.107.125690.
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ABBREVIATIONS: AA, arachidonic acid; PGI2, prostacyclin; TxA2, thromboxane A2; WT, wild-type; COX, cyclooxygenase; PGI2S, prostacyclin synthase; NOS, nitric-oxide synthase(s); nNOS, neuronal nitric-oxide synthase; iNOS, inducible nitric-oxide synthase; eNOS, endothelial nitricoxide synthase; ET-1, endothelin-1; MAP, mean arterial blood pressure; PBS, phosphate-buffered saline; BK, bradykinin; DET/NO, diethylenetriamine/nitric oxide; EIA, enzyme immunoassay; 6-keto PGF1α, 6-keto prostaglandin F1α; , superoxide anions.
- Received May 14, 2007.
- Accepted September 19, 2007.
- The American Society for Pharmacology and Experimental Therapeutics
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