Catalytic Consumption of Nitric Oxide by Prostaglandin H Synthase-1 Regulates Platelet Function

• Published in: The Journal of biological chemistry Vol. 275; no. 49; pp. 38239 - 38244
• Main Authors: O'Donnell, V B, Coles, B, Lewis, M J, Crews, B C, Marnett, L J, Freeman, B A
• Format: Journal Article
• Language: English
• Published: United States American Society for Biochemistry and Molecular Biology 08-12-2000
• Subjects: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid - pharmacology; Animals; Arachidonic Acid - pharmacology; Blood Platelets - physiology; Catalysis; Cattle; Cyclooxygenase 1; Glutathione - analogs & derivatives; Glutathione - pharmacology; Humans; Hydrogen Peroxide - metabolism; Isoenzymes - metabolism; Kinetics; Leukotrienes - metabolism; Lipid Peroxides - metabolism; Membrane Proteins; Nitric Oxide - metabolism; Nitroso Compounds - pharmacology; Platelet Aggregation - physiology; Platelet Aggregation Inhibitors - pharmacology; Prostaglandin-Endoperoxide Synthases - metabolism; S-Nitrosoglutathione; Sheep; Substrate Specificity; Thrombin - pharmacology
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M001802200

Nitric oxide ( ⋅ NO) plays a central role in vascular homeostasis via regulation of smooth muscle relaxation and platelet aggregation. Although
mechanisms for ⋅ NO formation are well known, removal pathways are less well characterized, particularly in cells that respond to ⋅ NO through activation of soluble guanylate cyclase. Herein, we report that ⋅ NO is catalytically consumed by prostaglandin H synthase-1 (PGHS-1) through acting as a reducing peroxidase substrate. With
purified ovine PGHS-1, ⋅ NO consumption requires peroxide (LOOH or H 2 O 2 ), with a K
m
 (app) for 15( S )hydroperoxyeicosatetraenoic acid (HPETE) of 3.27 ± 0.35 μ m . During this, 2 mol ⋅ NO are consumed per mol HPETE, and loss of HPETE hydroperoxy group occurs with retention of the conjugated diene spectrum.
Hydroperoxide-stimulated ⋅ NO consumption requires heme incorporation, is not inhibited by indomethacin, and is further stimulated by the reducing peroxidase
substrate, phenol. PGHS-1-dependent ⋅ NO consumption also occurs during arachidonate, thrombin, or A23187 activation of platelets (1–2 μ m ·min −1 for typical plasma platelet concentrations) and prevents ⋅ NO stimulation of platelet soluble guanylate cyclase. Platelet sensitivity to ⋅ NO as an inhibitor of aggregation is greater using a platelet-activating stimulus ( U46619 ) that does not cause ⋅ NO consumption, indicating that this mechanism overcomes the anti-aggregatory effects of ⋅ NO. Catalytic consumption of ⋅ NO during eicosanoid synthesis thus represents both a novel proaggregatory function for PGHS-1 and a regulated mechanism for
vascular ⋅ NO removal.