title: Myeloperoxidase potentiates nitric oxide-mediated nitrosation.
abstract: Nitrosation is an important reaction elicited by nitric oxide (NO). To better understand how nitrosation occurs in biological systems, we assessed the effect of myeloperoxidase (MPO), a mediator of inflammation, on nitrosation observed during NO autoxidation. Nitrosation of 2-amino-3-methylimidazo[4,5-f]quinoline (IQ; 10 mum) to 2-nitrosoamino-3-methylimidazo[4,5-f]quinoline (N-NO-IQ) was monitored by HPLC. Using the NO donor spermine NONOate at pH 7.4, MPO potentiated N-NO-IQ formation. The minimum effective quantity of necessary components was 8.5 nm MPO, 0.25 mum H(2)O(2)/min, and 0.024 mum NO/min. Autoxidation was only detected at >/=1.2 mum NO/min. MPO potentiation was not affected by a 40-fold excess flux of H(2)O(2) over NO or less than a 2.4-fold excess flux of NO over H(2)O(2). Potentiation was due to an 8.8-fold increased affinity of MPO-derived nitrosating species for IQ. Autoxidation was inhibited by azide, suggesting involvement of the nitrosonium ion, NO(+). MPO potentiation was inhibited by NADH, but not azide, suggesting oxidative nitrosylation with NO(2)(.) or an NO(2)(.)-like species. MPO nonnitrosative oxidation of IQ with 0.3 mm NO(2)(-) at pH 5.5 was inhibited by azide, but not NADH, demonstrating differences between MPO oxidation of IQ with NO compared with NO(2)(-). Using phorbol ester-stimulated human neutrophils, N-NO-IQ formation was increased with superoxide dismutase and inhibited by catalase and NADH, but not NaN(3). This is consistent with nitrosation potentiation by MPO, not peroxynitrite. Increased N-NO-IQ formation was not detected with polymorphonuclear neutrophils from two unrelated MPO-deficient patients. Results suggest that the highly diffusible stable gas NO could initiate nitrosation at sites of neutrophil infiltration.
authors.affiliation: Veterans Administration Medical Center, St. Louis, Missouri 63125, USA.
authors.forename: Vijaya M
authors.initials: VM
authors.lastname: Lakshmi
authors.forename: William M
authors.initials: WM
authors.lastname: Nauseef
authors.forename: Terry V
authors.initials: TV
authors.lastname: Zenser
mesh_terms: D002851:Chromatography, High Pressure Liquid; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism; D009504:Neutrophils / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism*; D010084:Oxidation-Reduction; D009195:Peroxidase / Q000378:metabolism*
chemical_list: D009569:Nitric Oxide; D006861:Hydrogen Peroxide; D009195:Peroxidase