title: Biphasic regulation of leukocyte superoxide generation by nitric oxide and peroxynitrite.
abstract: Activation of the NADPH oxidase-derived oxidant burst of polymorphonuclear leukocytes (PMNs) is of critical importance in inflammatory disease. PMN-derived superoxide (O(2)) can be scavenged by nitric oxide (NO( small middle dot)) with the formation of peroxynitrite (ONOO(-)); however, questions remain regarding the effects and mechanisms by which NO( small middle dot) and ONOO(-) modulate the PMN oxidative burst. Therefore, we directly measured the dose-dependent effects of NO( small middle dot) and ONOO(-) on O(2) generation from human PMNs stimulated with phorbol 12-myristate 13-acetate using EPR spin trapping. Pretreatment with low physiological (microm) concentrations of NO( small middle dot) from NO( small middle dot) gas had no effect on PMN O(2) generation, whereas high levels (> or =50 microm) exerted inhibition. With ONOO(-) pretreatment, however, a biphasic modulation of O(2) generation was seen with stimulation by microm levels, but inhibition at higher levels. With the NO( small middle dot) donor NOR-1, which provides more sustained release of NO( small middle dot) persisting at the time of O(2) generation, a similar biphasic modulation of O(2) generation was seen, and this was inhibited by ONOO(-) scavengers. The enhancement of O(2) generation by low concentrations of ONOO(-) or NOR-1 was associated with activation of the ERK MAPKs and was blocked by their inhibition. Thus, low physiological levels of NO( small middle dot) present following PMN activation are converted to ONOO(-), which enhances O(2) generation through activation of the ERK MAPK pathway, whereas higher levels of NO( small middle dot) or ONOO(-) feed back and inhibit O(2) generation. This biphasic concentration-dependent regulation of the PMN oxidant burst by NO( small middle dot)-derived ONOO(-) may be of critical importance in regulating the process of inflammation.
authors.affiliation: Molecular and Cellular Biophysics Laboratories, Department of Medicine, Division of Cardiology and the Electron Paramagnetic Resonance Center, The John Hopkins Institutions, Baltimore, MD 21224, USA.
authors.forename: C
authors.initials: C
authors.lastname: Lee
authors.forename: K
authors.initials: K
authors.lastname: Miura
authors.forename: X
authors.initials: X
authors.lastname: Liu
authors.forename: J L
authors.initials: JL
authors.lastname: Zweier
mesh_terms: D015153:Blotting, Western; D004268:DNA-Binding Proteins / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004578:Electron Spin Resonance Spectroscopy; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005290:Ferric Compounds / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D006801:Humans; D007249:Inflammation; D008665:Metalloporphyrins / Q000494:pharmacology; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D019255:NADPH Oxidases / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000378:metabolism; D009504:Neutrophils / Q000378:metabolism*; D009566:Nitrates / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism; D010766:Phosphorylation; D011987:Receptors, Steroid; D011988:Receptors, Thyroid Hormone; D019097:Spin Trapping; D013481:Superoxides / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013997:Time Factors
chemical_list: C112917:5,10,15,20-tetrakis(2,4,6-trimethyl-3,3-disulfonatophenyl)porphyrinato iron(III); D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D005290:Ferric Compounds; D005419:Flavonoids; D008665:Metalloporphyrins; C490412:NR4A3 protein, human; D009419:Nerve Tissue Proteins; D009566:Nitrates; D011987:Receptors, Steroid; D011988:Receptors, Thyroid Hormone; D013481:Superoxides; C039642:peroxynitric acid; D009569:Nitric Oxide; D019255:NADPH Oxidases; D020928:Mitogen-Activated Protein Kinases; D020929:Mitogen-Activated Protein Kinase Kinases; D013755:Tetradecanoylphorbol Acetate; D010100:Oxygen; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one