title: The inhibition of the constitutive and inducible nitric oxide synthase isoforms by indazole agents.
abstract: Citrulline formation by Ca(2+)-calmodulin (CaM)-dependent nitric oxide synthase from bovine brain is inhibited reversibly by indazole, 5-nitro-, 6-nitro-, and 7-nitroindazole with IC50 values of 2.3 mM, 1.15 mM, 40 microM, and 2.5 microM, respectively. Inhibition of citrulline formation by 7-nitroindazole exhibited a Ki value of 0.16 microM and was competitive versus both arginine substrate and (6R)-5,6,7,8-tetrahydrobiopterin cofactor. The NADPH oxidase activity of bovine brain CaM-dependent nitric oxide synthase was inhibited by 7-nitroindazole with an IC50 value of 0.6 microM. Citrulline formation by the interferon-gamma/lipopolysaccharide-inducible nitric oxide synthase of murine macrophages (264.7 cell line) is inhibited reversibly by indazole, 5-nitro-, 6-nitro-, and 7-nitroindazole with IC50 values of 470, 240, 56, and 20 microM, respectively. Inhibition of citrulline formation by 7-nitroindazole exhibited a Ki value of 1.6 microM and was noncompetitive versus arginine substrate but competitive versus (6R)-5,6,7,8-tetrahydrobiopterin cofactor. None of the indazoles tested inhibited the cytochrome c reductase activity of either nitric oxide synthase isoform at concentrations up to 1000-fold higher than their IC50 values for inhibition of citrulline formation. These observations are consistent with the proposal that the indazoles exert their inhibitory actions by interaction with the heme-iron of nitric oxide synthase such that oxygen does not bind.
authors.affiliation: Department of Pharmacology, University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, Piscataway 08854.
authors.forename: D J
authors.initials: DJ
authors.lastname: Wolff
authors.forename: B J
authors.initials: BJ
authors.lastname: Gribin
mesh_terms: D000594:Amino Acid Oxidoreductases / Q000037:antagonists & inhibitors* / Q000096:biosynthesis; D000818:Animals; D001921:Brain / Q000201:enzymology*; D002147:Calmodulin / Q000494:pharmacology*; D002417:Cattle; D002460:Cell Line; D002956:Citrulline / Q000378:metabolism; D004790:Enzyme Induction; D007093:Imidazoles / Q000494:pharmacology; D007191:Indazoles / Q000494:pharmacology*; D007527:Isoenzymes / Q000037:antagonists & inhibitors* / Q000096:biosynthesis; D007700:Kinetics; D008264:Macrophages / Q000201:enzymology; D051379:Mice; D015394:Molecular Structure; D019001:Nitric Oxide Synthase; D013329:Structure-Activity Relationship
chemical_list: D002147:Calmodulin; D007093:Imidazoles; D007191:Indazoles; D007527:Isoenzymes; D002956:Citrulline; C037738:1-phenylimidazole; D019001:Nitric Oxide Synthase; D000594:Amino Acid Oxidoreductases; C080122:7-nitroindazole