Inhibitory effects and spectral interactions of isomeric methoxyindazoles on recombinant nitric oxide synthases.
A series of isomeric methoxyindazoles has been evaluated as inhibitors of purified recombinant neuronal, inducible, and endothelial nitric oxide synthases (NOS). 7-Methoxyindazole (7-MI) was the most active compound of this series and displayed selectivity toward the constitutive neuronal (NOS I) and endothelial (NOS III) NOS isoforms, the inducible NOS II being almost insensitive to this inhibitor. 6-, 5-, and 4-Methoxyindazoles were almost inactive against all three NOS isoforms. Inhibition of NO and citrulline formation catalyzed by neuronal NOS in the presence of 7-MI appeared to be competitive versus both substrate L-arginine (L-arg) and (6R)-5,6,7,8-tetrahydrobiopterin (BH(4)) cofactor. 7-MI only slightly inhibited NADPH oxidase activity and was inactive against the cytochrome c (cyt c) reductase activity of neuronal NOS at concentrations up to 100-fold higher than its IC(50) value for inhibition of citrulline formation. UV/Vis and EPR studies indicated that 7-MI interacts with the oxygenase domain of neuronal NOS (NOS I(oxy)) in an identical manner but with a much lower affinity than 7-nitroindazole (7-NI). These results demonstrate that an indazole derivative bearing an electron-rich substituent in the 7-position is also a NOS I inhibitor and that such a compound presents strong similarities with the mechanism of inhibition of 7-NI.
Tuynman
Antonin
A
Laboratoire de Chimie et Biochimie Pharmacologiques et Toxicologiques, UMR CNRS 8601, Université R. Descartes, 45 rue des Saints Pères, 75270 Paris Cedex 06, France.
Pérollier
Céline
C
Frapart
Yves
Y
Schumann-Bard
Pascale
P
Collot
Valérie
V
Rault
Sylvain
S
Boucher
Jean-Luc
JL
D001120:Arginine / Q000378:metabolism; D002956:Citrulline / Q000378:metabolism; D045304:Cytochromes c / Q000378:metabolism; D004578:Electron Spin Resonance Spectroscopy; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D007191:Indazoles / Q000494:pharmacology*; D007527:Isoenzymes; D009249:NADP / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D013056:Spectrophotometry, Ultraviolet
D004791:Enzyme Inhibitors; D007191:Indazoles; D007527:Isoenzymes; D011994:Recombinant Proteins; D002956:Citrulline; D009249:NADP; D045304:Cytochromes c; D001120:Arginine; D019001:Nitric Oxide Synthase