title: Inhibition of myeloperoxidase by salicylhydroxamic acid.
abstract: Salicylhydroxamic acid inhibited the luminol-dependent chemiluminescence of human neutrophils stimulated by phorbol 12-myristate 13-acetate or the chemotactic peptide N-formylmethionyl-leucyl-phenylalanine (fMet-Leu-Phe). This compound had no inhibitory effect on the kinetics of O2.- generation or O2 uptake during the respiratory burst, but inhibited both the peroxidative activity of purified myeloperoxidase and the chemiluminescence generated by a cell-free myeloperoxidase/H2O2 system. The concentration of salicylhydroxamic acid necessary for complete inhibition of myeloperoxidase activity was 30-50 microM (I50 values of 3-5 microM) compared with the non-specific inhibitor NaN3, which exhibited maximal inhibition at 100-200 microM (I50 values of 30-50 microM). Whereas taurine inhibited the luminol chemiluminescence of an H2O2/HOC1 system by HOC1 scavenging, this compound had little effect on myeloperoxidase/H2O2-dependent luminol chemiluminescence; in contrast, 10 microM-salicylhydroxamic acid did not quench HOC1 significantly but greatly diminished myeloperoxidase/H2O2-dependent luminol chemiluminescence, indicating that its effects on myeloperoxidase chemiluminescence were largely due to peroxidase inhibition rather than non-specific HOC1 scavenging. Salicylhydroxamic acid prevented the formation of myeloperoxidase Compound II, but only at low H2O2 concentrations, suggesting that it may compete for the H2O2-binding site on the enzyme. These data suggest that salicylhydroxamic acid may be used as a potent inhibitor to delineate the function of myeloperoxidase in neutrophil-mediated inflammatory events.
authors.affiliation: Department of Biochemistry, University of Liverpool, U.K.
authors.forename: B
authors.initials: B
authors.lastname: Davies
authors.forename: S W
authors.initials: SW
authors.lastname: Edwards
mesh_terms: D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism; D008163:Luminescent Measurements; D009504:Neutrophils / Q000187:drug effects / Q000201:enzymology*; D009195:Peroxidase / Q000378:metabolism*; D012457:Salicylamides / Q000494:pharmacology*; D013654:Taurine / Q000494:pharmacology
chemical_list: D012457:Salicylamides; D013654:Taurine; C005703:salicylhydroxamic acid; D006861:Hydrogen Peroxide; D009195:Peroxidase