title: Role of myeloperoxidase in the killing of Staphylococcus aureus by human neutrophils: studies with the myeloperoxidase inhibitor salicylhydroxamic acid.
abstract: We have used salicylhydroxamic acid (SHAM) to inhibit intraphagosomal myeloperoxidase activity in order to evaluate the role of this enzyme in the killing of Staphylococcus aureus by human neutrophils. 50 microM-SHAM reduced the luminol-dependent chemiluminescence response stimulated during phagocytosis of unopsonized latex beads and opsonized S. aureus by over 80% and 60%, respectively. When opsonized S. aureus were incubated with neutrophils, 45% were killed within 15 min incubation and 60% by 1 h. However, in neutrophil suspensions incubated with 50 microM-SHAM, only 13% were killed by 15 min whilst 71% still remained viable after 1 h. This inhibitor had no effect upon the number of bacteria phagocytosed or upon degranulation. In a cell-free system, 2.5 microM-H2O2 alone killed 55% of the bacteria, whereas in the presence of myeloperoxidase (i.e. 10 mU myeloperoxidase and 2.5 microM-H2O2) virtually all of the bacteria were killed: the addition of 50 microM-SHAM abolished this myeloperoxidase-enhanced killing but did not affect the H2O2-dependent killing. We therefore conclude that in normal neutrophils whilst H2O2 is required for killing of this pathogen, both myeloperoxidase-dependent and -independent pathways exist.
authors.affiliation: Department of Biochemistry, University of Liverpool, UK.
authors.forename: J M
authors.initials: JM
authors.lastname: Humphreys
authors.forename: B
authors.initials: B
authors.lastname: Davies
authors.forename: C A
authors.initials: CA
authors.lastname: Hart
authors.forename: S W
authors.initials: SW
authors.lastname: Edwards
mesh_terms: D015550:Cell Degranulation; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism; D008163:Luminescent Measurements; D009504:Neutrophils / Q000201:enzymology* / Q000502:physiology; D009895:Opsonin Proteins / Q000276:immunology; D010100:Oxygen / Q000378:metabolism; D009195:Peroxidase / Q000037:antagonists & inhibitors / Q000502:physiology*; D010587:Phagocytosis; D012457:Salicylamides / Q000494:pharmacology*; D013211:Staphylococcus aureus
chemical_list: D009895:Opsonin Proteins; D012457:Salicylamides; C005703:salicylhydroxamic acid; D006861:Hydrogen Peroxide; D009195:Peroxidase; D010100:Oxygen