title: Electron spin resonance spectroscopy does not reveal hydroxyl radical production in activated natural killer lymphocytes.
abstract: We investigated hydroxyl radical (OH) production by human natural killer (NK) cells, using electron spin resonance (ESR) spectroscopy and 5.5 dimethyl-1-pyrroline-N-oxide (DMPO), a spin trap specific for OH. production. We confirmed that hydroxyl radical scavengers, n-propyl gallate and catechin, inhibited NK cell-mediated cytotoxicity (NK-CMC) in a dose-dependent manner and demonstrated that DMPO also inhibited NK-CMC. Polymorphonuclear leukocytes (PMNL) activated by opsonized zymosan (2.4 mg/ml) and mixed with DMPO (0.14 M) showed an early increase in hydroxyl radical production, leading to a net production of free radical of almost 400 pMol/10(6) cells. We then mixed NK cells with K562, an NK-sensitive tumor cell, at a 1:1 ratio and added DMPO (0.14 M). We pelleted the cells to increase EC to TC binding before taking the sample readings. Activated NK cells showed no increase in OH. production, leading to a net production of free radicals less than 1% that of activated PMNL. These data strongly suggest that hydroxyl radical production does not play a role in the early events of NK cell activation; they indicate a need to reevaluate the mechanism of inhibition of NK-CMC by OH. scavengers.
authors.affiliation: Department of Microbiology, Indiana University School of Medicine, Indianapolis 46223.
authors.forename: J J
authors.initials: JJ
authors.lastname: Gibboney
authors.forename: R A
authors.initials: RA
authors.lastname: Haak
authors.forename: F W
authors.initials: FW
authors.lastname: Kleinhans
authors.forename: Z
authors.initials: Z
authors.lastname: Brahmi
mesh_terms: D000920:Antibody-Dependent Cell Cytotoxicity; D003497:Cyclic N-Oxides / Q000494:pharmacology; D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals; D006801:Humans; D006878:Hydroxides; D017665:Hydroxyl Radical; D007694:Killer Cells, Natural / Q000378:metabolism*; D008213:Lymphocyte Activation; D009504:Neutrophils / Q000378:metabolism; D015054:Zymosan / Q000494:pharmacology
chemical_list: D003497:Cyclic N-Oxides; D005609:Free Radicals; D006878:Hydroxides; D017665:Hydroxyl Radical; C017245:5,5-dimethyl-1-pyrroline-1-oxide; D015054:Zymosan