title: Ionomycin-induced neutrophil NADPH oxidase activity is selectively inhibited by the serine protease inhibitor diisopropyl fluorophosphate.
abstract: The calcium-specific ionophore ionomycin triggers neutrophils to activate their NADPH oxidase and generate reactive oxygen species. This activation is restricted to intracellular sites and involves the neutrophil granules. Cells that have experienced an ionomycin-induced rise in intracellular calcium will also mobilize their intracellular granules and are primed to subsequent challenge with the chemoattractant formylmethionyl-leucyl-phenylalanine (fMLF), but have lost their ability to become desensitized to the same agonist. We have investigated the involvement of serine proteases in the calcium-induced effector functions using the inhibitor diisopropyl fluorophosphate (DFP). The ionomycin-induced NADPH oxidase activity was abrogated by the protease inhibitor, whereas the activity induced by fMLF was unaffected. The DFP-dependent inhibition was restricted to the NADPH oxidase activity, as all other ionomycin-induced cellular activities were largely unaffected. We thus suggest that a serine protease is of importance for the calcium ionophore-induced signal(s) to reach and activate the dormant NADPH oxidase in the neutrophil granules.
authors.affiliation: The Phagocyte Research Laboratory, Department of Rheumatology, University of Göteborg, Göteborg, Sweden. Claes.Dahlgren@microbio.gu.se
authors.forename: Claes
authors.initials: C
authors.lastname: Dahlgren
authors.forename: Anna
authors.initials: A
authors.lastname: Karlsson
mesh_terms: D002474:Cell-Free System; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D015759:Ionomycin / Q000494:pharmacology*; D007476:Ionophores / Q000494:pharmacology*; D007531:Isoflurophate / Q000494:pharmacology*; D008163:Luminescent Measurements; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology; D019255:NADPH Oxidases / Q000378:metabolism*; D009504:Neutrophils / Q000201:enzymology* / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism; D010587:Phagocytosis; D017382:Reactive Oxygen Species; D012694:Serine / Q000378:metabolism; D015842:Serine Proteinase Inhibitors / Q000494:pharmacology*; D013347:Subcellular Fractions / Q000378:metabolism; D013481:Superoxides; D013997:Time Factors
chemical_list: D007476:Ionophores; D017382:Reactive Oxygen Species; D015842:Serine Proteinase Inhibitors; D013481:Superoxides; D007531:Isoflurophate; D012694:Serine; D015759:Ionomycin; D009240:N-Formylmethionine Leucyl-Phenylalanine; D006861:Hydrogen Peroxide; D019255:NADPH Oxidases; D010100:Oxygen