title: Inhibition of phospholipase A(2) abrogates intracellular processing of NADPH-oxidase derived reactive oxygen species in human neutrophils.
abstract: Upon activation of human neutrophils, superoxide can be produced at two cellular sites; either in the plasma membrane, giving extracellular release of oxidants, or in intracellular organelles, resulting in oxidants being retained in the cell. The involvement of phospholipase A(2) (PLA(2)) in phorbol myristate acetate (PMA)-induced activation of the two pools of NADPH-oxidase was investigated using a variety of PLA(2) inhibitors and the oxidase activity was measured by luminol/isoluminol-amplified chemiluminescence (CL). Two of the seven inhibitors were without effect, two inhibitors inhibited both intra- and extracellular ROS production equally, and three inhibitors inhibited intracellular but not extracellular CL. Using another technique to measure ROS, PHPA oxidation, we found that intracellular ROS production was unaltered with the three last inhibitors, indicating that PLA(2) is not involved in the NADPH-oxidase activity per se, but in the intracellular processing of the radicals necessary for the CL reaction to take place. The PLA(2) inhibitors did not abolish the activity of myeloperoxidase (MPO), an enzyme necessary for intracellular CL to occur. Instead, we suggest that these PLA(2) inhibitors block heterotypic granule fusion and prohibit the colocalization of ROS and MPO needed for intracellular CL activity.
authors.affiliation: The Phagocyte Research Laboratory, Department of Rheumatology and Inflammation Research, Sahlgrenska Academy, University of Gothenburg, Gothenburg 41346, Sweden. halla.bjornsdottir@rheuma.gu.se
authors.forename: Halla
authors.initials: H
authors.lastname: Björnsdottir
authors.forename: Daniel
authors.initials: D
authors.lastname: Granfeldt
authors.forename: Amanda
authors.initials: A
authors.lastname: Welin
authors.forename: Johan
authors.initials: J
authors.lastname: Bylund
authors.forename: Anna
authors.initials: A
authors.lastname: Karlsson
mesh_terms: D002273:Carcinogens / Q000494:pharmacology; D002462:Cell Membrane / Q000378:metabolism*; D002478:Cells, Cultured; D025802:Electric Capacitance; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005434:Flow Cytometry; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism; D009249:NADP / Q000378:metabolism; D019255:NADPH Oxidases / Q000378:metabolism*; D009504:Neutrophils / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D010084:Oxidation-Reduction; D009195:Peroxidase / Q000378:metabolism; D064801:Phospholipase A2 Inhibitors; D054467:Phospholipases A2 / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism*; D013481:Superoxides / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
chemical_list: D002273:Carcinogens; D004791:Enzyme Inhibitors; D064801:Phospholipase A2 Inhibitors; D017382:Reactive Oxygen Species; D013481:Superoxides; D009249:NADP; D006861:Hydrogen Peroxide; D009195:Peroxidase; D019255:NADPH Oxidases; D054467:Phospholipases A2; D013755:Tetradecanoylphorbol Acetate