title: Neutrophil azurophilic granule exocytosis is primed by TNF-α and partially regulated by NADPH oxidase.
abstract: Neutrophil (polymorphonuclear leukocyte) activation with release of granule contents plays an important role in the pathogenesis of acute lung injury, prompting clinical trials of inhibitors of neutrophil elastase. Despite mounting evidence for neutrophil-mediated host tissue damage in a variety of disease processes, mechanisms regulating azurophilic granule exocytosis at the plasma membrane, and thus release of elastase and other proteases, are poorly characterized. We hypothesized that azurophilic granule exocytosis would be enhanced under priming conditions similar to those seen during acute inflammatory events and during chronic inflammatory disease, and selected the cytokine TNF-α to model this in vitro. Neutrophils stimulated with TNF-α alone elicited intracellular reactive oxygen species (ROS) generation and mobilization of secretory vesicles, specific, and gelatinase granules. p38 and ERK1/2 MAPK were involved in these components of priming. TNF-α priming alone did not mobilize azurophilic granules to the cell surface, but did markedly increase elastase release into the extracellular space in response to secondary stimulation with N-formyl-Met-Leu-Phe (fMLF). Priming of fMLF-stimulated elastase release was further augmented in the absence of NADPH oxidase-derived ROS. Our findings provide a mechanism for host tissue damage during neutrophil-mediated inflammation and suggest a novel anti-inflammatory role for the NADPH oxidase.
authors.affiliation: 1 Department of Pediatrics, University of Texas Southwestern Medical Center, USA.
authors.forename: Renee M
authors.initials: RM
authors.lastname: Potera
authors.affiliation: 2 Department of Pediatrics, The University of Iowa, USA.|3 The Inflammation Program, The University of Iowa and Veterans Affairs Medical Center, USA.
authors.forename: Melissa J
authors.initials: MJ
authors.lastname: Jensen
authors.affiliation: 2 Department of Pediatrics, The University of Iowa, USA.|3 The Inflammation Program, The University of Iowa and Veterans Affairs Medical Center, USA.
authors.forename: Brieanna M
authors.initials: BM
authors.lastname: Hilkin
authors.affiliation: 2 Department of Pediatrics, The University of Iowa, USA.
authors.forename: Gina K
authors.initials: GK
authors.lastname: South
authors.affiliation: 1 Department of Pediatrics, University of Texas Southwestern Medical Center, USA.|4 Department of Microbiology, University of Texas Southwestern Medical Center, USA.
authors.forename: Jessica S
authors.initials: JS
authors.lastname: Hook
authors.affiliation: 2 Department of Pediatrics, The University of Iowa, USA.|3 The Inflammation Program, The University of Iowa and Veterans Affairs Medical Center, USA.
authors.forename: Emily A
authors.initials: EA
authors.lastname: Gross
authors.affiliation: 1 Department of Pediatrics, University of Texas Southwestern Medical Center, USA.|4 Department of Microbiology, University of Texas Southwestern Medical Center, USA.
authors.forename: Jessica G
authors.initials: JG
authors.lastname: Moreland
mesh_terms: D055371:Acute Lung Injury / Q000276:immunology*; D001399:Azure Stains / Q000737:chemistry; D015550:Cell Degranulation; D002478:Cells, Cultured; D005089:Exocytosis; D018093:Gelatinases / Q000378:metabolism; D006801:Humans; D019272:Leukocyte Elastase / Q000378:metabolism*; D020935:MAP Kinase Signaling System; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000378:metabolism; D019255:NADPH Oxidases / Q000378:metabolism*; D018375:Neutrophil Activation; D009504:Neutrophils / Q000276:immunology*; D017382:Reactive Oxygen Species / Q000378:metabolism; D022142:Secretory Vesicles / Q000737:chemistry / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000276:immunology; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D001399:Azure Stains; D017382:Reactive Oxygen Species; D014409:Tumor Necrosis Factor-alpha; D009240:N-Formylmethionine Leucyl-Phenylalanine; D019255:NADPH Oxidases; D048051:p38 Mitogen-Activated Protein Kinases; D019272:Leukocyte Elastase; D018093:Gelatinases
keywords: Elastase; NADPH oxidase 2; inflammation; priming; reactive oxygen species; signaling