title: Priming of the neutrophil respiratory burst involves p38 mitogen-activated protein kinase-dependent exocytosis of flavocytochrome b558-containing granules.
abstract: The respiratory burst of human neutrophils is primed by a number of pro-inflammatory stimuli, including tumor necrosis factor-alpha (TNFalpha) and lipopolysaccharide (LPS); however, the mechanism of priming remains unknown. LPS has been shown previously to increase membrane expression of flavocytochrome b(558), a component of the NADPH oxidase. This study shows that TNFalpha also increases membrane expression of flavocytochrome b(558). Mitogen-activated protein kinase (MAPK) modules have been implicated in the action of priming agents. Pharmacologic inhibitors of MAPKs, SB203580 and PD098059, revealed that priming of the respiratory burst and up-regulation of flavocytochrome b(558) are dependent on p38 MAPK but not on extracellular-signal regulated kinase (ERK). TNFalpha and LPS primed respiratory burst activity and increased membrane expression of CD35 and CD66b, specific markers of secretory vesicles and specific granules that contain flavocytochrome b(558), with similar time courses and concentration dependences. These processes also required p38 MAPK but were independent of ERK. TNFalpha failed to prime respiratory burst activity or to increase membrane CD35 expression in enucleated neutrophil cytoplasts. These data suggest that one mechanism by which TNFalpha and LPS prime neutrophil respiratory burst activity is by increasing membrane expression of flavocytochrome b(558) through exocytosis of intracellular granules in a process regulated by p38 MAPK.
authors.affiliation: Molecular Signaling Group, Department of Medicine and the Department of Biochemistry and Molecular Biology, University of Louisville, Louisville, Kentucky 40202-1718, USA. richard.ward@louisville.du
authors.forename: R A
authors.initials: RA
authors.lastname: Ward
authors.forename: M
authors.initials: M
authors.lastname: Nakamura
authors.forename: K R
authors.initials: KR
authors.lastname: McLeish
mesh_terms: D015703:Antigens, CD; D000951:Antigens, Neoplasm; D015815:Cell Adhesion Molecules; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D003573:Cytochrome b Group / Q000378:metabolism*; D003594:Cytoplasmic Granules / Q000378:metabolism*; D004789:Enzyme Activation; D005089:Exocytosis; D058851:GPI-Linked Proteins; D006801:Humans; D008070:Lipopolysaccharides / Q000494:pharmacology; D008562:Membrane Glycoproteins / Q000096:biosynthesis; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D019255:NADPH Oxidases; D009504:Neutrophils / Q000502:physiology*; D010587:Phagocytosis / Q000187:drug effects; D017463:Receptors, Complement 3b / Q000096:biosynthesis; D016897:Respiratory Burst; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D048051:p38 Mitogen-Activated Protein Kinases
chemical_list: D015703:Antigens, CD; D000951:Antigens, Neoplasm; C504120:CEACAM8 protein, human; D015815:Cell Adhesion Molecules; D003573:Cytochrome b Group; D058851:GPI-Linked Proteins; D008070:Lipopolysaccharides; D008562:Membrane Glycoproteins; D017463:Receptors, Complement 3b; D014409:Tumor Necrosis Factor-alpha; C036888:cytochrome b558; D019255:NADPH Oxidases; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases