title: Synergistic effect of type II phospholipase A2 and platelet-activating factor on Mac-1 surface expression and exocytosis of gelatinase granules in human neutrophils: evidence for the 5-lipoxygenase-dependent mechanism.
abstract: Stimulation of human neutrophils with inflammatory mediators such as TNF-alpha or platelet-activating factor (PAF) induces translocation of adhesion molecule Mac-1 (CD11b/CD18) from secretory vesicles to the plasma membrane. Type II phospholipase A2 (PLA2-II) also induces translocation of Mac-1 from secretory vesicles. However, there are more Mac-1 molecules in gelatinase granules and specific granules than in secretory vesicles. Therefore, different combinations of PLA2-II and other mediators were examined for their ability to induce gelatinase granules and specific granules to induce Mac-1 surface expression. The combination of PLA2-II and PAF synergistically increased Mac-1 surface expression, and the effect was greater than the combinations of PLA2-II with TNF-alpha, IL-8, or FMLP. Additionally, the combination of PLA2-II and PAF induced exocytosis of both secretory vesicles and gelatinase granules, which did not occur with either PLA2-II alone or PAF alone. The induction was accompanied by marked production of leukotriene B4. AA861, an inhibitor of 5-lipoxygenase, did not inhibit exocytosis of secretory vesicles but did inhibit exocytosis of gelatinase granules and decrease Mac-1 surface expression. It was also found that Ca2+ influx is essential for 5-lipoxygenase activation, because Ni2+, which blocks the influx of extracellular Ca2+, inhibited the production of leukotriene B4. These results suggest that stimulation by the combination of PLA2-II and PAF, unlike stimulation by each mediator alone, causes exocytosis of gelatinase granules via the 5-lipoxygenase pathway, resulting in a synergistic increase in neutrophil Mac-1 surface expression during inflammatory processes.
authors.affiliation: Institute for Drug Discovery Research, Yamanouchi Pharmaceutical Co., Tsukuba, Ibaraki, Japan. takasaki@yamanouchi.co.jp
authors.forename: J
authors.initials: J
authors.lastname: Takasaki
authors.forename: Y
authors.initials: Y
authors.lastname: Kawauchi
authors.forename: Y
authors.initials: Y
authors.lastname: Masuho
mesh_terms: D001094:Arachidonate 5-Lipoxygenase / Q000502:physiology*; D016227:Benzoquinones / Q000494:pharmacology; D002118:Calcium / Q000502:physiology; D003594:Cytoplasmic Granules / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D005089:Exocytosis; D018093:Gelatinases / Q000378:metabolism*; D006801:Humans; D007975:Leukotriene B4 / Q000096:biosynthesis; D016177:Macrophage-1 Antigen / Q000032:analysis*; D009504:Neutrophils / Q000187:drug effects* / Q000378:metabolism; D010741:Phospholipases A / Q000494:pharmacology*; D054467:Phospholipases A2; D010972:Platelet Activating Factor / Q000494:pharmacology*
chemical_list: D016227:Benzoquinones; D016177:Macrophage-1 Antigen; D010972:Platelet Activating Factor; D007975:Leukotriene B4; C036837:2,3,5-trimethyl-6-(12-hydroxy-5,10-dodecadiynyl)-1,4-benzoquinone; D001094:Arachidonate 5-Lipoxygenase; D010741:Phospholipases A; D054467:Phospholipases A2; D018093:Gelatinases; D002118:Calcium