title: Enhancement of leukotriene B4 release in stimulated asthmatic neutrophils by platelet activating factor.
abstract: BACKGROUND
  The role of platelet activating factor (PAF) in asthma remains controversial. The priming effect of PAF on leukotriene B4 (LTB4) release, 5-lipoxygenase activity, and intracellular calcium levels in asthmatic neutrophils was examined.
  
  
  METHODS
  LTB4 and other lipoxygenase metabolites in neutrophils obtained from 17 asthmatic patients and 15 control subjects were measured by reverse phase-high performance liquid chromatography (RP-HPLC). Intracellular calcium levels were monitored using the fluorescent probe fura-2.
  
  
  RESULTS
  The mean (SD) basal LTB4, release from neutrophils was not significantly different between the two groups (0.05 (0.01) vs 0.03 (0.02) ng/10(6) cells); however, when stimulated with calcium ionophore A23187 (2.5 microM), neutrophils from asthma patients released more LTB4 than cells from control subjects (15.7 (1.2) vs 9.9 (1.6) ng/10(6) cells). Although PAF alone did not alter LTB4 release, it enhanced the response to subsequent A23187 stimulation. This effect was observed following treatment for five minutes with PAF at concentrations > 1.0 microM. The maximal effect was seen with 5.0 microM PAF + 2.5 microM A23187 (62.7 (2.2) vs 18.6 (2.3) ng/10(6) cells). Pretreatment with PAF also increased 5-lipoxygenase activity and intracellular calcium levels in neutrophils from asthmatic patients to a greater extent than in those from non-asthmatic patients.
  
  
  CONCLUSIONS
  These findings indicate that, in neutrophils from asthmatic patients, PAF enhances LTB4 release and increases 5-lipoxygenase activity and intracellular calcium to a greater extent than in neutrophils from non-asthmatic patients.
authors.affiliation: First Department of Internal Medicine, Yokohama City University School of Medicine, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Shindo
authors.forename: K
authors.initials: K
authors.lastname: Koide
authors.forename: M
authors.initials: M
authors.lastname: Fukumura
mesh_terms: D000328:Adult; D001094:Arachidonate 5-Lipoxygenase / Q000378:metabolism; D001249:Asthma / Q000276:immunology*; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D003600:Cytosol / Q000378:metabolism; D005260:Female; D006801:Humans; D007476:Ionophores / Q000494:pharmacology; D007975:Leukotriene B4 / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D009504:Neutrophils / Q000187:drug effects* / Q000378:metabolism; D010972:Platelet Activating Factor / Q000494:pharmacology*; D013268:Stimulation, Chemical
chemical_list: D007476:Ionophores; D010972:Platelet Activating Factor; D007975:Leukotriene B4; D000001:Calcimycin; D001094:Arachidonate 5-Lipoxygenase; D002118:Calcium