Platelet-activating factor increases leukotriene B4 release in stimulated alveolar macrophages from asthmatic patients.
This study was designed to examine further the role of platelet-activating factor (PAF) in asthma, comparing leukotriene B4 (LTB4) release, 5-lipoxygenase activity and intracellular calcium levels ([Ca2+]i) in macrophages. LTB4 and other lipoxygenase metabolites in macrophages in bronchoalveolar lavage fluids obtained from 23 asthmatic patients and 20 control subjects were measured by reverse-phase high-performance liquid chromatography. [Ca2+]i was monitored using the fluorescent probe fura-2. The basal LTB4 release of resting macrophages was not different between groups (0.02+/-0.01 versus 0.05+/-0.02 ng x 10(-6) cells). When stimulated with calcium ionophore A23187 (2.5 microM), however, macrophages from asthmatic patients released more LTB4 than cells from control subjects (30.2+/-3.4 versus 13.7+/-2.1 ng x 10(-6) cells). Although PAF alone did not alter LTB4 release, it enhanced the response to subsequent A23187 stimulation. This effect was noted following short treatment (i.e., 5 min) at concentrations of > or =1.0 microM PAF, with the maximal effect noted after treatment with 5.0 microM PAF + 2.5 microM A23187 (105.1+/-6.7 versus 15.3+/-2.6 ng x 10(-6) cells). Treatment of macrophages with PAF also increased 5-lipoxygenase activity and [Ca2+]i more in cytosols from asthmatic patients than in cytosols from control subjects. These findings support a role of intracellular calcium in the activation of 5-lipoxygenase which, in turn, augments the release of leukotriene B4. Because levels of platelet-activating factor may be increased in the lung during asthma and can increase the subsequent release of a chemotactic mediator leukotriene B4, from macrophages, these findings suggest that platelet-activating factor may prime the constitutive cells of the lung to augment inflammatory effects important in the pathogenesis of asthma.
Shindo
K
K
First Dept of Internal Medicine, Yokohama City University School of Medicine, Yokohama, Japan.
Koide
K
K
Fukumura
M
M
D000328:Adult; D001094:Arachidonate 5-Lipoxygenase / Q000378:metabolism; D001249:Asthma / Q000378:metabolism*; D001992:Bronchoalveolar Lavage Fluid / Q000166:cytology; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D003600:Cytosol / Q000378:metabolism; D005260:Female; D006801:Humans; D018836:Inflammation Mediators / Q000494:pharmacology; D007476:Ionophores / Q000494:pharmacology; D007975:Leukotriene B4 / Q000378:metabolism*; D016676:Macrophages, Alveolar / Q000187:drug effects* / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D009994:Osmolar Concentration; D010972:Platelet Activating Factor / Q000031:analogs & derivatives / Q000494:pharmacology*; D012016:Reference Values
D018836:Inflammation Mediators; D007476:Ionophores; C029271:O-deacetyl platelet activating factor; D010972:Platelet Activating Factor; D007975:Leukotriene B4; D000001:Calcimycin; D001094:Arachidonate 5-Lipoxygenase; D002118:Calcium