Enhancement of platelet-activating factor-induced leukotriene synthesis in neutrophils by granulocyte-macrophage colony-stimulating factor (GM-CSF): studies on the mechanism of action of GM-CSF.
Preincubation with granulocyte-macrophage colony-stimulating factor (GM-CSF) increased the synthesis of leukotriene B4 and its omega-oxidation products by neutrophils in response to 10(-7) M platelet-activating factor (PAF) by more than 10-fold compared to untreated cells. Pretreatment with GM-CSF also enabled the detection of these products in response to lower concentrations of PAF (greater than or equal to 10(-9) M), under which conditions synthesis of 5-lipoxygenase products was not observed in non-GM-CSF-treated cells. While PAF induced the release of arachidonic acid from neutrophils, GM-CSF alone did not stimulate the release of detectable amounts of the fatty acid. However, the levels of free arachidonic acid in response to PAF were enhanced in neutrophils pretreated with GM-CSF. Similarly, GM-CSF alone did not directly activate the 5-lipoxygenase as determined by the 5-lipoxygenase-mediated transformation of exogenous 15-hydroperoxyeicosatetraenoic acid into 5,15-dihydroxyeicosatetraenoic acid (5,15-diHETE). However, stimulation of neutrophils with PAF resulted in the transformation of the 15-hydroperoxy acid into the 5,15-diHETE, and furthermore, preincubation of neutrophils with GM-CSF resulted in enhanced formation of 5,15-diHETE in response to PAF. Taken together, these data indicate that GM-CSF does not enhance leukotriene synthesis in neutrophils in response to PAF by either directly activating the 5-lipoxygenase or stimulating the liberation of endogenous arachidonic acid, but rather by augmenting the effect of PAF on these two responses.
McColl
S R
SR
Unité de Recherche Inflammation et Immunologie-Rhumatologie, Centre Hospitalier de l'Université Laval, Sainte-Foy, Que., Canada.
Krump
E
E
McDonald
P P
PP
Braquet
M
M
Naccache
P H
PH
Borgeat
P
P
D001094:Arachidonate 5-Lipoxygenase / Q000378:metabolism; D016718:Arachidonic Acid / Q000378:metabolism; D004357:Drug Synergism; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000008:administration & dosage*; D006801:Humans; D006893:Hydroxyeicosatetraenoic Acids / Q000096:biosynthesis; D066298:In Vitro Techniques; D007975:Leukotriene B4 / Q000096:biosynthesis; D015289:Leukotrienes / Q000096:biosynthesis* / Q000378:metabolism; D008054:Lipid Peroxides / Q000378:metabolism; D009504:Neutrophils / Q000187:drug effects / Q000378:metabolism; D010972:Platelet Activating Factor / Q000008:administration & dosage*
D006893:Hydroxyeicosatetraenoic Acids; D015289:Leukotrienes; D008054:Lipid Peroxides; D010972:Platelet Activating Factor; D007975:Leukotriene B4; D016718:Arachidonic Acid; C025086:15-hydroperoxy-5,8,11,13-eicosatetraenoic acid; C034922:5,15-dihydroxy-6,8,11,13-eicosatetraenoic acid; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D001094:Arachidonate 5-Lipoxygenase