Effect of Arachidonic Acid Reacylation on Leukotriene Biosynthesis in Human Neutrophils Stimulated with Granulocyte-macrophage Colony-stimulating Factor and Formyl-methionyl-leucyl-phenylalanine

Simona Zarini, Miguel A. Gijón, Giancarlo Folco, Robert C. Murphy
2006 Journal of Biological Chemistry  
Priming of human neutrophils with granulocyte-macrophage colony-stimulating factor (GM-CSF) followed by treatment with formyl-methionyl-leucyl-phenylalanine (fMLP) stimulates cells in a physiologically relevant manner with modest 5-lipoxygenase activation and formation of leukotrienes. However, pretreatment of neutrophils with thimerosal, an organomercury thiosalicylic acid derivative, led to a dramatic increase (>50-fold) in the production of leukotriene B 4 and 5-hydroxyeicosatetraenoic acid,
more » ... osatetraenoic acid, significantly higher than that observed after stimulation with calcium ionophore A23187. Little or no effect was observed with thimerosal alone or in combination with either GM-CSF or fMLP. Elevation of [Ca 2؉ ] i induced by thimerosal in neutrophils stimulated with GM-CSF/ fMLP was similar but more sustained compared with samples where thimerosal was absent. However, [Ca 2؉ ] i was significantly lower compared with calcium ionophore-treated cells, suggesting that a sustained calcium rise was necessary but not sufficient to explain the effects of this compound on the GM-CSF/fMLP-stimulated neutrophil. Thimerosal was found to directly inhibit neutrophil lysophospholipid:acyl-CoA acyltransferase activity at the doses that stimulate leukotriene production, and analysis of lysates from neutrophil preparations stimulated in the presence of thimerosal showed a marked increase in free arachidonic acid, supporting the inhibition of the reincorporation of this fatty acid into the membrane phospholipids as a mechanism of action for this compound. The dramatic increase in production of leukotrienes by neutrophils when a physiological stimulus such as GM-CSF/fMLP is employed in the presence of thimerosal suggests a critical regulatory role of arachidonate reacylation that limits leukotriene biosynthesis in concert with 5-lipoxygenase and cytosolic phospholipase A 2 ␣ activation.
doi:10.1074/jbc.m510783200 pmid:16495221 fatcat:5fkeeynyknep5itcrsa5kg2gze