Leukotriene B4 promotes phospholipid acylation in human neutrophils

The present study was undertaken to test the hypothesis that leukotriene B4 (LTB4) may promote extracellular fatty acid incorporation into neutrophil choline glycerophospholipids (PC) to replenish phospholipids after deacylation. Incubation of human neutrophils with LTB4 (1.5 to 150 nM) for 1 to 5 min resulted in increased fatty acid incorporation into phosphatidylinositol (PI), diacyl-sn-glycero-3-phosphocholine (diacyl-GPC) and alkylacyl-GPC. The magnitude of stimulation (percentage of control) of fatty acid incorporation appears to reflect increased activity of the acyltransferase catalyzing acylation of the respective lysophospholipids. LTB4 stimulation of arachidonic acid incorporation into PI was greater than into PC, whereas the stimulation of palmitic acid incorporation into PC was greater than into PI. LTB4 stimulated phosphatidic acid labeling by palmitic acid but not by arachidonic acid. LTB4 and 1-O-alkyl-2-N-methylcarbamyl-sn-glycero-3-phosphocholine (cPAF) exhibited a similar stimulatory effect on fatty acid incorporation into the PC fraction. Phosphate analysis could not detect changes in the mass of PI or of PC in neutrophils exposed to LTB4 or cPAF. The results suggest that increased fatty acid incorporation into phospholipids in LTB4-activated neutrophils reflects activation of phospholipase A2 and acyltransferases as well as of de novo phospholipid synthesis.