Platelet-activating factor modulates phospholipid acylation in human neutrophils |
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Authors: | Jen-sie Tou |
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Affiliation: | (1) Department of Biochemistry, Tulane University School of Medicine, 70112 New Orleans, LA |
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Abstract: | The present study showed that platelet-activating factor (1-O-hexadecyl-2-acetyl-sn-glycero-3-phosphocholine, PAF), but not lysoPAF (1-O-hexadecyl-sn-glycero-3-phosphocholine) rapidly (within 15 sec) stimulated the incorporation of both 1-14C]arachidonate and 1-14C]docosahexaenoate into phosphatidylinositol (PI) and phosphatidylcholine (PC) in human neutrophils. Concomitantly, it inhibited
the formation of labeled phosphatidic acid from both fatty acids. The magnitude of stimulation (percentage of control) was
greater in PI than in PC for the incorporation of arachidonate and vice versa for the incorporation of docosahexaenoate. It
reached a maximum at 10−7 M and started to decline at 10−6 M. Extracellular Ca2+ was not essential for the action of PAF on phospholipid acylation. The distribution of labeled arachidonate in the molecular
species of PC was not altered by PAF after 1 min incubation, suggesting that the increased formation of arachidonyl-PC during
the early stage of neutrophil-PAF interaction was not originated from the added PAF. No measurable changes in the mass of
each phospholipid were detected in neutrophils challenged by PAF from 15 sec to 2 min. The data suggest that the increased
incorporated of extracellular fatty acids into PI and PC elicited by PAF may be secondary to increased deacylation of these
phospholipids, and the magnitude of stimulation reflects the specificity of acyltransferase catalyzing the acylation of lysoPI
and lysoPC by fatty acyl-CoA. |
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