Differential activation of phospholipids metabolism by formylated peptide and ionophore A23187 in guinea pig peritoneal macrophages.

Effect of formyl-methionyl-leucyl-phenylalanine (fMLP), Ca2+ ionophore A23187, migration inhibitory factor (MIF), or lipopolysaccharide (LPS) on the incorporation of [32P] Pi into various phospholipids was examined in guinea pig peritoneal macrophages. Formylated peptide activated [32P]Pi incorporation into phosphatidylinositol (PI) and phosphatidic acid (PA) without any effects on the labeling of other phospholipids. Ionophore A23187 also enhanced [32P]Pi incorporation into PI and PA, although unlike fMLP, it caused inhibition of [32P]Pi incorporation into phosphatidylethanolamine (PE), phosphatidylcholine (PC), and phosphatidylserine (PS). On the other hand, MIF and LPS did not affect [32P]Pi labeling of such phospholipids. Lysosomal enzyme N-acetyl-β-D-glucosaminidase secretion from cytochalasin B-treated macrophages was enhanced by fMLP and A23187. Furthermore, a close correlation between lysosomal enzyme secretion and PI response was obtained, namely, the dose-dependent relationship of secretion was similar to that of [32P]Pi labeling of PI or PA. Formylated peptide did not show any significant effect on the incorporation of [3H]glycerol into glycerolipids, suggesting that de novo synthesis of PI and PA from glycerol-3-phosphate was not stimulated. On the other hand, A23187 increased the incorporation of [3H]glycerol into PA and diacylglycerol (DG). Labeling of other lipids, such as PC, PE, PS, and triacylglycerol (TG) was rather suppressed. These results show that the synthetic pathway from DG or PA to PC, PE, PS, and TG was inhibited and may have caused a resultant accumulation of DG and PA. Effect of fMLP or A23187 on the degradation of [14C]glycerol-labeled lipids was also studied. The degradation of [14C]glycerol-PI was stimulated by fMLP, and a resultant increase in [14C]glycerol-DG was observed. A23187 did not increase the breakdown of [14C]glycerol-PI, -PE, -PC, and -PS, but enhanced that of TG to DG. Formylated peptide and A23187 also caused a significant change of [3H]arachidonic acid moiety in various lipids. When [3H]arachidonic acid-labeled macrophages were stimulated by fMLP, a loss of [3H]arachidonic acid moiety in PI and a resultant increase of it in DG, PA, and free [3H]arachidonic acid was demonstrated. Thus, it became clear that fMLP stimulated arachidonic acid release via pathway PI → DG → FFA. Ionophore A23187 also enhanced release of [3H]arachidonic acid and accumulation of [3H]arachidonyl-PA and -DG, whereas [3H]arachidonyl-PC, -PE, -PI, and -PS were decreased by A23187, suggesting that A23187 activates arachidonic acid release via transesterification from arachidonyl-phospholipids to PA and pathway PA → DG → FFA, in addition to phospholipase A2 activation.