Characteristics of 1- O-hexadecyl- and 1- O-octadecyl-2- O-acetyl-Sn-Glyceryl-3-phosphorylcholine-stimulated granule enzyme release from human neutrophils

Abstract

1- O-Hexadecyl-2- O-acetyl- sn-glyceryl-3-phosphorylcholine (C 16-AGEPC) and 1- O-octadecyl-2- O-acetyl- sn-glyceryl-3-phosphorylcholine (C 18-AGEPC) stimulated a time- and concentration-dependent release of granule-associated lysozyme and β-glucuronidase from human neutrophils. Maximum discharge of granule enzymes occurred between 30 and 60 sec after neutrophil exposure to C 16- or C 18-AGEPC (0.01–10 μ M). Less than 10% of total enzyme activity is released when cells are not preincubated with cytochalasin B prior to interaction with the AGEPC analogs. A time-dependent desensitization for granule exocytosis was observed in neutrophils which were stimulated with C 18-AGEPC prior to contact with cytochalasin B. The rate and amount of enzyme released by C 16- and C 18-AGEPC activated neutrophils was significantly enhanced in the presence of extracellular calcium. Trifluoperazine, an inhibitor of calmodulin, caused a dose-related suppression of C 18-AGEPC-induced degranulation. Granule enzyme extrusion from C 18-AGEPC-treated neutrophils was inhibited by the sulfhydryl reagents, N-ethylmaleimide and iodoacetic acid, and by the glycolytic inhibitor, 2-deoxy- d-glucose. Sodium cyanide was inactive. Pretreatment of neutrophils with C 16- or C 18-AGEPC rendered the cells unresponsive to subsequent exposure to either AGEPC analog. C 18-AGEPC-induced desensitization of neutrophil degranulation appears to be stimulus specific in that serum-treated zymosan and N-formyl-methionyl-leucyl-phenylalanine were capable of eliciting granule enzyme release from C 18-AGEPC-pretreated cells.