title: Platelet-activating factor as an intercellular signal in neutrophil-dependent platelet activation.
abstract: The role of platelet-activating factor (PAF) in heterotypic cell to cell interactions in a rabbit neutrophil-platelet mixture model was investigated. Platelets were exposed to each of three chemotactic agonists: PAF, leukotriene B4 (LTB4), or FMLP. Only PAF stimulated aggregation, [3H]serotonin secretion, and cytosolic Ca2+ mobilization in platelets alone. However, platelets were stimulated by LTB4 and FMLP in the presence of neutrophils. This neutrophil-dependent platelet activation was blocked by pretreatment of platelets with PAF receptor antagonists, and was prevented by desensitization of platelets to PAF. Furthermore, the time-course of platelet activation showed a positive correlation with PAF production by neutrophils stimulated with either LTB4 or FMLP. The PAF-mediated neutrophil-platelet interaction was dependent on direct cell to cell contact, as demonstrated by experiments in which the majority of newly formed PAF was neutrophil associated (rather than released). Platelet activation did not occur when the neutrophil-platelet mixture was not stirred, minimizing cell to cell contact, or when platelets were challenged with a cell-free supernatant prepared from neutrophils activated with LTB4 or FMLP. Finally, the neutrophil-platelet interaction was abolished by SC-49992, a peptidomimetic of the fibrinogen binding sequence Arg-Gly-Asp-Phe, indicating a Arg-Gly-Asp-specific recognition mechanism. Our results demonstrate that neutrophil-generated PAF plays a crucial role in neutrophil-dependent platelet activation in this model system. This type of intercellular signaling event may be important in certain inflammatory or thrombotic processes.
authors.affiliation: Department of Biochemistry, University of Texas Health Science Center, San Antonio 78284.
authors.forename: W
authors.initials: W
authors.lastname: Zhou
authors.forename: M A
authors.initials: MA
authors.lastname: Javors
authors.forename: M S
authors.initials: MS
authors.lastname: Olson
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001381:Azepines / Q000494:pharmacology; D001792:Blood Platelets / Q000378:metabolism; D002478:Cells, Cultured; D005340:Fibrinogen / Q000378:metabolism; D008969:Molecular Sequence Data; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology; D009504:Neutrophils / Q000502:physiology*; D009842:Oligopeptides / Q000494:pharmacology; D010972:Platelet Activating Factor / Q000502:physiology*; D015539:Platelet Activation; D010974:Platelet Aggregation; D010980:Platelet Membrane Glycoproteins / Q000378:metabolism; D011817:Rabbits; D015398:Signal Transduction; D013928:Thromboxane A2 / Q000096:biosynthesis; D014230:Triazoles / Q000494:pharmacology
chemical_list: D001381:Azepines; D009842:Oligopeptides; D010972:Platelet Activating Factor; D010980:Platelet Membrane Glycoproteins; D014230:Triazoles; C052518:WEB 2086; D013928:Thromboxane A2; D009240:N-Formylmethionine Leucyl-Phenylalanine; C047981:arginyl-glycyl-aspartic acid; D005340:Fibrinogen