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Intracellular platelet-activating factor regulates eicosanoid generation in guinea-pig resident peritoneal
1Department of Physiology, University of Melbourne, Victoria, Australia.
Abstract:
1. The role of intracellular platelet-activating factor (Paf) in arachidonic acid (AA) mobilization from guinea-pig peritoneal macrophages has been investigated by use of the potent and selective Paf receptor antagonists, WEB 2086 and CV 6209. 2. Adherent macrophages contained cell-associated Paf which was increased by exposure to formyl-methionyl-leucyl-phenylalanine (fMLP), endotoxin and the ionophore, A23187. However, only endotoxin and A23187 caused release of detectable amounts of Paf into the extracellular medium. 3. Exogenous Paf and each of the above stimuli mobilized previously incorporated [14C]-AA and increased the generation of prostacyclin (PGI2) in resident macrophages. 4. WEB 2086 (10-100 microM) and CV 6209 (0.1-10 microM) reduced both basal and stimulated PGI2 generation and WEB 2086 inhibited the mobilization of [14C]-AA. In addition, WEB 2086 (10 microM) inhibited fMLP-and Paf-induced superoxide anion generation. Responses to A23187 were not inhibited by either antagonist. 5. Activation of macrophages by fMLP caused a short burst of intracellular Paf generation but none was detected in the supernatants. The time-course of PGI2 synthesis followed closely that of Paf. 6. These data suggest that intracellular Paf generation is important for subsequent AA mobilization and may have a wider role in signal transduction processes.
Insights
Intracellular platelet-activating factor (Paf) plays a key role in arachidonic acid mobilization and prostacyclin generation in macrophages. Paf receptor antagonists inhibited these processes, suggesting Paf
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- Macrophages play a crucial role in immune responses.
- Platelet-activating factor (Paf) is a potent lipid mediator involved in inflammation.
- Arachidonic acid (AA) is a precursor to important inflammatory mediators like prostacyclin (PGI2).
Purpose of the Study:
- To investigate the role of intracellular Paf in AA mobilization in guinea-pig peritoneal macrophages.
- To examine the effects of Paf receptor antagonists on macrophage activation and mediator release.
Main Methods:
- Utilized potent Paf receptor antagonists WEB 2086 and CV 6209.
- Stimulated macrophages with formyl-methionyl-leucyl-phenylalanine (fMLP), endotoxin, and A23187.
- Measured intracellular and extracellular Paf levels, [14C]-AA mobilization, and prostacyclin (PGI2) generation.
Main Results:
- Intracellular Paf increased upon stimulation with fMLP, endotoxin, and A23187.
- WEB 2086 and CV 6209 significantly reduced basal and stimulated PGI2 generation.
- WEB 2086 inhibited AA mobilization and fMLP/Paf-induced superoxide anion generation.
Conclusions:
- Intracellular Paf generation is critical for subsequent AA mobilization and PGI2 synthesis in macrophages.
- Paf signaling pathways are involved in macrophage activation and inflammatory mediator production.
- Targeting intracellular Paf may offer therapeutic strategies for inflammatory diseases.