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Release of platelet-activating factor (PAF-acether) and leukotrienes C and D from inflammatory macrophages
Abstract:
Macrophages (M phi) isolated from the peritoneal cavity of C57BL/6 mice were either untreated or treated with various eliciting agents (thioglycollate, sodium caseinate) or with an activating agent bacillus Calmette Guérin (BCG). The various populations were assessed for their ability to release platelet-activating factor (PAF-acether), an ether phospholipid mediator, and slow-reacting substance (SRS), a lipoxygenase arachidonic acid derivative. PAF-acether was recovered in higher amounts form BCG M phi than from resident M phi, whereas elicited M phi exhibited a marked decreased ability to release this mediator. Such variations were only quantitative as evidenced by the similar enzyme sensitivity and high pressure liquid chromatography (HPLC) retention times of the various PAF-acether-containing supernatants. Resident, BCG- and sodium caseinate-induced M phi released similar amounts of SRS, whereas thioglycollate M phi exhibited once again a marked decreased ability to release this mediator. Comparing retention times on HPLC of resident and BCG M phi SRS with those of synthetic leukotrienes C and D, molecular variations were noted. Even though both M phi populations released higher amounts of leukotrienes C than D, the D/C ratio was higher in BCG M phi than in resident M phi. These results show that different environmental factors can influence the release of PAF-acether and leukotrienes from M phi.
Insights
Different environmental factors influence macrophage mediator release. Activated macrophages release more platelet-activating factor (PAF), while elicited macrophages show reduced release of both PAF and slow-reacting substance (SRS).
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- Macrophages (M phi) are key immune cells involved in inflammatory responses.
- Platelet-activating factor (PAF-acether) and slow-reacting substance (SRS) are critical inflammatory mediators.
- The influence of different activation and elicitation states on M phi mediator release is not fully understood.
Purpose of the Study:
- To investigate how different eliciting and activating agents affect M phi mediator release.
- To quantify the release of PAF-acether and SRS from various M phi populations.
- To analyze the molecular characteristics of released SRS.
Main Methods:
- Isolation of peritoneal macrophages from C57BL/6 mice.
- Treatment of macrophages with eliciting agents (thioglycollate, sodium caseinate) or activating agent (BCG).
- Quantification of PAF-acether and SRS release using biochemical assays and High-Pressure Liquid Chromatography (HPLC).
Main Results:
- BCG-activated macrophages released significantly higher amounts of PAF-acether compared to resident macrophages.
- Elicited macrophages (thioglycollate, sodium caseinate) showed reduced PAF-acether release.
- Thioglycollate-elicited macrophages exhibited decreased SRS release, while others released similar amounts; molecular variations in SRS were observed between resident and BCG-activated M phi.
Conclusions:
- Environmental factors significantly modulate macrophage mediator release profiles.
- Macrophage activation state dictates the quantitative and qualitative release of inflammatory mediators like PAF-acether and SRS.
- These findings highlight the plasticity of macrophages in response to different stimuli.