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Ethanol inhibits zymosan-stimulated eicosanoid production in mouse peritoneal macrophages
J Balsinde1, B Fernández, J A Solís-Herruzo
1Centro de Investigación del Hospital Universitario Doce de Octubre, Madrid, Spain.
Abstract:
Resident peritoneal macrophages synthesized and released eicosanoids when challenged by zymosan, a phagocytosable particle. Incubation of these cells with ethanol resulted in dose-dependent inhibition of arachidonic acid release and eicosanoid generation in response to zymosan. Ethanol affected the extent but not the ratio of eicosanoids released. When assayed in a cell-free system, endogenous phospholipase A2 activity was neither affected by the presence of ethanol in the incubation medium nor by preincubation of the cells with ethanol. Ethanol also inhibited arachidonic acid release in response to phorbol myristate acetate, a compound that, like zymosan, triggered a pertussis-toxin-sensitive response. When cells that had been previously treated with pertussis toxin were used, no further inhibitory effect of ethanol was seen in response to both zymosan and phorbol myristate acetate. On the other hand, ethanol had no effect on arachidonic acid release stimulated by ionophore A23187 or lipopolysaccharide, two compounds that triggered a pertussis-toxin-insensitive response. Moreover, ethanol was able to nearly abolish arachidonic acid release in response to fluoroaluminate, a direct activator of G-proteins. Altogether, the results of this study suggest that ethanol inhibits zymosan-stimulated eicosanoid production by interacting with a G-protein--or a G-protein-mediated process--that is critically involved in arachidonic acid mobilization.
Insights
Ethanol inhibits eicosanoid production by macrophages by interfering with G-protein signaling pathways. This study reveals ethanol
Area of Science:
- Immunology
- Cell Biology
- Pharmacology
Background:
- Macrophages produce eicosanoids, crucial inflammatory mediators.
- Zymosan stimulates eicosanoid release from macrophages.
- Ethanol's effects on inflammatory pathways are not fully understood.
Purpose of the Study:
- To investigate the mechanism by which ethanol inhibits zymosan-induced eicosanoid production in resident peritoneal macrophages.
- To determine if ethanol affects phospholipase A2 activity directly.
- To elucidate the specific signaling pathway involved in ethanol's inhibitory action.
Main Methods:
- Macrophages were challenged with zymosan, phorbol myristate acetate, ionophore A23187, lipopolysaccharide, and fluoroaluminate.
- Arachidonic acid release and eicosanoid generation were measured.
- Cells were pretreated with ethanol and/or pertussis toxin.
- Cell-free assays were used to assess phospholipase A2 activity.
Main Results:
- Ethanol inhibited arachidonic acid release and eicosanoid generation in response to zymosan and phorbol myristate acetate in a dose-dependent manner.
- Ethanol's inhibitory effect was abolished in pertussis toxin-treated cells, indicating involvement of a pertussis-toxin-sensitive pathway.
- Ethanol did not affect phospholipase A2 activity in cell-free systems.
- Ethanol inhibited arachidonic acid release stimulated by fluoroaluminate, a G-protein activator.
Conclusions:
- Ethanol inhibits zymosan-stimulated eicosanoid production by targeting a G-protein-mediated signaling process.
- The mechanism involves interference with G-protein-coupled pathways upstream of arachidonic acid mobilization.
- Ethanol does not directly inhibit phospholipase A2 activity.