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Inhibition of macrophage activation by calcium channel blockers and calmodulin antagonists
Abstract:
The biochemical mechanisms by which macrophages become activated to the tumoricidal state are poorly understood. To investigate the role of calcium in this process, the effect of calcium channel blockers and calmodulin antagonists on the acquisition of tumoricidal properties by macrophages activated by a number of different agents was examined. Activation of thioglycollate-stimulated C57BL/6 mouse peritoneal macrophages by macrophage activation factor (MAF) plus LPS, IFN-gamma plus LPS or the calcium ionophore, A23187, was inhibited in a dose-dependent fashion by the calcium channel blockers nifedipine and verapamil. These agents blocked the influx of 45Ca into macrophages activated by MAF plus LPS. Macrophage activation was also inhibited by chlorpromazine, W-7, and calmidazolium at concentrations known to perturb calmodulin function. The data suggest that activation of macrophages to the tumoricidal state is a calcium-dependent process involving the participation of calcium-regulated biochemical reactions whose activities can be modulated by pharmacological agents that frustrate transmembrane calcium fluxes and/or inhibit calmodulin function.
Insights
Macrophage activation to kill tumors depends on calcium influx. Calcium channel blockers and calmodulin inhibitors prevent this activation, indicating calcium
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- The precise biochemical pathways driving macrophage activation to a tumoricidal state remain unclear.
- Understanding these mechanisms is crucial for developing targeted cancer therapies.
Purpose of the Study:
- To investigate the critical role of calcium ions in macrophage activation towards tumoricidal capabilities.
- To examine the impact of calcium channel blockers and calmodulin antagonists on this activation process.
Main Methods:
- Utilized thioglycollate-stimulated mouse peritoneal macrophages.
- Assessed macrophage activation using agents like macrophage activation factor (MAF) + LPS, IFN-gamma + LPS, and the calcium ionophore A23187.
- Quantified the effects of calcium channel blockers (nifedipine, verapamil) and calmodulin antagonists (chlorpromazine, W-7, calmidazolium) on macrophage activation and calcium influx (using 45Ca).
Main Results:
- Calcium channel blockers (nifedipine, verapamil) dose-dependently inhibited macrophage activation induced by MAF + LPS and IFN-gamma + LPS.
- These blockers also reduced 45Ca influx into macrophages stimulated by MAF + LPS.
- Calmodulin antagonists inhibited macrophage activation, suggesting the involvement of calcium-regulated pathways.
Conclusions:
- Macrophage acquisition of tumoricidal properties is a calcium-dependent process.
- Transmembrane calcium flux and calmodulin function are critical for macrophage activation.
- Pharmacological agents interfering with calcium influx or calmodulin can modulate macrophage tumoricidal activity.