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Stimulation of Ca2+ efflux by N-formyl chemotactic peptides in guinea-pig peritoneal macrophages
Abstract:
Effects of N-formyl chemotactic peptides on the Ca2+ influx and efflux were investigated in guinea-pig peritoneal macrophages using an isotope tracer. fMet-Leu-Phe did not enhance the influx of 45Ca2+ into macrophages, whereas it stimulated the efflux of 45Ca2+ from macrophages at concentrations ranging from 10(-10) M to 10(-7) M. fMet-Met-Met and fMet-Leu also stimulated the 45Ca2+ efflux, albeit at much higher concentrations, while there was no stimulation with fMet. The mitochondrial inhibitors, oligomycin and NaN3, did not modify the 45Ca2+ efflux induced by the chemoattractants, yet they did induce the release of 45Ca2+ from the mitochondria. On the other hand, higher concentrations of the calmodulin antagonists, chlorpromazine and trifluoperazine, induced the release of 45Ca2+ from the NaN3-insensitive Ca2+ store site and mimicked the enhancement of the 45Ca2+ efflux by N-formyl chemotactic peptides. Thus, N-formyl chemotactic peptides appear to increase the levels of intracellular free Ca2+ in guinea-pig peritoneal macrophages, probably by inducing the release of Ca2+ from the NaN3-insensitive Ca2+ store site.
Insights
N-formyl chemotactic peptides, like fMet-Leu-Phe, stimulate calcium (Ca2+) efflux from macrophages, not influx. This suggests peptides increase intracellular free Ca2+ by releasing it from a specific store site.
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- N-formyl chemotactic peptides are crucial signaling molecules in immune responses.
- Calcium (Ca2+) ions play a vital role in macrophage activation and function.
- Understanding Ca2+ flux in macrophages is key to deciphering immune cell signaling.
Purpose of the Study:
- To investigate the effects of N-formyl chemotactic peptides on Ca2+ influx and efflux in guinea-pig peritoneal macrophages.
- To elucidate the mechanisms by which these peptides modulate intracellular Ca2+ levels.
Main Methods:
- Utilized isotope tracer techniques with 45Ca2+ to quantify Ca2+ movement.
- Administered various N-formyl chemotactic peptides (fMet-Leu-Phe, fMet-Met-Met, fMet-Leu) at different concentrations.
- Employed mitochondrial inhibitors (oligomycin, NaN3) and calmodulin antagonists (chlorpromazine, trifluoperazine) to probe Ca2+ stores and pathways.
Main Results:
- fMet-Leu-Phe significantly stimulated 45Ca2+ efflux from macrophages, without affecting influx.
- Other N-formyl peptides (fMet-Met-Met, fMet-Leu) also induced Ca2+ efflux at higher concentrations.
- Mitochondrial inhibitors did not affect peptide-induced Ca2+ efflux but released mitochondrial Ca2+.
- Calmodulin antagonists mimicked the peptide effect by releasing Ca2+ from a NaN3-insensitive store.
Conclusions:
- N-formyl chemotactic peptides likely increase intracellular free Ca2+ in macrophages.
- This increase is probably mediated by the release of Ca2+ from a specific, non-mitochondrial store.
- The findings provide insight into the calcium signaling mechanisms of immune cell activation.