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Flow cytometric investigation of neutrophil activation pathways by n-formyl-Met-Leu-Phe and phorbol myristate acetate
J Zhang1, C J Kaupke, S Yousefi
1Department of Medicine, University of California, Orange 92668, USA.
Abstract:
Recent evidence suggests that multiple pathways exist in PMN activation and that specific leukocyte response may be due to the activation of a particular signaling pathway. Using flow cytometry, PMN activation pathways were studied through the parallel comparison of n-formyl-Met-Leu-Phe (fMLP)- and phorbol-12-myristate-13-acetate (PMA)-induced stimulation and by simultaneous assays for CD11b expression and morphology. The maximal CD11b expression was higher with PMA than with fMLP, suggesting different activation pathways. Under these experimental conditions, a morphological response to fMLP was not observed. However, significant shape change was detected in PMA treated samples and was suppressed by either the removal of extracellular calcium or staurosporine at the concentrations above 14.5 microM. Calcium ionophore induced a similar light scattering pattern to that by PMA and enhanced CD11b expression, both of which were not inhibitable by staurosporine. These observations, for the first time, indicated that Ca2+ was a mediator in activation processes and that the treatment of PMN with PMA resulted in Ca2+ influx.
Insights
Polymorphonuclear neutrophil (PMN) activation involves distinct signaling pathways. This study reveals calcium influx as a key mediator in PMA-induced PMN activation, influencing CD11b expression and cell morphology.
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- Polymorphonuclear neutrophils (PMNs) are crucial immune cells.
- Evidence suggests multiple signaling pathways regulate PMN activation.
- Understanding these pathways is key to targeted immune response modulation.
Purpose of the Study:
- To investigate and compare distinct PMN activation pathways.
- To elucidate the role of calcium and specific signaling molecules in PMN activation.
Main Methods:
- Utilized flow cytometry to analyze PMN activation.
- Compared n-formyl-Met-Leu-Phe (fMLP) and phorbol-12-myristate-13-acetate (PMA) induced stimulation.
- Assayed for CD11b expression and cell morphology changes.
Main Results:
- Phorbol-12-myristate-13-acetate (PMA) induced higher maximal CD11b expression than fMLP.
- PMA treatment caused significant PMN shape change, unlike fMLP under tested conditions.
- Calcium influx was identified as a mediator in PMA-induced PMN activation, affecting morphology and CD11b expression.
Conclusions:
- PMN activation pathways differ significantly between fMLP and PMA stimuli.
- Calcium influx is a critical component of PMA-driven PMN activation.
- These findings offer insights into targeted therapeutic strategies for inflammatory conditions.