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Effects of trifluoperazine on human neutrophil function
Abstract:
The interaction of cytochalasin B-treated human neutrophils with the synthetic tripeptide, N-formyl-methionyl-leucyl-phenylalanine (FMLP) results in a time- and concentration-dependent generation of superoxide anion (O2-) by an extracellular release of granule-associated beta-glucuronidase and lysozyme from these cells. Granule exocytosis was not accompanied by significant cytoplasmic lactate dehydrogenase extrusion. FMLP-stimulated O2- production occurs but is significantly curtailed in the absence of extracellular calcium. Nevertheless, incubation of neutrophils with EGTA in calcium-free medium had no effect on the O2- -generating system. Trifluoperazine (TFP), an inhibitor of calmodulin (a calcium-binding protein), caused a dose-related inhibition of FMLP-elicited degranulation and O2- production in the presence of absence of extracellular calcium. This effect TFP could be reversed by washing the cells before contact with FMLP. These data suggest that TFP represents a useful tool for defining the relevance of calmodulin and calcium to neutrophil function.
Insights
Human neutrophils stimulated with N-formyl-methionyl-leucyl-phenylalanine (FMLP) release granules and generate superoxide anion (O2-). Calmodulin inhibition by trifluoperazine (TFP) affects these functions, highlighting calcium
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- Neutrophils are key immune cells involved in host defense.
- Neutrophil activation by N-formyl-methionyl-leucyl-phenylalanine (FMLP) triggers degranulation and superoxide anion (O2-) production.
- Calcium ions and calmodulin are implicated in cellular signaling pathways.
Purpose of the Study:
- To investigate the role of extracellular calcium and calmodulin in FMLP-induced neutrophil functions.
- To evaluate trifluoperazine (TFP) as a tool to probe calcium-calmodulin involvement.
Main Methods:
- Human neutrophils were treated with cytochalasin B.
- Cells were stimulated with FMLP in the presence or absence of extracellular calcium.
- Degranulation (beta-glucuronidase, lysozyme release) and O2- production were measured.
- The effect of trifluoperazine (TFP) on these responses was assessed.
Main Results:
- FMLP induced time- and concentration-dependent O2- generation and granule release.
- FMLP-stimulated O2- production was reduced in the absence of extracellular calcium.
- Trifluoperazine (TFP) inhibited both degranulation and O2- production in a dose-dependent manner.
- TFP's inhibitory effect was reversible upon washing the cells.
Conclusions:
- Extracellular calcium plays a significant role in FMLP-induced superoxide anion production by neutrophils.
- Calmodulin appears to be involved in FMLP-elicited degranulation and O2- generation.
- Trifluoperazine (TFP) is a valuable pharmacological tool for studying calcium-calmodulin-dependent neutrophil functions.