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Granulocyte-macrophage colony stimulating factor up-regulates CCR1 in human neutrophils
S S Cheng1, J J Lai, N W Lukacs
1Department of Pathology and Graduate Program in Cellular and Molecular Biology, University of Michigan Medical Center, and Department of Epidemiology, School of Public Health, University of Michigan, Ann Arbor, MI 48109, USA.
Abstract:
Neutrophils (polymorphonuclear leukocytes; PMN) are phagocytic cells instrumental in the clearance of infectious pathogens. Human PMN are commonly thought to respond primarily to chemokines from the CXC family. However, recent findings suggest that under specific cytokine activation conditions, PMN can also respond to some CC chemokines. In this study, the effect of GM-CSF, a well-characterized PMN priming and maturation factor, on CC-chemokine receptor (CCR) expression in PMN was investigated. Constitutive expression of CCR1 and CCR3 mRNA in PMN was detected by ribonuclease protection assay. Following incubation of PMN with GM-CSF (0.01-10 ng/ml; 6 h) CCR1 mRNA expression was rapidly (approximately 1 h) up-regulated. In contrast, no significant induction of CCR2, CCR3, CCR4, or CCR5 mRNA was observed. CCR1 protein was also up-regulated by GM-CSF stimulation. GM-CSF-induced up-regulation of CCR1 showed functional consequences because GM-CSF-treated PMN, but not control cells, responded to the CC chemokines macrophage inflammatory protein-1alpha, monocyte chemoattractant protein-3, and RANTES in assays of chemotactic migration and intracellular calcium mobilization. These results suggest that PMN activated by the proinflammatory cytokine GM-CSF can change their receptor expression pattern and become responsive to CC chemokines.
Insights
Granulocyte-macrophage colony-stimulating factor (GM-CSF) activates neutrophils (polymorphonuclear leukocytes; PMN) to express more CC-chemokine receptor 1 (CCR1). This allows PMN to respond to CC chemokines, enhancing immune cell function.
Area of Science:
- Immunology
- Cell Biology
Background:
- Neutrophils (polymorphonuclear leukocytes; PMN) are key phagocytic cells in pathogen clearance.
- Human PMN typically respond to CXC chemokines, but can respond to CC chemokines under specific cytokine conditions.
Purpose of the Study:
- To investigate the effect of GM-CSF on CC-chemokine receptor (CCR) expression in human PMN.
- To determine if GM-CSF priming alters PMN responsiveness to CC chemokines.
Main Methods:
- Ribonuclease protection assay to detect CCR mRNA expression.
- Incubation of PMN with varying concentrations of GM-CSF.
- Chemotaxis and intracellular calcium mobilization assays to assess functional responses.
Main Results:
- GM-CSF rapidly up-regulated CCR1 mRNA and protein expression in PMN.
- No significant induction of CCR2, CCR3, CCR4, or CCR5 mRNA was observed.
- GM-CSF-treated PMN exhibited chemotactic migration and calcium mobilization in response to specific CC chemokines (MIP-1α, MCP-3, RANTES).
Conclusions:
- Proinflammatory cytokine GM-CSF alters PMN receptor expression, enabling CC chemokine responsiveness.
- Activated PMN can exhibit functional responses to CC chemokines previously not associated with their primary signaling pathways.