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Granulocyte-macrophage colony-stimulating factor rescues human polymorphonuclear leukocytes from ultraviolet
J F Sweeney1, P K Nguyen, G Omann
1Departments of Surgery and Biological Chemistry, University of Michigan and Surgical Service, Ann Arbor, Michigan, 48105, USA.
Introduction:
Bacterial lipopolysaccharide (LPS) and granulocyte-macrophage colony-stimulating factor (GM-CSF) delay PMN apoptosis during in vitro culture. The present study was undertaken to determine if LPS and GM-CSF can rescue UV-irradiated PMN from undergoing apoptosis and to determine the role of extracellular signal-regulated kinase (ERK) in this process.
Materials And Methods:
PMN were preincubated with LPS (20 ng/ml) and GM-CSF (100 units/ml) for 60 min before being UV-irradiated for 15 min. Additional PMN were UV-irradiated for 15 min and then treated with LPS and GM-CSF. To determine the role of ERK in protection or rescue of PMN from apoptosis, PMN were preincubated with PD098059 for 30 min. Morphologic features of apoptosis were determined 4 h after UV irradiation. DNA laddering was confirmed by agarose gel electrophoresis.
Results:
LPS and GM-CSF pretreatment significantly protected PMN from UV-accelerated apoptosis, although GM-CSF was more effective than LPS. Only GM-CSF rescued PMN that had already been exposed to UV irradiation from undergoing apoptosis. Time response experiments demonstrated that GM-CSF rescued a significant percentage of PMN when added up to 90 min after UV irradiation. Inhibition of ERK with PD098059 abrogated the protective effect of LPS and GM-CSF and blocked rescue of PMN from apoptosis by GM-CSF.
Conclusions:
LPS and GM-CSF protect PMN, whereas only GM-CSF can rescue PMN from UV-accelerated apoptosis. The ERK-signaling pathway plays an important role in the protection and/or rescue of PMN from UV-accelerated apoptosis, but appears to be a proximal event in this process. This study provides further insight into factors that regulate PMN apoptosis and provides a novel approach for investigating signal transduction pathways involved in PMN apoptosis.
Insights
Bacterial lipopolysaccharide (LPS) and granulocyte-macrophage colony-stimulating factor (GM-CSF) protect neutrophils from UV-induced cell death. GM-CSF uniquely rescues UV-exposed neutrophils via the ERK pathway.
Area of Science:
- Immunology
- Cell Biology
- Molecular Biology
Background:
- Bacterial lipopolysaccharide (LPS) and granulocyte-macrophage colony-stimulating factor (GM-CSF) are known to delay polymorphonuclear neutrophil (PMN) apoptosis in vitro.
- UV irradiation accelerates PMN apoptosis.
Purpose of the Study:
- To investigate if LPS and GM-CSF can rescue UV-irradiated PMN from apoptosis.
- To determine the role of extracellular signal-regulated kinase (ERK) in this protective or rescue process.
Main Methods:
- PMN were pre-treated with LPS and GM-CSF before UV irradiation, or treated after irradiation.
- The ERK pathway was inhibited using PD098059.
- Morphological features of apoptosis and DNA laddering were assessed.
Main Results:
- LPS and GM-CSF pretreatment protected PMN from UV-accelerated apoptosis, with GM-CSF being more effective.
- Only GM-CSF could rescue already UV-irradiated PMN, up to 90 minutes post-irradiation.
- ERK inhibition abolished the protective and rescue effects of LPS and GM-CSF.
Conclusions:
- GM-CSF, but not LPS alone, can rescue UV-irradiated PMN from apoptosis.
- The ERK signaling pathway is crucial for both the protection and rescue of PMN from UV-induced apoptosis.
- This study highlights the role of specific signaling pathways in regulating PMN apoptosis.