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Macrophage-produced oxygen radical generating activities for polymorphonuclear leukocytes
Y Tsukamoto1, S Fukutani, M Nakatani
1Department of Pharmacology, Osaka Dental University, Japan.
Abstract:
Guinea pig peritoneal macrophages were stimulated in vitro by bacterial lipopolysaccharide. After incubation, the supernatants of macrophage cultures were collected and tested for O2- production on guinea pig peritoneal polymorphonuclear leukocytes. The supernatants of macrophage cultures stimulated by lipopolysaccharide had significantly higher levels of O2- -generating activities in polymorphonuclear leukocytes, and these activities appeared in the macrophage cultures within 2 h after stimulation by lipopolysaccharide. However, the supernatants obtained from the nonstimulated cultures could not produce these activities. These activities disappeared with heating or trypsin and were not produced in macrophage cultures by incubation with cycloheximide.
Insights
Bacterial lipopolysaccharide stimulation of guinea pig macrophages releases factors that enhance superoxide (O2-) production in other immune cells. These factors appear quickly and are sensitive to heat and enzymes.
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- Macrophages are key immune cells involved in host defense.
- Bacterial lipopolysaccharide (LPS) is a potent activator of macrophages.
- Superoxide (O2-) production is a critical function of phagocytic immune cells.
Purpose of the Study:
- To investigate the effect of LPS-stimulated guinea pig macrophages on polymorphonuclear leukocyte (PMN) O2- production.
- To characterize the nature of the factors released by macrophages.
Main Methods:
- Guinea pig peritoneal macrophages were stimulated in vitro with LPS.
- Supernatants from macrophage cultures were collected.
- Supernatants were tested for their ability to induce O2- production in guinea pig peritoneal PMNs.
- Sensitivity of the activity to heat and trypsin was assessed.
- Effect of cycloheximide on activity production was evaluated.
Main Results:
- LPS-stimulated macrophage supernatants significantly increased O2- generating activity in PMNs.
- This activity appeared within 2 hours of LPS stimulation.
- Supernatants from non-stimulated macrophages did not induce this activity.
- The activity was abolished by heating or trypsin treatment.
- Cycloheximide inhibited the production of these activities.
Conclusions:
- LPS-stimulated macrophages release soluble factors that enhance PMN superoxide production.
- These factors are likely proteins, as they are sensitive to heat and trypsin.
- Their production is dependent on de novo protein synthesis by macrophages.