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Cytotoxic activity of stimulated mouse macrophages exposed to various inhibitors
Abstract:
Mouse peritoneal macrophages were cultured for 3 days with or without zymosan and at the same time exposed to various inhibitors of cellular metabolism. The cells were assayed for selective release of a lysosomal enzyme, and for cytotoxic activity against a tumor cell line, L-929-cells. Selective release of beta-glucuronidase was demonstrated in the supernatants from zymosan-stimulated macrophages. The stimulated macrophages were cytotoxic for the tumors cells, evaluated by measuring release of radioactivity during subsequent 4 days' co-culture of macrophages and 14C-thymidine-labelled tumor cells, and by counting cells per culture. Colchicine caused a slight, variable reduction in enzyme release and no change in cytotoxic effect from stimulated macrophages. Monensin decreased extracellular enzyme secretion and reduced the cytotoxicity in stimulated macrophages to control levels. Chloroquine caused a similar reduction in lysosomal enzyme release and cytotoxic activity in zymosan-stimulated cells. This inhibitor increased the enzyme release from control cells and induced a small, variable cytotoxic effect from these cells. The data indicate co-variation between macrophage-mediated cytotoxicity and a secretory process which can be blocked by monensin. The need for intact lysosomal function was also demonstrated.
Insights
Zymosan-stimulated macrophages exhibit tumor cell cytotoxicity linked to lysosomal enzyme release. Inhibitors like monensin and chloroquine block this process, highlighting the role of lysosomal function in macrophage-mediated killing.
Area of Science:
- Immunology
- Cell Biology
Background:
- Macrophages are key immune cells involved in host defense and pathogen clearance.
- Macrophage activation by stimuli like zymosan triggers various effector functions, including cytotoxicity.
- Lysosomal enzymes play a role in cellular processes and immune responses.
Purpose of the Study:
- To investigate the relationship between lysosomal enzyme release and cytotoxic activity in zymosan-stimulated mouse peritoneal macrophages.
- To evaluate the effects of cellular metabolism inhibitors on macrophage-mediated cytotoxicity and enzyme secretion.
Main Methods:
- Primary mouse peritoneal macrophages were cultured for 3 days.
- Cells were stimulated with zymosan and treated with metabolic inhibitors (colchicine, monensin, chloroquine).
- Assays included measurement of beta-glucuronidase release (lysosomal enzyme) and cytotoxic activity against L-929 tumor cells.
Main Results:
- Zymosan stimulation induced selective release of beta-glucuronidase and cytotoxic activity against tumor cells.
- Monensin and chloroquine significantly reduced both enzyme release and cytotoxicity in stimulated macrophages.
- Colchicine showed minimal effects on enzyme release and cytotoxicity.
- Chloroquine increased enzyme release and induced minor cytotoxicity in unstimulated macrophages.
Conclusions:
- Macrophage-mediated cytotoxicity is closely associated with a secretory process involving lysosomal enzyme release.
- Inhibitors targeting cellular metabolism, specifically monensin and chloroquine, can effectively block this cytotoxic pathway.
- Intact lysosomal function is essential for the cytotoxic activity of zymosan-stimulated macrophages.