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Phorbol ester-stimulated superoxide production by murine bone marrow-derived macrophages requires preexposure to
1Department of Medicine, University of Melbourne, Victoria, Australia.
Abstract:
Murine resident peritoneal macrophages (RPM) generate superoxide (O2-) in response to stimulation with PMA or zymosan. Murine bone marrow-derived macrophages (BMM) generate O2- in response to zymosan but not PMA. However, the ability to generate O2- in response to PMA could be induced in BMM by pre-exposing the cells to certain cytokines, including granulocyte-macrophage CSF (GM-CSF), tumor necrosis factor-alpha (TNF-alpha), IFN-gamma, and, to a lesser extent, IL-1 alpha. Bacterial LPS also induced the ability to respond to PMA. These same agents were also shown to prime RPM for enhanced PMA-induced respiratory burst. In contrast to GM-CSF, CSF-1 did not enhance the ability of BMM or RPM to generate O2- in response to PMA. Pretreatment with GM-CSF or TNF-alpha did not significantly affect the zymosan-induced release of O2- by BMM. These results suggest that unprimed BMM have a deficiency in the PMA-dependent signaling pathway that is corrected by exposure to selected cytokines. The results also raise the possibility that the basal ability of tissue macrophages to generate a respiratory burst in response to PMA may be a reflection of in vivo exposure to cytokines.
Insights
Bone marrow-derived macrophages (BMM) lack the ability to produce superoxide in response to PMA. Cytokines like GM-CSF and TNF-alpha can induce this response, suggesting in vivo cytokine exposure influences macrophage function.
Area of Science:
- Immunology
- Cell Biology
Background:
- Macrophages are key immune cells involved in pathogen clearance.
- Superoxide generation is a critical component of the macrophage respiratory burst.
- Murine resident peritoneal macrophages (RPM) and bone marrow-derived macrophages (BMM) exhibit differential responses to stimuli.
Purpose of the Study:
- To investigate the deficiency in superoxide production in response to PMA in BMM.
- To determine the role of cytokines in modulating BMM and RPM responses to PMA.
- To explore the implications of cytokine priming on macrophage respiratory burst activity.
Main Methods:
- Culturing murine BMM and RPM.
- Stimulating macrophages with phorbol 12-myristate 13-acetate (PMA) and zymosan.
- Treating cells with cytokines (GM-CSF, TNF-alpha, IFN-gamma, IL-1 alpha) and lipopolysaccharide (LPS).
- Measuring superoxide (O2-) production.
Main Results:
- BMM produced O2- in response to zymosan but not PMA.
- Pre-exposure to GM-CSF, TNF-alpha, IFN-gamma, IL-1 alpha, or LPS induced PMA responsiveness in BMM.
- These cytokines also primed RPM for enhanced PMA-induced respiratory burst.
- CSF-1 did not enhance PMA-induced O2- production in either BMM or RPM.
- GM-CSF and TNF-alpha did not affect zymosan-induced O2- release by BMM.
Conclusions:
- Unprimed BMM possess a defect in the PMA-dependent signaling pathway for O2- generation.
- Cytokine exposure corrects this deficiency, enabling BMM to respond to PMA.
- Tissue macrophage responsiveness to PMA may reflect in vivo cytokine milieu.