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Auto-protective redox buffering systems in stimulated macrophages
Pierre-Jacques Ferret1, Emmanuelle Soum, Olivier Negre
1Université René Descartes, Paris V Inserm U477, Hôpital Cochin, 75014 Paris, France. pjferret@gmx.net
BMC Immunology
|March 27, 2002
Summary
Activated macrophages develop resistance to self-inflicted damage from reactive nitrogen species (RNS) by upregulating antioxidant enzymes and glutathione. This enhanced defense mechanism allows a fraction of macrophages to survive nitrosative stress.
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- Macrophages produce reactive oxygen and nitrogen species (ROS/RNS) to combat pathogens.
- High levels of RNS can induce apoptosis in macrophages themselves, posing a threat to host defense.
- Understanding macrophage self-protection mechanisms is crucial for immune response regulation.
Purpose of the Study:
- To investigate the mechanisms by which a fraction of activated macrophages survive nitrosative stress.
- To identify the molecular players involved in macrophage resistance to RNS-induced apoptosis.
Main Methods:
- Murine macrophage cell line (RAW 264.7) stimulated with lipopolysaccharide (LPS) and/or interferon-gamma (IFN-γ).
- Exposure to a nitric oxide (NO) donor (DETA-NO) to induce apoptosis.
- Analysis of mRNA and enzyme activity for antioxidant systems (SOD, catalase, glutathione pathway).
- Inhibition studies using specific inhibitors of antioxidant enzymes and glutathione synthesis.
Main Results:
- A subpopulation of activated macrophages (10-50%) acquired resistance to NO-induced apoptosis.
- Survivors exhibited increased mRNA and activity of manganese superoxide dismutase (Mn SOD), copper-zinc superoxide dismutase (CuZn SOD), and catalase.
- Intracellular glutathione levels significantly increased in resistant macrophages.
- Inhibition of these redox buffering systems prevented the acquisition of the resistant phenotype.
Conclusions:
- Macrophage survival during nitrosative stress is directly linked to the upregulation of intracellular antioxidant and glutathione systems.
- This auto-protective response involves the modulation of apoptotic molecules from the Bcl-2 family.
- These findings elucidate a critical self-preservation mechanism in activated macrophages.