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Selective induction of interleukin-6 in mouse microglia by granulocyte-macrophage colony-stimulating factor
A Suzumura1, M Sawada, T Marunouchi
1Department of Neurology, School of Medicine Fujita Health University, Aichi, Japan.
Abstract:
Astrocytes produce granulocyte/macrophage colony-stimulating factor (GM-CSF) and support the survival and proliferation of microglia. To study the functions of GM-CSF in the central nervous system (CNS), we examined the effects of GM-CSF on cytokine production by glial cells. GM-CSF induced interleukin-6 (IL-6) production by microglia, but not by astrocytes, in a dose-dependent manner as assessed by bioassay and the detection of IL-6 mRNA by reverse transcriptase-polymerase chain reaction (RT-PCR) analysis. GM-CSF did not induce tumor necrosis factor (TNF) alpha or IL-1 in microglia and astrocytes, whereas lipopolysaccharide induced all these cytokines. The induction of IL-6 by GM-CSF in microglia was completely inhibited by antibodies to GM-CSF. Neither IL-3 nor macrophage-CSF (M-CSF) induced IL-6 production in microglia. Given that IL-1 and TNF alpha, monokines derived from microglia, induce IL-6 production in astrocytes, but not in microglia, results indicate that astrocytes and microglia may mutually regulate IL-6 production by different cytokines.
Insights
Granulocyte/macrophage colony-stimulating factor (GM-CSF) stimulates interleukin-6 (IL-6) production in microglia but not astrocytes. This suggests a mutual regulation of IL-6 between these glial cells in the central nervous system (CNS).
Area of Science:
- Neuroscience
- Immunology
- Cell Biology
Background:
- Astrocytes produce granulocyte/macrophage colony-stimulating factor (GM-CSF), crucial for microglial survival and proliferation in the central nervous system (CNS).
- Understanding GM-CSF's role in CNS cytokine production is essential for neuroinflammatory research.
Purpose of the Study:
- To investigate the effects of GM-CSF on cytokine production by glial cells, specifically astrocytes and microglia.
- To elucidate the mechanisms of glial cell communication and immune response modulation in the CNS.
Main Methods:
- Dose-dependent induction of cytokine production by GM-CSF in primary glial cell cultures.
- Detection of interleukin-6 (IL-6) mRNA using reverse transcriptase-polymerase chain reaction (RT-PCR).
- Inhibition studies using antibodies against GM-CSF and testing of other colony-stimulating factors (IL-3, M-CSF).
Main Results:
- GM-CSF dose-dependently induced IL-6 production in microglia, confirmed by bioassay and RT-PCR.
- GM-CSF did not induce IL-6 in astrocytes, nor did it induce tumor necrosis factor (TNF)-alpha or IL-1 in either cell type.
- Lipopolysaccharide (LPS) induced IL-6, TNF-alpha, and IL-1 in both astrocytes and microglia, serving as a positive control.
- Antibodies to GM-CSF completely blocked IL-6 induction in microglia.
- IL-3 and M-CSF did not induce IL-6 production in microglia.
Conclusions:
- GM-CSF selectively stimulates IL-6 production in microglia, highlighting its specific role in microglial activation.
- Astrocytes and microglia exhibit differential responses to GM-CSF, suggesting distinct roles in CNS immune responses.
- The findings indicate a potential mutual regulatory loop for IL-6 production between astrocytes and microglia, mediated by different cytokines.