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Production of macrophage colony-stimulating factor by astrocytes and brain macrophages
K Frei1, K Nohava, U V Malipiero
1Section of Clinical Immunology, University Hospital, Zürich, Switzerland.
Abstract:
Morphological hallmarks of inflammatory and degenerative diseases of the brain are hypertrophy of astrocytes and accumulation of macrophages recruited from circulating blood monocytes and/or from resident macrophages, the so-called microglial cells. Recently, production of granulocyte-macrophage colony-stimulating factor (GM-CSF) by astrocytes has been suggested to contribute to the macrophage response. Here we report that in addition to GM-CSF, murine astrocytes also produce macrophage (M)-CSF upon stimulation with tumor necrosis factor alpha, interleukin-1 and lipopolysaccharides. The bioactivity detected in supernatant of astrocytes was characterized using the M-CSF-dependent cell line M-NFS-60 and neutralizing anti-M-CSF antibodies. RNase protection analysis showed M-CSF mRNA already in unstimulated astrocytes without striking up-regulation by the stimuli. Thus, in astrocytes the expression of the M-CSF gene is predominantly regulated at the posttranscriptional level.
Insights
Astrocytes produce macrophage colony-stimulating factor (M-CSF) in the brain, contributing to macrophage responses in inflammatory and degenerative diseases. This production is mainly regulated post-transcriptionally, offering new insights into brain immune cell dynamics.
Area of Science:
- Neuroimmunology
- Cellular Biology
Background:
- Brain inflammatory and degenerative diseases involve astrocyte hypertrophy and macrophage accumulation.
- Astrocytes are known to produce granulocyte-macrophage colony-stimulating factor (GM-CSF), influencing macrophage responses.
- The role of other colony-stimulating factors in astrocyte-mediated immune responses requires further elucidation.
Purpose of the Study:
- To investigate whether murine astrocytes produce macrophage colony-stimulating factor (M-CSF) upon stimulation.
- To characterize the bioactivity and regulation of astrocyte-derived M-CSF.
- To understand the contribution of astrocyte-derived M-CSF to brain immune responses.
Main Methods:
- Stimulation of murine astrocytes with tumor necrosis factor alpha, interleukin-1, and lipopolysaccharides.
- Bioactivity assays using the M-CSF-dependent cell line M-NFS-60.
- Neutralizing antibody experiments to confirm M-CSF specificity.
- RNase protection analysis to assess M-CSF mRNA levels.
Main Results:
- Murine astrocytes produce M-CSF upon stimulation with inflammatory cytokines and lipopolysaccharides.
- The bioactivity of astrocyte-derived M-CSF was confirmed using a specific cell line and neutralizing antibodies.
- M-CSF mRNA was detected in unstimulated astrocytes, with minimal upregulation upon stimulation.
- Astrocyte M-CSF gene expression is primarily regulated at the posttranscriptional level.
Conclusions:
- Astrocytes are a source of M-CSF in the brain, potentially contributing to macrophage accumulation in neurological diseases.
- The posttranscriptional regulation of M-CSF expression in astrocytes suggests a complex control mechanism.
- These findings highlight a novel pathway for astrocyte-macrophage communication in the central nervous system.