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Correlative transmission and scanning electron microscopy study of microglia activated by interferon-gamma and tumor
W R Anderson1, A Martella, Z M Drake
1Department of Pathology, University of Minnesota, Minneapolis, USA.
Abstract:
Microglia, in response to cytokines, demonstrate a number of enhanced biochemical and functional properties which reflect a state of activation. In this study, we evaluated the ultrastructural alterations of murine microglia that were associated with activation by interferon-gamma (IFN-gamma) plus tumor necrosis factor-alpha (TNF-alpha). Microglial cell culture treated with these cytokines generated significant amounts of the free radical nitric oxide (NO), a biochemical marker of activation. Correlative transmission (TEM) and scanning (SEM) electron microscopic analyses of these cytokine-activated microglia demonstrated two prominent features: proliferation of cell processes and increased formation of membrane bound dense bodies typical of lysosomes. Since activated microglia have been implicated in the pathogenesis of a number of neurodegenerative diseases, application of the ultrastructural findings in the in vitro study may prove useful in determining the state of activation of microglia in brain specimens from patients with these neurological disorders.
Insights
Activated microglia exhibit ultrastructural changes like cell process proliferation and increased dense bodies. These findings, observed after interferon-gamma and tumor necrosis factor-alpha treatment, may aid in diagnosing neurodegenerative diseases.
Area of Science:
- Neuroscience
- Immunology
- Cell Biology
Background:
- Microglia are key immune cells in the central nervous system.
- Cytokine stimulation leads to microglial activation, altering their function.
- Activated microglia are implicated in neurodegenerative disease pathogenesis.
Purpose of the Study:
- To investigate the ultrastructural changes in murine microglia activated by interferon-gamma (IFN-gamma) and tumor necrosis factor-alpha (TNF-alpha).
- To identify specific morphological markers of microglial activation.
Main Methods:
- Primary murine microglial cultures were treated with IFN-gamma and TNF-alpha.
- Nitric oxide (NO) production was measured as a marker of activation.
- Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were used for ultrastructural analysis.
Main Results:
- Cytokine-activated microglia produced significant amounts of nitric oxide (NO).
- TEM and SEM revealed proliferation of microglial cell processes.
- Increased formation of membrane-bound dense bodies, characteristic of lysosomes, was observed.
Conclusions:
- IFN-gamma and TNF-alpha induce distinct ultrastructural alterations in microglia, including process extension and lysosome formation.
- These morphological changes, alongside NO production, serve as reliable indicators of microglial activation.
- The identified ultrastructural features may be valuable for assessing microglial activation states in neurodegenerative disorders.