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Disialoganglioside GD3 is released by microglia and induces oligodendrocyte apoptosis
B M Simon1, F Malisan, R Testi
1Department of Molecular Toxicology, University of Konstanz, 78457 Konstanz, Germany.
Abstract:
Increased brain ganglioside levels are a hallmark of various neuroinflammatory pathologies. Here, we provide evidence that murine microglia can secrete disialoganglioside GD3 upon exposure to inflammatory stimuli. Comparison of different neural cell types revealed a particular and specific sensitivity of oligodendrocytes towards exogenous GD3. Oligodendrocyte death triggered by GD3 was preceded by degeneration of cellular processes, and associated with typical features of apoptosis, such as chromatin condensation, exposure of phosphatidylserine, release of cytochrome c from mitochondria, and loss of mitochondrial membrane potential, followed by the loss of plasma membrane integrity and detachment of disintegrated oligodendrocytes. Overexpression of bcl-2 partially protected oligodendrocytes from death. In contrast, treatment with the pan-caspase inhibitor zVAD-fmk did not prevent phosphatidylserine exposure, chromatin margination at the nuclear periphery, and death, although caspase-3 was blocked. Thus, GD3 produced by microglia under neuroinflammatory conditions may function as a novel mediator triggering mitochondria-mediated, but caspase-independent, apoptosis-like death of oligodendrocytes.
Insights
Microglia release disialoganglioside GD3 during inflammation, which triggers apoptosis-like death in oligodendrocytes. This process involves mitochondria but not caspases, suggesting GD3 as a novel neuroinflammatory mediator.
Area of Science:
- Neuroscience
- Immunology
- Cell Biology
Background:
- Elevated brain ganglioside levels are characteristic of neuroinflammatory diseases.
- Microglia are key immune cells in the central nervous system, responding to inflammatory stimuli.
Purpose of the Study:
- To investigate the role of microglia-secreted gangliosides in neuroinflammation.
- To determine the specific effects of disialoganglioside GD3 on neural cell types, particularly oligodendrocytes.
Main Methods:
- Murine microglia were exposed to inflammatory stimuli to assess GD3 secretion.
- Oligodendrocytes were treated with exogenous GD3 to evaluate cellular responses and death pathways.
- Analysis included assessment of apoptosis markers (phosphatidylserine exposure, mitochondrial pathway activation) and caspase activity.
Main Results:
- Microglia secrete disialoganglioside GD3 upon inflammatory stimulation.
- Oligodendrocytes exhibit specific sensitivity to GD3, leading to process degeneration and cell death.
- GD3-induced oligodendrocyte death involves mitochondrial dysfunction and caspase-independent apoptosis-like mechanisms.
Conclusions:
- Microglia-derived GD3 acts as a novel mediator in neuroinflammation.
- GD3 triggers a caspase-independent, mitochondria-mediated apoptotic pathway in oligodendrocytes.
- These findings highlight a new mechanism contributing to oligodendrocyte damage in neuroinflammatory conditions.