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Murine brain macrophages induced NMDA receptor mediated neurotoxicity in vitro by secreting glutamate
Abstract:
Supernatants (SN) of brain macrophages in culture induce death of cerebellar granule cells in vitro, while those of astrocytes and endothelial cells do not. This toxicity can be prevented by N-methyl-D-aspartate (NMDA) receptor antagonists. Macrophage SN contain high concentrations of glutamate. Reducing the glutamate level of macrophage SN, either by exposure to astrocytes or by enzymatic degradation abolished the toxic effect. Thus, macrophage neurotoxicity is mediated by glutamate acting on NMDA receptors, and might play a role in vivo in traumatic and cerebrovascular brain lesions.
Insights
Brain macrophages release glutamate, causing cerebellar cell death via N-methyl-D-aspartate (NMDA) receptors. This neurotoxicity, preventable by blocking NMDA receptors or reducing glutamate, may impact brain injuries.
Area of Science:
- Neuroscience
- Cell Biology
- Immunology
Background:
- Brain macrophages and astrocytes play critical roles in central nervous system homeostasis and injury.
- Neuroinflammation is implicated in various neurological disorders and brain lesions.
- Cerebellar granule cells are vulnerable neuronal populations in the brain.
Purpose of the Study:
- To investigate the neurotoxic potential of brain macrophage supernatants on cerebellar granule cells.
- To identify the specific mediator of macrophage-induced neurotoxicity.
- To explore the role of glutamate and N-methyl-D-aspartate (NMDA) receptors in this process.
Main Methods:
- Primary cultures of cerebellar granule cells were exposed to supernatants from cultured brain macrophages, astrocytes, and endothelial cells.
- N-methyl-D-aspartate (NMDA) receptor antagonists were used to assess the role of NMDA receptors in neurotoxicity.
- Glutamate levels in macrophage supernatants were measured and manipulated through co-culture with astrocytes or enzymatic degradation.
Main Results:
- Supernatants from brain macrophages, but not astrocytes or endothelial cells, induced significant death of cerebellar granule cells in vitro.
- The neurotoxic effect of macrophage supernatants was abolished by N-methyl-D-aspartate (NMDA) receptor antagonists.
- Macrophage supernatants contained high concentrations of glutamate, and reducing glutamate levels abrogated the toxicity.
Conclusions:
- Macrophage-derived glutamate mediates neurotoxicity to cerebellar granule cells via NMDA receptor activation.
- This mechanism highlights a potential role for macrophage-induced neurotoxicity in conditions like traumatic and cerebrovascular brain lesions.
- Targeting glutamate pathways or macrophage activity could be a therapeutic strategy for brain injuries.