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AMPA and kainate receptors each mediate excitotoxicity in oligodendroglial cultures
1Departamento de Neurociencias, Universidad del País Vasco, Leioa, Vizcaya, 48940, Spain.
Abstract:
Recent studies indicate that oligodendrocytes are vulnerable to excitotoxic insults mediated by glutamate receptors. The present study was carried out to characterize the type of glutamate receptors triggering cell death in optic nerve oligodendrocyte cultures. Acute activation of either AMPA or kainate receptors was toxic to oligodendrocytes, an effect that was prevented by CNQX. However, exposure to agonists of the NMDA and metabotropic glutamate receptors did not impair cell viability. Dose-response curves showed that toxicity was mediated by three distinct populations of receptors: an AMPA-type receptor and high- and low-affinity kainate-type receptors. Expression and immunocytochemical studies suggested that the glutamate receptor subunits give rise to the native receptors in each population. In all instances, Ca(2+) entry was a major determinant of glutamate receptor excitotoxicity. However, its influence varied for each receptor subtype. These results indicate that aberrantly enhanced activation of AMPA and/or kainate receptors may be involved in demyelinating diseases.
Insights
Oligodendrocytes, crucial for nerve insulation, are damaged by specific glutamate receptors, particularly AMPA and kainate types. This excitotoxicity, involving calcium influx, may contribute to demyelinating diseases.
Area of Science:
- Neuroscience
- Cell Biology
- Neuroimmunology
Background:
- Oligodendrocytes are vital for myelin sheath formation and maintenance in the central nervous system.
- These cells are known to be susceptible to excitotoxic damage mediated by glutamate receptors.
- Understanding specific receptor subtypes involved is crucial for neuroprotection strategies.
Purpose of the Study:
- To identify the specific types of glutamate receptors responsible for excitotoxic cell death in oligodendrocytes.
- To investigate the role of calcium (Ca2+) influx in this excitotoxicity.
- To explore the potential involvement of AMPA and kainate receptors in demyelinating diseases.
Main Methods:
- Utilized primary optic nerve oligodendrocyte cultures.
- Administered agonists for various glutamate receptor subtypes (AMPA, kainate, NMDA, metabotropic).
- Assessed cell viability and measured Ca2+ influx.
- Performed dose-response analyses and immunocytochemical studies.
Main Results:
- Activation of AMPA and kainate receptors, but not NMDA or metabotropic receptors, induced oligodendrocyte death.
- The neuroprotective agent CNQX blocked AMPA and kainate receptor-mediated toxicity.
- Toxicity was mediated by distinct AMPA-type and high- and low-affinity kainate-type receptor populations.
- Calcium (Ca2+) entry was critical for excitotoxicity, with varying degrees of influence across receptor subtypes.
Conclusions:
- Aberrant activation of AMPA and/or kainate receptors leads to oligodendrocyte death.
- Calcium influx is a key mediator of this excitotoxicity.
- These findings suggest a potential role for AMPA and kainate receptor overactivation in the pathogenesis of demyelinating diseases.