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Inhibition of phosphatidylcholine synthesis is associated with excitotoxic cell death in cerebellar granule cell
T Gasull1, N DeGregorio-Rocasolano, M Enguita
1Neurobiology Unit, Institut d'Investigacions Biomèdiques de Barcelona, Consejo Superior de Investigaciones Científicas (IDIBAPS), Barcelona, Spain.
Abstract:
Glucose deprivation (GD) enhances the sensitivity of cerebellar granule cells to die by excitotoxicity. Neither 70 min of GD, a treatment that depletes cell energy resources, nor exposure to 20 microM glutamate (GLU) for 30 min, induce significant cell death in cultures of cerebellar granule cells. However, the combined treatment with GLU and GD induces choline (Cho) release before excitotoxic cell death. We investigated whether the neurotoxic effect of this treatment is related with inhibition of phosphatidylcholine (PC) synthesis. We found that exposure to GLU for 30 min, to GD for 70 min, and to the combination of both, inhibited PC synthesis at the end of treatment by 71%, 92% and 91%, respectively. The inhibition of PC synthesis was accompanied by a decrease in the incorporation of [(3)H]Cho into phosphocholine and by an increase of the intracellular content of free [(3)H]Cho, indicating that these treatments inhibit the synthesis of PC by inhibiting choline kinase activity. However, only the combined treatment with GLU and GD induced a prolonged inhibition of PC synthesis that extended after the end of treatment. These results show that excitotoxic death is associated with sustained inhibition of PC synthesis and suggest that this effect of the combined treatment with GLU and GD on PC synthesis is produced by an action on an enzymatic step downstream of choline kinase activity.
Insights
Glucose deprivation and glutamate exposure increase cell death by inhibiting phosphatidylcholine synthesis. This sustained inhibition, particularly after combined treatment, suggests a link to excitotoxic neuronal death.
Area of Science:
- Neuroscience
- Cell Biology
- Biochemistry
Background:
- Cerebellar granule cells are vulnerable to excitotoxicity, especially under conditions of glucose deprivation.
- Glutamate excitotoxicity is a significant factor in neuronal damage.
Purpose of the Study:
- To investigate the role of phosphatidylcholine (PC) synthesis inhibition in excitotoxic cell death of cerebellar granule cells.
- To determine if combined glucose deprivation and glutamate exposure impact PC synthesis.
Main Methods:
- Cultures of cerebellar granule cells were subjected to glucose deprivation (GD) and/or glutamate (GLU) exposure.
- Phosphatidylcholine synthesis was measured by monitoring the incorporation of radiolabeled choline.
- Choline kinase activity was assessed by measuring the conversion of choline to phosphocholine.
Main Results:
- Both GD and GLU alone inhibited PC synthesis, with GD showing a more pronounced effect.
- Combined GLU and GD treatment resulted in significant and prolonged inhibition of PC synthesis.
- The inhibition of PC synthesis was linked to reduced choline kinase activity, but the sustained effect of combined treatment suggested downstream inhibition.
Conclusions:
- Excitotoxic cell death in cerebellar granule cells is associated with a sustained inhibition of phosphatidylcholine synthesis.
- Combined glucose deprivation and glutamate exposure induce a prolonged suppression of PC synthesis, potentially via an enzymatic step beyond choline kinase.