Choline release and inhibition of phosphatidylcholine synthesis precede excitotoxic neuronal death but not neurotoxicity induced by serum deprivation.
N-Methyl-d-aspartate (NMDA) receptor overactivation has been proposed to induce excitotoxic neuronal death by enhancing membrane phospholipid degradation. In previous studies, we have shown that NMDA releases choline and reduces membrane phosphatidylcholine in vivo. We now observed that glutamate and NMDA induce choline release in primary neuronal cortical cell cultures. This effect is Ca(2+)-dependent and is blocked by MK-801 ((+)-5-methyl-10, 11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine hydrogen maleate). In cortical neurons, the NMDA receptor-mediated choline release precedes excitotoxic cell death but not neuronal death induced by either osmotic lysis or serum deprivation. Glutamate, at concentrations that release arachidonic acid, does not release choline in cerebellar granule cells, unless these cells are rendered susceptible to excitotoxic death by energy deprivation. The NMDA-evoked release of choline is not mediated by phospholipases A(2) or C. Moreover, NMDA does not activate phospholipase D in cortical cells. However, NMDA inhibits incorporation of [methyl-(3)H]choline into both membrane phosphatidylcholine and sphingomyelin. These results show that the increase in extracellular choline induced by NMDA receptor activation is directly related with excitotoxic cell death and indicate that choline release is an early event of the excitotoxic process produced by inhibition of phosphatidylcholine synthesis and not by activation of membrane phospholipid degradation.
Gasull
T
T
Neurobiology Unit, Institut d'Investigacions Biomèdiques de Barcelona, Consejo Superior de Investigaciones Cientificas, Institut d'Investigacions Biomèdiques August Pi i Sunyer, Rosselló 161, 08036 Barcelona, Spain.
DeGregorio-Rocasolano
N
N
Zapata
A
A
Trullas
R
R
D000818:Animals; D001769:Blood; D016923:Cell Death; D002478:Cells, Cultured; D002531:Cerebellum / Q000166:cytology; D002540:Cerebral Cortex / Q000166:cytology; D002794:Choline / Q000378:metabolism*; D003566:Cytidine Diphosphate Choline / Q000378:metabolism; D018698:Glutamic Acid / Q000378:metabolism; D006868:Hydrolysis; D008563:Membrane Lipids / Q000378:metabolism; D016202:N-Methylaspartate / Q000378:metabolism; D009336:Necrosis; D009474:Neurons / Q000166:cytology* / Q000378:metabolism; D010713:Phosphatidylcholines / Q000096:biosynthesis*; D010743:Phospholipids / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism
D008563:Membrane Lipids; D010713:Phosphatidylcholines; D010743:Phospholipids; D016194:Receptors, N-Methyl-D-Aspartate; D018698:Glutamic Acid; D003566:Cytidine Diphosphate Choline; D016202:N-Methylaspartate; D002794:Choline