Neuroprotection afforded by prior citicoline administration in experimental brain ischemia: effects on glutamate transport.
OBJECTIVE
Cytidine-5'-diphosphocholine (citicoline or CDP-choline), an intermediate in the biosynthesis of phosphatidylcholine, has shown beneficial effects in a number of CNS injury models including cerebral ischemia. Citicoline is the only neuroprotectant that has proved efficacy in patients with moderate to severe stroke. However, the precise mechanism by which citicoline is neuroprotective is not fully known. The present study was designed to search for mechanisms of citicoline neuroprotective properties using in vivo and in vitro models of brain ischemia.


METHODS
Focal brain ischemia was produced in male adult Fischer rats by occluding both the common carotid and middle cerebral arteries. Brain glutamate levels were determined at fixed intervals after occlusion. Animals were then sacrificed, and infarct volume and brain ATP levels were measured. As in vitro model of ischemia, rat cultured cortical neurones or astrocytes, isolated or in co-culture, were exposed to oxygen-glucose deprivation (OGD) either in the absence or in the presence of citicoline (1-100 microM). Viability was studied by measuring LDH release. Glutamate release and uptake, and ATP levels were also determined.


RESULTS
Citicoline (0.5, 1 and 2 g/kg i.p. administered 1 h before the occlusion) produced a reduction of the infarct size measured at striatum (18, 27 and 42% inhibition, respectively, n = 8, P < 0.05 vs. ischemia), effect that correlated with the inhibition caused by citicoline on ischemia-induced increase in glutamate concentrations after the onset of the ischemia. Citicoline also inhibited ischemia-induced decrease in cortical and striatal ATP levels. Incubation of cultured rat cortical neurones with citicoline (10 and 100 microM) prevented OGD-induced LDH and glutamate release and caused a recovery in ATP levels after OGD, confirming our previous results. In addition, citicoline (100 microM) caused an increase in glutamate uptake and in EAAT2 glutamate transporter membrane expression in cultured rat astrocytes.


CONCLUSIONS
Our present findings show novel mechanisms for the neuroprotective effects of citicoline, which cooperate to decrease brain glutamate release after ischemia.
Hurtado
Olivia
O
Departamento de Farmacología, Facultad de Medicina, Universidad Complutense de Madrid (UCM), 28040 Madrid, Spain.
Moro
María A
MA
Cárdenas
Antonio
A
Sánchez
Verónica
V
Fernández-Tomé
Paz
P
Leza
Juan C
JC
Lorenzo
Pedro
P
Secades
Julio J
JJ
Lozano
Rafael
R
Dávalos
Antoni
A
Castillo
José
J
Lizasoain
Ignacio
I
D000255:Adenosine Triphosphate / Q000378:metabolism; D027322:Amino Acid Transport System X-AG / Q000187:drug effects / Q000378:metabolism; D000818:Animals; D000831:Animals, Newborn; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism; D001692:Biological Transport / Q000187:drug effects; D001921:Brain / Q000187:drug effects* / Q000378:metabolism / Q000503:physiopathology; D002545:Brain Ischemia / Q000188:drug therapy* / Q000378:metabolism / Q000503:physiopathology; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D002544:Cerebral Infarction / Q000188:drug therapy / Q000378:metabolism / Q000503:physiopathology; D018920:Coculture Techniques; D003566:Cytidine Diphosphate Choline / Q000494:pharmacology*; D019610:Cytoprotection / Q000187:drug effects / Q000502:physiology; D004195:Disease Models, Animal; D027342:Excitatory Amino Acid Transporter 2 / Q000187:drug effects / Q000378:metabolism; D050491:Glutamate Plasma Membrane Transport Proteins; D018698:Glutamic Acid / Q000378:metabolism*; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008297:Male; D009410:Nerve Degeneration / Q000188:drug therapy* / Q000378:metabolism / Q000517:prevention & control*; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D018696:Neuroprotective Agents / Q000494:pharmacology; D051381:Rats; D011916:Rats, Inbred F344; D017208:Rats, Wistar; D027981:Symporters / Q000187:drug effects / Q000378:metabolism
D027322:Amino Acid Transport System X-AG; D027342:Excitatory Amino Acid Transporter 2; D050491:Glutamate Plasma Membrane Transport Proteins; D018696:Neuroprotective Agents; C493395:Slc1a2 protein, rat; D027981:Symporters; D018698:Glutamic Acid; D003566:Cytidine Diphosphate Choline; D000255:Adenosine Triphosphate; D007770:L-Lactate Dehydrogenase