Pharmacological evidence that the activation of the Na(+)-Ca2+ exchanger protects C6 glioma cells during chemical hypoxia.
1. In C6 glioma cells exposed to chemical hypoxia a massive release of lactate dehydrogenase (LDH) occurred at 3 and 6 h, coupled with an increased number of propidium-iodide positive dead cells. 2. Extracellular Na+ removal, which activates the Na(+)-Ca2+ exchanger as a Na+ efflux pathway and prevents Na+ entrance, significantly reduced LDH release and the number of propidium iodide positive C6 cells. 3. During chemical hypoxia, in the presence of extracellular Na+ ions, a progressive increase of [Ca2+]i occurred; in the absence of extracellular Na+ ions [Ca2+]i was enhanced to a greater extent. 4. The blockade of the Na(+)-Ca2+ exchanger by the amiloride derivative 5-(N-4-chlorobenzyl)-2',4'-dimethylbenzamil (CB-DMB), lanthanum (La3+) and the Ca2+ chelator EGTA, completely reverted the protective effect exerted by the removal of Na+ ions on C6 glioma cells exposed to chemical hypoxia. 5. The inhibition of the Na(+)-Ca2+ antiporter enhanced chemical hypoxia-induced LDH release when C6 glioma cells were incubated in the presence of physiological concentrations of extracellular Na+ ions (145 mM), suggesting that the blockade of the Na(+)-Ca2+ antiporter during chemical hypoxia can lead to increased cell damage. 6. Collectively, these results suggest that activation of the Na(+)-Ca2+ exchanger protects C6 glioma cells exposed to chemical hypoxia, whereas its pharmacological blockade can exacerbate cellular injury.
Amoroso
S
S
Department of Neuroscience, School of Medicine, Federico II University of Naples, Italy.
De Maio
M
M
Russo
G M
GM
Catalano
A
A
Bassi
A
A
Montagnani
S
S
Renzo
G D
GD
Annunziato
L
L
D000584:Amiloride / Q000031:analogs & derivatives; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002118:Calcium / Q000378:metabolism*; D016923:Cell Death / Q000187:drug effects; D002478:Cells, Cultured / Q000187:drug effects; D004533:Egtazic Acid / Q000494:pharmacology*; D005910:Glioma / Q000188:drug therapy*; D000860:Hypoxia / Q000378:metabolism*; D007811:Lanthanum / Q000494:pharmacology*; D012964:Sodium / Q000378:metabolism*
D004533:Egtazic Acid; D007811:Lanthanum; D000584:Amiloride; D012964:Sodium; D002118:Calcium