Down-regulation of Cl− pump ClP55 subunit induced enhancement of glutamate neurotoxicity in cultured rat hippocampal neurons

To test whether the increased intracellular Cl− concentration ([Cl−]i) is responsible for the enhanced glutamate toxicity, antisense oligonucleotide of ClP55, a Cl−-ATPase/pump associated protein, was transfected in cultured rat hippocampal neurons. Neuronal [Cl−]i in the antisense oligonucleotide-transfected culture increased to a level 3- to 4-fold higher than that in control. Glutamate exposure (10 μM, 10 min) increased neuronal apoptosis and decreased Akt-pS473 level in the antisense oligonucleotide-transfected neurons, but not in control or sense oligonucleotide-transfected ones, suggesting the responsibility of elevated [Cl−]i in the enhancement of glutamate neurotoxicity.