Chloride-dependency of amyloid beta protein-induced enhancement of glutamate neurotoxicity in cultured rat hippocampal neurons.
In our previous studies, pathophysiological concentrations of amyloid-beta (Abeta) proteins increased intracellular Cl(-) concentration ([Cl(-)]i) and enhanced glutamate neurotoxicity in primary cultured neurons, suggesting Cl(-)-dependent changes in glutamate signaling. To test this possibility, we examined the effects of isethionate-replaced low Cl(-) medium on the Abeta-induced enhancement of glutamate neurotoxicity in the primary cultured rat hippocampal neurons. In a normal Cl(-) (135 mM) medium, treatment with 10 nM Abeta25-35 for 2 days increased neuronal [Cl(-)]i to a level three times higher than that of control as assayed using a Cl(-)-sensitive fluorescent dye, while in a low Cl(-) (16 mM) medium such an Abeta25-35-induced increase in [Cl(-)]i was not observed. The Abeta treatment aggravated glutamate neurotoxicity in a normal Cl(-) medium as measured by mitochondrial reducing activity and lactate dehydrogenase (LDH) release, while in a low Cl(-) medium the Abeta treatment did not enhance glutamate toxicity. Upon such Abeta plus glutamate treatment under a normal Cl(-) condition, activated anti-apoptotic molecule Akt (Akt-pS473) level monitored by Western blot significantly decreased to 74% of control. Under a low Cl(-) condition, a resting Akt-pS473 level was higher than that under a normal Cl(-) condition and did not significantly change upon Abeta plus glutamate treatment. Tyrosine phosphorylation levels of 110 and 60 kDa proteins (pp110 and pp60) increased upon Abeta plus glutamate treatment under a normal Cl(-), but not low Cl(-), condition. These findings indicated that Abeta-induced enhancement of glutamate neurotoxicity is Cl(-)-dependent. Chloride-sensitive Akt pathway and tyrosine phosphorylation of proteins (pp110 and pp60) may be involved in this process.
Department of Pharmacology, Kansai Medical University, Moriguchi, Osaka 570-8506, Japan.
Nan-Yan
NY
Zhang
Kaori
K
Kitagawa
Bo
B
Wu
Zheng-Mei
ZM
Xiong
Hitomi
H
Otani
Chiyoko
C
Inagaki
D016229:Amyloid beta-Peptides / Q000502:physiology* / Q000633:toxicity; D000818:Animals; D017209:Apoptosis; D002478:Cells, Cultured; D002712:Chlorides / Q000378:metabolism*; D004622:Embryo, Mammalian / Q000166:cytology; D018698:Glutamic Acid / Q000502:physiology* / Q000633:toxicity; D006624:Hippocampus / Q000166:cytology / Q000378:metabolism*; D042541:Intracellular Space / Q000378:metabolism; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D010446:Peptide Fragments / Q000502:physiology* / Q000633:toxicity; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D014443:Tyrosine / Q000378:metabolism
D016229:Amyloid beta-Peptides; D002712:Chlorides; D010446:Peptide Fragments; C074636:amyloid beta-protein (25-35); D018698:Glutamic Acid; D014443:Tyrosine; D007770:L-Lactate Dehydrogenase; D019869:Phosphatidylinositol 3-Kinases; D016392:Proto-Oncogene Proteins pp60(c-src); D051057:Proto-Oncogene Proteins c-akt