Amyloid beta proteins inhibit Cl(-)-ATPase activity in cultured rat hippocampal neurons.
Cl(-)-ATPase in the CNS is a candidate for an outwardly directed neuronal Cl(-) transporter requiring phosphatidylinositol-4-phosphate (PI4P) for its optimal activity. To test its pathophysiological changes in a phosphatidylinositol (PI) metabolism disorder, the effects of neurotoxic factors in Alzheimer's disease (AD), amyloid beta proteins (Abetas), on the Cl(-)-ATPase activity were examined using primary cultured rat hippocampal neurons. Amyloid beta proteins (1-40, 1-42 and 25-35) concentration-dependently (1-100 nM) and time-dependently (from 1 h to 6 day) decreased Cl(-)-ATPase activity and elevated intracellular Cl(-) concentrations ([Cl(-)]i), Abeta25-35 being the most potent. Addition of inositol or 8-Br-cyclic GMP completely reversed these Abeta-induced changes. The recoveries in enzyme activity were attenuated by an inhibitor of PI 4-kinase, 10 microM wortmannin or 20 microM quercetin, but not by a PI 3-kinase inhibitor, 50 nM wortmannin or 10 microM LY294002. The PI, PIP and PIP2 levels of the plasma membrane-rich fraction were lower in the Abeta-treated cells as compared with each control. In the Abeta-exposed culture, but not in control, stimulation by 10 microM glutamate for 10 min significantly increased fragmentation of DNA and decreased cell viability. Addition of inositol or 8-Br-cyclic GMP prevented the effect of Abeta-treatment on the neurotoxicity of glutamate. Thus, Abetas reduce neuronal Cl(-)-ATPase activity, resulting in an increase in [Cl(-)]i probably by lowering PI4P levels, and this may reflect a pre-apoptotic condition in early pathophysiological profiles of AD.
Yagyu
K
K
Department of Pharmacology, Kansai Medical University, Moriguchi, Osaka, Japan.
Kitagawa
K
K
Irie
T
T
Wu
B
B
Zeng
X T
XT
Hattori
N
N
Inagaki
C
C
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000251:Adenosine Triphosphatases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D000544:Alzheimer Disease / Q000503:physiopathology; D016229:Amyloid beta-Peptides / Q000494:pharmacology*; D000818:Animals; D027321:Anion Transport Proteins; D002458:Cell Fractionation; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D002712:Chlorides / Q000378:metabolism; D053938:DNA Fragmentation / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018698:Glutamic Acid / Q000494:pharmacology; D006624:Hippocampus / Q000166:cytology; D006801:Humans; D007294:Inositol / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects* / Q000201:enzymology; D010446:Peptide Fragments / Q000494:pharmacology*; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism; D010716:Phosphatidylinositols / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors
D016229:Amyloid beta-Peptides; D027321:Anion Transport Proteins; D002712:Chlorides; D004791:Enzyme Inhibitors; D010446:Peptide Fragments; D018129:Phosphatidylinositol Phosphates; D010716:Phosphatidylinositols; C078592:amyloid beta-protein (1-40); C074636:amyloid beta-protein (25-35); D015124:8-Bromo Cyclic Adenosine Monophosphate; D018698:Glutamic Acid; D007294:Inositol; D000251:Adenosine Triphosphatases; C031652:anion-sensitive ATPases