Phosphatidylinositol and PI-4-monophosphate recover amyloid beta protein-induced inhibition of Cl- -ATPase activity.
The neuronal Cl- -ATPase/pump is a candidate for an outwardly directed active Cl- transport system, which requires phosphatidylinositol-4-monophosphate (PI4P) for its optimal activity. We previously reported that low concentrations (1-10 nM) of amyloid beta proteins (Abetas, Abeta1-42, Abeta25-35), the neurotoxic peptides in Alzheimer's disease, reduced Cl- -ATPase activity in cultured rat hippocampal neurons without any changes in the activities of Na+/K+-ATPase or anion-insensitive Mg(2+)-ATPase, and decreased PI, PIP, and PIP2 levels in neuronal plasma membranes (Journal of Neurochemistry 2001, 78, 569-579). In this study, we examined the effects of exogenously applied PI and PI4P on the Abeta25-35-induced changes in Cl- -ATPase activity, the intracellular concentration of Cl- ([Cl- ]i), and glutamate neurotoxicity using primary cultured rat hippocampal neurons. The Abeta decreased Cl- -ATPase activity to 47% of control and increased [Cl- ]i in hippocampal pyramidal cell-like neurons to a level 3 times higher than the control. The addition of PI (50-750 nM) or PI4P (50-150 nM) dose-dependently blocked the inhibitory effects of Abeta on Cl- -ATPase activity. High doses of PI (750 nM) and PI4P (100-150 nM) reduced Na+/K+-ATPase activity to 41% and 35% of control, respectively, but this inhibition was attenuated by the co-application of phosphatidylserine (PS, 1 micro M). PI or PI4P (75 nM each) reversed the Abeta-induced increase in [Cl-]i. In the Abeta-exposed culture, stimulation by glutamate (10 micro M, 10 min) resulted in an increase in DNA fragmentation and decreases in cell viability. Addition of PI or PI4P prevented the Abeta-induced aggravation of glutamate neurotoxicity. Thus, PI and PI4P were demonstrated to prevent Abeta-induced decreases in Cl- -ATPase activity and increases in neuronal [Cl- ]i in parallel with the attenuation of Abeta-induced aggravation of glutamate neurotoxicity.
Wu
Bo
B
Department of Pharmacology, Kansai Medical University, Fumizono-cho 10-15, Moriguchi, 570-8506, Osaka, Japan.
Kitagawa
Kaori
K
Yagyu
Kyoko
K
Zhang
Nan-Yan
NY
Hattori
Naoki
N
Inagaki
Chiyoko
C
D000251:Adenosine Triphosphatases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D016229:Amyloid beta-Peptides / Q000037:antagonists & inhibitors* / Q000494:pharmacology*; D000818:Animals; D027321:Anion Transport Proteins; D002462:Cell Membrane / Q000187:drug effects / Q000201:enzymology; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D002712:Chlorides / Q000378:metabolism; D053938:DNA Fragmentation; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D018698:Glutamic Acid / Q000633:toxicity; D006624:Hippocampus / Q000166:cytology / Q000187:drug effects; D009474:Neurons / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D018129:Phosphatidylinositol Phosphates / Q000494:pharmacology*; D010716:Phosphatidylinositols / Q000494:pharmacology*; D051381:Rats
D016229:Amyloid beta-Peptides; D027321:Anion Transport Proteins; D002712:Chlorides; D004791:Enzyme Inhibitors; D018129:Phosphatidylinositol Phosphates; D010716:Phosphatidylinositols; C037178:phosphatidylinositol 4-phosphate; D018698:Glutamic Acid; D000251:Adenosine Triphosphatases; C031652:anion-sensitive ATPases