Suppression of Cl^- -ATPase activity in Alzheimer's disease brain

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Cl^- -ATPase enables the inhibitory neurotransmission by GABA by keeping the intracellular chloride concentration low. We previously reported that Cl^- -ATPase activity decreased in Alzheimer's disease brains and that low dose amyloid β(Aβ) inhibited Cl^- -ATPase activity leading to the elevation of intracellular chloride levels. In the present study, we investigated the effects of Aβ on Cl^- -ATPase activity in lymphocytes which are easily obtained from patients to see if the Cl^- -ATPase activity in lymphocytes reflects that of brains.[Materials and Methods]Effects Aβ on Cl^- -ATPase and Na-K ATPase activities, and on cell viability were examined in T-cell derived human leulemic cell line (Jurkat), myeloid cell derived human leukemic cell line (HL-60) and human peripheral lymphocytes. The cells were cultured in RPMI1640 containing 10% FCS with or without Aβ 25-35 (1μM) or Aβ 1-42 (100 nM), or 20μM quercetin as a PI4 kinase inhibitor or 0.05μM wartmannin as a PI3 kinase inhibitor.[Res … More ults]Membrane fractions from leukemic cell lines showed Cl^- -ATPase and Na-K ATPase activities. In peripheral blood from healthy volunteers, Cl^- -ATPase activity was detected in lymphocytes and neutrophils but not in red blood cells, while Na-K-ATPase activity was observed in all cells. Aβ 25-35 (1μM) or Aβ 1-42 (100 nM) significantly reduced Cl^- -ATPase in lymphocytes and had a tendency to decrease Na-K-ATPase activity. PI4 kinase inhibitor, 20μM quercetin significantly reduced Cl^- -ATPase, while PI3 kinase inhibitor, 0.5μM wartmannin did not alter the activity.[Discussion]The present study showed that Cl^- -ATPase was detectable in human lymphocytes and the activity was inhibited by Aβ and PI4 kinase inhibitor as observed in brains, suggesting that the same mechanisms are involved for the inhibition and that the effects of Aβ on brains can be reflected in those on lymphocytes which are easily obtainable. Measurement of Cl^- -ATPase in lymphocytes may possibly be used for early diagnosis of Alzheimer's disease. Less