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Memantine protects rat cortical cultured neurons against β-amyloid-induced toxicity by attenuating tau phosphorylation

Authors

  • M. S. Song,

    1. Department of Medicine, Centre for Prions and Protein Folding Diseases, University of Alberta, Edmonton, Alberta T6G 2M8, Canada
    2. Department of Psychiatry, Neurochemical Research Unit, University of Alberta, Edmonton, Alberta T6G 2G3, Canada
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  • G. Rauw,

    1. Department of Psychiatry, Neurochemical Research Unit, University of Alberta, Edmonton, Alberta T6G 2G3, Canada
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  • G. B. Baker,

    1. Department of Psychiatry, Neurochemical Research Unit, University of Alberta, Edmonton, Alberta T6G 2G3, Canada
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  • S. Kar

    1. Department of Medicine, Centre for Prions and Protein Folding Diseases, University of Alberta, Edmonton, Alberta T6G 2M8, Canada
    2. Department of Psychiatry, Neurochemical Research Unit, University of Alberta, Edmonton, Alberta T6G 2G3, Canada
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Dr S. Kar, 2Department of Psychiatry, as above.
E-mail: skar@ualberta.ca

Abstract

It has been suggested that accumulation of beta-amyloid (Aβ) peptide triggers neurodegeneration, at least in part, via glutamate-mediated excitotoxicity in Alzheimer’s disease (AD) brain. This is supported by observations that toxicity induced by Aβ peptide in cultured neurons and in adult rat brain is known to be mediated by activation of glutamatergic N-methyl-d-aspartate (NMDA) receptors. Additionally, recent clinical studies have shown that memantine, a noncompetitive NMDA receptor antagonist, can significantly improve cognitive functions in some AD patients. However, very little is currently known about the potential role of memantine against Aβ-induced toxicity. In the present study, we have shown that Aβ1–42-induced toxicity in rat primary cortical cultured neurons is accompanied by increased extracellular and decreased intracellular glutamate levels. We subsequently demonstrated that Aβ toxicity is induced by increased phosphorylation of tau protein and activation of tau kinases, i.e. glycogen synthase kinase-3β and extracellular signal-related kinase 1/2. Additionally, Aβ treatment induced cleavage of caspase-3 and decreased phosphorylation of cyclic AMP response element binding protein, which are critical in determining survival of neurons. Memantine treatment significantly protected cultured neurons against Aβ-induced toxicity by attenuating tau-phosphorylation and its associated signaling mechanisms. However, this drug did not alter either conformation or internalization of Aβ1–42 and it was unable to attenuate Aβ-induced potentiation of extracellular glutamate levels. These results, taken together, provide new insights into the possible neuroprotective action of memantine in AD pathology.

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