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P4‐032: Investigating the downstream targets of memantine in primary neuronal cell culture models
Author(s) -
Lahiri Debomoy,
Bailey Jason,
Ray Balmiki,
Banerjee Pradeep
Publication year - 2012
Publication title -
alzheimer's and dementia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.713
H-Index - 118
eISSN - 1552-5279
pISSN - 1552-5260
DOI - 10.1016/j.jalz.2012.05.1733
Subject(s) - memantine , nmda receptor , synaptophysin , neuroscience , glutamate receptor , pi3k/akt/mtor pathway , biology , synapse , amyloid precursor protein , microbiology and biotechnology , chemistry , pharmacology , alzheimer's disease , receptor , medicine , signal transduction , biochemistry , immunohistochemistry , immunology , disease
Background: Alzheimer’s disease (AD) is characterized by excess amyloid-b (Ab) and loss of cholinergic synapses in the cortex. Our goal is to study novel functions of established therapeutic agents in animal and cell culture models (Alley et al., 2010; Bailey et al., 2011). We have studied the effects of memantine on synaptic proteins and amyloid processing in cultured neuronal cells. We have identified the mammalian target of rapamycin (mTOR) and BDNF pathways as potentially important downstream targets of memantine. Methods: Primary rat and human neuronal cultures and neuronal SK-N-SH and PC12 cell lines were treated with memantine, and levels of secreted Ab and BDNF were measured by ELISA. Levels of secreted Ab precursor protein (APP) and the synaptic proteins synaptophysin, SNAP-25, and PSD95 were measured by Western blot. Neuronal and glial morphologies were examined by immunofluorescence techniques. Results:We observed decreases in APP and Ab secretion in primary cells and neuronal cell line models with memantine treatment, and BDNF was increased in the PC12 model. In degenerating primary neurons, memantine preserved neuronal viability and synaptic proteins. These effects were reversed by the mTOR antagonist rapamycin. In primary rat neurons, the more potent NMDA antagonist MK801 also preserved synaptic proteins in primary rat cultures, while this treatment was toxic in primary human neurons. Memantine was not toxic in any model tested, up to 20 mM. Neuronal morphology was also preserved by memantine in degenerating neurons. Conclusions: Our data suggest that the mechanisms of memantine include preservating synapses and neuronal morphology, and modulation of amyloid metabolism. The mTOR pathway is implicated in many processes, including rapid synaptogenesis elicited ketamine. Reversal of the synapsetopreservative effect of memantine by rapamycin suggests this pathway is involved in the neuron and synapse preserving effects of memantine. Further investigation of the relationship of rapamycin to APP processing pathways is underway, including effects mediated by non-amyloidogenic ADAM10 processing, and activation state of the mTOR kinase itself. The neuroprotective, synaptopreservative and non-amyloidogenic actions of memantine may be further optimized for the treatment or prevention of AD and other neurodegenerative disorders, and for the development of future drugs.