Study of neuroprotection of donepezil, a therapy for Alzheimer's disease

Donepezil is a potent acetylcholinesterase inhibitor used for the treatment of Alzheimer's disease. Although acetylcholinesterase inhibitors are thought to be symptomatic treatment of Alzheimer's disease, it is not clear whether they are effective against progressive degeneration of neuronal cells. In this study, we investigated the neuro protective effects of donepezil against ischemic damage. N-methyl-D-aspartate (NMDA) excitotoxicity, and amyloid-beta (A beta) toxicity using rat brain primary cultured neurons. Lactate dehydrogenase (LDH) released into the culture medium was measured as a market of neuronal cell damage. As an ischemic damage model, we used oxygen-glucose deprivation in rat cerebral cortex primary cultured neurons. Pretreatment with donepezil (0.1, 1 and 10 mu M) significantly decreased LDH release in a concentration-dependent manner. However. other acetylcholinesterase inhibitors (galantamine, tacrine and rivastigmine) did not significantly decrease LDH release. In a NMDA excitotoxicity model, pretreatment with donepezil (0.1, 1 and 10 mu M) decreased the LDH release in a concentration-dependent manner. In binding assay for glutamate receptors, donepezil at 100 mu M only slightly inhibited binding to the glycine and polyamine sites on NMDA receptor complex. We further examined the effect of donepezil on A beta (1-40)- and A beta (1-42)-induced toxicity in primary Cultures of rat septa) neurons. Pretreatment with donepezil (0.1, 1 and 10 mu M) significantly decreased LDH release induced by A beta s in a concentration-dependent manner. However, other acetylcholinesterase inhibitors (galantamine and tacrine) and NMDA receptor antagonists (memantine and dizocilpine (MK801)) did not significantly decrease LDH release. These results demonstrate that donepezil has protective effects against ischemic damage, glutamate excitotoxicity and A beta toxicity to rat primary cultured neurons and these effects are not dependent on acetylcholinesterase inhibition and antagonism of NMDA receptors. Thus, donepezil is expected to have a protective effect against progressive degeneration of brain neuronal cells in ischemic cerebrovascular disease and Alzheimer's disease. (C) 2008 Elsevier Ireland Ltd. All rights reserved.