title: Novel dimeric acetylcholinesterase inhibitor bis7-tacrine, but not donepezil, prevents glutamate-induced neuronal apoptosis by blocking N-methyl-D-aspartate receptors.
abstract: The neuroprotective properties of bis(7)-tacrine, a novel dimeric acetylcholinesterase (AChE) inhibitor, on glutamate-induced excitotoxicity were investigated in primary cultured cerebellar granule neurons (CGNs). Exposure of CGNs to 75 mum glutamate resulted in neuronal apoptosis as demonstrated by Hoechst staining, TUNEL, and DNA fragmentation assays. The bis(7)-tacrine treatment (0.01-1 mum) on CGNs markedly reduced glutamate-induced apoptosis in dose- and time-dependent manners. However, donepezil and other AChE inhibitors, even at concentrations of inhibiting AChE to the similar extents as 1 mum bis(7)-tacrine, failed to prevent glutamate-induced excitotoxicity in CGNs; moreover, both atropine and dihydro-beta-erythroidine, the cholinoreceptor antagonists, did not affect the anti-apoptotic properties of bis(7)-tacrine, suggesting that the neuroprotection of bis(7)-tacrine appears to be independent of inhibiting AChE and cholinergic transmission. In addition, ERK1/2 and p38 pathways, downstream signals of N-methyl-d-aspartate (NMDA) receptors, were rapidly activated after the exposure of glutamate to CGNs. Bis(7)-tacrine inhibited the apoptosis and the activation of these two signals with the same efficacy as the coapplication of PD98059 and SB203580. Furthermore, using fluorescence Ca(2+) imaging, patch clamp, and receptor-ligand binding techniques, bis(7)-tacrine was found effectively to buffer the intracellular Ca(2+) increase triggered by glutamate, to reduce NMDA-activated currents and to compete with [(3)H]MK-801 with an IC(50) value of 0.763 mum in rat cerebellar cortex membranes. These findings strongly suggest that bis(7)-tacrine prevents glutamate-induced neuronal apoptosis through directly blocking NMDA receptors at the MK-801-binding site, which offers a new and clinically significant modality as to how the agent exerts neuroprotective effects.
authors.affiliation: Department of Biochemistry and Biology, Hong Kong University of Science and Technology, Kowloon, Hong Kong.
authors.forename: Wenming
authors.initials: W
authors.lastname: Li
authors.forename: Rongbiao
authors.initials: R
authors.lastname: Pi
authors.forename: Hugh H N
authors.initials: HH
authors.lastname: Chan
authors.forename: Hongjun
authors.initials: H
authors.lastname: Fu
authors.forename: Nelson T K
authors.initials: NT
authors.lastname: Lee
authors.forename: Hing Wai
authors.initials: HW
authors.lastname: Tsang
authors.forename: Yongmei
authors.initials: Y
authors.lastname: Pu
authors.forename: Donald C
authors.initials: DC
authors.lastname: Chang
authors.forename: Chaoying
authors.initials: C
authors.lastname: Li
authors.forename: Jialie
authors.initials: J
authors.lastname: Luo
authors.forename: Keming
authors.initials: K
authors.lastname: Xiong
authors.forename: Zhiwang
authors.initials: Z
authors.lastname: Li
authors.forename: Hong
authors.initials: H
authors.lastname: Xue
authors.forename: Paul R
authors.initials: PR
authors.lastname: Carlier
authors.forename: Yuanping
authors.initials: Y
authors.lastname: Pang
authors.forename: Karl W K
authors.initials: KW
authors.lastname: Tsim
authors.forename: Mingtao
authors.initials: M
authors.lastname: Li
authors.forename: Yifan
authors.initials: Y
authors.lastname: Han
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D002478:Cells, Cultured; D002800:Cholinesterase Inhibitors / Q000737:chemistry / Q000494:pharmacology*; D019281:Dimerization; D000077265:Donepezil; D004305:Dose-Response Relationship, Drug; D018698:Glutamic Acid / Q000494:pharmacology*; D007189:Indans / Q000494:pharmacology*; D009474:Neurons / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology; D010880:Piperidines / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors* / Q000502:physiology; D013619:Tacrine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000494:pharmacology
chemical_list: C122128:1,7-N-heptylene-bis-9,9'-amino-1,2,3,4-tetrahydroacridine; D002800:Cholinesterase Inhibitors; D007189:Indans; D010880:Piperidines; D016194:Receptors, N-Methyl-D-Aspartate; D018698:Glutamic Acid; D013619:Tacrine; D000077265:Donepezil