Mechanisms of neuroprotective effects of nicotine and acetylcholinesterase inhibitors: role of alpha4 and alpha7 receptors in neuroprotection.
Neurotoxicity induced by glutamate and other excitatory amino acids has been implicated in various neurodegenerative disorders including hypoxic ischemic events, trauma, and Alzheimer's and Parkinson's diseases. We examined the roles of nicotinic acetylcholine receptors (nAChRs) in survival of CNS neurons during excitotoxic events. Nicotine as well as other nicotinic receptor agonists protected cortical neurons against glutamate neurotoxicity via alpha4 and alpha7 nAChRs at least partly by inhibiting the process of apoptosis in near-pure neuronal cultures obtained from the cerebral cortex of fetal rats. Donepezil, galanatamine and tacrine, therapeutic acetylcholinesterase (AChE) inhibitors currently being used for treatment of Alzheimer's disease also protected neuronal cells from glutamate neurotoxicity. Protective effects of nicotine and the AChE inhibitors were antagonized by nAChR antagonists. Moreover, nicotine and those AChE inhibitors induced up-regulation of nAChRs. Inhibitors for a non-receptor-type tyrosine kinase, Fyn, and janus-activated kinase 2, suppressed the neuroprotective effect of donepezil and galantamine. Furthermore, a phosphatidylinositol 3-kinase (PI3K) inhibitor also suppressed the neuroprotective effect of the AChE inhibitors. The phosphorylation of Akt, an effector of PI3K, and the expression level of Bcl-2, an anti-apoptotic protein, increased with donepezil and galantamine treatments. These results suggest that nicotine as well as AChE inhibitors, donepezil and galantamine, prevent glutamate neurotoxicity through alpha4 and alpha7 nAChRs and the PI3K-Akt pathway.
Akaike
Akinori
A
Department of Pharmacology, Graduate School of Pharmaceutical Sciences, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan. aakaike@pharm.kyoto-u.ac.jp
Takada-Takatori
Yuki
Y
Kume
Toshiaki
T
Izumi
Yasuhiko
Y
D000109:Acetylcholine / Q000378:metabolism; D000818:Animals; D001921:Brain / Q000187:drug effects / Q000378:metabolism / Q000503:physiopathology; D001927:Brain Diseases / Q000188:drug therapy* / Q000378:metabolism / Q000503:physiopathology; D002800:Cholinesterase Inhibitors / Q000494:pharmacology* / Q000627:therapeutic use; D019610:Cytoprotection / Q000187:drug effects / Q000502:physiology; D006801:Humans; D018696:Neuroprotective Agents / Q000494:pharmacology* / Q000627:therapeutic use; D009538:Nicotine / Q000494:pharmacology* / Q000627:therapeutic use; D051381:Rats; D011978:Receptors, Nicotinic / Q000187:drug effects* / Q000378:metabolism; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology; D064569:alpha7 Nicotinic Acetylcholine Receptor
D002800:Cholinesterase Inhibitors; C579167:Chrna7 protein, human; C579165:Chrna7 protein, rat; D018696:Neuroprotective Agents; D011978:Receptors, Nicotinic; D064569:alpha7 Nicotinic Acetylcholine Receptor; C403531:nicotinic receptor alpha4beta2; D009538:Nicotine; D000109:Acetylcholine