title: Synergistic neuroprotection by bis(7)-tacrine via concurrent blockade of N-methyl-D-aspartate receptors and neuronal nitric-oxide synthase.
abstract: The excessive activation of the N-methyl-D-aspartate receptor (NMDAR)/nitric oxide (NO) pathway has been proposed to be involved in the neuropathology of various neurodegenerative disorders. In this study, NO was found to mediate glutamate-induced excitotoxicity in primary cultured neurons. Compared with the NO synthase (NOS) inhibitor, N(G)-monomethyl-L-arginine (L-NMMA), and the NMDAR antagonist memantine, bis(7)-tacrine was found to be more potent in reducing NO-mediated excitotoxicity and the release of NO caused by glutamate. Moreover, like L-NMMA but not like 5H-dibenzo[a,d]cyclohepten-5,10-imine (MK-801) and memantine, bis(7)-tacrine showed greater neuroprotection and inhibition on NO release when neurons were pretreated for a prolonged time between 0 and 24 h and remained quite potent even when neurons were post-treated 1 h after the glutamate challenge. Bis(7)-tacrine was additionally found to be as moderately potent as memantine in competing with [(3)H]MK-801, inhibiting NMDA-evoked currents and reducing glutamate-triggered calcium influx, which eventually reduced neuronal NOS activity. More importantly, at neuroprotective concentrations, bis(7)-tacrine substantially reversed the overactivation of neuronal NOS caused by glutamate without interfering with the basal activity of NOS. Furthermore, in vitro pattern analysis demonstrated that bis(7)-tacrine competitively inhibited both purified neuronal and inducible NOS with IC(50) values at 2.9 and 9.3 microM but not endothelial NOS. This result was further supported by molecular docking simulations that showed hydrophobic interactions between bis(7)-tacrine and three NOS isozymes. Taken together, these results strongly suggest that the substantial neuroprotection against glutamate by bis(7)-tacrine might be mediated synergistically through the moderate blockade of NMDAR and selective inhibition of neuronal NOS.
authors.affiliation: Department of Biochemistry, Hong Kong University of Science and Technology, Hong Kong, China.
authors.forename: Wenming
authors.initials: W
authors.lastname: Li
authors.forename: Jian
authors.initials: J
authors.lastname: Xue
authors.forename: Chunying
authors.initials: C
authors.lastname: Niu
authors.forename: Hongjun
authors.initials: H
authors.lastname: Fu
authors.forename: Colin S C
authors.initials: CS
authors.lastname: Lam
authors.forename: Jialie
authors.initials: J
authors.lastname: Luo
authors.forename: Hugh H N
authors.initials: HH
authors.lastname: Chan
authors.forename: Huaiguo
authors.initials: H
authors.lastname: Xue
authors.forename: Kelvin K W
authors.initials: KK
authors.lastname: Kan
authors.forename: Nelson T K
authors.initials: NT
authors.lastname: Lee
authors.forename: Chaoying
authors.initials: C
authors.lastname: Li
authors.forename: Yuanping
authors.initials: Y
authors.lastname: Pang
authors.forename: Mingtao
authors.initials: M
authors.lastname: Li
authors.forename: Karl W K
authors.initials: KW
authors.lastname: Tsim
authors.forename: Hualiang
authors.initials: H
authors.lastname: Jiang
authors.forename: Kaixian
authors.initials: K
authors.lastname: Chen
authors.forename: Xiaoyuan
authors.initials: X
authors.lastname: Li
authors.forename: Yifan
authors.initials: Y
authors.lastname: Han
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001667:Binding, Competitive / Q000187:drug effects; D002478:Cells, Cultured; D003198:Computer Simulation; D004357:Drug Synergism; D018698:Glutamic Acid / Q000633:toxicity; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000378:metabolism; D008559:Memantine / Q000494:pharmacology; D008969:Molecular Sequence Data; D009474:Neurons / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D018696:Neuroprotective Agents / Q000494:pharmacology*; D009498:Neurotoxins; D009569:Nitric Oxide / Q000378:metabolism; D052248:Nitric Oxide Synthase Type I / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II / Q000037:antagonists & inhibitors / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors*; D013619:Tacrine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000494:pharmacology; D013997:Time Factors; D019323:omega-N-Methylarginine / Q000494:pharmacology
chemical_list: C122128:1,7-N-heptylene-bis-9,9'-amino-1,2,3,4-tetrahydroacridine; D007527:Isoenzymes; D018696:Neuroprotective Agents; D009498:Neurotoxins; D016194:Receptors, N-Methyl-D-Aspartate; D019323:omega-N-Methylarginine; D009569:Nitric Oxide; D018698:Glutamic Acid; D013619:Tacrine; D052248:Nitric Oxide Synthase Type I; D052247:Nitric Oxide Synthase Type II; D008559:Memantine