Synergistic neuroprotection by bis(7)-tacrine via concurrent blockade of N-methyl-D-aspartate receptors and neuronal nitric-oxide synthase.
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.
Li
Wenming
W
Department of Biochemistry, Hong Kong University of Science and Technology, Hong Kong, China.
Xue
Jian
J
Niu
Chunying
C
Fu
Hongjun
H
Lam
Colin S C
CS
Luo
Jialie
J
Chan
Hugh H N
HH
Xue
Huaiguo
H
Kan
Kelvin K W
KK
Lee
Nelson T K
NT
Li
Chaoying
C
Pang
Yuanping
Y
Li
Mingtao
M
Tsim
Karl W K
KW
Jiang
Hualiang
H
Chen
Kaixian
K
Li
Xiaoyuan
X
Han
Yifan
Y
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
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