Unequal Neuroprotection Afforded by the Acetylcholinesterase Inhibitors Galantamine, Donepezil, and Rivastigmine in SH-SY5Y Neuroblastoma Cells: Role of Nicotinic Receptors
ABSTRACT Donepezil, rivastigmine, and galantamine are three drugs with acetylcholinesterase (AChE)-inhibiting activity that are currently being used to treat patients suffering from Alzheimer's disease. We have studied the neuroprotective effects of these drugs, in comparison with nicotine, on cell death caused by beta-amyloid (Abeta) and okadaic acid, two models that are relevant to Alzheimer's pathology, in the human neuroblastoma cell line SH-SY5Y. Galantamine and donepezil showed a U-shaped neuroprotective curve against okadaic acid toxicity; maximum protection was achieved at 0.3 microM galantamine and at 1 microM donepezil; at higher concentrations, protection was diminished. Rivastigmine showed a concentration-dependent effect; maximum protection was achieved at 3 microM. When apoptosis was induced by Abeta25-35, galantamine, donepezil, and rivastigmine showed maximum protection at the same concentrations: 0.3, 1, and 3 microM, respectively. Nicotine also afforded protection against Abeta- and okadaic acid-induced toxicity. The neuroprotective effects of galantamine, donepezil, and nicotine were reversed by the alpha7 nicotinic antagonist methyllycaconitine but not by the alpha4beta2 nicotinic antagonist dihydro-beta-erythroidine. The phosphoinositide 3-kinase (PI3K)-Akt blocker 2-(4-morpholinyl)-8-phenyl-1(4H)-benzopyran-4-one hydrochloride (LY294002) reversed the protective effects of galantamine, donepezil, and nicotine but not that of rivastigmine. In contrast, the bcl-2 antagonist ethyl[2-amino-6-bromo-4-(1-cyano-2-ethoxy-2-oxoethyl)]-4H-chromene-3-carboxylate (HA 14-1) reversed the protective effects of the three AChE inhibitors and that of nicotine. Our results show that galantamine, donepezil, and rivastigmine afford neuroprotection through a mechanism that is likely unrelated to AChE inhibition. Such neuroprotection seemed to be linked to alpha7 nicotinic receptors and the PI3K-Akt pathway in the case of galantamine and donepezil but not for rivastigmine.
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ABSTRACT: In a previous work we have shown that exposure to aluminum (Al) chloride (AlCl3) enhanced the neurotoxicity of the amyloid beta25-35 fragment (Abeta25-35) in neuroblastoma cells and affected the expression of Alzheimer's disease (AD)-related genes. Caffein, a compound endowed with beneficial effects against AD, exerts neuroprotection primarily through its antagonist activity on A2A adenosine receptors (A2AR), although it also inhibits A1Rs with similar potency. Still, studies on the specific involvement of these receptors in neuroprotection in a model of combined neurotoxicity (Abeta25-35+AlCl3) are missing. To address this issue, cultured SH-SY5Y cells exposed to Abeta25-35+AlCl3 were assessed for cell viability, morphology, intracellular ROS activity and expression of apoptosis-, stress- and AD-related proteins. To define the role of A1R and A2ARs, pretreatment with caffein, specific receptor antagonists (DPCPX or SCH58261) or siRNA-mediated gene knockdown were delivered. Results indicate that AlCl3 treatment exacerbated Abeta25-35 toxicity, increased ROS production, lipid peroxidation, β-secretase-1 (BACE1) and amyloid precursor protein (APP). Interestingly, SCH58261 successfully prevented toxicity associated to Abeta25-35 only, whereas pretreatment with both DPCPX and SCH58261 was required to fully avert Abeta25-35+AlCl3-induced damage, suggesting that A1Rs might also be critically involved in protection during combined toxicity. The effects of caffein were mimicked by both N-acetyl cysteine, an antioxidant, and desferrioxamine, likely acting through distinct mechanisms. Altogether, our data establish a novel protective function associated with A1R inhibition in the setting of combined Abeta25-35+AlCl3 neurotoxicity, and expand our current knowledge on the potential beneficial role of caffein to prevent AD progression in subjects environmentally exposed to aluminum.The International Journal of Biochemistry & Cell Biology 07/2014; 54. DOI:10.1016/j.biocel.2014.07.009 · 4.24 Impact Factor
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ABSTRACT: To find the multi-target-directed compounds for the treatment of Alzheimer's disease (AD), we synthesized 7-(4-(diethylamino)butoxy)-5-hydroxy-3-(4-hydroxyphenyl)-4H-chromen-4-one, a novel 7-O-modified genistein derivative (GS-14), and investigated its acetylcholinesterase (AChE) inhibitory effect, estrogenic activity and neuroprotective effect. GS-14 acted as a selective AChE inhibitor in vitro, with an IC(50) value of 0.17 μM and showed no inhibition activity against butyrylcholinesterase (BuChE). The Lineweaver-Burk plot revealed that GS-14 was a non-competitive AChE inhibitor with a K(i) value of 0.23 μM and the molecular docking model indicated that GS-14 interacted with the peripheral anionic site (PAS) of AChE. The MCF-7 proliferation assay demonstrated that GS-14 possessed estrogenic activity and GS-14 exhibited a high specificity for estrogen receptor β (ERβ) with a dissociation constant (K(i)) of 2.86 nM compared with that of 1.01 μM for estrogen receptor α (ERα) in the molecular docking study. GS-14 also possessed a neuroprotective effect and showed the best protective effect against the β-amyloid protein-induced injury on SH-SY5Y cells at a concentration of 1 nM. Considering its AChE-inhibition activity, estrogenic activity and neuroprotective effect, GS-14 may be a potential multi-target agent for the treatment of AD.Archives of Pharmacal Research 09/2012; 35(9):1645-54. DOI:10.1007/s12272-012-0916-y · 1.75 Impact Factor
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ABSTRACT: Acetylcholinesterase (AChE) inhibitor donepezil is widely used for the treatment of Alzheimer's disease (AD). The mechanisms of therapeutic effects of the drug are not well understood. The ability of donepezil to reverse a known pathogenic effect of β-amyloid peptide (Abeta), namely, the impairment of hippocampal long-term potentiation (LTP), was not studied yet. The goal of the present study was to study the influence of donepezil in 0.1-10 μM concentrations on control and Abeta-impaired hippocampal LTP. Possible involvement of N-methyl-D: -aspartate receptors (NMDARs) into mechanisms of donepezil action was also studied. LTP of population spike (PS) was studied in the CA1 region of rat hippocampal slices. Change of LTP by donepezil treatment had a bell-shaped dose-response curve. The drug in concentrations of 0.1 and 1 μM did not change LTP while in concentration of 0.5 μM significantly increased it, and in concentration of 5 and 10 μM suppressed LTP partially or completely. Abeta (200 nM) markedly suppressed LTP. Addition of 0.1, 0.5 or 1 μM donepezil to Abeta solution caused a restoration of LTP. N-methyl-D: -aspartate (NMDA) currents were studied in acutely isolated pyramidal neurons from CA1 region of rat hippocampus. Neither Abeta, nor 0.5 μM donepezil were found to change NMDA currents, while 10 μM donepezil rapidly and reversibly depressed it. Results suggest that donepezil augments control and impaired by Abeta hippocampal LTP in NMDAR-independent manner. In general, our findings extend the understanding of mechanisms of therapeutic action of donepezil, especially at an early stage of AD, and maybe taken into account while considering the possibility of donepezil overdose.Cellular and Molecular Neurobiology 03/2012; 32(2):219-26. DOI:10.1007/s10571-011-9751-9 · 2.20 Impact Factor