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 ␤-amyloid (A␤) 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 M galantamine and at 1 M donepezil; at higher concentrations, protection was diminished. Rivastigmine showed a concentration-dependent effect; maximum protection was achieved at 3 M. When apoptosis was induced by A␤ [25][26][27][28][29][30][31][32][33][34][35] , galantamine, donepezil, and rivastigmine showed maximum protection at the same concentrations: 0.3, 1, and 3 M, respectively. Nicotine also afforded protection against A␤-and okadaic acid-induced toxicity. The neuroprotective effects of galantamine, donepezil, and nicotine were reversed by the ␣7 nicotinic antagonist methyllycaconitine but not by the ␣4␤2 nicotinic antagonist dihydro-␤-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 ␣7 nicotinic receptors and the PI3K-Akt pathway in the case of galantamine and donepezil but not for rivastigmine.Alzheimer's disease (AD) is a progressive neurodegenerative disease and the most common form of dementia in the elderly population. Clinically, patients with AD show progressive deterioration of all cognitive functions, resulting in their incapacitation. AD is characterized by the presence of two kinds of abnormal protein deposits, amyloid plaques and neurofibrillary tangles (NFTs) in specific areas of the brain, and finally by the atrophy of the affected brain regions, which results from extensive losses of synapses and neurons (Terry et al., 1981(Terry et al., , 1991Price et al., 1991;Arriagada et al., 1992). Amyloid plaques are extracellular deposits containing ␤-amyloid peptide (A␤) as the major core deposits. A␤ is a 39-to 43-amino acid peptide fragment derived through proteolysis from an integral membrane protein known as A␤ precursor protein. The basis for the ␤-amyloid hypothesis arises from various studies showing that A␤ is toxic to neurons; for example, there is increased A␤ release and apoptotic cell

Donepezil delays photoreceptor apoptosis induced by N-methyl-N-nitrosourea in mice

“…In experiments using rat cortical neurons, Takada et al (9) showed that the neuroprotection afforded by donepezil was prevented by methyllycaconitine (MLA), an α7-selective nAChR antagonist, but not by scopolamine, a muscarinic (m)AChR antagonist. These results were consistent with a previous study (31), which observed that the neuroprotective effect of donepezil was reversed by MLA in human neuroblastoma cells and that donepezil exerted neuroprotective effects via nAChRs. Conversely, Miki et al (12) reported that both mecamylamine, a nAChR antagonist, and scopolamine, were unable to affect the neuroprotective effect of donepezil on RGCs in vitro.…”

Amary llidaceae Perspectives In Alzheimer´S Disease

“…These data suggest a significant reduction in the levels of nAChRs α3, α7 and β2 protein subunits observed in cell lines exposed to peptide [37]. The progressive deterioration of the cholinergic system, together with the pharmacological evidence of AChEIs, have led to the development of cholinergic hypothesis, widely accepted and becomes evident by drugs such as donepezil, rivastigmine and galantamine, which act as AChEIs to increase the concentration of ACh between the synaptic cleft and modulate the nAChRs such as potent allosteric ligands [18].…”

“…Galantamine commercialized under the generic name of Reminil® was the first alkaloid isolated from different species of Amaryllidaceae (Leucojum spp., Narcissus species, Galanthus spp) and is the most recently ACHEI approved in many countries for the symptomatic treatment of Alzheimer´s disease [51]. However, the pharmacological history of galantamine shows that it has been used throughout Eastern Europe since 1950, and the plant extracts with this kind of active compound were initially used to treat nerve pain and poliomyelitis [52].Galantamine is a cholinergic drug with antioxidant properties; neuroprotective and anti-apoptotic action [18,53] by its dual mechanism of action; moreover, it regulates the cholinergic transmission as ACHEI and allosterically modulates nAChRs [54]. The drug stimulates choline acetyltransferase activity and enhances the release of acetylcholine neurotransmitter, increasing its concentration in the synaptic clefts [53].…”

“…Previous studies evaluating inhibitory action on GSK3 observed a correlation with reduced tauopathy and degeneration in a variety of animal models, in fact, GSK3 gene was previously associated with cancer [15][16][17]. In Alzheimer's conditions, the structural changes caused by tau hyperphosphorylation, interfere with the normal neurons function, lead to loss of biological activity and cell death [18]. Likewise, tau hyperphosphorylation may lead to defects in the mitotic spindle and result in a number of aneuploidies of chromosome 17 and 21, together with abnormal expression of tau protein, APP and Aβ peptide, which are discussed in terms of its association with Alzheimer [19].…”

Novel sulfoglycolipid IG20 causes neuroprotection by activating the phase II antioxidant response in rat hippocampal slices

“…Similar neurotoxicity experiments were performed in primary cultures of bovine adrenal chromaffin cells (BCCs) that were prepared as described by Moro et al (1990) as well as in the tumoral cell line from human neuroblastoma SH-SY5Y that were prepared as previously described (Arias et al, 2005).…”