[Show abstract][Hide abstract] ABSTRACT: Galantamine, currently used in Alzheimer's patients, has shown neuroprotection in hippocampal slices subjected to oxygenglucose deprivation. Here, we present an in vivo study to evaluate the potential neuroprotective effects of galantamine in a transient global cerebral ischemia model in gerbils. Three treatment protocols were used. In the pretreatment protocol, gerbils were treated before ischemia and for 3 consecutive days thereafter. Eight groups of animals were included: sham operation plus placebo, 10 mg/kg mecamylamine and 10 mg/kg galantamine, respectively; and ischemia plus placebo, 10 mg/kg mecamylamine, 1 mg/kg galantamine, and 10 mg/kg galantamine and 10 mg/kg mecamylamine plus galantamine, respectively. Postischemia protocols included three groups of animals: sham operation, ischemia plus placebo, and ischemia plus 10 mg/kg galantamine; substances were administered 3 or 6 h after ischemia and for 2 consecutive days thereafter. Pyramidal neurons surviving in the cornus ammonis 1 region of the hippocampus were evaluated 72 h after reperfusion, terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) histochemistry, caspase-3 and superoxide dismutase (SOD)-2 immunohistochemistries, and Western blottings were performed, and object placement tests were carried out. Galantamine significantly increased the number of living pyramidal neurons after ischemia-reperfusion injury. Galantamine significantly reduced TUNEL, active caspase-3, and SOD-2 immunoreactivity. The nicotinic antagonist mecamylamine blocked the protective effects of galantamine. The neuroprotective effects of galantamine were preserved even when first administered at 3 h postischemia. These results correlated with the performance in the object placement test. This study shows that galantamine provides in vivo neuroprotection and memory recovery against global cerebral ischemia, even when administration begins 3 h postischemia.
Full-text · Article · Sep 2007 · Journal of Pharmacology and Experimental Therapeutics
[Show abstract][Hide abstract] ABSTRACT: The hypothesis that K(+) channels and cell depolarization are involved in neuronal death and neuroprotection was tested in bovine chromaffin cells subjected to two treatment periods: the first period (preconditioning period) lasted 6 to 48 h and consisted of treatment with high K(+) solutions or with tetraethylammonium (TEA), a K(+) channel blocker; the second period consisted of incubation with veratridine for 24 h, to cause cell damage. Preconditioning with high K(+) (20-80 mM) or TEA (10-30 mM) for 24 h caused 20-60% cytoprotection against veratridine-induced cell death in bovine chromaffin cells. The absence of Ca(2+) ions during the first 9 h of an 18-h preconditioning period abolished the cytoprotection. Preconditioning with K(+) or TEA increased by 2.5-fold the expression of brain-derived neurotrophic factor and by nearly 2-fold the expression of the antiapoptotic protein Bcl-2. However, preconditioning did not modify the veratridine-evoked Ca(2+) signal. High K(+) shifted the Em by about 10 mV and TEA evoked a transient burst of action potentials superimposed on a sustained depolarization. We conclude that preconditioning may protect chromaffin cells from death by blocking K(+) channels that depolarize the cell and cause a cytosolic Ca(2+) signal, leading to enhanced expression of BDNF and Bcl-2.
No preview · Article · Jan 2007 · European Journal of Pharmacology
[Show abstract][Hide abstract] ABSTRACT: Galantamine is a drug in clinical use for the treatment of Alzheimer's disease, but its mechanism(s) of action remains controversial. Here we addressed the question whether galantamine could potentiate neurotransmitter release by inhibiting small conductance Ca2+ -activated K+ channels (KCa2). Galantamine potentiated catecholamine secretory responses induced by 10 s pulses of acetylcholine and high [K+]o applied to fast-superfused bovine adrenal chromaffin cell populations. Catecholamine release was significantly enhanced by galantamine although we did not find concentration dependence in the range 0.1-1 microM. The KCa2 channel blocker apamin (0.3 microM) occluded the potentiating effects of galantamine on acetylcholine-evoked secretion. Like apamin, galantamine also modified the firing of action potentials, but to a lesser extent. In addition, 1 microM galantamine reduced by 41% the KCa2 current without modifying the voltage-dependent Ca2+ currents. These results constitute the first direct evidence that galantamine can potentiate neurotransmitter release by blocking KCa2 channels, in addition to its already demonstrated capacity to mildly block acetylcholinesterase or potentiate allosterically nicotinic receptors.
Full-text · Article · Nov 2006 · European Journal of Pharmacology
[Show abstract][Hide abstract] ABSTRACT: The most frequent of the primary degenerative dementias is Alzheimer's disease (AD). The gradual loss of memory and attention in patients suffering from this illness are accompanied by aphasia, apraxia, agnosia, and alterations in visual-spatial perception. This group of symptoms is completed by emotional alterations, psychic instability, and changes in personality that appear in advanced phases of the illness. Different histopathological alterations have been described, like marked atrophy of the cerebral cortex with loss of cortical and subcortical neurons. Other histopathological hallmarks are the formation of senile plaques composed of beta-amyloid (Abeta) and neuro fibrillary tangles composed of hyperphosphorylation of tau protein.
Full-text · Article · Feb 2006 · Journal of Molecular Neuroscience
[Show abstract][Hide abstract] 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.
Preview · Article · Jan 2006 · Journal of Pharmacology and Experimental Therapeutics
[Show abstract][Hide abstract] ABSTRACT: Serum albumin protects against cell death elicited by various cytotoxic agents; however, conflicting views on the protective mechanism still remain. Hence, we have studied the ability of serum albumin to prevent apoptosis of human neuroblastoma SH-SY5Y cells elicited by four compounds known to release Ca2+ from the endoplasmic reticulum, i.e. dotarizine, flunarizine, thapsigargin and cyclopiazonic acid. Spontaneous basal apoptosis, after 24 h incubation in Dulbecco's Modified Eagle Medium (DMEM) containing 10% serum, was 5%. Dotarizine (30-50 μM) enhanced basal apoptosis to 18-43%, flunarizine (30-50 μM) to 15%, thapsigargin (1-10 μM) to 21-35%, and cyclopiazonic acid (100 μM) to 10%. Serum deprivation augmented basal apoptosis to 20%. Under serum-free medium, 30 μM dotarizine or flunarizine drastically enhanced apoptosis to 63% and 68%, respectively; the increase was milder with 1 μM thapsigargin (37%) and 30 μM cyclopiazonic acid (27%). In serum-free medium, albumin (29 or 49 mg/ml) fully prevented the apoptotic effects of dotarizine, flunarizine and cyclopiazonic acid. The four compounds increased the cytosolic Ca2+ concentration ([Ca2+]c) in fluo-4 loaded cells; such increase developed slowly to reach a plateau after several minutes, followed by a slow decline. Albumin did not modify the kinetic parameters of such increase. In the absence of serum, dotarizine, flunarizine, thapsigargin, and cyclopiazonic acid caused mitochondrial depolarization in tetramethylrhodamine ethyl ester (TMRE)-loaded cells; depolarization was inhibited by cytoprotective concentrations of albumin. These results suggest that albumin protects cells from entering into apoptosis by preventing mitochondrial depolarization. They also suggest that inhibition of mitochondrial depolarization might become a target to develop new antiapoptotic compounds with therapeutic neuroprotective potential in stroke, Alzheimer's disease, and other neurodegenerative diseases.
No preview · Article · Oct 2005 · European Journal of Pharmacology
[Show abstract][Hide abstract] ABSTRACT: The ability of nicotine to induce a cytoprotective or neuroprotective action occurs through several downstream mechanisms. One possibility is that the drug increases the expression of tyrosine kinase A (TrkA) nerve growth factor (NGF) receptors. Certain beta-amyloid peptides (e.g., Abeta1-42) have been shown to bind with high affinity to alpha7 nicotinic receptors and thus interfere with a potentially neurotrophic influence. Treatment of differentiated PC-12 cells with nicotine produced a concentration-dependent increase in cell-surface TrkA receptors that occurred concomitantly with cytoprotection. The effect of nicotine was blocked by either of the alpha7 receptor antagonists alpha-bungarotoxin (alpha-BTX) or methyllycaconatine. The cytoprotective action of nicotine also was inhibited by pretreatment with 10-100 nM Abeta1-42. Nicotine also was administered (four injections of 30 microg, spaced evenly over 24 h) to rats by direct injection into a lateral cerebral ventricle. Brain TrkA expression was increased significantly in hippocampus and entorhinal cortex (up to 32% above control), with no changes found in cerebral cortex or hypothalamus. The nicotine-induced increases in TrKA expression in hippocampus and entorhinal cortex were significantly inhibited by 10 microg alpha-BTXor by 10 nmol Abeta1-42. Therefore, physiologically relevant concentrations of Abeta1-42 can prevent nicotine-induced TrkA receptor expression in brain regions containing cholinergic neurons susceptible to the neurotoxicity associated with Alzheimer's disease.
No preview · Article · Feb 2005 · Journal of Molecular Neuroscience
[Show abstract][Hide abstract] ABSTRACT: The ability of choline to serve as a full, though low potency agonist for the alpha7 nicotinic receptor has provided the impetus to develop analogs that exhibit levels of potency and effectiveness suitable for use as therapeutic agents. Seven analogs of choline were synthesized based on previous work with the analog pyrrolidinecholine. The drugs were administered to differentiated PC-12 cells 24 hr prior to growth factor withdrawal which itself induced cytotoxicity in 30-40% of the cells. Three of 7 choline analogs exhibited potency and efficacy similar to that for nicotine as cytoprotective agents. Despite being tertiary amines, 4 of the choline analogs were more potent than choline in inhibiting [(3)H]choline uptake into cultured fibroblasts transfected with the high affinity, sodium-dependent choline transporter. One of the most effective analogs JAY 2-21-29 was shown to produce a potent (EC50 approximately 30 nM) cytoprotective action that was blocked by pretreatment with the alpha7 nicotinic receptor selective antagonist methyllycaconitine, but not by thealpha2 subtype-preferring antagonist dihydro-beta-erythroidin. These preliminary studies support the further neurochemical characterization of these compounds 1) as selectivealpha7 nicotinic receptor agonists and, 2) based on their interaction with the choline transporter, as potential cholinergic false neurotransmitters as has been demonstrated for pyrrolidinecholine.
No preview · Article · Jan 2005 · Journal of Alzheimer's disease: JAD
[Show abstract][Hide abstract] ABSTRACT: Ethyl 5-amino-6,7,8,9-tetrahydro-2-methyl-4-phenylbenzol[1,8] naphthyridine-3-carboxylate (ITH4012) is a novel tacrine derivative that can reduce cell death induced by various compounds with different mechanisms of action, such as thapsigargin (reticular stress), H2O2 (free radicals), and veratridine (calcium overload), in bovine chromaffin cell. Cell viability, quantified as lactic dehydrogenase release, was significantly reduced by ITH4012 at concentrations ranging from 0.01 to 3 microM. In the human neuroblastoma cell line SH-SY5Y, ITH4012 also reduced amyloid beta25-35-induced apoptosis, determined by flow cytometry. ITH4012 caused a slight elevation in the cytosolic concentration of Ca2+ in fura 2-loaded bovine chromaffin cells, which could be related to the induction of protein synthesis relevant for cell survival. Blockade of protein synthesis by cycloheximide or blockade of Bcl-2's active site with HA14-1 (ethyl 2-amino-6-bromo-4-(1-cyano-2-ethoxy-2-oxoethyl)-4H-chromene-3-carboxylate) reversed the cytoprotective action of ITH4012. Furthermore, exposure of bovine chromaffin cells for 24 or 48 h to neuroprotective concentrations of this compound enhanced, nearly 3-fold, the expression of the antiapoptotic protein Bcl-2. In conclusion, ITH4012 is a tacrine derivative that maintains acetylcholinesterase-inhibiting activity (IC50=0.8 microM) but has the additional property of acting as a calcium promotor, a property leading to neuroprotection through the induction of antiapoptotic proteins.
Full-text · Article · Oct 2004 · Journal of Pharmacology and Experimental Therapeutics
[Show abstract][Hide abstract] ABSTRACT: Galantamine is currently used to treat Alzheimer's disease patients; it behaves as a mild blocker of acetylcholinesterase (AChE) and has an allosteric modulating action on nicotinic acetylcholine receptors (nAChRs). In this study, we observed that galantamine prevented cell death induced by the peptide beta-amyloid(1-40) and thapsigargin in the human neuroblastoma cell line SH-SY5Y, as well as in bovine chromaffin cells. The protective effect of galantamine was concentration-dependent in both cell types; maximum protection was produced at 300 nM. The antiapoptotic effect of galantamine at 300 nM, against beta-amyloid(1-40) or thapsigargin-induced toxicity, was reversed by alpha-bungarotoxin. At neuroprotective concentrations, galantamine caused a mild and sustained elevation of the cytosolic concentration of calcium, [Ca2+]c, measured in single cells loaded with Fura-2. Incubation of the cells for 48 h with 300 nM galantamine doubled the density of alpha7 nicotinic receptors and tripled the expression of the antiapoptotic protein Bcl-2. These results strongly suggest that galantamine can prevent apoptotic cell death by inducing neuroprotection through a mechanism related to that described for nicotine, i.e. activation of nAChRs and upregulation of Bcl-2. These findings might explain the long-term beneficial effects of galantamine in patients suffering of Alzheimer's disease.
No preview · Article · Feb 2004 · Neuropharmacology
[Show abstract][Hide abstract] ABSTRACT: La peculiar historia de las estatinas se asemeja a la biografía de otros muchos medicamentos que hoy están en el mercado y que han sido redescubiertos con el tiempo. Un fármaco para la presión arterial elevada que favorece el crecimiento capilar (minoxidil); unos antibióticos (las tetraciclinas) que, además, tienen efectos beneficiosos en la artritis reumatoide; y la estrella, aspirina, un producto contra el dolor que reduce la inflamación, el riesgo de infarto y, probablemente, disminuya el riesgo de padecer ciertos tipos de cáncer. Como bien recordaba a "The Washington Post", Carl J. Vaughan, de la Weill Medical School of Cornell University (EEUU): "La farmacología está llena de hallazgos inesperados, incluso en fases tardías en la vida de un medicamento".