Acetylcholinesterase is increased in mouse neuronal and astrocyte cultures after treatment with beta-amyloid peptides

Amyloid precursor protein glycosylation is altered in the brain of patients with Alzheimer's disease

Background

The amyloid precursor protein (APP) is a transmembrane glycoprotein that undergoes alternative proteolytic processing. Its processing through the amyloidogenic pathway originates a large sAPPβ ectodomain fragment and the β-amyloid peptide, while non-amyloidogenic processing generates sAPPα and shorter non-fibrillar fragments. Hence, measuring sAPPα and sAPPβ has been proposed as a means to identify imbalances between the amyloidogenic/non-amyloidogenic pathways in the brain of Alzheimer’s disease (AD) patients. However, to date, no consistent changes in these proteolytic fragments have been identified in either the brain or cerebrospinal fluid of AD individuals.

Methods

In frontal cortex homogenates from AD patients (n = 7) and non-demented controls (NDC; n = 7), the expression of total APP mRNA and that of the APP isoforms generated by alternative splicing, APP695 and APP containing the Kunitz protease inhibitor (KPI), was analyzed by qRT-PCR using TaqMan and SYBR Green probes. The balance between the amyloidogenic/non-amyloidogenic pathways was examined in western blots estimating the sAPPα and sAPPβ fragments and their membrane-tethered C-terminal fragments CTFα and CTFβ. CHO-PS70 cells, stably over-expressing wild-type human APP, served to evaluate whether Aβ42 peptide treatment results in altered APP glycosylation. We determined the glycosylation pattern of sAPPα and sAPPβ in brain extracts and CHO-PS70 culture media by lectin-binding assays.

Results

In the cortex of AD patients, we detected an increase in total APP mRNA relative to the controls, due to an increase in both the APP695 and APP-KPI variants. However, the sAPPα or sAPPβ protein levels remained unchanged, as did those of CTFα and CTFβ. We studied the glycosylation of the brain sAPPα and sAPPβ using lectins and pan-specific antibodies to discriminate between the fragments originated from neuronal APP695 and glial/KPI variants. Lectin binding identified differences in the glycosylation of sAPPβ species derived from the APP695 and APP-KPI variants, probably reflecting their distinct cellular origin. Moreover, the lectin-binding pattern differed in the sAPPα and sAPPβ originated from all the variants. Finally, when the lectin-binding pattern was compared between AD and NDC groups, significant differences were evident in sAPPα glycosylation. Lectin binding of the soluble sAPPα and sAPPβ from CHO-PS70 cells were also altered in cells treated with the Aβ peptide.

Conclusion

Our analysis of the lectin binding to sAPPα and sAPPβ suggests that glycosylation dictates the proteolytic pathway for APP processing. Differences between the demented and controls indicate that changes in glycosylation may influence the generation of the different APP fragments and, consequently, the pathological progression of AD.

Telmisartan/17β-estradiol mitigated cognitive deficit in an ovariectomized rat model of Alzheimer's disease: Modulation of ACE1/ACE2 and AT1/AT2 ratio

AIMS

The higher incidence rate of Alzheimer's disease (AD) among women has led to explorations on the association between estrogen deficiency and AD. Also, usage of antihypertensive drugs has been suggested to reduce the incidence of AD in elderly hypertensive patients. Thus, this study aimed to investigate the effects of telmisartan and/or 17β-estradiol on a cognitively impaired ovariectomized rat model of AD.

MAIN METHODS

75 female Wistar rats were randomly allocated into five groups. One group was sham operated and the other four groups were subjected to ovariectomy, received D-galactose and either untreated or treated with telmisartan and/or 17β-estradiol for 6 weeks.

KEY FINDINGS

Ovariectomized rats showed cognitive impairment in Morris water maze and novel object recognition tests, increasing inflammatory biomarkers (tumor necrosis factor-α, and interleukin-1β), increasing AD biomarkers (amyloid beta1-42, and acetylcholine esterase), and over activation of classical arm of renin angiotensin system (RAS) (ACE1/Ang2/AT1) in hippocampi. Also, hippocampi histopathological examination revealed amyloid beta deposition. Whereas, administration of telmisartan and/or 17β-estradiol improved animals' behavior, alleviated histopathological alterations and reduced the level of inflammatory and AD biomarkers, modulated RAS activity favoring the novel neuroprotective arm (ACE2/Ang(1-7)/MasR).

SIGNIFICANCE

Our findings suggest that combined administration of both drugs has synergetic neuroprotective effects; supporting their potential application in AD treatment.

Astrocyte-Targeted Transporter-Utilizing Derivatives of Ferulic Acid Can Have Multifunctional Effects Ameliorating Inflammation and Oxidative Stress in the Brain

Ferulic acid (FA) is a natural phenolic antioxidant, which can exert also several other beneficial effects to combat neuroinflammation and neurodegenerative diseases, such as Alzheimer's disease. One of these properties is the inhibition of several enzymes and factors, such as β-site amyloid precursor protein (APP) cleaving enzyme 1 (BACE1), cyclooxygenases (COXs), lipoxygenases (LOXs), mammalian (or mechanistic) target for rapamycin (mTOR), and transcription factor NF-κB. We have previously synthesized three L-type amino acid transporter 1- (LAT1-) utilizing FA-derivatives with the aim to develop brain-targeted prodrugs of FA. In the present study, the cellular uptake and bioavailability of these FA-derivatives were evaluated in mouse primary astrocytic cell cultures together with their inhibitory effects towards BACE1, COX/LOX, mTOR, NF-κB, acetylcholinesterase (AChE), and oxidative stress. According to the results, all three FA-derivatives were taken up 200–600 times more effectively at 10 μM concentration into the astrocytes than FA, with one derivative having a high intracellular bioavailability (K_p,uu), particularly at low concentrations. Moreover, all of the derivatives were able to inhibit BACE1, COX/LOX, AChE, and oxidative stress measured as decreased cellular lipid peroxidation. Furthermore, one of the derivatives modified the total mTOR amount. Therefore, these derivatives have the potential to act as multifunctional compounds preventing β-amyloid accumulation as well as combating inflammation and reducing oxidative stress in the brain. Thus, this study shows that converting a parent drug into a transporter-utilizing derivative not only may increase its brain and cellular uptake, and bioavailability but can also broaden the spectrum of pharmacological effects elicited by the derivative.

In vivo localization of human acetylcholinesterase-derived species in a β-sheet conformation at the core of senile plaques in Alzheimer's disease

Many neurodegenerative diseases are characterized by amyloid deposition. In Alzheimer's disease (AD), β-amyloid (Aβ) peptides accumulate extracellularly in senile plaques. The AD amyloid cascade hypothesis proposes that Aβ production or reduced clearance leads to toxicity. In contrast, the cholinergic hypothesis argues for a specific pathology of brain cholinergic pathways. However, neither hypothesis in isolation explains the pattern of AD pathogenesis. Evidence suggests that a connection exists between these two scenarios: the synaptic form of human acetylcholinesterase (hAChE-S) associates with plaques in AD brains; among hAChE variants, only hAChE-S enhances Aβ fibrillization in vitro and Aβ deposition and toxicity in vivo Only hAChE-S contains an amphiphilic C-terminal domain (T40, AChE_575-614), with AChE_586-599 homologous to Aβ and forming amyloid fibrils, which implicates T40 in AD pathology. We previously showed that the amyloid scavenger, insulin-degrading enzyme (IDE), generates T40-derived amyloidogenic species that, as a peptide mixture, seed Aβ fibrillization. Here, we characterized 11 peptides from a T40-IDE digest for β-sheet conformation, surfactant activity, fibrillization, and seeding capability. We identified residues important for amyloidogenicity and raised polyclonal antibodies against the most amyloidogenic peptide. These new antisera, alongside other specific antibodies, labeled sections from control, hAChE-S, hAPPswe, and hAChE-S/hAPPswe transgenic mice. We observed that hAChE-S β-sheet species co-localized with Aβ in mature plaque cores, surrounded by hAChE-S α-helical species. This observation provides the first in vivo evidence of the conformation of hAChE-S species within plaques. Our results may explain the role of hAChE-S in Aβ deposition and aggregation, as amyloidogenic hAChE-S β-sheet species might seed Aβ aggregation.

Neuroprotective effects of bergenin in Alzheimer's disease: Investigation through molecular docking, in vitro and in vivo studies

Alzheimer's disease (AD) is an enervating and chronic progressive neurodegenerative disorder, occurring frequently in the elderly and adversely affecting intellectual capabilities and the cognitive processes. Bergenin possesses efficacious antioxidant, antiulcerogenic, anti-HIV, hepatoprotective, neuroprotective, anti-inflammatory and immunomodulatory activity along with antinociceptive effect and wound healing properties. Previous studies have shown that bergenin has in vitro bovine adrenal tyrosine hydroxylase inhibitory activity, mushroom tyrosinase inhibitory activities, β-secretase (BACE-1) enzyme inhibitory activity and prevented neuronal death in the primary culture of rat cortical neurons. Protein tyrosine phosphatase-1B (PTP1B) is an intriguing target for anticancer and antidiabetic drugs and has recently been implicated to act as a positive regulator of neuroinflammation. Bergenin is also found to inhibit human protein tyrosine phosphatase-1B (hPTP1B) in vitro. Thus, bergenin was screened by molecular docking study using GOLD suite (version 5.2), CCDC for predicting its activity against targets of AD management like acetylcholinesterase (AChE) (1B41), butyrylcholinesterase (BuChE) (1P0I), Tau protein kinase 1 (GSK-3β) (1J1B), BACE-1 (1FKN) wherein the GOLD score and fitness of bergenin were comparable to those of standard drugs like donepezil, galanthamine, physostigmine, etc. Bergenin demonstrated dose-dependent inhibition of both AChE and BuChE in vitro and found to be safe up to 50 μM when screened in vitro on SH-SY5Y cell lines by cytotoxicity studies using MTT and Alamar blue assays. It also led to dose-dependent prevention of NMDA induced toxicity in these cells. Pretreatment with bergenin (14 days) in rats at three dose levels (20, 40 and 80 mg/kg; p.o.) significantly (p < 0.01) and dose-dependently alleviated amnesia induced by scopolamine (2 mg/kg, i.p.). The therapeutic effect of bergenin supplementation for 28 days, at three dose levels, was also evaluated in streptozotocin (3 mg/kg, ICV, unilateral) induced AD model in Wistar rats using Morris water maze and Y maze on 7th, 14th, 21st and 28th days. STZ caused significant (p < 0.001) cognitive impairment and cholinergic deficit and increased oxidative stress in rats. Bergenin could significantly ameliorate STZ induced behavioral deficits, inhibit the AChE and BuChE activity in parallel with an increase in the diminished GSH levels in a dose-dependent fashion. The histopathological investigations were also supportive of this datum. The bergenin treatment at 80 mg/kg led to significant (p < 0.05) abatement of the raised Aβ-_1-42 levels and alleviated the perturbed p- tau levels leading to significantly low (p < 0.01) levels of p-tau in brain homogenates of rats as compared to ICV STZ injected rats. In conclusion, the observed effects might be attributed to the cholinesterase inhibitory activity of bergenin coupled with its antioxidant effect, anti-inflammatory activity and reduction of Aβ-_1-42 and p-tau levels which could have collectively helped in the attenuation of cognitive deficits. The current findings of the study are indicative of the promising preventive and ameliorative potential of bergenin in the management of AD through multiple targets.

N-acetylcysteine treatment attenuates the cognitive impairment and synaptic plasticity loss induced by streptozotocin

Alzheimer's disease (AD) is a neurodegenerative disorder pathologically characterized by severe neuronal and glial structural changes and progressive cognitive decline. N-acetylcysteine (NAC) is a well-known pharmacological agent with pro-neurogenic properties and neuroprotective effects. In this study, we evaluated NAC protective effects on cognitive impairment and associated pathological markers in a streptozotocin (STZ)-induced sporadic dementia of AD type mice model. Animals were divided into six groups: I) Sham, II) NAC, III) physostigmine (PHY), IV) STZ, V) NAC + STZ and VI) PHY + NAC. NAC (5 mg/kg) and PHY (0.25 mg/kg) were administrated orally for 30 consecutive days and STZ (2.5 mg/kg) intracerebroventricularly at the first and third days. Novel object recognition (NOR, days 26-27) and Morris water maze (MWM, days 26-30) tasks were assessed to evaluate learning and memory. On the thirty-first day animals were euthanized and brains collected for biochemical analysis. Interestingly, our results showed that STZ treatment induced cognitive impairment in mice in the NOR and MWM tasks. Both NAC and PHY treatments prevented from this impairment. The increase in AChE activity and decrease in pTrkB and MnSOD levels caused by STZ in the cerebral cortex and hippocampus, were prevented by the NAC and PHY treatments. The decrease in SYN, MAP2 and GFAP expressions were also prevented by NAC and PHY treatments. In conclusion, NAC treatment prevented the cognitive impairment induced by STZ, normalizing the AChE activity and rescuing the synaptic plasticity loss. Our results suggest that NAC is a promising therapeutic strategy for the treatment of AD.

(I) Pharmacological profiling of a novel modulator of the α7 nicotinic receptor: Blockade of a toxic acetylcholinesterase-derived peptide increased in Alzheimer brains

The primary cause of Alzheimer's disease is unlikely to be the much studied markers amyloid beta or tau. Their widespread distribution throughout the brain does not account for the specific identity and deep subcortical location of the primarily vulnerable neurons. Moreover an unusual and intriguing feature of these neurons is that, despite their diverse transmitters, they all contain acetylcholinesterase. Here we show for the first time that (1) a peptide derived from acetylcholinesterase, with independent trophic functions that turn toxic in maturity, is significantly raised in the Alzheimer midbrain and cerebrospinal fluid; (2) a synthetic version of this peptide enhances calcium influx and eventual production of amyloid beta and tau phosphorylation via an allosteric site on the α7 nicotinic receptor; (3) a synthetic cyclic version of this peptide is neuroprotective against the toxicity not only of its linear counterpart but also of amyloid beta, thereby opening up the prospect of a novel therapeutic approach.

Interaction of acetylcholinesterase with neurexin-1β regulates glutamatergic synaptic stability in hippocampal neurons

Background

Excess expression of acetylcholinesterase (AChE) in the cortex and hippocampus causes a decrease in the number of glutamatergic synapses and alters the expression of neurexin and neuroligin, trans-synaptic proteins that control synaptic stability. The molecular sequence and three-dimensional structure of AChE are homologous to the corresponding aspects of the ectodomain of neuroligin. This study investigated whether excess AChE interacts physically with neurexin to destabilize glutamatergic synapses.

Results

The results showed that AChE clusters colocalized with neurexin assemblies in the neurites of hippocampal neurons and that AChE co-immunoprecipitated with neurexin from the lysate of these neurons. Moreover, when expressed in human embryonic kidney 293 cells, N-glycosylated AChE co-immunoprecipitated with non-O–glycosylated neurexin-1β, with N-glycosylation of the AChE being required for this co-precipitation to occur. Increasing extracellular AChE decreased the association of neurexin with neuroligin and inhibited neuroligin-induced synaptogenesis. The number and activity of excitatory synapses in cultured hippocampal neurons were reduced by extracellular catalytically inactive AChE.

Conclusions

Excessive glycosylated AChE could competitively disrupt a subset of the neurexin–neuroligin junctions consequently impairing the integrity of glutamatergic synapses. This might serve a molecular mechanism of excessive AChE induced neurodegeneration.

Protective effects of Wu-Zi-Yan-Zong-Fang on amyloid beta-induced damage in vivo and in vitro

This study was designed to determine the effects of Wu-Zi-Yan-Zong-Fang on amyloid-beta(25-35)-induced cognitive deficits in rats and neurotoxicity in pheochromocytoma cells and the possible mechanism of action. In vivo studies showed that Wu-Zi-Yan-Zong-Fang significantly ameliorated the spatial memory and retention deficits, decreased acetylcholinesterase activity, and increased acetylcholine content caused by intracerebroventricular injection of amyloid-beta(25-35). In vitro results showed that Wu-Zi-Yan-Zong-Fang increased cell viability and the activity of superoxide dismutase and catalase and decreased the release of lactate dehydrogenase and the level of malondialdehyde. Wu-Zi-Yan-Zong-Fang also significantly reduced the percentage of apoptotic cells and blocked the increase in the intracellular concentration of Ca(2+). These data suggest that Wu-Zi-Yan-Zong-Fang has potent protective effects for the treatment of Alzheimer's disease in future.

Galantamine protects against oxidative stress induced by amyloid-beta peptide in cortical neurons

Galantamine is currently used in the treatment of patients with mild-to-moderate Alzheimer's disease (AD). Although its action is mostly directed at the regulation of cholinergic transmission, galantamine can also afford neuroprotection against amyloid-beta peptide (Abeta), which is involved in AD pathogenesis. In this study, we used cultured rat cortical neurons treated with two forms of Abeta(1-40), fresh and previously aged (enriched in fibrils). First, we confirmed that galantamine prevented neurodegeneration induced by both peptide forms in a concentration-dependent manner. Moreover, we observed that when neurons were co-incubated with fresh Abeta(1-40) plus galantamine, the amount of amyloid aggregates was reduced. As oxidative conditions influence Abeta aggregation, we investigated whether galantamine prevents oxidative stress induced by this peptide. The data show that either fresh or aged Abeta(1-40) significantly increased the amount of reactive oxygen species and lipoperoxidation, these effects being prevented by galantamine. In Abeta(1-40)-treated neurons, the depletion of reduced glutathione (GSH) seems to be related to the decrease in glutathione peroxidase and glutathione reductase activities(.) These alterations in the GSH antioxidant system were prevented by galantamine. Overall, these results constitute the first evidence that galantamine can prevent the neuronal oxidative damage induced by Abeta, providing an in vitro basis for the beneficial actions of galantamine in the AD neurodegenerative process.

Association between acetylcholinesterase and beta-amyloid peptide in Alzheimer's cerebrospinal fluid

The altered expression of acetylcholinesterase (AChE) in the brains of patients with Alzheimer's disease (AD) has raised much interest of late. Despite an overall decrease in the AD brain, the activity of AChE increases around beta-amyloid plaques and indeed, the beta-amyloid peptide (Abeta) can influence AChE levels. Such evidence stimulated our interest in the possibility that the levels of AChE and amyloid might vary together in AD. We previously found that the different AChE forms present in both the brain and in the cerebrospinal fluid (CSF) of AD patients varied in conjunction with abnormal glycosylation. Thus, the alterations in glycosylation are correlated with the accumulation of a minor subspecies of AChE monomers. We also recently analysed whether long-term exposure to the cholinesterase inhibitor (ChE-I) donepezil influences the AChE species found in AD CSF. The marked increase in CSF-AChE activity in AD patients following long-term treatment with donepezil was not paralleled by a rise in this subset of light variants. Hence, the correlation with the levels of CSF-Abeta is unique to these AChE species in patients receiving such treatment. The aim of this report is to review the links between AChE and beta-amyloid, and to discuss the significance of the responses of the distinct AChE species to ChE-I during the treatment of AD.

The significance of the cholinergic system in the brain during aging and in Alzheimer's disease

Acetylcholine is widely distributed in the nervous system and has been implicated to play a critical role in cerebral cortical development, cortical activity, controlling cerebral blood flow and sleep-wake cycle as well as in modulating cognitive performances and learning and memory processes. Cholinergic neurons of the basal forebrain complex have been described to undergo moderate degenerative changes during aging, resulting in cholinergic hypofunction that has been related to the progressing memory deficits with aging. Basal forebrain cholinergic cell loss is also a consistent feature of Alzheimer's disease, which has been suggested to cause, at least partly, the cognitive deficits observed, and has led to the formulation of the cholinergic hypotheses of geriatric memory dysfunction. Impaired cortical cholinergic neurotransmission may also contribute to beta-amyloid plaque pathology and increase phosphorylation of tau protein the main component of neurofibrillar tangles in Alzheimer's disease. Understanding the molecular mechanisms underlying the interrelationship between cortical cholinergic dysfunction, beta-amyloid formation and deposition, and tau pathology in Alzheimer's disease, would allow to derive potential treatment strategies to pharmacologically intervene in the disease-causing signaling cascade.

Basal forebrain cholinergic dysfunction in Alzheimer's disease--interrelationship with beta-amyloid, inflammation and neurotrophin signaling

Alzheimer's disease, the most common neurodegenerative disorder of senile dementia, is characterized by two major morpho-pathological hallmarks. Deposition of extracellular neuritic, beta-amyloid peptide-containing plaques (senile plaques) in cerebral cortical regions of Alzheimer patients is accompanied by the presence of intracellular neurofibrillary tangles in cerebral pyramidal neurons. Basal forebrain cholinergic dysfunction is also a consistent feature of Alzheimer's disease, which has been suggested to cause, at least partly, the cognitive deficits observed in patients with Alzheimer's disease. Impaired cortical cholinergic neurotransmission may also contribute to beta-amyloid plaque pathology in Alzheimer's disease by affecting expression and processing of the beta-amyloid precursor protein (APP). Vice versa, low level of soluble beta-amyloid has been observed to inhibit cholinergic synaptic function. Deposition of beta-amyloid plaques in Alzheimer's disease is also accompanied by a significant plaque-associated glial up-regulation of interleukin-1, which has been attributed to affect expression and metabolism of APP and to interfere with cholinergic transmission. Understanding the molecular mechanisms underlying the interrelationship between cortical cholinergic dysfunction, beta-amyloid formation and deposition, as well as local inflammatory upregulation, would allow to derive potential treatment strategies to pharmacologically intervene in the disease-causing signaling cascade.

Mutant presenilin 2 increases acetylcholinesterase activity in neuronal cells

A presenilin 2 mutation is believed to be involved in the development of Alzheimer's disease. In addition, transgenic mice with a presenilin 2 mutation have been reported to have learning and memory impairments. In this study, exposing PC12 cells expressing mutant presenilin 2 to 50 microM AP25-35, 30 mM L-glutamate and 50 microM H2O2 caused a significant increase in acetylcholine esterase activity. An in vivo study revealed high levels of this enzyme activity in the mutant presenilin 2 transgenic brains compared with the wild type presenilin 2 transgenic and nontransgenic samples. These results suggest that a mutant presenilin 2-induced neurodegeneration in Alzheimer's disease might be involved in the increase in acetylcholinesterase activity. These findings might help in the development of an appropriate therapeutic intervention targeting mutant presenilin 2-induced Alzheimer's disease.

Protective effect of donepezil against Aβ(1-40) neurotoxicity in rat septal neurons

Donepezil, a potent acetylcholinesterase (AChE) inhibitor used for the treatment of Alzheimer's disease (AD), is thought to have a neuroprotective effect in AD patients. Because a deficit in cholinergic neurotransmission is a major feature in AD, and amyloid-beta (Abeta) accumulation has been proposed as a possible causative phenomenon, we were interested to examine the effect of donepezil on Abeta(1-40) induced neurotoxicity in primary cultures of rat septal neurons. Using immunohistochemical staining, almost all the neurons were found to be positive for vesicular acetylcholine transporter (VAChT) in these septal cultures. Septal neuronal cells were cultured for 7 days and then 15 micromol/L of Abeta(1-40) was added to the cell medium for 48 h. The cultured septal neurons were highly susceptible to Abeta toxicity, as shown by morphological examination and lactate dehydrogenase (LDH) assay. Donepezil concentration-dependently reduced the LDH efflux induced by Abeta(1-40), and the effect was significant at 100 nmol/L and above. Donepezil decreased both the negative peak at around 215 nm in the circular dichroism (CD) spectrum and the fluorescence intensity of thioflavin T in the presence of Abeta(1-40). These results suggest that donepezil exerts a neuroprotective effect by reducing the amount of the toxic form of Abeta fibrils in septal neuron cultures. These findings support the idea that the clinical efficacy of donepezil in AD is due to not only activation of cholinergic transmission, but also attenuation of neuronal damage.

α7-Nicotinic acetylcholine receptors mediate an Aβ1−42-induced increase in the level of acetylcholinesterase in primary cortical neurones

The beta-amyloid protein (Abeta) is the major protein component of amyloid plaques found in the Alzheimer brain. Although there is a loss of acetylcholinesterase (AChE) from both cholinergic and non-cholinergic neurones in the brain of Alzheimer patients, the level of AChE is increased around amyloid plaques. Previous studies using P19 cells in culture and transgenic mice which overexpress human Abeta have suggested that this increase may be due to a direct action of Abeta on AChE expression in cells adjacent to amyloid plaques. The aim of the present study was to examine the mechanism by which Abeta increases levels of AChE in primary cortical neurones. Abeta1-42 was more potent than Abeta1-40 in its ability to increase AChE in primary cortical neurones. The increase in AChE was unrelated to the toxic effects of the Abeta peptides. The effect of Abeta1-42 on AChE was blocked by inhibitors of alpha7 nicotinic acetylcholine receptors (alpha7 nAChRs) as well as by inhibitors of L- or N-type voltage-dependent calcium channels (VDCCs), whereas agonists of alpha7 nAChRs (choline, nicotine) increased the level of AChE. The results demonstrate that the effect of Abeta1-42 on AChE is due to an agonist effect of Abeta1-42 on the alpha7 nAChR.