Cholinesterase inhibitors used in the treatment of Alzheimer's disease: the relationship between pharmacological effects and clinical efficacy

Benzoic acid-derived nitrones: A new class of potential acetylcholinesterase inhibitors and neuroprotective agents

The discovery of new chemical entities endowed with potent and selective acetylcholinesterase (AChE) and/or butyrylcholinesterase (BChE) inhibitory activity is still a relevant subject for Alzheimer's disease therapy. Therefore, a small library of benzoic based amide nitrones (compounds 24 to 42) was synthesized and screened toward cholinesterase enzymes. SAR studies showed that the tert-butyl moiety is the most favourable nitrone pattern. In general, tert-butyl derivatives effectively inhibited AChE, being compound 33 the most potent (IC₅₀ = 8.3 ± 0.3 μM; Ki 5.2 μM). The data pointed to a non-competitive inhibition mechanism of action, which was also observed for the standard donepezil. None of compounds showed BChE inhibitory activity. Molecular modelling studies provided insights into the enzyme-inhibitor interactions and rationalised the experimental data, confirming that the binding mode of nitrones 33 and 38 towards AChE has the most favourable binding free energy. The tert-butylnitrones 33 and 38 were not cytotoxic on different cell lines (SH-SY5Y and HepG2). Moreover, compound 33 was able to prevent t-BHP-induced oxidative stress in SH-SY5Y differentiated cells. Due to its AChE selectivity and promising cytoprotective properties, as well as its appropriate drug-like profile pointing toward blood-brain barrier permeability, compound 33 is proposed as a valid lead for a further optimization step.

Panax ginseng components and the pathogenesis of Alzheimer's disease (Review)

Ginseng is one of the main representatives of traditional Chinese medicine and presents a wide range of pharmacological actions. Ginsenosides are the main class of active compounds found in ginseng. They demonstrate unique biological activity and medicinal value, namely anti-tumour, anti-inflammatory and antioxidant properties, as well as anti-apoptotic properties. Increasing levels of stress in life are responsible for the increased incidence of nervous system diseases. Neurological diseases create a huge burden on the lives and health of individuals. In recent years, studies have indicated that ginsenosides play a pronounced positive role in the prevention and treatment of neurological diseases. Nevertheless, research is still at an early stage of development, and the complex mechanisms of action involved remain largely unknown. This review aimed to shed light into what is currently known about the mechanisms of action of ginsenosides in relation to Alzheimer's disease. Scientific material and theoretical bases for the treatment of nervous system diseases with purified Panax ginseng extracts are also discussed.

Design, synthesis and anti-Alzheimer's activity of novel 1,2,3-triazole-chromenone carboxamide derivatives

Alzheimer's disease (AD) is a well-known neurodegenerative disorder affecting millions of old people worldwide and the corresponding epidemiological data highlights the significance of the disease. As AD is a multifactorial illness, various single-target directed drugs that have reached clinical trials have failed. Therefore, various factors associated with outset of AD have been considered in targeted drug discovery and development. In this work, a wide range of 1,2,3-triazole-chromenone carboxamides were designed, synthesized, and evaluated for their cholinesterase inhibitory activity. Among them, N-(1-benzylpiperidin-4-yl)-7-((1-(3,4-dimethylbenzyl)-1H-1,2,3-triazol-4-yl)methoxy)-2-oxo-2H-chromene-3-carboxamide (11b) showed the best acetylcholinesterase inhibitory activity (IC₅₀ = 1.80 µM), however, it was inactive toward butyrylcholinesterase. It should be noted that compound 11b was evaluated for its BACE1 inhibitory activity and calculated IC₅₀ = 21.13 µM confirmed desired inhibitory activity. Also, this compound revealed satisfactory neuroprotective effect against H₂O₂-induced cell death in PC12 neurons at 50 µM as well as metal chelating ability toward Fe²⁺, Cu²⁺, and Zn²⁺ ions.

Stoichiometry of the Heteromeric Nicotinic Receptors of the Renshaw Cell

Neuronal nicotinic acetylcholine receptors (nAChRs) are pentamers built from a variety of subunits. Some are homomeric assemblies of α subunits, others heteromeric assemblies of α and β subunits which can adopt two stoichiometries (2α:3β or 3α:2β). There is evidence for the presence of heteromeric nAChRs with the two stoichiometries in the CNS, but it has not yet been possible to identify them at a given synapse. The 2α:3β receptors are highly sensitive to agonists, whereas the 3α:2β stoichiometric variants, initially described as low sensitivity receptors, are indeed activated by low and high concentrations of ACh. We have taken advantage of the discovery that two compounds (NS9283 and Zn) potentiate selectively the 3α:2β nAChRs to establish (in mice of either sex) the presence of these variants at the motoneuron-Renshaw cell (MN-RC) synapse. NS9283 prolonged the decay of the two-component EPSC mediated by heteromeric nAChRs. NS9283 and Zn also prolonged spontaneous EPSCs involving heteromeric nAChRs, and one could rule out prolongations resulting from AChE inhibition by NS9283. These results establish the presence of 3α:2β nAChRs at the MN-RC synapse. At the functional level, we had previously explained the duality of the EPSC by assuming that high ACh concentrations in the synaptic cleft account for the fast component and that spillover of ACh accounts for the slow component. The dual ACh sensitivity of 3α:2β nAChRs now allows to attribute to these receptors both components of the EPSC.SIGNIFICANCE STATEMENT Heteromeric nicotinic receptors assemble α and β subunits in pentameric structures, which can adopt two stoichiometries: 3α:2β or 2α:3β. Both stoichiometric variants are present in the CNS, but they have never been located and characterized functionally at the level of an identified synapse. Our data indicate that 3α:2β receptors are present at the spinal cord synapses between motoneurons and Renshaw cells, where their dual mode of activation (by high concentrations of ACh for synaptic receptors, by low concentrations of ACh for extrasynaptic receptors) likely accounts for the biphasic character of the synaptic current. More generally, 3α:2β nicotinic receptors appear unique by their capacity to operate both in the cleft of classical synapses and at extrasynaptic locations.

Molecular modeling and in vitro approaches towards cholinesterase inhibitory effect of some natural xanthohumol, naringenin, and acyl phloroglucinol derivatives

BACKGROUND

Many natural products, particularly phenolic compounds, have been reported to have a strong inhibition against acetylcholinesterase (AChE) and butyrylcholinesterase (BChE), the key enzymes in the pathology of Alzheimer's disease (AD).

HYPOTHESIS

Therefore, we hypothesized that some xanthahumol, naringenin, and acyl phloroglucinol derivatives (1-14) isolated from Humulus lupulus L. (hops) may have an inhibitory potential against AChE and BChE.

METHODS

Inhibitory potential of compounds 1-14 were tested against AChE and BChE using ELISA microtiter assay. Different molecular docking simulations, including IFD and GOLD protocols, were implemented to verify the interactions between the ligands and the active site amino acids and also their binding energies inside the catalytic crevices of AChE and BChE. ADME/Tox analysis were used to determine pharmacological activities of the compounds.

RESULTS

Among them, 3‑hydroxy‑xanthohumol (IC₅₀ = 51.25 ± 0.88 µM) and xanthohumol (IC₅₀ = 71.34 ± 2.09 µM), displayed a moderate AChE inhibition in comparison to that of the reference (galanthamine, IC₅₀ = 2.52 ± 0.15 µM). In addition to 3‑hydroxy‑xanthohumol (IC₅₀ = 63.07 ± 3.76 µM) and xanthohumol (IC₅₀ = 32.67 ± 2.82 µM), 8-prenylnaringenin (IC₅₀ = 86.58 ± 3.74 µM) also showed micromolar-range inhibition against BChE (galanthamine, IC₅₀ = 46.58 ± 0.91 µM). Rest of the compounds were found to be either inactive or having inhibition below 50%. Prediction of pharmacokinetic studies suggested that all the ligands revealed acceptable drug-like profiles. Docking simulations demonstrate not only the prediction of ligand binding energies of the compounds inside the catalytic domains of the targets, but also highlight the critical amino acids contributing to stabilizations of the ligands.

CONCLUSION

Our findings revealed that xanthohumol in particular could be considered as lead molecule to explore new cholinesterase inhibitors for AD.

Metallomics for Alzheimer's disease treatment: Use of new generation of chelators combining metal-cation binding and transport properties

Alzheimer's disease (AD) is a progressive neurodegenerative disorder affecting tens of million people. Currently marketed drugs have limited therapeutic efficacy and only slowing down the neurodegenerative process. Interestingly, it has been suggested that biometal cations in the amyloid beta (Aβ) aggregate deposits contribute to neurotoxicity and degenerative changes in AD. Thus, chelation therapy could represent novel mode of therapeutic intervention. Here we describe the features of chelators with therapeutically relevant mechanism of action. We have found that the tested compounds effectively reduce the toxicity of exogenous Aβ and suppress its endogenous production as well as decrease oxidative stress. Cholyl hydrazones were found to be the most active compounds. In summary, our data show that cation complexation, together with improving transport efficacy may represent basis for eventual treatment strategy in AD.

Acetylcholinesterase Inhibitors: Beneficial Effects on Comorbidities in Patients With Alzheimer's Disease

Elderly patients with Alzheimer's disease (AD) and other dementias are at high risk of polypharmacy and excessive polypharmacy for common coexisting medical conditions. Polypharmacy increases the risk of drug-drug and drug-disease interactions in these patients who may not be able to communicate early symptoms of adverse drug events. Three acetylcholinesterase inhibitors (ACHEIs) have been approved for AD: donepezil (Aricept), rivastigmine (Exelon), and galantamine (Razadyne). They are also used off-label for other causes of dementia such as Lewy body and vascular dementia. We here report evidence from the literature that ACHEI treatment, prescribed for cognitive impairment, can reduce the load of medications in patients with AD by also addressing cardiovascular, gastrointestinal, and other comorbidities. Using one drug to address multiple symptoms can reduce costs and improve medication compliance.

Current Perspectives regarding Stem Cell-Based Therapy for Alzheimer's Disease

Alzheimer's disease (AD), a progressive neurodegenerative disorder featuring memory loss and cognitive impairment, is caused by synaptic failure and the excessive accumulation of misfolded proteins. Many unsuccessful attempts have been made to develop new small molecules or antibodies to intervene in the disease's pathogenesis. Stem cell-based therapies cast a new hope for AD treatment as a replacement or regeneration strategy. The results from recent preclinical studies regarding stem cell-based therapies are promising. Human clinical trials are now underway. However, a number of questions remain to be answered prior to safe and effective clinical translation. This review explores the pathophysiology of AD and summarizes the relevant stem cell research according to cell type. We also briefly summarize related clinical trials. Finally, future perspectives are discussed with regard to their clinical applications.

Gene Expression and Methylation Analysis of ABCA7 in Patients with Alzheimer's Disease

BACKGROUND/OBJECTIVE

The aim of this study was to examine the blood gene expression and methylation of ATP-binding cassette sub-family A member 7 gene (ABCA7) as a biological marker of AD.

METHODS

AD subjects (n = 50; 11 males, 77.7±6.05 years old) and age- and sex-matched healthy controls (n = 50) were recruited. A single nucleotide polymorphism in ABCA7 (rs3764650), methylation rates of CpG sites in the ABCA7 promoter region, and ABCA7 mRNA expression levels in peripheral blood were examined.

RESULTS

The distribution of the rs3764650 polymorphism in AD subjects was not different from that of controls. Although the methylation rates of AD subjects were not significantly different from those of controls, the ABCA7 mRNA expression level in AD subjects was significantly higher than that in controls. Additionally, the ABCA7 mRNA expression level in AD subjects was significantly correlated with Mini-Mental State Examination recall, the Alzheimer's Disease Assessment Scale total score, and the Clinical Dementia Rating score. We also found a significant correlation between the ABCA7 mRNA expression level and duration of illness.

CONCLUSION

The ABCA7 mRNA expression level in peripheral blood may be a marker for early stages of AD and disease progression regardless of rs3764650 and the methylation rate of its promoter.

A Systematic Review of Antiamyloidogenic and Metal-Chelating Peptoids: Two Structural Motifs for the Treatment of Alzheimer's Disease

Alzheimer's disease (AD) is an incurable form of dementia affecting millions of people worldwide and costing billions of dollars in health care-related payments, making the discovery of a cure a top health, societal, and economic priority. Peptide-based drugs and immunotherapies targeting AD-associated beta-amyloid (Aβ) aggregation have been extensively explored; however, their therapeutic potential is limited by unfavorable pharmacokinetic (PK) properties. Peptoids (N-substituted glycine oligomers) are a promising class of peptidomimetics with highly tunable secondary structures and enhanced stabilities and membrane permeabilities. In this review, the biological activities, structures, and physicochemical properties for several amyloid-targeting peptoids will be described. In addition, metal-chelating peptoids with the potential to treat AD will be discussed since there are connections between the dysregulation of certain metals and the amyloid pathway.

Association Study and Meta-Analysis of Polymorphisms, Methylation Profiles, and Peripheral mRNA Expression of the Serotonin Transporter Gene in Patients with Alzheimer's Disease

BACKGROUND/AIM

The aim of this study was to elucidate the relationship between Alzheimer's disease (AD) and the serotonin transporter gene (SLC6A4).

METHODS

AD subjects (n = 43) and controls (n = 47) were recruited and evaluated. In leukocytes, we evaluated two polymorphisms in SLC6A4, the serotonin transporter length polymorphic region (5-HTT-LPR) and rs25531, as well as methylation rates of the SLC6A4 promoter region and the SLC6A4 mRNA expression level. We also performed a meta-analysis to examine the relationship between the frequency of the L allele and the risk of AD.

RESULTS

The distributions of 5-HTT-LPR and rs25531 polymorphisms in AD subjects were not different from those of controls. Although the methylation rates in AD subjects were not significantly different from those of controls, the expression level in AD subjects was significantly higher than in controls. Additionally, the expression level in AD subjects was significantly correlated with apathy. Meta-analysis revealed that the L/L genotype significantly reduced the risk of AD, but only in the Caucasian population.

CONCLUSION

Higher SLC6A4 mRNA expression in leukocytes in AD was associated with apathy regardless of SLC6A4 genotypes and methylation rates of the promoter region. The L/L genotype may reduce the risk of AD in the Caucasian population.

Correlation of cholinergic drug induced quenching of acetylcholinesterase bound thioflavin-T fluorescence with their inhibition activity

The development of new acetylcholinesterase inhibitors (AChEIs) and subsequent assay of their inhibition efficiency is considered to be a key step for AD treatment. The fluorescence intensity of thioflavin-T (ThT) bound in the active site of acetylcholinesterase (AChE) quenches substantially in presence of standard AChEI drugs due to the dynamic replacement of the fluorophore from the AChE active site as confirmed from steady state emission as well as time-resolved fluorescence anisotropy measurement and molecular dynamics simulation in conjunction with docking calculation. The parametrized % quenching data for individual system shows excellent correlation with enzyme inhibition activity measured independently by standard Ellman AChE assay method in a high throughput plate reader system. The results are encouraging towards design of a fluorescence intensity based AChE inhibition assay method and may provide a better toolset to rapidly evaluate as well as develop newer AChE-inhibitors for AD treatment.

A second wind for the cholinergic system in Alzheimer's therapy

Notwithstanding tremendous research efforts, the cause of Alzheimer's disease (AD) remains elusive and there is no curative treatment. The cholinergic hypothesis presented 35 years ago was the first major evidence-based hypothesis on the etiology of AD. It proposed that the depletion of brain acetylcholine was a primary cause of cognitive decline in advanced age and AD. It relied on a series of observations obtained in aged animals, elderly, and AD patients that pointed to dysfunctions of cholinergic basal forebrain, similarities between cognitive impairments induced by anticholinergic drugs and those found in advanced age and AD, and beneficial effects of drugs stimulating cholinergic activity. This review revisits these major results to show how this hypothesis provided the drive for the development of anticholinesterase inhibitor-based therapies of AD, the almost exclusively approved treatment in use despite transient and modest efficacy. New ideas for improving cholinergic therapies are also compared and discussed in light of the current revival of the cholinergic hypothesis on the basis of two sets of evidence from new animal models and refined imagery techniques in humans. First, human and animal studies agree in detecting signs of cholinergic dysfunctions much earlier than initially believed. Second, alterations of the cholinergic system are deeply intertwined with its reactive responses, providing the brain with efficient compensatory mechanisms to delay the conversion into AD. Active research in this field should provide new insight into development of multitherapies incorporating cholinergic manipulation, as well as early biomarkers of AD enabling earlier diagnostics. This is of prime importance to counteract a disease that is now recognized to start early in adult life.

Beyond symptomatic effects: potential of donepezil as a neuroprotective agent and disease modifier in Alzheimer's disease

Alzheimer's disease (AD) is associated with neurodegenerative changes resulting clinically in progressive cognitive and functional deficits. The only therapies are the cholinesterase inhibitors donepezil, galantamine and rivastigmine and the N-methyl-D-aspartate-receptor antagonist memantine. Donepezil acts primarily on the cholinergic system as a symptomatic treatment, but it also has potential for disease modification and may reduce the rate of progression of AD. This review explores the potential for disease modifying effects of donepezil. Several neuroprotective mechanisms that are independent of cholinesterase inhibition, are suggested. Donepezil has demonstrated a range of effects, including protecting against amyloid β, ischaemia and glutamate toxicity; slowing of progression of hippocampal atrophy; and up-regulation of nicotinic acetylcholine receptors. Clinically, early and continuous treatment with donepezil is considered to preserve cognitive function more effectively than delayed treatment. The possible neuroprotective effects of donepezil and the potential for disease pathway modification highlight the importance of early diagnosis and treatment initiation in AD.

Effects of donepezil on liver and kidney functions for the treatment of Alzheimer's disease

Aim of the present study is to investigate the effects of medication with donepezil (acetylcholinesterase inhibitor) on the liver and kidney function in Alzheimer's disease (AD) and to compare the effects of donepezil medication during short (one month) and long term (six years) follow-ups. We evaluated female and male patients from Cukurova [42 AD patients; short term (5 mg/day)] and Dokuz Eylul [68 AD patients; long term (10 mg/day)] University Hospital. The results compared with the geriatric population without dementia in other words who are not in medication with donepezil. For short term evaluation all subjects underwent periodic examination with tests regarding hepatic and renal functions; firstly, before starting treatment and then repeated one month later. For long term evaluation all subjects underwent periodic examination with tests regarding hepatic and renal functions; three times at the end of each two consecutive years of treatment with donepezil. AD patients' results were also compared with 79 neurologically healthy geriatric patients without dementia who were over 65 years of age and were not receiving medication with donepezil. For this task, serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels are used to predict possible liver damage, while the blood urea nitrogen (BUN) and creatinine (CRE) levels for kidney damage. No significant difference between the groups regarding the routine control of biochemical parameters was observed in short term drug medication. In long term patients' group; the effects of two years use of donepezil on renal and hepatic function were also evaluated and levels of AST, ALT, BUN and CRE were found to be increased significantly compared to pretreatment levels. But, they remained in the reference intervals. However, levels of AST and ALT at the end of the fourth year of therapy were similar to those measured at the end of the second year, levels of BUN and CRE continuing to increase with staying below the reference limits. Functional markers obtained at the end of the sixth year of therapy were not differing from those of the fourth year. No significant difference was found during comparisons within the results of the neurologically healthy geriatric patient group. During comparisons between the two groups, measurements obtained at all-time points were significantly high in donepezil treated AD patients. We concluded that customized dosage according to hepatic and renal functions is necessary for using acetylcholinesterase inhibitor in AD patients.

Pharmacotherapy for Dementia: A Practical Approach to the Use of Cholinesterase Inhibitors and Memantine

Cholinesterase inhibitors and memantine are the only classes of drugs approved for the treatment of dementia due to Alzheimer's disease. This article provides evidence-based recommendations to address the issues regarding the use of cholinesterase inhibitors and memantine in clinical practice. It includes their efficacy, timing, assessment, use in institutionalized patients, combined use, and use in other dementia types. However, most of the studies are of short duration (<1 year) and are mainly focused on cognitive and global improvement, whereas the practical issue of their use in daily practice such as optimal duration of treatment, long-term efficacy and delaying institutionalization are limited.

Salvia officinalis L. Essential Oils from Spain: Determination of Composition, Antioxidant Capacity, Antienzymatic, and Antimicrobial Bioactivities

Four essential oils (EOs) from Salvia officinalis L. cultivated in Spain (Murcia Province) were analyzed by gas chromatography coupled with mass spectrometry (GC/MS) to determine their relative and absolute compositions. The main components were α-thujone (22.8 - 41.7%), camphor (10.7 - 19.8%), 1,8-cineole (4.7 - 15.6%), and β-thujone (6.1 - 15.6%). Enantioselective gas chromatography identified (-)-α-thujone and (+)-camphor as the main enantiomers in all the analyzed EOs. Furthermore, when the EOs were tested to determine their antioxidant activity against free radicals and as ferric reducing and ferrous chelating agents, all were seen to have moderate activity due to the compounds they contained, such as linalool or terpinene. Because of their known relation with inflammatory illnesses and Alzheimer's disease, respectively, the inhibition of lipoxygenase and acetylcholinesterase was studied using the EOs. Some individual compounds also inhibited these enzymes. In addition, the studied EOs were able to inhibit the growth of Escherichia coli, Staphylococcus aureus, and Candida albicans. The characterization carried out increases our awareness of the possible uses of S. officinalis EO as natural additives in food, cosmetics, and pharmaceuticals.

Donepezil Plus Solifenacin (CPC-201) Treatment for Alzheimer's Disease

Available cholinergic drugs for treating Alzheimer's disease (AD) provide modest symptomatic benefit. We hypothesized that co-administration of a peripheral anticholinergic to reduce dose-limiting adverse effects (AEs) would enable the safe/tolerable use of higher cholinesterase inhibitor doses and thus improve their antidementia efficacy. A modified single-blind, ascending-dose, phase IIa study of donepezil plus solifenacin (CPC-201) lasting 26 weeks was conducted in 41 patients with probable AD of moderate severity. Entry criteria included the use of donepezil at a dose of 10 mg/day during the preceding 3 months. The primary outcome measure was the maximum tolerated dose (MTD) of donepezil achieved (to protocol limit of 40 mg/day) when administered with the anticholinergic solifenacin 15 mg/day. Secondary measures included assessments of cognitive and global function, as well as of AEs. The mean ± SD donepezil MTD increased to 38 ± 0.74 mg/day (median 40 mg/day; p < 0.001); 88% of the study population safely attained this dose at the end of titration. Markedly reduced donepezil AE frequency, especially gastrointestinal, allowed this dose increase. There were no drug-related serious AEs or clinically significant laboratory abnormalities. At 26 weeks, Alzheimer's Disease Assessment Scale Cognitive Component scores in the efficacy evaluable population improved by 0.35 ± 0.85 points over baseline (p < 0.05), an estimated 2.5 ± 0.84 points above 10 mg/day donepezil and 5.4 ± 0.84 points above historic placebo (both p < 0.05). Clinical Global Impression of Improvement scores improved by 0.94 ± 0.20 to 3.1 ± 0.20 points (p < 0.001). The findings suggest that limiting donepezil AEs by co-administration of solifenacin allows the safe administration of substantially higher cholinesterase inhibitors doses that may augment cognitive and global benefits in patients with AD.

The Anti-dementia Effects of Donepezil Involve miR-206-3p in the Hippocampus and Cortex

Alzheimer's disease (AD) is a most serious age-related neurodegenerative disorder accompanied with significant memory impairments in this world. Recently, microRNAs (miRNAs) have been reported to be invlolved in the pathophysiology of AD. Previous studies have shown that miRNA-206 (miR-206) is implicated in the pathogenesis of AD via suppressing the expression of brain-derived neurotrophic factor (BDNF) in the brain. Here, we examined the miR-206-3p and miR-206-5p expression in the hippocampus and cortex of Abeta precursor protein (APP)/presenilin-1 (PS1) transgenic mice treated with donepezil, a drug approved for treating AD in clinic. We found that the expression of miR-206-3p was significantly up-regulated in the hippocampus and cortex of APP/PS1 mice, while donepezil administration significantly reversed this dysfunction. In addition, enhancing the miR-206-3p level by the usage of AgomiR-206-3p significantly attenuated the anti-dementia effects of donepezil in APP/PS1 mice. Together, these results suggested that miR-206-3p is involved in the anti-dementia effects of donepezil, and could be a novel pharmacological target for treating AD.

Effects of medicinal plants on Alzheimer's disease and memory deficits

Alzheimer's disease is an age-related neurodegenerative disorder characterized by memory deficits. Various studies have been carried out to find therapeutic approaches for Alzheimer's disease. However, the proper treatment option is still not available. There is no cure for Alzheimer's disease, but symptomatic treatment may improve the memory and other dementia related problems. Traditional medicine is practiced worldwide as memory enhancer since ancient times. Natural therapy including herbs and medicinal plants has been used in the treatment of memory deficits such as dementia, amnesia, as well as Alzheimer's disease since a long time. Medicinal plants have been used in different systems of medicine, particularly Unani system of medicines and exhibited their powerful roles in the management and cure of memory disorders. Most of herbs and plants have been chemically evaluated and their efficacy has also been proven in clinical trials. However, the underlying mechanisms of actions are still on the way. In this paper, we have reviewed the role of different medicinal plants that play an important role in the treatment of Alzheimer's disease and memory deficits using conventional herbal therapy.

Development of an in-vivo active reversible butyrylcholinesterase inhibitor

Alzheimer’s disease (AD) is characterized by severe basal forebrain cholinergic deficit, which results in progressive and chronic deterioration of memory and cognitive functions. Similar to acetylcholinesterase, butyrylcholinesterase (BChE) contributes to the termination of cholinergic neurotransmission. Its enzymatic activity increases with the disease progression, thus classifying BChE as a viable therapeutic target in advanced AD. Potent, selective and reversible human BChE inhibitors were developed. The solved crystal structure of human BChE in complex with the most potent inhibitor reveals its binding mode and provides the molecular basis of its low nanomolar potency. Additionally, this compound is noncytotoxic and has neuroprotective properties. Furthermore, this inhibitor moderately crosses the blood-brain barrier and improves memory, cognitive functions and learning abilities of mice in a model of the cholinergic deficit that characterizes AD, without producing acute cholinergic adverse effects. Our study provides an advanced lead compound for developing drugs for alleviating symptoms caused by cholinergic hypofunction in advanced AD.

Galantamine and Environmental Enrichment Enhance Cognitive Recovery after Experimental Traumatic Brain Injury But Do Not Confer Additional Benefits When Combined

Environmental enrichment (EE) enhances cognition after traumatic brain injury (TBI). Galantamine (GAL) is an acetylcholinesterase inhibitor that also may promote benefits. Hence, the aims of this study were to assess the efficacy of GAL alone (standard [STD] housing) and in combination with EE in adult male rats after TBI. The hypothesis was that both therapies would confer motor, cognitive, and histological benefits when provided singly, but that their combination would be more efficacious. Anesthetized rats received a controlled cortical impact or sham injury, then were randomly assigned to receive GAL (1, 2, or 3 mg/kg; intraperitoneally [i.p.]) or saline vehicle (VEH; 1 mL/kg; i.p.) beginning 24 h after surgery and once daily for 21 days (experiment 1). Motor (beam-balance/walk) and cognitive (Morris water maze [MWM]) assessments were conducted on post-operative Days 1-5 and 14-19, respectively. Cortical lesion volumes were quantified on Day 21. Sham controls were better versus all TBI groups. No differences in motor function or lesion volumes were observed among the TBI groups (p > 0.05). In contrast, GAL (2 mg/kg) enhanced MWM performance versus VEH and GAL (1 and 3 mg/kg; p < 0.05). In experiment 2, GAL (2 mg/kg) or VEH was combined with EE and the data were compared with the STD-housed groups from experiment 1. EE alone enhanced motor performance over the VEH-treated and GAL-treated (2 mg/kg) STD-housed groups (p < 0.05). Moreover, both EE groups (VEH or GAL) facilitated spatial learning and reduced lesion size versus STD + VEH controls (p < 0.05). No additional benefits were observed with the combination paradigm, which does not support the hypothesis. Overall, the data demonstrate that EE and once daily GAL (2 mg/kg) promote cognitive recovery after TBI. Importantly, the combined therapies did not negatively affect outcome and thus this therapeutic protocol may have clinical utility.

Cholinesterase inhibitors do not alter the length of stay in nursing homes among patients with Alzheimer's disease: a prospective, observational study of factors affecting survival time from admission to death

BACKGROUND

The survival time in nursing homes (NHs) in Alzheimer's disease (AD) might be affected by sociodemographic/clinical characteristics, rate of disease progression, and use of specific medications and community-based services. Whether different aspects of cholinesterase inhibitor (ChEI) therapy modify time spent in NHs is unclear. Therefore, we examined the relationship between these potential predictors and survival time in NHs.

METHODS

This prospective, multicenter study of ChEI treatment in clinical practice included 220 deceased patients clinically diagnosed with mild-to-moderate AD who were admitted to NHs during the study. Cognitive and activities of daily living (ADL) performance, ChEI dose, and amount of services used/week were evaluated every 6 months over 3 years. Dates of nursing-home placement (NHP) and death were recorded. Variables that determined survival time in NHs were analyzed using general linear models.

RESULTS

The mean survival time in NHs was 4.06 years (men, 2.78 years; women, 4.53 years; P < 0.001). The multivariate model showed that a shorter stay in NHs was associated with the interaction term male living with a family member, use of antihypertensive/cardiac therapy or anxiolytics/sedatives/hypnotics, and worse basic ADL at NHP, but not with age or cognitive and instrumental ADL capacities.

CONCLUSIONS

Increased community-based care did not reduce the survival time in NHs among individuals with AD. Men living with family spent significantly less time in NHs compared with the corresponding women, which suggests that the situation of female spouses of AD patients may need attention and possibly support. There was no indication that different aspects of ChEI therapy, e.g., drug type, dose, or duration, alter survival time in NHs.

BACE1 molecular docking and anti-Alzheimer's disease activities of ginsenosides

ETHNOPHARMACOLOGICAL RELEVANCE

Ginsenosides are natural product steroid glycosides and triterpene saponins obtained from the Panax species. Panax ginseng has been widely used as a traditional Chinese medicine (TCM) for around a thousand years, especially in East Asian countries. Ginseng, the root and rhizome of the most popular species P. ginseng, used as tonic, prophylactic agent and restorative. In TCM, ginseng is highly valued herb and has been applied to a variety of pathological conditions and illnesses such as hypodynamia, anorexia, shortness of breath, palpitation, insomnia, impotence, hemorrhage and diabetes.

AIM OF THE STUDY

The basic aim of this study was to evaluate the anti-Alzheimer's disease activities of selected ginsenosides (Rb1, Rb2, Rc, Re, Rg1, and Rg3) according to peroxynitrite (ONOO(‒)) scavenging activity and inhibitory activity of ONOO(-)-mediated nitrotyrosine formation as a measure of changes in oxidative stress. In addition, molecular docking simulation studies were performed to predict binding energies of the ginsenosides with β-site amyloid precursor protein cleaving enzyme 1 (BACE1, β-secretase) and identify the interacting residues.

MATERIALS AND METHODS

In vitro cholinesterase enzyme assays by using acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and BACE1 were performed. In vitro authentic peroxynitrite scavenging activity and inhibitory activity against ONOO(-)-mediated nitrotyrosine formation were also performed. Molecular docking simulation studies were performed with Autodock Vina software and Discovery studio 4.1.

RESULTS

In vitro enzyme assays demonstrated that ginsenosides have significant inhibitory potential against AChE, BChE, and BACE1, as well as ONOO(-) and nitrotyrosine formation. Most importantly, significant AChE inhibitory activities were observed for Re; BChE for Rg3; and BACE1 for Rc, with IC50 values of 29.86±3.20, 16.80±0.36, and 59.81±2.74μg/mL, respectively. Among the tested ginsenosides, Rb1 exhibited a higher scavenging activity against ONOO(-) with an IC50 value of 27.86±1.34μg/mL, while Rc and Rg3 exhibited impressive inhibitory activity against the formation of nitrotyrosine. In addition, molecular docking studies revealed potential BACE1 inhibitory activity of ginsenosides, especially Rb1 and Rb2, which exhibited good binding affinities towards BACE1, with docking scores of -10kcal/mol.

CONCLUSION

The findings of the present study suggest the potential of ginsenosides (Rb1, Rb2, Rc, Re, Rg1, and Rg3) for use in the development of therapeutic or preventive agents for Alzheimer's disease, especially through inhibition of AChE, BChE and BACE1 activities, as well as scavenging of ONOO(-) and inhibition of nitrotyrosine formation.

Efficacy of Galantamine on Cognition in Mild-to-Moderate Alzheimer's Dementia after Failure to Respond to Donepezil

OBJECTIVE

This study compares the efficacy of the cholinesterase inhibitor (ChEI) galantamine on cognition in patients with mild-to-moderate Alzheimer's dementia (AD) who were either naïve to ChEI drugs or who had failed a trial of the ChEI donepezil.

METHODS

Outpatients with AD were sequentially referred for screening and enrollment. Current outpatients who had taken donepezil for at least 6 months without demonstrated efficacy on cognition were switched to galantamine (switched group). New outpatients with no ChEI prescription history were classified as the naïve group and were given galantamine. The primary outcome measures for the between-group comparison were response rate on cognition at 26 and 52 weeks (categorical) and change on the Korean version of the Alzheimer's Disease Assessment Scale-cognitive subscale (dimensional). Secondary cognitive outcomes were measured using the subset of frontal executive function and the Korean Mini-Mental State Examination.

RESULTS

Seventy outpatients were enrolled and 66 were analyzed by Intent-to-treat (ITT). There were 42 cases in the naïve group and 24 in the switched group. Response rates did not differ at 26 weeks (71.4% naïve vs. 58.3% switched; p=0.277) or at 52 weeks (59.5% naïve vs. 41.6% switched; p=0.162). No significant differences were observed in the pattern of change over the 52 weeks on the primary and secondary cognitive scales.

CONCLUSION

As the efficacy of galantamine on cognition was not inferior in the switched group compared to that in the naïve group, switching ChEI drugs is clinically feasible for non-responding patients with mild-to-moderate AD.

Characteristics of Pediatric Exposures to Antidementia Drugs Reported to a Poison Control System

OBJECTIVE

To characterize pediatric exposures to the antidementia drugs donepezil, memantine, rivastigmine, and galantamine by reviewing a poison control system's database.

STUDY DESIGN

A retrospective review of a statewide poison control system's database identified cases of pediatric (less than 19 years of age) exposures to antidementia drugs over an 11-year period. Data collected included age, sex, drug(s) involved, route of exposure, reason for exposure, symptoms, and interventions.

RESULTS

There were 189 cases identified (53% male, median age: 2.3 years, 99% unintentional exposures). Donepezil was the most commonly reported exposure (106 cases), followed by memantine (57), galantamine (18), oral rivastigmine (16), and transdermal rivastigmine (3). Coingestants were reported in 68 (36%) cases. Symptoms were reported in 38 (20%) cases. Gastrointestinal symptoms were most common (n = 21) followed by central nervous system depression (n = 15). Oral rivastigmine was associated with higher rates of symptoms. No bradycardia, seizures, or fasciculations were reported. Eighty-nine cases (47%) were evaluated at a health care facility, and 13 (7%) were admitted to a hospital. Oral rivastigmine exposures were associated with increased rate of health care facility evaluation. Activated charcoal was administered in 28 cases. Atropine was given only once, for drooling. There were no serious outcomes or deaths in this series.

CONCLUSIONS

Reported pediatric exposures to antidementia drugs resulted in minimal morbidity and no mortality. Oral rivastigmine exposures were found to be associated with more symptoms and health care facility evaluations.

One for All? Hitting Multiple Alzheimer's Disease Targets with One Drug

HIGHLIGHTS Many AD target combinations are being explored for multi-target drug design.New databases and models increase the potential of computational drug designLiraglutide and other antidiabetics are strong candidates for repurposing to AD.Donecopride a dual 5-HT/AChE inhibitor shows promise in pre-clinical studies Alzheimer's Disease is a complex and multifactorial disease for which the mechanism is still not fully understood. As new insights into disease progression are discovered, new drugs must be designed to target those aspects of the disease that cause neuronal damage rather than just the symptoms currently addressed by single target drugs. It is becoming possible to target several aspects of the disease pathology at once using multi-target drugs (MTDs). Intended as an introduction for non-experts, this review describes the key MTD design approaches, namely structure-based, in silico, and data-mining, to evaluate what is preventing compounds progressing through the clinic to the market. Repurposing current drugs using their off-target effects reduces the cost of development, time to launch, and the uncertainty associated with safety and pharmacokinetics. The most promising drugs currently being investigated for repurposing to Alzheimer's Disease are rasagiline, originally developed for the treatment of Parkinson's Disease, and liraglutide, an antidiabetic. Rational drug design can combine pharmacophores of multiple drugs, systematically change functional groups, and rank them by virtual screening. Hits confirmed experimentally are rationally modified to generate an effective multi-potent lead compound. Examples from this approach are ASS234 with properties similar to rasagiline, and donecopride, a hybrid of an acetylcholinesterase inhibitor and a 5-HT4 receptor agonist with pro-cognitive effects. Exploiting these interdisciplinary approaches, public-private collaborative lead factories promise faster delivery of new drugs to the clinic.

Human serum albumin reduces the potency of acetylcholinesterase inhibitor based drugs for Alzheimer's disease

Human serum albumin (HSA) induced modulation of acetylcholinesterase (AChE) inhibition activity of four well-known cholinergic inhibitors like tacrine hydrochloride (TAC), donepezil hydrochloride monohydrate (DON), (-) Huperzine A (HuPA), eserine (ESE) was monitored quantitatively by Ellman's method. Kinetic analysis of enzyme hydrolysis reaction revealed that while the mechanism of inhibition does not change significantly, the inhibition efficiency changes drastically in presence of HSA, particularly for DON and TAC. However, interestingly, no notable difference was observed in the cases of HuPA and/or ESE. For example, the IC50 value of AChE inhibition increases by almost 135% in presence of ∼250 μM HSA (IC50 = 159 ± 8 nM) while comparing with aqueous buffer solution of pH 8.0 (IC50 = 68 ± 4 nM) in DON. On the other hand, the change is almost insignificant (<10%) in case of HuPA under the similar condition. The experimentally observed difference in the extent of modulatory effect was correlated with the sequestration ability of HSA towards different drugs predicted from molecular docking calculations. The result in this study demonstrates the importance to consider the plasma protein binding tendency of a newly synthesized AD drug before claiming its potency over the existing one. Further, development of new and intelligent delivery medium that shields the administered drugs from serum adsorption may reduce the optimal drug dose requirement.

[Pharmacotherapy and dementia]

The review considers treatment aspects of dementia in Alzheimer's disease (DAD), vascular dementia (VD) and some other forms of dementia. Pathogenetic pharmacotherapy of DAD aims to maintain the activity of cholinergic neurons with anticholinesterase drugs including donepezil, which is used most often. The main objective of VD treatment is prevention of new cerebral infarctions using cardiotropic medications, antiaggregants, anticoagulants, hypotensive drugs and statins. In Russia, patients with DAD and VD receive polymodal drugs as well. These drugs have been included in the list of antidementia medications due to their wide use in treatment of discirculatory encephalopathy and chronic brain ischemia.

Adverse Effects of Cholinesterase Inhibitors in Dementia, According to the Pharmacovigilance Databases of the United-States and Canada

This survey analyzes two national pharmacovigilance databases in order to determine the major adverse reactions observed with the use of cholinesterase inhibitors in dementia. We conducted a statistical analysis of the Food and Drug Administration Adverse Event Reporting System (FAERS) and the Canada Vigilance Adverse Reaction Database (CVARD) concerning the side effects of cholinesterase inhibitors. The statistics calculated for each adverse event were the frequency and the reporting odds ratios (ROR). A total of 9877 and 2247 reports were extracted from the FAERS and CVARD databases, respectively. A disproportionately higher frequency of reports of death as an adverse event for rivastigmine, compared to the other acetylcholinesterase inhibiting drugs, was observed in both the FAERS (ROR = 3.42; CI95% = 2.94-3.98; P<0.0001) and CVARD (ROR = 3.67; CI95% = 1.92-7.00; P = 0.001) databases. While cholinesterase inhibitors remain to be an important therapeutic tool against Alzheimer's disease, the disproportionate prevalence of fatal outcomes with rivastigmine compared with alternatives should be taken into consideration.

Dietary and donepezil modulation of mTOR signaling and neuroinflammation in the brain

Recent clinical and laboratory evidences suggest that high fat diet (HFD) induced obesity and its associated metabolic syndrome conditions promotes neuropathology in aging and age-related neurological disorders. However, the effects of high fat diet on brain pathology are poorly understood, and the effective strategies to overcome these effects remain elusive. In the current study, we examined the effects of HFD on brain pathology and further evaluated whether donepezil, an AChE inhibitor with neuroprotective functions, could suppress the ongoing HFD induced pathological changes in the brain. Our data demonstrates that HFD induced obesity results in increased neuroinflammation and increased AChE activity in the brain when compared with the mice fed on low fat diet (LFD). HFD administration to mice activated mTOR pathway resulting in increased phosphorylation of mTOR(ser2448), AKT(thr308) and S6K proteins involved in the signaling. Interestingly, donepezil administration with HFD suppressed HFD induced increases in AChE activity, and partially reversed HFD effects on microglial reactivity and the levels of mTOR signaling proteins in the brain when compared to the mice on LFD alone. However, gross levels of synaptic proteins were not altered in the brain tissues of mice fed either diet with or without donepezil. In conclusion, these results present a new insight into the detrimental effects of HFD on brain via microglial activation and involvement of mTOR pathway, and further demonstrates the possible therapeutic role for donepezil in ameliorating the early effects of HFD that could help preserve the brain function in metabolic syndrome conditions.

Molecular Docking and Pharmacological Investigations of Rivastigmine-Fluoxetine and Coumarin-Tacrine hybrids against Acetyl Choline Esterase

The present AChE inhibitors have been successful in the treatment of Alzheimer׳s Diseases however suffers serious side effects. Therefore in this view, the present study was sought to identify compounds with appreciable pharmacological profile targeting AChE. Analogue of Rivastigmine and Fluoxetine hybrid synthesized by Toda et al, 2003 (dataset1), and Coumarin-Tacrine hybrids synthesized by Qi Sun et al (dataset2) formed the test compounds for the present pharmacological evaluation. p-cholorophenyl substituted Rivastigmine and Fluoxetine hybrid compound (26d) from dataset 1 and -OCH3 substitute Coumarin-Tacrine hybrids (1h) from dataset 2 demonstrated superior pharmacological profile. 26 d showed superior pharmacological profile comparison to the entire compounds in either dataset owing to its better electrostatic interactions and hydrogen bonding patterns. In order to identify still better compound with pharmacological profile than 26 d and 1h, virtual screening was performed. The best docked compound (PubCId: PubCid: 68874404) showed better affinity than its parent 26 d, however showed poor ADME profile and AMES toxicity. CHEMBL2391475 (PubCid: 71699632) similar to 1h had reduced affinity in comparison to its parent compound 1h. From, our extensive analysis involving binding affinity analysis, ADMET properties predictions and pharmacophoric mappings, we report p-cholorophenyl substituted rivastigmine and fluoxetine hybrid (26d) to be a potential candidate for AcHE inhibition which in addition can overcome narrow therapeutic window of present AChE inhibitors in clinical treatment of Alzheimer׳s disease.

ABBREVIATIONS

AD - Alzheimer׳s Disease, AChE - Acetyl Choline Estarase, OPLS - Optimized Potentials for Liquid Simulations, PDB - Protein Data Bank.

Conjugates of γ-Carbolines and Phenothiazine as new selective inhibitors of butyrylcholinesterase and blockers of NMDA receptors for Alzheimer Disease

Alzheimer disease is a multifactorial pathology and the development of new multitarget neuroprotective drugs is promising and attractive. We synthesized a group of original compounds, which combine in one molecule γ-carboline fragment of dimebon and phenothiazine core of methylene blue (MB) linked by 1-oxo- and 2-hydroxypropylene spacers. Inhibitory activity of the conjugates toward acetylcholinesterase (AChE), butyrylcholinesterase (BChE) and structurally close to them carboxylesterase (CaE), as well their binding to NMDA-receptors were evaluated in vitro and in silico. These newly synthesized compounds showed significantly higher inhibitory activity toward BChE with IC50 values in submicromolar and micromolar range and exhibited selective inhibitory action against BChE over AChE and CaE. Kinetic studies for the 9 most active compounds indicated that majority of them were mixed-type BChE inhibitors. The main specific protein-ligand interaction is π-π stacking of phenothiazine ring with indole group of Trp82. These compounds emerge as promising safe multitarget ligands for the further development of a therapeutic approach against aging-related neurodegenerative disorders such as Alzheimer and/or other pathological conditions.

Distinct roles of basal forebrain cholinergic neurons in spatial and object recognition memory

Recognition memory requires processing of various types of information such as objects and locations. Impairment in recognition memory is a prominent feature of amnesia and a symptom of Alzheimer’s disease (AD). Basal forebrain cholinergic neurons contain two major groups, one localized in the medial septum (MS)/vertical diagonal band of Broca (vDB), and the other in the nucleus basalis magnocellularis (NBM). The roles of these cell groups in recognition memory have been debated, and it remains unclear how they contribute to it. We use a genetic cell targeting technique to selectively eliminate cholinergic cell groups and then test spatial and object recognition memory through different behavioural tasks. Eliminating MS/vDB neurons impairs spatial but not object recognition memory in the reference and working memory tasks, whereas NBM elimination undermines only object recognition memory in the working memory task. These impairments are restored by treatment with acetylcholinesterase inhibitors, anti-dementia drugs for AD. Our results highlight that MS/vDB and NBM cholinergic neurons are not only implicated in recognition memory but also have essential roles in different types of recognition memory.

Neuronal histamine and cognitive symptoms in Alzheimer's disease

Alzheimer's disease is a neurodegenerative disorder characterized by extracellular amyloid plaque deposits, mainly composed of amyloid-beta peptide and intracellular neurofibrillary tangles consisting of aggregated hyperphosphorylated tau protein. Amyloid-beta represents a neurotoxic proteolytic cleavage product of amyloid precursor protein. The progressive cognitive decline that is associated with Alzheimer's disease has been mainly attributed to a deficit in cholinergic neurotransmission due to the continuous degeneration of cholinergic neurons e.g. in the basal forebrain. There is evidence suggesting that other neurotransmitter systems including neuronal histamine also contribute to the development and maintenance of Alzheimer's disease-related cognitive deficits. Pathological changes in the neuronal histaminergic system of such patients are highly predictive of ensuing cognitive deficits. Furthermore, histamine-related drugs, including histamine 3 receptor antagonists, have been demonstrated to alleviate cognitive symptoms in Alzheimer's disease. This review summarizes findings from animal and clinical research on the relationship between the neuronal histaminergic system and cognitive deterioration in Alzheimer's disease. The significance of the neuronal histaminergic system as a promising target for the development of more effective drugs for the treatment of cognitive symptoms is discussed. Furthermore, the option to use histamine-related agents as neurogenesis-stimulating therapy that counteracts progressive brain atrophy in Alzheimer's disease is considered. This article is part of a Special Issue entitled 'Histamine Receptors'.

Tacrine sinusoidal uptake and biliary excretion in sandwich-cultured primary rat hepatocytes

PURPOSE. The knowledge of hepatic disposition kinetics of tacrine, a first cholinesterase inhibitor was approved by FDA for the treatment of Alzheimer's disease (AD), would help to understand its hepatotoxicity, its therapeutic effect, and improve the management of patients with AD. The current study aims to characterize tacrine hepatic transport kinetics and study the role of organic cation transporters (OCTs), P-glycoprotein (P-gp) and multidrug resistance-associated protein (MRP2) in tacrine sinusoidal uptake and biliary excretion. METHODS. Modulation of tacrine hepatic uptake and efflux, biliary excretion index (BEI%), were performed in sandwich-cultured primary rat hepatocytes (SCHs) using transporters inhibitors. Conformation of the integrity of SCHs model was established by capturing images with light-contrast and fluorescence microscopy. RESULTS. Tacrine uptake in SCHs was carrier-mediated process and saturable with apparent Km of 31.5±9.6 µM and Vmax of 908±72 pmol/min/mg protein. Tetraethyl ammonium (TEA), cimetidine and verapamil significantly reduced tacrine uptake with more pronounced effect observed with verapamil which caused 3-fold reduction in tacrine uptake, indicating role for OCTs. Tacrine has a biliary excretion in SCHs with maximum BEI% value of 22.9±1.9% at 10 min of incubation. Addition of MK571 and valspodar decreased the BEI% of tacrine by 40 and 60% suggesting roles for canalicular MRP2 and P-gp, respectively. CONCLUSIONS. Our results show that in addition to metabolism, tacrine hepatic disposition is carrier-mediated process mediated by sinusoidal OCTs, and canalicular MRP2 and P-gp.

Tannoid principles of Emblica officinalis renovate cognitive deficits and attenuate amyloid pathologies against aluminum chloride induced rat model of Alzheimer's disease

BACKGROUND/AIMS

Emblica officinalis is mentioned as a maharasayana in many Ayurvedic texts and promotes intelligence, memory, freedom from disease, longevity, and strength of the senses. The present study has been designed to explore the memory-enhancing effect of the tannoid principles of E. officinalis (EoT) at the biochemical, anatomical, behavioral, and molecular levels against aluminum chloride (AlCl3) induced Alzheimer's disease (AD) in rats. Aluminum is reported to have an important role in the etiology, pathogenesis, and development of AD.

METHODS

Male Wistar rats were divided into control, AlCl3 treated, AlCl3 and EoT (50, 100, and 200 mg/kg bw) co-treated, and EoT (200 mg/kg bw) alone treated groups. In control and experimental rats, behavior tests including water maze and open field test, estimation of aluminum, assay of acetylcholinesterase (AChE) activity, and expression of amyloidogenic proteins were performed.

RESULTS

Intraperitonial injection of AlCl3 (100 mg/kg bw) for 60 days significantly elevated the concentration of aluminum (Al), activity of AChE and protein expressions of amyloid precursor protein, A-beta1-42, beta-, and gamma-secretases as compared to control group in hippocampus and cortex. Co-administration of EoT orally to AlCl3 rats for 60 days significantly revert back the Al concentration, AChE activity, and A-beta synthesis-related molecules in the studied brain regions. The spatial learning, memory, and locomotor impairments observed in AlCl3 treated rats were significantly attenuated by EoT.

CONCLUSION

Therefore, EoT may be a promising therapy in ameliorating neurotoxicity of aluminum, however further studies are warranted to elucidate the exact mechanism of action of EoT.

Identification and characterization of ML352: a novel, noncompetitive inhibitor of the presynaptic choline transporter

The high-affinity choline transporter (CHT) is the rate-limiting determinant of acetylcholine (ACh) synthesis, yet the transporter remains a largely undeveloped target for the detection and manipulation of synaptic cholinergic signaling. To expand CHT pharmacology, we pursued a high-throughput screen for novel CHT-targeted small molecules based on the electrogenic properties of transporter-mediated choline transport. In this effort, we identified five novel, structural classes of CHT-specific inhibitors. Chemical diversification and functional analysis of one of these classes identified ML352 as a high-affinity (K_i = 92 nM) and selective CHT inhibitor. At concentrations that fully antagonized CHT in transfected cells and nerve terminal preparations, ML352 exhibited no inhibition of acetylcholinesterase (AChE) or cholineacetyltransferase (ChAT) and also lacked activity at dopamine, serotonin, and norepinephrine transporters, as well as many receptors and ion channels. ML352 exhibited noncompetitive choline uptake inhibition in intact cells and synaptosomes and reduced the apparent density of hemicholinium-3 (HC-3) binding sites in membrane assays, suggesting allosteric transporter interactions. Pharmacokinetic studies revealed limited in vitro metabolism and significant CNS penetration, with features predicting rapid clearance. ML352 represents a novel, potent, and specific tool for the manipulation of CHT, providing a possible platform for the development of cholinergic imaging and therapeutic agents.