Biochemical differentiation of cholinesterases from normal and Alzheimer's disease cortex

Lead Optimization of a Butyrylcholinesterase Inhibitor for the Treatment of Alzheimer's Disease

Butyrylcholinesterase (BChE) is a promising drug target for alleviating the symptoms of canine cognitive dysfunction (CCD) and Alzheimer's disease (AD). We have recently developed lead compound 2, a racemic, nanomolar BChE inhibitor with procognitive effects in mice with scopolamine-induced AD-like symptoms and dogs suffering from CCD. To overcome its modest brain exposure, we developed compound (R)-(-)-3, a more potent BChE inhibitor with a 7-fold higher in vivo brain exposure. It has procognitive effects in mice with scopolamine-induced AD-like symptoms and, superior to compound 2, also in mice with Aβ1-42-induced AD-like symptoms. Compound (R)-(-)-3 produces no cholinergic adverse effects or motor deficits and has no acute toxic effects in mice. This makes sulfonamide (R)-(-)-3 an optimized lead compound for alleviating the symptoms of AD.

Naringenin: its chemistry and roles in neuroprotection

According to epidemiological research, as the population ages, neurological illnesses are becoming a bigger issue. Despite improvements in the treatment of these diseases, there are still widespread worries about how to find a long-lasting remedy. Several neurological diseases can be successfully treated with natural substances. As a result, current research has been concentrated on finding effective neuroprotective drugs with improved efficacy and fewer side effects. Naringenin is one potential treatment for neurodegenerative diseases. Many citrus fruits, tomatoes, bergamots, and other fruits are rich in naringenin, a flavonoid. This phytochemical is linked to a variety of biological functions. Naringenin has attracted a lot of interest for its ability to exhibit neuroprotection through several mechanisms. In the current article, we present evidence from the literature that naringenin reduces neurotoxicity and oxidative stress in brain tissues. Also, the literatures that are currently accessible shows that naringenin reduces neuroinflammation and other neurological anomalies. Additionally, we found several studies that touted naringenin as a promising anti-amyloidogenic, antidepressant, and neurotrophic treatment option. This review's major goal is to reflect on advancements in knowledge of the molecular processes that underlie naringenin's possible neuroprotective effects. Furthermore, this article also provides highlights of Naringenin with respect to its chemistry and pharmacokinetics.

Machine learning-based virtual screening and molecular modelling studies for identification of butyrylcholinesterase inhibitors as anti-Alzheimer's agent

Butyrylcholinesterase (BChE) is a hydrolase involved in the metabolism and detoxification of specific esters in the blood. It is also implicated in the progression of Alzheimer's disease, a type of dementia. As the disease progresses, the level of BChE tends to increase, opting for a major role as an acetylcholine-degrading enzyme and surpassing the role of acetylcholinesterase. Hence, the development of BChE inhibitors could be beneficial for the latter stages of the disease. In the present study, machine learning (ML) models were developed and employed to identify new BChE inhibitors. Further, the identified molecules were subjected to molecular property filters. The filtered ligands were studied through molecular modelling techniques, viz. molecular docking and molecular dynamics (MD). Support vector machine-based ML models resulted in the identification of 3291 compounds that would have predicted IC50 values less than 200 nM. The docking study showed that compounds ART13069594, ART17350769 and LEG19710163 have mean binding energies of -9.62, -9.26 and -8.93 kcal/mol, respectively. The MD study displayed that all the selected ligands showed stable complexes with BChE. The trajectories of all the ligands were stable similar to the standard BChE inhibitors.

The Unveiling of Therapeutic Targets for Alzheimer's Disease: An Integrative Review

Alzheimer's disease (AD) is characterized by a complex pathological landscape, necessitating a comprehensive treatment approach. This concise review paper delves into the idea of addressing multiple mechanisms in AD, summarizing the latest research findings on pathogenesis, risk factors, diagnostics, and therapeutic strategies. The etiology of AD is multifaceted, involving genetic, environmental, and lifestyle factors. The primary feature is the accumulation of amyloid-- beta and tau proteins, leading to neuroinflammation, synaptic dysfunction, oxidative stress, and neuronal loss. Conventional single-target therapies have shown limited effectiveness, prompting a shift toward simultaneously addressing multiple disease-related processes. Recent advancements in AD research underscore the potential of multifaceted therapies. This review explores strategies targeting both tau aggregation and amyloid-beta, along with interventions to alleviate neuroinflammation, enhance synaptic function, and reduce oxidative stress. In conclusion, the review emphasizes the growing importance of addressing various pathways in AD treatment. A holistic approach that targets different aspects of the disease holds promise for developing effective treatments and improving the quality of life for Alzheimer's patients and their caregivers.

Synthesis and molecular docking simulation of new benzimidazole-thiazole hybrids as cholinesterase inhibitors

Dementia is a cognitive disturbance that is generally correlated with central nervous system diseases, especially Alzheimer's disease. The limited number of medications available is insufficient to improve the lifestyle of the patients suffering from this disease. Thus, new benzimidazole-thiazole hybrids (3-10) were designed and synthesized as acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitory agents. The in vitro evaluation displayed that the derivatives 4b, 4d, 5b, 6a, 7a, and 8b demonstrated dual inhibitory efficiency against both AChE with IC50 ranging from 4.55 to 8.62 µM and BChE with IC50 ranging from 3.50 to 8.32 µM. By analyzing the Lineweaver-Burk plot, an uncompetitive form of inhibition was determined for the highly active compound 4d, revealing its inhibition type. The human telomerase reverse transcriptase-immortalized retinal pigment epithelial cell line was used to ensure the safety of the most potent cholinesterase inhibitors. Furthermore, compounds 4b, 4d, 5b, 6a, 7a, and 8b were evaluated for their neuroprotective and antioxidant properties, as well as their ability to suppress COX-2. The results demonstrated that compounds 4d, 5b, and 8b presented significant neuroprotection efficiency against H2 O2 -induced damage in SH-SY5Y cells with % cell viability of 67.42 ± 7.90%, 62.51 ± 6.71%, and 72.61 ± 8.10%, respectively, while the tested candidates did not reveal significant antioxidant activity. Otherwise, compounds 4b, 6a, 7a, and 8b displayed outstanding COX-2 inhibition effects with IC50 ranging from 0.050 to 0.080 μM relative to celecoxib (IC50  = 0.050 µM). In addition, molecular docking was carried out for the potent benzimidazole-thiazole hybrids with the active sites of both AChE (PDB ID: 4EY7) and BChE (PDB code: 1P0P). The tested candidates fit well in the active sites of both portions, with docking scores ranging from -8.65 to -6.64 kcal/mol (for AChE) and -8.71 to -7.73 kcal/mol (for BChE). In silico results show that the synthesized benzimidazole-thiazole hybrids have good physicochemical and pharmacokinetic properties with no Lipinski rule violations. The preceding results exhibited that compound 4d could be used as a new template for developing more significant cholinesterase inhibitors in the future.

Galantamine-memantine hybrids for Alzheimer's disease: The influence of linker rigidity in biological activity and pharmacokinetic properties

Neurodegenerative processes characterizing Alzheimer's disease (AD) are strictly related to the impairment of cholinergic and glutamatergic neurotransmitter systems which provoke synaptic loss. These experimental evidences still represent the foundation of the actual standard-of-care treatment for AD, albeit palliative, consisting on the coadministration of an acetylcholinesterase inhibitor and the NMDAR antagonist memantine. In looking for more effective treatments, we previously developed a series of galantamine-memantine hybrids where compound 1 (ARN14140) emerged with the best-balanced action toward the targets of interest paired to neuroprotective efficacy in a murine AD model. Unfortunately, it showed a suboptimal pharmacokinetic profile, which required intracerebroventricular administration for in vivo studies. In this work we designed and synthesized new hybrids with fewer rotatable bonds, which is related to higher brain exposure. Particularly, compound 2, bearing a double bond in the tether, ameliorated the biological profile of compound 1 in invitro studies, increasing cholinesterases inhibitory potencies and selective antagonism toward excitotoxic-related GluN1/2B NMDAR over beneficial GluN1/2A NMDAR. Furthermore, it showed increased plasma stability and comparable microsomal stability in vitro, paired with lower half-life and faster clearance in vivo. Remarkably, pharmacokinetic evaluations of compound 2 showed a promising increase in brain uptake in comparison to compound 1, representing the starting point for further chemical optimizations.

The structural modification and biological evaluation of tetrahydrothienopyridine derivatives as selective BChE inhibitors

A series of tetrahydrothienopyridine derivatives have been designed, synthesized, and evaluated as selective BChE inhibitors. Compounds were analyzed via HRMS, 1H NMR, and 13C NMR. The inhibitory effects were evaluated according to the method of Ellman et al. 6n was the most potent and selective inhibitor against BChE (eeAChE IC50 = 686.4 ± 478.6 μM, eqBChE IC50 = 10.5 ± 5.0 nM, SI = 6.5*104, hBChE IC50 = 32.5 ± 6.5 nM). Cell-based assays have confirmed the low neurotoxicity of 6a and 6n and their moderate neuroprotective effects. Compounds 6a and 6n provide novel chemical entities for the treatment of Alzheimer's disease.

Natural Alkaloids as Multi-Target Compounds towards Factors Implicated in Alzheimer's Disease

Alzheimer's disease (AD) is the most common cause of dementia in elderly people; currently, there is no efficient treatment. Considering the increase in life expectancy worldwide AD rates are predicted to increase enormously, and thus the search for new AD drugs is urgently needed. A great amount of experimental and clinical evidence indicated that AD is a complex disorder characterized by widespread neurodegeneration of the CNS, with major involvement of the cholinergic system, causing progressive cognitive decline and dementia. The current treatment, based on the cholinergic hypothesis, is only symptomatic and mainly involves the restoration of acetylcholine (ACh) levels through the inhibition of acetylcholinesterase (AChE). Since the introduction of the Amaryllidaceae alkaloid galanthamine as an antidementia drug in 2001, alkaloids have been one of the most attractive groups for searching for new AD drugs. The present review aims to comprehensively summarize alkaloids of various origins as multi-target compounds for AD. From this point of view, the most promising compounds seem to be the β-carboline alkaloid harmine and several isoquinoline alkaloids since they can simultaneously inhibit several key enzymes of AD's pathophysiology. However, this topic remains open for further research on detailed mechanisms of action and the synthesis of potentially better semi-synthetic analogues.

Naringenin: A prospective therapeutic agent for Alzheimer's and Parkinson's disease

Neurodegenerative disorders (NDs) are a cluster of progressive, severe, and disabling disorders that affect millions of people worldwide and are on the surge. These disorders are characterized by the gradual loss of a selectively vulnerable group of neurons. Due to the complex pathophysiological mechanisms behind neurodegeneration and despite enormous efforts and understanding of the occurrence and progression of NDs, there is still a lack of an effective treatment for such diseases. Therefore, the development of a new therapeutic strategy for NDs is an unmet clinical need. Various natural compounds extracted from medicinal plants or fruits have shown promising activities in treating different types of NDs by targeting multiple signaling pathways. Among natural entities, flavonoids have incited a rise in public and scientific interest in recent years because of their purported health-promoting effects. Dietary supplementation of flavonoids has been shown to mitigate the severity of NDs such as Parkinson's disease (PD), Alzheimer's disease (AD), and dementia by their antioxidant effects. Naringenin is a citrus flavonoid that is known to possess numerous biological activities like antioxidant, anti-proliferative, and anti-inflammatory activities. Therefore, naringenin has emerged as a potential therapeutic agent that exerts preventive and curative effects on several neurological disorders. Increasing evidence has attained special attention on the variety of therapeutic targets along with complex signaling pathways of naringenin, which suggest its possible therapeutic applications in several NDs. Derived from the results of several pre-clinical research and considering the therapeutic effects of this compound, this review focuses on the potential role of naringenin as a pharmacological agent for the treatment and management of Alzheimer's and Parkinson's disease. The overall neuroprotective effects and different possible underlying mechanisms related to naringenin are discussed. In the light of substantial evidence for naringenin's neuroprotective efficacy in several experimental paradigms, this review suggests that this molecule should be investigated further as a viable candidate for the management of Alzheimer's and Parkinson's disease, with an emphasis on mechanistic and clinical trials to determine its efficacy. PRACTICAL APPLICATIONS: Naringenin is a flavanone, aglycone of Naringin, predominantly found in citrus fruits with a variety of pharmacological actions. Naringenin has been shown to exhibit remarkable therapeutic efficacy and has emerged as a potential therapeutic agent for the management of a variety of diseases such as various heart, liver, and metabolic disorders. Similarly, it has shown efficacy in neurodegenerative illnesses. Therefore, this review enables us to better understand the neuroprotective effects and different possible underlying mechanisms of naringenin. Also, this review provides a new indication to manage the symptoms of NDs like AD and PD. Furthermore, naringenin will be useful in the field of medicine as a new active ingredient for the treatment of neurodegenerative disorders like AD and PD.

Neuroprotective Effects of Cholinesterase Inhibitors: Current Scenario in Therapies for Alzheimer's Disease and Future Perspectives

Alzheimer's disease (AD) is a slowly progressive neurodegenerative disease conceptualized as a continuous process, ranging from mild cognitive impairment (MCI), to the mild, moderate, and severe clinical stages of AD dementia. AD is considered a complex multifactorial disease. Currently, the use of cholinesterase inhibitors (ChEI), such as tacrine, donepezil, rivastigmine, and galantamine, has been the main treatment for AD patients. Interestingly, there is evidence that ChEI also promotes neuroprotective effects, bringing some benefits to AD patients. The mechanisms by which the ChEI act have been investigated in AD. ChEI can modulate the PI3K/AKT pathway, which is an important signaling cascade that is capable of causing a significant functional impact on neurons by activating cell survival pathways to promote neuroprotective effects. However, there is still a huge challenge in the field of neuroprotection, but in the context of unravelling the details of the PI3K/AKT pathway, a new scenario has emerged for the development of more efficient drugs that act on multiple protein targets. Thus, the mechanisms by which ChEI can promote neuroprotective effects and prospects for the development of new drug candidates for the treatment of AD are discussed in this review.

Rare genetic variability in human drug target genes modulates drug response and can guide precision medicine

Interindividual variability in drug response constitutes a major concern in pharmacotherapy. While polymorphisms in genes involved in drug disposition have been extensively studied, drug target variability remains underappreciated. By mapping the genomic variability of all human drug target genes onto high-resolution crystal structures of drug target complexes, we identified 1094 variants localized within 6 Å of drug-binding pockets and directly affecting their geometry, topology, or physicochemical properties. We experimentally show that binding site variants affect pharmacodynamics with marked drug- and variant-specific differences. In addition, we demonstrate that a common BCHE variant confers resistance to tacrine and rivastigmine, which can be overcome by the use of derivatives based on squaric acid scaffolds or tryptophan conjugation. These findings underscore the importance of genetic drug target variability and demonstrate that integration of genomic data and structural information can inform personalized drug selection and genetically guided drug development to overcome resistance.

Recent Progress on Biological Activity of Amaryllidaceae and Further Isoquinoline Alkaloids in Connection with Alzheimer's Disease

Alzheimer’s disease (AD) is a progressive age-related neurodegenerative disease recognized as the most common form of dementia among elderly people. Due to the fact that the exact pathogenesis of AD still remains to be fully elucidated, the treatment is only symptomatic and available drugs are not able to modify AD progression. Considering the increase in life expectancy worldwide, AD rates are predicted to increase enormously, and thus the search for new AD drugs is urgently needed. Due to their complex nitrogen-containing structures, alkaloids are considered to be promising candidates for use in the treatment of AD. Since the introduction of galanthamine as an antidementia drug in 2001, Amaryllidaceae alkaloids (AAs) and further isoquinoline alkaloids (IAs) have been one of the most studied groups of alkaloids. In the last few years, several compounds of new structure types have been isolated and evaluated for their biological activity connected with AD. The present review aims to comprehensively summarize recent progress on AAs and IAs since 2010 up to June 2021 as potential drugs for the treatment of AD.

Acetylcholinesterase Inhibitors in the Treatment of Neurodegenerative Diseases and the Role of Acetylcholinesterase in their Pathogenesis

Acetylcholinesterase (AChE) plays an important role in the pathogenesis of neurodegenerative diseases by influencing the inflammatory response, apoptosis, oxidative stress and aggregation of pathological proteins. There is a search for new compounds that can prevent the occurrence of neurodegenerative diseases and slow down their course. The aim of this review is to present the role of AChE in the pathomechanism of neurodegenerative diseases. In addition, this review aims to reveal the benefits of using AChE inhibitors to treat these diseases. The selected new AChE inhibitors were also assessed in terms of their potential use in the described disease entities. Designing and searching for new drugs targeting AChE may in the future allow the discovery of therapies that will be effective in the treatment of neurodegenerative diseases.

Fluorescence "Turn-On" Enzyme-Responsive Supra-Amphiphile Fabricated by Host-Guest Recognition between γ-Cyclodextrin and a Tetraphenylethylene-Sodium Glycyrrhetinate Conjugate

A novel fluorescence "turn-on" enzyme-responsive supra-amphiphile is developed based on the host-guest recognition between γ-cyclodextrin (γ-CD) and an amphiphilic tetraphenylethene-sodium glycyrrhetinate conjugate (TPE-SGA). The covalent amphiphile TPE-SGA displayed strong fluorescence in aqueous solution owing to the aggregation-induced emission. Upon addition of γ-CD, the fluorescence of TPE-SGA was effectively turned off due to the host-guest recognition with γ-CD prohibiting the aggregation of TPE-SGA in aqueous solution. The as-formed nonfluorescent supra-amphiphile (TPE-SGA/γ-CD) inherited the α-amylase-responsive property of γ-CD. In the presence of α-amylase, the fluorescence of the supra-amphiphile was gradually turned on owing to the hydrolysis of γ-CD, and the fluorescence intensity linearly correlated to the activity of α-amylase. This study enriches the field of supra-amphiphile on the basis of cyclodextrin-based host-guest chemistry and provides a novel strategy to construct fluorescence turn-on functioned self-assemblies. It is anticipated that the fluorescence turn-on supra-amphiphile has potential applications in biological analysis and diagnosis of pancreatic diseases.

In silico Exploration of Bioactive Phytochemicals Against Neurodegenerative Diseases Via Inhibition of Cholinesterases

Neurodegenerative disorders are estimated to become the second leading cause of death worldwide by 2040. Despite the widespread use of diverse allopathic drugs, these brain-associated disorders can only be partially addressed and long term treatment is often linked with dependency and other unwanted side effects. Nature, believed to be an arsenal of remedies for any illness, presents an interesting avenue for the development of novel neuroprotective agents. Interestingly, inhibition of cholinesterases, involved in the breakdown of acetylcholine in the synaptic cleft, has been proposed to be neuroprotective. This review therefore aims to provide additional insight via docking studies of previously studied compounds that have shown potent activity against acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) in vitro. Indeed, the determination of potent plant-based ligands for this purpose through in silico methods enables the elimination of lengthy and costly traditional methods of drug discovery. Herein, a literature search was conducted to identify active phytochemicals which are cholinesterase inhibitors. Following which in silico docking methods were applied to obtain docking scores. Compound structures were extracted from online ZINC database and optimized using AM1 implemented in gaussian09 software. Noteworthy ligands against AChE highlighted in this study include: 19,20-dihydroervahanine A and 19, 20-dihydrotabernamine. Regarding BChE inhibition, the best ligands were found to be 8-Clavandurylkaempferol, Na-methylepipachysamine D; ebeiedinone; and dictyophlebine. Thus, ligand optimization between such phytochemicals and cholinesterases coupled with in vitro, in vivo studies and randomized clinical trials can lead to the development of novel drugs against neurodegenerative disorders.

Therapeutic effects of rosemary (Rosmarinus officinalis L.) and its active constituents on nervous system disorders

Rosemary (Rosmarinus officinalis L.) is an evergreen bushy shrub which grows along the Mediterranean Sea, and sub-Himalayan areas. In folk medicine, it has been used as an antispasmodic, mild analgesic, to cure intercostal neuralgia, headaches, migraine, insomnia emotional upset, and depression. Different investigations have highlighted rosemary neuropharmacological properties as their main topics. Rosemary has significant antimicrobial, anti-inflammatory, anti-oxidant, anti-apoptotic, anti-tumorigenic, antinociceptive, and neuroprotective properties. Furthermore, it shows important clinical effects on mood, learning, memory, pain, anxiety, and sleep. The aim of the current work is to review the potential neuropharmacological effects of different rosemary extracts and its active constituents on nervous system disorders, their relevant mechanisms and its preclinical application to recall the therapeutic potential of this herb and more directions of future research projects. The data were gathered by searching the English articles in PubMed, Scopus, Google Scholar, and Web of Science. The keywords used as search terms were 'Rosmarinus officinalis', 'rosemary', 'nervous system', 'depression', 'memory', 'Alzheimer's disease' 'epilepsy', 'addiction', 'neuropathic pain', and 'disorders'. All kinds of related articles, abstracts and books were included. No time limitation was considered. Both in vitro and in vivo studies were subjected to this investigation. This review authenticates that rosemary has appeared as a worthy source for curing inflammation, analgesic, anti-anxiety, and memory boosting. It also arranges new perception for further investigations on isolated constituents, especially carnosic acid, rosmarinic acid, and essential oil to find exquisite therapeutics and support drug discovery with fewer side effects to help people suffering from nervous system disorders.

Synthesis, acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) activities, and molecular docking studies of a novel compound based on combination of flurbiprofen and isoniazide

A novel compound (1) shows ∼2.5 and ∼1.7 times enhanced AChE inhibition activity and BuChE inhibition activity respectively compared to flurbiprofen and standard drug (i.e. physostigmine). It has also been confirmed by comparative AutoDock studies.

On the Neuroprotective Effects of Naringenin: Pharmacological Targets, Signaling Pathways, Molecular Mechanisms, and Clinical Perspective

As a group of progressive, chronic, and disabling disorders, neurodegenerative diseases (NDs) affect millions of people worldwide, and are on the rise. NDs are known as the gradual loss of neurons; however, their pathophysiological mechanisms have not been precisely revealed. Due to the complex pathophysiological mechanisms behind the neurodegeneration, investigating effective and multi-target treatments has remained a clinical challenge. Besides, appropriate neuroprotective agents are still lacking, which raises the need for new therapeutic agents. In recent years, several reports have introduced naturally-derived compounds as promising alternative treatments for NDs. Among natural entities, flavonoids are multi-target alternatives affecting different pathogenesis mechanisms in neurodegeneration. Naringenin is a natural flavonoid possessing neuroprotective activities. Increasing evidence has attained special attention on the variety of therapeutic targets along with complex signaling pathways for naringenin, which suggest its possible therapeutic applications in several NDs. Here, in this review, the neuroprotective effects of naringenin, as well as its related pharmacological targets, signaling pathways, molecular mechanisms, and clinical perspective, are described. Moreover, the need to develop novel naringenin delivery systems is also discussed to solve its widespread pharmacokinetic limitation.

Structure-based virtual screening leading to discovery of highly selective butyrylcholinesterase inhibitors with solanaceous alkaloid scaffolds

According to recent research advance, it is interesting to identify new, potent and selective inhibitors of human butyrylcholinesterase (BChE) for therapeutic treatment of both the Alzheimer's disease (AD) and heroin abuse. In this study, we carried out a structure-based virtual screening followed by in vitro activity assays, with the goal to identify new inhibitors that are selective for BChE over acetylcholinesterase (AChE). As a result, a set of new, selective inhibitors of human BChE were identified from natural products with solanaceous alkaloid scaffolds. The most active one of the natural products (compound 1) identified has an IC50 of 16.8 nM against BChE. It has been demonstrated that the desirable selectivity of these inhibitors for BChE over AChE is mainly controlled by three key residues in the active site cavity, i.e. residues Q119, A277, and A328 in BChE versus the respective residues Y124, W286, and Y337 in AChE. Based on this structural insight, future rational design of new, potent and selective BChE inhibitors may focus on these key structural differences in the active site cavity.

Synthesis, molecular docking, and biological evaluation of novel 2-pyrazoline derivatives as multifunctional agents for the treatment of Alzheimer's disease

A novel series of 2-pyrazoline derivatives were designed, synthesized, and evaluated for cholinesterase (ChE) inhibitory, Aβ anti-aggregating and neuroprotective activities. Among these, 3d, 3e, 3g, and 3h were established as the most potent and selective BChE inhibitors (IC₅₀ = 0.5-3.9 μM), while 3f presented dual inhibitory activity against BChE and AChE (IC₅₀ = 6.0 and 6.5 μM, respectively). Kinetic analyses revealed that 3g is a partial noncompetitive inhibitor of BChE (Ki = 2.22 μM), while 3f exerts competitive inhibition on AChE (Ki = 0.63 μM). The active compounds were subsequently screened for further assessments. 3f, 3g and 3h reduced Aβ_1-42 aggregation levels significantly (72.6, 83.4 and 63.4%, respectively). In addition, 3f demonstrated outstanding neuroprotective effects against Aβ_1-42-induced and H₂O₂-induced cell toxicity (95.6 and 93.6%, respectively). Molecular docking studies were performed with 3g and 3f to investigate binding interactions inside the active sites of BChE and AChE. Compounds 3g and 3f might have the multifunctional potential for use against Alzheimer's disease.

Ursolic and oleanolic acid derivatives with cholinesterase inhibiting potential

Triterpenoids are in the focus of scientific interest, and they were evaluated for many pharmacological applications among them their ability to act as inhibitors of cholinesterases. These inhibitors are still of interest as drugs that improve the life quality of patients suffering from age-related dementia illnesses especially of Alzheimer's disease. Herein, we prepared several derivatives of ursolic and oleanolic acid and screened them in Ellman's assays for their ability to inhibit acetylcholinesterase and/or butyrylcholinesterase, and for each of the active compounds the type of inhibition was determined. As a result, several compounds were shown as good inhibitors for acetylcholinesterase and butyrylcholinesterase even in a micromolar range. An ursolic acid derived hydroxyl-propinyl derivative 10 was a competitive inhibitor for butyrylcholinesterase with an inhibition constant of Ki = 4.29 μM, and therefore being twice as active as gold standard galantamine hydrobromide. The best inhibitor for acetylcholinesterase, however, was 2-methyl-3-oxo-methyl-ursoloate (18), acting as a mixed-type inhibitor showing Ki = 1.72 µM and Ki' = 1.28 μM, respectively.

In Silico Docking and In Vitro Approaches towards BACE1 and Cholinesterases Inhibitory Effect of Citrus Flavanones

Alzheimer’s disease (AD) is the most prevalent neurodegenerative disease, distinctively characterized by senile plaques, neurofibrillary tangles, and synaptic loss, finally resulting in neuronal death. β-Site amyloid precursor protein (APP) cleaving enzyme 1 (BACE1) and cholinesterases have been identified as therapeutic targets for AD, and the discovery of their inhibitors is of critical importance for developing preventive strategies for AD. To discover natural multi-target compounds possessing BACE1, acetylcholinesterase (AChE), and butyrylcholinesterase (BChE) inhibitory properties, major citrus flavanones including hesperetin, naringenin, and hesperidin were evaluated. In vitro anti-AD activities were performed via BACE1 and cholinesterases inhibition assays, as well as enzyme kinetic predictions. For the design of potential inhibitors of AD-related enzymes, molecular docking analysis was performed. Based on the biological evaluation, hesperidin demonstrated the best inhibitory properties toward BACE1, AChE, and BChE, with IC₅₀ values of 10.02 ± 1.12, 22.80 ± 2.78, and 48.09 ± 0.74 µM, respectively. Kinetic studies revealed that all tested compounds were found to be noncompetitive inhibitors against BACE1 and cholineseterases. In addition, molecular docking studies of these compounds demonstrated negative binding energies for BACE1, AChE, and BChE, indicating high affinity and tight binding capacity for the target enzymes. The present study suggested that the selected citrus flavanones could act together as multiple inhibitors of BACE1, AChE, and BChE, indicating preventive and therapeutic potential against AD.

Multi-Target Directed Donepezil-Like Ligands for Alzheimer's Disease

HIGHLIGHTS ASS234 is a MTDL compound containing a moiety from Donepezil and the propargyl group from the PF 9601N, a potent and selective MAO B inhibitor. This compound is the most advanced anti-Alzheimer agent for preclinical studies identified in our laboratory.Derived from ASS234 both multipotent donepezil-indolyl (MTDL-1) and donepezil-pyridyl hybrids (MTDL-2) were designed and evaluated as inhibitors of AChE/BuChE and both MAO isoforms. MTDL-2 showed more high affinity toward the four enzymes than MTDL-1.MTDL-3 and MTDL-4, were designed containing the N-benzylpiperidinium moiety from Donepezil, a metal- chelating 8-hydroxyquinoline group and linked to a N-propargyl core and they were pharmacologically evaluated.The presence of the cyano group in MTDL-3, enhanced binding to AChE, BuChE and MAO A. It showed antioxidant behavior and it was able to strongly complex Cu(II), Zn(II) and Fe(III).MTDL-4 showed higher affinity toward AChE, BuChE.MTDL-3 exhibited good brain penetration capacity (ADMET) and less toxicity than Donepezil. Memory deficits in scopolamine-lesioned animals were restored by MTDL-3.MTDL-3 particularly emerged as a ligand showing remarkable potential benefits for its use in AD therapy. Alzheimer's disease (AD), the most common form of adult onset dementia, is an age-related neurodegenerative disorder characterized by progressive memory loss, decline in language skills, and other cognitive impairments. Although its etiology is not completely known, several factors including deficits of acetylcholine, β-amyloid deposits, τ-protein phosphorylation, oxidative stress, and neuroinflammation are considered to play significant roles in the pathophysiology of this disease. For a long time, AD patients have been treated with acetylcholinesterase inhibitors such as donepezil (Aricept®) but with limited therapeutic success. This might be due to the complex multifactorial nature of AD, a fact that has prompted the design of new Multi-Target-Directed Ligands (MTDL) based on the "one molecule, multiple targets" paradigm. Thus, in this context, different series of novel multifunctional molecules with antioxidant, anti-amyloid, anti-inflammatory, and metal-chelating properties able to interact with multiple enzymes of therapeutic interest in AD pathology including acetylcholinesterase, butyrylcholinesterase, and monoamine oxidases A and B have been designed and assessed biologically. This review describes the multiple targets, the design rationale and an in-house MTDL library, bearing the N-benzylpiperidine motif present in donepezil, linked to different heterocyclic ring systems (indole, pyridine, or 8-hydroxyquinoline) with special emphasis on compound ASS234, an N-propargylindole derivative. The description of the in vitro biological properties of the compounds and discussion of the corresponding structure-activity-relationships allows us to highlight new issues for the identification of more efficient MTDL for use in AD therapy.

Learning performances and vulnerability to amyloid toxicity in the butyrylcholinesterase knockout mouse

Butyrylcholinesterase (BChE) is an important enzyme for detoxication and metabolism of ester compounds. It also hydrolyzes the neurotransmitter acetylcholine (ACh) in pathological conditions and may play a role in Alzheimer's disease (AD). We here compared the learning ability and vulnerability to Aβ toxicity in male and female BChE knockout (KO) mice and their 129Sv wild-type (Wt) controls. Animals tested for place learning in the water-maze showed increased acquisition slopes and presence in the training quadrant during the probe test. An increased passive avoidance response was also observed for males. BChE KO mice therefore showed enhanced learning ability in spatial and non-spatial memory tests. Intracerebroventricular (ICV) injection of increasing doses of amyloid-β[25-35] (Aβ25-35) peptide oligomers resulted, in Wt mice, in learning and memory deficits, oxidative stress and decrease in ACh hippocampal content. In BChE KO mice, the Aβ25-35-induced deficit in place learning was attenuated in males and blocked in females. No change in lipid peroxidation or ACh levels was observed after Aβ25-35 treatment in male or female BChE KO mice. These data showed that the genetic invalidation of BChE in mice augmented learning capacities and lowered the vulnerability to Aβ toxicity.

Rosmarinus officinalis L. leaf extract improves memory impairment and affects acetylcholinesterase and butyrylcholinesterase activities in rat brain

Rosmarinus officinalis L. leaf as part of a diet and medication can be a valuable proposal for the prevention and treatment of dementia. The aim of the study was to assess the effects of subchronic (28-fold) administration of a plant extract (RE) (200 mg/kg, p.o.) on behavioral and cognitive responses of rats linked with acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) activity and their mRNA expression level in the hippocampus and frontal cortex. The passive avoidance test results showed that RE improved long-term memory in scopolamine-induced rats. The extract inhibited the AChE activity and showed a stimulatory effect on BuChE in both parts of rat brain. Moreover, RE produced a lower mRNA BuChE expression in the cortex and simultaneously an increase in the hippocampus. The study suggests that RE led to improved long-term memory in rats, which can be partially explained by its inhibition of AChE activity in rat brain.

A review of butyrylcholinesterase as a therapeutic target in the treatment of Alzheimer's disease

OBJECTIVE

To examine the role of butyrylcholinesterase (BuChE) in cholinergic signaling and neurologic conditions, such as Alzheimer's disease (AD). The rationale for inhibiting cholinesterases in the management of AD, including clinical evidence supporting use of the dual acetylcholinesterase (AChE) and BuChE inhibitor rivastigmine, is discussed.

DATA SOURCES

PubMed searches were performed using butyrylcholinesterase as a keyword. English-language articles referenced in PubMed as of September 2011 were included. Study Selection and Data Synthesis: English-language articles related to BuChE considered to be of clinical relevance to physicians were included. English-language articles specifically related to AChE were not included, as the role of AChE in cholinergic signaling and the underlying pathology of AD is well documented. Reference lists of included publications were used to supplement the search.

RESULTS

AChE and BuChE play a role in cholinergic signaling; BuChE can hydrolyze acetylcholine and compensate for AChE when levels are depleted. In the AD brain, AChE levels decrease, while BuChE levels are reportedly increased or unchanged, with changes becoming more pronounced during the disease course. Furthermore, BuChE genotype may influence AD risk and rate of disease progression. Strategies that increase acetylcholine levels (eg, cholinesterase inhibitors) demonstrate symptomatic efficacy in AD. Rivastigmine has proven cognitive efficacy in clinical trials, and data suggest that its action is mediated, in part, by inhibition of BuChE. Retrospective analyses of clinical trials provide evidence that BuChE genotype may also influence treatment response.

CONCLUSIONS

AChE-selective inhibitors and a dual AChE and BuChE inhibitor demonstrate symptomatic efficacy in AD. Mounting preclinical and clinical evidence for a role of BuChE in maintaining normal cholinergic function and the pathology of AD provides a rationale for further studies investigating use of rivastigmine in AD and the influence of BuChE genotype on observed efficacy.