Butyrylcholinesterase reactivity differentiates the amyloid plaques of aging from those of dementia

Synthesis, characterization and biological evaluation of aurones as potential neuroprotective agents

Aim: To synthesize aurone (Ar) derivatives and to demonstrate their effects against diabetes mellitus (DM) and neurodegeneration.Materials & methods: Five Ar (A-E) derivatives were synthesized, characterized by proton NMR and screened for antioxidant, anti-diabetic and anti-cholinesterase activities. They were further evaluated for neuroprotective effects in streptozotocin (STZ)-induced neurodegenerative model.Results: Among the aurone derivatives ArE demonstrated significant reversal of cognitive impairment, oxidative stress and neuroinflammation. Biochemical analysis revealed anti-diabetic and neuroprotective effects, possibly through downregulation of inflammatory markers and upregulation of antioxidant enzymes.Conclusion: Synthesized Ar (A-E) exhibits promising therapeutic potential against STZ-induced neurodegeneration and DM by modulating inflammatory and oxidative pathways, suggesting a novel avenue for disease management.

The Therapeutic Potential of Dalbergia pinnata (Lour.) Prain Essential Oil in Alzheimer's Disease: EEG Signal Analysis In Vivo, SH-SY5Y Cell Model In Vitro, and Network Pharmacology

Alzheimer's disease (AD) is a neurodegenerative disorder that is projected by the WHO to affect over 100 million people by 2050. Clinically, AD patients undergoing long-term antipsychotic treatment often experience severe anxiety or depression in later stages. Furthermore, early-stage AD manifests with weakened α waves in the brain, progressing to diminished α and β waves in late-stage disease, reflecting changes in emotional states and disease progression. In this study, EEG signal analysis revealed that inhalation of Dalbergia pinnata (Lour.) Prain essential oil (DPEO) enhanced δ, θ, α and β wave powers in the frontal and parietal lobes, with a rising trend in the β/α ratio in the temporal lobe. These findings suggest an alleviation of anxiety and an enhancement of cognitive functions. Treatment of the AD SH-SY5Y (human neuroblastoma cells) cell model with DPEO resulted in decreased intracellular levels of Aβ, GSK-3β, P-Tau, IL-1β, TNF-α, IL-6, COX-2, OFR, and HFR, alongside reduced AchE and BchE activities and increased SOD activity. Network pharmacology analysis indicated a potential pharmacological mechanism involving the JAK-STAT pathway. Our study provides evidence supporting DPEO's role in modulating anxiety and slowing AD pathological progression.

Interaction of exogenous acetylcholinesterase and butyrylcholinesterase with amyloid-β plaques in human brain tissue

Acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) are associated with amyloid-β (Aβ) plaques and exhibit altered biochemical properties in human Alzheimer's disease (AD), as well as in the transgenic 5XFAD mouse model of AD amyloidosis. In the brains of the 5XFAD mouse model devoid of BChE enzyme (5XFAD/BChE-KO), incubation of tissue sections with exogenous BChE purified from human plasma (pl-BChE) leads to its association with Aβ plaques and its biochemical properties are comparable to those reported for endogenous BChE associated with plaques in both human AD and in 5XFAD mouse brain tissue. We sought to determine whether these observations in 5XFAD/BChE-KO mice also apply to human brain tissues. To do so, endogenous ChE activity in human AD brain tissue sections was quenched with 50 % aqueous acetonitrile (MeCNaq) leaving the tissue suitable for further studies. Quenched sections were then incubated with recombinant AChE (r-AChE) or pl-BChE and stained for each enzymes' activity. Exogenous r-AChE or pl-BChE became associated with Aβ plaques, and when bound, had properties that were comparable to the endogenous ChE enzymes associated with plaques in AD brain tissues without acetonitrile treatment. These findings in human AD brain tissue extend previous observations in the 5XFAD/BChE-KO mouse model and demonstrate that exogenously applied r-AChE and pl-BChE have high affinity for Aβ plaques in human brain tissues. This association alters the biochemical properties of these enzymes, most likely due a conformational change. If incorporation of AChE and BChE in Aβ plaques facilitates AD pathogenesis, blocking this association could lead to disease-modifying approaches to AD. This work provides a method to study the mechanism of AChE and BChE interaction with Aβ plaque pathology in post-mortem human brain tissue.

Effect of fentanyl and remifentanil on neuron damage and oxidative stress during induction neurotoxicity

Opioids can be used for medical and non-medical purposes. Chronic pain such as cancer, as well as the frequent use of such drugs in places such as operating rooms and intensive care units, and in non-medical areas like drug abuse the effects and side effects of these drugs need to be examined in more detail. For this purpose, the effects of fentanyl and remifentanil drugs on neuroinflammation, oxidative stress and cholinesterase metabolism were investigated. Neuron cells (CRL-10742) were used for the evaluation of the toxicity of fentanyl and remifentanil. MTT, PON1 activity and total thiol levels for its effect on oxidative stress, AChE and BChE activities for its effect on the cholinergic system, and TNF, IL-8 and IL-10 gene levels for its neuroinflammation effect were determined. The highest neurotoxic dose of fentanyl and remifentanil was determined as 10 μg/mL. It was observed that the rate of neuron cells in this dose has decreased by up to 61.80% and 56.89%, respectively. The IL-8 gene expression level in both opioids was down-regulated while IL 10 gene level was up-regulated in a dose-dependent manner compared to the control. In our results, the TNF gene expression level differs between the two opioids. In the fentanyl group, it was seen to be up-regulated in a dose-dependent manner compared to the control. Fentanyl and remifentanil showed an inhibitory effect against PON1, while remifentanil showed an increase in total thiol levels. PON1, BChE and total thiol activities showed similarity with MTT.

Conjugates of amiridine and thiouracil derivatives as effective inhibitors of butyrylcholinesterase with the potential to block β-amyloid aggregation

New amiridine-thiouracil conjugates with different substituents in the pyrimidine fragment (R = CH3 , CF2 Н, CF3 , (CF2 )2 H) and different spacer lengths (n = 1-3) were synthesized. The conjugates rather weakly inhibit acetylcholinesterase (AChE) and exhibit high inhibitory activity (IC50 up to 0.752 ± 0.021 µM) and selectivity to butyrylcholinesterase (BChE), which increases with spacer elongation; the lead compounds are 11c, 12c, and 13c. The conjugates are mixed-type reversible inhibitors of both cholinesterases and practically do not inhibit the structurally related off-target enzyme carboxylesterase. The results of molecular docking to AChE and BChE are consistent with the experiment on enzyme inhibition and explain the structure-activity relationships, including the rather low anti-AChE activity and the high anti-BChE activity of long-chain conjugates. The lead compounds displace propidium from the AChE peripheral anion site (PAS) at the level of the reference compound donepezil, which agrees with the mixed-type mechanism of AChE inhibition and the main mode of binding of conjugates in the active site of AChE due to the interaction of the pyrimidine moiety with the PAS. This indicates the ability of the studied conjugates to block AChE-induced aggregation of β-amyloid, thereby exerting a disease-modifying effect. According to computer calculations, all synthesized conjugates have an ADME profile acceptable for drugs.

Monitoring Alzheimer's disease via ultraweak photon emission

In an innovative experiment, we detected ultraweak photon emission (UPE) from the hippocampus of male rat brains and found significant correlations between Alzheimer's disease (AD), memory decline, oxidative stress, and UPE intensity. These findings may open up novel methods for screening, detecting, diagnosing, and classifying neurodegenerative diseases, particularly AD. The study suggests that UPE from the brain's neural tissue can serve as a valuable indicator. It also proposes the development of a minimally invasive brain-computer interface (BCI) photonic chip for monitoring and diagnosing AD, offering high spatiotemporal resolution of brain activity. The study used a rodent model of sporadic AD, demonstrating that STZ-induced sAD resulted in increased hippocampal UPE, which was associated with oxidative stress. Treatment with donepezil reduced UPE and improved oxidative stress. These findings support the potential utility of UPE as a screening and diagnostic tool for AD and other neurodegenerative diseases.

Targeting Alzheimer's Disease: Evaluating the Efficacy of C-1 Functionalized N-Aryl-Tetrahydroisoquinolines as Cholinergic Enzyme Inhibitors and Promising Therapeutic Candidates

We have synthesized 22 C-1 functionalized-N-aryl-1,2,3,4-tetrahydroisoquinoline derivatives showing biological activities towards cholinergic enzymes. Synthesis was performed using visible-light-promoted photo-redox chemistry, starting from a common intermediate, and the application of this synthetic methodology drastically simplified synthetic routes and purification of desired compounds. All synthesized derivates were divided into four groups based on the substituents in the C-1 position, and their inhibition potencies towards two cholinergic enzymes, acetyl- and butyrylcholinesterase were evaluated. Most potent derivatives were selected, and kinetic analysis was further carried out to obtain insights into the mechanisms of inhibition of these two enzymes. Further validation of the mode of inhibition of cholinergic enzymes by the two most potent THIQ compounds, 3c and 3i, was performed using fluorescence-quenching titration studies. Molecular docking studies further confirmed the proposed mechanism of enzymes' inhibition. In silico predictions of physicochemical properties, pharmacokinetics, drug-likeness, and medicinal chemistry friendliness of the selected most potent derivatives were performed using Swiss ADME tool. This was followed by UPLC-assisted log P determination and in vitro BBB permeability studies performed in order to assess the potential of the synthesized compounds to pass the BBB.

A method for the efficient evaluation of substrate-based cholinesterase imaging probes for Alzheimer's disease

Cholinesterase (ChE) enzymes have been identified as diagnostic markers for Alzheimer disease (AD). Substrate-based probes have been synthesised to detect ChEs but they have not detected changes in ChE distribution associated with AD pathology. Probes are typically screened using spectrophotometric methods with pure enzyme for specificity and kinetics. However, the biochemical properties of ChEs associated with AD pathology are altered. The present work was undertaken to determine whether the Karnovsky-Roots (KR) histochemical method could be used to evaluate probes at the site of pathology. Thirty thioesters and esters were synthesised and evaluated using enzyme kinetic and KR methods. Spectrophotometric methods demonstrated all thioesters were ChE substrates, yet only a few provided staining in the brain with the KR method. Esters were ChE substrates with interactions with brain ChEs. These results suggest that the KR method may provide an efficient means to screen compounds as probes for imaging AD-associated ChEs.

Butyrylcholinesterase signal sequence self-aggregates and enhances amyloid fibril formation in vitro

Alzheimer's disease (AD) pathogenesis has been attributed to extracellular aggregates of amyloid β (Aβ) plaques and neurofibrillary tangles in the human brain. It has been reported that butyrylcholinesterase (BChE) also accumulates in the brain Aβ plaques in AD. We have previously found that the BChE substitution in 5'UTR caused an in-frame N-terminal extension of 41 amino acids of the BChE signal peptide. The resultant variant with a 69 amino acid signal peptide, designated N-BChE, could play a role in AD development. Here, we report that the signal sequence of the BChE, if produced in an extended 69 aa version, can self-aggregate and could form seeds that enhance amyloid fibril formation in vitro in a dose-dependent manner and create larger co-aggregates. Similar phenomena could have been observed in the human brain if such an extended form of the signal sequence had been, in some circumstances, translated.

Can Activation of Acetylcholinesterase by β-Amyloid Peptide Decrease the Effectiveness of Cholinesterase Inhibitors?

A central event in the pathogenesis of Alzheimer's disease (AD) is the accumulation of senile plaques composed of aggregated amyloid-β (Aβ) peptides. The main class of drugs currently used for the treatment of AD are the acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitors. In this study, it has been shown that Aβ augmented AChE activity in vitro, maximum activation of 548 ± 5% was achieved following 48 h of incubation with 10 μM of Aβ1-40, leading to a 7.7-fold increase in catalytic efficiency. The observed non-competitive type of AChE activation by Aβ1-40 was associated with increased Vmax and unchanged Km. Although BChE activity also increased following incubation with Aβ1-40, this was less efficiently achieved as compared with AChE. Ex vivo electrophysiological experiments showed that 10 μM of Aβ1-40 significantly decreased the effect of the AChE inhibitor huperzine A on the synaptic potential parameters.

Confirmed Synergy Between the ɛ4 Allele of Apolipoprotein E and the Variant K of Butyrylcholinesterase as a Risk Factor for Alzheimer's Disease: A Systematic Review and Meta-Analysis

Background

Alzheimer's disease (AD) has several risk factors. APOE4 is the main one, and it has been suggested that there may be a synergy between it and BCHE-K as a risk factor.

Objective

To investigate the association between APOE4 and BCHE-K as a risk factor for AD.

Methods

We searched PubMed, Web of Science, Embase, and Scopus on August 8, 2021 for studies that analyzed the association of APOE4 and BCHE-K with AD. The random effect model was performed in meta-analysis according to age group. A chi-square was performed with the meta-analysis data to verify if the effect found is not associated only with the E4 allele.

Results

Twenty-one studies with 6,853 subjects (3,528 AD and 3,325 Controls) were included in the meta-analysis. The quality of the evidence is moderate. There is a positive E4-K association for subjects with AD as shown by the odds ratio of 3.43. The chi-square meta test, which measures the probability that the E4-K association is due to chance, has an odds ratio of 6.155, indicating that the E4-K association is not a random event. The odds ratio of an E4-K association in subjects with AD increases to OR 4.46 for the 65- to 75-year-old group and OR 4.15 for subjects older than 75 years. The probability that the E4-K association is due to chance is ruled out by chi-square meta test values of OR 8.638 and OR 9.558.

Conclusion

The synergy between APOE4 and BCHE-K is a risk factor for late-onset AD.

Novel drug-like fluorenyl derivatives as selective butyrylcholinesterase and β-amyloid inhibitors for the treatment of Alzheimer's disease

Butyrylcholinesterase (BuChE) and amyloid β (Aβ) aggregation remain important biological target and mechanism in the search for effective treatment of Alzheimer's disease. Simultaneous inhibition thereof by the application of multifunctional agents may lead to improvement in terms of symptoms and causes of the disease. Here, we present the rational design, synthesis, biological evaluation and molecular modelling studies of novel series of fluorene-based BuChE and Aβ inhibitors with drug-like characteristics and advantageous Central Nervous System Multiparameter Optimization scores. Among 17 synthesized and tested compounds, we identified 22 as the most potent eqBuChE inhibitor with IC₅₀ of 38 nM and 37.4% of Aβ aggregation inhibition at 10 μM. Based on molecular modelling studies, including molecular dynamics, we determined the binding mode of the compounds within BuChE and explained the differences in the activity of the two enantiomers of compound 22. A novel series of fluorenyl compounds meeting the drug-likeness criteria seems to be a promising starting point for further development as anti-Alzheimer agents.

New Thienobenzo/Naphtho-Triazoles as Butyrylcholinesterase Inhibitors: Design, Synthesis and Computational Study

This study aims to test the inhibition potency of new thienobenzo/naphtho-triazoles toward cholinesterases, evaluate their inhibition selectivity, and interpret the obtained results by molecular modeling. The synthesis of 19 new thienobenzo/naphtho-triazoles by two different approaches resulted in a large group of molecules with different functionalities in the structure. As predicted, most prepared molecules show better inhibition of the enzyme butyrylcholinesterase (BChE), considering that the new molecules were designed according to the previous results. Interestingly, the binding affinity of BChE for even seven new compounds (1, 3, 4, 5, 6, 9, and 13) was similar to that reported for common cholinesterase inhibitors. According to computational study, the active thienobenzo- and naphtho-triazoles are accommodated by cholinesterases through H-bonds involving one of the triazole's nitrogens, π-π stacking between the aromatic moieties of the ligand and aromatic residues of the active sites of cholinesterases, as well as π-alkyl interactions. For the future design of cholinesterase inhibitors and search for therapeutics for neurological disorders, compounds with a thienobenzo/naphtho-triazole skeleton should be considered.

The pathomimetic oAβ25–35 model of Alzheimer's disease: Potential for screening of new therapeutic agents

Alzheimer's disease (AD) is the most common form of dementia in the elderly, currently affecting more than 40 million people worldwide. The two main histopathological hallmarks of AD were identified in the 1980s: senile plaques (composed of aggregated amyloid-β (Aβ) peptides) and neurofibrillary tangles (composed of hyperphosphorylated tau protein). In the human brain, both Aβ and tau show aggregation into soluble and insoluble oligomers. Soluble oligomers of Aβ include their most predominant forms - Aβ_1-40 and Aβ_1-42 - as well as shorter peptides such as Aβ_25-35 or Aβ_25-35/40. Most animal models of AD have been developed using transgenesis, based on identified human mutations. However, these familial forms of AD represent less than 1% of AD cases. In this context, the idea emerged in the 1990s to directly inject the Aβ_25-35 fragment into the rodent brain to develop an acute model of AD that could mimic the disease's sporadic forms (99% of all cases). This review aims to: (1) summarize the biological activity of Aβ_25-35, focusing on its impact on the main structural and functional alterations observed in AD (cognitive deficits, APP misprocessing, tau system dysfunction, neuroinflammation, oxidative stress, cholinergic and glutamatergic alterations, HPA axis dysregulation, synaptic deficits and cell death); and (2) confirm the interest of this pathomimetic model in AD research, as it has helped identify and characterize many molecules (marketed, in clinical development, and in preclinical testing), and to the development of alternative approaches for AD prevention and therapy. Today, the Aβ_25-35 model appears as a first-intent choice model to rapidly screen the symptomatic or neuroprotective potencies of new compounds, chemical series, or innovative therapeutic strategies.

Conjugates of Tacrine and Salicylic Acid Derivatives as New Promising Multitarget Agents for Alzheimer's Disease

A series of previously synthesized conjugates of tacrine and salicylamide was extended by varying the structure of the salicylamide fragment and using salicylic aldehyde to synthesize salicylimine derivatives. The hybrids exhibited broad-spectrum biological activity. All new conjugates were potent inhibitors of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) with selectivity toward BChE. The structure of the salicylamide moiety exerted little effect on anticholinesterase activity, but AChE inhibition increased with spacer elongation. The most active conjugates were salicylimine derivatives: IC₅₀ values of the lead compound 10c were 0.0826 µM (AChE) and 0.0156 µM (BChE), with weak inhibition of the off-target carboxylesterase. The hybrids were mixed-type reversible inhibitors of both cholinesterases and displayed dual binding to the catalytic and peripheral anionic sites of AChE in molecular docking, which, along with experimental results on propidium iodide displacement, suggested their potential to block AChE-induced β-amyloid aggregation. All conjugates inhibited Aβ₄₂ self-aggregation in the thioflavin test, and inhibition increased with spacer elongation. Salicylimine 10c and salicylamide 5c with (CH₂)₈ spacers were the lead compounds for inhibiting Aβ₄₂ self-aggregation, which was corroborated by molecular docking to Aβ₄₂. ABTS^•+-scavenging activity was highest for salicylamides 5a-c, intermediate for salicylimines 10a-c, low for F-containing salicylamides 7, and non-existent for methoxybenzoylamides 6 and difluoromethoxybenzoylamides 8. In the FRAP antioxidant (AO) assay, the test compounds displayed little or no activity. Quantum chemical analysis and molecular dynamics (MD) simulations with QM/MM potentials explained the AO structure-activity relationships. All conjugates were effective chelators of Cu²⁺, Fe²⁺, and Zn²⁺, with molar compound/metal (Cu²⁺) ratios of 2:1 (5b) and ~1:1 (10b). Conjugates exerted comparable or lower cytotoxicity than tacrine on mouse hepatocytes and had favorable predicted intestinal absorption and blood-brain barrier permeability. The overall results indicate that the synthesized conjugates are promising new multifunctional agents for the potential treatment of AD.

Fluorosulfate-containing pyrazole heterocycles as selective BuChE inhibitors: structure-activity relationship and biological evaluation for the treatment of Alzheimer's disease

Novel scaffolds are expected to treat Alzheimer’s disease, pyrazole-5-fluorosulfates were found as selective BuChE inhibitors. Compounds K1–K26 were assayed for ChE inhibitory activity, amongst them, compound K3 showed potent BuChE and hBuChE inhibition (IC₅₀ = 0.79 μM and 6.59 μM). SAR analysis showed that 1-, 3-, 4-subtituent and 5-fluorosulfate of pyrazole ring affected BuChE inhibitory activity. Molecular docking showed that the fluorosulfate increased the binding affinity of hBuChE through π-sulphur interaction. Compound K3 was a reversible, mixed and non-competitive BuChE inhibitor (K_i = 0.77 μM) and showed remarkable neuroprotection, safe toxicological profile and BBB penetration. In vivo behavioural study showed that K3 treatment improved the Aβ_1 − 42-induced cognitive impairment, and significantly prevented the effects of Aβ_1 − 42 toxicity. Therefore, selective BuChE inhibitor K3 has potential to be further developed as AD therapeutics.

APP accumulates with presynaptic proteins around amyloid plaques: A role for presynaptic mechanisms in Alzheimer's disease?

In Alzheimer's disease (AD), the distribution of the amyloid precursor protein (APP) and its fragments other than amyloid beta, has not been fully characterized. Here, we investigate the distribution of APP and its fragments in human AD brain samples and in mouse models of AD in reference to its proteases, synaptic proteins, and histopathological features characteristic of the AD brain, by combining an extensive set of histological and analytical tools. We report that the prominent somatic distribution of APP observed in control patients remarkably vanishes in human AD patients to the benefit of dense accumulations of extra-somatic APP, which surround dense-core amyloid plaques enriched in APP-Nter. These features are accentuated in patients with familial forms of the disease. Importantly, APP accumulations are enriched in phosphorylated tau and presynaptic proteins whereas they are depleted of post-synaptic proteins suggesting that the extra-somatic accumulations of APP are of presynaptic origin. Ultrastructural analyses unveil that APP concentrates in autophagosomes and in multivesicular bodies together with presynaptic vesicle proteins. Altogether, alteration of APP distribution and its accumulation together with presynaptic proteins around dense-core amyloid plaques is a key histopathological feature in AD, lending support to the notion that presynaptic failure is a strong physiopathological component of AD.

New Multifunctional Agents for Potential Alzheimer's Disease Treatment Based on Tacrine Conjugates with 2-Arylhydrazinylidene-1,3-Diketones

Alzheimer's disease (AD) is considered a modern epidemic because of its increasing prevalence worldwide and serious medico-social consequences, including the economic burden of treatment and patient care. The development of new effective therapeutic agents for AD is one of the most urgent and challenging tasks. To address this need, we used an aminoalkylene linker to combine the well-known anticholinesterase drug tacrine with antioxidant 2-tolylhydrazinylidene-1,3-diketones to create 3 groups of hybrid compounds as new multifunctional agents with the potential for AD treatment. Lead compounds of the new conjugates effectively inhibited acetylcholinesterase (AChE, IC50 0.24-0.34 µM) and butyrylcholinesterase (BChE, IC50 0.036-0.0745 µM), with weak inhibition of off-target carboxylesterase. Anti-AChE activity increased with elongation of the alkylene spacer, in agreement with molecular docking, which showed compounds binding to both the catalytic active site and peripheral anionic site (PAS) of AChE, consistent with mixed type reversible inhibition. PAS binding along with effective propidium displacement suggest the potential of the hybrids to block AChE-induced β-amyloid aggregation, a disease-modifying effect. All of the conjugates demonstrated metal chelating ability for Cu2+, Fe2+, and Zn2+, as well as high antiradical activity in the ABTS test. Non-fluorinated hybrid compounds 6 and 7 also showed Fe3+ reducing activity in the FRAP test. Predicted ADMET and physicochemical properties of conjugates indicated good CNS bioavailability and safety parameters acceptable for potential lead compounds at the early stages of anti-AD drug development.

Kinetics and computational study of butyrylcholinesterase inhibition by methylrosmarinate: relevance to Alzheimer's disease treatment

Butyrylcholinesterase (BChE) performs a significant function in Alzheimer’s disease progression. Experimental studies have shown that the function of BChE in the attenuation of cholinergic neurotransmission is essentially altered in brains of advanced AD patients. Here, using the complimentary methods of enzyme kinetic studies, molecular modeling and protein-ligand interaction profiling, we sought to reveal the mechanistic and structural features of BChE-methyrosmarinate interactions. Molecular docking simulations revealed that methylrosmarinate dwelled well in the active centre of BChE, where it got involved in stabilizing non-covalent associations with myriad subsites. Enzyme kinetic experiments showed that the V_m and K_s values were 156.20 ± 3.11 U mg⁻¹ protein and 0.13 ± 0.01 μM, respectively. The inhibition studies showed that methylrosmarinate apparently inhibited BChE in a linear mixed manner, with an IC₅₀ value of 10.31 μM and a K_i value of 3.73 ± 1.52 μM. Taken together, the extremely reduced K_i value and the increased number of BChE–methylrosmarinate interactions presuppose that methylrosmarinate is a good inhibitor of BChE, despite the fact that the mechanism for the effect of BChE inhibition on several pathological conditions in vivo remains unexplored.

Neuropathology and cholinesterase expression in the brains of octogenarians and older

A subset of octogenarians and older maintain normal cognitive function (CNOO) despite high prevalence and incidence of cognitive decline attributed to neurodegeneration or aging in the population. The rostral prefrontal cortex (rPFC) and hippocampal formation are brain regions integral to cognition, namely attention and memory, facilitated in part by cholinergic innervation. We hypothesized that preserved cholinergic neurotransmission in these regions contributes to intact cognition in the CNOO. To test this, we evaluated the burden of neuropathological and cholinesterase-associated protein aggregates in the rPFC and hippocampal formation. Tissues from age- and sex-matched CNOO and Alzheimer's disease (AD) rPFC and hippocampal formation were stained for β-amyloid (Aβ), tau, α-synuclein, phosphorylated TAR DNA-binding protein 43 (pTDP-43), acetylcholinesterase (AChE), and butyrylcholinesterase (BChE). The relative abundance of neuropathological aggregates was semi-quantitatively scored. Deposition of Aβ plaques, tau neurofibrillary tangles (NFT) and pTDP-43 inclusions were comparable between CNOO and AD cases. Intraneuronal Aβ and tau-positive thorny astrocytes consistent with aging-related tau astrogliopathy, were also noted in the rPFC. Abundance of BChE-positive plaque pathology was significantly higher in AD than in CNOO cases in most regions of interest, followed closely by abundance of AChE-positive plaque pathology. BChE- and AChE-activities were also associated with varied NFT morphologies. CNOO cases maintained cognition despite a high neuropathological burden in the rPFC and hippocampal formation. BChE-positive and, to a lesser extent, AChE-positive pathologies were significantly lower in most regions in the CNOO compared to AD. This suggests a specificity of cholinesterase-associated neuropathology with AD. We conclude that while CNOO have cholinesterase-associated neuropathology in the rPFC and hippocampal formation, abundance in this population is significantly lower compared to AD which may contribute to their intact cognition.

Bis-Amiridines as Acetylcholinesterase and Butyrylcholinesterase Inhibitors: N-Functionalization Determines the Multitarget Anti-Alzheimer’s Activity Profile

Using two ways of functionalizing amiridine—acylation with chloroacetic acid chloride and reaction with thiophosgene—we have synthesized new homobivalent bis-amiridines joined by two different spacers—bis-N-acyl-alkylene (3) and bis-N-thiourea-alkylene (5) —as potential multifunctional agents for the treatment of Alzheimer’s disease (AD). All compounds exhibited high inhibitory activity against acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) with selectivity for BChE. These new agents displayed negligible carboxylesterase inhibition, suggesting a probable lack of untoward drug–drug interactions arising from hydrolytic biotransformation. Compounds 3 with bis-N-acyl-alkylene spacers were more potent inhibitors of both cholinesterases compared to compounds 5 and the parent amiridine. The lead compounds 3a–c exhibited an IC₅₀(AChE) = 2.9–1.4 µM, IC₅₀(BChE) = 0.13–0.067 µM, and 14–18% propidium displacement at 20 μM. Kinetic studies of compounds 3a and 5d indicated mixed-type reversible inhibition. Molecular docking revealed favorable poses in both catalytic and peripheral AChE sites. Propidium displacement from the peripheral site by the hybrids suggests their potential to hinder AChE-assisted Aβ₄₂ aggregation. Conjugates 3 had no effect on Aβ₄₂ self-aggregation, whereas compounds 5c–e (m = 4, 5, 6) showed mild (13–17%) inhibition. The greatest difference between conjugates 3 and 5 was their antioxidant activity. Bis-amiridines 3 with N-acylalkylene spacers were nearly inactive in ABTS and FRAP tests, whereas compounds 5 with thiourea in the spacers demonstrated high antioxidant activity, especially in the ABTS test (TEAC = 1.2–2.1), in agreement with their significantly lower HOMO-LUMO gap values. Calculated ADMET parameters for all conjugates predicted favorable blood–brain barrier permeability and intestinal absorption, as well as a low propensity for cardiac toxicity. Thus, it was possible to obtain amiridine derivatives whose potencies against AChE and BChE equaled (5) or exceeded (3) that of the parent compound, amiridine. Overall, based on their expanded and balanced pharmacological profiles, conjugates 5c–e appear promising for future optimization and development as multitarget anti-AD agents.

Structure-activity relationship, in vitro and in vivo evaluation of novel dienyl sulphonyl fluorides as selective BuChE inhibitors for the treatment of Alzheimer's disease

To discover novel scaffolds as leads against dementia, a series of δ-aryl-1,3-dienesulfonyl fluorides with α-halo, α-aryl and α-alkynyl were assayed for ChE inhibitory activity, in which compound A10 was identified as a selective BuChE inhibitor (IC50 = 0.021 μM for eqBChE, 3.62 μM for hBuChE). SAR of BuChE inhibition showed: (i) o- > m- > p-; -OCH3 > -CH3 > -Cl (-Br) for δ-aryl; (ii) α-Br > α-Cl, α-I. Compound A10 exhibited neuroprotective, BBB penetration, mixed competitive inhibitory effect on BuChE (Ki = 29 nM), and benign neural and hepatic safety. Treatment with A10 could almost entirely recover the Aβ1-42-induced cognitive dysfunction to the normal level, and the assessment of total amount of Aβ1-42 confirmed its anti-amyloidogenic profile. Therefore, the potential BuChE inhibitor A10 is a promising effective lead for the treatment of AD.

Butyrylcholinesterase-Protein Interactions in Human Serum

Measuring various biochemical and cellular components in the blood is a routine procedure in clinical practice. Human serum contains hundreds of diverse proteins secreted from all cells and tissues in healthy and diseased states. Moreover, some serum proteins have specific strong interactions with other blood components, but most interactions are probably weak and transient. One of the serum proteins is butyrylcholinesterase (BChE), an enzyme existing mainly as a glycosylated soluble tetramer that plays an important role in the metabolism of many drugs. Our results suggest that BChE interacts with plasma proteins and forms much larger complexes than predicted from the molecular weight of the BChE tetramer. To investigate and isolate such complexes, we developed a two-step strategy to find specific protein–protein interactions by combining native size-exclusion chromatography (SEC) with affinity chromatography with the resin that specifically binds BChE. Second, to confirm protein complexes′ specificity, we fractionated blood serum proteins by density gradient ultracentrifugation followed by co-immunoprecipitation with anti-BChE monoclonal antibodies. The proteins coisolated in complexes with BChE were identified by mass spectroscopy. These binding studies revealed that BChE interacts with a number of proteins in the human serum. Some of these interactions seem to be more stable than transient. BChE copurification with ApoA-I and the density of some fractions containing BChE corresponding to high-density lipoprotein cholesterol (HDL) during ultracentrifugation suggest its interactions with HDL. Moreover, we observed lower BChE plasma activity in individuals with severely reduced HDL levels (≤20 mg/dL). The presented two-step methodology for determination of the BChE interactions can facilitate further analysis of such complexes, especially from the brain tissue, where BChE could be involved in the pathogenesis and progression of AD.

Conjugation of Aminoadamantane and γ-Carboline Pharmacophores Gives Rise to Unexpected Properties of Multifunctional Ligands

A new series of conjugates of aminoadamantane and γ-carboline, which are basic scaffolds of the known neuroactive agents, memantine and dimebon (Latrepirdine) was synthesized and characterized. Conjugates act simultaneously on several biological structures and processes involved in the pathogenesis of Alzheimer’s disease and some other neurodegenerative disorders. In particular, these compounds inhibit enzymes of the cholinesterase family, exhibiting higher inhibitory activity against butyrylcholinesterase (BChE), but having almost no effect on the activity of carboxylesterase (anti-target). The compounds serve as NMDA-subtype glutamate receptor ligands, show mitoprotective properties by preventing opening of the mitochondrial permeability transition (MPT) pore, and act as microtubule stabilizers, stimulating the polymerization of tubulin and microtubule-associated proteins. Structure–activity relationships were studied, with particular attention to the effect of the spacer on biological activity. The synthesized conjugates showed new properties compared to their prototypes (memantine and dimebon), including the ability to bind to the ifenprodil-binding site of the NMDA receptor and to occupy the peripheral anionic site of acetylcholinesterase (AChE), which indicates that these compounds can act as blockers of AChE-induced β-amyloid aggregation. These new attributes of the conjugates represent improvements to the pharmacological profiles of the separate components by conferring the potential to act as neuroprotectants and cognition enhancers with a multifunctional mode of action.

Adverse Drug Reactions of Acetylcholinesterase Inhibitors in Older People Living with Dementia: A Comprehensive Literature Review

The rising of global geriatric population has contributed to increased prevalence of dementia. Dementia is a neurodegenerative disease, which is characterized by progressive deterioration of cognitive functions, such as judgment, language, memory, attention and visuospatial ability. Dementia not only has profoundly devastating physical and psychological health outcomes, but it also poses a considerable healthcare expenditure and burdens. Acetylcholinesterase inhibitors (AChEIs), or so-called anti-dementia medications, have been developed to delay the progression of neurocognitive disorders and to decrease healthcare needs. AChEIs have been widely prescribed in clinical practice for the treatment of Alzheimer's disease, which account for 70% of dementia. The rising use of AChEIs results in increased adverse drug reactions (ADRs) such as cardiovascular and gastrointestinal adverse effects, resulting from overstimulation of peripheral cholinergic activity and muscarinic receptor activation. Changes in pharmacokinetics (PK), pharmacodynamics (PD) and pharmacogenetics (PGx), and occurrence of drug interactions are said to be major risk factors of ADRs of AChEIs in this population. To date, comprehensive reviews in ADRs of AChEIs have so far been scarcely studied. Therefore, we aimed to recapitulate and update the diverse aspects of AChEIs, including the mechanisms of action, characteristics and risk factors of ADRs, and preventive strategies of their ADRs. The collation of this knowledge is essential to facilitate efforts to reduce ADRs of AChEIs.

Interaction of Exogenous Butyrylcholinesterase with β-Amyloid Plaques in 5XFAD/Butyrylcholinesterase-Knockout Mouse Brain

BACKGROUND

In Alzheimer's disease (AD), and amyloid models such as the 5XFAD mouse, butyrylcholinesterase (BChE) is associated with β-amyloid (Aβ) plaques and has unique biochemical features which distinguish it from that found in neurons. It has been suggested that BChE associated with Aβ plaques may be involved in the maturation of this structure and thus disease progression.

OBJECTIVE

Currently, it is unknown whether BChE bound to Aβ plaques has altered biochemical properties due to a different primary structure or because of the association of this enzyme with Aβ plaques. Also, the source and binding mechanism of this BChE remains unknown.

METHODS

Brain tissue sections from the 5XFAD/BChE-KO mouse were incubated with exogenous sources of BChE and stained for this enzyme's activity. Efforts were made to determine what region of BChE or Aβ may be involved in this association.

RESULTS

We found that incubation of 5XFAD/BChE-KO brain tissues with exogenous BChE led to this enzyme becoming associated with Aβ plaques and neurons. In contrast to neuronal BChE, the BChE bound to Aβ plaques had similar biochemical properties to those seen in AD. Mutations to BChE and efforts to block Aβ epitomes failed to prevent this association.

CONCLUSION

The association of BChE with Aβ plaques, and the resultant biochemical changes, suggests that BChE may undergo a conformational change when bound to Aβ plaques but not neurons. The 5XFAD/BChE-KO model is ideally suited to explore the binding mechanism of BChE to Aβ plaques as well as the involvement of BChE in AD pathogenesis.

In silico, theoretical biointerface analysis and in vitro kinetic analysis of amine compounds interaction with acetylcholinesterase and butyrylcholinesterase

Acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) are considered important target for drug design against Alzheimer's disease. In the present study in silico analysis; theoretical analysis of biointerface between ligand and interacting amino acid residues of proteins; and in vitro analysis of enzyme inhibition kinetics were carried out to delineate the inhibitory property of amine compounds against AChE/BChE. High throughput virtual screening of amine compounds identified three compounds (2-aminoquinoline, 2-aminobenzimidazole and 2-amino-1-methylbenzimidazole) that best interacted with AChE/BChE. Molecular docking analysis revealed the interaction of these compounds in the active site gorge of AChE/BChE, in particular with amino acid residues present in the peripheral anionic site. Molecular dynamics simulation confirmed the stable binding of these compounds with AChE/BChE. Binding energy calculated through MMGBSA method identified the non-covalent interactions (electrostatic and Van der Waals interactions) have contributed to the stable binding of the amine compounds with the AChE/BChE. Biointerface between amine compounds and AChE/BChE were visualized through Hirshfeld surface analysis. The inter-fragment interaction energies for the possible contacts between amine compounds and amino acid residues were carried out for the first time. All the amine compounds showed mixed-type of inhibition with moderate Ki value in in vitro analysis.

Discovery of 2-(cyclopropanecarboxamido)-N-(5-((1-(4-fluorobenzyl)piperidin-4-yl)methoxy)pyridin-3-yl)isonicotinamide as a potent dual AChE/GSK3β inhibitor for the treatment of Alzheimer's disease: Significantly increasing the level of acetylcholine in the brain without affecting that in intestine

Acetylcholinesterase (AChE) inhibitors are currently the first-line drugs approved by the FDA for the treatment of Alzheimer's disease (AD). However, a short effective-window limits their therapeutic benefits. Clinical studies have confirmed that the combination of AChE inhibitors and neuroprotective agents exhibits better anti-AD effects. We have previously reported that the dual AChE/GSK3β (Glycogen synthase kinase 3β) modulators have both neuroprotective effects and cognitive impairment-improvement effects. In this study, we characterized a new backbone of the AChE/GSK3β inhibitor 11c. It was identified as a highly potent AChE inhibitor and was found superior to donepezil, the first-line drug for the treatment of AD. In vivo studies confirmed that 11c significantly inhibited the activity of AChE in the brain but had little effect on the activity of AChE in the intestine. This advantage of 11c was expected to reduce the peripheral side effects caused by donepezil. Furthermore, biomarker studies have shown that 11c also improved the levels of acetylcholine and synaptophysin in the brain and exhibited neuroprotective effects. Preliminary in vivo and in vitro research results underline the exciting potential of compound 11c in the treatment of AD.

Selective Pseudo-irreversible Butyrylcholinesterase Inhibitors Transferring Antioxidant Moieties to the Enzyme Show Pronounced Neuroprotective Efficacy In Vitro and In Vivo in an Alzheimer's Disease Mouse Model

A series of multitarget-directed ligands (MTDLs) was designed by functionalizing a pseudo-irreversible butyrylcholinesterase (BChE) inhibitor. The obtained hybrids were investigated in vitro regarding their hBChE and hAChE inhibition, their enzyme kinetics, and their antioxidant physicochemical properties (DPPH, ORAC, metal chelating). In addition, in vitro assays were applied to investigate antioxidant effects using murine hippocampal HT22 cells and immunomodulatory effects on the murine microglial N9 cell line. The MTDLs retained their antioxidative properties compared to the parent antioxidant-moieties in vitro and the inhibition of hBChE was maintained in the submicromolar range. Representative compounds were tested in a pharmacological Alzheimer's disease (AD) mouse model and demonstrated very high efficacy at doses as low as 0.1 mg/kg. The most promising compound was also tested in BChE^-/- mice and showed reduced efficacy. In vivo neuroprotection by BChE inhibition can be effectively enhanced by incorporation of structurally diverse antioxidant moieties.

Synthesis and Initial Characterization of a Selective, Pseudo-irreversible Inhibitor of Human Butyrylcholinesterase as PET Tracer

The enzyme butyrylcholinesterase (BChE) represents a promising target for imaging probes to potentially enable early diagnosis of neurodegenerative diseases like Alzheimer's disease (AD) and to monitor disease progression in some forms of cancer. In this study, we present the design, facile synthesis, in vitro and preliminary ex vivo and in vivo evaluation of a morpholine-based, selective inhibitor of human BChE as a positron emission tomography (PET) tracer with a pseudo-irreversible binding mode. We demonstrate a novel protecting group strategy for 18 F radiolabeling of carbamate precursors and show that the inhibitory potency as well as kinetic properties of our unlabeled reference compound were retained in comparison to the parent compound. In particular, the prolonged duration of enzyme inhibition of such a morpholinocarbamate motivated us to design a PET tracer, possibly enabling a precise mapping of BChE distribution.

Phenothiazine-Tacrine Heterodimers: Pursuing Multitarget Directed Approach in Alzheimer's Disease

Since 2002, no clinical candidate against Alzheimer's disease has reached the market; hence, an effective therapy is urgently needed. We followed the so-called "multitarget directed ligand" approach and designed 36 novel tacrine-phenothiazine heterodimers which were in vitro evaluated for their anticholinesterase properties. The assessment of the structure-activity relationships of such derivatives highlighted compound 1dC as a potent and selective acetylcholinesterase inhibitor with IC₅₀ = 8 nM and 1aA as a potent butyrylcholinesterase inhibitor with IC₅₀ = 15 nM. Selected hybrids, namely, 1aC, 1bC, 1cC, 1dC, and 2dC, showed a significant inhibitory activity toward τ_(306-336) peptide aggregation with percent inhibition ranging from 50.5 to 62.1%. Likewise, 1dC and 2dC exerted a remarkable ability to inhibit self-induced Aβ_1-42 aggregation. Notwithstanding, in vitro studies displayed cytotoxicity toward HepG2 cells and cerebellar granule neurons; no pathophysiological abnormality was observed when 1dC was administered to mice at 14 mg/kg (i.p.). 1dC was also able to permeate to the CNS as shown by in vitro and in vivo models. The maximum brain concentration was close to the IC₅₀ value for acetylcholinesterase inhibition with a relatively slow elimination half-time. 1dC showed an acceptable safety and good pharmacokinetic properties and a multifunctional biological profile.

Clinicopathological correlations and cholinesterase expression in early-onset familial Alzheimer's disease with the presenilin 1 mutation, Leu235Pro

In sporadic Alzheimer's disease (SpAD), acetylcholinesterase and butyrylcholinesterase, co-regulators of acetylcholine, are associated with β-amyloid plaques and tau neurofibrillary tangles in patterns suggesting a contribution to neurotoxicity. This association has not been explored in early-onset familial Alzheimer's disease (FAD). We investigated whether cholinesterases are observed in the neuropathological hallmarks in FAD expressing the presenilin 1 Leu235Pro mutation. Brain tissues from three FAD cases and one early-onset SpAD case were stained and analyzed for β-amyloid, tau, α-synuclein, acetylcholinesterase and butyrylcholinesterase. AD pathology was prominent throughout the rostrocaudal extent of all 4 brains but α-synuclein-positive neurites were present in only one familial case. In FAD and SpAD cases, cholinergic activity was associated with plaques and tangles but not with α-synuclein pathology. Both cholinesterases showed similar or decreased plaque staining than detected with β-amyloid immunostaining but greater plaque deposition than observed with thioflavin-S histofluorescence. Acetylcholinesterase and butyrylcholinesterase are highly associated with AD pathology in inherited disease and both may represent specific diagnostic and therapeutic targets for all AD forms.

Synthesis and Initial Characterization of a Reversible, Selective 18F-Labeled Radiotracer for Human Butyrylcholinesterase

PURPOSE

A neuropathological hallmark of Alzheimer's disease (AD) is the presence of amyloid-β (Aβ) plaques in the brain, which are observed in a significant number of cognitively normal, older adults as well. In AD, butyrylcholinesterase (BChE) becomes associated with A_β aggregates, making it a promising target for imaging probes to support diagnosis of AD. In this study, we present the synthesis, radiochemistry, in vitro and preliminary ex and in vivo investigations of a selective, reversible BChE inhibitor as PET-tracer for evaluation as an AD diagnostic.

PROCEDURES

Radiolabeling of the inhibitor was achieved by fluorination of a respective tosylated precursor using K[¹⁸F]. IC₅₀ values of the fluorinated compound were obtained in a colorimetric assay using recombinant, human (h) BChE. Dissociation constants were determined by measuring hBChE activity in the presence of different concentrations of inhibitor.

RESULTS

Radiofluorination of the tosylate precursor gave the desired radiotracer in an average radiochemical yield of 20 ± 3 %. Identity and > 95.5 % radiochemical purity were confirmed by HPLC and TLC autoradiography. The inhibitory potency determined in Ellman's assay gave an IC₅₀ value of 118.3 ± 19.6 nM. Dissociation constants measured in kinetic experiments revealed lower affinity of the inhibitor for binding to the acylated enzyme (K₂ = 68.0 nM) in comparison to the free enzyme (K₁ = 32.9 nM).

CONCLUSIONS

The reversibly acting, selective radiotracer is synthetically easily accessible and retains promising activity and binding potential on hBChE. Radiosynthesis with ¹⁸F labeling of tosylates was feasible in a reasonable time frame and good radiochemical yield.

Chalcone and its analogs: Therapeutic and diagnostic applications in Alzheimer's disease

Chalcone [(E)-1,3-diphenyl-2-propene-1-one], a small molecule with α, β unsaturated carbonyl group is a precursor or component of many natural flavonoids and isoflavonoids. It is one of the privileged structures in medicinal chemistry. It possesses a wide range of biological activities encouraging many medicinal chemists to study this scaffold for its usefulness to oncology, infectious diseases, virology and neurodegenerative diseases including Alzheimer's disease (AD). Small molecular size, convenient and cost-effective synthesis, and flexibility for modifications to modulate lipophilicity suitable for blood brain barrier (BBB) permeability make chalcones a preferred candidate for their therapeutic and diagnostic potential in AD. This review summarizes and highlights the importance of chalcone and its analogs as single target small therapeutic agents, multi-target directed ligands (MTDLs) as well as molecular imaging agents for AD. The information summarized here will guide many medicinal chemist and researchers involved in drug discovery to consider chalcone as a potential scaffold for the development of anti-AD agents including theranostics.

Biological Activities of Snowdrop (Galanthus spp., Family Amaryllidaceae)

Snowdrop is an iconic early spring flowering plant of the genus Galanthus (Amaryllidaceae). Galanthus species (Galanthus spp.) are economically important plants as ornaments. Galanthus spp has gained significance scientific and commercial interest due to the discovery of Galanthamine as symptomatic treatment drug for Alzhiermer disease. This review aims to discuss the bioactivities of Galanthus spp including anticholinesterase, antimicrobial, antioxidant and anticancer potential of the extracts and chemical constituents of Galanthus spp. This review highlights that Galanthus spp. as the exciting sources for drug discovery and nutraceutical development.

The Role of Butyrylcholinesterase and Iron in the Regulation of Cholinergic Network and Cognitive Dysfunction in Alzheimer's Disease Pathogenesis

Alzheimer’s disease (AD), the most common form of dementia in elderly individuals, is marked by progressive neuron loss. Despite more than 100 years of research on AD, there is still no treatment to cure or prevent the disease. High levels of amyloid-β (Aβ) plaques and neurofibrillary tangles (NFTs) in the brain are neuropathological hallmarks of AD. However, based on postmortem analyses, up to 44% of individuals have been shown to have high Aβ deposits with no clinical signs, due to having a “cognitive reserve”. The biochemical mechanism explaining the prevention of cognitive impairment in the presence of Aβ plaques is still unknown. It seems that in addition to protein aggregation, neuroinflammatory changes associated with aging are present in AD brains that are correlated with a higher level of brain iron and oxidative stress. It has been shown that iron accumulates around amyloid plaques in AD mouse models and postmortem brain tissues of AD patients. Iron is required for essential brain functions, including oxidative metabolism, myelination, and neurotransmitter synthesis. However, an imbalance in brain iron homeostasis caused by aging underlies many neurodegenerative diseases. It has been proposed that high iron levels trigger an avalanche of events that push the progress of the disease, accelerating cognitive decline. Patients with increased amyloid plaques and iron are highly likely to develop dementia. Our observations indicate that the butyrylcholinesterase (BChE) level seems to be iron-dependent, and reports show that BChE produced by reactive astrocytes can make cognitive functions worse by accelerating the decay of acetylcholine in aging brains. Why, even when there is a genetic risk, do symptoms of the disease appear after many years? Here, we discuss the relationship between genetic factors, age-dependent iron tissue accumulation, and inflammation, focusing on AD.

Novel arylcarbamate-N-acylhydrazones derivatives as promising BuChE inhibitors: Design, synthesis, molecular modeling and biological evaluation

A novel series of arylcarbamate-N-acylhydrazones derivatives have been designed and synthesized as potential anti-cholinesterase agents. In vitro studies revealed that these compounds demonstrated selective for butyrylcholinesterase (BuChE) with potent inhibitory activity. The compounds 10a-d, 12b and 12d were the most potent BuChE inhibitors with IC₅₀ values of 0.07-2.07 µM, highlighting the compound 10c (IC₅₀ = 0.07 µM) which showed inhibitory activity 50 times greater than the reference drug donepezil (IC₅₀ = 3.54 µM). The activity data indicates that the position of the carbamate group in the aromatic ring has a greater influence on the inhibitory activity of the derivatives. The enzyme kinetics studies indicate that the compound 10c has a non-competitive inhibition against BuChE with Ki value of 0.097 mM. Molecular modeling studies corroborated the in vitro inhibitory mode of interaction and show that compound 10c is stabilized into hBuChE by strong hydrogen bond interaction with Tyr128, π-π stacking interaction with Trp82 and CH⋯O interactions with His438, Gly121 and Glu197. Based on these data, compound10cwas identified as low-cost promising candidate for a drug prototype for AD treatment.

Amyloid Beta Hypothesis in Alzheimer's Disease: Major Culprits and Recent Therapeutic Strategies

Alzheimer's disease (AD) is one of the most common forms of dementia and has been a global concern for several years. Due to the multi-factorial nature of the disease, AD has become irreversible, fatal and imposes a tremendous socio-economic burden. Even though experimental medicines suggested moderate benefits, AD still lacks an effective treatment strategy for the management of symptoms or cure. Among the various hypotheses that describe development and progression of AD, the amyloid hypothesis has been a long-term adherent to the AD due to the involvement of various forms of Amyloid beta (Aβ) peptides in the impairment of neuronal and cognitive functions. Hence, majority of the drug discovery approaches in the past have focused on the prevention of the accumulation of Aβ peptides. Currently, there are several agents in the phase III clinical trials that target Aβ or the various macromolecules triggering Aβ deposition. In this review, we present the state of the art knowledge on the functional aspects of the key players involved in the amyloid hypothesis. Furthermore, we also discuss anti-amyloid agents present in the Phase III clinical trials.

Discovery of Natural Inhibitors of Cholinesterases from Hydrangea: In Vitro and In Silico Approaches

Alzheimer's disease (AD) is a neurodegenerative disease conceptualized as a clinical-biological neurodegenerative construct where amyloid-beta pathophysiology is supposed to play a role. The loss of cognitive functions is mostly characterized by the rapid hydrolysis of acetylcholine by cholinesterases including acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). Moreover, both enzymes are responsible for non-catalytic actions such as interacting with amyloid β peptide (Aβ) which further leads to promote senile plaque formation. In searching for a natural cholinesterase inhibitor, the present study focused on two isocoumarines from hydrangea, thunberginol C (TC) and hydrangenol 8-O-glucoside pentaacetate (HGP). Hydrangea-derived compounds were demonstrated to act as dual inhibitors of both AChE and BChE. Furthermore, the compounds exerted selective and non-competitive mode of inhibition via hydrophobic interaction with peripheral anionic site (PAS) of the enzymes. Overall results demonstrated that these natural hydrangea-derived compounds acted as selective dual inhibitors of AChE and BChE, which provides the possibility of potential source of new type of anti-cholinesterases with non-competitive binding property with PAS.

The role of acetylcholinesterase and butyrylcholinesterase activity in the development of delirium in acute stroke

•

Delirium is frequent in acute stroke.

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We tested if AchE or BChE activity could be related to the presence and intensity of delirium.

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Delirious patients had higher levels of BChE activity at discharge.

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BChE activity may be secondary to delirium related inflammatory processes.

Aim

Our study aimed to test whether plasma acetylcholinesterase and butyrylcholinesterase enzyme activity were related to the presence and intensity of delirium in acute stroke patients.

Methods

We carried out a matched (age and gender) case-control study, in a sample of consecutive patients with an acute infarct or intracerebral haemorrhage (≤7 days). We assessed delirium using the DSM-5 criteria and the Delirium Rating Scale, and we measured plasma acetylcholinesterase and butyrylcholinesterase enzyme activity after the patient's admission in the stroke unit and before hospital discharge. Mantel-Haenszel's chi-square was used to test bivariate associations between cases (delirious patients) and controls (non-delirious patients).

Results

At admission in the stroke unit, cases and controls did not present significant differences in plasma acetylcholinesterase or butyrylcholinesterase activity. At hospital discharge (18 cases and 21 controls) patients who have had delirium at admission had higher levels of butyrylcholinesterase activity. Butyrylcholinesterase activity may secondarily increase due to the inflammatory process associated with neuronal dysfunction in delirium patients.

New Hybrids of 4-Amino-2,3-polymethylene-quinoline and p-Tolylsulfonamide as Dual Inhibitors of Acetyl- and Butyrylcholinesterase and Potential Multifunctional Agents for Alzheimer's Disease Treatment

New hybrid compounds of 4-amino-2,3-polymethylene-quinoline containing different sizes of the aliphatic ring and linked to p-tolylsulfonamide with alkylene spacers of increasing length were synthesized as potential drugs for treatment of Alzheimer’s disease (AD). All compounds were potent inhibitors of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) with selectivity toward BChE. The lead compound 4-methyl-N-(5-(1,2,3,4-tetrahydro-acridin-9-ylamino)-pentyl)-benzenesulfonamide (7h) exhibited an IC₅₀ (AChE) = 0.131 ± 0.01 µM (five times more potent than tacrine), IC₅₀(BChE) = 0.0680 ± 0.0014 µM, and 17.5 ± 1.5% propidium displacement at 20 µM. The compounds possessed low activity against carboxylesterase, indicating a likely absence of unwanted drug-drug interactions in clinical use. Kinetics studies were consistent with mixed-type reversible inhibition of both cholinesterases. Molecular docking demonstrated dual binding sites of the conjugates in AChE and clarified the differences in the structure-activity relationships for AChE and BChE inhibition. The conjugates could bind to the AChE peripheral anionic site and displace propidium, indicating their potential to block AChE-induced β-amyloid aggregation, thereby exerting a disease-modifying effect. All compounds demonstrated low antioxidant activity. Computational ADMET profiles predicted that all compounds would have good intestinal absorption, medium blood-brain barrier permeability, and medium cardiac toxicity risk. Overall, the results indicate that the novel conjugates show promise for further development and optimization as multitarget anti-AD agents.

Cholinesterase Inhibitors for Alzheimer's Disease: Multitargeting Strategy Based on Anti-Alzheimer's Drugs Repositioning

In the brain, acetylcholine (ACh) is regarded as one of the major neurotransmitters. During the advancement of Alzheimer's disease (AD) cholinergic deficits occur and this can lead to extensive cognitive dysfunction and decline. Acetylcholinesterase (AChE) remains a highly feasible target for the symptomatic improvement of AD. Acetylcholinesterase (AChE) remains a highly viable target for the symptomatic improvement in AD because cholinergic deficit is a consistent and early finding in AD. The treatment approach of inhibiting peripheral AChE for myasthenia gravis had effectively proven that AChE inhibition was a reachable therapeutic target. Subsequently tacrine, donepezil, rivastigmine, and galantamine were developed and approved for the symptomatic treatment of AD. Since then, multiple cholinesterase inhibitors (ChEIs) have been continued to be developed. These include newer ChEIs, naturally derived ChEIs, hybrids, and synthetic analogues. In this paper, we summarize the different types of ChEIs which are under development and their respective mechanisms of actions.

Bis-γ-carbolines as new potential multitarget agents for Alzheimer’s disease

A new series of homobivalent Dimebon analogs, bis-γ-carbolines with alkylene, phenylenedialkylene, and triazole-containing spacers, was synthesized. Doubling the γ-carboline pharmacophore increased inhibitory potency against acetylcholinesterase (AChE) compared with Dimebon, while keeping Dimebon’s anti-butyrylcholinesterase activity; therefore, leading to inversion of selectivity. Molecular docking revealed the reasons for the increased anti-AChE activity and ability to block AChE-induced aggregation of β-amyloid for bis-γ-carbolines, which became double-site inhibitors of AChE. Conjugates with ditriazole-containing spacers were the most active antioxidants in both the ABTS-test and prevention of lipid peroxidation in brain homogenates without inhibiting the mitochondrial permeability transition (MPT). Conjugates with alkylene (4a–d), phenylenedialkylene (4e), and monotriazole (8) spacers were less active as antioxidants but prevented induction of the MPT and increased the calcium retention capacity of mitochondria. Lead compound 4e showed neuroprotective potential in a cellular calcium overload model of neurodegeneration. Computational studies showed that all the bis-γ-carbolines were expected to have high values for intestinal absorption and very good blood-brain barrier permeability along with good drug-likeness. Overall, the results showed that new homobivalent Dimebon analogs exhibit an expanded spectrum of biological activity and improved pharmacological properties, making them promising candidates for further research and optimization as multitarget agents for Alzheimer’s disease treatment.

In vivo evaluation of arsenic-associated behavioral and biochemical alterations in F0 and F1 mice

Groundwater contaminated with arsenic (As) is the biggest threat to public health in Bangladesh. The children of As-exposure parents are also exposing to As through drinking water. The effects of As on the children's health of As-exposure parents are poorly understood. An animal study was taken to evaluate the effects of As on behavioral and biochemical changes in F₁ mice. Swiss albino mice were separated into three groups: a) control, b) As-treated F₀ and c) As-treated F₁. Elevated plus maze and Morris water maze tests were used for evaluating anxiety, spatial memory and learning, respectively. We found that the effect of As on anxiety like behavior, spatial memory and learning impairment in As-treated F₁ mice was significantly higher than that of As-treated F₀ mice and control group. Additionally, we also evaluated the effects of As on biochemical parameters by measuring ALT, AST, ALP, BChE, SOD activities and the level of creatinine in As-induced mice, where we found that all of the blood parameters were significantly changed in F₁ generation. A significant portion of As accumulated in the brain, liver and kidney of F₁ mice than F₀ mice. Histological analysis revealed a significant change in tissue damage related to hepatic and renal dysfunctions that might be associated with As-induced biochemical alterations. In conclusion, arsenic plays an important role for the development of As-associated neurological disorders, hepatic toxicities, and renal dysfunctions in both F₀ and F₁ generations. Notably F₁ mice were much more vulnerable to As-exposure than F₀ mice.

Exploring the Multi-Target Performance of Mitochondriotropic Antioxidants against the Pivotal Alzheimer's Disease Pathophysiological Hallmarks

Alzheimer disease (AD) is the most common neurodegenerative disease featuring progressive and degenerative neurological impairments resulting in memory loss and cognitive decline. The specific mechanisms underlying AD are still poorly understood, but it is suggested that a deficiency in the brain neurotransmitter acetylcholine, the deposition of insoluble aggregates of fibrillar β-amyloid 1–42 (Aβ₄₂), and iron and glutamate accumulation play an important role in the disease progress. Despite the existence of approved cholinergic drugs, none of them demonstrated effectiveness in modifying disease progression. Accordingly, the development of new chemical entities acting on more than one target is attracting progressively more attention as they can tackle intricate network targets and modulate their effects. Within this endeavor, a series of mitochondriotropic antioxidants inspired on hydroxycinnamic (HCA’s) scaffold were synthesized, screened toward cholinesterases and evaluated as neuroprotectors in a differentiated human SH-SY5Y cell line. From the series, compounds 7 and 11 with a 10-carbon chain can be viewed as multi-target leads for the treatment of AD, as they act as dual and bifunctional cholinesterase inhibitors and prevent the neuronal damage caused by diverse aggressors related to protein misfolding and aggregation, iron accumulation and excitotoxicity.

Design, synthesis and cholinesterase inhibitory properties of new oxazole benzylamine derivatives

The enzymes acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) are primary targets in attenuating the symptoms of neurodegenerative diseases. Their inhibition results in elevated concentrations of the neurotransmitter acetylcholine which supports communication among nerve cells. It was previously shown for trans-4/5-arylethenyloxazole compounds to have moderate AChE and BChE inhibitory properties. A preliminary docking study showed that elongating oxazole molecules and adding a new NH group could make them more prone to bind to the active site of both enzymes. Therefore, new trans-amino-4-/5-arylethenyl-oxazoles were designed and synthesised by the Buchwald-Hartwig amination of a previously synthesised trans-chloro-arylethenyloxazole derivative. Additionally, naphthoxazole benzylamine photoproducts were obtained by efficient photochemical electrocyclization reaction. Novel compounds were tested as inhibitors of both AChE and BChE. All of the compounds exhibited binding preference for BChE over AChE, especially for trans-amino-4-/5-arylethenyl-oxazole derivatives which inhibited BChE potently (IC₅₀ in µM range) and AChE poorly (IC₅₀≫100 µM). Therefore, due to the selectivity of all of the tested compounds for binding to BChE, these compounds could be applied for further development of cholinesterase selective inhibitors.

HIGHLIGHTS

Series of oxazole benzylamines were designed and synthesised

The tested compounds showed binding selectivity for BChE

Naphthoxazoles were more potent AChE inhibitors