Acetylcholinesterase interaction with Alzheimer amyloid beta

Esterified Indole-3-propionic Acid: A Novel Inhibitor against Cholinesterase Identified through Experimental and Computational Approaches

Acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) are targeted for designing drugs against cognitive dysfunction. Curcumin (CUR) and indole-3-propionic acid (IPA) are known for their neuroprotective activity. The clinical application of CUR is hindered due to poor absorption and bioavailability. Hence, CUR was conjugated with IPA to form the CUR-IPA diester. CUR-IPA inhibition against electric eel AChE (eAChE), human AChE (hAChE), and hBChE was carried out. In silico and molecular dynamics (MD) analyses of the interaction of CUR-IPA with hAChE and hBChE were done. UV-visible spectroscopy (λmax at 415 and 276 nm), NMR spectrum, and ESI/MS/MS [m/z = 711 (M + H)] confirmed CUR-IPA formation. CUR-IPA showed in vitro antioxidant activity. The IC50 values of eAChE, hAChE, and hBChE enzyme inhibition were 5.66, 59.30, and 60.66 μM, respectively. MD simulation-based analysis such as RMSD, RMSF, free-energy calculation, PCA, FEL, and DCCM confirmed the stable binding of CUR-IPA with hAChE and hBChE. Further QM/MM analysis confirmed the stable interaction of CUR-IPA with hAChE and hBChE. Since CUR-IPA showed in vitro inhibition against AChE and BChE, a further neuroprotective effect in in vivo could be studied.

Anti-Alzheimer effects of the newly synthesized cationic compounds as multi-target dual hAChE/hBuChE inhibitor: An in silico, in vitro, and in vivo approach

Introduction

Multi-target anti-Alzheimer's disease (AD) compounds are promising leads for the development of AD modifying agents. Ionic compounds containing quaternary ammonium moiety were synthesized, and their multi-targeted anti-AD effects were examined.

Methods

Imidazole derivatives containing a quaternary ammonium moiety were synthesized and evaluated for their potential anti-Alzheimer properties using computational (in silico), cellular (in vitro), and animal (in vivo) models. The inhibition kinetics of both human acetylcholinesterase (hAChE) and butyrylcholinesterase (hBuChE) were assessed. Neuroprotective effects in amyloid-beta (Aβ)-exposed PC12 cells were also examined. Furthermore, the compounds' impact on Aβ-induced memory impairment in Wistar rats was evaluated, with a detailed analysis of the underlying mechanisms.

Results

Compound 5g demonstrated acceptable cytotoxicity against human cells. This compound exhibited non-competitive dual inhibition of both hAChE and hBuChE. Additionally, compound 5g mitigated the morphological changes induced by amyloid-beta (Aβ) in PC12 cells and decreased cell mortality. It exhibited anti-oxidative stress properties, evident by reduction in reactive oxygen species (ROS) production, and inhibition of lipid peroxidation. The compound also down regulated the expression of pro-inflammatory genes IL-1β and TNF-α. In vitro studies validated compound 5g's ability to inhibit lactate dehydrogenase (LDH), attenuate neuroinflammation, and prevent the autophagy-apoptosis cascade. When administered to rats with Aβ-induced memory dysfunction, compound 5g enhanced cognitive function and improved spatial memory. In the hippocampi of treated rats, there was a noted downregulation of TNF-α and NF-kB. Furthermore, compound 5g counteracted the elevated activity of AChE. Molecular modeling validated the binding of compound 5g to both steric and catalytic sites of cholinesterase enzymes.

Conclusion

The novel quaternary ammonium derivative, compound 5g, demonstrated multi-target anti-AD properties, as evidenced by in silico, in vitro and in vivo studies. Behavioral assessments and molecular analyses further confirmed its therapeutic efficacy in amyloid-beta (Aβ)-challenged rats.

Unraveling the mechanistic interplay of mediators orchestrating the neuroprotective potential of harmine

Neurodegenerative diseases (NDDs) encompass a range of conditions characterized by the specific dysfunction and continual decline of neurons, glial cells, and neural networks within the brain and spinal cord. The majority of NDDs exhibit similar underlying causes, including oxidative stress, neuroinflammation, and malfunctioning of mitochondria. Elevated levels of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE), alongside decreased expression of brain-derived neurotrophic factor (BDNF) and glutamate transporter subtype 1 (GLT-1), constitute significant factors contributing to the pathogenesis of NDDs. Additionally, the dual-specificity tyrosine phosphorylation-regulated kinase 1 A (DYRK1A) gene has emerged as a significant target for the treatment of NDDs at the preclinical level. It significantly contributes to developmental brain defects, early onset neurodegeneration, neuronal loss, and dementia in Down syndrome. Moreover, an impaired ubiquitin-proteosome system (UPS) also plays a pathological role in NDDs. Malfunctioning of UPS leads to abnormal protein buildup or aggregation of α-synuclein. α-Synuclein is a highly soluble unfolded protein that accumulates in Lewy bodies and Lewy neurites in Parkinson's disease and other synucleinopathies. Recent research highlights the promising potential of natural products in combating NDDs relative to conventional therapies. Alkaloids have emerged as promising candidates in the fight against NDDs. Harmine is a tricyclic β-carboline alkaloid (harmala alkaloid) with one indole nucleus and a six-membered pyrrole ring. It is extracted from Banisteria caapi and Peganum harmala L. and exhibits diverse pharmacological properties, encompassing neuroprotective, antioxidant, anti-inflammatory, antidepressant, etc. Harmine has been reported to mediate its neuroprotective via reducing the level of inflammatory mediators, NADPH oxidase, AChE, BChE and reactive oxygen species (ROS). Whereas, it has been observed to increase the levels of BDNF, GLT-1 and anti-oxidant enzymes, along with protein kinase-A (PKA)-mediated UPS activation. This review aims to discuss the mechanistic interplay of various mediators involved in the neuroprotective effect of harmine.

New 1,2,4-oxadiazole derivatives as potential multifunctional agents for the treatment of Alzheimer's disease: design, synthesis, and biological evaluation

A series of new 1,2,4-oxadiazole-based derivatives were synthesized and evaluated for their anti-AD potential. The results revealed that eleven compounds (1b, 2a-c, 3b, 4a-c, and 5a-c) exhibited excellent inhibitory potential against AChE, with IC50 values ranging from 0.00098 to 0.07920 µM. Their potency was 1.55 to 125.47 times higher than that of donepezil (IC50 = 0.12297 µM). In contrast, the newly synthesized oxadiazole derivatives with IC50 values in the range of 16.64-70.82 µM exhibited less selectivity towards BuChE when compared to rivastigmine (IC50 = 5.88 µM). Moreover, oxadiazole derivative 2c (IC50 = 463.85 µM) was more potent antioxidant than quercetin (IC50 = 491.23 µM). Compounds 3b (IC50 = 536.83 µM) and 3c (IC50 = 582.44 µM) exhibited comparable antioxidant activity to that of quercetin. Oxadiazole derivatives 3b (IC50 = 140.02 µM) and 4c (IC50 = 117.43 µM) showed prominent MAO-B inhibitory potential. They were more potent than biperiden (IC50 = 237.59 µM). Compounds 1a, 1b, 3a, 3c, and 4b exhibited remarkable MAO-A inhibitory potential, with IC50 values ranging from 47.25 to 129.7 µM. Their potency was 1.1 to 3.03 times higher than that of methylene blue (IC50 = 143.6 µM). Most of the synthesized oxadiazole derivatives provided significant protection against induced HRBCs lysis, revealing the nontoxic effect of the synthesized compounds, thus making them safe drug candidates. The results unveiled oxadiazole derivatives 2b, 2c, 3b, 4a, 4c, and 5a as multitarget anti-AD agents. The high AChE inhibitory potential can be computationally explained by the synthesized oxadiazole derivatives' significant interactions with the AChE active site. Compound 2b showed good physicochemical properties. All these data suggest that 2b could be considered as a promising candidate for future development.

Design, synthesis, and evaluation of novel bistrifluoromethyl-based hydrazones as dual inhibitors of acetylcholinesterase and carbonic anhydrase enzymes for Alzheimer's disease

In this project, non-sulfonamide bistrifluoromethyl-derived hydrazide-hydrazones were synthesized as multi-target-directed ligands to treat Alzheimer's disease and then, the novel derivatives were characterized by diverse spectral methods. Acetylcholinesterase (AChE), and human carbonic anhydrase (hCA) inhibitory qualifications of these compounds were determined. The reported compounds (2a-y) were determined to be effective inhibitors of the hCA I, hCA II and AChE enzymes with Ki values in the range of 1.130 ± 0.15-5.440 ± 0.93 μM for hCA I, 0.894 ± 0.05-6.647 ± 1.35 μM for hCA II, and 0.196 ± 0.03-4.222 ± 1.04 μM for AChE. In silico studies were also performed to illuminate the binding interactions.

Dual-target ligand discovery for Alzheimer's disease: triphenylphosphoranylidene derivatives as inhibitors of acetylcholinesterase and β-amyloid aggregation

Alzheimer disease (AD) is one of the major neurodegenerative diseases that could not be prevented or completely cured and may lead to death. Here, we target AChE and β-amyloid proteins. Synthesising new triphenylphosphporanylidene derivatives based on the surveyed literature and testing their biological activity revealed promising results especially for the acetyl triphenylphosphoranylidene derivative 8c, which showed good inhibitor activity against AChE enzyme with IC₅₀ in the nanomolar range (97.04 nM); on the other hand, it showed poor selectivity for AChE versus butyrylcholinesterase but with some futural structural modification, this selectivity can be improved. 8c showed MMP-2 IC₅₀ of 724.19 nM and Aβ_1-42 aggregation IC₅₀ of 302.36 nM. A kinetic study demonstrated that compound 8c uncompetitively inhibited AChE. Moreover, derivative 8c showed low cytotoxicity, good in vivo behavioural studies including Y-maze and passive avoidance tests with activity similar to that of donepezil. Finally, in silico studies for 8c predict its good penetration into BBB and good binding affinity in the AChE binding site.

Discovery of Novel Tryptanthrin Derivatives with Benzenesulfonamide Substituents as Multi-Target-Directed Ligands for the Treatment of Alzheimer's Disease

Based on the multi-target-directed ligands (MTDLs) approach, two series of tryptanthrin derivatives with benzenesulfonamide substituents were evaluated as multifunctional agents for the treatment of Alzheimer's disease (AD). In vitro biological assays indicated most of the derivatives had good cholinesterase inhibitory activity and neuroprotective properties. Among them, the target compound 4h was considered as a mixed reversible dual inhibitor of acetylcholinesterase (AChE, IC50 = 0.13 ± 0.04 μM) and butyrylcholinesterase (BuChE, IC50 = 6.11 ± 0.15 μM). And it could also potentially prevent the generation of amyloid plaques by inhibiting self-induced Aβ aggregation (63.16 ± 2.33%). Molecular docking studies were used to explore the interactions of AChE, BuChE, and Aβ. Furthermore, possessing significant anti-neuroinflammatory potency (NO, IL-1β, TNF-α; IC50 = 0.62 ± 0.07 μM, 1.78 ± 0.21 μM, 1.31 ± 0.28 μM, respectively) reduced ROS production, and chelated biometals were also found in compound 4h. Further studies showed that 4h had proper blood-brain barrier (BBB) permeability and suitable in vitro metabolic stability. In in vivo study, 4h effectively ameliorated the learning and memory impairment of the scopolamine-induced AD mice model. These findings suggested that 4h may be a promising compound for further development as a multifunctional agent for the treatment of AD.

Discovery of Multitarget-Directed Ligands from Piperidine Alkaloid Piperine as a Cap Group for the Management of Alzheimer's Disease

The naturally inspired multitarget-directed ligands (PC01-PC10 and PD01-PD26) were synthesized from piperine for the management of Alzheimer's disease (AD). The compound PD07 showed significant inhibitory activity on ChEs, BACE1, and Aβ1-42 aggregation in in vitro studies. Further, compound PD07 effectively displaced the propidium iodide at the AChE PAS site. The compound PD07 exhibited significant lipophilicity in PAMPA studies. Additionally, PD07 demonstrated neuroprotective properties in the Aβ1-42 induced SH-SY5Y cell line. Furthermore, DFT calculations were performed using B3LYP/6-311G(d,p) basis sets to explore the PD07 physical and chemical properties. The compound PD07 showed a similar binding interaction profile at active sites of AChE, BuChE, and BACE1 proteins as compared to reference ligands (donepezil, tacrine, and BSD) in molecular docking and dynamic simulation studies. In acute oral toxicity studies, compound PD07 exhibited no toxicity symptoms up to 300 mg/kg, po. The compound PD07 (10 mg/kg, po) improved memory and cognition in scopolamine-induced amnesia rats. Further, PD07 increased ACh levels in the brain by inhibiting the AChE activity. The results from in vitro, in silico, and in vivo studies suggested that compound PD07 is a potent multitarget-directed lead from piperine to overcome Alzheimer's disease.

Exploring the potential of a novel phenoxyethyl piperidine derivative with cholinesterase inhibitory properties as a treatment for dementia: Insights from STZ animal model of dementia

Alzheimer's disease (AD) is a neurodegenerative disease, often characterized by progressive deficits in memory and cognitive functions. Cholinesterase inhibitors have been introduced as promising agents to enhance cognition and memory in both human patients and animal models of AD. In the current study, we assessed the effects of a synthetic phenoxyethyl piperidine derivative, compound 7c, as a novel dual inhibitor of acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE), on learning and memory, as well as serum and hippocampal AChE levels in an animal model of AD. The model of dementia was induced by intracerebroventricular injection of streptozotocin (STZ, 2 mg/kg) to male Wistar rats. STZ-treated rats received compound 7c (3, 30, and 300 µg/kg) for five consecutive days. ​Passive avoidance (PA) learning and memory, as well as spatial learning and memory using Morris water maze, were evaluated. The level of AChE was measured in the serum and the left and right hippocampus. Findings demonstrated that compound 7c (300 µg/kg) was able to reverse STZ-induced impairments in PA memory, while also reduced the increased AChE level in the left hippocampus. Taken together, compound 7c appeared to act as a central AChE inhibitor, and its role in alleviating cognitive deficits in the AD animal model suggests that it may have therapeutic potential in AD dementia. Further research is required to assess the effectiveness of compound 7c in more reliable models of AD in light of these preliminary findings.

An ongoing journey of chalcone analogues as single and multi-target ligands in the field of Alzheimer's disease: A review with structural aspects

Alzheimer's disease (AD) is a chronic and irreversible neurodegenerative disorder with progressive dementia and cognitive impairment. AD poses severe health challenge in elderly people and become one of the leading causes of death worldwide. It possesses complex pathophysiology with several hypotheses (cholinergic hypothesis, amyloid hypothesis, tau hypothesis, oxidative stress, mitochondrial dysfunction etc.). Several attempts have been made for the management of multifactorial AD. Acetylcholinesterase is the only target has been widely explored in the management of AD to the date. The current review set forth the chalcone based natural, semi-synthetic and synthetic compounds in the search of potential anti-Alzheimer's agents. The main highlights of current review emphasizes on chalcone target different enzymes and pathways like Acetylcholinesterase, β-secretase (BACE1), tau proteins, MAO, free radicals, Advanced glycation end Products (AGEs) etc. and their structure activity relationships contributing in the inhibition of above mentioned various targets of AD.

Rapid discovery and crystallography study of highly potent and selective butylcholinesterase inhibitors based on oxime-containing libraries and conformational restriction strategies

Butyrylcholinesterase is regarded as a promising drug target in advanced Alzheimer's disease. In order to identify highly selective and potent BuChE inhibitors, a 53-membered compound library was constructed via the oxime-based tethering approach based on microscale synthesis. Although A2Q17 and A3Q12 exhibited higher BuChE selectivity versus acetylcholinesterase, the inhibitory activities were unsatisfactory and A3Q12 did not inhibit Aβ_1-42 peptide self-induced aggregation. With A2Q17 and A3Q12 as leads, a novel series of tacrine derivatives with nitrogen-containing heterocycles were designed based on conformation restriction strategy. The results demonstrated that 39 (IC₅₀ = 3.49 nM) and 43 (IC₅₀ = 7.44 nM) yielded much improved hBuChE inhibitory activity compared to the lead A3Q12 (IC₅₀ = 63 nM). Besides, the selectivity indexes (SI = AChE IC₅₀ / BChE IC₅₀) of 39 (SI = 33) and 43 (SI = 20) were also higher than A3Q12 (SI = 14). The results of the kinetic study showed that 39 and 43 exhibited a mixed-type inhibition against eqBuChE with respective K_i values of 1.715 nM and 0.781 nM. And 39 and 43 could inhibit Aβ_1-42 peptide self-induced aggregation into fibril. X-ray crystallography structures of 39 or 43 complexes with BuChE revealed the molecular basis for their high potency. Thus, 39 and 43 are deserve for further study to develop potential drug candidates for the treatment of Alzheimer's disease.

A novel rhein-huprine hybrid ameliorates disease-modifying properties in preclinical mice model of Alzheimer's disease exacerbated with high fat diet

BACKGROUND

Alzheimer's disease (AD) is characterized by a polyetiological origin. Despite the global burden of AD and the advances made in AD drug research and development, the cure of the disease remains elusive, since any developed drug has demonstrated effectiveness to cure AD. Strikingly, an increasing number of studies indicate a linkage between AD and type 2 diabetes mellitus (T2DM), as both diseases share some common pathophysiological features. In fact, β-secretase (BACE1) and acetylcholinesterase (AChE), two enzymes involved in both conditions, have been considered promising targets for both pathologies. In this regard, due to the multifactorial origin of these diseases, current research efforts are focusing on the development of multi-target drugs as a very promising option to derive effective treatments for both conditions. In the present study, we evaluated the effect of rhein-huprine hybrid (RHE-HUP), a synthesized BACE1 and AChE inhibitor, both considered key factors not only in AD but also in metabolic pathologies. Thus, the aim of this study is to evaluate the effects of this compound in APP/PS1 female mice, a well-established familial AD mouse model, challenged by high-fat diet (HFD) consumption to concomitantly simulate a T2DM-like condition.

RESULTS

Intraperitoneal treatment with RHE-HUP in APP/PS1 mice for 4 weeks reduced the main hallmarks of AD, including Tau hyperphosphorylation, Aβ₄₂ peptide levels and plaque formation. Moreover, we found a decreased inflammatory response together with an increase in different synaptic proteins, such as drebrin 1 (DBN1) or synaptophysin, and in neurotrophic factors, especially in BDNF levels, correlated with a recovery in the number of dendritic spines, which resulted in memory improvement. Notably, the improvement observed in this model can be attributed directly to a protein regulation at central level, since no peripheral modification of those alterations induced by HFD consumption was observed.

CONCLUSIONS

Our results suggest that RHE-HUP could be a new candidate for the treatment of AD, even for individuals with high risk due to peripheral metabolic disturbances, given its multi-target profile which allows for the improvement of some of the most important hallmarks of the disease.

Discovery of multi-target directed 3-OH pyrrolidine derivatives through a semisynthetic approach from alkaloid vasicine for the treatment of Alzheimer's disease

Vasicine is a pyrroloquinazoline alkaloid, which has been isolated from the plant Adhatoda vasica. Naturally inspired semi-synthetic transformations were prepared using vasicine as a synthetic precursor to overcome Alzheimer's disease (AD). These semi-synthetic analogs exhibited stable interactions and were well resided at AChE and BChE active sites in in-silico studies. Further, in-vitro experiments were performed to assess the cholinesterase inhibitory activity and reduction of amyloid-beta (Aβ_1-42) plaques potency, PAMPA assay permeability, and antioxidant activity, these findings suggested that compound VA10 can be a lead molecule among all the synthesized analogs. The compound VA10 binds towards AChE peripheral anionic site (PAS) property was established through propidium iodide displacement assay. Moreover, VA10 showed no notable cytotoxicity and exhibited neuroprotective nature on Aβ_1-42 treated SH-SY5Y cell line. In addition, VA10 was found to be safe in rats, which was confirmed by acute oral toxicity studies. Furthermore, in-vivo studies suggested that compound VA10 (10 mg/kg, p.o) ameliorated the memory and cognition impairment in scopolamine-induced amnesia model and Aβ_1-42 induced Alzheimer rat model. Ex-vivo studies of compound VA10 demonstrate improved ACh levels by inhibiting AChE activity in rat brain. Moreover, histopathological observations on rats brain sections indicate VA10 (10 mg/kg, p.o) recovered the neuronal cells at hippocampus region (DG, CA3, and CA1). These positive experimental data from in-silico, in-vitro and in-vivo studies, suggested that compound VA10 can be a lead compound for further preclinical development studies as a naturally derived alkaloid for anti-AD.

N-Substituted piperidine-3-carbohydrazide-hydrazones against Alzheimer's disease: Synthesis and evaluation of cholinesterase, beta-amyloid inhibitory activity, and antioxidant capacity

A series of piperidine-3-carbohydrazide-hydrazones bearing phenylethyl, phenylpropyl, and phenylbutyl substituents on piperidine nitrogen were designed and synthesized as cholinesterase (ChE) inhibitors. The title compounds were screened for acetylcholinesterase (AChE), butyrylcholinesterase (BuChE) inhibitory activities and antioxidant capacities, and the active ones for Aβ₄₂ self-aggregation inhibition, in vitro. The chemiluminescence method was used to determine the effect of the selected compounds on the reactive oxygen species (ROS) levels in brain tissue. Physicochemical properties were calculated by the MOE program. Kinetic analysis and molecular modeling studies were also carried out for the most active compounds. Generally, the final compounds exhibited moderate to good AChE or BuChE inhibitory activity. Among them, 3g and 3j showed the most potent activity against AChE (IC₅₀  = 4.32 µM) and BuChE (IC₅₀  = 1.27 µM), respectively. The kinetic results showed that both compounds exhibited mixed-type inhibition. Among the selected compounds, nitro derivatives (3g, 4g, and 5g) provided better Aβ₄₂ inhibition. According to the chemiluminescence assay, 4i exhibited the most active superoxide free-radical scavenger activity and 3g, 3j, and 4i showed similar scavenger activity on other ROS. All results suggested that 3g, 3j, and 4i have good AChE/BuChE, Aβ₄₂ inhibitory potentials and antioxidant capacities and can therefore be suggested as promising multifunctional agents to combat Alzheimer's disease.

Novel Coumarin–Pyridine Hybrids as Potent Multi-Target Directed Ligands Aiming at Symptoms of Alzheimer’s Disease

In this research, a series of coumarin-based scaffolds linked to pyridine derivatives via a flexible aliphatic linkage were synthesized and assessed as multifunctional anti-AD agents. All the compounds showed acceptable acetylcholinesterase (AChE) inhibition activity in the nanomolar range (IC50 = 2–144 nM) and remarkable butyrylcholinesterase (BuChE) inhibition property (IC50 = 9–123 nM) compared to donepezil as the standard drug (IC50 = 14 and 275 nM, respectively). Compound 3f as the best AChE inhibitor (IC50 = 2 nM) showed acceptable BuChE inhibition activity (IC50 = 24 nM), 100 times more active than the standard drug. Compound 3f could also significantly protect PC12 and SH-SY5Y cells against H2O2-induced cell death and amyloid toxicity, respectively, superior to the standard drugs. It could interestingly reduce β-amyloid self and AChE-induced aggregation, more potent than the standard drug. All the results suggest that compound 3f could be considered as a promising multi-target-directed ligand (MTDL) against AD.

New Synthetic Caffeine Analogs as Modulators of the Cholinergic System

Alzheimer's disease is a multifactorial neurodegenerative disorder. Since cholinergic deficit is a major factor in this disease, two molecular targets for its treatment are the acetylcholinesterase (AChE) and the nicotinic acetylcholine receptors (nAChRs). Given that caffeine is a natural compound that behaves as an AChE inhibitor and as a partial agonist of nAChRs, the aim of this work was to synthetize more potent bifunctional caffeine analogs that modulate these two molecular targets. To this end, a theophylline structure was connected to a pyrrolidine structure through a methylene chain of different lengths (3 to 7 carbon atoms) to give compounds 7-11 All caffeine derivatives inhibited the AChE, of which compound 11 showed the strongest effect. Electrophysiological studies showed that all compounds behave as agonists of the muscle and the neuronal α7 nAChR with greater potency than caffeine. To explore whether the different analogs could affect the nAChR conformational state, the nAChR conformational-sensitive probe crystal violet (CrV) was used. Compounds 9 and 10 conduced the nAChR to a different conformational state comparable with a control nAChR desensitized state. Finally, molecular docking experiments showed that all derivatives interacted with both the catalytic and anionic sites of AChE and with the orthosteric binding site of the nAChR. Thus, the new synthetized compounds can inhibit the AChE and activate muscle and α7 nAChRs with greater potency than caffeine, which suggests that they could be useful leaders for the development of new therapies for the treatment of different neurologic diseases. SIGNIFICANCE STATEMENT: In this work we synthetized caffeine derivatives which can inhibit acetylcholinesterase and activate both muscle and α7 nicotinic acetylcholine receptors (nAChRs) with higher potency than caffeine. These analogs can be divided into two groups: a non-desensitizing and a desensitizing nAChR group. From the nAChR non-desensitizing group, we propose compound 11 as the most interesting analog for further studies since it inhibits acetylcholinesterase with the highest potency and activates the nAChRs in the picomolar range without inducing receptor desensitization.

Selected Natural Products in Neuroprotective Strategies for Alzheimer's Disease-A Non-Systematic Review

Neurodegenerative disorders such as Alzheimer's disease (AD) are distinguished by the irreversible degeneration of central nervous system function and structure. AD is characterized by several different neuropathologies-among others, it interferes with neuropsychiatrical controls and cognitive functions. This disease is the number one neurodegenerative disorder; however, its treatment options are few and, unfortunately, ineffective. In the new strategies devised for AD prevention and treatment, the application of plant-based natural products is especially popular due to lesser side effects associated with their taking. Moreover, their neuroprotective activities target different pathological mechanisms. The current review presents the anti-AD properties of several natural plant substances. The paper throws light on products under in vitro and in vivo trials and compiles information on their mechanism of actions. Knowledge of the properties of such plant compounds and their combinations will surely lead to discovering new potent medicines for the treatment of AD with lesser side effects than the currently available pharmacological proceedings.

Chemical Constituents from the Wild Atractylodes macrocephala Koidz and Acetylcholinesterase Inhibitory Activity Evaluation as Well as Molecular Docking Study

Screening the lead compounds which could interact both with PAS and CAS of acetylcholinesterase (AChE) is an important trend in finding innovative drugs for Alzheimer's disease (AD). In this paper, four sesquiterpenes, i.e., atractylenolide III (1), atractylenolide IV (2), 3-acetyl-atractylon (3) and β-eudesmol (4), were obtained from the wild Atractylode macrocephala grown in Qimen for the first time. Their structures were elucidated mainly by NMR spectroscopy. To screen the potential dual site inhibitors of AChE, the compounds 1, 2, 3, as well as a novel and rare bisesquiterpenoid lactone, biatractylenolide II (5), which was also obtained from the tilted plant in our previous investigation, were evaluated their AChE inhibitory activities by using Ellman's colorimetric method. The results showed that biatractylenolide II displayed moderate inhibitory activity (IC₅₀ = 19.61 ± 1.11 μg/mL) on AChE. A further molecular docking study revealed that biatractylenolide II can interact with both the peripheral anionic site (PAS) and the catalytic active site (CAS) of AChE. These data suggest that biatractylenolide II can be considered a new lead compound to research and develop more potential dual site inhibitors of AChE.

The influence of vinpocetine alone or in combination with Epigallocatechin-3-gallate, Coenzyme COQ10, Vitamin E and Selenium as a potential neuroprotective combination against aluminium-induced Alzheimer's disease in Wistar Albino Rats

Alzheimer's disease (AD) is one of such diseases that represent the most prominent cause of dementia in elderly people. To explore the possible neuroprotective effect as well as mechanism of action of Vinpocetine either alone or in combination with EGCG, CoQ10, or VE & Se in ameliorating aluminum chloride-induced AD in rats. Rats were received AlCl₃ (70 mg/kg) intraperitoneal daily dose for 30 days along with EGCG (10 mg/kg, I.P), CoQ10 (200 mg/kg, P.O), VE (100 mg/kg, P.O) & Se (1 mg/kg, P.O) as well as Vinpocetine (20 mg/kg, P.O) either alone or in combination. Results revealed that the combination of Vinpocetine with EGCG showed the best neuroprotection. This protection in the brain was indicated by the significant decrease in Aβ and ACHE. The same pattern of results were shown in the levels of monoamines and BDNF. In addition, the combination of Vinpocetine with EGCG showed more pronounced anti-inflammatory (TNF-α, IL-1β) and antioxidant (MDA, SOD, TAC) effects in comparison to other combinations. These results were confirmed using histopathological examinations as well as DNA fragmentation assays. Vinpocetine with EGCG showed pronounced protection on neurons against AD induced by AlCl₃ in rats.

Donepezil Regulates LPS and Aβ-Stimulated Neuroinflammation through MAPK/NLRP3 Inflammasome/STAT3 Signaling

The acetylcholinesterase inhibitors donepezil and rivastigmine have been used as therapeutic drugs for Alzheimer's disease (AD), but their effects on LPS- and Aβ-induced neuroinflammatory responses and the underlying molecular pathways have not been studied in detail in vitro and in vivo. In the present study, we found that 10 or 50 μM donepezil significantly decreased the LPS-induced increases in the mRNA levels of a number of proinflammatory cytokines in BV2 microglial cells, whereas 50 μM rivastigmine significantly diminished only LPS-stimulated IL-6 mRNA levels. In subsequent experiments in primary astrocytes, donepezil suppressed only LPS-stimulated iNOS mRNA levels. To identify the molecular mechanisms by which donepezil regulates LPS-induced neuroinflammation, we examined whether donepezil alters LPS-stimulated proinflammatory responses by modulating LPS-induced downstream signaling and the NLRP3 inflammasome. Importantly, we found that donepezil suppressed LPS-induced AKT/MAPK signaling, the NLRP3 inflammasome, and transcription factor NF-kB/STAT3 phosphorylation to reduce neuroinflammatory responses. In LPS-treated wild-type mice, a model of neuroinflammatory disease, donepezil significantly attenuated LPS-induced microglial activation, microglial density/morphology, and proinflammatory cytokine COX-2 and IL-6 levels. In a mouse model of AD (5xFAD mice), donepezil significantly reduced Aβ-induced microglial and astrocytic activation, density, and morphology. Taken together, our findings indicate that donepezil significantly downregulates LPS- and Aβ-evoked neuroinflammatory responses in vitro and in vivo and may be a therapeutic agent for neuroinflammation-associated diseases such as AD.

Novel tacrine-based acetylcholinesterase inhibitors as potential agents for the treatment of Alzheimer's disease: Quinolotacrine hybrids

A new series of quinolotacrine hybrids including cyclopenta- and cyclohexa-quinolotacrine derivatives were designed, synthesized, and assessed as anti-cholinesterase (ChE) agents. The designed derivatives indicated higher inhibitory effect on the acetylcholinesterase (AChE) with IC₅₀ values of 0.285-100 µM compared to butyrylcholinesterase (BChE) with IC₅₀ values of > 100 µM. Of these compounds, cyclohexa-quinolotacrine hybrids displayed a little better anti-AChE activity than cyclopenta-quinolotacrine hybrids. Compound 8-amino-7-(3-hydroxyphenyl)-5,7,9,10,11,12-hexahydro-6H-pyrano[2,3-b:5,6-c'] diquinolin-6-one (6m) including 3-hydroxyphenyl and cyclohexane ring moieties exhibited the best AChE inhibitory activity with IC₅₀ value of 0.285 µM. The kinetic and molecular docking studies indicated that compound 6m occupied both the catalytic anionic site (CAS) and peripheral anionic site (PAS) of AChE as a mixed inhibitor. Using neuroprotective assay against H₂O₂-induced cell death in PC12 cells, the compound 6h illustrated significant protection among the assessed compounds. In silico ADME studies estimated good drug-likeness for the designed compounds. As a result, these quinolotacrine hybrids can be very encouraging AChE inhibitors to treat Alzheimer's disease. A novel series of quinolotacrine hybrids were designed, synthesized, and evaluated against AChE and BChE enzymes as potential agents for the treatment of AD. The hybrids showed good to significant inhibitory activity against AChE (0.285-100 μM) compared to butyrylcholinesterase (BChE) with IC₅₀ values of > 100 μM. Among them, compound 8-amino-7-(3-hydroxyphenyl)-5,7,9,10,11,12-hexahydro-6H-pyrano[2,3-b:5,6-c'] diquinolin-6-one (6 m) bearing 3-hydroxyphenyl moiety and cyclohexane ring exhibited the highest anti-AChE activity with IC₅₀ value of 0.285 μM. The kinetic and molecular docking studies illustrated that compound 6 m is a mixed inhibitor and binds to both the catalytic anionic site (CAS) and peripheral anionic site (PAS) of AChE.

Novel hydroxybenzylamine-deoxyvasicinone hybrids as anticholinesterase therapeutics for Alzheimer's disease

A series of novel 2-hydroxybenzylamine-deoxyvasicinone hybrid analogs (8a-8n) have been synthesized and evaluated as inhibitors of acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE), and as inhibitors of amyloid peptide (Aβ_1-42) aggregation, for treatment of Alzheimer's disease (AD). These dual acting compounds exhibited good AChE inhibitory activities ranging from 0.34 to 6.35 µM. Analogs8g and 8n were found to be the most potent AChE inhibitors in the series with IC₅₀values of 0.38 µM and 0.34 µM, respectively. All the analogs (8a-8n) exhibited weak BuChE inhibitory activities ranging from 14.60 to 21.65 µM. Analogs8g and 8n exhibited BuChE with IC₅₀values of 15.38 µM and 14.60 µM, respectively, demonstrating that these analogs were greater than 40-fold more selective for inhibition of AChE over BuChE. Additionally, compounds8g and 8n were also found to be the best inhibitors of self-induced Aβ_1-42 peptide aggregation with IC₅₀values of 3.91 µM and 3.22 µM, respectively; 8g and 8n also inhibited AChE-induced Aβ_1-42 peptide aggregation by 68.7% and 72.6%, respectively. Kinetic analysis and molecular docking studies indicate that analogs 8g and 8n bind to a new allosteric pocket (site B) on AChE. In addition, the observed inhibition of AChE-induced Aβ_1-42 peptide aggregation by 8n is likely due to allosteric inhibition of the binding of this peptide at the CAS site on AChE. Overall, these results indicate that 8g and 8n are examples of dual-acting lead compounds for the development of highly effective anti-AD drugs.

Dimeric Tacrine(10)-hupyridone as a Multitarget-Directed Ligand To Treat Alzheimer's Disease

Alzheimer's disease (AD) is a neurodegenerative disorder with multiple pathological features. Therefore, a multitarget-directed ligands (MTDLs) strategy has been developed to treat AD. We have previously designed and synthesized dimeric tacrine(10)-hupyridone (A10E), a novel tacrine derivative with acetylcholinesterase (AChE) inhibition and brain-derived neurotrophic factor (BDNF) activation activity, by linking tacrine and a fragment of huperzine A. However, it was largely unknown whether A10E could act on other AD targets and produce cognitive-enhancing ability in AD animal models. In this study, A10E could prevent cognitive impairments in APP/PS1 transgenic mice and β-amyloid (Aβ) oligomers-treated mice, with higher potency than tacrine and huperzine A. Moreover, A10E could effectively inhibit Aβ production and deposition, alleviate neuroinflammation, enhance BDNF expression, and elevate cholinergic neurotransmission in vivo. At nanomolar concentrations, A10E could inhibit Aβ oligomers-induced neurotoxicity via the activation of tyrosine kinase receptor B (TrkB)/Akt pathway in SH-SY5Y cells. Furthermore, Aβ oligomerization and fibrillization could be directly disrupted by A10E. Importantly, A10E at high concentrations did not produce obvious hepatotoxicity. Our results indicated that A10E could produce anti-AD neuroprotective effects via the inhibition of Aβ aggregation, the activation of the BDNF/TrkB pathway, the alleviation of neuroinflammation, and the decrease of AChE activity. As MTDLs could produce additional benefits, such as overcoming the deficits of drug combination and enhancing the compliance of AD patients, our results also suggested that A10E might be developed as a promising MTDL lead for the treatment of AD.

Purple grape juice consumption during the gestation reduces acetylcholinesterase activity and oxidative stress levels provoked by high-fat diet in hippocampus from adult female rats descendants

The enzyme acetylcholinesterase participates in the end of cholinergic transmission and it has been shown that its activity is increased in some diseases that affect the brain, including Alzheimer disease. The objective of this study was to investigate the effect of purple grape juice consumption with or without high-fat diet in the gestational and lactation period on acetylcholinesterase activity and oxidative stress parameters in the hippocampus of female descendants. During pregnancy and lactation, 40 female Wistar rats received a control diet or a high-fat diet, with half of them receiving grape juice. After lactation, the female descendants received water and control diet in ad libitum until euthanasia on the 120 postnatal day. Hippocampus from were removed for analysis of AChE activity, protein oxidation and lipid peroxidation. It was observed that high-fat diet consumption during the pregnancy increased the AChE activity and the grape juice reduced this activity in descendants. The same was observed in protein oxidation, the descendants from high-fat diet had significantly highest values, and grape juice decreased the levels. We conclude that dietary choices during pregnancy can alter the acetylcholinesterase levels and grape juice is an important alternative to improve this function in adulthood.

Chromone derivatives bearing pyridinium moiety as multi-target-directed ligands against Alzheimer's disease

A new serise of 7-hydroxy-chromone derivatives bearing pyridine moiety were synthesized, and evaluated as multifunctional agents against Alzheimer's disease (AD). Most of the compounds were good AChE inhibitors (IC₅₀ = 9.8-0.71 µM) and showed remarkable BuChE inhibition activity (IC₅₀ = 1.9-0.006 µM) compared with donepezil as the standard drug (IC₅₀ = 0.023 and 3.4 µM). Compounds 14 and 10 showed the best inhibitory activity toward AChE (IC₅₀ = 0.71 µM) and BuChE (IC₅₀ = 0.006 µM), respectively. The ligand-protein docking simulations and kinetic studies revealed that compound 14 and 10 could bind effectively to the peripheral anionic binding site (PAS) of the AChE and BuChE through mixed-type inhibition. In addition, the most potent compounds showed acceptable neuroprotective activity on H₂O₂- and Aβ-induced .neurotoxicity in PC12 cells, more than standard drugs. The compounds could block effectively self- and AChE-induced Aβ aggregation. All the results suggest that compounds 14 and 10 could be considered as promising multi-target-directed ligands against AD.

Interaction of amyloid beta with humanin and acetylcholinesterase is modulated by ATP

Humanin (HN) is known to bind amyloid beta (Aβ)‐inducing cytoprotective effects, while binding of acetylcholinesterase (AChE) to Aβ increases its aggregation and cytotoxicity. Previously, we showed that binding of HN to Aβ blocks aggregation induced by AChE and that HN decreases but does not abolish Aβ‐AChE interactions in A549 cell media. Here, we set out to shed light on factors that modulate the interactions of Aβ with HN and AChE. We found that binding of either HN or AChE to Aβ is not affected by heparan sulfate, while ATP, thought to reduce misfolding of Aβ, weakened interactions between AChE and Aβ but strengthened those between Aβ and HN. Using media from either A549 or H1299 lung cancer cells, we observed that more HN was bound to Aβ upon addition of ATP, while levels of AChE in a complex with Aβ were decreased by ATP addition to A549 cell media. Exogenous addition of ATP to either A549 or H1299 cell media increased interactions of endogenous HN with Aβ to a comparable extent despite differences in AChE expression in the two cell lines, and this was correlated with decreased binding of exogenously added HN to Aβ. Treatment with exogenous ATP had no effect on cell viability under all conditions examined. Exogenously added ATP did not affect viability of cells treated with AChE‐immunodepleted media, and there was no apparent protection against the cytotoxicity resulting from immunodepletion of HN. Moreover, exogenously added ATP had no effect on the relative abundance of oligomer versus total Aβ in either cell line.

Protective Effect and Mechanism of Fruit Extract of Aegle marmelos Against Amyloid-β Toxicity in a Transgenic Caenorhabditis elegans

Alzheimer’s disease (AD) is the most common form of dementia found in the elderly. AD is caused by the accumulation of toxic proteins including amyloid-β (Aβ). The purpose of this study was to investigate the effect of fruit extract of Aegle marmelos against Aβ toxicity in Caenorhabditis elegans. The fruit of A. marmelos has been used in a traditional Thai herb formula in fatigue patients recovering from illnesses such as fever and diarrhea. We used a transgenic C. elegans strain CL4176, which expresses the human Aβ42, to investigate the effects and the mechanisms of action of the extracts against Aβ toxicity. The extract of A. marmelos significantly delayed Aβ-induced paralysis. Aegle marmelos lost the ability to delay Aβ-induced paralysis in worms fed with daf-16 ribonucleic acid interference (RNAi) bacteria, but not in worms fed with hsf-1 and skin-1 RNAi bacteria. These results indicated that daf-16 transcription factor was required for A. marmelos-mediated delayed paralysis. Aegle marmelos enhanced the level of daf-16 gene. Taken together, these results indicated that A. marmelos reduced Aβ toxicity via the DAF-16-mediated cell signaling pathway. In addition, A. marmelos reduced toxic Aβ oligomers. Aegle marmelos also displayed antioxidative effect in in vivo as it enhanced resistance to paraquat-induced oxidative stress in wild type worms. All of the results suggested that A. marmelos can protect against Aβ-induced toxicity and can be a potential candidate for the prevention or treatment of AD.

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.

Humanin Blocks the Aggregation of Amyloid-β Induced by Acetylcholinesterase, an Effect Abolished in the Presence of IGFBP-3

It is known that the humanin (HN) peptide binding to amyloid-β (Aβ) protects against its cytotoxic effects, while acetylcholinesterase (AChE) binding to Aβ increases its aggregation and cytotoxicity. HN is also known to bind the insulin-like growth factor binding protein-3 (IGFBP-3). Here, we examined the regulation of Aβ conformations by HN, AChE, and IGFBP-3 both in vitro and in the conditioned media from A549 and H1299 lung cancer cells. Our in vitro results showed the following: IGFBP-3 binds HN and blocks it from binding Aβ in the absence or presence of AChE; HN and AChE can simultaneously bind Aβ but not when in the presence of IGFBP-3; HN is unable to reduce the aggregation of Aβ in the presence of IGFBP-3; and HN abolishes the aggregation of Aβ induced by the addition of AChE in the absence of IGFBP-3. In the media, AChE and HN can simultaneously bind Aβ. While both AChE and HN are detected when using 6E10 Aβ antibodies, only AChE is detected when using the Aβ 17-24 antibody 4G8, the anti-oligomer A11, and the anti-amyloid fibril LOC antibodies. No signal was observed for IGFBP-3 with any of the anti-amyloid antibodies used. Exogenously added IGFBP-3 reduced the amount of HN found in a complex when using 6E10 antibodies and correlated with a concomitant increase in the amyloid oligomers. Immunodepletion of HN from the media of the A549 and H1299 cells increased the relative abundance of the oligomer vs the total amount of Aβ, the A11-positive prefibrillar oligomers, and to a lesser extent the LOC-positive fibrillar oligomers, and was also correlated with diminished cell viability and increased apoptosis.

Rational design of novel benzisoxazole derivatives with acetylcholinesterase inhibitory and serotoninergic 5-HT4 receptors activities for the treatment of Alzheimer's disease

A rigidification strategy was applied to the preclinical candidate donecopride, an acetylcholinesterase inhibitor possessing 5-HT₄R agonist activity. Inspired by promising bioactive benzisoxazole compounds, we have conducted a pharmacomodulation study to generate a novel series of multitarget directed ligands. The chemical synthesis of the ligand was optimized and compounds were evaluated in vitro against each target and in cellulo. Structure-activity relationship was supported by docking analysis in human acetylcholinesterase binding site. Among the synthesized compounds, we have identified a novel hybrid 32a (3-[2-[1-(cyclohexylmethyl)-4-piperidyl]ethyl]-4-methoxy-1,2-benzoxazole) able to display nanomolar acetylcholinesterase inhibitory effects and nanomolar Ki for 5-HT₄R.

Multi-Target β-Protease Inhibitors from Andrographis paniculata: In Silico and In Vitro Studies

Natural products derived from plants play a vital role in the discovery of new drug candidates, and these are used for novel therapeutic drug development. Andrographis paniculata and Spilanthes paniculata are used extensively as medicinal herbs for the treatment of various ailments, and are reported to have neuroprotective properties. β-amyloid is a microscopic brain protein whose significant aggregation is detected in mild cognitive impairment and Alzheimer’s disease (AD) brains. The accumulation of β-amyloid disrupts cell communication and triggers inflammation by activating immune cells, leading to neuronal cell death and cognitive disabilities. The proteases acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and beta secretase-1 (BACE-1) have been reported to be correlated with the synthesis and growth of β-amyloid plaques in the brains of AD patients. In the present study, the phenolic compounds from A. paniculata and S. paniculata that have been reported in the literature were selected for the current investigation. Furthermore, we employed molecular docking and molecular dynamics studies of the phenolic compounds with the proteins AChE, BChE, and BACE-1 in order to evaluate the binding characteristics and identify potent anti-amyloid agents against the neurodegenerative diseases such as AD. In this investigation, we predicted three compounds from A. paniculata with maximum binding affinities with cholinesterases and BACE-1. The computational investigations predicted that these compounds follow the rule of five. We further evaluated these molecules for in vitro inhibition activity against all the enzymes. In the in vitro investigations, 3,4-di-o-caffeoylquinic acid (5281780), apigenin (5280443), and 7-o-methylwogonin (188316) were found to be strong inhibitors of AChE, BChE, and BACE-1. These findings suggest that these compounds can be potent multi-target inhibitors of the proteases that might cumulatively work and inhibit the initiation and formation of β-amyloid plaques, which is a prime cause of neurotoxicity and dementia. According to our knowledge, these findings are the first report on natural compounds isolated from A. paniculata as multi-target potent inhibitors and anti-amyloid agents.

Design, Synthesis, and Cholinesterase Inhibition Assay of Coumarin-3-carboxamide-N-morpholine Hybrids as New Anti-Alzheimer Agents

A new series of coumarin-3-carboxamide-N-morpholine hybrids 5a-5l was designed and synthesized as cholinesterases inhibitors. The synthetic approach for title compounds was started from the reaction between 2-hydroxybenzaldehyde derivatives and Meldrum's acid to afford corresponding coumarin-3-carboxylic acids. Then, amidation of the latter compounds with 2-morpholinoethylamine or N-(3-aminopropyl)morpholine led to the formation of the compounds 5a-5l. The in vitro inhibition screen against acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) revealed that most of the synthesized compounds had potent AChE inhibitory while their BuChE inhibitions are moderate to weak. Among them, propylmorpholine derivative 5g (N-[3-(morpholin-4-yl)propyl]-2-oxo-2H-chromene-3-carboxamide) bearing an unsubstituted coumarin moiety and ethylmorpholine derivative 5d (6-bromo-N-[2-(morpholin-4-yl)ethyl]-2-oxo-2H-chromene-3-carboxamide) bearing a 6-bromocoumarin moiety showed the most activity against AChE and BuChE, respectively. The inhibitory activity of compound 5g against AChE was 1.78 times more than that of rivastigmine and anti-BuChE activity of compound 5d is approximately same as rivastigmine. Kinetic and docking studies confirmed the dual binding site ability of compound 5g to inhibit AChE.

Investigation of plasma metabolomics and neurotransmitter dysfunction in the process of Alzheimer's disease rat induced by amyloid beta 25-35

Alzheimer's disease (AD) has become one of the major diseases endangering the health of the elderly. Clarifying the features of each AD animal model is valuable for understanding the onset and progression of diseases and developing potential treatments in the pharmaceutical industry. In this study, we aimed to clarify plasma metabolomics and neurotransmitter dysfunction in the process of AD model rat induced by amyloid beta 25-35 (Aβ 25-35). Firstly, Morris Water Maze (MWM) test was used to investigate cognitive impairment in AD rat after 2, 4 and 8 weeks of modelling. Based on this, the effects on levels of AD-related enzymes and eight neurotransmitters were analyzed. And plasma metabolomics analysis based on ultra high-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UHPLC-Q-TOF-MS) was used to research the metabolic disturbances in the process of AD rat. The results shown the injury on the spatial learning ability of AD rats was gradually aggravated within 4 weeks, reached the maximum at 4 weeks and then was stable until 8 weeks. During 8 weeks of modeling, the levels of enzymes including β-secretase, γ-secretase, glycogen synthase kinase-3β (GSK-3β), acetyl cholinesterase (AchE) and nitric oxide synthase (NOS) were significant increased in the plasma of AD rats. The neurotransmitter dysfunction was mainly involved in γ-aminobutyric acid (GABA), acetyl choline (Ach), glutamic acid (Glu), 5-hydroxytryptamine (5-HT), dopamine (DA) and norepinephrine (NE). 17 endogenous metabolites correlated with AD were successfully detected in the metabolomics analysis. These metabolites were mainly involved in fatty acids, sphingolipids, and sterols metabolisms, vitamin metabolism, and amino acid metabolism. These metabolites might be the potential biomarkers that correctly mark different stages of AD. The study on peripheral plasma indices reflecting the process of AD laid the foundation for understand the pathophysiology of AD and find an effective and radical cure. And the rules of endogenous metabolic disorder in AD rats also have a certain guiding significance for the future study of food-drug interactions at different stages of AD.

Meta-Analysis of Randomized Controlled Trials on the Efficacy and Safety of Donepezil, Galantamine, Rivastigmine, and Memantine for the Treatment of Alzheimer's Disease

To study the impact of donepezil, rivastigmine, galantamine, and memantine on cognitive, functional, behavioral, global changes and adverse effects in patients with mild, moderate and severe Alzheimer’s disease (AD), we screened the literature published before September 2017 in the Pubmed, Embase, Cochrane library and Web of Science Electronic databases according to the inclusion criteria. Thirty-six studies were finally determined from 1560 preliminary screened articles. The AD Assessment Scale-cognitive Subscale (ADAS-cog), AD Cooperative Study-Activities of Daily Living (ADCS-ADL), Neuropsychiatric Inventory (NPI), and Clinician’s Interview-Based Impression of Change Plus Caregiver Input scale (CIBIC+) were used as valid endpoints. Of the 36 trials included, meta-analyses of these placebo-control trials showed that there were significant differences between the donepezil, rivastigmine and placebo groups using ADAS-cog, ADCS-ADL, and CIBIC+. Meta-analyses of these placebo-controlled trials showed that there were significant differences between the galantamine and placebo groups using ADAS-cog, ADCS-ADL, NPI, and CIBIC+. These observations suggest that memantine is beneficial for stabilizing or slowing the decline in ADAS-cog and ADCS-ADL₁₉ changes in AD patients. However, there was no significant effect according to the ADCS-ADL₂₃, NPI, and CIBIC+ tests, which indicated that memantine treatment has no significant effect on these cognitive aspects of AD patients. Different effects of donepezil, rivastigmine, galantamine, or memantine on AD were found in this study. According to the results, we conclude that galantamine is effective in treating all aspects of AD and is the first choice for the treatment of AD. However, due to limited data, we should consider additional data to obtain more stable results.

Novel cinnamic acid-tryptamine hybrids as potent butyrylcholinesterase inhibitors: Synthesis, biological evaluation, and docking study

A novel series of cinnamic acid-tryptamine hybrids was designed, synthesized, and evaluated as cholinesterase inhibitors. Anticholinesterase assays showed that all of the synthesized compounds displayed a clearly selective inhibition of butyrylcholinesterase (BChE), but only a moderate inhibitory effect toward acetylcholinesterase (AChE) was detected. Among these cinnamic acid-tryptamine hybrids, compound 7d was found to be the most potent inhibitor of BChE with an IC₅₀ value of 0.55 ± 0.04 μM. This compound showed a 14-fold higher inhibitory potency than the standard drug donepezil (IC₅₀  = 7.79 ± 0.81 μM) and inhibited BChE through a mixed-type inhibition mode. Moreover, a docking study revealed that compound 7d binds to both the catalytic anionic site (CAS) and the peripheral anionic site (PAS) of BChE. Also, compound 7d was evaluated against β-secretase, which exhibited low activity (inhibition percentage: 38%).

Modulatory Effects of a Novel Cyclized Peptide in Reducing the Expression of Markers Linked to Alzheimer's Disease

Despite many studies attempt to identify the primary mechanisms underlying neurodegeneration in Alzheimer's disease (AD), the key events still remain elusive. We have previously shown that a peptide cleaved from the acetylcholinesterase (AChE) C-terminus (T14) can play a pivotal role as a signaling molecule in neurodegeneration, via its interaction with the α7 nicotinic acetylcholine receptor. The main goal of this study is to determine whether a cyclized variant (NBP14) of the toxic AChE-derived peptide can antagonize the effects of its linear counterpart, T14, in modulating well-known markers linked to neurodegeneration. We investigate this hypothesis applying NBP14 on ex-vivo rat brain slices containing the basal forebrain. Western blot analysis revealed an inhibitory action of NBP14 on naturally occurring T14 peptide, as well as on endogenous amyloid beta, whereas the expression of the nicotinic receptor and phosphorylated Tau was relatively unaffected. These results further confirm the neurotoxic properties of the AChE-peptide and show for the first time in an ex-vivo preparation the possible neuroprotective activity of NBP14, over a protracted period of hours, indicating that T14 pathway may offer a new prospect for therapeutic intervention in AD pathobiology.

Discovery of novel dual acetylcholinesterase inhibitors with antifibrillogenic activity related to Alzheimer's disease

AIM

Alzheimer's disease is a progressive and neurodegenerative disorder of the CNS, affecting elderly people. The current pharmacological approach is based on the improvement of cholinergic neurotransmission by inhibiting acetylcholinesterase (AChE) with AChE inhibitors. The disease is also characterized by the accelerated accumulation of β-amyloid plaques around neurons. Furthermore, in vitro studies revealed that AChE can induce β-amyloid peptide (Aβ) aggregation.

METHODOLOGY

Computer-aided molecular design by virtual screening was here employed to discover novel potential AChE inhibitors, with antifibrillogenic properties, in other words, inhibiting Aβ aggregation.

RESULTS

Compounds 1, 4 and 6 showed interesting AChE inhibition. In addition, they particularly inhibit Aβ aggregation in vitro, indicating to be promising novel anti-Alzheimer agents.

The concept of hybrid molecules of tacrine and benzyl quinolone carboxylic acid (BQCA) as multifunctional agents for Alzheimer's disease

Novel tacrine-benzyl quinolone carboxylic acid (tacrine-BQCA) hybrids were designed based on multi-target directed ligands (MTLDs) paradigm, synthesized and evaluated in vitro as inhibitors of human acetylcholinesterase (hAChE) and human butyrylcholinesterase (hBChE). Tacrine moiety is represented herein as 7-methoxytacrine, 6-chlorotacrine or unsubstituted tacrine forming three different families of seven members, i.e. 21 compounds in overall. Introducing BQCA, a positive modulator of M1 muscarinic acetylcholine receptors (mAChRs), the action of novel compounds on M1 mAChRs was evaluated via Fluo-4 NW assay on the Chinese hamster ovarian (CHO-M1WT2) cell line. All the novel tacrine-BQCA hybrids were able to block the action of hAChE and hBChE in micromolar to nanomolar range. The hAChE kinetic profile of 5p was found to be mixed-type which is consistent with our docking experiments. Moreover, selected ligands were assessed for their potential hepatotoxicity on HepG2 cell line and presumable permeation through the blood-brain barrier by PAMPA assay. Expected agonistic profile towards M1 mAChRs delivered by BQCA moiety was not confirmed. From all the hybrids, 5o can be highlighted as non-selective cholinesterase inhibitor (hAChE IC₅₀ = 74.5 nM; hBChE IC₅₀ = 83.3 nM) with micromolar antagonistic activity towards M1 mAChR (IC₅₀ = 4.23 μM). A non-selective pattern of cholinesterase inhibition is likely to be valuable during the onset as well as later stages of AD.

Involvement of Cholinergic Dysfunction and Oxidative Damage in the Effects of Simulated Weightlessness on Learning and Memory in Rats

The present study aimed to determine how the learning and memory gradually change with the prolonged hindlimb unloading (HU) treatment in rats. Different HU durations (7 d, 14 d, 21 d, and 28 d) in Sprague-Dawley (SD) rats were implemented. Cognitive function was assessed using the Morris water maze (MWM) and the shuttle box test. Additionally, parameters about cholinergic activity and oxidative stress were tested. Results showed that longer-than-14 d HU led to the inferior performances in the behavioral tasks. Besides, acetylcholine esterase (AChE) activity, malondialdehyde (MDA) level in brain, reactive oxygen species (ROS), and 8-hydroxy-2-deoxyguanosine (8-OHdG) concentrations of HU rats were significantly increased. Furthermore, choline acetyltransferase (ChAT), superoxide dismutase (SOD), and catalase (CAT) activity in brain were notably attenuated. Most of these effects were more pronounced after longer exposure (21 d and 28 d) to HU, although some indicators had their own characteristics of change. These results indicate that cholinergic dysfunction and oxidative damage were involved in the learning and memory impairments induced by longer-than-14 d HU. Moreover, the negative effects of HU tend to be augmented as the HU duration becomes longer. The results may be helpful to present possible biochemical targets for countermeasures development regarding the memory deficits under extreme environmental conditions.

Synthesis and bioevaluation of new tacrine-cinnamic acid hybrids as cholinesterase inhibitors against Alzheimer's disease

Small molecule cholinesterases inhibitor (ChEI) provides an effective therapeutic strategy to treat Alzheimer's disease (AD). Currently, the discovery of new ChEI with multi-target effect is still of great importance. Herein, we report the synthesis, structure-activity relationship study and biological evaluation of a series of tacrine-cinnamic acid hybrids as new ChEIs. All target compounds are evaluated for their in vitro cholinesterase inhibitory activities. The representatives which show potent activity on cholinesterase, are evaluated for the amyloid β-protein self-aggregation inhibition and in vivo assays. The optimal compound 19, 27, and 30 (human AChE IC₅₀ = 10.2 ± 1.2, 16.5 ± 1.7, and 15.3 ± 1.8 nM, respectively) show good performance in ameliorating the scopolamine-induced cognition impairment and preliminary safety in hepatotoxicity evaluation. These compounds deserve further evaluation for the development of new therapeutic agents against AD.

Lipidomics in translational research and the clinical significance of lipid-based biomarkers

Lipidomics is a rapidly developing field of study that focuses on the identification and quantitation of various lipid species in the lipidome. Lipidomics has now emerged in the forefront of scientific research due to the importance of lipids in metabolism, cancer, and disease. Using both targeted and untargeted mass spectrometry as a tool for analysis, progress in the field has rapidly progressed in the last decade. Having the ability to assess these small molecules in vivo has led to better understanding of several lipid-driven mechanisms and the identification of lipid-based biomarkers in neurodegenerative disease, cancer, sepsis, wound healing, and pre-eclampsia. Biomarker identification and mechanistic understanding of specific lipid pathways linked to a disease's pathologies can form the foundation in the development of novel therapeutics in hopes of curing human disease.

Exploring Anti-Prion Glyco-Based and Aromatic Scaffolds: A Chemical Strategy for the Quality of Life

Prion diseases are fatal neurodegenerative disorders caused by protein misfolding and aggregation, affecting the brain progressively and consequently the quality of life. Alzheimer’s is also a protein misfolding disease, causing dementia in over 40 million people worldwide. There are no therapeutics able to cure these diseases. Cellular prion protein is a high-affinity binding partner of amyloid β (Aβ) oligomers, the most toxic species in Alzheimer’s pathology. These findings motivate the development of new chemicals for a better understanding of the events involved. Disease control is far from being reached by the presently known therapeutics. In this review we describe the synthesis and mode of action of molecular entities with intervention in prion diseases’ biological processes and, if known, their role in Alzheimer’s. A diversity of structures is covered, based on glycans, steroids and terpenes, heterocycles, polyphenols, most of them embodying aromatics and a structural complexity. These molecules may be regarded as chemical tools to foster the understanding of the complex mechanisms involved, and to encourage the scientific community towards further developments for the cure of these devastating diseases.

Discovery of new acetylcholinesterase and butyrylcholinesterase inhibitors through structure-based virtual screening

Small molecule cholinesterase (ChE) inhibitors represent one of the most effective therapeutic strategies for the treatment of Alzheimer's disease (AD).

Design, synthesis, in vitro and in vivo evaluation of tacrine–cinnamic acid hybrids as multi-target acetyl- and butyrylcholinesterase inhibitors against Alzheimer's disease

A series of tacrine–cinnamic acid hybrids are synthesized as multi-target cholinesterase inhibitors against Alzheimer's disease.

Phytochemical and ethnomedicinal study of Huperzia species used in the traditional medicine of Saraguros in Southern Ecuador; AChE and MAO inhibitory activity

ETHNOBOTANICAL AND ETHNOMEDICINAL RELEVANCE

This study concerns seven Huperzia species (Lycopodiaceae), namely H. brevifolia, H. columnaris, H. compacta, H. crassa, H. espinosana, H. tetragona, H. weberbaueri, which are considered sacred plants by the Saraguro community, living in the Southern Andes of Ecuador; these plants are widely used in traditional medicine and ritual ceremonies.

MATERIAL AND METHODS

The plants were selected on the basis of written interviews with 10 visionary healers (yachak) (2 women, 8 men), indicated as the most credible by the Saraguro Healers Council. The Informant Consensus Factor (F_ic) was determined. The first phytochemical study of the plants was performed by standard procedures, while the AChE and MAO-A inhibition by fractions enriched in high MW alkaloids, was measured in vitro.

AIMS OF THE STUDY

i) to investigate the uses of some Huperzia plants in healing and magical-religious practices of Saraguros; ii) to identify the main components of plant hydromethanolic extracts; iiì) to test the effects of alkaloidal fractions on the activity of two enzymes linked to mental health.

RESULTS

All the interviewed Saraguro yachak showed a high consensus about the uses of the seven Huperzia plants as purgatives and against supernatural diseases, such as the "espanto" (startle). In admixtures with other plants, some species also induce a state of trance or hallucinations in participants in magical-religious rituals. GC-MS of the volatile alkaloid fractions allowed the identification of some lycodine-type and lycopodine-type alkaloids (1-5) in H. compacta, H. columnaris, and H. tetragona. The flavones selgin) (6) and tricin (7) were isolated from H. brevifolia and H. espinosana. Tricin (7) was also detected in the other five species. The rare serratene triterpenes serratenediol (8) serratenediol-3-O-acetate (9), 21-episerratenediol (10), and 21-episerratenediol-3-O-acetate (11) were isolated from H. crassa. In addition, the presence of an unprecedented group of high molecular weight alkaloids has been determined. Alkaloid fractions of H. brevifolia, H. compacta, H. espinosana, and H. tetragona significantly inhibited AChE and MAO-A activities in vitro.

CONCLUSIONS

The first phytochemical and ethnopharmacological study of seven Huperzia plants, widely used by Saraguro healers, led to the identification of several alkaloids and triterpenoids with different remarkable biological activities. In addition, alkaloid fractions exhibited a significant AChE and MAO-A inhibitory activity. These results may support the use of these plants in brews prepared for inducing psychoactive effects in participants in magical-religious ceremonies. This study confirms the rich traditional medical knowledge of Saraguro healers which must be documented and preserved for future generations.

Novel tacrine-1,2,3-triazole hybrids: In vitro, in vivo biological evaluation and docking study of cholinesterase inhibitors

A new series of tacrine-1,2,3-triazole hybrids were designed, synthesized, and evaluated as potent dual cholinesterase inhibitors. Most of synthesized compounds showed good in vitro inhibitory activities toward both acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). Among them, 7-chloro-N-((1-(4-methoxybenzyl)-1H-1,2,3-triazol-4-yl)methyl)-1,2,3,4-tetrahydroacridin-9-amine (5l) was found to be the most potent anti-AChE derivative (IC₅₀ = 0.521 μM) and N-((1-(4-methoxybenzyl)-1H-1,2,3-triazol-4-yl)methyl)-1,2,3,4-tetrahydroacridin-9-amine (5j) demonstrated the best anti-BChE activity (IC₅₀ = 0.055 μM). In vivo studies of compound 5l in Morris water maze task confirmed memory improvement in scopolamine-induced impairment. Also, molecular modeling and kinetic studies showed that compounds 5l and 5j bound simultaneously to the peripheral anionic site (PAS) and catalytic sites (CS) of the AChE and BChE.