Acetylcholinesterase inhibitor modifications: a promising strategy to delay the progression of Alzheimer's disease

Alzheimer＇s disease （AD）, a fatal, progressive, neurodegener- ative disorder, is the most common cause of old-age demen- tia, accounting for 50-75% of dementia patients. Early stages of AD are marked by vocabulary shrinkage, spatial disori- entation, depression, apraxia, and deterioration of recent forms of declarative memory. In course of time, the patients require close supervision due to the loss of cognitive and functional abilities, and at the terminal stages of the disease, all forms of memory are severely impaired with the patients needing nursing home care （World Alzheimer Report, 2013）.

Design,Synthesis,and Biological Evaluation of 5H-Thiazolo[3,2-a]pyrimidine-6-carboxylic Acid Ethyl Ester Derivatives as a Novel Series of Acetylcholinesterase Inhibitors

Acetylcholinesterase inhibitors are the most frequently prescribed anti-Alzheimer＇s drugs. A series of 5H-thiazolo[3,2-a]pyrimidine-6-carboxylic acid ethyl ester derivatives as the novel acetylcholinesterase inhibitors was designed based on virtual screening methods. The target compounds were synthesized with Biginelli reaction and Hantzsch-type condensation of dihydropyrimidines with substituted phenacyl chlorides, and were characterized with elemental analysis, IR, MS, ^1H NMR, and ^13C NMR. The biological evaluation against human acetylcholinesterase in vitro indicated all the target compounds show more than 50% inhibition at 10μmol/L by means of the Ellman method. The results provide a starting point for the development of novel drugs to treat Alzheimer＇s disease and lay the foundation of searching for improved acetylcholinesterase inhibitors with the novel scaffolds.

Isolation of Pleurotus fl orida derived acetylcholinesterase inhibitor for the treatment of cognitive dysfunction in mice

Our earlier work showed that hydromethanol extract(HME)of Pleurotus fl orida had antioxidant and anticholinesterase potential.This study aimed at isolating the constituent responsible for the activities.HME was subjected to bioactivity guided fractionation using in vitro anti-acetylcholinesterase(Ellman method)and antioxidant(DPPH scavenging assay).The most active constituent was evaluated in vivo employing i.c.v.streptozotocin(STZ)induced dementia in mice.Morris water maze test was used for evaluating memory,followed by biochemical estimations and histopathological studies.Bioactivity guided fractionation resulted in isolation of resveratrol(identifi ed by IR,NMR and MS)and its content in P.fl orida fruiting bodies was 0.0098%(m/m,by a validated TLC densitometric method).It improved STZ induced dementia and neurodegeneration in mice by reducing brain acetylcholinesterase action and oxidative stress.The observed effects might be the presence of resveratrol.Our results further endorse that P.fl orida derived resveratrol can be a promising therapy for Alzheimer’s disease.

Mimetic Preparation of Analogues of Territrem B, A Potent Acetylcholinesterase Inhibitor

A mimetic synthesis of a potent acetylcholinesterase inhibitor, Territrem B, was carried out from the naturally occurring jujubosides. The anti-AChE activity of the product, which possesses the 2-en-1-one pharmacophore and the aromatic ring, was measured. The aromatic ring moiety seemed to be less influencing when comparing with the 2-en-1-one moiety.

Preparation of AChE Inhibitors From Jujubogenin

A dammarane derivative dihydrojujubogenin-2-en-1-one, which possesses a skeleton and pharmacophore partially similar to those of Territrem B, a potent AChE inhibitor, was synthesized via three different paths. The anti-AChE activity of this compound and related analogue was measured.

Use of donepezil for neurocognitive recovery after brain injury in adult and pediatric populations:a scoping review

There are few pharmacologic options for the treatment of cognitive deficits associated with traumatic brain injury in pediatric patients.Acetylcholinesterase inhibitors such as donepezil have been evaluated in adult patients after traumatic brain injury,but relatively less is known about the effect in pediatric populations.The goal of this review is to identify knowledge gaps in the efficacy and safety of acetylcholinesterase inhibito rs as a potential a djuvant treatment fo r neurocognitive decline in pediatric patients with traumatic brain injury.Investigators queried PubMed to identify literature published from database inception thro ugh June 2023 desc ribing the use of donepezil in young adult traumatic brain injury and pediatric patients with predefined conditions.Based on preselected search criteria,340 unique papers we re selected for title and abstra ct screening.Thirty-two reco rds were reviewed in full after eliminating preclinical studies and pape rs outside the scope of the project.In adult traumatic brain injury,we review results from 14 papers detailing 227 subjects where evidence suggests donepezil is well tole rated and shows both objective and patient-reported efficacy for reducing cognitive impairment.In children,3 pape rs report on 5 children recovering from traumatic brain injury,showing limited efficacy.An additional 15 pediatric studies conducted in populations at risk for cognitive dysfunction provide a broader look at safety and efficacy in 210 patients in the pediatric age group.Given its promise for efficacy in adults with traumatic brain injury and tole rability in pediatric patients,we believe further study of donepezil for children and adolescents with traumatic brain injury is warranted.

Neuroprotection of N-benzylcinnamide on scopolamine-induced cholinergic dysfunction in human SH-SY5Y neuroblastoma cells

Alzheimer＇s disease, a progressive neurodegenerative disease, affects learning and memory resulting from cholinergic dysfunction. Scopolamine has been employed to induce Alzheimer＇s disease-like pathology in vivo and in vitro through alteration of cholinergic system. N-benzylcinnamide （PT-3）, purified from Piper submultinerve, has been shown to exhibit neuroprotective properties against amyloid-β-induced neuronal toxicity in rat cortical primary cell culture and to improve spatial learning and memory of aged rats through alleviating oxidative stress. We proposed a hypothesis that PT3 has a neuroprotective effect against scopolamine-induced cholinergic dysfunction. PT-3 （125-200 nM） pretreatment was performed in human neuroblastoma SH-SY5Y cell line following scopolamine induction. PT-3 （125-200 nM） inhibited scopolamine （2 mM）-induced generation of reactive oxygen species, cellular apoptosis, upregutation of ace- tylcholinesterase activity, downregulation of choline acetyltransferase level, and activation of p38 and JNK signalling pathways. These findings revealed the underlying mechanisms of scopolamine-induced Alzheimer＇s disease-like cellular dysfunctions, which provide evidence for developing drugs for the treatment of this de- bilitating disease.

Advances in the study of Alzheimer's disease

Alzheimer＇ s disease （AD） is the most common cause of dementia, and the only treatment currently available for the disease is acetylcholinesterase inhibitors. Recent progress in understanding the molecular and cellular pathophysiology of Alzheimer＇s disease has suggested possible pharmacological interventions, including acetylcholineseterase inhibitors; secretase inhibitors; cholesterol lowering drugs; metal chelators and amyloid immunization. The objective of this paper is to review the main drugs possibly used for AD and their future therapeutic effects.

The protective role of tacrine and donepezil in the retina of acetylcholinesterase knockout mice

AIM: To determine the effect of different concentrations of the acetylcholinesterase (AChE) inhibitors tacrine and donepezil on retinal protection in AChE(+/-) mice (AChE knockout mice) of various ages. METHODS: Cultured ARPE -19 cells were treated with hydrogen peroxide (H2O2) at concentrations of 0, 250, 500, 1000 and 2000 mu mol/L and protein levels were measured using Western blot. Intraperitoneal injections of tacrine and donepezil (0.1 mg/mL, 0.2 mg/mL and 0.4 mg/mL) were respectively given to AChE4- mice aged 2mo and 4mo and wild-type S129 mice for 7d; phosphate buffered saline (PBS) was administered to the control group. The mice were sacrificed after 30d by cardiac perfusion and retinal samples were taken. AChE(+/-) deficient mice were identified by polymerase chain reaction (PCR) analysis using specific genotyping protocols obtained from the Jackson Laboratory website. H&E staining, immunofluorescence and Western blot were performed to observe AChE protein expression changes in the retinal pigment epithelial (RPE) cell layer. RESULTS: Different concentrations of H2O2 induced AChE expression during RPE cell apoptosis. AChE(+/-) mice retina were thinner than those in wild -type mice (P< 0.05); the retinal structure was still intact at 2mo but became thinner with increasing age(P <0.05); furthermore, AChE'l- mice developed more slowly than wild-type mice (P <0.05). Increased concentrations of tacrine and donepezil did not significantly improve the protection of the retina function and morphology (P >0.05). CONCLUSION: in viva, tacrine and donepezil can inhibit the expression of AChE; the decrease of AChE expression in the retina is beneficial for the development of the retina.

Bis(7)-Tacrine Ameliorates Cognitive Impairment Caused by Cerebral Hypoperfusion in Rats

The effects ofbis(7)-tacrine, a novel acetylcholinesterase inhibitor, on cognitive impairment and neuronal degeneration induced by permanent ligation of bilateral common carotid arteries (2VO) were investigated using the Morris water maze in rats. Once daily oral administration ofbis(7)-tacrine (0.025, 0.05 and 0.1 mg?kg?1) was started 14 days after 2VO operation. Over a three-week treatmentbis(7)-tacrine effectively reversed 2VO-induced spatial memory deficits in a dose-dependent fashion. Furthermore, histological observation showedbis(7)-tacrine decreased the neuropathological changes in the 2VO rats brain. These results suggest thatbis(7)-tacrine has therapeutic potential for the treatment of dementia caused by chronic cerebral hypoperfusion.

Examination of Urinary Chlorpyrifos Biomarker Concentrations and Heart Rate in a Sample of US Children and Adolescents

Objective: The purpose of the investigation is to determine if a relationship exists between heart rate and urinary biomarkers of chronic, subacute chlorpyrifos pesticide exposure in youth. Methods: Using 2001-2002 NHANES data, a sample of 1233 children ages 6 - 18 was grouped based on detection status of 3,5,6-trichloropyridinol (TCPy) in urine. Radial pulse and brachial pulse were recorded as measures of heart rate by physicians. T-tests and linear regression analyses were performed to test for associations between TCPy concentrations and heart rate. Results: None of the associations between TCPy levels and heart rate outcomes were found to be significant. Nonsignificant effects in the TCPy-detected groups included a slightly reduced heart rate in girls, as well as a slightly elevated heart rate in boys when compared to the undetected controls. Neither was there any significant observable difference in heart rate due to detection status in the sample overall. Conclusions: At this time, an effect on heart rate attributable to chronic, low-level chlorpyrifos exposure in youth cannot be determined. Children and adolescents detected did not demonstrate a substantial change in pulse measures when compared to controls. It is recommended that subsequent studies examine chlorpyrifos biomarkers as they may relate to other indicators of cardiovascular health.

Roles of cholinergic receptors during attentional modulation of cue detection

Basal forebrain corticopetal cholinergic neurons are known to be necessary for normal attentional process-ing. Alterations of cholinergic system functioning have been associated with several neuropsychiatric diseases, such as Alzheimer’s disease and schizophrenia, in which attentional dysfunction is thought to be a key contrib-uting factor. Loss of cortical cholinergic inputs impairs performance in attention-demanding tasks. Moreover, measures of acetylcholine with microdialysis and, more recently, of choline with enzyme-coated microelectrodes have begun to elucidate the precise cognitive demands that activate the cholinergic system on distinct time scales. However, the receptor actions following acetyl-choline release under attentionally-challenging condi-tions are only beginning to be understood. The present review is designed to summarize the evidence regarding the actions of acetylcholine at muscarinic and nicotinic receptors under cognitively challenging conditions in order to evaluate the functions mediated by these two different cholinergic receptor classes. Moreover, evi-dence that supports beneficial effects of muscarinic muscarinic-1 receptor agonists and selective nicotinic receptor subtype agonists for cognitive processing will be discussed. Finally, some challenges and limitations of targeting the cholinergic system for treating cognitive defcits along with future research directions will be mentioned. In conclusion, multiple aspects of cholinergic neurotransmission must be considered when attempting to restore function of this neuromodulatory system.

Synthesis of 2-En-1-one-ebelactonyl Benzoates of Territrem B Analogues from Jujubogenin

Two series of territrem B analogues (10a-10c and 18) have been designed and synthesized from jujubogenin 5a which was prepared from jujubogenin glycosides 5b obtained from the leaves of Zizyphus jujuba. The structures of the new compounds were confirmed by H-, 1 13C-NMR and MS data. Compounds 10c and 18 showed weak inhibitory effect on AChE at 10-4 mol/L.

Two Series of Synthetic Territrem B Analogues and their Biological Activities

Two series of territrem B analogues (6, 11) were designed and synthesized from jujubogenin 2. Compound 11c inhibited AChE with the ratio of 70% at 10-4 mol/L. Compounds 5a, 5b, 6a and 11b showed moderate cytotoxicity on cultured KB cells at 10-6 mol/L. Compounds 5c and 6b alleviated injury arising from oxygen-glucose deprivation (OGD).

Design,synthesis characterization and in vitro biological activity of a series of 3-aryl-6-(bromoarylmethyl)-7H-thiazolo[3,2-b]-1,2,4-triazin-7-one derivatives as the novel acetylcholinesterase inhibitors

Bromination is used as a strategy to improve biological activity in medicinal chemistry.In order to study on the structure-activity relationships of the novel acetylcholinesterase inhibitors with 7H-thiazolo[3,2-b]-1,2,4-triazin-7-one scaffold,based on our previous work and molecular modeling,a series of novel 3-aryl-6-（bromoarylrnethyl）-7H-thiazolo[3,2-b]-1,2,4-triazin-7-one derivatives were designed by molecular docking,synthesized and characterized by mass spectra,infrared spectra,proton NMR and elemental analyses.The study of AChE inhibitory activity was carried out using the Ellman colorimetric assay with huperzine-A as the positive control.Most of all target compounds exhibited more than 45%inhibition at 10μmol/L.The preliminary structureactivity relationship was the bromine atoms and the hydroxyl group at the phenyl ring at the C6 position of the parent nucleus played significant roles in the AChE inhibitory activity of the target compounds.

Highly Sensitive Fluorometric Assay Method for Acetylcholine- sterase Inhibitor Based on Nile Red-Adsorbed Gold Nanoparticles

A new sensitive fluorometric assay method for acetylcholinesterase （ACHE） and its inhibitor was developed us- ing a fluorescent dye, nile red （NR）. Due to the fluorescence resonance energy transfer between the NR and the gold nanoparticle （AuNPs）, the fluorescence was quenched. AChE can break down acetylthiocholine to produce a thiol-bearing compound, thiocholine. In the presence of thiocholine, the nile red is replaced from the AuNPs sur- faces and simultaneously transformed to a derivative of nile red. The fluorescence intensity of the derivative is much stronger than that of the native nile red with the same concentration and its maximum emission wavelength has a blue shift so that the sensor achieves a good signal-to-background ratio. In addition, when organophosphate pesticide （OPs） exists, the activity of AChE can be inhibited, the generation of thiocholine will be prevented and no fluorescence enhancement occurs. The results show that the method is sensitive to AChE and paraoxon with the de- tection limits of 0.2 mU/mL and 0.05 ng/mL, respectively.

Synthesis, Biological Activity Evaluation and Molecular Modeling Study on the New Isoconessimine Derivatives as Acetylcholinesterase Inhibitors

New isoconessimine derivatives were synthesized from conessine （1） and evaluated as acetylcholinesterase （ACHE） inhibitors. The derivatives were prepared via two reaction steps, N-demethylation and nuc]eophilic substi- tution. All of the synthesized derivatives exhibited more potential anti-acetylcholinesterase activities than conessine （1） （IC50=16μmol·L^-1） and isoconessimine （2） （IC50〉300 μmol·L ^-1）. Compound 7b （3fl-[methyl-[2-（4-nitro- phenoxy）ethyl]amino]con-5-enine） showed the most potent inhibitory activity with an IC50 of 110 μmol/L which is close to that of reference compound huperzine A （IC50= 70 μmol/L）. The mode of AChE inhibition by 7h was re- versible and non-competitive. In addition, molecular modeling was performed to explore the binding mode of in- hibitor 7b at the active site of AChE and the results showed that 7b could be docked into the acetylcholinesterase active site and compound 7h had hydrophobic interactions with Trp279 and Leu282.

Synthesis and biological activity of 3,6-diaryl-7H-thiazolo[3,2-b][1,2,4]triazin-7-one derivatives as novel acetylcholinesterase inhibitors

Acetylcholinesterase inhibitors played significant roles in treatment of Alzheimer's disease.Based on the research foundation of our previous work and molecular modeling,twelve 3,6-diaryl-7H-thiazolo[3,2-b][1,2,4]triazin-7-one derivatives were synthesized and characterized by mass spectra,infrared spectra,NMR and elemental analyses.The study of AChE inhibitory activity was carried out using the Ellman colorimetric assay with huperzine-A as the positive control.All target compounds exhibited more than 40% inhibition at 10 μM.Some target compounds showed good inhibition against AChE.The preliminary structure-activity relationships were the halogen atoms at the phenyl ring at the C6 position,the hydroxy groups and the long side chains at the phenyl ring at the C3 position of the parent nucleus played significant roles in the AChE inhibitory activity of the target compounds.

Aptamer-induced in-situ growth of acetylcholinesterase-Cu_(3)(PO_(4))_(2)hybrid nanoflowers for electrochemical detection of organophosphorus inhibitors

Enzyme-inorganic hybrid nanoflowers(HNFs)have shown excellent sensing capabilities due to their large specific surface area as well as the simplicity and mildness of the preparation process.However,coupling HNFs to electrodes to fabricate a uniform and controllable enzymatic electrochemical sensing interface remains a challenge.Here,we proposed an aptamer-induced insitu fabrication strategy for preparing an HNF-based electrochemical sensor with ideal performance.Central to this strategy is the introduction of acetylcholinesterase(AChE)-specific binding aptamer(Apt),which induces the in-situ growth of AChE-copper phosphate(Cu_(3)(PO_(4))_(2))HNFs on the surface of carbon paper(CP).In addition,a dense gold nanoparticle(AuNP)layer was electrodeposited on the CP for anchoring Apt and further extending the electroactive surface area.The prepared AChECu_(3)(PO_(4))_(2)HNF/Apt/AuNP/CP biosensor exhibited a wide detection range from 1 to 107 pM for the four organophosphorus inhibitors,including isocarbophos,dichlorvos,methamidophos,and parathion,with detection limits down to 0.016,0.028,0.071,and 0.113 pM,respectively.With the reactivation of pralidoxime chloride,the electrode can still recover 98.1%of the response after five times of repeated use.In real sample detection,the biosensor achieved high recoveries from 96.45%to 100.13%.The detection target may be extendable to other AChE inhibitors(e.g.,drugs for Alzheimer’s disease).This study demonstrates for the first time the feasibility of using aptamers as an inducer to fabricate an electrochemical enzyme sensing interface in-situ.This strategy can be used to fabricate other enzyme-based biosensors and therefore has broader applications.

3D-QSAR Analysis of a Series of 1,2,3-Triazole-chromenone Derivatives as an Acetylcholinesterase Inhibitor against Alzheimer’s Disease

Chromenones have attracted much attention since they are excellent acetylcholinesterase inhibitor(AChEi).The 1,2,3-triazoles are multifunctional anti-acetylcholinesterase(AChE)agents.In this paper,we report the three-dimensional quantitative structure-activity relationship(3D-QSAR)study of 251,2,3-triazolechromenone derivatives based comparative molecular field analysis(CoMFA)and comparative molecular similarity indices analysis(CoMSIA).To construct CoMFA and CoMSIA models,the 25 active molecules were randomly divided into the training and test sets.The obtained cross-validation Q2 of the CoMFA model,the coefficient of non-cross-validation R2,and the test value F are 0.597,0.994,and 396.726,respectively.The cross-validation Q2 of the CoMSIA model,the coefficient of the non-cross-validation R2,and the test value F are 0.721,0.979,and 131.107,respectively.The predictive correlation coefficient(rpred2)is 0.728 for CoMFA and 0.805 for CoMSIA,which verifies that the model is predictable.Based on the potential maps of CoMFA and CoMSIA,a library containing a set of potent AChEi was designed.The inhibitory potential of the compounds in this library was found to be greater than the inhibitory potential of the most active compounds in the data set.The results obtained from this study laid the foundation for the development of effective drugs for AChEi.