Recombinant Human Acetylcholinesterase Research Articles

Structural Insights into the Marine Alkaloid Discorhabdin G as a Scaffold towards New Acetylcholinesterase Inhibitors.

In this study, Antarctic Latrunculia sponge-derived discorhabdin G was considered a hit for developing potential lead compounds acting as cholinesterase inhibitors. The hypothesis on the pharmacophore moiety suggested through molecular docking allowed us to simplify the structure of the metabolite. ADME prediction and drug-likeness consideration provided valuable support in selecting 5-methyl-2H-benzo[h]imidazo[1,5,4-de]quinoxalin-7(3H)-one as a candidate molecule. It was synthesized in a four-step sequence starting from 2,3-dichloronaphthalene-1,4-dione and evaluated as an inhibitor of electric eel acetylcholinesterase (eeAChE), human recombinant AChE (hAChE), and horse serum butyrylcholinesterase (BChE), together with other analogs obtained by the same synthesis. The candidate molecule showed a slightly lower inhibitory potential against eeAChE but better inhibitory activity against hAChE than discorhabdin G, with a higher selectivity for AChEs than for BChE. It acted as a reversible competitive inhibitor, as previously observed for the natural alkaloid. The findings from the in vitro assay were relatively consistent with the data available from the AutoDock Vina and Protein-Ligand ANTSystem (PLANTS) calculations.

A-series agent A-234: initial in vitro and in vivo characterization

A-series agent A-234 belongs to a new generation of nerve agents. The poisoning of a former Russian spy Sergei Skripal and his daughter in Salisbury, England, in March 2018 led to the inclusion of A-234 and other A-series agents into the Chemical Weapons Convention. Even though five years have already passed, there is still very little information on its chemical properties, biological activities, and treatment options with established antidotes. In this article, we first assessed A-234 stability in neutral pH for subsequent experiments. Then, we determined its inhibitory potential towards human recombinant acetylcholinesterase (HssAChE; EC 3.1.1.7) and butyrylcholinesterase (HssBChE; EC 3.1.1.8), the ability of HI-6, obidoxime, pralidoxime, methoxime, and trimedoxime to reactivate inhibited cholinesterases (ChEs), its toxicity in rats and therapeutic effects of different antidotal approaches. Finally, we utilized molecular dynamics to explain our findings. The results of spontaneous A-234 hydrolysis showed a slow process with a reaction rate displaying a triphasic course during the first 72 h (the residual concentration 86.2%). A-234 was found to be a potent inhibitor of both human ChEs (HssAChE IC50 = 0.101 ± 0.003 µM and HssBChE IC50 = 0.036 ± 0.002 µM), whereas the five marketed oximes have negligible reactivation ability toward A-234-inhibited HssAChE and HssBChE. The acute toxicity of A-234 is comparable to that of VX and in the context of therapy, atropine and diazepam effectively mitigate A-234 lethality. Even though oxime administration may induce minor improvements, selected oximes (HI-6 and methoxime) do not reactivate ChEs in vivo. Molecular dynamics implies that all marketed oximes are weak nucleophiles, which may explain the failure to reactivate the A-234 phosphorus-serine oxygen bond characterized by low partial charge, in particular, HI-6 and trimedoxime oxime oxygen may not be able to effectively approach the A-234 phosphorus, while pralidoxime displayed low interaction energy. This study is the first to provide essential experimental preclinical data on the A-234 compound.

Two new cyclohexenone derivatives: Synthesis, DFT estimation, biological activities and molecular docking study

Two new cyclohexenone carboxylate derivatives (6a-b) were synthesized through an additional ring-forming chalcone. FT-IR, 1H, 13C NMR, and Mass spectroscopy techniques confirmed the skeletons. The antibacterial, antioxidant, and colon cancer HT-29 cell activity of synthetic substances were assessed. Compound 6a's IC50 is 23.95 and 60.28 for its antioxidant and anticancer activities, whereas Compound 6b's IC50 is 27.56 and 62.72, respectively. MIC values for compound 6a are 15.75 ± 1.12, 10.25 ± 1.27, and 65.61 ± 1.72 against Staphylococcus aureus, Escherichia coli bacterial strains, and Candida albicans, respectively, whereas for compound 6b is equal to 18.32 ± 1.53, 12.63 ± 1.36, and 78.91 ± 1.94. Based on the extent of (B3LYP) and a 6-31G (d, p) basis set, the HOMO and LUMO of synthesized compounds were computed using the density functional theory (DFT) method. Energy gaps for products 6a and 6b are 2.8272 and 2.3360, respectively. Docked products had binding affinities of −9.5 and −9.1 for compounds 6a and 6b, respectively, with the crystal structure of recombinant human acetylcholinesterase in complex with donepezil (PDB ID: 4ey7). Consequently, according to experimental and computational studies, compound 6a is more active than compound 6b.

Design, synthesis and pharmacological evaluation of disubstituted 1,3,4 thiadiazoles derivatives for the treatment of cognitive dysfunction

Acetylcholinesterase has emerged as a promising target for the development of potential treatments for cognitive decline. The deleterious effect of oxidative stress on the learning and memory paradigms of an individual has also been well documented. As a result, the current study shows the design, synthesis, and pharmacological evaluation of 2, 5 disubstituted 1,3,4 thiadiazole derivatives. Twenty-seven molecules were designed and the molecular docking study performed to predict the binding mode of the designed compounds also suggested that these compounds bind appreciably to the amino acids present in the active site of the recombinant human acetylcholinesterase (rhAChE). Based on docking analysis, Five novel hybrids (8,14, 22, 24 and 27) have been synthesized by employing suitable synthetic procedures and characterized by various spectral and elemental techniques. Further, these synthesized compounds were studied the pharmacokinetic study and evaluated against behavioral alterations using step-down passive avoidance and escape learning protocol at a dose of 0.5 mg/kg with reference to the standard, donepezil. All the synthesized compounds were evaluated for their in vitro acetylcholinesterase (AChE) inhibition at five different concentrations using mice brain homogenate as the source of the enzyme. Biochemical estimation of markers of oxidative stress has also been carried out to assess the role of synthesized molecules on the oxidative damage induced by ascorbic acid. Compounds 14 and 22 demonstrated significant acetylcholinesterase inhibition activity. These compounds also decreased ascorbic acid-induced oxidative stress, thus serving as promising leads for the amelioration of oxidative stress-induced cognitive decline. The findings suggested that these compounds could be investigated further as AChE and oxidative stress inhibitors for the treatment of cognitive dysfunction.

Dimethyl Sulfoxide Enhances Acetylcholine-Induced Contractions in Rat Urinary Bladder Smooth Muscle by Inhibiting Acetylcholinesterase Activities.

Dimethyl sulfoxide (DMSO) has been used not only as an experimental solvent, but also as a therapeutic agent for interstitial cystitis. The therapeutic effects of DMSO on interstitial cystitis are presumed to involve anti-inflammatory and analgesic effects. However, the effects of DMSO on urinary bladder smooth muscle (UBSM) have not been fully investigated. Thus, in this study, we investigated the effects of DMSO on rat UBSM contractions, and these effects were compared with those of acetone, which has a structure in which the sulfur of DMSO is replaced with carbon. DMSO (0.5-5%) enhanced acetylcholine (ACh)-induced contractions, whereas acetone (3 and 5%) suppressed them. Additionally, DMSO (5%) suppressed carbachol-induced contractions. DMSO/acetone (0.5-5%) inhibited 80 mM KCl-induced contractions in a concentration-dependent manner; however, the inhibitory effects of DMSO were weaker than those of acetone. The enhancing/suppressing effects of DMSO and acetone were almost completely abolished by wash out. DMSO and acetone (0.5-5%) inhibited recombinant human acetylcholinesterase (rhAChE) activity in a concentration-dependent manner. At 0.5 and 1%, the inhibitory effects of DMSO on rhAChE activity were more potent than those of acetone. These findings suggest that DMSO can enhance ACh-induced UBSM contractions and promote urinary bladder motility by inhibiting acetylcholinesterase (AChE), although DMSO also inhibits Ca2+ influx-mediated UBSM contractions. In addition, the sulfur atom in DMSO might play an important role in its enhancing effect on ACh-induced contractions by inhibiting AChE, as acetone did not enhance these contractions.

The kinetic and molecular docking analysis of interactions between three V-type nerve agents and four human cholinesterases

G and V-type nerve agents represent the most toxic chemical warfare agents. Their primary toxicity was the consequence of the covalent inhibition of the pivotal acetylcholinesterase (AChE), which induces overstimulation of cholinergic receptors and overaccumulation of cholines, eventually leading to death by respiratory arrest. The inhibitory and reactivation kinetics of cholinesterase (ChE) are essential for the toxicology and countermeasures of nerve agents. Medical defensive research on V-type nerve agents (V agents) has been mainly reported on VX and VR. Here we demonstrated the first systematical kinetic analysis between the type of ChE [native or recombinant human AChE and butyrylcholinesterase (BChE)] and three V agents, including VX, VR, and Vs, another isomer of VX, and highlighted the effects of native and recombinant ChE differences. The spontaneous reactivation and aging kinetics data of Vs-inhibited BChEs were firstly reported here.The results showed that AChE was more easily inhibited by three V agent compared to BChE, regardless of whether it is native or recombinant. The increased inhibitory potency order on AChE was VX, Vs, then VR, and on BChE was VX, then Vs and VR. The difference between native and recombinant ChE could influence the inhibition, aging, and spontaneous reactivation kinetics of three V agents, whether AChE or BChE, which was systematically revealed for the first time. For inhibition kinetics, the ki of three V agents for recombinant AChE was significantly higher than native AChE, and the stronger the inhibitory potency of V agents, the more pronounced difference in ki. In terms of aging and spontaneous reactivation kinetics, recombinant ChE was found to be more prone to spontaneous reactivation, but more resistant to aging compared to native ChE, particularly for AChE. The performed covalent molecular docking results partially explained the effects of differences between native and recombinant ChE on enzyme kinetics from the perspective of binding energy and conformation.

Halogen substituents enhance oxime nucleophilicity for reactivation of cholinesterases inhibited by nerve agents

The fluorinated bis-pyridinium oximes were designed and synthesized with the aim of increasing their nucleophilicity and potential to reactivate phosphorylated human recombinant acetylcholinesterase (AChE) and human purified plasmatic butyrylcholinesterase (BChE) in relation to chlorinated and non-halogenated oxime analogues. Compared to non-halogenated oximes, halogenated oximes showed lower pKa of the oxime group (fluorinated < chlorinated < non-halogenated) along with higher level of oximate anion formation at the physiological pH, and had a higher binding affinity of both AChE and BChE. The stability tests showed that the fluorinated oximes were stable in water, while in buffered environment di-fluorinated oximes were prone to rapid degradation, which was reflected in their lower reactivation ability. Mono-fluorinated oximes showed comparable reactivation to non-halogenated (except asoxime) and mono-chlorinated oximes in case of AChE inhibited by sarin, cyclosarin, VX, and tabun, but were less efficient than di-chlorinated ones. The same trend was observed in the reactivation of inhibited BChE. The advantage of halogen substituents in the stabilization of oxime in a position optimal for in-line nucleophilic attack were confirmed by extensive molecular modelling of pre-reactivation complexes between the analogue oximes and phosphorylated AChE and BChE. Halogen substitution was shown to provide oximes with additional beneficial properties, e.g., fluorinated oximes gained antioxidative capacity, and moreover, halogens themselves did not increase cytotoxicity of oximes. Finally, the in vivo administration of highly efficient reactivator and the most promising analogue, 3,5-di-chloro-bispyridinium oxime with trimethylene linker, provided significant protection of mice exposed to sarin and cyclosarin.

In vitro studies of a series of synthetic compounds for their anti-acetylcholinesterase activities identified arylpyrano[2,3-f]coumarins as hit compounds

Alzheimer's disease is one of the most widespread neurodegenerative diseases in the world. Until now, the drugs used to control this disease have been developed to target acetylcholinesterase (AChE). With the aim to identify new pharmacophores that can promisingly inhibit this enzyme, a library of 72 compounds belonging to chalcones, pyranochromenes, chromenes, pyranopyrazoles and dihydropyridines, was evaluated against AChE. Nineteen of these compounds are newly reported and among the tested compounds, seven, bearing a pyranochromene skeleton, showed inhibitory effects with IC50 values ranging from 9.01 to 32.39 µM. The most potent was identified as 8-amino-10-(4-bromophenyl)-5‑hydroxy-4-methyl-2-oxo-2,10-dihydropyrano[2,3-f]chromeno-9-carbonitrile. In silico studies using human recombinant acetylcholinesterase (PDB: 4EY7) showed important proximities between the NH2 group of this compound and E202 in AChE, between W86 and the OH-5 group, between W86 and the aromatic bicyclic system (π-π stacking, 4.2 Å), and between Y133 and both the OH-7 and the NH2 groups. These pyranochromenes emerged as a promising prototype for the development of new candidates against AChE.

Charged pyridinium oximes with thiocarboxamide moiety are equally or less effective reactivators of organophosphate-inhibited cholinesterases compared to analogous carboxamides

The organophosphorus antidotes, so-called oximes, are able to restore the enzymatic function of acetylcholinesterase (AChE) or butyrylcholinesterase (BChE) via cleavage of organophosphate from the active site of the phosphylated enzyme. In this work, the charged pyridinium oximes containing thiocarboxamide moiety were designed, prepared and tested. Their stability and pKa properties were found to be analogous to parent carboxamides (K027, K048 and K203). The inhibitory ability of thiocarboxamides was found in low µM levels for AChE and high µM levels for BChE. Their reactivation properties were screened on human recombinant AChE and BChE inhibited by nerve agent surrogates and paraoxon. One thiocarboxamide was able to effectively restore function of NEMP- and NEDPA-AChE, whereas two thiocarboxamides were able to reactivate BChE inhibited by all tested organophosphates. These results were confirmed by reactivation kinetics, where thiocarboxamides were proved to be effective, but less potent reactivators if compared to carboxamides.

Derivatives of montanine-type alkaloids and their implication for the treatment of Alzheimer's disease: Synthesis, biological activity and in silico study

Alzheimeŕs disease (AD) is the most common neurodegenerative disorder, characterized by neuronal loss and cognitive impairment. Currently, very few drugs are available for AD treatment, and a search for new therapeutics is urgently needed. Thus, in the current study, twenty-eight new derivatives of montanine-type Amaryllidaceae alkaloids were synthesized and evaluated for their ability to inhibit human recombinant acetylcholinesterase (hAChE) and butyrylcholinesterase (hBuChE). Three derivatives (1n, 1o, and 1p) with different substitution patterns demonstrated significant selective inhibitory potency for hAChE (IC50 < 5 µM), and one analog, 1v, showed selective hBuChE inhibition activity (IC50 = 1.73 ± 0.05 µM). The prediction of CNS availability, as disclosed by the BBB score, suggests that the active compounds in this survey should be able pass through the blood–brain barrier (BBB). Cytotoxicity screening and docking studies were carried out for the two most pronounced cholinesterase inhibitors, 1n and 1v.

Interaction of recombinant human acetylcholinesterase with demeton-S-methyl

Interaction of recombinant human acetylcholinesterase with demeton-S-methyl

Covalent inhibition of hAChE by organophosphates causes homodimer dissociation through long-range allosteric effects

Acetylcholinesterase (EC 3.1.1.7), a key acetylcholine-hydrolyzing enzyme in cholinergic neurotransmission, is present in a variety of states in situ, including monomers, C-terminally disulfide-linked homodimers, homotetramers, and up to three tetramers covalently attached to structural subunits. Could oligomerization that ensures high local concentrations of catalytic sites necessary for efficient neurotransmission be affected by environmental factors? Using small-angle X-ray scattering (SAXS) and cryo-EM, we demonstrate that homodimerization of recombinant monomeric human acetylcholinesterase (hAChE) in solution occurs through a C-terminal four-helix bundle at micromolar concentrations. We show that diethylphosphorylation of the active serine in the catalytic gorge or isopropylmethylphosphonylation by the RP enantiomer of sarin promotes a 10-fold increase in homodimer dissociation. We also demonstrate the dissociation of organophosphate (OP)-conjugated dimers is reversed by structurally diverse oximes 2PAM, HI6, or RS194B, as demonstrated by SAXS of diethylphosphoryl-hAChE. However, binding of oximes to the native ligand-free hAChE, binding of high-affinity reversible ligands, or formation of an SP-sarin-hAChE conjugate had no effect on homodimerization. Dissociation monitored by time-resolved SAXS occurs in milliseconds, consistent with rates of hAChE covalent inhibition. OP-induced dissociation was not observed in the SAXS profiles of the double-mutant Y337A/F338A, where the active center gorge volume is larger than in wildtype hAChE. These observations suggest a key role of the tightly packed acyl pocket in allosterically triggered OP-induced dimer dissociation, with the potential for local reduction of acetylcholine-hydrolytic power in situ. Computational models predict allosteric correlated motions extending from the acyl pocket toward the four-helix bundle dimerization interface 25 Å away.

In silico molecular docking analysis for potential anti-Alzheimer's compounds from the methanolic leaf extract of Erythroxylum monogynum using Gas chromatography–mass spectrometry

BackgroundAlzheimer's disease is the major cause of dementia by two main factors includes an accumulation of acetylcholinesterase enzyme at cholinergic synapse and deposition of β-amyloid protein at neurofibrillary tangles. The present investigation explores the binding affinities of phytoconstituents present in the methanolic leaf extract of Erytrhroxylum monogynum identified by gas chromatography-mass spectrometry against selected targets, i.e., β-amyloid and acetylcholinesterase. ObjectivesThe main objective of present study was to explore anti-Alzheimer's potential of phytoconstituents from methanolic leaf extract of Erytrhroxylum monogynum. MethodsErytrhroxylum monogynum leaf material was subjected to Soxhlet extraction by three different solvents, namely n-hexane, chloroform and methanol. The methanolic leaf extract was subjected to Gas chromatography–mass spectrometric analysis for identification of novel phytoconstituents and chromatogram revealed the presence of 45 novel phytoconstituents. These phytoconstituents were not reported earlier from any part of this plant material. These phytoconstituents were explored for their anti-Alzheimer’s potential by iGEMDOCK software against selected targets, namely recombinant human acetylcholinesterase (protein data bank ID: 3LII) and β-amyloid (protein data bank ID: 2LMN). ResultsFrom the results of docking analysis, the top five phytoconstituents with the highest binding affinity towards the selected targets were further subjected to ADMET prediction by in silico admetSAR web portal. ConclusionsMolecular docking analysis revealed the presence of 7 phytoconstituents are having the highest binding affinity towards the selected targets when compared to their respective standard compounds namely 9, 12-octa-decadienoic acid, methyl ester, (E, E); octadecanoic acid, methyl ester; hexadecanoic acid, 2-hydroxy-1-(hydroxymethyl) ethyl ester; 3, 6-ditigloyloxy-7-hydroxytropane; 3, 7,11, 15-tetramethyl-2-hexa-decen-1-ol; neophytadiene and phytol. The lead hits were further subjected to LigPlot analysis to understand their intermolecular interactions. Thus the result collectively obtained from the in silico studies using computational approaches may become prospective novel lead compounds against the selected targets of Alzheimer's disease.

Synthesis of New Biscoumarin Derivatives, In Vitro Cholinesterase Inhibition, Molecular Modelling and Antiproliferative Effect in A549 Human Lung Carcinoma Cells.

A series of novel C4-C7-tethered biscoumarin derivatives (12a–e) linked through piperazine moiety was designed, synthesized, and evaluated biological/therapeutic potential. Biscoumarin 12d was found to be the most effective inhibitor of both acetylcholinesterase (AChE, IC50 = 6.30 µM) and butyrylcholinesterase (BChE, IC50 = 49 µM). Detailed molecular modelling studies compared the accommodation of ensaculin (well-established coumarin derivative tested in phase I of clinical trials) and 12d in the human recombinant AChE (hAChE) active site. The ability of novel compounds to cross the blood–brain barrier (BBB) was predicted with a positive outcome for compound 12e. The antiproliferative effects of newly synthesized biscoumarin derivatives were tested in vitro on human lung carcinoma cell line (A549) and normal colon fibroblast cell line (CCD-18Co). The effect of derivatives on cell proliferation was evaluated by MTT assay, quantification of cell numbers and viability, colony-forming assay, analysis of cell cycle distribution and mitotic activity. Intracellular localization of used derivatives in A549 cells was confirmed by confocal microscopy. Derivatives 12d and 12e showed significant antiproliferative activity in A549 cancer cells without a significant effect on normal CCD-18Co cells. The inhibition of hAChE/human recombinant BChE (hBChE), the antiproliferative activity on cancer cells, and the ability to cross the BBB suggest the high potential of biscoumarin derivatives. Beside the treatment of cancer, 12e might be applicable against disorders such as schizophrenia, and 12d could serve future development as therapeutic agents in the prevention and/or treatment of Alzheimer’s disease.

High performance liquid chromatographic assays with UV-detection for evaluation of inhibitors of acetylcholinesterase and butyrylcholinesterase

Acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) are considered as viable targets in the treatment of Alzheimer’s disease and other dementias. However, since clinically used AChE or dual AChE/BuChE inhibitors only provide some symptomatic treatment and lose their therapeutic effectiveness over time, in the last years an intensive search for multi-target compounds has started, which address additional targets besides AChE and BuChE, like endocannabinoid degrading enzymes. For the evaluation of the AChE and BuChE inhibitory potency of the test compounds in such drug development projects, usually the traditional Ellman’s method is used. Since this method has some analytical drawbacks, we have developed alternative robust HPLC/UV based assays using pyridin-2-ylmethyl acetate as substrate for AChE and benzoylcholine for BuChE. The enzyme products pyridin-2-ylmethanol and benzoic acid, respectively, were determined by reversed phase HPLC adding the ion pair reagent sodium octane-1-sulfonate to the mobile phase in case to the polar pyridine derivative. AChE from electric eel, human recombinant AChE and BuChE from equine serum were employed as enzymes. For method validation, the IC50-values of the known AChE and BuChE inhibitors physostigmine, rivastigmine and tacrine were measured. The obtained data were within the very wide range of the IC50-values given in the literature for these compounds.

Design and synthesis of novel coumarin derivatives as potential acetylcholinesterase inhibitors for Alzheimer's disease

Twenty novel 7-benzyloxycoumarin based compounds were synthesized with a variety of bioactive chemical fragments. The synthesized compounds showed remarkable acetylcholinesterase (AChE) inhibitory activity. In vitro assay revealed that compounds 7-benzyloxy-4-{[(4-phenylthiazol-2(3H)-ylidene)hydrazono]methyl}-2H-chromen-2-one (5b, IC50= 0.451μM), 7-benzyloxy-4-({[4-(4-methoxyphenyl)thiazol-2(3H)-ylidene]hydrazono}methyl)-2H-chromen-2-one (5d, IC50= 0.625μM), 5-amino-1-[2-(7-benzyloxy-2-oxo-2H-chromen-4-yl)acetyl]-1H-pyrazole-4-carbonitrile (13c, IC50= 0.466μM), 2-(7-benzyloxy-2-oxo-2H-chromen-4-yl)-N-(2-methylimino-4-phenylthiazol-3(2H)-yl)acetamide (16a, IC50= 0.500μM) and 2-(7-benzyloxy-2-oxo-2H-chromen-4-yl)-N-[4-(4-methoxyphenyl)-2-methyliminothiazol-3(2H)-yl]acetamide (16b, IC50= 0.590μM) exhibited promising AChE inhibitory activity even better than donepezil (IC50= 0.711μM). Kinetic study for compound 5b implied mixed type inhibitor which could bind peripheral anionic site (PAS) and catalytic active site (CAS) of AChE enzyme. In addition, in vivo evaluation of compounds 5b, 13c and 16a confirmed significant memory improvement in scopolamine-induced impairment model in tested mice. Furthermore, in silico studies were performed on the synthesized compounds which included molecular docking study at the active site of recombinant human acetylcholinesterase enzyme (rhAChE) as well as prediction of ADMET and other physicochemical parameters. A correlation between the docking results and IC50 of tested compounds was routinely observed and shared similar binding pattern to the co-crystallized ligand donepezil.

Synthesis of novel β-lactams: Antioxidant activity, acetylcholinesterase inhibition and computational studies

A convenient synthesis of some novel β-lactam derivatives with interesting pharmacological activities was described. Some of the synthesized compounds exhibited excellent antioxidant activity and showed acetylcholinesterase inhibition. Theoretical studies were carried out on the most potent compounds 5a and 5b to compare their potential interaction with crystal structure of recombinant human acetylcholinesterase in complex with Donepezil (PDB ID: 4EY7) and binary complex of native hAChE with Donepezil (PDBID:6O4W). The comprehensive theoretical and experimental mechanical studies of compounds 5b were compatible with its FT-IR, 1H NMR,13C NMR and Mass spectral data. The optimized molecular structure and the harmonic vibrational frequencies were examined DFT/B3LYP/6–31G(d) and Hartree-Fock HF/6–31G(d) energies and the difference in bond length and energies between compounds 5a and 5b was confirmed via theoretical studies.

[Mechanism of the Long-lasting Potentiating Effect of Distigmine on Urinary Bladder Motility].

Distigmine bromide (distigmine) is a carbamate cholinesterase (ChE) inhibitor, which is mainly used for the treatment of myasthenia gravis. Distigmine is also used in Japan for the treatment for underactive bladder and glaucoma. The effectiveness of distigmine for underactive bladder treatment has been confirmed by many clinical reports, and this effect is thought to be caused by potentiating urinary bladder smooth muscle contraction due to inhibition of acetylcholine degradation during micturition. However, the pharmacological effects of distigmine on urinary bladder smooth muscle have not been well studied. The most distinctive pharmacological feature of distigmine is that it shows long-lasting effects than other ChE inhibitors; however, few studies have investigated the persistence of the enhancing effect of distigmine on the contractile function of urinary bladder smooth muscle. Moreover, this mechanism remains unclear. In this review, we present our findings on the mechanism of the potentiating effect of distigmine on isolated guinea pig urinary bladder smooth muscle contraction. We also discuss the long-lasting potentiating effect of distigmine on urinary bladder motility and the mechanism of these effects using guinea pig urinary bladder smooth muscle in vivo and in vitro. In addition, we present our investigations on the long-lasting mechanism of distigmine using recombinant human acetylcholinesterase.

Pyridinium-2-carbaldoximes with quinolinium carboxamide moiety are simultaneous reactivators of acetylcholinesterase and butyrylcholinesterase inhibited by nerve agent surrogates

The pyridinium-2-carbaldoximes with quinolinium carboxamide moiety were designed and synthesised as cholinesterase reactivators. The prepared compounds showed intermediate-to-high inhibition of both cholinesterases when compared to standard oximes. Their reactivation ability was evaluated in vitro on human recombinant acetylcholinesterase (hrAChE) and human recombinant butyrylcholinesterase (hrBChE) inhibited by nerve agent surrogates (NIMP, NEMP, and NEDPA) or paraoxon. In the reactivation screening, one compound was able to reactivate hrAChE inhibited by all used organophosphates and two novel compounds were able to reactivate NIMP/NEMP-hrBChE. The reactivation kinetics revealed compound 11 that proved to be excellent reactivator of paraoxon-hrAChE better to obidoxime and showed increased reactivation of NIMP/NEMP-hrBChE, although worse to obidoxime. The molecular interactions of studied reactivators were further identified by in silico calculations. Molecular modelling results revealed the importance of creation of the pre-reactivation complex that could lead to better reactivation of both cholinesterases together with reducing particular interactions for lower intrinsic inhibition by the oxime.

Design, synthesis and biological evaluation of triazole-oxadiazole conjugates for the management of cognitive dysfunction

Acetylcholinesterase has been a promising target for the development of putative therapeutics against cognitive decline. The deleterious effect of oxidative stress on the learning and memory paradigms of an individual has also been well documented. In view of this, the present study demonstrates the design, synthesis and pharmacological evaluation of triazole-oxadiazole conjugates. Eighteen novel hybrids (6–23) have been synthesised by employing suitable synthetic procedures and characterized by various spectral and elemental techniques. Further these synthesised compounds were evaluated against behavioural alterations using step down passive avoidance and escape learning protocol at a dose of 0.5 mg/kg with reference to the standard, donepezil. All the synthesised compounds were evaluated for their in vitro acetylcholinesterase (AChE) inhibition at five different concentrations using mice brain homogenate as the source of the enzyme. Biochemical estimation of markers of oxidative stress (lipid peroxidation, superoxide dismutase, glutathione and catalase) has also been carried out to assess the role of synthesised molecules on the oxidative damage induced by scopolamine. The compounds 13, 17 and 23 displayed appreciable activity towards acetylcholinesterase inhibition. These compounds also decreased scopolamine induced oxidative stress, thus serving as promising leads for the amelioration of oxidative stress induced cognitive decline. The molecular docking study performed to predict the binding mode of the compounds also suggested that these compounds bind appreciably to the amino acids present in the active site of the recombinant human acetylcholinesterase (rhAChE). The results indicated that these compounds could be further traversed as inhibitors of AChE and oxidative stress for the treatment of cognitive dysfunction.