Reversible Acetylcholinesterase Inhibitor Research Articles

3D-QSAR studies of some reversible Acetyl cholinesterase inhibitors based on CoMFA and ligand protein interaction fingerprints using PC-LS-SVM and PLS-LS-SVM

A great challenge in medicinal chemistry is to develop different methods for structural design based on the pattern of the previously synthesized compounds. In this study two different QSAR methods were established and compared for a series of piperidine acetylcholinesterase inhibitors. In one novel approach, PC-LS-SVM and PLS-LS-SVM was used for modeling 3D interaction descriptors, and in the other method the same nonlinear techniques were used to build QSAR equations based on field descriptors. Different validation methods were used to evaluate the models and the results revealed the more applicability and predictive ability of the model generated by field descriptors (Q2LOO-CV=1, R2ext=0.97). External validation criteria revealed that both methods can be used in generating reasonable QSAR models. It was concluded that due to ability of interaction descriptors in prediction of binding mode, using this approach can be implemented in future 3D-QSAR softwares.

Long-term administration of pyridostigmine attenuates pressure overload-induced cardiac hypertrophy by inhibiting calcineurin signalling.

Cardiac hypertrophy is associated with autonomic imbalance, characterized by enhanced sympathetic activity and withdrawal of parasympathetic control. Increased parasympathetic function improves ventricular performance. However, whether pyridostigmine, a reversible acetylcholinesterase inhibitor, can offset cardiac hypertrophy induced by pressure overload remains unclear. Hence, this study aimed to determine whether pyridostigmine can ameliorate pressure overload‐induced cardiac hypertrophy and identify the underlying mechanisms. Rats were subjected to either sham or constriction of abdominal aorta surgery and treated with or without pyridostigmine for 8 weeks. Vagal activity and cardiac function were determined using PowerLab. Cardiac hypertrophy was evaluated using various histological stains. Protein markers for cardiac hypertrophy were quantitated by Western blot and immunoprecipitation. Pressure overload resulted in a marked reduction in vagal discharge and a profound increase in cardiac hypertrophy index and cardiac dysfunction. Pyridostigmine increased the acetylcholine levels by inhibiting acetylcholinesterase in rats with pressure overload. Pyridostigmine significantly attenuated cardiac hypertrophy based on reduction in left ventricular weight/body weight, suppression of the levels of atrial natriuretic peptide, brain natriuretic peptide and β‐myosin heavy chain, and a reduction in cardiac fibrosis. These effects were accompanied by marked improvement of cardiac function. Additionally, pyridostigmine inhibited the CaN/NFAT3/GATA4 pathway and suppressed Orai1/STIM1 complex formation. In conclusion, pressure overload resulted in cardiac hypertrophy, cardiac dysfunction and a significant reduction in vagal discharge. Pyridostigmine attenuated cardiac hypertrophy and improved cardiac function, which was related to improved cholinergic transmission efficiency (decreased acetylcholinesterase and increased acetylcholine), inhibition of the CaN/NFAT3/GATA4 pathway and suppression of the interaction of Orai1/STIM1.

The influence of modulators of acetylcholinesterase on the resistance of mice against soman and on the effectiveness of antidotal treatment of soman poisoning in mice

The potency of one reversible inhibitor of acetylcholinesterase (6-chlorotacrine), one reactivator of acetycholinesterase (K027) and their combination to increase the resistance of mice against soman and the efficacy of antidotal treatment of soman-poisoned mice was evaluated. While 6-chlorotacrine was able to markedly protect mice against acute toxicity of soman and the pharmacological pretreatment with 6-chlorotacrine increased the efficacy of antidotal treatment (the oxime HI-6 in combination with atropine) of soman-poisoned mice more than two times, the bispyridinium oxime K027 did not protect mice from acute toxicity of soman, however, the pharmacological pretreatment with this compound was able to markedly increase the efficacy of antidotal treatment of soman-poisoned mice. On the other hand, the combination of both modulators of acetylcholinesterase did not increase the prophylactic efficacy of 6-chlorotacrine alone. These findings demonstrate that pharmacological pretreatment of soman-poisoned mice can be promising and useful in the case of administration of 6-chlorotacrine while the administration of the oxime K027 did not bring any additional benefit when combined with 6-chlorotacrine.

Preliminary Study of the Possible Benefit of the Reversible Acetylcholinesterase Inhibitor Donepezil for Cognitive Impairment Associated with Corticorticosteroid Treatment for Presumptive Neurosarcoidsosis with a Lesion in the Right Basal Ganglia and Thalamus

Preliminary Study of the Possible Benefit of the Reversible Acetylcholinesterase Inhibitor Donepezil for Cognitive Impairment Associated with Corticorticosteroid Treatment for Presumptive Neurosarcoidsosis with a Lesion in the Right Basal Ganglia and Thalamus

Treatment with Sildenafil and Donepezil Improves Angiogenesis in Experimentally Induced Critical Limb Ischemia.

Objectives. In this study, we aimed to demonstrate the role of sildenafil (an antagonist of phosphodiesterase type 5 (PDE-5)) and donepezil (a specific and reversible inhibitor of acetylcholinesterase (Ach)) in increasing ischemia-induced angiogenesis. Method. Critical limb ischemia was induced by ligation of the common femoral artery followed by ligation of the common iliac artery. The operated animals were divided into 3 groups: receiving sildenafil, receiving donepezil, and surgery alone; the contralateral lower limb was used as a negative control. The results were controlled based on clinical score and Doppler ultrasound. Gastrocnemius muscle samples were taken from all animals, both from the ischemic and nonischemic limb and were used for histopathological and immunohistochemical examination for the evaluation of the number of nuclei/field, endothelial cells (CD31), dividing cells (Ki-67), and vascular endothelial growth factor (VEGFR-3). Results. An increasing tendency of the number of nuclei/field with time was observed both in the case of sildenafil and donepezil treatment. The formation of new capillaries (the angiogenesis process) was more strongly influenced by donepezil treatment compared to sildenafil or no treatment. This treatment significantly influenced the capillary/fiber ratio, which was increased compared to untreated ligated animals. Sildenafil treatment led to a gradual increase in the number of dividing cells, which was significantly compared to the negative control group and compared to the ligation control group. The same effect (increase in the number of Ki-67 positive cells) was more obvious in the case of donepezil treatment. Conclusion. Donepezil treatment has a better effect in ligation-induced ischemia compared to sildenafil, promoting angiogenesis in the first place, and also arteriogenesis.

The Evaluation of Benefit of Newly Prepared Reversible Inhibitors of Acetylcholinesterase and Commonly Used Pyridostigmine as Pharmacological Pretreatment of Soman-Poisoned Mice.

The ability of four newly prepared reversible inhibitors of acetylcholinesterase (6-chlorotacrine, 7-phenoxytacrine, compounds 1 and 2) and currently used carbamate pyridostigmine to increase the resistance of mice against soman and the efficacy of antidotal treatment of soman-poisoned mice was evaluated. The evaluation of the effect of pharmacological pretreatment is based on the identification of changes of soman-induced toxicity that was evaluated by the assessment of its LD50 value and its 95% confidence limit using probitlogarithmical analysis of death occurring within 24 h after administration of soman. 6-chlorotacrine was only able to markedly protect mice against acute toxicity of soman. In addition, the pharmacological pretreatment with 6-chlorotacrine or compound 2 was able to increase the efficacy of antidotal treatment (the oxime HI-6 in combination with atropine) of soman-poisoned mice. The other newly prepared reversible inhibitors of acetylcholinesterase (7-phenoxytacrine, compound 1) as well as commonly used pyridostigmine did not influence the efficacy of antidotal treatment. These findings demonstrate that pharmacological pretreatment of somanpoisoned mice can be promising and useful in the case of administration of 6-chlorotacrine and partly compound 2.

Dose Dependent Prophylactic Efficacy of 6-Chlorotacrine in Soman-Poisoned Mice.

The influence of the dose on the ability of promising newly prepared reversible inhibitor of acetylcholinesterase (6-chlorotacrine) to increase the resistance of mice against soman and the efficacy of antidotal treatment of soman-poisoned mice was evaluated. The evaluation of the effect of pharmacological pretreatment is based on the identification of changes of soman-induced toxicity that was evaluated by the assessment of its LD50 value and its 95% confidence limit using probit-logarithmical analysis of death occurring within 24 hrs after administration of soman. The dose of 6-chlorotacrine significantly influences the prophylactic efficacy of 6-chlorotacrine. Its highest dose was only able to significantly protect mice against acute toxicity of soman and increase the efficacy of antidotal treatment (atropine in combination with the oxime HI-6) of soman-poisoned mice. In addition, the highest dose of 6-chlorotacrine was significantly more effective to protect mice from soman poisoning than its lowest dose. These findings demonstrate the important influence of the dose of 6-chlorotacine on its prophylactic efficacy in the case of pharmacological pretreatment of soman poisoning in mice.

Time Course, Behavioral Safety, and Protective Efficacy of Centrally Active Reversible Acetylcholinesterase Inhibitors in Cynomolgus Macaques.

Galantamine hydrobromide and (-)huperzine A, centrally active reversible acetylcholinesterase inhibitors, are potentially superior to the current standard, pyridostigmine bromide, as a pretreatment for organophosphorus chemical warfare nerve agent intoxication. Galantamine, huperzine, and pyridostigmine were compared for time course of acetylcholinesterase inhibition in 12 cynomolgus macaques. Although both galantamine and huperzine shared a similar time course profile for acetylcholinesterase inhibition, huperzine was 88 times more potent than galantamine. The dose for 50% acetylcholinesterase inhibition (ID50) was 4.1ug/kg for huperzine, 362ug/kg for galantamine, and 30.9ug/kg for pyridostigmine. In a safety assessment, galantamine, huperzine, and pyridostigmine were examined using an operant time-estimation task. Huperzine and pyridostigmine were devoid of behavioral toxicity, whereas galantamine was behaviorally toxic at doses producing peak acetylcholinesterase inhibition of about 50% and higher. Following pretreatment with galantamine, huperzine or pyridostigmine, monkeys were challenged with the median lethal dose of soman at the time of peak acetylcholinesterase inhibition and evaluated for overt signs of soman toxicity (cholinergic crisis, convulsions). Both huperzine and galantamine were equally effective at preventing overt signs of soman toxicity, but neither drug was capable of preventing soman-induced neurobehavioral disruption. In contrast, three of four pyridostigmine-pretreated animals exposed to soman exhibited convulsions and required therapy. Full functional recovery required 3-16days. The degree of acetylcholinesterase inhibition was lower for pyridostigmine, but rates of recovery of acetylcholinesterase activity following soman challenge were comparable for all drug pretreatments. Huperzine may be the more promising centrally active reversible acetylcholinesterase inhibitor due to its greater potency and superior safety profile.

Huperzine A Provides Robust and Sustained Protection against Induced Seizures in Scn1a Mutant Mice.

De novo loss-of-function mutations in the voltage-gated sodium channel (VGSC) SCN1A (encoding Nav1.1) are the main cause of Dravet syndrome (DS), a catastrophic early-life encephalopathy associated with prolonged and recurrent early-life febrile seizures (FSs), refractory afebrile epilepsy, cognitive and behavioral deficits, and a 15–20% mortality rate. SCN1A mutations also lead to genetic epilepsy with febrile seizures plus (GEFS+), which is an inherited disorder characterized by early-life FSs and the development of a range of adult epilepsy subtypes. Current antiepileptic drugs often fail to protect against the severe seizures and behavioral and cognitive deficits found in patients with SCN1A mutations. To address the need for more efficacious treatments for SCN1A-derived epilepsies, we evaluated the therapeutic potential of Huperzine A, a naturally occurring reversible acetylcholinesterase inhibitor. In CF1 mice, Hup A (0.56 or 1 mg/kg) was found to confer protection against 6 Hz-, pentylenetetrazole (PTZ)-, and maximal electroshock (MES)-induced seizures. Robust protection against 6 Hz-, MES-, and hyperthermia-induced seizures was also achieved following Hup A administration in mouse models of DS (Scn1a+/−) and GEFS+ (Scn1aRH/+). Furthermore, Hup A-mediated seizure protection was sustained during 3 weeks of daily injections in Scn1aRH/+ mutants. Finally, we determined that muscarinic and GABAA receptors play a role in Hup A-mediated seizure protection. These findings indicate that Hup A might provide a novel therapeutic strategy for increasing seizure resistance in DS and GEFS+, and more broadly, in other forms of refractory epilepsy.

Reversal of cardiac vagal effects of physostigmine by adjunctive muscarinic blockade

Pre-treatment with reversible acetylcholinesterase (AChE) inhibitors is an effective strategy for reducing lethality following organophosphate nerve agent exposure. AChE inhibition may have unwanted cardiac side effects, which could be negated by adjunctive anti-cholinergic therapy. The aims of the present study were to examine the concentration-dependent effects of physostigmine on cardiac responses to vagus nerve stimulation (VNS), to test whether adjunctive treatment with hyoscine can reverse these effects and to assess the functional interaction and electrophysiological consequences of a combined pre-treatment. Studies were performed in an isolated innervated rabbit heart preparation. The reduction in heart rate with VNS was augmented by physostigmine (1–1000nmol/L), in a concentration-dependent manner – with an EC50 of 19nmol/L. Hyoscine was shown to be effective at blocking the cardiac responses to VNS with an IC50 of 11nmol/L. With concomitant perfusion of physostigmine, the concentration-response curve for hyoscine was shifted downward and to the right, increasing the concentration of hyoscine required to normalise (to control values) the effects of physostigmine on heart rate. At the lowest concentration of hyoscine examined (1nmol/L) a modest potentiation of heart rate response to VNS (+15±3%) was observed. We found no evidence of cardiac dysfunction or severe electrophysiological abnormalities with either physostigmine or hyoscine alone, or as a combined drug-therapy. The main finding of this study is that hyoscine, at concentrations greater than 10−8M, is effective at reversing the functional effects of physostigmine on the heart. However, low-concentrations of hyoscine may augment cardiac parasympathetic control.

Zebrafish is a predictive model for identifying compounds that protect against brain toxicity in severe acute organophosphorus intoxication

Acute organophosphorus (OP) intoxication is a worldwide clinical and public health problem. In addition to cholinergic crisis, neurodegeneration and brain damage are hallmarks of the severe form of this toxidrome. Recently, we generated a chemical model of severe acute OP intoxication in zebrafish that is characterized by altered head morphology and brain degeneration. The pathophysiological pathways resulting in brain toxicity in this model are similar to those described in humans. The aim of this study was to assess the predictive power of this zebrafish model by testing the effect of a panel of drugs that provide protection in mammalian models. The selected drugs included “standard therapy” drugs (atropine and pralidoxime), reversible acetylcholinesterase inhibitors (huperzine A, galantamine, physostigmine and pyridostigmine), N-methyl-d-aspartate (NMDA) receptor antagonists (MK-801 and memantine), dual-function NMDA receptor and acetylcholine receptor antagonists (caramiphen and benactyzine) and anti-inflammatory drugs (dexamethasone and ibuprofen). The effects of these drugs on zebrafish survival and the prevalence of abnormal head morphology in the larvae exposed to 4 µM chlorpyrifos oxon [1 × median lethal concentration (LC50)] were determined. Moreover, the neuroprotective effects of pralidoxime, memantine, caramiphen and dexamethasone at the gross morphological level were confirmed by histopathological and transcriptional analyses. Our results demonstrated that the zebrafish model for severe acute OP intoxication has a high predictive value and can be used to identify new compounds that provide neuroprotection against severe acute OP intoxication.

Neuroprotective effects of Danggui-Jakyak-San on rat stroke model through antioxidant/antiapoptotic pathway

Ethnopharmacological relevanceDangui-Jakyak-San (DJ) is a traditional Korean medicinal polyherb, prescribed typically in patients with insufficient blood supply in Eastern Asia. The DJ also has been reported to have neuroprotective effects in vitro and in vivo studies. Aim of studyThe therapeutic potential of DJ was examined in stroke rat model, in comparison with donepezil, a reversible acetylcholinesterase inhibitor. Materials and methodsIschemic stroke rat model was induced by surgery of permanent occlusion of middle cerebral artery (pMCAO). The model was orally administered with distilled water (pMCAO control), donepezil at 10mg/kg (Donepezil) and DJ at 200, 100 and 50mg/kg (DJ 200, DJ 100 and DJ 50, respectively). Sham had the same surgery excepting for the pMCAO, and it was administered with distilled water (sham control). ResultsAfter the administration for 28 days, the groups of DJ exhibited dose-dependent reduction in infarct/defect volumes with improvement in sensorimotor and cognitive motor function, comparing to pMCAO control. The DJ treatments seemed to enhance antiapoptotic and antioxidant effects; increases in antiapoptotic expressions (STAT3 and Pim-1) and decreases in lipid peroxidation (MDA) together with increases in contents of endogenous antioxidant (GSH) and activities of antioxidant enzymes (catalase and SOD). The histopathological analyses revealed significant reduction in neuronal apoptosis (caspase-3 and PARP) and neuronal degradation with atrophy and degeneration, in the DJ treatments. Furthermore, the oxidative stresses (nitrotyrosine as an iNOS factor and 4-HNE as a marker of lipid peroxidation) were observed mild. Although the similar neuroprotective effects were observed, the body weight loss was scarcely alleviated in Donepezil comparing to pMCAO control. ConclusionThese suggest that DJ ameliorate the neurological dysfunction of cerebral ischemia through augmentation of antioxidant defense system and up-regulation of STAT3 and Pim-1.

Kinetic analysis of interactions of amodiaquine with human cholinesterases and organophosphorus compounds.

Standard therapy of poisoning by organophosphorus compounds (OP) is a combined administration of an anti-muscarinic drug (e.g. atropine) and an oxime as reactivator of inhibited acetylcholinesterase (AChE). Limited efficacy of clinically used oximes against a variety of OPs was shown in numerous studies, calling for research on novel reactivators of OP-inhibited AChE. Recently, reactivation of OP-inhibited AChE by the antimalarial drug amodiaquine was reported. In the present study, amodiaquine and its interactions with human cholinesterases in presence or absence of OP nerve agents was investigated in vitro. Thereby, reversible inhibition of human cholinesterases by amodiaquine (AChE ≫ BChE) was observed. Additionally, a mixed competitive-non-competitive inhibition type of amodiaquine with human AChE was determined. Slow and partial reactivation of sarin-, cyclosarin- and VX-inhibited cholinesterases by amodiaquine was recorded, amodiaquine failed to reactivate tabun-inhibited human cholinesterases. Amodiaquine, being a potent, reversible AChE inhibitor, was tested for its potential benefit as a pretreatment to prevent complete irreversible AChE inhibition by the nerve agent soman. Hereby, amodiaquine failed to prevent phosphonylation and resulted only in a slight increase of AChE activity after removal of amodiaquine and soman. At present the molecular mechanism of amodiaquine-induced reactivation of OP-inhibited AChE is not known, nevertheless amodiaquine could be considered as a template for the design of more potent non-oxime reactivators.

Acquired Localized Hypertrichosis Induced by Rivastigmine.

Hypertrichosis is the excessive hair growth in any area of the skin surface. Acquired localized hypertrichosis may be secondary to multiple causes and there is a secondary form due to several drugs, which is usually reversible with discontinuation of the causative agent. Rivastigmine is a reversible and competitive inhibitor of acetylcholinesterase and butyrylcholinesterase used for symptomatic treatment of Alzheimer dementia and Parkinson's disease. It has an adequate safety profile and cutaneous side effects are unusual. Irritant contact dermatitis, allergic dermatitis, baboon syndrome, and cutaneous rash due to rivastigmine have been reported. We report on a Caucasian 80-year-old male with personal history of Alzheimer's disease. The patient started therapy with oral rivastigmine one month prior to clinical presentation of localized hypertrichosis on both forearms. Norgalanthamine has been shown to promote hair growth activity via the proliferation of dermal papilla. Acetylcholinesterase inhibitors can induce hair growth.

High-Throughput Screening for Positive Allosteric Modulators Identified Potential Therapeutics against Acetylcholinesterase Inhibition

The current standard of care for treatment of organophosphate (OP) poisoning includes pretreatment with the weak reversible acetylcholinesterase (AChE) inhibitor pyridostigmine bromide. Because this drug is an AChE inhibitor, similar side effects exist as with OP poisoning. In an attempt to provide a therapeutic capable of mitigating AChE inhibition without such side effects, high-throughput screening was performed to identify a compound capable of increasing the catalytic activity of AChE. Herein, two such novel positive allosteric modulators (PAMs) of AChE are presented. These PAMs increase AChE activity threefold, but they fail to upshift the apparent IC50 of a variety of OPs. Further development and optimization of these compounds may lead to pre- and/or postexposure therapeutics with broad-spectrum efficacy against pesticide and nerve agent poisoning. In addition, they could be used to complement the current therapeutic standard of care to increase the activity of uninhibited AChE, potentially increasing the efficacy of current therapeutics in addition to altering the therapeutic window.

In silico analysis of binding of neurotoxic venom ligands with acetylcholinesterase for therapeutic use in treatment of Alzheimer's disease.

Acetylcholinesterases (AChE) are enzymes that function in hydrolyzing the neurotransmitter acetylcholine. Diminished levels of acetylcholine have been reported for various neurodegenerative diseases, especially Alzheimer's. Therefore, acetylcholinesterase inhibitors are being considered quite effective in treating these diseases. Fasciculin 2 is a toxin isolated from Eastern green mamba that had been reported as a reversible acetylcholinesterase inhibitor. In this study, we have reported the in silico analysis of venom toxins via various computational tools used for drug designing, to find out the protein-protein interaction of these toxins in complex with acetylcholinesterase enzyme. In total 15 toxins have been selected from the venoms of various species as ligand dataset, to study their binding interactions with the acetylcholinesterase enzyme.

Formulation and evaluation of transdermal patches of donepezil.

Donepezil (DNZ) is a centrally acting reversible acetyl cholinesterase inhibitor. The main therapeutic use of donepezil is in the treatment of Alzheimer's disease. The present research work pertains to the preparation of transdermal patches of donepezil with the objective to improve its patient compliance, therapeutic efficacy and to reduce the frequency of dosing and side effects as well as to avoid its extensive first pass metabolism. The recent patents on Rivastigmine (WO2013150542A2), Xanomeline (US5980933A) and Propentofylline (CA2255580A1) helped in selecting the drug and polymers. The transdermal patches were prepared using various polymers in combination with the plasticizer and penetration enhancers. The physicochemical parameters like folding endurance, thickness, drug content, content uniformity, moisture absorption, weight variation, and drug permeation studies of the optimized patches were studied. The system containing Eudragit S -100, Eudragit E -100 and HPMC as matrix forming agent and glycerine as plasticizer was the best formulation. The in vitro release data was treated with kinetic equations and it followed zero order release. The diffusion study was carried out using rat skin showed 89% drug was released within 72 hours. Tween-80 (0.83 % w/w) was found to be the best among all penetration enhancers. All the transdermal patches had the desired physical properties like tensile strength, folding endurance, flatness and water vapor transmission rate etc. The study concluded that that transdermal patch can extend the release of donepezil for many hours and also ensure enhanced bioavailability, further it also helps in avoiding the first pass effect.

Dose-limiting inhibition of acetylcholinesterase by ladostigil results from the rapid formation and fast hydrolysis of the drug–enzyme complex formed by its major metabolite, R-MCPAI

Ladostigil is a pseudo reversible inhibitor of acetylcholinesterase (AChE) that differs from other carbamates in that the maximal enzyme inhibition obtainable does not exceed 50–55%. This could explain the low incidence of cholinergic adverse effects induced by ladostigil in rats and human subjects. The major metabolite, R-MCPAI is believed to be responsible for AChE inhibition by ladostigil in vivo. Therefore we determined whether the ceiling in AChE inhibition resulted from a limit in the metabolism of ladostigil to R-MCPAI by liver microsomal enzymes, or from the kinetics of enzyme inhibition by R-MCPAI. Ladostigil reduces TNF-α in lipopolysaccharide-activated microglia. In vivo, it may also reduce pro-inflammatory cytokines by inhibiting AChE and increasing the action of ACh on macrophages and splenic lymphocytes. We also assessed the contribution of AChE inhibition in the spleen of LPS-injected mice to the anti-inflammatory effect of ladostigil. As in other species, AChE inhibition by ladostigil in spleen, brain and plasma did not exceed 50–55%. Since levels of R-MCPAI increased with increasing doses of ladostigil we concluded that there was no dose or rate limitation of metabolism. The kinetics of enzyme inhibition by R-MCPAI are characterized by a rapid formation of the drug–enzyme complex and fast hydrolysis which limits the attainable degree of AChE inhibition. Ladostigil and its metabolites (1–100nM) decreased TNF-α in lipopolysaccharide-activated macrophages. Ladostigil (5 and 10mg/kg) also reduced TNF-α in the spleen after injection of lipopolysaccharide in mice. However, AChE inhibition contributed to the anti-inflammatory effect only at a dose of 10mg/kg.

Effect of Organic Solvent Composition on Dissociation Constants of Some Reversible Acetylcholinesterase Inhibitors

Reversible acetylcholinesterase inhibitors are an important group of drug compounds that are used medicinally to treat Alzheimer's disease. In this study, dissociation constant values (pKa) of some reversible acetylcholinesterase inhibitors (donepezil, rivastigmine and galantamine) having different functional groups were determined in different percentages of acetonitrile (MeCN)-water and methanol (MeOH)-water binary mixtures using reversed phase liquid chromatography (RPLC) method. In this way, a complete description of the retention behavior of each solute in the space defined by the pH and organic modifier percentages variables was obtained. The linear relationships established between retention factors of the species and the polarity parameter of the mobile phase (ETN) was proved to predict accurately retention in liquid chromatography (LC) as a function of the acetonitrile and methanol content. In result, the estimated aqueous pKa values of studied basic compounds were assessed by comparing them with literature data.

The interaction of quaternary reversible acetylcholinesterase inhibitors with the nicotinic receptor.

Acetylcholinesterase inhibitors (AChEIs) are used in the treatment of myasthenia gravis (MG). We investigated the effects of AChEIs on peripheral nicotinic receptors (nAChR), which play a crucial role in the treatment of MG symptoms. The positive modulation of those receptors by AChE inhibitors could have an added value to the anti-AChE activity and might be useful in the therapy of MG. Furthermore, to estimate the potential drawbacks of the compounds, cytotoxicity has been assessed on various cell lines. The whole-cell mode of the patch-clamp method was employed. The experiments were performed on medulloblastoma/rhabdomyosarcoma cell line TE671 expressing human embryonic muscle-like receptor with subunits alpha2betagammadelta. The effect of the compounds on cell viability was measured by standard MTT assay (Sigma Aldrich) on ACHN (renal cell adenocarcinoma), HeLa (immortal cell line derived from a cervical carcinoma), HEPG2 (hepatocellular carcinoma) and BJ (skin fibroblasts) cell lines. No positive modulation by the tested AChE inhibitors was observed. Moreover, the compounds exhibited antagonistic activity on the peripheral nAChR. Standard drugs used in MG treatment were shown to be less potent inhibitors of muscle-type nAChR than the newly synthesized compounds. The new compounds showed very little effect on cell viability, and toxicities were comparable to standards. Newly synthesized AChEIs inhibited peripheral nAChR. Furthermore, the inhibition was higher than that of standards used for the treatment of MG. They could be used for the study of nAChR function, thanks to their high antagonizing potency and fast recovery of receptor activity after their removal. However, since no positive modulation was observed, the new compounds do not seem to be promising candidates for MG treatment, even though their cytotoxic effect was relatively low.