Rapid Hydrolysis Of Acetylcholine Research Articles

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

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

Decreased Serum Cholinesterase Activity- A Reliable Diagnostic Aid for Tuberculosis

Introduction: Siderophore, the low molecular weight ferric iron chelator, is secreted extracellularly by Mycobacterium tuberculosis, an obligate aerobe. The pathogenic mycobacteria need iron as co-factor for the extracellularly secreted enzyme Superoxide Dismutase (SOD) for its pathogenicity as well as it requires iron for its metabolic functions like reduction of oxygen for synthesis of Adenosine Triphosphate (ATP), etc. The termination of impulse conduction is endorsed by the rapid hydrolysis of Acetylcholine (ACh) by Acetylcholinesterase (AChE) in the central as well as peripheral nervous system (cholinergic pathway). The inhibitors to Cholinesterase (ChE) might lead to accumulation of ACh, hyper stimulation of nicotinic and muscarinic receptors and also disruption of neurotransmission. Possibility of an inhibitor substance for AChE in Tuberculosis (TB) patients interestingly correlates with the symptom of night sweating in those subjects. Aim: To assay the level of serum ChE in normal control, lung disease control and tubercular subjects;circumvent the serum ChE level as a diagnostic potential in TB at an early stage. Materials and Methods: The study was conducted on total 124 subjects, and were divided into three groups: Group 1: normal control (n=31), Group 2: lung disease control (n=31) and Group 3: patients suffering from TB {3A: pulmonary TB (n=31) and 3B: extrapulmonary TB (n=31)}. Serum ChE activity for all the subjects were measured according to the method of Hestrin S. Serum ChE level was assayed for group 3 subjects after additional one month’s anti-TB drug treatment and also for group 2 subjects after one month with usual treatment. The level of significance was assessed using Student’s t-test. Results: There was a significant inhibition of serum ChE activity in both pulmonary and extrapulmonary TB patients in comparison to that of in normal control as well as lung disease control subjects (p<0.01). With the anti-tubercular drug therapy for one month, there was significant recovery in the serum ChE activity in pulmonary as well as extrapulmonary tubercular subjects (p<0.01). Conclusion: It appears that the high level of hydroxamate type of siderophores (secreted by Mycobacterium tuberculosis for acquiring iron) might form ACh ferric hydroxamate complex binding more strongly with serum ChE resulting in inhibition of serum ChE activity in tubercular subjects. With anti-tubercular drug therapy, there was decrease in serum ACh ferric hydroxamate complex level resulting in recovery of serum ChE activity.

The multiple biological roles of the cholinesterases

It is tacitly assumed that the biological role of acetylcholinesterase is termination of synaptic transmission at cholinergic synapses. However, together with its structural homolog, butyrylcholinesterase, it is widely distributed both within and outside the nervous system, and, in many cases, the role of both enzymes remains obscure. The transient appearance of the cholinesterases in embryonic tissues is especially enigmatic. The two enzymes’ extra-synaptic roles, which are known as ‘non-classical’ roles, are the topic of this review. Strong evidence has been presented that AChE and BChE play morphogenetic roles in a variety of eukaryotic systems, and they do so either by acting as adhesion proteins, or as trophic factors. As trophic factors, one mode of action is to directly regulate morphogenesis, such as neurite outgrowth, by poorly understood mechanisms. The other mode is by regulating levels of acetylcholine, which acts as the direct trophic factor. Alternate substrates have been sought for the cholinesterases. Quite recently, it was shown that levels of the aggression hormone, ghrelin, which also controls appetite, are regulated by butyrylcholinesterase. The rapid hydrolysis of acetylcholine by acetylcholinesterase generates high local proton concentrations. The possible biophysical and biological consequences of this effect are discussed. The biological significance of the acetylcholinesterases secreted by parasitic nematodes is reviewed, and, finally, the involvement of acetylcholinesterase in apoptosis is considered.

Multienzyme chemiluminescent foldable biosensor for on-site detection of acetylcholinesterase inhibitors

The rapid hydrolysis of acetylcholine (ACh), one of the key neurotransmitters in the human body, by the enzyme acetylcholinesterase (AChE) is fundamental for the termination of ACh impulse transmission. Several chemicals, including organophosphorus (OP) pesticides, warfare agents and drugs, are AChE reversible or irreversible inhibitors, thus their rapid on-site detection is of primary importance. Here we report for the first time a chemiluminescence (CL) foldable paper-based biosensor for detection of AChE inhibitors. The biosensor exploits three coupled enzymatic reactions catalyzed by AChE, choline oxidase and horseradish peroxidase, leading to production of hydrogen peroxide, which is measured with an optimized luminol substrate. The origami approach allows to add reagents and trigger the sequential reactions in separate steps. A compact 3D-printed device including a mini dark box was created to enable smartphone detection. The CL foldable paper-based biosensor showed suitable for the rapid detection of OP pesticides in food matrices with a total assay time of 25 min. It is thus a rapid, low cost portable test suitable for point-of-need detection of chemicals inhibiting AChE.

Effect of some Plants and Pesticides on Acetylcholinesterase

The principal role of acetylcholinesterase (AChE)is the termination of nerve impulse transmission at the cholinergic synapses by rapid hydrolysis of acetylcholine (ACh). Inhibition of AChE serves as a strategy for the treatment of Alzheimer's Disease (AD). Several acetylcholinesterase inhibitors (AChEIs) are used for the symptomatic treatment of AD A potential source of AChE inhibitors is certainly provided by the abundance of plants in nature. The aim of this article is study the effect of some plants and pesticides on acetylcholinesterase. Several plants considered as a source of acetylcholinesterase inhibitors and pesticides special organophosphorus. Cholinesterase inhibitors are the only approved drugs for treating patients with mild to moderately severe Alzheimer's disease, a disorder associated with progressive degeneration of memory and cognitive function. The memory impairment in patients with Alzheimer's disease results from a deficit of cholinergic function in the brain. The most important changes observed in the brain are a decrease in cortical levels of the neurotransmitter acetylcholine and associated enzyme choline transferees. Acetylcholinesterase inhibitors can restore the level of acetylcholine by inhibiting acetylcholinesterase. Principal role of acetyl cholinesterase (AChE) is the termination of nerve impulse transmission at the cholinergic synapses by rapid hydrolysis of acetylcholine (ACh). Inhibition of AChE serves as a strategy for the treatment of Alzheimer's Disease (AD), senile dementia, ataxia, myasthenia gravis and Parkinson's disease (Kumar et al., 2011). There are a few synthetic medicines, e.g., tacrine, donepezil and the natural product-based rivastigmine for treatment of cognitive dysfunction and memory loss associated with AD. There are two types of cholinesterase, AChE and butyrylcholinestrase (BuChE). The AChE is found primarily in the blood and neural synapses. The BuChE is found primarily in the liver. The biggest difference between the two is the substrates. The AChE hydrolyzes acetylcholine (ACh) more quickly and BuChE hydrolyzes butyrylcholine (BuCh) more quickly. The BuCh is a synthetic compound used to distinguish AChE receptors from BuChE receptors. Many of the drugs that are available for treatment of AD target both AChE and BuChE but some are more (Mehta et al., 2012). These compounds have been reported to have their adverse effects including gastrointestinal disturbances and problems associated with bioavailability, which necessitates the interest in finding better AChE inhibitors from natural resources. In traditional practices numerous plants have been used to treat cognitive disorders, including neurodegenerative diseases and different neuron pharmacological disorders.

Active and peripheral anionic sites of acetylcholinesterase have differential modulation effects on cell proliferation, adhesion and neuritogenesis in the NG108-15 cell line

The classical enzymatic role of acetylcholinesterase (AChE) is to terminate impulse transmission at cholinergic synapses through rapid hydrolysis of acetylcholine (ACh). Inactivation of this enzyme's catalytic site is the primary mechanism of acute toxicity of OP insecticides (e.g. parathion, chlorpyrifos). There is now sufficient evidence to suggest that AChE has a neurotrophic function that may be altered by organophosphate (OP) exposure, resulting in defects of neuronal growth and development, though the clarification of the mechanisms involved require further in vitro investigation. In the present study, the mouse neuroblastoma×rat glioma hybrid NG108-15 cell line was used to investigate the differential effects between inhibition of the catalytic site and peripheral anionic site (PAS) of acetylcholinesterase (AChE) on cell adhesion, proliferation and neuritogenesis, in the presence and absence of human red blood cell (hRBC) AChE (ED3.1.1.7). AChE active-site inhibitor paraoxon (PO; 0.1–1.0μM), when added to NG108-15 cells grown on AChE-coated plates, had no effect on cell proliferation, but exerted a significant reduction in strongly adherent viable cells accompanied by mostly short process formations, with 18% of cells considered to be neuritogenic, similar to that observed on uncoated plates. In contrast, PO had no significant effect on cell adhesion and proliferation of NG108-15 cells on uncoated plates. The PAS-ligand thioflavin-T (Th-T; 0.5–25μM), however, decreased cell adhesion and proliferation, on both uncoated and ACh-E coated plates, with less magnitude on AChE-coated plates. Taken together, these results suggest that strong cell adherence and neuritogenesis are sensitive to PO in this cell culture model, with no impact on proliferation, in the presence of membrane bound AChE-coating, while there is no sensitivity to PO on uncoated plates. On the other hand, binding of Th-T directly to the PAS affects both cell adherence and proliferation, with less magnitude in the presence of membrane-bound AChE. The current study indicates that PO is deleterious in neural development during critical periods of strong cell adhesion and differentiation, interfering with AChE trophic function.

An in silico approach for the identification of inhibitors against Acetylcholinesterase

Acetylcholinesterase (AChE) is one of the crucial enzymes involved in nerve response and function. The loss of cholinergic activity is mainly characterized by the rapid hydrolysis of acetylcholine by AChE, which leads to a neurodegenerative disorder called Alzheimer’s disease (AD). Donepezil, an efficient inhibitor of AChE, is widely used in the therapy of AD. The compounds which show above 50% similarity to donepezil were collected from ZINC database. Virtual screening and Induced Fit Docking analysis of these compounds against AChE were carried out to explore the compounds with better binding affinity than donepezil. ADME profile was carried out to identify the compounds having potential to be a drug. The biological activity spectrum of compounds was determined using a program called PASS. Binding potential of the selected compounds toward BChE was also analyzed. In silico analysis proved that compounds such as ZINC13802320, ZINC11709541, ZINC08750211, ZINC02040474, and ZINC49718337 can be used as a lead compounds for the development drugs against AD.

Analysis of Genetic Polymorphisms in Acetylcholinesterase as Reflected in Different Populations

Acetylcholinesterase (AChE) plays a crucial physiological role in termination of impulse transmission at cholinergic synapses through rapid hydrolysis of acetylcholine. In addition, it was implicated in amyloid plaque formation, a hallmark of Alzheimer's disease (AD), and most of the drugs used in AD treatment are AChE inhibitors. Thus ACHE is an obvious candidate gene for pharmacogenetic study of AD treatment. However, AChE is a highly conserved molecule, and only a few naturally occurring genetic polymorphisms have been reported in the human gene. The goals of this study were to make a systematic effort to identify natural single nucleotide polymorphisms (SNPs) in the human ACHE gene, and to reveal their population specific architecture. To this end, the genomic coding sequences for AChE of 96 unrelated control individuals from three distinct ethnic groups, African Americans, Ashkenazi Jews and Israeli Arabs, were analyzed. Thirteen ACHE SNPs were identified, ten of which are newly described, and five of which should produce amino-acid substitutions (Arg34Gln, Gly57Arg, Glu344Gly, His353Asn and Pro592Arg). Population frequencies of 11 of the 13 SNPs were established in four different populations, African Americans, Ashkenazi Jews, Sephardic Jews and Israeli Arabs; 17 haplotypes and 5 ethno-specific alleles were identified, and a cladogram of ACHE haplotypes was constructed. Among the SNPs resulting in an amino-acid substitution, three are within the mature protein, mapping on its external surface; they are thus unlikely to affect its catalytic properties, yet could have antigenic consequences or affect putative protein-protein interactions. Furthermore, the newly identified SNPs open the door to a study of the possible association of AChE with deleterious phenotypes - such as adverse drug responses to AChE inhibitors employed in treatment of AD patients and hypersensitivity to pesticides.

The synaptic acetylcholinesterase tetramer assembles around a polyproline II helix

Functional localization of acetylcholinesterase (AChE) in vertebrate muscle and brain depends on interaction of the tryptophan amphiphilic tetramerization (WAT) sequence, at the C-terminus of its major splice variant (T), with a proline-rich attachment domain (PRAD), of the anchoring proteins, collagenous (ColQ) and proline-rich membrane anchor. The crystal structure of the WAT/PRAD complex reveals a novel supercoil structure in which four parallel WAT chains form a left-handed superhelix around an antiparallel left-handed PRAD helix resembling polyproline II. The WAT coiled coils possess a WWW motif making repetitive hydrophobic stacking and hydrogen-bond interactions with the PRAD. The WAT chains are related by an approximately 4-fold screw axis around the PRAD. Each WAT makes similar but unique interactions, consistent with an asymmetric pattern of disulfide linkages between the AChE tetramer subunits and ColQ. The P59Q mutation in ColQ, which causes congenital endplate AChE deficiency, and is located within the PRAD, disrupts crucial WAT-WAT and WAT-PRAD interactions. A model is proposed for the synaptic AChE(T) tetramer.

A paradigm for single nucleotide polymorphism analysis: the case of the acetylcholinesterase gene.

Acetylcholinesterase (AChE) plays a crucial physiological role in termination of impulse transmission at cholinergic synapses through rapid hydrolysis of acetylcholine. It is a highly conserved molecule, and only a few naturally occurring genetic polymorphisms have been reported in the human gene. The goal of the present study was to make a systematic effort to identify natural single nucleotide polymorphisms (SNPs) in the human ACHE gene. To this end, the genomic coding sequences for acetylcholinesterase of 96 unrelated control individuals from three distinct ethnic groups were analyzed. A total of 13 ACHE SNPs were identified, 10 of which are newly described, and five that should produce amino acid substitutions [c.101G>A (p.Arg34Gln), c.169G>A (p.Gly57Arg), c.1031A>G (p.Glu344Gly), c.1057C>A (p.His353Asn), and c.1775C>G (p.Pro592Arg)]. Population frequencies of 11 of the 13 SNPs were established in four different populations: African Americans, Ashkenazi Jews, Sephardic Jews, and Israeli Arabs; 15 haplotypes and five ethnospecific alleles were identified. The low number of SNPs identified until now in the ACHE gene is ascribed to technical hurdles arising from the high GC content and the presence of numerous repeat sequences, and does not reflect its intrinsic heterozygosity. Among the SNPs resulting in an amino acid substitution, three are within the mature protein, mapping on its external surface: they are thus unlikely to affect its catalytic properties, yet could have antigenic consequences or affect putative protein-protein interactions. Furthermore, the newly identified SNPs open the door to a study of the possible association of AChE with deleterious phenotypes-such as adverse drug responses to AChE inhibitors employed in treatment of Alzheimer patients and hypersensitivity to pesticides.

The effect of trimethyltin on acetylcholine release in the guinea-pig trachea

The purpose of the present work was to characterise the effects of trimethyltin on the release of acetylcholine from parasympathetic nerves and its effect on the postjunctional cholinergic stimulation of a smooth muscle. The guinea-pig trachea has been used as a model. Prejunctionally, trimethyltin (3.0 × 10 −3 M) significantly enhanced in a reversible manner the high K + (75 mM) evoked release of endogenous acetylcholine and [ 3H]acetylcholine. The evoked release of endogenous acetylcholine and [ 3H]acetylcholine was released from a pool of acetylcholine being independent of extraneuronal Ca 2+ in the presence, but not in the absence of trimethyltin. The effect of trimethyltin on the release was not inhibited by low Ca 2+ (0 mM and 1.0 × 10 −4 M) or by Ca 2+ channel blockers (verapamil, 1.0 × 10 −4 M, flunarizine, 1.0 × 10 −4 M, ω-conotoxin GVIA, 2.0 × 10 −7 M and ω-agatoxin, 2.0 × 10 −7 M). The present results also demonstrate that trimethyltin induce emptying of a non-vesicular, probably a cytoplasmic storage pool of acetylcholine, since AH5183 (2.0 × 10 −5 M), an inhibitor of the translocation of acetylcholine into synaptic vesicles, and α-latrotoxin (1.0 × 10 −8 M), a toxin from black widow spider venom inducing vesicle depletion, had no inhibitory effects on the release of [ 3H]acetylcholine evoked by trimethyltin (3.0 × 10 −3 M). The release of [ 3H]acetylcholine was moreover enhanced by trimethyltin when the vesicular uptake of [ 3H]acetylcholine was inhibited by AH5183, probably as a result of a higher cytoplasmic concentration of [ 3H]acetylcholine. Trimethyltin also reduced the neuronal uptake of [ 3H]choline and this was probably due to a depolarising effect of trimethyltin on the cholinergic nerve terminals. A similar depolarisation induced by trimethyltin was observed during patch clamping of GH 4 C 1 neuronal cells. Postjunctionally, trimethyltin had no effect by itself or on the carbachol-induced smooth muscle contraction, indicating that trimethyltin did not have a general depolarising effect on smooth muscle cells or an effect on muscarinic receptors. Furthermore, the reduced electrical field-induced contraction and the subsequent increase in the basal smooth muscle tension that was observed by addition of trimethyltin was activity-dependent, and was most probably due to emptying of a nervous non-vesicular storage pool of acetylcholine, followed by rapid hydrolysis of acetylcholine by acetyl- and pseudocholinesterases.

Aerospace computer technology catches up with ground gear : C. Weitzman. Electronics, 11 September (1972), p. 112

The classical enzymatic role of acetylcholinesterase (AChE) is to terminate impulse transmission at cholinergic synapses through rapid hydrolysis of acetylcholine (ACh). Inactivation of this enzyme's catalytic site is the primary mechanism of acute toxicity of OP insecticides (e.g. parathion, chlorpyrifos). There is now sufficient evidence to suggest that AChE has a neurotrophic function that may be altered by organophosphate (OP) exposure, resulting in defects of neuronal growth and development, though the clarification of the mechanisms involved require further in vitro investigation. In the present study, the mouse neuroblastoma × rat glioma hybrid NG108-15 cell line was used to investigate the differential effects between inhibition of the catalytic site and peripheral anionic site (PAS) of acetylcholinesterase (AChE) on cell adhesion, proliferation and neuritogenesis, in the presence and absence of human red blood cell (hRBC) AChE (ED3.1.1.7). AChE active-site inhibitor paraoxon (PO; 0.1–1.0 μM), when added to NG108-15 cells grown on AChE-coated plates, had no effect on cell proliferation, but exerted a significant reduction in strongly adherent viable cells accompanied by mostly short process formations, with 18% of cells considered to be neuritogenic, similar to that observed on uncoated plates. In contrast, PO had no significant effect on cell adhesion and proliferation of NG108-15 cells on uncoated plates. The PAS-ligand thioflavin-T (Th-T; 0.5–25 μM), however, decreased cell adhesion and proliferation, on both uncoated and ACh-E coated plates, with less magnitude on AChE-coated plates. Taken together, these results suggest that strong cell adherence and neuritogenesis are sensitive to PO in this cell culture model, with no impact on proliferation, in the presence of membrane bound AChE-coating, while there is no sensitivity to PO on uncoated plates. On the other hand, binding of Th-T directly to the PAS affects both cell adherence and proliferation, with less magnitude in the presence of membrane-bound AChE. The current study indicates that PO is deleterious in neural development during critical periods of strong cell adhesion and differentiation, interfering with AChE trophic function.

Sixteen-bit conversion gets a lift from IC technology : W. Marshall and C. Brown. Electronics, 25 September (1972), p. 117

The classical enzymatic role of acetylcholinesterase (AChE) is to terminate impulse transmission at cholinergic synapses through rapid hydrolysis of acetylcholine (ACh). Inactivation of this enzyme's catalytic site is the primary mechanism of acute toxicity of OP insecticides (e.g. parathion, chlorpyrifos). There is now sufficient evidence to suggest that AChE has a neurotrophic function that may be altered by organophosphate (OP) exposure, resulting in defects of neuronal growth and development, though the clarification of the mechanisms involved require further in vitro investigation. In the present study, the mouse neuroblastoma × rat glioma hybrid NG108-15 cell line was used to investigate the differential effects between inhibition of the catalytic site and peripheral anionic site (PAS) of acetylcholinesterase (AChE) on cell adhesion, proliferation and neuritogenesis, in the presence and absence of human red blood cell (hRBC) AChE (ED3.1.1.7). AChE active-site inhibitor paraoxon (PO; 0.1–1.0 μM), when added to NG108-15 cells grown on AChE-coated plates, had no effect on cell proliferation, but exerted a significant reduction in strongly adherent viable cells accompanied by mostly short process formations, with 18% of cells considered to be neuritogenic, similar to that observed on uncoated plates. In contrast, PO had no significant effect on cell adhesion and proliferation of NG108-15 cells on uncoated plates. The PAS-ligand thioflavin-T (Th-T; 0.5–25 μM), however, decreased cell adhesion and proliferation, on both uncoated and ACh-E coated plates, with less magnitude on AChE-coated plates. Taken together, these results suggest that strong cell adherence and neuritogenesis are sensitive to PO in this cell culture model, with no impact on proliferation, in the presence of membrane bound AChE-coating, while there is no sensitivity to PO on uncoated plates. On the other hand, binding of Th-T directly to the PAS affects both cell adherence and proliferation, with less magnitude in the presence of membrane-bound AChE. The current study indicates that PO is deleterious in neural development during critical periods of strong cell adhesion and differentiation, interfering with AChE trophic function.