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Computational approaches have proved valuable in elucidating structure/function relationships in the cholinesterases in the context of their unusual three-dimensional structure. In this review we survey several recent studies that have enhanced our understanding of how these enzymes function, and have utilized computational approaches both to modulate their activity and to improve the design of lead compounds for their inhibition. An animated Interactive 3D Complement (I3DC) is available in Proteopedia at http://proteopedia.org/w/Journal:Neuropharmacology:2., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Cholinesterase activity in mixed saliva of patients with somatic pathology was investigated. The results showed differences in enzyme activity depending on the disease. The highest salivary cholinesterase activity was detected in patients with bronchopulmonary pathology, and the lowest - in cardiovascular diseases. A reliable relationship between the changes in the activity of cholinesterase in saliva and the rate of salivation, and with patients taking atypical antipsychotics and M, H-anticholinergic drugs, was revealed., Competing Interests: The authors declare no conflict of interest.

Cholinesterases are the main targets of organophosphorus compounds. The two enzymes present in the blood (butyrylcholinesterase, BChE; acetylcholinesterase, AChE) are biomarkers of their systemic toxicity. Activity of the plasma BChE is very often determined as it allows a rapid diagnostic of poisoning and is a marker of the persistence of the toxicant in the blood. The activity of the red blood cell AChE gives a better picture of the synaptic inhibition in the nervous system but the assay is less commonly available in routine laboratories. Better biomarker of the exposure, it allows a diagnosis of the severity of the poisoning and helps to assess the efficacy of oxime therapy. Besides the practical aspects of blood collection and sample processing, and the interpretation of the assays, this review stresses the complementarity of both enzyme assays and recalls their crucial interest for the confirmation of poisoning with an organophosphorus in a situation of war or terrorist attack and for the monitoring of occupational exposures., (Copyright © 2013. Published by Elsevier SAS.)

Objectives: Alzheimer's disease (AD) is the most common cause of dementia, being responsible for high healthcare costs and familial hardships. Despite the efforts of researchers, no treatment able to delay or stop AD progress exists. Currently, the available treatments are only symptomatic, cholinesterase inhibitors being the most widely used drugs. Here we describe several natural compounds with anticholinesterase (acetylcholinesterase and butyrylcholinesterase) activity and also some synthetic compounds whose structures are based on those of natural compounds., Key Findings: Galantamine and rivastigmine are two cholinesterase inhibitors used in therapeutics: galantamine is a natural alkaloid that was extracted for the first time from Galanthus nivalis L., while rivastigmine is a synthetic alkaloid, the structure of which is modelled on that of natural physostigmine. Alkaloids include a high number of compounds with anticholinesterases activity at the submicromolar range. Quinones and stilbenes are less well studied regarding cholinesterase inhibition, although some of them, such as sargaquinoic acid or (+)-α-viniferin, show promising activity. Among flavonoids, flavones and isoflavones are the most potent compounds. Xanthones and monoterpenes are generally weak cholinesterase inhibitors., Summary: Nature is an almost endless source of bioactive compounds. Several natural compounds have anticholinesterase activity and others can be used as leader compounds for the synthesis of new drugs., (© 2013 Royal Pharmaceutical Society.)

Objectives: The inhibition of acetylcholinesterase (AChE), the key enzyme in the breakdown of acetylcholine, is currently the main pharmacological strategy available for Alzheimer's disease (AD). In this sense, many alkaloids isolated from natural sources, such as physostigmine, have been long recognized as acetyl- and butyrylcholinesterase (BChE) inhibitors. Since the approval of galantamine for the treatment of AD patients, the search for new anticholinesterase alkaloids has escalated, leading to promising candidates such as huperzine A. This review aims to summarize recent advances in current knowledge on alkaloids as AChE and BChE inhibitors, highlighting structure-activity relationship (SAR) and docking studies., Key Findings: Natural alkaloids belonging to the steroidal/triterpenoidal, quinolizidine, isoquinoline and indole classes, mainly distributed within Buxaceae, Amaryllidaceae and Lycopodiaceae, are considered important sources of alkaloids with anti-enzymatic properties. Investigations into the possible SARs for some active compounds are based on molecular modelling studies, predicting the mode of interaction of the molecules with amino acid residues in the active site of the enzymes. Following this view, an increasing interest in achieving more potent and effective analogues makes alkaloids good chemical templates for the development of new cholinesterase inhibitors., Summary: The anticholinesterase activity of alkaloids, together with their structural diversity and physicochemical properties, makes them good candidate agents for the treatment of AD., (© 2013 Royal Pharmaceutical Society.)

For the second half of the XX century, Sechenov Institute of Evolutionary Physiology and Biochemistry of the Russian Academy of Sciences was the center of the Russian cholinesterase investigations ("the Russian cholinesterase club"). The close cooperation with chemists-syntheticians of different scientific schools provided success and fruitfulness of this scientific search. All these years, there was preserved dualism of this investigation: a study of the mechanism of functioning and kinetics of cholinesterase catalysis as well as the comparative-enzymological character of studies of cholinesterases of the animals being at different levels of evolutionary development.

There are exposed the main landmarks of the scientific biography of Professor Aleksandr Pavlovich Brestkin, connected with his investigations in the field of chemistry of high pressures, physiological chemistry of caisson disease, kinetics of esterase catalysis, and in comparative enzymology of cholinesterases.

Acetylcholinesterase (AChE) is a most remarkable protein, not only because it is one of the fastest enzymes in nature, but also since it appears in many molecular forms and is regulated by elaborate genetic networks. As revealed by sensitive histochemical procedures, AChE is expressed specifically in many tissues during development and in many mature organisms, as well as in healthy and diseased states. Therefore it is not surprising that there has been a long-standing search for additional, "non-classical" functions of cholinesterases (ChEs). In principle, AChE could either act nonenzymatically, e.g. exerting cell adhesive roles, or, alternatively, it could work within the frame of classic cholinergic systems, but in non-neural tissues. AChE might be considered a highly co-opting protein, since possibly it combines such various functions within one molecule. By presenting four different developmental cases, we here review i) the expression of ChEs in the neural tube and their close relation to cell proliferation and differentiation, ii) that AChE expression reflects a polycentric brain development, iii) the retina as a model for AChE functioning in neural network formation, and iv) nonneural ChEs in limb development and mature bones. Also, possible roles of AChE in neuritic growth and of cholinergic regulations in stem cells are briefly outlined.

Aim: To examine the protective effects of scutellarin (Scu) on rats with learning and memory deficit induced by β-amyloid peptide (Aβ)., Methods: Fifty male Wistar rats were randomly divided into 5 groups: control, sham operation, Aβ, Aβ+Scu, and Aβ+piracetam groups. Aβ(25-35) was injected into the lateral ventricle (10 μg each side). Scu (10 mg/2 mL) or piracetam (10 mg/2 mL was intragastrically administered per day for 20 consecutive days following Aβ treatment. Learning and memory was assessed with Morris water maze test. The protein and mRNA levels of nicotinic acetylcholine receptor (nAChR) α4, α7, and β2 subunits in the brain were examined using Western blotting and real-time PCR, respectively. The activities of acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) in the brain and plasma were measured using Ellman's colorimetric method., Results: In Aβ group, the escape latency period and first platform cross was significantly increased, and the total number of platform crossings was significantly decreased, as compared with the control and the sham operation groups. Both Scu and piracetam treatment significantly reduced the escape latency period and time to cross platform, and increased the number of platform crosses, but there were no significant differences between Aβ+Scu and Aβ+piracetam groups. In Aβ group, the protein levels of nAChR α4 and α7 subunits in the cerebral cortex were significantly decreased by 42%-47% and 58%-61%, respectively, as compared to the control and the sham operation groups. Scu treatment caused upregulation of α4 and α7 subunit proteins by around 24% and 30%, respectively, as compared to Aβ group, but there were no significant differences between Aβ+Scu and Aβ+piracetam groups. The protein level of nAChR β2 subunit had no significant difference among different groups. The mRNA levels of nAChR α4, α7, and β2 subunits were not significantly changed. In Aβ group, the activities of AChE and BuChE in the brain were significantly increased, but were significantly decreased in the plasma, as compared to the control and the sham operation groups. Scu or piracetam treatment restored the activities in brain and plasma nearly to the levels in the control group., Conclusion: The results suggest that Scu may rescue some of the deleterious effects of Aβ, possibly by stimulating nAChR protein translation and regulating cholinesterase activity.

The antagonism of steroidal nondepolarizing neuromuscular blockers (NDMBs) moved forward recently with the introduction of sugammadex, the only drug able to immediately reverse the effects of curarization produced by NDMBs. This advance has necessitated reflection on the future role of pseudocholinesterase. In spite of the side effects of succinylcholine and published opinions on its use, this NDMB continues to be used in clinical anesthesia. Pseudocholinesterase is mainly found in the liver, plasma, and nervous system. The enzyme is synthesized in the liver in greater amounts than required although certain conditions lead to deficiency, which is usually asymptomatic. The only clinical expression is the apnea which develops after administration of succinycholine because this NDMB cannot be metabolized. In some patients, slight reductions in the antagonism of succinylcholine lead to rising neuromuscular concentrations of the drug in accordance with the degree and duration of the blockade. We review the various forms of pseudocholinesterase deficiency, including a discussion of genetic variants, clinical manifestations, and management. In addition to discussing the diagnosis of this condition and the clinical implications, we highlight the importance of practice protocols and access to a referral laboratory if one is not available within the immediate hospital.

Background: Cholinesterases are a group of serine hydrolases that split the neurotransmitter acetylcholine (ACh) and terminate its action. Of the two types, butyrylcholinesterase and acetylcholinesterase (AChE), AChE plays the key role in ending cholinergic neurotransmission. Cholinesterase inhibitors are substances, either natural or man-made that interfere with the break-down of ACh and prolong its action. Hence their relevance to toxicology and pharmacology., Methods and Results: The present review summarizes current knowledge of the cholinesterases and their inhibition. Particular attention is paid to the toxicology and pharmacology of cholinesterase-related inhibitors such as nerve agents (e.g. sarin, soman, tabun, VX), pesticides (e.g. paraoxon, parathion, malathion, malaoxon, carbofuran), selected plants and fungal secondary metabolites (e.g. aflatoxins), drugs for Alzheimer's disease (e.g. huperzine, metrifonate, tacrine, donepezil) and Myasthenia gravis (e.g. pyridostigmine) treatment and other compounds (propidium, ethidium, decamethonium)., Conclusions: The crucial role of the cholinesterases in neural transmission makes them a primary target of a large number of cholinesterase-inhibiting drugs and toxins. In pharmacology, this has relevance to the treatment of neurodegenerative disorders.

To address the potential role of cholinesterase enzymes in the invasive capacity of species, the present study investigated ChE activity in the invasive freshwater bivalve Anodonta woodiana (Lea, 1834) comparing it with that of the indigenous species, Anodonta sp. (Linnaeus, 1758). The invasive capacity of pests has often been linked to their ecological plasticity and high intrinsic genetic variability; however the role played by molecular and cellular mechanisms, generally known as an organism's response to pollution, is unclear. Different substrates and selective ChE enzyme inhibitors were investigated in digestive gland, foot, gonad, adductor muscle and gill tissues while sensitivity to four organophosphate (OP) insecticides was investigated in vitro only in adductor muscle. The invasive species (A. woodiana) showed significantly greater (at least one order of magnitude) ChE activity than the endemic species (Anodonta sp.) (p<0.05) using acetylthiocholine (ASCh) as substrate and the activity was more widely distributed in tissues involved in movement (adductor muscle and foot), respiration, feeding (gills) and reproduction (gonads). Moreover, only the invasive species, A. woodiana, showed detectable ChE (vs. ASCh) activity in gill tissue. No substrate specificity was observed in any tissue of either species as already described for other bivalve species. ChE activity was not inhibited by Iso-OMPA but showed high sensitivity to BW248c51 and eserine. Both species showed moderate to low sensitivities in vitro to OP insecticides in the range 10(-7)-10(-2) M. Calculated IC(50) for fenitrothion and chlorpyrifos was in the range 10(-6)-10(-3) M in muscle of A. woodiana while a higher inhibition was observed for fenitrothion (10(-7) M) and lower for chlorpyrifos (10(-2) M) in the indigenous species Anodonta sp. Similar IC(50) of 10(-5)-10(-6) M were observed for DFP and azamethiphos in both species. The hypotheses of other authors that acetylcholinesterase (AChE) is involved in the control of many essential functions, such as frontal ciliary activity of gill epithelium, temperature resistance, ciliary activity for transport of suspended particulate, valve opening and embryo development, suggest that the high catalytic efficiency of the invasive species may endow it with a competitive advantage over the endemic species. In view of the peculiar reproductive strategy of these mussels, higher ChE vs. ASCh activity in gonads of the invasive species could also favour glochidium production and embryo development under a wider range of environmental conditions.

Mivacurium- pancuronium combination proved to be more potent than either drug given alone. The goal of this study was to evaluate the safety and efficacy of this combination in elderly group and its correlation to plasma butyryl cholinesterase (Bche) activity. Forty patients, ASA I or II scheduled for elective open cholecystectomy were allocated into two groups of twenty patients each: young group (18- 55 years) and elderly group (60-75 years). Anesthesia was induced with midazolam, fentanyl, and propofol then maintained with isoflurane and opioid supplementation. Neuromuscular blockade (NMB) was monitored by train-of-four (TOF) stimulation of the ulnar nerve. After calibration, NMB was achieved by 16 microg kg(-1) pancuronium followed by 32 microg kg(-1) mivacurium. The following parameters were recorded: The onset time, clinical duration, recovery index and the total dose of mivacurium and pancuronium together with hemodynamic data. Three blood samples for Bche activity were collected: before pancuronium injection, 3 min. and 30 min. afterwards in both groups. The onset time and the recovery index of NMB were comparable in both groups. The duration of action was significantly prolonged in elderly group (49.8 +/- 10.48 min.) compared to young one (37.13 +/- 7.81 min.). The total dose of mivacurium was significantly less in the elderly group (22.56 +/- 2.39 microg kg(-1) hr(-1)) when compared to the young group (25.78 +/- 3.05 microg kg(-1) hr(-1)). For all patients, the preoperative Bche activity was within the normal range. After pancuronium injecttion, it showed a significant reduction in both groups at three and thirty minutes except a non significant value in young at thirty minutes. This reduction showed a significantly higher percent change in the elderly group (30.37 +/- 22.01) than the young group (8.60 +/- 19.19) at thirty minutes. There were significant intra operative variations in the percent changes of hemodynamic data compared to the preoperative values, yet, still within the clinically acceptable range. So, the use of a small dose of pancuronium followed by a small dose of mivacurium with a ratio of 1:2 can produce synergism without affecting either the recovery profile of mivacurium or the clinical hemodynamic stability even in the elderly group.

The aging brain shows selective neurochemical changes involving several neural cell populations. Increased brain metal levels have been associated with normal aging and a variety of diseases, including Alzheimer's disease (AD). Melatonin levels are decreased in aging, particularly in AD subjects. The loss of melatonin, which is synthesized by the pineal gland, together with the degeneration of cholinergic neurons of the basal forebrain and the deposition of aggregated proteins, such as the amyloid beta peptides (Abeta), are believed to contribute to the development of cognitive symptoms of dementia. Aging and its variants, such as AD, should be viewed as the result of multiple "hits," including alterations in the levels of Abeta, metals, cholinesterase enzymes, and neuronal gene expression. Herein, we present evidence in support of this theory, based on several studies. We discuss melatonin's neuroprotective function, which plays an important role in aging, prolongation of life span, and health in the aged individual. It interacts with metals and, in some cases, neutralizes their toxic effects. Dietary supplementation of melatonin restores its age-related loss. In mice, an elevated brain melatonin significantly reduced levels of potentially toxic Abeta peptides. Thus, compensation of melatonin loss in aging by dietary supplementation could well be beneficial in terms of reducing metal-induced toxicity, lipid peroxidation, and losses in cholinergic signaling. We propose that certain cholinesterase inhibitors and the NMDA partial antagonist memantine, which are FDA-approved drugs for AD and useful to boost central nervous system functioning, can be made more effective by their combination with melatonin or other neuroprotectants. Herein, we highlight studies elucidating the role of the amyloid pathway, metals, melatonin, and the cholinergic system in the context of aging and AD. Finally, melatonin is present in edible plants and walnuts, and consuming foodstuffs containing melatonin would be beneficial by enhancing the antioxidative capacity of the organisms.

Vertebrates possess two cholinesterases, acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) which both hydrolyze acetylcholine, but differ in their specificity towards other substrates, and in their sensitivity to inhibitors. In mammals, the AChE gene produces three types of coding regions through the choice of 3' splice acceptor sites, generating proteins which possess the same catalytic domain, associated with distinct C-terminal peptides. AChE subunits of type R ('readthrough') produce soluble monomers; they are expressed during development and induced by stress in the mouse brain. AChE subunits of type H ('hydrophobic') produce GPI-anchored dimers, but also secreted molecules; they are mostly expressed in blood cells. Subunits of type T ('tailed') exist for both AChE and BChE. They represent the enzyme forms expressed in brain and muscle. These subunits generate a variety of quaternary structures, including homomeric oligomers (monomers, dimers, tetramers), as well as hetero-oligomeric assemblies with anchoring proteins, ColQ and PRiMA. Mutations in the four-helix bundle (FHB) zone of the catalytic domain indicate that subunits of type H and T use the same interaction for dimerization. On the other hand, the C-terminal T peptide is necessary for tetramerization. Four T peptides, organized as amphiphilic alpha helices, can assemble around proline-rich motifs of ColQ or PRiMA. The association of AChE(T) or BChE subunits with ColQ produces collagen-tailed molecules, which are inserted in the extracellular matrix, e.g. in the basal lamina of neuromuscular junctions. Their association with PRiMA produces membrane-bound tetramers which constitute the predominant form of cholinesterases in the mammalian brain; in muscles, the level of PRiMA-anchored tetramers is regulated by exercise, but their functional significance remains unknown. In brain and muscles, the hydrolysis of acetylcholine by cholinesterases, in different contexts, and their possible noncatalytic functions clearly depend on their localization by ColQ or PRiMA., (Copyright 2002 S. Karger AG, Basel)

The effects of a single or repeated dermal administration of methyl parathion on motor function, learning and memory were investigated in adult female rats and correlated with blood cholinesterase activity. Exposure to a single dose of 50 mg/kg methyl parathion (75% of the dermal LD(50)) resulted in an 88% inhibition of blood cholinesterase activity and was associated with severe acute toxicity. Spontaneous locomotor activity and neuromuscular coordination were also depressed. Rats treated with a lower dose of methyl parathion, i.e. 6.25 or 12.5 mg/kg, displayed minimal signs of acute toxicity. Blood cholinesterase activity and motor function, however, were depressed initially but recovered fully within 1-3 weeks. There were no delayed effects of a single dose of methyl parathion on learning acquisition or memory as assessed by a step-down inhibitory avoidance learning task. Repeated treatment with 1 mg/kg/day methyl parathion resulted in a 50% inhibition of blood cholinesterase activity. A decrease in locomotor activity and impairment of memory were also observed after 28 days of repeated treatment. Thus, a single dermal exposure of rats to doses of methyl parathion which are lower than those that elicit acute toxicity can cause decrements in both cholinesterase activity and motor function which are reversible. In contrast, repeated low-dose dermal treatment results in a sustained inhibition of cholinesterase activity and impairment of both motor function and memory., (Copyright 2001 National Science Council, ROC and S. Karger AG, Basel)

A monoclonal antibody (MAb) raised against human acetylcholinesterase was found to have catalytic activity. A similar phenomenon was observed in a polyclonal antibody raised against the same antigen. The antibodies were demonstrated to be pure, and no contamination with either acetylcholinesterase or butyrylcholinesterase was found. Both antibodies hydrolyzed acetylthiocholine, an acetylcholinesterase substrate, and the MAb followed Michaelis-Menten kinetics. Six other MAbs and one other polyclonal antibody showed no evidence of catalytic activity. Acetylcholinesterase is a key component in the transmission of the nerve impulse, and is also expressed nonsynaptically during embryonic development, and abnormalities in expression are seen in neural tumors and degenerative disorders. This unusual expression is believed to be associated with a novel function of the enzyme related to differentiation and cell adhesion. Autoantibodies to acetylcholinesterase have been observed in a variety of neurologic, muscular, and autoimmune disorders. In an investigation of the possible role of acetylcholinesterase in cell adhesion, we showed that the enzyme promoted neurite outgrowth in neuroblastoma cell lines, and conversely, that certain antiacetylcolinesterase antibodies abrogated cell-substrate adhesion. Interestingly, the antibodies most effective in this regard were catalytic. Preliminary epitope analysis indicated a conformational epitope in the N-terminal domain. This domain contains the active site within a deep gorge and the peripheral anionic site at the rim of the gorge. Peripheral-site inhibitors, but not active-site inhibitors, also interfered with adhesion, and competed with the catalytic monoclonal binding to acetylcholinesterase, indicating that the epitope recognized is associated with the peripheral anionic site. The inhibitor data also support the supposition that catalysis in these antibodies may have arisen from stable complexation of acetylcholinesterase with an inhibitor. We conclude that the catalytic antiacetylcholinesterase antibody interacts with structures associated with the peripheral anionic site, thus defining a novel site on the molecule involved in cell adhesion. This finding has implications for our understanding of the potential importance of this peripheral site in a variety of congenital, neoplastic, and degenerative conditions.

In the present study, the patch-clamp technique was applied to cultured hippocampal neurons to evaluate the effects of the nerve agent VX on evoked and spontaneous postsynaptic currents mediated by gamma-aminobutyric acid (GABA) and glutamate. At 0.01 nM, VX reduced the amplitude of evoked GABAergic currents, and only at concentrations >1 nM did it decrease the amplitude of evoked glutamatergic currents. The effect of VX on GABAergic currents, which was partially reversible upon washing of the neurons with VX-free external solution, could be prevented by the muscarinic antagonist atropine. In contrast, the effect of VX on glutamatergic currents, which was not reversible upon washing, appears to be related to the VX-induced reduction of the amplitude and frequency of repetitively firing by action potentials. In the presence of the Na(+)-channel blocker tetrodotoxin (TTX), VX (>/=10 nM) increased the frequency of GABA- and glutamate-mediated miniature postsynaptic currents (MPSCs). This effect of VX was unrelated to cholinesterase inhibition and was Ca(2+) dependent. The lack of effect of VX on MPSC kinetics indicates that VX-induced alterations of evoked and spontaneous currents are exclusively due to alterations of the transmitter release processes. The ability of VX to affect transmitter release in the brain may underlie some of its neurotoxic effects and may provide the basis for the development of therapeutic countermeasures to treat and/or prevent VX-induced neurotoxicity., (Copyright 1999 Academic Press.)

Ancient medicine men of Egypt and Arabia employed, under another name, the cholinergic agents, as did the hunters, warriors and shamans of Africa and South America. An explosion of cholinergic science occurred in the last and the current century, and the ISCMs witnessed and catalyzed this progress. The Xth ISCM emphasized the molecular characteristics of the receptors, cholinesterase and of the system engaged in liberation of Ach.

Objective: To review current data on butyrylcholinesterase., Data Sources: Search through Medline data bases of articles in French or English., Study Selection: Original articles and case reports were selected. Letters to editor were excluded., Data Extraction: The articles were analyzed in order to obtain current data on biochemical structure, action, major pathological variations, especially with regard to the recent informations obtained by molecular biology concerning the identification of genetic variants., Data Synthesis: Butyrylcholinesterase must be differentiated from acetylcholinesterase, which cannot hydrolyse succinylcholine. The physiological action of butyrylcholinesterase remains unknown, although it can hydrolyse many drugs. Excluding genetical mutations, several physiopathological situations alter butyryl-cholinesterase activity. Butyrylcholinesterase activity assessment does not allow the diagnosis of genetic variants. Whatever the origin, only deficits of more than 50% modify significantly the metabolism of succinylcholine or mivacurium. The diagnosis of a prolonged neuromuscular blockade is obtained with systematic monitoring of the neuromuscular function in case of administration of mivacurium or succinylcholine. Mivacurium should only be re-injected when one response at train of four is obtained. In case of prolonged neuromuscular blockade, the anticholinesterasic agent should not be administered when no response at train of four is obtained. The biochemical methods using inhibitors (dibucaine, fluoride) of the butyrylcholinesterase and a familial study lead to the diagnosis in most cases because the atypical and fluoride variants are the most frequent. When results are doubtful, genetic molecular methods with the use of PCR and restriction enzymes allow a rapid diagnosis.

Plasma cholinesterase is an enzyme which has importance to the anaesthetist primarily for its role in the metabolism of suxamethonium, although other anaesthetic related drugs that this enzyme metabolises are also increasingly important. In this article we review current thoughts on the function, profile and chemistry of plasma cholinesterase. Causes of variations in the activity of the enzyme are described and the basis of genetic variations is explained.

The cholinesterases are members of the serine hydrolase family, which utilize a serine residue at the active site. Acetylcholinesterase (AChE) is distinguished from butyrylcholinesterase (BChE) by its greater specificity for hydrolysing acetylcholine. The function of AChE at cholinergic synapses is to terminate cholinergic neurotransmission. However, AChE is expressed in tissues that are not directly innervated by cholinergic nerves. AChE and BChE are found in several types of haematopoietic cells. Transient expression of AChE in the brain during embryogenesis suggests that AChE may function in the regulation of neurite outgrowth. Overexpression of cholinesterases has also been correlated with tumorigenesis and abnormal megakaryocytopoiesis. Acetylcholine has been shown to influence cell proliferation and neurite outgrowth through nicotinic and muscarinic receptor-mediated mechanisms and thus, that the expression of AChE and BChE at non-synaptic sites may be associated with a cholinergic function. However, structural homologies between cholinesterases and adhesion proteins indicate that cholinesterases could also function as cell-cell or cell-substrate adhesion molecules. Abnormal expression of AChE and BChE has been detected around the amyloid plaques and neurofibrillary tangles in the brains of patients with Alzheimer's disease. The function of the cholinesterases in these regions of the Alzheimer brain is unknown, but this function is probably unrelated to cholinergic neurotransmission. The presence of abnormal cholinesterase expression in the Alzheimer brain has implications for the pathogenesis of Alzheimer's disease and for therapeutic strategies using cholinesterase inhibitors.

Many theories have been advanced but the true physiological function for serum cholinesterase has still not been identified. Evidence has been presented for the abnormal expression of cholinesterase genes in many types of human tumors. Cholinesterase measurements are still used to monitor exposure to organophosphate insecticides and their clinical application requires a good understanding of the inter and intra-individual variation, as well as some knowledge of the time sequence between exposure and measurement of the cholinesterase activity. The use of serum cholinesterase measurement in liver disease varies in different countries. A case has not been made for the cost-effectiveness of adding serum cholinesterase as part of a screening procedure for the diagnosis of liver disease. During the last 10 years much information has been obtained on the molecular biology and genetics of acetylcholinesterase and butyrylcholinesterase, distinct enzymes encoded by two different, but related genes. It has been established that BChE is included by a single gene which corresponds to the E1 locus. The complete amino acid sequence of human serum cholinesterase and the location of disulfide bonds within the sequence have been described. The molecular basis of many variants of human serum cholinesterase has been described in detail. It is not rare for multiple mutations to occur within a single butyrylcholinesterase gene or there may be combination of mutations. At least 11 silent variants of human butyrylcholinesterase have been identified. There still exists a wide variety of substrates and analytical conditions for butyrylcholinesterase measurement in a number of clinical situations. No real evidence has been provided for clinical value for their use in the diagnosis of Alzheimer disease or monitoring the use of cholinesterase inhibitors in the treatment of pre-senile dementia of Alzheimer type. However, the insights from molecular biology technology may well open up more challenges in a variety of clinical situations.

Cholinesterases form a family of serine esterases that arise in animals from at least two distinct genes. Multiple forms of these enzymes can be precisely localized and regulated by alternative mRNA splicing and by co- or posttranslational modifications. The high catalytic efficiency of the cholinesterases is quelled by certain very selective reversible and irreversible inhibitors. Owing largely to the important role of acetylcholine hydrolysis in neurotransmission, cholinesterase and its inhibitors have been studied extensively in vivo. In parallel, there has emerged an equally impressive enzyme chemistry literature. Cholinesterase inhibitors are used widely as pesticides; in this regard the compounds are beneficial with concomitant health risks. Poisoning by such compounds can result in an acute but usually manageable medical crisis and may damage the CNS and the PNS, as well as cardiac and skeletal muscle tissue. Some inhibitors have been useful for the treatment of glaucoma and myasthenia gravis, and others are in clinical trials as therapy for Alzheimer's dementia. Concurrently, the most potent inhibitors have been developed as highly toxic chemical warfare agents. We review treatments and sequelae of exposure to selected anticholinesterases, especially organophosphorus compounds and carbamates, as they relate to recent progress in enzyme chemistry.

Evidence about nonclassic functions of acetyl- (AChE) and butyryl-cholinesterase (BChE) during embryonic development of vertebrate brains is compared with evidence of their expression in Alzheimer disease (AD). Before axons extend in the early neural tube, BChE expression shortly precedes the expression of AChE. BChE is associated with neuronal and glial cell proliferation, and it may also regulate AChE. AChE is suggested to guide and stabilize growing axons. Pathologically, cholinesterase expression in AD shows some resemblance to that in the embryo. These findings are inconsistent with the "cholinergic hypothesis." Rather, it is suggested that cholinesterases in AD function nonclassically as in the embryo, possibly as part of a "neoembryonic" restorative program. These views may open new strategies for pharmacology and therapy for AD.

1. Both butyrylcholinesterase (BChE) and acetylcholinesterase (AChE) are present in the mouse uterus, BChE being more abundant. 2. Their molecular forms were sequentially solubilized by different extraction media obtaining three ChE fractions whose specific activity was different, depending on the stage of the estrous cycle: hydrosoluble (estrous: 75.5 +/- 6.6 and diestrous: 47.9 +/- 8.7 mU/mg prot); detergent-soluble or amphiphilic (estrous 26.6 +/- 2.4 and diestrous 14.7 +/- 3.3 mU/mg prot.), and high ionic strength-soluble (estrous: 18.7 +/- 4.2 and diestrous 12.8 +/- 1.2 mU/mg prot.). 3. Histochemical procedures demonstrated a different distribution for both ChE activities. AChE was found in nerves next to smooth muscle cells of the circular layer and blood vessels, while BChE was concentrated in the longitudinal stratum surrounding the smooth muscle cells. Under the predominance of progesterone, BChE was also found in the endometrial glands. 4. Maximal contractions evoked by the addition of ACh to the isolated organ bath were concentration dependent and greater in estrous than in diestrous. Nevertheless the difference at the two stages of the estrous cycle disappeared when contractions were normalized to smooth muscle cross-sectional area. 5. BChE but not AChE inhibition augmented maximal contractions elicited by ACh in longitudinal but not in circular smooth muscle. 6. The effect of BChE inhibition on the contractile force developed was greater at lower concentrations of ACh and did not depend on the stage of the estrous cycle.

Cholinesterases present homologies with some cell adhesion molecules; however, it is unclear whether and how they perform adhesive functions. Here, we provide the first direct evidence showing that neurite growth in vitro from various neuronal tissues of the chick embryo can be modified by some, but not all, anticholinesterase agents. By quantifying the neuritic G4 antigen in tectal cell cultures, the effect of anticholinesterases on neurite growth is directly compared with their cholinesterase inhibitory action. BW 284C51 and ethopropazine, inhibiting acetylcholinesterase (AChE) and butyrylcholinesterase (BChE), respectively, strongly decrease neurite growth in a dose-dependent manner. However, echothiophate which inhibits both cholinesterases, does not change neuritic growth. These quantitative data are supplemented by morphological observations in retinal explant cultures grown on striped laminin carpets, viz., defasciculation of neurite bundles by BW 284C51 and Bambuterol occurs, indicating that these drugs disturb adhesive mechanisms. These data strongly suggest that a) cholinesterases can participate in regulating axonal growth, b) both AChE and BChE can perform such a nonsynaptic function, and c) this function is not the result of the enzyme activity per se, since at least one drug was found that inhibits all cholinesterase activities but not neurite growth. Thus, a secondary site on cholinesterase molecules must be responsible for adhesive functions.

The aim of the present work was to evaluate the effect on the growth hormone (GH) secretion of eptastigmine, a new long-acting cholinesterase inhibitor, in unanesthetized beagle dogs. In a first study, 5 young dogs were given single doses (0.5, 1.0, and 2.0 mg/kg, i.m.) of the drug or saline in a randomized cross-over manner. Blood samples were collected immediately before and, at regular intervals, until 150 min after drug injection. GH plasma concentrations were determined by radioimmunoassay. Plasma cholinesterase activity was measured with a potentiometric method. There was a significant logistic relationship (r = 0.601, P < 0.01) between the administered dose of eptastigmine and the log-transformed areas under the GH plasma concentration-time curve (AUC) with a calculated ED50 for eptastigmine of 0.63 +/- 0.36 mg/kg. There was also a significant linear relationship (r = 0.630, P < 0.01) between log-transformed AUC of GH levels and AUC of plasma cholinesterase activity. In a second study we evaluate the ability of eptastigmine (2.0 mg/kg, i.m.) to potentiate the GH-releasing effect of the GH-releasing hormone (GHRH, 2.0 micrograms/kg, i.v.) in young and old dogs. Eptastigmine was administered 45 min before GHRH and blood collected every 15 min until 90 min after GHRH injection. In young dogs, maximum GH plasma levels (Cmax) were 6.1 +/- 1.0 ng/ml after GHRH compared to 22.5 +/- 2.3 ng/ml after GHRH preceded by eptastigmine (P < 0.01). In old animals, Cmax were 4.6 +/- 1.4 ng/ml after GHRH vs 13.2 +/- 7.4 ng/ml after combined administration of GHRH and eptastigmine (P < 0.05). These data indicate that eptastigmine is very effective in augmenting basal and stimulated GH secretion in old dog. The good activity also shown in old animals suggests a potential use of this drug to reverse the age-dependent decline in GH secretion responsible for many involutional changes of aging.

1. Rat hemidiaphragms were incubated in a physiological low-K+ medium without stimulation and the amount of acetylcholine (ACh) released was measured radioenzymatically. Cholinesterases were inhibited by paraoxon. 2. In the presence of 1 microM tetrodotoxin (TTX), the amount of ACh released during a 2 h incubation was lowered by 40%. A similar decrease was observed in the absence of Ca2+ and in the presence of 10 microM-d-tubocurarine (dTC). The effects of TTX combined with Ca2+ removal, and of TTX combined with dTC were no greater than those of TTX, dTC or Ca2+ removal alone. TTX and dTC had no effect on the release of ACh from diaphragms 4 days after denervation. 3. The reduction of spontaneous ACh release observed in the presence of TTX or dTC or in the absence of Ca2+ is best interpreted on the assumption that about 40% of the ACh release was due to the impulse activity known to be generated in intramuscular motor nerve branches by the ACh which accumulates after the inhibition of cholinesterases. 4. In the presence of 1 and 10 microM vesamicol (AH5183, 2-(4-phenylpiperidino)-cyclohexanol), the release of ACh was also diminished by approximately 40%. Vesamicol did not augment the inhibition of release produced by TTX or by the omission of Ca2+.(ABSTRACT TRUNCATED AT 250 WORDS)

After anticholinesterase treatment in vivo, depolarization of the postsynaptic muscle fibre membrane by about 4 mV develops due to non-quantally released acetylcholine from the motor nerve terminal. This conclusion was supported by experiments with the curarization of diaphragm slices from anticholinesterase treated mice during intracellular microelectrode recordings.

It was found that rat immobilization in small-size cages leb to physiological changes. On day 1 it was a stress-reaction that resulted in decreases of the fibrillation threshold and arrhythmia resistance. On day 5 it was an increase in the vagal tone that caused noticeable atropine-relieved bradycardia. The fibrillation level returned to the baseline. Heart resistance to ischemic and reperfusion arrhythmias increased drastically as compared to the control level. On day 15 the vagal effect declined to reach the baseline; in spite of this heart tolerance to reperfusion arrhythmias further increased. This was followed by enhanced resistance of isolated hearts of the adapted animals to the reperfusion paradox and tonic concentrations of epinephrine and Ca2+, which indicated the formation of the phenomenon of adaptation stabilization of cardiac structures. After termination of the 5-day stressogenic exposure the cholinergic stress-limiting protection of the heart disappeared rapidly, i. e. within 12 hours. The protective effect of the adaptation stabilization phenomenon, which developed during 15 days of the stressogenic exposure, proved to be more stable and persisted during 15 days after its cessation. It is concluded that, based on the coordination of short-term central and long-term cellular mechanisms, the animal body develops optimal adaptation that emerges rapidly and persists for an adequately long period of time. The step-by-step replacement of central mechanisms with cellular ones provides high reliability and efficiency of the protection of the heart and the entire body from extended environmental effects.

1. Long before onset of synaptogenesis in the chicken neural tube, the closely related enzymes butyrylcholinesterase (BChE) and acetylcholinesterase (AChE) are expressed in a mutually exclusive manner. Accordingly, neuroblasts on the ventricular side of the neural tube transiently express BChE before they abruptly accumulate AChE while approaching the outer brain surface. 2. By exploiting AChE as a sensitive and early histochemical differentiation marker, we have demonstrated complex polycentric waves of differentiation spreading upon the cranial part of the chicken neural tube but a smooth rostrocaudal wave along the spinal cord. Shortly after expression of AChE, these cells extend long projecting neurites. In particular, segmented spinal motor axons originate from AChE-positive motoneurones; they navigate through a BChE-active zone within the rostral half of the sclerotomes before contacting BChE/AChE-positive myotome cells. At synaptogenetic stages, cholinesterases additionally are detectable in neurofibrillar laminae foreshadowing the establishment of cholinergic synapses. 3. In order to elucidate the functional significance of cholinesterases at early stages, we have investigated specific cholinesterase molecules and their mechanisms of action in vivo and in vitro. A developmental shift from the low molecular weight forms to the tetramers of both enzymes has been determined. In vitro, the addition of a selective BChE inhibitor leads to a reduction of AChE gene expression. Thus, in vivo and in vitro data suggest roles of cholinesterases in the regulation of cell proliferation and neurite growth. 4. Future research has to show whether neurogenetic functioning of cholinesterases can help to understand their reported alterations in neural tube defects, mental retardations, dementias and in some tumours.

Neurotactin is a 135 kd membrane glycoprotein which consists of a core protein, with an apparent molecular weight of 120 kd, and of N-linked oligosaccharides. In vivo, the protein can be phosphorylated in presence of radioactive orthophosphate. Neurotactin expression in the larval CNS and in primary embryonic cell cultures suggests that it behaves as a contact molecule between neurons or epithelial cells. Electron microscopy studies reveal that neurotactin is uniformly expressed along the areas of contacts between cells, without, however, being restricted to a particular type of junction. It putative adhesive properties have been tested by transfecting non adhesive Drosophila S2 cells with neurotactin cDNA. Heat shocked transfected cells do not aggregate, suggesting that neurotactin does not mediate homophilic cell adhesion. However, these transfected cells bind to a subpopulation of embryonic cells which probably possess a related ligand. The location at cellular junctions between specific neurons or epithelial cells, the heterophilic binding to a putative ligand and the ability to be phosphorylated are consistent with the suggestion that neurotactin functions as an adhesion molecule.

The role of butyrylcholinesterase (BuChE) and acetylcholinesterase (AChE) in in regulating acetylcholine (ACh) lifetime was investigated by use of selective cholinesterase (ChE) inhibitors. Addition of 1 microM tetraisopropylpyrophosphoramide (iso-OMPA) led to a 98% inhibition of BuChE activity with little or no effect on AChE activity. This inhibition was accompanied by a 26% increase in the amplitude and a 43% prolongation in the half-relaxation time of contractions elicited by electric field stimulation (EFS). Coapplication of BW 284C51 (a selective AChE inhibitor) and 1 microM iso-OMPA resulted in increases of 2-fold in the amplitude and 10-fold in the half-relaxation time of EFS-induced contractions. These alterations were accompanied by small but sustained baseline contractures that were antagonized completely by incubation with exogenous BuChE (2.5 U/ml). The results suggest that BuChE serves to coregulate the lifetime of ACh in canine tracheal smooth muscle.

Physiological properties of the synapses formed between explants of spinal cord and dissociated autonomic ganglion neurons in tissue culture were studied using intracellular and extracellular stimulation and recording techniques (as well as iontophoresis) with a culture perfusion system allowing continuous microscopic observation during repeated changes of the bathing medium. The principal neurons of the superior cervical ganglion (SCGN) were dissociated from perinatal rats and the spinal cord explants were obtained from 15-day rat fetuses; these were allowed to mature for 3-10 weeks in co-culture. Recordings from over 1000 SCGN established that: (a) spontaneous small depolarizations and action potentials occurred in 20% of the SCGN studied, (b) the EPSPs observed in SCGN after spinal cord stimulation were sensitive to decreased Ca2+ and increased Mg2+, as well as to D-tubocurare, hexamethonium and mecamylamine, but not to atropine (at 10(-6) M concentration) or to the alpha-adrenergic blocking agents phentolamine or phenoxybenzamine; no potentiation of the EPSPs was seen with neostigmate or eserine, (c) acetylcholine directly applied to the SCGN was seen to mimic the responses seen after spinal cord stimulation; tetrodotoxin blocked both direct and iontophoretically fired action potentials, with only a suprathreshold acetylcholine potential remaining. These synapses were not sensitive to alpha-bungarotoxin. It is concluded that the synapses formed by spinal cord neurites on principal SCGN in tissue culture are nicotinic cholinergic, and that the evoked EPSPs recorded in this study are thus similar to the orthodromic fast EPSPs observed in vivo. No slow synaptic responses were observed and no demonstrable effects were noted that could be attributed to adrenergic transmission.