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PubMed2002

Prolonged neuromuscular block due to cholinesterase depletion by plasmapheresis.

Plasmapheresis is a well-known therapeutic procedure for several medical conditions in which removal of circulating antibodies or albumin-bound toxins is desired. Circulating plasma cholinesterase enzyme levels are also depleted with plasmapheresis. This action causes patients to be susceptible to prolonged neuromuscular blockade when neuromuscular blocking drugs that are metabolized by this enzyme are used. We describe a case of prolonged neuromuscular blockade following succinylcholine and mivacurium administration in a 24-year-old renal transplant patient undergoing repeated plasmapheresis for recurrence of focal segmental glomerulosclerosis and acute vascular rejection. Serum and plasma cholinesterase levels were less than 20% of normal at the time of the event. The patient had spontaneous recovery after 12 hours of conservative supportive care. She tolerated a similar procedure uneventfully two weeks later when she was not taking plasmapheresis. Anesthesiologists should be aware of plasmapheresis as a mechanism for plasma cholinesterase depletion when using neuromuscular blocking drugs that are metabolized by this enzyme.

Adult↗
PubMed2003

New principle of direct real-time monitoring of the interaction of cholinesterase and its inhibitors by piezolectric biosensor.

This paper describes a new method for the sensitive detection of cholinesterase inhibitors based on real-time monitoring using a piezoelectric biosensor. The cholinesterase inhibitor paraoxon was immobilized on the sensing surface via a chelate complex as the recognition element. At first, the conjugate of N-mercaptoundecanoic acid (MUA) with Nalpha,Nalpha-bis (carboxymethyl)-L-lysine (NTA-Lys) was chemisorbed to form a self-assembled monolayer on the surface of the gold electrode of the piezosensor. In the next step, paraoxon-spacer-hexahistidine conjugate was linked to the MUA-Lys-NTA layer via the chelate complex with Ni2+. The paraoxon-modified surface thus obtained was applied for the binding of human butyrylcholinesterase (BChE). Regeneration of the sensing surface was achieved by splitting the chelate complex with EDTA and depositing a fresh layer of Ni2+ followed by addition of the paraoxon-spacer-hexahistidine. In the presence of free inhibitors like diisopropylfluorophosphate (DFP), binding of BChE to the surface-bound paraoxon was decreased. In this way, a competitive affinity assay for organophosphorus compounds was developed. The limit of detection for DFP as a model compound was 10 nmol/l (ca. 2 microg/l). This new concept seems suitable for constructing biosensors for the group-specific detection of cholinesterase-inhibiting substances like insecticides in the field.

Biosensing Techniques↗
PubMed1997

External and internal electrostatic potentials of cholinesterase models.

The electrostatic potentials for the three-dimensional structures of cholinesterases from various species were calculated, using the Delphi algorithm, on the basis of the Poisson-Boltzmann equation. We used structures for Torpedo californica and mouse acetylcholinesterase, and built homology models of the human, Bungarus fasciatus, and Drosophila melanogaster acetylcholinesterases and human butyrylcholinesterase. All these structures reveal a negative external surface potential, in the area around the entrance to the active-site gorge, that becomes more negative as the rim of the gorge is approached. Moreover, in all cases, the potential becomes increasingly more negative along the central axis running down the gorge, and is largest at the base of the gorge, near the active site. Ten key acidic residues conserved in the sequence alignments of AChE from various species, both in the surface area near the entrance of the active-site gorge and at its base, appear to be primarily responsible for these potentials. The potentials are highly correlated among the structures examined, down to sequence identities as low as 35%. This indicates that they are a conserved property of the cholinesterase family, could serve to attract the positively charged substrate into and down the gorge to the active site, and may play other roles important for cholinesterase function.

Amino Acid Sequence↗
PubMed1998

Parallel regional quantification of choline acetyltransferase and cholinesterase activity in the central nervous system of an invertebrate (Sepia officinalis).

The present study describes (i) a procedure to dissect the central nervous system of the cuttlefish (Cephalopod) into ten, functionally distinct, anatomical regions of interest and (ii) the parallel measurement of acetylcholine synthesis (choline acetyltransferase) and degradation (cholinesterase) activities. Both aspects (dissection and parallel quantification of acetylcholine synthesis and degradation) could be of great importance for quantitative regional studies in neurochemistry in this animal model, it is interesting to study the cellular and molecular mechanisms involved in learning and aging processes. The parallel quantification of acetylcholine synthesis and degradation applicable to any animal model is pivotal since both enzymes are essential for the cholinergic neurotransmission and may be differentially modulated by specific functions such as learning and aging processes. Furthermore, since choline acetyltransferase and cholinesterase show different localization into the brain, their parallel quantification may underlie the involvement of cholinesterase in non-cholinergic functions, which remain unclear throughout the animal kingdom.

Aging↗
PubMed2004

Comparison studies of cholinesterase inhibitors for Alzheimer's disease.

There is uncertainty about which of the three available cholinesterase inhibitors should be prescribed as initial therapy for patients with Alzheimer's disease. We have assessed the reports of three trials that directly compared cholinesterase inhibitors. They were reviewed for sponsorship, authorship, main results, proportions of individuals who achieved maximum daily doses of the study cholinesterase inhibitors, and how the studies dealt with items on the CONSORT checklist for randomised controlled trials. All studies were funded by pharmaceutical companies, coauthored by their employees, and reported results that favoured the sponsor's product. In two studies, a significantly lower proportion of people achieved the target maximum daily dose for the comparator drug than for the sponsor's product. Between 27% and 55% of CONSORT items per study were rated as inadequately reported. The methodological limitations of these studies reduce our confidence in the validity of the conclusions drawn in the published reports.

Alzheimer Disease↗
PubMed2003

Different sensitivity of Ca(2+)-ATPase and cholinesterase to pure and commercial pesticides in nervous ganglia of Phyllocaulis soleiformis (Mollusca).

We measured the effects in vitro of pure and commercial pesticides on Ca(2+)-activated ATPase and cholinesterase (ChE) activities in the nervous system of the slug Phyllocaulis soleiformis. The pesticides used in this study included carbamate and organophosphates, which acts as reversible and irreversible anticholinesterases, respectively. Both enzymes were insensitive to pure carbofuran (1 mM), glyphosate (1 mM) and malathion (120 microM). However, the carbamate carbofuran, in the commercial formulation Furandan 350S, inhibited ATPase and ChE activities. The organophosphate glyphosate used in the commercial preparation of Gliz 480CS inhibited ATPase activity and increased cholinesterase activity. These effects are likely due to the action of adjuvant substances of the chemical formulation. The commercial formulation (Malatol 500CE) did not alter enzymes activities. Our results suggest that cholinesterase present in the slug nervous tissue has a different behavior to those identified in vertebrate nervous tissue, since it was insensitive to pure compounds, known as anticholinesterases in vertebrates. Considering the insensitivity of the Ca(2+)-activated ATPase, we suggested that the purinergic neurotransmission and other roles of ATP might not be affected by the pure pesticides tested.

Animals↗
PubMed2002

Progress in clinical neurosciences: Treatment of Alzheimer's disease and other dementias--review and comparison of the cholinesterase inhibitors.

BACKGROUND: Alzheimer's disease (AD) is the most common cause of dementia in older adults. Acceptance of the cholinergic hypothesis led to a search for medications which could enhance central cholinergic activity in this condition. There are now three cholinesterase inhibitors available for the treatment of AD in Canada. OBJECTIVES: To review the currently available cholinesterase inhibitors approved for the treatment of AD in Canada and to provide guidance on who and how to treat with these agents. RESULTS: Donepezil, rivastigmine, and galantamine are approved for the treatment of AD in Canada. In clinical trails, patients with mild to moderate AD treated with these agents experienced modest improvements in cognition, function, behaviour, and/or global clinical state. The magnitude of benefits seen with each agent appeared to be similar. While to date, there is no convincing evidence that one is more efficacious or effective, they do differ in their pharmacokinetics, additional mechanisms of action, and side effect profiles. Therefore, the selection of agent will be based on considerations such as side effect profiles, ease of administration, personal familiarity/experience, and beliefs about the importance of the noted differences in their pharmacokinetics and additional mechanisms of action. CONCLUSION: We believe that these agents should be offered to all individuals with a mild to moderate dementia where Alzheimer's pathology is felt to be a contributing factor. We view all three available cholinesterase inhibitors as first-line drugs.

Alzheimer Disease↗
PubMed2003

Antinociception of intrathecal cholinesterase inhibitors and cholinergic receptors in rats.

BACKGROUND: Intrathecal cholinesterase inhibitors have been shown to have an antinociceptive effect which is mediated through the spinal cholinergic receptors, mainly muscarinic receptor. Spinal nicotinic receptor also has been involved in the control of nociception. Authors characterized the respective role of muscarinic or nicotinic receptor for the antinociception of cholinesterase inhibitors and further determined the antinociceptive potency of them. METHODS: Rats were prepared with intrathecal catheters. Formalin-induced flinching response was regarded as a nociceptive behavior. RESULTS: Intrathecal neostigmine, physostigmine and edrophonium produced a dose-dependent suppression of flinching in both phases. Atropine and the M1 selective antagonist attenuated the effect of them, while the M2 selective antagonist did not affect. M3, M4 selective, and nicotinic receptor antagonists reversed the antinociception induced by edrophonium, but by neither neostigmine nor physostigmine. The ordering of potency was neostigmine > physostigmine > > edrophonium. CONCLUSION: These data indicate that the nicotinic receptor may be involved, at least in part, in the antinociceptive action of cholinesterase inhibitor at the spinal level, and M1 receptor subtype may be a common pharmacologic site of action. Moreover, neostigmine is more potent than physostigmine and edrophonium.

Analgesics↗
PubMed1966

Inhibition of cholinesterases by fluoride in vitro.

1. Series of colorimetric dynamic assays allowed the study of the inhibition of cholinesterases by F(-) ions in vitro, by using, as sources of enzyme, whole human blood, human serum, homogenized rat brain and two preparations of red blood cells (human and bovine) whose enzymic purity was ascertained. 2. The first evidence of inhibition of human serum pseudocholinesterase by fluoride was noticed at 15-25mum-fluoride. Ten times as much fluoride was needed to start inhibition of acetylcholinesterase of the red blood cells. 3. The action of fluoride on the enzymic reaction was immediate. The reversibility of the inhibition was shown by dialysis and dilution. 4. Kinetic measurements showed that the inhibition under study was not dependent on the substrate concentration and was of the uncompetitive type, similar to that observed in the presence of a heavy metal (cadmium). 5. The activity of serum cholinesterase did not change in the absence of Mg(2+) and Ca(2+) ions. Fluoride was shown to inhibit the enzyme in the absence of these ions as well as of phosphate. 6. Fluoride could inhibit cholinesterases in the presence of three different substrates and had no action on the non-enzymic hydrolysis. 7. It is thought that the halide is bound reversibly to the enzyme molecule, with the probable exclusion of the active site, but no firm conclusion could be reached on this point.

Animals↗
PubMed1987

Spatiotemporal relationship of embryonic cholinesterases with cell proliferation in chicken brain and eye.

Close relationships between acetylcholinesterase (AcChoEase; acetylcholine acetylhydrolase, true cholinesterase, EC, 3.1.1.7) and butyrylcholinesterase (BtChoEase, acylcholine acylhydrolase, pseudocholinesterase, EC, 3.1.1.8) with cell proliferation were observed in the early chicken brain. These include the following: BtChoEase is transiently accumulating in patchy fashion on the ventricular side of the neuroepithelium shortly before AcChoEase appears in cell bodies along the opposing mantle layer. The amount of BtChoEase in retina and brain is greatest in the early phase (E3-E5, or incubation periods of 3-5 days); in retina it decreases about 2 days later than in brain. However, AcChoEase expression increases with time, in inverse order to that of BtChoEase. In both tissues decrease of cell proliferation is closely followed by decrease in BtChoEase. A double-labeling technique of cholinesterase staining together with [3H]thymidine autoradiography reveals proliferation zones that are diffusely stained by BtChoEase but not by AcChoEase. Patches intensely stained for BtChoEase accompany clusters of cells in final stages of mitosis on their way to the differentiation zone, where they begin expressing AcChoEase. By applying different thymidine pulses, we identify an 11-hr lag from the last thymidine-uptake to full AcChoEase expression. (iv) These findings are confirmed by studying lens development, where areas of proliferation and differentiation are well separated. The spatiotemporal pattern of the transition of neuroblasts from a proliferating into a differentiating state correlates with the expression of BtChoEase just before and during mitosis and that of AcChoEase about 11 hr after mitosis. Thus cholinesterases could be involved in the regulation of this transition.

Acetylcholinesterase↗
PubMed1991

Cholinesterase-like domains in enzymes and structural proteins: functional and evolutionary relationships and identification of a catalytically essential aspartic acid.

Primary sequences of cholinesterases and related proteins have been systematically compared. The cholinesterase-like domain of these proteins, about 500 amino acids, may fulfill a catalytic and a structural function. We identified an aspartic acid residue that is conserved among esterases and lipases (Asp-397 in Torpedo acetylcholinesterase) but that had not been considered to be involved in the catalytic mechanism. Site-directed mutagenesis demonstrated that this residue is necessary for activity. Analysis of evolutionary relationships shows that the noncatalytic members of the family do not constitute a separate subgroup, suggesting that loss of catalytic activity occurred independently on several occasions, probably from bifunctional molecules. Cholinesterases may thus be involved in cell-cell interactions in addition to the hydrolysis of acetylcholine. This would explain their specific expression in well-defined territories during embryogenesis before the formation of cholinergic synapses and their presence in noncholinergic tissues.

Acetylcholinesterase↗
PubMed1991

Serum cholinesterase levels of vector control workers in Trinidad, West Indies (1979-1987).

During 1979-1987 studies were carried out in vitro on the serum cholinesterase levels of 46 vector control workers exposed to insecticides on a daily basis but without clinical manifestations of insecticide poisoning. The results were compared with those of a control group of workers who had not been exposed to insecticides at home or at work. Cholinesterase levels of both groups were determined by a standard colorimetric method. Suppressed serum cholinesterase levels were detected in all 46 workers exposed to insecticides, 25 of whom were aged 30-39 years. Four persons from the control group showed suppressed levels of enzyme; one of these had a genetically low level, and the other three were on medication when the low levels were recorded.

Adult↗
PubMedDate not supplied

Effect of exposure to organophosphate pesticides on serum cholinesterase levels.

In this paper are reported the effects of organophosphate pesticide exposure. Agricultural workers were compared with an age- and sex-matched control group selected from the general population. A significant difference was detected (Student's t = 1.99, p = .05) between the median activity levels of serum cholinesterase in agricultural workers at the end of the work day (mean 4.44, 95% CI = 4.12-4.77), compared with those in the control group (mean = 4.85, 95% CI = 4.57-5.13). The decrease in cholinesterase activity, measured at the beginning (mean = 4.70, 95% CI = 4.38-5.02) and end of the work day, was very significant (paired t = 2.70, p = .01). An interaction was identified between the type of work and the worker's age. Younger workers tended to perform more dangerous activities, and they experienced a greater decrease in cholinesterase activity. This study indicates that subclinical intoxication of agricultural workers, by pesticides, is occurring in Mexico and indicates the need for primary prevention programs that address occupational contact with such substances.

Adolescent↗
PubMed1982

Cholinesterase activities of workers exposed to organophosphorus insecticides in Pakistan and Haiti and an evaluation of the tintometric method.

Five reference laboratories were established in Pakistan for monitoring cholinesterase (ChE) activities of workers exposed to organophosphorus compounds. ChE activities were determined by the Michel and tintometric method. Observations of ChE activities were made during two malaria seasons. The first season showed that although a significant depression of cholinesterase occurred among some of the workers, the ChE activities of workers were within the normal range during the following season. The reason for the difference is discussed. Similar studies were undertaken in Haiti. Mean and standard deviations (SD) were calculated for comparison of the tintometric versus the Michel method. The data show a correlation between the methods. For further evaluation of the tintometric method, organophosphorus and oxon analog inhibition of cholinesterase were determined in vitro. The tabulated data show that the tintometric method is adequate for determining whether a worker is exposed to dangerous amounts of insecticides.

Agricultural Workers' Diseases↗
PubMed2000

Effect of streptozotocin-induced diabetes on activities of cholinesterases in the rat retina.

The effect of streptozotocin-induced diabetes on cholinesterases activities was studied in the retina and, for comparison, in other nervous and nonnervous tissues. Streptozotocin diabetes did not affect acetylcholinesterase activity in the retina but increased its activity in the cerebral cortex (100%) and in serum (55%), and decreased it by 30-40% in erythrocytes. The butyrylcholinesterase activity was decreased by 30-50% in retina and hippocampus and to a lesser extent in retinal pigment epithelium from rats treated with streptozotocin for one week. Changes observed in cholinesterase activities were not correlated with the fasting blood glucose concentration. The results suggest that diabetes might influence a specific subset of cells and isoforms of cholinesterases. This, in turn, could lead to alterations associated with diabetes complications.

Animals↗
PubMed2001

Inhibition of cholinesterase enzymes following a single dermal dose of chlorpyrifos and methyl parathion, alone and in combination, in pregnant rats.

Pregnant Sprague-Dawley rats (14-18 d of gestation) were treated with either a single dermal subclinical dose of 30 mg/kg (15% of dermal LD50) chlorpyrifos (O,O-diethyl-O-[3,5,6-trichloro-2-pyridinyl] phosphorothioate) or a single dermal subclinical dose of 10 mg/kg (15% of dermal LD50) methyl parathion (O,O-dimethyl O-4-nitrophenyl phosphorothioate) or the two in combination. Chlorpyrifos inhibited maternal and fetal brain acetylcholinesterase (AChE) activity within 24 h of dosing, (48% and 67% of control activity, respectively). Following application of methyl parathion, peak inhibition of maternal and fetal brain AChE activity occurred at 48 h and 24 h after dosing (17% and 48% of control activity, respectively). A combination of chlorpyrifos and methyl parathion produced peak inhibition of maternal and fetal brain AChE activity at 24 h postdosing (35% and 73% of control activity, respectively). Maternal and fetal brain AChE activity recovered to various degrees of percentage of control 96 h after dosing. Application of methyl parathion or chlorpyrifos alone or in combination significantly inhibited maternal plasma butyrylcholinesterase (BuChE) activity. No significant inhibition of fetal plasma BuChE activity was detected. Peak inhibition of maternal liver BuChE occurred 24 h after application of methyl parathion or chlorpyrifos alone or in combination (64%, 80%, and 61% of control activity, respectively). Significant inhibition of placental AChE occurred within 24 h after application of methyl parathion or chlorpyrifos alone or in combination. The results suggest that methyl parathion and chlorpyrifos, alone or in combination, were rapidly distributed in maternal and fetal tissues, resulting in rapid inhibition of cholinesterase enzyme activities. The lower inhibitory effect of the combination could be due to competition between chlorpyrifos and methyl parathion for cytochrome P-450 enzymes, resulting in inhibition of the formation of the potent cholinesterase inhibitor oxon forms. The faster recovery of fetal plasma BuChE is attributed to the de novo synthesis of cholinesterase by fetal tissues compared to maternal tissues.

Acetylcholinesterase↗
PubMed1975

Influence of ketamine on human plasma cholinesterase.

The influence of ketamine upon human plasma cholinesterase (E.C. 3.1.1.8) was determined by means of a colorimetric assay technique at 25 degrees C, pH 7.7 with butyrylthiocholine as substrate. Ketamine caused a reversible inhibition of cholinesterase (pI50= 2.75; apparent Ki=4.94X10(-4) M). The kinetic analysis of the inhibitory action revealed a mixed competitive/non-competitive type of mechanism with a prevalence of the non-competitive component (alpha-value = 4.9). A decrease in cholinesterase activity is thought to be a result of conformational change of the enzyme protein which is induced by a reversible binding of ketamine to anionic side receptors in the vicinity of the active centre.

Anesthesia, General↗
PubMed1977

Preoperative serum cholinesterase concentration in chronic renal failure. Clinical experience of suxamethonium in 81 patients undergoing renal transplant.

Serum cholinesterase concentrations were measured in 181 patients in chronic renal failure. Significant differences in cholinesterase concentrations were not found in patients undergoing dialysis and changes appear to be independent of the method of treatment used. Clinical experience with suxamethonium to facilitate tracheal intubation was satisfactory in 80 patients undergoing renal transplant. Apnoea occurred in one patient who was found subsequently to have atypical cholinesterase inheritance.

Cholinesterases↗