Acetylcholinesterase from Human Erythrocytes as a Surrogate Biomarker of Lead Induced Neurotoxicity

Prediction of chemical-induced acute toxicity using in vitro assay data and chemical structure

Exposure to various chemicals found in the environment and in the context of drug development can cause acute toxicity. To provide an alternative to in vivo animal toxicity testing, the U.S. Tox21 consortium developed in vitro assays to test a library of approximately 10,000 drugs and environmental chemicals (Tox21 10K compound library) in a quantitative high-throughput screening (qHTS) approach. In this study, we assessed the utility of Tox21 assay data in comparison with chemical structure information in predicting acute systemic toxicity. Prediction models were developed using four machine learning algorithms, namely Random Forest, Naïve Bayes, eXtreme Gradient Boosting, and Support Vector Machine, and their performance was assessed using the area under the receiver operating characteristic curve (AUC-ROC). The chemical structure-based models as well as the Tox21 assay data demonstrated good predictive power for acute toxicity, achieving AUC-ROC values ranging from 0.83 to 0.93 and 0.73 to 0.79, respectively. We applied the models to predict the acute toxicity potential of the compounds in the Tox21 10K compound library, most of which were found to be non-toxic. In addition, we identified the Tox21 assays that contributed the most to acute toxicity prediction, such as acetylcholinesterase (AChE) inhibition and p53 induction. Chemical features including organophosphates and carbamates were also identified to be significantly associated with acute toxicity. In conclusion, this study underscores the utility of in vitro assay data in predicting acute toxicity.

Synthesis and larvicidal efficacy of pyrazolopyrimidine derivatives conjugated with selenium nanoparticles against Culex pipiens L. and Musca domestica L. larvae

The synthesized pyrazolopyrimidine derivatives conjugated with selenium nanoparticles were prepared via a reaction of pyrazolone 1 with aryl-aldehyde and malononitrile or 3-oxo-3-phenylpropanenitrile in the presence ammonium acetate or pipridine using an ultrasonic bath as a modified method in the organic synthesis for such materials. The structure of the synthesized compounds was elucidated through various techniques. All the synthesized pyrazolopyrimidines were used in the synthesis of selenium nanoparticles (SeNPs). These nanoparticles were confirmed using UV-spectra, Dynamic Light scattering and (TEM) techniques. The larvicidal efficiency;of the synthesized;compounds; was investigated against some strains such as Culex pipiens;and Musca domestica larvae. Bioassay test showed pyrazolopyrimide derivatives to exhibit an acceptable larvicidal;bio-efficacy. The derivative (3) exhibited;the highest;efficiency for more than; lab strains of both species. Moreover, C. pipiens larvae were more sensitive towards the examined compounds than M. domestica. The field;strain displayed lower affinity for the 2 folds compounds. Some biochemical changes were tracked through analysis of insect main metabolites (protein, lipid and carbohydrate), in addition to measuring the changes in seven enzymes after treatment. Generally, there was a reduction in the protein, lipids and carbohydrates after treatment with all tested compounds. Moreover, a decrement was noticed for acetylcholine esterase and glutathione;S-transferase; enzymes. There was an increment in the acid;phosphatase; and alkaline phosphatase. In addition, there was elevation in Phenoloxidase level but it noticed the declination in both Cytochrome P450 and Ascorbate peroxidase activity after treatment both flies with derivatives of selenium-nanoparticles in both lab and field strain. Generally, the experiments carried out indicate that antioxidant and detoxification enzymes may play a significant role in mechanism of action of our novel nanocompounds. The cytotoxicity of the synthesized compounds and conjugated with SeNPs showed enhanced compatibility with human normal fibroblast cell line (BJ1) with no toxic effect.

Comparison of acetylcholinesterase among employees based on job positions and personal protective equipment in fuel station

The purpose of this study was to compare the levels of acetylcholinesterase (AChE) among employees based on job positions and the wearing of personal protective equipment (PPE) in fuel station areas. The sample group consisted of 200 people sorted into various groups, including (i) Inside fuel dispenser area (I-FDA) group consisting of 100 employees for refueling, cashier, and loading fuel into storage tanks, and (ii) Outside fuel dispenser area (O-FDA) group, consisting of 100 employees working in convenience stores, food stores, coffee shops, and offices, as well as general staff and car washers. Data were collected using interview questionnaires and blood samples were analyzed for AChE activity. The results showed that the I-FDA group had a significantly lower mean of serum AChE (7.38±1.73 U/ml) than the O-FDA group (7.85±1.49 U/ml) (p<0.05). The I-FDA group had a 2.43 times higher risk of abnormal serum AChE than the O-FDA group (OR=2.43, 95%CI=1.05-5.60). When considering the risk factors for job positions, it was found that refueling and cashier positions had lower AChE activity levels than those who did not (p<0.05). In the part, employees for food sales in a closed building and those wearing PPE masks had significantly higher AChE activity levels than those who did not or who wore them (p<0.05). Based on the aforementioned, employers at fuel stations should strictly determine the appropriate measures for wearing a PPE mask. Further, employees should be provided accommodation away from oil supply or enclosed buildings during breaks to reduce the effects on the neurotransmitter.

Advances in the Utilization of Zebrafish for Assessing and Understanding the Mechanisms of Nano-/Microparticles Toxicity in Water

A large amount of nano-/microparticles (MNPs) are released into water, not only causing severe water pollution, but also negatively affecting organisms. Therefore, it is crucial to evaluate MNP toxicity and mechanisms in water. There is a significant degree of similarity between the genes, the central nervous system, the liver, the kidney, and the intestines of zebrafish and the human body. It has been shown that zebrafish are exceptionally suitable for evaluating the toxicity and action mechanisms of MNPs in water on reproduction, the central nervous system, and metabolism. Providing ideas and methods for studying MNP toxicity, this article discusses the toxicity and mechanisms of MNPs from zebrafish.

Adverse effects of polystyrene nanoplastic and its binary mixtures with nonylphenol on zebrafish nervous system: From oxidative stress to impaired neurotransmitter system

Micro(nano)plastics generally co-exist with other chemicals in the environment, resulting in inevitable interaction and combined toxic effects on biota. Nevertheless, little is known regarding the interaction of nanoplastics (NPs) with other co-occurring insults. Hereby, we investigated single and combined effects of chronic exposure (45 days) to polystyrene nanoplastic particulates (PS-NPs) and nonylphenol (4-NP) on zebrafish nervous system. Multiple biomarkers concerning with oxidative-stress [catalase (CAT) activity and reduced glutathione (GSH) level], cholinergic system [Acetylcholinesterase (AchE) activity], glutamatergic system [glutamine synthetase (GS) and glutamate dehydrogenase (GDH) activities], energy metabolism [a-ketoglutarate dehydrogenase (a-KGDH) activity], and histological alterations were assessed. Both single and binary exposure to PS-NPs and 4-NP induced oxidative stress through reducing CAT activity and GSH level, in which a more sever effect was noticed in combined exposure. The AchE activity was significantly inhibited only in single treatment groups demonstrating antagonistic interaction between PS-NPs and 4-NP. Effects on GS activity was also alleviated in binary exposure as compared with single exposure to each contaminant. In addition, an increase in GDH activity was noticed in PS-NPs at 10 and 100 μg/L, and simultaneous presence of PS-NPs and 4-NP with a greater response were observed in combined treatments. PS-NPs and 4-NP either in separate or binary mixtures disrupted energy metabolism by deficiency of α-KGDH activity; however, co-exposure to PS-NPs and 4-NP induced more intense adverse impacts on this parameter. Furthermore, histological analysis revealed that 4-NP and PS-NPs, alone or in combination, reduced neural cells. These findings provide new insight into the neurotoxic effects of binary exposure to PS-NPs and 4-NP at environmentally relevant concentrations. Overall, our findings raise concerns about the presence and toxicity of nano-scale plastic particulates and highlight the importance of investigating the interaction of Micro(nano)plastics with other environmental irritants.

Microplastics exposure as an emerging threat to ancient lineage: A contaminant of concern for abnormal bending of amphioxus via neurotoxicity

Growing inputs of microplastics into marine sediment have increased significantly the needs for assessment of their potential risks to the marine benthos. A knowledge gap remains with regard to the effect of microplastics on benthos, such as cephalochordates. By employing amphioxus as a model benthic chordate, here we show that exposure to microplastics for 96 h at doses of 1 mg/L and 100 mg/L results in evident accumulation of the polyethylene microplastics. The accumulated microplastics are as much as 0.027% of body weight upon high-dose exposure, causing an abnormal body-bending phenotype that limits the locomotion capability of amphioxus. Mechanistic insight reveals that microplastics can bring about histological damages in gill, intestine and hepatic cecum; In-depth assay of relevant biomarkers including superoxide dismutase, catalase, glutathione, pyruvic acid and total cholesterol indicates the occurrence of oxidative damage and metabolic disorder; Further, microplastics exposure depresses the activity of acetylcholinesterase while allowing the level of acetylcholine to rise in muscle, suggesting the emergence of neurotoxicity. These consequences eventually contribute to the muscle dysfunction of amphioxus. This study rationalizes the abnormal response of the vulnerable notochord to microplastics, signifying the dilemma suffered by the ancient lineage under the emerging threat. Given the enrichment of microplastics through marine food chains, this study also raises significant concerns on the impact of microplastics to other marine organisms, and eventually human beings.

In silico, theoretical biointerface analysis and in vitro kinetic analysis of amine compounds interaction with acetylcholinesterase and butyrylcholinesterase

Acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) are considered important target for drug design against Alzheimer's disease. In the present study in silico analysis; theoretical analysis of biointerface between ligand and interacting amino acid residues of proteins; and in vitro analysis of enzyme inhibition kinetics were carried out to delineate the inhibitory property of amine compounds against AChE/BChE. High throughput virtual screening of amine compounds identified three compounds (2-aminoquinoline, 2-aminobenzimidazole and 2-amino-1-methylbenzimidazole) that best interacted with AChE/BChE. Molecular docking analysis revealed the interaction of these compounds in the active site gorge of AChE/BChE, in particular with amino acid residues present in the peripheral anionic site. Molecular dynamics simulation confirmed the stable binding of these compounds with AChE/BChE. Binding energy calculated through MMGBSA method identified the non-covalent interactions (electrostatic and Van der Waals interactions) have contributed to the stable binding of the amine compounds with the AChE/BChE. Biointerface between amine compounds and AChE/BChE were visualized through Hirshfeld surface analysis. The inter-fragment interaction energies for the possible contacts between amine compounds and amino acid residues were carried out for the first time. All the amine compounds showed mixed-type of inhibition with moderate Ki value in in vitro analysis.

Lead nitrate and cadmium chloride induced hepatotoxicity and nephrotoxicity: Protective effects of sesamol on biochemical indices and pathological changes

Lead nitrate (LN) and cadmium chloride (CdCl₂ ), regarded as environmental contaminants, are toxic heavy metals. Sesamol is a dietary phytochemical found in sesame oil. We aimed to analyze the hepatotoxic and nephrotoxic effects of LN and CdCl₂ and to evaluate the possible protective effect of sesamol. LN (90 mg/kg bw per day), CdCl₂ (3 mg/kg bw per day), and sesamol (50 mg/kg bw per day) were given to rats via gavage for 28 days. Total protein, albumin, alanine aminotransferase, aspartate aminotransferase, lactate dehydrogenase, total cholesterol, urea, uric acid, creatinine, superoxide dismutase, catalase, glutathione peroxidase, glutathione-S-transferase, malondialdehyde, acetylcholinesterase, and histopathological changes were investigated in liver and kidney tissues. Lead and cadmium were found to result in decreases in the antioxidant enzymes and acetylcholinesterase activities, increases in malondialdehyde levels, and changes in serum biochemical parameters and various pathological findings. An improvement in all these parameters was observed in the sesamol-treated groups. PRACTICAL APPLICATIONS: Heavy metals are used in many areas of the industry all over the world. Heavy metals which include lead nitrate and cadmium chloride cause cell damage by oxidative stress. Some of the examining parameters for oxidative stress are SOD, GST, MDA, GPx, and CAT. However, some chemicals such as sesamol are well-liked and widely used as antioxidants against xenobiotic toxicity. We also indicate that sesamol has been shown to protective effect against heavy metals caused cell damage.

Kinetic characterization of rat brain acetylcholinesterase modulated by lead and cartap: the ameliorative effect of Citrus limon fruit juice

Objectives Human exposure to heavy metals and pesticides is a worldwide major health problem. These environmental pollutants have been considered as the most neurotoxic agents and responsible to causing neurological toxicity. Plant-based therapeutic supplement may be used in the event of toxicity. Citrus limon contains several useful bioactive ingredients including flavonoids, dietary fiber, carotenoids, vitamins, pectin, minerals, and essential oils, which are responsible for its therapeutic potential. In the present investigation, we have studied the toxicity of heavy metals such as lead (Pb) and a carbamate pesticide such as cartap (Cp) on rat brain acetylcholinesterase (AChE). Methods The chemical characterization of C. limon involved determination of total antioxidants and 2,2-diphenyl-1-picryl-hydrazyl-hydrate free radical scavenging activity using known methods. The AChE activity and its kinetic characterization were performed by assaying the enzyme activity at varying substrate concentrations, pH, temperature, and time of reaction. Its different kinetic parameters such as K i , V max, K m , K cat, and K cat/K m were determined by using standard procedures. The amelioration potential of the extract was evaluated on the neurotransmission system of rat brain AChE treated with Pb, Cp, and their combination (Pb-Cp), considering their 50% inhibitory concentration (IC50) values. Results The optimal activity of rat brain AChE was recorded at 25 µg of protein, pH of 7.4, substrate concentration [S] of 0.5 mM, and temperature of 37.4-40°C. The enzyme was stable for 10 min when incubated at 37.4 °C in vitro. The enzyme displayed 70% of its activity remaining even after 160 min of incubation in this condition. It may be stable up to 1 month when stored at -20°C. The IC50 values for Pb, Cp, and Pb-Cp were found to be 75, 2.9, and 5 mM, respectively. Pb, Cp, and Pb-Cp inhibited the activity of rat brain AChE in the noncompetitive, mixed, and uncompetitive manners, respectively, with their respective K i values to be 675, 2.37, and 22.72 mM. Conclusions The results indicated that the Pb and Cp were able to cause significant alterations in the level and properties of AChE. However, the introduction of lemon juice on Pb- and Cp-treated AChE indicated protection of its activity from their adverse effects. The results may be useful in prospective therapeutic applications of lemon juice or as a food supplement to protect mammalian systems from adverse effects of these toxicants.

Sublethal effects of chronic exposure to CdO or PbO nanoparticles or their binary mixture on the honey bee (Apis millefera L.)

Cadmium and lead-based nanotechnologies are increasingly used in agricultural, industrial, and biological processes; however, potential adverse effects of nanomaterials on honey bees had not been assessed. In this study, effects of exposures to sublethal concentrations of PbO and CdO nanoparticles (NPs), either separately or in combination on honey bee (Apis mellifera) workers, were assessed. Honey bee workers were orally exposed for 9 days under laboratory conditions to sublethal concentrations (20% of LC₅₀) of CdO (0.01 mg/ml^-) and PbO (0.65 mg/ml^-) NPs either separately or combined. Effects on survival, feeding rate, activity of acetylcholinesterase (AChE), and expression of selected stress-related detoxifying enzymes were quantified. Survival and feeding rates decreased particularly in bees fed sugar syrup containing CdO NPs or binary mixtures of NPs of both metal oxides. Expressions of genes involved in detoxification of xenobiotics were affected by various combinations. Expression of catalase was 13.6-fold greater in bees consumed sugar syrup diet containing binary mixture of sublethal concentrations of both CdO and PbO NPs than it was in unexposed, control bees. AChE activity in heads of honey bees was inhibited by 3.8-, 3.0-, and 2.8-fold relative to control, respectively, in response to exposure to Cd or/and Pb oxide NPs. This result indicates potential neurotoxic effects of these NPs to honey bees. CdO NPs exhibited greater potency to honey bees. Overall, sublethal concentrations of CdO or/and PbO NPs resulted in detrimental effects on honeybee workers.

Positive and inverse correlation of blood lead level with erythrocyte acetylcholinesterase and intelligence quotient in children: implications for neurotoxicity

Blood lead level (BLL) is insufficiently sensitive for early detection of Lead-induced neurotoxicity (LIN). This study determined the possible role of the combination of BLL, intelligent quotient (IQ) and erythrocyte acetylcholinesterase (AChE) activity in the early detection of LIN in Children. Apparently healthy children (n=309) from eight public primary schools in Ibadan, Nigeria were recruited and classified into: children with Elevated BLL (EBLL) and children with Acceptable BLL (control) based on CDC cut-off for childhood lead exposure. Neurological indices (speech, memory, cranial nerves and cerebellar functions), IQ, BLL and erythrocyte AChE activity were assessed using standard methods, Standard Progressive Matrices, AAS and HPLC respectively. Statistical analysis involved Student’s t-test, Pearson’s correlation and multivariate regression. p<0.05 was considered significant. There were 169 (54.7%) children with EBLL while there were 140 (45.3%) control children. Both groups exhibited normal speech, memory, cranial nerves and cerebellar functions. However, IQ was lower in EBLL children (85.9±11.6) compared with control (91.5±14.0) while BLL and AChE activity were higher in EBLL children (0.4±0.1 μmol/l; 117.5±25.5 μkat/l) compared with control (0.2±0.0 μmol/l; 59.4±10.2 μkat/l). BLL showed inverse correlation with IQ (r=–0.134, p=0.019) but positive correlation with AChE (r=0.978, p≤0.001). 16.2% of the observed variation in BLL could be accounted for by AChE using the equation; [BLL=–0.007+0.003 AChE] p<0.05. Elevated blood lead level is prevalent among the school children and appears to have adverse effect on their IQ. Erythrocyte AChE could be a promising marker for early recognition of significant environmental lead exposure and lead-induced neurotoxicity in children.

Evaluation of single and combined effects of cadmium and micro-plastic particles on biochemical and immunological parameters of common carp (Cyprinus carpio)

The growing accumulation of microplastics (MPs) in aquatic environments is a global concern. MPs are capable to interact with other environmental contaminants, including heavy metals, altering their toxicity. The aim of the study was to investigate the sub-lethal effects of cadmium chloride (Cd) alone and in combination with MPs on common carp (Cyprinus carpio). Multi-biomarkers, including plasma biochemical parameters and intrinsic immunological factors, were measured after 30 days of exposure. Exposure to Cd or NPs reduced the plasma activities of acetylcholinesterase (AChE) and gamma-glutamyl-transferase (GGT) and increased aspartate aminotransferase (AST), alanine aminotransferase (ALT), lactate dehydrogenase (LDH) and alkaline phosphatase (ALP). Exposure to both compounds enhanced the observed effects except for AST activity and ALP at the highest concentrations, whereas evidenced an antagonistic interaction in ALT. Plasma total protein, albumin, and globulin levels were decreased, and the levels of glucose, triglyceride, and cholesterol levels increased mainly in the Cd groups with no additional effects derived from the co-exposure to both stressors. Lysozyme and alternative complement (ACH50) activities and the levels of total immunoglobulins, and complement C3 and C4 in fish exposed to Cd and MPs were lower than those in the control group and this decrease was more significant by the mixture of both compounds. These findings showed that the exposure to Cd or MPs alone is toxic to fish altering the biochemical and immunological parameters. Moreover, these alterations are even greater when the Cd and the MPS are combined suggesting synergistic effects in increasing Cd toxicity and vice versa.

Design and development of novel N-(pyrimidin-2-yl)-1,3,4-oxadiazole hybrids to treat cognitive dysfunctions

Novel hybrids bearing a 2-aminopyrimidine (2-AP) moiety linked to substituted 1,3,4-oxadiazoles were designed, synthesized and biologically evaluated. Among the developed compounds, 28 noncompetitively inhibited human acetylcholinesterase (hAChE; pIC₅₀ = 6.52; Ki = 0.17 µM) and showed potential in vitro antioxidant activity (60.0%) when evaluated using the Ellman's and DPPH assays, respectively. Compound 28 competitively displaced propidium iodide (PI) from the peripheral anionic site (PAS) of hAChE (17.6%) and showed high blood-brain barrier (BBB) permeability, as observed in the PAMPA-BBB assay. Additionally, compound 28 inhibited hAChE-induced Aβ aggregation in a concentration-dependent manner according to the thioflavin T assay and was devoid of neurotoxic liability towards SH-SY5Y cell lines, as demonstrated by the MTT assay. The behavioral studies of compound 28 in mice showed a significant reversal of scopolamine-induced amnesia, as observed in Y-maze and passive avoidance tests. Furthermore, compound 28 exhibited significant AChE inhibition in the brain in ex vivo studies. An evaluation of oxidative stress biomarkers revealed the antioxidant potential of 28. Moreover, in silico molecular docking and dynamics simulation studies were used as a computational tool to evaluate the interactions of compound 28 with the active site residues of hAChE.

Synergistic Effects of Heavy Metals and Pesticides in Living Systems

There is a widespread repeated exposure of the population to the pesticides and heavy metals of occupational and environmental origin. Such population is forced to undergo continuous stress imposed by combined exposure of the heavy metals and different classes of the pesticides used in agricultural as well as health practices. The existing reports from several workers have indicated that heavy metals and pesticides in combination may lead more severe impact on the human health when compared to their individual effects. Such a combination of pesticides and heavy metals may also change or influence the detection of exposure. Several studies in past have shown the synergistic toxic effects of heavy metals and pesticides. Such evaluations have revealed the synergistic interactions of various heavy metals and pesticides in animals as well as humans. The aim of the present article is to provide a synthesis of existing knowledge on the synergistic effects of heavy metal and pesticides in living systems. The information included in this article may be useful for different environment protection agencies and policy makers to consider the combined effects of heavy metals and pesticides on humans while designing strategies toward environmental protection and safety regulations about human health.

Human Erythrocyte Acetylcholinesterase in Health and Disease

The biochemical properties of erythrocyte or human red blood cell (RBC) membrane acetylcholinesterase (AChE) and its applications on laboratory class and on research are reviewed. Evidence of the biochemical and the pathophysiological properties like the association between the RBC AChE enzyme activity and the clinical and biophysical parameters implicated in several diseases are overviewed, and the achievement of RBC AChE as a biomarker and as a prognostic factor are presented. Beyond its function as an enzyme, a special focus is highlighted in this review for a new function of the RBC AChE, namely a component of the signal transduction pathway of nitric oxide.

Prevalence of chromosomal aberrations in Argentinean agricultural workers

Little is known about biosecurity measures and toxic effects during pesticide application in the province of Jujuy, Argentina, particularly concerning the protective measures and mixture of pesticides used by rural workers. We carried out an observational study of agricultural workers from Jujuy (76 exposed subjects and 53 controls) to investigate the prevalence of chromosomal aberrations (CAs) in human lymphocytes as well as the activity level of acetylcholinesterase (AChE) in red blood cell erythrocytes. Whole blood samples (5 mL) were collected in heparinized Vacutainer tubes for cytogenetic analysis and erythrocyte cholinesterase activity determination according to Ellman's method. Cytogenetic results showed a significant CA increase in pesticide-exposed individuals as compared with controls (4.20 ± 0.15 vs. 1.00 ± 0.05, respectively; p < 0.001), suggesting that pesticides are clastogenic agents causing DNA damage. Erythrocyte cholinesterase activity was significantly lower in exposed individuals, evidencing the possible occurrence of perturbations in blood as well as neurotoxicity in pesticide sprayers. These results suggest the need for periodic biomonitoring of these biomarkers together with education and training of occupational workers for the safe application of potentially harmful pesticides.

How and where to perform biomonitoring studies: different levels of toxic metal pollution are detected in the Alagados Reservoir in Southern Brazil

The Alagados Reservoir located in the Brazilian city of Ponta Grossa is used to supply water for human consumption but is impacted by toxic metals. The current study combined chemical, biochemical, and multivariate analyses to determine the bioavailability of toxic metals at three sites (AL-A, AL-B, and AL-C) within the Alagados Reservoir. Metal bioaccumulation was analyzed in the liver, gills, and muscle tissue of a native fish species (Geophagus brasiliensis), and neurotoxicity, xenobiotic metabolism, and oxidative stress were evaluated using biochemical biomarkers. Additionally, histopathological studies were performed on the gills and the liver using scanning electron microscopy (SEM) and conventional light microscopy (LM), respectively. Overall, the bioaccumulation of metals, biomarkers of oxidative stress, and melanomacrophage counts indicate that the AL-C and the AL-A sites are the most and least affected by metals, respectively. The AL-B site presented the lowest acetylcholinesterase enzyme activity, a finding which was probably associated with the agricultural activities around this area of the reservoir. The biomarkers clearly revealed that toxic metals negatively affect all three sites studied herein and that human activity is the major source of pollutants. Despite the existence of different pollution levels within the Alagados Reservoir, it is still used as a human water supply.

Differential inhibition of human erythrocyte acetylcholinesterase by polyphenols epigallocatechin-3-gallate and resveratrol. Relevance of the membrane-bound form

The activity of acetylcholinesterase (AChE) from human erythrocytes was tested in the presence of the phenolic compounds resveratrol and epigallocatechin-3-gallate (EGCG). Even though the stilbene barely changed this enzymatic activity, EGCG did inhibit AChE. Importantly, it preferentially acted on the membrane-bound enzyme rather than on its soluble form. Actually, it was shown that this flavonoid may bind to the red blood cell membrane surface, which may improve the interaction between EGCG and AChE. Therefore, caution should be taken when screening AChE inhibitors. In fact, testing compounds with the soluble form of the enzyme may underestimate the activity of some of these potential inhibitors, hence it would be advisable not to use them as a sole model system for screening. Moreover, erythrocyte AChE is proposed as a good model for these enzymatic assays. © 2016 BioFactors, 43(1):73-81, 2017.