Pesticide toxicity assessment and geographic information system (GIS) application in small-scale rice farming operations, Thailand.

The objectives of the study were to evaluate the impact of pesticide exposure on farmer health during non-active rice farming and active rice farming periods and present the change in the individual cholinesterase activities (%reduction) on the geographic information system (GIS) mapping in Nakhon Ratchasima Province, Thailand. Acetyl- and butyryl-cholinesterase (AChE and BuChE) activities were monitored during both study periods using Test-mate ChE (Model 400). The location of paddy fields was specified using Garmin geographic positioning system MAP 62s. Fifty-eight farmers who participated in this study had an average age of 49.2 ± 6.9 years. Higher prevalence of all health symptoms was observed among farmer participants during the active rice farming period comparing to the non-active rice farming period (p < 0.01). Furthermore, farmers had significantly lower activities of AChE and BuChE during the active rice farming period comparing to the non-active rice farming period (p < 0.01). Our findings indicate that the GIS mapping indicate that the cases with a significant enzyme inhibition have dispersed across the agricultural and the nearby residential areas. This, investigation can be used to promote safer use of pesticides among farmers and mitigate pesticide exposure among residents living in close proximity to a rice field.

Acute and long-term effects of VX in rat brain cell aggregate culture.

The contact poison VX (O-ethyl S-(2-diisopropylaminoethyl) methylphosphonothioate) is a chemical warfare agent that is one of the most toxic organophosphorus compounds known. Its primary mechanism of toxic action is through the inhibition of acetylcholinesterase and resultant respiratory paralysis. The majority of work on VX has thus concentrated on its potent anticholinesterase activity and acute toxicity, with few studies investigating potential long-term effects. In this report we describe the effects of VX in aggregating rat brain cell cultures out to 28 days post-exposure. Cholinesterase activity was rapidly inhibited (60 min IC50 = 0.73 +/- 0.27 nM), but recovered towards baseline values over the next four weeks. Apoptotic cell death, as measured using caspase-3 activity was evident only at 100 µM concentrations. Cell type specific enzymatic markers (glutamine synthase, choline acetyltransferase and 2',3'-cyclic nucleotide 3'-phosphodiesterase) showed no significant changes. Total Akt levels were unchanged, while an increased phosphorylation of this protein was noted only at the highest VX concentration on the first day post-exposure. In contrast, significant and delayed (28 days post-exposure) decreases were noted in vascular endothelial growth factor (VEGF) levels, a protein whose reduced levels are known to contribute to neurodegenerative disorders. These observations may indicate that the long-term effects noted in some survivors of nerve agent intoxication may be due to VX-induced declines in brain VEGF levels.

A ratiometric fluorescence strategy based on inner filter effect for Cu2+-mediated detection of acetylcholinesterase.

A novel ratiometric fluorescence strategy for detection of acetylcholestinerase (AChE) is proposed based on carbon nitride quantum dots (g-CNQD) and the complex (PA) formed between phenylboronic acid (PBA) and alizarin red S (ARS). PA showed fluorescence at 598 nm and quenched the fluorescence of g-CNQD at 438 nm. Through UV-visible absorption, fluorescence, and fluorescence lifetime measurements, the quenching effect was demonstrated as inner filter effect (IFE). When Cu2+ was added, the coordination of ARS and Cu2+ decreased the fluorescence of PA at 598 nm and recovered that of g-CNQD at 438 nm. In the presence of AChE it catalyzed the hydrolysis of acetylthiocholine (ATCh) to produce thiocholine (TCh) which competed with ARS for binding to Cu2+; thus, the fluorescence at 598 nm increased and that at 438 nm decreased again. Under the mediation of Cu2+, the fluorescence ratio F598/F438 of PA-CNQD probe had good linear relationship with AChE concentration in the range 0.5-15 mU/mL with a detection limit of 0.36 mU/mL. The method was successfully applied to the determination of AChE in human serum and the screening of inhibitors.

Pesticides use and health impacts on farmers in Thailand, Vietnam, and Lao PDR: Protocol for a survey of knowledge, behaviours and blood acetyl cholinesterase concentrations.

Pesticides use in Southeast Asia has increased steadily, driven by the growth of large-scale commercial farming, as well as a desire to maximise food production in rural subsistence economies. Given that use of chemical pesticides, such as organophosphates and carbamates, has known potential health impacts, there are concerns about the safety of agricultural workers, and a need for a better evidence base to underpin regulation and worker education. This study, undertaken in 9 districts in Lao PDR, Thailand and Vietnam, will interview agricultural workers to investigate how they use pesticides, their knowledge of risks and self-protective practices, and their self-reported illness symptoms. In each district researchers will recruit and interview 120 participants engaged in vegetable farming, who have recently used pesticides, making a total of 1080 subjects divided equally between the three study countries. Workers' degree of pesticides exposure will be determined from acetyl cholinesterase concentrations in capillary blood samples collected using field test kits, and these data will be analysed together with the interview findings. Country findings will be compared and contrasted, and general patterns noted. Knowledge gained about risky behaviours, self-protective practices and degree of association with serious pesticides exposure will assist policy makers and inform health improvement programmes.

Changes in serum biomarkers of inflammation in bovine besnoitiosis.

BACKGROUND: Acute and chronic besnoitiosis in extensive natural-service herds can have relevant effects in the health of bulls and negative consequences in their productive performance. Recent progress has been made in order to elucidate the pathogenesis of this disease. In this context, the study of biomarkers of inflammation in serum would contribute to gaining knowledge about the physiopathology of bovine besnoitiosis. Serological biomarkers could help in early diagnosis and prognosis, as seropositive bulls may have mild or severe testicular lesions. METHODS: Herein, we have investigated the diagnostic and/or prognostic value of a panel of serum (serological) biomarkers related to inflammation, including total protein, globulin and albumin, haptoglobin (Hp), adenosine deaminase (ADA) paraoxonase-1 (PON-1) and acetylcholinesterase (AChE) in naturally and experimentally B. besnoiti-infected males classified according to different clinical phases of the disease (acute, chronic and subclinical besnoitiosis). RESULTS: Results showed a similar response pattern in these biomarkers for naturally and experimentally infected cattle, with a few relevant variations. Most significant changes occurred during the acute phase of infection, although significant changes in a few biomarkers were also observed during the chronic infection. Haptoglobin, albumin, PON-1 and ADA were identified as the biomarkers that showed changes of higher magnitude in the acute phase of the infection, whereas high total protein and globulin values were found in chronically infected cattle. We have described the changes of a panel of inflammatory biomarkers of acute and chronic bovine besnoitiosis. CONCLUSIONS: In summary, several biomarkers with promising diagnostic value have been identified. The biomarkers associated with acute infection are related to previously reported molecular biomarkers in testicular parenchyma of infected bulls and could help in the diagnosis of early infections and complement results from specific immunoglobulin M (IgM) detection.

Attenuation of spatial memory in 5xFAD mice by targeting cholinesterases, oxidative stress and inflammatory signaling using 2-(hydroxyl-(2-nitrophenyl)methyl)cyclopentanone.

Alzheimer's disease (AD) is classified pathologically as a progressive neurological disorder associated with memory decline. The study was designed to assess the underlying molecular signaling involved in the neuroprotective effect of the 2-(hydroxyl-(2-nitrophenyl)methyl)cyclopentanone (2NCP) as a novel therapeutic agent for AD. In this connection, in vitro cholinesterases inhibitory and antioxidant activities were investigated. In vivo studies were carried out on a well-known 5xFAD mice model in different behavioural models such as light/dark box,balance beam, rotarod, elevated plus maze (EPM),novel object recognition (NOR), paddling Y-maze, and Morris water maze (MWM) tests. Hippocampus (HC) and frontal cortex (FC) homogenates were examined for acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) activities, 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radicals, glutathione S-transferase (GST), glutathione (GSH), and catalase. Further, we examined the expression of inflammatory cytokines and Nrf2 in the HC and FC through RT-PCR. Computational studies were conducted to predict the binding mode of the 2NCP with target sites of nuclear factor-κB (NF-κB) and cholinesterases. The findings of in vitro assays revealed that the IC50 values of the 2NCP against AChE and BChE were 17 and 23 µg/ml respectively. DPPH antioxidant assay displayed an IC50 value for the 2NCP was 62 µg/ml. Whereas, theex vivo study depicted that the activities of AChE and BChEwere significantly reduced. Moreover, free radicals load, GSH level, catalase and GST activities were significantly declined. Furthermore, in vivostudies showed that the 2NCP treated animals exhibited gradual memory improvement and improved motor functions. RT-PCR study revealed that mRNA levels of the inflammatory mediators (IL-1ß, IL-6, TNF-α) were significantly reduced, while the expression of antioxidant Nrf2 was significantly increased.The molecular docking studies further confirmed that the 2NCP showed excellent binding affinities for NF-κB and cholinesterases. Taken together, the 2NCP improves spatial memory and learning, short- and long-term memory,markedly inhibits cholinesterases, reduced neuroinflammation, and mitigated oxidative stress in the 5xFAD mice; hence the 2NCP may be a potential candidate for the management of AD.

Allium hookeri Extracts Improve Scopolamine-Induced Cognitive Impairment via Activation of the Cholinergic System and Anti-Neuroinflammation in Mice.

Allium hookeri (AH) is a medicinal food that has been used in Southeast Asia for various physiological activities. The objective of this study was to investigate the activation of the cholinergic system and the anti-neuroinflammation effects of AH on scopolamine-induced memory impairment in mice. Scopolamine (1 mg/kg body weight, i.p.) impaired the performance of the mice on the Y-maze test, passive avoidance test, and water maze test. However, the number of error actions was reduced in the AH groups supplemented with leaf and root extracts from AH. AH treatment improved working memory and avoidance times against electronic shock, increased step-through latency, and reduced the time to reach the escape zone in the water maze test. AH significantly improved the cholinergic system by decreasing acetylcholinesterase activity, and increasing acetylcholine concentration. The serum inflammatory cytokines (IL-1ß, IL-6, and IFN-γ) increased by scopolamine treatment were regulated by the administration of AH extracts. Overexpression of NF-κB signaling and cytokines in liver tissue due to scopolamine were controlled by administration of AH extracts. AH also significantly decreased Aß and caspase-3 expression but increased NeuN and ChAT. The results suggest that AH extracts improve cognitive effects, and the root extracts are more effective in relieving the scopolamine-induced memory impairment. They have neuroprotective effects and reduce the development of neuroinflammation.

Cholinesterase activity in serum during general anesthesia in patients with or without vascular disease.

Maintaining hemodynamic stability during the induction and maintenance of anesthesia is one of the challenges of the anesthesiologist. Patients with vascular disease are at increased risk of instability due to imbalance between the sympathetic and parasympathetic parts of the autonomic nervous system, a balance accessible by serum cholinesterase activity. We aim to characterize the dynamics of cholinesterase activity in patients undergoing general anesthesia (GA) and surgery. This was a prospective study of 57 patients undergoing ambulatory or vascular surgery under GA. Cholinesterase activity was measured before the induction of anesthesia, after 15 min and at the end of surgery by calculating the capacity of serum acetylcholinesterase (AChE) and butyrylcholinesterase to hydrolyze AcetylThioCholine. Data on atherosclerotic disease, anesthesia management were analyzed. Both AChE and total cholinergic status (CS) decreased significantly after GA induction at 15 min and even more so by the end of surgery. Vascular surgery patients had lower baseline cholinesterase activity compared to ambulatory surgery patients. Patients requiring intraoperative administration of phenylephrine for hemodynamic support (21.1%) had a significantly lower level of AChE and CS compared to untreated patients. Our findings serve as a mirror to the sympathetic/parasympathetic imbalance during GA, with a marked decrease in the parasympathetic tone. The data of a subgroup analysis show a correlation between low cholinesterase activity and an increase in the need for hemodynamic support.

Colorimetric detection of acetylcholinesterase and its inhibitor based on thiol-regulated oxidase-like activity of 2D palladium square nanoplates on reduced graphene oxide.

A convenient and sensitive colorimetric assay for acetylcholinesterase (AChE) and its inhibitor has been designed based on the oxidase-like activity of {100}-faceted Pd square nanoplates which are grown in situ on reduced graphene oxide (PdSP@rGO). PdSP@rGO can effectively catalyze the oxidation of colorless 3,3',5,5'-tetramethylbenzidine (TMB) without the assistance of H2O2 to generate blue oxidized TMB (oxTMB) with a characteristic absorption peak at 652 nm. In the presence of AChE, acetylthiocholine (ATCh), a typical AChE substrate, is hydrolyzed to thiocholine (TCh). The generated TCh can effectively inhibit the PdSP@rGO-triggered chromogenic reaction of TMB via cheating with Pd, resulting in color fading and decrease in absorbance. Thus, a sensitive probe for AChE activity is constructed with a working range of 0.25-5 mU mL-1 and  a limit of detection (LOD) of 0.0625 mU mL-1. Furthermore, because of the inhibition effect of tacrine on AChE, tacrine is also detected through the colorimetric AChE assay system within the concentrations range 0.025-0.4 µM with a LOD of 0.00229 µM. Hence, a rapid and facile colorimetric procedure to sensitively detect AChE and its inhibitor can be anticipated through modulating the oxidase-like activity of PdSP@rGO. Colorimetric method for detection of AChE and its inhibitor is established by modulating the oxidase mimetic activity of {100}-faceted Pd square nanoplates on reduced graphene oxide (PdSP@rGO).

Estimation of plasma and RBC acetylcholinesterase in children: An evaluation tool for Hirschsprung's disease?

BACKGROUND: Increased acetylcholinesterase (AChE) activity on frozen sections of rectal mucosal biopsies accurately diagnoses Hirschsprung disease (HD). But the quest for a biomarker in blood as a screening test prompts one to look for AChE in blood and study its role in HD diagnosis. AIM: To develop a low-cost reliable method to estimate the AChE activity in plasma and red blood cells (RBCs) in normal children (control) and study its role in HD (test). MATERIALS AND METHODS: Optimized method derived after modifying and standardizing known AChE assay protocols for blood were employed on 30 controls to define the AChE cut-off range, on 40 suspected HD cases to categorize them as HD/non-HD based on cut-off values and later compared with gold standard tissue AChE histochemistry of rectal mucosal biopsies. RESULTS: An optimal in-house modified methods of Ellman's was found best suited to analyze plasma AChE activity, method by Wilson and Henderson was optimal for extraction and AChE estimation in RBCs. AChE levels (controls) obtained were 1.03 ± 0.31 U/mL and 5.17 ± 1.52 U/mL in plasma and RBCs, respectively while the plasma AChE was 1.35 ± 0.84 U/mL (HD) and 1.62 ± 0.85 U/mL (non-HD) while RBC AChE was 4.29 ± 3.2 U/mL (HD) and 6.48 ± 4.31 U/mL (non-HD). Sensitivity was 66.67% and 55.56%, specificity was 22.73% and 45.45%, and an accuracy rate of 42.5% and 50% for plasma and RBC, respectively. CONCLUSIONS: Mutually exclusive AChE activity range identified for test blood samples overlapped with the normal and hence, not considered a diagnostic tool for HD.

In vitro age-related differences in rats to organophosphates.

The mechanism of toxic action for organophosphates (OPs) is the persistent inhibition of acetylcholinesterase (AChE) resulting in accumulation of acetylcholine and subsequent hyperstimulation of the nervous system. Organophosphates display a wide range of acute toxicities. Differences in the OP's chemistries results in differences in the compound's metabolism and toxicity. Acute toxicities of OPs appear to be principally dependent on compound specific efficiencies of detoxication, and less dependent upon efficiencies of bioactivation and sensitivity of AChE. Serine esterases, such as carboxylesterase (CaE) and butyrylcholinesterase (BChE), play a prominent role in OP detoxication. Organophosphates can stoichiometrically inhibit these enzymes, removing OPs from circulation thus providing protection for the target enzyme, AChE. This in vitro study investigated age-related sensitivity of AChE, BChE and CaE to twelve structurally different OPs in rat tissues. Sensitivity of esterases to these OPs was assessed by inhibitory concentration 50s (IC50s). The OPs displayed a wide range of inhibitory potency toward AChE with IC50s in the low nM-µM range with no differences among ages; however, the CaE IC50s generally increased with age reflecting greater protection in adults. These results suggest age-related differences in acute toxicities of OPs in mammals are primarily a result of their detoxication capacities.

Effects of low-level imidacloprid oral exposure on cholinesterase activity, oxidative stress responses, and primary DNA damage in the blood and brain of male Wistar rats.

Imidacloprid is a neonicotinoid insecticide that acts selectively as an agonist on insect nicotinic acetylcholine receptors. It is used for crop protection worldwide, as well as for non-agricultural uses. Imidacloprid systemic accumulation in food is an important source of imidacloprid exposure. Due to the undisputable need for investigations of imidacloprid toxicity in non-target species, we evaluated the effects of a 28-day oral exposure to low doses of imidacloprid (0.06 mg/kg b. w./day, 0.8 mg/kg b. w./day and 2.25 mg/kg b. w./day) on cholinesterase activity, oxidative stress responses and primary DNA damage in the blood and brain tissue of male Wistar rats. Exposure to imidacloprid did not cause significant changes in total cholinesterase, acetylcholinesterase and butyrylcholinesterase activities in plasma and brain tissue. Reactive oxygen species levels and lipid peroxidation increased significantly in the plasma of rats treated with the lowest dose of imidacloprid. Activities of glutathione-peroxidase in plasma and brain and superoxide dismutase in erythrocytes increased significantly at the highest applied dose. High performance liquid chromatography with UV diode array detector revealed the presence of imidacloprid in the plasma of all the treated animals and in the brain of the animals treated with the two higher doses. The alkaline comet assay results showed significant peripheral blood leukocyte damage at the lowest dose of imidacloprid and dose-dependent brain cell DNA damage. Oral 28-day exposure to low doses of imidacloprid in rats resulted in detectable levels of imidacloprid in plasma and brain tissue that directly induced DNA damage, particularly in brain tissue, with slight changes in plasma oxidative stress parameters.

Effect of allicin on antioxidant defense system, and immune response after carbofuran exposure in Nile tilapia, Oreochromis niloticus.

In this work, allicin was evaluated as an immunostimulant and antioxidant agent preventing Nile tilapia; Oreochromis niloticus against carbofuran toxicity. Fish (60 ± 8 g) were allocated to five groups; the first group (control), the second group was fed 1 g/kg allicin-supplemented diets without carbofuran intoxication, the third group exposed to 1/10 LC50 carbofuran (0.246 mg/L). While the fourth, and fifth groups were fed allicin supplemented diet at concentration of 0.5 and 1 g/kg diet, respectively, and exposed to carbofuran at the same concentration similar to the one of the third group. After 30 days, fish exposed to carbofuran showed high ALT, AST, ALP, cholesterol, glucose, cortisol, uric acid, and creatinine levels. However, serum AChE, total proteins, immunoglobulins, and lysozyme activity were markedly (P ≤ 0.05) reduced in carbofuran exposed tilapia fish. Moreover, malondialdehyde (MDA) level was significantly increased in liver, and kidneys tissues of carbofuran exposed fish. Whereas, catalase (CAT) activity, superoxide dismutase (SOD), and total antioxidant capacity (TAC) were decreased (P ≤ 0.05) significantly in both liver, and kidneys tissues after exposure to carbofuran. Interestingly, tilapia fish treated with carbofuran (0.246 mg/L) and fed (0.5 and 1 g/kg diet) allicin in both the 4th & 5th groups, respectively, decreased serum biochemical parameters; and hepatorenal (MDA) levels, as well as increased AChE, immunological profile, and oxidative stress biomarkers. The results suggested that co- administration of allicin at the high dose is more capable of improving the biochemical, and immunological parameters, and tissue antioxidant responses of carbofuran treated fish.

Pharmacokinetics and efficacy of atropine sulfate/obidoxime chloride co-formulation against VX in a guinea pig model.

Nerve agent exposure is generally treated by an antidote formulation composed of a muscarinic antagonist, atropine sulfate (ATR), and a reactivator of acetylcholinesterase (AChE) such as pralidoxime, obidoxime (OBI), methoxime, trimedoxime or HI-6 and an anticonvulsant. Organophosphates (OPs) irreversibly inhibit AChE, the enzyme responsible for termination of acetylcholine signal transduction. Inhibition of AChE leads to overstimulation of the central and peripheral nervous system with convulsive seizures, respiratory distress and death as result. The present study evaluated the efficacy and pharmacokinetics (PK) of ATR/OBI following exposure to two different VX dose levels. The PK of ATR and OBI administered either as a single drug, combined treatment but separately injected, or administered as the ATR/OBI co-formulation, was determined in plasma of naïve guinea pigs and found to be similar for all formulations. Following subcutaneous VX exposure, ATR/OBI-treated animals showed significant improvement in survival rate and progression of clinical signs compared to untreated animals. Moreover, AChE activity after VX exposure in both blood and brain tissue was significantly higher in ATR/OBI-treated animals compared to vehicle-treated control. In conclusion, ATR/OBI has been proven to be efficacious against exposure to VX and there were no PK interactions between ATR and OBI when administered as a co-formulation.

Occupational exposure to pesticides in female tea garden workers and adverse birth outcomes.

Pesticides are globally used to eliminate pests from crops and plants. The increased use of pesticides has posed a serious threat to human health. This study evaluates the effects of pesticide exposure on pregnancy outcomes in tea garden workers (TGW). The acetylcholinesterase (AChE) activity was measured in the maternal blood, placenta, and cord blood of TGW and housewives (HWs). The placental structure and expression of hypoxia-inducible factor (HIF)-1α were also analyzed in TGW and HW groups delivering low birth weight (LBW) and normal birth weight (NBW) babies. A significantly decreased AChE activity was observed in maternal blood and cord blood in TGW as compared with HW in the LBW group. However, it did not change significantly in the NBW group (p < .05). The adjusted regression analysis of birth outcomes (birth weight, head circumference, infant's length, and ponderal index) revealed a significant and positive association with the levels of AChE activity in maternal blood, placenta, and cord blood in TGW (p < .05). The histological analysis showed significantly higher placental syncytial knots, chorangiosis, fibrinoid deposition, necrosis, and stromal fibrosis in the LBW group of TGW. Microinfarction, increased fibrinoid deposition, and atypical villi characteristics, such as mushroom-like structures, were observed during scanning electron microscopy along with increased HIF-1α expression in placental tissues of TGW exposed to pesticides. Results suggest that occupational pesticide exposure during pregnancy may decrease AChE activity and cause in utero pathological changes accompanied by an increased HIF-1α expression, which also contributes to placental insufficiency and fetal growth restriction.

AChE-activity in critically ill patients with suspected septic encephalopathy: a prospective, single-centre study.

BACKGROUND: Up to 70% of septic patients develop a diffuse brain dysfunction named "septic associated encephalopathy" which is often solely based on clinical impressions. However, the diagnosis of septic associated encephalopathy is outcome-relevant due to an increase in mortality in these patients. Neuroinflammation as well as a disturbance of cholinergic transmission are assumed to be the causes of both delirium and septic associated encephalopathy. An alteration in cholinergic activity can be objectified by measuring the erythrocytic acetylcholinesterase-activity. Single-point measurements of acetylcholinesterase-activity are of limited value because individual and dynamic changes over time have to be anticipated. Therefore, the hypothesis should be tested whether a longitudinal analysis of acetylcholinesterase-activity in critically ill patients can help to diagnose a suspected septic-associated encephalopathy and whether acetylcholinesterase-activity differs in comparison to non-septic patients. METHODS: In this prospective, observational, single-center study, 175 patients (45 with sepsis, 130 without sepsis) were included. All patients were admitted to the surgical Intensive Care Unit of the University hospital Ulm, Germany. Patients were examined daily for the presence of delirium using the CAM-ICU. Daily measurement of the acetylcholinesterase-activity was performed in all patients. The possible time-dependent change in acetylcholinesterase-activity was analyzed with a linear regression model considering repeated measurements. Using a time-adjusted model further factors able to affect AChE-activity were investigated. For nonparametric distributions quantitative data were compared using Wilcoxon matched-pairs test. For analysis of independent samples the Mann-Whitney test was performed. RESULTS: About 90% of septic patients with suspected septic associated encephalopathy exhibited a statistically significant time-dependent in- or decrease in acetylcholinesterase-activity over a period of at least 5 consecutive days. CONCLUSION: Longitudinal measurement of acetylcholinesterase-activity over several consecutive days revealed a change from baseline only in septic patients with suspected septic-associated encephalopathy. Therefore, longitudinal measurement of acetylcholinesterase-activity is able to diagnose septic associated encephalopathy in septic patients with delirious symptoms. TRIAL REGISTRATION: Retrospectively registered at German Clinical Trials Register, registration number DRKS00020542 , date of registration: January 27, 2020.

Acetylcholinesterase inhibition in electric eel and human donor blood: an in vitro approach to investigate interspecies differences and human variability in toxicodynamics.

In chemical risk assessment, default uncertainty factors are used to account for interspecies and interindividual differences, and differences in toxicokinetics and toxicodynamics herein. However, these default factors come with little scientific support. Therefore, our aim was to develop an in vitro method, using acetylcholinesterase (AChE) inhibition as a proof of principle, to assess both interspecies and interindividual differences in toxicodynamics. Electric eel enzyme and human blood of 20 different donors (12 men/8 women) were exposed to eight different compounds (chlorpyrifos, chlorpyrifos-oxon, phosmet, phosmet-oxon, diazinon, diazinon-oxon, pirimicarb, rivastigmine) and inhibition of AChE was measured using the Ellman method. The organophosphate parent compounds, chlorpyrifos, phosmet and diazinon, did not show inhibition of AChE. All other compounds showed concentration-dependent inhibition of AChE, with IC50s in human blood ranging from 0.2-29 µM and IC20s ranging from 0.1-18 µM, indicating that AChE is inhibited at concentrations relevant to the in vivo human situation. The oxon analogues were more potent inhibitors of electric eel AChE compared to human AChE. The opposite was true for carbamates, pointing towards interspecies differences for AChE inhibition. Human interindividual variability was low and ranged from 5-25%, depending on the concentration. This study provides a reliable in vitro method for assessing human variability in AChE toxicodynamics. The data suggest that the default uncertainty factor of ~ 3.16 may overestimate human variability for this toxicity endpoint, implying that specific toxicodynamic-related adjustment factors can support quantitative in vitro to in vivo extrapolations that link kinetic and dynamic data to improve chemical risk assessment.

Altered tumor suppressor genes expression in Egyptian pesticide applicators exposed to organophosphate insecticides.

Occupational exposure in spraying and application of non-arsenical insecticides has been classified as a probable human carcinogen. The fundamental molecular mechanisms involved the tumor-related genes. This study aimed to investigate the carcinogenesis effects related to chronic exposure to organophosphate (OP) pesticides in pesticide applicators. This was a cross-sectional study conducted on 27 pesticide applicators and 24 matched controls through the period from June to December 2018. The level of acetylcholinesterase (AChE) was determined and the effects of OPs exposure on messenger RNA (mRNA) expression of the DNA-damage responsive genes P53, P21, GADD45a, and MDM2 were determined using real-time quantitative polymerase chain reaction. A significant reduction of serum AChE enzyme activities was observed in chronically exposed subjects in comparison with the control group (p = 0.001). The expression of P53, P21 mRNA was significantly downregulated in the exposed group compared with the healthy nonexposed control group (p < 0.05). Conversely, the expression of MDM2 and GADD45a did not significantly differ between the exposed subjects and the control group (p > 0.05). No significant differences were noted between the exposed and control groups regarding the genotype or allele distributions of P53 Arg72Pro polymorphism. These results suggested that chronic exposure to OP insecticides may have mitogenic and carcinogenicity activity for the exposed cases due to downregulation of P53 and P21 but did not demonstrate any DNA damage properties for the exposed cases, and finally, a regular follow-up of the exposed cases for tumor markers is recommended.

Monoclonal antibodies to fetal bovine serum acetylcholinesterase distinguish between acetylcholinesterases from ruminant and non-ruminant species.

Two types of cholinesterases (ChEs) are present in mammalian blood and tissues: acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). While AChE regulates neurotransmission by hydrolyzing acetylcholine at the postsynaptic membranes and neuromuscular junctions, BChE in plasma has been suggested to be involved in detoxifying toxic compounds. This study was undertaken to establish the identity of circulating ChE activity in plasmas from domestic animals (bovine, ovine, caprine, porcine and equine) by assessing sensitivity to AChE-specific inhibitors (BW284c51 and edrophonium) and BChE-specific inhibitors (dibucaine, ethopropazine and Iso-OMPA) as well as binding to anti-FBS AChE monoclonal antibodies (MAbs). Based on the inhibition of ChE activity by ChE-specific inhibitors, it was determined that bovine, ovine and caprine plasma predominantly contain AChE, while porcine and equine plasma contain BChE. Three of the anti-FBS AChE MAbs, 4E5, 5E8 and 6H9, inhibited 85-98% of enzyme activity in bovine, ovine and caprine plasma, confirming that the esterase in these plasmas was AChE. These MAbs did not bind to purified recombinant human or mouse AChE, demonstrating that these MAbs were specific for AChEs from ruminant species. These MAbs did not inhibit the activity of purified human BChE, or ChE activity in porcine and equine plasma, confirming that the ChE in these plasmas was BChE. Taken together, these results demonstrate that anti-FBS AChE MAbs can serve as useful tools for distinguishing between AChEs from ruminant and non-ruminant species and BChEs.

Oral Pretreatment with Galantamine Effectively Mitigates the Acute Toxicity of a Supralethal Dose of Soman in Cynomolgus Monkeys Posttreated with Conventional Antidotes.

Earlier reports suggested that galantamine, a drug approved to treat mild-to-moderate Alzheimer's disease (AD), and other centrally acting reversible acetylcholinesterase (AChE) inhibitors can serve as adjunct pretreatments against poisoning by organophosphorus compounds, including the nerve agent soman. The present study was designed to determine whether pretreatment with a clinically relevant oral dose of galantamine HBr mitigates the acute toxicity of 4.0×LD50 soman (15.08 µg/kg) in Macaca fascicularis posttreated intramuscularly with the conventional antidotes atropine (0.4 mg/kg), 2-pyridine aldoxime methyl chloride (30 mg/kg), and midazolam (0.32 mg/kg). The pharmacokinetic profile and maximal degree of blood AChE inhibition (∼25%-40%) revealed that the oral doses of 1.5 and 3.0 mg/kg galantamine HBr in these nonhuman primates (NHPs) translate to human-equivalent doses that are within the range used for AD treatment. Subsequent experiments demonstrated that 100% of NHPs pretreated with either dose of galantamine, challenged with soman, and posttreated with conventional antidotes survived 24 hours. By contrast, given the same posttreatments, 0% and 40% of the NHPs pretreated, respectively, with vehicle and pyridostigmine bromide (1.2 mg/kg, oral), a peripherally acting reversible AChE inhibitor approved as pretreatment for military personnel at risk of exposure to soman, survived 24 hours after the challenge. In addition, soman caused extensive neurodegeneration in the hippocampi of saline- or pyridostigmine-pretreated NHPs, but not in the hippocampi of galantamine-pretreated animals. To our knowledge, this is the first study to demonstrate the effectiveness of clinically relevant oral doses of galantamine to prevent the acute toxicity of supralethal doses of soman in NHPs. SIGNIFICANCE STATEMENT: This is the first study to demonstrate that a clinically relevant oral dose of galantamine effectively prevents lethality and neuropathology induced by a supralethal dose of the nerve agent soman in Cynomolgus monkeys posttreated with conventional antidotes. These findings are of major significance for the continued development of galantamine as an adjunct pretreatment against nerve agent poisoning.