Search

Organophosphate (OPs) insecticides are still widely used in pest control. The hydrolysis of OPs or oxons of organophosphorothionates by organophosphate hydrolases (OP-hydrolases) represents a major detoxification pathway of OPs. In this study, the response of insect OP-hydrolase activity to the allelochemical quercetin and the insecticide paraoxon, as well as changes in the activity of OP-hydrolases in malathion-resistance insects were characterized by using O,O-dimethyl-4-methylumbelliferyl phosphate (dMUP) and paraoxon as substrates. Hydrolase activity on dMUP was similar to hydrolase activity on paraoxon in Helicoverpa armigera and Musca domestica. Paraoxon-hydrolase activity was higher than dMUP-hydrolase activity in H. armigera fed on the artificial diet containing 0.2 % quercetin for 48 hours. In addition, similar induction of hydrolase activity on both paraoxon and dMUP was observed in H. armigera fed an artificial diet containing the LC10 or LC50 of paraoxon for 24 hours. In contrast, the hydrolysis activity onto dMUP was higher than the activity onto paraoxon in the malathion-resistant M. domestica. It was also found that the hydrolysis activity onto α-NA in malathion-resistant M. domestica was higher than that in malathion-susceptible M. domestica. These results provide a structural insight into the hydrolytic metabolism of organophosphates in insects. [ABSTRACT FROM AUTHOR]

Hierarchical organic-inorganic nanocomposites derived from polyethersulfone (PES) nanofibrous membranes with a post-modification of dopamine (DA) and polyethylenimine (PEI), comprising a high content (33 wt%) of MgO nanoparticles of smaller dimensions (12.7 ± 3.0 nm), were successively fabricated using electrospinning and DA/PEI self-polymerization methods. The obtained hybrid membranes have a rapid capture and great destructive capacity towards paraoxon-ethyl toxin degradation with a relatively short interaction time (up to 92% within 40 min) for effective environmental remediation. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Solubilization, antimicrobial properties, hemolytic activity of DHDHAB are displayed. • Mixed cationic liposomes overcome the BBB via the non-invasive intranasal route. • Higher bioavailability into the brain by intranasal administration is provided. • AChE reactivator, 2-PAM-loaded liposomes, were used for intranasal route. • 2-PAM-loaded liposomes led to reactivation of paraoxon-inhibited brain AChE. Abstract New mixed cationic liposomes based on L-α-phosphatidylcholine and dihexadecylmethylhydroxyethylammonium bromide (DHDHAB) were designed to overcome the BBB crossing by using the intranasal route. Synthesis and self-assembly of DHDHAB were performed. A low critical association concentration (0.01 mM), good solubilization properties toward hydrophobic dye Orange OT and antimicrobial activity against gram-positive bacteria Staphylococcus aureus (MIC=7.8 μg mL–1) and Bacillus cereus (MIC=7.8 μg mL–1), low hemolytic activities against human red blood cells (less than 10%) were achieved. Conditions for preparation of cationic vesicles and mixed liposomes with excellent colloidal stability at room temperature were determined. The intranasal administration of rhodamine B-loaded cationic liposomes was shown to increase bioavailability into the brain in comparison to the intravenous injection. The cholinesterase reactivator, 2-PAM, was used as model drug for the loading in cationic liposomes. 2-PAM-loaded cationic liposomes displayed high encapsulation efficiency (∼ 90%) and hydrodynamic diameter close to 100 nm. Intranasally administered 2-PAM-loaded cationic liposomes were effective against paraoxon-induced acetylcholinesterase inhibition in the brain. 2-PAM−loaded liposomes reactivated 12 ± 1% of brain acetylcholinesterase. This promising result opens the possibility to use marketed positively charged oximes in medical countermeasures against organophosphorus poisoning for reactivation of central acetylcholinesterase by implementing a non-invasive approach, via the "nose-brain" pathway. [ABSTRACT FROM AUTHOR]

We tested the hypothesis that the pesticides paraoxon and glyphosate cause DNA double-strand breaks (DSB) by poisoning the enzyme Type II topoisomerase (topo II). Peripheral lymphocytes in G0 phase, treated with the pesticides, plus or minus ICRF-187, an inhibitor of Topo II, were stimulated to proliferate; induced cytogenetic damage was measured. Micronuclei, chromatin buds, nucleoplasmic bridges, and extranuclear fragments were induced by treatments with the pesticides, irrespective of the pre-treatment with ICRF-187. These results indicate that the pesticides do not act as topo II poisons. The induction of DSB may occur by other mechanisms, such as effects on other proteins involved in recombination repair. • Paraoxon and glyphosate are clastogens and induce double-strand breaks. • Neither agent inhibits Type II topoisomerase. • Both agents produced extranuclear microfragments when administered in G0 phase. • The mechanism of action of these agents may be interference with recombination repair proteins. [ABSTRACT FROM AUTHOR]

Background & Objective: Paraoxon (POX) as one of the most toxic organophosphorus pesticides, is widely used in agriculture, which can reduce the antioxidant capacity of the cell. The aim of this study was to investigate the effect of N-acetyl cysteine (NAC) as an antioxidant against POX-induced oxidative stress in rat liver and kidney. Material & Methods: In the present experimental study, male Wistar rats were randomly divided into four groups; control (corn oil as POX solvent), POX (0.7 mg/kg), NAC (160 mg/kg), and NAC+POX. 24 hours after the intraperitoneal injection, animals were anesthetized and the liver and kidney tissues were quickly removed. Followed by the tissues hemogenation, superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST) and lactate dehydrogenase (LDH) activities, as well as glutathione (GSH) and malondialdehyde (MDA) levels were determined by the biochemical methods. The data were statistically analyzed using the analysis of variance (ANOVA) followed by the post hoc analysis using Tukey test. Results: POX increased SOD, CAT and GST activities and decreased GSH content in rat liver and kidney as compared to control. In addition, the increased MDA level and decreased LDH activity were observed in the liver. The administration of NAC inhibited changing of these parameters. Conclusion: The administration of NAC as antioxidant, ameliorates POX-induced oxidative stress in rat liver and kidney by scavenging the free radicals and GSH synthesis, but does not provide the complete protection.

Antidotes against organophosphates often possess physicochemical properties that mitigate their passage across the blood–brain barrier. Cucurbit[7]urils may be successfully used as a drug delivery system for bisquaternary oximes and improve central nervous system targeting. The main aim of these studies was to elucidate the relationship between cucurbit[7]uril, oxime K027, atropine, and paraoxon to define potential risks or advantages of this delivery system in a complex in vivo system. For this reason, in silico (molecular docking combined with umbrella sampling simulation) and in vivo (UHPLC—pharmacokinetics, toxicokinetics; acetylcholinesterase reactivation and functional observatory battery) methods were used. Based on our results, cucurbit[7]urils affect multiple factors in organophosphates poisoning and its therapy by (i) scavenging paraoxon and preventing free fraction of this toxin from entering the brain, (ii) enhancing the availability of atropine in the central nervous system and by (iii) increasing oxime passage into the brain. In conclusion, using cucurbit[7]urils with oximes might positively impact the overall treatment effectiveness and the benefits can outweigh the potential risks.

Organophosphates (OPs) are esters of substituted phosphates, phosphonates or phosphoramidates that react with acetylcholinesterase (AChE) by initially transferring the organophosphityl group to a serine residue in the enzyme active site, concomitant with loss of an alcohol or halide leaving group. With substituted phosphates, this transfer is followed by relatively slow hydrolysis of the organophosphoryl AChE, or dephosphorylation, that is often accompanied by an aging reaction that renders the enzyme irreversibly inactivated. Aging is a dealkylation that converts the phosphate triester to a diester. OPs are very effective AChE inhibitors and have been developed as insecticides and chemical warfare agents. We examined three reactions of two organophosphoryl AChEs, dimethyl- and diethylphosphorylated AChE, by comparing rate constants and solvent deuterium oxide isotope effects for hydrolysis, aging and oxime reactivation with pralidoxime (2-PAM). Our study was motivated (1) by a published x-ray crystal structure of diethylphosphorylated AChE, which showed severe distortion of the active site that was restored by the binding of pralidoxime, and (2) by published isotope effects for decarbamoylation that decreased from 2.8 for N-monomethylcarbamoyl AChE to 1.1 for N,N-diethylcarbamoyl AChE. We previously reconciled these results by proposing a shift in the rate-limiting step from proton transfer for the small carbamoyl group to a likely conformational change in the distorted active site of the large carbamoyl enzyme. This proposal was tested but was not supported in this report. The smaller dimethylphosphoryl AChE and the larger diethylphosphoryl AChE gave similar isotope effects for both oxime reactivation and hydrolysis, and the isotope effect values of about two indicated that proton transfer was rate limiting for both reactions.

Aims: Organophosphates (OPCs), useful agents as pesticides, also represent a serious health hazard. Standard therapy with atropine and established oxime-type enzyme reactivators is unsatisfactory. Experimental data indicate that superior therapeutic results can be obtained when reversible cholinesterase inhibitors are administered before OPC exposure. Comparing the protective efficacy of five such cholinesterase inhibitors (physostigmine, pyridostigmine, ranitidine, tacrine, or K-27), we observed best protection for the experimental oxime K-27. The present study was undertaken in order to determine if additional administration of K-27 immediately after OPC (paraoxon) exposure can improve the outcome. Methods: Therapeutic efficacy was assessed in rats by determining the relative risk of death (RR) by Cox survival analysis over a period of 48 h. Animals that received only pretreatment and paraoxon were compared with those that had received pretreatment and paraoxon followed by K-27 immediately after paraoxon exposure. Results: Best protection from paraoxon-induced mortality was observed after pretreatment with physostigmine (RR = 0.30) and K-27 (RR = 0.34). Both substances were significantly more efficacious than tacrine (RR = 0.67), ranitidine (RR = 0.72), and pyridostigmine (RR = 0.76), which were less efficacious but still significantly reduced the RR compared to the no-treatment group (paraoxon only). Additional administration of K-27 immediately after paraoxon exposure (posttreatment) did not further reduce mortality. Statistical analysis between pretreatment before paraoxon exposure alone and pretreatment plus K-27 posttreatment did not show any significant difference for any of the pretreatment regimens. Conclusions: Best outcome is achieved if physostigmine or K-27 are administered prophylactically before exposure to sublethal paraoxon dosages. Therapeutic outcome is not further improved by additional oxime therapy immediately thereafter.

Organophosphorus compounds (OPs) are highly toxic chemicals widely used as pesticides (e.g., paraoxon (PX)- the active metabolite of the insecticide parathion) and as chemical warfare nerve agents. Blood-brain barrier (BBB) leakage has been shown in rodents exposed to PX, which is an organophosphate oxon. In this study, we investigated the cellular mechanisms involved in BBB reaction after acute exposure to PX in an established in vitro BBB system made of stem-cell derived, human brain-like endothelial cells (BLECs) together with brain pericytes that closely mimic the in vivo BBB. Our results show that PX directly affects the BBB in vitro both at toxic and non-toxic concentrations by attenuating tight junctional (TJ) protein expression and that only above a certain threshold the paracellular barrier integrity is compromised. Below this threshold, BLECs exhibit a morphological coping mechanism in which they enlarge their cell area thus preventing the formation of meaningful intercellular gaps and maintaining barrier integrity. Importantly, we demonstrate that reversal of the apoptotic cell death induced by PX, by a pan-caspase-inhibitor ZVAD-FMK (ZVAD) can reduce PX-induced cell death and elevate cell area but do not prevent the induced BBB permeability, implying that TJ complex functionality is hindered. This is corroborated by formation of ROS at all toxic concentrations of PX and which are even higher with ZVAD. We suggest that while lower levels of ROS can induce compensating mechanisms, higher PX-induced oxidative stress levels interfere with barrier integrity.

Butyrylcholinesterase (BChE) is considered as an efficient stoichiometric antidote against organophosphorus (OP) poisons. Recently we utilized combination of calculations and ultrahigh-throughput screening (uHTS) to select BChE variants capable of catalytic destruction of OP pesticide paraoxon. The purpose of this study was to elucidate the molecular mechanism underlying enzymatic hydrolysis of paraoxon by BChE variants using hybrid quantum mechanical/molecular mechanical (QM/MM) calculations. Detailed analysis of accomplished QM/MM runs revealed that histidine residues introduced into the acyl-binding loop are always located in close proximity with aspartate residue at position 70. Histidine residue acts as general base thus leading to attacking water molecule activation and subsequent SN2 inline hydrolysis resulting in BChE reactivation. This combination resembles canonical catalytic triad found in active centers of various proteases. Carboxyl group activates histidine residue by altering its pKa, which in turn promotes the activation of water molecule in terms of its nucleophilicity. Observed re-protonation of catalytic serine residue at position 198 from histidine residue at position 438 recovers initial configuration of the enzyme’s active center, facilitating next catalytic cycle. We therefore suggest that utilization of uHTS platform in combination with deciphering of molecular mechanisms by QM/MM calculations may significantly improve our knowledge of enzyme function, propose new strategies for enzyme design and open new horizons in generation of catalytic bioscavengers against OP poisons.

Organophosphate (OP) pesticides are widely used in the agricultural field and in the prevention of pest infestation in private and public areas of cities. Despite their unquestionable utility, several of these compounds demonstrate toxic effects to the environment and human health. In particular, the occurrence of some organophosphate pesticides is correlated to the incidence of nervous system disorders, especially in children. The detection of pesticide residues in the human body represents an important task to preserve human health. In our work we propose the use of esterase-based biosensors as a viable alternative to the expensive and time-consuming systems currently used for their detection in human fluids. Using the esterase-2 activity, coupled with a fluorescence inhibition assay, we are able to detect very low concentration levels of diethyl (4-nitrophenyl) phosphate (paraoxon) in the range of the femtomole (fmol). Method robustness tests indicate the stability of esterase-2 in a diluted solution of 4% human urine, and we are able to accurately determine concentration levels of paraoxon in the range from 0.1 to 2 picomoles (pmol). The system sensitivity for OP detection is calculated at 524 ± 14.15 fmol of paraoxon recognized at 10% of inhibition, with an estimated limit of quantification of 262 ± 8.12 pmol mL−1. These values are comparable with the most recent analysis methods based on mass spectrometry carried out on human samples for pesticide detection. This research represents a starting point to develop cheap and fast testing methods for a rapid screening of toxic substances in human samples.

Nowadays extensive volumes of pesticides are employed for agricultural and environmental practices, but they have negative effects on human health. The levels of pesticides are necessarily restricted by international regulatory agencies, thus rapid, cost-effective and in-field analysis of pesticides is an important issue. In the present work, we propose a butyrylcholinesterase (BChE)-based biosensor embedded in a flow system for organophosphorus pesticide detection. The BChE was immobilized by cross-linking on a screen-printed electrode modified with Prussian Blue Nanoparticles. The detection of paraoxon (an organophosphorus pesticide) was carried out evaluating its inhibitory effect on BChE, and quantifying the enzymatic hydrolysis of butyrylthiocholine before and after the exposure of the biosensor to paraoxon, by measuring the thiocholine product at a working voltage of +200 mV. The operating conditions of the flow system were optimized. A flow rate of 0.25 mL/min was exploited for inhibition steps, while a 0.12 mL/min flow rate was used for substrate measurement. A substrate concentration of 5 mM and an incubation time of 10 min allowed a detection limit of 1 ppb of paraoxon (corresponding to 10% inhibition). The stability of the probe in working conditions was investigated for at least eight measurements, and the storage stability was evaluated up to 60 days at room temperature in dry condition. The analytical system was then challenged in drinking, river and lake water samples. Matrix effect was minimized by using a dilution step (1:4 v/v) in flow analysis. This biosensor, embedded in a flow system, showed the possibility to detect paraoxon at ppb level using an automatable and cost-effective bioanalytical system.

To reinforce skin protection against organophosphates (OPs), the development of new topical skin protectants (TSP) has received a great interest. Nanoparticles like cerium dioxide (CeO2) known to adsorb and neutralize OPs are interesting candidates for TSP. However, NPs are difficult to disperse into formulations and they are suspected of toxicological issues. Thus, we want to study: (1) the effect of the addition of CeO2 NPs in formulations for the skin protection (2) the impact of the doping of CeO2 NPs by calcium; (3) the effect of two methods of dispersion of CeO2 NPs: an O/W emulsion or a suspension of a fluorinated thickening polymer (HASE-F) grafted with these NPs. As a screening approach we used silicone membranes as a skin equivalent and Franz diffusion cells for permeation tests. The addition of pure CeO2 NPs in both formulations permits the penetration to decrease by a 3–4-fold factor. The O/W emulsion allows is the best approach to obtain a film-forming coating with a good reproducibility of the penetration results; whereas the grafting of NPs to a thickener is the best way to obtain an efficient homogenous suspension of CeO2 NPs with a decreased of toxicological impact but the coating is less film-forming which slightly impacts the reproducibility of the penetration results.

Organophosphorus compounds (OPs) are highly toxic chemicals widely used as pesticides (e.g., paraoxon (PX)- the active metabolite of the insecticide parathion) and as chemical warfare nerve agents. Blood-brain barrier (BBB) leakage has been shown in rodents exposed to PX, which is an organophosphate oxon. In this study, we investigated the cellular mechanisms involved in BBB reaction after acute exposure to PX in an established in vitro BBB system made of stem-cell derived, human brain-like endothelial cells (BLECs) together with brain pericytes that closely mimic the in vivo BBB. Our results show that PX directly affects the BBB in vitro both at toxic and non-toxic concentrations by attenuating tight junctional (TJ) protein expression and that only above a certain threshold the paracellular barrier integrity is compromised. Below this threshold, BLECs exhibit a morphological coping mechanism in which they enlarge their cell area thus preventing the formation of meaningful intercellular gaps and maintaining barrier integrity. Importantly, we demonstrate that reversal of the apoptotic cell death induced by PX, by a pan-caspase-inhibitor ZVAD-FMK (ZVAD) can reduce PX-induced cell death and elevate cell area but do not prevent the induced BBB permeability, implying that TJ complex functionality is hindered. This is corroborated by formation of ROS at all toxic concentrations of PX and which are even higher with ZVAD. We suggest that while lower levels of ROS can induce compensating mechanisms, higher PX-induced oxidative stress levels interfere with barrier integrity. [ABSTRACT FROM AUTHOR]

Holey graphene oxide (HGO) has been synthesized by one step hydrothermal method and applied to construct a highly sensitive acetylcholinesterase (AChE) biosensor. The developed system is characterized by using SEM, TEM, nitrogen adsorption‐desorption, Raman, and electrochemical impedance spectroscopy. It is proved that HGO can effectively immobilize AChE and accelerate electron transfer rate. The prepared biosensor AChE/HGO/glass carbon electrode (GCE) shows excellent affinity to the acetylthiocholine chloride (ATCl) with a Michaelis‐Menten constant value of 0.23 mM. Under optimum conditions, AChE/HGO/GCE can effectively detect paraoxon with a linear ranged from 10 to 45 ng/mL and a detection limit of 1.58 ng/mL. Furthermore, the prepared AChE/HGO/GCE biosensor demonstrates excellent stability and reproducibility, which provides a reliable method for the detection of organophosphate pesticides. The developed biosensor is used for detecting paraoxon in real samples of lettuce and cabbage and shows a satisfactory recovery. [ABSTRACT FROM AUTHOR]

Fatalities from organophosphate (OP) insecticide result from both occupational and deliberate exposure; significantly impacting human health. Like nerve agents, insecticides are neurotoxins which target and inhibit acetylcholinesterases (AChE) in central and peripheral synapses in the cholinergic nervous system. Post-exposure therapeutic countermeasures generally include administration of atropine with a pyridinium aldoxime e.g. pralidoxime, to reactivate the OP-inhibited AChE. However, commonly used oximes inefficiently cross the bloodbrain barrier and are rapidly cleared and their benefit is debated. Recent findings have demonstrated the ability of a novel zwitterionic, centrally acting, brain penetrating oxime (RS194B) to reverse severe symptoms and rapidly reactivate sarin-inhibited AChE in macaques, but it has not been tested following OP pesticide poisoning. In the present study, the symptoms following a lethal dose of inhaled paraoxon (100 ug/kg), were shown to mimic those in insecticide poisoned individuals and were also rapidly reversed in macaques by post-exposure IM administration of 80 mg/kg of RS194B. This occurred with a concomitant reactivation of AChE to 40–100% in < 1 hr and BChE (40% in 8 h). These findings will be used to develop a macaque model with RS194 B as a post-exposure treatment for insecticide poisoning and generate efficacy data for approval under the FDA Animal rule. [ABSTRACT FROM AUTHOR]

Butyrylcholinesterase (BChE) is considered as an efficient stoichiometric antidote against organophosphorus (OP) poisons. Recently we utilized combination of calculations and ultrahigh-throughput screening (uHTS) to select BChE variants capable of catalytic destruction of OP pesticide paraoxon. The purpose of this study was to elucidate the molecular mechanism underlying enzymatic hydrolysis of paraoxon by BChE variants using hybrid quantum mechanical/molecular mechanical (QM/MM) calculations. Detailed analysis of accomplished QM/MM runs revealed that histidine residues introduced into the acyl-binding loop are always located in close proximity with aspartate residue at position 70. Histidine residue acts as general base thus leading to attacking water molecule activation and subsequent SN2 inline hydrolysis resulting in BChE reactivation. This combination resembles canonical catalytic triad found in active centers of various proteases. Carboxyl group activates histidine residue by altering its pKa, which in turn promotes the activation of water molecule in terms of its nucleophilicity. Observed re-protonation of catalytic serine residue at position 198 from histidine residue at position 438 recovers initial configuration of the enzyme's active center, facilitating next catalytic cycle. We therefore suggest that utilization of uHTS platform in combination with deciphering of molecular mechanisms by QM/MM calculations may significantly improve our knowledge of enzyme function, propose new strategies for enzyme design and open new horizons in generation of catalytic bioscavengers against OP poisons. [ABSTRACT FROM AUTHOR]

The molecular targets of best known neurotoxic effects associated to acute exposure to organophosphorus compounds (OPs) are serine esterases located in the nervous system, although there are other less known neurotoxic adverse effects associated with chronic exposure to OPs whose toxicity targets are still not identified. In this work we studied sensitivity to the non-neuropathic OP paraoxon and to the neuropathic OP mipafox of phenyl valerate esterases (PVases) in intact and lysed human neuroblastoma SH-SY5Y cells. The main objective was to discriminate different unknown pools of esterases that might be potential targets of chronic effects from those esterases already known and recognized as targets to these acute neurotoxicity effects. Two components of PVases of different sensitivities were discriminated for paraoxon in both intact and lysed cells; while the two components inhibitable by mipafox were found only for intact cells. A completely resistant component to paraoxon of around 30% was found in both intact and lysed cells; while a component of slightly lower amplitude (around 20%) completely resistant to mipafox was also found for both preparations (intact and lysed cells). The comparison of the results between the intact cells and the lysed cells suggests that the plasma membrane could act as a barrier that reduced the bioavailability of mipafox to PVases. This would imply that the discrimination of the different esterases should be made in lysed cells. However, those studies which aim to determine the physiological role of these esterases should be necessarily conducted in intact cultured cells. [ABSTRACT FROM AUTHOR]

Abstract: A new series of 3‐hydroxy‐2‐pyridine aldoxime compounds have been designed, synthesised and tested in vitro, in silico, and ex vivo as reactivators of human acetylcholinesterase (hAChE) and butyrylcholinesterase (hBChE) inhibited by organophosphates (OPs), for example, VX, sarin, cyclosarin, tabun, and paraoxon. The reactivation rates of three oximes (16–18) were determined to be greater than that of 2‐PAM and comparable to that of HI‐6, two pyridinium aldoximes currently used by the armies of several countries. The interactions important for a productive orientation of the oxime group within the OP‐inhibited enzyme have been clarified by molecular‐modelling studies, and by the resolution of the crystal structure of the complex of oxime 17 with Torpedo californica AChE. Blood–brain barrier penetration was predicted for oximes 15–18 based on their physicochemical properties and an in vitro brain membrane permeation assay. Among the evaluated compounds, two morpholine‐3‐hydroxypyridine aldoxime conjugates proved to be promising reactivators of OP‐inhibited cholinesterases. Moreover, efficient ex vivo reactivation of phosphylated native cholinesterases by selected oximes enabled significant hydrolysis of VX, sarin, paraoxon, and cyclosarin in whole human blood, which indicates that the oximes have scavenging potential. [ABSTRACT FROM AUTHOR]

We demonstrate the utility of 4-chloro-7-nitrobenzofurazan (NBD-Cl), a simple, low-cost probe, for colorimetrically and fluorescently detecting and differentiating similar thiol species, including cysteine, homocysteine, and glutathione, as well as for assaying acetylcholinesterase (AChE) activity. This assay is a potential tool for investigating thiol functions in disease and diagnosis, and for screening AChE inhibitors. We envision that this versatile probe, which is commercially available and inexpensive, will be useful for further elucidating the roles of thiols in biology and also shows applicability for analysis of AChE inhibitors in physiological samples. [ABSTRACT FROM AUTHOR]

Organophosphorus compounds (OP) are irreversible inhibitors of both central and peripheral cholinesterases (ChE). They still represent a major health issue in some countries as well as a terrorist and military threat. In order to design appropriate medical counter-measures, a better understanding of the pathophysiology of the poisoning is needed. Little to nothing is known regarding the impact of the genetic background on OP-induced seizures and seizure-related cell injury. Using two different mouse strains, Swiss and C57BL/6J, exposed to a convulsing dose of the OP pesticide paraoxon-ethyl (POX), our study focused on seizure susceptibility, especially the occurrence of SE and related mortality. We also evaluated the initial neuropathological response and SE-induced cell injury. Following the administration of 2.4 mg/kg POX, more Swiss mice experienced SE than C57BL/6J (55.6% versus 17.2%) but the duration of their SE, based on EEG recordings, was shorter (64.3 ± 19.5 min versus 180.8 ± 36.8 min). No significant difference was observed between strains regarding mortality (33% versus 14%). In both strains limited cell injury was observed in the medial temporal cortex, the dentate gyrus and the CA3 field without inter-strain differences (Fluorojade C-positive cells/mm 2 ). Conversely, only C57BL/6J mice showed cell injury in the CA1 field. There was no obvious correlation between the number of Fluorojade C-positive cells and the duration of the EEG discharges. Our work suggests some differences between Swiss and C57BL/6J mice and lay ground to further studies on the impact of strains in the development of central nervous system toxicity of OP. [ABSTRACT FROM AUTHOR]

Abstract: This study was performed to evaluate the protective efficacy of metoclopramide (MCP) against the organophosphates paraoxon (POX)‐ and malathion (MLT)‐induced apoptosis in the murine L929 skin fibroblasts. L929 cells were exposed to either POX (10 n m) or 1.0 μ m MLT in the absence and presence of increased concentrations of MCP. The protective effect of MCP on these organophosphate‐stimulated apoptotic events was evaluated by flow cytometry analysis after staining with annexin‐V/propidium iodide, processing and activation of the executioner caspase‐3, cleavage of the poly‐ADP ribose polymerase, fragmentation of the nucleosomal DNA and disruption of the mitochondrial membrane potential (Δψ). Our results showed that increased doses of MCP alone (≥10 μ m) did not induce apoptosis or activation of caspase‐3. Pretreatment of the cells with MCP attenuated all the apoptotic events triggered by the organophosphate compounds in a dose‐dependent manner reaching ~70–80% protection when they were preincubated at 1 and 5 μ m of the drug before the addition of POX and MLT, respectively. Interestingly, MCP did not offer a significant protective effect against the cytotoxicity of tumor necrosis factor‐α, cisplatinum, etoposide or paclitaxel, which stimulate apoptosis by various mechanisms, suggesting that the anti‐apoptotic effect of the drug is specific to organophosphates. The strong and specific anti‐apoptotic activity of subclinical doses of MCP against the cytotoxicity of organophosphate compounds suggests its potential clinical application in treating their poisoning. [ABSTRACT FROM AUTHOR]

Background: Paraoxonase‐1 (PON‐1) is an antioxidant compound that is considered a negative acute phase protein. No information on the analytic performance of the paraoxon method for measuring PON‐1 in horse serum is available. Objectives: The aim of this study was to validate a paraoxon‐based method to measure PON‐1 in horses and to establish RIs in healthy horses and foals. Methods: Horses and foals classified as healthy after physical examination and routine biochemistry were used in the study. Serum PON‐1 activity was measured with an automated spectrophotometer and an enzymatic method validated in other species. After the analytic validation (precision, accuracy, interference studies), RIs were determined using the Reference Value Advisor software. The possible sex‐, age‐, and breed‐related differences were statistically investigated. Results: The healthy study population included 120 horses and 55 foals. The paraoxon‐based method was precise (CVs < 4.0%) and accurate (P < .001 in linearity under dilution and spike‐recovery testing) but was affected by interference from mild bilirubinemia, severe lipemia, and hemoglobinemia. The RIs recorded in the whole population were 38.1–80.8 U/mL. According to the Harris and Boyd test, it would be advisable to use separate RIs only for adult females and for Warmblood and Trotter adults. Conclusions: This study demonstrated that the analytic performances of the paraoxon‐based method for measurement of PON‐1 in horses are acceptable. The PON‐1 activity is lower in horses than in other domestic species. These results may provide a basis for further studies designed to establish whether healthy and sick horses can be correctly classified by using the PON‐1 assay. [ABSTRACT FROM AUTHOR]

The aim of this study was to determine optimal conditions forin vitroskin decontamination using water and detergents as decontamination agents and to test the cleansing efficiency of selected detergents. Experiments were performed using a peristaltic pump for showering of pig skin in modified static diffusion cells. Several conditions were tested including different flow rates (from 5 to 33 ml s−1), quantity of rinsing fluid (from 40 to 400 ml) and concentration of detergents (2; 5; 10%). Further, several types of detergents/commercial decontamination agents were evaluated under the selected conditions to find the most effective means of decontamination. The amount of paraoxon removed from the skin surface following wet-type decontamination was detected in the rinsing fluid spectrophotometrically after hydrolysis of paraoxon – a model contaminant. The efficacy of rinsing by water/Spolapon AES 253 increased with flow rate up to 25 ml s−1and a rinsing volume of 200 ml. Lutensol AT 25 achieved maximum efficacy at the lowest tested concentration (2%). A flow rate of 16 ml s−1, rinsing volume of 100 ml (values from the middle part of the sigmoid curve) and 5% concentration of decontaminant solution were used for further evaluation of detergents as cleansing agents under the selected conditions. Cetylpyridinium bromide (cationic surfactant), carbethopendecinii bromidum (cationic surfactant) and polyoxyethylene-10-tridecyl ether (non-ionic surfactant), SDS (anionic surfactant), althosan MB (cationic surfactant), sodium dodecylbenzene sulphonate (anionic surfactant), neodekont (mixture), tergitol NPX (non-ionic surfactant), Korynt P (non-ionic surfactant) were found to be the most effective. These decontaminants were able to wash away more than 92% of paraoxon from the contaminated skin. [ABSTRACT FROM PUBLISHER]

13 C NMR spectra showed that peroxymonocarbonate (HCO 4 − ) was generated in the NaHCO 3 -activated H 2 O 2 solution and pH was a key factor in its production. A cycle for the bicarbonate anion was proposed as HCO 3 − → HCO 3 → (CO 2 ) 2 * → CO 2 (aq) → HCO 4 − (H 2 CO 4 ) → HCO 3 − ( HCO 3 ) basing on the results of NMR, electron paramagnetic resonance, chemiluminescence analysis. In this cycle, (CO 2 ) 2 * was the key intermediate and (CO 2 ) 2 * → 2CO 2 + hv was the rate controlling step. Thioanisole and paraoxon, the simulants of sulfur mustard gas and nerve gas, respectively, were efficiently decontaminated by the NaHCO 3 -activated H 2 O 2 solution. While HCO 4 − was the primary oxidant for the oxidation of thioanisole, O 2 − generated during the decomposition of HCO 4 − or H 2 O 2 led to the secondary oxidation of the sulfide. Paraoxon was degraded in the NaHCO 3 -activated H 2 O 2 solution via nucleophilic substitution by OOH − and OH − , and the degradation rate increased exponentially with increasing pH. Alkali metal ions had a catalytic effect on the degradation of paraoxon. Mustard gas and soman degraded efficiently into nontoxic products in NaHCO 3 -activated H 2 O 2 . A pH range of 9–10 was found to be optimum for the broad-spectrum decontamination of chemical warfare agents and other eco-toxicants using NaHCO 3 -activated H 2 O 2 . [ABSTRACT FROM AUTHOR]

An electrochemical organophosphorus hydrolase-based sensor for direct organophosphorus pesticides determination was developed, analytically characterized and applied for paraoxon quantification. The biosensing platform was constructed by one-step electrodeposition onto the surface of a glassy carbon electrode of a bionanocomposite of chitosan with carbon nanotube (CNTs), hydroxyapatite (HA) and organophosphorus hydrolase. The sensor, optimized with respect to the CNTs and HA load, was characterized by the application of cyclic voltammetry and chronoamperometry. The limit of detection (LOD) was found to be as low as 0.1 µmol L−1, the linear concentration range was extended up to 80 µmol L−1, and the sensitivity was as high as 5.10 nA L µmol−1. The sensor possesses enhanced sensitivity towards organophosphorus pesticides (OPs), because of the CNTs and the HA nanoparticles synergistic action. [ABSTRACT FROM AUTHOR]

A selective sensing platform for the organophosphate paraoxon, a highly toxic organic pollutant, has been designed and tested on water samples. A porous hybrid organic–inorganic film, synthesised using tetraethoxysilane, 1,8‐bis(triethoxysilyl)octane and cetyltrimethylammonium bromide, has been molecularly imprinted with a structural analogue of paraoxon, the diethyl(4‐nitrobenzyl)phosphonate, to induce selective recognition. Exfoliated graphene has been incorporated into the porous matrix to provide enhancement of the Raman scattering signal. The Raman sensor has been tested on different concentrations of paraoxon in both ethanol and water/ethanol mixture. The molecular selectivity has been assessed by comparing the Raman signal enhancement of paraoxon with a similar organophosphate, the bis‐(4‐nitrophenyl) phosphate. The molecularly imprinted film has shown a fourfold increase of the paraoxon signal, when compared with the corresponding not‐imprinted. The evaluation of the density of molecular cavities into the molecularly imprinted samples (4.50 * 10−10 μmol μm−3) has allowed assuming that each molecular cavity is capable of providing a remarkable signal enhancement of 1.47 * 1012 count * μmol−1 only when recognising paraoxon. The material design has allowed coupling the sensitivity of the graphene‐mediated enhancement of Raman scattering with the selectivity of molecular imprinting into a single and potentially portable, analytical system. Copyright © 2017 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Organophosphate (OP) poisoning is a major global health issue; while compounds from this group have been used intensively over the last century, an effective antidote is still lacking. Oxime-type acetylcholinesterase (AChE) reactivators are used to reactivate the OP inhibited AChE. Pralidoxime is the only US Food and Drug Administration approved oxime for therapeutic use but its efficacy has been disappointing. Two novel oximes (K378 and K727) were investigatedin silicoandin vitroand compared with an experimental oxime (kamiloxime; K-27) and pralidoxime.In silicothe molecular interactions between AChE and oximes were examined and binding energies were assessed. LogP (predicted log of the octanol/water partition coefficient) was estimated.In vitrothe intrinsic ability of the oximes to inhibit AChE (IC50) and their reactivation potency (R50) when used in paraoxon inhibited human RBC-AChE was determined. Molecular docking revealed that K378 and K727 bind to the peripheral site(s) with high binding energies in contrast to the central binding of K-27 and pralidoxime. LogP values indicating that the novel compounds are significantly less hydrophilic than K-27 or pralidoxime. IC50of K378 and K727 were comparable (0.9 and 1 µM, respectively) but orders of magnitude lower than comparators.R50values revealed their inability to reactivate paraoxon inhibited AChE. It is concluded that the novel oximes K378 and K727 are unlikely to be clinically useful. Thein silicoandin vitrostudies described allow avoidance of unnecessaryin vivoanimal work and contribute to the reduction of laboratory animal use. [ABSTRACT FROM PUBLISHER]

In the present work the nanostructured carbon-doped TiO thin films with nanorod morphology were deposited on glass substrate by a combination of ultrasonic and chemical vapor deposition methods, and for the first time were applied for the photocatalytic degradation of paraoxon and parathion organophosphorus pesticides under visible light irradiation. X-ray Diffraction, X-ray photoelectron spectroscopy, diffuse reflectance spectroscopy, and scanning electron microscopy techniques were used for characterization of the prepared thin films. Obtained results show that presence of carbon element and also special nanorod morphology of the thin films remarkably improve the optical properties of TiO in visible light region and results in the good visible light photocatalytic activity of the thin films for degradation of the pesticides. The photonic efficiencies of the prepared thin films were also examined based on the international ISO-10678:2010 standard protocol for photocatalytic degradation of methylene blue under UV light irradiation. The results show a maximum photonic efficiency of 0.0312% for the carbon-doped TiO thin film with 570 nm thickness, which compared to a reference standard TiO films indicates a 30% improvement in photonic efficiency. [ABSTRACT FROM AUTHOR]

Overuse of the organophosphorus pesticides such as Paraoxon in agriculture industry has raised significant threats to the environment by contamination of soils and groundwaters. Therefore, extensive studies have been carried out to develop an effective method for removing of these poisonous pollutants from contaminated resources. In the current study, Pd nanoparticle loaded TiO nanocomposites with different weight percentages of Pd were prepared via a facile photoreduction method and for the first time, were used for photocatalytic degradation of Paraoxon under visible-light irradiation. The prepared samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, and photoluminescence spectroscopy techniques. In these nanocomposites, the presence of Pd nanoparticles enhances the photocatalytic activity of TiO by their surface plasmon resonance effect and also by narrowing the band gap energy of TiO. The results of photocatalytic activity measurements indicate that the nanocomposite with 0.8 wt% content of Pd (PT0.8) has the best photocatalytic activity. The result of total organic carbon test shows that Paraoxon was completely mineralized by PT0.8 photocatalyst after 120 min, under visible-light irradiation. [ABSTRACT FROM AUTHOR]

Serial nanocomposites consisting of blue fluorescent carbon dots (B-CDs) and MgO nanoparticles were facilely prepared. Then on-site detection and degradation of ethyl-paraoxon were achieved and evaluated. It was revealed that ethyl-paraoxon was firstly decomposed into p-nitrophenol by MgO. Then, p-nitrophenol could significantly quench the fluorescence of decorated B-CDs due to an inner filter effect (IFE). The 0.05B-CDs@MgO showed excellent comprehensive performance among the serial xB-CDs@MgO samples due to its relatively high degradation ability towards ethyl-paraoxon and potent initial fluorescence emission intensity at an excitation wavelength of 360 nm between pH 4 and 10. Finally, based on the IFE, on-site paper sensors via color recognition app on a smartphone were explored compared with a conventional fluorescence spectrometer. Both the quantitative fluorescence intensities and G/B values showed the multi-piecewise linear correlations to ethyl-paraoxon concentration up to 3000 μg/mL in river water with a limit of detection to 0.06 μg/mL and 3.48 μg/mL as well as high recovery rates between 99%-102% and 95%–116%, respectively. The in vitro cytotoxicity and phytotoxicity assessment of the 0.05B-CDs@MgO revealed dose-dependent effects. Such portable and integrated fluorescent B-CDs@MgO nanocomposites on paper arrays show excellent potential in shortening the detection time and reducing the detection cost as a new strategy for the on-site quantitative detection and degradation of ethyl-paraoxon in actual river water. Serial integrated xB-CDs@MgO nanocomposites were constructed and optimized as enzyme-free sensors for on-site detection and effective degradation of ethyl-paraoxon toxins simultaneously. The degradation capacity of ethyl-paraoxon was up to 50.89 mg/g. Furthermore, two detection setups, i.e., a conventional fluorescence method and a visual determination by a smartphone, were explored based on the inner filter effect (IFE). Both the quantitative fluorescence intensities and G/B values revealed the piecewise linear correlation to ethyl-paraoxon concentration up to 3000 μg/mL in river water with LOD of 0.06 μg/mL and 3.48 μg/mL, respectively. Moreover, both methods showed high recovery rates in river water between 99%–102% and 95%–116%. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • The multifunctional nanoreactor consisting of Fe-CDs and MOF-808 were developed. • The nanoreactor can achieve selective degradation and sensitive detection of OPs. • OPs were detoxified by catalytic hydrolysis and photocatalytic of the nanoreactor. • The nanoreactor reactor allowed fast detection of nanomolar OPs by its fluorescence. Organophosphorus pesticides (OPs) are the most widely used pesticides, hence it is crucial to effectively prevent and control OPs residues for agricultural product safety and ecological development. In this work, the nanoreactor consisting of Fe-doped carbon dots (Fe-CDs) and metal-organic framework (MOF-808) were developed for selective degradation as well as sensitive detection of paraoxon and parathion. MOF-808 was selected as the host and used to rapidly degrade paraoxon due to its excellent organophosphorus hydrolase activity. Fe-CDs were severed as guest molecules not only for photocatalytic degradation of parathion, but also for sensing to detect OPs. Through host–guest interaction, Fe-CDs/MOF-808 and Fe-CDs@MOF-808 were synthesized for cascade degradation and detection of paraoxon and parathion, respectively. Paraoxon and parathion were detoxified by catalytic hydrolysis and photocatalytic degradation by Fe-CDs/MOF-808 and Fe-CDs@MOF-808, respectively. Meanwhile, the fluorescence of the nanocomposites was quenched by the internal filtering effect with 4-nitrophenol (4-NP), the degradation product of OPs. Fe-CDs/MOF-808 has a wide linear range for detection of paraoxon from 0.001 to 360 μM, with a limit of detection (LOD) as low as 0.3 nM. Fe-CDs@MOF-808 exhibited a linear range of 0.01–100 μM for parathion, with an LOD about 3.3 nM. The reliability of the nanoreactor was verified by testing the recovery rate of OPs spiked water sample. Meanwhile, the nanoreactors were applied for degradation and detection of OPs in pakchoi. The OPs in pakchoi can be fully degraded within 5 min, and the analytical results are consistent with those by standard method (HPLC). Therefore, the proposed nanoreactor provides a feasible alternative for effective degradation and timely detection of OPs during agricultural production. [ABSTRACT FROM AUTHOR]