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International Journal of Molecular... Nov 2021Organophosphorus hydrolase (OPH) is a metalloenzyme that can hydrolyze organophosphorus agents resulting in products that are generally of reduced toxicity. The best OPH...
Organophosphorus hydrolase (OPH) is a metalloenzyme that can hydrolyze organophosphorus agents resulting in products that are generally of reduced toxicity. The best OPH substrate found to date is diethyl p-nitrophenyl phosphate (paraoxon). Most structural and kinetic studies assume that the binding orientation of paraoxon is identical to that of diethyl 4-methylbenzylphosphonate, which is the only substrate analog co-crystallized with OPH. In the current work, we used a combined docking and molecular dynamics (MD) approach to predict the likely binding mode of paraoxon. Then, we used the predicted binding mode to run MD simulations on the wild type (WT) OPH complexed with paraoxon, and OPH mutants complexed with paraoxon. Additionally, we identified three hot-spot residues (D253, H254, and I255) involved in the stability of the OPH active site. We then experimentally assayed single and double mutants involving these residues for paraoxon binding affinity. The binding free energy calculations and the experimental kinetics of the reactions between each OPH mutant and paraoxon show that mutated forms D253E, D253E-H254R, and D253E-I255G exhibit enhanced substrate binding affinity over WT OPH. Interestingly, our experimental results show that the substrate binding affinity of the double mutant D253E-H254R increased by 19-fold compared to WT OPH.
Topics: Aryldialkylphosphatase; Catalytic Domain; Crystallography, X-Ray; Models, Molecular; Molecular Dynamics Simulation; Molecular Structure; Mutation; Paraoxon; Protein Conformation
PubMed: 34884430
DOI: 10.3390/ijms222312624 -
Journal of Hazardous Materials Sep 2022The ever-constant threat of chemical warfare agents (CWA) motivates the design of materials to provide better protection to warfighters and civilians. Cerium and...
The ever-constant threat of chemical warfare agents (CWA) motivates the design of materials to provide better protection to warfighters and civilians. Cerium and titanium oxide are known to react with organophosphorus compounds such Sarin and Soman. To study the decomposition of methyl paraoxon (CWA simulant) on such materials, we synthesized ordered mesoporous metal oxides (MMO) TiO, CeTiO (x = 0.005, 0.5, 0.10, 0.15) and CeO. We fully characterized TiO and Ce-doped TiO and found phase-pure oxides with cylindrical hexagonally packed pores and high surface areas (176-252 m/g). Methyl paraoxon decomposition was tracked through UV/Vis and found CeTiO to decompose the most methyl paraoxon, but CeO to be the most reactive when normalized to surface area. The surface area normalized rate constant (k) for CeO was 3-4.6 times larger than that of TiO and the CeTiO series. While TiO and CeTiO for 0.05 ≤ x ≤ 0.10 displayed no significant differences in the kinetics, the mostly amorphous CeTiO displayed a slight increase in reactivity. Our findings indicate that the nature of the cation, Ce vs Ti, is less important to methyl paraoxon reactivity on these MMOs compared to other factors such as crystal structure type.
Topics: Catalysis; Cerium; Chemical Warfare Agents; Oxides; Paraoxon; Titanium
PubMed: 35999722
DOI: 10.1016/j.jhazmat.2022.129536 -
Acta Medica (Hradec Kralove) 2022Organophosphorus compounds induce irreversible inhibition of acetylcholinesterase, which then produces clinically manifested muscarinic, nicotinic and central effects....
Organophosphorus compounds induce irreversible inhibition of acetylcholinesterase, which then produces clinically manifested muscarinic, nicotinic and central effects. The aim of the study was to analyse the clinical signs of acute paraoxon poisoning in rats and to determine the relationship between the intensity of signs of poisoning and the dose of paraoxon and/or the outcome of poisoning in rats. Animals were treated with either saline or atropine (10 mg/kg intramuscularly). The median subcutaneous lethal dose (LD50) of paraoxon was 0.33 mg/kg and protective ratio of atropine was 2.73. The presence and intensity of signs of poisoning in rats (dyspnoea, lacrimation, exophthalmos, fasciculations, tremor, ataxia, seizures, piloerection, stereotypic movements) were observed and recorded for 4 h after the injection of paraoxon. Intensity of these toxic phenomena was evaluated as: 0 - absent, 1 - mild/moderate, 2 - severe. Fasciculations, seizures and tremor were more intense at higher doses of paraoxon and in non-survivors. In unprotected rats piloerection occurred more often and was more intense at higher doses of paraoxon as well as in non-survivors. In atropine-protected rats, piloerection did not correlate with paraoxon dose or outcome of poisoning. The intensity of fasciculations and seizures were very strong prognostic parameters of the poisoning severity.
Topics: Acetylcholinesterase; Animals; Atropine; Fasciculation; Paraoxon; Rats; Seizures; Tremor
PubMed: 35793503
DOI: 10.14712/18059694.2022.10 -
Scientific Reports Mar 2020Organophosphorus compounds (OP) are highly toxic molecules used as insecticides that inhibit cholinesterase enzymes involved in neuronal transmission. The intensive use...
Organophosphorus compounds (OP) are highly toxic molecules used as insecticides that inhibit cholinesterase enzymes involved in neuronal transmission. The intensive use of OP for vector control and agriculture has led to environmental pollutions responsible for severe intoxications and putative long-term effects on humans and wild animals. Many in vivo models were studied over the years to assess OP acute toxicity, but the long-term effects are poorly documented. Planarian, a freshwater flatworm having a cholinergic system, has emerged as a new original model for addressing both toxicity and developmental perturbations. We used Schmidtea mediterranea planarians to evaluate long-term effects of paraoxon-ethyl at two sublethal concentrations over three generations. Toxicity, developmental perturbations and disruption of behavior were rapidly observed and higher sensitivity to paraoxon-ethyl of next generations was noticed suggesting that low insecticide doses can induce transgenerational effects. With the view of limiting OP poisoning, SsoPox, an hyperthermostable enzyme issued from the archaea Saccharolobus solfataricus, was used to degrade paraoxon-ethyl prior to planarian exposure. The degradation products, although not lethal to the worms, were found to decrease cholinesterase activities for the last generation of planarians and to induce abnormalities albeit in lower proportion than insecticides.
Topics: Animals; Biodegradation, Environmental; Cholinesterases; Evolution, Molecular; Gene Expression Regulation, Enzymologic; Paraoxon; Planarians; Time Factors
PubMed: 32123261
DOI: 10.1038/s41598-020-60846-1 -
International Journal of Molecular... Dec 2021The delayed effects of acute intoxication by organophosphates (OPs) are poorly understood, and the various experimental animal models often do not take into account...
The delayed effects of acute intoxication by organophosphates (OPs) are poorly understood, and the various experimental animal models often do not take into account species characteristics. The principal biochemical feature of rodents is the presence of carboxylesterase in blood plasma, which is a target for OPs and can greatly distort their specific effects. The present study was designed to investigate the nephrotoxic effects of paraoxon (O,O-diethyl O-(4-nitrophenyl) phosphate, POX) using three models of acute poisoning in outbred Wistar rats. In the first model (, POX2x group), POX was administered twice at doses 110 µg/kg and 130 µg/kg subcutaneously, with an interval of 1 h. In the second model (, CBPOX group), 1 h prior to POX poisoning at a dose of 130 µg/kg subcutaneously, carboxylesterase activity was pre-inhibited by administration of specific inhibitor cresylbenzodioxaphosphorin oxide (CBDP, 3.3 mg/kg intraperitoneally). In the third model (), POX was administered subcutaneously just once at doses of LD16 (241 µg/kg), LD50 (250 µg/kg), and LD84 (259 µg/kg). Animal observation and sampling were performed 1, 3, and 7 days after the exposure. Endogenous creatinine clearance (ECC) decreased in 24 h in the POX2x group ( = 0.011). Glucosuria was observed in rats 24 h after exposure to POX in both M1 and M2 models. After 3 days, an increase in urinary excretion of chondroitin sulfate (CS, = 0.024) and calbindin ( = 0.006) was observed in rats of the CBPOX group. Morphometric analysis revealed a number of differences most significant for rats in the CBPOX group. Furthermore, there was an increase in the area of the renal corpuscles ( = 0.0006), an increase in the diameter of the lumen of the proximal convoluted tubules (PCT, = 0.0006), and narrowing of the diameter of the distal tubules ( = 0.001). After 7 days, the diameter of the PCT lumen was still increased in the nephrons of the CBPOX group ( = 0.0009). In the model, histopathological and ultrastructural changes in the kidneys were revealed after the exposure to POX at doses of LD50 and LD84. Over a period from 24 h to 3 days, a significant ( = 0.018) expansion of Bowman's capsule was observed in the kidneys of rats of both the LD50 and LD84 groups. In the epithelium of the proximal tubules, stretching of the basal labyrinth, pycnotic nuclei, and desquamation of microvilli on the apical surface were revealed. In the epithelium of the distal tubules, partial swelling and destruction of mitochondria and pycnotic nuclei was observed, and nuclei were displaced towards the apical surface of cells. After 7 days of the exposure to POX, an increase in the thickness of the glomerular basement membrane (GBM) was observed in the LD50 and LD84 groups ( = 0.019 and 0.026, respectively). Moreover, signs of damage to tubular epithelial cells persisted with blockage of the tubule lumen by cellular detritus and local destruction of the surface of apical cells. Comparison of results from the three models demonstrates that the nephrotoxic effects of POX, evaluated at 1 and 3 days, appear regardless of prior inhibition of carboxylesterase activity.
Topics: Animals; Biomarkers; Bowman Capsule; Creatinine; Kidney; Kidney Tubules, Proximal; Male; Nephrons; Paraoxon; Rats; Rats, Wistar
PubMed: 34948422
DOI: 10.3390/ijms222413625 -
Sensors (Basel, Switzerland) Jan 2022The development of faster, sensitive and real-time methods for detecting organophosphate (OP) pesticides is of utmost priority in the in situ monitoring of these...
The development of faster, sensitive and real-time methods for detecting organophosphate (OP) pesticides is of utmost priority in the in situ monitoring of these widespread compounds. Research on enzyme-based biosensors is increasing, and a promising candidate as a bioreceptor is the thermostable enzyme esterase-2 from (EST2), with a lipase-like Ser-His-Asp catalytic triad with a high affinity for OPs. This study aimed to evaluate the applicability of Förster resonance energy transfer (FRET) as a sensitive and reliable method to quantify OPs at environmentally relevant concentrations. For this purpose, the previously developed IAEDANS-labelled EST2-S35C mutant was used, in which tryptophan and IAEDANS fluorophores are the donor and the acceptor, respectively. Fluorometric measurements showed linearity with increased EST2-S35C concentrations. No significant interference was observed in the FRET measurements due to changes in the pH of the medium or the addition of other organic components (glucose, ascorbic acid or yeast extract). Fluorescence quenching due to the presence of paraoxon was observed at concentrations as low as 2 nM, which are considered harmful for the ecosystem. These results pave the way for further experiments encompassing more complex matrices.
Topics: Biosensing Techniques; Ecosystem; Fluorescence Resonance Energy Transfer; Insecticides; Paraoxon; Pesticides
PubMed: 35062524
DOI: 10.3390/s22020561 -
Zhongguo Yao Li Xue Bao = Acta... Jan 1986
Topics: Animals; Paraoxon; Rabbits; Radioimmunoassay
PubMed: 2945397
DOI: No ID Found -
Structure (London, England : 1993) Nov 2022Organophosphorus (OP) compounds, including nerve agents and some pesticides, covalently bind to the catalytic serine of human acetylcholinesterase (hAChE), thereby...
Organophosphorus (OP) compounds, including nerve agents and some pesticides, covalently bind to the catalytic serine of human acetylcholinesterase (hAChE), thereby inhibiting acetylcholine hydrolysis necessary for efficient neurotransmission. Oxime antidotes can reactivate the OP-conjugated hAChE, but reactivation efficiency can be low for pesticides, such as paraoxon (POX). Understanding structural and dynamic determinants of OP inhibition and reactivation can provide insights to design improved reactivators. Here, X-ray structures of hAChE with unaged POX, with POX and oximes MMB4 and RS170B, and with MMB4 are reported. A significant conformational distortion of the acyl loop was observed upon POX binding, being partially restored to the native conformation by oximes. Neutron vibrational spectroscopy combined with molecular dynamics simulations showed that picosecond vibrational dynamics of the acyl loop soften in the ∼20-50 cm frequency range. The acyl loop structural perturbations may be correlated with its picosecond vibrational dynamics to yield more comprehensive template for structure-based reactivator design.
Topics: Humans; Acetylcholinesterase; Paraoxon; Crystallography, X-Ray; Cholinesterase Inhibitors; Oximes; Organophosphorus Compounds; Neutrons; Pesticides
PubMed: 36265484
DOI: 10.1016/j.str.2022.09.006 -
Journal of Applied Toxicology : JAT Nov 2019Organophosphates, useful agents as pesticides, also represent a serious danger due to their high acute toxicity. There is indication that oximes, when administered...
Organophosphates, useful agents as pesticides, also represent a serious danger due to their high acute toxicity. There is indication that oximes, when administered before organophosphate exposure, can protect from these toxic effects. We have tested at equitoxic dosage (25% of LD ) the prophylactic efficacy of five experimental (K-48, K-53, K-74, K-75, K-203) and two established oximes (pralidoxime and obidoxime) to protect from mortality induced by the organophosphate paraoxon. Mortalities were quantified by Cox analysis and compared with those observed after pretreatment with a strong acetylcholinesterase inhibitor (10-methylacridine) and after the FDA-approved pretreatment compound pyridostigmine. All nine tested substances statistically significantly reduced paraoxon-induced mortality. Best protection was conferred by the experimental oxime K-48, reducing the relative risk of death (RR) to 0.10, which was statistically significantly superior to pyridostigmine (RR = 0.31). The other oximes reduced the RR to 0.13 (obidoxime), 0.20 (K-203), 0.21 (K-74), 0.24 (K-75) and 0.26 (pralidoxime), which were significantly more efficacious than 10-methylacridine (RR = 0.65). These data support the hypothesis that protective efficacy is not primarily due to cholinesterase inhibition and indicate that the tested experimental oximes may be considered promising alternatives to the established pretreatment compound pyridostigmine.
Topics: Animals; Cholinesterase Reactivators; Lethal Dose 50; Male; Obidoxime Chloride; Paraoxon; Pralidoxime Compounds; Proportional Hazards Models; Protective Agents; Rats, Wistar; Survival Analysis
PubMed: 31264735
DOI: 10.1002/jat.3835 -
Chemosphere Feb 2022Paraoxon is one of the pesticide that can induce toxicity to nervous system of living organisms. In this work, we focused on synthesizing the catalyst Bismuth Vanadate...
Paraoxon is one of the pesticide that can induce toxicity to nervous system of living organisms. In this work, we focused on synthesizing the catalyst Bismuth Vanadate with the properties that can sense the presence of organophosphorus compounds and characterized them with various characterization methods. The structural studies done by XRD, UV spectroscopy and FTIR spectroscopy. Morphological studies were carried by SEM and TEM. Elemental analysis using XPS spectra. The proposed electrocatalyst was successfully applied as the active electrode material modifying the screen printed carbon electrode for electrochemical sensor applications. The results of the studies indicate that bismuth vanadate modified electrode exhibited four electron transfer process for reduction of nitro group and this lead to the superior electrochemical sensing performance for ethyl Paraoxon with a detection limit of 0.03 μM and good sensitivity 0.345 μA μM cm with excellent reproducibility, repeatability, stability and selectivity over common interferents. Furthermore, the practical application was successfully carried using the proposed modified strips to determine Paraoxon presence in the river water sample with satisfactory results. This proposed catalyst can act as a desirable candidate for the rapid electrochemical sensor.
Topics: Electrodes; Paraoxon; Pesticides; Reproducibility of Results
PubMed: 34688713
DOI: 10.1016/j.chemosphere.2021.132511