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European Journal of Medicinal Chemistry Jan 2020New uncharged conjugates of 6-methyluracil derivatives with imidazole-2-aldoxime and 1,2,4-triazole-3-hydroxamic acid units were synthesized and studied as reactivators...
New uncharged conjugates of 6-methyluracil derivatives with imidazole-2-aldoxime and 1,2,4-triazole-3-hydroxamic acid units were synthesized and studied as reactivators of organophosphate-inhibited cholinesterase. Using paraoxon (POX) as a model organophosphate, it was shown that 6-methyluracil derivatives linked with hydroxamic acid are able to reactivate POX-inhibited human acetylcholinesterase (AChE) in vitro. The reactivating efficacy of one compound (5b) is lower than that of pyridinium-2-aldoxime (2-PAM). Meanwhile, unlike 2-PAM, in vivo study showed that the lead compound 5b is able: (1) to reactivate POX-inhibited AChE in the brain; (2) to decrease death of neurons and, (3) to prevent memory impairment in rat model of POX-induced neurodegeneration.
Topics: Acetylcholinesterase; Animals; Brain; Cholinesterase Inhibitors; Dose-Response Relationship, Drug; Humans; Hydroxamic Acids; Ligands; Maze Learning; Mice; Molecular Docking Simulation; Molecular Structure; Paraoxon; Quantum Theory; Rats; Rats, Wistar; Structure-Activity Relationship; Uracil
PubMed: 31675511
DOI: 10.1016/j.ejmech.2019.111787 -
Computational Biology and Chemistry Jun 2019Poisoning by organophosphates (OPs) takes one of the leading places in the total number of exotoxicoses. Detoxication of OPs at the first stage of the poison entering...
Poisoning by organophosphates (OPs) takes one of the leading places in the total number of exotoxicoses. Detoxication of OPs at the first stage of the poison entering the body could be achieved with the help of DNA- or RNA-aptamers, which are able to bind poisons in the bloodstream. The aim of the research was to develop an approach to rational in silico design of aptamers for OPs based on the example of paraoxon. From the published sequence of an aptamer binding organophosphorus pesticides, its three-dimensional model has been constructed. The most probable binding site for paraoxon was determined by molecular docking and molecular dynamics (MD) methods. Then the nucleotides of the binding site were mutated consequently and the values of free binding energy have been calculated using MD trajectories and MM-PBSA approach. On the basis of the energy values, two sequences that bind paraoxon most efficiently have been selected. The value of free binding energy of paraoxon with peripheral anionic site of acetylcholinesterase (AChE) has been calculated as well. It has been revealed that the aptamers found bind paraoxon more effectively than AChE. The peculiarities of paraoxon interaction with the aptamers nucleotides have been analyzed. The possibility of improving in silico approach for aptamer selection is discussed.
Topics: Acetylcholinesterase; Aptamers, Nucleotide; Binding Sites; Cholinesterase Reactivators; Drug Design; Humans; Hydrogen Bonding; Molecular Docking Simulation; Molecular Dynamics Simulation; Mutation; Paraoxon; Protein Binding; Static Electricity
PubMed: 31170561
DOI: 10.1016/j.compbiolchem.2019.05.004 -
Journal of Biochemical and Molecular... 1999Paraoxon, the active metabolite of parathion, can be detoxified through a noncatalytic pathway by carboxylesterases and a catalytic pathway by calcium-dependent...
Paraoxon, the active metabolite of parathion, can be detoxified through a noncatalytic pathway by carboxylesterases and a catalytic pathway by calcium-dependent A-esterases, producing p-nitrophenol as a common metabolite. The detoxication patterns of carboxylesterases and A-esterases were investigated in vitro in the present study with a high tissue concentration (75 mg/mL rat liver homogenate or 50% rat serum solution) to more closely reflect enzyme concentrations in intact tissues. A final paraoxon concentration of 3.75 microM was used to incubate with liver homogenates or serum solutions for 5 seconds or 3, 5, 15, or 25 minutes; also 0.625, 1.25, 2.5, 3.125, 3.75, or 5.0 microM paraoxon (final concentration) was incubated with liver homogenates or serum solutions for 15 minutes. Phenyl saligenin cyclic phosphate and EDTA were used to inhibit carboxylesterases and A-esterases, respectively. Significant amounts of p-nitrophenol were generated with or without either inhibitor during a 15 minute incubation with paraoxon from low (0.625 microM) to high (5.0 microM) concentrations. The amount of p-nitrophenol generated via carboxylesterase phosphorylation was greater than via A-esterase-mediated hydrolysis in the initial period of incubation or when incubating with a low concentration of paraoxon. Plateau shape curves of p-nitrophenol concentration versus time or paraoxon concentration indicated that carboxylesterase phosphorylation was saturable. When incubated for long time intervals or with high concentrations of paraoxon, more p-nitrophenol was generated via A-esterase-mediated hydrolysis than from carboxylesterase phosphorylation. The ratio of paraoxon concentration to tissue amount used in in vitro assays of this study was equivalent to dosing a rat with toxicologically relevant dosages. These in vitro data suggest that both carboxylesterases and A-esterases detoxify paraoxon in vivo; carboxylesterases may be an important mode of paraoxon detoxication in initial exposures to paraoxon or parathion before they become saturated, whereas A-esterases may contribute to paraoxon detoxication in repeated exposures to paraoxon or parathion because they will not become inhibited and will remain catalytically active unlike the carboxylesterases. The importance of carboxylesterases in detoxication of paraoxon was verified by an in vivo study. In rats pretreated with tri-o-tolyl phosphate, an in vivo carboxylesterase inhibitor, brain acetylcholinesterase was significantly inhibited after intravenous exposure to parathion. No significant inhibition of brain acetylcholinesterase was observed in rats pretreated with corn oil.
Topics: Acetylcholinesterase; Animals; Brain; Carboxylesterase; Carboxylic Ester Hydrolases; In Vitro Techniques; Inactivation, Metabolic; Insecticides; Liver; Male; Paraoxon; Parathion; Phosphorylation; Rats; Rats, Sprague-Dawley
PubMed: 10402560
DOI: 10.1002/(sici)1099-0461(1999)13:5<261::aid-jbt6>3.0.co;2-0 -
Biosensors & Bioelectronics Nov 2022Monitoring of pesticide residues in food and environmental matrices is undoubtedly crucial to guarantee food safety and ecological health, yet how to realize their...
Monitoring of pesticide residues in food and environmental matrices is undoubtedly crucial to guarantee food safety and ecological health, yet how to realize their sensitive and convenient detection is still challenging. Herein, we propose an all-in-one test strip that elaborately integrates bioenzyme, nanozyme and chromogen together, and achieve the highly sensitive and convenient sensing of pesticide residues assisted by a smartphone. A sequential self-assembly strategy was first explored to acquire an integrative bioenzyme-nanozyme-chromogen assembly, and then the assembly was confined in a biocompatible hydrogel to construct the test strip. Thanks to both the proximity and confinement effects, a ∼1.2-fold improvement of the cascade catalytic efficiency was gained to benefit high-sensitivity detection. More importantly, since all the sensing elements, including target recognition units and signal amplification modules, were rationally integrated in the test strip, detection operation was significantly simplified, making it possible for in-field rapid analysis. Besides, the microenvironment provided by the alginate hydrogel carrier endowed the test strip with an excellent sensing stability. By taking paraoxon as a typical pesticide, high-performance detection of the target was accomplished via the smartphone-assisted all-in-one test strip. Moreover, the test strip was successfully applied for paraoxon detection in various real samples and exhibited good correlations with commercial kits, demonstrating its great prospect for practical applications. Our work not only offers a new tool for the high-sensitivity and convenient monitoring of pesticide residues, but will also inspire the development of efficient multi-enzyme sensing platforms.
Topics: Biosensing Techniques; Hydrogels; Limit of Detection; Paraoxon; Pesticide Residues; Smartphone
PubMed: 35932555
DOI: 10.1016/j.bios.2022.114583 -
Toxicology and Applied Pharmacology Aug 1993The effect of phosphotriesterase (PTE) on the ip toxicity of paraoxon was studied in mice. The PTE preparation (0.1 ml; paraoxon-hydrolyzing activity, 1.5 mumol/min) was...
The effect of phosphotriesterase (PTE) on the ip toxicity of paraoxon was studied in mice. The PTE preparation (0.1 ml; paraoxon-hydrolyzing activity, 1.5 mumol/min) was given iv. Cholinesterase activities were measured 2 hr after paraoxon administration. The PTE treatment, given 10 min before paraoxon, did not protect serum cholinesterase (ChE) against the inhibiting effect of paraoxon, but it clearly prevented the decrease of the brain ChE activity. In PTE-nontreated animals ChE was reduced by 60% at the paraoxon dose of 0.5 mg/kg, whereas in PTE-treated mice a significant reduction was not seen until a paraoxon dose of 2.0 mg/kg. The iv injection of PTE did prevent the decrease in brain ChE activity by paraoxon, when it was administered before or immediately after the paraoxon. PTE, injected 15 min after paraoxon, resulted in a minor protection in the brain ChE activities. The iv injection of PTE increased the serum paraoxon-hydrolyzing activity up to 5.1-fold. When the same amounts of PTE were administered ip, im, or sc, the increases in the hydrolyzing activities were 4.7-, 2.5-, and 1.8-fold, respectively. The activities returned to the normal level within 24 hr after the PTE. The elimination half-life of the activity of PTE administered iv was approximately 5.5 hr. In conclusion, PTE substantially prevents the toxicity of paraoxon in mice by hydrolyzing paraoxon in circulation.
Topics: Animals; Aryldialkylphosphatase; Blood; Drug Administration Routes; Drug Interactions; Hydrolysis; Male; Mice; Mice, Inbred Strains; Paraoxon; Phosphoric Monoester Hydrolases; Substrate Specificity
PubMed: 8394035
DOI: 10.1006/taap.1993.1154 -
Annals of the New York Academy of... Nov 2020Organophosphorus (OP) compounds are chemical threat agents and are irreversible inhibitors of the enzyme acetylcholinesterase that lead to a hypercholinergic response... (Comparative Study)
Comparative Study
Organophosphorus (OP) compounds are chemical threat agents and are irreversible inhibitors of the enzyme acetylcholinesterase that lead to a hypercholinergic response that could include status epilepticus (SE). SE particularly targets the heart and brain and despite existing therapies, it is still associated with significant mortality and morbidity. Here, we investigated the effect of intramuscular (i.m.) adjunct therapy consisting of atenolol (AT) and levetiracetam (LV) when administered after paraoxon (POX)-induced SE. The combination therapy was administered twice daily for 2, 7, or 14 days. POX exposure in rats produced rapid SE onset that was treated with atropine, pralidoxime chloride, and midazolam. Here, AT + LV therapy produced significant reductions in POX SE mortality assessed at 30 days post-SE. AT + LV therapy exhibited muscle pathology inflammation scores that were not significantly different from saline-treated controls. Pharmacokinetic analyses revealed that the i.m. route achieved faster and stabler plasma therapeutic levels for both AT and LV under OP SE conditions compared with oral administrations. Our data provide evidence of the safety and efficacy of i.m. AT + LV therapy for reducing mortality following POX SE.
Topics: Administration, Oral; Animals; Atenolol; Injections, Intramuscular; Levetiracetam; Male; Paraoxon; Rats; Rats, Sprague-Dawley; Status Epilepticus
PubMed: 32961584
DOI: 10.1111/nyas.14500 -
Drug Metabolism and Disposition: the... 1985Hydrolysis and covalent binding to nonessential esterases are two biochemical processes which can prevent paraoxon from reacting with the essential enzyme,...
Hydrolysis and covalent binding to nonessential esterases are two biochemical processes which can prevent paraoxon from reacting with the essential enzyme, acetylcholinesterase. Both processes have been proposed as the primary route of paraoxon detoxification in vivo. These experiments were designed to assess the relative contribution of each pathway to the disappearance of paraoxon in the rabbit. In vitro, paraoxon disappeared from whole rabbit blood with a t 1/2 of 17.7 sec. Hydrolysis by paraoxonase (EC 3.1.1.2) accounted entirely for this disappearance and covalent binding contributed essentially nothing. In vivo, following an iv injection of 0.15 mg/kg paraoxon, serum paraoxonase hydrolyzed as much as 41% of the injected dose within the first 30 sec. Pretreatment of rabbits with an ip injection of tri-o-tolyl phosphate eliminated more than 95% of the paraoxon binding sites. However, pretreatment with tri-o-tolyl phosphate had no significant effect on the t 1/2 or volume of distribution of paraoxon, indicating that covalent binding sites did not contribute significantly to the clearance of paraoxon from whole rabbits under these conditions. Hydrolysis of paraoxon by tissue paraoxonases, in addition to that catalyzed by paraoxonase in the blood, could account for its rapid metabolism. These findings demonstrate that paraoxonase has a major role in the disappearance of paraoxon in the rabbit. This suggests that susceptibility of people to chronic paraoxon poisoning may vary, according to their inherited level and type of serum paraoxonase.
Topics: Animals; Aryldialkylphosphatase; Binding Sites; Hydrolysis; Kinetics; Male; Paraoxon; Phosphoric Monoester Hydrolases; Protein Binding; Rabbits; Serum Albumin; Tritolyl Phosphates
PubMed: 2867864
DOI: No ID Found -
Analytical Methods : Advancing Methods... Dec 2021Methyl paraoxon (MP) has attracted more and more attention in recent years because of its severe neurotoxicity and respiratory toxicity. Therefore, it is very urgent to...
Methyl paraoxon (MP) has attracted more and more attention in recent years because of its severe neurotoxicity and respiratory toxicity. Therefore, it is very urgent to develop new and sensitive MP detection methods for health protection and public safety. Covalent organic frameworks (COFs) are widely used in fluorescence detection because they can effectively transmit and amplify probe signals with multiple identical binding sites within an extended framework. Here, COF nanosheet material was synthesized by the solvothermal reaction of melem (ML) and 2,5-dihydroxyterephthalaldehyde (DHTA). The resulting COF exhibits remarkable luminescence quenching toward MP due to the relationship of competitive absorption and Förster resonance energy transfer between MP and COF. COF can be used for sensitive and selective detection of MP in a wide concentration range of 0.57 ng mL to 30 μg mL with a detection limit of 0.19 ng mL. The material has good chemical stability, excellent selectivity, good reusability and hydrophilicity, which provide more possibilities for COFs in the detection of pesticides.
Topics: Imines; Luminescence; Metal-Organic Frameworks; Paraoxon
PubMed: 34812807
DOI: 10.1039/d1ay01617b -
Medicinal Chemistry (Shariqah (United... 2022To synthesize and evaluate the fused heterocyclic imidazo[1,2-a]pyridine based oxime as a reactivator against paraoxon inhibited acetylcholinesterase.
AIM
To synthesize and evaluate the fused heterocyclic imidazo[1,2-a]pyridine based oxime as a reactivator against paraoxon inhibited acetylcholinesterase.
BACKGROUND
Organophosphorus compounds (OPs) include parathion, malathion, chlorpyrifos, monocrotophos, and diazinon, which are commonly used in agriculture for enhancing agricultural productivity via killing crop-damaging pests. However, people may get exposed to OPs pesticides unintentionally/intentionally via ingestion, inhalation, or dermal. The current treatment regimen includes reactivator such as mono or bis-pyridinium oximes along with anticholinergic and anticonvulsant drugs that are recommended for the treatment of OP poisoning. Unfortunately, the drawback of the existing reactivator is the permanent charge present on the pyridinium, making them inefficient to cross the blood-brain barrier (BBB) and reactivate OP-inhibited central nervous system (CNS) acetylcholinesterase. Therefore, there is a need of a reactivator that could cross the BBB and reactivate the OP inhibited acetylcholinesterase.
OBJECTIVE
The objectives of the study were synthesis, molecular docking, BSA binding, and in-vitro estimation of oximes of various substituted imidazo [1,2-a]pyridine against paraoxon inhibited acetylcholinesterase.
METHODS
The reactivators were synthesized in three steps and characterized using various spectroscopic techniques. The molecular docking study was performed on 2WHP and 3ZLV PDB using the Glide-XP software. The acid dissociation constant (pKa) of oximes was calculated experimentally, and the drug-likeness properties of the oximes were calculated in silico using Molinspiration and Swiss ADME software. The binding of oximes with bovine serum albumin (BSA) was also investigated using a Fluorescence spectrophotometer. The reactivation potential of the oximes was determined by in vitro enzymatic assay.
RESULTS
The In-silico study inferred that the synthesized molecules fulfilled the parameters required for a successful CNS drug candidate. Furthermore, in-vitro enzymatic assay indicated reasonable reactivation potential of the oximes against paraoxon-inhibited AChE. The binding of oximes with bovine serum albumin (BSA) revealed that there was a static quenching of intrinsic fluorescence of BSA by the oxime. The binding constant value and number of binding sites were found to be 0.24 x 10 mol and 1, respectively.
CONCLUSION
The results of the study concluded that this scaffold could be used for further designing of more efficient uncharged reactivators.
Topics: Acetylcholinesterase; Cholinesterase Reactivators; Humans; Imidazoles; Molecular Docking Simulation; Oximes; Paraoxon; Pyridines; Serum Albumin, Bovine
PubMed: 33563155
DOI: 10.2174/1573406417666210208223240 -
Toxicology Letters Nov 2004Acetylcholinesterase (AChE) sensitivity to the organophosphorus (OP) pesticide methyl-paraoxon was measured in fourteen species of Neotropical marine and freshwater fish... (Comparative Study)
Comparative Study
Acetylcholinesterase (AChE) sensitivity to the organophosphorus (OP) pesticide methyl-paraoxon was measured in fourteen species of Neotropical marine and freshwater fish found in the waters of Brazil. The rate constant for phosphorylation, kp, the dissociation constant, kd, the second order rate constant, ki, and the IC50 value were measured at 28 degrees C in pH 7.5 buffer for AChE extracted from brain. In addition, the substrate affinity constant, km, was measured with acetylthiocholine. The IC50 for 30 min of inhibition ranged from 123 nM (Prochilodus lineatus) to 3340 nM (Percophis brasiliensis), which corresponded to ki values of 187-6.9 mM(-1) min(-1). A 10-fold range in kp values from 0.21 min(-1) (Paralonchurus brasiliensis) to 2.1 min(-1) (Dules auriga) was associated with a 37-fold range in kd values from 4 to 150 microM. These large differences in reactivity with methyl-paraoxon were not reflected in the binding affinity for acetylthiocholine; km values were approximately 0.1-0.3 mM for all species. These results predict that the amino acid sequence involved in AChE sensitivity differs in these fishes, and that consequently some fish species may be resistant to the toxicity of methyl-paraoxon.
Topics: Acetylcholinesterase; Animals; Brain; Cholinesterase Inhibitors; Fishes; Kinetics; Paraoxon; Phosphorylation
PubMed: 15451556
DOI: 10.1016/j.toxlet.2004.04.026