Pralidoxime (2-PAM) is a monopyridinium aldoxime-type compound of acetylcholinesterase reactivators. 2-PAM was introduced about five decades ago for the treatment of organophosphorus poisoning in order to reactivate inhibited acetylcholinesterase. The application of organophosphorus compounds is varied, including warfare agents, insecticides and pesticides in agriculture, the chemical industry, etc. The exposure is not limited to certain groups of humans: rather everyone can be affected, including pregnant women, and consequently fetuses as well. The present study was aimed to determine the 2-PAM concentration in the plasma of pregnant mice, assuming a different physiological condition than non-pregnant ones. Blood-placenta penetration of 2-PAM was also investigated. 2-PAM was intraperitoneally injected into mice on gestational day 18 and mother blood was collected following 5, 15, 30 and 90 minutes. Four fetuses along with their placentas were collected at every time point. HPLC-UV method was employed to determine the 2-PAM concentrations. The result showed higher levels of 2-PAM at 15 minutes (tmax) in the plasma of pregnant mice compared to non-pregnant ones. Moreover, 2-PAM copiously reached the placenta, which is a store house of nutrients for the fetus. A higher concentration of 2-PAM was found in the brain of fetuses in comparison to that of the mothers’. Our study concludes that 2-PAM crosses the placenta barrier and reaches the brain of the fetus in a more ample quantity than that in the mother’s brain. The results provide an insight into a special condition of pregnancy when antidotal application of the acetylcholinesterase reactivator 2-PAM in organophosphorus poisoning results in 2-PAM exposure in the fetus.
- MeSH
- Antidotes pharmacology metabolism therapeutic use MeSH
- Maternal-Fetal Exchange MeSH
- Models, Animal MeSH
- Brain growth & development drug effects MeSH
- Mice MeSH
- Organophosphorus Compounds adverse effects MeSH
- Pralidoxime Compounds * pharmacology metabolism therapeutic use MeSH
- Cholinesterase Reactivators pharmacokinetics metabolism therapeutic use MeSH
- Pregnancy MeSH
- Fetal Development drug effects MeSH
- Check Tag
- Mice MeSH
- Pregnancy MeSH
- Publication type
- Research Support, Non-U.S. Gov't MeSH
Reactivation efficacy of three homologous and three isomeric series of pralidoxime-type reactivators with aldoxime group in position 2, 3 and 4 of the heterocycle was tested in reactivation of tabun-inhibited AChE. The experiments were performed with immobilized and stabilized porcine brain AChE. The enzyme activity was measured by Ellman method. Reactivation efficacy was determined by measurement of indicator fabric coloration intensity as a measure of AChE activity. Of the studied group of nine reactivators, isomers with the functional group in position 2 were the most effective. The highest value (30 %) for reactivation of inhibited AChE was found for 2PAE after treatment for 15 min at concentration 0.5 mg/cm(3). The efficacy of the isomers decreased in the order ortho > para > meta. No marked effect on the efficacy of the reactivators was observed on prolongation of the reactivation time. The reactivators efficacy decreased with decreasing concentration of their solutions.
- MeSH
- Acetylcholinesterase drug effects MeSH
- Cholinesterase Inhibitors toxicity MeSH
- Isomerism MeSH
- Organophosphates toxicity MeSH
- Pralidoxime Compounds chemistry pharmacology MeSH
- Swine MeSH
- Cholinesterase Reactivators pharmacology MeSH
- Animals MeSH
- Check Tag
- Animals MeSH
- Publication type
- Journal Article MeSH
Trichlorfon is a specific inhibitor of cholinesterases. It was typically used as an insecticide; however, trichlorfon was described as useful for symptomatic treatment of Alzheimer's disease some years ago. The presented study is aimed at reactivation of trichlorfon-inhibited butyrylcholinesterase since this enzyme play an important role in Alzheimer's disease as deputy for acetylcholinesterase and furthermore it could be applied as a scavenger in case of overdosing. We used in vitro reactivation test for considering only reactivation efficacy of butyrylcholinesterase that is inhibited by trichlorfon and not reactivation of butyrylcholinesterase inhibited by trichlorfon metabolic products. Four reactivators were used: HI-6, pralidoxime, obidoxime, and K048. Although all of the reactivators seem to be effective at 1 mM concentration, a lower concentration was not able ensure sufficient reactivation. There was also an observed lowering of reactivation efficacy when butyrylcholinesterase was exposed to trichlorfon for a longer time interval.
- MeSH
- Acetylcholinesterase metabolism MeSH
- Alzheimer Disease drug therapy enzymology pathology MeSH
- Butyrylcholinesterase metabolism MeSH
- Cholinesterase Inhibitors chemistry pharmacology therapeutic use MeSH
- Humans MeSH
- Obidoxime Chloride pharmacology MeSH
- Oximes pharmacology MeSH
- Pralidoxime Compounds pharmacology MeSH
- Pyridinium Compounds pharmacology MeSH
- Cholinesterase Reactivators chemistry pharmacology therapeutic use MeSH
- Trichlorfon chemistry pharmacology therapeutic use MeSH
- Check Tag
- Humans MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
OBJECTIVES: Quantification of efficacy of monopyridinium isomers and homologs derived from clinically used Pralidoxime within reactivation of acetylcholinesterase inhibited with organophosphorus nerve agents. METHODS: This work uses the colorimetric biosensor called Detehit - cotton cloth with immobilized enzyme acetylcholinesterase. Biosensor is based on the modificated Ellman's method. RESULTS: The highest reactivation was observed with sarin-inhibited acetylcholinesterase. Substantially lower reactivation was found with the cyclosarin-inhibited enzyme whereas AChE, inhibited by soman could not be effectively reactivated under the given conditions (enzyme inhibition for 2 minutes and subsequent treatment with the reactivator for 15 minutes). CONCLUSION: Our work gives comparison of efficacy of reactivators in dependence on the length of alkylene chain and position of aldoxime functional group. Evaluation of effectivity of aldoxime reactivators is provided by simple means. The method allows rapid in vitro evaluation of the reactivators without being disturbed by excess of the organophosphate or reactivator.
- MeSH
- Acetylcholinesterase metabolism MeSH
- Biosensing Techniques MeSH
- Cholinesterase Inhibitors chemistry toxicity MeSH
- Enzymes, Immobilized antagonists & inhibitors metabolism MeSH
- Isomerism MeSH
- Organophosphorus Compounds chemistry pharmacology MeSH
- Oximes chemistry pharmacology MeSH
- Pralidoxime Compounds chemistry pharmacology MeSH
- Cholinesterase Reactivators chemistry pharmacology MeSH
- Sarin toxicity MeSH
- Soman toxicity MeSH
- Publication type
- Journal Article MeSH
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 investigated in silico and in vitro and compared with an experimental oxime (kamiloxime; K-27) and pralidoxime. In silico the 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 vitro the 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. IC50 of K378 and K727 were comparable (0.9 and 1 µM, respectively) but orders of magnitude lower than comparators. R50 values revealed their inability to reactivate paraoxon inhibited AChE. It is concluded that the novel oximes K378 and K727 are unlikely to be clinically useful. The in silico and in vitro studies described allow avoidance of unnecessary in vivo animal work and contribute to the reduction of laboratory animal use.
- MeSH
- Acetylcholinesterase blood chemistry MeSH
- Antidotes chemistry metabolism pharmacology MeSH
- Cholinesterase Inhibitors chemistry metabolism toxicity MeSH
- GPI-Linked Proteins antagonists & inhibitors blood chemistry MeSH
- Protein Conformation MeSH
- Humans MeSH
- Organophosphate Poisoning blood drug therapy enzymology MeSH
- Oximes chemistry metabolism pharmacology MeSH
- Paraoxon analogs & derivatives chemistry metabolism toxicity MeSH
- Pralidoxime Compounds chemistry metabolism pharmacology MeSH
- Pyridinium Compounds chemistry metabolism pharmacology MeSH
- Cholinesterase Reactivators chemistry metabolism pharmacology MeSH
- Molecular Docking Simulation * MeSH
- Protein Binding MeSH
- Binding Sites MeSH
- Dose-Response Relationship, Drug MeSH
- Structure-Activity Relationship MeSH
- Check Tag
- Humans MeSH
- Male MeSH
- Publication type
- Journal Article MeSH
- Comparative Study MeSH
The efficacy of H oximes (HI-6, HLö-7), the oxime BI-6, and currently used oximes (pralidoxime, obidoxime, trimedoxime) to reactivate acetylcholinesterase inhibited by two nerve agents (tabun, VX agent) was tested in vitro. Both H oximes (HI-6, HLö-7) and the oxime BI-6 were found to be more efficacious reactivators of VX-inhibited acetylcholinesterase than pralidoxime and obidoxime. On the other hand, their potency to reactivate tabun-inhibited acetylcholinesterase was low and did not reach the reactivating efficacy of trimedoxime and obidoxime. Thus, none of these compounds can be considered to be a broad-spectrum reactivator of nerve agent-inhibited acetylcholinesterase in spite of high potency to reactivate acetylcholinesterase inhibited by some nerve agents. More than one oxime may be necessary for the antidotal treatment of nerve agent-exposed individuals.
- MeSH
- Acetylcholinesterase physiology MeSH
- Antidotes pharmacology MeSH
- Chemical Warfare Agents pharmacology MeSH
- Cholinesterase Inhibitors pharmacology MeSH
- Financing, Organized MeSH
- Rats MeSH
- Brain drug effects MeSH
- Obidoxime Chloride pharmacology MeSH
- Organophosphates pharmacology MeSH
- Organothiophosphorus Compounds pharmacology MeSH
- Oximes pharmacology MeSH
- Rats, Wistar MeSH
- Pralidoxime Compounds pharmacology MeSH
- Pyridinium Compounds pharmacology MeSH
- Pyridines pharmacology MeSH
- Cholinesterase Reactivators pharmacology MeSH
- Trimedoxime pharmacology MeSH
- Animals MeSH
- Check Tag
- Rats MeSH
- Male MeSH
- Animals MeSH
- MeSH
- Antidotes MeSH
- Cholinesterase Inhibitors MeSH
- Chlorpyrifos MeSH
- Research Support as Topic MeSH
- Organophosphorus Compounds adverse effects toxicity MeSH
- Oximes pharmacology therapeutic use MeSH
- Cholinesterase Reactivators administration & dosage pharmacology therapeutic use MeSH
- In Vitro Techniques MeSH
The potency of currently used oximes to reactivate sarin-inhibited acetylcholinesterase (AChE) in various parts of pig brain and whole pig brain was evaluated using in vitro methods. Significant differences in reactivation potency among all tested oximes were observed. At concentrations (10(-4) M) corresponding to recommended doses in vivo, the oxime HI-6 seems to be a more efficacious reactivator of sarin-inhibited AChE in whole pig brain as well as in cerebral hemispheres and cerebellum compared with the other oximes studied. Nevertheless, there are not any differences in the potency of oximes tested to reactivate sarin-inhibited AChE in medulla oblongata. Thus, the oxime HI-6 appears to be the most promising oxime among currently available oximes for the antidotal treatment of acute sarin poisoning, although it is not more efficacious than other currently used oximes in medulla oblongata, whose function is necessary for the vital functions of respiration and circulation.
- MeSH
- Acetylcholinesterase metabolism MeSH
- Cholinesterase Inhibitors pharmacology MeSH
- Kinetics MeSH
- Brain enzymology drug effects MeSH
- Obidoxime Chloride pharmacology MeSH
- Pralidoxime Compounds pharmacology MeSH
- Swine MeSH
- Pyridinium Compounds pharmacology MeSH
- Cholinesterase Reactivators pharmacology MeSH
- Sarin pharmacology MeSH
- Animals MeSH
- Check Tag
- Male MeSH
- Animals MeSH
- Publication type
- Comparative Study MeSH
In the present work, we performed a complementary quantum mechanical (QM) study to describe the mechanism by which deprotonated pralidoxime (2-PAM) could reactivate human (Homo sapiens sapiens) acetylcholinesterase (HssAChE) inhibited by the nerve agent VX. Such a reaction is proposed to occur in subsequent addition-elimination steps, starting with a nucleophile bimolecular substitution (SN2) mechanism through the formation of a trigonal bipyramidal transition state (TS). A near attack conformation (NAC), obtained in a former study using molecular mechanics (MM) calculations, was taken as a starting point for this project, where we described the possible formation of the TS. Together, this combined QM/MM study on AChE reactivation shows the feasibility of the reactivation occurring via attack of the deprotonated form of 2-PAM against the Ser203-VX adduct of HssAChE.
- MeSH
- Acetylcholinesterase chemistry drug effects MeSH
- Catalytic Domain MeSH
- Quantum Theory MeSH
- Humans MeSH
- Molecular Conformation MeSH
- Organothiophosphorus Compounds pharmacology MeSH
- Pralidoxime Compounds chemistry pharmacology MeSH
- Protons MeSH
- Serine chemistry MeSH
- Molecular Dynamics Simulation MeSH
- Check Tag
- Humans MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
