Organophosphorus poisoning caused by some pesticides and nerve agents is a life-threating condition that must be swiftly addressed to avoid casualties. Despite the availability of medical countermeasures, the clinically available compounds lack a broad spectrum, are not effective towards all organophosphorus toxins, and have poor pharmacokinetics properties to allow them crossing the blood-brain barrier, hampering cholinesterase reactivation at the central nervous system. In this work, we designed and synthesised novel isatin derivatives, linked to a pyridinium 4-oxime moiety by an alkyl chain with improved calculated properties, and tested their reactivation potency against paraoxon- and NEMP-inhibited acetylcholinesterase in comparison to the standard antidote pralidoxime. Our results showed that these compounds displayed comparable in vitro reactivation also pointed by the in silico studies, suggesting that they are promising compounds to tackle organophosphorus poisoning.

• Keywords
• Isatin, antidotes, cholinesterase reactivators, nerve agents, organophosphorus poisoning, pyridine oximes,
• MeSH
• Acetylcholinesterase drug effects   MeSH
• Isatin pharmacology   MeSH
• Computer Simulation MeSH
• Pyridines pharmacology   MeSH
• Cholinesterase Reactivators pharmacology   MeSH
• In Vitro Techniques MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Acetylcholinesterase MeSH
• Isatin MeSH
• pyridine MeSH Browser
• Pyridines MeSH
• Cholinesterase Reactivators 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.

• Keywords
• 2-PAM, QM/MM method, VX, acetylcholinesterase,
• 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
• Names of Substances
• Acetylcholinesterase MeSH
• Organothiophosphorus Compounds MeSH
• pralidoxime MeSH Browser
• Pralidoxime Compounds MeSH
• Protons MeSH
• Serine MeSH
• VX MeSH Browser

7-methoxytacrine-4-pyridinealdoxime (7-MEOTA-4-PA, named hybrid 5C) is a compound formerly synthesized and evaluated in vitro, together with 4-pyridine aldoxime (4-PA) and commercial reactivators of acetylcholinesterase (AChE). This compound was designed with the purpose of being a prophylactic reactivator, capable of interacting with different subdomains of the active site of AChE. To investigate these interactions, theoretical results from docking were first compared with experimental data of hybrid 5C, 4-PA, and two commercial oximes, on the reactivation of human AChE (HssAChE) inhibited by VX. Then, further docking studies, molecular dynamics simulations, and molecular mechanics Poisson-Boltzmann surface area calculations, were carried out to investigate reactivation performances, considering the near attack conformation (NAC) approach, prior to the nucleophilic substitution mechanism. Our results helped to elucidate the interactions of such molecules with the different subdomains of the active site of HssAChE. Additionally, NAC poses of each oxime were suggested for further theoretical studies on the reactivation reaction.

• Keywords
• 7-MEOTA-4-PA, Acetylcholinesterase, NAC, VX, molecular modeling,
• MeSH
• Acetylcholinesterase metabolism   MeSH
• Cholinesterase Inhibitors chemical synthesis   chemistry   pharmacology   MeSH
• Humans MeSH
• Models, Molecular MeSH
• Molecular Structure MeSH
• Obidoxime Chloride chemistry   pharmacology   MeSH
• Organothiophosphorus Compounds chemistry   pharmacology   MeSH
• Oximes chemistry   pharmacology   MeSH
• Pralidoxime Compounds chemistry   pharmacology   MeSH
• Pyridines chemistry   pharmacology   MeSH
• Dose-Response Relationship, Drug MeSH
• Structure-Activity Relationship MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• 7-methoxytacrine-4-pyridinealdoxime MeSH Browser
• Acetylcholinesterase MeSH
• Cholinesterase Inhibitors MeSH
• Obidoxime Chloride MeSH
• Organothiophosphorus Compounds MeSH
• Oximes MeSH
• pralidoxime MeSH Browser
• Pralidoxime Compounds MeSH
• pyridine-4-aldoxime MeSH Browser
• Pyridines MeSH
• VX MeSH Browser

Six quinoline-piperonal hybrids were synthesized and evaluated as potential drugs against Alzheimer's disease (AD). Theoretical analysis of the pharmacokinetic and toxicological properties of the compounds suggest that they present good oral bio-availability and are also capable of penetrating the blood-brain barrier, qualifying as leads for new drugs against AD. Evaluation of their inhibitory capacity against acetyl- and butyrilcholinesterases (AChE and BChE) through Ellmann's test showed that three compounds present promising results with one of them being capable of inhibiting both enzymes. Further docking studies of the six compounds synthesized helped to elucidate the main interactions that may be responsible for the inhibitory activities observed.

• Keywords
• Alzheimer’s disease, acetylcholinesterase, guanil-hydrazones, piperonal, quinolines,
• MeSH
• Alzheimer Disease drug therapy   metabolism   MeSH
• Benzaldehydes * chemistry   MeSH
• Benzodioxoles * chemistry   MeSH
• Quinolines * chemistry   MeSH
• Cholinesterase Inhibitors chemical synthesis   chemistry   pharmacokinetics   pharmacology   MeSH
• Kinetics MeSH
• Humans MeSH
• Magnetic Resonance Spectroscopy MeSH
• Molecular Structure MeSH
• Molecular Dynamics Simulation MeSH
• Molecular Docking Simulation MeSH
• Chemistry Techniques, Synthetic MeSH
• Structure-Activity Relationship MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Benzaldehydes * MeSH
• Benzodioxoles * MeSH
• Quinolines * MeSH
• Cholinesterase Inhibitors MeSH
• piperonal MeSH Browser
• quinoline MeSH Browser

Therapeutic application of newly developed oximes is limited due to their adverse effects on different tissues. Within this article, it has been investigated which morphological changes could be observed in Wistar rats after the treatment with increasing doses of selected acetyl cholinesterase reactivators - asoxime, obidoxime, K027, K048, and K075. Subsequently, heart, diaphragm and musculus popliteus were obtained for pathohistological and semiquantitative analysis 24 hrs and 7 days after im administration of a single dose of 0.1 LD50, 0.5 LD50, and 1.0 LD50 of each oxime. Different muscle damage score was based on an estimation scale from 0 (no damage) to 5 (strong damage). In rats treated with 0.1 LD50 of each oxime, muscle fibres did not show any change. The intensive degeneration was found in all muscles after treatment with 0.5 LD50 of asoxime and obidoxime, respectively. Acute toxic muscle injury was developed within 7 days following treatment with 0.5 LD50 and 1.0 LD50 of each oxime, with the highest values in K048 and K075 group (P < 0.001 vs. control and asoxime), respectively. The early muscle alterations observed in our study seem to contribute to the pathogenesis of the oxime-induced toxic muscle injury, which probably manifests as necrosis and/or inflammation.

• MeSH
• Diaphragm drug effects   injuries   MeSH
• Muscle, Skeletal drug effects   injuries   MeSH
• Rats MeSH
• Myositis chemically induced   MeSH
• Necrosis MeSH
• Oximes toxicity   MeSH
• Rats, Wistar MeSH
• Pyridinium Compounds toxicity   MeSH
• Heart drug effects   MeSH
• Muscles drug effects   pathology   MeSH
• Toxicity Tests, Acute MeSH
• Dose-Response Relationship, Drug MeSH
• Animals MeSH
• Check Tag
• Rats MeSH
• Male MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• 1-(4-hydroxyiminomethylpyridinium)-3-(carbamoylpyridinium) propane dibromide MeSH Browser
• 1-(4-hydroxyiminomethylpyridinium)-4-(4-carbamoylpyridinium)butane MeSH Browser
• K075 compound MeSH Browser
• Oximes MeSH
• Pyridinium Compounds MeSH

Nerve agents and oxon forms of organophosphorus pesticides act as strong irreversible inhibitors of two cholinesterases in the human body: acetylcholinesterase (AChE; EC 3.1.1.7) and butyrylcholinesterase (BChE; EC 3.1.1.8), and are therefore highly toxic compounds. For the recovery of inhibited AChE, antidotes from the group of pyridinium or bispyridinium aldoxime reactivators (pralidoxime, obidoxime, HI-6) are used in combination with anticholinergics and anticonvulsives. Therapeutic efficacy of reactivators (called “oximes”) depends on their chemical structure and also the type of organophosphorus inhibitor. Three novel oximes (K131, K142, K153) with an oxime group in position four of the pyridinium ring were designed and then tested for their potency to reactivate human (Homo sapiens sapiens) AChE (HssACHE) and BChE (HssBChE) inhibited by the pesticide paraoxon (diethyl 4-nitrophenyl phosphate). According to the obtained results, none of the prepared oximes were able to satisfactorily reactivate paraoxon-inhibited cholinesterases. On the contrary, extraordinary activity of obidoxime in the case of paraoxon-inhibited HssAChE reactivation was confirmed. Additional docking studies pointed to possible explanations for these results.

• Keywords
• acetylcholinesterase, antidote, butyrylcholinesterase, organophosphate, oxime, paraoxon,
• MeSH
• Acetylcholinesterase chemistry   MeSH
• Antidotes chemical synthesis   pharmacology   MeSH
• Butyrylcholinesterase chemistry   MeSH
• Cholinesterase Inhibitors chemistry   MeSH
• Enzyme Assays MeSH
• Erythrocytes drug effects   enzymology   MeSH
• Insecticides antagonists & inhibitors   chemistry   toxicity   MeSH
• Protein Interaction Domains and Motifs MeSH
• Humans MeSH
• Obidoxime Chloride chemistry   pharmacology   MeSH
• Oximes chemical synthesis   pharmacology   MeSH
• Paraoxon antagonists & inhibitors   chemistry   toxicity   MeSH
• Cholinesterase Reactivators chemical synthesis   pharmacology   MeSH
• Protein Structure, Secondary MeSH
• Molecular Docking Simulation MeSH
• Thermodynamics MeSH
• Protein Binding MeSH
• Structure-Activity Relationship MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Acetylcholinesterase MeSH
• Antidotes MeSH
• Butyrylcholinesterase MeSH
• Cholinesterase Inhibitors MeSH
• Insecticides MeSH
• Obidoxime Chloride MeSH
• Oximes MeSH
• Paraoxon MeSH
• Cholinesterase Reactivators MeSH

BACKGROUND: Based on in vitro and in vivo rat experiments, the newly developed acetylcholinesterase (AChE) reactivator, K203, appears to be much more effective in the treatment of tabun poisonings than currently fielded oximes. METHODS: To determine if this reactivating efficacy would extend to humans, studies were conducted in vitro using human brain homogenate as the source of AChE. The efficacy of K203 was compared with commercially available oximes; pralidoxime, obidoxime and asoxime (HI-6). RESULTS: Reactivation studies showed that K203 was the most effective reactivator with a second order kinetic constant (kr) of 2142 min- 1. M- 1, which was 51 times higher than that obtained for obidoxime (kr = 42 min- 1. M- 1). Both pralidoxime and asoxime (HI-6) failed to significantly reactivate tabun-inhibited human AChE. DISCUSSION: According to these results and previous studies, using K203, it appears that oxime K203 is the most effective reactivator of tabun-inhibited cholinesterase in several species including humans and should be considered as a possible medical countermeasure to tabun exposure.

• Keywords
• Antidotes, Chemical warfare agents, Oxime, Poisoning, Reactivator, Treatment,
• MeSH
• Acetylcholinesterase metabolism   MeSH
• Antidotes metabolism   MeSH
• Cholinesterase Inhibitors metabolism   MeSH
• Rats MeSH
• Humans MeSH
• Brain enzymology   MeSH
• Organophosphates metabolism   MeSH
• Oximes metabolism   MeSH
• Pyridinium Compounds metabolism   MeSH
• Cholinesterase Reactivators metabolism   MeSH
• Molecular Docking Simulation MeSH
• Animals MeSH
• Check Tag
• Rats MeSH
• Humans MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• 1-(4-carbamoylpyridinium)-4-(4-hydroxyiminomethylpyridinium)but-2-ene MeSH Browser
• Acetylcholinesterase MeSH
• Antidotes MeSH
• Cholinesterase Inhibitors MeSH
• Organophosphates MeSH
• Oximes MeSH
• Pyridinium Compounds MeSH
• Cholinesterase Reactivators MeSH
• tabun MeSH Browser