Organophosphorus compounds are highly toxic irreversible inhibitors of cholinesterases, causing the disruption of cholinergic functions. Treatment of poisoning includes causal antidotes (oximes) used as reactivators of inhibited cholinesterases, such as pralidoxime. In this work, new halogenated oxime reactivators derived from pralidoxime were developed. The oximes were designed with a halogen substituent that lowers the pK a and enhances oximate formation. Their synthesis, stability, physicochemical properties, inhibition of native cholinesterases, and in vitro reactivation of organophosphate-inhibited cholinesterases were investigated. A series of C4 and C6 halogenated oximes showed instability and their degradation products were identified, while C3 and C5 oximes exhibited sufficient stability for the evaluation. C3 oximes displayed overall low inhibition of cholinesterases and high reactivation ability of organophosphate-inhibited cholinesterases compared to pralidoxime, indicating the significant impact of halogen substitution on reactivation ability.

• Publication type
• Journal Article MeSH

Oxime reactivators of acetylcholinesterase (AChE) are used as causal antidotes for intended and unintended poisoning by organophosphate nerve agents and pesticides. Despite all efforts to develop new AChE reactivators, none of these drug candidates replaced conventional clinically used oximes. In addition to the therapeutic efficacy, determining the safety profile is crucial in preclinical drug evaluation. The exact mechanism of oxime toxicity and the structure-toxicity relationship are subjects of ongoing research, with oxidative stress proposed as a possible mechanism. In the present study, we investigated four promising bispyridinium oxime AChE reactivators, K048, K074, K075, and K203, and their ability to induce oxidative stress in vitro. Cultured human hepatoma cells were exposed to oximes at concentrations corresponding to their IC50 values determined by the MTT assay after 24 h. Their potency to generate reactive oxygen species, interfere with the thiol antioxidant system, and induce lipid peroxidation was evaluated at 1, 4, and 24 h of exposure. Reactivators without a double bond in the four-carbon linker, K048 and K074, showed a greater potential to induce oxidative stress compared with K075 and K203, which contain a double bond. Unlike oximes with a three-carbon-long linker, the number of aldoxime groups attached to the pyridinium moieties does not determine the oxidative stress induction for K048, K074, K075, and K203 oximes. In conclusion, our results emphasize that the structure of oximes plays a critical role in inducing oxidative stress, and this relationship does not correlate with their cytotoxicity expressed as the IC50 value. However, it is important to note that oxidative stress cannot be disregarded as a potential contributor to the side effects associated with oximes.

• MeSH
• Acetylcholinesterase metabolism   MeSH
• Antidotes pharmacology   MeSH
• Hep G2 Cells MeSH
• Cholinesterase Inhibitors toxicity   MeSH
• Humans MeSH
• Organophosphates toxicity   MeSH
• Oxidative Stress MeSH
• Oximes pharmacology   chemistry   MeSH
• Pyridinium Compounds pharmacology   chemistry   MeSH
• Cholinesterase Reactivators * pharmacology   chemistry   MeSH
• Carbon MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Acetylcholinesterase MeSH
• Antidotes MeSH
• Cholinesterase Inhibitors MeSH
• Organophosphates MeSH
• Oximes MeSH
• Pyridinium Compounds MeSH
• Cholinesterase Reactivators * MeSH
• Carbon MeSH

The series of symmetrical and unsymmetrical isoquinolinium-5-carbaldoximes was designed and prepared for cholinesterase reactivation purposes. The novel compounds were evaluated for intrinsic acetylcholinesterase (AChE) or butyrylcholinesterase (BChE) inhibition, when the majority of novel compounds resulted with high inhibition of both enzymes and only weak inhibitors were selected for reactivation experiments on human AChE or BChE inhibited by sarin, VX, or paraoxon. The AChE reactivation for all used organophosphates was found negligible if compared to the reactivation ability of obidoxime. Importantly, two compounds were found to reactivate BChE inhibited by sarin or VX better to obidoxime at human attainable concentration. One compound resulted as better reactivator of NEMP (VX surrogate)-inhibited BChE than obidoxime. The in vitro results were further rationalized by molecular docking studies showing future directions on designing potent BChE reactivators.

• Keywords
• Acetylcholinesterase, butyrylcholinesterase, organophosphate, oxime, reactivator,
• MeSH
• Acetylcholinesterase drug effects   MeSH
• Butyrylcholinesterase drug effects   MeSH
• Cholinesterase Inhibitors pharmacology   MeSH
• Isoquinolines chemical synthesis   chemistry   pharmacology   MeSH
• Humans MeSH
• Cholinesterase Reactivators pharmacology   MeSH
• Molecular Docking Simulation MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Acetylcholinesterase MeSH
• Butyrylcholinesterase MeSH
• Cholinesterase Inhibitors MeSH
• Isoquinolines MeSH
• Cholinesterase Reactivators MeSH

The present work aimed to compare the small, neutral and monoaromatic oxime, isatin-3-oxime (isatin-O), to the commercial ones, pralidoxime (2-PAM) and obidoxime, in a search for a new potential reactivator for acetylcholinesterase (AChE) inhibited by the pesticide paraoxon (AChE/POX) as well as a novel potential scaffold for further synthetic modifications. The multicriteria decision methods (MCDM) allowed the identification of the best docking poses of those molecules inside AChE/POX for further molecular dynamic (MD) studies, while Ellman's modified method enabled in vitro inhibition and reactivation assays. In corroboration with the theoretical studies, our experimental results showed that isatin-O have a reactivation potential capable of overcoming 2-PAM at the initial moments of the assay. Despite not achieving better results than obidoxime, this molecule is promising for being an active neutral oxime with capacity of crossing the blood⁻brain barrier (BBB), to reactivate AChE/POX inside the central and peripheral nervous systems. Moreover, the fact that isatin-O can also act as anticonvulsant makes this molecule a possible multipotent reactivator. Besides, the MCDM method showed to be an accurate method for the selection of the best docking poses generated in the docking studies.

• Keywords
• Ellman’s method, TOPSIS-AHP, acetylcholinesterase, molecular modeling, multicriteria decision making, neutral oxime,
• MeSH
• Cholinesterase Inhibitors pharmacology   MeSH
• Erythrocytes drug effects   enzymology   MeSH
• Models, Molecular * MeSH
• Molecular Structure MeSH
• Oximes chemistry   pharmacology   MeSH
• Paraoxon chemistry   pharmacology   MeSH
• Cholinesterase Reactivators chemistry   pharmacology   MeSH
• Molecular Dynamics Simulation MeSH
• Molecular Docking Simulation MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Cholinesterase Inhibitors MeSH
• Oximes MeSH
• Paraoxon MeSH
• Cholinesterase Reactivators MeSH

The acetylcholinesterase (AChE) reactivators (e.g., obidoxime, asoxime) became an essential part of organophosphorus (OP) poisoning treatment, together with atropine and diazepam. They are referred to as a causal treatment of OP poisoning, because they are able to split the OP moiety from AChE active site and thus renew its function. In this approach, fifteen novel AChE reactivators were determined. Their molecular design originated from former K-oxime compounds K048 and K074 with remaining oxime part of the molecule and modified part with heteroarenium moiety. The novel compounds were prepared, evaluated in vitro on human AChE (HssAChE) inhibited by tabun, paraoxon, methylparaoxon or DFP and compared to commercial HssAChE reactivators (pralidoxime, methoxime, trimedoxime, obidoxime, asoxime) or previously prepared compounds (K048, K074, K075, K203). Some of presented oxime reactivators showed promising ability to reactivate HssAChE comparable or higher than the used standards. The molecular modelling study was performed with one compound that presented the ability to reactivate GA-inhibited HssAChE. The SAR features concerning the heteroarenium part of the reactivator's molecule are described.

• Keywords
• acetylcholinesterase, in vitro, molecular docking, organophosphate, oxime, reactivation,
• MeSH
• Acetylcholinesterase metabolism   MeSH
• Cholinesterase Inhibitors toxicity   MeSH
• Spectrometry, Mass, Electrospray Ionization MeSH
• Inhibitory Concentration 50 MeSH
• Humans MeSH
• Carbon-13 Magnetic Resonance Spectroscopy MeSH
• Organophosphorus Compounds toxicity   MeSH
• Proton Magnetic Resonance Spectroscopy MeSH
• Cholinesterase Reactivators chemical synthesis   chemistry   pharmacology   MeSH
• Recombinant Proteins metabolism   MeSH
• Molecular Docking Simulation * MeSH
• In Vitro Techniques MeSH
• Structure-Activity Relationship MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Acetylcholinesterase MeSH
• Cholinesterase Inhibitors MeSH
• Organophosphorus Compounds MeSH
• Cholinesterase Reactivators MeSH
• Recombinant Proteins MeSH

BACKGROUND: Pharmaceuticals with targets in the cholinergic transmission have been used for decades and are still fundamental treatments in many diseases and conditions today. Both the transmission and the effects of the somatomotoric and the parasympathetic nervous systems may be targeted by such treatments. Irrespective of the knowledge that the effects of neuronal signalling in the nervous systems may include a number of different receptor subtypes of both the nicotinic and the muscarinic receptors, this complexity is generally overlooked when assessing the mechanisms of action of pharmaceuticals. METHODS: We have search of bibliographic databases for peer-reviewed research literature focused on the cholinergic system. Also, we have taken advantage of our expertise in this field to deduce the conclusions of this study. RESULTS: Presently, the life cycle of acetylcholine, muscarinic receptors and their effects are reviewed in the major organ systems of the body. Neuronal and non-neuronal sources of acetylcholine are elucidated. Examples of pharmaceuticals, in particular cholinesterase inhibitors, affecting these systems are discussed. The review focuses on salivary glands, the respiratory tract and the lower urinary tract, since the complexity of the interplay of different muscarinic receptor subtypes is of significance for physiological, pharmacological and toxicological effects in these organs. CONCLUSION: Most pharmaceuticals targeting muscarinic receptors are employed at such large doses that no selectivity can be expected. However, some differences in the adverse effect profile of muscarinic antagonists may still be explained by the variation of expression of muscarinic receptor subtypes in different organs. However, a complex pattern of interactions between muscarinic receptor subtypes occurs and needs to be considered when searching for selective pharmaceuticals. In the development of new entities for the treatment of for instance pesticide intoxication, the muscarinic receptor selectivity needs to be considered. Reactivators generally have a muscarinic M2 receptor acting profile. Such a blockade may engrave the situation since it may enlarge the effect of the muscarinic M3 receptor effect. This may explain why respiratory arrest is the major cause for deaths by esterase blocking.

• Keywords
• Acetylcholine, acetylcholinesterase, muscarinic receptor subtypes, pharmacotherapy,
• MeSH
• Cholinesterase Inhibitors pharmacology   MeSH
• Receptor Cross-Talk drug effects   MeSH
• Humans MeSH
• Receptors, Muscarinic drug effects   MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Review MeSH
• Names of Substances
• Cholinesterase Inhibitors MeSH
• Receptors, Muscarinic MeSH

Chemical weapons are a major worldwide problem, since they are inexpensive, easy to produce on a large scale and difficult to detect and control. Among the chemical warfare agents, we can highlight the organophosphorus compounds (OP), which contain the phosphorus element and that have a large number of applications. They affect the central nervous system and can lead to death, so there are a lot of works in order to design new effective antidotes for the intoxication caused by them. The standard treatment includes the use of an anticholinergic combined to a central nervous system depressor and an oxime. Oximes are compounds that reactivate Acetylcholinesterase (AChE), a regulatory enzyme responsible for the transmission of nerve impulses, which is one of the molecular targets most vulnerable to neurotoxic agents. Increasingly, enzymatic treatment becomes a promising alternative; therefore, other enzymes have been studied for the OP degradation function, such as phosphotriesterase (PTE) from bacteria, human serum paraoxonase 1 (HssPON1) and diisopropyl fluorophosphatase (DFPase) that showed significant performances in OP detoxification. The understanding of mechanisms by which enzymes act is of extreme importance for the projection of antidotes for warfare agents, and computational chemistry comes to aid and reduce the time and costs of the process. Molecular Docking, Molecular Dynamics and QM/MM (quantum-mechanics/molecular-mechanics) are techniques used to investigate the molecular interactions between ligands and proteins.

• Keywords
• computational methods, enzymatic biodegradation, oximes, warfare nerve agents,
• Publication type
• Journal Article MeSH

The complexes of Fe(II), Mn(II) and Ni(II) with a combination of a Schiff base, nitrogen-donor ligand or macrocyclic ligand and trithiocyanuric acid (ttcH3) were prepared and characterized by elemental analysis and spectroscopies. Crystal and molecular structures of the iron complex of composition [Fe(L1)](ttcH2)(ClO4)·EtOH·H2O (1), where L1 is Schiff base derived from tris(2-aminoethyl)amine and 2-pyridinecarboxaldehyde, were solved. It was found that the Schiff base is coordinated to the central iron atom by six nitrogens forming deformed octahedral arrangement, whereas trithiocyanurate(1-) anion, perchlorate and solvent molecules are not coordinated. The X-ray structure of the Schiff base sodium salt is also presented and compared with the iron complex. The anticholinesterase activity of the complexes was also studied.

• MeSH
• Cholinesterase Inhibitors chemical synthesis   chemistry   pharmacology   MeSH
• Cholinesterases metabolism   MeSH
• Enzyme Assays MeSH
• Ethylenediamines chemistry   MeSH
• Coordination Complexes chemical synthesis   chemistry   pharmacology   MeSH
• Complex Mixtures chemistry   MeSH
• Rats MeSH
• Crystallography, X-Ray MeSH
• Ligands MeSH
• Manganese chemistry   MeSH
• Brain drug effects   enzymology   MeSH
• Nickel chemistry   MeSH
• Pyridines chemistry   MeSH
• Schiff Bases chemistry   MeSH
• Triazines chemistry   MeSH
• Iron chemistry   MeSH
• Animals MeSH
• Check Tag
• Rats MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Cholinesterase Inhibitors MeSH
• Cholinesterases MeSH
• Ethylenediamines MeSH
• Coordination Complexes MeSH
• Complex Mixtures MeSH
• Ligands MeSH
• Manganese MeSH
• Nickel MeSH
• picolinaldehyde MeSH Browser
• Pyridines MeSH
• Schiff Bases MeSH
• Triazines MeSH
• tris(2-aminoethyl)amine MeSH Browser
• trithiocyanuric acid MeSH Browser
• Iron MeSH

Acetylcholinesterase (AChE) reactivators were developed for the treatment of organophosphate intoxication. Standard care involves the use of anticonvulsants (e.g., diazepam), parasympatolytics (e.g., atropine) and oximes that restore AChE activity. However, oximes also bind to the active site of AChE, simultaneously acting as reversible inhibitors. The goal of the present study is to determine how oxime structure influences the inhibition of human recombinant AChE (hrAChE). Therefore, 24 structurally different oximes were tested and the results compared to the previous eel AChE (EeAChE) experiments. Structural factors that were tested included the number of pyridinium rings, the length and structural features of the linker, and the number and position of the oxime group on the pyridinium ring.

• MeSH
• Acetylcholinesterase chemistry   MeSH
• Cholinesterase Inhibitors chemistry   MeSH
• Catalytic Domain MeSH
• Humans MeSH
• Oximes chemistry   MeSH
• Molecular Docking Simulation MeSH
• Protein Binding MeSH
• Hydrogen Bonding MeSH
• Structure-Activity Relationship MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Research Support, U.S. Gov't, Non-P.H.S. MeSH
• Names of Substances
• Acetylcholinesterase MeSH
• Cholinesterase Inhibitors MeSH
• Oximes MeSH