A-series agent A-234 belongs to a new generation of nerve agents. The poisoning of a former Russian spy Sergei Skripal and his daughter in Salisbury, England, in March 2018 led to the inclusion of A-234 and other A-series agents into the Chemical Weapons Convention. Even though five years have already passed, there is still very little information on its chemical properties, biological activities, and treatment options with established antidotes. In this article, we first assessed A-234 stability in neutral pH for subsequent experiments. Then, we determined its inhibitory potential towards human recombinant acetylcholinesterase (HssAChE; EC 3.1.1.7) and butyrylcholinesterase (HssBChE; EC 3.1.1.8), the ability of HI-6, obidoxime, pralidoxime, methoxime, and trimedoxime to reactivate inhibited cholinesterases (ChEs), its toxicity in rats and therapeutic effects of different antidotal approaches. Finally, we utilized molecular dynamics to explain our findings. The results of spontaneous A-234 hydrolysis showed a slow process with a reaction rate displaying a triphasic course during the first 72 h (the residual concentration 86.2%). A-234 was found to be a potent inhibitor of both human ChEs (HssAChE IC50 = 0.101 ± 0.003 μM and HssBChE IC50 = 0.036 ± 0.002 μM), whereas the five marketed oximes have negligible reactivation ability toward A-234-inhibited HssAChE and HssBChE. The acute toxicity of A-234 is comparable to that of VX and in the context of therapy, atropine and diazepam effectively mitigate A-234 lethality. Even though oxime administration may induce minor improvements, selected oximes (HI-6 and methoxime) do not reactivate ChEs in vivo. Molecular dynamics implies that all marketed oximes are weak nucleophiles, which may explain the failure to reactivate the A-234 phosphorus-serine oxygen bond characterized by low partial charge, in particular, HI-6 and trimedoxime oxime oxygen may not be able to effectively approach the A-234 phosphorus, while pralidoxime displayed low interaction energy. This study is the first to provide essential experimental preclinical data on the A-234 compound.

• MeSH
• acetylcholinesterasa MeSH
• antidota farmakologie   MeSH
• butyrylcholinesterasa MeSH
• cholinesterasové inhibitory toxicita   MeSH
• fosfor MeSH
• krysa rodu rattus MeSH
• kyslík MeSH
• lidé MeSH
• oximy farmakologie   MeSH
• pralidoximové sloučeniny * MeSH
• pyridinové sloučeniny farmakologie   MeSH
• reaktivátory cholinesterázy * farmakologie   MeSH
• taurin analogy a deriváty   MeSH
• trimedoxim farmakologie   MeSH
• zvířata MeSH
• Check Tag
• krysa rodu rattus MeSH
• lidé MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH

The nerve agents of the A-series are relatively recent chemical weapons with no antidote available yet. Once inside the human body, those chemicals act similarly to the classic nerve agents, by binding to the catalytic residue Serine 203 (Ser203) of human acetylcholinesterase (HssAChE) and thus preventing the proper function of this enzyme. However, there is no experimental evidence yet if the current antidotes for intoxication by nerve agents are also capable of restoring AChE inhibited by the nerve agents of the A-series. In order to launch some light on this issue, we used computational techniques (molecular docking, molecular dynamics and MM-PBSA interaction energy calculations) to assess the performances of the four currently available commercial oximes (2-PAM, HI-6, obidoxime and trimedoxime) when in contact with HssAChE inhibited by the agent A-242. Based on the near-attack conformation (NAC) criterion, our results suggest that the commercial oximes would have limited efficacy to reactivate the enzyme since they are not able to properly approach the adduct Ser203-A-242. Among those oximes, trimedoxime seems to be the most promising, since it showed lower values of energy in the MM-PBSA calculations, a higher stability inside the catalytic anionic center (CAS) of HssAChE, and was able to adopt a position closer to the NAC that could enable the reactivation mechanism.

• MeSH
• acetylcholinesterasa metabolismus   MeSH
• antidota farmakologie   MeSH
• cholinesterasové inhibitory chemie   toxicita   MeSH
• lidé MeSH
• nervová bojová látka * toxicita   MeSH
• organofosfáty MeSH
• oximy chemie   farmakologie   MeSH
• pyridinové sloučeniny farmakologie   MeSH
• reaktivátory cholinesterázy * farmakologie   MeSH
• simulace molekulového dockingu MeSH
• trimedoxim farmakologie   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH

Organophosphorus (OP) compounds are used as both chemical weapons and pesticides. However, these agents are very dangerous and toxic to humans, animals, and the environment. Thus, investigations with reactivators have been deeply developed in order to design new antidotes with better efficiency, as well as a greater spectrum of action in the acetylcholinesterase (AChE) reactivation process. With that in mind, in this work, we investigated the behavior of trimedoxime toward the Mus musculus acetylcholinesterase (MmAChE) inhibited by a range of nerve agents, such as chemical weapons. From experimental assays, reactivation percentages were obtained for the reactivation of different AChE-OP complexes. On the other hand, theoretical calculations were performed to assess the differences in interaction modes and the reactivity of trimedoxime within the AChE active site. Comparing theoretical and experimental data, it is possible to notice that the oxime, in most cases, showed better reactivation percentages at higher concentrations, with the best result for the reactivation of the AChE-VX adduct. From this work, it was revealed that the mechanistic process contributes most to the oxime efficiency than the interaction in the site. In this way, this study is important to better understand the reactivation process through trimedoxime, contributing to the proposal of novel antidotes.

• MeSH
• acetylcholinesterasa metabolismus   MeSH
• antidota farmakologie   MeSH
• cholinesterasové inhibitory metabolismus   farmakologie   MeSH
• krysa rodu rattus MeSH
• lidé MeSH
• myši MeSH
• nervová bojová látka chemie   MeSH
• organofosforové sloučeniny chemie   MeSH
• oximy chemie   MeSH
• reaktivátory cholinesterázy chemie   farmakologie   MeSH
• trimedoxim farmakologie   terapeutické užití   MeSH
• výpočetní biologie metody   MeSH
• zvířata MeSH
• Check Tag
• krysa rodu rattus MeSH
• lidé MeSH
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH

Beside the key inhibition of acetylcholinesterase (AChE), involvement of oxidative stress in organophosphate (OP)-induced toxicity has been supported by experimental and human studies. On the other hand, according to our best knowledge, possible antioxidant properties of oximes, the only causal antidotes to OP-inhibited AChE, have been examined only by a few studies. Thus, we have determined the effect of four conventional (obidoxime, trimedoxime, pralidoxime, asoxime) and two promising experimental oximes (K027, K203) on dichlorvos (DDVP)-induced oxidative changes in vivo. Wistar rats (5/group) were treated with oxime (5% LD50 i.m) immediately after DDVP challenge (75% LD50 s.c). Oxidative stress biomarkers were determined in plasma and brain 60 min after the treatment: prooxidative-superoxide anion (O2·-) and total oxidative status (TOS); antioxidative-superoxide dismutase (SOD), total thiol (SH) groups, total antioxidant status (TAS) and paraoxonase (PON1); tissue oxidative stress burden-prooxidative-antioxidative balance (PAB) and oxidative stress index (OSI); oxidative tissue damage-malondialdehyde (MDA) and advanced oxidation protein products (AOPP). All oximes were able to attenuate DDVP-induced oxidative stress in rat plasma and brain. Changes of determined parameters in brain were not as prominent as it was seen in plasma. Based on OSI, better abilities of oxime K027, K203 and obidoxime to maintain DDVP-induced oxidative stress in rat brain were shown as compared to trimedoxime, pralidoxime and asoxime. Oximes can influence the complex in vivo redox processes that might contribute to their overall therapeutic efficacy. Further research is needed to understand the underlying molecular mechanisms involved in this phenomenon.

• MeSH
• aryldialkylfosfatasa krev   MeSH
• biologické markery krev   MeSH
• cholinesterasové inhibitory farmakologie   MeSH
• dichlorvos toxicita   MeSH
• krysa rodu rattus MeSH
• malondialdehyd krev   MeSH
• mozek účinky léků   MeSH
• obidoxim chlorid farmakologie   MeSH
• otrava organofosfáty farmakoterapie   MeSH
• oxidační stres účinky léků   MeSH
• oximy farmakologie   MeSH
• pralidoximové sloučeniny MeSH
• pyridinové sloučeniny farmakologie   MeSH
• superoxiddismutasa krev   MeSH
• trimedoxim farmakologie   MeSH
• zvířata MeSH
• Check Tag
• krysa rodu rattus MeSH
• mužské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH

The reactivating and therapeutic efficacy of two newly developed oximes (K305, K307) was compared with the oxime K203 and trimedoxime using in vivo methods The study determining percentage of reactivation of tabun-inhibited acetylcholinesterase in the peripheral as well as central nervous system (diaphragm, brain) in tabun-poisoned rats showed that the reactivating efficacy of both newly developed oximes is lower compared to the reactivating efficacy of the oxime K203 and trimedoxime. The therapeutic efficacy of all oximes studied roughly corresponds to their reactivating efficacy. While the ability of the oxime K305 to reduce acute toxicity of tabun in mice is approaching to the therapeutic efficacy of trimedoxime, the ability of another novel bispyridinium oxime K307 to reduce acute toxicity of tabun is significantly lower compared to trimedoxime and the oxime K203. Thus, the reactivating and therapeutic efficacy of both examined newly developed oximes does not prevail the effectiveness of the oxime K203 and trimedoxime and, therefore, they are not suitable for their replacement of commonly used oximes for the treatment of acute tabun poisoning.

• MeSH
• acetylcholinesterasa účinky léků   MeSH
• antidota aplikace a dávkování   farmakologie   toxicita   MeSH
• atropin aplikace a dávkování   farmakologie   toxicita   MeSH
• bránice enzymologie   MeSH
• modely u zvířat MeSH
• mozek enzymologie   účinky léků   MeSH
• mutantní kmeny myší MeSH
• nervová bojová látka farmakologie   chemie   toxicita   MeSH
• organofosfáty farmakologie   toxicita   MeSH
• oximy * farmakologie   chemie   klasifikace   MeSH
• potkani Wistar MeSH
• reaktivátory cholinesterázy aplikace a dávkování   farmakologie   toxicita   MeSH
• trimedoxim farmakologie   chemie   klasifikace   MeSH
• zvířata MeSH
• Check Tag
• mužské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• práce podpořená grantem MeSH

AIM: The ability of two newly developed oximes (K727, K733) to reduce tabun-induced acute neurotoxic signs and symptoms was evaluated and compared with currently available trimedoxime in rats. METHODS: The neuroprotective effects of the oximes studied combined with atropine on Wistar rats poisoned with tabun at a lethal dose (380 µg/kg i.m.; 90% of LD50 value) were evaluated. Tabun-induced neurotoxicity was monitored by the functional observational battery consisting of 38 measurements of sensory, motor and autonomic nervous functions at 2 hours following tabun challenge. RESULTS: All tested oximes combined with atropine enable tabun-poisoned rats to survive till the end of experiment. Both newly developed oximes (K727, K733) combined with atropine were able to decrease tabun-induced neurotoxicity in the case of lethal poisoning although they did not eliminate all tabun-induced acute neurotoxic signs and symptoms. CONCLUSION: The ability of both novel bispyridinium oximes to decrease tabun-induced acute neurotoxicity was slightly lower than that of trimedoxime. Therefore, the newly developed oximes are not suitable for the replacement of commonly used oximes such as trimedoxime in the treatment of acute tabun poisonings.

• MeSH
• antagonisté muskarinových receptorů farmakologie   MeSH
• atropin farmakologie   MeSH
• cholinesterasové inhibitory toxicita   MeSH
• krysa rodu rattus MeSH
• nervový systém účinky léků   MeSH
• neuroprotektivní látky farmakologie   MeSH
• neurotoxické syndromy farmakoterapie   etiologie   MeSH
• organofosfáty toxicita   MeSH
• otrava organofosfáty farmakoterapie   etiologie   MeSH
• oximy farmakologie   MeSH
• potkani Wistar MeSH
• pyridinové sloučeniny farmakologie   MeSH
• reaktivátory cholinesterázy farmakologie   MeSH
• trimedoxim farmakologie   MeSH
• zvířata MeSH
• Check Tag
• krysa rodu rattus MeSH
• mužské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

The ability of two newly developed bispyridinium oximes (K456, K458) to reduce tabun-induced acute neurotoxic signs and symptoms was compared with oxime K203 and trimedoxime using the functional observational battery. The neuroprotective effects of the oximes studied combined with atropine on rats poisoned with tabun at a sublethal dose (200 μg/kg i.m.; 85% of LD50 value) were evaluated. Tabun-induced neurotoxicity was monitored by the functional observational battery and automatic measurement of motor activity at 2 hr after tabun challenge. The results indicate that all tested oximes combined with atropine enable tabun-poisoned rats to survive till the end of experiment. Both newly developed oximes (K456, K458) combined with atropine were able to decrease tabun-induced neurotoxicity in the case of sublethal poisonings although they did not eliminate all tabun-induced acute neurotoxic signs and symptoms. Their ability to decrease tabun-induced acute neurotoxicity was slightly higher than that of trimedoxime and oxime K203, but the difference in neuroprotective efficacy among all oximes studied is not large enough to make a decision about replacement of commonly used oximes (especially trimedoxime and obidoxime) in the treatment of acute tabun poisonings.

• MeSH
• atropin farmakologie   MeSH
• chemické bojové látky toxicita   MeSH
• krysa rodu rattus MeSH
• neuroprotektivní látky farmakologie   MeSH
• neurotoxické syndromy prevence a kontrola   MeSH
• organofosfáty toxicita   MeSH
• oximy farmakologie   MeSH
• potkani Wistar MeSH
• pyridinové sloučeniny farmakologie   MeSH
• trimedoxim farmakologie   MeSH
• zvířata MeSH
• Check Tag
• krysa rodu rattus MeSH
• mužské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• srovnávací studie MeSH

Administration of acetylcholinesterase (AChE) reactivators (oximes) is usually used in order to counteract the poisoning effects of nerve agents. The possibility was suggested that oximes may show some therapeutic and/or adverse effects through their action in central nervous system. There are no sufficient data about interaction of oximes with monoaminergic neurotransmitter's systems in the brain. Oxime-type AChE reactivators pralidoxime, obidoxime, trimedoxime, methoxime and HI-6 were tested for their potential to affect the activity of monoamine oxidase of type A (MAO-A) and type B (MAO-B) in crude mitochondrial fraction of pig brains. The compounds were found to inhibit fully MAO-A with half maximal inhibitory concentration (IC(50)) of 0.375 mmol/l (pralidoxime), 1.53 mmol/l (HI-6), 2.31 mmol/l (methoxime), 2.42 mmol/l (obidoxime) and 4.98 mmol/l (trimedoxime). Activity of MAO-B was fully inhibited by HI-6 and pralidoxime only with IC(50) 4.81 mmol/l and 11.01 mmol/l, respectively. Methoxime, obidoxime and trimedoxime displayed non-monotonic concentration dependent effect on MAO-B activity. Because oximes concentrations effective for MAO inhibition could not be achieved in vivo at the cerebral level, we suppose that oximes investigated do not interfere with brain MAO at therapeutically relevant concentrations.

• MeSH
• inhibitory MAO farmakologie   MeSH
• monoaminoxidasa metabolismus   MeSH
• mozek enzymologie   MeSH
• obidoxim chlorid farmakologie   MeSH
• oximy farmakologie   MeSH
• pralidoximové sloučeniny farmakologie   MeSH
• prasata MeSH
• pyridinové sloučeniny farmakologie   MeSH
• reaktivátory cholinesterázy farmakologie   MeSH
• trimedoxim farmakologie   MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

The penetration of acetylcholinesterase reactivators (oximes) into the central nervous system is typically restricted by the blood-brain barrier. Although oximes are highly hydrophilic compounds, some contradictory results confirming permeation into the brain exist. The aim of this study is to verify the penetration of oximes through the blood-brain barrier and to detect their levels achieved in different brain regions 60 min after the administration. It was confirmed that oximes are able to penetrate into the brain after injection of therapeutic doses corresponding with 5% of LD(50). The level in whole brain was 0.58% for trimedoxime and 0.85% for the experimental drug oxime K074 as the percentage of their plasma concentration. The highest concentration was found in frontal cortex (trimedoxime 2.27%; oxime K074 0.95%) and lowest in basal ganglia (trimedoxime 0.86%; oxime K074 0.42%). Entry of oximes into the brain is minimal, but some low reactivation effect should be expected. The reactivation potency of oximes might be higher or lower, depending on the real oxime concentration in a given area.

• MeSH
• butany aplikace a dávkování   krev   izolace a purifikace   farmakokinetika   farmakologie   MeSH
• injekce intramuskulární MeSH
• kalibrace MeSH
• krysa rodu rattus MeSH
• limita detekce MeSH
• molekulární struktura MeSH
• mozek metabolismus   MeSH
• oximy aplikace a dávkování   krev   izolace a purifikace   farmakokinetika   farmakologie   MeSH
• potkani Wistar MeSH
• pyridinové sloučeniny aplikace a dávkování   krev   izolace a purifikace   farmakokinetika   farmakologie   MeSH
• reaktivátory cholinesterázy aplikace a dávkování   krev   izolace a purifikace   farmakokinetika   farmakologie   MeSH
• referenční standardy MeSH
• regresní analýza MeSH
• reprodukovatelnost výsledků MeSH
• tkáňová distribuce MeSH
• trimedoxim aplikace a dávkování   krev   izolace a purifikace   farmakokinetika   farmakologie   MeSH
• vysokoúčinná kapalinová chromatografie přístrojové vybavení   MeSH
• zvířata MeSH
• Check Tag
• krysa rodu rattus MeSH
• mužské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

The potency of bispyridinium acetylcholinesterase reactivator KR-22934 in reactivating tabun-inhibited acetylcholinesterase and reducing tabun-induced lethal toxic effects was compared with the oxime K203 and commonly used oximes. Studies determining percentage of reactivation of tabun-inhibited blood and tissue acetylcholinesterase in rats showed that the reactivating efficacy of KR-22934 was slightly higher than the reactivating efficacy of K203 and roughly corresponded to the reactivating efficacy of obidoxime and trimedoxime in blood and diaphragm. On the other hand, the oxime KR-22934 was not able to reactivate tabun-inhibited acetylcholinesterase in the brain. The therapeutic efficacy of all oximes studied approximately corresponded to their reactivating efficacy. Based on the results, one can conclude that the oxime KR-22934 is not suitable for the replacement of commonly used oximes for the antidotal treatment of tabun poisoning in spite of its potency to reactivate tabun-inhibited acetylcholinesterase in the peripheral compartment (blood, diaphragm).

• MeSH
• acetylcholinesterasa metabolismus   MeSH
• antidota farmakologie   terapeutické užití   MeSH
• cholinesterasové inhibitory toxicita   MeSH
• krysa rodu rattus MeSH
• myši MeSH
• obidoxim chlorid farmakologie   terapeutické užití   MeSH
• organofosfáty toxicita   MeSH
• otrava farmakoterapie   MeSH
• oximy farmakologie   terapeutické užití   MeSH
• potkani Wistar MeSH
• pyridinové sloučeniny farmakologie   terapeutické užití   MeSH
• reaktivátory cholinesterázy farmakologie   terapeutické užití   MeSH
• trimedoxim farmakologie   terapeutické užití   MeSH
• zvířata MeSH
• Check Tag
• krysa rodu rattus MeSH
• mužské pohlaví MeSH
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• srovnávací studie MeSH