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Kamil Kuca - One of the best experts on this subject based on the ideXlab platform.
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Experimental hydrophilic reactivator: bisoxime with three positive charges
Chemical Papers, 2018Co-Authors: Kamil Kuca, Eugenie Nepovimova, Felipe Rodrigues De Souza, Teodorico C. Ramalho, Tanos C. C. França, Kamil MusilekAbstract:Within this study, experimental hydrophilic acetylcholinesterase (AChE) reactivator was evaluated in vitro against selected nerve agents (Cyclosarin, tabun, sarin, VX agent). High hydrophilicity of the reactivator is caused by the presence of three positive charges in its molecule. Quaternary moiety involved in the connecting chain can influence linker’s interaction with the inner of the AChE. For the detailed description of reactivator-AChE interaction, docking studies were performed on theoretical models constructed from the chrystallographic structure of Mus musculus AChE (MmAChE).
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Tetroxime: reactivation potency – in vitro and in silico study
RSC Advances, 2017Co-Authors: Kamil Kuca, Ondrej Soukup, Jan Korabecny, Rafael Dolezal, Eugenie Nepovimova, Lukas Gorecki, Kamil MusilekAbstract:Acetylcholinesterase (AChE) reactivators (oximes) are generally used as treatment in cases of nerve agent poisoning. There is no single oxime applicable in every case of nerve agent intoxication. Based on this fact, novel candidates with broader efficacy are still being sought. In this study, tetroxime – a bisquaternary compound bearing four oxime groups, was evaluated for its potency to reactivate rat brain AChE inhibited by selected nerve agents (tabun, sarin, Cyclosarin and VX agent). Despite the fact that this oxime contains four oxime groups that could be plausibly responsible for reactivation, it did not achieve broader reactivation activity. Satisfactory results were obtained only in the case of VX agent-inhibited AChE. In the cases of sarin- and Cyclosarin-inhibited AChE, acceptable results were reached at higher oxime concentration only. Tetroxime was unable to reactivate tabun-inhibited AChE. However, compared with the gold standard pralidoxime, this oxime achieved more promising results.
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EFFECTIVITY OF NEW ACETYLCHOLINESTERASE REACTIVATORS IN TREATMENT OF Cyclosarin POISONING IN MICE AND RATS
2016Co-Authors: Lucie Bartosova, Kamil Kuca, Gabriela KunešováAbstract:HI-6, BI-6 and HS-6 administered in equimolar doses and combined with atropine in Cyclosarin-poisoned mice and rats. It was demon-strated that all the therapeutic regimens tested, were able to decrease the Cyclosarin-induced toxicity significantly – at least 1.5 times. Higher therapeutic ratios, almost three times, were achieved in rats in comparison with mice. The highest therapeutic ratio was achieved for therapeutic regimen consisting of HI-6 and atropine in both mice and rats. Obidoxime was the least effective oxime in the treatment of Cyclosarin intoxication. The BI-6 oxime was significantly more efficacious than obidoxime (in both mice and rats) and HS-6 (in rats) but its effectiveness did not reach the efficacy of HI-6
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REVIEW PAPER Cyclosarin-An Organophosphate Nerve Agent
2016Co-Authors: Gabriela Krejčová, Kamil Kuca, Lucie ŠevelováAbstract:Organophosphorus compounds ascribed to as nerve agents (sarin, soman, tabun, Cyclosarin) are highly toxic, and are considered to be the most dangerous chemical compounds. All apparently share a common mechanism of cholinesterase inhibition and can cause similar svmotoms. The standard therapy, in the case of organophosphorus poisoning, has the prophylactic use of reversibly acting AChE inhibitors and antidotal administration of AChE reactivators-oximes. Unfortunately, none of these oximes can be regarded as a broad spectrum antidote, ie, effective against all nerve agents. While the presently available oximes (pralidoxime, ohidoxime) are not considered to be sufficiently effective against nerve agents, especially in the case of soman poisoning, the H oximes (HI-6, HLo7) appear to,be very promising antidotes against nerve agents because these are able to protect the experimental animals from toxic effects and improve survival of animals poisoned with supralethal doses. A lot of research has been pursued on the treatment of sarin, soman, and tabun, but Cyclosarin was not considered for such a study for a long time. Recently, attention of researchers has also turned to Cyclosarin because of its potential use as a chemical warfare agent. Cyclosarin is highly toxic organophosphorus compound which is resistant to conventional oxime therapy. This paper reviews the latest positionof Cyclosarin in standpoint of medical treatment by various reactivators considering the ability of various oximes, HI-6, HS-6, BI-6, and KO33 of their reactivation potency
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Reactivation kinetics of 31 structurally different bispyridinium oximes with organophosphate-inhibited human butyrylcholinesterase
Archives of Toxicology, 2015Co-Authors: Gabriele Horn, Kamil Kuca, Kamil Musilek, Horst Thiermann, Timo Wille, Franz WorekAbstract:Organophosphorus compounds (OP) are bound to human butyrylcholinesterase (BChE) and endogenous or exogenous BChE may act as a stoichiometric scavenger. Adequate amounts of BChE are required to minimize toxic OP effects. Simultaneous administration of BChE and oximes may transfer the enzyme into a pseudo-catalytic scavenger. The present study was initiated to determine the reactivation kinetics of 31 structurally different bispyridinium oximes with paraoxon-, tabun- and Cyclosarin-inhibited human BChE. Human plasma was incubated with OP and the reactivation of inhibited BChE was tested with multiple oxime concentrations followed by nonlinear regression analysis for the determination of reactivity, affinity and overall reactivation constants. The generated data indicate that the tested oximes have a low-to-negligible reactivating potency with paraoxon- and tabun-inhibited human BChE. Several oximes showed a moderate-to-high potency with Cyclosarin-inhibited BChE. Thus, the present study indicates that bispyridinium oximes are obviously not suitable to serve as reactivators of human BChE inhibited by different OP and it is doubtful whether further modifications of the bispyridinium template will lead to more potent reactivators. In the end, novel structures of oxime and non-oxime reactivators are urgently needed for the development of human BChE into an effective pseudo-catalytic scavenger.
Franz Worek - One of the best experts on this subject based on the ideXlab platform.
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The arrhythmogenic potential of nerve agents and a cardiac safety profile of antidotes - A proof-of-concept study using human induced pluripotent stem cells derived cardiomyocytes (hiPSC-CM).
Toxicology letters, 2019Co-Authors: Niko Amend, Franz Worek, Horst Thiermann, Timo WilleAbstract:Abstract The global use of organophosphorus compounds (OP) for pest control and nerve agents being used in military conflicts and for assassinations renders intoxications by these agents a public health concern. OP-poisoned patients often suffer from dysrhythmias which may ultimately result in death. In this study, human-induced pluripotent stem cells derived cardiomyocytes were exposed to OP compounds in a microelectrode array system (MEA). The MEA system is widely accepted to assess the proarrhythmic properties of (candidate) drugs. The directly acting cholinergic compounds acetylcholine and carbachol and the irreversible acetylcholinesterase inhibitor Cyclosarin - a highly toxic nerve agent - were assessed. All three compounds induced a dose-dependent (up to 600 nmol/L) corrected field potential duration (FPDc) prolongation of 9.7 ± 0.6% for carbachol, for 9.7 ± 1.2% acetylcholine and 9.4 ± 0.5% for Cyclosarin. Additionally, the electrophysiological alterations of the clinically approved oxime reactivators obidoxime, pralidoxime and the oximes in development HI-6 and MMB-4 were investigated in the absence of OP. Neither of these oximes (up to a concentration of 300 μmol/L) caused dysrhythmia nor beat arrest. The competitive muscarinic receptor antagonist atropine as a cornerstone in the treatment of OP poisoning was also analyzed. Interestingly, atropine caused a drop in the beat rate which might result from a non-receptor action of this substance in the absence of OP. Atropine in combination with the OP nerve agent Cyclosarin and the direct cholinergics acetylcholine or carabachol completely reversed the induced FPDc prolongation. However, the oxime HI-6 as potent reactivator of Cyclosarin-inhibited AChE was not able to prevent the FPDc prolongation in this model. In conclusion, the current model allows the assessment of FPDc prolongation by the nerve agent Cyclosarin, the cholinergic compounds carbachol, acetylcholine and the block of this effect by atropine.
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Reactivation kinetics of 31 structurally different bispyridinium oximes with organophosphate-inhibited human butyrylcholinesterase
Archives of Toxicology, 2015Co-Authors: Gabriele Horn, Kamil Kuca, Kamil Musilek, Horst Thiermann, Timo Wille, Franz WorekAbstract:Organophosphorus compounds (OP) are bound to human butyrylcholinesterase (BChE) and endogenous or exogenous BChE may act as a stoichiometric scavenger. Adequate amounts of BChE are required to minimize toxic OP effects. Simultaneous administration of BChE and oximes may transfer the enzyme into a pseudo-catalytic scavenger. The present study was initiated to determine the reactivation kinetics of 31 structurally different bispyridinium oximes with paraoxon-, tabun- and Cyclosarin-inhibited human BChE. Human plasma was incubated with OP and the reactivation of inhibited BChE was tested with multiple oxime concentrations followed by nonlinear regression analysis for the determination of reactivity, affinity and overall reactivation constants. The generated data indicate that the tested oximes have a low-to-negligible reactivating potency with paraoxon- and tabun-inhibited human BChE. Several oximes showed a moderate-to-high potency with Cyclosarin-inhibited BChE. Thus, the present study indicates that bispyridinium oximes are obviously not suitable to serve as reactivators of human BChE inhibited by different OP and it is doubtful whether further modifications of the bispyridinium template will lead to more potent reactivators. In the end, novel structures of oxime and non-oxime reactivators are urgently needed for the development of human BChE into an effective pseudo-catalytic scavenger.
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Adaptation of a dynamic in vitro model with real-time determination of butyrylcholinesterase activity in the presence of Cyclosarin and an oxime.
Toxicology in vitro : an international journal published in association with BIBRA, 2015Co-Authors: Franz Worek, Timo Wille, Gabriele Horn, Horst ThiermannAbstract:Abstract The well-established dynamic in vitro model for the real-time determination of acetylcholinesterase activity was modified for use of human butyrylcholinesterase (BChE) activity. Human plasma as BChE source was layered on a syringe filter and the enzyme reactor was continuously perfused with phosphate buffer, butyrylthiocholine and Ellman’s reagent at pH 7.4 and 37 °C which resulted in a stable BChE activity for up to 240 min. Then, the model was applied for investigating the suitability of human BChE in combination with an oxime (HLo 7) to serve as a ‘pseudo-catalytic’ scavenger of the organophosphorus nerve agent Cyclosarin. The application of different perfusion protocols demonstrated the ability of BChE-oxime combinations to prevent BChE from irreversible inhibition by Cyclosarin even at toxicologically relevant concentrations. In the end, this model seems to be suitable for the investigation of human plasma BChE as an endogenous, ‘pseudo-catalytic’ scavenger of a variety of nerve agents.
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Effectiveness of a substituted β-cyclodextrin to prevent Cyclosarin toxicity in vivo
Toxicology letters, 2014Co-Authors: Franz Worek, Michael Zengerle, Stefan Kubik, Horst Thiermann, Thomas Seeger, Timo WilleAbstract:Standard treatment of poisoning by organophosphorus (OP) nerve agents with atropine and an oxime has a limited efficacy. An alternative approach is the development of stoichiometric or catalytic (bio-)scavengers which should be able to prevent systemic toxicity. Recently, a β-cyclodextrin derivative, 6-OxP-CD, bearing a pyridinium oximate in 6-position of one glucose unit was synthetized and shown to possess a promising detoxification potential against a variety of alkyl methylfluorophosphonates in vitro. In order to investigate the suitability of 6-OxP-CD as a small molecule scavenger an in vivo guinea pig model was established to determine the protective effect of 6-OxP-CD against the highly toxic nerve agent Cyclosarin. Prophylactic i.v. injection of 6-OxP-CD (100mg/kg) prevented systemic toxicity in Cyclosarin (∼2LD50) poisoned guinea pigs, preserved brain acetylcholinesterase (AChE) activity but did not protect erythrocyte AChE activity. A lower 6-OxP-CD dose (50mg/kg) reduced systemic toxicity and prevented mortality in all animals. Thus, the results of this proof of concept study indicate that 6-OxP-CD may be considered as a potential small molecule scavenger to protect against the toxic effects of a range of highly toxic OP nerve agents.
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efficacy of the repon1 mutant iig1 to prevent Cyclosarin toxicity in vivo and to detoxify structurally different nerve agents in vitro
Archives of Toxicology, 2014Co-Authors: Franz Worek, Horst Thiermann, Moshe Goldsmith, Yacov Ashani, Haim Leader, Thomas Seeger, Joel S Sussman, Dan S Tawfik, Timo WilleAbstract:The potent human toxicity of organophosphorus (OP) nerve agents calls for the development of effective antidotes. Standard treatment for nerve agent poisoning with atropine and an oxime has a limited efficacy. An alternative approach is the development of catalytic bioscavengers using OP-hydrolyzing enzymes such as paraoxonases (PON1). Recently, a chimeric PON1 mutant, IIG1, was engineered toward the hydrolysis of the toxic isomers of soman and Cyclosarin with high in vitro catalytic efficiency. In order to investigate the suitability of IIG1 as a catalytic bioscavenger, an in vivo guinea pig model was established to determine the protective effect of IIG1 against the highly toxic nerve agent Cyclosarin. Prophylactic i.v. injection of IIG1 (1 mg/kg) prevented systemic toxicity in Cyclosarin (~2LD50)-poisoned guinea pigs, preserved brain acetylcholinesterase (AChE) activity, and protected erythrocyte AChE activity partially. A lower IIG1 dose (0.2 mg/kg) already prevented mortality and reduced systemic toxicity. IIG1 exhibited a high catalytic efficiency with a homologous series of alkylmethylfluorophosphonates but had low efficiency with the phosphoramidate tabun and was virtually ineffective with the nerve agent VX. This quantitative analysis validated the model for predicting in vivo protection by catalytic bioscavengers based on their catalytic efficiency, the level of circulating enzyme, and the dose of the intoxicating nerve agent. The in vitro and in vivo results indicate that IIG1 may be considered as a promising candidate bioscavenger to protect against the toxic effects of a range of highly toxic nerve agents.
Jiri Kassa - One of the best experts on this subject based on the ideXlab platform.
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some benefit from non oximes mb408 mb442 and mb444 in combination with the oximes hi 6 or obidoxime and atropine in antidoting sarin or Cyclosarin poisoned mice
Toxicology, 2018Co-Authors: Jiri Kassa, Christopher M Timperley, Mike Bird, Rebecca L Williams, Christopher A Green, John E H TattersallAbstract:Abstract The effect of three newly developed bispyridinium non-oxime compounds (MB408, MB442, and MB444) on the therapeutic efficacy of a standard antidotal treatment (atropine in combination with the oxime HI-6 or obidoxime) of acute poisoning by two nerve agents (sarin and Cyclosarin) in mice was studied. The therapeutic efficacy of atropine in combination with an oxime with or without one of the bispyridinium non-oximes was evaluated by determination of the 24 h LD50 values of the nerve agents studied and by measurement of the survival time after supralethal poisoning. Addition of all tested non-oximes increased the therapeutic efficacy of atropine in combination with an oxime against sarin poisoning; however, the differences were not significant. The non-oximes also positively influenced the number of surviving mice 6 h after supralethal poisoning with sarin. In the case of Cyclosarin, they were also slightly beneficial in the treatment of acute poisoning. The higher dose of MB444 was able to significantly increase the therapeutic efficacy of standard antidotal treatment of poisoning with Cyclosarin. The benefit of each bispyridinium non-oxime compound itself was obviously dose-dependent. In summary, the addition of MB compounds to the standard antidotal treatment of acute nerve agent poisoning was beneficial for the antidotal treatment of sarin or Cyclosarin poisoning, although their benefit at 24 h after poisoning was not significant, with the exception of the higher dose of MB444 against Cyclosarin.
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a comparison of reactivating and therapeutic efficacy of newly developed oximes k156 k203 and commonly used oximes obidoxime hi 6 in Cyclosarin poisoned rats and mice
Toxicology Mechanisms and Methods, 2009Co-Authors: Jiri Kassa, Jana Žďárová Karasová, Kamil Musilek, Kamil KucaAbstract:A potency of newly-developed oximes (K156, K203) and commonly used oximes (obidoxime, HI-6) to reactivate Cyclosarin-inhibited acetylcholinesterase and to reduce Cyclosarin-induced acute toxic effects was evaluated in this study. In vivo determined percentage of reactivation of Cyclosarin-inhibited blood and tissue acetylcholinesterase in poisoned rats showed that the potency of a newly-developed oxime (K203) to reactivate Cyclosarin-inhibited acetylcholinesterase and to reduce the acute lethal effects of Cyclosarin, corresponding to the relatively low reactivating and therapeutic efficacy of obidoxime. The potency of another newly-developed oxime (K156) to counteract the inhibitory and acute clinical effects of Cyclosarin is almost negligible. On the other hand, the oxime HI-6 is a very efficient reactivator of Cyclosarin-inhibited acetylcholinesterase in the peripheral (blood, diaphragm) as well as central (brain) compartment, and it is able to reduce the acute toxicity of Cyclosarin more than three times. Although the reactivating and therapeutic efficacy of the oxime K203 is higher compared to another newly-developed oxime K156, the reactivating and therapeutic potency of both newly-developed oximes is significantly lower in comparison with the oxime HI-6 and, therefore, none of them is suitable for replacement of HI-6 in the case of the treatment of Cyclosarin poisoning.
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evaluation of the neuroprotective efficacy of newly developed oximes k206 k269 and currently available oximes obidoxime hi 6 in Cyclosarin poisoned rats
Basic & Clinical Pharmacology & Toxicology, 2009Co-Authors: Jiri Kassa, Jiri Bajgar, Jana Žďárová Karasová, Kamil Kuca, Sandra Tesarova, Kamil MusilekAbstract:The neuroprotective effects of newly developed oximes (K206, K269) and currently available oximes (obidoxime, HI-6) in combination with atropine in rats poisoned with Cyclosarin were studied. The Cyclosarin-induced neurotoxicity was monitored using a functional observational battery at 24 hr following Cyclosarin challenge. The results indicate that a newly developed oxime K206 is able to counteract Cyclosarin-induced neurotoxicity while the neuroprotective potency of another newly developed oxime (K269) is negligible. The neuroprotective efficacy of K206 is markedly higher than commonly used obidoxime; nevertheless, its potency to eliminate Cyclosarin-induced neurotoxicity is slightly lower compared to the oxime HI-6. Thus, a newly developed oxime K206 seems to be a better oxime for the antidotal treatment of Cyclosarin poisonings than obidoxime due to higher neuroprotective potency although the oxime HI-6 is still the most suitable oxime for the antidotal treatment of acute poisonings with Cyclosarin.
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an evaluation of reactivating and therapeutic efficacy of newly developed oximes k206 k269 and commonly used oximes obidoxime hi 6 in Cyclosarin poisoned rats and mice
Clinical Toxicology, 2009Co-Authors: Jiri Kassa, Kamil Kuca, Jana Žďárová Karasová, Kamil Musilek, Jiri BajgarAbstract:Introduction. The ability of currently available reactivators to reactivate Cyclosarin is low. The aim of this study was to determine the reactivating and therapeutic efficacy of newly developed oximes (K206, K269) compared with currently available oximes against Cyclosarin. Methods. Rats and mice received atropine or atropine + oxime intramuscularly (i.m.) before or after an i.m. dose of Cyclosarin. Acetylcholine activity levels in blood and tissues were measured to calculate the reactivation efficacy and potency. Results and discussion. In vivo determined percentage of reactivation of Cyclosarin-inhibited blood and tissue acetylcholinesterase (AChE) in poisoned rats showed that the potency of both newly developed oximes (K206, K269) to reactivate Cyclosarin-inhibited AChE is comparable with that of obidoxime in blood and diaphragm, but slightly higher than that of obidoxime in brain. Their reactivating efficacy is significantly lower compared with that of the oxime HI-6. K206 and K269 are relatively eff...
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Effect of Seven Newly Synthesized and Currently Available Oxime Cholinesterase Reactivators on Cyclosarin-Intoxicated Rats
MDPI AG, 2009Co-Authors: Kamil Kuca, Miroslav Pohanka, Jiri Kassa, Kamil Musilek, Ladislav Novotny, Jana Žďárová KarasováAbstract:Seven new oxime-based acetylcholinesterase reactivators were compared with three currently available ones (obidoxime, trimedoxime, HI-6) for their ability to lessen cholinesterase inhibition in blood and brain of Cyclosarin-treated rats. Oximes were given at doses of 5% their LD50 along with 21 mg/kg atropine five min before the LD50 of Cyclosarin (120 ug/kg) was administered. Blood and brain samples were collected 30 minutes later. The greatest difference between acetylcholinesterase inhibition in blood of Cyclosarin-treated rats was found after administration of HI-6 (40%), compared to 22% for trimedoxime and 6% for obidoxime. Only two of the seven newly synthesized oximes had any effect (K203 at 7%, K156 at 5%). Effective oximes against Cyclosarin-inhibited plasma butyrylcholinesterase were HI-6 (42%), trimedoxime (11%), and K156 (4%). The oximes were less effective in brain than in blood, with reactivation values for HI-6 30% against acetylcholinesterase and 10% against butyrylcholinesterase. Values for newly synthesized oximes were less than 10% for K206, K269 and K203
Timo Wille - One of the best experts on this subject based on the ideXlab platform.
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The arrhythmogenic potential of nerve agents and a cardiac safety profile of antidotes - A proof-of-concept study using human induced pluripotent stem cells derived cardiomyocytes (hiPSC-CM).
Toxicology letters, 2019Co-Authors: Niko Amend, Franz Worek, Horst Thiermann, Timo WilleAbstract:Abstract The global use of organophosphorus compounds (OP) for pest control and nerve agents being used in military conflicts and for assassinations renders intoxications by these agents a public health concern. OP-poisoned patients often suffer from dysrhythmias which may ultimately result in death. In this study, human-induced pluripotent stem cells derived cardiomyocytes were exposed to OP compounds in a microelectrode array system (MEA). The MEA system is widely accepted to assess the proarrhythmic properties of (candidate) drugs. The directly acting cholinergic compounds acetylcholine and carbachol and the irreversible acetylcholinesterase inhibitor Cyclosarin - a highly toxic nerve agent - were assessed. All three compounds induced a dose-dependent (up to 600 nmol/L) corrected field potential duration (FPDc) prolongation of 9.7 ± 0.6% for carbachol, for 9.7 ± 1.2% acetylcholine and 9.4 ± 0.5% for Cyclosarin. Additionally, the electrophysiological alterations of the clinically approved oxime reactivators obidoxime, pralidoxime and the oximes in development HI-6 and MMB-4 were investigated in the absence of OP. Neither of these oximes (up to a concentration of 300 μmol/L) caused dysrhythmia nor beat arrest. The competitive muscarinic receptor antagonist atropine as a cornerstone in the treatment of OP poisoning was also analyzed. Interestingly, atropine caused a drop in the beat rate which might result from a non-receptor action of this substance in the absence of OP. Atropine in combination with the OP nerve agent Cyclosarin and the direct cholinergics acetylcholine or carabachol completely reversed the induced FPDc prolongation. However, the oxime HI-6 as potent reactivator of Cyclosarin-inhibited AChE was not able to prevent the FPDc prolongation in this model. In conclusion, the current model allows the assessment of FPDc prolongation by the nerve agent Cyclosarin, the cholinergic compounds carbachol, acetylcholine and the block of this effect by atropine.
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Reactivation kinetics of 31 structurally different bispyridinium oximes with organophosphate-inhibited human butyrylcholinesterase
Archives of Toxicology, 2015Co-Authors: Gabriele Horn, Kamil Kuca, Kamil Musilek, Horst Thiermann, Timo Wille, Franz WorekAbstract:Organophosphorus compounds (OP) are bound to human butyrylcholinesterase (BChE) and endogenous or exogenous BChE may act as a stoichiometric scavenger. Adequate amounts of BChE are required to minimize toxic OP effects. Simultaneous administration of BChE and oximes may transfer the enzyme into a pseudo-catalytic scavenger. The present study was initiated to determine the reactivation kinetics of 31 structurally different bispyridinium oximes with paraoxon-, tabun- and Cyclosarin-inhibited human BChE. Human plasma was incubated with OP and the reactivation of inhibited BChE was tested with multiple oxime concentrations followed by nonlinear regression analysis for the determination of reactivity, affinity and overall reactivation constants. The generated data indicate that the tested oximes have a low-to-negligible reactivating potency with paraoxon- and tabun-inhibited human BChE. Several oximes showed a moderate-to-high potency with Cyclosarin-inhibited BChE. Thus, the present study indicates that bispyridinium oximes are obviously not suitable to serve as reactivators of human BChE inhibited by different OP and it is doubtful whether further modifications of the bispyridinium template will lead to more potent reactivators. In the end, novel structures of oxime and non-oxime reactivators are urgently needed for the development of human BChE into an effective pseudo-catalytic scavenger.
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Adaptation of a dynamic in vitro model with real-time determination of butyrylcholinesterase activity in the presence of Cyclosarin and an oxime.
Toxicology in vitro : an international journal published in association with BIBRA, 2015Co-Authors: Franz Worek, Timo Wille, Gabriele Horn, Horst ThiermannAbstract:Abstract The well-established dynamic in vitro model for the real-time determination of acetylcholinesterase activity was modified for use of human butyrylcholinesterase (BChE) activity. Human plasma as BChE source was layered on a syringe filter and the enzyme reactor was continuously perfused with phosphate buffer, butyrylthiocholine and Ellman’s reagent at pH 7.4 and 37 °C which resulted in a stable BChE activity for up to 240 min. Then, the model was applied for investigating the suitability of human BChE in combination with an oxime (HLo 7) to serve as a ‘pseudo-catalytic’ scavenger of the organophosphorus nerve agent Cyclosarin. The application of different perfusion protocols demonstrated the ability of BChE-oxime combinations to prevent BChE from irreversible inhibition by Cyclosarin even at toxicologically relevant concentrations. In the end, this model seems to be suitable for the investigation of human plasma BChE as an endogenous, ‘pseudo-catalytic’ scavenger of a variety of nerve agents.
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Effectiveness of a substituted β-cyclodextrin to prevent Cyclosarin toxicity in vivo
Toxicology letters, 2014Co-Authors: Franz Worek, Michael Zengerle, Stefan Kubik, Horst Thiermann, Thomas Seeger, Timo WilleAbstract:Standard treatment of poisoning by organophosphorus (OP) nerve agents with atropine and an oxime has a limited efficacy. An alternative approach is the development of stoichiometric or catalytic (bio-)scavengers which should be able to prevent systemic toxicity. Recently, a β-cyclodextrin derivative, 6-OxP-CD, bearing a pyridinium oximate in 6-position of one glucose unit was synthetized and shown to possess a promising detoxification potential against a variety of alkyl methylfluorophosphonates in vitro. In order to investigate the suitability of 6-OxP-CD as a small molecule scavenger an in vivo guinea pig model was established to determine the protective effect of 6-OxP-CD against the highly toxic nerve agent Cyclosarin. Prophylactic i.v. injection of 6-OxP-CD (100mg/kg) prevented systemic toxicity in Cyclosarin (∼2LD50) poisoned guinea pigs, preserved brain acetylcholinesterase (AChE) activity but did not protect erythrocyte AChE activity. A lower 6-OxP-CD dose (50mg/kg) reduced systemic toxicity and prevented mortality in all animals. Thus, the results of this proof of concept study indicate that 6-OxP-CD may be considered as a potential small molecule scavenger to protect against the toxic effects of a range of highly toxic OP nerve agents.
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efficacy of the repon1 mutant iig1 to prevent Cyclosarin toxicity in vivo and to detoxify structurally different nerve agents in vitro
Archives of Toxicology, 2014Co-Authors: Franz Worek, Horst Thiermann, Moshe Goldsmith, Yacov Ashani, Haim Leader, Thomas Seeger, Joel S Sussman, Dan S Tawfik, Timo WilleAbstract:The potent human toxicity of organophosphorus (OP) nerve agents calls for the development of effective antidotes. Standard treatment for nerve agent poisoning with atropine and an oxime has a limited efficacy. An alternative approach is the development of catalytic bioscavengers using OP-hydrolyzing enzymes such as paraoxonases (PON1). Recently, a chimeric PON1 mutant, IIG1, was engineered toward the hydrolysis of the toxic isomers of soman and Cyclosarin with high in vitro catalytic efficiency. In order to investigate the suitability of IIG1 as a catalytic bioscavenger, an in vivo guinea pig model was established to determine the protective effect of IIG1 against the highly toxic nerve agent Cyclosarin. Prophylactic i.v. injection of IIG1 (1 mg/kg) prevented systemic toxicity in Cyclosarin (~2LD50)-poisoned guinea pigs, preserved brain acetylcholinesterase (AChE) activity, and protected erythrocyte AChE activity partially. A lower IIG1 dose (0.2 mg/kg) already prevented mortality and reduced systemic toxicity. IIG1 exhibited a high catalytic efficiency with a homologous series of alkylmethylfluorophosphonates but had low efficiency with the phosphoramidate tabun and was virtually ineffective with the nerve agent VX. This quantitative analysis validated the model for predicting in vivo protection by catalytic bioscavengers based on their catalytic efficiency, the level of circulating enzyme, and the dose of the intoxicating nerve agent. The in vitro and in vivo results indicate that IIG1 may be considered as a promising candidate bioscavenger to protect against the toxic effects of a range of highly toxic nerve agents.
Daniel Jun - One of the best experts on this subject based on the ideXlab platform.
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Oxime K027: novel low-toxic candidate for the universal reactivator of nerve agent- and pesticide-inhibited acetylcholinesterase
Journal of enzyme inhibition and medicinal chemistry, 2010Co-Authors: Kamil Kuca, Miroslav Pohanka, Kamil Musilek, Daniel Jun, Kallol K. Ghosh, Martina HrabinovaAbstract:Oxime K027 is a low-toxic bisquaternary compound originally developed as a reactivator of acetylcholinesterase (AChE) inhibited by nerve agents. The reactivation potency of K027 has been tested as a potential reactivator of AChE inhibited by tabun, sarin, Cyclosarin, soman, VX, Russian VX, paraoxon, methylchlorpyrifos, and DDVP. The results show that oxime K027 reactivated AChE inhibited by almost all tested inhibitors to more than 10%, which is believed to be enough for saving the lives of intoxicated organisms. In the case of Cyclosarin- and soman-inhibited AChE, oxime K027 did not reach sufficient reactivation potency.
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a comparison of reactivating efficacy of newly developed oximes k074 k075 and currently available oximes obidoxime hi 6 in soman Cyclosarin and tabun poisoned rats
Chemico-Biological Interactions, 2008Co-Authors: Jiri Kassa, Jiri Bajgar, Jana Žďárová Karasová, Daniel Jun, Kamil KucaAbstract:The potency of newly developed oximes (K074, K075) and commonly used oximes (obidoxime, HI-6) to reactivate nerve agent-inhibited acetylcholinesterase was evaluated in rats poisoned with soman, tabun or Cyclosarin at a lethal dose corresponding to their LD(50) value. In vivo determined percentage of reactivation of soman-inhibited blood and brain acetylcholinesterase in poisoned rats showed that only the oxime HI-6 was able to reactivate soman-inhibited acetylcholinesterase in the peripheral (blood) as well as central (brain) compartment. In vivo determined percentage of reactivation of tabun-inhibited blood and brain acetylcholinesterase in poisoned rats showed that obidoxime is the most efficacious reactivator of tabun-inhibited acetylcholinesterase among studied oximes in the peripheral compartment (blood) while K074 seems to be the most efficacious reactivator of tabun-inhibited acetylcholinesterase among studied oximes in the central compartment (brain). In vivo determined percentage of reactivation of Cyclosarin-inhibited blood and brain acetylcholinesterase in poisoned rats showed that HI-6 is the most efficacious reactivator of Cyclosarin-inhibited acetylcholinesterase among studied oximes. Due to their reactivating effects, both newly developed K oximes can be considered to be promising oximes for the antidotal treatment of acute tabun poisonings while the oxime HI-6 is still the most promising oxime for the treatment of acute soman and Cyclosarin poisonings.
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Structural Factors Influencing Potency of Currently Used Acetylcholinesterase Reactivators for Treatment of Cyclosarin Intoxications
Current pharmaceutical design, 2007Co-Authors: Kamil Kuca, Daniel Jun, Jiri BajgarAbstract:Cyclosarin is one member of nerve agent family. Recent treatment of intoxications by organophosphorus compounds, such as nerve agents or pesticides, consists of rapid administration of anticholinergics and AChE reactivators. Owing to the threat of terroristic use of these compounds during last years, improvement of antidotal therapy still continues. As the part of the development of new antidotes, many new AChE reactivators were synthesized and currently some of them are under consideration for introducing them to the medical practice. Their biological activity depends, as in the case of other drugs, on their chemical structure, which affects their pharmacokinetics (adsorption, distribution, metabolism and excretion) and pharmacodynamics. In this review, we would like to discuss relationship between structure of currently available AChE reactivators and their potency to reactivate Cyclosarin-inhibited AChE. All outlined structural factors presented in this work should be helpful for the design of new generation of reactivators of Cyclosarin-inhibited AChE.
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Targeted synthesis of 1-(4-hydroxyiminomethylpyridinium)-3-pyridiniumpropane dibromide--a new nerve agent reactivator.
Molecules (Basel Switzerland), 2007Co-Authors: Kamil Kuca, Kamil Musilek, Martina Hrabinova, Daniel Jun, Martin Paar, Petr Stodulka, Jan MarekAbstract:Preparation of 1-(4-hydroxy-iminomethylpyridinium)-3-pyridiniumpropane dibromide is described. This compound represents a new acetylcholinesterase (AChE) reactivator, which has no substituents on the second pyridinium ring as found in other commonly used AChE reactivators. The reactivation ability of this reactivator was tested on tabun- and Cyclosarin-inhibited AChE. According to the results obtained, the new compound (without substitution and with decreased molecule size) showed increased reactivation potency in case of Cyclosarin inhibited AChE. A potent oxime for treatment of tabun and Cyclosarin-caused intoxications was thus obtained via slight modification of the reactivator structure (compared to trimedoxime and K027).
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Potency of five structurally different acetylcholinesterase reactivators to reactivate human brain cholinesterases inhibited by Cyclosarin.
Clinical toxicology (Philadelphia Pa.), 2007Co-Authors: Kamil Kuca, Jiri Cabal, Daniel Jun, Martina HrabinovaAbstract:Acetylcholinesterase (AChE; EC 3.1.1.7) reactivators are used as a part of the antidotal therapy of organophosphorus pesticide and nerve agent intoxications. Cyclosarin is one member of the nerve agent family. In this article, we compared the reactivation potency of five structurally different AChE reactivators (pralidoxime, trimedoxime, methoxime, HS-6, and BI-6) to reactivate Cyclosarin-inhibited cholinesterases of human brain. The results demonstrate that the bisquaternary monooxime reactivator BI-6 seems to be the most potent reactivator of Cyclosarin-inhibited cholinesterases. Moreover, according to the results, we can describe basic structural requirements, which are necessary for the efficacious reactivation process.
