21 results on '"Wille, T."'
Search Results
2. AChE reactivation in precision-cut lung slices following organophosphorus compound poisoning.
- Author
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Gölitz F, Herbert J, Worek F, and Wille T
- Subjects
- Humans, Acetylcholinesterase, Cholinesterase Inhibitors, Organophosphorus Compounds toxicity, Oximes pharmacology, Oximes therapeutic use, Lung, Cholinesterase Reactivators pharmacology, Cholinesterase Reactivators therapeutic use, Organophosphate Poisoning drug therapy, Organothiophosphorus Compounds
- Abstract
Precision-cut lung slices (PCLS) are a suitable model for analyzing the acetylcholinesterase (AChE) activity and subsequent effects after exposure to organophosphorus (OP) compounds. In this study, the AChE activity was determined in intact PCLS for the first time. Since the current standard therapy for OP poisoning (atropine + oxime + benzodiazepine) lacks efficiency, reliable models to study novel therapeutic substances are needed. Models should depict pathophysiological mechanisms and help to evaluate the beneficial effects of new therapeutics. Here PCLS were exposed to three organophosphorus nerve agents (OPNAs): sarin (GB), cyclosarin (GF), and VX. They were then treated with three reactivators: HI-6, obidoxime (OBI), and a non-oxime (NOX-6). The endpoints investigated in this study were the AChE activity and the airway area (AA) change. OPNA exposure led to very low residual AChE activities. Depending on the reactivator properties different AChE reactivation results were measured. GB-inhibited PCLS-AChE was reactivated best, followed by VX and GF. To substantiate these findings and to understand the connection between the molecular and the functional levels in a more profound way the results were correlated to the AA changes. These investigations underline the importance of reactivator use and point to the possibilities for future improvements in the treatment of OPNA-exposed victims., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)
- Published
- 2024
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3. The suitability of a polydimethylsiloxane-based (PDMS) microfluidic two compartment system for the toxicokinetic analysis of organophosphorus compounds.
- Author
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Amend N, Koller M, Schmitt C, Worek F, and Wille T
- Subjects
- Organophosphorus Compounds toxicity, Microfluidics, Toxicokinetics, Dimethylpolysiloxanes, Organothiophosphorus Compounds toxicity, Parathion
- Abstract
Organ-on-a-chip platforms are an emerging technology in experimental and regulatory toxicology (species-specific differences, ethical considerations). They address gaps between in vivo and in vitro models. However, there are still certain limitations considering material, setup and applicability. The current study examined the suitability of a commercially available polydimethylsiloxane-based (PDMS) organ-chip for the toxicokinetic characterization of the highly toxic nerve agent VX and the organophosphate pesticide parathion. The respective concentrations of 1000 µmol/L and 100 µmol/L VX and parathion were chosen deliberately high in order to study concentrations even if high compound absorption by PDMS might occur. Neuronal and liver spheroids, totaling 2 × 10
6 cells were used to study concentration changes of VX and parathion. In addition, VX enantiomers were quantified. The current study suggests a significant absorption of VX, respectively parathion by PDMS. This might require future investigation of alternative materials or coatings to limit absorption for organophosphorus compounds in toxicokinetic studies., Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Prof. Dr. Franz Worek is a member of the Editorial Board of Toxicology Letters Dr. Niko Amend is Executive Guest Editor of the Special Issue in Toxicology Letters., (Copyright © 2023 Elsevier B.V. All rights reserved.)- Published
- 2023
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4. A pharmacologically pre-contracted smooth muscle bowel model for the study of highly-potent opioid receptor agonists and antagonists.
- Author
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Amend N, Thiermann H, Worek F, and Wille T
- Subjects
- Rats, Animals, Remifentanil, Narcotic Antagonists pharmacology, Naloxone pharmacology, Receptors, Opioid, Muscle, Smooth, Analgesics, Opioid toxicity, Naltrexone pharmacology
- Abstract
Isolated organ models are a versatile tool for pharmacological and toxicological research. Small bowel has been used to assess the inhibition of smooth muscle contraction by opioids. In the present study, we set out to establish a pharmacologically stimulated rat bowel model. The effects of carfentanil, remifentanil and the new synthetic opioid U-48800 and their respective antagonists naloxone, nalmefene and naltrexone were studied in a small bowel model in rats. The IC
50 values of the tested opioids were as follows: carfentanil (IC50 = 0.02 µmol/L, CI 0.02-0.03 µmol/L) ≫ remifentanil (IC50 = 0.51 µmol/L, CI 0.40-0.66 µmol/L) ≫ U-48800 (IC50 = 1.36 µmol/L, CI 1.20-1.54 µmol/L). The administration of the opioid receptor antagonists naloxone, naltrexone and nalmefene led to progressive, parallel rightward shifts of the dose-response curves. Naltrexone was most potent in antagonizing the effects of U-48800, whereas naltrexone and nalmefene were most effective in antagonizing the effects of carfentanil. In summary, the current model seems to be a robust tool to study opioid effects in a small bowel model without the necessity of using electrical stimulation., Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Prof. Dr. Franz Worek is a member of the editorial board of Toxicology Letters. Conflict of interest statement The authors declare that there are no conflicts of interest. The study was funded by the German Ministry of Defence. However, the design, performance, data interpretation and manuscript writing were under the control of the authors and has not been influenced by the German Ministry of Defence., (Copyright © 2023 The Authors. Published by Elsevier B.V. All rights reserved.)- Published
- 2023
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5. 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).
- Author
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Amend N, Thiermann H, Worek F, and Wille T
- Subjects
- Antidotes therapeutic use, Cell Culture Techniques, Cells, Cultured, Humans, Microelectrodes, Myocytes, Cardiac physiology, Organophosphate Poisoning physiopathology, Organophosphate Poisoning prevention & control, Action Potentials drug effects, Antidotes adverse effects, Chemical Warfare Agents toxicity, Induced Pluripotent Stem Cells cytology, Myocytes, Cardiac drug effects, Nerve Agents toxicity, Organophosphorus Compounds toxicity
- 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., (Copyright © 2019 Elsevier B.V. All rights reserved.)
- Published
- 2019
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6. The oximes HI-6 and MMB-4 fail to reactivate soman-inhibited human and guinea pig AChE: A kinetic in vitro study.
- Author
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Worek F, Thiermann H, and Wille T
- Subjects
- Acetylcholinesterase metabolism, Animals, Antidotes pharmacokinetics, Cholinesterase Reactivators pharmacokinetics, Erythrocyte Membrane drug effects, Erythrocytes drug effects, Guinea Pigs, Humans, Kinetics, Oximes pharmacokinetics, Pyridinium Compounds pharmacokinetics, Species Specificity, Antidotes pharmacology, Chemical Warfare Agents poisoning, Cholinesterase Inhibitors poisoning, Cholinesterase Reactivators pharmacology, Oximes pharmacology, Pyridinium Compounds pharmacology, Soman antagonists & inhibitors, Soman poisoning
- Abstract
Acetylcholinesterase (AChE) inhibited by the organophosphorus nerve (OP) agent soman underlies a spontaneous and extremely rapid dealkylation ("aging") reaction which prevents reactivation by oximes. However, in vivo studies in various, soman poisoned animal species showed a therapeutic effect of oximes, with the exact mechanism of this effect remaining still unclear. In order to get more insight and a basis for the extrapolation of animal data to humans, we applied a dynamic in vitro model with continuous online determination of AChE activity. This model allows to simulate the in vivo toxico- and pharmacokinetics between human and guinea pig AChE with soman and the oximes HI-6 and MMB-4 in order to unravel the species dependent kinetic interactions. It turned out that only HI-6 was able to slow down the ongoing inhibition of human AChE by soman without preventing final complete inhibition of the enzyme. Continuous perfusion of AChE with soman and simultaneous or delayed (8, 15 or 40min) oxime perfusion did not result in a relevant reactivation of AChE (less than 2%). In conclusion, the results of the present study indicate a negligible reactivation of soman-inhibited AChE by oximes at conditions simulating the in vivo poisoning by soman. The observed therapeutic effect of oximes in soman poisoned animals in vivo must be attributed to alternative mechanisms which may not be relevant in humans., (Copyright © 2017 Elsevier B.V. All rights reserved.)
- Published
- 2018
- Full Text
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7. Human small bowel as a useful tool to investigate smooth muscle effects of potential therapeutics in organophosphate poisoning.
- Author
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Marquart K, Prokopchuk O, Worek F, Thiermann H, Martignoni ME, and Wille T
- Subjects
- Aged, Aged, 80 and over, Animals, Carbachol pharmacology, Cholinesterase Reactivators pharmacology, Dose-Response Relationship, Drug, Female, Humans, Ileum drug effects, In Vitro Techniques, Jejunum drug effects, Male, Middle Aged, Models, Biological, Muscarinic Agonists pharmacology, Muscle Contraction drug effects, Rats, Rats, Wistar, Antidotes therapeutic use, Intestine, Small drug effects, Muscle, Smooth drug effects, Organophosphate Poisoning drug therapy
- Abstract
Isolated organs proofed to be a robust tool to study effects of (potential) therapeutics in organophosphate poisoning. Small bowel samples have been successfully used to reveal smooth muscle relaxing effects. In the present study, the effects of obidoxime, TMB-4, HI-6 and MB 327 were investigated on human small bowel tissue and compared with rat data. Hereby, the substances were tested in at least seven different concentrations in the jejunum or ileum both pre-contracted with carbamoylcholine. Additionally, the cholinesterase activity of native tissue was determined. Human small intestine specimens showed classical dose response-curves, similar to rat tissue, with MB 327 exerting the most potent smooth muscle relaxant effect in both species (human EC
50 =0.7×10-5 M and rat EC50 =0.7×10-5 M). The AChE activity for human and rat samples did not differ significantly (rat jejunum=1351±166 mU/mg wet weight; rat ileum=1078±123 mU/mg wet weight; human jejunum=1030±258 mU/mg wet weight; human ileum=1293±243 mU/mg wet weight). Summarizing, our isolated small bowel setup seems to be a solid tool to investigate the effects of (potential) therapeutics on pre-contracted smooth muscle, with data being transferable between rat and humans., (Copyright © 2017 Elsevier B.V. All rights reserved.)- Published
- 2018
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8. Development of a sensitive, generic and easy to use organophosphate skin disclosure kit.
- Author
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Worek F, Wosar A, Baumann M, Thiermann H, and Wille T
- Subjects
- Administration, Cutaneous, Animals, Chemical Warfare Agents chemistry, Colorimetry, Humans, Organophosphorus Compounds chemistry, Organophosphorus Compounds toxicity, Organothiophosphorus Compounds chemistry, Organothiophosphorus Compounds toxicity, Reagent Kits, Diagnostic
- Abstract
Various organophosphorus compounds (OP), primarily the nerve agent VX and other V-agents, are highly toxic to humans after skin exposure. Percutaneous exposure by such OP results in a delayed onset of toxic signs which enables the initiation of specific countermeasures if contamination is detected rapidly. Presently available mobile detection systems can hardly detect skin exposure by low volatile OP. In order to fill this gap an OP skin disclosure kit was developed which should fulfill different requirements, i.e. a high sensitivity, coverage of human toxic OP, easy handling, rapid results, small dimension and weight. The kit includes a cotton swab to sample skin, human AChE as target and chemicals for a color reaction based on the Ellman assay which is recorded by visual inspection. OP is dissolved from the sampler in a test tube filled with phosphate buffer (0.1M, pH 7.4) and incubated with lyophilized human AChE for 1min. The reaction with acetylthiocholine and 5,5'-dithio-bis-2-nitrobenzoic acid (1min) results in a rich yellow color in the absence of OP and in contrast, in transparent or pale yellow buffer in the presence of OP. At the recommended conditions, the limit of detection is 100ng VX and Russian VX and 50ng Chinese VX on plain surface and 200ng VX on rat skin. With activated pesticides, paraoxon and malaoxon, a concentration of ∼10μg can be detected on plain surface. The ready-to-use kit has a weight of 16g and a size of 10×12×1cm. In the end, this kit has the potential to fill a major gap and to enable timely detection of OP skin exposure and initiation of life-saving countermeasures., (Copyright © 2017 Elsevier B.V. All rights reserved.)
- Published
- 2017
- Full Text
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9. Blaptica dubia as sentinels for exposure to chemical warfare agents - a pilot study.
- Author
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Worek F, Seeger T, Neumaier K, Wille T, and Thiermann H
- Subjects
- Animals, Arsenicals, Blister chemically induced, Blister pathology, Chemical Warfare Agents chemistry, Cholinesterase Inhibitors toxicity, Female, Male, Mustard Gas toxicity, Nerve Agents toxicity, Organophosphorus Compounds toxicity, Pilot Projects, Sarin toxicity, Soman toxicity, Chemical Warfare Agents toxicity, Cockroaches drug effects
- Abstract
The increased interest of terrorist groups in toxic chemicals and chemical warfare agents presents a continuing threat to our societies. Early warning and detection is a key component for effective countermeasures against such deadly agents. Presently available and near term solutions have a number of major drawbacks, e.g. lack of automated, remote warning and detection of primarily low volatile chemical warfare agents. An alternative approach is the use of animals as sentinels for exposure to toxic chemicals. To overcome disadvantages of vertebrates the present pilot study was initiated to investigate the suitability of South American cockroaches (Blaptica dubia) as warning system for exposure to chemical warfare nerve and blister agents. Initial in vitro experiments with nerve agents showed an increasing inhibitory potency in the order tabun - cyclosarin - sarin - soman - VX of cockroach cholinesterase. Exposure of cockroaches to chemical warfare agents resulted in clearly visible and reproducible reactions, the onset being dependent on the agent and dose. With nerve agents the onset was related to the volatility of the agents. The blister agent lewisite induced signs largely comparable to those of nerve agents while sulfur mustard exposed animals exhibited a different sequence of events. In conclusion, this first pilot study indicates that Blaptica dubia could serve as a warning system to exposure of chemical warfare agents. A cockroach-based system will not detect or identify a particular chemical warfare agent but could trigger further actions, e.g. specific detection and increased protective status. By designing appropriate boxes with (IR) motion sensors and remote control (IR) camera automated off-site warning systems could be realized., (Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.)
- Published
- 2016
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10. Single treatment of VX poisoned guinea pigs with the phosphotriesterase mutant C23AL: Intraosseous versus intravenous injection.
- Author
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Wille T, Neumaier K, Koller M, Ehinger C, Aggarwal N, Ashani Y, Goldsmith M, Sussman JL, Tawfik DS, Thiermann H, and Worek F
- Subjects
- Animals, Animals, Outbred Strains, Antidotes metabolism, Antidotes pharmacokinetics, Antidotes therapeutic use, Bacterial Proteins administration & dosage, Bacterial Proteins genetics, Bacterial Proteins pharmacokinetics, Bacterial Proteins therapeutic use, Bone Marrow, Guinea Pigs, Inactivation, Metabolic, Injections, Intralesional, Injections, Intramuscular, Injections, Intravenous, Injections, Subcutaneous, Male, Nerve Agents analysis, Nerve Agents metabolism, Organophosphate Poisoning blood, Organophosphate Poisoning etiology, Organophosphate Poisoning metabolism, Organothiophosphorus Compounds administration & dosage, Organothiophosphorus Compounds antagonists & inhibitors, Organothiophosphorus Compounds metabolism, Peptide Fragments metabolism, Peptide Fragments pharmacokinetics, Peptide Fragments therapeutic use, Phosphoric Triester Hydrolases genetics, Phosphoric Triester Hydrolases pharmacokinetics, Phosphoric Triester Hydrolases therapeutic use, Proteolysis, Pseudomonas enzymology, Recombinant Proteins administration & dosage, Recombinant Proteins metabolism, Recombinant Proteins pharmacokinetics, Recombinant Proteins therapeutic use, Toxicokinetics, Antidotes administration & dosage, Mutation, Nerve Agents toxicity, Organophosphate Poisoning drug therapy, Organothiophosphorus Compounds toxicity, Peptide Fragments administration & dosage, Phosphoric Triester Hydrolases administration & dosage
- Abstract
The recent attacks with the nerve agent sarin in Syria reveal the necessity of effective countermeasures against highly toxic organophosphorus compounds. Multiple studies provide evidence that a rapid onset of antidotal therapy might be life-saving but current standard antidotal protocols comprising reactivators and competitive muscarinic antagonists show a limited efficacy for several nerve agents. We here set out to test the newly developed phosphotriesterase (PTE) mutant C23AL by intravenous (i.v.), intramuscular (i.m.; model for autoinjector) and intraosseous (i.o.; model for intraosseous insertion device) application in an in vivo guinea pig model after VX challenge (∼2LD50). C23AL showed a Cmax of 0.63μmolL(-1) after i.o. and i.v. administration of 2mgkg(-1) providing a stable plasma profile up to 180min experimental duration with 0.41 and 0.37μmolL(-1) respectively. The i.m. application of C23AL did not result in detectable plasma levels. All animals challenged with VX and subsequent i.o. or i.v. C23AL therapy survived although an in part substantial inhibition of erythrocyte, brain and diaphragm AChE was detected. Theoretical calculation of the time required to hydrolyze in vivo 96.75% of the toxic VX enantiomer is consistent with previous studies wherein similar activity of plasma containing catalytic scavengers of OPs resulted in non-lethal protection although accompanied with a variable severity of cholinergic symptoms. The relatively low C23AL plasma level observed immediately after its i.v. or i.o load, point at a possible volume of distribution greater than the guinea pig plasma content, and thus underlines the necessity of in vivo experiments in antidote research. In conclusion the i.o. application of PTE is efficient and resulted in comparable plasma levels to the i.v. application at a given time. Thus, i.o. vascular access systems could improve the post-exposure PTE therapy of nerve agent poisoning., (Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.)
- Published
- 2016
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11. On-site analysis of acetylcholinesterase and butyrylcholinesterase activity with the ChE check mobile test kit-Determination of reference values and their relevance for diagnosis of exposure to organophosphorus compounds.
- Author
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Worek F, Schilha M, Neumaier K, Aurbek N, Wille T, Thiermann H, and Kehe K
- Subjects
- Adolescent, Adult, Aged, Female, Humans, Male, Middle Aged, Reference Values, Acetylcholinesterase metabolism, Butyrylcholinesterase metabolism, Organophosphorus Compounds toxicity, Reagent Kits, Diagnostic
- Abstract
Poisoning by organophosphorus compounds (OP) still poses a major medical challenge. Diagnosis of clinical signs of OP poisoning is still the most important parameter for the initiation of specific treatment. However, in case of unspecific signs and of delayed onset of cholinergic crisis a rapid, reliable and on-site analysis of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) activity would be of great value. Recently the ChE check mobile, a CE-certified ready to use kit for the determination of whole blood AChE and BChE activities, was developed. Here, we evaluated whole blood AChE and BChE reference values with samples taken from 181 male and 61 female volunteers and analyzed them on-site with the ChE check mobile test kit. The analysis of the data revealed a large inter-individual variability (BChE>AChE), only a small sex difference for AChE but a significant difference for BChE activities. The now available normal range values enable an evaluation of determined AChE and BChE activities in case of suspected exposure to OP nerve agents and pesticides. However, the large inter-individual variability of AChE and BChE activities calls for the determination of pre-exposure values in specific subpopulations in order to enable the diagnosis of low-level OP exposure., (Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.)
- Published
- 2016
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12. Kinetic analysis of interactions of amodiaquine with human cholinesterases and organophosphorus compounds.
- Author
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Bierwisch A, Wille T, Thiermann H, and Worek F
- Subjects
- Humans, Kinetics, Soman pharmacology, Amodiaquine pharmacology, Cholinesterase Inhibitors pharmacology, Cholinesterase Reactivators pharmacology, Organophosphorus Compounds pharmacology
- Abstract
Standard therapy of poisoning by organophosphorus compounds (OP) is a combined administration of an anti-muscarinic drug (e.g. atropine) and an oxime as reactivator of inhibited acetylcholinesterase (AChE). Limited efficacy of clinically used oximes against a variety of OPs was shown in numerous studies, calling for research on novel reactivators of OP-inhibited AChE. Recently, reactivation of OP-inhibited AChE by the antimalarial drug amodiaquine was reported. In the present study, amodiaquine and its interactions with human cholinesterases in presence or absence of OP nerve agents was investigated in vitro. Thereby, reversible inhibition of human cholinesterases by amodiaquine (AChE ≫ BChE) was observed. Additionally, a mixed competitive-non-competitive inhibition type of amodiaquine with human AChE was determined. Slow and partial reactivation of sarin-, cyclosarin- and VX-inhibited cholinesterases by amodiaquine was recorded, amodiaquine failed to reactivate tabun-inhibited human cholinesterases. Amodiaquine, being a potent, reversible AChE inhibitor, was tested for its potential benefit as a pretreatment to prevent complete irreversible AChE inhibition by the nerve agent soman. Hereby, amodiaquine failed to prevent phosphonylation and resulted only in a slight increase of AChE activity after removal of amodiaquine and soman. At present the molecular mechanism of amodiaquine-induced reactivation of OP-inhibited AChE is not known, nevertheless amodiaquine could be considered as a template for the design of more potent non-oxime reactivators., (Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.)
- Published
- 2016
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13. Catalytic bioscavengers in nerve agent poisoning: A promising approach?
- Author
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Worek F, Thiermann H, and Wille T
- Subjects
- Animals, Biocatalysis, Biotransformation, Enzyme Stability, Half-Life, Humans, Nerve Agents pharmacokinetics, Poisoning blood, Substrate Specificity, Antidotes therapeutic use, Enzyme Therapy, Nerve Agents poisoning, Poisoning drug therapy
- Abstract
The repeated use of the nerve agent sarin against civilians in Syria in 2013 emphasizes the continuing threat by chemical warfare agents. Multiple studies demonstrated a limited efficacy of standard atropine-oxime treatment in nerve agent poisoning and called for the development of alternative and more effective treatment strategies. A novel approach is the use of stoichiometric or catalytic bioscavengers for detoxification of nerve agents in the systemic circulation prior to distribution into target tissues. Recent progress in the design of enzyme mutants with reversed stereo selectivity resulting in improved catalytic activity and their use in in vivo studies supports the concept of catalytic bioscavengers. Yet, further research is necessary to improve the catalytic activity, substrate spectrum and in vivo biological stability of enzyme mutants. The pros and cons of catalytic bioscavengers will be discussed in detail and future requirements for the development of catalytic bioscavengers will be proposed., (Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.)
- Published
- 2016
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14. Kinetics of pesticide degradation by human fresh frozen plasma (FFP) in vitro.
- Author
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von der Wellen J, Bierwisch A, Worek F, Thiermann H, and Wille T
- Subjects
- Aryldialkylphosphatase blood, Carboxylic Ester Hydrolases blood, Half-Life, Humans, Hydrolysis, Kinetics, Pesticides blood, Plasma metabolism
- Abstract
There is an ongoing debate about the benefit of fresh frozen plasma (FFP) infusion in organophosphorus (OP) pesticide-poisoned patients. This prompted us to investigate the kinetics of OP pesticide degradation by FFP with an enzymatic assay in vitro. Degradation was rapid with shortest half-lives of 19.5s for chlorpyrifos-oxon, 6.3min for paraoxon-ethyl and 17.9min for dichlorvos. Heptenophos (78.0min), mevinphos (101.8min), profenofos (162.3min) and malaoxon (179.7min) showed half-lives of up to 3h. Substantial longer degradation half-lives of 69.7-80.8h were determined with chlorfenvinphos and bromfenvinphos. Methamidophos and omethoate showed no degradation by FFP indicated by half-lives similar to spontaneous hydrolysis. In conclusion, degradation by FFP depends on the particular OP pesticide and the used FFP batch., (Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.)
- Published
- 2016
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15. A novel fluorogenic probe for the investigation of free thiols: Application to kinetic measurements of acetylcholinesterase activity.
- Author
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Mertens MD, Bierwisch A, Li T, Gütschow M, Thiermann H, Wille T, and Elsinghorst PW
- Subjects
- Algorithms, GPI-Linked Proteins metabolism, Humans, Kinetics, Least-Squares Analysis, Nonlinear Dynamics, Signal Processing, Computer-Assisted, Spectrometry, Fluorescence, Acetylcholinesterase metabolism, Coumarins metabolism, Fluorescent Dyes metabolism, Sulfhydryl Compounds metabolism
- Abstract
A novel coumarin-derived thiol probe, based on the thiol-promoted cleavage of a quenching 2,4-dinitrobenzenesulfonyl group is described. The probe shows a sensitive fluorescence turn-on and sufficient solubility in aqueous environments. As a proof of concept, a new assay for AChE activity was developed as a useful addition to the established Ellman method. The observed reaction kinetics followed an asymmetric sigmoidal pattern and were successfully evaluated applying a three parameter Gompertz equation. Providing a linear relationship between the detected fluorescence formation curves and corresponding enzyme activities, this probe appears as a valuable tool for AChE activity measurements., (Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.)
- Published
- 2016
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16. Investigation of the reactivation kinetics of a large series of bispyridinium oximes with organophosphate-inhibited human acetylcholinesterase.
- Author
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Winter M, Wille T, Musilek K, Kuca K, Thiermann H, and Worek F
- Subjects
- Acetylcholinesterase metabolism, Cholinesterase Reactivators chemistry, Dose-Response Relationship, Drug, GPI-Linked Proteins antagonists & inhibitors, GPI-Linked Proteins metabolism, Humans, Kinetics, Molecular Structure, Organophosphates toxicity, Organophosphorus Compounds toxicity, Oximes chemistry, Paraoxon toxicity, Pyridinium Compounds chemistry, Structure-Activity Relationship, Cholinesterase Inhibitors toxicity, Cholinesterase Reactivators pharmacology, Oximes pharmacology, Pyridinium Compounds pharmacology
- Abstract
The limited effectiveness of the established oximes obidoxime and pralidoxime resulted in ongoing research on novel oximes for the reactivation of acetylcholinesterase (AChE) inhibited by organophosphorus compounds (OP). In order to get more insight into the ability of bispyridinium oximes to reactivate human AChE inhibited by structurally different OP the reactivation kinetics of 31 compounds was determined with tabun-, cyclosarin- and paraoxon-inhibited AChE under identical experimental conditions. The determined affinity (KD), reactivity (kr) and hybrid reactivation rate constants (kr2) enabled theoretical calculations and gave insight into distinct structural features which are important for the reactivation of AChE inhibited by different OP. Several oximes with superior reactivating potency towards selective OP-AChE conjugates were identified but none of the tested oximes can be considered as a broad spectrum reactivator. In the end, the data of this and previous studies gives rise to the question whether further modifications of the bispyridinium structure could ever result in a universal reactivator or whether future research should be directed to different templates., (Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.)
- Published
- 2016
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17. Effectiveness of a substituted β-cyclodextrin to prevent cyclosarin toxicity in vivo.
- Author
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Worek F, Seeger T, Zengerle M, Kubik S, Thiermann H, and Wille T
- Subjects
- Acetylcholinesterase metabolism, Animals, Antidotes administration & dosage, Brain drug effects, Brain enzymology, Cytoprotection, Erythrocytes drug effects, Erythrocytes enzymology, Guinea Pigs, Injections, Intravenous, Lethal Dose 50, Male, Organophosphate Poisoning enzymology, Time Factors, beta-Cyclodextrins administration & dosage, Antidotes pharmacology, Chemical Warfare Agents toxicity, Cholinesterase Inhibitors toxicity, Organophosphate Poisoning prevention & control, Organophosphorus Compounds toxicity, beta-Cyclodextrins pharmacology
- Abstract
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., (Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.)
- Published
- 2014
- Full Text
- View/download PDF
18. New modified β-cyclodextrin derivatives as detoxifying agents of chemical warfare agents (I). Synthesis and preliminary screening: evaluation of the detoxification using a half-quantitative enzymatic assay.
- Author
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Kalakuntla RK, Wille T, Le Provost R, Letort S, Reiter G, Müller S, Thiermann H, Worek F, Gouhier G, Lafont O, and Estour F
- Subjects
- Acetylcholinesterase metabolism, Cholinesterase Inhibitors chemical synthesis, Cholinesterase Inhibitors chemistry, Magnetic Resonance Spectroscopy, Molecular Structure, Organophosphorus Compounds antagonists & inhibitors, Spectrometry, Mass, Electrospray Ionization, Stereoisomerism, beta-Cyclodextrins chemical synthesis, beta-Cyclodextrins chemistry, Chemical Warfare Agents pharmacokinetics, Cholinesterase Inhibitors pharmacology, Organophosphorus Compounds pharmacokinetics, beta-Cyclodextrins pharmacology
- Abstract
Current treatments of organophosphorus nerve agents poisoning are imperfect, and more efficient medical countermeasures need to be developed. Chemical scavengers based on β-cyclodextrin displayed promising results, but further investigations have to be performed to evaluate the possibility of application of substituted cyclodextrins as potential detoxification agents. Herein, five new cyclodextrins scavengers were synthesized. New optimal conditions for regioselectively monosubstitution of β-cyclodextrin at O-2 position were then studied to access to key intermediates. After these optimizations, a new series of three permethylated derivatives was developed, and two compounds bearing an α-nucleophilic group via a three carbon atoms linker were prepared. The ability of these five scavengers to detoxify nerve agents (cyclosarin, soman, tabun and VX) was evaluated by a semi-quantitative biological assay. All the modified cyclodextrins significantly decreased the inhibitory effect of chemical warfare G agents on acetylcholinesterase activity. For this purpose, we showed that the specific interactions between the organophosphorus compound and the oligosaccharidic moiety of the scavenger played a pivotal role in the detoxification process., (Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.)
- Published
- 2013
- Full Text
- View/download PDF
19. Kinetic interactions of a homologous series of bispyridinium monooximes (HGG oximes) with native and phosphonylated human acetylcholinesterase.
- Author
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Worek F, Bierwisch A, Wille T, Koller M, and Thiermann H
- Subjects
- Cholinesterase Reactivators pharmacology, Humans, Inhibitory Concentration 50, Kinetics, Linear Models, Oximes pharmacology, Acetylcholinesterase metabolism, Cholinesterase Reactivators pharmacokinetics, Organophosphorus Compounds pharmacology, Oximes pharmacokinetics
- Abstract
Inhibition of acetylcholinesterase (AChE) is the main toxic mechanism of organophosphorus compounds (OP) and reactivation of OP-inhibited AChE by oximes is a mainstay of antidotal treatment. The inadequate efficacy of clinically used oximes led to the synthesis of numerous new compounds in the past decades to identify more effective reactivators. Despite of extensive in vitro reactivation studies the structural features for the development of effective oximes are not well understood. In the present study we investigated the kinetic interactions of a homologous series of bispyridinium monoximes bearing C1 to C12 alkylketone groups on the second pyridinium ring with native and cyclosarin-inhibited human AChE. We observed a correlation of the length of the alkyl side chain with an up to 20-fold increased affinity towards native AChE. The effect of the alkyl side chain on the affinity and reactivity towards phosphonylated AChE was moderate, except of a markedly reduced reactivity of C10 and C12 oximes. In comparison to the reference oxime HI-6 all HGG oximes had a lower reactivating potency and these oximes are not considered as promising compounds for the reactivation of cyclosarin-inhibited AChE., (Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.)
- Published
- 2012
- Full Text
- View/download PDF
20. In vitro detoxification of cyclosarin (GF) by modified cyclodextrins.
- Author
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Müller S, Koller M, Le Provost R, Lafont O, Estour F, Wille T, Thiermann H, Worek F, and Reiter G
- Subjects
- Hydrolysis, In Vitro Techniques, Kinetics, Organophosphorus Compounds pharmacokinetics, beta-Cyclodextrins pharmacology, Antidotes pharmacology, Cholinesterase Inhibitors pharmacology, Cyclodextrins pharmacology, Organophosphorus Compounds antagonists & inhibitors
- Abstract
Developing potent detoxification strategies for prophylaxis and therapy against organophosphate (OP) intoxication still represents a challenging task. Clinical application of numerous investigated substances including enzymes and low molecular scavengers like metal ions or nucleophiles could not yet be realised due to profound disadvantages. Presenting a promising attempt, cyclodextrins (CDs) efficiently enhance the degradation of some organophosphorus compounds. The present study examined the in vitro GF degradation mediated by three CDs and a nucleophilic precursor performed by mass spectrometric detection with ammonia chemical ionisation. All four compounds caused a notable enhancement of GF detoxification that was synergistically accelerated in the case of 2-O-(3-carboxy-4-iodosobenzyl)-β-cyclodextrin (IBA-β-CD) with the alpha-nucleophile 2-iodosobenzoic acid (IBA) grafted on the secondary face of β-cyclodextrin (β-CD). In vitro toxicokinetic investigations of CD derivatives are needed to evaluate the effect of slow terminal elimination phase of the more toxic (-)-GF shown for two CD-derivatives underlining the necessity of detecting the complete kinetic course of inactivation. The observed effect of fast high affinity binding (20-30%) represents an additional therapeutic option of an extremely rapid reduction of GF concentration in vivo. Distinctive differences in the course of reaction are detected depending on β-CD-derivatives, allowing a first inference of possible mechanisms and relevance of attached substituents. However, further profound investigation needs to be done to evaluate the basis of a clinical application of substituted CDs as potential detoxification agents., (Copyright © 2010 Elsevier Ireland Ltd. All rights reserved.)
- Published
- 2011
- Full Text
- View/download PDF
21. Kinetic analysis of interactions of paraoxon and oximes with human, Rhesus monkey, swine, rabbit, rat and guinea pig acetylcholinesterase.
- Author
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Worek F, Aurbek N, Wille T, Eyer P, and Thiermann H
- Subjects
- Animals, Drug Interactions, Enzyme Reactivators pharmacology, Guinea Pigs, Humans, Kinetics, Macaca mulatta, Obidoxime Chloride pharmacology, Pralidoxime Compounds pharmacology, Pyridinium Compounds pharmacology, Rabbits, Rats, Rats, Wistar, Species Specificity, Swine, Acetylcholinesterase drug effects, Cholinesterase Inhibitors pharmacology, Oximes pharmacology, Paraoxon pharmacology
- Abstract
Previous in vitro studies showed marked species differences in the reactivating efficiency of oximes between human and animal acetylcholinesterase (AChE) inhibited by organophosphorus (OP) nerve agents. These findings provoked the present in vitro study which was designed to determine the inhibition, aging, spontaneous and oxime-induced reactivation kinetics of the pesticide paraoxon, serving as a model compound for diethyl-OP, and the oximes obidoxime, pralidoxime, HI 6 and MMB-4 with human, Rhesus monkey, swine, rabbit, rat and guinea pig erythrocyte AChE. Comparable results were obtained with human and monkey AChE. Differences between human, swine, rabbit, rat and guinea pig AChE were determined for the inhibition and reactivation kinetics. A six-fold difference of the inhibitory potency of paraoxon with human and guinea pig AChE was recorded while only moderate differences of the reactivation constants between human and animal AChE were determined. Obidoxime was by far the most effective reactivator with all tested species. Only minor species differences were found for the aging and spontaneous reactivation kinetics. The results of the present study underline the necessity to determine the inhibition, aging and reactivation kinetics in vitro as a basis for the development of meaningful therapeutic animal models, for the proper assessment of in vivo animal data and for the extrapolation of animal data to humans., (Copyright © 2010 Elsevier Ireland Ltd. All rights reserved.)
- Published
- 2011
- Full Text
- View/download PDF
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