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Alahakoon C, Dassanayake TL, Gawarammana IB, Weerasinghe VS. Can we predict intermediate syndrome? A review. Neurotoxicology 2017; 69:209-216. [PMID: 29217407 DOI: 10.1016/j.neuro.2017.12.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2017] [Revised: 11/27/2017] [Accepted: 12/03/2017] [Indexed: 10/18/2022]
Abstract
INTRODUCTION Ingestion of organophosphorus insecticides (OPI) is a common method of deliberate self harm in the developing world. Deaths mainly follow as a result of the respiratory failure associated with both cholinergic crisis and the intermediate syndrome. Even though death can be prevented by early mechanical ventilation of these patients, limited studies are available regarding the prediction of intermediate syndrome and subsequent respiratory failure. OBJECTIVE To systematically review articles that are published with regard to possible prediction of intermediate syndrome using clinical, biochemical and electrophysiological parameters. METHODS A systematic review on literature published in English language was done in the PubMed database without a date limitation. Two sets of search terms were used. The first set consisted of MeSH Terms "organophosphates", "organophosphate poisoning", "op poisoning" "organophosphate insecticide poisoning" and "organophosphorus". The second set included the MeSH Terms "Intermediate syndrome", "proximal muscle weakness", "cranial nerve palsies", "respiratory depression" and "neck muscle weakness". Articles containing at least one word from each set were reviewed. RESULTS At least one MeSH term from each set was incorporated in 179 articles. Of these, 69 were rejected as they were not related to organophosphate poisoning or intermediate syndrome. PREDICTION OF IMS Clinical prediction is mostly based on ICU scoring systems. Biochemical markers such as reduced levels of serum and erythrocyte acetylcholine esterase have been studied many times. Both clinical and biochemical markers show a modest relationship in predicting IMS. Single fibre electromyography show promising results as it directly assesses neuromuscular junction. CONCLUSION The intermediate syndrome which follows organophosphate poisoning still remains a significant problem with its high morbidity. Clinical and biochemical markers show modest results in predicting IMS. Neurophysiological markers such as single fibre EMG should be studied further as they measure activity of affected nicotinic receptors directly.
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Affiliation(s)
- Chanika Alahakoon
- Department of Physiology, University of Peradeniya, Peradeniya, 20400, Sri Lanka; South Asian Clinical Toxicology Research Collaboration, University of Peradeniya, Peradeniya, 20400, Sri Lanka.
| | - Tharaka Lagath Dassanayake
- Department of Physiology, University of Peradeniya, Peradeniya, 20400, Sri Lanka; South Asian Clinical Toxicology Research Collaboration, University of Peradeniya, Peradeniya, 20400, Sri Lanka; School of Psychology, The University of Newcastle, Sydney, Australia.
| | - Indika Bandara Gawarammana
- South Asian Clinical Toxicology Research Collaboration, University of Peradeniya, Peradeniya, 20400, Sri Lanka; Department of Medicine, University of Peradeniya, Peradeniya,20400, Sri Lanka.
| | - Vajira Senaka Weerasinghe
- Department of Physiology, University of Peradeniya, Peradeniya, 20400, Sri Lanka; South Asian Clinical Toxicology Research Collaboration, University of Peradeniya, Peradeniya, 20400, Sri Lanka.
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Worek F, Thiermann H, Wille T. The oximes HI-6 and MMB-4 fail to reactivate soman-inhibited human and guinea pig AChE: A kinetic in vitro study. Toxicol Lett 2017; 293:216-221. [PMID: 28993240 DOI: 10.1016/j.toxlet.2017.10.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2017] [Revised: 09/26/2017] [Accepted: 10/04/2017] [Indexed: 11/18/2022]
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.
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Affiliation(s)
- Franz Worek
- Bundeswehr Institute of Pharmacology and Toxicology, Munich, Germany.
| | - Horst Thiermann
- Bundeswehr Institute of Pharmacology and Toxicology, Munich, Germany
| | - Timo Wille
- Bundeswehr Institute of Pharmacology and Toxicology, Munich, Germany
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Neumaier K, Worek F, Thiermann H, Wille T. Bispyridinium non-oximes: An evaluation of cardiac effects in isolated hearts and smooth muscle relaxing effects in jejunum. Toxicol In Vitro 2016; 35:11-6. [DOI: 10.1016/j.tiv.2016.05.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2016] [Revised: 05/10/2016] [Accepted: 05/11/2016] [Indexed: 10/21/2022]
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Application of a dynamic in vitro model with real-time determination of acetylcholinesterase activity for the investigation of tabun analogues and oximes. Toxicol In Vitro 2015; 30:514-20. [DOI: 10.1016/j.tiv.2015.09.010] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2015] [Revised: 08/22/2015] [Accepted: 09/01/2015] [Indexed: 11/17/2022]
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Elsinghorst PW, Worek F, Thiermann H, Wille T. Drug development for the management of organophosphorus poisoning. Expert Opin Drug Discov 2013; 8:1467-77. [PMID: 24125474 DOI: 10.1517/17460441.2013.847920] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
INTRODUCTION The continuous application of organophosphate pesticides in developing countries, in addition to the remaining stock piles of chemical warfare nerve agents and their possible use is a significant threat to the public. Yet, today's options for a treatment of organophosphorus poisonings are still inadequate. AREAS COVERED This article provides a concise overview of current and future research trying to improve both prophylaxis and treatment of organophosphorus intoxications. The authors provide a summary of current oxime therapy and highlight several new concepts to overcome existing gaps. This overview of therapeutic options is accompanied by two sections on cyclodextrins, related compounds and bioscavengers, which may be used for either prophylaxis or treatment. For both groups, the authors review current drug design and screening approaches, the resulting developments and future challenges. EXPERT OPINION While the search for one multipotent oxime has been a fruitless endeavor, combination of multiple oximes with complemental and systemic reactivity appears as a valuable concept. Development of potential scavengers, be it cyclodextrins or bioscavengers, is still hampered by insufficient efficacy of these compounds. Future strategies will aim at improving their catalytic efficacy while minimizing immunogenicity.
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Affiliation(s)
- Paul Wilhelm Elsinghorst
- Bundeswehr Institute of Pharmacology and Toxicology , Neuherbergstraße 11, D-80937 München , Germany +49 89 3168 2305 ; +49 89 3168 2333 ;
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The value of novel oximes for treatment of poisoning by organophosphorus compounds. Pharmacol Ther 2013; 139:249-59. [DOI: 10.1016/j.pharmthera.2013.04.009] [Citation(s) in RCA: 120] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2013] [Accepted: 04/08/2013] [Indexed: 11/23/2022]
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Seeger T, Eichhorn M, Lindner M, Niessen K, Tattersall J, Timperley C, Bird M, Green A, Thiermann H, Worek F. Restoration of soman-blocked neuromuscular transmission in human and rat muscle by the bispyridinium non-oxime MB327 in vitro. Toxicology 2012; 294:80-4. [DOI: 10.1016/j.tox.2012.02.002] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2012] [Revised: 02/02/2012] [Accepted: 02/04/2012] [Indexed: 11/17/2022]
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Fišar Z, Hroudová J, Korábečný J, Musílek K, Kuča K. In vitro effects of acetylcholinesterase reactivators on monoamine oxidase activity. Toxicol Lett 2011; 201:176-80. [DOI: 10.1016/j.toxlet.2010.12.023] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2010] [Revised: 12/21/2010] [Accepted: 12/23/2010] [Indexed: 01/10/2023]
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Voicu VA, Bajgar J, Medvedovici A, Radulescu FS, Miron DS. Pharmacokinetics and pharmacodynamics of some oximes and associated therapeutic consequences: a critical review. J Appl Toxicol 2010; 30:719-29. [PMID: 20635332 DOI: 10.1002/jat.1561] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2010] [Revised: 05/21/2010] [Accepted: 05/21/2010] [Indexed: 11/10/2022]
Abstract
Undoubtedly, the use of oximes represents real progress in counteracting intoxications with organophosphates (OP), through potentiating antidotal effects of atropine. The penetration extent of these compounds through the blood-brain barrier (BBB) to significantly reactivate phosphorylated or phosphonylated acetylcholinesterase (AChE) in the brain still remains a debatable issue. Penetration of biological barriers by oximes was investigated mainly through determination of several quantitative parameters characterizing digestive absorption and BBB penetration. A weak penetration of biological barriers could be concluded from the available experimental data. The functional parameters/therapeutic effects following the penetration of oximes through BBB, more precisely the antagonism of OP-induced seizures and hypothermia, prevention of brain damage and respiratory center protection, leading to the final end-point, the survival of intoxicated organisms, are of high interest. It seems obvious that oximes are weakly penetrating the BBB, with minimal brain AChE reactivation (<5%) in important functional areas, such as the ponto-medullar. The cerebral protection achieved through administration of oximes is only partial, without major impact on the antagonism of OP-induced seizures, hypothermia and respiratory center inhibition. The antidotal effects probably result from synergic effects of other PD properties, different from the brain AChE reactivation process. Oxime structures especially designed for enhanced BBB penetration, through potentiating the hydrophobic characteristics, more often produce neurotoxic effects. Certainly, obtaining oximes with broad action spectrum (active against all OP types) would make a sense, but certainly, such a target is not achievable only through the increase in their penetrability in the brain.
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Affiliation(s)
- Victor A Voicu
- University of Medicine and Pharmacy Carol Davila, Clinical Pharmacology, Toxicology and Psychopharmacology, Bucharest, Romania.
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10
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Abstract
The use of organophosphorus pesticides results in toxicity risk to non-target organisms. Organophosphorus compounds share a common mode of action, exerting their toxic effects primarily via acetylcholinesterase (AChE) inhibition. Consequently, acetylcholine accumulates in the synaptic clefts of muscles and nerves, leading to overstimulation of cholinergic receptors. Acute cholinergic crisis immediately follows exposure to organophosphate and includes signs and symptoms resulting from hyperstimulation of central and peripheral muscarinic and nicotinic receptors. The current view of the treatment of organophosphate poisoning includes three strategies, i.e. the use of an anticholinergic drug (e.g., atropine), cholinesterase-reactivating agents (e.g., oximes) and anticonvulsant drugs (e.g., benzodiazepines). Oximes, as a part of antidotal therapy, ensure the recovery of phosphylated enzymes via a process denoted as reactivation of inhibited AChE. However, both experimental results and clinical findings have demonstrated that different oximes are not equally effective against poisonings caused by structurally different organophosphorus compounds. Therefore, antidotal characteristics of conventionally used oximes can be evaluated regarding how close the certain substance is to the theoretical concept of the universal oxime. Pralidoxime (PAM-2), trimedoxime (TMB-4), obidoxime (LüH-6), HI-6 and HLö-7 have all been demonstrated to be very effective in experimental poisonings with sarin and VX. TMB-4 and LüH-6 may reactivate tabun-inhibited AChE, whereas HI-6 possesses the ability to reactivate the soman-inhibited enzyme. An oxime HLö-7 seems to be an efficient reactivator of AChE inhibited by any of the four organophosphorus warfare agents. According to the available literature, the oximes LüH-6 and TMB-4, although relatively toxic, are the most potent to induce reactivation of AChE inhibited by the majority of organophosphorus pesticides. Since there are no reports of controlled clinical trials on the use of TMB-4 in human organophosphate pesticide poisoning, LüH-6 may be a better option.
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Affiliation(s)
- Biljana Antonijevic
- Institute of Toxicological Chemistry, Faculty of Pharmacy, University of Belgrade, Vojvode Stepe 450, 11221 Belgrade, Serbia.
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Worek F, Eyer P, Aurbek N, Szinicz L, Thiermann H. Recent advances in evaluation of oxime efficacy in nerve agent poisoning by in vitro analysis. Toxicol Appl Pharmacol 2007; 219:226-34. [DOI: 10.1016/j.taap.2006.10.001] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2006] [Revised: 09/30/2006] [Accepted: 10/02/2006] [Indexed: 10/24/2022]
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Lundy PM, Raveh L, Amitai G. Development of the Bisquaternary Oxime HI-6 Toward Clinical Use in the Treatment of Organophosphate Nerve Agent Poisoning. ACTA ACUST UNITED AC 2006; 25:231-43. [PMID: 17288495 DOI: 10.2165/00139709-200625040-00004] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The traditional therapeutic treatment of organophosphate cholinesterase inhibitor (nerve agents) poisoning consists of co-treatment with an antimuscarinic (atropine) and a reactivator of inhibited acetylcholinesterase (AChE), which contains a nucleophilic oxime function. Two oximes are presently widely available for clinical use, pralidoxime and obidoxime (toxogonin), but both offer little protection against important nerve agent threats. This has highlighted the real need for the development and availability of more effective oximes for human use, a search that has been going on for up to 30 years. However, despite the demonstration of more effective and safe oximes in animal experiments, no additional oximes have been licensed for human use. HI-6, (1-[[[4(aminocarbonyl)-pyridinio]methoxy]methyl]-2(hydroxyimino)pyridinium dichloride; CAS 34433-31-3) has been studied intensively and has been proved effective in a variety of species including non-human primates and appears from clinical experience to be safe in humans. These studies have led to the fielding of HI-6 for use against nerve agents by the militaries of the Czech republic, Sweden, Canada and under certain circumstances the Organisation for the Prohibition of Chemical Weapons. Nevertheless HI-6 has not been granted a license for clinical use, must be used only under restricted guidelines and is not available for civilian use as far as is known. This article will highlight those factors relating to HI-6 that pertain to the licensing of new compounds of this type, including the mechanism of action, the clinical and pre-clinical demonstration of safety and its efficacy against a variety of nerve agents particularly in non-human primates, since no relevant human population exists. This article also contains important data on the use of HI-6 in baboons, which has not been available previously. The article also discusses the possibility of successful therapy with HI-6 against poisoning in humans relative to doses used in non-human primates and relative to its ability to reactivate inhibited human AChE.
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Affiliation(s)
- Paul M Lundy
- Therapeutic Response, Medicine Hat, Alberta, Canada
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Antonijević B, Bokonjić D, Stojiljković MP, Kilibarda V, Milovanović ZA, Nedeljković M, Maksimović M. Efficacy of Trimedoxime in Mice Poisoned with Dichlorvos, Heptenophos or Monocrotophos. Basic Clin Pharmacol Toxicol 2005; 96:111-7. [PMID: 15679473 DOI: 10.1111/j.1742-7843.2005.pto960204.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The aim of the study was to examine antidotal potency of trimedoxime in mice poisoned with three direct dimethoxy-substituted organophosphorus inhibitors. In order to assess the protective efficacy of trimedoxime against dichlorvos, heptenophos or monocrotophos, median effective doses and efficacy half-times were calculated. Trimedoxime (24 mg/kg intravenously) was injected 5 min. before 1.3 LD50 intravenously of poisons. Activities of brain, diaphragmal and erythrocyte acetylcholinesterase, as well as of plasma carboxylesterases were determined at different time intervals (10, 40 and 60 min.) after administration of the antidotes. Protective effect of trimedoxime decreased according to the following order: monocrotophos > heptenophos > dichlorvos. Administration of the oxime produced a significant reactivation of central and peripheral acetylcholinesterase inhibited with dichlorvos and heptenophos, with the exception of erythrocyte acetylcholinesterase inhibited by heptenophos. Surprisingly, trimedoxime did not induce reactivation of monocrotophos-inhibited acetylcholinesterase in any of the tissues tested. These organophosphorus compounds produced a significant inhibition of plasma carboxylesterase activity, while administration of trimedoxime led to regeneration of the enzyme activity. The same dose of trimedoxime assured survival of experimental animals poisoned by all three organophosphorus compounds, although the biochemical findings were quite different.
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Affiliation(s)
- Biljana Antonijević
- Institute of Toxicological Chemistry, School of Pharmacy, University of Belgrade, Vojvode Stepe 450, Serbia and Montenegro.
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Leader H, Vincze A, Manisterski B, Rothschild N, Dosoretz C, Ashani Y. Characterization of O,O-diethylphosphoryl oximes as inhibitors of cholinesterases and substrates of phosphotriesterases. Biochem Pharmacol 1999; 58:503-15. [PMID: 10424771 DOI: 10.1016/s0006-2952(99)00117-3] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Reactivators of organophosphate (OP)-inhibited cholinesterases (ChEs) are believed to give rise to phosphorylated oximes (POX) that reinhibit the enzyme. Diethylphosphoryl oximes (DEP-OX) that were generated in situ were demonstrated in the past to be unstable, yet were more potent inhibitors of acetylcholinesterase (AChE) than the parent OPs. In view of the inconsistencies among reported results, and the potential toxicity of POXs, it seemed important to characterize authentic DEP-OXs, and to evaluate their interference with reactivation of diethylphosphoryl-ChE (DEP-ChE) conjugates. To this end, the diethylphosphoric acid esters of 1-methyl-2-pyridinium carboxaldehyde oxime (DEP-2PAM) and 1-methyl-4 pyridinium carboxaldehyde oxime (DEP-4PAM) were synthesized and chemically defined. The half-lives of DEP-2PAM and DEP-4PAM in 10 mM Tris buffer, pH 7.8, at 29 degrees were found to be 10 and 980 sec, respectively. The two DEP-OXs inhibited ChEs with the following ranking order: for DEP-2PAM, human butyrylcholinesterase (HuBChE, k(i) = 2.03 x 10(9) M(-1) min(-1)) > mouse AChE (MoAChE) approximately equal to fetal bovine serum AChE (FBS-AChE) approximately equal to equine BChE (EqBChE); for DEP-4PAM, HuBChE (k(i) = 0.71 x 10(9) M(-1) min(-1)) > EqBChE > MoAChE > FBS-AChE. A dialkylarylphosphate hydrolase (phosphotriesterase; PTE) from Pseudomonas sp. catalyzed the hydrolysis of DEP-4PAM with k(cat)/Km = 3.56 x 10(7) M(-1) min(-1) and Km = 0.78 mM. Reactivation of DEP-ChEs was enhanced by PTE when 4-PAM-based oximes were used as reactivators, whereas reactivation with 2-PAM-based oximes was not affected by PTE. This observation is attributed primarily to the short half-life of DEP-OXs derived from the latter oximes. Relatively low doses of PTE can detoxify large quantities of DEP-OXs rapidly, and thereby augment the efficacy of antidotes that contain the oxime function in position 4 of the pyridine ring.
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Affiliation(s)
- H Leader
- Israel Institute for Biological Research, Ness-Ziona
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Kassa J, Bajgar J. Changes of acetylcholinesterase activity in various parts of brain following nontreated and treated soman poisoning in rats. MOLECULAR AND CHEMICAL NEUROPATHOLOGY 1998; 33:175-84. [PMID: 9642671 DOI: 10.1007/bf02815180] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Changes of acetylcholinesterase (AChE) activity in various parts of the brain (frontal cortex, medulla oblongata, pons Varoli, cerebellum, hypothalamus, and hippocampus), following im sublethal non-treated and treated soman poisoning were studied. As a treatment, two antidotal mixtures containing atropine and either obidoxime or oxime HI-6 were used. This antidotal treatment was administered im for 30 s following soman intoxication. The AChE activities in the various brain tissues were evaluated at 1 and 3 h following soman administration. As expected, the highly toxic organophosphorus compound, soman, markedly inhibited AChE activity in all the brain sections at both time intervals. Both oximes had little influence on soman-induced AChE inhibition, but only the HI-6 mixture was able to reactivate soman-inhibited AChE significantly in some of the brain parts (frontal cortex, pons Varoli, hypothalamus). In the brain, the effect of HI-6 against soman-induced AChE inhibition is higher in comparison with obidoxime, but not quite satisfactory. Despite its limited effectiveness in the brain, HI-6 seems to be the most effective oxime yet found against soman poisoning because of its high reactivating effect in the peripheral compartment and other beneficial effects.
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Affiliation(s)
- J Kassa
- Purkynĕ Military Medical Academy, Hradec Králové, Czech Republic.
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Kassa J, Fusek J. Effect of Panpal pretreatment and antidotal treatment (HI-6 plus benactyzine) on respiratory and circulatory function in soman-poisoned rats. Hum Exp Toxicol 1997; 16:563-9. [PMID: 9363473 DOI: 10.1177/096032719701601003] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
1 The effect of pharmacological pretreatment (pyridostigmine, benactyzine and trihexyphenidyle), designated Panpal, and antidotal treatment (the oxime HI-6 plus benactyzine) in soman poisoning was investigated in a rat model with on-line monitoring of respiratory and circulatory parameters. 2 Soman poisoning caused a high decrease in respiratory rate as well as minute respiratory volume and an increase in mean arterial pressure from 30-120 min following soman challenge. Soman at sublethal dose also significantly inhibited acetylcholinesterase activity in diaphragm and various brain parts. 3 Panpal pretreatment as well as antidotal treatment were effective in improving the respiratory and circulatory function disturbed by soman without the ability to increase significantly soman-inhibited acetylcholinesterase activity in all brain parts studied. 4 The efficacy of combined Panpal pretreatment and antidotal treatment against sublethal soman poisoning was not different from the efficacy of Panpal pretreatment or antidotal treatment alone. 5 The results of this investigation suggest that Panpal pretreatment as well as antidotal treatment are able to restore respiratory and circulatory function in soman-poisoned rats without significant reactivation of brain acetylcholinesterase.
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Affiliation(s)
- J Kassa
- Purkynĕ Military Medical Academy, Hradec Králové, Czech Republic
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Cassel G, Karlsson L, Waara L, Ang KW, Göransson-Nyberg A. Pharmacokinetics and effects of HI 6 in blood and brain of soman-intoxicated rats: a microdialysis study. Eur J Pharmacol 1997; 332:43-52. [PMID: 9298924 DOI: 10.1016/s0014-2999(97)01058-3] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The bispyridinium oxime HI 6 (1-(((4-amino-carbonyl)pyridino)methoxy)methyl)-2-(hydroxyimino )methyl)-pyridinium dichloride monohydrate), combined with atropine, is effective for treating poisoning with organophosphate nerve agents. The protective action of HI 6 in soman poisoning has been attributed mainly to its peripheral reactivation of inhibited acetylcholinesterase. In the present study we investigated whether high intramuscular doses of HI 6 can reach the brain in a sufficient amount to reactivate inhibited brain acetylcholinesterase. Microdialysis probes were implanted in the jugular vein and striatum and dialysis samples were collected simultaneously from the two sites in awake, freely moving rats. Pharmacokinetic parameters of unbound HI 6 in blood and brain were calculated after administration of HI 6 (50, 75 or 100 mg/kg i.m.) in control rats and rats injected with soman (90 microg/kg s.c., 0.9 LD50) 1 min before HI 6 treatment. We found that signs of soman poisoning correlated positively to acetylcholinesterase inhibition and negatively to the concentration of unbound HI 6 in the brain and that soman intoxication significantly decreased uptake of HI 6 into the brain.
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Affiliation(s)
- G Cassel
- Department of Biomedicine, Defence Research Establishment, Umea, Sweden.
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Aas P. In vitro effects of toxogonin, HI-6 and HLö-7 on the release of [3H]acetylcholine from peripheral cholinergic nerves in rat airway smooth muscle. Eur J Pharmacol 1996; 301:59-66. [PMID: 8773447 DOI: 10.1016/0014-2999(96)00027-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The purpose of this work was to evaluate the possible non-reactivating effects of toxogonin (1,1'[oxybis(methylene)]bis[4-[hydroxyimino) methyl]pyridinium]-dichloride), HI-6 (1-[[[(4-aminocarbonyl)pyridinio] methoxy]methyl]-2-[(hydroxyimino)methyl]pyridinium-dichloride) and HLö-7 (pyridinium, 1-[[[4-(aminocarbonyl)pyridino]methoxy] methyl]-2,4-bis-[(hydroxyimino)methyl]diiodide) on the release of acetylcholine from cholinergic nerves. The oximes have been tested in our rat bronchial smooth muscle model, with respect to the effects of oximes on the K+ (51 mM)-evoked release of [3H]acetylcholine in the presence and absence of soman (1.0 microM). Toxogonin (100 microM) had no effect on the K(+)-evoked release of [3H]acetylcholine in the presence or absence of soman (1.0 microM). Similar results were found for HI-6 (100 microM). In contrast, HLö-7 (100 microM) enhanced the K(+)-evoked release of [3H]acetylcholine in the absence of soman. In the presence of soman HLö-7 did not alter the release of [3H]acetylcholine induced by K+ stimulation. The potentiating effect of HLö-7 on the release of [3H]acetylcholine could be blocked by the L-, N- and P-Ca2+ channel blockers verapamil (0.1 and 1.0 microM), omega-conotoxin GVIA (1.0 microM) and omega-agatoxin IV-A (0.2 microM), respectively. Muscarinic receptor antagonists (atropine (10 microM), pirenzepine (M1) (1.0 microM) and methoctramine (M2) (1.0 microM) had no effects on the HLö-7 (100 microM)-enhanced release of [3H]acetylcholine. Protein kinase inhibitors (H-7 (20 microM), calphostin C (1.0 microM) and KN-62 (10 microM) inhibited the HLö-7 (100 microM)-enhanced K(+)-evoked release of [3H]acetylcholine. The results showed that only HLö-7 had a direct enhancing effect on the release of acetylcholine through activation or opening of Ca2+ channels and a subsequent protein phosphorylation in the nerve terminal.
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Affiliation(s)
- P Aas
- Norwegian Defence Research Establishment, Division for Environmental Toxicology, Kjeller, Norway
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19
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Göransson-Nyberg A, Cassel G, Jeneskog T, Karlsson L, Larsson R, Lundström M, Persson SA. Treatment of organophosphate poisoning in pigs: antidote administration by a new binary autoinjector. Arch Toxicol 1995; 70:20-7. [PMID: 8750901 DOI: 10.1007/s002040050244] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The therapeutic effectiveness of a new binary autoinjector containing 500 mg HI-6 and 2 mg atropine sulphate was tested in anesthetized pigs poisoned by a lethal dose of soman i.v. (9 micrograms/kg per 20 min). Pharmacokinetics and pharmacodynamics of HI-6 were studied concomitantly on administration of HI-6 alone, together with atropine sulphate, or together with atropine sulphate during soman intoxication. Cardiopulmonary parameters were monitored and serum concentrations of oxime and acetylcholinesterase (AChE) were measured in blood samples taken at intervals over a 6-h period postinjection. Five minutes after the start of soman infusion, mean AChE activity was decreased to 27 +/- 4.3% of baseline and signs of poisoning appeared. The antidotes, HI-6 and atropine sulphate, were then administered i.m. One minute after this injection there was a transient significant increase in AChE activity of 76 +/- 8.2% of baseline (p < 0.01). It then again decreased and remained suppressed throughout the experiment. Mean respiratory rate was significantly decreased (p < 0.01) to 20 +/- 3.2% of baseline after 20 min of soman infusion and remained low during the rest of the experiment. The poisoning signs were counteracted 15-20 min after antidote therapy and all pigs survived soman intoxication without ventilatory assistance. Administration of either atropine or atropine and soman had no significant effect on the pharmacokinetics of HI-6 in anesthetized pigs.
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Affiliation(s)
- A Göransson-Nyberg
- Division of Biomedicine, National Defense Research Establishment, Umea, Sweden
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20
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Worek F, Kleine A, Szinicz L. Effect of pyridostigmine pretreatment on cardiorespiratory function in tabun poisoning. Hum Exp Toxicol 1995; 14:634-42. [PMID: 7576830 DOI: 10.1177/096032719501400803] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
1. The effect of pyridostigmine on cardiorespiratory function after oxime + atropine injection was investigated in tabun poisoned guinea-pigs and without tabun poisoning. 2. The trachea, a carotid artery and jugular vein were cannulated in female urethane-anaesthetised Pirbright-white guinea-pigs. After baseline measurements the animals received pyridostigmine (0.05 mumol kg-1) and 30 min later atropine (29.5 mumol kg-1) plus obidoxime, HI 6 or HLö 7 (30 or 100 mumol kg-1) or tabun (1.85 mumol kg-1 = 5 x LD50) followed by oxime + atropine treatment (all i.v.). Erythrocyte, brain and diaphragm acetylcholinesterase (AChE) activity were determined. Similar groups without pretreatment were included for comparison. 3. Pyridostigmine aggravated the oxime + atropine induced hypotension and prevented the increase in heart rate but not the respiratory stimulation. The pyridostigmine inhibited AChE recovered only in the 100 mumol kg-1 kg oxime groups at the end of the experiment. 4. In tabun poisoning, pyridostigmine reduced the oxime + atropine induced circulatory recovery and decreased the survival time and rate. It did not affect the therapeutic oxime + atropine effect on respiratory function. 5. These results suggest that pyridostigmine enhances oxime + atropine related circulatory depression which may be the reason for the reduced efficacy of oxime + atropine treatment in tabun poisoning. The possible mechanisms are discussed.
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Affiliation(s)
- F Worek
- Walther-Straub-Institut für Pharmakologie und Toxikologie, Ludwig-Maximilians-Universität, München, Germany
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21
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Worek F, Szinicz L. Cardiorespiratory function in nerve agent poisoned and oxime + atropine treated guinea-pigs: effect of pyridostigmine pretreatment. Arch Toxicol 1995; 69:322-9. [PMID: 7654137 DOI: 10.1007/s002040050178] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The effect of pyridostigmine pretreatment on the efficacy of oxime + atropine treatment in sarin and VX poisoning was investigated in a guinea-pig model with on-line monitoring of respiratory and circulatory parameters. The carotid artery, jugular vein and trachea were cannulated in female urethane-anesthetized Pirbright-white guinea-pigs. After baseline measurements the animals received pyridostigmine (PYR, 0.05 mumol/kg, i.v.), 30 min later sarin (100 or 200 micrograms/kg = 5 or 10 x LD50, i.v.) or VX (45 or 90 micrograms/kg = 10 or 20 x LD50, i.v.), followed 2 min later by atropine (10 mg/kg, i.v.) plus HI 6 or HLö 7 (30 mumol/kg each, i.v.). Sixty-minute survival time and rate and respiratory and circulatory parameters were recorded. Diaphragm acetylcholinesterase (AChE) activity was determined spectrophotometrically. Identical groups without PYR were included for comparison. With regard to survival time and rate, PYR pretreatment slightly improved the efficacy of HI 6 plus atropine in sarin 5 x LD50 poisoned animals, reduced the efficacy of oxime + atropine treatment in the other sarin groups and had no effect in VX poisoning. Compared to non-pretreated oxime + atropine groups, PYR slightly improved respiratory function in sarin and in VX poisoning (only HI 6). PYR did not affect circulatory function in VX poisoning but reduced circulatory parameters in sarin poisoning to varying extent's. The oxime efficacy in reactivating diaphragm AChE decreased in the order sarin > VX without significant differences between pretreated and non-pretreated groups. The data suggest that pyridostigmine pretreatment does not enhance the efficacy of oxime + atropine in sarin or VX poisoning.
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Affiliation(s)
- F Worek
- Institut für Pharmakologie und Toxikologie, Sanitätsakademie der Bundeswehr, Garching, Germany
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22
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Melchers BP, van der Laaken AL, Busker RW, Bruijnzeel PL, Van Helden HP. Non-reactivating effects of HI-6 on hippocampal neurotransmission. Arch Toxicol 1994; 69:118-26. [PMID: 7717860 DOI: 10.1007/s002040050146] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Effects of the oxime HI-6, unrelated to reactivation of acetylcholinesterase (AChE), on field potentials in the dentate gyrus of the rat hippocampus following AChE inhibition, were investigated both in vitro and in vivo. In hippocampal slices, AChE inhibition decreased the perforant path evoked population spike amplitude (PSA). This effect could be prevented by pre-incubation of the slices with atropine (0.1-1 microM) or with the M1 muscarinic receptor antagonist pirenzepine (1 microM). A similar preventive effect was found after pre-incubation with the GABAA antagonist picrotoxin (20 microM), suggesting that the effects of AChE inhibition in vitro may be due to an enhancement of GABAergic inhibitory activity via activation of M1-muscarinic receptors. The effects of AChE inhibition in vivo were variable; both increases and decreases of the PSA were found. Following AChE inhibition, HI-6 increased the PSA dose-dependently, both in the in vivo and in the in vitro hippocampus. At higher oxime doses the perforant path stimulation elicited multiple population spikes. The effects of the oxime were presumably not mediated by an antagonism of cholinergic receptors, since they could not be mimicked with cholinergic antagonists like atropine, mecamylamine or gallamine. Further testing of the nature of the HI-6 effect in hippocampal slices in vitro, using a paired antidromic-orthodromic stimulation protocol, showed that HI-6 may interfere with GABAergic inhibition.
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Affiliation(s)
- B P Melchers
- Department of Pharmacology, TNO-Pharma, Rijswijk, The Netherlands
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Chiou L, Chang C. Obidoxime Antagonizes the Neuromuscular Failure Induced by Neostigmine and Diisopropyl Fluorophosphate via Different Mechanisms. J Biomed Sci 1994; 1:19-27. [PMID: 11725003 DOI: 10.1007/bf02258336] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
Abstract
The efficacies and mechanisms of obidoxime in antagonizing the neuromuscular failure induced by neostigmine and diisopropyl fluorophosphate (DFP) were studied in mouse phrenic nerve/diaphragm preparations. Obidoxime antagonized neostigmine-induced tetanic fade (EC(50): 300 &mgr;M) by inhibiting the regenerative and sustained depolarization during repetitive stimulation. The antagonism was associated with a depression and shortening of single endplate potentials (EPPs) and miniature EPPs (MEPPs). In contrast, the neuromuscular failure induced irreversibly after treatment with DFP and followed by washout was restored by obidoxime at concentrations (EC(50): 0.6 &mgr;M) 500-fold lower than that against neostigmine. The regenerative depolarization was abolished with no depression of single EPPs and MEPPs, and the antagonistic action persisted after washout of obidoxime. The EC(50) of obidoxime was proportionately increased in the presence of increasing concentrations of DFP. Nevertheless, the EC(50) against DFP, at a concentration (30 &mgr;M) 15-fold in excess of that which caused tetanic fade, was still 10-fold lower than that which antagonized neostigmine. In both cases, the amplitudes of train EPPs were increased. It is concluded that obidoxime antagonizes neostigmine-induced neuromuscular failure by a curare-like action but antagonizes DFP by an enzyme reactivation. Copyright 1994 S. Karger AG, Basel
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Affiliation(s)
- L.C. Chiou
- Department of Pharmacology, College of Medicine, National Taiwan University, Taipei, Taiwan, ROC
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Wolthuis OL, van Helden HP, Melchers BP, Busker RW, de Groot DM. Search for a therapy against soman-intoxication. Neurosci Biobehav Rev 1994; 18:469-86. [PMID: 7708361 DOI: 10.1016/0149-7634(94)90002-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
This mini-review mainly describes a part of the pharmacological research carried out in our laboratory during the past decades, aimed at finding a therapy against intoxication by cholinesterase-inhibiting organophosphates, in particular against the nerve agent soman. In particular soman, because this is one of the nerve agents that consistently appears to be very resistant to treatment. Various experimental approaches are described. Yet, even after all these years of research an adequate (pre)treatment against poisoning by soman is still not available.
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Affiliation(s)
- O L Wolthuis
- Medical Biological Laboratory TNO Lange Kleiweg 139, Rijswijk, The Netherlands
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25
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Worek F, Kirchner T, Szinicz L. Effect of atropine, HLö 7 and HI 6 on respiratory and circulatory function in guinea-pigs poisoned by O-ethyl S-[2-(diisopropylamino) ethyl] methylphosponothioate (VX). PHARMACOLOGY & TOXICOLOGY 1994; 75:302-9. [PMID: 7870702 DOI: 10.1111/j.1600-0773.1994.tb00364.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
In a guinea-pig model with on-line respiratory and circulatory monitoring the therapeutic efficacy of atropine, HLö 7 and HI 6 in VX poisoning was compared. In female urethane-anaesthetized Pirbright-white guinea-pigs the a. carotis, v. jugularis and trachea were cannulated. After base line measurements the animals received VX (22.5, 45 or 90 micrograms/kg = 5, 10 or 20 x LD50) intravenously and 2 min. later the antidotes: HLö 7 or HI 6 (30 mumol/kg, each) or atropine 10 mg/kg or a combination of atropine and one of the oximes (all intravenously). Respiratory and circulatory parameters were recorded for 60 min. or until death of the animal. Erythrocyte, brain and diaphragm acetylcholinesterase (AChE) activity was determined after the experiment. VX poisoning caused a rapid respiratory arrest within 4-5 min. Atropine treatment was effective in improving the respiratory function after VX, 22.5 micrograms/kg, but had only a small effect after the higher VX doses. The treatment of VX (10 or 20 x LD50) poisoned animals with oxime plus atropine improved respiration to various extents, restored circulation and prolonged the survival time, HLö 7 being more effective than HI 6 after VX 90 micrograms/kg. Oximes alone were completely ineffective. Erythrocyte and diaphragm AChE was reactivated by HLö 7 and, less effectively, by HI 6, while brain AChE remained almost completely inhibited in all groups. The results of this investigation demonstrate a reasonable efficacy of atropine after lower VX doses and of HLö 7 and HI 6 (plus atropine) after high-dose VX poisoning, HLö 7 being slightly more effective than HI 6.
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Affiliation(s)
- F Worek
- Institute of Pharmacology and Toxicology, Federal Armed Forces Medical Academy, Garching, Germany
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26
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Busker RW, Zijlstra JJ, van der Wiel HJ, van Helden HP. The functional role of molecular forms of acetylcholinesterase in neuromuscular transmission. Neurochem Res 1994; 19:713-9. [PMID: 8065529 DOI: 10.1007/bf00967711] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The severity of poisoning following acetylcholinesterase (AChE) inhibition correlates weakly with total AChE activity. This may be partly due to the existence of functional and non-functional pools of AChE. AChE consists of several molecular forms. The aim of the present study was to investigate which of these forms will correlate best with neuromuscular transmission (NMT) remaining after partial inhibition of this enzyme. Following sublethal intoxication of rats with the irreversible AChE inhibitor soman, diaphragms were isolated after 0.5 or 3 h. It appeared that at 3 h after soman poisoning the percentage of G1 increased, while those of G4 and A12 decreased. NMT was inhibited more strongly than in preparations obtained from the 0.5 h rats with the same level of AChE inhibition, but with a normal ratio of molecular forms. NMT correlated positively with G4 as well as with A12, but inversely with G1. In vitro inhibition with the charged inhibitors DEMP and echothiophate resulted in higher levels of total AChE, relatively less G1 and more G4 and A12 than after incubation with soman, but led to less NMT. Treatment of soman-intoxicated rats with the reactivating compound HI-6 resulted in preferential reactivation of A12, persisting low levels of G1 and concurrent recovery of NMT as compared with saline-treated soman controls with equal total AChE activity. Apparently, in rat diaphragm G4 and A12 are the functional AChE forms.
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Affiliation(s)
- R W Busker
- Medical Biological Laboratory T.N.O., Rijswijk, The Netherlands
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27
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van Helden HP, van der Wiel HJ, Zijlstra JJ, Melchers BP, Busker RW. Comparison of the therapeutic effects and pharmacokinetics of HI-6, HLö-7, HGG-12, HGG-42 and obidoxime following non-reactivatable acetylcholinesterase inhibition in rats. Arch Toxicol 1994; 68:224-30. [PMID: 8067894 DOI: 10.1007/s002040050061] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The oximes HI-6, HLö-7, HGG-12, HGG-42 and obidoxime were used in a previously developed rat model to evaluate the therapeutic effects of oximes other than acetylcholinesterase (AChE) reactivation (so-called "non-reactivating effects"). To test this anaesthetized, atropinized and artificially ventilated rats (n = 8 or 16) were poisoned with a three times LD50 dose of the potent AChE-inhibitor crotylsarin (CRS, i.v.). CRS-inhibited rat AChE dealkylates instantaneously, thereby excluding AChE reactivation by the oximes. Five minutes after poisoning the rats were treated (i.v.) with an oxime or saline and 10 min later artificial ventilation was terminated. Survival times were determined. Saline-treated animals died within 15 min. In comparison, treatment with HI-6, HLö-7, HGG-12, HGG-42 or obidoxime resulted in a significant prolongation of survival time. In the groups treated with HLö-7, HI-6 or HGG-12, 12-37% of the animals survived more than 24 h. It was investigated whether differences in therapeutic effectiveness are caused by differences in pharmacokinetics of the oximes. The plasma half-lives of HI-6, HLö-7, HGG-12, HGG-42 and obidoxime amounted to 67, 63, 27, 55 and 179 min, respectively. At doses of 75 or 150 mumol/kg, all oximes could be detected in brain and medulla oblongata in similar amounts (6-10 nmol/g tissue). In vitro, all oximes were effective in restoring failure of neuromuscular transmission (NMT) caused by CRS, albeit with varying potency. All oximes bound with affinities in the micromolar range to rat brain muscarinic receptors.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- H P van Helden
- TNO Medical Biological Laboratory, Rijswijk, The Netherlands
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28
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Worek F, Kirchner T, Szinicz L. Treatment of tabun poisoned guinea-pigs with atropine, HLö 7 or HI 6: effect on respiratory and circulatory function. Arch Toxicol 1994; 68:231-9. [PMID: 8067895 DOI: 10.1007/s002040050062] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The oxime HI 6 (in combination with atropine) is considered to be an effective antidote in soman intoxication but was shown to be less effective in tabun poisoning. In contrast to HI 6, first in vitro studies with HLö 7 demonstrated a reasonable reactivating potency at acetylcholinesterase (AChE) inhibited by soman and tabun. Therefore, the therapeutic efficacy of HLö 7, HI 6 and obidoxime (with and without atropine) was compared in tabun poisoned guinea-pigs. In addition, the therapeutic effect of atropine in guinea-pigs poisoned by various doses of tabun was investigated. Female Pirbright-white guinea-pigs were anaesthetized with urethane (1.8 g/kg) and the carotid artery, jugular vein and trachea were cannulated. After baseline measurements the animals received tabun, 60, 180 or 300 micrograms/kg, and 2 min later the antidotes (all i.v.): obidoxine, HLö 7, or HI 6 (30 or 100 mumol/kg, each) or atropine 10 mg/kg or a combination of atropine and one of the oximes. Respiratory and circulatory parameters were recorded for 60 min or until the death of the animal. Erythrocyte, brain and diaphragm AChE activity was determined in every animal after the experiment. Poisoning by tabun resulted in a rapid deterioration of respiratory function and respiratory arrest within 5 min. Atropine treatment was very effective in improving the respiratory function after tabun 60 micrograms/kg but was ineffective after tabun 300 micrograms/kg. However, circulatory parameters were restored almost completely in all atropine therapy groups. Therapy of tabun 300 microns/kg poisoned animals with atropine plus oxime (30 micromol/kg) improved respiration to a variable extent and restored circulation.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- F Worek
- Institut für Pharmakologie und Toxikologie, Akademie des Sanitäts- und Gesundheitswesens der Bundeswehr, Garching, Germany
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Adler M, Maxwell DM, Filbert MG, Deshpande SS. Contribution of direct actions of the oxime HI-6 in reversing soman-induced muscle weakness in the rat diaphragm. Eur J Pharmacol 1994; 270:9-16. [PMID: 8157086 DOI: 10.1016/0926-6917(94)90075-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The actions of the bispyridinium oxime HI-6 ([[[(4-aminocarbonyl)pyridino]-methoxy]methyl]-2- [(hydroxyimino)methyl]-pyridinium dichloride) were investigated in vitro on rat phrenic nerve-hemidiaphragm preparations. Isometric twitch and tetanic tensions were elicited at 37 degrees C with supramaximal nerve stimulation at frequencies of 20 and 50 Hz. To approximate normal respiration patterns, trials consisting of 30 successive 0.55 s trains were alternated with 1.25 s rest periods. Under control conditions, the above stimulation pattern generated tensions that were well maintained at both frequencies. In contrast, a marked depression of muscle tension was observed in diaphragms removed from rats administered 339 micrograms/kg soman (3 LD50) and tested in vitro. Addition of HI-6, 4 h after soman exposure, led to a nearly complete recovery of muscle tension at 20 Hz. At 50 Hz, muscle tensions still declined especially when trains were elicited at 1.25 and 3 s intervals. The recovery by HI-6 observed in this study appears to be mediated by mechanisms unrelated to acetylcholinesterase reactivation since no increase of enzymatic activity was detected and the effect was reversed by a brief washout in oxime-free physiological solution. The results suggest that the direct action of HI-6 may play a role in restoring soman-induced diaphragmatic failure but this effect would be significant primarily under low use conditions.
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Affiliation(s)
- M Adler
- Neurotoxicology and Biochemical Pharmacology Branches, US Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, MD 21010
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Tattersall JE. Ion channel blockade by oximes and recovery of diaphragm muscle from soman poisoning in vitro. Br J Pharmacol 1993; 108:1006-15. [PMID: 7683561 PMCID: PMC1908129 DOI: 10.1111/j.1476-5381.1993.tb13498.x] [Citation(s) in RCA: 94] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
1. The actions of oximes and related compounds on the nicotinic acetylcholine receptor ion channel at the adult mouse muscle endplate were investigated by use of single-channel recording techniques. The aim of the study was to determine whether the channel-blocking properties of the compounds could contribute to their therapeutic effectiveness against soman poisoning in vitro. 2. Therapeutic effectiveness was assessed in guinea-pig phrenic nerve-hemidiaphragm preparations by measuring the degree of recovery of neuromuscular function produced by the compounds following poisoning by soman. A number of the compounds, including some which lacked the oxime group, produced a significant recovery of neuromuscular function which was unrelated to acetylcholinesterase (AChE) reactivation; this was reversed by washing off the compound, and was therefore attributed to a direct pharmacological action on the muscle. 3. Single channel recordings showed that some of the compounds blocked open nicotinic receptor ion channels in preparations of mouse muscle fibres. The compounds which showed the greatest direct pharmacological actions in diaphragms produce a very fast, flickering blockade of the channels. Several quantitative measures of channel-blocking activity correlated very well with the direct pharmacological action. Furthermore, for two compounds studied in greater detail, the direct action and channel-blocking showed similar concentration-response relationships. 4. The results of this study indicate that the direct pharmacological action of oximes and their analogues against neuromuscular blockade by soman in vitro is due to their channel-blocking activity. The direct action does not correlate well with protection against soman poisoning in vivo, however, which suggests that additional non-reactivating properties of these compounds, at sites other than the neuromuscular junction, may also be important for their therapeutic effectiveness.
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Affiliation(s)
- J E Tattersall
- Biology Division, Chemical and Biological Defence Establishment, Salisbury
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Walday P, Aas P, Haider T, Fonnum F. Effect of pyridostigmine pretreatment, HI-6 and Toxogonin treatment on rat tracheal smooth muscle response to cholinergic stimulation after organophosphorus inhalation exposure. Arch Toxicol 1993; 67:212-9. [PMID: 8494501 DOI: 10.1007/bf01973310] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The ex vivo contraction response of the rat tracheal smooth muscle was examined after 10 min in vivo inhalation of soman and/or pretreatment with pyridostigmine and/or post-exposure treatment with HI-6 ([[[(4-aminocarbonyl)pyridinio]methoxy]methyl]-2[(hydroxy imino) methyl]pyridinium dichloride) or Toxogonin (1,1'-[oxybis-(methylene)]bis[4-[(hydroxyimino)methyl]-py rid inium] dichloride). In vivo pretreatment with pyridostigmine was achieved by subcutaneous (s.c.) implantation of an osmotic pump that delivered pyridostigmine continuously (0.01 mg/h) in the neck region of the rat 18 h before soman exposure. The ex vivo cholinergic tracheal smooth muscle response increased during the first 60 min after soman exposure in animals pretreated with pyridostigmine. The amplitude of the contraction response in pyridostigmine pretreated animals was about 60% of control, compared to 15% of control without pyridostigmine pretreatment. Pyridostigmine pretreatment also produced significant recovery of the total cholinesterase (ChE) activity in plasma, but not in trachea and lung. Intraperitoneal (i.p.) injection of HI-6 or Toxogonin (50 mg/kg), immediately after 10 min inhalation exposure to soman, also significantly improved the ex vivo cholinergic contraction response of the trachea (decapitation 15 min after oxime administration). The recovery of the physiological response with Toxogonin was, however, not stable. HI-6 was superior to Toxogonin with respect to the initial airway contraction response, and the response increased up to a stable level not significantly different from control. There was no significant reactivation of the ChE activity after treatment with the oximes. Combination of pyridostigmine pretreatment and oxime treatment enhanced the recovery of the tracheal contraction response and the ChE activity in the trachea compared to treatment with oximes alone.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- P Walday
- Norwegian Defense Research Establishment, Division for Environmental Toxicology, Kjeller
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Worek F, Szinicz L. Atropine and oxime treatment in lethal soman poisoning of anaesthetized guinea-pigs: HLö 7 dimethanesulfonate versus HI 6 dichloride. PHARMACOLOGY & TOXICOLOGY 1993; 72:13-21. [PMID: 8441735 DOI: 10.1111/j.1600-0773.1993.tb01332.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The oxime HI 6 is considered to be effective in soman poisoning and less effective in tabun poisoning. Recently, HLö 7 was shown to reactivate acetylcholinesterase (AChE) inhibited by soman and tabun. Therefore, the efficacy of HLö 7 and HI 6 was compared in soman poisoned guinea-pigs. Female Pirbright-white guinea-pigs were anaesthetized with urethane (1.8 g/kg) and the a. carotis, v. jugularis and trachea were cannulated. After base line measurements soman 0.08 mg/kg (= 5 x LD50) or 0.16 mg/kg (= 10 x LD50) was injected intravenously, 2 min. later the antidotes were applied intravenously: HLö 7 0.03 or 0.1 mmol/kg, HI 6 0.03 or 0.1 mmol/kg, atropine 10 mg/kg, or a combination of atropine and an oxime. Respiratory and circulatory parameters were recorded for 60 min. or until the death of the animal. The injection of 5 x LD50 soman resulted in a rapid respiratory arrest followed by circulatory failure in the soman and soman plus oxime groups (survival time about 7 min). Atropine restored the circulatory parameters to base line but was unable to provide a sufficient respiratory function (survival time 26 min.). The combination therapy with atropine plus HLö 7 or HI 6 improved the respiration sufficiently, restored the circulation completely, and prolonged the survival time to about 50 min. Atropine treatment was insufficient in animals poisoned with 10 x LD50 soman. The combination of atropine and HLö 7 or HI 6 improved respiration, circulation, and survival time to various extent. Despite of the striking therapeutic effect no reactivation of erythrocyte AChE by the antidotes was observed.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- F Worek
- Institute of Pharmacology and Toxicology, Federal Armed Forces Medical Academy, BSW, Garching, Germany
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Eyer P, Hagedorn I, Klimmek R, Lippstreu P, Löffler M, Oldiges H, Spöhrer U, Steidl I, Szinicz L, Worek F. HLö 7 dimethanesulfonate, a potent bispyridinium-dioxime against anticholinesterases. Arch Toxicol 1992; 66:603-21. [PMID: 1482283 DOI: 10.1007/bf01981499] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
HLö 7 dimethanesulfonate (1-[[[4-(aminocarbonyl)pyridinio]methoxy]methyl]-2,4-bis [(hydroxyimino)methyl]pyridinium dimethanesulfonate) is a broad-spectrum reactivator against highly toxic organophosphorus compounds. The compound was synthesized by a new route with the carcinogenic bis(chloromethyl)ether being substituted by the non-mutagenic bis(methylsulfonoxymethyl)ether. The very soluble dimethanesulfonate of obidoxime was also prepared by this way. HLö 7 dimethanesulfonate is the first water-soluble salt of HLö 7 that should be suitable for the wet/dry autoinjector technology, because aqueous solutions of HLö 7 are not very stable (calculated shelf-life 0.2 years when stored at 8 degrees C, 1 M solution, pH 2.5). The crystalline preparation contains 96% of the syn/syn-isomer, less than 2% of the syn/anti-isomer and some minor identified by-products. HLö 7 was very efficient in reactivating acetylcholinesterase (AChE) blocked by organophosphates as long as ageing did not prevent dephosphylation. HLö 7 was superior to HI 6 (1-[[[4-(aminocarbonyl)pyridinio]methoxy]methyl]-2- [(hydroxyimino)methyl]pyridinium dichloride) in reactivating soman and sarin-inhibited AChE from erythrocytes, and literature data indicate that HLö 7 exceeds HI 6 by far in reactivating tabun-inhibited AChE. In atropine-protected, soman-poisoned mice HLö 7 was three times more potent than HI 6 (protective ratio 5 versus 2.5), and in sarin-poisoned mice HLö 7 was 10 times more potent than HI 6 (protective ratio 8 for both oximes). In atropine-protected guinea-pigs HLö 7 was less effective than HI 6 (protective ratio: 2.3 versus 5.2 for soman; 5.2 versus 6.8 for sarin; 4.3 versus 3.8 for tabun). The mean survival time of anaesthetized guinea-pigs exposed to 5 LD50 soman (6.3 min) was increased by atropine (27 min) and atropine + HLö (57 min). HLö 7 alone did not prolong the survival. The most impressive effect of HLö 7 was on respiration: 3 min after i.v. injection of HLö 7 and atropine, the depressed respiration increased rapidly to 60% of control and remained at that level during the observation period (60 min). With atropine alone, respiration recovered only slowly. Behavioural and physiologic parameters were determined in atropine-protected mice exposed to a sublethal soman dose. The running performance was significantly improved by HLö 7. Even central symptoms, e.g. hypothermia and convulsions, were decreased markedly by HLö 7 (evaluation 60 min after poisoning). The pharmacokinetic data for HLö 7 in male beagle dogs are similar to those of HI 6.(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- P Eyer
- Walther-Straub-Institut für Pharmakologie und Toxikologie, Ludwig-Maximilians-Universität München, Federal Republic of Germany
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Busker RW, Zijlstra JJ, van der Wiel HJ, Melchers BP, van Helden HP. Organophosphate poisoning: a method to test therapeutic effects of oximes other than acetylcholinesterase reactivation in the rat. Toxicology 1991; 69:331-44. [PMID: 1658986 DOI: 10.1016/0300-483x(91)90191-3] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
A method was developed to study exclusively those therapeutic effects of oximes that are not related to reactivation of organophosphate-inhibited acetylcholinesterase (AChE). The model uses the organophosphorus compound crotylsarin (CRS), which proved to be a potent, irreversible, peripherally and centrally active AChE inhibitor with a very short biological half-life. CRS-inhibited AChE appeared to age very rapidly, because in vitro addition of oximes immediately following inhibition, did not result in any AChE reactivation. Anaesthetized, atropinized and artificially ventilated rats were intoxicated with 3 x LD50 CRS and treated 5 min later with the bispyridinium oxime HI-6. Fifty percent of these animals survived more than 24 h following termination of artificial ventilation at 10 min after oxime treatment. The mean survival time of the remaining animals was 66 min, whereas all untreated animals died within 4 min. HI-6, when added in vitro to isolated intact hemidiaphragms, or to diaphragm or brain homogenates from rats which had been killed 1 min following 3 x LD50 CRS, failed to reactivate the inhibited AChE. If blood was sampled (before and) after HI-6 administration to CRS-intoxicated rats, no HI-6-induced AChE reactivation was observed. Yet, a clear improvement of the neuromuscular transmission in the hindleg muscles of these animals was found following HI-6 injection. With this model, decisive evidence is obtained that non-reactivating effects of HI-6 by themselves are therapeutically relevant.
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Affiliation(s)
- R W Busker
- Medical Biological Laboratory T.N.O., Rijswijk, The Netherlands
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