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Shajhutdinova Z, Pashirova T, Masson P. Kinetic Processes in Enzymatic Nanoreactors for In Vivo Detoxification. Biomedicines 2022; 10:biomedicines10040784. [PMID: 35453533 PMCID: PMC9025091 DOI: 10.3390/biomedicines10040784] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2022] [Revised: 03/24/2022] [Accepted: 03/25/2022] [Indexed: 12/20/2022] Open
Abstract
Enzymatic nanoreactors are enzyme-encapsulated nanobodies that are capable of performing biosynthetic or catabolic reactions. For this paper, we focused on therapeutic enzyme nanoreactors for the neutralization of toxicants, paying special attention to the inactivation of organophosphorus compounds (OP). Therapeutic enzymes that are capable of detoxifying OPs are known as bioscavengers. The encapsulation of injectable bioscavengers by nanoparticles was first used to prevent fast clearance and the immune response to heterologous enzymes. The aim of enzyme nanoreactors is also to provide a high concentration of the reactive enzyme in stable nanocontainers. Under these conditions, the detoxification reaction takes place inside the compartment, where the enzyme concentration is much higher than in the toxicant diffusing across the nanoreactor membrane. Thus, the determination of the concentration of the encapsulated enzyme is an important issue in nanoreactor biotechnology. The implications of second-order reaction conditions, the nanoreactor’s permeability in terms of substrates, and the reaction products and their possible osmotic, viscosity, and crowding effects are also examined.
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Affiliation(s)
- Zukhra Shajhutdinova
- Biochemical Neuropharmacology Laboratory, Kazan Federal University, Kremlevskaya Str. 18, 420111 Kazan, Russia;
- Arbuzov Institute of Organic and Physical Chemistry, FRC Kazan Scientific Center, Russian Academy of Sciences, Arbuzov Str. 8, 420088 Kazan, Russia;
| | - Tatiana Pashirova
- Arbuzov Institute of Organic and Physical Chemistry, FRC Kazan Scientific Center, Russian Academy of Sciences, Arbuzov Str. 8, 420088 Kazan, Russia;
| | - Patrick Masson
- Biochemical Neuropharmacology Laboratory, Kazan Federal University, Kremlevskaya Str. 18, 420111 Kazan, Russia;
- Correspondence:
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2
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Pashirova TN, Bogdanov A, Masson P. Therapeutic nanoreactors for detoxification of xenobiotics: Concepts, challenges and biotechnological trends with special emphasis to organophosphate bioscavenging. Chem Biol Interact 2021; 346:109577. [PMID: 34274336 DOI: 10.1016/j.cbi.2021.109577] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2021] [Revised: 06/19/2021] [Accepted: 07/12/2021] [Indexed: 12/20/2022]
Abstract
The introduction of enzyme nanoreactors in medicine is relatively new. However, this technology has already been experimentally successful in cancer treatments, struggle against toxicity of reactive oxygen species in inflammatory processes, detoxification of drugs and xenobiotics, and correction of metabolic and genetic defects by using encapsulated enzymes, acting in single or cascade reactions. Biomolecules, e.g. enzymes, antibodies, reactive proteins capable of inactivating toxicants in the body are called bioscavengers. In this review, we focus on enzyme-containing nanoreactors for in vivo detoxification of organophosphorous compounds (OP) to be used for prophylaxis and post-exposure treatment of OP poisoning. A particular attention is devoted to bioscavenger-containing injectable nanoreactors operating in the bloodstream. The nanoreactor concept implements single or multiple enzymes and cofactors co-encapsulated in polymeric semi-permeable nanocontainers. Thus, the detoxification processes take place in a confined space containing highly concentrated bioscavengers. The article deals with historical and theoretical backgrounds about enzymatic detoxification of OPs in nanoreactors, nanoreactor polymeric enveloppes, realizations and advantages over other approaches using bioscavengers.
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Affiliation(s)
- Tatiana N Pashirova
- Arbuzov Institute of Organic and Physical Chemistry, FRC Kazan Scientific Center, Russian Academy of Sciences, Arbuzov str., 8, Kazan, 420088, Russian Federation
| | - Andrei Bogdanov
- Arbuzov Institute of Organic and Physical Chemistry, FRC Kazan Scientific Center, Russian Academy of Sciences, Arbuzov str., 8, Kazan, 420088, Russian Federation
| | - Patrick Masson
- Kazan Federal University, Neuropharmacology Laboratory, Kremlevskaya str., 18, Kazan, 420111, Russian Federation.
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Jebli N, Arfaoui Y, Van Hecke K, Cavalier JF, Touil S. Experimental and computational investigation of Z/E isomerism, X-ray crystal structure and molecular docking study of (2-(hydroxyimino)cyclohexyl)diphenylphosphine sulfide, a potential antibacterial agent. J Mol Struct 2021. [DOI: 10.1016/j.molstruc.2020.129634] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Abstract
Standard therapy of Organophosphorus Compound (OPC) poisoning with
oxime-type acetylcholinesterase (AChE) reactivators is unsatisfactory. New bispyridinium
oximes have therefore been synthesized. This review summarizes in vitro characteristics
of established (pralidoxime, obidoxime, trimedoxime, HI-6) and experimental (K-)oximes,
and compares their protective efficacy in vivo, when administered shortly after exposure
to Diisopropylfluorophosphate (DFP) and three OPC pesticides (ethyl-paraoxon, methylparaoxon,
azinphos-methyl) in the same experimental setting.
In addition to reactivating cholinesterase, oximes also inhibit this enzyme; strongest
AChE inhibition (IC50 rat blood: 1-9 µM) is observed in vitro for the oximes with a xylene
linker (K-107, K-108, K-113). AChE inhibition is weakest for K-27, K-48 and HI-6 (IC50
>500 µM). Intrinsic AChE inhibition of oximes in vitro (IC50, rat) is strongly correlated with their LD50 (rat):
oximes with a high IC50 (K-27, K-48, pralidoxime, obidoxime) also show a high LD50, making them relatively
non-toxic, whereas oximes K-107, K-108 and K-113 (low IC50 and LD50) are far more toxic.
When given in vivo after OP exposure, best protection is conferred by K-27, reducing the relative risk of death
to 16-58% of controls, which is significantly superior to pralidoxime in DFP-, ethyl-paraoxon- and methylparaoxon-
exposure, and to obidoxime in ethyl-paraoxon- and methyl-paraoxon-exposure. Marked reduction in
mortality is also achieved by K-48, K-53, K-74 and K-75, whereas K-107, K-108 and K-113 have no or only a
very weak mortality-reducing effect. K-27 is the most promising K-oxime due to its strong reactivation potency,
weak cholinesterase inhibition and high LD50, allowing administration in large, very efficacious dosages.
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Affiliation(s)
- Dietrich E. Lorke
- Department of Cellular Biology & Pharmacology, Herbert Wertheim College of Medicine, Florida International University, Miami, Florida, University Park GL 495 D, 11200 SW 8th St, Miami 33199, Florida , United States
| | - Georg A. Petroianu
- Department of Cellular Biology & Pharmacology, Herbert Wertheim College of Medicine, Florida International University, Miami, Florida, University Park GL 495 D, 11200 SW 8th St, Miami 33199, Florida , United States
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Nepovimova E, Kuca K. Chemical warfare agent NOVICHOK - mini-review of available data. Food Chem Toxicol 2018; 121:343-350. [PMID: 30213549 DOI: 10.1016/j.fct.2018.09.015] [Citation(s) in RCA: 52] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2018] [Revised: 09/04/2018] [Accepted: 09/08/2018] [Indexed: 11/17/2022]
Abstract
The Cold War period is characterized by the infighting between the Western countries and the USSR in diverse areas. One of such fields was development of the weapons of mass destruction. Within various programs on both sides, a wide scale of different agents have been developed. However, information about some of them are still protected under the designation "top secret". Notwithstanding, in history several cases are known when such information beheld the daylight. One of such cases was the program FOLIANT and NOVICHOK. Both programs were developed by the USSR as a reaction to English/American invention of VX agent. If at least a part of available information is truthful, we can allege that these compounds belong among the most toxic synthetic agents ever. Within this contribution, we have reviewed available Eastern and Western data about the A-agents and their precursors, so-called NOVICHOKs, including their history, synthesis, physical-chemical properties, pharmacological characteristics and clinical manifestation.
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Affiliation(s)
- Eugenie Nepovimova
- Department of Chemistry, Faculty of Science, University of Hradec Kralove, Rokitanskeho 62, 500 03, Hradec Kralove, Czech Republic
| | - Kamil Kuca
- Philosophical Faculty, University of Hradec Kralove, Rokitanskeho 62, 500 03, Hradec Kralove, Czech Republic.
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Gorecki L, Korabecny J, Musilek K, Malinak D, Nepovimova E, Dolezal R, Jun D, Soukup O, Kuca K. SAR study to find optimal cholinesterase reactivator against organophosphorous nerve agents and pesticides. Arch Toxicol 2016; 90:2831-2859. [PMID: 27582056 DOI: 10.1007/s00204-016-1827-3] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2016] [Accepted: 08/22/2016] [Indexed: 01/13/2023]
Abstract
Irreversible inhibition of acetylcholinesterase (AChE) by organophosphates leads to many failures in living organism and ultimately in death. Organophosphorus compounds developed as nerve agents such as tabun, sarin, soman, VX and others belong to the most toxic chemical warfare agents and are one of the biggest threats to the modern civilization. Moreover, misuse of nerve agents together with organophosphorus pesticides (e.g. malathion, paraoxon, chlorpyrifos, etc.) which are annually implicated in millions of intoxications and hundreds of thousand deaths reminds us of insufficient protection against these compounds. Basic treatments for these intoxications are based on immediate administration of atropine and acetylcholinesterase reactivators which are currently represented by mono- or bis-pyridinium aldoximes. However, these antidotes are not sufficient to ensure 100 % treatment efficacy even they are administered immediately after intoxication, and in general, they possess several drawbacks. Herein, we have reviewed new efforts leading to the development of novel reactivators and proposition of new promising strategies to design novel and effective antidotes. Structure-activity relationships and biological activities of recently proposed acetylcholinesterase reactivators are discussed and summarized. Among further modifications of known oximes, the main attention has been paid to dual binding site ligands of AChE as the current mainstream strategy. We have also discussed new chemical entities as potential replacement of oxime functional group.
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Affiliation(s)
- Lukas Gorecki
- Biomedical Research Centre, University Hospital Hradec Kralove, Sokolska 581, 500 05, Hradec Kralove, Czech Republic.,Department of Toxicology and Military Pharmacy, Faculty of Military Health Sciences, University of Defence, Trebesska 1575, 500 01, Hradec Kralove, Czech Republic
| | - Jan Korabecny
- Biomedical Research Centre, University Hospital Hradec Kralove, Sokolska 581, 500 05, Hradec Kralove, Czech Republic.,Department of Toxicology and Military Pharmacy, Faculty of Military Health Sciences, University of Defence, Trebesska 1575, 500 01, Hradec Kralove, Czech Republic
| | - Kamil Musilek
- Biomedical Research Centre, University Hospital Hradec Kralove, Sokolska 581, 500 05, Hradec Kralove, Czech Republic.,Department of Toxicology and Military Pharmacy, Faculty of Military Health Sciences, University of Defence, Trebesska 1575, 500 01, Hradec Kralove, Czech Republic.,Department of Chemistry, Faculty of Science, University of Hradec Kralove, Rokitanskeho 62, 500 03, Hradec Kralove, Czech Republic
| | - David Malinak
- Biomedical Research Centre, University Hospital Hradec Kralove, Sokolska 581, 500 05, Hradec Kralove, Czech Republic.,Department of Physiology and Pathophysiology, Faculty of Medicine, University of Ostrava, Syllabova 19, 703 00, Ostrava, Czech Republic
| | - Eugenie Nepovimova
- Biomedical Research Centre, University Hospital Hradec Kralove, Sokolska 581, 500 05, Hradec Kralove, Czech Republic.,Department of Toxicology and Military Pharmacy, Faculty of Military Health Sciences, University of Defence, Trebesska 1575, 500 01, Hradec Kralove, Czech Republic
| | - Rafael Dolezal
- Biomedical Research Centre, University Hospital Hradec Kralove, Sokolska 581, 500 05, Hradec Kralove, Czech Republic.,Department of Chemistry, Faculty of Science, University of Hradec Kralove, Rokitanskeho 62, 500 03, Hradec Kralove, Czech Republic
| | - Daniel Jun
- Biomedical Research Centre, University Hospital Hradec Kralove, Sokolska 581, 500 05, Hradec Kralove, Czech Republic.,Department of Toxicology and Military Pharmacy, Faculty of Military Health Sciences, University of Defence, Trebesska 1575, 500 01, Hradec Kralove, Czech Republic
| | - Ondrej Soukup
- Biomedical Research Centre, University Hospital Hradec Kralove, Sokolska 581, 500 05, Hradec Kralove, Czech Republic.,Department of Toxicology and Military Pharmacy, Faculty of Military Health Sciences, University of Defence, Trebesska 1575, 500 01, Hradec Kralove, Czech Republic
| | - Kamil Kuca
- Biomedical Research Centre, University Hospital Hradec Kralove, Sokolska 581, 500 05, Hradec Kralove, Czech Republic. .,Department of Chemistry, Faculty of Science, University of Hradec Kralove, Rokitanskeho 62, 500 03, Hradec Kralove, Czech Republic.
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7
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Masson P. Novel approaches in prophylaxis/pretreatment and treatment of organophosphorus poisoning. PHOSPHORUS SULFUR 2016. [DOI: 10.1080/10426507.2016.1211652] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Affiliation(s)
- Patrick Masson
- Neuropharmacology Laboratory, Kazan Federal University, Kazan, Russian Federation
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8
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Worek F, Elsinghorst P, Koller M, Thiermann H. Reactions of methylphosphonic difluoride with human acetylcholinesterase and oximes--Possible therapeutic implications. Toxicol Lett 2014; 231:92-8. [PMID: 25240274 DOI: 10.1016/j.toxlet.2014.09.012] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2014] [Revised: 09/13/2014] [Accepted: 09/15/2014] [Indexed: 10/24/2022]
Abstract
Highly toxic organophosphorus (OP) nerve agents are well characterized regarding chemical, biological and toxicological properties and the effectiveness of standard atropine and oxime therapy. Open literature data on the key nerve agent precursor methylphosphonic difluoride (DF) are scarce. To fill this gap the reactions of DF and its main degradation product methylphosphonofluoridic acid (MF) with human acetylcholinesterase (AChE) and the oximes obidoxime, HI-6 and 2-PAM were investigated in vitro. DF and MF were found to be weak inhibitors of human AChE being at least five orders less potent compared to the nerve agent sarin. Incubation of human AChE with millimolar DF and MF and subsequent addition of obidoxime and HI-6 resulted in a concentration-dependent decrease of AChE activity. This effect was not observed when incubating highly diluted AChE with oximes. The most likely explanation for this phenomenon is an inhibitory effect of phosphonyloximes formed by direct reaction of DF or MF with obidoxime and HI-6. These data indicate that high DF doses, resulting in millimolar blood and tissue DF/MF concentrations, are necessary to induce cholinergic signs and that under these conditions treatment with obidoxime and HI-6 may even worsen the poisoning.
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Affiliation(s)
- Franz Worek
- Bundeswehr Institute of Pharmacology and Toxicology, Munich, Germany.
| | - Paul Elsinghorst
- Bundeswehr Institute of Pharmacology and Toxicology, Munich, Germany
| | - Marianne Koller
- Bundeswehr Institute of Pharmacology and Toxicology, Munich, Germany
| | - Horst Thiermann
- Bundeswehr Institute of Pharmacology and Toxicology, Munich, Germany
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9
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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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10
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Macharia M, Kengne AP, Blackhurst DM, Erasmus RT, Matsha TE. The impact of chronic untreated hyperglycaemia on the long-term stability of paraoxonase 1 (PON1) and antioxidant status in human sera. J Clin Pathol 2013; 67:55-9. [DOI: 10.1136/jclinpath-2013-201646] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
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11
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Voicu V, Rădulescu FŞ, Medvedovici A. Toxicological considerations of acetylcholinesterase reactivators. Expert Opin Drug Metab Toxicol 2012; 9:31-50. [DOI: 10.1517/17425255.2013.736489] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Worek F, Eyer P, Thiermann H. Determination of acetylcholinesterase activity by the Ellman assay: a versatile tool for in vitro research on medical countermeasures against organophosphate poisoning. Drug Test Anal 2011; 4:282-91. [PMID: 21998030 DOI: 10.1002/dta.337] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2011] [Revised: 07/01/2011] [Accepted: 07/05/2011] [Indexed: 11/08/2022]
Abstract
Inhibition of acetylcholinesterase (AChE) is the main mechanism of action of organophosphorus compounds (OP), and AChE reactivators (oximes) are at present the only causal therapeutic approach. Being the key target of OP toxicity, AChE may serve as a valuable tool for diagnosis of OP exposure as well as for the investigation of the kinetics of interactions between OP and oximes. At present, the rapid, simple, and cheap spectrophotometric Ellman assay is widely used for diagnosis, therapeutic monitoring and in vitro kinetic investigations. Application of the assay for investigation of the interactions between AChE, inhibitors, and oximes requires the consideration of potential matrix effects (e.g. hemoglobin), side reactions (e.g. oximolysis of substrate) and other determinants (e.g. pH, temperature). By taking these factors into account, the Ellman assay allows the precise and reproducible determination of kinetic constants as a basis for the understanding of toxic OP effects and for the development of improved therapies against poisoning by OP. In addition, advanced applications of the Ellman assay, for example, in a dynamic in vitro model for the real-time activity determination of membrane-bound AChE, enables the proper investigation of relevant tissue, primarily respiratory muscle, and extends the applicability of this method.
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Affiliation(s)
- Franz Worek
- Bundeswehr Institute of Pharmacology and Toxicology, Neuherbergstrasse 11, Munich, Germany.
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Jun D, Musilova L, Musilek K, Kuca K. In vitro ability of currently available oximes to reactivate organophosphate pesticide-inhibited human acetylcholinesterase and butyrylcholinesterase. Int J Mol Sci 2011; 12:2077-87. [PMID: 21673941 PMCID: PMC3111652 DOI: 10.3390/ijms12032077] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2011] [Accepted: 03/09/2011] [Indexed: 11/16/2022] Open
Abstract
We have in vitro tested the ability of common, commercially available, cholinesterase reactivators (pralidoxime, obidoxime, methoxime, trimedoxime and HI-6) to reactivate human acetylcholinesterase (AChE), inhibited by five structurally different organophosphate pesticides and inhibitors (paraoxon, dichlorvos, DFP, leptophos-oxon and methamidophos). We also tested reactivation of human butyrylcholinesterase (BChE) with the aim of finding a potent oxime, suitable to serve as a “pseudocatalytic” bioscavenger in combination with this enzyme. Such a combination could allow an increase of prophylactic and therapeutic efficacy of the administered enzyme. According to our results, the best broad-spectrum AChE reactivators were trimedoxime and obidoxime in the case of paraoxon, leptophos-oxon, and methamidophos-inhibited AChE. Methamidophos and leptophos-oxon were quite easily reactivatable by all tested reactivators. In the case of methamidophos-inhibited AChE, the lower oxime concentration (10−5 M) had higher reactivation ability than the 10−4 M concentration. Therefore, we evaluated the reactivation ability of obidoxime in a concentration range of 10−3–10−7 M. The reactivation of methamidophos-inhibited AChE with different obidoxime concentrations resulted in a bell shaped curve with maximum reactivation at 10−5 M. In the case of BChE, no reactivator exceeded 15% reactivation ability and therefore none of the oximes can be recommended as a candidate for “pseudocatalytic” bioscavengers with BChE.
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Affiliation(s)
- Daniel Jun
- Center of Advanced Studies, Faculty of Military Health Sciences, University of Defence, Trebesska 1575, Hradec Kralove, 500 01, Czech Republic
- Department of Water Resources and Environmental Modeling, Faculty of Environmental Sciences, Czech University of Life Sciences Prague, Kamycka 129, Praha 6—Suchdol, 16521, Czech Republic
- University Hospital Hradec Kralove, Sokolska 581, Hradec Kralove, 50005, Czech Republic
- Authors to whom correspondence should be addressed; E-Mails: (D.J.); (K.K.); Tel.: +420-973-255-193; Fax: +420-495-518-094
| | - Lucie Musilova
- Hospital Pharmacy, University Hospital Hradec Kralove, Sokolska 581, Hradec Kralove, 500 05, Czech Republic; E-Mail:
- Department of Biochemical Sciences, Charles University in Prague, Faculty of Pharmacy in Hradec Kralove, Heyrovskeho 1203, Hradec Kralove, 50005, Czech Republic
| | - Kamil Musilek
- Department of Toxicology, Faculty of Military Health Sciences, University of Defence, Trebesska 1575, Hradec Kralove, 50001, Czech Republic; E-Mail:
| | - Kamil Kuca
- Center of Advanced Studies, Faculty of Military Health Sciences, University of Defence, Trebesska 1575, Hradec Kralove, 500 01, Czech Republic
- Authors to whom correspondence should be addressed; E-Mails: (D.J.); (K.K.); Tel.: +420-973-255-193; Fax: +420-495-518-094
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Becker C, Worek F, John H. Chromatographic analysis of toxic phosphylated oximes (POX): a brief overview. Drug Test Anal 2011; 2:460-8. [PMID: 20882513 DOI: 10.1002/dta.167] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Poisoning with organophosphorus compounds (OP), e.g. pesticides and nerve agents, causes inhibition of acetylcholinesterase (AChE) by phosphylation of the active site serine residue. Consequently, accumulation of stimulating acetylcholine in the synaptic cleft induces cholinergic crisis which ultimately may lead to death. For standard causal therapy, enzyme reactivators are administered representing oxime derivatives of quarternary pyridinium compounds, e.g. pralidoxime (2-PAM), obidoxime and HI 6. The mechanism of action includes removal of the phosphyl moiety by a nucleophilic attack of the oximate molecule substituting the enzyme and forming a phosphylated oxime (POX). POX is produced in stoichiometric amounts of reactivated enzyme and exhibits a significantly enhanced toxicity (inhibition rate constant) when compared to the parent OP. However, stability of POX under physiological conditions appears to be highly limited. Nevertheless, the presence of POX reveals a potential critical issue for both therapeutic efficacy in vivo and pharmacokinetic and pharmacodynamic (PK-PD) modelling based on cholinesterase activity data. Detailed characterization represents an important need for elaboration of the entire oxime pharmacology.Nevertheless, reports on POX toxicity and analysis are quite rare and may therefore be indicative of the challenge of POX analysis. This review provides a concise overview of chromatographic approaches applied to POX separation. Chromatography represents the key technology for POX purification and quantification in kinetic in vitro studies using buffers and biological fluids. Applications based on reversed-phase chromatography (RPC), ion pair chromatography (IPC) and an affinity approach as well as thin layer chromatography (TLC) are discussed and novel applications and data are presented.
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Affiliation(s)
- Christian Becker
- Bundeswehr Institute of Pharmacology and Toxicology, Munich, Germany.
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Luo C, Chambers C, Pattabiraman N, Tong M, Tipparaju P, Saxena A. Y124 at the peripheral anionic site is important for the reactivation of nerve agent-inhibited acetylcholinesterase by H oximes. Biochem Pharmacol 2010; 80:1427-36. [PMID: 20655881 DOI: 10.1016/j.bcp.2010.07.020] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2010] [Revised: 07/09/2010] [Accepted: 07/13/2010] [Indexed: 10/19/2022]
Abstract
The toxicity of organophosphorus (OP) nerve agents is manifested through irreversible inhibition of acetylcholinesterase (AChE) at the cholinergic synapses, which stops nerve signal transmission, resulting in a cholinergic crisis and eventually death of the poisoned person. Oxime compounds used in nerve agent antidote regimen reactivate nerve agent-inhibited AChE and halt the development of this cholinergic crisis. Due to diversity in structures of OP nerve agents, none of the currently available oximes is able to reactivate AChE inhibited by different nerve agents. To understand the mechanism for the differential activities of oximes toward AChE inhibited by diverse nerve agents in order to aid the design of new broad-spectrum AChE reactivators, we undertook site-directed mutagenesis and molecular modeling studies. Recombinant wild-type and mutant bovine (Bo) AChEs were inhibited by two bulky side-chain nerve agents, GF and VR, and used for conducting reactivation kinetics with five oximes. A homology model for wild-type Bo AChE was built using the recently published crystal structure of human AChE and used to generate models of 2-PAM and HI-6 bound to the active-sites of GF- and VR-inhibited Bo AChEs before nucleophilic attack. Results revealed that the peripheral anionic site (PAS) of AChE as a whole plays a critical role in the reactivation of nerve agent-inhibited AChE by all 4 bis-pyridinium oximes examined, but not by the mono-pyridinium oxime 2-PAM. Of all the residues at the PAS, Y124 appears to be critical for the enhanced reactivation potency of H oximes.
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Affiliation(s)
- Chunyuan Luo
- Walter Reed Army Institute of Research, Silver Spring, MD 20910-7500, USA.
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Muscle force and acetylcholinesterase activity in mouse hemidiaphragms exposed to paraoxon and treated by oximes in vitro. Toxicology 2010; 272:46-51. [DOI: 10.1016/j.tox.2010.04.002] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2010] [Revised: 03/15/2010] [Accepted: 04/03/2010] [Indexed: 11/20/2022]
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17
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Pyridinium aldoxime analysis by HPLC: the method for studies on pharmacokinetics and stability. Anal Bioanal Chem 2010; 397:579-86. [DOI: 10.1007/s00216-010-3635-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2010] [Revised: 03/04/2010] [Accepted: 03/04/2010] [Indexed: 11/26/2022]
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Huen K, Harley K, Bradman A, Eskenazi B, Holland N. Longitudinal changes in PON1 enzymatic activities in Mexican-American mothers and children with different genotypes and haplotypes. Toxicol Appl Pharmacol 2010; 244:181-9. [PMID: 20045427 DOI: 10.1016/j.taap.2009.12.031] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2009] [Revised: 12/17/2009] [Accepted: 12/21/2009] [Indexed: 01/15/2023]
Abstract
The paraoxonase 1 (PON1) enzyme prevents low-density lipoprotein oxidation and also detoxifies the oxon derivatives of certain neurotoxic organophosphate (OP) pesticides. PON1 activity in infants is low compared to adults, rendering them with lower metabolic and antioxidant capacities. We made a longitudinal comparison of the role of genetic variability on control of PON1 phenotypes in Mexican-American mothers and their children at the time of delivery (n=388 and 338, respectively) and again 7 years later (n=280 and 281, respectively) using generalized estimating equations models. At age 7, children's mean PON1 activities were still lower than those of mothers. This difference was larger in children with genotypes associated with low PON1 activities (PON1(-108TT), PON1(192QQ), and PON1(-909CC)). In mothers, PON1 activities were elevated at delivery and during pregnancy compared to 7 years later when they were not pregnant (p<0.001). In non-pregnant mothers, PON1 polymorphisms and haplotypes accounted for almost 2-fold more variation of arylesterase (AREase) and chlorpyrifos-oxonase (CPOase) activity than in mothers at delivery. In both mothers and children, the five PON1 polymorphisms (192, 55, -108, -909, -162) explained a noticeably larger proportion of variance of paraoxonase activity (62-78%) than AREase activity (12.3-26.6%). Genetic control of PON1 enzymatic activity varies in children compared to adults and is also affected by pregnancy status. In addition to known PON1 polymorphisms, unidentified environmental, genetic, or epigenetic factors may also influence variability of PON1 expression and therefore susceptibility to OPs and oxidative stress.
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Affiliation(s)
- Karen Huen
- Center for Children's Environmental Health, 50 University Hall, School of Public Health, University of California, Berkeley, CA 94720-7360, USA
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Paradox findings may challenge orthodox reasoning in acute organophosphate poisoning. Chem Biol Interact 2009; 187:270-8. [PMID: 19883634 DOI: 10.1016/j.cbi.2009.10.014] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2009] [Revised: 10/17/2009] [Accepted: 10/20/2009] [Indexed: 12/15/2022]
Abstract
It is generally accepted that inhibition of acetylcholinesterase (AChE) is the most important acute toxic action of organophosphorus compounds, leading to accumulation of acetylcholine followed by a dysfunction of cholinergic signaling. However, the degree of AChE inhibition is not uniformly correlated with cholinergic dysfunction, probably because the excess of essential AChE varies among tissues. Moreover, the cholinergic system shows remarkable plasticity, allowing modulations to compensate for dysfunctions of the canonical pathway. A prominent example is the living (-/-) AChE knockout mouse. Clinical experience indicates that precipitous inhibition of AChE leads to more severe poisoning than more protracted yet finally complete inhibition. The former situation is seen in parathion, the latter in oxydemeton methyl poisoning. At first glance, this dichotomy is surprising since parathion is a pro-poison and has to be activated to the oxon, while the latter is still the ultimate inhibitor. Also oxime therapy in organophosphorus poisoning apparently gives perplexing results: Oximes are usually able to reactivate diethylphosphorylated AChE, but the efficiency may be occasionally markedly smaller than expected from kinetic data. Dimethylphosphorylated AChE is in general less amenable to oxime therapy, which largely fails in some cases of dimethoate poisoning where aging was much faster than expected from a dimethylphosphorylated enzyme. Similarly, poisoning by profenofos, an O,S-dialkyl phosphate, leads to a rapidly aged enzyme. Most surprisingly, these patients were usually well on admission, yet their erythrocyte AChE was completely inhibited. Analysis of the kinetic constants of the most important reaction pathways, determination of the reactant concentrations in vivo and comparison with computer simulations may reveal unexpected toxic reactions. Pertinent examples will be presented and the potentially underlying phenomena discussed.
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Thiermann H, Worek F, Eyer P, Eyer F, Felgenhauer N, Zilker T. Obidoxime in acute organophosphate poisoning: 2 - PK/PD relationships. Clin Toxicol (Phila) 2009; 47:807-13. [PMID: 19778190 DOI: 10.1080/15563650903206836] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
OBJECTIVE The effects of obidoxime in the treatment of organophosphate poisoning were assessed by biochemical and biological effect monitoring. In this article we report effects on neuromuscular function, oxime and atropine concentration, and relate them to acetylcholinesterase (AChE) activity. METHODS We measured the activity of cholinesterase in plasma and AChE in red blood cells (RBC) and related these data with neuromuscular transmission analysis (ulnar nerve stimulation). Concomitantly, poison and oxon along with plasma obidoxime and atropine levels were measured at regular intervals. RESULTS We found a close correlation between RBC-AChE activity and neuromuscular transmission and a reciprocal correlation between both the atropine maintenance dose and/or its plasma concentration. The steady state of RBC-AChE activity of reactivation and re-inhibition followed the course predicted by laboratory-determined reaction constants. CONCLUSIONS Intense monitoring of organophosphate-poisoned patients allowed assessment of why a given obidoxime concentration was, or was not, able to counteract the re-inhibition of the RBC-AChE. RBC-AChE activity mirrors the function of n-receptor- and m-receptor-mediated cholinergic signaling as measured by neuromuscular transmission and atropine requirements.
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Affiliation(s)
- Horst Thiermann
- Bundeswehr Institute of Pharmacology and Toxicology, Sanitätsakademie der Bundeswehr, Munich, Germany
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Huen K, Harley K, Brooks J, Hubbard A, Bradman A, Eskenazi B, Holland N. Developmental changes in PON1 enzyme activity in young children and effects of PON1 polymorphisms. ENVIRONMENTAL HEALTH PERSPECTIVES 2009; 117:1632-8. [PMID: 20019917 PMCID: PMC2790521 DOI: 10.1289/ehp.0900870] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2009] [Accepted: 06/09/2009] [Indexed: 05/21/2023]
Abstract
BACKGROUND Paraoxonase 1 (PON1) is an enzyme that detoxifies activated organophosphorus pesticides (OPs) and is also involved in oxidative stress pathways. OBJECTIVES PON1 activity in newborns is lower than in adults, but the ontogeny of PON1 activity is poorly characterized in young children. We examined the effects of age and PON1 genotype on enzyme activity in a birth cohort of Mexican-American children. METHODS We determined three substrate-specific measures of PON1 activity in 1,143 plasma samples collected longitudinally from 458 children at five time points from birth through 7 years of age, and genotyped PON1 polymorphisms at positions 192 and -108 in these children. RESULTS Contrary to previous reports that PON1 activities plateau by 2 years of age, we observed an age-dependent increase in all three PON1 measures from birth through 7 years of age (p < 0.0001). The PON1(192) genotype significantly modified the effect of age on paraoxonase (POase) activity (p < 0.0001) such that increases in enzyme activity with age were influenced by the number of R alleles in a dose-dependent manner. Children with the PON1(-108CC192RR) diplotype had significantly higher mean PON1 activities and also experienced steeper increases of POase activity over time compared with children with the PON1(-108TT192QQ) diplotype. CONCLUSIONS Lower levels of the PON1 enzyme, which is involved in protection against OPs and oxidative stress, persist in young children past 2 years of age through at least 7 years of age. Future policies addressing pesticide exposure in children should take into account that the window of vulnerability to OPs in young children may last beyond infancy.
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Affiliation(s)
| | | | | | | | | | | | - Nina Holland
- Address correspondence to N. Holland, 50 University Hall, School of Public Health, UC Berkeley, Berkeley, CA 94720-7360 USA. Telephone: (510) 455-0561. Fax: (510) 643-5426. E-mail:
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Eyer F, Roberts DM, Buckley NA, Eddleston M, Thiermann H, Worek F, Eyer P. Extreme variability in the formation of chlorpyrifos oxon (CPO) in patients poisoned by chlorpyrifos (CPF). Biochem Pharmacol 2009; 78:531-7. [PMID: 19433070 PMCID: PMC2714474 DOI: 10.1016/j.bcp.2009.05.004] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2009] [Revised: 04/20/2009] [Accepted: 05/04/2009] [Indexed: 11/20/2022]
Abstract
Chlorpyrifos (CPF) is a pesticide that causes tens of thousands of deaths per year worldwide. Chlorpyrifos oxon (CPO) is the active metabolite of CPF that inhibits acetylcholinesterase. However, this presumed metabolite has escaped detection in human samples by conventional methods (HPLC, GC-MS, LC-MS) until now. A recently developed enzyme-based assay allowed the determination of CPO in the nanomolar range and was successfully employed to detect this metabolite. CPO and CPF were analysed in consecutive plasma samples of 74 patients with intentional CPF poisoning. A wide concentration range of CPO and CPF was observed and the ratio of CPO/CPF varied considerably between individuals and over time. The ratio increased during the course of poisoning from a mean of 0.005 in the first few hours after ingestion up to an apparent steady-state mean of 0.03 between 30 and 72 h. There was a hundred-fold variation in the ratio between samples and the interquartile range (between individuals) indicated over half the samples had a 5-fold or greater variation from the mean. The ratio was independent of the CPF concentration and the pralidoxime regimen. CPO was present in sufficient quantities to explain any observed acetylcholinesterase inhibitory activity. The effectiveness of pralidoxime in reactivating the inhibited acetylcholinesterase is strongly dependent on the CPO concentration. Differences in clinical outcomes and the response to antidotes in patients with acute poisoning may occur due to inter-individual variability in metabolism.
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Affiliation(s)
- Florian Eyer
- Toxicological Department of the 2nd Medical Clinic, Technische Universität München, Ismaninger Str. 22, D-81664 Munich, Germany
| | - Darren M. Roberts
- South Asian Clinical Toxicology Research Collaboration, and Burns, Trauma and Critical Care Research Centre, University of Queensland, Brisbane, Australia
| | - Nicholas A. Buckley
- South Asian Clinical Toxicology Research Collaboration, and Professorial Medical Unit, University of NSW, Sydney, Australia
| | - Michael Eddleston
- Scottish Poisons Information Bureau, Royal Infirmary, and Clinical Pharmacology Unit, University of Edinburgh, UK
| | - Horst Thiermann
- Bundeswehr Institute of Pharmacology and Toxicology, Munich, Germany
| | - Franz Worek
- Bundeswehr Institute of Pharmacology and Toxicology, Munich, Germany
| | - Peter Eyer
- Walther-Straub-Institute of Pharmacology and Toxicology, Ludwig Maximilians University, Goethestr. 33, D-80336 Munich, Germany
- Corresponding author. Tel.: +49 89 2180 75722; fax: +49 89 2180 75701.
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Huen K, Richter R, Furlong C, Eskenazi B, Holland N. Validation of PON1 enzyme activity assays for longitudinal studies. Clin Chim Acta 2009; 402:67-74. [PMID: 19146843 PMCID: PMC2683673 DOI: 10.1016/j.cca.2008.12.019] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2008] [Revised: 12/13/2008] [Accepted: 12/14/2008] [Indexed: 11/16/2022]
Abstract
BACKGROUND Paraoxonase (PON1) enzymatic activity assays are used to characterize sensitivity to organophosphates and oxidative stress. Length of sample storage, temperature and other factors may influence variability of PON1 measurements, especially in longitudinal studies. METHODS Effects of assay temperature, storage duration up to 7 y (-80 degrees C), freeze-thaw cycles, the type of specimen (serum or heparinized plasma) and assay variability were evaluated for 4 PON1 substrate-specific assays using samples from two pediatric cohorts and laboratory volunteers. RESULTS Intra- and inter-assay variation, as well as inter-laboratory variability for PON1 activities were <10%. The effect of storage duration up to 2 y was minimal. However, after 7 y, arylesterase, paraoxonase, and chlorpyrifos-oxonase activities decreased more noticeably. Similarly, while freeze-thaw cycles did not affect the PON1 activities in samples stored <2 y, this factor was more significant after 7 y for arylesterase. Assay temperature and specimen type also influenced PON1 measurements. CONCLUSIONS Sources of technical variability of PON1 activity assays, including storage duration, freeze-thaw, and temperature should be monitored and minimized through study design, quality control procedures and statistical methods, especially in longitudinal studies where specimens may be stored for years prior to analysis.
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Affiliation(s)
- Karen Huen
- Center for Children’s Environmental Health, School of Public Health, University of California, Berkeley, CA
| | - Rebecca Richter
- Departments of Genome Sciences and Medicine, Division of Medical Genetics, University of Washington, Seattle, WA
| | - Clement Furlong
- Departments of Genome Sciences and Medicine, Division of Medical Genetics, University of Washington, Seattle, WA
| | - Brenda Eskenazi
- Center for Children’s Environmental Health, School of Public Health, University of California, Berkeley, CA
| | - Nina Holland
- Center for Children’s Environmental Health, School of Public Health, University of California, Berkeley, CA
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Reactions of isodimethoate with human red cell acetylcholinesterase. Biochem Pharmacol 2008; 75:2045-53. [DOI: 10.1016/j.bcp.2008.02.021] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2008] [Revised: 02/20/2008] [Accepted: 02/20/2008] [Indexed: 11/19/2022]
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