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Wong PT, Bhattacharjee S, Cannon J, Tang S, Yang K, Bowden S, Varnau V, O'Konek JJ, Choi SK. Reactivity and mechanism of α-nucleophile scaffolds as catalytic organophosphate scavengers. Org Biomol Chem 2019; 17:3951-3963. [PMID: 30942252 DOI: 10.1039/c9ob00503j] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Despite their unique benefits imparted by their structure and reactivity, certain α-nucleophile molecules remain underexplored as chemical inactivators for the topical decontamination of reactive organophosphates (OPs). Here, we present a library of thirty α-nucleophile scaffolds, each designed with either a pyridinium aldoxime (PAM) or hydroxamic acid (HA) α-nucleophile core tethered to a polar or charged scaffold for optimized physicochemical properties and reactivity. These library compounds were screened for their abilities to catalyze the hydrolysis of a model OP, paraoxon (POX), in kinetic assays. These screening experiments led to the identification of multiple lead compounds with the ability to inactivate POX two- to four-times more rapidly than Dekon 139-the active ingredient currently used for skin decontamination of OPs. Our mechanistic studies, performed under variable pH and temperature conditions suggested that the differences in the reactivity and activation energy of these compounds are fundamentally attributable to the core nucleophilicity and pKa. Following their screening and mechanistic studies, select lead compounds were further evaluated and demonstrated greater efficacy than Dekon 139 in the topical decontamination of POX in an ex vivo porcine skin model. In addition to OP reactivity, several compounds in the PAM class displayed a dual mode of activity, as they retained the ability to reactivate POX-inhibited acetylcholine esterase (AChE). In summary, this report describes a rationale for the hydrophilic scaffold design of α-nucleophiles, and it offers advanced insights into their chemical reactivity, mechanism, and practical utility as OP decontaminants.
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Affiliation(s)
- Pamela T Wong
- Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, Michigan 48109, USA.
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Bharate SB, Chao CK, Thompson CM. Comparison of the reactivation rates of acetylcholinesterase modified by structurally different organophosphates using novel pyridinium oximes. ENVIRONMENTAL TOXICOLOGY AND PHARMACOLOGY 2019; 71:103218. [PMID: 31302432 PMCID: PMC6736693 DOI: 10.1016/j.etap.2019.103218] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2018] [Revised: 03/27/2019] [Accepted: 06/24/2019] [Indexed: 06/10/2023]
Abstract
A novel panel of oximes were synthesized, which have displayed varying degree of reactivation ability towards different organophosphorus (OP) modified cholinesterases. In the present article, we report a comparative reactivation profile of a series of quaternary pyridinium-oximes for electric eel acetylcholinesterase (EEAChE) inhibited by the organophosphorus (OP) inhibitors methyl paraoxon (MePOX), ethyl paraoxon (POX; paraoxon) and diisopropyl fluorophosphate (DFP) that are distinguishable as dimethoxyphosphoryl, diethoxyphosphoryl and diisopropoxyphosphoryl AChE-OP-adducts. Most of the 59-oximes tested led to faster and more extensive reactivation of MePOX- and POX-inhibited EEAChE as compared to DFP-modified EEAChE. All were effective reactivators of three OP-modified EEAChE conjugates showing 18-21% reactivation for DFP-inhibited AChE and ≥45% reactivation for MePOX- and POX-inhibited EEAChE. Oximes 7 and 8 showed kr values better than pralidoxime (1) for DFP-inhibited EEAChE. Reactivation rates determined at different inhibition times showed no significant change in kr values during 0-90 min incubation with three OPs. However, a 34-72% decrease in kr for MePOX and POX and > 95% decrease in kr for DFP-inhibited EEAChE was observed after 24 h of OP-exposure (aging).
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Affiliation(s)
- Sandip B Bharate
- The Center for Structural and Functional Neuroscience, Department of Biomedical and Pharmaceutical Sciences, The University of Montana, Missoula, MT, 59812, USA; Medicinal Chemistry Division, CSIR-Indian Institute of Integrative Medicine, Canal Road, Jammu, 180001, India.
| | - Chih-Kai Chao
- The Center for Structural and Functional Neuroscience, Department of Biomedical and Pharmaceutical Sciences, The University of Montana, Missoula, MT, 59812, USA
| | - Charles M Thompson
- The Center for Structural and Functional Neuroscience, Department of Biomedical and Pharmaceutical Sciences, The University of Montana, Missoula, MT, 59812, USA.
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Franjesevic AJ, Sillart SB, Beck JM, Vyas S, Callam CS, Hadad CM. Resurrection and Reactivation of Acetylcholinesterase and Butyrylcholinesterase. Chemistry 2019; 25:5337-5371. [PMID: 30444932 PMCID: PMC6508893 DOI: 10.1002/chem.201805075] [Citation(s) in RCA: 57] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2018] [Revised: 11/15/2018] [Indexed: 01/10/2023]
Abstract
Organophosphorus (OP) nerve agents and pesticides present significant threats to civilian and military populations. OP compounds include the nefarious G and V chemical nerve agents, but more commonly, civilians are exposed to less toxic OP pesticides, resulting in the same negative toxicological effects and thousands of deaths on an annual basis. After decades of research, no new therapeutics have been realized since the mid-1900s. Upon phosphylation of the catalytic serine residue, a process known as inhibition, there is an accumulation of acetylcholine (ACh) in the brain synapses and neuromuscular junctions, leading to a cholinergic crisis and eventually death. Oxime nucleophiles can reactivate select OP-inhibited acetylcholinesterase (AChE). Yet, the fields of reactivation of AChE and butyrylcholinesterase encounter additional challenges as broad-spectrum reactivation of either enzyme is difficult. Additional problems include the ability to cross the blood brain barrier (BBB) and to provide therapy in the central nervous system. Yet another complication arises in a competitive reaction, known as aging, whereby OP-inhibited AChE is converted to an inactive form, which until very recently, had been impossible to reverse to an active, functional form. Evaluations of uncharged oximes and other neutral nucleophiles have been made. Non-oxime reactivators, such as aromatic general bases and Mannich bases, have been developed. The issue of aging, which generates an anionic phosphylated serine residue, has been historically recalcitrant to recovery by any therapeutic approach-that is, until earlier this year. Mannich bases not only serve as reactivators of OP-inhibited AChE, but this class of compounds can also recover activity from the aged form of AChE, a process referred to as resurrection. This review covers the modern efforts to address all of these issues and notes the complexities of therapeutic development along these different lines of research.
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Affiliation(s)
- Andrew J Franjesevic
- Department of Chemistry and Biochemistry, The Ohio State University, 100 West 18th Ave, Columbus, OH, 43210, USA
| | - Sydney B Sillart
- Department of Chemistry and Biochemistry, The Ohio State University, 100 West 18th Ave, Columbus, OH, 43210, USA
| | - Jeremy M Beck
- Department of Chemistry and Biochemistry, The Ohio State University, 100 West 18th Ave, Columbus, OH, 43210, USA
| | - Shubham Vyas
- Department of Chemistry and Biochemistry, The Ohio State University, 100 West 18th Ave, Columbus, OH, 43210, USA
- Current Address: Department of Chemistry, Colorado School of Mines, 1500 Illinois St., Golden, CO, 80401, USA
| | - Christopher S Callam
- Department of Chemistry and Biochemistry, The Ohio State University, 100 West 18th Ave, Columbus, OH, 43210, USA
| | - Christopher M Hadad
- Department of Chemistry and Biochemistry, The Ohio State University, 100 West 18th Ave, Columbus, OH, 43210, USA
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Horn G, de Koning MC, van Grol M, Thiermann H, Worek F. Interactions between acetylcholinesterase, toxic organophosphorus compounds and a short series of structurally related non-oxime reactivators: Analysis of reactivation and inhibition kinetics in vitro. Toxicol Lett 2018; 299:218-225. [PMID: 30312685 DOI: 10.1016/j.toxlet.2018.10.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2018] [Revised: 09/24/2018] [Accepted: 10/05/2018] [Indexed: 12/12/2022]
Abstract
Poisoning by organophosphorus compounds (OP) is characterized by inhibition of the key enzyme acetylcholinesterase (AChE) and potentially fatal outcomes in humans. Insufficient efficacy of the standard therapy with atropine and AChE reactivators (oximes) against certain OP initiated synthesis of novel non-oxime reactivators basing on the common structure 4-amino-2-((diethylamino)methyl)phenol (ADOC). Recently, we reported of a pyrrolidine-bearing ADOC analogue (3 l) with a remarkable ability to reactivate OP-inhibited AChE. This in vitro study was undertaken to determine reactivity, affinity and overall reactivation constants of 3 l, the reference compound ADOC and two structural analogues with human AChE inhibited by paraoxon, sarin, cyclosarin and VX. The data showed a 10 to 34-fold reactivating potency of 3 l compared to ADOC mainly due to improved affinity. Additionally, various interactions between non-oximes, human or guinea pig (GP) AChE and structurally different OP were investigated: OP-inhibited guinea pig AChE was less amenable to reactivation by ADOC and 3 l than human AChE. Compound 3 l was considered as potential pretreatment to prevent AChE from irreversible inhibition by OP: In the presence of 10 μM 3 l inhibition of native human AChE was attenuated resulting in protective indices (PI) ranging from about 2.7 to 6.0. A combination of 3 l and the bispyridinium oxime HI-6 was tested to reactivate OP-inhibited AChE: The superior reactivator of the respective OP-AChE combination dominated the reactivation process and a synergistic effect could not be observed. In conclusion, novel non-oxime reactivators like 3 l may be considered as promising templates for the design of more potent therapeutics against poisoning by highly toxic OP.
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Affiliation(s)
- Gabriele Horn
- Bundeswehr Institute of Pharmacology and Toxicology, Neuherbergstrasse 11, 80937 Munich, Germany
| | | | - Marco van Grol
- TNO, Lange Kleiweg 137, 2288 GJ Rijswijk, the Netherlands
| | - Horst Thiermann
- Bundeswehr Institute of Pharmacology and Toxicology, Neuherbergstrasse 11, 80937 Munich, Germany
| | - Franz Worek
- Bundeswehr Institute of Pharmacology and Toxicology, Neuherbergstrasse 11, 80937 Munich, Germany.
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Muckova L, Pejchal J, Jost P, Vanova N, Herman D, Jun D. Cytotoxicity of acetylcholinesterase reactivators evaluated in vitro and its relation to their structure. Drug Chem Toxicol 2018; 42:252-256. [DOI: 10.1080/01480545.2018.1432641] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Affiliation(s)
- Lubica Muckova
- Department of Toxicology and Military Pharmacy, Faculty of Military Health Sciences, University of Defence, Trebesska, Hradec Kralove, Czech Republic
| | - Jaroslav Pejchal
- Department of Toxicology and Military Pharmacy, Faculty of Military Health Sciences, University of Defence, Trebesska, Hradec Kralove, Czech Republic
| | - Petr Jost
- Department of Toxicology and Military Pharmacy, Faculty of Military Health Sciences, University of Defence, Trebesska, Hradec Kralove, Czech Republic
| | - Nela Vanova
- Department of Toxicology and Military Pharmacy, Faculty of Military Health Sciences, University of Defence, Trebesska, Hradec Kralove, Czech Republic
| | - David Herman
- Department of Toxicology and Military Pharmacy, Faculty of Military Health Sciences, University of Defence, Trebesska, Hradec Kralove, Czech Republic
| | - Daniel Jun
- Department of Toxicology and Military Pharmacy, Faculty of Military Health Sciences, University of Defence, Trebesska, Hradec Kralove, Czech Republic
- Biomedical Research Centre, University Hospital Hradec Kralove, Sokolska, Hradec Kralove, Czech Republic
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