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Wei Z, Zhang D, Liu X, Nie H, Ouyang Q, Zhang X, Zheng Z. Screening of efficient salicylaldoxime reactivators for DFP and paraoxon-inhibited acetylcholinesterase. RSC Med Chem 2024; 15:1225-1235. [PMID: 38665821 PMCID: PMC11042241 DOI: 10.1039/d3md00628j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2023] [Accepted: 01/25/2024] [Indexed: 04/28/2024] Open
Abstract
Previously we reported two salicylaldoxime conjugates (L7R3 and L7R5) showing equal or even higher reactivating efficiency for both organophosphorus nerve agent and pesticide inhibited acetylcholinesterase in comparison to obidoxime and HI-6. In this study, L7R3 and L7R5 were selected as lead compounds and refined by employing a fragment-based drug design strategy, and a total of 32 novel salicylaldoxime conjugates were constructed and screened for DFP and paraoxon inhibited acetylcholinesterase. The findings demonstrate that the conjugate L73R3, which contains a 4-nitrophenyl group, exhibited a higher reactivation efficacy against paraoxon-inhibited acetylcholinesterase compared to obidoxime and HI-6. It was confirmed that the combination of a 4-pyridinyl or 4-nitrophenyl peripheral site ligand, a piperazine linker and a methyl or chloro-substituted salicylaldoxime could construct efficient nonquaternary oxime reactivators. The results hold promise for developing a new generation of highly effective antidotes for organophosphate poisoning.
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Affiliation(s)
- Zhao Wei
- Department of Medicinal Chemistry and Pharmaceutical analysis, School of Pharmacy, Air Force Medical University Xi'an 300071 China
| | - Dongxu Zhang
- Department of Medicinal Chemistry and Pharmaceutical analysis, School of Pharmacy, Air Force Medical University Xi'an 300071 China
| | - Xueying Liu
- Department of Medicinal Chemistry and Pharmaceutical analysis, School of Pharmacy, Air Force Medical University Xi'an 300071 China
| | - Huifang Nie
- Department of Medicinal Chemistry and Pharmaceutical analysis, School of Pharmacy, Air Force Medical University Xi'an 300071 China
| | - Qin Ouyang
- Department of Medicinal Chemistry, School of Pharmacy, Third Military Medical University Chongqing 400038 China
| | - Xinlei Zhang
- Department of Medicinal Chemistry and Pharmaceutical analysis, School of Pharmacy, Air Force Medical University Xi'an 300071 China
| | - Zhibing Zheng
- Department of Medicinal Chemistry, Institute of Pharmacology and Toxicology, Academy of Military Medical Sciences Beijing 100850 China
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2
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Singh T, Ramakrishnan S, Wu X, Reddy DS. Sex Differences in Organophosphate Model of Benzodiazepine-Refractory Status Epilepticus and Neuronal Damage. J Pharmacol Exp Ther 2024; 388:313-324. [PMID: 37770202 PMCID: PMC10801723 DOI: 10.1124/jpet.123.001747] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2023] [Revised: 08/15/2023] [Accepted: 08/17/2023] [Indexed: 10/03/2023] Open
Abstract
Sex differences are common in human epilepsy. Although men are more susceptible to seizure than women, the mechanisms underlying sex-specific vulnerabilities to seizure are unclear. The organophosphate (OP) diisopropylfluorophosphate (DFP) is known to cause neurotoxicity and status epilepticus (SE), a serious neurologic condition that causes prolonged seizures and brain damage. Current therapies for OP poisoning and SE do not consider neuronal variations between male and female brains. Therefore, we investigated sex-dependent differences in electrographic seizure activity and neuronal injury using the DFP model of refractory SE in rats. Electroencephalogram recordings were used to monitor DFP-induced SE, and the extent of brain injury was determined using fluoro-jade-B staining to detect cellular necrosis. After DFP exposure, we observed striking sex-dependent differences in SE and seizure activity patterns as well as protective responses to midazolam treatment. Following acute DFP exposure, male animals displayed more severe SE with intense epileptiform spiking and greater mortality than females. In contrast, we observed significantly more injured cells and cellular necrosis in the hippocampus and other brain regions in females than in males. We also observed extensive neuronal injury in the somatosensory cortex of males. The anticonvulsant effect of midazolam against SE was limited in this model and found to be similar in males and females. However, unlike males, females exhibited substantially more protection against neuronal damage after midazolam treatment. Overall, these results demonstrate significant sex-dependent differences in DFP-induced refractory SE and neuronal damage patterns, suggesting that it may be possible to develop sex-specific neuroprotective strategies for OP intoxication and refractory SE. SIGNIFICANCE STATEMENT: Sex-dependent differences in neurotoxicity and status epilepticus (SE) are key biological variables after organophosphate (OP) exposure. Here, we investigated sex-dependent differences in SE and brain injury after acute diisopropylfluorophosphate exposure. Male rats had more severe SE and less survival than females, while females had more neuronal damage. Females had more neuroprotection to midazolam than males, while both sexes had similar but partial anticonvulsant effects. These findings suggest that a sex-specific therapeutic approach may prevent neurological complications of OP-induced SE.
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Affiliation(s)
- Tanveer Singh
- Department of Neuroscience and Experimental Therapeutics and Institute of Pharmacology and Neurotherapeutics, Texas A&M University School of Medicine, Bryan, Texas
| | - Sreevidhya Ramakrishnan
- Department of Neuroscience and Experimental Therapeutics and Institute of Pharmacology and Neurotherapeutics, Texas A&M University School of Medicine, Bryan, Texas
| | - Xin Wu
- Department of Neuroscience and Experimental Therapeutics and Institute of Pharmacology and Neurotherapeutics, Texas A&M University School of Medicine, Bryan, Texas
| | - Doodipala Samba Reddy
- Department of Neuroscience and Experimental Therapeutics and Institute of Pharmacology and Neurotherapeutics, Texas A&M University School of Medicine, Bryan, Texas
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3
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Lindgren C, Forsgren N, Hoster N, Akfur C, Artursson E, Edvinsson L, Svensson R, Worek F, Ekström F, Linusson A. Broad‐Spectrum Antidote Discovery by Untangling the Reactivation Mechanism of Nerve‐Agent‐Inhibited Acetylcholinesterase. Chemistry 2022; 28:e202200678. [PMID: 35420233 PMCID: PMC9400889 DOI: 10.1002/chem.202200678] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2022] [Indexed: 11/13/2022]
Abstract
Reactivators are vital for the treatment of organophosphorus nerve agent (OPNA) intoxication but new alternatives are needed due to their limited clinical applicability. The toxicity of OPNAs stems from covalent inhibition of the essential enzyme acetylcholinesterase (AChE), which reactivators relieve via a chemical reaction with the inactivated enzyme. Here, we present new strategies and tools for developing reactivators. We discover suitable inhibitor scaffolds by using an activity‐independent competition assay to study non‐covalent interactions with OPNA‐AChEs and transform these inhibitors into broad‐spectrum reactivators. Moreover, we identify determinants of reactivation efficiency by analysing reactivation and pre‐reactivation kinetics together with structural data. Our results show that new OPNA reactivators can be discovered rationally by exploiting detailed knowledge of the reactivation mechanism of OPNA‐inhibited AChE.
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Affiliation(s)
| | - Nina Forsgren
- CBRN Defense and Security Swedish Defense Research Agency 906 21 Umeå Sweden
| | - Norman Hoster
- Department of Chemistry Umeå University 901 87 Umeå Sweden
| | - Christine Akfur
- CBRN Defense and Security Swedish Defense Research Agency 906 21 Umeå Sweden
| | - Elisabet Artursson
- CBRN Defense and Security Swedish Defense Research Agency 906 21 Umeå Sweden
| | | | - Richard Svensson
- Biomedicinskt Centrum BMC Uppsala University 752 37 Uppsala Sweden
| | - Franz Worek
- Bundeswehr Institute of Pharmacology and Toxicology 80937 Munich Germany
| | - Fredrik Ekström
- CBRN Defense and Security Swedish Defense Research Agency 906 21 Umeå Sweden
| | - Anna Linusson
- Department of Chemistry Umeå University 901 87 Umeå Sweden
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4
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Countermeasures in organophosphorus intoxication: pitfalls and prospects. Trends Pharmacol Sci 2022; 43:593-606. [DOI: 10.1016/j.tips.2022.04.008] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2022] [Revised: 04/14/2022] [Accepted: 04/17/2022] [Indexed: 11/24/2022]
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5
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Wei Z, Zhang X, Nie H, Yao L, Liu Y, Zheng Z, Ouyang Q. Discovery of Novel Non-Oxime Reactivators Showing In Vivo Antidotal Efficiency for Sarin Poisoned Mice. MOLECULES (BASEL, SWITZERLAND) 2022; 27:molecules27031096. [PMID: 35164361 PMCID: PMC8840479 DOI: 10.3390/molecules27031096] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/04/2022] [Revised: 01/26/2022] [Accepted: 02/03/2022] [Indexed: 12/02/2022]
Abstract
A family of novel efficient non-oxime compounds exhibited promising reactivation efficacy for VX and sarin inhibited human acetylcholinesterase was discovered. It was found that aromatic groups coupled to Mannich phenols and the introduction of imidazole to the ortho position of phenols would dramatically enhance reactivation efficiency. Moreover, the in vivo experiment was conducted, and the results demonstrated that Mannich phenol L10R1 (30 mg/kg, ip) could afford 100% 48 h survival for mice of 2*LD50 sarin exposure, which is promising for the development of non-oxime reactivators with central efficiency.
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Affiliation(s)
- Zhao Wei
- Department of Medicinal Chemistry, School of Pharmacy, Air Force Medical University, Xi’an 300071, China; (X.Z.); (H.N.); (L.Y.)
- Correspondence: (Z.W.); (Z.Z.); (Q.O.)
| | - Xinlei Zhang
- Department of Medicinal Chemistry, School of Pharmacy, Air Force Medical University, Xi’an 300071, China; (X.Z.); (H.N.); (L.Y.)
| | - Huifang Nie
- Department of Medicinal Chemistry, School of Pharmacy, Air Force Medical University, Xi’an 300071, China; (X.Z.); (H.N.); (L.Y.)
| | - Lin Yao
- Department of Medicinal Chemistry, School of Pharmacy, Air Force Medical University, Xi’an 300071, China; (X.Z.); (H.N.); (L.Y.)
| | - Yanqin Liu
- Institute of Pharmacology and Toxicology, Academy of Military Medical Sciences, Beijing 100850, China;
| | - Zhibing Zheng
- Institute of Pharmacology and Toxicology, Academy of Military Medical Sciences, Beijing 100850, China;
- Correspondence: (Z.W.); (Z.Z.); (Q.O.)
| | - Qin Ouyang
- Department of Medicinal Chemistry, School of Pharmacy, Third Military Medical University, Chongqing 400038, China
- Correspondence: (Z.W.); (Z.Z.); (Q.O.)
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6
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Reddy DS, Zaayman M, Kuruba R, Wu X. Comparative profile of refractory status epilepticus models following exposure of cholinergic agents pilocarpine, DFP, and soman. Neuropharmacology 2021; 191:108571. [PMID: 33878303 DOI: 10.1016/j.neuropharm.2021.108571] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2021] [Revised: 03/24/2021] [Accepted: 04/13/2021] [Indexed: 12/12/2022]
Abstract
Status epilepticus (SE) is a medical emergency with continuous seizure activity that causes profound neuronal damage, morbidity, or death. SE incidents can arise spontaneously but mostly are elicited by seizurogenic triggers. Chemoconvulsants such as the muscarinic agonist pilocarpine and, organophosphates (OP) such as the pesticide diisopropylfluorophosphate (DFP) and, the nerve agent soman, can induce SE. Pilocarpine, DFP, and soman share a common feature of cholinergic crisis that transitions into a state of refractory SE, but their comparative profiles remain unclear. Here, we evaluated the comparative convulsant profile of pilocarpine, DFP, and soman to produce refractory SE and brain damage in rats. Behavioral and electrographic seizures were monitored for 24 h after exposure, and the extent of brain injury was determined by histological markers of neuronal injury and degeneration. Seizures were elicited rather slowly after pilocarpine as compared to DFP or soman, which caused rapid onset of spiking that swiftly developed into persistent SE. Time-course of SE activity after DFP was comparable to that after soman, a potent nerve agent. Diazepam controlled pilocarpine-induced SE, but it was ineffective in reducing OP-induced SE. All three agents produced modestly different degrees of neuronal injury and neurodegeneration in the brain. These results reveal distinct convulsant and neuronal injury patterns following exposure to cholinergic agonists, OP pesticides, and nerve agents. A battery of SE models, especially SE induced by cholinergic agents and other etiologies including epilepsy and brain tumors, is essential to identify novel anticonvulsant therapies for the management of refractory SE.
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Affiliation(s)
- Doodipala Samba Reddy
- Department of Neuroscience and Experimental Therapeutics, Texas A&M University Health Science Center College of Medicine, Bryan, TX, 77807, USA.
| | - Marcus Zaayman
- Department of Neuroscience and Experimental Therapeutics, Texas A&M University Health Science Center College of Medicine, Bryan, TX, 77807, USA
| | - Ramkumar Kuruba
- Department of Neuroscience and Experimental Therapeutics, Texas A&M University Health Science Center College of Medicine, Bryan, TX, 77807, USA
| | - Xin Wu
- Department of Neuroscience and Experimental Therapeutics, Texas A&M University Health Science Center College of Medicine, Bryan, TX, 77807, USA
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7
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Molecular modeling-guided optimization of acetylcholinesterase reactivators: A proof for reactivation of covalently inhibited targets. Eur J Med Chem 2021; 215:113286. [PMID: 33611189 PMCID: PMC7877871 DOI: 10.1016/j.ejmech.2021.113286] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2020] [Revised: 12/23/2020] [Accepted: 02/03/2021] [Indexed: 11/23/2022]
Abstract
Covalent drugs have been intensively studied in some very important fields such as anti-tumor and anti-virus, including the currently global-spread SARS-CoV-2. However, these drugs may interact with a variety of biological macromolecules and cause serious toxicology, so how to reactivate the inhibited targets seems to be imperative in the near future. Organophosphate was an extreme example, which could form a covalent bound easily with acetylcholinesterase and irreversibly inhibited the enzyme, causing high toxicology. Some nucleophilic oxime reactivators for organophosphate poisoned acetylcholinesterase had been developed, but the reactivation process was still less understanding. Herein, we proposed there should be a pre-reactivated pose during the reactivating process and compounds whose binding pose was easy to transfer to the pre-reactivated pose might be efficient reactivators. Then we refined the previous reactivators based on the molecular dynamic simulation results, the resulting compounds L7R3 and L7R5 were proven as much more efficient reactivators for organophosphate inhibited acetylcholinesterase than currently used oximes. This work might provide some insights for constructing reactivators of covalently inhibited targets by using computational methods.
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Hayes TR, Blecha JE, Chao CK, Huynh TL, VanBrocklin HF, Zinn KR, Taylor PW, Gerdes JM, Thompson CM. Positron emission tomography evaluation of oxime countermeasures in live rats using the tracer O-(2-[ 18 F]fluoroethyl)-O-(p-nitrophenyl)methylphosphonate [ 18 F]-VXS. Ann N Y Acad Sci 2020; 1479:180-195. [PMID: 32436233 DOI: 10.1111/nyas.14363] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2020] [Revised: 04/13/2020] [Accepted: 04/17/2020] [Indexed: 11/27/2022]
Abstract
Oxime antidotes regenerate organophosphate-inhibited acetylcholinesterase (AChE). Although they share a common mechanism of AChE reactivation, the rate and amount of oxime that enters the brain are critical to the efficacy, a process linked to the oxime structure and charge. Using a platform based on the organophosphate [18 F]-VXS as a positron emission tomography tracer for active AChE, the in vivo distribution of [18 F]-VXS was evaluated after an LD50 dose (250 μg/kg) of the organophosphate paraoxon (POX) and following oximes as antidotes. Rats given [18 F]-VXS tracer alone had significantly higher radioactivity (two- to threefold) in the heart and lung than rats given LD50 POX at 20 or 60 min prior to [18 F]-VXS. When rats were given LD50 POX followed by 2-PAM (cationic), RS194b (ionizable), or monoisonitrosoacetone (MINA) (neutral), central nervous system (CNS) radioactivity returned to levels at or above untreated naive rats (no POX), whereas CNS radioactivity did not increase in rats given the dication oximes HI-6 or MMB-4. MINA showed a significant, pairwise increase in CNS brain radioactivity compared with POX-treated rats. This new in vivo dynamic platform using [18 F]-VXS tracer measures and quantifies peripheral and CNS relative changes in AChE availability after POX exposure and is suitable for comparing oxime delivery and AChE reactivation in rats.
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Affiliation(s)
- Thomas R Hayes
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, California
| | - Joseph E Blecha
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, California
| | - Chih-Kai Chao
- Department of Biomedical and Pharmaceutical Sciences, University of Montana, Missoula, Montana
| | - Tony L Huynh
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, California
| | - Henry F VanBrocklin
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, California
| | - Kurt R Zinn
- Departments of Radiology, Small Animal Clinical Sciences, and Biomedical Engineering, Institute for Quantitative Health Science and Engineering, Michigan State University, East Lansing, Michigan
| | - Palmer W Taylor
- Department of Pharmacology, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California at San Diego, La Jolla, California
| | - John M Gerdes
- Department of Biomedical and Pharmaceutical Sciences, University of Montana, Missoula, Montana
| | - Charles M Thompson
- Department of Biomedical and Pharmaceutical Sciences, University of Montana, Missoula, Montana
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Thompson CM, Gerdes JM, VanBrocklin HF. Positron emission tomography studies of organophosphate chemical threats and oxime countermeasures. Neurobiol Dis 2019; 133:104455. [PMID: 31022458 DOI: 10.1016/j.nbd.2019.04.011] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2018] [Revised: 03/28/2019] [Accepted: 04/19/2019] [Indexed: 01/31/2023] Open
Abstract
There is a unique in vivo interplay involving the mechanism of inactivation of acetylcholinesterase (AChE) by toxic organophosphorus (OP) compounds and the restoration of AChE activity by oxime antidotes. OP compounds form covalent adducts to this critical enzyme target and oximes are introduced to directly displace the OP from AChE. For the most part, the in vivo inactivation of AChE leading to neurotoxicity and antidote-based therapeutic reversal of this mechanism are well understood, however, these molecular-level events have not been evaluated by dynamic imaging in living systems at millimeter resolution. A deeper understanding of these critically, time-dependent mechanisms is needed to develop new countermeasures. To address this void and to help accelerate the development of new countermeasures, positron-emission tomography (PET) has been investigated as a unique opportunity to create platform technologies to directly examine the interdependent toxicokinetic/pharmacokinetic and toxicodynamic/pharmacodynamic features of OPs and oximes in real time within live animals. This review will cover two first-in-class PET tracers representing an OP and an oxime antidote, including their preparation, requisite pharmacologic investigations, mechanistic interpretations, biodistribution and imaging.
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Affiliation(s)
- Charles M Thompson
- Department of Biomedical and Pharmaceutical Sciences, University of Montana, Missoula, MT 59812, USA.
| | - John M Gerdes
- Department of Biomedical and Pharmaceutical Sciences, University of Montana, Missoula, MT 59812, USA
| | - Henry F VanBrocklin
- Department of Radiology and Biomedical Imaging, University of California, San Francisco 185 Berry St. Suite 350, San Francisco, CA 94107, USA
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Wei Z, Bi H, Liu YQ, Nie HF, Yao L, Wang SZ, Yang J, Wang YA, Liu X, Zheng ZB. Design, synthesis and evaluation of new classes of nonquaternary reactivators for acetylcholinesterase inhibited by organophosphates. Bioorg Chem 2018; 81:681-688. [DOI: 10.1016/j.bioorg.2018.09.025] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2018] [Revised: 09/13/2018] [Accepted: 09/17/2018] [Indexed: 12/15/2022]
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11
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Wu X, Kuruba R, Reddy DS. Midazolam-Resistant Seizures and Brain Injury after Acute Intoxication of Diisopropylfluorophosphate, an Organophosphate Pesticide and Surrogate for Nerve Agents. J Pharmacol Exp Ther 2018; 367:302-321. [PMID: 30115757 DOI: 10.1124/jpet.117.247106] [Citation(s) in RCA: 59] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2017] [Accepted: 08/14/2018] [Indexed: 12/15/2022] Open
Abstract
Organophosphates (OP) such as the pesticide diisopropylfluorophosphate (DFP) and the nerve agent sarin are lethal chemicals that induce seizures, status epilepticus (SE), and brain damage. Midazolam, a benzodiazepine modulator of synaptic GABA-A receptors, is currently considered as a new anticonvulsant for nerve agents. Here, we characterized the time course of protective efficacy of midazolam (0.2-5 mg/kg, i.m.) in rats exposed to DFP, a chemical threat agent and surrogate for nerve agents. Behavioral and electroencephalogram (EEG) seizures were monitored for 24 hours after DFP exposure. The extent of brain injury was determined 3 days after DFP exposure by unbiased stereologic analyses of valid markers of neurodegeneration and neuroinflammation. Seizures were elicited within ∼8 minutes after DFP exposure that progressively developed into persistent SE lasting for hours. DFP exposure resulted in massive neuronal injury or necrosis, neurodegeneration of principal cells and interneurons, and neuroinflammation as evident by extensive activation of microglia and astrocytes in the hippocampus, amygdala, and other brain regions. Midazolam controlled seizures, neurodegeneration, and neuroinflammation when given early (10 minutes) after DFP exposure, but it was less effective when given at 40 minutes or later. Delayed therapy (≥40 minutes), a simulation of the practical therapeutic window for first responders or hospital admission, was associated with reduced seizure protection and neuroprotection. These results strongly reaffirm that the DFP-induced seizures and brain damage are progressively resistant to delayed treatment with midazolam, confirming the benzodiazepine refractory SE after OP intoxication. Thus, novel anticonvulsants superior to midazolam or adjunct therapies that enhance its efficacy are needed for effective treatment of refractory SE.
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Affiliation(s)
- Xin Wu
- Department of Neuroscience and Experimental Therapeutics, Texas A&M University Health Science Center College of Medicine, Bryan, Texas
| | - Ramkumar Kuruba
- Department of Neuroscience and Experimental Therapeutics, Texas A&M University Health Science Center College of Medicine, Bryan, Texas
| | - Doodipala Samba Reddy
- Department of Neuroscience and Experimental Therapeutics, Texas A&M University Health Science Center College of Medicine, Bryan, Texas
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12
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Wei Z, Liu YQ, Wang SZ, Yao L, Nie HF, Wang YA, Liu XY, Zheng ZB, Li S. Conjugates of salicylaldoximes and peripheral site ligands: Novel efficient nonquaternary reactivators for nerve agent-inhibited acetylcholinesterase. Bioorg Med Chem 2017; 25:4497-4505. [DOI: 10.1016/j.bmc.2017.06.041] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2017] [Revised: 06/13/2017] [Accepted: 06/25/2017] [Indexed: 10/19/2022]
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13
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Gorecki L, Korabecny J, Musilek K, Nepovimova E, Malinak D, Kucera T, Dolezal R, Jun D, Soukup O, Kuca K. Progress in acetylcholinesterase reactivators and in the treatment of organophosphorus intoxication: a patent review (2006-2016). Expert Opin Ther Pat 2017; 27:971-985. [PMID: 28569609 DOI: 10.1080/13543776.2017.1338275] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
INTRODUCTION organophosphorus compounds act as irreversible inhibitors of the vital enzyme acetylcholinesterase (AChE). this leads in the accumulation of acetylcholine (ACh) leading to cholinergic crisis and death. The main therapeutic approach is based on immediate administration of an ache reactivator as an antidote enabling recovery of the ache function. Areas covered: This review covers the development of AChE reactivators in order to introduce a new efficient drug that will overcome significant failures of common antidotes. Further options together with methods of detection are also discussed in order to assure a complete insight into the treatment of intoxication. Expert opinion: Since organophosphates belong to the most toxic chemical warfare agents, efficient antidotes are a matter of importance. The solution of how to limit the basic drawbacks of clinically used reactivators remained a spotlight for many researches worldwide. Recent strategies of the treatment of OP exposure bring us new possibilities which may overcome classic antidotes. The importance of detection of OP also has to be taken into consideration. Especially, with the fast spreading toxic effect when death can occur within minutes.
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Affiliation(s)
- Lukas Gorecki
- a Department of Toxicology and Military Pharmacy, Faculty of Military Health Sciences , University of Defence , Hradec Kralove , Czech Republic.,b Biomedical Research Centre , University Hospital Hradec Kralove , Hradec Kralove , Czech Republic
| | - Jan Korabecny
- a Department of Toxicology and Military Pharmacy, Faculty of Military Health Sciences , University of Defence , Hradec Kralove , Czech Republic.,b Biomedical Research Centre , University Hospital Hradec Kralove , Hradec Kralove , Czech Republic
| | - Kamil Musilek
- b Biomedical Research Centre , University Hospital Hradec Kralove , Hradec Kralove , Czech Republic.,c Faculty of Science, Department of Chemistry , University of Hradec Kralove , Hradec Kralove , Czech Republic
| | - Eugenie Nepovimova
- a Department of Toxicology and Military Pharmacy, Faculty of Military Health Sciences , University of Defence , Hradec Kralove , Czech Republic.,b Biomedical Research Centre , University Hospital Hradec Kralove , Hradec Kralove , Czech Republic
| | - David Malinak
- b Biomedical Research Centre , University Hospital Hradec Kralove , Hradec Kralove , Czech Republic.,d Department of Physiology and Pathophysiology, Faculty of Medicine , University of Ostrava , Ostrava , Czech Republic
| | - Tomas Kucera
- a Department of Toxicology and Military Pharmacy, Faculty of Military Health Sciences , University of Defence , Hradec Kralove , Czech Republic
| | - Rafael Dolezal
- b Biomedical Research Centre , University Hospital Hradec Kralove , Hradec Kralove , Czech Republic.,c Faculty of Science, Department of Chemistry , University of Hradec Kralove , Hradec Kralove , Czech Republic
| | - Daniel Jun
- a Department of Toxicology and Military Pharmacy, Faculty of Military Health Sciences , University of Defence , Hradec Kralove , Czech Republic.,b Biomedical Research Centre , University Hospital Hradec Kralove , Hradec Kralove , Czech Republic
| | - Ondrej Soukup
- a Department of Toxicology and Military Pharmacy, Faculty of Military Health Sciences , University of Defence , Hradec Kralove , Czech Republic.,b Biomedical Research Centre , University Hospital Hradec Kralove , Hradec Kralove , Czech Republic
| | - Kamil Kuca
- b Biomedical Research Centre , University Hospital Hradec Kralove , Hradec Kralove , Czech Republic.,c Faculty of Science, Department of Chemistry , University of Hradec Kralove , Hradec Kralove , Czech Republic
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14
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Joosen M, van den Berg R, de Jong A, van der Schans M, Noort D, Langenberg J. The impact of skin decontamination on the time window for effective treatment of percutaneous VX exposure. Chem Biol Interact 2017; 267:48-56. [DOI: 10.1016/j.cbi.2016.02.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2015] [Revised: 01/04/2016] [Accepted: 02/01/2016] [Indexed: 10/22/2022]
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15
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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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16
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Chambers JE, Meek EC, Chambers HW. Novel brain-penetrating oximes for reactivation of cholinesterase inhibited by sarin and VX surrogates. Ann N Y Acad Sci 2016; 1374:52-8. [PMID: 27153507 DOI: 10.1111/nyas.13053] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Current oxime reactivators for organophosphate-inhibited cholinesterase (ChE) do not effectively cross the blood-brain barrier and therefore cannot restore brain ChE activity in vivo. Our laboratories have studied highly relevant sarin and VX surrogates, which differ from their respective nerve agents only in the leaving group and thereby leave ChE phosphylated with the same chemical moiety as sarin and VX. Our laboratories have developed novel substituted phenoxyalkyl pyridinium oximes that lead to reduced ChE inhibition in the brains of rats challenged with a high sublethal dosage of the sarin surrogate, whereas 2-PAM did not, using a paradigm designed to demonstrate brain penetration. In addition, treatment of rats with these novel oximes is associated with attenuation of seizure-like behavior compared to rats treated with 2-PAM, providing additional evidence that the oximes penetrate the blood-brain barrier. Further, some of the oximes provided 24-h survival superior to 2-PAM, and shortened the duration of seizure-like behavior when rats were challenged with lethal dosages of the sarin and VX surrogates, providing additional support for the conclusion that these oximes penetrate the brain.
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Affiliation(s)
- Janice E Chambers
- Center for Environmental Health Sciences, College of Veterinary Medicine, Mississippi State University, Mississippi State, Mississippi
| | - Edward C Meek
- Center for Environmental Health Sciences, College of Veterinary Medicine, Mississippi State University, Mississippi State, Mississippi
| | - Howard W Chambers
- Department of Biochemistry, Molecular Biology, Entomology and Plant Pathology, Mississippi State University, Mississippi State, Mississippi
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17
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Voicu VA, Medvedovici AV, Sakurada K, Ohta H, Rădulescu FȘ, Miron DS. The forgotten or underestimated relevance of biopharmaceutical-based assessments for the oral absorption studies of oxime reactivators. Expert Opin Drug Metab Toxicol 2016; 12:743-52. [DOI: 10.1080/17425255.2016.1179282] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Affiliation(s)
- Victor A. Voicu
- Department of Pharmacology, Toxicology and Clinical Psychopharmacology, University of Medicine and Pharmacy ‘Carol Davilla’, Bucharest, Romania
- Medical Science Section, Romanian Academy, Bucharest, Romania
| | | | - Koichi Sakurada
- Department of Forensic Dentistry, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan
| | - Hikoto Ohta
- Department of Forensic Chemistry, Toxicology Section, National Research Institute of Police Science, National Police Agency, Kashiwa City, Chiba, Japan
| | | | - Dalia Simona Miron
- Faculty of Pharmacy, University of Medicine and Pharmacy Carol Davila, Bucharest, Romania
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18
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Novel nonquaternary reactivators showing reactivation efficiency for soman-inhibited human acetylcholinesterase. Toxicol Lett 2016; 246:1-6. [PMID: 26809136 DOI: 10.1016/j.toxlet.2016.01.015] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2015] [Revised: 01/18/2016] [Accepted: 01/20/2016] [Indexed: 11/20/2022]
Abstract
Soman is a highly toxic nerve agent with strong inhibition of acetylcholinesterase (AChE), but of the few reactivators showing antidotal efficiency for soman-inhibited AChE presently are all permanently charged cationic oximes with poor penetration of the blood-brain barrier. To overcome this problem, uncharged reactivators have been designed and synthesized, but few of them were efficient for treating soman poisoning. Herein, we used a dual site biding strategy to develop more efficient uncharged reactivators. The ortho-hydroxylbenzaldoximes were chosen as reactivation ligands of AChE to prevent the secondary poisoning of AChE, and simple aromatic groups were used as peripheral site ligands of AChE, which were linked to the oximes in a similar way as that found in the reactivator HI-6. The in vitro experiment demonstrated that some of the resulting conjugates have robust activity against soman-inhibited AChE, and oxime 8b was highlighted as the most efficient one. Although not good as HI-6 in vitro, these new compounds hold promise for development of more efficient centrally acting reactivators for soman poisoning due to their novel nonquaternary structures, which are predicted to be able to cross the blood-brain barrier.
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19
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20
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Wei Z, Liu YQ, Zhou XB, Luo Y, Huang CQ, Wang YA, Zheng ZB, Li S. New efficient imidazolium aldoxime reactivators for nerve agent-inhibited acetylcholinesterase. Bioorg Med Chem Lett 2014; 24:5743-5748. [PMID: 25453812 DOI: 10.1016/j.bmcl.2014.10.055] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2014] [Revised: 09/26/2014] [Accepted: 10/17/2014] [Indexed: 10/24/2022]
Abstract
Herein, we described a new class of uncharged non-pyridinium reactivators for nerve agent-inhibited acetylcholinesterase (AChE). Based on a dual site binding strategy, we conjugated the imidazolium aldoxime to different peripheral site ligands (PSLs) of AChE through alkyl chains. Compared with the known quaternary pyridinium reactivators, two of the resulting conjugates (7g and 7h) were highlighted to be the first efficient non-pyridinium oxime conjugates exhibiting similar or superior ability to reactivate sarin-, VX- and tabun-inhibited AChE. Moreover, they were more broad-spectrum reactivators.
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Affiliation(s)
- Zhao Wei
- Laboratory of Computer-Aided Drug Design & Discovery, Beijing Institute of Pharmacology and Toxicology, Beijing 100850, China
| | - Yan-Qin Liu
- Department of Military Toxicology and Biochemical Pharmacology, Institute of Pharmacology and Toxicology, Academy of Military Medical Sciences, Beijing 100850, China
| | - Xin-Bo Zhou
- Laboratory of Computer-Aided Drug Design & Discovery, Beijing Institute of Pharmacology and Toxicology, Beijing 100850, China
| | - Yuan Luo
- Department of Military Toxicology and Biochemical Pharmacology, Institute of Pharmacology and Toxicology, Academy of Military Medical Sciences, Beijing 100850, China
| | - Chun-Qian Huang
- Department of Military Toxicology and Biochemical Pharmacology, Institute of Pharmacology and Toxicology, Academy of Military Medical Sciences, Beijing 100850, China
| | - Yong-An Wang
- Department of Military Toxicology and Biochemical Pharmacology, Institute of Pharmacology and Toxicology, Academy of Military Medical Sciences, Beijing 100850, China
| | - Zhi-Bing Zheng
- Laboratory of Computer-Aided Drug Design & Discovery, Beijing Institute of Pharmacology and Toxicology, Beijing 100850, China.
| | - Song Li
- Laboratory of Computer-Aided Drug Design & Discovery, Beijing Institute of Pharmacology and Toxicology, Beijing 100850, China
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21
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McHardy SF, Bohmann JA, Corbett MR, Campos B, Tidwell MW, Thompson PM, Bemben CJ, Menchaca TA, Reeves TE, Cantrell WR, Bauta WE, Lopez A, Maxwell DM, Brecht KM, Sweeney RE, McDonough J. Design, synthesis, and characterization of novel, nonquaternary reactivators of GF-inhibited human acetylcholinesterase. Bioorg Med Chem Lett 2014; 24:1711-4. [DOI: 10.1016/j.bmcl.2014.02.049] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2013] [Revised: 02/13/2014] [Accepted: 02/18/2014] [Indexed: 10/25/2022]
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22
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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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23
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Gupta B, Sharma R, Singh N, Kuca K, Acharya JR, Ghosh KK. In vitro reactivation kinetics of paraoxon- and DFP-inhibited electric eel AChE using mono- and bis-pyridinium oximes. Arch Toxicol 2013; 88:381-90. [PMID: 24065055 DOI: 10.1007/s00204-013-1136-z] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2013] [Accepted: 09/12/2013] [Indexed: 11/25/2022]
Abstract
Oxime-assisted reactivation of organophosphate (OP)-inhibited acetylcholinesterase (AChE) is a crucial step in the post-inhibitory treatment of OP intoxication. The limited efficacy of oxime reactivators for all OP nerve agents and pesticides led to the development of various novel oximes and their thorough kinetic investigations. Hence, in the present investigation, we have tested 10 structurally different pyridinium oxime-based reactivators for their in vitro potency to reactivate paraoxon- and DFP-inhibited electric eel AChE. From structure activity relationship point of view, various oximes such as mono-quaternary (2-PAM, K100, K024) and bis-quaternary symmetric (obidoxime, TMB-4) and asymmetric (K027, K048, K203, K618, K628) oximes bearing different connecting linkers (oxybismethylene, trimethylene, propane, butane, butene, and xylene) have been studied. The observed kinetic data demonstrate that not only the position of oxime group is decisive for the increased reactivation ability of oximes, but the role of connecting linker is also significant. Oximes with aliphatic linkers are superior reactivators than the oximes with unsaturated and aromatic linkers. The optimal chain length for plausible reactivation ability for paraoxon- and DFP-inhibited AChE is 3 or 4 carbon-carbon connecting linker between prydinium rings.
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Affiliation(s)
- Bhanushree Gupta
- School of Studies in Chemistry, Pt. Ravishankar Shukla University, Raipur, 492010, CG, India
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24
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Gupta B, Sharma R, Singh N, Karpichev Y, Satnami ML, Ghosh KK. Reactivity studies of carbon, phosphorus and sulfur-based acyl sites with tertiary oximes in gemini surfactants. J PHYS ORG CHEM 2013. [DOI: 10.1002/poc.3142] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Bhanushree Gupta
- School of Studies in Chemistry; Pt. Ravishankar Shukla University; Raipur C.G 492010 India
| | - Rahul Sharma
- School of Studies in Chemistry; Pt. Ravishankar Shukla University; Raipur C.G 492010 India
| | - Namrata Singh
- School of Studies in Chemistry; Pt. Ravishankar Shukla University; Raipur C.G 492010 India
| | - Yevgen Karpichev
- L.M. Litvinenko Institute of Physical Organic and Coal Chemistry; Donetsk 83114 Ukraine
| | - Manmohan L. Satnami
- School of Studies in Chemistry; Pt. Ravishankar Shukla University; Raipur C.G 492010 India
| | - Kallol K. Ghosh
- School of Studies in Chemistry; Pt. Ravishankar Shukla University; Raipur C.G 492010 India
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25
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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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26
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de Araujo Furtado M, Rossetti F, Chanda S, Yourick D. Exposure to nerve agents: from status epilepticus to neuroinflammation, brain damage, neurogenesis and epilepsy. Neurotoxicology 2012; 33:1476-1490. [PMID: 23000013 DOI: 10.1016/j.neuro.2012.09.001] [Citation(s) in RCA: 90] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2012] [Revised: 07/25/2012] [Accepted: 09/03/2012] [Indexed: 12/17/2022]
Abstract
Epilepsy is a common neurological disorder characterized by an initial injury due to stroke, traumatic brain injury, brain infection, or febrile seizures causing status epilepticus (SE). This phenomenon precedes recurrent (secondary) seizures, the latent period (period without seizures) and downstream appearance of spontaneous recurrent seizures (SRS). Epilepsy inducers include the organophosphorous (OP) compounds modified as chemical warfare nerve agents, such as soman. SE induced by soman is a result of cholinergic system hyperactivity caused by the irreversible inhibition of acetylcholinesterase, and the subsequent increase in the amount of the neurotransmitter acetylcholine at central and peripheral sites. SE leads to profound, permanent, complex and widespread brain damage and associated cognitive and behavioral deficits, accompanied by impaired neurogenesis. Several anticonvulsant and neuroprotective strategies have been studied in order to avoid the epileptogenesis which occurs after SE caused by soman exposure. In recent studies, we showed that SRS occur post-soman exposure and neuropathology can be reduced with diazepam (DZP) and valproic acid (VPA) when administered in combination treatment. These effects are accompanied by neurogenesis seen 15 days post-exposure in the hippocampal dentate gyrus (DG). This review discusses several findings about epilepsy induced by soman exposure such as behavioral changes, EEG anomalies, neuropathology, neuroinflammation, neurogenesis, possible circuitry changes and current strategies for treatment. The soman seizure model is an important model of temporal lobe epilepsy (TLE) and comparable in certain respects with well studied models in the literature such as pilocarpine and kainic acid. All these models together allow for a greater understanding of the different mechanisms of seizure induction, propagation and options for treatment. These studies are very necessary for current military and civilian treatment regimens, against OP nerve agent exposure, which fail to prevent SE resulting in severe neuropathology and epilepsy.
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Affiliation(s)
- Marcio de Araujo Furtado
- Center for Military Psychiatry and Neuroscience, Walter Reed Army Institute of Research, Silver Spring, MD, United States
| | - Franco Rossetti
- Center for Military Psychiatry and Neuroscience, Walter Reed Army Institute of Research, Silver Spring, MD, United States
| | - Soma Chanda
- Center for Military Psychiatry and Neuroscience, Walter Reed Army Institute of Research, Silver Spring, MD, United States
| | - Debra Yourick
- Center for Military Psychiatry and Neuroscience, Walter Reed Army Institute of Research, Silver Spring, MD, United States.
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Khan FA, Campbell AJ, Hoyt B, Herdman C, Ku T, Thangavelu S, Gordon RK. Oxidative mechanisms for the biotransformation of 1-methyl-1,6-dihydropyridine-2-carbaldoxime to pralidoxime chloride. Life Sci 2011; 89:911-7. [PMID: 21989207 DOI: 10.1016/j.lfs.2011.09.019] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2011] [Revised: 08/02/2011] [Accepted: 09/13/2011] [Indexed: 01/02/2023]
Abstract
AIMS Due to pralidoxime chloride's (2-PAM) positive charge, it's penetration through the blood brain barrier (BBB) and reactivation of organophosphate (OP) inhibited central nervous system (CNS) acetylcholinesterase (AChE) is poor. The results of CNS inhibited AChE are seizures. Pro-2-PAM (1-methyl-1,6-dihydropyridine-2-carbaldoxime), a pro-drug of 2-PAM, due to higher hydrophobicity, penetrates the BBB better but must be oxidized to 2-PAM, the active form of the oxime to reactivate CNS AChE in order to abrogate seizures. In this study, we characterize the in vivo mechanism of pro-2-PAM oxidation. MAIN METHODS A high pressure liquid chromatography (HPLC) assay was developed to quantify the conversion of pro-2-PAM to 2-PAM. NADPH oxidase activity was measured by a photo-luminescence assay using lucigenin substrate. Upon analysis, the rate of NADPH induced oxidation suggested that an alternate mechanism may be involved. Therefore, various enzyme co-factors of oxidation-reduction enzyme systems were evaluated, including nicotinamide adenine dinucleotide (NAD), nicotinamide adenine dinucleotide phosphate (NADP), flavin adenine dinucleotide (FAD), riboflavin 5'-phosphate (FMN), and riboflavin. Next, a spectrophotometric assay was developed to measure the conversion of pro-2-PAM to 2-PAM in the presence of riboflavin. KEY FINDINGS In guinea pig brain homogenate, diphenyleneiodonium (DPI), a specific NADPH oxidase inhibitor, reduced pro-2-PAM to 2-PAM conversion to less than 25%. In contrast, riboflavin, FAD, and FMN rapidly oxidized all pro-2-PAM to 2-PAM in an in vitro assay. Riboflavin oxidized pro-2-PAM reactivated diisopropylfluorophosphate (DFP) inhibited AChE. SIGNIFICANCE The present study shows that pro-2-PAM was rapidly oxidized by riboflavin to 2-PAM, which reactivated organophosphate (OP)-inhibited AChE.
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Affiliation(s)
- Farhat A Khan
- Department of Regulated Laboratories, Division of Regulated Activities, Silver Spring, MD 20910, United States.
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Masson P. Evolution of and perspectives on therapeutic approaches to nerve agent poisoning. Toxicol Lett 2011; 206:5-13. [PMID: 21524695 DOI: 10.1016/j.toxlet.2011.04.006] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2011] [Accepted: 04/08/2011] [Indexed: 01/18/2023]
Abstract
After more than 70 years of considerable efforts, research on medical defense against nerve agents has come to a standstill. Major progress in medical countermeasures was achieved between the 50s and 70s with the development of anticholinergic drugs and carbamate-based pretreatment, the introduction of pyridinium oximes as antidotes, and benzodiazepines in emergency treatments. These drugs ensure good protection of the peripheral nervous system and mitigate the acute effects of exposure to lethal doses of nerve agents. However, pyridostigmine and cholinesterase reactivators currently used in the armed forces do not protect/reactivate central acetylcholinesterases. Moreover, other drugs used are not sufficiently effective in protecting the central nervous system against seizures, irreversible brain damages and long-term sequelae of nerve agent poisoning.New developments of medical counter-measures focus on: (a) detoxification of organophosphorus molecules before they react with acetylcholinesterase and other physiological targets by administration of stoichiometric or catalytic scavengers; (b) protection and reactivation of central acetylcholinesterases, and (c) improvement of neuroprotection following delayed therapy.Future developments will aim at treatment of acute and long-term effects of low level exposure to nerve agents, research on alternative routes for optimizing drug delivery, and therapies. Though gene therapy for in situ generation of bioscavengers, and cell therapy based on neural progenitor engraftment for neuronal regeneration have been successfully explored, more studies are needed before practical medical applications can be made of these new approaches.
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Affiliation(s)
- Patrick Masson
- IRBA-CRSSA, Toxicology Dept., 38702 La Tronche Cedex, France.
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29
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Sit RK, Radić Z, Gerardi V, Zhang L, Garcia E, Katalinić M, Amitai G, Kovarik Z, Fokin VV, Sharpless KB, Taylor P. New structural scaffolds for centrally acting oxime reactivators of phosphylated cholinesterases. J Biol Chem 2011; 286:19422-30. [PMID: 21464125 DOI: 10.1074/jbc.m111.230656] [Citation(s) in RCA: 101] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We describe here the synthesis and activity of a new series of oxime reactivators of cholinesterases (ChEs) that contain tertiary amine or imidazole protonatable functional groups. Equilibration between the neutral and protonated species at physiological pH enables the reactivators to cross the blood-brain barrier and distribute in the CNS aqueous space as dictated by interstitial and cellular pH values. Our structure-activity analysis of 134 novel compounds considers primarily imidazole aldoximes and N-substituted 2-hydroxyiminoacetamides. Reactivation capacities of novel oximes are rank ordered by their relative reactivation rate constants at 0.67 mm compared with 2-pyridinealdoxime methiodide for reactivation of four organophosphate (sarin, cyclosarin, VX, and paraoxon) conjugates of human acetylcholinesterase (hAChE). Rank order of the rates differs for reactivation of human butyrylcholinesterase (hBChE) conjugates. The 10 best reactivating oximes, predominantly hydroxyimino acetamide derivatives (for hAChE) and imidazole-containing aldoximes (for hBChE) also exhibited reasonable activity in the reactivation of tabun conjugates. Reactivation kinetics of the lead hydroxyimino acetamide reactivator of hAChE, when analyzed in terms of apparent affinity (1/K(ox)) and maximum reactivation rate (k(2)), is superior to the reference uncharged reactivators monoisonitrosoacetone and 2,3-butanedione monoxime and shows potential for further refinement. The disparate pH dependences for reactivation of ChE and the general base-catalyzed oximolysis of acetylthiocholine reveal that distinct reactivator ionization states are involved in the reactivation of ChE conjugates and in conferring nucleophilic reactivity of the oxime group.
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Affiliation(s)
- Rakesh K Sit
- Department of Chemistry and the Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, California 92037, USA
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Shih TM, Guarisco JA, Myers TM, Kan RK, McDonough JH. The oxime pro-2-PAM provides minimal protection against the CNS effects of the nerve agents sarin, cyclosarin, and VX in guinea pigs. Toxicol Mech Methods 2010; 21:53-62. [DOI: 10.3109/15376516.2010.529190] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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31
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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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