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Andrew PM, Lein PJ. Neuroinflammation as a Therapeutic Target for Mitigating the Long-Term Consequences of Acute Organophosphate Intoxication. Front Pharmacol 2021; 12:674325. [PMID: 34054549 PMCID: PMC8153682 DOI: 10.3389/fphar.2021.674325] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Accepted: 04/30/2021] [Indexed: 12/14/2022] Open
Abstract
Acute intoxication with organophosphates (OPs) can cause a potentially fatal cholinergic crisis characterized by peripheral parasympathomimetic symptoms and seizures that rapidly progress to status epilepticus (SE). While current therapeutic countermeasures for acute OP intoxication significantly improve the chances of survival when administered promptly, they are insufficient for protecting individuals from chronic neurologic outcomes such as cognitive deficits, affective disorders, and acquired epilepsy. Neuroinflammation is posited to contribute to the pathogenesis of these long-term neurologic sequelae. In this review, we summarize what is currently known regarding the progression of neuroinflammatory responses after acute OP intoxication, drawing parallels to other models of SE. We also discuss studies in which neuroinflammation was targeted following OP-induced SE, and explain possible reasons why such therapeutic interventions have inconsistently and only partially improved long-term outcomes. Finally, we suggest future directions for the development of therapeutic strategies that target neuroinflammation to mitigate the neurologic sequelae of acute OP intoxication.
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Affiliation(s)
| | - Pamela J. Lein
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, CA, United States
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Acute administration of diazepam or midazolam minimally alters long-term neuropathological effects in the rat brain following acute intoxication with diisopropylfluorophosphate. Eur J Pharmacol 2020; 886:173538. [PMID: 32898549 DOI: 10.1016/j.ejphar.2020.173538] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2020] [Revised: 09/01/2020] [Accepted: 09/03/2020] [Indexed: 12/30/2022]
Abstract
Acute intoxication with organophosphorus cholinesterase inhibitors (OPs) can trigger seizures that rapidly progress to life-threatening status epilepticus. Diazepam, long considered the standard of care for treating OP-induced seizures, is being replaced by midazolam. Whether midazolam is more effective than diazepam in mitigating the persistent effects of acute OP intoxication has not been rigorously evaluated. We compared the efficacy of diazepam vs. midazolam in preventing persistent neuropathology in adult male Sprague-Dawley rats acutely intoxicated with the OP diisopropylfluorophosphate (DFP). Subjects were administered pyridostigmine bromide (0.1 mg/kg, i.p.) 30 min prior to injection with DFP (4 mg/kg, s.c.) or vehicle (saline) followed 1 min later by atropine sulfate (2 mg/kg, i.m.) and pralidoxime (25 mg/kg, i.m.), and 40 min later by diazepam (5 mg/kg, i.p.), midazolam (0.73 mg/kg, i.m.), or vehicle. At 3 and 6 months post-exposure, neurodegeneration, reactive astrogliosis, microglial activation, and oxidative stress were assessed in multiple brain regions using quantitative immunohistochemistry. Brain mineralization was evaluated by in vivo micro-computed tomography (micro-CT). Acute DFP intoxication caused persistent neurodegeneration, neuroinflammation, and brain mineralization. Midazolam transiently mitigated neurodegeneration, and both benzodiazepines partially protected against reactive astrogliosis in a brain region-specific manner. Neither benzodiazepine attenuated microglial activation or brain mineralization. These findings indicate that neither benzodiazepine effectively protects against persistent neuropathological changes, and suggest that midazolam is not significantly better than diazepam. Overall, this study highlights the need for improved neuroprotective strategies for treating humans in the event of a chemical emergency involving OPs.
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Dail MB, Leach CA, Meek EC, Olivier AK, Pringle RB, Green CE, Chambers JE. Novel Brain-Penetrating Oxime Acetylcholinesterase Reactivators Attenuate Organophosphate-Induced Neuropathology in the Rat Hippocampus. Toxicol Sci 2020; 169:465-474. [PMID: 30835286 DOI: 10.1093/toxsci/kfz060] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Organophosphate (OP) anticholinesterases cause excess acetylcholine leading to seizures which, if prolonged, result in neuronal damage in the rodent brain. Novel substituted phenoxyalkyl pyridinium oximes have previously shown evidence of penetrating the rat blood-brain barrier (BBB) in in vivo tests with a sarin surrogate (nitrophenyl isopropyl methylphosphonate, NIMP) or the active metabolite of the insecticide parathion, paraoxon (PXN), by reducing the time to cessation of seizure-like behaviors and accumulation of glial fibrillary acidic protein, whereas 2-PAM did not. The neuroprotective ability of our lead oximes (15, 20, and 55) was tested using NeuN, Nissl, and Fluoro-Jade B staining in the rat hippocampus. Following lethal-level subcutaneous challenge with NIMP or PXN, rats were intramuscularly administered a novel oxime or 2-PAM plus atropine and euthanized at 4 days. There were statistically significant increases in the median damage scores of the NeuN-stained NIMP, NIMP/2-PAM, and NIMP/Oxime 15 groups compared with the control whereas the scores of the NIMP/Oxime 20 and NIMP/Oxime 55 were not significantly different from the control. The same pattern of statistical significance was observed with PXN. Nissl staining provided a similar pattern, but without statistical differences. Fluoro-Jade B indicated neuroprotection from PXN with novel oximes but not with 2-PAM. The longer blood residence times of Oximes 20 and 55 compared with Oxime 15 might have contributed to their greater efficacy. These results suggest that novel oximes 20 and 55 were able to penetrate the BBB and attenuate neuronal damage after NIMP and PXN exposure, indicating potential broad-spectrum usefulness.
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Affiliation(s)
- Mary B Dail
- *Department of Basic Sciences, Center for Environmental Health Sciences
| | - Charles A Leach
- *Department of Basic Sciences, Center for Environmental Health Sciences
| | - Edward C Meek
- *Department of Basic Sciences, Center for Environmental Health Sciences
| | - Alicia K Olivier
- Department of Pathobiology and Population Medicine, College of Veterinary Medicine, Mississippi State University, Mississippi State, Mississippi 39762
| | - Ronald B Pringle
- *Department of Basic Sciences, Center for Environmental Health Sciences
| | - Carol E Green
- Biosciences Division, SRI International, Menlo Park, California 94025
| | - Janice E Chambers
- *Department of Basic Sciences, Center for Environmental Health Sciences
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Baş O, Çankaya S, Enginyurt Ö, Aslan A, Uydu HA, Odaci E, Yılmaz A, Demir A, Gul T. The effect of acute organophosphate intoxication on female rat hippocampus cornu ammonis region pyramidal neuron numbers, biochemistry and morphology. J Chem Neuroanat 2019; 100:101652. [DOI: 10.1016/j.jchemneu.2019.101652] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2018] [Revised: 04/03/2019] [Accepted: 05/24/2019] [Indexed: 12/27/2022]
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Guignet M, Lein PJ. Neuroinflammation in organophosphate-induced neurotoxicity. ROLE OF INFLAMMATION IN ENVIRONMENTAL NEUROTOXICITY 2019. [DOI: 10.1016/bs.ant.2018.10.003] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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Myhrer T, Mariussen E, Aas P. Development of neuropathology following soman poisoning and medical countermeasures. Neurotoxicology 2018; 65:144-165. [DOI: 10.1016/j.neuro.2018.02.009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2017] [Revised: 02/12/2018] [Accepted: 02/14/2018] [Indexed: 01/12/2023]
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Piermartiri T, Pan H, Figueiredo TH, Marini AM. α-Linolenic Acid, A Nutraceutical with Pleiotropic Properties That Targets Endogenous Neuroprotective Pathways to Protect against Organophosphate Nerve Agent-Induced Neuropathology. Molecules 2015; 20:20355-80. [PMID: 26569216 PMCID: PMC6332275 DOI: 10.3390/molecules201119698] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2015] [Revised: 10/29/2015] [Accepted: 11/03/2015] [Indexed: 01/23/2023] Open
Abstract
α-Linolenic acid (ALA) is a nutraceutical found in vegetable products such as flax and walnuts. The pleiotropic properties of ALA target endogenous neuroprotective and neurorestorative pathways in brain and involve the transcription factor nuclear factor kappa B (NF-κB), brain-derived neurotrophic factor (BDNF), a major neuroprotective protein in brain, and downstream signaling pathways likely mediated via activation of TrkB, the cognate receptor of BDNF. In this review, we discuss possible mechanisms of ALA efficacy against the highly toxic OP nerve agent soman. Organophosphate (OP) nerve agents are highly toxic chemical warfare agents and a threat to military and civilian populations. Once considered only for battlefield use, these agents are now used by terrorists to inflict mass casualties. OP nerve agents inhibit the critical enzyme acetylcholinesterase (AChE) that rapidly leads to a cholinergic crisis involving multiple organs. Status epilepticus results from the excessive accumulation of synaptic acetylcholine which in turn leads to the overactivation of muscarinic receptors; prolonged seizures cause the neuropathology and long-term consequences in survivors. Current countermeasures mitigate symptoms and signs as well as reduce brain damage, but must be given within minutes after exposure to OP nerve agents supporting interest in newer and more effective therapies. The pleiotropic properties of ALA result in a coordinated molecular and cellular program to restore neuronal networks and improve cognitive function in soman-exposed animals. Collectively, ALA should be brought to the clinic to treat the long-term consequences of nerve agents in survivors. ALA may be an effective therapy for other acute and chronic neurodegenerative disorders.
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Affiliation(s)
- Tetsade Piermartiri
- Molecular and Cellular Biology Graduate School Program, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, MD 20814, USA.
| | - Hongna Pan
- Department of Neurology and Program in Neuroscience, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, MD 20814, USA.
| | - Taiza H Figueiredo
- Department of Anatomy, Physiology and Genetics, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, MD 20814, USA.
| | - Ann M Marini
- Department of Neurology and Program in Neuroscience, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, MD 20814, USA.
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Pan H, Piermartiri TCB, Chen J, McDonough J, Oppel C, Driwech W, Winter K, McFarland E, Black K, Figueiredo T, Grunberg N, Marini AM. Repeated systemic administration of the nutraceutical alpha-linolenic acid exerts neuroprotective efficacy, an antidepressant effect and improves cognitive performance when given after soman exposure. Neurotoxicology 2015; 51:38-50. [PMID: 26386148 DOI: 10.1016/j.neuro.2015.09.006] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2015] [Revised: 09/04/2015] [Accepted: 09/14/2015] [Indexed: 10/23/2022]
Abstract
Exposure to nerve agents results in severe seizures or status epilepticus caused by the inhibition of acetylcholinesterase, a critical enzyme that breaks down acetylcholine to terminate neurotransmission. Prolonged seizures cause brain damage and can lead to long-term consequences. Current countermeasures are only modestly effective against the brain damage supporting interest in the evaluation of new and efficacious therapies. The nutraceutical alpha-linolenic acid (LIN) is an essential omega-3 polyunsaturated fatty acid that has a wide safety margin. Previous work showed that a single intravenous injection of alpha-linolenic acid (500 nmol/kg) administered before or after soman significantly protected against soman-induced brain damage when analyzed 24h after exposure. Here, we show that administration of three intravenous injections of alpha-linolenic acid over a 7 day period after soman significantly improved motor performance on the rotarod, enhanced memory retention, exerted an anti-depressant-like activity and increased animal survival. This dosing schedule significantly reduced soman-induced neuronal degeneration in four major vulnerable brain regions up to 21 days. Taken together, alpha-linolenic acid reduces the profound behavioral deficits induced by soman possibly by decreasing neuronal cell death, and increases animal survival.
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Affiliation(s)
- Hongna Pan
- Department of Neurology, Uniformed Services University of the Health Sciences, Bethesda, MD, United States
| | - Tetsade C B Piermartiri
- Molecular and Cellular Biology Graduate School Program, Uniformed Services University of the Health Sciences, Bethesda, MD, United States
| | - Jun Chen
- Department of Neurology, Uniformed Services University of the Health Sciences, Bethesda, MD, United States
| | - John McDonough
- Department of Medical and Clinical Psychology, Uniformed Services University of the Health Sciences, Bethesda, MD, United States
| | - Craig Oppel
- Department of Medical and Clinical Psychology, Uniformed Services University of the Health Sciences, Bethesda, MD, United States
| | - Wafae Driwech
- Pharmacology Branch, Research Division, US Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, MD, United States
| | - Kristin Winter
- Pharmacology Branch, Research Division, US Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, MD, United States
| | - Emylee McFarland
- Pharmacology Branch, Research Division, US Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, MD, United States
| | - Katelyn Black
- Pharmacology Branch, Research Division, US Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, MD, United States
| | - Taiza Figueiredo
- Department of Anatomy, Physiology and Genetics, Uniformed Services University of the Health Sciences, Bethesda, MD, United States
| | - Neil Grunberg
- Department of Medical and Clinical Psychology, Uniformed Services University of the Health Sciences, Bethesda, MD, United States
| | - Ann M Marini
- Department of Neurology, Uniformed Services University of the Health Sciences, Bethesda, MD, United States.
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Eisenkraft A, Falk A, Finkelstein A. The role of glutamate and the immune system in organophosphate-induced CNS damage. Neurotox Res 2013; 24:265-79. [PMID: 23532600 DOI: 10.1007/s12640-013-9388-1] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2013] [Revised: 03/10/2013] [Accepted: 03/15/2013] [Indexed: 12/12/2022]
Abstract
Organophosphate (OP) poisoning is associated with long-lasting neurological damage, which is attributed mainly to the excessive levels of glutamate caused by the intoxication. Glutamate toxicity, however, is not specific to OP poisoning, and is linked to propagation of damage in both acute and chronic neurodegenerative conditions in the central nervous system (CNS). In addition to acute excitotoxic effects of glutamate, there is now a growing amount of evidence of its intricate immunomodulatory effects in the brain, involving both the innate and the adaptive immune systems. Moreover, it was demonstrated that immunomodulatory treatments, aimed at regulating the interaction between the resident immune cells of the brain (microglia) and the peripheral immune system, can support buffering of excessive levels of glutamate and restoration of the homeostasis. In this review, we will discuss the role of glutamate as an excitotoxic agent in the acute phase of OP poisoning, and the possible functions it may have as both a neuroprotectant and an immunomodulator in the sub-acute and chronic phases of OP poisoning. In addition, we will describe the novel immune-based neuroprotective strategies aimed at counteracting the long-term neurodegenerative effects of glutamate in the CNS.
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Magnesium sulfate treatment against sarin poisoning: dissociation between overt convulsions and recorded cortical seizure activity. Arch Toxicol 2012; 87:347-60. [DOI: 10.1007/s00204-012-0916-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2012] [Accepted: 07/24/2012] [Indexed: 10/27/2022]
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