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Tsai YH, González EA, Grodzki ACG, Bruun DA, Saito NH, Harvey DJ, Lein PJ. Acute intoxication with diisopropylfluorophosphate promotes cellular senescence in the adult male rat brain. FRONTIERS IN TOXICOLOGY 2024; 6:1360359. [PMID: 38745692 PMCID: PMC11091247 DOI: 10.3389/ftox.2024.1360359] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2023] [Accepted: 04/12/2024] [Indexed: 05/16/2024] Open
Abstract
Acute intoxication with high levels of organophosphate (OP) cholinesterase inhibitors can cause cholinergic crisis, which is associated with acute, life-threatening parasympathomimetic symptoms, respiratory depression and seizures that can rapidly progress to status epilepticus (SE). Clinical and experimental data demonstrate that individuals who survive these acute neurotoxic effects often develop significant chronic morbidity, including behavioral deficits. The pathogenic mechanism(s) that link acute OP intoxication to chronic neurological deficits remain speculative. Cellular senescence has been linked to behavioral deficits associated with aging and neurodegenerative disease, but whether acute OP intoxication triggers cellular senescence in the brain has not been investigated. Here, we test this hypothesis in a rat model of acute intoxication with the OP diisopropylfluorophosphate (DFP). Adult male Sprague-Dawley rats were administered DFP (4 mg/kg, s.c.). Control animals were administered an equal volume (300 µL) of sterile phosphate-buffered saline (s.c.). Both groups were subsequently injected with atropine sulfate (2 mg/kg, i.m.) and 2-pralidoxime (25 mg/kg, i.m.). DFP triggered seizure activity within minutes that rapidly progressed to SE, as determined using behavioral seizure criteria. Brains were collected from animals at 1, 3, and 6 months post-exposure for immunohistochemical analyses of p16, a biomarker of cellular senescence. While there was no immunohistochemical evidence of cellular senescence at 1-month post-exposure, at 3- and 6-months post-exposure, p16 immunoreactivity was significantly increased in the CA3 and dentate gyrus of the hippocampus, amygdala, piriform cortex and thalamus, but not the CA1 region of the hippocampus or the somatosensory cortex. Co-localization of p16 immunoreactivity with cell-specific biomarkers, specifically, NeuN, GFAP, S100β, IBA1 and CD31, revealed that p16 expression in the brain of DFP animals is neuron-specific. The spatial distribution of p16-immunopositive cells overlapped with expression of senescence associated β-galactosidase and with degenerating neurons identified by FluoroJade-C (FJC) staining. The co-occurrence of p16 and FJC was positively correlated. This study implicates cellular senescence as a novel pathogenic mechanism underlying the chronic neurological deficits observed in individuals who survive OP-induced cholinergic crisis.
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Affiliation(s)
- Yi-Hua Tsai
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, Davis, CA, United States
| | - Eduardo A. González
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, Davis, CA, United States
| | - Ana C. G. Grodzki
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, Davis, CA, United States
| | - Donald A. Bruun
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, Davis, CA, United States
| | - Naomi H. Saito
- Department of Public Health Sciences, School of Medicine, University of California, Davis, Davis, CA, United States
| | - Danielle J. Harvey
- Department of Public Health Sciences, School of Medicine, University of California, Davis, Davis, CA, United States
| | - Pamela J. Lein
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, Davis, CA, United States
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González EA, Calsbeek JJ, Tsai YH, Tang MY, Andrew P, Vu J, Berg EL, Saito NH, Harvey DJ, Supasai S, Gurkoff GG, Silverman JL, Lein PJ. Sex-specific acute and chronic neurotoxicity of acute diisopropylfluorophosphate (DFP)-intoxication in juvenile Sprague-Dawley rats. Curr Res Toxicol 2021; 2:341-356. [PMID: 34622217 PMCID: PMC8484742 DOI: 10.1016/j.crtox.2021.09.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2021] [Revised: 09/06/2021] [Accepted: 09/09/2021] [Indexed: 12/12/2022] Open
Abstract
Preclinical efforts to improve medical countermeasures against organophosphate (OP) chemical threat agents have largely focused on adult male models. However, age and sex have been shown to influence the neurotoxicity of repeated low-level OP exposure. Therefore, to determine the influence of sex and age on outcomes associated with acute OP intoxication, postnatal day 28 Sprague-Dawley male and female rats were exposed to the OP diisopropylfluorophosphate (DFP; 3.4 mg/kg, s.c.) or an equal volume of vehicle (∼80 µL saline, s.c.) followed by atropine sulfate (0.1 mg/kg, i.m.) and pralidoxime (2-PAM; 25 mg/kg, i.m.). Seizure activity was assessed during the first 4 h post-exposure using behavioral criteria and electroencephalographic (EEG) recordings. At 1 d post-exposure, acetylcholinesterase (AChE) activity was measured in cortical tissue, and at 1, 7, and 28 d post-exposure, brains were collected for neuropathologic analyses. At 1 month post-DFP, animals were analyzed for motor ability, learning and memory, and hippocampal neurogenesis. Acute DFP intoxication triggered more severe seizure behavior in males than females, which was supported by EEG recordings. DFP caused significant neurodegeneration and persistent microglial activation in numerous brain regions of both sexes, but astrogliosis occurred earlier and was more severe in males compared to females. DFP males and females exhibited pronounced memory deficits relative to sex-matched controls. In contrast, acute DFP intoxication altered hippocampal neurogenesis in males, but not females. These findings demonstrate that acute DFP intoxication triggers seizures in juvenile rats of both sexes, but the seizure severity varies by sex. Some, but not all, chronic neurotoxic outcomes also varied by sex. The spatiotemporal patterns of neurological damage suggest that microglial activation may be a more important factor than astrogliosis or altered neurogenesis in the pathogenesis of cognitive deficits in juvenile rats acutely intoxicated with OPs.
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Key Words
- 2-PAM, pralidoxime
- AChE, acetylcholinesterase
- AS, atropine-sulfate
- BChE, butyrylcholinesterase
- CT, computed tomography
- ChE, cholinesterase
- Cognitive deficits
- DFP, diisopropylfluorophosphate
- EEG, electroencephalogram
- FJC, Fluoro-Jade C
- Neurodegeneration
- Neurogenesis
- Neuroinflammation
- OP, organophosphate
- PBS, phosphate-buffered saline
- ROI, region of interest
- SE, status epilepticus
- Seizures
- Sex differences
- T2w, T2-weighted
- VEH, vehicle
- i.m., intramuscular
- i.p., intraperitoneal
- s.c., subcutaneous
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Affiliation(s)
- Eduardo A. González
- Department of Molecular Biosciences, University of California, Davis, School of Veterinary Medicine, 1089 Veterinary Medicine Drive, Davis, CA 95616, USA
| | - Jonas J. Calsbeek
- Department of Molecular Biosciences, University of California, Davis, School of Veterinary Medicine, 1089 Veterinary Medicine Drive, Davis, CA 95616, USA
| | - Yi-Hua Tsai
- Department of Molecular Biosciences, University of California, Davis, School of Veterinary Medicine, 1089 Veterinary Medicine Drive, Davis, CA 95616, USA
| | - Mei-Yun Tang
- Department of Molecular Biosciences, University of California, Davis, School of Veterinary Medicine, 1089 Veterinary Medicine Drive, Davis, CA 95616, USA
| | - Peter Andrew
- Department of Molecular Biosciences, University of California, Davis, School of Veterinary Medicine, 1089 Veterinary Medicine Drive, Davis, CA 95616, USA
| | - Joan Vu
- Department of Molecular Biosciences, University of California, Davis, School of Veterinary Medicine, 1089 Veterinary Medicine Drive, Davis, CA 95616, USA
| | - Elizabeth L. Berg
- Department of Psychiatry, University of California, Davis, School of Medicine, 2230, Stockton Boulevard, Sacramento, CA 95817, USA
| | - Naomi H. Saito
- Department of Public Health Sciences, University of California, Davis, One Shields Avenue, School of Medicine, Davis, CA 95616, USA
| | - Danielle J. Harvey
- Department of Public Health Sciences, University of California, Davis, One Shields Avenue, School of Medicine, Davis, CA 95616, USA
| | - Suangsuda Supasai
- Department of Molecular Biosciences, University of California, Davis, School of Veterinary Medicine, 1089 Veterinary Medicine Drive, Davis, CA 95616, USA
| | - Gene G. Gurkoff
- Department of Neurological Surgery, University of California, Davis, School of Medicine, 4860 Y Street, Sacramento, CA 95817, USA
- Center for Neuroscience, University of California, Davis, 1544 Newton Court, Davis, CA 95618, USA
| | - Jill L. Silverman
- Department of Psychiatry, University of California, Davis, School of Medicine, 2230, Stockton Boulevard, Sacramento, CA 95817, USA
- MIND Institute, University of California, Davis, 2825 50th Street, Sacramento, CA 95817, USA
| | - Pamela J. Lein
- Department of Molecular Biosciences, University of California, Davis, School of Veterinary Medicine, 1089 Veterinary Medicine Drive, Davis, CA 95616, USA
- MIND Institute, University of California, Davis, 2825 50th Street, Sacramento, CA 95817, USA
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Calsbeek JJ, González EA, Bruun DA, Guignet MA, Copping N, Dawson ME, Yu AJ, MacMahon JA, Saito NH, Harvey DJ, Silverman JL, Lein PJ. Persistent neuropathology and behavioral deficits in a mouse model of status epilepticus induced by acute intoxication with diisopropylfluorophosphate. Neurotoxicology 2021; 87:106-119. [PMID: 34509511 PMCID: PMC8595753 DOI: 10.1016/j.neuro.2021.09.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2021] [Revised: 08/27/2021] [Accepted: 09/06/2021] [Indexed: 01/01/2023]
Abstract
Organophosphate (OP) nerve agents and pesticides are a class of neurotoxic compounds that can cause status epilepticus (SE), and death following acute high-dose exposures. While the standard of care for acute OP intoxication (atropine, oxime, and high-dose benzodiazepine) can prevent mortality, survivors of OP poisoning often experience long-term brain damage and cognitive deficits. Preclinical studies of acute OP intoxication have primarily used rat models to identify candidate medical countermeasures. However, the mouse offers the advantage of readily available knockout strains for mechanistic studies of acute and chronic consequences of OP-induced SE. Therefore, the main objective of this study was to determine whether a mouse model of acute diisopropylfluorophosphate (DFP) intoxication would produce acute and chronic neurotoxicity similar to that observed in rat models and humans following acute OP intoxication. Adult male C57BL/6J mice injected with DFP (9.5 mg/kg, s.c.) followed 1 min later with atropine sulfate (0.1 mg/kg, i.m.) and 2-pralidoxime (25 mg/kg, i.m.) developed behavioral and electrographic signs of SE within minutes that continued for at least 4 h. Acetylcholinesterase inhibition persisted for at least 3 d in the blood and 14 d in the brain of DFP mice relative to vehicle (VEH) controls. Immunohistochemical analyses revealed significant neurodegeneration and neuroinflammation in multiple brain regions at 1, 7, and 28 d post-exposure in the brains of DFP mice relative to VEH controls. Deficits in locomotor and home-cage behavior were observed in DFP mice at 28 d post-exposure. These findings demonstrate that this mouse model replicates many of the outcomes observed in rats and humans acutely intoxicated with OPs, suggesting the feasibility of using this model for mechanistic studies and therapeutic screening.
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Affiliation(s)
- Jonas J Calsbeek
- Department of Molecular Biosciences, University of California, Davis, School of Veterinary Medicine, Davis, CA, 95616, USA.
| | - Eduardo A González
- Department of Molecular Biosciences, University of California, Davis, School of Veterinary Medicine, Davis, CA, 95616, USA.
| | - Donald A Bruun
- Department of Molecular Biosciences, University of California, Davis, School of Veterinary Medicine, Davis, CA, 95616, USA.
| | - Michelle A Guignet
- Department of Molecular Biosciences, University of California, Davis, School of Veterinary Medicine, Davis, CA, 95616, USA.
| | - Nycole Copping
- Department of Psychiatry and Behavioral Sciences, School of Medicine, University of California, Davis, Sacramento, CA, 95817, USA; MIND Institute, School of Medicine, University of California, Davis, Sacramento, CA, 95817, USA.
| | - Mallory E Dawson
- Department of Molecular Biosciences, University of California, Davis, School of Veterinary Medicine, Davis, CA, 95616, USA.
| | - Alexandria J Yu
- Department of Molecular Biosciences, University of California, Davis, School of Veterinary Medicine, Davis, CA, 95616, USA.
| | - Jeremy A MacMahon
- Department of Molecular Biosciences, University of California, Davis, School of Veterinary Medicine, Davis, CA, 95616, USA.
| | - Naomi H Saito
- Department of Public Health Sciences, University of California, Davis, School of Medicine, Davis, CA, 95616, USA.
| | - Danielle J Harvey
- Department of Public Health Sciences, University of California, Davis, School of Medicine, Davis, CA, 95616, USA.
| | - Jill L Silverman
- Department of Psychiatry and Behavioral Sciences, School of Medicine, University of California, Davis, Sacramento, CA, 95817, USA; MIND Institute, School of Medicine, University of California, Davis, Sacramento, CA, 95817, USA.
| | - Pamela J Lein
- Department of Molecular Biosciences, University of California, Davis, School of Veterinary Medicine, Davis, CA, 95616, USA; MIND Institute, School of Medicine, University of California, Davis, Sacramento, CA, 95817, USA.
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Calsbeek JJ, González EA, Boosalis CA, Zolkowska D, Bruun DA, Rowland DJ, Saito NH, Harvey DJ, Chaudhari AJ, Rogawski MA, Garbow JR, Lein PJ. Strain differences in the extent of brain injury in mice after tetramethylenedisulfotetramine-induced status epilepticus. Neurotoxicology 2021; 87:43-50. [PMID: 34478772 PMCID: PMC8595842 DOI: 10.1016/j.neuro.2021.08.011] [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: 07/13/2021] [Revised: 08/28/2021] [Accepted: 08/29/2021] [Indexed: 11/30/2022]
Abstract
Acute intoxication with tetramethylenedisulfotetramine (TETS) can trigger status epilepticus (SE) in humans. Survivors often exhibit long-term neurological effects, including electrographic abnormalities and cognitive deficits, but the pathogenic mechanisms linking the acute toxic effects of TETS to chronic outcomes are not known. Here, we use advanced in vivo imaging techniques to longitudinally monitor the neuropathological consequences of TETS-induced SE in two different mouse strains. Adult male NIH Swiss and C57BL/6J mice were injected with riluzole (10 mg/kg, i.p.), followed 10 min later by an acute dose of TETS (0.2 mg/kg in NIH Swiss; 0.3 mg/kg, i.p. in C57BL/6J) or an equal volume of vehicle (10% DMSO in 0.9% sterile saline). Different TETS doses were administered to trigger comparable seizure behavior between strains. Seizure behavior began within minutes of TETS exposure and rapidly progressed to SE that was terminated after 40 min by administration of midazolam (1.8 mg/kg, i.m.). The brains of vehicle and TETS-exposed mice were imaged using in vivo magnetic resonance (MR) and translocator protein (TSPO) positron emission tomography (PET) at 1, 3, 7, and 14 days post-exposure to monitor brain injury and neuroinflammation, respectively. When the brain scans of TETS mice were compared to those of vehicle controls, subtle and transient neuropathology was observed in both mouse strains, but more extensive and persistent TETS-induced neuropathology was observed in C57BL/6J mice. In addition, one NIH Swiss TETS mouse that did not respond to the midazolam therapy, but remained in SE for more than 2 h, displayed robust neuropathology as determined by in vivo imaging and confirmed by FluoroJade C staining and IBA-1 immunohistochemistry as readouts of neurodegeneration and neuroinflammation, respectively. These findings demonstrate that the extent of injury observed in the mouse brain after TETS-induced SE varied according to strain, dose of TETS and/or the duration of SE. These observations suggest that TETS-intoxicated humans who do not respond to antiseizure medication are at increased risk for brain injury.
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Affiliation(s)
- Jonas J Calsbeek
- Department of Molecular Biosciences, University of California, Davis, School of Veterinary Medicine, Davis, CA, 95616, USA.
| | - Eduardo A González
- Department of Molecular Biosciences, University of California, Davis, School of Veterinary Medicine, Davis, CA, 95616, USA.
| | - Casey A Boosalis
- Department of Molecular Biosciences, University of California, Davis, School of Veterinary Medicine, Davis, CA, 95616, USA.
| | - Dorota Zolkowska
- Department of Neurology, University of California, Davis, School of Medicine, Davis, CA, 95616, USA.
| | - Donald A Bruun
- Department of Molecular Biosciences, University of California, Davis, School of Veterinary Medicine, Davis, CA, 95616, USA.
| | - Douglas J Rowland
- Center for Molecular and Genomic Imaging, University of California, Davis, College of Engineering, Davis, CA, 95616, USA.
| | - Naomi H Saito
- Department of Public Health Sciences, University of California, Davis, School of Medicine, Davis, CA, 95616, USA.
| | - Danielle J Harvey
- Department of Public Health Sciences, University of California, Davis, School of Medicine, Davis, CA, 95616, USA.
| | - Abhijit J Chaudhari
- Center for Molecular and Genomic Imaging, University of California, Davis, College of Engineering, Davis, CA, 95616, USA.
| | - Michael A Rogawski
- Department of Neurology, University of California, Davis, School of Medicine, Davis, CA, 95616, USA.
| | - Joel R Garbow
- Biomedical Magnetic Resonance Laboratory, Mallinckrodt Institute of Radiology, Washington University in St. Louis, School of Medicine, St. Louis, MO, 63110, USA.
| | - Pamela J Lein
- Department of Molecular Biosciences, University of California, Davis, School of Veterinary Medicine, Davis, CA, 95616, USA.
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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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Antrobus S, Pressly B, Nik AM, Wulff H, Pessah IN. Structure-Activity Relationship of Neuroactive Steroids, Midazolam, and Perampanel Toward Mitigating Tetramine-Triggered Activity in Murine Hippocampal Neuronal Networks. Toxicol Sci 2021; 180:325-341. [PMID: 33483729 PMCID: PMC8599726 DOI: 10.1093/toxsci/kfab007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Tetramethylenedisulfotetramine (tetramine or TETS), a potent convulsant, triggers abnormal electrical spike activity (ESA) and synchronous Ca2+ oscillation (SCO) patterns in cultured neuronal networks by blocking gamma-aminobutyric acid (GABAA) receptors. Murine hippocampal neuronal/glial cocultures develop extensive dendritic connectivity between glutamatergic and GABAergic inputs and display two distinct SCO patterns when imaged with the Ca2+ indicator Fluo-4: Low amplitude SCO events (LASE) and High amplitude SCO events (HASE) that are dependent on TTX-sensitive network electrical spike activity (ESA). Acute TETS (3.0 µM) increased overall network SCO amplitude and decreased SCO frequency by stabilizing HASE and suppressing LASE while increasing ESA. In multielectrode arrays, TETS also increased burst frequency and synchronicity. In the presence of TETS (3.0 µM), the clinically used anticonvulsive perampanel (0.1-3.0 µM), a noncompetitive AMPAR antagonist, suppressed all SCO activity, whereas the GABAA receptor potentiator midazolam (1.0-30 µM), the current standard of care, reciprocally suppressed HASE and stabilized LASE. The neuroactive steroid (NAS) allopregnanolone (0.1-3.0 µM) normalized TETS-triggered patterns by selectively suppressing HASE and increasing LASE, a pharmacological pattern distinct from its epimeric form eltanolone, ganaxolone, alphaxolone, and XJ-42, which significantly potentiated TETS-triggered HASE in a biphasic manner. Cortisol failed to mitigate TETS-triggered patterns and at >1 µM augmented them. Combinations of allopregnanolone and midazolam were significantly more effective at normalizing TETS-triggered SCO patterns, ESA patterns, and more potently enhanced GABA-activated Cl- current, than either drug alone.
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Affiliation(s)
- Shane Antrobus
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, Davis, California 95616, USA
| | - Brandon Pressly
- Department of Pharmacology, School of Medicine, University of California, Davis, Davis, California 95616, USA
| | - Atefeh Mousavi Nik
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, Davis, California 95616, USA
| | - Heike Wulff
- Department of Pharmacology, School of Medicine, University of California, Davis, Davis, California 95616, USA
| | - Isaac N Pessah
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, Davis, California 95616, USA
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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: 22] [Impact Index Per Article: 5.5] [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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Evaluation of fosphenytoin, levetiracetam, and propofol as treatments for nerve agent-induced seizures in pediatric and adult rats. Neurotoxicology 2020; 79:58-66. [PMID: 32220603 DOI: 10.1016/j.neuro.2020.03.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2019] [Revised: 02/21/2020] [Accepted: 03/14/2020] [Indexed: 10/24/2022]
Abstract
Multiple recent instances of nerve agent (NA) exposure in civilian populations have occurred, resulting in a variety of negative effects and lethality in both adult and pediatric populations. Seizures are a prominent effect of NAs that can result in neurological damage and contribute to their lethality. Current anticonvulsant treatments for NAs are approved for adults, but no approved pediatric treatments exist. Further, the vast majority of NA-related research in animals has been conducted in adult male subjects. There is a need for research that includes female and pediatric populations in testing. In this project, adult and pediatric male and female rats were challenged with sarin or VX and then treated with fosphenytoin, levetiracetam, or propofol. In this study, fosphenytoin and levetiracetam failed to terminate seizure activity when animals were treated 5 min after seizure onset. Propofol was effective, exhibiting high efficacy and potency for terminating seizure activity quickly in pediatric and adult animals, suggesting it may be an effective anticonvulsant for NA-induced seizures in pediatric populations.
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Gage M, Golden M, Putra M, Sharma S, Thippeswamy T. Sex as a biological variable in the rat model of diisopropylfluorophosphate-induced long-term neurotoxicity. Ann N Y Acad Sci 2020; 1479:44-64. [PMID: 32090337 DOI: 10.1111/nyas.14315] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2019] [Revised: 01/24/2020] [Accepted: 01/25/2020] [Indexed: 01/13/2023]
Abstract
Sex differences in response to neurotoxicant exposure that initiates epileptogenesis are understudied. We used telemetry-implanted male and female adult rats exposed to an organophosphate (OP) neurotoxicant, diisopropylflourophosphate (DFP), to test sex differences in the severity of status epilepticus (SE) and the development of spontaneous recurrent seizures (SRS). Females had significantly less severe SE and decreased epileptiform spikes compared with males, although females received a higher dose of DFP than males. The estrous stages had no impact on seizure susceptibility, but rats with severe SE had a significantly prolonged diestrus. A previously demonstrated disease-modifying agent, an inducible nitric oxide synthase inhibitor, 1400W, was tested in both sexes. None of the eight males treated with 1400W developed convulsive SRS during 4 weeks post-DFP exposure, while two of seven females developed convulsive SRS. Concerning gliosis and neurodegeneration, there were region-specific differences in the interaction between sex and SE severity. As SE severity influences epileptogenesis, and as females had significantly less severe SE, sex as a biological variable should be factored into the design of future OP nerve agent experiments while evaluating neurotoxicity and optimizing potential disease-modifying agents.
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Affiliation(s)
- Meghan Gage
- Epilepsy Research Laboratory, Department of Biomedical Sciences, College of Veterinary Medicine, Iowa State University, Ames, Iowa
| | - Madison Golden
- Epilepsy Research Laboratory, Department of Biomedical Sciences, College of Veterinary Medicine, Iowa State University, Ames, Iowa
| | - Marson Putra
- Epilepsy Research Laboratory, Department of Biomedical Sciences, College of Veterinary Medicine, Iowa State University, Ames, Iowa
| | - Shaunik Sharma
- Epilepsy Research Laboratory, Department of Biomedical Sciences, College of Veterinary Medicine, Iowa State University, Ames, Iowa
| | - Thimmasettappa Thippeswamy
- Epilepsy Research Laboratory, Department of Biomedical Sciences, College of Veterinary Medicine, Iowa State University, Ames, Iowa
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10
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Targeting prostaglandin receptor EP2 for adjunctive treatment of status epilepticus. Pharmacol Ther 2020; 209:107504. [PMID: 32088247 DOI: 10.1016/j.pharmthera.2020.107504] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2019] [Accepted: 01/27/2020] [Indexed: 02/08/2023]
Abstract
Status epilepticus (SE) is an emergency condition that can cause permanent brain damage or even death when generalized convulsive seizures last longer than 30 min. Controlling the escalation and propagation of seizures quickly and properly is crucial to the prevention of irreversible neuronal death and the associated morbidity. However, SE often becomes refractory to current anticonvulsant medications, which primarily act on ion channels and commonly impose undesired effects. Identifying new molecular targets for SE might lead to adjunctive treatments that can be delivered even when SE is well established. Recent preclinical studies suggest that prostaglandin E2 (PGE2) is an essential inflammatory mediator for the brain injury and morbidity following prolonged seizures via activating four G protein-coupled receptors, namely, EP1-EP4. Given that EP2 receptor activation has been identified as a common culprit in several inflammation-associated neurological conditions, such as strokes and neurodegenerative diseases, selective small-molecule antagonists targeting EP2 have been recently developed and utilized to suppress PGE2-mediated neuroinflammation. Transient inhibition of the EP2 receptor by these bioavailable and brain-permeable antagonists consistently showed marked anti-inflammatory and neuroprotective effects in several rodent models of SE yet had no noticeable effect on seizures per se. This review provides overviews and perspectives of the EP2 receptor as an emerging target for adjunctive treatment, together with the current first-line anti-seizure drugs, to prevent acute brain inflammation and damage following SE.
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11
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Guignet M, Dhakal K, Flannery BM, Hobson BA, Zolkowska D, Dhir A, Bruun DA, Li S, Wahab A, Harvey DJ, Silverman JL, Rogawski MA, Lein PJ. Persistent behavior deficits, neuroinflammation, and oxidative stress in a rat model of acute organophosphate intoxication. Neurobiol Dis 2020; 133:104431. [PMID: 30905768 PMCID: PMC6754818 DOI: 10.1016/j.nbd.2019.03.019] [Citation(s) in RCA: 62] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2018] [Revised: 03/05/2019] [Accepted: 03/20/2019] [Indexed: 01/24/2023] Open
Abstract
Current medical countermeasures for organophosphate (OP)-induced status epilepticus (SE) are not effective in preventing long-term morbidity and there is an urgent need for improved therapies. Rat models of acute intoxication with the OP, diisopropylfluorophosphate (DFP), are increasingly being used to evaluate therapeutic candidates for efficacy in mitigating the long-term neurologic effects associated with OP-induced SE. Many of these therapeutic candidates target neuroinflammation and oxidative stress because of their implication in the pathogenesis of persistent neurologic deficits associated with OP-induced SE. Critical to these efforts is the rigorous characterization of the rat DFP model with respect to outcomes associated with acute OP intoxication in humans, which include long-term electroencephalographic, neurobehavioral, and neuropathologic effects, and their temporal relationship to neuroinflammation and oxidative stress. To address these needs, we examined a range of outcomes at later times post-exposure than have previously been reported for this model. Adult male Sprague-Dawley rats were given pyridostigmine bromide (0.1 mg/kg, im) 30 min prior to administration of DFP (4 mg/kg, sc), which was immediately followed by atropine sulfate (2 mg/kg, im) and pralidoxime (25 mg/kg, im). This exposure paradigm triggered robust electroencephalographic and behavioral seizures that rapidly progressed to SE lasting several hours in 90% of exposed animals. Animals that survived DFP-induced SE (~70%) exhibited spontaneous recurrent seizures and hyperreactive responses to tactile stimuli over the first 2 months post-exposure. Performance in the elevated plus maze, open field, and Pavlovian fear conditioning tests indicated that acute DFP intoxication reduced anxiety-like behavior and impaired learning and memory at 1 and 2 months post-exposure in the absence of effects on general locomotor behavior. Immunohistochemical analyses revealed significantly increased expression of biomarkers of reactive astrogliosis, microglial activation and oxidative stress in multiple brain regions at 1 and 2 months post-DFP, although there was significant spatiotemporal heterogeneity across these endpoints. Collectively, these data largely support the relevance of the rat model of acute DFP intoxication as a model for acute OP intoxication in the human, and support the hypothesis that neuroinflammation and/or oxidative stress represent potential therapeutic targets for mitigating the long-term neurologic sequelae of acute OP intoxication.
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Affiliation(s)
- Michelle Guignet
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California-Davis, 1089 Veterinary Medicine Drive, Davis, CA, 95616 USA, , , , , ,
| | - Kiran Dhakal
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California-Davis, 1089 Veterinary Medicine Drive, Davis, CA, 95616 USA, , , , , ,
| | - Brenna M. Flannery
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California-Davis, 1089 Veterinary Medicine Drive, Davis, CA, 95616 USA, , , , , ,
| | - Brad A. Hobson
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California-Davis, 1089 Veterinary Medicine Drive, Davis, CA, 95616 USA, , , , , ,
| | - Dorota Zolkowska
- Department of Neurology, School of Medicine, University of California-Davis, 4860 Y Street, Sacramento, CA 95817 USA, , , ;
| | - Ashish Dhir
- Department of Neurology, School of Medicine, University of California-Davis, 4860 Y Street, Sacramento, CA 95817 USA, , , ;
| | - Donald A. Bruun
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California-Davis, 1089 Veterinary Medicine Drive, Davis, CA, 95616 USA, , , , , ,
| | - Shuyang Li
- Department of Public Health Sciences, University of California-Davis, One Shields Avenue, Davis, CA 95616 USA, ,
| | - Abdul Wahab
- Department of Neurology, School of Medicine, University of California-Davis, 4860 Y Street, Sacramento, CA 95817 USA, , , ;
| | - Danielle J. Harvey
- Department of Public Health Sciences, University of California-Davis, One Shields Avenue, Davis, CA 95616 USA, ,
| | - Jill L. Silverman
- Department of Psychiatry and Behavioral Sciences, School of Medicine, University of California-Davis, 2230 Stockton Boulevard, Sacramento, CA 95817 USA,
- MIND Institute, School of Medicine, University of California-Davis, 2825 50 Street, Sacramento, CA 95817 USA
| | - Michael A. Rogawski
- Department of Neurology, School of Medicine, University of California-Davis, 4860 Y Street, Sacramento, CA 95817 USA, , , ;
| | - Pamela J. Lein
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California-Davis, 1089 Veterinary Medicine Drive, Davis, CA, 95616 USA, , , , , ,
- MIND Institute, School of Medicine, University of California-Davis, 2825 50 Street, Sacramento, CA 95817 USA
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12
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Rojas A, Ganesh T, Wang W, Wang J, Dingledine R. A rat model of organophosphate-induced status epilepticus and the beneficial effects of EP2 receptor inhibition. Neurobiol Dis 2020; 133:104399. [PMID: 30818067 PMCID: PMC6708729 DOI: 10.1016/j.nbd.2019.02.010] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2018] [Revised: 01/29/2019] [Accepted: 02/20/2019] [Indexed: 02/06/2023] Open
Abstract
This review describes an adult rat model of status epilepticus (SE) induced by diisopropyl fluorophosphate (DFP), and the beneficial outcomes of transient inhibition of the prostaglandin-E2 receptor EP2 with a small molecule antagonist, delayed by 2-4 h after SE onset. Administration of six doses of the selective EP2 antagonist TG6-10-1 over a 2-3 day period accelerates functional recovery, attenuates hippocampal neurodegeneration, neuroinflammation, gliosis and blood-brain barrier leakage, and prevents long-term cognitive deficits without blocking SE itself or altering acute seizure characteristics. This work has provided important information regarding organophosphate-induced seizure related pathologies in adults and revealed the effectiveness of delayed EP2 inhibition to combat these pathologies.
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Affiliation(s)
- Asheebo Rojas
- Department of Pharmacology, Emory University, 1510 Clifton Road NE, Atlanta, GA 30322, USA.
| | - Thota Ganesh
- Department of Pharmacology, Emory University, 1510 Clifton Road NE, Atlanta, GA 30322, USA
| | - Wenyi Wang
- Department of Pharmacology, Emory University, 1510 Clifton Road NE, Atlanta, GA 30322, USA
| | - Jennifer Wang
- Department of Pharmacology, Emory University, 1510 Clifton Road NE, Atlanta, GA 30322, USA
| | - Raymond Dingledine
- Department of Pharmacology, Emory University, 1510 Clifton Road NE, Atlanta, GA 30322, USA
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13
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Yang J, Bruun DA, Wang C, Wan D, McReynolds CB, Phu K, Inceoglu B, Lein PJ, Hammock BD. Lipidomes of brain from rats acutely intoxicated with diisopropylfluorophosphate identifies potential therapeutic targets. Toxicol Appl Pharmacol 2019; 382:114749. [PMID: 31521729 PMCID: PMC6957308 DOI: 10.1016/j.taap.2019.114749] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2019] [Revised: 08/30/2019] [Accepted: 09/07/2019] [Indexed: 01/28/2023]
Abstract
Organophosphates (OPs), a class of phosphorus-containing chemicals that act by disrupting cholinergic transmission, include both toxic and fast-acting chemical warfare agents as well as less toxic but more easily accessible OP pesticides. The classical atropine/2-PAM antidote fails to protect against long-term symptoms following acute intoxication with OPs at levels that trigger status epilepticus. Acute OP intoxication also causes a robust neuroinflammatory response, which is implicated in the pathogenesis of long-term effects. In this study, we characterized the profiles of lipid mediators, important players in neuroinflammation, in the rat model of acute DFP intoxication. The profiles of lipid mediators were monitored in three different regions of the brain (cortex, hippocampus, and cerebellum) at 0, 1, 3, 7, 14, and 28 days post-exposure. The distribution pattern of lipid mediators was distinct in the three brain regions. In the cerebellum, the profile is dominated by LOX metabolites, while the lipid mediator profiles in cortex and hippocampus are dominated by COX metabolites followed by LOX and CYP 450 metabolites. Following acute DFP intoxication, most of the pro-inflammatory lipid mediators (e.g., PGD2 and PGE2) increased rapidly from day 1, while the concentrations of some anti-inflammatory lipid mediators (e.g. 14,15 EpETrE) decreased after DFP intoxication but recovered by day 14 post-exposure. The lipidomics results suggest two potential treatment targets: blocking the formation of prostaglandins by inhibiting COX and stabilizing the anti-inflammatory lipid mediators containing epoxides by inhibiting the enzyme soluble epoxide hydrolase (sEH).
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Affiliation(s)
- Jun Yang
- Department of Entomology and Nematology, and UCD Comprehensive Cancer Center, University of California, Davis, Davis, CA 95616, USA
| | - Donald A Bruun
- Department of Molecular Biosciences, University of California, Davis, CA 95616, USA
| | - Chang Wang
- Department of Entomology and Nematology, and UCD Comprehensive Cancer Center, University of California, Davis, Davis, CA 95616, USA; School of Radiation Medicine and Protection, Medical College of Soochow University, School for Radiological and Interdisciplinary Sciences (RAD-X), Jiangsu Provincial Key Laboratory of Radiation Medicine and Protection, Suzhou 215123, PR China
| | - Debin Wan
- Department of Entomology and Nematology, and UCD Comprehensive Cancer Center, University of California, Davis, Davis, CA 95616, USA
| | - Cindy B McReynolds
- Department of Entomology and Nematology, and UCD Comprehensive Cancer Center, University of California, Davis, Davis, CA 95616, USA
| | - Kenny Phu
- Department of Entomology and Nematology, and UCD Comprehensive Cancer Center, University of California, Davis, Davis, CA 95616, USA
| | - Bora Inceoglu
- Department of Entomology and Nematology, and UCD Comprehensive Cancer Center, University of California, Davis, Davis, CA 95616, USA
| | - Pamela J Lein
- Department of Molecular Biosciences, University of California, Davis, CA 95616, USA
| | - Bruce D Hammock
- Department of Entomology and Nematology, and UCD Comprehensive Cancer Center, University of California, Davis, Davis, CA 95616, USA.
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14
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de A. Cavalcante SF, Simas ABC, Kuča K. Nerve Agents’ Surrogates: Invaluable Tools for Development of Acetylcholinesterase Reactivators. CURR ORG CHEM 2019. [DOI: 10.2174/1385272823666190806114017] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The use of nerve agents as warfare and in terrorist acts has drawn much attention from the governments and societies. Such toxic organophosphorus compounds are listed in Chemical Weapons Convention as Schedule 1 chemicals. The discussion about the chemical identity of the elusive Novichok agents, more potent compounds than best known G- and V-Agents, which have been implicated in recent rumorous assassination plots, clearly demonstrating the importance of the matter. Furthermore, accidents with pesticides or misuse thereof have been a pressing issue in many countries. In this context, the continued development of novel cholinesterase reactivators, antidotes for organophosphorus poisoning, a rather restricted class of pharmaceutical substances, is warranted. Testing of novel candidates may require use of actual nerve agents. Nonetheless, only a few laboratories comply with the requirements for storing, possession and manipulation of such toxic chemicals. To overcome such limitations, nerve agents’ surrogates may be a useful alternative, as they undergo the same reaction with cholinesterases, yielding similar adducts, allowing assays with novel antidote candidates, among other applications.
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Affiliation(s)
- Samir F. de A. Cavalcante
- Walter Mors Institute of Research on Natural Products (IPPN), Federal University of Rio de Janeiro (UFRJ), Rio de Janeiro, Brazil
| | - Alessandro B. C. Simas
- Walter Mors Institute of Research on Natural Products (IPPN), Federal University of Rio de Janeiro (UFRJ), Rio de Janeiro, Brazil
| | - Kamil Kuča
- Department of Chemistry, Faculty of Science, University of Hradec Kralove, Hradec Kralove, Czech Republic
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15
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Putra M, Sharma S, Gage M, Gasser G, Hinojo-Perez A, Olson A, Gregory-Flores A, Puttachary S, Wang C, Anantharam V, Thippeswamy T. Inducible nitric oxide synthase inhibitor, 1400W, mitigates DFP-induced long-term neurotoxicity in the rat model. Neurobiol Dis 2019; 133:104443. [PMID: 30940499 DOI: 10.1016/j.nbd.2019.03.031] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2018] [Revised: 02/22/2019] [Accepted: 03/28/2019] [Indexed: 11/26/2022] Open
Abstract
Chemical nerve agents (CNA) are increasingly becoming a threat to both civilians and military personnel. CNA-induced acute effects on the nervous system have been known for some time and the long-term consequences are beginning to emerge. In this study, we used diisopropylfluorophosphate (DFP), a seizurogenic CNA to investigate the long-term impact of its acute exposure on the brain and its mitigation by an inducible nitric oxide synthase (iNOS) inhibitor, 1400W as a neuroprotectant in the rat model. Several experimental studies have demonstrated that DFP-induced seizures and/or status epilepticus (SE) causes permanent brain injury, even after the countermeasure medication (atropine, oxime, and diazepam). In the present study, DFP-induced SE caused a significant increase in iNOS and 3-nitrotyrosine (3-NT) at 24 h, 48 h, 7d, and persisted for a long-term (12 weeks post-exposure), which led to the hypothesis that iNOS is a potential therapeutic target in DFP-induced brain injury. To test the hypothesis, we administered 1400W (20 mg/kg, i.m.) or the vehicle twice daily for the first three days of post-exposure. 1400W significantly reduced DFP-induced iNOS and 3-NT upregulation in the hippocampus and piriform cortex, and the serum nitrite levels at 24 h post-exposure. 1400W also prevented DFP-induced mortality in <24 h. The brain immunohistochemistry (IHC) at 7d post-exposure revealed a significant reduction in gliosis and neurodegeneration (NeuN+ FJB positive cells) in the 1400W-treated group. 1400W, in contrast to the vehicle, caused a significant reduction in the epileptiform spiking and spontaneous recurrent seizures (SRS) during 12 weeks of continuous video-EEG study. IHC of brain sections from the same animals revealed a significant reduction in reactive gliosis (both microgliosis and astrogliosis) and neurodegeneration across various brain regions in the 1400W-treated group when compared to the vehicle-treated group. A multiplex assay from hippocampal lysates at 6 weeks post-exposure showed a significant increase in several key pro-inflammatory cytokines/chemokines such as IL-1α, TNFα, IL-1β, IL-2, IL-6, IL-12, IL-17a, MCP-1, LIX, and Eotaxin, and a growth factor, VEGF in the vehicle-treated animals. 1400W significantly suppressed IL-1α, TNFα, IL-2, IL-12, and MCP-1 levels. It also suppressed DFP-induced serum nitrite levels at 6 weeks post-exposure. In the Morris water maze, the vehicle-treated animals spent significantly less time in the target quadrant in a probe trial at 9d post-exposure compared to their time spent in the same quadrant 11 days previously (i.e., 2 days prior to DFP exposure). Such a difference was not observed in the 1400W and control groups. However, learning and short-term memory were unaffected when tested at 10-16d and 28-34d post-exposure. Accelerated rotarod, horizontal bar test, and the forced swim test revealed no significant changes between groups. Overall, the findings from this study suggest that 1400W may be considered as a potential therapeutic agent as a follow-on therapy for CNA exposure, after controlling the acute symptoms, to prevent mortality and some of the long-term neurotoxicity parameters such as epileptiform spiking, SRS, neurodegeneration, reactive gliosis in some brain regions, and certain key proinflammatory cytokines and chemokine.
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Affiliation(s)
- Marson Putra
- Department of Biomedical Sciences, College of Veterinary Medicine, Iowa State University, Ames, IA 50011, United States
| | - Shaunik Sharma
- Department of Biomedical Sciences, College of Veterinary Medicine, Iowa State University, Ames, IA 50011, United States
| | - Meghan Gage
- Department of Biomedical Sciences, College of Veterinary Medicine, Iowa State University, Ames, IA 50011, United States
| | | | - Andy Hinojo-Perez
- Department of Biomedical Sciences, College of Veterinary Medicine, Iowa State University, Ames, IA 50011, United States
| | - Ashley Olson
- Department of Biomedical Sciences, College of Veterinary Medicine, Iowa State University, Ames, IA 50011, United States
| | - Adriana Gregory-Flores
- Department of Biomedical Sciences, College of Veterinary Medicine, Iowa State University, Ames, IA 50011, United States
| | - Sreekanth Puttachary
- Department of Biomedical Sciences, Carlson College of Veterinary Medicine, Oregon State University, Corvallis, OR 97331, United States
| | - Chong Wang
- Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA 50011, United States
| | | | - Thimmasettappa Thippeswamy
- Department of Biomedical Sciences, College of Veterinary Medicine, Iowa State University, Ames, IA 50011, United States.
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16
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Bruun DA, Guignet M, Harvey DJ, Lein PJ. Pretreatment with pyridostigmine bromide has no effect on seizure behavior or 24 hour survival in the rat model of acute diisopropylfluorophosphate intoxication. Neurotoxicology 2019; 73:81-84. [PMID: 30853371 DOI: 10.1016/j.neuro.2019.03.001] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2019] [Revised: 02/27/2019] [Accepted: 03/04/2019] [Indexed: 01/16/2023]
Abstract
Acute intoxication with organophosphate cholinesterase inhibitors (OPs) is a significant human health threat, and current medical countermeasures for OP poisoning are of limited therapeutic efficacy. The rat model of acute intoxication with diisopropylfluorophosphate (DFP) is increasingly being used to test candidate compounds for efficacy in protecting against the immediate and long-term consequences of acute OP toxicity. In this model, rats are typically pretreated with pyridostigmine bromide (PB), a reversible cholinesterase inhibitor, to enhance survival. However, PB pretreatment is not likely in most scenarios of civilian exposure to acutely neurotoxic levels of OPs. Therefore, the goal of this study was to determine whether PB pretreatment significantly increases survival in DFP-intoxicated rats. Adult male Sprague Dawley rats were injected with DFP (4 mg/kg, s.c.) or vehicle (VEH) followed 1 min later by combined i.m. injection of atropine sulfate (2 mg/kg) and 2-pralidoxime (25 mg/kg). Animals were pretreated 30 min prior to these injections with PB (0.1 mg/kg, i.m.) or an equal volume of saline. DFP triggered rapid and sustained seizure behavior irrespective of PB pretreatment, and there was no significant difference in average seizure behavior score during the first 4 h following injection between DFP animals pretreated with PB or not. PB pretreatment also had no significant effect on survival or brain AChE activity at 24 h post-DFP exposure. In summary, PB pretreatment is not necessary to ensure survival of rats acutely intoxicated with DFP, and eliminating PB pretreatment in the rat model of acute DFP intoxication would increase its relevance to acute OP intoxication in civilians.
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Affiliation(s)
- Donald A Bruun
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California-Davis, 1089 Veterinary Medicine Drive, Davis, CA, 95616, USA.
| | - Michelle Guignet
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California-Davis, 1089 Veterinary Medicine Drive, Davis, CA, 95616, USA.
| | - Danielle J Harvey
- Department of Public Health Sciences, University of California-Davis, One Shields Avenue, Davis, CA, 95616, USA.
| | - Pamela J Lein
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California-Davis, 1089 Veterinary Medicine Drive, Davis, CA, 95616, USA.
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17
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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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18
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Scholl EA, Miller-Smith SM, Bealer SL, Lehmkuhle MJ, Ekstrand JJ, Dudek FE, McDonough JH. Age-dependent behaviors, seizure severity and neuronal damage in response to nerve agents or the organophosphate DFP in immature and adult rats. Neurotoxicology 2018; 66:10-21. [PMID: 29510177 PMCID: PMC5996394 DOI: 10.1016/j.neuro.2018.02.018] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2017] [Revised: 02/07/2018] [Accepted: 02/27/2018] [Indexed: 01/15/2023]
Abstract
Exposure to nerve agents (NAs) and other organophosphates (OPs) can initiate seizures that rapidly progress to status epilepticus (SE). While the electrographic and neuropathological sequelae of SE evoked by NAs and OPs have been characterized in adult rodents, they have not been adequately investigated in immature animals. In this study postnatal day (PND) 14, 21 and 28 rat pups, along with PND70 animals as adult controls, were exposed to NAs (sarin, VX) or another OP (diisopropylfluorophosphate, DFP). We then evaluated behavioral and electrographic (EEG) correlates of seizure activity, and performed neuropathology using Fluoro-Jade B. Although all immature rats exhibited behaviors that are often characterized as seizures, the incidence, duration, and severity of the electrographic seizure activity were age-dependent. No (sarin and VX) or brief (DFP) EEG seizure activity was evoked in PND14 rats, while SE progressively increased in severity as a function of age in PND21, 28 and 70 animals. Fluoro-Jade B staining was observed in multiple brain regions of animals that exhibited prolonged seizure activity. Neuronal injury in PND14 animals treated with DFP was lower than in older animals and absent in rats exposed to sarin or VX. In conclusion, we found that NAs and an OP provoked robust SE and neuronal injury similar to adults in PND21 and PND28, but not in PND14, rat pups. Convulsive behaviors were often present independent of EEG seizures and were unaccompanied by neuronal damage. These differential responses should be considered when investigating medical countermeasures for NA and OP exposure in pediatric populations.
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Affiliation(s)
- Erika A Scholl
- Department of Neurosurgery, University of Utah, Salt Lake City, UT, 84108 USA
| | - Stephanie M Miller-Smith
- Neuroscience Branch, U.S. Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, MD, 21010-5400 USA
| | - Steven L Bealer
- Department of Neurosurgery, University of Utah, Salt Lake City, UT, 84108 USA; Department of Pharmacology and Toxicology, University of Utah, Salt Lake City, UT, 84108 USA
| | - Mark J Lehmkuhle
- Department of Neurosurgery, University of Utah, Salt Lake City, UT, 84108 USA; Epitel, Inc., Salt Lake City, UT, 84111 USA
| | - Jeffrey J Ekstrand
- Department of Pediatrics, University of Utah, Salt Lake City, UT, 84108 USA
| | - F Edward Dudek
- Department of Neurosurgery, University of Utah, Salt Lake City, UT, 84108 USA
| | - John H McDonough
- Neuroscience Branch, U.S. Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, MD, 21010-5400 USA.
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19
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Sisó S, Hobson BA, Harvey DJ, Bruun DA, Rowland DJ, Garbow JR, Lein PJ. Editor's Highlight: Spatiotemporal Progression and Remission of Lesions in the Rat Brain Following Acute Intoxication With Diisopropylfluorophosphate. Toxicol Sci 2018; 157:330-341. [PMID: 28329845 DOI: 10.1093/toxsci/kfx048] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Similar to organophosphate (OP) nerve agents, diisopropylfluorophosphate (DFP) rapidly and irreversibly inhibits acetylcholinesterase, leading to convulsions that can progress to status epilepticus (SE). However, in contrast to the OP nerve agents, the long-term consequences of DFP-induced SE are not well known. Thus, we characterized the spatiotemporal profile of neuropathology during the first 2 months following acute DFP intoxication. Adult, male Sprague Dawley rats administered pyridostigmine bromide (0.1 mg/kg, im) 30 min prior to successive administration of DFP (4 mg/kg, sc), atropine sulfate (2 mg/kg, im), and 2-pralidoxime (25 mg/kg, im), exhibited moderate-to-severe seizure behavior, yet survived until euthanized at 0.5 to 60 days post exposure. Analyses of brains and hearts stained with hematoxylin-eosin, or of brains immunostained for neuronal nuclei (NeuN), glial fibrillary acidic protein (GFAP), or ionized binding adapter molecule 1 (IBA1), revealed progressive neuronal cell death, neuroinflammation, and tissue remodeling across limbic brain regions and the cerebral cortex, with no detectable pathology in the cerebellum or the heart. The lesion type and progression varied according to brain region and time after exposure. Across multiple brain regions, neuronal necrosis peaked after the first week, and neuroinflammation persisted at least 2 months after intoxication. Notably, mineralization was observed at later times in the thalamus, and to a more limited extent, in the hippocampus. Lesion severity was influenced by the initial seizure severity, and spontaneous recurrent seizures were associated with more severe brain damage. These findings parallel descriptions of neuropathology in preclinical models of acute intoxication with OP nerve agents, and other seizurogenic chemicals, suggesting conserved mechanisms of pathology downstream of chemical-induced SE.
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Affiliation(s)
- Sílvia Sisó
- Translational Biology in the Department of Research, BioMarin Pharmaceuticals Inc, Novato, California, USA
| | - Brad A Hobson
- Department of Molecular Biosciences School of Veterinary Medicine, University of California-Davis, Davis, California, USA
| | - Danielle J Harvey
- Department of Public Health Sciences School of Medicine, University of California-Davis, Davis, California, USA
| | - Donald A Bruun
- Department of Molecular Biosciences School of Veterinary Medicine, University of California-Davis, Davis, California, USA
| | - Douglas J Rowland
- Department of Biomedical Engineering and the Center for Molecular and Genomic Imaging College of Engineering, University of California-Davis, Davis, California, USA
| | - Joel R Garbow
- Biomedical Magnetic Resonance Laboratory, Mallinckrodt Institute of Radiology, School of Medicine, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Pamela J Lein
- Department of Molecular Biosciences School of Veterinary Medicine, University of California-Davis, Davis, California, USA
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Zolkowska D, Wu CY, Rogawski MA. Intramuscular allopregnanolone and ganaxolone in a mouse model of treatment-resistant status epilepticus. Epilepsia 2018; 59 Suppl 2:220-227. [PMID: 29453777 DOI: 10.1111/epi.13999] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/03/2017] [Indexed: 11/28/2022]
Abstract
Allopregnanolone (5α-pregnan-3α-ol-20-one) and its synthetic 3β-methyl analog, ganaxolone, are positive allosteric modulators of synaptic and extrasynaptic γ-aminobutyric acid (GABA)A receptors that exhibit antiseizure activity in diverse animal seizure models, including models of status epilepticus (SE). The 2 neuroactive steroids are being investigated as treatments for SE, including as a treatment for SE induced by chemical threat agents. Intramuscular injection is the preferred route of administration in the prehospital treatment of SE. The objective of this study was to assess the efficacy of intramuscular allopregnanolone and ganaxolone in the treatment of SE induced by the chemical threat agent tetramethylenedisulfotetramine (TETS). The test agents were administered 40 minutes after the onset of SE when mice are refractory to treatment. Allopregnanolone and ganaxolone (each at 3 mg/kg) terminated SE in, respectively, 92% and 75% of animals, and prevented mortality in 85% and 50% of animals; the mean times to termination of behavioral seizures were, respectively, 172 ± 16 and 447 ± 52 seconds. In a separate series of experiments, mice were dosed with the neuroactive steroids by intramuscular injection, and plasma and brain levels were sampled at various time points following injection to estimate pharmacokinetic parameters. Plasma Cmax (maximum concentration) values for allopregnanolone and ganaxolone were 645 and 550 ng/mL, respectively. Brain exposure of both steroids was approximately 3-fold the plasma exposure. Two-compartment pharmacokinetic analysis revealed that the central compartment Vd (volume of distribution), CL (clearance), t½ (terminal half-life), and F (intramuscular bioavailability) values for allopregnanolone and ganaxolone were, respectively, 4.95 L/kg 12.88 L/kg/h,16 minutes, 97%, and 5.07 L/kg, 8.35 L/kg/h, 25 minutes, 95%. Allopregnanolone and ganaxolone are effective in the treatment of TETS-induced SE when administered by the intramuscular route. Allopregnanolone is more rapidly acting and modestly more effective, possibly because it has greater potency on GABAA receptors.
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Affiliation(s)
- Dorota Zolkowska
- Department of Neurology, School of Medicine, University of California, Davis, Sacramento, CA, USA
| | - Chun-Yi Wu
- Department of Neurology, School of Medicine, University of California, Davis, Sacramento, CA, USA.,Bioanalysis and Pharmacokinetics Core Facility, UC Davis Medical Center, Sacramento, CA, USA
| | - Michael A Rogawski
- Department of Neurology, School of Medicine, University of California, Davis, Sacramento, CA, USA.,Department of Pharmacology, School of Medicine, University of California, Davis, Sacramento, CA, USA
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Hobson BA, Rowland DJ, Supasai S, Harvey DJ, Lein PJ, Garbow JR. A magnetic resonance imaging study of early brain injury in a rat model of acute DFP intoxication. Neurotoxicology 2017; 66:170-178. [PMID: 29183789 DOI: 10.1016/j.neuro.2017.11.009] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2017] [Revised: 11/21/2017] [Accepted: 11/24/2017] [Indexed: 11/18/2022]
Abstract
Current treatments for seizures induced by organophosphates do not protect sufficiently against progressive neurodegeneration or delayed cognitive impairment. Developing more effective therapeutic approaches has been challenging because the pathogenesis of these delayed consequences is poorly defined. Using magnetic resonance imaging (MRI), we previously reported brain lesions that persist for months in a rat model of acute intoxication with the OP, diisopropylfluorophosphate (DFP). However, the early spatiotemporal progression of these lesions remains unknown. To address this data gap, we used in vivo MRI to longitudinally monitor brain lesions during the first 3 d following acute DFP intoxication. Adult male Sprague Dawley rats acutely intoxicated with DFP (4mg/kg, sc) were MR imaged at 6, 12, 18, 24, 48, 72h post-DFP, and their brains then taken for correlative histology to assess neurodegeneration using FluoroJade C (FJC) staining. Acute DFP intoxication elicited moderate-to-severe seizure activity. T2-weighted (T2w) anatomic imaging revealed prominent lesions within the thalamus, piriform cortex, cerebral cortex, hippocampus, corpus striatum, and substantia nigra that corresponded to neurodegeneration, evident as bands of FJC positive cells. Semi-quantitative assessment of lesion severity demonstrated significant regional variation in the onset and progression of injury, and suggested that lesion severity may be modulated by isoflurane anesthesia. These results imply that the timing of therapeutic intervention for attenuating brain injury following OP intoxication may be regionally dependent, and that longitudinal assessment of OP-induced damage by MRI may be a powerful tool for assessing therapeutic response.
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Affiliation(s)
- Brad A Hobson
- Department of Molecular Biosciences, University of California, Davis, School of Veterinary Medicine, Davis, CA, 95616, United States.
| | - Douglas J Rowland
- Center for Molecular and Genomic Imaging, University of California, Davis, College of Engineering, Davis, CA, 95616, United States.
| | - Suangsuda Supasai
- Department of Molecular Biosciences, University of California, Davis, School of Veterinary Medicine, Davis, CA, 95616, United States.
| | - Danielle J Harvey
- Department of Public Health Sciences, University of California, Davis, School of Medicine, Davis, CA, 95616, United States.
| | - Pamela J Lein
- Department of Molecular Biosciences, University of California, Davis, School of Veterinary Medicine, Davis, CA, 95616, United States.
| | - Joel R Garbow
- Biomedical Magnetic Resonance Laboratory, Mallinckrodt Institute of Radiology, School of Medicine,Washington University in St. Louis, St. Louis, MO, 63110, United States.
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