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Hobson BA, Rowland DJ, Dou Y, Saito N, Harmany ZT, Bruun DA, Harvey DJ, Chaudhari AJ, Garbow JR, Lein PJ. A longitudinal MRI and TSPO PET-based investigation of brain region-specific neuroprotection by diazepam versus midazolam following organophosphate-induced seizures. Neuropharmacology 2024; 251:109918. [PMID: 38527652 DOI: 10.1016/j.neuropharm.2024.109918] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2023] [Revised: 03/01/2024] [Accepted: 03/13/2024] [Indexed: 03/27/2024]
Abstract
Acute poisoning with organophosphorus cholinesterase inhibitors (OPs), such as OP nerve agents and pesticides, can cause life threatening cholinergic crisis and status epilepticus (SE). Survivors often experience significant morbidity, including brain injury, acquired epilepsy, and cognitive deficits. Current medical countermeasures for acute OP poisoning include a benzodiazepine to mitigate seizures. Diazepam was long the benzodiazepine included in autoinjectors used to treat OP-induced seizures, but it is now being replaced in many guidelines by midazolam, which terminates seizures more quickly, particularly when administered intramuscularly. While a direct correlation between seizure duration and the extent of brain injury has been widely reported, there are limited data comparing the neuroprotective efficacy of diazepam versus midazolam following acute OP intoxication. To address this data gap, we used non-invasive imaging techniques to longitudinally quantify neuropathology in a rat model of acute intoxication with the OP diisopropylfluorophosphate (DFP) with and without post-exposure intervention with diazepam or midazolam. Magnetic resonance imaging (MRI) was used to monitor neuropathology and brain atrophy, while positron emission tomography (PET) with a radiotracer targeting translocator protein (TSPO) was utilized to assess neuroinflammation. Animals were scanned at 3, 7, 28, 65, 91, and 168 days post-DFP and imaging metrics were quantitated for the hippocampus, amygdala, piriform cortex, thalamus, cerebral cortex and lateral ventricles. In the DFP-intoxicated rat, neuroinflammation persisted for the duration of the study coincident with progressive atrophy and ongoing tissue remodeling. Benzodiazepines attenuated neuropathology in a region-dependent manner, but neither benzodiazepine was effective in attenuating long-term neuroinflammation as detected by TSPO PET. Diffusion MRI and TSPO PET metrics were highly correlated with seizure severity, and early MRI and PET metrics were positively correlated with long-term brain atrophy. Collectively, these results suggest that anti-seizure therapy alone is insufficient to prevent long-lasting neuroinflammation and tissue remodeling.
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Affiliation(s)
- Brad A Hobson
- Department of Molecular Biosciences, University of California, Davis, School of Veterinary Medicine, Davis, CA 95616, USA; Center for Molecular and Genomic Imaging, University of California, Davis, College of Engineering, Davis, CA 95616, USA.
| | - Douglas J Rowland
- Center for Molecular and Genomic Imaging, University of California, Davis, College of Engineering, Davis, CA 95616, USA.
| | - Yimeng Dou
- Department of Molecular Biosciences, University of California, Davis, School of Veterinary Medicine, Davis, CA 95616, USA.
| | - Naomi Saito
- Department of Public Health Sciences, University of California, Davis, School of Medicine, California 95616, USA.
| | - Zachary T Harmany
- Center for Molecular and Genomic Imaging, University of California, Davis, College of Engineering, Davis, CA 95616, USA.
| | - Donald A Bruun
- Department of Molecular Biosciences, University of California, Davis, School of Veterinary Medicine, Davis, CA 95616, USA.
| | - Danielle J Harvey
- Department of Public Health Sciences, University of California, Davis, School of Medicine, California 95616, USA.
| | - Abhijit J Chaudhari
- Center for Molecular and Genomic Imaging, University of California, Davis, College of Engineering, Davis, CA 95616, USA; Department of Radiology, University of California, Davis, School of Medicine, California 95817, USA.
| | - Joel R Garbow
- Biomedical Magnetic Resonance Center, Mallinckrodt Institute of Radiology, School of Medicine, Washington University in St. Louis, St. Louis, Missouri, 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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Almeida AJD, Hobson BA, Saito N, Bruun DA, Porter VA, Harvey DJ, Garbow JR, Chaudhari AJ, Lein PJ. Quantitative T 2 mapping-based longitudinal assessment of brain injury and therapeutic rescue in the rat following acute organophosphate intoxication. Neuropharmacology 2024; 249:109895. [PMID: 38437913 PMCID: PMC11227117 DOI: 10.1016/j.neuropharm.2024.109895] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2023] [Revised: 02/07/2024] [Accepted: 02/29/2024] [Indexed: 03/06/2024]
Abstract
Acute intoxication with organophosphate (OP) cholinesterase inhibitors poses a significant public health risk. While currently approved medical countermeasures can improve survival rates, they often fail to prevent chronic neurological damage. Therefore, there is need to develop effective therapies and quantitative metrics for assessing OP-induced brain injury and its rescue by these therapies. In this study we used a rat model of acute intoxication with the OP, diisopropylfluorophosphate (DFP), to test the hypothesis that T2 measures obtained from brain magnetic resonance imaging (MRI) scans provide quantitative metrics of brain injury and therapeutic efficacy. Adult male Sprague Dawley rats were imaged on a 7T MRI scanner at 3, 7 and 28 days post-exposure to DFP or vehicle (VEH) with or without treatment with the standard of care antiseizure drug, midazolam (MDZ); a novel antiseizure medication, allopregnanolone (ALLO); or combination therapy with MDZ and ALLO (DUO). Our results show that mean T2 values in DFP-exposed animals were: (1) higher than VEH in all volumes of interest (VOIs) at day 3; (2) decreased with time; and (3) decreased in the thalamus at day 28. Treatment with ALLO or DUO, but not MDZ alone, significantly decreased mean T2 values relative to untreated DFP animals in the piriform cortex at day 3. On day 28, the DUO group showed the most favorable T2 characteristics. This study supports the utility of T2 mapping for longitudinally monitoring brain injury and highlights the therapeutic potential of ALLO as an adjunct therapy to mitigate chronic morbidity associated with acute OP intoxication.
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Affiliation(s)
- Alita Jesal D Almeida
- Department of Biomedical Engineering, University of California-Davis College of Engineering, Davis, CA, 95616, USA; Department of Radiology, University of California-Davis School of Medicine, Sacramento, CA, 95817, USA.
| | - Brad A Hobson
- Center for Molecular and Genomic Imaging, Department of Biomedical Engineering, University of California-Davis College of Engineering, Davis, CA, 95616, USA.
| | - Naomi Saito
- Department of Public Health Sciences, 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.
| | - Valerie A Porter
- Department of Biomedical Engineering, University of California-Davis College of Engineering, Davis, CA, 95616, USA; Department of Radiology, University of California-Davis School of Medicine, Sacramento, CA, 95817, USA.
| | - Danielle J Harvey
- Department of Public Health Sciences, University of California-Davis School of Medicine, Davis, CA, 95616, USA.
| | - Joel R Garbow
- Department of Radiology, Washington University School of Medicine, St Louis, MO, 63110, USA.
| | - Abhijit J Chaudhari
- Department of Radiology, University of California-Davis School of Medicine, Sacramento, CA, 95817, USA; Center for Molecular and Genomic Imaging, Department of Biomedical Engineering, University of California-Davis College of Engineering, Davis, CA, 95616, USA.
| | - Pamela J Lein
- Department of Molecular Biosciences, University of California-Davis School of Veterinary Medicine, Davis, CA, 95616, USA.
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Porter VA, Hobson BA, Foster B, Lein PJ, Chaudhari AJ. Fully automated whole brain segmentation from rat MRI scans with a convolutional neural network. J Neurosci Methods 2024; 405:110078. [PMID: 38340902 PMCID: PMC11000587 DOI: 10.1016/j.jneumeth.2024.110078] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2023] [Revised: 01/27/2024] [Accepted: 02/05/2024] [Indexed: 02/12/2024]
Abstract
BACKGROUND Whole brain delineation (WBD) is utilized in neuroimaging analysis for data preprocessing and deriving whole brain image metrics. Current automated WBD techniques for analysis of preclinical brain MRI data show limited accuracy when images present with significant neuropathology and anatomical deformations, such as that resulting from organophosphate intoxication (OPI) and Alzheimer's Disease (AD), and inadequate generalizability. METHODS A modified 2D U-Net framework was employed for WBD of MRI rodent brains, consisting of 27 convolutional layers, batch normalization, two dropout layers and data augmentation, after training parameter optimization. A total of 265 T2-weighted 7.0 T MRI scans were utilized for the study, including 125 scans of an OPI rat model for neural network training. For testing and validation, 20 OPI rat scans and 120 scans of an AD rat model were utilized. U-Net performance was evaluated using Dice coefficients (DC) and Hausdorff distances (HD) between the U-Net-generated and manually segmented WBDs. RESULTS The U-Net achieved a DC (median[range]) of 0.984[0.936-0.990] and HD of 1.69[1.01-6.78] mm for OPI rat model scans, and a DC (mean[range]) of 0.975[0.898-0.991] and HD of 1.49[0.86-3.89] for the AD rat model scans. COMPARISON WITH EXISTING METHODS The proposed approach is fully automated and robust across two rat strains and longitudinal brain changes with a computational speed of 8 seconds/scan, overcoming limitations of manual segmentation. CONCLUSIONS The modified 2D U-Net provided a fully automated, efficient, and generalizable segmentation approach that achieved high accuracy across two disparate rat models of neurological diseases.
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Affiliation(s)
- Valerie A Porter
- Department of Biomedical Engineering, University of California, Davis, CA 95616, USA; Department of Radiology, University of California, Davis, CA 95817, USA
| | - Brad A Hobson
- Department of Biomedical Engineering, University of California, Davis, CA 95616, USA; Center for Molecular and Genomic Imaging, University of California, Davis, CA 95616, USA
| | - Brent Foster
- TechMah Medical LLC, 2099 Thunderhead Rd, Knoxville, TN 37922, USA
| | - Pamela J Lein
- Department of Molecular Biosciences, University of California, Davis, CA 95616, USA
| | - Abhijit J Chaudhari
- Department of Radiology, University of California, Davis, CA 95817, USA; Center for Molecular and Genomic Imaging, University of California, Davis, CA 95616, USA.
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Andrew PM, Feng W, Calsbeek JJ, Antrobus SP, Cherednychenko GA, MacMahon JA, Bernardino PN, Liu X, Harvey DJ, Lein PJ, Pessah IN. The α4 Nicotinic Acetylcholine Receptor Is Necessary for the Initiation of Organophosphate-Induced Neuronal Hyperexcitability. TOXICS 2024; 12:263. [PMID: 38668486 PMCID: PMC11054284 DOI: 10.3390/toxics12040263] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2024] [Revised: 03/20/2024] [Accepted: 03/27/2024] [Indexed: 04/29/2024]
Abstract
Acute intoxication with organophosphorus (OP) cholinesterase inhibitors can produce seizures that rapidly progress to life-threatening status epilepticus. Significant research effort has been focused on investigating the involvement of muscarinic acetylcholine receptors (mAChRs) in OP-induced seizure activity. In contrast, there has been far less attention on nicotinic AChRs (nAChRs) in this context. Here, we address this data gap using a combination of in vitro and in vivo models. Pharmacological antagonism and genetic deletion of α4, but not α7, nAChR subunits prevented or significantly attenuated OP-induced electrical spike activity in acute hippocampal slices and seizure activity in mice, indicating that α4 nAChR activation is necessary for neuronal hyperexcitability triggered by acute OP exposures. These findings not only suggest that therapeutic strategies for inhibiting the α4 nAChR subunit warrant further investigation as prophylactic and immediate treatments for acute OP-induced seizures, but also provide mechanistic insight into the role of the nicotinic cholinergic system in seizure generation.
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Affiliation(s)
- Peter M. Andrew
- Department of Molecular Biosciences, UC Davis School of Veterinary Medicine, Davis, CA 95616, USA; (P.M.A.); (W.F.); (J.J.C.); (S.P.A.); (G.A.C.); (J.A.M.); (P.N.B.); (X.L.)
| | - Wei Feng
- Department of Molecular Biosciences, UC Davis School of Veterinary Medicine, Davis, CA 95616, USA; (P.M.A.); (W.F.); (J.J.C.); (S.P.A.); (G.A.C.); (J.A.M.); (P.N.B.); (X.L.)
| | - Jonas J. Calsbeek
- Department of Molecular Biosciences, UC Davis School of Veterinary Medicine, Davis, CA 95616, USA; (P.M.A.); (W.F.); (J.J.C.); (S.P.A.); (G.A.C.); (J.A.M.); (P.N.B.); (X.L.)
| | - Shane P. Antrobus
- Department of Molecular Biosciences, UC Davis School of Veterinary Medicine, Davis, CA 95616, USA; (P.M.A.); (W.F.); (J.J.C.); (S.P.A.); (G.A.C.); (J.A.M.); (P.N.B.); (X.L.)
| | - Gennady A. Cherednychenko
- Department of Molecular Biosciences, UC Davis School of Veterinary Medicine, Davis, CA 95616, USA; (P.M.A.); (W.F.); (J.J.C.); (S.P.A.); (G.A.C.); (J.A.M.); (P.N.B.); (X.L.)
| | - Jeremy A. MacMahon
- Department of Molecular Biosciences, UC Davis School of Veterinary Medicine, Davis, CA 95616, USA; (P.M.A.); (W.F.); (J.J.C.); (S.P.A.); (G.A.C.); (J.A.M.); (P.N.B.); (X.L.)
| | - Pedro N. Bernardino
- Department of Molecular Biosciences, UC Davis School of Veterinary Medicine, Davis, CA 95616, USA; (P.M.A.); (W.F.); (J.J.C.); (S.P.A.); (G.A.C.); (J.A.M.); (P.N.B.); (X.L.)
| | - Xiuzhen Liu
- Department of Molecular Biosciences, UC Davis School of Veterinary Medicine, Davis, CA 95616, USA; (P.M.A.); (W.F.); (J.J.C.); (S.P.A.); (G.A.C.); (J.A.M.); (P.N.B.); (X.L.)
| | - Danielle J. Harvey
- Department of Public Health Sciences, UC Davis School of Medicine, Davis, CA 95616, USA;
| | - Pamela J. Lein
- Department of Molecular Biosciences, UC Davis School of Veterinary Medicine, Davis, CA 95616, USA; (P.M.A.); (W.F.); (J.J.C.); (S.P.A.); (G.A.C.); (J.A.M.); (P.N.B.); (X.L.)
| | - Isaac N. Pessah
- Department of Molecular Biosciences, UC Davis School of Veterinary Medicine, Davis, CA 95616, USA; (P.M.A.); (W.F.); (J.J.C.); (S.P.A.); (G.A.C.); (J.A.M.); (P.N.B.); (X.L.)
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5
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Bernardino PN, Hobson BA, Huddleston SL, Andrew PM, MacMahon JA, Saito NH, Porter VA, Bruun DA, Harvey DJ, Garbow JR, Gelli A, Chaudhari AJ, Lein PJ. Time- and region-dependent blood-brain barrier impairment in a rat model of organophosphate-induced status epilepticus. Neurobiol Dis 2023; 187:106316. [PMID: 37797902 PMCID: PMC11000668 DOI: 10.1016/j.nbd.2023.106316] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2023] [Revised: 09/26/2023] [Accepted: 10/02/2023] [Indexed: 10/07/2023] Open
Abstract
Acute organophosphate (OP) intoxication can trigger seizures that progress to status epilepticus (SE), and survivors often develop chronic morbidities, including spontaneous recurrent seizures (SRS). The pathogenic mechanisms underlying OP-induced SRS are unknown, but increased BBB permeability is hypothesized to be involved. Previous studies reported BBB leakage following OP-induced SE, but key information regarding time and regional distribution of BBB impairment during the epileptogenic period is missing. To address this data gap, we characterized the spatiotemporal progression of BBB impairment during the first week post-exposure in a rat model of diisopropylfluorophosphate-induced SE, using MRI and albumin immunohistochemistry. Increased BBB permeability, which was detected at 6 h and persisted up to 7 d post-exposure, was most severe and persistent in the piriform cortex and amygdala, moderate but persistent in the thalamus, and less severe and transient in the hippocampus and somatosensory cortex. The extent of BBB leakage was positively correlated with behavioral seizure severity, with the strongest association identified in the piriform cortex and amygdala. These findings provide evidence of the duration, magnitude and spatial breakdown of the BBB during the epileptogenic period following OP-induced SE and support BBB regulation as a viable therapeutic target for preventing SRS following acute OP intoxication.
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Affiliation(s)
- Pedro N Bernardino
- Department of Molecular Biosciences, University of California, Davis, School of Veterinary Medicine, Davis, CA 95616, USA.
| | - Brad A Hobson
- Center for Molecular and Genomic Imaging, University of California, Davis, Davis, CA 95616, USA.
| | - Sydney L Huddleston
- Center for Molecular and Genomic Imaging, University of California, Davis, Davis, CA 95616, USA.
| | - Peter M Andrew
- 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.
| | - Valerie A Porter
- Department of Biomedical Engineering, University of California, Davis, College of Engineering, Davis, CA 95616, USA.
| | - Donald A Bruun
- Department of Molecular Biosciences, University of California, Davis, School of Veterinary Medicine, Davis, CA 95616, USA.
| | - Danielle J Harvey
- Department of Public Health Sciences, University of California, Davis, School of Medicine, Davis, CA 95616, USA.
| | - Joel R Garbow
- Biomedical Magnetic Resonance Center, Mallinckrodt Institute of Radiology, School of Medicine, Washington University in St. Louis, St. Louis, MO 63110, USA.
| | - Angie Gelli
- Department of Pharmacology, University of California, Davis, School of Medicine, Davis, CA 95616, USA.
| | - Abhijit J Chaudhari
- Center for Molecular and Genomic Imaging, University of California, Davis, Davis, CA 95616, USA; Department of Radiology, University of California, Davis, School of Medicine, Sacramento, CA 95817, USA.
| | - Pamela J Lein
- Department of Molecular Biosciences, University of California, Davis, School of Veterinary Medicine, Davis, CA 95616, USA.
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Somkhit J, Yanicostas C, Soussi-Yanicostas N. Microglia Remodelling and Neuroinflammation Parallel Neuronal Hyperactivation Following Acute Organophosphate Poisoning. Int J Mol Sci 2022; 23:ijms23158240. [PMID: 35897817 PMCID: PMC9332153 DOI: 10.3390/ijms23158240] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2022] [Revised: 07/08/2022] [Accepted: 07/13/2022] [Indexed: 01/27/2023] Open
Abstract
Organophosphate (OP) compounds include highly toxic chemicals widely used both as pesticides and as warfare nerve agents. Existing countermeasures are lifesaving, but do not alleviate all long-term neurological sequelae, making OP poisoning a public health concern worldwide and the search for fully efficient antidotes an urgent need. OPs cause irreversible acetylcholinesterase (AChE) inhibition, inducing the so-called cholinergic syndrome characterized by peripheral manifestations and seizures associated with permanent psychomotor deficits. Besides immediate neurotoxicity, recent data have also identified neuroinflammation and microglia activation as two processes that likely play an important, albeit poorly understood, role in the physiopathology of OP intoxication and its long-term consequences. To gain insight into the response of microglia to OP poisoning, we used a previously described model of diisopropylfluorophosphate (DFP) intoxication of zebrafish larvae. This model reproduces almost all the defects seen in poisoned humans and preclinical models, including AChE inhibition, neuronal epileptiform hyperexcitation, and increased neuronal death. Here, we investigated in vivo the consequences of acute DFP exposure on microglia morphology and behaviour, and on the expression of a set of pro- and anti-inflammatory cytokines. We also used a genetic method of microglial ablation to evaluate the role in the OP-induced neuropathology. We first showed that DFP intoxication rapidly induced deep microglial phenotypic remodelling resembling that seen in M1-type activated macrophages and characterized by an amoeboid morphology, reduced branching, and increased mobility. DFP intoxication also caused massive expression of genes encoding pro-inflammatory cytokines Il1β, Tnfα, Il8, and to a lesser extent, immuno-modulatory cytokine Il4, suggesting complex microglial reprogramming that included neuroinflammatory activities. Finally, microglia-depleted larvae were instrumental in showing that microglia were major actors in DFP-induced neuroinflammation and, more importantly, that OP-induced neuronal hyperactivation was markedly reduced in larvae fully devoid of microglia. DFP poisoning rapidly triggered massive microglia-mediated neuroinflammation, probably as a result of DFP-induced neuronal hyperexcitation, which in turn further exacerbated neuronal activation. Microglia are thus a relevant therapeutic target, and identifying substances reducing microglial activation could add efficacy to existing OP antidote cocktails.
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Schmidt CW. Hemispheres of Influence: Bridging the Disconnect between Environmental Neurotoxicology and Clinical Practice. ENVIRONMENTAL HEALTH PERSPECTIVES 2022; 130:52001. [PMID: 35543742 PMCID: PMC9093734 DOI: 10.1289/ehp9013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/22/2021] [Accepted: 02/23/2021] [Indexed: 06/14/2023]
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Long-term changes in neuroimaging markers, cognitive function and psychiatric symptoms in an experimental model of Gulf War Illness. Life Sci 2021; 285:119971. [PMID: 34560085 DOI: 10.1016/j.lfs.2021.119971] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2021] [Revised: 09/05/2021] [Accepted: 09/16/2021] [Indexed: 11/23/2022]
Abstract
AIMS Gulf War Illness (GWI) is a multi-symptom disease with debilitating cognitive and emotional impairments in veterans. GWI, like epilepsy, is caused by chemical neurotoxicity and manifests from disturbances in neuronal excitability. However, the mechanisms underlying such devastating neurological and psychiatric symptoms remain unclear. Here we investigated the long-term changes in neural behavior and brain structural abnormalities in a rat model of GWI. GWI is linked to exposure to GWI-related organophosphate chemicals (pyridostigmine bromide or PB and insecticide DEET, permethrin) during the stressful Gulf war. METHODS To mimic GWI, we generated an experimental GWI prototype in rats by daily exposure to GWI-related chemicals with restraint stress (GWIR-CS) for 4 weeks. Changes in MRI scan and cognitive function were assessed at 5- and 10- months post-exposure. KEY FINDINGS In MRI scans, rats displayed significant increases in lateral ventricle T2 relaxation times at both 5- and 10-months after GWIR-CS, indicating alterations in the cerebrospinal fluid (CSF) density. Furthermore, at 10 months, there were significant decreases in the volumes of the hippocampus and thalamus and an increase in the lateral ventricle volume. At both time points, they exhibited impairments in multiple neurobehavioral tests, confirming substantial deficits in memory and mood function. GWI-CS rats also displayed aggressive behavior and a marked decrease in social interaction and forced swimming, indicating depression. CONCLUSIONS These results confirm that chronic GWIR-CS exposure led to cognitive and psychiatric symptoms with concurrent neuroimaging abnormalities in CSF, with morphological neural lesions, demonstrating the role of divergent etiological mechanisms in GWI and its comorbidities.
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Image Features of Magnetic Resonance Imaging under the Deep Learning Algorithm in the Diagnosis and Nursing of Malignant Tumors. CONTRAST MEDIA & MOLECULAR IMAGING 2021; 2021:1104611. [PMID: 34548850 PMCID: PMC8423572 DOI: 10.1155/2021/1104611] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Revised: 07/16/2021] [Accepted: 08/14/2021] [Indexed: 12/15/2022]
Abstract
In order to explore the effect of convolutional neural network (CNN) algorithm based on deep learning on magnetic resonance imaging (MRI) images of brain tumor patients and evaluate the practical value of MRI image features based on deep learning algorithm in the clinical diagnosis and nursing of malignant tumors, in this study, a brain tumor MRI image model based on the CNN algorithm was constructed, and 80 patients with brain tumors were selected as the research objects. They were divided into an experimental group (CNN algorithm) and a control group (traditional algorithm). The patients were nursed in the whole process. The macroscopic characteristics and imaging index of the MRI image and anxiety of patients in two groups were compared and analyzed. In addition, the image quality after nursing was checked. The results of the study revealed that the MRI characteristics of brain tumors based on CNN algorithm were clearer and more accurate in the fluid-attenuated inversion recovery (FLAIR), MRI T1, T1c, and T2; in terms of accuracy, sensitivity, and specificity, the mean value was 0.83, 0.84, and 0.83, which had obvious advantages compared with the traditional algorithm (P < 0.05). The patients in the nursing group showed lower depression scores and better MRI images in contrast to the control group (P < 0.05). Therefore, the deep learning algorithm can further accurately analyze the MRI image characteristics of brain tumor patients on the basis of conventional algorithms, showing high sensitivity and specificity, which improved the application value of MRI image characteristics in the diagnosis of malignant tumors. In addition, effective nursing for patients undergoing analysis and diagnosis on brain tumor MRI image characteristics can alleviate the patient's anxiety and ensure that high-quality MRI images were obtained after the examination.
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10
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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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11
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Abstract
The canonical mechanism of organophosphate (OP) neurotoxicity is the inhibition of acetylcholinesterase (AChE). However, multiple lines of evidence suggest that mechanisms in addition to or other than AChE inhibition contribute to the neurotoxic effects associated with acute and chronic OP exposures. Characterizing the role(s) of AChE inhibition versus noncholinergic mechanisms in OP neurotoxicity remains an active area of research with significant diagnostic and therapeutic implications. Here, we review recently published studies that provide mechanistic insights regarding (1) OP-induced status epilepticus, (2) long-term neurologic consequences of acute OP exposures, and (3) neurotoxic effects associated with repeated low-level OP exposures. Key data gaps and challenges are also discussed.
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Affiliation(s)
- Yi-Hua Tsai
- Department of Molecular Sciences, University of California, Davis School of Veterinary Medicine, 1089 Veterinary Medicine Drive, Davis, CA, 95616, USA
| | - Pamela J Lein
- Department of Molecular Sciences, University of California, Davis School of Veterinary Medicine, 1089 Veterinary Medicine Drive, Davis, CA, 95616, USA
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12
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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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13
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Putra M, Gage M, Sharma S, Gardner C, Gasser G, Anantharam V, Thippeswamy T. Diapocynin, an NADPH oxidase inhibitor, counteracts diisopropylfluorophosphate-induced long-term neurotoxicity in the rat model. Ann N Y Acad Sci 2020; 1479:75-93. [PMID: 32037612 PMCID: PMC7415478 DOI: 10.1111/nyas.14314] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2019] [Revised: 01/14/2020] [Accepted: 01/25/2020] [Indexed: 12/18/2022]
Abstract
Organophosphate (OP) nerve agents are a threat to both the military and civilians. OP exposure causes cholinergic crisis and status epilepticus (SE) because of irreversible inhibition of acetylcholinesterase that can be life-threatening if left untreated. OP survivors develop long-term morbidity, such as cognitive impairment and motor dysfunction, because of oxidative stress and progressive neuroinflammation and neurodegeneration, which act as disease promoters. Current medical countermeasures (MCMs) do not mitigate these pathologies. Therefore, our goal was to target these disease promoters using diapocynin (DPO), an NADPH oxidase inhibitor, in addition to MCMs, in a rat diisopropylfluorophosphate (DFP) model. The DFP-intoxicated rats were treated with DPO (300 mg/kg, oral, six doses, 12-h intervals) or vehicle 2 h following behavioral SE termination with diazepam. The DPO treatment significantly rescued DFP-induced motor impairment and attenuated epileptiform spiking during the first 72 h after DFP exposure in severely seizing rats despite no difference in epileptiform spike rate between the vehicle and DPO groups in mild SE rats. DPO significantly reduced DFP-induced reactive astrogliosis, neurodegeneration, GP91phox , glutathiolated protein, serum nitrite, and proinflammatory cytokines and chemokines, such as interleukins (ILs) IL-1α, IL-6, IL-2, IL-17A, leptin, and IP-10, in the hippocampus. Collectively, these data support a neuroprotective role of DPO in an OP-induced neurotoxicity model.
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Affiliation(s)
- Marson Putra
- Neuroscience Graduate Program, Iowa State University, Ames, IA 50011
- Department of Biomedical Sciences, College of Veterinary Medicine, Iowa State University, Ames, IA 50011
| | - Meghan Gage
- Neuroscience Graduate Program, Iowa State University, Ames, IA 50011
- Department of Biomedical Sciences, College of Veterinary Medicine, Iowa State University, Ames, IA 50011
| | - Shaunik Sharma
- Department of Biomedical Sciences, College of Veterinary Medicine, Iowa State University, Ames, IA 50011
| | - Cara Gardner
- Department of Biomedical Sciences, College of Veterinary Medicine, Iowa State University, Ames, IA 50011
| | | | | | - Thimmasettappa Thippeswamy
- Neuroscience Graduate Program, Iowa State University, Ames, IA 50011
- Department of Biomedical Sciences, College of Veterinary Medicine, Iowa State University, Ames, IA 50011
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14
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Reddy SD, Wu X, Kuruba R, Sridhar V, Reddy DS. Magnetic resonance imaging analysis of long-term neuropathology after exposure to the nerve agent soman: correlation with histopathology and neurological dysfunction. Ann N Y Acad Sci 2020; 1480:116-135. [PMID: 32671850 PMCID: PMC7708405 DOI: 10.1111/nyas.14431] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2020] [Revised: 05/09/2020] [Accepted: 06/17/2020] [Indexed: 12/14/2022]
Abstract
Nerve agents (NAs) produce acute and long-term brain injury and dysfunction, as evident from the Japan and Syria incidents. Magnetic resonance imaging (MRI) is a versatile technique to examine such chronic anatomical, functional, and neuronal damage in the brain. The objective of this study was to investigate long-term structural and neuronal lesion abnormalities in rats exposed to acute soman intoxication. T2-weighted MRI images of 10 control and 17 soman-exposed rats were acquired using a Siemens MRI system at 90 days after soman exposure. Quantification of brain tissue volumes and T2 signal intensity was conducted using the Inveon Research Workplace software and the extent of damage was correlated with histopathology and cognitive function. Soman-exposed rats showed drastic hippocampal atrophy with neuronal loss and reduced hippocampal volume (HV), indicating severe damage, but had similar T2 relaxation times to the control group, suggesting limited scarring and fluid density changes despite the volume decrease. Conversely, soman-exposed rats displayed significant increases in lateral ventricle volumes and T2 times, signifying strong cerebrospinal fluid expansion in compensation for tissue atrophy. The total brain volume, thalamic volume, and thalamic T2 time were similar in both groups, however, suggesting that some brain regions remained more intact long-term after soman intoxication. The MRI neuronal lesions were positively correlated with the histological markers of neurodegeneration and neuroinflammation 90 days after soman exposure. The predominant MRI hippocampal atrophy (25%) was highly consistent with massive reduction (35%) of neuronal nuclear antigen-positive (NeuN+ ) principal neurons and parvalbumin-positive (PV+ ) inhibitory interneurons within this brain region. The HV was significantly correlated with both inflammatory markers of GFAP+ astrogliosis and IBA1+ microgliosis. The reduced HV was also directly correlated with significant memory deficits in the soman-exposed cohort, confirming a possible neurobiological basis for neurological dysfunction. Together, these findings provide powerful insight on long-term region-specific neurodegenerative patterns after soman exposure and demonstrate the feasibility of in vivo neuroimaging to monitor neuropathology, predict the risk of neurological deficits, and evaluate response to medical countermeasures for NAs.
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Affiliation(s)
- Sandesh D Reddy
- Department of Neuroscience and Experimental Therapeutics, College of Medicine, Texas A&M University Health Science Center, Bryan, Texas
- Biomedical Engineering, College of Engineering, Texas A&M University, College Station, Texas
| | - Xin Wu
- Department of Neuroscience and Experimental Therapeutics, College of Medicine, Texas A&M University Health Science Center, Bryan, Texas
| | - Ramkumar Kuruba
- Department of Neuroscience and Experimental Therapeutics, College of Medicine, Texas A&M University Health Science Center, Bryan, Texas
| | - Vidya Sridhar
- Texas A&M Institute for Preclinical Studies, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, Texas
| | - Doodipala Samba Reddy
- Department of Neuroscience and Experimental Therapeutics, College of Medicine, Texas A&M University Health Science Center, Bryan, Texas
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15
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Dhir A, Bruun DA, Guignet M, Tsai Y, González E, Calsbeek J, Vu J, Saito N, Tancredi DJ, Harvey DJ, Lein PJ, Rogawski MA. Allopregnanolone and perampanel as adjuncts to midazolam for treating diisopropylfluorophosphate-induced status epilepticus in rats. Ann N Y Acad Sci 2020; 1480:183-206. [PMID: 32915470 PMCID: PMC7756871 DOI: 10.1111/nyas.14479] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2020] [Revised: 07/29/2020] [Accepted: 08/06/2020] [Indexed: 12/11/2022]
Abstract
Combinations of midazolam, allopregnanolone, and perampanel were assessed for antiseizure activity in a rat diisopropylfluorophosphate (DFP) status epilepticus model. Animals receiving DFP followed by atropine and pralidoxime exhibited continuous high-amplitude rhythmical electroencephalography (EEG) spike activity and behavioral seizures for more than 5 hours. Treatments were administered intramuscularly 40 min after DFP. Seizures persisted following midazolam (1.8 mg/kg). The combination of midazolam with either allopregnanolone (6 mg/kg) or perampanel (2 mg/kg) terminated EEG and behavioral status epilepticus, but the onset of the perampanel effect was slow. The combination of midazolam, allopregnanolone, and perampanel caused rapid and complete suppression of EEG and behavioral seizures. In the absence of DFP, animals treated with the three-drug combination were sedated but not anesthetized. Animals that received midazolam alone exhibited spontaneous recurrent EEG seizures, whereas those that received the three-drug combination did not, demonstrating antiepileptogenic activity. All combination treatments reduced neurodegeneration as assessed with Fluoro-Jade C staining to a greater extent than midazolam alone, and most reduced astrogliosis as assessed by GFAP immunoreactivity but had mixed effects on markers of microglial activation. We conclude that allopregnanolone, a positive modulator of the GABAA receptor, and perampanel, an AMPA receptor antagonist, are potential adjuncts to midazolam in the treatment of benzodiazepine-refractory organophosphate nerve agent-induced status epilepticus.
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Affiliation(s)
- Ashish Dhir
- Department of Neurology, School of MedicineUniversity of California, DavisSacramentoCalifornia
| | - Donald A. Bruun
- Department of Molecular Biosciences, School of Veterinary MedicineUniversity of California, DavisDavisCalifornia
| | - Michelle Guignet
- Department of Molecular Biosciences, School of Veterinary MedicineUniversity of California, DavisDavisCalifornia
| | - Yi‐Hua Tsai
- Department of Molecular Biosciences, School of Veterinary MedicineUniversity of California, DavisDavisCalifornia
| | - Eduardo González
- Department of Molecular Biosciences, School of Veterinary MedicineUniversity of California, DavisDavisCalifornia
| | - Jonas Calsbeek
- Department of Molecular Biosciences, School of Veterinary MedicineUniversity of California, DavisDavisCalifornia
| | - Joan Vu
- Department of Molecular Biosciences, School of Veterinary MedicineUniversity of California, DavisDavisCalifornia
| | - Naomi Saito
- Department of Public Health Sciences, School of MedicineUniversity of California, DavisDavisCalifornia
| | - Daniel J. Tancredi
- Department of Pediatrics, School of MedicineUniversity of California, DavisSacramentoCalifornia
| | - Danielle J. Harvey
- Department of Public Health Sciences, School of MedicineUniversity of California, DavisDavisCalifornia
| | - Pamela J. Lein
- Department of Molecular Biosciences, School of Veterinary MedicineUniversity of California, DavisDavisCalifornia
| | - Michael A. Rogawski
- Department of Neurology, School of MedicineUniversity of California, DavisSacramentoCalifornia
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17
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Hobson BA, Rowland DJ, Sisó S, Guignet MA, Harmany ZT, Bandara SB, Saito N, Harvey DJ, Bruun DA, Garbow JR, Chaudhari AJ, Lein PJ. TSPO PET Using [18F]PBR111 Reveals Persistent Neuroinflammation Following Acute Diisopropylfluorophosphate Intoxication in the Rat. Toxicol Sci 2020; 170:330-344. [PMID: 31087103 DOI: 10.1093/toxsci/kfz096] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Acute intoxication with organophosphates (OPs) can trigger status epilepticus followed by persistent cognitive impairment and/or electroencephalographic abnormalities. Neuroinflammation is widely posited to influence these persistent neurological consequences. However, testing this hypothesis has been challenging, in part because traditional biometrics preclude longitudinal measures of neuroinflammation within the same animal. Therefore, we evaluated the performance of noninvasive positron emission tomography (PET), using the translocator protein (TSPO) radioligand [18F]PBR111 against classic histopathologic measures of neuroinflammation in a preclinical model of acute intoxication with the OP diisopropylfluorophosphate (DFP). Adult male Sprague Dawley rats administered pyridostigmine bromide (0.1 mg/kg, im) 30 min prior to 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. TSPO PET performed prior to DFP exposure and at 3, 7, 14, 21, and 28 days postexposure revealed distinct lesions, as defined by increased standardized uptake values (SUV). Increased SUV showed high spatial correspondence to immunohistochemical evidence of neuroinflammation, which was corroborated by cytokine gene and protein expression. Regional SUV metrics varied spatiotemporally with days postexposure and correlated with the degree of neuroinflammation detected immunohistochemically. Furthermore, SUV metrics were highly correlated with seizure severity, suggesting that early termination of OP-induced seizures may be critical for attenuating subsequent neuroinflammatory responses. Normalization of SUV values to a cerebellar reference region improved correlations to all outcome measures and seizure severity. Collectively, these results establish TSPO PET using [18F]PBR111 as a robust, noninvasive tool for longitudinal monitoring of neuroinflammation following acute OP intoxication.
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Affiliation(s)
- Brad A Hobson
- Department of Radiology, University of California Davis School of Medicine, Sacramento, California 95817
| | - Douglas J Rowland
- Center for Molecular and Genomic Imaging, Department of Biomedical Engineering, University of California Davis College of Engineering, Davis, California 95616
| | - Sílvia Sisó
- Department of Pathology, Microbiology and Immunology
| | - Michelle A Guignet
- Department of Molecular Biosciences, University of California Davis School of Veterinary Medicine, Davis, California 95616
| | - Zachary T Harmany
- Center for Molecular and Genomic Imaging, Department of Biomedical Engineering, University of California Davis College of Engineering, Davis, California 95616
| | - Suren B Bandara
- Department of Molecular Biosciences, University of California Davis School of Veterinary Medicine, Davis, California 95616
| | - Naomi Saito
- Department of Public Health Sciences, University of California Davis School of Medicine, Davis, California 95616
| | - Danielle J Harvey
- Department of Public Health Sciences, University of California Davis School of Medicine, Davis, California 95616
| | - Donald A Bruun
- Department of Molecular Biosciences, University of California Davis School of Veterinary Medicine, Davis, California 95616
| | - Joel R Garbow
- Department of Radiology, Washington University in St. Louis, St. Louis, Missouri 63110
| | - Abhijit J Chaudhari
- Department of Radiology, University of California Davis School of Medicine, Sacramento, California 95817.,Center for Molecular and Genomic Imaging, Department of Biomedical Engineering, University of California Davis College of Engineering, Davis, California 95616
| | - Pamela J Lein
- Department of Molecular Biosciences, University of California Davis School of Veterinary Medicine, Davis, California 95616
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18
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Quantitative T 2 MRI is predictive of neurodegeneration following organophosphate exposure in a rat model. Sci Rep 2020; 10:13007. [PMID: 32747689 PMCID: PMC7400670 DOI: 10.1038/s41598-020-69991-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2019] [Accepted: 07/13/2020] [Indexed: 02/03/2023] Open
Abstract
Organophosphorus compounds, such as chemical warfare nerve agents and pesticides, are known to cause neurological damage. This study measured nerve agent-related neuropathology and determined whether quantitative T2 MRI could be used as a biomarker of neurodegeneration. Quantitative T2 MRI was performed using a 9.4 T MRI on rats prior to and following soman exposure. T2 images were taken at least 24 h prior, 1 h and 18-24 h after soman exposure. Rats were pre- and post-treated with HI-6 dimethanesulfonate and atropine methyl nitrate. A multicomponent T2 acquisition and analysis was performed. Brains were stained with Fluoro-Jade C to assess neurodegeneration. Rats exposed to soman developed behavioral expression of electrographic seizures. At 18-24 h after soman exposure, significant increases in T2, a possible marker of edema, were found in multiple regions. The largest changes were in the piriform cortex (before: 47.7 ± 1.4 ms; 18-24 h: 82.3 ± 13.4 ms). Fluoro-Jade C staining showed significant neurodegeneration 18-24 h post exposure. The piriform cortex had the strongest correlation between the change in relaxation rate and percent neurodegeneration (r = 0.96, p < 0.001). These findings indicate there is regionally specific neurodegeneration 24 h after exposure to soman. The high correlation between T2 relaxivity and histopathology supports the use of T2 as a marker of injury.
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19
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Reddy DS, Perumal D, Golub V, Habib A, Kuruba R, Wu X. Phenobarbital as alternate anticonvulsant for organophosphate-induced benzodiazepine-refractory status epilepticus and neuronal injury. Epilepsia Open 2020; 5:198-212. [PMID: 32524045 PMCID: PMC7278559 DOI: 10.1002/epi4.12389] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2019] [Revised: 02/08/2020] [Accepted: 02/24/2020] [Indexed: 12/19/2022] Open
Abstract
Objective Organophosphates (OPs) such as diisopropylfluorophosphate (DFP) and soman are lethal chemical agents that can produce seizures, refractory status epilepticus (SE), and brain damage. There are few optimal treatments for late or refractory SE. Phenobarbital is a second‐line drug for SE, usually after lorazepam, diazepam, or midazolam have failed to stop SE. Practically, 40 minutes or less is often necessary for first responders to arrive and assist in a chemical incident. However, it remains unclear whether administration of phenobarbital 40 minutes after OP intoxication is still effective. Here, we investigated the efficacy of phenobarbital treatment at 40 minutes postexposure to OP intoxication. Methods Acute refractory SE was induced in rats by DFP injection as per a standard paradigm. After 40 minutes, subjects were given phenobarbital intramuscularly (30‐100 mg/kg) and progression of seizure activity was monitored by video‐EEG recording. The extent of brain damage was assessed 3 days after DFP injections by neuropathology analysis of neurodegeneration and neuronal injury by unbiased stereology. Results Phenobarbital produced a dose‐dependent seizure protection. A substantial decrease in SE was evident at 30 and 60 mg/kg, and a complete seizure termination was noted at 100 mg/kg within 40 minutes after treatment. Neuropathology findings showed significant neuroprotection in 100 mg/kg cohorts in brain regions associated with SE. Although higher doses resulted in greater protection against refractory SE and neuronal damage, they did not positively correlate with improved survival rate. Moreover, phenobarbital caused serious adverse effects including anesthetic or comatose state and even death. Significance Phenobarbital appears as an alternate anticonvulsant for OP‐induced refractive SE in hospital settings. A careful risk‐benefit analysis is required because of negative outcomes on survival and cardio‐respiratory function. However, the need for sophisticated support and critical monitoring in hospital may preclude its use as medical countermeasure in mass casualty situations.
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Affiliation(s)
- Doodipala Samba Reddy
- Department of Neuroscience and Experimental Therapeutics College of Medicine Texas A&M University Health Science Center Bryan TX USA
| | - Dheepthi Perumal
- Department of Neuroscience and Experimental Therapeutics College of Medicine Texas A&M University Health Science Center Bryan TX USA
| | - Victoria Golub
- Department of Neuroscience and Experimental Therapeutics College of Medicine Texas A&M University Health Science Center Bryan TX USA
| | - Andy Habib
- Department of Neuroscience and Experimental Therapeutics College of Medicine Texas A&M University Health Science Center Bryan TX USA
| | - Ramkumar Kuruba
- Department of Neuroscience and Experimental Therapeutics College of Medicine Texas A&M University Health Science Center Bryan TX USA
| | - Xin Wu
- Department of Neuroscience and Experimental Therapeutics College of Medicine Texas A&M University Health Science Center Bryan TX USA
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20
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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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21
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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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Neuroimaging Biomarkers of Experimental Epileptogenesis and Refractory Epilepsy. Int J Mol Sci 2019; 20:ijms20010220. [PMID: 30626103 PMCID: PMC6337422 DOI: 10.3390/ijms20010220] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2018] [Revised: 12/31/2018] [Accepted: 01/03/2019] [Indexed: 11/17/2022] Open
Abstract
This article provides an overview of neuroimaging biomarkers in experimental epileptogenesis and refractory epilepsy. Neuroimaging represents a gold standard and clinically translatable technique to identify neuropathological changes in epileptogenesis and longitudinally monitor its progression after a precipitating injury. Neuroimaging studies, along with molecular studies from animal models, have greatly improved our understanding of the neuropathology of epilepsy, such as the hallmark hippocampus sclerosis. Animal models are effective for differentiating the different stages of epileptogenesis. Neuroimaging in experimental epilepsy provides unique information about anatomic, functional, and metabolic alterations linked to epileptogenesis. Recently, several in vivo biomarkers for epileptogenesis have been investigated for characterizing neuronal loss, inflammation, blood-brain barrier alterations, changes in neurotransmitter density, neurovascular coupling, cerebral blood flow and volume, network connectivity, and metabolic activity in the brain. Magnetic resonance imaging (MRI) is a sensitive method for detecting structural and functional changes in the brain, especially to identify region-specific neuronal damage patterns in epilepsy. Positron emission tomography (PET) and single-photon emission computerized tomography are helpful to elucidate key functional alterations, especially in areas of brain metabolism and molecular patterns, and can help monitor pathology of epileptic disorders. Multimodal procedures such as PET-MRI integrated systems are desired for refractory epilepsy. Validated biomarkers are warranted for early identification of people at risk for epilepsy and monitoring of the progression of medical interventions.
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Jackson C, Ardinger C, Winter KM, McDonough JH, McCarren HS. Validating a model of benzodiazepine refractory nerve agent-induced status epilepticus by evaluating the anticonvulsant and neuroprotective effects of scopolamine, memantine, and phenobarbital. J Pharmacol Toxicol Methods 2019; 97:1-12. [PMID: 30790623 PMCID: PMC6529248 DOI: 10.1016/j.vascn.2019.02.006] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2018] [Revised: 02/05/2019] [Accepted: 02/14/2019] [Indexed: 12/26/2022]
Abstract
INTRODUCTION Organophosphorus nerve agents (OPNAs) irreversibly block acetylcholinesterase activity, resulting in accumulation of excess acetylcholine at neural synapses, which can lead to a state of prolonged seizures known as status epilepticus (SE). Benzodiazepines, the current standard of care for SE, become less effective as latency to treatment increases. In a mass civilian OPNA exposure, concurrent trauma and limited resources would likely cause a delay in first response time. To address this issue, we have developed a rat model to test novel anticonvulsant/ neuroprotectant adjuncts at delayed time points. METHODS For model development, adult male rats with cortical electroencephalographic (EEG) electrodes were exposed to soman and administered saline along with atropine, 2-PAM, and midazolam 5, 20, or 40 min after SE onset. We validated our model using three drugs: scopolamine, memantine, and phenobarbital. Using the same procedure outlined above, rats were given atropine, 2-PAM, midazolam and test treatment 20 min after SE onset. RESULTS Using gamma power, delta power, and spike rate to quantify EEG activity, we found that scopolamine was effective, memantine was minimally effective, and phenobarbital had a delayed effect on terminating SE. Fluoro-Jade B staining was used to assess neuroprotection in five brain regions. Each treatment provided significant protection compared to saline + midazolam in at least two brain regions. DISCUSSION Because our data agree with previously published studies on the efficacy of these compounds, we conclude that this model is a valid way to test novel anticonvulsants/ neuroprotectants for controlling benzodiazepine-resistant OPNA-induced SE and subsequent neuropathology.
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Affiliation(s)
| | | | | | | | - Hilary S. McCarren
- Corresponding author at: U.S. Army Medical Research Institute of Chemical Defense, 8350 Ricketts Point Road, Aberdeen Proving Ground, MD 21010, USA
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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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25
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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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McCarren HS, Arbutus JA, Ardinger C, Dunn EN, Jackson CE, McDonough JH. Dexmedetomidine stops benzodiazepine-refractory nerve agent-induced status epilepticus. Epilepsy Res 2018; 141:1-12. [PMID: 29414381 DOI: 10.1016/j.eplepsyres.2018.01.010] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2017] [Revised: 12/21/2017] [Accepted: 01/07/2018] [Indexed: 12/15/2022]
Abstract
Nerve agents are highly toxic chemicals that pose an imminent threat to soldiers and civilians alike. Nerve agent exposure leads to an increase in acetylcholine within the central nervous system, resulting in development of protracted seizures known as status epilepticus (SE). Currently, benzodiazepines are the standard of care for nerve agent-induced SE, but their efficacy quickly wanes as the time to treatment increases. Here, we examine the role of the α2-adrenoceptor in termination of nerve agent-induced SE using the highly specific agonist dexmedetomidine (DEX). Adult male rats were exposed to soman and entered SE as confirmed by electroencephalograph (EEG). We observed that administration of DEX in combination with the benzodiazepine midazolam (MDZ) 20 or 40 min after the onset of SE stopped seizures and returned processed EEG measurements to baseline levels. The protective effect of DEX was blocked by the α2-adrenoceptor antagonist atipamezole (ATI), but ATI failed to restore seizure activity after it was already halted by DEX in most cases, suggesting that α2-adrenoceptors may be involved in initiating SE cessation rather than merely suppressing seizure activity. Histologically, treatment with DEX + MDZ significantly reduced the number of dying neurons as measured by FluoroJade B in the amygdala, thalamus, and piriform cortex, but did not protect the hippocampus or parietal cortex even when SE was successfully halted. We conclude that DEX serves not just as a valuable potential addition to the anticonvulsant regimen for nerve agent exposure, but also as a tool for dissecting the neural circuitry that drives SE.
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Affiliation(s)
- Hilary S McCarren
- USAMRICD, Medical Toxicology Research Division, Neuroscience Branch, 2900 Ricketts Point Rd, Aberdeen Proving Ground, MD 21010, United States.
| | - Julia A Arbutus
- USAMRICD, Medical Toxicology Research Division, Neuroscience Branch, 2900 Ricketts Point Rd, Aberdeen Proving Ground, MD 21010, United States
| | - Cherish Ardinger
- USAMRICD, Medical Toxicology Research Division, Neuroscience Branch, 2900 Ricketts Point Rd, Aberdeen Proving Ground, MD 21010, United States
| | - Emily N Dunn
- USAMRICD, Medical Toxicology Research Division, Neuroscience Branch, 2900 Ricketts Point Rd, Aberdeen Proving Ground, MD 21010, United States
| | - Cecelia E Jackson
- USAMRICD, Medical Toxicology Research Division, Neuroscience Branch, 2900 Ricketts Point Rd, Aberdeen Proving Ground, MD 21010, United States
| | - John H McDonough
- USAMRICD, Medical Toxicology Research Division, Neuroscience Branch, 2900 Ricketts Point Rd, Aberdeen Proving Ground, MD 21010, United States
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27
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Anantharam P, Kim DS, Whitley EM, Mahama B, Imerman P, Padhi P, Rumbeiha WK. Midazolam Efficacy Against Acute Hydrogen Sulfide-Induced Mortality and Neurotoxicity. J Med Toxicol 2018; 14:79-90. [PMID: 29318511 PMCID: PMC6013736 DOI: 10.1007/s13181-017-0650-4] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2017] [Revised: 12/13/2017] [Accepted: 12/21/2017] [Indexed: 01/06/2023] Open
Abstract
Hydrogen sulfide (H2S) is a colorless, highly neurotoxic gas. It is not only an occupational and environmental hazard but also of concern to the Department of Homeland Security for potential nefarious use. Acute high-dose H2S exposure causes death, while survivors may develop neurological sequelae. Currently, there is no suitable antidote for treatment of acute H2S-induced neurotoxicity. Midazolam (MDZ), an anti-convulsant drug recommended for treatment of nerve agent intoxications, could also be of value in treating acute H2S intoxication. In this study, we tested the hypothesis that MDZ is effective in preventing/treating acute H2S-induced neurotoxicity. This proof-of-concept study had two objectives: to determine whether MDZ prevents/reduces H2S-induced mortality and to test whether MDZ prevents H2S-induced neurological sequelae. MDZ (4 mg/kg) was administered IM in mice, 5 min pre-exposure to a high concentration of H2S at 1000 ppm or 12 min post-exposure to 1000 ppm H2S followed by 30 min of continuous exposure. A separate experiment tested whether MDZ pre-treatment prevented neurological sequelae. Endpoints monitored included assessment of clinical signs, mortality, behavioral changes, and brain histopathological changes. MDZ significantly reduced H2S-induced lethality, seizures, knockdown, and behavioral deficits (p < 0.01). MDZ also significantly prevented H2S-induced neurological sequelae, including weight loss, behavior deficits, neuroinflammation, and histopathologic lesions (p < 0.01). Overall, our findings show that MDZ is a promising drug for reducing H2S-induced acute mortality, neurotoxicity, and neurological sequelae.
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Affiliation(s)
- Poojya Anantharam
- Department of Veterinary Diagnostic and Animal Production Medicine, Iowa State University, Ames, IA, USA
| | - Dong-Suk Kim
- Department of Veterinary Diagnostic and Animal Production Medicine, Iowa State University, Ames, IA, USA
| | | | - Belinda Mahama
- Department of Veterinary Diagnostic and Animal Production Medicine, Iowa State University, Ames, IA, USA
| | - Paula Imerman
- Department of Veterinary Diagnostic and Animal Production Medicine, Iowa State University, Ames, IA, USA
| | - Piyush Padhi
- Department of Veterinary Diagnostic and Animal Production Medicine, Iowa State University, Ames, IA, USA
| | - Wilson K Rumbeiha
- Department of Veterinary Diagnostic and Animal Production Medicine, Iowa State University, Ames, IA, USA.
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28
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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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29
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Anantharam P, Whitley EM, Mahama B, Kim DS, Sarkar S, Santana C, Chan A, Kanthasamy AG, Kanthasamy A, Boss GR, Rumbeiha WK. Cobinamide is effective for treatment of hydrogen sulfide-induced neurological sequelae in a mouse model. Ann N Y Acad Sci 2017; 1408:61-78. [PMID: 29239480 PMCID: PMC5734662 DOI: 10.1111/nyas.13559] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2017] [Revised: 10/16/2017] [Accepted: 10/30/2017] [Indexed: 12/21/2022]
Abstract
Hydrogen sulfide (H2 S) is a highly neurotoxic gas. Acute exposure can lead to neurological sequelae among survivors. A drug for treating neurological sequelae in survivors of acute H2 S intoxication is needed. Using a novel mouse model we evaluated the efficacy of cobinamide (Cob) for increasing survival of, and reducing neurological sequalae in, mice exposed to sublethal doses of H2 S. There were two objectives: (1) to determine the dose-response efficacy of Cob and (2) to determine the effective therapeutic time window of Cob. To explore objective 1, mice were injected intramuscularly with Cob at 0, 50, or 100 mg/kg at 2 min after H2 S exposure. For objective 2, mice were injected intramuscularly with 100 mg/kg Cob at 2, 15, and 30 min after H2 S exposure. For both objectives, mice were exposed to 765 ppm of H2 S gas. Cob significantly reduced H2 S-induced lethality in a dose-dependent manner (P < 0.05). Cob-treated mice exhibited significantly fewer seizures and knockdowns compared with the H2 S-exposed group. Cob also reversed H2 S-induced weight loss, behavioral deficits, neurochemical changes, cytochrome c oxidase enzyme inhibition, and neurodegeneration in a dose- and time-dependent manner (P < 0.01). Overall, these findings show that Cob increases survival and is neuroprotective in a mouse model of H2 S-induced neurological sequelae.
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Affiliation(s)
- Poojya Anantharam
- Department of Veterinary Diagnostic and Production Animal Medicine, Iowa State University, Ames, Iowa
| | | | - Belinda Mahama
- Department of Veterinary Diagnostic and Production Animal Medicine, Iowa State University, Ames, Iowa
| | - Dong-Suk Kim
- Department of Veterinary Diagnostic and Production Animal Medicine, Iowa State University, Ames, Iowa
| | - Souvarish Sarkar
- Department of Biomedical Sciences, Iowa State University, Ames, Iowa
| | - Cristina Santana
- Department of Veterinary Diagnostic and Production Animal Medicine, Iowa State University, Ames, Iowa
| | - Adriano Chan
- Department of Biomedical Sciences, Iowa State University, Ames, Iowa
| | | | - Arthi Kanthasamy
- Department of Biomedical Sciences, Iowa State University, Ames, Iowa
| | - Gerry R. Boss
- Department of Medicine, University of California, San Diego, San Diego, California
| | - Wilson K. Rumbeiha
- Department of Veterinary Diagnostic and Production Animal Medicine, Iowa State University, Ames, Iowa
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