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McDonough JH, McMonagle JD, Capacio BR. Anticonvulsant effectiveness of scopolamine against soman-induced seizures in African green monkeys. Drug Chem Toxicol 2021; 45:2185-2192. [PMID: 34251950 DOI: 10.1080/01480545.2021.1916171] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
Prolonged seizures are a hallmark feature of intoxication with anticholinesterase nerve agents such as soman. While benzodiazepine drugs are typically used to control these seizures, studies in both rats and guinea pigs have shown that potent, centrally acting anticholinergic drugs such as scopolamine can also terminate such seizures. The present study was performed to determine if scopolamine could produce similar anticonvulsant effects in a nonhuman primate model of soman intoxication. Adult male African green monkeys, implanted with telemetry devices to record cortical electroencephalographic activity, were pretreated with pyridostigmine (0.02 mg/kg, intramuscularly [im]) and 40 min later challenged with 15 µg/kg (im) of the nerve agent soman. One min after soman exposure the animals were treated with atropine (0.4 mg/kg, im) and the oxime 2-PAM (25.7 mg/kg, im). One min after the start of seizure activity the animals were administered scopolamine (0.01-0.1 mg/kg, im), using an up-down dosing design over successive animals. Scopolamine was highly effective in stopping soman-induced seizures with an ED50 = 0.0312 mg/kg (0.021-0.047 mg/kg = 95% confidence limits). Seizure control was rapid, with all epileptiform activity stopping on average 21.7 min after scopolamine treatment. A separate pK study showed that scopolamine absorption peaked approximately 10 min after im administration and a dose of 0.032 mg/kg produced maximum plasma levels of 17.62 ng/ml. The results show that scopolamine exerts potent and rapid anticonvulsant action against soman-induced seizures and that it may serve as a valuable adjunct to current antidote treatments for nerve agent intoxication.
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Affiliation(s)
- John H McDonough
- Neuroscience Department, US Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, MD, USA
| | - Joseph D McMonagle
- Neuroscience Department, US Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, MD, USA
| | - Benedict R Capacio
- Medical Toxicology Research Division, Pharmaceutical Sciences Department, US Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, MD, USA
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Barker BS, Spampanato J, McCarren HS, Berger K, Jackson CE, Yeung DT, Dudek FE, McDonough JH. The K v7 Modulator, Retigabine, is an Efficacious Antiseizure Drug for Delayed Treatment of Organophosphate-induced Status Epilepticus. Neuroscience 2021; 463:143-158. [PMID: 33836243 PMCID: PMC8142924 DOI: 10.1016/j.neuroscience.2021.03.029] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2021] [Revised: 03/23/2021] [Accepted: 03/25/2021] [Indexed: 10/21/2022]
Abstract
Benzodiazepines are the primary treatment option for organophosphate (OP)-induced status epilepticus (SE), but these antiseizure drugs (ASDs) lose efficacy as treatment is delayed. In the event of a mass civilian or military exposure, significant treatment delays are likely. New ASDs that combat benzodiazepine-resistant, OP-induced SE are critically needed, particularly if they can be efficacious after a long treatment delay. This study evaluated the efficacy of the Kv7 channel modulator, retigabine, as a novel therapy for OP-induced SE. Adult, male rats were exposed to soman or diisopropyl fluorophosphate (DFP) to elicit SE and monitored by electroencephalogram (EEG) recording. Retigabine was administered alone or adjunctive to midazolam (MDZ) at delays of 20- or 40-min in the soman model, and 60-min in the DFP model. Following EEG recordings, rats were euthanized and brain tissue was collected for Fluoro-Jade B (FJB) staining to quantify neuronal death. In the DFP model, MDZ + 15 mg/kg retigabine suppressed seizure activity and was neuroprotective. In the soman model, MDZ + 30 mg/kg retigabine suppressed seizures at 20- and 40-min delays. Without MDZ, 15 mg/kg retigabine provided partial antiseizure and neuroprotectant efficacy in the DFP model, while 30 mg/kg without MDZ failed to attenuate soman-induced SE. At 60 mg/kg, retigabine without MDZ strongly reduced seizure activity and neuronal degeneration against soman-induce SE. This study demonstrates the antiseizure and neuroprotective efficacy of retigabine against OP-induced SE. Our data suggest retigabine could be a useful adjunct to standard-of-care and has potential for use in the absence of MDZ.
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Affiliation(s)
- Bryan S Barker
- United States Army Medical Research Institute of Chemical Defense, Medical Toxicology Research Division, Neuroscience Department, 2900 Ricketts Point Rd, Aberdeen Proving Ground, MD 21010, USA
| | - Jay Spampanato
- Department of Neurosurgery, University of Utah School of Medicine, Salt Lake City, UT 84108, USA.
| | - Hilary S McCarren
- United States Army Medical Research Institute of Chemical Defense, Medical Toxicology Research Division, Neuroscience Department, 2900 Ricketts Point Rd, Aberdeen Proving Ground, MD 21010, USA
| | - Kyle Berger
- United States Army Medical Research Institute of Chemical Defense, Medical Toxicology Research Division, Neuroscience Department, 2900 Ricketts Point Rd, Aberdeen Proving Ground, MD 21010, USA
| | - Cecelia E Jackson
- United States Army Medical Research Institute of Chemical Defense, Medical Toxicology Research Division, Neuroscience Department, 2900 Ricketts Point Rd, Aberdeen Proving Ground, MD 21010, USA
| | - David T Yeung
- National Institutes of Health/National Institute of Allergy and Infectious Disease, Bethesda, MD 20892, USA
| | - F Edward Dudek
- Department of Neurosurgery, University of Utah School of Medicine, Salt Lake City, UT 84108, USA
| | - John H McDonough
- United States Army Medical Research Institute of Chemical Defense, Medical Toxicology Research Division, Neuroscience Department, 2900 Ricketts Point Rd, Aberdeen Proving Ground, MD 21010, USA
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Rojas A, McCarren HS, Wang J, Wang W, Abreu-Melon J, Wang S, McDonough JH, Dingledine R. Comparison of neuropathology in rats following status epilepticus induced by diisopropylfluorophosphate and soman. Neurotoxicology 2021; 83:14-27. [PMID: 33352274 PMCID: PMC7987879 DOI: 10.1016/j.neuro.2020.12.010] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2020] [Revised: 12/07/2020] [Accepted: 12/16/2020] [Indexed: 12/29/2022]
Abstract
The increasing number of cases involving the use of nerve agents as deadly weapons has spurred investigation into the molecular mechanisms underlying nerve agent-induced pathology. The highly toxic nature of nerve agents restrict their use in academic research laboratories. Less toxic organophosphorus (OP) based agents including diisopropylfluorophosphate (DFP) are used as surrogates in academic research laboratories to mimic nerve agent poisoning. However, neuropathology resulting from DFP-induced status epilepticus (SE) has not been compared directly to neuropathology observed following nerve agent poisoning in the same study. Here, the hypothesis that neuropathology measured four days after SE is the same for rats exposed to DFP and soman was tested. Adult Sprague-Dawley rats were injected with soman or DFP to induce SE. Cortical electroencephalography (EEG) was recorded prior to and during soman-induced SE. EEG power analysis of rats administered soman revealed prolonged electrographic SE similar to that of rats that endure uninterrupted SE following injection of DFP. Rats that experienced soman-induced SE displayed less hippocampal neuroinflammation and gliosis compared to rats administered DFP. Seizure-induced weight change, blood-brain barrier (BBB) leakiness and neurodegeneration in most seizure sensitive limbic brain regions were similar for rats that endured SE following soman or DFP. The amalgamated pathology score calculated by combining pathological measures (weight loss, hippocampal neuroinflammation, gliosis, BBB integrity and neurodegeneration) was similar in rats administered the OP agents. These findings support use of the rat DFP model of SE as a suitable surrogate for investigating some, but not all delayed consequences produced by nerve agents.
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Affiliation(s)
- Asheebo Rojas
- Department of Pharmacology and Chemical Biology, Emory University, 1510 Clifton Road NE, Atlanta, GA, 30322, United States.
| | - Hilary S McCarren
- Neuroscience Department, Medical Toxicology Research Division, United States Army Medical Research Institute of Chemical Defense, 8350 Ricketts Point Rd, Aberdeen Proving Ground, MD, 21010, United States
| | - Jennifer Wang
- Department of Pharmacology and Chemical Biology, Emory University, 1510 Clifton Road NE, Atlanta, GA, 30322, United States
| | - Wenyi Wang
- Department of Pharmacology and Chemical Biology, Emory University, 1510 Clifton Road NE, Atlanta, GA, 30322, United States
| | - JuanMartin Abreu-Melon
- Department of Pharmacology and Chemical Biology, Emory University, 1510 Clifton Road NE, Atlanta, GA, 30322, United States
| | - Sarah Wang
- Department of Pharmacology and Chemical Biology, Emory University, 1510 Clifton Road NE, Atlanta, GA, 30322, United States
| | - John H McDonough
- Neuroscience Department, Medical Toxicology Research Division, United States Army Medical Research Institute of Chemical Defense, 8350 Ricketts Point Rd, Aberdeen Proving Ground, MD, 21010, United States
| | - Raymond Dingledine
- Department of Pharmacology and Chemical Biology, Emory University, 1510 Clifton Road NE, Atlanta, GA, 30322, United States
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McCarren HS, Eisen MR, Nguyen DL, Dubée PB, Ardinger CE, Dunn EN, Haines KM, Santoro AN, Bodner PM, Ondeck CA, Honnold CL, McDonough JH, Beske PH, McNutt PM. Characterization and treatment of spontaneous recurrent seizures following nerve agent-induced status epilepticus in mice. Epilepsy Res 2020; 162:106320. [PMID: 32182542 PMCID: PMC7156324 DOI: 10.1016/j.eplepsyres.2020.106320] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2019] [Revised: 02/21/2020] [Accepted: 03/09/2020] [Indexed: 12/14/2022]
Abstract
PURPOSE To develop and characterize a mouse model of spontaneous recurrent seizures following nerve agent-induced status epilepticus (SE) and test the efficacy of existing antiepileptic drugs. METHODS SE was induced in telemeterized male C57Bl6/J mice by soman exposure, and electroencephalographic activity was recorded for 4-6 weeks. Mice were treated with antiepileptic drugs (levetiracetam, valproic acid, phenobarbital) or corresponding vehicles for 14 d after exposure, followed by 14 d of drug washout. Survival, body weight, seizure characteristics, and histopathology were used to characterize the acute and chronic effects of nerve agent exposure and to evaluate the efficacy of treatments in mitigating or preventing neurological effects. RESULTS Spontaneous recurrent seizures manifested in all survivors, but the number and frequency of seizures varied considerably among mice. In untreated mice, seizures became longer over time. Moderate to severe histopathology was observed in the amygdala, piriform cortex, and CA1. Levetiracetam provided modest improvements in neurological parameters such as reduced spike rate and improved histopathology scores, whereas valproic acid and phenobarbital were largely ineffective. CONCLUSIONS This model of post-SE spontaneous recurrent seizures differs from other experimental models in the brief latency to seizure development, the occurrence of seizures in 100 % of exposed animals, and the lack of damage to CA4/dentate gyrus. It may serve as a useful tool for rapidly and efficiently screening novel therapies that would be effective against severe epilepsy cases.
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Affiliation(s)
- Hilary S McCarren
- United States Army Medical Research Institute of Chemical Defense, 8350 Ricketts Point Rd Aberdeen Proving Ground, MD, 21010, United States.
| | - Margaret R Eisen
- United States Army Medical Research Institute of Chemical Defense, 8350 Ricketts Point Rd Aberdeen Proving Ground, MD, 21010, United States
| | - Dominique L Nguyen
- United States Army Medical Research Institute of Chemical Defense, 8350 Ricketts Point Rd Aberdeen Proving Ground, MD, 21010, United States
| | - Parker B Dubée
- United States Army Medical Research Institute of Chemical Defense, 8350 Ricketts Point Rd Aberdeen Proving Ground, MD, 21010, United States
| | - Cherish E Ardinger
- United States Army Medical Research Institute of Chemical Defense, 8350 Ricketts Point Rd Aberdeen Proving Ground, MD, 21010, United States
| | - Emily N Dunn
- United States Army Medical Research Institute of Chemical Defense, 8350 Ricketts Point Rd Aberdeen Proving Ground, MD, 21010, United States
| | - Kari M Haines
- United States Army Medical Research Institute of Chemical Defense, 8350 Ricketts Point Rd Aberdeen Proving Ground, MD, 21010, United States
| | - Antonia N Santoro
- United States Army Medical Research Institute of Chemical Defense, 8350 Ricketts Point Rd Aberdeen Proving Ground, MD, 21010, United States
| | - Paige M Bodner
- United States Army Medical Research Institute of Chemical Defense, 8350 Ricketts Point Rd Aberdeen Proving Ground, MD, 21010, United States
| | - Celinia A Ondeck
- United States Army Medical Research Institute of Chemical Defense, 8350 Ricketts Point Rd Aberdeen Proving Ground, MD, 21010, United States
| | - Cary L Honnold
- United States Army Medical Research Institute of Chemical Defense, 8350 Ricketts Point Rd Aberdeen Proving Ground, MD, 21010, United States
| | - John H McDonough
- United States Army Medical Research Institute of Chemical Defense, 8350 Ricketts Point Rd Aberdeen Proving Ground, MD, 21010, United States
| | - Phillip H Beske
- United States Army Medical Research Institute of Chemical Defense, 8350 Ricketts Point Rd Aberdeen Proving Ground, MD, 21010, United States
| | - Patrick M McNutt
- United States Army Medical Research Institute of Chemical Defense, 8350 Ricketts Point Rd Aberdeen Proving Ground, MD, 21010, United States
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Barker BS, Spampanato J, McCarren HS, Smolik M, Jackson CE, Hornung EN, Yeung DT, Dudek FE, McDonough JH. Screening for Efficacious Anticonvulsants and Neuroprotectants in Delayed Treatment Models of Organophosphate-induced Status Epilepticus. Neuroscience 2020; 425:280-300. [PMID: 31783100 PMCID: PMC6935402 DOI: 10.1016/j.neuroscience.2019.11.020] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2019] [Revised: 10/30/2019] [Accepted: 11/12/2019] [Indexed: 01/04/2023]
Abstract
Organophosphorus (OP) compounds are deadly chemicals that exert their intoxicating effects through the irreversible inhibition of acetylcholinesterase (AChE). In addition to an excess of peripheral ailments, OP intoxication induces status epilepticus (SE) which if left untreated may lead to permanent brain damage or death. Benzodiazepines are typically the primary therapies for OP-induced SE, but these drugs lose efficacy as treatment time is delayed. The CounterACT Neurotherapeutic Screening (CNS) Program was therefore established by the National Institutes of Health (NIH) to discover novel treatments that may be administered adjunctively with the currently approved medical countermeasures for OP-induced SE in a delayed treatment scenario. The CNS program utilizes in vivo EEG recordings and Fluoro-JadeB (FJB) histopathology in two established rat models of OP-induced SE, soman (GD) and diisopropylfluorophosphate (DFP), to evaluate the anticonvulsant and neuroprotectant efficacy of novel adjunct therapies when administered at 20 or 60 min after the induction of OP-induced SE. Here we report the results of multiple compounds that have previously shown anticonvulsant or neuroprotectant efficacy in other models of epilepsy or trauma. Drugs tested were ganaxolone, diazoxide, bumetanide, propylparaben, citicoline, MDL-28170, and chloroquine. EEG analysis revealed that ganaxolone demonstrated the most robust anticonvulsant activity, whereas all other drugs failed to attenuate ictal activity in both models of OP-induced SE. FJB staining demonstrated that none of the tested drugs had widespread neuroprotective abilities. Overall these data suggest that neurosteroids may represent the most promising anticonvulsant option for OP-induced SE out of the seven unique mechanisms tested here. Additionally, these results suggest that drugs that provide significant neuroprotection from OP-induced SE without some degree of anticonvulsant activity are elusive, which further highlights the necessity to continue screening novel adjunct treatments through the CNS program.
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Affiliation(s)
- Bryan S. Barker
- Medical Toxicology Research Division, Neuroscience Department, U.S. Army Medical Research Institute of Chemical Defense, 8350 Ricketts Point Rd, Aberdeen Proving Ground, MD 21010, USA,Corresponding Author,
| | - Jay Spampanato
- Department of Neurosurgery, University of Utah School of Medicine, Salt Lake City, UT 84108, USA
| | - Hilary S. McCarren
- Medical Toxicology Research Division, Neuroscience Department, U.S. Army Medical Research Institute of Chemical Defense, 8350 Ricketts Point Rd, Aberdeen Proving Ground, MD 21010, USA
| | - Melissa Smolik
- Department of Neurosurgery, University of Utah School of Medicine, Salt Lake City, UT 84108, USA
| | - Cecelia E. Jackson
- Medical Toxicology Research Division, Neuroscience Department, U.S. Army Medical Research Institute of Chemical Defense, 8350 Ricketts Point Rd, Aberdeen Proving Ground, MD 21010, USA
| | - Eden N. Hornung
- Medical Toxicology Research Division, Neuroscience Department, U.S. Army Medical Research Institute of Chemical Defense, 8350 Ricketts Point Rd, Aberdeen Proving Ground, MD 21010, USA
| | - David T. Yeung
- Chemical Countermeasures Research Program, National Institute of Allergy and Infectious Disease, National Institutes of Health, Bethesda, MD 20892, USA
| | - F. Edward Dudek
- Department of Neurosurgery, University of Utah School of Medicine, Salt Lake City, UT 84108, USA
| | - John H. McDonough
- Medical Toxicology Research Division, Neuroscience Department, U.S. Army Medical Research Institute of Chemical Defense, 8350 Ricketts Point Rd, Aberdeen Proving Ground, MD 21010, USA
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Johnstone TBC, McCarren HS, Spampanato J, Dudek FE, McDonough JH, Hogenkamp D, Gee KW. Enaminone Modulators of Extrasynaptic α 4β 3δ γ-Aminobutyric Acid A Receptors Reverse Electrographic Status Epilepticus in the Rat After Acute Organophosphorus Poisoning. Front Pharmacol 2019; 10:560. [PMID: 31178732 PMCID: PMC6543275 DOI: 10.3389/fphar.2019.00560] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2019] [Accepted: 05/03/2019] [Indexed: 01/22/2023] Open
Abstract
Seizures induced by organophosphorus nerve agent exposure become refractory to treatment with benzodiazepines because these drugs engage synaptic γ-aminobutyric acid-A receptors (GABAARs) that rapidly internalize during status epilepticus (SE). Extrasynaptic GABAARs, such as those containing α4β3δ subunits, are a putative pharmacological target to comprehensively manage nerve agent-induced seizures since they do not internalize during SE and are continuously available for activation. Neurosteroids related to allopregnanolone have been tested as a possible replacement for benzodiazepines because they target both synaptic and extrasynaptic GABAARs receptors. A longer effective treatment window, extended treatment efficacy, and enhanced neuroprotection represent significant advantages of neurosteroids over benzodiazepines. However, neurosteroid use is limited by poor physicochemical properties arising from the intrinsic requirement of the pregnane steroid core structure for efficacy rendering drug formulation problematic. We tested a non-steroidal enaminone GABAAR modulator that interacts with both synaptic and extrasynaptic GABAARs on a binding site distinct from neurosteroids or benzodiazepines for efficacy to control electrographic SE induced by diisopropyl fluorophosphate or soman intoxication in rats. Animals were treated with standard antidotes, and experimental therapeutic treatment was given following 1 h (diisopropyl fluorophosphate model) or 20 min (soman model) after SE onset. We found that the enaminone 2-261 had an extended duration of seizure termination (>10 h) in the diisopropyl fluorophosphate intoxication model in the presence or absence of midazolam (MDZ). 2-261 also moderately potentiated MDZ in the soman-induced seizure model but had limited efficacy as a stand-alone anticonvulsant treatment due to slow onset of action. 2-261 significantly reduced neuronal death in brain areas associated with either diisopropyl fluorophosphate- or soman-induced SE. 2-261 represents an alternate chemical template from neurosteroids for enhancing extrasynaptic α4β3δ GABAAR activity to reverse SE from organophosphorous intoxication.
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Affiliation(s)
- Timothy B C Johnstone
- Department of Pharmacology, School of Medicine, University of California, Irvine, Irvine, CA, United States
| | - Hilary S McCarren
- Neuroscience Department, Medical Toxicology Research Division, United States Army Research Institute of Chemical Defense, Aberdeen, MD, United States
| | - Jay Spampanato
- Department of Neurosurgery, University of Utah School of Medicine, Salt Lake City, UT, United States
| | - F Edward Dudek
- Department of Neurosurgery, University of Utah School of Medicine, Salt Lake City, UT, United States
| | - John H McDonough
- Neuroscience Department, Medical Toxicology Research Division, United States Army Research Institute of Chemical Defense, Aberdeen, MD, United States
| | - Derk Hogenkamp
- Department of Pharmacology, School of Medicine, University of California, Irvine, Irvine, CA, United States
| | - Kelvin W Gee
- Department of Pharmacology, School of Medicine, University of California, Irvine, Irvine, CA, United States
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Haines KM, Matson LM, Dunn EN, Ardinger CE, Lee-Stubbs R, Bibi D, McDonough JH, Bialer M. Comparative efficacy of valnoctamide and sec-butylpropylacetamide (SPD) in terminating nerve agent-induced seizures in pediatric rats. Epilepsia 2019; 60:315-321. [PMID: 30615805 DOI: 10.1111/epi.14630] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2018] [Revised: 12/02/2018] [Accepted: 12/03/2018] [Indexed: 01/13/2023]
Abstract
OBJECTIVES Children and adults are likely to be among the casualties in a civilian nerve agent exposure. This study evaluated the efficacy of valnoctamide (racemic-VCD), sec-butylpropylacetamide (racemic-SPD), and phenobarbital for stopping nerve agent seizures in both immature and adult rats. METHODS Female and male postnatal day (PND) 21, 28, and 70 (adult) rats, previously implanted with electroencephalography (EEG) electrodes were exposed to seizure-inducing doses of the nerve agents sarin or VX and EEG was recorded continuously. Five minutes after seizure onset, animals were treated with SPD, VCD, or phenobarbital. The up-down method was used over successive animals to determine the anticonvulsant median effective dose (ED50 ) of the drugs. RESULTS SPD-ED50 values in the VX model were the following: PND21, 53 mg/kg (male) and 48 mg/kg (female); PND28, 108 mg/kg (male) and 43 mg/kg (female); and PND70, 101 mg/kg (male) and 40 mg/kg (female). SPD-ED50 values in the sarin model were the following: PND21, 44 mg/kg (male) and 28 mg/kg (female); PND28, 79 mg/kg (male) and 34 mg/kg (female); and PND70, 53 mg/kg (male) and 53 mg/kg (female). VCD-ED50 values in the VX model were the following: PND21, 34 mg/kg (male) and 43 mg/kg (female); PND28, 165 mg/kg (male) and 59 mg/kg (female); and PND70, 87 mg/kg (male) and 91 mg/kg (female). VCD-ED50 values in the sarin model were the following: PND21, 45 mg/kg (male), 48 mg/kg (female); PND28, 152 mg/kg (male) 79 mg/kg (female); and PND70, 97 mg/kg (male) 79 mg/kg (female). Phenobarbital-ED50 values in the VX model were the following: PND21, 43 mg/kg (male) and 18 mg/kg (female); PND28, 48 mg/kg (male) and 97 mg/kg (female). Phenobarbital-ED50 values in the sarin model were the following: PND21, 32 mg/kg (male) and 32 mg/kg (female); PND28, 58 mg/kg (male) and 97 mg/kg (female); and PND70, 65 mg/kg (female). SIGNIFICANCE SPD and VCD demonstrated anticonvulsant activity in both immature and adult rats in the sarin- and VX-induced status epilepticus models. Phenobarbital was effective in immature rats, whereas in adult rats, higher doses were required that were accompanied by toxicity. Overall, significantly less drug was required to stop seizures in PND21 animals than in the older animals, and overall, males required higher amounts of drug than females.
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Affiliation(s)
- Kari M Haines
- Nerve Agent Countermeasures, Medical Toxicology Division, US Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, Maryland
| | - Liana M Matson
- Nerve Agent Countermeasures, Medical Toxicology Division, US Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, Maryland
| | - Emily N Dunn
- Nerve Agent Countermeasures, Medical Toxicology Division, US Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, Maryland
| | - Cherish E Ardinger
- Nerve Agent Countermeasures, Medical Toxicology Division, US Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, Maryland
| | - Robyn Lee-Stubbs
- Research Support Division, US Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, Maryland
| | - David Bibi
- Institute for Drug Research, School of Pharmacy, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - John H McDonough
- Nerve Agent Countermeasures, Medical Toxicology Division, US Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, Maryland
| | - Meir Bialer
- Institute for Drug Research, School of Pharmacy, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem, Israel.,David R. Bloom Center for Pharmacy, School of Pharmacy, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem, Israel
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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9
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Matson LM, Lee-Stubbs RB, Cadieux CL, Koenig JA, Ardinger CE, Chandler J, Johnson EA, Hoard-Fruchey HM, Shih TMA, Cerasoli DM, McDonough JH. Assessment of mouse strain differences in baseline esterase activities and toxic response to sarin. Toxicology 2018; 410:10-15. [PMID: 30172647 DOI: 10.1016/j.tox.2018.08.016] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2018] [Revised: 08/09/2018] [Accepted: 08/27/2018] [Indexed: 11/24/2022]
Abstract
Genetics likely play a role in various responses to nerve agent (NA) exposure, as genetic background plays an important role in behavioral, neurological, and physiological responses. This study uses different mouse strains to identify if mouse strain differences in sarin exposure exist. In Experiment 1, basal levels of acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and carboxylesterase (CE) were measured in different strains of naïve mice to account for potential pharmacokinetic determinants of individual differences. In Experiment 2, median lethal dose (MLD) levels were estimated in 8 inbred mouse strains following subcutaneous (s.c.) administration of sarin. Few strain or sex differences in esterase activity levels were observed, with the exception of erythrocyte AChE activity in the C57BL/6J strain. Both sex and strain differences in toxicity were observed, with the most resistant strains being the BALB/cByJ and FVB/NJ strains and the most sensitive strain being the DBA/2J strain. These findings can be expanded to explore pathways involved in NA response, which may provide an avenue to develop therapeutics for preventing and treating the damaging effects of NA exposure.
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Affiliation(s)
- Liana M Matson
- U.S. Army Medical Research Institute of Chemical Defense, 8350 Ricketts Point Rd, Aberdeen Proving Ground, MD 21010, United States.
| | - Robyn B Lee-Stubbs
- U.S. Army Medical Research Institute of Chemical Defense, 8350 Ricketts Point Rd, Aberdeen Proving Ground, MD 21010, United States.
| | - C Lin Cadieux
- U.S. Army Medical Research Institute of Chemical Defense, 8350 Ricketts Point Rd, Aberdeen Proving Ground, MD 21010, United States.
| | - Jeffrey A Koenig
- U.S. Army Medical Research Institute of Chemical Defense, 8350 Ricketts Point Rd, Aberdeen Proving Ground, MD 21010, United States.
| | - Cherish E Ardinger
- U.S. Army Medical Research Institute of Chemical Defense, 8350 Ricketts Point Rd, Aberdeen Proving Ground, MD 21010, United States.
| | - Jessica Chandler
- U.S. Army Medical Research Institute of Chemical Defense, 8350 Ricketts Point Rd, Aberdeen Proving Ground, MD 21010, United States.
| | - Erik A Johnson
- U.S. Army Medical Research Institute of Chemical Defense, 8350 Ricketts Point Rd, Aberdeen Proving Ground, MD 21010, United States.
| | - Heidi M Hoard-Fruchey
- U.S. Army Medical Research Institute of Chemical Defense, 8350 Ricketts Point Rd, Aberdeen Proving Ground, MD 21010, United States.
| | - Tsung-Ming A Shih
- U.S. Army Medical Research Institute of Chemical Defense, 8350 Ricketts Point Rd, Aberdeen Proving Ground, MD 21010, United States.
| | - Doug M Cerasoli
- U.S. Army Medical Research Institute of Chemical Defense, 8350 Ricketts Point Rd, Aberdeen Proving Ground, MD 21010, United States
| | - John H McDonough
- U.S. Army Medical Research Institute of Chemical Defense, 8350 Ricketts Point Rd, Aberdeen Proving Ground, MD 21010, United States.
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10
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Dunn EN, Ferrara-Bowens TM, Chachich ME, Honnold CL, Rothwell CC, Hoard-Fruchey HM, Lesyna CA, Johnson EA, Cerasoli DM, McDonough JH, Cadieux CL. Evaluating mice lacking serum carboxylesterase as a behavioral model for nerve agent intoxication. Toxicol Mech Methods 2018; 28:563-572. [PMID: 29768075 DOI: 10.1080/15376516.2018.1476637] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Mice and other rodents are typically utilized for chemical warfare nerve agent research. Rodents have large amounts of carboxylesterase in their blood, while humans do not. Carboxylesterase nonspecifically binds to and detoxifies nerve agent. The presence of this natural bioscavenger makes mice and other rodents poor models for studies identifying therapeutics to treat humans exposed to nerve agents. To obviate this problem, a serum carboxylesterase knockout (Es1 KO) mouse was created. In this study, Es1 KO and wild type (WT) mice were assessed for differences in gene expression, nerve agent (soman; GD) median lethal dose (MLD) values, and behavior prior to and following nerve agent exposure. No expression differences were detected between Es1 KO and WT mice in more than 34 000 mouse genes tested. There was a significant difference between Es1 KO and WT mice in MLD values, as the MLD for GD-exposed WT mice was significantly higher than the MLD for GD-exposed Es1 KO mice. Behavioral assessments of Es1 KO and WT mice included an open field test, a zero maze, a Barnes maze, and a sucrose preference test (SPT). While sex differences were observed in various measures of these tests, overall, Es1 KO mice behaved similarly to WT mice. The two genotypes also showed virtually identical neuropathological changes following GD exposure. Es1 KO mice appear to have an enhanced susceptibility to GD toxicity while retaining all other behavioral and physiological responses to this nerve agent, making the Es1 KO mouse a more human-like model for nerve agent research.
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Affiliation(s)
- Emily N Dunn
- a United States Army Medical Research Institute of Chemical Defense , Aberdeen Proving Ground , MD , USA
| | - Teresa M Ferrara-Bowens
- a United States Army Medical Research Institute of Chemical Defense , Aberdeen Proving Ground , MD , USA
| | - Mark E Chachich
- b Department of Psychology , Towson University , Towson , MD , USA
| | - Cary L Honnold
- a United States Army Medical Research Institute of Chemical Defense , Aberdeen Proving Ground , MD , USA
| | - Cristin C Rothwell
- a United States Army Medical Research Institute of Chemical Defense , Aberdeen Proving Ground , MD , USA
| | - Heidi M Hoard-Fruchey
- a United States Army Medical Research Institute of Chemical Defense , Aberdeen Proving Ground , MD , USA
| | - Catherine A Lesyna
- a United States Army Medical Research Institute of Chemical Defense , Aberdeen Proving Ground , MD , USA
| | - Erik A Johnson
- a United States Army Medical Research Institute of Chemical Defense , Aberdeen Proving Ground , MD , USA
| | - Douglas M Cerasoli
- a United States Army Medical Research Institute of Chemical Defense , Aberdeen Proving Ground , MD , USA
| | - John H McDonough
- a United States Army Medical Research Institute of Chemical Defense , Aberdeen Proving Ground , MD , USA
| | - C Linn Cadieux
- a United States Army Medical Research Institute of Chemical Defense , Aberdeen Proving Ground , MD , USA
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11
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Moffett MC, McDonough JH, McMonagle JD, Myers TM. Behavioral, Pharmacokinetic, and Cardiovascular Evaluation of Candidate Oximes in African Green Monkeys. Int J Toxicol 2018; 37:352-363. [DOI: 10.1177/1091581818779362] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Oxime reactivators are critical antidotes after organophosphate pesticide or nerve agent poisoning, directly restoring the function of inhibited acetylcholinesterase. In the continuing search for more broad-spectrum acetylcholinesterase reactivators, this study evaluated one of the leading next-generation oxime reactivators: methoxime, (1,1′-trimethylene bis[4-(hydroxyimino)methyl]pyridinium dichloride (MMB-4). The pharmacokinetics of both salts of MMB-4 (dichloride [2Cl] and dimethanesulphonate [DMS]) were characterized across a range of relevant doses (19, 58, and 116 µmol/kg, intramuscular) in a nonhuman primate model (male African green monkeys), and only subtle differences were observed between the salts. Additionally, the behavioral and cardiovascular safety of these MMB-4 salts was compared directly to other available oximes (HI-6 2Cl, HI-6 DMS, and pyridine-2-aldoxime chloride (2-PAM Cl)) at comparable projected doses. Automated operant behavioral tests were used to examine attention, motivation, visual discrimination, concept execution, and fine motor coordination after high doses of all oxime salts, and of all oximes studied, only the highest dose of 2-PAM Cl (447 µmol/kg) disrupted behavioral performance. Likewise, the effects of a range of doses of MMB-4 2Cl or DMS, HI-6 2Cl or DMS, or 2-PAM Cl on cardiovascular parameters were measured in African green monkeys implanted with telemetry devices. Only a small transient decrease in pulse pressure was observed following administration of the highest dose of MMB-4 DMS (116 µmol/kg). Thus, MMB-4 salts, up to the 9× equivalent of a projected autoinjector dose in humans, did not produce behavioral or cardiovascular toxicity in African green monkeys in the current study, and the pharmacokinetic parameters were orderly and predictable.
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Affiliation(s)
- Mark C. Moffett
- United States Army Medical Research Institute of Chemical Defense, MD, USA
| | - John H. McDonough
- United States Army Medical Research Institute of Chemical Defense, MD, USA
| | | | - Todd M. Myers
- United States Army Medical Research Institute of Chemical Defense, MD, USA
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12
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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13
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DeBus S, Dunn EN, Matson EM, Morgan KS, McDonough JH, Cerasoli DM, Cadieux CL. Characterization of Genetically Modified Mice as Improved Animal Models for Organophosphorus Nerve Agent Research. FASEB J 2018. [DOI: 10.1096/fasebj.2018.32.1_supplement.lb67] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Sandra DeBus
- United States Army Medical Research Institute of Chemical DefenseAberdeen Proving GroundMD
| | - Emily N. Dunn
- United States Army Medical Research Institute of Chemical DefenseAberdeen Proving GroundMD
| | - Erik M. Matson
- United States Army Medical Research Institute of Chemical DefenseAberdeen Proving GroundMD
| | - Keith S.L. Morgan
- United States Army Medical Research Institute of Chemical DefenseAberdeen Proving GroundMD
| | - John H. McDonough
- United States Army Medical Research Institute of Chemical DefenseAberdeen Proving GroundMD
| | - Douglas M. Cerasoli
- United States Army Medical Research Institute of Chemical DefenseAberdeen Proving GroundMD
| | - C. Linn Cadieux
- United States Army Medical Research Institute of Chemical DefenseAberdeen Proving GroundMD
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14
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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15
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Pugh KA, Reitnauer KJ, Lee RB, Wilkins WL, McDonough JH, Pennington MR, Litvin SR. Plasma Concentration of Meloxicam in Pediatric Rats. J Am Assoc Lab Anim Sci 2017; 56:762-767. [PMID: 29256371 PMCID: PMC5710155] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 04/12/2017] [Revised: 05/31/2017] [Accepted: 08/30/2017] [Indexed: 06/07/2023]
Abstract
In this study, we compared the plasma concentrations of meloxicam in pediatric rat pups (ages: 7, 14, 21, and 28 d) with those of young adult rats. Adult rats received 1.34 mg/kg SC meloxicam to determine the target peak plasma concentration (Cmax) for comparison with the pediatric animals. Pediatric rats received 1.34 mg/kg SC meloxicam, and in all age groups, Cmax met or exceeded that in adults (11.5 ±2.7 μg/mL). Plasma concentrations were similar between male and female pups within age groups, and peak plasma concentration was achieved more rapidly in rat pups than adults. The analgesic efficacy of this dose was not evaluated in this study.
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Affiliation(s)
- Kristina A Pugh
- Veterinary Medicine and Surgery Branch, United States Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, Maryland;,
| | - Kyle J Reitnauer
- Laboratory Services Branch, United States Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, Maryland
| | - Robyn B Lee
- Institutional Animal Care and Use Office, United States Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, Maryland
| | - William L Wilkins
- Comparative Pathology Branch, United States Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, Maryland
| | - John H McDonough
- Nerve Agent Countermeasures, Neuroscience Branch, United States Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, Maryland
| | - M Ross Pennington
- Analytical Toxicology Division, United States Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, Maryland
| | - Samantha R Litvin
- Analytical Toxicology Division, United States Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, Maryland
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16
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Althaus AL, McCarren HS, Alqazzaz A, Jackson C, McDonough JH, Smith CD, Hoffman E, Hammond RS, Robichaud AJ, Doherty JJ. The synthetic neuroactive steroid SGE-516 reduces status epilepticus and neuronal cell death in a rat model of soman intoxication. Epilepsy Behav 2017; 68:22-30. [PMID: 28109985 DOI: 10.1016/j.yebeh.2016.12.024] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/21/2016] [Revised: 11/18/2016] [Accepted: 12/17/2016] [Indexed: 12/18/2022]
Abstract
Organophosphorus nerve agents (OPNAs) are irreversible inhibitors of acetylcholinesterase that pose a serious threat to public health because of their use as chemical weapons. Exposure to high doses of OPNAs can dramatically potentiate cholinergic synaptic activity and cause status epilepticus (SE). Current standard of care for OPNA exposure involves treatment with cholinergic antagonists, oxime cholinesterase reactivators, and benzodiazepines. However, data from pre-clinical models suggest that OPNA-induced SE rapidly becomes refractory to benzodiazepines. Neuroactive steroids (NAS), such as allopregnanolone, retain anticonvulsant activity in rodent models of benzodiazepine-resistant SE, perhaps because they modulate a broader variety of GABAA receptor subtypes. SGE-516 is a novel, next generation NAS and a potent and selective GABAA receptor positive allosteric modulator (PAM). The present study first established that SGE-516 reduced electrographic seizures in the rat lithium-pilocarpine model of pharmacoresistant SE. Then the anticonvulsant activity of SGE-516 was investigated in the soman-intoxication model of OPNA-induced SE. SGE-516 (5.6, 7.5, and 10mg/kg, IP) significantly reduced electrographic seizure activity compared to control when administered 20min after SE onset. When 10mg/kg SGE-516 was administered 40min after SE onset, seizure activity was still significantly reduced compared to control. In addition, all cohorts of rats treated with SGE-516 exhibited significantly reduced neuronal cell death as measured by FluoroJade B immunohistochemistry. These data suggest synthetic NASs that positively modulate both synaptic and extrasynaptic GABAA receptors may be candidates for further study in the treatment of OPNA-induced SE.
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Affiliation(s)
| | - Hilary S McCarren
- United States Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, MD, USA
| | - Aymen Alqazzaz
- United States Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, MD, USA
| | - Cecelia Jackson
- United States Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, MD, USA
| | - John H McDonough
- United States Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, MD, USA
| | - Carl D Smith
- United States Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, MD, USA
| | - Ethan Hoffman
- Drug Discovery, Sage Therapeutics, Inc., Cambridge, MA, USA
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17
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McCarren HS, McDonough JH. Anticonvulsant discovery through animal models of status epilepticus induced by organophosphorus nerve agents and pesticides. Ann N Y Acad Sci 2016; 1374:144-50. [DOI: 10.1111/nyas.13092] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Hilary S. McCarren
- Pharmacology Department U.S. Army Medical Research Institute of Chemical Defense Aberdeen Proving Ground Maryland
| | - John H. McDonough
- Pharmacology Department U.S. Army Medical Research Institute of Chemical Defense Aberdeen Proving Ground Maryland
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18
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Appel AS, McDonough JH, McMonagle JD, Logue BA. Analysis of Nerve Agent Metabolites from Hair for Long-Term Verification of Nerve Agent Exposure. Anal Chem 2016; 88:6523-30. [DOI: 10.1021/acs.analchem.6b01274] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Amanda S. Appel
- Department
of Chemistry and Biochemistry, South Dakota State University, Avera
Health and Science, Box 2202, Brookings, South Dakota 57007, United States
| | - John H. McDonough
- Pharmacology
Branch, Research Division U.S. Army Medical Research Institute of Chemical Defense 3100 Ricketts Point Road, Aberdeen Proving Ground, Maryland 21010, United States
| | - Joseph D. McMonagle
- Pharmacology
Branch, Research Division U.S. Army Medical Research Institute of Chemical Defense 3100 Ricketts Point Road, Aberdeen Proving Ground, Maryland 21010, United States
| | - Brian A. Logue
- Department
of Chemistry and Biochemistry, South Dakota State University, Avera
Health and Science, Box 2202, Brookings, South Dakota 57007, United States
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19
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Shekh-Ahmad T, Mawasi H, McDonough JH, Yagen B, Bialer M. The potential of sec-butylpropylacetamide (SPD) and valnoctamide and their individual stereoisomers in status epilepticus. Epilepsy Behav 2015; 49:298-302. [PMID: 25979572 DOI: 10.1016/j.yebeh.2015.04.012] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/31/2015] [Accepted: 04/03/2015] [Indexed: 12/20/2022]
Abstract
sec-Butylpropylacetamide (SPD) is a one-carbon homologue of valnoctamide (VCD), a chiral constitutional isomer of valproic acid's (VPA) corresponding amide--valpromide. Racemic-SPD and racemic-VCD possess a unique and broad-spectrum antiseizure profile superior to that of VPA. In addition, SPD blocks behavioral and electrographic status epilepticus (SE) induced by pilocarpine and the organophosphates soman and paraoxon. Valnoctamide has similar activity as SPD in the soman-induced SE model. The activity of SPD and VCD against SE is superior to that of diazepam and midazolam in terms of rapid onset, potency, and ability to block SE when given 20 to 60 min after seizure onset. sec-Butylpropylacetamide and VCD possess two stereogenic carbons in their chemical structure and, thus, exist as a racemic mixture of four individual stereoisomers. The anticonvulsant activity of the individual stereoisomers of SPD and VCD was comparatively evaluated in several anticonvulsant rodent models including the benzodiazepine-resistant SE model. sec-Butylpropylacetamide has stereoselective pharmacokinetics (PK) and pharmacodynamics (PD). The higher clearance of (2R,3S)-SPD and (2S,3R)-SPD led to a 50% lower plasma exposure and, consequently, to a lower anticonvulsant activity compared to racemic-SPD and its two other stereoisomers. Racemic-SPD, (2S,3S)-SPD, and (2R,3R)-SPD have similar anticonvulsant activities and PK profiles that are better than those of (2R,3S)-SPD and (2S,3R)-SPD. Valnoctamide has a stereoselective PK with (2S,3S)-VCD exhibiting the lowest clearance and, consequently, a twice-higher plasma exposure than all other stereoisomers. Nevertheless, there was less stereoselectivity in VCD anticonvulsant activity, and each stereoisomer had similar ED50 values in most models. sec-Butylpropylacetamide and VCD stereoisomers did not cause teratogenicity (i.e., neural tube defect) in mice at doses 3-12 times higher than their anticonvulsant-ED50 values. This article is part of a Special Issue entitled "Status Epilepticus".
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Affiliation(s)
- Tawfeeq Shekh-Ahmad
- Institute for Drug Research, School of Pharmacy, Faculty of Medicine, The Hebrew University of Jerusalem, Israel
| | - Hafiz Mawasi
- Institute for Drug Research, School of Pharmacy, Faculty of Medicine, The Hebrew University of Jerusalem, Israel
| | - John H McDonough
- Pharmacology Branch, Research Division, US Army Medical Research Institute of Chemical Defense (MRICD), Aberdeen Proving Ground, MD, USA
| | - Boris Yagen
- Institute for Drug Research, School of Pharmacy, Faculty of Medicine, The Hebrew University of Jerusalem, Israel
| | - Meir Bialer
- Institute for Drug Research, School of Pharmacy, Faculty of Medicine, The Hebrew University of Jerusalem, Israel.
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20
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Shekh-Ahmad T, Mawasi H, McDonough JH, Finnell RH, Wlodarczyk BJ, Yavin E, Bialer M. Enantioselective pharmacodynamic and pharmacokinetic analysis of two chiral CNS-active carbamate derivatives of valproic acid. Epilepsia 2014; 55:1944-52. [DOI: 10.1111/epi.12857] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/30/2014] [Indexed: 12/29/2022]
Affiliation(s)
- Tawfeeq Shekh-Ahmad
- Faculty of Medicine; Institute for Drug Research; School of Pharmacy; The Hebrew University of Jerusalem; Jerusalem Israel
| | - Hafiz Mawasi
- Faculty of Medicine; Institute for Drug Research; School of Pharmacy; The Hebrew University of Jerusalem; Jerusalem Israel
| | - John H. McDonough
- Pharmacology Branch; Research Division; US Army Medical Research Institute of Chemical Defense; Aberdeen Proving Ground; Maryland U.S.A
| | - Richard H. Finnell
- Department of Nutritional Sciences; Dell Pediatric Research Institute; The University of Texas at Austin; Austin Texas U.S.A
| | - Bogdan J. Wlodarczyk
- Department of Nutritional Sciences; Dell Pediatric Research Institute; The University of Texas at Austin; Austin Texas U.S.A
| | - Eylon Yavin
- Faculty of Medicine; Institute for Drug Research; School of Pharmacy; The Hebrew University of Jerusalem; Jerusalem Israel
| | - Meir Bialer
- Faculty of Medicine; Institute for Drug Research; School of Pharmacy; The Hebrew University of Jerusalem; Jerusalem Israel
- David R. Bloom Center for Pharmacy; The Hebrew University of Jerusalem; Jerusalem Israel
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Chen J, Pan H, Chen C, Wu W, Iskandar K, He J, Piermartiri T, Jacobowitz DM, Yu QS, McDonough JH, Greig NH, Marini AM. (-)-Phenserine attenuates soman-induced neuropathology. PLoS One 2014; 9:e99818. [PMID: 24955574 PMCID: PMC4067273 DOI: 10.1371/journal.pone.0099818] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2014] [Accepted: 05/15/2014] [Indexed: 11/18/2022] Open
Abstract
Organophosphorus (OP) nerve agents are deadly chemical weapons that pose an alarming threat to military and civilian populations. The irreversible inhibition of the critical cholinergic degradative enzyme acetylcholinesterase (AChE) by OP nerve agents leads to cholinergic crisis. Resulting excessive synaptic acetylcholine levels leads to status epilepticus that, in turn, results in brain damage. Current countermeasures are only modestly effective in protecting against OP-induced brain damage, supporting interest for evaluation of new ones. (-)-Phenserine is a reversible AChE inhibitor possessing neuroprotective and amyloid precursor protein lowering actions that reached Phase III clinical trials for Alzheimer's Disease where it exhibited a wide safety margin. This compound preferentially enters the CNS and has potential to impede soman binding to the active site of AChE to, thereby, serve in a protective capacity. Herein, we demonstrate that (-)-phenserine protects neurons against soman-induced neuronal cell death in rats when administered either as a pretreatment or post-treatment paradigm, improves motoric movement in soman-exposed animals and reduces mortality when given as a pretreatment. Gene expression analysis, undertaken to elucidate mechanism, showed that (-)-phenserine pretreatment increased select neuroprotective genes and reversed a Homer1 expression elevation induced by soman exposure. These studies suggest that (-)-phenserine warrants further evaluation as an OP nerve agent protective strategy.
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Affiliation(s)
- Jun Chen
- Neurology Department, Uniformed Services University of Health Sciences, Bethesda, Maryland, United States of America
| | - Hongna Pan
- Neurology Department, Uniformed Services University of Health Sciences, Bethesda, Maryland, United States of America
| | - Cynthia Chen
- Neurology Department, Uniformed Services University of Health Sciences, Bethesda, Maryland, United States of America
| | - Wei Wu
- Neurology Department, Uniformed Services University of Health Sciences, Bethesda, Maryland, United States of America
| | - Kevin Iskandar
- Neurology Department, Uniformed Services University of Health Sciences, Bethesda, Maryland, United States of America
| | - Jeffrey He
- Neurology Department, Uniformed Services University of Health Sciences, Bethesda, Maryland, United States of America
| | - Tetsade Piermartiri
- Neurology Department, Uniformed Services University of Health Sciences, Bethesda, Maryland, United States of America
| | - David M. Jacobowitz
- Department of Anatomy, Physiology and Genetics, Uniformed Services University of the Health Sciences, Bethesda, Maryland, United States of America
| | - Qian-Sheng Yu
- Drug Design & Development Section, Translational Gerontology Branch, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America
| | - John H. McDonough
- Pharmacology Branch, Research Division, US Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, Maryland, United States of America
| | - Nigel H. Greig
- Drug Design & Development Section, Translational Gerontology Branch, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Ann M. Marini
- Neurology Department, Uniformed Services University of Health Sciences, Bethesda, Maryland, United States of America
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Shekh-Ahmad T, Hen N, Yagen B, McDonough JH, Finnell RH, Wlodarczyk BJ, Bialer M. Stereoselective anticonvulsant and pharmacokinetic analysis of valnoctamide, a CNS-active derivative of valproic acid with low teratogenic potential. Epilepsia 2014; 55:353-61. [PMID: 24313671 PMCID: PMC4963464 DOI: 10.1111/epi.12480] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/15/2013] [Indexed: 11/28/2022]
Abstract
OBJECTIVE Valnoctamide (VCD), a central nervous system (CNS)-active chiral constitutional isomer of valpromide, the corresponding amide of valproic acid (VPA), is currently undergoing phase IIb clinical trials in acute mania. VCD exhibits stereoselective pharmacokinetics (PK) in animals and humans. The current study comparatively evaluated the pharmacodynamics (PD; anticonvulsant activity and teratogenicity) and PK of the four individual stereoisomers of VCD. METHODS The anticonvulsant activity of VCD individual stereoisomers was evaluated in several rodent anticonvulsant models including maximal electroshock, 6 Hz psychomotor, subcutaneous metrazol, and the pilocarpine-induced and soman-induced status epilepticus (SE). The PK-PD (anticonvulsant activity) relationship of VCD stereoisomers was evaluated following intraperitoneal administration (70 mg/kg) to rats. Induction of neural tube defects (NTDs) by VCD stereoisomers was evaluated in a mouse strain that was highly susceptible to teratogen-induced NTDs. RESULTS VCD had a stereoselective PK, with (2S,3S)-VCD exhibiting the lowest clearance, and consequently a twice-higher plasma exposure than all other stereoisomers. Nervertheless, there was less stereoselectivity in VCD anticonvulsant activity and each stereoisomer had similar median effective dose (ED)50 values in most models. VCD stereoisomers (258 or 389 mg/kg) did not cause NTDs. These doses are 3-12 times higher than VCD anticonvulsant ED50 values. SIGNIFICANCE VCD displayed stereoselective PK that did not lead to significant stereoselective activity in various anticonvulsant rodent models. If VCD exerted its broad-spectrum anticonvulsant activity using a single mechanism of action (MOA), it is likely that it would exhibit a stereoselective PD. The fact that there was no significant difference between racemic VCD and its individual stereoisomers suggests that VCD's anticonvulsant activity is due to multiple MOAs.
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Affiliation(s)
- Tawfeeq Shekh-Ahmad
- School of Pharmacy, Institute for Drug Research, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem 91120, Israel
| | - Naama Hen
- School of Pharmacy, Institute for Drug Research, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem 91120, Israel
| | - Boris Yagen
- School of Pharmacy, Institute for Drug Research, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem 91120, Israel
- David R. Bloom Center for Pharmacy, The Hebrew University of Jerusalem, Israel
| | - John H. McDonough
- Pharmacology Branch, Research Division, US Army Medical Research Institute of Chemical Defense, Maryland, USA
| | - Richard H. Finnell
- Department of Nutritional Sciences, Dell Pediatric Research Institute, The University of Texas at Austin, Austin, Texas, USA
| | - Bogdan J. Wlodarczyk
- Department of Nutritional Sciences, Dell Pediatric Research Institute, The University of Texas at Austin, Austin, Texas, USA
| | - Meir Bialer
- School of Pharmacy, Institute for Drug Research, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem 91120, Israel
- David R. Bloom Center for Pharmacy, The Hebrew University of Jerusalem, Israel
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Shekh-Ahmad T, Hen N, McDonough JH, Yagen B, Bialer M. Valnoctamide and sec-butyl-propylacetamide (SPD) for acute seizures and status epilepticus. Epilepsia 2013; 54 Suppl 6:99-102. [PMID: 24001086 DOI: 10.1111/epi.12290] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
sec-Butyl-propylacetamide (SPD) is a one-carbon homolog of valnoctamide (VCD), a chiral constitutional isomer of valproic acid's (VPA) corresponding amide valpromide. VCD has potential as a therapy in epilepsy including status epilepticus (SE) and neuropathic pain, and is currently being developed for the treatment of bipolar disorder. Both VCD and SPD possess two stereogenic carbons in their chemical structure. SPD possesses a unique and broad-spectrum antiseizure profile superior to that of valproic acid (VPA) and better than that of VCD. In addition SPD blocked behavioral- and electrographic-SE induced by pilocarpine and soman (organophosphate nerve gas) and afforded in vivo neuroprotection that was associated with cognitive sparing. VCD has activity similar to that of SPD in pilocarpine-induced status epilepticus (SE), although at higher doses. The activity of SPD and VCD against SE is superior to that of diazepam in terms of rapid onset, potency, and ability to block SE when given 20-60 min after seizure onset. When administered 20 and 40 min after SE onset, SPD (100-174 mg/kg) produced long-lasting efficacy (e.g., 4-8 h) against soman-induced convulsive and electrographic SE in both rats and guinea pigs. SPD activity in the pilocarpine and soman-induced SE models when administered 20-60 min after seizure onset, differentiates SPD from benzodiazepines and all other antiepileptic drugs .
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Affiliation(s)
- Tawfeeq Shekh-Ahmad
- School of Pharmacy, Faculty of Medicine, Institute for Drug Research, The Hebrew University of Jerusalem, Ein-Karem, Jerusalem, Israel
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Hen N, Shekh-Ahmad T, Yagen B, McDonough JH, Finnell RH, Wlodarczyk B, Bialer M. Stereoselective pharmacodynamic and pharmacokinetic analysis of sec-Butylpropylacetamide (SPD), a new CNS-active derivative of valproic acid with unique activity against status epilepticus. J Med Chem 2013; 56:6467-77. [PMID: 23879329 DOI: 10.1021/jm4007565] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
sec-Butylpropylacetamide (racemic-SPD) is a chiral CNS-active amide derivative of valproic acid (VPA). This study describes synthesis and stereospecific comparative pharmacodynamics (PD, anticonvulsant activity and teratogenicity) and pharmacokinetic (PK) analysis of four individual SPD stereoisomers. SPD stereoisomers' anticonvulsant activity was comparatively evaluated in several anticonvulsant animal models including the benzodiazepine-resistant status epilepticus (SE). SPD stereoisomers' PK-PD relationship was evaluated in rats. Teratogenicity of SPD stereoisomers was evaluated in SWV mice strain, susceptible to VPA-induced neural tube defect (NTD). SPD stereoisomers (141 or 283 mg/kg) did not cause NTD. SPD has stereoselective PK and PD. (2R,3S)-SPD and (2S,3R)-SPD higher clearance led to a 50% lower plasma exposure that may contribute to their relative lower activity in the pilocarpine-induced SE model. (2S,3S)-SPD, (2R,3R)-SPD, and racemic-SPD have similar anticonvulsant activity and a PK profile that are better than those of (2R,3S)-SPD and (2S,3R)-SPD, making them good candidates for development as new, potent antiepileptics with a potential in benzodiazepine-resistant SE.
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Affiliation(s)
- Naama Hen
- Institute for Drug Research, Faculty of Medicine, School of Pharmacy, The Hebrew University of Jerusalem, Israel
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Skovira JW, Shih TM, McDonough JH. Neuropharmacological specificity of brain structures involved in soman-induced seizures. Neurotoxicology 2012; 33:463-8. [DOI: 10.1016/j.neuro.2012.03.006] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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26
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Finkelstein A, Kunis G, Berkutzki T, Ronen A, Krivoy A, Yoles E, Last D, Mardor Y, Van Shura K, McFarland E, Capacio BA, Eisner C, Gonzales M, Gregorowicz D, Eisenkraft A, McDonough JH, Schwartz M. Immunomodulation by poly-YE reduces organophosphate-induced brain damage. Brain Behav Immun 2012; 26:159-69. [PMID: 21925261 DOI: 10.1016/j.bbi.2011.09.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/08/2011] [Accepted: 09/01/2011] [Indexed: 10/17/2022] Open
Abstract
Accidental organophosphate poisoning resulting from environmental or occupational exposure, as well as the deliberate use of nerve agents on the battlefield or by terrorists, remain major threats for multi-casualty events, with no effective therapies yet available. Even transient exposure to organophosphorous compounds may lead to brain damage associated with microglial activation and to long-lasting neurological and psychological deficits. Regulation of the microglial response by adaptive immunity was previously shown to reduce the consequences of acute insult to the central nervous system (CNS). Here, we tested whether an immunization-based treatment that affects the properties of T regulatory cells (Tregs) can reduce brain damage following organophosphate intoxication, as a supplement to the standard antidotal protocol. Rats were intoxicated by acute exposure to the nerve agent soman, or the organophosphate pesticide, paraoxon, and after 24 h were treated with the immunomodulator, poly-YE. A single injection of poly-YE resulted in a significant increase in neuronal survival and tissue preservation. The beneficial effect of poly-YE treatment was associated with specific recruitment of CD4(+) T cells into the brain, reduced microglial activation, and an increase in the levels of brain derived neurotrophic factor (BDNF) in the piriform cortex. These results suggest therapeutic intervention with poly-YE as an immunomodulatory supplementary approach against consequences of organophosphate-induced brain damage.
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Affiliation(s)
- Arseny Finkelstein
- Department of Neurobiology, The Weizmann Institute of Science, Rehovot 76100, Israel
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White HS, Alex AB, Pollock A, Hen N, Shekh-Ahmad T, Wilcox KS, McDonough JH, Stables JP, Kaufmann D, Yagen B, Bialer M. A new derivative of valproic acid amide possesses a broad-spectrum antiseizure profile and unique activity against status epilepticus and organophosphate neuronal damage. Epilepsia 2011; 53:134-46. [PMID: 22150444 DOI: 10.1111/j.1528-1167.2011.03338.x] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
PURPOSE sec-Butyl-propylacetamide (SPD) is a one-carbon homolog of valnoctamide (VCD), a central nervous system (CNS)-active amide derivative of valproic acid (VPA) currently in phase II clinical trials. The study reported herein evaluated the anticonvulsant activity of SPD in a battery of rodent seizure and epilepsy models and assessed its efficacy in rat and guinea pig models of status epilepticus (SE) and neuroprotection in an organotypic hippocampal slice model of excitotoxic cell death. METHODS The anticonvulsant activity of SPD was evaluated in several rodent seizure and epilepsy models, including maximal electroshock (MES), 6-Hz psychomotor; subcutaneous (s.c.) metrazol-, s.c. picrotoxin, s.c. bicuculline, and audiogenic, corneal, and hippocampal kindled seizures following intraperitoneal administration. Results obtained with SPD are discussed in relationship to those obtained with VPA and VCD. SPD was also evaluated for its ability to block benzodiazepine-resistant SE induced by pilocarpine (rats) and soman (rats and guinea pigs) following intraperitoneal administration. SPD was tested for its ability to block excitotoxic cell death induced by the glutamate agonists N-methyl-D-aspartate (NMDA) and kainic acid (KA) using organotypic hippocampal slices and SE-induced hippocampal cell death using FluoroJade B staining. The cognitive function of SPD-treated rats that were protected against pilocarpine-induced convulsive SE was examined 10-14 days post-SE using the Morris water maze (MWM). The relationship between the pharmacokinetic profile of SPD and its efficacy against soman-induced SE was evaluated in two parallel studies following SPD (60 mg/kg, i.p.) administration in the soman SE rat model. KEY FINDINGS SPD was highly effective and displayed a wide protective index (PI = median neurotoxic dose/median effective dose [TD(50)/ED(50)]) in the standardized seizure and epilepsy models employed. The wide PI values of SPD demonstrate that it is effective at doses well below those that produce behavioral impairment. Unlike VCD, SPD also displayed anticonvulsant activity in the rat pilocarpine model of SE. Thirty minutes after the induction of SE, the calculated rat ED(50) for SPD against convulsive SE in this model was 84 mg/kg. SPD was not neuroprotective in the organotypic hippocampal slice preparation; however, it did display hippocampal neuroprotection in both SE models and cognitive sparing in the MWM, which was associated with its antiseizure effect against pilocarpine-induced SE. When administered 20 and 40 min after SE onset, SPD (100-174 mg/kg) produced long-lasting efficacy (e.g., 4-8 h) against soman-induced convulsive and electrographic SE in both rats and guinea pigs. SPD ED(50) values in guinea pigs were 67 and 92 mg/kg when administered at SE onset or 40 min after SE onset, respectively. Assuming linear pharmacokinetics (PK), the PK-PD (pharmacodynamic) results (rats) suggests that effective SPD plasma levels ranged between 8 and 40 mg/L (20 min after the onset of soman-induced seizures) and 12-50 mg/L (40 min after the onset of soman-induced seizures). The time to peak (t(max)) pharmacodynamic effect (PD-t(max)) occurred after the PK-t(max), suggesting that SPD undergoes slow distribution to extraplasmatic sites, which is likely responsible for antiseizure activity of SPD. SIGNIFICANCE The results demonstrate that SPD is a broad-spectrum antiseizure compound that blocks SE induced by pilocarpine and soman and affords in vivo neuroprotection that is associated with cognitive sparing. Its activity against SE is superior to that of diazepam in terms of rapid onset, potency, and its effect on animal mortality and functional improvement.
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Affiliation(s)
- H Steve White
- Anticonvulsant Drug Development Program, Department of Pharmacology and Toxicology, College of Pharmacy, University of Utah, Salt Lake City, Utah, USA
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O’Donnell JC, McDonough JH, Shih TM. In vivo microdialysis and electroencephalographic activity in freely moving guinea pigs exposed to organophosphorus nerve agents sarin and VX: analysis of acetylcholine and glutamate. Arch Toxicol 2011; 85:1607-16. [DOI: 10.1007/s00204-011-0724-z] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2011] [Accepted: 06/06/2011] [Indexed: 11/24/2022]
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Shih TM, Guarisco JA, Myers TM, Kan RK, McDonough JH. The oxime pro-2-PAM provides minimal protection against the CNS effects of the nerve agents sarin, cyclosarin, and VX in guinea pigs. Toxicol Mech Methods 2010; 21:53-62. [DOI: 10.3109/15376516.2010.529190] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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O’Donnell JC, Acon-Chen C, McDonough JH, Shih TM. Comparison of extracellular striatal acetylcholine and brain seizure activity following acute exposure to the nerve agents cyclosarin and tabun in freely moving guinea pigs. Toxicol Mech Methods 2010; 20:600-8. [DOI: 10.3109/15376516.2010.521208] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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Skovira JW, O’Donnell JC, Koplovitz I, Kan RK, McDonough JH, Shih TM. Reactivation of brain acetylcholinesterase by monoisonitrosoacetone increases the therapeutic efficacy against nerve agents in guinea pigs. Chem Biol Interact 2010; 187:318-24. [DOI: 10.1016/j.cbi.2010.03.010] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2009] [Revised: 02/15/2010] [Accepted: 03/05/2010] [Indexed: 10/19/2022]
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Angoa-Pérez M, Kreipke CW, Thomas DM, Van Shura KE, Lyman M, McDonough JH, Kuhn DM. Soman increases neuronal COX-2 levels: possible link between seizures and protracted neuronal damage. Neurotoxicology 2010; 31:738-46. [PMID: 20600289 DOI: 10.1016/j.neuro.2010.06.007] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2010] [Revised: 06/10/2010] [Accepted: 06/20/2010] [Indexed: 01/27/2023]
Abstract
Nerve agent-induced seizures cause neuronal damage in brain limbic and cortical circuits leading to persistent behavioral and cognitive deficits. Without aggressive anticholinergic and benzodiazepine therapy, seizures can be prolonged and neuronal damage progresses for extended periods of time. The objective of this study was to determine the effects of the nerve agent soman on expression of cyclooxygenase-2 (COX-2), the initial enzyme in the biosynthetic pathway of the proinflammatory prostaglandins and a factor that has been implicated in seizure initiation and propagation. Rats were exposed to a toxic dose of soman and scored behaviorally for seizure intensity. Expression of COX-2 was determined throughout brain from 4h to 7 days after exposure by immunohistochemistry and immunoblotting. Microglial activation and astrogliosis were assessed microscopically over the same time-course. Soman increased COX-2 expression in brain regions known to be damaged by nerve agents (e.g., hippocampus, amygdala, piriform cortex and thalamus). COX-2 expression was induced in neurons, and not in microglia or astrocytes, and remained elevated through 7 days. The magnitude of COX-2 induction was correlated with seizure intensity. COX-1 expression was not changed by soman. Increased expression of neuronal COX-2 by soman is a late-developing response relative to other signs of acute physiological distress caused by nerve agents. COX-2-mediated production of prostaglandins is a consequence of the seizure-induced neuronal damage, even after survival of the initial cholinergic crisis is assured. COX-2 inhibitors should be considered as adjunct therapy in nerve agent poisoning to minimize nerve agent-induced seizure activity.
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Affiliation(s)
- Mariana Angoa-Pérez
- Research & Development Service, John D. Dingell VA Medical Center, Detroit, MI, USA
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33
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McDonough JH, McMonagle JD, Shih TM. Time-dependent reduction in the anticonvulsant effectiveness of diazepam against soman-induced seizures in guinea pigs. Drug Chem Toxicol 2010; 33:279-83. [DOI: 10.3109/01480540903483417] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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Shih T, Koenig JA, Tarzia KA, Skovira JW, McDonough JH. Protective Effects of Midazolam and MMB‐4 plus Atropine Sulfate in Nerve Agent Intoxication. FASEB J 2010. [DOI: 10.1096/fasebj.24.1_supplement.763.1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Tsung‐Ming Shih
- Res DivUS Army Med Res Inst Chem DefnAberdeen Proving GroundMD
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35
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Shih T, Skovira JW, McDonough JH. Specificity of Brain Structures Sensitive to Initiating Nerve Agent‐Induced Seizures. FASEB J 2010. [DOI: 10.1096/fasebj.24.1_supplement.761.2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Tsung‐Ming Shih
- Res DivUS Army Med Res Inst Chem DefnAberdeen Proving GroundMD
| | - Jacob W Skovira
- Res DivUS Army Med Res Inst Chem DefnAberdeen Proving GroundMD
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36
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O’Donnell JC, McDonough JH, Shih TM. Changes in extracellular striatal acetylcholine and brain seizure activity following acute exposure to nerve agents in freely moving guinea pigs. Toxicol Mech Methods 2010; 20:143-52. [DOI: 10.3109/15376511003657439] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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Guarisco JA, O'Donnell JC, Skovira JW, McDonough JH, Shih TM. In vivo oxime administration does not influence Ellman acetylcholinesterase assay results. Toxicol Mech Methods 2009; 19:379-85. [PMID: 19778238 DOI: 10.1080/15376510903234773] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
Organophosphorus compounds (OPs) are potent inhibitors of acetylcholinesterase (AChE). Treatment for OP poisoning is by administration of atropine sulfate, an oxime, and diazepam. Oximes such as 2-PAM are used to reactivate OP-inhibited AChE so as to restore normal enzymatic function and serve as a true antidote. There are reports of non-enzymatic hydrolysis by oximes of acetylthiocholine in in vitro preparations in the widely used Ellman assay for AChE activity, which may confound the interpretation of AChE activity by producing elevated results. The purpose of this experiment was to determine if there is appreciable interference by therapeutic levels of oximes on the results of the Ellman assay in assessing AChE reactivation by oxime compounds in vivo. When therapeutic doses of oximes (2-PAM, HI-6, MMB-4, or MINA) were administered intramuscularly to guinea pigs and samples collected 60 min later, there was no statistical difference between oxime and saline control groups in measured AChE activity in various tissue samples, including blood. With appropriate dilution of samples prior to spectrophotometric assay, the Ellman assay is an acceptable method to measure in vivo oxime reactivation of inhibited AChE. Inclusion of an oxime control group to insure that this particular type of interference is not causing false readings in the assay is a prudent step.
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Affiliation(s)
- John A Guarisco
- Pharmacology Branch, Research Division, US Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, Maryland 21010-5400, USA
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38
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Shih TM, Skovira JW, O'Donnell JC, McDonough JH. Evaluation of nine oximes on in vivo reactivation of blood, brain, and tissue cholinesterase activity inhibited by organophosphorus nerve agents at lethal dose. Toxicol Mech Methods 2009; 19:386-400. [PMID: 19778239 DOI: 10.1080/15376510903213892] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
The capability of several oximes (HI-6, HLö7, MMB-4, TMB-4, carboxime, ICD 585, ICD 692, ICD 3805, and 2-PAM) to reactivate in vivo AChE inhibited by the nerve agents sarin, cyclosarin, VX, or VR in blood, brain regions, and peripheral tissues in guinea pigs was examined and compared. Animals were injected subcutaneously with 1.0 LD(50) of sarin, cyclosarin, VR, or VX, and treated intramuscularly 5 min later with one of these compounds. Toxic signs and lethality were monitored, and tissue AChE activities were determined at 60 min after nerve agent. The animals exposed to sarin or cyclosarin, alone or with non-oxime treatment, some died within 60 min; however, when treated with an oxime, no animal died. For VR or VX, all animals survived for 60 min after exposure, with or without non-oxime or oxime therapy. These nerve agents caused differential degrees of inhibition: in whole blood sarin = cyclosarin > VR = VX; in brain regions sarin > cyclosarin > VX > VR; and in peripheral tissues sarin > VX > cyclosarin > VR. These oximes exhibited differential potency in reactivating nerve agent-inhibited AChE in various peripheral tissues, but not AChE activity in the brain regions. There was no difference in the AChE reactivating potency between the dichloride and dimethanesulfonate salts of HI-6. AChE inhibited by sarin was the most and cyclosarin the least susceptible to oxime reactivation. Overall, MMB-4 appeared to be, among all oximes tested, the most effective in vivo AChE reactivator against the broadest spectrum of nerve agents.
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Affiliation(s)
- Tsung-Ming Shih
- Pharmacology Branch, Research Division, US Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, MD 21010-5400, USA.
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Affiliation(s)
- John H. McDonough
- Applied Pharmacology Branch, U.S. Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, Maryland
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Shih TM, Skovira JW, McDonough JH. Effects of 4-pyridine aldoxime on nerve agent-inhibited acetylcholinesterase activity in guinea pigs. Arch Toxicol 2009; 83:1083-9. [PMID: 19763542 DOI: 10.1007/s00204-009-0465-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2009] [Accepted: 08/20/2009] [Indexed: 11/27/2022]
Abstract
Methoxime (MMB-4) is a leading candidate oxime acetylcholinesterase (AChE) reactivator to replace pralidoxime (2-PAM) for therapeutic treatment of nerve agent intoxication. 4-Pyridine aldoxime (4-PA) is a synthetic starting material, a breakdown product, and a probable metabolite of MMB-4. There is a possibility that 4-PA may adversely interact with the nerve agent, thereby affecting nerve agent toxicity and biological AChE activity. This study evaluated the effects of 4-PA on sarin (GB)-, cyclosarin (GF)-, and VX-induced toxicity and AChE activity in blood, brain, and peripheral tissues of guinea pigs. Animals were pretreated with atropine methyl nitrate (1.0 mg/kg, im) 15 min prior to subcutaneous administration with 1.0 x LD(50) of GB, GF, or VX and then treated 15 min after the administration of nerve agents with 4-PA (3.5, 7.0, or 14.0 mg/kg, im). The dose-response effects of 4-PA alone were also examined. Toxic signs and lethality were monitored, blood and tissues were collected, and AChE activities were determined at 60 min after nerve agent administration. Under the condition of this study, all animals exposed to nerve agents exhibited some degree of toxic signs such as salivation, lacrimation, rhinorrhea, and convulsions. 4-PA at the three doses tested neither induced toxic signs nor altered the toxicity of GB, GF, or VX at the 1.0 x LD(50) exposure dose. Additionally, it did not modify the AChE activity in blood, brain, and peripheral tissues by itself or affect the AChE activity inhibited by a 1.0 x LD(50) dose of these three nerve agents in guinea pigs.
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Affiliation(s)
- Tsung-Ming Shih
- Pharmacology Branch, Research Division, US Army Medical Research Institute of Chemical Defense, ATTN: MCMR-CDR-P, 3100 Ricketts Point Road, Aberdeen Proving Ground, Aberdeen, MD 21010-5400, USA.
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Skovira JW, McDonough JH, Shih TM. Protection against sarin-induced seizures in rats by direct brain microinjection of scopolamine, midazolam or MK-801. J Mol Neurosci 2009; 40:56-62. [PMID: 19690985 DOI: 10.1007/s12031-009-9253-0] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2009] [Accepted: 07/20/2009] [Indexed: 12/29/2022]
Abstract
Control of seizure activity is critical to survival and neuroprotection following nerve agent exposure. Extensive research has shown that three classes of drugs, muscarinic antagonists, benzodiazepines, and N-methyl-D: -aspartate antagonists, are capable of moderating these seizures. This study began to map the neural areas in rat brain that respond to these three drug classes resulting in anticonvulsant effects. Drugs of each class (scopolamine, midazolam, MK-801) were evaluated for their ability to prevent sarin-induced seizures when injected into specific brain areas (lateral ventricle, anterior piriform cortex, basolateral amygdala, area tempestas). Animals were pretreated by microinjection with saline or a dose of drug from one of the three classes 30 min prior to receiving 150 microg/kg sarin, subcutaneously, followed by 2.0 mg/kg atropine methylnitrate, intramuscularly. Animals were then returned to their cages, where electroencephalographic activity was monitored for seizures. Anticonvulsant effective doses (ED(50)) were determined using an up-down dosing procedure over successive animals. Scopolamine provided anticonvulsant effects in each area tested, while midazolam was effective in each area except the lateral ventricle. MK-801 was only effective at preventing seizures when injected into the basolateral amygdala or area tempestas. The results show a unique neuroanatomical and pharmacological specificity for control of nerve agent-induced seizures.
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Affiliation(s)
- Jacob W Skovira
- Pharmacology Branch, Research Division, U.S. Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, MD 21010-5400, USA
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Shih TM, Skovira JW, O’Donnell JC, McDonough JH. Treatment with Tertiary Oximes Prevents Seizures and Improves Survival Following Sarin Intoxication. J Mol Neurosci 2009; 40:63-9. [DOI: 10.1007/s12031-009-9259-7] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2009] [Accepted: 07/20/2009] [Indexed: 10/20/2022]
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McDonough JH, Van Shura KE, LaMont JC, McMonagle JD, Shih TM. Comparison of the Intramuscular, Intranasal or Sublingual Routes of Midazolam Administration for the Control of Soman-Induced Seizures*. Basic Clin Pharmacol Toxicol 2009; 104:27-34. [DOI: 10.1111/j.1742-7843.2008.00326.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Despain KE, McDonough JH, McMonagle JD, McGinley MJ, Evans J. The Toxicity of Soman in the African Green Monkey (Chlorocebus aethiops). Toxicol Mech Methods 2008; 17:255-64. [DOI: 10.1080/15376510600972733] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Whalley CE, McGuire JM, Miller DB, Jakubowski EM, Mioduszewski RJ, Thomson SA, Lumley LA, McDonough JH, Shih TMA. Kinetics of sarin (GB) following a single sublethal inhalation exposure in the guinea pig. Inhal Toxicol 2007; 19:667-81. [PMID: 17510839 DOI: 10.1080/08958370701353296] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
To improve toxicity estimates from sublethal exposures to chemical warfare nerve agents (CWNA), it is necessary to generate mathematical models of the absorption, distribution, and elimination of nerve agents. However, current models are based on representative data sets generated with different routes of exposure and in different species and are designed to interpolate between limited laboratory data sets to predict a wide range of possible human exposure scenarios. This study was performed to integrate CWNA sublethal toxicity data in male Duncan Hartley guinea pigs. Specific goal was to compare uptake and clearance kinetics of different sublethal doses of sarin (either 0.1 x or 0.4 x LC50) in blood and tissues of guinea pigs exposed to agent by acute whole-body inhalation exposure after the 60-min LC50 was determined. Arterial catheterization allowed repeated blood sampling from the same animal at various time periods. Blood and tissue levels of acetylcholinesterase, butyrylcholinesterase, and regenerated sarin (rGB) were determined at various time points during and following sarin exposure. The following pharmacokinetic parameters were calculated from the graph of plasma or RBC rGB concentration versus time: time to reach the maximal concentration; maximal concentration; mean residence time; clearance; volume of distribution at steady state; terminal elimination-phase rate constant; and area under plasma concentration time curve extrapolated to infinity using the WinNonlin analysis program 5.0. Plasma and RBC t(1/2) for rGB was also calculated. Data will be used to develop mathematical model of absorption and distribution of sublethal sarin doses into susceptible tissues.
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Affiliation(s)
- Christopher E Whalley
- U.S. Army Edgewood Chemical Biological Center, Aberdeen Proving Ground, Maryland 21010-5424, USA.
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Shih TM, Rowland TC, McDonough JH. Anticonvulsants for nerve agent-induced seizures: The influence of the therapeutic dose of atropine. J Pharmacol Exp Ther 2006; 320:154-61. [PMID: 17015638 DOI: 10.1124/jpet.106.111252] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Two guinea pig models were used to study the anticonvulsant potency of diazepam, midazolam, and scopolamine against seizures induced by the nerve agents tabun, sarin, soman, cyclosarin, O-ethyl S-(2-(diisopropylamino)ethyl)methylphosphonothioate (VX), and O-isobutyl S-(2-diethylamino)ethyl)-methyl phosphonothioate (VR). Animals instrumented for electroencephalogram recording were pretreated with pyridostigmine bromide (0.026 mg/kg i.m.) 30 min before challenge with 2 x LD50 (s.c.) of a nerve agent. In model A, atropine sulfate (2.0 mg/kg i.m.) and pyridine-2-aldoxime methylchloride (2-PAM; 25.0 mg/kg i.m.) were given 1 min after nerve agent challenge, and the tested anticonvulsant was given (i.m.) 5 min after seizure onset. In model B, a lower dose of atropine sulfate (0.1 mg/kg i.m.) was given along with 2-PAM 1 min after nerve agent challenge, and the anticonvulsant was given at seizure onset. With the lower dose of atropine, seizure occurrence increased to virtually 100% for all agents; the time to seizure onset decreased for sarin, cyclosarin, and VX; the signs of nerve agent intoxication were more severe; and coma resulted frequently with cyclosarin. The anticonvulsant ED50 doses for scopolamine or diazepam were, in general, not different between the two models, whereas the anticonvulsant ED50 values of midazolam increased 3- to 17-fold with the lower atropine dose. Seizure termination times were not systematically effected by the different doses of atropine. The order of anticonvulsant effectiveness within each model was scopolamine > or = midazolam > diazepam. The findings indicate that the dose of atropine given as antidotal therapy can significantly influence measures of nerve agent toxicity and responsiveness to anticonvulsant therapy.
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Affiliation(s)
- Tsung-Ming Shih
- Pharmacology Branch, Research Division, United States Army Medical Research Institute of Chemical Defense, 3100 Ricketts Point Rd., Aberdeen Proving Ground, MD 21010-5400, USA.
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Shih TM, Hulet SW, McDonough JH. The effects of repeated low-dose sarin exposure. Toxicol Appl Pharmacol 2006; 215:119-34. [PMID: 16556454 DOI: 10.1016/j.taap.2006.02.003] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2005] [Revised: 02/06/2006] [Accepted: 02/10/2006] [Indexed: 11/18/2022]
Abstract
This project assessed the effects of repeated low-dose exposure of guinea pigs to the organophosphorus nerve agent sarin. Animals were injected once a day, 5 days per week (Monday-Friday), for 2 weeks with fractions (0.3x, 0.4x, 0.5x, or 0.6x) of the established LD(50) dose of sarin (42 microg/kg, s.c.). The animals were assessed for changes in body weight, red blood cell (RBC) acetylcholinesterase (AChE) levels, neurobehavioral reactions to a functional observational battery (FOB), cortical electroencephalographic (EEG) power spectrum, and intrinsic acetylcholine (ACh) neurotransmitter (NT) regulation over the 2 weeks of sarin exposure and for up to 12 days postinjection. No guinea pig receiving 0.3, 0.4 or 0.5 x LD(50) of sarin showed signs of cortical EEG seizures despite decreases in RBC AChE levels to as low as 10% of baseline, while seizures were evident in animals receiving 0.6 x LD(50) of sarin as early as the second day; subsequent injections led to incapacitation and death. Animals receiving 0.5 x LD(50) sarin showed obvious signs of cholinergic toxicity; overall, 2 of 13 animals receiving 0.5 x LD(50) sarin died before all 10 injections were given, and there was a significant increase in the angle of gait in the animals that lived. By the 10th day of injection, the animals receiving saline were significantly easier to remove from their cages and handle and significantly less responsive to an approaching pencil and touch on the rump in comparison with the first day of testing. In contrast, the animals receiving 0.4 x LD(50) sarin failed to show any significant reductions in their responses to an approaching pencil and a touch on the rump as compared with the first day. The 0.5 x LD(50) sarin animals also failed to show any significant changes to the approach and touch responses and did not adjust to handling or removal from the cage from the first day of injections to the last day of handling. Thus, the guinea pigs receiving the 0.4 and 0.5 x LD(50) doses of sarin failed to habituate to some aspects of neurobehavioral testing. Spectral analysis of EEG data suggested that repeated sarin exposure may disrupt normal sleeping patterns (i.e., lower frequency bandwidths). While these EEG changes returned to relative normalcy 6 days after the last injection in animals receiving 0.4 x LD(50) sarin, these changes were still observed in the animals that received 0.5 x LD(50) sarin. Ten to twelve days after the last sarin injection (in 0.4 x LD(50) group only), neurochemical data showed that striatal choline levels were reduced in comparison to the saline group. At this time, atropine sulfate (5 mg/kg, i.p.) challenge resulted in a transient elevation in striatal ACh levels in animals exposed to repeated 0.4 x LD(50) sarin as well as in control animals. No evidence of brain or heart pathology was found in any guinea pig that survived all 10 sarin injections.
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Affiliation(s)
- T-M Shih
- Pharmacology Branch, Research Division, U.S Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, MD 21010-5400, USA.
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Abstract
The purpose of this project was to determine and compare the time-related changes in blood, brain, and tissue acetylcholinesterase (AChE) activity during the first hour after exposure to six organophosphorus nerve agents (GA, GB, GD, GF, VR, and VX) in Hartley guinea pigs. Animals were pretreated with atropine methyl nitrate (1.0mg/kg, i.m.) to minimize peripheral toxic effects 15 min before they were given a 1.0 x LD50 subcutaneous dose of a nerve agent. At 0, 5, 10, 15, 30, and 60 min after nerve agent, animals were humanely euthanized. Blood was collected and brain regions (brainstem, cortex, hippocampus, midbrain, cerebellum, striatum, and spinal cord) and peripheral tissues (diaphragm, skeletal muscle, and heart) were dissected and processed for AChE activity. All six nerve agents produced maximum inhibition of AChE in red blood cells between 5 and 10% of the control within 10 min after exposure. In whole blood, differential effects were observed among the agents: GB, GD, and GF produced more rapid and greater inhibition than did GA, VR, and VX. GF was the most rapid, producing a maximum inhibition to 5% of the control in 5 min, while VR and VX were slower reaching maximum inhibition to 30% of the control at 15 min. The enzyme activity in the majority of the brain regions was more markedly inhibited by the G-agents than by the V-agents. The G-agents caused rapid AChE inhibition, reaching maximum levels (20-30% of control) at 15 min and GA produced the most rapid effects. V-agents produced much slower and less AChE inhibition, reaching maximum (35-60% of control) at 30 min. In the diaphragm, VR, VX, and GD produced more rapid and greater AChE inhibition than other G-agents; GA produced the slowest and least inhibition. In the skeletal muscle, VX induced the most rapid and severe inhibition, while GA the least inhibition. In the heart, all agents produced very rapid inhibition, and GD produced the most severe inhibition of AChE activity. These observations suggest that G-agents and V-agents are tissue compartment specific in their ability to inhibit AChE activity.
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Affiliation(s)
- Tsung-Ming Shih
- Pharmacology Division, U.S. Army Medical Research Institute of Chemical Defense, 3100 Ricketts Point Road, Aberdeen Proving Ground, MD 21010-5400, USA.
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Capacio BR, Byers CE, Merk KA, Smith JR, McDonough JH. Pharmacokinetic studies of intramuscular midazolam in guinea pigs challenged with soman. Drug Chem Toxicol 2005; 27:95-110. [PMID: 15198070 DOI: 10.1081/dct-120030727] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Studies have demonstrated that benzodiazepine compounds are effective at antagonizing seizure activity produced by the organophosphate (OP) cholinesterase inhibitor soman. In this present study we have investigated the pharmacokinetics of midazolam and its associated effects on electroencephalographic (EEG) activity following intramuscular (i.m.) injection to soman-exposed guinea pigs (Crl:(HA)BR). Prior to experiments, the animals were surgically implanted with EEG leads to monitor seizure activity. For the study, animals were administered the following pretreatment/OP/treatment regimen. Pyridostigmine bromide (0.026 mg/kg, i.m.) was given 30 min prior to soman (56 micrograms/kg, 2 x LD50; subcutaneously, s.c.), followed in one minute by atropine sulfate (2 mg/kg, i.m.) and pralidoxime chloride (25 mg/kg, i.m.). All animals receiving this regimen developed seizure activity. Midazolam 0.8 mg/kg, i.m., was administered 5 min after onset of seizure activity. Based on EEG data, animals were categorized as either seizure-terminated or seizure not-terminated at 30 min following anticonvulsant administration. Serial blood samples were collected for the plasma midazolam analysis; the assay was accomplished with a gas chromatograph/mass spectrometer. The mean time to seizure termination was 8.8 +/- 1.6 min. The mean time-plasma concentration data were fit to standard pharmacokinetic models. The following parameter estimates were determined from the model-fit for seizure terminated and not-terminated animals respectively: apparent volumes of distribution (Vd) were 1.4 and 1.7 l/kg; area under the time-concentration curves (AUC), 15,990 and 15,120 ng.min/ml; times to maximal plasma concentration (Tmax), 1.66 and 2.91 min and maximal plasma concentrations (Cmax) 535.1 and 436.6 ng/ml. These data indicate that i.m. injection of midazolam is effective at terminating ongoing soman-induced seizure activity. Additionally, the relatively short Tmax and latency to seizure termination demonstrate the rapidity of drug absorption and action respectively.
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Affiliation(s)
- Benedict R Capacio
- U.S. Army Medical Research Institute of Chemical Defense, 3100 Ricketts Road, Aberdeen Proving Ground, MD 21010-5400, USA.
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Abstract
This study evaluated the effectiveness of fosphenytoin as a single or adjunctive anticonvulsant treatment for nerve agent-induced status epilepticus. Guinea pigs, implanted with cortical electroencephalographic (EEG) recording electrodes, were pretreated with pyridostigmine bromide (0.026 mg/kg, intramuscular (i.m.)) 30 min before challenge with 56 micrograms/kg, subcutaneous (s.c.), (2 x LD50) of the nerve agent soman. One min after soman, the animals were treated (i.m.) with 2 mg/kg atropine sulfate admixed with 25 mg/kg of the oxime 2-pralidoxime chloride, and the EEG was observed for seizure onset. When administered (intraperitoneal, i.p.) therapeutically 5 min after seizure onset, only the highest fosphenytoin dose (180 mg/kg) was capable of terminating seizure activity in 50% of the animals tested (3 of 6). When fosphenytoin (18-180 mg/kg) was administered as a pretreatment, i.p., 30 min before soman challenge, seizures were blocked or terminated in a dose-dependent fashion (ED50 = 61.8 mg/kg; 40.5-94.7 mg/kg = 95% confidence limits). Combinations of diazepam and fosphenytoin were also tested for effectiveness. No dose of fosphenytoin (18-56 mg/kg), given in conjunction with a fixed dose of diazepam (4.8 mg/kg, i.m.) 5 min after seizure onset, enhanced the anticonvulsant effect of diazepam. When fosphenytoin (18 or 32 mg/kg, i.p.) was given as a pretreatment and diazepam was given 5 min after seizure onset, the 32 mg/kg dose of fosphenytoin significantly reduced the time for seizure control. These studies show that fosphenytoin, either alone or in combination with diazepam, has little or no therapeutic anticonvulsant effectiveness for nerve agent-induced status epilepticus.
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Affiliation(s)
- John H McDonough
- Pharmacology Division, US Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, 3100 Ricketts Point Road, APG-EA, MD 21010-5400, USA.
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