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Why won't it stop? The dynamics of benzodiazepine resistance in status epilepticus. Nat Rev Neurol 2022; 18:428-441. [PMID: 35538233 DOI: 10.1038/s41582-022-00664-3] [Citation(s) in RCA: 25] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/19/2022] [Indexed: 11/08/2022]
Abstract
Status epilepticus is a life-threatening neurological emergency that affects both adults and children. Approximately 36% of episodes of status epilepticus do not respond to the current preferred first-line treatment, benzodiazepines. The proportion of episodes that are refractory to benzodiazepines is higher in low-income and middle-income countries (LMICs) than in high-income countries (HICs). Evidence suggests that longer episodes of status epilepticus alter brain physiology, thereby contributing to the emergence of benzodiazepine resistance. Such changes include alterations in GABAA receptor function and in the transmembrane gradient for chloride, both of which erode the ability of benzodiazepines to enhance inhibitory synaptic signalling. Often, current management guidelines for status epilepticus do not account for these duration-related changes in pathophysiology, which might differentially impact individuals in LMICs, where the average time taken to reach medical attention is longer than in HICs. In this Perspective article, we aim to combine clinical insights and the latest evidence from basic science to inspire a new, context-specific approach to efficiently managing status epilepticus.
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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] [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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3
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Löscher W, Sills GJ, White HS. The ups and downs of alkyl-carbamates in epilepsy therapy: How does cenobamate differ? Epilepsia 2021; 62:596-614. [PMID: 33580520 DOI: 10.1111/epi.16832] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Revised: 01/11/2021] [Accepted: 01/13/2021] [Indexed: 12/13/2022]
Abstract
Since 1955, several alkyl-carbamates have been developed for the treatment of anxiety and epilepsy, including meprobamate, flupirtine, felbamate, retigabine, carisbamate, and cenobamate. They have each enjoyed varying levels of success as antiseizure drugs; however, they have all been plagued by the emergence of serious and sometimes life-threatening adverse events. In this review, we compare and contrast their predominant molecular mechanisms of action, their antiseizure profile, and where possible, their clinical efficacy. The preclinical, clinical, and mechanistic profile of the prototypical γ-aminobutyric acidergic (GABAergic) modulator phenobarbital is included for comparison. Like phenobarbital, all of the clinically approved alkyl-carbamates share an ability to enhance inhibitory neurotransmission through modulation of the GABAA receptor, although the specific mechanism of interaction differs among the different drugs discussed. In addition, several alkyl-carbamates have been shown to interact with voltage-gated ion channels. Flupirtine and retigabine share an ability to activate K+ currents mediated by KCNQ (Kv7) K+ channels, and felbamate, carisbamate, and cenobamate have been shown to block Na+ channels. In contrast to other alkyl-carbamates, cenobamate seems to be unique in its ability to preferentially attenuate the persistent rather than transient Na+ current. Results from recent randomized controlled clinical trials with cenobamate suggest that this newest antiseizure alkyl-carbamate possesses a degree of efficacy not witnessed since felbamate was approved in 1993. Given that ceno-bamate's mechanistic profile is unique among the alkyl-carbamates, it is not clear whether this impressive efficacy reflects an as yet undescribed mechanism of action or whether it possesses a unique synergy between its actions at the GABAA receptor and on persistent Na+ currents. The high efficacy of cenobamate is, however, tempered by the risk of serious rash and low tolerability at higher doses, meaning that further safety studies and clinical experience are needed to determine the true clinical value of cenobamate.
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Affiliation(s)
- Wolfgang Löscher
- Department of Pharmacology, Toxicology, and Pharmacy, University of Veterinary Medicine Hannover, Hannover, Germany.,Center for Systems Neuroscience Hannover, Hannover, Germany
| | - Graeme J Sills
- School of Life Sciences, University of Glasgow, Glasgow, UK
| | - H Steve White
- Department of Pharmacy, School of Pharmacy, University of Washington, Seattle, Washington, USA
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Acute administration of diazepam or midazolam minimally alters long-term neuropathological effects in the rat brain following acute intoxication with diisopropylfluorophosphate. Eur J Pharmacol 2020; 886:173538. [PMID: 32898549 DOI: 10.1016/j.ejphar.2020.173538] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2020] [Revised: 09/01/2020] [Accepted: 09/03/2020] [Indexed: 12/30/2022]
Abstract
Acute intoxication with organophosphorus cholinesterase inhibitors (OPs) can trigger seizures that rapidly progress to life-threatening status epilepticus. Diazepam, long considered the standard of care for treating OP-induced seizures, is being replaced by midazolam. Whether midazolam is more effective than diazepam in mitigating the persistent effects of acute OP intoxication has not been rigorously evaluated. We compared the efficacy of diazepam vs. midazolam in preventing persistent neuropathology in adult male Sprague-Dawley rats acutely intoxicated with the OP diisopropylfluorophosphate (DFP). Subjects were administered pyridostigmine bromide (0.1 mg/kg, i.p.) 30 min prior to injection with DFP (4 mg/kg, s.c.) or vehicle (saline) followed 1 min later by atropine sulfate (2 mg/kg, i.m.) and pralidoxime (25 mg/kg, i.m.), and 40 min later by diazepam (5 mg/kg, i.p.), midazolam (0.73 mg/kg, i.m.), or vehicle. At 3 and 6 months post-exposure, neurodegeneration, reactive astrogliosis, microglial activation, and oxidative stress were assessed in multiple brain regions using quantitative immunohistochemistry. Brain mineralization was evaluated by in vivo micro-computed tomography (micro-CT). Acute DFP intoxication caused persistent neurodegeneration, neuroinflammation, and brain mineralization. Midazolam transiently mitigated neurodegeneration, and both benzodiazepines partially protected against reactive astrogliosis in a brain region-specific manner. Neither benzodiazepine attenuated microglial activation or brain mineralization. These findings indicate that neither benzodiazepine effectively protects against persistent neuropathological changes, and suggest that midazolam is not significantly better than diazepam. Overall, this study highlights the need for improved neuroprotective strategies for treating humans in the event of a chemical emergency involving OPs.
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Burman RJ, Selfe JS, Lee JH, van den Berg M, Calin A, Codadu NK, Wright R, Newey SE, Parrish RR, Katz AA, Wilmshurst JM, Akerman CJ, Trevelyan AJ, Raimondo JV. Excitatory GABAergic signalling is associated with benzodiazepine resistance in status epilepticus. Brain 2020; 142:3482-3501. [PMID: 31553050 DOI: 10.1093/brain/awz283] [Citation(s) in RCA: 48] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2018] [Revised: 06/10/2019] [Accepted: 07/11/2019] [Indexed: 01/17/2023] Open
Abstract
Status epilepticus is defined as a state of unrelenting seizure activity. Generalized convulsive status epilepticus is associated with a rapidly rising mortality rate, and thus constitutes a medical emergency. Benzodiazepines, which act as positive modulators of chloride (Cl-) permeable GABAA receptors, are indicated as first-line treatment, but this is ineffective in many cases. We found that 48% of children presenting with status epilepticus were unresponsive to benzodiazepine treatment, and critically, that the duration of status epilepticus at the time of treatment is an important predictor of non-responsiveness. We therefore investigated the cellular mechanisms that underlie acquired benzodiazepine resistance, using rodent organotypic and acute brain slices. Removing Mg2+ ions leads to an evolving pattern of epileptiform activity, and eventually to a persistent state of repetitive discharges that strongly resembles clinical EEG recordings of status epilepticus. We found that diazepam loses its antiseizure efficacy and conversely exacerbates epileptiform activity during this stage of status epilepticus-like activity. Interestingly, a low concentration of the barbiturate phenobarbital had a similar exacerbating effect on status epilepticus-like activity, while a high concentration of phenobarbital was effective at reducing or preventing epileptiform discharges. We then show that the persistent status epilepticus-like activity is associated with a reduction in GABAA receptor conductance and Cl- extrusion capability. We explored the effect on intraneuronal Cl- using both gramicidin, perforated-patch clamp recordings and Cl- imaging. This showed that during status epilepticus-like activity, reduced Cl- extrusion capacity was further exacerbated by activity-dependent Cl- loading, resulting in a persistently high intraneuronal Cl-. Consistent with these results, we found that optogenetic stimulation of GABAergic interneurons in the status epilepticus-like state, actually enhanced epileptiform activity in a GABAAR dependent manner. Together our findings describe a novel potential mechanism underlying benzodiazepine-resistant status epilepticus, with relevance to how this life-threatening condition should be managed in the clinic.
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Affiliation(s)
- Richard J Burman
- Division of Cell Biology, Department of Human Biology, Neuroscience Institute and Institute of Infectious Disease and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa.,Department of Paediatric Neurology, Red Cross War Memorial Children's Hospital, Neuroscience Institute, University of Cape Town, Cape Town, South Africa.,Department of Pharmacology, University of Oxford, Oxford, UK
| | - Joshua S Selfe
- Division of Cell Biology, Department of Human Biology, Neuroscience Institute and Institute of Infectious Disease and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | - John Hamin Lee
- Division of Cell Biology, Department of Human Biology, Neuroscience Institute and Institute of Infectious Disease and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | - Maurits van den Berg
- Division of Cell Biology, Department of Human Biology, Neuroscience Institute and Institute of Infectious Disease and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | - Alexandru Calin
- Department of Pharmacology, University of Oxford, Oxford, UK
| | - Neela K Codadu
- Institute of Neuroscience, Medical School, Framlington Place, Newcastle upon Tyne, NE24HH, UK
| | - Rebecca Wright
- Department of Pharmacology, University of Oxford, Oxford, UK
| | - Sarah E Newey
- Department of Pharmacology, University of Oxford, Oxford, UK
| | - R Ryley Parrish
- Institute of Neuroscience, Medical School, Framlington Place, Newcastle upon Tyne, NE24HH, UK
| | - Arieh A Katz
- Division of Medical Biochemistry, Department of Integrated Biomedical Sciences and Institute of Infectious Disease and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | - Jo M Wilmshurst
- Department of Paediatric Neurology, Red Cross War Memorial Children's Hospital, Neuroscience Institute, University of Cape Town, Cape Town, South Africa
| | - Colin J Akerman
- Department of Pharmacology, University of Oxford, Oxford, UK
| | - Andrew J Trevelyan
- Institute of Neuroscience, Medical School, Framlington Place, Newcastle upon Tyne, NE24HH, UK
| | - Joseph V Raimondo
- Division of Cell Biology, Department of Human Biology, Neuroscience Institute and Institute of Infectious Disease and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
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Gore A, Neufeld-Cohen A, Egoz I, Baranes S, Gez R, Grauer E, Chapman S, Lazar S. Efficacy of retigabine in ameliorating the brain insult following sarin exposure in the rat. Toxicol Appl Pharmacol 2020; 395:114963. [PMID: 32209366 DOI: 10.1016/j.taap.2020.114963] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2020] [Revised: 03/17/2020] [Accepted: 03/20/2020] [Indexed: 12/20/2022]
Abstract
BACKGROUND Sarin is an irreversible organophosphate cholinesterase inhibitor. Following toxic signs, an extensive long-term brain damage is often reported. Thus, we evaluated the efficacy of a novel anticonvulsant drug retigabine, a modulator of neuronal voltage gated K+ channels, as a neuroprotective agent following sarin exposure. METHODS Rats were exposed to 1 LD50 or 1.2 LD50 sarin and treated at onset of convulsions with retigabine (5 mg/kg, i.p.) alone or in combination with 5 mg/kg atropine and 7.5 mg/kg TMB-4 (TA) respectively. Brain biochemical and immunohistopathological analyses were processed 24 h and 1 week following 1 LD50 sarin exposure and at 4 weeks following exposure to 1.2 LD50 sarin. EEG activity in freely moving rats was also monitored by telemetry during the first week following exposure to 1.2 LD50 and behavior in the Open Field was evaluated 3 weeks post exposure. RESULTS Treatment with retigabine following 1 LD50 sarin exposure or in combination with TA following 1.2 LD50 exposure significantly reduced mortality rate compared to the non-treated groups. In both experiments, the retigabine treatment significantly reduced gliosis, astrocytosis and brain damage as measured by translocator protein (TSPO). Following sarin exposure the combined treatment (retigabine+ TA) significantly minimized epileptiform seizure activity. Finally, in the Open Field behavioral test the non-treated sarin group showed an increased mobility which was reversed by the combined treatment. CONCLUSIONS The M current modulator retigabine has been shown to be an effective adjunct therapy following OP induced convulsion, minimizing epileptiform seizure activity and attenuating the ensuing brain damage.
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Affiliation(s)
- Ariel Gore
- Department. of Pharmacology, Israel Institute for Biological Research, Ness Ziona 74100, Israel.
| | - Adi Neufeld-Cohen
- Department. of Pharmacology, Israel Institute for Biological Research, Ness Ziona 74100, Israel
| | - Inbal Egoz
- Department. of Pharmacology, Israel Institute for Biological Research, Ness Ziona 74100, Israel
| | - Shlomi Baranes
- Department. of Pharmacology, Israel Institute for Biological Research, Ness Ziona 74100, Israel
| | - Rellie Gez
- Department. of Pharmacology, Israel Institute for Biological Research, Ness Ziona 74100, Israel
| | - Ettie Grauer
- Department. of Pharmacology, Israel Institute for Biological Research, Ness Ziona 74100, Israel
| | - Shira Chapman
- Department. of Pharmacology, Israel Institute for Biological Research, Ness Ziona 74100, Israel
| | - Shlomi Lazar
- Department. of Pharmacology, Israel Institute for Biological Research, Ness Ziona 74100, Israel.
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Pilli NR, Narayanasamy S, Xu L, Chockalingam A, Shea KI, Stewart S, Rouse R, Patel V, Matta MK. A high-throughput bioanalytical assay to support pharmacokinetic interaction study of oxycodone and diazepam in Sprague Dawley rats. RSC Adv 2020; 10:886-896. [PMID: 35494453 PMCID: PMC9047970 DOI: 10.1039/c9ra05785d] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2019] [Accepted: 12/23/2019] [Indexed: 11/23/2022] Open
Abstract
Benzodiazepines potentiate respiratory depression when combined with an opioid leading the U.S Food and Drug Administration (FDA) to recommend updating the labels of these products with a boxed warning for respiratory depression with co-use. Potential respiratory depression upon co-administration of opioids with some psychotropic drugs is not well understood. The FDA is currently investigating various psychotropic drug interactions with the commonly used opioid, oxycodone, in a rat model assessing respiratory depression. Pharmacokinetic and/or pharmacodynamic (PK/PD) interaction between oxycodone and diazepam was evaluated in a positive control arm of these experiments. Understanding the systemic exposure of these drugs alone and in combination exposures was used to identify PK/PD interactions. The authors developed a simple, high throughput liquid chromatography-tandem mass spectrometric (LC-MS/MS) assay for the simultaneous determination of oxycodone and diazepam in rat plasma. Sample preparation was performed in 96-well protein precipitation plates using acetonitrile. Processed samples were analyzed using a C18 column with a gradient mobile phase composed of 2 mM aqueous ammonium formate with 0.1% formic acid and acetonitrile. A Thermo TSQ Quantum Ultra AM triple quadrupole mass spectrometer with multiple reaction monitoring (MRM) mode was used to acquire data. The method was validated for selectivity, specificity, linearity, precision and accuracy, dilution integrity and stability. The validated LC-MS/MS assay was utilized for quantifying oxycodone and diazepam in concomitantly treated Sprague Dawley (SD) rats. A high-throughput bioanalytical method for the simulataneous determination of oxycodone and diazepam to support the evaluation of respiratory depression in rats upon co-administration of oxycodone and diazepam.![]()
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Affiliation(s)
- Nageswara R. Pilli
- Division of Applied Regulatory Science
- Office of Clinical Pharmacology
- Office of Translational Sciences
- Center for Drug Evaluation and Research
- Food and Drug Administration
| | - Suresh Narayanasamy
- Division of Applied Regulatory Science
- Office of Clinical Pharmacology
- Office of Translational Sciences
- Center for Drug Evaluation and Research
- Food and Drug Administration
| | - Lin Xu
- Division of Applied Regulatory Science
- Office of Clinical Pharmacology
- Office of Translational Sciences
- Center for Drug Evaluation and Research
- Food and Drug Administration
| | - Ashok Chockalingam
- Division of Applied Regulatory Science
- Office of Clinical Pharmacology
- Office of Translational Sciences
- Center for Drug Evaluation and Research
- Food and Drug Administration
| | - Katherine I. Shea
- Division of Applied Regulatory Science
- Office of Clinical Pharmacology
- Office of Translational Sciences
- Center for Drug Evaluation and Research
- Food and Drug Administration
| | - Sharron Stewart
- Division of Applied Regulatory Science
- Office of Clinical Pharmacology
- Office of Translational Sciences
- Center for Drug Evaluation and Research
- Food and Drug Administration
| | - Rodney Rouse
- Division of Applied Regulatory Science
- Office of Clinical Pharmacology
- Office of Translational Sciences
- Center for Drug Evaluation and Research
- Food and Drug Administration
| | - Vikram Patel
- Division of Applied Regulatory Science
- Office of Clinical Pharmacology
- Office of Translational Sciences
- Center for Drug Evaluation and Research
- Food and Drug Administration
| | - Murali K. Matta
- Division of Applied Regulatory Science
- Office of Clinical Pharmacology
- Office of Translational Sciences
- Center for Drug Evaluation and Research
- Food and Drug Administration
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Gaínza-Lein M, Fernández IS, Ulate-Campos A, Loddenkemper T, Ostendorf AP. Timing in the treatment of status epilepticus: From basics to the clinic. Seizure 2019; 68:22-30. [DOI: 10.1016/j.seizure.2018.05.021] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2018] [Revised: 05/18/2018] [Accepted: 05/29/2018] [Indexed: 02/07/2023] Open
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9
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Bock C, Surur AS, Beirow K, Kindermann MK, Schulig L, Bodtke A, Bednarski PJ, Link A. Sulfide Analogues of Flupirtine and Retigabine with Nanomolar K V 7.2/K V 7.3 Channel Opening Activity. ChemMedChem 2019; 14:952-964. [PMID: 30861620 DOI: 10.1002/cmdc.201900112] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2019] [Indexed: 12/18/2022]
Abstract
The potassium channel openers flupirtine and retigabine have proven to be valuable analgesics or antiepileptics. Their recent withdrawal due to occasional hepatotoxicity and tissue discoloration, respectively, leaves a therapeutic niche unfilled. Metabolic oxidation of both drugs gives rise to the formation of electrophilic quinones. These elusive, highly reactive metabolites may induce liver injury in the case of flupirtine and blue tissue discoloration after prolonged intake of retigabine. We examined which structural features can be altered to avoid the detrimental oxidation of the aromatic ring and shift oxidation toward the formation of more benign metabolites. Structure-activity relationship studies were performed to evaluate the KV 7.2/3 channel opening activity of 45 derivatives. Sulfide analogues were identified that are devoid of the risk of quinone formation, but possess potent KV 7.2/3 opening activity. For example, flupirtine analogue 3-(3,5-difluorophenyl)-N-(6-(isobutylthio)-2-(pyrrolidin-1-yl)pyridin-3-yl)propanamide (48) has 100-fold enhanced activity (EC50 =1.4 nm), a vastly improved toxicity/activity ratio, and the same efficacy as retigabine in vitro.
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Affiliation(s)
- Christian Bock
- Institute of Pharmacy, University of Greifswald, Friedrich-Ludwig-Jahn-Str. 17, 17489, Greifswald, Germany
| | - Abdrrahman S Surur
- Institute of Pharmacy, University of Greifswald, Friedrich-Ludwig-Jahn-Str. 17, 17489, Greifswald, Germany
| | - Kristin Beirow
- Institute of Pharmacy, University of Greifswald, Friedrich-Ludwig-Jahn-Str. 17, 17489, Greifswald, Germany
| | - Markus K Kindermann
- Institute of Pharmacy, University of Greifswald, Friedrich-Ludwig-Jahn-Str. 17, 17489, Greifswald, Germany
| | - Lukas Schulig
- Institute of Pharmacy, University of Greifswald, Friedrich-Ludwig-Jahn-Str. 17, 17489, Greifswald, Germany
| | - Anja Bodtke
- Institute of Pharmacy, University of Greifswald, Friedrich-Ludwig-Jahn-Str. 17, 17489, Greifswald, Germany
| | - Patrick J Bednarski
- Institute of Pharmacy, University of Greifswald, Friedrich-Ludwig-Jahn-Str. 17, 17489, Greifswald, Germany
| | - Andreas Link
- Institute of Pharmacy, University of Greifswald, Friedrich-Ludwig-Jahn-Str. 17, 17489, Greifswald, Germany
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Putra M, Sharma S, Gage M, Gasser G, Hinojo-Perez A, Olson A, Gregory-Flores A, Puttachary S, Wang C, Anantharam V, Thippeswamy T. Inducible nitric oxide synthase inhibitor, 1400W, mitigates DFP-induced long-term neurotoxicity in the rat model. Neurobiol Dis 2019; 133:104443. [PMID: 30940499 DOI: 10.1016/j.nbd.2019.03.031] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2018] [Revised: 02/22/2019] [Accepted: 03/28/2019] [Indexed: 11/26/2022] Open
Abstract
Chemical nerve agents (CNA) are increasingly becoming a threat to both civilians and military personnel. CNA-induced acute effects on the nervous system have been known for some time and the long-term consequences are beginning to emerge. In this study, we used diisopropylfluorophosphate (DFP), a seizurogenic CNA to investigate the long-term impact of its acute exposure on the brain and its mitigation by an inducible nitric oxide synthase (iNOS) inhibitor, 1400W as a neuroprotectant in the rat model. Several experimental studies have demonstrated that DFP-induced seizures and/or status epilepticus (SE) causes permanent brain injury, even after the countermeasure medication (atropine, oxime, and diazepam). In the present study, DFP-induced SE caused a significant increase in iNOS and 3-nitrotyrosine (3-NT) at 24 h, 48 h, 7d, and persisted for a long-term (12 weeks post-exposure), which led to the hypothesis that iNOS is a potential therapeutic target in DFP-induced brain injury. To test the hypothesis, we administered 1400W (20 mg/kg, i.m.) or the vehicle twice daily for the first three days of post-exposure. 1400W significantly reduced DFP-induced iNOS and 3-NT upregulation in the hippocampus and piriform cortex, and the serum nitrite levels at 24 h post-exposure. 1400W also prevented DFP-induced mortality in <24 h. The brain immunohistochemistry (IHC) at 7d post-exposure revealed a significant reduction in gliosis and neurodegeneration (NeuN+ FJB positive cells) in the 1400W-treated group. 1400W, in contrast to the vehicle, caused a significant reduction in the epileptiform spiking and spontaneous recurrent seizures (SRS) during 12 weeks of continuous video-EEG study. IHC of brain sections from the same animals revealed a significant reduction in reactive gliosis (both microgliosis and astrogliosis) and neurodegeneration across various brain regions in the 1400W-treated group when compared to the vehicle-treated group. A multiplex assay from hippocampal lysates at 6 weeks post-exposure showed a significant increase in several key pro-inflammatory cytokines/chemokines such as IL-1α, TNFα, IL-1β, IL-2, IL-6, IL-12, IL-17a, MCP-1, LIX, and Eotaxin, and a growth factor, VEGF in the vehicle-treated animals. 1400W significantly suppressed IL-1α, TNFα, IL-2, IL-12, and MCP-1 levels. It also suppressed DFP-induced serum nitrite levels at 6 weeks post-exposure. In the Morris water maze, the vehicle-treated animals spent significantly less time in the target quadrant in a probe trial at 9d post-exposure compared to their time spent in the same quadrant 11 days previously (i.e., 2 days prior to DFP exposure). Such a difference was not observed in the 1400W and control groups. However, learning and short-term memory were unaffected when tested at 10-16d and 28-34d post-exposure. Accelerated rotarod, horizontal bar test, and the forced swim test revealed no significant changes between groups. Overall, the findings from this study suggest that 1400W may be considered as a potential therapeutic agent as a follow-on therapy for CNA exposure, after controlling the acute symptoms, to prevent mortality and some of the long-term neurotoxicity parameters such as epileptiform spiking, SRS, neurodegeneration, reactive gliosis in some brain regions, and certain key proinflammatory cytokines and chemokine.
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Affiliation(s)
- Marson Putra
- Department of Biomedical Sciences, College of Veterinary Medicine, Iowa State University, Ames, IA 50011, United States
| | - Shaunik Sharma
- Department of Biomedical Sciences, College of Veterinary Medicine, Iowa State University, Ames, IA 50011, United States
| | - Meghan Gage
- Department of Biomedical Sciences, College of Veterinary Medicine, Iowa State University, Ames, IA 50011, United States
| | | | - Andy Hinojo-Perez
- Department of Biomedical Sciences, College of Veterinary Medicine, Iowa State University, Ames, IA 50011, United States
| | - Ashley Olson
- Department of Biomedical Sciences, College of Veterinary Medicine, Iowa State University, Ames, IA 50011, United States
| | - Adriana Gregory-Flores
- Department of Biomedical Sciences, College of Veterinary Medicine, Iowa State University, Ames, IA 50011, United States
| | - Sreekanth Puttachary
- Department of Biomedical Sciences, Carlson College of Veterinary Medicine, Oregon State University, Corvallis, OR 97331, United States
| | - Chong Wang
- Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA 50011, United States
| | | | - Thimmasettappa Thippeswamy
- Department of Biomedical Sciences, College of Veterinary Medicine, Iowa State University, Ames, IA 50011, United States.
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11
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Abstract
The highly structurally similar drugs flupirtine and retigabine have been regarded as safe and effective for many years but lately they turned out to exert intolerable side effects. While the twin molecules share the mode of action, both stabilize the open state of voltage-gated potassium channels, the form and severity of adverse effects is different. The analgesic flupirtine caused drug-induced liver injury in rare but fatal cases, whereas prolonged use of the antiepileptic retigabine led to blue tissue discoloration. Because the adverse effects seem unrelated to the mode of action, it is likely, that both drugs that occupied important therapeutic niches, could be replaced. Reasons for the clinically relevant toxicity will be clarified and future substitutes for these drugs presented in this review.
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12
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Lawson K. Pharmacology and clinical applications of flupirtine: Current and future options. World J Pharmacol 2019; 8:1-13. [DOI: 10.5497/wjp.v8.i1.1] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/20/2018] [Revised: 11/17/2018] [Accepted: 01/05/2019] [Indexed: 02/06/2023] Open
Abstract
Flupirtine is the first representative in a class of triaminopyridines that exhibits pharmacological properties leading to the suppression of over-excitability of neuronal and non-neuronal cells. Consequently, this drug has been used as a centrally acting analgesic in patients with a range of acute and persistent pain conditions without the adverse effects characteristic of opioids and non-steroidal anti-inflammatory drug and is well tolerated. The pharmacological profile exhibited involves actions on several cellular targets, including Kv7 channels, G-protein-regulated inwardly rectifying K channels and γ-aminobutyric acid type A receptors, but also there is evidence of additional as yet unidentified mechanisms of action involved in the effects of flupirtine. Flupirtine has exhibited effects in a range of cells and tissues related to the locations of these targets. In additional to analgesia, flupirtine has demonstrated pharmacological properties consistent with use as an anticonvulsant, a neuroprotectant, skeletal and smooth muscle relaxant, in treatment of auditory and visual disorders, and treatment of memory and cognitive impairment. Flupirtine is providing important information and clues regarding novel mechanistic approaches to the treatment of a range of clinical conditions involving hyper-excitability of cells. Identification of molecules exhibiting specificity for the pharmacological targets (e.g., Kv7 isoforms) involved in the actions of flupirtine will provide further insight into clinical applications. Whether the broad-spectrum pharmacology of flupirtine or target-specific actions is preferential to gain benefit, especially in complex clinical conditions, requires further investigation. This review will consider recent advancement in understanding of the pharmacological profile and related clinical applications of flupirtine.
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Affiliation(s)
- Kim Lawson
- Department of Biosciences and Chemistry, Biomolecular Sciences Research Centre, Sheffield Hallam University, Sheffield S1 1WB, United Kingdom
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13
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Surur AS, Beirow K, Bock C, Schulig L, Kindermann MK, Bodtke A, Siegmund W, Bednarski PJ, Link A. Flupirtine Analogues: Explorative Synthesis and Influence of Chemical Structure on K V7.2/K V7.3 Channel Opening Activity. ChemistryOpen 2019; 8:41-44. [PMID: 30652063 PMCID: PMC6331712 DOI: 10.1002/open.201800244] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2018] [Revised: 11/26/2018] [Indexed: 12/19/2022] Open
Abstract
Neuronal voltage‐gated potassium channels KV7.2/KV7.3 are sensitive to small‐molecule drugs such as flupirtine, even though physiological response occurs in the absence of ligands. Clinically, prolonged use of flupirtine as a pain medication is associated with rare cases of drug‐induced liver injury. Thus, safety concerns prevent a broader use of this non‐opioid and non‐steroidal analgesic in therapeutic areas with unmet medical needs such as hyperactive bladder or neonatal seizures. With the goal of studying influences of chemical structure on activity and toxicity of flupirtine, we explored modifications of the benzylamino bridge and the substitution pattern in both rings of flupirtine. Among twelve derivatives, four novel thioether derivatives showed the desired activity in cellular assays and may serve as leads for safer KV channel openers.
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Affiliation(s)
- Abdrrahman S Surur
- Institute of Pharmacy University of Greifswald Friedrich-Ludwig-Jahn-Str. 17 17489 Greifswald Germany
| | - Kristin Beirow
- Institute of Pharmacy University of Greifswald Friedrich-Ludwig-Jahn-Str. 17 17489 Greifswald Germany
| | - Christian Bock
- Institute of Pharmacy University of Greifswald Friedrich-Ludwig-Jahn-Str. 17 17489 Greifswald Germany
| | - Lukas Schulig
- Institute of Pharmacy University of Greifswald Friedrich-Ludwig-Jahn-Str. 17 17489 Greifswald Germany
| | - Markus K Kindermann
- Institute of Pharmacy University of Greifswald Friedrich-Ludwig-Jahn-Str. 17 17489 Greifswald Germany
| | - Anja Bodtke
- Institute of Pharmacy University of Greifswald Friedrich-Ludwig-Jahn-Str. 17 17489 Greifswald Germany
| | | | - Patrick J Bednarski
- Institute of Pharmacy University of Greifswald Friedrich-Ludwig-Jahn-Str. 17 17489 Greifswald Germany
| | - Andreas Link
- Institute of Pharmacy University of Greifswald Friedrich-Ludwig-Jahn-Str. 17 17489 Greifswald Germany
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