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Reddy DS. Neurosteroids as Novel Anticonvulsants for Refractory Status Epilepticus and Medical Countermeasures for Nerve Agents: A 15-Year Journey to Bring Ganaxolone from Bench to Clinic. J Pharmacol Exp Ther 2024; 388:273-300. [PMID: 37977814 PMCID: PMC10801762 DOI: 10.1124/jpet.123.001816] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2023] [Revised: 10/05/2023] [Accepted: 10/23/2023] [Indexed: 11/19/2023] Open
Abstract
This article describes recent advances in the use of neurosteroids as novel anticonvulsants for refractory status epilepticus (RSE) and as medical countermeasures (MCs) for organophosphates and chemical nerve agents (OPNAs). We highlight a comprehensive 15-year journey to bring the synthetic neurosteroid ganaxolone (GX) from bench to clinic. RSE, including when caused by nerve agents, is associated with devastating morbidity and permanent long-term neurologic dysfunction. Although recent approval of benzodiazepines such as intranasal midazolam and intranasal midazolam offers improved control of acute seizures, novel anticonvulsants are needed to suppress RSE and improve neurologic function outcomes. Currently, few anticonvulsant MCs exist for victims of OPNA exposure and RSE. Standard-of-care MCs for postexposure treatment include benzodiazepines, which do not effectively prevent or mitigate seizures resulting from nerve agent intoxication, leaving an urgent unmet medical need for new anticonvulsants for RSE. Recently, we pioneered neurosteroids as next-generation anticonvulsants that are superior to benzodiazepines for treatment of OPNA intoxication and RSE. Because GX and related neurosteroids that activate extrasynaptic GABA-A receptors rapidly control seizures and offer robust neuroprotection by reducing neuronal damage and neuroinflammation, they effectively improve neurologic outcomes after acute OPNA exposure and RSE. GX has been selected for advanced, Biomedical Advanced Research and Development Authority-supported phase 3 trials of RSE and nerve agent seizures. In addition, in mechanistic studies of neurosteroids at extrasynaptic receptors, we identified novel synthetic analogs with features that are superior to GX for current medical needs. Development of new MCs for RSE is complex, tedious, and uncertain due to scientific and regulatory challenges. Thus, further research will be critical to fill key gaps in evaluating RSE and anticonvulsants in vulnerable (pediatric and geriatric) populations and military persons. SIGNIFICANCE STATEMENT: Following organophosphate and nerve agent intoxication, refractory status epilepticus (RSE) occurs despite benzodiazepine treatment. RSE occurs in 40% of status epilepticus patients, with a 35% mortality rate and significant neurological morbidity in survivors. To treat RSE, neurosteroids are better anticonvulsants than benzodiazepines. Our pioneering use of neurosteroids for RSE and nerve agents led us to develop ganaxolone as a novel anticonvulsant and neuroprotectant with significantly improved neurological outcomes. This article describes the bench-to-bedside journey of bringing neurosteroid therapy to patients, with ganaxolone leading the way.
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Affiliation(s)
- Doodipala Samba Reddy
- Department of Neuroscience and Experimental Therapeutics, Texas A&M University School of Medicine, Bryan, Texas and Institute of Pharmacology and Neurotherapeutics, Texas A&M University Health Science Center, Bryan, Texas
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Reddy DS, Singh T, Ramakrishnan S, Huber M, Wu X. Neuroprotectant Activity of Novel Water-Soluble Synthetic Neurosteroids on Organophosphate Intoxication and Status Epilepticus-Induced Long-Term Neurological Dysfunction, Neurodegeneration, and Neuroinflammation. J Pharmacol Exp Ther 2024; 388:399-415. [PMID: 38071567 PMCID: PMC10801736 DOI: 10.1124/jpet.123.001819] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2023] [Accepted: 09/18/2023] [Indexed: 01/19/2024] Open
Abstract
Organophosphates (OPs) and nerve agents are potent neurotoxic compounds that cause seizures, status epilepticus (SE), brain injury, or death. There are persistent long-term neurologic and neurodegenerative effects that manifest months to years after the initial exposure. Current antidotes are ineffective in preventing these long-term neurobehavioral and neuropathological changes. Additionally, there are few effective neuroprotectants for mitigating the long-term effects of acute OP intoxication. We have pioneered neurosteroids as novel anticonvulsants and neuroprotectants for OP intoxication and seizures. In this study, we evaluated the efficacy of two novel synthetic, water-soluble neurosteroids, valaxanolone (VX) and lysaxanolone (LX), in combating the long-term behavioral and neuropathological impairments caused by acute OP intoxication and SE. Animals were exposed to the OP nerve agent surrogate diisopropylfluorophosphate (DFP) and were treated with VX or LX in addition to midazolam at 40 minutes postexposure. The extent of neurodegeneration, along with various behavioral and memory deficits, were assessed at 3 months postexposure. VX significantly reduced deficits of aggressive behavior, anxiety, memory, and depressive-like traits in control (DFP-exposed, midazolam-treated) animals; VX also significantly prevented the DFP-induced chronic loss of NeuN(+) principal neurons and PV(+) inhibitory neurons in the hippocampus and other regions. Additionally, VX-treated animals exhibited a reduced inflammatory response with decreased GFAP(+) astrogliosis and IBA1(+) microgliosis in the hippocampus, amygdala, and other regions. Similarly, LX showed significant improvement in behavioral and memory deficits, and reduced neurodegeneration and cellular neuroinflammation. Together, these results demonstrate the neuroprotectant effects of the novel synthetic neurosteroids in mitigating the long-term neurologic dysfunction and neurodegeneration associated with OP exposure. SIGNIFICANCE STATEMENT: Survivors of nerve agents and organophosphate (OP) exposures suffer from long-term neurological deficits. Currently, there is no specific drug therapy for mitigating the impact of OP exposure. However, novel synthetic neurosteroids that activate tonic inhibition provide a viable option for treating OP intoxication. The data from this study indicates the neuroprotective effects of synthetic, water-soluble neurosteroids for attenuation of long-term neurological deficits after OP intoxication. These findings establish valaxanolone and lysaxanolone as potent and efficacious neuroprotectants suitable for injectable dosing.
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Affiliation(s)
- Doodipala Samba Reddy
- Department of Neuroscience and Experimental Therapeutics, Texas A&M University School of Medicine, Bryan, Texas (D.S.R., T.S., S.R., M.H., X.W.) and Institute of Pharmacology and Neurotherapeutics, Texas A&M University Health Science Center, Bryan, Texas (D.S.R., S.R., X.W.)
| | - Tanveer Singh
- Department of Neuroscience and Experimental Therapeutics, Texas A&M University School of Medicine, Bryan, Texas (D.S.R., T.S., S.R., M.H., X.W.) and Institute of Pharmacology and Neurotherapeutics, Texas A&M University Health Science Center, Bryan, Texas (D.S.R., S.R., X.W.)
| | - Sreevidhya Ramakrishnan
- Department of Neuroscience and Experimental Therapeutics, Texas A&M University School of Medicine, Bryan, Texas (D.S.R., T.S., S.R., M.H., X.W.) and Institute of Pharmacology and Neurotherapeutics, Texas A&M University Health Science Center, Bryan, Texas (D.S.R., S.R., X.W.)
| | - Madeline Huber
- Department of Neuroscience and Experimental Therapeutics, Texas A&M University School of Medicine, Bryan, Texas (D.S.R., T.S., S.R., M.H., X.W.) and Institute of Pharmacology and Neurotherapeutics, Texas A&M University Health Science Center, Bryan, Texas (D.S.R., S.R., X.W.)
| | - Xin Wu
- Department of Neuroscience and Experimental Therapeutics, Texas A&M University School of Medicine, Bryan, Texas (D.S.R., T.S., S.R., M.H., X.W.) and Institute of Pharmacology and Neurotherapeutics, Texas A&M University Health Science Center, Bryan, Texas (D.S.R., S.R., X.W.)
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Ramakrishnan S, Singh T, Reddy DS. Protective Activity of Novel Hydrophilic Synthetic Neurosteroids on Organophosphate Status Epilepticus-induced Chronic Epileptic Seizures, Non-Convulsive Discharges, High-Frequency Oscillations, and Electrographic Ictal Biomarkers. J Pharmacol Exp Ther 2024; 388:386-398. [PMID: 38050069 PMCID: PMC10801763 DOI: 10.1124/jpet.123.001817] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2023] [Revised: 11/07/2023] [Accepted: 11/08/2023] [Indexed: 12/06/2023] Open
Abstract
Nerve agents and organophosphates (OP) are neurotoxic chemicals that induce acute seizures, status epilepticus (SE), and mortality. Long-term neurologic and neurodegenerative effects manifest months to years after OP exposure. Current benzodiazepine anticonvulsants are ineffective in preventing such long-term neurobehavioral and neuropathological changes. New and effective anticonvulsants are needed for OP intoxication, especially for mitigating the long-term sequelae after acute exposure. We developed neurosteroids as novel anticonvulsants and neuroprotectants in OP exposure models. In this study, we evaluated the long-term efficacy of novel synthetic neurosteroids in preventing the development of chronic epilepsy and hyperexcitable ictal events in a rat OP model of SE. Rats were exposed to the OP nerve agent surrogate diisopropylfluorophosphate (DFP), and the experimental groups were treated with the synthetic neurosteroid valaxanolone (VX) or lysaxanolone (LX) 40 minutes post-exposure in conjunction with midazolam. Video-electroencephalography was monitored for two months to assess spontaneous recurrent seizures (SRS), epileptiform discharges, interictal spikes, and high-frequency oscillations (HFOs). Within 60 days of DFP exposure, rats developed chronic epilepsy characterized by frequent SRS, epileptiform discharges, and HFOs. LX treatment was associated with a dose-dependent reduction of epilepsy occurrence and overall seizure burden with a significant decrease in SRS and epileptiform discharges. It also significantly reduced the occurrence of epileptic biomarkers of HFOs and interictal spikes, indicating potential disease-modifying activity. Similarly, the neurosteroid analog VX also significantly attenuated SRS, discharges, HFOs, and ictal events. These results demonstrate the long-term protective effects of synthetic neurosteroids in the OP-exposed post-SE model, indicating their disease-modifying potential to prevent epilepsy and ictal abnormalities. SIGNIFICANCE STATEMENT: The effects of nerve agents and organophosphate (OP) exposure are persistent, and survivors suffer from a number of devastating, chronic neurological dysfunctions. Currently, there is no specific therapy for preventing this disastrous impact of OP exposure. We propose synthetic neurosteroids that activate tonic inhibition provide viable options for preventing the long-term neurological effects of OP intoxication. The results from this study reveal the disease-modifying potential of two novel synthetic neurosteroids in preventing epileptogenesis and chronic epileptic seizures after OP-induced SE.
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Affiliation(s)
- Sreevidhya Ramakrishnan
- Department of Neuroscience and Experimental Therapeutics (S.R., T.S., D.S.R.) and Institute of Pharmacology and Neurotherapeutics (D.S.R.), School of Medicine, Texas A&M University Health Science Center, Bryan, Texas
| | - Tanveer Singh
- Department of Neuroscience and Experimental Therapeutics (S.R., T.S., D.S.R.) and Institute of Pharmacology and Neurotherapeutics (D.S.R.), School of Medicine, Texas A&M University Health Science Center, Bryan, Texas
| | - Doodipala Samba Reddy
- Department of Neuroscience and Experimental Therapeutics (S.R., T.S., D.S.R.) and Institute of Pharmacology and Neurotherapeutics (D.S.R.), School of Medicine, Texas A&M University Health Science Center, Bryan, Texas
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Yang CS, Wu MC, Lai MC, Wu SN, Huang CW. Identification of New Antiseizure Medication Candidates in Preclinical Animal Studies. Int J Mol Sci 2023; 24:13143. [PMID: 37685950 PMCID: PMC10487685 DOI: 10.3390/ijms241713143] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2023] [Revised: 08/09/2023] [Accepted: 08/17/2023] [Indexed: 09/10/2023] Open
Abstract
Epilepsy is a multifactorial neurologic disease that often leads to many devastating disabilities and an enormous burden on the healthcare system. Until now, drug-resistant epilepsy has presented a major challenge for approximately 30% of the epileptic population. The present article summarizes the validated rodent models of seizures employed in pharmacological researches and comprehensively reviews updated advances of novel antiseizure candidates in the preclinical phase. Newly discovered compounds that demonstrate antiseizure efficacy in preclinical trials will be discussed in the review. It is inspiring that several candidates exert promising antiseizure activities in drug-resistant seizure models. The representative compounds consist of derivatives of hybrid compounds that integrate multiple approved antiseizure medications, novel positive allosteric modulators targeting subtype-selective γ-Aminobutyric acid type A receptors, and a derivative of cinnamamide. Although the precise molecular mechanism, pharmacokinetic properties, and safety are not yet fully clear in every novel antiseizure candidate, the adapted approaches to design novel antiseizure medications provide new insights to overcome drug-resistant epilepsy.
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Affiliation(s)
- Chih-Sheng Yang
- Department of Neurology, Taichung Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation, Taichung City 42743, Taiwan;
- School of Post-Baccalaureate Chinese Medicine, Tzu Chi University, Hualien City 97004, Taiwan
| | - Man-Chun Wu
- Department of Family Medicine and Preventive Medicine Center, Taichung Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation, Taichung City 42743, Taiwan
| | - Ming-Chi Lai
- Department of Pediatrics, Chi-Mei Medical Center, Tainan City 71004, Taiwan;
| | - Sheng-Nan Wu
- Department of Physiology, College of Medicine, National Cheng Kung University, Tainan City 70101, Taiwan;
- Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan City 70101, Taiwan
| | - Chin-Wei Huang
- Department of Neurology, National Cheng Kung University Hospital, College of Medicine, National Cheng Kung University, Tainan City 70101, Taiwan
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Balan I, Aurelian L, Williams KS, Campbell B, Meeker RB, Morrow AL. Inhibition of human macrophage activation via pregnane neurosteroid interactions with toll-like receptors: Sex differences and structural requirements. Front Immunol 2022; 13:940095. [PMID: 35967446 PMCID: PMC9373802 DOI: 10.3389/fimmu.2022.940095] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2022] [Accepted: 07/07/2022] [Indexed: 11/13/2022] Open
Abstract
We recently discovered that (3α,5α)3-hydroxypregnan-20-one (allopregnanolone) inhibits pro-inflammatory toll-like receptor (TLR) activation and cytokine/chemokine production in mouse macrophage RAW264.7 cells. The present studies evaluate neurosteroid actions upon TLR activation in human macrophages from male and female healthy donors. Buffy coat leukocytes were obtained from donors at the New York Blood Center (http://nybloodcenter.org/), and peripheral blood mononuclear cells were isolated and cultured to achieve macrophage differentiation. TLR4 and TLR7 were activated by lipopolysaccharide (LPS) or imiquimod in the presence/absence of allopregnanolone or related neurosteroids and pro-inflammatory markers were detected by ELISA or western blotting. Cultured human monocyte-derived-macrophages exhibited typical morphology, a mixed immune profile of both inflammatory and anti-inflammatory markers, with no sex difference at baseline. Allopregnanolone inhibited TLR4 activation in male and female donors, preventing LPS-induced elevations of TNF-α, MCP-1, pCREB and pSTAT1. In contrast, 3α,5α-THDOC and SGE-516 inhibited the TLR4 pathway activation in female, but not male donors. Allopregnanolone completely inhibited TLR7 activation by imiquimod, blocking IL-1-β, IL-6, pSTAT1 and pIRF7 elevations in females only. 3α,5α-THDOC and SGE-516 partially inhibited TLR7 activation, only in female donors. The results indicate that allopregnanolone inhibits TLR4 and TLR7 activation in cultured human macrophages resulting in diminished cytokine/chemokine production. Allopregnanolone inhibition of TLR4 activation was found in males and females, but inhibition of TLR7 signals exhibited specificity for female donors. 3α,5α-THDOC and SGE-516 inhibited TLR4 and TLR7 pathways only in females. These studies demonstrate anti-inflammatory effects of allopregnanolone in human macrophages for the first time and suggest that inhibition of pro-inflammatory cytokines/chemokines may contribute to its therapeutic actions.
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Affiliation(s)
- Irina Balan
- Department of Psychiatry, Department of Pharmacology, Bowles Center for Alcohol Studies, University of North Carolina at Chapel Hill, School of Medicine, Chapel Hill, NC, United States
| | - Laure Aurelian
- Stanford University School of Medicine, Stanford, CA, United States
| | - Kimberly S. Williams
- Department of Neurology, University of North Carolina at Chapel Hill, School of Medicine, Chapel Hill, NC, United States
| | - Brian Campbell
- Translational Sciences, Sage Therapeutics Inc., Cambridge, MA, United States
| | - Rick B. Meeker
- Department of Neurology, University of North Carolina at Chapel Hill, School of Medicine, Chapel Hill, NC, United States
| | - A. Leslie Morrow
- Department of Psychiatry, Department of Pharmacology, Bowles Center for Alcohol Studies, University of North Carolina at Chapel Hill, School of Medicine, Chapel Hill, NC, United States
- *Correspondence: A. Leslie Morrow,
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6
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Cerne R, Lippa A, Poe MM, Smith JL, Jin X, Ping X, Golani LK, Cook JM, Witkin JM. GABAkines - Advances in the discovery, development, and commercialization of positive allosteric modulators of GABA A receptors. Pharmacol Ther 2022; 234:108035. [PMID: 34793859 PMCID: PMC9787737 DOI: 10.1016/j.pharmthera.2021.108035] [Citation(s) in RCA: 51] [Impact Index Per Article: 25.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2021] [Accepted: 11/08/2021] [Indexed: 12/25/2022]
Abstract
Positive allosteric modulators of γ-aminobutyric acid-A (GABAA) receptors or GABAkines have been widely used medicines for over 70 years for anxiety, epilepsy, sleep, and other disorders. Traditional GABAkines like diazepam have safety and tolerability concerns that include sedation, motor-impairment, respiratory depression, tolerance and dependence. Multiple GABAkines have entered clinical development but the issue of side-effects has not been fully solved. The compounds that are presently being developed and commercialized include several neuroactive steroids (an allopregnanolone formulation (brexanolone), an allopregnanolone prodrug (LYT-300), Sage-324, zuranolone, and ganaxolone), the α2/3-preferring GABAkine, KRM-II-81, and the α2/3/5-preferring GABAkine PF-06372865 (darigabat). The neuroactive steroids are in clinical development for post-partum depression, intractable epilepsy, tremor, status epilepticus, and genetic epilepsy disorders. Darigabat is in development for epilepsy and anxiety. The imidazodiazepine, KRM-II-81 is efficacious in animal models for the treatment of epilepsy and post-traumatic epilepsy, acute and chronic pain, as well as anxiety and depression. The efficacy of KRM-II-81 in models of pharmacoresistant epilepsy, preventing the development of seizure sensitization, and in brain tissue of intractable epileptic patients bodes well for improved therapeutics. Medicinal chemistry efforts are also ongoing to identify novel and improved GABAkines. The data document gaps in our understanding of the molecular pharmacology of GABAkines that drive differential pharmacological profiles, but emphasize advancements in the ability to successfully utilize GABAA receptor potentiation for therapeutic gain in neurology and psychiatry.
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Affiliation(s)
- Rok Cerne
- Laboratory of Antiepileptic Drug Discovery, Ascension St. Vincent, Indianapolis, IN USA,Faculty of Medicine, University of Ljubljana, Zaloška cesta 4, Ljubljana, Slovenia.,RespireRx Pharmaceuticals Inc, Glen Rock, NJ, USA,Department of Anatomy and Cell Biology, Indiana University/Purdue University, Indianapolis, IN, USA
| | - Arnold Lippa
- RespireRx Pharmaceuticals Inc, Glen Rock, NJ, USA
| | | | - Jodi L. Smith
- Laboratory of Antiepileptic Drug Discovery, Ascension St. Vincent, Indianapolis, IN USA
| | - Xiaoming Jin
- Department of Anatomy and Cell Biology, Indiana University/Purdue University, Indianapolis, IN, USA
| | - Xingjie Ping
- Department of Anatomy and Cell Biology, Indiana University/Purdue University, Indianapolis, IN, USA
| | - Lalit K. Golani
- Department of Chemistry and Biochemistry, Milwaukee Institute of Drug Discovery, University of Wisconsin-Milwaukee, Milwaukee, WI, USA
| | - James M. Cook
- RespireRx Pharmaceuticals Inc, Glen Rock, NJ, USA,Department of Chemistry and Biochemistry, Milwaukee Institute of Drug Discovery, University of Wisconsin-Milwaukee, Milwaukee, WI, USA
| | - Jeffrey M. Witkin
- Laboratory of Antiepileptic Drug Discovery, Ascension St. Vincent, Indianapolis, IN USA,RespireRx Pharmaceuticals Inc, Glen Rock, NJ, USA,Department of Chemistry and Biochemistry, Milwaukee Institute of Drug Discovery, University of Wisconsin-Milwaukee, Milwaukee, WI, USA
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7
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Vien TN, Ackley MA, Doherty JJ, Moss SJ, Davies PA. Preventing Phosphorylation of the GABAAR β3 Subunit Compromises the Behavioral Effects of Neuroactive Steroids. Front Mol Neurosci 2022; 15:817996. [PMID: 35431797 PMCID: PMC9009507 DOI: 10.3389/fnmol.2022.817996] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2021] [Accepted: 03/09/2022] [Indexed: 11/26/2022] Open
Abstract
Neuroactive steroids (NASs) have potent anxiolytic, anticonvulsant, sedative, and hypnotic actions, that reflect in part their efficacy as GABAAR positive allosteric modulators (PAM). In addition to this, NAS exert metabotropic effects on GABAergic inhibition via the activation of membrane progesterone receptors (mPRs), which are G-protein coupled receptors. mPR activation enhances the phosphorylation of residues serine 408 and 409 (S408/9) in the β3 subunit of GABAARs, increasing their accumulation in the plasma membrane leading to a sustained increase in tonic inhibition. To explore the significance of NAS-induced phosphorylation of GABAARs, we used mice in which S408/9 in the β3 subunit have been mutated to alanines, mutations that prevent the metabotropic actions of NASs on GABAAR function while preserving NAS allosteric potentiation of GABAergic current. While the sedative actions of NAS were comparable to WT, their anxiolytic actions were reduced in S408/9A mice. Although the induction of hypnosis by NAS were maintained in the mutant mice the duration of the loss of righting reflex was significantly shortened. Finally, ability of NAS to terminate diazepam pharmacoresistant seizures was abolished in S408/9A mice. In conclusion, our results suggest that S408/9 in the GABAAR β3 subunit contribute to the anxiolytic and anticonvulsant efficacy of NAS, in addition to their ability to regulate the loss of righting reflex.
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Affiliation(s)
- Thuy N. Vien
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA, United States
| | - Michael A. Ackley
- Research and Non-clinical Development, Sage Therapeutics, Inc., Cambridge, MA, United States
| | - James J. Doherty
- Research and Non-clinical Development, Sage Therapeutics, Inc., Cambridge, MA, United States
| | - Stephen J. Moss
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA, United States
- *Correspondence: Stephen J. Moss,
| | - Paul A. Davies
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA, United States
- Paul A. Davies,
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8
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Diviccaro S, Cioffi L, Falvo E, Giatti S, Melcangi RC. Allopregnanolone: An overview on its synthesis and effects. J Neuroendocrinol 2022; 34:e12996. [PMID: 34189791 PMCID: PMC9285581 DOI: 10.1111/jne.12996] [Citation(s) in RCA: 27] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/25/2021] [Revised: 05/20/2021] [Accepted: 05/26/2021] [Indexed: 12/23/2022]
Abstract
Allopregnanolone, a 3α,5α-progesterone metabolite, acts as a potent allosteric modulator of the γ-aminobutyric acid type A receptor. In the present review, the synthesis of this neuroactive steroid occurring in the nervous system is discussed with respect to physiological and pathological conditions. In addition, its physiological and neuroprotective effects are also reported. Interestingly, the levels of this neuroactive steroid, as well as its effects, are sex-dimorphic, suggesting a possible gender medicine based on this neuroactive steroid for neurological disorders. However, allopregnanolone presents low bioavailability and extensive hepatic metabolism, limiting its use as a drug. Therefore, synthetic analogues or a different therapeutic strategy able to increase allopregnanolone levels have been proposed to overcome any pharmacokinetic issues.
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Affiliation(s)
- Silvia Diviccaro
- Dipartimento di Scienze Farmacologiche e BiomolecolariUniversità degli Studi di MilanoMilanoItaly
| | - Lucia Cioffi
- Dipartimento di Scienze Farmacologiche e BiomolecolariUniversità degli Studi di MilanoMilanoItaly
| | - Eva Falvo
- Dipartimento di Scienze Farmacologiche e BiomolecolariUniversità degli Studi di MilanoMilanoItaly
| | - Silvia Giatti
- Dipartimento di Scienze Farmacologiche e BiomolecolariUniversità degli Studi di MilanoMilanoItaly
| | - Roberto Cosimo Melcangi
- Dipartimento di Scienze Farmacologiche e BiomolecolariUniversità degli Studi di MilanoMilanoItaly
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9
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Morgan JE, Wilson SC, Travis BJ, Bagri KH, Pagarigan KT, Belski HM, Jackson C, Bounader KM, Coppola JM, Hornung EN, Johnson JE, McCarren HS. Refractory and Super-Refractory Status Epilepticus in Nerve Agent-Poisoned Rats Following Application of Standard Clinical Treatment Guidelines. Front Neurosci 2021; 15:732213. [PMID: 34566572 PMCID: PMC8462486 DOI: 10.3389/fnins.2021.732213] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2021] [Accepted: 08/16/2021] [Indexed: 12/24/2022] Open
Abstract
Nerve agents (NAs) induce a severe cholinergic crisis that can lead to status epilepticus (SE). Current guidelines for treatment of NA-induced SE only include prehospital benzodiazepines, which may not fully resolve this life-threatening condition. This study examined the efficacy of general clinical protocols for treatment of SE in the specific context of NA poisoning in adult male rats. Treatment with both intramuscular and intravenous benzodiazepines was entirely insufficient to control SE. Second line intervention with valproate (VPA) initially terminated SE in 35% of rats, but seizures always returned. Phenobarbital (PHB) was more effective, with SE terminating in 56% of rats and 19% of rats remaining seizure-free for at least 24 h. The majority of rats demonstrated refractory SE (RSE) and required treatment with a continuous third-line anesthetic. Both ketamine (KET) and propofol (PRO) led to high levels of mortality, and nearly all rats on these therapies had breakthrough seizure activity, demonstrating super-refractory SE (SRSE). For the small subset of rats in which SE was fully resolved, significant improvements over controls were observed in recovery metrics, behavioral assays, and brain pathology. Together these data suggest that NA-induced SE is particularly severe, but aggressive treatment in the intensive care setting can lead to positive functional outcomes for casualties.
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Affiliation(s)
- Julia E Morgan
- Neuroscience Department, US Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, MD, United States
| | - Sara C Wilson
- Neuroscience Department, US Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, MD, United States
| | - Benjamin J Travis
- Neuroscience Department, US Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, MD, United States
| | - Kathryn H Bagri
- Neuroscience Department, US Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, MD, United States
| | - Kathleen T Pagarigan
- Neuroscience Department, US Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, MD, United States
| | - Hannah M Belski
- Neuroscience Department, US Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, MD, United States
| | - Cecelia Jackson
- Neuroscience Department, US Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, MD, United States
| | - Kevin M Bounader
- Neuroscience Department, US Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, MD, United States
| | - Jessica M Coppola
- Neuroscience Department, US Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, MD, United States
| | - Eden N Hornung
- Neuroscience Department, US Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, MD, United States
| | - James E Johnson
- Comparative Pathology Department, US Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, MD, United States
| | - Hilary S McCarren
- Neuroscience Department, US Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, MD, United States
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10
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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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11
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Althaus AL, Ackley MA, Belfort GM, Gee SM, Dai J, Nguyen DP, Kazdoba TM, Modgil A, Davies PA, Moss SJ, Salituro FG, Hoffmann E, Hammond RS, Robichaud AJ, Quirk MC, Doherty JJ. Preclinical characterization of zuranolone (SAGE-217), a selective neuroactive steroid GABA A receptor positive allosteric modulator. Neuropharmacology 2020; 181:108333. [PMID: 32976892 PMCID: PMC8265595 DOI: 10.1016/j.neuropharm.2020.108333] [Citation(s) in RCA: 70] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2020] [Revised: 08/26/2020] [Accepted: 09/18/2020] [Indexed: 01/04/2023]
Abstract
Zuranolone (SAGE-217) is a novel, synthetic, clinical stage neuroactive steroid GABAA receptor positive allosteric modulator designed with the pharmacokinetic properties to support oral daily dosing. In vitro, zuranolone enhanced GABAA receptor current at nine unique human recombinant receptor subtypes, including representative receptors for both synaptic (γ subunit-containing) and extrasynaptic (δ subunit-containing) configurations. At a representative synaptic subunit configuration, α1β2γ2, zuranolone potentiated GABA currents synergistically with the benzodiazepine diazepam, consistent with the non-competitive activity and distinct binding sites of the two classes of compounds at synaptic receptors. In a brain slice preparation, zuranolone produced a sustained increase in GABA currents consistent with metabotropic trafficking of GABAA receptors to the cell surface. In vivo, zuranolone exhibited potent activity, indicating its ability to modulate GABAA receptors in the central nervous system after oral dosing by protecting against chemo-convulsant seizures in a mouse model and enhancing electroencephalogram β-frequency power in rats. Together, these data establish zuranolone as a potent and efficacious neuroactive steroid GABAA receptor positive allosteric modulator with drug-like properties and CNS exposure in preclinical models. Recent clinical data support the therapeutic promise of neuroactive steroid GABAA receptor positive modulators for treating mood disorders; brexanolone is the first therapeutic approved specifically for the treatment of postpartum depression. Zuranolone is currently under clinical investigation for the treatment of major depressive episodes in major depressive disorder, postpartum depression, and bipolar depression.
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Affiliation(s)
- Alison L Althaus
- Research and Nonclinical Development, Sage Therapeutics, Inc., Cambridge, MA, USA.
| | - Michael A Ackley
- Research and Nonclinical Development, Sage Therapeutics, Inc., Cambridge, MA, USA
| | - Gabriel M Belfort
- Research and Nonclinical Development, Sage Therapeutics, Inc., Cambridge, MA, USA
| | - Steven M Gee
- Research and Nonclinical Development, Sage Therapeutics, Inc., Cambridge, MA, USA
| | - Jing Dai
- Research and Nonclinical Development, Sage Therapeutics, Inc., Cambridge, MA, USA
| | - David P Nguyen
- Research and Nonclinical Development, Sage Therapeutics, Inc., Cambridge, MA, USA
| | - Tatiana M Kazdoba
- Research and Nonclinical Development, Sage Therapeutics, Inc., Cambridge, MA, USA
| | - Amit Modgil
- Department of Neuroscience, Tufts University, Boston, MA, USA
| | - Paul A Davies
- Department of Neuroscience, Tufts University, Boston, MA, USA
| | - Stephen J Moss
- Department of Neuroscience, Tufts University, Boston, MA, USA
| | - Francesco G Salituro
- Research and Nonclinical Development, Sage Therapeutics, Inc., Cambridge, MA, USA
| | - Ethan Hoffmann
- Research and Nonclinical Development, Sage Therapeutics, Inc., Cambridge, MA, USA
| | - Rebecca S Hammond
- Research and Nonclinical Development, Sage Therapeutics, Inc., Cambridge, MA, USA
| | - Albert J Robichaud
- Research and Nonclinical Development, Sage Therapeutics, Inc., Cambridge, MA, USA
| | - Michael C Quirk
- Research and Nonclinical Development, Sage Therapeutics, Inc., Cambridge, MA, USA
| | - James J Doherty
- Research and Nonclinical Development, Sage Therapeutics, Inc., Cambridge, MA, USA
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Aroniadou-Anderjaska V, Apland JP, Figueiredo TH, De Araujo Furtado M, Braga MF. Acetylcholinesterase inhibitors (nerve agents) as weapons of mass destruction: History, mechanisms of action, and medical countermeasures. Neuropharmacology 2020; 181:108298. [DOI: 10.1016/j.neuropharm.2020.108298] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2020] [Revised: 08/21/2020] [Accepted: 09/02/2020] [Indexed: 02/07/2023]
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13
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Giatti S, Diviccaro S, Falvo E, Garcia-Segura LM, Melcangi RC. Physiopathological role of the enzymatic complex 5α-reductase and 3α/β-hydroxysteroid oxidoreductase in the generation of progesterone and testosterone neuroactive metabolites. Front Neuroendocrinol 2020; 57:100836. [PMID: 32217094 DOI: 10.1016/j.yfrne.2020.100836] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/27/2020] [Revised: 03/04/2020] [Accepted: 03/18/2020] [Indexed: 12/22/2022]
Abstract
The enzymatic complex 5α-reductase (5α-R) and 3α/3β-hydroxysteroid oxidoreductase (HSOR) is expressed in the nervous system, where it transforms progesterone (PROG) and testosterone (T) into neuroactive metabolites. These metabolites regulate myelination, brain maturation, neurotransmission, reproductive behavior and the stress response. The expression of 5α-R and 3α-HSOR and the levels of PROG and T reduced metabolites show regional and sex differences in the nervous system and are affected by changing physiological conditions as well as by neurodegenerative and psychiatric disorders. A decrease in their nervous tissue levels may negatively impact the course and outcome of some pathological events. However, in other pathological conditions their increased levels may have a negative impact. Thus, the use of synthetic analogues of these steroids or 5α-R modulation have been proposed as therapeutic approaches for several nervous system pathologies. However, further research is needed to fully understand the consequences of these manipulations, in particular with 5α-R inhibitors.
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Affiliation(s)
- Silvia Giatti
- Dipartimento di Scienze Farmacologiche e Biomolecolari, Università degli Studi di Milano, Milan, Italy
| | - Silvia Diviccaro
- Dipartimento di Scienze Farmacologiche e Biomolecolari, Università degli Studi di Milano, Milan, Italy
| | - Eva Falvo
- Dipartimento di Scienze Farmacologiche e Biomolecolari, Università degli Studi di Milano, Milan, Italy
| | - Luis Miguel Garcia-Segura
- Instituto Cajal, Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain; Centro de Investigación Biomédica en Red de Fragilidad y Envejecimiento Saludable (CIBERFES), Instituto de Salud Carlos III, Madrid, Spain
| | - Roberto Cosimo Melcangi
- Dipartimento di Scienze Farmacologiche e Biomolecolari, Università degli Studi di Milano, Milan, Italy.
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14
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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] [Abstract] [Key Words] [MESH Headings] [Grants] [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.
| | - 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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15
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Abstract
This article describes current pursuits for developing novel antidotes for organophosphate (OP) intoxication. Recent mechanistic studies of benzodiazepine-resistant seizures have key consequences for victims of OP pesticide and nerve agent attacks. We uncovered why current therapies are not able to stop the OP-induced seizures and brain cell death and what type of drug might be better. OP exposure down regulates critical inhibitory GABA-A receptors, kills neurons, and causes massive neuroinflammation that will cause more neuronal death, which causes the problem of too few benzodiazepine receptors. The loss of inhibitory interneurons creates a self-sustaining seizure circuit and refractory status epilepticus. Thus, there is an urgent need for mechanism-based, new antidotes for OP intoxication. We have discovered neurosteroids as next-generation anticonvulsants superior to midazolam for the treatment of OP poisoning. Neurosteroids that activate both extrasynaptic and synaptic GABA-A receptors have the potential to stop seizures more effectively and safely than benzodiazepines. In addition, neurosteroids confers robust neuroprotection by reducing neuronal injury and neuroinflammation. The synthetic neurosteroid ganaxolone is being considered for advanced development as a future anticonvulsant for nerve agents. Experimental studies shows striking efficacy of ganaxolone and its analogs in OP exposure models. They are also effective in attenuating long-term neuropsychiatric deficits caused by OP exposure. Overall, neurosteroids represent rational anticonvulsants for OP intoxication, even when given late after exposure.
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16
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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] [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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17
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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: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2018] [Revised: 02/05/2019] [Accepted: 02/14/2019] [Indexed: 12/26/2022]
Abstract
INTRODUCTION Organophosphorus nerve agents (OPNAs) irreversibly block acetylcholinesterase activity, resulting in accumulation of excess acetylcholine at neural synapses, which can lead to a state of prolonged seizures known as status epilepticus (SE). Benzodiazepines, the current standard of care for SE, become less effective as latency to treatment increases. In a mass civilian OPNA exposure, concurrent trauma and limited resources would likely cause a delay in first response time. To address this issue, we have developed a rat model to test novel anticonvulsant/ neuroprotectant adjuncts at delayed time points. METHODS For model development, adult male rats with cortical electroencephalographic (EEG) electrodes were exposed to soman and administered saline along with atropine, 2-PAM, and midazolam 5, 20, or 40 min after SE onset. We validated our model using three drugs: scopolamine, memantine, and phenobarbital. Using the same procedure outlined above, rats were given atropine, 2-PAM, midazolam and test treatment 20 min after SE onset. RESULTS Using gamma power, delta power, and spike rate to quantify EEG activity, we found that scopolamine was effective, memantine was minimally effective, and phenobarbital had a delayed effect on terminating SE. Fluoro-Jade B staining was used to assess neuroprotection in five brain regions. Each treatment provided significant protection compared to saline + midazolam in at least two brain regions. DISCUSSION Because our data agree with previously published studies on the efficacy of these compounds, we conclude that this model is a valid way to test novel anticonvulsants/ neuroprotectants for controlling benzodiazepine-resistant OPNA-induced SE and subsequent neuropathology.
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Affiliation(s)
| | | | | | | | - Hilary S. McCarren
- Corresponding author at: U.S. Army Medical Research Institute of Chemical Defense, 8350 Ricketts Point Road, Aberdeen Proving Ground, MD 21010, USA
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18
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Abstract
Status epilepticus (SE) is a medical emergency characterized by uncontrolled, prolonged seizures with rapid and widespread neuronal damage. Patients that suffer from longer episodes of SE are more likely to have poorer clinical outcomes and a higher cost of healthcare. Understanding novel molecular mechanisms that regulate inhibitory and excitatory neurotransmission that initiate SE and the necessary medical infrastructure to stop SE could help identify targets for early intervention. Intranasal administration of benzodiazepines may shorten the time between initiation and cessation of seizures when compared to other routes of administration. Current pharmaceutical administration guidelines are appropriate for sporadic incidences of SE, but exploring other approaches is necessary to prepare for situations involving multiple patients outside of a hospital, such as a massive chemical weapons attack. Intranasal drug delivery helps to circumvent the blood–brain barrier and offers a noninvasive way to quickly administer drugs in settings that require an immediate response, such as nerve agent exposure. In addition, examining the intranasal delivery of new drugs, such as nanotherapeutics, may lead to more effective, noninvasive, scalable, and portable methods of treating SE.
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19
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Amengual-Gual M, Sánchez Fernández I, Wainwright MS. Novel drugs and early polypharmacotherapy in status epilepticus. Seizure 2018; 68:79-88. [PMID: 30473267 DOI: 10.1016/j.seizure.2018.08.004] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2018] [Accepted: 08/05/2018] [Indexed: 12/11/2022] Open
Abstract
PURPOSE Rescue medications for status epilepticus (SE) have a relatively high rate of failure. The purpose of this review is to summarize the evidence for the efficacy of novel drugs and early polypharmacotherapy for SE. METHOD Literature review. RESULTS New drugs and treatment strategies aim to target the pathophysiology of SE in order to improve seizure control and outcomes. Changes at the synapse level during SE include a progressive decrease in synaptic GABAA receptors and increase in synaptic NMDA receptors. These changes tend to promote self-sustaining seizures. Current SE guidelines recommend a rapid stepwise treatment using benzodiazepines in monotherapy as the first-line treatment, targeting GABAA synaptic receptors. Novel treatment approaches target GABAA synaptic and extrasynaptic receptors with allopregnanolone, and NMDA receptors with ketamine. Novel rescue treatments used for SE include topiramate, brivaracetam, and perampanel, which are already marketed in epilepsy. Some available drugs not marketed for use in epilepsy have been used in the treatment of SE, and other agents are being studied for this purpose. Early polytherapy, most frequently combining a benzodiazepine with a second-line drug or an NMDA receptor antagonist, might potentially increase seizure control with relatively minor increase in side effects. Although many preclinical studies support novel drugs and early polytherapy in SE, human studies are scarce and inconclusive. Currently, evidence is lacking to recommend specific combinations of these new agents. CONCLUSIONS Novel drugs and strategies target the underlying pathophysiology of SE with the intent to improve seizure control and outcomes.
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Affiliation(s)
- Marta Amengual-Gual
- Division of Epilepsy and Clinical Neurophysiology, Department of Neurology, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA; Pediatric Neurology Unit, Department of Pediatrics, Hospital Universitari Son Espases, Universitat de les Illes Balears, Palma, Spain.
| | - Iván Sánchez Fernández
- Division of Epilepsy and Clinical Neurophysiology, Department of Neurology, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA; Department of Child Neurology, Hospital Sant Joan de Déu, Universidad de Barcelona, Spain
| | - Mark S Wainwright
- Department of Neurology, Division of Pediatric Neurology. University of Washington School of Medicine, Seattle, WA, USA
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20
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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: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2017] [Revised: 12/21/2017] [Accepted: 01/07/2018] [Indexed: 12/15/2022]
Abstract
Nerve agents are highly toxic chemicals that pose an imminent threat to soldiers and civilians alike. Nerve agent exposure leads to an increase in acetylcholine within the central nervous system, resulting in development of protracted seizures known as status epilepticus (SE). Currently, benzodiazepines are the standard of care for nerve agent-induced SE, but their efficacy quickly wanes as the time to treatment increases. Here, we examine the role of the α2-adrenoceptor in termination of nerve agent-induced SE using the highly specific agonist dexmedetomidine (DEX). Adult male rats were exposed to soman and entered SE as confirmed by electroencephalograph (EEG). We observed that administration of DEX in combination with the benzodiazepine midazolam (MDZ) 20 or 40 min after the onset of SE stopped seizures and returned processed EEG measurements to baseline levels. The protective effect of DEX was blocked by the α2-adrenoceptor antagonist atipamezole (ATI), but ATI failed to restore seizure activity after it was already halted by DEX in most cases, suggesting that α2-adrenoceptors may be involved in initiating SE cessation rather than merely suppressing seizure activity. Histologically, treatment with DEX + MDZ significantly reduced the number of dying neurons as measured by FluoroJade B in the amygdala, thalamus, and piriform cortex, but did not protect the hippocampus or parietal cortex even when SE was successfully halted. We conclude that DEX serves not just as a valuable potential addition to the anticonvulsant regimen for nerve agent exposure, but also as a tool for dissecting the neural circuitry that drives SE.
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Affiliation(s)
- Hilary S McCarren
- USAMRICD, Medical Toxicology Research Division, Neuroscience Branch, 2900 Ricketts Point Rd, Aberdeen Proving Ground, MD 21010, United States.
| | - Julia A Arbutus
- USAMRICD, Medical Toxicology Research Division, Neuroscience Branch, 2900 Ricketts Point Rd, Aberdeen Proving Ground, MD 21010, United States
| | - Cherish Ardinger
- USAMRICD, Medical Toxicology Research Division, Neuroscience Branch, 2900 Ricketts Point Rd, Aberdeen Proving Ground, MD 21010, United States
| | - Emily N Dunn
- USAMRICD, Medical Toxicology Research Division, Neuroscience Branch, 2900 Ricketts Point Rd, Aberdeen Proving Ground, MD 21010, United States
| | - Cecelia E Jackson
- USAMRICD, Medical Toxicology Research Division, Neuroscience Branch, 2900 Ricketts Point Rd, Aberdeen Proving Ground, MD 21010, United States
| | - John H McDonough
- USAMRICD, Medical Toxicology Research Division, Neuroscience Branch, 2900 Ricketts Point Rd, Aberdeen Proving Ground, MD 21010, United States
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21
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Hawkins NA, Lewis M, Hammond RS, Doherty JJ, Kearney JA. The synthetic neuroactive steroid SGE-516 reduces seizure burden and improves survival in a Dravet syndrome mouse model. Sci Rep 2017; 7:15327. [PMID: 29127345 PMCID: PMC5681541 DOI: 10.1038/s41598-017-15609-w] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2017] [Accepted: 10/30/2017] [Indexed: 12/31/2022] Open
Abstract
Dravet syndrome is an infant-onset epileptic encephalopathy with multiple seizure types that are often refractory to conventional therapies. Treatment with standard benzodiazepines like clobazam, in combination with valproate and stiripentol, provides only modest seizure control. While benzodiazepines are a first-line therapy for Dravet syndrome, they are limited by their ability to only modulate synaptic receptors. Unlike benzodiazepines, neuroactive steroids potentiate a wider-range of GABAA receptors. The synthetic neuroactive steroid SGE-516 is a potent positive allosteric modulator of both synaptic and extrasynaptic GABAA receptors. Prior work demonstrated anticonvulsant activity of SGE-516 in acute seizure assays in rodents. In this study, we evaluated activity of SGE-516 on epilepsy phenotypes in the Scn1a+/− mouse model that recapitulates many features of Dravet syndrome, including spontaneous seizures, premature death and seizures triggered by hyperthermia. To evaluate SGE-516 in Scn1a+/− mice, we determined the effect of treatment on hyperthermia-induced seizures, spontaneous seizure frequency and survival. SGE-516 treatment protected against hyperthermia-induced seizures, reduced spontaneous seizure frequency and prolonged survival in the Scn1a+/− mice. This provides the first evidence of SGE-516 activity in a mouse model of Dravet syndrome, and supports further investigation of neuroactive steroids as potential anticonvulsant compounds for refractory epilepsies.
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Affiliation(s)
- Nicole A Hawkins
- Department of Pharmacology Northwestern University Feinberg School of Medicine, Chicago, IL, USA
| | - Michael Lewis
- Drug Discovery and Development Sage Therapeutics, Cambridge, MA, USA
| | - Rebecca S Hammond
- Drug Discovery and Development Sage Therapeutics, Cambridge, MA, USA
| | - James J Doherty
- Drug Discovery and Development Sage Therapeutics, Cambridge, MA, USA
| | - Jennifer A Kearney
- Department of Pharmacology Northwestern University Feinberg School of Medicine, Chicago, IL, USA.
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