Mitigation of Neurological Damage Following Seizures

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Project Summary – Project 3 Convulsant chemical threat agents, such as the GABAA receptor blocker tetramethylenedisulfotetramine (TETS) and the organophosphate (OP) cholinesterase inhibitor diisopropylfluorophosphate (DFP), can trigger seizures that progress to life-threatening status epilepticus (SE). Survivors face significant, long-term morbidity, including mild-to-severe memory loss, affective disorders and recurrent seizures (epilepsy). Current medical counter- measures fail to sufficiently protect against these neurological deficits. It is hypothesized that neuroprotection will be enhanced by: (1) improving seizure control, and (2) combining antiseizure treatment with agents that mitigate neuroinflammation and/or Ca2+ dysregulation. During the first project period, we developed a mouse model of TETS-induced SE and refined a rat model of DFP-induced SE for use in neuroprotection studies. Using these preclinical models, Projects 1 and 2 showed that allopregnanolone, a positive allosteric modulator of GABAA receptors, was a superior countermeasure for TETS-induced SE, particularly when administered at delayed times. Allopregnanolone alone or in combination with midazolam did not terminate DFP-induced SE, but the combined intramuscular administration of midazolam, allopregnanolone and a low dose of perampanel, a potent AMPA receptor antagonist, was highly effective in terminating DFP-induced behavioral and electrographic SE without causing significant sedation. We also discovered in a screen of candidate neuro- protectants that post-exposure treatment with dantrolene, a Ca2+ channel stabilizer, reduced neurodegeneration, and that a novel small molecule dual inhibitor of soluble epoxide hydrolase (sEH) and cyclooxygenase-2 (COX- 2) attenuated microglial activation. Core A found that sEH inhibitors (sEHI) also normalized the hypotension associated with high-dose diazepam or midazolam. In the second project period, we will quantify the effects of antiseizure and neuroprotective treatments on neurodegenerative, neuroinflammatory and functional outcomes using in vivo imaging to longitudinally monitor brain damage with corroborative histology, 24 h video electroencephalography to quantify recurrent seizures, and behavioral assessments of cognitive, affective and motor function. Our goals are to: (1) obtain neuroprotection data to support the advance of our antiseizure lead allopregnanolone; (2) obtain proof-of-concept neuroprotective efficacy data for perampanel alone or in combination with allopregnanolone; and (3) identify neuroprotectant leads, with an initial focus on our most promising candidate compounds: sEHI, the dual sEH-COX-2 inhibitor and dantrolene. We will continue testing additional antiseizure candidates identified by Project 2 and novel neuroprotective treatments identified in Project 1 using in vitro models. Superior neuroprotective treatments identified in this project will be tested by Project 2 to assess whether they interact with antiseizure treatments. Results from this project will support transition of allopregnanolone to advanced development and assess whether perampanel, other candidate antiseizure treatments, or candidate neuroprotective treatments, should become development leads.