Abstracts

Rationale: Status epilepticus (SE) is a dynamic condition in which EEG patterns and clinical behavior evolve if seizure activity continues. To understand the pathophysiology of SE we studied hippocampal expression of microRNAs in rats at defined EEG stages of SE (Treiman et al., Epilepsy Res 5:49-60, 1990). Methods: Five days after implantation of epidural screw electrodes, SE was induced in 180g male Sprague-Dawley rats by 3 mmol/kg LiCl IP followed 20 hours later by pilocarpine, 30mg/kg SC. Control rats were given LiCl plus saline and did not develop SE. Experimental rats were sacrificed 5 minutes after onset of SE EEG stage I, III, and V by isoflurane anesthetization and decapitation. Brains were removed and dissected for hippocampal samples. MicroRNA was extracted, pooled, and then amplified by PCR and analyzed using Qiagen miRNOME miRNA PCR arrays. Statistical significance was set at p < 0.05 using a Student’s t-test. Results: Seventy-four miRNAs were significantly deregulated in animals subjected to SE at one or more EEG stage compared with controls. Of the miRNAs with significantly altered expression during SE, 9 displayed expression changes across multiple EEG stages: rno-miR-139-3p, Rno-miR-206-3p, Rno-miR-760-3p, Rno-miR-383-5p, Rno-miR-101a-5p, Rno-miR-770-5p, Rno-mir-294, Rno-mir-328a-5p and Rno-miR-2985. Four (Rno-mir-2985, Rno-mir-101a-5p, Rno-mir-294, Rno-mir-328a-5p) exhibited a pattern of initial downregulation and subsequent upregulation similar to that we observed in certain messenger RNAs in rat brains at specific SE EEG stages (Treiman et al., Epilepsia 56(Suppl 1):260, 2015). Conclusions: A subgroup of miRNAs displayed deregulation of expression across specific EEG stages during the progression of experimental SE. The observations may provide further insight into the underlying pathophysiology of SE and dynamic changes that occur during ongoing SE. The functional roles of these miRNAs are only beginning to be understood. Rno-miR-139-3p targets norrin cysteine knot growth factor; disorders attributed to norrin include seizures and behavioral disorders. Rno-miR-206-3p targets BDNF in humans. Rno-miR-760-3p targets KCNJ3, a K+ voltage-gated channel member. Rno-miR-383-5p may target transforming growth factor-ß receptor 1 and has been associated with seizure-like activity in rat cortical slices. Rno-miR-101a-5p targets glutamate decarboxylase 1 (GAD1), which catalyzes GABA synthesis. Rno-miR-770-5p may regulate GAP43, a significant protein in neurite formation/regeneration and plasticity, and Rno-mir-294 targets proteolipid protein 1 (PLP1), one of the main proteins found in CNS myelin. Finally, Rno-mir-328a-5p (mir-328 in humans) targets c-type lectin domain family 2 member B (CLEC2B). Members of this family have inflammatory and immune response roles. This is the first study to evaluate acute miRNA expression changes in defined EEG stages of SE. Funding: Supported by the Barrow Neurological Foundation.