Abstracts

Rationale: Epileptogenesis occurs in approximately 50% of people whose first seizure was attributed to an episode of status epilepticus (SE). Thus it is known that SE increases the risk that an individual will develop epilepsy but the underlying pathophysiological mechanisms of post-SE epileptogenesis are not well understood. This study sought to further elaborate on findings related to miRNA expression changes due to SE. Methods: Thirty-seven adult male Sprague-Dawley rats were implanted with depth wire electrodes for continuous electrocorticography (EEG) recording. Following surgery, SE was induced by injection of 3mmol/kg LiCl IP followed 20 hours later by pilocarpine, 30mg/kg SC. SE was stopped using an AED cocktail consisting of 10mg/kg diazepam plus 35mg/kg phenobarbital IP at EEG Stage V (Treiman et al., Epilepsy Res 5:49-60, 1990). Following this episode of SE, rats were then continuously monitored using a 128 channel Xltek EEG recording machine system for 16 weeks to determine the time of onset, frequency, and duration of spontaneous seizures. Blood samples were collected prior to surgery as well as 4, 8, 12, and 16 weeks post-surgery and stored in Qiagen RNAprotect Animal Blood Tubes. MicroRNA was extracted, pooled, and then amplified by polymerase chain reaction and analyzed using Qiagen miRNOME miRNA PCR arrays. Statistical significance was set at p < 0.05 using a Student’s t-test. Results: Three miRNAs were found to have significantly altered expression in animals subjected to chemically induced SE which went on to develop epilepsy: Rno-miR-3579, Rno-miR-298-3p, and Rno-miR-466c-3p. Both rno-miR-3579 and rno-miR-466c-3p were upregulated (+1.34/+2.58 fold change) while rno-miR-298-3p was downregulated compared to control samples. Rno-miR-298-3p displayed opposite deregulation compared to EEG Stage V hippocampal tissue from a related study (Schooley et al., this meeting). Conclusions: A small group of miRNAs were observed to be dysregulated compared to control blood samples after seizure onset. This study sought to determine if blood miRNAs were altered in response to epileptogenesis. Initial results displayed three miRNAs with altered expression, two of which have potential gene targets that have been associated with epilepsy: rno-miR-298-3p and rno-miR-466c-3p. The results of this study suggest that there may be a predictable underlying miRNA pathophysiology due to SE and epileptogenesis. Further investigation is needed to better characterize and expand upon the miRNAs which were found to be significantly altered. Rno-miR-298 may potentially target SLC4A10, which helps regulate the intracellular pH of neurons and the pH of the brain’s extracellular fluid and has been associated with complex partial epilepsy. In humans, hsa-miR-466 may help regulate the LGI1 gene which has been linked to autosomal dominant lateral temporal epilepsy. Funding: Supported by the Barrow Neurological Foundation.