Abstracts

Rationale: Pilocarpine-induced status epilepticus (SE) activates the JAK/STAT pathway in the dentate gyrus (DG) of the hippocampus. Decreased transcription of GABA_A receptor ?1 subunit (GABAR?1) after SE is mediated by ICER and phosphorylated cAMP response element-binding protein (CREB) binding to the GABAR?1 CRE site. Infusion of pyridone 6 (P6), a pan-JAK inhibitor, blocks JAK/STAT pathway activation after SE as shown by the absence of increases in pSTAT3 protein levels, blockage of increases in protein and mRNA expression of inducible cAMP early repressor (ICER), and the consequential reduction in downregulation of the ?1 subunit in the DG. These distinctive properties suggest that JAK/STAT inhibitors may be a novel addition to current therapy for refractory seizures, which occur in ~40% of temporal lobe epilepsy (TLE) patients. Methods: Four weeks after SE was induced, epileptic rats were sacrificed within 3-4 hours after a spontaneous seizure to determine protein levels of ICER and pSTAT3 in microdissected DG of hippocampus. To further evaluate the potential disease modifying effects of JAK/STAT inhibitors, SE rats (i.e., pooled SE only (n=2) and SE DMSO (n=7)) were compared to SE rats treated with 50 mg/kg WP1066 i.p. at onset of SE and 50-100 mg/kg WP1066 i.p. 1 hour after SE onset (n=4). Results: Current studies demonstrate that spontaneous recurrent seizures that define chronic epilepsy reactivate the JAK/STAT pathway, specifically that increased levels of pSTAT3 are expressed in the DG within 3 hours of a spontaneous seizure in pilocarpine-treated rats 4 weeks after SE relative to control rats that received a subconvulsive dose of pilocarpine, did not experience SE, and did not have spontaneous seizures. Increased levels of ICER protein expression were also observed in the DG of chronically epileptic rats sacrificed within 3 hours of a spontaneous seizure when compared to age-matched controls without spontaneous seizures, but this was not a statistically significant difference. WP1066 administration (i.p.) at the onset of SE effectively blocked increases in pSTAT3 in DG 6 hrs after SE onset. Continuous video-EEG monitoring for two weeks demonstrated that administration of i.p. WP1066 at onset of pilocarpine-induced SE significantly reduces the duration of SE 3-fold and impedes the progressive increase in spontaneous seizure number over time observed in SE only and SE DMSO rats. Latency to first seizure was not affected by WP1066 administration; and the first spontaneous seizure appeared at 3-7 days after SE for untreated rats or rats treated with DMSO and 4-9 days after SE for WP1066 treated rats. Conclusions: This data suggests that 100-150 mg/kg total WP1066 treatment at SE potentially reduces the severity and duration of SE, and slows the acquisition of increasing seizure frequencies over time inherent to post-SE models, suggesting that JAK/ STAT inhibitors may reduce the progression of epileptogenesis and be disease modifying. Continuous video-EEG monitoring from SE for a longer duration with more animals is required to further evaluate this hypothesis.