Abstracts

Rationale: Pilocarpine-induced status epilepticus (SE), which results in temporal lobe epilepsy (TLE) in rodents, activates the JAK/STAT pathway. Previous studies have demonstrated inhibition of STAT3 phosphorylation by WP1066 early after SE onset reduces later spontaneous seizure frequency. STAT3 affects many different signaling families including those in cell cycle progression, cellular proliferation, cell survival, and angiogenesis. These studies aim to determine whether WP1066 inhibition results in altered STAT3-regulated gene transcription to identify potential mediators of the antiepileptogenic effects of WP1066. Methods: Potential changes in STAT3-regulated genes including c-myc, mcl-1, bcl-2, bcl-xl, cyclin D1, VEGF and ICER were evaluated in microdissected dentate gyrus (DG) via RT-PCR 6 h and 24 h after pilocarpine-induced SE. To assess whether early inhibition of STAT3 phosphorylation could suppress changes in expression of STAT3 target genes in the DG during early epileptogenesis, RT-PCR was used to quantify mRNA levels of cyclin D1, c-myc, mcl-1, bcl-xl, and ICER in DG 24 h after SE and WP1066 (50 mg/kg at onset of SE and 50 mg/kg 45 minutes later) or vehicle treatment. Results: SE caused a significant increase in c-myc (p<0.001), mcl-1 (p<0.01), and ICER (p<0.001) mRNA expression in DG of rats 6 h after SE compared to controls. SE also induced significant increases in c-myc (p<0.01), cyclin D1 (p<0.01), bcl-xl (p<0.05), and mcl-1 (p<0.01), and ICER (p<0.01) 24 h after SE. Cyclin D1 mRNA expression was 58.3% lower (p<0.001) and mcl-1 mRNA expression was reduced by 27.8% (p<0.01) in WP1066 treated rats 24 h after SE onset relative to vehicle treated rats. WP1066 results in no significant change in other STAT3-target genes at 24 hours after SE.Conclusions: Early WP1066 administration reduces known downstream targets of STAT3 transcription 24 hours after SE including cyclin D1 and mcl-1 levels, known for their roles in cell-cycle progression and cell survival, respectively. These findings uncover a potential effect of the JAK/STAT pathway after brain injury that is physiologically important and may provide a new therapeutic target that can be harnessed for the prevention of epilepsy development and/or progression.