Abstracts

Rationale: Animal model studies have implicated oxidative stress and inflammation in the pathogenesis of chronic epilepsy and its associated co-morbidities. The two cellular processes are tightly regulated by the coordinated activity of two pleiotropic transcription factors: the nuclearfactor-2 erythroid related factor-2 (Nrf2) and the nuclear factor-kappa light chain enhancer of B cells (NF-κB). Nrf2 is a redox regulated transcription factor involved in regulating antioxidant responses, while NF-κB has critical immunologic functions. The present study was aimed to evaluate the activation status of Nrf2 and NF-κB signaling in human temporal lobe epilepsy (TLE), with the hypothesis that this balance may be altered and could represent a basis for increased excitability and cognitive dysfunction. Methods: Hippocampal and cortical TLE samples were prospectively collected following brain surgeries performed for resection of epileptogenic region at the Hospital of the University of Pennsylvania (n=13, ages 20-56 years). These were compared to age and region matched control autopsy samples (n=6, ages 17-58 years) obtained from the NIH NeuroBioBank. The study was approved by the local Institutional Review Board. The expression levels of Nrf2- regulated protein NAD(P)H:quinone oxidoreductase 1 (NQO1), NF-κβ p65 subunit, phospho-NF-κβ p65 (Ser536), and astrocytic and microglial markers GFAP and CD11b were quantified by Western blotting. Student’s t-tests were used to determine statistical significance (p < 0.05). Results: NQO1 levels were significantly downregulated in both hippocampus (62% of control, p < 0.001) and temporal lobe cortex (56% of control, p < 0.001). In contrast, levels of total NF-kβ p65 and active phospho-NF-kβ p65 (Ser536) were significantly increased in hippocampus (426% of control, p < 0.0001 and 2397% of control, p < 0.05 respectively), as well as in the cortex (437%, p < 0.001 and 950%, p < 0.05 respectively). The expression levels of GFAP and CD11b were significantly increased only in hippocampus (267% for GFAP and 223% for CD11b; p < 0.01). Conclusions: Our data indicate that the TLE brain, in particularly the hippocampus, may be more vulnerable to oxidative damage and inflammation due to diminished Nrf2 and enhanced NF-κB signaling. Therapies that induce Nrf2 signaling, or inhibit pro-inflammatory NF-κB activities may be useful to restore cellular homeostasis and improve clinical outcome in TLE patients. Funding: University Research Foundation. NIHR01NS031718. Control human tissue was obtained from University of Maryland Brain and Tissue Bank, which is a Brain and Tissue Repository of the NIH NeuroBioBank.