Abstracts

Rationale: Knowledge about the mechanisms of the progression of drug-resistant temporal lobe epilepsy (TLE) remain limited. An in-depth understanding of molecular pathophysiological processes is crucial for the rational selection of innovative biomarkers and target candidates. The current study assessed the proteomic and metabolomic changes in a rat model of chronic drug-resistant TLE treated with or without antiepileptic agents. Methods: Eleven-week old Wistar rats underwent kainic acid induced-status epilepticus (SE) for four hours. Nine weeks post-SE, rats were implanted with EEG recording electrodes and video-EEG was recorded for one week. After this initial EEG recording period, rats were randomly assigned to one of four treatment groups delivered through osmotic pumps for four weeks: post-SE + sodium selenate (1mg/kg/day, n=8); post-SE + levetiracetam (200mg/kg/day, n=8); post-SE + vehicle (n=8); sham (n=8). Animals underwent 1 week of EEG recordings before treatment, during treatment and 8 weeks after the last day of treatment. 24 weeks after the induction of SE, hippocampus and somatosensory cortex (SCx) were immediately dissected and snap frozen for proteomic and metabolomics analyses. Results: Following drug washout, post-SE animals treated with sodium selenate had fewer seizures (p< 0.05) per day when compared to vehicle-treated animals. In the hippocampus, proteome analysis showed a >2-fold expression change of glutamate receptor 1 (Gria1), voltage-gated calcium channel gamma subunit, nitric oxide synthase (Nos1), neurosecretory protein VGF, protein S100 (S100a4), CD44, annexin 1 and calretinin in SE-animals relevant to shams. In SCx, a >2-fold increase in expression of protein kinase C (PKC), GABA receptor subunit alpha, metabotropic glutamate receptor 2, zinc transporter 3, brain acid soluble protein, phosphatidylinositol kinase and synaptotagmin 1 was observed post-SE animals relevant to shams. In contrast, treatment with sodium selenate reduced the protein changes observed in the animals treated with vehicle and levetiracetam in both the hippocampus and SCx. Moreover, sodium selenate treatment reduced the expression of Ras, an important signalling pathway involved in NMDA mediated excitotoxic neuronal damage in comparison to vehicle and levetiracetam treated rats. Metabolomics, protein network, and pathway analysis studies are ongoing. Conclusions: This study provides evidence that sodium selenate treatment of chronic epileptic rats in the post-kainic acid SE model of TLE has an enduring disease modifying effect, with fewer spontaneous seizures and a modified proteomic expression profile in comparison to vehicle treated rats. Furthermore, the study highlights candidate prognostic biomarkers, which might inform the design of novel targeted molecular disease modifying-treatment approaches. Funding: NHMRC Peter Doherty Early-Career Research Fellowship