Abstracts

Rationale: Mitochondrial dysfunction contributes to neuronal damage following status epilepticus (SE). NMDA-mediated activation of poly(ADP-ribose) polymerase-1 (PARP-1) likely at least in part contributes to this finding. PARP-1 inhibition decreased neuronal death following direct chemoconvulsant stimulation in vivo and NMDA application in vitro. However, whether PARP-1 inhibition preserves mitochondrial function in SE remains to be determined. We hypothesize that PARP-1 inhibition will preserve mitochondrial function and prevent cell death following experimental SE. Methods: Sprague-Dawley rats (male, 150-200g) received intraperitoneal (i.p.) administration of either a PARP-1 inhibitor (PJ-34, 15mg/kg) or vehicle prior to the induction of SE using kainate (15mg/kg, i.p.). Following 1h of SE we isolated hippocampal mitochondria and assessed mitochondrial function by measuring O₂ consumption using a Clark-type electrode. We measured mitochondrial respiration using complex I and complex II substrates (malate/glutamate, succinate n=5/group). We measured state 3 (in the presence of ADP) and state 4 (in the absence of ADP) respiration and calculated respiratory control ratio (RCR = state 3/state 4) as an indicator of intact mitochondrial respiration. To assess neuronal damage, we performed Fluoro-Jade B (FJ-B), TUNEL and Nissl staining on the cryopreserved brain slices (n=3/group). Results: Status epilepticus was associated with decreased complex I- and II-mediated RCR (59.35±12.26%, 52.25±13.96 of sham respectively, p<0.05). PJ-34 treated animals exhibited preserved complex I and II-mediated RCR following SE (79.35±12.56%, 113±24.21% of sham, p<0.05) and decreased FJ-B and TUNEL staining with preserved CA1 pyramidal neurons 72h after SE. Vehicle-treated animals showed increased FJ-B and TUNEL staining and decreased CA1 and CA3 neurons 72h after SE suggesting increased neuronal damage and death. Conclusions: Our finding that PARP-1 inhibition preserved mitochondrial respiration suggests that PARP-1 activation contributes to mitochondrial dysfunction in SE. The inhibitor studies suggest that PARP-1 activation following SE contributes to mitochondrial dysfunction and neuronal damage. Studies are on-going to further delineate the mechanisms of PARP-1 mediated mitochondrial dysfunction in SE. Support: K12HD41648, K08NS063117, R01NS049427, RO1NS039943