Abstracts

Rationale: Status epilepticus (SE) triggers multiple pathological mechanisms including mitochondrial dysfunction. Because mitochondria play an essential role in energy metabolism, Ca2+ buffering and is the major source of free radicals, impairment in mitochondrial function could further exacerbate neuronal damage following SE. Activation of poly(ADP-ribose) polymerase-1 (PARP-1) has been shown to contribute to mitochondrial dysfunction in many experimental brain injury models, partly mediated through intracellular NAD+ depletion. PARP-1 is activated following chemoconvulsant-induced SE models. Therefore, we sought to determine whether inhibiting PARP-1 activation would preserve mitochondrial function through the preservation of intracellular NAD+ content and improve outcome following SE.Methods: PARP-1 inhibitor (PJ-34) or vehicle (normal saline) was administered (15mg/kg, i.p.) prior to SE induction. SE was induced in male Sprague-Dawley rats using kainate (KA, 15mg/kg, i.p.). The animals were allowed to remain in SE for 1h. SE was subsequently terminated using pentobarbital (20mg/kg, i.p.). Sham animals that received only saline were used as the control group. Hippocampal mitochondrial O2 consumption was measured using a Clark-type electrode 24h following KA induced SE. Whole cell NAD+ content was measured using an enzymatic cycling assay. Hippocampal neuronal damage was assessed using Fluoro-Jade B (FJB) staining and stereology 72h following SE. Data were analyzed using analysis of variance or student t test.Results: SE was associated with impaired mitochondrial O2 consumption (100.0% v. 76.7 4.8%, sham v. SE, mean SEM, n=6/group, p <0.05) and decreased NAD+ (100 5.0% v. 85.4 3.3%, sham v. SE, n=6-7/group, p<0.05). FJB positive cells were observed in CA1 and CA3 regions of SE animals, none in sham. There were fewer CA1 and CA3 neurons in SE animals (CA1=36.1 6.4%, CA3=49.4 6.2% of sham, n=6/group, p<0.001). PARP-1 inhibition was associated with preserved mitochondrial O2 consumption (76.7 4.8v. 100.0 10.2%, vehicle v. PJ-34, n=6/group, p<0.05), fewer FJB positive cells in CA1 (238.5 67.5 v. 82.0 79.0 cells, vehicle v. PJ-34, n=2/group) and preserved CA1 neurons (36.1 6.4% v. 64.2 10.9 of sham, vehicle v. PJ-34, n=6/group, p<0.05). Preliminary data suggest higher NAD+ content in PARP-1 inhibited animals following SE.Conclusions: Our data suggest that mitochondrial dysfunction occurs following SE and is in part mediated through PARP-1 activation and NAD+ depletion. Furthermore, our data suggest that PARP-1 activation contributes to CA1 neuronal damage and cell death following SE. Together, these findings suggest that PARP-1 activation may play an important role in the hippocampal neuronal damage following SE. Support: K08NS063117, R01NS049427, RO1NS039943