Abstracts

Rationale: Inflammation has been identified as a major epileptogenic factor in temporal lobe epilepsy (TLE). Understanding the mechanisms underlying seizure-induced neuroinflammation could lead to the development of novel anti-epileptogenic therapies. Reactive oxygen species (ROS) are recognized as key mediators of seizure-induced neuronal damage and known to increase in models of TLE. Whether and how ROS levels and altered redox status contribute to seizure-induced inflammation in TLE is unknown. We tested the role of ROS in seizure-induced neuroinflammation (pro-inflammatory cytokines and microgliosis) and neuronal injury using a catalytic antioxidant. Methods: Adult male Sprague-Dawley rats were subjected to pilocarpine-induced status epilepticus (SE) following pretreatment with scopolamine and post-treatment with diazepam. Proinflammatory cytokine production was assessed in the hippocampus and piriform cortex 6, 24, 48 hours and 1 week post-pilocarpine using a multiplex cytokine array (Mesoscale Discovery).To determine the role of ROS in SE-induced cytokine production, a separate cohort of rats were treated with AEOL10150 [Mn(III) tetrakis (N,N - diethylimidizolium-2-yl) porphyrin], a catalytic antioxidant with high superoxide dismutase (SOD) and catalase activities beginning 60 min after pilocapine and every 4h until sacrifice (24h). Hippocampus and piriform cortex was collected 24 hours after pilocarpine injection for HPLC analysis of the glutathione redox status (GSH/GSSG), 3-nitrotyrosine/tyrosine (3NT/Tyr) ratios and multiplex cytokine measurement. Whole brains were collected for immmunohistochemical staining for microgliosis (Iba-1) and neuronal injury (fluoro jade B staining).Results: The time course study of pro-inflammatory cytokines revealed increases in the levels of TNF- , IL-1 , IL-6 and KC/GRO at 6, 24 and 48 hours after pilocarpine in the hippocampus and piriform cortex with a return to control values at the 1 week time-point. Treatment with pilocarpine significantly increased 3NT/Tyr ratio and decreased GSH/GSSG ratio in the hippocampus which were significantly reversed by AEOL10150. AEOL10150 treatment attenuated pro-inflammatory cytokine production in the hippocampus and piriform cortices as well as microgliosis and neuronal injury without altering pilocarpine-induced behavioral seizures. Conclusions: These results demonstrate that scavenging ROS can decrease indices of seizure-induced neuroinflammation and highlight the importance of redox mechanisms in controlling inflammation in TLE. This work was supported by R21NS072099 (NIHOD/NINDS) and R01 NS39587 (NIH, NINDS).