Abstracts

Rationale: Status epilepticus (SE) and other potential brain insults may lead to the development of temporal lobe epilepsy via the induction of neuronal network alterations in the hippocampal formation. Neuroinflammation identified in epileptic focus of humans and experimental animals has been suspected to participate in the formation of neuronal cell death, reactive gliosis, aberrant neurogenesis and synaptic reorganization. Recent studies with hypoxia and ischemic preconditioning experiments have shown that the increase in the cerebral level of epoxyeicosatrienoic acid (EET), a fatty acid signaling molecule, may confer protection from ischemic stroke. Soluble epoxide hydrolase (sEH) is a key enzyme for metabolic conversion of EETs into their less active form, DHET. By using pharmacologic inhibitor or genetic deletion, previous studies have demonstrated that inhibition of sEH attenuated the vascular and neural injury induced by cerebral ischemia, suggesting that this enzyme might be a novel target in treatment of stroke. However, it remains unknown whether sEH is involved in neuroinflammation-related epileptogenesis. The present study aimed to examine 1). the temporal and spatial distributions of sEH in mice with pilocarpine-induced SE, 2). the corresponding change in inflammatory cytokines, and 3) the effect of sEH inhibitor on local neuroinflammation following SE. Methods: Pilocarpine (325 mg/kg) was intra-peritoneally administered to induce SE in adult male C57BL/6 mice. The coronal brain sections of SE mice obtained at 1, 3, 7, 14, 21, 28 and 35 days post-SE (n=4 in each group) were analyzed for sEH expression by immunohistochemistry with anti-sEH antibody. The hippocampal proteins were extracted for measuring the expression of sEH and cytokines (IL-1, IL-6) by western blot and ELISA, respectively. In another experimental group, daily injection of the sEH inhibitor adamantyl-ureido-dodecanoic acid (AUDA, 20 mg/kg, i.p.) was given at days 1 ~ 6 after SE induction, and then the mice were sacrificed at day 7 for measuring the cytokine expression.Results: Double-labeling staining with an antibody against glial fibrillary acidic protein (GFAP) clearly revealed sEH immunoreactivity in astrocytes in the molecular layer of CA1, CA3 and dentate hilus in SE mice. Compared to control mice, the sEH expression was higher at day 7 after SE. The inflammatory cytokines (IL-1, IL-6) were significantly increased after SE, and the IL-1 and IL-6 expressions peaked at day 7. Moreover, the expressions of IL-1 and IL-6 were dramatically decreased in the mice treated with AUDA in comparison with those treated with vehicle.Conclusions: Our findings suggest that sEH is involved in SE-induced neuroinflammation under SE mouse model.