TPPU pre-treatment rescues dendritic spine loss and alleviates depressive behaviours during the latent period in the lithium chloride-pilocarpine-induced status epilepticus rat model

Epileptogenesis may be responsible for both of recurrent seizures and comorbid depression in epilepsy. Disease-modifying treatments targeting the latent period before spontaneous recurrent seizures may contribute to the remission of seizures and comorbid depression. We hypothesized that pre-treatment with 1-trifluoromethoxyphenyl-3-(1-propionylpiperidin-4-yl) urea (TPPU), a soluble epoxide hydrolase (sEH) inhibitor, which has anti-inflammatory and neuroprotective effects might rescue status epilepticus (SE)-induced dendritic spine loss and alleviate depressive behaviours. Rats were either pre-treated with TPPU (0.1 mg/kg/d) intragastrically or with vehicle (40% polyethylene glycol 400) from 7 days before to 7 days after SE that was induced with lithium chloride and pilocarpine intraperitoneally. Rats in the Control group were given saline instead. The forced swim test (FST) was performed on the 8th day after SE to evaluate the depression-like behaviours in rats. The results showed that seizures severity during SE was significantly decreased, and the immobility time during FST was significantly increased through TPPU pre-treatment. Moreover, pre-treatment with TPPU attenuated inflammations including microglial gliosis and the level of proinflammatory cytokine IL-1β in the hippocampus; in addition, neuronal and dendritic spine loss in the subfields of hippocampus was selectively rescued, and the expression of NR1 subunit of N-methyl-D-aspartate (NMDA) receptor, ERK1/2, CREB, and their phosphorylated forms involved in the dendritic spine development were all significantly increased. We concluded that pre-treatment with TPPU attenuated seizures severity during SE and depressive behaviours during the period of epileptogenesis probably by rescuing dendritic spine loss in the hippocampus.