FosL1 Is a Novel Target of Levetiracetam for Suppressing the Microglial Inflammatory Reaction.

We previously showed that the antiepileptic drug levetiracetam (LEV) inhibits microglial activation, but the mechanism remains unclear. The purpose of this study was to identify the target of LEV in microglial activity suppression. The mouse microglial BV-2 cell line, cultured in a ramified form, was pretreated with LEV and then treated with lipopolysaccharide (LPS). A comprehensive analysis of LEV targets was performed by cap analysis gene expression sequencing using BV-2 cells, indicating the transcription factors BATF, Nrf-2, FosL1 (Fra1), MAFF, and Spic as candidates. LPS increased AP-1 and Spic transcriptional activity, and LEV only suppressed AP-1 activity. FosL1, MAFF, and Spic mRNA levels were increased by LPS, and LEV only attenuated FosL1 mRNA expression, suggesting FosL1 as an LEV target. FosL1 protein levels were increased by LPS treatment and decreased by LEV pretreatment, similar to FosL1 mRNA levels. The FosL1 siRNA clearly suppressed the expression of TNFα and IL-1ß. Pilocarpine-induced status epilepticus increased hippocampus FosL1 expression, along with inflammation. LEV treatment significantly suppressed FosL1 expression. Together, LEV reduces FosL1 expression and AP-1 activity in activated microglia, thereby suppressing neuroinflammation. LEV might be a candidate for the treatment of several neurological diseases involving microglial activation.

Suppressive effects of levetiracetam on neuroinflammation and phagocytic microglia: A comparative study of levetiracetam, valproate and carbamazepine.

We previously reported that treatment with levetiracetam (LEV) after status epilepticus (SE) termination by diazepam (DZP) prevents the development of spontaneous recurrent seizures. LEV suppresses increased expression levels of proinflammatory mediators during epileptogenesis after SE, but how LEV acts in neuroinflammatory processes is not yet known. In this study, we examined the effects of LEV on neuroinflammation and phagocytic microglia in vivo and in vitro and compared the effects of LEV with those of representative antiepileptic drugs valproate (VPA) and carbamazepine (CBZ). Repeated treatment with LEV for 30 days after the termination of pilocarpine-induced SE by DZP almost completely prevented the incidence of spontaneous recurrent seizures, while administration of VPA or CBZ showed no effect on the seizures. LEV clearly suppressed phagocytosis of mononuclear phagocytes, and cytokine expression was observed 2 days after SE. VPA attenuated neuroinflammation only, and CBZ showed no effect on changes after SE. Treatment with LEV significantly suppressed BV-2 microglial activation, which was defined by morphological changes, phagocytic activity and cytokine expression. By contrast, VPA and CBZ did not affect BV-2 microglial activity. In summary, LEV directly suppresses excess microglial phagocytosis during epileptogenesis, which might prevent the occurrence of spontaneous recurrent seizures after SE.

Levetiracetam treatment influences blood-brain barrier failure associated with angiogenesis and inflammatory responses in the acute phase of epileptogenesis in post-status epilepticus mice.

Our previous study showed that treatment with levetiracetam (LEV) after status epilepticus (SE) termination by diazepam might prevent the development of spontaneous recurrent seizures via the inhibition of neurotoxicity induced by brain edema events. In the present study, we determined the possible molecular and cellular mechanisms of LEV treatment after termination of SE. To assess the effect of LEV against the brain alterations after SE, we focused on blood-brain barrier (BBB) dysfunction associated with angiogenesis and brain inflammation. The consecutive treatment of LEV inhibited the temporarily increased BBB leakage in the hippocampus two days after SE. At the same time point, the LEV treatment significantly inhibited the increase in the number of CD31-positive endothelial immature cells and in the expression of angiogenic factors. These findings suggested that the increase in neovascularization led to an increase in BBB permeability by SE-induced BBB failure, and these brain alterations were prevented by LEV treatment. Furthermore, in the acute phase of the latent period, pro-inflammatory responses for epileptogenic targets in microglia and astrocytes of the hippocampus activated, and these upregulations of pro-inflammatory-related molecules were inhibited by LEV treatment. These findings suggest that LEV is likely involved in neuroprotection via anti-angiogenesis and anti-inflammatory activities against BBB dysfunction in the acute phase of epileptogenesis after SE.