Levetiracetam Suppresses the Infiltration of Neutrophils and Monocytes and Downregulates Many Inflammatory Cytokines during Epileptogenesis in Pilocarpine-Induced Status Epilepticus Mice

Acute brain inflammation after status epilepticus (SE) is involved in blood-brain barrier (BBB) dysfunction and brain edema, which cause the development of post-SE symptomatic epilepsy. Using pilocarpine-induced SE mice, we previously reported that treatment with levetiracetam (LEV) after SE suppresses increased expression levels of proinflammatory mediators during epileptogenesis and prevents the development of spontaneous recurrent seizures. However, it remains unclear how LEV suppresses neuroinflammation after SE. In this study, we demonstrated that LEV suppressed the infiltration of CD11b(+)CD45(high) cells into the brain after SE. CD11b(+)CD45(high) cells appeared in the hippocampus between 1 and 4 days after SE and contained Ly6G(+)Ly6C(+) and Ly6G(-)Ly6C(+) cells. Ly6G(+)Ly6C(+) cells expressed higher levels of proinflammatory cytokines such as IL-1 beta and TNF alpha suggesting that these cells were inflammatory neutrophils. Depletion of peripheral Ly6G(+)Ly6C(+) cells prior to SE by anti-Ly6G antibody (NIMP-R14) treatment completely suppressed the infiltration of Ly6G(+)Ly6C(+) cells into the brain. Proteome analysis revealed the downregulation of a variety of inflammatory cytokines, which exhibited increased expression in the post-SE hippocampus. These results suggest that Ly6G(+)Ly6C(+) neutrophils are involved in the induction of acute brain inflammation after SE. The proteome expression profile of the hippocampus treated with LEV after SE was similar to that after NIMP-R14 treatment. Therefore, LEV may prevent acute brain inflammation after SE by suppressing inflammatory neutrophil infiltration.