The role of Infiltrating Macrophages in Seizure Generation Following CNS Infection - Abstract/Project Summary Temporal lobe epilepsy (TLE) is the most prevalent form of acquired epilepsy. 30% of the patients are refractory to therapy and new treatments are urgently needed. Viral infection of the central nervous system (CNS) is a significant cause of TLE, and, while encephalitis is an important contributor, the mechanisms of how inflammation leads to seizures is unclear. Using the first mouse model of viral-induced TLE, which was developed by our laboratory, we found that induction of acute seizures is associated with blood peripheral macrophage infiltration into the brain and secretion of pro-inflammatory cytokines, primarily IL-6. Through RNA sequencing (RNAseq) of infiltrating macrophages isolated from the brains of TMEV-infected mice at the peak of seizure activity, I found that a population of CNS-infiltrating macrophages expresses high levels of the triggering receptor expressed on myeloid cells-1 (TREM1). Activation of TREM1 leads to the secretion of pro-inflammatory cytokines. Increased TREM1 expression is associated with inflammatory conditions, and inhibition of TREM1 function ameliorates inflammation and disease severity in several animal models of inflammatory diseases. However, the involvement of TREM1 in the development of acute seizures is unknown. In Aim 1 I will determine the time course of TREM1 expression in brain-infiltrating macrophages, and address whether genetic and pharmacological inhibition of TREM1 decreases the development of acute seizures in TMEV-infected mice, via videoEEG. The pro-inflammatory cytokine IL-6, which is mainly produced by brain infiltrating macrophages during TMEV infection, plays a pivotal role in inducing seizures; however how IL-6 does it is unknown. In Aim 2, I will determine whether IL-6 induces downregulation of neuronal GABA receptors, via biotinylation assay, and address which IL-6 pathway (classical or trans-signaling) is involved in acute seizures. Since inflammatory macrophages in the brain are associated with generation of acute seizures in TMEV-infected mice, in Aim 3 I will determine whether skewing macrophages towards an anti-inflammatory phenotype will affect the development of acute seizures, via videoEEG. I will also identify microRNAs in brain-infiltrating macrophages that are driving inflammation during the course of acute seizure generation in TMEV-infected mice. VideoEEG and receptor biotinylation assay are critical techniques I will learn during my mentored phase (Aim1/Aim2a), that will be essential to carry out experiments in Phase II (Aim2b/Aim3). These new skills, combined to my previous training, will put me in a unique position to address crucial questions related to neuroinflammation and epilepsy in my own laboratory using cutting edge approaches, and will substantially impact my research and career. These aims will improve the knowledge of the relationship between inflammation and seizures, and has the great potential of revealing inflammatory macrophages as a novel therapeutic target of neuroinflammation, allowing for the development of novel intervention to prevent and treat the development of acquired epilepsy.
