Innate immune reaction in response to seizures: implications for the neuropathology associated with epilepsy

Abstract

In the present study, the expression of pro-inflammatory transcripts was assessed across the brain of mice having undertaken pilocarpine-induced seizures. Pilocarpine-induced marked neurodegeneration and demyelination in multiple regions of the forebrain. The pattern of genes encoding toll-like receptor type 2 (TLR2) and I kappa B alpha (index of NF-kappa B activation) was associated with the neurodegenerating areas, but this was not the case for the mRNA encoding other inflammatory proteins. Scattered tumor necrosis factor-alpha (TNF-alpha)-expressing cells were found across brain, whereas the signals for monocyte-chemoattractant protein-1 and microsomal prostaglandin mPGES E synthase were robust in thalamus and cerebral cortex and weak in the hippocampus and amygdala. TLR2 and TNF-alpha transcripts were expressed mainly in microglia/macrophages. Cyclooxygenase-2 was induced specifically in the hippocampus and piriform cortex. A low increase in interleukin-12 mRNA was detected in the brain, but the signal for interferon gamma (IFN-gamma) remained undetectable. Although pro-inflammatory markers were induced in a different manner across the CNS, their patterns were not characteristic of those caused by other inflammatory challenges, such as endotoxin. These data suggest a different mechanism involved in regulating the innate immune reaction in response to seizures and could have direct implications for the neuropathology associated with epilepsy.