Abstracts

Rationale: Toll-like receptors (TLR) are innate immune receptors that are important in early host defense against pathogens. TLRs recognize pathogen- or damage-associated molecular patterns (PAMPs/DAMPs). TLR4 is expressed on the cell surface and is most well-known for recognizing lipopolysaccharide (LPS), a component present in many bacteria. TLR9 is expressed intracellularly and recognizes unmethylated CpG DNA motifs, characteristic of DNA viruses and prokaryotic genomes. TLR4 has been implicated in both experimental and human epilepsy; TLR9 has yet to be studied. Here we investigated the gene expression changes of TLR 4 and 9 during epileptogenesis in rodent models of acquired epilepsy and acute, non-injurious seizures. Methods: Freely moving, male Sprague-Dawley rats (n=4 per group) received either 8 h or 30 min of perforant pathway stimulation (PPS). The former induces hippocampal sclerosis and hippocampal-onset epilepsy after around three weeks; the latter is a model of non-injurious seizures. Whole hippocampi were removed 4 and 14-days post-PPS. qPCR was performed for TLRs 4 and 9 on an ABI StepOnePlus instrument with custom-designed primers. Cq values (technical replicates) were averaged and geometric means were calculated using REST software. Results: TLR expression was not enhanced after 1 d in any group. The 8 h PPS group showed increased expression of both TLRs at 4 d, which was further enhanced at 14 d. The 30 min PPS group exhibited slight upregulation at 4 d, but downregulation at 14 d. Conclusions: TLR 4 and 9 expression is enhanced and prolonged during epileptogenesis. Evoked seizures also upregulate expression of these TLRs, but transiently and not to the same extent. These data warrant the further investigation on the role of these TLRs in epilepto- and ictogenesis. Funding: Funding was provided by the CURE Foundation.