Abstracts

Rationale: Systems genetics approaches integrating preclinical and clinical transcriptomic data confirmed that microglia-mediated inflammatory responses are playing an important role in epilepsy (1). Furthermore, the colony-stimulating factor 1 receptor (CSF-1R) was identified as a potential target controlling both a microglia-specific gene network and seizure activity in vivo1. In the present study we have used the organotypic hippocampal slice model of post-traumatic epileptogenesis, which was previously used to validate the involvement of a pro-inflammatory cytokine in epileptogenenesis (2). This in vitro model allows longitudinal assessment of both epileptiform activity and inflammatory responses in vitro. Consequently, we evaluated the effects of two CSF-1R antagonists (PLX-3397 and compound B) on the development of epileptiform activity and pro-inflammatory cytokine levels. Methods: Hippocampal slices were prepared from 7-9 days-old rats and cultured on multi-electrodes arrays (MEAs) during ~21 days-in-vitro (DIV) in a CO2 incubator at 35°C. Culture supernatants were collected twice a week and electrophysiological evaluation was performed once per slice at either 7-8DIV, 14-15DIV or 21-22DIV. Tested compounds (1µM) were added to the culture medium from 0DIV until the end of the culture period (~21DIV). The incidence of spontaneous epileptiform discharges was evaluated during 30 min. epochs of local field potential recordings. The levels of lactate dehydrogenase (LDH), a cell death marker, and of pro-inflammatory cytokines (IL-1beta, IL-6 and TNF-alpha) were analyzed in culture supernatants using standard biochemical and Elisa assays. Results: No difference in LDH levels was observed between control slices and compound-treated slices suggesting that the tested compounds did not change the slice viability. PLX-3397 did not modify cytokines release at early stages of the culture, but prevented the secondary increase of cytokine release (after 14DIV). Compound B had stronger effects on the reduction of cytokine release starting from early stages until the end of the culture period. PLX-3397 prevented the development of ictal epileptiform activity at ~DIV7, but this effect was no longer observed at subsequent DIVs. Interestingly, a similar effect of compound B on the development of ictal activity was maintained until 14DIV. PLX-3397 reduced the duration of individual ictal discharges, whilst compound B did not affect this parameter. Conclusions: The present study indicates that both tested CSF-1R antagonists consistently attenuate the development of epileptogenic process. This effect is associated with significant reduction of pro-inflammatory cytokine levels. Slightly different pharmacological profiles of the two tested compounds (i.e. efficacy and duration) may be attributed to the differences in their selectivity towards CSF-1R. References: 1. A systems-level framework for drug discovery identifies Csf1R as a novel anti-epileptic drug target. Johnson MR, Srivastava PK, van Eyll J, Godard P, Mazzuferi M, Danis B, Vandenplas C, Foerch P, Leclercq K, Mairet-Coello G, Vanclef F Shkura K, Laaniste L, Delahaye-Duriez A, Petretto E, Kaminski RM. (submitted to AES) 2. Intrinsic inflammation is a potential anti-epileptogenic target in the organotypic hippocampal slice model. Chong S-A, Balosso S, Vandenplas C, Szczesny G, Hanon E, Claes K, Van Damme X, Danis B, van Eyll J, Wolff C, Vezzani A, Kaminski RM, Niespodziany I. (J. Neuroinflammation, under review) Funding: