Abstracts

Proinflammatory cytokines are rapidly synthesized by neuroglia in the brain during seizures. In agreement with their modulatory functions on neuronal excitability, we previously found that application of IL-1beta in rodent brain increases epileptic activity in various models of limbic seizures.
Our aim is to study whether seizures can be inhibited by blocking the brain production of mature IL-1beta using a new class of protease inhibitors that specifically inhibit the interleukin converting enzyme (ICE/caspase-1). EEG seizures were induced in freely-moving adult male Sprague-Dawley rats by intrahippocampal injection of 40 ng kainic acid (KA).
The effects of caspase-1 inhibitors (pralnacasan and VX-765) on IL-1beta production were assessed: (1) in rats injected with KA by western blot analysis of hippocampal homogenates; (2) in hippocampal slice cultures derived from 7-day-old C57BL6 mice, exposed to 10 ng/ml lipopolysaccaride (LPS) + 1mM ATP. Cytokines were measured in slices and their medium by ELISA. Intraventricular administration of pralnacasan (2x25[micro]g) or intraperitoneal injection of 50-200 mg/kg VX-765 reduced by [sim]50% the time spent in KA-induced seizures and delayed by 2-fold their onset time. Similar effects were observed using 50 mg/kg phenytoin. Caspase-1 inihibitors blocked the production of IL-1beta induced by seizures in the rat hippocampus. Exposure of organotypic slices to 1 [micro]M pralnacasan or VX-765 inhibited by [gt]80% the release of IL-1 beta induced in the medium by LPS+ATP, with modest effects on IL-6 and TNF-alpha release. This study indicates that systemic administration of caspase-1 inhibitors may represent an effective, specific and novel strategy to inhibit seizures by preventing the brain production of mature IL-1beta. (Supported by Fondazione Mariani Onlus, Vertex Pharmaceuticals Inc.)