Presentations

Abstract

Introduction: Pathological High Frequency Oscillations (pHFO, >180 Hz) are a marker of neuronal disarray. Recent studies have associated pHFO with the development of epilepsy and the progression towards overt seizures. pHFOs are a specific manifestation of neuronal hyperexcitability and neuroinflammation. The upregulation of CD40-CD40L, a potent inflammatory system, mediates seizure susceptibility through unknown molecular mechanisms. This research aims to investigate the potential biological mechanism underlying CD40 neuronal excitability.

Methods: Pentylenetetrazole (PTZ) or pilocarpine -induced status epilepticus (SE) was performed in adult male mice deficient in CD40 (CD40KO) genetic matched controls (WT). A subgroup of mice was selected to receive siRNACD40 or shRNA (control) injection before PTZ. After PTZ or SE, seizures were analyzed clinically using Racine's score and electronically using multielectrodes assembled in a silicon probe across the cortex-hippocampal axis. Spontaneous local field potentials (LFPs), a representation of summed synaptic activity, were recorded in freely moving mice. Signal morphology and frequency analysis was conducted using signal analysis software to identify HFO. After euthanasia, neural tissue was histologically processed to evaluate CD40 expression. sCD40L (as a marker activation of CD40-CD40L), NR2B (NMDA sub-unit as component of excitability) and Integrin (as a marker of synaptic plasticity) was measured using ELISA.

Results: Preliminary data indicates that CD40 deficiency alters neural network functionally and morphologically. Neural oscillations of CD40KO demonstrate lower pHFOs rate with decreased baseline gamma/theta (functional activity) compared to controls. CD40KO reduces status epilepticus. After the administration of PTZ, CD40KO downregulates the expression of NR2B - limiting seizure susceptibility in concordance with decrease of pHFO rate.

Conclusion: This preliminary data suggests that activation of the pro-inflammatory CD40 cascade promotes seizure susceptibility through the upregulation of excitatory NMDA receptors. This mechanism could participate in epileptogenesis by promoting the formation of an epileptogenic network through the expression of pHFO.