Abstract

I: Neuroinflammation in chronic diseases, such as epilepsy, may be the cause of the tissue dysfunction that characterizes the disease. The hemichannels formed by connexin43 (Cx43 HCs), the main connexin isoform found in astroglial cells, play a critical role in neuroinflammation. Cx43 is coexpressed with Cx30 and Cx26. They allow the influx of Ca2+, which promotes astrocyte reactivity, and permit the release of glutamate and ATP, which overstimulate neurons. Under these conditions, the inflammasome is activated and generates pro-inflammatory cytokines. Current antiepileptic drugs, such as valproate (VPA), have a pleiotropic action on neuronal molecular targets and their action on glial HCs remains elusive. MM: Through molecular docking studies, we predicted the preferred binding orientation of VPA on Cx43 HCs. We used HeLa cells transfected with Cx43, Cx30 or Cx26 HCs, to determine the effect of VPA on the astrocytic HCs activity. R: The bioinformatic study suggested that VPA could bind to Cx43 HCs modulating their activity. VPA slightly increased the activity of Cx43, Cx30 and Cx26 HCs on basal conditions, but its effect was significantly increased after an increased open probability of Cxs HCs. VPA also increased the ATP release through Cx43 HCs. D: The opening of HCs caused by VPA is consistent with the bioinformatic study, since its predicted binding site to Cx43 HC is on the intracellular side, suggesting that VPA might enter through HCs when their activity is increased due to the reduction of extracellular Ca2+, as it occurs during seizures. The increased ATP release through Cx43 HCs induced by VPA suggests that it promotes neuroinflammation, which may contribute to explaining why ~30% of epileptic patients are resistant to this drug. A: Doctoral fellowship from Universidad de Valparaíso (to CGR), Fondecyt grant 1191329 (to JCS), and grant ICM677 ANID, Project P09 from the Centro Interdisciplinario de Neurociencias de Valparaíso (to JCS).