Evaluation of neurotoxic and neuroprotective pathways affected by antiepileptic drugs in cultured hippocampal neurons

• ESL and its in vivo metabolites, as well as LTG and CBZ, are not toxic to hippocampal neurons.
• Exposure to OXC and VPA induced the appearance of markers related to cell death.
• OXC was the most neurotoxic AED.
• AEDs affected differently the levels of phosphorylation of ERK1/2, AKT and SAPK/JNK.
• Lamotrigine may be neuroprotective via the activation of the SAPK/JNK pathway.

In this study we evaluated the neurotoxicity of eslicarbazepine acetate (ESL), and of its in vivo metabolites eslicarbazepine (S-Lic) and R-licarbazepine (R-Lic), as compared to the structurally-related compounds carbamazepine (CBZ) and oxcarbazepine (OXC), in an in vitro model of cultured rat hippocampal neurons. The non-related antiepileptic drugs (AEDs) lamotrigine (LTG) and sodium valproate (VPA) were also studied. We assessed whether AEDs modulate pro-survival/pro-apoptotic pathways, such as extracellular-regulated kinase (ERK1/2), Akt and stress activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK).We found that neither ESL nor its metabolites, CBZ or LTG, up to 0.3 mM, for 24 h of exposure, decreased cell viability. OXC was the most toxic drug decreasing cell viability in a concentration-dependent manner, leading to activation of caspase-3 and PARP cleavage. VPA caused the appearance of the apoptotic markers, but did not alter cell viability. ESL, S-Lic and OXC decreased the levels of phospho-ERK1/2 and of phospho-Akt, when compared to basal levels, whereas CBZ decreased phospho-SAPK/JNK and phospho-Akt levels. LTG and VPA increased the phosphorylation levels of SAPK/JNK.These results suggest that ESL and its main metabolite S-Lic, as well as CBZ, LTG and VPA, are less toxic to hippocampal neurons than OXC, which was the most toxic agent.