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

Abstract

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 0.3mM, for 24h 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.

Keywords: AEDs; AIF; BCA; BSA; CBZ; CNS; Carbamazepine; DTT; ERK; ESL; Eslicarbazepine; GABA; LTG; Lamotrigine; MAPK; Neurotoxicity; OXC; Oxcarbazepine; PARP; PBS; PMSF; R-Lic; R-licarbazepine; S-Lic; S-licarbazepine; SAPK/JNK; SDS; TBS; Thr; Tyr; VPA; Valproate; antiepileptic drugs; apoptosis-inducing factor; bicinchoninic acid; bovine serum albumin; carbamazepine; central nervous system; dithiothreitol; eslicarbazepine acetate; extracellular signal-regulated kinase; gamma-aminobutyric acid; lamotrigine; mitogen-activated protein kinase; oxcarbazepine; phenylmethylsulphonyl fluoride; phosphate-buffered saline; poly-ADP ribose polymerase; sodium dodecyl sulphate; stress-activated protein kinase/c-Jun N-terminal kinase; threonine; tris-buffered saline; tyrosine; valproate.