In vitro assessment of P-glycoprotein-mediated antiseizure medications efflux in a blood-brain barrier cell model

Abstract

Objectives: Drug-resistant epilepsy affects 30% of patients, where antiseizure medications (ASMs) are non-effective. A possible mechanism is the presence of the P-glycoprotein (P-gp) transporter in the blood-brain barrier (BBB), which may cause ASM efflux and limit bioavailability. Therefore, this study aimed to evaluate the potential of ASMs as P-gp substrates.

Methods: The study was conducted using the BBB model cell line human cerebral microvascular endothelial cells (hCMEC/D3). Ten widely used ASMs were assessed for their interaction with P-gp through in vitro assays: ATPase, competitive substrate efflux, and bidirectional transport assay, followed by quantification using HPLC or liquid chromatography-tandem mass spectrometry.

Key findings: Valproic acid, lamotrigine, and topiramate stimulated basal ATPase activity of P-gp. In a competitive substrate efflux assay, valproic acid, lamotrigine, and topiramate increased rhodamine123 intracellular accumulation, thereby influencing its P-gp-mediated efflux. Valproic acid and lamotrigine exhibited an efflux ratio > 1.5 in a bidirectional transport assay, which was significantly reduced in the presence of a P-gp inhibitor (P < .01).

Conclusions: The findings support that valproic acid and lamotrigine are likely substrates of P-gp at the BBB. Thus, targeting the P-gp-mediated efflux may represent a promising strategy for managing drug-resistant epilepsy against these ASMs.

Keywords: ATPase assay; P-glycoprotein; antiseizure medications; bidirectional transport assay; drug-resistant epilepsy; hCMEC/D3 cells.