Drug-resistant epilepsy (DRE) is present in 20-30% of all patients who develop epilepsy. Growing evidences demonstrated that glutamate released during seizures to increase the brain P-glycoprotein (P-gp) expression. Carbamazepine (CBZ) is known to influence the P-gp and cytochrome P450 (CYP) expression. However, the exact molecular mechanism is still unknown. We investigated that the effects of NF-κB and pregnane X receptor (PXR) activity on P-gp and CYP3A expression in mouse brain endothelial (bEnd.3) cells treated with l-glutamate (mimicking the seizure conditions), CBZ (mimicking the AED treating conditions) or both (l-glutamate plus CBZ) through qPCR and Western blotting assay. Mean fluorescence intensity was used to observe P-gp efflux function by analysis of intracellular Rhodamine123 (Rho123) accumulation. P-gp, CYP3A, PXR and NF-κB p65 were elevated in bEnd.3 cells incubated with l-glutamate, CBZ or CBZ pretreated by l-glutamate for 30 min. Both the mRNA and protein levels of P-gp and CYP3A were remarkably reduced by PXR or NF-κB p65 knock-down by siRNA transfections. The decreased intracellular accumulation of Rho123 suggested that the expression of P-gp was enhanced in bEnd.3 cells. These data suggested that overexpression of P-gp and CYP3A during seizures and treated with CBZ may be regulated by PXR or NF-κB p65 activity and expression, which revealed a mechanism underlying the development of DRE.
Keywords: Brain microvascular endothelial cells; Carbamazepine; Cytochrome P450; Drug-resistant epilepsy; Nuclear factor kappa B; P-glycoprotein; Pregnane X receptor.
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