The following are the supplementary data related to this art
The following are the supplementary data related to this article.
Introduction Drug-resistant epilepsy (DRE) occurs in approximate 30% of patients who suffer from epilepsy . Temporal lobe epilepsy (TLE) is one of the most common partial seizures and the common cause of DRE , and carbamazepine (CBZ) is one of the first line antiepileptic drug (AED) for treating TLE. The mechanisms involved in DRE are not clearly understood. Therefore, a better understanding of the cellular and molecular mechanisms in DRE is possible to obtain a new therapy for patients in the future. Mounting evidences show that the Cathepsin Inhibitor 1 glutamate metabolism plays an essential role in the pathophysiology of epilepsy. Administrating glutamate to experimental animals can contribute to seizure onset , by contrast, the symptom of seizures alleviated by coadministration of glutamate antagonists . Additionally, the concentration of extracellular glutamate was significantly higher in the epileptogenic hippocampal formation compared to the nonepileptogenic hippocampal formation in the patients . Likewise, patients have an elevated concentration of extracellular glutamate during a seizure . The overexpression of P-glycoprotein (P-gp) is implicated as one of the major reasons for DRE. It is a member of the ATP-binding cassette (ABC) superfamily of transmembrane proteins , localized at multiply pharmacological barriers, mostly in liver, kidney, colon and jejunum  as well as capillary endothelial cells of brain . CBZ is a substrate for P-gp, which can interfere with its efficacy by effluxing it out . P-gp expression was increased under stimulation with l-glutamate via different signaling pathways [, , ]. Furthermore, the aberrant expression of cytochrome P450 is another reason for DRE. CYP3A can metabolize thousands of endogenous and exogenous chemicals . Xenobiotics and endogenous toxins are known to influence the expression of P-gp and CYP3A. PXR, one of nuclear receptors, is a key factor in modifying drug metabolism in the liver. Its critical role is to regulate different efflux transporters and phase I and II enzymes . CBZ is confirmed to exert its effect by activated PXR . PXR can also bind to the CYP3A promoter to induce its protein expression . A recent study showed that PXR and some subtypes of CYP in the endothelial cells obtained from epileptic brain tissues remarkably higher than the control . The inflammation is involved in the process of seizures . The NF-κB signaling pathway plays a key role in regulating the immune response to inflammation. Our previous study demonstrated that high mobility group box 1 (HMGB1), a transcription factor, lead to the overexpression of P-gp through activation of TLR4/RAGE/NF-κB-p65 in bEnd.3 cells, and also showed that NF-κB can bind the mdr1 gene promoter regions to enhance P-gp expression . Additionally, P-gp expression in the rat brain of kainic acid-induced seizure was significantly up-regulated or down-regulated via the accommodation of NF-κB . NF-κB can also bind the CYP450 promoter regions to regulate its expression .
Materials and methods
Discussion In the current study, we have demonstrated for the first time that expression of P-gp and CYP3A were up-regulated via PXR/NF-κB p65 signaling pathway by l-glutamate, mimicked the phase of the seizure. Similarly, P-gp and CYP3A were elevated via PXR/ NF-κB p65 signaling pathway following exposure to CBZ with or without stimulated by l-glutamate, which mimicked the environment of epilepsy and treated with CBZ. These findings also showed that it may be a novel molecular mechanism on DRE. In general, there are mainly three well-known hypotheses to explain the biological mechanism underlying DRE: the transporter hypotheses, the chemical structure modification of the drug hypothesis and alteration of drug targets hypotheses. Multidrug transporters are supposed to result in AEDs resistance as their overexpression at blood brain barrier (BBB) entraps AEDs in brain, resulting in decreased bioavailability . P-gp is the critical transporter protein. The chemical structure modification of the drug hypothesis indicates that the primary drug has been changed to a novel chemical substance that leads to activation, inactivation or brings to side effect. CBZ is mainly oxidized to carbamazepine-10, 11-epoxide and other metabolites by the cytochrome P450 enzyme . The drug targets hypothesis shows that the structural change, decreasing or increasing of receptors result in an altered sensitivity for AEDs .