Abstracts

Rationale: Drug delivery to the epileptic brain is hampered by over expression of multiple drug resistance proteins at the blood-brain barrier (BBB). The possibility that BBB endothelial cells may also act as a metabolic barrier for commonly prescribed anti-epileptic drugs (AED) was not previously considered. Thus, while cytochrome P450 iso-enzymes play a major role in liver metabolism of AED, it is not clear whether (1) these enzymes are expressed at the BBB, and (2) overexpressed in epileptic brain. The goal of this study was to investigate the presence of P450-related cytochrome in brain endothelial cells derived from drug resistant epileptic patients or from patients suffering from arterial-vascular malformations (AVM). Methods: Primary brain endothelial cells derived from patients affected by drug resistant epilepsy or arterial-vascular malformations (AVM) were cultured either in a dynamic in vitro blood-brain barrier model (DIV-BBB; cells are exposed to laminar flow) or in a static model (i.e., no flow present). A cell line of human brain microvascular endothelial cells was used as control. Cytochrome P450 enzymes levels were assessed by cDNA microarray technology and confirmed by reverse-transcriptase polymerase chain reaction (RT-PCR). Results: 1) Primary brain endothelial cells derived from patients affected by drug resistant epileptic brain or AVM displayed increased mRNA levels for Cyp3A4, Cyp2J2, Cyp33, Cyp4A11, Cyp2E1 and Cyp11b compared to control; 2) Exposure to flow increased mRNA levels of a broad spectrum of enzymes: Cyp33, Cyp2J2, CARS-Cyp, Cyp4A11, Cyp2C9, Cyp3A4, Cyp2E1, Cyp11b, Cyp2A6, Cyp1B1 and Cyp2C; 3) Among these enzymes, Cyp3A4, Cyp2C9, Cyp2A6 and Cyp2J2 are involved in the metabolic conversion of AED. In particular, CYP-3A4, which is responsible for the conversion of carbamazepine into its metabolites, was increased in epileptic endothelial cells and by subsequent exposures to flow. Conclusions: Our results reveal for the first time presence of P450 enzymes at the human BBB. Further, some of these P450 enzymes are involved in the metabolism of AED. These findings imply that levels of mRNA of these specific P450 enzymes are dependent both on the disease state (e.g., epilepsy) and regulated by intraluminal flow.