Imaging of P-glycoprotein Function and Expression to Elucidate Mechanisms of Pharmacoresistance in Epilepsy
Abstract:The issue of pharmacoresistance in epilepsy has received considerable attention in recent years, and a number of plausible hypotheses have been proposed. Of these, the so-called transporter hypothesis is the most extensively researched and documented. This hypothesis assumes that refractory epilepsy is associated with a localised over-expression of drug transporter proteins such as P-glycoprotein (Pgp) in the region of the epileptic focus, which actively extrudes antiepileptic drugs (AEDs) from their intended site of action. However, although this hypothesis has biological plausibility, there is no clinical evidence to support the assertion that AEDs are sufficiently strong substrates for transportermediated extrusion from the brain. The use of modern brain imaging techniques to determine Pgp function in patients with refractory epilepsy has started only recently, and may ultimately determine whether increased expression and function of Pgp or other efflux transporters are involved in AED resistance.
Keywords: (R)-enantiomer; (S)-enantiomer; Antiepileptic drugs (AEDs); Brain imaging; CNS disorder; Chinese hamster ovary resistant cells (CHrB30); Cytochrome P450-mediated metabolism; Epilepsy; Erapamil; Magnetic resonance spectroscopy (MRS); Multidrug transporters; P-glycoprotein; Pgp expression; Pgp function; Pgp substrates; Positron emission tomography; Radiotracers; Single nucleotide polymorphism (SNP); Single photon emission computed tomography (SPECT); Tariquidar; Temporal lobe epilepsy (TLE); [11C]-Ndesmethyl-loperamide; [11C]carvedilol; [11C]colchicine; [11C]daunorubicin; [11C]loperamide; [11C]phenobarbital; [11C]phenytoin; [18F]paclitaxel; [99mTc]sestamibi; antiepileptic drugs; blood-brain barrier (BBB); brain imaging; cyclosporin A (CsA); liquid chromatography tandem mass spectrometry (LC/MS/MS); positron emission tomography; tariquidar; verapamil
Document Type: Research Article
Affiliations: Department of Pharmacology,Toxicology and Pharmacy, University of Veterinary Medicine Hannover, Bünteweg 17, D-30559 Hannover, Germany.
Publication date: 2010-12-01