TiHo Bibliothek elib - Tierärztliche Hochschule Hannover

SUMMARY
cause of increased functionality of MDTs especially Pgp in epileptic patients is not
adequately defined. One aim was to investigate, if AEDs induce Pgp functionality.
For this purpose the immortalized human cell line hCMEC/D3, which was derived
from the temporal lobe of a pharmacoresistant epilepsy patient (WEKSLER et al.
2005), was chosen. These cells express characteristic endothelial marker proteins
and are used for in vitro studies (WEKSLER et al. 2005; POLLER et al. 2008; CARL
et al. 2010). In preliminary studies, primary rat brain endothelial cells (rBCEC) were
also used in a transwell model.
Expression of Pgp was detected by Western blot in all immortalized cell lines
(hCMEC/D3, GPNT, RBE4) and in the primary rBCEC cells. Functional analysis was
performed by accumulation assays (or uptake assays) with the Pgp substrate
rhodamine 123. Therefore, hCMEC/D3, GPNT, and RBE4 cells were exposed to the
widely used AEDs carbamazepine, levetiracetam, phenobarbital, phenytoin,
topiramate, and valproate at different therapeutic concentrations. For rBCEC cells,
carbamazepine and phenytoin were investigated. Typically, the cells were treated for
three days. In the uptake experiments functional Pgp in the cell lines hCMEC/D3,
GPNT, and RBE4 as well as in rBCEC cells was detected, which could be modulated
by known Pgp inducers and the known Pgp inhibitor tariquidar. The hCMEC/D3 cells
showed only little inducing effects for Pgp-mediated efflux although the expression of
this protein was relatively low compared to other cell lines. Data of the accumulation
assays varied widely in cells of the different species. Pgp functionality was not
affected by all tested AEDs in the chosen concentrations. In hCMEC/D3 cells, robust
effects were detected after the treatment with carbamazepine (100 µM) and valproate
(300 µM). In RBE4 cells, carbamazepine and topiramate induced Pgp functionality. In
experiments with rBCEC cells carbamazepine and phenytoin led to an decreased
efflux of the Pgp substrate rhodamine 123 and therefore the used concentrations of
these AEDs seemed to have inhibiting effects on the Pgp functionality. Although
known Pgp inducers in GPNT cells induced the rhodamine efflux, no effects were
detected after treatment with AEDs. Because of varying results the analysis of
additional concentrations of the AEDs is important to detect possible concentrationdependent
effects. Data of the rhodamine uptake assays lead to the conclusion that
several AEDs affect the functionality of Pgp.
The transport studies revealed variable data. For primary brain cultures similar
variable results were already described due to many different preparation and
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