Dynamic Regulation of P-glycoprotein in Human Brain Capillaries

Abstract

Considering its role as a major blood-brain barrier gatekeeper, the dynamic regulation of the efflux transporter P-glycoprotein is of considerable functional relevance. In particular, disease-associated alterations in transport function might affect central nervous system drug efficacy. Thus, targeting regulatory signaling cascades might render a basis for novel therapeutic approaches. Using capillaries freshly prepared from patient tissue resected during epilepsy surgery, we demonstrate dynamic regulation of P-glycoprotein in human brain capillaries. Glutamate proved to up-regulate P-glycoprotein efflux transport in a significant manner via endothelial NMDA receptors. Both inhibition of cyclooxygenase-2 and antagonism at the glycine-binding site of the NMDA receptor prevented the glutamate-mediated induction of P-glycoprotein transport function in human capillaries. In conclusion, the data argue against species differences in the signaling factors increasing endothelial P-glycoprotein transport function in response to glutamate exposure. Targeting of cyclooxygenase-2 and of the NMDA receptor glycine-binding site was confirmed as an efficacious approach to control P-glycoprotein function. The findings might render a basis for translational development of add-on approaches to improve brain penetration and efficacy of drugs.

Glutamate-Mediated Upregulation of the Multidrug Resistance Protein 2 in Porcine and Human Brain Capillaries

“…2B). The concentration of glutamate for this and further experiments was chosen based on previous experimental and clinical studies demonstrating a respective extracellular concentration of glutamate during epileptic seizures and confirming an impact of this concentration on P-glycoprotein expression and function (Thomas et al, 2003(Thomas et al, , 2004(Thomas et al, , 2005Bauer et al, 2008b;Avemary et al, 2013). As expected, MK-571 exerted a relevant inhibitory effect on MRP2-mediated luminal Texas Red accumulation (Fig.…”

“…Previous studies have reported a glutamate-induced signaling at ASPET Journals on May 11, 2018 jpet.aspetjournals.org via NMDA receptors to activate a cascade of intracellular events that culminates with P-glycoprotein upregulation (Bauer et al, 2008b;Avemary et al, 2013). Thus, we hypothesized that the upregulation of MRP2 might also be related to signaling via NMDA receptors.…”

“…Capillaries from human and porcine (10-12 animals per preparation) brain were isolated using a partially modified protocol based on previous studies (Miller et al, 2000;Hartz et al, 2004;Avemary et al, 2013). All steps in the isolation procedure were carried out in freshly prepared solutions maintained at 4°C.…”

“…activated by elevated glutamate concentrations and which drives overexpression of the major multidrug transporter P-glycoprotein (Zhu and Liu, 2004;Bauer et al, 2008b;Avemary et al, 2013). The pathway involves the endothelial NMDA receptor and subsequent activation of arachidonic acid signaling mediated by cyclooxygenase-2 and the prostaglandin E 2 EP1 receptor (Bauer et al, 2008b;Pekcec et al, 2009;Zibell et al, 2009;Potschka, 2010;van Vliet et al, 2010;Avemary et al, 2013).…”

“…In the field of epileptology, studies in rodent and human brain capillaries have revealed that glutamate can upregulate P-glycoprotein via an N-methyl-D-aspartic acid (NMDA) receptor/cyclooxygenase-2 signaling pathway (Bauer et al, 2008b;Zibell et al, 2009;van Vliet et al, 2010;Avemary et al, 2013). Considering the excessive extracellular glutamate concentrations reached during epileptic seizures, this signaling pathway explains the overexpression of P-glycoprotein, which has been repeatedly found in the epileptic brain (Tishler et al, 1995;Thomas et al, 2003Thomas et al, , 2004Thomas et al, , 2005Aronica et al, 2004;Kubota et al, 2006;Ak et al, 2007).…”