P-gp Protein Expression and Transport Activity in Rodent Seizure Models and Human Epilepsy

Abstract

A cure for epilepsy is currently not available, and seizure genesis, seizure recurrence, and resistance to antiseizure drugs remain serious clinical problems. Studies show that the blood–brain barrier is altered in animal models of epilepsy and in epileptic patients. In this regard, seizures increase expression of blood–brain barrier efflux transporters such as P-glycoprotein (P-gp), which is thought to reduce brain uptake of antiseizure drugs, and thus, contribute to antiseizure drug resistance. The goal of the current study was to assess the viability of combining in vivo and ex vivo preparations of isolated brain capillaries from animal models of seizures and epilepsy as well as from patients with epilepsy to study P-gp at the blood–brain barrier. Exposing isolated rat brain capillaries to glutamate ex vivo upregulated P-gp expression to levels that were similar to those in capillaries isolated from rats that had status epilepticus or chronic epilepsy. Moreover, the fold-increase in P-gp protein expression seen in animal models is consistent with the fold-increase in P-gp observed in human brain capillaries isolated from patients with epilepsy compared to age-matched control individuals. Overall, the in vivo/ex vivo approach presented here allows detailed analysis of the mechanisms underlying seizure-induced changes of P-gp expression and transport activity at the blood–brain barrier. This approach can be extended to other blood–brain barrier proteins that might contribute to drug-resistant epilepsy or other CNS disorders as well.

Modulation of glucocorticoid receptor in human epileptic endothelial cells impacts drug biotransformation in an in vitro blood–brain barrier model

“…Pharmacoresistance in epilepsy has been supported by several theories . The role of drug‐metabolizing enzymes and the formation of reactive metabolites due to enzymatic conversion by local ECs affecting drug bioavailability to the brain in DRE is one such theory .…”

Downregulation of peripheral PTGS2/COX-2 in response to valproate treatment in patients with epilepsy

“…Elucidating the molecular mechanisms regulating these transporters is crucial to understand AED efficacy and to identify neurotherapeutic targets for developing better efficacious pharmacotherapy. P-gp, a multidrug efflux transporter, is highly expressed in brain capillary endothelial cells and its upregulation in the surgically-removed brain samples of PWE is widely acknowledged as the major cause for AED resistance 40,[42][43][44] . It has been proposed that seizures induce COX-2 expression 45,46 which further regulates P-gp by producing increased levels of PGE 2 36,37 .…”

“…Rhodamine 123 efflux assay, a P-gp-specific transport assay, also showed induced P-gp activity in the hCMEC/D3 cells upon glutamate exposure which was significantly blocked by the NMDA receptor antagonist, MK-801 and EP1 receptor antagonist, SC-51089 confirming the involvement of the two receptors in glutamate-mediated transcriptional activation of P-gp. Several investigations demonstrated P-gp upregulation in brain and BBB in patients with refractory epilepsy [40][41][42][43][44] . Drug-resistant rodent epilepsy models were also reported to have higher brain P-gp levels than the drug-responsive ones 55 .…”

Cannabidiol (CBD) Inhibited Rhodamine-123 Efflux in Cultured Vascular Endothelial Cells and Astrocytes Under Hypoxic Conditions

“…P-gp expression is regulated by hypoxia, inflammation, and stress-related transcriptional factors such as HIF-1α, NFκB, STAT3, or PXR (Ho and Piquette-Miller, 2006;Jain et al, 2014;Zhang Z.-L. et al, 2018). Moreover, upregulation of P-gp was reported in a wide spectrum of experimental models and clinical studies of RE (Lazarowski et al, 2004b(Lazarowski et al, , 2007bHartz et al, 2017;Deng et al, 2018;Weidner et al, 2018). During hypoxia, P-gp was overexpressed in different tissues, including brain and heart (Lazarowski et al, 2007a;Aviles-Reyes et al, 2010;Merelli et al, 2011a,b).…”