P-glycoprotein traffics from the nucleus to the plasma membrane in rat brain endothelium during inflammatory pain

Abstract

P-glycoprotein (PgP), a drug efflux pump in blood-brain barrier endothelial cells, is a major clinical obstacle for effective central nervous system drug delivery. Identifying PgP regulatory pathways that can be exploited clinically is critical for improving central nervous system drug delivery. We previously found that PgP activity increases in rat brain microvessels concomitant with decreased central nervous system drug delivery in response to acute peripheral inflammatory pain. In the current study, we tested the hypothesis that PgP traffics to the luminal plasma membrane of the microvessel endothelial cells from intracellular stores during peripheral inflammatory pain. Using immunofluorescence microscopy, we detected PgP in endothelial cell nuclei and in the luminal plasma membrane in control animals. Following peripheral inflammatory pain, luminal PgP staining increased while staining in the nucleus decreased. Biochemical analysis of nuclear PgP content confirmed our visual observations. Peripheral inflammatory pain also increased endothelial cell luminal staining of polymerase 1 and transcript release factor/cavin1 and serum deprivation response protein/cavin2, two caveolar scaffold proteins, without changing caveolin1 or protein kinase C delta binding protein/cavin3 location. Our data (a) indicate that PgP traffics from stores in the nucleus to the endothelial cell luminal membrane in response to peripheral inflammatory pain; (b) provide an explanation for our previous observation that peripheral inflammatory pain inhibits central nervous system drug uptake; and (c) suggest a novel regulatory mechanism for PgP activity in rat brain. KeywordsCaveolin1, P-glycoprotein, protein kinase C delta binding protein/cavin3, polymerase 1 and transcript release factor/ cavin1, serum deprivation response protein/cavin2, trafficking

Isogenic blood–brain barrier models based on patient‐derived stem cells display inter‐individual differences in cell maturation and functionality

“…We speculate that the difference between protein expression and activity maybe partially explained by a distribution of some of these efflux transporters within intracellular compartments and their trafficking to the cell surface as recently described by Tome and colleagues (Tome et al . ). Therefore, further investigation focused on elucidating such differences between transporter expression and activities will provide us with a better understanding.…”

Functional Expression of P-glycoprotein and Organic Anion Transporting Polypeptides at the Blood-Brain Barrier: Understanding Transport Mechanisms for Improved CNS Drug Delivery?

“…Targeting P-gp with small molecules has been challenging because first and second P-gp inhibitors have exhibited toxicity issues as well as inhibition of CYP3A4 and other transporters, respectively (30,31,40). Future advances in targeting P-gp for CNS drug delivery are likely to involve targeting of regulatory pathways (95, 96) or transporter trafficking in brain microvascular endothelial cells (45). We propose an alternative approach to optimization of CNS drug delivery via targeting of endogenous SLC uptake transporters expressed at the BBB, such as Oatps.…”

“…As such, it is recommended that P-gp inhibition should be relied upon only in short-term use to treat diseases such as brain tumors when the goal is to increase drug concentrations for a short period of time (16). Alternative strategies, such as targeting signaling pathways that regulate P-gp expression and/or activity, may be a better approach to improve drug delivery (4,44,45). …”

“…Selective regulation of P-gp at the BBB could promote improved permeability of CNS drugs into brain parenchyma, thus enabling a drug to reach its site of action at therapeutic concentrations (44,45). For example, Cannon and colleagues showed, in vivo, that targeting sphingolipid signaling with fingolimod, an clinically approved drug used in multiple sclerosis treatment, reduced basal P-gp activity and promoted improved CNS drug delivery (44).…”

Chronic morphine exposure potentiates p-glycoprotein trafficking from nuclear reservoirs in cortical rat brain microvessels

“…This effect can be reversed by administration of a nerve block, demonstrating a clear relationship between nociceptive relay and reduction of the analgesic effect of morphine [ 19 ]. The decrease in morphine analgesic efficacy is accompanied by redistribution of p-gp within membrane microdomains [ 20 ] and trafficking of p-gp from nuclear reservoirs to the luminal surface of the brain endothelial cells [ 21 ]. This trafficking moves p-gp to an intracellular location where it can function to increase the export of substrates, including opioids, into the blood.…”