scholarly journals 2,4,6-Tribromophenol Exposure Decreases P-Glycoprotein Transport at the Blood-Brain Barrier

2019 ◽  
Vol 171 (2) ◽  
pp. 463-472 ◽  
Author(s):  
Andrew W Trexler ◽  
Gabriel A Knudsen ◽  
Sascha C T Nicklisch ◽  
Linda S Birnbaum ◽  
Ronald E Cannon
Keyword(s):  
Blood Brain Barrier ◽  
Ex Vivo ◽  
Female Rats ◽  
Brain Barrier ◽  
Transport Activity ◽  
Fish Food ◽  
P Glycoprotein ◽  
Blood Brain ◽  
Male And Female Rats

Abstract 2,4,6-Tribromophenol (TBP, CAS No. 118-79-6) is a brominated chemical used in the production of flame-retardant epoxy resins and as a wood preservative. In marine environments, TBP is incorporated into shellfish and consumed by predatory fish. Food processing and water treatment facilities produce TBP as a byproduct. 2,4,6-Tribromophenol has been detected in human blood and breast milk. Biologically, TBP interferes with estrogen and thyroid hormone signaling, which regulate important transporters of the blood-brain barrier (BBB). The BBB is a selectively permeable barrier characterized by brain microvessels which are composed of endothelial cells mortared by tight-junction proteins. ATP-binding cassette (ABC) efflux transporters on the luminal membrane facilitate the removal of unwanted endobiotics and xenobiotics from the brain. In this study, we examined the in vivo and ex vivo effects of TBP on two important transporters of the BBB: P-glycoprotein (P-gp, ABCB1) and Multidrug Resistance-associated Protein 2 (MRP2, ABCC2), using male and female rats and mice. 2,4,6-Tribromophenol exposure ex vivo resulted in a time- (1–3 h) and dose- (1–100 nM) dependent decrease in P-gp transport activity. MRP2 transport activity was unchanged under identical conditions. Immunofluorescence and western blotting measured decreases in P-gp expression after TBP treatment. ATPase assays indicate that TBP is not a substrate and does not directly interact with P-gp. In vivo dosing with TBP (0.4 µmol/kg) produced decreases in P-gp transport. Co-treatment with selective protein kinase C (PKC) inhibitors prevented the TBP-mediated decreases in P-gp transport activity.

scholarly journals Tariquidar, a Selective P-glycoprotein Inhibitor, Does Not Potentiate Loperamide’s Opioid Brain Effects in Humans despite Full Inhibition of Lymphocyte P-glycoprotein

2008 ◽  
Vol 109 (6) ◽  
pp. 1092-1099 ◽  
Author(s):  
Daniel Kurnik ◽  
Gbenga G. Sofowora ◽  
John P. Donahue ◽  
Usha B. Nair ◽  
Grant R. Wilkinson ◽  
...  
Keyword(s):  
Blood Brain Barrier ◽  
Pupil Diameter ◽  
Ex Vivo ◽  
Area Under The Curve ◽  
Brain Barrier ◽  
Double Blind ◽  
P Glycoprotein ◽  
Blood Brain ◽  
Double Blind Crossover Study

Background Loperamide, a potent opioid, has been used as an in vivo probe to assess P-glycoprotein activity at the blood-brain barrier, because P-glycoprotein inhibition allows loperamide to cross the blood-brain barrier and exert its central opioid effects. In humans, studies with nonselective and moderately potent inhibitors resulted in mild opioid effects but were confounded by the concurrent inhibition of loperamide's metabolism. The authors studied the effect of the highly selective, potent P-glycoprotein inhibitor tariquidar on loperamide's central opioid effects. Methods In a randomized, double-blind, crossover study, nine healthy subjects received on 2 study days oral loperamide (32 mg) followed by an intravenous infusion of either tariquidar (150 mg) or placebo. Central opioid effects (pupil diameter, sedation) were measured for 12 h, and blood samples were drawn up to 48 h after drug administration to determine plasma loperamide concentrations and ex vivo P-glycoprotein activity in T lymphocytes. Values for pupil diameter and loperamide concentrations were plotted over time, and the areas under the curves on the tariquidar and placebo study day were compared within each subject. Results Tariquidar did not significantly affect loperamide's central effects (median reduction in pupil diameter area under the curve, 6.9% [interquartile range, -1.4 to 12.1%]; P = 0.11) or plasma loperamide concentrations (P = 0.12) but profoundly inhibited P-glycoprotein in lymphocytes by 93.7% (95% confidence interval, 92.0-95.3%). Conclusion These results suggest that despite full inhibition of lymphocyte P-glycoprotein, the selective P-glycoprotein inhibitor tariquidar does not potentiate loperamide's opioid brain effects in humans.

scholarly journals Protecting P-glycoprotein at the blood–brain barrier from degradation in an Alzheimer’s disease mouse model

2021 ◽  
Vol 18 (1) ◽  
Author(s):  
Yujie Ding ◽  
Yu Zhong ◽  
Andrea Baldeshwiler ◽  
Erin L. Abner ◽  
Björn Bauer ◽  
...  
Keyword(s):  
Mouse Model ◽  
Protein Expression ◽  
Blood Brain Barrier ◽  
Brain Barrier ◽  
Activity Levels ◽  
Transport Activity ◽  
Brain Capillaries ◽  
P Glycoprotein ◽  
Blood Brain

AbstractBackgroundFailure to clear Aβ from the brain is partly responsible for Aβ brain accumulation in Alzheimer’s disease (AD). A critical protein for clearing Aβ across the blood-brain barrier is the efflux transporter P-glycoprotein (P-gp). In AD, P-gp levels are reduced, which contributes to impaired Aβ brain clearance. However, the mechanism responsible for decreased P-gp levels is poorly understood and there are no strategies available to protect P-gp. We previously demonstrated in isolated brain capillariesex vivothat human Aβ40 (hAβ40) triggers P-gp degradation by activating the ubiquitin-proteasome pathway. In this pathway, hAβ40 initiates P-gp ubiquitination, leading to internalization and proteasomal degradation of P-gp, which then results in decreased P-gp protein expression and transport activity levels. Here, we extend this line of research and present results from anin vivostudy using a transgenic mouse model of AD (human amyloid precursor protein (hAPP)-overexpressing mice; Tg2576).MethodsIn our study, hAPP mice were treated with vehicle, nocodazole (NCZ, microtubule inhibitor to block P-gp internalization), or a combination of NCZ and the P-gp inhibitor cyclosporin A (CSA). We determined P-gp protein expression and transport activity levels in isolated mouse brain capillaries and Aβ levels in plasma and brain tissue.ResultsTreating hAPP mice with 5 mg/kg NCZ for 14 days increased P-gp levels to levels found in WT mice. Consistent with this, P-gp-mediated hAβ42 transport in brain capillaries was increased in NCZ-treated hAPP mice compared to untreated hAPP mice. Importantly, NCZ treatment significantly lowered hAβ40 and hAβ42 brain levels in hAPP mice, whereas hAβ40 and hAβ42 levels in plasma remained unchanged.ConclusionsThese findings provide in vivo evidence that microtubule inhibition maintains P-gp protein expression and transport activity levels, which in turn helps to lower hAβ brain levels in hAPP mice. Thus, protecting P-gp at the blood-brain barrier may provide a novel therapeutic strategy for AD and other Aβ-based pathologies.

scholarly journals Protecting P-glycoprotein at the Blood-Brain Barrier from Degradation in an Alzheimer’s Disease Mouse Model

2020 ◽  
Author(s):  
Yujie Ding ◽  
Yu Zhong ◽  
Andrea Baldeshwiler ◽  
Erin L. Abner ◽  
Björn Bauer ◽  
...  
Keyword(s):  
Mouse Model ◽  
Protein Expression ◽  
Blood Brain Barrier ◽  
Brain Barrier ◽  
Activity Levels ◽  
Transport Activity ◽  
Brain Capillaries ◽  
P Glycoprotein ◽  
Blood Brain

Abstract Background. Failure to clear Aβ from the brain is partly responsible for Aβ brain accumulation in Alzheimer’s disease (AD). A critical protein for clearing Aβ across the blood-brain barrier is the efflux transporter P-glycoprotein (P-gp). In AD, P-gp levels are reduced, which contributes to impaired Aβ brain clearance. However, the mechanism responsible for decreased P-gp levels is poorly understood and there are no strategies available to protect P-gp. We previously demonstrated in isolated brain capillaries ex vivo that human Aβ40 (hAβ40) triggers P-gp degradation by activating the ubiquitin-proteasome pathway. In this pathway, hAβ40 initiates P-gp ubiquitination, leading to internalization and proteasomal degradation of P-gp, which then results in decreased P-gp protein expression and transport activity levels. Here, we extend this line of research and present results from an in vivo study using a transgenic mouse model of AD (human amyloid precursor protein (hAPP)-overexpressing mice; Tg2576). Methods. In our study, hAPP mice were treated with vehicle, nocodazole (NCZ, microtubule inhibitor to block P-gp internalization), or a combination of NCZ and the P-gp inhibitor cyclosporin A (CSA). We determined P-gp protein expression and transport activity levels in isolated mouse brain capillaries and Aβ levels in plasma and brain tissue. Results. Treating hAPP mice with 5 mg/kg NCZ for 14 days protected P-gp from degradation. Consistent with this, P-gp-mediated hAβ42 transport in brain capillaries was increased in NCZ-treated hAPP mice compared to untreated hAPP mice. Importantly, NCZ treatment significantly lowered hAβ40 and hAβ42 brain levels in hAPP mice, whereas hAβ40 and hAβ42 levels in plasma remained unchanged. Conclusions. These findings provide in vivo proof that blocking P-gp internalization protects P-gp from degradation and maintains P-gp protein expression and transport activity levels, which in turn lowers hAβ brain levels. Thus, protecting P-gp at the blood-brain barrier may provide a novel therapeutic target for AD and other Aβ-based pathologies.

scholarly journals 17-β-Estradiol: A Powerful Modulator of Blood–Brain Barrier BCRP Activity

2010 ◽  
Vol 30 (10) ◽  
pp. 1742-1755 ◽  
Author(s):  
Anika MS Hartz ◽  
Anne Mahringer ◽  
David S Miller ◽  
Björn Bauer
Keyword(s):  
Blood Brain Barrier ◽  
Ex Vivo ◽  
Brain Barrier ◽  
Cancer Resistance ◽  
Transport Activity ◽  
Brain Capillaries ◽  
Therapeutic Drugs ◽  
Blood Brain ◽  
Capillary Membranes ◽  
Blood Brain Barrier Model

The ATP-driven efflux transporter, breast cancer resistance protein (BCRP), handles many therapeutic drugs, including chemotherapeutics, limiting their ability to cross the blood–brain barrier. This study provides new insight into rapid, nongenomic regulation of BCRP transport activity at the blood–brain barrier. Using isolated brain capillaries from rats and mice as an ex vivo blood–brain barrier model, we show that BCRP protein is highly expressed in brain capillary membranes and functionally active in intact capillaries. We show that nanomolar concentrations of 17-β-estradiol (E2) rapidly reduced BCRP transport activity in the brain capillaries. This E2-mediated effect occurred within minutes and did not involve transcription, translation, or proteasomal degradation, indicating a nongenomic mechanism. Removing E2 after 1 h fully reversed the loss of BCRP activity. Experiments using agonists and antagonists for estrogen receptor (ER)α and ERβ and brain capillaries from ERα and ERβ knockout mice demonstrated that E2 could signal through either receptor to reduce BCRP transport function. We speculate that this nongenomic E2-signaling pathway could potentially be used for targeting BCRP at the blood–brain barrier, in brain tumors, and in brain tumor stem cells to improve chemotherapy of the central nervous system.

scholarly journals EXTH-67. IDENTIFICATION AND DEVELOPMENT OF NEURAL ECM-BINDING LAMPREY ANTIBODIES (VARIABLE LYMPHOCYTE RECEPTORS) THAT TARGET GLIOBLASTOMA

2019 ◽  
Vol 21 (Supplement_6) ◽  
pp. vi96-vi96
Author(s):  
Benjamin Umlauf ◽  
Paul Clark ◽  
Jason Lajoie ◽  
Julia Georgieva ◽  
Samantha Bremner ◽  
...  
Keyword(s):  
Blood Brain Barrier ◽  
Ex Vivo ◽  
High Specificity ◽  
Recognition System ◽  
Brain Barrier ◽  
Disease Markers ◽  
Blood Brain ◽  
Lymphocyte Receptors

Abstract INTRODUCTION The median survival of glioblastoma (GBM) patients remains less than two years even with state-of-the-art treatment. Current targeted GBM therapies demonstrate initial therapeutic benefit; however, patients relapse due to therapeutic selection of treatment resistant GBM cellular populations. Therefore, we propose targeting pathologic disruption of the blood brain barrier (BBB) via exposure of neural ECM, rather than disease markers, to overcome therapy-resistant GBM. METHODS We identify Variable Lymphocyte Receptors (VLRs, the antigen recognition system used by lamprey) that demonstrate high specificity for neural ECM. Candidate VLRs underwent further refinement using in vitro binding assays and ex vivo tissue staining. Utilizing pathologic disruption of BBB as an approach for targeting GBM was confirmed in vivo using intracranial murine glioblastoma models. RESULTS The lead neural ECM-binding VLR candidate, named P1C10, demonstrates diffuse binding to parenchymal neural ECM, without detectable binding to other tissues. P1C10 demonstrates nanomolar affinity for in vitro derived neural ECM, and preferentially accumulates at intracranial GL261 and U87 lesions in murine GBM models. Finally, administration of P1C10-targeted doxorubicin-loaded liposomes significantly extends the survival of mice bearing intracranial U87 GBM. CONCLUSIONS We identified VLRs that bind neural ECM, and demonstrate their utility for delivering compounds and nanoparticles to sites of GBM induced blood brain barrier disruption. This novel strategy allows for targeting therapeutics via the underlying physiology of GBM rather than relying on cellular disease markers that are often lost in patients that relapse after targeting therapies.

scholarly journals Rapid Loss of Blood–Brain Barrier P-Glycoprotein Activity through Transporter Internalization Demonstrated Using a Novel in Situ Proteolysis Protection Assay

2010 ◽  
Vol 30 (9) ◽  
pp. 1593-1597 ◽  
Author(s):  
Brian T Hawkins ◽  
Robert R Rigor ◽  
David S Miller
Keyword(s):  
Blood Brain Barrier ◽  
Underlying Mechanism ◽  
Brain Barrier ◽  
Proteinase K ◽  
Protection Assay ◽  
Luminal Membrane ◽  
P Glycoprotein ◽  
Blood Brain ◽  
Factor Α

Blood–brain barrier (BBB) P-glycoprotein activity is rapidly reduced by vascular endothelial growth factor (VEGF) acting via Src and by tumor necrosis factor-α acting via protein kinase C (PKC)β1. To probe underlying mechanism(s), we developed an in vivo, immunoblot-based proteinase K (PK) protection assay to assess the changes in the P-glycoprotein content of the BBB's luminal membrane. Infusion of PK into the brain vasculature selectively cleaved luminal membrane P-glycoprotein, leaving intracellular proteins intact. Intracerebroventricular injection of VEGF partially protected P-glycoprotein from proteolytic cleavage, consistent with transporter internalization. Activation of PKCβ1 did not protect P-glycoprotein. Thus, VEGF and PKCβ1 reduce P-glycoprotein activity by distinct mechanisms.

scholarly journals Comparative vulnerability of PET radioligands to partial inhibition of P-glycoprotein at the blood-brain barrier: A criterion of choice?

2021 ◽  
pp. 0271678X2110454
Author(s):  
Louise Breuil ◽  
Solène Marie ◽  
Sébastien Goutal ◽  
Sylvain Auvity ◽  
Charles Truillet ◽  
...  
Keyword(s):  
Blood Brain Barrier ◽  
Pet Imaging ◽  
Brain Barrier ◽  
Maximal Response ◽  
Half Maximum ◽  
Partial Inhibition ◽  
P Glycoprotein ◽  
Blood Brain

Only partial deficiency/inhibition of P-glycoprotein (P-gp, ABCB1) function at the blood-brain barrier (BBB) is likely to occur in pathophysiological situations or drug-drug interactions. This raises questions regarding the sensitivity of available PET imaging probes to detect moderate changes in P-gp function at the living BBB. In vitro, the half-maximum inhibitory concentration (IC50) of the potent P-gp inhibitor tariquidar in P-gp-overexpressing cells was significantly different using either [11C]verapamil (44 nM), [11C] N-desmethyl-loperamide (19 nM) or [11C]metoclopramide (4 nM) as substrate probes. In vivo PET imaging in rats showed that the half-maximum inhibition of P-gp-mediated efflux of [11C]metoclopramide, achieved using 1 mg/kg tariquidar ( in vivo IC50 = 82 nM in plasma), increased brain exposure by 2.1-fold for [11C]metoclopramide (p < 0.05, n = 4) and 2.4-fold for [11C]verapamil (p < 0.05, n = 4), whereby cerebral uptake of the “avid” substrate [11C] N-desmethyl-loperamide was unaffected (p > 0.05, n = 4). This comparative study points to differences in the “vulnerability” to P-gp inhibition among radiolabeled substrates, which were apparently unrelated to their “avidity” (maximal response to P-gp inhibition). Herein, we advocate that partial inhibition of transporter function, in addition to complete inhibition, should be a primary criterion of evaluation regarding the sensitivity of radiolabeled substrates to detect moderate but physiologically-relevant changes in transporter function in vivo.

scholarly journals Sphingolipids signal rapid loss of P‐glycoprotein transport activity at the blood‐brain barrier

2012 ◽  
Vol 26 (S1) ◽  
Author(s):  
David S. Miller ◽  
Christopher R. Campos ◽  
Brian T. Hawkins ◽  
Ronald Cannon
Keyword(s):  
Blood Brain Barrier ◽  
Brain Barrier ◽  
Transport Activity ◽  
Rapid Loss ◽  
P Glycoprotein ◽  
Blood Brain ◽  
Glycoprotein Transport
Sign in / Sign up

Export Citation Format

Share Document