P-glycoprotein is strongly expressed in the luminal membranes of the endothelium of blood vessels in the brain

Luminal membranes of the vascular endothelium were isolated from brain, heart and lungs by modification of their density. The presence of P-glycoprotein (P-gp) was detected by Western blotting in luminal membranes from the endothelium of the three tissues. Strong enrichment in brain capillary luminal membranes, compared with brain capillaries (17-fold) and whole membranes (400–500-fold), indicates that P-gp is mainly located on the luminal side of the brain endothelium. Western blotting was also performed with antibodies directed against GLUT1, glial fibrillary acidic protein, adaptin, IP3R-3, integrins αv and collagen IV as controls to determine whether the preparations were contaminated by other membranes. Strong enrichment of GLUT1 in brain capillary luminal membranes (9.9-fold) showed that the preparation consisted mainly of endothelial cell plasma membranes. Poor enrichment of glial fibrillary acidic protein (1.4-fold) and adaptin (2.4-fold) and a decreased level of IP3R-3, integrins αv and collagen IV excludes the possibility of major contamination by astrocytes or internal and anti-luminal membranes. High levels of P-gp in the luminal membranes of brain capillary endothelial cells suggests that it may play an important role in limiting the access of anti-cancer drugs to the brain.

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P-Glycoprotein-Mediated Transport of Itraconazole across the Blood-Brain Barrier

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.42.7.1738 ◽

1998 ◽

Vol 42 (7) ◽

pp. 1738-1744 ◽

Cited By ~ 72

Author(s):

Tetsuo Miyama ◽

Hitomi Takanaga ◽

Hirotami Matsuo ◽

Katsuhiro Yamano ◽

Koujirou Yamamoto ◽

...

Keyword(s):

Endothelial Cells ◽

Brain Tissue ◽

Blood Brain Barrier ◽

Half Life ◽

Liver Tissue ◽

Brain Barrier ◽

Brain Capillary ◽

P Glycoprotein ◽

Capillary Endothelial Cells ◽

The Brain

ABSTRACT The mechanism for the accumulation of itraconazole (ITZ) in its elimination from the brain was studied in rats and mice. The concentration of ITZ in liver tissue declined in parallel with the plasma ITZ concentration until 24 h after intravenous injection of the drug (half-life, 5 h); however, the ITZ in brain tissue rapidly disappeared (half-life, 0.4 h). The time profiles of the brain/plasma ITZ concentration ratio (Kp value) showed a marked overshooting, and the Kp value increased with increasing dose; these phenomena were not observed in the liver tissue. This finding indicates the occurrence of a nonlinear efflux of ITZ from the brain to the blood. Moreover, based on a pharmacokinetic model which hypothesized processes for both nonlinear and linear effluxes of ITZ from the brain to the blood, we found that the efflux rate constant in the saturable process was approximately sevenfold larger than that in the nonsaturable process. TheKp value for the brain tissue was significantly increased in the presence of ketoconazole or verapamil. The brainKp value for mdr1a knockout mice was also significantly increased compared with that of control mice. Moreover, the uptake of vincristine or vinblastine, both of which are substrates of the P glycoprotein (P-gp), into mouse brain capillary endothelial cells was also significantly increased by ITZ or verapamil. In conclusion, P-gp in the brain capillary endothelial cells participates in a process of active efflux of ITZ from the brain to the blood at the blood-brain barrier, and ITZ can be an inhibitor of various substrates of P-gp.

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Modulation of p-Glycoprotein Transport Function at the Blood-Brain Barrier

Experimental Biology and Medicine ◽

10.1177/153537020523000206 ◽

2005 ◽

Vol 230 (2) ◽

pp. 118-127 ◽

Cited By ~ 95

Author(s):

Björn Bauer ◽

Anika M. S. Hartz ◽

Gert Fricker ◽

David S. Miller

Keyword(s):

Blood Brain Barrier ◽

Viral Infections ◽

Brain Barrier ◽

Capillary Endothelium ◽

Brain Capillary ◽

P Glycoprotein ◽

Blood Brain ◽

Junctional Permeability ◽

Capillary Endothelial Cells ◽

The Brain

The central nervous system (CNS) effects of many therapeutic drugs are blunted because of restricted entry into the brain. The basis for this poor permeability is the brain capillary endothelium, which comprises the blood-brain barrier. This tissue exhibits very low paracellular (tight-junctional) permeability and expresses potent, multispecific, drug export pumps. Together, these combine to limit use of pharmacotherapy to treat CNS disorders such as brain cancer and bacterial or viral infections. Of all the xenobiotic efflux pumps highly expressed in brain capillary endothelial cells, p-glycoprotein handles the largest fraction of commonly prescribed drugs and thus is an obvious target for manipulation. Here we review recent studies focused on understanding the mechanisms by which p-glycoprotein activity in the blood-brain barrier can be modulated. These include (i) direct inhibition by specific competitors, (ii) functional modulation, and (iii) transcriptional modulation. Each has the potential to specifically reduce p-glycoprotein function and thus selectively increase brain permeability of p-glycoprotein substrates.

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Age influences susceptibility of brain capillary endothelial cells to La Crosse virus infection and cell death

Journal of Neuroinflammation ◽

10.1186/s12974-021-02173-4 ◽

2021 ◽

Vol 18 (1) ◽

Author(s):

Rahul Basu ◽

Vinod Nair ◽

Clayton W. Winkler ◽

Tyson A. Woods ◽

Iain D. C. Fraser ◽

...

Keyword(s):

Endothelial Cells ◽

Cell Death ◽

Virus Infection ◽

La Crosse Virus ◽

Brain Capillary ◽

Adult Mice ◽

Age Related ◽

Capillary Endothelial Cells ◽

The Brain

Abstract Background A key factor in the development of viral encephalitis is a virus crossing the blood-brain barrier (BBB). We have previously shown that age-related susceptibility of mice to the La Crosse virus (LACV), the leading cause of pediatric arbovirus encephalitis in the USA, was associated with the ability of the virus to cross the BBB. LACV infection in weanling mice (aged around 3 weeks) results in vascular leakage in the olfactory bulb/tract (OB/OT) region of the brain, which is not observed in adult mice aged > 6–8 weeks. Thus, we studied age-specific differences in the response of brain capillary endothelial cells (BCECs) to LACV infection. Methods To examine mechanisms of LACV-induced BBB breakdown and infection of the CNS, we analyzed BCECs directly isolated from weanling and adult mice as well as established a model where these cells were infected in vitro and cultured for a short period to determine susceptibility to virus infection and cell death. Additionally, we utilized correlative light electron microscopy (CLEM) to examine whether changes in cell morphology and function were also observed in BCECs in vivo. Results BCECs from weanling, but not adult mice, had detectable infection after several days in culture when taken ex vivo from infected mice suggesting that these cells could be infected in vitro. Further analysis of BCECs from uninfected mice, infected in vitro, showed that weanling BCECs were more susceptible to virus infection than adult BCECs, with higher levels of infected cells, released virus as well as cytopathic effects (CPE) and cell death. Although direct LACV infection is not detected in the weanling BCECs, CLEM analysis of brain tissue from weanling mice indicated that LACV infection induced significant cerebrovascular damage which allowed virus-sized particles to enter the brain parenchyma. Conclusions These findings indicate that BCECs isolated from adult and weanling mice have differential viral load, infectivity, and susceptibility to LACV. These age-related differences in susceptibility may strongly influence LACV-induced BBB leakage and neurovascular damage allowing virus invasion of the CNS and the development of neurological disease.

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P-glycoprotein expression in brain capillary endothelial cells after focal ischaemia in the rat

Neurological Research ◽

10.1080/01616412.1994.11740231 ◽

1994 ◽

Vol 16 (3) ◽

pp. 217-223 ◽

Cited By ~ 9

Author(s):

Ken Samoto ◽

Kiyonobu Ikezaki ◽

Nobuhiko Yokoyama ◽

Masashi Fukui

Keyword(s):

Endothelial Cells ◽

Brain Capillary ◽

Brain Capillary Endothelial Cells ◽

P Glycoprotein ◽

Capillary Endothelial Cells ◽

Focal Ischaemia

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P-glycoprotein as the drug efflux pump in primary cultured bovine brain capillary endothelial cells

Life Sciences ◽

10.1016/0024-3205(92)90537-y ◽

1992 ◽

Vol 51 (18) ◽

pp. 1427-1437 ◽

Cited By ~ 197

Author(s):

Akira Tsuji ◽

Tetsuya Terasaki ◽

Yasushi Takabatake ◽

Yoshiyuki Tenda ◽

Ikumi Tamai ◽

...

Keyword(s):

Endothelial Cells ◽

Efflux Pump ◽

Bovine Brain ◽

Drug Efflux ◽

Brain Capillary ◽

Brain Capillary Endothelial Cells ◽

P Glycoprotein ◽

Capillary Endothelial Cells ◽

Drug Efflux Pump

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Characterization and tissue localization of zebrafish homologs of the human ABCB1 multidrug transporter

10.1101/2021.02.18.431829 ◽

2021 ◽

Author(s):

Robert W. Robey ◽

Andrea N. Robinson ◽

Fatima Ali-Rahmani ◽

Lyn M. Huff ◽

Sabrina Lusvarghi ◽

...

Keyword(s):

Endothelial Cells ◽

Multidrug Transporter ◽

Glycoprotein P ◽

Tissue Localization ◽

Brain Vasculature ◽

P Glycoprotein ◽

Capillary Endothelial Cells ◽

The Brain ◽

Viable Model

ABSTRACTGiven its similarities with mammalian systems, the zebrafish has emerged as a potential model to study the blood-brain barrier (BBB). Capillary endothelial cells at the human BBB express high levels of P-glycoprotein (P-gp, encoded by the ABCB1 gene) and ABCG2 (encoded by the ABCG2 gene). However, little information has been available about ATP-binding cassette transporters expressed at the zebrafish BBB. In this study, we focus on the characterization and tissue localization of two genes that are similar to human ABCB1, zebrafish abcb4 and abcb5. Cytotoxicity assays with stably-transfected cell lines revealed that zebrafish Abcb5 cannot efficiently transport the substrates doxorubicin and mitoxantrone compared to human P-gp and zebrafish Abcb4. Additionally, zebrafish Abcb5 did not transport the fluorescent probes BODIPY-ethylenediamine or LDS 751, while they were readily transported by Abcb4 and P-gp. A high-throughput screen conducted with 90 human P-gp substrates confirmed that zebrafish Abcb4 has overlapping substrate specificity with P-gp. Basal ATPase activity of zebrafish Abcb4 and Abcb5 was comparable to that of human P-gp. In the brain vasculature, RNAscope probes to detect abcb4 colocalized with staining by the P-gp antibody C219, while abcb5 was not detected. Zebrafish abcb4 also colocalized with claudin-5 expression in brain endothelial cells. Abcb4 and Abcb5 had different tissue localizations in multiple zebrafish tissues, consistent with different functions. The data suggest that zebrafish Abcb4 most closely phenocopies P-gp and that the zebrafish may be a viable model to study the role of the multidrug transporter P-gp at the BBB.

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