scholarly journals Effects of Rapamycin on Insulin Brain Endothelial Cell Binding and Blood–Brain Barrier Transport

2021 ◽  
Vol 9 (3) ◽  
pp. 56
Author(s):  
Steven Nguyen ◽  
William A. Banks ◽  
Elizabeth M. Rhea
Keyword(s):  
Endothelial Cells ◽  
Endothelial Cell ◽  
Insulin Receptor ◽  
Blood Brain Barrier ◽  
Brain Barrier ◽  
Receptor Signaling ◽  
Brain Endothelial Cells ◽  
Serum Factors ◽  
Rapamycin Treatment ◽  
Insulin Receptor Signaling

Rapamycin is an exogenous compound that has been shown to improve cognition in Alzheimer’s disease mouse models and can regulate pathways downstream of the insulin receptor signaling pathway. Insulin is also known to improve cognition in rodent models of Alzheimer’s disease. Central nervous system (CNS) insulin must first cross the blood–brain barrier (BBB), a specialized network of brain endothelial cells. This transport process is regulated by physiological factors, such as insulin itself, triglycerides, cytokines, and starvation. Since rapamycin treatment can alter the metabolic state of rodents, increase the circulating triglycerides, and acts as a starvation mimetic, we hypothesized rapamycin could alter the rate of insulin transport across the BBB, providing a potential mechanism for the beneficial effects of rapamycin on cognition. Using young male and female CD-1 mice, we measured the effects of rapamycin on the basal levels of serum factors, insulin receptor signaling, vascular binding, and BBB pharmacokinetics. We found chronic rapamycin treatment was able to affect basal levels of circulating serum factors and endothelial cell insulin receptor signaling. In addition, while acute rapamycin treatment did affect insulin binding at the BBB, overall transport was unaltered. Chronic rapamycin slowed insulin BBB transport non-significantly (p = 0.055). These results suggest that rapamycin may not directly impact the transport of insulin at the BBB but could be acting to alter insulin signaling within brain endothelial cells, which can affect downstream signaling.

scholarly journals SCIDOT-21. IMPROVING DRUG DELIVERY TO GLIOBLASTOMA BY TARGETING CANONICAL WNT/β-CATENIN SIGNALING IN THE BLOOD-BRAIN BARRIER

2019 ◽  
Vol 21 (Supplement_6) ◽  
pp. vi275-vi276 ◽  
Author(s):  
Amelie Vezina ◽  
Sadhana Jackson
Keyword(s):  
Drug Delivery ◽  
Endothelial Cells ◽  
Endothelial Cell ◽  
Blood Brain Barrier ◽  
Cell Interaction ◽  
Brain Barrier ◽  
Beta Catenin ◽  
Brain Endothelial Cells ◽  
Junctional Proteins ◽  
Blood Brain

Abstract BACKGROUND Glioblastoma (GBM) patient survival and therapy response is greatly hindered by the presence of invasive glioma stem cells (GSC) and the blood-brain barrier (BBB) which limits effective drug delivery. WNT/beta-catenin signaling is important in the development and maintenance of the BBB by mediating transcription of growth factors, multidrug resistance proteins, and junctional proteins. In WNT-subtype medulloblastoma, activating mutations of beta-catenin lead to reciprocal secretion of WNT antagonists such as WIF1 and DKK1 into the tumor microenvironment. These WNT antagonists can act upon the surrounding endothelium and induce a leaky BBB. Therefore, we hypothesize that pharmacological inhibition of WNT/beta-catenin signaling in brain endothelial cells will decrease BBB integrity, enabling enhanced paracellular drug delivery to infiltrative GSCs. METHODS We recapitulated the WNT-medulloblastoma phenotype in GBM by activating WNT/beta-catenin signaling in primary human GSCs, inducing secretion of downstream WNT antagonists. Conditioned-media (CM) from GSCs was then applied to human brain microvascular endothelial cells (HBMEC) to indirectly inhibit WNT signaling. Additionally, we directly inhibited WNT/beta-catenin signaling in HBMECs with the small molecule inhibitor ICG-001. Endothelial cell-cell interaction was measured by electrical impedance using the ACEA xCELLigence system. Fenestration and junctional expression were evaluated by immunoblotting and immunofluorescence. RESULTS ICG-001 or WNT-GSC-CM, but not control GSC-CM, upregulated fenestration related protein, PLVAP, and downregulated junctional proteins claudin-5, ZO-1, and VE-Cadherin in HBMECs. Endothelial cell-cell interaction was transiently decreased by ICG-001 or WNT-GSC-CM. Pre-clinical studies are underway to evaluate the functional impact of WNT/beta-catenin inhibition on BBB integrity and permeability in rodent glioma models. Altogether, these results support targeting WNT/beta-catenin signaling in brain endothelial cells to enhance drug delivery to CNS tumors. CONCLUSION Modulation of intratumoral Wnt/beta-catenin signaling, particularly in highly resistant GSCs, may enhance chemotherapy drug delivery, potentially expanding the drug portfolio and improving the prognosis of GBM.

scholarly journals The insulin receptor is expressed and functional in cultured blood-brain barrier endothelial cells but does not mediate insulin entry from blood to brain

2018 ◽  
Vol 315 (4) ◽  
pp. E531-E542 ◽  
Author(s):  
Maria Hersom ◽  
Hans C. Helms ◽  
Christoffer Schmalz ◽  
Thomas Å. Pedersen ◽  
Stephen T. Buckley ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Insulin Receptor ◽  
Blood Brain Barrier ◽  
Brain Barrier ◽  
Brain Endothelial Cells ◽  
Insulin Transport ◽  
Blood Brain ◽  
The Brain ◽  
Receptor Inhibitor

Insulin and its receptor are known to be present and functional in the brain. Insulin cerebrospinal fluid concentrations have been shown to correlate with plasma levels of insulin in a nonlinear fashion, indicative of a saturable transport pathway from the blood to the brain interstitial fluid. The aim of the present study was to investigate whether insulin was transported across brain endothelial cells in vitro via an insulin receptor-dependent pathway. The study showed that the insulin receptor was expressed at both the mRNA and protein levels in bovine brain endothelial cells. Luminally applied radiolabeled insulin showed insulin receptor-mediated binding to the endothelial cells. This caused a dose-dependent increase in Akt-phosphorylation, which was inhibited by coapplication of an insulin receptor inhibitor, s961, demonstrating activation of insulin receptor signaling pathways. Transport of insulin across the blood-brain barrier in vitro was low and comparable to that of a similarly sized paracellular marker. Furthermore, insulin transport was not inhibited by coapplication of an excess of unlabeled insulin or an insulin receptor inhibitor. The insulin transport and uptake studies were repeated in mouse brain endothelial cells demonstrating similar results. Although it cannot be ruled out that culture-induced changes in the cell model could have impaired a potential insulin transport mechanism, these in vitro data indicate that peripheral insulin must reach the brain parenchyma through alternative pathways rather than crossing the blood-brain barrier via receptor mediated transcytosis.

scholarly journals Extracellular Vesicles Deliver Mitochondria and HSP27 Protein to Protect the Blood-Brain Barrier

2021 ◽  
Author(s):  
Kandarp Dave ◽  
Michael John Reynolds ◽  
Donna B Stolz ◽  
Riyan Babidhan ◽  
Duncan X Dobbins ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Ischemic Stroke ◽  
Endothelial Cell ◽  
Tight Junction ◽  
Human Brain ◽  
Blood Brain Barrier ◽  
Extracellular Vesicles ◽  
Brain Barrier ◽  
Brain Endothelial Cell ◽  
Brain Endothelial Cells

Ischemic stroke causes brain endothelial cell death and damages tight junction integrity of the blood-brain barrier (BBB). We engineered endothelial cell-derived extracellular vesicles (EVs) for the delivery of exogenous heat shock protein 27 (HSP27) and harnessed the innate EV mitochondrial load as a one, two-punch strategy to increase brain endothelial cell survival (via mitochondrial delivery) and preserve their tight junction integrity (via HSP27 delivery). We demonstrated that endothelial microvesicles but not exosomes transferred their mitochondrial load that subsequently underwent fusion with the mitochondrial network of the recipient primary human brain endothelial cells. This mitochondrial transfer increased the relative ATP levels and mitochondrial function in the recipient endothelial cells. EV-mediated HSP27 delivery to primary human brain endothelial cells decreased the paracellular permeability of small and large molecular mass fluorescent tracers in an in vitro model of ischemia/reperfusion injury. This one, two-punch approach to increase the metabolic function and structural integrity of brain endothelial cells is a promising strategy for BBB protection and prevention of long-term neurological dysfunction post-ischemic stroke. 

Neural precursor cell influences on blood–brain barrier characteristics in rat brain endothelial cells

2007 ◽  
Vol 1159 ◽  
pp. 67-76 ◽  
Author(s):  
Joseph C. Lim ◽  
Adam J. Wolpaw ◽  
Maeve A. Caldwell ◽  
Stephen B. Hladky ◽  
Margery A. Barrand
Keyword(s):  
Endothelial Cells ◽  
Rat Brain ◽  
Blood Brain Barrier ◽  
Precursor Cell ◽  
Brain Barrier ◽  
Neural Precursor ◽  
Brain Endothelial Cells ◽  
Neural Precursor Cell ◽  
Blood Brain ◽  
Rat Brain Endothelial Cells

scholarly journals Characterization of a Primate Blood-Brain Barrier Co-Culture Model Prepared from Primary Brain Endothelial Cells, Pericytes and Astrocytes

Pharmaceutics ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 1484
Author(s):  
Daisuke Watanabe ◽  
Shinsuke Nakagawa ◽  
Yoichi Morofuji ◽  
Andrea E. Tóth ◽  
Monika Vastag ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Blood Brain Barrier ◽  
Brain Barrier ◽  
Transport Systems ◽  
Brain Endothelial Cells ◽  
Monkey Brain ◽  
Blood Brain ◽  
Culture Model ◽  
Culture Models ◽  
Human Primate

Culture models of the blood-brain barrier (BBB) are important research tools. Their role in the preclinical phase of drug development to estimate the permeability for potential neuropharmaceuticals is especially relevant. Since species differences in BBB transport systems exist, primate models are considered as predictive for drug transport to brain in humans. Based on our previous expertise we have developed and characterized a non-human primate co-culture BBB model using primary cultures of monkey brain endothelial cells, rat brain pericytes, and rat astrocytes. Monkey brain endothelial cells in the presence of both pericytes and astrocytes (EPA model) expressed enhanced barrier properties and increased levels of tight junction proteins occludin, claudin-5, and ZO-1. Co-culture conditions also elevated the expression of key BBB influx and efflux transporters, including glucose transporter-1, MFSD2A, ABCB1, and ABCG2. The correlation between the endothelial permeability coefficients of 10 well known drugs was higher (R2 = 0.8788) when the monkey and rat BBB culture models were compared than when the monkey culture model was compared to mouse in vivo data (R2 = 0.6619), hinting at transporter differences. The applicability of the new non-human primate model in drug discovery has been proven in several studies.

Modulation of tight junction structure in blood-brain barrier endothelial cells. Effects of tissue culture, second messengers and cocultured astrocytes

1994 ◽  
Vol 107 (5) ◽  
pp. 1347-1357 ◽  
Author(s):  
H. Wolburg ◽  
J. Neuhaus ◽  
U. Kniesel ◽  
B. Krauss ◽  
E.M. Schmid ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Tight Junction ◽  
Tight Junctions ◽  
Blood Brain Barrier ◽  
Barrier Function ◽  
Primary Cultures ◽  
Brain Barrier ◽  
Brain Endothelial Cells ◽  
Blood Brain ◽  
Camp Levels

Tight junctions between endothelial cells of brain capillaries are the most important structural elements of the blood-brain barrier. Cultured brain endothelial cells are known to loose tight junction-dependent blood-brain barrier characteristics such as macromolecular impermeability and high electrical resistance. We have directly analyzed the structure and function of tight junctions in primary cultures of bovine brain endothelial cells using quantitative freeze-fracture electron microscopy, and ion and inulin permeability. The complexity of tight junctions, defined as the number of branch points per unit length of tight junctional strands, decreased 5 hours after culture but thereafter remained almost constant. In contrast, the association of tight junction particles with the cytoplasmic leaflet of the endothelial membrane bilayer (P-face) decreased continuously with a major drop between 16 hours and 24 hours. The complexity of tight junctions could be increased by elevation of intracellular cAMP levels while phorbol esters had the opposite effect. On the other hand, the P-face association of tight junction particles was enhanced by elevation of cAMP levels and by coculture of endothelial cells with astrocytes or exposure to astrocyte-conditioned medium. The latter effect on P-face association was induced by astrocytes but not fibroblasts. Elevation of cAMP levels together with astrocyte-conditioned medium synergistically increased transendothelial electrical resistance and decreased inulin permeability of primary cultures, thus confirming the effects on tight junction structure and barrier function. P-face association of tight junction particles in brain endothelial cells may therefore be a critical feature of blood-brain barrier function that can be specifically modulated by astrocytes and cAMP levels. Our results suggest an important functional role for the cytoplasmic anchorage of tight junction particles for brain endothelial barrier function in particular and probably paracellular permeability in general.

Upregulation of the Low Density Lipoprotein Receptor at the Blood-Brain Barrier: Intercommunications between Brain Capillary Endothelial Cells and Astrocytes

1987 ◽  
Vol 84 (1) ◽  
pp. 465-473
Author(s):  
Bénédicte Dehouck ◽  
Marie-Pierre Dehouck ◽  
Jean-Charles Fruchart ◽  
Roméo Cecchelli
Keyword(s):  
Endothelial Cells ◽  
Endothelial Cell ◽  
Blood Brain Barrier ◽  
Ldl Receptor ◽  
Receptor Expression ◽  
Brain Barrier ◽  
Brain Capillary ◽  
Ldl Receptors ◽  
Brain Capillary Endothelial Cells ◽  
Capillary Endothelial Cells

In contrast to the endothelial cells in large vessels where LDL receptors are downregulated, brain capillary endothelial cells in vivo express an LDL receptor. Using a cell culture model of the blood-brain barrier consisting of a coculture of brain capillary endothelial cells and astrocytes, we observed that the capacity of endothelial cells to bind LDL is enhanced threefold when cocultured with astrocytes. We next investigated the ability of astrocytes to modulate endothelial cell LDL receptor expression. We have shown that the lipid requirement of astrocytes increases the expression of endothelial cell LDL receptors. Experiments with dialysis membranes of different pore size showed that this effect is mediated by a soluble factor(s) with relative molecular mass somewhere between 3,500 and 14,000. Substituting astrocytes with smooth muscle cells or brain endothelium with endothelium from the aorta or the adrenal cortex did not enhance the luminal LDL receptor expression on endothelial cells, demonstrating the specificity of the interactions. This factor(s) is exclusively secreted by astrocytes cocultured with brain capillary endothelial cells, but it also upregulates the LDL receptor on other cell types. This study confirms the notion that the final fine tuning of cell differentiation is under local control.

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