Transport of Proteins Across the Blood-Brain Barrier via the Transferrin Receptor

We develop and analyze mathematical models for receptor-mediated transcytosis of monoclonal antibodies (MAb) targeting the transferrin receptor (TfR) or the insulin receptor (IR), which are expressed at the blood-brain barrier (BBB). The mass-action kinetic model for both the TfR and IR antibodies were solved numerically to generate predictions for the concentrations of all species in all compartments considered. Using these models, we estimated the rates of MAb endocytosis into brain capillary endothelium, which forms the BBB in vivo, the rates of MAb exocytosis from the intra-endothelial compartment into brain extracellular space, and the rates of receptor recycling from the endothelial space back to the luminal endothelial plasma membrane. Our analysis highlights the optimal rates of MAb association with the targeted receptor. An important role of the endogenous ligand, transferrin (Tf) or insulin, in receptor-mediated-transport (RMT) of the associated MAb was found and was attributed to the five order magnitude difference between plasma concentrations of Tf (25,000 nM) and insulin (0.3 nM). Our modeling shows that the very high plasma concentration of Tf leads to only 5% of the endothelial TfR expressed on the luminal endothelial membrane.

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Transferrin Receptor Mediated Brain Uptake During Ischemia and Reperfusion

Journal of Pharmacy & Pharmaceutical Sciences ◽

10.18433/j3b303 ◽

2013 ◽

Vol 16 (4) ◽

pp. 541 ◽

Cited By ~ 3

Author(s):

Jiukuan Hao ◽

Ulrich Bickel

Keyword(s):

Drug Delivery ◽

Blood Flow ◽

Blood Brain Barrier ◽

Transferrin Receptor ◽

Complete Recovery ◽

Apparent Volume ◽

Healthy Tissue ◽

Brain Barrier ◽

Brain Uptake ◽

Blood Brain

Purpose. Drug delivery by transferrin receptor-mediated transport at the blood-brain barrier has shown beneficial effects in animal models of stroke, but it is unclear whether receptor mediated uptake remains functional in the ischemic tissue. The present study addressed that question in a mouse model of brain focal ischemia, permanent or transient middle cerebral artery occlusion (MCAO). Methods. Brain accumulation of 125I-labeled 8D3, a mouse-specific transferrin receptor antibody, or of the isotype control UPC-10 used as vascular marker, was measured autoradiographically by phosphorimaging in the core ischemic region on cryostat brain sections up to 24h after ischemia or reperfusion. Cerebral blood flow was quantitatively determined in the same animals after administration of 99mTc-ECD (Neurolite). Results. Apparent volume of distribution obtained with UPC-10 indicated no significant nonspecific leakage of the blood-brain barrier at any time point. Although brain uptake of 8D3 gradually declined compared to healthy tissue under MCAO, VD remained significantly higher than VD of UPC-10 up to 5h. In transient MCAO the brain uptake recovered to levels as in healthy tissue immediately after reperfusion. Conclusion. Transferrin receptor-mediated brain uptake, which is an energy dependent vesicular transport process, is sensitive to reduction in blood supply but remains partially functional for several hours after onset of ischemia. The uptake shows complete recovery after reperfusion. These results support the use of transferrin receptor-mediated brain drug delivery in the early phase of ischemia and in the phase when blood flow is restored. This article is open to POST-PUBLICATION REVIEW. Registered readers (see “For Readers”) may comment by clicking on ABSTRACT on the issue’s contents page.

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Comparison of polypeptides that bind the transferrin receptor for targeting gold nanocarriers

PLoS ONE ◽

10.1371/journal.pone.0252341 ◽

2021 ◽

Vol 16 (6) ◽

pp. e0252341

Author(s):

Conor McQuaid ◽

Andrea Halsey ◽

Maëva Dubois ◽

Ignacio Romero ◽

David Male

Keyword(s):

Blood Brain Barrier ◽

Transferrin Receptor ◽

Cyclic Peptides ◽

Cyclic Peptide ◽

Therapeutic Agents ◽

Brain Barrier ◽

Brain Endothelium ◽

Linear Peptide ◽

Blood Brain ◽

Dividing Cells

The ability to target therapeutic agents to specific tissues is an important element in the development of new disease treatments. The transferrin receptor (TfR) is one potential target for drug delivery, as it expressed on many dividing cells and on brain endothelium, the key cellular component of the blood-brain barrier. The aim of this study was to compare a set of new and previously-described polypeptides for their ability to bind to brain endothelium, and investigate their potential for targeting therapeutic agents to the CNS. Six polypeptides were ranked for their rate of endocytosis by the human brain endothelial cell line hCMEC/D3 and the murine line bEnd.3. One linear polypeptide and two cyclic polypeptides showed high rates of uptake. These peptides were investigated to determine whether serum components, including transferrin itself affected uptake by the endothelium. One of the cyclic peptides was strongly inhibited by transferrin and the other cyclic peptide weakly inhibited. As proof of principle the linear peptide was attached to 2nm glucose coated gold-nanoparticles, and the rate of uptake of the nanoparticles measured in a hydrogel model of the blood-brain barrier. Attachment of the TfR-targeting polypeptide significantly increased the rates of endocytosis by brain endothelium and increased movement of nanoparticles across the cells.

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