Claudin-5-Binders Enhance Permeation of Solutes across the Blood-Brain Barrier in a Mammalian Model

Abstract

A current bottleneck in the development of central nervous system (CNS) drugs is the lack of drug delivery systems targeting the CNS. The intercellular space between endothelial cells of the blood-brain barrier (BBB) is sealed by complex protein-based structures called tight junctions (TJs). Claudin-5 (CLDN-5), a tetra-transmembrane protein is a key component of the TJ seal that prevents the paracellular diffusion of drugs into the CNS. In the present study, to investigate whether CLDN-5 binders can be used for delivery of drugs to the CNS, we generated monoclonal antibodies (mAbs) specific to the extracellular domains of CLDN-5. In an in vitro model of the BBB, the anti-CLDN-5 mAbs attenuated trans-epithelial/endothelial electrical resistance and enhanced solute permeation. These anti-CLDN-5 mAbs are potential leads for the development of novel drug delivery systems targeting the CNS.

A blood–brain barrier overview on structure, function, impairment, and biomarkers of integrity

“…The disappearance of claudin-5 from the tight junctional complexes can result in a compromised BBB as mice genetically altered to lack claudin-5 have shown severely compromised and leaky BBB and die shortly after birth [ 67 ], although their death is probably not solely related to the BBB defects [ 2 ]. Double knockdown of claudin-5 with occludin also increased the permeation of tracers between 3 and 10 kDa [ 68 ]. Furthermore, knock-down of claudin-5 was found to change the mRNA expression of other TJ proteins such as claudin-1 [ 69 ].…”

Blood-Brain Barrier Protein Claudin-5 Expressed in Paired Xenopus laevis Oocytes Mediates Cell-Cell Interaction

“…The first extracellular loop of claudins (ECL1) is important for the barrier properties of the tight junction, while the second extracellular loop (ECL2) is involved in strand formation of trans-interaction (Piontek et al, 2008;Rossa et al, 2014;Greene et al, 2019). Claudin-5 binders targeting ECL1 or ECL2 of claudin-5 may induce intracellular uptake of the tight junction protein, thereby thwarting the claudin-5 trans-interactions in the tight junction seal between adjacent cells and loosening the paracellular space (Hashimoto et al, 2017).…”

Anti-Claudin Antibodies as a Concept for Development of Claudin-Directed Drugs

“…The immunization of rats with plasmid DNA encoding CLDN-5 or their treatment with liposomes containing CLDN-5 led to the generation of CLDN-5-specific mAbs (Hashimoto et al, 2017b(Hashimoto et al, , 2018b. In a popular in vitro BBB model, treatment of the cells with anti-CLDN-5 mAbs loosened TJ integrity and thus enhanced the permeability of solutes (sodium fluorescein, 376 Da; dextran, 4 kDa) (Hashimoto et al, 2017b), thus demonstrating CLDN-5 binder as a promising lead for drug delivery to the brain. However, CLDN-5-deficient mice die within 10 hours after birth (Nitta et al, 2003).…”