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Sodium caprate transiently opens claudin-5-containing barriers at tight junctions of epithelial and endothelial cells.

Molecular pharmaceutics (2012-07-26)
G Del Vecchio, C Tscheik, K Tenz, H C Helms, L Winkler, R Blasig, I E Blasig
ABSTRACT

Claudin-5 is a tight junction (TJ) protein which limits the diffusion of small hydrophilic molecules. Thus, it represents a potential pharmacological target to improve drug delivery to the tissues protected by claudin-5-dependent barriers. Sodium caprate is known as an absorption enhancer which opens the paracellular space acting on TJ proteins and actin cytoskeleton. Its action on claudin-5 is not understood so far. Epithelial and endothelial systems were used to evaluate the effect of caprate on claudin-5 in TJ-free cells and on claudin-5 fully integrated in TJ. To this aim, confocal microscopy on live and fixed cells and isolated mouse brain capillaries, Western blotting and permeability assays were employed. Caprate reversibly reduced claudin-5 trans-interactions in TJ-free human embryonic kidney-293 cells expressing claudin-5-YFP. It decreased the membranous claudin-5 and the F-actin content in Madin-Darby canine kidney-II cells expressing Flag-claudin-5, thereby increasing the permeability to the small molecule lucifer yellow. Interestingly, zonula occludens protein 1 (ZO-1), which links transmembranous TJ proteins to the actin cytoskeleton, was not affected by caprate treatment. Similarly, endogenous claudin-5 in the membrane of brain endothelia was displaced together with F-actin, whereas ZO-1 remained unaffected. Caprate transiently opens the paracellular space, reducing the intercellular claudin-5/claudin-5 interactions and the polymerized actin at the perijunctional region of endothelial and epithelial cells. In conclusion, the study further elucidates the cellular effects of caprate at the tight junctions.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Sodium decanoate, ≥98%
Sigma-Aldrich
Decanoic acid, natural, ≥98%, FCC, FG
Supelco
Decanoic acid, analytical standard
Sigma-Aldrich
Decanoic acid, ≥98.0%
Sigma-Aldrich
Decanoic acid, ≥99.5%, FCC, FG