The blood-brain and gut-vascular barriers: from the perspective of claudins

In some organs, such as the brain, endothelial cells form a robust and highly selective blood-to-tissue barrier. However, in other organs, such as the intestine, endothelial cells provide less stringent permeability, to allow rapid exchange of solutes and nutrients where needed. To maintain the structural and functional integrity of the highly dynamic blood-brain and gut-vascular barriers, endothelial cells form highly specialized cell-cell junctions, known as adherens junctions and tight junctions. Claudins are a family of four-membrane-spanning proteins at tight junctions and they have both barrier-forming and pore-forming properties. Tissue-specific expression of claudins has been linked to different diseases that are characterized by barrier impairment. In this review, we summarize the more recent progress in the field of the claudins, with particular attention to their expression and function in the blood-brain barrier and the recently described gut-vascular barrier, under physiological and pathological conditions.

Automated summary

Endothelial cells form barriers of varying permeability in different organs, with claudins playing a key role in tight junctions. Tissue-specific expression of claudins is linked to diseases characterized by barrier impairment.