Diapedesis of monocytes is associated with MMP-mediated occludin disappearance in brain endothelial cells

Arie Reijerkerk, Gijs Kooij, Susanne M A van der Pol, Shadi Khazen, Christine D Dijkstra, Helga E de Vries

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The blood-brain barrier (BBB), a selective barrier formed by endothelial cells and dependent on the presence of tight junctions, is compromised during neuroinflammation. A detailed study of tight junction dynamics during transendothelial migration of leukocytes has been lacking. Therefore, we retrovirally expressed green fluorescent protein (GFP) fused to the N-terminus of the tight junction protein occludin in the rat brain endothelial cell line GP8/3.9. Confocal microscopy analyses revealed that GFP-occludin colocalized with the intracellular tight junction protein, ZO-1, localized at intercellular connections, and was absent at cell borders lacking apposing cells. Using live cell imaging we found that monocytes scroll over the brain endothelial cell surface toward cell-cell contacts, induce gap formation, which is associated with local disappearance of GFP-occludin, and subsequently traverse the endothelium paracellularly. Immunoblot analyses indicated that loss of occludin was due to protein degradation. The broad spectrum matrix metalloproteinase (MMP) inhibitor BB-3103 significantly inhibited endothelial gap formation, occludin loss, and the ability of monocytes to pass the endothelium. Our results provide a novel insight into the mechanism by which leukocytes traverse the BBB and illustrate that therapeutics aimed at the stabilization of the tight junction may be beneficial to resist a neuroinflammatory attack.

Original languageEnglish
Pages (from-to)2550-2
Number of pages3
JournalFASEB Journal
Issue number14
Publication statusPublished - Dec 2006

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