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Bradykinin increases blood–tumor barrier permeability by down-regulating the expression levels of ZO-1, occludin, and claudin-5 and rearranging actin cytoskeleton

Authors

  • Li-bo Liu,

    1. Department of Neurobiology, College of Basic Medicine, China Medical University, Shenyang, People's Republic of China
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    • The first two authors contributed equally to this work.

  • Yi-xue Xue,

    Corresponding author
    1. Department of Neurobiology, College of Basic Medicine, China Medical University, Shenyang, People's Republic of China
    • Department of Neurobiology, College of Basic Medicine, China Medical University, Shenyang, Liaoning, People's Republic of China 110001
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    • The first two authors contributed equally to this work.

  • Yun-hui Liu,

    1. Department of Neurosurgery, the second affiliated hospital of China Medical University, Shenyang, People's Republic of China
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  • Yi-bao Wang

    1. Department of Neurosurgery, the second affiliated hospital of China Medical University, Shenyang, People's Republic of China
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Abstract

Bradykinin (BK) has been shown to open blood-tumor barrier (BTB) selectively and to increase permeability of the BTB transiently, but the mechanism is unclear. This study was performed to determine whether BK opens the BTB by affecting the tight junction (TJ)-associated proteins zonula occluden-1 (ZO-1), occludin, and caludin-5 and cytoskeleton protein filamentous actin (F-actin). In rat brain glioma model and BTB model in vitro, we find that the protein expression levels of ZO-1, occludin, and claudin-5 are attenuated by BK induction. Immunohistochemistry and immunofluorescence assays show that the attenuated expression of ZO-1, occludin, and claudin-5 and F-actin is most obvious in the smaller tumor capillaries (<20 μm) after BK infusion, and there is no change in the larger tumor capillaries (>20 μm). The redistribution of ZO-1, occludin, and claudin-5 and rearrangement of F-actin in brain microvascular endothelial cells are observed at the same time. Meanwhile, Evans blue assay shows that the permeability of BTB increases after BK infusion. Transmission electron microscopy indicates that TJ is opened and that pinocytotic vesicular density is increased. Transendothelial electrical resistance (TEER) and horseradish peroxidase flux assays also reveal that TJ is opened by BK induction. In addition, radioimmunity and Western blot assay reveal a significant decrease in expression levels of cAMP and catalytic subunit of protien kinase A (PKAcs) of tumor tissue. This study demonstrates that the increase of BK-mediated BTB permeability is associated with the down-regulation of ZO-1, occludin, and claudin-5 and the rearrangement of F-actin and that cAMP/PKA signal transduction system might be involved in the modulating process. © 2008 Wiley-Liss, Inc.

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