title: Bradykinin increases blood-tumor barrier permeability by down-regulating the expression levels of ZO-1, occludin, and claudin-5 and rearranging actin cytoskeleton.
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 microm) after BK infusion, and there is no change in the larger tumor capillaries (>20 microm). 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.
authors.affiliation: Department of Neurobiology, College of Basic Medicine, China Medical University, Shenyang, People's Republic of China.
authors.forename: Li-Bo
authors.initials: LB
authors.lastname: Liu
authors.forename: Yi-Xue
authors.initials: YX
authors.lastname: Xue
authors.forename: Yun-Hui
authors.initials: YH
authors.lastname: Liu
authors.forename: Yi-Bao
authors.initials: YB
authors.lastname: Wang
mesh_terms: D000199:Actins / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D001812:Blood-Brain Barrier / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D001920:Bradykinin / Q000378:metabolism* / Q000494:pharmacology; D001932:Brain Neoplasms / Q000098:blood supply / Q000378:metabolism* / Q000503:physiopathology; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D062507:Claudin-5; D000242:Cyclic AMP / Q000378:metabolism; D022162:Cytoplasmic Vesicles / Q000378:metabolism / Q000648:ultrastructure; D004195:Disease Models, Animal; D015536:Down-Regulation / Q000187:drug effects; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism / Q000503:physiopathology; D005260:Female; D005910:Glioma / Q000098:blood supply / Q000378:metabolism* / Q000503:physiopathology; D008565:Membrane Proteins / Q000187:drug effects / Q000378:metabolism; D046529:Microscopy, Electron, Transmission; D062793:Occludin; D010750:Phosphoproteins / Q000187:drug effects / Q000378:metabolism; D010873:Pinocytosis / Q000187:drug effects / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction / Q000502:physiology; D019108:Tight Junctions / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D062826:Zonula Occludens-1 Protein
chemical_list: D000199:Actins; C107466:CLDN5 protein, human; D062507:Claudin-5; D008565:Membrane Proteins; C568985:OCLN protein, human; D062793:Occludin; C568987:Ocln protein, rat; D010750:Phosphoproteins; C569042:TJP1 protein, human; C569044:Tjp1 protein, rat; D062826:Zonula Occludens-1 Protein; D000242:Cyclic AMP; D001920:Bradykinin