Abstract 19483: Vitronectin Increases Vascular Permeability by Promoting Ve-Cadherin Internalization at Cell Junctions
Background: Cross-talk between integrins and cadherins regulates cell function. We tested the hypothesis that vitronectin (VN), a multi-functional adhesion molecule present in extracellular matrix and plasma, regulates vascular permeability via effects on VE-cadherin (VE-Cad), a critical regulator of endothelial cell (EC) adhesion.
Methods: We used confocal fluorescence microscopy, an in vitro permeability assay, and in vivo experiments involving wild-type (WT) and VN-deficient (Vn−/−) mice to study the role of VN in regulating VE-cad trafficking in EC monolayers and endothelial cell barrier function.
Results: Addition of multimeric VN (10 μg/mL) significantly increased VE-cadherin internalization in human umbilical vein EC (HUVEC) monolayers. This effect was blocked by anti-αVβ3 antibody and pharmacological inhibition and knockdown of Src kinase. Surprisingly, blockade of αVβ3 integrin and Src kinase after VN treatment triggered rapid translocation of internalized VE-Cad back to the cell surface, demonstrating the reversible nature of VE-Cad trafficking. In contrast to multimeric VN, monomeric VN did not trigger VE-Cad internalization. In a modified Miles assay, VN deficiency impaired vascular endothelial growth factor-induced permeability. Furthermore, ischemia-induced enhancement of vascular permeability, expressed as the ratio of FITC-dextran leakage from the circulation into ischemic and non-ischemic hindlimb muscle, was significantly greater in WT mice than in Vn−/− mice (1.64x105 ± 0.09 vs. 1.05x105 ± 0.15, respectively, n=6/group; p=0.02). Similarly, ischemia-induced angiogenesis and macrophage infiltration were significantly reduced in Vn−/− mice vs. WT controls.
Conclusions: VN plays a previously unrecognized role in regulating endothelial permeability via conformational- and integrin-dependent effects on VE-Cad trafficking. VN regulates vascular permeability in vivo. These results have important implications regarding the regulation of endothelial function and angiogenesis by VN under normal and pathological conditions.
- © 2010 by American Heart Association, Inc.