Submitted July 13, 2006
Accepted September 25, 2006
Caveolin-1 regulates expression of junction-associated proteins in brain microvascular endothelial cells
Li Song, Shujun Ge, and Joel S. Pachter*
University of Connecticut Health Center
* Corresponding author; email: pachter{at}nso1.uchc.edu.
Recent evidence from this laboratory indicated that reduced expression of caveolin-1 accompanied the diminished expression of tight junction (TJ)-associated proteins occludin and zonula occludens-1 (ZO-1), following stimulation of brain microvascular endothelial cells (BMEC) with the chemokine CCL2 (formerly called MCP-1). As attenuated caveolin-1 levels have also been correlated with heightened permeability of other endothelia, the objective of this study was to test the hypothesis that reduced caveolin-1 expression is causally linked to the action of CCL2 on BMEC junctional protein expression and barrier integrity. This was achieved using adenovirus to nondestructively deliver caveolin-1 siRNA (Ad-siCav-1) to BMEC monolayers, which model the blood-brain barrier (BBB). siRNA-treatment reduced caveolin-1 protein level, as well as occludin and ZO-1. Additionally, occludin exhibited dissociation from the cytoskeletal framework. These changes were attended by comparable alterations in adherens junction (AJ)-associated proteins, VE-cadherin and 
-catenin, increased BMEC paracellular permeability, and facilitated ability of CCL2 to stimulate monocytic transendothelial migration. Furthermore, treating BMEC with cavtratin, a synthetic cell-permeable peptide encoding the caveolin-1 scaffolding domain, antagonized effects of both Ad-siCav-1 and CCL2. These results collectively highlight caveolin-1 loss as a critical step in CCL2-induced modulation of BMEC junctional protein expression and integrity, and possibly crucial role in regulating inflammation at the BBB.
