Caveolin-1 regulates expression of junction-associated proteins in brain microvascular endothelial cells.
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 (BMECs) with the chemokine CCL2 (formerly called MCP-1). Because 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). Treatment with siRNA reduced the 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 beta-catenin, increased BMEC paracellular permeability, and facilitated the ability of CCL2 to stimulate monocytic transendothelial migration. Furthermore, treating BMECs 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 serve a crucial role in regulating inflammation at the BBB.
Song
Li
L
Blood-Brain Barrier Laboratory, Department of Pharmacology, University of Connecticut Health Center, Farmington 06030, USA.
Ge
Shujun
S
Pachter
Joel S
JS
D000818:Animals; D001812:Blood-Brain Barrier; D001921:Brain / Q000098:blood supply*; D002196:Capillaries / Q000166:cytology; D002199:Capillary Permeability; D051242:Caveolin 1 / Q000502:physiology*; D018932:Chemokine CCL2; D017630:Connexins / Q000235:genetics*; D042783:Endothelial Cells; D004730:Endothelium, Vascular / Q000166:cytology*; D005786:Gene Expression Regulation; D051379:Mice
D051242:Caveolin 1; C491768:Ccl2 protein, mouse; D018932:Chemokine CCL2; D017630:Connexins