Reversibility of increased microvessel permeability in response to VE-cadherin disassembly

We determined the role of vascular endothelial (VE)-cadherin complex in regulating the permeability of pulmonary microvessels. Studies were made in mouse lungs perfused with albumin-Krebs containing EDTA, a Ca(2+) chelator, added to study the VE-cadherin junctional disassembly. We then repleted the perfusate with Ca(2+) to restore VE-cadherin integrity. Confocal microscopy showed a disappearance of VE-cadherin immunostaining in a time- and dose-dependent manner after Ca(2+) chelation and reassembly of the VE-cadherin complex within 5 min after Ca(2+) repletion. We determined the (125)I-labeled albumin permeability-surface area product and capillary filtration coefficient (K(fc)) to quantify alterations in the pulmonary microvessel barrier. The addition of EDTA increased (125)I-albumin permeability-surface area product and K(fc) in a concentration-dependent manner within 5 min. The permeability response was reversed within 5 min after repletion of Ca(2+). An anti-VE-cadherin monoclonal antibody against epitopes responsible for homotypic adhesion augmented the increase in K(fc) induced by Ca(2+) chelation and prevented reversal of the response. We conclude that the disassembled VE-cadherins in endothelial cells are mobilized at the junctional plasmalemmal membrane such that VE-cadherins can rapidly form adhesive contact and restore microvessel permeability by reannealing the adherens junctions.