Abstract
Objective: Diapedesis occurs through endothelial cell–cell junctions (paracellular) or through individual endothelial cells without disrupting junctions (transcellular). While in vitro studies have provided considerable insight into mechanisms controlling paracellular diapedesis, little is known about what regulates transcellular diapedesis. The authors investigated whether transcellular diapedesis is susceptible to IL-1β exposure of the endothelium.
Methods: Laser scanning confocal microscopy and biochemical analysis were used to determine the effect of IL-1β pretreatment of the endothelium on adherens junctional morphology and monocyte transcellular diapedesis in cocultures of human peripheral blood monocytes and coronary artery endothelial cells.
Results: IL-1β pretreatment caused a 40% decrease in the number of migrating monocytes that used a transcellular route of diapedesis, and resulted in elongate endothelial cell morphology, a reorganization of the F-actin cytoskeleton, and a significant decrease in transendothelial electrical resistance. In IL-1β treated monolayers, VE-cadherin and its associated catenins were distributed in a punctate pattern in comparison to the lacy pattern seen in control monolayers. Coimmunoprecipitation of VE-cadherin molecular assemblies revealed that IL-1β-mediated changes in distribution were associated with a decrease in the presence of cadherin/catenin complexes in the detergent insoluble fraction.
Conclusions: IL-1β-induced rearrangement of interendothelial adherens junctions facilitates paracellular diapedesis at the expense of transcellular diapedesis.
This work was supported by grants from the Canadian Institute of Health Research (MOP 53276) and the Heart and Stroke Foundation of Ontario (T4674 & T3723). We thank Walter Rushlow for the gift of the rabbit anti-α-catenin antibody. AMF and CJM were supported by studentships from the Ontario government. CJM was also supported by a studentship from the National Science and Engineering Research Council of Canada.