VCAM-1-mediated Rac signaling controls endothelial cell-cell contacts and leukocyte transmigration

Abstract

Leukocyte adhesion is mediated totally and transendothelial migration partially by heterotypic interactions between the beta1- and beta2-integrins on the leukocytes and their ligands, Ig-like cell adhesion molecules (Ig-CAM), VCAM-1, and ICAM-1, on the endothelium. Both integrins and Ig-CAMs are known to have signaling capacities. In this study we analyzed the role of VCAM-1-mediated signaling in the control of endothelial cell-cell adhesion and leukocyte transendothelial migration. Antibody-mediated cross-linking of VCAM-1 on IL-1beta-activated primary human umbilical vein endothelial cells (pHUVEC) induced actin stress fiber formation, contractility, and intercellular gaps. The effects induced by VCAM-1 cross-linking were inhibited by C3 toxin, indicating that the small GTPase p21Rho is involved. In addition, the effects of VCAM-1 were accompanied by activation of Rac, which we recently showed induce intercellular gaps in pHUVEC in a Rho-dependent fashion. With the use of a cell-permeable peptide inhibitor, it was shown that Rac signaling is required for VCAM-1-mediated loss of cell-cell adhesion. Furthermore, VCAM-1-mediated signaling toward cell-cell junctions was accompanied by, and dependent on, Rac-mediated production of reactive oxygen species and activation of p38 MAPK. In addition, it was found that inhibition of Rac-mediated signaling blocks transendothelial migration of monocytic U937 cells. Together, these data indicate that VCAM-1-induced, Rac-dependent signaling plays a key role in the modulation of vascular-endothelial cadherin-mediated endothelial cell-cell adhesion and leukocyte extravasation.

Tumour-derived SPARC drives vascular permeability and extravasation through endothelial VCAM1 signalling to promote metastasis

“…The ensuing cell retraction promotes gap formation and vascular permeability 52 . Previous studies have shown that antibody-mediated crosslinking of VCAM1 stimulated a Rac/ROS/p38 signalling cascade in endothelial cell during leukocyte transmigration 29 . Accordingly, we found that intracellular ROS production contributes to activation of p38 MAPK and MLC2 in endothelial cells stimulated by SPARC-competent melanoma secretome.…”

“…As VCAM1 has been shown to mediate endothelial junction disruption through Rac-dependent production of reactive oxygen species (ROS) and activation of p38 during leukocyte transmigration 29 , ROS levels were monitored in endothelial cells exposed to CM prepared from 1205Lu melanoma cells ( Supplementary Fig. 9e,f).…”

DNA-damaging reagents induce apoptosis through reactive oxygen species-dependent Fas aggregation

“…The mechanism by which ROS influences Fas clustering is unknown at present and requires investigation. Presumably, ROS activate signals that eventually result in cytoskeleton reorganization and membrane protein clustering van Wetering et al, 2002). We are in the progress of determining the exact cellular processes involved in cisplatin-mediated apoptosis, from ROS generation to Fas aggregation.…”

Reactive Oxygen Species in Inflammation and Tissue Injury

“…The expression of the active Rac1 mutant V12Rac1 resulted in enhanced ROS production and loss of endothelial barrier integrity (427). Rac1 activation has also been demonstrated in trafficking of inflammatory cells across the endothelial barrier (428). Cross-linking of vascular cell adhesion molecule-1 (VCAM-1) on endothelial cell surface induced Rac1 activation and ROS generation, and resulted in loss of endothelial cell-cell adhesion and transendothelial leukocyte migration (428).…”