Cortactin deficiency is associated with reduced neutrophil recruitment but increased vascular permeability in vivo

Abstract

The maintenance of vascular barrier integrity is crucial during many pathophysiological processes and requires coordinated molecular events including signaling and cytoskeletal remodeling. Cortactin is an actin‐binding protein that regulates actin dynamics and related signaling events. To analyze the role of cortactin in vascular barrier functions, we generated cortactin‐deficient mice. Classical Miles assays revealed that vascular permeability is increased in these mice. Despite this leakiness, leukocyte extravasation in the TNF‐α‐stimulated cremaster was inhibited. Mechanistically, the permeability defect in the absence of cortactin was caused by reduced levels of active Rap1 in endothelial cells and could be rescued by activating Rap1 via the GTPase exchange factor EPAC. The defect in leukocyte extravasation was due to impaired interactions between leukocytes and endothelial cells, as documented by an increased rolling velocity and decreased numbers of adhering leukocytes in postcapillary venules. Impaired rolling interactions were linked to contributions of β2‐integrin‐ligands to this process and firm adhesion was compromised by the loss of ICAM‐1‐containing leukocyte docking structures. These results are the first physiological evidence that cortactin is crucial for orchestrating molecular events leading to proper endothelial barrier function and leukocyte recruitment in vivo.

Role of N-WASP in Endothelial Monolayer Formation and Integrity

“…Our results with N-WASP depletion are important and striking because loss of function phenotypes for many actin regulatory proteins, including regulators of Arp2/3 complex, feature defects in endothelial monolayer integrity (8,13,24). However, biochemical and cell biological studies reveal that different Arp2/3 regulators, present at the same time and location in the cell, have different functions (25,26).…”

Integrin Regulation during Leukocyte Recruitment

“…Activated endothelium forms ring-like membrane structures enriched with ICAM-1 and VCAM-1 that are maintained for the duration of transmigration (55). Recent studies have found evidence that neutrophil integrin engagement of ICAM-1 may trigger the disassembly of the VE-cadherin and consecutive encapsulation of the transmigrating leukocyte in "domes," as mice lacking cortactin, a cytoskeletal molecule serving as an adaptor protein to ICAM-1, failed to initiate transmigration (56). For a detailed review of the endothelial molecules involved in this step, see Williams et al (54).…”

Lidocaine Reduces Neutrophil Recruitment by Abolishing Chemokine-Induced Arrest and Transendothelial Migration in Septic Patients

“…The transendothelial migration of isolated human neutrophils through a monolayer of cultured HUVECs was performed, as described previously (24). Briefly, 6.5-mm Transwell filters (Corning Life Sciences, Corning, NY) were coated with fibronectin (0.01%) for 1 h. HUVECs were seeded into the wells and grown to confluence for 2 d. HUVECs were stimulated with TNF-a (5 nM; PeproTech) for 16 h. Human neutrophils were isolated from whole blood by Histopaque density centrifugation, resuspended in control plasma or plasma obtained from placebo-or lidocaine-treated septic patients at different time points, and incubated at 37˚C for 30 min.…”