A Critical Role for P-Rex1 in Endothelial Junction Disruption and Vascular Hyper-Permeability
Rationale: The small GTPase Rac is critical to vascular endothelial functions, yet its regulation in endothelial cells remains unclear. Understanding the upstream pathway may delineate Rac activation mechanisms and its role in maintaining vascular endothelial barrier integrity.
Objective: By investigating P-Rex1, one of the Rac-specific guanine nucleotide exchange factors (GEFs) previously known for G protein-coupled receptor (GPCR) signaling, we sought to determine whether Rac-GEF is a nodal for signal integration and potential target for drug intervention.
Methods and Results: Using gene deletion and siRNA silencing approach, we investigated the role of P-Rex1 in lung microvascular endothelial cells (HLMVECs). TNF-α exposure led to disruption of endothelial junctions, and silencing P-Rex1 protected junction integrity. TNF-α stimulated Rac activation and ROS production in a P-Rex1-dependent manner. Removal of P-Rex1 significantly reduced ICAM-1 expression, PMN transendothelial migration and leukocyte sequestration in TNF-α challenged mouse lungs. The P-Rex1 knockout mice were also refractory to lung vascular hyper-permeability and edema in a LPS-induced sepsis model.
Conclusions: These results demonstrate for the first time that P-Rex1 expressed in endothelial cells is activated downstream of TNF-α, which is not a GPCR agonist. Our data identify P-Rex1 as a critical mediator of vascular barrier disruption. Targeting P-Rex1 may effectively protect against TNF-α; and LPS-induced endothelial junction disruption and vascular hyper-permeability.
- Endothelial dysfunction
- Pulmonary edema
- Reactive oxygen species
- Tumor necrosis factor-_
- Vascular permeability
- acute lung injury
- small GTPases
- guanine nucleotide exchange factors
- Received May 3, 2012.
- Accepted September 10, 2012.
- Copyright © 2012, American Heart Association