eNOS derived nitric oxide regulates endothelial barrier function via VE cadherin and Rho GTPases

Abstract

Transient disruption of endothelial adherens junctions and cytoskeletal remodeling are responsible for increases in vascular permeability induced by inflammatory stimuli and vascular endothelial growth factor (VEGF). Nitric oxide (NO) produced by endothelial NO synthase (eNOS) is critical for VEGF induced changes in permeability in vivo, however, the molecular mechanisms by which endogenous NO modulates endothelial permeability is not clear. Here we show that the lack of eNOS reduces VEGF induced permeability, an effect mediated by enhanced Rac-GTPase activation and stabilization of cortical actin. The loss of NO, increased the recruitment of the Rac-GEF, Tiam-1, to adherens junctions and VE-cadherin and reduced Rho-activation and stress fiber formation. In addition, NO deficiency reduced VEGF-induced VE-cadherin phosphorylation, and impaired the localization, but not the activation, of c-src to cell junctions. The physiological role of eNOS activation is clear since VEGF, histamine and inflammation induced vascular permeability is reduced in mice with bearing the knockin mutation of the key phosphorylation site S1176. Thus, NO is critical for Rho GTPase dependent regulation of cytoskeletal architecture leading to reversible changes in vascular permeability.