Abstract 206: Endothelium-derived 5-methoxytryptophan Protects Endothelial VE-cadherin and Barrier Function by Inhibiting p38 Mitogen-activated Protein Kinase Activation

Abstract

VE-cadherin at adherens junction is important in maintaining the integrity of endothelium. Inflammatory cytokines and growth factors such as TNFα and VEGF have been reported to suppress endothelial VE-cadherin level and increase endothelial permeability. 5-methoxytryptophan was first identified by our group as an endogenous factor produced by human fibroblasts and endothelial cells to control the expression of cyclooxygenase-2 and proinflammatory cytokines. Since endothelial cells are the major source of 5-methoxytryptophan production, we assessed the hypothesis that 5-methoxytryptophan plays a role in maintaining vascular integrity. In this study, we determined the influence of proinflammatory mediators on 5-methoxytryptophan production in human umbilical vein endothelial cells and assessed the relation between 5-methoxytryptophan production and VE-cadherin and endothelial permeability. TNFα, IL-1β, lipopolysaccharide (LPS) as well as VEGF reduced VE-cadherin and increased endothelial permeability. They did not affect cell viability as evaluated by MTT assay but reduced 5-methoxytryptophan production by >70% compared to vehicle control. Addition of synthetic 5-methoxytryptophan rescued VE-cadherin and prevented endothelial leakage. TNFα, IL-1β, LPS or VEGF activated p38 mitogen-activated protein kinase (MAPK) as analyzed by phosphorylated p38. 5-methoxytryptophan pretreatment abrogated p38 MAPK activation accompanied by preservation of VE-cadherin and maintenance of barrier function. In conclusion, our findings show for the first time that endothelium-derived 5-methoxytryptophan protects VE-cadherin and endothelial barrier function from damage by endotoxins and cytokines via inhibition of p38 MAPK activation.