Green Tea Polyphenol (–)-Epigallocatechin-3-gallate Protects Endothelial Barrier Function via Myosin Phosphatase and Rho-Kinase

Vascular endothelial cells form a selective barrier that regulates the passage of substances and leukocytes between the bloodstream and surrounding tissues, thereby maintaining vascular homeostasis. Although endothelial barrier dysfunction is implicated in numerous diseases, the molecular mechanisms that protect against such dysfunction remain incompletely defined. Thrombin, an inflammatory mediator, increases endothelial permeability by inducing myosin light chain (MLC) phosphorylation through Rho/Rho-associated kinase (Rho-kinase)-mediated inhibition of myosin phosphatase. This process disrupts vascular endothelial cadherin (VE-cadherin)-based junctions and promotes radial stress fiber formation. Here, we demonstrate that the green tea catechin (–)-epigallocatechin-3-gallate (EGCG) reduces phosphorylation of the myosin phosphatase regulatory subunit MYPT1 at inhibitory sites and suppresses Rho-kinase signaling in endothelial cells. Together, these EGCG-mediated effects reduce MLC phosphorylation, inhibit radial stress fiber formation, and preserve VE-cadherin-mediated cell–cell adhesion, thereby maintaining endothelial barrier integrity.