Study on the mechanisms of an extract of Salvia miltiorrhiza on the regulation of permeability of endothelial cells exposed to tumour necrosis factor-α

Abstract

Exposure of endothelial cells to tumour necrosis factor-α (TNF-α) results in increased endothelial permeability, accompanied by a loss of cell-cell adherence junctions. The importance of tyrosine phosphatase and kinase activity in oxidant-mediated loss of cell junction structures has been demonstrated. The purpose of this study was to determine whether tyrosine phosphorylation contributes to TNF-α-imediated disorganization of endothelial cell junctions and how an extract of Salvia miltiorrhiza (ESM) and its active ingredients, Danshensu (DSS) and salvianolic acid B (Sal B), exert their protective effect in maintaining cell integrity. Immunoblotting results indicated that TNF-α exposure resulted in tyrosine phosphorylation of junctional proteins such as vascular endothelial cadherin and β-catenin, which was attenuated by ESM and its active ingredients DSS and Sal B. In addition, immunoprecipitation showed ESM and its active ingredients prevented β-catenin disassociation from the cytoskeleton in TNF-α-treated human umbilical vein endothelial cells. The results suggest that TNF-α produced biological effects at least partly by junctional protein phosphotyrosine modifications by increasing the total cellular phosphorylation level. It could be concluded that ESM and its active ingredients were effective at eliminating the factors leading to the rise in cellular phosphorylation, thus helping to maintain the integrity of endothelial junction structure.