Thioredoxin inhibits the expression of human vascular endothelial cell adhesion molecules by down-regulating Nox4 activity

Abstract

Objective To investigate the effect of Thioredoxin(Trx)on dihydronicotinamide adenine dinucleotide phosphate(NADPH)oxidase subtype Nox4, and the molecular mechanisms of Nox4 regulating intracellular adhesion molecular-1(ICAM-1)expression in human vascular endothelial cells during the initiation of atherosclerosis. Methods Adenovirus vector gene transfer technology was used in human umbilical vein endothelial cells(HUVECs)to establish the cell models of Trx-overexpression cells(Ad-Trx)and their control cells(Ad-GFP). Oxidized low density lipoprotein, a risk factor for atherosclerosis, was used as a stimulator.Western blot was conducted to detect protein expression levels of intracellular adhesion molecule-1(ICAM-1), Nox4 and P22 phox.Indirect immunofluorescence was used to detect Trx expression in endothelial cells.Cell membrane tissues were extracted, and the activity of NADPH oxidase in endothelial cells was determined by an enzymatic method.Production of cellular reactive oxygen species(ROS)was detected by the fluorescent probe dichloro-dihydro-fluorescein diacetate(DCFH-DA). Results Both overexpression of Trx and the specific inhibitor of NADPH oxidase(apocynin)significantly reduced ICAM-1 expression and ROS generation in ox-LDL stimulated endothelial cells.Compare with the control group, Trx overexpression inhibited NOX4 expression of cell membrane fractions, the increase of NADPH oxidase activity and P22 phox expression in ox-LDL stimulated endothelial cells. Conclusions Trx inhibits ox-LDL-induced ICAM-1 expression by down-regulating endothelial Nox4 activity, thus reduces inflammatory damage and protects endothelial cell function. Key words: Thioredoxins; Intercellular adhesion molecule-1; NADPH oxidase; Endothelial cells