Upregulation of TRAF-3 by shear stress blocks CD40-mediated endothelial activation
Carmen Urbich, Ziad Mallat, Alain Tedgui, Matthias Clauss, Andreas M. Zeiher, Stefanie Dimmeler
Carmen Urbich, Ziad Mallat, Alain Tedgui, Matthias Clauss, Andreas M. Zeiher, Stefanie Dimmeler
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Upregulation of TRAF-3 by shear stress blocks CD40-mediated endothelial activation

Abstract

Atherosclerosis is an inflammatory disease of large arteries that is initiated through the activation of endothelium by proinflammatory mediators. CD40 receptor stimulation has been implicated in the pathogenesis of atherosclerosis. One of the most important atheroprotective stimuli is the viscous drag (shear stress) generated by the streaming blood acting on the endothelial monolayer. Here, we demonstrate that shear stress prevents CD40 ligand–induced endothelial cell activation, and we identify upregulation of TNF receptor–associated factor-3 (TRAF-3) as a potent CD40-inhibitory mechanism. Shear stress specifically upregulates TRAF-3 in cultured endothelial cells. Moreover, in the endothelial cells overlying human atherosclerotic plaques, TRAF-3 expression is upregulated in areas with high shear stress. Overexpression of TRAF-3 inhibits endothelial expression of proinflammatory cytokines and tissue factor and blocks DNA-binding activity of the transcription factor AP-1; it thereby prevents CD40-induced endothelial activation. Thus, upregulation of TRAF-3 represents a novel mechanism for preserving the functional integrity of the endothelial monolayer.

Authors

Carmen Urbich, Ziad Mallat, Alain Tedgui, Matthias Clauss, Andreas M. Zeiher, Stefanie Dimmeler

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Shear stress upregulates TRAF-3 in vitro and in vivo. (a) HUVECs were ex...
Shear stress upregulates TRAF-3 in vitro and in vivo. (a) HUVECs were exposed to shear stress, and TRAF-3 mRNA was detected by RNase protection assay, with GAPDH as loading control (mean ± SEM; n = 3). (b and c) Time- and dose-dependent upregulation of TRAF-3 protein by shear stress exposure. HUVECs were exposed to shear stress as indicated and TRAF-3 protein was detected by Western blot analysis. Representative figures from three to four experiments are shown. (d and e) HUVECs were exposed to shear stress, and expression of TRAF-2, TRAF-5 (d), and CD40 receptor (e) were detected by Western blot analysis (n = 3). (f) Human atherosclerotic plaques from nine patients with coronary artery disease were stained with TRAF-3 antibody (right), and endothelial cells were stained in serial sections with a CD31 antibody (left) to confirm cell type–specific expression. The scheme depicts different regions of the vessel (upstream and downstream areas of the plaques and in the maximal stenosis) with the local flow conditions. Representative sections are shown.