Summary
Increased consumption of sodium is a risk factor for hypertension and cardiovascular
diseases. In vivo studies indicated that high dietary sodium may have a direct negative influence on
endothelium. We investigated the effects of high sodium on the endothelial activation
during early steps of atherogenesis. Endothelial cells (HUVECs) grown in a model of
arterial bifurcations were exposed to shear stress in the presence of normal or high
(+ 30 mmol/l) sodium. Adherent THP-1 cells, and the adhesion molecule expression were
quantified. Sodium channel blockers, pathways’ inhibitors, and siRNA against tonicity-responsive
enhancer binding protein (TonEBP) were used to identify the mechanisms of sodium effects
on endothelium. ApoE-deficient mice on low-fat diet received water containing normal
or high salt (8% w/v) for four weeks, and the influence of dietary salt on inflammatory
cell adhesion in the common carotid artery and carotid bifurcation was measured by
intravital microscopy. In vitro, high sodium dramatically increased the endothelial responsiveness to tumour necrosis
factor-α under non-uniform shear stress. Sodium-induced increase in monocytic cell
adhesion was mediated by reactive oxygen species and the endothelial nitric oxygen
synthase, and was sensitive to the knockdown of TonEBP. The results were subsequently
confirmed in the ApoE-deficient mice. As compared with normal-salt group, high-salt
intake significantly enhanced the adhesion of circulating CD11b+ cells to carotid
bifurcations, but not to the straight segment of common carotid artery. In conclusion,
elevated sodium has a direct effect on endothelial activation under atherogenic shear
stress in vitro and in vivo, and promotes the endothelial-leukocyte interactions even in the absence of increased
lipid concentrations.
Keywords
Atherosclerosis - high sodium - endothelial-leukocyte interactions - shear stress
- TonEBP