Regulation of the endothelin system by shear stress in human endothelial cells

1. In this study, the effect of shear stress on the expression of genes of the human endothelin-1 system was examined. Primary cultures of human umbilical vein endothelial cells (HUVEC) were exposed to laminar shear stress of 1, 15 or 30 dyn cm(-2) (i.e. 0.1, 1.5 or 3 N m(-2)) (venous and two different arterial levels of sheer stress) in a cone-and-plate viscometer. 2. Laminar shear stress transiently upregulates preproendothelin-1 (ppET-1) mRNA, reaching its maximum alter 30 min (approx 1.7-fold increase). In contrast, long-term application of shear stress (24 h) causes downregulation of ppET-1 mRNA in a dose-dependent manner. 3. Arterial levels of shear stress result in downregulation of endothelin-converting enzyme-1 isoform ECE-1a (predominating in HUVEC) to 36.2 +/- 8.5%, and isoform ECE-1b mRNA to 72.3 +/- 1.9% of static control level. 4. The endothelin-1 (ET-1) release is downregulated by laminar shear stress in a dose dependent manner. 5. This downregulation of ppET-1 mRNA and ET-1 release is not affected by inhibition of protein kinase C (PKC), or tyrosine kinase. Inhibition of endothelial NO synthase (L-NAME, 500 mu M) prevents downregulation of ppET-1 mRNA by shear stress. 6. In contrast, increasing degrees of long-term shear stress upregulate endothelin receptor type B (ETB) mRNA by a NO- and PKC-, but not tyrosine kinase-dependent mechanism. 7. In conclusion, our data suggest the downregulation of human endothelin synthesis, and an upregulation of the ETB receptor by long-term arterial laminar sheer stress. These effects might contribute to the vasoprotective and anti-arteriosclerotic potential of arterial laminar shear stress.