Transcriptional and posttranscriptional regulation of cyclooxygenase-2 expression by fluid shear stress in vascular endothelial cells.

OBJECTIVE Fluid shear stress induces cyclooxygenase (COX)-2 gene expression in vascular endothelial cells. We investigated the underlying mechanism of this induction. METHODS AND RESULTS Exposure of human umbilical vein endothelial cells to laminar shear stress in the physiological range (1 to 30 dyne/cm2) upregulated the expression of COX-2 but not COX-1, a constitutive isozyme of COX. The expression of COX-2 mRNA began to increase within 0.5 hour after the loading of shear stress and reached a maximal level at 4 hours. Roles of the promoter region and the 3'-untranslated region in the human COX-2 gene were evaluated by the transient transfection of luciferase reporter vectors into bovine arterial endothelial cells. Shear stress elevated luciferase activity via the region between -327 and 59 bp. Mutation analysis indicated that cAMP-responsive element (-59/-53 bp) was mainly involved in this response. On the other hand, shear stress selectively stabilized COX-2 mRNA. Moreover, shear stress elevated luciferase activity when a 3'-untranslated region of COX-2 gene containing 17 copies of the AUUUA mRNA instability motif was inserted into the vector. CONCLUSIONS Transcriptional activation and posttranscriptional mRNA stabilization contribute to the rapid and sustained expression of COX-2 in response to shear stress.