MOLECULAR PHARMACOLOGICAL STUDY ON INTERACTION BETWEEN CYCLOOXYGENASE PATHWAY AND NUCLEAR RECEPTORS

流体切应力诱导血管内皮细胞环氧合酶（考克斯）-2基因表达。我们研究了这种诱导的潜在机制，将人脐静脉内皮细胞暴露于生理范围（1 - 30 dyne/cm ^2）的层流剪切应力下，可上调考克斯-2的表达，但不上调考克斯-1（考克斯的组成型同工酶）的表达。考克斯-2 mRNA表达在切应力作用后0.5 h内开始增加，4 h达高峰。通过荧光素酶报告载体瞬时转染牛动脉内皮细胞，研究了人考克斯-2基因启动子区和3 '端非翻译区的功能。剪切应力通过-327和+59 bp之间的区域提高荧光素酶活性。突变分析表明，cAMP反应元件（-59/-53bp）主要参与这种反应。另一方面，剪切应力选择性地稳定考克斯-2 mRNA。此外，将含有17拷贝AUUUA mRNA不稳定基序的考克斯-2基因3 '端非翻译区插入载体，剪切应力可提高荧光素酶活性，转录激活和转录后mRNA稳定均有助于考克斯-2在剪切应力下的快速、持续表达。

Fluid shear stress induces cyclooxygenase (COX) -2 gene expression in vascular endothelial cells. We investigated the underlying mechanism for this induction.Exposure of human umbilical vein endothelial cells to laminar shear stress in the physiological range (1 to 30 dyne/cm^2) 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 hours after the loading of the 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.Transcriptional activation and post-transcriptional mRNA stabilization both contribute to the rapid and sustained expression of COX-2 in response to shear stress.