MOLECULAR PHARMACOLOGICAL STUDY ON INTERACTION BETWEEN CYCLOOXYGENASE PATHWAY AND NUCLEAR RECEPTORS

流体剪切应力诱导血管内皮细胞环氧合酶(COX) -2基因表达我们研究了这种诱导的潜在机制。人脐静脉内皮细胞暴露于生理范围（1至30达因/厘米^2）的层状剪切应力下，上调COX-2的表达，但不上调COX-1 （COX的一种组成同工酶）的表达。COX-2 mRNA的表达在剪切应力加载后0.5 h内开始升高，在4 h时达到最大值。用荧光素酶报告载体瞬时转染牛动脉内皮细胞，评价了人COX-2基因启动子区和3'-未翻译区在牛动脉内皮细胞中的作用。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响应元件（-59/-53 bp）主要参与该反应。另一方面，剪切应力选择性地稳定了COX-2 mRNA。此外，当将含有17个AUUUA mRNA不稳定性基序的COX-2基因的3'-非翻译区插入到载体中时，剪切应力会提高荧光素酶的活性。转录激活和转录后mRNA稳定都有助于COX-2在剪切胁迫下的快速和持续表达。

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.