Liu Yong, Mladinov Domagoj, Pietrusz Jennifer L, Usa Kristie, Liang Mingyu
Department of Physiology, Medical College of Wisconsin, Milwaukee, WI 53226, USA.
Cardiovasc Res. 2009 Jan 1;81(1):140-7. doi: 10.1093/cvr/cvn231. Epub 2008 Aug 20.
Hypertensive and other effects of excess glucocorticoids might be in part mediated by the suppression of endothelial nitric oxide synthase (eNOS) expression. We studied the transcriptional and biochemical mechanisms that mediate or modulate the suppression of eNOS expression by glucocorticoids.
We found that a mere three-fold increase in the concentration of the natural glucocorticoid cortisol (from 30 to 100 nmol/L) significantly decreased the expression level of eNOS in human endothelial cells. Deletion analysis of the eNOS promoter indicated that the segment within -119 bp upstream from the transcription start site was significantly involved in the effect of cortisol. Site-directed mutagenesis and chromatin immunoprecipitation analyses demonstrated the presence of a suppressive glucocorticoid response element (GRE) at -111 to -105 bp. 11 beta-hydroxysteroid dehydrogenases (11 beta-HSD) catalyse the interconversion of active and inactive glucocorticoids. The suppression of 11 beta-HSD2 using small interfering RNA markedly exacerbated the inhibition of eNOS by cortisol. The suppression of 11 beta-HSD1 abolished the inhibition of eNOS expression by cortisol.
We identified the first GRE in the eNOS promoter region and demonstrated that endogenous 11 beta-HSD1 and 11 beta-HSD2 play significant and distinct roles in modulating the effect of glucocorticoids on eNOS expression.
过量糖皮质激素引起的高血压及其他效应可能部分是由内皮型一氧化氮合酶（eNOS）表达受抑制介导的。我们研究了介导或调节糖皮质激素对eNOS表达抑制作用的转录和生化机制。
我们发现天然糖皮质激素皮质醇浓度仅三倍的增加（从30至100 nmol/L）就显著降低了人内皮细胞中eNOS的表达水平。对eNOS启动子的缺失分析表明，转录起始位点上游-119 bp内的片段显著参与了皮质醇的作用。定点诱变和染色质免疫沉淀分析证明在-111至-105 bp处存在一个抑制性糖皮质激素反应元件（GRE）。11β-羟基类固醇脱氢酶（11β-HSD）催化活性和非活性糖皮质激素的相互转化。使用小干扰RNA抑制11β-HSD2可显著加剧皮质醇对eNOS的抑制作用。抑制11β-HSD1可消除皮质醇对eNOS表达的抑制作用。
我们在eNOS启动子区域鉴定出首个GRE，并证明内源性11β-HSD1和11β-HSD2在调节糖皮质激素对eNOS表达的作用中发挥着重要且不同的作用。
