Division of Biomedical Sciences, University of California-Riverside, 92521, USA.
Circulation. 2011 Aug 2;124(5):633-41. doi: 10.1161/CIRCULATIONAHA.110.005108. Epub 2011 Jul 18.
Upregulated by atheroprotective flow, the transcription factor Krüppel-like factor 2 (KLF2) is crucial for maintaining endothelial function. MicroRNAs (miRNAs) are noncoding small RNAs that regulate gene expression at the posttranscriptional level. We examined the role of miRNAs, particularly miR-92a, in the atheroprotective flow-regulated KLF2.
Dicer knockdown increased the level of KLF2 mRNA in human umbilical vein endothelial cells, suggesting that KLF2 is regulated by miRNA. In silico analysis predicted that miR-92a could bind to the 3' untranslated region of KLF2 mRNA. Overexpression of miR-92a decreased the expression of KLF2 and the KLF2-regulated endothelial nitric oxide synthase and thrombomodulin at mRNA and protein levels. A complementary finding is that miR-92a inhibitor increased the mRNA and protein expression of KLF2, endothelial nitric oxide synthase, and thrombomodulin. Subsequent studies revealed that atheroprotective laminar flow downregulated the level of miR-92a precursor to induce KLF2, and the level of this flow-induced KLF2 was reduced by miR-92a precursor. Furthermore, miR-92a level was lower in human umbilical vein endothelial cells exposed to the atheroprotective pulsatile shear flow than under atheroprone oscillatory shear flow. Anti-Ago1/2 immunoprecipitation coupled with real-time polymerase chain reaction revealed that pulsatile shear flow decreased the functional targeting of miR-92a precursor/KLF2 mRNA in human umbilical vein endothelial cells. Consistent with these findings, mouse carotid arteries receiving miR-92a precursor exhibited impaired vasodilatory response to flow.
Atheroprotective flow patterns decrease the level of miR-92a, which in turn increases KLF2 expression to maintain endothelial homeostasis.
转录因子 Krüppel 样因子 2（KLF2）受保护性血流上调，对维持内皮功能至关重要。微小 RNA（miRNA）是一种非编码的小 RNA，可在转录后水平调节基因表达。我们研究了 miRNA，特别是 miR-92a，在保护性血流调节 KLF2 中的作用。
Dicer 敲低增加了人脐静脉内皮细胞中 KLF2 mRNA 的水平，表明 KLF2 受 miRNA 调节。计算机分析预测 miR-92a 可与 KLF2 mRNA 的 3'非翻译区结合。miR-92a 的过表达降低了 KLF2 及其 KLF2 调节的内皮型一氧化氮合酶和血栓调节蛋白的 mRNA 和蛋白水平。相应的发现是 miR-92a 抑制剂增加了 KLF2、内皮型一氧化氮合酶和血栓调节蛋白的 mRNA 和蛋白表达。随后的研究表明，保护性层流降低了 miR-92a 前体的水平，以诱导 KLF2，而这种由 miR-92a 前体诱导的 KLF2 水平则降低。此外，暴露于保护性脉动切变流中的人脐静脉内皮细胞中的 miR-92a 水平低于易受动脉粥样硬化影响的振荡切变流。抗 Ago1/2 免疫沉淀与实时聚合酶链反应相结合表明，脉动切变流降低了人脐静脉内皮细胞中 miR-92a 前体/KLF2 mRNA 的功能靶向。这些发现与小鼠颈动脉接受 miR-92a 前体后血流扩张反应受损的结果一致。
保护性血流模式降低了 miR-92a 的水平，从而增加了 KLF2 的表达，以维持内皮稳态。
