title: Flow-Dependent Regulation of Kruppel-Like Factor 2 Is Mediated by MicroRNA-92a.
abstract: BACKGROUND
  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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  Atheroprotective flow patterns decrease the level of miR-92a, which in turn increases KLF2 expression to maintain endothelial homeostasis.
authors.affiliation: Division of Biomedical Sciences, University of California-Riverside, 92521, USA.
authors.forename: Wei
authors.initials: W
authors.lastname: Wu
authors.forename: Han
authors.initials: H
authors.lastname: Xiao
authors.forename: Andrés
authors.initials: A
authors.lastname: Laguna-Fernandez
authors.forename: Guadalupe
authors.initials: G
authors.lastname: Villarreal
authors.forename: Kuei-Chun
authors.initials: KC
authors.lastname: Wang
authors.forename: Greg G
authors.initials: GG
authors.lastname: Geary
authors.forename: Yuzhi
authors.initials: Y
authors.lastname: Zhang
authors.forename: Wei-Chi
authors.initials: WC
authors.lastname: Wang
authors.forename: Hsien-Da
authors.initials: HD
authors.lastname: Huang
authors.forename: Jing
authors.initials: J
authors.lastname: Zhou
authors.forename: Yi-Shuan
authors.initials: YS
authors.lastname: Li
authors.forename: Shu
authors.initials: S
authors.lastname: Chien
authors.forename: Guillermo
authors.initials: G
authors.lastname: Garcia-Cardena
authors.forename: John Y-J
authors.initials: JY
authors.lastname: Shyy
mesh_terms: D020413:3' Untranslated Regions / Q000235:genetics; D050197:Atherosclerosis / Q000235:genetics / Q000473:pathology / Q000503:physiopathology*; D002478:Cells, Cultured; D042783:Endothelial Cells / Q000166:cytology / Q000502:physiology*; D005786:Gene Expression Regulation / Q000502:physiology; D055785:Gene Knockdown Techniques; D006706:Homeostasis / Q000502:physiology; D006801:Humans; D051741:Kruppel-Like Transcription Factors / Q000235:genetics* / Q000378:metabolism; D035683:MicroRNAs / Q000502:physiology*; D009569:Nitric Oxide / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III / Q000235:genetics / Q000378:metabolism; D011673:Pulsatile Flow / Q000502:physiology*; D012333:RNA, Messenger / Q000235:genetics; D013314:Stress, Mechanical; D018180:Thrombomodulin / Q000235:genetics / Q000378:metabolism; D014471:Umbilical Veins / Q000166:cytology; D014664:Vasodilation / Q000502:physiology
chemical_list: D020413:3' Untranslated Regions; C096161:KLF2 protein, human; D051741:Kruppel-Like Transcription Factors; C541874:MIRN92 microRNA, human; D035683:MicroRNAs; D012333:RNA, Messenger; D018180:Thrombomodulin; D009569:Nitric Oxide; C496314:NOS3 protein, human; D052250:Nitric Oxide Synthase Type III