title: MicroRNA-21 negatively regulates Treg cells through a TGF-β1/Smad-independent pathway in patients with coronary heart disease.
abstract: BACKGROUND
  CD4+CD25+FoxP3+ regulatory T cells (Treg cells) play a protective role against the development and progression of the inflammatory disease atherosclerosis (AS). MicroRNA-21 (miR-21) is expressed in Treg cells and is up-regulated in the context of AS and other inflammatory diseases.
  
  
  OBJECTIVE
  This study aimed to determine the role of miR-21 in Treg cell regulation and gene expression during the development of AS in patients with coronary heart disease (CHD).
  
  
  RESULTS
  MiR-21 expression in peripheral blood mononuclear cells (PBMCs) was significantly up-regulated in patients with CHD (acute myocardial infarction (AMI) group, n=24; unstable angina (UA) group, n=21; stable angina (SA) group, n=24) compared with patients with chest pain syndrome (CPS, n=27), and miR-21 expression showed an increasing trend from SA to UA to AMI patients. Moreover, flow cytometry analysis indicated that the frequencies of circulating Treg cells decreased in a manner proportionate opposite with the level of miR-21. Quantitative real-time PCR (qRT-PCR) revealed a decrease in mRNA expression of forkhead box P3 (foxp3), transforming cell growth factor beta 1(TGF-β1) and smad7 (a known target gene of miR-21). ELISA analysis revealed a decrease in TGF-β1 secreted into the plasma. In addition, we transfected PBMCs with a miRNA negative control (NS-m), a miR-21 mimic (miR-21-m), a miRNA inhibitor negative control (NS-i), or a miR-21 inhibitor(miR-21-i). Up-regulation of miR-21 decreased the frequency of circulating Treg cells, decreased the expression levels of foxp3, TGF-β1 and smad7, and decreased the amount of TGF-β1 secreted into the plasma. Consistent with these observations, miR-21 down-regulation increased the frequency of circulating Treg cells, increased the expression of foxp3, TGF-β1 and smad7, and increased the amount of TGF-β1 secreted into the plasma.
  
  
  CONCLUSIONS
  Because the smad7 expression pattern was similar to that of TGF-β, our study suggests that miR-21 can negatively regulate the frequency of circulating Treg cells through a TGF-β1/smad-independent signaling pathway in PBMCs.
authors.affiliation: Laboratory of Cardiovascular Immunology, Institute of Cardiology, Union Hospital, Huazhong University of Science and Technology, Wuhan, China.
authors.forename: Sihui
authors.initials: S
authors.lastname: Li
authors.forename: Qian
authors.initials: Q
authors.lastname: Fan
authors.forename: Shaolin
authors.initials: S
authors.lastname: He
authors.forename: Tingting
authors.initials: T
authors.lastname: Tang
authors.forename: Yuhua
authors.initials: Y
authors.lastname: Liao
authors.forename: Jiangjiao
authors.initials: J
authors.lastname: Xie
mesh_terms: D000328:Adult; D003324:Coronary Artery Disease / Q000235:genetics* / Q000276:immunology; D005260:Female; D051858:Forkhead Transcription Factors / Q000235:genetics; D006801:Humans; D007963:Leukocytes, Mononuclear / Q000378:metabolism; D008297:Male; D035683:MicroRNAs / Q000235:genetics* / Q000378:metabolism; D008875:Middle Aged; D015398:Signal Transduction; D051906:Smad7 Protein / Q000235:genetics*; D050378:T-Lymphocytes, Regulatory / Q000378:metabolism*; D053773:Transforming Growth Factor beta1 / Q000235:genetics*; D015854:Up-Regulation
chemical_list: C418974:FOXP3 protein, human; D051858:Forkhead Transcription Factors; C524940:MIRN21 microRNA, human; D035683:MicroRNAs; C497806:SMAD7 protein, human; D051906:Smad7 Protein; C508960:TGFB1 protein, human; D053773:Transforming Growth Factor beta1