title: microRNA-122 regulates hypoxia-inducible factor-1 and vimentin in hepatocytes and correlates with fibrosis in diet-induced steatohepatitis.
abstract: OBJECTIVE
  miR-122 is the most abundant miRNA in the liver particularly in hepatocytes where it targets cholesterol metabolism. Steatosis, a key component of non-alcoholic fatty liver disease, is regulated by hypoxia-inducible factor-1α (HIF-1α). Here, we hypothesized that reduced miR-122 has a pathogenic role in steatohepatitis.
  
  
  METHODS
  miR-122 and its target genes were evaluated in mouse livers and/or isolated hepatocytes after methionine-choline-deficient (MCD) or methionine-choline-supplemented (MCS) diet.
  
  
  RESULTS
  Liver and hepatocyte miR-122 expression was significantly decreased in steatohepatitis. A maximum reduction in miR-122 occurred at the fibrosis stage (8 weeks of MCD diet). MAP3K3, a miR-122 target gene, was induced at all stages of non-alcoholic steatohepatitis (NASH; 3-8 weeks) only at the mRNA level. Increased NF-κB activation was found in MCD diet-fed mice and MAP3K3 regulated the NF-κB DNA binding in naive hepatocytes. HIF-1α mRNA and DNA binding and expression of the HIF-1α target gene, profibrotic lysyl oxidase, was increased in advanced steatohepatitis (8 weeks). In addition, increase in vimentin and Sirius red staining (liver fibrosis) was found at 8 weeks of MCD diet. Using miR-122 overexpression and inhibition approaches, we confirmed that HIF-1α, vimentin and MAP3K3 are novel miR-122 targets in hepatocytes. We report transcriptional repression of miR-122 in NASH. Decreased liver miR-122 was associated with elevated circulating miR-122 in both exosome-rich and protein-rich serum fractions.
  
  
  CONCLUSIONS
  Our novel data suggest that decreased liver miR-122 contributes to upregulation of modulators of tissue remodelling (HIF-1α, vimentin and MAP3K3) and might play a role in NASH-induced liver fibrosis.
authors.affiliation: Department of Medicine, University of Massachusetts Medical School, Worcester, MA, USA.
authors.forename: Timea
authors.initials: T
authors.lastname: Csak
authors.forename: Shashi
authors.initials: S
authors.lastname: Bala
authors.forename: Dora
authors.initials: D
authors.lastname: Lippai
authors.forename: Abishek
authors.initials: A
authors.lastname: Satishchandran
authors.forename: Donna
authors.initials: D
authors.lastname: Catalano
authors.forename: Karen
authors.initials: K
authors.lastname: Kodys
authors.forename: Gyongyi
authors.initials: G
authors.lastname: Szabo
mesh_terms: D000818:Animals; D015153:Blotting, Western; D024202:Electrophoretic Mobility Shift Assay; D022781:Hepatocytes / Q000378:metabolism; D051793:Hypoxia-Inducible Factor 1 / Q000378:metabolism*; D007150:Immunohistochemistry; D008103:Liver Cirrhosis / Q000209:etiology / Q000473:pathology*; D048748:MAP Kinase Kinase Kinase 3 / Q000378:metabolism; D051379:Mice; D035683:MicroRNAs / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism; D065626:Non-alcoholic Fatty Liver Disease / Q000150:complications / Q000378:metabolism*; D060888:Real-Time Polymerase Chain Reaction; D018709:Statistics, Nonparametric; D014746:Vimentin / Q000378:metabolism*
chemical_list: D051793:Hypoxia-Inducible Factor 1; D035683:MicroRNAs; C544354:Mirn122 microRNA, mouse; D016328:NF-kappa B; D014746:Vimentin; D048748:MAP Kinase Kinase Kinase 3; C482626:Map3k3 protein, mouse
keywords: HIF-1α; MAP3K3; exosomes; fibrosis; hepatocyte; miR-122; vimentin