title: Tumor necrosis factor α-induced microRNA-18a activates rheumatoid arthritis synovial fibroblasts through a feedback loop in NF-κB signaling.
abstract: OBJECTIVE
  To elucidate whether the microRNA (miRNA) cluster miR-17-92 contributes to the activated phenotype of rheumatoid arthritis synovial fibroblasts (RASFs).
  
  
  METHODS
  RASFs were stimulated with tumor necrosis factor α (TNFα), and the expression and regulation of the miR-17-92 cluster were studied using real-time quantitative PCR (PCR) and promoter activity assays. RASFs were transfected with single precursor molecules of miRNAs from miR-17-92 and the expression of matrix-degrading enzymes and cytokines was measured by quantitative PCR and enzyme-linked immunosorbent assay. Potential miRNA targets were identified by computational prediction and were validated using reporter gene assays and Western blotting. The activity of NF-κB signaling was determined by reporter gene assays.
  
  
  RESULTS
  We found that TNFα induces the expression of miR-17-92 in RASFs in an NF-κB-dependent manner. Transfection of RASFs with precursor molecules of single members of miR-17-92 revealed significantly increased expression levels of matrix-degrading enzymes, proinflammatory cytokines, and chemokines in precursor miR-18a (pre-miR-18a)-transfected RASFs. Using reporter gene assays, we identified the NF-κB pathway inhibitor TNFα-induced protein 3 as a new target of miR-18a. In addition, pre-miR-18a-transfected RASFs showed stronger activation of NF-κB signaling, both constitutively and in response to TNFα stimulation.
  
  
  CONCLUSIONS
  Our data suggest that the miR-17-92-derived miR-18a contributes to cartilage destruction and chronic inflammation in the joint through a positive feedback loop in NF-κB signaling, with concomitant up-regulation of matrix-degrading enzymes and mediators of inflammation in RASFs.
authors.affiliation: Center of Experimental Rheumatology, University Hospital Zurich, Zurich, Switzerland. michelle.trenkmann@usz.ch
authors.forename: Michelle
authors.initials: M
authors.lastname: Trenkmann
authors.forename: Matthias
authors.initials: M
authors.lastname: Brock
authors.forename: Renate E
authors.initials: RE
authors.lastname: Gay
authors.forename: Beat A
authors.initials: BA
authors.lastname: Michel
authors.forename: Steffen
authors.initials: S
authors.lastname: Gay
authors.forename: Lars C
authors.initials: LC
authors.lastname: Huber
mesh_terms: D001172:Arthritis, Rheumatoid / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D016207:Cytokines / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D025461:Feedback, Physiological; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D018014:Gene Transfer Techniques; D006801:Humans; D018836:Inflammation Mediators / Q000378:metabolism; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism*; D062085:RNA, Long Noncoding; D060888:Real-Time Polymerase Chain Reaction; D015398:Signal Transduction; D013583:Synovial Membrane / Q000166:cytology* / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D016207:Cytokines; D004268:DNA-Binding Proteins; D018836:Inflammation Mediators; C568997:MIR17HG, human; C522576:MIRN18A microRNA, human; D035683:MicroRNAs; D016328:NF-kappa B; D062085:RNA, Long Noncoding; C117046:TNIP1 protein, human; D014409:Tumor Necrosis Factor-alpha