title: miR-31 dysregulation in cystic fibrosis airways contributes to increased pulmonary cathepsin S production.
abstract: BACKGROUND
  Cathepsin S (CTSS) activity is increased in bronchoalveolar lavage (BAL) fluid from patients with cystic fibrosis (CF). This activity contributes to lung inflammation via degradation of antimicrobial proteins, such as lactoferrin and members of the β-defensin family.
  
  
  OBJECTIVE
  In this study, we investigated the hypothesis that airway epithelial cells are a source of CTSS, and mechanisms underlying CTSS expression in the CF lung.
  
  
  METHODS
  Protease activity was determined using fluorogenic activity assays. Protein and mRNA expression were analyzed by ELISA, Western blotting, and reverse-transcriptase polymerase chain reaction.
  
  
  RESULTS
  In contrast to neutrophil elastase, CTSS activity was detectable in 100% of CF BAL fluid samples from patients without Pseudomonas aeruginosa infection. In this study, we identified epithelial cells as a source of pulmonary CTSS activity with the demonstration that CF airway epithelial cells express and secrete significantly more CTSS than non-CF control cells in the absence of proinflammatory stimulation. Furthermore, levels of the transcription factor IRF-1 correlated with increased levels of its target gene CTSS. We discovered that miR-31, which is decreased in the CF airways, regulates IRF-1 in CF epithelial cells. Treating CF bronchial epithelial cells with a miR-31 mimic decreased IRF-1 protein levels with concomitant knockdown of CTSS expression and secretion.
  
  
  CONCLUSIONS
  The miR-31/IRF-1/CTSS pathway may play a functional role in the pathogenesis of CF lung disease and may open up new avenues for exploration in the search for an effective therapeutic target.
authors.affiliation: 1 Centre for Infection and Immunity, School of Medicine, Dentistry and Biomedical Sciences, and.
authors.forename: Sinéad
authors.initials: S
authors.lastname: Weldon
authors.forename: Paul
authors.initials: P
authors.lastname: McNally
authors.forename: Danny F
authors.initials: DF
authors.lastname: McAuley
authors.forename: Irene K
authors.initials: IK
authors.lastname: Oglesby
authors.forename: Christine L
authors.initials: CL
authors.lastname: Wohlford-Lenane
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: Bartlett
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Scott
authors.forename: Noel G
authors.initials: NG
authors.lastname: McElvaney
authors.forename: Catherine M
authors.initials: CM
authors.lastname: Greene
authors.forename: Paul B
authors.initials: PB
authors.lastname: McCray
authors.forename: Clifford C
authors.initials: CC
authors.lastname: Taggart
mesh_terms: D000293:Adolescent; D015415:Biomarkers / Q000378:metabolism; D015153:Blotting, Western; D001992:Bronchoalveolar Lavage Fluid / Q000737:chemistry* / Q000382:microbiology; D002403:Cathepsins / Q000378:metabolism*; D002460:Cell Line; D002648:Child; D002675:Child, Preschool; D003550:Cystic Fibrosis / Q000235:genetics* / Q000378:metabolism / Q000382:microbiology; D015536:Down-Regulation; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D007223:Infant; D050856:Interferon Regulatory Factor-1 / Q000378:metabolism*; D035683:MicroRNAs / Q000378:metabolism*; D010447:Peptide Hydrolases / Q000378:metabolism; D011552:Pseudomonas Infections / Q000150:complications / Q000175:diagnosis / Q000378:metabolism; D011550:Pseudomonas aeruginosa / Q000302:isolation & purification; D020545:Respiratory Mucosa / Q000378:metabolism* / Q000382:microbiology; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D015415:Biomarkers; C494257:IRF1 protein, human; D050856:Interferon Regulatory Factor-1; C534612:MIRN31 microRNA, human; D035683:MicroRNAs; D002403:Cathepsins; D010447:Peptide Hydrolases; C028217:cathepsin S
keywords: cystic fibrosis; epithelium; microRNA; protease