title: Human cystatin C: a new biomarker of idiopathic pulmonary fibrosis?
abstract: OBJECTIVE
  Human idiopathic pulmonary fibrosis (IPF) is a progressive interstitial lung disorder with a poor prognosis. The identification of a new and specific biomarker in bronchoalveolar lavage fluids (BALFs) may assist in the diagnosis of the disease.
  
  
  METHODS
  Characterization of cysteine Cats and their endogenous inhibitor, cystatin C, was conducted by immunochemical analysis and measurement of endopeptidase activity of control (n = 11) and IPF (n = 25) BALFs (normalized conditions, 20 μg protein/assay).
  
  
  RESULTS
  Cathepsin (Cat) B was detected as proform and mature enzyme for both control and IPF samples, while Cats K, L, and S were found as zymogens with a strengthened staining in IPF BALFs. The overall endopeptidase activity related mainly to Cat B and did not vary significantly between control and IPF samples. Conversely a significant increase of immunoreactive cystatin C was measured in BALFs for each of three IPF grades.
  
  
  CONCLUSIONS
  An excessive deposition of extracellular matrix proteins is the hallmark of fibrotic disorders. Cats are potent collagenases and might be essential for lung homeostasis. Taken together, increase of cystatin C in IPF BALFs may reflect abnormal regulation of proteolytic activity of Cats in lung, which in turn can promote the development of fibrosis.
authors.affiliation: INSERM U1100, Pathologies Pulmonaires: Protéolyse et Aérosolthérapie, Equipe 2: Mécanismes Protéolytiques dans l'Inflammation; Faculté de Médecine, Centre d'Etude des Pathologies Respiratoires (CEPR), Université François Rabelais, Tours, France.
authors.forename: Mariana
authors.initials: M
authors.lastname: Kasabova
authors.forename: Alix
authors.initials: A
authors.lastname: Joulin-Giet
authors.forename: Fabien
authors.initials: F
authors.lastname: Lecaille
authors.forename: Ahlame
authors.initials: A
authors.lastname: Saidi
authors.forename: Sylvain
authors.initials: S
authors.lastname: Marchand-Adam
authors.forename: Gilles
authors.initials: G
authors.lastname: Lalmanach
mesh_terms: D015415:Biomarkers / Q000378:metabolism; D001992:Bronchoalveolar Lavage Fluid; D002403:Cathepsins / Q000378:metabolism; D055316:Cystatin C / Q000378:metabolism*; D005260:Female; D006801:Humans; D054990:Idiopathic Pulmonary Fibrosis / Q000201:enzymology / Q000378:metabolism*; D008297:Male
chemical_list: D015415:Biomarkers; D055316:Cystatin C; D002403:Cathepsins
keywords: Cathepsin; Cystatin C; Lung fibrosis; Protease; Protease inhibitor