Absence of proteinase-activated receptor-1 signaling affords protection from bleomycin-induced lung inflammation and fibrosis

Am J Pathol. 2005 May;166(5):1353-65. doi: 10.1016/S0002-9440(10)62354-1.


Activation of the coagulation cascade is commonly observed in the lungs of patients with both acute and chronic inflammatory and fibrotic lung disorders, as well as in animal models of these disorders. The aim of this study was to examine the contribution of the major thrombin receptor, proteinase-activated receptor-1 (PAR-1), during the acute inflammatory and chronic fibrotic phases of lung injury induced by intratracheal instillation of bleomycin in mice. Inflammatory cell recruitment and increases in bronchoalveolar lavage fluid (BALF) protein were attenuated by 56 +/- 10% (P < 0.05) and 53 +/- 12% (P < 0.05), respectively, in PAR-1-deficient (PAR-1-/-) mice compared with wild-type (WT) mice. PAR-1-/- mice were also protected from bleomycin-induced pulmonary fibrosis with total lung collagen accumulation reduced by 59 +/- 5% (P < 0.05). The protection afforded by PAR-1 deficiency was accompanied by significant reductions in pulmonary levels of the potent PAR-1-inducible proinflammatory and profibrotic mediators, monocyte chemoattractant protein-1 (MCP-1), transforming growth factor-beta-1 (TGF-beta1), and connective tissue growth factor/fibroblast-inducible secreted protein-12 (CTGF/FISP12). In addition, PAR-1 was highly expressed in inflammatory and fibroproliferative lesions in lung sections obtained from patients with fibrotic lung disease. These data show for the first time that PAR-1 signaling plays a key role in experimentally induced lung injury, and they further identify PAR-1 as one of the critical receptors involved in orchestrating the interplay between coagulation, inflammation, and remodeling in response to tissue injury.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Biopsy
  • Bleomycin*
  • Bronchoalveolar Lavage Fluid / cytology
  • Capillary Permeability
  • Cell Count
  • Connective Tissue Growth Factor
  • Cytoprotection
  • Humans
  • Immediate-Early Proteins / metabolism
  • Immunohistochemistry
  • Intercellular Signaling Peptides and Proteins / metabolism
  • Lung / metabolism
  • Lung / pathology
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Pneumonia / chemically induced*
  • Pneumonia / metabolism
  • Pneumonia / pathology
  • Pneumonia / physiopathology
  • Pulmonary Fibrosis / chemically induced*
  • Pulmonary Fibrosis / metabolism
  • Pulmonary Fibrosis / pathology
  • Pulmonary Fibrosis / physiopathology
  • Receptor, PAR-1 / deficiency
  • Receptor, PAR-1 / metabolism*
  • Signal Transduction*
  • Transforming Growth Factor beta / metabolism
  • Transforming Growth Factor beta1


  • CCN2 protein, human
  • CCN2 protein, mouse
  • Immediate-Early Proteins
  • Intercellular Signaling Peptides and Proteins
  • Receptor, PAR-1
  • TGFB1 protein, human
  • Tgfb1 protein, mouse
  • Transforming Growth Factor beta
  • Transforming Growth Factor beta1
  • Bleomycin
  • Connective Tissue Growth Factor