title: Protease-activated receptor (PAR)-2 is required for PAR-1 signalling in pulmonary fibrosis.
abstract: Idiopathic pulmonary fibrosis is the most devastating diffuse fibrosing lung disease of unknown aetiology. Compelling evidence suggests that both protease-activated receptor (PAR)-1 and PAR-2 participate in the development of pulmonary fibrosis. Previous studies have shown that bleomycin-induced lung fibrosis is diminished in both PAR-1 and PAR-2 deficient mice. We thus have been suggested that combined inactivation of PAR-1 and PAR-2 would be more effective in blocking pulmonary fibrosis. Human and murine fibroblasts were stimulated with PAR-1 and PAR-2 agonists in the absence or presence of specific PAR-1 or PAR-2 antagonists after which fibrotic markers like collagen and smooth muscle actin were analysed by Western blot. Pulmonary fibrosis was induced by intranasal instillation of bleomycin into wild-type and PAR-2 deficient mice with or without a specific PAR-1 antagonist (P1pal-12). Fibrosis was assessed by hydroxyproline quantification and (immuno)histochemical analysis. We show that specific PAR-1 and/or PAR-2 activating proteases induce fibroblast migration, differentiation and extracellular matrix production. Interestingly, however, combined activation of PAR-1 and PAR-2 did not show any additive effects on these pro-fibrotic responses. Strikingly, PAR-2 deficiency as well as pharmacological PAR-1 inhibition reduced bleomycin-induced pulmonary fibrosis to a similar extent. PAR-1 inhibition in PAR-2 deficient mice did not further diminish bleomycin-induced pulmonary fibrosis. Finally, we show that the PAR-1-dependent pro-fibrotic responses are inhibited by the PAR-2 specific antagonist. Targeting PAR-1 and PAR-2 simultaneously is not superior to targeting either receptor alone in bleomycin-induced pulmonary fibrosis. We postulate that the pro-fibrotic effects of PAR-1 require the presence of PAR-2.
authors.affiliation: Center for Experimental and Molecular Medicine, Academic Medical Center, Amsterdam, The Netherlands.
authors.forename: Cong
authors.initials: C
authors.lastname: Lin
authors.affiliation: Department of Pathology, Medisch Centrum Haaglanden, Den Haag, The Netherlands.
authors.forename: Jan
authors.initials: J
authors.lastname: von der Thüsen
authors.affiliation: Center for Experimental and Molecular Medicine, Academic Medical Center, Amsterdam, The Netherlands.
authors.forename: Joost
authors.initials: J
authors.lastname: Daalhuisen
authors.affiliation: Center for Experimental and Molecular Medicine, Academic Medical Center, Amsterdam, The Netherlands.
authors.forename: Marieke
authors.initials: M
authors.lastname: ten Brink
authors.affiliation: Faculté de Médecine Paris 7 Diderot, Institut National de la Santé et de la Recherche Médicale, Paris, France.
authors.forename: Bruno
authors.initials: B
authors.lastname: Crestani
authors.affiliation: Center for Experimental and Molecular Medicine, Academic Medical Center, Amsterdam, The Netherlands.
authors.forename: Tom
authors.initials: T
authors.lastname: van der Poll
authors.affiliation: Center for Experimental and Molecular Medicine, Academic Medical Center, Amsterdam, The Netherlands.|Faculté de Médecine Paris 7 Diderot, Institut National de la Santé et de la Recherche Médicale, Paris, France.
authors.forename: Keren
authors.initials: K
authors.lastname: Borensztajn
authors.affiliation: Center for Experimental and Molecular Medicine, Academic Medical Center, Amsterdam, The Netherlands.
authors.forename: C Arnold
authors.initials: CA
authors.lastname: Spek
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D001761:Bleomycin; D015153:Blotting, Western; D003094:Collagen / Q000378:metabolism; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D006909:Hydroxyproline / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D041681:NIH 3T3 Cells; D010446:Peptide Fragments / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D011658:Pulmonary Fibrosis / Q000139:chemically induced / Q000235:genetics / Q000378:metabolism*; D044463:Receptor, PAR-1 / Q000235:genetics / Q000378:metabolism*; D044464:Receptor, PAR-2 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D013917:Thrombin / Q000494:pharmacology; D014357:Trypsin / Q000494:pharmacology; D010975:Platelet Aggregation Inhibitors
chemical_list: D000199:Actins; C587066:P1pal-12 peptide; D010446:Peptide Fragments; D044463:Receptor, PAR-1; D044464:Receptor, PAR-2; D001761:Bleomycin; D003094:Collagen; D048049:Extracellular Signal-Regulated MAP Kinases; D014357:Trypsin; D013917:Thrombin; D006909:Hydroxyproline; D010975:Platelet Aggregation Inhibitors
keywords: bleomycin; protease-activated receptors (PARs); pulmonary fibrosis