Pharmacological Targeting of Protease-Activated Receptor 2 Affords Protection from Bleomycin-Induced Pulmonary Fibrosis.

Cong Lin,C Arnold Spek,Bruno Crestani,Marieke Ten Brink,Joost Daalhuisen,Tom Van Der Poll,Jan Von Der Thüsen,Keren Borensztajn

doi:10.2119/molmed.2015.00094

Abstract

Idiopathic pulmonary fibrosis is the most devastating diffuse fibrosing lung disease that remains refractory to therapy. Despite increasing evidence that protease-activated receptor 2 (PAR-2) contributes to fibrosis, its importance in pulmonary fibrosis is under debate. We addressed whether PAR-2 deficiency persistently reduces bleomycin-induced pulmonary fibrosis or merely delays disease progression and whether pharmacological PAR-2 inhibition limits experimental pulmonary fibrosis. Bleomycin was instilled intranasally into wild-type or PAR-2-deficient mice in the presence/absence of a specific PAR-2 antagonist (P2pal-18S). Pulmonary fibrosis was consistently reduced in PAR-2-deficient mice throughout the fibrotic phase, as evident from reduced Ashcroft scores (29%) and hydroxyproline levels (26%) at d 28. Moreover, P2pal-18S inhibited PAR-2-induced profibrotic responses in both murine and primary human pulmonary fibroblasts (p < 0.05). Once daily treatment with P2pal-18S reduced the severity and extent of fibrotic lesions in lungs of bleomycin-treated wild-type mice but did not further reduce fibrosis in PAR-2-deficient mice. Importantly, P2pal-18S treatment starting even 7 d after the onset of fibrosis limits pulmonary fibrosis as effectively as when treatment was started together with bleomycin instillation. Overall, PAR-2 contributes to the progression of pulmonary fibrosis, and targeting PAR-2 may be a promising therapeutic strategy for treating pulmonary fibrosis.

Highlights

Idiopathic pulmonary fibrosis (IPF) is a lethal diffuse fibrosing lung disease with a 5-year mortality rate greater than 50%, which exceeds many types of cancers [1,2,3]
To determine whether protease-activated receptor 2 (PAR-2) drives the progression of pulmonary fibrosis or whether its absence would merely delay the onset of fibrosis, we compared lungs from wild-type and protease-activated receptors (PARs)-2–deficient mice at d 28 and 48 after the instillation of bleomycin
These results show that PAR-2 deficiency provides protection against bleomycin-induced pulmonary fibrosis throughout the fibrotic stage and does not merely delay disease onset

Summary

Introduction

Idiopathic pulmonary fibrosis (IPF) is a lethal diffuse fibrosing lung disease with a 5-year mortality rate greater than 50%, which exceeds many types of cancers [1,2,3]. PAR-2 is one of four members of the PAR family that is widely expressed in many different cell types such as (among others) fibroblasts and epithelial cells [9] Proteases such as trypsin, factor (F)VIIa, FXa, mast cell tryptase or matriptase cleave the N-terminal extracellular domain of PAR-2, thereby revealing a novel tethered ligand that binds to PAR-2 and activates its transmembrane signaling to intracellular G proteins [10,11,12]. This study provided in vitro evidence that FVIIa exerts profibrotic effects in human fibroblasts by activating PAR-2 In line with this finding, the prototypical PAR-2 agonist tryptase stimulates the growth of human lung fibroblasts and potentiates extracellular matrix production in a PAR-2–dependent manner [17]. We reaffirmed the importance of PAR-2 and subsequently evaluated the efficacy of pharmacological PAR2 inhibition in pulmonary fibrosis

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