Pirfenidone mitigates TGF-β1-mediated fibrosis in an idiopathic inflammatory myositis-associated interstitial lung disease model

Idiopathic inflammatory myositis (IIM) is a group of rare diseases of unknown etiology, with a pathognomonic muscular deficiency. Antisynthetase syndrome is a subtype of IIM with an associated interstitial lung disease (ILD), characterized by pulmonary inflammation and fibrosis mediated by TGF-β. Pirfenidone is a new molecule with anti-inflammatory and anti-fibrotic properties, used for the treatment of idiopathic ILD, but has never been assessed in IIM. The aim of our study is to evaluate the effect of pirfenidone on IIM-associated ILD. Thirty-two BALB/c male mice were divided into three groups: Sham, IIM-untreated (IIM), and IIM pirfenidone-treated (IIM + PIR). IIM was induced by intramuscular injections of guinea pig muscle myosin extract and intraperitoneal injections of Pertussis toxin. Pirfenidone was given orally at a dose of 30 mg kg-1 day-1 for two months. Muscle force, blood and bronchoalveolar lavage fluid samples, as well as muscle and lung tissues, were analyzed. Progressive deterioration of muscle force and infiltration of the muscular tissue by inflammatory cells were observed with IIM. Auto-immune antibodies specific to the antisynthetase syndrome were also increased in IIM mice. Pirfenidone attenuated IIM-associated ILD with anti-inflammatory properties evidenced by decreased peribronchial inflammation and TGF-β1 in bronchoalveolar lavage fluid. Likewise, pirfenidone attenuated pulmonary fibrosis by fine-tuning TGF-β1-mediated epithelial-to-mesenchymal and fibrotic signaling pathways; pro-fibrotic SMAD3, ZEB2 and STAT1 expression and activation were decreased, whereas anti-fibrotic SMAD2 activation was increased. This study unravels for the first time that pirfenidone has the potential to fine-tune TGF-β1 fibrotic signaling in IIM-associated ILD.