Pirfenidone inhibits myofibroblast differentiation and lung fibrosis development during insufficient mitophagy

Yusuke Kurita,Kenji Kobayashi,Hiroko Yanagisawa ,Kazuya Tsubouchi,Nahoko Sato,Mitsuo Hashimoto,Nayuta Saito,Jun Araya,Masahiro Yoshida,Shunsuke Minagawa,Yoshiaki Kaneko ,Katsutoshi Nakayama,Hirofumi Utsumi,Yu Fujita,Hiromichi Hara,Takanori Numata,Saburo Ito,Toshiaki Morikawa,Makoto Yamashita,Takeo Ishikawa,Yutaka Yoshii,Hiroaki Asano ,Akihiro Ichikawa,Makoto Odaka,Tsukasa Kadota,Hiroshi Wakui,Kazuyoshi Kuwano

doi:10.1186/s12931-017-0600-3

Abstract

BackgroundPirfenidone (PFD) is an anti-fibrotic agent used to treat idiopathic pulmonary fibrosis (IPF), but its precise mechanism of action remains elusive. Accumulation of profibrotic myofibroblasts is a crucial process for fibrotic remodeling in IPF. Recent findings show participation of autophagy/mitophagy, part of the lysosomal degradation machinery, in IPF pathogenesis. Mitophagy has been implicated in myofibroblast differentiation through regulating mitochondrial reactive oxygen species (ROS)-mediated platelet-derived growth factor receptor (PDGFR) activation. In this study, the effect of PFD on autophagy/mitophagy activation in lung fibroblasts (LF) was evaluated, specifically the anti-fibrotic property of PFD for modulation of myofibroblast differentiation during insufficient mitophagy.MethodsTransforming growth factor-β (TGF-β)-induced or ATG5, ATG7, and PARK2 knockdown-mediated myofibroblast differentiation in LF were used for in vitro models. The anti-fibrotic role of PFD was examined in a bleomycin (BLM)-induced lung fibrosis model using PARK2 knockout (KO) mice.ResultsWe found that PFD induced autophagy/mitophagy activation via enhanced PARK2 expression, which was partly involved in the inhibition of myofibroblast differentiation in the presence of TGF-β. PFD inhibited the myofibroblast differentiation induced by PARK2 knockdown by reducing mitochondrial ROS and PDGFR-PI3K-Akt activation. BLM-treated PARK2 KO mice demonstrated augmentation of lung fibrosis and oxidative modifications compared to those of BLM-treated wild type mice, which were efficiently attenuated by PFD.ConclusionsThese results suggest that PFD induces PARK2-mediated mitophagy and also inhibits lung fibrosis development in the setting of insufficient mitophagy, which may at least partly explain the anti-fibrotic mechanisms of PFD for IPF treatment.

Highlights

Pirfenidone (PFD) is an anti-fibrotic agent used to treat idiopathic pulmonary fibrosis (IPF), but its precise mechanism of action remains elusive
We have recently reported that insufficient autophagy/mitophagy-mediated enhanced mitochondrial reactive oxygen species (ROS) is responsible for myofibroblast differentiation through regulation of the platelet-derived growth factor receptor (PDGFR) signaling pathway [20]
Our preliminary experiments demonstrated that 500 μg/ml of PFD was needed to efficiently inhibit Transforming growth factor-β (TGF-β)-induced myofibroblast differentiation in lung fibroblasts (LF), 500 μg/ml of PFD was selected for in vitro experiments

Summary

Introduction

Pirfenidone (PFD) is an anti-fibrotic agent used to treat idiopathic pulmonary fibrosis (IPF), but its precise mechanism of action remains elusive. The effect of PFD on autophagy/mitophagy activation in lung fibroblasts (LF) was evaluated, the anti-fibrotic property of PFD for modulation of myofibroblast differentiation during insufficient mitophagy. Recently available treatments of nintedanib and pirfenidone (PFD) are considered to be effective mainly through anti-fibrotic mechanisms, including inhibition of myofibrobast differentiation and proliferation [5, 6]. Despite the wide array of pharmacological inhibition of fibrotic processes that have been reported for PFD, the exact molecular mechanisms for attenuating lung fibrosis progression remain elusive [15]

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