Involvement of GPx4-regulated lipid peroxidation in IPF pathogenesis.

Abstract

Introduction: Reactive oxygen species (ROS) play a pivotal role in TGF-b signaling and Idiopathic pulmonary fibrosis (IPF) pathogenesis. Glutathione peroxidase 4 (GPx4) can directly reduce phospholipid peroxidation, a representative oxidative modification by ROS. We attempted to elucidate the involvement of GPx4-regulated lipid peroxidation in modulating TGF-b signaling in terms of IPF pathogenesis. Methods: Using human lung tissues and lung fibroblasts (LFB) isolated from normal lungs and IPF lungs, immunohistochamical staining and western blotting (WB) were performed to evaluate GPx4 expression levels. SiRNA-mediated knockdown experiments were conducted to elucidate the role of GPx4 in TGF-b-induced myofibroblast differentiation. To clarify the role of GPx4 in physiological conditions, we used a bleomycin (BLM)-induced lung fibrosis model in GPx4+/-, GPx4+/+, GPx4 transgenic mice. Results: Immunohistochamical staining demonstrated decreased GPx4 and increased 4 hydroxynonenal (4HNE) expression levels, a major end product of lipid peroxidation, in IPF lungs. Reduced GPx4 expression levels were also detected in LFB isolated from IPF lungs. GPx4 siRNA increased TGF-b-induced lipid peroxidation and myofibroblast differentiation with concomitantly enhanced SMAD2/SMAD3 phosphorylation, which were efficiently inhibited by N-acetylcystein treatment. GPx4+/- mice showed marked enhancement of BLM-induced lung fibrosis development but significant attenuation was demonstrated in GPx4 transgenic mice. Conclusion: These findings suggest that GPx4 expression levels were reduced in IPF and GPx4-regulated lipid peroxidation can be involved in IPF pathogenesis via modulating TGF-b-induced myofibroblast differentiation.