title: Mitochondrial reactive oxygen species regulate transforming growth factor-β signaling.
abstract: TGF-β signaling is required for normal tissue repair; however, excessive TGF-β signaling can lead to robust profibrotic gene expression in fibroblasts, resulting in tissue fibrosis. TGF-β binds to cell-surface receptors, resulting in the phosphorylation of the Smad family of transcription factors to initiate gene expression. TGF-β also initiates Smad-independent pathways, which augment gene expression. Here, we report that mitochondrial reactive oxygen species (ROS) generated at complex III are required for TGF-β-induced gene expression in primary normal human lung fibroblasts. TGF-β-induced ROS could be detected in both the mitochondrial matrix and cytosol. Mitochondrially targeted antioxidants markedly attenuated TGF-β-induced gene expression without affecting Smad phosphorylation or nuclear translocation. Genetically disrupting mitochondrial complex III-generated ROS production attenuated TGF-β-induced profibrotic gene expression. Furthermore, inhibiting mitochondrial ROS generation attenuated NOX4 (NADPH oxidase 4) expression, which is required for TGF-β induced myofibroblast differentiation. Lung fibroblasts from patients with pulmonary fibrosis generated more mitochondrial ROS than normal human lung fibroblasts, and mitochondrially targeted antioxidants attenuated profibrotic gene expression in both normal and fibrotic lung fibroblasts. Collectively, our results indicate that mitochondrial ROS are essential for normal TGF-β-mediated gene expression and that targeting mitochondrial ROS might be beneficial in diseases associated with excessive fibrosis.
authors.affiliation: Division of Pulmonary and Critical Care, Department of Medicine, Northwestern University Medical School, Chicago, Illinois 60611, USA. m-jain@northwestern.edu
authors.forename: Manu
authors.initials: M
authors.lastname: Jain
authors.forename: Stephanie
authors.initials: S
authors.lastname: Rivera
authors.forename: Elena A
authors.initials: EA
authors.lastname: Monclus
authors.forename: Lauren
authors.initials: L
authors.lastname: Synenki
authors.forename: Aaron
authors.initials: A
authors.lastname: Zirk
authors.forename: James
authors.initials: J
authors.lastname: Eisenbart
authors.forename: Carol
authors.initials: C
authors.lastname: Feghali-Bostwick
authors.forename: Gokhan M
authors.initials: GM
authors.lastname: Mutlu
authors.forename: G R Scott
authors.initials: GR
authors.lastname: Budinger
authors.forename: Navdeep S
authors.initials: NS
authors.lastname: Chandel
mesh_terms: D001483:Base Sequence; D015153:Blotting, Western; D002478:Cells, Cultured; D003600:Cytosol / Q000378:metabolism; D017931:DNA Primers; D014450:Electron Transport Complex III / Q000378:metabolism; D006801:Humans; D008928:Mitochondria / Q000201:enzymology / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000378:metabolism*; D060888:Real-Time Polymerase Chain Reaction; D015398:Signal Transduction; D016212:Transforming Growth Factor beta / Q000378:metabolism*
chemical_list: D017931:DNA Primers; D017382:Reactive Oxygen Species; D016212:Transforming Growth Factor beta; D014450:Electron Transport Complex III