Cu,Zn-Superoxide Dismutase-Mediated Redox Regulation of Jumonji Domain Containing 3 Modulates Macrophage Polarization and Pulmonary Fibrosis

Our plain-English summary of Cu,Zn-Superoxide Dismutase-Mediated Redox Regulation of Jumonji Domain Containing 3 Modulates Macrophage Polarization and Pulmonary Fibrosis, by C. He, J.L. Larson-Casey, L. Gu, et al (American Journal of Respiratory Cell and Molecular Biology, 2016).

The study

• Authors: C. He, J.L. Larson-Casey, L. Gu, A.J. Ryan, S. Murthy, A.B. Carter
• Journal: American Journal of Respiratory Cell and Molecular Biology
• Published: 2016;55(1):58-71
• Cited by: 58 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

M2 macrophages are implicated in the development of pulmonary fibrosis as they generate profibrotic signals. The polarization process, at least in part, is regulated by epigenetic modulation. Because Cu,Zn-superoxide dismutase-induced H2O2 can polarize macrophages to a profibrotic M2 phenotype, we hypothesized that modulation of the redox state of the cell is involved in the epigenetic modulation of the macrophage phenotype. In this study, we show that signal transducer and activator of transcription 6 (STAT6) regulates Jumonji domain containing (Jmjd) 3, a histone H3 lysine 27 demethylase, and mutation of a redox-sensitive cysteine in STAT6 attenuates jmjd3 expression. Moreover, Jmjd3 deficiency abrogates profibrotic M2 gene expression. Treatment with leflunomide, which reduces mitochondrial reactive oxygen species production and tyrosine phosphorylation, inhibits jmjd3 expression and M2 polarization, as well as development of a fibrotic phenotype. Taken together, these observations provide evidence that the redox regulation of Jmjd3 is a unique regulatory mechanism for Cu,Zn-superoxide dismutase-mediated profibrotic M2 polarization. Furthermore, leflunomide, which reduces reactive oxygen species production and tyrosine phosphorylation, may prove to be therapeutic in the treatment of asbestos-induced pulmonary fibrosis.

In plain English

This was a laboratory study of how lung immune cells called macrophages may drive lung scarring (pulmonary fibrosis) after asbestos exposure. The authors used mice, cultured cells, and alveolar macrophages taken from asbestosis patients and from normal subjects. Mice were given 100 µg of chrysotile asbestos into the airway and examined 21 days later. After chrysotile, mice lacking a protein called STAT6 had less collagen, a measure of scarring, in their lungs than normal mice. Macrophages from asbestosis patients showed significantly greater activity of an enzyme called Jmjd3 than those from normal subjects. They also showed nearly 20-fold more expression of arginase-1, a marker of the scar-promoting macrophage type. Chrysotile-exposed mice given the rheumatoid arthritis drug leflunomide had near-normal lung tissue. Chrysotile-exposed mice given the vehicle (the carrier solution) instead of leflunomide showed widespread collagen deposition. The authors concluded that this chain of chemical signals, which runs through Jmjd3, helps turn macrophages scar-promoting. They also concluded that leflunomide may prove to be therapeutic for asbestos-induced pulmonary fibrosis. The leflunomide results come from mice and cultured cells, not from treated patients.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Laboratory study combining animal experiments (genetically modified and normal mice exposed to chrysotile), cell-culture experiments, and measurements on human alveolar macrophages
• Who was studied: The mice were normal (WT) mice, mice that overproduce Cu,Zn-SOD, and mice that lack STAT6. The study also used mouse and human macrophage cell lines. Human alveolar macrophages came from asbestosis patients and normal subjects under a University of Iowa protocol. The number of human subjects is not stated in the text; figure legends give n = 3 and n = 6 for the human comparisons.
• Exposure: Mice received 100 µg of chrysotile asbestos into the airway (intratracheally), with titanium dioxide (TiO2) as a comparison dust. Cells were exposed to chrysotile in culture. In some mouse experiments, leflunomide (1.4 mg/kg) or vehicle was injected every other day.
• Main results:
  • After chrysotile exposure, STAT6-deficient mice had lower lung hydroxyproline (a measure of collagen) than WT mice
  • In lung (BAL) cells from chrysotile-exposed STAT6-deficient mice, expression of the inflammatory gene tnf-α was increased more than 25-fold compared with WT mice
  • Alveolar macrophages from asbestosis patients had significantly greater Jmjd3 activity than those from normal subjects (figure legend n = 3)
  • Alveolar macrophages from asbestosis patients had nearly 20-fold more arginase-1 expression than those from normal subjects (figure legend n = 6)
  • In cultured macrophages exposed to chrysotile, reducing Jmjd3 lowered the scar-promoting marker fizz1 below control levels
  • Cu,Zn-SOD was significantly increased in lung (BAL) cells from chrysotile-exposed WT mice compared with TiO2-exposed mice
  • TiO2-exposed WT mice had no collagen deposition whether given vehicle or leflunomide
  • Chrysotile-exposed WT mice given vehicle showed widespread collagen deposition in lung tissue, while chrysotile-exposed WT mice given leflunomide had near normal lung tissue. Hydroxyproline measurements confirmed this (n = 5 per group in the legend).
  • After chrysotile exposure, leflunomide-treated mice had significantly lower jmjd3 expression in alveolar macrophages than vehicle-treated mice
  • In cultured macrophages, chrysotile significantly increased hydrogen peroxide generation, while IL-4 did not change it compared with vehicle
• The authors' conclusion: The authors concluded that redox regulation of Jmjd3 is a regulatory mechanism for Cu,Zn-SOD-driven scar-promoting (M2) macrophage polarization. They also concluded that leflunomide may prove to be therapeutic in the treatment of asbestos-induced pulmonary fibrosis.
• Limitations the authors state:
  • The authors noted that the protective effect of STAT6 loss in pulmonary fibrosis may have several causes, and that how specific it is to macrophage polarization needs further investigation

Topics

Medical terms in this study, explained in our Lexicon: Superoxide, Macrophage, Pulmonary Fibrosis, Reactive Oxygen Species (ROS).

Related studies

• NOX4 modulates macrophage phenotype and mitochondrial biogenesis in asbestosis — C. He, J.L. Larson-Casey, et al. (2019)
• Alternative activation of macrophages and pulmonary fibrosis are modulated by scavenger receptor, macrophage receptor with collagenous structure — S. Murthy, J.L. Larson-Casey, et al. (2015)
• Mitochondrial Cu,Zn-superoxide dismutase mediates pulmonary fibrosis by augmenting H2O2 generation — C. He, S. Murthy, et al. (2011)
• Macrophages utilize the mitochondrial calcium uniporter for profibrotic polarization — L. Gu, J.L. Larson-Casey, et al. (2017)
• Transfection of a manganese-containing superoxide dismutase gene into hamster tracheal epithelial cells ameliorates asbestos-mediated cytotoxicity — B.T. Mossman, P. Surinrut, et al. (1996)
• Extracellular superoxide dismutase in pulmonary fibrosis — F. Gao, V.L. Kinnula, et al. (2008)

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