Alteration of fibroblast phenotype by asbestos-induced autoantibodies

Our plain-English summary of Alteration of fibroblast phenotype by asbestos-induced autoantibodies, by J.C. Pfau, S. Li, S. Holland, et al (Journal of Immunotoxicology, 2011).

The study

• Authors: J.C. Pfau, S. Li, S. Holland, J.J. Sentissi
• Journal: Journal of Immunotoxicology
• Published: 2011;8(2):159-69
• Cited by: 18 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Pulmonary fibrosis is a relentlessly progressive disease for which the etiology can be idiopathic or associated with environmental or occupational exposures. There is not a clear explanation for the chronic and progressive nature of the disease, leaving treatment and prevention options limited. However, there is increasing evidence of an autoimmune component, since fibrotic diseases are often accompanied by production of autoantibodies. Because exposure to silicates such as silica and asbestos can lead to both autoantibodies and pulmonary/pleural fibrosis, these exposures provide an excellent tool for examining the relationship between these outcomes. This study explored the possibility that autoantibodies induced by asbestos exposure in mice would affect fibroblast phenotype. L929 fibroblasts and primary lung fibroblasts were treated with serum IgG from asbestos- or saline-treated mice, and tested for binding using cell-based ELISA, and for phenotypic changes using immunofluorescence, laser scanning cytometry and Sirius Red collagen assay. Autoantibodies in the serum of C57Bl/6 mice exposed to asbestos (but not sera from untreated mice) bound to mouse fibroblasts. The autoantibodies induced differentiation to a myofibroblast phenotype, as demonstrated by increased expression of smooth muscle α-actin (SMA), which was lost when the serum was cleared of IgG. Cells treated with purified IgG of exposed mice produced excess collagen. Using ELISA, we tested serum antibody binding to DNA topoisomerase (Topo) I, vimentin, TGFβ-R, and PDGF-Rα. Antibodies to DNA Topo I and to PDGF-Rα were detected, both of which have been shown by others to be able to affect fibroblast phenotype. The anti-fibroblast antibodies (AFA) also induced STAT-1 activation, implicating the PDGF-R pathway as part of the response to AFA binding. These data support the hypothesis that asbestos induces AFA that modify fibroblast phenotype, and suggest a mechanism whereby autoantibodies may mediate some of the fibrotic manifestations of asbestos exposure.

In plain English

This was a laboratory study in mice. Female C57Bl/6 mice received two intratracheal instillations, one week apart at the start of 6–7 month experiments, of either saline alone or 60 µg per dose of Korean tremolite or Libby amphibole (6-Mix) fibers. Their serum was then collected and applied to L929 mouse fibroblasts and to primary mouse skin and lung fibroblasts. Serum antibodies from asbestos-instilled mice bound fibroblasts, while serum from saline-instilled mice bound minimally; in a live-cell ELISA the optical density was 2.05 (SEM 0.03) for tremolite serum versus 0.72 (SEM 0.07) for saline serum. Clearing IgG from the serum removed binding. Asbestos-mouse serum increased smooth muscle alpha-actin expression (lost after IgG clearance), and purified IgG increased Type I collagen production. Serum TGFbeta was not increased. Antibodies to DNA topoisomerase I and PDGF-Ralpha were detected, but not to vimentin or TGFbeta-RII; STAT-1, but not SMAD2/3, translocated to the nucleus. The authors concluded that asbestos exposure in mice induces autoantibodies that activate fibroblasts toward a myofibroblast-like phenotype.

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: Controlled animal/in vitro experiment: serum from asbestos- or saline-instilled mice applied to cultured mouse fibroblasts
• Who was studied: Female 8-week-old C57Bl/6 mice (serum donors), and cultured L929 mouse fibroblasts plus primary skin and lung fibroblasts from untreated C57Bl/6 mice; work done at Idaho State University and University of Montana
• Exposure: Intratracheal instillation of saline alone (controls) or of Korean tremolite or Libby amphibole (6-Mix), two doses given one week apart, each asbestos dose being 60 µg of fibers; in some in vitro assays tremolite asbestos was added to fibroblasts at 40 µg/cm2
• Main results:
  • In a live-cell ELISA with mouse lung fibroblasts, binding by serum antibodies from asbestos-instilled mice was nearly three times that of saline mice (tremolite serum OD 2.05, SEM 0.03; saline serum OD 0.72, SEM 0.07; secondary antibody only OD 0.5)
  • Clearing IgG from asbestos-mouse serum with Protein G reduced fibroblast binding in the cell-based ELISA to background levels
  • In primary lung fibroblasts, SMA fluorescence was significantly increased by serum from tremolite-exposed mice compared with untreated cells (N = 3, P less than 0.01); IgG-cleared serum abrogated the increase
  • Purified IgG from tremolite-instilled mice, with or without asbestos, significantly raised collagen production by L929 cells above untreated cells, whereas tremolite asbestos alone did not (N = 4 per group, P less than 0.05)
  • No increase in total or active serum TGFbeta in asbestos-treated mice; all samples had less than 1 ng/ml total TGFbeta and none was detectable in purified IgG
  • Anti-DNA topoisomerase I (Scl-70) antibodies were significantly higher in asbestos-instilled mouse sera than saline (N = 5 mice, P less than 0.05)
  • Antibodies to PDGF-Ralpha showed a significantly higher mean OD in asbestos-treated mice, with about 25% exceeding two standard deviations above the saline-group mean (N = 24 mice, tremolite and 6-Mix combined); no significant difference between 6-Mix and tremolite groups
  • No serum reactivity to TGFbeta-RII or vimentin was found when asbestos- and saline-treated mouse sera were compared
  • Serum from asbestos-treated mice induced STAT-1 nuclear translocation in L929 cells (N = 3 wells per treatment, P less than 0.05); cleared serum did not, and SMAD2/3 did not translocate
• The authors' conclusion: The authors concluded that asbestos exposure in mice induces autoantibodies that bind and activate normal fibroblasts to a myofibroblast-like phenotype, suggesting a possible role of autoimmunity in the progression of asbestos-induced fibrosis
• Limitations the authors state:
  • The authors did not test for local TGFbeta production in the lung
  • The authors state the presence of these anti-fibroblast antibodies in vivo and their isotype in the lung still need to be shown
  • The target of anti-Topo 1 binding on fibroblasts remained unclear, and the binding did not saturate even at high antibody concentrations
  • Not all exposed mice had anti-PDGF-R antibodies, so other anti-fibroblast antibodies are likely involved
  • The authors note the findings do not indicate that all pulmonary fibrosis has an autoimmune component

Mines named here

Asbestos mines this study is about. Each mine's page says who ran it, when it worked, and what it produced.

• Libby vermiculite mine, Montana

All asbestos mines

Topics

Medical terms in this study, explained in our Lexicon: Fibroblast, Pulmonary Fibrosis, Etiology, Idiopathic, Occupational Exposure, Silicate, Fibrosis, Asbestos Exposure.

Related studies

• Asbestos-associated mesothelial cell autoantibodies promote collagen deposition in vitro — K.M. Serve, B. Black, et al. (2013)
• Cytotoxicity and multinucleate giant cell formation in Chinese hamster lung fibroblast caused by crocidolite and chrysotile — Y.C. Hong, S.S. Choi (1997)
• Early-passage rat lung fibroblasts do not migrate in vitro to transforming growth factor-beta — A.R. Osornio-Vargas, V.G. Kalter, et al. (1993)
• Libby amphibole-induced mesothelial cell autoantibodies promote collagen deposition in mice — J. Gilmer, K. Serve, et al. (2016)
• Immunoregulation of lung fibroblast growth: alteration in asbestos-induced pulmonary fibrosis — I. Lemaire, C. Dubois, et al. (1986)
• Fibre-induced lipid peroxidation leads to DNA adduct formation in Salmonella typhimurium TA104 and rat lung fibroblasts — P.J. Howden, S.P. Faux (1996)

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