Libby amphibole-induced mesothelial cell autoantibodies promote collagen deposition in mice

Our plain-English summary of Libby amphibole-induced mesothelial cell autoantibodies promote collagen deposition in mice, by J. Gilmer, K. Serve, C. Davis, et al (American Journal of Physiology. Lung Cellular and Molecular Physiology, 2016).

The study

• Authors: J. Gilmer, K. Serve, C. Davis, M. Anthony, R. Hanson, T. Harding, J.C. Pfau
• Journal: American Journal of Physiology. Lung Cellular and Molecular Physiology
• Published: 2016;310(11):L1071-7
• Cited by: 10 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Libby amphibole (LA) causes a unique progressive lamellar pleural fibrosis (LPF) that is associated with pulmonary function decline. Pleural fibrosis among the LA-exposed population of Libby, MT, has been associated with the production of anti-mesothelial cell autoantibodies (MCAA), which induce collagen production from cultured human mesothelial cells. We hypothesized that the progressive nature of LPF could be at least partially attributed to an autoimmune process and sought to demonstrate that LA-induced MCAA trigger collagen deposition in vivo. C57BL/6 mice were exposed to LA for 7 mo, and serum was tested for MCAA by cell-based ELISA on primary mouse mesothelial cells. When treated in vitro with serum from mice exposed to LA, mesothelial cells upregulated collagen matrix production. This effect was lost when the serum was cleared of IgG using protein G beads, implicating IgG autoantibodies. Using the peritoneal cavity as a surrogate for the pleural cavity, groups of naïve (non-asbestos-exposed) mice were injected intraperitoneally with 1) control serum, 2) one dose of serum from LA-exposed mice (LA serum), 3) two doses of LA serum, or 4) two doses of LA serum cleared of IgG. After 1 mo, analysis of collagen in peritoneal walls using two-photon confocal microscopy (SHG analysis) and a hydroxyproline assay demonstrated significant increases in collagen by LA serum but not control or cleared serum. These data support the hypothesis that MCAA in LA-exposed mice induce fibrotic responses in vivo, demonstrating that an autoimmune component may be contributing to the progressive pleural fibrosis seen in LA-exposed patients.

Copyright © 2016 the American Physiological Society.

In plain English

In this laboratory study, the authors placed Libby amphibole, a mixture of asbestos-type amphibole minerals that contaminated vermiculite from a mine near Libby, Montana, into the windpipes of C57BL/6 mice. They collected the mice's serum 7 months later. Autoantibodies that bind mesothelial cells (the cells lining body cavities) were found in 7 of 11 exposed mice (63.6%) and in none of the saline-exposed mice. In cell culture, serum from exposed mice made mouse mesothelial cells produce more collagen, a scar-tissue protein. This effect was lost when IgG antibodies were removed from the serum. The authors then injected serum into the abdominal cavity of mice never given fibers, using the abdomen as a stand-in for the chest, with four mice per group. Two doses of serum from exposed mice led to significantly more collagen in the peritoneal wall, the lining of the abdominal cavity, than serum from saline-exposed mice or a single dose. Antibody-cleared serum did not. The authors concluded that an autoimmune process may contribute to the progressive pleural fibrosis in exposed people. They said a causal link in humans remains to be shown.

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: Animal experiment in mice, combined with laboratory (in vitro) experiments on cultured mouse mesothelial cells
• Who was studied: Wild-type C57BL/6 mice raised at Idaho State University. Serum from 11 Libby amphibole-exposed mice was tested individually. Four naive (never fiber-exposed) mice were used per treatment group for the abdominal serum injections. Primary mesothelial cells were cultured from mouse peritoneal walls.
• Exposure: Libby amphibole, described by the article as a combination of asbestiform amphibole minerals contaminating Libby vermiculite (sample from the U.S. Geological Survey). It was given by injection into the trachea as 30 microliters of a 1 mg/ml fiber suspension; control mice received saline. Serum was collected after 7 months. Naive mice were then given that serum in the abdominal cavity (diluted to 150 micrograms of IgG in 300 microliters) as one or two doses 2 weeks apart. The serum was either from saline-exposed mice, from LA-exposed mice, or LA serum cleared of IgG.
• Main results:
  • Tested individually, 7 of 11 Libby amphibole-exposed mice (63.6%) had mesothelial cell autoantibodies, compared with none of the saline-exposed mice. The P value was printed as 0.03 by Fisher's exact test; the comparison symbol was lost in the text.
  • Naive mice were given serum in the abdominal cavity. In those given two doses of serum from LA-exposed mice, collagen density in the peritoneal wall (measured by multiphoton microscopy) was significantly higher than in mice given one dose of LA serum or two doses of serum from saline-exposed mice. This increase was lost when the LA serum was cleared of IgG.
  • A single injection of LA serum did not significantly increase collagen compared with a single injection of saline serum.
  • A hydroxyproline (QuickZyme) assay showed significantly more deposited collagen in the peritoneal walls of mice given two injections of LA serum than in mice given saline serum.
  • One week after injection, soluble collagen in peritoneal wash fluid was significantly higher in mice given LA serum than in mice given saline serum.
  • In cell culture, mouse mesothelial cells treated with LA serum produced significantly more collagen than cells treated with saline serum. The effect was lost when the LA serum was cleared of IgG.
  • One month after two doses, the serum groups did not differ significantly in peritoneal immune cell types. They also did not differ in how often antinuclear antibody tests were positive, which was 25% in both the saline serum and LA serum groups.
• The authors' conclusion: The authors concluded that the antibodies, not other serum components, caused the collagen responses. They stated that the data support the idea that mesothelial cell autoantibodies in LA-exposed mice induce fibrotic responses in the body. In their view, an autoimmune component may be contributing to the progressive pleural fibrosis seen in LA-exposed patients.
• Limitations the authors state:
  • The peritoneal (abdominal) cavity was used as a stand-in for the pleural (chest) cavity, because injecting into and dissecting the mouse pleural space is difficult.
  • Further studies are needed to fully characterize the mechanism and to show a causal link between these autoantibodies and pleural fibrosis in humans.
  • The test cut-off (three standard deviations above control) may miss low levels of autoantibodies in some people and mice.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Asbestosis.

Medical terms in this study, explained in our Lexicon: Libby amphiboles, Mesothelial Cells, Collagen, Deposition, Fibrosis, Peritoneal Cavity, Pleural Cavity.

Related studies

• Libby amphibole-induced mesothelial cell autoantibodies bind to surface plasminogen and alter collagen matrix remodeling — R. Hanson, C. Evilia, et al. (2016)
• Asbestos-associated mesothelial cell autoantibodies promote collagen deposition in vitro — K.M. Serve, B. Black, et al. (2013)
• Autoantibodies from mice exposed to Libby amphibole asbestos bind SSA/Ro52-enriched apoptotic blebs of murine macrophages — D.J. Blake, S.A. Wetzel, et al. (2008)
• Mesothelial cell autoantibodies upregulate transcription factors associated with fibrosis — J. Gilmer, T. Harding, et al. (2017)
• Synthetic secoisolariciresinol diglucoside (LGM2605) inhibits Libby amphibole fiber-induced acute inflammation in mice — M. Christofidou-Solomidou, R.A. Pietrofesa, et al. (2019)
• Comparative health effects in mice of Libby amphibole asbestos and a fibrous amphibole from Arizona — J.C. Pfau, B. Buck, et al. (2017)

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