Gene expression profiles reveal increased mClca3 (Gob5) expression and mucin production in a murine model of asbestos-induced fibrogenesis

Our plain-English summary of Gene expression profiles reveal increased mClca3 (Gob5) expression and mucin production in a murine model of asbestos-induced fibrogenesis, by T. Sabo-Attwood, M. Ramos-Nino, J. Bond, et al (The American Journal of Pathology, 2005).

The study

• Authors: T. Sabo-Attwood, M. Ramos-Nino, J. Bond, K.J. Butnor, N. Heintz, A.D. Gruber, C. Steele, D.J. Taatjes, P. Vacek, B.T. Mossman
• Journal: The American Journal of Pathology
• Published: 2005;167(5):1243-56
• Cited by: 62 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

To elucidate genes important in development or repair of asbestos-induced lung diseases, gene expression was examined in mice after inhalation of chrysotile asbestos for 3, 9, and 40 days. We identified changes in the expression of genes linked to proliferation (cyclin B2, CDC20, and CDC28 protein kinase regulatory subunit 2), inflammation (CCL9, CCL6, complement component 1, chitinase3-like 3, TNF superfamily member 10, and IL-1B), and matrix remodeling (MMP12, MMP3, integrin alphaX, and cathepsins K, Z, B, and S). The most highly induced gene at all time points was mclca3 (gob5), a putative calcium-activated chloride channel involved in the regulation of mucus production and/or secretion. Using histochemistry, we demonstrated accumulation of mucus and increased mClca3 protein in the bronchiolar epithelium of asbestos-exposed mice at all time points but peaking at 9 days. Cytokine levels (interleukin-1beta, interleukin-4, interleukin-6) in bronchoalveolar lavage fluid also increased at 9 days, suggesting Th2-mediated immunity may play a role in asbestos-induced mucus production. In contrast, levels of cathepsin K, a potent elastase, increased between 3 and 40 days at both the mRNA and protein levels, localizing primarily in CD45-positive leukocytes and interstitial cells. Identification of genes involved in lung injury and remodeling after asbestos exposure could aid in defining mechanisms of airborne particulate-induced disease and in developing therapeutic strategies.

In plain English

Male C57BL/6 mice in this laboratory experiment breathed chrysotile asbestos at 5.0 mg/m3, 6 hours a day, 5 days a week, for 3, 9 or 40 days. Control mice breathed air. One group breathed titanium dioxide, used as a nonpathogenic control particle, for 3 days. The authors measured about 12,000 genes in lung tissue. Of these, 312 changed twofold or more at one or more time points. The most strongly increased gene at every time point was mclca3 (gob5), linked to mucus production. It reached 79.2, 76.3 and 73.8 times control levels at 3, 9 and 40 days. Titanium dioxide raised it about fourfold. Cell proliferation in the airway lining peaked at 3 days and inflammation at 9 days. Scarring around small airways (peribronchiolar fibrosis) appeared by 40 days. Airway mucus peaked at 9 days and subsided by 40 days. IL-1beta, IL-4, IL-5 and IL-6 were raised in lung washing fluid at 9 days. The authors concluded that their correlative data implicate a Th2-type immune response as a possible inducer of mclca3 and mucus production by asbestos.

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 inhalation experiment with gene-expression (microarray) analysis of lung tissue, plus microscopic examination of the lungs
• Who was studied: Male C57BL/6 mice aged 8 to 12 weeks, kept at the University of Vermont inhalation facility. There were 3 mice per group per time point for the microarray studies and 5 to 6 per group per time point for histopathology and immunohistochemistry.
• Exposure: Inhaled chrysotile asbestos (a National Institute of Environmental Health Sciences reference sample) at 5.0 mg/m3, 6 hours/day, 5 days/week, for 3, 9 and 40 days. Controls breathed ambient air. A further group inhaled fine titanium dioxide (5.0 mg/m3) for 3 days as a nonpathogenic control particle.
• Main results:
  • In asbestos-exposed mice, 312 of about 12,000 genes were significantly increased or decreased twofold or more at one or more time points.
  • mclca3 (gob5) was the most highly induced gene at all time points in asbestos-exposed mice: 79.2-fold at 3 days, 76.3-fold at 9 days and 73.8-fold at 40 days compared with controls.
  • In titanium dioxide-exposed mice, mclca3 rose fourfold at 3 days, which the authors called minimal compared with chrysotile.
  • In asbestos-exposed mice, proliferating (Ki-67-positive) bronchiolar lining cells peaked at 3 days and returned to sham levels by 40 days.
  • In asbestos-exposed mice, infiltration of immune cells was maximal at 9 days.
  • By 40 days of chrysotile exposure, collagen staining showed peribronchiolar fibrosis.
  • In asbestos-exposed mice, mucus in the distal bronchiolar lining was increased by 3 days, peaked at 9 days and subsided by 40 days. mClca3 protein followed a parallel pattern.
  • At 9 days, several cytokines (IL-1beta, IL-4, IL-5 and IL-6) were significantly increased in bronchoalveolar lavage fluid of asbestos-exposed mice compared with air-exposed mice. The scan dropped the Greek letter; the article's published abstract identifies the form as interleukin-1beta. IL-10 and IL-13 were not significantly induced.
  • Cathepsin K increased at 3, 9 and 40 days in asbestos-exposed mice. It was found mainly in CD45-positive cells (leukocytes) and interstitial cells, with minimal presence in the bronchiolar lining.
• The authors' conclusion: The authors concluded that, although correlative, their data implicate Th2-mediated immunity as a possible inducer of mclca3 expression and mucus metaplasia by asbestos in the lung.
• Limitations the authors state:
  • The authors describe the link between cytokines and mucus/mclca3 as correlative.
  • The authors state that the relevance of asbestos-induced mucus production to the development of fibrosis is unclear.
  • The size of the cathepsin K increase differed between the microarray and the QRT-PCR validation, although the trends were the same.

Topics

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

Medical terms in this study, explained in our Lexicon: Chrysotile, Inflammation, Epithelium, Cytokine, Bronchoalveolar Lavage (BAL), Interstitial, Asbestos Exposure.

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• Patterns of inflammation, cell proliferation, and related gene expression in lung after inhalation of chrysotile asbestos — T.R. Quinlan, K.A. BéruBé, et al. (1995)
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