Cellular and molecular mechanisms of asbestosis

Our plain-English summary of Cellular and molecular mechanisms of asbestosis, by B.T. Mossman, R. Gilbert, J. Doherty, et al (Chest, 1986).

The study

• Authors: B.T. Mossman, R. Gilbert, J. Doherty, M.A. Shatos, J. Marsh, K. Cutroneo
• Journal: Chest
• Published: 1986;89(3 Suppl):160S-161S
• Cited by: 11 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Summary of the article

The authors asked whether asbestosis involves more replication of lung fibroblasts, a greater ability of individual fibroblasts to produce collagen, or both. They used in vitro and in vivo approaches. In vitro, a normal rat lung fibroblast cell line (RL-82, from Fischer 344 rats) was exposed to UICC crocidolite asbestos at 1, 2.5 and 5 µg/cm2. Collagen synthesis was measured with 3H-proline and bacterial collagenase, cell replication with 3H-thymidine autoradiography, and procollagen type I mRNA by quick-blot analysis. Asbestos increased total cell layer-associated collagen at 48 and 72 hours. For example, at 72 hours it was 37.69 cpm/ng DNA at 5.0 µg/cm2 versus 23.66 in controls. Fibroblast replication did not increase, and procollagen type I mRNA levels did not differ from controls. In vivo, male Fischer 344 rats (3-5 per group) inhaled crocidolite for 30 days (5 hr/day, 5 days/week). Their lungs showed fibrotic changes starting at the alveolar duct. Labeling indices rose in alveolar epithelial cells (4.13% vs 0.8%) and interstitial fibroblasts (3.07% vs 1.13%) but were comparable in bronchiolar epithelial cells. The authors concluded that at least two mechanisms result in asbestosis: increased procollagen synthesis by individual fibroblasts, which does not reflect higher steady-state procollagen type I mRNA levels, and enhanced replication of interstitial fibroblasts after inhalation.

PubMed has no abstract for this study, and the article doesn't print one. We wrote this summary from the full article with the help of AI. It is not the authors' wording.

In plain English

This short conference report described laboratory experiments on mechanisms of asbestosis, a scarring of lung tissue. First, the researchers exposed a rat lung fibroblast cell line to crocidolite asbestos in culture dishes. Fibroblasts are the cells that make collagen, the main scar protein. At 48 hours, exposed cells had more collagen than unexposed cells at all three doses (25.59, 24.75 and 24.05 versus 18.38, measured per nanogram of DNA). At 72 hours, only the highest dose was higher (37.69 versus 23.66). The exposed cells did not multiply more, and the amount of type I procollagen genetic message did not differ. Second, rats breathed crocidolite for 30 days. Their lungs showed fibrotic changes. The researchers used a marker of DNA synthesis (tritiated thymidine). It labeled more alveolar epithelial cells (4.13% versus 0.8% in controls) and more interstitial cells identified as fibroblasts (3.07% versus 1.13%). The labeling of bronchiolar epithelial cells was comparable between the groups. The authors concluded that their work suggests at least two mechanisms. Individual fibroblasts make more collagen, and interstitial fibroblasts have an enhanced replicative potential in the lung after rats inhale 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: Laboratory study combining cell culture (in vitro) experiments and an animal inhalation experiment; short conference report
• Who was studied: A normal lung fibroblast cell line (RL-82) from Fischer 344 rats (4 cultures per group), and 6-8-week-old male Fischer 344 rats (3-5 per group)
• Exposure: Crocidolite asbestos (UICC reference sample). Cell cultures received 1, 2.5 or 5 micrograms per square centimetre of dish. Rats inhaled it for 30 days, 5 hours a day, 5 days a week, using a modified Timbrell generator.
• Main results:
  • In cultured rat lung fibroblasts, asbestos exposure increased total cell layer-associated collagen at 48 and 72 hours
  • Collagen in unexposed cells (counts per nanogram of DNA) was 8.52 at 24 hours, 18.38 at 48 hours and 23.66 at 72 hours
  • At 48 hours, collagen in exposed cells was 25.59 (1.0 dose), 24.75 (2.5 dose) and 24.05 (5.0 dose). At 72 hours it was 21.92 (1.0 dose) and 19.55 (2.5 dose), both below the unexposed value, and 37.69 at the highest dose (5.0 micrograms per square centimetre).
  • In culture, fibroblast replication, measured by the number of cells incorporating tritiated thymidine, did not increase with asbestos exposure
  • Amounts of procollagen type I mRNA did not differ between control and asbestos-exposed cells
  • Lungs of rats that inhaled asbestos showed fibrotic changes (increased collagen-staining material), unlike controls
  • The thymidine labeling index of alveolar epithelial cells was 0.8% in control rats and 4.13% in asbestos-exposed rats (p less than 0.001)
  • The thymidine labeling index of interstitial (SOD-negative, fibroblast) cells was 1.13% in control rats and 3.07% in asbestos-exposed rats (p less than 0.001)
  • The thymidine labeling index of bronchiolar epithelial cells was comparable in control rats (0.78%) and asbestos-exposed rats (1.26%)
• The authors' conclusion: The authors concluded that their work suggests at least two mechanisms result in asbestosis. Asbestos stimulates individual fibroblasts to make more procollagen, without an increase in procollagen type I mRNA levels. Interstitial fibroblasts also have an enhanced replicative potential in the lung after inhalation of asbestos by rats.

Topics

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

Medical terms in this study, explained in our Lexicon: Fibroblast, Collagen, UICC, Crocidolite, Interstitial.

Related studies

• Possible cellular and molecular mechanisms for asbestos carcinogenicity — C. Walker, J. Everitt, et al. (1992)
• Cellular and molecular mechanisms of asbestos-induced fibrosis — R. Robledo, B. Mossman (1999)
• Cellular and molecular mechanisms of asbestos carcinogenicity: implications for biopersistence — J.C. Barrett (1994)
• Molecular and Cellular Mechanism of Action of Chrysotile Asbestos in MRC5 Cell Line — A. Kussainova, O. Bulgakova, et al. (2023)
• Inhibition of lung injury, inflammation, and interstitial pulmonary fibrosis by polyethylene glycol-conjugated catalase in a rapid inhalation model of asbestosis — B.T. Mossman, J.P. Marsh, et al. (1990)
• Differential in vitro cellular response induced by exposure to synthetic vitreous fibers (SVFs) and asbestos crocidolite fibers — G. Cardinali, D. Kovacs, et al. (2006)

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