Asbestos induces tissue factor in Beas-2B human lung bronchial epithelial cells in vitro

Our plain-English summary of Asbestos induces tissue factor in Beas-2B human lung bronchial epithelial cells in vitro, by A. Iakhiaev, U. Pendurthi, S. Idell (Lung, 2004).

The study

• Authors: A. Iakhiaev, U. Pendurthi, S. Idell
• Journal: Lung
• Published: 2004;182(4):251-64
• Cited by: 3 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Asbestos has been implicated in the pathogenesis of interstitial lung diseases including asbestosis. Tissue factor (TF) initiates blood coagulation in vivo contributing to inflammation and tissue remodeling via extravascular fibrin deposition and signaling for profibrogenic mediators. We hypothesized that asbestos could induce TF expression by lung epithelial cells. We found that TF mRNA and TF-dependent procoagulant activity were induced in asbestos-treated Beas-2B human airway epithelial cells, which we used as a model system. The effect was increased by crocidolite and chrysotile versus control particulates, including titanium dioxide (TiO2) and Wollastonite (W). Transcription factors that bind the TF gene promoter, including NF-kappaB, AP1 and Sp1, were induced by asbestos while TF mRNA was unstable. TF mRNA was inhibited by mithramycin in asbestos-treated as well as control cells suggesting that Sp1 contributes to TF maintenance in Beas-2B cells. Sp1 knockdown with specific siRNA decreased TF antigen, which is consistent with Sp1-mediated control of TF in Beas-2B cells. The results demonstrate that asbestos induces TF expression in lung epithelial cells in vitro, representing a newly recognized potential mechanism by which asbestos may modulate epithelial cell responses germane to lung remodeling. The mechanism involves alterations in steady-state TF mRNA that do not involve posttranscriptional regulation, implicating control of TF gene expression at the transcriptional level through Sp1 or other transcription factors.

In plain English

This was a laboratory study of cells, not people. The authors exposed Beas-2B human bronchial epithelial cells, a cell line from the airway lining, to chrysotile or crocidolite asbestos and to two comparison dusts, titanium dioxide and wollastonite, at 10 micrograms per square centimetre. They measured tissue factor, a protein that starts blood clotting. At this dose the particulates did not visibly harm the cells. After 18 hours, tissue factor messenger RNA in asbestos-treated cells was 2 to 3 times that of untreated cells, and higher than with titanium dioxide or wollastonite. Tissue factor-linked clotting activity rose significantly with both asbestos types (p less than 0.05), while titanium dioxide and wollastonite raised it less. Tissue factor protein rose in a similar way. Crocidolite activated the gene-control proteins AP-1, NF-kappaB and Sp1, and a drug that blocks Sp1 stopped tissue factor RNA production. Two tests of direct gene activation did not show an increase after asbestos. The authors suggested technical problems, or changes too small to detect, as possible reasons. The authors concluded that asbestos-induced tissue factor in lung lining cells could contribute to the development of asbestosis.

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: In vitro laboratory experiment on a human lung cell line (cell culture study)
• Who was studied: Beas-2B human bronchial (airway) epithelial cells obtained from ATCC and grown in culture; no human subjects
• Exposure: Chrysotile asbestos (fiber length 1 to 5 micrometres) and crocidolite asbestos (2 to 10 micrometres) from NIEHS, compared with control particulates wollastonite and titanium dioxide. Most experiments used 10 micrograms per square centimetre. Particulates were baked to remove endotoxin.
• Main results:
  • At the concentration used, neither asbestos type nor the control particulates showed signs of harming the cells (data not shown).
  • Tissue factor mRNA in asbestos-treated cells was 2 to 3 times higher than in untreated control cells.
  • Tissue factor mRNA was higher in asbestos-treated cells than in cells treated with titanium dioxide or wollastonite.
  • The rise in tissue factor mRNA with asbestos depended on time and on concentration, and was detectable as early as 4 hours.
  • Tissue factor mRNA broke down quickly after transcription was blocked, and asbestos appeared to speed this breakdown. The authors took this to mean the rise was not due to the RNA becoming more stable.
  • Tissue factor-dependent clotting (factor X activating) activity was increased by chrysotile and crocidolite (p less than 0.05). Titanium dioxide and wollastonite increased it to a lesser extent.
  • In the discussion, the authors noted that titanium dioxide also induced tissue factor-related factor X activating activity, indicating that non-asbestos particulates may also influence it.
  • Tissue factor protein (antigen) was similarly induced by asbestos treatment.
  • Crocidolite activated the transcription factors AP-1, NF-kappaB and Sp1 more strongly and for longer than titanium dioxide. Chrysotile had a similar effect to crocidolite (data not shown).
  • Mithramycin, an Sp1 inhibitor, blocked tissue factor mRNA synthesis.
  • The NF-kappaB inhibitor TPCK did not affect tissue factor mRNA in control cells, but reduced it by about 50% in asbestos-treated cells.
  • Nuclear run-on and promoter assays showed transcription of the tissue factor gene in Beas-2B cells, but did not show the expected increase after asbestos treatment.
  • Reducing Sp1 with siRNA was associated with a decrease in tissue factor protein. This was tested in cells not treated with asbestos.
• The authors' conclusion: The authors concluded that asbestos-induced tissue factor in lung epithelial cells could contribute to the pathogenesis of asbestosis, and that the process may involve control of the gene through Sp1.
• Limitations the authors state:
  • The nuclear run-on assays were inconclusive because of technical problems, likely an inability to remove asbestos from the cell nuclei.
  • The tissue factor promoter assays failed to show asbestos-induced transcription, possibly because the changes were too small to detect or because transfection was difficult in the presence of asbestos fibers.
  • Because of technical problems, the authors could not directly show that the asbestos-induced rise in tissue factor depended on Sp1 in the siRNA experiments.
  • The findings come from a cell line in culture. The authors framed any relevance to the lung as conditional on primary airway or alveolar cells responding in a similar way in the body.

Topics

Medical terms in this study, explained in our Lexicon: Interstitial Lung Disease, Inflammation, Deposition, Crocidolite, Chrysotile, Wollastonite.

Related studies

• Asbestos induces tissue factor in Beas-2B cells via PI3 kinase-PKC-mediated signaling — A. Iakhiaev, S. Idell (2004)
• Multi-walled carbon nanotubes directly induce epithelial-mesenchymal transition in human bronchial epithelial cells via the TGF-β-mediated Akt/GSK-3β/SNAIL-1 signalling pathway — M. Polimeni, G.R. Gulino, et al. (2016)
• Uptake and cytotoxic effects of multi-walled carbon nanotubes in human bronchial epithelial cells — S. Hirano, Y. Fujitani, et al. (2010)
• Cellular ingestion, toxic effects, and lesions observed in human bronchial epithelial tissue and cells cultured with asbestos and glass fibers — A. Haugen, P.W. Schafer, et al. (1982)
• Asbestos-induced activation of cell signaling pathways in human bronchial epithelial cells — X. Wang, J.M. Samet, et al. (2006)
• Aberrations of chromosome 19 in asbestos-associated lung cancer and in asbestos-induced micronuclei of bronchial epithelial cells in vitro — S.T. Ruosaari, P.E. Nymark, et al. (2008)

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