Asbestos fibre length-dependent detachment injury to alveolar epithelial cells in vitro: role of a fibronectin-binding receptor

Our plain-English summary of Asbestos fibre length-dependent detachment injury to alveolar epithelial cells in vitro: role of a fibronectin-binding receptor, by K. Donaldson, B.G. Miller, E. Sara, et al (International Journal of Experimental Pathology, 1993).

The study

• Authors: K. Donaldson, B.G. Miller, E. Sara, J. Slight, R.C. Brown
• Journal: International Journal of Experimental Pathology
• Published: 1993;74(3):243-50
• Cited by: 24 articles, as counted by NIH iCite
• Read it: PubMed · Free full text

Abstract

A short and a long fibre sample of amosite asbestos were tested for their effects on cells of the human Type 2 alveolar epithelial cell-line A549 in vitro. The long amosite sample was found to cause a rapid detachment of the epithelial cells live from their substratum. At the highest dose, on average 28% of the cells present were detached in this way. Studies on the mechanism of the detachment injury showed that it did not involve oxidants since it was not ameliorated by scavengers of active oxygen species. Neither was the effect reduced by treatment of the fibres with the iron chelator Desferal. Treatments reported to increase the interaction between fibres and cells, serum and poly-L-lysine, did not influence the detachment injury, nor did lung lining fluid. Conversely, the fibronectin tripeptide RGD alone could cause detachment which suggested that a fibronectin-binding integrin was involved. This receptor could be reduced in activity by long fibre exposure, leading to detachment. The detaching effect of fibre could be mimicked by the protein kinase C activator PMA, and so the second messenger system of the cell could also be involved. This type of injury could be important in the pathology associated with exposure to long fibres.

In plain English

This laboratory study tested two samples of amosite asbestos on a line of human lung cells grown in dishes. The cells were the A549 line, described as Type 2 alveolar epithelial cells. One sample was mostly long fibres and the other mostly short fibres, of closely similar diameter. Cells were exposed for 4 hours to 10 to 100 micrograms of fibre per millilitre. The long-fibre sample caused significantly more cells to come loose, still alive, from the dish surface than the short-fibre sample. At the highest dose, on average 28% of cells detached. Neither sample caused significant cell bursting (lysis). Detachment by long fibres was not significantly changed by the iron-binding agent Desferal, poly-L-lysine, extra serum, rat lung lining fluid, or the antioxidants tested. A fragment of the protein fibronectin, called RGD, caused detachment by itself, and growing cells on fibronectin reduced detachment. The chemical PMA also caused detachment. The authors concluded that this type of injury could be important in disease linked to long fibres. They noted that their lung fluid sample was diluted.

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 cultured human cells
• Who was studied: Cells of the human Type 2 alveolar epithelial cell line A549, grown in culture plates. Each experiment was repeated at least three times.
• Exposure: Short and long fibre amosite asbestos of similar diameter. In the short sample, less than 10% of fibres were longer than 10 micrometres; in the long sample, about 70% were. Above 20 micrometres, the short sample had virtually none and the long sample had about 40%. Fibres were tested at 10 to 100 micrograms per ml for 4 hours.
• Main results:
  • Long amosite caused significantly more detachment of cells than short amosite (F = 9.02, P less than 0.05).
  • At the highest dose of long amosite, on average 28% of the cells present detached.
  • Neither fibre type nor dose had an effect on lysis (cell bursting): fibre type F = 1.04, P greater than 0.25; dose F = 1.62, P greater than 0.1.
  • Pretreating long amosite with the iron chelator Desferal did not significantly affect detachment (F = 0.002, P greater than 0.25).
  • Poly-L-lysine treatment of fibres was not a significant factor in detachment (F = 1.46, P greater than 0.25).
  • Raising the serum concentration up to 25% did not significantly change detachment by long amosite (F = 0.60, P greater than 0.25).
  • The antioxidant glutathione (GSH) reduced detachment in 6 of 9 experiments, but the effect just failed to reach statistical significance.
  • Pretreating fibres in rat lung lining fluid had no significant effect on detachment (F = 0.11, P greater than 0.25).
  • The fibronectin tripeptide RGD alone, without fibres, significantly caused cells to detach (F = 54.93, P less than 0.05).
  • Mean detachment was 5214 (s.e.m. 746) c.p.m. in RGD-treated cells, compared with 1751 (s.e.m. 343) in untreated cells.
  • Growing cells on fibronectin significantly reduced both spontaneous and long-amosite-caused detachment (F = 199.04, P less than 0.01).
  • The protein kinase C activator PMA caused detachment, with a significant dose effect (F = 5.22, P less than 0.05).
• The authors' conclusion: The authors concluded that this detachment injury could be important in the disease associated with exposure to long fibres.
• Limitations the authors state:
  • The lung lining fluid was diluted up to 6 times during collection, which could have influenced the findings.
  • The authors said the reason for the shape of the dose-response curve was unclear and more work was needed.
  • Cell size was not measured after fibre treatment.
  • The effect of long fibres in the living body may be less extreme than in the cell experiments.

Topics

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

Medical terms in this study, explained in our Lexicon: Amosite, Lung Lining Fluid, Pathology.

Related studies

• The ability of inflammatory bronchoalveolar leucocyte populations elicited with microbes or mineral dust to injure alveolar epithelial cells and degrade extracellular matrix in vitro — K. Donaldson, J. Slight, et al. (1988)
• Cigarette smoke augments asbestos-induced alveolar epithelial cell injury: role of free radicals — D.W. Kamp, M.J. Greenberger, et al. (1998)
• Fibroblast growth factor-10 prevents asbestos-induced alveolar epithelial cell apoptosis by a mitogen-activated protein kinase-dependent mechanism — D. Upadhyay, V. Panduri, et al. (2005)
• Asbestos-stimulated tumour necrosis factor release from alveolar macrophages depends on fibre length and opsonization — K. Donaldson, X.Y. Li, et al. (1992)
• In vitro reactivity of alveolar macrophages and red blood cells with asbestos fibres treated with oxalic acid, sulfur dioxide and benzo-3,4-pyrene — M.C. Jaurand, L. Magne, et al. (1981)
• Mineral fibre toxicity: expression of retinoblastoma (Rb) and phospho-retinoblastoma (pRb) protein in alveolar epithelial and mesothelial cell lines exposed to fluoro-edenite fibres — G. Musumeci, V. Cardile, et al. (2011)

Browse more research in International Journal of Experimental Pathology, or return to medical research.