p53, Cip1, and Gadd153 expression following treatment of A549 cells with natural and man-made vitreous fibers

Our plain-English summary of p53, Cip1, and Gadd153 expression following treatment of A549 cells with natural and man-made vitreous fibers, by N.F. Johnson, R.J. Jaramillo (Environmental Health Perspectives, 1997).

The study

• Authors: N.F. Johnson, R.J. Jaramillo
• Journal: Environmental Health Perspectives
• Published: 1997;105 Suppl 5(Suppl 5):1143-5
• Cited by: 20 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

DNA damage induced by chemicals and ionizing radiation is associated with the expression of negative regulators of the cell cycle. The arrest of cells in G1 and G2 phases of the cell cycle provides time for DNA repair. Asbestos fibers are carcinogenic when inhaled by both humans and animals; however, the mechanism by which the fibers exert their effect is unknown. This work was undertaken to determine whether the expression of DNA damage-inducible genes differs between crocidolite, a fiber positive for lung tumors, and JM 100 glass microfiber, which is negative for lung tumors when inhaled by rats. Temporal and dose-related expressions of p53, Cip1, and Gadd153 proteins were determined in cultured A549 cells treated with either Union Internationale Contre le Cancer crocidolite or JM 100 for 20 hr and cultured in fresh media. Immunolabeled cells were analyzed by flow cytometry, and the increased number of protein-expressing cells was determined by subtracting the expression in unexposed cells from exposed cells. Crocidolite induced the expression of all three proteins with a maximum expression after approximately 18 hr in fresh media. At a similar time point, JM 100 did not markedly induce the three proteins. Crocidolite also induced a dose-dependent increase in the number of cells in the G2 phase of the cell cycle. These results show that asbestos behaves like ionizing radiation and genotoxic chemicals by inducing proteins associated with DNA damage and cell-cycle arrest. The clear difference in response between crocidolite and JM 100 may help elucidate the mechanism of action of toxic and nontoxic fibers.

In plain English

This was a laboratory study of cultured cells. The authors exposed A549 cells to UICC crocidolite asbestos or JM 100 glass microfiber. The authors noted that JM 100, a man-made fiber, had not produced an elevated risk of lung or pleural tumors in rat inhalation studies. The protein tests used 20-hour exposures at doses up to 3.0 micrograms per square centimetre. A separate colony-forming test used concentrations up to 50 micrograms per millilitre. Flow cytometry then measured the cells' cell-cycle stage and three proteins linked to DNA damage and cell-cycle arrest: p53, Cip1 and Gadd153. Both fibers were more toxic at higher doses, and JM 100 was the more toxic. In crocidolite-treated cells, the share of cells in the G2 phase rose with dose, as did all three proteins. This did not happen with JM 100. The authors concluded that asbestos behaves like genotoxic chemicals and ionizing radiation in inducing these proteins. They said the mechanism is unknown but may be DNA damage. Measured percentages appeared only in graphs, and some findings over time were described as data not 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: Laboratory (in vitro) cell culture experiment comparing two fibers, using flow cytometry to measure protein expression and cell-cycle stage
• Who was studied: Cultured A549 cells obtained from the American Type Culture Collection; no humans or animals were studied
• Exposure: UICC crocidolite asbestos compared with JM 100 glass microfiber. For the time-course, cells were exposed to 2.0 µg/cm2 (printed 'pg/cm2' in the scanned text) for 20 hours, in a single experiment. For dose-response, triplicate cultures were exposed to 0.0, 0.1, 0.5, 1.0, 2.0 and 3.0 µg/cm2 and harvested 18 hours after exposure ended. The separate colony-forming efficiency tests used concentrations up to 50 µg/ml.
• Main results:
  • Both crocidolite and JM 100 showed dose-dependent toxicity to A549 cells, and the toxicity was more marked for JM 100 than for crocidolite
  • In crocidolite-exposed cells, the number of cells in the G2 phase of the cell cycle 18 hours after exposure increased with dose. The persistent G2 elevation over time was reported as data not shown.
  • Expression of p53, Cip1 and Gadd153 increased with dose in crocidolite-exposed cells, but not in cells treated with JM 100
  • In crocidolite-exposed cells, expression of the three proteins reached its maximum after approximately 18 hours in fresh medium
  • Over time, the protein response of JM 100-exposed cells was much less marked than that of crocidolite-exposed cells (data not shown)
• The authors' conclusion: The authors concluded that asbestos behaves like genotoxic chemicals and ionizing radiation by inducing proteins associated with DNA damage and cell-cycle arrest. They suggested that the difference between crocidolite and JM 100 may help explain how toxic and nontoxic fibers act.
• Limitations the authors state:
  • The authors stated that the mechanism by which crocidolite induces these proteins is unknown, though it may be a result of DNA damage

Topics

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

Medical terms in this study, explained in our Lexicon: A549 Cells, Vitreous, Carcinogenic, Crocidolite.

Related studies

• DNA damage-inducible genes as biomarkers for exposures to environmental agents — N.F. Johnson, T.R. Carpenter, et al. (1997)
• Repression of GADD153/CHOP by NF-kappaB: a possible cellular defense against endoplasmic reticulum stress-induced cell death — S. Nozaki, G.W. Sledge, et al. (2001)
• Cytotoxic and oxidative effects induced by man-made vitreous fibers (MMVFs) in a human mesothelial cell line — D. Cavallo, A. Campopiano, et al. (2004)
• Biopersistences of man-made vitreous fibers and crocidolite fibers in rat lungs following short-term exposures — R.P. Musselman, W.C. Miiller, et al. (1994)
• Analysis of cell cycle disruptions in cultures of rat pleural mesothelial cells exposed to asbestos fibers — V. Levresse, A. Renier, et al. (1997)
• Effects of asbestos and man-made vitreous fibers on cell division in cultured human mesothelial cells in comparison to rodent cells — K. Pelin, P. Kivipensas, et al. (1995)

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