Amosite, chrysotile and crocidolite asbestos are mutagenic in Chinese hamster lung cells

Our plain-English summary of Amosite, chrysotile and crocidolite asbestos are mutagenic in Chinese hamster lung cells, by S.L. Huang (Mutation Research, 1979).

The study

• Author: S.L. Huang
• Journal: Mutation Research
• Published: 1979;68(3):265-74
• Cited by: 49 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Chinese hamster lung cells cultured in the presence of amosite, chrysotile or crocidolite displayed inhibition of cell growth. Phagocytosis of asbestos by cells was observed. Amosite and chrysotile appeared to be twice as toxic as crocidolite based on an equal weight/volume basis. Induction of 6-thioguanine resistance was studied. After treatment at 10 microgram/cm2 for 24 h, and with a 48-h expression time, numerically the cells did not change significantly from 6-thioguanine-sensitive to 6-thioguanine-resistant for each pair of control and experimental mutation frequencies. When all data points were considered as a whole, use of Student's t-test on paired samples showed that all 3 types of asbestos were mutagenic in Chinese hamster lung cells. It was reported that benzo[a]anthracene was an organic contaminant of abestos. Used as a positive control compound, 7,12-dimethylbenz[a]anthracene was metabolized by rat-liver microsomes and was found mutagenic in Chinese hamster lung cells. Microsome activation did not increase the mutagenic potential of asbestos. These findings point to the weak mutagenic potential of asbestos. Chinese hamster lung cells phagocytize particles and are ideal materials to study mutagenesis of environmental agents that exist in a particulate form.

In plain English

This laboratory study exposed cultured Chinese hamster lung cells to amosite, chrysotile or crocidolite asbestos to test whether the fibers cause mutations (changes in genes). Mutations were measured as cells becoming resistant to the drug 6-thioguanine. The cells engulfed asbestos fibers within hours, and asbestos slowed cell growth. By weight, amosite and chrysotile appeared about twice as toxic to the cells as crocidolite. The author ran 10 experiments for each fiber type at 10 micrograms per square centimetre for 24 hours. In no single experiment was the rise in mutations over its control statistically significant. When the experiments were analysed together with a paired Student's t-test, all three types showed significantly higher average mutation frequencies than controls: amosite 5.10 versus 2.94, chrysotile 6.31 versus 2.24, and crocidolite 5.42 versus 3.61 mutants per million surviving cells. No dose-response relationship was seen. Adding rat-liver enzymes did not increase the effect of asbestos, although it did activate a comparison chemical. The author concluded that the three asbestos types are weak mutagens.

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 experiment on cultured animal cells (in vitro mutagenicity test, 6-thioguanine resistance), with and without rat-liver microsome activation
• Who was studied: Chinese hamster lung cells (strain CCL 39) obtained from the American Tissue Culture Collection and grown in culture. Liver preparations from 8 to 10-week-old Sprague-Dawley rats were used for metabolic activation.
• Exposure: Amosite, chrysotile and crocidolite asbestos supplied by Ohio State University. The main mutation tests used 10 micrograms per square centimetre for 24 hours, followed by a 48-hour expression time. 7,12-dimethylbenz[a]anthracene, with rat-liver microsomes, was used as a positive control.
• Main results:
  • The cells rapidly took up (phagocytized) asbestos fibers.
  • Crocidolite completely inhibited cell growth at a concentration of 30 micrograms per square centimetre.
  • On a weight/volume basis, amosite and chrysotile appeared to be twice as toxic to the cells as crocidolite.
  • Treated cells had average relative cloning efficiencies of 55.3% (amosite), 53% (chrysotile) and 74.8% (crocidolite).
  • Judged one pair at a time (binomial approximation), no mutation frequency in asbestos-treated cells was statistically significantly higher than in its control.
  • For amosite and chrysotile, the mutation frequency in treated cells was higher than in control cells at every data point.
  • When all data points were analysed together with Student's t-test, all three asbestos types were found to be mutagenic.
  • Amosite: average mutation frequency 5.10 plus or minus 1.69 per million surviving cells in treated cells, versus 2.94 plus or minus 1.18 in controls (mean plus or minus standard error). The difference was significant at the 1% level.
  • Chrysotile: average mutation frequency 6.31 plus or minus 2.17 per million surviving cells in treated cells, versus 2.24 plus or minus 0.68 in controls. The difference was significant at the 1% level.
  • Crocidolite: average mutation frequency 5.42 plus or minus 2.16 per million surviving cells in treated cells, versus 3.61 plus or minus 1.79 in controls. The difference was significant at the 5% level.
  • Several asbestos doses were tested, and no dose-mutation relationship was observed. Longer expression or treatment times did not increase mutation frequency.
  • Adding rat-liver microsomes did not change the results for asbestos.
  • With microsomes, the positive control 7,12-dimethylbenz[a]anthracene raised mutation frequency in proportion to dose: from 2.51 to 5.70, 9.39 and 13.99 per 100,000 surviving cells at 25, 50 and 100 micrograms per ml. Without microsomes it had no mutagenic effect.
• The authors' conclusion: The author concluded that amosite, chrysotile and crocidolite are weak mutagens and that microsome activation does not enhance their mutagenic activity. The author also concluded that Chinese hamster lung cells, because they engulf particles, are ideal for mutation tests of agents that exist as particles.
• Limitations the authors state:
  • Longer treatment or expression times did not increase mutation frequency (and no dose-mutation relationship was seen), and the author made no attempt to explain this.
  • Because the mutagenic effect was weak, the author stated that larger numbers of cells are needed for such tests.
  • Background mutation frequencies differed between batches (ampules) of frozen cell cultures.

Topics

Medical terms in this study, explained in our Lexicon: Amosite, Chrysotile, Crocidolite, Phagocytosis.

Related studies

• Cytotoxicity and multinucleate giant cell formation in Chinese hamster lung fibroblast caused by crocidolite and chrysotile — Y.C. Hong, S.S. Choi (1997)
• Effects of asbestos fibers on cell division, cell survival, and formation of thioguanine-resistant mutants in Chinese hamster ovary cells — K. Kenne, S. Ljungquist, et al. (1986)
• Genetic effects of crocidolite asbestos in Chinese hamster lung cells — S.L. Huang, D. Saggioro, et al. (1978)
• Effect of mineral dusts on metabolic cooperation between Chinese hamster V79 cells in vitro — M. Chamberlain (1983)
• Genotoxicity and cytotoxicity of multi-wall carbon nanotubes in cultured Chinese hamster lung cells in comparison with chrysotile A fibers — M. Asakura, T. Sasaki, et al. (2010)
• A comparison of the cytogenetic response to asbestos and glass fibre in Chinese hamster and human cell lines. Demonstration of growth inhibition in primary human fibroblasts — A.M. Sincock, J.D. Delhanty, et al. (1982)

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