In vitro response of rat pleural mesothelial cells to talc samples in genotoxicity assays (sister chromatid exchanges and DNA repair)

Our plain-English summary of In vitro response of rat pleural mesothelial cells to talc samples in genotoxicity assays (sister chromatid exchanges and DNA repair), by S. Endo-Capron, A. Renier, X. Janson, et al (Toxicology in Vitro, 1993).

The study

• Authors: S. Endo-Capron, A. Renier, X. Janson, L. Kheuang, M.C. Jaurand
• Journal: Toxicology in Vitro
• Published: 1993;7(1):7-14
• Cited by: 13 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The genotoxicity of three samples of talc has been determined using in vitro cell systems previously developed for testing asbestos fibres. The talc samples used consisted of particles of respirable size in order to test the effect of particles likely to be deposited in the lung. Genotoxicity was tested in cultures of rat pleural mesothelial cells (RPMC) using genotoxicity assays for unscheduled DNA synthesis (UDS) and sister chromatid exchanges (SCEs). The effects were compared with those obtained with negative controls (attapulgite and anatase) and positive controls (chrysotile and crocidolite asbestos). In contrast to asbestos, none of the talc samples, nor the negative controls, induced enhancement of UDS or SCEs in treated cultures in comparison with the untreated cultures.

In plain English

This laboratory study used cultured rat pleural mesothelial cells, which line the chest. The authors tested whether three European talc samples damaged genetic material (genotoxicity). The samples, French no. 7841, Italian no. 5726 and Spanish no. 5725, contained 90-95% talc, with chlorite and dolomite. The authors used two tests: unscheduled DNA synthesis, a measure of DNA repair, and sister chromatid exchanges, swaps between chromosome copies. They compared talc with UICC chrysotile and crocidolite asbestos, anatase and attapulgite. Electron microscopy found no asbestos fibres in the talc, and the cells took up talc particles. No talc sample increased DNA repair at 10 to 50 micrograms per square centimetre or sister chromatid exchanges at 2 to 15. Chromosome numbers in talc-treated cells were unchanged. Crocidolite at 10 micrograms per square centimetre and chrysotile at 4 or 10 always significantly increased DNA repair; crocidolite at 4 did so in two of three experiments. Chrysotile and crocidolite increased sister chromatid exchanges in two of four and three of eight experiments, respectively. The authors said the inconsistent crocidolite result lessened the weight of talc's negative result in that test.

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 (cell culture) laboratory experiment using two genotoxicity assays, unscheduled DNA synthesis and sister chromatid exchanges, with negative and positive reference particles
• Who was studied: Rat pleural mesothelial cells (RPMC) obtained by scraping the parietal pleura, grown in culture and used between passages 5 and 15; no human subjects
• Exposure: Three respirable-size European talc samples supplied by Eurotalc (French no. 7841, Italian no. 5726, Spanish no. 5725), containing 90-95% talc with chlorite and dolomite. Doses were 10, 20 and 50 micrograms per square centimetre in the DNA synthesis test and 2 to 15 micrograms per square centimetre in the sister chromatid exchange test. Comparisons were anatase and attapulgite (negative reference particles); UICC Rhodesian chrysotile and crocidolite (positive reference particles); and the chemicals mitomycin C and K2CrO4.
• Main results:
  • Electron microscopy found no asbestos fibres in any of the three talc samples.
  • The asbestos samples contained 20-100 times more particles longer than 4 micrometres than the talc samples.
  • The cells ingested talc particles.
  • None of the talc samples enhanced unscheduled DNA synthesis.
  • Cells treated with crocidolite at 10, or chrysotile at 4 or 10, micrograms per square centimetre always showed a significant increase in unscheduled DNA synthesis compared with untreated cells.
  • Crocidolite at 4 micrograms per square centimetre significantly increased unscheduled DNA synthesis in experiments 1 and 3. The value for experiment 2 (1425 plus or minus 926, against 1327 plus or minus 57 untreated) is not marked as significant in Table 2.
  • Talc at 2 to 15 micrograms per square centimetre did not increase sister chromatid exchange frequency (0 of 3 experiments significant for each talc sample).
  • Sister chromatid exchanges were significantly increased by chrysotile at 1 microgram per square centimetre (15.2 plus or minus 1.6 untreated vs 20.2 plus or minus 3.7 per metaphase, P less than 0.005). They were also significantly increased by crocidolite at 2 (14.9 plus or minus 4.6 vs 16.8 plus or minus 5.0, P less than 0.05). The increase was significant in 2 of 4 chrysotile experiments and 3 of 8 crocidolite experiments.
  • Talc-treated cells showed no difference in the number of chromosomes per metaphase compared with untreated cells.
• The authors' conclusion: The authors concluded that the three talc samples did not increase unscheduled DNA synthesis or sister chromatid exchanges, or produce aneuploidy, in these cells, in contrast to chrysotile and crocidolite. They suggested this might be related to talc's different mechanical or physicochemical properties compared with mineral fibres.
• Limitations the authors state:
  • The sister chromatid exchange results were less convincing because crocidolite did not consistently increase exchanges. The authors said this lessened the significance of talc's negative result in that test.

Topics

Medical terms in this study, explained in our Lexicon: Mesothelial Cells, Talc, Genotoxicity, Palygorskite (Attapulgite), Chrysotile, Crocidolite.

Related studies

• Sister chromatid exchanges in rat pleural mesothelial cells treated with crocidolite, attapulgite, or benzo 3-4 pyrene — S. Achard, M. Perderiset, et al. (1987)
• Sister-chromatid exchange and cell kinetics in CHO-K1 cells, human fibroblasts and lymphoblastoid cells exposed in vitro to asbestos and glass fibre — G. Casey (1983)
• Sister chromatid exchange frequency in inhabitants exposed to asbestos in Turkey — H. Dönmez, Y. Ozkul, et al. (1996)
• Dose-Response Relationships in Expression of Biomarkers of Cell Proliferation in in vitro Assays and Inhalation Experiments — A. Shukla, P. Vacek, et al. (2004)
• Induction of metaphase and anaphase/telophase abnormalities by asbestos fibers in rat pleural mesothelial cells in vitro — M. Yegles, L. Saint-Etienne, et al. (1993)
• Role of fibre characteristics on cytotoxicity and induction of anaphase/telophase aberrations in rat pleural mesothelial cells in vitro: correlations with in vivo animal findings — M. Yegles, X. Janson, et al. (1995)

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