Analysis of cell cycle disruptions in cultures of rat pleural mesothelial cells exposed to asbestos fibers

Our plain-English summary of Analysis of cell cycle disruptions in cultures of rat pleural mesothelial cells exposed to asbestos fibers, by V. Levresse, A. Renier, J. Fleury-Feith, et al (American Journal of Respiratory Cell and Molecular Biology, 1997).

The study

• Authors: V. Levresse, A. Renier, J. Fleury-Feith, F. Levy, S. Moritz, C. Vivo, Y. Pilatte, M.C. Jaurand
• Journal: American Journal of Respiratory Cell and Molecular Biology
• Published: 1997;17(6):660-71
• Cited by: 33 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The control of DNA integrity in mammalian cells is important to maintain the cell homeostasis and prevent neoplastic transformation. Control of cell division and cell death permits repair or elimination of damaged cells. Since asbestos fibers can produce DNA damage, chromosome alterations and apoptosis in several sorts of cells, including mesothelial cells, it was interesting to investigate cell cycle disturbances in rat pleural mesothelial cells (RPMC) treated with asbestos fibers. Cell cycle analyses were performed in RPMC exposed to crocidolite (10 and 20 microg/cm2) and chrysotile (5 and 10 microg/cm2) for different times (4 to 48 h). Both fiber types entailed a G2/M accumulation in agreement with a delay in the mitosis course. Chrysotile fibers produced a G0/G1 accumulation associated with a time-dependent p53 and p21 expression. Crocidolite exposure resulted in a delay in the G1/S transition paralleling a low rate of p53 expression. These results are in agreement with a DNA damaging potential of asbestos fibers since similar results were found following RPMC exposure to gamma rays. In asbestos-treated RPMC, a low rate of apoptosis was found suggesting that RPMC may follow a DNA repair pathway that could contribute to the formation of DNA lesions. In addition, the cell cycle disturbances at the G2/M checkpoint suggest that genetically altered cells have progressed through the cycle and support the already published findings on the ability of asbestos fibers to impair cell division.

In plain English

This laboratory study used normal rat pleural mesothelial cells grown in dishes, not people. For the cell cycle tests, cells were exposed to UICC Rhodesian chrysotile (5 and 10 micrograms per square centimetre) or crocidolite (10 and 20 micrograms per square centimetre) for 4 to 48 hours; other tests used exposures from 1 to 72 hours. The authors also measured apoptosis (programmed cell death), p53 and p21. Chrysotile blocked cells before they copied their DNA. After 48 hours with 10 micrograms per square centimetre of chrysotile, 1.5% of cells were copying DNA, versus 10.5% untreated. Crocidolite delayed this step rather than stopping it. Both fibers caused cells to build up at the G2/M (division) stage, and chrysotile produced cells with two or more nuclei. Chrysotile raised p53 and p21 after 24 and 48 hours, while p53 rose less with crocidolite. Apoptosis stayed low; the highest rate, 4%, came after 72 hours with 10 micrograms per square centimetre of chrysotile. Gamma radiation caused changes similar to chrysotile. The authors concluded that asbestos fibers behaved like known DNA-damaging agents.

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
• Who was studied: Normal rat pleural mesothelial cells (RPMC) taken from rat parietal pleura and grown in culture; only diploid cells up to 25 passages were used
• Exposure: UICC Rhodesian chrysotile and crocidolite. Overall, fiber concentrations were 0.5, 2, 10 and 20 micrograms per square centimetre, for 1, 4, 24, 48 and 72 hours. The cell cycle analyses used chrysotile at 5 and 10 and crocidolite at 10 and 20 micrograms per square centimetre, for 4, 24 and 48 hours. Camptothecin and 24 Gy gamma irradiation were used for comparison.
• Main results:
  • After 48 hours with 10 micrograms per square centimetre of chrysotile, 1.5% of cells were in the replicative (DNA-copying) phase, versus 10.5% of untreated cells at 48 hours (Table 1)
  • With longer labeling, no DNA-copying cells were seen after 48 hours of chrysotile, which the authors read as a block in the G1 phase
  • Crocidolite-treated cells kept progressing; the authors interpreted this as a delay rather than an arrest at the G1 to S transition
  • With 10 micrograms per square centimetre of crocidolite, G2/M accumulation was 1.3 times untreated at 24 hours and 3.2 times at 48 hours; the difference was significant only at 48 hours
  • Chrysotile-treated cultures contained bi- or multinucleated cells
  • Comparing similar numbers of fibers (about 110 million chrysotile versus 106 million crocidolite fibers per square centimetre), chrysotile caused more cell cycle disturbance, especially at the G1 to S transition
  • Gamma irradiation produced cell cycle changes similar to chrysotile
  • p53 increased after 24 and 48 hours of chrysotile; the increase was lower with crocidolite
  • p21 appeared after 24 and 48 hours of chrysotile; after crocidolite it was detected only at 48 hours
  • Maximum loss of cell viability was 60% with chrysotile; it did not exceed 40% with crocidolite
  • Apoptosis: the highest rate was 4%, after 72 hours with 10 micrograms per square centimetre of chrysotile; it was below 1% with crocidolite; the spontaneous rate in untreated cultures was 0.05% at 24 hours and 0.1% at 48 hours
  • No change in bcl2 protein was found after chrysotile treatment
• The authors' conclusion: The authors concluded that asbestos fibers behaved like known DNA-damaging agents (camptothecin, gamma irradiation), causing cell cycle disruptions with a low rate of apoptosis. They suggested that cells may preferentially follow a DNA repair pathway that could contribute to fixing DNA lesions, and that asbestos might impair some cell cycle checkpoints.
• Limitations the authors state:
  • A high antibody concentration was used to detect p53, which the authors say could partly explain the high background and the extra bands on the blots
  • The apoptosis levels were lower than in other studies; the authors attribute this to different fiber samples (NIEHS versus UICC, with different fiber lengths) and different culture conditions

Topics

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

Medical terms in this study, explained in our Lexicon: Mesothelial Cells, Apoptosis, Crocidolite, Chrysotile, DNA lesions.

Related studies

• Effect of simian virus large T antigen expression on cell cycle control and apoptosis in rat pleural mesothelial cells exposed to DNA damaging agents — V. Levresse, S. Moritz, et al. (1998)
• 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)
• Phagocytosis of chrysotile fibers by pleural mesothelial cells in culture — M.C. Jaurand, H. Kaplan, et al. (1979)
• Synthesis of poly(ADP-ribose) in asbestos treated rat pleural mesothelial cells in culture — H.Y. Dong, A. Buard, et al. (1995)
• Increased expression of epidermal growth factor receptor in rat pleural mesothelial cells correlates with carcinogenicity of mineral fibres — S.P. Faux, C.E. Houghton, et al. (2000)
• The interactions between asbestos fibers and metaphase chromosomes of rat pleural mesothelial cells in culture. A scanning and transmission electron microscopic study — N.S. Wang, M.C. Jaurand, et al. (1987)

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