Role of oxygen derivatives in the cytotoxicity and DNA damage produced by asbestos on rat pleural mesothelial cells in vitro

Our plain-English summary of Role of oxygen derivatives in the cytotoxicity and DNA damage produced by asbestos on rat pleural mesothelial cells in vitro, by H. Dong, A. Buard, A. Renier, et al (Carcinogenesis, 1994).

The study

• Authors: H. Dong, A. Buard, A. Renier, F. Lévy, L. Saint-Etienne, M.C. Jaurand
• Journal: Carcinogenesis
• Published: 1994;15(6):1251-5
• Cited by: 49 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The role of reactive oxygen metabolites in the toxic effects of asbestos on pleural mesothelial cells is not well defined. We exposed rat pleural mesothelial cells (RPMC) to chrysotile and crocidolite fibers (0-40 micrograms/cm2) in the presence or absence of catalase and superoxide dismutase (SOD). Cell injury was measured using the colorimetric 3-4 (5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and DNA damage was evaluated in terms of unscheduled DNA synthesis (UDS). Catalase (100 U/ml) and SOD (250 U/ml) protected RPMC against asbestos-induced cytotoxicity and DNA damage. However, the inactivated enzymes and bovine serum albumin also showed some protection, suggesting that the effect of antioxidant enzymes may be partly related to their protein nature. These results suggest that oxygen derivatives are partly involved in the toxic effects of asbestos on cultures of RPMC. The presence of extracellular proteins may also decrease asbestos-produced toxicity by reducing the degree of RPMC-fiber interaction.

In plain English

This laboratory study tested whether reactive oxygen compounds help explain how asbestos harms rat pleural mesothelial cells grown in culture. The authors exposed the cells to UICC Rhodesian chrysotile or crocidolite fibers, with or without two antioxidant enzymes, catalase and superoxide dismutase (SOD). For comparison, some cells received boiled (inactivated) enzymes or bovine serum albumin (BSA), a plain protein. After 24 hours, MTT test results (a dye test of cell metabolism, not a direct count of living cells) fell as fiber concentration rose. Active catalase and SOD reduced this effect, while inactivated enzymes and BSA protected less. DNA repair synthesis, used as a sign of DNA damage, rose with fiber concentration for both fibers. At 10 micrograms per square centimetre it was 29 ± 5% above control for chrysotile and 24 ± 4% for crocidolite. Active enzymes reduced this rise, but inactivated enzymes and BSA also gave some protection in certain conditions. The authors concluded that oxygen derivatives are partly involved in asbestos toxicity to these cells, and that added proteins may reduce toxicity by lessening cell-fiber contact.

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 cells (cytotoxicity measured by MTT assay; DNA damage measured as unscheduled DNA synthesis)
• Who was studied: Rat pleural mesothelial cells (RPMC) established and cultured in the authors' laboratory (INSERM Unit 139, Créteil, France), used between passages 6 and 19
• Exposure: UICC crocidolite and UICC Rhodesian chrysotile fibers: 2 to 40 micrograms per square centimetre for 24 hours in the cytotoxicity tests and 2, 4 and 10 micrograms per square centimetre in the DNA repair tests. Exposures were given with or without catalase (100 units/ml) or SOD (250 units/ml), inactivated enzymes, or BSA. Hydrogen peroxide was used as a control exposure.
• Main results:
  • MTT reduction, a dye test of cell metabolism, by asbestos-treated RPMC fell as fiber concentration increased, in all experiments
  • At 10 micrograms per square centimetre of chrysotile, about 90% of RPMC were viable by trypan blue exclusion compared with about 50% by the MTT assay. The authors attributed the difference to mitochondrial metabolism being affected before the cell membrane is damaged.
  • Catalase (100 units/ml) and SOD (250 units/ml) reduced asbestos cytotoxicity; inactivated enzymes and BSA had a lesser protective effect than the active enzymes
  • Hydrogen peroxide alone was strongly toxic to RPMC; 0.1 mM produced complete loss of cell viability, and catalase completely inhibited this toxicity
  • Asbestos did not increase the proportion of S-phase (dividing) cells in blocked cultures: 2.0 ± 0.5% (crocidolite) and 1.8 ± 0.5% (chrysotile) labeled cells, versus control values of 2.3 ± 0.4% and 2.1 ± 0.4%
  • Unscheduled DNA synthesis increased with fiber concentration for chrysotile (r = 0.98, P < 0.05) and for crocidolite (r = 0.99, P < 0.05)
  • Enhancement of UDS with fibers alone (percent of control, mean ± SE): chrysotile 9 ± 2, 15 ± 2 and 29 ± 5 at 2, 4 and 10 micrograms per square centimetre; crocidolite 9 ± 2, 17 ± 2 and 24 ± 4
  • Both active and inactivated SOD reduced the chrysotile-induced increase in DNA repair. Active catalase prevented the crocidolite-induced increase. Inactivated catalase suppressed it at 2 and 4 micrograms per square centimetre. Inactivated SOD did not abolish it at any concentration.
  • BSA inhibited the chrysotile-induced increase in DNA repair only at the lowest asbestos concentration (2 micrograms per square centimetre), not at higher concentrations
  • DNA repair produced by hydrogen peroxide was suppressed by active catalase but not by inactivated catalase
• The authors' conclusion: The authors concluded that oxygen derivatives are partly involved in the toxic effects of asbestos on cultured RPMC. They also concluded that extracellular proteins may reduce asbestos toxicity by reducing cell-fiber interaction.
• Limitations the authors state:
  • The authors noted that the MTT assay is a rather uncommon method for studying fiber cytotoxicity. They chose it because a colony assay is difficult with their cells.
  • The authors stated that it is difficult to determine where the harmful oxygen derivatives come from
  • Uptake of catalase and SOD by the cells was not studied
  • The authors cautioned that comparing chrysotile and crocidolite on a per-weight basis may be misleading. The two fibers differ greatly in the number of fibers per unit weight.

Topics

Medical terms in this study, explained in our Lexicon: Mesothelial Cells, Chrysotile, Crocidolite, Superoxide.

Related studies

• 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)
• Synthesis of poly(ADP-ribose) in asbestos treated rat pleural mesothelial cells in culture — H.Y. Dong, A. Buard, et al. (1995)
• Cytotoxicity of oxidants and asbestos fibers in cultured human mesothelial cells — V.L. Kinnula, K. Aalto, et al. (1994)
• Detection of 8-oxo-2'-deoxyguanosine, a marker of oxidative DNA damage, in culture medium from human mesothelial cells exposed to crocidolite asbestos — Q. Chen, J. Marsh, et al. (1996)
• Exposure to nano-size titanium dioxide causes oxidative damages in human mesothelial cells: The crystal form rather than size of particle contributes to cytotoxicity — K. Hattori, K. Nakadate, et al. (2017)
• 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)

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