Mineral fibers induce apoptosis in Syrian hamster embryo fibroblasts

Our plain-English summary of Mineral fibers induce apoptosis in Syrian hamster embryo fibroblasts, by E. Dopp, B. Nebe, C. Hahnel, et al (Pathobiology, 1995).

The study

• Authors: E. Dopp, B. Nebe, C. Hahnel, T. Papp, B. Alonso, M. Simkó, D. Schiffmann
• Journal: Pathobiology
• Published: 1995;63(4):213-21
• Cited by: 12 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

It is known that asbestos and other mineral fibers induce lung cancer and mesothelioma. However, the primary mechanisms of fiber-induced carcinogenesis still remain to be elucidated. Previous studies, including our own, have shown that asbestos causes specific mitotic disturbances, micronucleus formation and typical changes in chromatin structure resembling those of apoptosis. This effect has been considered as programmed cell death removing damaged or pre-cancerous cells. We investigated the induction of apoptosis by asbestos (amosite, crocidolite, chrysotile) and ceramic fibers. The typical ladder pattern of DNA fragments was identified by means of gel electrophoresis, the intracellular calcium concentration was measured and flow cytometry analyses were carried out to determine the percentage of apoptotic cells. The different fibers showed different potencies for the induction of apoptosis in Syrian hamster embryo (SHE) cells. Depending on the type of fiber applied 3-33% of cells underwent apoptosis. Chrysotile proved to be the most potent inducer of apoptosis compared to the other fibers. In addition, an increase intracellular calcium level was observed in apoptotic SHE cells. Chrysotile induced apoptosis after a considerably longer exposure time (66-72 h) than cisplatin (24 h). In view of these findings we hypothesize that chrysotile induces apoptosis resulting from long-term changes in intracellular regulation pathways.

In plain English

This was a laboratory study. The authors exposed Syrian hamster embryo (SHE) fibroblast cells in culture to three types of asbestos (amosite, crocidolite and Rhodesian chrysotile) and to ceramic fibers, and looked for apoptosis, a form of programmed cell death. Gypsum was the negative control and the drug cisplatin the positive control. Measured by flow cytometry after 66-72 hours, apoptotic cells in chrysotile-treated cultures rose with dose, from 5.0% at 1.0 to 33.4% at 10.0 micrograms per square centimetre. In amosite-treated cultures the figures were 3.0-3.8%, and with gypsum 1.1-1.5%. Apoptosis after amosite and crocidolite was comparable to that after ceramic fibers, and only chrysotile acted in a dose-dependent way. All fiber-treated cells had significantly raised calcium inside the cell. With chrysotile it was 8 times the untreated level. Chrysotile also produced the DNA breakdown pattern typical of apoptosis, but after 66-72 hours, compared with 24 hours for cisplatin. The authors hypothesized that chrysotile acts through long-term changes in the cell's internal regulation. They said the mechanism remains to be identified.

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: Fibroblast cells from Syrian hamster embryos (cultures from 13-day-old embryos), grown in the laboratory at the University of Rostock, Germany. No humans or live animals were exposed.
• Exposure: UICC standard amosite, crocidolite and Rhodesian chrysotile asbestos, and ceramic fibers, applied to cells at concentrations of about 0.5 to 10.0 micrograms per square centimetre for 18 to 72 hours. Gypsum was the negative control and cisplatin the positive control. The asbestos fibers averaged about 1.7-2.2 micrometres long, with about 5% longer than 5 micrometres. The ceramic fibers were longer and thicker (average 12.03 micrometres long).
• Main results:
  • By flow cytometry after 66-72 hours, apoptotic cells in chrysotile-treated cultures were 5.0%, 7.2% and 33.4% at 1.0, 5.0 and 10.0 micrograms per square centimetre.
  • In the same flow cytometry table, amosite-treated cultures had 3.8%, 3.0% and 3.4% apoptotic cells at those concentrations, and gypsum (negative control) cultures had 1.1%, 1.5% and 1.3%.
  • Apoptosis after amosite and crocidolite was comparable to that after ceramic fibers (given as 3-8%).
  • Only chrysotile produced apoptosis that increased with fiber concentration.
  • By microscopy of fixed, stained cells, up to 16% of cells were apoptotic after 72 hours at 5.0 micrograms per square centimetre chrysotile. With ceramic fibers the figure was up to 3%.
  • Intracellular calcium in chrysotile-treated cells was 8 times higher than in untreated cells. The difference between treated and untreated cells was significant for all fiber types tested (p less than 0.001).
  • Chrysotile at 10 micrograms per square centimetre for 66-72 hours, and cisplatin for 24 hours, both produced the DNA fragmentation pattern typical of apoptosis. DNA from untreated cells did not show this pattern.
  • At exposures longer than 72 hours and concentrations above 10.0 micrograms per square centimetre, more cells died by necrosis rather than apoptosis.
• The authors' conclusion: The authors hypothesized that chrysotile causes apoptosis indirectly, through long-term changes in the cell's internal regulation pathways that last several cell cycles before apoptosis occurs.
• Limitations the authors state:
  • Microscopy of fixed, stained cells gave lower apoptosis figures than flow cytometry, because cells in later apoptotic stages detached and were lost.
  • Live-cell microscopy could only be done after 24 hours of exposure, because of technical difficulties at longer times.
  • The mechanism by which chrysotile induces apoptosis was not identified.

Topics

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

Medical terms in this study, explained in our Lexicon: Mineral Fiber, Apoptosis, Fibroblast, Lung Cancer, Mesothelioma, Carcinogenesis, Amosite, Crocidolite.

Related studies

• Kerosene soot genotoxicity: enhanced effect upon co-exposure with chrysotile asbestos in Syrian hamster embryo fibroblasts — M. Lohani, E. Dopp, et al. (2000)
• Mitotic disturbances and micronucleus induction in Syrian hamster embryo fibroblast cells caused by asbestos fibers — E. Dopp, J. Saedler, et al. (1995)
• In vitro cytotoxicity and transforming potential of industrial carbon dust (fibers and particles) in syrian hamster embryo (SHE) cells — C. Darne, F. Terzetti, et al. (2010)
• Morphological transformation of Syrian hamster embryo cells induced by mineral fibres and the alleged enhancement of benzo[a]pyrene — S.O. Mikalsen, E. Rivedal, et al. (1988)
• Detection of aneuploidy-inducing carcinogens in the Syrian hamster embryo (SHE) cell transformation assay — D.P. Gibson, M.J. Aardema, et al. (1995)
• Man-made mineral fibers induce apoptosis of human peripheral blood mononuclear cells similarly to chrysotile B — Z. Ma, T. Otsuki, et al. (1999)

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