Differential cytotoxic, growth-inhibiting and lipid-peroxidative activities of four different asbestos fibres in vitro

Our plain-English summary of Differential cytotoxic, growth-inhibiting and lipid-peroxidative activities of four different asbestos fibres in vitro, by M. Wydler, P. Maier, G. Zbinden (Toxicology in Vitro, 1988).

The study

• Authors: M. Wydler, P. Maier, G. Zbinden
• Journal: Toxicology in Vitro
• Published: 1988;2(4):297-302
• Cited by: 9 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

An attempt was made to characterize the carcinogenic hazard of asbestos fibres by using a set of in vitro screening tests. The fibres tested were the serpentine chrysotile and the three amphiboles anthophyllite, crocidolite and amosite. Their cytotoxic and cytostatic activities in rat primary fibroblast-like cells were assessed along with their effects on enzymic lipid peroxidation by liver homogenates. After 24 hr exposure of fibroblast-like cells to 2.1 μg fibres/cm(2), chrysotile induced the highest cytotoxicity, followed by crocidolite, anthophyllite and amosite. Similarly, after 48 hr exposure, chrysotile had the most growth inhibiting effect, followed by crocidolite, anthophyllite and amosite. Enzymic lipid peroxidation, as measured by pentane or malondialdehyde production, was determined at ambient (21% O(2)) or tissue (4% O(2)) oxygen tension in incubation mixtures containing rat-liver homogenate and asbestos fibres. At 4% O(2), only the two iron-containing fibres, crocidolite and amosite, stimulated lipid peroxidation. The results suggest that the cytotoxic activity is influenced by the surface charge, structure and dimensions of the fibres, and that cell-growth inhibition is associated with surface charge, structure and the Mg(2+) content of the fibres. Effects on enzymic lipid peroxidation appear to be associated with the structure and iron content of the tested fibres. When these results are considered along with epidemiological data, it seems that the carcinogenic potency of asbestos fibres is characterized by an ability to induce high levels of enzymic lipid peroxidation along with moderate cytotoxic and growth inhibiting activities.

In plain English

This laboratory study tested whether simple test-tube experiments could help rank how likely different asbestos fibres are to cause cancer. The authors used standard reference samples of chrysotile, crocidolite, amosite and anthophyllite. They exposed fibroblast-like cells taken from rats to the fibres. Separately, they mixed the fibres with rat liver tissue to measure lipid peroxidation, a chemical process that produces reactive molecules. Chrysotile killed cells at the lowest concentration, followed by crocidolite, anthophyllite and amosite. Chrysotile was about ten times more effective at slowing cell division than the other three fibres. At an oxygen level similar to body tissue (4%), the authors reported that only the iron-containing fibres, crocidolite and amosite, drove lipid peroxidation, with crocidolite about four times as active as amosite. Considering these results alongside data on people, the authors suggested that cancer-causing potency seems to be marked by strong lipid peroxidation with moderate cell-killing and growth-slowing effects. On that basis, they predicted a ranking of crocidolite, then amosite, anthophyllite and chrysotile. The experiments did not measure cancer, no people were studied, and the fibres were not given to live animals.

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 study (cell culture tests and liver-homogenate lipid peroxidation assays)
• Who was studied: Primary fibroblast-like cells isolated from male Sprague-Dawley rats, and homogenate made from freshly dissected rat liver; Institute of Toxicology, Schwerzenbach, Switzerland
• Exposure: UICC reference standard samples of chrysotile (serpentine) and the amphiboles anthophyllite, crocidolite and amosite. Cells were exposed to concentrations from 0.17 to 4.3 micrograms per square centimetre. Liver homogenate was exposed to 1.8 mg fibres per ml.
• Main results:
  • After 24 hours, chrysotile was the most toxic to the rat cells, followed by crocidolite, anthophyllite and amosite. The concentrations detaching 5% of cells were 0.4, 1.3, 1.4 and 2.7 micrograms per square centimetre respectively.
  • No detached cells were seen 4 hours after exposure to crocidolite. Cell detachment appeared only after 24 hours.
  • Chrysotile was an order of magnitude more effective at reducing cell division than the other three fibres. The concentrations halving the mitotic index were 0.4 micrograms per square centimetre for chrysotile, 3.2 for crocidolite, 2.8 for anthophyllite and 3.2 for amosite.
  • In tests with crocidolite, pentane formation (a lipid peroxidation marker) was highest at 4% oxygen.
  • At 4% oxygen, the authors reported that only the iron-containing fibres, crocidolite and amosite, catalysed lipid peroxidation. Crocidolite showed about fourfold higher activity than amosite.
  • At 4% oxygen, pentane formation was 53.1 (plus or minus 28.9) nmol per g tissue with crocidolite, 11.4 (plus or minus 17.3) with amosite and 2.3 (plus or minus 3.5) with anthophyllite. None was detected with chrysotile.
  • From this pattern of results, the authors predicted that the carcinogenic potential of the fibres would rank crocidolite, then amosite, then anthophyllite, then chrysotile.
• The authors' conclusion: The authors tentatively suggested that, when their results are considered alongside epidemiological data, the carcinogenic potency of asbestos fibres seems to be characterized by high levels of enzymic lipid peroxidation together with moderate cell-killing and growth-inhibiting activity.
• Limitations the authors state:
  • The authors noted that data on the carcinogenicity of asbestos fibres, against which they compared their ranking, are contradictory.

Topics

Medical terms in this study, explained in our Lexicon: Carcinogenic, Serpentine Group, Chrysotile, Amphibole Group, Anthophyllite, Crocidolite, Amosite, Fibroblast.

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