Cooperative stimulation by sulfite and crocidolite asbestos fibres of enzyme catalyzed production of reactive oxygen species

Our plain-English summary of Cooperative stimulation by sulfite and crocidolite asbestos fibres of enzyme catalyzed production of reactive oxygen species, by E.F. Elstner, W. Schütz, G. Vogl (Archives of Toxicology, 1988).

The study

• Authors: E.F. Elstner, W. Schütz, G. Vogl
• Journal: Archives of Toxicology
• Published: 1988;62(6):424-7
• Cited by: 11 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Methylthioketobutyric acid has been used as an indicator for the production of reactive oxygen species during incubation with xanthine oxidase or NADH diaphorase in the presence of an autooxidizable quinone. The production of OH-radical-type oxidants is enhanced in the presence of crocidolite but not by the asbestos types chrysotile or amosite. This activity of crocidolite in the diaphorase system is further stimulated by bisulfite. Crocidolite-dependent ethylene formation from methylthioketo-butyric acid is inhibited by both superoxide dismutase and catalase. In the presence of both crocidolite and bisulfite, however, the inhibition by superoxide dismutase is preserved, but the inhibition by catalase is lost. Since in some respect the NADH-diaphorase quinone system may reflect the situation in the activated macrophage, crocidolite activation may represent a biochemical model system describing potential asbestos toxicity.

In plain English

This was a test-tube laboratory experiment, not a study of people or animals. The authors used two cell-free enzyme systems that produce reactive oxygen species: xanthine oxidase, and NADH diaphorase with a quinone. They measured these reactive species by the ethylene gas released from an indicator chemical. In the xanthine oxidase system, adding crocidolite asbestos raised ethylene from 3420 to 7640 pmol. The same amounts of amosite or chrysotile had only an insignificant influence. Bisulfite, a form of the air pollutant sulfur dioxide, increased ethylene further only when crocidolite was present. It also largely removed the blocking effect of the enzyme catalase: at 100 units, catalase gave 85% inhibition without sulfite and 0% with it. In the diaphorase system, crocidolite alone had no influence. With bisulfite, though, ethylene release was at least double what their separate effects would predict. In a further diaphorase test, crocidolite plus the chemical EDTA produced 2160 pmol of ethylene, against 683 pmol for EDTA alone and 29 pmol for crocidolite alone. The authors stated that these model reactions are no proof of reactions in the body.

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) biochemical experiment using cell-free enzyme systems. Experiments were repeated independently by two workers three times, with six parallels each.
• Who was studied: No human or animal subjects. Two enzyme reaction systems were tested: xanthine oxidase with xanthine, and NADH diaphorase from Clostridium cluyveri with the quinone juglone. The work was done at the Technical University of Munich.
• Exposure: Crocidolite asbestos fibres: 0.5 mg in the xanthine oxidase mixture and 0.2 mg in the diaphorase mixture. Identical amounts of amosite and chrysotile were used for comparison. Other additions were bisulfite (100 to 2500 micromolar in the xanthine oxidase tests) and EDTA (1 mM).
• Main results:
  • In the xanthine oxidase system, ethylene production was 3420 pmol without crocidolite and 7640 pmol with crocidolite.
  • In the xanthine oxidase system, amosite or chrysotile in place of crocidolite had only an insignificant influence on ethylene release.
  • In the xanthine oxidase system, sulfite increased ethylene formation only when crocidolite was present. With crocidolite, formation rose from 3.2 nmol per 30 min with no sulfite to 8.8 nmol at 2500 micromolar sulfite. Without crocidolite it stayed between 2.5 and 2.7 nmol (Table 3a).
  • In the xanthine oxidase plus crocidolite system, inhibition by catalase was lost when 500 micromolar sulfite was present. Without sulfite, inhibition was 51% at 10 units, 74% at 50 units and 85% at 100 units of catalase. With sulfite, the figures were 9%, 5% and 0%.
  • The diaphorase system alone produced 150 pmol ethylene in 30 min. Crocidolite had no influence on this.
  • With bisulfite, the diaphorase system produced 480 pmol ethylene. An additive effect of crocidolite and bisulfite would predict about 500 pmol, but at least double that was measured.
  • In the diaphorase system with both bisulfite and crocidolite, inhibition by superoxide dismutase was preserved, but inhibition by catalase seemed to be lost (Fig. 1).
  • In the diaphorase system, ethylene formed in 30 min was 33 pmol with no additions, 29 pmol with crocidolite, 683 pmol with EDTA, and 2160 pmol with crocidolite plus EDTA (Table 4).
• The authors' conclusion: The authors concluded that, of the three asbestos types, only crocidolite showed significant activity in these model reactions. They also concluded that molecules such as sulfur dioxide or certain quinones may enhance the reactions and change their mechanism. They stated that the model reactions are not proof of actual pathways in the body, but may help to explain certain clinical observations.
• Limitations the authors state:
  • The authors stated that the model reactions are no proof that these reactions or pathways actually exist.

Topics

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

Medical terms in this study, explained in our Lexicon: Crocidolite, Reactive Oxygen Species (ROS), Chrysotile, Amosite, Superoxide, Macrophage.

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