Asbestos catalyzes the formation of the 6-oxobenzo\[a\]pyrene radical from 6-hydroxybenzo\[a\]pyrene

Our plain-English summary of Asbestos catalyzes the formation of the 6-oxobenzo[a]pyrene radical from 6-hydroxybenzo[a]pyrene, by P. Graceffa, S.A. Weitzman (Archives of Biochemistry and Biophysics, 1987).

The study

• Authors: P. Graceffa, S.A. Weitzman
• Journal: Archives of Biochemistry and Biophysics
• Published: 1987;257(2):481-4
• Cited by: 15 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Crocidolite asbestos catalyzes the oxidation of 6-hydroxybenzo[a]pyrene, a metabolite of benzo[a]pyrene, to the 6-oxobenzo[a]pyrene radical as determined by electron spin resonance spectroscopy. This may be a mechanism whereby inhaled asbestos enhances the incidence of lung cancer induced by cigarette smoke, which contains benzo[a]pyrene.

In plain English

This was a test-tube chemistry experiment. No people or animals were studied. The authors mixed crocidolite asbestos (a standard reference sample) with benzo[a]pyrene, a cancer-causing chemical found in cigarette smoke. They also mixed it with 6-hydroxybenzo[a]pyrene, a chemical the body makes from benzo[a]pyrene. They used electron spin resonance spectroscopy, which detects reactive molecules called radicals. Crocidolite with benzo[a]pyrene produced no signal. Crocidolite with 6-hydroxybenzo[a]pyrene produced a signal that grew over time, which the authors identified as the 6-oxobenzo[a]pyrene radical. Without asbestos there was little or no signal. After 30 minutes the radical was roughly 7% of the starting chemical, an estimate the authors called only an approximation. Treating the asbestos with desferroxamine, a drug that binds iron, did not change the signal. The authors said this strongly suggests iron in the asbestos was not responsible, though they did not rule it out. Lowering the oxygen did not reduce the signal. The authors concluded this may be one way inhaled asbestos increases lung cancer caused by cigarette smoke.

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 chemistry experiment (test tube), using electron spin resonance spectroscopy
• Who was studied: No human or animal subjects. A UICC reference standard sample of crocidolite asbestos, suspended in water, was incubated with a solution of 6-hydroxybenzo[a]pyrene (and, separately, benzo[a]pyrene).
• Exposure: Crocidolite asbestos at 0.5 mg/ml incubated for 30 minutes with 6-hydroxybenzo[a]pyrene (a metabolite of benzo[a]pyrene). Comparison samples had no asbestos. Other tests used desferroxamine-treated asbestos, untreated asbestos with 1 mM desferroxamine added, and solutions with oxygen reduced by nitrogen bubbling.
• Main results:
  • Crocidolite asbestos incubated with benzo[a]pyrene itself produced no electron spin resonance signal.
  • Crocidolite asbestos incubated with 6-hydroxybenzo[a]pyrene produced a signal whose size increased with time.
  • Without asbestos, 6-hydroxybenzo[a]pyrene gave little or no signal.
  • By comparison with published values, the authors assigned the signal to the 6-oxobenzo[a]pyrene radical.
  • After 30 minutes of incubation with asbestos, the radical amounted to roughly 7% of the starting 6-hydroxybenzo[a]pyrene.
  • With desferroxamine-treated asbestos, and with untreated asbestos plus desferroxamine, the signal was unchanged. The authors said this strongly suggests iron in the asbestos was not responsible for the activity.
  • With oxygen reduced by nitrogen bubbling, the signal was the same or somewhat larger. The authors said this suggests oxygen does not take part and that asbestos oxidizes 6-hydroxybenzo[a]pyrene directly.
• The authors' conclusion: The authors concluded that this may be a mechanism by which inhaled asbestos increases the incidence of lung cancer caused by cigarette smoke, which contains benzo[a]pyrene. They added that asbestos should also be considered as a chemical catalyst when assessing its toxic and cancer-causing properties.
• Limitations the authors state:
  • The method used to estimate the amount of radical present is only an approximation.
  • Iron could still be responsible if desferroxamine does not block this particular activity of iron.
  • The activity could instead be due to other transition metals in the asbestos or to some other type of catalytic site.
  • The nitrogen-bubbling experiment does not rigorously rule out a role for oxygen.

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, Lung Cancer.

Related studies

• Asbestos catalyzes hydroxyl and superoxide radical generation from hydrogen peroxide — S.A. Weitzman, P. Graceffa (1984)
• Transport of a carcinogen, benzo[a]pyrene, from particulates to lipid bilayers: a model for the fate of particle-adsorbed polynuclear aromatic hydrocarbons which are retained in the lungs — J.R. Lakowicz, D.R. Bevan, et al. (1980)
• Effects of asbetos, iron oxide, silica, and carbon black on the microsomal availability of benzo[a]pyrene — J.R. Lakowicz, D.R. Bevan (1979)
• Effects of asbestos on membrane transport and metabolism of benzo(a)pyrene — C. Kandaswami, P.J. O'Brien (1980)
• Studies on in vitro chrysotile-pleural mesothelial cell interaction: morphological aspects and metabolism of benzo-3,4-pyrene — M.C. Jaurand, I. Bastie-Sigeac, et al. (1983)
• Effects of crocidolite and chrysotile asbestos on cellular uptake and metabolism of benzo(a)pyrene in hamster tracheal epithelial cells — B.T. Mossman, A. Eastman, et al. (1983)

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