In vivo evidence of free radical formation after asbestos instillation: an ESR spin trapping investigation

Our plain-English summary of In vivo evidence of free radical formation after asbestos instillation: an ESR spin trapping investigation, by A.J. Ghio, M.B. Kadiiska, Q.H. Xiang, et al (Free Radical Biology & Medicine, 1998).

The study

• Authors: A.J. Ghio, M.B. Kadiiska, Q.H. Xiang, R.P. Mason
• Journal: Free Radical Biology & Medicine
• Published: 1998;24(1):11-7
• Cited by: 25 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

It has been postulated that the in vivo toxicity of asbestos results from its catalysis of free radical generation. We examined in vivo radical production using electron spin resonance (ESR) coupled with the spin trap alpha-(4-pyridyl-1-oxide)-N-t-butylnitrone (4-POBN); 180 day-old rats were intratracheally instilled with either 500 microg crocidolite or saline. Twenty-four hours later, histologic examination revealed a neutrophilic inflammatory response. ESR spectroscopy of the chloroform extract from lungs exposed to asbestos gave a spectrum consistent with a carbon-centered radical adduct, while those spectra from lungs instilled with saline revealed a much weaker signal. This same radical formation persisted and, even one month after instillation, could be detected in the lungs of rats exposed to asbestos. The 4-POBN adducts detected by ESR are very similar to, if not identical with, ethyl and pentyl radical adducts, providing evidence of in vivo lipid peroxidation resulting from asbestos exposure. We conclude that, after instillation of crocidolite in the rat, ESR analysis of lung tissue demonstrates in vivo free radical production.

In plain English

This was a laboratory experiment in rats, not a study of people. The authors tested whether crocidolite asbestos placed in the lung produces free radicals (reactive molecules) inside the living animal. They used electron spin resonance (ESR) with a chemical 'spin trap' called 4-POBN. Male 180-day-old Sprague–Dawley rats had crocidolite or saline instilled into the windpipe. Compared with saline, crocidolite-exposed rats had significantly more neutrophils (inflammatory cells) in lung washings at 1, 7 and 30 days. Lung extracts from crocidolite-exposed rats gave a prominent ESR signal at 24 hours, and the signal was still detected at 7 and 30 days. Saline-exposed rats gave a much weaker signal. Control tests produced no signal when crocidolite and the spin trap were added to lung tissue outside the body. Cutting neutrophil numbers with cyclophosphamide had no significant effect on the signal, and the iron-binding drug deferoxamine did not reduce it. The authors concluded that ESR showed free radical production in the living lung after crocidolite instillation, consistent with ethyl- and pentyl-type radicals and with lipid peroxidation. They noted the method cannot definitively identify the radical.

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: Animal experiment (rats), using electron spin resonance spin trapping on lung tissue, with in vitro control experiments
• Who was studied: Male 180-day-old Sprague–Dawley rats from Charles River Breeding Laboratories, Raleigh, NC, studied in small groups per exposure and time point (1, 7 and 30 days after instillation)
• Exposure: A single intratracheal instillation of crocidolite, compared with saline. The scanned text prints the dose as 500 mg per rat; the PubMed abstract gives 500 micrograms.
• Main results:
  • At 1, 7 and 30 days, lung lavage neutrophils were significantly higher in crocidolite-instilled rats than in saline-instilled rats. Lavage protein was also significantly higher, which the authors said suggested injury.
  • Twenty-four hours after crocidolite instillation, a prominent six-line ESR spectrum was detected in lung lipid extracts.
  • The same ESR spectrum was still detected 7 days and 30 days after crocidolite exposure.
  • Rats given saline instead of crocidolite showed a much weaker ESR spectrum.
  • The radical adducts from crocidolite-exposed lungs differed only slightly from laboratory-made ethyl and pentyl radical adducts. The authors proposed that the spin trap reacted with ethyl and pentyl radicals or structurally similar radicals.
  • Adding crocidolite and 4-POBN to lung tissue from unexposed rats outside the body produced no detectable ESR signal (data not shown).
  • Neutrophil depletion with cyclophosphamide had no significant effect on the ESR signal in rats given crocidolite or saline (data not shown).
  • Instilling 10% dextran drew neutrophils into the lung but produced no detectable increase in the ESR signal compared with saline (data not shown).
  • Deferoxamine treatment did not reduce the ESR signal in crocidolite-instilled rats compared with saline treatment (data not shown).
• The authors' conclusion: The authors concluded that, after crocidolite instillation in the rat, ESR of lung tissue demonstrates free radical production in the living animal. They said the adducts are consistent with ethyl- and pentyl-type radicals, providing evidence of lipid peroxidation associated with asbestos exposure.
• Limitations the authors state:
  • The ESR measurements cannot definitively identify which free radical was detected.
  • The failure of deferoxamine to reduce the signal does not prove that iron plays no part in the damage in living animals.

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, Asbestos Exposure.

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