In vivo accumulation of iron on crocidolite is associated with decrements in oxidant generation by the fiber

Our plain-English summary of In vivo accumulation of iron on crocidolite is associated with decrements in oxidant generation by the fiber, by A.J. Ghio, A. LeFurgey, V.L. Roggli (Journal of Toxicology and Environmental Health, 1997).

The study

• Authors: A.J. Ghio, A. LeFurgey, V.L. Roggli
• Journal: Journal of Toxicology and Environmental Health
• Published: 1997;50(2):125-42
• Cited by: 20 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

In vivo exposures to fibrous silicates are characterized by the formation of asbestos bodies. These structures consist of the original fiber with a coating of inexact composition, but it will include iron and protein. We tested the hypothesis that this iron, accumulated on asbestos bodies, participates in electron transport and oxidant generation. Thirty-day-old, male guinea pigs were intratracheally instilled with 1.0 mg crocidolite. Six months later, the animals were anesthetized, euthanized, and the fibers were isolated from the lungs. Energy-dispersive x-ray analysis and x-ray photoelectron spectroscopy confirmed an accumulation of metal onto the fiber after in vivo exposure. Stains for iron demonstrated a heterogeneous distribution of the metal on the silicate, while the uptake of a commercially available polyclonal antibody to ferritin localized to beaded enlargements along the coated fibers. Chelatable [Fe3+] associated with the fiber increased after in vivo exposure. However, oxidant generation by asbestos bodies was decreased relative to uncoated fibers despite the elevation in the concentration of metal associated with the crocidolite. We conclude that iron is accumulated onto fibers in the lungs of guinea pigs. Some portion of this accumulation of iron is in the form of ferritin, and this metal is not chemically reactive in oxidant production. Asbestos bodies may represent a successful attempt by the host to sequester the metal adsorbed to the surface of a fiber and diminish the oxidative challenge introduced by a fibrous silicate. Subsequently, the generation of free radicals by the fibrous silicate is diminished.

In plain English

In this animal experiment, the authors placed 1.0 mg of crocidolite asbestos into the windpipes of twelve 30-day-old male guinea pigs. Six months later, fibers were recovered from the lungs. In the laboratory these were compared with crocidolite that had never been in an animal. The lungs held about 3.5 million uncoated and 56,000 to 70,000 coated fibers (asbestos bodies) per gram of wet lung, roughly 50 uncoated fibers for each coated one. Fibers taken from the lungs carried more iron. In one surface measurement, the iron-to-silicon signal ratio rose from 0.43 before exposure to 1.00 afterward. Chemically extractable iron also increased. Stains for iron and for ferritin, an iron-storage protein, gathered at bead-like swellings along the coated fibers. Even so, in two test-tube assays the lung-recovered fibers produced fewer oxidants than unexposed crocidolite. The authors concluded that part of the accumulated iron is stored in ferritin and is not chemically reactive. They saw asbestos bodies as a successful attempt by the host to reduce the fiber's oxidative challenge, which they described as diminished but not totally eliminated.

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 (intratracheal instillation in guinea pigs), followed by laboratory analysis of the recovered fibers compared with unexposed fibers
• Who was studied: Twelve 30-day-old male guinea pigs from Charles River Laboratories, Raleigh, North Carolina, examined 6 months after instillation
• Exposure: A single intratracheal instillation of 1.0 mg NIEHS crocidolite in 0.5 ml normal saline. Fibers were recovered from the lungs after 6 months.
• Main results:
  • In the exposed guinea pigs there were 3.5 × 10^6 (printed as "3.5 × 106") uncoated and 56,000 to 70,000 coated fibers per gram of wet lung
  • The ratio of uncoated to coated fibers was approximately 50 to 1
  • By energy-dispersive x-ray analysis, the iron-to-silicon ratio of the fibers increased after in vivo exposure compared with the fibers before instillation
  • By x-ray photoelectron spectroscopy, the Fe 2p/Si 2p surface signal ratio rose from 0.43 before exposure to 1.00 for fibers isolated from the lungs of instilled guinea pigs
  • Iron staining showed an uneven distribution of iron on the fibers, corresponding to bead-like enlargements along the fiber
  • Stains for ferritin showed uptake by the coated fibers
  • Chelatable (chemically extractable) iron on the fibers increased after in vivo exposure
  • In a deoxyribose assay, asbestos bodies generated significantly less oxidized product than crocidolite without in vivo exposure
  • Oxidant generation measured as salicylate hydroxylation was diminished after in vivo exposure. Unexposed crocidolite significantly increased hydroxylation, while asbestos bodies did not.
• The authors' conclusion: The authors concluded that iron accumulates on fibers retained in guinea pig lungs and that part of it is in the form of ferritin, which is not chemically reactive. They described asbestos bodies as a successful attempt by the host to sequester the metal and diminish the fiber's oxidative challenge. In their view, free radical generation is diminished but not totally eliminated.

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, Silicate, Asbestos Bodies, Ferritin.

Related studies

• Asbestos body formation and iron accumulation in mouse peritoneal granulomas after the introduction of crocidolite asbestos fibers — H.K. Koerten, J. Hazekamp, et al. (1990)
• The release of iron from different asbestos structures by hydrogen peroxide with concomitant O2 generation — A.J. Ghio, D.E. Taylor, et al. (1998)
• Synchrotron X-ray microscopy reveals early calcium and iron interaction with crocidolite fibers in the lung of exposed mice — L. Pascolo, G. Zabucchi, et al. (2016)
• Mobilization of iron from urban particulates leads to generation of reactive oxygen species in vitro and induction of ferritin synthesis in human lung epithelial cells — K.R. Smith, A.E. Aust (1997)
• Potential toxicity of nonregulated asbestiform minerals: balangeroite from the western Alps. Part 2: Oxidant activity of the fibers — F. Turci, M. Tomatis, et al. (2005)
• Free radical generation in the toxicity of inhaled mineral particles: the role of iron speciation at the surface of asbestos and silica — I. Fenoglio, L. Prandi, et al. (2001)

Browse more research in Journal of Toxicology and Environmental Health, or return to medical research.