Active oxygen species mediate asbestos fiber uptake by tracheal epithelial cells

Our plain-English summary of Active oxygen species mediate asbestos fiber uptake by tracheal epithelial cells, by J. Hobson, J.L. Wright, A. Churg (FASEB Journal, 1990).

The study

• Authors: J. Hobson, J.L. Wright, A. Churg
• Journal: FASEB Journal
• Published: 1990;4(13):3135-9
• Cited by: 30 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

To examine the mechanism whereby asbestos fibers penetrate tracheal epithelial cells, we exposed rat tracheal explants to amosite asbestos alone, or with varying concentrations of substances that scavenge active oxygen species (catalase and superoxide dismutase) or prevent formation of active oxygen species (deferoxamine). All three agents decreased asbestos fiber uptake in a dose-response fashion, but no agent provided complete protection against fiber penetration. We conclude that uptake of amosite asbestos fibers is mediated in part by active oxygen species (most likely OH.), but that other mechanisms of fiber uptake must also exist.

In plain English

This was a laboratory experiment on pieces of rat windpipe (tracheal explants) kept in organ culture. The authors asked how asbestos fibers get into the airway's lining (epithelial) cells. Explants were exposed for 1 hour to one of four preparations, each agent at several concentrations: amosite asbestos alone; amosite mixed with superoxide dismutase; amosite mixed with catalase; or amosite fibers first soaked for 18 hours in deferoxamine and then washed. Deferoxamine prevents formation of active oxygen species, and the two enzymes scavenge them. Some explants received boiled, inactivated enzyme. After 1 or 3 days, fibers longer than 4 micrometers in or under the epithelial cells were counted per millimeter of lining. All three agents reduced fiber uptake in a dose-related way, but none stopped it completely, and boiled enzymes gave no protection. Explants exposed to cigarette smoke before asbestos took up more fibers, and catalase totally abolished this increase at the higher doses. The authors concluded that amosite uptake is mediated in part by active oxygen species, most likely the hydroxyl radical (OH), but that other mechanisms must also exist.

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 laboratory experiment using rat tracheal explants in organ culture
• Who was studied: Tracheal explants from 200-g Sprague-Dawley rats; six tracheas were removed for examination at each time point (1 day and 3 days in culture)
• Exposure: A 2.5 mg/ml suspension of amosite asbestos (UICC Standard Reference sample) was applied for 1 hour at 37°C, in four preparations. (1) Amosite alone. (2) Amosite fibers preincubated for 18 hours with deferoxamine (0.01, 0.1, 1.0, 10 mM), then washed twice to remove excess deferoxamine and resuspended before being added to the cultures. (3) Amosite with superoxide dismutase (150, 300, 600, 1200 U/ml) added to the suspension just before use. (4) Amosite with catalase (325, 650, 900, 1300 U/ml) added the same way. Boiled, inactivated enzyme was also tested. In a fourth experiment, explants were exposed to six puffs of cigarette smoke or air before asbestos, with or without catalase. Only fibers longer than 4 µm were counted.
• Main results:
  • Fiber uptake decreased progressively as the concentration of deferoxamine increased, with a tendency for the protective effect to level off at higher doses
  • Superoxide dismutase and catalase each produced a dose-related decrease in fiber uptake
  • Inactivating the enzymes by boiling abolished their protective effect
  • No dose of any scavenger or inhibitor completely abolished fiber uptake in explants not exposed to smoke
  • Cigarette smoke enhanced fiber uptake; catalase diminished this smoke-enhanced uptake in a dose-response fashion, with total abolition at the higher doses
• The authors' conclusion: The authors concluded that uptake of amosite asbestos fibers is mediated in part by active oxygen species (most likely OH), but that other mechanisms of fiber uptake must also exist. They also suggested that the action of cigarette smoke is in many respects an exaggeration of the usual reaction to asbestos.

Topics

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

Medical terms in this study, explained in our Lexicon: Amosite, Superoxide, Dose-response relationship.

Related studies

• Scavengers of active oxygen species prevent cigarette smoke-induced asbestos fiber penetration in rat tracheal explants — A. Churg, J. Hobson, et al. (1989)
• Effects of cigarette smoke dose and time after smoke exposure on uptake of asbestos fibers by rat tracheal epithelial cells — A. Churg, J. Hobson, et al. (1990)
• Relationship of fiber surface iron and active oxygen species to expression of procollagen, PDGF-A, and TGF-beta(1) in tracheal explants exposed to amosite asbestos — J. Dai, A. Churg (2001)
• Cigarette smoke increases amosite asbestos fiber binding to the surface of tracheal epithelial cells — A. Churg, J. Sun, et al. (1998)
• Iron enhances uptake of mineral particles and increases lipid peroxidation in tracheal epithelial cells — B. Keeling, K.Y. Li, et al. (1994)
• Effects of cigarette smoke on epithelial uptake of non-asbestos mineral particles in tracheal organ culture — B. Keeling, J. Hobson, et al. (1993)

Browse more research in FASEB Journal, or return to medical research.