Effects of cigarette smoke on epithelial uptake of non-asbestos mineral particles in tracheal organ culture

Our plain-English summary of Effects of cigarette smoke on epithelial uptake of non-asbestos mineral particles in tracheal organ culture, by B. Keeling, J. Hobson, A. Churg (American Journal of Respiratory Cell and Molecular Biology, 1993).

The study

• Authors: B. Keeling, J. Hobson, A. Churg
• Journal: American Journal of Respiratory Cell and Molecular Biology
• Published: 1993;9(3):335-40
• Cited by: 16 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Cigarette smoke is believed to increase the pulmonary retention of many different types of mineral dusts, but the mechanisms of this process are unclear. We have previously shown, using a tracheal organ culture system, that exposure to cigarette smoke directly increases the uptake of asbestos fibers by tracheal epithelial cells, and that this process is mediated by active oxygen species. To determine whether the same effects are seen with other types of mineral dust, we exposed rat tracheal explants to cigarette smoke or air (control) and then to a variety of dusts generally considered "inert" or of low pathogenicity. Explants were maintained in organ culture to allow dust uptake, and segments fixed and prepared for light microscopy at various times up to 1 wk; particle uptake was determined morphometrically. We observed that cigarette smoke significantly increased the epithelial uptake of nonfibrous titanium dioxide and talc, and of fibrous silicon carbide, but not of fibrous or nonfibrous iron oxide, nonfibrous silicon carbide, or fibrous wollastonite. Scavengers of active oxygen species (catalase) or agents that prevent the formation of active oxygen species (deferoxamine) blocked the effects of smoke in enhancing titanium dioxide uptake but did not block the effects of smoke on talc uptake. These observations indicate that cigarette smoke may potentiate the effects of many types of dust, including relatively inert dusts, by directly increasing the numbers of particles entering the tracheobronchial epithelium and eventually reaching the interstitium. However, smoke does not directly enhance the uptake of every dust.(ABSTRACT TRUNCATED AT 250 WORDS)

In plain English

This was a laboratory experiment using short pieces of windpipe (tracheal explants) taken from female Sprague-Dawley rats. The authors tested whether cigarette smoke increased the uptake of various mineral dusts by the windpipe's lining cells. Half the segments were exposed to six puffs of smoke from a nonfilter cigarette over 10 minutes and half to air. The segments were then exposed to one dust: amosite asbestos (used as a positive control), fibrous or nonfibrous iron oxide, silicon carbide, talc, titanium dioxide (rutile) or wollastonite. Uptake was measured under the microscope after up to 7 days in culture. Smoke roughly doubled amosite uptake at 3 and 7 days. Smoke significantly increased uptake of titanium dioxide, talc and fibrous silicon carbide. It did not increase uptake of wollastonite, either form of iron oxide, or nonfibrous silicon carbide. Catalase and deferoxamine, agents that counter active oxygen species, blocked the smoke effect for titanium dioxide but not for talc. The authors concluded that smoke enhancement of dust uptake is widespread but not universal. They cautioned that windpipe results may not apply to the lung's air sacs (alveoli).

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 (organ culture) experiment. Rat tracheal explants were exposed to cigarette smoke or air, then to mineral dusts, kept in culture, and examined by light microscopy at times up to 1 week.
• Who was studied: Two-millimeter tracheal segments from 250-g female Sprague-Dawley rats. Five to nine segments from each test group were examined at each time point.
• Exposure: Six puffs of whole smoke from a commercial nonfilter cigarette over 10 minutes, or air (control). This was followed by 1 hour in a suspension of one dust: amosite asbestos (positive control), fibrous iron oxide, nonfibrous iron oxide, silicon carbide (fibrous and nonfibrous particles), talc, titanium dioxide (rutile) or wollastonite.
• Main results:
  • Amosite asbestos, the positive control: smoke-exposed tracheas showed a roughly 2-fold increase in fiber uptake at 3 and 7 days.
  • Titanium dioxide (rutile): smoke significantly increased uptake at 1, 3 and 7 days.
  • Talc: smoke significantly increased uptake at 3 and 7 days.
  • Silicon carbide (7-day cultures only): smoke significantly increased uptake of fibers but not of nonfibrous particles.
  • Smoke did not significantly enhance uptake of wollastonite, fibrous or nonfibrous iron oxide, or nonfibrous silicon carbide.
  • Where smoke did enhance uptake, the effect was at least as great as, and usually greater than, the effect seen with asbestos.
  • At 7 days, catalase and deferoxamine abolished the smoke effect on titanium dioxide uptake.
  • For talc, none of the active oxygen scavengers had a statistically significant effect in preventing smoke-enhanced uptake.
• The authors' conclusion: The authors concluded that smoke directly enhancing the uptake of mineral dust particles by the epithelium is widespread but not universal.
• Limitations the authors state:
  • The tracheobronchial lining differs from the alveolar lining, so the results may or may not apply to events in the alveoli.
  • Only a small quantity of silicon carbide was available, so only a 7-day culture was prepared for it.
  • Not enough silicon carbide was available to test the effects of catalase or deferoxamine on it.

Topics

Medical terms in this study, explained in our Lexicon: Talc, Wollastonite, Epithelium.

Related studies

• Ozone enhances the uptake of mineral particles by tracheobronchial epithelial cells in organ culture — A. Churg, M. Brauer, et al. (1996)
• 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)
• Iron enhances uptake of mineral particles and increases lipid peroxidation in tracheal epithelial cells — B. Keeling, K.Y. Li, et al. (1994)
• Cigarette smoke increases amosite asbestos fiber binding to the surface of tracheal epithelial cells — A. Churg, J. Sun, et al. (1998)
• Effect of mineral particles containing iron on primary cultures of rabbit tracheal epithelial cells: possible implication of oxidative stress — C. Guilianelli, A. Baeza-Squiban, et al. (1993)
• Active oxygen species mediate asbestos fiber uptake by tracheal epithelial cells — J. Hobson, J.L. Wright, et al. (1990)

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