Ascorbic acid inhibits the squamous metaplasia that results from treatment of tracheal explants with asbestos or benzo\[a\]pyrene-coated asbestos

Our plain-English summary of Ascorbic acid inhibits the squamous metaplasia that results from treatment of tracheal explants with asbestos or benzo[a]pyrene-coated asbestos, by G. Holtz, E. Bresnick (Cancer Letters, 1988).

The study

• Authors: G. Holtz, E. Bresnick
• Journal: Cancer Letters
• Published: 1988;42(1-2):23-8
• Cited by: 6 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Hamster tracheal explants were maintained in culture in the presence or absence of benzo[a]pyrene (BP), crocidolite asbestos, or BP-coated crocidolite. Dose-dependent squamous metaplasia was observed in the treated samples. L-Ascorbic acid and DL-alpha-tocopherol were able to partially protect the tracheal explants from the metaplastic response induced by crocidolite. Furthermore, ascorbic acid reduced the extent of metaplasia observed in hamster tracheal explants that were exposed to BP-crocidolite.

In plain English

This was a laboratory experiment on pieces of windpipe (tracheal explants) taken from young male golden Syrian hamsters and kept in culture for 2 weeks. The explants were exposed to crocidolite asbestos, to benzo[a]pyrene (BP, a polycyclic aromatic hydrocarbon), or to crocidolite coated with BP. They were then examined under the microscope for squamous metaplasia, a change in the lining cells that the authors describe as a preneoplastic lesion that is reversible in its early stages. Changes were graded from 1 (normal lining) to 4 (extensive metaplasia). Untreated explants averaged grade 1.2. The highest crocidolite dose averaged 2.7, the highest BP dose 2.5, and BP-coated crocidolite 2.7 to 3.6. Ascorbic acid (vitamin C) was added one hour after crocidolite exposure, and metaplasia fell as the dose rose. At 4 mM the average was 1.5, against 2.6 for crocidolite alone in that experiment. Vitamin E also lowered the response. With BP-coated crocidolite, 4 mM ascorbic acid gave averages of 1.8 and 2.0. The authors concluded that ascorbic acid showed potential to reduce this change in hamster trachea. No people were studied.

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 using hamster tracheal explants
• Who was studied: Tracheal explants (hemisected tracheal rings) from 4 to 6 week old male golden Syrian hamsters, kept in culture for 2 weeks. The number of animals is not stated; tables give numbers of observations per group (for example 30 control observations).
• Exposure: Crocidolite asbestos suspension for 1 hour (4 per ml, or as indicated; the unit is printed as micrograms in the methods but as milligrams in the tables), BP for 48 hours, or BP-coated crocidolite. Treatment with L-ascorbic acid (0.5 to 4 mM) or DL-alpha-tocopherol (vitamin E) began 1 hour after exposure.
• Main results:
  • Control explants averaged a metaplasia grade of 1.2 plus or minus 0.07 (30 observations). Crocidolite at 4.0 averaged 2.7 plus or minus 0.07 (52 observations), significantly different from control.
  • BP at 5.0 micrograms per ml averaged grade 2.5 plus or minus 0.20 (5 observations), significantly different from control. Lower BP doses did not produce significant metaplasia.
  • BP-coated crocidolite averaged grade 3.6 plus or minus 0.34 at 0.5 to 0.5 (5 observations) and 2.7 plus or minus 0.25 at 1.0 to 1.0 (6 observations). Both were significantly different from control.
  • In the vitamin experiment, crocidolite alone averaged grade 2.6 plus or minus 0.20 (16 observations).
  • Ascorbic acid at 4 mM after crocidolite exposure left metaplasia 25% above control (mean grade 1.5 plus or minus 0.16, 13 observations). At 1 mM the grade (2.1) was still significantly above control.
  • Vitamin E reduced the metaplastic response to crocidolite to 25% above control levels.
  • In explants exposed to BP-coated crocidolite, 4 mM ascorbic acid reduced metaplasia to 46 to 62% above control. Mean grades were 1.8 and 2.0, compared with 3.6 and 2.7 without ascorbic acid.
• The authors' conclusion: The authors concluded that their data indicate the potential efficacy of ascorbic acid in reducing the severity of squamous metaplasia in hamster trachea exposed to crocidolite or BP-coated crocidolite. They suggested this may have import for people chronically exposed to asbestos. They also gave a rough calculated estimate, not tested in this study, of about 15 g daily to reach approximately 2 mM in the human bronchus.
• Limitations the authors state:
  • The authors state that the mechanism by which ascorbic acid may act on crocidolite-stimulated metaplasia is not known, and that whether it works by blocking reactive oxygen species remains to be established.

Topics

Medical terms in this study, explained in our Lexicon: Crocidolite.

Related studies

• Asbestos and benzo[a]pyrene act synergistically to induce squamous metaplasia and incorporation of [3H]thymidine in hamster tracheal epithelium — B.T. Mossman, A. Eastman, et al. (1984)
• 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)
• Morphological transformation of Syrian hamster embryo cells induced by mineral fibres and the alleged enhancement of benzo[a]pyrene — S.O. Mikalsen, E. Rivedal, et al. (1988)
• Pulmonary response of hamsters to fibrous glass: chronic effects of repeated intratracheal instillation with or without benzo[a]pyrene — V.J. Feron, P.M. Scherrenberg, et al. (1985)
• Effects of 6-month daily supplementation with oral beta-carotene in combination or not with benzo[a]pyrene on cell-cycle markers in the lung of ferrets — A. Fuster, C. Picó, et al. (2008)
• Mechanisms of asbestos-induced squamous metaplasia in tracheobronchial epithelial cells — G. Cameron, C.D. Woodworth, et al. (1989)

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