Effects of chrysotile co-exposure on BaP binding in normal human fibroblasts

Our plain-English summary of Effects of chrysotile co-exposure on BaP binding in normal human fibroblasts, by M.J. Chang, N.P. Singh, R.W. Hart (Environmental Health Perspectives, 1983).

The study

• Authors: M.J. Chang, N.P. Singh, R.W. Hart
• Journal: Environmental Health Perspectives
• Published: 1983;51:241-4
• Cited by: 3 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

The effects of chrysotile and benzo(a)pyrene (BaP) co-exposure on uptake, metabolism and BaP binding to nucleic acids were investigated in normal human fibroblasts. A significant enhancement in these parameters was found when co-exposure was carried out under serum-free conditions. In the presence of serum, only a slight enhancement of BaP uptake was detected, while metabolism and binding to nucleic acids were not affected over the 8-hr incubation period studied.

In plain English

This laboratory study tested whether chrysotile asbestos changes how normal human skin fibroblasts, cells grown in dishes, take up, process and bind benzo(a)pyrene (BaP), a cancer-causing chemical in cigarette smoke. Cultures were exposed for 8 hours to 3 micrograms per mL of radioactively labeled BaP, with or without 10 micrograms per mL of chrysotile, in medium with or without 10% fetal bovine serum. Without serum, chrysotile increased BaP uptake by approximately 35-40% over control levels. It also raised the share of radioactivity in the medium's water-soluble fraction, which the authors read as more BaP being metabolized, and increased binding to DNA and RNA. Treated-to-control DNA binding ratios were 2.76 and 2.21 in the two culture types. With serum, uptake was unchanged in one culture type and slightly higher in the other (p less than 0.02), and nucleic acid binding was not changed. The authors interpreted the extra binding as meaning more BaP was available inside cells. They noted that serum-containing conditions are more representative of the living body. Only cells were studied, not people.

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 cell culture experiment (in vitro)
• Who was studied: Normal human skin fibroblasts grown in culture, studied as reseeded high-density cultures and as confluent cultures of the same density. Three plates were used per sample group per experiment. The work was done at the FDA National Center for Toxicological Research, Jefferson, Arkansas.
• Exposure: Chrysotile (NIEHS sample; mean width 0.17 micrometers, mean length 21 micrometers) at 10 micrograms per mL, together with radioactively labeled benzo(a)pyrene at 3 micrograms per mL. Exposure lasted 8 hours, with or without 10% fetal bovine serum. Controls received BaP without chrysotile.
• Main results:
  • Combined chrysotile and BaP caused no observable cell killing after 8 hours in reseeded cultures. It slightly induced cell killing in confluent cultures without serum: viable cell counts were 39.6 ± 0.2 for control and 36.3 ± 0.2 for chrysotile-treated, in the article's units.
  • With serum, BaP uptake was essentially the same in control and chrysotile-treated reseeded cultures (radioactivity left in medium 76.3% in both). In confluent cultures with serum, uptake was enhanced with chrysotile (76.2% vs 71.3% left in medium; p < 0.02).
  • Without serum, control cultures took up approximately twice as much BaP as with serum. Chrysotile further enhanced uptake by approximately 35-40% over control levels. Radioactivity left in medium was 51.3% for control vs 31.7% for chrysotile in reseeded cultures, and 50.0% vs 32.4% in confluent cultures.
  • Without serum, a significantly higher percentage of radioactivity was recovered in the aqueous (water-soluble) phase of chrysotile-treated medium. The figures were 14.8% control vs 20.9% chrysotile in reseeded cultures and 27.4% vs 33.7% in confluent cultures. The authors took this to indicate more BaP was metabolized. With serum, there was no observable difference.
  • With serum, BaP binding to nucleic acids was not changed by chrysotile. Treated/control ratios were RNA 1.03 ± 0.16 and DNA 1.15 ± 0.10 in reseeded cultures, and RNA 0.99 ± 0.03 and DNA 1.00 ± 0.17 in confluent cultures.
  • Without serum, chrysotile significantly enhanced BaP binding to nucleic acids in both culture types. Treated/control ratios were RNA 1.29 ± 0.39 and DNA 2.76 ± 0.33 in reseeded cultures, and RNA 1.72 ± 0.41 and DNA 2.21 ± 0.48 in confluent cultures.
• The authors' conclusion: The authors interpreted the enhanced binding without serum as meaning simply that more BaP was available inside the cells to be processed by cytochrome P450 enzymes. They noted that chrysotile's apparent role as a vehicle bringing BaP into cells does not appear to hold under serum-added conditions, which they said are more representative of in vivo conditions.
• Limitations the authors state:
  • The serum-free conditions under which chrysotile increased uptake, metabolism and binding are, according to the authors, less representative of in vivo conditions than serum-added conditions, under which these effects were not seen.
  • Recovery of radioactivity from serum-containing medium was incomplete. The authors suggested this may be due to BaP or its metabolites associating with denatured proteins.

Topics

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

Medical terms in this study, explained in our Lexicon: Chrysotile, Fibroblast.

Related studies

• Interactions of chrysotile and benzopyrene in a human cell culture systems — R.E. Stephens, L.B. Joseph, et al. (1983)
• Morphological transformation in vitro of normal human fibroblasts by chrysotile — L.B. Joseph, R.E. Stephens, et al. (1983)
• Study of the cell-transforming ability of amosite and crocidolite asbestos and the ability to induce changes in the metabolism and macromolecular binding of benzo(a)pyrene in C3H10T1/2 cells — A. Poole, R.C. Brown, et al. (1983)
• Xeroderma pigmentosum fibroblasts are more sensitive to asbestos fibers than are normal human fibroblasts — L.L. Yang, R.E. Kouri, et al. (1984)
• Intracellular protein binding to asbestos induces aneuploidy in human lung fibroblasts — R.A. MacCorkle, S.D. Slattery, et al. (2006)
• Studies on in vitro chrysotile-pleural mesothelial cell interaction: morphological aspects and metabolism of benzo-3,4-pyrene — M.C. Jaurand, I. Bastie-Sigeac, et al. (1983)

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