Interactions of chrysotile and benzopyrene in a human cell culture systems

Our plain-English summary of Interactions of chrysotile and benzopyrene in a human cell culture systems, by R.E. Stephens, L.B. Joseph, F.B. Daniel, et al (Environmental Health Perspectives, 1983).

The study

• Authors: R.E. Stephens, L.B. Joseph, F.B. Daniel, K.M. Schenck, H.A. Newman, P.D. Lipetz, J.R. Millette
• Journal: Environmental Health Perspectives
• Published: 1983;51:257-65
• Cited by: 2 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

The risk of lung cancer related to asbestos exposure has been shown to increase disproportionately by cigarette smoking, suggesting a synergistic effect. Differing lengths of NIEHS chrysotile with benzopyrene [B(a)P, B(e)P] (organic by-products of combustion) were applied on normal human fibroblasts (cell line CI) to test for cytotoxicity (survival determined by colony-forming efficiency), binding of benzopyrene to DNA, and the production of benzopyrene metabolites. At concentrations of 100 micrograms/mL, NIEHS short chrysotile was more cytotoxic than NIEHS intermediate chrysotile (3% and 17% survival, respectively); B(a)P and B(e)P concentrations up to and including 10 microM were not cytotoxic. Simultaneous application of NIEHS short chrysotile with B(a)P or B(e)P did not decrease survival synergistically. On the contrary, application of B(a)P simultaneously with NIEHS intermediate chrysotile resulted in increased survival over that of intermediate chrysotile alone (25% and 17% survival, respectively). There were low levels of B(a)P bound to DNA in the presence of NIEHS short chrysotile or NIEHS intermediate chrysotile. Measurable levels of B(a)P-DNA adducts were formed both in the absence and in the presence of each size of NIEHS chrysotile. However, there was no strong indication of a perturbation of the level of DNA-B(a)P binding following simultaneous administration of increasing levels of asbestos in addition to 1 microM hydrocarbon. The asbestos had no demonstrable influence on the level of B(a)P metabolism during the 24-hr period following simultaneous exposure of asbestos and hyrdocarbons.(ABSTRACT TRUNCATED AT 250 WORDS)

In plain English

This was a laboratory study of normal human skin cells (fibroblasts, cell line CI, grown from newborn foreskin tissue). The authors exposed the cells for 24 hours to two sizes of NIEHS chrysotile asbestos, short and intermediate. The fibers were given alone or together with benzo(a)pyrene or benzo(e)pyrene, which are by-products of combustion. The authors measured cell survival, binding of benzo(a)pyrene to DNA, and how much benzo(a)pyrene the cells broke down. Short chrysotile was more toxic than intermediate chrysotile: at 100 micrograms per mL, survival was 3% versus 17%. The benzopyrenes alone, at up to 10 micromolar, did not reduce cell survival. Adding them to short chrysotile did not increase its toxicity. Adding benzo(a)pyrene to intermediate chrysotile raised survival from 17% to 25%. Increasing doses of short chrysotile showed no clear pattern of more benzo(a)pyrene binding to DNA. Less than 10% of the benzo(a)pyrene was broken down at every asbestos concentration. One type of DNA damage product seen in cultures without fiber was missing at the highest fiber dose; the authors said its significance was unclear. The authors suggested fiber surface area may play a major role in toxicity.

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 (in vitro) cell culture experiment
• Who was studied: Normal human dermal fibroblast cell line (CI), derived from normal newborn foreskin tissue, established at The Ohio State University
• Exposure: NIEHS chrysotile in two sizes: short (mean 6.8 by 0.16 micrometers) and intermediate (mean 21.0 by 0.17 micrometers), at 0.1 micrograms per mL to 1 mg/mL. Given alone or together with benzo(a)pyrene or benzo(e)pyrene at 0.1 to 10 micromolar, for 24 hours. DNA binding and metabolism were tested with short chrysotile plus 1 micromolar radiolabeled benzo(a)pyrene.
• Main results:
  • At 100 micrograms per mL, short chrysotile was more toxic to the fibroblasts than intermediate chrysotile (3% and 17% survival, respectively).
  • Benzo(a)pyrene and benzo(e)pyrene alone, at concentrations up to and including 10 micromolar, were not cytotoxic. They did not reduce cell survival in this colony-forming test.
  • Giving short chrysotile together with benzo(a)pyrene or benzo(e)pyrene did not decrease survival synergistically.
  • Giving benzo(a)pyrene together with intermediate chrysotile increased survival compared with intermediate chrysotile alone (25% and 17% survival, respectively). Intermediate chrysotile alone differed significantly from intermediate chrysotile plus benzo(a)pyrene and from intermediate chrysotile plus benzo(e)pyrene.
  • With data pooled by concentration, short and intermediate chrysotile did not differ significantly at 1 microgram per mL or less. They differed significantly at 10 and 100 micrograms per mL. At 1000 micrograms per mL, both types were extremely toxic, with no significant difference.
  • Increasing doses of short chrysotile produced no clear pattern of more benzo(a)pyrene binding to DNA. Binding was 1.73 plus or minus 0.50 pmole/mole deoxyribonucleotide with no chrysotile and 2.40 plus or minus 0.35 at 1000 micrograms per mL (3 replicate samples each).
  • Less than 10% of the benzo(a)pyrene was metabolized by the fibroblasts at all asbestos concentrations.
  • One benzo(a)pyrene-DNA adduct (7S-BPDE I-dG) was seen only in control cultures without fiber. It was missing in cultures given 1 mg/mL short chrysotile.
• The authors' conclusion: The authors concluded that benzopyrene showed no synergism with either short or intermediate chrysotile in this system. They suggested that available reactive surface area may play a major role in fiber toxicity: short chrysotile has more surface area per weight than intermediate chrysotile. They also suggested that organic compounds masking reactive sites could possibly decrease toxicity, and that low enzyme levels in fibroblasts could explain the low benzo(a)pyrene metabolism.
• Limitations the authors state:
  • The authors stated that the significance, if any, of the missing 7S-BPDE I-dG adduct in fiber-treated cultures was unclear. They were still investigating whether this change is dose-related.

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, Lung Cancer, Asbestos Exposure, Synergistic Effect, Fibroblast, DNA adducts.

Related studies

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• Effects of chrysotile co-exposure on BaP binding in normal human fibroblasts — M.J. Chang, N.P. Singh, et al. (1983)
• Coinhibition of viral interferon induction by benzo[a]pyrene and chrysotile asbestos — N. Hahon, J.A. Booth (1986)
• 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)
• 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)
• Enhancement of benzo[a]pyrene mutagenicity by chrysotile asbestos in rat liver epithelial cells — B. Reiss, C. Tong, et al. (1983)

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