Activation of protein kinase C by crocidolite asbestos in hamster tracheal epithelial cells

Our plain-English summary of Activation of protein kinase C by crocidolite asbestos in hamster tracheal epithelial cells, by M. Perderiset, J.P. Marsh, B.T. Mossman (Carcinogenesis, 1991).

The study

• Authors: M. Perderiset, J.P. Marsh, B.T. Mossman
• Journal: Carcinogenesis
• Published: 1991;12(8):1499-502
• Cited by: 27 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

To determine the mechanisms of cell signalling by asbestos in epithelial cells of the respiratory tract, the activity of protein kinase C (PKC) was examined in hamster tracheal epithelial (HTE) cells exposed to mitogenic concentrations of crocidolite asbestos. In the histone phosphorylation assay, asbestos significantly increased activity of PKC associated with the membrane fraction of HTE cells. However, in contrast to 12-O-tetradecanoylphorbol-13-acetate, which caused redistribution of almost all PKC activity from the cytosolic to the membrane fraction, the majority of the PKC activity was associated with the cytosolic fraction at all time periods examined. Asbestos did not inhibit binding of [3H]phorbol-12,13-dibutyrate to intact HTE cells, whereas binding was inhibited by the phorbol compounds phorbol dibutyrate and phorbol dibenzoate. Thus, crocidolite-induced activation of PKC does not appear to be mediated through the same mechanism as classical phorbol ester tumor promoters, compounds which activate PKC by structurally resembling diacylglycerol.

In plain English

This was a laboratory study of a hamster tracheal epithelial (HTE) cell line, carried out in the Department of Pathology at the University of Vermont. These cells line the windpipe. The authors exposed the cells to crocidolite asbestos (a UICC reference sample at 0.5, 1.0 and 1.5 micrograms per square centimeter of dish). For comparison they also exposed cells to TPA, a chemical tumor promoter. They then measured the activity and location of protein kinase C (PKC), an enzyme that passes growth signals inside cells. TPA caused a sharp drop in PKC activity in the cell fluid (cytosol) and moved the enzyme to the membrane fraction. Crocidolite also increased PKC activity in the membrane fraction. In cells given 1.0 microgram per square centimeter, this increase began by 30 minutes and peaked at 1 hour, but most of the enzyme stayed in the cytosol. Two phorbol compounds blocked a labeled phorbol ester from binding to the cells. Crocidolite did not. The authors concluded that asbestos does not appear to activate PKC through a receptor-like interaction, unlike TPA.

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) experiment on a cultured hamster tracheal epithelial cell line, measuring PKC activity and phorbol ester binding after exposure to crocidolite asbestos or phorbol compounds
• Who was studied: A hamster tracheal epithelial (HTE) cell line grown in culture dishes, Department of Pathology, University of Vermont College of Medicine, Burlington, Vermont; no human subjects
• Exposure: Crocidolite asbestos (UICC reference sample) at 0.5, 1.0 and 1.5 micrograms per square centimeter of dish, or the tumor promoter TPA (0.1 micrograms per ml), for 30 minutes to 24 hours. The phorbol compounds PDBu and PDBz were also tested in binding experiments.
• Main results:
  • In TPA-exposed cells, PKC activity in the cytosol fell sharply and PKC moved to the membrane fraction.
  • In crocidolite-exposed cells, PKC activity in the membrane fraction increased, but most of the enzyme remained in the cytosol.
  • In a time-course study, membrane PKC activity in cells exposed to crocidolite at 1.0 micrograms per square centimeter rose as early as 30 minutes and peaked at 1 hour. Table I lists membrane-fraction activity of 329 at time 0, 828 at 30 min, 5440 at 1 h and 4000 at 3 h, in picomoles of 32P incorporated per 3 min per total volume of each fraction.
  • Saturation binding analysis indicated that HTE cells have one type of binding site for the phorbol ester PDBu.
  • The phorbol compounds PDBu and PDBz both inhibited binding of labeled PDBu to HTE cells. Calculated dissociation constants were 3.87 plus or minus 1.5 micromolar for PDBu and 2.58 plus or minus 2.32 micromolar for PDBz, from triplicate experiments.
  • Crocidolite asbestos did not compete with labeled PDBu for its binding site at the fiber concentrations tested.
• The authors' conclusion: The authors concluded the following:
• Asbestos does not appear to activate PKC by a receptor-like interaction.
• Asbestos and TPA act through a common second messenger pathway in HTE cells, but by dissimilar mechanisms.
• Their results support the view that PKC activation by insoluble fibers may be of critical importance to tumor promotion in respiratory tract epithelial cells.

Topics

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

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

Related studies

• 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)
• Transfection of a manganese-containing superoxide dismutase gene into hamster tracheal epithelial cells ameliorates asbestos-mediated cytotoxicity — B.T. Mossman, P. Surinrut, et al. (1996)
• Asbestos induces nuclear factor kappa B (NF-kappa B) DNA-binding activity and NF-kappa B-dependent gene expression in tracheal epithelial cells — Y.M. Janssen, A. Barchowsky, et al. (1995)
• Asbestos-induced apoptosis is protein kinase C delta-dependent — A. Shukla, M. Stern, et al. (2003)
• Mineralogical features associated with cytotoxic and proliferative effects of fibrous talc and asbestos on rodent tracheal epithelial and pleural mesothelial cells — A.G. Wylie, H.C. Skinner, et al. (1997)
• Use of hamster tracheal organ cultures for assessing the cocarcinogenic effects of inorganic particulates on the respiratory epithelium — B.T. Mossman, J.E. Craighead (1979)

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