Apoptosis is observed in mesothelial cells after exposure to crocidolite asbestos

Our plain-English summary of Apoptosis is observed in mesothelial cells after exposure to crocidolite asbestos, by K.A. BéruBé, T.R. Quinlan, H. Fung, et al (American Journal of Respiratory Cell and Molecular Biology, 1996).

The study

• Authors: K.A. BéruBé, T.R. Quinlan, H. Fung, J. Magae, P. Vacek, D.J. Taatjes, B.T. Mossman
• Journal: American Journal of Respiratory Cell and Molecular Biology
• Published: 1996;15(1):141-7
• Cited by: 80 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Asbestos causes protracted, dose-dependent increases in steady-state mRNA levels of the proto-oncogenes c-fos and c-jun, and AP-1 DNA-binding activity in normal rat pleural mesothelial (RPM) cells (1). To determine the phenotypic end points of overexpression of these early response genes by asbestos, both cell proliferation and apoptosis were examined in confluent RPM cells exposed to a range of concentrations (1.25 to 10 micrograms/cm2 dish) of crocidolite asbestos for 24 and 48 h. Quantitation of RPM cells pulsed with 5-bromo-2'-deoxyuridine revealed that asbestos caused dose-dependent decreases in cells undergoing DNA synthesis. Decreases in cell proliferation were accompanied by dose-related increases in apoptosis using (1) terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling (i.e., ApopTag technique), (2) 4',6-diamidino-2-phenylindole cell staining, and (3) fluorescent-activated cell sorter after incorporation of propidium iodide. Less striking but significant dose-related increases in apoptosis were observed in RPM cells exposed to H2O2 (300 microM), and no apoptosis was seen after exposure of cells to high concentrations (10 micrograms/cm2 dish) of glass beads. Our results are unique in that they demonstrate that asbestos induces apoptosis in mesothelial cells at concentrations eliciting increased expression of the proto-oncogenes c-fos and c-jun.

In plain English

This laboratory study exposed normal rat pleural mesothelial cells, from the lining of the chest cavity, to crocidolite asbestos. Cells in culture dishes received 1.25 to 10 micrograms per square centimeter of dish for 24 and 48 hours. The researchers measured how many cells were copying their DNA, a sign of cell division. They also measured apoptosis, a form of programmed cell death, using three separate methods. Asbestos caused significant dose-related decreases in DNA copying at both time points. All three methods found significant increases in apoptosis at 5.0 micrograms per square centimeter, but not at 1.25. In one representative cell-sorting analysis, 3.6% of untreated cells were apoptotic, compared with 36.6% of cells exposed to 5.0 for 48 hours. Glass beads did not significantly increase apoptosis. Hydrogen peroxide did so at its highest concentration tested, 300 micromolar. The authors concluded that their work was the first to show that asbestos induces apoptosis in a target cell of disease. They noted that at 5.0, too many cells came loose by 72 hours to analyze.

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 cultured rat cells
• Who was studied: Normal rat pleural mesothelial (RPM) cells grown in culture and used at passages 5 through 10, in a laboratory at the University of Vermont. Experiments were performed in triplicate. Dates are not stated.
• Exposure: Crocidolite asbestos (mean fiber length 11.4 micrometers) at 1.25 to 10 micrograms per square centimeter of dish for 24 and 48 hours. Apoptosis was measured at 1.25 and 5.0. For comparison, cells were also exposed to glass beads (10 micrograms per square centimeter) and to hydrogen peroxide (100 to 300 micromolar) for 24 hours.
• Main results:
  • Compared with untreated control cells, crocidolite caused significant (P less than 0.05) dose-related decreases in DNA synthesis (BrdU incorporation) at both 24 and 48 hours.
  • All three apoptosis methods showed significant increases (P less than 0.05) in apoptosis in cells exposed to 5.0 micrograms per square centimeter of crocidolite, but not at 1.25 micrograms per square centimeter.
  • In representative cell-sorting (FACS) profiles, 3.6% of untreated control cells were apoptotic.
  • In the representative FACS profile of cells exposed to 5.0 micrograms per square centimeter of crocidolite for 48 hours, 36.6% of cells were apoptotic.
  • In the same representative profile, exposed cells showed about a 2-fold decrease in the share of cells in S phase (dividing), compared with controls.
  • At 5.0 micrograms per square centimeter, most cells were in contact with fibers, but apoptotic cells were not the majority of cells in culture.
  • Apoptosis was not significantly increased at the earlier times examined (2 to 6 hours) after exposure to 5.0 micrograms per square centimeter of crocidolite.
  • Glass beads (10 micrograms per square centimeter, 24 hours) did not significantly increase apoptosis: 3.65 plus or minus 0.05% versus 3.2% in controls.
  • Hydrogen peroxide at 300 micromolar for 24 hours produced 8.1 plus or minus 1.60% apoptotic cells, versus 3.2% in controls (p less than 0.05). Lower concentrations did not produce significant increases.
• The authors' conclusion: The authors concluded that their work was the first to show that asbestos induces apoptosis in a target cell of disease.
• Limitations the authors state:
  • At 72 hours at 5.0 micrograms per square centimeter, increased cell sloughing left too few cells for analysis, so results are reported only for 24 and 48 hours.

Topics

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

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

Related studies

• Novel cell imaging techniques show induction of apoptosis and proliferation in mesothelial cells by asbestos — J.L. Goldberg, C.L. Zanella, et al. (1997)
• Apoptosis induced by crocidolite asbestos in human lung epithelial cells involves inactivation of Akt and MAPK pathways — A. Baldys, P. Pande, et al. (2007)
• Patterns of c-fos and c-jun proto-oncogene expression, apoptosis, and proliferation in rat pleural mesothelial cells exposed to erionite or asbestos fibers — C.R. Timblin, G.D. Guthrie, et al. (1998)
• Phagocytosis of crocidolite asbestos induces oxidative stress, DNA damage, and apoptosis in mesothelial cells — W. Liu, J.D. Ernst, et al. (2000)
• Dielectric changes in membrane properties and cell interiors of human mesothelial cells in vitro after crocidolite asbestos exposure — E. Dopp, L. Jonas, et al. (2000)
• Patterns of 8-hydroxydeoxyguanosine formation in DNA and indications of oxidative stress in rat and human pleural mesothelial cells after exposure to crocidolite asbestos — H. Fung, Y.W. Kow, et al. (1997)

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