Asbestos induces mitochondrial DNA damage and dysfunction linked to the development of apoptosis

Our plain-English summary of Asbestos induces mitochondrial DNA damage and dysfunction linked to the development of apoptosis, by A. Shukla, M. Jung, M. Stern, et al (American Journal of Physiology. Lung Cellular and Molecular Physiology, 2003).

The study

• Authors: A. Shukla, M. Jung, M. Stern, N.K. Fukagawa, D.J. Taatjes, D. Sawyer, B. Van Houten, B.T. Mossman
• Journal: American Journal of Physiology. Lung Cellular and Molecular Physiology
• Published: 2003;285(5):L1018-25
• Cited by: 66 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

To test the hypothesis that asbestos-mediated cell injury is mediated through an oxidant-dependent mitochondrial pathway, isolated mesothelial cells were examined for mitochondrial DNA damage as determined by quantitative PCR. Mitochondrial DNA damage occurred at fourfold lower concentrations of crocidolite asbestos compared with concentrations required for nuclear DNA damage. DNA damage by asbestos was preceded by oxidant stress as shown by confocal scanning laser microscopy using MitoTracker Green FM and the oxidant probe Redox Sensor Red CC-1. These events were associated with dose-related decreases in steady-state mRNA levels of cytochrome c oxidase, subunit 3 (COIII), and NADH dehydrogenase 5. Subsequently, dose-dependent decreases in formazan production, an indication of mitochondrial dysfunction, increased mRNA expression of pro- and antiapoptotic genes, and increased numbers of apoptotic cells were observed in asbestos-exposed mesothelial cells. The possible contribution of mitochondrial-derived pathways to asbestos-induced apoptosis was confirmed by its significant reduction after pretreatment of cells with a caspase-9 inhibitor. Apoptosis was decreased in the presence of catalase. Last, use of HeLa cells transfected with a mitochondrial transport sequence targeting the human DNA repair enzyme 8-oxoguanine DNA glycosylase to mitochondria demonstrated that asbestos-induced apoptosis was ameliorated with increased cell survival. Studies collectively indicate that mitochondria are initial targets of asbestos-induced DNA damage and apoptosis via an oxidant-related mechanism.

In plain English

This was a laboratory study of cells grown in dishes, not a study of people. The authors exposed mesothelial cells, taken from the chest lining (parietal pleura) of rats, to crocidolite asbestos at 1.25, 2.5 or 5.0 micrograms per square centimeter of dish. They also used hydrogen peroxide and, in some experiments, human HeLa cells. At 24 hours, asbestos caused dose-related damage to mitochondrial DNA, the DNA inside the cell's energy-producing structures. Nuclear DNA was damaged at the higher concentration but not the lowest, and it had fully recovered by 48 hours. Asbestos produced oxidants that collected in mitochondria near the fibers. It also lowered messenger RNA levels (the working copies of genes) for two mitochondrial genes, reduced a measure of mitochondrial function, and increased programmed cell death (apoptosis). Apoptosis was reduced by a caspase-9 inhibitor and by the enzyme catalase. It was also reduced in HeLa cells engineered to deliver a DNA repair enzyme (hOGG) to mitochondria. The authors concluded that mitochondrial genes were more sensitive than nuclear genes to asbestos-induced DNA damage.

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: Pleural mesothelial cells from Fischer 344 rats (University of Vermont), used between passages 4 and 10. Also HeLa cells carrying either a mitochondrial-targeted DNA repair enzyme (hOGG) or a control vector.
• Exposure: Crocidolite asbestos (National Institute of Environmental Health Sciences reference sample) at 1.25, 2.5 or 5.0 micrograms per square centimeter of dish, with glass beads as a control particle. Hydrogen peroxide (100 to 300 micromolar) was used as a comparison oxidant. HeLa cells were exposed to 2.5, 5 and 10 micrograms per square centimeter of dish.
• Main results:
  • In rat mesothelial cells, mitochondrial DNA damage occurred at lower asbestos concentrations and persisted longer (48 hours) than nuclear DNA damage.
  • Nuclear DNA showed no damage at the lowest asbestos concentration (1.25 micrograms per square centimeter) and had completely recovered by 48 hours.
  • At 8 hours, asbestos caused oxidants to localize in mitochondria, focally at sites where fibers were deposited.
  • Asbestos lowered steady-state mRNA levels of the mitochondrial genes COIII (persisting for 8 hours) and ND5 (transiently but significantly).
  • At 24 hours, the highest asbestos concentration (5 micrograms per square centimeter) significantly reduced formazan production, a sign of mitochondrial dysfunction.
  • Asbestos increased expression of bax, bcl-2, bcl-xL, caspase-2, caspase-3 and fas. Caspase-1 and fas ligand did not change.
  • A caspase-9 inhibitor significantly reduced both asbestos- and hydrogen peroxide-induced apoptosis in rat mesothelial cells.
  • Catalase reduced asbestos-associated apoptosis compared with asbestos alone. Cells given boiled (inactivated) catalase still showed elevated apoptosis.
  • In HeLa cells with mitochondrial-targeted hOGG, asbestos-induced apoptosis was selectively and significantly inhibited.
  • Control-vector HeLa cells showed dose-related decreases in cell numbers after asbestos. HeLa cells with hOGG showed increased numbers of viable cells at all asbestos concentrations.
• The authors' conclusion: The authors concluded that mitochondrial genes were more sensitive than nuclear genes to asbestos-induced DNA damage. They suggested that mitochondria are initial targets of asbestos-induced DNA damage and apoptosis through an oxidant-related mechanism.
• Limitations the authors state:
  • The authors noted that hydrogen peroxide was not evaluated for comparison in the mitochondrial gene expression (COIII and ND5) experiments.

Topics

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

Related studies

• Phagocytosis of crocidolite asbestos induces oxidative stress, DNA damage, and apoptosis in mesothelial cells — W. Liu, J.D. Ernst, et al. (2000)
• SIRT3 deficiency promotes lung fibrosis by augmenting alveolar epithelial cell mitochondrial DNA damage and apoptosis — R.P. Jablonski, S.J. Kim, et al. (2017)
• Mitochondria-targeted Ogg1 and aconitase-2 prevent oxidant-induced mitochondrial DNA damage in alveolar epithelial cells — S.J. Kim, P. Cheresh, et al. (2014)
• The Role of Mitochondrial DNA in Mediating Alveolar Epithelial Cell Apoptosis and Pulmonary Fibrosis — S.J. Kim, P. Cheresh, et al. (2015)
• Asbestos-induced phosphorylation of epidermal growth factor receptor is linked to c-fos and apoptosis — C.L. Zanella, C.R. Timblin, et al. (1999)
• Asbestos-induced pulmonary toxicity: role of DNA damage and apoptosis — D. Upadhyay, D.W. Kamp (2003)

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