Modulation of cell and DNA damage by poly(ADP)ribose polymerase in lung cells exposed to H(2)O(2) or asbestos fibres

Our plain-English summary of Modulation of cell and DNA damage by poly(ADP)ribose polymerase in lung cells exposed to H(2)O(2) or asbestos fibres, by T. Ollikainen, A. Puhakka, K. Kahlos, et al (Mutation Research, 2000).

The study

• Authors: T. Ollikainen, A. Puhakka, K. Kahlos, K. Linnainmaa, V.L. Kinnula
• Journal: Mutation Research
• Published: 2000;470(1):77-84
• Cited by: 29 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Poly(ADP)ribose polymerase (PARP) may participate in cell survival, apoptosis and development of DNA damage. We investigated the role of PARP in transformed human pleural mesothelial (MeT-5A) and alveolar epithelial (A549) cells exposed from 0.05 to 5mM hydrogen peroxide (H(2)O(2)) or crocidolite asbestos fibres (1-10 microg/cm(2)) in the presence and absence of 3-aminobenzamide (ABA), a PARP inhibitor. The cells were investigated for the development of cell injury, DNA single strand breaks and depletion of the cellular high-energy nucleotides. Compared to H(2)O(2), fibres caused a minor decrease in cell viability and effect on the cellular high-energy nucleotide depletion, and a marginal effect on the development of DNA strand breaks when assessed by the single cell gel electrophoresis (the Comet assay). Inhibition of PARP transiently protected the cells against acute H(2)O(2) related irreversible cell injury when assessed by microculture tetrazolium dye (XTT) assay and potentiated oxidant related DNA damage when assessed by the Comet assay. However, PARP inhibition had no significant effect on fibre-induced cell or DNA toxicity with the exception of one fibre concentration (2 microg/cm(2)) in MeT-5A cells. Apoptosis is often associated with PARP cleavage and caspase activation. Fibres did not cause PARP cleavage or activation of caspase 3 further confirming previous results about relatively low apoptotic potential of asbestos fibres. In conclusion, maintenance of cellular high-energy nucleotide pool and high viability of asbestos exposed cells may contribute to the survival and malignant conversion of lung cells exposed to the fibres.

In plain English

This was a laboratory study of cultured human cells. The authors exposed two transformed human cell lines, pleural mesothelial (MeT-5A) and alveolar epithelial (A549) cells, to hydrogen peroxide or crocidolite asbestos fibres for 6 to 48 hours. Some cells were also given 3-aminobenzamide, a drug that blocks the enzyme PARP. At the highest fibre dose, 48-hour relative viability (XTT assay) was 77% in MeT-5A and 96% in A549 cells; only MeT-5A injury was significant. Only hydrogen peroxide depleted the cells' high-energy nucleotides. Fibres raised DNA strand breaks slightly but significantly in both cell types. Blocking PARP temporarily protected cells against acute hydrogen peroxide injury and increased the DNA damage it caused. With fibres, blocking PARP slightly but significantly increased DNA strand breaks only at one lower dose in MeT-5A cells; it did not change their injury at the highest dose. Fibres caused no PARP or caspase 3 cleavage, which are markers of programmed cell death. The authors concluded that PARP may play a minor role in direct fibre toxicity. They cautioned that cell-culture results are difficult to extrapolate to the body.

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 human cell lines
• Who was studied: Two transformed human cell lines from the American Type Culture Collection: pleural mesothelial cells (MeT-5A) and alveolar epithelial cells (A549)
• Exposure: Hydrogen peroxide (0.05 to 5 mM) or crocidolite asbestos fibres (1 to 10 per square centimetre; the article prints 'mg/cm2', while the PubMed abstract gives micrograms) for 6 to 48 hours. Some experiments added 10 mM 3-aminobenzamide (ABA), a PARP inhibitor.
• Main results:
  • At the 10 fibre concentration for 48 hours, there was significant cell injury in MeT-5A cells but not in A549 cells. Relative viability in the XTT assay was 96% in A549 cells and 77% in MeT-5A cells.
  • PARP inhibition by ABA prevented acute cell injury caused by hydrogen peroxide in A549 and MeT-5A cells. In the authors' discussion, this protection is described as transient. It had no effect on crocidolite toxicity (10 concentration) in MeT-5A cells.
  • Depletion of high-energy nucleotides occurred only in cells exposed to hydrogen peroxide, not crocidolite, in both cell types.
  • In the Comet assay, fibres slightly but significantly increased DNA strand breaks (mean tail extent moment) in both cell types.
  • PARP inhibition increased DNA strand breaks clearly in both cell types exposed to hydrogen peroxide. In fibre-exposed cells, it increased them slightly but significantly only at the 2 fibre concentration in MeT-5A cells.
  • No PARP cleavage was seen in either cell type, and fibres caused no caspase 3 cleavage with or without ABA.
• The authors' conclusion: The authors concluded that PARP activation may play a minor role in direct fibre-induced toxicity of the target cells. They also concluded that the maintenance of the high-energy nucleotide pool and cell viability may be of importance for malignant transformation of asbestos-exposed cells.
• Limitations the authors state:
  • The Comet assay may be insensitive for some toxicants and cell types. High variation between individual cells makes minor changes hard to interpret.
  • Cell-culture results are difficult to extrapolate to the body. They underestimate the effects of chronic inflammation and oxidant stress during prolonged exposure.
  • In MeT-5A cells at the 10 fibre concentration, marked loss of viability made DNA damage assessment difficult.

Topics

Medical terms in this study, explained in our Lexicon: Apoptosis, Crocidolite, Comet Assay, MeT-5A Cells.

Related studies

• Asbestos exposure affects poly(ADP-ribose) polymerase-1 activity: role in asbestos-induced carcinogenesis — M. Tomasetti, M. Amati, et al. (2011)
• Cigarette smoke and asbestos activate poly-ADP-ribose polymerase in alveolar epithelial cells — D.W. Kamp, M. Srinivasan, et al. (2001)
• Modulation of DNA single-strand breaks by intracellular glutathione in human lung cells exposed to asbestos fibers — A. Puhakka, T. Ollikainen, et al. (2002)
• Synthesis of poly(ADP-ribose) in asbestos treated rat pleural mesothelial cells in culture — H.Y. Dong, A. Buard, et al. (1995)
• Cytotoxicity of oxidants and asbestos fibers in cultured human mesothelial cells — V.L. Kinnula, K. Aalto, et al. (1994)
• Role of oxygen derivatives in the cytotoxicity and DNA damage produced by asbestos on rat pleural mesothelial cells in vitro — H. Dong, A. Buard, et al. (1994)

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