Phosphorylation of p53 protein in A549 human pulmonary epithelial cells exposed to asbestos fibers

Our plain-English summary of Phosphorylation of p53 protein in A549 human pulmonary epithelial cells exposed to asbestos fibers, by M. Matsuoka, H. Igisu, Y. Morimoto (Environmental Health Perspectives, 2003).

The study

• Authors: M. Matsuoka, H. Igisu, Y. Morimoto
• Journal: Environmental Health Perspectives
• Published: 2003;111(4):509-12
• Cited by: 19 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

We examined effects of asbestos exposure on the phosphorylation of p53 protein in human pulmonary epithelial type II cells (A549), which express wild-type p53. In cells exposed to two different types of asbestos, chrysotile (approximately 1-6% iron content) and crocidolite (approximately 27% iron content) fibers, at the doses of 1, 5, and 10 microg/cm2 for 24 hr, the levels of p53 phosphorylated at Ser15 and p53 protein were correlated with the dose. On a per-weight basis, chrysotile was more potent in inducing Ser15 phosphorylation and accumulation of p53 protein than was crocidolite. After exposure to 10 micro g/cm2 chrysotile, the levels of p53 phosphorylated at Ser15 and of p53 protein increased after 18 hr. Among serines in p53 protein immunoprecipitated from A549 cells treated with chrysotile, only Ser15 was markedly phosphorylated. In contrast, no clear phosphorylation was observed at Ser6, Ser9, Ser20, Ser37, Ser46, or Ser392. Blocking of the extracellular signal-regulated protein kinase pathway with U0126 or inhibition of p38 activity with SB203580 did not suppress chrysotile-induced Ser15 phosphorylation. On the other hand, treatment with wortmannin, an inhibitor of DNA-activated protein kinase and ataxia-telangiectasia mutated, suppressed both chrysotile-induced Ser15 phosphorylation and accumulation of p53 protein. Treatment with either catalase or N-acetylcysteine failed to suppress chrysotile-induced Ser15 phosphorylation, suggesting that reactive oxygen species do not play a major role in the phosphorylation of p53 protein. The present results show that asbestos, particularly chrysotile, induces phosphorylation of p53 protein at Ser15 in A549 cells depending on a DNA damage-signaling pathway.

In plain English

This was a laboratory study of a line of human lung cells grown in dishes (A549 cells), not a study of people. The authors exposed the cells to standard UICC samples of chrysotile and crocidolite asbestos at 1, 5 or 10 µg per square centimetre of dish for 24 hours. They then measured p53, a protein the article says helps protect the cell's genetic material. They also measured p53 carrying a chemical tag (phosphorylation) at a site called Ser15. Both fiber types raised both measures, more so at higher doses. At every dose, weight for weight, chrysotile had a stronger effect than crocidolite. With chrysotile, the rise appeared after 18 hours. Of seven sites tested, only Ser15 was clearly tagged. Wortmannin, a drug that blocks the DNA-damage enzymes DNA-PK and ATM, reduced the effect. Drugs blocking the ERK pathway or the enzyme p38 did not, and neither did the antioxidants catalase or N-acetylcysteine. The authors concluded that the chrysotile effect depends on enzymes such as DNA-PK and ATM and might not be based on reactive oxygen species.

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 lung cells
• Who was studied: A549 human pulmonary epithelial type II cells (a cell line expressing wild-type p53), obtained from the Health Science Research Resources Bank, Osaka, Japan; blot results described as representative of three independent experiments
• Exposure: UICC standard samples of Rhodesian chrysotile and of crocidolite asbestos at 1, 5 or 10 µg of fibers per cm2 of culture vessel for 24 hr; time-course study at 10 µg/cm2 for 3 to 24 hr; 20 µM cadmium chloride used as a reference
• Main results:
  • In A549 cells exposed to 1 to 10 µg/cm2 of chrysotile or crocidolite for 24 hr, p53 phosphorylated at Ser15 and p53 protein accumulated depending on the dose
  • Chrysotile induced more marked accumulation of Ser15-phosphorylated p53 and p53 protein than crocidolite at each dose of 1, 5 and 10 µg/cm2
  • After exposure to 10 µg/cm2 chrysotile, levels of Ser15-phosphorylated p53 and p53 protein increased after 18 hr
  • In cells exposed to 10 µg/cm2 crocidolite, clear Ser15 phosphorylation was not found at 3 to 18 hr (data not shown)
  • In p53 from chrysotile-exposed cells, marked phosphorylation was found only at Ser15, not at Ser6, Ser9, Ser20, Ser37, Ser46 or Ser392
  • The ERK-pathway blocker U0126 and the p38 inhibitor SB203580, at 5, 20 and 50 µM, did not suppress chrysotile-induced Ser15 phosphorylation
  • Wortmannin (1 and 5 µM), an inhibitor of DNA-PK and ATM, suppressed chrysotile-induced Ser15 phosphorylation and p53 accumulation depending on the concentration
  • Catalase (1 and 5 KU/mL) and N-acetylcysteine (1 and 5 mM) did not suppress chrysotile-induced Ser15 phosphorylation
• The authors' conclusion: The authors concluded that chrysotile-induced Ser15 phosphorylation is dependent on the PIKK enzyme family, such as DNA-PK and ATM, and that it might be caused by mechanisms not based on reactive oxygen species

Topics

Medical terms in this study, explained in our Lexicon: Asbestos Exposure, Chrysotile, Crocidolite, A549 Cells, Reactive Oxygen Species (ROS).

Related studies

• Long and short fiber amosite asbestos alters at a different extent the redox metabolism in human lung epithelial cells — C. Riganti, E. Aldieri, et al. (2003)
• Asbestos causes translocation of p65 protein and increases NF-kappa B DNA binding activity in rat lung epithelial and pleural mesothelial cells — Y.M. Janssen, K.E. Driscoll, et al. (1997)
• Different accumulation of activated extracellular signal-regulated kinases (ERK 1/2) and role in cell-cycle alterations by epidermal growth factor, hydrogen peroxide, or asbestos in pulmonary epithelial cells — S. Buder-Hoffmann, C. Palmer, et al. (2001)
• Apoptosis induced by crocidolite asbestos in human lung epithelial cells involves inactivation of Akt and MAPK pathways — A. Baldys, P. Pande, et al. (2007)
• Efflux of reduced glutathione after exposure of human lung epithelial cells to crocidolite asbestos — S.A. Golladay, S.H. Park, et al. (1997)
• Effects of asbestos on initiation of DNA damage, induction of DNA-strand breaks, P53-expression and apoptosis in primary, SV40-transformed and malignant human mesothelial cells — B. Burmeister, T. Schwerdtle, et al. (2004)

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