Asbestos induces nuclear factor kappa B (NF-kappa B) DNA-binding activity and NF-kappa B-dependent gene expression in tracheal epithelial cells

Our plain-English summary of Asbestos induces nuclear factor kappa B (NF-kappa B) DNA-binding activity and NF-kappa B-dependent gene expression in tracheal epithelial cells, by Y.M. Janssen, A. Barchowsky, M. Treadwell, et al (Proceedings of the National Academy of Sciences of the United States of America, 1995).

The study

• Authors: Y.M. Janssen, A. Barchowsky, M. Treadwell, K.E. Driscoll, B.T. Mossman
• Journal: Proceedings of the National Academy of Sciences of the United States of America
• Published: 1995;92(18):8458-62
• Cited by: 138 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Nuclear factor kappa B (NF-kappa B) is a transcription factor regulating expression of genes intrinsic to inflammation and cell proliferation--features of asbestos-associated diseases. In studies here, crocidolite asbestos caused protracted and dose-responsive increases in proteins binding to nuclear NF-kappa B-binding DNA elements in hamster tracheal epithelial (HTE) cells. This binding was modulated by cellular glutathione levels. Antibodies recognizing p65 and p50 protein members of the NF-kappa B family revealed these proteins in two of the DNA complexes. Transient transfection assays with a construct containing six NF-kappa B-binding DNA consensus sites linked to a luciferase reporter gene indicated that asbestos induced transcriptional activation of NF-kappa B-dependent genes, an observation that was confirmed by northern blot analyses for c-myc mRNA levels in HTE cells. Studies suggest that NF-kappa B induction by asbestos is a key event in regulation of multiple genes involved in the pathogenesis of asbestos-related lung cancers.

In plain English

This was a laboratory study of hamster tracheal epithelial (HTE) cells grown in dishes, not a study of people. The authors exposed the cells to crocidolite asbestos and measured NF-kappa B, a protein that switches on genes involved in inflammation and cell growth. At 1.25 or 5 micrograms per square centimeter of dish, crocidolite increased NF-kappa B binding to its DNA target in a dose-dependent way for up to 24 hours. The increase in the complex containing the p65 and p50 proteins was statistically significant at 4 and 24 hours. Smaller increases in the p50-only complex were not statistically significant. Pretreating cells with the antioxidant N-acetyl-L-cysteine reduced the asbestos-related increase. In cells carrying an NF-kappa B-controlled reporter gene, crocidolite significantly raised reporter activity only at 16 hours. Crocidolite also raised levels of c-myc gene messages, significantly from 4 hours on, increasing over time. The authors suggested that NF-kappa B activation by asbestos is a key event in regulating multiple genes involved in asbestos-related lung cancers.

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 cell line, using gel-shift assays, transient transfection with a reporter gene, and Northern blots
• Who was studied: A line of hamster tracheal epithelial (HTE) cells, which the authors describe as a progenitor cell type of bronchogenic carcinoma, isolated and kept in the authors' laboratory (University of Vermont)
• Exposure: NIEHS-processed crocidolite asbestos from the Thermal Insulation Manufacturers Association Fiber Repository. It was added to the culture medium at concentrations the authors describe as nontoxic: 1.25 or 5 micrograms per square centimeter of dish for the binding and reporter studies, and 2.5 micrograms per square centimeter for the c-myc studies. Lipopolysaccharide (LPS) served as a positive control. In some experiments the antioxidant NAC (10 mM) was added before the asbestos.
• Main results:
  • In HTE cells, NF-kappa B DNA-binding complexes increased with crocidolite dose, for as long as 24 hours of exposure.
  • The complex containing both p65 and p50 increased significantly after 4 and 24 hours of crocidolite exposure (P < 0.05). Increases in the p50 complex were smaller and not statistically significant.
  • Antibody tests showed that the upper binding complex contained both p65 and p50, while the lower complex contained p50.
  • Pretreatment with NAC (10 mM) reduced the asbestos-related increases in NF-kappa B DNA binding (P < 0.05). NAC alone, without asbestos, did not affect binding.
  • In HTE cells carrying the NF-kappa B reporter construct, crocidolite (5 micrograms per square centimeter) significantly increased reporter (luciferase) activity only at 16 hours. LPS increased it at both 4 and 16 hours.
  • No changes were seen in HTE cells carrying the empty control construct.
  • In HTE cells exposed to crocidolite (2.5 micrograms per square centimeter), c-myc messenger RNA levels rose. The rise was statistically significant from 4 hours of exposure (P < 0.05) and increased over time (P < 0.001 by linear trend analysis).
• The authors' conclusion: The authors suggested that induction of NF-kappa B by asbestos is a key event in regulating multiple genes involved in the development of asbestos-related lung cancers. They also suggested that oxidative stress caused by asbestos may be involved in the increased NF-kappa B binding.

Topics

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

Medical terms in this study, explained in our Lexicon: Nuclear Factor kappa B (NF-κB), Inflammation, Crocidolite, Glutathione (GSH), Lung Cancer.

Related studies

• 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)
• Crocidolite activates NF-kappa B and MIP-2 gene expression in rat alveolar epithelial cells. Role of mitochondrial-derived oxidants — K.E. Driscoll, J.M. Carter, et al. (1998)
• 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)
• Cigarette smoke increases amosite asbestos fiber binding to the surface of tracheal epithelial cells — A. Churg, J. Sun, et al. (1998)
• 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)
• 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)

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