Gene expression changes after exposure to six-mix in a mouse model

Our plain-English summary of Gene expression changes after exposure to six-mix in a mouse model, by E.A. Putnam, A. Smartt, A. Groves, et al (Journal of Immunotoxicology, 2008).

The study

• Authors: E.A. Putnam, A. Smartt, A. Groves, C. Schwanke, M. Brezinski, M.A. Pershouse
• Journal: Journal of Immunotoxicology
• Published: 2008;5(2):139-44
• Type of article: Historical article
• Cited by: 12 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The exposure of Libby MT residents to amphibole-contaminated vermiculite is well known. To explore the gene-environment interactions in the development of asbestos-related diseases (ARD), a mouse model of asbestos exposure using Six-mix (a combination of amphibole fibers gathered from six sites at the Libby vermiculite mine), crocidolite asbestos, or saline as a negative control was used to determine both gene expression responses by using mouse 10,000 oligonucleotide array and to visualize these changes histologically. Mice were sacrificed and whole lungs harvested for histology and microarray analysis six months following exposure via intratracheal instillation. Using an arbitrary cutoff of 1.25-fold change, genes whose RNA expression levels were specifically altered in response to the different amphibole exposures were grouped into categories by a gene ontology analysis program, GoMiner. Our hypothesis was that assessment of asbestos-responsive genes would provide a better understanding of response mechanisms. These experiments have provided new candidates for genes involved in the asbestos response pathways.

In plain English

This laboratory experiment in mice compared lung responses to Six-mix (a composite sample of the six primary amphibole varieties contaminating vermiculite from the Libby, Montana mine), crocidolite asbestos, and saline. Young C57Bl/6 mice had 100 µg of either fiber, or saline alone, placed directly into the windpipe. Their lungs were examined six months later. Under the microscope, lungs from both fiber groups showed areas of fibrosis (scarring with collagen buildup). The fibrosis was less extensive in the Six-mix group than in the crocidolite group, and saline lungs showed none. A collagen stain was measured in four mice per group. Compared with saline, the increase was statistically significant for crocidolite but not for Six-mix. Gene activity was measured on pooled lung RNA from seven to eight mice per group. It changed significantly in several gene categories after both fibers, most notably genes linked to cell membranes. The authors concluded that the experiments provided new candidate genes for asbestos response pathways. They noted that changes should also be studied at other times after exposure.

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: Animal experiment: fibers or saline instilled into the windpipe of mice, lungs harvested 6 months later for microscopy, collagen measurement and gene expression (microarray) analysis
• Who was studied: C57Bl/6 mice aged 6 to 8 weeks, in three groups (Six-mix, crocidolite, saline) of at least seven mice each
• Exposure: A single dose of 100 µg Six-mix (a US Geological Survey composite of the six primary varieties of Libby amphibole) or 100 µg crocidolite asbestos in saline, or saline alone as control
• Main results:
  • Fibrotic areas were seen in lungs of Six-mix-treated mice, but not to the same extent as in crocidolite-treated mice. No fibrotic areas were seen in saline-treated mice.
  • In the collagen (lucifer yellow) measurement, crocidolite-treated mice showed a statistically significant increase over saline-treated mice, with 4 mice in each group.
  • In Six-mix-treated mice, the change in collagen level compared with saline-treated controls was not statistically significant.
  • Gene expression was analyzed on pooled RNA from seven to eight animals per exposure group.
  • Both Six-mix-treated and crocidolite-treated lungs showed significant gene expression changes in multiple gene categories, most notably membrane-associated genes.
  • Effects shared by the two fibers included changes in transport channel and signal transduction genes.
  • Changes in genes involved in cell proliferation and several other processes (including fibrosis, tumor formation and oxidative stress) were numerous but not statistically significant.
• The authors' conclusion: The authors concluded that the experiments provided new candidate genes involved in asbestos response pathways.
• Limitations the authors state:
  • The authors noted that fibrotic and gene expression changes need to be assessed at various times after exposure. This study examined one time point (6 months).

Mines named here

Asbestos mines this study is about. Each mine's page says who ran it, when it worked, and what it produced.

• Libby vermiculite mine, Montana

All asbestos mines

Topics

The National Library of Medicine indexes this study under subjects our site covers: Asbestosis, Talc and vermiculite.

Medical terms in this study, explained in our Lexicon: Amphibole Group, vermiculite, Asbestos Exposure, Libby Vermiculite, Crocidolite, Histology.

Related studies

• Low-level fiber-induced radiographic changes caused by Libby vermiculite: a 25-year follow-up study — A.M. Rohs, J.E. Lockey, et al. (2008)
• Exposure to asbestos-containing vermiculite ore and respiratory symptoms among individuals who were children while the mine was active in Libby, Montana — L.C. Vinikoor, T.C. Larson, et al. (2010)
• Lung function, radiological changes and exposure: analysis of ATSDR data from Libby, MT, USA — D. Weill, G. Dhillon, et al. (2011)
• The morbidity and mortality of vermiculite miners and millers exposed to tremolite-actinolite: Part I. Exposure estimates — H.E. Amandus, R. Wheeler, et al. (1987)
• The morbidity and mortality of vermiculite miners and millers exposed to tremolite-actinolite: Part III. Radiographic findings — H.E. Amandus, R. Althouse, et al. (1987)
• Differences in gene expression profiles from asbestos-treated SPARC-null and wild-type mouse lungs — M.A. Pershouse, A.M. Smartt, et al. (2009)

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