Induction of altered mRNA expression profiles caused by fibrous and granular dust

Our plain-English summary of Induction of altered mRNA expression profiles caused by fibrous and granular dust, by S. Helmig, E. Dopp, S. Wenzel, et al (Molecular Medicine Reports, 2014).

The study

• Authors: S. Helmig, E. Dopp, S. Wenzel, D. Walter, J. Schneider
• Journal: Molecular Medicine Reports
• Published: 2014;9(1):217-28
• Cited by: 7 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Natural and synthetic fibres and particles are being introduced into the workplace and environment daily. Comparative analyses of the induced signalling pathways are essential in order to understand the potential hazards of these particles. To identify the molecular characteristics of particles and fibres, we selected crocidolite and chrysotile asbestos as representatives for fibered dust and titanium dioxide (TiO2) (100-200 nm), zirconium dioxide (ZrO2) (50-100 nm) and hematite (Fe2O3) (20 nm) as representatives for bio-persistent granular dust. SV-40 virus-transformed human bronchial epithelial cells (BEAS-2B) were exposed to well-defined fibres and particles. RT2 Profiler™ PCR Array Human Stress & Toxicity PathwayFinder was used to compare the relative mRNA expression of 84 genes. A detailed characterization of the dust samples used in this study was accomplished to ensure comparability to other studies. Investigation of mRNA expression of 84 signalling molecules attributed to pathways such as DNA damage and repair; oxidative/metabolic stress; growth arrest and senescence; inflammation, proliferation and carcinogenesis; and heat shock and apoptosis revealed that crocidolite and chrysotile asbestos induced mRNA expression of pathway molecules involved in proliferation and carcinogenesis, as well as inflammation. Titanium dioxide, zirconium dioxide and hematite mainly induced pathway molecules responsible for oxidative/metabolic stress and inflammation. Our findings suggest that the hazards of fibered dust mainly include the induction of direct toxicity by altering signalling pathways such as carcinogenesis and proliferation, while granular dust shows indirect toxicity by altering signalling pathways involved in inflammatory processes. PCR arrays, therefore, may be a helpful tool to estimate the hazard risk of new materials.

In plain English

This was a laboratory study of cells, not people. The authors exposed human bronchial (airway lining) cells of the BEAS-2B line to two types of asbestos, crocidolite and chrysotile. They also exposed them to three non-fibrous dusts: titanium dioxide, zirconium dioxide and hematite, an iron oxide. After 48 hours they measured the activity (mRNA expression) of 84 genes and compared exposed with unexposed cells, repeating each experiment four times. The genes covered DNA damage and repair, oxidative stress, growth arrest, inflammation, proliferation and cancer development, heat shock, and cell death. DNA damage and repair genes were raised mainly by crocidolite, then chrysotile. Titanium dioxide and hematite did not change them. Inflammation genes were raised mainly by crocidolite. One gene, cyclin D1, rose with crocidolite (1.57-fold, 95% confidence interval 1.28 to 1.87), chrysotile (1.89-fold, 1.33 to 2.44) and titanium dioxide (2.36-fold, 1.33 to 2.44). The authors reported that the asbestos fibres caused the most relevant gene changes overall. They concluded that fibrous dust appears to act mainly through direct effects on cancer-development and proliferation pathways, and granular dust indirectly through inflammatory pathways.

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 measuring gene activity (mRNA expression of 84 genes by PCR array) after exposure to dusts, compared with unexposed control cells
• Who was studied: SV-40 virus-transformed human bronchial epithelial cells (BEAS-2B cell line) from the European collection of cell cultures; unexposed cells served as controls; all experiments were repeated 4 times
• Exposure: UICC crocidolite asbestos (5 µg/cm2), UICC chrysotile asbestos (1 µg/cm2), and the granular dusts zirconium dioxide, titanium dioxide and hematite (each 10 µg/cm2), each for 48 hours
• Main results:
  • Gene activity in the DNA damage and repair pathway was increased mainly by crocidolite, followed by chrysotile. Titanium dioxide and hematite did not alter this pathway.
  • Zirconium dioxide raised one DNA repair gene, UNG (1.31; P=0.043), and lowered another, RAD50 (-1.45; P=0.038).
  • Inflammation pathway genes were increased mainly by crocidolite. Chrysotile and hematite gave a comparable moderate increase. Titanium dioxide raised CCL3 (2.79, P=0.007). Zirconium dioxide caused no changes in this pathway.
  • Cyclin D1 was the only gene in the proliferation and carcinogenesis pathway that was increased. It rose with crocidolite (1.57, P=0.004), chrysotile (1.89, P=0.019) and titanium dioxide (2.36, P=0.007).
  • Table VI gives 95% confidence intervals for these cyclin D1 (CCND1) fold changes: 1.28-1.87 for crocidolite, 1.33-2.44 for chrysotile and 1.33-2.44 for titanium dioxide. The chrysotile and titanium dioxide intervals are printed identically.
  • The largest changes were in the heat shock and apoptosis (cell death) pathways. Crocidolite, titanium dioxide and hematite changed the most heat shock genes. Crocidolite and zirconium dioxide changed the most apoptosis genes.
  • The authors stated that the asbestos fibres caused the most relevant changes in gene expression across all tested pathways.
• The authors' conclusion: The authors concluded that their findings suggest fibrous dust acts mainly through direct toxicity, altering pathways such as carcinogenesis and proliferation. They concluded that granular dust shows indirect toxicity through inflammatory pathways, and that PCR arrays may help estimate the hazard of new materials.

Topics

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

Medical terms in this study, explained in our Lexicon: Crocidolite, Chrysotile, Hematite, Inflammation, Carcinogenesis, Apoptosis.

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