Toxicogenomic comparison of multi-wall carbon nanotubes (MWCNTs) and asbestos

Our plain-English summary of Toxicogenomic comparison of multi-wall carbon nanotubes (MWCNTs) and asbestos, by J.S. Kim, K.S. Song, J.K. Lee, et al (Archives of Toxicology, 2012).

The study

• Authors: J.S. Kim, K.S. Song, J.K. Lee, Y.C. Choi, I.S. Bang, C.S. Kang, I.J. Yu
• Journal: Archives of Toxicology
• Published: 2012;86(4):553-62
• Cited by: 27 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Carbon nanotubes (CNTs) have specific properties, including electrical and thermal conductivity, great strength, and rigidity, that allow them to be used in many fields. However, this increasing contact with humans and the environment is also raising health and safety concerns. Thus, research on the safety of CNTs has attracted much interest, including a comparison of the toxic effects of asbestos and carbon nanotubes, due to their physical similarity of a high aspect ratio (length/diameter). Nonetheless, there has not yet been a toxicogenomic comparison. Therefore, to examine toxicogenomic effects, the 50% growth inhibition (GI(50)) concentration was determined for multi-wall carbon nanotubes (MWCNTs) and asbestos (crocidolite) and found to be approximately 0.0135 and 0.066%, respectively, in the case of 24-h treatment of normal human bronchial epithelia (NHBE) cells. Using these GI(50) concentrations, NHBE cells were then treated with MWCNTs and asbestos for 6 and 24 h, followed by a DNA microarray analysis. Among 31,647 genes, 1,201 and 1,252 were up-regulated by both asbestos and MWCNTs after 6 and 24 h of exposure, respectively. Meanwhile, 1,977 and 1,542 genes were down-regulated by both asbestos and MWNCTs after 6 and 24 h of exposure, respectively. In particular, the asbestos and MWCNTs both induced an over twofold up- and down-regulated expression of 12 mesothelioma-related genes and 22 lung cancer-related genes when compared with the negative control. Plus, the genes induced by the MWCNT exposure were expressed in the brain, lungs, epithelium, liver, and colon.

In plain English

This laboratory study compared gene activity changes caused by multi-wall carbon nanotubes (MWCNTs) and crocidolite asbestos (the positive control) in normal human bronchial epithelial (NHBE) cells. The authors first found the concentration that halved cell growth over 24 hours: 0.0135% for MWCNTs and 0.066% for crocidolite. Cells were then exposed at these concentrations for 6 and 24 hours and tested with DNA microarrays. Of 31,647 genes, both materials raised the activity of 1,201 at 6 hours and 1,252 at 24 hours, and lowered 1,977 and 1,542 at those times. The authors reported that both materials changed by more than twofold 12 genes they classed as mesothelioma-related and 22 as lung cancer-related, compared with the negative control. The authors reported that TNF and interleukins (IL6, IL8, IL10) were raised by both, generally more strongly by asbestos. However, at 24 hours IL10 rose more with MWCNTs (2.82-fold) than with asbestos (1.63-fold). The authors concluded that the analysis revealed many similarities in the two materials' effects on these cells. They noted that the results do not reflect everything that happens in animals and humans.

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 study comparing gene expression by DNA microarray (toxicogenomic comparison)
• Who was studied: Normal human bronchial epithelial (NHBE) cell lines obtained from a commercial supplier (Cambrex, USA), grown in culture. No people or animals were studied.
• Exposure: MWCNTs from Hanwha Nanotech (Korea) and crocidolite asbestos from the South African National Institute of Occupational Health (positive control), both dispersed in a DPPC solution. Cells were treated at each material's 50% growth inhibition concentration (0.0135% MWCNTs, 0.066% crocidolite) for 6 and 24 hours. The negative control was treatment with DPPC alone.
• Main results:
  • After 24 hours, the concentration causing 50% growth inhibition of NHBE cells was 0.0135% for MWCNTs and 0.066% for crocidolite.
  • Of 31,647 genes, 1,201 (at 6 hours) and 1,252 (at 24 hours) were up-regulated by both asbestos and MWCNTs.
  • 1,977 (at 6 hours) and 1,542 (at 24 hours) genes were down-regulated by both asbestos and MWCNTs.
  • Compared with the negative control, asbestos and MWCNTs both changed by more than twofold (up or down) the expression of 12 mesothelioma-related genes and 22 lung cancer-related genes.
  • The authors stated that TNF and interleukins (IL6, IL8, IL10) were up-regulated by both treatments but were more affected by asbestos than by MWCNTs. For example, the IL8 ratio was 28.58 (asbestos, 6 h), 2.05 (MWCNTs, 6 h), 53.77 (asbestos, 24 h) and 6.64 (MWCNTs, 24 h).
  • The tables show an exception for IL10: the ratio was 2.92 (asbestos, 6 h), 2.54 (MWCNTs, 6 h), 1.63 (asbestos, 24 h) and 2.82 (MWCNTs, 24 h). At 24 hours, therefore, IL10 was higher with MWCNTs than with asbestos.
  • TGF b1 expression was slightly up-regulated after the short-term (6 h) treatment and reversed after the long-term (24 h) treatment with both asbestos and MWCNTs.
  • In database analysis of MWCNT-affected genes, genes down-regulated by MWCNTs were associated with colorectal, lung and gastric cancer. MWCNTs down-regulated control genes in the brain, lungs and liver.
• The authors' conclusion: The authors concluded that the microarray analysis revealed many similarities in the physiological effects of MWCNTs and asbestos on NHBE cells. They also concluded that MWCNT treatment induced genes associated with neuropathy and cancer.
• Limitations the authors state:
  • The authors stated that the cell results do not reflect all the phenomena in the living systems of animals and humans.

Topics

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

Medical terms in this study, explained in our Lexicon: Aspect Ratio (Length-to-diameter ratio), Crocidolite, Mesothelioma, Lung Cancer, Epithelium.

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