Raw single-wall carbon nanotubes induce oxidative stress and activate MAPKs, AP-1, NF-kappaB, and Akt in normal and malignant human mesothelial cells

Our plain-English summary of Raw single-wall carbon nanotubes induce oxidative stress and activate MAPKs, AP-1, NF-kappaB, and Akt in normal and malignant human mesothelial cells, by M. Pacurari, X.J. Yin, J. Zhao, et al (Environmental Health Perspectives, 2008).

The study

• Authors: M. Pacurari, X.J. Yin, J. Zhao, M. Ding, S.S. Leonard, D. Schwegler-Berry, B.S. Ducatman, D. Sbarra, M.D. Hoover, V. Castranova, V. Vallyathan
• Journal: Environmental Health Perspectives
• Published: 2008;116(9):1211-7
• Cited by: 218 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background: Single-wall carbon nanotubes (SWCNTs), with their unique physicochemical and mechanical properties, have many potential new applications in medicine and industry. There has been great concern subsequent to preliminary investigations of the toxicity, biopersistence, pathogenicity, and ability of SWCNTs to translocate to subpleural areas. These results compel studies of potential interactions of SWCNTs with mesothelial cells.

Objective: Exposure to asbestos is the primary cause of malignant mesothelioma in 80-90% of individuals who develop the disease. Because the mesothelial cells are the primary target cells of asbestos-induced molecular changes mediated through an oxidant-linked mechanism, we used normal mesothelial and malignant mesothelial cells to investigate alterations in molecular signaling in response to a commercially manufactured SWCNT.

Methods: In the present study, we exposed mesothelial cells to SWCNTs and investigated reactive oxygen species (ROS) generation, cell viability, DNA damage, histone H2AX phosphorylation, activation of poly(ADP-ribose) polymerase 1 (PARP-1), stimulation of extracellular signal-regulated kinase (ERKs), Jun N-terminal kinases (JNKs), protein p38, and activation of activator protein-1 (AP-1), nuclear factor kappaB (NF-kappaB), and protein serine-threonine kinase (Akt).

Results: Exposure to SWCNTs induced ROS generation, increased cell death, enhanced DNA damage and H2AX phosphorylation, and activated PARP, AP-1, NF-kappaB, p38, and Akt in a dose-dependent manner. These events recapitulate some of the key molecular events involved in mesothelioma development associated with asbestos exposure.

Conclusions: The cellular and molecular findings reported here do suggest that SWCNTs can cause potentially adverse cellular responses in mesothelial cells through activation of molecular signaling associated with oxidative stress, which is of sufficient significance to warrant in vivo animal exposure studies.

In plain English

This was a laboratory study of cultured normal and malignant human mesothelial cells. No people or animals were studied. The cells were exposed to commercially made raw single-wall carbon nanotubes. These contained nickel (20.6%), yttrium (6.2%) and iron (0.07%). Some effects were compared with crocidolite asbestos. The nanotubes caused both cell types to produce reactive oxygen species, more so in the normal cells. They lowered cell survival as the dose increased, and they damaged DNA. At 50 micrograms per square centimetre, crocidolite reduced cell viability by 75–77%, while nanotubes reduced it by 30% in normal cells and 27% in malignant cells. In normal cells, two nanotube doses increased DNA tail migration 5.2-fold and 6.6-fold. The nanotubes also switched on several cell-signalling proteins, and some of these (ERK, p38, Akt) responded mainly or only in the malignant cells. Crocidolite produced stronger effects in several tests. The authors concluded that the nanotubes were biologically active on these cells, though less so than crocidolite. They said it remains uncertain whether nanotube exposure is a mesothelioma risk in 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: In vitro laboratory study of cultured human cells (cell-culture experiment), with some comparisons to crocidolite asbestos
• Who was studied: Cultured normal human mesothelial (NM) cells and malignant mesothelial (MM) cells; most assays reported as three experiments. No cell sources or dates are given in the main text (details are in supplemental material)
• Exposure: Commercially manufactured raw single-wall carbon nanotubes (diameters 0.8 to 2.0 nm) containing nickel 20.6%, yttrium 6.2% and iron 0.07%, at doses mostly from 12.5 to 125 micrograms per square centimetre. Some results were compared with crocidolite asbestos
• Main results:
  • Nanotube exposure produced reactive oxygen species (hydroxyl radicals) in both cell types, more in normal than in malignant cells
  • Catalase reduced the nanotube-induced hydroxyl radical signal by 39% in normal cells (p less than 0.05) and by 43% in malignant cells. Deferoxamine reduced it by 38% and 44% respectively
  • At 50 micrograms per square centimetre, crocidolite reduced cell viability by 75–77%. Nanotubes reduced it by 30% in normal cells and 27% in malignant cells
  • In normal cells, 25 or 50 micrograms per square centimetre of nanotubes for 24 hours increased DNA tail migration 5.2-fold and 6.6-fold respectively (comet assay)
  • In malignant cells, adding catalase, SOD or deferoxamine to nanotubes reduced DNA damage by 35%, 30% and 32% respectively
  • Nanotubes caused a nominal increase in H2AX phosphorylation (a marker of DNA double-strand breaks), moderately higher in malignant cells. Crocidolite caused significantly greater phosphorylation in both cell types
  • Nanotubes and crocidolite both produced time-dependent activation of cleaved PARP in normal cells
  • In malignant cells, NF-kappaB activation peaked only after 4 hours, at 2-fold above the basal level
  • Nanotubes increased phosphorylation of ERKs and p38 but not JNKs in malignant cells. Changes in normal cells were very minimal
  • Akt was activated only in malignant cells: a 1.6-fold increase at 125 micrograms per square centimetre of nanotubes, compared with 1.7-fold for the positive control EGF, at 60 minutes. No p-Akt was seen in normal cells
• The authors' conclusion: The authors concluded that normal mesothelial cells were more susceptible to raw nanotube-induced injury, and that the nanotubes were bioactive on mesothelial cells in vitro, though with lower activity than crocidolite. They called for in vivo animal studies
• Limitations the authors state:
  • The authors state it remains uncertain whether nanotube exposure is a risk for mesothelioma in humans, and that animal studies are needed
  • The LDH viability test could not be used because the nanotubes adsorbed the enzyme, so only MTT and trypan blue results were presented
  • The exact mechanism by which nanotubes damage DNA is not known

Topics

Medical terms in this study, explained in our Lexicon: Oxidative Stress, Mesothelial Cells, biopersistence, Malignant Mesothelioma, Reactive Oxygen Species (ROS), Mesothelioma, Asbestos Exposure.

Related studies

• Single- and multi-wall carbon nanotubes versus asbestos: are the carbon nanotubes a new health risk to humans? — M. Pacurari, V. Castranova, et al. (2010)
• Activation of p38 MAP kinase by asbestos in rat mesothelial cells is mediated by oxidative stress — W.A. Swain, K.J. O'Byrne, et al. (2004)
• Apoptosis induced by crocidolite asbestos in human lung epithelial cells involves inactivation of Akt and MAPK pathways — A. Baldys, P. Pande, et al. (2007)
• Dispersion medium modulates oxidative stress response of human lung epithelial cells upon exposure to carbon nanomaterial samples — E. Herzog, H.J. Byrne, et al. (2009)
• Carboxylated short single-walled carbon nanotubes but not plain and multi-walled short carbon nanotubes show in vitro genotoxicity — M. Mrakovcic, C. Meindl, et al. (2015)
• Chronic exposure to carbon nanotubes induces invasion of human mesothelial cells through matrix metalloproteinase-2 — W. Lohcharoenkal, L. Wang, et al. (2013)

Browse more research in Environmental Health Perspectives, or return to medical research.