A comparison of acute and long-term effects of industrial multiwalled carbon nanotubes on human lung and immune cells in vitro

Our plain-English summary of A comparison of acute and long-term effects of industrial multiwalled carbon nanotubes on human lung and immune cells in vitro, by T. Thurnherr, C. Brandenberger, K. Fischer, et al (Toxicology Letters, 2011).

The study

• Authors: T. Thurnherr, C. Brandenberger, K. Fischer, L. Diener, P. Manser, X. Maeder-Althaus, J.P. Kaiser, H.F. Krug, B. Rothen-Rutishauser, P. Wick
• Journal: Toxicology Letters
• Published: 2011;200(3):176-86
• Cited by: 107 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The close resemblance of carbon nanotubes to asbestos fibers regarding their high aspect ratio, biopersistence and reactivity increases public concerns on the widespread use of these materials. The purpose of this study was not only to address the acute adverse effects of industrially produced multiwalled carbon nanotubes (MWCNTs) on human lung and immune cells in vitro but also to further understand if their accumulation and biopersistence leads to long-term consequences or induces adaptive changes in these cells. In contrast to asbestos fibers, pristine MWCNTs did not induce overt cell death in A549 lung epithelial cells and Jurkat T lymphocytes after acute exposure to high doses of this material (up to 30 μg/ml). Nevertheless, very high levels of reactive oxygen species (ROS) and decreased metabolic activity were observed which might affect long-term viability of these cells. However, the continuous presence of low amounts of MWCNTs (0.5 μg/ml) for 6 months did not have major adverse long-term effects although large amounts of nanotubes accumulated at least in A549 cells. Moreover, MWCNTs did not appear to induce adaptive mechanisms against particle stress in long-term treated A549 cells. Our study demonstrates that despite the high potential for ROS formation, pristine MWCNTs can accumulate and persist within cells without having major long-term consequences or inducing adaptive mechanisms.

© 2010 Elsevier Ireland Ltd. All rights reserved.

In plain English

This laboratory study tested industrially produced multiwalled carbon nanotubes (MWCNTs) on two human cell lines grown in dishes: A549 lung epithelial cells and Jurkat cells, a leukemic T-cell line. No people or animals were studied. Crocidolite asbestos was used for comparison. In short-term tests at up to 30 micrograms per ml, MWCNTs did not cause major death of A549 cells, while crocidolite asbestos caused a clear dose-related rise in dying cells. MWCNTs raised levels of reactive oxygen species (a sign of oxidative stress); asbestos did not. Both materials lowered the cells' metabolic activity. Neither caused DNA damage in the tests used. When cells were grown with 0.5 micrograms per ml of MWCNTs for about 6 months, nanotubes built up inside A549 cells but hardly at all in Jurkat cells. Growth and survival did not differ from untreated cells. The long-exposed A549 cells were no better than untreated A549 cells at withstanding a later high dose of particles. The authors concluded that the long-term presence and build-up of this material did not have major impacts on cell viability and functionality. They noted that they measured only some cell functions.

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 (cell culture) laboratory experiment with short-term (up to 6 days) and long-term (up to 6 months) exposures
• Who was studied: Two human cell lines: A549 lung epithelial cells and Jurkat-neo, a leukemic T-cell line. No human subjects or animals. Work done at Swiss laboratories (Empa St. Gallen and University of Bern).
• Exposure: Industrially produced multiwalled carbon nanotubes from Bayer Technologies Service, compared with crocidolite asbestos. Short-term doses went up to 30 micrograms per ml. Long-term exposure was 0.5 micrograms per ml for about 6 months. Uncoated iron oxide (Fe2O3) nanoparticles were also used in challenge tests.
• Main results:
  • Short-term exposure of A549 cells to MWCNTs for up to 6 days did not induce major cell death.
  • In A549 cells, crocidolite asbestos caused a clear concentration-dependent increase in apoptotic and late apoptotic/necrotic cells.
  • After 2 hours, MWCNTs significantly increased reactive oxygen species in A549 cells in a concentration-dependent way; crocidolite asbestos did not.
  • Increasing doses of MWCNTs significantly reduced metabolic (MTT) activity in A549 cells; asbestos also caused a concentration-dependent decrease.
  • In A549 cells, neither MWCNTs nor asbestos caused DNA damage in the comet assay at up to 30 micrograms per ml after 24 or 72 hours.
  • In A549 cells, neither material increased micronucleated cells (a sign of chromosome damage) at any tested dose after 24 hours.
  • After about 6 months of exposure, A549 cell pellets turned black, indicating nanotube uptake. Hardly any MWCNTs were found in similarly treated Jurkat cells.
  • In long-term exposed A549 and Jurkat cells, cell growth at passages 3, 9, 19 and 23 did not differ from untreated controls.
  • In long-term exposed A549 cells challenged with high doses of MWCNTs, Fe2O3 nanoparticles or asbestos, cell survival was not improved compared with untreated A549 cells.
  • When long-term exposed A549 cells were challenged with a high dose (30 micrograms per ml) of MWCNTs, they produced the same reactive oxygen species levels as control cells. The authors took this and similar results as showing no protective adaptation.
• The authors' conclusion: The authors concluded that although short-term MWCNT exposure caused sub-lethal adverse effects, the long-term presence and build-up of this material did not have major impacts on cell viability and functionality.
• Limitations the authors state:
  • No statistical significance was determined for the long-term studies.
  • Nanotube uptake could not be quantified.
  • Only cell growth, survival and some enzyme activity were measured. Other sub-lethal effects, such as release of inflammatory factors, remain possible.
  • Secondary DNA damage involving macrophages could not be examined because no macrophages were present in the assays.
  • Small changes in protein expression were not excluded.
  • It is not yet known whether this cell-line model predicts effects in living bodies.

Topics

Medical terms in this study, explained in our Lexicon: Aspect Ratio (Length-to-diameter ratio), biopersistence, Reactive Oxygen Species (ROS), A549 Cells.

Related studies

• Stromelysin-2 (MMP-10) facilitates clearance and moderates inflammation and cell death following lung exposure to long multiwalled carbon nanotubes — T.C. Vandivort, T.P. Birkland, et al. (2017)
• Different Cellular Response of Human Mesothelial Cell MeT-5A to Short-Term and Long-Term Multiwalled Carbon Nanotubes Exposure — L. Ju, W. Wu, et al. (2017)
• Adverse effects of industrial multiwalled carbon nanotubes on human pulmonary cells — L. Tabet, C. Bussy, et al. (2009)
• Endocytosis of Multiwalled Carbon Nanotubes in Bronchial Epithelial and Mesothelial Cells — K. Maruyama, H. Haniu, et al. (2015)
• Induction and recovery of CpG site specific methylation changes in human bronchial cells after long-term exposure to carbon nanotubes and asbestos — D. Öner, M. Ghosh, et al. (2020)
• In vitro and in vivo genotoxic effects of straight versus tangled multi-walled carbon nanotubes — J. Catalán, K.M. Siivola, et al. (2016)

Browse more research in Toxicology Letters, or return to medical research.