Assessing nanotoxicity in cells in vitro

Our plain-English summary of Assessing nanotoxicity in cells in vitro, by J.M. Hillegass, A. Shukla, S.A. Lathrop, et al (Wiley Interdisciplinary Reviews. Nanomedicine and Nanobiotechnology, 2010).

The study

• Authors: J.M. Hillegass, A. Shukla, S.A. Lathrop, M.B. MacPherson, N.K. Fukagawa, B.T. Mossman
• Journal: Wiley Interdisciplinary Reviews. Nanomedicine and Nanobiotechnology
• Published: 2010;2(3):219-31
• Type of article: Review
• Cited by: 122 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Nanomaterials are commonly defined as particles or fibers of less than 1 microm in diameter. For these reasons, they may be respirable in humans and have the potential, based upon their geometry, composition, size, and transport or durability in the body, to cause adverse effects on human health, especially if they are inhaled at high concentrations. Rodent inhalation models to predict the toxicity and pathogenicity of nanomaterials are prohibitive in terms of time and expense. For these reasons, a panel of in vitro assays is described below. These include cell culture assays for cytotoxicity (altered metabolism, decreased growth, lytic or apoptotic cell death), proliferation, genotoxicity, and altered gene expression. The choice of cell type for these assays may be dictated by the procedure or endpoint selected. Most of these assays have been standardized in our laboratory using pathogenic minerals (asbestos and silica) and non-pathogenic particles (fine titanium dioxide or glass beads) as negative controls. The results of these in vitro assays should predict whether testing of selected nanomaterials should be pursued in animal inhalation models that simulate physiologic exposure to inhaled nanomaterials. Conversely, intrathoracic or intrapleural injection of nanomaterials into rodents can be misleading because they bypass normal clearance mechanisms, and non-pathogenic fibers and particles can test positively in these assays.

In plain English

This article was a review, not a new study. The authors described laboratory cell-culture tests for screening nanomaterials for harmful effects. The tests measured cell death, cell growth, DNA and chromosome damage, and changes in gene activity. The authors wrote that most of the tests had been standardized in their laboratory. They used asbestos and silica as disease-causing minerals, and fine titanium dioxide or glass beads as non-pathogenic comparison particles. Citing their earlier work, the authors reported that crocidolite asbestos, at a surface-area concentration of 75 µm2 per cm2, was cytotoxic to a human mesothelial cell line (50% or less cell viability compared with untreated cells). At the same concentration in the same cells, glass beads or fine titanium dioxide showed no significant toxic effects. The authors noted that bacterial mutation (Ames) studies of nanomaterials had all been negative. The authors concluded that more than one test and cell type should be used, with asbestos fibers as a positive control and glass beads as a negative control. They also wrote that injecting nanomaterials into the chest or pleural space of rodents can be misleading.

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: Review article (published as an 'Advanced Review') of in vitro (laboratory cell-culture and bacterial) assays for testing nanomaterials; no new study was reported
• Who was studied: No human or animal study population. The article reviewed a panel of in vitro assays for cytotoxicity, proliferation, genotoxicity and gene expression, illustrated with published studies on various cell types
• Exposure: Nanomaterials, defined as particles or fibers less than 1 µm in diameter. Asbestos (crocidolite in the authors' own examples) and silica were used as reference pathogenic minerals; fine titanium dioxide and glass beads were used as non-pathogenic comparison particles (negative controls)
• Main results:
  • The authors stated that most of the assays had been standardized in their laboratory using pathogenic minerals (asbestos and silica) and non-pathogenic particles (fine titanium dioxide or glass beads) as negative controls
  • In the authors' earlier work on the human mesothelial cell line LP9/TERT-1, crocidolite asbestos at a surface area concentration of 75 µm2 per cm2 was cytotoxic, with 50% or less cell viability compared with control
  • In the same earlier work, at the same surface area concentration and in the same mesothelial cells, glass beads or fine titanium dioxide showed no significant toxic effects
  • The authors cited their earlier finding that hamster tracheal epithelial cells had increased numbers of colonies after exposure to low concentrations of crocidolite asbestos fibers. They interpreted this as increased survival and/or proliferation
  • The authors cited their earlier work showing that crocidolite asbestos at 5 µg/cm2 dish induced apoptosis (programmed cell death) in mouse alveolar type II (C10) cells
  • The authors cited their laboratory's finding of an increase in PCNA-positive (dividing) lung epithelial cells after exposure to crocidolite asbestos
  • The Ames mutation studies of nanomaterials that the authors reviewed were all negative. A study by another group (Faux et al.) showed a positive correlation between iron-dependent crocidolite asbestos exposure and mutagenicity in S. typhimurium TA102
  • The authors wrote that intrathoracic or intrapleural injection of nanomaterials into rodents can be misleading, because it bypasses normal clearance mechanisms
  • The authors called for proper positive controls (asbestos fibers) and negative controls (amorphous particles such as glass beads)
• The authors' conclusion: The authors concluded that, because asbestos and silica injure cells by multiple cell-type-specific mechanisms, more than one assay and cell type should be used to test an uncharacterized material
• Limitations the authors state:
  • The authors stated that their list of cytotoxicity assays was far from complete
  • The authors stated that cell-free assays to predict how nanomaterials dissolve in the body were not discussed in detail

Topics

Medical terms in this study, explained in our Lexicon: Genotoxicity, Intrathoracic.

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