Chronic exposure to carbon nanotubes induces invasion of human mesothelial cells through matrix metalloproteinase-2

Our plain-English summary of Chronic exposure to carbon nanotubes induces invasion of human mesothelial cells through matrix metalloproteinase-2, by W. Lohcharoenkal, L. Wang, T.A. Stueckle, et al (ACS Nano, 2013).

The study

• Authors: W. Lohcharoenkal, L. Wang, T.A. Stueckle, C.Z. Dinu, V. Castranova, Y. Liu, Y. Rojanasakul
• Journal: ACS Nano
• Published: 2013;7(9):7711-23
• Cited by: 34 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Malignant mesothelioma is one of the most aggressive forms of cancer known. Recent studies have shown that carbon nanotubes (CNTs) are biopersistent and induce mesothelioma in animals, but the underlying mechanisms are not known. Here, we investigate the effect of long-term exposure to high aspect ratio CNTs on the aggressive behaviors of human pleural mesothelial cells, the primary cellular target of human lung mesothelioma. We show that chronic exposure (4 months) to single- and multiwalled CNTs induced proliferation, migration, and invasion of the cells similar to that observed in asbestos-exposed cells. An up-regulation of several key genes known to be important in cell invasion, notably matrix metalloproteinase-2 (MMP-2), was observed in the exposed mesothelial cells as determined by real-time PCR. Western blot and enzyme activity assays confirmed the increased expression and activity of MMP-2. Whole genome microarray analysis further indicated the importance of MMP-2 in the invasion gene signaling network of the exposed cells. Knockdown of MMP-2 in CNT and asbestos-exposed cells by shRNA-mediated gene silencing effectively inhibited the aggressive phenotypes. This study demonstrates CNT-induced cell invasion and indicates the role of MMP-2 in the process.

In plain English

This laboratory study used a non-cancerous human pleural mesothelial cell line (MeT5A). The cells were exposed continuously for 4 months to a low dose (0.02 μg/cm2) that did not kill cells. The exposures were single-walled carbon nanotubes, multiwalled carbon nanotubes, crocidolite asbestos, or ultrafine carbon black, and results were compared with control cells. No people or animals were studied. Cells exposed to either nanotube or asbestos grew faster than controls, but only after 16 weeks. Nanotube-exposed cells showed 5.4- to 6.3-fold more invasion and 2.5- to 2.7-fold more migration than vehicle-treated controls. Asbestos-exposed cells also moved more, but less than the nanotube cells. Carbon black raised growth but affected invasion and migration significantly less than nanotubes, so it was dropped. Of 12 genes tested, MMP-2 rose most: 51-fold in single-walled and 23-fold in multiwalled nanotube cells. MMP-2 was also among the most strongly raised genes in asbestos-exposed cells. Silencing MMP-2 reduced invasion and migration in all three exposed groups. The authors concluded that nanotubes or asbestos gave the cells cancer-like properties, with MMP-2 a key regulator.

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 with chronic exposure of a human cell line
• Who was studied: Nontumorigenic human pleural mesothelial MeT5A cells (a cell line obtained from the American Type Culture Collection); no human subjects or animals
• Exposure: Continuous exposure for 4 months at 0.02 μg/cm2 to single-walled carbon nanotubes (SWCNTs), multiwalled carbon nanotubes (MWCNTs, Mitsui MWNT-7), crocidolite asbestos, or ultrafine carbon black (UFCB), compared with vehicle (Survanta) and saline/passage controls
• Main results:
  • Cells exposed to SWCNTs, MWCNTs or asbestos grew faster than controls, but the increase in growth was not seen until after 16 weeks of exposure
  • SWCNT- and MWCNT-exposed cells showed a 5.4- to 6.3-fold increase in invasion and a 2.5- to 2.7-fold increase in migration compared with Survanta-treated control cells
  • Asbestos-exposed cells showed increased movement compared with saline-treated control cells, but to a lesser extent than the nanotube-exposed cells
  • MMP-2 gene activity (mRNA) rose 51-fold in SWCNT-exposed cells and 23-fold in MWCNT-exposed cells compared with control cells
  • In asbestos-exposed cells, MMP-2 and SERPINE1 were the most strongly raised genes
  • MMP-2 staining intensity was 136.1 units/square inch in SWCNT cells, 112.4 in MWCNT cells and 97.1 in asbestos cells, compared with 94.5 in Survanta-treated and 61.8 in saline-treated control cells
  • In whole-genome analysis, MMP-2 held a central position in the invasion-related gene networks of both nanotube-exposed and asbestos-exposed cells
  • Silencing MMP-2 reduced MMP-2 mRNA in SWCNT-, MWCNT- and asbestos-exposed cells. The reduction is printed as '7382%', which appears to be a range of 73 to 82% with the dash lost in scanning.
  • Cells with MMP-2 silenced showed a decrease in invasion compared with control-transfected cells. The decrease is printed as '6090%', which appears to be 60 to 90% with the dash lost. Migration was also reduced.
  • Ultrafine carbon black (a comparison particle that is not fiber-shaped) increased cell growth, but its effect on invasion and migration was significantly lower than that of the nanotubes, so it was excluded from further study
• The authors' conclusion: The authors concluded that chronic exposure of human pleural mesothelial cells to carbon nanotubes or asbestos produced cancer-like properties (rapid growth, increased invasion and migration). Based on gene expression and knockdown data, they identified MMP-2 as a key regulator of these behaviors.

Topics

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

Medical terms in this study, explained in our Lexicon: Mesothelial Cells, Mesothelioma, Aspect Ratio (Length-to-diameter ratio).

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• Iron-related toxicity of single-walled carbon nanotubes and crocidolite fibres in human mesothelial cells investigated by Synchrotron XRF microscopy — F. Cammisuli, S. Giordani, et al. (2018)
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