The role of asbestos morphology on their cellular toxicity: an in vitro 3D Raman/Rayleigh imaging study

Our plain-English summary of The role of asbestos morphology on their cellular toxicity: an in vitro 3D Raman/Rayleigh imaging study, by S. Yao, H.H. Chen, E. Harte, et al (Analytical and Bioanalytical Chemistry, 2013).

The study

• Authors: S. Yao, H.H. Chen, E. Harte, G.D. Ventura, C. Petibois
• Journal: Analytical and Bioanalytical Chemistry
• Published: 2013;405(27):8701-7
• Cited by: 8 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Amphiboles caused cohorts of deaths in exposed workers, leading to some of the largest class actions in the industry. Once inhaled, these inorganic fibers are thought to be both chemically and morphologically toxic, and their biopersistence in the lungs over decades lead to progressive pathologies, mesothelioma, and asbestosis. However, this exceptionally long chronicity for human pathologies suggests that chemical toxicity is certainly low, suggesting that morphological parameters could be more relevant in the pathology. Here, we developed a 3D Raman/optical imaging methodology in vitro to characterize both morphological and chemical parameters of cell/fiber interactions. We determined that lung cells could vesiculate amphiboles with length below 5 μm or could embed those not exceeding 15 μm in their fibrous extracellular matrix. Lung cells can thus develop defense strategies for handling the biopersistence of inorganic species, which may thus have major impact for biosafety issues related to nanomaterials.

In plain English

This was a laboratory study of lung cells grown in dishes (the A549 type II epithelial lung cell line), not of people. The authors exposed the cells to two natural asbestos fibers from a Paris museum collection: a crocidolite from South Africa and a manganese-rich cummingtonite. Fast 3D optical (Rayleigh) and Raman imaging showed where individual fibers sat in relation to living cells. In cell-survival tests, 10 micrograms per square centimeter of fiber caused moderate toxicity. A higher concentration, reaching 20 micrograms per square centimeter, was described as highly toxic, with at least 10% of cells dying. Across 39 measurements, fibers no longer than 5 micrometers were found inside the cell (cytosol) or fully embedded in the surrounding matrix, and short fibers appeared to be enclosed in small sacs (vesicles). Fibers longer than 15 micrometers were seen crossing cells or only partly embedded. The authors concluded that how cells and fibers interact depends on fiber shape and size. The fiber concentration is stated inconsistently. The toxicity and fiber-location findings are not reported separately for each fiber type.

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 experiment on a cultured lung cell line, using 3D optical (Rayleigh) and Raman imaging plus a cell-viability (MTT) assay
• Who was studied: Living cells of the A549 type II epithelial lung cell line, grown on silicon wafers; 39 imaging measurements of single cells with fibers
• Exposure: Two natural asbestos fibers from the Museum National d'Histoire Naturelle of Paris: a crocidolite from Buchanawald (South Africa), labeled MNHN 134-86, with riebeckite composition, and a cummingtonite, labeled MNHN 137.96, close to mangano-cummingtonite. The fibers were ground, baked and sonicated in cell medium. Viability tests used concentrations of 1 to 100 micrograms per square centimeter. Imaging was reported at 10 micrograms per square centimeter, although the Methods state 5.
• Main results:
  • Each fiber type had its own Raman peaks that could serve as a fingerprint: 1,023 and 1,050 cm−1 for crocidolite and 925 cm−1 for cummingtonite. All fibers shared a peak between 650 and 710 cm−1.
  • In the cell-viability assays, 10 micrograms per square centimeter of asbestos fiber caused moderate toxicity. A concentration reaching 20 micrograms per square centimeter was highly toxic, with at least 10% of cells dying. These results were not reported separately by fiber type.
  • A total of 39 measurements were made to locate fibers according to their length, with video confirming that the cells were still alive and in position
  • Fibers no longer than 5 micrometers were always found within the cytosol or fully embedded in the extracellular matrix (ECM)
  • Fibers up to 5 micrometers were vesiculated or embedded in the ECM, and fibers below 15 micrometers were embedded in the ECM
  • Fibers longer than 15 micrometers were seen crossing the cell or not fully embedded in the ECM
  • Raman imaging showed short fibers taken into vesicles, based on stronger lipid signals right next to the fibers inside the cytosol
  • Fibers embedded in the ECM showed a stronger protein (amide) signal right next to them, which the authors took to suggest a fibrous matrix forming around the fibers
• The authors' conclusion: The authors concluded that how cells and fibers interact depends on the fibers' shape and size. They also concluded that lung cells can isolate fibers, enclosing short ones in vesicles or embedding them in the extracellular matrix.
• Limitations the authors state:
  • The authors noted that the experiments were done in vitro, without the deformation of the extracellular matrix caused by lung movements during breathing
  • The article's own text states that the fixed fiber concentration it reports contradicts the Introduction and Results, which describe changing concentrations

Topics

Medical terms in this study, explained in our Lexicon: Amphibole Group, Class Action, biopersistence, Mesothelioma, Pathology.

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