In vitro toxicity of fibrous glaucophane

Our plain-English summary of In vitro toxicity of fibrous glaucophane, by A.F. Gualtieri, A. Zoboli, M. Filaferro, et al (Toxicology, 2021).

The study

• Authors: A.F. Gualtieri, A. Zoboli, M. Filaferro, M. Benassi, S. Scarfì, S. Mirata, R. Avallone, G. Vitale, M. Bailey, M. Harper, D. Di Giuseppe
• Journal: Toxicology
• Published: 2021;454:152743
• Cited by: 9 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The health hazard represented by the exposure to asbestos may also concern other minerals with asbestos-like crystal habit. One of these potentially hazardous minerals is fibrous glaucophane. Fibrous glaucophane is a major component of blueschist rocks of California (USA) currently mined for construction purposes. Dust generated by the excavation activities might potentially expose workers and the general public. The aim of this study was to determine whether fibrous glaucophane induces in vitro toxicity effects on lung cells by assessing the biological responses of cultured human pleural mesothelial cells (Met-5A) and THP-1 derived macrophages exposed for 24 h and 48 h to glaucophane fibres. Crocidolite asbestos was tested for comparison. The experimental configuration of the in vitro tests included a cell culture without fibres (i.e., control), cell cultures treated with 50 μg/mL (i.e., 15.6 μg/cm2) of crocidolite fibres and 25-50-100 μg/mL (i.e., 7.8-15.6-31.2 μg/cm2) of glaucophane fibres. Results showed that fibrous glaucophane may induce a decrease in cell viability and an increase in extra-cellular lactate dehydrogenase release in the tested cell cultures in a concentration dependent mode. Moreover, it was found that fibrous glaucophane has a potency to cause oxidative stress. The biological reactivity of fibrous glaucophane confirms that it is a toxic agent and, although it apparently induces lower toxic effects compared to crocidolite, exposure to this fibre may be responsible for the development of lung diseases in exposed unprotected workers and population.

Copyright © 2021 Elsevier B.V. All rights reserved.

In plain English

This laboratory study tested whether fibrous glaucophane harms human cells grown in culture. Glaucophane is a mineral in blueschist rock of California's Franciscan Complex, which is mined for construction. The fibres came from rock at San Anselmo, Marin County, and averaged 4.0 μm long. The authors exposed human pleural mesothelial cells (Met-5A) and macrophage-type cells (THP-1) to 25, 50 or 100 μg/mL of glaucophane for 24 and 48 hours. They compared these with crocidolite asbestos at 50 μg/mL. A549 cells were also used in oxidative stress tests. Glaucophane lowered cell survival and raised release of LDH, an enzyme leaking from damaged cells, more at higher concentrations. The macrophages were more affected than the mesothelial cells. At the same doses, glaucophane caused less loss of survival, less LDH release and less DNA damage than crocidolite. Glaucophane increased reactive oxygen species, more at higher concentrations. The authors concluded that fibrous glaucophane can cause cell death, DNA damage and oxidative stress in these tests. They said animal studies should follow.

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) toxicity experiment, with crocidolite asbestos as a comparison
• Who was studied: Human cell lines grown in the laboratory: Met-5A human pleural mesothelial cells and THP-1-derived macrophages, plus A549 cells for oxidative stress tests. The glaucophane fibres came from blueschist rock collected at San Anselmo, Marin County, California
• Exposure: Fibrous glaucophane (average fibre length 4.0 μm, width 0.2 μm) at 25, 50 and 100 μg/mL for 24 and 48 hours, compared with UICC crocidolite asbestos at 50 μg/mL. The oxidative stress tests used other concentrations.
• Main results:
  • After 24 hours, viability of Met-5A mesothelial cells fell by 10%, 13% and 17% at 25, 50 and 100 μg/mL of glaucophane
  • At 100 μg/mL of glaucophane, viability of THP-1 macrophages fell by 40% after 24 hours and 60% after 48 hours compared with control. Viability of Met-5A cells fell by 30% after 48 hours.
  • After 48 hours in THP-1 macrophages, LDH release relative to control was 201% for crocidolite (50 μg/mL). For glaucophane it was 136%, 180% and 265% at 25, 50 and 100 μg/mL.
  • At the same doses, glaucophane caused less reduction in cell viability and less LDH release than crocidolite
  • In the Comet test of DNA damage (3 hours, 50 μg/mL), glaucophane increased DNA damage compared with control in both cell lines, but at an intermediate level compared with crocidolite
  • In the DCF test of reactive oxygen species, glaucophane at 50 and 100 μg/mL gave 1.47- and 1.5-fold increases in THP-1 cells and 1.45- and 1.56-fold increases in Met-5A cells over control
  • In the hydrogen peroxide test, glaucophane at 100 μg/mL gave a 1.4-fold increase in Met-5A cells and a 1.5-fold increase in A549 cells compared with control
• The authors' conclusion: The authors concluded that, in these in vitro tests, fibrous glaucophane has the potential to induce cell death, DNA damage and oxidative stress. They concluded that it apparently induces lower toxic effects than crocidolite.
• Limitations the authors state:
  • Animal (in vivo) tests are still needed for a conclusive understanding of how cells and tissues respond to fibrous glaucophane
  • There are no standard protocols for in vitro testing of mineral fibres, so comparison with other published studies is difficult

Topics

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

Medical terms in this study, explained in our Lexicon: Habit, Mesothelial Cells, Macrophage, Crocidolite, Lactate Dehydrogenase (LDH), Oxidative Stress.

Related studies

• Characterization and assessment of the potential toxicity/pathogenicity of fibrous glaucophane — D. Di Giuseppe, M. Harper, et al. (2019)
• Functional expression of system x(c)- is upregulated by asbestos but not crystalline silica in murine macrophages — J.C. Pfau, T. Seib, et al. (2012)
• Internalization of Libby amphibole asbestos and induction of oxidative stress in murine macrophages — D.J. Blake, C.M. Bolin, et al. (2007)
• Correlation of in vitro and in vivo methods by means of mass dose and fiber distribution for amosite and fibrous ferroactinolite — D.L. Coffin, L.D. Palekar, et al. (1983)
• Structure Model and Toxicity of the Product of Biodissolution of Chrysotile Asbestos in the Lungs — A.F. Gualtieri, G. Lusvardi, et al. (2019)
• Patterns of 8-hydroxydeoxyguanosine formation in DNA and indications of oxidative stress in rat and human pleural mesothelial cells after exposure to crocidolite asbestos — H. Fung, Y.W. Kow, et al. (1997)

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