Differential in vitro cellular response induced by exposure to synthetic vitreous fibers (SVFs) and asbestos crocidolite fibers

Our plain-English summary of Differential in vitro cellular response induced by exposure to synthetic vitreous fibers (SVFs) and asbestos crocidolite fibers, by G. Cardinali, D. Kovacs, V. Maresca, et al (Experimental and Molecular Pathology, 2006).

The study

• Authors: G. Cardinali, D. Kovacs, V. Maresca, E. Flori, M.L. Dell'Anna, A. Campopiano, S. Casciardi, G. Spagnoli, M.R. Torrisi, M. Picardo
• Journal: Experimental and Molecular Pathology
• Published: 2006;81(1):31-41
• Cited by: 9 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

In this study, we analyzed the effects of synthetic vitreous fibers (SVFs) on a mesothelial (MeT5A) and a fibroblast cell line (NIH3T3), compared to those exerted by crocidolite asbestos fibers. SVFs (glass wool, rock wools) do not induce significant changes in cell mortality, whereas crocidolite asbestos fibers caused a dose-dependent cytotoxicity. We investigated the correlation between the fiber-induced cytotoxicity and the extent and type of interaction of the fibers with the cell surface, and we observed that SVFs, unlike crocidolite asbestos fibers, establish few and weak interactions. Moreover, after internalization, crocidolite asbestos fibers are often found free in the cytoplasm, whereas glass wool fibers are mainly localized inside cytoplasmic vacuoles. After treatments, we also detected signs of oxidative stress, revealed by an increased reactive oxygen species (ROS) production and by an induction of superoxide dismutase (SOD) activity. The lipoperoxidative damage was characterized by a decrease in polyunsaturated fatty acids (PUFA), an increase in the content of thiobarbituric reactive species (TBARS) and a consumption of vitamin E, as a lipophilic antioxidant. Furthermore, we investigated the effect of fiber exposure on cell proliferation. and it was found that, unlike crocidolite asbestos fibers, SVFs did not induce a significant increase in DNA synthesis.

In plain English

This laboratory study used cells grown in dishes, not people. The authors exposed a human mesothelial cell line (MeT5A) and a mouse embryo fibroblast cell line (NIH3T3) to crocidolite asbestos and to three synthetic vitreous fibers (glass wool, rock wool and a Danish rock wool). Doses ranged from 2 to 25 micrograms per square centimetre, mainly for 24 hours. Crocidolite killed more cells as the dose rose: in MeT5A cells, mortality was 1.1–3.8% in unexposed cells and 11–14.6% at the highest dose. The synthetic fibers did not raise mortality. Crocidolite was in contact with far more mesothelial cells (87.6–90.7%) than glass wool was (20–33.5%) or either rock wool. All fibers produced signs of oxidative stress in MeT5A cells, and the oxidative stress was more pronounced with crocidolite. Glass wool did not change TBARS, a marker of membrane fat damage. Crocidolite, but not the synthetic fibers, increased the share of mesothelial cells making new DNA. The authors concluded that the synthetic fibers' lack of effect on cell survival and growth could be due to their different chemical composition and weak interaction with cells.

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 comparing synthetic vitreous fibers with crocidolite asbestos
• Who was studied: Cultured cell lines, not people: MeT5A human mesothelial cells and NIH3T3 mouse (murine) embryo fibroblast cells. A human macrophage cell line (THP-1) was also used in the fiber–cell contact observations.
• Exposure: Crocidolite asbestos (a sample supplied to NIEHS by the Federal Bureau of Mines), glass wool and rock wool from two Italian manufacturers, and a Danish rock wool. Concentrations were 2, 5, 10 and 25 μg/cm2, or equal fiber numbers, for 24 or 48 hours.
• Main results:
  • MeT5A mesothelial cells, 24 hours: cell mortality was 1.1–3.8% in unexposed cells. After crocidolite it was 4.2–5.9%, 10–11.2% and 11–14.6% at 2, 5 and 25 μg/cm2.
  • MeT5A cells exposed to glass wool showed no increase in cell mortality compared with untreated cells. The authors report similar results for the rock wools.
  • NIH3T3 fibroblasts: crocidolite raised mortality in a dose-dependent way, to 2.9–4.7%, 5.7–8.5% and 9.3–12% at 2, 5 and 25 μg/cm2. Unexposed cells ranged from 1.1 to 3.2%.
  • Crocidolite fibers interacted with 87.6–90.7% of MeT5A cells.
  • Glass wool fibers interacted with only 20–33.5% of MeT5A cells.
  • Under the electron microscope, crocidolite fibers inside cells were often free in the cytoplasm. Glass wool fibers were mainly inside cytoplasmic vacuoles.
  • Signs of oxidative stress and peroxidative damage were seen in MeT5A cells 24 hours after treatment with asbestos or the synthetic fibers.
  • MeT5A cells: TBARS (a marker of membrane fat damage) rose from 0.018 ± 0.004 nmol/mg protein in untreated cells to 0.056 ± 0.012 nmol/mg protein after crocidolite.
  • MeT5A cells: glass wool did not change TBARS (0.021 ± 0.005 nmol/mg protein).
  • MeT5A cells: membrane polyunsaturated fatty acids (PUFA) fell from 0.99 ± 0.25 μg/mg protein to 0.095 ± 0.018 μg/mg protein after crocidolite, the largest drop of any fiber.
  • MeT5A cells, vitamin E: 78.41 ± 10.39 μg/mg protein in untreated cells; 63.00 ± 12.13 after Danish rock wool; 60.07 ± 10.60 after glass wool and 58.24 ± 12.13 after rock wool (each p less than 0.05); 30.41 ± 5.61 after crocidolite (p less than 0.01).
  • Adding vitamin E to MeT5A cells beforehand reduced the crocidolite-induced rise in TBARS by 62.95%.
  • MeT5A cells, reactive oxygen species (ROS): mean fluorescence was 146 ± 7.9 in untreated cells and 172 ± 4.58 in crocidolite-exposed cells.
  • MeT5A cells: rock wool did not produce a statistically significant increase in ROS (154.3 ± 8).
  • MeT5A cells: all treatments significantly increased superoxide dismutase (SOD) activity. It rose from 6.9 ± 0.49 U/mg protein in untreated cells to 8.38 ± 0.61 after crocidolite.
  • MeT5A cells: SOD activity was 14.16 ± 1.53 U/mg protein after rock wool, 11.81 ± 0.75 after Danish rock wool and 14.24 ± 1.44 after glass wool.
  • MeT5A cells: catalase activity showed no statistically significant changes after any treatment.
  • The authors state that the synthetic fibers produced less pronounced oxidative stress than crocidolite.
  • MeT5A cells, new DNA synthesis (BrdU): 57.6% to 83% of nuclei were positive in unexposed cells, and 90.7% to 93% after crocidolite.
  • MeT5A cells interacting with glass wool, rock wool or Danish rock wool showed no increase in new DNA synthesis compared with controls (56–87%, 59–82% and 56.5–75.8%).
• The authors' conclusion: The authors concluded that the synthetic fibers' lack of effect on cell viability and proliferation, unlike crocidolite, could be due to their different chemical composition and their weak and limited interaction with the cells.

Topics

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

Medical terms in this study, explained in our Lexicon: Vitreous, Crocidolite, Fibroblast, Oxidative Stress, Reactive Oxygen Species (ROS), Superoxide.

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