Biological effects and comparative cytotoxicity of thermal transformed asbestos-containing materials in a human alveolar epithelial cell line

Our plain-English summary of Biological effects and comparative cytotoxicity of thermal transformed asbestos-containing materials in a human alveolar epithelial cell line, by F. Giantomassi, A.F. Gualtieri, L. Santarelli, et al (Toxicology in Vitro, 2010).

The study

• Authors: F. Giantomassi, A.F. Gualtieri, L. Santarelli, M. Tomasetti, G. Lusvardi, G. Lucarini, M. Governa, A. Pugnaloni
• Journal: Toxicology in Vitro
• Published: 2010;24(6):1521-31
• Cited by: 16 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Asbestos fibres can be transformed into potentially non-hazardous silicates by high-temperature treatment via complete solid-state transformation. A549 cells were exposed to standard concentrations of raw cement asbestos (RCA), chrysotile and cement asbestos subjected to an industrial process at 1200 degrees C (Cry_1200 and KRY.AS, respectively), raw commercial grey cement (GC). Cell growth rate and viability (MTT test) were detected in vitro. RCA and KRY.AS subjected to comprehensive microstructural study by electron microscopy were further in vitro assayed to compare their cytotoxic potential by morphostructural studies, proliferation index (Ki-67 antigen), apoptosis induction (AO/EB staining) assays and detection of intracellular reactive oxygen species (ROS) with the fluorescent DCFA dye. More severe cytotoxic damage was induced by RCA than by KRY.AS after each incubation period. Exposure to KRY.AS and GC resulted in comparable cell growth rates and cytotoxic effects. Cells incubated with RCA showed greater apoptotic induction and ROS production and a lower cell proliferation index than those exposed to KRY.AS. Chrysotile asbestos and RCA subjected to heat treatment underwent complete microstructure transformation. The final product of heat treatment of cement asbestos, KRY.AS, was considerably more inert and had lower cytotoxic potential than the original asbestos material in all in vitro tests.

Copyright 2010 Elsevier Ltd. All rights reserved.

In plain English

This laboratory study used A549 cells, a cancer-derived human lung cell line with some features of alveolar lining cells. The authors exposed the cells to four powders: a commercial cement asbestos used to make outdoor roofing slates (containing chrysotile), the same cement asbestos after heating at about 1200 degrees C in a semi-industrial pilot plant (called KRYAS), standard chrysotile heated the same way, and ordinary grey cement. Electron microscopy showed asbestos fibres in the raw material but no individual fibres in KRYAS. Raw cement asbestos and KRYAS were tested at several concentrations; at 96 hours only raw cement asbestos caused 50% cell death, at 75 micrograms per millilitre. Compared with KRYAS and untreated cells, cells exposed to raw cement asbestos had the fewest live cells and lower cell division at 48 hours. They also had more reactive oxygen species than untreated cells. At 24 and 48 hours, every powder, including KRYAS and plain cement, left fewer living cells than untreated cultures. The authors concluded that high-temperature treatment is a safe approach and that KRYAS is considerably more inert than the original asbestos material.

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 human cell line (cell culture study)
• Who was studied: A549 cells, a human lung cancer cell line with some features of alveolar epithelial cells (no human subjects); each test run in three independent experiments
• Exposure: Four materials were tested over 24, 48, 72 and 96 h. (1) Raw cement asbestos (RCA), a commercial cement asbestos used to make outdoor roofing slates, containing chrysotile. (2) KRYAS, cement asbestos heated at about 1200 degrees C for 16 h in a semi-industrial pilot plant. (3) Standard chrysotile SRM 1866A given the same heat treatment (Cry_1200). (4) Commercial grey cement (GC), used as a negative control. RCA and KRYAS were tested at 10, 50 and 100 µg/ml. All four materials were compared at 50 µg/ml.
• Main results:
  • Under the electron microscope, RCA showed asbestos fibres. In KRYAS, individual fibres no longer existed.
  • RCA and KRYAS were tested for dose response in the cell viability (MTT) test. At 96 h, only RCA reached 50% cell death, at 75 µg/ml. KRYAS did not reach 50% cell death.
  • In the viability test at 50 µg/ml, cells exposed to heated chrysotile (Cry_1200) or grey cement did not differ significantly from untreated controls at any time point.
  • In cell counts at 24 h and 48 h, all treated cultures, including KRYAS, Cry_1200 and grey cement, had significantly fewer living cells than controls.
  • For the cell proliferation marker Ki-67 at 48 h, 70.00 ± 15.81% of RCA-treated cells were positive. This compared with 92.00 ± 4.95% of controls and 95.20 ± 3.11% of KRYAS-treated cells. The RCA reduction was significant.
  • In apoptosis staining, RCA-treated cultures had the fewest live cells at all time points. At 48 h, 38.62 ± 4.83% of RCA-treated cells were live. This compared with 96.55 ± 3.61% of controls and 87.43 ± 15.12% of KRYAS-treated cells.
  • KRYAS-treated cultures had significantly more necrotic cells than controls at 24 h, though fewer than RCA-treated cultures.
  • Reactive oxygen species rose significantly in RCA-treated cells compared with controls at all time points. After KRYAS they rose, but not significantly, and never reached RCA levels.
  • Electron microscopy of RCA-treated cells often showed cells dying by apoptosis, with chrysotile fibres seen inside cells.
• The authors' conclusion: The authors concluded that high-temperature treatment of asbestos-containing materials is a safe approach to storing or recycling them. They also concluded that KRYAS was considerably more inert than the original asbestos material and should be considered biologically non-hazardous.

Topics

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

Medical terms in this study, explained in our Lexicon: Asbestos-Containing Material (ACM), Silicate, A549 Cells, Chrysotile, Ki-67, Apoptosis, Reactive Oxygen Species (ROS).

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