Molecular and Cellular Mechanism of Action of Chrysotile Asbestos in MRC5 Cell Line

Our plain-English summary of Molecular and Cellular Mechanism of Action of Chrysotile Asbestos in MRC5 Cell Line, by A. Kussainova, O. Bulgakova, A. Aripova, et al (Journal of Personalized Medicine, 2023).

The study

• Authors: A. Kussainova, O. Bulgakova, A. Aripova, M. Ibragimova, A. Pulliero, D. Begimbetova, R. Bersimbaev, A. Izzotti
• Journal: Journal of Personalized Medicine
• Published: 2023;13(11)
• Cited by: 1 article, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Asbestos is a known carcinogen; however, the influence of chrysotile asbestos on the development of tumor-related diseases remains a subject of intense debate within the scientific community. To analyze the effect of asbestos, we conducted a study using the MRC5 cell line. We were able to demonstrate that chrysotile asbestos stimulated the production of reactive oxygen species (ROS), leading to cell death and DNA damage in the MRC5 cell line, using various techniques such as ROS measurement, comet assay, MTT assay, and qPCR. In addition, we found that chrysotile asbestos treatment significantly increased extracellular mitochondrial DNA levels in the culture medium and induced significant changes in the expression profile of several miRNAs, which was the first of its kind. Thus, our research highlights the importance of studying the effects of chrysotile asbestos on human health and reveals multiple adverse effects of chrysotile asbestos.

In plain English

This was a laboratory study of cells, not of people. The authors exposed MRC5 cells, a line of human lung fibroblasts, to chrysotile asbestos from the Kostanay Minerals plant in Kazakhstan, mainly at doses of 2.5, 5 and 10 µg/cm2, for periods of up to 48 hours. After 24 hours, reactive oxygen species (reactive molecules linked to cell stress) were about twice the level in untreated cells at the lowest dose, and 3.63 and 5.48 times that level at the two higher doses. DNA damage measured by the comet assay rose with dose, from 9.87% to 38% of DNA in comet tails, against less than 1% in untreated cells. After 48 hours at the highest dose, 65.9% of cells were still alive. Mitochondrial DNA released into the culture medium increased with time. Of six selected microRNAs, all except hsa-miR-1228 changed, without a clear dose pattern. The authors concluded that the results call into question claims that chrysotile is safe, and they called for population studies. They noted that the doses modeled a high, acute exposure.

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
• Who was studied: MRC5 human lung fibroblast cell line, obtained from Nazarbayev University (Kazakhstan); no human subjects
• Exposure: Chrysotile asbestos from the Kostanay Minerals JSC mining and processing plant (Zhitikara, Kazakhstan). Doses of 1 and 50 µg/cm2 were tried in preliminary experiments: 1 µg/cm2 produced no response and 50 µg/cm2 was too cytotoxic. Main experiments used 2.5, 5 and 10 µg/cm2, for times from 1 to 48 hours depending on the test.
• Main results:
  • Reactive oxygen species in MRC5 cells showed no change at 1 and 3 hours of exposure.
  • After 24 hours, reactive oxygen species rose twofold at 2.5 µg/cm2 (p < 0.0001) and 3.63 and 5.48 times at 5 and 10 µg/cm2 (p < 0.0001), compared with control cells.
  • Comet assay after 24 hours: DNA in comet tails was 9.87% at 2.5 µg/cm2, 27% at 5 µg/cm2 and 38% at 10 µg/cm2, versus less than 1% in cells without asbestos.
  • Cell viability (MTT assay): no obvious cytotoxic effect at 6 and 12 hours. Survival fell to 75.8% at 10 µg/cm2 after 24 hours (p < 0.0001). After 48 hours, viable cells were 83%, 74% and 65.9% at the corresponding doses.
  • Cell-free mitochondrial DNA in the culture medium rose significantly at 4 and 24 hours only at 10 µg/cm2. After 48 hours it rose significantly at all three doses, reaching a median of 1.37 × 10^16 copies/mL at 10 µg/cm2 (p less than or equal to 0.0001).
  • Six microRNAs were tested. All except hsa-miR-1228 changed expression at some dose or time, mostly after 48 hours. The authors found it difficult to trace a dose or time pattern.
• The authors' conclusion: The authors concluded that their results call into question the assertion that chrysotile asbestos is safe for human health, because it can induce adverse cellular effects at molecular and epigenetic levels. They called for further population-based studies.
• Limitations the authors state:
  • No correlation was found between cellular reactive oxygen species levels and DNA damage.
  • There was a relationship between cell viability and the number of extracellular mitochondrial DNA copies, but no correlation was found between them.
  • No definite conclusion about a dose-dependent effect on microRNAs was possible.
  • Scaled to adult lung surface area, the doses are high; the study modeled acute exposure rather than typical workplace inhalation.

Topics

Medical terms in this study, explained in our Lexicon: Chrysotile, Reactive Oxygen Species (ROS), Comet Assay.

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