Dielectric changes in membrane properties and cell interiors of human mesothelial cells in vitro after crocidolite asbestos exposure

Our plain-English summary of Dielectric changes in membrane properties and cell interiors of human mesothelial cells in vitro after crocidolite asbestos exposure, by E. Dopp, L. Jonas, B. Nebe, et al (Environmental Health Perspectives, 2000).

The study

• Authors: E. Dopp, L. Jonas, B. Nebe, A. Budde, E. Knippel
• Journal: Environmental Health Perspectives
• Published: 2000;108(2):153-8
• Cited by: 9 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Asbestos induces cytogenetic and genotoxic effects in cultured cell lines in vitro. For further investigations of the fiber-induced cellular changes, electrorotation (ROT) measurements can be used to determine early changes of surface properties and dielectric cellular changes. In the present study, human mesothelial cells (HMC) were exposed to nontoxic concentrations of crocidolite asbestos (1 microg/cm(2)) for 12, 24, 30, 50, and 72 hr, and were investigated for changes in dielectric properties, morphologic and biochemical changes using ROT measurements, electron microscopy, and flow cytometry, respectively. The results of ROT measurements revealed slightly increased internal conductivity and decreased membrane conductance of HMC during the first 12 hr of exposure to crocidolite. This may be due to functional changes of ion channels of the cellular membrane. However, after exposures of >= 30 hr, reduced internal conductivity and increased membrane conductance of HMC occurred. These effects may be caused by permeabilization of the cell membrane and the leakage of ions into the surrounding medium. The membrane capacitance of HMC is always decreased during exposure of cells to crocidolite fibers. This decreased membrane capacitance may result from the observed reduction in the number of microvilli and from the shrinkage of cells as observed by electron microscopy and flow cytometry. Changes in composition of the plasma membrane were also observed after the labeling of phosphatidylserines (PS) on the cell surface. These observed changes can be related to apoptotic events. Whereas during the first 50 hr of exposure only a small number of HMC with increased exposure of PS on the cell surface was detected by flow cytometry, the dielectric properties of HMC showed marked changes during this time. Our results show that surface property changes of the cellular membrane of HMC as well as interior dielectric changes occur after the exposure of cells to crocidolite fibers. The observed changes are discussed in terms of complex combined cellular effects after amphibole asbestos exposure.

In plain English

This was a laboratory study. Human mesothelial cells were obtained from the ascites (abdominal) fluid of noncancerous patients at the University Hospital in Rostock, Germany. They were exposed to crocidolite asbestos for 12 to 72 hours at a concentration the authors called nontoxic (1 microgram per square centimetre). The authors measured how the cells spun in a rotating electric field (electrorotation) and also used electron microscopy and flow cytometry. After 12 hours, the cells' peak rotation moved from 15 kHz to 40 kHz. After 30 hours, treated cells rotated up to 75% slower than untreated cells. By 72 hours the difference from controls was only 15%. The authors read the later changes as a leakier cell membrane. Exposed cells lost microvilli (fine surface projections) and shrank. Within 50 hours, 16-18% of exposed cells carried a surface marker that can be related to apoptosis (programmed cell death), compared with up to 12% of untreated cells. This rose to up to 40% only after 70 hours. The authors suggested that these early changes might be part of the first step of cancer development.

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) experiment on cultured human cells
• Who was studied: Human mesothelial cells (first passage only) obtained from ascites fluid of noncancerous patients at the University Hospital in Rostock, Germany. The number of patients is not given. Syrian hamster embryo fibroblasts were also tested for comparison.
• Exposure: UICC standard crocidolite asbestos at 1 microgram per square centimetre (printed as '1 pg/cm2' because of scanning damage; the abstract gives 1 microg/cm2), for 12, 24, 30, 50 and 72 hours. UICC chrysotile at the same concentration was used for comparison in some tests.
• Main results:
  • Untreated cells rotated fastest at 15 kHz. After 12 hours of crocidolite exposure, this peak moved to 40 kHz and rotation speed increased about four times.
  • After 30 hours of crocidolite exposure, the rotation peak shifted to 200 kHz and the treated cells' rotation speed decreased by up to 75% compared with untreated cells.
  • After 72 hours of crocidolite exposure, the difference from control measurements was only 15%.
  • The authors interpreted the measurements as showing two phases. Early on, internal conductivity increased and membrane conductivity decreased. After more than 30 hours, internal conductivity decreased and membrane conductivity increased, which the authors interpreted as permeabilization of the cell membrane.
  • Electron microscopy showed fewer microvilli on crocidolite-exposed mesothelial cells after 12 hours and an extensive loss of microvilli after 48 hours.
  • Exposed cells were smaller. Measured on 30 untreated and 30 crocidolite-treated cells, mean size was 311.6 square micrometres for controls and 228.2 square micrometres for crocidolite-treated cells.
  • Within 50 hours of crocidolite exposure, 16-18% of the mesothelial cells bound annexin V, a marker of phosphatidylserine on the cell surface that the authors relate to apoptotic events. Up to 12% of untreated control cells did so (mean 8.7%).
  • An increase in annexin V binding, up to 40% of cells, was seen only after 70 hours of crocidolite exposure.
  • Features the authors describe as typical of apoptotic cells were seen by transmission electron microscopy in asbestos-exposed mesothelial cells after more than 70 hours.
  • In the later phase (more than 30 hours), the main rotation peak frequency increased for the human mesothelial cells but decreased for the Syrian hamster embryo fibroblasts.
  • The authors described the annexin V results after chrysotile exposure (same concentration) as completely different from those after crocidolite.
• The authors' conclusion: The authors concluded that crocidolite changes the electrical properties of the mesothelial cell membrane and cell interior, detectable after 12 hours, together with loss of microvilli, reduced cell size and increased phosphatidylserine on the cell surface. They suggested it is possible that these early changes are components of the initiation step of the multistage process of carcinogenesis.
• Limitations the authors state:
  • Only annexin V and propidium iodide labeling were done. The authors state that detecting apoptotic cells requires more biologic end points.
  • The relatively high annexin V binding in untreated controls may reflect membrane damage from trypsinizing the adherent cultures for flow cytometry, which can give some false-positive results.
  • The weaker effect seen at 50 and 72 hours may reflect the cultures continuing to grow after exposure, increasing the share of normal 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: Mesothelial Cells, Crocidolite, Asbestos Exposure, Amphibole Asbestos.

Related studies

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• Changes in DNA 8-hydroxyguanine levels, 8-hydroxyguanine repair activity, and hOGG1 and hMTH1 mRNA expression in human lung alveolar epithelial cells induced by crocidolite asbestos — H.N. Kim, Y. Morimoto, et al. (2001)
• Iron-related toxicity of single-walled carbon nanotubes and crocidolite fibres in human mesothelial cells investigated by Synchrotron XRF microscopy — F. Cammisuli, S. Giordani, et al. (2018)
• DNA damage in bronchial epithelial and mesothelial cells with and without associated crocidolite asbestos fibers — J. Nygren, S. Suhonen, et al. (2004)
• Apoptosis induced by crocidolite asbestos in human lung epithelial cells involves inactivation of Akt and MAPK pathways — A. Baldys, P. Pande, et al. (2007)

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