Magnetometric evaluation for the effect of chrysotile on alveolar macrophages

Our plain-English summary of Magnetometric evaluation for the effect of chrysotile on alveolar macrophages, by T. Keira, M. Okada, H. Katagiri, et al (The Tohoku Journal of Experimental Medicine, 1998).

The study

• Authors: T. Keira, M. Okada, H. Katagiri, Y. Aizawa, I. Okayasu, M. Kotani
• Journal: The Tohoku Journal of Experimental Medicine
• Published: 1998;186(2):87-98
• Cited by: 16 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Alveolar macrophages are thought to play an important role in fibrogenesis due to asbestos exposure. In this experiment, we evaluated the effect mainly by unique magnetometry and also by conventional methods such as lactate dehydrogenase (LDH) activity measurement and morphological observations. Alveolar macrophages obtained from Syrian golden hamsters by bronchoalveolar lavages were exposed 18 hours in vitro to Fe3O4 as an indicator for magnetometry and chrysotile for experiments. A rapid decrease of the remanent magnetic field, so called "relaxation", was observed after the cessation of an external magnetic field in macrophages phagocytizing Fe3O4 alone, while relaxation was delayed in those concurrently exposed to chrysotile. Since relaxation is thought due to the cytoskeleton-driven random rotation of phagosomes containing iron oxide particles, chrysotile is considered to interfere with the cytoskeletal function of macrophages. Release of LDH from chrysotile-exposed macrophages into the medium was recognized, but it was not significantly higher than the controls. Apoptosis was negligible in macrophages exposed to chrysotile by the DNA ladder detection, the terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling method and morphological observations. Electron microscopical examinations revealed early necrotic changes in macrophages exposed to chrysotile. These findings indicate that cell magnetometry detects impaired cytoskeletal function due to in vitro exposure to chrysotile.

In plain English

This laboratory experiment tested whether chrysotile asbestos affects alveolar macrophages, the lung's scavenger cells. The cells were collected by lung washing from golden hamsters. In dishes, they were given tiny iron oxide particles plus 20, 40 or 60 µg/ml of UICC standard sample B chrysotile, or salt solution as a control, for 18 hours. The main test, cell magnetometry, measured how quickly the magnetic signal from swallowed iron particles faded after magnetization. Fading was slower in all chrysotile-exposed groups than in controls (p less than 0.01). The authors interpret slower fading as impaired function of the cell's internal skeleton. Release of LDH, an enzyme that leaks from damaged cells, was slightly higher with chrysotile, but the difference was not statistically significant. Tests for apoptosis (programmed cell death) showed no difference from controls. Electron microscopy showed fibers penetrating cells and internal changes such as vacuoles, but no obvious membrane destruction. The authors concluded that cell magnetometry is a sensitive method for detecting chrysotile's effect on these cells. They said the short exposure, serum in the medium and fibers shortened by ultrasonic stirring may explain the weak LDH and apoptosis results.

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) laboratory experiment using cell magnetometry, LDH release measurement, apoptosis tests (DNA ladder and TUNEL) and electron microscopy
• Who was studied: Alveolar macrophages obtained by bronchoalveolar lavage from male golden hamsters (about 100 g each); results from six animals in each group
• Exposure: UICC standard sample B chrysotile at 20, 40 or 60 µg/ml for 18 hours in vitro, with iron oxide (Fe3O4) particles added to all wells as a magnetometry indicator; controls received phosphate-buffered saline
• Main results:
  • Relaxation (fading of the remanent magnetic field) was delayed in all chrysotile-exposed groups compared with controls, with significant differences at the 1% level
  • Decay constant (× 10^-3 per second) was 4.49±0.32 in controls versus 2.34±0.35, 1.97±0.34 and 2.22±0.34 in the chrysotile groups, each p less than 0.01 compared with controls (the scanned table's column headings are jumbled, so which dose each value belongs to is unclear)
  • Mean LDH release rates from chrysotile-exposed macrophages were slightly higher than controls, but the difference was not statistically significant (p = 0.28)
  • No DNA fragmentation was found by the DNA ladder method, and the proportion of TUNEL-positive (apoptotic) cells in chrysotile-exposed macrophages did not differ significantly from controls (p = 0.24)
  • Under scanning electron microscopy, chrysotile-exposed macrophages were penetrated by fibers, but obvious destruction of cell membranes was not seen
  • Under transmission electron microscopy, a macrophage that had taken up many chrysotile fibers showed vacuoles and unclear margins of mitochondria and other organelles
• The authors' conclusion: The authors concluded that chrysotile is considered to interfere with the cytoskeletal function of macrophages, and that cell magnetometry is a sensitive method for detecting the effect of chrysotile on alveolar macrophages
• Limitations the authors state:
  • The exposure time was 18 hours, shorter than the 24 or 48 hours used in other studies, which the authors suggest contributed to low LDH release and negative apoptosis findings
  • Fetal bovine serum in the culture medium may have coated the fibers and reduced their toxicity to cell membranes
  • Fibers were likely shortened by repeated ultrasonic stirring, and shorter fibers produce milder LDH release
  • The detailed mechanism linking delayed relaxation to cytoskeletal dysfunction is still to be explained

Topics

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

Medical terms in this study, explained in our Lexicon: Chrysotile, Alveolar Macrophage, Asbestos Exposure, Lactate Dehydrogenase (LDH), Bronchoalveolar Lavage (BAL), Macrophage, Apoptosis.

Related studies

• Magnetometric evaluation of the effects of man-made mineral fibers on the function of macrophages using the macrophage cell line RAW 264.7 — K. Shibata, Y. Kudo, et al. (2007)
• Comparative cytotoxicity study of rock wool and chrysotile by cell magnetometric evaluation — Y. Kudo, M. Watanabe, et al. (2003)
• Cytotoxicity study of rock wool by cell magnetometric evaluation — Y. Kudo, M. Kotani, et al. (2009)
• Cytotoxicity study of high temperature wool (HT wool) by cell magnetometric evaluation — Y. Kudo, M. Kotani, et al. (2010)
• Asbestos induces apoptosis in human alveolar macrophages — R.F. Hamilton, L.L. Iyer, et al. (1996)
• Evaluation of hazardousness of refractory fibers by cell magnetometry — Y. Kudo, M. Kotani, et al. (2010)

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