Cytotoxicity study of high temperature wool (HT wool) by cell magnetometric evaluation

Our plain-English summary of Cytotoxicity study of high temperature wool (HT wool) by cell magnetometric evaluation, by Y. Kudo, M. Kotani, Y. Aizawa (Journal of Occupational Health, 2010).

The study

• Authors: Y. Kudo, M. Kotani, Y. Aizawa
• Journal: Journal of Occupational Health
• Published: 2010;52(2):106-14
• Read it: PubMed · Publisher

Abstract

Objectives: We performed a cytotoxicity study by cell magnetometry, measured lactate dehydrogenase (LDH) activity by enzyme assay, detected DNA ladder formation, and performed morphological examination by electron microscopy in order to evaluate the safety of high temperature wool (HT wool), an asbestos substitute, using long and short chrysotile fibers (CF) as positive controls and phosphate buffered saline (PBS) as a negative control.

Methods: Alveolar macrophages were isolated from male Fisher rats. Following the addition of iron oxide particles (Fe(3)O(4)) to macrophages, HT wool, long or short CF was added. Then, the remanence strength was measured for 20 min after magnetization by an external field. Percent LDH release was calculated after determining LDH activity. DNA was detected using an apoptosis detection kit. Morphological observation was performed by taking electron micrographs of macrophages in the groups treated with HT wool and long- and short-CF.

Results: Rapid relaxation, an indicator of decay of cytotoxicity, was observed by cell magnetometry immediately after magnetization was ended in the groups treated with HT wool and PBS, showing that HT wool causes no harmful effect on the cytoskeleton. The CF-treated groups had higher LDH activity than the PBS- and HT wool-treated groups. No fragmentation of DNA was observed in any group. In morphological observation, cytotoxicity in macrophages was lower in the HT wool-treated groups than in the CF-treated groups.

Conclusions: The results suggest that HT wool has no cytotoxicity, as evaluated by cell magnetometry, enzyme assay, DNA ladder detection and morphological examination.

In plain English

This laboratory experiment used lung immune cells (alveolar macrophages) from six male Fisher rats in Japan. The authors tested high temperature wool (HT wool), a rock wool asbestos substitute, at 50, 100 and 150 micrograms per millilitre. They compared it with long and short chrysotile fibers (50 micrograms per millilitre) and buffered salt solution (PBS). They used four tests: movement of magnetic particles inside the cells (slower movement, called delayed relaxation, indicates damage), leakage of enzyme LDH, DNA breakdown, and electron microscopy. In chrysotile groups, relaxation was slower and LDH release was higher (33.68% and 34.19%) than in HT wool groups (21.82% to 23.45%) and PBS (18.00%). The text reported the HT wool versus chrysotile differences as statistically significant and HT wool versus PBS as not significant; two magnetometry figure captions name fewer significant comparisons. No DNA breakdown was seen in any group. Short chrysotile caused the most severe microscopic cell damage. The authors concluded the results suggest HT wool has no cytotoxicity by these methods. They called for animal inhalation studies to further evaluate its safety.

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 rat alveolar macrophages using cell magnetometry, LDH enzyme assay, DNA ladder detection and electron microscopy
• Who was studied: Alveolar macrophages collected by lung lavage from six male Fisher rats (F344/N Slc) weighing 200–250 g, Kitasato University School of Medicine, Japan; study dates not stated
• Exposure: HT wool (high-alumina, low-silica stone wool) at 50, 100 and 150 µg/ml; long and short chrysotile fibers (CF) at 50 µg/ml as positive controls; PBS as negative control; 18-hour incubation
• Main results:
  • Relaxation values (remanence) were 38.55 ± 6.40% in the PBS group and 30.95 ± 2.85, 30.55 ± 3.60 and 39.41 ± 6.10% in the 50, 100 and 150 µg/ml HT wool groups, described as rapid relaxation
  • Relaxation was delayed in the chrysotile groups: 51.80 ± 6.01% (long CF) and 53.90 ± 3.88% (short CF)
  • By Scheffe's test, relaxation did not differ significantly between PBS and HT wool groups; the text reports significant differences (p less than 0.05) between HT wool and both chrysotile groups. Significance of chrysotile versus PBS is not reported.
  • Decay constants at 2 minutes were 3.25 ± 0.34 (PBS), 3.06 ± 0.29, 2.97 ± 0.26 and 2.93 ± 0.42 (HT wool 50, 100, 150 µg/ml), versus 1.80 ± 0.30 (long CF) and 1.54 ± 0.29 (short CF), all times 10 to the minus 3 per second
  • Percent LDH release was 18.00 ± 2.88% (PBS), 21.82 ± 6.15, 23.45 ± 4.73 and 23.24 ± 7.85% (HT wool 50, 100, 150 µg/ml), and 33.68 ± 7.57 and 34.19 ± 4.32% (long and short CF)
  • LDH release differed significantly (p less than 0.05) between HT wool and both chrysotile groups, but not between PBS and HT wool groups; chrysotile versus PBS significance is not reported
  • No DNA fragmentation was seen in any group, including the chrysotile groups (data not shown)
  • With 150 µg/ml HT wool, fiber cross sections were seen in macrophages but no apparent degeneration of the cytoplasm
  • Short chrysotile caused more vacuolization and more cells with condensed nuclei than long chrysotile, and the most severe damage to macrophages
• The authors' conclusion: The authors concluded that the results suggest HT wool has no cytotoxicity as evaluated by cell magnetometry, enzyme assay and DNA ladder detection (and morphological examination). In the discussion they described its cytotoxicity after short-term in vitro exposure as less marked than that of chrysotile.
• Limitations the authors state:
  • The findings come from short-term in vitro exposure; the authors said HT wool safety should be further evaluated in in vivo inhalation studies

Topics

Medical terms in this study, explained in our Lexicon: Lactate Dehydrogenase (LDH), Chrysotile, Alveolar Macrophage, Macrophage, LDH Release, Apoptosis.

Related studies

• 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)
• 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)
• Magnetometric evaluation for the effect of chrysotile on alveolar macrophages — T. Keira, M. Okada, et al. (1998)
• Cytotoxicity and solubility evaluation of two types of whiskers by cell magnetometry — Y. Kudo, Y. Aizawa (2011)
• Evaluation of hazardousness of refractory fibers by cell magnetometry — Y. Kudo, M. Kotani, et al. (2010)

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