Cytotoxicity and solubility evaluation of two types of whiskers by cell magnetometry

Our plain-English summary of Cytotoxicity and solubility evaluation of two types of whiskers by cell magnetometry, by Y. Kudo, Y. Aizawa (Environmental Health and Preventive Medicine, 2011).

The study

• Authors: Y. Kudo, Y. Aizawa
• Journal: Environmental Health and Preventive Medicine
• Published: 2011;16(5):327-34
• Read it: PubMed · Publisher · Free full text

Abstract

Objectives: We investigated two types of whiskers, an antimony-containing tin-oxide-coated aluminum borate whisker (CABW) and an aluminum borate whisker (ABW), which are asbestos substitutes, in order to evaluate the safety of these fibers.

Methods: The cytotoxicity and solubility of CABW and ABW were evaluated by cell magnetometry, LDH assay and solubility test.

Results: ABW was found to be cytotoxic by cell magnetometry and slightly less soluble than CABW. In addition, it was found that the solubility of both fibers was intermediate between that of chrysotile and rock wool, as compared to our previous test results. Regarding the LDH assay, no significant difference was found among the fibers tested. These findings suggested that CABW, the surface of which is coated with antimony-containing tin oxide, had lower cytotoxicity and slightly higher solubility than ABW.

Conclusions: This study was only a short-term cytotoxicity and solubility study. Therefore, further safety assessment should be carried out in long-term experiments to examine the half-life of these fibers and monitor the potential development of lung carcinoma or mesothelioma after intratracheal instillation of these fibers in rats.

In plain English

This laboratory study from Japan tested two man-made fibers used as asbestos substitutes: an aluminum borate whisker (ABW) and an aluminum borate whisker coated with antimony-containing tin oxide (CABW). Lung immune cells (alveolar macrophages) collected from six male rats were exposed to each fiber at 40, 80 or 160 micrograms per milliliter for 18 hours. A magnetic method tracking movement inside cells showed significant slowing with ABW at 80 and 160 micrograms per milliliter compared with unexposed cells. There was no marked change with CABW. A test for cell damage (LDH release) found no significant difference from unexposed cells for either fiber, although levels tended to rise with dose. Under the electron microscope, exposed cells took fibers inside them, and more cells had condensed nuclei. In flowing-fluid tests, CABW dissolved slightly faster than ABW. In physiological saline, both dissolved faster than chrysotile but slower than rock wool, reference fibers from the authors' earlier work. The authors concluded that CABW showed lower toxicity than ABW. Because this was only a short-term test, they called for long-term rat studies looking for lung cancer and mesothelioma.

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 rat lung macrophages exposed to fibers, using cell magnetometry, LDH assay and electron microscopy. It also included a flow-type fiber solubility test in physiological saline and in simulated body fluid (Gamble's solution).
• Who was studied: Alveolar macrophages collected by lung washing (bronchoalveolar lavage) from six male Fisher rats (F344/N Slc) weighing 200 to 250 g; results are expressed with n = 6.
• Exposure: Two whiskers supplied by Konica Minolta Business Expert Inc. CABW was 60 to 80% aluminum borate, 16 to 38% tin oxide, 2 to 5% titanium dioxide and 2 to 4% antimony trioxide. ABW was 97% aluminum borate. Both had a mean length of 10 to 30 micrometers and a mean width of 0.5 to 1.0 micrometers. Cells were exposed at 40, 80 or 160 micrograms per ml for 18 hours. Solubility was compared with chrysotile and rock wool fibers.
• Main results:
  • Cell magnetometry showed rapid relaxation in the control and CABW groups. Relaxation was significantly delayed in the ABW groups at 80 and 160 micrograms per ml compared with controls (p less than 0.05).
  • The relaxation coefficient showed no marked difference between CABW and controls. It was significantly lower in the 160 micrograms per ml ABW group (p less than 0.05).
  • LDH release showed no significant difference between controls and either the CABW or the ABW groups, although there was a trend to an increase with increasing concentration.
  • Electron microscopy of macrophages given 160 micrograms per ml of CABW or ABW showed fewer surface projections, fibers taken into phagocytic vacuoles, and more cells with condensed nuclei. The authors interpreted this as higher cytotoxicity than in controls.
  • Dissolution rate constants of CABW were a little higher than those of ABW.
  • In physiological saline, the dissolution rate constants of both whiskers were higher than that of chrysotile but lower than that of rock wool. The introduction describes chrysotile and rock wool as fibers whose solubility was previously examined in the authors' laboratory. Numerical values are shown only in a figure.
• The authors' conclusion: The authors concluded that ABW showed cytotoxicity in cell magnetometry and slightly lower solubility than CABW. They concluded that CABW, whose surface is coated with antimony-containing tin oxide, showed lower toxicity and slightly higher solubility than ABW. They called for further safety assessment examining fiber half-life and the development of lung carcinoma and mesothelioma after intratracheal instillation in rats.
• Limitations the authors state:
  • The authors state this was only a short-term cytotoxicity and solubility test.

Topics

Medical terms in this study, explained in our Lexicon: Chrysotile, Carcinoma, Mesothelioma.

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)
• Cytotoxicity study of high temperature wool (HT wool) by cell magnetometric evaluation — Y. Kudo, M. Kotani, et al. (2010)
• Evaluation of hazardousness of refractory fibers by cell magnetometry — Y. Kudo, M. Kotani, et al. (2010)
• Comparison of cytotoxicity of man-made vitreous fibres — K. Luoto, M. Holopainen, et al. (1997)
• In vitro activity of silicon carbide whiskers in comparison to other industrial fibers using four cell culture systems — N.F. Johnson, M.D. Hoover, et al. (1992)

Browse more research in Environmental Health and Preventive Medicine, or return to medical research.