Magnetometric evaluation of the effects of man-made mineral fibers on the function of macrophages using the macrophage cell line RAW 264.7

Our plain-English summary of Magnetometric evaluation of the effects of man-made mineral fibers on the function of macrophages using the macrophage cell line RAW 264.7, by K. Shibata, Y. Kudo, M. Tsunoda, et al (Industrial Health, 2007).

The study

• Authors: K. Shibata, Y. Kudo, M. Tsunoda, M. Hosokawa, Y. Sakai, M. Kotani, Y. Aizawa
• Journal: Industrial Health
• Published: 2007;45(3):426-36
• Cited by: 4 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The toxic effects of man-made mineral fibers (MMMFs) have been evaluated by cell magnetometry using alveolar macrophages (AMs). Recently, on the other hand, the murine macrophage cell line, RAW 264.7, became available and has been used as an in vitro model of AMs. The objective of this study was to determine whether or not cell magnetometry using RAW 264.7 cells can be used to evaluate the toxic effects of MMMFs. RAW 264.7 cells were exposed to one of the MMMFs, potassium octatitanate (PT) or silicon carbide whisker (SiC) at 0, 20, 40 and 60 microg/ml, or chrysotile as a positive control at 0, 15, 20 and 25 microg/ml. The toxic effects of fibers were evaluated by cell magnetometry and LDH assay. For this comparison, AMs were also exposed to chrysotile fibers (CF). In the RAW 264.7 cells exposed to PT 20, 40, 60 or SiC 20, 40, 60, CF 15, 20 and 25 microg/ml, significant delayed relaxation were observed compared with the respective control. In the LDH assay, significant increases in LDH in the supernatant of the cells exposed to PT 20, 40, 60, SiC 20, 40, 60 and CF 15, 20, 25 microg/ml were observed. In AMs exposed to CF 20, 25 microg/ml significant delayed relaxation and significant increases in LDH compared with the control were observed. The levels of MMMFs that induced significant differences were similar for cell magnetometry and LDH. The levels of CF that induced significant differences in cell magnetometry and LDH were identical for RAW 264.7 cells and AMs. Our results suggest that cell magnetometry using RAW 264.7 cells is adequate to evaluate the cytotoxicity of exposure to MMMFs.

In plain English

This laboratory study tested whether a mouse macrophage cell line, RAW 264.7, could stand in for macrophages taken from rat lungs (alveolar macrophages) in a method called cell magnetometry. Macrophages are immune cells that engulf inhaled particles, and the method tracks how cells move tiny magnetic particles inside them. RAW 264.7 cells were exposed to two man-made mineral fibers, potassium octatitanate whiskers (PT) and silicon carbide whiskers (SiC), at 20, 40 and 60 µg/ml. Other RAW 264.7 cells were exposed to chrysotile asbestos at 15, 20 and 25 µg/ml as a known toxic comparison. Rat alveolar macrophages were exposed to chrysotile only. Cell damage was also measured by release of the enzyme LDH. In RAW 264.7 cells, every tested dose of PT, SiC and chrysotile significantly slowed particle movement (called delayed relaxation) and raised LDH compared with unexposed cells. The slowing grew with dose for PT and SiC. In rat alveolar macrophages, chrysotile effects were significant at 20 and 25 µg/ml. Microscopy showed the cells had engulfed the fibers. The authors concluded that cell magnetometry using RAW 264.7 cells is useful for evaluating the toxic effects of these fibers.

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 comparing a macrophage cell line with rat alveolar macrophages
• Who was studied: The murine (mouse) peritoneal macrophage cell line RAW 264.7, plus alveolar macrophages obtained by lung lavage from male F344 rats (six rats per experiment), Japan; 6 tubes per concentration
• Exposure: RAW 264.7 cells: chrysotile fibers (positive control) at 0, 15, 20 or 25 µg/ml, and potassium octatitanate whiskers (PT) or silicon carbide whiskers (SiC) at 20, 40 or 60 µg/ml, for 48 h. Rat alveolar macrophages: chrysotile at 0, 15, 20 or 25 µg/ml for 18 h
• Main results:
  • RAW 264.7 cells exposed to chrysotile at 15, 20 and 25 µg/ml had significantly higher B20 (%) (delayed relaxation) than the PBS (unexposed) groups
  • Rat alveolar macrophages exposed to chrysotile at 20 and 25 µg/ml had significantly higher B20 (%) than the PBS groups
  • RAW 264.7 cells exposed to PT or SiC at 20, 40 and 60 µg/ml showed significantly delayed relaxation, increasing with dose
  • LDH in the supernatant of RAW 264.7 cells was significantly higher at PT 20, 40 and 60 µg/ml and SiC 20, 40 and 60 µg/ml than in controls
  • LDH was significantly raised in RAW 264.7 cells at chrysotile 15, 20 and 25 µg/ml, and in alveolar macrophages at chrysotile 20 and 25 µg/ml
  • Electron microscopy showed RAW 264.7 cells engulfed chrysotile, PT and SiC fibers; exposed cells showed microtubule aggregation and loss of surface microvilli
• The authors' conclusion: The authors concluded that cell magnetometry using RAW 264.7 cells is useful for evaluating the toxic effects of man-made mineral fibers, and that combining LDH with cell magnetometry may be the most efficacious approach
• Limitations the authors state:
  • SiC was so hard that samples were difficult to slice, so the electron micrograph of SiC-exposed cells was relatively unclear

Topics

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

Medical terms in this study, explained in our Lexicon: Mineral Fiber, Macrophage, Alveolar Macrophage, Chrysotile.

Related studies

• Magnetometric evaluation for the effect of chrysotile on alveolar macrophages — T. Keira, M. Okada, et al. (1998)
• Comparative cytotoxicity study of rock wool and chrysotile by cell magnetometric evaluation — Y. Kudo, M. Watanabe, et al. (2003)
• 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)
• Cytotoxicity study of rock wool by cell magnetometric evaluation — Y. Kudo, M. Kotani, et al. (2009)
• N-acetylcysteine prevents cytotoxic effects induced by man-made mineral fibers in a human bronchial epithelial cell line — M. Zhang, H. Xia, et al. (2018)

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