Macrophage functions after exposure to mineral fibers

Our plain-English summary of Macrophage functions after exposure to mineral fibers, by F. Tilkes, E.G. Beck (Environmental Health Perspectives, 1983).

The study

• Authors: F. Tilkes, E.G. Beck
• Journal: Environmental Health Perspectives
• Published: 1983;51:67-72
• Cited by: 26 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

UICC, other well-defined asbestos samples and different man-made mineral fibers (MMM) such as glass fiber and synthetic amphibole asbestos were studied in vitro by using rat and guinea pig lung macrophages. These samples had relatively narrow length and diameter spectra. Most of the fiber samples were added to the cultures on a gravimetric basis, although some were added on a numerical basis. Electrocorundum and DQ12 (Dorentruper Quartz) were used as controls at comparable gravimetrical concentrations. The assays used were the release of lactate dehydrogenase (to demonstrate plasma membrane permeability) and the release of beta-glucuronidase (to indicate lysosomal permeability). Carbohydrate metabolism was monitored by the measurement of lactic acid production and, as one of the tests for macrophage function, the production of lysozyme was determined. The phagocytic ability of the cells was measured, after the addition of opsonized zymosan, by bioluminescence following luminol enhancement. Only some results could be evaluated, however, due to technical difficulties. A length- and dose-dependent cytotoxicity of the fibers was found in this system which was similar to that previously described with permanent cell lines. No great differences were found between fibers having different physicochemical compositions if their geometric dimensions were similar. Long, very thin fibers of glass, chrysotile, crocidolite and synthetic fluoroamphiboles were all toxic in the test system.

In plain English

In this laboratory study, the authors exposed lung macrophages (immune cells washed out of guinea pig and rat lungs) to asbestos and man-made mineral fibers in culture. The fibers included UICC chrysotile, crocidolite and amosite, other defined fractions of chrysotile and crocidolite, glass fibers and synthetic fluoroamphiboles. Quartz (DQ12) and electrocorundum served as comparison dusts. The authors measured enzyme release as a sign of cell damage, lactic acid and lysozyme production, and the cells' ability to engulf particles. In guinea pig macrophages, cell damage depended on fiber length, except for the synthetic amphibole in the 15-fraction experiment. For glass fibers it depended on both length and diameter. Very thin fibers could be highly toxic even when short, while glass fiber samples 3 micrometers thick were not toxic. At equal fiber numbers, chrysotile appeared less toxic than crocidolite, amosite and glass fiber, which the authors suggested may reflect weight differences. At 100 micrograms of dust per milliliter, all four fiber types tested significantly reduced engulfing ability, though only some of these results could be evaluated. The authors concluded that fibers of different composition but similar dimensions differed little in toxicity.

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 lung macrophage cell cultures
• Who was studied: Unstimulated alveolar (lung) macrophages obtained by lung lavage from guinea pigs and rats. The reported results are from guinea pig macrophages. The number of animals is not stated.
• Exposure: UICC asbestos samples (chrysotile, crocidolite, amosite), defined length and diameter fractions of chrysotile (Jeffrey and Munroe fibrils) and crocidolite, glass fibers (including JM 100) and synthetic fluoroamphiboles. Doses were given either by number (100 fibers per cell) or by weight (100 micrograms of dust per million cells). DQ12 quartz and electrocorundum were the control dusts.
• Main results:
  • At 100 fibers per cell, guinea pig macrophage damage (release of the enzymes LDH and beta-glucuronidase) depended on fiber length for all four fiber types tested.
  • At this low concentration, the authors found no significant difference between the two enzyme measures (LDH and beta-glucuronidase release).
  • At equal fiber numbers, chrysotile showed relatively low toxicity compared with crocidolite, amosite and glass fiber. The authors suggested this may be due to weight differences at the same numerical dose.
  • With the 15 new fiber fractions, LDH release depended on fiber length, with or without serum, for all fiber types except the synthetic amphibole.
  • Comparing pairs of glass fiber samples, toxicity depended on both diameter and length. Very thin fibers could be highly toxic even when short. Among fibers about 1.0 micrometer in diameter, only the longer fibers caused high LDH release. The glass fiber samples 3 micrometers in diameter were not toxic in this system.
  • Glass fiber reduced lactic acid production considerably less than chrysotile and crocidolite fractions of similar dimensions.
  • UICC asbestos samples had a small effect on lysozyme production, detected only at high concentrations. At very low concentrations the authors found an enhancement of cellular activity.
  • At 100 micrograms of dust per mL, the UICC asbestos samples and JM 100 glass fiber caused a significant depression of phagocytosis (particle engulfing) for all four fiber types.
• The authors' conclusion: The authors concluded that fibers of different physicochemical composition showed no great differences in toxicity if their dimensions were similar. Long, very thin fibers of glass, chrysotile, crocidolite and synthetic fluoroamphiboles were all toxic in the test system. They also stated that more fiber fractions with narrowly defined length and diameter are needed for better comparisons.
• Limitations the authors state:
  • Because of technical problems, only some results of the phagocytosis assay could be evaluated.
  • No data were available on the number of fibers per unit weight, so tests at different numerical concentrations could not be done.

Topics

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

Medical terms in this study, explained in our Lexicon: Macrophage, Mineral Fiber, UICC, Amphibole Asbestos, Lactate Dehydrogenase (LDH), Chrysotile, Crocidolite.

Related studies

• Interleukin 1 production and accessory cell function of rat alveolar macrophages exposed to mineral dust particles — Y. Oghiso, Y. Kubota (1987)
• Effects of chrysotile and acid-treated chrysotile on macrophage cultures — E.G. Beck, P.F. Holt, et al. (1971)
• Response of cell cultures to asbestos fibers — J. Bruch (1974)
• 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)
• Secretion of fibronectin by mineral dust-derived alveolar macrophages and activated peritoneal macrophages — R. Davies, G. Erdogdu (1989)
• Polyvinylpyridine-N-oxide and carboxymethyl cellulose inhibit mineral dust-induced production of reactive oxygen species by human macrophages — P. Nyberg (1991)

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