Differential release of superoxide anions by macrophages treated with long and short fibre amosite asbestos is a consequence of differential affinity for opsonin

Our plain-English summary of Differential release of superoxide anions by macrophages treated with long and short fibre amosite asbestos is a consequence of differential affinity for opsonin, by I.M. Hill, P.H. Beswick, K. Donaldson (Occupational and Environmental Medicine, 1995).

The study

• Authors: I.M. Hill, P.H. Beswick, K. Donaldson
• Journal: Occupational and Environmental Medicine
• Published: 1995;52(2):92-6
• Cited by: 45 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Objective: To investigate the ability of short and long fibre samples of amosite asbestos to stimulate superoxide production in isolated rat alveolar macrophages, and to determine how opsonisation with rat immunoglobulin might modify this response.

Methods: Macrophages were isolated from rat lung by bronchoalveolar lavage and challenged with both opsonised and non-opsonised long and short fibres of amosite asbestos. Release of superoxide anions was measured by the spectrophotometric reduction of cytochrome c, in the presence and absence of superoxide dismutase.

Results: Both long and short fibre samples of amosite asbestos without opsonisation were ineffective in stimulating isolated rat alveolar macrophages to release superoxide anions in vitro. After opsonisation with immunoglobulin, however, a dramatic enhancement of release of superoxide anion was seen with long fibres, but not short, which confirms the importance of fibre length in mediating biological effects. The increased biological activity of the long fibre sample is explained by increased binding of the opsonin to the fibre surface as, at equal mass, the long fibres bound threefold more immunoglobulin than the short fibres.

Conclusion: Opsonisation is an important factor in modulation of the biological activity of fibres at the cellular level. Differences in binding of opsonin to samples of fibre previously considered to be identical apart from length, suggest that surface reactivity needs to be taken into account when fibres are compared. Binding of biological molecules, in vivo, may thus be an important modifying factor in the pathological processes initiated by fibres.

In plain English

This was a laboratory study on rat cells. The authors washed alveolar macrophages (lung scavenger cells) out of male Wistar rats' lungs and exposed them to long-fibre and short-fibre amosite asbestos samples. The short sample had been made by ball milling the long one, and only 37% of it by mass counted as fibre under the WHO definition. Fibres were tested bare or coated with rat immunoglobulin G (IgG), an antibody protein. The authors measured release of superoxide, a reactive form of oxygen. Uncoated fibres of either length did not stimulate release. Coated long fibres raised release by a mean of 19.4 nM per million cells above background. Coated short fibres gave a modest mean rise of 4.1 nM per million cells above background. At equal mass, long fibres bound threefold more IgG. The authors concluded that this coating affects fibre activity in cells and that differing IgG binding may explain the long fibres' greater activity. They noted that ball milling may have changed the short fibres' surface, and that the coating's role in living lungs needs further study.

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 isolated rat lung cells; each experiment was repeated at least three times
• Who was studied: Alveolar macrophages obtained by washing the lungs (bronchoalveolar lavage) of male Wistar rats; the number of rats is not stated
• Exposure: Long-fibre and short-fibre amosite asbestos samples, the short made by ball milling the long, each tested uncoated or coated (opsonised) with rat IgG; only 37% of the short sample by mass met the WHO fibre definition (longer than 5 micrometres, less than 3 micrometres in diameter, aspect ratio greater than 3 to 1)
• Main results:
  • Without IgG coating, neither the long nor the short amosite fibres stimulated rat alveolar macrophages to release superoxide
  • IgG-coated long amosite fibres stimulated superoxide release by a mean of 19.4 nM per million cells above background (printed as '19-4'); the effect of coating was statistically significant (P less than 0.001)
  • IgG-coated short amosite fibres produced a modest increase in superoxide release, a mean of 4.1 nM per million cells over background (printed as '4-1')
  • Across all experiments, fibre length had a highly significant effect, with long fibres more stimulating (P less than 0.001)
  • At equal mass, the long-fibre sample bound threefold more radiolabelled IgG than the short-fibre sample (P less than 0.001)
  • No treatment caused obvious toxicity to the macrophages, judged by release of the enzyme lactate dehydrogenase (data not shown)
• The authors' conclusion: The authors concluded that coating with opsonin (IgG) modulates the biological activity of fibres at the cellular level, and that differences in protein binding between samples previously considered identical apart from length may explain the fibres' biological activity
• Limitations the authors state:
  • The authors did not investigate the mechanism behind the increased superoxide release from coated long fibres
  • The authors described the suggestion that short amosite inhibits superoxide release as speculative and did not test it
  • Ball milling used to make the short sample may have changed its surface reactivity, so a less energetic method would be needed to obtain comparable long and short samples
  • The relative importance of opsonisation inside the living lung was not studied and needs further work

Topics

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

Medical terms in this study, explained in our Lexicon: Superoxide, Macrophage, Amosite, Alveolar Macrophage, Bronchoalveolar Lavage (BAL), Surface Reactivity.

Related studies

• Superoxide anion release by alveolar macrophages exposed to respirable industrial fibres: modifying effect of fibre opsonisation — K. Donaldson, I.M. Hill, et al. (1995)
• Enhancement of the macrophage oxidative burst by immunoglobulin coating of respirable fibers: fiber-specific differences between asbestos and man-made fibers — I.M. Hill, P.H. Beswick, et al. (1996)
• IgG specifically enhances chrysotile asbestos-stimulated superoxide anion production by the alveolar macrophage — R.K. Scheule, A. Holian (1989)
• Distinct Pro-Inflammatory Mechanisms Elicited by Short and Long Amosite Asbestos Fibers in Macrophages — R. Leinardi, J.R. Petriglieri, et al. (2023)
• Dehydroepiandrosterone inhibits the spontaneous release of superoxide radical by alveolar macrophages in vitro in asbestosis — W.N. Rom, T. Harkin (1991)
• Asbestos fibres and man made mineral fibres: induction and release of tumour necrosis factor-alpha from rat alveolar macrophages — A.G. Ljungman, M. Lindahl, et al. (1994)

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