Phagocytosis of asbestos fibers by human pulmonary alveolar macrophages

Our plain-English summary of Phagocytosis of asbestos fibers by human pulmonary alveolar macrophages, by T. McLemore, M. Corson, M. Mace, et al (Cancer Letters, 1979).

The study

• Authors: T. McLemore, M. Corson, M. Mace, M. Arnott, T. Jenkins, D. Snodgrass, R. Martin, N. Wray, B.R. Brinkley
• Journal: Cancer Letters
• Published: 1979;6(4-5):183-92
• Cited by: 23 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Human pulmonary alveolar macrophages (PAMs) were cultured for 24--72 h with varying concentrations (0--300 microgram/ml) of amosite asbestos (AS). At lower AS concentrations, (less than 100 microgram/ml) no decrease in cell viability occurred during the first 24 h of culture. Significant cytotoxicity (P less than 0.005 in all instances) was observed, however, following incubation for 24 h with higher AS concentrations (greater than 100 microgram/ml). Even following incubation with lower concentrations of AS, significant cytotoxicity (P less than 0.006 in all instances) was observed after 48 or 72 h of culture. Scanning electron microscopy (SEM) clearly illustrates the various stages of AS phagocytosis by PAMs. SEM also documented morphological changes in PAMs following AS exposure. These included increased zeiosis and the appearance of a fibrous-like material on the surface of AS fibers following initial contact with the PAM cytoplasmic membrane. Further study of the biological interactions between AS and human cells, such as PAMs, might provide valuable information regarding the etiology of AS-related lung disorders.

In plain English

This was a laboratory study in which the authors exposed human lung immune cells, called pulmonary alveolar macrophages, to amosite asbestos. The cells were rinsed from the lungs of 8 healthy non-smoking volunteers aged 19 to 29. They were cultured for 24 to 72 hours with amosite fibers (5 to 100 micrometers long) at 0 to 300 micrograms per milliliter, and cell survival was measured with a dye test. The authors reported that the damage to the cells depended on both dose and time. After 24 hours, 50 and 100 micrograms per milliliter did not significantly lower average survival compared with untreated cells (93%), while 300 micrograms per milliliter lowered it to 64%. After 72 hours, survival was 77% at 50 and 38% at 300 micrograms per milliliter, against 92% in untreated cells. Electron microscope images showed the cells engulfing fibers in two ways, increased blebbing of the cell surface, and a fibrous-like material on fibers where the cells touched them. The nature of this material was unknown. The authors concluded that amosite was only slightly toxic to these cells at low concentrations but significantly toxic at higher ones.

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 human cells in culture, using light microscopy and scanning electron microscopy
• Who was studied: Pulmonary alveolar macrophages (lung immune cells) obtained by saline lavage through a bronchoscope from 8 normal, healthy, non-smoking volunteers aged 19 to 29, in Houston, Texas. The viability table reports N = 5 per value. Dates of the study are not given (the article was received in October 1978).
• Exposure: Amosite asbestos fibers 5 to 100 micrometers long, washed with acetone, added to cell cultures at 0, 50, 100, 200 and 300 micrograms per milliliter for 24, 48 or 72 hours
• Main results:
  • Asbestos damage to the macrophages depended on both dose and time.
  • At 24 hours, mean viability was 93% in untreated cells, 92% at 50 micrograms per milliliter and 90% at 100 micrograms per milliliter. The authors marked the 50 and 100 values as not significant. Viability was 64% at 300 micrograms per milliliter.
  • At 48 hours, mean viability was 93% in untreated cells and 80%, 76%, 64% and 51% at 50, 100, 200 and 300 micrograms per milliliter. At 72 hours it was 92% in untreated cells and 77%, 70%, 49% and 38% at those concentrations. All values other than the 24-hour 50 and 100 microgram values differed from controls at p less than 0.005.
  • Even at the lower concentrations, cell viability significantly decreased after 48 or 72 hours of culture.
  • Under the electron microscope, cells exposed to 300 micrograms per milliliter for 24 hours were heavily laden with fibers. Some fibers were too large to be fully engulfed and protruded through the cell.
  • Electron microscopy showed two basic ways the macrophages engulfed fibers: starting at one end of the fiber, or starting near its middle and spreading toward both ends.
  • Cytoplasmic blebbing (zeiosis) of the cell surface increased during phagocytosis.
  • A fibrous-like material appeared on the surface of the fibers shortly after the cells contacted them, before the fibers were enclosed by the cell membrane.
• The authors' conclusion: The authors concluded that amosite asbestos was only slightly toxic to cultured human alveolar macrophages at low concentrations but showed significant cytotoxicity at higher concentrations. They added that further study of interactions between asbestos and human cells might help explain asbestos-related lung disease.
• Limitations the authors state:
  • The authors stated that the biochemical nature of the fibrous-like material seen on the fibers was unknown and still under study.

Topics

Medical terms in this study, explained in our Lexicon: Phagocytosis, Alveolar Macrophage, Amosite, Scanning Electron Microscopy (SEM), Etiology.

Related studies

• Comparison of phagocytosis of uncoated versus coated asbestos fibers by cultured human pulmonary alveolar macrophages — T.L. McLemore, V. Roggli, et al. (1981)
• Asbestos body phagocytosis by human free alveolar macrophages — T.L. McLemore, M.L. Mace, et al. (1980)
• Leaching of chrysotile asbestos in human lungs. Correlation with in vitro studies using rabbit alveolar macrophages — M.C. Jaurand, J. Bignon, et al. (1977)
• Asbestos-stimulated tumour necrosis factor release from alveolar macrophages depends on fibre length and opsonization — K. Donaldson, X.Y. Li, et al. (1992)
• Effects of asbestos on the random migration of rabbit alveolar macrophages — Q.N. Myrvik, E.A. Knox, et al. (1985)
• Sialic acid mediates the initial binding of positively charged inorganic particles to alveolar macrophage membranes — J.E. Gallagher, G. George, et al. (1987)

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