Effects of chrysotile on a lysosomal enzyme preparation and on the hydrolytic enzyme activity of cultured alveolar macrophages

Our plain-English summary of Effects of chrysotile on a lysosomal enzyme preparation and on the hydrolytic enzyme activity of cultured alveolar macrophages, by R. Desai, R.J. Richards (Environmental Health Perspectives, 1983).

The study

• Authors: R. Desai, R.J. Richards
• Journal: Environmental Health Perspectives
• Published: 1983;51:125-30
• Cited by: 2 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

The interaction between chrysotile and three lysosomal enzymes (acid phosphatase, acid RNase and acid protease) in isolated lysosomal enzyme-rich preparations (LEP), from sheep alveolar macrophages maintained in the presence and absence of serum components or pulmonary surfactant at pH 5.0 and pH 7.0 for up to 22 days, is investigated. It is concluded that chrysotile does not inhibit or enhance lysosomal enzyme activity at either pH but may preferentially absorb specific enzymes and that the binding reaction between any given enzyme and mineral can be dependent on the presence of other organic compounds. The release of three hydrolytic enzymes (beta-galactosidase, acid RNase and protease) from cultured rabbit alveolar macrophages, in the presence of different concentrations of bovine serum (5-20%) and in the presence and absence of chrysotile for 72 hr, was also studied. Chrysotile enhances early differential release of each hydrolytic enzyme, but after 72 hr both control and chrysotile-treated cultures (maintained in 10-20% serum) have very similar intra- and extracellular levels of hydrolytic activity. The apparent differential release of lysosomal enzymes by untreated macrophages, which is dependent on serum concentration and time in vitro, is discussed.

In plain English

This was a laboratory study of cells and enzymes, not of people. The authors took a lysosomal enzyme-rich preparation from sheep alveolar (lung air-sac) macrophages and kept it with or without UICC chrysotile A for up to 22 days at pH 5.0 and pH 7.0, with and without serum or pulmonary surfactant. Chrysotile did not inhibit, destroy or enhance the enzymes' activity at either pH. At pH 5.0 it did appear to absorb some enzymes from solution: acid RNase more readily than acid protease, and not acid phosphatase. Serum components reduced this binding, most noticeably for acid RNase; surfactant interfered less with acid RNase binding. At pH 7.0, less acid RNase and protease appeared bound. In cultured rabbit alveolar macrophages kept for 3 days in 5% to 20% serum, chrysotile caused an early release of enzymes, and cell viability stayed above 98%. Except in 5% serum, after 72 hours enzyme levels outside the cells were no higher in chrysotile-treated cultures than in untreated ones. The authors asked whether chrysotile merely speeds up a natural release process in this laboratory system.

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) experiments on an isolated lysosomal enzyme preparation and on cultured alveolar macrophages
• Who was studied: A lysosomal enzyme-rich preparation (LEP) from alveolar macrophages washed out of fresh sheep lungs obtained from a slaughterhouse; and rabbit alveolar macrophages collected by lavage, cultured at 1 x 10^6 cells per culture in 5%, 10%, 15% or 20% fetal bovine serum medium
• Exposure: UICC chrysotile A: 1 mg/mL with the enzyme preparation for up to 22 days, and heat-sterilized chrysotile added to macrophage cultures for 3 days (dose printed as '100 gg/culture' in the scanned text, apparently 100 micrograms)
• Main results:
  • In the enzyme preparation at pH 5.0, chrysotile did not enhance or inhibit lysosomal enzyme activity
  • Without chrysotile, enzyme activity in the preparation fell over 22 days at pH 5.0 by 42% for acid ribonuclease and 76% for acid protease (acid phosphatase fell 71%)
  • At pH 5.0, chrysotile appeared to remove acid RNase from solution more readily than acid protease, and did not absorb acid phosphatase
  • At pH 5.0, serum components reduced the absorption of enzymes by chrysotile, most noticeably for acid RNase
  • At pH 5.0, pulmonary surfactant did not interfere with chrysotile's binding of acid RNase to the same extent as serum
  • At pH 7.0 chrysotile also did not enhance or destroy enzyme activity
  • At pH 7.0, less acid RNase and protease appeared bound to the mineral than at pH 5.0
  • In cultured rabbit macrophages, chrysotile started an early release of hydrolytic enzymes, largely regardless of serum concentration
  • Except in 5% serum, levels of enzymes outside the cells after 72 hours were no higher in chrysotile-treated cultures than in control cultures
  • Cell viability was greater than 98% throughout the macrophage experiments, as assessed by eosin dye exclusion
  • In 5% serum cultures, total beta-galactosidase and acid RNase activities rose by 35% and 22% after 3 days
• The authors' conclusion: The authors concluded that chrysotile does not inhibit or enhance lysosomal enzyme activity at either pH but may preferentially absorb specific enzymes. They also raised the question of whether chrysotile merely accelerates a natural process of enzyme release in this in vitro system.
• Limitations the authors state:
  • The authors stated that their suggested explanations need more knowledge of lysosomal structure and of how the enzymes are held within it

Topics

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

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

Related studies

• Lysosomal enzyme secretion by macrophages during intracellular storage of particles — R.T. Dean, W. Hylton, et al. (1979)
• Spontaneous lysosomal enzyme secretion by a murine macrophage-like cell line — W. Jessup, R.T. Dean (1980)
• In vitro biodegradation of chrysotile fibres by alveolar macrophages and mesothelial cells in culture: comparison with a pH effect — M.C. Jaurand, A. Gaudichet, et al. (1984)
• Enhanced lipid peroxidation and lysosomal enzyme activity in the lungs of rats with prolonged pulmonary deposition of crocidolite asbestos — J. Jajte, I. Lao, et al. (1987)
• Effects of asbestos and beryllium on release of alveolar macrophage enzymes — K.Y. Kang, D. Bice, et al. (1979)
• Asbestos induces selective release of lysosomal enzymes from mononuclear phagocytes — P. Davies, A.C. Allison, et al. (1974)

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