Putative inhibitory effects of chrysotile, crocidolite, and amosite mineral fibers on the more complex surface membrane glycolipids and glycoproteins

Our plain-English summary of Putative inhibitory effects of chrysotile, crocidolite, and amosite mineral fibers on the more complex surface membrane glycolipids and glycoproteins, by H.A. Newman, Y.A. Saat, R.W. Hart (Environmental Health Perspectives, 1980).

The study

• Authors: H.A. Newman, Y.A. Saat, R.W. Hart
• Journal: Environmental Health Perspectives
• Published: 1980;34:103-11
• Cited by: 4 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Syrian hamster embryo cells were treated with galactose oxidase, followed by reduction with tritiated sodium borohydride at pH 7.4. The labeling patterns of galactosyl and N-acetyl galactosaminyl residues on the cell surface were altered in comparing scraped vs. unscraped and buffer vs. media-soaked cells treated with galactose oxidase. From these preliminary studies, the procedure to be used in most of the asbestos treatment studies was to treat cells in situ, in buffer with galactose oxidase, and then to label treated scraped cells with NaB(3)H(4). After 20 hr interaction between chrysotile asbestos and Syrian hamster cell cultures, an alteration in surface labeling of glycolipids and glycoproteins was observed. Tritiated disialogangliosides (G(Dla)) and the higher molecular weight labeled glycoproteins were significantly reduced by asbestos treatment. Similar chrysotile asbestos-treated cultures were grown in monolayers in MEM (Eagles) with 10% fetal bovine serum for 2, 24, 48, and 72 hr and then surface-labeled with galactose oxidase-. NaB(3)H(4) in phosphate buffer. Little or no difference was observed between surface-labeled lipid or protein distribution in untreated cells and those treated with asbestos for 2 hr. Asbestos-induced polar and neutral glycolipid pattern changes were observed at 24, 48, and 72 hr. Disialo- and trisialogangliosides (the more complex gangliosides) were decreased 85%, whereas globoside GL-4 was decreased by 60% at 72 hr. An overall decrease of labeled glycoproteins was observed at 24-48 hr. By 72 hr there was a complete loss of labeled protein bands with 80,000 dalton molecular mass. Since the changes in glycoproteins and glycolipids occur only after extended exposure of the cells to asbestos, the present studies support the concept that a metabolic rather than immediate masking effect is involved. Comparisons of treatment of Syrian hamster embryo cells with various asbestos fibers for 48 hr in the order of decreasing reduction in complex gangliosides were crocidolite>chrysotile (intermediate)>amosite. Effects of the above fibers on high molecular weight glycoproteins labeling followed the same order. The labeling pattern is reminiscent of the increased simplification of glycolipids and glycoproteins found in transformed cells. In the case of asbestos which appears to have no independent mutagenic capability, it is more likely that the membrane changes induced by asbestos serve to allow other mutagens to pass into the cell so as to act on the nuclear structure.

In plain English

This laboratory study exposed Syrian hamster embryo cells in culture to asbestos fibers (10 micrograms per milliliter). It tracked changes in sugar-containing fats (glycolipids, including gangliosides) and proteins (glycoproteins) on the cell surface, using radioactive labeling that measured each component's relative share. After 20 hours with chrysotile, the labeling of the disialoganglioside GD1a and of higher molecular weight glycoproteins was significantly reduced. Chrysotile caused little or no change at 2 hours, but changes appeared at 24, 48 and 72 hours. By 72 hours the more complex gangliosides were reported decreased by 85% and globoside GL-4 by 60%, and labeled protein bands of 80,000 daltons were completely lost. In a 48-hour comparison of fiber types, the reduction in complex gangliosides and high molecular weight glycoproteins was greatest with crocidolite, intermediate with chrysotile and smallest with amosite. The authors said that because the changes appeared only after extended exposure, the results supported a metabolic rather than an immediate masking effect. They proposed that asbestos may modify the cell surface so that carcinogens and viruses gain greater access to the cell nucleus.

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) cell culture experiment
• Who was studied: Syrian hamster embryo cells at passage 2, grown in culture dishes (14 glass Petri dishes in the first experiments), with matched untreated control cultures
• Exposure: Chrysotile asbestos at 10 micrograms per milliliter for 20 hours, and for 2, 24, 48 and 72 hours. Amosite, crocidolite and intermediate-sized chrysotile fibers at 10 micrograms per milliliter for 48 hours.
• Main results:
  • After 20 hours of chrysotile treatment, labeled disialogangliosides (GD1a) and higher molecular weight labeled glycoproteins were significantly reduced
  • Cells treated with chrysotile for 2 hours showed little or no difference from untreated cells in surface-labeled lipid or protein distribution
  • At 72 hours of chrysotile treatment, disialo- and trisialogangliosides (the more complex gangliosides) were reported decreased by 85%, and globoside GL-4 by 60%
  • By 72 hours of chrysotile treatment, labeled protein bands with a molecular mass of 80,000 daltons were completely lost
  • After 48 hours, the reduction in complex gangliosides was greatest with crocidolite, intermediate with chrysotile (intermediate-sized fibers) and least with amosite
  • As a percentage of untreated control at 48 hours, GD1a labeling was 21.9 with crocidolite, while the monosialoganglioside GM1 rose to 190
  • As a percentage of untreated control at 48 hours, trisialoganglioside GT1 was 22.0 with crocidolite, 45.8 with chrysotile (intermediate) and 98.3 with amosite. GD1a was 24.2 with chrysotile (intermediate) and 65.5 with amosite.
  • Labeled glycoproteins of intermediate molecular mass (80,000 daltons) were absent from crocidolite-treated cells
• The authors' conclusion: The authors stated that because the changes appeared only after extended exposure, their studies supported the concept of a metabolic rather than an immediate masking effect. They proposed that asbestos's role in cancer may be to modify the cell surface so that carcinogens and viruses gain greater access to the cell nucleus, promoting cell transformation. They noted that asbestos had not been shown to be a mutagen in earlier work they cited.
• Limitations the authors state:
  • The authors stated that whether the changes come from altered Golgi and/or lysosome metabolism requires additional study
  • The authors noted that the overall reduction in ganglioside labeling could reflect either masking of labeling sites or less ganglioside on the cell surface

Topics

Medical terms in this study, explained in our Lexicon: Chrysotile, Crocidolite, Amosite, Mineral Fiber, Glycoprotein.

Related studies

• Changes in lipid ordering of model phospholipid membranes treated with chrysotile and crocidolite asbestos — E.G. Gendek, A.R. Brody (1990)
• Trophoblast Glycoprotein is Associated With a Favorable Outcome for Mesothelioma and a Target for Antibody Drug Conjugates — L.M. Schunselaar, K. Monkhorst, et al. (2018)
• Mineral fibers induce apoptosis in Syrian hamster embryo fibroblasts — E. Dopp, B. Nebe, et al. (1995)
• Fiber dimensions and aspect ratio of crocidolite, chrysotile and amosite particles detected in lung tissue specimens — F.D. Pooley, N. Clark (1979)
• A study of the effect of chrysotile fiber surface composition on genotoxicity in vitro — M.J. Keane, J.W. Stephens, et al. (1999)
• Relationship of fiber surface iron and active oxygen species to expression of procollagen, PDGF-A, and TGF-beta(1) in tracheal explants exposed to amosite asbestos — J. Dai, A. Churg (2001)

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