Changes in lipid ordering of model phospholipid membranes treated with chrysotile and crocidolite asbestos

Our plain-English summary of Changes in lipid ordering of model phospholipid membranes treated with chrysotile and crocidolite asbestos, by E.G. Gendek, A.R. Brody (Environmental Research, 1990).

The study

• Authors: E.G. Gendek, A.R. Brody
• Journal: Environmental Research
• Published: 1990;53(2):152-67
• Cited by: 6 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

A variety of inorganic particles bind to cell membranes and cause alterations in phagocytosis, migration, and metabolism leading to eventual cell death. The mechanism which mediate these events at the complex membrane level are not known. In attempting to define the mechanisms of asbestos-induced membrane changes, we have prepared small unilamellar vesicles (SUV) of dipalmitoyl phosphatidylcholine as a simplified model of the cell membrane. Negatively stained preparations for electron microscopy demonstrated that the SUVs bind to both chrysotile and crocidolite asbestos fibers. Electron spin resonance showed that both asbestos types caused increased membrane rigidity at the level of the 12th carbon, whereas chrysotile induced increased rigidity at the 5th carbon level as well. Studies using DPPC membranes compared to SUVs made of phosphatidylcholine from egg yolk support the view that lipid peroxidation may play no significant role in alterations of membrane rigidity induced by the asbestos particle binding. Similar alterations of membrane rigidity and lipid peroxidation at the depth of the 12th carbon have been reported in complex naturally occurring erythrocyte membranes. This suggests that our observations may be relevant to biological membranes and that the model system of SUVs is appropriate for additional studies on the mechanisms of particle-induced membrane injury.

In plain English

This was a laboratory experiment, not a study of people. The authors made tiny artificial vesicles from pure phospholipids as a simplified cell membrane model and mixed them with chrysotile or crocidolite asbestos. Electron microscopy showed intact vesicles stuck to both fiber types; crocidolite adsorbed about half as much lipid as chrysotile. Using electron spin resonance, the authors measured membrane rigidity at different depths. Chrysotile raised the order parameter, a measure of lipid ordering (rigidity), near the 5th carbon by 11.1% over control (plus or minus 1.0%, standard error) in DPPC vesicles; crocidolite caused no measurable change there. Both fiber types caused statistically significant changes in a rigidity measure at the 12th carbon in all vesicle types. No changes were seen at the 16th carbon. On rat red blood cell membranes, all asbestos types except tremolite significantly increased lipid peroxidation; wollastonite, kaolinite and talc did not appear to. DPPC vesicles showed no peroxidation yet still changed, so the authors concluded that lipid peroxidation plays no significant role in these changes. They noted it is unknown whether such changes occur in more complex membranes, like those of macrophages, or affect cell function.

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 using model phospholipid membranes (small unilamellar vesicles) and rat erythrocyte membranes, studied by electron microscopy, electron spin resonance, lipid adsorption analysis and a lipid peroxidation assay
• Who was studied: No human or animal subjects. Artificial vesicles made of dipalmitoyl phosphatidylcholine (DPPC), egg yolk phosphatidylcholine (PC), phosphatidylglycerol (PG) and phosphatidylinositol (PI), plus membranes prepared from rat red blood cells. Work was done at the National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina.
• Exposure: Chrysotile and crocidolite asbestos in most experiments, at 2 mg/ml for the adsorption studies and 10 mg per 0.7 ml of vesicle preparation for the spin resonance studies, incubated at 37°C for 1 hour. The lipid peroxidation studies also used amosite and tremolite fibers and the non-asbestos dusts wollastonite, kaolin and talc.
• Main results:
  • Fiber surface area, calculated from measured length and diameter, was similar for the two asbestos types: 15.7 m2/g for chrysotile and 12.2 m2/g for crocidolite.
  • Intact vesicles were tightly adsorbed onto both chrysotile and crocidolite fibers. Larger portions of the crocidolite surfaces remained uncovered.
  • Average lipid adsorption onto crocidolite was about half of that onto chrysotile.
  • At the depth of the 5th carbon, the ESR order parameter S of DPPC vesicles rose 11.1% over control after chrysotile treatment, plus or minus 1.0% (relative values are given as mean plus or minus standard error of the mean). Crocidolite produced no alterations.
  • Changes in ESR parameters were expressed as a percentage of control values and presented as mean plus or minus the standard error of the mean.
  • After chrysotile treatment, the order parameter at the 5th carbon rose 25.5 plus or minus 4.0% over control in phosphatidylglycerol vesicles and 18.7 plus or minus 2.5% in phosphatidylinositol vesicles. Crocidolite caused no detectable changes at this depth.
  • The chrysotile increases in the order parameter at the 5th carbon were statistically significant (P less than 0.05) for all lipids except the egg yolk PC membranes.
  • At the depth of the 12th carbon, both chrysotile and crocidolite caused statistically significant (P less than 0.05) changes in the C:A ratio, a rigidity measure, in all vesicle types.
  • No quantitative alterations were noted at the depth of the 16th carbon (data not shown).
  • DPPC vesicles, which have no unsaturated bonds, showed no lipid peroxidation products.
  • In rat red blood cell membranes, all asbestos varieties except tremolite caused statistically significant increases in lipid peroxidation compared with untreated controls. The non-asbestos dusts did not appear to affect peroxidation.
  • Lipid peroxidation in egg yolk phosphatidylcholine vesicles was also stimulated by the asbestos fibers.
• The authors' conclusion: The authors concluded that lipid peroxidation plays no significant role in the membrane changes they measured by electron spin resonance. They also suggested that their observations may be relevant to biological membranes and that the vesicle model is appropriate for further studies of particle-induced membrane injury.
• Limitations the authors state:
  • The authors stated that there is no clear mechanistic explanation for the asbestos-induced changes in lipid ordering.
  • The authors stated that it is not known whether similar changes occur in more complex membranes such as those of macrophages, or whether these changes play any role in altering cell function.
  • Surface area was calculated only from fiber length and diameter. The authors noted that other techniques have shown chrysotile has a greater surface area because of its tubular structure.

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: Chrysotile, Crocidolite, Phagocytosis.

Related studies

• Chemical and photoelectron spectrometry analysis of the adsorption of phospholipid model membranes and red blood cell membranes on to chrysotile fibres — M.C. Jaurand, J.H. Thomassin, et al. (1980)
• Putative inhibitory effects of chrysotile, crocidolite, and amosite mineral fibers on the more complex surface membrane glycolipids and glycoproteins — H.A. Newman, Y.A. Saat, et al. (1980)
• A spin label study of the effect of chrysotile asbestos on erythrocyte membranes — E. Gendek, G. Bartosz, et al. (1984)
• Interactions of chrysotile asbestos with erythrocyte membranes — A.R. Brody, L.H. Hill (1983)
• A spin label study of the effects of asbestos, quartz, and titanium dioxide dusts on the bovine erythrocyte membrane — W. Leyko, E. Gendek (1985)
• Hemolysis by chrysotile asbestos fibers. I. Influence of the sialic acid content in human, rat, and sheep red blood cell membranes — J.P. Pelé, R. Calvert (1983)

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