Crocidolite-induced lipid peroxidation in rat lung microsomes. I. Role of different ions

Our plain-English summary of Crocidolite-induced lipid peroxidation in rat lung microsomes. I. Role of different ions, by M. Gulumian, T.A. Kilroe-Smith (Environmental Research, 1987).

The study

• Authors: M. Gulumian, T.A. Kilroe-Smith
• Journal: Environmental Research
• Published: 1987;43(1):267-73
• Cited by: 18 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Lipid peroxidation is increased by ferrous or ferric ions in rat lung microsomes both from rats pretreated with 3-methylcholanthrene and from untreated controls. This increase was dependent on the concentration of these ions in the reaction mixture. Crocidolite alone increased peroxidation in microsomal fractions. However, addition of ferric or ferrous ions with the crocidolite did not give a greater increase in the amount of peroxidation in microsomes. Chelation with EDTA of iron, whether originally present as free ions in the solution or attached to crocidolite, prevented lipid peroxidation. NADPH alone, when added to the microsomal fractions, did not produce any significant effect. However, when added concomitantly with crocidolite fibers, NADPH reduced the effect of crocidolite on lipid peroxidation. Magnesium, manganese, and calcium ions did not produce any significant effect on lipid peroxidation in the presence or absence of crocidolite. A reduced pH enhanced the rate of lipid peroxidation in line with increased solubility of iron salts at these pH values. All the above observations, taken together, lead to the conclusion that it is the iron in the crocidolite that is responsible for the latter's ability to enhance lipid peroxidation.

In plain English

This was a laboratory experiment, not a study of people. The authors, working in Johannesburg, South Africa, tested how crocidolite asbestos fibers affect lipid peroxidation, a form of chemical damage to fats, in microsomes (cell fractions) prepared from rat lungs. Microsomes came from untreated rats and from rats pretreated with the chemical 3-methylcholanthrene. Peroxidation was measured as formation of malondialdehyde. Crocidolite alone increased peroxidation. Added ferrous or ferric iron also substantially increased it in microsomes without fibers, but adding iron together with crocidolite gave no further increase. EDTA, a chemical that binds iron, protected against fiber-induced peroxidation, more so at higher concentrations. NADPH alone had no significant effect and slightly reduced the crocidolite effect. Magnesium, manganese and calcium had no significant effect. Acidic conditions increased peroxidation only when crocidolite was present. The authors concluded that the iron in crocidolite is responsible for its ability to enhance lipid peroxidation. They noted the acid effect may lack physiological significance, since cell pH is unlikely to reach 2, although localized low pH conditions are possible.

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 rat lung microsomes
• Who was studied: Lung microsomes from untreated control rats and from rats pretreated with 3-methylcholanthrene (3-MC). The number of rats is not given. The work was done at the National Centre for Occupational Health, Johannesburg, South Africa. Each figure point is the mean of two experiments.
• Exposure: Crocidolite fibers (UICC crocidolite) at 10 mg/ml, incubated at 37°C for 1 hour. Some mixtures also had ferrous or ferric iron, NADPH, EDTA, magnesium, manganese or calcium ions added, or were run at different pH values.
• Main results:
  • Crocidolite alone increased lipid peroxidation in the lung microsome preparations.
  • Ferrous or ferric ions substantially increased lipid peroxidation in both control and 3-MC-induced lung microsomes (P < 0.001). Mixtures that already contained crocidolite were not affected by these ions.
  • EDTA protected lung microsomes from fiber-induced lipid peroxidation (P < 0.001), and the protection increased with increasing EDTA concentration.
  • NADPH did not increase lipid peroxidation in control or induced lung microsomes, and had a slight protective effect in samples containing crocidolite.
  • Manganese, calcium and magnesium ions produced no significant change in lipid peroxidation in control or 3-MC-induced lung microsomes, with or without crocidolite.
  • With crocidolite present, low pH significantly increased lipid peroxidation above the level at physiological pH. pH had no effect on microsomes without crocidolite, and pH above 7.4 did not affect peroxidation.
  • Elemental analysis of the crocidolite found 28.0% iron, 23.3% silicon, 1.14% magnesium, 0.6% calcium, 0.086% manganese, and copper below 0.02% (below the detectable limit).
• The authors' conclusion: The authors concluded that it is the iron in crocidolite that is responsible for its ability to enhance lipid peroxidation. They suggested that iron might be of particular significance in asbestos cancers in men also exposed to chemical carcinogens.
• Limitations the authors state:
  • The effect of acidic pH might not have physiological significance, because cell pH is unlikely to reach 2, although localized low pH is possible.
  • A test found no ferrous iron contaminating the ferric chloride solution, but the authors could not exclude that ferric iron was converted to ferrous iron in the reaction mixture.

Topics

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

Medical terms in this study, explained in our Lexicon: Crocidolite.

Related studies

• Lipid peroxidation in microsomes induced by crocidolite fibres — M. Gulumian, F. Sardianos, et al. (1983)
• The stimulatory effects of asbestos on NADPH-dependent lipid peroxidation in rat liver microsomes — M. Fontecave, D. Mansuy, et al. (1987)
• Chrysotile inhibits glutathione-dependent protection against the onset of lipid peroxidation in rat lung microsomes — J.M. Arif, I. Ahmad, et al. (1996)
• The role of catalytic iron in asbestos induced lipid peroxidation and DNA-strand breakage in C3H10T1/2 cells — C.J. Turver, R.C. Brown (1987)
• Interrelationship between hemolysis and lipid peroxidation of human erythrocytes induced by silicic acid and silicate dusts — S.V. Singh, Q. Rahman (1987)
• 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)

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