Fibre-induced lipid peroxidation leads to DNA adduct formation in Salmonella typhimurium TA104 and rat lung fibroblasts

Our plain-English summary of Fibre-induced lipid peroxidation leads to DNA adduct formation in Salmonella typhimurium TA104 and rat lung fibroblasts, by P.J. Howden, S.P. Faux (Carcinogenesis, 1996).

The study

• Authors: P.J. Howden, S.P. Faux
• Journal: Carcinogenesis
• Published: 1996;17(3):413-9
• Cited by: 28 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Certain end-products of lipid peroxidation bind to DNA forming a fluorescent chromophore. Incubation of both Salmonella typhimurium TA104 and a rat lung fibroblast cell line, RFL-6, with various types of mineral fibre resulted in a time- and dose-dependent increase in DNA fluorescence. The increase in DNA fluorescence was shown to be directly related to the amount of iron that could be mobilized from the fibre surface using in vitro studies in the absence of cells or bacteria. Crocidolite and man-made vitreous fibre-21 (MMVF-21) mobilized significant quantities of iron and were significantly more active than chrysotile and refactory ceramic fibre-1 (RCF-1). Fibre-induced malondialdehyde-DNA adduct formation, the fluorescent product, was increased by incubating cells with buthionine sulfoximine and ameliorated by co-treatment with N-acetylcysteine, indicating a protective role for glutathione. Similarly, vitamin E was also shown to inhibit DNA adduct formation. These results suggest that mineral fibre-induced lipid peroxidation produced genotoxic products which can diffuse into nucleus and interact with cellular DNA. In conclusion, fibre-induced lipid peroxidation may be a possible mechanism in the genotoxic action of fibrous materials.

In plain English

This was a laboratory study in which the authors incubated Salmonella typhimurium TA104 and a rat lung fibroblast cell line (RFL-6) with mineral fibres and measured DNA fluorescence (the fluorescent product attributed to malondialdehyde-DNA adducts, though the authors noted other lipid peroxidation products give similar spectra), lipid peroxidation (thiobarbituric acid reactive substances, TBARS) and iron mobilised from fibre surfaces in cell-free tests. The fibres were UICC crocidolite and chrysotile, man-made vitreous fibre-21 (MMVF-21) and refractory ceramic fibre-1 (RCF-1). In TA104, to which hydrogen peroxide was added to enhance assay sensitivity, crocidolite and MMVF-21 produced time- and concentration-dependent increases in DNA fluorescence (P less than 0.005), while chrysotile and RCF-1 gave small but statistically significant increases (P less than 0.02). Total iron mobilised was 149 nmol/mg for crocidolite, 121 for MMVF-21, 69 for chrysotile and 10 for RCF-1. In RFL-6 cells, MMVF-21 at 2 micrograms/cm2 and crocidolite at 5 micrograms/cm2 significantly increased DNA fluorescence (P less than 0.01); chrysotile gave a slight increase and RCF-1 none. Removing fibre iron with chelators reduced or abolished adduct formation; buthionine sulfoximine increased adducts, co-treatment with N-acetylcysteine returned levels to those without buthionine sulfoximine, and vitamin E reduced adducts. The authors concluded fibre-induced lipid peroxidation may be a possible mechanism in the genotoxic action of fibrous materials.

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 experimental study using bacteria (Salmonella typhimurium TA104), a rat lung fibroblast cell line and cell-free chemical assays
• Who was studied: Salmonella typhimurium TA104 cultures, RFL-6 rat lung fibroblasts (passages 21-27), and isolated calf thymus DNA; laboratory work at the Institute of Occupational Health, University of Birmingham, UK
• Exposure: UICC crocidolite and chrysotile asbestos, MMVF-21 and RCF-1; bacteria exposed to 0.4 or 0.8 mg fibre (with 0.5 mM H2O2), RFL-6 cells to 2 and 5 micrograms/cm2, with or without BSO, NAC or vitamin E
• Main results:
  • In TA104, crocidolite and MMVF-21 gave time- and concentration-dependent increases in DNA fluorescence (P less than 0.005)
  • In TA104, chrysotile and RCF-1 gave only small but statistically significant increases over background fluorescence (P less than 0.02)
  • Hydrogen peroxide (0.5 mM) was added to the bacterial incubations to enhance assay sensitivity and itself caused a small increase over background DNA fluorescence at 24 h and 48 h
  • Pre-treating fibres with the iron chelators desferrioxamine and ferrozine significantly reduced fluorescent adduct formation in TA104 (P less than 0.05)
  • Iron mobilised per mg of fibre (cell-free): crocidolite Fe(II) 69, Fe(III) 80, total 149 nmol/mg; chrysotile 33, 36, total 69; MMVF-21 103, 18, total 121; RCF-1 5, 5, total 10
  • In RFL-6 cells, DNA fluorescence rose dose-dependently and significantly with MMVF-21 at 2 micrograms/cm2 and crocidolite at 5 micrograms/cm2 (P less than 0.01); chrysotile gave a slight increase and RCF-1 no effect
  • In RFL-6 cells, removing the iron from crocidolite and MMVF-21 ameliorated all the activity of these fibres
  • In TA104, BSO pretreatment increased fibre-induced DNA fluorescence (P less than 0.05) and NAC co-treatment returned adduct levels to those without BSO
  • Vitamin E protected TA104 against fluorescent DNA adduct formation (P less than 0.05)
  • Glutathione in TA104 (nmol GSH/mg protein): none 94 plus or minus 32; BSO (1 mM) 38 plus or minus 22; BSO plus NAC 154 plus or minus 48; NAC (5 mM) 164 plus or minus 9
  • Lipid peroxidation (TBARS) rose dose-dependently with crocidolite and MMVF-21; in TA104 at 48 h, no fibre 0.50 plus or minus 0.21 versus crocidolite 0.8 mg 6.16 plus or minus 0.72 and MMVF-21 0.8 mg 7.26 plus or minus 1.2 nmol TBARS/mg protein
  • The authors noted that the same fluorescence can arise from DNA reacting with other lipid peroxidation products, not only malondialdehyde
• The authors' conclusion: The authors concluded that fibres induce lipid peroxidation by an iron-dependent mechanism, that the products formed can bind DNA to form adducts, that glutathione and vitamin E are protective, and that these adducts may be potential genotoxic lesions relevant to the pathogenesis of fibrous materials
• Limitations the authors state:
  • The authors noted that at physiological pH malondialdehyde exists mainly as the less reactive enolate ion, so the extent of MDA-DNA binding under physiological conditions is likely to be small
  • Hydrogen peroxide was deliberately added to the bacterial assay to enhance its sensitivity, and H2O2 alone raised background DNA fluorescence
  • The authors noted that the fluorescence measured is not specific to malondialdehyde, since other lipid peroxidation products give similar spectra

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: Fibroblast, Crocidolite, Vitreous, Chrysotile, Glutathione (GSH).

Related studies

• Glutathione modulates the formation of 8-hydroxydeoxyguanosine in isolated DNA and mutagenicity in Salmonella typhimurium TA100 induced by mineral fibres — P.J. Howden, S.P. Faux (1996)
• Iron-dependent formation of 8-hydroxydeoxyguanosine in isolated DNA and mutagenicity in Salmonella typhimurium TA102 induced by crocidolite — S.P. Faux, P.J. Howden, et al. (1994)
• Lipid peroxidation and disintegration of the cell membrane structure in cultures of rat lung fibroblasts treated with asbestos — H. Iguchi, S. Kojo, et al. (1993)
• Microsomal lipid peroxidation and oxy-radicals formation are induced by insoluble iron-containing minerals — M. Fontecave, M. Jaouen, et al. (1990)
• Possible role of lipid peroxidation in the induction of NF-kappa B and AP-1 in RFL-6 cells by crocidolite asbestos: evidence following protection by vitamin E — S.P. Faux, P.J. Howden (1997)
• Chrysotile inhibits glutathione-dependent protection against the onset of lipid peroxidation in rat lung microsomes — J.M. Arif, I. Ahmad, et al. (1996)

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