Effect of mineral particles containing iron on primary cultures of rabbit tracheal epithelial cells: possible implication of oxidative stress

Our plain-English summary of Effect of mineral particles containing iron on primary cultures of rabbit tracheal epithelial cells: possible implication of oxidative stress, by C. Guilianelli, A. Baeza-Squiban, E. Boisvieux-Ulrich, et al (Environmental Health Perspectives, 1993).

The study

• Authors: C. Guilianelli, A. Baeza-Squiban, E. Boisvieux-Ulrich, O. Houcine, R. Zalma, C. Guennou, H. Pezerat, F. Marano
• Journal: Environmental Health Perspectives
• Published: 1993;101(5):436-42
• Cited by: 25 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Environmental mineral particles such as asbestos are responsible for numerous respiratory diseases. In addition to effects related to their geometry, particles are now assumed to act by triggering an oxidative stress process. Iron-containing particles, in particular, can produce oxygen-activated species by oxidizing their iron. To evaluate the involvement of iron-containing particles in respiratory diseases, three mineral particles (chrysotile, nemalite, and hematite) were tested in primary cultures of tracheal epithelium. Because of the ciliary beat, the three mineral particles were quickly concentrated at the periphery of the mucociliary epithelium, reconstituted in vitro where they induced cellular lesions. Endocytosis of the three types of particles was observed. Cytotoxicity studies have indicated that among the tested particles, the most cytostatic after 24 hr of treatment was the one that contained more Fe2+ available on the surface, nemalite. Moreover, the effect of nemalite was reduced by pretreatment with desferrioxamine. As mineral particles, especially asbestos, are suspected to induce squamous metaplasia, we chose to study two specific transformations of the epithelium: the expression of cytokeratin-13 and the formation of cross-linked envelopes. Under our culture conditions, nemalite and chrysotile increased the expression of the cytokeratin-13, a specific marker of squamous metaplasia, whereas nemalite was the only particle able to strongly induce the formation of cross-linked envelopes. Nemalite was the most cytostatic particle and the most efficient at inducing squamous metaplasia. Measures of oxidizing power by electron-spin resonance revealed that nemalite produced the most oxygen-activated species.(ABSTRACT TRUNCATED AT 250 WORDS)

In plain English

In this laboratory study, the authors grew rabbit windpipe-lining (tracheal epithelial) cells in culture. They exposed the cells to three iron-containing minerals: Canadian chrysotile asbestos (which contained some nemalite and magnetite), nemalite (a fibrous mineral containing divalent iron) and hematite (a ferric iron oxide). Beating cilia swept most particles to the culture edges, where cells were damaged, and all three particle types were taken up into cells. After 24 hours, two cell-viability tests showed no significant difference from untreated cultures at the two concentrations tested (50 and 100 micrograms per square centimetre), but the minerals slowed culture growth: nemalite most in the short term, chrysotile most with longer treatment. Pre-treating nemalite with desferrioxamine, an iron-binding chemical, reduced its effect. Nemalite was the only particle that significantly increased cross-linked envelopes, a late sign of squamous metaplasia (airway cells changing toward a flat, skin-like type). Nemalite and chrysotile both increased the marker cytokeratin-13. In a chemical test, nemalite produced the most oxidizing species, chrysotile fewer, and hematite was inactive. The authors postulated that nemalite acts on these cells through oxidative stress linked to its divalent iron.

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 primary cultures of rabbit tracheal epithelial cells grown from explants, combined with a chemical test (electron spin resonance) of the particles' oxidizing power
• Who was studied: Tracheal epithelial cells from 1-month-old Fauve de Bourgogne rabbits, grown as explant cultures; each mineral concentration was tested on three culture dishes
• Exposure: Three iron-containing minerals at concentrations of about 10 to 100 micrograms per square centimetre: Canadian chrysotile (UICC) contaminated with about 5% nemalite and with magnetite; nemalite, a fibrous brucite in which 8% of the magnesium is replaced by divalent iron; and hematite, a ferric iron oxide
• Main results:
  • Because of ciliary beating, most particles had collected at the edge of the culture after 24 hours
  • All three particle types (hematite, nemalite and chrysotile) were taken up (phagocytosed) by the cultured cells
  • After 24 hours, cell viability measured by lactate dehydrogenase release and by trypan blue was not significantly different from controls for any particle at the two concentrations tested, 50 and 100 micrograms per square centimetre
  • Each particle type had a dose-dependent effect on culture growth
  • After 24 hours at 50 micrograms per square centimetre, nemalite inhibited culture growth by 33% plus or minus 4 compared with control, versus 12% plus or minus 1.7 for hematite
  • After 24 hours, chrysotile affected culture growth only at 100 micrograms per square centimetre (37% plus or minus 1.7)
  • With longer treatment, chrysotile was the most growth-inhibiting (cytostatic) particle
  • Nemalite pre-treated with the iron chelator desferrioxamine had a reduced effect on cell growth, given in the article as 48.2% plus or minus 9.2 after 24 hours
  • Nemalite was the only particle that significantly increased cross-linked envelopes (a late stage of squamous metaplasia) compared with controls; the percentage in nemalite-treated cultures was 544% plus or minus 82 of control
  • Chrysotile slightly increased cross-linked envelopes, but the authors described the difference as significant only at p less than 0.5
  • Expression of cytokeratin-13, a marker of squamous metaplasia, was greater in cultures treated with nemalite and chrysotile
  • In the oxidizing-power test (arbitrary scale), the signal was 1200 plus or minus 100 for nemalite, 500 plus or minus 50 for chrysotile and 0 to 50 for hematite, which the authors called totally inactive
• The authors' conclusion: The authors postulated that nemalite, the mineral most effective at inhibiting growth and inducing squamous metaplasia in the short term, acts on rabbit tracheal epithelial cells through oxidative stress linked to its divalent iron content
• Limitations the authors state:
  • The short lifetime of the primary cultures meant cells could not be treated for more than 16 days
  • Because cilia redistributed the particles unevenly, the nominal dose did not reflect the actual particle concentration on different parts of the culture
  • For chrysotile, terminal squamous differentiation was probably not reached because treatment time was short
  • The role of particle uptake (phagocytosis) in toxicity was not measured and still needs to be evaluated
  • The number of cytokeratin-13-positive cells was difficult to assess by microscopy alone

Mines named here

Asbestos mines this study is about. Each mine's page says who ran it, when it worked, and what it produced.

• Jeffrey mine, Asbestos, Quebec

All asbestos mines

Topics

Medical terms in this study, explained in our Lexicon: Oxidative Stress, Chrysotile, Hematite, Epithelium, Mucociliary Clearance.

Related studies

• Cultured airway epithelium responses to mineral particles: role of the oxidative stress — C. Guilianelli, A. Baeza-Squiban, et al. (1996)
• Iron enhances uptake of mineral particles and increases lipid peroxidation in tracheal epithelial cells — B. Keeling, K.Y. Li, et al. (1994)
• Effects of cigarette smoke on epithelial uptake of non-asbestos mineral particles in tracheal organ culture — B. Keeling, J. Hobson, et al. (1993)
• Ozone enhances the uptake of mineral particles by tracheobronchial epithelial cells in organ culture — A. Churg, M. Brauer, et al. (1996)
• Microsomal lipid peroxidation and oxy-radicals formation are induced by insoluble iron-containing minerals — M. Fontecave, M. Jaouen, et al. (1990)
• Transfection of a manganese-containing superoxide dismutase gene into hamster tracheal epithelial cells ameliorates asbestos-mediated cytotoxicity — B.T. Mossman, P. Surinrut, et al. (1996)

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