Iron mobilization from crocidolite as enhancer of collagen content in rat lung fibroblasts

Our plain-English summary of Iron mobilization from crocidolite as enhancer of collagen content in rat lung fibroblasts, by C. Gardi, P. Calzoni, M. Ferrali, et al (Biochemical Pharmacology, 1997).

The study

• Authors: C. Gardi, P. Calzoni, M. Ferrali, M. Comporti
• Journal: Biochemical Pharmacology
• Published: 1997;53(11):1659-65
• Cited by: 11 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Asbestos exposure causes pulmonary fibrosis by mechanisms that remain uncertain. There is increasing evidence that iron from asbestos is responsible for many of its effects. In this paper, we investigated the effect of iron mobilized from crocidolite asbestos on collagen content in rat lung fibroblast cultures under serum-free conditions. Crocidolite (2, 4, 6 microg/cm2 well) increased collagen content in a dose-dependent manner (+42 +/- 8, +92 +/- 10, and +129 +/- 13% vs controls). This effect was specific for collagen, since it did not alter total protein content and was inhibited by the iron chelator deferoxamine (DFO). Preincubation of crocidolite with citrate (1 mM) for 48 hr resulted in iron mobilization (51 microM) and increased collagen production (>3-fold) in treated cells. These effects occurred without the intervention of serum factors. The absence of cell damage, proliferation or lipid peroxidation leads to the supposition that iron from crocidolite per se may act as a profibrogenic agent. Although the in vivo participation of other cells and factors cannot be excluded, we conclude that iron released from crocidolite plays a role in collagen increase occurring during asbestosis.

In plain English

In this laboratory study, the authors exposed lung fibroblasts (cells that make the scar protein collagen) from young rats to crocidolite asbestos, which contained 27% iron by weight. Doses were 2, 4 and 6 micrograms per square centimeter for 48 hours, without serum. Collagen rose by 42%, 92% and 129% over untreated cells, while total protein did not change. Treating the fibers beforehand with the iron-binding drug deferoxamine strongly reduced this increase. Soaking crocidolite in citrate released about 50 nmol of iron per mg, and this mixture raised collagen about 3-fold compared with untreated cells. The released iron alone, without fibers, raised collagen about 40%, and the leftover fibers about 60%. DNA and protein content did not change significantly, and no change in lipid peroxidation was detected. The highest dose did significantly increase release of LDH, a sign of cell damage. The authors concluded that iron released from crocidolite plays a role in the collagen increase occurring during asbestosis. They noted that responses in living animals involve other cells and factors.

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: Lung fibroblasts isolated from specific pathogen-free Sprague-Dawley rats aged 2-3 weeks (University of Siena, Italy). Results are means from 6 replicate cultures.
• Exposure: Crocidolite asbestos containing 27% iron by weight, at 2, 4 and 6 micrograms per square centimeter of culture well for 48 hours, with or without the iron chelator deferoxamine (100 micromolar). Some crocidolite was first preincubated with 1 mM citrate to release iron. Other cultures received the released iron alone, the leftover fibers alone, or a freshly prepared iron(III) chloride-citrate solution.
• Main results:
  • Collagen increased with dose: +42%, +92% and +129% compared with controls at 2, 4 and 6 micrograms of crocidolite per square centimeter.
  • Crocidolite did not change total protein content.
  • Deferoxamine added to the fibers beforehand strongly reduced the crocidolite-induced collagen increase at every dose.
  • After 48 hours in citrate, about 50 nmol of iron per mg of crocidolite was released.
  • Crocidolite (4 micrograms per square centimeter) preincubated with citrate increased collagen about 3-fold compared with controls and about 1.5-fold compared with crocidolite alone.
  • The fiber-free supernatant containing the released iron increased collagen by about 40% compared with controls, and deferoxamine strongly inhibited this effect.
  • The leftover fibers (pellet) increased collagen by 60% compared with controls; deferoxamine reduced collagen content by 50%.
  • A freshly prepared iron(III) chloride-citrate solution with a similar amount of iron increased collagen by 36%, close to the supernatant result.
  • At 6 micrograms per square centimeter, LDH release (a cell-damage marker) was significantly higher than in controls: 14.7% versus 7.2% of total. The increases at 2 and 4 micrograms were not significant.
  • DNA and protein content per well (measures of cell proliferation) did not change significantly after exposure to crocidolite or iron.
  • No detectable change in lipid peroxidation (TBARS) was found with crocidolite or crocidolite plus citrate (data not shown).
• The authors' conclusion: The authors concluded that iron released from crocidolite plays a role in the collagen increase occurring during asbestosis.
• Limitations the authors state:
  • The experiments were done in cell culture without serum, and the authors note that responses in living organisms are more complex, involving many interacting cells and soluble factors.
  • The authors could not rule out a role of the fibers themselves in the collagen increase.

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, Collagen, Fibroblast, Asbestos Exposure, Pulmonary Fibrosis.

Related studies

• Iron mobilization from crocidolite asbestos greatly enhances crocidolite-dependent formation of DNA single-strand breaks in phi X174 RFI DNA — L.G. Lund, A.E. Aust (1992)
• Soil fungi reduce the iron content and the DNA damaging effects of asbestos fibers — S. Daghino, F. Turci, et al. (2006)
• Biochemical effects of asbestiform minerals on lung fibroblast cultures — P.M. Hext, R.J. Richards (1976)
• Lung mesothelial cell and fibroblast responses to pleural and alveolar macrophage supernatants and to lavage fluids from crocidolite-exposed rats — I.Y. Adamson, H. Prieditis, et al. (1997)
• Synchrotron X-ray microscopy reveals early calcium and iron interaction with crocidolite fibers in the lung of exposed mice — L. Pascolo, G. Zabucchi, et al. (2016)
• Mobilization of iron from urban particulates leads to generation of reactive oxygen species in vitro and induction of ferritin synthesis in human lung epithelial cells — K.R. Smith, A.E. Aust (1997)

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