Biochemical effects of asbestiform minerals on lung fibroblast cultures

Our plain-English summary of Biochemical effects of asbestiform minerals on lung fibroblast cultures, by P.M. Hext, R.J. Richards (British Journal of Experimental Pathology, 1976).

The study

• Authors: P.M. Hext, R.J. Richards
• Journal: British Journal of Experimental Pathology
• Published: 1976;57(3):281-5
• Cited by: 17 articles, as counted by NIH iCite
• Read it: PubMed · Free full text

Abstract

The ability of different types of asbestiform minerals to enhance or suppress the levels of fibrous collagen in cultures of lung fibroblasts was tested. All commercially important asbestos dusts produced both effects, a lower dose favouring a fibrogenic response whereas a higher dose favoured an opposite effect.

In plain English

This laboratory study exposed rabbit lung fibroblast cultures (cells that make collagen, a connective-tissue protein) for 3 weeks to reference samples of chrysotile, anthophyllite, amosite and crocidolite asbestos, to chrysotile with 20% or 80% of its magnesium removed, and to brucite fibres. Doses ranged from 50 to 200 micrograms per ml of culture medium. At lower doses, all the asbestos samples could raise fibrous collagen levels, a fibrosis-like response. With chrysotile at 50 micrograms per ml, this happened in 37 of 52 experiments, and collagen fell in the other 15. At 200 micrograms per ml, amosite and crocidolite raised collagen in none of 8 experiments each. At 100, collagen rose in 10 of 14 amosite and 3 of 11 crocidolite experiments. Brucite did not significantly change collagen levels. Where collagen fell, RNA levels were lower in all but one set of cultures. The authors concluded that all the main asbestos groups studied can enhance or depress fibrous collagen in these cultures, depending on dose. They ranked chrysotile as most reactive, then anthophyllite, then amosite and crocidolite. They could not fully explain why the same dose sometimes had opposite effects.

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. Dusts were added as a single dose to 3-day-old cultures, which were analysed after 3 weeks.
• Who was studied: Rabbit lung fibroblast cultures grown in the Department of Biochemistry, University College, Cardiff, U.K. (article received November 1975). No humans or live animals were studied.
• Exposure: UICC standard reference samples of Rhodesian chrysotile, anthophyllite, amosite and crocidolite; chrysotile with 20% and 80% of its magnesium removed; and finely ground brucite fibres. Doses were 50, 100 and 200 micrograms per ml of culture medium, and exposure lasted 3 weeks.
• Main results:
  • The fibrogenic effect (increased fibrous collagen) was predominant at the lower doses of anthophyllite, amosite and crocidolite, as previously found with chrysotile.
  • Chrysotile at 50 micrograms per ml: of 52 experiments, 37 showed enhancement of fibrous collagen and 15 showed depression (Table I).
  • Amosite (Table I): at 50 micrograms per ml, collagen was enhanced in 15 of 23 experiments; at 100, in 10 of 14; at 200, in 0 of 8 (all 8 showed depression).
  • Crocidolite (Table I): at 50 micrograms per ml, collagen was enhanced in 15 of 26 experiments; at 100, in 3 of 11; at 200, in 0 of 8 (all 8 showed depression).
  • Brucite, the main component of chrysotile's outer layer, did not significantly affect the collagen measure (cell mat hydroxyproline).
  • Both the 20% and the 80% magnesium-depleted chrysotiles, at 50 micrograms per ml, produced a lower fibrogenic response than the same weight of ordinary chrysotile. The authors suggested this was because a given weight of depleted sample contains more fibres.
  • The fibrogenic reaction caused by chrysotile or crocidolite was not accompanied by a significant change in DNA levels. Anthophyllite and amosite increased cell mat DNA.
  • In cultures where fibrous collagen was depressed, RNA levels were lower in all cases except cultures treated with 50 micrograms per ml amosite. These cultures also secreted relatively less sulphated proteoglycan.
  • In terms of biological reactivity in these cultures, chrysotile was the most reactive, followed by anthophyllite, then amosite and crocidolite.
• The authors' conclusion: The authors concluded that all the main groups of asbestos dusts studied can enhance or depress fibrous collagen in lung fibroblast cultures, and that these effects are dose-dependent. They suggested that asbestos disturbs the balance of proteoglycans secreted by the cells and that changes in RNA metabolism are probably an earlier step.
• Limitations the authors state:
  • The authors could not fully explain why the same concentration of a dust could produce opposite effects on collagen.
  • The authors said it is difficult to tell whether pure fibrous brucite behaves like the brucite coat on chrysotile, because brucite is highly soluble.
  • Dusts were compared by equal weight rather than equal fibre numbers. The authors said future studies should compare equivalent numbers of fibres.

Topics

Medical terms in this study, explained in our Lexicon: Asbestiform, Fibroblast, Collagen, Fibrogenic.

Related studies

• Reaction of mineral dusts with primary lung fibroblast cultures — R.J. Richards, J. Hunt (1983)
• The effects of long-term exposure of lung fibroblast strains to chrysotile asbestos — P.M. Hext, J. Hunt, et al. (1977)
• Ultrastructural changes in lung fibroblast cultures exposed to chrysotile asbestos — R.J. Richards, P.M. Hext, et al. (1974)
• Iron mobilization from crocidolite as enhancer of collagen content in rat lung fibroblasts — C. Gardi, P. Calzoni, et al. (1997)
• Biological reactivity of PVC dust — R.J. Richards, R. Desai, et al. (1975)
• A novel method for accurate collagen and biochemical assessment of pulmonary tissue utilizing one animal — C.R. Kliment, J.M. Englert, et al. (2011)

Browse more research in British Journal of Experimental Pathology, or return to medical research.