Distinctive profile of alveolar macrophage-derived cytokine release induced by fibrogenic and nonfibrogenic mineral dusts

Our plain-English summary of Distinctive profile of alveolar macrophage-derived cytokine release induced by fibrogenic and nonfibrogenic mineral dusts, by I. Lemaire, S. Ouellet (Journal of Toxicology and Environmental Health, 1996).

The study

• Authors: I. Lemaire, S. Ouellet
• Journal: Journal of Toxicology and Environmental Health
• Published: 1996;47(5):465-78
• Cited by: 39 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Groups of 7 Wistar rats each received a single intratracheal instillation of either saline (control), UICC chrysotile B asbestos (5 mg), or very short 4T30 chrysotile asbestos fibers (5 mg). Five animals in each group were killed at 1, 3, and 6 wk posttreatment and analyzed by bronchoalveolar lavage (BAL) for BAL cell populations and cytokine production in conjunction with histopathological assessment of lung tissue. Chrysotile B and short 4T30 chrysotile fibers induced chronic inflammatory reactions characterized by alveolar macrophage (AM) accumulation that resulted, respectively, in lung fibrosis and resolving granuloma. Alveolar macrophages (AM) obtained from rats treated with UICC chrysotile B and short 4T30 chrysotile produced enhanced levels of interleukin-1 (IL-1) and interleukin-6 (IL-6), both spontaneously and in response to lipopolysaccharide (LPS). A different pattern of response was observed for tumor necrosis factor-alpha (TNF-alpha). Fibrogenic chrysotile B caused biphasic changes characterized by significant inhibition of LPS-induced TNF-alpha release by AM 1 and 3 wk after treatment, followed by stimulation of spontaneous and LPS-induced TNF-alpha at 6 wk. In contrast, no significant change in spontaneous and LPS-induced TNF-alpha release was seen with AM from animals with resolving granuloma (4T30 group). Thus, modulation of AM-derived TNF-alpha was correlated under these conditions with the fibrogenic potential of asbestos dusts. These data support a role for TNF-alpha in fibrosis and suggest that TNF-alpha may represent a useful marker of lung damage induced by fibrogenic dusts.

In plain English

In this animal experiment, male Wistar rats received a single intratracheal instillation of saline, UICC chrysotile B asbestos (5 mg), or very short 4T30 chrysotile fibers (5 mg). They were examined 1, 3, and 6 weeks later by lung lavage, macrophage cytokine tests, and lung histology. Group sizes are unclear. The opening describes groups of 7 rats, with 5 killed at each time point. The figures pool two separate experiments, with 5 to 10 animals per group at each time point. Short 4T30 fibers caused a granulomatous reaction described as not evolving toward fibrosis. UICC chrysotile B caused lung fibrosis within 1 week. Both dusts increased alveolar macrophage (AM) numbers and IL-1 and IL-6 release. By 6 weeks, IL-6 had returned toward control with 4T30 but stayed significantly elevated with chrysotile B. TNF-alpha did not change significantly with 4T30. Chrysotile B suppressed LPS-induced TNF-alpha at 1 and 3 weeks and significantly raised it at 6 weeks. In vitro, recombinant IL-1 (5 to 50 pg/ml) did not significantly alter TNF-alpha release. IL-6 (10 pg/ml and higher) significantly inhibited LPS-induced release, by up to 50%. The authors concluded that modulation of AM TNF-alpha release is a property of fibrogenic but not nonfibrogenic chrysotile fibers.

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: animal experiment (controlled in vivo rat study with in vitro cytokine assays)
• Who was studied: Male Wistar rats weighing 250-300 g, from Charles River Canada, studied at 1, 3 and 6 weeks after a single intratracheal instillation. The laboratory was in Ottawa, Ontario, Canada. The opening summary describes groups of 7 rats with 5 killed at each time point. The figure legends report results pooled from two separate experiments, with 5 to 10 animals per group at each time point.
• Exposure: Single intratracheal instillation of UICC Canadian chrysotile B asbestos (5 mg; 21% of fibers longer than 10 micrometres) or very short 4T30 chrysotile fibers (5 mg; 100% shorter than 5 micrometres), compared with saline
• Main results:
  • Lung tissue response: short 4T30 fibers caused a granulomatous reaction reported as not evolving to fibrosis. UICC chrysotile B caused granulomatous reaction and lung fibrosis within 1 week.
  • BAL cells: 4T30 increased alveolar macrophages at all time points, with no change in neutrophils or lymphocytes. UICC chrysotile B gave a similar macrophage increase plus a small, transient neutrophil rise at 1 week.
  • IL-1: both asbestos-treated groups had significantly higher spontaneous IL-1 from 1 week up to 6 weeks. LPS-induced IL-1 was also enhanced, with maximal enhancement at 3 weeks.
  • IL-6: release increased in both treated groups at 1 and 3 weeks. By 6 weeks, levels returned toward control in the 4T30 group but stayed significantly elevated in the chrysotile B group.
  • TNF-alpha: there was no significant change in LPS-induced release in the 4T30 group at any time. The UICC chrysotile B group showed suppression at 1 and 3 weeks and significantly higher levels at 6 weeks.
  • Spontaneous TNF-alpha release was not significant in control or treated rats, except in the UICC group at 6 weeks
  • In vitro, using macrophages from normal rats: recombinant IL-1 (5 to 50 pg/ml) had no significant effect on spontaneous or LPS-induced TNF-alpha release.
  • In vitro, using macrophages from normal rats: recombinant IL-6 at 10 pg/ml and higher caused a significant inhibition, of up to 50%, of LPS-induced TNF-alpha release.
• The authors' conclusion: The authors concluded that modulation of AM-derived TNF-alpha release is a property of fibrogenic but not nonfibrogenic chrysotile fibers. They saw this as supporting a role for TNF-alpha in fibrosis and suggested it as a potentially useful marker of lung damage.

Topics

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

Medical terms in this study, explained in our Lexicon: Alveolar Macrophage, Cytokine, Fibrogenic, UICC, Chrysotile, Bronchoalveolar Lavage (BAL), Fibrosis, Granuloma.

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