Intratracheal injection of crocidolite asbestos depresses the secretion of tumor necrosis factor by pleural leukocytes in vitro

Our plain-English summary of Intratracheal injection of crocidolite asbestos depresses the secretion of tumor necrosis factor by pleural leukocytes in vitro, by X.Y. Li, D. Lamb, K. Donaldson (Experimental Lung Research, 1992).

The study

• Authors: X.Y. Li, D. Lamb, K. Donaldson
• Journal: Experimental Lung Research
• Published: 1992;18(3):359-72
• Cited by: 8 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Tumor necrosis factor (TNF) is a cytokine released predominantly by monocytes/macrophages that has been shown to modulate a variety of different immune and metabolic functions. To understand the regulatory mechanisms of TNF in governing responses in the pleural cavity following deposition of fibrous dust in the airspace of the lung, we studied the capability of leukocytes, lavaged from the pleural cavity, to release TNF in culture. TNF production by lavaged pleural leukocytes was measured using the L-929 TNF-sensitive cell line, after intratracheal instillation of crocidolite asbestos. A high level of TNF activity was found in the supernatants of normal, unstimulated pleural leukocytes; the addition of 100 ng/ml lipopolysaccharide to the culture increased the activity up to threefold. Following intratracheal instillation of 5 mg crocidolite asbestos, the pleural leukocytes secreted less TNF than the control. With increasing mass of intratracheally instilled asbestos, there was a dose-dependent reduction in TNF release. Changes in the population of the pleural leukocytes or their number could not be related to variation in TNF activity. These results suggest that exposure of rat lungs to crocidolite asbestos by intratracheal instillation affects the response of pleural leukocytes without causing changes in the population. Such changes in the bronchoalveolar space may be related to the pleural pathology found in asbestos-exposed individuals.

In plain English

This was a laboratory study in rats. The authors injected UICC crocidolite asbestos into the windpipe (intratracheal instillation) of PVG rats. They then washed out cells from the pleural cavity, the space around the lungs, and measured how much tumor necrosis factor (TNF), an immune signaling protein, those cells released in culture. Pleural cells from untreated rats released high levels of TNF, about 600 U/ml, and adding lipopolysaccharide raised this several times. After a 5 mg dose, TNF release was significantly lower than in controls up to 30 days, with no detectable time-related effect. One day after doses of 1, 5 or 10 mg, TNF release fell as the dose rose and was almost completely inhibited at 10 mg. Macrophage and eosinophil numbers rose from 3 to 30 days after 5 mg, but the authors found no link between cell numbers and TNF. Normal pleural washing fluid reduced TNF activity, more so at higher concentrations. The authors concluded that TNF secretion by pleural leukocytes was reduced in a dose-dependent way. Two figure captions contradict the text on the effect's direction.

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 (rats), with laboratory measurement of TNF released by pleural cells in culture
• Who was studied: Male or female inbred PVG rats aged 12 weeks or older, from the Institute of Occupational Medicine, Edinburgh, United Kingdom. The total number of rats is not given; figure legends give 5 to 22 separate experiments per data point.
• Exposure: UICC crocidolite asbestos given by a single intratracheal injection in 0.5 ml of phosphate buffered saline. Doses were 1, 5 or 10 mg, and rats were followed for up to 1 month. Controls were uninjected or injected with saline alone.
• Main results:
  • Untreated control rats: mean pleural leukocyte count 4.51 x 10^6, made up of macrophages 83%, lymphocytes 1%, mast cells 11% and eosinophils 5%.
  • After 5 mg crocidolite: total numbers of macrophages were significantly higher than control from 3 to 30 days (P less than .05 to P less than .01).
  • After 5 mg crocidolite: total numbers of eosinophils were significantly higher than control from 3 to 30 days (P less than .01 to P less than .001). At 1 day there was only a modest neutrophil increase.
  • Normal pleural leukocytes without stimulation released TNF at about 600 U/ml. Adding 100 ng/ml lipopolysaccharide increased production several times.
  • Removing endotoxin from the culture medium made no significant difference to TNF release. Activity at 1:16 dilution was 1062.72 plus or minus 81.2 units/ml (n = 12) with ordinary medium and 1086.24 plus or minus 171.6 (n = 12) with endotoxin-depleted medium.
  • Pleural leukocytes from rats given 5 mg crocidolite released significantly less TNF than controls at times up to 30 days. The authors detected no time-related effect on this reduction: activity at 1 day was similar to that at 1 month.
  • One day after 1, 5 or 10 mg crocidolite, TNF release decreased gradually with increasing dose. In the 10 mg group it was almost completely inhibited.
  • No TNF activity was detected in pleural lavage fluid from either normal or crocidolite-instilled rats.
  • Normal pleural lavage fluid inhibited TNF activity in a concentration-related way. At 1:4 dilution it almost completely abolished TNF activity in both the cell supernatant and the TNF standard.
• The authors' conclusion: The authors concluded that normal pleural leukocytes secrete high levels of TNF in culture and that intratracheal crocidolite reduced this secretion in a dose-dependent way. They suggested this suppression might prevent needed defensive responses of the pleura and, if persistent, could lead to pleural injury.
• Limitations the authors state:
  • The authors noted that pleural leukocytes also secrete interleukin 1, which could affect the L929 assay used to measure TNF. They judged it unlikely to explain the results.

Topics

Medical terms in this study, explained in our Lexicon: Crocidolite, Necrosis, Cytokine, Macrophage, Pleural Cavity, Deposition, Pathology.

Related studies

• The production of TNF-alpha and IL-1-like activity by bronchoalveolar leucocytes after intratracheal instillation of crocidolite asbestos — X.Y. Li, D. Lamb, et al. (1993)
• Increased production of plasminogen activator inhibitor in vitro by pleural leukocytes from rats intratracheally instilled with crocidolite asbestos — X.Y. Li, G.M. Brown, et al. (1991)
• Asbestos fibers and silica particles stimulate rat alveolar macrophages to release tumor necrosis factor. Autoregulatory role of leukotriene B4 — C.M. Dubois, E. Bissonnette, et al. (1989)
• Production of interleukin 1 by rat pleural leucocytes in culture after intratracheal instillation of crocidolite asbestos — X.Y. Li, D. Lamb, et al. (1993)
• Asbestos-stimulated tumour necrosis factor release from alveolar macrophages depends on fibre length and opsonization — K. Donaldson, X.Y. Li, et al. (1992)
• Iron and reactive oxygen species in the asbestos-induced tumor necrosis factor-alpha response from alveolar macrophages — P.P. Simeonova, M.I. Luster (1995)

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