Evidence of a role for mesothelial cell-derived interleukin 8 in the pathogenesis of asbestos-induced pleurisy in rabbits

Our plain-English summary of Evidence of a role for mesothelial cell-derived interleukin 8 in the pathogenesis of asbestos-induced pleurisy in rabbits, by A.M. Boylan, C. Rüegg, K.J. Kim, et al (The Journal of Clinical Investigation, 1992).

The study

• Authors: A.M. Boylan, C. Rüegg, K.J. Kim, C.A. Hébert, J.M. Hoeffel, R. Pytela, D. Sheppard, I.M. Goldstein, V.C. Broaddus
• Journal: The Journal of Clinical Investigation
• Published: 1992;89(4):1257-67
• Cited by: 74 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Although acute asbestos-induced pleurisy is characterized by an influx of neutrophils, the identity of the factors that attract these cells to the pleural space and the source of the factors are unknown. We found that instillation of crocidolite asbestos into the pleural space of rabbits led to the appearance in pleural liquid of chemotactic activity for neutrophils, and that this chemotactic activity was inhibited significantly by a neutralizing antibody to human interleukin 8 (IL-8). Cultured rabbit pleural mesothelial cells incubated with crocidolite asbestos also released chemotactic activity for neutrophils, which was inhibited significantly by the anti-IL-8 antibody. To determine whether rabbit pleural mesothelial cells synthesize IL-8, we generated a probe for rabbit IL-8 mRNA by amplifying cDNA prepared from stimulated pleural mesothelial cells using the polymerase chain reaction (PCR) and primers based on homologous sequences in human and sheep IL-8 cDNAs. Homology-based PCR yielded a single cDNA fragment with a nucleotide sequence 88% identical to that of a corresponding region of human IL-8 cDNA. With the radiolabeled PCR product as a probe, we demonstrated rapid induction of IL-8 mRNA expression in pleural mesothelial cells exposed to asbestos. As expected, tumor necrosis factor-alpha also led to the appearance of IL-8 in the rabbit pleural space and stimulated cultured pleural mesothelial cells to synthesize and release IL-8. We conclude that asbestos directly stimulates pleural mesothelial cells to synthesize IL-8 and that mesothelial cell-derived IL-8 may play an important role in mediating asbestos-induced pleural inflammation.

In plain English

This laboratory study in rabbits and rabbit cells looked at how crocidolite asbestos sets off acute inflammation of the pleura, the lining around the lungs. The authors placed crocidolite into one pleural space of anesthetized rabbits and plain cell-culture fluid into the other. Six hours later the asbestos side held about 10 times more neutrophils, a type of white blood cell, than the opposite or control sides. Glass beads and asbestos-free filtrate did not cause this. Fluid from the asbestos side attracted neutrophils. An antibody against human interleukin 8 (IL-8), a signaling protein, cut that attraction by 72 percent (plus or minus 8) in five experiments. Cultured rabbit mesothelial cells, the cells lining the pleura, also released neutrophil-attracting activity when exposed to crocidolite. The same antibody reduced it by 70 percent (plus or minus 7). The cells showed IL-8 genetic messages (mRNA) by 2 hours. The authors concluded that asbestos directly stimulates mesothelial cells to make IL-8, which may play an important role in pleural inflammation. They noted that their antibody targeted human, not rabbit, IL-8. They also said they did not know how much of the IL-8 in the animals came from mesothelial cells.

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 (asbestos instilled into the pleural spaces of live rabbits) combined with cell-culture (in vitro) and molecular experiments on rabbit pleural mesothelial cells
• Who was studied: 21 healthy male New Zealand white rabbits: 5 asbestos, 5 TNF, 5 control, 2 glass bead, 2 asbestos filtrate and 2 asbestos-plus-polymixin experiments. The study also used pleural mesothelial cells harvested from New Zealand white rabbits and grown in culture. The authors were at San Francisco General Hospital, the University of California San Francisco, and Genentech. Study dates are not stated.
• Exposure: Crocidolite asbestos at 30 micrograms per ml in 10 ml of fluid, instilled into one pleural space. The opposite pleural space received control fluid. Comparison stimuli were tumor necrosis factor-alpha (TNF, 20 ng/ml), glass beads, asbestos filtrate, and asbestos plus polymixin (to bind endotoxin). Cultured mesothelial cells were exposed to crocidolite (30 micrograms per ml) or TNF for 2, 4 or 6 hours.
• Main results:
  • At 6 hours, the pleural spaces given asbestos held 23.8 plus or minus 10.1 million neutrophils, against 2.2 plus or minus 0.5 million on the opposite side (5 rabbits). Rabbits given medium alone had 1.9 million on each side. The authors described this as a 10-fold difference.
  • Glass beads and asbestos filtrate did not produce the effect. Neutrophils at 6 hours were 0.8 million on the experimental side for each (2 rabbits each), and cultured cells exposed to either released no chemotactic activity.
  • Adding polymixin, which binds endotoxin, did not reduce the neutrophil influx to asbestos (2 rabbits).
  • Pleural fluid taken 3 hours after asbestos attracted neutrophils. Antibody fragments against human IL-8 reduced this attraction by 72 plus or minus 8% (mean plus or minus SE, 5 experiments). An anti-IL-6 antibody had no significant effect (9 plus or minus 7% reduction).
  • In cultured rabbit pleural mesothelial cells exposed to asbestos for 2 hours, the medium attracted neutrophils. The anti-IL-8 antibody fragments reduced this by 70 plus or minus 7% (4 experiments), and the anti-IL-6 antibody did not affect it.
  • A rabbit IL-8 gene fragment made from stimulated mesothelial cells was 88% identical in nucleotide sequence to the corresponding region of human IL-8.
  • IL-8 mRNA was found in mesothelial cells exposed to asbestos or TNF but not in unexposed cells. It was evident at 2 hours, and after asbestos it continued to increase over the 6 hours studied.
  • TNF instilled into the pleural space raised neutrophils at 6 hours to 10.3 plus or minus 2.7 million, versus 2.8 plus or minus 1.5 million on the opposite side. The resulting chemotactic activity was inhibited by the anti-IL-8 antibody by 82 plus or minus 9% (5 experiments).
• The authors' conclusion: The authors concluded that pleural mesothelial cells produce IL-8 directly after exposure to asbestos fibers. They wrote that mesothelial cell-derived IL-8 may play an important role in mediating many types of pleural inflammation, including that due to asbestos.
• Limitations the authors state:
  • The neutralizing antibody was made against human IL-8, not rabbit IL-8.
  • The authors did not know how much of the IL-8 detected in the live rabbits was produced by mesothelial cells rather than other cells.
  • Because neutralizing antibodies to rabbit TNF or IL-1 were not available, the authors could not test whether these cytokines acted as intermediate steps in the animals.

Topics

Medical terms in this study, explained in our Lexicon: Mesothelial Cells, Pleurisy, Crocidolite, Tumor Necrosis Factor-alpha (TNF-α), Inflammation.

Related studies

• Benign asbestos pleurisy in the rabbit. A model for the study of pathogenesis — B.L. Shore, C.C. Daughaday, et al. (1983)
• Interleukin-1-mediated release of interleukin-8 by asbestos-stimulated human pleural mesothelial cells — D.E. Griffith, E.J. Miller, et al. (1994)
• Pathogenesis of pleurisy, pleural fibrosis, and mesothelial proliferation — A. Herbert (1986)
• Vitronectin enhances internalization of crocidolite asbestos by rabbit pleural mesothelial cells via the integrin alpha v beta 5 — A.M. Boylan, D.A. Sanan, et al. (1995)
• Asbestos induction of nuclear transcription factors and interleukin 8 gene regulation — P.P. Simeonova, M.I. Luster (1996)
• Cause of Asbestos-Induced Pleurisy Forgotten — E. Böhm (2019)

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