Asbestos-induced injury to cultured human pulmonary epithelial-like cells: role of neutrophil elastase

Our plain-English summary of Asbestos-induced injury to cultured human pulmonary epithelial-like cells: role of neutrophil elastase, by D.W. Kamp, M. Dunne, M.S. Dykewicz, et al (Journal of Leukocyte Biology, 1993).

The study

• Authors: D.W. Kamp, M. Dunne, M.S. Dykewicz, J.S. Sbalchiero, S.A. Weitzman, M.M. Dunn
• Journal: Journal of Leukocyte Biology
• Published: 1993;54(1):73-80
• Cited by: 6 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The mechanisms responsible for asbestos-induced pulmonary epithelial cell cytotoxicity, especially oxidant-independent mechanisms, are not established. We determined whether human polymorphonuclear leukocyte (PMN) proteases contribute to asbestos-induced damage to human pulmonary epithelial-like cells (PECs) assessed using an in vitro chromium-51 release assay. Serine antiproteases, phenylmethylsulfonyl fluoride and alpha 1-antitrypsin, each ameliorated PEC injury induced by amosite asbestos and PMNs. A role for a specific proteinase, human neutrophil elastase (HNE), is supported by the facts that (1) asbestos increased HNE release assessed by an enzyme-linked immunosorbent assay technique (1.7 +/- 0.5 vs. 2.8 +/- 0.5 micrograms/ml; P < .025), (2) purified HNE or porcine pancreatic elastase (PPE) each alone caused PEC detachment, (3) asbestos plus either HNE or PPE caused PEC lysis similar to that mediated by asbestos and PMNs, and (4) cationic agents released from PMNs were unlikely to be involved because polyanions did not ameliorate injury resulting from asbestos and PMNs. Compared to elastase, cathepsin G caused less PEC detachment and negligible augmentation in asbestos-induced PEC lysis. Asbestos increased the association of 125I-labeled elastase with PECs nearly 50-fold compared with PPE alone (14.4% vs. 0.3%, respectively; P < .01) and nearly 10-fold compared with another particle, opsonized zymosan. We conclude that PMN-derived proteases, especially elastase, may contribute to asbestos-induced lung damage by augmenting pulmonary epithelial cell injury.

In plain English

This laboratory study used cells grown in dishes, not people. The authors exposed human lung-lining-like cells, a line from embryonic lung, to amosite asbestos plus neutrophils (white blood cells from healthy donors) for 18 hours. This caused 30.2% of cells to detach and 20.7% to break open. Two enzyme inhibitors, PMSF and alpha-1-antitrypsin, reduced breakage to 9.7% and 12.1%. Asbestos-exposed neutrophils released more neutrophil elastase, a protein-cutting enzyme, than unexposed ones (2.8 versus 1.7 micrograms per ml). Purified elastase alone mainly made cells detach. Human neutrophil elastase (5 micrograms per ml) plus asbestos broke open 18.2% of cells, versus 1.4% for that elastase alone and 8.8% for asbestos alone. Cathepsin G, a related enzyme, caused less detachment than elastase, and at 0.5 micrograms per ml did not increase breakage beyond asbestos alone. Asbestos raised the share of labeled pig elastase associated with the cells from 0.3% to 14.4%. The authors concluded that elastase is involved in one asbestos injury mechanism that does not depend on oxidants. They stated that whether the findings apply in the living body awaits further investigation.

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: In vitro (laboratory cell culture) experiment
• Who was studied: A cultured human pulmonary epithelial-like cell line (ATCC WI-26 VA4) isolated from human embryonal lung, exposed together with neutrophils (PMNs) isolated from the blood of normal healthy donors. At least six separate experiments were run per group unless noted otherwise.
• Exposure: UICC reference standard amosite asbestos (mainly 500 micrograms/ml) with human neutrophils (10^6 cells/ml). Purified human neutrophil elastase, porcine pancreatic elastase and cathepsin G were also tested, as were the serine protease inhibitors PMSF and alpha-1-antitrypsin.
• Main results:
  • Amosite asbestos plus neutrophils caused 30.2 ± 7.5% detachment and 20.7 ± 4.5% lysis of the cultured lung epithelial-like cells.
  • Serine protease inhibitors reduced lysis caused by asbestos plus neutrophils to 9.7 ± 3.0% with PMSF (2.5 mM) and to 12.1 ± 3.0% with alpha-1-antitrypsin (250 micrograms/ml); P less than .01 for each versus asbestos plus neutrophils.
  • Neutrophils released 1.7 ± 0.5 micrograms/ml of human neutrophil elastase without asbestos and 2.8 ± 0.5 micrograms/ml with asbestos (P less than .025).
  • Human neutrophil elastase (5 micrograms/ml) plus asbestos caused 18.2 ± 5.1% cell lysis, versus 1.4 ± 0.7% for human neutrophil elastase alone and 8.8 ± 4.2% for asbestos alone (P less than .05).
  • Porcine pancreatic elastase (0.7 micrograms/ml) plus asbestos caused 26.1 ± 4.3% lysis, greater than the 16.6 ± 2.8% expected from simply adding the two effects (n = 7, P less than .005).
  • Cathepsin G (2.5 micrograms/ml) caused 10.7 ± 6.3% cell detachment, versus 40.1 ± 11.3% for human neutrophil elastase (1.0 micrograms/ml).
  • Cathepsin G (0.5 micrograms/ml) plus asbestos caused 25.6 ± 3.0% lysis, versus 25.1 ± 1.7% for asbestos alone (n = 4).
  • The polyanions heparin and dextran sulfate did not reduce cell detachment or lysis caused by asbestos plus neutrophils.
  • Asbestos (500 micrograms/ml) increased the cell-associated (bound) share of labeled porcine pancreatic elastase to 14.4%, compared with 0.3% for elastase alone (P less than .01).
  • With opsonized zymosan, another particle, cell-associated elastase was 1.4%, compared with 14.4% with asbestos.
• The authors' conclusion: The authors concluded that oxidant-independent mechanisms of asbestos-related injury to these cells exist, and that neutrophil-derived elastase is involved in one such mechanism.
• Limitations the authors state:
  • The authors stated that the in vivo relevance of these in vitro findings must await validation by further investigations.
  • The authors stated that the precise mechanism by which asbestos and elastase interact to damage the cells is unclear.
  • The authors stated that their studies did not address where the elastase binds to the cells.
  • The authors noted that the binding results, obtained with porcine elastase, may apply only to porcine and not to human neutrophil elastase, although they considered this unlikely in their model.
  • The authors noted that some elastase release may result from neutrophil injury, because asbestos is toxic to neutrophils.

Topics

Medical terms in this study, explained in our Lexicon: Amosite.

Related studies

• Contrasting effects of alveolar macrophages and neutrophils on asbestos-induced pulmonary epithelial cell injury — D.W. Kamp, M.M. Dunn, et al. (1994)
• Neutrophil elastase promotes myofibroblast differentiation in lung fibrosis — A.D. Gregory, C.R. Kliment, et al. (2015)
• Dibutyryl cAMP attenuates asbestos-induced pulmonary epithelial cell cytotoxicity and decline in ATP levels — V.A. Israbian, S.A. Weitzman, et al. (1994)
• Cyto-genotoxicity of amphibole asbestos fibers in cultured human lung epithelial cell line: role of surface iron — R.K. Srivastava, M. Lohani, et al. (2010)
• Studies on the role of oxygen radicals in asbestos-induced cytopathology of cultured human lung mesothelial cells — E.W. Gabrielson, G.M. Rosen, et al. (1986)
• Cigarette smoke augments asbestos-induced alveolar epithelial cell injury: role of free radicals — D.W. Kamp, M.J. Greenberger, et al. (1998)

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