Vitronectin adsorption to chrysotile asbestos increases fiber phagocytosis and toxicity for mesothelial cells

Our plain-English summary of Vitronectin adsorption to chrysotile asbestos increases fiber phagocytosis and toxicity for mesothelial cells, by J. Wu, W. Liu, K. Koenig, et al (American Journal of Physiology. Lung Cellular and Molecular Physiology, 2000).

The study

• Authors: J. Wu, W. Liu, K. Koenig, S. Idell, V.C. Broaddus
• Journal: American Journal of Physiology. Lung Cellular and Molecular Physiology
• Published: 2000;279(5):L916-23
• Cited by: 25 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Biological modification of asbestos fibers can alter their interaction with target cells. We have shown that vitronectin (VN), a major adhesive protein in serum, adsorbs to crocidolite asbestos and increases fiber phagocytosis by mesothelial cells via integrins. Because chrysotile asbestos differs significantly from crocidolite in charge and shape, we asked whether VN would also adsorb to chrysotile asbestos and increase its toxicity for mesothelial cells. We found that VN, either from purified solutions or from serum, adsorbed to chrysotile but at a lower amount per surface area than to crocidolite. Nevertheless, VN coating increased the phagocytosis of chrysotile as well as of crocidolite asbestos. VN coating of both chrysotile and crocidolite, but not of glass beads, increased intracellular oxidation and apoptosis of mesothelial cells. The additional apoptosis could be blocked by integrin-ligand blockade with arginine-glycine-aspartic acid peptides, confirming a role for integrins in the fiber-induced toxicity. We conclude that VN increases the phagocytosis of chrysotile as well as of crocidolite asbestos and that phagocytosis is important in fiber-induced toxicity for mesothelial cells.

In plain English

This was an in vitro laboratory study of how vitronectin (VN), the major adhesive protein in serum, affects the interaction of chrysotile and crocidolite asbestos with rabbit pleural mesothelial cells. The authors used NIEHS and UICC chrysotile and crocidolite fibers, with glass beads as control particles, and coated fibers with purified radiolabeled VN or BSA, or with human serum. Western blotting confirmed that VN adsorbed to both fiber types from serum. Significantly more VN than BSA bound to crocidolite, while no preferential VN adsorption was found for chrysotile, and chrysotile adsorbed less VN per unit surface area than crocidolite. At 4°C, adherence of VN- and BSA-coated fibers was similar; at 37°C, VN-coated chrysotile and crocidolite showed significantly greater association with cells, interpreted as greater phagocytosis. VN coating increased intracellular oxidation for crocidolite and for sonicated (shortened) chrysotile, but not standard chrysotile, and increased apoptosis for both fibers; VN-coated glass beads did not. RGD, but not RGE, peptides reduced apoptosis from VN-coated chrysotile. The authors concluded that VN coating increases fiber phagocytosis and toxicity.

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 cell-culture and fiber-protein adsorption experiments using cultured rabbit pleural mesothelial cells
• Who was studied: Cultured rabbit pleural mesothelial cells (passages 3 to 7) exposed to asbestos fibers or glass beads in laboratory experiments
• Exposure: NIEHS and UICC chrysotile and crocidolite asbestos fibers (some chrysotile sonicated to shorten fibers), coated with purified vitronectin, BSA, or human serum; glass beads as control particles
• Main results:
  • Vitronectin from serum adsorbed to both crocidolite and chrysotile fibers, as shown by Western blot of eluted serum proteins
  • With purified proteins, significantly more VN than BSA bound to crocidolite, but no such preferential binding was seen for chrysotile
  • Per unit surface area, chrysotile adsorbed less vitronectin than crocidolite (significant difference reported in Table 1)
  • At 4°C (phagocytosis blocked), adherence of VN-coated and BSA-coated fibers to mesothelial cells was similar
  • At 37°C, VN-coated chrysotile and crocidolite associated with mesothelial cells more than BSA-coated fibers, interpreted by the authors as increased phagocytosis
  • VN coating increased intracellular oxidation for crocidolite but not for standard (unsonicated) chrysotile; sonicated, shorter chrysotile did show increased oxidation with VN coating
  • VN coating of glass beads, which were also phagocytosed, did not increase intracellular oxidation in mesothelial cells
  • VN-coated crocidolite and chrysotile (NIEHS) induced more apoptosis of mesothelial cells than BSA-coated fibers; VN-coated glass beads induced no apoptosis
  • RGD-containing peptides, but not control RGE peptides, reduced apoptosis caused by VN-coated chrysotile; RGD had no effect on BSA-coated chrysotile
• The authors' conclusion: The authors concluded that both fiber types become coated with vitronectin, that this coating increases phagocytosis of chrysotile as well as crocidolite, and that increased phagocytosis leads to increased intracellular oxidation and apoptosis of mesothelial cells, so biological modification by protein adsorption can enhance toxicity in vitro and possibly in vivo
• Limitations the authors state:
  • The authors state the phagocytosis assay could be affected by loss of cells during washing (about 10% at 37°C)
  • The authors state they could not test RGD peptides or cytochalasin in the phagocytosis assay because these increased cell loss during washing
  • The authors note that findings in vitro may not translate directly, since in vivo factors may inhibit apoptosis

Topics

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

Medical terms in this study, explained in our Lexicon: Vitronectin, Chrysotile, Phagocytosis, Mesothelial Cells, Crocidolite, Apoptosis.

Related studies

• 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)
• Phagocytosis of crocidolite asbestos induces oxidative stress, DNA damage, and apoptosis in mesothelial cells — W. Liu, J.D. Ernst, et al. (2000)
• Phagocytosis of chrysotile fibers by pleural mesothelial cells in culture — M.C. Jaurand, H. Kaplan, et al. (1979)
• Asbestos-induced endothelial cell activation and injury. Demonstration of fiber phagocytosis and oxidant-dependent toxicity — J.G. Garcia, L.D. Gray, et al. (1988)
• In vitro determinants of asbestos fiber toxicity: effect on the relative toxicity of Libby amphibole in primary human airway epithelial cells — K.E. Duncan, P.M. Cook, et al. (2014)
• Crocidolite induces prostaglandin I(2) release mediated by vitronectin receptor and cyclooxygenase-2 in lung cells — F.J. Leyva, K. Roberts (2010)

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