Exosomes from asbestos-exposed cells modulate gene expression in mesothelial cells

Our plain-English summary of Exosomes from asbestos-exposed cells modulate gene expression in mesothelial cells, by P. Munson, Y.W. Lam, J. Dragon, et al (FASEB Journal, 2018).

The study

• Authors: P. Munson, Y.W. Lam, J. Dragon, M. MacPherson, A. Shukla
• Journal: FASEB Journal
• Published: 2018;32(8):4328-4342
• Cited by: 25 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Asbestos exposure is a determinate cause of many diseases, such as mesothelioma, fibrosis, and lung cancer, and poses a major human health hazard. At this time, there are no identified biomarkers to demarcate asbestos exposure before the presentation of disease and symptoms, and there is only limited understanding of the underlying biology that governs asbestos-induced disease. In our study, we used exosomes, 30-140 nm extracellular vesicles, to gain insight into these knowledge gaps. As inhaled asbestos is first encountered by lung epithelial cells and macrophages, we hypothesize that asbestos-exposed cells secrete exosomes with signature proteomic cargo that can alter the gene expression of mesothelial cells, contributing to disease outcomes like mesothelioma. In the present study using lung epithelial cells (BEAS2B) and macrophages (THP-1), we first show that asbestos exposure causes changes in abundance of some proteins in the exosomes secreted from these cells. Furthermore, exposure of human mesothelial cells (HPM3) to these exosomes resulted in gene expression changes related to epithelial-to-mesenchymal transition and other cancer-related genes. This is the first report to indicate that asbestos-exposed cells secrete exosomes with differentially abundant proteins and that those exosomes have a gene-altering effect on mesothelial cells.-Munson, P., Lam, Y.-W., Dragon, J. MacPherson, M., Shukla, A. Exosomes from asbestos-exposed cells modulate gene expression in mesothelial cells.

In plain English

This was a laboratory study in cultured human cells, not in people. The authors exposed human bronchial epithelial cells (BEAS2B) and a macrophage cell line (THP-1) to crocidolite asbestos for 72 hours. They compared the exosomes, tiny vesicles the cells release, with those from unexposed cells. In BEAS2B exosomes, 55 of 145 identified proteins differed after asbestos exposure at an unadjusted P of 0.05 or less; 34 met the stricter adjusted threshold. THP-1 exosomes contained 785 identified proteins, 15 more abundant after asbestos exposure. The exosomes were then added to human pleural mesothelial cells (HPM3). Exosomes from asbestos-exposed BEAS2B cells changed genes linked to epithelial-to-mesenchymal transition. Retesting three of these genes gave results that were not statistically significant. Compared with exosomes from unexposed THP-1 cells, exosomes from asbestos-exposed THP-1 cells changed 498 genes. Direct fiber exposure, compared with the unexposed-cell exosomes, changed 3788 genes; 206 genes changed in both comparisons. The authors concluded that these exosomes mirrored many gene changes caused by direct fiber contact. They named the lack of in vivo data as a limitation.

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 study using human cell cultures (proteomic analysis of exosomes, followed by exposure of mesothelial cells to those exosomes and gene expression analysis)
• Who was studied: Human bronchial epithelial cells (BEAS2B) and a macrophage cell line (THP-1), both purchased from American Type Culture Collection, plus primary human pleural mesothelial cells (HPM3) from Brigham and Women's Hospital; experiments at the University of Vermont. The BEAS2B proteomics used 3 biologic replicates; the THP-1 proteomics used 2 independent experiments.
• Exposure: NIEHS reference sample crocidolite asbestos added to BEAS2B and THP-1 cells for 72 hours, at a dose printed as '5 mg/cm2'. THP-1 cells were tested with and without priming by phorbol myristate acetate (PMA). Exosomes from exposed or unexposed cells were then given to mesothelial cells for 96 hours. One mesothelial group was exposed directly to asbestos fibers as a positive control.
• Main results:
  • BEAS2B exosomes: 145 proteins were identified in total.
  • BEAS2B exosomes from asbestos-exposed cells compared with controls: 55 proteins differed in abundance with P less than or equal to 0.05, and 34 with adjusted P less than or equal to 0.05.
  • Western blot confirmed that glypican-1 and thrombospondin were increased in exosomes from asbestos-exposed epithelial cells.
  • 50 to 60% of mesothelial cells took up labeled BEAS2B exosomes.
  • In mesothelial cells given exosomes from asbestos-exposed BEAS2B cells, qRT-PCR retesting of E-cadherin, desmoplakin and IL-1 receptor antagonist showed a downward trend. These results were not statistically significant.
  • THP-1 exosomes: 785 proteins were identified across all groups.
  • THP-1 exosomes: 32 proteins differed in abundance between the asbestos-treated and control groups (P less than 0.05); 15 were more abundant in the asbestos-exposed groups.
  • Western blot confirmed increased SOD2 and vimentin in exosomes from asbestos-exposed macrophages.
  • PMA priming had no added effect on the exosomal protein signature compared with asbestos alone.
  • Mesothelial cells given exosomes from asbestos-exposed THP-1 cells, compared with control exosomes, at a 1.5-fold cutoff: 498 genes changed significantly (241 up, 257 down).
  • Mesothelial cells exposed directly to asbestos fibers, compared with control exosome-exposed cells: 3788 genes differed (1803 up, 1985 down).
  • 206 genes were differentially expressed in both comparisons.
  • At a 2-fold cutoff, asbestos exosomes compared with control exosomes: 80 significant gene changes (32 up, 48 down).
  • qRT-PCR of 6 selected genes (CCNB2, EGR1 and FANCD2 up; CRELD2, ERO1B and JAG1 down) showed the same trends as the microarray.
• The authors' conclusion: The authors concluded that exosomes from asbestos-exposed macrophages mirrored many of the gene expression changes seen when mesothelial cells were exposed directly to asbestos fibers. They said this supports their hypothesis that exosomes may carry information from asbestos-exposed cells to mesothelial cells.
• Limitations the authors state:
  • The study had no in vivo data. The authors also did not examine the role of inflammasomes and reactive oxygen species in how exosomes are packaged and secreted.
  • The authors suggested that the lack of significance in some results could be due to a shorter exposure of mesothelial cells to exosomes or a lower exosome concentration.

Topics

Medical terms in this study, explained in our Lexicon: Mesothelial Cells, Asbestos Exposure, Mesothelioma, Fibrosis, Lung Cancer, Biomarker, Macrophage.

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• Indications for distinct pathogenic mechanisms of asbestos and silica through gene expression profiling of the response of lung epithelial cells — T.N. Perkins, P.M. Peeters, et al. (2015)
• Mechanisms of oxidative stress and alterations in gene expression by Libby six-mix in human mesothelial cells — J.M. Hillegass, A. Shukla, et al. (2010)
• Utilization of gene profiling and proteomics to determine mineral pathogenicity in a human mesothelial cell line (LP9/TERT-1) — J.M. Hillegass, A. Shukla, et al. (2010)
• Potential Roles of Exosomes in the Development and Detection of Malignant Mesothelioma: An Update — P. Munson, A. Shukla (2022)

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