Asbestos-induced peribronchiolar cell proliferation and cytokine production are attenuated in lungs of protein kinase C-delta knockout mice

Our plain-English summary of Asbestos-induced peribronchiolar cell proliferation and cytokine production are attenuated in lungs of protein kinase C-delta knockout mice, by A. Shukla, K.M. Lounsbury, T.F. Barrett, et al (The American Journal of Pathology, 2007).

The study

• Authors: A. Shukla, K.M. Lounsbury, T.F. Barrett, J. Gell, M. Rincon, K.J. Butnor, D.J. Taatjes, G.S. Davis, P. Vacek, K.I. Nakayama, K. Nakayama, C. Steele, B.T. Mossman
• Journal: The American Journal of Pathology
• Published: 2007;170(1):140-51
• Cited by: 42 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

The signaling pathways leading to the development of asbestos-associated diseases are poorly understood. Here we used normal and protein kinase C (PKC)-delta knockout (PKCdelta-/-) mice to demonstrate multiple roles of PKC-delta in the development of cell proliferation and inflammation after inhalation of chrysotile asbestos. At 3 days, asbestos-induced peribronchiolar cell proliferation in wild-type mice was attenuated in PKCdelta-/- mice. Cytokine profiles in bronchoalveolar lavage fluids showed increases in interleukin (IL)-1beta, IL-4, IL-6, and IL-13 that were decreased in PKCdelta-/- mice. At 9 days, microarray and quantitative reverse transcriptase-polymerase chain reaction analysis of lung tissues revealed increased mRNA levels of the profibrotic cytokine, IL-4, in asbestos-exposed wild-type mice but not PKCdelta-/- mice. PKCdelta-/- mice also exhibited decreased lung infiltration of polymorphonuclear cells, natural killer cells, and macrophages in bronchoalveolar lavage fluid and lung, as well as increased numbers of B lymphocytes and plasma cells. These changes were accompanied by elevated mRNA levels of immunoglobulin chains. These data show that modulation of PKC-delta has multiple effects on peribronchiolar cell proliferation, proinflammatory and profibrotic cytokine expression, and immune cell profiles in lung. These results also implicate targeted interruption of PKC-delta as a potential therapeutic option in asbestos-induced lung diseases.

In plain English

This was an animal inhalation experiment comparing wild-type C57BL/6 mice with protein kinase C-delta knockout (PKC-delta-/-) mice. Mice aged 8 to 12 weeks breathed either ambient air or a National Institute of Environmental Health Sciences reference sample of chrysotile asbestos (7 mg/m3 air, 6 hours/day, 5 days/week) for 3, 9 or 40 days. The authors measured cell proliferation (Ki-67 staining), bronchoalveolar lavage fluid (BALF) cytokines, inflammatory cell counts, flow cytometry of lung, BALF and spleen, lung histopathology, microarray and quantitative RT-PCR. Peribronchiolar cell proliferation peaked at 3 days in asbestos-exposed wild-type mice but was significantly inhibited in asbestos-exposed knockout mice, while bronchiolar epithelial proliferation rose in both strains. Many BALF cytokines rose at 3 days in wild-type mice and were attenuated in knockout mice; polymorphonuclear cells in BALF reached about 30 percent at 3 days and 80 percent at 9 days in wild-type mice. Knockout lungs showed plasma cell patches and raised immunoglobulin chain mRNA.

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: controlled animal inhalation experiment in genetically modified (PKC-delta knockout) and wild-type mice
• Who was studied: Wild-type C57BL/6 mice and PKC-delta knockout mice, 8 to 12 weeks old, studied in duplicate inhalation experiments at the University of Vermont; five to eight mice per time point in each of four groups (sham wild-type, asbestos wild-type, sham knockout, asbestos knockout), with 7 to 9 mice per group for proliferation counts, 3 per group for microarray and 8 to 13 mice per group for fibrosis scoring
• Exposure: Inhalation of the National Institute of Environmental Health Sciences reference sample of chrysotile asbestos at 7 mg/m3 air, 6 hours/day, 5 days/week, for 3, 9 or 40 days; controls breathed ambient air
• Main results:
  • Peribronchiolar cell proliferation (Ki-67) peaked at 3 days in asbestos-exposed wild-type mice and was significantly inhibited in asbestos-exposed PKC-delta knockout mice at that time point
  • Distal bronchiolar epithelial cell proliferation increased in both knockout and wild-type mice at all time points
  • At 3 days many BALF cytokines and chemokines were increased in asbestos-exposed wild-type mice (the scan loses the Greek subtype letters for IL-1 and MIP-1), and many of these were significantly attenuated in asbestos-exposed knockout mice
  • Polymorphonuclear cells in BALF of asbestos-exposed wild-type mice reached the printed figures of 30 percent at 3 days and 80 percent at 9 days, whereas asbestos-exposed knockout mice showed no increase at 3 days and only modest increases at 9 days
  • Natural killer cell numbers in BALF were attenuated in both sham- and asbestos-exposed knockout mice, as in lung tissue
  • IL-4 mRNA in lung at 9 days was attenuated in asbestos-exposed knockout mice compared with wild-type mice (microarray, validated by real-time quantitative PCR)
  • Lung microarray at 9 days showed increased mRNA for several immunoglobulin chains in both sham- and asbestos-exposed knockout mice compared with wild-type groups
  • Both sham- and asbestos-exposed knockout mice had peribronchiolar aggregates of plasma cells with fewer interspersed lymphocytes
• The authors' conclusion: The authors concluded that PKC-delta modulation has multiple effects on peribronchiolar cell proliferation, proinflammatory and profibrotic cytokine expression and lung immune cell profiles, and they suggested that targeted interruption of PKC-delta is a potential therapeutic option in asbestos-induced lung diseases
• Limitations the authors state:
  • The authors stated that biochemical confirmation of fibrosis after chrysotile inhalation in mice may need longer exposure periods
  • The authors stated it was difficult to determine whether the inhibition of asbestosis in knockout mice reflected indirect or direct effects of PKC-delta on lung matrix, and that longer inhalation with more fibrogenic amphibole asbestos would be required
  • The authors stated that, because the knockout mice develop autoimmune disease, an effect of that disease on any inhibition of asbestosis could not be excluded

Topics

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

Medical terms in this study, explained in our Lexicon: Cytokine, Inflammation, Chrysotile, Bronchoalveolar Lavage (BAL), Macrophage.

Related studies

• Asbestos-induced apoptosis is protein kinase C delta-dependent — A. Shukla, M. Stern, et al. (2003)
• Transcriptional up-regulation of MMP12 and MMP13 by asbestos occurs via a PKCdelta-dependent pathway in murine lung — A. Shukla, T.F. Barrett, et al. (2006)
• Airway epithelial NF-kappaB activation modulates asbestos-induced inflammation and mucin production in vivo — A. Haegens, T.F. Barrett, et al. (2007)
• Increased sensitivity to asbestos-induced lung injury in mice lacking extracellular superoxide dismutase — C.L. Fattman, R.J. Tan, et al. (2006)
• Activated TNF-alpha/NF-kappaB signaling via down-regulation of Fas-associated factor 1 in asbestos-induced mesotheliomas from Arf knockout mice — D.A. Altomare, C.W. Menges, et al. (2009)
• A protein kinase Cdelta-dependent protein kinase D pathway modulates ERK1/2 and JNK1/2 phosphorylation and Bim-associated apoptosis by asbestos — S.A. Buder-Hoffmann, A. Shukla, et al. (2009)

Browse more research in The American Journal of Pathology, or return to medical research.