Apoptotic cell clearance by bronchial epithelial cells critically influences airway inflammation (original) (raw)

Nature volume 493, pages 547–551 (2013)Cite this article

Subjects

Abstract

Lung epithelial cells can influence immune responses to airway allergens1,2. Airway epithelial cells also undergo apoptosis after encountering environmental allergens3; yet, relatively little is known about how these are cleared, and their effect on airway inflammation. Here we show that airway epithelial cells efficiently engulf apoptotic epithelial cells and secrete anti-inflammatory cytokines, dependent upon intracellular signalling by the small GTPase Rac1. Inducible deletion of Rac1 expression specifically in airway epithelial cells in a mouse model resulted in defective engulfment by epithelial cells and aberrant anti-inflammatory cytokine production. Intranasal priming and challenge of these mice with house dust mite extract or ovalbumin as allergens led to exacerbated inflammation, augmented Th2 cytokines and airway hyper-responsiveness, with decreased interleukin (IL)-10 in bronchial lavages. Rac1-deficient epithelial cells produced much higher IL-33 upon allergen or apoptotic cell encounter, with increased numbers of nuocyte-like cells1,4,5. Administration of exogenous IL-10 ‘rescued’ the airway inflammation phenotype in Rac1-deficient mice, with decreased IL-33. Collectively, these genetic and functional studies suggest a new role for Rac1-dependent engulfment by airway epithelial cells and in establishing the anti-inflammatory environment, and that defects in cell clearance in the airways could contribute to inflammatory responses towards common allergens.

This is a preview of subscription content, access via your institution

Access options

Subscribe to this journal

Receive 51 print issues and online access

$199.00 per year

only $3.90 per issue

Buy this article

Prices may be subject to local taxes which are calculated during checkout

Additional access options:

Similar content being viewed by others

References

  1. Fahy, J. V. & Locksley, R. M. The airway epithelium as a regulator of Th2 responses in asthma. Am. J. Respir. Crit. Care Med. 184, 390–392 (2011)
    Article CAS Google Scholar
  2. Lambrecht, B. N. & Hammad, H. The airway epithelium in asthma. Nature Med. 18, 684–692 (2012)
    Article CAS Google Scholar
  3. Jyonouchi, H. Airway epithelium and apoptosis. Apoptosis 4, 407–417 (1999)
    Article CAS Google Scholar
  4. Locksley, R. M. Asthma and allergic inflammation. Cell 140, 777–783 (2010)
    Article CAS Google Scholar
  5. Hammad, H. et al. House dust mite allergen induces asthma via Toll-like receptor 4 triggering of airway structural cells. Nature Med. 15, 410–416 (2009)
    Article CAS Google Scholar
  6. White, S. R. Apoptosis and the airway epithelium. J. Allergy 2011, 948406 (2011)
    Article Google Scholar
  7. Daidoji, T. et al. H5N1 avian influenza virus induces apoptotic cell death in mammalian airway epithelial cells. J. Virol. 82, 11294–11307 (2008)
    Article CAS Google Scholar
  8. Naylor, B. The shedding of the mucosa of the bronchial tree in asthma. Thorax 17, 69–72 (1962)
    Article CAS Google Scholar
  9. Yamada, Y., Yoshihara, S. & Arisaka, O. Creola bodies in wheezing infants predict the development of asthma. Pediatr. Allergy Immunol. 15, 159–162 (2004)
    Article Google Scholar
  10. Monks, J. et al. Epithelial cells as phagocytes: apoptotic epithelial cells are engulfed by mammary alveolar epithelial cells and repress inflammatory mediator release. Cell Death Differ. 12, 107–114 (2005)
    Article CAS Google Scholar
  11. Kirsch, T. et al. Engulfment of apoptotic cells by microvascular endothelial cells induces proinflammatory responses. Blood 109, 2854–2862 (2007)
    CAS PubMed Google Scholar
  12. Park, D. et al. Continued clearance of apoptotic cells critically depends on the phagocyte Ucp2 protein. Nature 477, 220–224 (2011)
    Article ADS CAS Google Scholar
  13. Park, D., Hochreiter-Hufford, A. & Ravichandran, K. S. The phosphatidylserine receptor TIM-4 does not mediate direct signaling. Curr. Biol. 19, 346–351 (2009)
    Article Google Scholar
  14. Fadok, V. A. et al. Macrophages that have ingested apoptotic cells in vitro inhibit proinflammatory cytokine production through autocrine/paracrine mechanisms involving TGF-β, PGE2, and PAF. J. Clin. Invest. 101, 890–898 (1998)
    Article CAS Google Scholar
  15. Ravichandran, K. S. & Lorenz, U. Engulfment of apoptotic cells: signals for a good meal. Nature Rev. Immunol. 7, 964–974 (2007)
    Article CAS Google Scholar
  16. Ravichandran, K. S. Beginnings of a good apoptotic meal: the find-me and eat-me signaling pathways. Immunity 35, 445–455 (2011)
    Article CAS Google Scholar
  17. Elliott, M. R. & Ravichandran, K. S. ELMO1 signaling in apoptotic germ cell clearance and spermatogenesis. Ann. NY Acad. Sci. 1209, 30–36 (2010)
    Article ADS CAS Google Scholar
  18. Perl, A. K., Tichelaar, J. W. & Whitsett, J. A. Conditional gene expression in the respiratory epithelium of the mouse. Transgenic Res. 11, 21–29 (2002)
    Article CAS Google Scholar
  19. Glogauer, M. et al. Rac1 deletion in mouse neutrophils has selective effects on neutrophil functions. J. Immunol. 170, 5652–5657 (2003)
    Article CAS Google Scholar
  20. Cates, E. C. et al. Intranasal exposure of mice to house dust mite elicits allergic airway inflammation via a GM-CSF-mediated mechanism. J. Immunol. 173, 6384–6392 (2004)
    Article CAS Google Scholar
  21. Thomas, W. R., Hales, B. J. & Smith, W. A. House dust mite allergens in asthma and allergy. Trends Mol. Med. 16, 321–328 (2010)
    Article CAS Google Scholar
  22. Borish, L. et al. Interleukin-10 regulation in normal subjects and patients with asthma. J. Allergy Clin. Immunol. 97, 1288–1296 (1996)
    Article CAS Google Scholar
  23. Thomas, W. R. Molecular mimicry as the key to the dominance of the house dust mite allergen Der p 2. Expert Rev. Clin. Immunol. 5, 233–237 (2009)
    Article CAS Google Scholar
  24. Trompette, A. et al. Allergenicity resulting from functional mimicry of a Toll-like receptor complex protein. Nature 457, 585–588 (2009)
    Article ADS CAS Google Scholar
  25. Eisenbarth, S. C. et al. Lipopolysaccharide-enhanced, toll-like receptor 4-dependent T helper cell type 2 responses to inhaled antigen. J. Exp. Med. 196, 1645–1651 (2002)
    Article CAS Google Scholar
  26. Soumelis, V. et al. Human epithelial cells trigger dendritic cell mediated allergic inflammation by producing TSLP. Nature Immunol. 3, 673–680 (2002)
    Article CAS Google Scholar
  27. Lloyd, C. M. IL-33 family members and asthma – bridging innate and adaptive immune responses. Curr. Opin. Immunol. 22, 800–806 (2010)
    Article CAS Google Scholar
  28. Liew, F. Y., Pitman, N. I. & McInnes, I. B. Disease-associated functions of IL-33: the new kid in the IL-1 family. Nature Rev. Immunol. 10, 103–110 (2010)
    Article CAS Google Scholar
  29. Barlow, J. L. et al. Innate IL-13-producing nuocytes arise during allergic lung inflammation and contribute to airways hyperreactivity. J. Allergy Clin. Immunol. 129, 191–198 (2012)
    Article CAS Google Scholar
  30. Shutes, A. et al. Specificity and mechanism of action of EHT 1864, a novel small molecule inhibitor of Rac family small GTPases. J. Biol. Chem. 282, 35666–35678 (2007)
    Article CAS Google Scholar

Download references

Acknowledgements

We thank the members of the Ravichandran laboratory for their suggestions, especially J. Kinchen and P. Trampont. We thank J. Whitsett for the rtTA-CCSP/Cre mice, X. Liu for the TGF-β responsive cell line PE25, and J. Steinke and J. Kennedy for providing human nasal epithelial cells. This work was supported by an Immunology Training Grant (I.J.J.), a F32 postdoctoral fellowship from the NHLBI (I.J.J.), and grants from the American Asthma Foundation and the National Institutes of Health (K.S.R.). K.S.R. has been a William Benter Senior Fellow of the American Asthma Foundation.

Author information

Authors and Affiliations

  1. Carter Immunology Center, University of Virginia, Charlottesville, 22908, Virginia, USA
    Ignacio J. Juncadella, Amelia Hochreiter-Hufford, Larry Borish & Kodi S. Ravichandran
  2. Department of Microbiology, University of Virginia, Charlottesville, 22908, Virginia, USA
    Ignacio J. Juncadella, Amelia Hochreiter-Hufford & Kodi S. Ravichandran
  3. The Center for Cell Clearance, University of Virginia, Charlottesville, 22908, Virginia, USA
    Ignacio J. Juncadella, Amelia Hochreiter-Hufford & Kodi S. Ravichandran
  4. Department of Medicine, University of Virginia, Charlottesville, 22908, Virginia, USA
    Alexandra Kadl, Yun M. Shim & Larry Borish
  5. Department of Surgery, University of Virginia, Charlottesville, 22908, Virginia, USA
    Ashish K. Sharma
  6. Center for Asthma and Allergic Diseases, University of Virginia, Charlottesville, 22908, Virginia, USA
    Larry Borish

Authors

  1. Ignacio J. Juncadella
    You can also search for this author inPubMed Google Scholar
  2. Alexandra Kadl
    You can also search for this author inPubMed Google Scholar
  3. Ashish K. Sharma
    You can also search for this author inPubMed Google Scholar
  4. Yun M. Shim
    You can also search for this author inPubMed Google Scholar
  5. Amelia Hochreiter-Hufford
    You can also search for this author inPubMed Google Scholar
  6. Larry Borish
    You can also search for this author inPubMed Google Scholar
  7. Kodi S. Ravichandran
    You can also search for this author inPubMed Google Scholar

Contributions

I.J.J. designed, performed and analysed most of the experiments in this study with input from K.S.R. A.K. optimized and performed the isolations and ex vivo cultures of primary epithelial cells and the nitrotetrazoleum staining. A.K.S. performed the lung function analysis. Y.M.S. performed the airway hyper-responsiveness experiments to determine the degree of airway resistance. L.B. provided intellectual input on specific experiments and helped with the human tissue studies. I.J.J. and K.S.R. wrote the manuscript with comments from co-authors.

Corresponding author

Correspondence toKodi S. Ravichandran.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Supplementary information

PowerPoint slides

Rights and permissions

About this article

Cite this article

Juncadella, I., Kadl, A., Sharma, A. et al. Apoptotic cell clearance by bronchial epithelial cells critically influences airway inflammation.Nature 493, 547–551 (2013). https://doi.org/10.1038/nature11714

Download citation

Editorial Summary

Immune-protective action of lung cells

Airway epithelial cells have been shown to activate immune responses on exposure to inhaled antigens. Kodi Ravichandran and colleagues now demonstrate that they also have an important role in immune homeostasis by dampening immune activation through clearing dying cells and secreting anti-inflammatory cytokines. These functions depend on the GTPase Rac1. Activated epithelial cells lacking Rac1 produce less of the anti-inflammatory cytokine interleukin-10, and express higher levels of interleukin-33, correlating with higher numbers of innate lymphocytes and enhanced airway inflammation in response to inhaled allergens. This work also suggests that apart from a physical barrier, phagocytosis in the airways may be part of an additional line of immune protection against innocuous antigens.