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Interleukin-8 up-regulation by neutrophil elastase is mediated by MyD88/IRAK/TRAF-6 in human bronchial epithelium.

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posted on 22.11.2019 by Deirdre E. Walsh, Catherine M. Greene, Tomás P. Carroll, Clifford C. Taggart, Paula M. Gallagher, Shane J. O'Neill, Noel G. McElvaney

Cystic fibrosis is characterized in the lungs by neutrophil-dominated inflammation mediated significantly by neutrophil elastase (NE). Previous work has shown that NE induces interleukin-8 (IL-8) gene expression and protein secretion in bronchial epithelial cells. We sought to determine the intracellular mechanisms by which NE up-regulates IL-8 in bronchial epithelial cells. The data show that stimulation of 16HBE14o(-) cells with NE induced IL-8 protein production and gene expression. Both responses were abrogated by actinomycin D, indicating that regulation is at the transcriptional level. Electrophoretic mobility shift assays demonstrated that nuclear factor kappaB (NFkappaB) was activated in 16HBE14o(-) cells stimulated with NE. Western blot analysis demonstrated that activation of NFkappaB by NE was preceded by phosphorylation and degradation of IkappaB proteins, principally IkappaBbeta. In addition, we observed that interleukin-1 receptor-associated kinase (IRAK) was degraded in 16HBE14o(-) cells stimulated with NE. Quantification of IL-8 reporter gene activity by luminometry demonstrated that dominant negative MyD88 (MyD88Delta) or TRAF-6 (TRAF-6Delta) inhibited IL-8 reporter gene expression in response to NE. Furthermore, MyD88Delta inhibited NE-induced IRAK degradation. These results show that NE induces IL-8 gene up-regulation in bronchial epithelial cells through an IRAK signaling pathway involving both MyD88 and TRAF-6, resulting in degradation of IkappaBbeta and nuclear translocation of NFkappaB. These findings may have implications for therapeutic treatments in the cystic fibrosis condition.

Funding

The Higher Education Authority. The Health Research Board. The Cystic Fibrosis Association of Ireland. The Royal College of Surgeons in Ireland. The Charitable Infirmary Charitable Trust.

History

Comments

The original article is available at www.jbc.org

Published Citation

Walsh DE, Greene CM, Carroll TP, Taggart CC, Gallagher PM, O'Neill SJ, McElvaney NG. Interleukin-8 up-regulation by neutrophil elastase is mediated by MyD88/IRAK/TRAF-6 in human bronchial epithelium. Journal of Biological Chemistry. 2001;276(38):35494-9.

Publication Date

21/09/2001

Publisher

American Society for Biochemistry and Molecular Biology

PubMed ID

11461907

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