Journal of Biological Chemistry
Volume 276, Issue 38, 21 September 2001, Pages 35494-35499
Journal home page for Journal of Biological Chemistry

MECHANISMS OF SIGNAL TRANSDUCTION
Interleukin-8 Up-regulation by Neutrophil Elastase Is Mediated by MyD88/IRAK/TRAF-6 in Human Bronchial Epithelium*

https://doi.org/10.1074/jbc.M103543200Get rights and content
Under a Creative Commons license
open access

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 κB (NFκB) was activated in 16HBE14o cells stimulated with NE. Western blot analysis demonstrated that activation of NFκB by NE was preceded by phosphorylation and degradation of IκB proteins, principally IκBβ. 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 (MyD88Δ) or TRAF-6 (TRAF-6Δ) inhibited IL-8 reporter gene expression in response to NE. Furthermore, MyD88Δ 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 IκBβ and nuclear translocation of NFκB. These findings may have implications for therapeutic treatments in the cystic fibrosis condition.

Cited by (0)

Published, JBC Papers in Press, July 18, 2001, DOI 10.1074/jbc.M103543200

*

This work was supported by The Higher Education Authority, The Health Research Board, The Cystic Fibrosis Association of Ireland, The Royal College of Surgeons in Ireland, and The Charitable Infirmary Charitable Trust.The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.