Viral Inhibition of IL-1- and Neutrophil Elastase-Induced Inflammatory Responses in Bronchial Epithelial Cells

Abstract

Previously, we elucidated the intracellular mechanisms by which neutrophil elastase (NE) up-regulates inflammatory gene expression in bronchial epithelial cells. In this study, we examine the effects of both IL-1 and NE on inflammatory gene expression in 16HBE14o− bronchial epithelial cells and investigate approaches to abrogate these inflammatory responses. IL-1 induced IL-8 protein production in time- and dose-dependent fashions, an important observation given that IL-8 is a potent neutrophil chemoattractant and a key inflammatory mediator. IL-1 and NE were shown to activate the p38 MAPK pathway in 16HBE14o− cells. Western blot analysis demonstrated IL-1R-associated kinase 1 (IRAK-1) degradation in response to stimulation with both IL-1 and NE. In addition, the expression of dominant negative IRAK-1 (IRAK-1Δ), IRAK-2Δ, or IRAK-4Δ inhibited IL-1- and NE-induced NF-κB-linked reporter gene expression. Dominant negative versions of the intracellular adaptor proteins MyD88 (MyD88Δ) and MyD88 adaptor-like (Mal P/H) abrogated NE-induced NF-κB reporter gene expression. In contrast, only MyD88Δ was found to inhibit IL-1-induced NF-κB reporter activity. We also investigated the vaccinia virus proteins, A46R and A52R, which have been shown to antagonize IL-1 signaling. Transfection with A46R or A52R cDNA inhibited IL-1- and NE-induced NF-κB and IL-8R gene expression and IL-8 protein production in primary and transformed bronchial epithelial cells. Furthermore, cytokine array studies demonstrated that IL-1 and NE can up-regulate the expression of IL-6, oncostatin M, epithelial cell-derived neutrophil activating peptide-78, growth-related oncogene family members, vascular endothelial growth factor, and GM-CSF, with induction of these proteins inhibited by the viral proteins. These findings identify vaccinia virus proteins as possible therapeutic agents for the manifestations of several inflammatory lung diseases.

Activation of the Epidermal Growth Factor Receptor (EGFR) by a Novel Metalloprotease Pathway

“…Previous studies have identified in part the intracellular signaling pathway regulated by NE (11) and established that NE can induce IL-8 via TLR4 (12). Other studies have demonstrated partial inhibition of NE-induced IL-8 production by using specific inhibitors of TLR signaling in airway epithelial cells (12,13).…”

miR-126 Is Downregulated in Cystic Fibrosis Airway Epithelial Cells and Regulates TOM1 Expression

“…For example, in airway epithelial cells of non-CF and CF origin triacylated lipopeptide, LPS or unmethylated CpG DNA can induce IL-6, IL-8, and TNF-a production via TLRs 2, 4, and 9 (1). Similarly, IL-1b can upregulate production of a plethora of proinflammatory cytokines (2). Therefore, TLRs and their signaling intermediates represent potential therapeutic targets for CF.…”

“…IL-1RI and TLRs are present on a variety of cell types, including both immune cells and epithelial cells within the lung. In the context of CF, airway epithelial cells have been shown to promote proinflammatory gene transcription following stimulation with their cognate agonists (1,2). For example, in airway epithelial cells of non-CF and CF origin triacylated lipopeptide, LPS or unmethylated CpG DNA can induce IL-6, IL-8, and TNF-a production via TLRs 2, 4, and 9 (1).…”

TLR3 Sensing of Viral Infection~!2009-10-01~!2010-03-30~!2010-04-28~!

“…The vaccinia proteins A46R and A52R inhibit NE and IL-1 induced NF-B activation and IL-8 secretion in airway epithelial cells [114]. A46R also inhibits NF-B activation following stimulation with agonists of TLRs 1, 2, 4, 5, 6, 7 and 9 possibly by virtue of its association with the adaptor protein MyD88.…”