The Role of IκB Kinase 2, but Not Activation of NF-κB, in the Release of CXCR3 Ligands from IFN-γ-Stimulated Human Bronchial Epithelial Cells

Abstract

The severity of chronic obstructive pulmonary disease correlates with increased numbers of cytotoxic CD8+ T lymphocytes in the lung parenchyma. CD8+ T lymphocytes release IFN-γ which stimulates airway epithelial cells to produce CXCR3 chemokines leading to further recruitment of CD8+ T lymphocytes. To evaluate the signaling pathways involved in regulation of CXCR3 ligands, the human bronchial epithelial cell line BEAS-2B was stimulated with IFN-γ and the release of the CXCR3 ligands was measured by ELISA. The release of CXCL9, CXCL10, and CXCL11 was inhibited by an IκB kinase 2 (IKK2) selective inhibitor 2-[(Aminocarbonyl)amino]-5-[4-fluorophenyl]-3-thiophenecarboxamide (TPCA-1) (EC50 values were 0.50 ± 0.03, 0.17 ± 0.06, and 0.45 ± 0.10 μM, respectively (n = 6)) and an IKK1/2 selective inhibitor 2-amino-6-(2′cyclopropylemethoxy-6′-hydroxy-phenyl)-4-piperidin-3-yl-pyridine-3-carbonitrile (EC50 values 0.74 ± 0.40, 0.27 ± 0.06, and 0.88 ± 0.29 μM, respectively (n = 6)). The glucocorticosteroid dexamethasone had no effect on CXCR3 ligand release. The release of CXCL10 was most sensitive to inhibition by IKK2 and a role for IKK2 in CXCL10 release was confirmed by overexpression of dominant-negative adenoviral constructs to IKK2 (68.2 ± 8.3% n = 5), but not of IKK1. Neither phosphorylation of IκBα, translocation of p65 to the nucleus, or activation of a NF-κB-dependent reporter (Ad-NF-κB-luc) were detected following stimulation of BEAS-2B cells with IFN-γ. These data suggest that IKK2 is also involved in the IFN-γ-stimulated release of the CXCR3 ligands through a novel mechanism that is independent NF-κB.

The role of interleukin 1β in the anti-adipogenic action of macrophages on human preadipocytes

“…It is known that IKKb phosphorylation does not always lead to IkB degradation and NF-kB activation, and that other established IKKb cellular targets could potentially mediate the anti-adipogenic action, including IRS-1, FOXO3, and 14-3-3b (Chariot 2009). Another group has reported the same response pattern of IKKb phosphorylation without IkB degradation in human bronchial epithelial cells stimulated with interferon-g (Tudhope et al 2007). …”

Candidate genes for COPD in two large data sets

“…The chemokines act as ligands at the CXCR3 receptor, with expression peaking 8-12 h after stimulation with IFN-c [20]. This pathway is thought to be dependent on STAT1 [21]. It is worth noting that TUDHOPE et al [21] observed that this pathway was dexamethasone-resistant, a finding that is consistent with the limited impact of corticosteroids on the inflammatory profile in COPD [22].…”

Loss of Epithelial RelA Results in Deregulated Intestinal Proliferative/Apoptotic Homeostasis and Susceptibility to Inflammation

“…However, recent work suggests that blocking IKK activity may have widely differing results in various cell types, with its loss in activated immune cells suppressing inflammation via decreased cytokine production, and epithelial-specific ablation causing apoptosis-induced barrier disruption and initiation of mucosal inflammation (14,40,51). Additionally, as the number of IKK substrates grows, it is now clear that the IKK subunits have both pro-and anti-inflammatory functions as well as NF-B-independent targets (3,(52)(53)(54)(55). Furthermore, determining the best approach for therapeutic manipulation of this signaling pathway in intestinal disease has been hampered by the lack of tissue-specific genetic removal of NF-B subunits in the intestine.…”