The role of IkappaB kinase 2, but not activation of NF-kappaB, in the release of CXCR3 ligands from IFN-gamma-stimulated human bronchial epithelial cells.
Tudhope SJ., Catley MC., Fenwick PS., Russell REK., Rumsey WL., Newton R., Barnes PJ., Donnelly LE.
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-gamma 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-gamma and the release of the CXCR3 ligands was measured by ELISA. The release of CXCL9, CXCL10, and CXCL11 was inhibited by an IkappaB kinase 2 (IKK2) selective inhibitor 2-[(Aminocarbonyl)amino]-5-[4-fluorophenyl]-3-thiophenecarboxamide (TPCA-1) (EC(50) values were 0.50 +/- 0.03, 0.17 +/- 0.06, and 0.45 +/- 0.10 microM, respectively (n = 6)) and an IKK1/2 selective inhibitor 2-amino-6-(2'cyclopropylemethoxy-6'-hydroxy-phenyl)-4-piperidin-3-yl-pyridine-3-carbonitrile (EC(50) values 0.74 +/- 0.40, 0.27 +/- 0.06, and 0.88 +/- 0.29 microM, 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 IkappaBalpha, translocation of p65 to the nucleus, or activation of a NF-kappaB-dependent reporter (Ad-NF-kappaB-luc) were detected following stimulation of BEAS-2B cells with IFN-gamma. These data suggest that IKK2 is also involved in the IFN-gamma-stimulated release of the CXCR3 ligands through a novel mechanism that is independent NF-kappaB.