Through DNA microarray analysis and quantitative PCR verification, we have identified additional IL-17A-inducible genes-IL-19, CXCL-1, -2, -3, -5, and -6 - in well-differentiated normal human bronchial epithelial cells. These genes, similar to previously described human β-defensin-2 (HBD-2) and CCL-20, were induced by a basolateral treatment of IL-17A, and regulated by PI3K signaling and NF-κB activation. For PI3K signaling, increases of cellular PIP 3 and phosphorylation of downstream molecules, such as Akt and glycogen synthase kinase-3β (GSK3β) (S9), were detected. Induced gene expression and HBD-2 promoter activity were attenuated by LY294002, p110α small-interfering RNA (siRNA), as well as by an overexpression of constitutively active GSK3β(S9A) or wild-type phosphatase and tensin homolog. Increased phosphorylation of JAK1/2 after IL-17A treatment was detected in primary normal human bronchial epithelium cells. Transfected siRNAs of JAK molecules and JAK inhibitor I decreased IL-17A-induced gene expression and GSK3β(S9) phosphorylation. However, both JAK inhibitor I and PI3K inhibitor had no effect on the DNA-binding activities of p65 and p50 to NF-κB consensus sequences. This result suggested a JAK-associated PI3K signaling axis is independent from NF-κB activation. With siRNA to knockdown STIR (similar expression to fibroblast growth factor and IL-17R; Toll-IL-1R)-related signaling molecules, such as Act1, TNFR-associated factor 6 (TRAF6), and TGF-β-activated kinase 1 (TAK1), and transfection of A52R, an inhibitor of the MyD88/TRAF6 complex, or dominant-negative TAK1, IL-17A-inducible gene expression and HBD-2 promoter activity were reduced. Additionally, IL-17A-induced p65 and p50 NF-κB activations were confirmed and their nuclear translocations were down-regulated by siRNAs of TRAF6 and TAK1. These results suggest that two independent and indispensable signaling pathways - 1) JAK1-associated PI3K signaling and 2) Act1/TRAF6/TAK1-mediated NF-κB activation - are stimulated by IL-17A to regulate gene induction in human airway epithelial cells.
|Original language||English (US)|
|Number of pages||10|
|Journal||Journal of Immunology|
|State||Published - Nov 15 2007|
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