Regulatory mechanisms of Th2 cytokine-induced eotaxin-3 production in bronchial epithelial cells: possible role of interleukin 4 receptor and nuclear factor-kappaB.

BACKGROUND: Several cytokine combinations have been shown to induce eotaxins in bronchial epithelium. The mechanism for differential regulation of eotaxin expression remains unclear. OBJECTIVE: To investigate the regulatory mechanisms of eotaxin-3 production vs eotaxin-1 production in cultured bronchial epithelium. METHODS: Messenger RNA (mRNA) expression levels of eotaxin-1, eotaxin-2, and eotaxin-3 in a human bronchial epithelial cell line (BEAS-2B) and a normal human bronchial epithelial cell were examined using reverse transcriptase-polymerase chain reaction. Protein production was determined by enzyme-linked immunosorbent assay. Receptor expression was examined by flow cytometry. Phosphorylation of signal transducer and activator of transcription factor 6 (STAT6) was examined by immunoblotting. RESULTS: Eotaxin-1 and eotaxin-3, but not eotaxin-2, mRNA expressions were induced by stimulation with interleukin (IL) 13 or IL-4. However, eotaxin-3 was the only protein detected after stimulation. A consistent 10-fold difference in the potency of IL-13- and IL-4-mediated induction of eotaxin-3 mRNA expression was observed. Interleukin 4 induced more potent induction of STAT6 phosphorylation compared with IL-13. The BEAS-2B cells were observed to express types 1 and 2 IL-4 receptors. Pretreatment with tumor necrosis factor a enhanced IL-4-induced eotaxin-1, but not eotaxin-3, mRNA expression. An inhibitor of nuclear factor-KB inhibited IL-13- and IL-4-induced eotaxin-1 gene expressions. However, it enhanced eotaxin-3 gene expression. CONCLUSIONS: These results suggest that differences in the potency of IL-13- and IL-4-mediated induction of eotaxin-3 might be explained by expression of types 1 and 2 IL-4 receptors in bronchial epithelium. Differences in eotaxin-1 and eotaxin-3 mRNA and protein expression might be due to differential effects of nuclear factor-kappaB on gene expression.

Upregulation of interleukin-4 receptor by interferon-gamma: enhanced interleukin-4-induced eotaxin-3 production in airway epithelium.

Airway epithelial cells produce a number of chemokines, including eotaxins. Among the three known eotaxins, T helper (Th) type 2 cytokines have been observed to induce the expression of eotaxin-3 mRNA. This study investigated the effect of interferon (IFN)-gamma, a Th1 cytokine, on Th2 cytokine-induced eotaxin-3 production in a bronchial epithelial cell line, BEAS-2B. BEAS-2B cells produced eotaxin-3 after stimulation with the Th2 cytokines interleukin (IL)-13 and IL-4. When BEAS-2B cells were cultured with varying concentrations of IFN-gamma for 24 h, dose-dependent inhibition of Th2 cytokine-induced eotaxin-3 mRNA expression and protein production was observed. This was associated with downregulation of signal transducer and activator of transcription 6 activation. On the other hand, 2-d pretreatment of BEAS-2B cells with IFN-gamma dose-dependently enhanced Th2 cytokine-induced eotaxin-3 mRNA expression and production. IFN-gamma also increased the mRNA expression and protein production of IL-4 receptor (R) alpha in a time- and dose-dependent manner. In addition, IL-2Rgamma, a component of the type 1 IL-4R, was also upregulated by IFN-gamma. These results indicate that IFN-gamma has opposite effects on Th2 cytokine-induced eotaxin-3 production in BEAS-2B cells, depending on the length of exposure. Because high levels of IFN-gamma are produced during viral infection, airway viral infection may affect allergic airway inflammation in vivo by modulation of eotaxin-3 production.