FIGURE 4.

An intact JAK-Stat1 signaling pathway and Stat1 up-regulation are essential for IFN-γ-induced Duox2 and DuoxA2 expression. A, signaling pathways involved in the regulation of Duox2 expression in BxPC-3 cells by IFN-γ. BxPC-3 cells were grown in serum-free medium and then exposed to IFN-γ for various times; the expression levels of Stat1, phospho-Stat1 (Ser⁷²⁷ and Tyr⁷⁰¹), and IRFs 1–3 were determined subsequently by Western analysis. B, the effect of a 30-min exposure to the JAK inhibitor AG490 on IFN-γ-induced Duox expression and Stat1-related signaling proteins was examined after either 6 (left panel) or 24 h (right panel) of IFN-γ treatment. C, the effect of silencing Stat1 on IFN-γ-induced Duox expression was determined in BxPC-3 cells. Control siRNA and two Stat1-specific siRNAs targeting different domains of human Stat1 were transiently transfected into BxPC-3 cells. Twenty-four hours after transfection, cells were grown for another 24 h in serum-free medium with or without 25 ng/ml of IFN-γ. Western analysis shows the protein expression of Duox, Stat1, and IRF-1 following Stat1 knockdown.