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Helicobacter pylori (H. pylori) induces the activation of nuclear factor-kB (NF-ΚB) and cytokine expression in gastric epithelial cells. The Janus kinase/signal transducers and activators of transcription (Jak/Stat) cascade is the inflammatory signaling in various cells. The purpose of the present study is to determine whether H. pyloriinduced activation of NF-ΚB and the expression of interleukin-8 (IL-8) are mediated by the activation of Jak1/Stat3 in gastric epithelial (AGS) cells. Thus, gastric epithelial AGS cells were infected with H. pylori in Korean isolates (HP99) at bacterium/cell ratio of 300:1, and the level of IL-8 in the medium was determined by enzyme-linked immonosorbent assay. Phospho-specific and total forms of Jak1/Stat3 and IΚBα were assessed by Western blot analysis, and NF-ΚB activation was determined by electrophoretic mobility shift assay. The results showed that H. pylori induced the activation of Jak1/Stat3 and IL-8 production, which was inhibited by a Jak/Stat3 specific inhibitor AG490 in AGS cells in a dose-dependent manner. H. pylori-induced activation of NF-ΚB, determined by phosphorylation of IΚBα and NF-ΚB-DNA binding activity, were inhibited by AG490. In conclusion, Jak1/Stat3 activation may mediate the activation of NF-ΚB and the expression of IL-8 in H. pylori-infected AGS cells. Inhibition of Jak1/Stat3 may be beneficial for the treatment of H. pylori-induced gastric inflammation, since the activation of NF-ΚB is inhibited and inflammatory cytokine expression is suppressed. [ABSTRACT FROM AUTHOR]