This study analyzed IL-23p19 expression in inflamed mucosa of IBD and the role in the induction of IEL and NK cell activation as well as Th17 cell differentiation. Expression of IL-23p19 was performed by immunohistochemistry and quantitative real-time PCR. Expression of IL-23R was assessed by flow cytometry. Cytolytic activities of IEL and NK cells by IL-23 were determined by a standard (51)Cr-release assay. Cytokine levels were analyzed by ELISA and quantitative real-time PCR. Expression of IL-23p19 was increased significantly in inflamed mucosa of CD compared with that in UC and healthy controls. Double-staining confirmed that IL-23p19(+) cells were mainly CD68(+) macrophages/DCs. IL-23R(+) cells were increased significantly in PB- and LP-CD4(+) and -CD8(+) T and NK cells. IL-23 markedly promoted IBD IEL and NK cell activation and cytotoxicity and triggered IBD PB- and LP-T cells to secrete significantly higher levels of IFN-γ, TNF, IL-2, and IL-17A compared with controls. Importantly, IL-23 promoted IBD PB- or LP-CD4(+) T cells to differentiate into Th17 cells, characterized by increased expression of IL-17A and RORC. Anti-TNF treatment could markedly reduce IL-23 expression and Th17 cell infiltration in inflamed mucosa of CD patients. These data indicate that IL-23 is highly expressed in inflamed mucosa of IBD and plays an important role in the induction of IEL, NK, and T cell activation, proinflammatory cytokine secretion, and Th17 cell differentiation. Targeted therapy directed against IL-23p19 may have a therapeutic role in treatment of IBD.

Etk/BMX is a non-receptor protein tyrosine kinase that requires a functional phosphatidylinositol 3-kinase via the pleckstrin homology domain to be activated by cytokine. In the present study, a conditionally active form of Etk was constructed by fusing the hormonebinding domain of estrogen receptor (ER) to an amino terminus truncated form of Etk, PH⌬1-68Etk, to generate ⌬Etk:ER. In stably transfected Pa-4⌬Etk:ER cells, the activity of ⌬Etk:ER was stimulated within minutes by the treatment of ⌬Etk:ER stimulant, estradiol, and sustained for greater than 24 h. A robust induction in the phosphorylation of signal transducers and activators of transcription (STAT) proteins, including STAT1, STAT3, and STAT5, was accompanied with ⌬Etk:ER activation. Moreover, the conditionally activated Etk stimulated STAT1-and STAT5-dependent reporter activities by ϳ160-and ϳ15-fold, respectively, however, elicited only a modest STAT3-mediated reporter activation. Qualitatively comparable results were obtained in lung A549 cells, indicating that ⌬Etk:ER inducible system could function in an analogous fashion in different epithelial cells. Furthermore, we demonstrated that Etk activation alone augmented cyclin D1 promoter/enhancer activity via its STAT5 response element in both Pa-4⌬Etk:ER and A549 cells. Altogether, these findings support the notion that the activation of Etk kinase is sufficient to transactivate STAT-mediated gene expression. Hence, our inducible ⌬Etk:ER system represents a novel approach to investigate the biochemical events following Etk activation and to evaluate the contribution by kinase activation of Etk alone or in conjunction with other signaling pathway(s) to the ultimate biological responses.Epithelial and endothelial tyrosine kinase (Etk), 1 also known as BMX, is a non-receptor tyrosine kinase that contains a pleckstrin homology (PH) domain at its amino terminus followed by Src homology SH3 and SH2 domains, and a tyrosine kinase domain (1, 2) (Fig. 1). Interest in the function and regulation of Etk/BMX activity has been invigorated by the findings that this enzyme belongs to the Tec family of nonreceptor protein-tyrosine kinases including additional members of Btk, Itk, Tec, and Txk (reviewed in Ref.3). For example, Etk/BMX compensates for the lack of Btk activity in B-cell receptor signal transduction by reconstituting phospholipase C␥2-dependent responses in Btk-deficient DT40 cells (4). However, these activities may not be the primary in vivo function of Etk/BMX, since Etk/BMX is predominantly expressed in lung and prostate tissues, as well as in salivary epithelial, endothelial, and granulomonocytic cells (1, 2, and this report), but not in B-cells.The PH domain, located at the Etk amino terminus, is a protein module that has been found in many signal transduction proteins to mediate either protein-lipid or protein-protein interactions (5). Activation of PI 3-kinase is a prerequisite for Etk/BMX activation, presumably due to the direct interaction between the resultant lipid product and the Etk/BMX PH...

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In mouse models of MPE, IFN-γ inhibited Th17-cell differentiation, whereas IL-17 inhibited Th1-cell differentiation. IL-17 inhibited the formation of MPE and improved the survival of mice bearing MPE; in contrast, IFN-γ promoted MPE formation and mouse death.