STAT3 Genotypic Variation and Cellular STAT3 Activation and Colon Leukocyte Recruitment in Pediatric Crohn Disease

Division of Gastroenterology, Hepatology, and Nutrition, Cincinnati Children's Hospital Medical Center, University of Cincinnati College of Medicine, Cincinnati, OH, USA.
Journal of pediatric gastroenterology and nutrition (Impact Factor: 2.63). 12/2011; 55(1):32-43. DOI: 10.1097/MPG.0b013e318246be78
Source: PubMed


Genotypic variation in signal transducer and activator of transcription 3 (STAT3) increases risk for inflammatory bowel disease (IBD), and STAT3-dependent inflammatory networks are induced in the colon in these patients. We hypothesized that STAT3 "A" risk allele carriage would be associated with increased cellular STAT3 activation and colon leukocyte recruitment.
Colonic expression of genes regulating STAT3 signaling and leukocyte recruitment and function was measured in pediatric patients with Crohn disease (CD) stratified by STAT3 genotype. The frequency of colonic pSTAT3* and CXCR2* neutrophils was determined using immunohistochemistry. STAT3 tyrosine phosphorylation (pSTAT3) was measured in circulating leukocytes by flow cytometry, and mechanisms regulating STAT3 activation were tested in IBD Epstein-Barr virus (EBV)-transformed lymphocytes (EBL).
Colonic expression of interleukin 6 (IL-6), the STAT3 target gene SOCS3, the neutrophil chemoattractants IL-8, CXCL1, and CXCL3, and the neutrophil products S100A8, S100A9, and S100A12 were increased in patients carrying the STAT3 "A" risk allele. The frequency of neutrophils expressing the cognate receptor for IL-8, CXCR2, was increased in colonic biopsies from patients carrying the risk allele, and the frequency of pSTAT3* or CXCR2* neutrophils correlated with histologic severity. The frequency of CD4 lymphocytes and granulocytes expressing pSTAT3 was increased in patients carrying the STAT3 "A" risk allele. EBLs from patients carrying the STAT3 "A" risk allele exhibited increased basal and IL-6-stimulated STAT3 tyrosine phosphorylation, increased transcription of STAT3 and SOCS3 after IL-6 stimulation, and increased membrane localization of the IL-6 receptor, GP130, and Janus-associated kinase 2.
The STAT3 "A" risk allele is associated with increased cellular STAT3 activation and upregulation of pathways that promote recruitment of CXCR2* neutrophils to the gut.

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    • "Removal of STAT3-mediated suppression in myeloid cells leads to enterocolitis [46]. In contrast, STAT3 activity in T cells is critically involved in the differentiation of the phenotype that produces IL-17A/F [47], cytokines clearly implicated in CD [48], [49], and increased IL-6-induced STAT3 phosphorylation in peripheral blood T cells and granulocytes has been reported [50] in children with CD-associated genetic variant of STAT3 [27]. Inflammation-related bystander mechanisms cannot be excluded based on our data, either, although most findings of altered signaling were not associated with disease activity. "
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    ABSTRACT: Abnormalities of dendritic cells (DCs) and STAT proteins have been reported in Crohn's disease (CD). Studies on JAK/STAT signaling in DCs are, however, lacking in CD. We applied a flowcytometric single-cell-based phosphoepitope assay to evaluate STAT1 and STAT3 pathways in DC subsets from CD patients. In addition, circulating DC counts were determined, together with the activation-related immunophenotype. We found that IL-6- and IFN-α-induced STAT3 phosphorylation and IFN-α-induced STAT1 phosphorylation were impaired in plasmacytoid DCs (pDCs) from CD patients (P = 0.005, P = 0.013, and P = 0.006, respectively). In myeloid DCs (mDCs), IFN-α-induced STAT1 and STAT3 phosphorylation were attenuated (P<0.001 and P = 0.048, respectively), but IL-10-induced STAT3 phosphorylation was enhanced (P = 0.026). IFN-γ-induced STAT1 signaling was intact in both DC subtypes. Elevated plasma IL-6 levels were detected in CD (P = 0.004), which strongly correlated with disease activity (ρ = 0.690, P<0.001) but not with IL-6-induced STAT3 phosphorylation. The numbers of pDCs and BDCA3+ mDCs were decreased, and CD40 expression on CD1c+ mDCs was increased in CD. When elucidating the effect of IL-6 signaling on pDC function, we observed that IL-6 treatment of healthy donor pDCs affected the maturation of and modified the T-cell priming by pDCs, favoring Th2 over Th1 type of response and the expression of IL-10 in T cells. Our results implicate DC signaling in human CD. Reduced IL-6 responsiveness in pDCs, together with the attenuated IFN-α-induced signaling in both DC subtypes, may contribute to the immunological dysregulation in CD patients.
    PLoS ONE 08/2013; 8(8):e70738. DOI:10.1371/journal.pone.0070738 · 3.23 Impact Factor
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    ABSTRACT: Introduction: STAT3 is a key transcription factor for many regulatory factors that modulate gene transcription. Particularly important are cytokines and growth factors that maintain homeostasis by regulating immunocytes, stromal and epithelial cells. Dysregulation of STAT3 by constitutive activation plays an important role in the initiation of inflammation and cellular transformation in numerous cancers, especially of epithelial origin. This review focuses on STAT3 drive in gastric cancer initiation and progression, with emphasis on its activation by cytokines, and how targeting the primary drivers or gastric STAT3 therapeutically may prevent or slow stomach cancer development. Areas covered: This review will discuss the mechanics of STAT3 signalling, how constitutive STAT3 activation promotes gastric tumourigenesis in both human adenocarcinomas and mouse models, the nature of the upstream regulators of STAT3, and their association with chronic Helicobacter pylori infection, STAT3-activated genes that promote transformation and progression, and finally the development and use of STAT3 and upstream cytokine inhibitors as therapeutics. Expert opinion: Chronic STAT3 activation is a key event in gastric cancer induction and progression. Specific targeting of stomach epithelial STAT3 or blocking IL-11Rα/gp130 and/or EGFR signal transduction in chronic gastric inflammation and metaplasia may be therapeutically effective in preventing gastric carcinogenesis.
    Expert Opinion on Therapeutic Targets 07/2012; 16(9):889-901. DOI:10.1517/14728222.2012.709238 · 5.14 Impact Factor
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    ABSTRACT: : Intestinal epithelial cell (IEC) STAT3 is required for wound healing following acute dextran sodium sulfate (DSS) injury. We hypothesized that loss of IEC STAT3 would promote the development of chronic colitis following acute DSS injury. : Colitis was induced in IEC-specific STAT3-deficient mice (STAT3) and littermate controls (STAT3) with 4% DSS for 7 days, followed by water consumption for 21 days. Epithelial and immune mediators and severity of colitis were determined. : Survival, colon length, and histologic injury were significantly worse at day 28 in STAT3 mice. IEC proliferation and apoptosis did not vary by genotype at day 14 or day 28. The colonic lamina propria frequency of pSTAT3 cells was increased at day 28 and correlated with histologic injury in STAT3 mice. The frequency of colonic F480 pSTAT3 macrophages and CD3 pSTAT3 T lymphocytes were increased in STAT3 mice as compared with STAT3 controls. In STAT3 mice, colonic expression of STAT3 target genes Reg3β and Reg3γ, which mediate epithelial restitution, were significantly decreased, whereas expression of interleukin (IL)-17a, IFNγ, CXCL2, CXCL10, and CCL2 were significantly increased and correlated with the increase in histologic severity at day 28(P < 0.05). IL-17a expression also correlated with the increased lamina propria frequency of CD3 pSTAT3 T lymphocytes. : Loss of intestinal epithelial STAT3 leads to more severe chronic inflammation following acute injury, which is not accounted for by a sustained defect in epithelial proliferation or apoptosis 7 or 21 days after 1 cycle of DSS but rather defective REG3 expression and expansion of pSTAT3 lymphocytes and IL-17A expression.
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