IL-22 is produced by activated T cells and signals through a receptor complex consisting of IL-22R1 and IL-10R2. The aim of this study was to analyze IL-22 receptor expression, signal transduction, and specific biological functions of this cytokine system in intestinal epithelial cells (IEC). Expression studies were performed by RT-PCR. Signal transduction was analyzed by Western blot experiments, cell proliferation by 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium assay and Fas-induced apoptosis by flow cytometry. IEC migration was studied in wounding assays. The IEC lines Caco-2, DLD-1, SW480, HCT116, and HT-29 express both IL-22 receptor subunits IL-22R1 and IL-10R2. Stimulation with TNF-alpha, IL-1beta, and LPS significantly upregulated IL-22R1 without affecting IL-10R2 mRNA expression. IL-22 binding to its receptor complex activates STAT1/3, Akt, ERK1/2, and SAPK/JNK MAP kinases. IL-22 significantly increased cell proliferation (P = 0.002) and phosphatidylinsitol 3-kinase-dependent IEC cell migration (P < 0.00001) as well as mRNA expression of TNF-alpha, IL-8, and human beta-defensin-2. IL-22 had no effect on Fas-induced apoptosis. IL-22 mRNA expression was increased in inflamed colonic lesions of patients with Crohn's disease and correlated highly with the IL-8 expression in these lesions (r = 0.840). Moreover, IL-22 expression was increased in murine dextran sulfate sodium-induced colitis. IEC express functional receptors for IL-22, which increases the expression of proinflammatory cytokines and promotes the innate immune response by increased defensin expression. Moreover, our data indicate intestinal barrier functions for this cytokine-promoting IEC migration, which suggests an important function in intestinal inflammation and wound healing. IL-22 is increased in active Crohn's disease and promotes proinflammatory gene expression and IEC migration.

Human cytomegalovirus virus (CMV) is a major cause of morbidity and mortality in immunocompromised individuals. Recently, a novel group of cytokines [interleukin (IL)-28A/B and IL-29, also termed interferon (IFN)-lambdas] has been described. Here, we demonstrate that intestinal epithelial cell (IEC) lines as well as murine and human colonic tissue express the IFN-lambda receptor subunits IL-28R and IL-10R2. IL-28A and IL-29 binding to their receptor complex activates ERK-1/2 and stress-activated protein kinase/c-Jun NH2-terminal kinase MAPKs and Akt, resulting in increased IL-8 protein expression. IFN-lambdas also induce phosphorylation of signal transducer and activator of transcription 1 and significantly increase mRNA expression of suppressor of cytokine signaling 3 and the antiviral proteins myxovirus resistance A and 2',5'-oligoadenylate synthetase. These signals result in an up to 83% reduction of cells positive for human CMV immediate-early protein after human CMV infection. In mice, IL-28A mRNA expression is upregulated after infection with murine CMV in vivo. Both IL-28A and IL-29 significantly decrease cell proliferation but have no effect on Fas-induced apoptosis. In conclusion, IECs express functional receptors for IFN-lambdas, which mediate antiviral and antiproliferative signals in IECs, suggesting a potential for therapeutic use in certain viral infections and as (antiproliferative) anticancer therapy.

No abstract

The expression of CCL20 (MIP-3alpha), which chemoattracts leukocytes to sites of inflammation, has been shown in intestinal epithelial cells (IEC). Aim of this study was to analyze the role of the CCL20 receptor CCR6 in IEC and colorectal cancer (CRC) cells. Expression of CCR6 and CCL20 was analyzed by RT-PCR and immunohistochemistry. Signaling was investigated by Western blotting, proliferation by MTS assays and chemotactic cell migration by wounding assays. The effect of CCL20 on Fas-induced apoptosis was determined by flow cytometry. CCR6 and its ligand CCL20 are expressed in IEC. Moreover, CRC and CRC metastases express CCR6, which is upregulated during IEC differentiation. Stimulation of IEC with CCL20 and proinflammatory stimuli (TNF-alpha, IL-1beta, LPS) significantly upregulates CCL20 mRNA expression. CCL20 expression was significantly increased in inflamed colonic lesions in Crohn's disease and correlated significantly with the IL-8 mRNA expression in these lesions (r = 0.71) but was downregulated in CRC metastases. CCL20 activated Akt, ERK-1/2, and SAPK/JNK MAP kinases and increased IL-8 protein expression. The CCL20 mediated activation of these pathways resulted in a 2.6-fold increase of cell migration (P = 0.001) and in a significant increase of cell proliferation (P < 0.05) but did not influence Fas-induced apoptosis. In conclusion, IEC and CRC express CCL20 and its receptor CCR6. CCL20 expression is increased in intestinal inflammation, while CCR6 is upregulated during cell differentiation. CCR6 mediated signals result in increased IEC migration and proliferation suggesting an important role in intestinal homeostasis and intestinal inflammation by mediating chemotaxis of IEC but also in mediating migration of CRC cells.

No abstract

Limiting microbial threats, maintenance and re-establishment of the mucosal barrier are vital for intestinal homeostasis. Antimicrobial peptides have been recognized as essential defence molecules and decreased expression of these peptides has been attributed to chronic inflammation of the human intestinal mucosa. Recently, pluripotent properties, including stimulation of proliferation and migration have been suggested for a number of antimicrobial peptides. However, it is currently unknown, whether the human beta-defensin 2 (hBD-2) in addition to its known antimicrobial properties has further effects on healing and protection of the intestinal epithelial barrier. Caco-2 and HT-29 cells were stimulated with 0.1-10 microg/ml hBD-2 for 6-72 h. Effects on cell viability and apoptosis were monitored and proliferation was quantified by bromo-deoxyuridine incorporation. Migration was quantified in wounding assays and characterized by immunohistochemistry. Expression of mucins was determined by quantitative PCR and slot-blot analysis. Furthermore, anti-apoptotic capacities of hBD-2 were studied. Over a broad range of concentrations and stimulation periods, hBD-2 was well tolerated by IECs and did not induce apoptosis. hBD-2 significantly increased migration but not proliferation of intestinal epithelial cells. Furthermore, hBD-2 induced cell line specific the expression of mucins 2 and 3 and ameliorated TNF-related apoptosis-inducing ligand (TRAIL) induced apoptosis. In addition to its known antimicrobial properties, hBD-2 might have further protective effects on the intestinal epithelium. Results of this in vitro study suggest, that hBD-2 expression may play a dual role in vivo, i.e. in impaired intestinal barrier function observed in patients with inflammatory bowel disease.

Structural alterations of CCK-B/gastrin receptors may account for increased growth-promoting effects of amidated gastrins in colorectal cancer.

Background: Hepatocyte growth factor (HGF) stimulates proliferation, migration and morphogenesis of epithelial cells by specific binding to its receptor c-met. Overexpression of HGF or c-met has been reported for human gastric or pancreatic cancer. In colorectal cancer overexpression of c-met but not HGF has been shown. However, elevated HGF serum levels have been detected in colorectal cancer patients. Therefore, the present study was performed to investigate expression patterns of both c-met and HGF in colorectal cancers and metastasis in comparison to normal mucosa. Furthermore, the mitogenic actions of HGF on colorectal cancer cells were studied in vitro. Methods: Expression of c-met and HGF were analyzed by RT-PCR and Western blotting and localized in the tissues utilizing immunohistochemistry. Mitogenic effects of HGF were determined in four human colon cancer cell lines by ³H-thymidine incorporation studies. Results: C-met and HGF mRNA were detectable in 60% of the normal specimen, but in the majority of cancer samples, and in just 33% of the liver metastasis. In cancer samples a coexpression of c-met and HGF was detected in 77% of the specimens. The extent of protein expression of receptor and ligand correlated with the mRNA expression. Moreover, c-met protein expression was increased 2- to 3-fold in colorectal cancers. C-met was detected in cells of epithelial origin, whereas HGF was expressed by mesenchymal cells. In vitro, HGF significantly stimulated cell growth in all four cell lines. Conclusion: Overexpression of c-met protein in colorectal cancers is combined with an expression of HGF in the majority of cases suggesting a paracrine manner of growth enhancement, while only a weak expression of c-met or HGF was detected in metastatic tissues.