Mucosal T cells: mediators or guardians of inflammatory bowel disease?

Total Glycosides of Peony Protects Against Inflammatory Bowel Disease by Regulating IL-23/IL-17 Axis and Th17/Treg Balance

Inflammatory bowel disease (IBD) is a group of autoimmune diseases, including ulcerative colitis and Crohn’s disease, characterized by nonspecific inflammation in the gut. Total glycoside of peony (TGP) has been widely used for treatment of autoimmune diseases because of its pharmacological effects. However, it is lack of depth in whether TGP regulate T helper 17 cell (Th17) / T regulatory cell (Treg) immune balance or interleukin 23 (IL-23) / IL-17 axis to achieve the goal of treating IBD. Hence, the aim of this study was to investigate the effects of TGP on experimental colitis mice and the related mechanisms. In the present study, we demonstrated that administration of TGP effectively attenuates colonic inflammation of TNBS-induced colitis mice, mainly reflected in significantly improved clinical parameters, reduced inflammatory response and myeloperoxidase (MPO) activity, even stronger systemic immune ability and effective improvement of Th17/Treg immune disorders. In addition, there was a stronger immunosuppressive ability in a positive cluster of differentiation 4 (CD4[Formula: see text]) T-lymphocytes from the TGP treated mouse colon, characterized by the inhibition of high levels of inflammatory factors and increased regulatory T cells. Importantly, high-dose TGP has similar therapeutic effects as salicylazosulfapyridine (SASP) on IBD treatment. The potential mechanisms might be, at least in part, related to the adjustment of imbalance of Th17/Treg cells and the inhibition of IL-23/IL17 inflammatory signal axis.

Dietary fish oil and curcumin combine to modulate colonic cytokinetics and gene expression in dextran sodium sulphate-treated mice

Both fish oil (FO) and curcumin have potential as anti-tumour and anti-inflammatory agents. To further explore their combined effects on dextran sodium sulphate (DSS)-induced colitis, C57BL/6 mice were randomised to four diets (2 × 2 design) differing in fatty acid content with or without curcumin supplementation (FO, FO+2 % curcumin, maize oil (control, MO) or MO+2 % curcumin). Mice were exposed to one or two cycles of DSS in the drinking-water to induce either acute or chronic intestinal inflammation, respectively. FO-fed mice exposed to the single-cycle DSS treatment exhibited the highest mortality (40 %, seventeen of forty-three) compared with MO with the lowest mortality (3 %, one of twenty-nine) (P = 0·0008). Addition of curcumin to MO increased (P = 0·003) mortality to 37 % compared with the control. Consistent with animal survival data, following the one- or two-cycle DSS treatment, both dietary FO and curcumin promoted mucosal injury/ulceration compared with MO. In contrast, compared with other diets, combined FO and curcumin feeding enhanced the resolution of chronic inflammation and suppressed (P < 0·05) a key inflammatory mediator, NF-κB, in the colon mucosa. Mucosal microarray analysis revealed that dietary FO, curcumin and FO plus curcumin combination differentially modulated the expression of genes induced by DSS treatment. These results suggest that dietary lipids and curcumin interact to regulate mucosal homeostasis and the resolution of chronic inflammation in the colon.

Coriolus versicolor suppresses inflammatory bowel disease by Inhibiting the expression of STAT1 and STAT6 associated with IFN-γ and IL-4 expression

To investigate the effects of Coriolus versicolor extract (CVE) on infl ammatory bowel disease (IBD), ulcerative colitis was induced in male BALb/c mice by administering drinking water containing dextran-sulfate sodium (DSS). The mice were divided into the following four experimental groups: control, DSS-induced colitis, CVE treatment and CVE treatment + DSS-induced colitis. Mice receiving DSS treatment developed clinical and macroscopic signs of ulcerative colitis. However, treatment with CVE relieved the symptoms of IBD, including the decrease in body and organ weight. The levels of serum, spleen and mesenteric lymph node IgE in the CVE-treated groups was lower compared with the untreated groups. The antiinfl ammatory response upon CVE treatment correlated with the reduced expression of TNF-α, IL-1β and IL-6. Also, there was a significant reduction in the expression of STAT1 and STAT6 molecules, thereby leading to lower IFN-γ and IL-4 expression. Therefore, the antiinfl ammatory effects of Coriolus versicolor can be explained by its ability to inhibit certain proinflammatory cytokines.

Increased expression of chemokine receptor CCR3 and its ligands in ulcerative colitis: the role of colonic epithelial cells in in vitro studies

Human colonic epithelial cells express T helper type 1 (Th1)-associated chemoattractants, yet little is known about the production of Th2-associated chemoattractants. CCL11/eotaxin-1, CCL24/eotaxin-2 and CCL26/eotaxin-3 are known to attract CCR3-expressing, Th2-polarized lymphocytes. We studied constitutive and inflammation-induced expression and production of CCR3 together with its ligands in the colon and peripheral blood of patients with inflammatory bowel disease (IBD) by flow cytometry, reverse transcription–polymerase chain reaction (RT–PCR) and enzyme-linked immunosorbent assay (ELISA). We further defined the regulated expression of these chemokines by RT–PCR and ELISA using cultured human epithelial cell lines. A higher fraction of peripheral T lymphocytes were found to be positive for CCR3 in patients with ulcerative colitis (UC) compared to Crohn’s disease (CD), while almost no CCR3(+) T cells were found in normal controls (NC). Similarly, higher and more frequent expression of CCR3 was observed in colonic biopsies from patients with UC, regardless of the disease activity, when compared to CD or NCs. Serum CCL11/eotaxin-1 was increased significantly in UC (306 ± 87 pg/ml) and less so in CD (257 ± 43 pg/ml), whereas CCL24/eotaxin-2, and CCL26/eotaxin-3 were increased only in UC. Colonic expression of the three chemokines was minimal in NCs but high in inflammatory bowel diseases (especially UC) and was independent of disease activity. Th2, and to a lesser extent Th1, cytokines were able to induce expression and production of all three eotaxins from colonic epithelial cells in culture. CCR3 and ligands over-expression would appear to be a characteristic of UC. The production of CCR3 ligands by human colonic epithelial cells suggests further that epithelium can play a role in modulating pathological T cell-mediated mucosal inflammation.

Strong overexpression of CXCR3 axis components in childhood inflammatory bowel disease

BACKGROUND

Inflammatory bowel disease (IBD) is a polygenetic disorder. Our group previously showed that a variant within the CXCL9 gene is associated with pediatric Crohn's disease. As CXCL9, CXCL10, and CXCL11 are the 3 ligands to the receptor CXCR3, the aim of this study was to investigate the colonic transcriptional activity of the CXCR3 axis and to perform SNP genotyping of a CXCL11 polymorphism in a large pediatric and adult IBD cohort.

METHODS

mRNA expression of CXCR3, CXCL9, CXCL10, CXCL11, and IL8 was analyzed in colonic biopsies using real-time PCR. CXCL11 rs6817952 nucleotide substitution was determined in 501 German individuals with IBD (336 CD, 165 UC) including 258 children and 243 adults as well as in 231 controls by a TaqMan SNP genotyping assay.

RESULTS

CXCR3 axis genes were significantly overexpressed in inflamed colonic tissue of pediatric CD and UC patients. The prevalence of hetero- and homozygous variants of the rs6817952 genotype was higher in pediatric but not in adult CD patients compared with that in controls (P = 0.04). Moreover, carriers of the hetero- and homozygous genotype variants of rs6817952 were at increased risk for UC in all age groups (P = 0.009).

CONCLUSIONS

Our study provides evidence of the significant overexpression of the CXCR3 axis in active IBD, suggesting it has a role in IBD pathogenesis. The rs6817952 A variant is a risk allele for pediatric CD and UC in all age groups. Therapeutic studies will have to show whether the blockade of chemokine receptors such as CXCR3 can modulate intestinal inflammation in a clinical application.

Therapeutic potential of helminth soluble proteins in TNBS-induced colitis in mice

BACKGROUND

The hygiene hypothesis suggests an inverse relationship between the incidence of parasitic infections and chronic inflammatory bowel diseases (IBD). We investigated the therapeutic potential of Schistosoma mansoni and Ancylostoma caninum soluble proteins on experimental colitis in mice.

METHODS

Colitis was induced by intrarectal administration of 10 mg trinitrobenzene sulfonic acid (TNBS) in 30% ethanol. Six hours after TNBS injection, mice were treated intraperitoneally with helminth proteins. Three days later, colonic inflammation was scored based on 5 inflammatory parameters: clinical disease activity, macroscopic and microscopic inflammation score, extent of inflammation, and myeloperoxidase (MPO) activity. To determine immunological pathways induced by S. mansoni proteins we measured cytokine profiles of T-lymphocytes from colon, mesenteric lymph nodes (MLN), and spleen by real-time reverse-transcriptase polymerase chain reaction (RT-PCR).

RESULTS

Control mice showed no signs of inflammation, whereas all inflammatory parameters were significantly increased in mice with colitis. Treatment of mice with colitis with S. mansoni or A. caninum proteins decreased the macroscopic inflammation score, extent of inflammation, and MPO activity. Immunologically, induction of colitis significantly increased expression of IFN-gamma mRNA in the inflamed colon. Treatment with S. mansoni proteins caused a decrease of proinflammatory cytokines (IFN-gamma, IL-17) in colon and MLN, whereas the production of regulatory cytokines (IL-10, TGF-beta) increased significantly in colon tissue.

CONCLUSIONS

Treatment with proteins of S. mansoni and A. caninum ameliorated TNBS-induced colitis in mice. S. mansoni proteins increased mRNA expression of regulatory cytokines while suppressing expression of proinflammatory cytokines. Therefore, we suggest a therapeutic potential for helminth proteins in the treatment of IBD.

Expression of a splice variant of CXCR3 in Crohn's disease patients; indication for a lymphocyte--epithelial cell interaction

BACKGROUND AND AIM

T-lymphocyte migration is implicated in the pathogenesis of Crohn's disease (CD) and ulcerative colitis (UC). CXC chemokines MIG, IP-10, and I-TAC act by binding to CXCR3 receptor on T-lymphocytes. We investigated the role of these chemokines and their receptor in patients with UC, CD, and normal controls (NC).

METHODS

Chemokine expression and serum levels were examined in colonic biopsies from patients and NC using reverse transcription-polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay. HT-29 and Caco2 colonic epithelial cells were studied following in vitro stimulation with proinflammatory (Th1) and Th2-derived cytokines. CXCR3 receptor expression was assessed in CD3+ peripheral blood lymphocytes (PBL) from patients and NC and in stimulated Jurkat leukaemia cells, using RT-PCR and flow cytometry.

RESULTS

Full size CXCR3 mRNA (FS) expression was found in CD3+ PBL from controls and UC, but not from CD patients. In contrast, CD3+ PBL from CD patients showed a marked mRNA expression of the spliced variant CXCR3 (TV). This finding explains the high expression of CXCR3 on CD3+ PBL from CD patients in flow cytometry. Increased chemokine expression and production was found in colonic biopsies and serum from CD compared to UC patients and controls. Stimulation of epithelial cells with proinflammatory cytokines significantly induced chemokine production. The addition of Th2 cytokines had an inhibitory effect. Stimulation of Jurkat cells with cytokines and supernatant conditioned media from epithelial cells induced CXCR3TV expression.

CONCLUSIONS

These data demonstrate that PBL from CD patients express a spliced variant of the CXCR3 receptor and suggest a role for the colonic epithelial cells in T-lymphocyte migration in intestinal inflammation.

The transcription factor IFN regulatory factor-4 controls experimental colitis in mice via T cell-derived IL-6

The proinflammatory cytokine IL-6 seems to have an important role in the intestinal inflammation that characterizes inflammatory bowel diseases (IBDs) such as Crohn disease and ulcerative colitis. However, little is known about the molecular mechanisms regulating IL-6 production in IBD. Here, we assessed the role of the transcriptional regulator IFN regulatory factor-4 (IRF4) in this process. Patients with either Crohn disease or ulcerative colitis exhibited increased IRF4 expression in lamina propria CD3+ T cells as compared with control patients. Consistent with IRF4 having a regulatory function in T cells, in a mouse model of IBD whereby colitis is induced in RAG-deficient mice by transplantation with CD4+CD45RB(hi) T cells, adoptive transfer of wild-type but not IRF4-deficient T cells resulted in severe colitis. Furthermore, IRF4-deficient mice were protected from T cell-dependent chronic intestinal inflammation in trinitrobenzene sulfonic acid- and oxazolone-induced colitis. In addition, IRF4-deficient mice with induced colitis had reduced mucosal IL-6 production, and IRF4 was required for IL-6 production by mucosal CD90+ T cells, which it protected from apoptosis. Finally, the protective effect of IRF4 deficiency could be abrogated by systemic administration of either recombinant IL-6 or a combination of soluble IL-6 receptor (sIL-6R) plus IL-6 (hyper-IL-6). Taken together, our data identify IRF4 as a key regulator of mucosal IL-6 production in T cell-dependent experimental colitis and suggest that IRF4 might provide a therapeutic target for IBDs.

Reduced colitis-associated colon cancer in Fat-1 (n-3 fatty acid desaturase) transgenic mice

Bioactive food components containing n-3 polyunsaturated fatty acids (PUFA) modulate multiple determinants that link inflammation to cancer initiation and progression. Therefore, in this study, fat-1 transgenic mice, which convert endogenous n-6 PUFA to n-3 PUFA in multiple tissues, were injected with azoxymethane followed by three cycles of dextran sodium sulfate (DSS) to induce colitis-associated cancer. Fat-1 mice exhibited a reduced number of colonic adenocarcinomas per mouse (1.05 +/- 0.29 versus 2.12 +/- 0.51, P = 0.033), elevated apoptosis (P = 0.03), and a decrease in n-6 PUFA-derived eicosanoids, compared with wild-type (wt) mice. To determine whether the chemoprotective effects of n-3 PUFA could be attributed to its pleiotropic anti-inflammatory properties, colonic inflammation and injury scores were evaluated 5 days after DSS exposure followed by either a 3-day or 2-week recovery period. There was no effect of n-3 PUFA at 3 days. However, following a 2-week recovery period, colonic inflammation and ulceration scores returned to pretreatment levels compared with 3-day recovery only in fat-1 mice. For the purpose of examining the specific reactivity of lymphoid elements in the intestine, CD3(+) T cells, CD4(+) T helper cells, and macrophages from colonic lamina propria were quantified. Comparison of 3-day versus 2-week recovery time points revealed that fat-1 mice exhibited decreased (P < 0.05) CD3(+), CD4(+) T helper, and macrophage cell numbers per colon as compared with wt mice. These results suggest that the antitumorigenic effect of n-3 PUFA may be mediated, in part, via its anti-inflammatory properties.

Oral administration of taurolidine ameliorates chronic DSS colitis in mice

Taurolidine (TRD) has antimicrobial and anti-inflammatory properties. However, the anti-inflammatory effects of TRD in inflammatory bowel diseases (IBD) have not been investigated. Here, we have analyzed the toxicity of TRD after oral long-term application in mice and examined the impact of oral TRD in a dextran sulfate sodium (DSS) model of experimental colitis. Female C57/BL6 mice received TRD in various concentrations (0.1% to 0.4%) for 60 days. Toxicity was evaluated by use of a disease activity index (DAI) and histological examination of major metabolic organs. Furthermore, the impact of 0.2% TRD on a chronic DSS colitis was examined by daily DAI, histological crypt damage score (CDS), bacterial translocation into mesenteric lymph nodes (MLN), and colonic expression of tumor necrosis factor (TNF) alpha, transforming growth factor (TGF) beta, interleukin (IL)-1beta, IL-6, cytochrome oxidase (COX)-2, and monocyte chemotactic protein (MCP)-1 by real-time polymerase chain reaction (PCR). Oral TRD administration for 60 days was well tolerated by the animals and did not show any toxic effects in terms of DAI and histological changes. TRD treatment of DSS colitis led to increased survival of 100%, compared to 33% in the untreated colitis group (p < or = .005). Clinical amelioration was mirrored by significantly reduced DAI and CDS in the TRD treated colitis. Colonic cytokine expression and bacterial translocation into MLN showed no differences between both groups. We thus report for the first time that oral application of TRD results in amelioration of an experimental IBD model. We hypothesize direct intraluminal antimicrobial effects of TRD as well as anti-inflammatory effects during the acute phase of DSS colitis.

The immune response in inflammatory bowel disease

Ulcerative colitis (UC) and Crohn's disease (CD), collectively referred to as inflammatory bowel disease (IBD), present with differing histologic and cytokine profiles. While the precise mechanisms underlying the development of IBD are not known, sufficient data have been collected to suggest that it results from a complex interplay of genetic, environmental, and immunologic factors. Animal models of colitis, along with a more detailed understanding of the immune response in the normal bowel, have led to unifying hypotheses regarding the pathogenesis. An inappropriate mucosal immune response to normal intestinal constituents is a key feature, leading to an imbalance in local pro- and anti-inflammatory cytokines. Neutrophil and monocyte influx occurs with subsequent secretion of oxygen radicals and enzymes, leading to tissue damage. Therapy of IBD has improved and expanded as the understanding of disease mechanisms has evolved. Pharmacologic agents such as aminosalicylates, azathioprine/6-mercaptopurine, or steroids are the mainstays of therapy. Newer agents including monoclonal antibodies targeted to specific proinflammatory cytokines, such as tumor necrosis factor-alpha (TNF-alpha), have emerged and provide great clinical benefit, but unknown long-term toxicity and immunogenicity may limit their use.

Genetic deletion of JNK1 and JNK2 aggravates the DSS-induced colitis in mice

The c-Jun N-terminal kinases (JNKs) are considered as novel targets for therapy of inflammatory bowel diseases (IBD). However, the relevant JNK isoforms have to be elucidated. Here, we analyze the individual contribution of the JNK1 and JNK2 isoforms in a dextran sulfate sodium (DSS) model of experimental colitis. JNK1 and JNK2 knockout mice (JNK1 ko, JNK2 ko) and their wild-type controls (WT1, WT2) received three cycles of DSS treatment, each consisting of 1.7% DSS for 5 days, followed by 5 days with water. Animals were daily evaluated by a disease activity index (DAI) comprising measurement of body weight, estimation of stool consistency, and test for occult blood/gross rectal bleeding. After 30 days all animals were sacrificed, and the inflamed intestine was histologically evaluated by a crypt damage score. Unexpectedly, neither JNK1 ko nor JNK2 ko prevented mice from developing a chronic colitis when compared to wild-type controls WT1 and WT2, respectively. On the contrary, DAI and mortality were aggravated in JNK2 ko compared to WT2. DAI and mortality did not differ between JNK1 ko and WT1, but the histological crypt damage score was significantly enhanced in the cecum of JNK1 ko mice. Genetic deletion of JNK2 worsens the disease outcome in an experimental model of murine colitis. We hypothesize that the functional deletion of the otherwise proapoptotic JNK2 prolongs the activity of proinflammatory immune cells with deterioration of disease activity.

Epithelia: lymphocyte interactions in the gut

The mucosal immune system is governed by a unique set of rules and regulations. The local microenvironment dictates the necessity for these differences. The intestinal epithelial cell (IEC) sits at the interface between an antigen-rich lumen and a lymphocyte-rich lamina propria (LP). The cross talk that occurs between these compartments serves to maintain intestinal homeostasis. IECs have the capacity to talk to LP lymphocytes, activating populations of unique regulatory T cells. These cells have the capacity to talk back to the epithelium, influencing epithelial cell growth and differentiation. This review looks at this cross talk and places it in the context of mucosal immunoregulation.

Colon cancer, fatty acids and anti-inflammatory compounds

PURPOSE OF REVIEW

To outline recent findings on the efficacy of n-3 polyunsaturated fatty acids in the prevention/treatment of inflammatory bowel disease and colorectal cancer.

RECENT FINDINGS

Compelling data indicate a functional link between chronic inflammation and colon cancer. With respect to environmental risk factors, there is growing evidence that long-chain n-3 polyunsaturated fatty acids found in fish oil suppress inflammatory bowel diseases and colon cancer risk in humans. Unfortunately, the molecular basis of the effect of n-3 polyunsaturated fatty acids on inflammation/colitis-associated colon cancer risk is still largely obscure. In this review, we focus on recent studies which address three emerging mechanisms of n-3 polyunsaturated fatty acids action: (1) metabolic interconversion into bioactive eicosanoids, (2) modulation of nuclear receptor activation, and (3) alteration of membrane phospholipid composition and functionality of lipid microdomains.

SUMMARY

The consumption of dietary fish oil may prove to be an effective adjuvant therapy in colon cancer. Therefore, it is both appropriate and timely to determine precisely how n-3 polyunsaturated fatty acids modulate cell signaling networks, and reduce the risk of developing colon cancer and inflammatory disorders of the intestine.

What is the origin of ulcerative colitis? Still more questions than answers

Despite more than a century of existence as a clinical entity, the true origin of ulcerative colitis still remains elusive. Several factors probably contribute to the development of this condition. Recently discovered technologies have clarified the role of bacterial species, which may account for intestinal dysbiosis, as a factor triggering ulcerative colitis. Genetic susceptibility together with abnormal innate immunoreactivity probably comprise the essential prerequisites for the initiation and perpetuation of ulcerative colitis. Although the genetic background has been more clearly recognised in patients with Crohn's disease than in those with ulcerative colitis, some candidate loci associated with ulcerative colitis have also been intensively studied. Additionally, environmental factors may interfere with inherent predispositions to ulcerative colitis, and either suppress or reinforce them. Whatever the origin, the search for the aetiology of ulcerative colitis must have the same goal: the improvement of treatment and the quality of life in patients with ulcerative colitis.

Association of CTLA-4 gene microsatellite polymorphism with ulcerative colitis in Chinese patients

Ulcerative colitis (UC) is characterized by chronic intestinal inflammation as a result of an exaggerated T cell response. Cytotoxic T lymphocyte associated antigen-4 (CTLA-4), expressed mainly in activated T cells, inhibits T cell activation and proliferation by combining B7 through competing CD28 and maintains immune homeostasis. Polymorphisms of the CTLA-4 gene are known to be associated with several autoimmune diseases. The aim of this study was to investigate the association between the CTLA-4 gene microsatellite polymorphism and UC in Chinese patients. Unrelated 100 Chinese patients with UC and 140 healthy controls were studied. The (AT) repeats in the 3' untranslated region of exon 4 of the CTLA-4 gene were amplified by allele-specific polymerase chain reaction (PCR). The amplified products were electrophoresed on a 12% polyacrylamide gel, followed by silver staining. Twenty alleles were found in Chinese patients and healthy controls. The 122-bp allele was increased in UC compared with healthy controls (9.5% vs 0.7%, P = 0.0001/Pc = 0.002, OR = 14.591, 95%CI 3.357-63.420). The frequency of the longer alleles (>or=118 bp) of UC was higher than that in healthy controls (26% vs 4%, P = 0.0001/Pc = 0.0002, OR = 7.644, 95%CI 3.950-14.792), but was not associated with location and severity of the disease. Furthermore, the longer alleles were not associated with haplotypes of C-318T/A+49G of the CTLA-4 gene in Chinese patients with UC. The longer alleles of the CTLA-4 gene microsatellite polymorphism were strongly associated with UC in Chinese patients.

Leukocytapheresis Therapy Modulates Circulating T cell Subsets in Patients With Ulcerative Colitis

The aim of this study was to elucidate the molecular mechanisms responsible for the therapeutic effects of leukocytapheresis (LCAP). We investigated the alterations in circulating T cell subsets after LCAP therapy in ulcerative colitis (UC) patients. Eighteen patients with UC were enrolled. Fourteen patients were responders, and four patients were non-responders. Peripheral venous blood was obtained within 5 min before and 5 min after LCAP therapy. Flow cytometric analysis for T cell markers and intracellular interferon (IFN)-gamma (Th1) and interleukin (IL)-4 (Th2) was then performed. The average numbers of lymphocytes, T and B cells were significantly decreased after LCAP therapy, respectively (P < 0.01). The numbers of CD4+ and CD8+ T cells were also significantly decreased, respectively (P < 0.01), but the CD4+/CD8+ ratio was not changed. The number of CD45RO+ CD4+ memory T cells was significantly decreased. The number of CD25+ CD4+ T cells tended to decrease after LCAP therapy (not significant). However, the ratio of CD25+ CD4+-cells/CD25- CD4+-cells was significantly increased (P < 0.05). The number of IFN-gamma-positive (Th1) cells was significantly decreased after LCAP therapy, but there was no significant change in the number of IL-4-positive (Th2) cells. The Th1/Th2 ratio was significantly decreased after LCAP therapy. Some of the immuno-suppressive effects of LCAP therapy may be associated with a modulation of circulating T cell subsets.

Activation pattern of signal transducers and activators of transcription (STAT) factors in inflammatory bowel diseases

OBJECTIVES

Cytokine signaling pathways involving transcription factors of the signal transducers and activators of transcription (STAT) family play a key role in the pathogenesis of inflammatory bowel diseases (IBD). STAT proteins are latent cytoplasmic transcription factors that induce transcription upon phosphorylation, dimerization, and nuclear translocation. However, their activation pattern in IBD is poorly understood. The aim of our study was to characterize STAT-expression in IBD.

METHODS

Mononuclear cells were isolated from 36 colonic specimens of Crohn's disease, ulcerative colitis, or from control patients. Cells were stimulated overnight with antibodies against human CD2 and CD28 and mononuclear cells were analyzed by flow cytometry. Alternatively, CD4(+) T cells were immunomagnetically separated and then assessed by flow cytometry. Intracellular stainings of the following transcription factors were performed: STAT-1, STAT-2, STAT-3, STAT-4, and STAT-6. In addition, immunofluorescence staining on cryosections for phosphorylated STAT-1 and STAT-3 was performed.

RESULTS

Average expression of the IFN-gamma inducible transcription factor STAT-1 was increased in Crohn's disease as compared to patients with ulcerative colitis and control patients. However, levels of phospho-STAT-1 were surprisingly not markedly upregulated in IBD as compared to controls. In contrast, STAT-3 and phospho-STAT-3 levels were significantly increased in IBD patients as compared to controls (p < 0.01). No differences could be detected in STAT-6 levels. Finally, average expression of STAT-2, which is involved in type I interferon signalling, was downregulated in IBD as compared to control patients.

CONCLUSIONS

The analysis of STAT activation patterns could serve as a helpful tool to characterize intestinal inflammation. Furthermore, the IL-6/STAT-3 rather than the IFN-gamma/STAT-1 signaling pathway emerges as a key target for the development of future therapeutic concepts in IBD.