6-thio-GTP Derivatives

Targeting of the transcription factor STAT4 by antisense phosphorothioate oligonucleotides suppresses collagen-induced arthritis

Abstract The transcription factor STAT4 mediates signals of various proinflammatory cytokines, such as IL-12, IL-15, and IL-23, that initiate and stabilize Th1 cytokine production. Although Th1 cytokine production has been suggested to play a major pathogenic role in rheumatoid arthritis, the role of STAT4 in this disease is poorly understood. In this study, we demonstrate a key functional role of STAT4 in murine collagen-induced arthritis (CIA). In initial studies we found that STAT4 expression is strongly induced in CD4+ T cells and to a lesser extent in CD11b+ APCs during CIA. To analyze the role of STAT4 for arthritis manifestation, we next investigated the outcome of interfering with S…

Antibodies against tumor necrosis factor (TNF) induce T-cell apoptosis in patients with inflammatory bowel diseases via TNF receptor 2 and intestinal CD14⁺ macrophages.

Background & Aims The anti–tumor necrosis factor (TNF) antibodies infliximab, adalimumab, and certolizumab pegol have proven clinical efficacy in Crohn's disease. Here, we assessed the effects of anti-TNF antibodies on apoptosis in inflammatory bowel disease (IBD). Methods CD14 + macrophages and CD4 + T cells were isolated from peripheral blood and lamina propria mononuclear cells from patients with IBD and control patients. Cell surface markers and apoptosis were assessed by immunohistology and fluorescence-activated cell sorting techniques. Results Lamina propria CD14 + macrophages showed significantly more frequent and higher membrane-bound TNF (mTNF) expression than CD4 + T cells in IBD…

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 transp…

Novel Signal Transduction Pathways: Analysis of STAT-3 and Rac-1 Signaling in Inflammatory Bowel Disease

Although the precise etiology of inflammatory bowel disease still remains unclear, considerable progress has been made in the identification of novel signal transduction pathways that elucidate the immunopathogenesis involved in the perpetuation of the inflammatory process. Augmented T cell resistance against apoptosis is regarded as a pivotal factor in the pathogenesis, as it impairs mucosal homeostasis and leads to unrestrained accumulation of activated T cells, which subsequently lead to the amplification of the inflammatory response. Therefore novel therapeutic strategies aim at restoring mucosal T cell susceptibility to apoptosis through targeting of signal transduction pathways that a…

The T-box transcription factor eomesodermin controls CD8 T cell activity and lymph node metastasis in human colorectal cancer.

An efficient cytolytic T cell function is essential for immune mediated rejection of colorectal cancer. However, the molecular mechanisms driving T cell mediated cancer rejection are still poorly understood. Here, we assessed the relevance of the T-box transcription factor eomesodermin in colorectal cancer. METHODS/ RESULTS: By analysing tissue probes from 88 different colorectal tumours, a significant (p0.02) inverse correlation between eomesodermin expression in colorectal cancers and the presence of lymph node metastases could be shown, whereas no such correlation was noted for the master transcription factor of regulatory T cells, FoxP3 and CD8 alpha expression. To evaluate whether this…

NF-κB in inflammatory bowel disease

Apart from genetic and environmental factors, the mucosal immune system of the gut plays a central role in the pathogenesis of inflammatory bowel disease (IBD). In the healthy gut, the mucosal immune system ensures the balance between pro- and anti-inflammatory mediators and thereby allows an effective defence against luminal pathogens but at the same time prevents an overwhelming immune reaction directed against the huge amount of harmless luminal antigens (for example, components of food or nonpathological bacteria). In both entities of IBD (Crohn's disease and ulcerative colitis) this immunological balance is severely impaired and shifted towards the pro-inflammatory side. The chronic mu…

Designer Thiopurine-analogues for Optimised Immunosuppression in Inflammatory Bowel Diseases.

Background and Aims: The clinical use of azathioprine and 6-mercaptopurine is limited by their delayed onset of action and potential side effects such as myelosuppression and hepatotoxicity. As these drugs specifically target the Vav1/Rac1 signalling pathway in T lamina propria lymphocytes via their metabolite 6-thio-GTP, we studied expression and optimised suppression of this pathway in inflammatory bowel diseases [IBD]. Methods: Rac1 and Vav1 expressions were analysed in mucosal immune cells in IBD patients. Targeted molecular modelling of the 6-thio-GTP molecule was performed to optimise Rac1 blockade; 44 modified designer thiopurine-analogues were tested for apoptosis induction, potenti…

Liver-primed memory T cells generated under noninflammatory conditions provide anti-infectious immunity.

SummaryDevelopment of CD8+ T cell (CTL) immunity or tolerance is linked to the conditions during T cell priming. Dendritic cells (DCs) matured during inflammation generate effector/memory T cells, whereas immature DCs cause T cell deletion/anergy. We identify a third outcome of T cell priming in absence of inflammation enabled by cross-presenting liver sinusoidal endothelial cells. Such priming generated memory T cells that were spared from deletion by immature DCs. Similar to central memory T cells, liver-primed T cells differentiated into effector CTLs upon antigen re-encounter on matured DCs even after prolonged absence of antigen. Their reactivation required combinatorial signaling thro…

IL-28A Is a Key Regulator of T-Cell–Mediated Liver Injury via the T-Box Transcription Factor T-Bet

Background & Aims: T-cell–mediated fulminant hepatitis is a potentially life-threatening event for which the underlying pathogenic mechanisms are not fully understood. Here, we demonstrate a key regulatory role of IL-28A in T-cell–mediated hepatitis. Methods: We cloned the murine IL-28A gene by reverse-transcription polymerase chain reaction, assessed the effects of recombinant IL-28A, and generated IL-28A–transgenic mice. Results: IL-28A induced TH1 cytokine production by CD4+ T lymphocytes in a T-bet–dependent manner and was up-regulated in a murine model of T-cell–mediated hepatitis upon Con A administration. In vivo, CD4+ T cells from newly created IL-28A–transgenic animals revealed an …

Understanding the delayed onset of action of azathioprine in IBD: are we there yet?

In this issue of Gut , Ben-Horin et al propose an innovative explanation for the well known phenomenon of the delayed onset of action of thiopurines ( see page 396 ). They thereby contribute to an improved insight into the exact mode of action of the classic immunosuppressive drug azathioprine.1 Developing azathioprine as an innovative immunosuppressive drug in 1957, Gertrude Elion and George Hitchings laid the basis for the currently utilised concept of steroid-sparing treatment strategies in inflammatory bowel diseases (IBD).2 With regard to the evidence-based immunosuppressive capacity and clinical efficacy of azathioprine in the context of IBD as well as considering the proven long-term…

Azathioprine in inflammatory bowel disease: improved molecular insights and resulting clinical implications

Azathioprine and 6-mercaptopurine represent important first-line immunosuppressive drugs in the treatment of inflammatory bowel disease. Owing to 45 years of clinical experience with thiopurines in inflammatory bowel disease, there currently exist strong data from numerous clinical trials and meta-analyses, which clearly document the therapeutic efficacy of azathioprine and 6-mercaptopurine in the treatment of inflammatory bowel disease. However, the exact molecular mechanism of action of these drugs was insufficiently understood for a long time. During the last few years, important new insights into the intracellular effects of azathioprine have been gained and thiopurines have been identi…

Immune cells in colorectal cancer: prognostic relevance and therapeutic strategies.

During the last two decades, considerable efforts have been made to improve the prevention, early diagnosis and therapy of colorectal cancer by gaining enhanced insights into disease-specific pathogenesis. Along these lines, tumor-infiltrating immune cells turned out to be critical indicators for an efficient antitumor immune response and the number and type of tumor-infiltrating immune cells determined the resulting tumor prognosis. This review aims to describe the prognostic relevance of the different subsets of tumor-infiltrating immune cells and highlights their specific function in the complex process of immune system-mediated rejection of colorectal cancer cells. Considering the clini…