Anja Schirbel

Inflammatory bowel disease: Established and evolving considerations on its etiopathogenesis and therapy

Modern studies of inflammatory bowel disease (IBD) pathogenesis have been pursued for about four decades, a period of time where the pace of progress has been steadily increasing. This progress has occurred in parallel with and is largely due to developments in multiple basic scientific disciplines that range from population and social studies, genetics, microbiology, immunology, biochemistry, cellular and molecular biology, and DNA engineering. From this cumulative and constantly expanding knowledge base the fundamental pillars of IBD pathogenesis appear to have been identified and consolidated during the last couple of decades. Presently there is a general consensus among basic IBD investigators that both Crohns disease (CD) and ulcerative colitis (UC) are the result of the combined effects of four basic components: global changes in the environment, the input of multiple genetic variations, alterations in the intestinal microbiota, and aberrations of innate and adaptive immune responses. There is also agreement on the conclusion that none of these four components can by itself trigger or maintain intestinal inflammation. A combination of various factors, and most likely of all four factors, is probably needed to bring about CD or UC in individual patients, but each patient or set of patients seems to have a different combination of alterations leading to the disease. This would imply that different causes and diverse mechanisms underlie IBD, and this could also explain why every patient displays his or her own clinical manifestations and a personalized response to therapy, and requires tailored approaches with different medications. While we are becoming increasingly aware of the importance of this individual variability, we have only a superficial notion of the reasons why this occurs, as hinted by the uniqueness of the genetic background and of the gut flora in each person. So, we are apparently facing the paradox of having to deal with the tremendous complexity of the mechanisms responsible for chronic intestinal inflammation in the setting of each patients individuality in the response to this biological complexity. This obviously poses considerable challenges to reaching a full understanding of IBD pathogenesis, but being aware of the difficulties is the first step in finding answers to them.

The probiotic Escherichia coli strain Nissle 1917 induces γδ T cell apoptosis via caspase- and FasL-dependent pathways

Human gammadelta T cells play a vital role in the innate and adaptive immune response to microbial antigens by acting as antigen-presenting cells while at the same time being capable of directly activating CD4(+) T cells. Pathogenic microbes or loss of tolerance toward the hosts own microflora trigger many diseases including inflammatory bowel diseases. We previously demonstrated that Escherichia coli Nissle 1917 directly interacts with the adaptive immune system by regulating central T cell functions. Here we aimed to investigate whether E. coli Nissle regulates gammadelta T cell function, thereby linking the innate and adaptive immune system. In our study, we demonstrate that, in contrast to the other probiotic strains tested, E. coli Nissle increased activation, cell cycling and expansion of gammadelta, but not alphabeta T cells. In gammadelta T cells, E. coli Nissle reduced tumor necrosis factor-alpha secretion but increased IL-6 and CXCL8 release. However, after activation, only E. coli Nissle induced gammadelta T cell apoptosis, mediated via Toll-like receptor-2 by caspase- and FasLigand-dependent pathways. gammadelta T cells play an important role in the recognition of microbial antigens and the perpetuation of inflammatory processes. The demonstration that E. coli Nissle, but not the other bacteria tested, profoundly regulate gammadelta T cell function contributes to explaining the biological function of this probiotic strain in inflammatory diseases and provides us with a better understanding of the role of gammadelta T cells.

Enteral and parenteral nutrition distinctively modulate intestinal permeability and T cell function in vitro.

BackgroundNutritional support is an established element of therapy for various indications. However, its impact on the mucosal barrier function is not well understood.Aim of the studyWe investigated the influence of EN and PN on intestinal epithelial cells and peripheral blood (PBMC) and lamina propria mononuclear cells (LPMC), all of which are involved in the mucosal defense against bacterial translocation and systemic inflammation.MethodsIntegrity of epithelial cells was measured as transepithelial electrical resistance (TER) of confluent Caco-2 monolayers in the presence of 1% EN, PN and a parenteral amino acid mixture (AM). To determine wound healing capacities, an established migration model with IEC-6 cells was used. Furthermore, we investigated apoptosis, cell activation, proliferation and cytokine secretion of Caco-2, HT29 and of stimulated PBMC and LPMC cultured with or without 1 and 5% EN, AM or PN.ResultsWe demonstrated that EN, AM and PN promoted the integrity of the epithelial monolayer and reconstituted epithelial cell continuity TGF-β-dependently and -independently. Interestingly, only PN induced apoptosis and decreased the mitochondrial membrane potential. The activation status of PBMC was significantly reduced by EN and AM. Specifically, EN leads to an increased apoptosis rate, inhibited cell cycle progression and increased pro-inflammatory cytokine secretion. Both EN and PN reduced the activation status and the release of pro- and anti-inflammatory cytokines.ConclusionsOur study provides evidence that by promoting wound healing and regulating T cell function, EN, AM, and PN potently interact with the intestinal barrier and immune system, thus justifying its use in diseases accompanied by impaired mucosal barrier function.

Results of the 2nd scientific workshop of the ECCO (III): basic mechanisms of intestinal healing.

The second scientific workshop of the European Crohns and Colitis Organization (ECCO) focused on the relevance of intestinal healing for the disease course of inflammatory bowel disease (IBD). The objective was to better understand basic mechanisms, markers for disease prediction, detection and monitoring of intestinal healing, impact of intestinal healing on the disease course of IBD as well as therapeutic strategies. The results of this workshop are presented in four separate manuscripts. This section describes basic mechanisms of intestinal healing, identifies open questions in the field and provides a framework for future studies.

TNFα inhibitors restrict T cell activation and cycling via Notch-1 signalling in inflammatory bowel disease

Background Tumour necrosis factor α (TNFα) inhibitors such as adalimumab and infliximab are frequently prescribed for inflammatory bowel disease (IBD). Despite the clinical success of TNFα inhibitors, their physiological mode of action is not fully understood. The aim of this study was to investigate the mode of action of anti-TNFα agents in IBD. Methods It was hypothesised that Notch mediates anti-TNFα action in T cells. A study was carried out to identify Notch-1 as a link by which anti-TNFα antibodies mediate their inhibitory functions. Results TNFα inhibitors induced T cell apoptosis, inhibited activation, reduced cytokine secretion and restricted cell cycling. TNFα blockade at several levels showed that TNFα is responsible for inducing apoptosis by anti-TNFα but not for cell cycle restriction. By linking Notch and TNFα it was shown that (1) Notch-1 mucosal expression differs in inflamed and non-inflamed mucosa and increases in response to anti-TNFα treatment; (2) Notch-1 function is regulated by TNFα inhibitors; (3) Notch-1 binds to TNFα; and (4) Notch-1 inhibition prevents anti-TNFα-induced T cell cycle arrest but not apoptosis. Conclusions TNFα inhibitors potently inhibit T cell function. By demonstrating for the first time that Notch-1 mediates the inhibitory effects of adalimumab and infliximab on T cell cycling, this study reveals a new mode of action and also an underlying signalling pathway by which biological agents act in IBD.

Targeting the innate immune system in pediatric inflammatory bowel disease

The pathogenesis of inflammatory bowel disease (IBD) is complex and involves both innate and adaptive immune responses. This article addresses, in a selective and speculative fashion, the topic of how the various components of the intestinal innate immune system can be manipulated for the purpose of developing new therapeutic approaches. These various components include: agents that stimulate mucosal innate immune responses, such as food components and the gut microbiota; cells that directly respond to these stimuli, including epithelial cells, macrophages and dendritic cells; and molecules that mediate innate immune responses, such as Toll-like receptors and protein kinases. Downregulation of excessive innate immune responses makes therapeutic sense in both pediatric and adult IBD. However, because IBD is complex and characteristically chronic, major alterations of adaptive immunity are also involved in the mediation of inflammation. Thus, novel and truly effective approaches to treat IBD will undoubtedly require intervening in the innate as well as the adaptive branches of the mucosal immunity.

Imaging in Inflammatory Bowel Disease Mucosal Healing in Ulcerative Colitis: Relevance for Clinical Outcomes

There is growing evidence of the importance of mucosal healing (MH) in ulcerative colitis, but whether or not it should be a future primary treatment goal is still under intense discussion. Within the last decade many clinical trials have focused not only on response and remission rates but also on achievement of MH, while in clinical practice we still make treatment decisions on the basis of clinical symptoms. There is so far no internationally accepted definition of MH and the tools for assessment of MH vary from biomarkers to endoscopy with histological evaluation on the basis of several different scores and indices. This review will focus on present data dealing with methods to assess MH and the importance of MH for the future course of disease, the need for colectomy or risk of developing colorectal cancer and the patients quality of life. Many questions remain: How and when do we best assess MH? How rapidly do we need to achieve MH? What is the optimal time point to discontinue treatment after achieving MH? Well defined prospective studies are needed to address these important questions.

Intestinal epithelial cells and T cells differentially recognize and respond to Candida albicans yeast and hypha

Inflammatory bowel diseases (IBD) are a multifactorial disorder. Our understanding of the role of bacteria in the pathogenesis of IBD has increased substantially; however, only scarce data exist regarding the role of commensal fungi in maintaining intestinal homeostasis and triggering IBD. Candida albicans (C. albicans) is a member of the intestinal mycobiome and proposed to contribute to IBD pathogenesis. We aimed to investigate the influence of the two morphologies of C. albicans, yeast and hypha, on epithelial cells and T cells from IBD patients versus healthy controls. We found that C. albicans was recognized by both epithelial cells lines and T cells. In the intestinal epithelial cell line, Caco‐2, response to hypha was different than to yeast cells, and this was mimicked by synthetic β‐glucans and Pam3CSK4. Unstimulated T cells exhibited increased activation and pro‐inflammatory cytokine secretion upon exposure, while there was no effect on apoptosis or proliferation. In contrast, C. albicans‐challenged CD3‐stimulated T‐cells exhibited decreased activation, cytokine secretion, apoptosis, and proliferation, suggesting reciprocal responsiveness to C. albicans. Glycans alone did not mimic abovementioned influences on T cells, suggesting alternative modes of recognition. In conclusion, we provide evidence for glycan dependent and independent recognition of C. albicans by epithelial cells and T cells.

P157 Reasons for a delayed diagnosis in inflammatory bowel disease

to follow-up, ADA-treated patients had significant reductions whereas IMS-treated patients had increases in UC-related hospitalizations and LOS (table). UC-related outpatient service utilization and costs, as well as total inpatient and outpatient service costs, decreased significantly for ADA-treated patients vs. a small increase for IMS-treated patients. ADA-treated patients also had a significantly greater reduction in hospital LOS for colectomy. Conclusions: In this retrospective claims database analysis, ADA therapy was associated with greater reductions in UCrelated hospitalization rates, length of hospitalization for colectomy, and total inpatient and outpatient medical service costs compared with IMS therapy.

871 Eosinophilic Esophagitis (EoE)-Associated Eosinophil Products and Cytokines Reduce Neurogenic Esophageal Smooth Muscle Contractility

In the intestinal epithelium, the Cdx, GATA and HNF transcription factor families are responsible for the expression of differentiation markers such as sucrase-isomaltase. Although previous studies have shown that Cdx-2 can induce differentiation in rat intestinal IEC-6 cells, no data are available concerning the direct implication of transcription factors on differentiation in human normal intestinal epithelial cell types. We investigated the role of Cdx-2, GATA-4 and HNF-1α using the undifferentiated human intestinal epithelial crypt cell line HIEC. These transcription factors were tested on proliferation and expression of polarization and differentiation markers. Ectopic expression of Cdx-2 or HNF-1α, alone and in combination, altered cell proliferation abilities through the regulation of cyclin D1 and p27 expression. HNF-1α and GATA-4 together induced morphological modifications of the cells towards polarization resulting in the appearance of functional features such as microvilli. HNF-1α was also sufficient to induce the expression of cadherins and dipeptidylpeptidase while in combination with Cdx-2 it allowed the expression of the late differentiation marker sucrase-isomaltase. Large scale analysis of gene expression confirmed the cooperative effects of these factors. Finally, while DCAMKL1 and Musashi-1 expression were downregulated in differentiated HIEC, other intestinal stem cell markers, such as Bmi-1 and Lgr5, were unaffected. These observations show that, cooperatively with Cdx2, HNF-1α acts as a key factor on human intestinal cells to trigger the onset of their functional differentiation program whereas GATA-4 initiates the establishment of cell polarity.