Defective expression of gp180, a novel CD8 ligand on intestinal epithelial cells, in inflammatory bowel disease

Hippuric acid alleviates dextran sulfate sodium-induced colitis via suppressing inflammatory activity and modulating gut microbiota

Inflammatory bowel disease (IBD) is a chronic inflammatory disease associated with metabolic disorder and gut dysbiosis. Decreased abundance of hippuric acid (HA) was found in patients with IBD. HA, metabolized directly from benzoic acid in the intestine and indirectly from polyphenols, serves as a marker of polyphenol catabolism. While polyphenols and benzoic acid have been shown to alleviate intestinal inflammation, the role of HA in this context remains unknown. Herein, we investigated the effects and mechanism of HA on DSS-induced colitis mice. The results revealed that HA alleviated clinical activity and intestinal barrier damage, decreased pro-inflammatory cytokine production. Metagenomic sequencing suggested that HA treatment restored the gut microbiota, including an increase in beneficial gut bacteria such as Adlercreutzia, Eubacterium, Schaedlerella and Bifidobacterium_pseudolongum. Furthermore, we identified 113 candidate genes associated with IBD that are potentially under HA regulation through network pharmacological analyses. 10 hub genes including ALB, IL-6, HSP90AA1, and others were identified using PPI analysis and validated using molecular docking and mRNA expression analysis. Additionally, KEGG analysis suggested that the renin-angiotensin system (RAS), NF-κB signaling and Rap1 signaling pathways were important pathways in the response of HA to colitis. Thus, HA may provide novel biotherapy options for IBD.

SARS-Cov-2 spike induces intestinal barrier dysfunction through the interaction between CEACAM5 and Galectin-9

Background

Carcinoembryonic antigen-related cell adhesion molecule 5 (CEACAM5), as a typical tumor marker, has been found to exert immunomodulatory effects in many diseases. We previously reported the clinical and molecular evidences supporting that SARS-Cov-2 infected the gastrointestinal (GI) tract and found a reduction of CEACAM5 in COVID-19 patients' feces which associated with gut dysbiosis. Yet the role of CEACAM5 in GI infection is ill-defined.

Methods

Mice models were established through intraperitoneally injecting with recombinant viral spike-Fc to mimic the intestinal inflammation. We collected duodenum, jejunum, ileum and colon samples after 6h, 2 days, 4 days and 7 days of spike-Fc or control-Fc injection to perform proteomic analysis. Blood was collected from healthy donors and peripheral blood mononuclear cells (PBMC) were separated by density gradient centrifugation, then CD4+ T cells were isolated with magnetic beads and co-cultured with Caco-2 cells.

Results

In addition to intestinal CEACAM5, the expression of tight junction and the percent of CD4+ T lymphocytes were significantly decreased in spike-Fc group compared to control (p < 0.05), accompanied with increased level of inflammatory factors. The KEGG analysis revealed differentially expressed proteins were mainly enriched in the coronavirus disease (COVID-19), tight junction, focal adhesion, adherens junction and PI3K-Akt signaling pathway. Protein-protein interaction (PPI) network analysis identified the interaction between CEACAM5 and Galectin-9 that was also verified by molecular docking and co-IP assay. We further confirmed a reduction of CEACAM5 in SARS-CoV-2 spike stimulated enterocytes could promote the expression of Galectin-9 protein in CD4+T cells. Then it gave rise to the increasing release of inflammatory factors and increased apoptosis of CD4+T cells by inhibition of PI3K/AKT/mTOR pathway. Ultimately intestinal barrier dysfunction happened.

Conclusion

Our results indicated that CEACAM5 overexpression and Galectin-9 knockdown played a protective role in intestinal barrier injury upon spike-Fc stimulation. Collectively, our findings identified firstly that SARS-CoV-2 spike induced intestinal barrier dysfunction through the interaction between CEACAM5 and Galectin-9. The result provides potential therapeutic targets in intestinal barrier dysfunction for treating severe COVID patients.

Harnessing CD8+CD28- Regulatory T Cells as a Tool to Treat Autoimmune Disease

T regulatory cell therapy presents a novel therapeutic strategy for patients with autoimmune diseases or who are undergoing transplantation. At present, the CD4⁺ Treg population has been extensively characterized, as a result of defined phenotypic and functional readouts. In this review article, we discuss the development and biology of CD8⁺ Tregs and their role in murine and human disease indications. A subset of CD8⁺ Tregs that lack the surface expression of CD28 (CD8⁺CD28⁻ Treg) has proved efficacious in preclinical models. CD8⁺CD28⁻ Tregs are present in healthy individuals, but their impaired functionality in disease renders them less effective in mediating immunosuppression. We primarily focus on harnessing CD8⁺ Treg cell therapy in the clinic to support current treatment for patients with autoimmune or inflammatory conditions.

Fecal multi-omics analysis reveals diverse molecular alterations of gut ecosystem in COVID-19 patients

Gut ecosystem has profound effects on host physiology and health. Gastrointestinal (GI) symptoms were frequently observed in patients with COVID-19. Compared with other organs, gut antiviral response can result in more complicated immune responses because of the interactions between the gut microbiota and host immunity. However, there are still large knowledge gaps in the impact of COVID-19 on gut molecular profiles and commensal microbiome, hindering our comprehensive understanding of the pathogenesis of SARS-CoV-2 and the treatment of COVID-19. We performed longitudinal stool multi-omics profiling to systemically investigate the molecular phenomics alterations of gut ecosystem in COVID-19. Gut proteomes of COVID-19 were characterized by disturbed immune, proteolysis and redox homeostasis. The expression and glycosylation of proteins involved in neutrophil degranulation and migration were suppressed, while those of proteases were upregulated. The variable domains of Ig heavy chains were downregulated and the overall glycosylation of IgA heavy chain constant regions, IgGFc-binding protein, and J chain were suppressed with glycan-specific variations. There was a reduction of beneficial gut bacteria and an enrichment of bacteria derived deleterious metabolites potentially associated with multiple types of diseases (such as ethyl glucuronide). The reduction of Ig heave chain variable domains may contribute to the increase of some Bacteroidetes species. Many bacteria ceramide lipids with a C17-sphingoid based were downregulated in COVID-19. In many cases, the gut phenome did not restore two months after symptom onset. Our study indicates widely disturbed gut molecular profiles which may play a role in the development of symptoms in COVID-19. Our findings also emphasis the need for ongoing investigation of the long-term gut molecular and microbial alterations during COVID-19 recovery process. Considering the gut ecosystem as a potential target could offer a valuable approach in managing the disease.

Intestinal enteroids/organoids: A novel platform for drug discovery in inflammatory bowel diseases

The introduction of biologics such as anti-tumor necrosis factor (TNF) monoclonal antibodies followed by anti-integrins has dramatically changed the therapeutic paradigm of inflammatory bowel diseases (IBD). Furthermore, a newly developed anti-p40 subunit of interleukin (IL)-12 and IL-23 (ustekinumab) has been recently approved in the United States for patients with moderate to severe Crohn’s disease who have failed treatment with anti-TNFs. However, these immunosuppressive therapeutics which focus on anti-inflammatory mechanisms or immune cells still fail to achieve long-term remission in a significant percentage of patients. This strongly underlines the need to identify novel treatment targets beyond immune suppression to treat IBD. Recent studies have revealed the critical role of intestinal epithelial cells (IECs) in the pathogenesis of IBD. Physical, biochemical and immunologic driven barrier dysfunctions of epithelial cells contribute to the development of IBD. In addition, the recent establishment of adult stem cell-derived intestinal enteroid/organoid culture technology has allowed an exciting opportunity to study human IECs comprising all normal epithelial cells. This long-term epithelial culture model can be generated from endoscopic biopsies or surgical resections and recapitulates the tissue of origin, representing a promising platform for novel drug discovery in IBD. This review describes the advantages of intestinal enteroids/organoids as a research tool for intestinal diseases, introduces studies with these models in IBD, and gives a description of the current status of therapeutic approaches in IBD. Finally, we provide an overview of the current endeavors to identify a novel drug target for IBD therapy based on studies with human enteroids/organoids and describe the challenges in using enteroids/organoids as an IBD model.

Carcinoembryonic antigen (CEACAM) family members and Inflammatory Bowel Disease

Inflammatory bowel disease (IBD), encompassing Crohn's disease (CD) and ulcerative colitis (UC), is a chronic intestinal inflammatory condition with increasing incidence worldwide and whose pathogenesis remains largely unknown. The collected evidence indicates that genetic, environmental and microbial factors and a dysregulated immune response are responsible for the disease. IBD has an early onset and long term sufferers present a higher risk of developing colitis associated cancer (CAC). The carcinoembryonic antigen-related adhesion molecules (CEACAM) are a subgroup of the CEA family, found in a range of different cell types and organs including epithelial cells in the intestine. They can act as intercellular adhesions molecules for e.g. bacteria and soluble antigens. CEACAMs are involved in a number of different processes including cell adhesion, proliferation, differentiation and tumour suppression. Some CEACAMs such as CEACAM1, CEACAM5 and CEACAM6 are highly associated with cancer and are even recognised as valid clinical markers for certain cancer forms. However, their role in IBD pathogenesis is less understood. The purpose of this review is to provide a comprehensive summary of published literature on CEACAMs and intestinal inflammation (IBD). The interactions between CEACAMs and bacteria adhesion in relation to IBD pathophysiology will be addressed and potential new therapeutic and diagnostic opportunities will be identified.

Novel Insights into the Mechanisms of Gut Homing and Antiadhesion Therapies in Inflammatory Bowel Diseases

Therapeutic compounds interfering with T cell trafficking are a new column of inflammatory bowel disease (IBD) treatment. Currently, the anti-α4β7 integrin antibody vedolizumab is successfully used in the clinic and further drugs are likely to follow. Despite these clinical advances, the precise mechanistic background of their action is only gradually elucidated and still a matter of intensive research. Only recently, advances made with the help of new in vivo models and human studies have contributed to shape our concept of T cell trafficking in IBD by deciphering some important and so far unanswered questions. At the same time, basic and clinical data have generated new issues to be addressed on the way toward a clear perception of trafficking mechanisms and toward elucidation of the action of compounds interfering with this process. In this review, we will give a comprehensive outline of all components of T cell trafficking in regard to IBD before discussing the current knowledge concerning targeted interference with integrins in this complex network. Moreover, we will summarize remaining ambiguity and give an outlook on potential future targets.

Identification of Candidate Genes Related to Inflammatory Bowel Disease Using Minimum Redundancy Maximum Relevance, Incremental Feature Selection, and the Shortest-Path Approach

Identification of disease genes is a hot topic in biomedicine and genomics. However, it is a challenging problem because of the complexity of diseases. Inflammatory bowel disease (IBD) is an idiopathic disease caused by a dysregulated immune response to host intestinal microflora. It has been proven to be associated with the development of intestinal malignancies. Although the specific pathological characteristics and genetic background of IBD have been partially revealed, it is still an overdetermined disease and the blueprint of all genetic variants still needs to be improved. In this study, a novel computational method was built to identify genes related to IBD. Samples from two subtypes of IBD (ulcerative colitis and Crohn's disease) and normal samples were employed. By analyzing the gene expression profiles of these samples using minimum redundancy maximum relevance and incremental feature selection, 21 genes were obtained that could effectively distinguish samples from the two subtypes of IBD and the normal samples. Then, the shortest-path approach was used to search for an additional 20 genes in a large network constructed using protein-protein interactions based on the above-mentioned 21 genes. Analyses of the 41 genes obtained indicate that they are closely associated with this disease.

Characterizing CEACAM5 interaction with CD8α and CD1d in intestinal homeostasis

Normal intestinal epithelial cells (IECs) could act as non-professional antigen-presenting cells, selectively activating CD8(+)-suppressor T cells. An epithelial cell surface glycoprotein, gp180, recognized by monoclonal antibodies B9 and L12 was determined to be critical in this process. Purification and sequence analysis of mAb B9 reactive material revealed amino-acid sequence homology with CEACAM5. We demonstrate that CEACAM5 has properties attributed to gp180, such as CD8α binding and activation of CD8-associated Lck. CEACAM5 is the only CEACAM member interacting with CD1d through the B3 domain. Its N domain (recognized by B9) is required for CD8α binding. Removal of the N-domain glycosylated residues reduces B9 recognition, CD8α binding affinity, and activation of LcK. Therefore, conformational changes in CEACAM5 glycosylation site are critical for its interaction with CD8α. CEACAM5-activated CD8(+) T cells acquire the ability to suppress the proliferation of CD4(+) T cells in vitro in the presence of interleukin (IL)-15 or IL-7. We provide new insights into the role of CEACAM5 and define its specific immunoregulatory properties among the CEACAMs expressed on IECs. We suggest that unique set of interactions between CEACAM5, CD1d, and CD8 render CD1d more class I-like molecule, facilitating antigen presentation and activation of CD8(+)-suppressor regulatory T cells.

Intestinal epithelial cells in inflammatory bowel diseases

The pathogenesis of inflammatory bowel diseases (IBDs) seems to involve a primary defect in one or more of the elements responsible for the maintenance of intestinal homeostasis and oral tolerance. The most important element is represented by the intestinal barrier, a complex system formed mostly by intestinal epithelial cells (IECs). IECs have an active role in producing mucus and regulating its composition; they provide a physical barrier capable of controlling antigen traffic through the intestinal mucosa. At the same time, they are able to play the role of non-professional antigen presenting cells, by processing and presenting antigens directly to the cells of the intestinal immune system. On the other hand, immune cells regulate epithelial growth and differentiation, producing a continuous bi-directional cross-talk within the barrier. Several alterations of the barrier function have been identified in IBD, starting from mucus features up to its components, from epithelial junctions up to the Toll-like receptors, and altered immune responses. It remains to be understood whether these defects are primary causes of epithelial damage or secondary effects. We review the possible role of the epithelial barrier and particularly describe the role of IECs in the pathogenesis of IBD.

Defect in CEACAM family member expression in Crohn's disease IECs is regulated by the transcription factor SOX9

BACKGROUND

CEACAM1, CEACAM5, and CEACAM6 represent 3 of the CEACAM (carcinoembryonic antigen-related cell adhesion molecule) subfamily members expressed on intestinal epithelial cells (IECs). Deficiency in their expression, as seen in inflammatory bowel disease (IBD), results in the lack of activation of CD8+ regulatory T cells in the mucosa. Since CEACAM expression was shown to be regulated by the transcription factor SOX9, we sought to determine whether the defect in CEACAM expression in IBD was related to aberrant SOX9 expression.

METHODS

IECs and lamina propria lymphocytes (LPLs) were freshly isolated from colonic tissues. T84 and HT29 16E cells were cocultured with LPLs. SOX9 and CEACAM subfamily member expression was assessed by real-time polymerase chain reaction (PCR), Western blot, immunohistochemistry, and immunofluorescence.

RESULTS

In Crohn's disease (CD) but not in ulcerative colitis (UC), a significant reduction in mRNA and protein expression for CEACAM1 and 5 was noted; in contrast, no difference in SOX9 mRNA expression was seen. However, nuclear SOX9 immunostaining was increased in CD IECs. Furthermore, SOX9 protein was reduced in the cytoplasm of LPL-stimulated T84 and HT29 16E cells, while CEACAM5 expression was increased.

CONCLUSIONS

The defect in CEACAM family members in CD IECs appears to be related to the aberrant nuclear localization of SOX9. Changes in SOX9 expression in the CD mucosa relate to the local microenvironment and altered IEC:LPL crosstalk.

Alterations of phospholipid concentration and species composition of the intestinal mucus barrier in ulcerative colitis: a clue to pathogenesis

BACKGROUND

Phospholipids are essential for the normal function of the intestinal mucus barrier. The objective of this study was to systematically investigate phospholipids in the intestinal mucus of humans suffering from inflammatory bowel diseases, where a barrier defect is strongly supposed to be pathogenetic.

METHODS

Optimal mucus recovery was first validated in healthy mice and the method was then transferred to the endoscopic acquisition of ileal and colonic mucus from 21 patients with ulcerative colitis (UC), 10 patients with Crohn's disease (CD), and 29 healthy controls. Nano-electrospray ionization tandem mass spectrometry (ESI-MS/MS) was used to determine phosphatidylcholine (PC), lysophosphatidylcholine (LPC), and sphingomyelin (SM) in lipid extracts of mucus specimens.

RESULTS

Human and rodent mucus contained very similar phospholipid species. In the ileal and colonic mucus from patients suffering from UC, the concentration of PC was highly significantly lower (607 +/- 147 pmol/100 microg protein and 745 +/- 148 pmol/100 microg protein) compared to that of patients with CD (3223 +/- 1519 pmol/100 microg protein and 2450 +/- 431 pmol/100 microg protein) and to controls (3870 +/- 760 pmol/100 microg protein and 2790 +/- 354 pmol/100 microg protein); overall, P = 0.0002 for ileal specimens and P < 0.0001 for colonic specimens. Independent of disease activity, patients suffering from UC showed an increased saturation grade of PC fatty acid residues and a higher LPC-to-PC ratio.

CONCLUSIONS

The intestinal mucus barrier of patients with UC is significantly altered concerning its phospholipid concentration and species composition. These alterations may be very important for the pathogenesis of this disease and underline new therapeutic strategies.

Intestinal epithelial cell proteome from wild-type and TNFDeltaARE/WT mice: effect of iron on the development of chronic ileitis

Environmental factors substantially contribute to the development of chronic intestinal inflammation in the genetically susceptible host. Nutritional components like iron may act as pro-oxidative mediators affecting inflammatory processes and cell stress mechanisms. To better characterize effects of dietary iron on epithelial cell responses under the pathological conditions of chronic intestinal inflammation, we characterized the protein expression profile (proteome) in primary intestinal epithelial cells (IEC) from iron-adequate and low-iron fed wild-type (WT) and TNFDeltaARE/WT mice. We performed all possible comparisons between the 4 groups according to genotype or diet. Histological analysis of iron-adequate fed TNFDeltaARE/WT mice (approximately 0.54 mg of iron/day) revealed severe ileal inflammation with a histopathology score of 8.3+/-0.91 (score range from 0-12). Interestingly, low-iron fed mice (approximately 0.03 mg of iron/day) were almost completely protected from the development of inflammatory tissue destruction (histopathology score of 2.30+/-0.73). In total, we identified 74 target proteins with significantly altered steady state expression levels in primary IEC using 2D-gel electrophoresis (2D SDS-PAGE) and peptide mass fingerprinting via MALDI-TOF mass spectrometry (MS). Interestingly, the overlap between the comparison of iron-adequate fed WT and TNFDeltaARE/WT mice (inflamed conditions) and the comparison between the iron-adequate and iron-low fed TNFDeltaARE/WT mice (absence of inflammation) revealed 4 contrarily regulated proteins including aconitase 2, catalase, intelectin 1 and fumarylacetoacetate hydrolase (FAH). These proteins are associated with energy homeostasis, host defense, oxidative and endoplasmic reticulum (ER) stress responses. In conclusion, the iron-low diet affected the epithelial cell proteome and inhibited the development of chronic intestinal inflammation, suggesting a critical role for nutritional factors in the pathogenesis of IBD.

Multivesicular bodies in intestinal epithelial cells: responsible for MHC class II-restricted antigen processing and origin of exosomes

In normal conditions intestinal epithelial cells (IECs) constitutively stimulate regulatory CD4(+) T cells. However, in Crohn's disease (CD), this major histocompatibility complex (MHC) class II-restricted antigen presentation results in stimulation of proinflammatory CD4(+) T cells. We hypothesized that these alternative functions might be mediated by differential sorting and processing of antigens into distinct MHC II-enriched compartments (MIICs). Accordingly, we analysed the endocytic pathways of lumenally applied ovalbumin (OVA) in IECs of the jejunum and ileum of wild-type (WT) and TNFDeltaARE/WT mice that develop a CD-resembling ileitis. Using quantitative reverse transcription polymerase chain reaction, we found that messenger RNA levels of interferon-gamma, tumour necrosis factor-alpha, interleukin-17 and interleukin-10 were significantly up-regulated in the inflamed ileum of TNFDeltaARE/WT mice, confirming CD-like inflammation. Fluorescence and immunoelectron microscopy revealed the presence of MHC II and invariant chain throughout the late endocytic compartments, with most molecules concentrated in the multivesicular bodies (MVB). OVA was targeted into MVB and, in contrast to other MIICs, accumulated in these structures within 120 min of exposure. The IEC-specific A33 antigen localized to internal vesicles of MVB and A33/class II-bearing exosomes were identified in intercellular spaces. Remarkably, the expression pattern of MHC II/invariant chain molecules and the trafficking of OVA were independent of mucosal inflammation and the specific region in the small intestine. MVB seem to be principally responsible for class II-associated antigen processing in IECs and to constitute the origin of MHC II-loaded exosomes. The distinctive functions of IECs in antigen presentation to CD4(+) T cells might arise as a result of differential processing within the MVB identified here.

Generation and function of human regulatory CD8+ T cells induced by a humanized OKT3 monoclonal antibody hOKT3gamma1 (Ala-Ala)

Recent studies with a humanized anti-CD3 antibody in clinical trials suggested that this drug can induce regulatory CD8+ T cells. In this review, we discuss how these regulatory human CD8+ cells can be generated and the possible molecular tools they may use to inhibit immune responses. We compare our data on CD8+ regulatory cells induced by anti-CD3 stimulation with those reported in other experimental systems to identify both common and unique features of these cells.

Current view of the immunopathogenesis in inflammatory bowel disease and its implications for therapy

Although the aetiology of inflammatory bowel disease (IBD) remains unknown, the pathogenesis is gradually being unravelled, seeming to be the result of a combination of environmental, genetic, and immunological factors in which an uncontrolled immune response within the intestinal lumen leads to inflammation in genetically predisposed individuals. Multifactorial evidence suggests that a defect of innate immune response to microbial agents is involved in IBD. This editorial outlines the immunopathogenesis of IBD and their current and future therapy. We present IBD as a result of dysregulated mucosal response in the intestinal wall facilitated by defects in epithelial barrier function and the mucosal immune system with excessive production of cytokines growth factors, adhesion molecules, and reactive oxygen metabolites, resulting in tissue injury. Established and evolving therapies are discussed in the second part of this editorial and at the end of this section we review new therapies to modulate the immune system in patients with IBD.

Increased basolateral sorting of carcinoembryonic antigen in a polarized colon carcinoma cell line after cholesterol depletion-Implications for treatment of inflammatory bowel disease

AIM: To investigate a possible increase of basolateral expression of carcinoembryonic antigen (CEA) by interfering with the apical transport machinery, we studied the effect of cholesterol depletion on CEA sorting and secretion.

METHODS: Cholesterol depletion was performed in polarized Caco-2 cells using lovastatin and methyl-β-cyclodextrin.

RESULTS: We show that CEA is predominantly expressed and secreted at the apical surface. Reduction of the cholesterol level of the cell by 40%-50% with lovastatin and methyl-β-cyclodextrin led to a significant change of the apical-to-basolateral transport ratio towards the basolateral membrane.

CONCLUSION: As basolateral expression of CEA has been suggested to have anti-inflammatory properties, Cholesterol depletion of enterocytes might be a potential approach to influence the course of inflammatory bowel disease.

Luminal antigens access late endosomes of intestinal epithelial cells enriched in MHC I and MHC II molecules: in vivo study in Crohn's ileitis

In contrast to healthy conditions, intestinal epithelial cells (IECs) stimulate proinflammatory CD4+ and CD8+ T cells during Crohn's disease (CD). The underlying regulatory mechanisms remain unknown. Here we investigated the epithelial expression of major histocompatibility complex (MHC) I and MHC II and its interference with endocytic pathways, in vivo. During ileoscopy, ovalbumin (OVA) was sprayed onto ileal mucosa of CD patients (ileitis and remission) and controls. The epithelial traffic of OVA and MHC I/II pathways were studied in biopsies using fluorescence and electron microscopy. We found MHC I and MHC II to accumulate within multivesicular late endosomes (MVLE) of IECs. Faint labeling for these molecules was seen in early endosomes and lysosomes. MVLE were entered by OVA 10 min after exposure. Exosomes carrying MHC I, MHC II, and OVA were detected in intercellular spaces of the epithelium. OVA trafficking and labeling patterns for MHC I and MHC II in IECs showed no differences between CD patients and controls. Independent of inflammatory stimuli, MHC I and MHC II pathways intersect MVLE in IECs, which were efficiently targeted by luminal antigens. Similar to MHC II-enriched compartments in professional antigen presenting cells, these MVLE might be critically involved in MHC I- and MHC II-related antigen processing in IECs and the source of epithelial-released exosomes. The access of luminal antigens to MHC I in MVLE might indicate that the presentation of exogenous antigens by IECs must not be restricted to MHC II but might also occur as "cross-presentation" via MHC I to CD8+ T cells.

Crucial role of the protein C pathway in governing microvascular inflammation in inflammatory bowel disease

Endothelial protein C receptor (EPCR) and thrombomodulin (TM) are expressed at high levels in the resting microvasculature and convert protein C (PC) into its activated form, which is a potent anticoagulant and antiinflammatory molecule. Here we provide evidence that in Crohn disease (CD) and ulcerative colitis (UC), the 2 major forms of inflammatory bowel disease (IBD), there was loss of expression of endothelial EPCR and TM, which in turns caused impairment of PC activation by the inflamed mucosal microvasculature. In isolated human intestinal endothelial cells, administration of recombinant activated PC had a potent antiinflammatory effect, as demonstrated by downregulated cytokine-dependent cell adhesion molecule expression and chemokine production as well as inhibited leukocyte adhesion. In vivo, administration of activated PC was therapeutically effective in ameliorating experimental colitis as evidenced by reduced weight loss, disease activity index, and histological colitis scores as well as inhibited leukocyte adhesion to the inflamed intestinal vessels. The results suggest that the PC pathway represents a new system crucially involved in governing intestinal homeostasis mediated by the mucosal microvasculature. Restoring the PC pathway may represent a new therapeutic approach to suppress intestinal inflammation in IBD.

Intestinal epithelial cell signalling and chronic inflammation: From the proteome to specific molecular mechanisms

Advancing knowledge regarding the cellular mechanisms of intestinal inflammation has led to a better understanding of the disease pathology in patients with inflammatory bowel disease (IBD) including Crohn's disease and ulcerative colitis. It has become clear from numerous studies that enteric bacteria are a critical component in the development and prevention/treatment of chronic intestinal inflammation. An emerging new paradigm suggests that changes in the homeostasis of bacteria- and host-derived signal transduction at the intestinal epithelial cell (IEC) level may lead to a break in barrier function and the development of adaptive immune disturbances. The functional loss of anti-inflammatory host-derived signals in the gut including the immunosuppressive cytokines Interleukin 10 (IL-10) and transforming growth factor (TGF)-beta are of high relevance to the pathogenesis of IBD. The development of analytical tools including two-dimensional (2D) high-resolution protein separation techniques and peptide mass fingerprinting via high-sensitivity mass-spectrometers (MS) allows the quantitative assessment of protein expression changes in disease-relevant cell types. By using these advanced methods, the characterization of the epithelial cell proteome from murine models of experimental colitis and human IBD patients identified novel disease-related mechanisms with respect to the regulation of the glucose-regulated endoplasmic reticulum stress response protein 78 (grp-78). In conclusion, the identification and functional analysis of differentially expressed proteins in purified intestinal target cell types will help to add important insights to the understanding of the molecular pathogenesis of these immune-mediated chronic intestinal disorders.

Intestinal epithelial cells from inflammatory bowel disease patients preferentially stimulate CD4+ T cells to proliferate and secrete interferon-gamma

Previous studies have suggested that intestinal epithelial cells (IECs) have the capacity to function as nonprofessional antigen presenting cells that in the normal state preferentially activate CD8+ T cells. However, under pathological conditions, such as those found in inflammatory bowel disease (IBD), persistent activation of CD4+ T cells is seen. The aim of this study was to determine whether the IBD IECs contribute to CD4+ T cell activation. Freshly isolated human IECs were obtained from surgical specimens of patients with or without IBD and cocultured with autologous or allogeneic peripheral blood T lymphocytes. Cocultures of normal T cells and IECs derived from IBD patients resulted in the preferential activation of CD4+ T cell proliferation that was associated with significant IFN-gamma, but not IL-2, secretion. Cytokine secretion and CD4+ T cell proliferation was inhibited by pretreatment of the IBD IECs with the anti-DR MAb L243. In contrast, normal IECs stimulated the proliferation and cytokine secretion by CD4+ T cells to a significantly lesser degree than IBD IECs. Furthermore, blockade of human leukocyte antigen-DR had a lesser effect in the normal IEC-CD4+ T cell cocultures. We conclude that IECs can contribute to the ongoing CD4+ T cell activation seen in IBD. We suggest that the apparent differences between the secreted levels of IFN-gamma indicate that it may play a dual role in intestinal homeostasis, in which low levels contribute to physiological inflammation whereas higher levels are associated with an uncontrolled inflammatory state.

Expression of nonclassical class I molecules by intestinal epithelial cells

It is well recognized that the nature of the immune response is different in the intestinal tract than in peripheral lymphoid organs. The immunologic tone of the gut-associated lymphoid tissue is one of suppression rather than active immunity, distinguishing pathogens from normal flora. Failure to control mucosal immune responses may lead to inflammatory diseases such as Crohn's disease (CD) and ulcerative colitis (UC) and celiac disease. It has been suggested that this normally immunosuppressed state may relate to unique antigen-presenting cells and unique T-cell populations. The intestinal epithelial cell (IEC) has been proposed to act as a nonprofessional antigen-presenting cell (APC). Previous studies have suggested that antigens presented by IECs result in the activation a CD8(+) regulatory T-cell subset in a nonclassical MHC I molecule restricted manner. We therefore analyzed the expression of nonclassical MHC I molecules by normal IECs and compared this to those expressed by inflammatory bowel disease (IBD) IECs. Normal surface IEC from the colon and, to a much lesser extent, the small bowel express nonclassical MHC I molecules on their surface. In contrast, mRNA is expressed in all intestinal epithelial cells. Surface IEC express CD1d, MICA/B, and HLA-E protein. In contrast, crypt IECs express less or no nonclassical MHC I molecules but do express mRNA for these molecules. Furthermore, the regulation of expression of distinct nonclassical class I molecules is different depending on the molecule analyzed. Interestingly, IECs derived from patients with UC fail to express any nonclassical MHC I molecules (protein and HLA-E mRNA). IECs from CD patients express HLA-E and MICA/B comparable to that seen in normal controls but fail to express CD1d. Thus, in UC there may be a failure to activate any nonclassical MHC I molecule restricted regulatory T cells that may result in unopposed active inflammatory responses. In CD only the CD1d-regulated T cells would be affected.

Recent understanding of IBD pathogenesis: implications for future therapies

The inflammatory bowel diseases (IBD) are comprised of two major phenotypes, Crohn's disease (CD) and ulcerative colitis (UC). Research over the last couple of years has led to great advances in understanding the inflammatory bowel diseases and their underlying pathophysiologic mechanisms. From the current understanding, it is likely that chronic inflammation in IBD is due to aggressive cellular immune responses to a subset of luminal bacteria. Susceptibility to disease is thereby determined by genes encoding immune responses which are triggered by environmental stimuli. Based on extensive research over the last decade, there are several new and novel pathways and specific targets on which to focus new therapeutics. The following review summarizes the current view on the four basic tenets of the pathophysiological basis of IBD and its implications for therapies of IBD: genetics, immune dysregulation, barrier dysfunction and the role of the microbial flora.

Expression profile and clonality of T-cell receptor beta variable genes in normal human endometrium

PROBLEM

In spite of their key immunological role, alphabeta+ T cells residing in endometrium have not been extensively explored. We analyzed here expression profile of TCRBV genes in normal human endometrium compared with peripheral blood.

METHODS

Samples were taken from normal reproductive women. RT-PCR using BV-gene specific primers was performed on blood and endometrial samples. After blotting, hybridization with radiolabelled probe and autoradiography, relative expression of each TCRBV family was determined. Clonal expansions of the over-expressed genes were assessed by CDR3 length polymorphism.

RESULTS

Only one gene (TCRBV7) was expressed significantly and two other genes marginally more in the endometrium compared with blood. All three TCRBV genes examined showed a rather restricted pattern in the endometrium in contrast to polyclonal patterns in the blood.

CONCLUSION

Our results stress the similarities between T cells residing in different mucosal tissues and provide a basis for future investigations about endometrial T cells and their antigen specificities in gynecological problems.

Intestinal epithelial cell signalling and host-derived negative regulators under chronic inflammation: to be or not to be activated determines the balance towards commensal bacteria

Advancing knowledge regarding the cellular mechanisms of intestinal inflammation has led to a better understanding of the disease pathology in patients with chronic disorders of the gut including inflammatory bowel disease, coeliac disease, lymphocytic colitis and irritable bowel syndrome. An emerging new paradigm suggests that changes in the homeostasis of bacteria- and host-derived signal transduction at the epithelial cell level may lead to functional and immune disturbances of the intestinal epithelium. It has become clear from numerous studies that enteric bacteria are a critical component in the development and prevention/treatment of chronic intestinal inflammation. Signal-specific activation of mitogen-activated protein kinases (MAPK), interferon-regulated factors (IRF) and the transcription factor NF-kappaB through pattern recognition receptor signalling effectively induce inflammatory defence mechanisms. Unbalanced activation of these innate signalling pathways because of host genetic predispositions and/or the lack of adequate anti-inflammatory feedback mechanisms may turn a physiological response into a pathological situation including failure of bacterial clearance and development of chronic inflammation. Host-derived regulators from the immune and enteric nerve system crosstalk to the innate signalling network of the intestinal epithelium in order to shape the extent and duration of inflammatory processes.

Antigen targeting to MHC class II-enriched late endosomes in colonic epithelial cells: trafficking of luminal antigens studied in vivo in Crohn's colitis patients

In Crohn's disease (CD), colonic epithelial cells (CECs) are suggested to stimulate pro-inflammatory CD4+ T cells. However, the endocytic pathways of luminal antigens involved in underlying MHC class II presentation by CECs remain unknown. Our aim was to elucidate antigen trafficking and associated MHC class II expression in CECs of CD patients in vivo. In CD patients (Crohn's colitis and remission) and healthy controls undergoing colonoscopy, ovalbumin (OVA) was sprayed onto inflamed or healthy mucosa. The subcellular localization of OVA and MHC class II was visualized in biopsies taken from OVA-incubated mucosa using fluorescence and cryoelectron microscopy. Targeting of OVA into late endosomes of CECs was found in healthy (controls and CD in remission) and inflamed mucosa (Crohn's colitis). MHC class II expression in CECs was not detected in healthy mucosa but strongly up-regulated during CD inflammation. Induced MHC class II in CECs was predominantly seen at basolateral membranes and in late endosomes, which were efficiently accessed by internalized OVA. Our data provide in vivo evidence that the endocytic pathway of luminal antigens in CECs of Crohn's colitis patients intersects MHC class II-enriched late endosomes and support the postulated role of CECs in MHC class II-associated antigen presentation during CD.

Oral tolerance and inflammatory bowel disease

PURPOSE OF REVIEW

Oral tolerance refers to the ability of the mucosal immune system to actively inhibit systemic immune responses to fed antigens. Recently, clinical trials have used oral tolerance as a therapy for certain chronic inflammatory and autoimmune diseases such as multiple sclerosis and type I diabetes. Inflammatory bowel disease is now widely thought to be caused by the breakdown of oral tolerance through a combination of genetic and environmental factors. Therefore, it seems incongruous that clinicians would try to use oral tolerance therapy to alleviate the symptoms of inflammatory bowel disease. Yet, armed with the results of select animal models, trials have begun for oral tolerance therapy for Crohn's disease. This review will outline the recent advances in understanding oral tolerance, explore the relation between oral tolerance and inflammatory bowel disease, and comment on the likelihood of successful oral tolerance therapy for inflammatory bowel disease.

RECENT FINDINGS

The results of an oral tolerance trial in Crohn's disease patients in Israel have shown some promising results, whereas the results of studies of experimentally induced oral tolerance in patients with inflammatory bowel disease from the authors' laboratory have shown that feeding a neoantigen in an attempt to induce oral tolerance is not successful in patients with inflammatory bowel disease.

SUMMARY

The fundamental difference in the mechanisms of oral tolerance in mice and humans requires a more focused effort to understand the human mucosal immune system before oral tolerance therapy for autoimmune and chronic inflammatory disorders reaches its full potential.

Activation of CD8+ regulatory T cells by human placental trophoblasts

The immunological basis by which a mother tolerates her semi-allogeneic fetus remains poorly understood. Several mechanisms are likely to contribute to this phenomenon including active immune regulation by regulatory T cells. In this article, we report that human placental trophoblasts activate a clonal population of CD8(+) T cells with regulatory function. These cells are not MHC class I restricted, but require costimulation through a member of the carcinoembryonic Ag family present on early gestation trophoblasts. These regulatory T cells express the mucosal markers CD101 and CD103 and display selective usage of the TCR gene Vbeta9. CD8(+) T cells isolated from the peripheral blood of pregnant mothers (16-28 wk) also demonstrate expansions in the same Vbeta family (Vbeta9), signaling a possible role for these cells in preventing fetal rejection in vivo. We have previously characterized a subset of CD8(+) regulatory T cells activated by the combination of the nonclassical class I molecule CD1d and a costimulatory molecule of the carcinoembryonic Ag family present on the intestinal epithelium. These data support the concept that distinct regulatory T cell populations exist at different sites and may be regulated locally by unique restriction elements, costimulatory signals, and Ags.

Non-classical MHC class I molecules on intestinal epithelial cells: mediators of mucosal crosstalk

The mucosal immune environment consists of a complex combination of lymphoid cells, non-lymphoid cells, and lumenal bacteria. Signals from lumenal bacteria are constantly transmitted to the underlying tissues across the intestinal epithelial barrier. Intestinal epithelial cells (IECs) can sense these signals, integrate them, and interpret them for lamina propria lymphoid populations. One mechanism by which these signals are communicated is by the expression of non-classical major histocompatibility complex (MHC) class I molecules by IECs. Epithelial cells can express a surprising variety of non-classical MHC class I molecules. In some cases, IECs can act as non-professional antigen-presenting cells utilizing the expression of such non-classical MHC class I molecules to directly present bacterial antigens. In other cases, the expression of non-classical MHC class I molecules may act as a co-stimulatory molecule or adhesion molecule that can modify the mucosal immune response. Finally, the expression of these molecules on IECs can lead to a broad array of responses ranging from tolerance to inflammation. Overall, the IEC, via the expression of non-classical MHC class I molecules, is a central mediator of the constant crosstalk between the intestinal lumen and the mucosal immune system.

Defects in CD8+ regulatory T cells in the lamina propria of patients with inflammatory bowel disease

Mucosal tolerance is believed to be partly mediated by regulatory T cells. Intestinal epithelial cells (IECs) may play an important role in the generation of such regulatory cells, because they are able to process and present Ag to T cells. Furthermore, we have previously demonstrated that IECs are able to generate regulatory CD8(+) T cells in vitro. In the present study, we have analyzed lamina propria (LP) lymphocytes for the presence of such regulatory CD8(+) T cells in normal individuals as well as in patients with inflammatory bowel disease (IBD). The results of the present study show that LP CD8(+) T cells derived from normal controls possess regulatory activity, whereas both unfractionated LP lymphocytes and purified LP CD4(+) T cells do not. The LP CD8(+) T cells suppress Ig production by pokeweed mitogen-stimulated PBMCs by 31-80%, in a cell contact-dependent manner. No significant difference in suppression between CD28(+) and CD28(-)CD8(+) LP T cells was observed. In contrast to CD8(+) T cells from normal LP, CD8(+) T cells isolated from LP of IBD patients, did not suppress Ig production by pokeweed mitogen-stimulated PBMC (five of six ulcerative colitis specimens; six of six Crohn's disease specimens). Furthermore, we demonstrate that the frequency of TCR Vbeta5.1-positive CD8(+) T cells, which we previously have demonstrated to be regulatory and to be expanded by IECs in vitro, is decreased in IBD LP compared with normal LP. In conclusion, this study demonstrates that CD8(+) T cells with regulatory activity are present in the LP of normal healthy individuals, but not in patients with IBD, suggesting that these cells might play an active role in mucosal tolerance.

Failure to induce oral tolerance in Crohn's and ulcerative colitis patients: possible genetic risk

It has been proposed that defective activation of suppressor or regulatory T cells is one mechanism involved in the uncontrolled inflammatory process seen in inflammatory bowel disease (IBD). Because suppressor/regulatory T cells are thought to play a role in the promotion of oral tolerance, we attempted to induce oral tolerance in normal controls (n = 21) and patients with either Crohn's disease (CD; n = 12) or ulcerative colitis (UC; n = 13). In the first study, subjects were fed the neoantigen keyhole limpet hemocyanin (KLH) on days 1 to 5 and 11 to 15. Subcutaneous immunization with KLH was performed on day 26, with a booster immunization on day 35. Blood for KLH-induced T cell proliferation and serum for anti-KLH antibody production was obtained at baseline, on day 26 preimmunization (postfed), on day 35 after the first immunization, and again on day 42 after the second immunization. In normal individuals, KLH feeding prior to immunization and booster resulted in reduced KLH-specific T cell proliferation compared with the group that was not fed KLH. However, although on the same KLH-feeding protocol, both CD and UC patients demonstrated significantly enhanced proliferation without oral tolerance induction when compared with baseline values. These data suggest that oral tolerance induction is defective in patients with IBD. This may reflect an in vivo functional defect in mucosal suppression of immune responses in IBD. Both UC and CD appear to be multigenic disorders with evidence of familial segregation. We analyzed four multiplex Crohn's and two UC families to determine whether the defect in tolerance induction was genetically regulated. In three of the four CD families at least one unaffected family member also failed to tolerate (total 5 of 14 unaffected family members). In the UC families, the defect in tolerance segregated with disease. These data suggest a genetic defect in tolerance induction in Crohn's disease.

Keratin-8-deficient mice develop chronic spontaneous Th2 colitis amenable to antibiotic treatment

Keratin 8 (K8) is the major intermediate filament protein present in intestinal epithelia. Depending on the mouse genetic background, absence of K8 causes embryonic lethality or colonic hyperplasia and colitis. We studied disease progression, the inflammatory responses, and role of luminal bacteria in K8-null mice in order to characterize the intestinal pathology of K8-associated colitis. Colon lymphocytes were isolated for analysis of their phenotype and cytokine production, and vascular and lymphocyte adhesion molecule expression in K8-/- mice of varying ages. K8-/- mice had a marked increase in TCR(beta)-positive/CD4-positive T cells infiltrating the colon lamina propria, in association with enhanced Th2 cytokine (IL-4, IL-5 and IL-13) production. K8-/- mice show early signs of inflammation even prior to weaning, that increases with age, and their epithelial cells overexpress MHC class II antigens. The chronic colitis is related to increased CD4-positive infiltrating T cells displaying memory and naive phenotypes, and an altered vascular endothelium with aberrant expression of peripheral node addressin. Analysis of normal gut-specific homing molecules, reveals an increased number of alpha(4)beta(7)-positive cells and vascular mucosal addressin cell adhesion molecule-1 in K8-null colons. Antibiotic treatment markedly decreased colon inflammation and ion transporter AE1/2 mistargeting, indicating that luminal bacteria play an important role in the observed phenotype. Therefore, K8-null mice develop chronic spontaneous Th2-type colitis due to a primary epithelial rather than immune cell defect, which is amenable to antibiotic therapy. These mice provide a model to investigate epithelial-leukocyte and epithelial-microbial cross-talk.

Activation of a Unique Population of CD8+T Cells by Intestinal Epithelial Cells

Intestinal epithelial cells may play a role in the regulation of immune responses toward luminal antigens. We show that a subset of CD8(+) T cells undergoes oligoclonal expansion in the intestinal mucosa, probably through interaction with a unique complex expressed on epithelial cells, formed by a CEA subfamily member (gp180) and CD1d. This subset, which is regulatory in vitro, may play a role in the control of intestinal immune responses toward luminal antigens. A lack of expansion of these CD8(+) regulatory T cells, probably related to the defective expression of the gp180/CD1d complex, is observed in inflammatory bowel disease.

Regulatory T cells: peace keepers in the gut

The mucosa-associated lymphoid tissue (MALT) has the task of protecting the host from pathogens while maintaining the integrity of the gut. Immune responses are tightly regulated such that there is tolerance of nonpathogenic bacteria as well as dietary antigens present in the intestinal lumen. The failure to control these responses leads to a disruption in tolerance, which has been proposed as one mechanism involved in the development of inflammatory bowel disease (IBD). Different mechanisms are involved in the control of immune responses in the intestinal tract, including active suppression by regulatory T cells. Distinct subsets of regulatory T cells coexist in the intestinal mucosa, which is a fertile environment for their growth. Most of these are defined by their phenotype and/or their ability to produce regulatory cytokines such as interleukin-10 and transforming growth factor-beta A lack of activation and/or expansion of regulatory cells could play a role in the uncontrolled inflammation seen in IBD. Regulatory T cells may be activated by cytokines, and their inductive phase may be antigen-driven. There are limited data relating to the true surface interactions regulating the activation of these cells. Most of the CD4 regulatory T cells (Tr1, Th3, and CD4 CD25+) are thought to interact with dendritic cells. Subsets of regulatory T cells (such as CD8 TrE cells) may recognize antigens presented by intestinal epithelial cells. A better understanding of the mechanisms by which these regulatory T cells are expanded and/or activated in the intestinal mucosa may provide clues as how to use them as a novel therapeutic tool in the treatment of patients with IBD.

The expression and function of costimulatory molecules B7H and B7-H1 on colonic epithelial cells

BACKGROUND & AIMS

Previous studies have suggested that intestinal epithelial cells (IECs) may function as antigen-presenting cells for CD4+ and CD8+ T cells. However, these cells fail to express conventional costimulatory molecules (CD80, CD86), leading to the possibility that antigen presented by normal IECs could result in anergy. Other members of the B7 family have recently been identified. B7h interacts with inducible costimulator (ICOS) on T cells and provides a positive signal, whereas B7-H1 and B7-DC interact with PD-1 and transmit an inhibitory signal. Our aim was to determine whether IECs express novel B7 family members and whether these molecules play a role in IEC:T-cell interactions.

METHODS

B7h and B7-H1 expression was assessed in isolated IECs and IEC lines. The functional role of B7h and B7-H1 in the interaction between IECs and T cells was assessed in coculture experiments using purified anti-B7h or B7-H1 monoclonal antibodies (mAbs), B7h immunoglobulin (Ig), or B7-H1 fusion proteins.

RESULTS

B7h and B7-H1 messenger RNA was detected in IEC lines and IECs from healthy controls and patients with inflammatory bowel disease (IBD). IECs from patients with IBD but not healthy controls expressed B7h and B7-H1 protein on their surface. Proliferation of IEC-stimulated T cells was inhibited only by B7h immunoglobulin treatment, whereas interferon gamma secretion in these cocultures was inhibited by both anti-B7h mAb and B7h Ig. No difference was seen between IBD or normal IEC populations.

CONCLUSIONS

These data suggest that the B7h-ICOS costimulatory pathway may be important in IEC:T-cell interactions.

Inflammatory bowel disease-associated gene expression in intestinal epithelial cells by differential cDNA screening and mRNA display

Intestinal epithelial cells are actively involved in the pathogenesis of inflammatory bowel disease resulting in an altered functional phenotype. The modulation of epithelial gene expression may occur as a consequence of proliferative, metabolic, immune, inflammatory, or genetic abnormalities. Differential screening of epithelial-cell-derived cDNA libraries (from control, ulcerative colitis, and Crohn's disease epithelial cells) and differential display of mRNA were used for investigation of disease-associated gene expression and modulation. Intestinal epithelial gene expression was successfully analyzed by both approaches. Using differential screening with clones encoding mitochondrial genes, quantitative overexpression was observed in both ulcerative colitis and Crohn's disease, while a unique expression of small RNA was noticed in Crohn's disease cells using Alu-homologous clones. Differential display demonstrated that several genes were differentially displayed among control, ulcerative colitis, and Crohn's disease epithelial cells. This was confirmed by immunohistochemical staining of pleckstrin, desmoglein 2 and voltage-dependent anion channel in control and inflammatory bowel disease mucosal samples. In summary, several inflammatory bowel disease-related associations were found. Since both differential screening and display have advantages and limitations, the combination of both techniques can generate complementary information, facilitate search for novel genes, and potentially identify genes uniquely associated with inflammatory bowel disease.

The immunological and genetic basis of inflammatory bowel disease

The inflammatory bowel diseases (IBDs), Crohn's disease and ulcerative colitis, are chronic inflammatory disorders of the gastrointestinal tract. Enormous progress has been made recently in understanding the pathogenesis of these diseases. Through the study of patients and mouse models, it has emerged that Crohn's disease is driven by the production of interleukin-12 (IL-12) and interferon-gamma (IFN-gamma), whereas ulcerative colitis is probably driven by the production of IL-13. A second area of progress is in the identification of specific genetic abnormalities that are responsible for disease. The most important finding is the identification of mutations in the gene that encodes NOD2 (nucleotide-binding oligomerization domain 2) protein in a subgroup of patients with Crohn's disease. Here, we discuss these recent findings and the implications for therapy.

Colonic epithelial functional phenotype varies with type and phase of experimental colitis

BACKGROUND & AIMS

Colonic crypt elongation occurs during both chronic colitis and in the recovery phase of acute colitis. The impact of these alterations on epithelial cell functions is not fully defined.

METHODS

DNA microarray analysis of freshly isolated colonic epithelial cells (CECs) from acute and chronic colitis was performed, and the results were confirmed by reverse transcription polymerase chain reaction. Localization of the selected molecules was examined by immunohistochemistry using newly generated antibodies. The function of selected molecules detected in this study was examined by administering the specific inhibitors in dextran sodium sulfate (DSS) colitis.

RESULTS

Several detoxification-associated molecules, which contribute to prevent inflammation by regulating physiological balance under normal conditions, were markedly down-regulated, and anti-inflammatory molecules, which are not normally expressed, were up-regulated in the CEC under the chronic colitis. Among the detoxification-associated molecules, carbonic anhydrase IV was specifically down-regulated in CEC of Th2- but not Th1-mediated colitis. Functionally, inhibition of carbonic anhydrase activity led to the enhancement of recovery from DSS-induced acute colitis by directly stimulating CEC proliferation. Increased expression of regeneration-associated molecules such as regenerating gene-III gamma was detectable in the CEC of acute and chronic colitis but not in the recovery phase of colitis. The expression of this molecule was restricted in surface epithelium and upper crypts but not lower crypts.

CONCLUSIONS

These studies suggest that functional alterations, which result in either the exacerbation or the suppression of colitis, coexist in the CEC during chronic colitis. CEC functions are likely to be differentially regulated in the context of the stage and mechanism of colitis.

Card15 gene overexpression in mononuclear and epithelial cells of the inflamed Crohn's disease colon

BACKGROUND

Crohn's disease is one of the principal human chronic inflammatory bowel diseases. Although its aetiology is still unknown, its complex pathogenesis has environmental, immunological, and genetic determinants. CARD15 is the first susceptibility gene implicated in the predisposition to Crohn's disease and is known to be expressed only in monocytes. However, its expression in situ has not yet been studied.

AIMS

To analyse the tissue distribution of CARD15 and identify cells producing CARD15 in samples of colon from patients with Crohn's disease and control subjects.

PATIENTS AND METHODS

We analysed CARD15 gene expression in surgical specimens of colon from eight children with Crohn's disease and nine controls by immunohistochemistry, in situ hybridisation, and reverse transcription-polymerase chain reaction (RT-PCR).

RESULTS

We showed that CARD15 was present only in the cytoplasm of macrophages in the normal colon. Increased CARD15 expression was detected in Crohn's disease lesions. There were more CARD15 positive cells in Crohn's disease lesions than in uninvolved areas. Both intestinal epithelial cells, macrophages, and their derivatives overproduced CARD15 in Crohn's disease. To further assess CARD15 expression by intestinal epithelial cells, we performed RT-PCR on freshly isolated intestinal epithelial cells, and showed that these cells isolated from Crohn's disease samples contained more CARD15 mRNA than intestinal epithelial cells from controls.

CONCLUSIONS

We have demonstrated that colonic involvement in active Crohn's disease is associated with increased CARD15 gene expression in both macrophages and intestinal epithelial cells. Therefore, this deregulation can affect the host-environment interaction and thus contribute to the pathogenesis of this disease.

Impaired expression of peroxisome proliferator-activated receptor gamma in ulcerative colitis

BACKGROUND & AIMS

The peroxisome proliferator-activated receptor gamma (PPAR gamma) has been proposed as a key inhibitor of colitis through attenuation of nuclear factor kappa B (NF-kappa B) activity. In inflammatory bowel disease, activators of NF-kappa B, including the bacterial receptor toll-like receptor (TLR)4, are elevated. We aimed to determine the role of bacteria and their signaling effects on PPAR gamma regulation during inflammatory bowel disease (IBD).

METHODS

TLR4-transfected Caco-2 cells, germ-free mice, and mice devoid of functional TLR4 (Lps(d)/Lps(d) mice) were assessed for their expression of PPAR gamma in colonic tissues in the presence or absence of bacteria. This nuclear receptor expression and the polymorphisms of gene also were assessed in patients with Crohn's disease (CD) and ulcerative colitis (UC), 2 inflammatory bowel diseases resulting from an abnormal immune response to bacterial antigens.

RESULTS

TLR4-transfected Caco-2 cells showed that the TLR4 signaling pathway elevated PPAR gamma expression and a PPAR gamma-dependent reporter in an I kappa kappa beta dependent fashion. Murine and human intestinal flora induced PPAR gamma expression in colonic epithelial cells of control mice. PPAR gamma expression was significantly higher in the colon of control compared with Lps(d)/Lps(d) mice. Although PPAR gamma levels appeared normal in patients with CD and controls, UC patients displayed a reduced expression of PPAR gamma confined to colonic epithelial cells, without any mutation in the PPAR gamma gene.

CONCLUSIONS

These data showed that the commensal intestinal flora affects the expression of PPAR gamma and that PPAR gamma expression is considerably impaired in patients with UC.

Delineation of a CD1d-restricted antigen presentation pathway associated with human and mouse intestinal epithelial cells

BACKGROUND & AIMS

CD1d, a major histocompatibility complex (MHC) class I-related molecule that is responsible for the presentation of glycolipid antigens to subsets of natural killer T (NK-T) cells, is expressed by intestinal epithelial cells (IECs). However, CD1d-restricted antigen presentation has not yet been examined on IECs.

METHODS

A mouse intestinal epithelial cell line (MODE-K), a human epithelial cell line (T84), T84 cells transfected with CD1d and/or MHC class II, and freshly isolated human IECs were examined for their ability to present model glycolipid antigens to NK-T cells as defined by interleukin (IL)-2 or IL-4 secretion.

RESULTS

MODE-K and freshly isolated human IECs exhibited dose-dependent, CD1d-restricted presentation of the functional glycolipid antigen, alpha-galactosylceramide (alpha GalCer), to the mouse NK-T cell hybridoma, DN32.D3. The human IEC line, T84, mainly presented alpha GalCer when transfected with human CD1d. Presentation of alpha GalCer by CD1d-transfected T84 cells (T84d) to DN32.D3 cells was greater along the basal surface in comparison with the apical surface. Induction of the MHC class II antigen presentation machinery by cotransfecting T84d with the MHC class I transactivator (CIITA) did not alter this polarity of presentation. Neither MODE-K nor T84 cells transfected with CD1d, CD1d plus CIITA, or CD1d plus HLA-DR were able to present glycolipid antigens requiring intracellular processing. The MODE-K cell line could also present alpha GalCer to primary mouse NK-T cells.

CONCLUSIONS

CD1d is expressed functionally on IECs with a polarity of presentation (basal > apical) predicting a role in presentation of mucosal glycolipid antigens to local CD1d-restricted T cells.

Expansion of CD8+ T cells with regulatory function after interaction with intestinal epithelial cells

BACKGROUND & AIMS

Regulatory T cells play a role in the control of immune responses in the intestinal mucosa and their absence may predispose to inflammatory bowel disease (IBD). We have previously shown that T cells activated by intestinal epithelial cells (IECs) are suppressive in function. Our goal was to characterize the phenotype and function of T cells proliferating after interaction with IECs.

METHODS

Irradiated human IECs, isolated from normal resection specimens, were cultured with carboxy fluorescein succinimidyl ester (CFSE) labeled T cells. Flow cytometric analysis of T cells was performed at days 5-10. CD8+ T cells proliferating in culture with IECs were sorted and added to suppressive assays.

RESULTS

The precursor frequency of T cells proliferating in response to IECs ranged from 0.3%-0.9%. Several subpopulations were shown to proliferate (CD8+CD28-/CD8+CD28+/CD4+CD25+), but one population (CD8+CD28-CD101+CD103+) appeared to be dependent on contact with the CD8 ligand gp180. After sorting, culture in the presence of interleukin (IL)-7 and IL-15 allowed for the generation of cell lines. IEC-activated CD8+ T cells, but not nonactivated CD8+ T cells, were suppressive in function. Suppression belonged to the CD101+CD103+ subset of IEC-activated CD8+ T cells and appeared to require cell contact. CD8+ lamina propria T cells also showed suppressive function, suggesting the presence of CD8+ regulatory T cells in the mucosa.

CONCLUSIONS

IECs are able to induce the proliferation of a small fraction of CD8+ peripheral T cells. The CD8+CD28- subset of IEC-activated CD8+ T cells, which express CD101 and CD103, interacts with IECs through gp180 and has regulatory function.

CD8+CD28- T cells: certainties and uncertainties of a prevalent human T-cell subset

Human peripheral blood CD8+ T cells comprise cells that are in different states of differentiation and under the control of complex homeostatic processes. In a number of situations ranging from chronic inflammatory conditions and infectious diseases to ageing, immunodeficiency, iron overload and heavy alcohol intake, major phenotypic changes, usually associated with an increase in CD8+ T cells lacking CD28 expression, take place. CD8+CD28- T cells are characterized by a low proliferative capacity to conventional stimulation in vitro and by morphological and functional features of activated/memory T cells. Although the nature of the signals that give origin to this T-cell subset is uncertain, growing evidence argues for the existence of an interplay between epithelial cells, molecules with the MHC-class I fold and CD8+ T cells. The possibility that the generation of CD8+CD28- T cells is the combination of TCR/CD3zeta- and regulatory factor-mediated signals as a result of the sensing of modifications of the internal environment is discussed.