Transforming growth factor-beta (TGF-beta) and tissue transglutaminase expression in the small intestine in children with coeliac disease

Microscopic Colitis and Celiac Disease: Sharing More than a Diagnostic Overlap

Microscopic colitis (MC) is an emergent group of chronic inflammatory diseases of the colon, and celiac disease (CD) is a chronic gluten-induced immune-mediated enteropathy affecting the small bowel. We performed a narrative review to provide an overview regarding the relationship between both disorders, analyzing the most recent studies published at the epidemiological, clinical and pathophysiological levels. In fact, MC and CD are concomitantly prevalent in approximately 6% of the cases, mainly in the subset of refractory patients. Thus, physicians should screen refractory patients with CD against MC and vice versa. Both disorders share more than a simple epidemiological association, being multifactorial diseases involving innate and adaptive immune responses to known or unknown luminal factors based on a rather common genetic ground. Moreover, autoimmunity is a shared characteristic between the patients with MC and those with CD, with autoimmunity in the latter being quite well-established. Furthermore, CD and MC share some common clinical symptoms and risk factors and overlap with other gastrointestinal diseases, but some differences exist between both disorders. More studies are therefore needed to better understand the complex mechanisms involving the common pathogenetic ground contributing to the CD and MC epidemiological association.

Novel Bacteroides Vulgatus strain protects against gluten-induced break of human celiac gut epithelial homeostasis: a pre-clinical proof-of-concept study

BACKGROUND AND AIMS

We have identified a decreased abundance of microbial species known to have a potential anti-inflammatory, protective effect in subjects that developed Celiac Disease (CeD) compared to those who did not. We aim to confirm the potential protective role of one of these species, namely Bacteroides vulgatus, and to mechanistically establish the effect of bacterial bioproducts on gluten-dependent changes on human gut epithelial functions.

METHODS

We identified, isolated, cultivated, and sequenced a unique novel strain (20220303-A2) of B. vulgatus found only in control subjects. Using a human gut organoid system developed from pre-celiac patients, we monitored epithelial phenotype and innate immune cytokines at baseline, after exposure to gliadin, or gliadin plus B. vulgatus cell free supernatant (CFS).

RESULTS

Following gliadin exposure, we observed increases in epithelial cell death, epithelial monolayer permeability, and secretion of pro-inflammatory cytokines. These effects were mitigated upon exposure to B. vulgatus 20220303-A2 CFS, which had matched phenotype gene product mutations. These protective effects were mediated by epigenetic reprogramming of the organoids treated with B. vulgatus CFS.

CONCLUSIONS

We identified a unique strain of B. vulgatus that may exert a beneficial role by protecting CeD epithelium against a gluten-induced break of epithelial tolerance through miRNA reprogramming.

IMPACT

Gut dysbiosis precedes the onset of celiac disease in genetically at-risk infants. This dysbiosis is characterized by the loss of protective bacterial strains in those children who will go on to develop celiac disease. The paper reports the mechanism by which one of these protective strains, B. vulgatus, ameliorates the gluten-induced break of gut epithelial homeostasis by epigenetically re-programming the target intestinal epithelium involving pathways controlling permeability, immune response, and cell turnover.

Role of Regulatory T Cells and Their Potential Therapeutic Applications in Celiac Disease

Celiac disease (CeD) is a T-cell-mediated immune disease, in which gluten-derived peptides activate lamina propria effector CD4+ T cells. While this effector T cell subset produces proinflammatory cytokines, which cause substantial tissue injury in vivo, additional subsets of T cells exist with regulatory functions (Treg). These subsets include CD4+ type 1 regulatory T cells (Tr1) and CD4+ CD25+ T cells expressing the master transcription factor forkhead box P3 (Foxp3) that may have important implications in disease pathogenesis. In this review, we provide an overview of the current knowledge about the effects of immunomodulating cytokines on CeD inflammatory status. Moreover, we outline the main Treg cell populations found in CeD and how their regulatory activity could be influenced by the intestinal microenvironment. Finally, we discuss the Treg therapeutic potential for the development of alternative strategies to the gluten-free diet (GFD).

High Frequency of Glucose-6-Phosphate Dehydrogenase Deficiency in Patients Diagnosed with Celiac Disease

Celiac disease (CD) is characterized by a proinflammatory state associated with the production of reactive oxygen species, i.e., a condition of oxidative stress. In this study, we tested the hypothesis that the inherited deficiency of glucose-6-phosphate dehydrogenase (G6PD), by causing impaired antioxidant defense, may increase the risk of CD.

METHODS

A retrospective monocentric case-control study was performed using the clinical records of 8338 outpatients (64.6% women) scheduled for upper endoscopy between 2002 and 2021 in Northern Sardinia. Overall, 627 were found to have CD (7.5%), and 1027 resulted to be G6PD-deficiency carriers (12.3%). Since randomization was impractical, the potential covariates imbalance between cases and controls was minimized using a 1:2 propensity-score-matched (PSM) analysis.

RESULTS

Overall, G6PD deficiency was associated with increased risk of CD (odds ratio (OR) 1.50; 95% confidence interval (CI) 1.19-1.90). The PSM procedure identified 1027 G6PD-deficient and 2054 normal patients. Logistic regression including the propensity score detected for G6PD deficiency an OR of 1.48 (95%CI 1.13-1.95; p = 0.004).

CONCLUSIONS

Our findings show that the enzyme defect was significantly and positively associated with CD, in line with the pro-oxidant impact of the enzyme defect observed in animal models and humans.

The gliadin p31-43 peptide: Inducer of multiple proinflammatory effects

Coeliac disease (CD) is the prototype of an inflammatory chronic disease induced by food. In this context, gliadin p31-43 peptide comes into the spotlight as an important player of the inflammatory/innate immune response to gliadin in CD. The p31-43 peptide is part of the p31-55 peptide from α-gliadins that remains undigested for a long time, and can be present in the small intestine after ingestion of a gluten-containing diet. Different biophysical methods and molecular dynamic simulations have shown that p31-43 spontaneously forms oligomeric nanostructures, whereas experimental approaches using in vitro assays, mouse models, and human duodenal tissues have shown that p31-43 is able to induce different forms of cellular stress by driving multiple inflammatory pathways. Increased proliferative activity of the epithelial cells in the crypts, enterocyte stress, activation of TG2, induction of Ca²⁺, IL-15, and NFκB signaling, inhibition of CFTR, alteration of vesicular trafficking, and activation of the inflammasome platform are some of the biological effects of p31-43, which, in the presence of appropriate genetic susceptibility and environmental factors, may act together to drive CD.

A Peptide from Kiwifruit Exerts Anti-Inflammatory Effects in Celiac Disease Mucosa

Objective: Celiac disease is an immune-mediated disease of the intestine triggered by gluten. Gluten elicits, in genetically susceptible individuals, cytokine responses that are then transmitted to the immunocompetent cells. Vegetables and fruit have anti-inflammatory and antioxidant properties with a protective effect on intestinal epithelium. Kiwifruit is known to have beneficial effects on the intestinal tissues, and it is the only plant food containing the peptide kissper, with anti-inflammatory properties. The aim of this study was the evaluation of the kissper effect on the gluten-induced inflammation in celiac disease. Methods: We used an in vitro model of intestinal culture explant from celiac disease patients and non-celiac disease patients, cultured for 24 hours with the toxic gliadin peptide P31-43 and kissper preincubation. Results: Our data showed HLA-DR and TG2 reduction in the celiac disease mucosa pretreated with kissper, as well as a reduction of COX-2 in two patients. No differences we observed for the TGF-b1 and IL-15 levels in supernatants upon kissper pretreatment. Conclusions: The preliminary results suggest that kissper has a potential anti-inflammatory role in celiac disease.

Celiac Disease in Children, Particularly with Accompanying Type 1 Diabetes, Is Characterized by Substantial Changes in the Blood Cytokine Balance, Which May Reflect Inflammatory Processes in the Small Intestinal Mucosa

Cytokines play a pivotal role in the maintenance of intestinal homeostasis inducing pro- or anti-inflammatory response and mucosal barrier function in celiac disease (CD) and type 1 diabetes (T1D). We aimed to compare the levels of pro- and anti-inflammatory cytokines in CD patients without and with coexisting T1D, as well as to evaluate its association with the presence of enteroviruses (EV), regulatory T cells (Tregs), and dendritic cells (DCs) in small bowel mucosa. Altogether, 72 patients (median age 10.1 years) who had undergone small bowel biopsy were studied. The study group consisted of 24 patients with CD (median age 6.5 years), 9 patients with CD and concomitant T1D (median age 7.0 years), two patients with T1D (median age 8.5 years), and 37 patients (median age 14.0 years) with functional gastrointestinal disorders (FGD) and a normal small bowel mucosa as controls. The levels of 33 cytokines in serum were measured by multiple analysis using the Milliplex® MAP Magnetic Bead assay. The densities of FOXP3+ Tregs, CD11c+ DC, indoleamine 2,3-dioxygenase+ (IDO+) DC, langerin+ (CD207+) DCs, and EV were evaluated by immunohistochemistry as described in our previous studies. Circulating anti-EV IgA and IgG were evaluated using ELISA. The most important finding of the study is the significant increase of the serum levels of IL-5, IL-8, IL-13, IL-15, IL-17F, IL-22, IL-27, IP-10, MIP-1β, sIL-2Rα, sTNFRII, and TNFα in CD patients compared to controls and its correlation with the degree of small bowel mucosa damage graded according to the Marsh classification. The leptin level was higher in females in all study groups. The levels of IL-2, IL-6, IL-12 (P70), IL-15, IP-10, and IFNγ correlated significantly with the density of FOXP3+ Tregs in lamina propria of the small bowel mucosa, which supports the evidence about the signaling role of these cytokines in the peripheral maintenance of FOXP3+ Tregs. At the same time, a significant negative correlation occurred between the level of IL-4 and density of FOXP3+ Tregs in controls. Another important finding of our study was the correlation of IL-17F, IP-10, sTNFRII, MCP-1, and GM-CSF with the density of EV-positive cells in the lamina propria of the small bowel mucosa. Correlation of MIP-1 (CCL-4) with CD103+ DC and langerin+ DC densities may point to their significance in the recruitment of immune cells into the lamina propria and in driving the inflammatory response in CD patients. Our results suggest the predominance of Th1 and Th17 immune responses over EV VP1 protein in CD and T1D patients. The significant elevation of Th2 cytokines, like IL-5 and IL-13, but not IL-4, in CD patients and its correlation with the degree of small bowel mucosa damage could reflect the role of these cytokines in gut defense and inflammation.

Transcriptional and functional profiling defines human small intestinal macrophage subsets

Macrophages (Mfs) are instrumental in maintaining immune homeostasis in the intestine, yet studies on the origin and heterogeneity of human intestinal Mfs are scarce. Here, we identified four distinct Mf subpopulations in human small intestine (SI). Assessment of their turnover in duodenal transplants revealed that all Mf subsets were completely replaced over time; Mf1 and Mf2, phenotypically similar to peripheral blood monocytes (PBMos), were largely replaced within 3 wk, whereas two subsets with features of mature Mfs, Mf3 and Mf4, exhibited significantly slower replacement. Mf3 and Mf4 localized differently in SI; Mf3 formed a dense network in mucosal lamina propria, whereas Mf4 was enriched in submucosa. Transcriptional analysis showed that all Mf subsets were markedly distinct from PBMos and dendritic cells. Compared with PBMos, Mf subpopulations showed reduced responsiveness to proinflammatory stimuli but were proficient at endocytosis of particulate and soluble material. These data provide a comprehensive analysis of human SI Mf population and suggest a precursor-progeny relationship with PBMos.

TL1A blocking ameliorates intestinal fibrosis in the T cell transfer model of chronic colitis in mice

Tumor necrosis factor like cytokine 1A (TL1A) is a member of the TNF superfamily. Accumulating evidence demonstrated the importance of TL1A in the pathogenesis of inflammatory bowel disease (IBD) and suggested a potential role of TL1A blocking in IBD therapy. Here we aimed to explore whether the anti-TL1A antibody could ameliorate intestinal inflammation and fibrosis in IBD. A T cell transfer model of chronic colitis was induced by intraperitoneal injection of CD4+CD45RBhigh naive T cells isolated from either C57BL/6 wild type (WT) mice or LCK-CD2-Tl1a-GFP transgenic (L-Tg) mice into recombinase activating gene-1-deficient (RAG-/-) mice. The colitis model mice were treated prophylactically or therapeutically with anti-Tl1a antibody or IgG isotype control. Haematoxylin and eosin staining (H&E staining), Masson's trichrome staining (MT staining) and sirius red staining were used to detect histopathological changes in colonic tissue; immunohistochemical staining was used to detect the expressions of collagen I, collagen III, TIMP1, vimentin, α-SMA and TGF-β1/Smad3. Results showed that anti-Tl1a antibody could reduce intestinal inflammation and fibrosis by inhibiting the activation of intestinal fibroblasts and reducing the collagen synthesis in the T cell transfer model of chronic colitis. The mechanism may be related to the inhibition of TGF-1/Smad3 signaling pathway.

The Role of T-Cell Subsets in Chronic Inflammation in Celiac Disease and Inflammatory Bowel Disease Patients: More Common Mechanisms or More Differences?

Background

Chronic intestinal inflammation due to noninfectious causes represents a growing health issue all over the world. Celiac disease as well as inflammatory bowel diseases (IBD) like Crohn's disease and ulcerative and microscopic colitis involve uncontrolled T-cell activation and T-cell-mediated damage as common denominators. Therefore, diagnosis and treatment decisions clearly benefit from the knowledge of the intricacies of the systemic and the local T-cell activity.

Summary

Depending on the cytokine milieu, CD4⁺ T cells can differentiate into proinflammatory T helper 1 (Th1), anti-inflammatory Th2, antimicrobial Th17, pleiotropic Th9, tissue-instructing Th22 cells, and in the regulatory compartment forkhead box protein 3⁺ Treg, suppressive Tr1 or Th3 cells. Additionally, follicular Th cells provide B-cell help in antibody class switching; cytotoxic CD8⁺ T cells target virus-infected or tumor cells. This review discusses our current knowledge on the contribution of defined T-cell subpopulations to establishing and maintaining chronic intestinal inflammation in either of the above entities. It also puts emphasis on the differences in the prevalence of these diseases between Eastern and Western countries.

Key Messages

In celiac disease, the driving role of T cells in the lamina propria and in the epithelium mainly specific for two defined antigens is well established. Differences in genetics and lifestyle between Western and Eastern countries were instrumental in understanding underlying mechanisms. In IBD, the vast amount of potential antigens and the corresponding antigen-specific T cells makes it unlikely to find universal triggers. Increased mucosal CD4⁺ regulatory T cells in all four entities fail to control or abrogate local inflammatory processes. Thus, prevailing differences in the functional T-cell subtypes driving chronic intestinal inflammation in celiac disease and IBD at best allow some overlap in the treatment options for either disease.

Celiac disease: role of intestinal compartments in the mucosal immune response

Different approaches have been used to study the pattern of cytokines in celiac disease (CD). Laser capture microdissection (LCM) is a powerful tool for the isolation of specific tissue compartments. We aimed to investigate the mucosal immune response that takes place in different intestinal compartments of CD patients, dissected by LCM, analyzing cytokine expression profile. Frozen section of jejunum was obtained from 15 untreated CD and 15 control. Surface epithelium and lamina propria compartment were isolated by LCM. RNA from each LCM sample was extracted and, after a retrotranscription step, messenger RNA levels for MxA, IL-15, TNF-α, IFN-γ, IL-17α, IL-21, IL-10, and TGF-β were determined by quantitative reverse transcriptase-PCR. Increased gene expression levels of MxA, IL-15, TNF-α, IL-10, and TGF-β was observed in the surface epithelium of untreated CD with respect to control. Furthermore, all the cytokines investigated were upregulated in the lamina propria of untreated CD as compared to control. Within the untreated CD group the expression of IL-15 was higher, in the surface epithelium than in the lamina propria, whereas the expression levels of IL-17 and IL-21 were higher in the lamina propria than in the surface epithelium. Finally, high levels of IL-10 and TGF-β were detected in both compartments of untreated CD biopsies. In CD, surface epithelium and lamina propria compartments, play a prominent role in determining innate and adaptive immunity, respectively. Conversely, surface epithelium and lamina propria produce high levels of anti-inflammatory cytokines, suggesting that both compartments are involved in the immunoregulatory response.

Non-celiac gluten sensitivity: literature review

BACKGROUND

A significant percentage of the general population report problems caused by wheat and/or gluten ingestion, even though they do not have celiac disease (CD) or wheat allergy (WA), because they test negative both for CD-specific serology and histopathology and for immunoglobulin E (IgE)-mediated assays. Most patients report both gastrointestinal and nongastrointestinal symptoms, and all report improvement of symptoms on a gluten-free diet. This clinical condition has been named non-celiac gluten sensitivity (NCGS).

AIM

We attempt to define the current pathogenic, clinical, and diagnostic criteria of this "new" disease, to provide a practical view that might be useful to evaluate, diagnose, and manage NCGS patients.

METHODS

We reviewed the international literature through PubMed and Medline, using the search terms "wheat (hyper)sensitivity," "wheat allergy," "wheat intolerance," "gluten (hyper)sensitivity," and "gluten intolerance," and we discuss current knowledge about NCGS.

RESULTS

It has been demonstrated that patients suffering from NCGS are a heterogeneous group, composed of several subgroups, each characterized by different pathogenesis, clinical history, and, probably, clinical course. NCGS diagnosis can be reached only by excluding CD and WA. Recent evidence shows that a personal history of food allergy in infancy, coexistent atopy, positive for immunoglobulin G (IgG) antigliadin antibodies and flow cytometric basophil activation test, with wheat and duodenal and/or ileum-colon intraepithelial and lamina propria eosinophil counts, could be useful to identify NCGS patients.

CONCLUSIONS

Future research should aim to identify reliable biomarkers for NCGS diagnosis and to better define the different NCGS subgroups. Key teaching points: • Most patients report both gastrointestinal and nongastrointestinal symptoms, and all agree that there is an improvement of symptoms on a gluten-free diet. • NCGS diagnosis can be reached only by excluding celiac disease and wheat allergy. • Patients suffering from NCGS are a heterogeneous group, composed of several subgroups, each characterized by different pathogenesis, clinical history, and, probably, clinical course. • A personal history of food allergy in infancy, coexistent atopy, positive IgG antigliadin antibodies (AGA) and flow cytometric basophil activation test, with wheat and duodenal and/or ileum-colon intraepithelial and lamina propria eosinophil counts, could be useful to identify NCGS patients. • Future research should aim to identify reliable biomarkers for NCGS diagnosis and to better define the different NCGS subgroup.

Gliadin intake alters the small intestinal mucosa in indomethacin-treated HLA-DQ8 transgenic mice

Celiac disease (CD) is an enteropathy caused by the ingestion of wheat gluten in genetically susceptible individuals. A complete understanding of the pathogenic mechanisms in CD has been hindered because of the lack of adequate in vivo models. In the present study, we explored the events after the intragastric administration of gliadin and of the albumin/globulin fraction from wheat in human leukocyte antigen-DQ8 transgenic mice (DQ8 mice) treated with indomethacin, an inhibitor of cyclooxygenases (COXs). After 10 days of treatment, mice showed a significant reduction of villus height, increased crypt depth, increased number of lamina propria-activated macrophages, and high basal interferon-γ secretion in mesenteric lymph nodes, all of which were specifically related to gliadin intake, whereas the albumin/globulin fraction of wheat was unable to induce similar changes. Cotreatment with NS-398, a specific inhibitor of COX-2, also induced the intestinal lesion. Enteropathy onset was further characterized by high levels of oxidative stress markers, similar to CD. Biochemical assessment of the small intestine revealed the specific activation of matrix metalloproteinases 2 and 9, high caspase-3 activity, and a significant increase of tissue transglutaminase protein levels associated with the intestinal lesion. Notably, after 30 days of treatment, enteropathic mice developed serum antibodies toward gliadin (IgA) and tissue transglutaminase (IgG). We concluded that gliadin intake in combination with COX inhibition caused a basal inflammatory status and an oxidative stress condition in the small intestine of DQ8 mice, thus triggering the mucosal lesion and, subsequently, an antigen-specific immunity.

Molecular mechanisms of the adaptive, innate and regulatory immune responses in the intestinal mucosa of celiac disease patients

Celiac disease is a complex genetic disorder that affects the small intestine of genetically predisposed individuals when they ingest gluten, a dietary protein. Although several genome screens have been successful in identifying susceptibility loci in celiac disease, the only genetic contributors identified so far are the human leukocyte antigen (HLA)-DQ2/DQ8 molecules. One of the most important aspects in the pathogenesis of celiac disease is the activation of a T-helper 1 immune response, when the antigen-presenting cells that express HLA-DQ2/DQ8 molecules present the toxic gluten peptides to reactive CD4(+) T-cells. Recently, new insights into the activation of an innate immune response have also been described. It is generally accepted that the immune response triggers destruction of the mucosa in the small intestine of celiac disease patients. Hence, the activation of a detrimental immune response in the intestine of celiac disease patients appears to be key in the initiation and progression of the disease. This review summarizes the immunologic pathways that have been studied in celiac disease thus far, and will point to new potential candidate genes and pathways involved in the etiopathogenesis of celiac disease, which should lead to novel alternatives for diagnosis and treatment.

The role of transforming growth factor (TGF)-β in modulating the immune response and fibrogenesis in the gut

Transforming growth factor (TGF)-β, a pleiotropic cytokine released by both immune and non-immune cells in the gut, exerts an important tolerogenic action by promoting regulatory T cell differentiation. TGF-β also enhances enterocyte migration and regulates extracellular matrix turnover, thereby playing a crucial role in tissue remodeling in the gut. In this review we describe the mechanisms by which abnormal TGF-β signaling impairs intestinal immune tolerance and tissue repair, thus predisposing to the onset of immune-mediated bowel disorders, such as inflammatory bowel disease and celiac disease. Additionally, we will discuss potential therapeutic strategies aiming at restoring physiologic TGF-β signaling in chronic intestinal diseases.

Non-celiac gluten sensitivity: questions still to be answered despite increasing awareness

Recently, the increasing number of patients worldwide who are sensitive to dietary gluten without evidence of celiac disease or wheat allergy has contributed to the identification of a new gluten-related syndrome defined as non-celiac gluten sensitivity. Our knowledge regarding this syndrome is still lacking, and many aspects of this syndrome remain unknown. Its pathogenesis is heterogeneous, with a recognized pivotal role for innate immunity; many other factors also contribute, including low-grade intestinal inflammation, increased intestinal barrier function and changes in the intestinal microbiota. Gluten and other wheat proteins, such as amylase trypsin inhibitors, are the primary triggers of this syndrome, but it has also been hypothesized that a diet rich in fermentable monosaccharides and polyols may elicit its functional gastrointestinal symptoms. The epidemiology of this condition is far from established; its prevalence in the general population is highly variable, ranging from 0.63% to 6%. From a clinical point of view, non-celiac gluten sensitivity is characterized by a wide array of gastrointestinal and extraintestinal symptoms that occur shortly after the ingestion of gluten and improve or disappear when gluten is withdrawn from the diet. These symptoms recur when gluten is reintroduced. Because diagnostic biomarkers have not yet been identified, a double-blind placebo-controlled gluten challenge is currently the diagnostic method with the highest accuracy. Future research is needed to generate more knowledge regarding non-celiac gluten sensitivity, a condition that has global acceptance but has only a few certainties and many unresolved issues.

Mucosal cytokine response after short-term gluten challenge in celiac disease and non-celiac gluten sensitivity

OBJECTIVES

In celiac disease (CD), gluten induces both adaptive and innate immune responses. Non-celiac gluten sensitivity (NCGS) is another form of gluten intolerance where the immune response is less characterized. The aim of our study was to explore and compare the early mucosal immunological events in CD and NCGS.

METHODS

We challenged 30 HLA-DQ2(+) NCGS and 15 CD patients, all on a gluten-free diet, with four slices of gluten-containing bread daily for 3 days. Duodenal biopsy specimens were collected before and after challenge. The specimens were examined for cytokine mRNA by quantitative reverse transcriptase-PCR and for MxA-expression and CD3(+) intraepithelial lymphocytes (IELs) by immunohistochemistry and compared with specimens from untreated CD patients and disease controls.

RESULTS

In CD patients, tumor necrosis factor alpha (P=0.02) and interleukin 8 (P=0.002) mRNA increased after in vivo gluten challenge. The interferon gamma (IFN-γ) level of treated CD patients was high both before and after challenge and did not increase significantly (P=0.06). Four IFN-γ-related genes increased significantly. Treated and untreated CD patients had comparable levels of IFN-γ. Increased expression of MxA in treated CD patients after challenge suggested that IFN-α was activated on gluten challenge. In NCGS patients only IFN-γ increased significantly (P=0.03). mRNA for heat shock protein (Hsp) 27 or Hsp70 did not change in any of the groups. Importantly, we found that the density of IELs was higher in NCGS patients compared with disease controls, independent of challenge, although lower than the level for treated CD patients.

CONCLUSIONS

CD patients mounted a concomitant innate and adaptive immune response to gluten challenge. NCGS patients had increased density of intraepithelial CD3(+) T cells before challenge compared with disease controls and increased IFN-γ mRNA after challenge. Our results warrant further search for the pathogenic mechanisms for NCGS.

New understanding of gluten sensitivity

Among gluten-related disorders, gluten sensitivity is an emerging entity that is characterized by a wide array of manifestations. In particular, patients complain of IBS-like symptoms and extraintestinal manifestations that occur shortly after the ingestion of gluten. Symptoms improve or disappear when gluten is withdrawn from the diet, and recur if gluten is reintroduced. Laboratory tests are usually unhelpful for diagnosis, although ~50% of patients are positive for IgG antigliadin antibodies. The natural history of gluten sensitivity is unknown; in particular, it is still to be clarified whether this disorder is permanent or transient and whether it is linked to autoimmunity. The pathogenesis of gluten sensitivity is unclear; data so far demonstrate a predominant activation of innate immune responses. Further research is necessary to establish the main clinicopathological features of gluten sensitivity, thus enabling physicians to improve their management of the increasing number of patients who are sensitive to dietary gluten.

Divergence of gut permeability and mucosal immune gene expression in two gluten-associated conditions: celiac disease and gluten sensitivity

BACKGROUND

Celiac disease (CD) is an autoimmune enteropathy triggered by the ingestion of gluten. Gluten-sensitive individuals (GS) cannot tolerate gluten and may develop gastrointestinal symptoms similar to those in CD, but the overall clinical picture is generally less severe and is not accompanied by the concurrence of tissue transglutaminase autoantibodies or autoimmune comorbidities. By studying and comparing mucosal expression of genes associated with intestinal barrier function, as well as innate and adaptive immunity in CD compared with GS, we sought to better understand the similarities and differences between these two gluten-associated disorders.

METHODS

CD, GS and healthy, gluten-tolerant individuals were enrolled in this study. Intestinal permeability was evaluated using a lactulose and mannitol probe, and mucosal biopsy specimens were collected to study the expression of genes involved in barrier function and immunity.

RESULTS

Unlike CD, GS is not associated with increased intestinal permeability. In fact, this was significantly reduced in GS compared with controls (P = 0.0308), paralleled by significantly increased expression of claudin (CLDN) 4 (P = 0.0286). Relative to controls, adaptive immunity markers interleukin (IL)-6 (P = 0.0124) and IL-21 (P = 0.0572) were expressed at higher levels in CD but not in GS, while expression of the innate immunity marker Toll-like receptor (TLR) 2 was increased in GS but not in CD (P = 0.0295). Finally, expression of the T-regulatory cell marker FOXP3 was significantly reduced in GS relative to controls (P = 0.0325) and CD patients (P = 0.0293).

CONCLUSIONS

This study shows that the two gluten-associated disorders, CD and GS, are different clinical entities, and it contributes to the characterization of GS as a condition associated with prevalent gluten-induced activation of innate, rather than adaptive, immune responses in the absence of detectable changes in mucosal barrier function.

Increased expression of serum- and glucocorticoid-regulated kinase-1 in the duodenal mucosa of children with coeliac disease

OBJECTIVES

Enterocyte apoptosis induced by activated intraepithelial lymphocytes is increased in coeliac disease (CD). Serum- and glucocorticoid-regulated kinase-1 (SGK1) is a serine/threonine protein kinase that may inhibit apoptosis and compensate for the excessive death of surface epithelial cells. The significance of SGK1 in CD is elusive so far. The aim of this study was to characterise the expression and localisation of SGK1 in duodenal biopsy samples taken from children with untreated CD, children with treated CD, and controls.

PATIENTS AND METHODS

Duodenal biopsy specimens were collected from 16 children with untreated CD, 9 children with treated CD, and 10 controls. The mRNA expression of SGK1 was determined by real-time reverse transcription-polymerase chain reaction. SGK1 and phosphorylated (P)-SGK1 protein levels and their localisation were determined by Western blot and immunofluorescent staining, respectively.

RESULTS

We found increased SGK1-mRNA expression as well as higher SGK1 and P-SGK1 protein levels in the duodenal mucosa of children with untreated CD compared with controls. In the duodenal mucosa of children with treated CD, SGK1-mRNA expression was decreased and SGK1 and P-SGK1 protein levels were lower than in untreated CD. SGK1 and P-SGK1 staining intensity was stronger in duodenal villous enterocytes of children with untreated CD compared with treated CD.

CONCLUSIONS

Our results of increased expression of SGK1 in untreated CD may suggest its contribution to the enterocyte survival in this disease.

Altered gene expression in highly purified enterocytes from patients with active coeliac disease

Background

Coeliac disease is a multifactorial inflammatory disorder of the intestine caused by ingestion of gluten in genetically susceptible individuals. Genes within the HLA-DQ locus are considered to contribute some 40% of the genetic influence on this disease. However, information on other disease causing genes is sparse. Since enterocytes are considered to play a central role in coeliac pathology, the aim of this study was to examine gene expression in a highly purified isolate of these cells taken from patients with active disease. Epithelial cells were isolated from duodenal biopsies taken from five coeliac patients with active disease and five non-coeliac control subjects. Contaminating T cells were removed by magnetic sorting. The gene expression profile of the cells was examined using microarray analysis. Validation of significantly altered genes was performed by real-time RT-PCR and immunohistochemistry.

Results

Enterocyte suspensions of high purity (98–99%) were isolated from intestinal biopsies. Of the 3,800 genes investigated, 102 genes were found to have significantly altered expression between coeliac disease patients and controls (p < 0.05). Analysis of these altered genes revealed a number of biological processes that are potentially modified in active coeliac disease. These processes include events likely to contibute to coeliac pathology, such as altered cell proliferation, differentiation, survival, structure and transport.

Conclusion

This study provides a profile of the molecular changes that occur in the intestinal epithelium of coeliac patients with active disease. Novel candidate genes were revealed which highlight the contribution of the epithelial cell to the pathogenesis of coeliac disease.

Transglutaminase and the pathogenesis of coeliac disease

In 1997, a German group demonstrated that the antigen of the biomarker EMA (endomysial antibodies) in coeliac disease is a calcium-dependent thiol enzyme, transglutaminase type 2 (TG2). This most important discovery opened up an exciting field of research aimed at a better understanding of the pathogenesis of coeliac disease, a T-cell-driven autoimmune disorder with a prevalence of about 1%. The accidental activation of TG2, possibly caused by a stress-induced local deficiency of zinc in the intestinal wall, might play a key role where the enzyme catalyzes an atypical deamidation of specific glutamine residues of food gliadins. The genetic contribution is HLA DQ2 or DQ8, which can form a complex with the TG2-modified gliadin residues, resulting in an immune response with the formation of antibodies against both gliadin and the enzyme. Indeed, the immunopathogenesis of coeliac disease can now be recognized partly at the molecular level. Progress has already improved the opportunities for laboratory diagnostics and, hopefully, new ways of treating and preventing coeliac disease will become available. These exciting developments might stimulate research within other fields of autoimmune disorders. With its focus on TG2, this review highlights some of the intriguing mechanisms of the pathogenesis of coeliac disease, such as the structure of the neo-antigen, the involvement of calcium and zinc, and the effects of coeliac antibodies on TG2 activity. Moreover, the many pitfalls due to dubious laboratory practice are addressed, as is the potential when a fundamental biological mechanism is understood at the molecular level.

Tryptophan metabolism and indoleamine 2,3-dioxygenase expression in coeliac disease

We have investigated the possible role of the metabolism of tryptophan and activity of the enzyme indoleamine 2,3-dioxygenase (IDO) in the immune regulation of coeliac disease (CD). Serum concentrations of tryptophan and its metabolites kinurenines were determined by high performance liquid chromatography in 24 patients with CD, seven patients with Crohn's disease and five healthy patients. We detected an increase of kynurenine (4.2 micromol/l +/- 0.27 versus 2.6 micromol/l +/- 0.54, P < 0002) and of the kynurenine/tryptophan ratio in supernatants of coeliac patients (11.5 micromol/l +/- 1.01 versus 6.5 micromol/l +/- 1.57, P < 0005) in comparison with healthy patients, respectively, and we found no differences with Crohn's disease patients. Immunohistochemistry analysis of intestinal biopsies from CD patients showed an increased expression of IDO, interferon-gamma, interleukin-10 and transforming growth factor-beta. Our data suggest that a mechanism(s) dependent on tryptophan catabolism might regulate the immune responses in CD.

Recent advances in the understanding of celiac disease: therapeutic implications for the management of pediatric patients

Celiac disease (CD) is an autoimmune condition occurring in genetically susceptible individuals characterized by inflammatory injury to the mucosa of the small intestine after the ingestion of wheat glutens or related barley and rye products. Originally thought to be highly prevalent only in Northern European populations, growing evidence indicates a much higher prevalence in many other regions, including the US as well as South America, North Africa, and Asia. The growing awareness that pediatric patients may present with quite diverse and protean manifestations and the significant impact of CD on childhood development has prompted efforts to increase CD awareness for the early diagnosis and treatment of this disease. The current diagnostic criteria for CD requires characteristic histologic findings in small bowel biopsies and clinical remission when placed on a gluten-free diet. Serologic testing for CD can provide additional support for the diagnosis of CD or a means to assess efficacy and adherence to a gluten-free diet. The mainstay of treatment remains the institution of a gluten-free diet. However, patients with refractory CD may require treatment with immunosuppressant medications. With the increased identification of specific gluten epitopes and understanding of the pathogenesis of CD, future therapies may rely on genetically altering gluten proteins, immunization techniques, or therapies focused on either the development of specific immune tolerance or regulation of mucosal inflammation.

New aspects in celiac disease

Celiac disease (CD) is a common autoimmune disorder characterized by an immune response to ingested gluten and has a strong HLA association with HLA-DQ2 and HLA-DQ8 molecules, but human HLA-DQ risk factors do not explain the entire genetic susceptibility to gluten intolerance. CD is caused by the lack of immune tolerance (oral tolerance) to wheat gluten. In this sense, the expression of soluble HLA-G in CD is of special interest because the molecule plays an important role in the induction of immune tolerance. The enhanced expression of soluble HLA-G found in CD may be part of a mechanism to restore the gluten intolerance. In this editorial, we review recent progress in understanding CD in relation to its prevalence, diagnosis and possible mechanisms of pathogenesis.

Synthesis of collagen I in collagenous sprue

BACKGROUND & AIMS

Collagenous sprue (CS) is a rare severe malabsorption syndrome of unknown etiology, characterized by villus atrophy and a broad subepithelial collagen band. We studied the expression patterns of genes involved in fibrogenesis and fibrolysis and analyzed the composition of the subepithelial collagen band in CS compared with untreated celiac diseases (CDs).

METHODS

Duodenal biopsies from 2 patients with CS were hybridized with (35)S-labeled RNA probes for procollagen alpha1(I), matrix metalloproteinases (MMPs)-1 and -3, and tissue inhibitor of MMP-1 (TIMP-1). Numbers of positive subepithelial and lamina propria cells and grain density per cell were determined microscopically. Immunohistochemistry for collagens I, III, IV, XIV, and tenascin was performed by the immunoalkaline phosphatase method. Findings were compared with earlier data from patients with untreated CD.

RESULTS

Numbers of cells expressing procollagen I, MMP-1, and MMP-3 mRNA were similar, but subepithelial procollagen I transcripts per cell were significantly increased (42 and 38 vs 18 [13-23]; P < .05) in CS compared with CD, whereas cellular transcript densities for MMP-1 and MMP-3 mRNA were similar. In addition, the number of TIMP-1 mRNA-positive cells was higher in CS compared with CD (32 and 25 vs 16.5 [4-25]; P < .05). The subepithelial collagenous bands stained for collagen I, collagen III, and tenascin.

CONCLUSIONS

The prominent subepithelial matrix deposition in CS is due to increased expression of the main fibrogenic genes (procollagen I and TIMP-1) by myofibroblastic cells, whereas expression of fibrolytic MMPs remains unaltered.

Transglutaminase 2 in the enterocytes is coeliac specific and gluten dependent

BACKGROUND

Tissue transglutaminase, the coeliac autoantigen, was shown to localise in the enterocytes of coeliac patients and controls. It was speculated that surface tissue transglutaminase has a role in the pathogenesis of coeliac disease.

AIMS

To study localisation of tissue transglutaminase in different stages of coeliac disease and other enteropathies with and without villous flattening.

METHODS

Immunofluorescent and immunoblotting assays were used. Duodenal cryostat sections from 23 coeliac patients (10 untreated, 8 treated, 5 potential) and 18 controls (2 autoimmune enteropathy and 16 normal duodenal mucosa) were incubated with an anti-tissue transglutaminase monoclonal antibody. Slides were blindly examined.

RESULTS

The immunofluorescent assay showed that monoclonal antibody localised in the subepithelial layer, in the lamina propria, and in the pericryptal connective tissue of all samples. It also bound to surface enterocytes in 8/10 untreated, 1/8 treated, and 3/5 potential coeliac patients. None of the controls showed an epithelial distribution of tissue transglutaminase. Immunoblotting experiments performed in enterocytes freshly isolated from duodenal biopsy confirmed these findings.

CONCLUSION

Epithelial distribution of tissue transglutaminase is specific for coeliac disease rather than due to a non-specific mucosal inflammation. Analysis of different stages of coeliac disease suggests that the epithelial distribution of tissue transglutaminase is gluten dependent.

Citocinas en la patogenia de la enfermedad celíaca

Celiac disease is manifested by an enteropathy caused by intolerance to gluten, a family of proteins found in wheat and other cereals. Following intestinal T-cell activation in predisposed individuals, different inflammatory mechanisms are triggered under the control of the cytokine balance including those with a pro-inflammatory Th1 pattern such as IFNgamma, TNFalpha, IL-15 and IL-18; and regulatory cytokines such as TGFbeta and IL-10. These cytokines, besides increasing the intensity of the activation and the number of immune cells within the intestinal mucosa, regulate the activity of epithelial growth factors and metalloproteinases, a group of molecules involved in the maintenance and turnover of the intestinal mucosa structure; in inflammatory conditions, they also induce the intestinal lesion responsible for malabsorption syndrome.

Autoantibodies against soluble and immobilized human recombinant tissue transglutaminase in children with celiac disease

OBJECTIVES

The conformation of tissue transglutaminase might influence the performance of immunoassays to detect autoantibodies from patients with celiac disease. The present study investigated how the exposure of tissue transglutaminase kept in a liquid phase and fixed to a solid support affected the binding of immunoglobulin (Ig)A and IgG autoantibodies in children with untreated and treated celiac disease.

METHODS

Included were 73 untreated celiac disease children, 50 controls and 80 children with treated celiac disease. IgA and IgG antitissue transglutaminase were measured with solid phase enzyme-linked immunoassay (ELISA) and liquid phase radioligand binding assays. For IgG antitissue transglutaminase detection with radioligand binding assays antihuman IgG and protein A were used. IgA endomysial autoantibodies were measured by indirect immunofluorescence.

RESULTS

Both ELISA and radioligand binding assays detected IgA antitissue transglutaminase in 65 of 73 untreated celiac disease children and in 2 of 50 controls. One additional control child was detected with radioligand binding assays. Endomysial autoantibodies were present in 62 of 73 celiac disease children and in 2 of 50 controls. IgG antitissue transglutaminase was detected with both ELISA and radioligand binding assays in 40 of 73 untreated celiac disease children and in 2 of 50 controls. Radioligand binding assays using protein A detected 20 of 73 additional untreated celiac disease children and one control child with increased IgG antitissue transglutaminase. In treated celiac disease children, 21 of 80 were IgA antitissue transglutaminase positive with radioligand binding assays, 3 of 80 with ELISA, whereas none had endomysial autoantibodies.

CONCLUSIONS

No qualitative differences between radioligand binding assays and ELISA in IgA or IgG antitissue transglutaminase binding from untreated celiac disease children was demonstrated. However, discrepancies in the binding of IgA antitissue transglutaminase from a subgroup of treated celiac disease children indicated that alterations of tissue transglutaminase might occur on fixation of the antigen. Protein A used for radioligand binding assays seemed not to assess IgG autoantibodies exclusively. IgA antitissue transglutaminase detection in screening of childhood celiac disease can be performed either by ELISA or radioligand binding assays because the two assays are interchangeable.

Localization of tissue transglutaminase and N (epsilon)-(gamma) -glutamyl lysine in duodenal cucosa during the development of mucosal atrophy in coeliac disease

Expression and transamidation activity of tissue transglutaminase (tTG) may be involved in the morphological modifications leading to the mucosal atrophy observed in coeliac disease (CD). We aimed to investigate the localization of tTG within the duodenal mucosa during the development of villous atrophy. The localization and level of expression of N epsilon-(gamma-glutamyl) lysine isopeptides which could reflect the transamidation activity of tTG were also analyzed. tTG and N epsilon-(gamma-glutamyl) lysine were localized using an immunohistochemical technique on duodenal biopsies obtained from 75 patients with CD and 51 subjects with normal mucosa (control group). The number of cases displaying tTG-expressing cells in the basement membrane and lamina propria was significantly higher in CD patients than in the control group. Moreover, the intensity of tTG staining in these areas was higher in CD. In contrast, the number of biopsies with tTG-expressing enterocytes was significantly lower in CD than in the control group. There was no difference in N epsilon-(gamma-glutamyl) lysine between the two populations. Tissue transglutaminase was differently expressed in the various areas of the mucosa according to the stage of atrophy, whereas the localization and the intensity of the labelling of N epsilon-(gamma-glutamyl) lysine isopeptides did not show any modification. The preferential localization in the basement membrane and lamina propria may reflect the involvement of tTG in the development of mucosal atrophy in CD.

Enhanced interleukin-18 levels in the peripheral blood of children with coeliac disease

Coeliac disease (CoD) is a small intestinal disorder characterized by villous atrophy, crypt cell hyperplasia and an increased production of T helper cell type 1 (Th1) cytokines. Interleukin (IL)-18 is a pro-inflammatory cytokine that has a crucial role in maintaining the Th1 response. In this study, the serum levels of IL-18 were measured in children with CoD or other gastrointestinal diseases in order to evaluate the possibility of using IL-18 as a disease activity marker. IL-18 levels were higher in samples from CoD patients [median 443 pg/ml (148-885)] compared to healthy controls [median 205 pg/ml (11-379)], P <0.05. In contrast, the levels of IL-18 were not enhanced significantly in the serum from patients with inflammatory bowel disease (IBD) [median 324 pg/ml (207-546)] or in the disease control group [median 303 pg/ml (2-689)]. In CoD patients, after 2 weeks of gluten challenge (GC), serum IL-18 was unchanged [median 268 pg/ml (59-458)] compared to patients on a gluten-free diet [median 220 pg/ml (53-600)], while IL-18 was increased after 12 weeks of GC [median 551 pg/ml (94-952)], P <0.01. The IL-18 levels correlated with IgA anti-transglutaminase antibody levels (rs=0.59, P=0.016) in serum from untreated CoD patients, and IL-18 also followed the degree of small intestinal villous atrophy in 12 out of 19 CoD patients. Our results support the view that serum IL-18 concentrations in children with CoD follow disease activity, suggesting a role for IL-18 in the induction of an inflammatory Th1-response after gluten exposure.

Cytokine Gene Polymorphisms and Genetic Association with Coeliac Disease in the Finnish Population

Coeliac disease (CD) is an intestinal disorder caused by intolerance to dietary gluten in susceptible individuals. The HLA-DQ genes are major risk factors for CD, but other genes also play an important role in the disease susceptibility. Immune-mediated mechanisms are known to underlie the pathogenesis of CD. We studied single-nucleotide polymorphisms in transforming growth factor (TGF)-beta1, interleukin (IL)-10, IL-6, interferon (IFN)-gamma and tumour necrosis factor (TNF)-alpha genes in the Finnish population using family-based association approach. In addition, we genotyped a trinucleotide repeat polymorphism in the major histocompatibility complex (MHC) class I chain-related protein A (MICA) gene, located in the human leucocyte antigen (HLA) region in the vicinity of TNF-alpha. To control the effect of linkage disequilibrium between HLA-DQ genes and MICA and TNF-alpha, an HLA-stratified association analysis was performed. We did not find evidence of association between TGF-beta1, IL-10, IL-6 and IFN-gamma polymorphisms and CD susceptibility. No association was found for any of the MICA alleles independently of DQ genes, whereas TNF-alpha-308 A allele was slightly overrepresented on chromosomes carried by CD patients compared with control chromosomes, indicating that either TNF-alpha, or another gene in linkage disequilibrium with it, could confer increased susceptibility to CD. This result supports the earlier findings that the HLA region harbours a novel susceptibility factor in addition to HLA-DQ.

Intestinal tissue transglutaminase in coeliac disease of children and adults: ultrastructural localization and variation in expression

BACKGROUND

Tissue transglutaminase is the main antigen for the anti-endomysial antibodies used for diagnosis of coeliac disease and can with some specificity in vitro deamidate gliadins generating potent epitopes. The intestinal levels and the ultrastructural localization of tissue transglutaminase in normal and affected persons were investigated to provide further information on its role in this disease. Intestinal biopsies were taken from normal and coeliac children and adults.

METHODS

The level of transglutaminase was analysed by means of a quantitative enzymatic assay and its ultrastructural localization by immunogold electronmicroscopy using a monoclonal antibody against tissue transglutaminase.

RESULTS

In relation to normal individuals, the enzymatic activity of tissue transglutaminase in adult coeliac patients was increased. The enzyme was found in the enterocytes and in increased amount just beneath the enterocytes, where cytosolic and nuclear labelling of distinct elongated cells was seen in addition to extracellular labelling close to collagen fibrils. In children, the enzymatic activity and the immunogold labelling could not be shown to be related to disease. In all cases the enzyme activity was EDTA-sensitive.

CONCLUSIONS

The increased amount of tissue transglutaminase activity in coeliac adults was shown to be due to the appearance of the enzyme in enterocytes and increased expression in the lamina propria. No evidence was found to support the idea of a changed localization or changed amounts as primary elements in coeliac disease pathogenesis, nor for the involvement of non-calcium dependent microbial transglutaminases.

Tissue transglutaminase--the key player in celiac disease: a review

Gluten-sensitive enteropathy, otherwise known as celiac sprue, is characterized by an abnormal proximal small intestinal mucosa arising as a result of an inappropriate inflammatory response to ingested gluten antigens present in wheat in genetically susceptible individuals. This immune response is directed to a 33-mer peptide of the alpha gliadin component of gluten. The generation of an epitope for the recognition by CD4+ T cells requires deamination of the protein by tissue transglutaminase (tTG). Moreover, IgA anti tTG is highly sensitive and is specific serologic marker (95-99%) of celiac disease. They can be easily determined quantitatively, by ELISA of an accurate and relatively inexpensive technique. Therefore, tTG can be used as the first line diagnostic test in the work-up of celiac disease, as well as for screening purposes. Finally, tTG may contribute to future strategies in treating celiac disease either by producing nontoxic wheat or by generating oral vaccination that can prevent the disease.

Pathomechanisms in Celiac Disease

Celiac disease is a complex autoimmune disease which is characterized by a strong genetic association (HLA-DQ2 or -DQ8), gluten as nutritional etiological factor, and the enzyme tissue transglutaminase as endomysial autoantigen. Patients develop highly predictive IgA autoantibodies to tTG. Certain gluten peptides are presented by the disease-associated HLA-DQ2/DQ8 molecules leading to stimulation of gluten-specific T cells. This immune response which is driven in the lamina propria causes the mucosal transformation characteristic for celiac disease. Increased intestinal expression of tTG in patients with CD appears to play an important role in the pathogenesis of CD. Thus, modification of gluten peptides by tTG, especially deamidation of certain glutamine residues, can enhance their binding to HLA-DQ2 or -DQ8 and potentiate T cell stimulation. Furthermore, tTG-catalyzed cross-linking and consequent haptenization of gluten with extracellular matrix proteins allows for storage and extended availability of gluten in the mucosa. New therapeutic approaches aim at proteolytic destruction of immunodominant gliadin peptides that are resistant to intestinal enzymes by bacterial prolyl endopeptidases, the inhibition of tTG activity with highly specific enzyme inhibitors or at HLA-DQ2/DQ8 blocking peptide analogues.