Celiac disease (CD) is a frequent inflammatory intestinal disease, with a genetic background, caused by gliadin-containing food. Undigested gliadin peptides induce innate and adaptive T cell-mediated immune responses. The major mediator of the stress and innate immune response to gliadin peptides (i.e., peptide 31-43, P31-43) is the cytokine interleukin-15 (IL-15). The role of epithelial growth factor (EGF) as a mediator of enterocyte proliferation and the innate immune response has been described. In this paper, we review the most recent literature on the mechanisms responsible for triggering the up-regulation of these mediators in CD by gliadin peptides. We will discuss the role of P31-43 in enterocyte proliferation, structural changes and the innate immune response in CD mucosa in cooperation with EGF and IL-15, and the mechanism of up-regulation of these mediators related to vesicular trafficking. We will also review the literature that focuses on constitutive alterations of the structure, signalling/proliferation and stress/innate immunity pathways of CD cells. Finally, we will discuss how these pathways can be triggered by gliadin peptide P31-43 in controls, mimicking the celiac cellular phenotype.
Abstract Several recent reports describe a role of probiotics as a therapeutic approach for celiac disease (CD). Two undigested A-gliadin peptides, P31-43 and P57-68, are central to CD pathogenesis, inducing an innate and an adaptive immune response, respectively. They enter enterocytes and localize to vesicular compartment to induce their toxic/immunogenics effects. In this article, we tested the effect of probiotic Lactobacillus paracasei (LP) CBA L74 (International Depository Accession Number LMG P-24778), its supernatant and LP-fermented cereals on gliadin peptides, P31-43 and P57-68, entrance in Caco-2 cells. Both LP CBA L74 and its supernatant inhibit P31-43 (intensity of fluorescence; FI: 75%) and P57-68 (FI: 50%) entrance in Caco2 cells, indicating that this biological effect is due to some product included in LP CBA L74 supernatant. This effect was present also after fermentation of cereals. This study describes a novel effect of probiotics in the prevention of undigested gliadin peptides toxic effects.
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-? 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.
On ingestion of gliadin, the major protein component of wheat and other cereals, the celiac intestine is characterized by the proliferation of crypt enterocytes with an inversion of the differentiation/proliferation program. Gliadins and A-gliadin peptide P31-43, in particular, act as growth factors for crypt enterocytes in patients with celiac disease (CD). The effects of gliadin on crypt enterocyte proliferation and activation of innate immunity are mediated by epidermal growth factors (EGFs) and innate immunity mediators [interleukin 15 (IL15)].
Tissue transglutaminase (TG2) plays a central role in celiac disease (CD) pathogenesis by strongly enhancing the immunogenicity of gluten, the CD-triggering antigen. By deamidating specific glutamine (Q) residues, TG2 favors the binding of gluten peptides to DQ2/8 molecules and, subsequently, their recognition by cognate T cells. Six peptides were previously identified within wheat gliadin whole extracts by tagging the TG2-susceptible Q residues with monodansylcadaverine (MDC) and nanospray tandem mass spectrometry (nanoESI-MS/MS). The immunogenicity of these peptides was next tested in gliadin-specific T-cell lines established from CD intestinal mucosa. Four peptides, corresponding to known epitopes of ?- and ?-gliadins, induced cell proliferation and interferon (IFN)-? production. Interestingly, one of the two non-T-cell stimulatory peptides corresponded to the 31-49 ?-gliadin peptide implicated in the innate immune activation in CD mucosa. This study describes a strategy for identifying immunogenic gluten peptides potentially relevant for CD pathogenesis in protein extracts from wheat and other edible cereals.
Celiac disease (CD) is a frequent inflammatory intestinal disease, with a genetic background, caused by gliadin-containing food. Undigested gliadin peptides P31-43 and P57-68 induce innate and adaptive T cell-mediated immune responses, respectively. Alterations in the cell shape and actin cytoskeleton are present in celiac enterocytes, and gliadin peptides induce actin rearrangements in both the CD mucosa and cell lines. Cell shape is maintained by the actin cytoskeleton and focal adhesions, sites of membrane attachment to the extracellular matrix. The locus of the human Lipoma Preferred Partner (LPP) gene was identified as strongly associated with CD using genome-wide association studies (GWAS). The LPP protein plays an important role in focal adhesion architecture and acts as a transcription factor in the nucleus. In this study, we examined the hypothesis that a constitutive alteration of the cell shape and the cytoskeleton, involving LPP, occurs in a cell compartment far from the main inflammation site in CD fibroblasts from skin explants. We analyzed the cell shape, actin organization, focal adhesion number, focal adhesion proteins, LPP sub-cellular distribution and adhesion to fibronectin of fibroblasts obtained from CD patients on a Gluten-Free Diet (GFD) and controls, without and with treatment with A-gliadin peptide P31-43. We observed a "CD cellular phenotype" in these fibroblasts, characterized by an altered cell shape and actin organization, increased number of focal adhesions, and altered intracellular LPP protein distribution. The treatment of controls fibroblasts with gliadin peptide P31-43 mimics the CD cellular phenotype regarding the cell shape, adhesion capacity, focal adhesion number and LPP sub-cellular distribution, suggesting a close association between these alterations and CD pathogenesis.
Celiac disease (CD) occurs frequently, and is caused by ingestion of prolamins from cereals in subjects with a genetic predisposition. The small intestinal damage depends on an intestinal stress/innate immune response to certain gliadin peptides (e.g., A-gliadin P31-43) in association with an adaptive immune response to other gliadin peptides (e.g., A-gliadin P57-68). Gliadin and peptide P31-43 affect epithelial growth factor receptor (EGFR) signaling and CD enterocyte proliferation. The reason why the stress/innate immune and proliferative responses to certain gliadin peptides are present in CD and not in control intestine is so far unknown. The aim of this work is to investigate if, in CD, a constitutive alteration of enterocyte proliferation and signaling exists that may represent a predisposing condition to the damaging effects of gliadin. Immunofluorescence and immunohistochemistry were used to study signaling in CD fibroblasts and intestinal biopsies. Western blot (WB) analysis, immunoprecipitation, and quantitative PCR were also used. We found in CD enterocytes enhancement of both proliferation and Epidermal Growth Factor Receptor (EGFR)/ligand system. In CD enterocytes and fibroblasts we found increase of the phosphorylated downstream signaling molecule Extracellular Signal Regulated Kinase (ERK); block of the ERK activation normalizes enterocytes proliferation in CD mucosa. In conclusion the same pathway, which gliadin and gliadin peptide P31-43 can interfere with, is constitutively altered in CD cells. This observation potentially explains the specificity of the damaging effects of certain gliadin peptides on CD intestine.
Most of the recent studies suggest that oats are well tolerated by celiac disease (CD) patients. However, it is still possible that different oat cultivars may display different biological properties relevant for CD pathogenesis. We aimed to investigate biological and immunological properties of two oat varieties, Avena genziana and Avena potenza, in relation to their safety for CD patients.
Celiac disease (CD) is caused by loss of tolerance toward gluten and related cereal products. The delivery of gliadin peptides (GP) to HLA-DR-positive late endosomes (LE) of enterocytes is required for antigen presentation and tolerance generation. We hypothesized that anti-gliadin antibodies in CD serum modify gliadin transport into LE within enterocytes. CD and control duodenal biopsies were incubated with digests of gluten as well as with serum of CD patients. Lissamin-labeled GP AA31-43 and AA56-68 were endocytozed by Caco-2 cells with serum of CD- or control patients. Colocalization of gliadin with the LE marker LAMP-2 and cathepsin D was determined and quantified on immunofluorescence and immunoelectron microscopical level. Up to 13% of internalized gliadin was located in LE of CD biopsies incubated with CD serum compared with less than 4% in CD biopsies without CD serum as well as in control biopsies. In Caco-2 cells, the colocalization coefficient of GP AA31-43 and LE was 0.82 with CD serum, 0.42 with control serum, and 0.48 with culture medium. Incubation with CD serum can direct GP AA31-43 into LE of enterocytes which is required for antigen presentation.
Celiac disease (CD) is a condition in which the regulation of the mucosal immune response to dietary gliadin might be altered. The transcription factor forkhead box P3 (Foxp3) has been identified as a marker of a subset of regulatory T cells (Treg). In this study, we have investigated the presence and the suppressive function of Treg cells in the celiac small intestinal mucosa, their correlation with the disease state, and the inducibility by gliadin in an organ culture system; moreover, we tried to define whether interleukin 15 (IL-15), overexpressed in CD, could influence the regulatory activity of such cells.
Potential celiacs have the celiac type HLA, positive anti-transglutaminase antibodies but no damage at small intestinal mucosa. Only a minority of them develops mucosal lesion. More than 40 genes were associated to Celiac Disease (CD) but we still do not know how those pathways transform a genetically predisposed individual into an affected person. The aim of the study is to explore the genetic features of Potential CD individuals.
Damage to intestinal mucosa in celiac disease (CD) is mediated both by inflammation due to adaptive and innate immune responses, with IL-15 as a major mediator of the innate immune response, and by proliferation of crypt enterocytes as an early alteration of CD mucosa causing crypts hyperplasia. We have previously shown that gliadin peptide P31-43 induces proliferation of cell lines and celiac enterocytes by delaying degradation of the active epidermal growth factor receptor (EGFR) due to delayed maturation of endocytic vesicles. IL-15 is increased in the intestine of patients affected by CD and has pleiotropic activity that ultimately results in immunoregulatory cross-talk between cells belonging to the innate and adaptive branches of the immune response. Aims of this study were to investigate the role of P31-43 in the induction of cellular proliferation and innate immune activation.
Celiac disease (CD) is characterized by an inflammatory response to wheat gluten, rye, and barley proteins. Fermentation of wheat flour with sourdough lactobacilli and fungal proteases decreases the concentration of gluten. We evaluated the safety of daily administration of baked goods made from this hydrolyzed form of wheat flour to patients with CD.
Celiac disease is characterized by the secretion of IgA-class autoantibodies that target tissue transglutaminase (tTG). It is now recognized that anti-tTG antibodies are functional and not mere bystanders in the pathogenesis of celiac disease. Here we report that interaction between anti-tTG antibodies and extracellular membrane-bound tTG inhibits peptide 31-43 (but not peptide 57-68) uptake by cells, thereby impairing the ability of p31-43 to drive Caco-2 cells into S-phase. This effect did not involve tTG catalytic activity. Because anti-tTG antibodies interfered with epidermal growth factor endocytosis, we assume that they exert their effect by reducing peptide 31-43 endocytosis. Our results suggest that cell-surface tTG plays a hitherto unknown role in the regulation of gliadin peptide uptake and endocytosis.
Celiac Disease (CD) is both a frequent disease (1:100) and an interesting model of a disease induced by food. It consists in an immunogenic reaction to wheat gluten and glutenins that has been found to arise in a specific genetic background; however, this reaction is still only partially understood. Activation of innate immunity by gliadin peptides is an important component of the early events of the disease. In particular the so-called "toxic" A-gliadin peptide P31-43 induces several pleiotropic effects including Epidermal Growth Factor Receptor (EGFR)-dependent actin remodelling and proliferation in cultured cell lines and in enterocytes from CD patients. These effects are mediated by delayed EGFR degradation and prolonged EGFR activation in endocytic vesicles. In the present study we investigated the effects of gliadin peptides on the trafficking and maturation of endocytic vesicles.
Celiac disease (CD) is an enteropathy triggered by gluten and mediated by CD4+ T cells. A complete understanding of CD immunopathogenesis has been hindered due to the lack of adequate in vivo models. Here, we explored the effect of the inhibition of COX by indomethacin in wheat gliadin-sensitized transgenic mice expressing the HLA-DQ8 heterodimer, a molecule associated with CD. Treated mice showed a gliadin-specific immune response with a significant reduction of villus height, not linked to crypt hyperplasia and to expansion of intraepithelial T cells. Notably, treated mice showed increased numbers of CD25+ and apoptotic cells in the lamina propria, whereas high basal levels of IFN-gamma secretion, along with a reduced gliadin-specific IL-2 expression were detected in MLN. Biochemical assessment of the lesion revealed increased mRNA of Lamb3 and Adamts2, encoding for ECM proteins, and enhanced activities of metalloproteinases MMP1, 2 and 7. We conclude that an intestinal sensitivity to gliadin, in connection with COX inhibition, caused a decreased villus height in DQ8 tg mice. The lesion was induced by a deregulated mucosal cell immunity to gliadin, thus triggering activation of a specific ECM protein pathway responsible for lamina propria remodeling.
The identification of gluten peptides eliciting intestinal T cell responses is crucial for the design of a peptide-based immunotherapy in celiac disease (CD). To date, several gluten peptides have been identified to be active in CD. In the present study, we investigated the recognition profile of gluten immunogenic peptides in adult HLA-DQ2(+) celiac patients. Polyclonal, gliadin-reactive T cell lines were generated from jejunal mucosa and assayed for both proliferation and IFN-gamma production in response to 21 peptides from wheat glutenins and alpha-, gamma-, and omega-gliadins. A magnitude analysis of the IFN-gamma responses was performed to assess the hierarchy of peptide potency. Remarkably, 12 of the 14 patients recognized a different array of peptides. All alpha-gliadin stimulatory peptides mapped the 57-89 N-terminal region, thus confirming the relevance of the known polyepitope 33-mer, although it was recognized by only 50% of the patients. By contrast, gamma-gliadin peptides were collectively recognized by the great majority (11 of 14, 78%) of CD volunteers. A 17-mer variant of 33-mer, QLQPFPQPQLPYPQPQP, containing only one copy of DQ2-alpha-I and DQ2-alpha-II epitopes, was as potent as 33-mer in stimulating intestinal T cell responses. A peptide from omega-gliadin, QPQQPFPQPQQPFPWQP, although structurally related to the alpha-gliadin 17-mer, is a distinct epitope and was active in 5 out of 14 patients. In conclusion, these results showed that there is a substantial heterogeneity in intestinal T cell responses to gluten and highlighted the relevance of gamma- and omega-gliadin peptides for CD pathogenesis. Our findings indicated that alpha-gliadin (57-73), gamma-gliadin (139-153), and omega-gliadin (102-118) are the most active gluten peptides in DQ2(+) celiac patients.
Celiac disease (CD) is an intestinal inflammatory condition that develops in genetically susceptible individuals after exposure to dietary wheat gliadin. The role of post-translational modifications of gliadin catalyzed by tissue transglutaminase (tTG) seems to play a crucial role in CD. However, it remains to be established how and where tTG is activated in vivo. We have investigated whether gliadin peptides modulate intracellular Ca(2+) homeostasis and tTG activity.
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