Peptic-tryptic Digest Research Articles

Phosphatidylcholine Surface Hydration-Dependent Adsorption to Mucin Enhances Intestinal Mucus Barrier Function.

The crucial role of zwitterionic phosphatidylcholines (PC) within mucus gel is essential for maintaining intestinal homeostasis, while the underlying mechanism remains incompletely understood. Herein, we compared the dynamic interfacial adsorption behavior of saturated dipalmitoylphosphatidylcholine (DPPC) and unsaturated dioleoylphosphatidylcholine (DOPC) to intestinal mucin and their impact on the intestinal mucus barrier function. Results of quartz crystal microbalance with dissipation showed that the highly surface-hydrated DPPC vesicles exhibited significantly faster and more extensive adsorption to purified intestinal mucin than the slightly surface-hydrated DOPC vesicles. Utilizing an intestinal Caco-2/HT29-MTX coculture model, we observed that DPPC vesicles adsorbed much more to the mucus gel compared to DOPC vesicles. Additionally, DPPC vesicle adsorption displayed increased wetting, and converse for DOPC vesicles. Interestingly, both of them exhibited nearly the same protective effects against cell injury induced by peptic-tryptic digests of gliadin (PTG). The partial mechanism involved the binding of PTG to DPPC and DOPC within the mucus gel, thereby restricting PTG contact with the underlying epithelial cells. These findings shed light on the intricate interfacial dynamics of PC adsorption to mucin and their implications for maintaining the integrity of the intestinal mucus barrier.

An essential role of adenosine deaminase acting on RNA 1 in coeliac disease mucosa.

Type I interferons (IFNs) are highly expressed in the gut mucosa of celiac disease (CD) gut mucosa and stimulates immune response prompted by gluten ingestion, but the processes that maintain the production of these inflammatory molecules are not well understood. Adenosine deaminase acting on RNA 1 (ADAR1), an RNA-editing enzyme, plays a crucial role in inhibiting self or viral RNAs from activating auto-immune mediated responses, most notably within the type-I IFN production pathway. The aim of this study was to assess whether ADAR1 could contribute to the induction and/or progression of gut inflammation in patients with celiac disease. ADAR1 expression was assessed by Real time PCR and Western blotting in duodenal biopsy taken from inactive and active celiac disease (CD) patients and normal controls (CTR). To analyze the role of ADAR1 in inflamed CD mucosa, lamina propria mononuclear cells (LPMC) were isolated from inactive CD and ADAR1 was silenced in with a specific antisense oligonucleotide (AS) and then incubated with a synthetic analogue of viral dsRNA (poly I:C). IFN-inducing pathways (IRF3, IRF7) in these cells were evaluated with Western blotting and inflammatory cytokines were evaluated with flow cytometry. Lastly, the role of ADAR1 was investigated in a mouse model of poly I:C-driven small intestine atrophy. Reduced ADAR1 expression was seen in duodenal biopsies compared to inactive CD and normal controls. Ex vivo organ cultures of duodenal mucosal biopsies, taken from inactive CD patients, stimulated with a peptic-tryptic digest of gliadin displayed a decreased expression of ADAR1. ADAR1 silencing in LPMC stimulated with a synthetic analogue of viral dsRNA strongly boosted the activation of IRF3 and IRF7 and the production of type-I IFN, TNF-α and IFN-γ. Administration of ADAR1 antisense but not sense oligonucleotide to mice with poly I:C-induced intestinal atrophy, significantly increased gut damage and inflammatory cytokines production. These data show that ADAR1 is an important regulator of intestinal immune homeostasis and demonstrate that defective ADAR1 expression could provide to amplifying pathogenic responses in CD intestinal mucosa.

Abstract 154: Endothelial Dysfunction In Experimental Celiac Disease Is Mediated By Gut-Derived Vascular Inflammation And Oxidative Stress

Objective: Celiac disease (CeD) is an autoimmune enteropathy triggered by dietary gluten, with a prevalence around 1%. Since many patients show heterogeneous symptoms, it is vastly underdiagnosed and yet without any treatment option besides lifelong gluten restriction. Vascular function in CeD patients compared to healthy controls has been assessed and hypothesized CeD as a cardiovascular risk factor. Herewith we aimed to explore the cardiovascular effects of CeD in a murine model, with special emphasis on endothelial dysfunction, vascular inflammation, and oxidative stress, known triggers for cardiovascular disease. Methods: NOD.DQ8 mice were raised on a zein-based, gluten-free diet. During the experiment, mice received gavage with peptic-tryptic digest of gliadin and were switched to a gluten-containing diet (Gliadin group). A control group (Zein group) was continued on gluten-free diet and received accordingly digested zein. Results: Blood pressure measurements revealed arterial hypertension in the Gliadin group. Endothelium-dependent relaxation was impaired in the Gliadin group compared to Zein, whereas no change in endothelium-independent was observed, tested by isometric tension recordings. Pro-inflammatory genes, like Tnfa and Nox2 were upregulated in the Gliadin group measured by quantitative rtPCR in aortic and intestinal tissue. Infiltration by intraepithelial T-lymphocytes into the epithelium of the small intestine was shown by IHC. In cardiac tissue, gliadin-treatment increased the oxidative stress parameters 3-nitrotyrosine and 4-hydroxy-2-nonenal shown in dot blots. To investigate the inflammatory link between gut and the cardiovascular system plasma proteomics were performed and revealed elevated levels of IL-17A. Conclusion: CeD is a cardiovascular risk factor. However, the mechanism remains unresolved. In a mouse model, we demonstrate that gluten treatment elevates blood pressure and impairs vascular function. Intestinal inflammation conveys to the cardiovascular system, leads to oxidative stress, and thereby impairs endothelial function. A potential mediator might be IL-17A, whose role in other autoimmunity-based cardiovascular risk factors (e.g., psoriasis) has already been demonstrated.

Gliadin Peptide P31-43 Induces mTOR/NFkβ Activation and Reduces Autophagy: The Role of Lactobacillus paracasei CBA L74 Postbiotc.

Celiac disease (CD) is an autoimmune disease characterized by an altered immune response stimulated by gliadin peptides that are not digested and cause damage to the intestinal mucosa. The aim of this study was to investigate whether the postbiotic Lactobacillus paracasei (LP) could prevent the action of gliadin peptides on mTOR, autophagy, and the inflammatory response. Most of the experiments performed were conducted on intestinal epithelial cells Caco-2 treated with a peptic-tryptic digest of gliadin (PTG) and P31-43. Furthermore, we pretreated the Caco-2 with the postbiotic LP before treatment with the previously described stimuli. In both cases, we evaluated the levels of pmTOR, p70S6k, and p4EBP-1 for the mTOR pathway, pNFkβ, and pERK for inflammation and LC 3 and p62 for autophagy. For autophagy, we also used immunofluorescence analysis. Using intestinal organoids derivate from celiac (CD) patients, we analyzed the effect of gliadin after postbiotic pretreatment with LP on inflammation marker NFkβ. Through these experiments, we showed that gliadin peptides are able to induce the increase of the inflammatory response in a more complex model of intestinal epithelial cells. LP postbiotic was able to induce autophagy in Caco-2 cells and prevent gliadin effects. In conclusion, postbiotic pretreatment with LP could be considered for in vivo clinical trials.

Activity of the peptic-tryptic caseinate digest with caseinate oligochitosan-glycation in rat intestinal epithelial (IEC-6) cells via the Wnt/β-catenin signaling pathway

The caseinate and glycated caseinate generated from the transglutaminase-catalyzed reaction of caseinate and oligochitosan were digested using pepsin and trypsin, and the activity of the resultant digests was measured in rat intestinal epithelial cell line (IEC-6) using several biological responses as indicators. Compared with the caseinate digest, the glycated caseinate digest had similar contents in 17 amino acids but less reactable –NH2 contents, and 6.57 g glucosamine per kg protein; moreover, it showed higher activity in the cells (P < 0.05) to promote cell growth, accumulate the cell-cycle progression at the S-phase, and prevent the camptothecin-induced cell apoptosis. The glycated caseinate digest also showed higher differentiation activity in the cells than the caseinate digest, resulting in enhanced activities of the three brush-border membrane enzymes (P < 0.05) and increased microvilli on the cell surfaces. The real-time reverse transcription-polymerase chain reaction, Western-blot assay, and Dickkopf-1 (a receptor inhibitor of the Wnt/β-catenin signaling pathway) were used to determine both gene and protein expression changes in the cells. A Wnt/β-catenin signaling pathway responsible for these enhanced effects was proposed because the five genes (glycogen synthase kinase 3β, Wnt3a, β-catenin, c-Myc, and cyclin D1) and three proteins (nuclear and cytosolic β-catenin, cyclin D1, and c-Myc) as part of this signaling pathway were regulated in the treated cells. The oligochitosan glycation of caseinate induced by transglutaminase is thus suggested endowing the peptic-tryptic caseinate digest with higher activity in the cells through its effects on the Wnt/β-catenin signaling pathway.

The murine enterocyte cell line Mode-K is a novel and reliable in vitro model for studies on gluten toxicity

The resemblance of physiological traits of cell lines with their target/original tissue is an important prerequisite for the choice of the in vitro model. Although cytoprotective defenses, activated by the nuclear factor erythroid 2-related factor2 (Nrf2), have a preeminent importance in intestinal protection, nevertheless their levels inin vitro models have been never compared with those of their original tissue.Basal level of Nrf2-mediated defenses in murine enterocyte cells (Mode-K) and in human colon adenocarcinoma cells -at differentiated (DCaco2) or confluent stage (CCaco2)- were compared with those found in mouse or human duodenum. The pro-oxidant and cytotoxic effects of peptic-tryptic digest of gluten prepared from wheat bread (PT-b), einkorn (PT-e) or durum wheat (PT-d) were evaluated in Mode-k and DCaco2 by combining enzymatic, immune-enzymatic and real-time PCR assay.The results presented reveal that Mode-k cells resemble cytoprotective defenses of human/murine duodenum and are more susceptible to pro-oxidant, cytotoxic and pro-inflammatory effect of gliadin digest (in comparison with Caco2). Prolamins digests from the considered wheat exhibit different inhibitory effect on Nrf2-mediated defenses (PT-b > PT-e > PT-d). These data indicate, for the first time, that Mode-k are a reliable model for investigating wheat prolamins toxicity and for evaluating the signaling pathway of gluten-associated disease.

Protective Effects of Aryl Hydrocarbon Receptor Signaling in Celiac Disease Mucosa and in Poly I:C-Induced Small Intestinal Atrophy Mouse Model

Aryl hydrocarbon receptor (AhR), a transcription factor activated by a large number of natural and synthetic agents, modulates the activity of immune cells in the gut and represents an important link between the environment and immune-mediated pathologies. In this study, we investigated the role of AhR in celiac disease (CD), a gluten-driven enteropathy. AhR expression was evaluated in intestinal biopsies taken from patients with CD and controls by real-time polymerase chain reaction (PCR), immunohistochemistry and flow cytometry. AhR was also analyzed in ex vivo organ cultures of duodenal biopsies taken from inactive CD patients incubated in presence or absence of peptic-tryptic digest of gliadin. IFN-γ, TNF-α, granzyme B, and perforin expression was evaluated in anti-CD3/CD28-activated intestinal lamina propria mononuclear cells (LPMC) and intestinal intra-epithelial cells (IEL) of active CD patients cultured in the presence or absence of the AhR agonist 6-formylindolo(3, 2-b)carbazole (Ficz). Finally, the protective role of AhR was evaluated in a mouse model of poly I:C-driven small intestine damage. AhR RNA transcripts were reduced in active CD samples as compared to inactive CD and normal controls. Flow cytometry confirmed such results and showed a reduction of AhR in both IEL and LPMC of active CD patients. The addition of a peptic-tryptic digest of gliadin to ex vivo organ cultures of duodenal biopsies taken from inactive CD patients reduced AhR expression. Treatment of CD IEL and LPMC with Ficz reduced the levels of inflammatory cytokines, granzyme B and perforin. Mice injected with Ficz were protected against poly I:C-induced intestinal lesions. Our findings suggest that defective AhR-driven signals could contribute to amplify pathogenic responses in the gut of CD patients.

Similar Responses of Intestinal T Cells From Untreated Children and Adults With Celiac Disease to Deamidated Gluten Epitopes

Celiac disease is a chronic small intestinal inflammatory disorder mediated by an immune response to gluten peptides in genetically susceptible individuals. Celiac disease is often diagnosed in early childhood, but some patients receive a diagnosis late in life. It is uncertain whether pediatric celiac disease is distinct from adult celiac disease. It has been proposed that gluten-reactive T cells in children recognize deamidated and native gluten epitopes, whereas T cells from adults only recognize deamidated gluten peptides. We studied the repertoire of gluten epitopes recognized by T cells from children and adults. We examined T-cell responses against gluten by generating T-cell lines and T-cell clones from intestinal biopsies of adults and children and tested proliferative response to various gluten peptides. We analyzed T cells from 14 children (2-5 years old) at high risk for celiac disease who were followed for celiac disease development. We also analyzed T cells from 6 adults (26-55 years old) with untreated celiac disease. All children and adults were positive for HLA-DQ2.5. Biopsies were incubated with gluten digested with chymotrypsin (modified or unmodified by the enzyme transglutaminase 2) or the peptic-tryptic digest of gliadin (in native and deamidated forms) before T-cell collection. Levels of T-cell responses were higher to deamidated gluten than to native gluten in children and adults. T cells from children and adults each reacted to multiple gluten epitopes. Several T-cell clones were cross-reactive, especially clones that recognized epitopes from γ-and ω-gliadin. About half of the generated T-cell clones from children and adults reacted to unknown epitopes. T-cell responses to different gluten peptides appear to be similar between adults and children at the time of diagnosis of celiac disease.

Identification of coeliac disease triggering glutenin peptides in adults

ABSTRACTObjective: Coeliac disease affects approximately 1% of Northern American and European populations. It is caused by an inappropriate immune response to dietary gluten. Gluten comprises of two major protein fractions: gliadins and glutenins. Glutenins have recently been found to be toxic to coeliac individuals. Proliferation assays suggest in some but not all paediatric coeliac individuals there may be immunological stimulation with high molecular weight (HMW) glutenins. Less evidence pertains to low molecular weight (LMW) glutenins. The aim is to assess adaptive, T-cell driven, and innate immune response in adult coeliac individuals towards HMW glutenin peptide, glut04, and LMW glutenin peptide, glt156.Materials and methods: Coeliac patients were recruited attending endoscopy for routine monitoring. Adaptive immune response towards glut04 and glt156 was measured by proliferation assays and measurement of interferon-γ secretion in 28 T-cell lines. The innate immune response was assessed by measurement of enterocyte cell height (ECH) in coeliac small intestinal biopsies following overnight incubation in organ culture chambers in a further nine individuals.Results: There were 3/28 and 2/28 positive proliferation results using gluten-sensitive T-cells with glut04 and glt156, respectively. All coeliac biopsies tested in organ culture chambers demonstrated clear reduction in ECH with peptic-tryptic digest of whole industrial gluten, glut04 and glt156 when compared to negative control ovalbumin (p < 0.005). Three individuals had both T-cell and organ culture study data. Their proliferation assays showed no stimulation of the T-cells.Conclusions: This study demonstrates glutenin epitopes glut04 and glt156, while minor T-cell epitopes, are important in their ability to trigger the innate immune response.

Intestinal titres of anti-tissue transglutaminase 2 antibodies correlate positively with mucosal damage degree and inversely with gluten-free diet duration in coeliac disease.

It has always been known that anti-tissue transglutaminase 2 (anti-TG2) antibodies are produced in the small intestine. Their serum titres correlate with mucosal damage degree and decrease on a gluten-free diet (GFD). We aimed to correlate intestinal anti-TG2 antibodies levels with degree of mucosal damage and GFD duration. Thirty-four active, 71 potential and 24 CD patients on GFD for at least 2 years were enrolled. Anti-TG2 deposits were detected in intestinal biopsies by double immunofluorescence. Biopsies were cultured for 24 h with medium, and with gliadin peptic tryptic digest (PTG) or A-gliadin peptide 31-43 (P31-43). Anti-TG2 antibodies secreted into supernatants were measured by enzyme-linked immunosorbent assay (ELISA). All active CD patients secreted high titres of anti-TG2 antibodies into culture medium that increased with the worsening of mucosal injury (Spearman's r = 0·71; P < 0·0001). Seventy of 71 potential CD patients and 15 of 24 treated CD patients secreted low titres of anti-TG2 antibodies into supernatants, eight of nine negative treated patients being on GFD for more than 10 years. An inverse correlation between antibody titres and duration of GFD was found, (Spearman's r = -0·52; P < 0·01). All active, 53 of 71 potential and six of 24 treated, CD patients showed anti-TG2 mucosal deposits. Five of six positive treated CD patients had been on GFD for fewer than 6 years and were also positive for secreted anti-TG2. In treated patients, PTG/P31-43 was not able to induce secretion of anti-TG2 antibodies into culture medium. Measurement of anti-TG2 antibodies in biopsy supernatants proved to be more sensitive than detection by immunofluorescence to reveal their intestinal production. Intestinal antiTG2 antibodies titres correlated positively with the degree of mucosal damage and inversely with the duration of GFD.

Increase in Neuroendocrine Cells in the Duodenal Mucosa of Patients with Refractory Celiac Disease

Several immune-mediated gastrointestinal disorders, including celiac disease (CD), are associated with neuroendocrine cell hyperplasia. However, neuroendocrine cells have never been explored in refractory CD (RCD). Serial duodenal sections from 17 patients with RCD (6 type 1 and 11 type 2), 16 uncomplicated CD patients before and after gluten-free diet, 14 patients with potential CD, 27 patients with non-CD villous atrophy, i.e., common variable immunodeficiency (n=12), Whipple's disease (n=10) and giardiasis (n=5), and 16 healthy subjects were processed for the immunohistochemical detection of chromogranin A (CgA), serotonin, and somatostatin. Mucosal tryptophan hydroxylase (TpH)-1 and serotonin-selective reuptake transporter (SERT) transcripts were measured by quantitative reverse transcription-PCR. Serum CgA and 24-h urine 5-hydroxyindoleacetic acid (5-HIAA) were assessed. Biopsies from treated CD patients were cultured with serotonin or peptic tryptic digest of gliadin (PT-gliadin), and interferon (IFN)-γ was detected by ELISA in culture supernatants. Epithelial cells positive for CgA and serotonin, but not somatostatin, were significantly increased in RCD. Raised mucosal transcripts of TpH-1, but not SERT, were found in RCD. On biopsies from treated CD patients, serotonin upregulated IFN-γ production at levels comparable to those induced by PT-gliadin. Serum CgA, but not urine 5-HIAA, was increased in RCD. No significant difference was found between RCD type 1 and type 2 in terms of neuroendocrine cells, mucosal TpH-1 transcripts, and serum CgA. Serotonin-producing neuroendocrine cells are increased in RCD mucosa. IFN-γ upregulation induced by serotonin suggests that this monoamine may have a role in sustaining the local inflammatory response in CD.

Elevated CD8 T cell responses in type 1 diabetes patients to a 13 amino acid coeliac-active peptide from α-gliadin

Some type 1 diabetes (T1D) patients have been reported to exhibit T cell reactivity to wheat gluten. We tested the hypothesis that this T cell reactivity could be abolished by using prolyl-endopeptidase (PEP), an enzyme that cleaves peptide bonds after proline. Peripheral blood mononuclear cells (PBMCs) were isolated from T1D patients and healthy controls. PBMCs were stimulated with a peptic-tryptic digest of wheat gluten; a peptic-tryptic-PEP digest of wheat gluten; and a 13 amino acid peptide from wheat gluten. Fluorescent-labelled antibodies to CD3, CD4 and CD8 cell marker proteins were utilized to determine proliferative responses of CD3, CD4 and CD8 T cells. There were no significant differences in proliferative responses of CD3 or CD4 T cells to the wheat gluten antigens. A significantly higher proportion of CD8(+) T cells from T1D patients proliferated in the presence of the 13 amino acid peptide than when challenged with the peptic-tryptic or the peptic-tryptic-PEP digests of wheat gluten. PEP treatment had no significant effect on CD8 T cell reactivity to the peptic-trytic digest of wheat gluten. Our results suggest that wheat gluten-derived peptides, containing ≤ 13 amino acids, may evoke T cell responses in T1D patients.

Two wheat decapeptides prevent gliadin-dependent maturation of human dendritic cells

Celiac disease (CD) is a small intestinal enteropathy, triggered in susceptible individuals by the ingestion of dietary gluten.Dendritic cells (DC) are instrumental in the generation and regulation of immune responses and oversee intestinal immune homeostasis promoting and maintaining oral tolerance to food antigens.The aim of this study was to monitor the effect of peptic-tryptic digest of gliadin (PT-gliadin) on the maturation of human monocyte-derived DC and the impact of pDAV and pRPQ decapeptides in the modulation of PT-gliadin-induced phenotypic and functional DC maturation.Immature DC (iDC) were challenged in vitro with PT-gliadin. In some experiments iDC were pre-treated with pDAV or pRPQ and after 2h PT-gliadin was added to the cultures.We found that PT-gliadin up-regulates the expression of the maturation markers HLA-DR, CD83, CD80 and CD86. The functional consequence of PT-gliadin treatment of iDC is a significant increase in IL-12, TNF-alpha production as well as in their T cell stimulatory capacity. On the contrary, the digest of zein had no effect on DC maturation. Interestingly, we found that pre-treatment of iDC with pDAV or pRPQ decapeptides significantly prevents the functional maturation of DC induced by PT-gliadin. On the other hand, pDAV and pRPQ did not revert the PT-gliadin-induced phenotypic maturation of DC.Here we report, for the first time, that naturally occurring peptides are able to prevent the gliadin-dependent DC maturation. This finding could have implication for CD, raising the perspective of a potential therapeutic strategy alternative to a gluten free diet.

Diversity of oat varieties in eliciting the early inflammatory events in celiac disease

Purpose Celiac disease (CD) is an autoimmune enteropathy, triggered by dietary gluten. The only treatment is a strict gluten-free diet. Oats are included in the list of gluten-free ingredients by European Regulation, but the safety of oats in CD is still a matter of debate. The present study examined the capability of different oat cultivars of activating the gliadin-induced transglutaminase-2 (TG2)-dependent events in some in vitro models of CD. In addition, we compared this capability with the electrophoresis pattern of peptic–tryptic digests of the proteins of the oat cultivars.MethodsK562(S) cells agglutination, transepithelial electrical resistance of T84-cell monolayers, intracellular levels of TG2 and phosphorylated form of protein 42–44 in T84 cells were the early gliadin-dependent events studied.ResultsThe results showed that the Nave oat cultivar elicited these events, whereas Irina and Potenza varieties did not. The ability of a cultivar to activate the above-described events was associated with the electrophoretic pattern of oat proteins and their reactivity to anti-gliadin antibodies.ConclusionWe found significant differences among oat cultivars in eliciting the TG2-mediated events of CD inflammation. Therefore, the safety of an oat cultivar in CD might be screened in vitro by means of biochemical and biological assays, before starting a clinical trial to definitely assess its safety.

Altered Expression of Type-1 and Type-2 Cannabinoid Receptors in Celiac Disease

Anandamide (AEA) is the prominent member of the endocannabinoid family and its biological action is mediated through the binding to both type-1 (CB1) and type-2 (CB2) cannabinoid receptors (CBR). The presence of AEA and CBR in the gastrointestinal tract highlighted their pathophysiological role in several gut diseases, including celiac disease. Here, we aimed to investigate the expression of CBR at transcriptional and translational levels in the duodenal mucosa of untreated celiac patients, celiac patients on a gluten-free diet for at least 12 months and control subjects. Also biopsies from treated celiac patients cultured ex vivo with peptic-tryptic digest of gliadin were investigated. Our data show higher levels of both CB1 and CB2 receptors during active disease and normal CBR levels in treated celiac patients. In conclusion, we demonstrate an up-regulation of CB1 and CB2 mRNA and protein expression, that points to the therapeutic potential of targeting CBR in patients with celiac disease.

IL-15 positively regulates IL-21 production in celiac disease mucosa.

Celiac disease (CD)-associated inflammation is characterized by high interleukin- 21 (IL-21), but the mechanisms that control IL-21 production are not fully understood. Here we analyzed IL-21 cell sources and examined how IL-21 production is regulated in CD. Intraepithelial lymphocytes (IELs) and lamina propria lymphocytes (LPLs), isolated from CD patients and non-CD controls, were analyzed for cell markers, cytokines, and transcription factors by flow cytometry. IL-21 was highly produced by CD4+ and CD4+/CD8+ IELs and LPLs in active CD. IL-21-producing cells coexpressed interferon-γ (IFN-γ) and to a lesser extent T helper type 17 (Th17) cytokines. Treatment of control LPLs with IL-15, a cytokine overproduced in CD, activated Akt and STAT3 (signal transducer and activator of transcription 3), thus enhancing IL-21 synthesis. Active CD biopsies contained elevated levels of Akt, and blockade of IL-15 in those samples reduced IL-21. Similarly, neutralization of IL-15 in biopsies of inactive CD patients inhibited peptic-tryptic digest of gliadin-induced IL-21 expression. These findings indicate that in CD, IL-15 positively regulates IL-21 production.

Gluten Fragment Detection with a Competitive ELISA

The second generation of a competitive ELISA for prolamin quantification based on the R5 antibody was studied for method performance and suitability to detect partially hydrolyzed prolamins in food. To be able to convert signal intensities to gluten concentrations, as required by the Codex Alimentarius Standard, a new calibrator consisting of a peptic-tryptic digest of wheat, rye, and barley prolamins was used for the first time. LOD and LOQ of the assay were 1.36 and 5.0 mg prolamin/kg food, respectively. Analysis of beer samples and a hydrolyzed wheat product showed that the assay provided significantly higher prolamin concentrations, compared to the sandwich ELISA based on the same antibody, which is only suitable for the detection of intact prolamins. Spiking experiments with defined concentrations of partially hydrolyzed prolamins gave recoveries ranging from 92 to 136%.

Early tissue transglutaminase–mediated response underlies K562(S)-cell gliadin-dependent agglutination

[corrected] K562(S) agglutination has been used as a rapid and economic tool for the in vitro screening of the toxicity of cereal fractions and prolamins in celiac disease (CD). A strict correlation has been reported between the toxicity of cereals and cereal fractions for celiac patients and their ability to agglutinate K562(S) cells. Whether this specificity of K562(S)-cell agglutination is caused by the activation of the same pathogenic events triggered by toxic cereal fractions in CD intestine or simply represents a bystander event of gluten toxicity is, however, unknown. K562(S) cells were incubated in vitro with the peptic-tryptic digest of wheat gliadin. The agglutination of K562(S) cells by wheat gliadin peptides is orchestrated by a cascade of very early events occurring at the K562(S)-cell surface similar to those occurring at the intestinal epithelial surface. They involve a rapid increase in intracellular calcium levels that activate tissue transglutaminase (TG2), leading to a rapid actin reorganization that is pivotal in driving cell agglutination. These specific effects of toxic cereals are phenocopied by the gliadin-derived peptide p31-43, which orchestrates the activation of innate response to gliadin in CD. Our study provides the rationale for the extensive use of K562(S)-cell agglutination as a valuable tool for screening cereal toxicity.

Maize Prolamins Resistant to Peptic-tryptic Digestion Maintain Immune-recognition by IgA from Some Celiac Disease Patients

Maize is used as an alternative to wheat to elaborate food stuffs for celiac patients in a gluten-free diet.However, some maize prolamins (zeins) contain amino acid sequences that resemble the wheat gluten immunodominant peptides and their integrity after gastrointestinal proteolysisis unknown. In this study, the celiac IgA-immunoreactivity to zeins from raw or nixtamalized grains, before and after peptic/tryptic digestion was evaluated and their possible immunogenicity was investigated by in silico methods.IgA from some celiac patients with HLA-DQ2 or DQ8 haplotypes recognized two alpha-zeins even after peptic/ tryptic proteolysis. However, digestion affected zeins after denaturation, reduction, and alkylation, used for identification of prolamins as alpha-zein A20 and A30 by MS/MS sequencing. An in silico analysis indicated that other zeins contain similar sequences, or sequences that may bind even better to the HLA-DQ2/DQ8 molecules compared to the already identified ones. Results concur to indicate that relative abundance of these zeins, along with factors affecting their resistance to proteolysis, may be of paramount clinical relevance, and the use of maize in the formulation and preparation of gluten-free foods must be reevaluated in some cases of celiac disease.

Abnormal anandamide metabolism in celiac disease

The endocannabinoid system has been extensively investigated in experimental colitis and inflammatory bowel disease, but not in celiac disease, where only a single study showed increased levels of the major endocannabinoid anandamide in the atrophic mucosa. On this basis, we aimed to investigate anandamide metabolism in celiac disease by analyzing transcript levels (through quantitative real-time reverse transcriptase–polymerase chain reaction), protein concentration (through immunoblotting) and activity (through radioassays) of enzymes responsible for anandamide synthesis (N-acylphosphatidyl-ethanolamine specific phospholipase D, NAPE-PLD) and degradation (fatty acid amide hydrolase, FAAH) in the duodenal mucosa of untreated celiac patients, celiac patients on a gluten-free diet for at least 12 months and control subjects. Also, treated celiac biopsies cultured ex vivo with peptic–tryptic digest of gliadin were investigated. Our in vivo experiments showed that mucosal NAPE-PLD expression and activity are higher in untreated celiac patients than treated celiac patients and controls, with no significant difference between the latter two groups. In keeping with the in vivo data, the ex vivo activity of NAPE-PLD was significantly enhanced by incubation of peptic–tryptic digest of gliadin with treated celiac biopsies. On the contrary, in vivo mucosal FAAH expression and activity did not change in the three groups of patients, and accordingly, mucosal FAAH activity was not influenced by treatment with peptic–tryptic digest of gliadin. In conclusion, our findings provide a possible pathophysiological explanation for the increased anandamide concentration previously shown in active celiac mucosa.