A decapeptide from durum wheat prevents celiac peripheral blood lymphocytes from activation by gliadin peptides

Glutamine-derived peptides: Current progress and future directions

Glutamine, the most abundant amino acid in the body, plays a critical role in preserving immune function, nitrogen balance, intestinal integrity, and resistance to infection. However, its limited solubility and instability present challenges for its use a functional nutrient. Consequently, there is a preference for utilizing glutamine-derived peptides as an alternative to achieve enhanced functionality. This article aims to review the applications of glutamine monomers in clinical, sports, and enteral nutrition. It compares the functional effectiveness of monomers and glutamine-derived peptides and provides a comprehensive assessment of glutamine-derived peptides in terms of their classification, preparation, mechanism of absorption, and biological activity. Furthermore, this study explores the potential integration of artificial intelligence (AI)-based peptidomics and synthetic biology in the de novo design and large-scale production of these peptides. The findings reveal that glutamine-derived peptides possess significant structure-related bioactivities, with the smaller molecular weight fraction serving as the primary active ingredient. These peptides possess the ability to promote intestinal homeostasis, exert hypotensive and hypoglycemic effects, and display antioxidant properties. However, our understanding of the structure-function relationships of glutamine-derived peptides remains largely exploratory at current stage. The combination of AI based peptidomics and synthetic biology presents an opportunity to explore the untapped resources of glutamine-derived peptides as functional food ingredients. Additionally, the utilization and bioavailability of these peptides can be enhanced through the use of delivery systems in vivo. This review serves as a valuable reference for future investigations of and developments in the discovery, functional validation, and biomanufacturing of glutamine-derived peptides in food science.

An Integrated Comprehensive Peptidomics and In Silico Analysis of Bioactive Peptide-Rich Milk Fermented by Three Autochthonous Cocci Strains

Bioactive peptides (BPs) are molecules of paramount importance with great potential for the development of functional foods, nutraceuticals or therapeutics for the prevention or treatment of various diseases. A functional BP-rich dairy product was produced by lyophilisation of bovine milk fermented by the autochthonous strains Lactococcus lactis subsp. lactis ZGBP5-51, Enterococcus faecium ZGBP5-52 and Enterococcus faecalis ZGBP5-53 isolated from the same artisanal fresh cheese. The efficiency of the proteolytic system of the implemented strains in the production of BPs was confirmed by a combined high-throughput mass spectrometry (MS)-based peptidome profiling and an in silico approach. First, peptides released by microbial fermentation were identified via a non-targeted peptide analysis (NTA) comprising reversed-phase nano-liquid chromatography (RP nano-LC) coupled with matrix-assisted laser desorption/ionisation-time-of-flight/time-of-flight (MALDI-TOF/TOF) MS, and then quantified by targeted peptide analysis (TA) involving RP ultrahigh-performance LC (RP-UHPLC) coupled with triple-quadrupole MS (QQQ-MS). A combined database and literature search revealed that 10 of the 25 peptides identified in this work have bioactive properties described in the literature. Finally, by combining the output of MS-based peptidome profiling with in silico bioactivity prediction tools, three peptides (75QFLPYPYYAKPA86, 40VAPFPEVFGK49, 117ARHPHPHLSF126), whose bioactive properties have not been previously reported in the literature, were identified as potential BP candidates.

Immunomodulatory peptides-A promising source for novel functional food production and drug discovery

Immunomodulatory peptides are a complex class of bioactive peptides that encompasses substances with different mechanisms of action. Immunomodulatory peptides could also be used in vaccines as adjuvants which would be extremely desirable, especially in response to pandemics. Thus, immunomodulatory peptides in food of plant origin could be regarded both as valuable suplements of novel functional food preparation and/or as precursors or possible active ingredients for drugs design for treatment variety of conditions arising from impaired function of immune system. Given variety of mechanisms, different tests are required to assess effects of immunomodulatory peptides. Some of those effects show good correlation with in vivo results but others, less so. Certain plant peptides, such as defensins, show both immunomodulatory and antimicrobial effect, which makes them interesting candidates for preparation of functional food and feed, as well as templates for design of synthetic peptides.

The use of peripheral blood mononuclear cells in celiac disease diagnosis and treatment

Introduction: Celiac disease is characterized by an abnormal immune activation driven by the ingestion of gluten from wheat, barley, and rye. Gluten-specific CD4⁺ T cells play an important role in disease pathogenesis and are detectable among peripheral blood mononuclear cells (PBMCs). Areas covered: This review summarizes the use of celiac disease patient PBMCs in clinical applications focusing on their exploitation in the development of diagnostic approaches and novel drugs to replace or complement gluten-free diet. Expert opinion: The most used PBMC-based methods applied in celiac disease research include ELISpot and HLA-DQ:gluten tetramer technology. ELISpot has been utilized particularly in research aiming to develop a celiac disease vaccine and in studies addressing the toxicity of different grains in celiac disease. HLA-DQ:gluten tetramer technology on the other hand initially focused on improving current diagnostics but in combination with additional markers it is also a useful outcome measure in clinical trials to monitor the efficacy of drug candidates. In addition, the technology serves well in the more detailed characterization of celiac disease-specific T cells, thereby possibly revealing novel therapeutic targets. Future studies may also reveal clinical applications for PBMC microRNAs and/or dendritic cells or monocytes present among PBMCs.

Despite sequence homologies to gluten, salivary proline-rich proteins do not elicit immune responses central to the pathogenesis of celiac disease

Celiac disease (CD) is an inflammatory disorder triggered by ingested gluten, causing immune-mediated damage to the small-intestinal mucosa. Gluten proteins are strikingly similar in amino acid composition and sequence to proline-rich proteins (PRPs) in human saliva. On the basis of this feature and their shared destination in the gastrointestinal tract, we hypothesized that salivary PRPs may modulate gluten-mediated immune responses in CD. Parotid salivary secretions were collected from CD patients, refractory CD patients, non-CD patients with functional gastrointestinal complaints, and healthy controls. Structural similarities of PRPs with gluten were probed with anti-gliadin antibodies. Immune responses to PRPs were investigated toward CD patient-derived peripheral blood mononuclear cells and in a humanized transgenic HLA-DQ2/DQ8 mouse model for CD. Anti-gliadin antibodies weakly cross-reacted with the abundant salivary amylase but not with PRPs. Likewise, the R5 antibody, recognizing potential antigenic gluten epitopes, showed negligible reactivity to salivary proteins from all groups. Inflammatory responses in peripheral blood mononuclear cells were provoked by gliadins whereas responses to PRPs were similar to control levels, and PRPs did not compete with gliadins in immune stimulation. In vivo, PRP peptides were well tolerated and nonimmunogenic in the transgenic HLA-DQ2/DQ8 mouse model. Collectively, although structurally similar to dietary gluten, salivary PRPs were nonimmunogenic in CD patients and in a transgenic HLA-DQ2/DQ8 mouse model for CD. It is possible that salivary PRPs play a role in tolerance induction to gluten early in life. Deciphering the structural basis for the lack of immunogenicity of salivary PRPs may further our understanding of the toxicity of gluten.

Current and emerging therapy for celiac disease

At present, strict and lifelong gluten-free diet is the only effective treatment for celiac disease. Even small amounts of gluten (50 mg/day) can be immunogenic; therefore all food and food items and drugs that contain gluten and its derivatives must be eliminated completely from the diet. While prescribing gluten-free diet is easy; the key to the success is the dietary counseling by a nutrition specialist and maintenance of adherence to GFD by the patient. In recent times, a number of targets to halt the process of immunological injury have been explored to find out alternative treatment for celiac disease. These targets include exploration of ancient wheat if they are less immunogenic, intra-luminal digestion of gluten using prolylendopeptidases, pretreatment of whole gluten with bacterial-derived peptidase before ingestion; prevention of passage of immunogenic peptides through the tight junctions such as zonulin antagonists, Blocking of HLA-DQ2 to prevent binding of immunogenic peptides, inhibition of transglutaminase 2, immune-modulation, and induction of tolerance to gluten using gluten tolerizing vaccines, use of gluten-sequestering polymers, use of anti-inflammatory drugs (glucocorticoids, budesonides) and anti-cytokines such as anti TNF-α, and anti-interleukin-15. While many of these targets are still in the pre-clinical phase, some of them including zonulin antagonist and endopeptidases have already reached phase II and phase III clinical trials. Furthermore, while these targets appear very exciting; they at best are likely to be used as adjunctive therapy rather than a complete replacement for gluten-free diet.

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.

Modulatory Effect of Gliadin Peptide 10-mer on Epithelial Intestinal CACO-2 Cell Inflammatory Response

Celiac Disease (CD) is a chronic inflammatory enteropathy, triggered in genetically susceptible individuals by dietary gluten. Gluten is able to elicit proliferation of specific T cells and secretion of inflammatory cytokines in the small intestine. In this study we investigated the possibility that p10-mer, a decapeptide from durum wheat (QQPQDAVQPF), which was previously shown to prevent the activation of celiac peripheral lymphocytes, may exert an inhibitory effect on peptic-tryptic digested gliadin (PT-Gly)-stimulated intestinal carcinoma CACO-2 cells. In these cells, incubated with PT-Gly or p31-43 α-gliadin derived peptide in the presence or in the absence of p10-mer, IRAK1 activation and NF-kB, ERK1/2 and p38 MAPK phosphorylation were measured by immunoblotting, Cyclooxigenase 2 (COX-2) activity by PGE-2 release assay, and production of cytokines in the cell supernatants by ELISA. Our results showed that pre-treatment of CACO-2 cells with p10-mer significantly inhibited IRAK1 activation and NF-kB, ERK1/2 and p38 MAPK phosphorylation, as well as COX-2 activity (i.e. PGE-2 release) and production of the IL-6 and IL-8 pro-inflammatory cytokines, induced by gliadin peptides. These findings demonstrate the inhibitory effect of the p10-mer peptide on inflammatory response in CACO-2 cells. The results of the present study show that this p10-mer peptide can modulate "in vitro" the inflammatory response induced by gliadin peptides, allowing to move towards new therapeutic strategies. Turning off the inflammatory response, may in fact represent a key target in the immunotherapy of celiac disease.

Nondietary therapies for celiac disease

Currently, the only available therapy for celiac disease is strict lifelong adherence to a gluten-free diet (GFD). Although safe and effective, the GFD is not ideal. It is frequently expensive, of limited nutritional value, and not readily available in many countries. Consequently, a need exists for novel, nondietary therapies for celiac disease. Based on the current understanding of celiac disease pathogenesis, several potential targets of therapeutic intervention exist. These novel strategies provide promise of alternative, adjunctive treatment options but also raise important questions regarding safety, efficacy, and monitoring of long-term treatment effect.

Gliadin peptides induce tissue transglutaminase activation and ER-stress through Ca2+ mobilization in Caco-2 cells

BACKGROUND

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.

METHODS/PRINCIPAL FINDINGS

We studied Ca(2+) homeostasis in Caco-2 cells by single cell microfluorimetry. Under our conditions, A-gliadin peptides 31-43 and 57-68 rapidly mobilized Ca(2+) from intracellular stores. Specifically, peptide 31-43 mobilized Ca(2+) from the endoplasmic reticulum (ER) and mitochondria, whereas peptide 57-68 mobilized Ca(2+) only from mitochondria. We also found that gliadin peptide-induced Ca(2+) mobilization activates the enzymatic function of intracellular tTG as revealed by in situ tTG activity using the tTG substrate pentylamine-biotin. Moreover, we demonstrate that peptide 31-43, but not peptide 57-68, induces an increase of tTG expression. Finally, we monitored the expression of glucose-regulated protein-78 and of CCAAT/enhancer binding protein-homologous protein, which are two biochemical markers of ER-stress, by real-time RT-PCR and western blot. We found that chronic administration of peptide 31-43, but not of peptide 57-68, induces the expression of both genes.

CONCLUSIONS

By inducing Ca(2+) mobilization from the ER, peptide 31-43 could promote an ER-stress pathway that may be relevant in CD pathogenesis. Furthermore, peptides 31-43 and 57-68, by activating intracellular tTG, could alter inflammatory key regulators, and induce deamidation of immunogenic peptides and gliadin-tTG crosslinking in enterocytes and specialized antigen-presenting cells.

Celiac disease in pediatric patients with autoimmune hepatitis: etiology, diagnosis, and management

Celiac disease (CD) is defined as a permanent intolerance to ingested wheat gliadins and other cereal prolamins, occurring in genetically susceptible people. Persistent elevation of serum aminotransferase activity is expression of liver damage related to CD, which occurs in two distinctive forms. The most frequent is a mild asymptomatic liver injury, with a moderate increase of serum aminotransferase activities and a mild inflammatory portal and lobular infiltrate on liver biopsy (celiac hepatitis), reversible on a gluten-free diet (GFD). More rarely, severe and progressive inflammatory liver damage, induced by an autoimmune process and identified as autoimmune hepatitis (AIH), can develop and it is generally unaffected by gluten withdrawal. Surveys that included only pediatric patients report a wide range of prevalence of CD in AIH of 11.5-46% (mean 21.5%). CD and AIH share selected combinations of genes coding for class II human leukocyte antigens, which could explain their coexistence. Increased intestinal permeability and circulation of anti-tissue transglutaminase (tTG) have also been considered as further potential causes of liver damage in CD patients. tTG in the liver and in other extraintestinal tissues could modify other external- or self-antigens and generate different neo-antigens, which are responsible for liver injury in patients with CD. Patients with AIH represent a population at high risk for developing CD; screening for CD should be integrated into the diagnostic routine of all patients with AIH, with or without gastrointestinal manifestations, before starting immunosuppressive treatments. The only currently available treatment for CD is the GFD and the supportive nutritional care for iron, calcium, and vitamin deficiencies. Due to the difficulties of a GFD, in the past decade researchers have become increasingly interested in therapeutic alternatives to continuous or intermittent use of a GFD in patients with CD. Interventions addressed to correct the defect in the intestinal barrier are currently at the most advanced stage of clinical trials. The impact of a GFD on the outcome of AIH is not clear but it seems to be ineffective in the treatment of AIH. The early detection and treatment of CD, however, may prevent progression to end-stage liver failure.

Pharmacotherapy and management strategies for coeliac disease

INTRODUCTION

Coeliac disease is a common disease that affects approximately 1% of Northern European and American populations. Evidence suggests it is caused by an inappropriate immune response in genetically susceptible patients to dietary gluten found in wheat, rye, barley and, in a small minority of patients, oats. Treatment involves a lifelong gluten-free diet. This diet limits nutritional variety and is costly and difficult to maintain.

AREAS COVERED

This review covers the current treatment options available and discusses novel emerging therapies for coeliac disease.

EXPERT OPINION

Novel therapies are still in early stages of development and therefore, at present, a gluten-free diet remains the treatment of choice in coeliac disease due to its low side-effect profile. A replacement for a gluten-free diet would be superior to an adjunct; in this case dietary modification of gluten may well have the least side effects, be tolerated by a wider group of coeliac patients and therefore be accepted. Search terms used: Pubmed, Medline and clinicaltrials.gov were searched with 'celiac disease' and 'therapy' as MESH terms. Patent database was searched using the term 'celiac disease'. Conference attendance at DDW Chicago 2011 and Columbia 2010 was also used to gain further information from conference abstracts.

Celiac disease: prevention and treatment

Celiac disease is a common multisystemic disorder that may be diagnosed at any age. Owing to the increasing prevalence, prevention strategies, including encouragement of breastfeeding and introduction of small amounts of gluten whereas still on breastfeeding at fourth to sixth month of age, become more important than before. For avoiding complications of celiac disease, a strict gluten-free diet is essential. A lifelong gluten-free diet may bring about difficulties as avoiding gluten completely is problematic owing to the contamination with gluten of presumably gluten free foods. New therapeutic approaches include enzyme supplementation, correction of the intestinal barrier defect against gluten entry, blocking of gliadin presentation by human leukocyte antigen blockers and tissue transglutaminase inhibitors.

Celiac disease: from pathogenesis to novel therapies

Celiac disease has become one of the best-understood HLA-linked disorders. Although it shares many immunologic features with inflammatory bowel disease, celiac disease is uniquely characterized by (1) a defined trigger (gluten proteins from wheat and related cereals), (2) the necessary presence of HLA-DQ2 or HLA-DQ8, and (3) the generation of circulating autoantibodies to the enzyme tissue transglutaminase (TG2). TG2 deamidates certain gluten peptides, increasing their affinity to HLA-DQ2 or HLA-DQ8. This generates a more vigorous CD4(+) T-helper 1 T-cell activation, which can result in intestinal mucosal inflammation, malabsorption, and numerous secondary symptoms and autoimmune diseases. Moreover, gluten elicits innate immune responses that act in concert with the adaptive immunity. Exclusion of gluten from the diet reverses many disease manifestations but is usually not or less efficient in patients with refractory celiac disease or associated autoimmune diseases. Based on the advanced understanding of the pathogenesis of celiac disease, targeted nondietary therapies have been devised, and some of these are already in phase 1 or 2 clinical trials. Examples are modified flours that have been depleted of immunogenic gluten epitopes, degradation of immunodominant gliadin peptides that resist intestinal proteases by exogenous endopeptidases, decrease of intestinal permeability by blockage of the epithelial ZOT receptor, inhibition of intestinal TG2 activity by transglutaminase inhibitors, inhibition of gluten peptide presentation by HLA-DQ2 antagonists, modulation or inhibition of proinflammatory cytokines, and induction of oral tolerance to gluten. These and other experimental therapies will be discussed critically.

Two prolamin peptides from durum wheat preclude celiac disease-specific T cell activation by gluten proteins

PURPOSE

Celiac disease (CD) is a permanent intolerance to wheat prolamins and related proteins displayed by genetically susceptible individuals. Blocking or modulation of CD-specific T cell response by altered prolamin peptides are currently considered as a potential alternative to the only effective therapy of CD based on a life-long gluten-free diet. Two prolamin peptides, the 9-mer ASRVAPGQQ and the 10-mer GTVGVAPGQQ sequences, were identified by mass spectrometry in the peptic/tryptic digest of prolamins (PTP) from durum wheat (Triticum turgidum ssp. durum) cv. Adamello, and investigated for their ability to preclude the stimulation of CD-specific mucosal T cells by gluten proteins.

METHODS

Gluten-specific polyclonal intestinal T cell lines from five CD children (mean age 5 years) were exposed to 50 microg/ml of a deamidated PTP from whole flour of common wheat (T. aestivum) cv. San Pastore, and tested for proliferation and production of interferon-gamma (INF-gamma) and interleukin 10 (IL-10). The same experiment was performed in the presence of 20 microg/ml of the 9-mer or the 10-mer peptide.

RESULTS

T cells exposed to PTP showed a threefold increase in proliferation and INF-gamma production, and a significant (P <or= 0.05) reduction in IL-10 secretion as compared with control cells incubated with the culture medium. Addition of either the 9-mer or the 10-mer peptide to PTP downregulated T cell proliferation and INF-gamma production, and caused a significant (P <or= 0.05) increase in IL-10 secretion.

CONCLUSIONS

The T cell reactivity elicited by PTP is precluded by both the 9-mer and the 10-mer sequence, suggesting that over-expression of these proteolytically stable peptides may result in a wheat flour with reduced toxicity for CD patients.

New therapeutic strategies for celiac disease

Celiac disease is an autoimmune condition affecting genetically susceptible individuals, characterized by inflammatory damage to the small intestine following ingestion of wheat gluten or barley and rye products. The only life-long treatment is strict gluten-free diet which is difficult personally and socially, affects quality of life, not widely available, more expensive, with lower palatability, resulting in low compliance. No doubt, there is therefore an urgent need for alternative therapeutic modalities. Based on the increasing knowledge on the sequential pathophysiological events driving the intestinal inflammatory cascade, new attractive and potential therapies were starting to immerge: selecting, changing, degrading, manipulating or binding the dietary toxic environmental factors, decreasing intestinal permeability toward gluten or blocking the deamination of gluten by inhibiting tissue transglutaminase or the HLA-DQ presenting groove by carefully designed false peptide, shifting the typical Th1 to Th2 inflammatory reaction or antagonizing major proinflammatory cytokines, enhancing regulatory immune function or developing preventive vaccines, blocking adhesion molecule, inducing gluten oral or intranasal tolerance or applying epithelial repairing mitogens to oppose the mucosal destruction. Safety, effectiveness, cost and affordability are prime issues to consider. Some modalities have shown promising results in vitro. Future will show who will win the race.

Antagonist peptides of the gliadin T-cell stimulatory sequences: a therapeutic strategy for celiac disease

Celiac disease (CD) is a T helper 1-driven autoimmune permanent enteropathy, triggered in susceptible individuals by the ingestion of gluten, the alcohol-soluble protein fraction of some cereals, such as wheat, rye, and barley. The only available treatment for CD is the life-long withdrawal of gluten-containing foods from the diet. Complying with gluten-free diet is difficult and affects the quality of life. Therefore, alternative therapies are being investigated. In this paper, we review a new therapeutic strategy for CD, relying upon peptides that are analogs of gliadin T-cell epitopes that show the ability to down-modulate the immune response pathogenic of CD. These peptides have been obtained artificially by amino acids substitution of gliadin T-cell stimulatory sequences and an immunomodulatory sequence has been identified in the alcohol-soluble protein fraction of cultivars of durum wheat.

Avenins from different cultivars of oats elicit response by coeliac peripheral lymphocytes

OBJECTIVE

The avoidance of oats in coeliac patients is still controversial. If oats is confirmed to be safe, it would be a valuable component and offer more variation in a gluten-free diet. The aim of this work was to evaluate whether avenins from different varieties of oats show different abilities in the activation of coeliac peripheral lymphocytes.

MATERIAL AND METHODS

In order to assess whether the immunogenic effect of oats varies according to the cultivar, peripheral lymphocytes from 10 coeliac children were exposed to avenins from four different oats varieties: Lampton, Astra, Ava and Nave. Lymphocyte proliferation and interferon-gamma (IFN-gamma) release in the culture medium were measured as indexes of immune activation.

RESULTS

All the varieties of oats tested were immunogenic, with Lampton and Ava avenins inducing lymphocyte activation similar to that activated by wheat gliadin, while Astra and Nave avenins showed less immunogenicity, but still with a measurable effect.

CONCLUSIONS

There are still concerns about the suitability of including oats in a gluten-free diet. Coeliac patients consuming oats-containing food should be carefully monitored, until there is more evidence to show the safety of oats and varieties of low-toxicity oats.