Gliadin Induces Neutrophil Migration via Engagement of the Formyl Peptide Receptor, FPR1

Fecal calprotectin levels in patients with non-celiac wheat sensitivity: a proof of concept

Some data suggest the existence of intestinal inflammation in patients with non-celiac wheat sensitivity (NCWS). We aimed to verify whether fecal calprotectin (FCP), a marker of intestinal inflammation, could be used to confirm this inflammatory status and to test its diagnostic performance in differentiating NCWS from irritable bowel syndrome/functional dyspepsia (IBS/FD). We conducted a multicenter study, comparing NCWS patients, diagnosed by a double-blind placebo-controlled wheat challenge, with IBS/FD subjects. In the retrospective phase, FCP values were analyzed to define the prevalence of its positivity and its role as a NCWS diagnostic biomarker. In the prospective phase we tested the effects of a strict 6-month wheat-free diet (WFD) on FCP values. 31.3% (n = 63/201) of NCWS patients had above normal FCP values (NCWS FCP +), whereas all IBS/FD patients proved negative (P = 0.0001). FCP using a cut-off value > 41 µg/g showed a 58.6% sensitivity and a 98.0% specificity (AUC 0.755, 95% C.I. 0.702-0.837) in distinguishing NCWS from IBS/FD patients. Of the 63 NCWS FCP+, 65.1% had negative FCP values after ≥ 6 months of WFD, with a significant reduction in FCP values (P < 0.0001). All NCWS FCP- subjects still preserved negative FCP values after ≥ 6 months of WFD. Our study showed that FCP can be a useful but supplementary diagnostic marker for differentiating between NCWS and IBS/FD. Strict WFD adherence reduced FCP values, normalizing them in 65.1% of NCWS FCP + subjects. These data suggest the existence of two NCWS subgroups: NCWS FCP + characterized by a probable predominantly inflammatory/immunologic pattern and NCWS FCP- featuring non-immuno-mediated etiopathogenetic mechanisms. (Registration number NCT01762579).

Intravital imaging of immune responses in intestinal inflammation

To date, many kinds of immune cells have been identified, but their precise roles in intestinal immunity remain unclear. Understanding the in vivo behavior of these immune cells and their function in gastrointestinal inflammation, including colitis, inflammatory bowel disease, ischemia-reperfusion injury, and neutrophil extracellular traps, is critical for gastrointestinal research to proceed to the next step. Additionally, understanding the immune responses involved in gastrointestinal tumors and tissue repair is becoming increasingly important for the elucidation of disease mechanisms that have been unknown. In recent years, the application of intravital microscopy in gastrointestinal research has provided novel insights into the mechanisms of intestine-specific events including innate and adaptive immunities. In this review, we focus on the emerging role of intravital imaging in gastrointestinal research and describe how to observe the intestines and immune cells using intravital microscopy. Additionally, we outline novel findings obtained by this new technique.

Peptides Derived from Soybean β-Conglycinin Induce the Migration of Human Peripheral Polymorphonuclear Leukocytes

Food-derived peptides have various biological activities. When food proteins are ingested orally, they are digested into peptides by endogenous digestive enzymes and absorbed by the immune cell-rich intestinal tract. However, little is known about the effects of food-derived peptides on the motility of human immune cells. In this study, we aimed to understand the effects of peptides derived from a soybean protein β-conglycinin on the motility of human peripheral polymorphonuclear leukocytes. We illustrated that MITL and MITLAIPVNKPGR, produced by digestion using in-vivo enzymes (trypsin and pancreatic elastase) of β-conglycinin, induces the migration of dibutyryl cAMP (Bt₂ cAMP)-differentiated human promyelocytic leukemia 60 (HL-60) cells and human polymorphonuclear leukocytes in a dose- and time-dependent manner. This migration was more pronounced in Bt₂ cAMP-differentiated HL-60 cells; mRNA expression of formyl peptide receptor (FPR) 1 increased significantly than in all-trans-retinoic acid (ATRA)-differentiated HL-60 cells. This migration was inhibited by tert-butoxycarbonyl (Boc)-MLP, an inhibitor of FPR, and by pretreatment with pertussis toxin (PTX). However, the effect was weak when treated with WRW4, a selective inhibitor of the FPR2. We then demonstrated that MITLAIPVNKPGR induced intracellular calcium responses in human polymorphonuclear leukocytes and Bt₂ cAMP-HL60 cells. Furthermore, pre-treatment by fMLP desensitized the calcium response of MITLAIPVNKPGR in these cells. From the above, MITLAIPVNKPGR and MITL derived from soybean β-conglycinin induced polymorphonuclear leukocyte migration via the FPR1-dependent mechanism. We found chemotactic peptides to human polymorphonuclear leukocytes, which are the endogenous enzyme digests of soybean protein.

Pepsin-trypsin digested gliadin treatment in intestinal cells

Celiac disease (CD) is an intestinal autoimmune disorder developed in genetically susceptible individuals upon gluten ingestion. Gliadin is known to be the most immunogenic gluten component, which can activate the host immune response represented by NFkB activation and release of proinflammatory cytokines as IL8. However, many aspects of the involvement of gliadin in CD pathophysiology is not well understood yet. Lack of a CD animal model increases difficulty elucidating key steps in CD development, what increases the importance of in vitro experiments. Here we present a protocol for in vitro pepsin-trypsin digested gliadin (PTG) treatment for long term studies in HCT116 intestinal cell line.

Promiscuous Receptors and Neuroinflammation: The Formyl Peptide Class

Formyl peptide receptors, abbreviated as FPRs in humans, are G-protein coupled receptors (GPCRs) mainly found in mammalian leukocytes. However, they are also expressed in cell types crucial for homeostatic brain regulation, including microglia and blood-brain barrier endothelial cells. Thus, the roles of these immune-associated receptors are extensive, from governing cellular adhesion and directed migration through chemotaxis, to granule release and superoxide formation, to phagocytosis and efferocytosis. In this review, we will describe the similarities and differences between the two principal pro-inflammatory and anti-inflammatory FPRs, FPR1 and FPR2, and the evidence for their importance in the development of neuroinflammatory disease, alongside their potential as therapeutic targets.

Non-Celiac Gluten Sensitivity and Protective Role of Dietary Polyphenols

Pathogenetically characterized by the absence of celiac disease and wheat allergy, non-celiac gluten sensitivity (NCGS) is a clinical entity triggered by the consumption of gluten-containing foods that relieved by a gluten-free diet. Since it is very difficult to maintain a complete gluten-free diet, there is a high interest in discovering alternative strategies aimed at reducing gluten concentration or mitigating its toxic effects. Plant-based dietary models are usually rich in bioactive compounds, such as polyphenols, recognized to prevent, delay, or even reverse chronic diseases, including intestinal disorders. However, research on the role of polyphenols in mitigating the toxicity of gluten-containing foods is currently limited. We address the metabolic fate of dietary polyphenols, both as free and bound macromolecule-linked forms, with particular reference to the gastrointestinal compartment, where the concentration of polyphenols can reach high levels. We analyze the potential targets of polyphenols including the gluten peptide bioavailability, the dysfunction of the intestinal epithelial barrier, intestinal immune response, oxidative stress and inflammation, and dysbiosis. Overall, this review provides an updated overview of the effects of polyphenols as possible dietary strategies to counteract the toxic effects of gluten, potentially resulting in the improved quality of life of patients with gluten-related disorders.

From celiac disease to coccidia infection and vice-versa: The polyQ peptide CXCR3-interaction axis

Zonulin is a physiological modulator of intercellular tight junctions, which upregulation is involved in several diseases like celiac disease (CeD). The polyQ gliadin fragment binds to the CXCR3 chemokine receptor that activates zonulin upregulation, leading to increased intestinal permeability in humans. Here, we report a general hypothesis based on the structural connection between the polyQ sequence of the immunogenic CeD protein, gliadin, and enteric coccidian parasites proteins. Firstly, a novel interaction pathway between the parasites and the host is described based on the structural similarities between polyQ gliadin fragments and the parasite proteins. Secondly, a potential connection between coccidial infections as a novel environmental trigger of CeD is hypothesized. Therefore, this report represents a promising breakthrough for coccidian research and points out the potential role of coccidian parasites as a novel trigger of CeD that might define a preventive strategy for gluten-related disorders in general. Also see the video abstract here: https://youtu.be/oMaQasStcFI.

Wheat/Gluten-Related Disorders and Gluten-Free Diet Misconceptions: A Review

In the last 10,000 years, wheat has become one of the most important cereals in the human diet and today, it is widely consumed in many processed food products. Mostly considered a source of energy, wheat also contains other essential nutrients, including fiber, proteins, and minor components, such as phytochemicals, vitamins, lipids, and minerals, that together promote a healthy diet. Apart from its nutritional properties, wheat has a set of proteins, the gluten, which confer key technical properties, but also trigger severe immune-mediated diseases, such as celiac disease. We are currently witnessing a rise in the number of people adhering to gluten-free diets unwarranted by any medical need. In this dynamic context, this review aims to critically discuss the nutritional components of wheat, highlighting both the health benefits and wheat/gluten-related disorders, in order to address common misconceptions associated with wheat consumption.

No impact of cancer and plague-relevant FPR1 polymorphisms on COVID-19

Formyl peptide receptor 1 (FPR1) is a pattern-recognition receptor that detects bacterial as well as endogenous danger-associated molecular patterns to trigger innate immune responses by myeloid cells. A single nucleotide polymorphism, rs867228 (allelic frequency 19–20%), in the gene coding for FPR1 accelerates the manifestation of multiple carcinomas, likely due to reduced anticancer immunosurveillance secondary to a defect in antigen presentation by dendritic cells. Another polymorphism in FPR1, rs5030880 (allelic frequency 12–13%), has been involved in the resistance to plague, correlating with the fact that FPR1 is the receptor for Yersinia pestis. Driven by the reported preclinical effects of FPR1 on lung inflammation and fibrosis, we investigated whether rs867228 or rs5030880 would affect the severity of coronavirus disease-19 (COVID-19). Data obtained on patients from two different hospitals in Paris refute the hypothesis that rs867228 or rs5030880 would affect the severity of COVID-19.

Formyl peptide receptors in the mucosal immune system

Formyl peptide receptors (FPRs) belong to the G protein-coupled receptor (GPCR) family and are well known as chemotactic receptors and pattern recognition receptors (PRRs) that recognize bacterial and mitochondria-derived formylated peptides. FPRs are also known to detect a wide range of ligands, including host-derived peptides and lipids. FPRs are highly expressed not only in phagocytes such as neutrophils, monocytes, and macrophages but also in nonhematopoietic cells such as epithelial cells and endothelial cells. Mucosal surfaces, including the gastrointestinal tract, the respiratory tract, the oral cavity, the eye, and the reproductive tract, separate the external environment from the host system. In mucosal surfaces, the interaction between the microbiota and host cells needs to be strictly regulated to maintain homeostasis. By sharing the same FPRs, immune cells and epithelial cells may coordinate pathophysiological responses to various stimuli, including microbial molecules derived from the normal flora. Accumulating evidence shows that FPRs play important roles in maintaining mucosal homeostasis. In this review, we summarize the roles of FPRs at mucosal surfaces.

Celiac Disease and Non-celiac Wheat Sensitivity: State of Art of Non-dietary Therapies

Gluten related disorders (GRD), which include celiac disease, non-celiac wheat sensitivity and wheat allergy are heterogeneous conditions triggered by ingestion of gluten-containing grains. Together, their prevalence is estimated to be ~5% in the general population, however, in the last years the number of diagnoses has been rapidly increasing. To this day, the gold standard treatment for these disorders is the complete removal of gluten-containing grains from the diet. Although this therapy results effective in the majority of patients, up to 30% of individuals affected by GRD continue to present persistent symptoms. In addition, gluten-free diet has been shown to have poor nutritional quality and to cause a socio-economic burden in patients' quality of life. In order to respond to these issues, the scientific community has been focusing on finding additional and adjuvant non-dietary therapies. In this review, we focus on two main gluten related disorders, celiac disease and non-celiac wheat sensitivity. We delineate the actual knowledge about potential treatments and their relative efficacy in pre-clinical and clinical trials.

Brain Opioid Activity and Oxidative Injury: Different Molecular Scenarios Connecting Celiac Disease and Autistic Spectrum Disorder

Celiac Disease (CD) is an immune-mediated disease triggered by the ingestion of wheat gliadin and related prolamins from other cereals, such as barley and rye. Immunity against these cereal-derived proteins is mediated by pro-inflammatory cytokines produced by both innate and adaptive system response in individuals unable to adequately digest them. Peptides generated in this condition are absorbed across the gut barrier, which in these patients is characterized by the deregulation of its permeability. Here, we discuss a possible correlation between CD and Autistic Spectrum Disorder (ASD) pathogenesis. ASD can be induced by an excessive and inappropriate brain opioid activity during the neonatal period. Cereal-derived peptides produced in celiac patients cross the blood–brain barrier and bind to endogenous opioid receptors interfering with neurotransmission and generating deleterious effects on brain maturation, learning and social relations. Moreover, an increase in oxidative stress and a decrease in the antioxidant capacity, as well as an extended mitochondrial impairment in the brain, could represent a possible connection between ASD and CD. Therefore, we critically discuss the proposed relationship between ASD and CD and the possible usefulness of a gluten-free diet in ASD patients.

Coeliac Disease Pathogenesis: The Uncertainties of a Well-Known Immune Mediated Disorder

Coeliac disease is a common small bowel enteropathy arising in genetically predisposed individuals and caused by ingestion of gluten in the diet. Great advances have been made in understanding the role of the adaptive immune system in response to gluten peptides. Despite detailed knowledge of these adaptive immune mechanisms, the complete series of pathogenic events responsible for development of the tissue lesion remains less certain. This review contributes to the field by discussing additional mechanisms which may also contribute to pathogenesis. These include the production of cytokines such as interleukin-15 by intestinal epithelial cells and local antigen presenting cells as a pivotal event in the disease process. A subset of unconventional T cells called gamma/delta T cells are also persistently expanded in the coeliac disease (CD) small intestinal epithelium and recent analysis has shown that these cells contribute to pathogenic inflammation. Other unconventional T cell subsets may play a local immunoregulatory role and require further study. It has also been suggested that, in addition to activation of pathogenic T helper cells by gluten peptides, other peptides may directly interact with the intestinal mucosa, further contributing to the disease process. We also discuss how myofibroblasts, a major source of tissue transglutaminase and metalloproteases, may play a key role in intestinal tissue remodeling. Contribution of each of these factors to pathogenesis is discussed to enhance our view of this complex disorder and to contribute to a wider understanding of chronic immune-mediated disease.

Wheat gluten intake increases the severity of experimental colitis and bacterial translocation by weakening of the proteins of the junctional complex

Gluten is only partially digested by intestinal enzymes and can generate peptides that can alter intestinal permeability, facilitating bacterial translocation, thus affecting the immune system. Few studies addressed the role of diet with gluten in the development of colitis. Therefore, we investigate the effects of wheat gluten-containing diet on the evolution of sodium dextran sulphate (DSS)-induced colitis. Mice were fed a standard diet without (colitis group) or with 4·5 % wheat gluten (colitis + gluten) for 15 d and received DSS solution (1·5 %, w/v) instead of water during the last 7 d. Compared with the colitis group, colitis + gluten mice presented a worse clinical score, a larger extension of colonic injury area, and increased mucosal inflammation. Both intestinal permeability and bacterial translocation were increased, propitiating bacteria migration for peripheral organs. The mechanism by which diet with gluten exacerbates colitis appears to be related to changes in protein production and organisation in adhesion junctions and desmosomes. The protein α-E-catenin was especially reduced in mice fed gluten, which compromised the localisation of E-cadherin and β-catenin proteins, weakening the structure of desmosomes. The epithelial damage caused by gluten included shortening of microvilli, a high number of digestive vacuoles, and changes in the endosome/lysosome system. In conclusion, our results show that wheat gluten-containing diet exacerbates the mucosal damage caused by colitis, reducing intestinal barrier function and increasing bacterial translocation. These effects are related to the induction of weakness and disorganisation of adhesion junctions and desmosomes as well as shortening of microvilli and modification of the endocytic vesicle route.

Intestinal Epithelium Modulates Macrophage Response to Gliadin in Celiac Disease

Celiac disease is an immune-mediated enteropathy triggered by ingestion of gluten. Although its pathogenesis has been extensively studied and the contribution from both innate and adaptive immune responses has been reported, little is still known about the contribution of macrophages to the onset or maintenance of the disease. Macrophages are extremely plastic immune cells that can be directed toward a pro- or anti-inflammatory phenotype by the surrounding microenvironment. Of note, gliadin, the most prominent causative agent of the disease, has been reported to trigger the production of pro-inflammatory cytokines in this cell population. In the present study, we aimed at investigating how the intestinal milieu and more specifically the epithelium can shape the macrophage response to gliadin. Using patient-derived organoids we showed that the intestinal epithelium derived from celiac disease donors releases anti-inflammatory factors that curb the macrophage response to gliadin. Furthermore, we uncovered that the celiac macrophages were better responders than macrophages derived from non-celiac controls. Finally, we demonstrated that IFNγ released by the epithelium is in part responsible of the observed anti-inflammatory effect. Our data shed light on the cross–talk between the immune system and the epithelium and its critical role in the intestinal homeostasis. Furthermore, we provide more evidence how alterations in the innate immune machinery in celiac patients may contribute to the onset of the disease.

Gluten-related disorders: Celiac disease, wheat allergy, and nonceliac gluten sensitivity

The consumption of gluten-free products is becoming an increased alimentary habit in the general population. The scientific unfounded perception suggesting that the avoidance of gluten would improve health or that gluten could be toxic for humans are fostering medically unjustified adherences to a gluten-free diet. Currently, only patients diagnosed with celiac disease are advised to follow a strict lifelong gluten-free diet. In the same way, patients diagnosed with IgE-mediated wheat allergy must avoid exposure to wheat in any form. In that context, a third disorder, called nonceliac gluten sensitivity, characterized by distress after gluten consumption and in which neither celiac disease nor IgE-mediated allergy plays a role, has gained increased attention in the last years. Although important scientific advances have been made in the understanding of the pathologic mechanisms behind nonceliac gluten sensitivity, this disorder is still a matter of active debate in the scientific community. In the present review, the most recent advances in the immunopathology, diagnostic biomarkers and susceptibility determinants of gluten-related diseases are summarized and discussed. Furthermore, an updated overview of the new potential therapies that are currently underway for the treatment of gluten-related disorders is also provided.

Celiac disease: a comprehensive current review

BACKGROUND

Celiac disease remains a challenging condition because of a steady increase in knowledge tackling its pathophysiology, diagnosis, management, and possible therapeutic options.

MAIN BODY

A major milestone in the history of celiac disease was the identification of tissue transglutaminase as the autoantigen, thereby confirming the autoimmune nature of this disorder. A genetic background (HLA-DQ2/DQ8 positivity and non-HLA genes) is a mandatory determinant of the development of the disease, which occurs with the contribution of environmental factors (e.g., viral infections and dysbiosis of gut microbiota). Its prevalence in the general population is of approximately 1%, with female predominance. The disease can occur at any age, with a variety of symptoms/manifestations. This multifaceted clinical presentation leads to several phenotypes, i.e., gastrointestinal, extraintestinal, subclinical, potential, seronegative, non-responsive, and refractory. Although small intestinal biopsy remains the diagnostic 'gold standard', highly sensitive and specific serological tests, such as tissue transglutaminase, endomysial and deamidated gliadin peptide antibodies, have become gradually more important in the diagnostic work-up of celiac disease. Currently, the only treatment for celiac disease is a life-long, strict gluten-free diet leading to improvement in quality of life, ameliorating symptoms, and preventing the occurrence of refractory celiac disease, ulcerative jejunoileitis, and small intestinal adenocarcinoma and lymphoma.

CONCLUSIONS

The present review is timely and provides a thorough appraisal of various aspects characterizing celiac disease. Remaining challenges include obtaining a better understanding of still-unclear phenotypes such as slow-responsive, potential (minimal lesions) and seronegative celiac disease. The identification of alternative or complementary treatments to the gluten-free diet brings hope for patients unavoidably burdened by diet restrictions.

Genetic and Environmental Contributors for Celiac Disease

PURPOSE OF REVIEW

Celiac disease (CD) is an autoimmune enteropathy triggered by gluten. The purpose of this review is to examine the major genetic and environmental factors that contribute to CD pathogenesis.

RECENT FINDINGS

We reviewed the current state of knowledge on the genetic and environmental components that play a role in CD onset. A genome-wide association study (GWAS) analysis has highlighted several genes other than HLA involved in CD. Recent studies have shown that HLA haplotype influences the microbiome composition in infants and that dysbiosis in the intestinal microflora, in turn, contributes to loss of tolerance to gluten. Recently, observational studies have discussed the hypothesis stating that breast-feeding had a protective role against CD onset. CD etiology is influenced by genetic and environmental factors. A better understanding of these components would deepen our knowledge on the mechanisms that lead to loss of tolerance and could help in developing a more "personalized medicine."

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.

Human gut derived-organoids provide model to study gluten response and effects of microbiota-derived molecules in celiac disease

Celiac disease (CD) is an immune-mediated disorder triggered by gluten exposure. The contribution of the adaptive immune response to CD pathogenesis has been extensively studied, but the absence of valid experimental models has hampered our understanding of the early steps leading to loss of gluten tolerance. Using intestinal organoids developed from duodenal biopsies from both non-celiac (NC) and celiac (CD) patients, we explored the contribution of gut epithelium to CD pathogenesis and the role of microbiota-derived molecules in modulating the epithelium’s response to gluten. When compared to NC, RNA sequencing of CD organoids revealed significantly altered expression of genes associated with gut barrier, innate immune response, and stem cell functions. Monolayers derived from CD organoids exposed to gliadin showed increased intestinal permeability and enhanced secretion of pro-inflammatory cytokines compared to NC controls. Microbiota-derived bioproducts butyrate, lactate, and polysaccharide A improved barrier function and reduced gliadin-induced cytokine secretion. We concluded that: (1) patient-derived organoids faithfully express established and newly identified molecular signatures characteristic of CD. (2) microbiota-derived bioproducts can be used to modulate the epithelial response to gluten. Finally, we validated the use of patient-derived organoids monolayers as a novel tool for the study of CD.

RNA sequencing of intestinal mucosa reveals novel pathways functionally linked to celiac disease pathogenesis

BACKGROUND & AIMS

The early steps in the pathophysiology of celiac disease (CD) leading to loss of tolerance to gluten are poorly described. Our aim was to use RNA sequencing of duodenal biopsies in patients with active CD, CD in remission, and non-CD controls to gain insight into CD pathophysiology, identify additional genetic signatures linked to CD, and possibly uncover targets for future therapeutic agents.

METHODS

We performed whole transcriptome shotgun sequencing of intestinal biopsies in subjects with active and remission CD and non-CD controls. We also performed functional pathway analysis of differentially expressed genes to identify statistically significant pathways that are up or down regulated in subjects with active CD compared to remission CD.

RESULTS

We identified the upregulation of novel genes including IL12R, ITGAM and IGSF4 involved in the immune response machinery and cell adhesion process in the mucosa of subjects with active CD compared to those in remission. We identified a unique signature of genes, related to innate immunity, perturbed exclusively in CD irrespective of disease status. Finally, we highlight novel pathways of interest that may contribute to the early steps of CD pathogenesis and its comorbidities such as the spliceosome, pathways related to the innate immune response, and pathways related to autoimmunity.

CONCLUSIONS

Our study confirmed previous findings based on GWAS and immunological studies pertinent to CD pathogenesis and describes novel genes and pathways that with further validation may be found to contribute to the early steps in the pathogenesis of CD, ongoing inflammation, and comorbidities associated with CD.

Nondietary Therapies for Celiac Disease

Celiac disease (CD) is an autoimmune enteropathy triggered by gluten. Gluten-free diets can be challenging because of their restrictive nature, inadvertent cross-contaminations, and the high cost of gluten-free food. Novel nondietary therapies are at the preclinical stage, clinical trial phase, or have already been developed for other indications and are now being applied to CD. These therapies include enzymatic gluten degradation, binding and sequestration of gluten, restoration of epithelial tight junction barrier function, inhibition of tissue transglutaminase-mediated potentiation of gliadin oligopeptide immunogenicity or of human leukocyte antigen-mediated gliadin presentation, induction of tolerance to gluten, and antiinflammatory interventions.

Involvement of gliadin, a component of wheat gluten, in increased intestinal permeability leading to non-steroidal anti-inflammatory drug-induced small-intestinal damage

Gliadin, a component of wheat gluten known to be an important factor in the etiology of celiac disease, is related to several other diseases through its enhancing effect on intestinal paracellular permeability. We investigated the significance of gliadin in non-steroidal anti-inflammatory drug (NSAID)-induced small-intestinal damage in mice. 7-week-old C57BL/6 male mice were divided into the following groups: standard diet group, in which mice were fed with wheat-containing standard rodent diet (CE-2); gluten-free diet group, in which mice were fed with gluten-free diet (AIN-76A); and gliadin-administered group, in which mice fed with gluten-free diet were administered with gliadin (~250 mg/kg BW). Each group was subdivided into negative, healthy control group and NSAID-treated group. To some mice fed with gluten-free diet and administered with gliadin, epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor was administered for clarification of the significance of EGFR in NSAID-induced small intestinal damage and intestinal permeability. In mice fed with a gluten-free diet, indomethacin or diclofenac induced very mild mucosal damage in the small intestine compared with that in mice fed with a wheat-containing standard diet. Gliadin exacerbated the NSAID-induced small-intestinal damage in mice fed with a gluten-free diet. With the administration of indomethacin, MPO activity, a marker of neutrophil infiltration into the mucosa and mRNA expression level of tumor necrosis factor α and interleukin-1β in the small intestine were higher in the gliadin-administered mice. Gliadin increased the intestinal paracellular permeability without indomethacin administration (4.3-fold) and further increased the permeability after indomethacin administration (2.1-fold). Gliadin induced phosphorylation of epidermal growth factor receptor (EGFR) in small-intestinal tissues, and erlotinib (an EGFR tyrosine kinase inhibitor) attenuated the indomethacin-induced intestinal damage and permeability exacerbated by gliadin, accompanied by inhibition of EGFR phosphorylation. These results suggest that gliadin plays an important role in the induction and exacerbation of NSAID-induced small-intestinal damage, and that increase in intestinal permeability via the EGFR signalling pathway is involved in its mechanism.

FPR1 mediates the tumorigenicity of human cervical cancer cells

Purpose

The present study aimed to investigate the role of FPR1 and the downstream effectors such as NF-κB and IL-6/8 in the development of cervical cancer.

Patients and methods

FPR1 protein expression was detected via immunohistochemical staining in tissue microarrays containing cervical cancer tissues from 185 patients. Following FPR1 silencing in SiHa cells using lentiviral siRNA delivery, biological characteristics and tumor formation were evaluated in vitro and in vivo, respectively. Phosphorylated NF-κB levels were detected by Western blotting, while IL-6 and IL-8 secretion were detected by ELISA in both FPR1 knockdown and control SiHa cells. Human umbilical vein endothelial cell tube formation assays were performed to evaluate the angiogenesis-promoting ability of IL-6 and IL-8 secretion in FPR1 knockdown and control SiHa cells. Neovascularization, proliferation and apoptosis markers were detected by immunohistochemical staining to analyze the tumorigenic role of FPR1.

Results

Immunohistochemistry of cervical cancer tissues from 185 patients revealed high FPR1 expression levels in patients with advanced-stage disease and/or poor prognosis. Compared with control cells, cervical cancer cells in which FPR1 was silenced exhibited inhibition of cell invasion, migration and proliferation and higher levels of apoptosis. NF-κB was inhibited in FPR1 knockdown in SiHa cells. IL-6/8 upregulation by FPR1 activation stimulated angiogenesis. FPR1 deficiency inhibited the tumorigenicity of cervical cancer cells in nude mice. FPR1, IL-6, IL-8, CD31 and Ki67 levels were all reduced, whereas cleaved caspase-3 was upregulated, in the FPR1 knockdown group compared with the levels in the control group.

Conclusion

High FPR1 expression was associated with advanced stage and poor prognosis in cervical cancer patients. FPR1 activation induced NF-κB nuclear translocation to promote cervical cancer development through the upregulation of IL-6 and IL-8 expression. Inhibiting FPR1 activity may thus have potential therapeutic value in cervical cancer patients.

Translational Chemistry Meets Gluten-Related Disorders

Gluten‐related disorders are a complex group of diseases that involve the activation of the immune system triggered by the ingestion of gluten. Among these, celiac disease, with a prevalence of 1 %, is the most investigated, but recently, a new pathology, named nonceliac gluten sensitivity, was reported with a general prevalence of 7 %. Finally, there other less‐prevalent gluten‐related diseases such as wheat allergy, gluten ataxia, and dermatitis herpetiformis (with an overall prevalence of less than 0.1 %). As mentioned, the common molecular trigger is gluten, a complex mixture of storage proteins present in wheat, barley, and a variety of oats that are not fully degraded by humans. The most‐studied protein related to disease is gliadin, present in wheat, which possesses in its sequence many pathological fragments. Despite a lot of effort to treat these disorders, the only effective method is a long‐life gluten‐free diet. This Review summarizes the actual knowledge of gluten‐related disorders from a translational chemistry point of view. We discuss what is currently known from the literature about the interaction of gluten with the gut and the critical host responses it evokes and, finally, connect them to our current and novel molecular understanding of the supramolecular organization of gliadin and the 33‐mer gliadin peptide fragment under physiological conditions.

Use of Probiotics to Prevent Celiac Disease and IBD in Pediatrics

The incidence of chronic inflammatory diseases (CIDs) is increasing worldwide. Their dramatic rise associated with limited effective strategies to slow down these epidemics calls for a better understanding of their pathophysiology in order to decrease the burdens on childhood. Several cross-sectional studies have demonstrated the association between intestinal dysbiosis and active diseases. Although informative, these studies do not mechanistically link alterations of the microflora with disease pathogenesis and, therefore, with potential therapeutic targets. More prospective studies are needed to determine whether intestinal dysbiosis plays a causative role in the onset and development of CIDs. Furthermore, given the complexity of the microflora interaction with the host, it is necessary to design a systems-level model of interactions between the host and the development of disease by integrating microbiome, metagenomics, metatranscriptomics, and metabolomics with either clinical either environmental data.In this chapter we will discuss the current knowledge regarding the microbiome's contribution to celiac disease and inflammatory bowel disease with a particular focus on how probiotics may be used as potential preventive therapy for CIDs.

Microbes and Viruses Are Bugging the Gut in Celiac Disease. Are They Friends or Foes?

The links between microorganisms/viruses and autoimmunity are complex and multidirectional. A huge number of studies demonstrated the triggering impact of microbes and viruses as the major environmental factors on the autoimmune and inflammatory diseases. However, growing evidences suggest that infectious agents can also play a protective role or even abrogate these processes. This protective crosstalk between microbes/viruses and us might represent a mutual beneficial equilibrium relationship between two cohabiting ecosystems. The protective pathways might involve post-translational modification of proteins, decreased intestinal permeability, Th1 to Th2 immune shift, induction of apoptosis, auto-aggressive cells relocation from the target organ, immunosuppressive extracellular vesicles and down regulation of auto-reactive cells by the microbial derived proteins. Our analysis demonstrates that the interaction of the microorganisms/viruses and celiac disease (CD) is always a set of multidirectional processes. A deeper inquiry into the CD interplay with Herpes viruses and Helicobacter pylori demonstrates that the role of these infections, suggested to be potential CD protectors, is not as controversial as for the other infectious agents. The outcome of these interactions might be due to a balance between these multidirectional processes.

4-Aroyl-3-hydroxy-5-phenyl-1H-pyrrol-2(5H)-ones as N-formyl peptide receptor 1 (FPR1) antagonists

Formyl peptide receptors (FPRs) are expressed on a variety of leukocytes and play important roles in inflammation. Thus, FPR antagonists may represent novel therapeutics for modulating innate immunity and treating inflammatory diseases. Previously, 1H-pyrrol-2(5H)-ones were reported to be potent and competitive FPR1 antagonists. In the present studies, 42 additional 1H-pyrrol-2(5H)-one analogs were evaluated for FPR1 antagonist activity. We identified a number of novel competitive FPR1 antagonists that inhibited N-formylmethionyl-leucyl-phenylalanine (fMLF)-induced intracellular Ca²⁺ mobilization in FPR1-transfected HL60 cells and effectively competed with WKYMVm-FITC for binding to FPR1 in FPR1-transfected RBL cells. The most active pyrroles inhibited human neutrophil Ca²⁺ flux, chemotaxis, and adhesion to human epithelial cells, with the most potent being compounds 14 (4-benzoyl-1-hexyl-3-hydroxy-5-(4-hydroxy-3-methoxyphenyl)-2,5-dihydro-1H-pyrrol-2-one) and 17 (4-benzoyl-5-(2,5-dimethoxyphenyl)-3-hydroxy-1-(2-methoxyethyl)-2,5-dihydro-1H-pyrrol-2-one). In addition, these FPR1 antagonists inhibited fMLF-induced phosphorylation of extracellular signal-regulated kinases (ERK1/2) in FPR1-RBL cells, differentiated HL-60 cells, and human neutrophils. Most of the antagonists were specific for FPR1 and did not inhibit WKYMVM/WKYMVm-induced intracellular Ca²⁺ mobilization in FPR2-HL60 cells, FPR3-HL60 cells, or interleukin 8-induced Ca²⁺ flux in human neutrophils. Moreover, molecular modeling showed that the active pyrroles had a significantly higher degree of similarity with the FPR1 antagonist pharmacophore template as compared to inactive analogs. Thus, the 4-aroyl-3-hydroxy-5-phenyl-1H-pyrrol-2(5H)-one scaffold represents an important backbone for the development of novel FPR1 antagonists and could provide important clues for understanding the molecular structural requirements of FPR1 antagonists.

Marine Natural Product Inhibitors of Neutrophil-Associated Inflammation

Neutrophils are widely recognized to play an important role in acute inflammatory responses, and recent evidence has expanded their role to modulating chronic inflammatory and autoimmune diseases. Reactive oxygen species (ROS) and microbicidal compounds released from neutrophils that are recruited to the site of inflammation contribute to the pathogenesis of multiple inflammation-associated diseases such as chronic obstructive pulmonary disease, atherosclerosis, and hepatitis. Marine organisms are a valuable source of bioactive compounds with potential for industrial and pharmaceutical application. Marine natural products that inhibit neutrophil activation could be used as drugs for the treatment of inflammatory diseases. Numerous studies investigating marine natural products have reported novel anti-inflammatory agents. Nevertheless, the detailed mechanisms underlying their actions, which could facilitate our understanding of the molecular events occurring in neutrophils, have not been reported in most of the associated research studies. Therefore, in this review, we will present marine products that inhibit neutrophil-associated inflammation. Furthermore, we will be limiting the detailed discussion to agents with well-investigated molecular targets.

Nutritional Keys for Intestinal Barrier Modulation

The intestinal tract represents the largest interface between the external environment and the human body. Nutrient uptake mostly happens in the intestinal tract, where the epithelial surface is constantly exposed to dietary antigens. Since inflammatory response toward these antigens may be deleterious for the host, a plethora of protective mechanisms take place to avoid or attenuate local damage. For instance, the intestinal barrier is able to elicit a dynamic response that either promotes or impairs luminal antigens adhesion and crossing. Regulation of intestinal barrier is crucial to control intestinal permeability whose increase is associated with chronic inflammatory conditions. The cross talk among bacteria, immune, and dietary factors is able to modulate the mucosal barrier function, as well as the intestinal permeability. Several nutritional products have recently been proposed as regulators of the epithelial barrier, even if their effects are in part contradictory. At the same time, the metabolic function of the microbiota generates new products with different effects based on the dietary content. Besides conventional treatments, novel therapies based on complementary nutrients are now growing. Fecal therapy has been recently used for the clinical treatment of refractory Clostridium difficile infection instead of the classical antibiotic therapy. In the present review, we will outline the epithelial response to nutritional components derived from dietary intake and microbial fermentation focusing on the consequent effects on the integrity of the epithelial barrier.