Latest in vitro and in vivo models of celiac disease

The Gliadin Hydrolysis Capacity of B. longum, L. acidophilus, and L. plantarum and Their Protective Effects on Caco-2 Cells against Gliadin-Induced Inflammatory Responses

BACKGROUND

Non-celiac wheat sensitivity (NCWS) is a poorly understood gluten-related disorder (GRD) and its prominent symptoms can be ameliorated by gluten avoidance. This study aimed to determine the effectiveness of a probiotic mixture in hydrolyzing gliadin peptides (toxic components of gluten) and suppressing gliadin-induced inflammatory responses in Caco-2 cells.

METHODS

Wheat dough was fermented with a probiotic mix for 0, 2, 4, and 6 h. The effect of the probiotic mix on gliadin degradation was monitored by SDS-PAGE. The expression levels of IL-6, IL-17A, INF-γ, IL-10, and TGF-β were evaluated using ELISA and qRT-PCR methods.

RESULTS

According to our findings, fermenting wheat dough with a mix of B. longum, L. acidophilus, and L. plantarum for 6 h was effective in gliadin degradation. This process also reduced levels of IL-6 (p = 0.004), IL-17A (p = 0.004), and IFN-γ (p = 0.01) mRNA, as well as decreased IL-6 (p = 0.006) and IFN-γ (p = 0.0009) protein secretion. 4 h fermentation led to a significant decrease in IL-17A (p = 0.001) and IFN-γ (p = 0.003) mRNA, as well as reduced levels of IL-6 (p = 0.002) and IFN-γ (p < 0.0001) protein secretion. This process was also observed to increase the expression levels of IL-10 (p < 0.0001) and TGF-β (p < 0.0001) mRNA.

CONCLUSIONS

4 h fermentation of wheat flour with the proposed probiotic mix might be a good strategy to develop an affordable gluten-free wheat dough for NCWS and probably other GRD patients.

How does a celiac iceberg really float? The relationship between celiac disease and gluten

Celiac disease (CD) is an autoimmune intestinal disease caused by intolerance of genetically susceptible individuals after intake of gluten-containing grains (including wheat, barley, etc.) and their products. Currently, CD, with "iceberg" characteristics, affects a large population and is distributed over a wide range of individuals. This present review summarizes the latest research progress on the relationship between CD and gluten. Furthermore, the structure and function of gluten peptides related to CD, gluten detection methods, the effects of processing on gluten and gluten-free diets are emphatically reviewed. In addition, the current limitations in CD research are also discussed. The present work facilitates a comprehensive understanding of CD as well as gluten, which can provide a theoretical reference for future research.

Advances in quantification and analysis of the celiac-related immunogenic potential of gluten

Gluten-free products have emerged in response to the increasing prevalence of gluten-related disorders, namely celiac disease. Therefore, the quantification of gluten in products intended for consumption by individuals who may suffer from these pathologies must be accurate and reproducible, in a way that allows their proper labeling and protects the health of consumers. Immunochemical methods have been the methods of choice for quantifying gluten, and several kits are commercially available. Nevertheless, they still face problems such as the initial extraction of gluten in complex matrices or the use of a standardized reference material to validate the results. Lately, other methodologies relying mostly on mass spectrometry-based techniques have been explored, and that may allow, in addition to quantitative analysis, the characterizationof gluten proteins. On the other hand, although the level of 20 mg/kg of gluten detected by these methods is sufficient for a product to be considered gluten-free, its immunogenic potential for celiac patients has not been clinically validated. In this sense, in vitro and in vivo models, such as the organoid technology applied in gut-on-chip devices and the transgenic humanized mouse models, respectively, are being developed for investigating both the gluten-induced pathogenesis and the treatment of celiac disease. Due to the ubiquitous nature of gluten in the food industry, as well as the increased prevalence of gluten-related disorders, here we intend to summarize the available methods for gluten quantification in food matrices and for the evaluation of its immunogenic potential concerning the development of novel therapies for celiac disease to highlight active research and discuss knowledge gaps and current challenges in this field.

Human gut-derived commensal suppresses generation of T-cell response to gliadin in humanized mice by modulating gut microbiota

The human intestinal tract is colonized by a large number of diverse microorganisms that play various important physiologic functions. In inflammatory gut diseases including celiac disease (CeD), a dysbiotic state of microbiome has been observed. Interestingly, this perturbed microbiome is normalized towards eubiosis in patients showing recovery after treatment. The treatment has been observed to increase the abundance of beneficial microbes in comparison to non-treated patients. In this study, we investigated the effect of Prevotella histicola or Prevotella melaninogenica, isolated from the duodenum of a treated CeD patient, on the induction and maintenance of oral tolerance to gliadin, a CeD associated subgroup of gluten proteins, in NOD.DQ8.ABo transgenic mice. Conventionally raised mice on a gluten free diet were orally gavaged with bacteria before and after injection with pepsin trypsin digested gliadin (PTD-gliadin). P. histicola suppressed the cellular response to gliadin, whereas P. melaninogenica failed to suppress an immune response against gliadin. Interestingly, tolerance to gliadin in NOD.DQ8.ABo mice may be associated with gut microbiota as mice gavaged with P melaninogenica harbored a different microbial diversity as compared to P. histicola treated mice. This study provides experimental evidence that gut microbes like P. histicola from treated patients can suppress the immune response against gliadin epitopes.

Celiac disease-on-chip: Modeling a multifactorial disease in vitro

Conventional model systems cannot fully recapitulate the multifactorial character of complex diseases like celiac disease (CeD), a common chronic intestinal disorder in which many different genetic risk factors interact with environmental factors such as dietary gluten. However, by combining recently developed human induced pluripotent stem cell (hiPSC) technology and organ-on-chip technology, in vitro intestine-on-chip systems can now be developed that integrate the genetic background of complex diseases, the different interacting cell types involved in disease pathology, and the modulating environmental factors such as gluten and the gut microbiome. The hiPSCs that are the basis of these systems can be generated from both diseased and healthy individuals, which means they can be stratified based on their load of genetic risk factors. A CeD-on-chip model system has great potential to improve our understanding of disease etiology and accelerate the development of novel treatments and preventive therapies in CeD and other complex diseases.

Diverse Profiles of Toll-Like Receptors 2, 4, 7, and 9 mRNA in Peripheral Blood and Biopsy Specimens of Patients with Celiac Disease

Background and Aims

Both adaptive and innate immunity are involved in the development of celiac disease (CD). Altered Toll-like receptors (TLR) expression and activation may be partially responsible for the inflammation and subsequently crypt hyperplasia, but the main driver for inflammation is gliadin-reactive T-cells. Therefore, the aim of this study was to investigate the TLRs 2, 4, 7, and 9 gene expressions in both peripheral blood and intestinal mucosa of patients with celiac disease compared to healthy control (HC).

Material and Methods

Blood samples from 120 confirmed active CD patients and 120 age- and sex-matched healthy volunteers served as control group were collected during 2015-2016. Also, 20 biopsy specimens from the study group were randomly collected. Total RNA was isolated using a standard commercial kit. The mRNA expression of TLRs was quantified by relative qPCR with β2 microglobulin (β2m) as a reference gene.

Results

TLR4 (P = 0.01) and TLR9 (P = 0.02) mRNA were significantly elevated in blood samples from CD patients compared to the healthy controls. Moreover, TLR2 (P = 0.03) and TLR4 (P = 0.0003) expression level was increased in CD biopsy specimens compared to controls, whereas expression of TLR9 mRNA was significantly decreased in CD patients. There was no significant difference in the expression of TLR7 in biopsy and blood specimens.

Conclusions

The alteration of TLR4 and TLR9 expression in the blood and biopsy samples of patients with CD supports the critical role of the innate immune system in the pathogenesis of this disease. Upregulation of TLR4 and TLR9 suggests the contribution of gut microbiota or dysregulation of the immune response to commensal flora in small bowel mucosa in celiac patients.

Microfluidic Organ-on-a-Chip Models of Human Intestine

Microfluidic organ-on-a-chip models of human intestine have been developed and used to study intestinal physiology and pathophysiology. In this article, we review this field and describe how microfluidic Intestine Chips offer new capabilities not possible with conventional culture systems or organoid cultures, including the ability to analyze contributions of individual cellular, chemical, and physical control parameters one-at-a-time; to coculture human intestinal cells with commensal microbiome for extended times; and to create human-relevant disease models. We also discuss potential future applications of human Intestine Chips, including how they might be used for drug development and personalized medicine.

Isolation and characterization of gluten protein types from wheat, rye, barley and oats for use as reference materials

Gluten proteins from wheat, rye, barley and, in rare cases, oats, are responsible for triggering hypersensitivity reactions such as celiac disease, non-celiac gluten sensitivity and wheat allergy. Well-defined reference materials (RM) are essential for clinical studies, diagnostics, elucidation of disease mechanisms and food analyses to ensure the safety of gluten-free foods. Various RM are currently used, but a thorough characterization of the gluten source, content and composition is often missing. However, this characterization is essential due to the complexity and heterogeneity of gluten to avoid ambiguous results caused by differences in the RM used. A comprehensive strategy to isolate gluten protein fractions and gluten protein types (GPT) from wheat, rye, barley and oat flours was developed to obtain well-defined RM for clinical assays and gluten-free compliance testing. All isolated GPT (ω5-gliadins, ω1,2-gliadins, α-gliadins, γ-gliadins and high- and low-molecular-weight glutenin subunits from wheat, ω-secalins, γ-75k-secalins, γ-40k-secalins and high-molecular-weight secalins from rye, C-hordeins, γ-hordeins, B-hordeins and D-hordeins from barley and avenins from oats) were fully characterized using analytical reversed-phase high-performance liquid chromatography (RP-HPLC), sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), N-terminal sequencing, electrospray-ionization quadrupole time-of-flight mass spectrometry (LC-ESI-QTOF-MS) and untargeted LC-MS/MS of chymotryptic hydrolyzates of the single GPT. Taken together, the analytical methods confirmed that all GPT were reproducibly isolated in high purity from the flours and were suitable to be used as RM, e.g., for calibration of LC-MS/MS methods or enzyme-linked immunosorbent assays (ELISAs).

Twenty-Four Hour Ex Vivo Culture of Celiac Duodenal Biopsies

Organ culture is a valuable technique in celiac disease research. It provides the opportunity to examine interactions between different cell types during the disease process without the need for invasive in vivo studies. Biopsies are maintained in an oxygen-rich environment, in contact with, but not submerged in, culture medium. A very straightforward and successful method of organ culture is described here.

Genetics of celiac disease

New insights into the underlying molecular pathophysiology of celiac disease (CeD) over the last few years have been guided by major advances in the fields of genetics and genomics. The development and use of the Immunochip genotyping platform paved the way for the discovery of 39 non-HLA loci associated to CeD, and for follow-up functional genomics studies that pinpointed new disease genes, biological pathways and regulatory elements. By combining information from genetics with gene expression data, it has become clear that CeD is a disease with a dysregulated immune response, which can probably occur in a variety of immune cells. This type of information is crucial for our understanding of the disease and for providing leads for developing alternative therapies to the current gluten-free diet. In this review, we place these genetic findings in a wider context and suggest how they can assist the clinical care of CeD patients.

Adaptive response activated by dietary cis9, trans11 conjugated linoleic acid prevents distinct signs of gliadin-induced enteropathy in mice

PURPOSE

The beneficial effects of conjugated linoleic acid (CLA) mixture (cis9, trans11, c9; trans10, cis12, t10) against gliadin-induced toxicity in HLA-DQ8-transgenic mice (DQ8) have been associated with improved duodenal cytoprotective mechanisms [nuclear factor-E2-related factor-2, Nrf2; acylpeptide hydrolase (APEH)/proteasome]. The present study was aimed at investigating the ability of individual CLA isomers to improve the efficacy of these defensive mechanisms and to protect against duodenal injury caused by the combined administration of gliadin and indomethacin (GI).

METHODS

Gluten-mediated enteropathy was induced in DQ8 mice by three intra-gastric administration of gliadin (20 mg kg(-1)/bw) and indomethacin (15 mg L(-1)) in drinking water for 10 days (GI). C9 or t10 CLA (520 mg kg(-1)/bw/day) were orally administered for 2 weeks. Pro-oxidant and toxic effects associated with GI treatment, anti-oxidant/detoxifying ability of c9 or t10-CLA and the protective effect induced by c9 pre-treatment (c9 + GI) were evaluated in DQ8 mice duodenum by combining enzymatic, immunoblotting, histological evaluation and quantitative real-time PCR assays.

RESULTS

GI treatment produces the time-dependent decline of the considered detoxifying mechanisms thus leading to pro-apoptotic and pro-oxidant effects. APEH/proteasome pathway was not markedly affected by individual CLA isomers, but duodenal redox status and activity/mRNA levels of Nrf2-activated enzymes were significantly improved by c9 administration. c9 pre-treatment protects against GI-mediated accumulation of oxidative stress markers, and histological examination reveals the increase of goblet cells number in mouse duodenum but induces only a partial recovery of APEH/proteasome activity.

CONCLUSIONS

The activation of and adaptive response by low doses of c9 supplementation prevents distinct signs of gliadin-induced enteropathy in DQ8 mice.

Helicobacter pylori-Mediated Protection against Extra-Gastric Immune and Inflammatory Disorders: The Evidence and Controversies

A large number of studies link H. pylori infection with a reduced risk of developing extra-gastric conditions such as allergy, asthma, inflammatory bowel disease, coeliac disease and multiple sclerosis. The strength of the evidence for these protective associations is quite variable, and published studies often do not agree. This review article discusses some of the reasons for these discrepancies, and the difficulties faced when designing studies. Examples of some protective disease associations are described in detail, where the evidence is most abundant and thought to be more reliable. The most convincing of these are supported by published mechanistic data, for example with animal models, or incidence of disease exacerbation in humans following H. pylori eradication. Although controversial, this field is very important as the prevalence of H. pylori is decreasing throughout the world whilst many chronic diseases are becoming more common. These trends are likely to continue in the future, therefore it is important that we fully understand if and how H. pylori confers protection.

Does the microbiota play a role in the pathogenesis of autoimmune diseases?

The microbiota of the human metaorganism is not a mere bystander. These microbes have coevolved with us and are pivotal to normal development and homoeostasis. Dysbiosis of the GI microbiota is associated with many disease susceptibilities, including obesity, malignancy, liver disease and GI pathology such as IBD. It is clear that there is direct and indirect crosstalk between this microbial community and host immune response. However, the precise mechanism of this microbial influence in disease pathogenesis remains elusive and is now a major research focus. There is emerging literature on the role of the microbiota in the pathogenesis of autoimmune disease, with clear and increasing evidence that changes in the microbiota are associated with some of these diseases. Examples include type 1 diabetes, coeliac disease and rheumatoid arthritis, and these contribute significantly to global morbidity and mortality. Understanding the role of the microbiota in autoimmune diseases may offer novel insight into factors that initiate and drive disease progression, stratify patient risk for complications and ultimately deliver new therapeutic strategies. This review summarises the current status on the role of the microbiota in autoimmune diseases.

Generation of food-grade recombinant Lactobacillus casei delivering Myxococcus xanthus prolyl endopeptidase

Prolyl endopeptidases (PEP) (EC 3.4.21.26), a family of serine proteases with the ability to hydrolyze the peptide bond on the carboxyl side of an internal proline residue, are able to degrade immunotoxic peptides responsible for celiac disease (CD), such as a 33-residue gluten peptide (33-mer). Oral administration of PEP has been suggested as a potential therapeutic approach for CD, although delivery of the enzyme to the small intestine requires intrinsic gastric stability or advanced formulation technologies. We have engineered two food-grade Lactobacillus casei strains to deliver PEP in an in vitro model of small intestine environment. One strain secretes PEP into the extracellular medium, whereas the other retains PEP in the intracellular environment. The strain that secretes PEP into the extracellular medium is the most effective to degrade the 33-mer and is resistant to simulated gastrointestinal stress. Our results suggest that in the future, after more studies and clinical trials, an engineered food-grade Lactobacillus strain may be useful as a vector for in situ production of PEP in the upper small intestine of CD patients.