Sensitization to gliadin induces moderate enteropathy and insulitis in nonobese diabetic-DQ8 mice

Gliadin intake alters the small intestinal mucosa in indomethacin-treated HLA-DQ8 transgenic mice

Celiac disease (CD) is an enteropathy caused by the ingestion of wheat gluten in genetically susceptible individuals. A complete understanding of the pathogenic mechanisms in CD has been hindered because of the lack of adequate in vivo models. In the present study, we explored the events after the intragastric administration of gliadin and of the albumin/globulin fraction from wheat in human leukocyte antigen-DQ8 transgenic mice (DQ8 mice) treated with indomethacin, an inhibitor of cyclooxygenases (COXs). After 10 days of treatment, mice showed a significant reduction of villus height, increased crypt depth, increased number of lamina propria-activated macrophages, and high basal interferon-γ secretion in mesenteric lymph nodes, all of which were specifically related to gliadin intake, whereas the albumin/globulin fraction of wheat was unable to induce similar changes. Cotreatment with NS-398, a specific inhibitor of COX-2, also induced the intestinal lesion. Enteropathy onset was further characterized by high levels of oxidative stress markers, similar to CD. Biochemical assessment of the small intestine revealed the specific activation of matrix metalloproteinases 2 and 9, high caspase-3 activity, and a significant increase of tissue transglutaminase protein levels associated with the intestinal lesion. Notably, after 30 days of treatment, enteropathic mice developed serum antibodies toward gliadin (IgA) and tissue transglutaminase (IgG). We concluded that gliadin intake in combination with COX inhibition caused a basal inflammatory status and an oxidative stress condition in the small intestine of DQ8 mice, thus triggering the mucosal lesion and, subsequently, an antigen-specific immunity.

Intraluminal administration of poly I:C causes an enteropathy that is exacerbated by administration of oral dietary antigen

Systemic administration of polyinosinic:polycytidylic acid (poly I:C), mimics virally-induced activation of TLR3 signalling causing acute small intestine damage, but whether and how mucosal administration of poly I:C causes enteropathy is less clear. Our aim was to investigate the inflammatory pathways elicited after intraluminal administration of poly I:C and determine acute and delayed consequences of this locally induced immune activation. Intraluminal poly I:C induced rapid mucosal immune activation in C57BL/6 mice involving IFNβ and the CXCL10/CXCR3 axis, that may drive inflammation towards a Th1 profile. Intraluminal poly I:C also caused enteropathy and gut dysfunction in gliadin-sensitive NOD-DQ8 mice, and this was prolonged by concomitant oral administration of gliadin. Our results indicate that small intestine pathology can be induced in mice by intraluminal administration of poly I:C and that this is exacerbated by subsequent oral delivery of a relevant dietary antigen.

Novel role of the serine protease inhibitor elafin in gluten-related disorders

OBJECTIVES

Elafin, an endogenous serine protease inhibitor, modulates colonic inflammation. We investigated the role of elafin in celiac disease (CD) using human small intestinal tissues and in vitro assays of gliadin deamidation. We also investigated the potential beneficial effects of elafin in a mouse model of gluten sensitivity.

METHODS

Epithelial elafin expression in the small intestine of patients with active CD, treated CD, and controls without CD was determined by immunofluorescence. Interaction of elafin with human tissue transglutaminase-2 (TG-2) was investigated in vitro. The 33-mer peptide, a highly immunogenic gliadin peptide, was incubated with TG-2 and elafin at different concentrations. The degree of deamidation of the 33-mer peptide was analyzed by liquid chromatography-mass spectrometry. Elafin was delivered to the intestine of gluten-sensitive mice using a recombinant Lactococcus lactis vector. Small intestinal barrier function, inflammation, proteolytic activity, and zonula occludens-1 (ZO-1) expression were assessed.

RESULTS

Elafin expression in the small intestinal epithelium was lower in patients with active CD compared with control patients. In vitro, elafin significantly slowed the kinetics of the deamidation of the 33-mer peptide to its more immunogenic form. Treatment of gluten-sensitive mice with elafin delivered by the L. lactis vector normalized inflammation, improved permeability, and maintained ZO-1 expression.

CONCLUSIONS

The decreased elafin expression in the small intestine of patients with active CD, the reduction of 33-mer peptide deamidation by elafin, coupled to the barrier enhancing and anti-inflammatory effects observed in gluten-sensitive mice, suggest that this molecule may have pathophysiological and therapeutic importance in gluten-related disorders.

Prevention or early cure of type 1 diabetes by intranasal administration of gliadin in NOD mice

Induction of long-term tolerance to β-cell autoantigens has been investigated both in animal models and in human type 1 diabetes (T1D) in order to prevent the disease. As regards external compounds, the dietary plant protein fraction has been associated with high penetrance of the disease, whereas gluten-free diets prevent T1D in animal models. Herewith we investigated whether intranasal (i.n.) administration of gliadin or gluten may arrest the diabetogenic process. I.n. administration of gliadin to 4-week-old NOD mice significantly reduced the diabetes incidence. Similarly, the insulitis was lowered. Intranasal gliadin also rescued a fraction of prediabetic 13-week-old NOD mice from progressing to clinical onset of diabetes compared to OVA-treated controls. Vaccination with i.n. gliadin led to an induction of CD4⁺Foxp3⁺ T cells and even more significant induction of γδ T cells in mucosal, but not in non-mucosal lymphoid compartments. This prevention strategy was characterized by an increased proportion of IL-10 and a decreased proportion of IL-2, IL-4 and IFN-γ-positive CD4⁺Foxp3⁺ T cells, and IFN-γ-positive γδ T cells, preferentially in mucosal lymphoid organs. In conclusion, i.n. vaccination with gliadin, an environmental antigen with possible etiological influence in T1D, may represent a novel, safer strategy for prevention or even early cure of T1D.

Bridging immunity and lipid metabolism by gut microbiota

The human gut is a unique organ in which hundreds of different microbial species find their habitat and in which different host physiologic functions, such as digestion, nutrition, and immunity, coexist. Although all these players were studied separately for decades, recently, there has been an explosion of studies demonstrating the essential role for interactions between these components in gut function. Furthermore, new systems biology methods provide essential tools to study this complex system as a whole and to identify key elements that define the crosstalk between the gut microbiota, immunity, and metabolism. This review is devoted to several human diseases resulting from the disruption in this crosstalk, including immunodeficiency-associated and environmental enteropathies, celiac disease, inflammatory bowel disease, and obesity. We describe findings in experimental models of these diseases and in germ-free animals that help us understand the mechanisms and test new therapeutic strategies. We also discuss current challenges that the field is facing and propose that a new generation of antibiotics, prebiotics, and probiotics coupled with novel, systems biology-driven diagnostics will provide the basis for future personalized therapy.

Is type 1 diabetes a food-induced disease?

The incidence of type 1 diabetes among children has almost doubled during the last decades in Sweden. Type 1 diabetes is considered as an autoimmune disease with unknown aetiology. Here we propose that the immune reaction may be initiated by food-derived mechanisms. The incidence of diabetes parallels an increased consumption of pasta, white bread, meat, cheese, low-fat milk, exotic fruits, soda, and snacks. Simultaneously, the consumption of potatoes, butter, high-fat milk, and domestic fruit has decreased. Three categories of food related reaction mechanisms are discussed against the following items (1) proteins from wheat, meat, and milk, (2) fat from processed food, and (3) exotic fruits. The current food consumption is suggested to initiate a pro-inflammatory reaction in the intestine and thereby reduce the intestinal barrier function. This may influence tolerance development and thus pave the way for an autoimmune attack on pancreatic beta cells.

Dietary gluten alters the balance of pro-inflammatory and anti-inflammatory cytokines in T cells of BALB/c mice

Several studies have documented that dietary modifications influence the development of type 1 diabetes. However, little is known about the interplay of dietary components and the penetration of diabetes incidence. In this study we tested if wheat gluten is able to induce differences in the cytokine pattern of Foxp3(+) regulatory T cells, as well as Foxp3(-) T cells, isolated from intestinal mucosal lymphoid tissue and non-mucosal lymphoid compartments in BALB/c mice. The gluten-containing standard diet markedly changed the cytokine expression within Foxp3(-) T cells, in all lymphoid organs tested, towards a higher expression of pro-inflammatory interferon-γ (IFN-γ), interleukin-17 (IL-17) and IL-2. In Foxp3(+) regulatory T cells, gluten ingestion resulted in a mucosal increase in IL-17 and IL-2 and an overall increase in IFN-γ and IL-4. The gluten-free diet induced an anti-inflammatory cytokine profile with higher proportion of transforming growth factor-β (TGF-β)(+) Foxp3(-) T cells in all tested lymphoid tissues and higher IL-10 expression within non-T cells in spleen, and a tendency towards a mucosal increase in TGF-β(+) Foxp3(+) regulatory T cells. Our data shows that the gluten-containing standard diet modifies the cytokine pattern of both Foxp3(-) T cells and Foxp3(+) regulatory T cells towards a more inflammatory cytokine profile. This immune profile may contribute to the higher type 1 diabetes incidence associated with gluten intake.

Latest in vitro and in vivo models of celiac disease

INTRODUCTION

Currently, the only treatment for celiac disease is a gluten-free diet, and there is an increased desire for alternative therapies. In vitro and in vivo models of celiac disease have been generated in order to better understand the pathogenesis of celiac disease, and this review will discuss these models as well as the testing of alternative therapies using these models.

AREAS COVERED

The research discussed describes the different in vitro and in vivo models of celiac disease that currently exist and how they have contributed to our understanding of how gluten can stimulate both innate and adaptive immune responses in celiac patients. We also provide a summary on the alternative therapies that have been tested with these models and discuss whether subsequent clinical trials were done based on these tests done with these models of celiac disease.

EXPERT OPINION

Only a few of the alternative therapies that have been tested with animal models have gone on to clinical trials; however, those that did go on to clinical trial have provided promising results from a safety standpoint. Further trials are required to determine if some of these therapies may serve as an effective adjunct to a gluten-free diet to alleviate the adverse affects associated with accidental gluten exposure. A "magic-bullet" approach may not be the answer to celiac disease, but possibly a future cocktail of these different therapeutics may allow celiac patients to consume an unrestricted diet.

Animal models to study gluten sensitivity

The initial development and maintenance of tolerance to dietary antigens is a complex process that, when prevented or interrupted, can lead to human disease. Understanding the mechanisms by which tolerance to specific dietary antigens is attained and maintained is crucial to our understanding of the pathogenesis of diseases related to intolerance of specific dietary antigens. Two diseases that are the result of intolerance to a dietary antigen are celiac disease (CD) and dermatitis herpetiformis (DH). Both of these diseases are dependent upon the ingestion of gluten (the protein fraction of wheat, rye, and barley) and manifest in the gastrointestinal tract and skin, respectively. These gluten-sensitive diseases are two examples of how devastating abnormal immune responses to a ubiquitous food can be. The well-recognized risk genotype for both is conferred by either of the HLA class II molecules DQ2 or DQ8. However, only a minority of individuals who carry these molecules will develop either disease. Also of interest is that the age at diagnosis can range from infancy to 70-80 years of age. This would indicate that intolerance to gluten may potentially be the result of two different phenomena. The first would be that, for various reasons, tolerance to gluten never developed in certain individuals, but that for other individuals, prior tolerance to gluten was lost at some point after childhood. Of recent interest is the concept of non-celiac gluten sensitivity, which manifests as chronic digestive or neurologic symptoms due to gluten, but through mechanisms that remain to be elucidated. This review will address how animal models of gluten-sensitive disorders have substantially contributed to a better understanding of how gluten intolerance can arise and cause disease.

Remission without insulin therapy on gluten-free diet in a 6-year old boy with type 1 diabetes mellitus

A 5-year and 10-month old boy was diagnosed with classical type 1 diabetes mellitus (T1DM) without celiac disease. He started on a gluten-free diet after 2-3 week without need of insulin treatment. At the initiation of gluten-free diet, HbA1c was 7.8% and was stabilised at 5.8%-6.0% without insulin therapy. Fasting blood glucose was maintained at 4.0-5.0 mmol/l. At 16 months after diagnosis the fasting blood glucose was 4.1 mmol/l and after 20 months he is still without daily insulin therapy. There was no alteration in glutamic acid decarboxylase positivity. The gluten-free diet was safe and without side effects. The authors propose that the gluten-free diet has prolonged remission in this patient with T1DM and that further trials are indicated.