Role of Intestinal Bacteria in Gliadin-Induced Changes in Intestinal Mucosa: Study in Germ-Free Rats

10 pages, 6 figures.[Background and Aims]: Celiac disease (CD) is a chronic inflammatory disorder of the small intestine that is induced by dietary wheat gluten proteins (gliadins) in genetically predisposed individuals. The overgrowth of potentially pathogenic bacteria and infections has been suggested to contribute to CD pathogenesis. We aimed to study the effects of gliadin and various intestinal bacterial strains on mucosal barrier integrity, gliadin translocation, and cytokine production.[Methodology/Principal Findings]: Changes in gut mucosa were assessed in the intestinal loops of inbred Wistar-AVN rats that were reared under germ-free conditions in the presence of various intestinal bacteria (enterobacteria and bifidobacteria isolated from CD patients and healthy children, respectively) and CD-triggering agents (gliadin and IFN-γ) by histology, scanning electron microscopy, immunofluorescence, and a rat cytokine antibody array. Adhesion of the bacterial strains to the IEC-6 rat cell line was evaluated in vitro. Gliadin fragments alone or together with the proinflammatory cytokine interferon (IFN)-γ significantly decreased the number of goblet cells in the small intestine; this effect was more pronounced in the presence of Escherichia coli CBL2 and Shigella CBD8. Shigella CBD8 and IFN-γ induced the highest mucin secretion and greatest impairment in tight junctions and, consequently, translocation of gliadin fragments into the lamina propria. Shigella CBD8 and E. coli CBL2 strongly adhered to IEC-6 epithelial cells. The number of goblet cells in small intestine increased by the simultaneous incubation of Bifidobacterium bifidum IATA-ES2 with gliadin, IFN-γ and enterobacteria. B. bifidum IATA-ES2 also enhanced the production of chemotactic factors and inhibitors of metalloproteinases, which can contribute to gut mucosal protection.[Conclusions]: Our results suggest that the composition of the intestinal microbiota affects the permeability of the intestinal mucosa and, consequently, could be involved in the early stages of CD pathogenesis.This work was supported by grants 310/07/0414, 303/08/0367, P304/10/P406 of the Grant Agency of the Czech Republic; IAA500200801, IAA500200710, KJB50020094 of the Academy of Sciences; AV CR-C.S.I.C. 09/10, Project 2B06155 of the Ministry of Education; and Institutional Research Concept AVOZ50200510. This work was also supported by grants 2006CZ0030 and 2008CZ0023 from Consejo Superior de Investigaciones Científicas (CSIC, Spain) and AGL2008-01440/ALI and Consolider Fun-C-Food CSD2007-00063 from the Spanish Ministry of Science and Innovation. The scholarship to G. De Palma from Junta de Ampliación de Estudios - Consejo Superior de Investigaciones Científicas (JAE-CSIC; Spain) is fully acknowledged.Peer reviewe

Colonization of germ-free mice with a mixture of three lactobacillus strains enhances the integrity of gut mucosa and ameliorates allergic sensitization

Increasing numbers of clinical trials and animal experiments have shown that probiotic bacteria are promising tools for allergy prevention. Here, we analyzed the immunomodulatory properties of three selected lactobacillus strains and the impact of their mixture on allergic sensitization to Bet v 1 using a gnotobiotic mouse model. We showed that Lactobacillus (L.) rhamnosus LOCK0900, L. rhamnosus LOCK0908 and L. casei LOCK0919 are recognized via Toll-like receptor 2 (TLR2) and nucleotide-binding oligomerization domain-containing protein 2 (NOD2) receptors and stimulate bone marrow-derived dendritic cells to produce cytokines in species- and strain-dependent manners. Colonization of germ-free (GF) mice with a mixture of all three strains (Lmix) improved the intestinal barrier by strengthening the apical junctional complexes of enterocytes and restoring the structures of microfilaments extending into the terminal web. Mice colonized with Lmix and sensitized to the Bet v 1 allergen showed significantly lower levels of allergen-specific IgE, IgG1 and IgG2a and an elevated total IgA level in the sera and intestinal lavages as well as an increased transforming growth factor (TGF)-β level compared with the sensitized GF mice. Splenocytes and mesenteric lymph node cells from the Lmix-colonized mice showed the significant upregulation of TGF-β after in vitro stimulation with Bet v 1. Our results show that Lmix colonization improved the gut epithelial barrier and reduced allergic sensitization to Bet v 1. Furthermore, these findings were accompanied by the increased production of circulating and secretory IgA and the regulatory cytokine TGF-β. Thus, this mixture of three lactobacillus strains shows potential for use in the prevention of increased gut permeability and the onset of allergies in humans

Germ-Free Mice Exhibit Mast Cells With Impaired Functionality and Gut Homing and Do Not Develop Food Allergy

Background: Mucosal mast cells (MC) are key players in IgE-mediated food allergy (FA). The evidence on the interaction between gut microbiota, MC and susceptibility to FA is contradictory.Objective: We tested the hypothesis that commensal bacteria are essential for MC migration to the gut and their maturation impacting the susceptibility to FA.Methods: The development and severity of FA symptoms was studied in sensitized germ-free (GF), conventional (CV), and mice mono-colonized with L. plantarum WCFS1 or co-housed with CV mice. MC were phenotypically and functionally characterized.Results: Systemic sensitization and oral challenge of GF mice with ovalbumin led to increased levels of specific IgE in serum compared to CV mice. Remarkably, despite the high levels of sensitization, GF mice did not develop diarrhea or anaphylactic hypothermia, common symptoms of FA. In the gut, GF mice expressed low levels of the MC tissue-homing markers CXCL1 and CXCL2, and harbored fewer MC which exhibited lower levels of MC protease-1 after challenge. Additionally, MC in GF mice were less mature as confirmed by flow-cytometry and their functionality was impaired as shown by reduced edema formation after injection of degranulation-provoking compound 48/80. Co-housing of GF mice with CV mice fully restored their susceptibility to develop FA. However, this did not occur when mice were mono-colonized with L. plantarum.Conclusion: Our results demonstrate that microbiota-induced maturation and gut-homing of MC is a critical step for the development of symptoms of experimental FA. This new mechanistic insight into microbiota-MC-FA axis can be exploited in the prevention and treatment of FA in humans

Heat-Induced Structural Changes Affect OVA-Antigen Processing and Reduce Allergic Response in Mouse Model of Food Allergy

BACKGROUND AND AIMS: The egg protein ovalbumin (OVA) belongs to six most frequent food allergens. We investigated how thermal processing influences its ability to induce allergic symptoms and immune responses in mouse model of food allergy. METHODOLOGY/PRINCIPAL FINDINGS: Effect of increased temperature (70°C and 95°C) on OVA secondary structure was characterized by circular dichroism and by the kinetics of pepsin digestion with subsequent HPLC. BALB/c mice were sensitized intraperitoneally and challenged with repeated gavages of OVA or OVA heated to 70°C (h-OVA). Levels of allergen-specific serum antibodies were determined by ELISA (IgA and IgGs) or by β-hexosaminidase release test (IgE). Specific activities of digestive enzymes were determined in brush border membrane vesicles of jejunal enterocytes. Cytokine production and changes in regulatory T cells in mesenteric lymph nodes and spleen were assessed by ELISA and FACS. Heating of OVA to 70°C caused mild irreversible changes in secondary structure compared to boiling to 95°C (b-OVA), but both OVA treatments led to markedly different digestion kinetics and Tregs induction ability in vitro, compared to native OVA. Heating of OVA significantly decreased clinical symptoms (allergic diarrhea) and immune allergic response on the level of IgE, IL-4, IL-5, IL-13. Furthermore, h-OVA induced lower activities of serum mast cell protease-1 and enterocyte brush border membrane alkaline phosphatase as compared to native OVA. On the other hand h-OVA stimulated higher IgG2a in sera and IFN-γ secretion by splenocytes. CONCLUSIONS: Minor irreversible changes in OVA secondary structure caused by thermal processing changes both its digestion and antigenic epitopes formation, which leads to activation of different T cell subpopulations, induces shift towards Th1 response and ultimately reduces its allergenicity

Charakterizace autoantigenu a patogeneticke mechanismy

Celiac disease is one of the frequent chronic diseases affecting gut mucosa, occuring in genetically susceptible individuals after ingestion of gluten. It is characterised by a flattened mucosa, villous atrophy, and crypt hyperplasia in the small intestine. The treatment of the disease, dietary avoidance of gluten, leads to renewal of gut architecture. The presence of autoantibodies in celiac patients sera, a strong genetic major histocompatibility complex linked susceptibility, a local inflammatory response, association with other autoimmune diseases and higher occurence in females than in males, suggest that celiac disease has many characteristic features of autoimmune diseases. One of the mechanisms involved in development of the disease may include the generation of antibodies against gliadin, which could recognize similar structures on selfcomponents. Sera of patients with celiac disease contain high concentration of IgA and IgG antigliadin Abs and also IgA anti-reticulin, antiendomysial and antijejunal autoantibodies, that are used as serological markers for diagnostic screening of the disease. The molecular nature of target structures of these autoantigens is being intensively studied. The tissue transglutaminase has recently been identified as a main endomysila autoantigen. We have found that sera and media from cultured biopsies of patients with celiac disease also contain Abs against isolated rat and human enterocytes. Furthermore, we have observed that some monoclonal Abs to gliadin, as well as antigliadin Abs of celiac patients with active form of the disease, cross-react with similar epitopes on rat and human enterocytes. Interesting was that, both types of antigliadin Abs, monoclonal and isolated from celiac patients sera, recognized two main proteins and two minor proteins. In a pilot study we have found significantly elevated levels of IgA autoantibodies to enterocytes and calreticulin in sera of patients with active celiac disease than in sera of patients on gluten-free diet and healthy controls and we have suggested a possible role of the cross reactive Abs in pathogenesis of celiac disease. In the following comparative study we have detected significantly higher level of IgA anti-CRT Abs in 94 percents of celiac disease and low level of these Abs in sera of some patients with autoimmune thyroiditis and inflammatory bowel disease. The level of IgG antiCRT was increased in sera of about 35 percents of patients with systemic lupus erythematosus, but the mean level reaching only half of that detected in celiac patients. In the occasional patients with malabsorbtion and histological findings consistent with celiac disease, who fail to respond to gluten free diet, the diagnosis cannot be firmly established. After exclusion of other causes of flat mucosa they are considered to suffer from so called unclassified or refractory sprue, difficult therapeutic problem with poor prognosis. We have found that these patients when on gluten-free diet, have decreased level of IgA antigladin Abs and also of anti tTg and anti EMA autoantibodies, but the level of antienterocyte and anti CRT autoantibodies remain still high. When confirmed in large scale study the testing of enterocyte autoantibodies could help to diagnose and to follow up treatment of this serious diseaseAvailable from STL Prague, CZ / NTK - National Technical LibrarySIGLECZCzech Republi

Cytokine array analysis of rat intestinal loops washes.

<p>Layout of the arrays (A), cytokine profiles from loops treated with PBS (control) (B), gliadin (C), gliadin+IFN-γ (D), <i>B. bifidum</i> IATA-ES2+gliadin+IFN-γ (E), <i>E. coli</i> CBL2+gliadin+IFN-γ (F), and <i>E. coli</i> CBL2+<i>B. bifidum</i> IATA-ES2+gliadin+IFN-γ (G). The data are expressed as relative levels of selected cytokines (percentage of positive controls). Cytokine-induced neutrophil chemoattractant (CINC)-2 and -3, monocyte chemoattractant protein (MCP)-1, macrophage inflammatory protein (MIP)-3α, nerve growth factor β-(NGF), tumor necrosis factor (TNF)-α, vascular endothelial growth factor (VEGF). The signal intensity was measured using the LAS-1000 luminescence detector (Fujifilm, Tokyo, Japan).</p