Gliadin, zonulin and gut permeability: Effects on celiac and non-celiac intestinal mucosa and intestinal cell lines

Stress induces endotoxemia and low-grade inflammation by increasing barrier permeability

Chronic non-communicable diseases (NCDs) are the leading causes of work absence, disability, and mortality worldwide. Most of these diseases are associated with low-grade inflammation. Here, we hypothesize that stresses (defined as homeostatic disturbances) can induce low-grade inflammation by increasing the availability of water, sodium, and energy-rich substances to meet the increased metabolic demand induced by the stressor. One way of triggering low-grade inflammation is by increasing intestinal barrier permeability through activation of various components of the stress system. Although beneficial to meet the demands necessary during stress, increased intestinal barrier permeability also raises the possibility of the translocation of bacteria and their toxins across the intestinal lumen into the blood circulation. In combination with modern life-style factors, the increase in bacteria/bacterial toxin translocation arising from a more permeable intestinal wall causes a low-grade inflammatory state. We support this hypothesis with numerous studies finding associations with NCDs and markers of endotoxemia, suggesting that this process plays a pivotal and perhaps even a causal role in the development of low-grade inflammation and its related diseases.

CD4⁺ T-cell proliferation responses to wheat polypeptide stimulation in children at different stages of type 1 diabetes autoimmunity

AIMS

Our aim was to study whether immune responses to wheat-based proteins are related to the development of type 1 diabetes.

METHODS

We analysed proliferative T-cell responses after in vitro gliadin, gluten, whole wheat, and tetanus toxoid stimulation with a carboxyfluorescein succinimidyl ester (CFSE) based T-cell proliferation assay in children at various phases of type 1 diabetes autoimmunity and in healthy autoantibody-negative control children.

RESULTS

At an early stage of beta cell autoimmunity the strength and frequencies of positive proliferation responses to gliadin, gluten, and whole wheat did not differ between newly seroconverted children positive for one islet autoantibody and the controls. However, in prediabetic children with at least two islet autoantibodies and also in children with newly diagnosed type 1 diabetes positive T-cell responses to gliadin were significantly less frequent and the strength of gliadin responses was reduced when compared to the controls. No differences were seen in T-cell responses to wheat-based antigens when comparing children with long-lasting type 1 diabetes with healthy controls.

CONCLUSIONS/INTERPRETATION

Decreased in vitro T-cell responses to wheat-based antigens were observed in children with multiple islet autoantibodies and in those with newly diagnosed type 1 diabetes, probably reflecting a generally aberrant immune response during the development of type 1 diabetes.

Are stem cells a potential therapeutic tool in coeliac disease?

Despite the growing understanding of its pathogenesis, the treatment of coeliac disease is still based on a lifelong gluten-free diet that, although efficacious, is troublesome for affected patients, and a definitive cure is still an unmet need. In this regard, the development of new chemical- and biological-derived agents has often resulted in unsatisfactory effects when tested in vivo, probably because of their ability to target only a single pathway, whilst the immunological cascade responsible for tissue injury is complex and redundant. The advent of cellular therapies, mainly based on the use of stem cells, is an emerging area of interest since it has the advantage of a multi-target strategy. Both haematopoietic and mesenchymal stem cells have been employed in the treatment of refractory patients suffering from autoimmune diseases, with promising results. However, the lack of immunogenicity makes mesenchymal stem cells more suitable than their haematopoietic counterpart, since their transplantation may be performed in the absence of a myeloablative conditioning regimen. In addition, mesenchymal stem cells have been shown to harbour strong modulatory effects on almost all cells involved in immune response, together with a potent regenerative action. It is therefore conceivable that over the next few years their therapeutic use will increase as their biological interactions with injured tissues become clearer.

Effect of gliadin on permeability of intestinal biopsy explants from celiac disease patients and patients with non-celiac gluten sensitivity

Background: Intestinal exposure to gliadin leads to zonulin upregulation and consequent disassembly of intercellular tight junctions and increased intestinal permeability. We aimed to study response to gliadin exposure, in terms of barrier function and cytokine secretion, using intestinal biopsies obtained from four groups: celiac patients with active disease (ACD), celiac patients in remission (RCD), non-celiac patients with gluten sensitivity (GS) and non-celiac controls (NC). Methods: Ex-vivo human duodenal biopsies were mounted in microsnapwells and luminally incubated with either gliadin or media alone. Changes in transepithelial electrical resistance were monitored over 120 min. Media was subsequently collected and cytokines quantified. Results: Intestinal explants from all groups (ACD (n = 6), RCD (n = 6), GS (n = 6), and NC (n = 5)) demonstrated a greater increase in permeability when exposed to gliadin vs. media alone. The increase in permeability in the ACD group was greater than in the RCD and NC groups. There was a greater increase in permeability in the GS group compared to the RCD group. There was no difference in permeability between the ACD and GS groups, between the RCD and NC groups, or between the NC and GS groups. IL-10 was significantly greater in the media of the NC group compared to the RCD and GS groups. Conclusions: Increased intestinal permeability after gliadin exposure occurs in all individuals. Following gliadin exposure, both patients with gluten sensitivity and those with active celiac disease demonstrate a greater increase in intestinal permeability than celiacs in disease remission. A higher concentration of IL-10 was measured in the media exposed to control explants compared to celiac disease in remission or gluten sensitivity.

Intestinal microbiota and probiotics in celiac disease

Celiac disease (CD) is a common chronic autoimmune enteropathy caused by gluten intake. To date, the only therapy for CD is the complete exclusion of dietary sources of grains and any food containing gluten. It has been hypothesized that the intestinal microbiota is somehow involved in CD. For this reason, probiotics are appearing as an interesting adjuvant in the dietetic management of CD. This review aims to discuss the characteristics of the microbiota in CD subjects and the use of probiotics as a novel therapy for CD. Comparisons between children with CD and controls show that their microbiota profiles differ; the former have fewer lactobacilli and bifidobacteria. Specific probiotics have been found to digest or alter gluten polypeptides. It has also been demonstrated that some bacterial species belonging to the genera Lactobacillus and Bifidobacterium exert protective properties on epithelial cells from damage caused by gliadin.

Increased circulating zonulin in children with biopsy-proven nonalcoholic fatty liver disease

AIM: To investigate the potential association of circulating zonulin with the stage of liver disease in obese children with biopsy-confirmed nonalcoholic fatty liver disease (NAFLD).

METHODS: A case-control study was performed. Cases were 40 obese children with NAFLD. The diagnosis of NAFLD was based on magnetic resonance imaging (MRI) with high hepatic fat fraction (HFF ≥ 5%), and confirmed by liver biopsy with ≥ 5% of hepatocytes containing macrovesicular fat. Controls were selected from obese children with normal levels of aminotransferases, and without MRI evidence of fatty liver as well as of other causes of chronic liver diseases. Controls were matched (1-to 1) with the cases on age, gender, pubertal stage and as closely as possible on body mass index- standard deviation score. All participants underwent clinical examination, laboratory tests including zonulin, inflammatory and metabolic parameters, and MRI for measurement of HFF and visceral adipose tissue.

RESULTS: Zonulin values were significantly greater in obese subjects with NAFLD than in those without NAFLD [median (interquartile range), 4.23 (3.18-5.89) vs 3.31 (2.05-4.63), P < 0.01]. In patients with NAFLD, zonulin concentrations increased significantly with the severity of steatosis and the Spearman’s coefficient revealed a positive correlation between zonulin values and steatosis (r = 0.372, P < 0.05); however, we did not find a significant correlation between zonulin and lobular inflammation (P = 0.23), ballooning (P = 0.10), fibrosis score (P = 0.18), or presence of nonalcoholic steatohepatitis (P = 0.17). Within the entire study population, zonulin levels were positively associated with gamma-glutamyl transferase, 2-h insulin, HFF, and negatively associated with whole-body insulin sensitivity index (WBISI), after adjustment for age, gender and pubertal status. When the associations were restricted to the group of NAFLD patients, 2-h insulin, hepatic fat, and WBISI retained statistical significance.

CONCLUSION: Circulating zonulin is increased in children and adolescents with NAFLD and correlates with the severity of steatosis.

Epithelial transport of immunogenic and toxic gliadin peptides in vitro

Scope

Celiac disease is an autoimmune disorder caused by failure of oral tolerance against gluten in genetically predisposed individuals. The epithelial translocation of gluten-derived gliadin peptides is an important pathogenetic step; the underlying mechanisms, however, are poorly understood. Thus, we investigated the degradation and epithelial translocation of two different gliadin peptides, the toxic P31–43 and the immunogenic P56–68. As the size, and hence, the molecular weight of peptides might have an effect on the transport efficiency we chose two peptides of the same, rather short chain length.

Methods and Results

Fluorescence labeled P31–43 and P56–68 were synthesized and studied in a transwell system with human enterocytes. Fluorometric measurements were done to reveal antigen translocation and flow cytometry as well as confocal microscopy were used to investigate cellular uptake of peptides. Structural changes of these peptides were analysed by MALDI-TOF-MS. According to fluorescence intensities, significantly more P31–43 compared to P56–68 was transported through the enterocyte layer after 24 h incubation. In contrast to previous reports, however, mass spectrometric data do not only show a time-dependent cleavage of the immunogenic P56–68, but we observed for the first time the degradation of the toxic peptide P31–43 at the apical side of epithelial cells.

Conclusion

Considering the degradation of gliadin peptides by enterocytes, measurement of fluorescence signals do not completely represent translocated intact gliadin peptides. From our experiments it is obvious that even short peptides can be digested prior to the translocation across the epithelial barrier. Thus, the chain length and the sensibility to degradations of gliadin peptides as well as the integrity of the epithelial barrier seem to be critical for the uptake of gliadin peptides and the subsequent inflammatory immune response.

Effects of topical steroids on tight junction proteins and spongiosis in esophageal epithelia of patients with eosinophilic esophagitis

BACKGROUND & AIMS

The allergic response associated with eosinophilic esophagitis (EoE) occurs when food antigens permeate tight junction-mediated epithelial dilated intercellular spaces. We assessed whether levels of tight junction proteins correlate with the dilation of intercellular spaces (spongiosis) and the effects of topical steroids on these parameters.

METHODS

We assessed esophageal biopsy samples from 10 patients with active EoE treated with topical fluticasone, 10 untreated patients, and 10 patients without esophageal disease (controls) for degree of spongiosis. Immunohistochemical assays were used to determine the levels of the tight junction proteins filaggrin, zonula occludens (ZO)-1, ZO-2, ZO-3, and claudin-1. Histology and immunohistochemistry results were assessed blindly, with levels of tight junction proteins and degree of spongiosis rated on scales of 0 to 3.

RESULTS

The mean degrees of spongiosis in untreated and treated patients with EoE were 1.3 and 0.4, respectively (P = .016). Esophageal epithelia did not stain significantly for ZO-1 or ZO-2. Filaggrin was observed in a predominant cytoplasmic pattern, compared with the cytoplasmic and membranous patterns of ZO-3 and claudin-1. In biopsy specimens from patients with active EoE, the mean staining intensities for filaggrin, ZO-3, and claudin-1 were 1.6, 1.4, and 0.7, respectively. In biopsy specimens from patients treated with fluticasone, levels of filaggrin, ZO-3, and claudin-1 were 2.8 (P = .002 compared with untreated patients), 1.7 (P = .46 compared with untreated patients), and 1.3 (P = .25 compared with untreated patients), respectively. The correlation between the level of filaggrin and the degree of spongiosis was r = 0.23, and between ZO-3 staining and the degree of spongiosis was r = .016 (P = .001 for filaggrin vs ZO-3 staining).

CONCLUSIONS

Filaggrin, ZO-3, and claudin-1 (but not ZO-1 or ZO-2) are detected in the esophageal mucosa of patients with EoE treated with steroids and individuals without esophageal disease. Without treatment, spongiosis increases, corresponding with reduced levels of filaggrin, ZO-3, and claudin-1. Loss of tight junction regulators and dilation of intercellular spaces appear to be involved in the pathophysiology of EoE and could be targets for treatment.

Non-celiac gluten sensitivity: literature review

BACKGROUND

A significant percentage of the general population report problems caused by wheat and/or gluten ingestion, even though they do not have celiac disease (CD) or wheat allergy (WA), because they test negative both for CD-specific serology and histopathology and for immunoglobulin E (IgE)-mediated assays. Most patients report both gastrointestinal and nongastrointestinal symptoms, and all report improvement of symptoms on a gluten-free diet. This clinical condition has been named non-celiac gluten sensitivity (NCGS).

AIM

We attempt to define the current pathogenic, clinical, and diagnostic criteria of this "new" disease, to provide a practical view that might be useful to evaluate, diagnose, and manage NCGS patients.

METHODS

We reviewed the international literature through PubMed and Medline, using the search terms "wheat (hyper)sensitivity," "wheat allergy," "wheat intolerance," "gluten (hyper)sensitivity," and "gluten intolerance," and we discuss current knowledge about NCGS.

RESULTS

It has been demonstrated that patients suffering from NCGS are a heterogeneous group, composed of several subgroups, each characterized by different pathogenesis, clinical history, and, probably, clinical course. NCGS diagnosis can be reached only by excluding CD and WA. Recent evidence shows that a personal history of food allergy in infancy, coexistent atopy, positive for immunoglobulin G (IgG) antigliadin antibodies and flow cytometric basophil activation test, with wheat and duodenal and/or ileum-colon intraepithelial and lamina propria eosinophil counts, could be useful to identify NCGS patients.

CONCLUSIONS

Future research should aim to identify reliable biomarkers for NCGS diagnosis and to better define the different NCGS subgroups. Key teaching points: • Most patients report both gastrointestinal and nongastrointestinal symptoms, and all agree that there is an improvement of symptoms on a gluten-free diet. • NCGS diagnosis can be reached only by excluding celiac disease and wheat allergy. • Patients suffering from NCGS are a heterogeneous group, composed of several subgroups, each characterized by different pathogenesis, clinical history, and, probably, clinical course. • A personal history of food allergy in infancy, coexistent atopy, positive IgG antigliadin antibodies (AGA) and flow cytometric basophil activation test, with wheat and duodenal and/or ileum-colon intraepithelial and lamina propria eosinophil counts, could be useful to identify NCGS patients. • Future research should aim to identify reliable biomarkers for NCGS diagnosis and to better define the different NCGS subgroup.

Are alterations of tight junctions at molecular and ultrastructural level different in duodenal biopsies of patients with celiac disease and Crohn's disease?

Abnormalities of transmembrane and cytoplasmic proteins of tight junctions (TJ) have been implicated in pathogenesis of both celiac (CeD) and Crohn's diseases (CD). Since disease pathogenesis in CeD and CD are different, we planned to study if there is any differential expression pattern of TJ marker proteins and ultrastructural changes, respectively, in duodenal villi vs crypts. Endoscopic duodenal biopsies from treatment naïve patients with CeD (n = 24), active CD (n = 28), and functional dyspepsia (as controls, n = 15), both at baseline and 6 months after treatment, were subjected to light microscopic analysis (modified Marsh grading); immune-histochemical staining and Western blot analysis to see the expression of key TJ proteins [trans-membrane proteins (claudin-2, claudin-3, claudin-4, occludin, and JAM) and cytoplasmic protein (ZO-1)]. Transmission electron microscopy and image analysis of the TJs were also performed. There was significant overexpression of claudin-2 (pore-forming) and occludin (protein maintaining cell polarity) with under-expression of claudin-3 and claudin-4 (pore-sealing proteins) in treatment naïve CeD and active CD with simultaneous alteration in ultrastructure of TJs such as loss of penta-laminar structure and TJ dilatation. Normalization of some of these TJ proteins was noted 6 months after treatment. These changes were not disease specific and were not different in duodenal villi and crypts. Overexpression of pore-forming and under-expression of pore-sealing TJ proteins lead to dilatation of TJ. These changes are neither disease specific nor site specific and the end result of mucosal inflammation.

Dietary gluten increases natural killer cell cytotoxicity and cytokine secretion

Dietary gluten influences the development of type 1 diabetes in nonobese diabetic (NOD) mice and biobreeding rats, and has been shown to influence a wide range of immunological factors in the pancreas and gut. In the present study, the effects of gluten on NK cells were studied in vitro and in vivo. We demonstrated that gliadin increased direct cytotoxicity and IFN-γ secretion from murine splenocytes and NK cells toward the pancreatic beta-cell line MIN6 cells. Additionally, stimulation of MIN6 cells led to a significantly increased proportion of degranulating C57BL/6 CD107a(+) NK cells. Stimulation of C57BL/6 pancreatic islets with gliadin significantly increased secretion of IL-6 more than ninefold. In vivo, the gluten-containing diet led to a higher expression of NKG2D and CD71 on NKp46(+) cells in all lymphoid organs in BALB/c and NOD mice compared with the gluten-free diet. Collectively, our data suggest that dietary gluten increases murine NK-cell activity against pancreatic beta cells. This mechanism may contribute to development of type 1 diabetes and explain the higher disease incidence associated with gluten intake in NOD mice.

Intestinal microbiota: its role in digestive diseases

It is now well known that intestinal microbiota exerts not only several physiological functions, but has also been implied in the mechanisms of many conditions, both intestinal and extraintestinal. These advances, to the best of our knowledge, have been made possible by the development of new ways of studying gut flora. Metagenomics, the study of genetic material taken directly from environmental samples, avoiding individual culture, has become an excellent tool to study the human microbiota. Therefore, it has demonstrated an association between an altered intestinal microbiota and inflammatory bowel disease or irritable bowel syndrome, perhaps the most extensively studied conditions associated with this particular subject. However, microbiota has a potential role in the development of other diseases; their manifestations are not confined to the intestine only. In this article, an extensive updated review is conducted on the role intestinal microbiota has in health and in different diseases. Focus is made on the following conditions: inflammatory bowel disease, irritable bowel syndrome, celiac disease, hepatic encephalopathy, and obesity.

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.

Alteration of tight junction gene expression in celiac disease

OBJECTIVE

The aim of the present study was to characterize the deregulation of epithelial tight junction genes and investigate its reversibility on removal of dietary gluten in small intestinal mucosa in celiac disease (CD).

METHODS

The expression levels of 23 genes related to tight junctions were studied in biopsies from 16 patients with active CD and compared with biopsies from the same patients taken after 2 years on gluten-free diet (GFD) and with 16 non-CD controls.

RESULTS

Nine genes showed altered expression levels in patients with active disease (CLDN2, PARD6A, ZAK, SYMPK, MYH14, and ACTB were upregulated, whereas MAGI1, TJP1, and PPP2R3A were downregulated). Alterations were reversible after 2 years on treatment, except for PPP2R3A, implicated in the negative control of cell growth and division. At the biological network level, important dysfunctions in several processes within the pathway were observed, including intestinal permeability, apicobasal polarity, and cell proliferation.

CONCLUSIONS

Our work confirms the involvement of tight junction genes related to permeability, polarity, and cell proliferation in the epithelial destruction observed in CD. Coexpression patterns of several genes support the idea of a common regulatory mechanism that seems to be altered in active CD. In general, GFD normalization confirms the reversibility of the process, except for the constitutive downregulation of PPP2R3A suggestive of a genetic implication. Further studies in proteins and cells or tissues are necessary to confirm these findings.

Seroreactive marker for inflammatory bowel disease and associations with antibodies to dietary proteins in bipolar disorder

OBJECTIVES

Immune sensitivity to wheat glutens and bovine milk caseins may affect a subset of individuals with bipolar disorder. Digested byproducts of these foods are exorphins that have the potential to impact brain physiology through action at opioid receptors. Inflammation in the gastrointestinal (GI) tract might accelerate exposure of food antigens to systemic circulation and help explain elevated gluten and casein antibody levels in individuals with bipolar disorder.

METHODS

We measured a marker of GI inflammation, anti-Saccharomyces cerevisiae antibodies (ASCA), in non-psychiatric controls (n = 207), in patients with bipolar disorder without a recent onset of psychosis (n = 226), and in patients with bipolar disorder with a recent onset of psychosis (n = 38). We compared ASCA levels to antibodies against gluten, casein, Epstein-Barr virus (EBV), herpes simplex virus 1 (HSV-1), influenza A, influenza B, measles, and Toxoplasma gondii.

RESULTS

Elevated ASCA conferred a 3.5-4.4-fold increased odds ratio of disease association (age-, race-, and gender-corrected multinomial logistic regressions, p ≤ 0.00001) that was independent of type of medication received. ASCA correlated with food antibodies in both bipolar disorder groups (R(2)  = 0.29-0.59, p ≤ 0.0005), and with measles and T. gondii immunoglobulin G (IgG) in the recent onset psychosis bipolar disorder group (R(2)  = 0.31-0.36, p ≤ 0.004-0.01).

CONCLUSIONS

Elevated seropositivity of a GI-related marker and its association with antibodies to food-derived proteins and self-reported GI symptoms suggest a GI comorbidity in at least a subgroup of individuals with bipolar disorder. Marker seroreactivity may also represent part of an overall heightened activated immune state inherent to this mood disorder.

Celiac disease: the search for adjunctive or alternative therapies

Celiac disease is a widespread disorder caused by intolerance to gluten, a common protein in food. Currently, a life-long gluten-free diet is the only available treatment for patients with celiac disease. However, adherence to gluten-free diet is difficult due to the widespread use of wheat-derived gluten in the food industry. Therefore, there is a pressing need for the development of novel non-dietary therapies. In this article, we will review several promising strategies focusing on reducing gluten immunogenicity or sequestering to gluten prevent its uptake by the intestinal epithelium. Other possible treatment strategies that will be reviewed include the suppression of the adaptive immune response, permeability modulation and the use of systemic T-cell or cytokine blockers.

Lactobacillus GG restoration of the gliadin induced epithelial barrier disruption: the role of cellular polyamines

Background

Celiac disease is characterized by enhanced intestinal paracellular permeability due to alterations of function and expression of tight junction (TJ) proteins including ZO-1, Claudin-1 and Occludin. Polyamines are pivotal in the control of intestinal barrier function and are also involved in the regulation of intercellular junction proteins. Different probiotic strains may inhibit gliadin-induced toxic effects and the Lactobacillus rhamnosus GG (L.GG) is effective in the prevention and treatment of gastrointestinal diseases. Aims of the study were to establish in epithelial Caco-2 cells whether i) gliadin affects paracellular permeability and polyamine profile; ii) co-administration of viable L.GG, heat-killed L.GG (L.GG-HK) or its conditioned medium (L.GG-CM) preserves the intestinal epithelial barrier integrity. Additionally, the effects of L.GG on TJ protein expression were tested in presence or absence of polyamines.

Results

Administration of gliadin (1 mg/ml) to Caco-2 cells for 6 h caused a significant alteration of paracellular permeability as demonstrated by the rapid decrease in transepithelial resistance with a concomitant zonulin release. These events were followed by a significant increase in lactulose paracellular transport and a slight lowering in ZO-1 and Occludin expression without affecting Claudin-1. Besides, the single and total polyamine content increased significantly. The co-administration of viable L.GG (10⁸ CFU/ml), L.GG-HK and L.GG-CM with gliadin significantly restored barrier function as demonstrated by transepithelial resistance, lactulose flux and zonulin release. Viable L.GG and L.GG-HK, but not L.GG-CM, led to a significant reduction in the single and total polyamine levels. Additionally, only the co-administration of viable L.GG with gliadin significantly increased ZO-1, Claudin-1 and Occludin gene expression compared to control cells. When Caco-2 cells treated with viable L.GG and gliadin were deprived in the polyamine content by α-Difluoromethylornithine, the expression of TJ protein mRNAs was not significantly different from that in controls or cells treated with gliadin alone.

Conclusions

Gliadin modifies the intestinal paracellular permeability and significantly increases the polyamine content in Caco-2 cells. Concomitant administration of L.GG is able to counteract these effects. Interestingly, the presence of cellular polyamines is necessary for this probiotic to exert its capability in restoring paracellular permeability by affecting the expression of different TJ proteins.

Advances in the treatment of coeliac disease: an immunopathogenic perspective

Coeliac disease is a common and fairly well-characterized systemic disorder that mainly affects the small intestine, but also has extraintestinal manifestations. The environmental trigger (gluten derived from wheat, rye and barley), the genetic predisposition conferred by the HLA-DQ2 and HLA-DQ8 haplotypes and many steps in the disease pathogenesis are known. This knowledge has enabled researchers to suggest novel alternative treatments or adjunctive therapies to the gluten-free diet, which is currently the only available and effective treatment for the condition. This Review focuses on emerging and potential treatment strategies that are based on the current concept of the disease pathophysiology. The search for novel future treatment modes, including nonpharmacological and pharmacological approaches, is also outlined. The potential pitfalls associated with the various research avenues are also discussed.

The role of Haptoglobin and its related protein, Zonulin, in inflammatory bowel disease

Crohn's disease (CD) and ulcerative colitis (UC), collectively called inflammatory bowel disease (IBD), are immune-mediated conditions characterized by a chronic inflammation of the gut. Their precise etiology is unknown, although an increased intestinal permeability has been shown to play a central role in the pathogenesis of IBD. The intestinal epithelium provides the largest interface between the external environment and the host, and is thus a crucial regulation site of innate and adaptive immunity. Zonulin is one of the few known physiological mediators of paracellular intestinal permeability. It was found upregulated in different immune diseases like Celiac disease and Type 1 Diabetes (T1D). Recently, human zonulin was identified as prehaptoglobin-2 (pre-HP2) which before only had been regarded as the inactive precursor for HP2. Haptoglobin (HP) is a hemoglobin-binding protein with immunomodulatory properties. Its gene harbors a common polymorphism with 2 different alleles: HP1 and HP2. Allele HP2 and genotype HP22 has been shown to be overrepresented in different immune diseases like Rheumatoid Arthritis (RA), Systemic Lupus Erythematosus (SLE) and T1D, and has also been found to be more frequent in patients with IBD (UC and CD) than in healthy controls.   In order to get some clues about the mechanism of action of HP(2) in IBD pathogenesis, we here review the current state of knowledge about zonulin and haptoglobin structure and function, and their plausible role in immune mediated diseases with an emphasis on IBD.

A celiac cellular phenotype, with altered LPP sub-cellular distribution, is inducible in controls by the toxic gliadin peptide P31-43

Celiac disease (CD) is a frequent inflammatory intestinal disease, with a genetic background, caused by gliadin-containing food. Undigested gliadin peptides P31-43 and P57-68 induce innate and adaptive T cell-mediated immune responses, respectively. Alterations in the cell shape and actin cytoskeleton are present in celiac enterocytes, and gliadin peptides induce actin rearrangements in both the CD mucosa and cell lines. Cell shape is maintained by the actin cytoskeleton and focal adhesions, sites of membrane attachment to the extracellular matrix. The locus of the human Lipoma Preferred Partner (LPP) gene was identified as strongly associated with CD using genome-wide association studies (GWAS). The LPP protein plays an important role in focal adhesion architecture and acts as a transcription factor in the nucleus. In this study, we examined the hypothesis that a constitutive alteration of the cell shape and the cytoskeleton, involving LPP, occurs in a cell compartment far from the main inflammation site in CD fibroblasts from skin explants. We analyzed the cell shape, actin organization, focal adhesion number, focal adhesion proteins, LPP sub-cellular distribution and adhesion to fibronectin of fibroblasts obtained from CD patients on a Gluten-Free Diet (GFD) and controls, without and with treatment with A-gliadin peptide P31-43. We observed a “CD cellular phenotype” in these fibroblasts, characterized by an altered cell shape and actin organization, increased number of focal adhesions, and altered intracellular LPP protein distribution. The treatment of controls fibroblasts with gliadin peptide P31-43 mimics the CD cellular phenotype regarding the cell shape, adhesion capacity, focal adhesion number and LPP sub-cellular distribution, suggesting a close association between these alterations and CD pathogenesis.

Non-dietary forms of treatment for adult celiac disease

At present, treatment for celiac disease includes a strict gluten-free diet. Compliance, however, is difficult and gluten-free food products are costly, and, sometimes very inconvenient. A number of potential alternative measures have been proposed to either replace or supplement gluten-free diet therapy. In the past, non-dietary forms of treatment were used (e.g., corticosteroids) by some clinicians, often to supplement a gluten-free diet in patients that appeared to be poorly responsive to a gluten-free diet. Some of new and novel non-dietary measures have already advanced to a clinical trial phase. There are still some difficulties even if initial studies suggest a particularly exciting and novel form of non-dietary treatment. In particular, precise monitoring of the response to these agents will become critical. Symptom or laboratory improvement may be important, but it will be critical to ensure that ongoing inflammatory change and mucosal injury are not present. Therapeutic trials will be made more difficult because there is already an effective treatment regimen.

Defining suitable reference genes for RT-qPCR analysis on intestinal epithelial cells

The study of the mammalian intestinal epithelium concerns several aspects of cellular and molecular biology. In fact, most of these studies aim to define molecular components or mechanisms related with the control of stemness and the balance between cell proliferation and differentiation in physiopathological conditions. It is worth mentioning that real-time quantitative reverse transcription-polymerase chain reaction (RT-qPCR) approaches are commonly used, but only a few studies are available regarding suitable reference genes to normalize gene expression data. The present study was designed to validate potential reference genes in freshly isolated proliferating or differentiated epithelial cells from the mouse intestine. We also extended our analysis to the IEC6 intestinal epithelial cells, as a promising model to study intestinal physiopathology in vitro. The stability of six potential reference genes (Hprt1, Ppia, Gapdh, Rplp0, Ppib, and Vil1) has been tested both in epithelial cells isolated from the mouse intestine and in the IEC6 cell line. The software programs-geNorm and Normfinder-were used to obtain an estimation of the expression stability of each gene and, by comparing the results, to identify the most suitable genes for RT-qPCR data normalization. These multiple approaches allowed us to select different suitable reference genes for the correct quantification of mRNAs depending on the differentiated or proliferative nature of the cells.

Effects of soybean agglutinin on mechanical barrier function and tight junction protein expression in intestinal epithelial cells from piglets

In this study, we sought to investigate the role of soybean agglutinin (SBA) in mediating membrane permeability and the mechanical barrier function of intestinal epithelial cells. The IPEC-J2 cells were cultured and treated with 0, 0.5, 1.0, 1.5, 2.0, 2.5, or 3.0 mg/mL SBA. Transepithelial electrical resistance (TEER) and alkaline phosphatase (AP) activity were measured to evaluate membrane permeability. The results showed a significant decrease in TEER values (p < 0.05) in a time- and dose-dependent manner, and a pronounced increase in AP activity (p < 0.05). Cell growth and cell morphology were used to evaluate the cell viability. A significant cell growth inhibition (p < 0.05) and alteration of morphology were observed when the concentration of SBA was increased. The results of western blotting showed that the expression levels of occludin and claudin-3 were decreased by 31% and 64% compared to those of the control, respectively (p < 0.05). In addition, immunofluorescence labeling indicated an obvious decrease in staining of these targets and changes in their localizations. In conclusion, SBA increased the membrane permeability, inhibited the cell viability and reduced the levels of tight junction proteins (occludin and claudin-3), leading to a decrease in mechanical barrier function in intestinal epithelial cells.

Maize prolamins could induce a gluten-like cellular immune response in some celiac disease patients

Celiac disease (CD) is an autoimmune-mediated enteropathy triggered by dietary gluten in genetically prone individuals. The current treatment for CD is a strict lifelong gluten-free diet. However, in some CD patients following a strict gluten-free diet, the symptoms do not remit. These cases may be refractory CD or due to gluten contamination; however, the lack of response could be related to other dietary ingredients, such as maize, which is one of the most common alternatives to wheat used in the gluten-free diet. In some CD patients, as a rare event, peptides from maize prolamins could induce a celiac-like immune response by similar or alternative pathogenic mechanisms to those used by wheat gluten peptides. This is supported by several shared features between wheat and maize prolamins and by some experimental results. Given that gluten peptides induce an immune response of the intestinal mucosa both in vivo and in vitro, peptides from maize prolamins could also be tested to determine whether they also induce a cellular immune response. Hypothetically, maize prolamins could be harmful for a very limited subgroup of CD patients, especially those that are non-responsive, and if it is confirmed, they should follow, in addition to a gluten-free, a maize-free diet.

Non-celiac gluten sensitivity: questions still to be answered despite increasing awareness

Recently, the increasing number of patients worldwide who are sensitive to dietary gluten without evidence of celiac disease or wheat allergy has contributed to the identification of a new gluten-related syndrome defined as non-celiac gluten sensitivity. Our knowledge regarding this syndrome is still lacking, and many aspects of this syndrome remain unknown. Its pathogenesis is heterogeneous, with a recognized pivotal role for innate immunity; many other factors also contribute, including low-grade intestinal inflammation, increased intestinal barrier function and changes in the intestinal microbiota. Gluten and other wheat proteins, such as amylase trypsin inhibitors, are the primary triggers of this syndrome, but it has also been hypothesized that a diet rich in fermentable monosaccharides and polyols may elicit its functional gastrointestinal symptoms. The epidemiology of this condition is far from established; its prevalence in the general population is highly variable, ranging from 0.63% to 6%. From a clinical point of view, non-celiac gluten sensitivity is characterized by a wide array of gastrointestinal and extraintestinal symptoms that occur shortly after the ingestion of gluten and improve or disappear when gluten is withdrawn from the diet. These symptoms recur when gluten is reintroduced. Because diagnostic biomarkers have not yet been identified, a double-blind placebo-controlled gluten challenge is currently the diagnostic method with the highest accuracy. Future research is needed to generate more knowledge regarding non-celiac gluten sensitivity, a condition that has global acceptance but has only a few certainties and many unresolved issues.

Naringenin enhances intestinal barrier function through the expression and cytoskeletal association of tight junction proteins in Caco-2 cells

SCOPE

We have previously reported that naringenin promotes the tight junction (TJ) integrity in intestinal Caco-2 cells. This study investigated the naringenin-mediated effect in Caco-2 cells with a particular focus on the modulation of TJ structure and claudin-4 transcriptional regulation.

METHODS AND RESULTS

Naringenin (10~100 μM) dose-dependently enhanced TJ barrier integrity of Caco-2 cells, indicated by transepithelial electrical resistance and FITC-dextran flux. Immunoblot analysis showed that naringenin increased the cytoskeletal association of TJ proteins, zonula occludens-2, occludin, claudin-1, and claudin-4, simultaneously with increased occludin phosphorylation. The total expression of claudin-4 was also increased by naringenin. Quantitative RT-PCR and luciferase reporter assay revealed that naringenin transcriptionally increased the claudin-4 expression with activation of claudin-4 promoter. The mutation of the binding site of the transcriptional factor Sp1 in the claudin-4 promoter sequence and the pharmacological inhibition of Sp1 partially suppressed the naringenin-mediated activation of the claudin-4 promoter. Further, naringenin induced the heat shock protein 70 expression in the cells.

CONCLUSION

Naringenin enhances barrier integrity through the assembly and expression of TJ proteins in intestinal epithelial cells. Naringenin-mediated claudin-4 expression occurs, at least partially, through Sp1-dependent transcriptional regulation. The induction of heat shock protein 70 may be also involved in the increased claudin-4 expression.

Modeling of celiac disease immune response and the therapeutic effect of potential drugs

Background

Celiac disease (CD) is an autoimmune disorder that occurs in genetically predisposed people and is caused by a reaction to the gluten protein found in wheat, which leads to intestinal villous atrophy. Currently there is no drug for treatment of CD. The only known treatment is lifelong gluten-free diet. The main aim of this work is to develop a mathematical model of the immune response in CD patients and to predict the efficacy of a transglutaminase-2 (TG-2) inhibitor as a potential drug for treatment of CD.

Results

A thorough analysis of the developed model provided the following results:

1. TG-2 inhibitor treatment leads to insignificant decrease in antibody levels, and hence remains higher than in healthy individuals.

2. TG-2 inhibitor treatment does not lead to any significant increase in villous area.

3. The model predicts that the most effective treatment of CD would be the use of gluten peptide analogs that antagonize the binding of immunogenic gluten peptides to APC. The model predicts that the treatment of CD by such gluten peptide analogs can lead to a decrease in antibody levels to those of normal healthy people, and to a significant increase in villous area.

Conclusions

The developed mathematical model of immune response in CD allows prediction of the efficacy of TG-2 inhibitors and other possible drugs for the treatment of CD: their influence on the intestinal villous area and on the antibody levels. The model also allows to understand what processes in the immune response have the strongest influence on the efficacy of different drugs. This model could be applied in the pharmaceutical R&D arena for the design of drugs against autoimmune small intestine disorders and on the design of their corresponding clinical trials.

Gliadin fragments and a specific gliadin 33-mer peptide close KATP channels and induce insulin secretion in INS-1E cells and rat islets of langerhans

In non-obese diabetic (NOD) mice, diabetes incidence is reduced by a gluten-free diet. Gluten peptides, such as the compound gliadin, can cross the intestinal barrier and may directly affect pancreatic beta cells. We investigated the effects of enzymatically-digested gliadin in NOD mice, INS-1E cells and rat islets. Six injections of gliadin digest in 6-week-old NOD mice did not affect diabetes development, but increased weight gain (20% increase by day 100). In INS-1E cells, incubation with gliadin digest induced a dose-dependent increase in insulin secretion, up to 2.5-fold after 24 hours. A similar effect was observed in isolated rat islets (1.6-fold increase). In INS-1E cells, diazoxide reduced the stimulatory effect of gliadin digest. Additionally, gliadin digest was shown to decrease current through K_ATP-channels. A specific gliadin 33-mer had a similar effect, both on current and insulin secretion. Finally, INS-1E incubation with gliadin digest potentiated palmitate-induced insulin secretion by 13% compared to controls. Our data suggest that gliadin fragments may contribute to the beta-cell hyperactivity observed prior to the development of type 1 diabetes.

Pediatric celiac disease, cryptogenic hypertransaminasemia, and autoimmune hepatitis

OBJECTIVE

The association between celiac disease (CD) and liver disease in pediatrics is widely recognized, but its prevalence is unknown. This study aims to conduct a systematic review and meta-analysis to evaluate the prevalence of CD in children with cryptogenic persistent hypertransaminasemia (HTS) or autoimmune hepatitis (AIH), and vice versa.

METHODS

We searched MEDLINE/PubMed, the Cochrane Library, Web of Science, and MD Consult from 1977 to May 2012 for studies reporting either CD and HTS or AIH. Pooled prevalences with 95% confidence intervals (CI) and relative risk (RR) were calculated.

RESULTS

Nine studies (2046 patients) were identified. Pooled prevalences of CD in children with mild, nonspecific cryptogenic persistent HTS and vice versa were 12.0% (95% CI 4.17-29.96) and 36.0% (95% CI 32.15-40.11), respectively. A gluten-free diet normalized transaminase levels in 77% to 100% of patients with CD within 4 to 8 months. Pooled prevalences of CD in children with AIH and vice versa were 6.3% (95% CI 3.87-11.73) and 1.4% (95% CI 0.84-2.15), respectively. The RR of HTS in children with CD versus the general population, and of CD in children with HTS was 6.55 (95% CI 5.65-7.60) and 11.59 (95% CI 3.80-35.33), respectively. The corresponding RR of AIH in children with CD was 188.54 (95% CI 92.23-385.43). The RR of CD in children with AIH was 6.63 (95% CI 3.86-11.40).

CONCLUSIONS

CD is associated with elevated transaminase levels in about one-third of newly diagnosed children. Cryptogenic persistent HTS may signal gluten-dependent nonspecific mild hepatitis (12.0% of cases) or more rarely (6.3%) severe CD-related autoimmune hepatopathy. RRs confirm these trends in the considered associations.

Effects of enteral nutrition on Crohn's disease: clues to the impact of diet on disease pathogenesis

Crohn's disease is a complex inherited disorder of unknown pathogenesis with environmental, genetic, and microbial factors involved in the development of the disease. A remarkable feature of this disease, especially, but not limited to childhood, is the effective response to exclusive enteral nutrition therapy and the observed benefit from exclusion of normal diet (principle of exclusivity). We reviewed the possible mechanisms of action of enteral nutrition for induction of remission and provided a hypothetical model (herein termed bacterial penetration cycle) that integrates dietary components, bacteria, susceptibility genes, and the innate immune response in the pathogenesis of Crohn's disease.

Molecular diagnosis of celiac disease: are we there yet?

BACKGROUND

Celiac disease (CD) is a complex genetic disorder of the small intestine resulting from aberrant cellular responses to gluten peptides. It may affect as much as 1% of the Western population and the only treatment is a lifelong gluten-free diet. Allelic variants of the HLA-DQ locus, coding for the HLA-DQ2 and HLA-DQ8 molecules, contribute to ∼ 40% of CD etiology, whereas other genes, such as MYO9B, CTLA4, IL2, IL21, PARD3 and MAGI2, have only a modest effect. Most of these genes have shown varied association among different populations and an overlap with other autoimmune or inflammatory disorders, indicating that such disorders may share common pathways.

OBJECTIVES

In this review, a molecular approach into diagnostics of celiac disease is shown.

CONCLUSIONS

Genome-wide association studies will allow more genes to be identified, and knowing how risk variants combine will help to predict better the risk for the individual. HLA typing can already be used to identify high-risk individuals.

The dietary intake of wheat and other cereal grains and their role in inflammation

Wheat is one of the most consumed cereal grains worldwide and makes up a substantial part of the human diet. Although government-supported dietary guidelines in Europe and the U.S.A advise individuals to eat adequate amounts of (whole) grain products per day, cereal grains contain “anti-nutrients,” such as wheat gluten and wheat lectin, that in humans can elicit dysfunction and disease. In this review we discuss evidence from in vitro, in vivo and human intervention studies that describe how the consumption of wheat, but also other cereal grains, can contribute to the manifestation of chronic inflammation and autoimmune diseases by increasing intestinal permeability and initiating a pro-inflammatory immune response.

Advances in research of non-coeliac gluten sensitivity

Non-celiac gluten sensitivity (NCGS) is a newly recognized clinical entity that is characterized by a wide variety of intestinal or extra-intestinal manifestations, and it may be the most common one in the spectrum of gluten-related disorders. The symptoms of NCGS improve or disappear after gluten withdrawal and relapse if gluten is reintroduced. There are no specific serological markers for NCGS although nearly half of patients are positive for antigliadin IgG antibodies. Since small intestinal biopsy is normal, the double-blind, placebo-controlled food challenge (DBPCFC) and an exclusion of wheat allergy or coeliac disease are necessary for diagnosis. The pathogenesis is still unclear although immunology may play a role in its pathogenesis. This review will summarize our current knowledge about non-coeliac gluten sensitivity and outline pathogenic and epidemiological differences between NCGS and coeliac disease.

The effects of fluorouracil, epirubicin, and cyclophosphamide (FEC60) on the intestinal barrier function and gut peptides in breast cancer patients: an observational study

Background

Several GI peptides linked to intestinal barrier function could be involved in the modification of intestinal permeability and the onset of diarrhea during adjuvant chemotherapy. The aim of the study was to evaluate the circulating levels of zonulin, glucagon-like peptide-2 (GLP-2), epidermal growth factor (EGF) and ghrelin and their relationship with intestinal permeability and chemotherapy induced diarrhea (CTD).

Methods

Sixty breast cancer patients undergoing an FEC60 regimen were enrolled, 37 patients completed the study. CTD(+) patients were discriminated by appropriate questionnaire and criteria. During chemotherapy, intestinal permeability was assessed by lactulose/mannitol urinary test on day 0 and day 14. Zonulin, GLP-2, EGF and ghrelin circulating levels were evaluated by ELISA tests at five time-points (days 0, 3, 10, 14, and 21).

Results

During FEC60 administration, the lactulose/mannitol ratio was significantly higher on day 14 than at baseline. Zonulin levels were not affected by chemotherapy, whereas GLP-2 and EGF levels decreased significantly. GLP-2 levels on day 14 were significantly lower than those on day 0 and day 3, while EGF values were significantly lower on day 10 than at the baseline. In contrast, the total concentrations of ghrelin increased significantly at day 3 compared to days 0 and 21, respectively. Ten patients (27%) suffered from diarrhea. On day 14 of chemotherapy, a significant increase of the La/Ma ratio occurred in CTD(+) patients compared to CTD(−) patients. With regards to circulating gut peptides, the AUCg of GLP-2 and ghrelin were significantly lower and higher in CTD(+) patients than CTD(−) ones, respectively. Finally in CTD(+) patients a significant and inverse correlation between GLP-2 and La/Ma ratio was found on day 14.

Conclusions

Breast cancer patients undergoing FEC60 showed alterations in the intestinal permeability, which was associated with modifications in the levels of GLP-2, ghrelin and EGF. In CTD(+) patients, a different GI peptide profile and increased intestinal permeability was found in comparison to CTD(−) patients. This evidence deserves further studies for investigating the potentially different intestinal luminal and microbiota conditions.

Trial registration

Clinical trial NCT01382667

Regulation of intestinal epithelial permeability by tight junctions

The gastrointestinal epithelium forms the boundary between the body and external environment. It effectively provides a selective permeable barrier that limits the permeation of luminal noxious molecules, such as pathogens, toxins, and antigens, while allowing the appropriate absorption of nutrients and water. This selective permeable barrier is achieved by intercellular tight junction (TJ) structures, which regulate paracellular permeability. Disruption of the intestinal TJ barrier, followed by permeation of luminal noxious molecules, induces a perturbation of the mucosal immune system and inflammation, and can act as a trigger for the development of intestinal and systemic diseases. In this context, much effort has been taken to understand the roles of extracellular factors, including cytokines, pathogens, and food factors, for the regulation of the intestinal TJ barrier. Here, I discuss the regulation of the intestinal TJ barrier together with its implications for the pathogenesis of diseases.

Anti-gluten immune response following Toxoplasma gondii infection in mice

Gluten sensitivity may affect disease pathogenesis in a subset of individuals who have schizophrenia, bipolar disorder or autism. Exposure to Toxoplasma gondii is a known risk factor for the development of schizophrenia, presumably through a direct pathological effect of the parasite on brain and behavior. A co-association of antibodies to wheat gluten and to T. gondii in individuals with schizophrenia was recently uncovered, suggesting a coordinated gastrointestinal means by which T. gondii and dietary gluten might generate an immune response. Here, we evaluated the connection between these infectious- and food-based antigens in mouse models. BALB/c mice receiving a standard wheat-based rodent chow were infected with T. gondii via intraperitoneal, peroral and prenatal exposure methods. Significant increases in the levels of anti-gluten IgG were documented in all infected mice and in offspring from chronically infected dams compared to uninfected controls (repetitive measures ANOVAs, two-tailed t-tests, all p≤0.00001). Activation of the complement system accompanied this immune response (p≤0.002–0.00001). Perorally-infected females showed higher levels of anti-gluten IgG than males (p≤0.009) indicating that T. gondii-generated gastrointestinal infection led to a significant anti-gluten immune response in a sex-dependent manner. These findings support a gastrointestinal basis by which two risk factors for schizophrenia, T. gondii infection and sensitivity to dietary gluten, might be connected to produce the immune activation that is becoming an increasingly recognized pathology of psychiatric disorders.

Celiac disease: prevalence, diagnosis, pathogenesis and treatment

Celiac disease (CD) is one of the most common diseases, resulting from both environmental (gluten) and genetic factors [human leukocyte antigen (HLA) and non-HLA genes]. The prevalence of CD has been estimated to approximate 0.5%-1% in different parts of the world. However, the population with diabetes, autoimmune disorder or relatives of CD individuals have even higher risk for the development of CD, at least in part, because of shared HLA typing. Gliadin gains access to the basal surface of the epithelium, and interact directly with the immune system, via both trans- and para-cellular routes. From a diagnostic perspective, symptoms may be viewed as either "typical" or "atypical". In both positive serological screening results suggestive of CD, should lead to small bowel biopsy followed by a favourable clinical and serological response to the gluten-free diet (GFD) to confirm the diagnosis. Positive anti-tissue transglutaminase antibody or anti-endomysial antibody during the clinical course helps to confirm the diagnosis of CD because of their over 99% specificities when small bowel villous atrophy is present on biopsy. Currently, the only treatment available for CD individuals is a strict life-long GFD. A greater understanding of the pathogenesis of CD allows alternative future CD treatments to hydrolyse toxic gliadin peptide, prevent toxic gliadin peptide absorption, blockage of selective deamidation of specific glutamine residues by tissue, restore immune tolerance towards gluten, modulation of immune response to dietary gliadin, and restoration of intestinal architecture.

Novel therapeutic/integrative approaches for celiac disease and dermatitis herpetiformis

Celiac disease (CD) is an immune-mediated enteropathy triggered by the ingestion of gluten in genetically susceptible individuals. Gluten is a protein component in wheat and other cereals like rye and barley. At present, the only available treatment is a strict gluten-free diet. Recent advances have increased our understanding of the molecular basis for this disorder. Last decade has seen new scientific developments in this disease and led to the formulation of new concepts of pathophysiology that offer possible targets for new treatments or interventions integrative to the gluten-free diet.

Nondietary therapies for celiac disease

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

Irritable bowel syndrome: methods, mechanisms, and pathophysiology. The confluence of increased permeability, inflammation, and pain in irritable bowel syndrome

Irritable bowel syndrome (IBS) is one of the most common gastrointestinal ailments among those seeking health care for gastrointestinal disorders. Despite its prevalence, IBS pathophysiology is still not completely understood. Continued elucidation of IBS etiological mechanisms will lead to a greater appreciation of possible therapeutic targets. In the past decade, there has been increasing focus on the possible connection between increased intestinal mucosal permeability, inflammation, and visceral hypersensitivity. Increased permeability in subsets of IBS patients has been observed and the possible mechanisms underlying this defect are just beginning to be understood. The objectives of this review are to summarize the role of the healthy intestinal epithelium as a barrier between the lumen and the rest of the body with a focus on tight junctions; to examine the lines of evidence that suggest that different triggers lead to increased intestinal mucosal permeability and disruption of tight junctions in IBS patients; and to explore how this increased permeability may elicit immune responses that affect afferent nerves, resulting in the pain associated with IBS.

Serological tests in gluten sensitivity (nonceliac gluten intolerance)

GOALS

To characterize the serological pattern of gluten sensitivity (GS) and to compare it with that found in celiac disease.

BACKGROUND

GS has recently been identified as a new clinical entity included in the spectrum of gluten-related disorders, but it is still lacking of diagnostic markers.

STUDY

Sera from 78 patients with GS and 80 patients with celiac disease were retrospectively assessed for immunoglobulin (Ig)G/IgA antigliadin antibodies (AGA), IgG deamidated gliadin peptide antibodies (DGP-AGA), IgA tissue transglutaminase antibodies (tTGA), and IgA endomysial antibodies (EmA).

RESULTS

IgG AGA were positive in 56.4% of GS patients and in 81.2% of celiac patients, with high antibody titers in both groups. IgA AGA were detected in 7.7% of GS patients and in 75% of celiac patients, showing lower enzyme-linked immunosorbent assay activities in GS than those found in celiac disease. Only 1 of the 78 patients with GS was positive for IgG DGP-AGA (detected in 88.7% of patients with celiac disease). IgA tTGA and IgA EmA were negative in all GS patients, whereas their positivity in celiac patients was 98.7% and 95%, respectively. Patients with GS displayed a variegated clinical picture with intestinal and extraintestinal symptoms (abdominal pain, bloating, diarrhea, constipation, foggy mind, tiredness, eczema/skin rash, headache, joint/muscle pain, numbness of legs/arms, depression, and anemia) together with normal or mildly abnormal small intestinal mucosa.

CONCLUSIONS

The serological pattern of GS is characterized by IgG AGA positivity in more than half of cases associated to IgA AGA in a few patients, but without EmA, tTGA, and DGP-AGA, which are the specific markers of celiac disease.

Recent advances in the development of new treatments for celiac disease

INTRODUCTION

Celiac disease is a common autoimmune condition induced by dietary gluten in genetically susceptible individuals. So far, the only available treatment for the disorder is a lifelong strict gluten-free diet, because of which small intestinal histological changes recover and symptoms disappear. However, gluten-free dieting is restrictive, and nutritionally less than optimal, and gluten is difficult to avoid.

AREAS COVERED

With improving insight into the pathogenesis of celiac disease, several possible drug targets have been suggested. The new strategies include degradation of gluten intraluminally, reduction of mucosal permeability, inhibition of the transglutaminase 2 enzyme, blocking antigen presentation by HLA-DQ2 or HLA-DQ8, modulation of the immune responses of many cytokines, and vaccination.

EXPERT OPINION

Non-dietary treatment options are warranted either as adjunctive therapy together with dieting or to replace the gluten-free diet. The key question is whether the envisaged novel drug is able to prevent gluten-induced small intestinal mucosal injury as efficiently as a strict gluten-free diet, alleviating symptoms and signs of the disease. Furthermore, the gluten dose that can be detoxified, if at all, must be established. The new drug should also be as safe as dietary treatment. Several novel treatment options are under development.

Biomarkers of antioxidant status, inflammation, and cartilage metabolism are affected by acute intense exercise but not superoxide dismutase supplementation in horses

Objectives were to evaluate effects of (1) repetitive arthrocentesis on biomarkers of inflammation (prostaglandin E(2), PGE(2)) and aggrecan synthesis (chondroitin sulfate-846; CS) in synovial fluid (SF); (2) exercise and superoxide dismutase (SOD) supplementation on biomarkers of inflammation, antioxidant status, and aggrecan synthesis, in horses. Preliminary trial. Standardbreds underwent four arthrocentesis procedures within 48 h and exhibited elevated CS and no changes in PGE(2). Exercise trial. this randomized crossover design used twelve Standardbred mares which received either treatment (3000 IU d(-1) oral SOD powder) or placebo (cellulose powder) for 6 wks which culminated with them running a repeated sprint exercise test (RSET). Samples were collected before (PRE), during (PEAK), and following exercise (POST). Exercise resulted in increased (P < 0.05) antioxidant defenses including erythrocyte SOD, total glutathione, glutathione peroxidase, gene transcripts for interferon-gamma, interleukin-10, and interleukin-1β in blood, and decreased plasma nitric oxide. Exercise increased (P < 0.05) SF CS and adjusted-PGE(2), and higher (P < 0.05) CS and PGE(2) were found in hock versus carpus joints. No treatment effects were detected. Results suggest normal adaptive responses likely due to exercise-induced tissue microdamage and oxidative stress. Additional research is needed to identify benefit(s) of SOD supplementation in horses.

Non-systemic drugs: a critical review

Non-systemic drugs act within the intestinal lumen without reaching the systemic circulation. The first generation included polymeric resins that sequester phosphate ions, potassium ions, or bile acids for the treatment of electrolyte imbalances or hypercholesteremia. The field has evolved towards non-absorbable small molecules or peptides targeting luminal enzymes or transporters for the treatment of mineral metabolism disorders, diabetes, gastrointestinal (GI) disorders, and enteric infections. From a drug design and development perspective, non-systemic agents offer novel opportunities to address unmet medical needs while minimizing toxicity risks, but also present new challenges, including developing a better understanding and control of non-transcellular leakage pathways into the systemic circulation. The pharmacokinetic-pharmacodynamic relationship of drugs acting in the GI tract can be complex due to the variability of intestinal transit, interaction with chyme, and the complex environment of the surface epithelia. We review the main classes of nonabsorbable agents at various stages of development, and their therapeutic potential and limitations. The rapid progress in the identification of intestinal receptors and transporters, their functional characterization and role in metabolic and inflammatory disorders, will undoubtedly renew interest in the development of novel, safe, non-systemic therapeutics.

Leaky gut and autoimmune diseases

Autoimmune diseases are characterized by tissue damage and loss of function due to an immune response that is directed against specific organs. This review is focused on the role of impaired intestinal barrier function on autoimmune pathogenesis. Together with the gut-associated lymphoid tissue and the neuroendocrine network, the intestinal epithelial barrier, with its intercellular tight junctions, controls the equilibrium between tolerance and immunity to non-self antigens. Zonulin is the only physiologic modulator of intercellular tight junctions described so far that is involved in trafficking of macromolecules and, therefore, in tolerance/immune response balance. When the zonulin pathway is deregulated in genetically susceptible individuals, autoimmune disorders can occur. This new paradigm subverts traditional theories underlying the development of these diseases and suggests that these processes can be arrested if the interplay between genes and environmental triggers is prevented by re-establishing the zonulin-dependent intestinal barrier function. Both animal models and recent clinical evidence support this new paradigm and provide the rationale for innovative approaches to prevent and treat autoimmune diseases.

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.