Transglutaminase and the pathogenesis of coeliac disease

Zinc Deficiency and Therapeutic Value of Zinc Supplementation in Pediatric Gastrointestinal Diseases

The benefits of zinc in treating certain gastrointestinal (GI) diseases have been recognized for over two decades. This review aims to explore zinc deficiency (ZD) and the potential therapeutic value and safety of zinc supplementation in pediatric GI diseases. A systematic review of published articles on ZD and zinc as adjuvant treatments for GI diseases was conducted using various databases. Children with inflammatory bowel disease (IBD), celiac disease, and those receiving long-term proton pump inhibitor treatments are particularly susceptible to ZD. ZD in children with celiac disease and IBD is attributed to insufficient intake, reduced absorption, and increased intestinal loss as a result of the inflammatory process. Zinc plays a crucial role in maintaining the integrity of the gastric mucosa and exerts a gastroprotective action against gastric lesions. Although considerable evidence supports the use of zinc as adjuvant therapy for certain GI diseases in adults, its use is unspecified in children except for infectious diarrhea. Current evidence suggests that zinc supplementation with well-documented dosages helps reduce the duration of diarrhea in children with acute or persistent diarrhea, while there are no specific guidelines for zinc supplementation in children with IBD and celiac disease. Zinc supplementation appears to be beneficial in peptic ulcer disease or gastroesophageal reflux disease. The available evidence highlights the need for intervention programs to enhance zinc status and reduce the morbidity of certain GI diseases in children.

Zinc and gut microbiota in health and gastrointestinal disease under the COVID-19 suggestion

Microelements represent an emerging resource for medicine and its preventive branch. Zinc is the second most abundant element in our organism with peculiar physiologic functions and pathophysiologic implications in systemic and gastrointestinal (GI) diseases. It interacts very often with gut microbiota (GM) and can affect natural course of GI diseases through a bidirectional relationship with intestinal bugs. We aimed to review literature data regarding zinc chemistry, role in health, and GI diseases in man with a special focus on its interaction with GM. We conducted a search on the main medical databases for original articles, reviews, meta-analyses, randomized clinical trials and case series using the following keywords and acronyms and their associations: zinc, microelements, gut microbiota, gut health, and COVID-19. Zinc has a rapid and simple metabolism and limited storage within our body. Its efficacy on immune system modulation reflects on improved response to pathogens, reduced inflammatory response, and improved atopic/allergic reactions. Zinc is also involved in cell cycle regulation (namely, apoptosis) with potential anti-cancerogenic effects. All these effects are in a "symbiotic" relationship with GM. Finally, zinc shows preliminary viral antireplicative effects. Zinc seems to gain more and more evidences on its efficacy in allergic, atopic and infectious diseases treatment, and prevention. COVID-19 can be the booster for research on future applications of zinc as perfect "postbiotic" in medicine.

Clinical significance of IgM and IgA class anti-NMDAR antibodies in herpes simplex encephalitis

BACKGROUND

Herpes simplex encephalitis (HSE) is a devastating disease, often leaving patients with severe disabilities. It has been shown that IgG anti-N-methyl-d-aspartate receptor (NMDAR) antibodies appear in approximately 25% of HSE patients and could be associated with impaired recovery of cognitive performance.

OBJECTIVES

To characterize the prevalence of IgM and IgA anti-NMDAR antibodies in HSE patients, in relation to subsequent development of IgG anti-NMDAR and correlation to cognitive performance.

STUDY DESIGN

A total of 48 subjects were included from a previously described cohort of patients with HSE verified by HSV-1 PCR. Cerebrospinal fluid (CSF) and serum samples drawn close to onset of disease, after 14-21 days of iv aciclovir treatment and after 90 days of follow-up, were analyzed for the presence of IgM and IgA anti-NMDAR, and related to IgG anti-NMDAR. Antibody levels were correlated to the recovery of cognitive performance, as estimated by the Mattis Dementia Rating Scale (MDRS), for a total of 24 months.

RESULTS

In total, 27 of 48 (56%) study subjects were anti-NMDAR positive, defined as the presence of IgG (12/48, 25%), IgM (14/48, 29%) or IgA (13/48, 27%) antibodies in CSF and/or serum. IgM or IgA anti-NMDAR did not predict subsequent IgG autoimmunization and did not correlate to cognitive outcome. IgG anti-NMDAR serostatus, but not antibody titers, correlated to impaired recovery of cognitive performance.

CONCLUSIONS

A majority of HSE patients develop IgG, IgM or IgA anti-NMDAR antibodies. However, the predictive value and clinical relevance of non-IgG isotypes remains to be shown in this setting.

Coeliac disease: immunogenicity studies of barley hordein and rye secalin-derived peptides

Coeliac disease (CD) is an inflammatory disorder of the small intestine. It includes aberrant adaptive immunity with presentation of CD toxic gluten peptides by HLA-DQ2 or DQ8 molecules to gluten-sensitive T cells. A ω-gliadin/C-hordein peptide (QPFPQPEQPFPW) and a rye-derived secalin peptide (QPFPQPQQPIPQ) were proposed to be toxic in CD, as they yielded positive responses when assessed with peripheral blood T-cell clones derived from individuals with CD. We sought to assess the immunogenicity of the candidate peptides using gluten-sensitive T-cell lines obtained from CD small intestinal biopsies. We also sought to investigate the potential cross-reactivity of wheat gluten-sensitive T-cell lines with peptic-tryptic digested barley hordein (PTH) and rye secalin (PTS). Synthesised candidate peptides were deamidated with tissue transglutaminase (tTG). Gluten-sensitive T-cell lines were generated by culturing small intestinal biopsies from CD patients with peptic-tryptic gluten (PTG), PTH or PTS, along with autologous PBMCs for antigen presentation. The stimulation indices were determined by measuring the relative cellular proliferation via incorporation of 3 H-thymidine. The majority of T-cell lines reacted to the peptides studied. There was also cross-reactivity between wheat gluten-sensitive T-cell lines and the hordein, gliadin and secalin peptides. PTH, PTS, barley hordein and rye secalin-derived CD antigen-sensitive T-cell lines showed positive stimulation with PTG. ω-gliadin/C-hordein peptide and rye-derived peptide are immunogenic to gluten-sensitive T-cell lines and potentially present in wheat, rye and barley. Additional CD toxic peptides may be shared.

Zinc is the modulator of the calcium-dependent activation of post-translationally acting thiol-enzymes in autoimmune diseases

Post-translational modifications of proteins can generate antigenic conformations that may cause autoimmune diseases in persons with specific HLA-haplotypes. Monocytes and macrophages, attracted to an inflamed site, can release post-translationally acting enzymes, such as transglutaminases and peptidylarginine deiminases. In vivo, the activation of these enzymes is crucial for the further course of event. Our hypothesis is that zinc modulates the activation of these calcium-dependent thiol-enzymes. Persons with celiac disease carry antibodies against deamidated dietary gluten and against transglutaminase type 2. Similarly, antibodies against citrulline-containing peptides and against peptidylarginine deiminase are detected in patients with rheumatoid arthritis. Thus, in two major autoimmune diseases, antibodies are detected against post-translationally modified proteins and against the thiol-enzymes responsible for catalyzing the modifications. In vitro, physiological concentrations of zinc reversibly inhibit the calcium-dependent activation of transglutaminases. Zinc attenuates the calcium-induced increase in affinity between transglutaminase 2 and serum from patients with celiac disease. Peptidylarginine deiminases are also inhibited by zinc. Moreover, zinc is rapidly redistributed in animals when an infection is induced. This pathway starting with an unspecific inflammation and ending up with an immune reaction against a specific tissue constitutes a theme with variations in other autoimmune diseases, such as dermatitis herpetiformis, multiple sclerosis, and type 1 diabetes. Inhibitors against transglutaminases and peptidylarginine deiminases have a great pharmacological potential. Interestingly, a large portion of the population may have been exposed to such an inhibitor. The primary metabolite of ethanol, acetaldehyde, can probably function as an irreversible inhibitor of these enzymes by forming a hemithioacetal with the thiol group of the active site. Not surprisingly, epidemiological studies have shown that alcohol is beneficial in rheumatoid arthritis. We predict that a similar situation will be observed in multiple sclerosis. The affinity of chelators such as EDTA and EGTA for Zn(2+) is three orders of magnitude greater than that for Ca(2+). This frequently overlooked complication imposes problems in biomedical research since a restoration of the zinc level can never be achieved in a blood sample which has been anti-coagulated by calcium chelators. The new synthetic direct thrombin inhibitors may offer a better way of preventing coagulation in vitro.

CONCLUSIONS

Post-translational modifications are of potential interest in autoimmune diseases. The in vivo activation of calcium-dependent thiol-enzymes catalyzing these alterations, such as the transglutaminases and the peptidylarginine deiminases, is crucial for this pathway. According to our hypothesis, zinc is the modulator of this key function.

Zinc and gastrointestinal disease

This review is a current summary of the role that both zinc deficiency and zinc supplementation can play in the etiology and therapy of a wide range of gastrointestinal diseases. The recent literature describing zinc action on gastrointestinal epithelial tight junctions and epithelial barrier function is described. Zinc enhancement of gastrointestinal epithelial barrier function may figure prominently in its potential therapeutic action in several gastrointestinal diseases.

Immunological effects of transglutaminase-treated gluten in coeliac disease

Coeliac disease pathogenesis is characterized by an immune response triggered, in genetically predisposed subjects, by ingested gluten and its withdrawal from the diet is the only available therapy. However, enzymatic modification of gluten through the insertion of lysine to avoid antigen presentation could represent a new therapeutical approach for patients. Sixty-six duodenal biopsies from 17 coeliac patients were cultured for 48 h with gluten or enzymatically-modified gluten (treated with human recombinant transglutaminase type 2 or bacterial transglutaminase, with or without lysine). Interferonγ, anti endomisium and anti transglutaminase IgA antibodies, lactate dehydrogenase and transglutaminase activity were measured in the culture medium. Transglutaminase type 2 expression was evaluated on biopsies by immunohistochemistry. Gluten and transglutaminase-treated gluten increased by 13-15 fold interferon γ release, as well as antibodies, transglutaminase activity, and the immunohistochemical expression of transglutaminase type 2. Addition of lysine to the enzymatic modification of gluten normalized interferon γ, antibodies, transglutaminase activity and immunohistochemical expression of transglutaminase type 2. Lactate dehydrogenase did not differ among the studied groups. Enzymatic modification of gluten by transglutaminase plus lysine prevents the immunologic effects on cultured duodenal biopsies from coeliac patients and could be tested as an alternative therapy in coeliac disease.

Children with screening-detected coeliac disease show increased levels of nitric oxide products in urine

AIM

Increased concentration of nitric oxide (NO) metabolites, nitrite and nitrate, in the urine is a strong indication of ongoing small intestinal inflammation, which is a hallmark of the enteropathy of coeliac disease (CD). It has previously been shown that children with symptomatic, untreated CD have increased levels of NO oxidation products in their urine. The aim of this study was to investigate whether screening-detected, asymptomatic coeliac children display the same urinary nitrite/nitrate pattern.

METHODS

In a multicenter screening study, serum samples were collected from 7208 12-year-old children without previously diagnosed CD. Sera were analysed for anti-human tissue transglutaminase (tTG) of isotype IgA. Small bowel biopsy was performed in antibody-positive children, yielding 153 new cases of CD. In the screening-detected individuals, the sum of nitrite and nitrate concentrations in the urine was analysed and used as an indicator of NO production. For comparison, 73 children with untreated, symptomatic CD were studied.

RESULTS

The nitrite/nitrate levels in children with screening-detected CD and those with untreated symptomatic CD did not differ significantly. Both groups had significantly increased urinary nitrite/nitrate concentrations compared to the children with normal small bowel biopsy (p < 0.001).

CONCLUSION

  Children with screening-detected CD have increased production of NO just as children with untreated symptomatic CD. High NO metabolite levels in the urine may indicate a pathogenetic feature of CD and be a marker of major clinical importance.

FOXP3 expression in duodenal mucosa in pediatric patients with celiac disease

OBJECTIVE

It was the aim of this study to evaluate the number of 2 lymphoid subpopulations, CD8(+) cells and FOXP3(+), in the duodenum mucosa from pediatric celiac patients.

METHODS

Tissue sections prepared from paraffin-embedded biopsies of the descending duodenum of 61 celiac patients with Marsh grade 1 (M1), M2 and M3 disease and biopsies from 21 age-matched non-celiac (NC) patients were immunohistostained with anti-CD8 or FOXP3 antibodies.

RESULTS

The histological Marsh grade correlated with the mean number of FOXP3(+) cells in the lamina propria (LP) mucosa (8.9 ± 1.1, 6.8 ± 2.4, 24.5 ± 2.6 and 31.1 ± 2.8 for NC, M1, M2 and M3 biopsies, respectively; p < 0.001). Using a cutoff point of 15 cells, 95% of NC and 88% of M1 biopsies had a mean of <15 FOXP3(+) cells compared with 14% for M2 and 13% for M3 biopsies. The number of FOXP3(+) cells in the epithelial mucosa also correlated with transglutaminase type 2 serum levels from the celiac patients. Unlike the FOXP3(+) cells, CD8(+) lymphocytes were present in both LP and surface epithelial mucosa and significantly different only in the LP mucosa of the M2 and M3 groups.

CONCLUSION

The number of FOXP3(+) cells is substantially increased in the mucosa of celiac patients at advanced stages. Characterization of the activity of these cells in celiac and in other inflammatory bowel diseases will enable us to understand the significance of these cells in celiac disease.

Elevated adenosine deaminase levels in celiac disease

Celiac disease (CD) is a genetically based chronic inflammatory disorder of the small bowel induced by the dietary gluten and possibly other environmental cofactors. The objective of this study was to investigate the relation of adenosine deaminase (ADA), a cytoplasmic enzyme involved in the catabolism of purine bases, as an index of altered immune response, with adult CD patients. ADA has been shown to increase in several inflammatory conditions, but there is no literature data indicating an alteration in CD. Serum levels of ADA were investigated in newly diagnosed 20 CD patients. ADA levels were compared in patients with CD and in healthy controls. Correlation analysis was also performed between ADA and other serum markers of CD (anti-gliadin and anti-endomysial antibodies) Mean serum ADA levels were significantly elevated in CD patients compared with control group. ROC curve analysis suggested that the optimum ADA level cut-off point for CD was 12.27 U/l. At a cut-off value of 12.27 U/l, the sensitivity was 80% and specificity was 100%. There was no statistically significant correlation between ADA and anti-gliadin and anti-endomisium antibodies. Serum ADA levels elevated significantly in CD patients, suggesting a partial role in activated T-cell response in the disease pathophysiology. ADA can be used as a supportive diagnostic marker in patients with CD.

Peptidylarginine deiminases and the pathogenesis of rheumatoid arthritis: a reflection of the involvement of transglutaminase in coeliac disease

Post-translational modifications are associated with certain autoimmune diseases. For example, in the initial steps of coeliac disease (CD), transglutaminase type 2 (TG2) catalyzes a post-translational deamidation of specific glutamine residues in dietary gluten, resulting in antibodies against both modified gliadin and against TG2. Anti-TG2 has become a specific biomarker for CD. In rheumatoid arthritis (RA), the presence of antibodies against citrullinated peptides (ACPA) characterizes a distinct subset of this inflammatory disorder. Moreover, antibodies against the enzyme that catalyzes the citrullination (peptidylarginine deiminase; PAD) are found in RA. Their relation to disease severity indicates a possible pathogenetic role. Thus, in two major autoimmune diseases (CD and RA), antibodies are present against a post-translationally modified substrate and against the calcium-dependent thiol-enzyme (TG2 and PAD, respectively) responsible for the modification. This review highlights the similarities between the TGs and the PADs and their putative pathogenetic roles in autoimmune diseases. Possible mechanisms of the effects of cigarette smoking and alcohol consumption on RA are discussed. By reflecting the progress in CD, the pathogenesis of ACPA-positive RA can be hypothesized where expression and regulation of PADs play significant roles. Indeed, autoimmune diseases should be studied collectively as well as individually. The new insight may lead towards innovative pharmacotherapeutic principles.

Zinc and micronutrient combinations to combat gastrointestinal inflammation

PURPOSE OF REVIEW

To examine current evidence for dietary supplementation with zinc and other micronutrients for primary prevention of multiple micronutrient deficiencies that are known to result from therapies used in the treatment of gastrointestinal inflammatory disorders.

RECENT FINDINGS

Epidemiological observations and clinical findings have strengthened the concept that both nutritional deficiencies and nutritional excesses impair the gastrointestinal response(s) and alter susceptibility to inflammation and other diseases. The interaction of micronutrient intake, biochemical indicators of nutritional status, and four specific gastrointestinal inflammation states are reviewed. These conditions include celiac disease and concomitant micronutrient deficiencies resulting from the sustained adherence to a gluten-free diet; micronutrient nutrition as an important determinant of immunity for two major types of inflammatory bowel disease: ulcerative colitis and Crohn's disease; and HIV/AIDS-related diarrhea and concomitant micronutrient deficiencies which may be exacerbated by the initiation of highly active antiretroviral therapy.

SUMMARY

For each inflammation 'state', enhancement of micronutrient status can improve immunocompetance and minimize therapeutic side-effects. The impact of single-micronutrient deficiencies on immune responses, and the possible impact of uncorrected micronutrient status are discussed.

Development of an isoenzyme-specific colorimetric assay for tissue transglutaminase 2 cross-linking activity

Tissue transglutaminase (TGase 2) belongs to the multigene transglutaminase family of Ca2+-dependent protein cross-linking enzymes. Based on the transamidation activity of TGase 2, a novel colorimetric assay has been developed using covalently coupled spermine to carboxy-substituted polystyrene plates and biotinylated pepT26, an excellent acyl-donor substrate, highly specific for TGase 2. The assay is based on the incorporation of the gamma-carboxamide of glutamine of pepT26 into the immobilized spermine. The amount of biotinylated pepT26 bound to the plate, as measured by the activity of streptavidin-peroxidase, is directly proportional to the TGase activity. The colorimetric procedure showed a good correlation (r=0.995) with the commonly used radiometric filter paper method for TGase2, and provides linear dose-response curves over a wide range of hrTGase2 concentrations (2.5-40 microU/ml). In addition, the assay shows higher sensitivity when compared with our previous TG-colorimetric test (more than 50-fold increase) and other existing assays. PepT26 displays strong reactivity with TGase 2, and no reactivity with TGases 1, 3, and FXIII. The procedure constitutes a rapid, TG2-specific, sensitive, and nonisotopic method for the measurement of TGase 2 activity in as low as 4ng of hrTGase 2 and purified guinea pig liver transglutaminase, and 1.25mug of guinea pig liver extracts.

Serum zinc in small children with coeliac disease

In coeliac disease (CD) there is a gluten-induced small bowel enteropathy leading to malabsorption of various nutrients, vitamins and trace elements. Low levels of serum zinc have been reported in adults with untreated CD. In the present study we related the serum concentration of zinc to the morphology of the small bowel mucosa in 58 children, all under 4 years of age and under investigation for coeliac disease. The mean serum concentration of zinc (mean +/- SD; mumol/L) was significantly lower in children with untreated CD (9.7 +/- 2.0) (n = 11) compared to non-coeliac children without enteropathy (15.1 +/- 2.3) (n = 16) (p < 0.001), coeliac children on a gluten-free diet without enteropathy (14.2 +/- 1.6) (n = 14) (p < 0.001), coeliac children on gluten challenge with enteropathy (14.1 +/- 2.1) (n = 12) (p < 0.001) and coeliac children on gluten challenge without enteropathy (13.8 +/- 1.9) (n = 6) (p < 0.005).

CONCLUSION

Serum zinc concentration is decreased in untreated coeliac children with enteropathy and normalizes on gluten-free diet. A low serum zinc value in a child being investigated for possible CD on clinical grounds can thus be used as a complementary marker for enteropathy indicating further investigation with small bowel biopsy. The hypothetical role of zinc in the pathogenesis of CD is discussed.

Transglutaminase 2 cross-linking of matrix proteins: biological significance and medical applications

This review summarises the functions of the enzyme tissue transglutaminase (TG2) in the extracellular matrix (ECM) both as a matrix stabiliser through its protein cross-linking activity and as an important cell adhesion protein involved in cell survival. The contribution of extracellular TG2 to the pathology of important diseases such as cancer and fibrosis are discussed with a view to the potential importance of TG2 as a therapeutic target. The medical applications of TG2 are further expanded by detailing the use of transglutaminase cross-linking in the development of novel biocompatible biomaterials for use in soft and hard tissue repair.

Tissue transglutaminase in celiac disease: role of autoantibodies

In celiac disease (CD), gluten, the disease-inducing toxic component in wheat, induces the secretion of IgA-class autoantibodies which target tissue transglutaminase (tTG). These autoantibodies are produced in the small-intestinal mucosa, and, during gluten consumption, they can also be detected in patients' serum but disappear slowly from the circulation on a gluten-free diet. Interestingly, after adoption of a gluten-free diet the serum autoantibodies disappear from the circulation more rapidly than the small-intestinal mucosal autoantibody deposits. The finding of IgA deposits on extracellular tTG in the liver, kidney, lymph nodes and muscles of patients with CD indicates that tTG is accessible to the gut-derived autoantibodies. Although the specific autoantibody response directed against tTG is very characteristic in celiac patients, their role in the immunopathology of the celiac mucosal lesion is a matter of debate. Here we report a brief summary of anti-tTG antibody effects demonstrating that these antibodies are functional and not mere bystanders in the disease pathogenesis. In fact, they inhibit intestinal epithelial cell differentiation, induce intestinal epithelial cell proliferation, increase epithelial permeability and activate monocytes and disturb angiogenesis.