Expression of intrinsic factor in rat and murine gastric mucosal cell lineages is modified by inflammation

The Relation of Cytotoxin-Associated Gene-A Seropositivity with Vitamin B12 Deficiency in Helicobacter pylori-Positive Patients

Background and Aim

As a worldwide infectious bacterium, H. pylori leads to stomach pathologies such as gastritis, peptic ulcer, gastric cancer, MALToma, and various extragastric manifestations. In our study, we aimed to investigate the association between serum vitamin B12 level and cytotoxin-associated gene-A (CagA) seropositivity, which is one of the virulence factors of Helicobacter pylori (H. pylori).

Method

This study has been conducted on 289 patients who have met the inclusion criteria. Within these patients, 213 of them were H. pylori positive and 76 were negative. Vitamin B12 and CagA-IgG levels were assessed in consecutive dyspeptic patients undergoing upper endoscopy.

Results

Out of 289 patients, 51.9% were women (n = 150) and H. pylori was detected in 213 (73.7%) patients. Histopathological evaluation with modified Sydney classification revealed lymphocyte infiltration in 66.8% (n = 193), activation in 46% (n = 133), metaplasia in 11.4% (n = 33), atrophy in 11.4% (n = 33), and lymphoid follicles in 21.1% (n = 61) of the patients. Within H. pylori-positive patients, the ratio of CagA positivity was 57.3% (n = 122). Low B12 vitamin level was significantly correlated with existence of H. pylori (p=0.02), CagA (p=0.002), lymphocyte (p=0.006), metaplasia (p=0.001), atrophy (p=0.001), and lymphoid follicles (p=0.006). Positivity of CagA has been detected to be statistically corelated with lymphocyte (p=0.001) and activation (p=0.005); however, the same relation was not present with atrophy (p=0.236).

Conclusion

In conclusion, B12 deficiency was positively correlated with CagA positivity and gastric inflammatory activity.

Intrinsic factor recognition promotes T helper 17/T helper 1 autoimmune gastric inflammation in patients with pernicious anemia

The intrinsic factor is the major humoral autoantigen in pernicious anemia/autoimmune gastritis. Although many studies have examined the autoantibody response to intrinsic factor and H⁺,K⁺-ATPase, no information is available on possible pathogenic mechanisms mediated by intrinsic factor - specific gastric T cells. Aim of this study was to investigate intrinsic factor-specific T cells in the gastric mucosa of pernicious anemia patients and define their functional properties. For the first time we provide evidence that gastric mucosa of pernicious anemia patients harbour a high proportion (20%) of autoreactive activated CD4⁺ T-cell clones that specifically recognize intrinsic factor. Most of these clones (94%) showed a T helper 17 or T helper 1 profile. All intrinsic factor-specific clones produced tumor necrosis factor-α, interleukin-21 and provided substantial help for B-cell immunoglobulin production. Most mucosa-derived intrinsic factor-specific T-cell clones expressed cytotoxicity against target cells. Our results indicate that activation of intrinsic factor-specific T helper 17 and T helper 1 T cells in the gastric mucosa represent a key effector mechanism in pernicious anemia suggesting that the T helper 17/T helper 1 pathway may represent a novel target for the prevention and treatment of the disease.

Gastrointestinal Handling of Water-Soluble Vitamins

Nine compounds are classified as water-soluble vitamins, eight B vitamins and one vitamin C. The vitamins are mandatory for the function of numerous enzymes and lack of one or more of the vitamins may lead to severe medical conditions. All the vitamins are supplied by food in microgram to milligram quantities and in addition some of the vitamins are synthesized by the intestinal microbiota. In the gastrointestinal tract, the vitamins are liberated from binding proteins and for some of the vitamins modified prior to absorption. Due to their solubility in water, they all require specific carriers to be absorbed. Our current knowledge concerning each of the vitamins differs in depth and focus and is influenced by the prevalence of conditions and diseases related to lack of the individual vitamin. Because of that we have chosen to cover slightly different aspects for the individual vitamins. For each of the vitamins, we summarize the physiological role, the steps involved in the absorption, and the factors influencing the absorption. In addition, for some of the vitamins, the molecular base for absorption is described in details, while for others new aspects of relevance for human deficiency are included. © 2018 American Physiological Society. Compr Physiol 8:1291-1311, 2018.

Gastric intrinsic factor: the gastric and small intestinal stages of cobalamin absorption. a personal journey

Intrinsic factor (IF) was first identified as a component of the gastric mucosa that reacted with an extrinsic factor, later discovered to be vitamin B12 (VB12). IF has been extensively characterized, and its cloned cDNA used to produce sufficient IF to produce high quality antibodies, and to elucidate its 3-dimensional structure bound to cobalamin (Cbl, VB12). The absorption of the IF-Cbl complex involves internalization by endocytosis, incorporation into multivesicular/lysosomal bodies, release of Cbl by lysosomal proteolysis and pH effects, with subsequent binding to transcobalamin (TC). Hereditary IF deficiency is rare, consistent with the need for IF to absorb Cbl, a vitamin essential for cell replication. When mutations occur, they are most often associated with loss of function, but some mutations occur outside the coding region. The IF-mediated intestinal uptake of Cbl has been harnessed for use as a transporter for peptides, proteins and even nanoparticles. Nanoparticle (NP) technology has produced Cbl-coated NPs that can incorporate peptides (insulin, IgG) that can be absorbed orally to function as hormones and antibodies in rodent models, but these systems are not yet ready for clinical use.

Deficiency of claudin-18 causes paracellular H+ leakage, up-regulation of interleukin-1β, and atrophic gastritis in mice

BACKGROUND & AIMS

Although defects in tight junction (TJ) epithelial paracellular barrier function are believed to be a primary cause of inflammation, the mechanisms responsible remain largely unknown.

METHODS

We generated knockout mice of stomach-type claudin-18, a major component of TJs in the stomach.

RESULTS

Cldn18(-/-) mice were afflicted with atrophic gastritis that started on postnatal day 3. This coincided with a decrease in intragastric pH due to H(+) secretion from parietal cells and concomitant up-regulation of the cytokines, interleukin-1β, cyclooxygenase-2, and KC, resulting in spasmolytic polypeptide-expressing metaplasia (SPEM). Oral administration of hydrochloric acid on postnatal day 1 induced the expression of these cytokines in Cldn18(-/-) infant stomach, but not in Cldn18(+/+) mice. A paracellular H(+) leak in Cldn18(-/-) stomach was detected by electrophysiology and H(+) titration, and freeze-fracture electron microscopy showed structural defects in the TJs, in which the tightly packed claudin-18 (stomach-type)-based TJ strands were lost, leaving a loose meshwork of strands consisting of other claudin species.

CONCLUSIONS

These findings provide evidence that claudin-18 normally forms a paracellular barrier against H(+) in the stomach and that its deficiency causes paracellular H(+) leak, a persistent up-regulation of proinflammatory cytokines, chronic recruitment of neutrophils, and the subsequent development of SPEM in atrophic gastritis.

Production of ectopic gastric intrinsic factor in gastric mucosa of humans with chronic gastritis

BACKGROUND

Ectopic expression of gastric intrinsic factor (IF) has been described in rodent models of chronic gastritis.

AIMS

The current study undertook to determine if ectopic IF was also present in chronic gastritis in humans and might identify the process of ectopic protein expression as part of the response to chronic injury.

METHODS

Archived biopsies from mid-body, angularis and prepylorus of 9 patients with and without chronic gastritis and food-cobalamin malabsorption were examined in a blinded fashion by immunocytochemistry as were biopsies from 5 normal subjects. Cells with ectopic IF were further examined with antibodies against pepsin or with Griffonia simplicifolia II (GSII) to identity cells in the mucous neck cell compartment.

RESULTS

Ectopic IF production in non-parietal cells was identified in cells that were H(+),K(+)-ATPase-negative but IF-positive in 7 of the 9 patients (6/9 in the angularis and/or prepylorus biopsies and 1/9 only in the mid-body). These included 5 of the 6 H. pylori-infected patients and all 5 patients with severe food-cobalamin malabsorption. No normal control subjects demonstrated ectopic IF. The cells with ectopic IF were pepsinogen-positive peptic cells and were not GSII-positive. Expression was most extensive in patients and gastric regions with inflammation. In all but one sample, ectopic IF was observed near anatomical mucosal junctions, such as antral/body and prepylorus/duodenum junctions.

CONCLUSIONS

These data in humans with and without gastritis are consistent with the hypothesis that local factors influence ectopic gastric IF expression, arising from either the anatomical location, the focal inflammation, or both.

Impaired gastric gland differentiation in Peutz-Jeghers syndrome

Gastrointestinal hamartomatous polyps in the Peutz-Jeghers cancer predisposition syndrome and its mouse model (Lkb1(+/-)) are presumed to contain all cell types native to the site of their occurrence. This study aimed to explore the pathogenesis of Peutz-Jeghers syndrome polyposis by characterizing cell types and differentiation of the epithelium of gastric polyps and predisposed mucosa. Both antral and fundic polyps were characterized by a deficit of pepsinogen C-expressing differentiated gland cells (antral gland, mucopeptic, and chief cells); in large fundic polyps, parietal cells were also absent. Gland cell loss was associated with an increase in precursor neck cells, an expansion of the proliferative zone, and an increase in smooth muscle alpha-actin expressing myofibroblasts in the polyp stroma. Lack of pepsinogen C-positive gland cells identified incipient polyps, and even the unaffected mucosa of young predisposed mice displayed an increase in pepsinogen C negative glands (25%; P = 0045). In addition, in small intestinal polyps, gland cell differentiation was defective, with the absence of Paneth cells. There were no signs of metaplastic differentiation in any of the tissues studied, and both the gastric and small intestinal defects were seen in Lkb1(+/-) mice, as well as polyps from patients with Peutz-Jeghers syndrome. These results identify impaired epithelial differentiation as the earliest pathological sign likely to contribute to tumorigenesis in individuals with inherited Lkb1 mutations.

Murine experimental autoimmune gastritis models refractive to development of intrinsic factor autoantibodies, cobalamin deficiency and pernicious anemia

Researchers have developed murine lymphopenic, non-lymphopenic, transgenic, spontaneous and infectious agent based models to induce an experimental autoimmune gastritis (EAG) for the study of human organ-specific autoimmune disease. These models result in a chronic inflammatory mononuclear cell infiltrate in the gastric mucosa, destruction of parietal and zymogenic cells with autoantibodies reactive to the gastric parietal cells and the gastric H+/K+ ATPase (ATP4), arguably hallmarks of a human autoimmune gastritis (AIG). In the case of AIG, it is well documented that, in addition to parietal cell antibodies being detected in up to 90% of patients, up to 70% have intrinsic factor antibodies with the later antibodies considered highly specific to patients with pernicious anemia. This is the first report specifically investigating the occurrence of intrinsic factor antibodies, cobalamin deficiency and pernicious anemia in EAG models. We conclude, in contrast to AIG, that, in the three EAG models examined, intrinsic factor is not selected as a critical autoantigen.

Gastritis in Neonatal BALB/cCrSlc Mice Induced by Immunization Without Adjuvant can be Transferred to Syngeneic nu/nu Recipients

The popularly exploited murine neonatal thymectomy experimental autoimmune gastritis (nTx:EAG) model requires the animal to be in a state of lymphopenia. Here we report on a novel murine immunization (without adjuvant) model that can establish a lasting gastritis. We demonstrate that the immunization model (imm:EAG) results in a bona fide autoimmune disease and define the resulting pathology and serology observed and compare it with that reported for human autoimmune gastritis. Immune cells present in the stomachs of imm:EAG gastritic mice include CD8 T cells, CD11b and Gr1 (granulocytes/monocytes) and B cells. We detected circulating antibodies of immunoglobulin G1 (IgG1) subclass, with some IgG(2a) and IgG(2b) reactive to stomach membranes and the parietal cell proton pump. The class and subclass of autoreactive antibodies resulting from imm:EAG suggest a T helper 1 (Th1)/Th2 immune response. We establish that both self-reactive T and B cells from BALB/cCrSlc imm:EAG gastritic mice have the potential to induce a gastritis in BALB/c syngeneic nu/nu recipients. We conclude that this model is likely to be superior to the currently popularly exploited nTx:EAG and provide insight into and an understanding of the mechanisms of and remedies for autoimmunity in an intact immune system.

KCNQ1-dependent transport in renal and gastrointestinal epithelia

Mutations in the gene encoding for the K+ channel alpha-subunit KCNQ1 have been associated with long QT syndrome and deafness. Besides heart and inner ear epithelial cells, KCNQ1 is expressed in a variety of epithelial cells including renal proximal tubule and gastrointestinal tract epithelial cells. At these sites, cellular K+ ions exit through KCNQ1 channel complexes, which may serve to recycle K+ or to maintain cell membrane potential and thus the driving force for electrogenic transepithelial transport, e.g., Na+/glucose cotransport. Employing pharmacologic inhibition and gene knockout, the present study demonstrates the importance of KCNQ1 K+ channel complexes for the maintenance of the driving force for proximal tubular and intestinal Na+ absorption, gastric acid secretion, and cAMP-induced jejunal Cl- secretion. In the kidney, KCNQ1 appears dispensable under basal conditions because of limited substrate delivery for electrogenic Na+ reabsorption to KCNQ1-expressing mid to late proximal tubule. During conditions of increased substrate load, however, luminal KCNQ1 serves to repolarize the proximal tubule and stabilize the driving force for Na+ reabsorption. In mice lacking functional KCNQ1, impaired intestinal absorption is associated with reduced serum vitamin B12 concentrations, mild macrocytic anemia, and fecal loss of Na+ and K+, the latter affecting K+ homeostasis.

Rat enterocytes secrete SLPs containing alkaline phosphatase and cubilin in response to corn oil feeding

Surfactant-like particles (SLP) are unilamellar secreted membranes associated with the process of lipid absorption and isolated previously only from the apical surface of enterocytes. In this paper, the intracellular membrane has been isolated from corn oil-fed animals, identified by its content of the marker protein intestinal alkaline phosphatase (IAP). Another brush-border protein, cubilin, and its anchoring protein megalin have been identified as components of extracellular SLP, but only cubilin is present to any extent in intracellular SLP. During fat absorption, IAP is modestly enriched in intracellular SLP, but full-length cubilin (migrating at 210 kDa in fat-fed mucosal fractions) falls by one-half, although fragments of cubilin are abundant in the intracellular SLP. Both IAP and cubilin colocalize to the same cells during corn oil absorption and colocalize around lipid droplets. This localization is more intense during feeding of corn oil with Pluronic L-81, a detergent that allows uptake of fatty acids and monoglycerides from the lumen, but blocks chylomicron secretion. Confocal microscopy confirms the colocalization of IAP and the ligand for cubilin, intrinsic factor. Possible roles for cubilin in intracellular SLP include facilitating movement of the lipid droplet through the cell and binding to the basolateral membrane before reverse endocytosis.

Impact of Helicobacter pylori on the development of vitamin B12 deficiency in the absence of gastric atrophy

BACKGROUND

Cobalamin (vitamin B12) deficiency is associated with Helicobacter pylori infection. This study examined how serum vitamin B12 levels relate to gastric mucosa H. pylori density and histology, and to hematological findings in patients with minimal or no gastric atrophy. A second aim was to confirm that H. pylori eradication therapy increases serum B12.

MATERIALS AND METHODS

Biopsies of the gastric mucosa from a population of dyspeptic patients were graded for level of chronic inflammation, neutrophil activity, atrophy, and H. pylori density. A total of 145 H. pylori-infected patients with minimal or no atrophy were included in the study. Serum cobalamin level, hemoglobin level, and mean corpuscular volume were measured in the 145 patients before eradication therapy, and in 65 of the subjects after treatment. The hematologic findings before and after eradication therapy and correlations between serum vitamin B12 level and histologic parameters, hematologic findings, and patient age were statistically analyzed.

RESULTS

There was no significant correlation between serum cobalamin level and patient age. Before treatment all the histopathological scores were inversely correlated with serum vitamin B12 level (p <.01) on univariate analysis. Only H. pylori density was significantly associated with B12 level on multivariate analysis. Serum hemoglobin and cobalamin levels were significantly increased after treatment, regardless of H. pylori eradication status (p <.001).

CONCLUSION

The findings provide strong evidence that H. pylori infection is associated with cobalamin deficiency, and show that this is true even in patients with non-ulcer dyspepsia and minimal or no gastric atrophy.

Animal models of human disease: experimental autoimmune gastritis--a model for autoimmune gastritis and pernicious anemia

Human autoimmune gastritis is an organ-specific autoimmune disease of the stomach. It is characterized by the development of disease-specific autoantibodies and a pathology that specifically targets specialized cells within the gastric environment. The autoantigens associated with this disease have been defined as the gastric H+/K+ ATPase and intrinsic factor. The development of experimental disease models has been pivotal in our contemporary understanding of autoimmunity. Here we review mouse models of autoimmune gastritis and their relevance to human autoimmune gastritis associated with pernicious anemia. We appraise some historical as well as recent studies of experimental autoimmune gastritis (EAG), highlighting key findings that have formed the basis of our current understanding of the etiology and mechanism(s) associated with autoimmune gastritis. A precise understanding of the pathogenesis of autoimmune gastritis will permit the design of innovative and rational therapeutic strategies to prevent, arrest, ameliorate or reverse the disease.