Localization of antigen-presenting cells in Helicobacter pylori-infected gastric mucosa

Two Distinct Etiologies of Gastric Cancer: Infection and Autoimmunity

Gastric cancer is a leading cause of mortality worldwide. The risk of developing gastric adenocarcinoma, which comprises >90% of gastric cancers, is multifactorial, but most associated with Helicobacter pylori infection. Autoimmune gastritis is a chronic autoinflammatory syndrome where self-reactive immune cells are activated by gastric epithelial cell autoantigens. This cause of gastritis is more so associated with the development of neuroendocrine tumors. However, in both autoimmune and infection-induced gastritis, high risk metaplastic lesions develop within the gastric mucosa. This warrants concern for carcinogenesis in both inflammatory settings. There are many similarities and differences in disease progression between these two etiologies of chronic gastritis. Both diseases have an increased risk of gastric adenocarcinoma development, but each have their own unique comorbidities. Autoimmune gastritis is a primary cause of pernicious anemia, whereas chronic infection typically causes gastrointestinal ulceration. Both immune responses are driven by T cells, primarily CD4⁺ T cells of the IFN-γ producing, Th1 phenotype. Neutrophilic infiltrates help clear H. pylori infection, but neutrophils are not necessarily recruited in the autoimmune setting. There have also been hypotheses that infection with H. pylori initiates autoimmune gastritis, but the literature is far from definitive with evidence of infection-independent autoimmune gastric disease. Gastric cancer incidence is increasing among young women in the United States, a population at higher risk of developing autoimmune disease, and H. pylori infection rates are falling. Therefore, a better understanding of these two chronic inflammatory diseases is needed to identify their roles in initiating gastric cancer.

Gastric Microenvironment-A Partnership between Innate Immunity and Gastric Microbiota Tricks Helicobacter pylori

Helicobacter pylori (H. pylori) carcinogenicity depends on three major factors: bacterial virulence constituents, environmental factors and host's genetic susceptibility. The relationship between microenvironmental factors and H. pylori virulence factors are incontestable. H. pylori infection has a major impact on both gastric and colonic microbiota. The presence of non-H. pylori bacteria within the gastric ecosystem is particularly important since they might persistently act as an antigenic stimulus or establish a partnership with H. pylori in order to augment the subsequent inflammatory responses. The gastric ecosystem, i.e., microbiota composition in children with H. pylori infection is dominated by Streptoccocus, Neisseria, Rothia and Staphylococcus. The impairment of this ecosystem enhances growth and invasion of different pathogenic bacteria, further impairing the balance between the immune system and mucosal barrier. Moreover, altered microbiota due to H. pylori infection is involved in increasing the gastric T regulatory cells response in children. Since gastric homeostasis is defined by the partnership between commensal bacteria and host's immune system, this review is focused on how pathogen recognition through toll-like receptors (TLRs-an essential class of pathogen recognition receptors-PRRs) on the surface of macrophages and dendritic cells impact the immune response in the setting of H. pylori infection. Further studies are required for delineate precise role of bacterial community features and of immune system components.

Comparison of clinical outcomes and FOXP3, IL-17A responses in Helicobacter pylori infection in children versus adults

BACKGROUND

The purpose of this study was to compare the clinical symptoms and pathological consequences of Helicobacter pylori (H. pylori) infection between children and adults and determine the levels of expression of FOX3P and IL-17A to examine the Th17/Treg balance.

METHODS

Forty pediatric and 40 adult patients who were followed up at the Pediatric Gastroenterology and Internal Medicine Gastroenterology Departments were enrolled in the study. In our case-control study, gastric tissue specimens were evaluated using the updated Sydney system, and the number of cells expressing FOXP3/IL-17A (T_reg and Th17 cell markers) was analyzed immunohistochemically. In addition, each case was evaluated using a clinical follow-up questionnaire.

RESULTS

Clinical signs and symptoms of children and adults were similar. IL-17A and FOXP3 levels were significantly higher in children and adults with H. pylori (+) than in those without H. pylori (-) (p < .001). In patients with H. pylori (+), the mean FOXP3 level was significantly higher, whereas the mean IL-17A level was significantly lower in children than in adults (p < 0001 for both groups). In children with H. pylori (+), bacterial density was negatively correlated with IL-17A level and positively correlated with FOXP3 level. In adults with H. pylori (+), there was a statistically significant, highly positive correlation between bacterial density and levels of IL-17A and FOXP3.

CONCLUSIONS

T_reg cells are suggested to more predominant in children than in adults, IL-17A levels decrease as H. pylori bacterial density increases. In conclusion, immune responses incline toward T_reg , which increases the susceptibility to persistent infections.

An Overview of Helicobacter pylori Infection

Helicobacter pylori (H. pylori) represents one of the most widespread bacterial infections globally. Infection causes chronic gastritis and increases the risk of peptic ulcer disease, gastric adenocarcinoma, and mucosa-associated lymphoid tissue lymphoma. The pioneering discovery of H. pylori by Marshall and Warren in the early 1980s has initiated fervent research into H. pylori as a pathogen ever since. This chapter aims to provide an overview of our understanding of H. pylori infection and its management, with a focus on current options for diagnosis, the challenges associated with H. pylori eradication, and the need for alternative therapeutic strategies based on furthering our understanding of host: H. pylori interactions.

T Cell Cytokines Impact Epithelial Cell Responses during Helicobacter pylori Infection

The goal of this Brief Review is to highlight literature that demonstrates how cytokines made by T lymphocytes impact the gastric epithelium, especially during Helicobacter pylori infection. These cytokines effect many of the diverse functions of the epithelium and the epithelium's interactions with H. pylori The focal point of this Brief Review will be on how T cell cytokines impact antimicrobial function and barrier function and how T cell cytokines influence the development and progression of cancer. Furthermore, the modulation of epithelial-derived chemokines by H. pylori infection will be discussed.

DEC205 mediates local and systemic immune responses to Helicobacter pylori infection in humans

Helicobacter pylori infections cause gastritis and affect systemic immune responses; however, no direct association between immune cells and stomach bacteria has yet been reported. The present study investigated DEC205-mediated phagocytosis of H. pylori and the role of DEC205-positive macrophages in the human gastric mucosa. DEC205 mediated phagocytosis of H. pylori was detected immunocytochemically in PMA-stimulated macrophages differentiated from NOMO1 cells. Expression of DEC205 mRNA in peripheral blood mononuclear cells (PBMCs) from H. pylori-infected patients was analyzed following stimulation with H. pylori cell lysate. We found that anti-DEC205 antibodies inhibited phagocytosis of H. pylori. The number of cells double-positive for DEC205 and CD14 in human gastric mucosa was higher in H. pylori-infected patients. DEC205-positive macrophages invaded the extracellular space between epithelial cells within gastric pits. In addition, DEC205 mRNA expression was upregulated in human PBMCs stimulated with H. pylori lysate. These findings suggest DEC205-expressing macrophages are important for recognition of H. pylori in human gastric mucosa, which affects systemic immunity.

Therapy with omeprazole modulates regulatory T cell/T helper 17 immune response in children with duodenal ulcers

The purpose of this study was to determine the effect of omeprazole on the regulatory T cell (Treg) and T helper 17 (Th17)-mediated response in patients with duodenal ulcers (DUs). DU patients were randomly divided into omeprazole and colloid bismuth subcitrate treatment groups. The ratios of Th17 and Treg in peripheral blood mononuclear cells (PBMCs) were measured. Cytokine production and Foxp3⁺- and RORγt-positive cells were detected. The expressions of STAT3, p-STAT3, STAT5 and p-STAT5 were detected by Western blot. The results showed that DU patients had an imbalanced Treg/Th17 response, as reflected by the higher IL-17 level and Th17 ratio and lower IL-10 level and Treg proportion in serum compared with those in the healthy volunteers. The administration of omeprazole to the patients significantly increased Treg and IL-10 levels and reduced Th17 and IL-17 levels. Omeprazole markedly increased the number of Foxp3-positive cells, decreased the number of RORγt-positive cells and restored the balanced ratio of IL-10/IL-17 in the ulcer tissue. Interestingly, we observed a negative correlation between the ratios of Treg/Th17 and the pathological scores in damaged tissues. Of note, H. pylori-infected PBMCs showed decreased Treg and an increased Th17 proportion, which could be reversed by omeprazole. Finally, omeprazole increased the expression of p-STAT5 and reduced the level of p-STAT3 without any effects on the total expression of STAT5 and STAT3. Our data suggest that omeprazole treatment restores the equilibrium of the Treg/Th17-mediated response in DU patients. Moreover, the modulation of p-STAT3 and p-STAT5 expression by omeprazole induced balanced polarisation of Treg/Th17.

Comparative Immune Response in Children and Adults with H. pylori Infection

Helicobacter pylori (H. pylori) infection is generally acquired during early childhood; therefore, the immune response which usually takes place at this age may influence or even determine susceptibility to the infection contributing to the clinical outcomes in adulthood. Several cytokines including IL-6, IL-10, and TGF-β1 as well as Foxp3(+) cell numbers have been shown to be higher; however, some other cytokines consisting of IL-1β, IL-17A, and IL-23 are lower in infected children than in infected adults. Immune response to H. pylori infection in children is predominant Treg instead of Th17 cell response. These results indicate that immune system responses probably play a role in persistent H. pylori infection. Childhood H. pylori infection is also associated with significantly lower levels of inflammation and ulceration compared with adults. This review, therefore, aimed to provide critical findings of the available literature about comparative immune system in children and adults with H. pylori infection.

Helicobacter pylori infection and eye diseases: a systematic review

The connection between Helicobacter pylori (Hp) infection and eye diseases has been increasingly reported in the literature and in active research. The implication of this bacterium in chronic eye diseases, such as blepharitis, glaucoma, central serous chorioretinopathy and others, has been hypothesized. Although the mechanisms by which this association occurs are currently unknown, this review describes shared pathogenetic mechanisms in an attempt to identify a lowest common denominator between eye diseases and Hp infection. The aim of this review is to assess whether different studies could be compared and to establish whether or not Hp infection and Eye diseases share common pathogenetic aspects. In particular, it has been focused on oxidative damage as a possible link between these pathologies. Text word search in Medline from 1998 to July 2014. 152 studies were included in our review. Were taken into considerations only studies that related eye diseases more frequent and/or known. Likely oxidative stress plays a key role. All of the diseases studied seem to follow a common pattern that implicates a cellular response correlated with a sublethal dose of oxidative stress. These alterations seem to be shared by both Hp infections and ocular diseases and include the following: decline in mitochondrial function, increases in the rate of reactive oxygen species production, accumulation of mitochondrial DNA mutations, increases in the levels of oxidative damage to DNA, proteins and lipids, and decreases in the capacity to degrade oxidatively damaged proteins and other macromolecules. This cascade of events appears to repeat itself in different diseases, regardless of the identity of the affected tissue. The trabecular meshwork, conjunctiva, and retina can each show how oxidative stress may acts as a common disease effector as the Helicobacter infection spreads, supported by the increased oxidative damage and other inflammation.

Immune responses to Helicobacter pylori infection

Helicobacter pylori (H. pylori) infection is one of the most common infections in human beings worldwide. H. pylori express lipopolysaccharides and flagellin that do not activate efficiently Toll-like receptors and express dedicated effectors, such as γ-glutamyl transpeptidase, vacuolating cytotoxin (vacA), arginase, that actively induce tolerogenic signals. In this perspective, H. pylori can be considered as a commensal bacteria belonging to the stomach microbiota. However, when present in the stomach, H. pylori reduce the overall diversity of the gastric microbiota and promote gastric inflammation by inducing Nod1-dependent pro-inflammatory program and by activating neutrophils through the production of a neutrophil activating protein. The maintenance of a chronic inflammation in the gastric mucosa and the direct action of virulence factors (vacA and cytotoxin-associated gene A) confer pro-carcinogenic activities to H. pylori. Hence, H. pylori cannot be considered as symbiotic bacteria but rather as part of the pathobiont. The development of a H. pylori vaccine will bring health benefits for individuals infected with antibiotic resistant H. pylori strains and population of underdeveloped countries.

A role for altered phagosome maturation in the long-term persistence of Helicobacter pylori infection

The vigorous host immune response that is mounted against Helicobacter pylori is unable to eliminate this pathogenic bacterium from its niche in the human gastric mucosa. This results in chronic inflammation, which can develop into gastric or duodenal ulcers in 10% of infected individuals and gastric cancer in 1% of infections. The determinants for these more severe pathologies include host (e.g., high IL-1β expression polymorphisms), bacterial [e.g., cytotoxicity-associated gene (cag) pathogenicity island], and environmental (e.g., dietary nitrites) factors. However, it is the failure of host immune effector cells to eliminate H. pylori that underlies its persistence and the subsequent H. pylori-associated disease. Here we discuss the mechanisms used by H. pylori to survive the host immune response and, in particular, the role played by altered phagosome maturation.

PPK knockout attenuates evasion of immune elimination of Helicobacter pylori by macrophages

AIM: To evaluate the impact of knockout of the polyphosphate kinase gene in Helicobacter pylori (H. pylori) on bacterial evasion of immune elimination by macrophages.

METHODS: A PPK null mutant of H. pylori was constructed by gene homologous recombination. The polyphosphate was extracted from the PPK null mutant and wild type bacteria to compare the amount of polyphosphate by conversion into ATP. PPK null mutant H. pylori or wild type bacteria were co-cultured with murine macrophage cell line Raw 264.1 to compare the bacterial survival in macrophages at 24 h.

RESULTS: A PPK null mutant H. pylori strain was successfully constructed. The amount of polyphosphate in PPK null mutant bacteria was significantly lower than that in wild type bacteria (0.46 nmol Pi/mg Protein ± 0.25 nmol Pi/mg Protein vs 175.33 nmol Pi/mg Protein ± 21.22 nmol Pi/mg Protein, P < 0.01). Compared to wild type H. pylori, the survival rate of PPK null mutant bacteria in macrophages was similar at 2 h but was significantly reduced at 24 h.

CONCLUSION: PPK plays a critical role in synthesizing polyphosphate in H. pylori. PPK knockout in H. pylori significantly impaired their ability to synthesize polyphosphate and to evade immune elimination by macrophages.

Expression of DEC205 in the gastric mucosa of Helicobacter pylori-infected patients

AIM: To investigate the expression of DEC205 in the gastric mucosa of Helicobacter pylori (H. pylori)-infected patients.

METHODS: Thirteen H. pylori-positive patients with gastritis received eradication therapy. Gastroscopy was performed in all the 13 patients before eradication therapy and in 7 seven patients after treatment to take gastric mucosa samples, which were used to prepare frozen section to detect the expression of DEC205 and CD14 in human gastric mucosa by immunofluorescence.

RESULTS: Cells which were positive for both DEC205 and CD14 in the gastric mucosa significantly increased in H. pylori-infected patients. Furthermore, DEC205-positive macrophages invaded into gastric pits in the gastric mucosa of H. pylori-positive patients.

CONCLUSION: Macrophage expressing DEC205 in the gastric mucosa may play an immunological role in H. pylori infection.

Immunological response to parenteral vaccination with recombinant hepatitis B virus surface antigen virus-like particles expressing Helicobacter pylori KatA epitopes in a murine H. pylori challenge model

Virus-like particles (VLPs) based on the small envelope protein of hepatitis B virus (HBsAg-S) are immunogenic at the B- and T-cell level. In this study, we inserted overlapping sequences encoding the carboxy terminus of the Helicobacter pylori katA gene product into HBsAg-S. The HBsAg-S-KatA fusion proteins were able to assemble into secretion-competent VLPs (VLP-KatA). The VLP-KatA proteins were able to induce KatA-specific antibodies in immunized mice. The mean total IgG antibody titers 41 days post-primary immunization with VLP-KatA (2.3 × 10(3)) were significantly greater (P < 0.05) than those observed for vaccination with VLP alone (5.2 × 10(2)). Measurement of IgG isotypes revealed responses to both IgG1 and IgG2a (mean titers, 9.0 × 10(4) and 2.6 × 10(4), respectively), with the IgG2a response to vaccination with VLP-KatA being significantly higher than that for mice immunized with KatA alone (P < 0.05). Following challenge of mice with H. pylori, a significantly reduced bacterial load in the gastric mucosa was observed (P < 0.05). This is the first report describing the use of VLPs as a delivery vehicle for H. pylori antigens.

Helicobacter pylori phagosome maturation in primary human macrophages

Background

Helicobacter pylori (H. pylori) is a micro-aerophilic, spiral-shaped, motile bacterium that is the principal cause of gastric and duodenal ulcers in humans and is a major risk factor for the development of gastric cancer. Despite provoking a strong innate and adaptive immune response in the host, H. pylori persists in the gastric mucosa, avoiding eradication by macrophages and other phagocytic cells, which are recruited to the site of infection. Here we have characterised the critical degradative process of phagosome maturation in primary human macrophages for five genotypically and phenotypically distinct clinical strains of H. pylori.

Results

All of the H. pylori strains examined showed some disruption to the phagosome maturation process, when compared to control E. coli. The early endosome marker EEA1 and late endosome marker Rab7 were retained on H. pylori phagosomes, while the late endosome-lysosome markers CD63, LAMP-1 and LAMP-2 were acquired in an apparently normal manner. Acquisition of EEA1 by H. pylori phagosomes appeared to occur by two distinct, strain specific modes. H. pylori strains that were negative for the cancer associated virulence factor CagA were detected in phagosomes that recruited large amounts of EEA1 relative to Rab5, compared to CagA positive strains. There were also strain specific differences in the timing of Rab7 acquisition which correlated with differences in the rate of intracellular trafficking of phagosomes and the timing of megasome formation. Megasomes were observed for all of the H. pylori strains examined.

Conclusions

H. pylori appeared to disrupt the normal process of phagosome maturation in primary human macrophages, appearing to block endosome fission. This resulted in the formation of a hybrid phagosome-endosome-lysosome compartment, which we propose has reduced degradative capacity. Reduced killing by phagocytes is consistent with the persistence of H. pylori in the host, and would contribute to the chronic stimulation of the inflammatory immune response, which underlies H. pylori-associated disease.

Pediatric Helicobacter pylori infection and circulating T-lymphocyte activation and differentiation

BACKGROUND

In this study, H. pylori-infected and noninfected children with gastritis were compared to a control group with respect to circulating CD4(+) and CD8(+) T lymphocytes expressing activation and differentiation markers. Additionally, the lymphocyte phenotypes of children with gastritis were correlated with the gastric inflammation scores.

MATERIALS AND METHODS

H. pylori infection status was assessed based on [¹³C]urea breath test, rapid urease test, and histology. Analysis of the lymphocyte surface molecule expression was carried out by triple-color flow cytometry.

RESULTS

The group of H. pylori-infected children showed an elevated proportion of peripheral B cells with CD19(low) , along with a twofold increase in the percentage of memory (CD45RO(+)) CD4(+) and CD8(+) T-cell subsets (p < .05). Moreover, a positive correlation between the age and the percentage of these subsets was seen (r = .38, p = .04 and r = .56, p < .01, respectively). Children with gastritis but without infection had a slightly increased percentage of CD8(+) T cells and CD56(+) NK cells, CD3(high) T cells and CD45RO(high) CD4(+) T-cell subsets (p < .05). Both H. pylori-infected and noninfected children with gastritis were characterized by an increased percentage of memory/effector CD4(+) T cells, the presence of NK cells with CD56(high), memory T-cell subset with CD4(high), and naive, memory, memory/effector, and effector T-cell subsets with CD8(high) (p < .05). Gastric inflammation scores correlated positively with the percentage of CD4(+) T lymphocytes in H. pylori-infected children (r = .42, p = .03). In noninfected children, gastric inflammation scores correlated positively with the percentage of B cells (r = .45, p = .04).

CONCLUSION

In H. pylori-negative children, gastritis was associated with an increased percentage of activated NK and T cells, and intermediate-differentiated peripheral blood CD4(+) T cells, which was more pronounced in H. pylori-positive children who also showed an increased B-cell response. However, increased inflammation was only associated with the elevation of CD4(+) T-cell percentage in H. pylori-positive children as well as B-cell percentage in H. pylori-negative children with gastritis.

Human primary gastric dendritic cells induce a Th1 response to H. pylori

Adaptive CD4 T-cell responses are important in the pathogenesis of chronic Helicobacter pylori gastritis. However, the gastric antigen-presenting cells that induce these responses have not yet been identified. Here we show that dendritic cells (DCs) are present in the gastric mucosa of healthy subjects and are more prevalent and more activated in the gastric mucosa of H. pylori-infected subjects. H. pylori induced gastric DCs isolated from noninfected subjects to express increased levels of CD11c, CD86 and CD83, and to secrete proinflammatory cytokines, particularly interleukin (IL)-6 and IL-8. Importantly, gastric DCs pulsed with live H. pylori, but not control DCs, mediated T-cell secretion of interferon-gamma. The ability of H. pylori to induce gastric DC maturation and stimulate gastric DC activation of Th1 cells implicates gastric DCs as initiators of the immune response to H. pylori.

Advances in vaccination against Helicobacter pylori

A vaccination against Helicobacter pylori may represent both prophylactic and therapeutic approaches to the control of H. pylori infection. Different protective H. pylori-derived antigens, such as urease, vacuolating cytotoxin A, cytotoxin-associated antigen, neutrophil-activating protein and others can be produced at low cost in prokaryote expression systems and most of these antigens have already been administered to humans and shown to be safe. The recent development by Graham et al. of the model of H. pylori challenge in humans, the recent published clinical trials and the last insight generated in animal models of H. pylori infection regarding the immune mechanisms leading to vaccine-induced Helicobacter clearance will facilitate the evaluation of immunogenicity and efficacy of H. pylori vaccine candidates in Phase II and III clinical trials.

Expression of DEC205 in Helicobacter pylori-infected macrophages

AIM: To investigate the relationship between Helicobacter pylori (H. pylori) infection and the expression of DEC205.

METHODS: H. pylori-HSP60 was prepared by a recombinant DNA procedure. After monocytic cells (NOMO1 line) were infected with H. pylori or stimulated with H. pylori-HSP60 or E.coli-LPS, whole cell protein was extracted and analyzed by Western blot. NOMO1 cells were then treated with PMA to induce their differentiation into macrophages, and infected with H. pylori or stimulated with H. pylori-HSP60. The expression of DEC205 mRNA was detected by real-time PCR. The expression of DEC205 protein on the surface of NOMO1 cells was analyzed by flow cytometry.

RESULTS: The expression of DEC205 protein was markedly increased following H. pylori infection, whereas the protein expression was only slightly upregulated after stimulation with H. pylori-HSP60 or E.coli-LPS. After treatment of NOMO1 cells with PMA, the expression of DEC205 mRNA was enhanced. Subsequent infection with H. pylori or stimulation with H. pylori-HSP60 could induce the expression of DEC205 mRNA in differentiated NOMO1 cells. Flow cytometry analysis indicated that the expression of DEC205 protein was upregulated obviously on the surface of H. pylori-infected NOMO1 cells (88.10% vs 7.84%, P < 0.05). Moreover, H. pylori infection and H. pylori-HSP60 stimulation could also increase DEC205 expression in differentiated NOMO1 cells (74.73% and 51.31% vs 43.77%, both P < 0.05).

CONCLUSION: H. pylori infection may be closely related with the expression of DEC205 on the surface of macrophages in gastric mucosa.

Natural killer cell receptor T-lymphocytes in normal and Helicobacter pylori-infected human gastric mucosa

BACKGROUND

Helicobacter pylori infection is associated with development of chronic inflammation and infiltration of immune cells into the gastric mucosa. As unconventional T-lymphocytes expressing natural killer cell receptors are considered to play central roles in the immune response against infection, a study investigating their frequencies in normal and H. pylori-infected gastric mucosa was undertaken.

MATERIALS AND METHODS

Flow cytometry was used to quantify T-cells expressing the natural killer cell markers CD161, CD56, and CD94 in freshly isolated lymphocytes from the epithelial and lamina propria layers of gastric mucosa. Thirteen H. pylori-positive and 24 H. pylori-negative individuals were studied.

RESULTS

CD94(+) T-cells were the most abundant (up to 40%) natural killer receptor-positive T-cell population in epithelial and lamina propria layers of H. pylori-negative gastric mucosa. CD161(+) T-cells accounted for about one-third of all T-cells in both compartments, but the lowest proportion were of CD56(+) T-cells. Compared with H. pylori-negative mucosa, in H. pylori-infected mucosa the numbers of CD161(+) T-cells were significantly greater (p = .04) in the epithelium, whereas the numbers of CD56(+) T-cells were lower (p = .01) in the lamina propria. A minor population (< 2%) of T-cells in both mucosal layers of H. pylori-negative subjects were natural killer T-cells, and whose proportions were not significantly different (p > .05) to those in H. pylori-infected individuals.

CONCLUSIONS

The predominance, heterogeneity, and distribution of natural killer cell receptor-positive T-cells at different locations within the gastric mucosa reflects a potential functional role during H. pylori infection and warrants further investigation.

Enhanced gastric IL-18 mRNA expression in Helicobacter pylori-infected children is associated with macrophage infiltration, IL-8, and IL-1 beta mRNA expression

OBJECTIVE

To investigate IL-18 mRNA expression in the gastric mucosa in Helicobacter pylori-infected children and its association with macrophage infiltration, IL-8, and IL-1 beta mRNA expression.

METHODS

From 39 children, blood samples were taken for IL-1 beta gene polymorphism analysis and antral biopsies were obtained for histology (including macrophage immunostaining), culture and semiquantitative analysis of IL-18, IL-8, IL-1 beta, and CD14 mRNA expression by reverse transcription-PCR (RT-PCR). RT-PCR was used for H. pylori ureA and cagA mRNA detection in gastric tissue.

RESULTS

H. pylori-infected patients had significantly higher IL-18, IL-8, and IL-1 beta transcript levels and macrophage numbers in the antral mucosa than H. pylori-negative children. IL-1 beta-511/31 gene polymorphism had no impact on gastric IL-1 beta mRNA levels. IL-18 mRNA expression correlated with mRNA expression of IL-8 and IL-1 beta, and transcript levels of all three cytokines were associated with macrophage infiltration and CD14 mRNA expression in the gastric tissue. Significant correlation was also observed between macrophage numbers and histological parameters of gastritis.

CONCLUSION

These results suggest that interleukin(IL)-18 and macrophages may have an important function in gastric inflammatory response to H. pylori infection in children. IL-18, and possibly CD14 receptor signalling pathway, may be involved in macrophage activation and subsequent IL-8 and IL-1 beta release.

Macrophages are mediators of gastritis in acute Helicobacter pylori infection in C57BL/6 mice

Helicobacter pylori is the etiological agent of human chronic gastritis, a condition seen as a precursor to the development of gastrointestinal ulcers or gastric cancer. This study utilized the murine model of chronic H. pylori infection to characterize the role of macrophages in the induction of specific immune responses and gastritis and in the control of the bacterial burden following H. pylori infection and vaccination. Drug-loaded liposomes were injected intravenously to deplete macrophages from C57BL/6 mice, and effective removal of CD11b+ cells from the spleens and stomachs of mice was confirmed by immunofluorescence microscopy. Transient elimination of macrophages from C57BL/6 mice during the early period of infection reduced the gastric pathology induced by H. pylori SS1 but did not affect the bacterial load in the stomach. These data suggest that macrophages are important to the severity of gastric inflammation during H. pylori infection.

Host response to Helicobacter pylori infection before initiation of the adaptive immune response

Helicobacter pylori persistently colonizes the human stomach. In this study, immune responses to H. pylori that occur in the early stages of infection were investigated. Within the first 2 days after orogastric infection of mice with H. pylori, there was a transient infiltration of macrophages and neutrophils into the glandular stomach. By day 10 postinfection, the numbers of macrophages and neutrophils decreased to baseline levels. By 3 weeks postinfection, an adaptive immune response was detected, marked by gastric infiltration of T lymphocytes, macrophages, and neutrophils, as well as increased numbers of H. pylori-specific T cells, macrophages, and dendritic cells in paragastric lymph nodes. Neutrophil-attracting and macrophage-attracting chemokines were expressed at higher levels in the stomachs of H. pylori-infected mice than in the stomachs of uninfected mice. Increased expression of TNFalpha and IFNgamma (Th1-type inflammatory cytokines) and IL-17 (a Th17-type cytokine) was detected in the stomachs of H. pylori-infected mice, but increased expression of IL-4 (a Th2-type cytokine) was not detected. These data indicate that a transient gastric inflammatory response to H. pylori occurs within the first few days after infection, before the priming of T cells and initiation of an adaptive immune response. It is speculated that inappropriate waning of the innate immune response during early stages of infection may be a factor that contributes to H. pylori persistence.

Helicobacter pylori heat-shock protein 60 induces interleukin-8 via a Toll-like receptor (TLR)2 and mitogen-activated protein (MAP) kinase pathway in human monocytes

Previous reports have indicated that Helicobacter pylori heat-shock protein 60 (H. pylori-HSP60), as an immunodominant antigen, induces interleukin (IL)-8 production in human monocytes. The exact mechanism by which H. pylori-HSP60 induces IL-8 production in monocytes has not been fully elucidated. In the present study, the downstream pathway by which H. pylori-HSP60 induces IL-8 secretion in human monocytic cell lines was investigated. Intact H. pylori, heat-killed H. pylori and H. pylori recombinant HSP60 (rHpHSP60) all induced the secretion of IL-8 and the activation of mitogen-activated protein kinase (MAPK), extracellular signal-regulated kinase (ERK) and p38, but not c-Jun N-terminal kinase (JNK), up to 24 h in NOMO1 cells. The specific inhibitors PD98059 and U0126 (for ERK1/2 signalling) and SB203580 (for p38 MAPK signalling) down-regulated IL-8 secretion from rHpHSP60-treated NOMO1 cells. An anti-Toll-like receptor (TLR)2 antibody or TLR2 small interfering RNA (siRNA) partially inhibited the secretion of IL-8, and anti-TLR2 antibody also suppressed activation of ERK and p38 MAPK in rHpHSP60-treated NOMO1 cells. These reactions were associated with nuclear factor-kappaB (NF-kappaB)-mediated transcriptional activation, since U0126, SB203580 and the anti-TLR2 antibody decreased NF-kappaB activation. Taken together, the results suggest that ERK and p38 MAPK signalling linked to the TLR2 recognition receptor in human monocytes may be an important pathway in H. pylori-HSP60-induced IL-8 secretion.

Helicobacter pylori persistence: an overview of interactions between H. pylori and host immune defenses

Helicobacter pylori is a gram-negative bacterium that persistently colonizes more than half of the global human population. In order to successfully colonize the human stomach, H. pylori must initially overcome multiple innate host defenses. Remarkably, H. pylori can persistently colonize the stomach for decades or an entire lifetime despite development of an acquired immune response. This review focuses on the immune response to H. pylori and the mechanisms by which H. pylori resists immune clearance. Three main sections of the review are devoted to (i) analysis of the immune response to H. pylori in humans, (ii) analysis of interactions of H. pylori with host immune defenses in animal models, and (iii) interactions of H. pylori with immune cells in vitro. The topics addressed in this review are important for understanding how H. pylori resists immune clearance and also are relevant for understanding the pathogenesis of diseases caused by H. pylori (peptic ulcer disease, gastric adenocarcinoma, and gastric lymphoma).

Alzheimer's disease and Helicobacter pylori infection: Defective immune regulation and apoptosis as proposed common links

Although degenerative diseases of the central nervous system, including Alzheimer's disease (AD), have an increasingly high impact on aged population their association with Helicobacter pylori (H. pylori) infection has not as yet been thoroughly researched. Current H. pylori infection appears to induce irregular humoral and cellular immune responses that, owing to the sharing of homologous epitopes (molecular mimicry), cross-react with components of nerves, thereby contributing and possibly perpetuating the apoptotic neural tissue damage observed in neurodegenerative diseases including AD. An association between AD and H. pylori infection has been recently addressed by two studies. A higher seropositivity for anti-H. pylori immunoglobulin G antibodies in 30 patients with AD than in 30 age-matched controls was reported in one study; this serological test, however, has limitations because it does not discriminate between current and old infections. In the other study, by introducing the histological method (the actual gold standard) for diagnosis of H. pylori infection, we reported a higher prevalence of H. pylori infection in 50 AD patients than in 30 anemic controls. This pathogen may influence the pathophysiology of AD by promoting platelet and platelet-leukocyte aggregation; releasing various pro-inflammatory and vasoactive substances; developing cross-mimicry with host antigens; producing reactive oxygen metabolites and circulating lipid peroxides; influencing the apoptotic process; and increasing, through induction of atrophic gastritis, homocysteine, which contributes to vascular disorders implicated in endothelial damage and neurodegeneration.

Interleukin-6 induction by Helicobacter pylori in human macrophages is dependent on phagocytosis

BACKGROUND

The colonization of the gastric mucosa with Helicobacter pylori is accompanied by elevated levels of proinflammatory cytokines, such as interleukin-1 (IL-1), IL-6, and IL-8. The aim of our study was to determine the mechanisms of IL-6 stimulation in phagocytes upon H. pylori infection.

MATERIALS AND METHODS

We investigated the secretion of IL-6 by different professional phagocytes from murine and human origin, including granulocyte- and monocyte-like cells and macrophages derived from human peripheral blood monocytes (PBMCs). The influence of viability, phagocytosis, and the impact of different subcellular fractions of H. pylori bacteria were evaluated.

RESULTS

IL-6 levels induced by H. pylori were low in cell lines derived from murine and human monocytes and in human granulocyte-like cells. By contrast, macrophages derived from human PBMCs were highly responsive to both H. pylori and Escherichia coli. IL-6 induction was blocked by inhibition of actin-dependent processes prior to infection with H. pylori, but not with E. coli or E. coli lipopolysaccharide (LPS). Using cell fractionation, the most activity was found in the H. pylori membrane. H. pylori LPS exhibited a 10(3)- to 10(4)-fold lower biologic activity than E. coli LPS, suggesting a minor role for toll-like receptor 4 (TLR4)-mediated signalling from the exterior.

CONCLUSIONS

From these data, we conclude that macrophages may be a major source of IL-6 in the gastric mucosa upon H. pylori infection. The IL-6 induction by H. pylori in these cells is a multifactorial process, which requires the uptake and presumably degradation of H. pylori bacteria.

Sensory system-predominant distribution of leukotriene A4 hydrolase and its colocalization with calretinin in the mouse nervous system

Leukotriene B4 is a potent lipid mediator, which has been identified as a potent proinflammatory and immunomodulatory compound. Although there has been robust evidence indicating that leukotriene B4 is synthesized in the normal brain, detailed distribution and its functions in the nervous system have been unclear. To obtain insight into the possible neural function of leukotriene B4, we examined the immunohistochemical distribution of leukotriene A4 hydrolase, an enzyme catalyzing the final and committed step in leukotriene B4 biosynthesis, in the mouse nervous system. Immunoreactivity for leukotriene A4 hydrolase showed widespread distribution with preference to the sensory-associated structures; i.e. neurons in the olfactory epithelium and vomeronasal organ, olfactory glomeruli, possibly amacrine cells, neurons in the ganglion cell layer and three bands in the inner plexiform layer of the retina, axons in the optic nerve and tract up to the superior colliculus, inner and outer hair cells and the spiral ganglion cells in the cochlea, vestibulocochlear nerve bundle, spinal trigeminal tract, and lamina II of the spinal cord. Double immunofluorescence staining demonstrated that most of the leukotriene A4-hydrolase-immunopositive neurons coexpressed calretinin, a calcium-binding protein in neurons. The ubiquitous distribution of leukotriene A4 hydrolase was in sharp contrast with the distribution of leukotriene C4 synthase [Shimada A, Satoh M, Chiba Y, Saitoh Y, Kawamura N, Keino H, Hosokawa M, Shimizu T (2005) Highly selective localization of leukotriene C4 synthase in hypothalamic and extrahypothalamic vasopressin systems of mouse brain. Neuroscience 131:683-689] which was confined to the hypothalamic and extrahypothalamic vasopressinergic neurons. These results suggest that leukotriene B4 may exert some neuromodulatory function mainly in the sensory nervous system, in concert with calretinin.

Helicobacter pylori has stimulatory effects on naive T cells

BACKGROUND

Despite an apparently active host response, Helicobacter pylori infection can persist for life. Unexpectedly, T cells from apparently uninfected individuals respond to H. pylori antigen by proliferating. Also, the T-cell proliferative response appears to be less in infected compared with uninfected individuals.

MATERIALS AND METHODS

We have investigated the T-cell response of isolated human peripheral blood, naive, and memory CD4+ T cells to H. pylori antigen in infected and uninfected subjects.

RESULTS

In agreement with previous findings, the peripheral blood proliferative response was higher in uninfected compared with infected subjects. Interestingly, there was a response in CD4+ CD45RO+ (memory) and CD4+CD45RA+ (naive) subsets. The RO/RA ratio of the response to H. pylori antigen was 0.8-2.1 in both H. pylori-positive and H. pylori-negative subjects, which was similar to that of a known superantigen (2.5 and 2.2 in Helicobacter-positive and -negative subjects, respectively) whereas the RO/RA response ratio to a recall antigen (tetanus toxoid) was 9.8 and 18.7 in Helicobacter-positive and -negative subjects, respectively. Mononuclear cells isolated from cord blood also responded to H. pylori antigen, whereas there was no response to tetanus toxoid. The cord blood response and CD4+ CD45RA+ cell response to H. pylori antigen were inhibited predominantly by anti-HLA-DR and to some extent by anti-HLA-DQ antibodies. Investigation of the response to five different recombinant H. pylori antigens identified two that produced a response in naive T cells.

CONCLUSIONS

These data suggest that H. pylori possesses molecules that cause higher than expected proliferation of naive T cells.

Major histocompatibility complex class II inhibits fas antigen-mediated gastric mucosal cell apoptosis through actin-dependent inhibition of receptor aggregation

Escape from normal apoptotic controls is thought to be essential for the development of cancer. During Helicobacter pylori infection, the leading cause of gastric cancer, activation of the Fas antigen (Fas Ag) apoptotic pathway is responsible for early atrophy and tissue loss. As disease progresses, metaplastic and dysplastic glands arise which express Fas Ag but are resistant to apoptosis and are believed to be the precursor cells for adenocarcinoma. In this report, we show that one mechanism of acquired Fas resistance is inhibition of receptor aggregation via a major histocompatibility complex class II (MHCII)-mediated, actin-dependent mechanism. For these studies we used the well-described C57BL/6 mouse model of Helicobacter pylori and Helicobacter felis infection. Under normal conditions, Fas Ag is expressed at low levels, and MHCII expression on gastric mucosal cells is negligible. With infection and inflammation, both receptors are upregulated, and 6.1% of gastric mucosal cells express MHCII in combination with Fas Ag. Using the rat gastric mucosal cell line RGM-1 transfected with murine Fas Ag and MHCIIalphabeta chains, we demonstrate that MHCII prevents Fas receptor aggregation and inhibits Fas-mediated signaling through its effects on the actin cytoskeleton. Depolymerization of actin with cytochalasin D allows receptors to aggregate and restores Fas sensitivity. These findings offer one mechanism by which gastric mucosal cells acquire Fas resistance.

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Highly selective localization of leukotriene C4 synthase in hypothalamic and extrahypothalamic vasopressin systems of mouse brain

While leukotriene C4 (LTC4) was originally identified as a potent bronchoconstrictor, the compound has versatile biological activities besides inflammatory reactions. Although the high content of LTC4 has been reported in the hypothalamus and median eminence, the precise localization of the compound remained obscure. To elucidate its possible functions in the neuroendocrine systems, we determined immunohistochemical localization of LTC4 synthase, a key enzyme to produce LTC4 using mouse brains. Light microscopy and confocal laser scanning microscopy showed that LTC4 synthase was selectively localized in the vasopressinergic magnocellular neurons of the hypothalamic paraventricular, supraoptic and suprachiasmatic nuclei and in the retrochiasmatic area, as well as in axons that emanated from these neurons to the pars nervosa of the pituitary gland. At subcellular level, however, LTC4 synthase and arginine vasopressin appeared to localize differently within individual neurons. LTC4 synthase immunoreactivity was also observed in the axons of the extrahypothalamic system including the bed nucleus of the stria terminalis, lateral habenular nucleus, midbrain central gray, medial amygdaloid nucleus and ventral septal area, although this immunoreactivity was relatively minor. The other brain regions did not contain LTC4 synthase immunoreactivity. The distribution of LTC4 synthase did not overlap with that of either oxytocin or luteinizing hormone releasing hormone. Therefore, LTC4 is considered to be involved in neural functions of the brain magnocellular vasopressinergic system such as water retention. LTC4 may also be involved in extrahypothalamic vasopressinergic neural functions including the regulation of learning and memory, social recognition memory, sexual and aggressive behavior, etc.