Helicobacter pylori-Induced Changes in Gastric Acid Secretion and Upper Gastrointestinal Disease

Role of the Microbiome in the Diagnosis and Management of Gastroesophageal Cancers

PURPOSE

Stomach and esophageal cancers are among the highest mortality from cancers worldwide. Microbiota has an interplaying role within the human gastrointestinal (GI) tract. Dysbiosis occurs when a disruption of the balance between the microbiota and the host happens. With this narrative review, we discuss the main alterations in the microbiome of gastroesophageal cancer, revealing its potential role in the pathogenesis, early detection, and treatment.

RESULTS

Helicobacter pylori plays a major role the development of a cascade of preneoplastic conditions ranging from atrophic gastritis to metaplasia and dysplasia, ultimately culminating in gastric cancer, while other pathogenic agents are Fusobacterium nucleatum, Bacteroides fragilis, Escherichia coli, and Lactobacillus. Campylobacter species (spp.)'s role in the progression of esophageal adenocarcinoma may parallel that of Helicobacter pylori in the context of gastric cancer, with other esophageal carcinogenic agents being Escherichia coli, Bacteroides fragilis, and Fusobacterium nucleatum. Moreover, gut microbiome could significantly alter the outcomes of chemotherapy and immunotherapy. The gut microbiome can be modulated through interventions such as antibiotics, probiotics, or prebiotics intake. Fecal microbiota transplantation has emerged as a therapeutic strategy as well.

CONCLUSIONS

Nowadays, it is widely accepted that changes in the normal gut microbiome causing dysbiosis and immune dysregulation play a role gastroesophageal cancer. Different interventions, including probiotics and prebiotics intake are being developed to improve therapeutic outcomes and mitigate toxicities associated with anticancer treatment. Further studies are required in order to introduce the microbiome among the available tools of precision medicine in the field of anticancer treatment.

Transcriptome sequencing identifies prognostic genes involved in gastric adenocarcinoma

Gastric adenocarcinoma (GAC) is one of the world's most lethal malignant tumors. It has been established that the occurrence and progression of GAC are linked to molecular changes. However, the pathogenesis mechanism of GAC remains unclear. In this study, we sequenced 6 pairs of GAC tumor tissues and adjacent normal tissues and collected GAC gene expression profile data from the TCGA database. Analysis of this data revealed 465 differentially expressed genes (DEGs), of which 246 were upregulated and 219 were downregulated. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis demonstrated that DEGs were observably enriched in ECM-receptor interaction, protein digestion and absorption, and gastric acid secretion pathways. Six key genes (MATN3, COL1A1, COL5A2, P4HA3, SERPINE1 and VCAN) associated with poor GAC prognosis were screened from the protein‒protein interaction (PPI) network by survival analysis, and P4HA3 and MATN3 have rarely been reported to be associated with GAC. We further analyzed the function of P4HA3 in the GAC cell line SGC-7901 by RT‒qPCR, MTT, flow cytometry, colony formation, wound healing, Transwell and western blot assays. We found that P4HA3 was upregulated in the SGC-7901 cell line versus normal control cells. The outcomes of the loss-of-function assay illustrated that P4HA3 significantly enhanced the ability of GAC cells to proliferate and migrate. This study provides a new basis for the selection of prognostic markers and therapeutic targets for GAC.

Duped by dumping syndrome: non-endemic Vibrio cholerae bacteremia in an immunocompetent host with gastric bypass surgery, a case report

Extra-intestinal infection with non-O1/non-O139 strains of Vibrio cholerae (NOVC) is rare, though bacteremia and hepatobiliary manifestations have been reported. Reduced stomach acid, or hypochlorhydria, can increase risk of V. cholerae infection. We describe a 42-year-old woman with hypochlorhydria due to untreated Helicobacter pylori infection, gastric-bypass surgery, and chronic proton pump inhibitors (PPI) exposure, who developed acute diarrhoea following raw oyster consumption. Her symptoms were attributed to rapid gastric emptying (dumping syndrome) after a negative limited stool work-up. She had persistent diarrhoea, weight loss, and after 5 months was admitted with acute cholecystitis and NOVC bacteremia, requiring cholecystectomy. This is the first reported case of NOVC bacteremia and cholecystitis in a patient with gastric bypass. This case highlights the potential for NOVC biliary carriage, the role of hypochlorhydria as a risk factor for Vibrio infection, and the importance of excluding infectious diarrhoea in patients with new onset of symptoms compatible with dumping syndrome and a relevant travel history.

Epstein-Barr Virus Infection Is Associated with Elevated Hepcidin Levels

EBV and Helicobacter pylori (H. pylori) cause highly prevalent persistent infections as early as in childhood. Both pathogens are associated with gastric carcinogenesis. H. pylori interferes with iron metabolism, enhancing the synthesis of acute-phase proteins hepcidin, C-reactive protein (CRP), and α-1 glycoprotein (AGP), but we do not know whether EBV does the same. In this study, we correlated the EBV antibody levels and the serum levels of hepcidin, CRP, and AGP in 145 children from boarding schools in Mexico City. We found that children IgG positive to EBV antigens (VCA, EBNA1, and EA) presented hepcidin, AGP, and CRP levels higher than uninfected children. Hepcidin and AGP remained high in children solely infected with EBV, while CRP was only significantly high in coinfected children. We observed positive correlations between hepcidin and EBV IgG antibodies (p < 0.5). Using the TCGA gastric cancer database, we also observed an association between EBV and hepcidin upregulation. The TCGA database also allowed us to analyze the two important pathways controlling hepcidin expression, BMP−SMAD and IL-1β/IL-6. We observed only the IL-1β/IL-6-dependent inflammatory pathway being significantly associated with EBV infection. We showed here for the first time an association between EBV and enhanced levels of hepcidin. Further studies should consider EBV when evaluating iron metabolism and anemia, and whether in the long run this is an important mechanism of undernourishment and EBV gastric carcinogenesis.

Gastric microbiota dysbiosis and Helicobacter pylori infection

Helicobacter pylori (H. pylori) infection is one of the most common causes of gastric disease. The persistent increase in antibiotic resistance worldwide has made H. pylori eradication challenging for clinicians. The stomach is unsterile and characterized by a unique niche. Communication among microorganisms in the stomach results in diverse microbial fitness, population dynamics, and functional capacities, which may be positive, negative, or neutral. Here, we review gastric microecology, its imbalance, and gastric diseases. Moreover, we summarize the relationship between H. pylori and gastric microecology, including non-H. pylori bacteria, fungi, and viruses and the possibility of facilitating H. pylori eradication by gastric microecology modulation, including probiotics, prebiotics, postbiotics, synbiotics, and microbiota transplantation.

Proteolytic Landscapes in Gastric Pathology and Cancerogenesis

Gastric cancer is a leading cause of cancer-related death, and a large proportion of cases are inseparably linked to infections with the bacterial pathogen and type I carcinogen Helicobacter pylori. The development of gastric cancer follows a cascade of transformative tissue events in an inflammatory environment. Proteases of host origin as well as H. pylori-derived proteases contribute to disease progression at every stage, from chronic gastritis to gastric cancer. In the present article, we discuss the importance of (metallo-)proteases in colonization, epithelial inflammation, and barrier disruption in tissue transformation, deregulation of cell proliferation and cell death, as well as tumor metastasis and neoangiogenesis. Proteases of the matrix metalloproteinase (MMP) and a disintegrin and metalloproteinase domain-containing protein (ADAM) families, caspases, calpain, and the H. pylori proteases HtrA, Hp1012, and Hp0169 cleave substrates including extracellular matrix molecules, chemokines, and cytokines, as well as their cognate receptors, and thus shape the pathogenic microenvironment. This review aims to summarize the current understanding of how proteases contribute to disease progression in the gastric compartment.

Helicobacter pylori infection and hypochlorhydria in Zambian adults and children: A secondary data analysis

Background

Hypochlorhydria (gastric pH >4) increases susceptibility to diarrhoea, iron deficiency, and gastric cancer. We sought to clarify the prevalence of this condition and its predisposing factors in Zambia by pooling data from previous studies conducted in hospital and community settings.

Methods

Gastric pH was measured in participants from five separate studies by collecting gastric aspirate from fasted adults and children under 3 years of age undergoing gastroscopy. Gastric pH was correlated with serological testing for Human Immunodeficiency Virus (HIV) and Helicobacter pylori (H. pylori) infections.

Results

We studied 597 individuals (487 adults and 110 children). Hypochlorhydria was present in 53% of adults and 31% of children. HIV infection was detected in 41% of adults and 11% of children. H. pylori serology was available for 366 individuals: 93% of adults and 6% of children were seropositive. In univariate analysis, hypochlorhydria was significantly associated with HIV seropositivity (OR 1.7; 95% CI 1.2–2.4; p = 0.004) and H. pylori antibody seropositivity (OR 4.9; 95% CI 2.8–8.6; p<0.0001), and with advancing age in HIV negative individuals (p = 0.0001). In multivariable analysis, only H. pylori was associated with hypochlorhydria (OR 4.0; 95% CI 2.2–7.2; p<0.0001) while excluding possible exposure to proton pump inhibitors.

Conclusions

Hypochlorhydria is common in our population, with H. pylori being the dominant factor. Only young HIV seronegative individuals had a low prevalence of hypochlorhydria. This may have implications for the risk of other health conditions including gastric cancer.

Helicobacter pylori infection and micronutrient deficiency in pregnant women: a systematic review and meta-analysis

Background

Over the last few years, epidemiological studies have shown that infection with Helicobacter pylori has a major effect on micronutrient deficiency as well as on adverse pregnancy outcomes. Importantly, there are gaps in understanding the linkage of H. pylori infection with micronutrients deficiency in pregnant women.

Objective

We conducted a systematic review and meta-analysis to estimate the association between H. pylori infection and micronutrient deficiencies in pregnant women.

Methods

A systematic literature search was conducted for relevant articles using PubMed, Web of Science, and Scopus database from inception to March 2020. The OR with 95% CIs was determined by meta-analysis of data extracted from the selected studies.

Results

From 2384 primary articles, 6 studies were selected for systematic reviews and 4 studies distinctively (with 1274 participants: 553 cases and 721 controls) were selected for meta-analysis. The meta-analysed fixed effect model estimated the odds of having H. pylori infection was not significantly higher among pregnant women with micronutrient deficiencies than those without deficiencies (OR=1.12, 95% CI 0.88 to 1.42, p=0.37). In the subgroup analysis, no correlation was found between H. pylori infection and vitamin B₁₂ (OR=0.74, 95% CI 0.45 to 1.21, p=0.22), folate (OR=1.07, 95% CI 0.73 to 1.58, p=0.73), and ferritin (OR=0.81, 95% CI 0.51 to 1.31, p=0.4). However, a positive correlation was found between iron-deficiency anaemia (IDA) and H. pylori infection (OR=16.23, 95% CI 4.19 to 62.93, p<0.0001) during pregnancy.

Conclusion

H. pylori infection is associated with increased risk of IDA but not with deficiency of other micronutrients in pregnancy.

PROSPERO registration number

CRD42019135683.

Gastrin and the Moderate Hypergastrinemias

The antral hormone gastrin potently regulates gastric acid secretion and fundic mucosal growth. Consequently, appropriate gastrin secretion and plasma concentrations are important for the early phases of digestion. This review describes as the first premise the normal biogenesis of gastrin in the antral mucosa, but also mentions the extraantral expression. Subsequently, the molecular nature and concentration levels of gastrin in serum or plasma are overviewed. Third, assays for accurate measurements of plasma or serum concentrations are commented. Finally, the problem of moderate hypergastrinemia due to Helicobacter pylori infections and/or treatment with proton-pump inhibitors (PPI) is discussed. The review concludes that accurate measurement of the true concentrations of bioactive gastrins in plasma is important. Moreover, it suggests that moderate hypergastrinemias are also essential health issues that require serious attention.

The prevalence of Helicobacter pylori infection in inflammatory bowel disease in China: A case-control study

Background & aims

Helicobacter pylori (H. pylori) infection remains high in China though the incidence of inflammatory bowel disease (IBD) has increased. Our aim was to investigate the relationship between the prevalence of H. pylori and inflammatory bowel disease.

Methods

Hospitalized IBD patients including Crohn’s disease (CD) and ulcerative colitis (UC) who had tested H. pylori antibody were enrolled. Controls were chose from age- and sex- matched healthy physical examination people who had H. pylori antibody test in a 1:2 fashion (IBD patients:controls). IBD medical history was recorded. All patients were typed by the Montreal classification. Mayo Clinic score and the Harvey-Bradshaw Severity Index were used to evaluate their disease activity. Patients and controls that had H. pylori eradication therapy before were excluded.

Results

Two hundred and sixty IBD patients including 213 CD patients and 47 UC patients, and 520 controls were involved in this study. The prevalence of H. pylori infection in IBD patients (9.6%, 25/260) and IBD newly diagnosed patients (12.1%, 8/66), as well as CD patients (8.9%, 19/213) including CD newly diagnosed patients (10.6%, 5/47) and UC patients (12.8%, 6/47) was significantly lower than controls (29.8%, 155/520) (p = 2.796*10⁻¹⁰, 0.007, 5.723*10⁻⁹, 0.016, 0.014), while there was no statistically difference between UC newly diagnosed patients and the controls, and IBD patients with different disease type, disease activity and treatment history.

Conclusions

H. pylori infection had a negative association with IBD, especially CD.

Features That Aid Identification of Autoimmune Gastritis in a Background of Active Helicobacter pylori Infection

CONTEXT.—

Helicobacter pylori-associated and autoimmune gastritis may coexist in a subset of patients who require treatment for both disorders.

OBJECTIVE.—

To delineate findings that identify autoimmune gastritis in the background of H pylori infection.

DESIGN.—

We examined cases of (1) patients with H pylori-associated gastritis who had successful eradication therapy and subsequent biopsies diagnostic of autoimmune gastritis and (2) H pylori-associated gastritis wherein pathologists noted features of autoimmune gastritis during original interpretation. Control patients underwent H pylori eradication but lacked evidence of autoimmune gastritis or H pylori infection after 10 years of follow-up.

RESULTS.—

Eight subjects had H pylori-associated gastritis followed by H pylori-negative sampling that showed autoimmune gastritis. Review of original samples showed full-thickness inflammation of oxyntic mucosa in 8 of 8 and oxyntic gland loss in 7 of 8 cases. Enterochromaffin-like (ECL) cell hyperplasia, pyloric metaplasia, and intestinal metaplasia were present in 4 of 8 (80% of 5 tested cases), 4 of 8, and 3 of 8 cases, respectively. Features of autoimmune gastritis were noted at the time of their original H pylori diagnosis in 11 study subjects. Ten of 11 samples displayed full-thickness inflammation of oxyntic mucosa and/or partial loss of oxyntic glands, 8 of 11 had ECL cell hyperplasia (all tested cases), 6 of 11 showed pyloric metaplasia, and 4 of 11 harbored intestinal metaplasia. Except for full-thickness oxyntic mucosa inflammation, these features were absent in control cases.

CONCLUSIONS.—

Full-thickness inflammation combined with oxyntic gland loss and ECL cell hyperplasia may help to identify autoimmune gastritis in patients with concomitant H pylori infection.

Immunostimulatory membrane proteins potentiate H. pylori-induced carcinogenesis by enabling CagA translocation

Infection with Helicobacter pylori is the single greatest risk factor for developing gastric adenocarcinoma. In prospective, population-based studies, seropositivity to the uncharacterized H. pylori proteins Hp0305 and Hp1564 was significantly associated with cancer risk in East Asia. However, the mechanism underlying this observation has not been elucidated. Here, we show that Hp0305 and Hp1564 act in concert with previously ascribed H. pylori virulence mechanisms to orchestrate cellular alterations that promote gastric carcinogenesis. In samples from 546 patients exhibiting premalignant gastric lesions, seropositivity to Hp0305 and Hp1564 was significantly associated with increased gastric atrophy across all stomach conditions. In vitro, depletion of Hp0305 and Hp1564 significantly reduced levels of gastric cell-associated bacteria and markedly impaired the ability of H. pylori to stimulate pro-inflammatory cytokine production. Remarkably, our studies revealed that Hp1564 is required for translocation of the oncoprotein CagA into gastric epithelial cells. Our data provide experimental insight into the molecular mechanisms governing novel H. pylori pathogenicity factors that are strongly associated with gastric disease and highlight the potential of Hp0305 and Hp1564 as robust molecular tools that can improve identification of individuals that are highly susceptible to gastric cancer. We demonstrate that Hp0305 and Hp1564 augment H. pylori-mediated inflammation and gastric cancer risk by promoting key bacteria-gastric cell interactions that facilitate delivery of oncogenic microbial cargo to target cells. Thus, therapeutically targeting microbial interactions driven by Hp0305/Hp1564 may enable focused H. pylori eradication strategies to prevent development of gastric malignancies in high-risk populations.

Evaluation of Better Staining Method among Hematoxylin and Eosin, Giemsa and Periodic Acid Schiff-Alcian Blue for the Detection of Helicobacter pylori in Gastric Biopsies

Background

This study was undertaken to evaluate the preferred method (Giemsa or periodic acid Schiff-Alcian blue [PAS-AB] stains) of detecting Helicobacter pylori (H. pylori) in gastric mucosal biopsies in terms of sensitivity, specificity and applicability. To the best of my knowledge, this is the first report comparing Giemsa and PAS-AB staining for the detection of H. pylori in such biopsies.

Methods

The formalin-fixed paraffin-embedded blocks of 49 gastric biopsies from different patients were collected from the archive of anatomical pathology at King Abdulaziz Medical City, National Guard, Riyadh, Saudi Arabia. From each block, three slides were prepared and analysed using the hematoxylin and eosin (H&E), Giemsa and PAS-AB stains to detect the presence/absence of H. pylori, and the results were compared in terms of sensitivity, specificity and applicability.

Results

The majority of the biopsies in this study showed antrum-type gastric mucosa. Only 15 biopsies showed active gastritis, whereas the rest showed chronic gastritis. Three biopsies showed intestinal metaplasia. All were detected by PAS-AB stain, but only two-thirds were detected by H&E stain. Fifteen gastric biopsies showed H. pylori infection in general and in 13 of them, active gastritis cases were discovered. Fourteen out of these 15 H. pylori infection cases were detected by Giemsa stain, whereas only 13 cases were detected by H&E stain. PAS-AB stain showed the worst results since it demonstrated only 40% sensitivity and 67.65% specificity in H. pylori detection.

Conclusion

Giemsa stain has better sensitivity and specificity in gastric H. pylori infection detection than PAS-AB. Therefore, using PAS-AB stain to detect H. pylori infection is not recommended.

H. Pylori is related to osteoporosis but only in premenopausal female: a cross-sectional study

Background

Recently, an increasing number of studies have focused on the extra-gastrointestinal effects of Helicobacter pylori (H. pylori), including metabolic syndrome, fatty liver, and rheumatic and skin diseases. Osteoporosis is an asymptomatic disease that can eventually lead to fractures and has a significant impact on the quality of life of elderly individuals. Sex is an influential factor that plays a crucial role in the development of osteoporosis. The aim of this study was to investigate the relationship between H. pylori infection and osteoporosis and to identify potential influencing factors.

Methods

We conducted a cross-sectional study of individuals older than 50 years old, who had undergone regular physical examinations at the Beijing Shijitan Hospital Health Examination Center from July to October 2018. We evaluated the associations of osteopenia and osteoporosis with H. pylori infection and related serum markers by using multiple linear regression and logistic regression. Then, we analysed the correlation between sex and potential serum biomarkers.

Results

There were significant relationships between H. pylori infection status and bone density in premenopausal females but not in males (P = 0.381) according to Fisher’s exact test. In females, H. pylori positivity (OR = 0.132, P = 0.023), Body Mass Index (BMI) (OR = 28.163, P = 0.021), and homocysteine (HCY) (OR = 17.218, P = 0.045) were associated with osteoporosis. Calcium had a trend but no statistically significant (OR = 0.060, P = 0.076) relationship with osteoporosis. Furthermore, the waist-to-hip ratio (OR = 5.783, P = 0.029), BMI (OR = 0.152, P = 0.014) and triglyceride levels (OR = 0.201, P = 0.036) were significantly different by sex, after adjusting for age as a confounder.

Conclusion

H. pylori positivity, BMI and HCY are associated with osteoporosis in premenopausal females. Chronic inflammation may be involved in the relationship between H. pylori and osteoporosis.

Epstein-Barr Virus and Helicobacter Pylori Co-Infection in Non-Malignant Gastroduodenal Disorders

Epstein–Barr virus (EBV) and Helicobacter pylori (H. pylori) are two pathogens associated with the development of various human cancers. The coexistence of both microorganisms in gastric cancer specimens has been increasingly reported, suggesting that crosstalk of both pathogens may be implicated in the carcinogenesis process. Considering that chronic inflammation is an initial step in the development of several cancers, including gastric cancer, we conducted a systematic review to comprehensively evaluate publications in which EBV and H. pylori co-infection has been documented in patients with non-malignant gastroduodenal disorders (NMGDs), including gastritis, peptic ulcer disease (PUD), and dyspepsia. We searched the PubMed database up to August 2019, as well as publication references and, among the nine studies that met the inclusion criteria, we identified six studies assessing EBV infection directly in gastric tissues (total 949 patients) and three studies in which EBV infection status was determined by serological methods (total 662 patients). Due to the substantial methodological and clinical heterogeneity among studies identified, we could not conduct a meta-analysis. The overall prevalence of EBV + H. pylori co-infection in NMGDs was 34% (range 1.8% to 60%). A higher co-infection rate (EBV + H. pylori) was reported in studies in which EBV was documented by serological methods in comparison with studies in which EBV infection was directly assessed in gastric specimens. The majority of these studies were conducted in Latin-America and India, with most of them comparing NMGDs with gastric cancer, but there were no studies comparing the co-infection rate in NMGDs with that in asymptomatic individuals. In comparison with gastritis caused by only one of these pathogens, EBV + H. pylori co-infection was associated with increased severity of gastric inflammation. In conclusion, only relatively small studies testing EBV and H. pylori co-infection in NMGDs have been published to date and the variable report results are likely influenced by geographic factors and detection methods.

FN1, SPARC, and SERPINE1 are highly expressed and significantly related to a poor prognosis of gastric adenocarcinoma revealed by microarray and bioinformatics

Gastric adenocarcinoma (GAC), also known as stomach adenocarcinoma (STAD), is one of the most lethal malignancies in the world. It is vital to classify and detect the hub genes and key pathways participated in the initiation and progression of GAC. In this study, we collected and sequenced 15 pairs of GAC tumor tissues and the adjacent normal tissues. Differentially expressed genes (DEGs) were analyzed and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway and Gene Ontology (GO) analysis were used to annotate the unique biological significance and important pathways of enriched DEGs. Moreover, we constructed the protein-protein interaction (PPI) network by Cytoscape and conducted KEGG enrichment analysis of the prime module. We further applied the TCGA database to start the survival analysis of these hub genes by Kaplan-Meier estimates. Finally, we obtained total 233 DEGs consisted of 64 up-regulated genes and 169 down-regulated genes. GO enrichment analysis found that DEGs most significantly enriched in single organism process, extracellular region, and extracellular region part. KEGG pathway enrichment analysis suggested that DEGs most significantly enriched in Protein digestion and absorption, Gastric acid secretion, and ECM-receptor interaction. Furthermore, the PPI network showed that the top 10 hub genes in GAC were IL8, COL1A1, MMP9, SST, COL1A2, TIMP1, FN1, SPARC, ALDH1A1, and SERPINE1 respectively. The prime gene interaction module in PPI network was enriched in protein digestion and absorption, ECM receptor interaction, the PI3K-Akt signaling pathway, and pathway in cancer. Survival analysis based on the TCGA database found that the expression of the FN1, SERPINE1, and SPARC significantly predicted poor prognosis of GAC. Collectively, we identified several hub genes and key pathways associated with GAC initiation and progression by analyzing the microarray data on DEGs, which provided a detailed molecular mechanism underlying GAC occurrence and progression.

Helicobacter pylori and its relationship with variations of gut microbiota in asymptomatic children between 6 and 12 years

Objective

To determine the variations in the composition of the intestinal microbiota in asymptomatic children infected with Helicobacter pylori in comparison with children without the infection.

Results

Children infected with H. pylori doubled their probability of presenting 3 of 9 genera of bacteria from the gut microbiota, including: Proteobacteria (p = 0.008), Clostridium (p = 0.040), Firmicutes (p = 0.001) and Prevotella (p = 0.006) in comparison to patients without the infection. We performed a nutritional assessment and found that growth stunting was statistically significantly higher in patients infected with H. pylori (p = 0.046).

Electronic supplementary material

The online version of this article (10.1186/s13104-018-3565-5) contains supplementary material, which is available to authorized users.

Diagnosis of Helicobacter pylori Using Invasive and Noninvasive Approaches

Helicobacter pylori (H. pylori) as gram-negative and spiral microorganism is responsible for colonization in the gastric microniche for more than 50% of world population. Recent studies have shown a critical role of H. pylori in the development of peptic ulcers, gastric mucosa-associated lymphoid tissue (MALT) lymphoma, and gastric cancer. Over the past decade, there has been a sharp interest to use noninvasive tests in diagnosis of the H. pylori infection. During the years after discovery by Marshall and Warren, it has been frequently declared that the rapid urease test (RUT) is one of the cheapest and rapid diagnostic approaches used in detecting the infection. Although the specificity and sensitivity are durable for this test, clinical experiences had shown that the ideal results are only achieved only if we take biopsies from both corpus and antrum at the same time. Given the diagnosis of the H. pylori in clinical samples, gastroenterologists are facing a long list of various molecular and nonmolecular tests. We need more in-depth researches and investigations to correctly generalize rapid and accurate molecular tests determining both bacterial identity and antibiotic resistance profile.

Peripheral N-methyl-D-aspartate receptor localization and role in gastric acid secretion regulation: immunofluorescence and pharmacological studies

The enteric nervous system (ENS) and a glutamate receptor (GluR), N-methyl-D-aspartate receptor (NMDAR), participate in gastric acid secretion (GAS) regulation. NMDARs are localized in different stomach cells; however, knowledge of NMDAR expression and function in the ENS is limited. In the present study, we clarified the types of stomach cells that express the NMDARs that are involved in GAS regulation. The pharmacological method of isolated stomach perfusion by Ghosh and Shild combined with direct mapping of NMDARs by fluorescence microscopy in the rat stomach was employed. By immunofluorescence labeling with an anti-NMDA-NR1 antibody, NMDARs were found to be highly expressed in nerve cells of the submucosal and myenteric plexuses in the stomach. The exact localization of the NMDARs relevant to GAS and its mechanism of action were determined by stimulating different receptors of neuronal and stomach cells using specific secretagogues for NMDA and by selectively blocking those receptors. NMDARs relevant to GAS stimulation are mainly localized in cholinergic interneurons; however, all of the nerve cells of the submucosal ganglia are involved in the stimulating process. In addition, the NMDARs in parietal cells are involved in gastric acid inhibition via influencing H₂-histamine receptors.

Amino-Terminal Processing of Helicobacter pylori Serine Protease HtrA: Role in Oligomerization and Activity Regulation

The HtrA family of serine proteases is found in most bacteria, and plays an essential role in the virulence of the gastric pathogen Helicobacter pylori. Secreted H. pylori HtrA (HtrA ^Hp ) cleaves various junctional proteins such as E-cadherin disrupting the epithelial barrier, which is crucial for bacterial transmigration across the polarized epithelium. Recent studies indicated the presence of two characteristic HtrA ^Hp forms of 55 and 52 kDa (termed p55 and p52, respectively), in worldwide strains. In addition, p55 and p52 were produced by recombinant HtrA ^Hp , indicating auto-cleavage. However, the cleavage sites and their functional importance are yet unclear. Here, we determined the amino-terminal ends of p55 and p52 by Edman sequencing. Two proteolytic cleavage sites were identified (H46/D47 and K50/D51). Remarkably, the cleavage site sequences are conserved in HtrA ^Hp from worldwide isolates, but not in other Gram-negative pathogens, suggesting a highly specific assignment in H. pylori. We analyzed the role of the amino-terminal cleavage sites on activity, secretion and function of HtrA ^Hp . Three-dimensional modeling suggested a trimeric structure and a role of amino-terminal processing in oligomerization and regulation of proteolytic activity of HtrA ^Hp . Furthermore, point and deletion mutants of these processing sites were generated in the recently reported Campylobacter jejuni ΔhtrA/htrA^Hp genetic complementation system and the minimal sequence requirements for processing were determined. Polarized Caco-2 epithelial cells were infected with these strains and analyzed by immunofluorescence microscopy. The results indicated that HtrA ^Hp processing strongly affected the ability of the protease to disrupt the E-cadherin-based cell-to-cell junctions. Casein zymography confirmed that the amino-terminal region is required for maintaining the proteolytic activity of HtrA ^Hp . Furthermore, we demonstrated that this cleavage influences the secretion of HtrA ^Hp in the extracellular space as an important prerequisite for its virulence activity. Taken together, our data demonstrate that amino-terminal cleavage of HtrA ^Hp is conserved in this pathogen and affects oligomerization and thus, secretion and regulatory activities, suggesting an important role in the pathogenesis of H. pylori.