H pylori and host interactions that influence pathogenesis

Helicobacter pylori and Its Role in Gastric Cancer

Gastric cancer is a challenging public health concern worldwide and remains a leading cause of cancer-related mortality. The primary risk factor implicated in gastric cancer development is infection with Helicobacter pylori. H. pylori induces chronic inflammation affecting the gastric epithelium, which can lead to DNA damage and the promotion of precancerous lesions. Disease manifestations associated with H. pylori are attributed to virulence factors with multiple activities, and its capacity to subvert host immunity. One of the most significant H. pylori virulence determinants is the cagPAI gene cluster, which encodes a type IV secretion system and the CagA toxin. This secretion system allows H. pylori to inject the CagA oncoprotein into host cells, causing multiple cellular perturbations. Despite the high prevalence of H. pylori infection, only a small percentage of affected individuals develop significant clinical outcomes, while most remain asymptomatic. Therefore, understanding how H. pylori triggers carcinogenesis and its immune evasion mechanisms is critical in preventing gastric cancer and mitigating the burden of this life-threatening disease. This review aims to provide an overview of our current understanding of H. pylori infection, its association with gastric cancer and other gastric diseases, and how it subverts the host immune system to establish persistent infection.

Detection of Helicobacter pylori by invasive tests in adult dyspeptic patients and antibacterial resistance to six antibiotics, including rifampicin in Turkey. Is clarithromycin resistance rate decreasing?

Background/aim

The prevalence of Helicobacter pylori is reported to be roughly 80% in Turkey, and only very few culture-based studies are available on antibacterial resistance in adult dyspeptic patients. This study was carried out in adult dyspeptic patients with an aim to: (i) detect H. pylori by invasive tests (culture, polymerase chain reaction, and histopathology) and (ii) determine the current resistance rates of H. pylori isolates to six antibiotics, including rifampicin.

Materials and methods

This study was conducted in 422 adult dyspeptic patients. The presence of H. pylori was demonstrated by culture, polymerase chain reaction, and the histopathology of gastric biopsy material. Antibacterial susceptibility was determined with the E-test.

Results

The mean age of the patients was 50 ± 15 (range 18–90), and 265 (63%) of them were female. By culture, polymerase chain reaction, and histopathology, the presence of H. pylori was detected at rates of 35% (148/422), 67% (281/422), and 53% (224/422), respectively. The prevalence of H. pylori was determined as 75.6% (319/422). Metronidazole, levofloxacin, clarithromycin, and rifampicin resistance rates were 62%, 36%, 19%, and 12%, respectively. Monodrug, dual-drug, and multidrug resistance rates were ascertained as 36.9%, 29.4%, and 10.5%, respectively. All of the isolates were susceptible to amoxicillin and tetracycline.

Conclusion

This study revealed the current prevalence of H. pylori in adult dyspeptic patients as 75.6%, and thereby, showed that infection with this pathogen remains highly prevalent. Although resistance to metronidazole and levofloxacin has increased over time, clarithromycin resistance rate has decreased. The high levels of resistance to metronidazole and levofloxacin limit the empirical use of these antibiotics in the eradication protocol. Owing to the low level of resistance determined for rifampicin, this antibiotic could be included in the eradication protocol, in the event of the need for rescue therapy in Turkey.

Two cases of rare subglottic MALT lymphoma of the larynx

BACKGROUND

Primary MALT lymphoma of the larynx is a rare condition first described in 1990. There have been only 43 reported cases as of 2015. The disease appears to be indolent in nature and responds well to radiation therapy. Symptoms are non-specific and may be limited to a combination of hoarseness, sore throat, shortness of breath, or cough.

METHODS

We describe two cases of subglottic laryngeal MALT lymphoma identified from one academic medical center within five years of each other. Though identical in pathology, the presentation of the two cases were distinct in both patient demographic and tumor appearance. One patient required dilation of a subglottic stenosis caused by tumor, and the other required surgical debulking of a ball-valve-like mass. Neither patient presented with B-symptoms (fever, night sweats, weight loss) that often characterize other lymphomas.

RESULTS

In both cases, histopathological exam revealed extensive infiltration of mucosa with atypical monomorphous lymphocytes, consistent with MALT lymphoma.

CONCLUSION

MALT lymphoma of the larynx may present with non-specific symptoms such as cough and/or hoarseness. Thorough evaluation including flexible laryngoscopy should be performed should these symptoms persist without a known cause. Surgical biopsy and histopathological exam are crucial to determine the etiology of unknown subglottic masses.

The cell surface adhesins of Mycobacterium tuberculosis

Bacterial cell surface adhesins play a major role in facilitating host colonization and subsequent establishment of infection. The surface of Mycobacterium tuberculosis, owing to the complex architecture of its cell envelope, expresses numerous adhesins with varied chemical nature, including proteins, lipids, lipoproteins, glycoproteins and glycopolymers. Studies on mycobacterial adhesins show that they bind with multifarious host receptors and extracellular matrix (ECM) components. In this review we have highlighted the adhesins that are abundantly present on the mycobacterial surface and their interactions with host receptors. M. tuberculosis interacts with various host cell surface receptors such as toll like receptors, C-type lectin receptors, scavenger receptors, and Fc and complement receptors. Apart from these, ECM components like fibronectin, collagen, elastin, laminin, fibrillin and vitronectin also provide binding sites for surface adhesins of the tubercle bacilli. M. tuberculosis adhesins include proteins with and without signal peptide sequence and transmembrane proteins. Other surface adhesin macromolecules of M. tuberculosis comprises of lipids, glycolipids and glycopolymers. The interaction between the mycobacterial adhesins and their host receptors result in adhesion of the microbe to the host cells, induction of immune response and aid in the pathogenesis of the disease. A thorough understanding of the different M. tuberculosis surface adhesins and host receptors will provide a better picture of interaction between them at molecular level. The information gained on adhesins and host receptors will prove beneficial in developing novel therapeutic strategies such as the use of anti-adhesin molecules to hinder the adhesion of bacteria to the host cells, thereby preventing establishment of infection. The surface molecules discussed in this review will also benefit in identification of new drug targets, diagnostic markers or vaccine candidates against the deadly pathogen.

Correlation between macrophage migration inhibitory factor and autophagy in Helicobacter pylori-associated gastric carcinogenesis

The role of macrophage migration inhibitory factor (MIF) and autophagy in gastric cancer is not clear. We determined H. pylori infection status of the subjects and investigated the expression of MIF and autophagy markers (Atg5, LC3A and LC3B) in human gastric tissue at baseline. Then H. pylori eradication was done for H. pylori positive patients and MIF and Atg5 levels were investigated on each follow-up for both H. pylori-eradicated and H. pylori negative patients. Baseline tissue mRNA expression of MIF, Atg5, LC3A and LC3B was measured by real-time PCR in 453 patients (control 165, gastric dysplasia 82, and gastric cancer 206). Three hundred three patients (66.9%) had H. pylori infection at the time of enrollment. Only within H. pylori-positive group, MIF level was significantly elevated in patients with cancer than in control or dysplasia groups (P<0.05). LC3A and LC3B levels also showed significant differences within H. pylori-positive subgroups. H. pylori-positive dysplasia subgroup showed significantly lower (LC3A) (P<0.05) and higher (LC3B) mRNA levels (P<0.05) than in other subgroups. On follow-up, within H. pylori-eradicated group, Atg5 expression increased sequentially from control to dysplasia and cancer subgroups. Multiple linear regression showed autophagy markers (LC3A, LC3B, and Atg5) directly predicted MIF level (adjusted R² = 0.492, P<0.001). Serial follow-up showed longitudinal increase in Atg5 level in general, with constantly higher levels in H. pylori-eradicated group than in -negative group. Intestinal metaplasia (IM) group initially showed higher Atg5 expression than the IM-negative group. However, it was reversed between the groups eventually because of the lower rate of increase in IM group. These results suggest a role of MIF and autophagy markers and their interaction in H. pylori-associated gastric carcinogenesis.

Prevalence of Primary Antimicrobial Resistance of H. pylori in Turkey: A Systematic Review

BACKGROUND

The prevalence of clarithromycin resistance has increased to the 20% or more in different regions of the world. Clarithromycin resistance is known to be responsible for most of the treatment failures in Helicobacter pylori (H. pylori) infection. The aim of this systematic review was to summarize the prevalence of primary antibiotic resistance (amoxicillin, clarithromycin, metronidazole, levofloxacin, tetracycline) of H. pylori strains in different geographical regions of Turkey.

MATERIAL AND METHODS

An Internet search was performed using PubMed and the ULAKBIM Turkish Medical Database. The terms "primary antibiotic resistance (separately; amoxicillin, clarithromycin, metronidazole, levofloxacin, tetracycline) of H. pylori" with and without "Turkey" or "different geographical regions of Turkey" were searched among articles published in both English and Turkish language within the time span from 1999 to 2015. Data analysis was performed using MedCalc 12.7.0. Each article was weighted according to the number of isolated H. pylori strains. Pooled proportion analysis was performed.

RESULTS

Twenty-one Turkish studies including 1059 H. pylori strains were included in this review. The overall primary antibiotic resistance rates of H. pylori strains isolated in Turkey were as follows: amoxicillin 3 (0.971%), clarithromycin 425 (24.864%), metronidazole 75 (33.747%), tetracycline 2 (3.511%), and levofloxacin 31 (23.769%).

CONCLUSIONS

Primary antibiotic resistance against H. pylori in Turkey shows differences between geographical regions and population densities. There is an increase in primary resistance rates to clarithromycin and metronidazole in different years. The data are not sufficient for tetracycline, amoxicillin, and levofloxacin. High clarithromycin resistance rates were mostly detected in overpopulated cities like Ankara (north), Izmir (west), Istanbul (west), and Bursa (west).

Immunomodulatory Effect of H. Pylori CagA Genotype and Gastric Hormones On Gastric Versus Inflammatory Cells Fas Gene Expression in Iraqi Patients with Gastroduodenal Disorders

AIM:

To evaluate the Immunomodulatory effects of CagA expression; pepsinogen I, II & gastrin-17 on PMNs and lymphocytes Fas expression in inflammatory and gastric cells; demographic distribution of Fas molecule in gastric tissue and inflammatory cells.

METHODS:

Gastroduodenal biopsies were taken from 80 patients for histopathology and H. pylori diagnosis. Serum samples were used for evaluation of pepsinogen I (PGI); (PGII); gastrin-17 (G-17).

RESULTS:

Significant difference (p < 0.001) in lymphocytes & PMNs Fas expression; epithelial & lamina propria Fas localization among H. pylori associated gastric disorders. No correlation between grade of lymphocytes & PMNs Fas expression in gastric epithelia; lamina propria and types of gastric disorder. Significant difference (p < 0.001) in total gastric Fas expression, epithelial Fas; lamina propria and gastric gland Fas expression according to CagA, PGI; PGII; PGI/PGII; Gastrin-17. Total gastric Fas expression has significant correlation with CagA, PGII levels. Gastric epithelial and gastric lamina propria Fas expression have significant correlation with CagA, PGI; PGII levels. Significant difference (p < 0.001) was found in lymphocytes & PMNs Fas expression; epithelial & lamina propria localization of lymphocytes & PMNs Fas expression according to CagA, PGI; PGII; PGI/PGII; Gastrin-17. Lymphocytes Fas expression have correlation with PGI, PGII, PGI/PGII. PMNs Fas expression have correlation with PGI, PGII.

CONCLUSION:

Fas gene expression and localization on gastric and inflammatory cells affected directly by H. pylori CagA and indirectly by gastric hormones. This contributes to progression of various gastric disorders according to severity of CagA induced gastric pathology and gastric hormones disturbance throughout the course of infection and disease.

Helicobacter pylori bab Paralog Distribution and Association with cagA, vacA, and homA/B Genotypes in American and South Korean Clinical Isolates

Helicobacter pylori genetic variation is a crucial component of colonization and persistence within the inhospitable niche of the gastric mucosa. As such, numerous H. pylori genes have been shown to vary in terms of presence and genomic location within this pathogen. Among the variable factors, the Bab family of outer membrane proteins (OMPs) has been shown to differ within subsets of strains. To better understand genetic variation among the bab genes and to determine whether this variation differed among isolates obtained from different geographic locations, we characterized the distribution of the Bab family members in 80 American H. pylori clinical isolates (AH) and 80 South Korean H. pylori clinical isolates (KH). Overall, we identified 23 different bab genotypes (19 in AH and 11 in KH), but only 5 occurred in greater than 5 isolates. Regardless of strain origin, a strain in which locus A and locus B were both occupied by a bab gene was the most common (85%); locus C was only occupied in those isolates that carried bab paralog at locus A and B. While the babA/babB/- genotype predominated in the KH (78.8%), no single genotype could account for greater than 40% in the AH collection. In addition to basic genotyping, we also identified associations between bab genotype and well known virulence factors cagA and vacA. Specifically, significant associations between babA at locus A and the cagA EPIYA-ABD motif (P<0.0001) and the vacA s1/i1/m1 allele (P<0.0001) were identified. Log-linear modeling further revealed a three-way association between bab carried at locus A, vacA, and number of OMPs from the HOM family (P<0.002). En masse this study provides a detailed characterization of the bab genotypes from two distinct populations. Our analysis suggests greater variability in the AH, perhaps due to adaptation to a more diverse host population. Furthermore, when considering the presence or absence of both the bab and homA/B paralogs at their given loci and the vacA genotype, an association was observed. Our results highlight the multifactorial nature of H. pylori mediated disease and the importance of considering how the specific combinations of H. pylori virulence genes and their multiple interactions with the host will collectively impact disease progression.

The Efficacy of Saccharomyces boulardii CNCM I-745 in Addition to Standard Helicobacter pylori Eradication Treatment in Children

PURPOSE

This study aims to investigate Saccharomyces boulardii CNCM I-745 during Helicobacter pylori eradication in children.

METHODS

One hundred ninety-four H. pylori positive children were randomized in two groups. Therapy (omeprazole+clarithromycin+amoxicillin or omeprazole+clarithromycin+metronidazole in case of penicillin allergy) was given to both groups during two weeks. In the treatment group (n: 102) S. boulardii was added to the triple therapy, while the control group (n: 92) only received triple therapy. The incidence, onset, duration and severity of diarrhea and compliance to the eradication treatment were compared. A (13)C urea breath test was done 4 weeks after the end of eradication therapy in two groups of 21 patients aged 12 years and older to test the H. pylori eradication rate.

RESULTS

In the treatment group, diarrhea occurred in 12 cases (11.76%), starting after 6.25±1.24 days, lasting 3.17±1.08 days, and compliance to eradication treatment was 100%. In the control group, diarrhea occurred in 26 cases (28.26%), starting after 4.05±1.11 days, lasting 4.02±0.87 days, and in six cases eradication treatment was stopped prematurely (p<0.05). The (13)C urea breath test showed successful H. pylori eradication in 71.4% of the patients in the treatment and in 61.9 % in the control group (not significant).

CONCLUSION

S. boulardii has a beneficial effect on the prevention and treatment of diarrhea during H. pylori eradication in children. Although S. boulardii did only slightly increase H. pylori eradication rate, compliance to eradication treatment was improved.

Ultimate eradication rate of Helicobacter pylori after first, second, or third-line therapy in Korea

BACKGROUND AND AIMS

Resistance rates of Helicobacter pylori to clarithromycin, metronidazole, and quinolone are over 30% in South Korea. The aim of this prospective study was to evaluate the ultimate eradication rate of H. pylori after first, second, or third-line therapy in Korea.

METHODS

A cohort of 2202 patients with H. pylori was treated with proton pump inhibitor (PPI)-based triple therapy for seven days. In case of treatment failure or recurrence, moxifloxacin-based triple therapy (MA) or bismuth-based quadruple therapy (QUAD) was randomly given. When the second-line treatment failed or H. pylori recurred, the unused MA or QUAD was used as a third-line treatment.

RESULTS

Eighty-six patients had recurrence at least once during consecutive lines of treatments. Among 2116 patients (intention-to-treat [ITT]) without recurrence, 1644 (77.7%, per-protocol [PP]) completely followed our treatment flow. The ITT and PP rates of first-line treatment were 69.8% and 89.3%. After second line, they reached 78.4% (ITT) and 98.4% (PP). The "final" eradication rate up to third line treatment were 80.0% (1692/2116) and 99.8% (1641/1644), respectively. Resistance to clarithromycin showed significantly lower eradication rate (OR 0.358, P < 0.001) than those with susceptible strains in multivariate analysis. However in PP analysis, there was no significant difference in ultimate success rate regarding resistance pattern.

CONCLUSION

Final success rate of PP was high, 99.8% in Korea in spite of high antibiotic resistance rates. However, high rate of refusal of further treatment and follow-up loss made ITT eradication rate low. Proper strategy to improve the treatment adherence is needed.

A Case of a Laryngeal MALT Lymphoma in a Patient with a History of Gastric MALT

We are reporting a case of a 62-year-old African American woman with a history of gastric MALT lymphoma successfully treated with radiation who presented with a laryngeal MALT lymphoma 4 years after her original diagnosis. She received definitive radiation with a complete response. The case presented is unique for the rare presentation of a MALT lymphoma in the larynx, especially in light of the patient's previously treated gastric MALT lymphoma years ago.

Helicobacter pylori in Iran: A systematic review on the antibiotic resistance

OBJECTIVES

Helicobacter pylori (H. pylori) is a pathogenic bacterium that colonizes the stomachs of approximately 50% of the world's population. Resistance of H. pylori to antibiotics is considered as the main reason for the failure to eradicate this bacterium. The aim of this study was to determine the rate of resistant H. pylori strains to various antimicrobial agents in different areas of Iran.

MATERIALS AND METHODS

A systematic review of literatures on H. pylori antibiotic resistance in Iran was performed within the time span of 1997 to 2013. Data obtained from various studies were tabulated as following, 1) year of research and number strains tested, 2) number of H. pylori positive patients, 3) study place, 4) resistance of H. pylori to various antibiotics as percentage, and 5) methods used for evaluation of antibiotic resistance.

RESULTS

Over the period, a total of 21 studies on H. pylori antibiotic resistance have been conducted in different parts of Iran. In these studies, H. pylori resistance to various antibiotics, including metronidazole, clarithromycin, amoxicillin, tetracycline, ciprofloxacin, levofloxacin and furazolidone were 61.6%, 22.4%, 16.0%, 12.2%, 21.0%, 5.3% and 21.6%, respectively. We found no study on H. pylori resistance to rifabutin in Iran.

CONCLUSION

Compared to the global average, we noted that the prevalence of H. pylori resistance to metronidazole, clarithromycin, amoxicillin, and tetracycline has been rapidly growing in Iran. This study showed that in order to determine an appropriate drug regimen against H. pylori, information on antibiotic susceptibility of the bacterium within different geographical areas of Iran is required.

Therapeutic efficacy of the multi-epitope vaccine CTB-UE against Helicobacter pylori infection in a Mongolian gerbil model and its microRNA-155-associated immuno-protective mechanism

Vaccination is an effective means of preventing infectious diseases, including those caused by Helicobacter pylori. In this study, we constructed a novel multi-epitope vaccine, CTB-UE, composed of the cholera toxin B subunit and tandem copies of the B and Th cell epitopes from the H. pylori urease A and B subunits. We evaluated the therapeutic efficacy of the multi-epitope vaccine CTB-UE against H. pylori infection in a Mongolian gerbil model and studied its immuno-protective mechanisms. The experimental results indicated that urease activity, H. pylori colonisation density, the levels of IL-8 and TNF-α in the serum, and the levels of COX-2 and NAP in gastric tissue were significantly lower and the IgG level in the serum and the IFN-γ level in spleen lymphocytes were significantly higher in the vaccinated group compared with the model control group; additionally, gastric mucosal inflammation was notably alleviated following vaccination. The results showed that CTB-UE had a good therapeutic effect on H. pylori infection. The immuno-protective mechanism was closely related to the immune response mediated by microRNA-155, the expression of which was strongly up-regulated after CTB-UE administration. The expression levels of the microRNA-155 target proteins IFN-γRα, AID, and PU.1 were significantly down-regulated; these results indicated that CTB-UE induced an immune response biased towards Th1 cells by up-regulating microRNA-155 to inhibit IFN-γRα expression and induced a humoral immune response towards B cells by up-regulating microRNA-155 to inhibit PU.1 and AID expression. These results demonstrate that the multi-epitope vaccine CTB-UE may be a promising therapeutic vaccine against H. pylori infection and is a new therapeutic tool for human use.

Recognition of nontrivial remote homology relationships involving proteins of Helicobacter pylori: implications for function recognition

This chapter explains techniques for recognition of nontrivial remote homology relationships involving proteins of Helicobacter pylori and their implications for function recognition. Using the remote homology detection method, employing multiple-profile representations for every protein domain family, remotely related domain family information has been assigned for the 122, 77, and 95 protein sequences of 26695, and J99, and HPAG1 strains of H. pylori, respectively. Relationships for some of the H. pylori protein sequences with Pfam domain families are reported for the first time. In publicly available domain databases such as Pfam, for some of the H. pylori protein sequences functional domain information is associated only with part(s) of the proteins. In the current study other parts of such proteins have been shown to be remotely related to known domain families, raising the possibility of identifying functions for parts of the proteins that do not yet have domains assigned. Further, homologues of enzymes that potentially catalyze step(s) in various metabolic processes in H. pylori have been identified for the first time.

Helicobacter pylori: an overview

Infection with Helicobacter pylori is directly responsible for substantial morbidity and mortality worldwide. This ubiquitous organism causes disease through the interaction of multiple factors including bacterial factors, host immune responses, and environmental factors. The following chapters address the bacterial specific contributions to disease.

ChePep controls Helicobacter pylori Infection of the gastric glands and chemotaxis in the Epsilonproteobacteria

Microbes use directed motility to colonize harsh and dynamic environments. We discovered that Helicobacter pylori strains establish bacterial colonies deep in the gastric glands and identified a novel protein, ChePep, necessary to colonize this niche. ChePep is preferentially localized to the flagellar pole. Although mutants lacking ChePep have normal flagellar ultrastructure and are motile, they have a slight defect in swarming ability. By tracking the movement of single bacteria, we found that ΔChePep mutants cannot control the rotation of their flagella and swim with abnormally frequent reversals. These mutants even sustain bursts of movement backwards with the flagella pulling the bacteria. Genetic analysis of the chemotaxis signaling pathway shows that ChePep regulates flagellar rotation through the chemotaxis system. By examining H. pylori within a microscopic pH gradient, we determined that ChePep is critical for regulating chemotactic behavior. The chePep gene is unique to the Epsilonproteobacteria but is found throughout this diverse group. We expressed ChePep from other members of the Epsilonproteobacteria, including the zoonotic pathogen Campylobacter jejuni and the deep sea hydrothermal vent inhabitant Caminibacter mediatlanticus, in H. pylori and found that ChePep is functionally conserved across this class. ChePep represents a new family of chemotaxis regulators unique to the Epsilonproteobacteria and illustrates the different strategies that microbes have evolved to control motility.

IMPORTANCE

Helicobacter pylori strains infect half of all humans worldwide and contribute to the development of peptic ulcers and gastric cancer. H. pylori cannot survive within the acidic lumen of the stomach and uses flagella to actively swim to and colonize the protective mucus and epithelium. The chemotaxis system allows H. pylori to navigate by regulating the rotation of its flagella. We identified a new protein, ChePep, which controls chemotaxis in H. pylori. ChePep mutants fail to colonize the gastric glands of mice and are completely outcompeted by normal H. pylori. Genes encoding ChePep are found only in the class Epsilonproteobacteria, which includes the human pathogen Campylobacter jejuni and environmental microbes like the deep-sea hydrothermal vent colonizer Caminibacter mediatlanticus, and we show that ChePep function is conserved in this class. Our study identifies a new colonization factor in H. pylori and also provides insight into the control and evolution of bacterial chemotaxis.

Suppressive Effects of Selected Food Phytochemicals on CD74 Expression in NCI-N87 Gastric Carcinoma Cells

Helicobacter pylori (H. pylori) is one of the most widespread human pathogens, and plays major roles in chronic gastritis and gastric cancer. CD74 of gastric epithelial cells has recently been identified as an adhesion molecule to urease in H. pylori. In this study, we found that CD74 is highly expressed in a constitutive manner in NCI-N87 human gastric carcinoma cells at both the protein and mRNA levels as compared with Hs738St./Int fetal gastric cells. Subsequently, a novel cell-based ELISA able to rapidly screen the suppressive agents of CD74 expression was established. NCI-N87 cells were treated separately with 25 different food phytochemicals (4–100 µM) for 48 h and subjected to our novel assay. From those results, a citrus coumarin, bergamottin, was indicated to be the most promising compound with an LC₅₀/IC₅₀ value greater than 7.1, followed by luteolin (>5.4), nobiletin (>5.3), and quercetin (>5.1). Our findings suggest that these CD74 suppressants are unique candidates for preventing H. pylori adhesion and subsequent infection with reasonable action mechanisms.

Prevention of Gastric Cancer: When is Treatment of Helicobacter Pylori Warranted?

Chronic gastritis induced by Helicobacter pylori (H. pylori) is the strongest known risk factor for adenocarcinoma of the distal stomach, yet the effects of bacterial eradication on carcinogenesis remain unclear. H. pylori isolates possess substantial genotypic diversity, which engenders differential host inflammatory responses that influence clinical outcome. H. pylori strains that possess the cag pathogenicity island and secrete a functional cytotoxin induce more severe gastric injury and further augment the risk for developing distal gastric cancer. Carcinogenesis is also influenced by host genetic diversity, particularly involving immune response genes such as interleukin-1ß and tumor necrosis factor-α. Human trials and anima studies have indicated that eradication of H. pylori prior to the development of atrophic gastritis offers the best chance for prevention of gastric cancer. However, although the timing of intervention influences the magnitude of suppression of premalignant and neoplastic lesions, bacterial eradication, even in longstanding infections, is of clear benefit to the host. It is important to gain insight into the pathogenesis of H. pylori-induced gastritis and adenocarcinoma not only to develop more effective treatments for gastric cancer, but also because it might serve as a paradigm for the role of chronic inflammation in the genesis of other malignancies that arise within the gastrointestinal tract.

Helicobacter pylori Infection, Intestinal Metaplasia, and Gastric Cancer Risk in Eastern Siberia

BACKGROUND

The incidence of gastric cancer (GC) is extremely high in Russia and eastern Siberia, where information on the epidemiology of Helicobacter pylori infection is fragmentary.

AIMS

To assess the prevalence of both H. pylori infection (including CagA status) and intestinal metaplasia (IM) in Russian and eastern Siberian populations carrying a different risk of GC.

MATERIALS AND METHODS

 A sample of 2129 consecutive patients was considered, including 689 Europoids and 1440 Mongoloids (493 Evenks, 533 Khakass people, and 414 Tuvans), who all underwent serum sampling and upper gastrointestinal endoscopy. H. pylori status was established (ELISA, urease test, and histology), and IgG anti-CagA antibodies were assessed (ELISA) in H. pylori-positive cases. At least 3 biopsy samples per patient were considered, and IM was scored as present versus absent. The prevalence of H. pylori, CagA+ve status, and IM was compared with the incidence of GC according to the regional cancer registries.

RESULTS

The prevalence of H. pylori was similar for the Europoids and Mongoloids (93.6 vs 94.3%). The prevalence of CagA+ve infection was as follows: Europoids 61.2%, Evenks 36.4%, Khakass 44.0%, Tuvans 60.0% (p(1vs2) < .001; p(1vs3) < .001; p(2vs4) < .001; p(3vs4) < .001). The prevalence of IM was as follows: Europoids 10.7%, Evenks 5.1%, Khakass 9.8%, and Tuvans 23.4% (p(1vs2) = .001; p(1vs4) < .001; p(2vs4) < .001; p(3vs4) < .001). The incidence of GC (per 100,000 population/year) was as follows: Europoids 33.2; Evenks 18.2; Khakass 20.2; Tuvans 50.7 (p(1vs2) = 0.04; p(1vs3) = .05; p(2vs4) < .001; p(3vs4) < .001).

CONCLUSION

 H. pylori infection is consistently high in Russian and eastern Siberian populations; ethnicities with similar prevalence of CagA+ve status had different prevalence of IM and incidence of GC. As expected, IM prevalence correlated with the incidence of GC. Host-related and/or environmental factors may explain discrepancies between H. pylori status, the prevalence of IM, and the incidence of GC.

Evaluation of different cryoprotective agents in maintenance of viability of Helicobacter pylori in stock culture media

Four different cryoprotective supplemented stock media were evaluated for maintaining better survival and recovery of H. pylori type strain NCTC 11637 at two different maintenance temperatures of -20°C and -80°C after one month preservation as frozen stocks. The spread plate colony count method was used to investigate the recovery rate of H. pylori from equally inoculated bacterial suspensions in differently prepared stock cultures. After the preservation of H. pylori for one month in different cryoprotectant-supplemented stock media, the recovery rates for -20°C obtained for stock cultures supplemented with dimethyl sulfoxide (DMSO), polyethylene glycol (PEG), glycerol and glycerol+sucrose, as well as controls with and without human serum alone were 7.13, 6.97, 7.93, 7.99, 6.95 and 0.0 log CFU/ml, respectively. Maintenance of bacteria at -80°C gave statistically higher recovery rates compared to preservation at -20°C with the values of 8.55, 8.24, 8.59, 8.66, 8.01 and 0.0 log CFU/ml for these above mentioned stock cultures. The stock cultures supplemented with glycerol+sucrose and glycerol showed the highest recovery rates, 7.99 and 7.93 for -20°C vs. 8.66 and 8.59 for -80°C respectively, which were statistically different from the others. Our study revealed that H. pylori type strain NCTC 11637 could be better preserved at -80°C than -20°C. The best stock media which supported viability or culturability of bacteria were brain heart infusion broth (BHI)+glycerol+human serum and BHI+glycerol+sucrose+human serum, where the latter yielded the higher recovery rate.

Suppression of CD74 expression and Helicobacter pylori adhesion by auraptene targeting serum starvation-activated ERK1/2 in NCI-N87 gastric carcinoma cells

Helicobacter pylori (H. pylori) is a major human pathogen and plays a central role in chronic gastritis and gastric cancer. Since the adhesion of H. pylori to the human gastric epithelium is the initial and critical step of its infection, anti-H. pylori adhesion agents may be effective for the prevention and therapy of H. pylori-associated diseases. CD74 has recently been identified as a new receptor for H. pylori urease, and we have previously reported that several citrus components strongly suppressed CD74 expression in NCI-N87 gastric carcinoma cells. We found in this present study that auraptene (citrus coumarin) disrupted serum starvation-induced extracellular signaling-regulated kinase (ERK) 1/2 activation and attenuated H. pylori adhesion and IL-8 production in a co-culture system. In addition, the knockdown of CD74 expression led to a significant decrease of H. pylori adhesion, but unexpectedly increased IL-8 production. However, PD98059 (a MEK1/2 inhibitor) dramatically down-regulated this cytokine, suggesting MEK/ERK-dependent IL-8 production. Our results suggest that auraptene suppressed H. pylori adhesion and resulting chemokine production by disrupting ERK1/2 activation.

Regulation of the Helicobacter pylori cellular receptor decay-accelerating factor

Chronic gastritis induced by Helicobacter pylori is the strongest known risk factor for peptic ulceration and distal gastric cancer, and adherence of H. pylori to gastric epithelial cells is critical for induction of inflammation. One H. pylori constituent that increases disease risk is the cag pathogenicity island, which encodes a secretion system that translocates bacterial effector molecules into host cells. Decay-accelerating factor (DAF) is a cellular receptor for H. pylori and a mediator of the inflammatory response to this pathogen. H. pylori induces DAF expression in human gastric epithelial cells; therefore, we sought to define the mechanism by which H. pylori up-regulates DAF and to extend these findings into a murine model of H. pylori-induced injury. Co-culture of MKN28 gastric epithelial cells with the wild-type H. pylori cag(+) strain J166 induced transcriptional expression of DAF, which was attenuated by disruption of a structural component of the cag secretion system (cagE). H. pylori-induced expression of DAF was dependent upon activation of the p38 mitogen-activated protein kinase pathway but not NF-kappaB. Hypergastrinemic INS-GAS mice infected with wild-type H. pylori demonstrated significantly increased DAF expression in gastric epithelium versus uninfected controls or mice infected with an H. pylori cagE(-) isogenic mutant strain. These results indicate that H. pylori cag(+) strains induce up-regulation of a cognate cellular receptor in vitro and in vivo in a cag-dependent manner, representing the first evidence of regulation of an H. pylori host receptor by the cag pathogenicity island.

Macrophage migration inhibitory factor and interleukin-8 produced by gastric epithelial cells during Helicobacter pylori exposure induce expression and activation of the epidermal growth factor receptor

While a link between Helicobacter pylori exposure and gastric cancer has been established, the underlying mechanisms remain unclear. H. pylori induces a chronic inflammatory response in infected individuals. A link between chronic inflammation and carcinogenesis has long been suggested but never elucidated. Epidermal growth factor receptor (EGFR) signaling plays an important role in both proinflammatory and procarcinogenic mechanisms and is upregulated on gastric epithelial cells (GECs) during H. pylori exposure. The aim of this study was to examine the effects of two important proinflammatory cytokines released during H. pylori infection, macrophage migration inhibitory factor (MIF) and interleukin-8 (IL-8), on the expression and transactivation of EGFR and on the proliferation of GECs during H. pylori exposure. The expression of EGFR by GECs was increased by exposure to either H. pylori, recombinant MIF, or recombinant IL-8. However, cag pathogenicity island knockout strains of H. pylori had very little effect on expression. MIF and IL-8 also induced phosphorylation of EGFR, signaling events, and proliferation during H. pylori exposure, all of which were decreased when they were neutralized by these cytokines or were blocked from their receptors. The overall role of EGFR in these responses to H. pylori exposure was assessed by knocking down EGFR expression by small interfering RNA.

Host-pathogen systems biology: logical modelling of hepatocyte growth factor and Helicobacter pylori induced c-Met signal transduction

Background

The hepatocyte growth factor (HGF) stimulates mitogenesis, motogenesis, and morphogenesis in a wide range of tissues, including epithelial cells, on binding to the receptor tyrosine kinase c-Met. Abnormal c-Met signalling contributes to tumour genesis, in particular to the development of invasive and metastatic phenotypes. The human microbial pathogen Helicobacter pylori can induce chronic gastritis, peptic ulceration and more rarely, gastric adenocarcinoma. The H. pylori effector protein cytotoxin associated gene A (CagA), which is translocated via a type IV secretion system (T4SS) into epithelial cells, intracellularly modulates the c-Met receptor and promotes cellular processes leading to cell scattering, which could contribute to the invasiveness of tumour cells. Using a logical modelling framework, the presented work aims at analysing the c-Met signal transduction network and how it is interfered by H. pylori infection, which might be of importance for tumour development.

Results

A logical model of HGF and H. pylori induced c-Met signal transduction is presented in this work. The formalism of logical interaction hypergraphs (LIH) was used to construct the network model. The molecular interactions included in the model were all assembled manually based on a careful meta-analysis of published experimental results. Our model reveals the differences and commonalities of the response of the network upon HGF and H. pylori induced c-Met signalling. As another important result, using the formalism of minimal intervention sets, phospholipase Cγ1 (PLCγ1) was identified as knockout target for repressing the activation of the extracellular signal regulated kinase 1/2 (ERK1/2), a signalling molecule directly linked to cell scattering in H. pylori infected cells. The model predicted only an effect on ERK1/2 for the H. pylori stimulus, but not for HGF treatment. This result could be confirmed experimentally in MDCK cells using a specific pharmacological inhibitor against PLCγ1. The in silico predictions for the knockout of two other network components were also verified experimentally.

Conclusion

This work represents one of the first approaches in the direction of host-pathogen systems biology aiming at deciphering signalling changes brought about by pathogenic bacteria. The suitability of our network model is demonstrated by an in silico prediction of a relevant target against pathogen infection.

Progress of research into the pathogenic mechanism of Helicobacter pylori and the preventive role of probiotics in H. pylori infection

Helicobacter pylori, a highly prevalent pathogen, is a major cause of chronic gastritis and peptic ulcer and a risk factor for gastric malignancies or gastric mucosa-associated lymphoid tissue (MALT) lymphoma. Antibiotic-based H. pylori eradication is currently regarded as the gold standard. However, it is expensive and causes side effects, and the rapid development of antibiotic-resistant strains may soon prevent their large-scale use. Recently, many new therapeutic strategies are being studied to improve the H. pylori eradication rate. The use of probiotics in the field of H. pylori infection has been proposed for improving eradication, tolerability and compliance with multiple antibiotic regimens. In addition, probiotics have a possible role in the stabilization of the gastric barrier function and reducing mucosal inflammation. In this article, we review the development of research on the molecular mechanism of H. pylori infection and the mechanisms of action and clinical significance of probiotics.

Clinical application progress of Rifaximin in the treatment of digestive diseases

Rifaximin, a derivative of rifamycin, has high antibacterial activity on various kinds of Gram-positive and -negative aerobes and anaerobes, and it is a new drug in the treatment of giardiasis. Rifaximin is not easy to be absorbed after oral administration, and mild systemic adverse reaction is the main characteristic. Recently, Rifaximin has been widely and effectively used in the therapy of many diseases related to intestinal bacterial infection such as hepatic encephalopathy, diverticular disease, overgrowth of intestinal bacteria, inflammatory bowel disease (IBD) and H. pylori infection. The above advances were reviewed in the present article.

Expression of Sonic hedgehog gene, interleukin-1β, tumor necrosis factor-α in gastric epithelium of mongolian gerbils after H pylori inoculation

AIM: To investigate the expression of morphogene Sonic hedgehog (Shh), interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α) in gastric epithelium of mongolian gerbils after H pylori inoculation and their correlations with the pathologic changes of Helicobacter pylori related gastritis.

METHODS: A total of 50 male mongolian gerbils were inoculated with H pylori and another 50 gerbils served as controls. The levels of Shh, IL-1β and TNF-α mRNA expression were detected by reverse transcription-polymerase chain reaction (RT-PCR), and the level of Shh protein expression was examined by immunohistochemistry 4, 12, 24, 36 and 48 weeks after inoculation.

RESULTS: As compared with those in the controls, both the expression levels of Shh mRNA and protein were decreased significantly at the 36^th (t = 3.24, P < 0.05; Z = 4.84, P < 0.001) and 48^th week (t = 3.01, P < 0.05; Z = 4.65, P < 0.001) after H pylori inoculation. Furthermore, the level of Shh mRNA expression was negatively correlated with the expression of IL-1β mRNA, TNF-α mRNA and the grade of gastritis, respectively (r = -0.372, P < 0.01; r = -0.301, P < 0.05; r = -0.397, P < 0.001). Similarly, the level of Shh protein expression was negatively correlated with the expression of IL-1β mRNA, TNF-α mRNA and the grade of gastritis (r = -0.321, P < 0.05; r = -0.313, P < 0.05; r = -0.371, P < 0.001) respectively.

CONCLUSION: After H pylori infection, the expression of IL-1β and TNF-α is increased and positively correlated with the grade of gastritis, and while the expression of Shh is decreased and negatively correlated with the expression of IL-1β, TNF-α and gastritis grades.