Pathogenesis of Helicobacter pylori infection

Gastrointestinal Microbiota in Gastric Cancer: Potential Mechanisms and Clinical Applications-A Literature Review

Emerging evidence highlights the crucial role of gastrointestinal microbiota in the pathogenesis of gastric cancer. Helicobacter pylori (H. pylori) infection stands out as a primary pathogenic factor. However, interventions such as anti-H. pylori therapy, gastric surgeries, immunotherapy, and chronic inflammation significantly remodel the gastric microbiome, implicating a broader spectrum of microorganisms in cancer development. These microbial populations can modulate gastric carcinogenesis through various mechanisms, including sustained chronic inflammation, bacterial genotoxins, alterations in short-chain fatty acids, elevated gastrointestinal bile acids, impaired mucus barrier function, and increased concentrations of N-nitrosamines and lactic acid. The dynamic changes in gut microbiota also critically influence the outcomes of anti-cancer therapies by modifying drug bioavailability and metabolism, thus affecting therapeutic efficacy and side effect profiles. Additionally, the effectiveness of radiotherapy can be significantly impacted by gut microbiota alterations. Novel therapeutic strategies targeting the microbiome, such as dietary interventions, probiotic and synbiotic supplementation, and fecal microbiota transplantation, are showing promise in cancer treatment. Understanding the intricate relationship between the gut microbiota and gastric cancer is essential for developing new, evidence-based approaches to the prevention and treatment of this malignancy.

Effect of in vitro simulated digestion on the anti-Helicobacter Pylori activity of different Propolis extracts

Helicobacter pylori (HP) is among the most common pathogens causing infection in humans worldwide. Oxidative stress and gastric inflammation are involved in the progression of HP-related gastric diseases, and they can be targeted by integrating conventional antibiotic treatment with polyphenol-enriched natural products. In this work, we characterised three different propolis extracts and evaluated their stability under in vitro simulated gastric digestion, compared to their main constituents alone. The extract with the highest stability to digestion (namely, the dark propolis extract, DPE) showed a minimum bactericidal concentration (MBC) lower than 1 mg/mL on HP strains with different virulence factors. Finally, since urease is one of the virulence factors contributing to the establishment of a microenvironment that promotes HP infection, we evaluated the possible inhibition of this enzyme by using molecular docking simulations and in vitro colorimetric assay, showing that galangin and pinocembrin may be involved in this activity.

Anti-Inflammatory Effect of Korean Propolis on Helicobacter pylori-Infected Gastric Mucosal Injury Mice Model

Propolis, a natural resinous substance obtained from a variety of buds and plants, has been reported to possess various biological functions. Several recent studies have demonstrated the inhibitory effects of propolis on the growth of Helicobacter pylori (H. pylori) in vitro; however, current research efforts on Korean propolis (KP) remain insufficient especially in vivo. Our study aims to investigate the anti-inflammatory effect and molecular mechanism of KP on mouse gastric mucosa during H. pylori infection. We examined an in vivo H. pylori-induced gastric mucosal injury mice model. We found that KP inhibited the growth of H. pylori and attenuated the expression of H. pylori virulence factors such as cytotoxin-associated gene A, encoding urease A subunit, surface antigen gene and neutrophil-activating protein A. Moreover, KP reduced both gross lesions and pathological scores in H. pylori-challenged mice. In addition, KP markedly restrained the production of pro-inflammatory cytokines and nitric oxide levels compared with an untreated H. pylori-infected group. In particular, we found that KP repressed the phosphorylation of IκBα and NF-κB p65 subunit, and subsequently suppressed their downstream target genes. Taken together, these findings demonstrate the beneficial effects of KP on inflammation through the inhibition of NF-κB signaling as well as inhibition of H. pylori growth in a mouse model infected with H. pylori. This suggests the potential application of KP as a natural supplement for patient’s suffering from gastric mucosal injury caused by H. pylori infection.

Helicobacter Pylori-Induced Gastric Infections: From Pathogenesis to Novel Therapeutic Approaches Using Silver Nanoparticles

Helicobacter pylori is the first formally recognized bacterial carcinogen and the most important single digestive pathogen responsible for the induction of gastroduodenal diseases such as gastritis, peptic ulcer, and, finally, gastric neoplasia. The recently reported high rates of antimicrobial drug resistance hamper the current therapies of H. pylori, with therapeutic failure reaching up to 40% of patients. In this context, new treatment options and strategies are urgently needed, but the successful development of these new therapeutic tools is conditioned by the understanding of the high adaptability of H. pylori to the gastric acidic environment and the complex pathogenic mechanism. Due to several advantages, including good antibacterial efficiency, possible targeted delivery, and long tissular persistence, silver nanoparticles (AgNPs) offer the opportunity of exploring new strategies to improve the H. pylori therapy. A new paradigm in the therapy of H. pylori gastric infections using AgNPs has the potential to overcome the current medical limitations imposed by the H. pylori drug resistance, which is reported for most of the current organic antibiotics employed in the classical therapies. This manuscript provides an extensive overview of the pathology of H. pylori-induced gastritis, gastric cancer, and extradigestive diseases and highlights the possible benefits and limitations of employing AgNPs in the therapeutic strategies against H. pylori infections.

An Immune Signature for Risk Stratification and Therapeutic Prediction in Helicobacter Pylori-Infected Gastric Cancer

Simple Summary

Helicobacter pylori (HP) infection is the greatest risk factor for gastric cancer (GC), and over half of the world’s population is colonized with HP. Up to now, many gene signatures are designed for predicting the prognosis of GC patients, while there are no signatures designed specifically for HP+ GC patients. Considering the tight association between HP infection and tumor immune microenvironment, we constructed an immune-related signature named IRSHG in this study, aiming to provide new insight into the treatment for HP+ GC patients. IRSHG was the first prognostic signature for HP+ GC patients, demonstrating high reliability and feasibility in predicting the prognosis. In addition, IRSHG could help investigate potential therapies and guide anti-PD-1 immunotherapy for HP+ GC patients, providing new insight for the personalized treatment of GC.

Abstract

Helicobacter pylori (HP) infection is the greatest risk factor for gastric cancer (GC). Increasing evidence has clarified that tumor immune microenvironment (TIME) is closely related to the prognosis and therapeutic efficacy of HP-positive (HP+) GC patients. In this study, we aimed to construct a novel immune-related signature for predicting the prognosis and immunotherapy efficacy of HP+ GC patients. A total of 153 HP+ GC from three different cohorts were included in this study. An Immune-Related prognostic Signature for HP+ GC patients (IRSHG) was established using Univariate Cox regression, the LASSO algorithm, and Multivariate Cox regression. Univariate and Multivariate analyses proved IRSHG was an independent prognostic predictor for HP+ GC patients, and an IRSHG-integrated nomogram was established to quantitatively assessthe prognostic risk. The low-IRSHG group exhibited higher copy number load and distinct mutation profiles compared with the high-IRSHG group. In addition, the difference of hallmark pathways and immune cells infiltration between the two groups was investigated. Notably, tumor immune dysfunction and exclusion (TIDE) analysis indicated that the low-IRSHG group had a higher sensitivity to anti-PD-1 immunotherapy, which was validated by an external pabolizumab treatment cohort. Moreover, 98 chemotherapeutic drugs and corresponding potential biomarkers were identified for two groups, and several drugs with potential ability to reverse IRSHG score were identified using CMap analysis. Collectively, IRSHG may serve as a promising biomarker for survival outcome as well as immunotherapy efficacy. Furthermore, it can also help to prioritize potential therapeutics for HP+ GC patients, providing new insight for the personalized treatment of HP-infected GC.

Identifying the Demographic, Clinical, and Endoscopic Findings of Gastroesophageal Reflux Disease in Patients With Helicobacter pylori Infection at King Abdulaziz University Hospital, Jeddah, Saudi Arabia

Background: Helicobacter pylori (H. pylori) infection and gastroesophageal reflux disease (GERD) are widely spread clinical terms. GERD refers to the backflow of gastric acid to the esophagus and upper gastrointestinal tract, causing irritation. H. pylori is a gram-negative bacillus that adheres mainly to the gastric mucosa, causing peptic ulcers and gastritis. The nature of the relationship between GERD and H. pylori is yet to be explored, and few studies have been conducted. In contrast, some studies suggest a protective role of H. pylori against GERD. This study aimed to identify the demographic, clinical, and endoscopic findings of patients with GERD who underwent H. pylori testing.

Methods: A retrospective review of medical records at King Abdulaziz University Hospital, Jeddah, Saudi Arabia, between 2015 and 2021 was conducted in June 2021. Our sample consisted of 255 individuals enrolled based on age and H. pylori status. In univariate analysis, we used frequency tests for qualitative data and measure of central tendency (MCT) for quantitative data. In bivariate analysis, we used the t-test and Pearson’s chi-square test.

Results: Of 255 GERD patients enrolled, 90 were positive and 165 were negative for H. pylori. The majority were females (54 were positive and 93 were negative for H. pylori). Both groups mainly complained of abdominal pain. Endoscopically, gastritis was higher in the H. pylori-positive group than in the H. pylori-negative group.

Conclusion: In conclusion, the majority of GERD patients were H. pylori-negative, females, Saudis, and non-smokers.

Application of PCR and Microscopy to Detect Helicobacter pylori in Gastric Biopsy Specimen among Acid Peptic Disorders at Tertiary Care Centre in Eastern Nepal

BACKGROUND

Helicobacter pylori infection is most prevalent in developing countries. It is an etiological agent of peptic ulcer, gastric adenocarcinoma, and mucosal-associated lymphoid tissue (MALT) lymphoma. Despite the development of different assays to confirm H. pylori infection, the diagnosis of infection is challenged by precision of the applied assay. Hence, the aim of this study was to understand the diagnostic accuracy of PCR and microscopy to detect the H. pylori in the gastric antrum biopsy specimen from gastric disorder patients.

METHODS

A total of 52 patients with gastric disorders underwent upper gastrointestinal endoscopy with biopsy. The H. pylori infection in gastric biopsies was identified after examination by microscopy and 23S rRNA specific PCR. The agreement between two test results were analysed by McNemar's test and Kappa coefficient.

RESULT

H. pylori infection was confirmed in 9 (17.30%) patients by both assays, 6.25% in antral gastritis, 22.22% in gastric ulcer, 100% in gastric ulcer with duodenitis, 50% in gastric ulcer with duodenal ulcer, and 33.33% in severe erosive duodenitis with antral gastritis. Out of nine H. pylori infection confirmed patients, 3 patients were confirmed by microscopy and 8 patients by PCR. In case of two patients, both microscopy and PCR assay confirmed the H. pylori infection. The agreement between two test results was 86.54% and disagreed by 13.46% (p value > 0.05).

CONCLUSION

We found that PCR assay to detect H. pylori is more sensitive than microscopy. However, we advocate for the combination of both assays to increase the strength of diagnostic accuracy due to the absence of the gold standard assay for H. pylori infection.

Mutual amplification of HNF4α and IL-1R1 composes an inflammatory circuit in Helicobacter pylori associated gastric carcinogenesis

Helicobacter pylori (Hp) is an environmental inducer of gastritis and gastric cancer (GC). The immune response to Hp and the associated changes in somatic gene expression are key determinants governing the transition from gastritis to GC. We show that hepatocyte nuclear factor 4α (HNF4α) is upregulated by Hp infection via NF-κB signaling and that its protein and mRNA levels are elevated in GC. HNF4α in turn stimulates expression of interleukin-1 receptor 1(IL-1R1), which amplifies the inflammatory response evoked by its ligand IL-1β. IL-1β/IL-1R1 activates NF-κB signaling, thereby increasing HNF4α expression and forming a feedback loop that sustains activation of the NF-κB pathway and drives the inflammation towards GC. Examination of clinical samples revealed that HNF4α and IL-1R1 levels increase with increasing severity of Hp-induced gastritis and reach their highest levels in GC. Co-expression of HNF4α and IL-1R1 was a crucial indicator of malignant transformation from gastritis to GC, and was associated with a poorer prognosis in GC patients. Disruption of the HNF4α/IL-1R1/IL-1β/NF-κB circuit during Hp infection maybe an effective means of preventing the associated GC.

Correlation between mast cell density and histological parameters in Helicobacter pylori-associated gastritis

Background: Helicobacter pylori (H. pylori) are a major cause of chronic gastritis and peptic ulcer. This organism plays a role in gastric carcinoma and B-cell lymphoma. However, the exact pathogenesis of gastric inflammation is still unclear. Mast cells, the important inflammatory cells for allergic process, may participate in the pathogenesis of gastritis related to H. pylori infection.

Objective: Analyze the relationship between mast cell density, H. pylori intensity, histological alterations, and their severity of biopsy proven gastritis.

Methods: One hundred eleven biopsied specimens were collected from Thai patients who were diagnosed H. pylori-associated gastritis of the antrum at King Chulalongkorn Memorial Hospital between 2002 and 2005. All biopsied specimens were examined according to the Updated Sydney System. Mast cell density was evaluated by 0.1% toluidine-stained sections.

Results: The higher mast cell density was correlated with increased neutrophilic infiltration (r = 0.220, p = 0.020), chronic inflammatory cell infiltration (r = 0.381, p <0.001), and lymphoid aggregation (r = 0.271, p = 0.004). No relationship was found between mast cell density and intensity of H. pylori, glandular atrophy, or intestinal metaplasia.

Conclusion: Mast cells might take part in the pathogenesis of H. pylori gastritis.

Helicobacter pylori in Dyspepsia: Phenotypic and Genotypic Methods of Diagnosis

Background:

Helicobacter pylori affects almost half of the world's population and therefore is one of the most frequent and persistent bacterial infections worldwide. H. pylori is associated with chronic gastritis, ulcer disease (gastric and duodenal), mucosa-associated lymphoid tissue lymphoma, and gastric cancer. Several diagnostic methods exist to detect infection and the option of one method or another depends on various genes, such as availability, advantages and disadvantages of each method, monetary value, and the age of patients.

Materials and Methods:

Patients with complaints of abdominal pain, discomfort, acidity, and loss of appetite were chosen for endoscopy, detailed history was contained, and a physical examination was conducted before endoscopy. Biopsies (antrum + body) were received from each patient and subjected to rapid urease test (RUT), histopathological examination (HPE), polymerase chain reaction (PCR), and culture.

Results:

Of the total 223 biopsy specimens obtained from dyspeptic patients, 122 (54.7%) were positive for H. pylori for HPE, 109 (48.9%) by RUT, 65 (29.1%) by culture, and 117 (52.5%) by PCR. The specificity and sensitivity were as follows: RUT (99% and 88.5%), phosphoglucosamine mutase PCR assay (100% and 95.9%), and culture (100% and 53.3%), respectively.

Conclusion:

In this study, we compared the various diagnostic methods used to identify H. pylori infection indicating that, in comparison with histology as gold standard for detection of H. pylori infection, culture and PCR showed 100% specificity whereas RUT and PCR showed 99% and 100% sensitivity, respectively.

Helicobacter pylori activates NF-κB by inducing Ubc13-mediated ubiquitination of lysine 158 of TAK1

The Helicobacter pylori virulence factor CagA targets a variety of host proteins to alter different cellular responses, including the induction of pro-inflammatory cytokines. We have previously shown that CagA-facilitated lysine 63-linked ubiquitination of TAK1 is essential for the H. pylori-induced NF-κB activation and the expression of proinflammatory cytokines. However, the molecular mechanism for TAK1 ubiquitination and activation in H. pylori-mediated NF-κB activation remains elusive. Here, we identify lysine 158 of TAK1 as the key residue undergoing lysine 63-linked ubiquitination in response to H. pylori infection. Mutation of lysine 158 to arginine prevents the ubiquitination of TAK1 and impairs H. pylori-induced TAK1 and NF-κB activation. Moreover, we demonstrate that E2 ubiquitin conjugating enzyme Ubc13 is involved in H. pylori-mediated TAK1 ubiquitination. Suppressing the activity of Ubc13 by a dominant-negative mutant or siRNA abolishes CagA-facilitated and H. pylori-induced TAK1 and NF-κB activation. These findings further underscore the importance of lysine 63-linked ubiquitination of TAK1 in H. pylori-induced NF-κB activation and NF-κB-mediated inflammatory response.

Role of the Helicobacter pylori-induced inflammatory response in the development of gastric cancer

Helicobacter pylori (H. pylori) infection causes chronic gastritis and peptic ulceration and is the strongest risk factor for the development of gastric cancer. The pathogenesis of H. pylori is believed to be associated with infection-initiated chronic gastritis, which is characterized by enhanced expression of many inflammatory genes. H. pylori utilizes various virulence factors, targeting different cellular proteins, to modulate the host inflammatory response. In this review, we explore the many different ways by which H. pylori initiates inflammation, leveling many "hits" on the gastric mucosa which can lead to the development of cancer. We also discuss some recent findings in understanding the pathogen-host interactions and the role of transcription factor NF-κB in H. pylori-induced inflammation.

Helicobacter, Inflammation, and Gastric Cancer

Helicobacter pylori infection leads to long-lasting chronic inflammation and represents the most common risk factor underlying gastric cancer. Recently, new insights into the mechanisms through which H. pylori and mucosal inflammation lead to cancer development have emerged. H. pylori virulence factors, in particular specific CagA genotypes, represent main factors in gastric cancer, inducing altered intracellular signaling in epithelial cells. The chronic nature of H. pylori infection appears to relate to the VacA virulence factor and Th17/Treg mechanisms. A role of H. pylori infection in epigenetic and microRNA deregulation has been shown. Mutation of the epithelial cell genome, a hallmark of cancer, was demonstrated to accumulate in H. pylori infected stomach partly due to inadequate DNA repair. Gastric stem cells were shown to be targets of oxidative injury in the Helicobacter-inflammatory milieu. Recent advances emphasizing the contribution of bacterial factors, inflammatory mediators, and the host epithelial response in gastric carcinogenesis are reviewed.

Diversity of Helicobacter Pylori cagA and vacA Genes and Its Relationship with Clinical Outcomes in Azerbaijan, Iran

PURPOSE

The purpose of this research was to analyze cagA and vacA genotypes status in H. pylori isolates and relationship with clinical outcomes.

METHODS

Gastric biopsy specimens were cultured for H. pylori isolation and cagA and vacA genes were detected in these isolates. Data were collected and the results were analyzed using χ2 and Fishers exact tests by SPSS software version. 16.

RESULTS

Of the total 115 H. pylori isolates, 79 (68.7 %) were cagA positive and 82 (71.3%) of isolates contained the s1 allele which 33 (28.7%) were subtype s2. s1m2 was the most frequent vacA allelic combination in the H. pylori isolates examined (63 cases), followed by s2m2 (31 cases), s1m1 (19 cases) and s2m1 (2 case). Strains cagA positive were more frequent in peptic ulcer diseases patients than non ulcer diseases patients, as 47 (59.5%) and 32 (40.5%), while cagA negative were low, as 15 (41.7%) and 21 (58.3%), respectively.

CONCLUSION

We found that the cagA and vacA status were not related to clinical outcomes in this area. Overall, in the present study, vacA s1/m2, cagA-positive strains were predominant irrespective of clinical outcome, but s2/m1 was rare.

Enhancement of Helicobacter pylori outer inflammatory protein DNA vaccine efficacy by co-delivery of interleukin-2 and B subunit heat-labile toxin gene encoded plasmids

Development of an effective vaccine for controlling H. pylori-associated infection, which is present in about half the people in the world, is a priority. The H. pylori outer inflammatory protein (oipA) has been demonstrated to be a potential antigen for a vaccine. In the present study, use of oipA gene encoded construct (poipA) for C57BL/6 mice vaccination was investigated. Whether co-delivery of IL-2 gene encoded construct (pIL-2) and B subunit heat-labile toxin of Escherichia coli gene encoded construct (pLTB) can modulate the immune response and enhance DNA vaccine efficacy was also explored. Our results demonstrated that poipA administered intradermally ('gene gun' immunization) promoted a strong Th2 immune response, whereas co-delivery of either pIL-2 or pLTB adjuvant elicited a Th1-biased immune response. PoipA administered with both pIL-2 and pLTB adjuvants promoted a strong Th1 immune response. Regardless of the different immune responses promoted by the various vaccination regimes, all immunized mice had smaller bacterial loads after H. pylori challenge than did PBS negative and pVAX1 mock controls. Co-delivery of adjuvant(s) enhances poipA DNA vaccine efficacy by shifting the immune response from being Th2 to being Th1-biased, which results in a greater reduction in bacterial load after H. pylori challenge. Both prophylactic and therapeutic vaccination can achieve sterile immunity in some subjects.

Helicobacter pylori arginase mutant colonizes arginase II knockout mice

AIM: To investigate the role of host and bacterial arginases in the colonization of mice by Helicobacter pylori (H. pylori).

METHODS: H. pylori produces a very powerful urease that hydrolyzes urea to carbon dioxide and ammonium, which neutralizes acid. Urease is absolutely essential to H. pylori pathogenesis; therefore, the urea substrate must be in ample supply for urease to work efficiently. The urea substrate is most likely provided by arginase activity, which hydrolyzes L-arginine to L-ornithine and urea. Previous work has demonstrated that H. pylori arginase is surprisingly not required for colonization of wild-type mice. Hence, another in vivo source of the critical urea substrate must exist. We hypothesized that the urea source was provided by host arginase II, since this enzyme is expressed in the stomach, and H. pylori has previously been shown to induce the expression of murine gastric arginase II. To test this hypothesis, wild-type and arginase (rocF) mutant H. pylori strain SS1 were inoculated into arginase II knockout mice.

RESULTS: Surprisingly, both the wild-type and rocF mutant bacteria still colonized arginase II knockout mice. Moreover, feeding arginase II knockout mice the host arginase inhibitor S-(2-boronoethyl)-L-cysteine (BEC), while inhibiting > 50% of the host arginase I activity in several tissues, did not block the ability of the rocF mutant H. pylori to colonize. In contrast, BEC poorly inhibited H. pylori arginase activity.

CONCLUSION: The in vivo source for the essential urea utilized by H. pylori urease is neither bacterial arginase nor host arginase II; instead, either residual host arginase I or agmatinase is probably responsible.

Identification of S-nitrosylation of proteins of Helicobacter pylori in response to nitric oxide stress

Innate and adaptive immune responses are activated in humans when Helicobacter pylori invades the gastric mucosa. Nitric oxide (NO) and reactive nitrogen species are important immune effectors, which can exert their functions through oxidation and S-nitrosylation of proteins. S-nitrosoglutathione and sodium nitroprus-side were used as NO donors and H. pylori cells were incubated with these compounds to analyze the inhibitory effect of NO. The suppressing effect of NO on H. pylori has been shown in vitro. Furthermore, the proteins modified by S-nitrosylation in H. pylori were identified through the biotin switch method in association with matrix-assisted laser desorption ionization/time-of-flight tandem mass spectrometry (MALDI-TOF-MS/MS). Five S-nitrosylated proteins identified were a chaperone and heat-shock protein (GroEL), alkyl hydroperoxide reductase (TsaA), urease alpha subunit (UreA), HP0721, and HP0129. Importantly, S-nitrosylation of TsaA and UreA were confirmed using purified recombinant proteins. Considering the importance of these enzymes in antioxidant defenses, adherence, and colonization, NO may exert its antibacterial actions by targeting enzymes through S-nitrosylation. Identification of protein S-nitrosylation may contribute to an understanding of the antibacterial actions of NO. Our findings provide an insight into potential targets for the development of novel therapeutic agents against H. pylori infection.

A Five-Year-Old Boy with Marked Hypergastrinemia Associated with H. pylori Infection

A 5-year-old boy was referred to our department for persistent epigastric discomfort. Serum gastrin level was 635 pg/ml with a pepsinogen (PG) I level of 102.7 ng/ml and a PG I/II ratio of 23.2, indicating a hyperacidic state. Upper gastrointestinal endoscopy showed normal gastric mucosal folds and no abnormalities including no gastric mucosal atrophy. To investigate the cause of hypergastrinemia, a Ca injection test was performed and the patient showed no definitive response to a large load of Ca. Contrast-enhanced dynamic CT revealed no space-occupying lesions. The results from these two studies were not consistent with the presence of gastrinoma. A urea breath test showed 2.8%, and a test for the fecal H. pylori antigen was positive. Since H. pylori infection was considered to be a possible cause of hypergastrinemia, eradication therapy was introduced. The therapy was shown to be successful by using a repeated urea breath test that showed a normalization to 0.6%. 7 months after the therapy blood examination showed a gastrin level of 191 pg/ml, a PG I level of 36.7 ng/ml, and a PG I/II ratio of 7.3. An immunostaining study of the gastric mucosa suggested that a decrease in somatostatin secretion due to a reduction in D cell population might have induced hypergastrinemia in this case. In children with H. pylori infection showing marked hypergastrinemia, immunohistochemical examination and therapeutic diagnosis by eradication may be helpful in the differential diagnosis of gastrinoma.

Ureases as a target for the treatment of gastric and urinary infections

Urease is known to be a major contributor to pathologies induced by Helicobacter pylori and Proteus species. In H pylori, urease allows the bacteria to survive in an acidic gastric environment during colonisation, playing an important role in the pathogenesis of gastric and peptic ulcers. Ureolytic activity also results in the production of ammonia in close proximity to the gastric epithelium, causing cell damage and inflammation. In the case of Proteus species (notably Proteus mirabilis) infection, stones are formed due to the presence of ammonia and carbon dioxide released by urease action. In addition, the ammonia released is able to damage the glycosaminoglycan layer, which protects the urothelial surface against bacterial infection. In this context, the administration of urease inhibitors may be an effective therapy for urease-dependent pathogenic bacteria. This is a review of the role of ureases in H pylori and Proteus species infections, focussing on the biochemical and clinical aspects of the most promising and/or potent urease inhibitors for the treatment of gastric and urinary tract infections.

Helicobacter pylori proteins response to nitric oxide stress

Helicobacter pylori is a highly pathogenic microorganism with various strategies to evade human immune responses. Nitric oxide (NO) and reactive nitrogen species (RNS) generated via nitric oxide synthase pathway are important effectors during the innate immune response. However, the mechanisms of H. pylori to survive the nitrosative stress are not clear. Here the proteomic approach has been used to define the adaptive response of H. pylori to nitrosative stress. Proteomic analysis showed that 38 protein spots were regulated by NO donor, sodium nitroprusside (SNP). These proteins were involved in protein processing, anti-oxidation, general stress response, and virulence, as well as some unknown functions. Particularly, some of them were participated in iron metabolism, potentially under the control of ferric uptake regulator (Fur). Real time PCR revealed that fur was induced under nitrosative stress, consistent with our deduction. One stress-related protein up-regulated under nitrosative conditions was thioredoxin reductase (TrxR). Inactivation of fur or trxR can lead to increased susceptivity to nitrosative stress respectively. These studies described the adaptive response of H. pylori to nitric oxide stress, and analyzed the relevant role of Fur regulon and TrxR in nitrosative stress management.

Helicobacter pylori infection in developing countries: the burden for how long?

Approximately 50% (over 3 billion) of the world populations are known to be infected with Helicobacter pylori , mainly in the developing countries . Among those, hundreds of millions of people develop peptic ulceration during their lifetime and still tens of millions might progress to gastric cancer. Possible modes of H. pylori transmission generally described are through direct contact between family members and also through contaminated water and food. Because the high prevalence of infection occurs mainly in developing countries and because the test-and-treat strategy puts a huge economic burden on many of these countries, it is time to take an immediate action toward this bacterial infection and adopt a strategy to prevent it. To address this issue, an updated prevalence of infection, modes of transmission, economics of infection and preventative measures to block the infection process have been discussed.

The aggravatory effect of nicotine on Helicobacter pylori-induced gastric mucosa injury: role of asymmetric dimethylarginine

BACKGROUND AND GOAL

Nitric oxide (NO) is a well-known gastric mucosa protection factor. Recently, it has been reported that methylated arginine compound such as asymmetric dimethylarginine (ADMA), which inhibits nitric oxide synthesis, may be related to the development of gastric mucosa injury in patients with Helicobacter pylori infection. In the present study, we tested the relationship between endogenous ADMA and gastric mucosa injury in H. pylor- infected patients and cultured gastric epithelial cells.

METHODS

One hundred and fifty subjects with gastric diseases were entered in this study. The levels of ADMA in gastric juice and plasma were measured in both H. pylori+ and H. pylori- patients. We analyzed independent risk factors that contribute to ADMA levels by multiple linear regression analyses. Mucosal epithelium cells were treated with nicotine (10 microM) for 24 hours in the presence or absence of H. pylori. The concentrations of ADMA in the culture medium and the rate of cell apoptosis were determined.

RESULTS

The ADMA level in gastric juice was significantly increased in H. pylori+ patients (P<0.05), whereas there were no differences in the content of ADMA in the plasma between H. pylori+ patients and H. pylori- patients. Smoking and H. pylori infection were 2 independent risk factors contributing to ADMA levels, and in the population of H. pylori+ patients, the level of ADMA in smokers was higher compared with nonsmokers. Incubation of nicotine (10 microM) with epithelial cells for 24 hours further increased the elevated level of ADMA and the rate of cell apoptosis owing to H. pylori infection.

CONCLUSIONS

H. pylori infection caused an increase of ADMA levels in gastric juice, which was aggravated by smoking. Endogenous ADMA may be an important factor contributing to gastric mucosa injury.

A redox basis for metronidazole resistance in Helicobacter pylori

Metronidazole resistance in Helicobacter pylori has been attributed to mutations in rdxA or frxA. Insufficient data correlating RdxA and/or FrxA with the resistant phenotype, and the emergence of resistant strains with no mutations in either rdxA or frxA, indicated that the molecular basis of H. pylori resistance to metronidazole required further characterization. The rdxA and frxA genes of four matched pairs of metronidazole-susceptible and -resistant strains were sequenced. The resistant strains had mutations in either rdxA, frxA, neither gene, or both genes. The reduction rates of five substrates suggested that metabolic differences between susceptible and resistant strains cannot be explained only by mutations in rdxA and/or frxA. A more global approach to understanding the resistance phenotype was taken by employing two-dimensional gel electrophoresis combined with tandem mass spectrometry analyses to identify proteins differentially expressed by the matched pair of strains with no mutations in rdxA or frxA. Proteins involved in the oxireduction of ferredoxin were downregulated in the resistant strain. Other redox enzymes, such as thioredoxin reductase, alkyl hydroperoxide reductase, and superoxide dismutase, showed a pI change in the resistant strain. The data suggested that metronidazole resistance involved more complex metabolic changes than specific gene mutations, and they provided evidence of a role for the intracellular redox potential in the development of resistance.

The relationship between virulence factors of Helicobacter pylori and severity of gastritis in infected patients

The outcome of Helicobacter pylori infection has been related to specific virulence-associated bacterial genotypes. The best known genotypic virulence factors of H. pylori are cytotoxin-associated gene A (cagA) and vacuolating cytotoxin gene A (vacA). The objective of this study was to assess the relationship between H. pylori cagA and vacA status and histopathological findings. Esophagogastrodoedonoscopy was performed in 80 dyspeptic patients. Antrum and corpus biopsies were obtained for isolation of H. pylori and for histopathological assessment. The polymerase chain reaction was used to detect cagA and vacA genes of H. pylori using specific primers. Biopsy samples were stained with hematoxylin and eosin, and histopathological findings were graded using the "updated Sydney system". H. pylori from 57 of the 80 patients was incubated. Of the 57 patients, 44 were cagA positive. In the corpus biopsy specimens there was a significant relationship between the density of H. pylori colonization (P = 0.02) and chronic inflammation (P = 0.02) and cagA-positive genotypes. In the antrum specimens there was a significant relationship between cagA positivity and neutrophil activity (P = 0.003) and glandular atrophy (P = 0.002), but not with H. pylori density, chronic inflammation, and intestinal metaplasia. The odds ratio of cagA-positive vs. cagA-negative strains for the presence of glandular atrophy, irrespective of grading and of gastric localization, was 4.62 (95% CI, 1.18-18.08, P = 0.041). No significant relationships were observed between vacA s1 and s2 genotypes and histopathological parameters. Corpus neutrophil infiltration was found to be more severe in the m1 group than in the m2 group (P = 0.004). Other histopathological features showed no difference between m1 and m2 genotypes. In conclusion H. pylori strains showing cagA positivity are associated with more severe gastritis in some histological features but virulence factors of H. pylori do not appear to determine the overall pattern of gastritis.

Prevention of cancer through immunization: Prospects and challenges for the 21st century

Persistent infection by several microbial agents is responsible for at least 15% of cancer globally, including most cancers of the liver, stomach, and cervix. The recent development of vaccines that can prevent infection and premalignant disease caused by human papillomaviruses (HPV), which cause virtually all cases of cervical cancer as well as some other cancers, has focused renewed attention on infection control as a means of reducing the global cancer burden. For vaccines to prevent cancer-causing infection with hepatitis C virus, Helicobacter pylori, or Epstein Barr virus, new vaccine technologies to induce more effective protective responses are required. For the two available cancer control vaccines, designed to prevent infection with HPV and hepatitis B virus, the major challenge is to promote effective vaccine deployment through education programs and increased affordability/accessibility for underserved populations, particularly in the developing world, where the cancer burden attributable to infection by these two viruses is greatest.

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.

Circulating insulin-like growth factors in patients infected with Helicobacter pylori

OBJECTIVES

The level of insulin-like growth factors (IGFs) and their binding proteins may change in acutely ill humans. The aim of this work was to examine the changes in the IGF system in patients suffering from infection induced by Helicobacter pylori (H. pylori).

DESIGN AND METHODS

The serum concentrations of IGF-I, IGF-II and cortisol were measured by radioimmunoassay. IGFBP patterns were characterized by ligand-affinity blotting, and a lectin-binding assay was used to investigate the possible changes in the glycocomponent of IGFBP-3.

RESULTS

Both IGF-I and IGF-II concentrations were significantly lower in patients with H. pylori infection (P < 0.001 for IGF-I and P = 0.016 for IGF-II) compared to healthy individuals, whereas the level of cortisol was significantly elevated in analyzed patients (P < 0.001). Autoradiography demonstrated the increased presence of IGFBP-2 and IGFBP-1, together with a decreased level of IGFBP-3.

CONCLUSIONS

The circulating IGF/IGFBP system is altered in patients infected with H. pylori. The increased level of cortisol suggests the involvement of the hypothalamic/pituitary/adrenal axis that stimulates the elevation of blood glucose, probably in coordination with decreased IGF activity to minimize anabolic metabolism.

The Helicobacter pylori flbA flagellar biosynthesis and regulatory gene is required for motility and virulence and modulates urease of H. pylori and Proteus mirabilis

Helicobacter pylori and Proteus mirabilis ureases are nickel-requiring metallo-enzymes that hydrolyse urea to NH3 and CO2. In both H. pylori and in an Escherichia coli model of H. pylori urease activity, a high affinity nickel transporter, NixA, is required for optimal urease activity, whereas the urea-dependent UreR positive transcriptional activator governs optimal urease expression in P. mirabilis. The H. pylori flbA gene is a flagellar biosynthesis and regulatory gene that modulates urease activity in the E. coli model of H. pylori urease activity. All flbA mutants of eight strains of H. pylori were non-motile and five had a strain-dependent alteration in urease activity. The flbA gene decreased urease activity 15-fold when expressed in E. coli containing the H. pylori urease locus and the nixA gene; this was reversed by disruption of flbA. The flbA gene decreased nixA transcription. flbA also decreased urease activity three-fold in E. coli containing the P. mirabilis urease locus in a urea- and UreR-dependent fashion. Here the flbA gene repressed the P. mirabilis urease promoter. Thus, FlbA decreased urease activity of both H. pylori and P. mirabilis, but through distinct mechanisms. H. pylori wild-type strain SS1 colonised gerbils at a mean of 5.4 x 10(6) cfu/g of antrum and caused chronic gastritis and lesions in the antrum. In contrast, the flbA mutant did not colonise five of six gerbils and caused no lesions, indicating that motility mediated by flbA was required for colonisation. Because FlbA regulates flagellar biosynthesis and secretion, as well as forming a structural component of the flagellar secretion apparatus, two seemingly unrelated virulence attributes, motility and urease, may be coupled in H. pylori and P. mirabilis and possibly also in other motile, ureolytic bacteria.

Host cell signaling in Helicobacter pylori infection

Helicobacter pylori represents a highly successful human microbial pathogen that has infected approximately half of the world's population. This gram-negative microorganism colonizes the human epithelial layer in the stomach and induces a state of chronic inflammation that does not resolve the underlying infection and often leads to gastric or duodenal ulcers, or more rarely to gastric cancer. Among the reactions in H. pylori-infected epithelial cells the induction of proinflammatory cytokines, cell spreading and movement, as well as a scattered phenotype appear strictly dependent on the expression of pathogenicity island-encoded proteins in H. pylori. This review will discuss the features of the H. pylori-induced signal transduction leading to changes in host cellular function. Topics discussed comprise the signaling and the phenotypes associated with the type IV secretion system, the activation of target genes involved in gastric physiology, and putative mechanisms leading to the development of gastric cancer.