Helicobacter pylori counteracts the apoptotic action of its VacA toxin by injecting the CagA protein into gastric epithelial cells. PLoS Pathog. 2009;5:e1000603. [PMID: 19798427 PMCID: PMC2745580 DOI: 10.1371/journal.ppat.1000603]

Exploring the pathogenesis of chronic atrophic gastritis with atherosclerosis via microarray data analysis

Although several studies have reported a link between chronic atrophic gastritis (CAG) and atherosclerosis, the underlying mechanisms have not been elucidated. The present study aimed to investigate the molecular mechanisms common to both diseases from a bioinformatics perspective. Gene expression profiles were obtained from the Gene Expression Omnibus database. Data on atherosclerosis and CAG were downloaded from the GSE28829 and GSE60662 datasets, respectively. We identified the differentially expressed genes co-expressed in CAG and atherosclerosis before subsequent analyses. We constructed and identified the hub genes and performed functional annotation. Finally, the transcription factor (TF)-target genes regulatory network was constructed. In addition, we validated core genes and certain TFs. We identified 116 common differentially expressed genes after analyzing the 2 datasets (GSE60662 and GSE28829). Functional analysis highlighted the significant contribution of immune responses and the positive regulation of tumor necrosis factor production and T cells. In addition, phagosomes, leukocyte transendothelial migration, and cell adhesion molecules strongly correlated with both diseases. Furthermore, 16 essential hub genes were selected with cytoHubba, including PTPRC, TYROBP, ITGB2, LCP2, ITGAM, FCGR3A, CSF1R, IRF8, C1QB, TLR2, IL10RA, ITGAX, CYBB, LAPTM5, CD53, CCL4, and LY86. Finally, we searched for key gene-related TFs, especially SPI1. Our findings reveal a shared pathogenesis between CAG and atherosclerosis. Such joint pathways and hub genes provide new insights for further studies.

There Are No Insurmountable Barriers: Passage of the Helicobacter pylori VacA Toxin from Bacterial Cytoplasm to Eukaryotic Cell Organelle

The Gram-negative bacterium Helicobacter pylori is a very successful pathogen, one of the most commonly identified causes of bacterial infections in humans worldwide. H. pylori produces several virulence factors that contribute to its persistence in the hostile host habitat and to its pathogenicity. The most extensively studied are cytotoxin-associated gene A (CagA) and vacuolating cytotoxin A (VacA). VacA is present in almost all H. pylori strains. As a secreted multifunctional toxin, it assists bacterial colonization, survival, and proliferation during long-lasting infections. To exert its effect on gastric epithelium and other cell types, VacA undergoes several modifications and crosses multiple membrane barriers. Once inside the gastric epithelial cell, VacA disrupts many cellular-signaling pathways and processes, leading mainly to changes in the efflux of various ions, the depolarization of membrane potential, and perturbations in endocytic trafficking and mitochondrial function. The most notable effect of VacA is the formation of vacuole-like structures, which may lead to apoptosis. This review focuses on the processes involved in VacA secretion, processing, and entry into host cells, with a particular emphasis on the interaction of the mature toxin with host membranes and the formation of transmembrane pores.

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.

Pathogenomics of Helicobacter pylori

The human stomach bacterium Helicobacter pylori, the causative agent of gastritis, ulcers and adenocarcinoma, possesses very high genetic diversity. H. pylori has been associated with anatomically modern humans since their origins over 100,000 years ago and has co-evolved with its human host ever since. Predominantly intrafamilial and local transmission, along with genetic isolation, genetic drift, and selection have facilitated the development of distinct bacterial populations that are characteristic for large geographical areas. H. pylori utilizes a large arsenal of virulence and colonization factors to mediate the interaction with its host. Those include various adhesins, the vacuolating cytotoxin VacA, urease, serine protease HtrA, the cytotoxin-associated genes pathogenicity island (cagPAI)-encoded type-IV secretion system and its effector protein CagA, all of which contribute to disease development. While many pathogenicity-related factors are present in all strains, some belong to the auxiliary genome and are associated with specific phylogeographic populations. H. pylori is naturally competent for DNA uptake and recombination, and its genome evolution is driven by extraordinarily high recombination and mutation rates that are by far exceeding those in other bacteria. Comparative genome analyses revealed that adaptation of H. pylori to individual hosts is associated with strong selection for particular protein variants that facilitate immune evasion, especially in surface-exposed and in secreted virulence factors. Recent studies identified single-nucleotide polymorphisms (SNPs) in H. pylori that are associated with the development of severe gastric disease, including gastric cancer. Here, we review the current knowledge about the pathogenomics of H. pylori.

Gastric Epithelial Barrier Disruption, Inflammation and Oncogenic Signal Transduction by Helicobacter pylori

Helicobacter pylori exemplifies one of the most favourable bacterial pathogens worldwide. The bacterium colonizes the gastric mucosa in about half of the human population and constitutes a major risk factor for triggering gastric diseases such as stomach cancer. H. pylori infection represents a prime example of chronic inflammation and cancer-inducing bacterial pathogens. The microbe utilizes a remarkable set of virulence factors and strategies to control cellular checkpoints of inflammation and oncogenic signal transduction. This chapter emphasizes on the pathogenicity determinants of H. pylori such as the cytotoxin-associated genes pathogenicity island (cagPAI)-encoded type-IV secretion system (T4SS), effector protein CagA, lipopolysaccharide (LPS) metabolite ADP-glycero-β-D-manno-heptose (ADP-heptose), cytotoxin VacA, serine protease HtrA, and urease, and how they manipulate various key host cell signaling networks in the gastric epithelium. In particular, we highlight the H. pylori-induced disruption of cell-to-cell junctions, pro-inflammatory activities, as well as proliferative, pro-apoptotic and anti-apoptotic responses. Here we review these hijacked signal transduction events and their impact on gastric disease development.

The impact of the human microbiome in tumorigenesis, cancer progression, and biotherapeutic development

Background

Cancer impacts millions of lives globally each year, with approximately 10 million cancer-related deaths recorded worldwide in 2020. Mounting research has recognised the human microbiome as a key area of interest in the pathophysiology of various human diseases including cancer tumorigenesis, progression and in disease outcome. It is suggested that approximately 20% of human cancers may be linked to microbes. Certain residents of the human microbiome have been identified as potentially playing a role, including: Helicobacter pylori, Fusobacterium nucleatum, Escherichia coli, Bacteroides fragilis and Porphyromonas gingivalis.

Main body

In this review, we explore the current evidence that indicate a link between the human microbiome and cancer. Microbiome compositional changes have been well documented in cancer patients. Furthermore, pathogenic microbes harbouring specific virulence factors have been implicated in driving the carcinogenic activity of various malignancies including colorectal, gastric and pancreatic cancer. The associated genetic mechanisms with possible roles in cancer will be outlined. It will be indicated which microbes have a potential direct link with cancer cell proliferation, tumorigenesis and disease progression. Recent studies have also linked certain microbial cytotoxins and probiotic strains to cancer cell death, suggesting their potential to target the tumour microenvironment given that cancer cells are integral to its composition. Studies pertaining to such cytotoxic activity have suggested the benefit of microbial therapies in oncological treatment regimes. It is also apparent that bacterial pathogenic protein products encoded for by certain loci may have potential as oncogenic therapeutic targets given their possible role in tumorigenesis.

Conclusion

Research investigating the impact of the human microbiome in cancer has recently gathered pace. Vast amounts of evidence indicate the human microbiome as a potential player in tumorigenesis and progression. Promise in the development of cancer biomarkers and in targeted oncological therapies has also been demonstrated, although more studies are needed. Despite extensive in vitro and in vivo research, clinical studies involving large cohorts of human patients are lacking. The current literature suggests that further intensive research is necessary to validate both the role of the human microbiome in cancer, and the use of microbiome modification in cancer therapy.

Induction and Regulation of the Innate Immune Response in Helicobacter pylori Infection

Gastric cancer (GC) is the fifth most common cancer and the fourth most common cause of cancer-related death worldwide. The intestinal type of GC progresses from acute to chronic gastritis, multifocal atrophic gastritis, intestinal metaplasia, dysplasia, and carcinoma. Infection of the stomach by Helicobacter pylori, a Gram-negative bacterium that infects approximately 50% of the world's population, is the causal determinant that initiates the gastric inflammation and then disease progression. In this context, the induction of the innate immune response of gastric epithelial cells and myeloid cells by H. pylori effectors plays a critical role in the outcome of the infection. However, only 1% to 3% of infected patients develop gastric adenocarcinoma, emphasizing that other mechanisms regulate the localized non-specific response, including the gastric microbiota and genetic factors. This review summarizes studies describing the factors that induce and regulate the mucosal innate immune response during H. pylori infection.

Cortactin Promotes Effective AGS Cell Scattering by Helicobacter pylori CagA, but Not Cellular Vacuolization and Apoptosis Induced by the Vacuolating Cytotoxin VacA

Cortactin is an actin-binding protein and actin-nucleation promoting factor regulating cytoskeletal rearrangements in eukaryotes. Helicobacter pylori is a gastric pathogen that exploits cortactin to its own benefit. During infection of gastric epithelial cells, H. pylori hijacks multiple cellular signaling pathways, leading to the disruption of key cell functions. Two bacterial virulence factors play important roles in this scenario, the vacuolating cytotoxin VacA and the translocated effector protein CagA of the cag type IV secretion system (T4SS). Specifically, by overruling the phosphorylation status of cortactin, H. pylori alternates the activity of molecular interaction partners of this important protein, thereby manipulating the performance of cytoskeletal rearrangements, endosomal trafficking and cell movement. Based on shRNA knockdown and other studies, it was previously reported that VacA utilizes cortactin for its cellular uptake, intracellular travel and induction of apoptosis by a mitochondria-dependent mechanism, while CagA induces cell scattering, motility and elongation. To investigate the role of cortactin in these phenotypes in more detail, we produced a complete knockout mutant of cortactin in the gastric adenocarcinoma cell line AGS by CRISPR-Cas9. These cells were infected with H. pylori wild-type or various isogenic mutant strains. Unexpectedly, cortactin deficiency did not prevent the uptake and formation of VacA-dependent vacuoles, nor the induction of apoptosis by internalized VacA, while the induction of T4SS- and CagA-dependent AGS cell movement and elongation were strongly reduced. Thus, we provide evidence that cortactin is required for the function of internalized CagA, but not VacA.

Under the Radar: Strategies Used by Helicobacter pylori to Evade Host Responses

The body depends on its physical barriers and innate and adaptive immune responses to defend against the constant assault of potentially harmful microbes. In turn, successful pathogens have evolved unique mechanisms to adapt to the host environment and manipulate host defenses. Helicobacter pylori (Hp), a human gastric pathogen that is acquired in childhood and persists throughout life, is an example of a bacterium that is very successful at remodeling the host-pathogen interface to promote a long-term persistent infection. Using a combination of secreted virulence factors, immune subversion, and manipulation of cellular mechanisms, Hp can colonize and persist in the hostile environment of the human stomach. Here, we review the most recent and relevant information regarding how this successful pathogen overcomes gastric epithelial host defense responses to facilitate its own survival and establish a chronic infection. Expected final online publication date for the Annual Review of Physiology, Volume 84 is February 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

The Helicobacter pylori type IV secretion system upregulates epithelial cortactin expression by a CagA- and JNK-dependent pathway

Cortactin represents an important actin-binding factor, which controls actin-cytoskeletal remodelling in host cells. In this way, cortactin has been shown to exhibit crucial functions both for cell movement and tumour cell invasion. In addition, the cortactin gene cttn is amplified in various cancer types of humans. Helicobacter pylori is the causative agent of multiple gastric diseases and represents a significant risk factor for the development of gastric adenocarcinoma. It has been repeatedly shown that H. pylori manipulates cancer-related signal transduction events in infected gastric epithelial cells such as the phosphorylation status of cortactin. In fact, H. pylori modifies the activity of cortactin's binding partners to stimulate changes in the actin-cytoskeleton, cell adhesion and motility. Here we show that H. pylori infection of cultured AGS and Caco-2 cells for 24-48 hr leads to the overexpression of cortactin by 2-3 fold at the protein level. We demonstrate that this activity requires the integrity of the type IV secretion system (T4SS) encoded by the cag pathogenicity island (cagPAI) as well as the translocated effector protein CagA. We further show that ectopic expression of CagA is sufficient to stimulate cortactin overexpression. Furthermore, phosphorylation of CagA at the EPIYA-repeat region is not required, suggesting that this CagA activity proceeds in a phosphorylation-independent fashion. Inhibitor studies further demonstrate that the involved signalling pathway comprises the mitogen-activated protein kinase JNK (c-Jun N-terminal kinase), but not ERK1/2 or p38. Taken together, using H. pylori as a model system, this study discovered a previously unrecognised cortactin activation cascade by a microbial pathogen. We suggest that H. pylori targets cortactin to manipulate the cellular architecture and epithelial barrier functions that can impact gastric cancer development. TAKE AWAYS: Helicobacter pylori infection induces overexpression of cortactin at the protein level Cortactin upregulation requires the T4SS and effector protein CagA Ectopic expression of CagA is sufficient to stimulate cortactin overexpression Overexpression of cortactin proceeds CagA phosphorylation-independent The involved host cell signalling pathway comprises the MAP kinase JNK.

The Spectrum of Helicobacter-Mediated Diseases

Helicobacter pylori is the leading cause of peptic ulcer disease. The infection has been implicated in more than 75% of duodenal ulcer cases and 17% of gastric ulcer cases. H. pylori has been classified as a human carcinogen, since it is the main cause of distal gastric adenocarcinoma and B cell mucosa-associated lymphoid tissue lymphoma. Evidence also links H. pylori with extragastric conditions including iron deficiency anemia, idiopathic thrombocytopenic purpura, and vitamin B₁₂ deficiency. Studies indicate that H. pylori may be protective against other conditions of the gastrointestinal tract (e.g., reflux esophagitis and related pathologies) and elsewhere in the body (e.g., asthma). The infection is asymptomatic in the vast majority of cases; more serious outcomes occur in only 10-15% of infected individuals. Despite extensive research over the past 3 decades, there is no effective vaccine, and the circumstances leading to disease development remain unclear. In addition, there is now a growing prevalence of antimicrobial resistance in H. pylori. This review discusses these important issues.

H. pylori infection confers resistance to apoptosis via Brd4-dependent BIRC3 eRNA synthesis

H. pylori infection is one of the leading causes of gastric cancer and the pathogenicity of H. pylori infection is associated with its ability to induce chronic inflammation and apoptosis resistance. While H. pylori infection-induced expression of pro-inflammatory cytokines for chronic inflammation is well studied, the molecular mechanism underlying the apoptosis resistance in infected cells is not well understood. In this study, we demonstrated that H. pylori infection-induced apoptosis resistance in gastric epithelial cells triggered by Raptinal, a drug that directly activates caspase-3. This resistance resulted from the induction of cIAP2 (encoded by BIRC3) since depletion of BIRC3 by siRNA or inhibition of cIAP2 via BV6 reversed H. pylori-suppressed caspase-3 activation. The induction of cIAP2 was regulated by H. pylori-induced BIRC3 eRNA synthesis. Depletion of BIRC3 eRNA decreased H. pylori-induced cIAP2 and reversed H. pylori-suppressed caspase-3 activation. Mechanistically, H. pylori stimulated the recruitment of bromodomain-containing factor Brd4 to the enhancer of BIRC3 and promoted BIRC3 eRNA and mRNA synthesis. Inhibition of Brd4 diminished the expression of BIRC3 eRNA and the anti-apoptotic response to H. pylori infection. Importantly, H. pylori isogenic cagA-deficient mutant failed to activate the synthesis of BIRC3 eRNA and the associated apoptosis resistance. Finally, in primary human gastric epithelial cells, H. pylori also induced resistance to Raptinal-triggered caspase-3 activation by activating the Brd4-dependent BIRC3 eRNA synthesis in a CagA-dependent manner. These results identify a novel function of Brd4 in H. pylori-mediated apoptosis resistance via activating BIRC3 eRNA synthesis, suggesting that Brd4 could be a potential therapeutic target for H. pylori-induced gastric cancer.

Role of vacuolating cytotoxin A in Helicobacter pylori infection and its impact on gastric pathogenesis

Introduction Helicobacter pylori causes, via the influence of several virulence factors, persistent infection of the stomach, which leads to severe complications. Vacuolating cytotoxin A (VacA) is observed in almost all clinical strains of H. pylori; however, only some strains produce the toxigenic and pathogenic VacA, which is influenced by the gene sequence variations. VacA exerts its action by causing cell vacuolation and apoptosis. We performed a PubMed search to review the latest literatures published in English language. Areas covered Articles regarding H. pylori VacA and its genotypes, architecture, internalization, and role in gastric infection and pathogenicity are reviewed. We included the search for recently published literature until January 2020. Expert opinion H. pylori VacA plays a crucial role in severe gastric pathogenicity. In addition, VacA mediated in vivo bacterial survival leads to persistent infection and an enhanced bacterial evasion from the action of antibiotics and the innate host defense system, which leads to drug evasion. VacA as a co-stimulator for the CagA phosphorylation may exert a synergistic effect playing an important role in the CagA-mediated pathogenicity.

Chronic in vivo exposure to Helicobacter pylori VacA: Assessing the efficacy of automated and long-term intragastric toxin infusion

Helicobacter pylori (Hp) secrete VacA, a diffusible pore-forming exotoxin that is epidemiologically linked to gastric disease in humans. In vitro studies indicate that VacA modulates gastric epithelial and immune cells, but the in vivo contributions of VacA as an important determinant of Hp colonization and chronic infection remain poorly understood. To identify perturbations in the stomachs of C57BL/6 or BALB/C mice that result specifically from extended VacA exposure, we evaluated the efficacy of administering purified toxin using automated infusion via surgically-implanted, intragastric catheters. At 3 and 30 days of interrupted infusion, VacA was detected in association with gastric glands. In contrast to previously-reported tissue damage resulting from short term exposure to Hp extracts administered by oral gavage, extended infusion of VacA did not damage stomach, esophageal, intestinal, or liver tissue. However, several alterations previously reported during Hp infection were detected in animals infused with VacA, including reduction of the gastric mucus layer, and increased vacuolation of parietal cells. VacA infusion invoked an immune response, as indicated by the detection of circulating VacA antibodies. These foundational studies support the use of VacA infusion for identifying gastric alterations that are unambiguously attributable to long-term exposure to toxin.

Immune-Inflammation in Atherosclerosis: A New Twist in an Old Tale

Background and Objective:

Atherosclerosis, a chronic and progressive inflammatory disease, is triggered by the activation of endothelial cells followed by infiltration of innate and adaptive immune cells including monocytes and T cells in arterial walls. Major populations of T cells found in human atherosclerotic lesions are antigen-specific activated CD4+ effectors and/or memory T cells from Th1, Th17, Th2 and Treg subsets. In this review, we will discuss the significance of T cell orchestrated immune inflammation in the development and progression of atherosclerosis.

Discussion:

Pathogen/oxidative stress/lipid induced primary endothelial wound cannot develop to a full-blown atherosclerotic lesion in the absence of chronically induced inflammation. While the primary inflammatory response might be viewed as a lone innate response, the persistence of such a profound response over time must be (and is) associated with diverse local and systemic T cell responses. The interplay between T cells and innate cells contributes to a phenomenon called immuneinflammation and has an impact on the progression and outcome of the lesion. In recent years immuneinflammation, an old term, has had a comeback in connecting the puzzle pieces of chronic inflammatory diseases.

Conclusion:

Taking one-step back and looking from afar at the players of immune-inflammation may help us provide a broader perspective of these complicated interactions. This may lead to the identification of new drug targets and the development of new therapies as well as preventative measures.

The correlation between lncRNAs and Helicobacter pylori in gastric cancer

Helicobacter pylori infection performs a key role in gastric tumorigenesis. Long non-coding RNAs (lncRNAs) have demonstrated a great potential to be regarded as effective malignancy biomarkers for various gastrointestinal diseases including gastric cancer (GC). The present review highlights the relationship between lncRNAs and H. pylori in GC. Several studies have examined not only the involvement of lncRNAs in H. pylori-associated GC progression but also their molecular mechanisms of action. Among the pertinent studies, some have addressed the effects of H. pylori infection on modulatory networks of lncRNAs, while others have evaluated the effects of changes in the expression level of lncRNAs in H. pylori-associated gastric diseases, especially GC. The relationship between lncRNAs and H. pylori was found to be modulated by various molecular pathways.

Stenotrophomonas maltophilia Encodes a VirB/VirD4 Type IV Secretion System That Modulates Apoptosis in Human Cells and Promotes Competition against Heterologous Bacteria, Including Pseudomonas aeruginosa

Stenotrophomonas maltophilia is an emerging opportunistic and nosocomial pathogen. S. maltophilia is also a risk factor for lung exacerbations in cystic fibrosis patients. S. maltophilia attaches to various mammalian cells, and we recently documented that the bacterium encodes a type II secretion system which triggers detachment-induced apoptosis in lung epithelial cells. We have now confirmed that S. maltophilia also encodes a type IVA secretion system (VirB/VirD4 [VirB/D4] T4SS) that is highly conserved among S. maltophilia strains and, looking beyond the Stenotrophomonas genus, is most similar to the T4SS of Xanthomonas To define the role(s) of this T4SS, we constructed a mutant of strain K279a that is devoid of secretion activity due to loss of the VirB10 component. The mutant induced a higher level of apoptosis upon infection of human lung epithelial cells, indicating that a T4SS effector(s) has antiapoptotic activity. However, when we infected human macrophages, the mutant triggered a lower level of apoptosis, implying that the T4SS also elaborates a proapoptotic factor(s). Moreover, when we cocultured K279a with strains of Pseudomonas aeruginosa, the T4SS promoted the growth of S. maltophilia and reduced the numbers of heterologous bacteria, signaling that another effector(s) has antibacterial activity. In all cases, the effect of the T4SS required S. maltophilia contact with its target. Thus, S. maltophilia VirB/D4 T4SS appears to secrete multiple effectors capable of modulating death pathways. That a T4SS can have anti- and prokilling effects on different targets, including both human and bacterial cells, has, to our knowledge, not been seen before.

Crosstalk Between DNA Damage and Inflammation in the Multiple Steps of Gastric Carcinogenesis

Over the last years, intensive investigations in molecular biology and cell physiology extended tremendously the knowledge about the association of inflammation and cancer. In frame of this paradigm, the human pathogen Helicobacter pylori triggers gastritis and gastric ulcer disease, and contributes to the development of gastric cancer. Mechanisms, by which the bacteria-induced inflammation in gastric mucosa leads to intestinal metaplasia and carcinoma, are represented in this review. An altered cell-signaling response and increased production of free radicals by epithelial and immune cells account for the accumulation of DNA damage in gastric mucosa, if infection stays untreated. Host genetics and environmental factors, especially diet, can accelerate the process, which offers the opportunity of intervention based on a balanced nutrition. It is supposed that inflammation might influence stem- or progenitor cells in gastric tissue predisposing for metaplasia or tumor relapse. Herein, DNA is strongly mutated and labile, which restricts therapy options. Thus, the understanding of the mechanisms that underlie gastric carcinogenesis will be of preeminent importance for the development of strategies for screening and early detection. As most gastric cancer patients face late-stage disease with a poor overall survival, the development of multi-targeted therapeutic intervention strategies is a major challenge for the future.

Intracellular Degradation of Helicobacter pylori VacA Toxin as a Determinant of Gastric Epithelial Cell Viability

Helicobacter pylori VacA is a secreted pore-forming toxin that induces cell vacuolation in vitro and contributes to the pathogenesis of gastric cancer and peptic ulcer disease. We observed that purified VacA has relatively little effect on the viability of AGS gastric epithelial cells, but the presence of exogenous weak bases such as ammonium chloride (NH₄Cl) enhances the susceptibility of these cells to VacA-induced vacuolation and cell death. Therefore, we tested the hypothesis that NH₄Cl augments VacA toxicity by altering the intracellular trafficking of VacA or inhibiting intracellular VacA degradation. We observed VacA colocalization with LAMP1- and LC3-positive vesicles in both the presence and absence of NH₄Cl, indicating that NH₄Cl does not alter VacA trafficking to lysosomes or autophagosomes. Conversely, we found that supplemental NH₄Cl significantly increases the intracellular stability of VacA. By conducting experiments using chemical inhibitors, stable ATG5 knockdown cell lines, and ATG16L1 knockout cells (generated using CRISPR/Cas9), we show that VacA degradation is independent of autophagy and proteasome activity but dependent on lysosomal acidification. We conclude that weak bases like ammonia, potentially generated during H. pylori infection by urease and other enzymes, enhance VacA toxicity by inhibiting toxin degradation.

Helicobacter pylori VacA, a distinct toxin exerts diverse functionalities in numerous cells: An overview

BACKGROUND

Helicobacter pylori, gastric cancer-causing bacteria, survive in their gastric environment of more than 50% of the world population. The presence of H. pylori in the gastric vicinity promotes the development of various diseases including peptic ulcer and gastric carcinoma. H. pylori produce and secret Vacuolating cytotoxin A (VacA), a major toxin facilitating the bacteria against the host defense system. The toxin causes multiple effects in epithelial cells and immune cells, especially T cells, B cells, and Macrophages.

METHODS

This review describes the diverse functionalities of protein toxin VacA. The specific objective of this review is to address the overall structure, mechanism, and functions of VacA in various cell types. The recent advancements are summarized and discussed and thus conclusion is drawn based on the overall reported evidences.

RESULTS

The searched articles on H. pylori VacA were evaluated and limited up to 66 articles for this review. The articles were divided into four major categories including articles on vacA gene, VacA toxin, distinct effects of VacA toxin, and their effects on various cells. Based on these studies, the review article was prepared.

CONCLUSIONS

This review describes an overview of how VacA is secreted by H. pylori and contributes to colonization and virulence in multiple ways by affecting epithelial cells, T cells, Dendritic cells, B cells, and Macrophages. The reported evidence suggests that the comprehensive outlook need to be developed for understanding distinctive functionalities of VacA.

VacA promotes CagA accumulation in gastric epithelial cells during Helicobacter pylori infection

Helicobacter pylori (H. pylori) is the causative agent of gastric cancer, making it the only bacterium to be recognized as a Class I carcinogen by the World Health Organization. The virulence factor cytotoxin associated gene A (CagA) is a known oncoprotein that contributes to the development of gastric cancer. The other major virulence factor vacuolating cytotoxin A (VacA), disrupts endolysosomal vesicular trafficking and impairs the autophagy pathway. Studies indicate that there is a functional interplay between these virulence factors by unknown mechanisms. We show that in the absence of VacA, both host-cell autophagy and the proteasome degrade CagA during infection with H. pylori. In the presence of VacA, CagA accumulates in gastric epithelial cells. However, VacA does not affect proteasome function during infection with H. pylori suggesting that VacA−disrupted autophagy is the predominant means by which CagA accumulates. Our studies support a model where in the presence of VacA, CagA accumulates in dysfunctional autophagosomes providing a possible explanation for the functional interplay of VacA and CagA.

Structural-dynamic insights into the H. pylori cytotoxin-associated gene A (CagA) and its abrogation to interact with the tumor suppressor protein ASPP2 using decoy peptides

Helicobacter pylori (H. pylori) is one of the most extensively studied Gram-negative bacteria due to its implication in gastric cancer. The oncogenicity of H. pylori is associated with cytotoxin-associated gene A (CagA), which is injected into epithelial cells lining the stomach. Both the C- and N-termini of CagA are involved in the interaction with several host proteins, thereby disrupting vital cellular functions, such as cell adhesion, cell cycle, intracellular signal transduction, and cytoskeletal structure. The N-terminus of CagA interacts with the tumor-suppressing protein, apoptosis-stimulating protein of p53 (ASPP2), subsequently disrupting the apoptotic function of tumor suppressor gene p53. Here, we present the in-depth molecular dynamic mechanism of the CagA-ASPP2 interaction and highlight hot-spot residues through in silico mutagenesis. Our findings are in agreement with previous studies and further suggest other residues that are crucial for the CagA-ASPP2 interaction. Furthermore, the ASPP2-binding pocket possesses potential druggability and could be engaged by decoy peptides, identified through a machine-learning system and suggested in this study. The binding affinities of these peptides with CagA were monitored through extensive computational procedures and reported herein. While CagA is crucial for the oncogenicity of H. pylori, our designed peptides possess the potential to inhibit CagA and restore the tumor suppressor function of ASPP2.

Helicobacter pylori Infection Modulates Host Cell Metabolism through VacA-Dependent Inhibition of mTORC1

Helicobacter pylori (Hp) vacuolating cytotoxin (VacA) is a bacterial exotoxin that enters host cells and induces mitochondrial dysfunction. However, the extent to which VacA-dependent mitochondrial perturbations affect overall cellular metabolism is poorly understood. We report that VacA perturbations in mitochondria are linked to alterations in cellular amino acid homeostasis, which results in the inhibition of mammalian target of rapamycin complex 1 (mTORC1) and subsequent autophagy. mTORC1, which regulates cellular metabolism during nutrient stress, is inhibited during Hp infection by a VacA-dependent mechanism. This VacA-dependent inhibition of mTORC1 signaling is linked to the dissociation of mTORC1 from the lysosomal surface and results in activation of cellular autophagy through the Unc 51-like kinase 1 (Ulk1) complex. VacA intoxication results in reduced cellular amino acids, and bolstering amino acid pools prevents VacA-mediated mTORC1 inhibition. Overall, these studies support a model that Hp modulate host cell metabolism through the action of VacA at mitochondria.

Helicobacter pylori Vacuolating Toxin and Gastric Cancer

Helicobacter pylori VacA is a channel-forming toxin unrelated to other known bacterial toxins. Most H. pylori strains contain a vacA gene, but there is marked variation among strains in VacA toxin activity. This variation is attributable to strain-specific variations in VacA amino acid sequences, as well as variations in the levels of VacA transcription and secretion. In this review, we discuss epidemiologic studies showing an association between specific vacA allelic types and gastric cancer, as well as studies that have used animal models to investigate VacA activities relevant to gastric cancer. We also discuss the mechanisms by which VacA-induced cellular alterations may contribute to the pathogenesis of gastric cancer.

Binding of the Helicobacter pylori OipA causes apoptosis of host cells via modulation of Bax/Bcl-2 levels

The H. pylori outer inflammatory protein A (OipA) is an outer membrane protein that contributes to gastric inflammation. OipA is believed to affect intra-cellular signalling and modulate the host signalling pathways. The aim of the current study was to clarify the role of OipA in H. pylori pathogenesis and its effect on host cell signalling pathways. To this end, the oipA gene was isolated and inserted into cloning and expression vectors. The recombinant plasmid was transferred into an expression host to produce OipA, which was subsequently purified by affinity chromatography and used for antibody production. A confluent monolayer of gastric cell lines was treated with various concentrations of OipA and investigated for attachment, toxicity, and apoptosis and alterations in signalling pathways. OipA bound to gastric cell lines confirming its role in the attachment of H. pylori to host cells. The ratio of Bax/Bcl-2 and caspase3, 8, FasL in the host cells were assessed and the results showed that the Bax/Bcl-2 ratio as well as the level of cleaved-caspase 3 was elevated in OipA-treated cells. These findings suggest that OipA can bind and induce toxic events as well as triggering apoptotic cascade in host gastric cells through intrinsic pathway.

Survival of Helicobacter pylori in gastric acidic territory

BACKGROUND

Helicobacter pylori is well adapted to colonize the epithelial surface of the human gastric mucosa and can cause persistent infections. In order to infect the gastric mucosa, it has to survive in the gastric acidic pH. This organism has well developed mechanisms to neutralize the effects of acidic pH.

OBJECTIVE

This review article was designed to summarize the various functional and molecular aspects by which the bacterium can combat and survive the gastric acidic pH in order to establish the persistent infections.

METHODS

We used the keywords (acid acclimation, gastric acidic environment, H. pylori and survival) in combination or alone for pubmed search of recent scientific literatures. One hundred and forty one papers published between 1989 and 2016 were sorted out. The articles published with only abstracts, other than in English language, case reports and reviews were excluded.

RESULTS

Many literatures describing the role of several factors in acid survival were found. Recently, the role of several other factors has been claimed to participate in acid survival.

CONCLUSION

In conclusion, this organism has well characterized mechanisms for acid survival.

The Human Stomach in Health and Disease: Infection Strategies by Helicobacter pylori

Helicobacter pylori is a bacterial pathogen which commonly colonizes the human gastric mucosa from early childhood and persists throughout life. In the vast majority of cases, the infection is asymptomatic. H. pylori is the leading cause of peptic ulcer disease and gastric cancer, however, and these outcomes occur in 10-15% of those infected. Gastric adenocarcinoma is the third most common cause of cancer-associated death, and peptic ulcer disease is a significant cause of morbidity. Disease risk is related to the interplay of numerous bacterial host and environmental factors, many of which influence chronic inflammation and damage to the gastric mucosa. This chapter summarizes what is known about health and disease in H. pylori infection, and highlights the need for additional research in this area.

Pathogen-induced ubiquitin-editing enzyme A20 bifunctionally shuts off NF-κB and caspase-8-dependent apoptotic cell death

The human pathogen Helicobacter pylori infects more than half of the world’s population and is a paradigm for persistent yet asymptomatic infection but increases the risk for chronic gastritis and gastric adenocarcinoma. For successful colonization, H. pylori needs to subvert the host cell death response, which serves to confine pathogen infection by killing infected cells and preventing malignant transformation. Infection of gastric epithelial cells by H. pylori provokes direct and fast activation of the proinflammatory and survival factor NF-κB, which regulates target genes, such as CXCL8, BIRC3 and TNFAIP3. However, it is not known how H. pylori exploits NF-κB activation and suppresses the inflammatory response and host apoptotic cell death, in order to avert the innate immune response and avoid cell loss, and thereby enhance colonization to establish long-term infection. Here we assign for the first time that H. pylori and also Campylobacter jejuni-induced ubiquitin-editing enzyme A20 bifunctionally terminates NF-κB activity and negatively regulates apoptotic cell death. Mechanistically, we show that the deubiquitinylase activity of A20 counteracts cullin3-mediated K63-linked ubiquitinylation of procaspase-8, therefore restricting the activity of caspase-8. Interestingly, another inducible NF-κB target gene, the scaffold protein p62, ameliorates the interaction of A20 with procaspase-8. In conclusion, pathogen-induced de novo synthesis of A20 regulates the shut-off of the survival factor NF-κB but, on the other hand, also impedes caspase-8-dependent apoptotic cell death so as to promote the persistence of pathogens.

Pleiotropic cytotoxicity of VacA toxin in host cells and its impact on immunotherapy

Introduction: In the recent decades, a number of studies have highlighted the importance of Helicobacter pylori in the initiation and development of peptic ulcer and gastric cancer. Some potential virulence factors (e.g., urease, CagA, VacA, BabA) are exploited by this microorganism, facilitating its persistence through evading human defense mechanisms. Among these toxins and enzymes, vacuolating toxin A (VacA) is of a great importance in the pathogenesis of H. pylori. VacA toxin shows different pattern of cytotoxicity through binding to different cell surface receptors in various cells.

Methods: To highlight attempts in treatment for H. pylori infection, here, we discussed the VacA potential as a candidate for development of vaccine and targeted immunotherapy. Furthermore, we reviewed the related literature to provide key insights on association of the genetic variants of VacA with the toxicity of the toxin in cells.

Results: A number of investigations on the receptor(s) binding of VacA toxin confirmed the pleiotropic nature of VacA that uses a unique mechanism for internalization through some membrane components such as lipid rafts and glycophosphatidylinositol (GPI)-anchored proteins (GPI-AP). Considering the high potency of VacA toxin in the clinical presentations in infection and assisting persistence and colonization of H. pylori, it is considered as one of the pivotal components in production vaccines and monoclonal antibodies (mAbs).

Conclusion: It is possible to generate mAbs with a considerable potential to convert into secretory immunoglobulins that could penetrate into the niche of H. pylori and inhibit its normal functionalities. Further, conjugation of H. pylori targeting Ab fragments with the toxic agents or drug delivery systems (DDSs) offers new generation of H. pylori treatments.

Molecular and Proteomic Analysis of Levofloxacin and Metronidazole Resistant Helicobacter pylori

Antibiotic resistance in bacteria incurs fitness cost, but compensatory mechanisms may ameliorate the cost and sustain the resistance even under antibiotics-free conditions. The aim of this study was to determine compensatory mechanisms of antibiotic resistance in H. pylori. Five strains of levofloxacin-sensitive H. pylori were induced in vitro to develop resistance. In addition, four pairs of metronidazole-sensitive and -resistant H. pylori strains were isolated from patients carrying dual H. pylori populations that consist of both sensitive and resistant phenotypes. Growth rate, virulence and biofilm-forming ability of the sensitive and resistant strains were compared to determine effects of compensatory response. Proteome profiles of paired sensitive and resistant strains were analyzed by liquid chromatography/mass spectrophotometry (LC/MS). Although there were no significant differences in growth rate between sensitive and resistant pairs, bacterial virulence (in terms of abilities to induce apoptosis and form biofilm) differs from pair to pair. These findings demonstrate the complex and strain-specific phenotypic changes in compensation for antibiotics resistance. Compensation for in vitro induced levofloxacin resistance involving mutations of gyrA and gyrB was functionally random. Furthermore, higher protein translation and non-functional protein degradation capabilities in naturally-occuring dual population metronidazole sensitive-resistant strains may be a possible alternative mechanism underlying resistance to metronidazole without mutations in rdxA and frxA. This may explain the lack of mutations in target genes in ~10% of metronidazole resistant strains.

Inflammatory and Apoptotic Regulatory Activity of Tanshinone IIA in Helicobacter pylori-Infected Cells

Helicobacter pylori infections induce host cell inflammation and apoptosis, however, they are conflicting. Tanshinone IIA is an active compound of Salvia miltiorrhiza Bge. In this study, we investigated the regulatory effects of tanshinone IIA on H. pylori-induced inflammation and apoptosis in vitro. Tanshinone IIA treatments (13.6-54.4[Formula: see text][Formula: see text]M) significantly decreased nuclear factor kappa B (NF-kB) and mitogen-activated protein kinase (MAPK) [p-38 and C-terminal Jun-kinase 1/2 (JNK1/2)] protein expressions and inflammatory substance [cyclooxygenase-2 (COX-2), 5-lipooxygenase (5-LOX), intercellular adhesion molecule-1 (ICAM-1), reactive oxygen species (ROS), nitric oxide (NO), inducible nitric oxide synthase (iNOS), interleukin-1[Formula: see text] (IL-1[Formula: see text], IL-6, and IL-8] production in the H. pylori-infected cells. In contrast, tanshinone IIA treatments significantly increased apoptotic relevant protein [Bcl-2-associated X protein (Bax) and caspase 9] expressions and increased mitochondrial transmembrane potential ([Formula: see text] disruption, mitochondrial cytochrome [Formula: see text] (cyt [Formula: see text] release, and caspase cascades. Tanshinone IIA treatments effectively decreased H. pylori-induced inflammation and significantly promoted H. pylori-induced intrinsic apoptosis through NF-kB and MAPK (p-38 and JNK) pathways. Tanshinone IIA has great potential as a candidate to protect host cells from H. pylori-induced severe inflammation and gastric cancer.

Helicobacter pylori infection, H19 and LINC00152 expression in serum and risk of gastric cancer in a Chinese population

Gastric cancer (GC) is a consequence of multifactorial and multistep processes. Helicobacter pylori (H. pylori) infection plays a crucial role in gastric carcinogenesis. Long non-coding RNAs (lncRNAs) have shown great potential as powerful cancer biomarkers. To investigate the possible roles of lncRNAs and H. pylori infection in GC development, we measured expression levels of three lncRNAs (H19, LINC00152, uc001lsz) in serum from a total of 285 Chinese participants using reverse transcription-quantitative polymerase chain reaction. We found significant associations between high expression of both H19 and LINC00152 in serum and increased risk of GC; the adjusted OR for H19 was 2.17 (95% CI: 1.21-3.88), and for LINC00152 was 2.09 (95% CI: 1.18-3.70). Further analyses indicated an elevated risk of GC in subjects with both high H19 expression and H. pylori infection (OR: 13.75, 95% CI: 4.75-39.84). Significant joint effect between LINC00152 and H. pylori infection on risk of GC was also found (OR: 17.49, 95% CI: 4.78-63.92). Serum H19 and LINC00152 may serve as potential biomarkers for diagnosis of GC, particularly for those with H. pylori infection.

An Overview of Helicobacter pylori VacA Toxin Biology

The VacA toxin secreted by Helicobacter pylori enhances the ability of the bacteria to colonize the stomach and contributes to the pathogenesis of gastric adenocarcinoma and peptic ulcer disease. The amino acid sequence and structure of VacA are unrelated to corresponding features of other known bacterial toxins. VacA is classified as a pore-forming toxin, and many of its effects on host cells are attributed to formation of channels in intracellular sites. The most extensively studied VacA activity is its capacity to stimulate vacuole formation, but the toxin has many additional effects on host cells. Multiple cell types are susceptible to VacA, including gastric epithelial cells, parietal cells, T cells, and other types of immune cells. This review focuses on the wide range of VacA actions that are detectable in vitro, as well as actions of VacA in vivo that are relevant for H. pylori colonization of the stomach and development of gastric disease.

Vacuolating cytotoxin A (VacA) - A multi-talented pore-forming toxin from Helicobacter pylori

Helicobacter pylori is associated with severe and chronic diseases of the stomach and duodenum such as peptic ulcer, non-cardial adenocarcinoma and gastric lymphoma, making Helicobacter pylori the only bacterial pathogen which is known to cause cancer. The worldwide rate of incidence for these diseases is extremely high and it is estimated that about half of the world's population is infected with H. pylori. Among the bacterial virulence factors is the vacuolating cytotoxin A (VacA), which represents an important determinant of pathogenicity. Intensive characterization of VacA over the past years has provided insight into an ample variety of mechanisms contributing to host-pathogen interactions. The toxin is considered as an important target for ongoing research for several reasons: i) VacA displays unique features and structural properties and its mechanism of action is unrelated to any other known bacterial toxin; ii) the toxin is involved in disease progress and colonization by H. pylori of the stomach; iii) VacA is a potential and promising candidate for the inclusion as antigen in a vaccine directed against H. pylori and iv) the vacA gene is characterized by a high allelic diversity, and allelic variants contribute differently to the pathogenicity of H. pylori. Despite the accumulation of substantial data related to VacA over the past years, several aspects of VacA-related activity have been characterized only to a limited extent. The biologically most significant effect of VacA activity on host cells is the formation of membrane pores and the induction of vacuole formation. This review discusses recent findings and advances on structure-function relations of the H. pylori VacA toxin, in particular with a view to membrane channel formation, oligomerization, receptor binding and apoptosis.

Helicobacter pylori Diversity and Gastric Cancer Risk

Gastric cancer is a leading cause of cancer-related death worldwide. Helicobacter pylori infection is the strongest known risk factor for this malignancy. An important goal is to identify H. pylori-infected persons at high risk for gastric cancer, so that these individuals can be targeted for therapeutic intervention. H. pylori exhibits a high level of intraspecies genetic diversity, and over the past two decades, many studies have endeavored to identify strain-specific features of H. pylori that are linked to development of gastric cancer. One of the most prominent differences among H. pylori strains is the presence or absence of a 40-kb chromosomal region known as the cag pathogenicity island (PAI). Current evidence suggests that the risk of gastric cancer is very low among persons harboring H. pylori strains that lack the cag PAI. Among persons harboring strains that contain the cag PAI, the risk of gastric cancer is shaped by a complex interplay among multiple strain-specific bacterial factors as well as host factors. This review discusses the strain-specific properties of H. pylori that correlate with increased gastric cancer risk, focusing in particular on secreted proteins and surface-exposed proteins, and describes evidence from cell culture and animal models linking these factors to gastric cancer pathogenesis. Strain-specific features of H. pylori that may account for geographic variation in gastric cancer incidence are also discussed.

Pathobiology of Helicobacter pylori-Induced Gastric Cancer

Colonization of the human stomach by Helicobacter pylori and its role in causing gastric cancer is one of the richest examples of a complex relationship among human cells, microbes, and their environment. It is also a puzzle of enormous medical importance given the incidence and lethality of gastric cancer worldwide. We review recent findings that have changed how we view these relationships and affected the direction of gastric cancer research. For example, recent data have indicated that subtle mismatches between host and microbe genetic traits greatly affect the risk of gastric cancer. The ability of H pylori and its oncoprotein CagA to reprogram epithelial cells and activate properties of stemness show the sophisticated relationship between H pylori and progenitor cells in the gastric mucosa. The observation that cell-associated H pylori can colonize the gastric glands and directly affect precursor and stem cells supports these observations. The ability to mimic these interactions in human gastric organoid cultures as well as animal models will allow investigators to more fully unravel the extent of H pylori control on the renewing gastric epithelium. Finally, our realization that external environmental factors, such as dietary components and essential micronutrients, as well as the gastrointestinal microbiota, can change the balance between H pylori's activity as a commensal or a pathogen has provided direction to studies aimed at defining the full carcinogenic potential of this organism.

Helicobacter pylori CagA Suppresses Apoptosis through Activation of AKT in a Nontransformed Epithelial Cell Model of Glandular Acini Formation

H. pylori infection is the most important environmental risk to develop gastric cancer, mainly through its virulence factor CagA. In vitro models of CagA function have demonstrated a phosphoprotein activity targeting multiple cellular signaling pathways, while cagA transgenic mice develop carcinomas of the gastrointestinal tract, supporting oncogenic functions. However, it is still not completely clear how CagA alters cellular processes associated with carcinogenic events. In this study, we evaluated the capacity of H. pylori CagA positive and negative strains to alter nontransformed MCF-10A glandular acini formation. We found that CagA positive strains inhibited lumen formation arguing for an evasion of apoptosis activity of central acini cells. In agreement, CagA positive strains induced a cell survival activity that correlated with phosphorylation of AKT and of proapoptotic proteins BIM and BAD. Anoikis is a specific type of apoptosis characterized by AKT and BIM activation and it is the mechanism responsible for lumen formation of MCF-10A acini in vitro and mammary glands in vivo. Anoikis resistance is also a common mechanism of invading tumor cells. Our data support that CagA positive strains signaling function targets the AKT and BIM signaling pathway and this could contribute to its oncogenic activity through anoikis evasion.

Molecular Pathogenesis of Helicobacter pylori-Related Gastric Cancer

Helicobacter pylori infection plays a crucial role in gastric carcinogenesis. H pylori exerts oncogenic effects on gastric mucosa through complex interaction between bacterial virulence factors and host inflammatory responses. On the other hand, gastric cancer develops via stepwise accumulation of genetic and epigenetic alterations in H pylori-infected gastric mucosa. Recent comprehensive analyses of gastric cancer genomes indicate a multistep process of genetic alterations as well as possible molecular mechanisms of gastric carcinogenesis. Both genetic processes of gastric cancer development and molecular oncogenic pathways related to H pylori infection are important to completely understand the pathogenesis of H pylori-related gastric cancer.

Reciprocal impact of host factors and Helicobacter pylori genotypes on gastric diseases

AIM: To assess the impact of Helicobacter pylori (H. pylori) genotypes and patient age and sex on the development of gastric diseases.

METHODS: H. pylori-infected patients (n = 233) referred to the endoscopy unit at Tehran University of Medical Sciences (Tehran, Iran) were diagnosed with chronic gastritis (CG), gastric ulcer (GU), or duodenal ulcer (DU). Brucella blood agar was used for biopsy cultures and H. pylori isolation under microaerobic conditions. H. pylori isolates were confirmed with biochemical tests and through amplification of the 16S rRNA gene. DNA was extracted from fresh cultures of the H. pylori isolates and used for amplification of vacA alleles and the cagA gene. Statistical analysis was performed to determine the association between H. pylori genotypes, age (< 40 years vs > 40 years) and sex of the patient, and gastric diseases.

RESULTS: CG was the most prevalent gastric disease (113/233; 48.5%), compared to GU (64/233; 27.5%) and DU (56/233; 24%). More patients were male, and gastric diseases were more frequent in patients > 40 years (P < 0.05). The percentage of CG and GU patients that were male and female did not show a significant difference; however DU was more common in males (P < 0.05). Interestingly, a diagnosis of CG in patients > 40 years was more common in females (18.5%) than males (11.6%) (P = 0.05), whereas a diagnosis of GU or DU in patients > 40 years was more frequent in males (14.6% vs 10.7% and 12.4% vs 4.3%, respectively). Overall, genotyping of the H. pylori isolates revealed that the vacA s1 (82%), vacA m2 (70%), and cagA⁺ (72.5%) alleles were more frequent than vacA s2 (18%), vacA m1 (29.2%), and cagA^- (all P < 0.05). The vacA s1m2cagA⁺ genotype was the most prevalent within the three disease groups. vacA s1m2 frequency was 56.2% with a similar occurrence in all diagnoses, while vacA s1m1 appeared more often in DU patients (33.9%). A genotype of vacA s2m2 occurred in 15% of isolates and was more common in CG patients (21.2%); vacA s2m1 was the least common genotype (3%). The vacA s1 allele was found to be a risk factor for DU, vacA s2 for CG, and vacA s1 and vacA s2 for GU (all P < 0.05). The vacA s2m2 genotype was associated with the development of CG and GU compared to DU (P < 0.05). No correlation was found between vacA m or cagA and gastric diseases.

CONCLUSION: The outcome of H. pylori infection is the result of interaction between bacterial genotypes and the age and sex of infected individuals.

Differential inflammatory response to Helicobacter pylori infection: etiology and clinical outcomes

The bacterial pathogen Helicobacter pylori commonly colonizes the human gastric mucosa during early childhood and persists throughout life. The organism has evolved multiple mechanisms for evading clearance by the immune system and, despite inducing inflammation in the stomach, the majority of infections are asymptomatic. H. pylori is the leading cause of peptic ulcer disease and gastric cancer. However, disease outcomes are related to the pattern and severity of chronic inflammation in the gastric mucosa, which in turn is influenced by both bacterial and host factors. Despite over 2 decades of intensive research, there remains an incomplete understanding of the circumstances leading to disease development, due to the fascinating complexity of the host-pathogen interactions. There is accumulating data concerning the virulence factors associated with increased risk of disease, and the majority of these have pro-inflammatory activities. Despite this, only a small proportion of those infected with virulent strains develop disease. Several H. pylori virulence factors have multiple effects on different cell types, including the induction of pro- and anti-inflammatory, immune stimulatory, and immune modulatory responses. The expression of multiple virulence factors is also often linked, making it difficult to assess the meaning of their effects in isolation. Overall, H. pylori is thought to usually modulate inflammation and limit acute damage to the mucosa, enabling the bacteria to persist. If this delicate balance is disturbed, disease may then develop.

Inflammatory response of macrophages cultured with Helicobacter pylori strains was regulated by miR-155

MicroRNA-155 plays an important role in the inflammatory response macrophages, while present studies identified that miR-155 was up-expressed in gastritis induced by Helicobacter pylori. We found that miR-155 was over expressed in macrophages infected with H. pylori in vivo or in vitro. Subsequently, inflammatory cytokines IL-23, IL-10, TNF-α and IL-8 were increased significantly, and the expression of CD80, CD86 or COX2, NOS2. Were enhanced in H. pylori infection macrophages by regulated with miR-155mimics. Furthermore, the apoptosis of macrophages induced by H. pylori was increased obviously due to the over-expression of miR-155. Therefore, these observations indicated that miR-155 may act as a inflammatory promoter in H. pylori infected macrophages. These findings contribute us to understand the functions of miR-155 in gastritis induced by H. pylori furtherly.

Helicobacter pylori protein JHP0290 exhibits proliferative and anti-apoptotic effects in gastric epithelial cells

The influence of Helicobacter pylori infection on gastric epithelial cell proliferation, apoptosis and signaling pathways contributes to the development of infection-associated diseases. Here we report that JHP0290, which is a poorly functionally characterized protein from H. pylori, regulates multiple responses in human gastric epithelial cells. The differential expression and release of JHP0290 homologues was observed among H. pylori strains. JHP0290 existed in monomeric and dimeric forms in H. pylori cell extracts and culture broth. Recombinant purified JHP0290 (rJHP0290) also showed monomeric and dimeric forms, whereas the rJHP0290 C162A mutant exhibited only a monomeric form. The dimeric form of the protein was found to bind more efficiently to gastric epithelial cells than the monomeric form. The exposure of gastric epithelial cells to rJHP0290 induced proliferation in a dose-dependent manner. Faster progression into the cell cycle was observed in rJHP0290-challenged gastric epithelial cells. Furthermore, we detected an anti-apoptotic effect of rJHP0290 in gastric epithelial cells when the cells were treated with rJHP0290 in combination with Camptothecin (CPT), which is an inducer of apoptosis. CPT-induced caspase 3 activation was significantly reduced in the presence of rJHP0290. In addition, the activation of ERK MAPK and the transcription factor NFκB was observed in rJHP0290-challenged gastric epithelial cells lines. Our results suggest that JHP0290 may affect H. pylori-induced gastric diseases via the regulation of gastric epithelial cell proliferation and anti-apoptotic pathways.

Relationship between tobacco, cagA and vacA i1 virulence factors and bacterial load in patients infected by Helicobacter pylori

Background and Aim

Several biological and epidemiological studies support a relationship between smoking and Helicobacter pylori (H. pylori) to increase the risk of pathology. However, there have been few studies on the potential synergistic association between specific cagA and vacA virulence factors and smoking in patients infected by Helicobacter pylori. We studied the relationship between smoking and cagA, vacA i1 virulence factors and bacterial load in H. pylori infected patients.

Methods

Biopsies of the gastric corpus and antrum from 155 consecutive patients in whom there was clinical suspicion of infection by H. pylori were processed. In 106 patients H. pylori infection was detected. Molecular methods were used to quantify the number of microorganisms and presence of cagA and vacA i1 genes. A standardized questionnaire was used to obtain patients’ clinical data and lifestyle variables, including tobacco and alcohol consumption. Adjusted Odds Ratios (OR_adjusted) were estimated by unconditional logistic regression.

Results

cagA was significantly associated with active-smoking at endoscope: OR_adjusted 4.52. Evidence of association was found for vacA i1 (OR_adjusted 3.15). Bacterial load was higher in active-smokers, although these differences did not yield statistical significance (median of 262.2 versus 79.4 copies of H. pylori per cell).

Conclusions

The association between smoking and a higher risk of being infected by a virulent bacterial population and with higher bacterial load, support a complex interaction between H. pylori infection and environmental factors.

Use of larvae of the wax moth Galleria mellonella as an in vivo model to study the virulence of Helicobacter pylori

Background

Helicobacter pylori is the first bacterium formally recognized as a carcinogen and is one of the most successful human pathogens, as over half of the world’s population is colonized by the bacterium. H. pylori-induced gastroduodenal disease depends on the inflammatory response of the host and on the production of specific bacterial virulence factors. The study of Helicobacter pylori pathogenic action would greatly benefit by easy-to-use models of infection.

Results

In the present study, we examined the effectiveness of the larvae of the wax moth Galleria mellonella as a new model for H. pylori infection. G. mellonella larvae were inoculated with bacterial suspensions or broth culture filtrates from either different wild-type H. pylori strains or their mutants defective in specific virulence determinants, such as VacA, CagA, CagE, the whole pathogenicity island (PAI) cag, urease, and gamma-glutamyl transpeptidase (GGT). We also tested purified VacA cytotoxin. Survival curves were plotted using the Kaplan-Meier method and LD₅₀ lethal doses were calculated. Viable bacteria in the hemocoel were counted at different time points post-infection, while apoptosis in larval hemocytes was evaluated by annexin V staining. We found that wild-type and mutant H. pylori strains were able to survive and replicate in G. mellonella larvae which underwent death rapidly after infection. H. pylori mutant strains defective in either VacA, or CagA, or CagE, or cag PAI, or urease, but not GGT-defective mutants, were less virulent than the respective parental strain. Broth culture filtrates from wild-type strains G27 and 60190 and their mutants replicated the effects observed using their respective bacterial suspension. Also, purified VacA cytotoxin was able to kill the larvae. The killing of larvae always correlated with the induction of apoptosis in hemocytes.

Conclusions

G. mellonella larvae are susceptible to H. pylori infection and may represent an easy to use in vivo model to identify virulence factors and pathogenic mechanisms of H. pylori. The experimental model described can be useful to screen a large number of clinical H. pylori strain and to correlate virulence of H. pylori strains with patients’ disease status.