What a disorder: proinflammatory signaling pathways induced by Helicobacter pylori

The immunopathogenesis of Helicobacter pylori-induced gastric cancer: a narrative review

Helicobacter pylori infection is a well-established risk factor for the development of gastric cancer (GC). Understanding the immunopathogenesis underlying this association is crucial for developing effective preventive and therapeutic strategies. This narrative review comprehensively explores the immunopathogenesis of H. pylori-induced GC by delving into several key aspects, emphasizing the pivotal roles played by H. pylori virulence factors, including cytotoxin-associated gene A (cagA) and vacuolating cytotoxin A (vacA), blood group antigen-binding adhesin (babA), and sialic acid binding adhesin (sabA). Moreover, the review focuses on the role of toll-like receptors (TLRs) and cytokines in the complex interplay between chronic infection and gastric carcinogenesis. Finally, the study examines the association between H. pylori evasion of the innate and adaptive immune response and development of GC. A comprehensive understanding of the immunopathogenesis of H. pylori-induced GC is essential for designing targeted interventions to prevent and manage this disease. Further research is warranted to elucidate the intricate immune responses involved and identify potential therapeutic targets to improve patient outcomes.

Lnc-PLCB1 is stabilized by METTL14 induced m6A modification and inhibits Helicobacter pylori mediated gastric cancer by destabilizing DDX21

Helicobacter pylori (H. pylori) infection is considered to be an important factor in gastric cancer (GC). Long noncoding RNA (lncRNA) and m6A modification are involved in the occurrence and development of GC, but the role of lncRNA m6A modification in the development of GC mediated by H. pylori is still unclear. Here, we found that H. pylori infection downregulated the expression of lnc-PLCB1 through METTL14-mediated m6A modification and IRF2-mediated transcriptional regulation. Overexpression of lnc-PLCB1 inhibited the proliferation and migration of GC cells, while downregulation of lnc-PLCB1 promoted the proliferation and migration ability of GC cells. In addition, clinical analysis showed that lnc-PLCB1 is lower in GC tissues than in normal tissues. Further study found that lnc-PLCB1 reduced the protein stability of its binding protein DEAD-box helicase 21 (DDX21) and then downregulated the expression of CCND1 and Slug, thereby playing tumour suppressing role in the occurrence and development of GC. In conclusion, the METTL14/lnc-PLCB1/DDX21 axis plays an important role in H. pylori-mediated GC, and lnc-PLCB1 can be used as a new target for GC treatment.

Infiltration to infection: key virulence players of Helicobacter pylori pathogenicity

PURPOSE

This study aims to comprehensively review the multifaceted factors underlying the successful colonization and infection process of Helicobacter pylori (H. pylori), a prominent Gram-negative pathogen in humans. The focus is on elucidating the functions, mechanisms, genetic regulation, and potential cross-interactions of these elements.

METHODS

Employing a literature review approach, this study examines the intricate interactions between H. pylori and its host. It delves into virulence factors like VacA, CagA, DupA, Urease, along with phase variable genes, such as babA, babC, hopZ, etc., giving insights about the bacterial perspective of the infection The association of these factors with the infection has also been added in the form of statistical data via Funnel and Forest plots, citing the potential of the virulence and also adding an aspect of geographical biasness to the virulence factors. The biochemical characteristics and clinical relevance of these factors and their effects on host cells are individually examined, both comprehensively and statistically.

RESULTS

H. pylori is a Gram-negative, spiral bacterium that successfully colonises the stomach of more than half of the world's population, causing peptic ulcers, gastric cancer, MALT lymphoma, and other gastro-duodenal disorders. The clinical outcomes of H. pylori infection are influenced by a complex interplay between virulence factors and phase variable genes produced by the infecting strain and the host genetic background. A meta-analysis of the prevalence of all the major virulence factors has also been appended.

CONCLUSION

This study illuminates the diverse elements contributing to H. pylori's colonization and infection. The interplay between virulence factors, phase variable genes, and host genetics determines the outcome of the infection. Despite biochemical insights into many factors, their comprehensive regulation remains an understudied area. By offering a panoramic view of these factors and their functions, this study enhances understanding of the bacterium's perspective, i.e. H. pylori's journey from infiltration to successful establishment within the host's stomach.

Pazopanib alleviates neuroinflammation and protects dopaminergic neurons in LPS-stimulated mouse model by inhibiting MEK4-JNK-AP-1 pathway

Parkinson's disease (PD) is a progressive neurodegenerative disease characterized by the loss of dopaminergic (DA) neurons and the accumulation of Lewy bodies (LB) in the substantia nigra (SN). Evidence shows that microglia-mediated neuroinflammation plays a key role in PD pathogenesis. Using TNF-α as an indicator for microglial activation, we established a cellular model to screen compounds that could inhibit neuroinflammation. From 2471 compounds in a small molecular compound library composed of FDA-approved drugs, we found 77 candidates with a significant anti-inflammatory effect. In this study, we further characterized pazopanib, a pan-VEGF receptor tyrosine kinase inhibitor (that was approved by the FDA for the treatment of advanced renal cell carcinoma and advanced soft tissue sarcoma). We showed that pretreatment with pazopanib (1, 5, 10 μM) dose-dependently suppressed LPS-induced BV2 cell activation evidenced by inhibiting the transcription of proinflammatory factors iNOS, COX2, Il-1β, and Il-6 through the MEK4-JNK-AP-1 pathway. The conditioned medium from LPS-treated microglia caused mouse DA neuronal MES23.5 cell damage, which was greatly attenuated by pretreatment of the microglia with pazopanib. We established an LPS-stimulated mouse model by stereotactic injection of LPS into mouse substantia nigra. Administration of pazopanib (10 mg·kg-1·d-1, i.p., for 10 days) exerted significant anti-inflammatory and neuronal protective effects, and improved motor abilities impaired by LPS in the mice. Together, we discover a promising candidate compound for anti-neuroinflammation and provide a potential repositioning of pazopanib in the treatment of PD.

Low-grade intestinal metaplasia in Indonesia: Insights into the expression of proinflammatory cytokines during Helicobacter pylori infection and unique East-Asian CagA characteristics

Helicobacter pylori infection is a major cause of intestinal metaplasia. In this study, we aimed to understand the reason underlying the low grade and incidence of intestinal metaplasia in Indonesia, based on the expression of genes encoding proinflammatory cytokines in gastric biopsy specimens. The possible reasons for the lesser virulence of the East-Asian-type CagA in Indonesia than that of the Western-type CagA, which is not common in other countries, were also investigated. The mRNA expression of cytokines was evaluated using real-time PCR. CagA characteristics were analyzed using in silico analysis. The expression of cytokines was typically not robust, among H. pylori-infected subjects in Indonesia, despite them predominantly demonstrating the East-Asian-type CagA. This might partially be explained by the characteristics of the East-Asian-type CagA in Indonesia, which showed a higher instability index and required higher energy to interact with proteins related to the cytokine induction pathway compared with the other types (p < 0.001 and p < 0.05, respectively). Taken together, besides the low prevalence of H. pylori, the low inflammatory response of the host and low CagA virulence, even among populations with high infection rates, may play an essential role in the low grade and low incidence of intestinal metaplasia in Indonesia. We believe that these findings would be relevant for better understanding of intestinal metaplasia, which is closely associated with the development of gastric cancer.

Contributions of the receptor for advanced glycation end products axis activation in gastric cancer

Compelling shreds of evidence derived from both clinical and experimental research have demonstrated the crucial contribution of receptor for advanced glycation end products (RAGE) axis activation in the development of neoplasms, including gastric cancer (GC). This new actor in tumor biology plays an important role in the onset of a crucial and long-lasting inflammatory milieu, not only by supporting phenotypic changes favoring growth and dissemination of tumor cells, but also by functioning as a pattern-recognition receptor in the inflammatory response to Helicobacter pylori infection. In the present review, we aim to highlight how the overexpression and activation of the RAGE axis contributes to the proliferation and survival of GC cells as and their acquisition of more invasive phenotypes that promote dissemination and metastasis. Finally, the contribution of some single nucleotide polymorphisms in the RAGE gene as susceptibility or poor prognosis factors is also discussed.

Gastric Stem Cell Biology and Helicobacter pylori Infection

Helicobacter pylori colonizes the human gastric mucosa and persists lifelong. An interactive network between the bacteria and host cells shapes a unique microbial niche within gastric glands that alters epithelial behavior, leading to pathologies such as chronic gastritis and eventually gastric cancer. Gland colonization by the bacterium initiates aberrant trajectories by inducing long-term inflammatory and regenerative gland responses, which involve various specialized epithelial and stromal cells. Recent studies using cell lineage tracing, organoids and scRNA-seq techniques have significantly advanced our knowledge of the molecular "identity" of epithelial and stromal cell subtypes during normal homeostasis and upon infection, and revealed the principles that underly stem cell (niche) behavior under homeostatic conditions as well as upon H. pylori infection. The activation of long-lived stem cells deep in the gastric glands has emerged as a key prerequisite of H. pylori-associated gastric site-specific pathologies such as hyperplasia in the antrum, and atrophy or metaplasia in the corpus, that are considered premalignant lesions. In addition to altering the behaviour of bona fide stem cells, injury-driven de-differentiation and trans-differentation programs, such as "paligenosis", subsequently allow highly specialized secretory cells to re-acquire stem cell functions, driving gland regeneration. This plastic regenerative capacity of gastric glands is required to maintain homeostasis and repair mucosal injuries. However, these processes are co-opted in the context of stepwise malignant transformation in chronic H. pylori infection, causing the emergence, selection and expansion of cancer-promoting stem cells.

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.

3D Human Organoids: The Next "Viral" Model for the Molecular Basis of Infectious Diseases

The COVID-19 pandemic has driven the scientific community to adopt an efficient and reliable model that could keep up with the infectious disease arms race. Coinciding with the pandemic, three dimensional (3D) human organoids technology has also gained traction in the field of infectious disease. An in vitro construct that can closely resemble the in vivo organ, organoid technology could bridge the gap between the traditional two-dimensional (2D) cell culture and animal models. By harnessing the multi-lineage characteristic of the organoid that allows for the recapitulation of the organotypic structure and functions, 3D human organoids have emerged as an essential tool in the field of infectious disease research. In this review, we will be providing a comparison between conventional systems and organoid models. We will also be highlighting how organoids played a role in modelling common infectious diseases and molecular mechanisms behind the pathogenesis of causative agents. Additionally, we present the limitations associated with the current organoid models and innovative strategies that could resolve these shortcomings.

Gastric organoids: Advancing the study of H. pylori pathogenesis and inflammation

For decades, traditional in vitro and in vivo models used for the study of Helicobacter pylori infection have relied heavily on the use of gastric cancer cell lines and rodents. Major challenges faced by these methods have been the inability to study cancer initiation in already cancerous cell lines, and the difficulty in translating results obtained in animal models due to genetic differences. These challenges have prevented a thorough understanding of the pathogenesis of disease and slowed the development of cancer therapies and a suitable vaccine against the pathogen. In recent years, the development of gastric organoids has provided great advantages over the traditional in vivo and in vitro models due to their similarities to the human stomach in vivo, their ease of use, and the capacity for long-term culture. This review discusses the advantages and limitations of existing in vivo and in vitro models of H. pylori infection, and how gastric organoids have been applied to study H. pylori pathogenesis, with a focus on how the pathogen interacts with the gastric epithelium, inflammatory processes, epithelial repair, and cancer initiation. The potential applications of organoids to address more complex questions on the role of hormones, vaccine-induced immunity are also discussed.

Comparative transcriptome analysis to investigate the mechanism of anti-Helicobacter pylori activity of zinc

As a potential anti-Helicobacter pylori agent, zinc causes impairment of Helicobacter pylori growth, and this property of zinc is of broad interest to biological investigators. However, little is known about the molecular mechanisms by which zinc inhibits the growth of Helicobacter pylori. Here, an in vitro experiment revealed that zinc at specific concentrations inhibits Helicobacter pylori growth. Furthermore, an RNA sequencing-based investigation of the global regulatory response to zinc revealed that exposure to zinc altered the Helicobacter pylori transcriptional profile in numerous ways. A high concentration of zinc induced the upregulation of genes related to ribosomal subunit, ribosome biosynthesis, chaperone and adhesins. However, flagellar assembly genes and some type IV secretion system genes were repressed. In addition, the expression levels of some genes that encode transporters of metal ions and that play key roles in Helicobacter pylori pathogenicity were altered under conditions of zinc-induced stress. In summary, high concentrations of zinc initiated antimicrobial activity to Helicobacter pylori under the combined effect of multiple repressed or altered pathogenetic genes and metabolic pathways associated with bacteria growth. This result has significant implications for understanding not only the antimicrobial activity mechanism of zinc but also the role of zinc-mediated homeostasis in Helicobacter pylori.

Helicobacter pylori and the Role of Lipopolysaccharide Variation in Innate Immune Evasion

Helicobacter pylori is an important human pathogen that infects half the human population and can lead to significant clinical outcomes such as acute and chronic gastritis, duodenal ulcer, and gastric adenocarcinoma. To establish infection, H. pylori employs several mechanisms to overcome the innate and adaptive immune systems. H. pylori can modulate interleukin (IL) secretion and innate immune cell function by the action of several virulence factors such as VacA, CagA and the type IV secretion system. Additionally, H. pylori can modulate local dendritic cells (DC) negatively impacting the function of these cells, reducing the secretion of immune signaling molecules, and influencing the differentiation of CD4⁺ T helper cells causing a bias to Th1 type cells. Furthermore, the lipopolysaccharide (LPS) of H. pylori displays a high degree of phase variation and contains human blood group carbohydrate determinants such as the Lewis system antigens, which are proposed to be involved in molecular mimicry of the host. Lastly, the H. pylori group of outer membrane proteins such as BabA play an important role in attachment and interaction with host Lewis and other carbohydrate antigens. This review examines the various mechanisms that H. pylori utilises to evade the innate immune system as well as discussing how the structure of the H. pylori LPS plays a role in immune evasion.

Homeostasis and Cancer Initiation: Organoids as Models to Study the Initiation of Gastric Cancer

Gastric cancer represents a significant disease burden worldwide. The factors that initiate cancer are not well understood. Chronic inflammation such as that triggered by H. pylori infection is the most significant cause of gastric cancer. In recent years, organoid cultures developed from human and animal adult stem cells have facilitated great advances in our understanding of gastric homeostasis. Organoid models are now being exploited to investigate the role of host genetics and bacterial factors on proliferation and DNA damage in gastric stem cells. The impact of a chronic inflammatory state on gastric stem cells and the stroma has been less well addressed. This review discusses what we have learned from the use of organoid models to investigate cancer initiation, and highlights questions on the contribution of the microbiota, chronic inflammatory milieu, and stromal cells that can now be addressed by more complex coculture models.

Importance of cortactin for efficient epithelial NF-ĸB activation by Helicobacter pylori, Salmonella enterica and Pseudomonas aeruginosa, but not Campylobacter spp

Transcription factors of the nuclear factor kappa‐light‐chain‐enhancer of activated B cells (NF-ĸB) family control important signaling pathways in the regulation of the host innate immune system. Various bacterial pathogens in the human gastrointestinal tract induce NF-ĸB activity and provoke pro-inflammatory signaling events in infected epithelial cells. NF-ĸB activation requires the phosphorylation-dependent proteolysis of inhibitor of ĸB (IĸB) molecules including the NF-ĸB precursors through ubiquitin-mediated proteolysis. The canonical NF-ĸB pathway merges on IĸB kinases (IKKs), which are required for signal transduction. Using CRISPR-Cas9 technology, secreted embryonic alkaline phosphatase (SEAP) reporter assays and cytokine enzyme-linked immunosorbent assay (ELISA), we demonstrate that the actin-binding protein cortactin is involved in NF-ĸB activation and subsequent interleukin-8 (IL-8) production upon infection by Helicobacter pylori, Salmonella enterica and Pseudomonas aeruginosa. Our data indicate that cortactin is needed to efficiently activate the c-Sarcoma (Src) kinase, which can positively stimulate NF-ĸB during infection. In contrast, cortactin is not involved in activation of NF-ĸB and IL-8 expression upon infection with Campylobacter species C. jejuni, C. coli or C. consisus, suggesting that Campylobacter species pluralis (spp.) induce a different signaling pathway upstream of cortactin to trigger the innate immune response.

Peripheral Cytokine Levels as a Prognostic Indicator in Gastric Cancer: A Review of Existing Literature

Although strong connections exist between the carcinogenesis of gastric cancer and chronic inflammation, gastric cancer is unique in that the chronic gastritis which frequently precedes carcinogenesis is strongly associated with H. pylori infection. The interplay between H. pylori virulence factors and host immune cells is complex but culminates in the activation of inflammatory pathways and transcription factors such as NF-κB, STAT3, and AP-1, all of which upregulate cytokine production. Due to the key role of cytokines in modulating the immune response against tumour cells as well as possibly stimulating tumour growth and proliferation, different patterns of cytokine secretion may be associated with varying patient outcomes. In relation to gastric cancer, interleukin-6, 8, 10, 17A, TNF, and IFN-γ may have pro-tumour properties, although interleukin-10, TNF, and IFN-γ may have anti-tumour effects. However, due to the lack of studies investigating patient outcomes, only a link between higher interleukin-6 levels and poorer prognosis has been demonstrated. Further investigations which link peripheral cytokine levels to patient prognosis may elucidate important pathological mechanisms in gastric cancer which adversely impact patient survival and allow treatments targeting these processes to be developed.

Cannabidiol selectively modulates interleukin (IL)-1β and IL-6 production in toll-like receptor activated human peripheral blood monocytes

Cannabidiol (CBD) is a major non-euphoric cannabis-derived compound that has become popular in its over-the-counter use. CBD possesses low affinity for cannabinoid receptors, while the primary molecular target(s) by which it mediates biological activity remain poorly defined. Individuals commonly self-medicate using CBD products with little knowledge of its specific immunopharmacological effects on the human immune system; however, research has established primarily in rodent models that CBD possesses immune modulating properties. The objective of this study was to evaluate whether CBD modulates the innate immune response by human primary monocytes activated through toll-like receptors (TLR) 1-9. Monocytes were activated through each TLR and treated with CBD (0.5-10 μM) for 22 h. Monocyte secretion profiles for 13 immune mediators were quantified including: IL-4, IL-2, IP-10, IL-1β, TNFα, MCP-1, IL-17a, IL-6, IL-10, IFNγ, IL-12p70, IL-8, and TGF-β1. CBD treatment significantly suppressed secretion of proinflammatory cytokine IL-1β by monocytes activated through most TLRs, apart from TLRs 3 and 8. Additionally, CBD treatment induced significant modulation of IL-6 production by monocytes activated through most TLRs, except for TLRs 1 and 3. Most other monocyte-derived factors assayed were refractory to CBD modulation. Overall, CBD selectively altered monocyte-derived IL-1β and IL-6 when activated through most TLRs. This study is of particular importance as it provides a direct and comprehensive assessment of the effects of CBD on TLR-activated primary human monocytes at a time when CBD containing products are being widely used by the public.

Helicobacter pylori-derived outer membrane vesicles stimulate interleukin 8 secretion through nuclear factor kappa B activation

BACKGROUND/AIMS

Bacteria-derived outer membrane vesicles (OMVs) are commonly associated with various biological activities and functions. Helicobacter pylori-derived OMVs are thought to contribute to pathogenesis. This study aimed to investigate the effects of H. pylori-derived OMVs.

METHODS

H. pylori strains were isolated from patients with gastritis, gastric ulcer, or gastric cancer using endoscopic biopsy. The U-937, AGS, and MKN-45 cell lines were exposed to H. pylori and H. pylori-derived OMVs. The expression of interleukin 8 (IL-8) messenger RNA (mRNA) was assessed using reverse transcription-polymerase chain reaction (RT-PCR) and real-time RT-PCR, and IL-8 secretion was analyzed using enzyme-linked immunosorbent assay. Nuclear factor kappa B (NF-κB) activation was evaluated by Western blotting.

RESULTS

H. pylori and H. pylori-derived OMVs induced the expression of IL-8 mRNA and protein. Importantly, the bacteria induced higher IL-8 mRNA and protein expression than the OMVs. IL-8 expression was induced to different levels in response to H. pylori-derived OMVs from hosts with different gastric diseases. Western blotting revealed the increased phosphorylation and reduced degradation of inhibitor of NF-κB alpha in cells exposed to OMVs.

CONCLUSION

H. pylori-derived OMVs may aid the development of various gastric diseases by inducing IL-8 production and NF-κB activation.

Trefoil Factor Family (TFF) Peptides and Their Links to Inflammation: A Re-evaluation and New Medical Perspectives

Trefoil factor family peptides (TFF1, TFF2, TFF3), together with mucins, are typical exocrine products of mucous epithelia. Here, they act as a gastric tumor suppressor (TFF1) or they play different roles in mucosal innate immune defense (TFF2, TFF3). Minute amounts are also secreted as endocrine, e.g., by the immune and central nervous systems. As a hallmark, TFF peptides have different lectin activities, best characterized for TFF2, but also TFF1. Pathologically, ectopic expression occurs during inflammation and in various tumors. In this review, the role of TFF peptides during inflammation is discussed on two levels. On the one hand, the expression of TFF1-3 is regulated by inflammatory signals in different ways (upstream links). On the other hand, TFF peptides influence inflammatory processes (downstream links). The latter are recognized best in various Tff-deficient mice, which have completely different phenotypes. In particular, TFF2 is secreted by myeloid cells (e.g., macrophages) and lymphocytes (e.g., memory T cells), where it modulates immune reactions triggering inflammation. As a new concept, in addition to lectin-triggered activation, a hypothetical lectin-triggered inhibition of glycosylated transmembrane receptors by TFF peptides is discussed. Thus, TFFs are promising players in the field of glycoimmunology, such as galectins and C-type lectins.

Manifold role of ubiquitin in Helicobacter pylori infection and gastric cancer

Infection with H. pylori induces a strong host cellular response represented by induction of a set of molecular signaling pathways, expression of proinflammatory cytokines and changes in proliferation. Chronic infection and inflammation accompanied by secretory dysfunction can result in the development of gastric metaplasia and gastric cancer. Currently, it has been determined that the regulation of many cellular processes involves ubiquitinylation of molecular effectors. The binding of ubiquitin allows the substrate to undergo a change in function, to interact within multimolecular signaling complexes and/or to be degraded. Dysregulation of the ubiquitinylation machinery contributes to several pathologies, including cancer. It is not understood in detail how H. pylori impacts the ubiquitinylation of host substrate proteins. The aim of this review is to summarize the existing literature in this field, with an emphasis on the role of E3 ubiquitin ligases in host cell homeodynamics, gastric pathophysiology and gastric cancer.

A bacterial small RNA regulates the adaptation of Helicobacter pylori to the host environment

Long-term infection of the stomach with Helicobacter pylori can cause gastric cancer. However, the mechanisms by which the bacteria adapt to the stomach environment are poorly understood. Here, we show that a small non-coding RNA of H. pylori (HPnc4160, also known as IsoB or NikS) regulates the pathogen’s adaptation to the host environment as well as bacterial oncoprotein production. In a rodent model of H. pylori infection, the genomes of bacteria isolated from the stomach possess an increased number of T-repeats upstream of the HPnc4160-coding region, and this leads to reduced HPnc4160 expression. We use RNA-seq and iTRAQ analyses to identify eight targets of HPnc4160, including genes encoding outer membrane proteins and oncoprotein CagA. Mutant strains with HPnc4160 deficiency display increased colonization ability of the mouse stomach, in comparison with the wild-type strain. Furthermore, HPnc4160 expression is lower in clinical isolates from gastric cancer patients than in isolates derived from non-cancer patients, while the expression of HPnc4160’s targets is higher in the isolates from gastric cancer patients. Therefore, the small RNA HPnc4160 regulates H. pylori adaptation to the host environment and, potentially, gastric carcinogenesis.

Long-term infection of the stomach with Helicobacter pylori can cause gastric cancer. Here, Kinoshita-Daitoku et al. show that a small non-coding RNA of H. pylori regulates bacterial adaptation to the stomach environment and bacterial oncoprotein production.

AI-2 represses CagA expression and bacterial adhesion, attenuating the Helicobacter pylori-induced inflammatory response of gastric epithelial cells

BACKGROUND

Helicobacter pylori (H. pylori) infection of gastric epithelial cells induces inflammatory response. Outer membrane proteins (OMPs), Type 4 secretion system (T4SS) encoded by cagPAI, and the effector protein CagA are involved in the pathogenesis of H. pylori. H. pylori possesses a gene encoding LuxS which synthesizes AI-2, a quorum sensing signal molecule. The aim of this study was to investigate the role of AI-2 in the expression of virulence factors and the inflammatory response of gastric epithelial (AGS) cells induced by H. pylori.

MATERIALS AND METHODS

H. pylori ΔluxS mutant was constructed, and AI-2 activity was measured with Vibrio harveyi BB170. NF-κB activation, IL-8 production, expression of OMPs (outer membrane proteins), CagA, and T4SS encoded by cagPAI were investigated in H. pylori wild type, and ΔluxS with or without supplementation of AI-2.

RESULTS

H. pylori produced approximately 7 μM of AI-2 in the medium. AI-2 inhibited expression and translocation of CagA after infection of AGS cells. AI-2 upregulated the expression of CagM, CagE, and CagX, while had no effect to the interaction between T4SS and α5β1 integrin. AI-2 also reduced expression of adhesins and bacterial adhesion to AGS cells. Finally, AI-2 reduced the activation of NF-κB and expression of IL-8 in H. pylori-infected AGS.

CONCLUSIONS

AI-2 plays an important role in the pathogenesis of H. pylori. AI-2 inhibits the bacterial adhesion, expression, and translocation of CagA, and attenuates the inflammatory response of AGS cells induced by H. pylori.

The Role of a Dipeptide Transporter in the Virulence of Human Pathogen, Helicobacter pylori

Helicobacter pylori harbors a dipeptide (Dpp) transporter consisting of a substrate-binding protein (DppA), two permeases (DppB and C), and two ATPases (DppD and F). The Dpp transporter is responsible for the transportation of dipeptides and short peptides. We found that its expression is important for the growth of H. pylori. To understand the role of the Dpp transporter in the pathogenesis of H. pylori, the expression of virulence factors and H. pylori-induced IL-8 production were investigated in H. pylori wild-type and isogenic H. pylori Dpp transporter mutants. We found that expression of CagA was downregulated, while expression of type 4 secretion system (T4SS) components was upregulated in Dpp transporter mutants. The DppA mutant strain expressed higher levels of outer membrane proteins (OMPs), including BabA, HopZ, OipA, and SabA, and showed a higher adhesion level to gastric epithelial AGS cells compared with the H. pylori 26695 wild-type strain. After infection of AGS cells, H. pylori ΔdppA induced a higher level of NF-κB activation and IL-8 production compared with wild-type. These results suggested that in addition to supporting the growth of H. pylori, the Dpp transporter causes bacteria to alter the expression of virulence factors and reduces H. pylori-induced NF-κB activation and IL-8 production in gastric epithelial cells.

The Potential Role of IL1RAP on Tumor Microenvironment-Related Inflammatory Factors in Stomach Adenocarcinoma

This study was performed to investigate the role of interleukin-1 receptor accessory protein (IL1RAP) in stomach carcinoma in vitro and in vivo, determine whether IL1RAP knockdown could regulate the development of stomach carcinoma, and elucidate the relationship between IL1RAP knockdown and inflammation by tumor microenvironment-related inflammatory factors in stomach carcinoma. We first used TCGA and GEPIA systems to predict the potential function of IL1RAP. Second, western blot and RT-PCR were used to analyze the expression, or mRNA level, of IL1RAP at different tissue or cell lines. Third, the occurrence and development of stomach carcinoma in vitro and in vivo were observed by using IL1RAP knockdown lentivirus. Finally, the inflammation of stomach carcinoma in vitro and in vivo was observed. Results show that in GEPIA and TCGA systems, IL1RAP expression in STAD tumor tissue was higher than normal, and high expression of IL1RAP in STAD patients had a worse prognostic outcome. Besides, GSEA shown IL1RAP was negative correlation of apopopsis, TLR4 and NF-κB signaling pathway. We also predicted that IL1RAP may related to IL-1 s, IL-33, and IL-36 s in STAD. The IL1RAP expression and mRNA level in tumor, or MGC803, cells were increased. Furthermore, IL1RAP knockdown by lentivirus could inhibit stomach carcinoma development in vitro and in vivo through weakening tumor cell proliferation, migration, invasion, therefore reducing tumor volume, weight, and biomarker levels, and increasing apoptotic level. Finally, we found IL1RAP knockdown could increase inflammation of tumor microenvironment-related inflammatory factors of stomach carcinoma, in vitro and in vivo. Our study demonstrates that IL1RAP is possibly able to regulate inflammation and apoptosis in stomach carcinoma. Furthermore, TLR4, NF-κB, IL-1 s, IL-33, and IL-36 s maybe the downstream target factor of IL1RAP in inflammation. These results may provide a new strategy for stomach carcinoma development by regulating inflammation.

Anti-inflammatory and anti-oxidative effect of Korean propolis on Helicobacter pylori-induced gastric damage in vitro

Helicobacter pylori, present in the stomach lining, is a Gramnegative bacterium that causes various gastrointestinal diseases, including gastritis and peptic ulcers. Propolis is a natural resinous substance collected from a variety of plants, and contains several natural bioactive substances. The aim of this study was to investigate the anti-inflammatory and antioxidative effects of Korean propolis on H. pylori-induced damage in the human adenocarcinoma gastric cell line. The propolis used in this study was obtained from the Korea Beekeeping Association in South Korea. The expression of pro-inflammatory interleukins (ILs), such as IL-8, IL-12, IL-1β, tumor necrosis factor alpha, cyclooxygenase-2, and inducible nitric oxide synthase, which was increased after H. pylori infection, significantly decreased in a dose-dependent manner upon pretreatment with Korean propolis, because of the suppression of mitogen-activated protein kinases and nuclear factor kB pathway. The anti-oxidative activity of propolis was assessed using the 2,2-diphenyl-1-picrylhydrazyl hydrate free radical assay. Korean propolis showed significant anti-oxidative effects via reactive oxygen species scavenging. In addition, pretreatment with Korean propolis upregulated the expression of anti-oxidant enzymes through Nrf2 signaling activation. These findings indicate that the use of Korean propolis, which has anti-inflammatory and anti-oxidative effects, can be promising for the prevention of H. pylori-induced gastric damage.

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.

Peptic ulcer does not increase the risk of dementia: A nested case control study using a national sample cohort

Studies have shown that peptic ulcer disease (PUD) increases the risk of dementia via the mechanism of systemic inflammation. We examined the association between PUD and the risk of dementia using a population-based national sample cohort from South Korea.Using the national cohort study from the Korean National Health Insurance Service, we extracted data for patients with dementia (n = 11,434) and for 1:4 matched control participants (n = 45,736) and then analyzed the previous histories of PUD from 2002 to 2013 using conditional logistic regression analyses. The controls were matched to the patients according to age, sex, income, region of residence, and past medical history. Subgroup analyses were performed based on age and sex.There was no statistically significant difference in the incidence of PUD between the dementia and control groups (18.0% vs 17.4%, P = .107). The adjusted odds ratio (OR) for PUD was 0.92 (95% confidence interval [CI] = 0.88-0.97, P = .002). In the subgroup analysis based on age, the adjusted ORs for PUD were 0.93 (95% CI = 0.88-0.99) in the <80-year-old group and 0.90 (95% CI = 0.82-1.00) in the ≥80-year-old group (each P < .05). In the subgroup analysis based on sex, the adjusted ORs for PUD were 0.89 (95% CI = 0.81-0.97; P < .05) in men and 0.94 (95% CI = 0.89-1.00; P = .06) in women.PUD does not increase the risk of dementia at any age or in either sex after adjusting for age and the history of hypertension, diabetes mellitus, dyslipidemia, ischemic heart disease, stroke, and depression.

Four Chromosomal Type IV Secretion Systems in Helicobacter pylori: Composition, Structure and Function

The pathogenic bacterium Helicobacter pylori is genetically highly diverse and a major risk factor for the development of peptic ulcer disease and gastric adenocarcinoma in humans. During evolution, H. pylori has acquired multiple type IV secretion systems (T4SSs), and then adapted for various purposes. These T4SSs represent remarkable molecular transporter machines, often associated with an extracellular pilus structure present in many bacteria, which are commonly composed of multiple structural proteins spanning the inner and outer membranes. By definition, these T4SSs exhibit central functions mediated through the contact-dependent conjugative transfer of mobile DNA elements, the contact-independent release and uptake of DNA into and from the extracellular environment as well as the secretion of effector proteins in mammalian host target cells. In recent years, numerous features on the molecular functionality of these T4SSs were disclosed. H. pylori encodes up to four T4SSs on its chromosome, namely the Cag T4SS present in the cag pathogenicity island (cagPAI), the ComB system, as well as the Tfs3 and Tfs4 T4SSs, some of which exhibit unique T4SS functions. The Cag T4SS facilitates the delivery of the CagA effector protein and pro-inflammatory signal transduction through translocated ADP-heptose and chromosomal DNA, while various structural pilus proteins can target host cell receptors such as integrins or TLR5. The ComB apparatus mediates the import of free DNA from the extracellular milieu, whereas Tfs3 may accomplish the secretion or translocation of effector protein CtkA. Both Tfs3 and Tfs4 are furthermore presumed to act as conjugative DNA transfer machineries due to the presence of tyrosine recombinases with cognate recognition sequences, conjugational relaxases, and potential origins of transfer (oriT) found within the tfs3 and tfs4 genome islands. In addition, some extrachromosomal plasmids, transposons and phages have been discovered in multiple H. pylori isolates. The genetic exchange mediated by DNA mobilization events of chromosomal genes and plasmids combined with recombination events could account for much of the genetic diversity found in H. pylori. In this review, we highlight our current knowledge on the four T4SSs and the involved mechanisms with consequences for H. pylori adaptation to the hostile environment in the human stomach.

Helicobacter pylori Avoids the Critical Activation of NLRP3 Inflammasome-Mediated Production of Oncogenic Mature IL-1β in Human Immune Cells

Helicobacter pylori persistently colonizes the human stomach, and is associated with inflammation-induced gastric cancer. Bacterial crosstalk with the host immune system produces various inflammatory mediators and subsequent reactions in the host, but not bacterial clearance. Interleukin-1β (IL-1β) is implicated in gastric cancer development and certain gene polymorphisms play a role in this scenario. Mature IL-1β production depends on inflammasome activation, and the NLRP3 inflammasome is a major driver in H. pylori-infected mice, while recent studies demonstrated the down-regulation of NLRP3 expression in human immune cells, indicating a differential NLRP3 regulation in human vs. mice. In addition to the formation of mature IL-1β or IL-18, inflammasome activation induces pyroptotic death in cells. We demonstrate that H. pylori infection indeed upregulated the expression of pro-IL-1β in human immune cells, but secreted only very low amounts of mature IL-1β. However, application of exogenous control activators such as Nigericin or ATP to infected cells readily induced NLRP3 inflammasome formation and secretion of high amounts of mature IL-1β. This suggests that chronic H. pylori infection in humans manipulates inflammasome activation and pyroptosis for bacterial persistence. This inflammasome deregulation during H. pylori infection, however, is prone to external stimulation by microbial, environmental or host molecules of inflammasome activators for the production of high amounts of mature IL-1β and signaling-mediated gastric tumorigenesis in humans.

Different cytokine patterns induced by Helicobacter pylori and Lactobacillus acidophilus extracts in PBMCs of patients with abdominal aortic aneurysm

Abdominal aortic aneurysm (AAA) is a degenerative inflammatory disease with unknown etiology. AAA is characterized by abdominal aortic dilatation more than 3 cm and is often asymptomatic, but the rupture of aneurysm can lead to death. Age, smoking and male sex are major predisposing factors of AAA. This study compares the effect of Helicobacter (H.) pylori and Lactobacillus (L.) acidophilus on the cytokine profile of PBMCs of 5 men with abdominal aortic aneurysm (AAA) and 5 men with normal/insignificant angiography, CT-Scan and ultrasonography results in the single-culture and in the co-culture with HUVECs. IL-2, IL-4, IL-5, IL-6, IL-9, IL-10, IL-13, IL-17A, IL-17 F, IL-21, IL-22, IFN-γ and TNF-α were measured in culture supernatants using a commercial fluorescent-labeled-bead assay. In general, CagA+ H. pylori-extract induced higher production of IFN-γ, IL-13 and IL-21 by PBMCs. Treatment of patients' PBMCs with CagA⁺H. pylori-extract induced Th2 cytokines while treatment of controls' PBMCs with CagA⁺H. pylori-extract increased Th1 cytokines. In the co-culture, however, patients' PBMCs produced Th1 cytokines irrespective of extract treatment, while controls' PBMCs produced Th2 cytokines and decreased IL-10. CagA+ H. pylori- as well as L. acidophilus-extract induced higher levels of IL-9 by controls' PBMCs in co-culture with HUVECs than patients (P = 0.05 and P = 0.01). The cytokine pattern of PBMCs induced by CagA+ H. pylori- and L. acidophilus-extracts in the co-culture with HUVECs shows differences in AAA patients and in comparison to controls. Decreased secretion of IL-9, IL-21 and IL-22 by PBMCs of patients treated with CagA+ H. pylori extract in co-culture, as opposed to non-AAA controls may indicate the active role ECs play in AAA. Simultaneous production of IL-10 and Th1 cytokines in patients and pronounced Th2 cytokines in controls in response to both bacteria may point to the inherent differences between patients and controls, which need further investigation.

virB11 gene potentially involves in ATP metabolism to provide energy in H. pylori infection

Helicobater pylori (H. pylori) is the most important bacteria known to be associated with various gastroduodenal diseases. virB11 gene is a structural gene of tfs3a genes cluster in the plasticity region of H. pylori. In this study, the structure and biology of virB11 gene were analyzed and elucidated with bioinformatics analysis. After cloning, expression and purification, VirB11 protein was generated for the cytotoxicity to GES-1 cells and the anti-VirB11 protein antibody production for localization and interaction proteins analysis. The results showed that VirB11 protein is a hydrophilic protein, mainly locates in cell membrane. IL-8 productions from GES-1 cells co-culture with VirB11 protein were increased gradually with time (p < 0.001). The interaction proteins of VirB11 protein were F0F1 ATP synthase subunit alpha, ATP synthase subunit beta and isocitrate dehydrogenase. We demonstrate that VirB11 protein possesses cytotoxicity and potentially plays important roles in ATP metabolism to provide energy in the course of H. pylori infection.

Mechanisms of persistence, innate immune activation and immunomodulation by the gastric pathogen Helicobacter pylori

The gastric bacterium Helicobacter pylori efficiently evades innate immune detection and persistently colonizes its human host. Understanding the genetic determinants that H. pylori uses to establish and maintain persistence, along with their cellular targets, is key to our understanding of the pathogenesis of this extraordinarily successful bacterial colonizer of the human stomach. This review highlights recent advances in elucidating innate immune recognition of H. pylori, its interactions with myeloid cells and the consequences that this very local infection has for immune responses at extragastric sites in models of allergy, autoimmunity and parasitic infection. The human-specific, gram-negative gastric colonizer and carcinogen H. pylori represents the prototype of a persistent bacterial pathogen. It is transmitted during early childhood, typically from mother to infant, and is believed to persist in its human host from the cradle to the grave. The tremendous success of H. pylori in infecting and colonizing half of the world's population, and in continuously accompanying humans since they migrated out of Africa over 60000 years ago, can largely be attributed to its ability to manipulate the host immune system to its own advantage, and to thereby ensure its own persistence and chronicity. In his final years as an active PI, Stanley Falkow increasingly recognized the need to understand bacterial persistence strategies as a prerequisite of understanding the pathogenesis of chronic bacterial infections, and, inspired in large part by Denise Monack's work on Salmonella persistence, many of our discussions at the time revolved around this topic. Multiple labs have since made important contributions to our understanding of innate immune detection of H. pylori, the types and polarization of adaptive immune responses that ensue, the ability of H. pylori to skew such immune responses to its advantage, and its ability to manipulate the host immune system with far-reaching, even systemic consequences. This review attempts to cover some of these topics, with a particular focus on the most recent contributions by researchers in the field.

Immune Cell Signaling by Helicobacter pylori: Impact on Gastric Pathology

Helicobacter pylori represents a highly successful colonizer of the human stomach. Infections with this Gram-negative bacterium can persist lifelong, and although in the majority of cases colonization is asymptomatic, it can trigger pathologies ranging from chronic gastritis and peptic ulceration to gastric cancer. The interaction of the bacteria with the human host modulates immune responses in different ways to enable bacterial survival and persistence. H. pylori uses various pathogenicity-associated factors such as VacA, NapA, CGT, GGT, lipopolysaccharide, peptidoglycan, heptose 1,7-bisphosphate, ADP-heptose, cholesterol glucosides, urease and a type IV secretion system for controlling immune signaling and cellular functions. It appears that H. pylori manipulates multiple extracellular immune receptors such as integrin-β₂ (CD18), EGFR, CD74, CD300E, DC-SIGN, MINCLE, TRPM2, T-cell and Toll-like receptors as well as a number of intracellular receptors including NLRP3, NOD1, NOD2, TIFA and ALPK1. Consequently, downstream signaling pathways are hijacked, inducing tolerogenic dendritic cells, inhibiting effector T cell responses and changing the gastrointestinal microbiota. Here, we discuss in detail the interplay of bacterial factors with multiple immuno-regulatory cells and summarize the main immune evasion and persistence strategies employed by H. pylori.

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.

Changes of tight junction and interleukin-8 expression using a human gastroid monolayer model of Helicobacter pylori infection

BACKGROUND

Lack of a model that mirrors Helicobacter pylori-induced gastric mucosal inflammation has hampered investigation of early host-bacterial interactions. We used an ex vivo model of human stomach, gastric epithelial organoid monolayers (gastroid monolayers) to investigate interactions of H pylori infection and the apical junctional complex and interleukin-8 (IL-8) expression.

METHOD

Morphology of human antral mucosal gastroid monolayers was evaluated using histology, immunohistochemical (IHC) staining, and transmission electron microscopy (TEM). Functional and gross changes in the apical junctional complexes were assessed using transepithelial electrical resistance (TEER), cytotoxicity assays, and confocal laser scanning microscopy. IL-8 expression was evaluated by real-time quantitative PCR and ELISA.

RESULTS

When evaluated by IHC and TEM, the morphology of gastroid monolayers closely resembled in vivo human stomach. Following inoculation of H pylori, TEER transiently declined (up to 51%) in an H pylori density-dependent manner. TEER recovered by 48 hours post-infection and remained normal despite continued presence and replication of H pylori. Confocal scanning microscopy showed minimal disruption of zonula occludens-1 or E-cadherin structure. IL-8 production was unchanged by infection with either CagA-positive or CagA-negative H pylori and JNK and MEK inhibitors did not suppress IL-8 production, whereas p38 and IKK inhibitor significantly did.

CONCLUSION

Human gastroid monolayers provide a model for experimental H pylori infection more consistent with in vivo human infections than seen with typical gastric epithelial cell lines. This ex vivo system should lead to better understanding of H pylori host-pathogen interactions.

Increased LIGHT expression and activation of non-canonical NF-κB are observed in gastric lesions of MyD88-deficient mice upon Helicobacter felis infection

Helicobacter pylori infection induces a number of pro-inflammatory signaling pathways contributing to gastric inflammation and carcinogenesis. Among those, NF-κB signaling plays a pivotal role during infection and malignant transformation of the gastric epithelium. However, deficiency of the adaptor molecule myeloid differentiation primary response 88 (MyD88), which signals through NF-κB, led to an accelerated development of gastric pathology upon H. felis infection, but the mechanisms leading to this phenotype remained elusive. Non-canonical NF-κB signaling was shown to aggravate H. pylori-induced gastric inflammation via activation of the lymphotoxin β receptor (LTβR). In the present study, we explored whether the exacerbated pathology observed in MyD88-deficient (Myd88^−/−) mice was associated with aberrant activation of non-canonical NF-κB. Our results indicate that, in the absence of MyD88, H. felis infection enhances the activation of non-canonical NF-κB that is associated with increase in Cxcl9 and Icam1 gene expression and CD3⁺ lymphocyte recruitment. In addition, activation of signal transducer and activator of transcription 3 (STAT3) signaling was higher in Myd88^−/− compared to wild type (WT) mice, indicating a link between MyD88 deficiency and STAT3 activation in response to H. felis infection. Thereby, MyD88 deficiency results in accelerated and aggravated gastric pathology induced by Helicobacter through activation of non-canonical NF-κB.

Syk: a new target for attenuation of Helicobacter pylori-induced gastric mucosal inflammatory responses

The magnitude of gastric mucosal inflammatory response to H. pylori relies primarily on the extent of its key endotoxin, LPS, engagement of Toll-like receptor-4 (TLR4) and the initiation of signal transduction events converging on mitogen-activated protein kinase (MAPK) and IκB complex (IKK) cascades. These cascades, in turn, exert their control over the assembly of transcription factors, NFκB and AP1, implicated in the induction of the expression of iNOS and COX-2 proinflammatory genes. The LPS-induced TLR4 activation and the ensuing phosphorylation of its intracellular tyrosine domain by Src-family kinases not only leads to recruitment to the cytoplasmic domain of TLR4 of adaptor molecules directly involved in propagation of the signaling cascades converging on MAPK and IKK, but also provides a propitious docking site for a non-receptor tyrosine kinase, spleen tyrosine kinase (Syk), the activation of which apparently leads to upregulation in the expression of proinflammatory genes. Here, we review the pathways engaged by H. pylori in the recruitment and interaction of Syk with TLR4 in gastric mucosa, and discuss the cascades involved in Syk-mediated amplification in proinflammatory signaling. We focus, moreover, on the potential role of drugs targeting Syk and TLR4 in the treatment of H. pylori-related gastric disease.

Genetic Polymorphisms in Inflammatory and Other Regulators in Gastric Cancer: Risks and Clinical Consequences

Helicobacter pylori infection is associated with the development of a chronic inflammatory response, which may induce peptic ulcers, gastric cancer (GC), and mucosa-associated lymphoid tissue (MALT) lymphoma. Chronic H. pylori infection promotes the genetic instability of gastric epithelial cells and interferes with the DNA repair systems in host cells. Colonization of the stomach with H. pylori is an important cause of non-cardia GC and gastric MALT lymphoma. The reduction of GC development in patients who underwent anti-H. pylori eradication schemes has also been well described. Individual susceptibility to GC development depends on the host's genetic predisposition, H. pylori virulence factors, environmental conditions, and geographical determinants. Biological determinants are urgently sought to predict the clinical course of infection in individuals with confirmed H. pylori infection. Possible candidates for such biomarkers include genetic aberrations such as single-nucleotide polymorphisms (SNPs) found in various cytokines/growth factors (e.g., IL-1β, IL-2, IL-6, IL-8, IL-10, IL-13, IL-17A/B, IFN-γ, TNF, TGF-β) and their receptors (IL-RN, TGFR), innate immunity receptors (TLR2, TLR4, CD14, NOD1, NOD2), enzymes involved in signal transduction cascades (PLCE1, PKLR, PRKAA1) as well as glycoproteins (MUC1, PSCA), and DNA repair enzymes (ERCC2, XRCC1, XRCC3). Bacterial determinants related to GC development include infection with CagA-positive (particularly with a high number of EPIYA-C phosphorylation motifs) and VacA-positive isolates (in particular s1/m1 allele strains). The combined genotyping of bacterial and host determinants suggests that the accumulation of polymorphisms favoring host and bacterial features increases the risk for precancerous and cancerous lesions in patients.

MALT Lymphoma as a Model of Chronic Inflammation-Induced Gastric Tumor Development

Mucosa-associated lymphoid tissue (MALT) lymphoma, or extranodal marginal zone lymphoma of MALT, is an indolent B-cell non-Hodgkin lymphoma linked with preexisting chronic inflammation. The stomach is the most commonly affected organ and the MALT lymphoma pathogenesis is clearly associated with Helicobacter pylori gastroduodenitis. Inflammation induces the lymphoid infiltrates in extranodal sites, where the lymphoma then subsequently develops. Genetic aberrations arise through the release of reactive oxygen species (ROS), H. pylori-induced endonucleases, and other effects. The involvement of nuclear factor kappa B (NF-κB) pathway activation, a critical regulator of pro-inflammatory responses, further highlights the role of inflammation in gastric MALT lymphoma. The NF-κB pathway regulates key elements of normal lymphocyte function, including the transcription of proliferation-promoting and anti-apoptotic genes. Aberrant constitutive activation of NF-κB signaling can lead to autoimmunity and malignancy. NF-κB pathway activation can happen through both the canonical and non-canonical pathways and can be caused by multiple genetic aberrations such as t(11;18)(q12;q21), t(1;14)(p22;q32), and t(14;18)(q32;q21) translocations, chronic inflammation and even directly by H. pylori-associated mechanisms. Gastric MALT lymphoma is considered one of the best models of how inflammation initiates genetic events that lead to oncogenesis, determines tumor biology, dictates clinical behavior and leads to viable therapeutic targets. The purpose of this review is to present gastric MALT lymphoma as an outstanding example of the close pathogenetic link between chronic inflammation and tumor development and to describe how this information can be integrated into daily clinical practice.

The Sweeping Role of Cholesterol Depletion in the Persistence of Helicobacter pylori Infections

The ability of Helicobacter pylori to persist lifelong in the human gastric mucosa is a striking phenomenon. It is even more surprising since infection is typically associated with a vivid inflammatory response. Recent studies revealed the mechanism by which this pathogen inhibits the epithelial responses to IFN-γ and other central inflammatory cytokines in order to abolish an effective antimicrobial defense. The mechanism is based on the modification and depletion of cholesterol by the pathogen's cholesterol-α-glucosyltransferase. It abrogates the assembly of numerous cytokine receptors due to the reduction of lipid rafts. Particularly, the receptors for IFN-γ, IL-22, and IL-6 then fail to assemble properly and to activate JAK/STAT signaling. Consequently, cholesterol depletion prevents the release of antimicrobial peptides, including the highly effective β-defensin-3. Intriguingly, the inhibition is spatially restricted to heavily infected cells, while the surrounding epithelium continues to respond normally to cytokine stimulation, thus providing a platform of the intense inflammation typically observed in H. pylori infections. It appears that pathogen and host establish a homeostatic balance between tightly colonized and rather inflamed sites. This homeostasis is influenced by the levels of available cholesterol, which potentially exacerbate H. pylori-induced inflammation. The observed blockage of epithelial effector mechanisms by H. pylori constitutes a convincing explanation for the previous failures of T-cell-based vaccination against H. pylori, since infected epithelial cells remain inert upon stimulation by effector cytokines. Moreover, the mechanism provides a rationale for the carcinogenic action of this pathogen in that persistent infection and chronic inflammation represent a pro-carcinogenic environment. Thus, cholesterol-α-glucosyltransferase has been revealed as a central pathogenesis determinant of H. pylori.

Role of NOD1 and ALPK1/TIFA Signalling in Innate Immunity Against Helicobacter pylori Infection

The human pathogen Helicobacter pylori interacts intimately with gastric epithelial cells to induce inflammatory responses that are a hallmark of the infection. This inflammation is a critical precursor to the development of peptic ulcer disease and gastric cancer. A major driver of this inflammation is a type IV secretion system (T4SS) encoded by the cag pathogenicity island (cagPAI), present in a subpopulation of more virulent H. pylori strains. The cagPAI T4SS specifically activates signalling pathways in gastric epithelial cells that converge on the transcription factor, nuclear factor-κB (NF-κB), which in turn upregulates key immune and inflammatory genes, resulting in various host responses. It is now clear that H. pylori possesses several mechanisms to activate NF-κB in gastric epithelial cells and, moreover, that multiple signalling pathways are involved in these responses. Two of the dominant signalling pathways implicated in NF-κB-dependent responses in epithelial cells are nucleotide-binding oligomerisation domain 1 (NOD1) and a newly described pathway involving alpha-kinase 1 (ALPK1) and tumour necrosis factor (TNF) receptor-associated factor (TRAF)-interacting protein with forkhead-associated domain (TIFA). Although the relative roles of these two pathways in regulating NF-κB-dependent responses still need to be clearly defined, it is likely that they work cooperatively and non-redundantly. This chapter will give an overview of the various mechanisms and pathways involved in H. pylori induction of NF-κB-dependent responses in gastric epithelial cells, including a 'state-of-the-art' review on the respective roles of NOD1 and ALPK1/TIFA pathways in these responses.

Mechanisms of Inflammasome Signaling, microRNA Induction and Resolution of Inflammation by Helicobacter pylori

Inflammasome-controlled transcription and subsequent cleavage-mediated activation of mature IL-1β and IL-18 cytokines exemplify a crucial innate immune mechanism to combat intruding pathogens. Helicobacter pylori represents a predominant persistent infection in humans, affecting approximately half of the population worldwide, and is associated with the development of chronic gastritis, peptic ulcer disease, and gastric cancer. Studies in knockout mice have demonstrated that the pro-inflammatory cytokine IL-1β plays a central role in gastric tumorigenesis. Infection by H. pylori was recently reported to stimulate the inflammasome both in cells of the mouse and human immune systems. Using mouse models and in vitro cultured cell systems, the bacterial pathogenicity factors and molecular mechanisms of inflammasome activation have been analyzed. On the one hand, it appears that H. pylori-stimulated IL-1β production is triggered by engagement of the immune receptors TLR2 and NLRP3, and caspase-1. On the other hand, microRNA hsa-miR-223-3p is induced by the bacteria, which controls the expression of NLRP3. This regulating effect by H. pylori on microRNA expression was also described for more than 60 additionally identified microRNAs, indicating a prominent role for inflammatory and other responses. Besides TLR2, TLR9 becomes activated by H. pylori DNA and further TLR10 stimulated by the bacteria induce the secretion of IL-8 and TNF, respectively. Interestingly, TLR-dependent pathways can accelerate both pro- and anti-inflammatory responses during H. pylori infection. Balancing from a pro-inflammation to anti-inflammation phenotype results in a reduction in immune attack, allowing H. pylori to persistently colonize and to survive in the gastric niche. In this chapter, we will pinpoint the role of H. pylori in TLR- and NLRP3 inflammasome-dependent signaling together with the differential functions of pro- and anti-inflammatory cytokines. Moreover, the impact of microRNAs on H. pylori-host interaction will be discussed, and its role in resolution of infection versus chronic infection, as well as in gastric disease development.

Importance of Toll-like Receptors in Pro-inflammatory and Anti-inflammatory Responses by Helicobacter pylori Infection

Infectious diseases have been paramount among the threats to human health and survival throughout evolutionary history. Bacterial cell-surface molecules are key factors in the microorganism-host crosstalk, as they can interact with host pattern-recognition receptors (PRRs) of the gastrointestinal mucosa. The best-studied PRRs are toll-like receptors (TLRs). Because TLRs play an important key role in host defense, they have received increasing interest in the evolutionary and population genetics literature, and their variation represents a potential target of adaptive evolution. Helicobacter pylori is one of the commensal bacteria in our body and can have pathogenic properties in a subset of infected people. The history of H. pylori research indicated that humans and bacteria co-evolved during evolution. A genome-wide association study (GWAS) has opened the way for investigating the genomic evolution of bacterial pathogens during the colonization and infection of humans. Recent GWAS research emphasized the importance of TLRs, especially TLR10 during pathogenesis in H. pylori infection. We demonstrated that TLR10, whose ligand was unknown for a long time, can recognize H. pylori LPS. Our results of H. pylori research suggest that TLR10 might play an important role to also recognize other commensal bacteria. In this review, we discuss the importance of TLRs in pro-inflammatory and anti-inflammatory responses by H. pylori infection. Especially, we highlight the TLR10 interaction with H. pylori infection, providing new insights about TLR10 signaling.

Genomic features of the Helicobacter pylori strain PMSS1 and its virulence attributes as deduced from its in vivo colonisation patterns

The human gastric pathogen Helicobacter pylori occurs in two basic variants, either exhibiting a functional cagPAI-encoded type-4-secretion-system (T4SS) or not. Only a few cagPAI-positive strains have been successfully adapted for long-term infection of mice, including the pre-mouse Sydney strain 1 (PMSS1). Here we confirm that PMSS1 induces gastric inflammation and neutrophil infiltration in mice, progressing to intestinal metaplasia. Complete genome analysis of PMSS1 revealed 1,423 coding sequences, encompassing the cagPAI gene cluster and, unusually, the location of the cytotoxin-associated gene A (cagA) approximately 15 kb downstream of the island. PMSS1 harbours three genetically exchangeable loci that are occupied by the hopQ coding sequences. HopQ represents a critical co-factor required for the translocation of CagA into the host cell and activation of NF-κB via the T4SS. Long-term colonisation of mice led to an impairment of cagPAI functionality. One of the bacterial clones re-isolated at four months post-infection revealed a mutation in the cagPAI gene cagW, resulting in a frame shift mutation, which prevented CagA translocation, possibly due to an impairment of T4SS function. Rescue of the mutant cagW re-established CagA translocation. Our data reveal intriguing insights into the adaptive abilities of PMSS1, suggesting functional modulation of the H. pylori cagPAI virulence attribute.

Characterization of morphological conversion of Helicobacter pylori under anaerobic conditions

Helicobacter pylori (H. pylori), a gram-negative microaerophilic bacterial pathogen that colonizes the stomachs of more than half of all humans, is linked to chronic gastritis, peptic ulcers and gastric cancer. Spiral-shaped H. pylori undergo morphologic conversion to a viable but not culturable coccoid form when they transit from the microaerobic stomach into the anaerobic intestinal tract. However, little is known about the morphological and pathogenic characteristics of H. pylori under prolonged anaerobic conditions. In this study, scanning electron microscopy was used to document anaerobiosis-induced morphological changes of H. pylori, from helical to coccoid to a newly defined fragmented form. Western blot analysis indicated that all three forms express certain pathogenic proteins, including the bacterial cytotoxin-associated gene A (CagA), components of the cag-Type IV secretion system (TFSS), the blood group antigen-binding adhesin BabA, and UreA (an apoenzyme of urease), almost equally. Similar urease activities were also detected in all three forms of H. pylori. However, in contrast to the helical form, bacterial motility and TFSS activity were found to have been abrogated in the anaerobiosis-induced coccoid and fragmented forms of H. pylori. Notably, it was demonstrated that some of the anaerobiosis-induced fragmented state cells could be converted to proliferation-competent helical bacteria in vitro. These results indicate that prolonged exposure to the anaerobic intestine may not eliminate the potential for H. pylori to revert to the helical pathogenic state.

Helicobacter pylori associated factors in the development of gastric cancer with special reference to the early-onset subtype

Nowadays, gastric cancer is one of the most common neoplasms and the fourth cause of cancer-related death on the world. Regarding the age at the diagnosis it is divided into early-onset gastric carcinoma (45 years or younger) and conventional gastric cancer (older than 45). Gastric carcinomas are rarely observed in young population and rely mostly on genetic factors, therefore provide the unique model to study genetic and environmental alternations. The latest research on early-onset gastric cancer are trying to explain molecular and genetic basis, because young patients are less exposed to environmental factors predisposing to cancer. In the general population, Helicobacter pylori, has been particularly associated with intestinal subtype of gastric cancers. The significant association of Helicobacter pylori infection in young patients with gastric cancers suggests that the bacterium has an etiologic role in both diffuse and intestinal subtypes of early-onset gastric cancers. In this paper we would like to ascertain the possible role of Helicobacter pylori infection in the development of gastric carcinoma in young patients. The review summarizes recent literature on early-onset gastric cancers with special reference to Helicobacter pylori infection.

Interactome analysis of transforming growth factor-β-activated kinase 1 in Helicobacter pylori-infected cells revealed novel regulators tripartite motif 28 and CDC37

Transforming growth factor-β (TGFβ)-activated kinase 1 (TAK1) plays a central role in controlling the cellular pro-inflammatory response via the activation of the nuclear factor κB (NF-κB)- and mitogen-activated protein (MAP) kinases-dependent transcriptional programs. Here, we show that depletion of TAK1 and the TAK1-binding proteins TAB1 and TAB2 affects NF-κB, JNK and p38 phosphorylation and suppresses NF-κB activity in AGS cells infected with Helicobacter pylori or stimulated with the cytokines TNF and IL-1β. To increase our understanding of TAK1 regulation and function, we performed mass spectrometry (MS)-based TAK1 interactomics. In addition to the identification of known and novel TAK1 interacting proteins, including TRIM28, CDC37 and STOML2, analysis of the MS data revealed various post-translational modifications within the TAK1/TAB complex. By applying siRNAs, TRIM28 and CDC37 were found to regulate phosphorylations of TAK1, IκB kinases IKKα/IKKβ and MAP kinases, NF-κB transactivation activity and IL-8 expression in the infected epithelial cells.

Helicobacter pylori LPS-induced gastric mucosal spleen tyrosine kinase (Syk) recruitment to TLR4 and activation occurs with the involvement of protein kinase Cδ

Spleen tyrosine kinase (Syk) has emerged recently as a major effector of proinflammatory genes expression induced by LPS-elicited TLR4 activation, and manifested by the up-amplification in the production of inflammatory mediators, including PGE2 and NO. Here, we investigated the nature of factors involved in the recruitment and interaction of Syk with TLR4 in gastric mucosa in response to H. pylori LPS. We show that stimulation of gastric mucosal cells with the LPS leads to localization of Syk with the membrane-associated TLR4 complex and its activation through phosphorylation on Tyr. Furthermore, we reveal that the membrane translocation of Syk upon the LPS stimulation occurs with the involvement of protein kinase Cδ (PKCδ)-mediated phosphorylation of Syk on Ser. Thus, our findings demonstrate that H. pylori LPS-induced up-regulation in Syk activity proceeds through the stage of PKCδ-mediated Syk phosphorylation on Ser, required for its recruitment to the membrane-anchored TLR4, followed by the kinase activation through phosphorylation on Tyr. Hence, the phase of PKCδ-mediated Syk phosphorylation on Ser affects the extent of amplification in gastric mucosal inflammatory response to H. pylori.

Metaplasia in the Stomach-Precursor of Gastric Cancer?

Despite a significant decrease in the incidence of gastric cancer in Western countries over the past century, gastric cancer is still one of the leading causes of cancer-related deaths worldwide. Most human gastric cancers develop after long-term Helicobacter pylori infection via the Correa pathway: the progression is from gastritis, atrophy, intestinal metaplasia, dysplasia, to cancer. However, it remains unclear whether metaplasia is a direct precursor of gastric cancer or merely a marker of high cancer risk. Here, we review human studies on the relationship between metaplasia and cancer in the stomach, data from mouse models of metaplasia regarding the mechanism of metaplasia development, and the cellular responses induced by H. pylori infection.

Interleukin-17C in Human Helicobacter pylori Gastritis

The interleukin-17 (IL-17) family of cytokines (IL-17A to IL-17F) is involved in many inflammatory diseases. Although IL-17A is recognized as being involved in the pathophysiology of Helicobacter pylori-associated diseases, the role of other IL-17 cytokine family members remains unclear. Microarray analysis of IL-17 family cytokines was performed in H. pylori-infected and uninfected gastric biopsy specimens. IL-17C mRNA was upregulated approximately 4.5-fold in H. pylori-infected gastric biopsy specimens. This was confirmed by quantitative reverse transcriptase PCR in infected and uninfected gastric mucosa obtained from Bhutan and from the Dominican Republic. Immunohistochemical analysis showed that IL-17C expression in H. pylori-infected gastric biopsy specimens was predominantly localized to epithelial and chromogranin A-positive endocrine cells. IL-17C mRNA levels were also significantly greater among cagA-positive than cagA-negative H. pylori infections (P = 0.012). In vitro studies confirmed an increase in IL-17C mRNA and protein levels in cells infected with cagA-positive infections compared to cells infected with either cagA-negative or cag pathogenicity island (PAI) mutant. Chemical inhibition of IκB kinase (IKK), mitogen-activated protein extracellular signal-regulated kinase (MEK), and Jun N-terminal kinase (JNK) inhibited induction of IL-17C proteins in infected cells, whereas p38 inhibition had no effect on IL-17C protein secretion. In conclusion, H. pylori infection was associated with a significant increase in IL-17C expression in human gastric mucosa. The role of IL-17C in the pathogenesis of H. pylori-induced diseases remains to be determined.