Regulation and functions of inflammasome-mediated cytokines in Helicobacter pylori infection

VacA promotes pyroptosis via TNFAIP3/TRAF1 signaling to induce onset of atrophic gastritis

BACKGROUND

Atrophic gastritis (AG) is a chronic inflammation where gastric glandular cells are replaced by intestinal-type epithelium. Gastric epithelial cell loss is often linked to multiple cell death signaling pathways. While Helicobacter pylori (H. pylori) infection is the main cause of AG, its role in inducing cell death goes beyond apoptosis and autophagy. Pyroptosis could promote development of inflammation related cancers, but its involvement in H. pylori-induced malignant transformation remains unclear.

METHODS

The enrichment of pyroptosis signaling across pathological stages was assessed using immunohistochemistry and bioinformatic analysis. Gastric epithelial cells were co-cultured with VacA recombinant protein or VacA+H. pylori to investigate the role of VacA in pyroptosis, and its downstream targets. TNFAIP3 or TRAF1 was silenced/overexpressed in gastric epithelial cells to explore their impact on pyroptosis. Finally, the interaction between TNFAIP3 and TRAF1 was examined using Western Blot, immunofluorescence, co-immunoprecipitation and ubiquitin assays.

RESULTS

Expression of pyroptosis components and pyroptosis enrichment score were upregulated in AG and gastric cancer tissues compared to normal or non-atrophic gastritis tissues. Upon incubation with VacA recombinant protein or VacA+H. pylori, pyroptosis and TNFAIP3/TRAF1 were elevated in gastric epithelial cells. TRAF1 promoted expression of downstream pyroptosis components and release of IL-1β/IL18. TRAF1 ablation could reverse pyroptosis activation caused by VacA. Finally, we proved TNFAIP3 as deubiquitinating enzyme to increase TRAF1 stability, further inducing pyroptosis.

CONCLUSIONS

The VacA/TNFAIP3/TRAF1 signaling cascade facilitates pyroptosis in H. pylori- infected tissue. Overactivation of Pyroptosis caused the atrophy-like morphological changes of gastric epithelium, further inducing sustainable malignant transformation.

The Role of the Immune Response to Helicobacter pylori Antigens and Its Relevance in Gastric Disorders

Helicobacter pylori (H.p.) is a Gram-negative bacterium endowed with gastric tropism. H.p. infection is widely spread throughout the world, accounting for various pathologies, such as peptic ulcer, gastric cancer, mucosa-associated lymphoid tissue lymphoma, and extra-gastric manifestations. This bacterium possesses several virulence factors, e.g., lipopolysaccharides (LPS), the toxins CagA and VacA, and adhesins, which elicit a robust immune response during the initial phase of the infection. Of note, the lipid A moiety of the LPS exhibits a lower endotoxic potency than that of other LPSs, thus facilitating infection through a mechanism of immune escape. H.p. colonization of the gastric mucosa induces an initial protective immune response with innate immune cells, e.g., neutrophils, monocytes, and macrophages, which engulf and kill bacteria. Moreover, the same cells, along with gastric epithelial cells, secrete cytokines and chemokines, which recruit T cells [T helper (h)1 and Th17 cells] to the site of infection, thus leading to H.p. eradication. In a large subset of individuals, the perturbation of such an immune equilibrium leads to a harmful response, with an expansion of T regulatory (TREG) cells, which suppress the protective immune response. In fact, TREG cells, via the production of interleukin (IL)-10, downregulate Th1- and Th17-related cytokines, thus allowing H.p. survival and the perpetuation of inflammation. As far as the humoral immune response is concerned, B cells, upon H.p. stimulation, produce autoreactive antibodies, and IgG anti-Lex antibodies are harmful to the gastric mucosa. In this review, the structure and function of H.p. antigenic components and immune mechanisms elicited by this bacterium will be described in relation to gastric damage.

Selected Markers of Inflammation in the Saliva of Children Infected with Helicobacter pylori

Helicobacter pylori has been of interest to scientists and clinicians for many years, often causing diagnostic difficulties, especially in the youngest age group, in children. The presence of this bacterium in the population depends on the geographic region. However, it is assumed that even half of the world's population may be infected with H. pylori. Children infected with H. pylori-the study group (Hp(+)) and control group (Hp(-)), were chosen for further examination. The aim of the study was to analyze the concentrations of selected inflammatory markers in saliva (TNF-α, IL-8) and other markers (neutrophil defensin-1, sICAM-1, calprotectin, metalloproteinase-9, metalloproteinase-2, lactotransferrin, TLR-2) using ELISA technique. We confirmed the increased concentrations of IL-8, ND-1, and TLR-2 in the group of children infected with Helicobacter pylori. Moreover, there was also a positive, significant correlation between the concentration of ND-1 and MMP-2, sICAM-1, and calprotectin as well as MMP-9 and MMP-2 in the group of infected children. The study created new possibilities of insight into the pathogenetic mechanisms of developing inflammation in the mouth. This type of comprehensive research is also used to monitor the current disease process and create new opportunities for better in-depth diagnostics of children infected with H. pylori.

Current research on the interaction between Helicobacter pylori and macrophages

Helicobacter pylori (H. pylori) is a gram-negative bacteria with a worldwide infection rate of 50%, known to induce gastritis, ulcers and gastric cancer. The interplay between H. pylori and immune cells within the gastric mucosa is pivotal in the pathogenesis of H. pylori-related disease. Following H. pylori infection, there is an observed increase in gastric mucosal macrophages, which are associated with the progression of gastritis. H. pylori elicits macrophage polarization, releases cytokines, reactive oxygen species (ROS) and nitric oxide (NO) to promote inflammatory response and eliminate H. pylori. Meanwhile, H. pylori has developed mechanisms to evade the host immune response in order to maintain the persistent infection, including interference with macrophage phagocytosis and antigen presentation, as well as induction of macrophage apoptosis. Consequently, the interaction between H. pylori and macrophages can significantly impact the progression, pathogenesis, and resolution of H. pylori infection. Moreover, macrophages are emerging as potential therapeutic targets for H. pylori-associated gastritis. Therefore, elucidating the involvement of macrophages in H. pylori infection may provide novel insights into the pathogenesis, progression, and management of H. pylori-related disease.

Changes in the tissue elements of the gastric mucosa interacting with different strains of Helicobacter pylori, taking into consideration the patient's genotype

The present study aimed to investigate the peculiarities of adaptation of tissue elements of the gastric mucosa during interaction with Helicobacter pylori, as determined by genetic characteristics of the bacterium and the host. Venous blood and biopsy samples of the mucosa of the antrum and body of the stomach from young patients (18 to 25 years old) were examined. The condition of the gastric mucosa was assessed using stained histological preparations. Venous blood was collected from the patients to ascertain the polymorphisms of the IL-lß and IL-IRN genes. The most pronounced changes were observed in the parameters of reparative regeneration of epithelial differentiation during colonization of the gastric mucosa by H. pylori strains carrying the CagA(+) and BabA2(+) genes. These included an increase in proliferation and apoptosis rates and alterations in epithelial differentiation markers characterized by elevated production of Shh and MUC5AC, as well as a reduction in the production of the protective mucin MUC6 by isthmus gland cells. The presence of the vacAs1 and vacAs2 genes of H. pylori results in a high level of apoptosis in epithelial cells without accelerating proliferation. It was found that after eradication, patients with preserved cellular infiltrates in their gastric mucosa plates were carriers of mainly the IL-1ß*T/IL-1RN*2R haplotypes after 12 months.

Strategies of Helicobacter pylori in evading host innate and adaptive immunity: insights and prospects for therapeutic targeting

Helicobacter pylori (H. pylori) is the predominant pathogen causing chronic gastric mucosal infections globally. During the period from 2011 to 2022, the global prevalence of H. pylori infection was estimated at 43.1%, while in China, it was slightly higher at approximately 44.2%. Persistent colonization by H. pylori can lead to gastritis, peptic ulcers, and malignancies such as mucosa-associated lymphoid tissue (MALT) lymphomas and gastric adenocarcinomas. Despite eliciting robust immune responses from the host, H. pylori thrives in the gastric mucosa by modulating host immunity, particularly by altering the functions of innate and adaptive immune cells, and dampening inflammatory responses adverse to its survival, posing challenges to clinical management. The interaction between H. pylori and host immune defenses is intricate, involving evasion of host recognition by modifying surface molecules, manipulating macrophage functionality, and modulating T cell responses to evade immune surveillance. This review analyzes the immunopathogenic and immune evasion mechanisms of H. pylori, underscoring the importance of identifying new therapeutic targets and developing effective treatment strategies, and discusses how the development of vaccines against H. pylori offers new hope for eradicating such infections.

Role of Helicobacter pylori Infection in Pathogenesis, Evolution, and Complication of Atherosclerotic Plaque

The therapeutic management of atherosclerosis focuses almost exclusively on the reduction of plasma cholesterol levels. An important role in the genesis and evolution of atherosclerosis is played by chronic inflammation in promoting thrombosis phenomena after atheroma rupture. This review aims to take stock of the knowledge so far accumulated on the role of endemic HP infection in atherosclerosis. The studies produced so far have demonstrated a causal relationship between Helicobacter pylori (HP) and CVD. In a previous study, we demonstrated in HP-positive patients that thrombin and plasma fragment 1 + 2 production was proportionally related to tumor necrosis factor-alpha levels and that eradication of the infection resulted in a reduction of inflammation. At the end of our review, we can state that HP slightly affects the risk of CVD, particularly if the infection is associated with cytotoxic damage, and HP screening could have a clinically significant role in patients with a high risk of CVD. Considering the high prevalence of HP infection, an infection screening could be of great clinical utility in patients at high risk of CVD.

Helicobacter pylori infection and inflammasomes

Helicobacter pylori (H. pylori) causes the most prevalent bacterial infection worldwide, and more than half of the world's population is infected with H. pylori. Classified as a group 1 carcinogen of gastric cancer, H. pylori infection causes the most common chronic gastritis, which is able to progress to chronic atrophic gastritis, dysplasia, and even gastric cancer. The inflammasomes are important cytosolic multiprotein complexes to coordinate the host defense against foreign microorganisms and control the inflammatory response. It is also well‐known that inflammasome plays an important role in the occurrence of H. pylori‐induced gastric inflammation. During infection and inflammation, the activation process of inflammasome is tightly regulated by host immune system. However, excessive activation of inflammasome is closely related to the production of excessive cytokines that cause the body injury and resulting in various inflammatory diseases. In this review, we elaborate the activation and assembly mechanisms of inflammasome, the structure of different inflammasome complexes, host factors in vivo and drugs in vitro that regulate inflammasome signaling during H. pylori infection, aiming to provide novel insights and strategies for identifying new therapeutic targets for the treatment of H. pylori‐associated gastric mucosal diseases.

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.

Helicobacter pylori and gastric cancer: a lysosomal protease perspective

The intimate involvement of pathogens with the heightened risk for developing certain cancers is an area of research that has captured a great deal of attention over the last 10 years. One firmly established paradigm that highlights this aspect of disease progression is in the instance of Helicobacter pylori infection and the contribution it makes in elevating the risk for developing gastric cancer. Whilst the molecular mechanisms that pinpoint the contribution that this microorganism inflicts towards host cells during gastric cancer initiation have come into greater focus, another picture that has also emerged is one that implicates the host's immune system, and the chronic inflammation that can arise therefrom, as being a central contributory factor in disease progression. Consequently, when taken with the underlying role that the extracellular matrix plays in the development of most cancers, and how this dynamic can be modulated by proteases expressed from the tumor or inflammatory cells, a complex and detailed relationship shared between the individual cellular components and their surroundings is coming into focus. In this review article, we draw attention to the emerging role played by the cathepsin proteases in modulating the stage-specific progression of Helicobacter pylori-initiated gastric cancer and the underlying immune response, while highlighting the therapeutic significance of this dynamic and how it may be amenable for novel intervention strategies within a basic research or clinical setting.

Purification of Total RNA from Stomach Tissue Biopsies

In order to further our understanding of the physiological consequences of Helicobacter pylori infection , analysis of clinical tissue specimens is required. To this end, RNA is frequently isolated from stomach biopsies of H. pylori-infected patients and compared to samples from uninfected controls to monitor gene expression using molecular methods such as reverse-transcription real-time PCR, microarrays, and next-generation sequencing. The successful purification of sufficient quantities of high-quality RNA is essential for accurate and reproducible downstream analysis. This chapter describes the key steps for high-quality RNA purification from human tissue samples, including sample collection and storage, tissue disruption and lysis, RNA purification, and assessment of RNA yield and quality.

An Overview of Helicobacter pylori Infection

Helicobacter pylori (H. pylori) represents one of the most widespread bacterial infections globally. Infection causes chronic gastritis and increases the risk of peptic ulcer disease, gastric adenocarcinoma, and mucosa-associated lymphoid tissue lymphoma. The pioneering discovery of H. pylori by Marshall and Warren in the early 1980s has initiated fervent research into H. pylori as a pathogen ever since. This chapter aims to provide an overview of our understanding of H. pylori infection and its management, with a focus on current options for diagnosis, the challenges associated with H. pylori eradication, and the need for alternative therapeutic strategies based on furthering our understanding of host: H. pylori interactions.

The effect of 6-gingerol on inflammatory response and Th17/Treg balance in DSS-induced ulcerative colitis mice

Background

Ulcerative colitis (UC) is a non-specific chronic intestinal inflammatory disease with unclear etiology. Previous studies have suggested that the imbalance of Treg/Thl7 cells may be involved in the development of UC. It was found that 6-gingerol can alleviate the intestinal inflammatory damage and improve the weight loss of colitis mice. However, whether 6-gingerol can regulate the balance of Th17/Treg cells and inhibit the intestinal inflammatory response remains to be clarified.

Methods

In this study, a dextran sulfate sodium (DSS)-induced colitis mouse model was established, and the effects of 6-gingerol on cytokines and the balance of Th17/Treg cells were observed usingserial assays, including enzyme-linked immunosorbent assay (ELISA), quantitative real time-polymerase chain reaction (qPCR), and Western blotting.

Results

DSS caused the damage of bowel tissue and a 100% weight loss rate in colitis mice. The treatment of 6-gingerol can significantly relieve bowel damage and reduce incidence of weight loss to 16.7% at a low or high dose (P<0.05), which was similar to the therapeutic effect of mesalazine. It was found that DSS can up-regulate the mRNA levels of IL-6 and IL-17 in serum (by qPCR), and the serum and bowel levels of IL-6 and IL-17 (by ELISA); these levels were significantly different from those of the blank group (P<0.05). Furthermore, 6-gingerol was found to inhibit the increase of mRNA levels and serum and bowel levels of IL-6 and IL-17 induced by DSS, which is similar with mesalazine. It was also found that DSS can down-regulate the mRNA level of IL-10 in serum, along with the serum and bowel level of IL-10, with this being significantly different from the levels of the blank group (P<0.05). 6-gingerol could also inhibit the decrease of mRNA levels and serum and bowel levels of IL-10 induced by DSS, which is also similar to mesalazine. In addition, DSS could increase Th17 cell count and decrease Treg cell count in blood, with significant difference from that of the blank group (P<0.05). 6-gingerol could significantly (P<0.05) inhibit the increase of Th17 cells and the decrease of Treg cells induced by DSS, which is similar to the effect of mesalazine. The detection of expression levels of transcription factors RORγT for Th17 and FOXP3 for Treg at both mRNA and protein levels showed that DSS can up-regulate the mRNA and protein levels of RORγT, and down-regulate the mRNA and protein levels of FOXP3. Furthermore, 6-gingerol could significantly (P<0.05) inhibit the up-regulation of RORγT mRNA and protein, and the down-regulation of FOXP3 mRNA and protein induced by DSS, which is similar to the effect of mesalazine.

Conclusions

6-gingerol showed efficacy in the treatment of DSS-induced UC in mice, by regulating the cell balance of Th17/Treg, and by relieving inflammatory responses both systematically and locally.

Immune Response in H. pylori-Associated Gastritis and Gastric Cancer

Helicobacter pylori (H. pylori) is the dominant member of the gastric microbiota and has infected more than half of the human population, of whom 5–15% develop gastric diseases ranging from gastritis and metaplasia to gastric cancer. These diseases always follow inflammation induced by cell surface and intracellular receptors and subsequent signaling, such as the NF-κB pathway and inflammasomes. Some types of immune cells are recruited to enforce an antibacterial response, which could be impeded by H. pylori virulence factors with or without a specific immune cell. Following decreased inflammation, neoplasm may appear with a little immune surveillance and may inhibit antitumor immunity. Therefore, the balance between H. pylori-associated inflammation and anti-inflammation is crucial for human health and remains to be determined. Here, we discuss multiple inflammation and immunoregulatory cells in gastritis and summarize the main immune evasion strategies employed by gastric cancer.

Carcinogenic Helicobacter pylori Strains Selectively Dysregulate the In Vivo Gastric Proteome, Which May Be Associated with Stomach Cancer Progression

Helicobacter pylori is the strongest risk factor for gastric cancer. Initial interactions between H. pylori and its host originate at the microbial-gastric epithelial cell interface, and contact between H. pylori and gastric epithelium activates signaling pathways that drive oncogenesis. One microbial constituent that increases gastric cancer risk is the cag pathogenicity island, which encodes a type IV secretion system that translocates the effector protein, CagA, into host cells. We previously demonstrated that infection of Mongolian gerbils with a carcinogenic cag+H. pylori strain, 7.13, recapitulates many features of H. pylori-induced gastric cancer in humans. Therefore, we sought to define gastric proteomic changes induced by H. pylori that are critical for initiation of the gastric carcinogenic cascade. Gastric cell scrapings were harvested from H. pylori-infected and uninfected gerbils for quantitative proteomic analyses using isobaric tags for relative and absolute quantitation (iTRAQ). Quantitative proteomic analysis of samples from two biological replicate experiments quantified a total of 2764 proteins, 166 of which were significantly altered in abundance by H. pylori infection. Pathway mapping identified significantly altered inflammatory and cancer-signaling pathways that included Rab/Ras signaling proteins. Consistent with the iTRAQ results, RABEP2 and G3BP2 were significantly up-regulated in vitro, ex vivo in primary human gastric monolayers, and in vivo in gerbil gastric epithelium following infection with H. pylori strain 7.13 in a cag-dependent manner. Within human stomachs, RABEP2 and G3BP2 expression in gastric epithelium increased in parallel with the severity of premalignant and malignant lesions and was significantly elevated in intestinal metaplasia and dysplasia, as well as gastric adenocarcinoma, compared with gastritis alone. These results indicate that carcinogenic strains of H. pylori induce dramatic and specific changes within the gastric proteome in vivo and that a subset of altered proteins within pathways with oncogenic potential may facilitate the progression of gastric carcinogenesis in humans.

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.

Immune response and immune escape mechanism in Helicobacter pylori infection

Helicobacter pylori (H. pylori) is a Gram-negative bacterium which is parasitic on the surface of the gastric mucosa, and it is a causative agent in the development of chronic gastritis, gastric and duodenal peptic ulcer, gastric adenocarcinoma, and lymphoid tissue lymphoma associated with the gastric mucosa. After H. pylori infection, the bacterium is first recognized by the pattern recognition receptors of immune cells, which in turn causes the innate immune and adaptive immune responses, but these responses are usually insufficient to eliminate bacterial infections. H. pylori can evade the identification and clearance by the immune system by modifying and attenuating the immunogenicity of its pathogen-associated molecular patterns, regulating the immune responses of innate immune cells and T cells, and leading to persistent infection. A thorough understanding of the immune response and immune escape mechanism in H. pylori infection is of great significance for eliminating H. pylori infection and controlling the occurrence of H. pylori infection-related diseases.

Helicobacter Pylori Infection and Lung Cancer: New Insights and Future Challenges

Helicobacter pylori (H. pylori) is the causative agent of chronic gastritis and peptic ulcer diseases and is an important risk factor for the development functional dyspepsia, peptic ulceration, gastric adenocarcinoma and mucosa-associated lymphoid tissue lymphoma. H. pylori has very high rates of infection in human populations, and it is estimated that over 50% of the world population is infected. Recently, certain extra-gastric manifestations, linked to H. pylori infection, have been widely investigated. Noteworthy, a growing body of evidences supports an association between H. pylori infection with lung cancer. The present review intend to highlight not only the most recent evidences supporting this association, but also some missed points, which must be considered to validate this emerging association.

Helicobacter pylori in human health and disease: Mechanisms for local gastric and systemic effects

Helicobacter pylori (H. pylori) is present in roughly 50% of the human population worldwide and infection levels reach over 70% in developing countries. The infection has classically been associated with different gastro-intestinal diseases, but also with extra gastric diseases. Despite such associations, the bacterium frequently persists in the human host without inducing disease, and it has been suggested that H. pylori may also play a beneficial role in health. To understand how H. pylori can produce such diverse effects in the human host, several studies have focused on understanding the local and systemic effects triggered by this bacterium. One of the main mechanisms by which H. pylori is thought to damage the host is by inducing local and systemic inflammation. However, more recently, studies are beginning to focus on the effects of H. pylori and its metabolism on the gastric and intestinal microbiome. The objective of this review is to discuss how H. pylori has co-evolved with humans, how H. pylori presence is associated with positive and negative effects in human health and how inflammation and/or changes in the microbiome are associated with the observed outcomes.