Effects of Helicobacter pylori infection on gastric inflammation and local cytokine production in histamine-deficient (histidine decarboxylase knock-out) mice

A comprehensive evaluation of an animal model for Helicobacter pylori-associated stomach cancer: Fact and controversy

Even though Helicobacter pylori infection was the most causative factor of gastric cancer, numerous in vivo studies failed to induce gastric cancer using H. pylori infection only. The utilization of established animal studies in cancer research is crucial as they aim to investigate the coincidental association between suspected oncogenes and pathogenesis as well as generate models for the development and testing of potential treatments. The methods to establish gastric cancer using infected animal models remain limited, diverse in methods, and showed different results. This study investigates the differences in animal models, which highlight different pathological results in gaster by literature research. Electronic databases searched were performed in PubMed, Science Direct, and Cochrane, without a period filter. A total of 135 articles were used in this study after a full-text assessment was conducted. The most frequent animal models used for gastric cancer were Mice, while Mongolian gerbils and Transgenic mice were the most susceptible model for gastric cancer associated with H. pylori infection. Additionally, transgenic mice showed that the susceptibility to gastric cancer progression was due to genetic and epigenetic factors. These studies showed that in Mongolian gerbil models, H. pylori could function as a single agent to trigger stomach cancer. However, most gastric cancer susceptibilities were not solely relying on H. pylori infection, and numerous factors are involved in cancer progression. Further study using Mongolian gerbils and Transgenic mice is crucial to conduct and establish the best models for gastric cancer associated H. pylori.

Histamine Signaling Is Essential for Tissue Macrophage Differentiation and Suppression of Bacterial Overgrowth in the Stomach

BACKGROUND & AIMS

Histamine in the stomach traditionally is considered to regulate acid secretion but also has been reported to participate in macrophage differentiation, which plays an important role in tissue homeostasis. Therefore, this study aimed to uncover the precise role of histamine in mediating macrophage differentiation and in maintaining stomach homeostasis.

METHODS

Here, we expand on this role using histidine decarboxylase knockout (Hdc^-/-) mice with hypertrophic gastropathy. In-depth in vivo studies were performed in Hdc^-/- mice, germ-free Hdc^-/- mice, and bone-marrow-transplanted Hdc^-/- mice. The stomach macrophage populations and function were characterized by flow cytometry. To identify stomach macrophages and find the new macrophage population, we performed single-cell RNA sequencing analysis on Hdc^+/+ and Hdc^-/- stomach tissues.

RESULTS

Single-cell RNA sequencing and flow cytometry of the stomach cells of Hdc^-/- mice showed alterations in the ratios of 3 distinct tissue macrophage populations (F4/80⁺Il1b^high, F4/80⁺CD93⁺, and F4/80^-MHC class II^highCD74^high). Tissue macrophages of the stomachs of Hdc^-/- mice showed impaired phagocytic activity, increasing the bacterial burden of the stomach and attenuating hypertrophic gastropathy in germ-free Hdc^-/- mice. The transplantation of bone marrow cells of Hdc^+/+ mice to Hdc^-/- mice recovered the normal differentiation of stomach macrophages and relieved the hypertrophic gastropathy of Hdc^-/- mice.

CONCLUSIONS

This study showed the importance of histamine signaling in tissue macrophage differentiation and maintenance of gastric homeostasis through the suppression of bacterial overgrowth in the stomach.

The Effect of Helicobacter pylori on the Presentation and Clinical Course of Coronavirus Disease 2019 Infection

OBJECTIVES

Novel coronavirus 2019 (corona virus disease 2019 [COVID-19]) binds angiotensin-converting enzyme-2 (ACE-2) receptors to enter the cell. These receptors are widely expressed in the intestine, and COVID-19 may cause gastrointestinal symptoms via these receptors during the course of the disease. Helicobacter pylori is known to increase the expression of ACE-2 receptors in the gastrointestinal tract. The aim of this study was to investigate the effects of H pylori on the presentation and clinical course of COVID-19 infections.

METHODS

This study was carried out from June 1 to July 20, 2020. Patients diagnosed with COVID-19 infections by PCR tests were included in the study. Antigen screening tests were performed on stool samples to determine the presence of H pylori. All patients were evaluated for manifestations of COVID-19 infection, severity of the course, hospitalized days because of the virus and outcome of the disease process.

RESULTS

Of 108 COVID-19 positive patients evaluated, 31 with a mean age of 49.54 ± 17.94 years were H pylori-positive (8 girls [25.8%]) and 77 with a mean age of 47.85 ± 20.51 years; (31 girls [40.3%]) were H pylori-negative. Abdominal pain (19.4% vs 2.6%) and diarrhea (32.3% vs 9.1%) were significantly higher in patients with H pylori than those without (P = 0.007 and P = 0.006, respectively). There was no statistically significant difference between H pylori positivity and the number of hospitalized days, the severity of the course of COVID-19 infection, or the outcome of the disease (P > 0.05).

CONCLUSION

Our results revealed that the findings of abdominal pain and diarrhea strongly correlated with the presence of H pylori in COVID-19 patients.

Helicobacter pylori neutrophil-activating protein induces release of histamine and interleukin-6 through G protein-mediated MAPKs and PI3K/Akt pathways in HMC-1 cells

Helicobacter pylori neutrophil-activating protein (HP-NAP) activates several innate leukocytes including neutrophils, monocytes, and mast cells. It has been reported that HP-NAP induces degranulation and interleukin-6 (IL-6) secretion of rat peritoneal mast cells. However, the molecular mechanism is not very clear. Here, we show that HP-NAP activates human mast cell line-1 (HMC-1) cells to secrete histamine and IL-6. The secretion depends on pertussis toxin (PTX)-sensitive heterotrimeric G proteins but not on Toll-like receptor 2. Moreover, HP-NAP induces PTX-sensitive G protein-mediated activation of extracellular signal-regulated kinase 1/2 (ERK1/2), p38-mitogen-activated protein kinase (p38 MAPK), and Akt in HMC-1 cells. Inhibition of ERK1/2, p38 MAPK, or phosphatidylinositol 3-kinase (PI3K) suppresses HP-NAP-induced release of histamine and IL-6 from HMC-1 cells. Thus, the activation of HMC-1 cells by HP-NAP is through Gi-linked G protein-coupled receptor-mediated MAPKs and PI3K/Akt pathways.

Pharmacological potential of biogenic amine-polyamine interactions beyond neurotransmission

Histamine, serotonin and dopamine are biogenic amines involved in intercellular communication with multiple effects on human pathophysiology. They are products of two highly homologous enzymes, histidine decarboxylase and l-aromatic amino acid decarboxylase, and transmit their signals through different receptors and signal transduction mechanisms. Polyamines derived from ornithine (putrescine, spermidine and spermine) are mainly involved in intracellular effects related to cell proliferation and death mechanisms. This review summarizes structural and functional evidence for interactions between components of all these amine metabolic and signalling networks (decarboxylases, transporters, oxidases, receptors etc.) at cellular and tissue levels, distinct from nervous and neuroendocrine systems, where the crosstalk among these amine-related components can also have important pathophysiological consequences. The discussion highlights aspects that could help to predict and discuss the effects of intervention strategies.

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

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

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

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

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

Inflammation, immunity, and vaccines for Helicobacter infection

Pro-inflammatory cytokines such as IL-18, IFN-gamma, and IL-1beta play a significant role in the inflammation induced by Helicobacter. During the recent years of H. pylori research, the main focus has been on development of vaccines for therapeutic or prophylactic use against the infection. Both bacterial components of H. pylori as well as engineered vaccines have been tested as well as different forms of administration including systemic and oral/intranasal pathways.

Mast cells are critical mediators of vaccine-induced Helicobacter clearance in the mouse model

BACKGROUND & AIMS

Despite the proven ability of immunization to prevent Helicobacter infection in mouse models, the precise mechanism of protection has remained elusive.

METHODS

We explored the cellular events associated with Helicobacter clearance from the stomach following vaccination by flow cytometry analysis and histological and molecular studies.

RESULTS

Kinetic studies showed that the infection is undetectable in vaccinated mice at day 5 postbacterial challenge. Flow cytometry analysis showed that the percentages of mast cells (CD3 - CD117 + ) increased in the lymphoid cells isolated from the stomach at day 4 postchallenge in urease + cholera toxin (CT)-vaccinated mice in comparison with mice administered with CT alone (9.4% +/- 4.4% and 3.1% +/- 1%, respectively, for vaccinated and CT administered, n = 5; P < .01). Quantitative PCR analysis showed an increased messenger RNA (mRNA) expression of the mast cell proteases 1 and 2 at day 5 postchallenge in the stomach of vaccinated mice. In contrast to wild-type mice, mast cell-deficient mice (W/W v mice) were not protected from H felis colonization after vaccination. Indeed only 1 out of 12 vaccinated W/W v mice showed a negative urease test. Remarkably, vaccinated W/W v mice reconstituted with cultured bone marrow-derived mast cells recovered the ability to clear the infection after vaccination (8 out of 10 mast cell-reconstituted mice showed negative urease tests [ P < .006 as compared with wild-type mice]).

CONCLUSIONS

These experiments show that mast cells are, unexpectedly, critical mediators of anti- Helicobacter vaccination.