Immune response to Helicobacter pylori and its association with the dynamics of chronic gastritis in the antrum and corpus

PHKG2 regulates RSL3-induced ferroptosis in Helicobacter pylori related gastric cancer

Ferroptosis is a newly discovered form of regulatory cell death induced by iron-dependent lipid peroxidation. Infection with Helicobacter pylori (H. pylori) is regarded as a high-risk factor for the development of gastric cancer (GC) and is associated with an increase in the levels of reactive oxygen species with activation of oncogenic signaling pathways. However, whether GC arising in the context of infection with H. pylori is correlated with ferroptosis is still unknown. In this study, we demonstrate that H. pylori infection increased the sensitivity of GC cells to RSL3 (RAS-selective lethal3)-induced ferroptosis. The molecular subtypes mediated by ferroptosis-related genes are associated with tumor microenvironment (TME) cell infiltration and patient survival. Importantly, we identified that the expression of phosphorylase kinase G2 (PHKG2) was remarkably correlated with H. pylori infection, metabolic biological processes, patient survival and therapy response. We further found the mechanism of H. pylori-induced cell sensitivity to ferroptosis, which involves PHKG2 regulation of the lipoxygenase enzyme Arachidonate 5-Lipoxygenase (ALOX5). In conclusion, PHKG2 facilitates RSL3-induced ferroptosis in H. pylori-positive GC cells by promoting ALOX5 expression. These findings may contribute to a better understanding of the unique pathogenesis of H. pylori-induced GC and allow for maximum efficacy of genetic, cellular, and immune therapies for controlling ferroptosis in diverse contexts.

Chronic gastritis

Prevalence of chronic gastritis has markedly declined in developed populations during the past decades. However, chronic gastritis is still one of the most common serious pandemic infections with such severe killing sequelae as peptic ulcer or gastric cancer. Globally, on average, even more than half of people may have a chronic gastritis at present. Helicobacter pylori infection in childhood is the main cause of chronic gastritis, which microbial origin is the key for the understanding of the bizarre epidemiology and course of the disease. A life-long and aggressive inflammation in gastritis results in destruction (atrophic gastritis) of stomach mucosa with time (years and decades). The progressive worsening of atrophic gastritis results subsequently in dysfunctions of stomach mucosa. Atrophic gastritis will finally end up in a permanently acid-free stomach in the most extreme cases. Severe atrophic gastritis and acid-free stomach are the highest independent risk conditions for gastric cancer known so far. In addition to the risks of malignancy and peptic ulcer, acid-free stomach and severe forms of atrophic gastritis may associate with failures in absorption of essential vitamins, like vitamin B12, micronutrients (like iron, calcium, magnesium and zinc), diet and medicines.

Predictive value of neutrophil infiltration as a marker of Helicobacter pylori infection

AIM: To evaluate the predictive value of neutrophil infiltration as a marker of Helicobacter pylori (H. pylori) infection.

METHODS: A total of 315 patients with dyspepsia symptoms who underwent upper gastrointestinal endoscopy were enrolled in this study. Biopsies were evaluated using the updated Sydney system. The medication history of all patients in the preceding 4 wk was recorded. The diagnosis of H. pylori infection was based on ¹³C-urea breath test at least 4 wk after withdrawal of antisecretory drugs, antibiotics and related drugs. For the patients with subtotal gastrectomy, the diagnosis of H. pylori infection was based on anti-H. pylori immunoglobulin G (IgG) antibody. Serum anti-H. pylori IgG antibody was measured by enzyme-linked immunosorbent assays (Biohit, Finland).

RESULTS: The sensitivity, specificity, positive predictive value and negative predictive value of neutrophil infiltration in the diagnosis of H. pylori infection were 92.3%, 83.5%, 77.4% and 94.7%, respectively. Neutrophil infiltration of gastric mucosa in the histological analysis was strongly associated with H. pylori infection (77.4% vs 5.3% in the neutrophil infiltration negative group, P = 0.000). Moderate neutrophil infiltration was more frequent in H. pylori infection when compared to mild infiltration (81.8% and 75%, respectively), but did not reach statistical significance. For those patients with negative rapid urease test, H. pylori was detected in 73.2% of patients with positive neutrophil infiltration on histology. In patients with subtotal gastrectomy, the diagnostic accuracy of neutrophil infiltration in H. pylori infection was 50%.

CONCLUSION: Neutrophil infiltration is closely associated with H. pylori and may be recognized as a sign of this infection.

Helicobacter pylori Omp18 and its application in serologic screening of infection

Helicobacter pylori (Hp) is a major risk factor for gastrointestinal disorders including gastric cancer. We evaluated host serum antibody responses toward outer membrane protein18 in comparison with Urease A and B subunits. omp18 and ureA-ureB gene fragments were PCR amplified, cloned, and expressed in E. coli expression system. The expressed proteins were visualized on SDS-PAGE and confirmed by immuno-blotting. Purified proteins were applied in western blotting assays in comparison with local and foreign ELISA kits. ROC curve analysis identified the optimum cut-off points for each protein. rOmp18 represented the highest rates of sensitivity (94%), specificity (89%), PPV (97.4%), NPV (77.4%), and accuracy (93.2%) in comparison with urease A and B subunits. These immunologic indices were in "substantial" agreement (Κ = 0.7) with the gold standard tests for Hp detection. This study recommends Hp conserved Omp18 as a reliable serologic marker for accurate detection of Hp infection particularly for application in population screening approaches.

Incidence of chronic atrophic gastritis: systematic review and meta-analysis of follow-up studies

Chronic atrophic gastritis (CAG) is an important precursor lesion of intestinal gastric cancer. As it is typically asymptomatic, epidemiological data on the incidence of CAG are sparse. We aimed to provide an overview of published data on CAG incidence (overall and according to risk factors) from follow-up studies. Articles with information on incidence of CAG published in English until 26th of July 2009 were identified through a systematic MEDLINE and EMBASE search. Data extracted include study characteristics and key findings regarding the incidence of CAG. A meta-analysis was performed on the association between Helicobacter pylori infection and CAG incidence. Overall, data on CAG incidence were available from 14 studies, in 7 studies incidence could be estimated according to H. pylori infection. Most studies were conducted in symptomatic or high risk populations and the maximum number of incident cases was 284. Incidence estimates ranged from 0 to 11% per year and were consistently below 1% in patients not infected with H. pylori. The highest incidence was observed in a special study conducted on ulcer patients treated by proximal gastric vagotomy. Rate ratios for the association between H. pylori infection and CAG incidence ranged from 2.4 to 7.6 with a summary estimate of 5.0 (95% confidence interval: 3.1-8.3). Incidence of CAG is very low in the absence of H. pylori infection. There is a need for more population-based studies to provide comparable estimates of incidence and the impact of risk factors in the development of CAG.

Incidence and risk factors for the development of chronic atrophic gastritis: five year follow-up of a population-based cohort study

Chronic atrophic gastritis (CAG) is a well-established precursor of intestinal gastric cancer. However, data on incidence of CAG are rare, especially from population-based studies. The aim of this analysis was to estimate the incidence of CAG in a large population-based study among older adults from Germany and to identify major risk factors associated with its development. In the baseline and 5-year follow-up examinations of the ESTHER study, serological measurements of pepsinogen (PG) I and II and Helicobacter pylori antibodies were performed in 5,229 women and men, aged 50-74 years at baseline. Information on additional potential risk factors was obtained by questionnaire. CAG was defined by PGI < 70 ng/mL and PGI/PGII < 3. In total, there were 58 (1.1%) incident CAG cases. CAG incidence increased with increasing age from 0.5% in age group 50-54 years to 2.1% in age group 70-74 years. Seropositivity with H. pylori was strongly associated with CAG incidence, with adjusted odds ratios of 5.0 [95% confidence interval (CI): 1.6-15.8] and 11.3 (95% CI: 4.2-30.0) for participants with cytotoxin associated gene A (cagA) negative and cagA positive H. pylori infection at both baseline and follow-up compared to those without H. pylori infection, respectively. Gender, education, smoking, alcohol consumption and family history of gastric cancer were not significantly associated with CAG incidence. Incidence of CAG is rather low in the German population. Older age and infection with H. pylori are key risk factors for the development of CAG.

Corpus predominant gastritis: what does it mean?

PURPOSE OF REVIEW

To summarize this year's relevant literature on the causes and mechanisms of autoimmune gastritis.

RECENT FINDINGS

It is increasingly recognized that parietal cell antibodies, previously assumed exclusive to autoimmune gastritis, are associated with Helicobacter pylori infection. Successful H. pylori eradication with antibiotic treatment decreases antiparietal cell antibodies. Interestingly, vitamin B(12) deficiency, previously associated with autoimmune gastritis, is increasingly described in the elderly, irrespective of H. pylori status. Autoimmune gastritis that mostly affects patients of Scandinavian descent, was reported this year from China, and corpus predominant gastritis (autoimmune associated) was reported from Japan. It is difficult to evaluate the role played by genetics, increased use of proton pump inhibitors, and H. pylori infection, as current patient work-up does not regularly include screening for parietal cell and intrinsic-factor antibodies. As these clinicopathologic changes are seen in both H. pylori-positive patients, and in H. pylori-naïve patients, the debate continues for mechanisms involved in H. pylori-naïve patients.

SUMMARY

The clinical features commonly associated with autoimmune gastritis are increasingly seen in the elderly, irrespective of H. pylori status. Though some patients are genetically predisposed, long-term proton pump inhibitor use increases the prevalence of clinicopathologic features irrespective of genetic tendency.

Inflammation, immunity, and vaccines for Helicobacter pylori

Helicobacter pylori infects almost half of the population worldwide and represents the major cause of gastroduodenal diseases, such as duodenal and gastric ulcer, gastric adenocarcinoma, autoimmune gastritis, and B-cell lymphoma of mucosa-associated lymphoid tissue. Helicobacter pylori induces the activation of a complex and fascinating cytokine and chemokine network in the gastric mucosa. Different bacterial and environmental factors, other concomitant infections, and host genetics may influence the balance between mucosal tolerance and inflammation in the course of H. pylori infection. An inverse association between H. pylori prevalence and the frequencies of asthma and allergies was demonstrated, and the neutrophil activating protein of H. pylori was shown to inhibit the allergic inflammation of bronchial asthma. During the last year, significant progress was made on the road to the first efficient vaccine for H. pylori that will represent a novel and very important bullet against both infection and gastric cancer.

Diagnosis of Helicobacter pylori infection

The articles published this last year in the field of Helicobacter pylori diagnosis reported the development of in vivo histology, small improvements in some invasive methods (urease test, culture, and histology) and new kits for the stool antigen tests. They also contributed to increasing our knowledge, by further exploration into specific conditions for the urea breath test and into the significance of cagA antibodies. The role of serum markers of atrophy was also confirmed. Molecular methods are still being developed for direct genotyping, detection of H. pylori and its clarithromycin resistance, either by polymerase chain reaction or fluorescent in-situ hybridization. For the first time, there was a report on a possible interest of magnetic resonance spectroscopy.

Effect of Helicobacter pylori infection on telomerase-associated genes, cell proliferation and apoptosis in gastric precancerous lesion

AIM: To analyze expression of human telomerase RNA (hTR), human telomerase reverse transcriptase (hTERT), c-Myc and proliferating cell nuclear antigen (PCNA) and their relationship, and to explore the mechanism of H pylori in gastric precancerous lesions.

METHODS: Thirty three cases of gastric precancerous lesions including 19 H pylori-positive cases and 14 H pylori-negative cases were included in the study. hTR was determined using in situ RNA hybridization; hTERT, c-Myc and PCNA were detected using streptavidin-peroxidase immunohistochemical method; apoptosis was detected using terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling.

RESULTS: The expression of hTR, hTERT and c-Myc were 63.2%, 68.4% and 47.4% in H pylori-positive group and 28.6%, 21.4% and 7.1% in H pylori-negative group (P < 0.01); the proliferation index (PI) and apoptotic index (AI) were significant higher in H pylori-positive group than in H pylori-negative group (17.5 ± 5.4 vs 8.3 ± 3.6, 17.7 ± 3.9 vs 9.2 ± 5.2, P < 0.01). There were significant correlations between hTERT and hTR (r_s = 0.45, P < 0.01), hTERT and c-Myc protein (r_s = 0.54, P < 0.01) in gastric precancerous lesions.

CONCLUSION: H pylori infection induces the over-expression of telomerase-associated genes, c-Myc and prompts cell proliferation and apoptosis in gastric precancerous lesions.

Serum antibodies positivity to 12 Helicobacter pylori virulence antigens in patients with benign or malignant gastroduodenal diseases--cross-sectional study

AIM

To investigate the association of gastric histological and endoscopic findings in patients with Helicobacter pylori (H. pylori), according to presence of seropositivity to 12 bacterial virulence antigens.

METHODS

This is a cross-sectional single-center study of 360 consecutive outpatients referred in the period of one year to upper gastrointestinal endoscopy because of dyspeptic complaints. Patients sera were tested by Western blot method to determine the presence of serum antibodies to bacterial virulence antigens--p120 (CagA--cytotoxin-associated antigen), p95 (VacA - vacuolating cytotoxin), p67 (FSH--flagellar sheath protein), p66 (UreB--urease enzyme heavy subunit), p57 (HSP homologue--heath shock protein homologue), p54 (flagellin), p33, p30 (OMP--outer membrane protein), p29 (UreA--urease enzyme light subunit), p26, p19, and p17. Upper gastrointestinal endoscopy was performed, endoscopic diagnosis recorded, and 4 mucosal biopsy samples were obtained and assessed according to Updated Sydney protocol.

RESULTS

The sera of 207 patients were analyzed. Thirty patients had gastric adenocarcinoma, 126 peptic ulcers, and 51 normal finding. p120 (CagA) seropositivity was significantly more often present in patients with higher activity grade in the antrum (P = 0.025), p30 in patients with greater inflammation in the antrum (P = 0.025) and the corpus (P = 0.010), p33 in patients with greater inflammation in the corpus (P = 0.050), and p19 (OMP) in patients with lower intestinal metaplasia grades in the corpus (P = 0.025). Seroreactivity to all other bacterial proteins showed no association with the histological status of the stomach mucosa. Except for the seropositivity to protein p95 (VacA), which was more often present in patients with duodenal ulcer (P = 0.006), there was no difference in seroreactivity to other bacterial proteins and upper gastrointestinal endoscopic findings.

CONCLUSIONS

p120 (CagA), p33, p30 (OMP), and p19 (OMP) seropositivity was more often present in patients with higher grades of the histological parameters of gastritis and seropositivity to protein p95 (VacA) with endoscopic presence of duodenal ulcer. Histological parameters of gastritis are more associated with bacterial virulence than endoscopic findings.