Creation and Initial Characterization of Isogenic Helicobacter pylori CagA EPIYA Variants Reveals Differential Activation of Host Cell Signaling Pathways

Association of Helicobacter pylori CagA seropositivity with gastric precancerous lesions: a systematic review and meta-analysis

The objective of this meta-analysis is to delineate the association between H. pylori CagA serological status and the prevalence of gastric precancerous lesions (GPL). We searched peer-reviewed articles up to October 2023. The extraction of data from the included studies was carried out as well as the quality assessment. Pooled effect sizes were calculated using a random effect model. Thirteen studies met the inclusion criteria, comprising 2728 patients with GPL and 17 612 controls. The aggregate odds ratio (OR) for the association between serum CagA and GPL was 2.74 (95% CI = 2.25-3.32; P  = 0.00; I 2  = 60.4%), irrespective of H. pylori infection status. Within the H. pylori -infected cohort, the OR was 2.25 (95% CI = 1.99-2.56; P  = 0.00; I 2  = 0.0%). Conversely, among the non-infected individuals, the OR was 1.63 (95% CI = 1.04-2.54; P  = 0.038; I 2  = 0.0%). Heterogeneity was explored using subgroup and meta-regression analyses, indicating that the variability between studies likely stemmed from differences in disease classification. Our results demonstrated robustness and negligible publication bias. The meta-analysis underscores a more pronounced association between H. pylori CagA seropositivity and the risk of developing GPL than between seronegativity and the same risk, irrespective of H. pylori infection status at the time. Additionally, the strength of the association was heightened in the presence of an active H. pylori infection. The implications of these findings advocate for the utility of CagA serostatus as a potential biomarker for screening GPL.

Investigating associations between HLA DQA1 ~ DQB1 haplotypes, H. pylori infection, metaplasia, and anti-CagA IgA seropositivity in a Turkish gastritis cohort

Helicobacter pylori was reported as an important cause of gastritis, and gastric ulcers and CagA oncoprotein-producing H. pylori subgroups were blamed to increase the severity of gastritis. Disparities were reported in that the presence of serum anti-CagA IgA was not parallel with CagA-positive H. pylori cohabitation. We hypothesized that the HLA-DQA1 ~ DQB1 haplotypes in human populations include protective haplotypes that more effectively present immunogenic CagA peptides and susceptible haplotypes with an impaired capacity to present CagA peptides. We recruited patients (n = 201) admitted for gastroendoscopy procedures and performed high-resolution HLA-DQA1 and DQB1 typing. Serum anti-CagA IgA levels were analyzed by ELISA (23.0% positive), and H. pylori was classified as positive or negative in gastric mucosal tissue slides (72.6% positive). The HLA DQA1*05:05 allele (29.1%) and HLA DQB1*03:01 allele (32.8%) were found at the highest frequency among gastritis patients of Turkish descent. In HLA DQA1*05:05 ~ DQB1*03:01 double homozygous (7.3%) and heterozygous (40.7%) haplotype carriers, the presence of anti-CagA IgA decreased dramatically, the presence of H. pylori increased, and the presence of metaplasia followed a decreasing trend. The DQ protein encoded by HLA DQA1*05:05-DQ*03:01 showed a low binding affinity to the CagA peptide when binding capacity was analyzed by the NetMHCIIPan 4.0 prediction method. In conclusion, HLA DQA1 ~ DQB1 polymorphisms are crucial as host defense mechanisms against CagA H. pylori since antigen binding capacity plays a crucial role in anti-CagA IgA production.

G-protein-coupled estrogen receptor prevents nuclear factor-kappa B promoter activation by Helicobacter pylori cytotoxin-associated gene A in gastric cancer cells

Helicobacter pylori is a well-known pathogen that causes chronic gastritis, leading to the development of gastric cancer. This bacterium has also been detected in dogs, and symptoms similar to those in humans have been reported. The cytotoxin-associated gene A (CagA) is involved in pathogenesis through aberrant activation of host signal transduction, including the nuclear factor-kappa B (NF-κB) pathway. We have previously shown the anti-inflammatory effect of the G-protein-coupled estrogen receptor (GPER) via inhibiting of NF-κB activation in several cells. Therefore, here, we investigated the effect of GPER on CagA-mediated NF-κB promoter activity and showed that CagA overexpression in gastric cancer cells activated the NF-κB reporter and induced interleukin 8 (il-8) expression, both of which were inhibited by the GPER agonist.

Coptisine inhibits Helicobacter pylori and reduces the expression of CagA to alleviate host inflammation in vitro and in vivo

ETHNOPHARMACOLOGICAL RELEVANCE

Helicobacter pylori (H. pylori) is a major pathogen colonized in the human stomach and is implicated in gastritis, peptic ulcer, and gastric carcinoma. Antibiotics are useful for eradicating H. pylori but failed for drug resistance, making it urgent to develop effective and safe drugs. Rhizoma Coptidis was reported as one of the most effective Chinese medicines to treat H. pylori-related gastrointestinal diseases, while the precise antimicrobial mechanism remains unclear. Thus, it is of great significance to study the antimicrobial ingredients and corresponding mechanisms of Rhizoma Coptidis.

AIM OF THE STUDY

To search for the most effective alkaloid against H. pylori in Rhizoma Coptidis and illustrate the probable mechanisms.

MATERIALS AND METHODS

Five main alkaloids in Rhizoma Coptidis were isolated. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were tested to determine the most effective one. Bacterial growth experiments, Annexin V-FITC/PI staining, TUNEL staining, and transmission electron microscopy (TEM) were performed to further study the anti-H. pylori activity of coptisine (Cop). The in vivo effect of Cop on H. pylori eradication rate and H. pylori-induced inflammation was investigated in mice. Transcriptomics was used to understand the underlying mechanism of eradicating H. pylori and reducing host inflammation. Western blot, RT-PCR, and ELISA experiments were utilized and confirmed that cagA was one of the targets of Cop.

RESULTS

According to the MIC and MBC, Cop was the most effective alkaloid against H. pylori, especially with no drug resistance developed. In vitro experiments showed that Cop inhibited H. pylori by inducing DNA fragmentation, phosphatidylserine exposure, and membrane damage. Cop (150 mg/kg/day) effectively eradicated H. pylori in mice and reduced the levels of IL-2 and IL-6 to relieve gastric inflammation. Transcriptomic analysis revealed that virulence factor cagA was one of the hub genes associated with the inflammation-improving effect of Cop. That is, Cop could decrease the expression of CagA and subsequently reduce the translocation of CagA to gastric epithelial cells, thereby improving the morphology of hummingbird-like phenotype induced by CagA and alleviating inflammation.

CONCLUSIONS

Cop is the most effective alkaloid in Rhizoma Coptidis and might act through multiple mechanisms for H. pylori eradication along with reducing the expression of CagA to alleviate inflammation.

Correlation analysis of gastric mucosal lesions with Helicobacter pylori infection and its virulence genotype in Guiyang, Guizhou province, China

Background

Helicobacter Pylori (H. pylori) infection is the most important factor affecting clinical outcome in patients with gastric mucosal lesions. This study aimed to investigate H. pylori infection in patients with gastric mucosal lesions and their virulence genotype in Guiyang, China.

Methods

Pathological examinations of 1,364 biopsies from patients with upper gastrointestinal symptoms and H. pylori infection were analyzed according to different pathological types. The bacterial genome DNA was extracted from H. pylori strains isolated from gastric biopsies, and the cagA, vacA, and iceA virulence genes were detected and typed to analyze the correlation of their genotypes between different pathological lesions.

Results

The positive rate of H. pylori infection was approximately 19.9% (272/1,364), as determined by histopathological examination (HPE). It was more frequently detected in men than in women. A total of 85 H. pylori isolates were obtained from 280 clinical samples (positive rate 30.4%, 85/280). Of these 85 strains, cagA, vacA, and iceA genes were identified in 85.9%, 100%, and 83.5% of samples, respectively. Approximately 74.1% of strains were cagA East Asian type (cagA-ABD), and 11.8% of were cagA Western strains (cagA-AB, cagA-ABC), only present in patients with chronic non-atrophic gastritis. Gastric intraepithelial neoplasia and gastric cancer harbored both Asian strains. A total of 7 combinations of vacA genotypes were noted, among which s1c/m1b (30.6%) and s1c/m2 (41.2%) were the dominant genotypes. The predominant iceA genotype was iceA1 (64.7%).

Conclusions

We observed that the positive rate of H. pylori infection was related to the pathological type of patients' gastric mucosal lesions. Isolated H. pylori strains showed a unique genotype, mainly East Asian type cagA (ABD), vacA s1c/m2 genotype, and iceA1. These results provide an important reference for further studies of H. pylori in Guizhou province, China.

CagA and VacA inhibit gastric mucosal epithelial cell autophagy and promote the progression of gastric precancerous lesions

Cytotoxin-associated gene A (CagA) and vacuolating cytotoxin A (VacA) are the keys to the pathogenic role of Helicobacter pylori and the high-risk factors for the progression of gastric precancerous lesions. Autophagy can stabilize the intracellular environment, resist Helicobacter pylori infection, prevent the accumulation of damaged DNA, and inhibit the proliferation of gastric precancerous variant cells. However, CagA and VacA can inhibit the activation of upstream signals of autophagy and the maturation of autophagy-lysosomes in various ways, thus inhibiting the autophagy of gastric mucosal cells in precancerous lesions of gastric cancer. This change can cause Helicobacter pylori to be unable to be effectively cleared by autophagy, so CagA and VacA can persist and promote the inflammation, oxidative stress, apoptosis of gastric mucosal tissue cells, and the glycolytic activity and proliferation of variant cells in gastric precancerous lesions and a series of malignant biological processes. In recent years, the research on drugs specifically inhibiting the activities of CagA and VacA has become a new direction for the prevention and treatment of Helicobacter pylori-related severe gastric diseases, and a variety of drugs or components that can precisely and effectively regulate the factors for the treatment of gastric precancerous lesions are emerged, which opens a new strategy for the treatment of gastric precancerous lesions in the future.

Helicobacter pylori: an up-to-date overview on the virulence and pathogenesis mechanisms

Helicobacter pylori is an organism associated with ulcer disease and gastric cancer. The latter is one of the most prevalent malignancies and currently the fourth major cause of cancer-related deaths globally. The pathogen infects about 50% of the world population, and currently, no treatment ensures its total elimination. There has been an increase in our understanding of the pathophysiology and pathogenesis mechanisms of H. pylori over the years. H. pylori can induce several genetic alterations, express numerous virulence factors, and trigger diverse adaptive mechanisms during its adherence and colonization. For successful colonization and infection establishment, several effector proteins/toxins are released by the organism. Evidence is also available reporting spiral to coccoid transition as a unique tactic H. pylori uses to survive in the host’s gastrointestinal tract (GIT). Thus, the virulence and pathogenicity of H. pylori are under the control of complex interplay between the virulence factors, host, and environmental factors. Expounding the role of the various virulence factors in H. pylori pathogenesis and clinical outcomes is crucial for vaccine development and in providing and developing a more effective therapeutic intervention. Here we critically reflect on H. pylori infection and delineate what is currently known about the virulence and pathogenesis mechanisms of H. pylori.

Characterization of East-Asian Helicobacter pylori encoding Western EPIYA-ABC CagA

The polymorphic bacterial oncoprotein, CagA shows geography-dependent variation in the C-terminal Glu-Pro-Ile-Tyr-Ala (EPIYA) motifs; East-Asian H. pylori isolates carry the ABD type while Western isolates carry the ABC type. In Western isolates, the EPIYA-C motif is sometimes found in multi-copy and this genotype is associated with disease severity. Interestingly, a small number of East-Asian H. pylori isolates have been found to carry Western ABC-type CagA. To gain a better understanding of these unusual isolates, the genomes of four Korean H. pylori clinical isolates carrying ABC-type CagA were sequenced via third generation (Pac-Bio SMRT) sequencing technology. The obtained data were utilized for phylogenetic analysis as well as comparison of additional virulence factors that are known to show geographic-dependent polymorphisms. Three of four isolates indeed belonged to the hpEastAsia group and showed typical East-Asian polymorphism in virulence factors such as homA/B/C, babA/B/C, and oipA. One isolate grouped to HpAfrica and showed typical Western polymorphism of virulence factors such as cagA, homA/B/C, and oipA. To understand the occurrence of the multi-copy EPIYA-C motif genotype in an East-Asian H. pylori background, the Korean clinical isolate, K154 was analyzed; this strain belonged to hpEastAsia but encoded CagA EPIYA-ABCCCC. Based on DNA sequence homology within the CagA multimerization (CM) sequence that flanked the EPIYA-C motifs, we predicted that the number of C motifs might change via homologous recombination. To test this hypothesis, K154 was cultured for one generation and 287 single colonies were analyzed for the number of EPIYA-C motifs using PCR-based screening and DNA sequencing verification. Three out of 284 (1%) single colony isolates showed changes in the number of EPIYA-C motifs in vitro; one isolate increased to five EPIYA-C motifs, one decreased to three EPIYA-C motifs, and one completely deleted the EPIYA-C motifs. The capacity for dynamic changes in the number of EPIYA-C repeats of CagA may play a role in generating important intraspecies diversity in East-Asian H. pylori.

EPIYA motifs of Helicobacter pylori cagA genotypes and gastrointestinal diseases in the Iranian population: a systematic review and meta-analysis

Helicobacter pylori is one of the best risk factors for gastric cancer. Recent studies have examined the relationship between virulence factors, in particular CagA toxin, and the development of gastrointestinal diseases. According to the literature, there is a significant relationship between the polymorphism of cagA-EPIYA motifs and progression to severe clinical outcomes. The main goal of our study was to determine the possible association between cagA genotypes and the risk of severe clinical outcomes in the Iranian population. We investigated these ambiguities using a comprehensive meta-analysis study, in which we evaluated data from 1762 Iranian patients for a potential correlation between all cagA gene genotypes and gastrointestinal diseases. According to statistical analysis, the frequencies of cagA genotypes including ABC, ABCC, AB and ABCCC in the Iranian population were estimated at 80.18%, 22.81%, 5.52% and 2.76%, respectively; the ABD genotype was not detected in these PCR-based studies. There was a significant relationship between cagA genotypes ABCC and ABCCC and severe clinical outcomes of infection such as peptic ulcer and gastric cancer. Overall, it can be concluded that there is a positive correlation with the number of copies of EPIYA-C and the increase of gastric cancer. Therefore, according to our results, it seems that the EPIYA-ABCCC motif has a strong positive relationship with gastric cancer in the Iranian population.

Helicobacter pylori Virulence Factors-Mechanisms of Bacterial Pathogenicity in the Gastric Microenvironment

Gastric cancer constitutes one of the most prevalent malignancies in both sexes; it is currently the fourth major cause of cancer-related deaths worldwide. The pathogenesis of gastric cancer is associated with the interaction between genetic and environmental factors, among which infection by Helicobacter pylori (H. pylori) is of major importance. The invasion, survival, colonization, and stimulation of further inflammation within the gastric mucosa are possible due to several evasive mechanisms induced by the virulence factors that are expressed by the bacterium. The knowledge concerning the mechanisms of H. pylori pathogenicity is crucial to ameliorate eradication strategies preventing the possible induction of carcinogenesis. This review highlights the current state of knowledge and the most recent findings regarding H. pylori virulence factors and their relationship with gastric premalignant lesions and further carcinogenesis.

N-terminal region of Helicobacter pylori CagA induces IL-8 production in gastric epithelial cells via the β1 integrin receptor

Introduction. Helicobacter pylori is associated with gastrointestinal disease, most notably gastric cancer. Cytotoxin-associated antigen A (CagA), an important virulence factor for H. pylori pathogenicity, induces host cells to release inflammatory factors, especially interleukin-8 (IL-8). The mechanism by which C-terminal CagA induces IL-8 production has been studied extensively, but little is known about the role of the N-terminus.

Aim. To investigate the effect of CagA303–456aa (a peptide in the N-terminal CagA) on IL-8 production by gastric epithelial cells.

Methodology. CagA303-456aa was produced by a prokaryotic expression system and purified by Strep-tag affinity chromatography. An integrin β1 (ITGB1)-deficient AGS cell line was constructed using the CRISPR/Cas9 technique, and NCTC 11637 cagA and/or cagL knockout mutants were constructed via homologous recombination. The levels of IL-8 production were determined by enzyme-linked immunosorbent assay (ELISA), and p38 and ERK1/2 phosphorylation were examined by Western blot.

Results. CagA303-456aa induced IL-8 expression by AGS cells. IL-8 induction by CagA303-456aawas specifically inhibited by ITGB1 deficiency. Notably, CagA303-456aa activated the phosphorylation of both p38 and ERK1/2, and blocking p38 and ERK1/2 activity significantly reduced IL-8 induction by CagA303-456aa. ITGB1 deficiency also inhibited the activation of p38 phosphorylation by CagA303-456aa. Finally, experiments in CagA and/or CagL knockout bacterial lines demonstrated that extracellular CagA might induce IL-8 production by AGS cells.

Conclusion. Residues 303–456 of the N-terminal region of CagA induce IL-8 production via a CagA303-456–ITGB1–p38–IL-8 pathway, and ERK1/2 is also involved in the release of IL-8. Extracellular CagA might induce IL-8 production before translocation into AGS cells.

Molecular anatomy and pathogenic actions of Helicobacter pylori CagA that underpin gastric carcinogenesis

Chronic infection with Helicobacter pylori cagA-positive strains is the strongest risk factor for gastric cancer. The cagA gene product, CagA, is delivered into gastric epithelial cells via the bacterial type IV secretion system. Delivered CagA then undergoes tyrosine phosphorylation at the Glu-Pro-Ile-Tyr-Ala (EPIYA) motifs in its C-terminal region and acts as an oncogenic scaffold protein that physically interacts with multiple host signaling proteins in both tyrosine phosphorylation-dependent and -independent manners. Analysis of CagA using in vitro cultured gastric epithelial cells has indicated that the nonphysiological scaffolding actions of CagA cell-autonomously promote the malignant transformation of the cells by endowing the cells with multiple phenotypic cancer hallmarks: sustained proliferation, evasion of growth suppressors, invasiveness, resistance to cell death, and genomic instability. Transgenic expression of CagA in mice leads to in vivo oncogenic action of CagA without any overt inflammation. The in vivo oncogenic activity of CagA is further potentiated in the presence of chronic inflammation. Since Helicobacter pylori infection triggers a proinflammatory response in host cells, a feedforward stimulation loop that augments the oncogenic actions of CagA and inflammation is created in CagA-injected gastric mucosa. Given that Helicobacter pylori is no longer colonized in established gastric cancer lesions, the multistep nature of gastric cancer development should include a “hit-and-run” process of CagA action. Thus, acquisition of genetic and epigenetic alterations that compensate for CagA-directed cancer hallmarks may be required for completion of the “hit-and-run” process of gastric carcinogenesis.