The Middle Fragment of Helicobacter pylori CagA Induces Actin Rearrangement and Triggers Its Own Uptake into Gastric Epithelial Cells

Biochemical characterization of paralyzed flagellum proteins A (PflA) and B (PflB) from Helicobacter pylori flagellar motor

Motility by means of flagella plays an important role in the persistent colonization of Helicobacter pylori in the human stomach. The H. pylori flagellar motor has a complex structure that includes a periplasmic scaffold, the components of which are still being identified. Here, we report the isolation and characterization of the soluble forms of two putative essential H. pylori motor scaffold components, proteins PflA and PflB. We developed an on-column refolding procedure, overcoming the challenge of inclusion body formation in Escherichia coli. We employed mild detergent sarkosyl to enhance protein recovery and n-dodecyl-N,N-dimethylamine-N-oxide (LDAO)-containing buffers to achieve optimal solubility and monodispersity. In addition, we showed that PflA lacking the β-rich N-terminal domain is expressed in a soluble form, and behaves as a monodisperse monomer in solution. The methods for producing the soluble, folded forms of H. pylori PflA and PflB established in this work will facilitate future biophysical and structural studies aimed at deciphering their location and their function within the flagellar motor.

The Helicobacter pylori infection alters the intercellular junctions on the pancreas of gerbils (Meriones unguiculatus)

Helicobacter pylori is a common resident in the stomach of at least half of the world's population and recent evidence suggest its emergence in other organs such as the pancreas. In this organ, the presence of H. pylori DNA has been reported in cats, although the functional implications remain unknown. In this work, we determined distinct features related to the H. pylori manifestation in pancreas in a rodent model, in order to analyse its functional and structural effect. Gerbils inoculated with H. pylori exhibited the presence of this bacterium, as revealed by the expression of some virulence factors, as CagA and OMPs in stomach and pancreas, and confirmed by urease activity, bacterial culture, PCR and immunofluorescence assays. Non-apparent morphological changes were observed in pancreatic tissue of infected animals; however, delocalization of intercellular junction proteins (claudin-1, claudin-4, occludin, ZO-1, E-cadherin, β-catenin, desmoglein-2 and desmoplakin I/II) and rearrangement of the actin-cytoskeleton were exhibited. This structural damage was consistent with alterations in the distribution of insulin and glucagon, and a systemic inflammation, event demonstrated by elevated IL-8 levels. Overall, these findings indicate that H. pylori can reach the pancreas, possibly affecting its function and contributing to the development of pancreatic diseases.

Pal power: Demonstration of the functional association of the Helicobacter pylori flagellar motor with peptidoglycan-associated lipoprotein (Pal) and its preliminary crystallographic analysis

The bacterial flagellar motor is a molecular nanomachine, the assembly and regulation of which requires many accessory proteins. Their identity, structure and function are often discovered through characterisation of mutants with impaired motility. Here, we demonstrate the functional association of the Helicobacter pylori peptidoglycan-associated lipoprotein (HpPal) with the flagellar motor by analysing the motility phenotype of the ∆pal mutant, and present the results of the preliminary X-ray crystallographic analysis of its globular C-terminal domain HpPal-C. Purified HpPal-C behaved as a dimer in solution. Crystals of HpPal-C were grown by the hanging drop vapour diffusion method using medium molecular weight polyethylene glycol (PEG) Smear as the precipitating agent. The crystals belong to the primitive orthorhombic space group P1 with unit cell parameters a = 50.7, b = 63.0, c = 75.1 Å. X-ray diffraction data were collected to 1.8 Å resolution on the Australian Synchrotron beamline MX2. Calculation of the Matthews coefficient (VM=2.24 Å3/Da) and molecular replacement showed that the asymmetric unit contains two protein subunits. This study is an important step towards elucidation of the non-canonical role of H. pylori Pal in the regulation, or function of, the flagellar motor.

Influence of the Microbiome Metagenomics and Epigenomics on Gastric Cancer

Gastric cancer (GC) is one of the major causes of cancer deaths worldwide. The disease is seldomly detected early and this limits treatment options. Because of its heterogeneous and complex nature, the disease remains poorly understood. The literature supports the contribution of the gut microbiome in the carcinogenesis and chemoresistance of GC. Drug resistance is the major challenge in GC therapy, occurring as a result of rewired metabolism. Metabolic rewiring stems from recurring genetic and epigenetic factors affecting cell development. The gut microbiome consists of pathogens such as H. pylori, which can foster both epigenetic alterations and mutagenesis on the host genome. Most of the bacteria implicated in GC development are Gram-negative, which makes it challenging to eradicate the disease. Gram-negative bacterium co-infections with viruses such as EBV are known as risk factors for GC. In this review, we discuss the role of microbiome-induced GC carcinogenesis. The disease risk factors associated with the presence of microorganisms and microbial dysbiosis are also discussed. In doing so, we aim to emphasize the critical role of the microbiome on cancer pathological phenotypes, and how microbiomics could serve as a potential breakthrough in determining effective GC therapeutic targets. Additionally, consideration of microbial dysbiosis in the GC classification system might aid in diagnosis and treatment decision-making, taking the specific pathogen/s involved into account.

Inhibitory and Injury-Protection Effects of O-Glycan on Gastric Epithelial Cells Infected with Helicobacter pylori

Helicobacter pylori (H. pylori) is an important pathogen that can cause gastric cancer. Multiple adhesion molecules mediated H. pylori adherence to cells is the initial step in the infection of host cells. H. pylori cholesterol-α-glucosyltransferase (CGT) recognizes and extracts cholesterol from cell membranes to destroy lipid raft structure, further promotes H. pylori adhesion to gastric epithelial cells. O-Glycan, a substance secreted by the deep gastric mucosa, can competitively inhibit CGT activity and may serve as an important factor to prevent H. pylori colonization in the deep gastric mucosa. However, the inhibitory and injury-protection effects of O-Glycan against H. pylori infection has not been well investigated. In this study, we found that O-Glycan significantly inhibited the relative urease content in the coinfection system. In the presence of O-glycan, the injury of GES-1 cells in H. pylori persistent infection model was attenuated and the cell viability was increased. We use fluorescein isothiocyanate-conjugated cholera toxin subunit B (FITC-CTX-B) to detect lipid rafts on gastric epithelial cells and observed that O-glycan can protect H. pylori from damaging lipid raft structures on cell membranes. In addition, transcriptome data showed that O-glycan treatment significantly reduced the activation of inflammatory cancer transformation pathway caused by H. pylori infection. Our results suggest that O-Glycan is able to inhibit H. pylori persistent infection of gastric epithelial cells, reduce the damage caused by H. pylori, and could serve as a potential medicine to treat patients infected with H. pylori.

Angiopep-2-functionalized nanoparticles enhance transport of protein drugs across intestinal epithelia by self-regulation of targeted receptors

Ligand-modified nanoparticles (NPs) have been widely used in oral drug delivery systems to promote endocytosis on intestinal epithelia. However, their transcytosis across the intestinal epithelia is still limited. Except for complex intracellular trafficking, recycling again from the apical sides into the intestinal lumen of the endocytosed NPs cannot be ignored. In this study, we modified NP surfaces with angiopep-2 (ANG) that targeted the low-density lipoprotein receptor-related protein 1 (LRP-1) expressed on the intestine to increase both the apical endocytosis and basolateral transcytosis of NPs. Notably, our finding revealed that ANG NPs could increase the apical expression and further basolateral redistribution of LRP-1 on Caco-2 cells, thus generating an apical-to-basolateral absorption pattern. Because of the enhanced transcytosis, insulin loaded ANG NPs possessed much stronger absorption efficiency and induced maximal blood glucose reduction to 61.46% in diabetic rats. Self-regulating the distribution of receptors on polarized intestine cells to promote basolateral transcytosis will provide promising insights for the rational design of oral delivery systems of protein/peptide drugs.

Campylobacter jejuni Cytolethal Distending Toxin C Exploits Lipid Rafts to Mitigate Helicobacter pylori-Induced Pathogenesis

Helicobacter pylori infection is associated with several gastrointestinal diseases, including gastritis, peptic ulcer, and gastrointestinal adenocarcinoma. Two major cytotoxins, vacuolating cytotoxin A (VacA) and cytotoxin-associated gene A (CagA), interact closely with lipid rafts, contributing to H. pylori-associated disease progression. The Campylobacter jejuni cytolethal distending toxin consists of three subunits: CdtA, CdtB, and CdtC. Among them, CdtA and CdtC bind to membrane lipid rafts, which is crucial for CdtB entry into cells. In this study, we employed recombinant CdtC (rCdtC) to antagonize the functions of H. pylori cytotoxin in cells. Our results showed that rCdtC alleviates cell vacuolation induced by H. pylori VacA. Furthermore, rCdtC reduces H. pylori CagA translocation, which decreases nuclear factor kappa-B activation and interleukin-8 production, resulting in the mitigation of gastric epithelial cell inflammation. These results reveal that CdtC hijacks cholesterol to compete for H. pylori cytotoxin actions via lipid rafts, ameliorating H. pylori-induced pathogenesis.

Influence of the MUC1 Cell Surface Mucin on Gastric Mucosal Gene Expression Profiles in Response to Helicobacter pylori Infection in Mice

The cell surface mucin MUC1 is an important host factor limiting Helicobacter pylori (H. pylori) pathogenesis in both humans and mice by providing a protective barrier and modulating mucosal epithelial and leukocyte responses. The aim of this study was to establish the time-course of molecular events in MUC1-modulated gene expression profiles in response to H. pylori infection in wild type (WT) and MUC1-deficient mice using microarray-determined mRNA expression, gene network analysis and Ingenuity Pathway Analysis (IPA). A time-course over the first 72 h of infection showed significantly higher mucosal loads of bacteria at 8 h of infection in Muc1^−/− mice compared with WT, confirming its importance in the early stages of infection (P = 0.0003). Microarray analysis revealed 266 differentially expressed genes at one or more time-points over 72 h in the gastric mucosa of Muc1^−/− mice compared with WT control using a threshold of 2-fold change. The SPINK1 pancreatic cancer canonical pathway was strongly inhibited in Muc1^−/− mice compared with WT at sham and 8 h infection (P = 6.08E-14 and P = 2.25 E-19, respectively) but potently activated at 24 and 72 h post-infection (P = 1.38E-22 and P = 5.87E-13, respectively). The changes in this pathway are reflective of higher expression of genes mediating digestion and absorption of lipids, carbohydrates, and proteins at sham and 8 h infection in the absence of MUC1, but that this transcriptional signature is highly down regulated as infection progresses in the absence of MUC1. Uninfected Muc1^−/− gastric tissue was highly enriched for expression of factors involved in lipid metabolism and 8 h infection further activated this network compared with WT. As infection progressed, a network of antimicrobial and anti-inflammatory response genes was more highly activated in Muc1^−/− than WT mice. Key target genes identified by time-course microarrays were independently validated using RT-qPCR. These results highlight the dynamic interplay between the host and H. pylori, and the role of MUC1 in host defense, and provide a general picture of changes in cellular gene expression modulated by MUC1 in a time-dependent manner in response to H. pylori infection.

Detection of Novel Amino Acid Polymorphisms in the East Asian CagA of Helicobacter Pylori with Full Sequencing Data

Cytotoxin-associated gene A (CagA) is generally accepted to be the most important virulence factor of Helicobacter pylori and increases the risk of developing gastric cancer. East Asian CagA, which includes the EPIYA-D segment at the C-terminal region, has a significantly higher gastric carcinogenic rate than Western CagA including the EPIYA-C segment. Although the amino acid polymorphism surrounding the EPIYA motif in the C-terminal region has been examined in detail, limited information is currently available on the amino acid polymorphism of the N-terminal region of East Asian CagA. In the present study, we analyzed the sequencing data of East Asian CagA that we obtained previously to detect amino acid changes (AACs) in the N-terminal region of East Asian CagA. Four highly frequent AACs in the N-terminal region of East Asian CagA were detected in our datasets, two of which (V356A, Y677F) exhibited reproducible specificity using a validation dataset from the NCBI database, which are candidate AACs related to the pathogenic function of CagA. We examined whether these AACs affect the functions of CagA in silico model. The computational docking simulation model showed that binding affinity between CagA and phosphatidylserine remained unchanged in the model of mutant CagA reflecting both AAC, whereas that between CagA and α5β1 integrin significantly increased. Based on whole genome sequencing data we herein identified novel specific AACs in the N-terminal regions of EPIYA-D that have the potential to change the function of CagA.

The Helicobacter pylori Cag Type IV Secretion System

Colonization of the human stomach with Helicobacter pylori strains containing the cag pathogenicity island is a risk factor for development of gastric cancer. The cag pathogenicity island contains genes encoding a secreted effector protein (CagA) and components of a type IV secretion system (Cag T4SS). The molecular architecture of the H. pylori Cag T4SS is substantially more complex than that of prototype T4SSs in other bacterial species. In this review, we discuss recent discoveries pertaining to the structure and function of the Cag T4SS and its role in gastric cancer pathogenesis.

Cellular evasion strategies of Helicobacter pylori in regulating its intracellular fate

Helicobacter pylori colonizes human stomach mucosa and its infection causes gastrointestinal diseases with variable severity. Bacterial infection stimulates autophagy, which is a part of innate immunity used to eliminate intracellular pathogens. Several intracellular bacteria have evolved multipronged strategies to circumvent this conserved system and thereby enhance their chance of intracellular survival. Nonetheless, studies on H. pylori have produced inconsistent results, showing either elevated or reduced clearance efficiency of intracellular bacteria through autophagy. In this review, we summarize recent studies on the mechanisms involved in autophagy induced by H. pylori and the fate of intracellular bacteria.

Roles of Cyclooxygenase-2 gene -765G > C (rs20417) and -1195G > A (rs689466) polymorphisms in gastric cancer: A systematic review and meta-analysis

BACKGROUND

The roles of cyclooxygenase-2 (COX2) -765G > C (rs20417) and -1195G > A (rs689466) polymorphisms in gastric cancer were intensively analyzed, but the results of these studies were inconsistent. We conducted a meta-analysis and trial sequential analysis to elucidate the associations between these two COX2 polymorphisms and gastric cancer risk.

METHODS

Eligible studies were searched in PubMed, Embase, Cochrane library databases, China National Knowledge Infrastructure, Vip, and Wanfang databases. Odds ratios (ORs) with 95% confidence intervals (CIs) were used to assess the genetic correlation between COX2 polymorphisms and gastric cancer susceptibility in five genetic models. Trial sequential analysis (TSA) was conducted to estimate whether the evidence of the results is sufficient. Furthermore, their interactions with Helicobacter pylori (H. pylori) or smoking in gastric cancer were also assessed using a case-only method.

RESULTS

The COX2 gene -765G > C polymorphism showed no significant association with gastric cancer susceptibility under all the five genetic models (take the allelic model for example: OR = 1.41, 95% CI: 0.95-2.09) in total analysis, and the stratification analysis by ethnicity indicated a similar association in Caucasian group under four genetic models (allelic model, dominant model, homozygous model, and heterozygous model). But in the subgroup of the Asian population, the -765G > C polymorphism was significantly associated with gastric cancer risk under the same contrast. The COX2 -1195G > A polymorphism showed significant correlation with gastric cancer susceptibility in total analysis, and stratification analysis by ethnicity also revealed a similar association in both Asian and Caucasian groups under the same contrast. Moreover, TSA confirmed such associations. Both H. pylori infection and cigarette smoking interacted with -765 C allele in gastric cancer (OR = 3.79, 95% CI: 1.15-12.43 and OR = 2.48, 95% CI: 1.38-4.48, respectively), but not in -1195 A allele (OR = 1.96, 95% CI: 0.62-6.21, and OR = 1.24, 95% CI: 0.93-1.64, respectively).

CONCLUSIONS

COX2 -765G > C polymorphism may serve as a genetic biomarker of gastric cancer in Asians, but not in Caucasians. COX2 -1195G > A polymorphism may serve as a genetic biomarker of gastric cancer in both Asians and Caucasians. The -765G > C, rather than -1195G > A polymorphism interacted with H. pylori infection or cigarette smoking to increase gastric cancer risk.

Epigenetic Regulation of Tumor Suppressors by Helicobacter pylori Enhances EBV-Induced Proliferation of Gastric Epithelial Cells

Helicobacter pylori and Epstein-Barr virus (EBV) are two well-known contributors to cancer and can establish lifelong persistent infection in the host. This leads to chronic inflammation, which also contributes to development of cancer. Association with H. pylori increases the risk of gastric carcinoma, and coexistence with EBV enhances proliferation of infected cells. Further, H. pylori-EBV coinfection causes chronic inflammation in pediatric patients. We have established an H. pylori-EBV coinfection model system using human gastric epithelial cells. We showed that H. pylori infection can increase the oncogenic phenotype of EBV-infected cells and that the cytotoxin-associated gene (CagA) protein encoded by H. pylori stimulated EBV-mediated cell proliferation in this coinfection model system. This led to increased expression of DNA methyl transferases (DNMTs), which reprogrammed cellular transcriptional profiles, including those of tumor suppressor genes (TSGs), through hypermethylation. These findings provide new insights into a molecular mechanism whereby cooperativity between two oncogenic agents leads to enhanced oncogenic activity of gastric cancer cells.IMPORTANCE We have studied the cooperativity between H. pylori and EBV, two known oncogenic agents. This led to an enhanced oncogenic phenotype in gastric epithelial cells. We now demonstrate that EBV-driven epigenetic modifications are enhanced in the presence of H. pylori, more specifically, in the presence of its CagA secretory antigen. This results in increased proliferation of the infected gastric cells. Our findings now elucidate a molecular mechanism whereby expression of cellular DNA methyl transferases is induced influencing infection by EBV. Hypermethylation of the regulatory genomic regions of tumor suppressor genes results in their silencing. This drastically affects the expression of cell cycle, apoptosis, and DNA repair genes, which dysregulates their associated processes, and promotion of the oncogenic phenotype.