Helicobacter pylori: an evolutionary perspective

Study of the relationships among known virulence genes, coccoid transformation and cytotoxicity of Helicobacter pylori in different clinical diseases

BACKGROUND

Helicobacter pylori (H. pylori) has infected approximately 4.4 billion individuals worldwide. The known virulence genes and the existing H. pylori typing methods have not been shown to have a recognized correlation with its infectivity. The aim of this study was to elucidate the relationships among known important virulence genes, coccoid transformation, and cytotoxicity of H. pylori isolated from individuals with different clinical diseases to provide guidance for the development of new virulence typing methods for H. pylori.

METHODS

The known important virulence genes of 35 H. pylori strains were identified by whole-gene next-generation sequencing (WGS) and polymerase chain reaction (PCR). The chronological changes in the proportion of coccoid forms of H. pylori and their ultramicroscopic structures were observed chronologically using transmission electron microscopy. Human gastric mucosal epithelial cells (GES-1) were infected with H. pylori strains in vitro to evaluate cytotoxicity of H. pylori.

RESULTS

There were no significant correlations among the known important virulence genes, coccoid transformation and cytotoxicity of H. pylori isolated from patients with different clinical diseases. We developed a new virulence classification based on the defensive and offensive abilities of H. pylori.

CONCLUSIONS

Coccoid transformation and virulence are two independent characteristics of H. pylori that reflect its defensive and offensive abilities, respectively. These two abilities work synergistically, warranting the construction of a new virulence typing method for H. pylori. However, the correlation between the new virulence classification and pathogenic ability still needs to be further verified.

The pursuit of new alternative ways to eradicate Helicobacter pylori continues: Detailed characterization of interactions in the adenylosuccinate synthetase active site

Purine nucleotide synthesis is realised only through the salvage pathway in pathogenic bacterium Helicobacter pylori. Therefore, the enzymes of this pathway, among them also the adenylosuccinate synthetase (AdSS), present potential new drug targets. This paper describes characterization of His₆-tagged AdSS from H. pylori. Thorough analysis of 3D-structures of fully ligated AdSS (in a complex with guanosine diphosphate, 6-phosphoryl-inosine monophosphate, hadacidin and Mg²⁺) and AdSS in a complex with inosine monophosphate (IMP) only, enabled identification of active site interactions crucial for ligand binding and enzyme activity. Combination of experimental and molecular dynamics (MD) simulations data, particularly emphasized the importance of hydrogen bond Arg135-IMP for enzyme dimerization and active site formation. The synergistic effect of substrates (IMP and guanosine triphosphate) binding was suggested by MD simulations. Several flexible elements of the structure (loops) are stabilized by the presence of IMP alone, however loops comprising residues 287-293 and 40-44 occupy different positions in two solved H. pylori AdSS structures. MD simulations discovered the hydrogen bond network that stabilizes the closed conformation of the residues 40-50 loop, only in the presence of IMP. Presented findings provide a solid basis for the design of new AdSS inhibitors as potential drugs against H. pylori.

The tibetan medicine Zuozhu-Daxi can prevent Helicobacter pylori induced-gastric mucosa inflammation by inhibiting lipid metabolism

Background

Tibetan medicine has been used in clinical practice for more than 3800 years. Zuozhu-Daxi (ZZDX), a classic traditional Tibetan medicine, has been proved to be effective in the treatment of digestive diseases, such as chronic gastritis, gastric ulcer, etc. Helicobacter pylori (H. pylori), one of the most common pathogenic microbes, is regarded as the most common cause of gastritis. Researching on the effects of ZZDX on H. pylori-induced gastric mucosa inflammation could provide more evidences on H. pylori treatment and promote the development of Tibetan medicine. This study aimed to explore whether ZZDX could rescue H. pylori-induced gastric mucosa inflammation and its mechanism.

Methods

Male C57BL/6 mice were infected with H. pylori, and orally treated with ZZDX to rescue gastric mucosa inflammation induced by H. pylori infection. Pathology of gastric mucosa inflammation was evaluated under microscopy by hematoxylin–eosin (HE) staining. The infection status of H. pylori was evaluated by immunohistochemical (IHC) staining. The reactive oxygen species (ROS) level in serum was evaluated using a detection kit. IL-1α, IL-6, and PGE2 expression levels in serum were measured using ELISA. IL-1α, IL-8, TNF-α, and NOD1 expression levels in gastric tissues were measured using real-time PCR. RNA sequencing and gene certification of interest were performed to explore the mechanisms in vivo and in vitro.

Results

The results showed that ZZDX could significantly inhibit H. pylori-induced gastric mucosa inflammation using HE staining. IL-1α, IL-6, and PGE2 expression levels in serum were significantly decreased after treatment with ZZDX. ZZDX treatment significantly decreased the mRNA expression of IL-8 induced by H. pylori infection in gastric tissues. Elovl4, Acot1 and Scd1 might be involved in the mechanisms of ZZDX treatment. However, the H. pylori infection status in the gastric mucosa was not reduced after ZZDX treatment.

Conclusions

ZZDX reversed gastric mucosal injury and alleviated gastric mucosa inflammation induced by H. pylori infection.

Effect and Safety of Helicobacter pylori Eradication Treatment Based on Molecular Pathologic Antibiotic Resistance in Chinese Elderly People

Background

The elderly people generally have poor tolerance to drugs and an increased risk of adverse effects. Our study was designed to determine the effect and safety of Helicobacter pylori (H. pylori) eradication treatment based on molecular pathologic antibiotic resistance in Chinese elderly people over the age of 60 years.

Methods

A total of 364 people were retrospectively analyzed, including 113 older people over 60 and 251 young and middle-aged people in the age of 20–59 years. Real-time PCR detection and conventional PCR and sequencing method were used for drug susceptibility testing. As the main outcome measure, the eradication rates (ERs) with their 95% confidence intervals (CIs) were analyzed by intention to treat (ITT) and per protocol (PP). For the safety of therapy, adverse events were analyzed.

Results

For the total people, the resistance rates to clarithromycin (CLR), amoxicillin (AMX), fluoroquinolone (FLQ) and tetracycline (TET) were 65.06%, 7.54%, 61.39% and 20.37%, respectively. After they were divided into two groups, the resistance rates were 62.39% (CLR), 9.09% (AMX), 69.64% (FLQ) and 22.45% (TET) in the 113 older people over 60, and 66.26%, 6.85%, 57.66% and 19.47% in the 251 young and middle-aged people in 20–59. By the ITT analysis, the ERs were 92.04% (95% CI, 86.97–97.10%, n=113) in the older people and 92.43% (95% CI, 89.14–95.73%, n=251) in the young and middle-aged people. By the PP analysis, the ERs were 96.30% (95% CI, 92.68–99.92%, n=108) and 94.69% (95% CI, 91.87–97.52%, n=245), respectively. No significant differences were shown both in the ITT analysis (P=0.896) and in the PP analysis (P=0.517). The three most common adverse events were black stool, dysgeusia and diarrhea, and no serious adverse event was reported.

Conclusion

H. pylori eradication treatment based on molecular pathologic antibiotic resistance showed good effect and safety in Chinese elderly people.

The Helicobacter pylori type IV secretion system upregulates epithelial cortactin expression by a CagA- and JNK-dependent pathway

Cortactin represents an important actin-binding factor, which controls actin-cytoskeletal remodelling in host cells. In this way, cortactin has been shown to exhibit crucial functions both for cell movement and tumour cell invasion. In addition, the cortactin gene cttn is amplified in various cancer types of humans. Helicobacter pylori is the causative agent of multiple gastric diseases and represents a significant risk factor for the development of gastric adenocarcinoma. It has been repeatedly shown that H. pylori manipulates cancer-related signal transduction events in infected gastric epithelial cells such as the phosphorylation status of cortactin. In fact, H. pylori modifies the activity of cortactin's binding partners to stimulate changes in the actin-cytoskeleton, cell adhesion and motility. Here we show that H. pylori infection of cultured AGS and Caco-2 cells for 24-48 hr leads to the overexpression of cortactin by 2-3 fold at the protein level. We demonstrate that this activity requires the integrity of the type IV secretion system (T4SS) encoded by the cag pathogenicity island (cagPAI) as well as the translocated effector protein CagA. We further show that ectopic expression of CagA is sufficient to stimulate cortactin overexpression. Furthermore, phosphorylation of CagA at the EPIYA-repeat region is not required, suggesting that this CagA activity proceeds in a phosphorylation-independent fashion. Inhibitor studies further demonstrate that the involved signalling pathway comprises the mitogen-activated protein kinase JNK (c-Jun N-terminal kinase), but not ERK1/2 or p38. Taken together, using H. pylori as a model system, this study discovered a previously unrecognised cortactin activation cascade by a microbial pathogen. We suggest that H. pylori targets cortactin to manipulate the cellular architecture and epithelial barrier functions that can impact gastric cancer development. TAKE AWAYS: Helicobacter pylori infection induces overexpression of cortactin at the protein level Cortactin upregulation requires the T4SS and effector protein CagA Ectopic expression of CagA is sufficient to stimulate cortactin overexpression Overexpression of cortactin proceeds CagA phosphorylation-independent The involved host cell signalling pathway comprises the MAP kinase JNK.