The type IV secretion system in Helicobacter pylori

A Versatile Nanoluciferase Reporter Reveals Structural Properties Associated with a Highly Efficient, N-Terminal Legionella pneumophila Type IV Secretion Translocation Signal

Many Gram-negative pathogens rely on type IV secretion systems (T4SS) for infection. One limitation has been the lack of ideal reporters to identify T4SS translocated effectors and study T4SS function. Most reporter systems make use of fusions to reporter proteins, in particular, β-lactamase (TEM) and calmodulin-dependent adenylate cyclase (CYA), that allow detection of translocated enzymatic activity inside host cells. However, both systems require costly reagents and use complex, multistep procedures for loading host cells with substrate (TEM) or for analysis (CYA). Therefore, we have developed and characterized a novel reporter system using nanoluciferase (NLuc) fusions to address these limitations. Serendipitously, we discovered that Nluc itself is efficiently translocated by Legionella pneumophila T4SS in an IcmSW chaperone-dependent manner via an N-terminal translocation signal. Extensive mutagenesis in the NLuc N terminus suggested the importance of an α-helical domain spanning D5 to V9, as mutations predicted to disrupt this structure, with one exception, were translocation defective. Notably, NLuc was capable of translocating several proteins examined when fused to the N or C terminus, while maintaining robust luciferase activity. In particular, it delivered the split GFP11 fragment into J774 macrophages transfected with GFPopt, thereby resulting in in vivo assembly of superfolder green fluorescent protein (GFP). This provided a bifunctional assay in which translocation could be assayed by fluorescence microplate, confocal microscopy, and/or luciferase assays. We further identified an optimal NLuc substrate which allowed a robust, inexpensive, one-step, high-throughput screening assay to identify T4SS translocation substrates and inhibitors. Taken together, these results indicate that NLuc provides both new insight into and also tools for studying T4SS biology. IMPORTANCE Type IV secretion systems (T4SS) are used by Gram-negative pathogens to coopt host cell function. However, the translocation signals recognized by T4SS are not fully explained by primary amino acid sequence, suggesting yet-to-be-defined contributions of secondary and tertiary structure. Here, we unexpectedly identified nanoluciferase (NLuc) as an efficient IcmSW-dependent translocated T4SS substrate, and we provide extensive mutagenesis data suggesting that the first N-terminal, alpha-helix domain is a critical translocation recognition motif. Notably, most existing reporter systems for studying translocated proteins make use of fusions to reporters to permit detection of translocated enzymatic activity inside the host cell. However, existing systems require extremely costly substrates, complex technical procedures to isolate eukaryotic cytoplasm for analysis, and/or are insensitive. Importantly, we found that NLuc provides a powerful, cost-effective new tool to address these limitations and facilitate high-throughput exploration of secretion system biology.

Helicobacter pylori and gastric microbiota homeostasis: progress and prospects

Helicobacter pylori, a Gram-negative microaerobic bacteria belonging to the phylum Proteobacteria, can colonize in the stomach and duodenum, and cause a series of gastrointestinal diseases such as gastritis, gastric ulcer and even gastric cancer. At present, the high diversity of the microorganisms in the stomach has been confirmed with culture-independent methods; some researchers have also studied the stomach microbiota composition at different stages of H. pylori carcinogenesis. Here, we mainly review the possible role of H. pylori-mediated microbiota changes in the occurrence and development of gastric cancer to provide new ideas for preventing H. pylori infection and regulating microecological imbalance.

Long-chain fatty acids alter transcription of Helicobacter pylori virulence and regulatory genes

Infection with Helicobacter pylori is one of the most important risk factors for developing gastric cancer (GC). The type IV secretion system (T4SS) encoded in the cag pathogenicity island is the main virulence factor of H. pylori associated with GC. Additionally, other virulence factors have been shown to play a role in the H. pylori virulence, such as vacuolizing cytotoxin (VacA), urease, flagella, and adhesins. Long-chain fatty acids (LCFAs) are signaling molecules that affect the transcription of virulence genes in several pathogenic bacteria such as Salmonella enterica, Vibrio cholerae, Pseudomonas aeruginosa and Mycobacterium tuberculosis. However, the effect of LCFAs on the transcription of H. pylori virulence and regulatory genes remains unknown. Here we analyzed whether the transcription of virulence genes that encode T4SS and cellular envelope components, flagellins, adhesins, toxins, urease, as well as the transcription of different regulatory genes of the H. pylori strain 26695, are altered by the presence of five distinct LCFAs: palmitic, stearic, oleic, linoleic, and linolenic acids. Palmitic and oleic acids up-regulated the transcription of most of the virulence genes tested, including cagL, cagM, flaB, sabA, mraY and vacA, as well as that of the genes encoding the transcriptional regulators NikR, Fur, CheY, ArsR, FlgR, HspR, HsrA, Hup, and CrdR. In contrast, the other LCFAs differentially affected the transcription of the virulence and regulatory genes assessed. Our data show that LCFAs can act as signaling molecules that control the transcription of the H. pylori virulome.

Isolation and characterization of Helicobacter suis from human stomach

Helicobacter suis, a bacterial species naturally hosted by pigs, can colonize the human stomach in the context of gastric diseases such as gastric mucosa-associated lymphoid tissue (MALT) lymphoma. Because H. suis has been successfully isolated from pigs, but not from humans, evidence linking human H. suis infection to gastric diseases has remained incomplete. In this study, we successfully in vitro cultured H. suis directly from human stomachs. Unlike Helicobacter pylori, the viability of H. suis decreases significantly on neutral pH; therefore, we achieved this using a low-pH medium for transport of gastric biopsies. Ultimately, we isolated H. suis from three patients with gastric diseases, including gastric MALT lymphoma. Successful eradication of H. suis yielded significant improvements in endoscopic and histopathological findings. Oral infection of mice with H. suis clinical isolates elicited gastric and systemic inflammatory responses; in addition, progression of gastric mucosal metaplasia was observed 4 mo postinfection. Because H. suis could be isolated from the stomachs of infected mice, our findings satisfied Koch's postulates. Although further prospective clinical studies are needed, H. suis, like H. pylori, is likely a gastric pathogen in humans. Furthermore, comparative genomic analysis of H. suis using complete genomes of clinical isolates revealed that the genome of each H. suis isolate contained highly plastic genomic regions encoding putative strain-specific virulence factors, including type IV secretion system-associated genes, and that H. suis isolates from humans and pigs were genetically very similar, suggesting possible pig-to-human transmission.

Highlighting the use of micro and nanoparticles based-drug delivery systems for the treatment of Helicobacter pylori infections

Due to the high adaptability of Helicobacter pylori and the low targeting specificity of the drugs normally used in pharmacological therapy, the strains are becoming increasingly resistant to these drugs, making it difficult to eradicate the infection. Thus, the search for new therapeutic approaches has been considered urgent. The incorporation of drugs in advanced drug delivery systems, such as nano and microparticles, would allow the improvement of the retention time in the stomach and the prolongation of drug release rates at the target site. Because of this, the present review article aims to highlight the use of micro and nanoparticles as important technological tools for the treatment of H. pylori infections, focussing on the main nanotechnological systems, including nanostructured lipid carriers, liposomes, nanoemulsion, metallic nanoparticles, and polymeric nanoparticles, as well as microtechnological systems such as gastroretentive dosage forms, among them mucoadhesive, magnetic and floating systems were highlighted.

Transcriptional Profile of Helicobacter pylori Virulence Genes in Patients with Gastritis and Gastric Cancer

Introduction

Numerous molecular epidemiology studies have been performed about the frequency of Helicobacter pylori virulence genes in patients with H. pylori infection so far. This study was conducted to detect transcriptional profile by cDNA of H. pylori virulence genes in gastric biopsy samples of gastritis and gastric carcinoma patients.

Materials and Methods

In a case-control study, based on the prevalence of gastritis and gastric cancer in Sanandaj city during 2018 and 2019, 23 and 11 gastric antral biopsy samples with H. pylori infection were collected from gastritis and gastric carcinoma patients by the consecutive and available sampling method. Pathological characters, including tumor grades and tumor areas for gastric carcinoma biopsy samples prepared from gastric cancer areas, were determined by the pathologist. Total RNA of gastric antral biopsy samples was extracted, and their cDNA was synthesized by TaKaRa kit. H. pylori virulence genes' cDNA using specific primers and PCR was detected. This study's results were analyzed by SPSS version 25 and statics chi-square tests for determination of relationship and correlation between cDNAs of H. pylori transcriptional profile and clinical outcomes of H. pylori infection, including gastritis, gastric carcinoma, tumor grades, and tumor area.

Results

The positive statistical correlations were observed between transcripts of cagA, cagA-EPIYAC, cagE, and cagY genes and H. pylori infection clinical outcomes (P < 0.05).

Conclusion

Detection of the H. pylori virulence genes' cDNA in gastric biopsy samples can help provide the prognosis of clinical outcomes.

Acute and chronic infection of H. pylori caused the difference in apoptosis of gastric epithelial cells

Helicobacter pylori (H. pylori) is one of the most important pathogenic bacteria associated with various gastrointestinal diseases. At present, its apoptotic or antiapoptotic mechanism on gastric epithelial cells remains unknown and needs further illustrated. In this study, acute infection model (H. pylori and GES-1 cells were co-cultured for 24 h at a multiplicity of infection MOI of 100:1) and chronic infection model (GES-1 cells were infected repeatedly every 24 h at a multiplicity of infection MOI of 100:1 for approximately 8 weeks) were established, respectively. the chronic H. pylori infected GES-1 cells underwent a typically morphological change and Western Blot results showed that there was slight decrease in expression of E-cadherin, and obvious increase in expression of Vimentin. Apoptosis of these two models were analyzed by flow cytometry compared with the control cells, meanwhile, apoptosis associated markers (Bcl-xL, Bcl-2, Bax, etc) were detected by Western blot, additional in clinical H. pylori-positive gastric cancer tissues. Results showed that compared with the control cells, acute infection of H. pylori significantly accelerated the apoptosis of GES-1, increased the expression of Bax and Cleaved caspase-3, down-regulated expression of Bcl-xL and Bcl-2. Moreover, an opposite result was found in chronic infection of model and clinical gastric cancer tissues, and enhanced expression of NF-κB p65. Taken together, these findings suggest that H. pylori infection plays differential effects on apoptosis of gastric epithelial cells.

Genetic requirements and transcriptomics of Helicobacter pylori biofilm formation on abiotic and biotic surfaces

Biofilm growth is a widespread mechanism that protects bacteria against harsh environments, antimicrobials, and immune responses. These types of conditions challenge chronic colonizers such as Helicobacter pylori but it is not fully understood how H. pylori biofilm growth is defined and its impact on H. pylori survival. To provide insights into H. pylori biofilm growth properties, we characterized biofilm formation on abiotic and biotic surfaces, identified genes required for biofilm formation, and defined the biofilm-associated gene expression of the laboratory model H. pylori strain G27. We report that H. pylori G27 forms biofilms with a high biomass and complex flagella-filled 3D structures on both plastic and gastric epithelial cells. Using a screen for biofilm-defective mutants and transcriptomics, we discovered that biofilm cells demonstrated lower transcripts for TCA cycle enzymes but higher ones for flagellar formation, two type four secretion systems, hydrogenase, and acetone metabolism. We confirmed that biofilm formation requires flagella, hydrogenase, and acetone metabolism on both abiotic and biotic surfaces. Altogether, these data suggest that H. pylori is capable of adjusting its phenotype when grown as biofilm, changing its metabolism, and re-shaping flagella, typically locomotion organelles, into adhesive structures.

The role of Helicobacter pylori in cardiovascular toxicity mechanisms

Despite the long history of the concept where infection plays a significant role in cardiovascular diseases (atherosclerosis in particular), today it is relevant and represented a significant interest.

This article discusses H. pylori role in mechanisms of cardiovascular homeostasis disturbance. H. pylori involvement in atherogenic damage of arteries, and/or plaque destabilization is no doubt. This vidence is detailed in this review article.

A lucid review of Helicobacter pylori-induced DNA damage in gastric cancer

Helicobacter pylori (H pylori) is the main risk factor for gastric cancer (GC). In recent years, many studies have addressed the effects of H pylori itself and of H pylori-induced chronic inflammation on DNA damage. Unrepaired or inappropriately repaired DNA damage is one possible carcinogenic mechanism. We may conclude that H pylori-induced DNA damage is one of the carcinogenic mechanisms of GC. In this review, we summarize the interactions between H pylori and DNA damage and the effects of H pylori-induced DNA damage on GC. Then, focusing on oxidative stress, we introduce the application of antioxidants in GC. At the end of this review, we discuss the outlook for further research on H pylori-induced DNA damage.