mRNA expression profiling reveals a role of Helicobacter pylori vacuolating toxin in escaping host defense

Helicobacter pylori-Associated Iron Deficiency Anemia in Childhood and Adolescence-Pathogenesis and Clinical Management Strategy

Many epidemiological studies and meta-analyses show that persistent Helicobacter pylori infection in the gastric mucosa can lead to iron deficiency or iron deficiency anemia (IDA), particularly in certain populations of children and adolescents. Moreover, it has been demonstrated that H. pylori infection can lead to and be closely associated with recurrent and/or refractory iron deficiency and IDA. However, the pathogenesis and specific risk factors leading to this clinical outcome in H. pylori-infected children remain poorly understood. In general, most of pediatric patients with H. pylori-associated IDA do not show evidence of overt blood loss due to gastrointestinal hemorrhagic lesions. In adult populations, H. pylori atrophic gastritis is reported to cause impaired iron absorption due to impaired gastric acid secretion, which, subsequently, results in IDA. However, significant gastric atrophy, and the resultant substantial reduction in gastric acid secretion, has not been shown in H. pylori-infected children. Recently, it has been hypothesized that competition between H. pylori and humans for iron availability in the upper gastrointestinal tract could lead to IDA. Many genes, including those encoding major outer membrane proteins (OMPs), are known to be involved in iron-uptake mechanisms in H. pylori. Recent studies have been published that describe H. pylori virulence factors, including specific OMP genes that may be associated with the pathogenesis of IDA. Daily iron demand substantively increases in children as they begin pubertal development starting with the associated growth spurt, and this important physiological mechanism may play a synergistic role for the microorganisms as a host pathogenetic factor of IDA. Like in the most recent pediatric guidelines, a test-and-treat strategy in H. pylori infection should be considered, especially for children and adolescents in whom IDA is recurrent or refractory to iron supplementation and other definitive causes have not been identified. This review will focus on providing the evidence that supports a clear biological plausibility for H. pylori infection and iron deficiency, as well as IDA.

Helicobacter pylori induced reactive oxygen Species: A new and developing platform for detection

BACKGROUND

Gastric cancer is the third leading cause of cancer-related deaths worldwide. Approximately 70% of cases are caused by a microaerophilic gram-negative bacteria, Helicobacter pylori (H. pylori), which potentially infect almost 50% of world's population. H. pylori is mainly responsible for persistent oxidative stress in stomach and induction of chronic immune responses which ultimately result into DNA damage that eventually can lead to gastric cancer. Oxidative stress is the result of excessive release of ROS/RNS by activated neutrophils whereas bacteria itself also produce ROS in host cells. Therefore, ROS detection is an important factor for development of new strategies related to identification of H. pylori infection.

METHODS

The review summarizes the various available techniques for ROS detection with their advantages, disadvantages, and limitations. All of the information included in this review have been retrieved from published studies on ROS generation and its detection methods.

RESULTS

Precisely, 71 articles have been incorporated and evaluated for this review. The studied articles were divided into two major categories including articles on H. pylori-related pathogenesis and various ROS detection methods for example probe-based methods, immunoassays, gene expression profiling, and other techniques. The major part of probe activity is based on fluorescence, chemiluminescence, or bioluminescence and detected by complementary techniques such as LC-MS, HPLC, EPR, and redox blotting.

CONCLUSION

The review describes the methods for ROS detection but due to some limitations in conventional methods, there is a need of cost-effective, early and fast detection methods like biosensors to diagnose the infection at its initial stage.

Helicobacter pylori sabA gene is associated with iron deficiency anemia in childhood and adolescence

Background

Gastric Helicobacter pylori colonization leads to iron deficiency anemia (IDA), especially in children and adolescents. However the pathogenesis is poorly understood.

Objective

We sought to identify specific H. pylori genes involved in IDA development, by comparing bacterial genome-wide expression profiling in patients affected or not.

Methods

H. pylori were isolated from four children with IDA and four from matched controls without IDA. Based on these isolates, cDNA microarrays under iron-replete or depleted conditions were systematically performed to compare gene expression profiles at the whole genome level. Real-time reverse-transcription (RT-) PCR and protein assays were performed for further assessing the profile differentiation of the identified H. pylori IDA-associated genes.

Results

We identified 29 and 11 genes with significantly higher or lower expression in the IDA isolates compared to non-IDA isolates, respectively. Especially notable were higher expression of sabA gene encoding sialic acid-binding adhesin in the IDA isolates, which was confirmed by real-time RT-PCR study. Moreover, iron-depletion in vitro led to up-regulation of fecA1 and frpB1 genes and down-regulation of pfr, as predicted. Known iron-regulated genes such as fur, pfr, fecA, and feoB did not significantly differ between both groups. The IDA isolates had significantly higher expression of vacuolating cytotoxin gene vacA than non-IDA isolates, consistent with the results of VacA protein assays. There were no significant differences in bacterial growth value between IDA and non-IDA isolates.

Conclusions

It is likely that H. pylori carrying high expression of sabA causes IDA, especially in children and adolescents who have increased daily iron demand. In addition, it is possible that several host-interactive genes, including vacA, may play a synergistic role for sabA in IDA development.

Chemical compounds from anthropogenic environment and immune evasion mechanisms: potential interactions

An increasing number of studies suggest an important role of host immunity as a barrier to tumor formation and progression. Complex mechanisms and multiple pathways are involved in evading innate and adaptive immune responses, with a broad spectrum of chemicals displaying the potential to adversely influence immunosurveillance. The evaluation of the cumulative effects of low-dose exposures from the occupational and natural environment, especially if multiple chemicals target the same gene(s) or pathway(s), is a challenge. We reviewed common environmental chemicals and discussed their potential effects on immunosurveillance. Our overarching objective was to review related signaling pathways influencing immune surveillance such as the pathways involving PI3K/Akt, chemokines, TGF-β, FAK, IGF-1, HIF-1α, IL-6, IL-1α, CTLA-4 and PD-1/PDL-1 could individually or collectively impact immunosurveillance. A number of chemicals that are common in the anthropogenic environment such as fungicides (maneb, fluoxastrobin and pyroclostrobin), herbicides (atrazine), insecticides (pyridaben and azamethiphos), the components of personal care products (triclosan and bisphenol A) and diethylhexylphthalate with pathways critical to tumor immunosurveillance. At this time, these chemicals are not recognized as human carcinogens; however, it is known that they these chemicalscan simultaneously persist in the environment and appear to have some potential interfere with the host immune response, therefore potentially contributing to promotion interacting with of immune evasion mechanisms, and promoting subsequent tumor growth and progression.

Gene expression profiling in gastric mucosa from Helicobacter pylori-infected and uninfected patients undergoing chronic superficial gastritis

Helicobacter pylori infection reprograms host gene expression and influences various cellular processes, which have been investigated by cDNA microarray using in vitro culture cells and in vivo gastric biopsies from patients of the Chronic Abdominal Complaint. To further explore the effects of H. pylori infection on host gene expression, we have collected the gastric antral mucosa samples from 6 untreated patients with gastroscopic and pathologic confirmation of chronic superficial gastritis. Among them three patients were infected by H. pylori and the other three patients were not. These samples were analyzed by a microarray chip which contains 14,112 cloned cDNAs, and microarray data were analyzed via BRB ArrayTools software and Ingenuity Pathways Analysis (IPA) website. The results showed 34 genes of 38 differentially expressed genes regulated by H. pylori infection had been annotated. The annotated genes were involved in protein metabolism, inflammatory and immunological reaction, signal transduction, gene transcription, trace element metabolism, and so on. The 82% of these genes (28/34) were categorized in three molecular interaction networks involved in gene expression, cancer progress, antigen presentation and inflammatory response. The expression data of the array hybridization was confirmed by quantitative real-time PCR assays. Taken together, these data indicated that H. pylori infection could alter cellular gene expression processes, escape host defense mechanism, increase inflammatory and immune responses, activate NF-κB and Wnt/β-catenin signaling pathway, disturb metal ion homeostasis, and induce carcinogenesis. All of these might help to explain H. pylori pathogenic mechanism and the gastroduodenal pathogenesis induced by H. pylori infection.

Ran GTPase regulates hemocytic phagocytosis of shrimp by interaction with myosin

Ran GTPases, one family of small G protein superfamily, have been widely demonstrated to be involved in the transport system between cytoplasm and the nucleus. However, the function of Ran GTPase in immunity remains unclear. In our study, it was found that the Ran GTPase (designated as PjRan) was up-regulated in virus-resistant shrimp, indicating that the PjRan might be implicated in the innate immune system against virus infection. On the basis of protein interactions, it was found that the PjRan interacted with myosin, a crucial protein in the process of phagocytosis to form a protein complex. The RNAi and mRNA assays showed that the PjRan could regulate shrimp hemocytic phagocytosis. Further data evidenced that the depletion of PjRan by RNAi caused a significant increase of virus copies, and the overexpression of PjRan resulted in a significant decrease of virus copies, suggesting that the PjRan participated in the antiviral immunity by regulating phagocytosis. Therefore, our study revealed a completely novel aspect of Ran GTPase in phagocytosis by the direct interaction with the cytoskeleton protein and presented a novel pathway concerning to antiviral immunity, which will help to better understand the molecular events in immune response against virus infection in invertebrates.

Host gene expression profiling in pathogen–host interactions

Microarray technology is a powerful high-throughput tool for the analysis of host-pathogen interactions that permits simultaneous interrogation of the transcriptional status of thousands of genes. Emerging topics from microarray-based studies employing diverse pathogens and cell types suggest an initial common host response largely characterised by features of the innate immune response. However, specific host gene expression patterns that reflect differences between bacteria of related genera, different species of a particular genus, as well as strains within a single species can also be discerned. These differences are indicative of virulence determinant functions and suggest adaptive survival strategies. These studies have led to a more comprehensive understanding of the host response and identified new avenues of research for potential control strategies against pathogens.

NF-kappaB and ERK-signaling pathways contribute to the gene expression induced by cag PAI-positive-Helicobacter pylori infection

AIM

To elucidate the sequential gene expression profile in AGS cells co-cultured with wild-type Helicobacter pylori (H pylori) as a model of H pylori-infected gastric epithelium, and to further examine the contribution of cag-pathogenicity islands (cagPAI)-coding type IV secretion system and the two pathways, nuclear factor kappa B (NF-kappaB) and extracellular signal-regulated kinases (ERK) on wild-type H pylori-induced gene expression.

METHODS

Gene expression profiles induced by H pylori were evaluated in AGS gastric epithelial cells using cDNA microarray, which were present in the 4 600 independent clones picked up from the human gastric tissue. We also analyzed the contribution of NF-kappaB and ERK signaling on H pylori-induced gene expression by using inhibitors of specific signal pathways. The isogenic mutant with disrupted cagE (Delta cagE) was used to elucidate the role of cagPAI-encoding type IV secretion system in the gene expression profile.

RESULTS

According to the expression profile, the genes were classified into four clusters. Among them, the clusters characterized by continuous upregulation were most conspicuous, and it contained many signal transducer activity-associated genes. The role of cagPAI on cultured cells was also investigated using isogenic mutant cagE, which carries non-functional cagPAI. Then the upregulation of more than 80% of the induced genes (476/566) was found to depend on cagPAI. Signal transducer pathway through NF-kappaB or ERK are the major pathways which are known to be activated by cagPAI-positive H pylori. The role of these pathways in the whole signal activation by cagPAI-positive H pylori was analyzed. The specific inhibitors against NF-kappaB or ERK pathway blocked the activation of gene expression in 65% (367/566) or 76% (429/566) of the genes whose activation appealed to depend on cagPAI.

CONCLUSION

These results suggest that more than half of the genes induced by cagPAI-positive H pylori depend on NF-kappaB and ERK signaling activation, and these pathways may play a role in the gene expression induced by host-bacterial interaction which may associate with H pylori-related gastro-duodenal diseases.