Helicobacter pylori-induced posttranscriptional regulation of H-K-ATPase α-subunit gene expression by miRNA

MicroRNA-1289 Functions as a Novel Tumor Suppressor in Oral Squamous Cell Carcinoma

Recently, numerous tumor-suppressive microRNAs (TS-miRs) have been identified in human malignancies. Here, we attempted to identify novel TS-miRs in oral squamous cell carcinoma (OSCC). First, we transfected human OSCC cells individually with 968 synthetic miRs mimicking human mature miRs individually, and the growth of these cells was evaluated using the WST-8 assay. Five miR mimics significantly reduced the cell growth rate by less than 30%, and the miR-1289 mimic had the most potent growth inhibitory effect among these miRs. Subsequently, we assessed the in vivo growth-inhibitory effects of miR-1289 using a mouse model. The administration of the miR-1289 mimic-atelocollagen complex significantly reduced the size of subcutaneously xenografted human OSCC tumors. Next, we investigated the expression of miR-1289 in OSCC tissues using reverse transcription-quantitative PCR. The expression level of miR-1289 was significantly lower in OSCC tissues than in the adjacent normal oral mucosa. Furthermore, 15 genes were identified as target genes of miR-1289 via microarray and Ingenuity Pathway Analysis (IPA) microRNA target filtering. Among these genes, the knockdown of magnesium transporter 1 (MAGT1) resulted in the most remarkable cell growth inhibition in human OSCC cells. These results suggested that miR-1289 functions as a novel TS-miR in OSCC and may be a useful therapeutic tool for patients with OSCC.

Overexpression of LINC00607 inhibits cell growth and aggressiveness by regulating the miR-1289/EFNA5 axis in non-small-cell lung cancer

Long non-coding RNAs (lncRNAs) play a key role in cancer progression, including non-small-cell lung cancer (NSCLC). LncRNA long intergenic non-protein-coding RNA 00607 (LINC00607) was previously discovered to be downregulated in lung adenocarcinoma tissues. Nevertheless, the potential role of LINC00607 in NSCLC is still unclear. The expression of LINC00607, miR-1289, and ephrin A5 (EFNA5) in NSCLC tissues and cells was tested by reverse transcription quantitative polymerase chain reaction. Cell viability, proliferation, migration, and invasion were measured by 3-(4,5-dimethylthiazole-2-y1)-2,5-diphenyl tetrazolium bromide, colony formation, wound healing, and Transwell assays. The relationship among LINC00607, miR-1289, and EFNA5 in NSCLC cells was verified by the luciferase reporter assay, RNA pull-down assay, and RNA immunoprecipitation assay. In this study, LINC00607 was downregulated in NSCLC, and its low level is associated with poor prognosis of NSCLC patients. Furthermore, LINC00607 overexpression repressed NSCLC cell viability, proliferation, migration, and invasion. LINC00607 bound with miR-1289 in NSCLC. EFNA5 was a downstream target of miR-1289. EFNA5 overexpression also inhibited NSCLC cell viability, proliferation, migration, and invasion. EFNA5 knockdown antagonized the influence of LINC00607 overexpression on NSCLC cell phenotypes. Overall, LINC00607 serves as a tumor suppressor gene in NSCLC through binding with miR-1289 and modulating the level of EFNA5.

An emphasis on the interaction of signaling pathways highlights the role of miRNAs in the etiology and treatment resistance of gastric cancer

Gastric cancer (GC) is 4th in incidence and mortality rates globally. Several genetic and epigenetic factors, including microRNAs (miRNAs), affect its initiation and progression. miRNAs are short chains of nucleic acids that can regulate several cellular processes by controlling their gene expression. So, dysregulation of miRNAs expressions is associated with GC initiation, progression, invasion capacity, apoptosis evasions, angiogenesis, promotion and EMT enhancement. Of important pathways in GC and controlled by miRNAs are Wnt/β-catenin signaling, HMGA2/mTOR/P-gp, PI3K/AKT/c-Myc, VEGFR and TGFb signaling. Hence, this review was conducted to review an updated view of the role of miRNAs in GC pathogenesis and their modulatory effects on responses to different GC treatment modalities.

Host miRNAs-microbiota interactions in gastric cancer

It is widely acknowledged that gastric cancer seriously affects the quality of life and survival of patients. The correlation between the microbiota and gastric cancer has attracted extensive attention in recent years, nonetheless the specific mechanism of its impact on gastric cancer remain largely unclear. Recent studies have shown that in addition to its role in the host’s inflammatory and immune response, the microbiota can also affect the occurrence and development of gastric cancer by affecting the expression of miRNAs. This paper brings together all currently available data on miRNAs, microbiota and gastric cancer, and preliminarily describes the relationship among them.

Under the Radar: Strategies Used by Helicobacter pylori to Evade Host Responses

The body depends on its physical barriers and innate and adaptive immune responses to defend against the constant assault of potentially harmful microbes. In turn, successful pathogens have evolved unique mechanisms to adapt to the host environment and manipulate host defenses. Helicobacter pylori (Hp), a human gastric pathogen that is acquired in childhood and persists throughout life, is an example of a bacterium that is very successful at remodeling the host-pathogen interface to promote a long-term persistent infection. Using a combination of secreted virulence factors, immune subversion, and manipulation of cellular mechanisms, Hp can colonize and persist in the hostile environment of the human stomach. Here, we review the most recent and relevant information regarding how this successful pathogen overcomes gastric epithelial host defense responses to facilitate its own survival and establish a chronic infection. Expected final online publication date for the Annual Review of Physiology, Volume 84 is February 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Function of Non-coding RNA in Helicobacter pylori-Infected Gastric Cancer

Gastric cancer is a common malignant tumor of the digestive system. Its occurrence and development are the result of a combination of genetic, environmental, and microbial factors. Helicobacter pylori infection is a chronic infection that is closely related to the occurrence of gastric tumorigenesis. Non-coding RNA has been demonstrated to play a very important role in the organism, exerting a prominent role in the carcinogenesis, proliferation, apoptosis, invasion, metastasis, and chemoresistance of tumor progression. H. pylori infection affects the expression of non-coding RNA at multiple levels such as genetic polymorphisms and signaling pathways, thereby promoting or inhibiting tumor progression or chemoresistance. This paper mainly introduces the relationship between H. pylori-infected gastric cancer and non-coding RNA, providing a new perspective for gastric cancer treatment.

MicroRNAs in the interaction between host-bacterial pathogens: A new perspective

Gene expression regulation plays a critical role in host-pathogen interactions, and RNAs function is essential in this process. miRNAs are small noncoding, endogenous RNA fragments that affect stability and/or translation of mRNAs, act as major posttranscriptional regulators of gene expression. miRNA is involved in regulating many biological or pathological processes through targeting specific mRNAs, including development, differentiation, apoptosis, cell cycle, cytoskeleton organization, and autophagy. Deregulated microRNA expression is associated with many types of diseases, including cancers, immune disturbances, and infection. miRNAs are a vital section of the host immune response to bacterial-made infection. Bacterial pathogens suppress host miRNA expression for their benefit, promoting survival, replication, and persistence. The role played through miRNAs in interaction with host-bacterial pathogen has been extensively studied in the past 10 years, and knowledge about these staggering molecules' function can clarify the complicated and ambiguous interactions of the host-bacterial pathogen. Here, we review how pathogens prevent the host miRNA expression. We briefly discuss emerging themes in this field, including their role as biomarkers in identifying bacterial infections, as part of the gut microbiota, on host miRNA expression.

[Advances in oral bacteria influencing host epigenetic regulation]

Epigenetics refers to a steady change in the level of gene expression caused by non-DNA sequence changes. Microbes can modulate host inflammation through epigenetic pathways to evade or expend immune responses. As an important part of human microbes, oral bacteria also have various epigenetic regulation mechanisms to affect host inflammatory responses. This article reviews the common pathways of epigenetic regulation in microbe infection and the regulation of host epigenetics by using oral microbes to provide a reference for the study of epigenetic-related mechanisms in oral diseases.

Chronic in vivo exposure to Helicobacter pylori VacA: Assessing the efficacy of automated and long-term intragastric toxin infusion

Helicobacter pylori (Hp) secrete VacA, a diffusible pore-forming exotoxin that is epidemiologically linked to gastric disease in humans. In vitro studies indicate that VacA modulates gastric epithelial and immune cells, but the in vivo contributions of VacA as an important determinant of Hp colonization and chronic infection remain poorly understood. To identify perturbations in the stomachs of C57BL/6 or BALB/C mice that result specifically from extended VacA exposure, we evaluated the efficacy of administering purified toxin using automated infusion via surgically-implanted, intragastric catheters. At 3 and 30 days of interrupted infusion, VacA was detected in association with gastric glands. In contrast to previously-reported tissue damage resulting from short term exposure to Hp extracts administered by oral gavage, extended infusion of VacA did not damage stomach, esophageal, intestinal, or liver tissue. However, several alterations previously reported during Hp infection were detected in animals infused with VacA, including reduction of the gastric mucus layer, and increased vacuolation of parietal cells. VacA infusion invoked an immune response, as indicated by the detection of circulating VacA antibodies. These foundational studies support the use of VacA infusion for identifying gastric alterations that are unambiguously attributable to long-term exposure to toxin.

From Gene to Protein-How Bacterial Virulence Factors Manipulate Host Gene Expression During Infection

Bacteria evolved many strategies to survive and persist within host cells. Secretion of bacterial effectors enables bacteria not only to enter the host cell but also to manipulate host gene expression to circumvent clearance by the host immune response. Some effectors were also shown to evade the nucleus to manipulate epigenetic processes as well as transcription and mRNA procession and are therefore classified as nucleomodulins. Others were shown to interfere downstream with gene expression at the level of mRNA stability, favoring either mRNA stabilization or mRNA degradation, translation or protein stability, including mechanisms of protein activation and degradation. Finally, manipulation of innate immune signaling and nutrient supply creates a replicative niche that enables bacterial intracellular persistence and survival. In this review, we want to highlight the divergent strategies applied by intracellular bacteria to evade host immune responses through subversion of host gene expression via bacterial effectors. Since these virulence proteins mimic host cell enzymes or own novel enzymatic functions, characterizing their properties could help to understand the complex interactions between host and pathogen during infections. Additionally, these insights could propose potential targets for medical therapy.

The correlation between microRNAs and Helicobacter pylori in gastric cancer

Helicobacter pylori infection and H. pylori-related gastric inflammation can be considered as the most significant promoter of gastric cancer (GC). Recent investigations have evaluated the regulatory function of microRNAs (miRNAs) in H. pylori pathogenesis and H. pylori-related diseases, especially GC. The present study reviewed the correlation between miRNAs and H. pylori in gastrointestinal diseases. Furthermore, the current review highlighted the role of H. pylori pathogen and some H. pylori-related virulence factors in the deregulation of various miRNAs, especially oncogenic miRNAs (miRs) and their associated molecular pathways. Among the related studies, some have focused on the effects of H. pylori infection on regulatory networks of miRs, while others have highlighted the effects of alterations in the expression level of miRs in H. pylori-related diseases. The connectivity between miRNAs and H. pylori is regulated by various molecular pathways and different molecular targets of miRNAs.

Gastric Parietal Cell Physiology and Helicobacter pylori-Induced Disease

Acidification of the gastric lumen poses a barrier to transit of potentially pathogenic bacteria and enables activation of pepsin to complement nutrient proteolysis initiated by salivary proteases. Histamine-induced activation of the PKA signaling pathway in gastric corpus parietal cells causes insertion of proton pumps into their apical plasma membranes. Parietal cell secretion and homeostasis are regulated by signaling pathways that control cytoskeletal changes required for apical membrane remodeling and organelle and proton pump activities. Helicobacter pylori colonization of human gastric mucosa affects gastric epithelial cell plasticity and homeostasis, promoting epithelial progression to neoplasia. By intervening in proton pump expression, H pylori regulates the abundance and diversity of microbiota that populate the intestinal lumen. We review stimulation-secretion coupling and renewal mechanisms in parietal cells and the mechanisms by which H pylori toxins and effectors alter cell secretory pathways (constitutive and regulated) and organelles to establish and maintain their inter- and intracellular niches. Studies of bacterial toxins and their effector proteins have provided insights into parietal cell physiology and the mechanisms by which pathogens gain control of cell activities, increasing our understanding of gastrointestinal physiology, microbial infectious disease, and immunology.

Multifaceted Roles of microRNAs in Host-Bacterial Pathogen Interaction

MicroRNAs (miRNAs) are a well-characterized class of small noncoding RNAs that act as major posttranscriptional regulators of gene expression. Accordingly, miRNAs have been associated with a wide range of fundamental biological processes and implicated in human diseases. During the past decade, miRNAs have also been recognized for their role in the complex interplay between the host and bacterial pathogens, either as part of the host response to counteract infection or as a molecular strategy employed by bacteria to subvert host pathways for their own benefit. Importantly, the characterization of downstream miRNA targets and their underlying mechanisms of action has uncovered novel molecular factors and pathways relevant to infection. In this article, we review the current knowledge of the miRNA response to bacterial infection, focusing on different bacterial pathogens, including Salmonella enterica, Listeria monocytogenes, Mycobacterium spp., and Helicobacter pylori, among others.

Immunologic balance of regulatory T cell/T helper 17 responses in gastrointestinal infectious diseases: Role of miRNAs

Gastrointestinal Infectious diseases (GIDs) are the second cause of death worldwide. T helper17 cells (Th17) play an important role in GIDs through production of IL-17A, IL-17F, and IL-22 cytokines. Because of their increased activities in GID, Th17 and its inflammatory cytokines can inhibit the progression and eliminate the infection. Actually, although Th17 have the best performance in the acute phase, regulatory T cells (Treg cells) are enhanced in the chronic phase and infection progress through its suppressive function. In addition, Treg cells prevent undesirable inflammatory damages developed by immune system components. On the other hand, miRNAs have important roles in the regulation of immune responses to eliminate bacterial infections and protect host organisms from harmful effects. Actually, miRNAs can reinforce innate and adaptive immunity to remove infections. Of note, miRNAs can develop a regulatory network with the immune system. Additionally, miRNAs can also serve in favor of bacteria to reduce immune responses. Therefore, balance of immune responses in Treg and Th17 cells can influence outcome of many infectious diseases. In conclusion, there is an imbalance in the Treg/Th17 ratio in GIDs; importantly, sets of miRNAs, particularly miR155 and miR146, were determined to be involved clearly in GIDs.

Mechanisms of Inflammasome Signaling, microRNA Induction and Resolution of Inflammation by Helicobacter pylori

Inflammasome-controlled transcription and subsequent cleavage-mediated activation of mature IL-1β and IL-18 cytokines exemplify a crucial innate immune mechanism to combat intruding pathogens. Helicobacter pylori represents a predominant persistent infection in humans, affecting approximately half of the population worldwide, and is associated with the development of chronic gastritis, peptic ulcer disease, and gastric cancer. Studies in knockout mice have demonstrated that the pro-inflammatory cytokine IL-1β plays a central role in gastric tumorigenesis. Infection by H. pylori was recently reported to stimulate the inflammasome both in cells of the mouse and human immune systems. Using mouse models and in vitro cultured cell systems, the bacterial pathogenicity factors and molecular mechanisms of inflammasome activation have been analyzed. On the one hand, it appears that H. pylori-stimulated IL-1β production is triggered by engagement of the immune receptors TLR2 and NLRP3, and caspase-1. On the other hand, microRNA hsa-miR-223-3p is induced by the bacteria, which controls the expression of NLRP3. This regulating effect by H. pylori on microRNA expression was also described for more than 60 additionally identified microRNAs, indicating a prominent role for inflammatory and other responses. Besides TLR2, TLR9 becomes activated by H. pylori DNA and further TLR10 stimulated by the bacteria induce the secretion of IL-8 and TNF, respectively. Interestingly, TLR-dependent pathways can accelerate both pro- and anti-inflammatory responses during H. pylori infection. Balancing from a pro-inflammation to anti-inflammation phenotype results in a reduction in immune attack, allowing H. pylori to persistently colonize and to survive in the gastric niche. In this chapter, we will pinpoint the role of H. pylori in TLR- and NLRP3 inflammasome-dependent signaling together with the differential functions of pro- and anti-inflammatory cytokines. Moreover, the impact of microRNAs on H. pylori-host interaction will be discussed, and its role in resolution of infection versus chronic infection, as well as in gastric disease development.

miRNAs reshape immunity and inflammatory responses in bacterial infection

Pathogenic bacteria cause various infections worldwide, especially in immunocompromised and other susceptible individuals, and are also associated with high infant mortality rates in developing countries. MicroRNAs (miRNAs), small non-coding RNAs with evolutionarily conserved sequences, are expressed in various tissues and cells that play key part in various physiological and pathologic processes. Increasing evidence implies roles for miRNAs in bacterial infectious diseases by modulating inflammatory responses, cell penetration, tissue remodeling, and innate and adaptive immunity. This review highlights some recent intriguing findings, ranging from the correlation between aberrant expression of miRNAs with bacterial infection progression to their profound impact on host immune responses. Harnessing of dysregulated miRNAs in bacterial infection may be an approach to improving the diagnosis, prevention and therapy of infectious diseases.

Changes in production of tiny cellular RNAs in response to bacterial infection could guide the development of better diagnostics and therapies. MicroRNAs regulate other genes by binding to messenger RNA strands and controlling their translation into proteins. Xikun Zhou, Min Wu and colleagues of the University of North Dakota have now reviewed current knowledge about how microRNA levels shift during infection with various bacterial pathogens. These microRNAs can modulate the immune response as well as pathways that influence metabolic activity and cell survival. Increasing studies have indicated that shifts in microRNA levels in response to different infections could provide a potential bacterial ‘fingerprint’ for achieving accurate diagnosis. With deeper insight into how different microRNAs influence infection, it might one day day become possible to target these molecules with ‘antisense’ or ‘agonist’ drugs that modulate their activity.

New insights of Helicobacter pylori host-pathogen interactions: The triangle of virulence factors, epigenetic modifications and non-coding RNAs

Helicobacter pylori (H. pylori) is a model organism for understanding host-pathogen interactions and infection-mediated carcinogenesis. Gastric cancer and H. pylori colonization indicates the strong correlation. The progression and exacerbation of H. pylori infection are influenced by some factors of pathogen and host. Several virulence factors involved in the proper adherence and attenuation of immune defense to contribute the risk of emerging gastric cancer, therefore analysis of them is very important. H. pylori also modulates inflammatory and autophagy process to intensify its pathogenicity. From the host regard, different genetic factors particularly affect the development of gastric cancer. Indeed, epigenetic modifications, MicroRNA and long non-coding RNA received more attention. Generally, various factors related to pathogen and host that modulate gastric cancer development in response to H. pylori need more attention due to develop an efficacious therapeutic intervention. Therefore, this paper will present a brief overview of host-pathogen interaction especially emphases on bacterial virulence factors, interruption of host cellular signaling, the role of epigenetic modifications and non-coding RNAs.

Overexpression of serine protease HtrA enhances disruption of adherens junctions, paracellular transmigration and type IV secretion of CagA by Helicobacter pylori

BACKGROUND

The serine protease HtrA is an important factor for regulating stress responses and protein quality control in bacteria. In recent studies, we have demonstrated that the gastric pathogen Helicobacter pylori can secrete HtrA into the extracellular environment, where it cleaves-off the ectodomain of the tumor suppressor and adherens junction protein E-cadherin on gastric epithelial cells.

RESULTS

E-cadherin cleavage opens cell-to-cell junctions, allowing paracellular transmigration of the bacteria across polarized monolayers of MKN-28 and Caco-2 epithelial cells. However, rapid research progress on HtrA function is mainly hampered by the lack of ΔhtrA knockout mutants, suggesting that htrA may represent an essential gene in H. pylori. To circumvent this major handicap and to investigate the role of HtrA further, we overexpressed HtrA by introducing a second functional htrA gene copy in the chromosome and studied various virulence properties of the bacteria. The resulting data demonstrate that overexpression of HtrA in H. pylori gives rise to elevated rates of HtrA secretion, cleavage of E-cadherin, bacterial transmigration and delivery of the type IV secretion system (T4SS) effector protein CagA into polarized epithelial cells, but did not affect IL-8 chemokine production or the secretion of vacuolating cytotoxin VacA and γ-glutamyl-transpeptidase GGT.

CONCLUSIONS

These data provide for the first time genetic evidence in H. pylori that HtrA is a novel major virulence factor controlling multiple pathogenic activities of this important microbe.

Helicobacter pylori-Induced Changes in Gastric Acid Secretion and Upper Gastrointestinal Disease

Appropriate management of Helicobacter pylori infection of the human stomach is evolving and remains a significant clinical challenge. Acute infection results in hypochlorhydria, whereas chronic infection results in either hypo- or hyperchlorhydria, depending upon the anatomic site of infection. Acute hypochlorhydria facilitates survival of the bacterium and its infection of the stomach. Interestingly, most patients chronically infected with H. pylori manifest a pangastritis with reduced acid secretion due to bacterial virulence factors, inflammatory cytokines, and various degrees of gastric atrophy. While these patients are predisposed to develop gastric adenocarcinoma (~1%), there is increasing evidence from population studies that they are also protected from gastroesophageal reflux disease (GERD), Barrett's esophagus (BE), and esophageal adenocarcinoma (EAC). Eradication of H. pylori, in these patients, may provoke GERD in predisposed individuals and may be a contributory factor for the rising incidence of refractory GERD, BE, and EAC observed in Westernized societies. Only ~10% of chronically infected patients, mainly the young, manifest an antral predominant gastritis with increased acid secretion due to a decrease in somatostatin and increase in gastrin secretion; these patients are predisposed to develop peptic ulcer disease. H. pylori-induced changes in acid secretion, in particular hypochlorhydria, may allow ingested microorganisms to survive transit through the stomach and colonize the distal intestine and colon. Such perturbation of gut microbiota, i.e. dysbiosis, may influence human health and disease.

Mammalian microRNAs and long noncoding RNAs in the host-bacterial pathogen crosstalk

Gene expression regulation is a critical question in host-pathogen interactions, and RNAs act as key players in this process. In this review, we focus on the mammalian RNA response to bacterial infection, with a special interest on microRNAs and long non-coding RNAs. We discuss the role of cellular miRNAs in immunity, the implication of circulating miRNAs as well as the influence of the microbiome on the miRNA response. We also review how pathogens counteract the host miRNA expression. Interestingly, bacterial non-coding RNAs regulate host gene expression and conversely eukaryotic miRNAs may regulate bacterial gene expression. Overall, the characterization of RNA regulatory networks represents an emerging theme in the field of host pathogen interactions.

Systematic analysis of phosphotyrosine antibodies recognizing single phosphorylated EPIYA-motifs in CagA of East Asian-type Helicobacter pylori strains

BACKGROUND

Highly virulent strains of the gastric pathogen Helicobacter pylori encode a type IV secretion system (T4SS) that delivers the effector protein CagA into gastric epithelial cells. Translocated CagA undergoes tyrosine phosphorylation by members of the oncogenic c-Src and c-Abl host kinases at EPIYA-sequence motifs A, B and D in East Asian-type strains. These phosphorylated EPIYA-motifs serve as recognition sites for various SH2-domains containing human proteins, mediating interactions of CagA with host signaling factors to manipulate signal transduction pathways. Recognition of phospho-CagA is mainly based on the use of commercial pan-phosphotyrosine antibodies that were originally designed to detect phosphotyrosines in mammalian proteins. Specific anti-phospho-EPIYA antibodies for each of the three sites in CagA are not forthcoming.

RESULTS

This study was designed to systematically analyze the detection preferences of each phosphorylated East Asian CagA EPIYA-motif by pan-phosphotyrosine antibodies and to determine a minimal recognition sequence. We synthesized phospho- and non-phosphopeptides derived from each predominant EPIYA-site, and determined the recognition patterns by seven different pan-phosphotyrosine antibodies using Western blotting, and also investigated representative East Asian H. pylori isolates during infection. The results indicate that a total of only 9-11 amino acids containing the phosphorylated East Asian EPIYA-types are required and sufficient to detect the phosphopeptides with high specificity. However, the sequence recognition by the different antibodies was found to bear high variability. From the seven antibodies used, only four recognized all three phosphorylated EPIYA-motifs A, B and D similarly well. Two of the phosphotyrosine antibodies preferentially bound primarily to the phosphorylated motif A and D, while the seventh antibody failed to react with any of the phosphorylated EPIYA-motifs. Control experiments confirmed that none of the antibodies reacted with non-phospho-CagA peptides and in accordance were able to recognize phosphotyrosine proteins in human cells.

CONCLUSIONS

The results of this study disclose the various binding preferences of commercial anti-phosphotyrosine antibodies for phospho-EPIYA-motifs, and are valuable in the application for further characterization of CagA phosphorylation events during infection with H. pylori and risk prediction for gastric disease development.

Characterisation of worldwide Helicobacter pylori strains reveals genetic conservation and essentiality of serine protease HtrA

HtrA proteases and chaperones exhibit important roles in periplasmic protein quality control and stress responses. The genetic inactivation of htrA has been described for many bacterial pathogens. However, in some cases such as the gastric pathogen Helicobacter pylori, HtrA is secreted where it cleaves the tumour‐suppressor E‐cadherin interfering with gastric disease development, but the generation of htrA mutants is still lacking. Here, we show that the htrA gene locus is highly conserved in worldwide strains. HtrA presence was confirmed in 992 H. pylori isolates in gastric biopsy material from infected patients. Differential RNA‐sequencing (dRNA‐seq) indicated that htrA is encoded in an operon with two subsequent genes, HP1020 and HP1021. Genetic mutagenesis and complementation studies revealed that HP1020 and HP1021, but not htrA, can be mutated. In addition, we demonstrate that suppression of HtrA proteolytic activity with a newly developed inhibitor is sufficient to effectively kill H. pylori, but not other bacteria. We show that Helicobacter  htrA is an essential bifunctional gene with crucial intracellular and extracellular functions. Thus, we describe here the first microbe in which htrA is an indispensable gene, a situation unique in the bacterial kingdom. HtrA can therefore be considered a promising new target for anti‐bacterial therapy.

Helicobacter pylori and microRNAs: Relation with innate immunity and progression of preneoplastic conditions

The accepted paradigm for intestinal-type gastric cancer pathogenesis is a multistep progression from chronic gastritis induced by Helicobacter pylori (H. pylori) to gastric atrophy, intestinal metaplasia, dysplasia and ultimately gastric cancer. The genetic and molecular mechanisms underlying disease progression are still not completely understood as only a fraction of colonized individuals ever develop neoplasia suggesting that bacterial, host and environmental factors are involved. MicroRNAs are noncoding RNAs that may influence H. pylori-related pathology through the regulation of the transcription and expression of various genes, playing an important role in inflammation, cell proliferation, apoptosis and differentiation. Indeed, H. pylori have been shown to modify microRNA expression in the gastric mucosa and microRNAs are involved in the immune host response to the bacteria and in the regulation of the inflammatory response. MicroRNAs have a key role in the regulation of inflammatory pathways and H. pylori may influence inflammation-mediated gastric carcinogenesis possibly through DNA methylation and epigenetic silencing of tumor suppressor microRNAs. Furthermore, microRNAs influenced by H. pylori also have been found to be involved in cell cycle regulation, apoptosis and epithelial-mesenchymal transition. Altogether, microRNAs seem to have an important role in the progression from gastritis to preneoplastic conditions and neoplastic lesions and since each microRNA can control the expression of hundreds to thousands of genes, knowledge of microRNAs target genes and their functions are of paramount importance. In this article we present a comprehensive review about the role of microRNAs in H. pylori gastric carcinogenesis, identifying the microRNAs downregulated and upregulated in the infection and clarifying their biological role in the link between immune host response, inflammation, DNA methylation and gastric carcinogenesis.

Helicobacter pylori virulence factors affecting gastric proton pump expression and acid secretion

Acute Helicobacter pylori infection of gastric epithelial cells and human gastric biopsies represses H,K-ATPase α subunit (HKα) gene expression and inhibits acid secretion, causing transient hypochlorhydria and supporting gastric H. pylori colonization. Infection by H. pylori strains deficient in the cag pathogenicity island (cag PAI) genes cagL, cagE, or cagM, which do not transfer CagA into host cells or induce interleukin-8 secretion, does not inhibit HKα expression, nor does a cagA-deficient strain that induces IL-8. To test the hypothesis that virulence factors other than those mediating CagA translocation or IL-8 induction participate in HKα repression by activating NF-κB, AGS cells transfected with HKα promoter-Luc reporter constructs containing an intact or mutated NF-κB binding site were infected with wild-type H. pylori strain 7.13, isogenic mutants lacking cag PAI genes responsible for CagA translocation and/or IL-8 induction (cagA, cagζ, cagε, cagZ, and cagβ), or deficient in genes encoding two peptidoglycan hydrolases (slt and cagγ). H. pylori-induced AGS cell HKα promoter activities, translocated CagA, and IL-8 secretion were measured by luminometry, immunoblotting, and ELISA, respectively. Human gastric biopsy acid secretion was measured by microphysiometry. Taken together, the data showed that HKα repression is independent of IL-8 expression, and that CagA translocation together with H. pylori transglycosylases encoded by slt and cagγ participate in NF-κB-dependent HKα repression and acid inhibition. The findings are significant because H. pylori factors other than CagA and IL-8 secretion are now implicated in transient hypochlorhydria which facilitates gastric colonization and potential triggering of epithelial progression to neoplasia.

Gastric secretion

PURPOSE OF REVIEW

This review summarizes the past year's literature regarding the neural, paracrine, hormonal, and intracellular regulation of gastric acid secretion.

RECENT FINDINGS

Gastric acid facilitates the digestion of protein as well as the absorption of iron, calcium, vitamin B12, and certain medications. High gastric acidity, in combination with pepsin and lipase, kills ingested microorganisms and may play a role in preventing bacterial overgrowth, enteric infection, and possibly spontaneous bacterial peritonitis, community-acquired pneumonia, and infection with Mycobacterium tuberculosis. Stimulants of acid secretion include histamine, gastrin, acetylcholine, and ghrelin. Inhibitors include somatostatin, gastric inhibitory polypeptide, calcitonin gene-related peptide, and adrenomedullin. Helicobacter pylori stimulates or inhibits depending upon the time course of infection and the area of the stomach predominantly infected. Proteins implicated in H-K-ATPase membrane trafficking include myosin IIB, F-actin, ezrin, and Rab GTPases.

SUMMARY

Our understanding of the regulation of gastric acid secretion continues to advance. Such knowledge is crucial for the management of acid-peptic disorders and the development of novel medications, such as cholecystokinin-2 receptor antagonists.

MicroRNAs in the interaction between host and bacterial pathogens

MicroRNAs (miRNAs) are small non-coding RNAs with a central role in the post-transcriptional control of gene expression, that have been implicated in a wide-range of biological processes. Regulation of miRNA expression is increasingly recognized as a crucial part of the host response to infection by bacterial pathogens, as well as a novel molecular strategy exploited by bacteria to manipulate host cell pathways. Here, we review the current knowledge of bacterial pathogens that modulate host miRNA expression, focusing on mammalian host cells, and the implications of miRNA regulation on the outcome of infection. The emerging role of commensal bacteria, as part of the gut microbiota, on host miRNA expression in the presence or absence of bacterial pathogens is also discussed.