PMCC PMCC

Search tips
Search criteria

Advanced
Results 1-25 (1079142)

Clipboard (0)
None

Related Articles

1.  The impact of autophagic processes on the intracellular fate of Helicobacter pylori 
Autophagy  2013;9(5):639-652.
Helicobacter pylori is a Gram-negative pathogen that colonizes the gastric epithelium of 50–60% of the world’s population. Approximately one-fifth of the infected individuals manifest severe diseases such as peptic ulcers or gastric cancer. H. pylori infection has proven difficult to cure despite intensive antibiotic treatment. One possible reason for the relatively high resistance to antimicrobial therapy is the ability of H. pylori to reside inside host cells. Although considered by most as an extracellular pathogen, H. pylori can invade both gastric epithelial cells and immunocytes to some extent. The intracellular survival of H. pylori has been implicated in its ability to persist in the stomach, evade host immune responses and resist eradication by membrane-impermeable antibiotics. Interestingly, recent evidence suggests that macroautophagy, a cellular self-degradation process characterized by the formation of double-membraned autophagosomes, plays an important role in determining the intracellular fate of H. pylori. Detailed understanding of the interaction between H. pylori and host cell autophagic processes is anticipated to provide novel insights into the molecular mechanisms of macroautophagy and H. pylori pathogenesis, opening new avenues for the therapeutic intervention of autophagy-related and H. pylori-related disorders.
doi:10.4161/auto.23782
PMCID: PMC3669176  PMID: 23396129
Helicobacter pylori; autophagy; infection; bacteria; VacA; intracellular survival; antibiotic resistance; LC3-associated phagocytosis; pathogenesis
2.  Helicobacter pylori versus the Host: Remodeling of the Bacterial Outer Membrane Is Required for Survival in the Gastric Mucosa 
PLoS Pathogens  2011;7(12):e1002454.
Modification of bacterial surface structures, such as the lipid A portion of lipopolysaccharide (LPS), is used by many pathogenic bacteria to help evade the host innate immune response. Helicobacter pylori, a gram-negative bacterium capable of chronic colonization of the human stomach, modifies its lipid A by removal of phosphate groups from the 1- and 4′-positions of the lipid A backbone. In this study, we identify the enzyme responsible for dephosphorylation of the lipid A 4′-phosphate group in H. pylori, Jhp1487 (LpxF). To ascertain the role these modifications play in the pathogenesis of H. pylori, we created mutants in lpxE (1-phosphatase), lpxF (4′-phosphatase) and a double lpxE/F mutant. Analysis of lipid A isolated from lpxE and lpxF mutants revealed lipid A species with a 1 or 4′-phosphate group, respectively while the double lpxE/F mutant revealed a bis-phosphorylated lipid A. Mutants lacking lpxE, lpxF, or lpxE/F show a 16, 360 and 1020 fold increase in sensitivity to the cationic antimicrobial peptide polymyxin B, respectively. Moreover, a similar loss of resistance is seen against a variety of CAMPs found in the human body including LL37, β-defensin 2, and P-113. Using a fluorescent derivative of polymyxin we demonstrate that, unlike wild type bacteria, polymyxin readily associates with the lpxE/F mutant. Presumably, the increase in the negative charge of H. pylori LPS allows for binding of the peptide to the bacterial surface. Interestingly, the action of LpxE and LpxF was shown to decrease recognition of Helicobacter LPS by the innate immune receptor, Toll-like Receptor 4. Furthermore, lpxE/F mutants were unable to colonize the gastric mucosa of C57BL/6J and C57BL/6J tlr4 -/- mice when compared to wild type H. pylori. Our results demonstrate that dephosphorylation of the lipid A domain of H. pylori LPS by LpxE and LpxF is key to its ability to colonize a mammalian host.
Author Summary
Since its discovery in 1982 Helicobacter pylori has been identified as the leading cause of gastritis and peptic ulcer disease, infecting around 50% of the world's population. Infected patients are at increased risk for gastric cancers, allowing for classification of H. pylori as a class I carcinogen by the World Health Organization. H. pylori has only one well defined niche, the human stomach. Since no other reservoirs exist, a unique balance must be established during infection permitting long-term survival of both the bacterium and its human host. Here, we show that H. pylori modifies its primary surface component, lipopolysaccharide (LPS), making the bacterium undetectable by components of the innate immune system and highly resistant to antimicrobial compounds secreted by host cells. Mutant strains of H. pylori unable to modify their surface show increased sensitivity to antimicrobial peptides (∼1000 fold) and increased recognition by components of the innate immune system. H. pylori mutants were unable to colonize mouse models, suggesting that remodeling of LPS is essential for survival within the gastric mucosa. Understanding the adaptations used by H. pylori to survive and persist within the human host is key towards unraveling how this unique organism impacts gastric disease.
doi:10.1371/journal.ppat.1002454
PMCID: PMC3245313  PMID: 22216004
3.  Early-Life Family Structure and Microbially Induced Cancer Risk 
PLoS Medicine  2007;4(1):e7.
Background
Cancer may follow exposure to an environmental agent after many decades. The bacterium Helicobacter pylori, known to be acquired early in life, increases risk for gastric adenocarcinoma, but other factors are also important. In this study, we considered whether early-life family structure affects the risk of later developing gastric cancer among H. pylori+ men.
Methods and Findings
We examined a long-term cohort of Japanese-American men followed for 28 y, and performed a nested case-control study among those carrying H. pylori or the subset carrying the most virulent cagA+ H. pylori strains to address whether family structure predicted cancer development. We found that among the men who were H. pylori+ and/or cagA+ (it is possible to be cagA+ and H. pylori− if the H. pylori test is falsely negative), belonging to a large sibship or higher birth order was associated with a significantly increased risk of developing gastric adenocarcinoma late in life. For those with cagA+ strains, the risk of developing gastric cancer was more than twice as high (odds ratio 2.2; 95% confidence interval 1.2–4.0) among those in a sibship of seven or more individuals than in a sibship of between one and three persons.
Conclusions
These results provide evidence that early-life social environment plays a significant role in risk of microbially induced malignancies expressing five to eight decades later, and these findings lead to new models to explain these interactions.
This study suggests that early-life social environment has a significant role in risk of microbially induced malignancies such as gastric adenocarcinoma occuring five to eight decades later.
Editors' Summary
Background.
Although the theory that certain cancers might be caused by infectious agents (such as bacteria and viruses) has been around for some time, concrete evidence linking specific cancers and infections is only recently beginning to emerge. There is now very good evidence that stomach cancer, once one of the frequent types worldwide but now less common, is strongly associated with a particular infection of the stomach lining. This specific bacterium colonizing the stomach, Helicobacter pylori (or H. pylori), often infects people early in childhood through close contact with other people, and tends to stay in the body throughout life. However, most people do not suffer any symptoms as a result of being colonized with H. pylori. Researchers are interested in the relationship between stomach cancer and aspects of someone's upbringing, for example whether an individual has a large number of sisters and brothers and whether they are the youngest or oldest in a large group of siblings. One reason for being interested in this topic is that if H. pylori is mainly spread from one child to another in the home, we might expect children from large sibling groups, and the youngest children in a group, to be at greater risk of being infected, and then more likely to get stomach cancer later in life. Furthermore—and this was the primary reason for the study—the researchers wished to determine whether, among H. pylori+ people, the structure of the family affects the risk of developing stomach cancer much later in life. With all study participants being H. pylori+, the essential comparison was between people of high and low birth order.
Why Was This Study Done?
This group of researchers had already done a previous study that had shown that people who carry H. pylori in their stomachs are more likely to get stomach cancer, and also that younger children in a sibling group are more likely to get stomach cancer. In the period following that study, the examined population has become older and more of the people concerned have developed stomach cancer. This meant that the researchers could go back and extend their previous work to see, more reliably, whether stomach cancer was linked to family structure. It also meant that the researchers could look at the effects of each factor not only in isolation, but also the combined effect of all the different factors. The researchers also stratified for the most virulent strains (those that were cagA+).
What Did the Researchers Do and Find?
In this study, the researchers started out with a pool of 7,429 Japanese-American men living in Hawaii, USA, who had donated blood samples between 1967 and 1975. Of these men, 261 eventually developed stomach cancer. Each of the 261 men was then matched with a similarly aged man from the original pool of 7,429 men who did not have stomach cancer. The researchers then went back to the original blood samples taken many years before and tested the samples to see if the men were infected with H. pylori at the time the sample was taken and, if so, whether a particular strain of the bacterium, cagA, was present. The researchers then looked at whether the risk of getting stomach cancer was associated with the number of siblings a man had and whether he was older or younger than the other siblings.
Similar to the prior study, they found that men who had stomach cancer were three times more likely to carry H. pylori compared to men who did not develop stomach cancer. In men who had H. pylori, those with large numbers of siblings were more likely to get stomach cancer, and this was especially true for men who had the cagA strain of H. pylori. In the whole group of men with cancer, the order of birth (whether a man was older or younger in his sibling group) did not seem to be particularly linked to development of stomach cancer. However, in men who had the cagA strain of H. pylori, those from the largest sibships were at highest risk of developing gastric cancer; in this group, one particular type of cancer (the most common type—intestinal-type gastric cancer) was also associated with later birth order.
What Do These Findings Mean?
The researchers initially thought that men with H. pylori would be at a higher risk of getting stomach cancer if they had a large number of sisters and brothers, and especially if they were a younger sibling in a large group. This idea was supported by their data. These findings support the idea that people often get H. pylori from their older sisters and brothers, but there is not conclusive proof of this. There might be some other factor that explains the association between large family size and stomach cancer, for example that people from large families might be poorer and more at risk from stomach cancer for some other reason. Currently, most doctors do not recommend routinely testing people without any symptoms to see if they have H. pylori, but people with pain or discomfort in the upper abdomen would generally be screened for H. pylori and then treated to eliminate the infection if it is found. The main novel idea is that those people who are born in a large sibship, and/or are of higher birth order, are more likely to acquire their H. pylori from a genetically related person (a sibling) than from an unrelated person (friend/classmate). This “family-structure effect” could be the explanation as to why there is a higher risk of stomach cancer developing later—the strain from a genetically related person already is “preadapted” to the new host, and has a “head-start” on immunity, compared to a strain from an unrelated person. The researchers hypothesize that it is the nature of that initial interaction with the host that sets the stage for the kind of events that lead to cancers decades later.
Additional Information.
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.0040007.
A Perspective article by Dimitrios Trichopoulos and Pagona Lagiou discusses these findings further
MedLine Plus encyclopedia entry on stomach cancer
Wikipedia entry on Helicobacter pylori (Wikipedia is an internet encyclopedia that anyone can edit)
The US National Cancer Institute publishes information about stomach cancer
doi:10.1371/journal.pmed.0040007
PMCID: PMC1769414  PMID: 17227131
4.  Caveolin-1 Protects B6129 Mice against Helicobacter pylori Gastritis 
PLoS Pathogens  2013;9(4):e1003251.
Caveolin-1 (Cav1) is a scaffold protein and pathogen receptor in the mucosa of the gastrointestinal tract. Chronic infection of gastric epithelial cells by Helicobacter pylori (H. pylori) is a major risk factor for human gastric cancer (GC) where Cav1 is frequently down-regulated. However, the function of Cav1 in H. pylori infection and pathogenesis of GC remained unknown. We show here that Cav1-deficient mice, infected for 11 months with the CagA-delivery deficient H. pylori strain SS1, developed more severe gastritis and tissue damage, including loss of parietal cells and foveolar hyperplasia, and displayed lower colonisation of the gastric mucosa than wild-type B6129 littermates. Cav1-null mice showed enhanced infiltration of macrophages and B-cells and secretion of chemokines (RANTES) but had reduced levels of CD25+ regulatory T-cells. Cav1-deficient human GC cells (AGS), infected with the CagA-delivery proficient H. pylori strain G27, were more sensitive to CagA-related cytoskeletal stress morphologies (“humming bird”) compared to AGS cells stably transfected with Cav1 (AGS/Cav1). Infection of AGS/Cav1 cells triggered the recruitment of p120 RhoGTPase-activating protein/deleted in liver cancer-1 (p120RhoGAP/DLC1) to Cav1 and counteracted CagA-induced cytoskeletal rearrangements. In human GC cell lines (MKN45, N87) and mouse stomach tissue, H. pylori down-regulated endogenous expression of Cav1 independently of CagA. Mechanistically, H. pylori activated sterol-responsive element-binding protein-1 (SREBP1) to repress transcription of the human Cav1 gene from sterol-responsive elements (SREs) in the proximal Cav1 promoter. These data suggested a protective role of Cav1 against H. pylori-induced inflammation and tissue damage. We propose that H. pylori exploits down-regulation of Cav1 to subvert the host's immune response and to promote signalling of its virulence factors in host cells.
Author Summary
Infection with the bacterium Helicobacter pylori (H. pylori) mainly affects children in the developing countries who are at risk to progress to gastric cancer (GC) as adults after many years of persistent infection, especially with strains which are positive for the oncogenic virulence factor CagA. Eradication of H. pylori by antibiotics is a treatment of choice but may also alter the susceptibility to allergies and other tumor types. Thus, novel diagnostic or prognostic markers are needed which detect early molecular changes in the stomach mucosa during the transition of chronic inflammation to cancer. In our study, we found that the tumor suppressor caveolin-1 (Cav1) is reduced upon infection with H. pylori, and CagA was sufficient but not necessary for this down-regulation. Loss of Cav1 was caused by H. pylori-dependent activation of sterol-responsive element-binding protein-1 (SREBP1), and this event abolished the interaction of Cav1 with p120 RhoGTPase-activating protein/deleted in liver cancer-1 (p120RhoGAP/DLC1), a second bona fide tumor suppressor in gastric tissue. Conclusively, Cav1 and DLC1 may constitute novel molecular markers in the H. pylori-infected gastric mucosa before neoplastic transformation of the epithelium.
doi:10.1371/journal.ppat.1003251
PMCID: PMC3623771  PMID: 23592983
5.  Helicobacter pylori Impairs Murine Dendritic Cell Responses to Infection 
PLoS ONE  2010;5(5):e10844.
Background
Helicobacter pylori, a human pathogen associated with chronic gastritis, peptic ulcer and gastric malignancies, is generally viewed as an extracellular microorganism. Here, we show that H. pylori replicates in murine bone marrow derived-dendritic cells (BMDCs) within autophagosomes.
Methodology/Principal Findings
A 10-fold increase of CFU is found between 2 h and 6 h p.i. in H. pylori-infected BMDCs. Autophagy is induced around the bacterium and participates at late time points of infection for the clearance of intracellular H. pylori. As a consequence of infection, LC3, LAMP1 and MHC class II molecules are retained within the H. pylori-containing vacuoles and export of MHC class II molecules to cell surface is blocked. However, formalin-fixed H. pylori still maintain this inhibitory activity in BMDC derived from wild type mice, but not in from either TLR4 or TLR2-deficient mice, suggesting the involvement of H. pylori-LPS in this process. TNF-alpha, IL-6 and IL-10 expression was also modulated upon infection showing a TLR2-specific dependent IL-10 secretion. No IL-12 was detected favoring the hypothesis of a down modulation of DC functions during H. pylori infection. Furthermore, antigen-specific T cells proliferation was also impaired upon infection.
Conclusions/Significance
H. pylori can infect and replicate in BMDCs and thereby affects DC-mediated immune responses. The implication of this new finding is discussed for the biological life cycle of H. pylori in the host.
doi:10.1371/journal.pone.0010844
PMCID: PMC2877707  PMID: 20523725
6.  Crohn disease ATG16L1 polymorphism increases susceptibility to infection with Helicobacter pylori in humans 
Autophagy  2012;8(9):1387-1388.
Autophagy plays key roles both in host defense against bacterial infection and in tumor biology. Helicobacter pylori (H. pylori) infection causes chronic gastritis and is the single most important risk factor for the development of gastric cancer in humans. Its vacuolating cytotoxin (VacA) promotes gastric colonization and is associated with more severe disease. Acute exposure to VacA initially triggers host autophagy to mitigate the effects of the toxin in epithelial cells. Recently, we demonstrated that chronic exposure to VacA leads to the formation of defective autophagosomes that lack CTSD/cathepsin D and have reduced catalytic activity. Disrupted autophagy results in accumulation of reactive oxygen species and SQSTM1/p62 both in vitro and in vivo in biopsy samples from patients infected with VacA+ but not VacA- strains. We also determined that the Crohn disease susceptibility polymorphism in the essential autophagy gene ATG16L1 increases susceptibility to H. pylori infection. Furthermore, peripheral blood monocytes from individuals with the ATG16L1 risk variant show impaired autophagic responses to VacA exposure. This is the first study to identify both a host autophagy susceptibility gene for H. pylori infection and to define the mechanism by which the autophagy pathway is affected following H. pylori infection. Collectively, these findings highlight the synergistic effects of host and bacterial autophagy factors on H. pylori pathogenesis and the potential for subsequent cancer susceptibility.
doi:10.4161/auto.21007
PMCID: PMC3442886  PMID: 22885761
H. pylori; ATG16L1; VacA; autophagy; gastric cancer
7.  Vacuolating Cytotoxin and Variants in Atg16L1 that Disrupt Autophagy Promote Helicobacter pylori Infection in Humans 
Gastroenterology  2012;142(5):1160-1171.
Background & Aims
The Helicobacter pylori toxin vacuolating cytotoxin (VacA) promotes gastric colonization and its presence (VacA+) is associated with more-severe disease. The exact mechanisms by which VacA contributes to infection are unclear. We previously found that limited exposure to VacA induces autophagy of gastric cells, which eliminates the toxin; we investigated whether autophagy serves as a defense mechanism against H pylori infection.
Methods
We investigated the effect of VacA on autophagy in human gastric epithelial cells (AGS) and primary gastric cells from mice. Expression of p62, a marker of autophagy, was also assessed in gastric tissues from patients infected with toxigenic (VacA+) or nontoxigenic strains. We analyzed the effect of VacA on autophagy in peripheral blood monocytes obtained from subjects with different genotypes of ATG16L1, which regulates autophagy. We performed genotyping for ATG16L1 in two cohorts of infected and uninfected subjects.
Results
Prolonged exposure of AGS and mouse gastric cells to VacA disrupted induction of autophagy in response to the toxin, because the cells lacked cathepsin-D in autophagosomes. Loss of autophagy resulted in the accumulation of p62 and reactive oxygen species. Gastric biopsies samples from patients infected with VacA+, but not nontoxigenic strains of H pylori, had increased levels of p62. Peripheral blood monocytes isolated from individuals with polymorphisms in ATG16L1 that increase susceptibility to Crohn's disease had reduced induction of autophagy in response to VacA+ compared to cells from individuals that did not have these polymorphisms. The presence of the ATG16L1 Crohn’s disease risk variant increased susceptibility to H pylori infection in 2 separate cohorts.
Conclusions
Autophagy protects against infection with H pylori; the toxin VacA disrupts autophagy to promote infection, which could contribute to inflammation and eventual carcinogenesis.
doi:10.1053/j.gastro.2012.01.043
PMCID: PMC3336037  PMID: 22333951
stomach cancer; genetic; bacteria toxin; tumor
8.  Helicobacter pylori infection 
Clinical Evidence  2009;2009:0406.
Introduction
The principal effect of Helicobacter pylori infection is lifelong chronic gastritis, affecting up to 20% of younger adults but 50% to 80% of adults born in resource-rich countries before 1950.
Methods and outcomes
We conducted a systematic review and aimed to answer the following clinical questions: What are the effects of H pylori eradication treatment in people with a confirmed duodenal ulcer, a confirmed gastric ulcer, confirmed gastro-oesophageal reflux disease (GORD), confirmed non-ulcer dyspepsia, uninvestigated dyspepsia, localised B cell lymphoma of the stomach, and non-steroidal anti-inflammatory drug (NSAID)-related peptic ulcers? What are the effects of H pylori eradication treatment for preventing NSAID-related peptic ulcers in people with or without previous ulcers or dyspepsia? What are the effects of H pylori eradication treatment on the risk of developing gastric cancer? Do H pylori eradication treatments differ in their effects? We searched: Medline, Embase, The Cochrane Library, and other important databases up to September 2007 (Clinical Evidence reviews are updated periodically; please check our website for the most up-to-date version of this review). We included harms alerts from relevant organisations such as the US Food and Drug Administration (FDA) and the UK Medicines and Healthcare products Regulatory Agency (MHRA).
Results
We found 58 systematic reviews, RCTs, or observational studies that met our inclusion criteria. We performed a GRADE evaluation of the quality of evidence for interventions.
Conclusions
In this systematic review we present information relating to the effectiveness and safety of the following interventions: effects of H pylori eradication in different populations; relative effects of triple regimens, quadruple regimens, and sequential regimens.
Key Points
The principal effect of Helicobacter pylori infection is lifelong chronic gastritis, affecting up to 20% of younger adults but 50% to 80% of adults born before 1950 in resource-rich countries. H pylori infection can be identified indirectly by the C13 urea breath test and stool antigen tests, which are more accurate than serology.Transmission and prevalence rates are higher in areas of childhood poverty. Adult reinfection rates are less than 1% a year.In people with H pylori infection, about 15% will develop a peptic ulcer and 1% will develop gastric cancer during their lifetime.
Eradication of H pylori makes healing of duodenal ulcers more likely and reduces the risk of bleeding with gastric and duodenal ulcers, either alone or when added to antisecretory drug treatment. Eradication also greatly reduces the risk of recurrence of a duodenal ulcer. Eradication reduces recurrence after healing of a gastric ulcer; however, we don't know whether it increases healing of gastric ulcers.Eradication of H pylori may reduce the risk of NSAID-related ulcers in people without previous ulcers; however, we don't know whether it reduces NSAID-related ulcers or bleeding in people with previous ulcers.
In areas of low prevalence of H pylori, few ulcers are caused by H pylori infection. Eradication may be less effective in preventing ulcers in these areas compared with higher-prevalence areas.
Eradication of H pylori reduces symptoms of dyspepsia, but not of GORD. Eradicating H pylori has been shown to reduce dyspeptic symptoms in people with non-ulcer dyspepsia or uninvestigated dyspepsia compared with placebo.
Despite the association between H pylori infection and gastric cancer, no studies have shown a reduced risk after eradication treatment. Gastric B cell lymphoma lesions may regress after H pylori eradication, but we don't know this for sure.
Quadruple and triple regimens seem equally effective at eradicating H pylori as first-line treatments. Quadruple regimens may be more effective as second-line treatment than triple regimens when a first-line triple regimen has failed to eradicate the infection. However, the evidence is limited in that, in comparisons of second-line quadruple versus triple regimens, most triple regimens did not contain a nitroimidazole.
Ten-day sequential therapy may be more effective at eradicating H pylori than a 7-day triple regimen.
Nitroimidazole-based triple regimens and amoxicillin-based triple regimens seem equally effective at eradicating H pylori. High-dose clarithromycin within an amoxicillin-based triple regimen seems more effective at eradicating H pylori than low-dose clarithromycin. However, the dose of clarithromycin within a nitroimidazole-based triple regimen does not seem to have an effect on eradication rates.
Triple regimens using different proton pump inhibitors seem equally effective at eradicating H pylori. Pre-treatment with a proton pump inhibitor before triple regimen does not seem to increase H pylori eradication rates compared with no pre-treatment. Two-week triple proton pump inhibitor regimens may be more effective than 1-week regimens for eradicating H pylori.
Lower eradication rates are achieved in people infected with strains of H pylori that are resistant to antibiotics included in the eradication regimen than are achieved in people infected with sensitive strains of H pylori.
Antibiotics can cause adverse effects such as nausea and diarrhoea. Bismuth may turn the stools black.
PMCID: PMC2907775  PMID: 21718575
9.  Motility and Chemotaxis Mediate the Preferential Colonization of Gastric Injury Sites by Helicobacter pylori 
PLoS Pathogens  2014;10(7):e1004275.
Helicobacter pylori (H. pylori) is a pathogen contributing to peptic inflammation, ulceration, and cancer. A crucial step in the pathogenic sequence is when the bacterium first interacts with gastric tissue, an event that is poorly understood in vivo. We have shown that the luminal space adjacent to gastric epithelial damage is a microenvironment, and we hypothesized that this microenvironment might enhance H. pylori colonization. Inoculation with 106 H. pylori (wild-type Sydney Strain 1, SS1) significantly delayed healing of acetic-acid induced ulcers at Day 1, 7 and 30 post-inoculation, and wild-type SS1 preferentially colonized the ulcerated area compared to uninjured gastric tissue in the same animal at all time points. Gastric resident Lactobacillus spp. did not preferentially colonize ulcerated tissue. To determine whether bacterial motility and chemotaxis are important to ulcer healing and colonization, we analyzed isogenic H. pylori mutants defective in motility (ΔmotB) or chemotaxis (ΔcheY). ΔmotB (106) failed to colonize ulcerated or healthy stomach tissue. ΔcheY (106) colonized both tissues, but without preferential colonization of ulcerated tissue. However, ΔcheY did modestly delay ulcer healing, suggesting that chemotaxis is not required for this process. We used two-photon microscopy to induce microscopic epithelial lesions in vivo, and evaluated accumulation of fluorescently labeled H. pylori at gastric damage sites in the time frame of minutes instead of days. By 5 min after inducing damage, H. pylori SS1 preferentially accumulated at the site of damage and inhibited gastric epithelial restitution. H. pylori ΔcheY modestly accumulated at the gastric surface and inhibited restitution, but did not preferentially accumulate at the injury site. H. pylori ΔmotB neither accumulated at the surface nor inhibited restitution. We conclude that bacterial chemosensing and motility rapidly promote H. pylori colonization of injury sites, and thereby biases the injured tissue towards sustained gastric damage.
Author Summary
H. pylori is a disease-causing bacterium that commonly infects the human stomach in both developed and underdeveloped countries. Infected individuals can develop digestive diseases, including stomach inflammation, peptic ulcer, and cancer. There has been only limited investigation into the events when H. pylori first interacts with stomach tissue. Using anesthetized mice in which we have induced microscopic damage to the stomach surface, we find that H. pylori is able to rapidly detect and navigate towards this damage site. Within minutes, bacterial accumulation slows repair of the damage. This is the earliest event of H. pylori pathogenesis that has been reported in vivo. We further define that this pathology is due to the bacterial accumulation at damage sites and that this also occurs in a model of larger stomach damage (ulceration). The broader implications of our work are that even sub-clinical insults to the stomach that occur in daily life (damage from grinding of food, ingestion of alcohol, taking an aspirin) can potentially attract H. pylori and not only slow repair of any existing damage, but maybe also provide an initiation site that can start the pathogenic sequence of stomach disease caused by H. pylori.
doi:10.1371/journal.ppat.1004275
PMCID: PMC4102597  PMID: 25033386
10.  Systems Modeling of the Role of Interleukin-21 in the Maintenance of Effector CD4+ T Cell Responses during Chronic Helicobacter pylori Infection 
mBio  2014;5(4):e01243-14.
ABSTRACT
The development of gastritis during Helicobacter pylori infection is dependent on an activated adaptive immune response orchestrated by T helper (Th) cells. However, the relative contributions of the Th1 and Th17 subsets to gastritis and control of infection are still under investigation. To investigate the role of interleukin-21 (IL-21) in the gastric mucosa during H. pylori infection, we combined mathematical modeling of CD4+ T cell differentiation with in vivo mechanistic studies. We infected IL-21-deficient and wild-type mice with H. pylori strain SS1 and assessed colonization, gastric inflammation, cellular infiltration, and cytokine profiles. Chronically H. pylori-infected IL-21-deficient mice had higher H. pylori colonization, significantly less gastritis, and reduced expression of proinflammatory cytokines and chemokines compared to these parameters in infected wild-type littermates. These in vivo data were used to calibrate an H. pylori infection-dependent, CD4+ T cell-specific computational model, which then described the mechanism by which IL-21 activates the production of interferon gamma (IFN-γ) and IL-17 during chronic H. pylori infection. The model predicted activated expression of T-bet and RORγt and the phosphorylation of STAT3 and STAT1 and suggested a potential role of IL-21 in the modulation of IL-10. Driven by our modeling-derived predictions, we found reduced levels of CD4+ splenocyte-specific tbx21 and rorc expression, reduced phosphorylation of STAT1 and STAT3, and an increase in CD4+ T cell-specific IL-10 expression in H. pylori-infected IL-21-deficient mice. Our results indicate that IL-21 regulates Th1 and Th17 effector responses during chronic H. pylori infection in a STAT1- and STAT3-dependent manner, therefore playing a major role controlling H. pylori infection and gastritis.
IMPORTANCE
Helicobacter pylori is the dominant member of the gastric microbiota in more than 50% of the world’s population. H. pylori colonization has been implicated in gastritis and gastric cancer, as infection with H. pylori is the single most common risk factor for gastric cancer. Current data suggest that, in addition to bacterial virulence factors, the magnitude and types of immune responses influence the outcome of colonization and chronic infection. This study uses a combined computational and experimental approach to investigate how IL-21, a proinflammatory T cell-derived cytokine, maintains the chronic proinflammatory T cell immune response driving chronic gastritis during H. pylori infection. This research will also provide insight into a myriad of other infectious and immune disorders in which IL-21 is increasingly recognized to play a central role. The use of IL-21-related therapies may provide treatment options for individuals chronically colonized with H. pylori as an alternative to aggressive antibiotics.
doi:10.1128/mBio.01243-14
PMCID: PMC4120195  PMID: 25053783
11.  Potential implications of Helicobacter pylori-related neutrophil-activating protein 
Helicobacter pylori (H. pylori) virulence factors promote the release of various chemoattractants/inflammatory mediators, including mainly the neutrophil-attractant chemokine interleukin-8 and neutrophil-activating protein (NAP), involved in H. pylori-induced gastric pathologies. Co-administration of Chios mastic gum (CMG), which inhibits H. pylori NAP, with an H. pylori eradication regimen might add clinical benefits against H. pylori-related gastric pathologies, but possibly not CMG as main therapy. Although H. pylori NAP and other H. pylori-related cytotoxins [i.e., vaculating cytotoxin (VacA)] appear to play a major role in generating and maintaining the H. pylori-associated gastric inflammatory response and H. pylori NAP is a promising vaccine candidate against H. pylori infection (H. pylori-I), concerns regarding its potential drawbacks, particularly neurogenic ones, due to possible cross-mimicry, should be considered. Possible cross-mimicry between H. pylori NAP and/or bacterial aquaporin (AQP) and neural tissues may be associated with the anti-AQP-4 antibody-related neural damage in multiple sclerosis (MS)/neuromyelitis optica patients. Moreover, the sequence homology found between H. pylori VacA and human Na+/K+-ATPase A subunit suggests that antibodies to VacA involve ion channels in abaxonal Schwann cell plasmalemma resulting in demyelination in some patients. A series of factors have been implicated in inducing blood-brain barrier (BBB) disruption, including inflammatory mediators (e.g., cytokines and chemokines induced by H. pylori-I) and oxidative stress. BBB disruption permits access of AQP4-specific antibodies and T lymphocytes to the central nervous system, thereby playing a major role in multiple sclerosis pathogenesis. Relative studies show a strong association between H. pylori-I and MS. H. pylori-I induces humoral and cellular immune responses that, owing to the sharing of homologous epitopes (molecular mimicry), cross-react with components of nerves, thereby contributing and perpetuating neural tissue damage. Finally, H. pylori NAP also plays a possible pathogenetic role in both gastric and colon oncogenesis.
doi:10.3748/wjg.v18.i5.489
PMCID: PMC3270508  PMID: 22346256
Helicobacter pylori; Neutrophil-activating protein; Chios mastic gum; Cross-mimicry; Multiple sclerosis; Demyelination; Gastric carcinogenesis
12.  Helicobacter pylori-induced gastritis in the domestic cat. 
Infection and Immunity  1995;63(7):2674-2681.
Helicobacter pylori has been cultured from the inflamed gastric mucosae of naturally infected cats; the lesions in H. pylori-infected cat stomachs mimic many of the features seen in H. pylori-infected human stomachs. To determine whether H. pylori-negative specific-pathogen-free cats with normal gastric mucosae were susceptible to colonization by this bacterium and whether gastritis developed after infections, four H. pylori-negative cats treated with cimetidine were orally dosed three times with 3 ml (1.5 x 10(8) CFU/ml) of H. pylori every 4 days. All four cats became persistently colonized as determined by gastric cultures and PCRs from serial gastric biopsy samples and necropsy samples at 7 months postinfection. H. pylori was not isolated from the two control cats, nor were their gastric tissues positive by PCR; one of the two cats had a few focal lymphocytic aggregates in the body submucosa, whereas the second cat had a normal gastric mucosa. All four H. pylori-infected cats had multifocal gastritis consisting of lymphoid aggregates plus multiple large lymphoid nodules, which were most noticeable in the antral mucosa. In addition, one H. pylori-infected cat had a moderate diffuse infiltration of polymorphonuclear leukocytes in the subglandular region of the antrum. H. pylori-like organisms were focally distributed in glandular crypts of the antrum. Two of the H. pylori-infected cats had significant (eightfold) increases over baseline in levels of immunoglobulin G H. pylori serum antibody. The H. pylori isolates from the four experimentally infected cats had restriction fragment length polymorphism patterns specific for the flaA gene that were identical to those of the inoculating strain. H. pylori readily colonizes the cat stomach and produces persistent gastritis.
PMCID: PMC173358  PMID: 7790084
13.  Immune evasion strategies used by Helicobacter pylori 
World Journal of Gastroenterology : WJG  2014;20(36):12753-12766.
Helicobacter pylori (H. pylori) is perhaps the most ubiquitous and successful human pathogen, since it colonizes the stomach of more than half of humankind. Infection with this bacterium is commonly acquired during childhood. Once infected, people carry the bacteria for decades or even for life, if not treated. Persistent infection with this pathogen causes gastritis, peptic ulcer disease and is also strongly associated with the development of gastric cancer. Despite induction of innate and adaptive immune responses in the infected individual, the host is unable to clear the bacteria. One widely accepted hallmark of H. pylori is that it successfully and stealthily evades host defense mechanisms. Though the gastric mucosa is well protected against infection, H. pylori is able to reside under the mucus, attach to gastric epithelial cells and cause persistent infection by evading immune responses mediated by host. In this review, we discuss how H. pylori avoids innate and acquired immune response elements, uses gastric epithelial cells as mediators to manipulate host T cell responses and uses virulence factors to avoid adaptive immune responses by T cells to establish a persistent infection. We also discuss in this review how the genetic diversity of this pathogen helps for its survival.
doi:10.3748/wjg.v20.i36.12753
PMCID: PMC4177461  PMID: 25278676
Helicobacter pylori; Immune response; Pattern recognition receptors; Phagocytes; T cells; Antigen presenting cells; Gastric epithelial cells; Vacuolating cytotoxin; T4SS
14.  Helicobacter pylori Counteracts the Apoptotic Action of Its VacA Toxin by Injecting the CagA Protein into Gastric Epithelial Cells 
PLoS Pathogens  2009;5(10):e1000603.
Infection with Helicobacter pylori is responsible for gastritis and gastroduodenal ulcers but is also a high risk factor for the development of gastric adenocarcinoma and lymphoma. The most pathogenic H. pylori strains (i.e., the so-called type I strains) associate the CagA virulence protein with an active VacA cytotoxin but the rationale for this association is unknown. CagA, directly injected by the bacterium into colonized epithelium via a type IV secretion system, leads to cellular morphological, anti-apoptotic and proinflammatory effects responsible in the long-term (years or decades) for ulcer and cancer. VacA, via pinocytosis and intracellular trafficking, induces epithelial cell apoptosis and vacuolation. Using human gastric epithelial cells in culture transfected with cDNA encoding for either the wild-type 38 kDa C-terminal signaling domain of CagA or its non-tyrosine-phosphorylatable mutant form, we found that, depending on tyrosine-phosphorylation by host kinases, CagA inhibited VacA-induced apoptosis by two complementary mechanisms. Tyrosine-phosphorylated CagA prevented pinocytosed VacA to reach its target intracellular compartments. Unphosphorylated CagA triggered an anti-apoptotic activity blocking VacA-induced apoptosis at the mitochondrial level without affecting the intracellular trafficking of the toxin. Assaying the level of apoptosis of gastric epithelial cells infected with wild-type CagA+/VacA+ H. pylori or isogenic mutants lacking of either CagA or VacA, we confirmed the results obtained in cells transfected with the CagA C-ter constructions showing that CagA antagonizes VacA-induced apoptosis. VacA toxin plays a role during H. pylori stomach colonization. However, once bacteria have colonized the gastric niche, the apoptotic action of VacA might be detrimental for the survival of H. pylori adherent to the mucosa. CagA association with VacA is thus a novel, highly ingenious microbial strategy to locally protect its ecological niche against a bacterial virulence factor, with however detrimental consequences for the human host.
Author Summary
The gram-negative bacterium Helicobacter pylori is the main causative agent of peptic ulcer and gastric cancer in humans. Our work sheds light on a new molecular mechanism by which H. pylori would exert its highly efficient colonization strategy of the human host. In this paper, we show that the H. pylori CagA protein counteracts, by two distinct non-overlapping mechanisms, the apoptotic activity of the H. pylori VacA toxin on human gastric epithelial cells so as to allow a protection of the bacterium niche against VacA, giving a rationale for the association of these two virulence factors in the most pathogenic H. pylori strains. This is a new, highly ingenious mechanism by which a bacterium locally protects its ecological niche against the action of one of its own virulence factors. However, while exerting a beneficial role for survival and growth of the bacterium by counteracting VacA toxin, CagA injection in the gastric epithelial cells triggers proinflammatory and anti-apoptotic responses which are detrimental for the human host in the long-term and favor the development of ulcer and cancer.
doi:10.1371/journal.ppat.1000603
PMCID: PMC2745580  PMID: 19798427
15.  MIR106B and MIR93 Prevent Removal of Bacteria from Epithelial Cells by Disrupting ATG16L1-Mediated Autophagy 
Gastroenterology  2013;146(1):10.1053/j.gastro.2013.09.006.
BACKGROUND & AIMS
Variants in genes that regulate autophagy have been associated with Crohn’s disease (CD). Defects in autophagy-mediated removal of pathogenic microbes could contribute to pathogenesis of CD. We investigated the role of the micro-RNAs (miRs) MIR106B and MIR93 in induction of autophagy and bacterial clearance in human cell lines, and the correlation between MIR106B and autophagy-related gene 16L1 (ATG16L1) expression in tissues from patients with CD.
METHODS
We studied the ability of MIR106B and MIR93 to regulate ATG transcripts in human cancer cell lines (HCT116, SW480, HeLa, and U2OS) using luciferase report assays and bioinformatics analyses; MIR106B and MIR93 mimics and antagonists were transfected into cells to modify levels of miRs. Cells were infected with LF82, a CD-associated adherent-invasive strain of Escherichia coli, and monitored by confocal microscopy and for colony-forming units. Colon tissues from 41 healthy individuals (controls), 22 with active CD, 16 with inactive CD, and 7 with chronic inflammation were assessed for levels of MIR106B and ATG16L1 by in situ hybridization and immunohistochemistry.
RESULTS
Silencing Dicer 1, an essential processor of miRs, increased levels of ATG protein and formation of autophagosomes in cells, indicating that miRs regulate autophagy. Luciferase reporter assays indicated that MIR106B and MIR93 targeted ATG16L1 mRNA. MIR106B and MIR93 reduced levels of ATG16L1 and autophagy; these increased following expression of ectopic ATG16L1. In contrast, MIR106B and MIR93 antagonists increased formation of autophagosomes. Levels of MIR106B were increased in intestinal epithelia from patients with active CD, whereas levels of ATG16L1 were reduced, compared with controls. Levels of CMYC were also increased in intestinal epithelia of patients with active CD, compared with controls. These alterations could impair removal of CD-associated bacteria by autophagy.
CONCLUSIONS
In human cell lines, MIR106B and MIR93 reduce levels of ATG16L1 and autophagy, and prevent autophagy-dependent eradication of intracellular bacteria. This process also appears to be altered in colon tissues from patients with active CD.
doi:10.1053/j.gastro.2013.09.006
PMCID: PMC3870037  PMID: 24036151
inflammatory bowel disease; microRNA; cell biology; infection
16.  Epigenetic silencing of miR-210 increases the proliferation of gastric epithelium during chronic Helicobacter pylori infection  
Nature Communications  2014;5:4497.
Persistent colonization of the gastric mucosa by Helicobacter pylori (Hp) elicits chronic inflammation and aberrant epithelial cell proliferation, which increases the risk of gastric cancer. Here we examine the ability of microRNAs to modulate gastric cell proliferation in response to persistent Hp infection and find that epigenetic silencing of miR-210 plays a key role in gastric disease progression. Importantly, DNA methylation of the miR-210 gene is increased in Hp-positive human gastric biopsies as compared with Hp-negative controls. Moreover, silencing of miR-210 in gastric epithelial cells promotes proliferation. We identify STMN1 and DIMT1 as miR-210 target genes and demonstrate that inhibition of miR-210 expression augments cell proliferation by activating STMN1 and DIMT1 . Together, our results highlight inflammation-induced epigenetic silencing of miR-210 as a mechanism of induction of chronic gastric diseases, including cancer, during Hp infection.
Chronic infection with the bacterium Helicobacter pylori is associated with inflammation and increased risk of gastric cancer. Kiga et al. show that methylation and silencing of the microRNA gene miR-210 is associated with infection in humans, and promotes proliferation of gastric epithelial cells in culture.
doi:10.1038/ncomms5497
PMCID: PMC4279363  PMID: 25187177
17.  Helicobacter pylori VacA Suppresses Lactobacillus acidophilus-Induced Interferon Beta Signaling in Macrophages via Alterations in the Endocytic Pathway 
mBio  2013;4(3):e00609-12.
ABSTRACT
Helicobacter pylori causes chronic gastritis and avoids elimination by the immune system of the infected host. The commensal bacterium Lactobacillus acidophilus has been suggested to exert beneficial effects as a supplement during H. pylori eradication therapy. In the present study, we applied whole-genome microarray analysis to compare the immune responses induced in murine bone marrow-derived macrophages (BMDMs) stimulated with L. acidophilus, H. pylori, or both bacteria in combination. While L. acidophilus induced a Th1-polarizing response characterized by high expression of interferon beta (IFN-β) and interleukin 12 (IL-12), H. pylori strongly induced the innate cytokines IL-1β and IL-1α. In BMDMs prestimulated with L. acidophilus, H. pylori blocked the expression of L. acidophilus-induced IFN-β and IL-12 and suppressed the expression of key regulators of the Rho, Rac, and Cdc42 GTPases. The inhibition of L. acidophilus-induced IFN-β was independent of H. pylori viability and the virulence factor CagPAI; however, a vacuolating cytotoxin (vacA) mutant was unable to block IFN-β. Confocal microscopy demonstrated that the addition of H. pylori to L. acidophilus-stimulated BMDMs redirects intracellular processing, leading to an accumulation of L. acidophilus in the endosomal and lysosomal compartments. Thus, our findings indicate that H. pylori inhibits the development of a strong Th1-polarizing response in BMDMs stimulated with L. acidophilus by blocking the production of IFN-β in a VacA-dependent manner. We suggest that this abrogation is caused by a redirection of the endocytotic pathway in the processing of L. acidophilus.
IMPORTANCE
Approximately half of the world’s population is infected with Helicobacter pylori. The factors that allow this pathogen to persist in the stomach and cause chronic infections have not yet been fully elucidated. In particular, how H. pylori avoids killing by macrophages, one of the main types of immune cell underlying the epithelium, remains elusive. Here we have shown that the H. pylori virulence factor VacA plays a key role by blocking the activation of innate cytokines induced by the probiotic Lactobacillus acidophilus in macrophages and suppresses the expression of key regulators required for the organization and dynamics of the intracellular cytoskeleton. Our results identify potential targets for the treatment of H. pylori infection and vaccination, since specific inhibition of the toxin VacA possibly allows the activation of an efficient immune response and thereby eradication of H. pylori in the host.
doi:10.1128/mBio.00609-12
PMCID: PMC3685213  PMID: 23760466
18.  Contribution of H. pylori and Smoking Trends to US Incidence of Intestinal-Type Noncardia Gastric Adenocarcinoma: A Microsimulation Model 
PLoS Medicine  2013;10(5):e1001451.
Jennifer Yeh and colleagues examine the contribution of IHelicobacter pyloriI and smoking trends to the incidence of past and future intestinal-type noncardia gastric adenocarcinoma.
Please see later in the article for the Editors' Summary
Background
Although gastric cancer has declined dramatically in the US, the disease remains the second leading cause of cancer mortality worldwide. A better understanding of reasons for the decline can provide important insights into effective preventive strategies. We sought to estimate the contribution of risk factor trends on past and future intestinal-type noncardia gastric adenocarcinoma (NCGA) incidence.
Methods and Findings
We developed a population-based microsimulation model of intestinal-type NCGA and calibrated it to US epidemiologic data on precancerous lesions and cancer. The model explicitly incorporated the impact of Helicobacter pylori and smoking on disease natural history, for which birth cohort-specific trends were derived from the National Health and Nutrition Examination Survey (NHANES) and National Health Interview Survey (NHIS). Between 1978 and 2008, the model estimated that intestinal-type NCGA incidence declined 60% from 11.0 to 4.4 per 100,000 men, <3% discrepancy from national statistics. H. pylori and smoking trends combined accounted for 47% (range = 30%–58%) of the observed decline. With no tobacco control, incidence would have declined only 56%, suggesting that lower smoking initiation and higher cessation rates observed after the 1960s accelerated the relative decline in cancer incidence by 7% (range = 0%–21%). With continued risk factor trends, incidence is projected to decline an additional 47% between 2008 and 2040, the majority of which will be attributable to H. pylori and smoking (81%; range = 61%–100%). Limitations include assuming all other risk factors influenced gastric carcinogenesis as one factor and restricting the analysis to men.
Conclusions
Trends in modifiable risk factors explain a significant proportion of the decline of intestinal-type NCGA incidence in the US, and are projected to continue. Although past tobacco control efforts have hastened the decline, full benefits will take decades to be realized, and further discouragement of smoking and reduction of H. pylori should be priorities for gastric cancer control efforts.
Please see later in the article for the Editors' Summary
Editors' Summary
Background
Cancer of the stomach (gastric cancer) is responsible for a tenth of all cancer deaths world-wide, with an estimated 700,000 people dying from this malignancy every year, making it the second most common cause of global cancer-related deaths after lung cancer. Unfortunately, the projected global burden of this disease estimate that deaths from gastric cancer will double by 2030. Gastric cancer has a poor prognosis with only a quarter of people with this type of cancer surviving more than five years. In order to reduce deaths, it is therefore of utmost importance to identify and reduce the modifiable risk factors associated with gastric cancer. Smoking and chronic gastric infection with the bacteria Helicobacter pylori (H. pylori), are known to be two common modifiable risk factors for gastric cancer, particularly for a type of gastric cancer called intestinal-type noncardia gastric adenocarcinoma (NCGA), which occurs at the distal end of the stomach and accounts for more than half of all cases of gastric cancer in US men.
Why Was This Study Done?
H. pylori initiates a precancerous process, and so infection with this bacteria can increase intestinal-type NCGA risk by as much as 6-fold while smoking doubles cancer risk by advancing increasing progression of existing lesions. Changes in these two risk factors over the past century (especially following the US Surgeon General's Report on Smoking and Health in 1964) have led to a dramatic decline in the rates of gastric cancer in US men. Understanding the combined effects of underlying risk factor trends on health outcomes for intestinal-type NCGA at the population level can help to predict future cancer trends and burden in the US. So in this study, the researchers used a mathematical model to estimate the contribution of H. pylori and smoking trends on the decline in intestinal-type NCGA incidence in US men.
What Did the Researchers Do and Find?
The researchers used birth cohorts derived from data in two national databases, the National Health and Nutrition Examination Survey (NHANES) and National Health Interview Survey (NHIS) to develop a population-based model of intestinal-type NCGA. To ensure model predictions were consistent with epidemiologic data, the researchers calibrated the model to data on cancer and precancerous lesions and using the model, projected population outcomes between 1978 and 2040 for a base-case scenario (in which all risk factor trends were allowed to vary over time). The researchers then evaluated alternative risk factors scenarios to provide insights on the potential benefit of past and future efforts to control gastric cancer.
Using these methods, the researchers estimated that the incidence of intestinal-type NCGA (standardized by age) fell from 11.0 to 4.4 per 100,000 men between 1978 and 2008, a drop of 60%. When the researchers incorporated only H. pylori prevalence and smoking trends into the model (both of which fell dramatically over the time period) they found that intestinal-type NCGA incidence fell by only 28% (from 12.7 to 9.2 per 100,000 men), suggesting that H. pylori and smoking trends are responsible for 47% of the observed decline. The researchers found that H. pylori trends alone were responsible for 43% of the decrease in cancer but smoking trends were responsible for only a 3% drop. The researchers also found evidence that after the 1960s, observed trends in lower smoking initiation and higher cessation accelerated the decline in intestinal-type NCGA incidence by 7%. Finally, the researchers found that intestinal-type NCGA incidence is projected to decline an additional 47% between 2008 and 2040 (4.4 to 2.3 per 100,000 men) with H. pylori and smoking trends accounting for more than 80% of the observed fall.
What Do These Findings Mean?
These findings suggest that, combined with a fall in smoking rates, almost half of the observed fall in rates of intestinal-type NCGA cancer in US men between 1978 and 2008 was attributable to the decline in infection rates of H. pylori. Rates for this cancer are projected to continue to fall by 2040, with trends for both H. pylori infection and smoking accounting for more than 80% of the observed fall, highlighting the importance of the relationship between risk factors changes over time and achieving long-term reduction in cancer rates. This study is limited by the assumptions made in the model and in that it only examined one type of gastric cancer and excluded women. Nevertheless, this modeling study highlights that continued efforts to reduce rates of smoking and H. pylori infection will help to reduce rates of gastric cancer.
Additional Information
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1001451.
The National Cancer Institute gives detailed information about gastric cancer
The Gastric Cancer Foundation has information on gastric cancer for patients and professionals
Cancer Research UK explains types of gastric cancer
doi:10.1371/journal.pmed.1001451
PMCID: PMC3660292  PMID: 23700390
19.  Helicobacter pylori induces β3GnT5 in human gastric cell lines, modulating expression of the SabA ligand sialyl–Lewis x  
The Journal of Clinical Investigation  2008;118(6):2325-2336.
Chronic Helicobacter pylori infection is recognized as a cause of gastric cancer. H. pylori adhesion to gastric cells is mediated by bacterial adhesins such as sialic acid–binding adhesin (SabA), which binds the carbohydrate structure sialyl–Lewis x. Sialyl–Lewis x expression in the gastric epithelium is induced during persistent H. pylori infection, suggesting that H. pylori modulates host cell glycosylation patterns for enhanced adhesion. Here, we evaluate changes in the glycosylation-related gene expression profile of a human gastric carcinoma cell line following H. pylori infection. We observed that H. pylori significantly altered expression of 168 of the 1,031 human genes tested by microarray, and the extent of these alterations was associated with the pathogenicity of the H. pylori strain. A highly pathogenic strain altered expression of several genes involved in glycan biosynthesis, in particular that encoding β3 GlcNAc T5 (β3GnT5), a GlcNAc transferase essential for the biosynthesis of Lewis antigens. β3GnT5 induction was specific to infection with highly pathogenic strains of H. pylori carrying a cluster of genes known as the cag pathogenicity island, and was dependent on CagA and CagE. Further, β3GnT5 overexpression in human gastric carcinoma cell lines led to increased sialyl–Lewis x expression and H. pylori adhesion. This study identifies what we believe to be a novel mechanism by which H. pylori modulates the biosynthesis of the SabA ligand in gastric cells, thereby strengthening the epithelial attachment necessary to achieve successful colonization.
doi:10.1172/JCI34324
PMCID: PMC2381748  PMID: 18483624
20.  SabA Is the H. pylori Hemagglutinin and Is Polymorphic in Binding to Sialylated Glycans 
PLoS Pathogens  2006;2(10):e110.
Adherence of Helicobacter pylori to inflamed gastric mucosa is dependent on the sialic acid–binding adhesin (SabA) and cognate sialylated/fucosylated glycans on the host cell surface. By in situ hybridization, H. pylori bacteria were observed in close association with erythrocytes in capillaries and post-capillary venules of the lamina propria of gastric mucosa in both infected humans and Rhesus monkeys. In vivo adherence of H. pylori to erythrocytes may require molecular mechanisms similar to the sialic acid–dependent in vitro agglutination of erythrocytes (i.e., sialic acid–dependent hemagglutination). In this context, the SabA adhesin was identified as the sialic acid–dependent hemagglutinin based on sialidase-sensitive hemagglutination, binding assays with sialylated glycoconjugates, and analysis of a series of isogenic sabA deletion mutants. The topographic presentation of binding sites for SabA on the erythrocyte membrane was mapped to gangliosides with extended core chains. However, receptor mapping revealed that the NeuAcα2–3Gal-disaccharide constitutes the minimal sialylated binding epitope required for SabA binding. Furthermore, clinical isolates demonstrated polymorphism in sialyl binding and complementation analysis of sabA mutants demonstrated that polymorphism in sialyl binding is an inherent property of the SabA protein itself. Gastric inflammation is associated with periodic changes in the composition of mucosal sialylation patterns. We suggest that dynamic adaptation in sialyl-binding properties during persistent infection specializes H. pylori both for individual variation in mucosal glycosylation and tropism for local areas of inflamed and/or dysplastic tissue.
Synopsis
Helicobacter pylori infections are very common worldwide and cause chronic inflammation in the stomach (gastritis), which may progress to peptic ulcer disease and stomach cancer. In the gastric epithelium, H. pylori infections induce expression of inflammation-associated “sialylated” carbohydrates. The ability to bind to the glycosylated epithelial cells is considered to be essential for H. pylori to cause persistent infection and disease. Here the authors show that during established infection, H. pylori also binds to red blood cells in gastric mucosal blood vessels in both infected humans and Rhesus monkeys. The authors found that “sialic acid–binding adhesin” (SabA), is the bacterial surface protein that mediates binding of H. pylori to red blood cells. Furthermore, they show that clinical H. pylori isolates demonstrate “polymorphism” in their abilities to bind various sialylated carbohydrates, and that the variation in binding properties depends on the sialic acid–binding adhesin protein itself. This variability may adapt the binding properties of H. pylori both to individual hosts and the changing epithelial glycosylation patterns during chronic inflammation. Continuous adaptation to inflamed tissue during persistent infections is probably a general feature of microbial pathogens, although their binding properties have not yet been explored in detail.
doi:10.1371/journal.ppat.0020110
PMCID: PMC1626103  PMID: 17121461
21.  Use of PCR and culture to detect Helicobacter pylori in naturally infected cats following triple antimicrobial therapy. 
Helicobacter pylori causes gastritis and peptic ulcers and is linked to gastric cancer. Domestic cats from a commercial source were found to be naturally infected with H. pylori, and studies were undertaken to eradicate H. pylori from infected cats by using triple antimicrobial therapy. Eight cats infected with H. pylori were used in the study. Six cats received a 21-day course of oral amoxicillin, metronidazole, and omeprazole, and two cats served as controls. Two weeks and 4 weeks posttreatment (p.t.), all six treated cats were negative at several sites (saliva, gastric juice, and gastric mucosa) for H. pylori by culture. However, as determined by PCR with primers specific for the 26-kDa product, the majority of cats at 2 and 4 weeks p.t. had gastric fluid samples which were positive for H. pylori and three of three cats at 2 weeks p.t. had dental plaque which was positive for H. pylori. At 6 weeks p.t., all six cats had H. pylori-negative cultures for samples from several gastric sites taken at necropsy, and only one cat had H. pylori cultured from gastric juice. PCR analysis revealed that five of six cats had H. pylori DNA amplification products from plaque, saliva, and/or gastric fluid samples. Negative bacterial cultures for cats for which there was demonstrable PCR amplification of H. pylori DNA may reflect the inability of in vitro culture techniques to isolate small numbers of H. pylori organisms, focal colonization at sites not cultured, or a failure of the antibiotics to successfully eradicate H. pylori from extragastric sites which allowed subsequent recolonization of the stomach after cessation of therapy. Alternatively, the treatment strategy may have induced in vivo viable but nonculturable coccoid forms of H. pylori. The H. pylori cat model should allow further studies to test these hypotheses as well as the efficacies of other combined therapeutic regimens. Also, because 100% of these cats were naturally infected with H.pylori, this model should prove useful in exploring mechanisms whereby human populations in underdeveloped countries, which have H. pylori infection rates approaching 100%, have a high rate of recurrence of H. pylori infection after use of prescribed antibiotic therapies that successfully eradicate H. pylori in individuals in developed countries.
PMCID: PMC163354  PMID: 8726024
22.  A Repetitive DNA Element Regulates Expression of the Helicobacter pylori Sialic Acid Binding Adhesin by a Rheostat-like Mechanism 
PLoS Pathogens  2014;10(7):e1004234.
During persistent infection, optimal expression of bacterial factors is required to match the ever-changing host environment. The gastric pathogen Helicobacter pylori has a large set of simple sequence repeats (SSR), which constitute contingency loci. Through a slipped strand mispairing mechanism, the SSRs generate heterogeneous populations that facilitate adaptation. Here, we present a model that explains, in molecular terms, how an intergenically located T-tract, via slipped strand mispairing, operates with a rheostat-like function, to fine-tune activity of the promoter that drives expression of the sialic acid binding adhesin, SabA. Using T-tract variants, in an isogenic strain background, we show that the length of the T-tract generates multiphasic output from the sabA promoter. Consequently, this alters the H. pylori binding to sialyl-Lewis x receptors on gastric mucosa. Fragment length analysis of post-infection isolated clones shows that the T-tract length is a highly variable feature in H. pylori. This mirrors the host-pathogen interplay, where the bacterium generates a set of clones from which the best-fit phenotypes are selected in the host. In silico and functional in vitro analyzes revealed that the length of the T-tract affects the local DNA structure and thereby binding of the RNA polymerase, through shifting of the axial alignment between the core promoter and UP-like elements. We identified additional genes in H. pylori, with T- or A-tracts positioned similar to that of sabA, and show that variations in the tract length likewise acted as rheostats to modulate cognate promoter output. Thus, we propose that this generally applicable mechanism, mediated by promoter-proximal SSRs, provides an alternative mechanism for transcriptional regulation in bacteria, such as H. pylori, which possesses a limited repertoire of classical trans-acting regulatory factors.
Author Summary
During persistent H. pylori infection, the local gastric milieu is constantly altered by host responses and inflammation fluxes. As adhesion is crucial to maintain infection, appropriate adaptation of bacterial adherence properties is required to meet these environmental fluctuations. H. pylori uses the SabA protein to bind glycan receptors present on inflamed stomach mucosa. SabA expression can be turned on or off via known genetic mechanisms; however, how fine-tuning of SabA expression occurs to match changes in receptor levels is still unknown. The H. pylori genome encodes few trans-acting regulators but has numerous simple sequence repeats (SSR), i.e. hypermutable DNA segments. Here, we have deciphered a mechanism where a T-repeat tract, located in the sabA promoter region, affects SabA expression. The mechanism involves structural alterations of the promoter DNA that affects interaction of the RNA polymerase, without input from known trans-acting regulators. This mechanism is likely not unique for SabA or to H. pylori, but also applicable to other pathogens with high abundance of SSRs and limited set of transcription factors. Our findings contribute to understanding of the important bacterial-host interplay, and to mechanisms that generate heterogeneous populations of best-fit clones, i.e. stochastic switching.
doi:10.1371/journal.ppat.1004234
PMCID: PMC4081817  PMID: 24991812
23.  Flagellar Localization of a Helicobacter pylori Autotransporter Protein 
mBio  2013;4(2):e00613-12.
ABSTRACT
Helicobacter pylori contains four genes that are predicted to encode proteins secreted by the autotransporter (type V) pathway. One of these, the pore-forming toxin VacA, has been studied in great detail, but thus far there has been very little investigation of three VacA-like proteins. We show here that all three VacA-like proteins are >250 kDa in mass and localized on the surface of H. pylori. The expression of the three vacA-like genes is upregulated during H. pylori colonization of the mouse stomach compared to H. pylori growth in vitro, and a wild-type H. pylori strain outcompeted each of the three corresponding isogenic mutant strains in its ability to colonize the mouse stomach. One of the VacA-like proteins localizes to a sheath that overlies the flagellar filament and bulb, and therefore, we designate it FaaA (flagella-associated autotransporter A). In comparison to a wild-type H. pylori strain, an isogenic faaA mutant strain exhibits decreased motility, decreased flagellar stability, and an increased proportion of flagella in a nonpolar site. The flagellar localization of FaaA differs markedly from the localization of other known autotransporters, and the current results reveal an important role of FaaA in flagellar localization and motility.
IMPORTANCE
The pathogenesis of most bacterial infections is dependent on the actions of secreted proteins, and proteins secreted by the autotransporter pathway constitute the largest family of secreted proteins in pathogenic Gram-negative bacteria. In this study, we analyzed three autotransporter proteins (VacA-like proteins) produced by Helicobacter pylori, a Gram-negative bacterium that colonizes the human stomach and contributes to the pathogenesis of gastric cancer and peptic ulcer disease. We demonstrate that these three proteins each enhance the capacity of H. pylori to colonize the stomach. Unexpectedly, one of these proteins (FaaA) is localized to a sheath that overlies H. pylori flagella. The absence of FaaA results in decreased H. pylori motility as well as a reduction in flagellar stability and a change in flagellar localization. The atypical localization of FaaA reflects a specialized function of this autotransporter designed to optimize H. pylori colonization of the gastric niche.
doi:10.1128/mBio.00613-12
PMCID: PMC3622936  PMID: 23572556
24.  MiR-216a: a link between endothelial dysfunction and autophagy 
Cell Death & Disease  2014;5(1):e1029-.
Endothelial dysfunction and impaired autophagic activity have a crucial role in aging-related diseases such as cardiovascular dysfunction and atherosclerosis. We have identified miR-216a as a microRNA that is induced during endothelial aging and, according to the computational analysis, among its targets includes two autophagy-related genes, Beclin1 (BECN1) and ATG5. Therefore, we have evaluated the role of miR-216a as a molecular component involved in the loss of autophagic function during endothelial aging. The inverse correlation between miR-216a and autophagic genes was conserved during human umbilical vein endothelial cells (HUVECs) aging and in vivo models of human atherosclerosis and heart failure. Luciferase experiments indicated BECN1, but not ATG5 as a direct target of miR-216a. HUVECs were transfected in order to modulate miR-216a expression and stimulated with 100 μg/ml oxidized low-density lipoprotein (ox-LDL) to induce a stress repairing autophagic process. We found that in young HUVECs, miR-216a overexpression repressed BECN1 and ATG5 expression and the ox-LDL induced autophagy, as evaluated by microtubule-associated protein 1 light chain 3 (LC3B) analysis and cytofluorimetric assay. Moreover, miR-216a stimulated ox-LDL accumulation and monocyte adhesion in HUVECs. Conversely, inhibition of miR-216a in old HUVECs rescued the ability to induce a protective autophagy in response to ox-LDL stimulus. In conclusion, mir-216a controls ox-LDL induced autophagy in HUVECs by regulating intracellular levels of BECN1 and may have a relevant role in the pathogenesis of cardiovascular disorders and atherosclerosis.
doi:10.1038/cddis.2013.556
PMCID: PMC4040670  PMID: 24481443
atherosclerosis; autophagy; endothelial dysfunction; microRNAs
25.  Helicobacter pylori Lipopolysaccharide Is Synthesized via a Novel Pathway with an Evolutionary Connection to Protein N-Glycosylation 
PLoS Pathogens  2010;6(3):e1000819.
Lipopolysaccharide (LPS) is a major component on the surface of Gram negative bacteria and is composed of lipid A-core and the O antigen polysaccharide. O polysaccharides of the gastric pathogen Helicobacter pylori contain Lewis antigens, mimicking glycan structures produced by human cells. The interaction of Lewis antigens with human dendritic cells induces a modulation of the immune response, contributing to the H. pylori virulence. The amount and position of Lewis antigens in the LPS varies among H. pylori isolates, indicating an adaptation to the host. In contrast to most bacteria, the genes for H. pylori O antigen biosynthesis are spread throughout the chromosome, which likely contributed to the fact that the LPS assembly pathway remained uncharacterized. In this study, two enzymes typically involved in LPS biosynthesis were found encoded in the H. pylori genome; the initiating glycosyltransferase WecA, and the O antigen ligase WaaL. Fluorescence microscopy and analysis of LPS from H. pylori mutants revealed that WecA and WaaL are involved in LPS production. Activity of WecA was additionally demonstrated with complementation experiments in Escherichia coli. WaaL ligase activity was shown in vitro. Analysis of the H. pylori genome failed to detect a flippase typically involved in O antigen synthesis. Instead, we identified a homolog of a flippase involved in protein N-glycosylation in other bacteria, although this pathway is not present in H. pylori. This flippase named Wzk was essential for O antigen display in H. pylori and was able to transport various glycans in E. coli. Whereas the O antigen mutants showed normal swimming motility and injection of the toxin CagA into host cells, the uptake of DNA seemed to be affected. We conclude that H. pylori uses a novel LPS biosynthetic pathway, evolutionarily connected to bacterial protein N-glycosylation.
Author Summary
Bacterial surfaces are decorated with glycans. The human stomach pathogen Helicobacter pylori exposes lipopolysaccharide (LPS) containing Lewis antigens that mimic human glycan structures. H. pylori alters its Lewis antigen display in adaptation to the individual host. Lewis antigens can interact with human dendritic cells, thereby inducing a suppression of the immune response and facilitating a chronic H. pylori infection. Whereas three general LPS biosynthesis pathways are known, the route of LPS assembly in H. pylori remained to be elucidated. We identified and characterized two components of the H. pylori LPS pathway, WecA and WaaL, which demonstrated that, as in other bacteria, the glycan is initially assembled onto a polyprenoid lipid carrier. This intermediate then has to cross a membrane barrier, requiring specialized translocases. H. pylori does not employ a translocase from common LPS pathways. We show that instead H. pylori uses a translocase named Wzk, which is involved in protein N-glycosylation in other bacteria. Wzk was able to translocate various glycan structures. The identification of Wzk as the H. pylori translocase involved in LPS biosynthesis indicates an evolutionary connection between LPS and glycoprotein biosynthesis pathways.
doi:10.1371/journal.ppat.1000819
PMCID: PMC2841628  PMID: 20333251

Results 1-25 (1079142)