IV. Helicobacter pylori strain-specific activation of signal transduction cascades related to gastric inflammation

Intersections between innate immune response and gastric cancer development

Worldwide, gastric cancer (GC) is the fifth most commonly diagnosed malignancy. It has a reduced prevalence but has maintained its poor prognosis being the fourth leading cause of deaths related to cancer. The highest mortality rates occur in Asian and Latin American countries, where cases are usually diagnosed at advanced stages. Overall, GC is viewed as the consequence of a multifactorial process, involving the virulence of the Helicobacter pylori (H. pylori) strains, as well as some environmental factors, dietary habits, and host intrinsic factors. The tumor microenvironment in GC appears to be chronically inflamed which promotes tumor progression and reduces the therapeutic opportunities. It has been suggested that inflammation assessment needs to be measured qualitatively and quantitatively, considering cell-infiltration types, availability of receptors to detect damage and pathogens, and presence or absence of aggressive H. pylori strains. Gastrointestinal epithelial cells express several Toll-like receptors and determine the first defensive line against pathogens, and have been also described as mediators of tumorigenesis. However, other molecules, such as cytokines related to inflammation and innate immunity, including immune checkpoint molecules, interferon-gamma pathway and NETosis have been associated with an increased risk of GC. Therefore, this review will explore innate immune activation in the context of premalignant lesions of the gastric epithelium and established gastric tumors.

Epigenetic Regulation of Tumor Suppressors by Helicobacter pylori Enhances EBV-Induced Proliferation of Gastric Epithelial Cells

Helicobacter pylori and Epstein-Barr virus (EBV) are two well-known contributors to cancer and can establish lifelong persistent infection in the host. This leads to chronic inflammation, which also contributes to development of cancer. Association with H. pylori increases the risk of gastric carcinoma, and coexistence with EBV enhances proliferation of infected cells. Further, H. pylori-EBV coinfection causes chronic inflammation in pediatric patients. We have established an H. pylori-EBV coinfection model system using human gastric epithelial cells. We showed that H. pylori infection can increase the oncogenic phenotype of EBV-infected cells and that the cytotoxin-associated gene (CagA) protein encoded by H. pylori stimulated EBV-mediated cell proliferation in this coinfection model system. This led to increased expression of DNA methyl transferases (DNMTs), which reprogrammed cellular transcriptional profiles, including those of tumor suppressor genes (TSGs), through hypermethylation. These findings provide new insights into a molecular mechanism whereby cooperativity between two oncogenic agents leads to enhanced oncogenic activity of gastric cancer cells.IMPORTANCE We have studied the cooperativity between H. pylori and EBV, two known oncogenic agents. This led to an enhanced oncogenic phenotype in gastric epithelial cells. We now demonstrate that EBV-driven epigenetic modifications are enhanced in the presence of H. pylori, more specifically, in the presence of its CagA secretory antigen. This results in increased proliferation of the infected gastric cells. Our findings now elucidate a molecular mechanism whereby expression of cellular DNA methyl transferases is induced influencing infection by EBV. Hypermethylation of the regulatory genomic regions of tumor suppressor genes results in their silencing. This drastically affects the expression of cell cycle, apoptosis, and DNA repair genes, which dysregulates their associated processes, and promotion of the oncogenic phenotype.

Regulation of Gastric Lgr5+ve Cell Homeostasis by Bone Morphogenetic Protein (BMP) Signaling and Inflammatory Stimuli

BACKGROUND & AIMS

Gastric Leucine-rich repeat-containing G-protein-coupled receptor 5 (Lgr5) cells exert important functions during injury and homeostasis. Bone morphogenetic protein (BMP) signaling regulates gastric inflammation and epithelial homeostasis. We investigated if BMP signaling controls the fate of Lgr5^+ve cells during inflammation.

METHODS

The H⁺/K⁺-adenosine triphosphatase β-subunit promoter was used to express the BMP inhibitor noggin (Nog) in the stomach (H⁺/K⁺-Nog mice). Inhibition of BMP signaling in Lgr5 cells was achieved by crossing Lgr5-EGFP-ires-CreERT2 (Lgr5-Cre) mice to mice with floxed alleles of BMP receptor 1A (Lgr5-Cre;Bmpr1a^flox/flox mice). Lgr5/GFP^+ve cells were isolated using flow cytometry. Lineage tracing studies were conducted by crossing Lgr5-Cre mice to mice that express Nog and tdTomato (Lgr5-Cre;H⁺/K⁺-Nog;Rosa26-tdTom). Infection with Helicobacter felis was used to induce inflammation. Morphology of the mucosa was analyzed by H&E staining. Distribution of H⁺/K⁺-adenosine triphosphatase-, IF-, Ki67-, CD44-, CD44v9-, and bromodeoxyuridine-positive cells was analyzed by immunostaining. Expression of neck and pit cell mucins was determined by staining with the lectins Griffonia (Bandeiraea) simplicifolia lectin II and Ulex europaeus agglutinin 1, respectively. Id1, Bmpr1a, Lgr5, c-Myc, and Cd44 messenger RNAs were measured by quantitative reverse-transcription polymerase chain reaction.

RESULTS

Lgr5-Cre;Bmpr1a^flox/flox mice showed diminished expression of Bmpr1a in Lgr5/GFP^+ve cells. Infection of Lgr5-Cre;Bmpr1a^flox/flox mice with H felis led to enhanced inflammation, increased cell proliferation, parietal cell loss, and to the development of metaplasia and dysplasia. Infected Lgr5-Cre;H⁺/K⁺-Nog;Rosa26-tdTom mice, but not control mice, showed the presence of tomato^+ve glands lining the lesser curvature that stained positively with Griffonia (Bandeiraea) simplicifolia lectin II and Ulex europaeus agglutinin 1, and with anti-IF, -CD44, -CD44v9, and -bromodeoxyuridine antibodies.

CONCLUSIONS

Inflammation and inhibition of BMP signaling activate Lgr5^+ve cells, which give rise to metaplastic, dysplastic, proliferating lineages that express markers of mucus neck and zymogenic cell differentiation.

Regulation of Gastric Metaplasia, Dysplasia, and Neoplasia by Bone Morphogenetic Protein Signaling

The bone morphogenetic proteins, (BMP)s are regulatory peptides that have significant effects on the growth and differentiation of gastrointestinal tissues. In addition, the BMPs have been shown to exert anti-inflammatory actions in the gut and to negatively regulate the growth of gastric neoplasms. The role of BMP signaling in the regulation of gastric metaplasia, dysplasia and neoplasia has been poorly characterized. Transgenic expression in the mouse stomach of the BMP inhibitor noggin leads to decreased parietal cell number, increased epithelial cell proliferation, and to the emergence of SPEM. Moreover, expression of noggin increases Helicobacter-induced inflammation and epithelial cell proliferation, accelerates the development of dysplasia, and it increases the expression of signal transducer and activator of transcription 3 (STAT3) and of activation-induced cytidine deaminase (AID). These findings provide new clues for a better understanding of the pathophysiological mechanisms that regulate gastric inflammation and the development of both dysplastic and neoplastic lesions of the stomach.

Repurposing Drugs in Oncology (ReDO)-clarithromycin as an anti-cancer agent

Clarithromycin (CAM) is a well-known macrolide antibiotic available as a generic drug. CAM is traditionally used for many types of bacterial infections, treatment of Lyme disease and eradication of gastric infection with Helicobacter pylori. Extensive preclinical and clinical data demonstrate a potential role for CAM to treat various tumours in combination with conventional treatment. The mechanisms of action underlying the anti-tumour activity of CAM are multiple and include prolonged reduction of pro-inflammatory cytokines, autophagy inhibition, and anti-angiogenesis. Here, we present an overview of the current preclinical (in vitro and in vivo) and clinical evidence supporting the role of CAM in cancer. Overall these findings justify further research with CAM in many tumour types, with multiple myeloma, lymphoma, chronic myeloid leukaemia (CML), and lung cancer having the highest level of evidence. Finally, a series of proposals are being made to further investigate the use of CAM in clinical trials which offer the greatest prospect of clinical benefit to patients.

Anti-inflammatory activity of bone morphogenetic protein signaling pathways in stomachs of mice

BACKGROUND & AIMS

Bone morphogenetic protein (BMP)4 is a mesenchymal peptide that regulates cells of the gastric epithelium. We investigated whether BMP signaling pathways affect gastric inflammation after bacterial infection of mice.

METHODS

We studied transgenic mice that express either the BMP inhibitor noggin or the β- galactosidase gene under the control of a BMP-responsive element and BMP4(βgal/+) mice. Gastric inflammation was induced by infection of mice with either Helicobacter pylori or Helicobacter felis. Eight to 12 weeks after inoculation, gastric tissue samples were collected and immunohistochemical, quantitative, reverse-transcription polymerase chain reaction and immunoblot analyses were performed. We used enzyme-linked immunosorbent assays to measure cytokine levels in supernatants from cultures of mouse splenocytes and dendritic cells, as well as from human gastric epithelial cells (AGS cell line). We also measured the effects of BMP-2, BMP-4, BMP-7, and the BMP inhibitor LDN-193189 on the expression of interleukin (IL)8 messenger RNA by AGS cells and primary cultures of canine parietal and mucus cells. The effect of BMP-4 on NFkB activation in parietal and AGS cells was examined by immunoblot and luciferase assays.

RESULTS

Transgenic expression of noggin in mice increased H pylori- or H felis-induced inflammation and epithelial cell proliferation, accelerated the development of dysplasia, and increased expression of the signal transducer and activator of transcription 3 and activation-induced cytidine deaminase. BMP-4 was expressed in mesenchymal cells that expressed α-smooth muscle actin and activated BMP signaling pathways in the gastric epithelium. Neither BMP-4 expression nor BMP signaling were detected in immune cells of C57BL/6, BRE-β-galactosidase, or BMP-4(βgal/+) mice. Incubation of dendritic cells or splenocytes with BMP-4 did not affect lipopolysaccharide-stimulated production of cytokines. BMP-4, BMP-2, and BMP-7 inhibited basal and tumor necrosis factor α-stimulated expression of IL8 in canine gastric epithelial cells. LDN-193189 prevented BMP4-mediated inhibition of basal and tumor necrosis factor α-stimulated expression of IL8 in AGS cells. BMP-4 had no effect on TNFα-stimulated phosphorylation and degradation of IκBα, or on TNFα induction of a NFκβ reporter gene.

CONCLUSIONS

BMP signaling reduces inflammation and inhibits dysplastic changes in the gastric mucosa after infection of mice with H pylori or H felis.

Interplay between DNA repair and inflammation, and the link to cancer

DNA damage and repair are linked to cancer. DNA damage that is induced endogenously or from exogenous sources has the potential to result in mutations and genomic instability if not properly repaired, eventually leading to cancer. Inflammation is also linked to cancer. Reactive oxygen and nitrogen species (RONs) produced by inflammatory cells at sites of infection can induce DNA damage. RONs can also amplify inflammatory responses, leading to increased DNA damage. Here, we focus on the links between DNA damage, repair, and inflammation, as they relate to cancer. We examine the interplay between chronic inflammation, DNA damage and repair and review recent findings in this rapidly emerging field, including the links between DNA damage and the innate immune system, and the roles of inflammation in altering the microbiome, which subsequently leads to the induction of DNA damage in the colon. Mouse models of defective DNA repair and inflammatory control are extensively reviewed, including treatment of mouse models with pathogens, which leads to DNA damage. The roles of microRNAs in regulating inflammation and DNA repair are discussed. Importantly, DNA repair and inflammation are linked in many important ways, and in some cases balance each other to maintain homeostasis. The failure to repair DNA damage or to control inflammatory responses has the potential to lead to cancer.

Detection of Helicobacter pylori in Oral Lesions

Background and aims. Helicobacter pylori is a microaerophilic gram-negative spiral organism. It is recognized as the etiologic factor for peptic ulcers, gastric adenocarcinoma and gastric lymphoma. Recently, it has been isolated from dental plaque and the dorsum of the tongue. This study was designed to assess the association between H. pylori and oral lesions such as ulcerative/inflammatory lesions, squamous cell carcinoma (SCC) and primary lymphoma.

Materials and methods. A total of 228 biopsies diagnosed as oral ulcerative/inflammatory lesions, oral squamous cell carcinoma (OSCC) and oral primary lymphoma were selected from the archives of the Pathology Department. Thirty-two samples that were diagnosed as being without any pathological changes were selected as the control group. All the paraffin blocks were cut for hematoxylin and eosin staining to confirm the diagnoses and then the samples were prepared for immunohistochemistry staining. Data were collected and analyzed.

Results. Chi-squared test showed significant differences between the frequency of H. pylori positivity in normal tissue and the lesions were examined (P=0.000). In addition, there was a statistically significant difference between the lesions examined (P=0.042). Chi-squared test showed significant differences between H. pylori positivity and different tissue types except inside the muscle layer as follows: in epithelium and in lamina propria (P=0.000), inside the blood vessels (P=0.003), inside the salivary gland duct (P=0.036), and muscle layer (P=0.122).

Conclusion. There might be a relation between the presence of H. pylori and oral lesions. Therefore, early detection and eradication of H. pylori in high-risk patients are suggested.

Inflammation-mediated genomic instability: roles of activation-induced cytidine deaminase in carcinogenesis

Chronic inflammation is a strong risk factor for the development of cancer. Many previous studies have demonstrated that a transcriptional factor, nuclear factor (NF)-κB, plays an important role in the association between inflammation and cancer development, particularly tumor promotion and tumor progression. Although it is well recognized that cancer develops via stepwise accumulation of genetic aberrations, the mechanisms underlying the generation of these genetic alterations in normal epithelial cells under inflammatory conditions are not known. We recently demonstrated that pathogenic bacterial or viral factors and the subsequent inflammatory reactions lead to the aberrant expression of a DNA mutator enzyme, activation-induced cytidine deaminase (AID), in various epithelial cells via NF-κB activation, which causes the accumulation of genetic alterations in tumor-related genes. AID activation is widely observed in gastrointestinal tissues with cancer-associated inflammation, such as chronic viral hepatitis, Helicobacter pylori-related gastritis, Barrett's esophagus and inflammatory bowel disease. Furthermore, a deficiency of endogenous AID expression reduces both accumulation of somatic mutations in tumor-related genes and tumor incidence in a mouse model of inflammation-associated cancer development. These findings strongly suggest that AID plays an integral role in inflammation-associated carcinogenesis and is therefore a potential target molecule for the prevention and treatment of cancers.

Acquisition of Genetic Aberrations by Activation-Induced Cytidine Deaminase (AID) during Inflammation-Associated Carcinogenesis

Genetic abnormalities such as nucleotide alterations and chromosomal disorders that accumulate in various tumor-related genes have an important role in cancer development. The precise mechanism of the acquisition of genetic aberrations, however, remains unclear. Activation-induced cytidine deaminase (AID), a nucleotide editing enzyme, is essential for the diversification of antibody production. AID is expressed only in activated B lymphocytes under physiologic conditions and induces somatic hypermutation and class switch recombination in immunoglobulin genes. Inflammation leads to aberrant AID expression in various gastrointestinal organs and increased AID expression contributes to cancer development by inducing genetic alterations in epithelial cells. Studies of how AID induces genetic disorders are expected to elucidate the mechanism of inflammation-associated carcinogenesis.

Inflammatory Animal Model for Parkinson's Disease: The Intranigral Injection of LPS Induced the Inflammatory Process along with the Selective Degeneration of Nigrostriatal Dopaminergic Neurons

We have developed an animal model of degeneration of the nigrostriatal dopaminergic neurons, the neuronal system involved in Parkinson's disease (PD). The implication of neuroinflammation on this disease was originally established in 1988, when the presence of activated microglia in the substantia nigra (SN) of parkinsonians was reported by McGeer et al. Neuroinflammation could be involved in the progression of the disease or even has more direct implications. We injected 2 μg of the potent proinflammatory compound lipopolysaccharide (LPS) in different areas of the CNS, finding that SN displayed the highest inflammatory response and that dopaminergic (body) neurons showed a special and specific sensitivity to this process with the induction of selective dopaminergic degeneration. Neurodegeneration is induced by inflammation since it is prevented by anti-inflammatory compounds. The special sensitivity of dopaminergic neurons seems to be related to the endogenous dopaminergic content, since it is overcome by dopamine depletion. Compounds that activate microglia or induce inflammation have similar effects to LPS. This model suggest that inflammation is an important component of the degeneration of the nigrostriatal dopaminergic system, probably also in PD. Anti-inflammatory treatments could be useful to prevent or slow down the rate of dopaminergic degeneration in this disease.

Peripheral inflammation increases the damage in animal models of nigrostriatal dopaminergic neurodegeneration: possible implication in Parkinson's disease incidence

Inflammatory processes described in Parkinson's disease (PD) and its animal models appear to be important in the progression of the pathogenesis, or even a triggering factor. Here we review that peripheral inflammation enhances the degeneration of the nigrostriatal dopaminergic system induced by different insults; different peripheral inflammations have been used, such as IL-1β and the ulcerative colitis model, as well as insults to the dopaminergic system such as 6-hydroxydopamine or lipopolysaccharide. In all cases, an increased loss of dopaminergic neurons was described; inflammation in the substantia nigra increased, displaying a great activation of microglia along with an increase in the production of cytokines such as IL-1β and TNF-α. Increased permeability or disruption of the BBB, with overexpression of the ICAM-1 adhesion molecule and infiltration of circulating monocytes into the substantia nigra, is also involved, since the depletion of circulating monocytes prevents the effects of peripheral inflammation. Data are reviewed in relation to epidemiological studies of PD.

Role of virulence factors and host cell signaling in the recognition of Helicobacter pylori and the generation of immune responses

Helicobacter pylori colonizes a large proportion of the world's population, with infection invariably leading to chronic, lifelong gastritis. While the infection often persists undiagnosed and without causing severe pathology, there are a number of host, bacterial and environmental factors that can influence whether infection provokes a mild inflammatory response or results in significant morbidity. Intriguingly, the most virulent H. pylori strains appear to deliberately induce the epithelial signaling cascades responsible for activating the innate immune system. While the reason for this remains unclear, the resulting adaptive immune responses are largely ineffective in clearing the bacterium once infection has become established and, as a result, inflammation likely causes more damage to the host itself.

Ulcerative colitis exacerbates lipopolysaccharide-induced damage to the nigral dopaminergic system: potential risk factor in Parkinson`s disease

Peripheral inflammation could play a role in the origin and development of certain neurodegenerative disorders. To ascertain this possibility, a model of dopaminergic neurodegeneration based on the injection of the inflammatory agent lipopolysaccharide (LPS) within the substantia nigra was assayed in rats with ulcerative colitis (UC) induced by the ingestion of dextran sulphate sodium. We found an increase in the levels of inflammatory markers from serum (tumor necrosis factor-α, IL-1β, IL-6 and the acute phase protein C-reactive protein) and substantia nigra (tumor necrosis factor-α, IL-1β, IL-6, inducible nitric oxide synthase, intercellular adhesion molecule-1, microglial and astroglial populations) of rats with UC, as well as an alteration of the blood-brain barrier permeability and the loss of dopaminergic neurons. UC reinforced the inflammatory and deleterious effects of LPS. On the contrary, clodronate encapsulated in liposomes (ClodLip), which depletes peripheral macrophages, ameliorated the effect of LPS and UC. Peripheral inflammation might represent a risk factor in the development of Parkinson's disease.

Role of innate immunity in Helicobacter pylori-induced gastric malignancy

Helicobacter pylori colonizes the majority of persons worldwide, and the ensuing gastric inflammatory response is the strongest singular risk factor for peptic ulceration and gastric cancer. However, only a fraction of colonized individuals ever develop clinically significant outcomes. Disease risk is combinatorial and can be modified by bacterial factors, host responses, and/or specific interactions between host and microbe. Several H. pylori constituents that are required for colonization or virulence have been identified, and their ability to manipulate the host innate immune response will be the focus of this review. Identification of bacterial and host mediators that augment disease risk has profound ramifications for both biomedical researchers and clinicians as such findings will not only provide mechanistic insights into inflammatory carcinogenesis but may also serve to identify high-risk populations of H. pylori-infected individuals who can then be targeted for therapeutic intervention.

Investigation of the anti-inflammatory effect of Curcuma longa in Helicobacter pylori-infected patients

Helicobacter pylori infection of the lining of the stomach induces an array of inflammatory cytokine production leading to gastritis and peptic ulcer disease. The aim of this study was to investigate the effect of curcumin on the production of interleukin (IL)-8, IL-1beta, tumor necrosis factor (TNF)-alpha and cyclooxygenase (COX)-2 in gastric mucosa from H. pylori-infected gastritis patients. Patients were randomly assigned to receive either OAM (Omeprazole, Amoxicillin and Metronidazole) treatment or a course of curcumin. Gastric biopsies were collected before and after treatment and were examined for the level of inflammatory cytokines mRNA by semi-quantitative reverse transcription polymerase chain reaction. The eradication rate of H. pylori in patients that received OAM treatment was significantly higher than the patients that received curcumin (78.9% versus 5.9%). The levels of IL-8 mRNA expression in the OAM group significantly decreased after treatment, but no changes of other cytokines were found. This emphasizes an important role of IL-8 in H. pylori infection. The decreases of cytokine production were not found in the curcumin group. We concluded that curcumin alone may have limited anti-bactericidal effect on H. pylori, and on the production of inflammatory cytokines. Nevertheless, other studies have reported that patients treated with curcumin had relieved symptoms. Further investigation should be carried out as the use of curcumin in combination with therapeutic regimens may be beneficial as an alternative treatment.

Association of c.802C>T polymorphism of NOD2/CARD15 gene with the chronic gastritis and predisposition to cancer in H. pylori infected patients

This paper shows analysis of the association of the 802C>T polymorphism of the NOD2/CARD15 gene with the occurrence of the chronic inflammation of the gastric mucosa associated with the Helicobacter pylori infections, development of intestinal metaplasia and dysplasia and, in the result of this, gastric cancer. Genomic DNA samples were extracted from paraffin blocks of gastric mucosal biopsies and from peripheral blood. H. pylori infection was confirmed by histological analysis and urease test. Pyrosequencing of 802C>T polymorphism of the NOD2/CARD15 gene was performed for H. pylori infected patients (131) and population group (100). Analysis of the NOD2/CARD15 gene showed that frequency of the T allele was significantly higher (32.8%) in the group of patients in comparison with the population group (18.1%), with the relative risk of 1.8. In the patient group, the frequency of the CC genotype was 51.1%, CT 32.1% and TT 16.8% (relative risk: 0.7, 1.1 and 4.2, respectively), while in the population group it was 69.0%, 25.7% and 5.3% (relative risk: 1.0, 0.9 and 1.3, respectively). The increasing frequency of the T allele and CT and TT genotypes in the patients with increasingly deeper changes in the gastric mucosa becomes apparent. Our findings suggest that polymorphism 802C>T is associated with changes in gastric mucosa and plays a significant role in the initiation and the progression of carcinogenesis. The number of observed mutations in gastric mucosa correlated with severity of disease.

Helicobacter pylori infection generates genetic instability in gastric cells

The discovery that Helicobacter pylori is associated with gastric cancer has led to numerous studies that investigate the mechanisms by which H. pylori induces carcinogenesis. Gastric cancer shows genetic instability both in nuclear and mitochondrial DNA, besides impairment of important DNA repair pathways. As such, this review highlights the consequences of H. pylori infection on the integrity of DNA in the host cells. By down-regulating major DNA repair pathways, H. pylori infection has the potential to generate mutations. In addition, H. pylori infection can induce direct changes on the DNA of the host, such as oxidative damage, methylation, chromosomal instability, microsatellite instability, and mutations. Interestingly, H. pylori infection generates genetic instability in nuclear and mitochondrial DNA. Based on the reviewed literature we conclude that H. pylori infection promotes gastric carcinogenesis by at least three different mechanisms: (1) a combination of increased endogenous DNA damage and decreased repair activities, (2) induction of mutations in the mitochondrial DNA, and (3) generation of a transient mutator phenotype that induces mutations in the nuclear genome.

Effect of the flavonoid quercetin on inflammation and lipid peroxidation induced by Helicobacter pylori in gastric mucosa of guinea pig

BACKGROUND

Helicobacter pylori infection induces an inflammatory response in the gastric mucosa. Activation of polymorphonuclear leukocytes can produce oxidative damage to gastric tissue through intermediary radicals of oxygen and nitrogen. Vegetable extracts containing polyphenols of the flavonoid family have antibacterial activity, and the flavonoid quercetin possesses anti-H. pylori activity in vitro. The aim of this study was to analyze the effect of oral administration of pure quercetin on inflammation and lipid peroxidation induced by H. pylori in the gastric mucosa of the guinea pig.

METHODS

Sixty days after oral infection with H. pylori guinea pigs received 200 mg/kg of quercetin daily by mouth for 15 days. The infiltration index of inflammatory cells and bacterial density in both the pyloric antrum and corpus were histologically determined by myeloperoxidase histochemistry, hematoxylin-eosin, and modified Giemsa stains. The lipid hydroperoxide content was assessed by the orange xylenol spectrophotometric method.

RESULTS

Quercetin significantly reduced the infiltration index of mononuclear cell and bacterial colonization in the pyloric antrum and corpus. In the antrum of infected quercetin-treated animals, a significant diminution of neutrophil leukocyte infiltration was observed compared with the infected nonquercetin-treated animals. In the antrum, the lipid hydroperoxide concentration was significantly decreased in infected animals treated with quercetin, whereas in the corpus no significant differences were observed.

CONCLUSIONS

Our results indicate that in vivo oral quercetin administration decreases H. pylori infection in the gastric mucosa and reduces both the inflammatory response and lipid peroxidation.

Helicobacter pylori infection triggers aberrant expression of activation-induced cytidine deaminase in gastric epithelium

Infection with Helicobacter pylori (H. pylori) is a risk factor for the development of gastric cancer. Here we show that infection of gastric epithelial cells with 'cag' pathogenicity island (cagPAI)-positive H. pylori induced aberrant expression of activation-induced cytidine deaminase (AID), a member of the cytidine-deaminase family that acts as a DNA- and RNA-editing enzyme, via the IkappaB kinase-dependent nuclear factor-kappaB activation pathway. H. pylori-mediated upregulation of AID resulted in the accumulation of nucleotide alterations in the TP53 tumor suppressor gene in gastric cells in vitro. Our findings provide evidence that aberrant AID expression caused by H. pylori infection might be a mechanism of mutation accumulation in the gastric mucosa during H. pylori-associated gastric carcinogenesis.

The translation of Helicobacter pylori basic research to patient care

In 1984, Barry Marshall and Robin Warren proposed a role for bacterial infections in the pathogenesis of gastroduodenal disease, which triggered an avalanche of research intended to prove or disprove their theory. The result has been a series of advances that have enhanced our understanding of these diseases and completely modernized the clinical approach to their management. In just over 20 years, many aspects of the immunopathogenesis of these diseases have been dissected at the molecular level, with key pathogenic mechanisms being validated by the identification of genes that are associated with the development of gastric cancer. There has been particular emphasis on understanding the molecular structures associated with Helicobacter pylori and their role in modifying the host responses. Gastric immune and inflammatory responses have emerged as key elements in the pathogenesis of gastritis and epithelial cell damage. This review summarizes important findings emanating from basic research primarily related to the immunopathogenesis of H pylori that have advanced the practice of medicine or our understanding of gastroduodenal disease.

Role of serum factors in epithelial cell responses to Helicobacter pylori infection in vitro

BACKGROUND

Gastric epithelial cell lines have been utilized extensively as tools to define aspects of the interactions between Helicobacter pylori and host epithelial cells. Fetal calf serum (FCS) is employed as a growth stimulant, but it is unclear whether this agent may in itself alter host responses.

METHODS

Two gastric epithelial cell lines were utilized to ascertain the effects of varying FCS concentration on cellular responses following H. pylori infection. Media containing 0%, 5% or 10% FCS was added to cell lines prior to infection with H. pylori of defined genotype. Cellular interleukin (IL)-8 production was measured as a marker of cellular response. Effects of altered FCS upon cell viability were also determined by trypan blue exclusion.

RESULTS

Interleukin-8 production by AGS cells following H. pylori infection was not altered by variation of media FCS concentration. However, KATO-III cells produced greater amounts of IL-8 when media was FCS-free than at 5% or 10% FCS. Although cellular viability was not altered in AGS cells exposed to varied concentrations of FCS, viability was decreased in serum-free KATO-III cells, but not when cells were kept at 5% FCS.

CONCLUSIONS

Serum-derived factors alter cellular responses to H. pylori infection in a cell-line-dependent manner and impaired cellular viability may relate to this effect. However, the mechanisms for these observations are unclear and further work is now required to determine the nature of these important interactions.

Gastric transcription profile of Helicobacter pylori infection in the rhesus macaque

Infection with Helicobacter pylori is usually asymptomatic but sometimes progresses to peptic ulcer disease or gastric adenocarcinoma. The development of disease involves both host and bacterial factors. In order to better understand host factors in pathogenesis, we studied the gastric transcription profile of H. pylori infection in the rhesus macaque by using DNA microarrays. Significant changes were found in the expression of genes important for innate immunity, chemokines and cytokines, cell growth and differentiation, apoptosis, structural proteins, and signal transduction and transcription factors. This broad transcription profile demonstrated expected up-regulation of cell structural elements and the host inflammatory and immune response, as well as the novel finding of down-regulation of heat shock proteins. These results provide a unique view of acute H. pylori infection in a relevant animal model system and will direct future studies regarding the host response to H. pylori infection.

Helicobacter pylori outer membrane vesicles modulate proliferation and interleukin-8 production by gastric epithelial cells

Helicobacter pylori infection, which is always associated with gastritis, can progress to ulceration or malignancy. The diversity in clinical outcomes is partly attributed to the expression of virulence factors and adhesins by H. pylori. However, H. pylori may not have to adhere to the epithelium to cause gastritis. We hypothesize that outer membrane vesicles (OMV), which are constantly shed from the surface of H. pylori, play a role as independent activators of host cell responses. In this study, we found that low doses of OMV from cag PAI+ toxigenic and cag PAI- nontoxigenic strains increased proliferation of AGS gastric epithelial cells. At higher doses, we detected growth arrest, increased toxicity, and interleukin-8 (IL-8) production. The only strain differences detected were vacuolation with the toxigenic strain and higher levels of IL-8 production with OMV from the cag PAI- nontoxigenic strain. In summary, we suggest that constitutively shed OMV play a role in promoting the low-grade gastritis associated with H. pylori infection.

Effects of Helicobacter pylori on intracellular Ca2+ signaling in normal human gastric mucous epithelial cells

In stomach, Helicobacter pylori (Hp) adheres to gastric mucous epithelial cells (GMEC) and initiates several different signal transduction events. Alteration of intracellular Ca2+ concentration ([Ca2+]i) is an important signaling mechanism in numerous bacteria-host model systems. Changes in [Ca2+]i induced by Hp in normal human GMEC have not yet been described; therefore, we examined effects of Hp on [Ca2+]i in normal human GMEC and a nontransformed GMEC line (HFE-145). Cultured cells were grown on glass slides, porous filters, or 96-well plates and loaded with fura 2 or fluo 4. Hp wild-type strain 60190 and vacA-, cagA-, and picB-/cagE- isogenic mutants were incubated with cells. Changes in [Ca2+]i were recorded with a fluorimeter or fluorescence plate reader. Wild-type Hp produced dose-dependent biphasic transient [Ca2+]i peak and plateau changes in both cell lines. Hp vacA- isogenic mutant produced changes in [Ca2+]i similar to those produced by wild type. Compared with wild type, cagA- and picB-/cagE- isogenic mutants produced lower peak changes and did not generate a plateau change. Preloading cultures with intracellular Ca2+ chelator BAPTA blocked all Hp-induced [Ca2+]i changes. Thapsigargin pretreatment of cultures to release Ca2+ from internal stores reduced peak change. Extracellular Ca2+ removal reduced plateau response. Hp-induced peak response was sensitive to G proteins and PLC inhibitors. Hp-induced plateau change was sensitive to G protein inhibitors, src kinases, and PLA2. These findings are the first to show that H. pylori alters [Ca2+]i in normal GMEC through a Ca2+ release/influx mechanism that depends on expression of cagA and picB/cagE genes.

Helicobacter pylori enter and survive within multivesicular vacuoles of epithelial cells

Although intracellular Helicobacter pylori have been described in biopsy specimens and in cultured epithelial cells, the fate of these bacteria is unknown. Using differential interference contrast (DIC) video and immunofluorescence microscopy, we document that a proportion of cell-associated H. pylori enter large cytoplasmic vacuoles, where they remain viable and motile and can survive lethal concentrations of extracellular gentamicin. Entry into vacuoles occurs in multiple epithelial cell lines including AGS gastric adenocarcinoma, Caco-2 colon adenocarcinoma and MDCK kidney cell line, and depends on the actin cytoskeleton. Time-lapse microscopy over several hours was used to follow the movement of live H. pylori within vacuoles of a single cell. Pulsed, extracellular gentamicin treatments show that the half-life of intravacuolar bacteria is on the order of 24 h. Viable H. pylori repopulate the extracellular environment in parallel with the disappearance of intravacuolar bacteria, suggesting release from the intravacuolar niche. Using electron microscopy and live fluorescent staining with endosomal dyes, we observe that H. pylori-containing vacuoles are similar in morphology to late endosomal multivesicular bodies. VacA is not required for these events, as isogenic vacA- mutants still enter and survive within the intravacuolar niche. The exploitation of an intravacuolar niche is a new aspect of the biological life cycle of H. pylori that could explain the difficulties in eradicating this infection.

Helicobacter pylori infection: pathogenesis

Helicobacter pylori is known to be the cause of most gastric diseases, including both peptic ulcer disease and gastric cancer. In the absence of eradication, infection tends to be lifelong and the immune response ineffective in clearing the bacteria. A number of groups have investigated whether the immune clearance of infection can be achieved through a vaccination strategy, but to date, the results have been inconclusive. In fact, in most cases of natural infection, the host immune response leads to a chronic inflammation within the gastric mucosa that actually promotes the development of atrophy and neoplasia. In most cases, eradication of the organism leads to resolution of inflammation, which in many instances can result in reduction in atrophy and gastric cancer risk. This finding suggests that even at late stages, cancer progression is dependent, to a large extent, on infection/immune response. Work from a number of laboratories has led to the hypothesis that T-cells and the Th1 immune response, governed largely by host genetic factors, are strongly associated with the H. pylori-mediated induction of atrophy and cancer. Interleukin-1beta appears to be a particularly important cytokine that inhibits acid secretion and increases serum gastrin levels, factors strongly associated with cancer induction. The induction by H. pylori of cytokines and chemokines and growth-related genes is mediated by the MAPK and NF-kappaB signaling pathway. Recent studies have shown that NF-kappaB is activated through a NF-kappaB-inducing kinase/p21-activated kinase 1 pathway. H. pylori can also promote cellular apoptosis through a number of mechanisms, the most important of which is upregulation of the Fas/FasL pathway. Finally, understanding of H. pylori pathogenesis has been broadened and deepened by the application of genomics and proteomics to the organism.