Helicobacter pylori infection induces gastric cancer in mongolian gerbils

Specific entry of Helicobacter pylori into cultured gastric epithelial cells via a zipper-like mechanism

Although Helicobacter pylori has generally been considered an extracellular pathogen, a number of in vitro infection experiments and biopsy examinations have shown that it is capable of occasionally entering mammalian host cells. Here, we characterized this entry process by using AGS cells as a host cell model. In gentamicin protection-invasion assays, the number of H. pylori colonies recovered was lower than that for Salmonella enterica serovar Typhimurium X22, Escherichia coli expressing InvA, and Yersinia enterocolitica YO:9 grown at 25 degrees C but higher than that for Neisseria gonorrhoeae VP1 and Y. enterocolitica YO:9 grown at 37 degrees C. At the ultrastructural level, the entry process was observed to occur via a zipper-like mechanism. Internalized H. pylori was bound in tight LAMP-1-containing vacuoles in close association with condensed filamentous actin and tyrosine phosphorylation signals. Wortmannin, a potent inhibitor of phosphatidylinositol 3-kinase, and calphostin C, an inhibitor of protein kinase C, both inhibited the entry of H. pylori in a sensitive and dose-dependent manner; however, the level of entry was enhanced by sodium vanadate, an inhibitor of tyrosine phosphatases and ATPases. Furthermore, the cytokine tumor necrosis factor alpha antagonized the entry of H. pylori into AGS cells. Collectively, these results demonstrate that the entry of H. pylori into AGS cells occurs via a zipper-like mechanism which involves various host signal transduction events.

No difference in the level of gastric mucosal cell apoptosis and proliferation in Helicobacter pylori-colonized p53 heterozygous knockout mice

BACKGROUND

We previously reported that attenuated epithelial apoptosis and enhanced proliferation in comparison with mice might link to the specific carcinogenesis in Mongolian gerbils and suggested that the difference in both strains might be due to a difference in genetic background. p53 is a well-known tumour suppressor gene, mutation of which is also known to be involved in gastric cancer formation.

AIM

The present study was designed to examine the level of gastric epithelial apoptosis and proliferation in p53 heterozygous knockout mice (p53+/-) colonized with Helicobacter pylori (Sydney strain: SS1).

METHODS

Female p53+/- mice and wild-type controls were orally inoculated with SS1 and the stomachs were examined 24 weeks later. DNA fragmentation was measured by levels of cytoplasmic mono- & oligo-nucleosomes as well as by the TUNEL method. Gastric mucosal proliferative activity was morphometrically evaluated from the PCNA-stained tissue specimens. Gastric mucosal myeloperoxidase (MPO) activity was measured to evaluate mucosal inflammation.

RESULTS

DNA fragmentation and the number of TUNEL-positive cells, as well as PCNA-positive cell number increased significantly in both groups of H. pylori-infected mice, suggesting that levels of apoptosis and proliferation may be independent of a deficiency of one p53 allele. MPO activity in p53+/- mice and wild-type controls increased to the same level.

CONCLUSION

Although H. pylori inoculation per se induces an increase in cell turnover in mice, heterozygous mutation of p53 did not significantly modify the balance in cell apoptosis and proliferation.

Gastric cancer: laboratory bench to clinic

Gastric cancer is the second most common cause of cancer-related mortality worldwide and the 14th overall cause of death. Detection of disease usually occurs at an advanced stage and overall survival rates for gastric cancer are poor. Our current model for gastric cancer progression clearly maintains Helicobacter infection as the primary inducer of gastric metaplastic and neoplastic disease. Helicobacter pylori is a ubiquitous organism, infecting more than half the world's population. It has been suggested that this infection directly contributes to the formation of gastric cancer in up to 80% of cases; however, gastric malignancy develops in only a subset (< 1%) of infected patients. Therefore, predisposition to Helicobacter-associated gastric cancer is most likely multifactorial, including the interaction of bacterial, host and environmental components. Our understanding of how the organism interacts with the gastric mucosa and synergizes with dietary and other environmental factors to induce malignant mucosal changes is evolving. Indeed, H. pylori has direct effects on the gastric mucosa, but the major factor in disease progression appears to be a robust host Th1 immune response in the setting of a permissive environment. In combination, these factors predispose to the formation of atrophy, metaplasia and gastric cancer. Understanding the interaction of the bacterium with the host and the environment can potentially identify patients most at risk. Identifying potentially removable factors (in addition to H. pylori infection) in the acquisition and progression of neoplastic disease may provide targets for early intervention and prevention strategies.

Gastric adenocarcinoma in a patient re-infected with H. pylori after regression of MALT lymphoma with successful anti-H. pylori therapy and gastric resection: a case report

BACKGROUND

Helicobacter pylori (H. pylori) has been etiologically linked with primary gastric lymphoma (PGL) and gastric carcinoma (GC). There are a few reports of occurrence of both diseases in the same patients with H. pylori infection.

CASE PRESENTATION

We report a patient with PGL in whom the tumor regressed after surgical resection combined with eradication of H. pylori infection. However, he developed GC on follow up; this was temporally associated with recrudescence/re-infection of H. pylori. This is perhaps first report of such occurrence.

CONCLUSIONS

Possible cause and effect relationship between H. pylori infection and both PGL and GC is discussed. This case also documents a unique problem in management of PGL in tropical countries where re-infection with H. pylori is supposed to be high.

Helicobacter pylori activates the proto-oncogene c-fos through SRE transactivation

Epidemiological studies have demonstrated a strong association between Helicobacter pylori infection and gastric cancer. However, there have been few detailed studies on the mechanism of cellular proliferation by H. pylori. Thus, we examined activation of the proto-oncogene c-fos to elucidate the underlying mechanism of cell proliferation caused by H. pylori. Activation of c-fos was evaluated in human gastric cancer cells (TMK1) by Northern blot and reporter assays with deletion analysis of the c-fos transcriptional control region. c-fos promoter activation and transcription were enhanced when cocultured with cag-positive strains. H. pylori-mediated c-fos promoter activation was inhibited by MEK1/2 inhibitor (U0126). The deletion analysis indicated that serum response element (SRE) was required for the activation of c-fos by H. pylori. In conclusion, c-fos promoter activation and transcription were enhanced through the activation of extracellular signal-regulated kinases (ERK)/mitogen-activated protein kinase (MAPK) cascade in gastric cancer cells when cocultured with H. pylori possessing intact cag PAI. SRE is required for the activation of c-fos by H. pylori. These results suggest a direct involvement of H. pylori infection in cellular proliferation, which may play a role in neoplastic transformation.

Helicobacter pylori infection promotes gastric carcinogenesis in a mice model

BACKGROUND AND AIM

Debate that Helicobacter pylori might play a causative role in gastric carcinogenesis still exists in spite of the World Health Organization's definition of H. pylori as a class I carcinogen. In order to define the exact role of H. pylori infection in gastric carcinogenesis, we established a mice model of H. pylori infection.

METHODS

One hundred and forty-four female C57BL/6 mice were divided into nine groups according to N-methyl-N-nitrosourea (MNU) treatment and H. pylori infection. All mice were killed at the 50th or 80th week after treatment, and their histopathological changes were evaluated according to group.

RESULTS

The incidence of gastric adenocarcinoma at the 50th week was 80% in mice treated with both MNU 240 microg/L and H. pylori infection, whereas the incidence was only 27% in mice treated with only MNU 240 microg/L. Although H. pylori caused marked expansion of the proliferative zone at the surface epithelium, H. pylori infection alone caused only chronic atrophic gastritis without any evidence of carcinomas until 80 weeks. The combination of MNU and H. pylori infection also resulted in a significantly higher incidence of gastric adenoma and adenocarcinoma. Significantly higher expressions of proliferating cell nuclear antigen were noted in the gastric mucosa infected with H. pylori compared to controls.

CONCLUSIONS

These results clearly demonstrated the role of H. pylori infection, rather than direct carcinogens, in promoting gastric carcinogenesis in a mice model.

Review article: Helicobacter pylori and gastric adenocarcinoma

Gastric adenocarcinoma is still the second most common cause of death from cancer, even though it is on the decline in developed countries. Although H. pylori gastritis appears to be a necessary antecedent to the development of gastric adenocarcinoma, it is not a sufficient factor in and of itself. Other required factors for the progression of this disease are poorly understood. Patients with antral predominant gastritis seem protected from the disease, while patients with pangastritis are predisposed to both diffuse- and intestinal-type adenocarcinoma. Development of a vaccine against H. pylori might yield promising results in decreasing the incidence of gastric adenocarcinoma.

Overexpression of cyclin E in Mongolian gerbil with Helicobacter pylori- induced gastric precancerosis

AIM: To explore dysregulation of cyclin E in malignancies, and to further investigate the role of cyclin E in Helicobacter pylori (H. pylori)-induced gastric precancerosis.

METHODS: Four-week-old specific pathogen-free male Mongolian gerbils were employed in the study. 0.5 mL 1 × 10⁸ cfu·L^-1 suspension of H. pylori NTCC11637 in Brucella broth was inoculated orally into each of 20 Mongolian gerbils, and a further 20 gerbils were inoculated with Brucella broth as controls. 10 of the infected gerbils and 10 of the non-infected control gerbils were sacrificed at 25, 45 wk after infection. The expression of cyclin E was analyzed by RT-PCR and immunohistochemical studies with monoclonal antibody to cyclin E in Mongolian gerbil of H. pylori-induced gastric precancerosis.

RESULTS: H. pylori was constantly detected in all infected animals throughout the study. At 25 wk after infection of H. pylori. ulcers were observed in the antral and body of stomach (n = 6). Histological examination showed that all animals developed severe inflammation and multifocal lymphoid follicles appeared in the lamina propria and submucosa of gastric antrum. At 45 wk after infection of H. pylori, severe atrophic gastritis (n = 10). intestinal metaplasia (n = 8) and dysplasia (n = 6) could be observed. Cyclin E mRNA levels were significantly more at 25 wk after infection of H. pylori (1.27 ± 0.26), and at 45 wk after infection of H. pylori ( 1.82 ± 0.39) than control-animals (0.59 ± 0.20,P < 0.01); cyclin E mRNA levels were evaluated by 2.2-fold at 25 wk (P < 0.01) and 3.1-fold at 45 wk (P < 0.01) precancerosis induced by H. pylori, when compared with control gastric epithelium of Mongolian gerbil. Immunohistochemical staining revealed exclusive nuclear staining of cyclin E. Furthermore, there was a sequential increase in cyclin E positive cells from normal epithelium to precancerosis.

CONCLUSION: Overexpression of cyclin E occurs relatively early in gastric tumorigenesis in this model.

Columnar-lined esophagus. Definitions

Recognition of a columnar-lined esophagus requires precise criteria by which to delimit the esophagus and the stomach. Endoscopically recognizable landmarks such as the squamocolumnar junction (SCJ or Z-line) can be used to identify structures at the gastroesophageal junction. Once the SCJ is located proximal to the gastroesophageal junction, a columnar-lined segment of esophagus is visible. If biopsy specimens from the columnar-lined segment show specialized intestinal metaplasia, then the patient has Barrett's esophagus (BE), and the extent of the columnar lining determines if it is short- or long-segment BE.

Helicobacter pylori does not promote N-methyl-N-nitrosourea-induced gastric carcinogenesis in SPF C57BL/6 mice

Helicobacter pylori (H. pylori) infection has been acknowledged as a promoter and an initiator for gastric carcinogenesis in experimental models using Mongolian gerbils with H. pylori strains TN2GF4 and ATCC 43504, which have + ve cagA and vacA phenotype s1 / m1. To get more insight into the role of H. pylori in gastric carcinogenesis, we studied the effect of H. pylori SS1, which has + ve cagA and vacA phenotype s2 / m2, on N-methyl-N-nitrosourea (MNU)-induced chemical gastric carcinogenesis using SPF C57BL / 6 mice. Thus, H. pylori SS1 was inoculated 1 week after the completion of MNU treatment to examine the promoting effect of this bacterium. The incidences of polypoid lesions, differentiated adenocarcinomas, and adenomatous hyperplasias were 67% (10 / 15), 47% (7 / 15) and 80% (12 / 15), respectively, in the MNU-alone group. The corresponding figures were 31% (8 / 26), 23% (6 / 26) and 35% (9 / 26) in the MNU + H. pylori group. The incidences of polypoid lesions and adenomatous hyperplasia were significantly different between the groups. Thus, the results indicate that H. pylori SS1 infection reduced susceptibility to chemical gastric carcinogenesis in this model. The discrepancy between the present result and previous results is likely to have been caused by differences in host factors and bacterial factors. Further study of the relationship between gastric carcinogenesis and H. pylori infection is needed.

Helicobacter pylori strain-specific modulation of gastric mucosal cellular turnover: implications for carcinogenesis

Helicobacter pylori colonization induces inflammation in essentially all hosts, a persistent process that increases the risk of developing distal gastric adenocarcinoma. However, only a small percentage of persons carrying H. pylori develop neoplasia; enhanced risk may be related to differences in expression of specific bacterial products, differences in the host response to the bacteria, or the interaction between host and microbe. H. pylori strains that have the cag pathogenicity island are associated with further increased risk for developing distal gastric cancer; however, host responses to H. pylori, such as altered epithelial cell proliferation and apoptosis, also may be important in lowering the threshold for carcinogenesis. H. pylori cag+ strains selectively enhance proliferation and attenuate apoptosis in human mucosa compared to cag- strains. However, cag+ strains also induce more severe gastritis, suggesting that host inflammatory mediators such as cytokines, prostaglandins, and hormones may modulate H. pylori-induced alterations in cellular turnover. In the Mongolian gerbil model of gastric carcinogenesis, apoptosis increases early and transiently following H. pylori infection, but scores progressively decline despite worsening gastric inflammation. Epithelial cell proliferation peaks later and is significantly related to increased gastrin levels, suggesting that epithelial cell growth in H. pylori-colonized mucosa may be mediated by gastrin-dependent mechanisms. An emerging model invoked by these data is one in which H. pylori cag+ strains, in conjunction with host mediators, enhance gastric epithelial cell proliferation but not apoptosis in vivo. The combination of increased proliferation without a concordant increase in apoptosis may therefore contribute to the heightened retention of mutagenized cells, which over decades may increase the subsequent risk for gastric cancer.

Treatment with a proton pump inhibitor promotes corpus gastritis in patients with Helicobacter pylori-infected antrum-predominant gastritis

BACKGROUND

Proton pump inhibitors have been reported to modify the level of Helicobacter pylori gastritis.

AIM

To quantitatively investigate the effect of a proton pump inhibitor on the mucosal neutrophil reaction.

METHODS

Forty-six H. pylori-infected patients (17 duodenal ulcer, 29 gastric ulcer) were enrolled. During endoscopic examination, biopsy samples were obtained from the antrum and the corpus. The tissue content of neutrophil myeloperoxidase was measured by enzyme-linked immunoabsorbent assay, and H. pylori infection was histologically assessed. A proton pump inhibitor was administered orally for 8 weeks.

RESULTS

In the patients as a whole, antral myeloperoxidase decreased significantly after proton pump inhibitor treatment, but corpus myeloperoxidase remained largely unchanged. In duodenal ulcer patients, myeloperoxidase significantly decreased in the antrum, but increased in the corpus. In gastric ulcer patients, a significant reduction was observed in antral myeloperoxidase, but corpus myeloperoxidase remained unchanged. In the antral myeloperoxidase > corpus myeloperoxidase subgroup (n=24), antral myeloperoxidase significantly decreased, whereas corpus myeloperoxidase increased. No changes were observed at either site in the corpus myeloperoxidase > antral myeloperoxidase subgroup. Histology showed that the antral bacterial load of H. pylori decreased in all subgroups, but that it was mostly unchanged in the corpus.

CONCLUSIONS

Proton pump inhibitor treatment stimulated the neutrophil reaction in the corpus mucosa of duodenal ulcer patients and of patients in whom antral neutrophil accumulation was more predominant than that of the corpus. This phenomenon may not be caused by increased bacterial density.

Helicobacter pylori and gastrointestinal tract adenocarcinomas

Although gastric adenocarcinoma is associated with the presence of Helicobacter pylori in the stomach, only a small fraction of colonized individuals develop this common malignancy. H. pylori strain and host genotypes probably influence the risk of carcinogenesis by differentially affecting host inflammatory responses and epithelial-cell physiology. Understanding the host-microbial interactions that lead to neoplasia will improve cancer-targeted therapeutics and diagnostics, and provide mechanistic insights into other malignancies that arise within the context of microbially initiated inflammatory states.

Helicobacter pylori infection and molecular changes in gastric carcinogenesis

In recent years there has been much progress in understanding the pathogenesis of gastric cancer. The role of individual factors in gastric carcinogenesis continues to be debated and is also subject to further analysis. In addition to the activation of oncogenes and the inactivation of tumor suppressor genes, alteration of adhesion molecules seems to be critical for the development of gastric cancer. Helicobacter pylori has been linked to an increased risk of developing gastric cancer, and the molecular changes induced by H. pylori are currently being investigated. Recent studies indicate that H. pylori induces cell proliferation and apoptosis during the early phase of chronic inflammation of the gastric mucosa, whereas in the malignant transformation of the gastric mucosa apoptosis is inhibited and adhesion of gastric epithelial cells is impaired. This review focuses on the role of H. pylori in the development of molecular changes in gastric cancer and its preneoplastic lesions.

Effect of Helicobacter pylori infection on gastric cell proliferation and genomic instability in a paediatric population of southern Italy

BACKGROUND

The incidence of gastric cancer is high in areas with a high prevalence of Helicobacter pylori infection. Cell transformation and tumour progression occur over a long period of time and markers of genomic instability usually precede morphological changes.

AIM

To evaluate the effect of Helicobacter pylori infection on cell proliferation, DNA status and oncogene expression in children.

PATIENTS AND METHODS

Morphometric and immunohistochemical techniques were used to analyse DNA content, p53 and c-myc oncogene expression and cell proliferation on gastric biopsies of 53 children (27 Helicobacter pylori-negative and 26 Helicobacter pylori-positive).

RESULTS

Gastric mucosa was normal in 11% of Helicobacter pylori-positive and in 33% of Helicobacter pylori-negative subjects. Most children had chronic non-atrophic gastritis regardless of Helicobacter pylori infection, and only a minority of children affected by Helicobacter pylori had mild atrophic gastritis. Cell proliferation was significantly higher in children with Helicobacter pylori-positive gastritis than in those with Helicobacter pylori-negative gastritis. No metaplasia, dysplasia, p53 overexpression or altered DNA content was found in any child. Interestingly, 46% of children with and 29% without Helicobacter pylori infection had c-myc overexpression closely related to the cell proliferation rate.

CONCLUSION

Helicobacter pylori infection in children may coexist with a normal gastric mucosa, and it is not associated with genomic instability markers in cases of chronic gastritis.

The relationship between Helicobacter pylori infection, the virulence genotypes of the infecting strain and gastric cancer in the African setting

BACKGROUND

The relationship between Helicobacter pylori infection and gastric carcinoma remains controversial, especially in the African setting where infection is common, while gastric cancer is perceived to be uncommon, the basis of the so called 'African enigma'. This discrepancy between infection and the development of disease is commonly attributed to differences in host, environment and bacterial factors. Interest in the bacterial factors has focused on heterogeneity in the so-called 'virulence genes'.

AIM

The aim of this prospective, case-controlled study was to establish whether H. pylori infection is significantly associated with gastric cancer and to investigate whether gastric cancer is associated with genotypically distinct (as it relates to the candidate virulence genes) organisms in this population.

METHODS

Patients with histologically confirmed gastric cancer were matched with nonulcer dyspeptic controls for age (within 5 years), gender and ethnicity. Helicobacter pylori status was determined by RUT, histology, culture and serology (locally validated and used as default determinant of H. pylori status). Tumors were classified according to the Lauren classification. The 'virulence genotype' of 17 paired culture samples was determined by previously described and validated molecular techniques (cagA presence, vacA alleles, structure of the cag pathogenicity island and analysis of the iceA alleles). Categorical variables were analysed by the chi2 test.

RESULTS

Forty-eight patients (median age 59 years) could be adequately matched to controls. 39/48 (81%) cases and 43/48 (90%) controls were H. pylori positive (NS). Significant differences in the virulence genotypes of infecting strains were noted: vacAs2-controls 24%, cases 0%, p < .00001; vacAs1 present - cases 100%, controls 76%, p < .05; cagA-3'-length > 650 bp - cases 47%, controls 0%, p < .002; cag pathogenicity island intact - cases 82%, controls 43%, p < .04; iceA1 - cases 53%, controls 6%, p < .005. cagA was found in all subjects.

CONCLUSION

This study indicates that, in this African population at least, there is no difference in the prevalence of H. pylori infection when comparing gastric cancer cases with matched controls. However, the findings suggest that gastric cancer may be associated with infection by organisms that are genotypically different from those not associated with disease.

Distinct mechanism of Helicobacter pylori-mediated NF-kappa B activation between gastric cancer cells and monocytic cells

NF-kappaB is a critical regulator of genes involved in inflammation. Gastric epithelial cells and macrophages are considered the main sources of pro-inflammatory cytokines. We investigated NF-kappaB activation by Helicobacter pylori in MKN45 gastric epithelial cells and THP-1 monocytic cells. Although, cag pathogenicity island (PAI)-positive H. pylori (wild type) activated NF-kappaB in both cells, isogenic mutant of cagE (DeltacagE) activated it only in THP-1 cells. Supernatant from the wild type culture could activate NF-kappaB in THP-1 cells but not in MKN45 cells. High density cDNA array analysis revealed that mRNA expression of NF-kappaB-regulated genes such as interleukin (IL)-8, tumor necrosis factor-alpha (TNFalpha), and IL-1beta was significantly up-regulated by the wild type in both cells, whereas it was up-regulated by DeltacagE only in THP-1 cells. Experiments using CD14-neutralizing antibody and IL-1 receptor-associated kinase (IRAK) assay showed that both wild type and DeltacagE H. pylori activated NF-kappaB through CD14 and IRAK in THP-1 cells but not in MKN45 cells. Macrophages from C3H/HeJ mice carrying point mutation in the Toll-like receptor 4 (TLR4) gene showed decreased NF-kappaB activation and TNFalpha secretion compared with C3H/HeN mouse macrophage when treated with H. pylori. In conclusion, H. pylori-induced NF-kappaB activation in epithelial cells is dependent on cag PAI and contact but does not involve CD14 and IRAK, whereas in macrophage/monocytic cells it is independent of cag PAI or contact but involves CD14 and TLR4.

Analysis of cytokines in the early development of gastric secondary lymphoid follicles in Helicobacter pylori-infected BALB/c mice with neonatal thymectomy

Immunological interaction between the host and Helicobacter pylori seems to play a critical role in follicular formation in gastric mucosa. We reported H. pylori-induced follicular gastritis model using neonatally thymectomized mice. In this study, we investigated the involvement of various cytokines in this model. BALB/c mice were thymectomized on the third day after birth (nTx). At 6 weeks old, these mice were orally infected with H. pylori. Histological studies showed that follicular formation occurred from 8 weeks after the infection and that most of the infiltrating lymphocytes were CD4(+) and B cells. Neutrophils increased transiently at 1 week after the infection. Gamma interferon, interleukin-7 (IL-7), and IL-7 receptor were expressed in the stomach of the nTx mice irrespective of the infection. In contrast, expressions of the tumor necrosis factor alpha, IL-4 and lymphotoxin-alpha genes were remarkably upregulated by the infection. Our findings suggest that follicular formation may require cooperative involvement of a Th2-type immune response, tumor necrosis factor alpha and lymphotoxin-alpha in addition to the Th1-type immune response in H. pylori-induced gastritis in nTx mice.

Helicobacter pylori: ulcers and more: the beginning of an era

Helicobacter pylori (H. pylori) may be found in up to 50% of the world's population, making it the most common infectious disease worldwide. H. pylori is a gram-negative, microaerophilic rod with flagella and normally resides in the stomach. It can be diagnosed endoscopically, via breath tests, or through a simple blood test. H. pylori can usually be eradicated with a combination of proton pump inhibitors and antibiotics. Although most people infected with this organism never develop a complication, H. pylori infection in others may produce significant mucosal inflammation leading to ulcers in the stomach and duodenum. H. pylori has also been recognized as a risk factor for the development of both gastric carcinoma and mucosal-associated lymphoid tumor. Although not widely known, H. pylori can also affect organ systems outside of the gastrointestinal tract. It is now apparent that H. pylori can infect the skin, liver and heart and that these infections may produce a number of different disease states. In addition, H. pylori infection can adversely affect the nutritional status of both children and adults. This article discusses the epidemiology and bacteriology of H. pylori, reviews the different methods of diagnosing and treating this common infection, and then focuses on the effects that H. pylori has on different organ systems within the body, including the nutritional status of those affected.

[Pharmacological study on the pathological changes of the gastric mucosa in Helicobacter pylori-infected Mongolian gerbils]

Helicobacter pylori (H. pylori) infection has been recognized to be a causal factor of gastritis, ulcers and gastric cancer in man. Using Mongolian gerbils (M. gerbils), which are suitable for an H. pylori infection animal model, we examined 1) how H. pylori infection, indomethacin and their combination affects the healing of gastric ulcers and whether or not such factors provoke a relapse of healed acetic acid ulcers; and 2) whether or not eradication of the bacteria with drugs at specified times after infection prevents the development of mucosal changes, including gastric adenocarcinoma. 1) H. pylori infection significantly delayed ulcer healing 4 weeks following infection. Indomethacin treatment showed a tendency to delay ulcer healing. Ulcer healing in H. pylori-infected M. gerbils was significantly delayed by indomethacin. H. pylori infection resulted in a relapse of healed ulcers from 1 to 6 months after infection, with a gradual increase in size. Omeprazole markedly prevented the ulcer relapse caused by H. pylori infection. 2) Four or 8 months after H. pylori inoculation, eradication was performed by concurrent treatment with omeprazole + clarithromycin. Immediately after treatment ended in both the 5 and 9 month groups, it was verified that H. pylori were completely eradicated. Autopsy performed 18 months after H. pylori inoculation revealed gastric hyperplastic polyps with erosive lesions and ulcers that were grossly visible; and atrophic gastritis, intestinal metaplasia, carcinoids, and adenocarcinomas were histologically observed in the non-treated control group. In animals eradicated after 4 months and autopsied after 18 months, however, such mucosal changes were not observed. In contrast, intestinal metaplasia and mucosal atrophy was observed in animals eradicated after 8 months and autopsied after 18 months. It was concluded that 1) H. pylori infection delayed the healing of preexisting gastric ulcers and resulted in the relapse of healed ulcers, yet indomethacin had little or no effect on ulcer healing or relapse; and 2) early eradication of H. pylori infection with drug therapy can prevent severe gastric mucosal changes, to include adenocarcinomas, in M gerbils.

In vivo and in vitro studies of cytosolic phospholipase A2 expression in Helicobacter pylori infection

Modifications of mucosal phospholipids have been detected in samples from patients with Helicobacter pylori-positive gastritis. These alterations appear secondary to increased phospholipase A2 activity (PLA2). The cytosolic form of this enzyme (cPLA2), normally involved in cellular signaling and growth, has been implicated in cancer pathogenesis. The aim of this study was to investigate cPLA2 expression and PLA2 activity in the gastric mucosae of patients with and without H. pylori infection. In gastric biopsies from 10 H. pylori-positive patients, cPLA2 levels, levels of mRNA as determined by reverse transcriptase PCR, levels of protein as determined by immunohistochemistry, and total PLA2 activity were higher than in 10 H. pylori-negative gastritis patients. To clarify whether H. pylori had a direct effect on the cellular expression of cPLA2, we studied cPLA2 expression in vitro with different human epithelial cell lines, one from a patient with larynx carcinoma (i.e., HEp-2 cells) and two from patients with gastric adenocarcinoma (i.e., AGS and MKN 28 cells), incubated with different H. pylori strains. The levels of cPLA2, mRNA, and protein expression were unchanged in Hep-2 cells independently of cellular adhesion or invasion of the bacteria. Moreover, no change in cPLA2 protein expression was observed in AGS or MKN 28 cells treated with wild-type H. pylori. In conclusion, our study shows increased cPLA2 expression and PLA2 activity in the gastric mucosae of patients with H. pylori infection and no change in epithelial cell lines exposed to H. pylori.

Gastric intestinal metaplasia: subtypes and natural history

BACKGROUND

It has been suggested that the subtyping of intestinal metaplasia in the stomach is useful in stratifying patients with regard to risk of developing gastric cancer.

AIM

To determine whether subtyping intestinal metaplasia provided useful information regarding the natural history of intestinal metaplasia.

METHODS

The study used large cup gastric biopsy specimens from predetermined locations (gastric mapping). Follow up biopsies were obtained at one, two, and/or nine years. Biopsies with intestinal metaplasia were stained with high iron diamine/Alcian blue (HID/AB) to determine whether they expressed neutral mucins, sialomucins, or sulphomucins.

RESULTS

Seventy nine patients with intestinal metaplasia were studied and characterised with regard to the most advanced subtype of intestinal metaplasia. The most severe type of intestinal metaplasia was type II in 33 patients and type III in 34 patients. Helicobacter pylori was cured in 67 patients. Follow up showed that changes in type of metaplasia (apparent regression or progression) occurred in both directions and were independent of H pylori status. For example, biopsy sites with "loss" of metaplasia at a follow up visit might have it "reappear" at a subsequent visit. During follow up, no patient developed gastric dysplasia or died from gastric cancer.

CONCLUSION

HID subtyping did not provide useful information to the clinician or the pathologist. The data are consistent with the notion that the pattern, extent, and severity of atrophy with/without intestinal metaplasia is a far more important predictor of increased cancer risk than intestinal metaplasia subtype.

Host cell signaling in Helicobacter pylori infection

Helicobacter pylori represents a highly successful human microbial pathogen that has infected approximately half of the world's population. This gram-negative microorganism colonizes the human epithelial layer in the stomach and induces a state of chronic inflammation that does not resolve the underlying infection and often leads to gastric or duodenal ulcers, or more rarely to gastric cancer. Among the reactions in H. pylori-infected epithelial cells the induction of proinflammatory cytokines, cell spreading and movement, as well as a scattered phenotype appear strictly dependent on the expression of pathogenicity island-encoded proteins in H. pylori. This review will discuss the features of the H. pylori-induced signal transduction leading to changes in host cellular function. Topics discussed comprise the signaling and the phenotypes associated with the type IV secretion system, the activation of target genes involved in gastric physiology, and putative mechanisms leading to the development of gastric cancer.

DNase I is present in the chief cells of human and rat stomachs

The distribution of deoxyribonuclease I (DNase I) in human and rat stomachs was examined by biochemical, molecular biological and immunohistochemical techniques. By the use of monoclonal anti-human DNase I and polyclonal anti-rat DNase I antibodies, we determined that strong immunoreactivity was present in the cytoplasm of chief cells of the human fundus and the rat pars glandularis, respectively. High DNase I enzyme activity was detected in tissue homogenates of both human fundus and rat pars glandularis. The presence of DNase I-specific mRNA was verified by reverse transcriptase-polymerase chain reaction analysis of the total RNAs extracted from human and rat stomachs. Immunoelectron microscopy revealed gold particles localized in the chief cells, with most labelling in exocrine secretory granules. These results show that the chief cells of human and rat stomach produce DNase I. This is the first report to demonstrate that secretion of DNase I is controlled by the chief cells in human and rat stomachs.

The design of vaccines against Helicobacter pylori and their development

Helicobacter pylori is a gram negative, spiral, microaerophylic bacterium that infects the stomach of more than 50% of the human population worldwide. It is mostly acquired during childhood and, if not treated, persists chronically, causing chronic gastritis, peptic ulcer disease, and in some individuals, gastric adenocarcinoma and gastric B cell lymphoma. The current therapy, based on the use of a proton-pump inhibitor and antibiotics, is efficacious but faces problems such as patient compliance, antibiotic resistance, and possible recurrence of infection. The development of an efficacious vaccine against H. pylori would thus offer several advantages. Various approaches have been followed in the development of vaccines against H. pylori, most of which have been based on the use of selected antigens known to be involved in the pathogenesis of the infection, such as urease, the vacuolating cytotoxin (VacA), the cytotoxin-associated antigen (CagA), the neutrophil-activating protein (NAP), and others, and intended to confer protection prophylactically and/or therapeutically in animal models of infection. However, very little is known of the natural history of H. pylori infection and of the kinetics of the induced immune responses. Several lines of evidence suggest that H. pylori infection is accompanied by a pronounced Th1-type CD4(+) T cell response. It appears, however, that after immunization, the antigen-specific response is predominantly polarized toward a Th2-type response, with production of cytokines that can inhibit the activation of Th1 cells and of macrophages, and the production of proinflammatory cytokines. The exact effector mechanisms of protection induced after immunization are still poorly understood. The next couple of years will be crucial for the development of vaccines against H. pylori. Several trials are foreseen in humans, and expectations are that most of the questions being asked now on the host-microbe interactions will be answered.

A critical role for IL-7R signaling in the development of Helicobacter felis-induced gastritis in mice

BACKGROUND & AIMS

Interleukin (IL)-7 is a critical cytokine in the development of T and B cells and is involved in gastrointestinal pathophysiology. The aim of this study was to investigate the involvement of IL-7 receptor (IL-7R) signaling in Helicobacter-induced gastritis.

METHODS

C57BL/6 mice (n = 40) were inoculated with H. felis. Twenty mice were injected intraperitoneally with neutralizing IL-7R antibody (A7R34) every seventh day for 3 months. Histology, serum anti-H. felis antibody, and gene expression of IL-7, IL-7R, and proinflammatory cytokines in the gastric mucosa were evaluated.

RESULTS

Seventeen of 20 (85%) infected mice without A7R34 developed severe atrophic gastritis, whereas there was no gastritis in A7R34-treated infected mice. There was no difference in the serum levels of anti-H. felis antibody between the 2 groups. IL-7, IL-7R, IL-1alpha, tumor necrosis factor alpha, and interferon gamma messenger RNA expressions were up-regulated in control infected mice, whereas only IL-7 messenger RNA was up-regulated in A7R34-treated infected mice. Immunohistochemistry indicated positive cytoplasmic staining of IL-7 in the gastric epithelial cells.

CONCLUSIONS

These data suggest a critical role for IL-7 receptor signaling in the development of Helicobacter-induced gastritis in mice.

Expression of hepatocyte growth factor, transforming growth factor alpha, apoptosis related proteins Bax and Bcl-2, and gastrin in human gastric cancer

BACKGROUND

Gastric cancer is one of the most frequent neoplasms and a leading cause of the death world-wide. In recent years, epidemiological and animal studies demonstrated a link between gastric cancer and chronic infection with H. pylori. The exact mechanism responsible for the development of gastric cancer in H. pylori-infected patients still remains unclear. There is evidence that the up-regulation of certain growth factors could play an important role in the promotion of the gastric carcinogenesis.

AIMS

The present study was designed to determine the gene expression of major known growth factors such as transforming growth factor alpha (TGFalpha), hepatocyte growth factor (HGF) and gastrin in the gastric cancer tissue, the surrounding mucosa and, for comparison, in the normal gastric mucosa. Furthermore, the luminal and plasma levels of gastrin in patients with gastric cancer were determined. In addition, the gene and protein expressions of apoptosis-related proteins such as Bax and Bcl-2 were investigated by reverse transcription-polymerase chain reaction and Western blot. Twenty-five gastric cancer patients and 40 age- and gender-matched control subjects hospitalized with non-ulcer dyspepsia were included into this study.

RESULTS

An overall H. pylori-seropositivity among gastric cancer patients was about 72% and was significantly higher than in the controls (56%). The prevalence of CagA-positive strains was also significantly higher among gastric cancer patients than in controls (56% vs. 32%). The gene expression of HGF and TGFalpha was detected more frequently in gastric cancer tissue samples than in normal gastric mucosa (52% vs. 12% for HGF and 48% vs. 24% for TGFalpha). The extent of protein expression in Western blotting analysis for HGF and TGFalpha correlated with the mRNA expression of these factors. Gene expression of gastrin was detected in the antrum of all tested patients and in the majority (84%) of gastric cancer patients. The median plasma and luminal concentrations of gastrin in gastric cancer patients were significantly higher than in controls. The gene expression of bcl-2 was detected in all (100%) and that of proapoptotic bax only in 56% of gastric cancer samples. In comparison to the surrounding non-tumorous tisssue, the gene expression of bax was significantly down-regulated and the gene expression of bcl-2 was up-regulated in gastric cancer tissue. At the protein level, Bax was not detectable and Bcl-2 was seen in 80% of gastric cancer samples.

CONCLUSIONS

It is concluded that the patients infected with H. pylori, especially with CagA-positive strains, are at a higher risk of developing a gastric cancer. An increased production and release of gastrin, as well as an over-expression of growth factors such as HGF and TGFalpha, might contribute to the gastric carcinogenesis. In addition, a dysregulation of the Bax/Bcl-2 system with significant up-regulation of Bcl-2 is observed in gastric cancer.

Helicobacter pylori: strategies for treatment

Helicobacter pylori (Hp) is a Gram-negative bacteria able to live in the human stomach, a very surprising fact considering the acid environment of gastric mucosa. Identified by Marshall and Warren in 1982 [1,2], this bacterium seems aetiologically related to many gastric diseases, previously known as 'acid related diseases'. Compelling evidence demonstrates that Hp is the most important aetiological agent of gastritis [3], the principal causal factor in peptic ulcer [4], contributes to the genesis of gastric cancer [5] and has a critical role in the development of many mucosa-associated lymphoid tissue (MALT) lymphomas [6]. Although experimental data have recently provided hard evidence to support the role of Hp in the genesis of gastritis, ulcer and carcinoma [7], a critical argument for Hp generating peptic ulcer disease has been, in fact, the change in the natural history of peptic ulcer that follows the cure of the infection.

Helicobacter pylori activates the cyclin D1 gene through mitogen-activated protein kinase pathway in gastric cancer cells

Helicobacter pylori induces cellular proliferation in host cells, but the mechanism remains unclear. Thus, we examined the effect of H. pylori on cyclin D1, an important regulator of the cell cycle, especially in relation to intracellular signaling pathways. In a Northern blot analysis, cyclin D1 transcription in gastric cancer (AGS) cells was enhanced by coculture with H. pylori strain TN2 in a time-dependent and multiplicity-of-infection-dependent manner. An isogenic mutant form of vacA also increased cyclin D1 transcription, but mutant forms of cagE or the entire cag pathogenicity island did not enhance cyclin D1 transcription. These effects were confirmed with a luciferase assay of the cyclin D1 promoter (pD1luc). Cyclin D1 promoter activation by H. pylori was inhibited by MEK inhibitors (U0126 and PD98059), indicating that the mitogen-activated protein kinase pathway may be involved in intracellular signal transduction. In contrast, transfection of a reporter plasmid having any point mutations of the NF-kappaB binding sites in the promoter (pD1-kappaB1M, pD1-kappaB2M, or pD1-kappaB1/2M) or cotransfection of dominant negative IkappaBalpha did not affect cyclin D1 activation by H. pylori. In conclusion, H. pylori activates cyclin D1 through the mitogen-activated protein kinase pathway and not through NF-kappaB activation in AGS cells. This activation of cyclin D1 is partly dependent on the cag pathogenicity island but not on vacA.

cDNA microarray analysis of Helicobacter pylori-mediated alteration of gene expression in gastric cancer cells

Helicobacter pylori infection stimulates several intracellular signaling pathways and is accompanied by increased gene expression in gastric epithelial cells. High-density cDNA microarray was used to characterize the mRNA expression profile of genes in human gastric cancer cells (MKN45, AGS) cocultured with H. pylori. Coculture with cag pathogenicity island (PAI)-positive H. pylori (wild-type) significantly up-regulated mRNA expression in 8 of 2304 genes tested. In 6 (interleukin-8, I(kappaB)alpha, A20, ERF-1, keratin K7, glutathione peroxidase) of the 8 genes, up-regulation was confirmed by RT-PCR. In coculture with isogenic cagE-negative mutant ((Delta)cagE), which encodes a type IV secretion system with other genes in the cag PAI, no significant up-regulation was found. We further analyzed the role of A20. Transfection of expression vector encoding A20 resulted in an inhibition of H. pylori-mediated NF-kappaB activation, indicating that H. pylori-mediated A20 expression could be a negative regulator of NF-kappaB activation. Taken together, these results indicate the importance of microarray technology as a tool for analyzing the complex interplay between H. pylori and the host.

Relation between cytokines and Helicobacter pylori in gastric cancer

BACKGROUND

Helicobacter pylori is etiologically involved in the development of gastric cancer and infected gastric mucosa has been shown to possess elevated levels of cytokines [for example interleukin (IL)-1beta, IL-6 and IL-8]. Because specific cytokines have also been shown to enhance the development of certain cancers, we examined the relationship between the levels of cytokines, the type and stage of gastric cancers, and the H. pylori infection.

MATERIALS AND METHODS

Cytokines were measured from gastric cancer tissues, adjacent normal appearing mucosa, and the serum in 66 patients with early or advanced gastric cancer and from controls using semiquantitative RT-PCR and ELISA.

RESULTS

IL-6 and IL-8 levels were more than 10-fold increased in cancer tissues as compared with normal gastric tissues. IL-8 levels in cancer tissues were more than 2-fold higher in advanced gastric cancer as compared with early gastric cancer irrespective of H. pylori status. IL-6 levels were significantly higher in early gastric cancer with active H. pylori infection as compared with early cancer without H. pylori infection (8.7 + 1.4 vs. 1.2 + 0.3 pg/mg protein, p <.001) and decreased significantly after the cure of H. pylori (11.1 + 2.9-8.2 + 2.3 pg/mg protein, p <.05).

CONCLUSIONS

IL-8 levels in gastric cancer tissue are largely independent of H. pylori infection. In contrast, tissue IL-6 levels were high in H. pylori infected early gastric cancer and fell significantly after the cure of H. pylori suggesting a relationship between H. pylori infection and early gastric cancer.

Hemorrhagic gastric carcinoma in an acromegalic patient

A rare case of hemorrhagic gastric carcinoma in an acromegalic patient is reported. A 79-year-old Japanese man was referred to our hospital with diagnoses of upper gastrointestinal hemorrhage and angina pectoris. This patient showed typical clinical features of acromegaly, with increased serum growth hormone (GH) and insulin-like growth factor I (IGF-I) level. A high titer of serum anti-Helicobacter pylori (H. pylori) IgG was also observed. After percutaneous transluminal coronary angioplasty treatment for stenosis of the right coronary artery, the patient underwent distal gastrectomy. Gastric cancer was Type 2 macroscopically and was diagnosed histologically as a papillary and well to moderately differentiated tubular adenocarcinoma. Reverse transcription-polymerase chain reaction analysis estimated that the amount of IGF-I receptor mRNA expression in the gastric cancer tissue was 1.6 times higher than that in the adjacent atrophic mucosa, whereas the amount of IGF-I mRNA expression in the cancer tissue was only half that in the atrophic mucosa. Both the stimulatory effects of GH and/or IGF-I on cell proliferation and H. pylori infection in gastric tumorigenesis may have been responsible for the development and growth of gastric carcinoma in this patient.

Involvement of cyclooxygenase-2 in hyperplastic gastritis induced by Helicobacter pylori infection in C57BL/6 mice

BACKGROUND AND AIMS

The hyperplastic changes observed in Helicobacter pylori-associated gastritis have been considered to increase the risk of gastric cancer. The aim of this study was to determine whether cyclooxygenase-2 is involved in the hyperplastic changes in mice infected with H. pylori.

METHODS

Seven-week-old, male C57BL/6 mice (n=40) were inoculated with the Sydney strain of H. pylori. Control mice (n=40) were treated with vehicle only. Half of the infected and control mice were fed an experimental diet containing etodolac (10 mg/kg/day) from 1 week after inoculation until the end of the experiment. The thickness of gastric pits, COX-2 mRNA and protein levels, and prostaglandin E2 (PGE2) levels in the gastric mucosa were determined before and 12, and 24 weeks after inoculation.

RESULTS

The thickness of gastric pits, COX-2 mRNA and protein levels, and PGE2 levels were significantly increased at 24 weeks after inoculation of H. pylori compared with the control groups. Treatment with etodolac resulted in significant decreases in PGE2 production and in the thickness of gastric pits in the infected groups at 24 weeks after inoculation.

CONCLUSIONS

Our findings suggest that COX-2 is involved in the development of hyperplastic gastritis caused by H. pylori infection via the production of PGE2.

Effects of Helicobacter pylori infection on gastric acid secretion and serum gastrin levels in Mongolian gerbils

BACKGROUND AND AIMS

Body gastritis caused by Helicobacter pylori infection appears to inhibit gastric acid secretion. The aim of this study was to determine the effects of H pylori infection on gastric acid secretion and clarify its mechanisms with reference to interleukin 1beta (IL-1beta).

METHODS

(1) Mongolian gerbils were inoculated orally with H pylori. Before, six, and 12 weeks after inoculation, serum gastrin levels, gastric acid output, and IL-1beta mRNA levels in the gastric mucosa were determined. Pathological changes were also determined according to the updated Sydney system. (2) Effects of recombinant human IL-1 receptor antagonist (rhIL-1ra) on gastric acid output and serum gastrin levels were also determined.

RESULTS

(1) Scores for activity and inflammation of gastritis and serum gastrin levels were significantly increased, and gastric acid output was significantly decreased six and 12 weeks after inoculation with H pylori. IL-1beta mRNA levels in the gastric mucosa were also elevated six and 12 weeks after inoculation with H pylori. (2) Acid output and serum gastrin levels in the infected groups returned to control levels after rhIL-1ra injection.

CONCLUSIONS

Gastric acid secretion is decreased and serum gastrin levels are increased in Mongolian gerbils infected with H pylori. This change in gastric acid secretion appears to be mediated by IL-1beta induced by H pylori infection.

Helicobacter pylori infection induces hyperammonaemia in Mongolian gerbils with liver cirrhosis

BACKGROUND AND AIMS

We previously reported the effect of Helicobacter pylori eradication on hyperammonaemia in patients with liver cirrhosis. However, the role of H pylori as a cause of hyperammonaemia is controversial. We developed an animal model with liver cirrhosis and investigated the effect of H pylori infection on hyperammonaemia.

MATERIALS AND METHODS

Five week old male Mongolian gerbils were inoculated orally with broth culture of H pylori. Forty eight gerbils were divided into four groups. Gerbils not inoculated with H pylori were fed a commercial rodent diet (group A) or a choline deficient diet (group C). Gerbils inoculated with H pylori were fed the commercial rodent diet (group B) or the choline deficient diet (group D). Blood ammonia levels of the femoral vein and portal vein were measured 30 weeks later.

RESULTS

All gerbils fed the choline deficient diet developed liver cirrhosis with fatty metamorphosis. The survival rate of group D was significantly lower than that of the other groups. Systemic and portal blood ammonia levels in group D were significantly higher than those in the other groups.

CONCLUSIONS

H pylori infection induces hyperammonaemia in gerbils with liver cirrhosis.

Molecular testing of Helicobacter pylori-associated chronic gastritis and premalignant gastric lesions: clinical implications

Helicobacter pylori-associated gastritis may progress or be complicated by peptic ulcer and gastric malignancy, including gastric carcinoma and mucosa-associated lymphoid tissue lymphoma. Predicting who develops malignancy remains a clinical challenge. The molecular understanding of pathways that are associated with progression of the normal gastric epithelium to malignancy together with classic histologic parameters are promising ways of tackling this problem. Ideally, molecular tools used for screening should be available as noninvasive tests, such as examination of markers detectable in blood samples, but these are not currently available. In contrast, molecular markers that correlate with cancer risk can be examined in the epithelium after endoscopic biopsy and can be of importance in identifying individuals at risk, especially if combined with other parameters of gastric cancer risk.

Serum immunoglobulin G immune response to Helicobacter pylori antigens in Mongolian gerbils

The Mongolian gerbil model for Helicobacter pylori infection is an animal model that mimics human disease. We examined the serum immune response to H. pylori infection in gerbils by enzyme-linked immunosorbent assay (ELISA) and Western blotting, both with whole-cell (H. pylori) extracts. A total of 66 7-week-old specific-pathogen-free male gerbils were inoculated orogastrically with H. pylori strain ATCC 43504. Sera were collected 1, 2, 4, 8, 12, 26, 38, and 52 weeks after H. pylori inoculation. Sixty-nine noninfected gerbils and their sera were used as controls. The specificity of the ELISA was 95.7%. The frequency of seropositivity increased over time: 2 of 10 (20%), 7 of 10 (70%), and 7 of 7 (100%) samples of sera from inoculated gerbils were positive for H. pylori at 2, 4, and 8 weeks postinoculation, respectively. Western blot assays showed that the primary immunoglobulin G (IgG) response against low-molecular-mass (25-, 30-, and 20-kDa) proteins appeared after a lag period of 2 to 8 weeks after inoculation. Antibodies against 160-, 150-, 110-, 120-, 80-, 66-, and 63-kDa proteins were observed 12 weeks after inoculation. The early reactive 30-kDa protein was identified as a urease alpha subunit by N-terminal amino acid sequencing. After 26 weeks, two groups of animals could be distinguished: one group developed ulcers (n = 5), and the other developed hyperplastic polyps without ulcers (n = 19). Gerbils in the gastric ulcer group showed significantly higher serum anti-H. pylori IgG levels than did gerbils in the hyperplastic group (P = 0.001) as measured by ELISA. Furthermore, a higher proportion of animals developed antibodies to H. pylori proteins of 26, 25, and 20 kDa in the ulcer group than those animals with hyperplastic polyps (75 to 100% versus 17 to 50%) in Western blot assays. These results highlight the importance of the immune response of the host in the development of H. pylori-related gastric lesions.

Helicobacter pylori decreases gastric mucosal glutathione

Activation of oxidative stress pathways may contribute to gastric epithelial damage and mutagenesis caused by Helicobacter pylori. We measured the effect of H. pylori on the concentrations of reduced glutathione (GSH), an important endogenous defense against oxidant damage, in gastric epithelial cells in vivo and in vitro. GSH concentrations were significantly lower in gastric biopsies from 19 H. pylori-infected patients than 38 normal controls, and correlated inversely with inflammatory cell numbers. In vitro, H. pylori initially increased GSH levels in AGS cells, but subsequently depleted intracellular GSH stores completely after 24 h. No GSH was detected in H. pylori. Our data suggest that diminished GSH levels with H. pylori colonization of the gastric mucosa may be due to a direct effect of the bacterium as well as through the associated inflammatory response.

Comparison of gastritis and gastric epithelial proliferation in Helicobacter heilmannii-infected nude and BALB/c mice

Gastric mucosal hypertrophy/nodular hyperplasia occurs as a consequence of Helicobacter infection in mice and humans. The pathogenesis of this hyperplastic response is not understood. To determine the role of host cellular immunity in gastric mucosal hypertrophy/hyperplasia, 6-8-week-old female euthymic BALB/c (n = 30) or NIH athymic nude (n = 40) mice were inoculated with H. heilmannii. Equal numbers of uninoculated mice of each strain served as controls. Mice from each group were euthanatized at 0.5, 6, 12, and 18 months postinoculation (PI). Lymphoplasmacytic gastritis and lymphoid follicle development were less severe in nude mice than in euthymic mice at <6 months PI. The prevalence of gastritis at 0.5, 6, 12, and 18 months PI was 0%, 17%, 67%, and 88%, respectively, in infected nude mice and 33%, 83%, 71%, and 100%, respectively, in infected BALB/c mice. CD4+ T cells in infected nude mice were evident at > or =6 months PI but were less numerous than in infected BALB/c mice at comparable time intervals. However, numbers of CD4+ T cells increased substantially throughout the experiment in infected BALB/c mice. The prevalence of nodular mucosal hyperplasia at 0.5, 6, 12, and 18 months PI was 0%, 0%, 33%, and 20%, respectively, in infected nude mice and 0%, 33%, 80%, and 80%, respectively, in infected BALB/c mice. Nodular hyperplasia occurred in association with the appearance of chronic lymphoplasmacytic inflammation and CD4+ T cells at 12 and 18 months PI in nude mice. H. heilmannii-associated gastritis and mucosal remodeling is reduced in immunodeficient mouse strains lacking normal CD4+ T cell numbers as compared with the response in immunocompetent mice. Additionally, CD4 immunocompetence is an integral aspect of the mucosal hypertrophy/nodular hyperplasia in experimental H. heilmannii-associated disease of mice.

Helicobacter pylori strain-specific differences in genetic content, identified by microarray, influence host inflammatory responses

Helicobacter pylori enhances the risk for ulcer disease and gastric cancer, yet only a minority of H. pylori-colonized individuals develop disease. We examined the ability of two H. pylori isolates to induce differential host responses in vivo or in vitro, and then used an H. pylori whole genome microarray to identify bacterial determinants related to pathogenesis. Gastric ulcer strain B128 induced more severe gastritis, proliferation, and apoptosis in gerbil mucosa than did duodenal ulcer strain G1.1, and gastric ulceration and atrophy occurred only in B128+ gerbils. In vitro, gerbil-passaged B128 derivatives significantly increased IL-8 secretion and apoptosis compared with G1.1 strains. DNA hybridization to the microarray identified several strain-specific differences in gene composition including a large deletion of the cag pathogenicity island in strain G1.1. Partial and complete disruption of the cag island in strain B128 attenuated induction of IL-8 in vitro and significantly decreased gastric inflammation in vivo. These results indicate that the ability of H. pylori to regulate epithelial cell responses related to inflammation depends on the presence of an intact cag pathogenicity island. Use of an H pylori whole genome microarray is an effective method to identify differences in gene content between H. pylori strains that induce distinct pathological outcomes in a rodent model of H. pylori infection.

The disease spectrum of Helicobacter pylori: the immunopathogenesis of gastroduodenal ulcer and gastric cancer

Helicobacter pylori is a gram-negative bacterium that resides under microaerobic conditions in a neutral microenvironment between the mucus and the superficial epithelium of the stomach. From this site, it stimulates cytokine production by epithelial cells that recruit and activate immune and inflammatory cells in the underlying lamina propria, causing chronic, active gastritis. Although epidemiological evidence shows that infection generally occurs in children, the inflammatory changes progress throughout life. H. pylori has also been recognized as a pathogen that causes gastroduodenal ulcers and gastric cancer. These more severe manifestations of the infection usually occur later in life and in a minority of infected subjects. To intervene and protect those who might be at greatest risk of the more severe disease outcomes, it is of great interest to determine whether bacterial, host, or environmental factors can be used to predict these events. To date, several epidemiological studies have attempted to define the factors affecting the transmission of H. pylori and the expression of gastroduodenal disease caused by this infection. Many other laboratories have focused on identifying bacterial factors that explain the variable expression of clinical disease associated with this infection. An alternative hypothesis is that microorganisms that cause lifelong infections can ill afford to express virulence factors that directly cause disease, because the risk of losing the host is too great. Rather, we propose that gastroduodenal disease associated with H. pylori infection is predominantly a result of inappropriately regulated gastric immune responses to the infection. In this model, the interactions between the immune/inflammatory response, gastric physiology, and host repair mechanisms would dictate the disease outcome in response to infection.

Helicobacter pylori seropositivity and subsite-specific gastric cancer risks in Linxian, China

BACKGROUND

Helicobacter pylori carriage (i.e., persistent exposure to the organism without gastric epithelial cell invasion) is an established risk factor for noncardia gastric cancer. However, its association with the risk of cancer of the gastric cardia is controversial. Consequently, we designed this prospective, nested case-control study to further explore the subsite-specific gastric cancer risks associated with H. pylori seropositivity (a surrogate marker for persistent exposure).

METHODS

A total of 99 patients with gastric cardia cancer, 82 patients with noncardia gastric cancer, and 192 cancer-free subjects were selected from among the participants (n = 29 584) of a nutrition intervention trial previously conducted in Linxian, China. H. pylori seropositivity was determined by assaying for the presence of H. pylori whole cell and CagA antibodies in baseline serum samples from all subjects. Seropositivity was defined as one or both serum assays being positive. Odds ratios (ORs) for subsite-specific gastric cancer were estimated by multivariate logistic regression analyses. All statistical comparisons were two-sided (alpha =.05).

RESULTS

H. pylori seropositivity rates for subjects with gastric cardia cancer, noncardia gastric cancer, and gastric cardia and noncardia cancers combined were 70% (P =.02), 72% (P: =.01), and 71% (P =.003) compared with 56% for cancer-free control subjects. OR estimates for H. pylori seropositivity were 1.87 (95% confidence interval [CI] = 1.10 to 3.17) for gastric cardia cancer, 2.29 (95% CI = 1.26 to 4.14) for noncardia gastric cancer, and 2.04 (95% CI = 1.31 to 3.18) for gastric cardia and noncardia cancers combined.

CONCLUSIONS

H. pylori seropositivity was associated with increased risks for both gastric cardia cancer and noncardia gastric cancer in this well-characterized cohort. Thus, H. pylori carriage may increase the risk of cancer throughout the stomach.

Is Helicobacter pylori infection in childhood a risk factor for gastric cancer?

Helicobacter pylori infection is associated with chronic gastritis and peptic ulcer disease. Furthermore, the World Health Organization has classified this organism as a carcinogen for gastric cancer. H pylori infection is mainly acquired in childhood. Children with H pylori infection are asymptomatic except for a very small number that develop peptic ulcer disease. However, if H pylori gastritis is associated with gastric cancer, do pediatricians need to screen children for this infection and treat those who are infected? In an attempt to determine the significance of the association between H pylori and gastric cancer, we have reviewed all of the English language literature on this topic. H pylori infection seems to be associated with an increased risk of developing gastric cancer. However, only a small number of infected individuals (~1%) will develop gastric cancer. Furthermore, there are potential cofactors other than H pylori that could be equally important. The effect of the eradication of H pylori alone on the development of gastric cancer is unknown. Based on our knowledge to date, we suggest that it is not indicated to treat all children with H pylori infection because of the risk of developing gastric cancer or to institute a screening and treatment program.