Helicobacter pylori infection induces gastric cancer in mongolian gerbils

Infection of Mongolian gerbils with Chinese Helicobacter pylori strains

To date only a few Helicobacter pylori strains have been demonstrated to colonise Mongolian gerbils successfully. The aim of this study was to establish stable colonisation of Chinese strains of H. pylori in gerbils. Fresh clinical isolates from Chinese patients were inoculated into gerbils. At 4-6 weeks post inoculation, infection status was evaluated by culture, biopsy urease test and pathology. Sequencing of glmM and random amplified polymorphic DNA (RAPD) fingerprinting of DNA from cultured H. pylori were used to evaluate the genetic identity of pre-inoculated and post-inoculated strains. The ability of pre- and post-inoculated strains to stimulate interleukin-8 transcription in L5F11 gastric epithelial cells was analysed. Three of five clinical isolates colonised gerbils. The three pre- and post-inoculation strains had identical glmM sequences and RAPD profiles, and stimulated luciferase secretion from L5F11 epithelial cells. The strain that caused severe pathological changes was selected for repeat infection to prove reproducible and stable colonisation. The cagA+ strain 42GX gave stable colonisation in the gerbil and induced severe gastritis.

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Recombinant Helicobacter pylori catalase

AIM: To construct a recombinant strain which highly expresses catalase of Helicobacter pylori (H. pylori) and assay the activity of H. pylori catalase.

METHODS: The catalase DNA was amplified from H. pylori chromosomal DNA with PCR techniques and inserted into the prokaryotie expression vector pET-22b (+), and then was transformed into the BL21 (DE3) E. coli strain which expressed catalase recombinant protein. The activity of H. pylori catalase was assayed by the Beers&Sizers.

RESULTS: DNA sequence analysis showed that the sequence of catalase DNA was the same as GenBank’s research. The catalase recombinant protein amounted to 24.4% of the total bacterial protein after induced with IPTG for 3 hours at 37 °C and the activity of H. pylori catalase was high in the BL21 (DE3) E. coli strain.

CONCLUSION: A clone expressing high activity H. pylori catalase is obtained, laying a good foundation for further studies.

Chronic Helicobacter pylori infections induce gastric mutations in mice

BACKGROUND & AIMS

Helicobacter pylori is an important etiologic factor in the development of gastric cancer. The aim of this study was to analyze the role of H. pylori infections in the induction of mutagenic events in gastric epithelial cells. The effect of a high-salt diet as a genotoxic risk factor was also investigated.

METHODS

Big Blue transgenic male mice (C57Bl/6) were inoculated with H. pylori (strain SS1) or Helicobacter felis (strain CS1) for 6 and 12 months. The frequency and spectrum of mutations at the stomach level were assessed. Inflammatory host response and inducible nitric oxide synthase (iNOS) expression by reverse-transcription polymerase chain reaction and immunohistochemistry analysis were also performed.

RESULTS

After 6 months, the gastric mutant frequency was 4-fold and 1.7-fold higher in mice infected with H. pylori and H. felis, respectively, than in uninfected mice. It was associated with a high frequency of transversions (AT --> CG and GC --> TA) known to result from oxidative damages. The Helicobacter-infected mice exhibited severe gastritis and a high level of iNOS messenger RNA expression. Hyperplasia developed 12 months after inoculation, and both the mutagenic effects and iNOS expression decreased in H. pylori- and H. felis-infected mice. No synergistic effects of a high-salt diet and Helicobacter infection were observed regarding the frequency of gastric mutation.

CONCLUSIONS

A direct gastric mutagenic effect due to H. pylori infection in the Big Blue transgenic mouse model has been shown 6 months after inoculation. This genotoxicity can be attributable to oxidative DNA damage involving the inflammatory host response.

Profiling and identification of eubacteria in the stomach of Mongolian gerbils with and without Helicobacter pylori infection

BACKGROUND

Mongolian gerbils are frequently used to study Helicobacter pylori-induced gastritis and its consequences. The presence of an indigenous bacterial flora with suppressive effect on H. pylori may cause difficulties with establishing this experimental model.

AIM

The aim of the present study was to determine bacterial profiles in the stomach of Mongolian gerbils with and without (controls) H. pylori infection.

METHODS

Gastric tissue from H. pylori ATCC 43504 and CCUG 17874 infected and control animals were subjected to microbial culturing and histology. In addition, gastric mucosal samples from H. pylori ATCC 43504 infected and control animals were analyzed for bacterial profiling by temporal temperature gradient gel electrophoresis (TTGE), cloning and pyrosequencing of 16S rDNA variable V3 region derived PCR amplicons.

RESULTS

Oral administration of H. pylori ATCC 43504, but not CCUG 17874, induced colonization and gastric inflammation in the stomach of Mongolian gerbils. Temporal temperature gradient gel electrophoresis (TTGE) and partial 16S rDNA pyrosequencing revealed the presence of DNA representing a mixed bacterial flora in the stomach of both H. pylori ATCC 43504 infected and control animals. In both cases, lactobacilli appeared to be dominant.

CONCLUSION

These findings suggest that indigenous bacteria, particularly lactobacilli, may have an impact on the colonization and growth of H. pylori strains in the stomach of Mongolian gerbils.

Work, salt intake and the development of stomach cancer

An excess of stomach cancer among workers has been observed and it could be argued that men whose occupation involves heavy work eat more and are consequently exposed to a greater quantity of carcinogens in their food. Working under conditions of heat stress greatly increases a worker's salt excretion by as much as 0.1-15.0 g through sweating during one shift of work. Workers exposed to heat stress had consumed daily as much as from 13.0 to 38.0 g of salt, which is much higher than the safe level of 6 g/person/day recommended by the WHO, to keep a balance of salt in the body. Because salt strongly enhances and promotes chemical gastric carcinogenesis and Helicobacter pylori infection in both humans and animals, there is an association between work, salt intake, and the development of stomach cancer among workers in particular and in humans in general.

Pharmacological control of gastric acid secretion for the treatment of acid-related peptic disease: past, present, and future

Pharmacological agents, such as histamine H(2) receptor antagonists and acid pump inhibitors, are now the most frequently used treatment for such acid-related diseases as gastroduodenal ulcers and reflux esophagitis. Based on increased understanding of the precise mechanisms of gastric acid secretion at the level of receptors, enzymes, and cytoplasmic signal transduction systems, further possibilities exist for the development of effective antisecretory pharmacotherapy. Gastrin CCK(2) receptor antagonists and locally active agents appear to represent promising therapies for the future. Development of gene targeting techniques has allowed production of genetically engineered transgenic and knockout mice. Such genetic technology has increased the investigative power for pharmacotherapy for not only antisecretory agents, but also treatment of mucosal diseases, such as atrophy, hyperplasia, and cancer. Elucidation of the origin of gastric parietal cells also represents an interesting investigative target that should allow a better understanding of not only acid-related diseases, but also the evolution of the stomach as an acid-secreting organ.

Duodenogastric reflux and Helicobacter pylori infection synergistically increase gastric mucosal cell proliferative activity in Mongolian gerbils

BACKGROUND

Helicobacter pylori and duodenogastric reflux (DGR) are both recognized as aetiological factors in chronic gastritis and gastric carcinogenesis. In this study, a Mongolian gerbil (MG) model was used to investigate the histopathological changes in the gastric mucosa resulting from DGR and/or H. pylori infection.

METHODS

One-hundred-and-eleven 7-week-old, specific-pathogen-free, male MGs were divided into four groups: normal controls, gerbils with surgically induced DGR, and H. pylori-infected gerbils with and without DGR. Gerbils were killed 4, 12 and 26 weeks after DGR surgery, their stomachs removed and sections prepared. Sections were fixed immediately in 20% phosphate-buffered formalin and subjected to haematoxylin and eosin staining, Alcian blue at pH 2.5/periodic acid-Schiff staining, and immunostaining for smooth muscle cells, H. pylori and 5'-bromo-2'-deoxyuridine (BrdU).

RESULTS

The gastric mucosa of H. pylori-infected gerbils showed chronic active gastritis irrespective of DGR throughout the experimental period. The gastric mucosa of H. pylori-infected gerbils with DGR demonstrated higher BrdU labelling than in the other groups.

CONCLUSIONS

In MGs, DGR and H. pylori infection synergistically increased gastric mucosal cell proliferative activity. DGR and H. pylori infection may be involved synergistically in gastric carcinogenesis by increasing cell proliferative activity.

Two-year follow-up of Helicobacter pylori infection in C57BL/6 and Balb/cA mice

Helicobacter pylori infection is associated with chronic gastritis, peptic ulcer disease, gastric adenocarcinoma and MALT lymphoma. We previously found high-grade lymphoma after 13 months' H. pylori infection in C57BL/6 mice. In this study we followed H. pylori infection by three different isolates in C57BL/6 and Balb/cA mice for 23 months. Six-week-old C57BL/6 and Balb/cA mice were infected with H. pylori strains 119p (CagA+, VacA+), SS1 (CagA+, VacA+) and G50 (CagA-, VacA-). Mice were followed at 2 weeks, 10 weeks and 23 months post-inoculation (p.i.) by culture, histopathology and serology. Strain G50 was only reisolated from mice 2 weeks p.i. There was no difference in colonization between strain 119p and SS1 at 10 weeks p.i., whereas SS1 gave 100% colonization versus 119p gave 50% 23 months p.i. Interestingly, the inflammation score was higher in mice infected with strain 119p than with SS1 10-week p.i., and there were lymphoepithelial lesions in mice infected with strain 119p and G50 but not with SS1 at 23 months post-infection. Eight mice infected with strains 119p and G50 developed gastric lymphoma (grade 5 and 4). One C57BL/6 mouse infected with strain 119p developed hepatocellular carcinoma after 23 months. Immunoblot showed specific bands of 26-33 kDa against H. pylori in infected mice, and two mice infected with strain SSI reacted with antibodies to the 120 kDa CagA toxin.

CONCLUSION

A reproducible animal model for H. pylori-induced lymphoma and possibly hepatocellular carcinoma is described. Strain diversity may lead to different outcomes of H. pylori infection.

Long-term Treatment with Sterigmatocystin, a Fungus Toxin, Enhances the Development of Intestinal Metaplasia of Gastric Mucosa in Helicobacter pylori-infected Mongolian Gerbils

BACKGROUND

Helicobacter pylori is a human gastric carcinogen. Sterigmatocystin (ST), a fungus toxin, is a risk factor of gastric cancer. Cytotoxin-vacuolation toxin A (VacA) present in supernatants of H. pylori suspensions can cause gastritis and ulcer. The aim of this study was to examine the effects of H. pylori, ST and VacA in Mongolian gerbils.

METHODS

Male Mongolian gerbils (n = 196) were treated with H. pylori supernatants (10 ml/1000 mg) mixed with diet or inoculated intragastrically with H. pylori alone or with ST (100 or 1000 ppb), and then killed 27 months later. Gastric tissue sections were stained with haematoxylin and eosin (H&E), periodic acid-Schiff (PAS), Alcian blue (AB, pH 2.5) and with immunostaining for PCNA and p53 expression.

RESULTS

In H. pylori-infected gerbils, the normal mucosa was replaced by hyperplastic epithelium. Severe gastritis, cystic dilatation of gastric glands, hyperplastic polyps and intestinal metaplasia were observed. In H. pylori + ST (1000 ppb) gerbils, intestinal metaplasia was significantly more frequent than in H. pylori alone animals. No pathological changes were observed in the H. pylori supernatant group. Osseous metaplasia was observed in the H. pylori + ST (100 ppb) group. Serum gastrin levels of the H. pylori + ST (1000 ppb) group were significantly higher than those of the other groups. PCNA labelling index and p53 index of infected gerbils were significantly higher than those of uninfected groups.

CONCLUSION

H. pylori causes gastritis, ulcer and intestinal metaplasia. ST enhances the development of intestinal metaplasia and increases gastrin levels in H. pylori-infected Mongolian gerbils.

Involvement of myeloid dendritic cells in the development of gastric secondary lymphoid follicles in Helicobacter pylori-infected neonatally thymectomized BALB/c mice

We previously described an animal model of Helicobacter pylori-induced follicular gastritis in neonatally thymectomized (nTx) mice. However, it is still not clear whether antigen-presenting dendritic cells (DCs) in the stomach have a role in the development of secondary follicles in H. pylori-infected nTx mice. We investigated the distribution of DC subsets using this model and examined their roles. To identify lymphoid and myeloid DCs, sections were stained with anti-CD11c (pan-DC marker) in combination with anti-CD8alpha (lymphoid DC marker) or anti-CD11b (myeloid DC marker) and were examined with a confocal microscope. Expression of macrophage inflammatory protein 3alpha (MIP-3alpha), which chemoattracts immature DCs, was analyzed by real-time PCR and immunohistochemistry. Follicular dendritic cells (FDCs) were stained with anti-SKY28 antibodies. In noninfected nTx mice, a few myeloid and lymphoid DCs were observed in the bottom portion of the lamina propria, whereas in H. pylori-infected nTx mice, there was an increased influx of myeloid DCs throughout the lamina propria. FDC staining was also observed in the stomachs of members of the infected group. MIP-3alpha gene expression was upregulated in the infected nTx group, and the immunohistochemistry analysis revealed MIP-3alpha-positive epithelial cells. These data suggest that H. pylori infection upregulates MIP-3alpha gene expression in gastric epithelial cells and induces an influx of myeloid DCs in the lamina propria of the gastric mucosa in nTx mice. Myeloid DCs and FDCs might contribute to the development of gastric secondary lymphoid follicles in H. pylori-infected nTx mice.

Spontaneous mutations in the Helicobacter pylori rpsL gene

Several studies have revealed that the Helicobacter pylori genome differs markedly from strain to strain, perhaps as a result of mutations arising during persistent infection and/or related to the observed variation in virulence. The development of a detection system for mutations in H. pylori genes might therefore help us to develop a better understanding of its mutability, and in this way help us to develop plans for investigating the relationship between its genomic variability and the pathogenesis of various gastric and duodenal diseases associated with the long-term H. pylori infections. We have therefore begun a study of H. pylori mutability using the endogenous rpsL gene as a marker. Spontaneous mutant frequencies were measured and compared among H. pylori strains, after incubation on plates containing 50 microg/ml of streptomycin for 10 days as a selection procedure. The rpsL gene of each streptomycin-resistant (Str(r)) mutant was amplified by polymerase-chain-reaction (PCR) and sequenced. All of the mutations we characterized were localized at codons 43 or 88 of the rpsL gene and were base transitions from A to G, replacing lysine with arginine. This is in contrast to the spontaneous Str(r) mutants isolated from Escherichia coli, which resulted from either A to G transitions at lysine codons 42 and 87, or A to T or C transversions at lysine codon 42. The spontaneous mutant frequencies of the rpsL gene in H. pylori were of the order of 10(-9), and there were significant differences in spontaneous mutant frequencies among the strains tested. This mutation detection system might be of value in screening clinical isolates for H. pylori mutator phenotypes.

Family history of gastric cancer: should we test and treat for Helicobacter pylori?

A close link has been established between infection and gastric cancer. In this article, we suggest that using a risk stratification technique (like that for colorectal cancer), the high-risk group of first-degree relatives of patients with gastric cancer can be separated out for testing and treatment. This would be more manageable and more cost-effective than screening the whole population, in which the mortality from distal gastric cancer has declined concomitant with the eradication of infection. Support for the feasibility of this approach is derived from studies showing that the family is the core unit of transmission and that childhood colonization, especially with a virulent strain, is apparently a major risk factor for disease progression to the neoplastic stage. When there is a case of gastric cancer in the family, first-degree relatives, who might be infected by a bacterium with an identical genetic fingerprint, are at higher risk than normal for developing gastric cancer. Furthermore, genetic and epidemiologic studies based on the Correa model have shown that both primary and secondary prevention of gastric cancer is possible. Calculations done in high-risk populations, such as Japanese-Americans, confirm the savings in cost and the safety of the test-and-treat strategy. Considering that eradication should be done as early as possible, at a point in the cascade when the changes are still reversible, and that gastric cancer is associated with a high mortality rate, we suggest that this strategy be applied to this high-risk population.

Tumor initiating activity of Helicobacter pylori water extract on mouse skin carcinogenesis

Helicobacter pylori (H. pylori) infection has been associated with gastric carcinogenesis, but responsible and detail mechanisms are insufficient by the absence of adequate data. To obtain direct evidence regarding the carcinogenicity of H. pylori, we investigated the initiating and promoting activity of H. pylori water extract (HPE) in two-stage mouse skin carcinogenesis model. HPE treatment, as an initiation, significantly enhanced tumor formation compared with control group. Moreover, HPE treatment increased production of 8-hydroxydeoxyguanosine in epidermal cells and HPE-initiated/TPA-promoted papillomas demonstrated a point mutation of the Ha-ras gene. These results suggest an initiating activity of HPE on two-stage mouse skin carcinogenesis.

Helicobacter pylori CagA--a potential bacterial oncoprotein that functionally mimics the mammalian Gab family of adaptor proteins

Helicobacter pylori virulence factor CagA is injected into gastric epithelial cells and undergoes tyrosine phosphorylation. Similar to mammalian Gab protein, tyrosine-phosphorylated CagA recruits and activates SHP-2 phosphatase at the plasma membrane, thereby inducing a growth factor-like effect. CagA-SHP-2 interaction may play an important role in bacterial pathogenesis, leading to gastric carcinoma.

Effect of inhibition of extracellular signal-regulated kinase 1 and 2 pathway on apoptosis and bcl-2 expression in Helicobacter pylori-infected AGS cells

Helicobacter pylori induces activation of mitogen-activated protein kinases (MAPKs). However, its effect on H. pylori-induced apoptosis has not been evaluated. Thus, we examined whether H. pylori-induced extracellular signal-regulated kinase 1 and 2 (ERK1/2) and p38 MAPK activation affects gastric epithelial cell apoptosis and bcl-2 family gene expression, especially in relation to the cagA status of an H. pylori strain. In flow cytometric and oligonucleosome-bound DNA enzyme-linked immunosorbent assay analyses, infection with cagA(+) H. pylori strains induced gastric cancer cell apoptosis in AGS cells more prominently than infection with cagA mutants. Activation of ERK1/2 and p38 MAPKs was also more prominent in cagA(+) strains. Pretreatment with a MEK inhibitor (PD98059) inhibited ERK1/2 activation and increased H. pylori-induced apoptosis significantly. This increased apoptosis was accompanied by decreased antiapoptotic bcl-2 mRNA expression among bcl-2-related genes (bcl-2, bax, bak, mcl-1, and bcl-X(L/S)), and the effect was also more prominent in the cagA(+) strains. However, the alteration of bcl-2 gene expression was not accompanied by protein level changes. Inhibition of p38 using specific inhibitor SB203580 decreased H. pylori-induced apoptosis but resulted in little alteration of bcl-2-related gene expression. In conclusion, H. pylori-induced ERK1/2 activation, especially by the cagA(+) H. pylori strain, may play a protective role against gastric epithelial cell apoptosis partially through maintenance of bcl-2 gene expression.

p16Ink4a is overexpressed in H. pylori-associated gastritis and is correlated with increased epithelial apoptosis

BACKGROUND

Cell cycle regulatory proteins may be critical targets during carcinogenesis. We have previously shown that chronic H. pylori infection is associated with decreased expression of the cyclin dependent kinase inhibitor (CDI) p27kip1. Loss of p27kip1 and p16Ink4a (p16) expression, another CDI, has been reported during the progression of gastric tubular adenomas to advanced gastric cancer. The aim of the current study was to examine whether H. pylori infection also affects the expression of p16 in the gastric mucosa of H. pylori-infected patients.

METHODS

p16 expression was evaluated in gastric antral biopsies by immunohistochemistry in 50 patients with nonulcer dyspepsia (n = 18 uninfected, n = 32 H. pylori infected, 24 by cagA+ strains). Adjacent sections were stained for proliferating epithelial cells (by Ki67) and for apoptotic cells (by TUNEL assay).

RESULTS

Both in H. pylori infected and uninfected patients the expression of p16 was higher in the neck and base of the gland than in the foveolar region. Epithelial staining for p16 was increased with H. pylori infection (31.3% vs. 11.1% in the foveolar region, 68.8% vs. 27.8% in the neck and 75% vs. 50% in the glandular base). There was no correlation between the expression of 16 and proliferation but there was a significant positive correlation between apoptosis and 16 immunostaining.

CONCLUSIONS

The tumor suppressor gene 16 is over expressed in gastric epithelial cells of H. pylori infected patients and this is associated with an increase in apoptosis. These findings suggest a possible role for this cell cycle regulator in the increase in gastric cell turnover that is associated with H. pylori infection.

Development of an H. pylori-infected animal model and gastric cancer: recent progress and issues

Gastric cancer is one of the most common malignancies in the world. Gastric carcinogenesis is multifactorial. Although some environmental factors, such as excessive intake of salt and N-nitroso compounds in foods, are involved in this process, Helicobacter pylori has been closely linked to an increased risk of the development of gastric adenocarcinoma. The IARC/WHO in 1994 concluded that H. pylori is a definite carcinogen in humans based on seroepidemiological evidence. H. pylori infection is associated with both intestinal and diffuse types of gastric cancer. Strong evidence has accumulated that H. pylori infection has been active in the development of gastric adenocarcinoma in the Mongolian gerbil (MG) model after long term infection and with or without treatment using low-dose chemical carcinogens. There are several criticisms of these reports. The most troublesome issue is the diagnostic criteria for gastric cancer in MGs, especially for well-differentiated cancers induced by H. pylori infection. Hence, common criteria for the diagnosis of gastric cancer in MGs is required. Another scientific approach is to find genetic-evidence to confirm the diagnosis. Such evidence could indicate directly that H. pylori infection itself is a promoter, initiator, or both in the development of gastric adenocarcinoma.

Analysis of p53 mutations and Helicobacter pylori infection in human and animal models

BACKGROUND

p53 gene mutations are believed to play a critical role in the development of gastric carcinoma. We examined the relation between Helicobacter pylori infection and p53 gene mutations of the gastric mucosa in human and animal models.

METHODS

To detect the original p53 DNA sequences of the Japanese monkey and Mongolian gerbil, the p53 genes of these animals were amplified using the nested polymerase chain reaction method with primers for the human p53 gene. Direct DNA sequencing of exons 5, 6, 7, and 8 of the p53 genes was performed by the dideoxy terminator method for gastric mucosa of humans, the Japanese monkey, and the Mongolian gerbil. The expression of p53 was examined immunohistochemically in a Japanese monkey model.

RESULTS

Mutations of the p53 gene were identified in 52.4% of human H. pylori-positive mucosa and in 100% of monkey H. pylori-positive mucosa. However, no mutations of the p53 gene were found in the H. pylori-positive gastric mucosa of Mongolian gerbils. There were no mutations in H. pylori-negative gastritis mucosa of humans, monkeys, or Mongolian gerbils. Nuclear staining of p53 was seen in the glandular cells of the H. pylori-infected mucosa of Japanese monkeys, especially in the neck region of the glands.

CONCLUSIONS

These findings demonstrate that the H. pylori infection can induce p53 point mutations in humans and the Japanese monkey and appear to be involved in the pathway leading to dysplasia or carcinoma. However, our direct DNA sequencing method showed no p53 mutations in the Mongolian gerbil model at present. Further studies with this model are needed.

Pathological issues of gastric and lower esophageal cancer: helicobacter pylori infection and its eradication

Gastric carcinoma is thought to develop via the actions of inducers and promoters of carcinogenesis. Tryptophan in charred fish or animal meat, ultraviolet rays, and irradiation, which damage genes of normal cells, have long been regarded as inducers of carcinoma, and agents such as alcohol, tobacco, aflatoxin, and nitrosoamine as promoters, with tobacco having both activities. The interaction between these environmental factors, principally diet, and Helicobacter pylori (Hp) is important in the genesis of gastric carcinoma. In this report, the histopathological feature of the Hp gastritis-carcinoma sequence is outlined, and the pathological characteristics of gastroesophageal reflux disease (GERD) and endoscopically negative reflux disease (ENRD) and the risk factors for lower esophageal carcinoma after Hp eradicated status in particular are discussed regarding aspects of cell cycle-associated factors. We conclude that (1) Infection with Hp increases the risk of gastric cancer in two histological phenotypes (i.e., diffuse undifferentiated type and intestinal differentiated type). Excessive cell replication and interrupting the mucus secretion mechanism may result in a large proportion of cells with genetic abnormalities. (2) Genetic alterations in gastric carcinogenesis may differ from those in colonic carcinogenesis. (3) The degree of GERD in Japanese patients is milder than that in patients from Western countries, although the incidence of GERD increases the status after successful eradication of Hp. It is also possible that accumulation of genetic abnormalities increases the number of cardiac and lower esophageal cancers. Investigation of cell cycle factors in GERD including ENRD can be expected to reveal the risk of carcinogenesis.

Plural transformation-processes from spiral to coccoid Helicobacter pylori and its viability

OBJECTIVES

Helicobacter pylori (H. pylori), present in a half of the world's population, is a very successful pathogen. The infection by this bacterium causes several gastric diseases in human. H. pylori is morphologically divided into two types; a spiral and a coccoid form. Both types are observed in human stomach. Although the former is converted into the latter in vitro, the process of coccoid formation remains obscure. Furthermore, whether coccoid forms possess viability arouses much controversy among scientists. We investigated both the process of coccoid formation by electron microscopy and the viability of coccoid H. pylori.

METHODS

A laboratory strain, ATCC43504, was cultured in liquid medium (Brucella Broth medium with 10% heat inactivated horse serum) for seven days. In each culture day, the organisms were observed by scanning-, conventional transmission- and immuno-electron microscopy and were simultaneously examined the culturability of H. pylori to identify the viability of coccoid form.

RESULTS

As the days went by, spiral forms were replaced by coccoid forms in each medium which possessed culturability to some degree until the 4th day. By the detailed observation of ultrastructural features, coccoid forms were classified into two types on the ground that represents different transformation-processes and distinctive ultrastructures. One was the coccoid form that we named Type A with an irregularly surface- and intracytoplasmic-structure which adhered to one another. The other was Type B having a smooth surface with flagella coiled around its own body and the strictly membranous structure. This type was not adhered to another organism. In later days, each type came to be similar external structure and lost the culturability.

CONCLUSIONS

The coccoid forms of H. pylori can be classified into two types by electron microscopy which represent different transformation-processes and consist of the dying bacteria, the living ones with culturability and the viable but non-culturable ones.

Enterocromaffin-like cell tumor induced by Helicobacter pylori infection in Mongolian gerbils

BACKGROUND

Gastric carcinoids are strongly associated with chronic atrophic gastritis A, and it is suggested that hypergastrinemia plays a critical role in development of gastric carcinoids. Since Helicobacter pylori infection causes hypergastrinemia, it is held that H. pylori infection produces gastric carcinoids. We followed the histological changes of H. pylori-infected stomachs of Mongolian gerbils for a long time.

MATERIALS AND METHODS

Five-week-old-male Mongolian gerbils were infected with H. pylori ATCC 43504 with cagA gene, expressing vacuolating cytotoxin. Determination of the serum gastrin and histopathological examination of the stomach at 6, 12, 18, and 24 months after H. pylori inoculation was studied and compared with uninfected animals.

RESULTS

In infected animals, the gastric carcinomas appeared 18 and 24 months after infection. Endocrine cell dysplasias and carcinoids with marked atrophic gastritis of the oxyntic mucosa were observed in the infected animals 24 months after H. pylori inoculation. The serum gastrin level in the infected group increased from an average of 86.2 pg/ml at the beginning of the study to an average of 498 pg/ml and 989 pg/ml at 18 and 24 months after infection, respectively. These changes in the serum gastrin levels were significant compared with uninfected controls that showed no changes.

CONCLUSIONS

H. pylori infection caused not only gastric carcinomas but also enterochromaffin-like cell tumors in Mongolian gerbils, due to hypergastrinemia. This model is thought to be useful to study the relationship between hypergastrinemia and gastric carcinoids.

Expression of UreI is required for intragastric transit and colonization of gerbil gastric mucosa by Helicobacter pylori

Helicobacter pylori colonizes the antral mucosa of the human stomach. There is a controversy as to whether the microorganism is exposed to acidity in its ecological niche. In vitro, the microorganism requires urease for gastric colonization and survival at pH < 4.0. UreI encodes an acid activated urea channel enabling urea access to intrabacterial urease at acidic pH. UreI is also necessary for survival at pH < 4.0. However, the role of UreI for both intragastric transit and colonization of the epithelial gastric mucosa has never been analyzed in detail. We therefore infected gerbils, whose intragastric pH and response to infection resemble those of man, with H. pylori G1.1 wild type bacteria and their corresponding isogenic ureI mutants. Inhibitors of gastric acid secretion and colonization were used for manipulation of gastric pH. Gastric colonization was determined by urease assay and PCR. Gastric pH was measured with pH electrodes. Whereas H. pylori wild type or ureI complemented ureI knockout bacteria colonized the antrum, ureI deletion mutants were unable to colonize. However, continuous inhibition of acid secretion resulted in gastric colonization by the ureI mutants, as also observed with the wild type strain. Restoration of acid secretion resulted in eradication of ureI mutants but not wild type bacteria. The data show that ureI is essential for both gastric transit after inoculation and mucosal colonization in the untreated stomach. The eradication of ureI mutants following restoration of acid secretion suggests that the organism is exposed to pH < 4.0 at the surface of the antral mucosa and that UreI provides a target for specific monotherapy of H. pylori infections.

Topographic association of gastric epithelial expression of Ki-67, Bax, and Bcl-2 with antralization in the gastric incisura, body, and fundus

OBJECTIVES

Helicobacter pylori (H. pylon) infection seems to induce antralization (ie., gastric mucosal transformation from transitional or body type to antral type), which is strongly associated with gastric atrophy and intestinal metaplasia. The aim of this study was to determine the topographic associations of Ki-67 (a protein expressed in proliferative cells), Bax (a pro-apoptotic protein), and Bcl-2 (an antiapoptotic protein) expression with antralization.

METHODS

In each of 104 patients, eight biopsy specimens were taken from the gastric antrum, incisura, body, and fundus for the determination of H. pylori infection, histological changes, and epithelial expression of Ki-67, Bax, and Bcl-2. A labeling index (LI), i.e., the rate of positive cells over total cells counted, was used for Ki-67 and Bax expression. Bcl-2 overexpression was considered to be present if the rate of Bcl-2 positive cells over total cells counted was > or = 5%.

RESULTS

H. pylori infection was present at the gastric antrum, incisura, body, and fundus in 50, 48, 51, and 49 patients, respectively. Ki-67 LI was greater in the presence vs absence) of H. pylori infection at the antrum (51 vs 40), incisura (47 vs 36), body (43 vs 30), and fundus (41 vs 31) (all p < 0.001). At the incisura, Ki-67 LI was greater (47 vs 32, p < 0.001), Bax LI was lower (22 vs 30, p < 0.05), and prevalence of Bcl-2 overexpression was higher (44% vs 18%, p < 0.001) in the presence (vs absence) of antralization. Compared with normal mucosa, gastric atrophy/intestinal metaplasia were associated with an increased Ki-67 LI and decreased Bax LI at the antrum (49 vs 32 and 15 vs 23, respectively), incisura (47 vs 32 and 15 vs 26, respectively) (all p < 0.001). Bcl-2 overexpression was more frequent in gastric atrophy/intestinal metaplasia at the antrum (56% vs 11%, p < 0.001) and incisura (63% vs 19%, p < 0.001) compared with normal mucosa.

CONCLUSIONS

Antralization at the incisura is topographically associated with increased cell proliferation, reduced Bax expression, and Bcl-2 overexpression, which implies that antralization may be an important histological marker for future cancer risk.

Helicobacter pylori-Associated Diseases

Since the initial report 20 years ago by Marshall and Warren of an unidentified curved bacillus located on the gastric epithelium of patients with chronic active gastritis, the discovery of Helicobacter pylori and its association with a number of gastrointestinal diseases has revolutionized the field of gastroenterology. Although the association of H. pylori infection with peptic ulcer disease, chronic gastritis, mucosa-associated lymphoid tissue lymphoma, and gastric adenocarcinoma has been well documented over the past two decades, other areas remain less clear, including the role of H. pylori in gastropathy associated with nonsteroidal anti-inflammatory drugs, gastroesophageal reflux disease, and both uninvestigated and nonulcer dyspepsia. Although these areas still remain somewhat controversial, recent reports further clarify the role of H. pylori in these conditions. A review of the recent literature regarding H. pylori-associated diseases is presented along with recommendations for diagnosis and treatment of H. pylori infection.

Biological activity of the Helicobacter pylori virulence factor CagA is determined by variation in the tyrosine phosphorylation sites

Helicobacter pylori is a causative agent of gastritis and peptic ulcer. cagA(+) H. pylori strains are more virulent than cagA(-) strains and are associated with gastric carcinoma. The cagA gene product, CagA, is injected by the bacterium into gastric epithelial cells and subsequently undergoes tyrosine phosphorylation. The phosphorylated CagA specifically binds SHP-2 phosphatase, activates the phosphatase activity, and thereby induces morphological transformation of cells. CagA proteins of most Western H. pylori isolates have a 34-amino acid sequence that variably repeats among different strains. Here, we show that the repeat sequence contains a tyrosine phosphorylation site. CagA proteins having more repeats were found to undergo greater tyrosine phosphorylation, to exhibit increased SHP-2 binding, and to induce greater morphological changes. In contrast, predominant CagA proteins specified by H. pylori strains isolated in East Asia, where gastric carcinoma is prevalent, had a distinct tyrosine phosphorylation sequence at the region corresponding to the repeat sequence of Western CagA. This East Asian-specific sequence conferred stronger SHP-2 binding and morphologically transforming activities to Western CagA. Finally, a critical amino acid residue that determines SHP-2 binding activity among different CagA proteins was identified. Our results indicate that the potential of individual CagA to perturb host-cell functions is determined by the degree of SHP-2 binding activity, which depends in turn on the number and sequences of tyrosine phosphorylation sites. The presence of distinctly structured CagA proteins in Western and East Asian H. pylori isolates may underlie the strikingly different incidences of gastric carcinoma in these two geographic areas.

Emergence of clarithromycin-resistant Helicobacter pylori (CRHP) with a high prevalence in children compared with their parents

BACKGROUND

Clarithromycin-resistant Helicobacter pylori (CRHP) is increasing worldwide. Clarithromycin resistance in H. pylori from familial members has not been investigated.

MATERIALS AND METHODS

Biopsy specimens were taken from 13 families living in Tokyo, Yokohama, and Niigata between 1998 and 2001. Drug resistance was tested with the replica plating method. The minimum inhibitory concentrations of antimicrobial agents for H. pylori strains were determined by the agar dilution method. Molecular analyses of H. pylori strains were performed by ribosomal RNA gene restriction pattern analysis. The DNA region, associated with clarithromycin resistance, was analyzed by PCR and sequencing.

RESULTS

Helicobacter pylori strains isolated from a 5-year-old-son displayed clarithromycin resistance with a mutation (A --> G at position 2143) in the 23S ribosomal RNA, whereas H. pylori strains from his parents did not. DNA analyses revealed that the boy was infected with his father's strain. The boy had repeatedly developed otitis media and received clarithromycin since the age of 2 years. Studies on an additional 12 families demonstrated that clarithromycin resistance in the children's strains reached 42.9% and was significantly higher than those of H. pylori strains from their parents (0%) or from adult patients (11.1%) (p <.05).

CONCLUSIONS

The rate of clarithromycin resistance in H. pylori strains from Japanese children was extremely high, in contrast to those from their parents or adult patients. Prior history of clarithromycin usage in a child suggested development of clarithromycin resistance in resident H. pylori, which was originated from a parent.

Analysis of apoptotic and antiapoptotic signalling pathways induced by Helicobacter pylori

BACKGROUND AND AIMS

Although it is reported that Helicobacter pylori induces apoptosis on gastric epithelial cells, the mechanism remains unknown. Antiapoptotic effects generated by H pylori have not yet been evaluated.

METHODS

(1) H pylori strains (type 1 wild, TN2-deltacagE, TN2-deltavacA) were cocultured with MKN45, TMK1, and HeLa cells, and cell viability and apoptosis were assessed by trypan blue exclusion and DNA laddering, respectively. (2) Activation of caspases-3, 7, and 8, cytochrome c release from the mitochondria, and Fas, Fas associated death domain protein (FADD), Bax, Bak, and Bcl-X expression were evaluated by immunoblot analysis. (3) To investigate whether nuclear factor kappa B (NFkappaB) activation induced by cag pathogenicity island (PAI) positive H pylori affects antiapoptosis, MKN45 cells stably expressing super-repressor IkappaBalpha were cocultured with H pylori, and cell viability and caspase activation were evaluated. NFkappaB regulated gene expression was also evaluated by ribonuclease protection assay.

RESULTS

(1) Wild-type and deltavacA mutant H pylori induced apoptosis more potently than the deltacagE mutant. Inhibition of cell contact between H pylori and cancer cells and heat killing H pylori diminished cell death. (2) Caspases-3, 7, and 8 were activated time dependently by H pylori as well as by the agonist anti-Fas. Cytochrome c release from mitochondria was observed and was not inhibited by caspase-8 inhibitor. Although protein expression of Fas, FADD, Bax, Bak, and Bcl-X in the whole cell lysates was not changed by H pylori, Bax was decreased from mitochondria free cytosol suggesting that Bax was translocated into mitochondria. (3) Cell death and the activities of caspases-3 and 8 were promoted in MKN45 cells stably expressing super-repressor IkappaBalpha that inhibits NFkappaB activation. Antiapoptotic proteins c-IAP1 and c-IAP2 were upregulated by the wild-type strains.

CONCLUSION

cag PAI positive H pylori is capable of inducing apoptotic effects mainly through the mitochondrial pathway. Antiapoptotic effects mediated by NFkappaB activation were also observed.

The effect of Helicobacter pylori infection on levels of DNA damage in gastric epithelial cells

BACKGROUND

Helicobacter pylori infection leads to an increased risk of developing gastric cancer. The mechanism through which this occurs is not known. We aimed to determine the effect of H. pylori and gastritis on levels of DNA damage in gastric epithelial cells.

METHODS

Epithelial cells were isolated from antral biopsies from 111 patients. DNA damage was determined using single cell gel electrophoresis and the proportion of cells with damage calculated before and 6 weeks after eradication of H. pylori. Cell suspensions generated by sequential digestions of the same biopsies were assayed to determine the effect of cell position within the gastric pit on DNA damage.

RESULTS

DNA damage was significantly higher in normal gastric mucosa than in H. pylori gastritis [median (interquartile range) 65% (58.5-75.8), n = 18 and 21% (11.9-29.8), n = 65, respectively, p <.001]. Intermediate levels were found in reactive gastritis [55.5% (41.3-71.7), n = 13] and H. pylori negative chronic gastritis [50.5% (36.3-60.0), n = 15]. DNA damage rose 6 weeks after successful eradication of H. pylori[to 39.5% (26.3-51.0), p =.007] but was still lower than in normal mucosa. Chronic inflammation was the most important histological factor that determined DNA damage. DNA damage fell with increasing digestion times (r = -.92 and -.88 for normal mucosa and H. pylori gastritis, respectively).

CONCLUSIONS

Lower levels of DNA damage in cells isolated from H. pylori infected gastric biopsies may be a reflection of increased cell turnover in H. pylori gastritis. The investigation of mature gastric epithelial cells for DNA damage is unlikely to elucidate the mechanisms underlying gastric carcinogenesis.

Helicobacter pylori infection and expression of the angiogenic factor platelet-derived endothelial cell growth factor by pre-neoplastic gastric mucosal lesions and gastric carcinoma

BACKGROUND

Expression of the angiogenic factor platelet-derived endothelial cell growth factor is induced in some gastric carcinomas. Whether angiogenesis is induced early in the development of gastric pre-neoplastic lesions and whether Helicobacter pylori infection affects platelet-derived endothelial cell growth factor expression is not known.

AIM

To assess whether chronic gastritis, intestinal metaplasia, gastric dysplasia and gastric carcinomas express platelet-derived endothelial cell growth factor and whether Helicobacter pylori infection might affect the expression of platelet-derived endothelial cell growth factor in these lesions.

PATIENTS AND METHODS

Patients with gastric carcinomas, atrophic gastritis with associated intestinal metaplasia, dysplasia and controls without infection or carcinoma were studied.

RESULTS

Platelet-derived endothelial cell growth factor was detected by immunohistochemistry in 9 out 19 gastric carcinomas (45%). Only focal immunostaining was detected in intestinal metaplasia adjacent to dysplasia and in dysplastic cells. Of the tumours, 90% contained platelet-derived endothelial cell growth factor-positive interstitial cells. A significant correlation was found between active Helicobacter pylori infection and a larger number of platelet-derived endothelial cell growth factor-positive interstitial cells in areas of intestinal metaplasia (p<0.05).

CONCLUSION

Helicobacter pylori infection does not influence the expression of platelet-derived endothelial cell growth factor, once gastric cancer has developed. However, Helicobacter pylori infection may increase the extension of expression of platelet-derived endothelial cell growth factor by infiltrating interstitial cells in premalignant lesions, such as intestinal metaplasia, which may help create a favourable environment for tumour development. This may possibly be due to non-specific increase in recruitment of inflammatory cells caused by Helicobacter pylori infection. Further studies, with a larger number of samples, are now needed in order to confirm this finding.

Helicobacter pylori impairs DNA mismatch repair in gastric epithelial cells

BACKGROUND & AIMS

Helicobacter pylori infection is a major gastric cancer risk factor. H. pylori gastritis occurs more frequently in individuals with microsatellite instability-positive than those with microsatellite instability-negative gastric cancers, raising the possibility that H. pylori infection affects DNA mismatch repair (MMR). The aim of this study was to determine the effect of H. pylori on the expression of DNA MMR proteins and RNA in gastric epithelial cells.

METHODS

Gastric cancer cell lines were cocultured with H. pylori, bacterial extracts, and Campylobacter jejuni or Escherichia coli. MutS (hMSH2 and hMSH6) and MutL (hMLH1, hPMS2, and hPMS1) DNA MMR protein and RNA levels were determined.

RESULTS

All cell lines examined showed decreased levels of MutS and MutL DNA MMR proteins in a dose-dependent manner after coculture with H. pylori strains. The reduction in DNA MMR protein levels was caused by heat-sensitive H. pylori products. The levels of DNA MMR proteins were affected by C. jejuni but not by E. coli. RNA levels of hMSH2 and hMSH6 were also reduced after exposure to H. pylori.

CONCLUSIONS

H. pylori infection of gastric epithelial cells leads to a decrease in DNA MMR proteins that is at least in part related to an H. pylori-induced decrease in messenger RNA levels of repair genes. These data suggest that H. pylori infection might lead to a deficiency of DNA MMR in gastric epithelial cells that may increase the risk of mutation accumulation in gastric mucosa cells and the risk of gastric cancer during chronic H. pylori infection.

Up-regulation of heparin binding epidermal growth factor-like growth factor and amphiregulin expression in Helicobacter pylori-infected human gastric mucosa

BACKGROUND

Host response plays a major role in pathogenesis of Helicobacter pylori-induced gastroduodenal disease including adenocarcinoma of distal stomach. Epidermal growth factor-related growth factors are important modulators of gastric homeostasis in normal and damaged gastrointestinal mucosa.

AIM

To evaluate expression of heparin binding epidermal growth factor and amphiregulin in antral mucosa of Helicobacter pylori-infected and non-infected dyspeptic patients and to correlate levels of heparin binding-epidermal growth factor and amphiregulin mRNA with mitogenic activity of gastric epithelial cells.

METHODS

A total of 10 Helicobacter pylori-infected and 15 Helicobacter pylori non-infected (10 with and 5 without gastritis) dyspeptic patients were studied. Diagnosis of Helicobacter pylori infection was based on rapid urease test and histology. Heparin binding-epidermal growth factor and amphiregulin mRNA expression in antral mucosa were assessed by reverse transcriptase-polymerase chain reaction. Protein expression and localization of both peptides were determined by immunohistochemistry. Mitogenic activity of antral gastric mucosa was assessed by determination of proliferating cell nuclear antigen labelling index by immunohistochemistry.

RESULTS

Heparin binding-epidermal growth factor and amphiregulin mRNA expression increased in Helicobacter pylori-infected vs Helicobacter pylori non-infected patients. Heparin binding-epidermal growth factor and amphiregulin immunostaining was more intense and deeper in gastric gland compartment in infected mucosa than in non-infected mucosa. Increase in heparin binding-epidermal growth factor and amphiregulin mRNA expression significantly correlated with increase in proliferating cell nuclear antigen labelling index.

CONCLUSIONS

Helicobacter pylori gastritis is associated with up-regulation of heparin binding-epidermal growth factor and amphiregulin which correlates with increased mitogenic activity of gastric mucosa. Increased heparin binding-epidermal growth factor and amphiregulin expression is postulated to contribute to reparative response of gastric mucosa to Helicobacter pylori infection.

Review article: after gastritis--an imaginary journey into a Helicobacter-free world

This article explores the consequences of the world-wide trend that may result--at different times for different populations--in the disappearance of Helicobacter pylori and gastritis. After a brief historical introduction, some of the factors that contribute to the decrease in the prevalence of H. pylori are presented. The most apparent results of this trend in the industrialized world have been a decrease in the incidence of peptic ulcer and distal gastric adenocarcinoma. However, some other conditions of the upper digestive tract, such as acid reflux disease and adenocarcinoma of the cardio-oesophageal junction have been increasing. This simultaneous increase has led to the speculation that it may be causally related to the decreased prevalence of gastritis, and currents of thought supporting a laissez faire attitude with regards to H. pylori infection have developed. If these trends continue, future research aimed at understanding the pathogenesis of H. pylori-related conditions, including gastric carcinogenesis, will hinge on access to populations in which H. pylori is still highly prevalent, and on further refinement of the recently introduced Mongolian gerbil model.

Review article: gastric cancer and Helicobacter pylori

Gastric cancer is the second commonest cause of death from malignancy in the world. Its pathogenesis is comparatively well understood and its aetiology multifactorial. Non-cardia gastric cancer usually arises in a stomach that has been inflamed over a long period and where atrophy and intestinal metaplasia have supervened. The commonest cause of gastric inflammation is infection with Helicobacter pylori. Colonization with this organism increases the relative risk of developing this cancer by about six [Helicobacter and Cancer Collaborative Group. Gut 2001; 49: 347-53]. Its likelihood increases with the severity and extent of the gastritis. Severity is influenced by the virulence of the infecting organism, the genetics of the host, bile reflux, dietary factors and the presence of hypochlorhydria which influences the extent, as well as the severity, of the inflammation. The only predisposing factor which can easily be manipulated is H. pylori infection, which can be successfully treated in 80-90% of cases using a 1-week therapeutic regimen.

Aberrant expression of CDX2 in the gastric mucosa with and without intestinal metaplasia: effect of eradication of Helicobacter pylori

BACKGROUND

The intestine-specific transcription factor CDX2 plays an important role in differentiation and maintenance of intestinal epithelial cells. Development and progression of intestinal metaplasia (IM) in the stomach is closely associated with Helicobacter pylori-gastritis. We investigated expression of CDX2 protein in the gastric mucosa with and without IM before and after eradication of H. pylori.

MATERIALS AND METHODS

The subjects comprised five normal controls and 29 H. pylori-positive patients (15 with antral IM and 14 without IM), who were followed for 12 months after eradication of H. pylori. Biopsies were taken from the greater curvatures of the antrum and middle body. Expression of CDX2 was evaluated immunohistochemically using anti-CDX2 antibody.

RESULTS

CDX2 expression was not found in controls. Strong nuclear staining was observed extensively in IM, but rarely in the gastric epithelium, except for the focal area in only four antral biopsies (three with and one without IM). Fine granular cytoplasmic staining was also observed in the perinuclear regions of IM and the gastric epithelial cells in half of the patients. In 13 of the 15 patients with IM, IM did not regress after eradication of H. pylori, and the extent of nuclear staining in IM did not change. The extent of cytoplasmic staining did not change either.

CONCLUSIONS

Our results indicate that CDX2 expression in the gastric mucosa is found in patients with chronic gastritis and is closely associated with IM. CDX2 expression in IM or the gastric epithelial cells did not disappear after eradication of H. pylori.

Role of Helicobacter pylori in gastric carcinogenesis

Peptic ulcers and gastric malignancies are the two major complication of the course of Helicobacter pylori-associated chronic gastritis. Both gastric adenocarcinomas and MALT lymphomas occur in association with H. pylori infection, and studies support an etiological association. This article discusses the natural history of H. pylori-related gastric carcinogenesis and criteria to identify people susceptible to H. pylori infection-associated gastric cancer. It then reviews the molecular and genetic mechanisms underlying the malignant transformation of the gastric mucosa associated with H. pylori.

How bacteria could cause cancer: one step at a time

Helicobacter pylori highlighted the potential for bacteria to cause cancer. It is becoming clear that chronic infection with other bacteria, notably Salmonella typhi, can also facilitate tumour development. Infections caused by several bacteria (e.g. Bartonella spp., Lawsonia intracellularis and Citrobacter rodentium) can induce cellular proliferation that can be reversed by antibiotic treatment. Other chronic bacterial infections have the effect of blocking apoptosis. However, the underlying cellular mechanisms are far from clear. Conversely, several bacterial toxins interfere with cellular signalling mechanisms in a way that is characteristic of tumour promoters. These include Pasteurella multocida toxin, which uniquely acts as a mitogen, and Escherichia coli cytotoxic necrotizing factor, which activates Rho family signalling. This leads to activation of COX2, which is involved in several stages of tumour development, including inhibition of apoptosis. Such toxins could provide valuable models for bacterial involvement in cancer, but more significantly they could play a direct role in cancer causation and progression.

Long-term Helicobacter pylori infection in Japanese monkeys induces atrophic gastritis and accumulation of mutations in the p53 tumor suppressor gene

BACKGROUND

Helicobacter pylori is accepted as a definite human gastric carcinogen from an epidemiological point of view despite insufficient experimental data. Although we previously showed that the number of p53 immunopositive cells in the atrophic gastric mucosa of H. pylori-infected Japanese monkeys gradually increased over time, data on p53 gene mutations were not obtained in that study. To obtain direct evidence of carcinogenesis associated with H. pylori infection, we investigated whether p53 gene mutations are present in the gastric mucosa of a nonhuman primate model susceptible to H. pylori.

MATERIALS AND METHODS

Using the DNA from gastric tissues obtained from six H. pylori-uninfected monkeys of different ages, nucleotide sequence of the wild-type p53 gene was determined by amplification of exons (Ex) 5, 6, 7 and 8 and sequencing. Gastric specimens obtained from eight Japanese monkeys that had been infected with H. pylori for different lengths of time (1.5-7.5 years), were analyzed for mutations in exons 5-8 of p53.

RESULTS

In the six H. pylori-uninfected monkeys, nucleotide sequences of p53 Ex 5-8 were completely common and no mutations were noted. However, among the monkeys that were infected with H. pylori over various periods of time, there was an accumulation of p53 nucleotide (amino acid) substitutions as the gastric atrophy score increased.

CONCLUSIONS

We conclude that the appearance of p53 gene mutation may be closely associated with the degree of gastric mucosal atrophy, which depends on the duration of H. pylori infection. Searching for p53 gene mutations may be useful for studying the progression of gastric carcinogenesis associated with H. pylori.

Do plant and human pathogens have a common pathogenicity strategy?

Recently, a novel 'two-step' model of pathogenicity has been described that suggests host-cell-derived vasculoproliferative factors play a crucial role in the pathogenesis of bacillary angiomatosis, a disease caused by the human pathogenic bacterium Bartonella henselae. The resulting proliferation of endothelial cells could be interpreted as bacterial pathogens triggering the promotion of their own habitat: the host cell. Similar disease mechanisms are well known in the plant pathogen Agrobacterium tumefaciens, which causes crown gall disease. There are notable similarities between the pathogenicity of A. tumefaciens leading to tumourous disease in plants and to the B. henselae-triggered proliferation of endothelial cells in humans. Here, we hypothesize that this pathogenicity strategy might be common to several bacterial species in different hosts owing to shared pathogenicity factors.

Helicobacter pylori infection in patients with idiopathic short stature

BACKGROUND

Some investigators have recently described an association between Helicobacter pylori infection and children with short stature. In the present study, we aimed to evaluate children with short stature with different etiologies.

METHODS

This study evaluated short patients aged from 1 to 16 years. These patients were divided into a growth hormone deficient short stature group (n = 27) and an idiopathic short stature group (n = 14). A control group included children with normal growth and no abdominal pain (n = 47). Anti-H. pylori antibodies were measured in each group (total of 88).

RESULTS

The antibody positivity rates for each group were as follows: growth hormone deficient short stature group, 7.4%; idiopathic short stature group, 28.6%; and control group, 6.4%. The H. pylori antibody positivity rate in the idiopathic short stature group was significantly higher than in the control group.

CONCLUSION

Our findings suggest an association between H. pylori infection and idiopathic short stature.

Reduced activation of inflammatory responses in host cells by mouse-adapted Helicobacter pylory isolates

Helicobacter pylori strains that harbour the Cag pathogenicity island (Cag PAI) induce interleukin (IL)-8 secretion in gastric epithelial cells, via the activation of NF- kappa B, and are associated with severe inflammation in humans. To investigate the influence of Cag PAI-mediated inflammatory responses on H. pylori adaptation to mice, a selection of H. pylori clinical isolates (n = 12) was cag PAI genotyped and tested in co-culture assays with AGS gastric epithelial cells, and in mouse colonization studies. Six isolates were shown to harbour a complete cag PAI and to induce NF- kappa B activation and IL-8 secretion in AGS cells. Of the eight isolates that spontaneously colonized mice, six had a cag PAI(-) genotype and did not induce pro-inflammatory responses in these cells. Mouse-to-mouse passage of the two cag PAI(+) -colonizing strains yielded host-adapted variants that infected mice with bacterial loads 100-fold higher than those of the respective parental strains (P= 0.001). These mouse-adapted variants were affected in their capacity to induce pro-inflammatory responses in host cells, yet no changes in cag PAI gene content were detected between the strains by DNA microarray analysis. This work provides evidence for in vivo selection of H. pylori bacteria with a reduced capacity to induce inflammatory responses and suggests that such bacteria are better adapted to colonize mice.

Expression of mucins (MUC1, MUC2, MUC5AC, and MUC6) and type 1 Lewis antigens in cases with and without Helicobacter pylori colonization in metaplastic glands of the human stomach

Helicobacter pylori (H. pylori) causes gastritis and intestinal metaplasia (TM) that may evolve to gastric carcinoma. Paradoxically, IM leads to clearing of H. pylori, except for some cases in which it persists in damaging the mucosa. The objective of this study was to compare the profile of mucins and type 1 Lewis antigens in IM cases with and without H. pylori. Gastric biopsies (n=32) were double-stained using immunohistochemistry (MUC1, MUC2, MUC5AC, MUC6, Le(a), sialyl-Le(a), and Le(b)) and histochemistry for H. pylori. H. pylori was observed in association with IM in 4 of 22 biopsies with IM (complete IM - 6; incomplete IM - 16). The four biopsies with IM and H. pylori displayed a particular pattern of incomplete IM: expression of MUC1 and MUC5AC and little/no expression of MUC2. The 18 biopsies with IM and without H. pylori had high levels of MUC2 expression, regardless of the IM type. The pattern of expression of type 1 Lewis antigens was similar in IM, regardless of the presence or absence of H. pylori. It is concluded that H. pylori is able to colonize incomplete IM whenever it contains foci expressing MUCI and MUC5AC and no MUC2, independently from Le(a), sialyl-Le(a) and Le(b). The results suggest, furthermore, that MUC2 expression affects the ability of H. pylori to colonize IM areas, regardless of the levels of expression of MUC1 and MUC5AC.

Duodenogastric reflux increases the penetration of N-3H-methyl-N-nitro-N-nitrosoguanidine into the antral mucosa of rats: a possible role for mucosal erosions and increased cell proliferation in gastric carcinogenesis

Duodenogastric reflux is a risk factor for gastric carcinogenesis, but the pathogenesis is not fully understood. We studied the risk of N-methyl-N-nitro-N-nitrosoguanidine (MNNG)-induced carcinogenesis in the antrum of rats with duodenogastric reflux. Duodenal fluid was directed into the stomach through the pylorus (pyloric reflux group) or through a gastrojejunostomy (jejunal reflux group). After twenty-four weeks, 5-bromo-2-deoxyuridine (BrdU) was injected intravenously and the stomach was exposed to N-(3)H-methyl-N-nitro-N-nitrosoguanidine ((3)H-MNNG). The antral mucosa was examined with immunohistochemistry and autoradiography for identification of proliferating cells (BrdU labelled) and cells at risk of MNNG-induced carcinogenesis ((3)H-MNNG and BrdU-labelled cells). Duodenogastric reflux increased the number of double-labelled cells in the antral mucosa from 4.8 +/- 0.6 per mm in the control group to 11.3 +/- 1.9 in the jejunal reflux group (P < 0.05) and 12.7 +/- 0.9 in the pyloric reflux group (P < 0.05). Mucosal erosions were observed in 15 of 28 animals with pyloric reflux and the number of double-labelled cells in the erosion area (4.3 +/- 0.7) was higher than in the same area of animals without erosion (1.4 +/- 0.5) (P < 0.05). Duodeno-gastric reflux increased the cell proliferation and significantly changed the distance between the surface epithelial lining and the proliferating cells when compared to the controls. These results indicate that duodenogastric reflux increases the penetration of (3)H-MNNG into the antrum mucosa of rats. Increased cell proliferation and erosions increase the number of cells at risk of an initiation process from a penetrating gastric carcinogen.

A study of recombinant protective H. pylori antigens

AIM: To construct a recombinant vector which can express M_r26000 outer membrane protein (OMP) from Helicobacter pylori (H. pylori), and to obtain the vaccine protecting against H. pylori infection and a diagnostic reagent kit quickly detecting H. pylori infection.

METHODS: The gene encoding the structural M_r26000 outer membrane protein of H. pylori was amplified from H. pylori chromosomal DNA by PCR, and inserted in the prokaryotic expression vector pET32a(+), which was transformed into the Top10 E. coli strain. Recombinant vector was selected, identified and transformed into BL-21(DE3) E. coli strain. The recombinant fusion proteins were expressed. The antigenicity of recombinant protein was studied by ELISA or immunoblotting and immunized Balb/c mice.

RESULTS: The gene of M_r26000 OMP was amplified to be 594 base pairs, 1.1% of the cloned genes was mutated and 1.51% of amino acid residues was changed, but there was homogeneity between them. The recombinant fusion protein encoded objective polypeptides of 198 amino acid residues, corresponding to calculated molecular masses of M_r26000. The level of soluble expression products was about 38.96% of the total cell protein. After purification by Ni-NTA agarose resin columniation, the purity of objective protein became about 90%. The ELISA results showed that recombinant fusion protein could be recognized by patient serum infected with H. pylori and rabbit serum immunized with the recombinant protein. Furthermore, Balb/c mice immunized with the recombinant protein were protected against H. pylori infection.

CONCLUSION: M_r26000 OMP may be a candidate vaccine preventing H. pylori infection.

Effect of interlukin-1beta on proliferation of gastric epithelial cells in culture

BACKGROUND

Helicobacter pylori is the main risk factor for the development of non-cardia gastric cancer. Increased proliferation of the gastric mucosa is a feature of H. pylori infection. Mucosal interkeukin-1beta production is increased in H. pylori infection and IL-1beta genotypes associated with increased pro-inflammatory activity are risk factors for the development of gastric cancer. The effect of IL-1beta on gastric epithelial cell proliferation has been examined in this study.

METHODS

AGS cells were cultured with IL-1beta. DNA synthesis was assed by [3H]thymidine incorporation and total viable cell numbers by MTT assay.

RESULTS

IL-1beta dose dependently increased DNA synthesis and cell numbers. The enhanced proliferation was blocked by interleukin-1 receptor antagonist. Addition of neutralising antibody to GM-CSF reduced IL-1beta-stimulated proliferation by 31 +/- 4 %. GM-CSF alone significantly stimulated proliferation. Addition or neutralisation of IL-8 had no effect on basal or IL-1beta-stimulated proliferation. The tyrosine kinase inhibitor genistein completely blocked IL-1beta-stimulated proliferation and inhibition of the extracellular signal related kinase pathway with PD 98059 inhibited IL-1beta stimulated proliferation by 58 +/- 5 %.

CONCLUSIONS

IL-1beta stimulates proliferation in gastric epithelial cells. Autocrine stimulation by GM-CSF contributes to this proliferative response. Signalling via tyrosine kinase activity is essential to the mitogenic response to IL-1beta. The extracellular signal related kinase pathway is involved in, but not essential to downstream signalling. IL-1beta may contribute to the hyperproliferation seen in H. pylori- infected gastric mucosa, and be involved in the carcinogenic process.

Effect of Helicobacter pylori-induced cyclooxygenase-2 on gastric epithelial cell kinetics: implication for gastric carcinogenesis

BACKGROUND

Cyclooxygenase (COX)-2 induced by Helicobacter pylori is thought to enhance gastric carcinogenesis by affecting the maintenance of epithelial homeostasis.

MATERIALS AND METHODS

Gastric biopsies from 160 subjects, 97 with nonulcer dyspepsia (47 H. pylori negative, 50 H. pylori positive) and 63 with gastric cancer were examined immunohistochemically for COX-2 expression, cell proliferation and apoptotic indices.

RESULTS

COX-2 expression in corpus was significantly higher in H. pylori positive than in negative non-ulcer dyspepsia (NUD) (p <.05). Regardless of site, gastric cancer subjects had higher COX-2 expression in both antrum and corpus compared with H. pylori negative and positive NUD (p <.005). Proliferation was higher in cancer and H. pylori positive than in negative NUD (p <.0001). Moreover, cancer had enhanced proliferation than H. pylori positive NUD in corpus greater (p =.0454) and antrum lesser (p =.0215) curvatures. Apoptosis was higher in H. pylori positive than in negative NUD (p <.05). However, both had a higher index than the cancer subjects (p <.0001). Apoptosis : proliferation ratio was higher in corpus of H. pylori negative than in positive NUD in greater (p =.0122) and lesser (p =.0009) curvatures. However, both had a higher A:P ratio than cancer cases (p =.0001). A negative correlation between COX-2 expression and A:P ratio was found in corpus greater (r = -.176, p =.0437) and lesser (r = -.188, p =.0312) curvatures.

CONCLUSION

The expression of COX-2 is associated with disruption in gastric epithelial kinetics and hence may play a role in gastric carcinogenesis.

Reversibility of heterotopic proliferative glands in glandular stomach of Helicobacter pylori-infected Mongolian gerbils on eradication

Helicobacter pylori (Hp) infection is an important factor in human gastric disorders. Mongolian gerbils can be easily infected with Hp and represent excellent experimental models to clarify the role of Hp in chronic active gastritis, peptic ulcers, intestinal metaplasia, and gastric carcinoma. We have proved the enhancing effects of Hp infection on all histological types of gastric cancers in Mongolian gerbils exposed to chemical carcinogens. Heterotopic proliferative glands (HPGs) also frequently develop with Hp infection in the glandular stomach of infected gerbils, with a slightly dysplastic change of constituent cells. Distinguishing reversible inflammatory lesions from true neoplasms upon eradication is necessary for further biological or histochemical investigations using this model. We employed an experimental model of long-term Hp infection and eradication in gerbils. HPGs finally developed with a phenotypic shift of intestinalization with Paneth cells. After eradication, HPGs were obviously reduced, and gastric lesions in mucosa also improved with few remnants of the former injury. This shows that reversible HPGs are frequently induced solely by Hp infection in this animal species, and are related to severe gastritis, rather than being malignant in character. Thus, distinguishing reversible lesions from true neoplasms is necessary to investigate the relationship of Hp infection and gastric carcinogenesis in this animal model.

Conditional loss of TGF-beta signalling leads to increased susceptibility to gastrointestinal carcinogenesis in mice

BACKGROUND

Downregulation of TGF-beta receptors is implicated in colon cancer development. Inactivation of either of the two transmembrane serine/threonine kinases, TGF-beta1 types I/II receptors, is now implicated in carcinogenesis, especially gastrointestinal carcinogenesis.

METHODS

We generated transgenic mice, called pS2-dnRII or ITF-dnRII, of which the dominant negative mutant of the TGF-beta type II receptor was expressed under the control of tissue-specific promoters, the pS2 promoter for stomach and ITF for intestine. They were either infected with H.pylori (ATCC 43504 strain, CagA+ and VacA+) or administered with azoxymethane to determine the significance of loss of TGF-beta signalling in gastrointestinal carcinogenesis.

RESULTS

Gastric adenocarcinoma developed in pS2-dnRII mice, whereas only chronic active gastritis was noted in wild-type littermates after 36 weeks of H.pylori infection. Mice lacking in TGF-beta signalling specifically in the stomach showed a significantly higher proliferation cell nuclear antigen-labelling index when infected with H.pylori than wild-type littermates (P < 0.01). Development of colonic aberrant crypt foci was provoked in mice by intraperitoneal injections of azoxymethane, and ITF-dnRII mice showed significantly higher incidences of ACF and colon cancers than wild-type littermates.

CONCLUSIONS

Maintaining normal TGF-beta signalling in the gastrointestinal tract seems to be important either for preventing abnormal mucosal proliferation, or for suppressing or retarding carcinogenesis.