Helicobacter pylori infection induces gastric cancer in mongolian gerbils

Histological and immunohistochemical detection of different Helicobacter species in the gastric mucosa of cats

Detailed histopathological evaluation of the gastric mucosa of Helicobacter-infected cats is complicated by the difficulty of recognizing Helicobacter organisms on hematoxylin and eosin (HE)-stained sections and the ability of multiple Helicobacter species to infect cats. In this study, the presence and localization of different species of Helicobacter in the stomachs of cats was investigated using silver staining and immunohistochemistry. Five groups containing 5 cats each were established (group 1: urease negative and Helicobacter free; groups 2, 3, 4, and 5: urease positive and infected with Helicobacter heilmannii, unclassified Helicobacter spp., Helicobacter felis, and Helicobacter pylori, respectively). Gastric samples were evaluated by HE and silver staining and by immunohistochemistry with 3 different anti-Helicobacter primary antibodies. Helicobacter were detected by Steiner stain in all infected cats at the mucosal surface, in the lumen of gastric glands, and in the cytoplasm of parietal cells. In silver-stained sections, H. pylori was easily differentiated from H. felis, H. heilmannii, and unclassified Helicobacter spp., which were larger and more tightly coiled. No organisms were seen in uninfected cats. Helicobacter antigen paralleled the distribution of organisms observed in Steiner-stained sections for 2 of the 3 primary antibodies tested. The antisera were not able to discriminate between the different Helicobacter species examined. A small amount of Helicobacter antigen was present in the lamina propria of 3 H. pylori-, 3 H. felis-, and 1 H. heilmannii-infected cat. Minimal mononuclear inflammation was present in uninfected cats and in those infected with unclassified Helicobacter spp. and H. heilmannii cats. In H. felis-infected cats, lymphoid follicular hyperplasia with mild pangastric mononuclear inflammation and eosinophilic infiltrates were present. The H. pylori-infected cats had severe lymphoid follicular hyperplasia and mild to moderate mononuclear inflammation accompanied by the presence of neutrophils and eosinophils. These findings indicate that Steiner staining and immunohistochemistry are useful for detecting Helicobacter infections, particularly when different Helicobacter species can be present. Monoclonal antibodies specific for the different Helicobacter species could be important diagnostic aids. There appear to be differences in the severity of gastritis in cats infected with different Helicobacter species.

Recent advances in gastrointestinal pathophysiology: role of heat shock proteins in mucosal defense and ulcer healing

The defense mechanism of the gastrointestinal mucosa against aggressive factors, such as hydrochloric acid, bile acid and non-steroidal anti-inflammatory drugs, mainly consists of functional, humoral and neuronal factors. Mucus-alkaline secretion, mucosal microcirculation, and motility act as functional factors, while prostaglandins and nitric oxide act as humoral factors, and capsaicin sensitive sensory neurons act as neuronal factors. All the above factors are known to contribute to mucosal protection. In recent years, heat shock proteins (HSPs), to include HSP70, have been implicated to be an additional factor utilized for the defense mechanisms of the gastrointestinal mucosa at the intracellular level. The expression of HSP70 and HSP47 markedly changes during the development and healing of chronic gastric ulcers in rats. It was revealed that HSC70 (a constitutive form of HSP70) is coprecipitated with cyclooxygenase-1 and the neuronal form of nitric oxide synthase after treatment with a mild irritant (20% ethanol). A positive relationship between enhanced interaction of HSC70 with either cyclooxygenase-1 or nitric oxide synthase and mucosal protection against a strong irritant (100% ethanol) was observed. It was concluded that HSPs might contribute to mucosal defense mechanisms and ulcer healing, most probably through protecting key enzymes related to cytoprotection.

Gastric mucosal changes induced by long term infection with Helicobacter pylori in Mongolian gerbils: effects of bacteria eradication

Helicobacter pylori infection has been reported to induce various mucosal changes, including gastric adenocarcinoma, in Mongolian gerbils 62 weeks after inoculation. Using Mongolian gerbils, this study examined whether or not eradication of the bacteria with drugs at specified times after infection prevents the development of mucosal changes. After orally inoculating with H. pylori (TN2GF4, vacA- and cagA-positive), the animals were killed 18 months later. 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 was completely eradicated. Autopsy performed 18 months after H. pylori inoculation revealed gastric hyperplastic polyps with erosive lesions and ulcers that were grossly visible in the non-treated control group. In addition, atrophic gastritis, intestinal metaplasia, carcinoids, and adenocarcinomas were histologically observed in the animals. 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 early eradication of H. pylori infection with drug therapy can prevent severe gastric mucosal changes, to include adenocarcinomas, in Mongolian gerbils.

Apoptosis in gastric epithelium induced by Helicobacter pylori infection: implications in gastric carcinogenesis

OBJECTIVES

Helicobacter pylori is an identified carcinogen for gastric cancer, however, the underlying mechanisms remain to be defined. In this review, we sought to elucidate the role of apoptosis in gastric carcinogenesis, to determine the influence of H. pylori infection on apoptosis, and finally to provide insights into the mechanisms by which H. pylori may lead to gastric carcinogenesis.

METHODS

A broad-based MEDLINE and Current Contents literature search was performed to identify relevant publications between 1966 and March 2000 addressing H. pylori infection, apoptosis, cell proliferation, gastric carcinoma, oncogenes, and tumor suppressor genes, as well as the products of these genes. Abstracts from recent major conferences that provided adequate additional data were also included.

RESULTS

Apoptotic cells are rare in the glandular neck region (the generative cell zone) of normal gastric mucosa. With progression of atrophic gastritis, the generative cell zone shifts downward and a relatively large number of apoptotic cells occur. In intestinalized glands, both apoptotic cells and proliferative cells are present in deeper portions of the glands, corresponding to the generative zone. A higher frequency of apoptosis has been observed in gastric dysplasia than in coexisting gastric carcinomas, whereas the number of proliferative cells is significantly higher in gastric carcinoma than in dysplasia. Upregulation of oncogene bcl-2 in premalignant lesions and "downregulation" of the gene after malignant change is probably a common event. Accumulation of p53 protein is first detected in dysplasia, although mutation of the pS3 gene may occur in intestinal metaplasia. H. pylori infection induces apoptosis in gastric epithelial cells, which returns to normal after eradication of the infection. Numerous molecules produced by H. pylori including cytotoxin (VacA), lipopolysaccharide, monochloramine, and nitric oxide may directly induce apoptosis. Moreover, H. pylori-stimulated host inflammatory/immune responses lead to release of a large amount of cytokines. Cytokines produced by type 1 T helper cells, such as TNF-alpha and IFN-gamma, markedly potentiate apoptosis. Gastric cell proliferation is significantly higher in patients with H. pylori infection than in normal controls, and eradication of the infection leads to a reduction in cell proliferation. Apoptosis and cell proliferation are also increased in precancerous lesions such as gastric atrophy, intestinal metaplasia, and dysplasia in the presence of H. pylori infection. However, H. pylori-induced apoptosis may no longer be cell cycle-dependent in these lesions because of the occurrence of alterations and mutations of apoptosis-regulating genes, resulting in a loss of balance between apoptosis and cell proliferation.

CONCLUSIONS

It is hypothesized that H. pylori-induced apoptosis may play a key role in gastric carcinogenesis by increasing cell proliferation and/or resulting in gastric atrophy.

Acid, helicobacter and immunity: a new paradigm for oesophagogastric cancer

Epidemiological evidence has clearly shown a highly significant relationship between Helicobacter pylori infection and the development of duodenal ulcer and distal gastric adenocarcinoma. Despite H. pylori being a common aetiological factor for both disorders, the two disease phenotypes are virtually mutually exclusive. This indicates that the host response to infection has a pivotal role in determining outcome; these disease phenotypes relate to the effect of infection on gastric acid secretion, duodenal ulcer being closely related to sustained acid secretion whereas gastric cancer follows gastric atrophy and impaired gastric acid secretion. Cancer at the oesophageal junction and that associated with Barrett's oesophagus is now the most rapidly increasing tumour in the gastrointestinal tract. The challenge for the next millennium, therefore, is to try and develop methods for identifying patients at risk of developing oesophagogastric cancer. A common feature in the pathogenesis of both gastric and oesophageal adenocarcinoma is inflammation presenting clinically as gastritis and oesophagitis. The pathway from gastritis to gastric atrophy, dysplasia and carcinoma is thought to be a multi-step process, probably triggered by free radicals within the gastric epithelium and increased exposure to luminal carcinogens. However, it has been unclear as to which aspect of the host response determines whether an individual will move along the neoplasia pathway. Recent work has shown that qualitative aspects of the immune environment in the stomach may account for a substantial part of the phenotypic divergence following H. pylori infection. Interleukin-1 beta polymorphisms relate closely to the propensity for an individual to develop distal gastric cancer and maybe useful for predicting risk in family members. In Barrett's oesophagus, we have recently shown that the immune environment may also be important in determining whether an individual will develop cancer. Although we did not find that Barrett's oesophagus was a profoundly inflammatory condition (unlike esophagitis in the squamous epithelium), where there was evidence of inflammation it was qualitatively different from that of oesophagitis in that a Th-2 response with increased expression of IL-4 predominated in Barrett's, whereas a Th-1 proinflammatory response characterised oesophagitis in squamous epithelium. It seems likely that the specific immune environment within Barrett's metaplasia may be an important driver towards dysplasia and carcinoma. Thus, the immune environment in the stomach and esophagus may be critical in determining whether an individual is at risk of developing neoplastic complications of H. pylori infection and gastroesophageal reflux. Identification of the genetic factors which underpin these responses may ultimately result in development of methods to identify individuals at high risk.

Virulence factors of Helicobacter pylori responsible for gastric diseases in Mongolian gerbil

Helicobacter pylori infection induces various gastroduodenal diseases. We examined the role of two genes, vacA and cagE, in the gastric pathogenesis induced by H. pylori using a long-term (62 wk) animal model. Reportedly, both genes are associated with the virulence of H. pylori: vacA encodes vacuolating cytotoxin, and cagE, with other genes in the cag pathogenicity islands, encodes a type IV secretion system. Mongolian gerbils were challenged in this study by a wild-type TN2 strain and its isogenic mutants of cagE or vacA. The wild-type and vacA mutants induced severe gastritis, whereas cagE mutants induced far milder changes. Gastric ulcer was induced at the highest rate (22/23) by the wild-type TN2, followed by the vacA mutant (19/28). No ulcer was found in the gerbils infected with the cagE mutant (0/27) or in controls (0/27). Intestinal metaplasia was also found in the gerbils infected with the wild-type (14/23) or vacA mutant (15/28). Gastric cancer developed in one gerbil with wild-type infection and in one with vacA mutant infection. In conclusion, the knocking out of the cagE gene deprived wild-type H. pylori of the pathogenicity for gastritis and gastric ulcer, suggesting that the secretion system encoded by cag pathogenicity island genes plays an essential role.

Recombinant human lactoferrin is effective in the treatment of Helicobacter felis-infected mice

Recombinant human lactoferrin possesses in-vitro antibiotic and anti-inflammatory activity similar to the native form. It was tested for in-vivo activity in mice infected with the gastritis-inducing bacterium Helicobacter felis. A two-week course of treatment with lactoferrin was sufficient to partially reverse both infection-induced gastritis and the infection rate, and fully reverse gastric surface hydrophobicity changes. A comparison of lactoferrin with amoxicillin and standard triple therapy revealed no differences in infection rate. These results show that recombinant human lactoferrin is effective in a mouse model of Helicobacter infection, and support further testing of this promising agent for this application.

Peptic ulcer and Helicobacter pylori

Although there has been an explosion of data not only since the discovery of H. pylori in 1982, but also since the first comprehensive review of H. pylori in the Gastroenterology Clinics in 1993, much remains to be learned. In 1993, there were many skeptics doubting the importance of H. pylori in ulcer disease. Although this skepticism has dissipated, many ulcer patients infected with H. pylori still do not receive appropriate therapy. This situation possibly relates to the safety, efficacy, and simplicity of prescribing acid-suppressive therapy in contrast to the confusion regarding anti-H. pylori treatment regimens. Among the many continuing unanswered questions regarding the role of H. pylori and PUD are the still enigmatic nature of host, environmental, and H. pylori-related factors that determine outcome. Why do only some infected individuals (and why do more men than women) develop PUD, and what determines whether gastric ulcers or duodenal ulcers develop? What is the explanation for the seasonal variation in ulcer disease? Although PUD is an infectious disease, are other environmental factors critical for the manifestation of ulcers in association with infection? What factors govern the outcome of the combination of H. pylori infection and NSAID use? Has attention been too focused first on the pathophysiology of acid secretion and now on H. pylori? In curing H. pylori in association with PUD, are clinicians going to displace disease northward, substituting erosions, inflammation, and neoplasia (and associated symptoms) in the esophagus and gastroesophageal junction for an ulcer crater (and its associated symptoms) in the duodenum or stomach? The epidemiology of PUD is changing--in more recent reports of ulcer patients, H. pylori and NSAID use are less prevalent than in earlier reports. These questions and comments should not be misinterpreted as advocating a lack of aggressiveness in diagnosis and treatment of H. pylori in the setting of PUD, however. Nevertheless, the pendulum is swinging.

Effect of Helicobacter pylori eradication on subsequent development of cancer after endoscopic resection of early gastric cancer in Japan

This article describes the characteristics of H. pylori infection dynamics in early gastric cancer cases in Japan and the reduced likelihood of metachronous cancer development and growth inhibition by H. pylori eradication based on healing of background gastric mucosa. In the future, these clinical studies and experimental studies in Mongolian gerbils and mice should elucidate the role of H. pylori infection in the development of gastric carcinogenesis to clinical cancer on the genetic level so that gastric cancer prevention by H. pylori eradication is established.

Timing of N-methyl-N-nitrosourea administration affects gastric carcinogenesis in Mongolian gerbils infected with Helicobacter pylori

In Mongolian gerbils, the gastric mucosa shows dramatic changes after Helicobacter pylori inoculation. The influence of the timing of N-methyl-N-nitrosourea (MNU) administration after H. pylori inoculation on gastric carcinogenesis was investigated. Ninety-two gerbils were divided into four groups. One group was given MNU at 24 weeks, and another at 1 week, after H. pylori inoculation. The other groups received only MNU. Stomachs were excised for histological examination 20 weeks after completing the MNU treatment. Carcinomas arose only in animals given MNU 1 week after H. pylori inoculation. In the relationship between H. pylori and gastric carcinogenesis, H. pylori is a promoter rather than an initiator, and other environmental factors (the timing of MNU administration) play important roles.

A novel action of the proton pump inhibitor rabeprazole and its thioether derivative against the motility of Helicobacter pylori

The motility of Helicobacter pylori was maximum at 37 degrees C and at pH 6. A newly developed proton pump inhibitor, rabeprazole (RPZ), and its thioether derivative (RPZ-TH) markedly inhibited the motility of H. pylori. The concentrations of the drug necessary to inhibit 50% of the motility were 0.25, 16, 16, and >64 microgram/ml for RPZ-TH, RPZ, lansoprazole, and omeprazole, respectively. No such inhibitory effects were observed with H(2) blockers or anti-H. pylori agents. The motilities of Campylobacter jejuni and C. coli-but not those of Vibrio cholerae O1 and O139, Vibrio parahaemolyticus, Salmonella enterica serovar Typhimurium, and Proteus mirabilis-were also inhibited. Prolonged incubation with RPZ or RPZ-TH inhibited bacterial growth of only H. pylori, except for a turbid colony mutant. The results indicate that RPZ and RPZ-TH have a characteristic inhibitory effect against the motility of H. pylori (spiral-shaped bacteria), which is distinguished from that against bacterial growth.

Gastritis and intestinal metaplasia in Syrian hamsters infected with Helicobacter aurati and two other microaerobes

Chronic gastritis and intestinal metaplasia associated with naturally occurring colonization by Helicobacter aurati and two other microaerobic species were observed in Syrian hamsters. Thirty-five hamsters, between 7 and 12 months of age, were evaluated from two research and three commercial facilities. Microaerobic bacteria were cultured from the hamster stomachs. These bacteria included H. aurati, a fusiform, urease-positive species; a second novel helical, urease-negative Helicobacter sp.; as well as a smaller, urease-negative Campylobacter sp. Southern blot analysis detected Helicobacter spp. DNA in the gastric tissues of all 35 hamsters; 15 hamsters also had Campylobacter sp. DNA in their gastric tissues. When examined by light microscopy, argyrophilic bacteria consistent with H. aurati or the second Helicobacter sp. were present in antral sections of 12 out of the 15 hamsters where bacteria were seen, while 9 out of the 15 hamsters had bacteria resembling the Campylobacter sp. The presence of Helicobacter spp. but not the presence of Campylobacter sp. was significantly correlated to gastritis severity (P < 0.0001 for Helicobacter spp., P = 0.6025 for Campylobacter sp.) and intestinal metaplasia, as measured by numbers of goblet cells (P = 0.0239 for Helicobacter spp., P = 0.5525 for Campylobacter sp.). Severely affected hamsters also had Giardia sp. within their metaplastic gastric pits. Hamsters with naturally occurring helicobacter-associated gastritis provide a model for studying the development of intestinal metaplasia and gastric giardiasis in H. pylori-infected humans.

Nonsteroidal anti-inflammatory drug-induced acute gastric injury in Helicobacter pylori gastritis in Mongolian gerbils

We examined the acute ulcerogenic effects of indomethacin and N-(2, cyclohexyloxy-4-nitrophenyl)methane sulfonamide (NS-398) on the gastric mucosa in Helicobacter pylori-infected Mongolian gerbils. H. pylori infection for 4 and 12 weeks caused moderate and severe gastritis, respectively, with cyclooxygenase-2 expression and an increase in prostaglandin E(2) production. In normal animals, gastric injury was caused by indomethacin, but not by NS-398. At 4 weeks infection, gastric lesions were synergistically aggravated by indomethacin, and NS-398 at high doses. However, at 12 weeks, the synergistic effects of indomethacin and NS-398 with H. pylori were not observed. Indomethacin and NS-398 at high doses inhibited prostaglandin E(2) production in both normal and the infected mucosa. NS-398 at low dose reduced only the H. pylori-increased prostaglandin production. These results suggest that nonsteroidal anti-inflammatory drugs (NSAIDs) synergistically aggravate gastric lesions in moderate H. pylori gastritis, but not in severe gastritis. Cyclooxygenase-2 inhibition only might not induce acute gastric injury in H. pylori gastritis.

Suppressive effects of DNA vaccines encoding heat shock protein on Helicobacter pylori-induced gastritis in mice

We investigated the effect of DNA vaccines encoding H. pylori-heat shock protein A and B (pcDNA3.1-hspA and -hspB) on inducing immune responses against H. pylori in mice. C57BL/six mice aged 5 weeks were immunized by single injection of 10 microg of pcDNA3.1-hspA and pcDNA3.1-hspB into intracutaneous tissue. Plasmid DNA lacking the inserted hsp were injected as a control. Three months after vaccination, significant specific antibodies against H. pylori were detected by ELISA in the sera of vaccinated mice. Antibody isotypes were predominantly IgG2a (Th1-like) with pcDNA3.1-hspA and mixed IgG1/IgG2a (Th0-like) with pcDNA3.1-hspB. DNA vaccination dramatically suppressed colonies of bacteria in stomach of vaccinated mice (28,400 +/- 21,600/mm(2) for pcDNA3.1-hspA and 6800 +/- 3470/mm(2) for pcDNA3.1-hspB) compared to control mice (128,000 +/- 42,200/mm(2)). Histological analysis of the gastric mucosa demonstrated that the degree of gastritis was significantly lower in the vaccinated mice than in control mice. These results demonstrated that DNA vaccines encoding H. pylori-Hsp induce significant immune response against H. pylori to decrease gastric mucosal inflammation, indicating that a DNA vaccine can be a new approach against H. pylori in humans.

[Helicobacter pylori and stomach cancer]

A number of epidemiological studies and summaries of such studies in the form of meta-analyses have shown a significant relationship between Helicobacter pylori infections of the gastric mucosa and the incidence of gastric cancer. The risk of developing stomach cancer is on average six times higher in the presence of H.p. In countries such as Austria, some 1% of H.p. positives develop gastric cancer in the course of their lives, while only one per 750 noninfected individuals do so. The molecular basis is unclear, but a defect in the tumor-suppressor gene p53 seems to play an important role. As H.p. infection is common (some 30% of the total population in Austria is infected) and gastric cancer without H.p. eradication has become less common (in 1997 there were 24 new cases per 100,000 population), H.p. eradication is not advised as prophylaxis for gastric cancer. Patients who have a positive family history of gastric cancer and those who have had surgery for gastric cancer should, however, according to the Maastricht recommendations, undergo eradication. An example is given to show that in comparison with other measures for cancer screening or prevention, the cost of 120,000 ATS per prevented gastric cancer would be a very good investment with general eradication of H.p. in all individuals over 50 years of age.

Role of cyclooxygenase-2 in Helicobacter pylori- induced gastritis in Mongolian gerbils

Cyclooxygenase (COX)-2 expression is induced in the gastric mucosa of Helicobacter pylori-infected patients, but its role remains unclear. We examined the effects of NS-398 and indomethacin on gastric pathology in H. pylori-infected Mongolian gerbils. COX-1 was detected in both normal and H. pylori-infected mucosa, whereas COX-2 was expressed only in the infected mucosa. PGE(2) production was elevated by H. pylori infection, and the increased production was reduced by NS-398, which did not affect PGE(2) production in normal mucosa. Indomethacin inhibited PGE(2) production in both normal and infected mucosa. Hemorrhagic erosions, neutrophil infiltration, lymphoid follicles, and epithelium damage were induced by H. pylori infection. NS-398 and indomethacin aggravated these pathological changes but did not increase viable H. pylori number. H. pylori-increased production of neutrophil chemokine and interferon-gamma was potentiated by NS-398 and indomethacin. Neither NS-398 nor indomethacin caused any pathological changes or cytokine production in normal animals. These results indicate that COX-2 as well as COX-1 might play anti-inflammatory roles in H. pylori-induced gastritis.

Association of Helicobacter pylori infection with atrophic gastritis and intestinal metaplasia

AIMS

To evaluate the effect of Helicobacter pylori infection and aging on atrophy and intestinal metaplasia of the gastric mucosa.

METHODS

One hundred and sixty-three patients were divided into three age groups and underwent an upper gastrointestinal endoscopy where no esophagitis, peptic ulcers, or malignancies were detected. Two biopsy specimens were obtained from the anterior and posterior walls of the antrum and of the fundus. These were used to evaluate the grade of gastritis, bacterial culture and histologic evidence of H. pylori infection.

RESULTS

Helicobacter pylori infection was found to be directly associated with an increased risk of gastritis grade (odds ratio (OR) = 90 (95% CI; 30-270)). An age of 60 years and older along with H. pylori infection was also strongly associated with an increased risk of atrophy (OR = 6.6, (95% CI; 2.9-15.2)); OR = 9.8, (95% CI; 2.7-35.4)), as was intestinal metaplasia of the gastric mucosa (OR = 5.5, (95% CI; 1.7-17.6)); OR = 7.9, (95% CI; 2.8-46.1)). The prevalence of atrophic gastritis increased with advancing age in H. pylori-infected patients, but no such phenomenon was observed in H. pylori-uninfected patients. The prevalence of intestinal metaplasia significantly increased with advancing age, irrespective of the presence of H. pylori infection. In addition, H. pylori uninfected female patients had a decreased risk of intestinal metaplasia.

CONCLUSIONS

These results suggest that atrophic gastritis is not a normal aging process, but instead is likely to be the result of H. pylori infection, while intestinal metaplasia is caused by both the aging process and H. pylori infection. A decreased risk of intestinal metaplasia found in uninfected female subjects may partly explain the lower prevalence of gastric cancer in females than in males.

Review article: Helicobacter pylori and gastric cancer--the clinicians'point of view

Although the incidence of gastric cancer has declined dramatically in Western countries, the most recent data from the International Agency for Research on Cancer show that it remains the second most common cancer worldwide and caused 628 000 deaths in 1990. The incidence and prevalence of gastric cancer are projected to increase over the next few decades in less developed countries as a result of the increased longevity of H. pylori-infected populations and improved therapies. Gastric carcinogenesis is a multistep and multifactorial process beginning with H. pylori-associated gastritis in most cases. H. pylori infection, together with other environmental factors and individual susceptibility, determine the final risk for the development of gastric cancer. The magnitude of H. pylori infection as a risk factor for gastric cancer in the published H. pylori and gastric cancer epidemiology studies may have been underestimated due to the inclusion of improperly selected controls. Eradication of the infection has been shown to prevent the occurrence of metachronous gastric cancer following endoscopic resection of early gastric cancer in a Japanese study. However, the generalization of this study to other populations is difficult because of the vast differences in the definition of gastric atrophy and early gastric cancer between Japanese and Western pathologists. Until an international consensus on the pathological diagnosis of gastric atrophy and early gastric cancer is reached, interpretation of studies performed in different countries remains difficult. Clinicians rely on the correct pathological diagnosis to guide the management of H. pylori infection-associated gastrointestinal diseases.

Barrett's oesophagus: diagnosis and management

Gastro-oesophageal reflux disease and its sequela, Barrett's oesophagus, are the major recognized risk factors for oesophageal adenocarcinoma, a tumour whose frequency has increased dramatically in Western countries over the past few decades. Barrett's oesophagus develops through the process of metaplasia in which one adult cell type replaces another. The metaplastic, intestinal-type cells of Barrett's oesophagus are predisposed to develop genetic changes that eventuate in cancer. This report reviews the recent controversy regarding diagnostic criteria for Barrett's oesophagus, and provides practical guidelines for identifying the condition. The risks and benefits of the proposed medical, surgical and endoscopic therapies for Barrett's oesophagus are discussed in detail, and the approach to management recently endorsed by the American College of Gastroenterology is summarized.

Chronic Helicobacter pylori infection induces an apoptosis-resistant phenotype associated with decreased expression of p27(kip1)

Helicobacter pylori infection is associated with the development of gastric cancer. In short-term coculture with AGS gastric cells, H. pylori inhibits cell cycle progression and induces dose-dependent apoptosis. Based on the concept that an imbalance between proliferation and apoptosis may contribute to the emergence of gastric cancer, we chronically exposed AGS cells to H. pylori as a model of chronic exposure in humans. The AGS derivatives selected by this process were stably resistant not only to H. pylori-induced apoptosis but also to apoptosis induced by other enteric bacteria and by several toxic agents including radiation and cancer chemotherapy. Like the parental AGS cells, the derivatives underwent G(1)/S-phase cell cycle inhibition in response to H. pylori. The AGS derivatives displayed a marked decrease in cellular levels of the cell cycle control protein p27(kip1). We found a similar decrease in epithelial cell p27(kip1) expression in gastric biopsy specimens from H. pylori-infected patients. These findings are consistent with observations that link decreases in the p27(kip1) level to increased susceptibility to cancer in mice with p27(kip1) deleted and to a poor prognosis of gastric cancer in humans. This is the first demonstration that bacterial infection can lead to apoptosis resistance and to cross-resistance to other inducers of apoptosis such as bacteria, chemotherapeutic agents, and radiation. The development of apoptosis resistance and downmodulation of p27(kip1) may contribute to the increased risk for gastric cancer observed in humans chronically exposed to H. pylori.

Mutagenicity of Helicobacter pylori in the Ames test using Salmonella typhimurium TA100

Infection with Helicobacter pylori has been recognized as a risk factor for gastric cancer, although it is still unclear whether strains of this organism behave as carcinogens. We have studied 30 H. pylori clinical isolates from 15 patients with gastric cancer and 15 patients with other gastroduodenal diseases. Bacterial pellet and supernatant fluid of broth cultures were tested for mutagenicity by means of the Ames test using the pre-incubation technique. The average Ames ratio was 1.111 in the bacterial pellet and 1.312 in the supernatant of strains from the gastric-cancer group, and 0.858 and 0.950 in those from the non-gastric-cancer group, respectively. The strains from the gastric-cancer group had a significantly higher ratio than those from the non-gastric-cancer group, although all results were below the cut-off ratio of the Ames test, and were thus regarded as having no mutagenicity. The Ames ratio of the supernatant was higher than that of the bacterial pellet in both groups. The results indicate that all of the H. pylori strains tested revealed no mutagenicity, but the difference in Ames ratio between strains might reflect differences in genotoxicity between the strains.

Quantitative analysis of Helicobacter pylori infection in a mouse model

Progress in elucidating the pathogenesis of Helicobacter pylori gastric infection and in developing an H. pylori vaccine will be aided by an animal model in which H. pylori can be reliably detected. To validate the use of the mouse model of H. pylori infection, we determined the susceptibility of three inbred strains of mice (C57BL/6J, C57BL/10J and BALB/c) to two VacA+/CagA+ isolates of H. pylori (SPM326 and M1.16) and determined the effectiveness of microbiological, histological and molecular assays for H. pylori detection. For the detection of H. pylori in inoculated mice, reverse transcriptase-polymerase chain reaction was the most sensitive assay (82%), histological evaluation the next most sensitive (66%) and microbiological evaluation the least sensitive (38%); the assays were equally specific (100%). Of the two H. pylori isolates, M1.16 showed the highest rate of colonization, but SPM326 displayed the highest rate of persistent infection. Among the three mouse strains, C57BL/6J mice showed the highest level of both susceptibility to colonization and persistent infection. Anti-H. pylori antibody responses were induced in all inoculated mice and persisted for up to 8 weeks after H. pylori clearance. These results indicate that inbred mice experimentally infected with H. pylori is a reliable model for human infection, but host susceptibility to colonization and persistence of infection are dependent on the H. pylori isolate and the mouse strain.

Association of Helicobacter pylori-dependent gastritis with gastric carcinomas in young Japanese patients: histopathological comparison of diffuse and intestinal type cancer cases

AIMS

The causal relationship of H. pylori gastric colonization with gastric cancer development has not as yet been fully elucidated. The prevalence of H. pylori infection increases with age in the asymptomatic population in Japan, and reaches a high plateau in those older than 40 years. The objective of this study was to assess the link between H. pylori and gastric carcinomas in patients younger than 40 years.

METHODS AND RESULTS

Detection of H. pylori and assessment of background mucosa based on the Sydney system was performed histopathologically for 40 Japanese gastric cancer cases younger than 40 years and compared with 40 age- and sex-matched controls. H. pylori infection in gastric mucosa was detected significantly more frequently (P < 0.001) in patients with cancer (29/40; 72.5%) than in controls (11/40; 27.5%). Additionally, by histopathological comparison between intestinal (18 cases) and diffuse (70 cases) types of young gastric cancer patients, mucosal atrophy and intestinal metaplasia were found to coexist with acute and chronic inflammation in the background mucosa of both intestinal and diffuse types, being significantly more prevalent than in young controls.

CONCLUSIONS

As well as the high prevalence of H. pylori in young subjects with gastric cancer, it is clear that persistent infection induces mucosal damage, resulting in atrophy and intestinal metaplasia. Thus, acute/chronic gastritis could play an essential role in the early development of neoplasia in the stomach.

Marked enhancement by fish meal of Helicobacter pylori-induced gastritis in Mongolian gerbils

In a search for dietary factors influencing Helicobacter pylori-induced gastritis, the effects of fish meal in the diet were examined in Mongolian gerbils. When a conventional diet containing 10% fish meal was given to Mongolian gerbils for 4 weeks after inoculation of H. pylori, edematous thickening with severe neutrophil and mononuclear cell infiltration in both the mucosa and submucosa was observed in the glandular stomach of 19 out of the 20 animals, and hemorrhagic spots were evident in 11 cases. These gastric lesions were enhanced by a 20% fish meal supplement, and edema and hemorrhage in the gastric mucosa were observed in 19 and 17 out of 20 animals, respectively. Although almost the same levels of viable bacteria were detected independent of the diet, edema and hemorrhage were seen in only 2 and 1 of 20 gerbils fed a diet containing 10% casein, instead of 10% fish meal, respectively. Neither edema nor hemorrhage was observed in 10% beef diet animals. These results suggest that fish meal contains factors which greatly enhance H. pylori-induced gastritis in Mongolian gerbils. Since the incidences of gastritis and gastric cancer are very high throughout the world, it is very important to identify these gastritis-enhancing factors.

Helicobacter pylori urease suppresses bactericidal activity of peroxynitrite via carbon dioxide production

Helicobacter pylori can produce a persistent infection in the human stomach, where chronic and active inflammation, including the infiltration of phagocytes such as neutrophils and monocytes, is induced. H. pylori may have a defense system against the antimicrobial actions of phagocytes. We studied the defense mechanism of H. pylori against host-derived peroxynitrite (ONOO(-)), a bactericidal metabolite of nitric oxide, focusing on the role of H. pylori urease, which produces CO(2) and NH(3) from urea and is known to be an essential factor for colonization. The viability of H. pylori decreased in a time-dependent manner with continuous exposure to 1 microM ONOO(-), i.e., 0.2% of the initial bacteria remained after a 5-min treatment without urea. The bactericidal action of ONOO(-) against H. pylori was significantly attenuated by the addition of 10 mM urea, the substrate for urease, whereas ONOO(-)-induced killing of a urease-deficient mutant of H. pylori or Campylobacter jejuni, another microaerophilic bacterium lacking urease, was not affected by the addition of urea. Such a protective effect of urea was potentiated by supplementation with exogenous urease, and it was almost completely nullified by 10 microM flurofamide, a specific inhibitor of urease. The bactericidal action of ONOO(-) was also suppressed by the addition of 20 mM NaHCO(3) but not by the addition of 20 mM NH(3). In addition, the nitration of L-tyrosine of H. pylori after treatment with ONOO(-) was significantly reduced by the addition of urea or NaHCO(3), as assessed by high-performance liquid chromatography with electrochemical detection. These results suggest that H. pylori-associated urease functions to produce a potent ONOO(-) scavenger, CO(2)/HCO(3)(-), that defends the bacteria from ONOO(-) cytotoxicity. The protective effect of urease may thus facilitate sustained bacterial colonization in the infected gastric mucosa.

H. pylori activates NF-kappaB through a signaling pathway involving IkappaB kinases, NF-kappaB-inducing kinase, TRAF2, and TRAF6 in gastric cancer cells

BACKGROUND & AIMS

H. pylori infection on gastric epithelial cells has been shown to induce NF-kappaB activation, but the mechanism of intracellular signal conduction that leads to NF-kappaB activation is not clear. The aim of this study was to analyze the molecular mechanism responsible for H. pylori-mediated NF-kappaB activation on gastric cancer cells.

METHODS

NF-kappaB activation by H. pylori was tested by using luciferase reporter assay. IkappaBalpha degradation by H. pylori infection was assessed by immunoblotting. IKKalpha and IKKbeta activation was analyzed by kinase assay. In transfection experiments, effects of dominant negative IkappaBalpha, IKKalpha, IKKbeta, NF-kappaB-inducing kinase (NIK), TRAF2, and TRAF6 mutants were investigated. The effects of an IKKbeta-specific inhibitor, aspirin, on NF-kappaB activation and IL-8 secretion were also analyzed.

RESULTS

H. pylori promotes degradation of IkappaBalpha, a cytoplasmic inhibitor of NF-kappaB. In kinase assay, H. pylori induced IKKalpha and IKKbeta catalytic activity in gastric cancer cells. Transfection of kinase-deficient mutant of either IKK inhibited H. pylori-mediated NF-kappaB activation dose-dependently. Aspirin inhibited both NF-kappaB activation and IL-8 secretion induced by H. pylori. NF-kappaB activation was also inhibited by transfection of kinase-deficient NIK or a dominant negative mutant of upstream adapter protein TRAF2 or TRAF6.

CONCLUSIONS

H. pylori induces NF-kappaB activation through an intracellular signaling pathway that involves IKKalpha, IKKbeta, NIK, TRAF2, and TRAF6.

Identification of the urease operon in Helicobacter pylori and its control by mRNA decay in response to pH

We investigated the transcription of the urease gene cluster ureABIEFGH in Helicobacter pylori to determine the regulation of gene expression of the highly produced enzyme urease. Northern blot hybridization analysis demonstrated that cells of the wild-type strain grown in an ordinary broth had transcripts of ureAB, ureABI, ureI, ureIE' and ure'FGH, but cells of a ureI-disrupted mutant had only the ureAB transcript. When the wild-type cells were exposed to pH 8 for 30 min, very little mRNA was detected. However, when exposed to pH 6, a large amount of the ureIE" transcript, which was longer than the ureIE' transcript, together with the additional transcripts ureABIEFGH and ure'EFGH were detected. Rifampicin addition experiments demonstrated that urease mRNAs, and the ureIE' transcripts in particular, are more stable at pH 5.5 than at pH 7. In accord with these results, urease activity in the crude cell extract of the pH 5.5 culture was twice as much as that of the pH 7 culture, although the amounts of UreA and UreB detected by immunoblot analysis were similar. The transcription start point of ureI was identified by primer extension using a ureA promoter-deleted mutant, and a consensus sequence of RpoD-RNA polymerase was found in the ureI promoter. The 3' end of the ureIE" mRNA, determined using S1 nuclease mapping, revealed that the transcript is able to cover the majority of the ureE open reading frame (ORF) that might be sufficient for UreE activity. Based on the above results, we conclude that the urease gene cluster of H. pylori consists of two operons, ureAB and ureIEFGH, and that primary transcripts of the latter as well as the read-through transcript, ureABIEFGH, are cleaved to produce several species of mRNA. It has been suggested that the ureIEFGH operon is regulated post-transcriptionally by mRNA decay in response to environmental pH. We are tempted to speculate that the ureE" transcript present in acidic pH may contribute to produce an active product that can proceed the nickel incorporation to the active centre, the final step of urease biosynthesis.

Helicobacter pylori activates mitogen-activated protein kinase cascades and induces expression of the proto-oncogenes c-fos and c-jun

Helicobacter pylori is an etiological agent in the development of mucosa-associated lymphoid tissue lymphoma and gastric adenocarcinoma. Patients infected with H. pylori carry a 3-6-fold increased risk of developing cancer compared with uninfected individuals. H. pylori strains expressing the cytotoxin-associated antigen A (CagA) are more frequently associated with the development of neoplasia than cagA-negative strains. However, the molecular mechanism by which H. pylori causes neoplastic transformation remains unclear. Here we report that exposure of gastric epithelial cells to H. pylori induces activation of the transcription factor activator protein 1. Activation of the proto-oncogenes c-fos and c-jun is strongly induced. We show that H. pylori activates the ERK/MAP kinase cascade, resulting in Elk-1 phosphorylation and increased c-fos transcription. H. pylori strains that do not express CagA or that are mutated in cag genes encoded by the CagI pathogenicity island do not induce activator protein 1, MAP kinase activity, or c-fos or c-jun activation. Proto-oncogene activation may represent a crucial step in the pathomechanism of H. pylori induced neoplasia.

Morphologic differentiation of HL-60 cells is associated with appearance of RPTPbeta and induction of Helicobacter pylori VacA sensitivity

Phorbol 12-myristate 13-acetate (PMA) induces differentiation of human leukemic HL-60 cells into cells with macrophage-like characteristics and enhances the susceptibility of HL-60 cells to the Helicobacter pylori VacA toxin (de Bernard, M., Moschioni., M., Papini, E., Telford, J. L., Rappuoli, R., and Montecucco, C. (1998) FEBS Lett. 436, 218-222). We examined the mechanism by which HL-60 cells acquire sensitivity to VacA, in particular, looking for expression of RPTPbeta, a VacA-binding protein postulated to be the VacA receptor (Yahiro, K., Niidome, T., Kimura, M., Hatakeyama, T., Aoyagi, H., Kurazono, H., Imagawa, K., Wada, A., Moss, J., and Hirayama, T. (1999) J. Biol. Chem. 274, 36693-36699). PMA induced expression of RPTPbeta mRNA and protein as determined by RNase protection assay and indirect immunofluorescence studies, respectively. Vitamin D(3) and interferon-gamma, which stimulate differentiation of HL-60 cells into monocyte-like cells, also induced VacA sensitivity and expression of RPTPbeta mRNA, whereas 1. 2% Me(2)SO and retinoic acid, which stimulated the maturation of HL-60 into granulocyte-like cells, did not. RPTPbeta antisense oligonucleotide inhibited induction of VacA sensitivity and expression of RPTPbeta. Double immunostaining studies also indicated that newly expressed RPTPbeta colocalized with VacA in PMA-treated HL-60 cells. In agreement with these data, BHK-21 cells, which are insensitive to VacA, when transfected with the RPTPbeta cDNA, acquired VacA sensitivity. All data are consistent with the conclusion that acquisition of VacA sensitivity by PMA-treated HL-60 cells results from induction of RPTPbeta, a protein that functions as the VacA receptor.

Antibody response of patients with Helicobacter pylori-related gastric adenocarcinoma: significance of anti-cagA antibodies

The aim of this study was to search for a specific antibody pattern in sera from patients suffering from Helicobacter pylori-related gastric adenocarcinoma (GAC). The serological response of 22 patients suffering from GAC, 31 patients with gastroduodenal ulcer, and 39 asymptomatic subjects was analyzed using immunoblotting performed with three H. pylori strains: strain ATCC 43579; strain B110, isolated from a patient with ulcers; and strain B225, isolated from a patient with GAC. In addition, the latex agglutination test Pyloriset Dry was used to analyze ambiguous sera. H. pylori seropositivity was 75% in the GAC group, 61.3% in the ulcer group, and 56.4% in the asymptomatic group. Anti-CagA antibodies were found more often in the GAC group (48.8%) and in the ulcer group (47.3%) than in the asymptomatic group (21.2%). These percentages depended on the strain used as an antigen: in the GAC group, the anti-CagA frequencies were 93.3, 40, and 13.3% with strains B225, B110, and ATCC 43579, respectively. Thus the presence of anti-CagA antibodies was increased in patients suffering from H. pylori-related GAC, in particular when the CagA antigen was from a GAC strain. These data suggest the existence of a CagA protein specifically expressed by H. pylori strains isolated from GAC patients.

Helicobacter pylori induces DNA damage in vitro

A close association between Helicobacter pylori infection and the development of gastric adenocarcinoma in humans has been demonstrated. Therefore, the direct induction of DNA damage by H. pylori was investigated here using the in vitro micronucleus assay. After 5 days of incubation with bacterial lysate a dose-dependent formation of micronuclei was found, which was not limited to cytotoxic protein concentrations and was not observed after treatment with Escherichia coli lysate (control). This induction of DNA damage may be a link between chronic H. pylori infection and development of adenocarcinoma of the stomach.

A novel in vitro effect of the mucosal protective agent sofalcone--inhibition of chemotactic motility in Helicobacter pylori

BACKGROUND

Motility of Helicobacter pylori is essential for colonization. H. pylori has been shown to exhibit chemotactic activity toward urea and sodium and bicarbonate ions, which are secreted from the gastric epithelia. The importance of urease activity for chemotactic motility of H. pylori in a viscous environment has also been shown. Consequently, application of drugs inhibiting chemotactic motility has been proposed as a strategy for H. pylori eradication. This inhibitory effect can be evaluated through assay of chemotaxis and swarming.

MATERIALS AND METHODS

H. pylori CPY3401 and ATCC43504 were grown on brucella agar plates/broth supplemented with 3% horse serum under microaerobic conditions (N2, 85%; O2, 5%; CO2, 10%). For motility assay, H. pylori cells grown on brucella-serum agar were stabbed into motility agar containing 0.35% refined agar in brucella-serum broth and the swarming zone was measured. For the chemotaxis assay, cells were suspended in 10 mM potassium phosphate buffer, pH 7.0, with 3% polyvinyl-pyrrolidone and assayed as described previously. Bacterial swimming in the fluid environment was observed under dark-field microscopy.

RESULTS

Numbers of bacteria attracted toward 1 microM flurofamide were reduced with increasing concentrations of sofalcone (0.2-222 microM). In addition, the size of the swarming zone was reduced in motility agar containing 22 and 222 microM sofalcone. On the other hand, 22 microM sofalcone did not inhibit bacterial growth on day 3. Bacterial swimming speed in brucella broth was slower in the presence of 22 and 222 microM sofalcone than in its absence.

CONCLUSION

Sofalcone was found to inhibit chemotactic motility of H. pylori. This drug may be useful for inhibiting the bacterium's ability to colonize the human stomach.

The effect of sofalcone on indomethacin-induced gastric ulcers in a Helicobacter pylori-infected gnotobiotic murine model

BACKGROUND

Sofalcone has been reported to exert anti-ulcer and gastroprotective actions, but its exact mechanism of action remains unknown. In our laboratory, we found that indomethacin-induced gastric ulcers become worse when associated with Helicobacter pylori infection.

METHODS

We employed the H. pylori-infected gnotobiotic murine model to examine the effect of sofalcone on indomethacin-induced gastric ulcers in the presence of H. pylori infection. In vitro experiments were also done to evaluate the effects of sofalcone on H. pylori growth, adherence of H. pylori to the MKN45 cells (a human gastric epithelial cell line), and these cells' IL-8 production in the presence of H. pylori.

RESULTS

We found that sofalcone produced a significant improvement in ulcer size as well as a substantial reduction in the number of H. pylori colonies in H. pylori-infected gnotobiotic mice. In vitro sofalcone has a significant bacteriocidal effect against H. pylori and can also significantly prevent adherence of this bacterium to MKN45 cells, thus remarkably reducing IL-8 production of these cells in response to stimulation by H. pylori.

CONCLUSION

Our results suggest that sofalcone can improve ulcer healing by the mechanisms mentioned above.

Induction and maintenance of immune effector cells in the gastric tissue of mice orally immunized to Helicobacter pylori requires salivary glands

BACKGROUND & AIMS

Helicobactor pylori mostly colonizes the gastric mucus that contains salivary antibodies. We studied the role of saliva in the induction and maintenance of gastric immunity conferred by oral vaccination against H. pylori.

METHODS

C57BL/6 mice underwent a sialoadenectomy before and after intragastric immunization using whole-cell sonicates of H. pylori and cholera toxin as an adjuvant. At 1 and 6 months after oral inoculation, we assessed the density of the H. pylori colonizing the stomach, specific antibodies in gastric secretion and sera, and the constituents of cellular infiltrates in the tissue.

RESULTS

A sialoadenectomy before, but not after, immunization abrogated protection by the vaccination at 1 month after inoculation. Protected mice had more neutrophils, plasma cells, and lymphocytes, but fewer eosinophils, in the gastric tissue than nonprotected mice. Protected mice had a greater increase of immunoglobulin (Ig) G1 specific to H. pylori than IgG2a in sera. At 6 months after inoculation, oral immunization was less effective in mice who had a sialoadenectomy than in control immunized mice. The antibody titers in both gastric secretion and in sera did not correlate with the density of bacteria colonizing the stomach.

CONCLUSIONS

It is suggested that, in intragastric immunization against H. pylori, saliva is necessary for both the induction and maintenance of optimal immunity in the stomach. Effective immunity was associated with an increased number of neutrophils and lymphocytes in gastric tissue.

Helicobacter pylori infection and gastric carcinoma in animal models

Many epidemiological studies have shown a strong association between chronic Helicobacter pylori infection and the subsequent development of gastric carcinoma in humans. To confirm this link more clearly, it is necessary to use this bacterium in experimental studies to develop gastric carcinoma in suitable experimental animals. Persistent H. pylori infection has recently been achieved in the Mongolian gerbil model, with results demonstrating that the sequential histopathological changes in the gastric mucosa closely mimic the gastric mucosal changes caused by H. pylori infection in humans. These studies have demonstrated that H. pylori infection enhances gastric carcinogenesis in combination with known carcinogens, such as N-methyl-N-nitroso-urea and N-methyl-N-nitro-N'-nitrosoguanidine and have also demonstrated that H. pylori infection alone can result in the development of gastric carcinoma. These important results provide a starting point for further studies to clarify the mechanism of gastric carcinogenesis as a result of H. pylori infection and assist the planning of eradication therapy to prevent gastric carcinoma.

Functional dyspepsia and Helicobacter pylori infection: a recent consensus up to 1999

With accumulated evidence for a close relationship between Helicobacter pylori infection and many gastric disorders, the idea that this infection may invoke dyspeptic symptoms appears realistic. If curative therapy for H. pylori can bring about relief of symptoms in these patients, we would possess a new therapeutic tool for functional dyspepsia. Although there have been many clinical trials on this issue, the benefits of H. pylori treatment have been controversial. However, several large-scale clinical studies have been very recently published, and suggest a specific direction on this clinical question. From these results, the current consensus is that H. pylori infection does not directly affect symptoms in patients with functional dyspepsia. However, most clinical trials have been performed on Western populations, and there are few reports from Asian countries. Our recent study on the Japanese population also supported the consensus, that is, a negative relationship between H. pylori infection and symptoms in functional dyspepsia patients.

Clarithromycin for Helicobacter pylori infection

Helicobacter pylori, a Gram-negative organism that survives in the deep mucus layer and attaches to the gastric surface cells, is estimated to be present in up to one-half of the US population. Chronic H. pylori infection causes chronic gastritis, peptic ulcer diseases and even gastric cancer. Cure of the infection leads to healing of gastric inflammation, prevention of development of peptic ulcer, as well as accelerated healing of peptic ulcers, and prevention of ulcer recurrence. Treatment of H. pylori has undergone substantial evolution over the past decade. Despite the in vitro susceptibility, results from single or even dual drug therapy is typically unsatisfactory and the best therapy is yet to be defined. The best current therapies for H. pylori infection consist of a proton pump inhibitor (PPI) or ranitidine bismuth citrate and two antibiotics (triple therapies), or bismuth, tetracycline, metronidazole and a PPI (quadruple therapy). Clarithromycin is one of the most useful antimicrobials against H. pylori. It is an acid-stable macrolide with a broad spectrum of antibacterial activity, well absorbed with a wide tissue distribution and with mild side effects. Clarithromycin has a low minimum inhibitory concentration (MIC50) for H. pylori and its effect is potentiated by acid inhibition. When combined with a PPI or ranitidine bismuth citrate and amoxicillin or metronidazole, eradication rates of more than 95% can be achieved with susceptible organisms. However, the prevalence of primary and acquired clarithromycin resistance, which is due to mutations within a conserved loop of 23S rRNA of H. pylori, is increasing. In practice, the presence of clarithromycin resistance usually implies reduced success when clarithromycin-containing regimes are used. There is a need for improved therapies for H. pylori where antibiotic resistance is less of a problem.

Role of apoptosis in Helicobacter pylori-associated gastric mucosal injury

Apoptosis, a programmed cell death, was ignored, just like Helicobacter pylori, only to reappear recently. However, the number of current publications dealing with apoptosis or H. pylori has increased exponentially. Although gastric epithelial apoptosis is a programmed physiological event in the superficial aspect of the mucosa and is important for healthy cell turnover, H. pylori infection reportedly promotes such a cell death sequence. Because apoptosis regulates the cycle of cell turnover in balance with proliferation, dysregulation of apoptosis or proliferation evoked by H. pylori colonization would be linked to the gastric carcinogenesis. In other words, a reduced level of apoptosis could contribute to the generation of gastric cancer. Herein, we review apoptosis as well as its associated pathological events, such as hyperproliferation, in H. pylori-colonized gastric mucosa.

Do mucosal defensive agents improve the cure rate when used with dual or triple therapy regimens for eradicating Helicobacter pylori infection?

BACKGROUND

Some of mucosal defensive agents have anti-Helicobacter pylori activities. However, their effectiveness in eradicating H. pylori infection has not been evaluated.

AIM

To assess the additive effect of mucosal defensive agents in eradication regimens using statistical analysis.

METHODS

Pertinent studies were retrieved using the Medline and the Igaku-chuo-zasshi databases in Japan, reference and congress abstract lists. Studies in which regimens consisted of dual or triple therapy with mucosal defensive agents and without them, were selected from the retrieved studies. Eradication rates were extracted from studies according to intention-to-treat analysis. We evaluated the efficacies of mucosal defensive agents by pooled relative risk of eradication rates and its 95% confidence intervals (95% CI), which were calculated by Mantel-Haenszel method. Heterogeneity among the studies in treatment effect was evaluated by a chi2-test.

RESULTS

In dual therapy regimens, mucosal defensive agents demonstrated significant additive effects (pooled relative risk 1.41; 95% CI: 1.24-1.61). In triple therapy regimens, these agents did not provide significant additive effect. The clinical usefulness of specific agents could not be established, when each agent was analysed independently.

CONCLUSIONS

Mucosal defensive agents improve the cure rate when used with existing dual therapy regimens for eradicating H. pylori infection.

Animal models of gastroduodenal ulcer disease

Animal models have played a significant role in research that aims to understand peptic ulceration. Firstly, they have helped define basic mechanisms of gastric mucosal defence and repair. The basis for gastric injury following NSAID administration was facilitated by animal models that correlated well with disease in humans. In early studies, ulceration was induced by grossly damaging insults to the gastric mucosa that were unphysiological. With refinement these models provided a clearer appreciation of stress ulceration. The discovery of Helicobacter pylori (H. pylori), as the cause of most ulcers, resulted in a need to re-evaluate the early literature and to look for new models. To date, these have contributed little to our understanding of the pathogenesis of H. pylori-induced ulcer. A major aim of this chapter is to suggest that thorough understanding of the animal models of Helicobacter infection may provide important new insights, in particular the factors controlling gastritis, the essential precursor lesion of ulceration. Available models include primates, cats, guinea pigs, ferrets and pigs. The mouse models provide opportunity for identifying both essential bacterial and host factors. The most severe pathologies are seen in the H. pylori-infected Mongolian gerbil with ulcers being formed in most animals. This is likely to become the standard animal model for investigation of peptic ulcer disease.

Induction of follicular gastritis following postthymectomy autoimmune gastritis in Helicobacter pylori-infected BALB/c mice

Helicobacter pylori is the major causative agent of chronic antral gastritis and is thought to be involved in the pathogenesis of mucosa-associated lymphoid tissue lymphoma (MALToma) developing in the human stomach. The aim of this study was to clarify whether corporal autoimmune gastritis (AIG), which is known to decrease acidity due to destruction of parietal cells, predisposes mice to H. pylori infection, thereby leading to MALToma-like pathology. BALB/c mice in which AIG had been induced by thymectomy 3 days after birth (AIG mice) were used. The AIG mice were orally administered mouse-adapted H. pylori at the age of 6 weeks and were examined histologically and serologically after 2 to 12 months. The results were compared with those obtained from uninfected AIG mice and infected normal mice. Germinal centers were induced in the corpus in 57% of the H. pylori-infected AIG mice, which elicited anti-H. pylori antibody responses in association with upregulation of interleukin-4 (IL-4) mRNA. In these mice, parietal cells remained in the corpus mucosa. These findings were in contrast to those with the uninfected AIG mice: fundic gland atrophy due to disappearance of parietal cells associated with upregulation of gamma interferon, but not IL-4, mRNA and no germinal center formation in the corpus. These observations suggest that AIG alters the infectivity of H. pylori, leading to MALToma-like follicular gastritis, at an early stage after H. pylori infection.

Helicobacter pylori alters gastric epithelial cell cycle events and gastrin secretion in Mongolian gerbils

BACKGROUND & AIMS

Human colonization with Helicobacter pylori increases the risk for distal gastric adenocarcinoma, possibly by altering gastric epithelial cell cycle events and/or gastrin secretion. This study aimed to determine whether H. pylori virulence-related characteristics affect apoptosis, proliferation, and gastrin levels in a rodent model of gastric adenocarcinoma.

METHODS

Mongolian gerbils were challenged with H. pylori wild-type or isogenic cagA(-) and vacA(-) mutants, and apoptotic and proliferating cells were identified by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling and proliferating cell nuclear antigen immunohistochemistry, respectively. Serum gastrin levels were determined by radioimmunoassay.

RESULTS

Gastric epithelial cell turnover was no different after infection with the wild-type, cagA(-), or vacA(-) strains. H. pylori infection significantly increased antral apoptosis 2-4 weeks after challenge, before apoptotic indices decreased to baseline. In contrast, antral proliferation rates were significantly higher 16-20 weeks after inoculation, but then decreased by 40 weeks. Antral proliferation was significantly related to serum gastrin levels, whereas antral apoptosis was inversely related to acute inflammation and lymphoid follicles.

CONCLUSIONS

In H. pylori-infected gerbils, enhanced antral apoptosis is an early and transient cell cycle event. 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.

Unique mechanism of Helicobacter pylori for colonizing the gastric mucus

Helicobacter pylori is a human gastric pathogen causing chronic infection. Urease and motility using flagella are essential factors for its colonization. Urease of H. pylori exists both on the surface and in the cytoplasm, and is involved in neutralizing gastric acid and in chemotactic motility. H. pylori senses the concentration gradients of urea in the gastric mucus layer, then moves toward the epithelial surface by chemotactic movement. The energy source for the flagella movement is the proton motive force. The hydrolysis of urea by the cytoplasmic urease possibly generates additional energy for the flagellar rotation in the mucus gel layer.

Synergistic interaction between hypergastrinemia and Helicobacter infection in a mouse model of gastric cancer

BACKGROUND & AIMS

Hypergastrinemia occurs frequently in association with acid suppression and Helicobacter infection, but its role in the progression to gastric atrophy and gastric cancer has not been well defined.

METHODS

The effects of hypergastrinemia, and possible synergy with Helicobacter felis infection, were investigated in insulin-gastrin (INS-GAS) transgenic mice.

RESULTS

INS-GAS mice initially showed mild hypergastrinemia, increased maximal gastric acid secretion, and increased parietal cell number but later progressed to decreased parietal cell number and hypochlorhydria. Development of gastric atrophy was associated with increased expression of growth factors, heparin-binding epidermal growth factor and transforming growth factor alpha. At 20 months of age, INS-GAS mice showed no evidence of increased enterochromaffin-like cell number, but instead exhibited gastric metaplasia, dysplasia, carcinoma in situ, and gastric cancer with vascular invasion. Invasive gastric carcinoma was observed in 6 of 8 INS-GAS mice that were >20 months old. Helicobacter felis infection of INS-GAS mice led to accelerated (< or = 8 mo) development of intramucosal carcinoma (85%), with submucosal invasion (54%) and intravascular invasion (46%; P < or = 0.05).

CONCLUSIONS

These findings support the unexpected conclusion that chronic hypergastrinemia in mice can synergize with Helicobacter infection and contribute to eventual parietal cell loss and progression to gastric cancer.