methylnitronitrosoguanidine and Helicobacter-Infections

Helicobacter pylori infection is well accepted to be a very important factor for the development of gastric carcinogenesis in the human stomach. In Mongolian gerbils treated with chemical carcinogens, H. pylori infection enhances glandular stomach carcinogenesis, and eradication of infection and results in curtailment of enhancing effects, particularly at early stages of associated inflammation. A high-salt diet exacerbates the effects of H. pylori infection on gastric carcinogenesis, and these two factors act synergistically to promote the development of gastric cancers in this animal model. However, the bacterium exerts the greater effects. Early acquisition significantly increases gastric chemical carcinogenesis in Mongolian gerbils, as compared to later infection. While heterotopic proliferative glands, hyperplastic and dilated glands localized beneath the muscularis mucosae, frequently develop with H. pylori infection alone in this animal model, they obviously regress on eradication, suggesting a relation to severe gastritis, rather than a malignant character. Furthermore, endocrine cells, positive for chromogranin A, are observed in the heterotopic proliferative glands, in contrast to cancerous lesions which lack endocrine elements. In conclusion, H. pylori is not an initiator, but rather a strong promoter of gastric carcinogenesis, whose eradication, together with reduction in salt intake, might effectively prevent gastric cancer development.

Topics: Adenocarcinoma; Animals; Cocarcinogenesis; Disease Models, Animal; Gerbillinae; Helicobacter Infections; Helicobacter pylori; Humans; Methylnitronitrosoguanidine; Methylnitrosourea; Precancerous Conditions; Sodium Chloride, Dietary; Stem Cells; Stomach Neoplasms

Helicobacter pylori (Hp) was concluded to be 'a definite carcinogen' by WHO/IARC in 1994. We have demonstrated that Hp infection enhances chemical carcinogen-induced stomach carcinogenesis in Mongolian gerbils (MGs) using N-methyl-N'-nitro-N-nitrosoguanidine or N-methyl-N-nitrosourea. Not only well-differentiated but also poorly differentiated and signet ring cell types of cancers are observed, mimicking the human case. Eradication of Hp was found to be effective of preventing enhancing effects. Hp infection alone, without chemical carcinogens, caused submucosal proliferating lesions, but not gastric carcinomas, in contrast to reports that Hp infection alone may act on a complete carcinogen. Precise pathological assessment is required to solve this controversy. Here we demonstrate alleviation of Hp induced gastric lesions with eradication in MGs.

Topics: Animals; Disease Models, Animal; Gastric Mucosa; Gerbillinae; Helicobacter Infections; Helicobacter pylori; Humans; Metaplasia; Methylnitronitrosoguanidine; Methylnitrosourea; Stomach Neoplasms

To explore the 'causal link' between Helicobacter pylori(Hp) infection and stomach carcinogenesis, we have established experimental models of stomach carcinogenesis in Mongolian Gerbils(MGs) using the chemical carcinogen, N-methyl-N'-nitro-N-nitrosoguanidine(MNNG) and N-methyl-N-nitrosourea(MNU). The incidence of adenocarcinoma was significantly higher in animals treated with Hp than in the controls. Eradication of Hp was effective in reducing the incidence of adenocarcinoma. No gastric carcinoma was found without any chemical carcinogen. Hp infection enhances glandular stomach carcinogenesis not only of well-differentiated type but also poorly differentiated type and signet ring cell type. Eradication of Hp, apparently a gastric promoter rather than gastric carcinogen, may be useful as a measure for prevention of stomach cancer.

Topics: Adenocarcinoma; Animals; Carcinogens; Disease Models, Animal; Gerbillinae; Helicobacter Infections; Helicobacter pylori; Humans; Methylnitronitrosoguanidine; Methylnitrosourea; Stomach Neoplasms

Animal models are being used to study the mechanisms by which Helicobacter spp. induce gastric disease. To assess the effects of a natural gastric pathogen, Helicobacter mustelae, in the development of chronic gastritis, premalignancy and cancer, the ferret model was studied under natural and experimental conditions.. H. mustelae-infected ferrets were used to study the metabolism of nitrates/nitrites, which are dietary and endogenously formed substances that have been linked to gastric cancer. The ferret was also manipulated by performing gastric reconstructive surgery to study the processing of nitrite and nitrate and to assess the effect of surgery on gastric pathology. In addition, the ferret was tested for its suitability as an animal model for the induction of gastric cancer by oral dosing with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). The influence of these variables on gastric pathology and/or metabolic outcomes was examined, and the results in ferrets were compared to findings in humans.. The ferret appears to be an ideal model for studying various gastric parameters and how these factors influence the development of H. mustelae-associated gastric disease. Gastric reconstructive surgery did not effect nitrite processing or overall severity of gastritis in ferrets. However, a single dose of MNNG (50 mg/kg) produced an unprecedented 90% gastric carcinoma in H. mustelae-infected ferrets. This implies that chronic inflammation induced by the bacterium is a cofactor in gastric carcinogenesis.

Topics: Adenocarcinoma; Animals; Disease Models, Animal; Ferrets; Gastric Mucosa; Gastritis; Helicobacter; Helicobacter Infections; Methylnitronitrosoguanidine; Nitrosamines; Proliferating Cell Nuclear Antigen; Stomach; Stomach Neoplasms

To observe the curative effect of Weiansan (WAS) on gastric precancerous lesions (GPL) and H pylori elimination.. Seventy-six patients with GPL were randomly divided into two groups: WAS group (n = 42) and Weifuchun (WFC) group (n = 34). The patients in the WAS group were administered 5 g WAS 3 times a day, and the patients in the WFC group took WFC (4 tablets) 3 times a day. To monitor inflammation of gastric mucosa, degree of glandular atrophy (GA), intestinal metaplasia (IM) and dysplasia, and H pylori infection, all patients underwent gastroscopy and biopsy with pathological examination before and after treatment. Fifty male Sprague-Dawley (SD) rats were used in animal experiments. Of these, 10 served as the control group (n = 10), 40 were given ranitidine combined with N-methyl-N(1)-nitro-N-nitrosoguanidine (MNNG) for 12 wk and divided into 4 groups randomly: model group (n = 10), high-dose WAS group (n = 10), low-dose WAS group (n = 10) and WFC group (n = 10). Twelve weeks later, all rats were killed and a 2 cm multiply 1 cm tissue was taken from the lesser curvature of the gastric antrum. H pylori infection was determined by the fast urease method.. The curative effect in WAS groups was similar to that in WFC groups. There was no statistical difference in degree of GA, IM and dysplasia between WAS and WFC groups. The rate of H pylori infection in the model group (positive/negative: 9/1) was significantly higher than that in the control group (positive/negative: 1/9) (P < 0.01). H pylori elimination in the high-dose WAS group (positive/negative: 4/6) and low-dose WAS group (positive/negative: 6/4) was similar to that in the WFC group (positive/negative: 4/6) (P > 0.05).. WAS improves clinical symptoms by suppressing GA, IM and dysplasia and eliminating H pylori.

Topics: Adult; Aged; Animals; Female; Helicobacter Infections; Helicobacter pylori; Humans; Male; Medicine, Chinese Traditional; Methylnitronitrosoguanidine; Middle Aged; Precancerous Conditions; Rats; Rats, Sprague-Dawley; Stomach Diseases; Stomach Neoplasms; Time Factors; Treatment Outcome

We examined the development of gastric cancer risk screening, from rat pepsinogen studies in an experimental rat gastric carcinogenesis model induced with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and human pepsinogen studies in the 1970s and 1980s to the recent "ABC method" for human gastric cancer risk screening. First, decreased expression or absence of a major pepsinogen isozyme, PG1, was observed in the rat gastric mucosa from the early stages of gastric carcinogenesis to adenocarcinomas following treatment with MNNG. In the 1980s, decreases in PGI in the human gastric mucosa and serum were identified as markers of atrophic gastritis. In the 1990s, other researchers revealed that chronic infection with Helicobacter pylori (Hp) causes atrophic gastritis and later gastric cancer. In the 2000s, a gastric cancer risk screening method combining assays to detect serum anti-Hp IgG antibody and serum PGI and PGII levels, the "ABC method", was established. Eradication of Hp and endoscopic follow-up examination after the ABC method are recommended to prevent gastric cancer.

Topics: Animals; Carcinogenesis; Early Detection of Cancer; Gastritis, Atrophic; Helicobacter Infections; Helicobacter pylori; Humans; Methylnitronitrosoguanidine; Pepsinogen A; Persistent Infection; Rats; Stomach Neoplasms

A CagA-positive Helicobacter pylori (H. pylori) infection can cause malignant transformation of human gastric mucosal epithelial cells, and N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) is a chemical carcinogen that induces gastric carcinogenesis. Whether this environmental chemocarcinogen may synergistically enhance the risk of H. pylori-infected gastric cancer remains unclear. In this study, we adopted a chronic CagA-positive H. pylori infection with or without MNNG coinduction to establish a cellular model in GES-1 cells and an animal model in C57BL/6J mice. The proliferation, cell phenotype, apoptosis, epithelial-mesenchymal transition (EMT), stemness and tumorigenicity of gastric mucosal epithelial cells were analyzed in vitro and in vivo. The results showed that chronic H. pylori-infected GES-1 cells displayed inhibited apoptosis, abnormal proliferation, enhanced invasion, and migration, increased EMT/mesenchymal phenotype, colony formation and stem cell-like properties, and enhanced tumorsphere-formatting efficiency as well as CD44 expression, a known gastric cancer stem cell (CSC) marker. MNNG synergistically promoted the above actions of chronic H. pylori infection. Further studies in chronic H. pylori-infected C57BL/6J mice models showed that an increased incidence of premalignant lesions in the gastric mucosa tissue of the H. pylori-infected mice had occurred, the mouse gastric mucosa cells exhibited similar mesenchymal and CSC-like properties in the above GES-1 cells, and precancerous lesions and EMT/CSC-like phenotypes were reinforced by the synergistic action of MNNG stimulation. H. pylori infection and/or MNNG induction were capable of causing enhanced expression and activation of Wnt2 and β-catenin, indicating that the Wnt/β-catenin pathway is involved in the actions of H. pylori and MNNG. Taken together, these findings suggest that chronic CagA-positive H. pylori infection with MNNG stimulation synergistically induces mesenchymal and CSC-like properties of gastric mucosal epithelial cells.

Topics: Animals; Antigens, Bacterial; Apoptosis; Bacterial Proteins; Cell Line; Cell Movement; Cell Proliferation; Epithelial Cells; Epithelial-Mesenchymal Transition; Female; Gastric Mucosa; Helicobacter Infections; Helicobacter pylori; Humans; Mesoderm; Methylnitronitrosoguanidine; Mice, Inbred C57BL; Neoplastic Stem Cells; Wnt Signaling Pathway

Gastric cancer results from a combination of Helicobacter pylori (H pylori) infection, exposure to dietary carcinogens, and predisposing genetic make-up. Because the role of these factors in gastric carcinogenesis cannot be determined readily in human beings, the present study examined the role of an oral carcinogen and H pylori infection in rhesus monkeys.. Gastroscopies were performed in 23 monkeys assigned to 4 groups: controls; nitrosating carcinogen ethyl-nitro-nitrosoguanidine administration alone; inoculation of a virulent H pylori strain alone (H); and ethyl-nitro-nitrosoguanidine in combination with H pylori (EH). Follow-up gastroscopies and biopsies were performed at 3-month intervals for 5 years for pathologic and molecular studies.. Postinoculation, H and EH groups showed persistent infection and antral gastritis. Starting at 2 and 5 years, respectively, gastric intestinal metaplasia and intraepithelial neoplasia developed in 3 EH monkeys but in no other groups. Transcriptional analysis of biopsy specimens at 5 years revealed group-specific expression profiles, with striking changes in EH monkeys, plus a neoplasia-specific expression profile characterized by changes in multiple cancer-associated genes. Importantly, this neoplastic profile was evident in nonneoplastic mucosa, suggesting that the identified genes may represent markers preceding cancer.. Gastric intraglandular neoplasia is induced in primates when H pylori infection is associated with consumption of a carcinogen similar to the nitrosamines found in pickled vegetables, suggesting that H pylori and the carcinogen synergistically induce gastric neoplasia in primates.

Topics: Animals; Biopsy; Carcinogens; Carcinoma in Situ; Cell Transformation, Neoplastic; Cluster Analysis; Diet; Disease Models, Animal; Disease Progression; DNA Repair; Female; Gastritis; Gastroscopy; Gene Expression Profiling; Gene Expression Regulation, Neoplastic; Helicobacter Infections; Helicobacter pylori; Macaca mulatta; Male; Metaplasia; Methylnitronitrosoguanidine; Oligonucleotide Array Sequence Analysis; Precancerous Conditions; Stomach Neoplasms; Time Factors

To establish a model of long-term infection with Helicobacter pylori (Hp) in Mongolian gerbil (Meriones unguiculatus), and to investigate if Hp combined with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) has a synergistic effect to induce gastric mucosa injury. To investigate pathological changes of gastric mucosa during long-term Hp infection in Mongolian gerbil model.. 90 healthy male Mongolian gerbils were randomly divided into 4 groups: Hp group (n = 24) undergoing gastric perfusion of Hp suspension of the line NCTC11637 in brain-heart infusion (BHI) 10(8)-10(9) CFU/ml once a day for 10 days and then gastric perfusion of 1 ml normal saline (NS) once a day for 10 days since the 4th week after Hp perfusion, Hp + MNNG group (n = 24) undergoing gastric perfusion of Hp solution once a day for 10 days and then MNNG 1 ml (2 mg/ml) once a day for 10 days, MNNG group (n = 20) undergoing gastric perfusion of BHI once a day for 10 days and then gastric perfusion of MNNC once a day for 10 day since the 4th week after BHI perfusion, and control group (n = 22) undergoing gastric perfusion of BHI once a day for 10 days and then gastric perfusion of NS again once a day for 10 day since the 4th week after the BHI perfusion. 4 and 8 weeks 1 gerbil from the control group and 2 gerbils from the Hp and Hp + MNNG groups each were killed to observe the pathological changes and Hp colonization by liquid-based urease test and Warthin-Starry silver staining. 20 and 40 weeks after the Hp inoculation 10 gerbils from each group were killed to observe the pathology of the gastric mucosa.. (1) A Mongolian gerbil model of long-term Hp infection was successfully established. (2) Hp induced the process progressing from normal gastric mucosa --> chronic atrophic gastritis --> intestinal metaplasia --> dysplasia. Until 40 weeks after Hp infection, the gastric mucosa of the control group remained normal. Twenty weeks after Hp infection 3 gerbils in the Hp group and 1 gerbil in the Hp + MNNC group showed glandular atrophy and intestinal metaplasia respectively, and 40 weeks after infection, glandular atrophy, intestinal metaplasia, and dysplasia at different degrees in the gastric mucosa were seen in the three experimental groups. The pathological changes of the Hp + MNNG group were the most severe. The incidence rates of precancerous lesions of the Hp + MNNG group were significantly higher than those of the other groups, but no gastric carcinoma was found in the experimental animals.. Hp colonizes stably in the glandular gastric mucosa of Mongolian gerbils. The histological changes after infection are similar to those of the Hp infected human being. Hp and MNNG both cause the injury of gastric mucosa. With synergistic effect, the two pathogenic agents attack the gastric mucosa, they cause more severe injury.

Topics: Animals; Disease Models, Animal; Gastric Mucosa; Gerbillinae; Helicobacter Infections; Helicobacter pylori; Humans; Male; Methylnitronitrosoguanidine

The pathogenesis of stomach cells can be associated with their susceptibility to exogenous dietary irritants, like nitrosamines such as dimethylnitrosamines (DMNA), and to the effects of non-dietary factors, including Helicobacter pylori infection. We used N-methyl-N'-nitro N-nitrosoguanidyne (MNNG) as a surrogate agent that induces a spectrum of DNA damage similar to DMNA. Using the alkaline comet assay, we showed that antioxidants--vitamins C and E, quercetin, and melatonin--reduced the genotoxic effect of MNNG in H. pylori-infected and non-infected human gastric mucosa cells (GMCs). To compare the sensitivity of the stomach and the blood, the experiment was also carried out in peripheral blood. We observed a higher level of DNA damage induced by MNNG in H. pylori-infected than in noninfected GMCs. We did not note any difference in the efficacy of the repair of the damage in either type of GMC. H. pylori infection may play an important role in the pathogenesis of GMCs, as it can modulate their susceptibility to dietary mutagens/carcinogens, thus contributing to gastric cancer.

Topics: Adult; Aged; Carcinogens; Cells, Cultured; DNA Damage; Gastric Mucosa; Genetic Predisposition to Disease; Helicobacter Infections; Helicobacter pylori; Humans; Male; Methylnitronitrosoguanidine; Middle Aged; Mutagens

Both Helicobacter pylori (Hp) and bile acids are gastric carcinogens. An experimental model of duodenogastric reflux in Mongolian gerbils was developed and was used to study the effects of Hp infection and duodenogastric reflux on N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced glandular stomach tumorigenesis independently and synergistically. Male Mongolian gerbils underwent both inoculation with Hp, and had duodenogastric reflux (DR) induced, or neither, followed by MNNG administration. Animals were sacrificed at week 40, and histopathological examination of their excised stomachs and serological investigation were performed. Glandular stomach adenocarcinomas were observed in animals that underwent Hp inoculation and/or induction of DR after MNNG administration, and glandular stomach adenomas were found in animals inoculated with Hp after MNNG administration. The incidence of glandular stomach tumors was significantly higher in animals inoculated with Hp after MNNG administration and in animals undergoing combined Hp inoculation, DR induction and MNNG administration than in animals only administered MNNG. These findings indicate that Hp infection has a stronger tumorigenic effect than the exposure to duodenal contents, and duodenal contents may attenuate the effect of Hp on glandular stomach tumorigenesis.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Animals; Deoxyguanosine; Duodenogastric Reflux; Gastrointestinal Contents; Gerbillinae; Helicobacter Infections; Inflammation; Male; Methylnitronitrosoguanidine; Mongolia; Neoplasms, Glandular and Epithelial; Stomach Neoplasms

The effect of prolonged administration of the cytokine interleukin (IL)-1beta on gastric carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) was examined in Wistar rats. In addition, we examined the effects on the proliferating cell nuclear antigen (PCNA) labeling index and the hepatocyte growth factor (HGF) immunoreactivity of the gastric mucosa. The rats received intraperitoneal injections of 0.1 or 0.3 microg/kg body weight of IL-1beta every other day after oral treatment with MNNG for 25 weeks. Long-term administration of IL-1beta at high dose, but not at low dose, significantly increased the incidence of gastric cancer in week 52. Administration of IL-1beta at high dose also significantly increased the labeling index and the HGF immunoreactivity of the gastric antral mucosa, and induced inflammatory cell infiltration and glandular atrophy of the gastric mucosa. Because IL-1beta production in the gastric mucosa is increased in patients with Helicobacter pylori-associated gastritis and eradiation of the organism significantly decreases the IL-1beta production, these findings suggest that Helicobacter pylori-associated gastric carcinogenesis may be in part mediated through IL-1beta.

Topics: Adenocarcinoma; Animals; Cell Division; Drug Synergism; Gastric Mucosa; Gastritis; Helicobacter Infections; Helicobacter pylori; Interleukin-1; Male; Methylnitronitrosoguanidine; Neoplasm Invasiveness; Proliferating Cell Nuclear Antigen; Rats; Rats, Wistar; Stomach; Stomach Neoplasms

Cyclooxygenase-2 (COX-2) and Bcl-2 have been implicated in upper gastrointestinal tract carcinomas, but the underlying mechanisms are not known. In the present study we assessed the correlation of COX-2 and Bcl-2 to known cell kinetics in the glandular stomach mucosa of 104 Wistar rats given combinations of Helicobacter pylori, MNNG ( N'-methyl- N'-nitro- N-nitrosoguanidine) and bile. COX-2 expression, Bcl-2 and cell proliferation (Ki-67) in antral and corpus mucosa were determined immunohistochemically. Apoptotic cells were detected using terminal uridine deoxynucleotidyl nick end labelling technique. Expression of COX-2 was found in the lower portion of glandular corpus epithelium, and Bcl-2 positivity was mainly seen in the proliferative zone of both antrum and corpus mucosa. COX-2 expression in histologically normal-appearing corpus mucosa was associated with cell proliferation, atrophy and intestinal metaplasia in antrum and with Bcl-2 expression in corpus mucosa. No correlation was found between apoptosis and Bcl-2 expression. MNNG but not H. pylori significantly increased COX-2 in corpus mucosa. H. pylori, however, promoted the COX-2 expression in corpus when bile was added and Bcl-2 expression in antrum. Abnormal expression of both COX-2 and Bcl-2 seem to be involved in H. pylori-induced gastric carcinogenesis by altering the gastric cell kinetics.

Topics: Animals; Apoptosis; Bile; Cell Division; Cyclooxygenase 2; Gastric Mucosa; Helicobacter Infections; Helicobacter pylori; Immunohistochemistry; Isoenzymes; Male; Methylnitronitrosoguanidine; Prostaglandin-Endoperoxide Synthases; Proto-Oncogene Proteins c-bcl-2; Rats; Rats, Wistar

The effects of combined administration of a reactive oxidant, monochloramine, and a mucoregulatory agent, ambroxol, on the development of gastric cancers induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) were investigated in inbred Wistar rats. After receiving oral MNNG and regular chow pellets for 25 weeks, rats received regular chow pellets or chow pellets containing 20% ammonium acetate, and normal tap water or water containing 30 mM sodium hypochlorite, with or without subcutaneous injection of ambroxol at high or low doses, until the end of the experiment at week 52. Treatment with both ammonium acetate and sodium hypochlorite, which produce monochloramine, significantly increased the incidence of gastric cancers at week 52, whereas concomitant administration of ambroxol with ammonium acetate and sodium hypochlorite significantly attenuated this enhanced gastric carcinogenesis. Results also revealed that ambroxol scavenged monochloramine. Because monochloramine is closely related to Helicobacter pylori-associated gastric carcinogenesis, these findings suggest that ambroxol may prevent H. pylori-associated gastric carcinogenesis.

Topics: Ambroxol; Animals; Anticarcinogenic Agents; Apoptosis; Carcinogens; Chloramines; Drug Interactions; Free Radical Scavengers; Gastric Mucosa; Helicobacter Infections; Helicobacter pylori; Male; Methylnitronitrosoguanidine; Rats; Rats, Wistar; Stomach Neoplasms

Helicobacter pylori infection is a risk factor for gastric cancer. How the bacterium contributes to this process is still unclear. We present a new Wistar rat model that was used to evaluate the effect of H. pylori on early preneoplastic events as judged from epithelial cell turnover and histopathological changes. One hundred and four rats were colonized with H. pylori and exposed MNNG (N-methyl-N'-nitro-N'-nitrosoguanidine) and/or taurocholic acid. Inflammation, goblet cell-like metaplasia, atrophy, dysplasia, and adenocarcinoma were scored in a blinded manner. Apoptotic cells were counted after staining with terminal uridine deoxynucleotidyl nick end labeling, and epithelial cell proliferation was determined by means of the Ki-67 labeling index. No early tumor enhancement with H. pylori could be found in ordinary histology. However, H. pylori significantly enhanced the epithelial cell proliferation compared with the control group, and the combination with taurocholic acid appeared to have a synergistic effect. MNNG significantly increased the normal gastric epithelial apoptosis. This increase was reduced in antral mucosa with H. pylori infection. The findings suggest that H. pylori, especially when combined with bile. has an influence on cell kinetics, contributing to the development of gastric cancer. The reduced apoptosis of MNNG also observed in infected animals indicates a dual function of H. pylori.

Topics: Adenocarcinoma; Animals; Apoptosis; Carcinogens; Disease Models, Animal; Gastric Mucosa; Helicobacter Infections; Helicobacter pylori; Immunohistochemistry; In Situ Nick-End Labeling; Ki-67 Antigen; Kinetics; Male; Methylnitronitrosoguanidine; Rats; Rats, Wistar; Stomach Neoplasms; Taurocholic Acid

The aim of this study was to evaluate the early influence of Helicobacter pylori infection on cell kinetics in the antral mucosa of mice exposed to N-methyl-N'-nitro-N'-nitrosoguanidine (MNNG) and bile alone or in combinations. Four hundred and one C57BL/6 male and female mice were assigned into seven treatment groups and one non-treated control group. The gastric antrums were assessed by histology and immunohistochemistry for studies of cell proliferation and apoptosis at 32 and 44 weeks. One female and one male mouse had developed dysplastic adenomas in the pylorus mucosa and one male animal had dysplastic proliferation in the antrum. Only one of these lesions occurred in a H. pylori colonized animal. H. pylori infection significantly increased the cell proliferation at 32 weeks and promoted the cell proliferation in the MNNG and bile group at 44 weeks. Female mice showed less increase in cell proliferation than did the males. No change in apoptosis was seen in any of the groups. Bile had no promotional effect on cell proliferation. These results indicate that H. pylori infection has the potential to alter epithelial cell kinetics as well as antrum mucosa of an animal species that is regarded as resistant to MNNG. However, this change is not sufficient to promote the early development of neoplastic lesions.

Topics: Adenoma; Animals; Apoptosis; Carcinogens; Disease Models, Animal; Epithelium; Female; Gastric Mucosa; Helicobacter Infections; Helicobacter pylori; Immunohistochemistry; In Situ Nick-End Labeling; Ki-67 Antigen; Kinetics; Male; Methylnitronitrosoguanidine; Mice; Mice, Inbred C57BL; Pyloric Antrum; Stomach Neoplasms; Taurocholic Acid

Helicobacter pylori (Hp) is thought to be a stomach carcinogen from epidemiological findings. To determine the effects of infection with the bacteria on experimental carcinogenesis, a study of the glandular stomach of Mongolian gerbils (MGs) was performed. Male MGs were treated with N-methyl-N'-nitro-N-nitrosoguanidine followed by inoculation with Hp or infected with Hp followed by N-methyl-N'-nitro-N-nitrosoguanidine administration. Animals were killed at week 50, and their excised stomachs underwent microbiological and histopathological examinations. In addition, a serological investigation was performed. The incidences of adenocarcinomas were significantly higher in animals treated with 60 or 300 p.p.m. N-methyl-N'-nitro-N-nitrosoguanidine for 10 weeks followed by Hp inoculation or Hp followed by 20 p.p.m. N-methyl-N'-nitro-N-nitrosoguanidine for 30 weeks than in the respective controls. Moreover, tumour-bearing animals had higher titres of anti-Hp antibodies than tumour-free animals. Of interest was the finding that a dose of 100 p.p.m. N-methyl-N'-nitro-N-nitrosoguanidine given to infected gerbils eradicated the Hp in about half the animals, with a concomitant reduction in the promoting effect. No tumours were found in animals infected with Hp without N-methyl-N'-nitro-N-nitrosoguanidine or non-treated gerbils. Hp infection enhances glandular stomach carcinogenesis in MGs treated with N-methyl-N'-nitro-N-nitrosoguanidine. Animals with high titres of anti-Hp antibodies are at greatest risk of developing neoplasms.

Topics: Adenocarcinoma; Animals; Antibodies, Bacterial; Carcinogens; Cell Differentiation; Cocarcinogenesis; Drug Administration Schedule; Edema; Gastric Mucosa; Gastritis; Gastrointestinal Hemorrhage; Gerbillinae; Helicobacter Infections; Helicobacter pylori; Hyperplasia; Male; Metaplasia; Methylnitronitrosoguanidine; Precancerous Conditions; Specific Pathogen-Free Organisms; Stomach Neoplasms; Stomach Ulcer; Time Factors

The effect of Helicobacter pylori infection on N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced gastric cancer was studied using a Mongolian gerbil model. Five-week-old male Mongolian gerbils were divided into four groups of 25-30 animals each and challenged for 20 weeks with H.pylori, MNNG, a combination of H.pylori and MNNG, or neither of them. Four to 20 animals from each group were killed at 16, 24 and 52 weeks after H.pylori inoculation, and histopathological changes in their stomachs were examined. A well-differentiated adenocarcinoma was first observed 24 weeks after inoculation in the combination group. At 52 weeks, only six of 15 animals were colonized with H.pylori persistently, and four of them showed well-differentiated adenocarcinomas; on the other hand, neither of the animals with disappearance of H.pylori from the combination group showed adenocarcinoma. At the same observation time, three of 17 animals from MNNG group showed poorly differentiated adenocarcinomas. The incidence of gastric carcinoma in the combination group was significantly higher than that in the MNNG group (P < 0.05). However, no tumors were seen in the control and H.pylori groups. The present findings demonstrate that H.pylori infection enhances the carcinogenic action of MNNG.

Topics: Adenocarcinoma; Animals; Carcinogenicity Tests; Gastric Mucosa; Gerbillinae; Helicobacter Infections; Helicobacter pylori; Male; Methylnitronitrosoguanidine; Stomach Neoplasms; Time Factors

In 1994 WHO/IARC concluded that "Helicobacter pylori is a definite carcinogen" based on epidemiological studies, but there have been few reports demonstrating a relation between H. pylori and stomach cancer in animal models. We have succeeded in producing adenocarcinomas in the glandular stomachs of Mongolian gerbils with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) or N-methyl-N-nitrosourea as carcinogens and hope to establish an experimental stomach carcinogenesis model using H. pylori. Male Mongolian gerbils, 7 weeks old, were infected with H. pylori followed by MNNG administration at a concentration of 100ppm administration or treated with MNNG at a concentration of 300ppm in their drinking water followed by inoculation with H. pylori. They were then killed sequentially, and their excised stomachs underwent microbiological and histopathological examinations. H. pylori were detected in all infected gerbils. Hyperplastic change of pyloric mucosa was observed with high 5-bromo-2'-deoxyuridine incorporation in affected animals. H. pylori infection persists on administration of MMNG and enhances glandular stomach proliferation in Mongolian gerbils. Whether long-term colonization promotes carcinogenesis in the glandular stomach of Mongolian gerbils is a matter of great interest.

Topics: Adenocarcinoma; Animals; Carcinogens; Colony Count, Microbial; Disease Models, Animal; Gerbillinae; Helicobacter Infections; Helicobacter pylori; Immunohistochemistry; Male; Methylnitronitrosoguanidine; Specific Pathogen-Free Organisms; Stomach Neoplasms

An animal model of stomach carcinogenesis was established using Mongolian gerbils with N-methyl-N-nitrosourea (MNU) and N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) as the carcinogens. In addition, the sensitivity of these gerbils to Helicobacter pylori (H. pylori) was confirmed. One hundred and sixty specific pathogen-free male MGS/Sea animals, 7 weeks old, were treated with MNU in the drinking water (30 ppm for alternate weeks to give 10 weeks exposure, or 10 ppm or 3 ppm for 20 weeks continuous exposure), or given MNNG in the drinking water at 400 ppm or 200 ppm for 20 weeks, or orally inoculated with ATCC43504 H. pylori (1.7 x 10(8) CFUs/animal). Adenocarcinomas in the glandular stomach were found in 2 out of 12 effective animals (2/ 12) treated with 30 ppm MNU at week 20, although all were dead or moribund by week 30 due to MNU toxicity. At week 50, the incidences of gastric adenocarcinomas in groups treated with 10 ppm MNU, 3 ppm MNU, 400 ppm MNNG, and 200 ppm MNNG were 2/21 (9.5%), 1/23 (4.3%), 7/ 11 (63.6%), and 1/10 (10.0%). The lesions were generally well differentiated, although poorly differentiated adenocarcinoma was also found in a single gerbil in each of the 10 ppm MNU and 400 ppm MNNG groups. In control animals no tumors were found. In the infection study, the animals were killed at week 20, and H. pylori was detected in all cases, causing multiple erosions with marked inflammatory cell infiltration in the lamina propria and submucosa, and frequent formation of lymphoid follicles. Thus, MNU and MNNG in the drinking water induced neoplastic lesions in the glandular stomach epithelium of H. pylori-sensitive gerbils.

Topics: Adenocarcinoma; Administration, Oral; Animals; Carcinogens; Cocarcinogenesis; Disease Models, Animal; Disease Susceptibility; Drinking; Gerbillinae; Helicobacter Infections; Helicobacter pylori; Male; Methylnitronitrosoguanidine; Methylnitrosourea; Stomach Neoplasms; Water

The aim of this study was to determine whether gastric epithelial proliferation due to gastric Helicobacter infection in mice represents a preneoplastic lesion.. Helicobacter heilmannii infected and uninfected mice were treated with 150 microg/ml N-methyl-N'-nitro-N-nitrosoguanidine in drinking water for either 20 or 38 weeks. Mice were killed 12 or 18 months after bacterial inoculation.. All infected mice developed lymphoplasmocytic gastritis and epithelial hyperplasia. Proliferative gastric lesions were characterised by nodular hypertrophy of the glandular mucosa, multifocal epithelial hyperplasia, and elevated BrdU labeling index. Intestinal metaplasia and true atrophy were not present but proliferative glands were poorly differentiated, lined by mucus-type epithelial cells with no parietal, chief or other specialized cell types. Neoplasms developed only in MNNG-treated mice. of the 180 treated mice the following neoplasms developed: 14 squamous cell carcinomas of mouth and forestomach; 37 hemangiosarcomas of the intestinal serosa; and 15 splenic lymphomas. No tumors were present in the glandular gastric mucosa, and infection did not affect tumor incidence. p53 overexpression occurred in 79% of hemangiosarcomas and 71% of squamous cell carcinomas but not in normal or proliferative gastric glandular mucosa.. Gastric proliferative lesions in Helicobacter-infected mice are not preneoplastic, and the combination of an alkylating agent and non-neoplastic proliferation does not result in gastric carcinogenesis in mice.

Topics: Animals; Bromodeoxyuridine; Carcinogens; Disease Models, Animal; Female; Gastric Mucosa; Gastritis; Gene Expression Regulation, Neoplastic; Genes, p53; Helicobacter; Helicobacter Infections; Methylnitronitrosoguanidine; Mice; Mice, Inbred BALB C; Neoplasms, Experimental; Stomach Neoplasms

The effects of cytotoxic monochloramine on the development of gastric cancers induced by N-methyl-N'-nitro-N-nitrosoguanidine were investigated in Wistar rats. After oral administration of drinking water containing the carcinogen and regular chow pellets for 25 weeks, rats received regular chow pellets or chow pellets containing 20% ammonium acetate, and normal tap water or water containing 30 mM sodium hypochlorite, with or without s.c. injection of taurine, until the end of the experiment in week 52. Treatment with both ammonium acetate and sodium hypochlorite significantly increased the incidence of gastric cancers in week 52, while the concomitant use of taurine with ammonium acetate and sodium hypochlorite significantly attenuated the enhanced gastric carcinogenesis. Spectrophotometric examinations revealed that taurine scavenged monochloramine. These findings suggest that Helicobacter pylori-associated gastric carcinogenesis may be mediated by monochloramine.

Topics: Animals; Body Weight; Chloramines; Cocarcinogenesis; Gastric Mucosa; Helicobacter Infections; Helicobacter pylori; Male; Methylnitronitrosoguanidine; Rats; Rats, Wistar; Sodium Acetate; Sodium Hypochlorite; Stomach Neoplasms; Taurine

The effect of Helicobacter mustelae infection on gastric epithelial proliferation was studied in ferrets colonized with H.mustelae and specific pathogen-free (SPF) ferrets not infected with H.mustelae. Thirteen H. mustelae-infected ferrets between the ages of 13 and 32 months and 16 SPF ferrets between 6 and 18 months were analyzed. Bacterial cultures, urease tests and Warthin-Starry stains were used to identify H.mustelae. Tissues obtained from the antrum and the body regions of the stomach were assayed by proliferating cell nuclear antigen (PCNA) immunohistochemistry and measured using a computerized color image analysis system. PCNA-expressing gastric epithelia in the antrum and the body regions were significantly increased in the H.mustelae-infected ferrets versus the SPF ferrets (P < 0.001). PCNA positivity in the antrum regions of both the H.mustelae-infected ferrets and SPF ferrets was significantly higher than that of the body regions (P < 0.001). Comparison of the histopathology of infected ferrets indicated that PCNA positivity correlated with the histological severity of gastritis. This study suggests that cell proliferation in ferret gastric mucosa increases with H.mustelae infection and provides evidence that PCNA is a useful biomarker for studying the changes in cell kinetics in the ferret stomach. The data also further support the use of the H.mustelae-infected ferret as an animal model for studying the pathogenesis of Helicobacter pylori-induced gastric diseases of humans.

Topics: Animals; Cell Division; Epithelium; Female; Ferrets; Helicobacter Infections; Male; Methylnitronitrosoguanidine; Proliferating Cell Nuclear Antigen; Stomach

N-Methyl-N-nitro-N'-nitrosoguanidine (MNNG) is a gastric carcinogen in several animal species and has been used in a number of systems to dissect the co-carcinogenic potential of various compounds in the induction of gastric adenocarcinoma. Recent epidemiological evidence suggests that Helicobacter pylori may play a role as a co-carcinogen in the etiology of this tumor in humans and we have been interested in developing an animal model to study this possibility. A related organism, H. mustelae, naturally colonizes the ferret stomach and causes persistent chronic gastritis. The pathology elicited by H. mustelae in ferrets has many similarities with the human disease including different stages of multifocal atrophic gastritis which underlie the gastric ulcer and gastric carcinoma syndrome. There is little evidence, however, demonstrating the susceptibility of ferrets toward chemical carcinogenesis. We have consequently undertaken a study to ascertain whether 10 6-month-old female ferrets given a single oral dose of MNNG (50-100 mg/kg) would develop adenocarcinoma of the stomach. Five age-matched unmanipulated control animals were included for comparative purposes. All 15 ferrets were infected with H. mustelae. Nine of 10 ferrets dosed with MNNG developed gastric adenocarcinoma (29-55 months after dosing), while none of the five historical control ferrets examined an average of 63 months after the initiation of the study developed gastric tumors. By comparison, we have not observed gastric adenocarcinoma, nor has it been reported, in > 10 years of observation of untreated ferrets naturally infected with H. mustelae. The H. mustelae-infected ferret, with demonstrated susceptibility to a gastric carcinogen, plus the recent availability of specific pathogen-free ferrets, should now allow longitudinal studies in vivo to probe the role of Helicobacter in the development of gastric cancer.

Topics: Adenocarcinoma; Animals; Biopsy; Cocarcinogenesis; Disease Models, Animal; Female; Ferrets; Gastritis; Helicobacter Infections; Longitudinal Studies; Methylnitronitrosoguanidine; Pyloric Antrum; Stomach; Stomach Neoplasms