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Background/aim: Recently, it has been shown that serine proteases derived from microorganisms stimulate epithelial cells to produce inflammatory mediators through protease-activated receptor (PAR). We investigated the involvement of PAR2 in the interleukin (IL)-8 production by Helicobacter pylori-infected gastric epithelial cells., Methods and Results: Human gastric epithelial cells, MKN45 cells, were used. The expression of PAR2 was assessed by real-time PCR and immunocytochemistry, and IL-8 protein was measured by an enzyme-linked immunosorbent assay. PAR2 mRNA and protein were constitutively expressed on unstimulated MKN45 cells. The treatment of cells with H. pylori resulted in a significant increase in PAR2 expression. In addition, trypsin (a natural PAR2 agonist), SLIGKV amide (a synthetic PAR2 agonist), H. pylori live bacteria or H. pylori culture supernatant significantly induced IL-8 production from MKN45 cells. H. pylori-induced IL-8 production was inhibited by nafamostat mesilate (a serine protease inhibitor), neutralizing antibody to PAR2 and in PAR2-deficient cells treated with siRNA., Conclusions: These results reveal that H. pylori-derived protease activates gastric epithelial cells to produce inflammatory cytokines through PAR2, suggesting an important role for PAR2 in the modulation of gastric inflammation associated with H. pylori.

Y-754, a novel benzimidazole compound, was investigated for in vitro and in vivo antibacterial activity. Unlike amoxicillin, clarithromycin, and metronidazole, the compound had no activity against common aerobic and anaerobic bacteria other than Helicobacter pylori. The minimum inhibitory concentration of Y-754 against H. pylori, at 0.025 microg/ml, was nearly equal to that of amoxicillin and clarithromycin. The respective concentrations of Y-754, amoxicillin, clarithromycin, and metronidazole required to inhibit 90% of 39 isolates of H. pylori were 0.05, 0.39, 6.25, and 25 microg/ml, indicating the potent activity of Y-754, including activity against clarithromycin- and metronidazole-resistant strains. The anti-H. pylori activity of Y-754 was potent even at pH 5.5 and was bactericidal at concentrations of 0.1 microg/ml and above. Exposure of H. pylori to Y-754 did not result in the induction of drug-resistant mutation. Oral administration (10 mg/kg twice a day for 7 days) to Mongolian gerbils infected with strain ATCC 43504 demonstrated that Y-754 was effective in H. pylori eradication and that its eradication efficacy increased in line with the progress of damage to the gastric mucosa caused by H. pylori infection. Y-754 was also efficacious in the treatment of infection by the clarithromycin-resistant strain OIT-36. The results obtained lead to the expectation that the new benzimidazole Y-754 will, in the near future, be used for H. pylori eradication therapy in peptic ulcer patients.

Y-904 is a new fluoroquinolone with a broad antimicrobial spectrum. In particular, it has anti- Helicobacter pylori activity superior to that of existing fluoroquinolones. In the present study it was examined for its in vitro antibacterial activity against 51 clinical isolates of H. pylori, including clarithromycin- and metronidazole-resistant strains. The minimum inhibitory concentration of Y-904 at which 90% of isolates were inhibited was close to that of amoxicillin and clarithromycin and lower than that of levofloxacin and metronidazole (0.1, 0.1, 0.2, 3.13, and 12.5 micrograms/ml, respectively). Y-904 showed equally strong activity at pH 5.5 as at pH 7.0. At 10 times the minimum inhibitory concentration, Y-904 decreased the viable count of H. pylori to below 10(-5) within 2 h after exposure. No significant change in the minimum inhibitory concentration was observed when H. pylori, Staphylococcus aureus, and Escherichia coli were successively subcultured in medium containing subinhibitory concentrations of Y-904. Y-904 also strongly inhibited the supercoiling activity of DNA gyrase from H. pylori ATCC43504 (IC(50), 1.48 micrograms/ml). A study of Y-904 treatment in H. pylori-infected Mongolian gerbils using twice-daily oral administration for 7 days demonstrated that the complete clearance dose of Y-904 was 1 mg/kg and that its potency was around 10, 30, and 30 times that of amoxicillin, clarithromycin, and levofloxacin, respectively. These results indicate that Y-904 is a promising candidate for the eradication of H. pylori infection.

Background: Helicobacter pylori infection and non-steroidal anti-inflammatory drugs are two major causes of gastric ulceration but interactions between H pylori and these drugs in gastric mucosal injury are unclear., Aims: We studied the influence of experimental H pylori infection on gastric mucosal injury induced by aspirin., Subjects: Male Mongolian gerbils free of specific pathogens were used., Methods: H pylori ATCC43504 culture broth was administered by oral gavage at seven weeks of age. After three weeks, acidified aspirin (400 mg/kg) was administered orally, and three hours later the total area of gastric erosions, myeloperoxidase (MPO) activity (an index of neutrophil accumulation), thiobarbituric acid reactive substances (TBARS, an index of lipid peroxidation), and KC/GRO (a chemoattractive cytokine in rodents) were measured in gastric mucosa. To determine the role of neutrophils in these circumstances, antigerbil neutrophil rabbit serum (ANS) was administered to some animals 18 hours before aspirin., Results: Aspirin caused more extensive haemorrhagic erosions (33.1 (12.3) mm2) associated with greater MPO activity (1887.7 (598.5) microU/mg protein) and TBARS (0.33 (0.14) nmol/mg protein) and KC/GRO concentrations (28.3 (9.5) pg/mg protein) in infected than in uninfected gerbils (13.7 (2.3); 204.0 (68.9); 0.12 (0.06); 3.1 (0.8), respectively) Pretreatment with ANS inhibited the increases in gastric erosions, MPO activity, and TBARS but not KC/GRO concentration. The reduction in aspirin induced mucosal injury by administration of ANS was much greater in H pylori infected animals (65%) than in uninfected animals (31%)., Conclusions: H pylori infection potentiates aspirin induced gastric mucosal injury by mechanisms that include accumulation of activated neutrophils.

Background: In this study, to clarify whether Helicobacter pylori eradication alters the course of the development of gastric mucosal changes in the stomach, we examined the long-term effects of H. pylori eradication on H. pylori-inoculated gerbils., Methods: A total of 40 H. pylori-inoculated gerbils were randomized and subjected, at 22 months after inoculation, to eradication treatment with dual therapy of omeprazole plus clarithromycin, or with therapy with a novel quinolone compound, Y-34867, alone. The animals were killed at the start of administration (control group) or at 8 months after the completion of therapy (vehicle or eradication-treatment groups)., Results: Severe histopathological changes in the gastric mucosa were observed in all H. pylori-inoculated gerbils at the start of administration. At 8 months after completion of therapy, the frequency of gastritis, erosion, intestinal metaplasia, and gastric carcinoid in the eradication therapy groups was markedly reduced compared with that in the control and vehicle groups. Values for anti- H. pylori IgG titer, bacterial counts, and gastrin also decreased significantly., Conclusions: These results suggest that H. pylori eradication may have had a therapeutic effect not only on gastritis, erosion, and gastric ulcer but also on glandular atrophy, intestinal metaplasia, and gastric carcinoid.

Helicobacter pylori is recognized to possess a number of virulence factors. We investigated the role of motility, vacuolating cytotoxin, and urease in gastric colonization by H. pylori. Mongolian gerbils (SPF, 7 weeks old) were challenged orally with a single administration of a 24-h culture broth of H. pylori and then were killed 6 and 26 weeks after challenge. Gastric colonization, severe gastritis, ulceration, and high levels of serum anti-H. pylori immunoglobulin G were observed in the gerbils challenged with strains motile in the semisolid medium (ATCC43504, HPY-127, HPY-204), but not in gerbils challenged with strains nonmotile in the medium (ATCC49503, HPY-205, HPY-206). Only strains ATCC43504, ATCC49503, HPY-204, and HPY-206 had vacuolating cytotoxin activity against HeLa and Vero cells. Thus, motile strains were able to colonize regardless of their vacuolating cytotoxin activities, and vacuolating cytotoxin was not associated with epithelial damage in the gastric mucosa. Furthermore, the phenotypic variants of strains with the ability to colonize that lacked either motility or urease activity lost their ability to colonize. In conclusion, motility and urease activity, but not vacuolating cytotoxin activity, are essential for gastric colonization by H. pylori in Mongolian gerbils.

A series of the titled compounds was synthesized and tested for anti-Helicobacter pylori activities. We discovered Y-34867 having the most potent activity against Helicobacter pylori among the quinolones tested along with high photostability. Furthermore, Y-34867 showed an excellent therapeutic effect in the experimental Helicobacter pylori infected Mongolian gerbil model.

Mongolian gerbils are a laboratory host for gastric colonization with Helicobacter pylori, showing gastritis followed by typical gastric ulcer after infection with H. pylori. In such gerbils, we evaluated combined therapies of amoxicillin (AMPC) and clarithromycin (CAM) as antibiotics, and omeprazole (OPZ) as a H+/K+ adenosine triphosphatase (ATPase) inhibitor. The gerbils were orally inoculated with 2 x 10(8) bacilli of H. pylori ATCC 43504. Four weeks after inoculation, the infected gerbils were orally treated singly with OPZ, AMPC, and CAM, and their insufficient efficacy on bacterial clearance was confirmed by a polymerase chain reaction technique, and by a culture method. In contrast, combined therapy of OPZ plus either AMPC or CAM showed significant bacterial clearance, demonstrating the efficacy of this combined therapy in the gerbil model. Mongolian gerbils are suggested to be useful for the pharmacological evaluation of anti-H. pylori compounds.

An animal model of Helicobacter pylori infection was obtained with Mongolian gerbils. Culture broth of H. pylori ATCC 43504 was orally administered to the gerbils. Animals were killed 1, 7, 14, 21, and 42 days after the oral inoculation and the stomachs were excised. Colonization of H. pylori was maintained in the stomachs of all animals throughout the study period of up to 42 days. On microscopic examination after immunological and hematoxylin and eosin staining, the organisms were detected in the mucus layer of the gastric epithelium. All gerbils exhibited a slowly progressive but typical gastritis, showing superficial erosion with increasing numbers of infiltrating neutrophils and mononuclear cells. Forty-two days after the inoculation, lymph follicles were detected in the gastric submucosa. These features are similar to the manifestations of H. pylori infection in humans and, accordingly, this model could be of value for studying H. pylori pathogenicity and for research into agents for the treatment of H. pylori infection in humans.

Recent international consensus statements have concluded that Helicobacter pylori is a causal factor in peptic ulcer disease and a Group 1 carcinogen in humans, and that all patients with peptic ulcer associated with H. pylori infection should receive eradication therapy. There are marked differences in the presentation of peptic ulcer disease between Japanese patients and those from other countries, however, and thus a committee of the Japanese Society of Gastroenterology has been set up to develop guidelines for clinical trials in patients with gastric or duodenal ulcers associated with H. pylori. According to these guidelines, eradication therapy should normally consist of dual therapy with a proton pump inhibitor, such as omeprazole, and an antibiotic; a nitroimidazole can be added, however, if necessary. The diagnosis of H. pylori should be made on the basis of a positive culture of the organism or histological examination of gastric biopsies, together with a positive urease test or 13C-urea breath test. Eradication should be confirmed by the same means 4-6 weeks after treatment. Other research is investigating the relationship between H. pylori and gastric cancer, an important issue in view of the high incidence of this condition in Japan. There is evidence that the Mongolian gerbil may be a useful animal model to investigate this question.

A Mongolian gerbil model was used to clarify whether long-term colonization by Helicobacter pylori is an important risk factor for the development of gastric cancer. Fifty-nine gerbils (3 controls and 56 gerbils inoculated with H. pylori) were killed at various times (average, 23 months) more than 12 months after H. pylori inoculation. In the H. pylori-inoculated group, poorly differentiated adenocarcinoma was observed in the pylorus of 1 gerbil, and carcinoid was observed in the fundus of the stomach in 18 gerbils. No lesions were found in the stomachs of the 3 control gerbils. The results imply that long-term colonization by H. pylori is an important risk factor for the development of gastric adenocarcinoma and carcinoid. [ABSTRACT FROM AUTHOR]