Helicobacter pylori-Infected Japanese Monkeys

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

BACKGROUND

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSIONS

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

A short-term eradication therapy for Helicobacter pylori acute gastritis

BACKGROUND AND AIMS

Acute gastritis, caused by an initial infection of Helicobacter pylori (H. pylori), may resolve spontaneously, but the infection sometimes becomes chronic. We examined the efficacy of a short-term H. pylori eradication therapy on acute gastritis.

METHODS

Among the 15 patients with hemorrhagic acute gastritis who were randomly allocated to group A (eradication therapy) or group B (Lansoprazole, LPZ), 10 of them started to receive treatment within 1 day after the disease onset. The other five patients began the eradication therapy 4-6 days after disease onset (group C). Eradication therapy consisted of a daily oral administration of each of 30 mg lansoprazole (LPZ), once a day; 400 mg clarithromycin, twice a day; 1000 mg amoxicillin, twice a day; and 300 mg rebamipide, three times a day, for one week. If the endoscopy was normal, medication was stopped for the following 4 weeks before gastric endoscopy was performed again in order to assess H. pylori eradication.

RESULTS

All group A patients were cured after the 1-week treatment and therefore, they became H. pylori negative. Group B and C patients had erosions or ulcers after the 1-week treatment and so received an additional 3-week administration of LPZ. Four weeks later, their gastritis was cured and except for one group B patient, they became H. pylori-negative.

CONCLUSION

In patients with acute gastritis, caused by an initial H. pylori infection, eradication therapy was efficacious in achieving early healing. This therapy should be started as soon as possible after disease onset.

p53 expression in gastric mucosa with Helicobacter pylori infection

Expression of p53 was examined immunohistochemically in the Japanese monkey model with Helicobacter pylori infection of the gastric mucosa to investigate the association between H. pylori infection and gastric carcinogenesis for a period of 4 years. In the course of these observations, from 3 years after H. pylori inoculation, nuclear staining for p53 was seen in the glandular cells of the mucosa infected with H. pylori, especially in the neck region of the glands. There was a gradual increase in the number of immunopositive cases among the infected animals. Three years after inoculation, three out of six cases, and 4 years after inoculation, four out of six cases exhibited positive staining for p53. Before inoculation, and up to 2 years after inoculation, the infected group showed no immunoreaction for p53. The non-infected group likewise displayed no immunostaining for p53 through 4 years of observation. These results suggest that p53 alterations occur in the H. pylori-infected gastric mucosa and that H. pylori infection may play an important role in gastric carcinogenesis.