Chronic Helicobacter pylori infections induce gastric mutations in mice

doi:10.1016/S0016-5085(03)00266-X

Gastroenterology

Volume 124, Issue 5, May 2003, Pages 1408-1419

https://doi.org/10.1016/S0016-5085(03)00266-X Get rights and content

Abstract

Background & Aims:

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

Methods:

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

Results:

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

Conclusions:

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

Section snippets

Animals

Six-week-old specific pathogen-free C57BL/6 male mice carrying the λ lacI transgene (Big Blue transgenic mice) were purchased from Stratagene (La Jolla, CA). Animals were housed in microisolators in polycarbonate cages. Food and water were supplied ad libitum. Standard diet and high-salt diet (NaCl 0.75% and NaCl 7.5%, respectively) were purchased from SAFE (Epinay/Orge, France). Animals were acclimatized for 1 week before inoculation.

The experiments reported here were approved in advance by

Assessment of infections by serologic analyses

None of the control mice, intragastrically inoculated with peptone trypsin broth without Helicobacter, were seropositive for Helicobacter at the time of death. In both H. pylori SS1- and H. felis CS1-inoculated mice, the H. pylori or H. felis antigen-specific antibody responses rapidly increased for the first 3 months after infection and remained stable thereafter (Figure 1). Agreement of 86% was found with the infection status analyzed by Warthin-Starry staining (Figure 2).

Inflammatory response induced by H. pylori infections

Macroscopically

Discussion

DNA-adduct formation and the resulting genetic changes are key events in carcinogenesis. We investigated whether H. pylori infection, which stimulates host immune responses and causes inflammation, also has genotoxic effects, including DNA damage and mutation events. Any such direct mutagenic effect would explain the association between this bacterial infection and gastric carcinogenesis. Using Big Blue mice, we defined experimental conditions for measuring the mutagenic effect of Helicobacter

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In gastritis patients, reflectance modifications were significant in near-infrared spectrum, with a decrease between 610 and 725 nm and an increase between 750 and 840 nm. Autofluorescence was also modified, showing variations around 550 nm of emission. In H. pylori infected mice developing gastric inflammatory lesions, we observed significant reflectance modifications 18 months after infection, with increased intensity between 617 and 672 nm. Autofluorescence was significantly modified after 1, 3 and 6 months around 550 and 630 nm. Both in human and in mouse, these reflectance data can be considered as biomarkers and accurately predicted inflammatory state.
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View all citing articles on Scopus

^☆: Supported by the Institut Pasteur (Paris) as a Transversal Research Program (PTR).

¹: This report is dedicated to the memory of Prof. Maurice Hofnung.

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Chronic Helicobacter pylori infections induce gastric mutations in mice1 ☆,

Abstract

Background & Aims:

Methods:

Results:

Conclusions:

Section snippets

Animals

Assessment of infections by serologic analyses

Inflammatory response induced by H. pylori infections

Discussion

Gastroenterology

Gastroenterology

Gastroenterology

Gastroenterology

Gastroenterology

Mutat Res

Gastroenterology

Gastroenterology

Gastroenterology

FEBS Lett

J Biol Chem

Mutat Res

Is gastric carcinoma an infectious disease?

N Engl J Med

An international association between Helicobacter pylori and risk of gastric cancer

Lancet

Helicobacter pylori infection and the risk of gastric carcinoma

N Engl J Med

Helicobacter pylori infection and gastric lymphoma

N Engl J Med

Helicobacter pylori infection and the development of gastric cancer

N Engl J Med

Human gastric carcinogenesisa multistep and multifactorial process. First American Cancer Society Award Lecture on Cancer Epidemiology and Prevention

Cancer Res

Gastric cancer

Oxidative DNA damage accumulation in gastric carcinogenesis

Gut

Helicobacter pylori causes DNA damage in gastric epithelial cells

Carcinogenesis

Nitric oxide in gastrointestinal epithelial cell carcinogenesislinking inflammation to oncogenesis

Am J Physiol

Inducible nitric oxide synthase, nitrotyrosine, and apoptosis in Helicobacter pylori gastritiseffect of antibiotics and antioxidants

Cancer Res

Inducible nitric oxide synthase, antioxydant enzymes and Helicobacter pylori infection in gastritis and gastric precancerous lesions in humans

Eur J Cancer Prev

Interleukin-1 polymorphisms associated with increased risk of gastric cancer

Nature

Salt and gastrointestinal cancer

Nutr Cancer

Helicobacter pylori, dietary factors, and atrophic gastritis in five Japanese populations with different gastric cancer mortality

Cancer Causes Control

Dietary salt, nitrate and stomach cancer mortality in 24 countries

Int J Epidemiol

High-salt diet induces gastric epithelial hyperplasia and parietal cell loss, and enhances Helicobacter pylori colonization in C57BL/6 mice

Cancer Res

Outbred mice with long-term Helicobacter felis infection develop both gastric lymphoid tissue and glandular hyperplastic lesions

J Pathol

Chronic Helicobacter pylori infections induce gastric mutations in mice¹ ☆,