Gastric epithelial cell proliferation and apoptosis in Helicobacter pylori-infected mice

GRB7-mediated enhancement of cell malignant characteristics induced by Helicobacter pylori infection

Growth factor receptor bound protein 7 (GRB7) is reportedly upregulated in human gastric cancer (GC), which is closely associated with tumor progression and prognosis. However, the mechanism underlying its dysregulation in GC remains poorly understood. In this study, we found that GRB7 overexpression was associated with Helicobacter pylori (H. pylori) infection. GC cells (AGS and MGC-803) infection assays revealed that this upregulation was mediated by the transcription factor STAT3, and activation of STAT3 by H. pylori promoted GRB7 expression in infected GC cells. Moreover, CagA, the key virulence factor of H. pylori, was found involved in STAT3-mediated GRB7 overexpression. The overexpressed GRB7 further promoted GC cell proliferation, migration, and invasion by activating ERK signaling. Mice infection was further used to investigate the action of GRB7. In H. pylori infection, GRB7 expression in mice gastric mucosa was elevated, and higher STAT3 and ERK activation were also detected. These results revealed GRB7-mediated pathogenesis in H. pylori infection, in which H. pylori activates STAT3, leading to increased GRB7 expression, then promotes activation of the ERK signal, and finally enhances malignant properties of infected cells. Our findings elucidate the role of GRB7 in H. pylori-induced gastric disorders, offering new prospects for the treatment and prevention of H. pylori-associated gastric carcinogenesis by targeting GRB7.

Mitochondrial DNA Haplogroup Related to the Prevalence of Helicobacter pylori

Mitochondria are essential organelles that are not only responsible for energy production but are also involved in cell metabolism, calcium homeostasis, and apoptosis. Targeting mitochondria is a key strategy for bacteria to subvert host cells' physiology and promote infection. Helicobacter (H.) pylori targets mitochondria directly. However, mitochondrial genome (mtDNA) polymorphism (haplogroup) is not yet considered an important factor for H. pylori infection. Here, we clarified the association of mitochondrial haplogroups with H. pylori prevalence and the ability to perform damage. Seven mtDNA haplogroups were identified among 28 H. pylori-positive subjects. Haplogroup B was present at a higher frequency and haplotype D at a lower one in the H. pylori population than in that of the H. pylori-negative one. The fibroblasts carrying high-frequency haplogroup displayed a higher apoptotic rate and diminished mitochondrial respiration following H. pylori infection. mtDNA mutations were accumulated more in the H. pylori-positive population than in that of the H. pylori-negative one in old age. Among the mutations, 57% were located in RNA genes or nonsynonymous protein-coding regions in the H. pylori-positive population, while 35% were in the H. pylori-negative one. We concluded that gastric disease caused by Helicobacter virulence could be associated with haplogroups and mtDNA mutations.

Histomorphological Characteristics and Pathological Types of Hyperproliferation of Gastric Surface Epithelial Cells

Objective

To investigate the histomorphological characteristics and pathological types of hyperproliferation of gastric surface epithelial cells.

Methods

Hematoxylin and Eosin, Periodic acid–Schiff, and immunohistochemical staining were performed on biopsy specimens obtained from 723 patients with hyperproliferation of gastric surface epithelial cells and/or hyperplasia of gastric pits. Follow-up gastroscopic reexaminations were performed on 475 patients included. Improvement probability was analyzed using Kaplan-Meyer as well as Cox proportional hazards models.

Results

Seven different histomorphologies and clinicopathologies of hyperproliferation of gastric surface epithelial cells were identified: (1) common hyperplasia of gastric epithelial cells, which was characterized by focal glandular epithelial hyperplasia of gastric pits with chronic inflammation; (2) drug-induced hyperplasia of gastric epithelial cells, which was characterized by increased hyperplasia of gastric pits and cells arranged in a monolayer; (3) Helicobacter pylori (Hp) infection-induced hyperplasia of gastric epithelial cells, which was characterized by the disappearance of oval, spherical, and bounded membrane-enclosed mucus-containing granules in the cytoplasm and on the nucleus together with cytoplasmic swelling and vacuolation; (4) metaplastic hyperplasia of gastric epithelial cells, which was characterized by the coexistence of intestinal metaplastic cells with hyperplastic gastric epithelial cells; (5) atrophic hyperplasia of gastric epithelial cells, which was characterized by the mucosal atrophy accompanied with hyperplasia of gastric pits; (6) low-grade neoplasia of epithelial cells, which was characterized by the mild to moderate dysplasia of gastric epithelial cells; and (7) high-grade neoplasia of epithelial cells, which was characterized by the evident dysplasia of hyperplastic epithelial cells and losses of cell polarity. The different pathological types are associated with different improvement probabilities.

Conclusions

This study demonstrated the histomorphological characteristics and pathological types, which might guide clinicians to track malignant cell transformation, perform precise treatment, predict the clinical prognosis, and control the development of gastric cancer.

The Expression of Murine Double Minute 2 (MDM2) on Helicobacter pylori-Infected Intestinal Metaplasia and Gastric Cancer

The overexpression of murine double minute 2 (MDM2) is found in several human tumors, and increased expression of MDM2 inactivates the apoptotic and cell cycle arrest function of p53. Interleukin-16 (IL-16) is a pleiotrophic cytokine and the properties of IL-16 suggest that it involve in the pathophysiological process of chronic inflammatory diseases. In this study, we investigated the expression of MDM2 in intestinal metaplasia and gastric cancer as well as the effect of H. pylori infection and IL-16 on epithelial cell proliferation and MDM2 expression in gastric cells in vitro. The expression of MDM2 on gastric biopsies was studied immunohistochemistry. AGS cells were incubated with a combination of IL-16 and Helicobacter pylori (H. pylori). Gastric epithelial cell proliferation was studied by BrdU uptake and the expressions of MDM2 were studied by ELISA. There was no significant difference on the expression of MDM2 between with and without H. pylori infected chronic gastritis. In H. pylori infected gastric mucosa; the MDM2 expression was higher on intestinal metaplasia and gastric cancer than chronic gastritis. IL-16 administration was increased MDM2 expression and cell proliferation on AGS cells, which was decreased by H. pylori infection. In conclusion, the expression of MDM2 in long-term H. pylori infected gastric mucosa may indicate a risk for carcinogenesis. IL-16 secretion in H. pylori infected mucosa is one of the factors for gastric cancer. The expression of MDM2 on mucosa can be a mediator for gastric cancer.

Green Tea Polyphenols Reduce Gastric Epithelial Cell Proliferation and Apoptosis Stimulated by Helicobacter pylori Infection

Recently the finding of gastric cancer in Helicobacter pylori (H. pylori)-infected mouse models was reported. Studies of humans and animal models have shown that H. pylori infection stimulates gastric epithelial cell proliferation and apoptosis. Polyphenols contained in green tea and related compounds were reported to have a variety anti-tumor effects and bactericidal properties. We studied the effect of green tea polyphenols on gastric cell proliferation and apoptosis in an H. pylori-infected mouse model. This model was prepared by inoculating Balb/c mice with 10(8) cfu of H. pylori (NCTC 11637 strain) by gavage. Beginning 18 weeks after inoculation, 0.5% polyphenols were given in drinking water every day for 2 weeks. Mice were sacrificed 1 h after bromodeoxyuridine (BrdU) was given i.p. for preparation of paraffin-embedded specimens. Cell proliferation and apoptosis were examined by the avidin-biotin complex method using anti-BrdU antibody and the TUNEL method, respectively. H. pylori infection resulted in increased BrdU-labeled cells in both the antrum and the bodies. Administration of polyphenols suppressed this increased proliferation. H. pylori infection increased apoptotic cells in both the antrum and the corpus in comparison with controls. This increase was not seen in H. pylori-infected mice given polyphenols. We conclude the administration with polyphenols might suppress gastric carcinogenesis that is in part related to H. pylori infection.

Gene-expression profiles in gastric epithelial cells stimulated with spiral and coccoid Helicobacter pylori

Human gastric epithelial immortalized GES-1 cells were infected with spiral and coccoid Helicobacter pylori. Scanning electron microscopy was used to determine the ability of the two forms of H. pylori to adhere to GES-1 cells. GES-1 cell apoptosis induced by coccoid and spiral H. pylori was analysed using flow cytometry. A cDNA microarray for 22,000 human genes was used to identify the gene-expression differences in GES-1 cells infected with the two forms of H. pylori, and the gene expression identified by the cDNA microarray was confirmed by RT-PCR. Scanning electron microscope observation showed that both coccoid and spiral bacteria can adhere to GES-1 cells. After 4 h infection, apoptosis induction was 27.4% for spiral-form infection and 10.2% for coccoid-form infection. Of 268 differentially expressed genes identified by cDNA microarray, 166 showed higher expression with the spiral H. pylori infection than with the coccoid H. pylori infection. To the best of the authors' knowledge, this is the first report that GES-1 cells infected with spiral H. pylori have higher expression of cxcl10, ccl11, ccl5, groalpha, TLR5, ATF3, fos, fosl2, gadd45a and myc. The cells infected with coccoid H. pylori had higher expression of survivin. The global profile of gene expression in GES-1 cells infected with coccoid and spiral H. pylori is described for the first time.

Infection with Helicobacter pylori affects all major secretory cell populations in the human antrum

We have investigated how gastric H. pylori infection affects antrum secretory cell types by studying the expression of secretory proteins in antrum epithelium. Antrum biopsy specimens were prospectively collected from 102 individuals (49 H. pylori-infected). Immunohistochemistry was performed for secretory mucins (MUC5AC, MUC5B, MUC6), Trefoil factor family (TFF)-peptides (TFF1, TFF2), endocrine peptides (gastrin, chromogranin A), and proliferating cells (Ki-67). Protein expression was quantified morphometrically. H. pylori infection was significantly correlated to mucosal inflammation and to epithelial atrophy and proliferation. In H. pylori-infected patients the number of proliferating cells increased significantly, and the zone of proliferating cells shifted toward the surface epithelium of the antral glands. Infection was correlated with decreased MUC5AC, TFF1, and TFF2 expression and increased MUC6 and MUC5B expression. Endocrine cells expressing chromagranin A and gastrin shifted toward the surface epithelium of the antral glands in H. pylori-infected patients. H. pylori infection and concomitant inflammation induced increased epithelial proliferation and triggered coordinate deregulation of secretory cell populations in the antrum. In particular, infection led to a coordinated increase in cells expressing MUC6 and MUC5B at the expense of MUC5AC-producing cells.

Review article: How useful are the rodent animal models of gastric adenocarcinoma?

Gastric cancer is the second most common cause of cancer-related mortality world-wide. In most cases, it develops via the pre-malignant stages of atrophic gastritis, intestinal metaplasia and dysplasia, following Helicobacter pylori infection of susceptible individuals. A number of rodent models have recently provided valuable insights into the host, bacterial and environmental factors involved in gastric carcinogenesis. Wild-type rodents do not develop gastric adenocarcinoma, but early studies showed that the disease could be induced in several rodent species by chemical carcinogens. More recently, it has been demonstrated that gastric adenocarcinoma can be induced in Mongolian gerbils by H. pylori infection and in C57BL/6 mice by long-term H. felis infection. These models have allowed the importance of Helicobacter virulence genes, host factors, such as gender, strain and immune response, and environmental factors, such as dietary salt, to be explored. A number of transgenic mice with alterations in various pathways, including the immune response, gastrin biosynthesis, parietal cell development, growth factors and tumour suppressors, have also provided models of various stages of gastric carcinogenesis. One model that has proved to be particularly valuable is the hypergastrinaemic INS-GAS mouse, in which gastric carcinoma develops spontaneously in old animals, but the process is greatly accelerated by Helicobacter infection.

Effects of Ginkgo biloba extract on cytoprotective factors in rats with duodenal ulcer

AIM: To investigate the effects of Ginkgo biloba extract on cytoprotective factors in rats with duodenal ulcer.

METHODS: Sprague-Dawley rats were randomly divided into four groups: sham operation without ginkgo, sham operation with ginkgo, duodenal ulcer without ginkgo, and duodenal ulcer with ginkgo. Rats with duodenal ulcer were induced by 500 mL/L acetic acid. Rats with ginkgo were intravenously injected with Ginkgo biloba extract from the tail at a dose of 0.5 mg/(kg·d) for 7 and 14 days.

RESULTS: Pathological result showed that duodenal ulcer rats with ginkgo improved mucosal healing and inflammation compared with those without ginkgo after 7 d treatment. After 14 d treatment, duodenal ulcer rats with ginkgo significantly increased weight gain (34.0 ± 4.5 g versus 24.5 ± 9.5 g, P < 0.05) compared with those without ginkgo. Duodenal ulcer rats significantly increased cell proliferation (27.4 ± 4.0 and 27.8 ± 2.3 BrdU-labeled cells in duodenal ulcer rats with and without ginkgo versus 22.4 ± 3.5 and 20.8 ± 0.5 BrdU-labeled cells in sham operation rats with and without ginkgo, P < 0.05) compared with sham operation rats. Mucosal prostaglandin E₂ concentration significantly increased by 129% (P < 0.05) in duodenal ulcer rats with ginkgo compared with that in those without ginkgo. Duodenal ulcer rats without ginkgo significantly decreased superoxide dismutase activity in the duodenal mucosa and erythrocytes (19.4 ± 6.7 U/mg protein versus 38.1 ± 18.9 U/mg protein in the duodenal mucosa, and 4.87 ± 1.49 U/mg protein versus 7.78 ± 2.16 U/mg protein in erythrocytes, P < 0.05) compared with sham operation rats without ginkgo. However, duodenal ulcer rats with ginkgo significantly increased erythrocyte superoxide dismutase activity (8.22 ± 1.92 U/mg protein versus 4.87 ± 1.49 U/mg protein, P < 0.05) compared with those without ginkgo. Duodenal ulcer rats without ginkgo significantly increased plasma lipid peroxides (4.18 ± 1.12 μmol/mL versus 1.60 ± 1.10 μmol/mL and 1.80 ± 0.73 μmol/mL, P < 0.05) compared with sham operation rats without ginkgo and duodenal ulcer rats with ginkgo during the experimental period.

CONCLUSION: Ginkgo biloba extract can improve weight gain and mucosal healing in duodenal ulcer rats by the actions of cytoprotection and antioxidation.

Effect of Helicobacter pylori on apoptosis and apoptosis related genes in gastric cancer cells

BACKGROUND/AIMS

Helicobacter pylori induces the apoptosis of gastric epithelial cells in vivo and in vitro. However, the molecular mechanism has not been clarified. The aim of this study was to investigate the effect of H pylori on the apoptosis of gastric epithelial cells and the expression of apoptosis related genes in vitro.

METHODS

Human gastric adenocarcinoma SGC-7901 cells were co-cultured with a cytotoxic H pylori strain, NCTC 11637, at various densities ranging from 3.2 x 10(4) to 1.0 x 10(8) colony forming units (CFU)/ml for 48 hours. Apoptosis in gastric cells was determined by transmission electron microscopy, Hoechst 33258 fluorochrome staining, and flow cytometry. The expression of apoptosis related proteins, Bcl-2, Bax, and c-Myc, was measured by an immunohistochemical method, and c-Myc mRNA expression was determined by the reverse transcription-polymerase chain reaction.

RESULTS

Helicobacter pylori induces morphological changes typical of apoptosis. Both fluorochrome staining and flow cytometry showed that the apoptotic index began to increase when H pylori were at a density of > 1.6 x 10(4) CFU/ml, and in a density dependent manner (p < 0.01; one way ANOVA). The expression of the Bax and c-Myc proteins and of c-Myc mRNA was increased, whereas Bcl-2 expression was decreased after co-culture for 48 hours.

CONCLUSIONS

Helicobacter pylori induced apoptosis in gastric epithelial cells is mediated by altered expression of the products of the Bcl-2, Bax, and c-Myc genes.

Role of Helicobacter pylori in gastric carcinogenesis

Peptic ulcers and gastric malignancies are the two major complication of the course of Helicobacter pylori-associated chronic gastritis. Both gastric adenocarcinomas and MALT lymphomas occur in association with H. pylori infection, and studies support an etiological association. This article discusses the natural history of H. pylori-related gastric carcinogenesis and criteria to identify people susceptible to H. pylori infection-associated gastric cancer. It then reviews the molecular and genetic mechanisms underlying the malignant transformation of the gastric mucosa associated with H. pylori.