Effect of eradication of Helicobacter pylori on gastric epithelial cell proliferation

EGFR tyrosine kinase inhibitory peptide attenuates Helicobacter pylori-mediated hyper-proliferation in AGS enteric epithelial cells

Helicobacter pylori infection is one of the most critical causes of stomach cancer. The current study was conducted to explore the protective effects of an isolated active peptide H-P-6 (Pro-Gln-Pro-Lys-Val-Leu-Asp-Ser) from microbial hydrolysates of Chlamydomonas sp. against H. pylori-induced carcinogenesis. The peptide H-P-6 has effectively suppressed H. pylori-induced hyper-proliferation and migration of gastric epithelial cells (AGS). However, the peptide did not inhibit the viability of the bacteria or invasion into AGS cells. Therefore, the effect of the peptide on regulating H. pylori-induced molecular signaling was investigated. The results indicated that H. pylori activates the EGFR tyrosine kinase signaling and nuclear translocation of the β-catenin. The EGFR activation has led to the up-regulation of PI3K/Akt signaling pathway. Moreover, the nuclear translocation levels of β-catenin were significantly increased as a result of Akt mediated down-regulation of GSK3/β protein levels in the cytoplasm. Both of these consequences have resulted in increased expression of cell survival and migration related genes such as c-Myc, cyclin-D, MMP-2 and matrilysin. Interestingly, the isolated peptide potently inhibited H. pylori-mediated EGFR activation and thereby down-regulated the subsequent P13K/Akt signaling leading to β-catenin nuclear translocation. The effect of the peptide was confirmed with the use of EGFR tyrosine kinase inhibitor AG1487 and molecular docking studies. Collectively this study identifies a potent peptide which regulates the H. pylori-induced hyper-proliferation and migration of AGS cells at molecular level.

Upregulation of progranulin by Helicobacter pylori in human gastric epithelial cells via p38MAPK and MEK1/2 signaling pathway: role in epithelial cell proliferation and migration

Helicobacter pylori is a major human pathogen associated with gastric diseases such as chronic active gastritis, peptic ulcer, and gastric carcinoma. The growth factor progranulin (PGRN) is a secreted glycoprotein that functions as an important regulator of cell growth, migration, and transformation. We aimed to determine the molecular mechanisms by which H. pylori upregulates the expression of PGRN and the relationship between H. pylori infection and production of PGRN in controlling cell proliferation and migration. Levels of PGRN were examined in gastric tissues from patients and in vitro in gastric epithelial cells. Cell proliferation was measured by colony formation assay. Cell migration was monitored by wound healing migration assay. PGRN protein levels were increased in patients with gastritis and gastric cancer tissue. Infection of gastric epithelial cells with H. pylori significantly increased PGRN expression in a time-dependent manner. Blockade of the p38 and MEK1/2 pathway by inhibitor inhibited H. pylori-mediated PGRN upregulation. Activation of p38 and MEK1/2 pathway by H. pylori was also identified. Knockdown of PGRN attenuated the H. pylori-induced proliferative activity and migration of cancer cells. These findings suggest that the upregulation of PGRN in H. pylori-infected gastric epithelial cells may contribute to the carcinogenic process.

The specific linker phosphorylation of Smad2/3 indicates epithelial stem cells in stomach; particularly increasing in mucosae of Helicobacter-associated gastritis

BACKGROUND

The gastric corpus and antrum are believed to contain epithelial stem cells in the isthmus. However, the lack of useful markers has hindered studies of their origin. We explored whether Smad2/3, phosphorylated at specific linker threonine residues (pSmad2/3L-Thr), could serve as a marker for stem cells.

METHODS

Stomachs, small intestines, and colons from Helicobacter felis-infected and noninfected C57BL/6 mice were examined. Double immunofluorescent staining of pSmad2/3L-Thr with Ki67, cytokeratin 8, or doublecortin and calcium/calmodulin-dependent protein kinase-like-1 (DCAMKL1) was performed, and pSmad2/3L-Thr immunostaining-positive cells were counted. After immunofluorescent staining, we stained the same sections with hematoxylin-eosin and observed these cells under a light microscope.

RESULTS

In infected mice, pSmad2/3L-Thr immunostaining-positive cells were significantly increased in the corpus and antrum compared with those of noninfected mice (p < 0.0001). The number of Ki67 immunostaining-positive cells in the corpus and antrum of infected mice was also much greater than in the noninfected mice. Although pSmad2/3L-Thr immunostaining-positive cells were detected among the Ki67 cells, immunohistochemical co-localization of pSmad2/3L-Thr with Ki67 was never observed. pSmad2/3L-Thr immunostaining-positive cells showed immunohistochemical co-localization with cytokeratin 8, but some of them showed co-localization or adjacent localization with DCAMKL1 immunostaining-positive cells. Under a light microscope, pSmad2/3L-Thr immunostaining-positive cells indicated undifferentiated morphological features and were confirmed in the isthmus. In small intestines and colons, pSmad2/3L-Thr immunostaining-positive cells were detected in specific epithelial cells around crypt bases, where the respective putative stem cells are thought to exist.

CONCLUSIONS

We have identified the significant expression of pSmad2/3L-Thr in specific epithelial cells of the murine stomach and have suggested these cells to be epithelial stem cells.

Helicobacter pylori infection generates genetic instability in gastric cells

The discovery that Helicobacter pylori is associated with gastric cancer has led to numerous studies that investigate the mechanisms by which H. pylori induces carcinogenesis. Gastric cancer shows genetic instability both in nuclear and mitochondrial DNA, besides impairment of important DNA repair pathways. As such, this review highlights the consequences of H. pylori infection on the integrity of DNA in the host cells. By down-regulating major DNA repair pathways, H. pylori infection has the potential to generate mutations. In addition, H. pylori infection can induce direct changes on the DNA of the host, such as oxidative damage, methylation, chromosomal instability, microsatellite instability, and mutations. Interestingly, H. pylori infection generates genetic instability in nuclear and mitochondrial DNA. Based on the reviewed literature we conclude that H. pylori infection promotes gastric carcinogenesis by at least three different mechanisms: (1) a combination of increased endogenous DNA damage and decreased repair activities, (2) induction of mutations in the mitochondrial DNA, and (3) generation of a transient mutator phenotype that induces mutations in the nuclear genome.

Helicobacter pylori regulates cellular migration and apoptosis by activation of phosphatidylinositol 3-kinase signaling

Helicobacter pylori is the strongest identified risk factor for gastric adenocarcinoma. One H. pylori virulence constituent that augments cancer risk is the cag secretion system, which translocates CagA and peptidoglycan into host cells, eventuating in activation of signal transduction pathways. AKT is a target of phosphatidylinositol 3-kinase (PI3K) and is activated in gastric cancer, but the relationship between PI3K-AKT and H. pylori-induced cellular responses with carcinogenic potential remains unclear. We defined the molecular pathways mediating H. pylori-stimulated AKT activation and the biological consequences of these events in gastric epithelial cells. H. pylori enhanced PI3K-AKT signaling in a Src- and epidermal growth factor receptor-dependent manner, which was also mediated by a functional cag secretion system and peptidoglycan. PI3K activation attenuated apoptosis in response to infection and was required for H. pylori-induced cell migration. These results indicate that PI3K-AKT signaling regulates pathophysiologic responses to H. pylori that may lower the threshold for carcinogenesis.

Effects of H pylori infection on gap-junctional intercellular communication and proliferation of gastric epithelial cells in vitro

AIM: To explore the effects of H pylori infection on gap-junctional intercellular communication (GJIC) and proliferation of gastric epithelial cells in vitro.

METHODS: A human gastric epithelial cell line (SGC-7901) cultured on coverslips was exposed overnight to intact H pylori (CagA⁺ or CagA^- strains) and sonicated extracts, respectively. GJIC between the cells was detected by fluorescence redistribution after photobleaching (FRAP) technique. Proliferation of SGC cells was determined by methylthiazolyl tetrazolium (MTT) assay.

RESULTS: When compared with control in which cells were cultured with simple medium alone, both CagA⁺ and CagA^-H pylori isolates could inhibit GJIC (CagA⁺: F = 57.98, P < 0.01; CagA^-: F = 29.59, P < 0.01) and proliferation (CagA⁺: F = 42.65, P < 0.01; CagA^-: F = 58.14, P < 0.01) of SGC-7901 cells. Compared with CagA^- strains, CagA⁺H pylori more significantly down-regulated GJIC of gastric cells (intact H pylori: t = 13.86, P < 0.01; sonicated extracts: t = 11.87, P < 0.01) and inhibited proliferation gastric cells to a lesser extent in vitro (intact H pylori: t = 3.06, P < 0.05; sonicated extracts: t = 3.94, P < 0.01).

CONCLUSION: Compared with CagA^-H pylori strains, CagA⁺ strains down-regulate GJIC of gastric epithelial cells more significantly and inhibit proliferation of gastric cells to a lesser extent in vitro. H pylori, especially CagA⁺ strains, may play an important role in gastric carcinogenesis.

Helicobacter pylori eradication and associated changes in the gastric mucosa

Persistent Helicobacter pylori infection contributes towards the development of chronic gastritis. To clarify the changes in chronic gastritis as a precursor of gastric cancer secondary to H. pylori eradication is an important issue, as it has significant implications for reducing the risk of gastric cancer. Studies published to date, however, are far from consistent with regard to the morphologic changes reported following H. pylori eradication. Of these, some papers reported improvement in gastric atrophy or intestinal metaplasia, versus others reporting no improvement, with the majority of papers published after 2000 reporting improvement in these end points. The inconsistent results concerning the impact of H. pylori eradication on gastric atrophy could be due to the inconsistency of the diagnostic criteria employed for evaluation of the morphology, confounded by the difficulties involved in evaluating atrophic changes in the gastric mucosa. While adherence to the Updated Sydney System available for evaluation of gastritis is primarily required worldwide to ensure consistency in evaluating gastritis, long-term research into the morphologic changes associated with H. pylori eradication is also required to explore strategies for the prevention of gastric cancer with H. pylori eradication.

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.

Cellular stress-related protein expression in Helicobacter pylori-infected gastric epithelial AGS cells

Helicobacter pylori infection leads to gastroduodenal inflammation, peptic ulceration, and gastric carcinoma. Moreover, H. pylori may induce disease-specific protein expression in gastric epithelial cells. The present study was aimed at determining differentially expressed proteins in H. pylori-infected gastric epithelial AGS cells. AGS cells were treated with H. pylori at a bacterium/cell ratio of 300:1 for 12 h. Altered protein patterns as separated by two-dimensional electrophoresis using pH gradients of 4-7 were conclusively identified by matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS) analysis of the peptide digests. Four differentially expressed proteins, whose expression levels were increased by more than two-fold in H. pylori-infected cells, were analyzed. These proteins (14-3-3 protein alpha/beta, cullin homolog 3, alpha-enolase, ezrin) are known to be related to cell proliferation, cell adhesion, and carcinogenesis, and may be mediated by cellular stress, such as reactive oxygen species. In conclusion, the identification of these differentially expressed proteins provide valuable information for the understanding of the pathophysiologic mechanisms of H. pylori-induced gastric diseases, and may be useful as prognostic indices of H. pylori-related gastric disorders.

Helicobacter pylori and gastric diseases: a dangerous association

The bacterium Helicobacter pylori is linked to the appearance of several gastric diseases and in particular is associated with a progression to gastric cancer. Thistrun -1 bacterium colonizes the gastric mucosa directly interacting with epithelial cells. It is well known that H. pylori is associated with alterations in the gastric epithelial cell cycle, and apoptosis, higher levels of mononuclear and neutrophilic infiltrates, more severe atrophy and intestinal metaplasia. In last years, two mechanisms that interact with each other or not have been proposed: the hyperproliferation of gastric cells and oxidative damage of stomach mucosa. In particular, cell cycle alterations induce mitogenic signals and proto-oncogene expression that may trigger the development of cancer. Contemporary, H. pylori is able to induce polymorphonuclear and mononuclear cells that produce oxygen free radicals that could cause DNA damage to the adjacent cells leading to cancer development. Due to dangerous infection of this bacterium, the scientific community must point out its attention on the development of detection and prevention strategies.

Roles of Helicobacter pylori infection and cyclooxygenase-2 expression in gastric carcinogenesis

AIM: Cyclooxygenase (COX)-2 is over expressed in gastrointestinal neoplasm. Helicobacter pylori (H pylori) infection is causally linked to gastric cancer. However, the expression of COX-2 in various stages of H pylori-associated gastric carcinogenesis pathway has not been elucidated. Therefore, the aim of this study was to clarify the role of H pylori induced COX-2 expression during carcinogenesis in the stomach.

METHODS: Gastric biopsies from 138 subjects [30 cases of chronic superficial gastritis (CSG), 28 cases of gastric glandular atrophy (GA), 45 cases of gastric mucosal intestinal metaplasia (IM), 12 cases of moderate gastric epithelial dysplasia and 23 cases of gastric cancer] were enrolled. H pylori infection was assessed by a rapid urease test and histological examination (modified Giemsa staining). The expression of COX-1 and COX-2 in human gastric mucosa was detected by immunohistochemical staining.

RESULTS: H pylori infection rate was 64.3% in GA and 69.5% in gastric cancer, which was significantly higher than that (36.7%) in CSG (P < 0.05). The positive expression rates of COX-2 were 10.0%, 35.7%, 37.8%, 41.7% and 69.5% in CSG, GA, IM, dysplasia and gastric cancer, respectively. From CSG to GA, IM, dysplasia and finally to gastric cancer, expression of COX-2 showed an ascending tendency, whereas COX-1 expression did not change significantly in the gastric mucosa. The level of COX-2 expression in IM and dysplasia was significantly higher in H pylori-positive than in H pylori-negative subjects (P < 0.01).

CONCLUSION: COX-2 expression induced by H pylori infection is a relatively early event during carcinogenesis in the stomach.

Increased oxidative DNA damage, inducible nitric oxide synthase, nuclear factor κB expression and enhanced antiapoptosis-related proteins in Helicobacter pylori-infected non-cardiac gastric adenocarcinoma

AIM: Several epidemiological studies have demonstrated a close association between Helicobacter pylori (H Pylori) infection and non-cardiac carcinoma of the stomach. H pylori infection induces active inflammation with neutrophilic infiltrations as well as production of oxygen free radicals that can cause DNA damage. The DNA damage induced by oxygen free radicals could have very harmful consequences, leading to gene modifications that are potentially mutagenic and/or carcinogenic. The aims of the present study were to assess the effect of H pylori infection on the expression of inducible nitric oxidative synthase (iNOS) and the production of 8 -hydroxy-deoxyguanosine (8-OHdG), a sensitive marker of oxidative DNA injury in human gastric mucosa with and without tumor lesions, and to assess the possible factors affecting cell death signaling due to oxidative DNA damage.

METHODS: In this study, 40 gastric carcinoma specimens and adjacent specimens were obtained from surgical resection. We determined the level of 8-OHdG formation by HPLC-ECD, and the expression of iNOS and mechanism of cell death signaling [including nuclear factor-κB(NFκB), MEKK-1, Caspase 3, B Cell lymphomal leukemia-2 (Bcl-2), inhibitor of apoptosis protein (IAP ) and myeloid cell leukemia-1 (Mcl-1)] by Western-blot assay.

RESULTS: The concentrations of 8-OHdG, iNOS, NFκB, Mcl-1 and IAP were significantly higher in cancer tissues than in adjacent non-cancer tissues. In addition, significantly higher concentrations of 8-OHdG, iNOS, NFκB, Mcl-1 and IAP were detected in patients infected with H pylori compared with patients who were not infected with H pylori. Furthermore, 8-OHdG, iNOS, NFκB, Mcl-1 and IAP concentrations were significantly higher in stage 3 and 4 patients than in stage 1 and 2 patients.

CONCLUSION: Chronic H pylori infection induces iNOS expression and subsequent DNA damage as well as enhances anti-apoptosis signal transduction. This sequence of events supports the hypothesis that oxygen-free radical-mediated damage due to H pylori plays a pivotal role in the development of gastric carcinoma in patients with chronic gastritis.

Helicobacter pylori eradication treatment modulates epithelial cell proliferation and tissue content of hepatocyte growth factor in the gastric mucosa

BACKGROUND

Although Helicobacter pylori infection is now acknowledged as a major promoter of gastric cancer in humans, the carcinogenetic process of this effect has not been fully elucidated. Precancerous lesions such as intestinal metaplasia, enhanced proliferation of epithelial cells and elevated level of growth factors have been postulated to play a role.

AIM

To analyse a relationship between gastric mucosal proliferation, mucosal content of hepatocyte growth factor and prevalence of intestinal metaplasia before and after successful H. pylori eradication therapy.

METHODS

We evaluated 25 H. pylori-eradicated patients. At initial endoscopic examination, two biopsy tissue samples each were obtained from the antrum and great curvature of the corpus. Tissue content of hepatocyte growth factor and neutrophil myeloperoxidase were measured using an ELISA method, and histological assessment of intestinal metaplasia (haematoxylin and eosin) and proliferating cells (Ki-67 immunostaining) was performed. The patients were treated with a 1-week course of triple therapy. At 10 months after successful eradication, biochemical and histological assessments were repeated.

RESULTS

Among all patients (n = 25), no intestinal metaplasia was detected in the corpus mucosa, but was observed in 10 patients (40%) in the antrum. This prevalence ratio was not changed after eradication. A slight decrease in HGF content was demonstrated in both sites, but the level of antral hepatocyte growth factor was significantly decreased in patients with intestinal metaplasia but not in those without. Proliferative index (Ki-67 positive cells/epithelium) was decreased after eradication therapy in both sites. An increase in proliferative index was observed in the antrum with intestinal metaplasia compared with that without, which significantly decreased after eradication therapy.

CONCLUSIONS

H. pylori eradication therapy in the present study afforded an inhibitory effect on epithelial cell proliferation and on the mucosal content of HGF.

Amelioration of oxidative stress with ensuing inflammation contributes to chemoprevention of H. pylori-associated gastric carcinogenesis

The gastric inflammatory response provoked by Helicobacter pylori (H. pylori) consists of infiltrations by neutrophils, lymphocytes, and macrophages, resulting in varying degrees of epithelial cell damage. H. pylori-associated inflammation not only activates various oxidant-producing enzymes such as NADPH oxidase and inducible nitric oxide synthase, but also lowers the antioxidant ascorbic acid in the stomach. Reactive oxygen metabolites and nitrogen metabolites generated by these enzymes react with each other to generate new or more potent reactive species. The specific types of cellular damage resulting from reactive oxygen metabolites include lipid peroxidation, protein oxidation, and oxidative DNA damage. All of these oxidative products can result in biochemical changes leading to cancer. A positive association has been demonstrated between H. pylori infection and gastric adenocarcinoma with increased oxidative stress. Therefore, appropriate treatment to reduce oxidative stress would be expected to prevent subsequent gastric carcinogenesis through lessening of H. pylori-associated inflammation. This review will provide evidence that antiinflammatory regimens can decrease the development of tumors and the amelioration of gastric inflammation might lead to chemoprevention strategies by the attenuation of oxidative stress.

Prevention of gastric cancer by Helicobacter pylori eradication

The evidence supporting the important role of Helicobacter pylori causing gastric cancer is getting stronger. The mechanisms by which H. pylori can influence the progression to severe changes in the gastric mucosa are under investigation. An increased gastric epithelial cell proliferation has been observed in individuals infected with H. pylori. This lifelong increased cell turnover is deemed to be a major risk factor for increased mutational changes and may lead to the development of gastric cancer. Successful eradication of H. pylori infection induces the healing of the gastritis and a significant decrease in gastric epithelial cell proliferation. Nevertheless, it is right now unknown at which time the point of no return, meaning at which time an eradication therapy leads to a benefit for the individual to prevent gastric cancer, has been reached. Therefore the major question that arises is to whom an eradication therapy should be offered to prevent gastric cancer. A general elimination of the infection might be worthwhile, but seems to be unrealistic now because of the high prevalence of the infection and the missing of a vaccine. This review reflects possible mechanisms of gastric cancer development induced by chronic H. pylori infection and recent investigational trials for prevention of gastric cancer by H. pylori eradication therapy will be discussed.

Effects ofHelicobacter pylori infection on cell cycle progression and the expression of cell cycle regulatory proteins

Helicobacter pylori lives in the stomach lumen adhering and specifically interacting with gastric epithelial cells. H. pylori infection can cause a broad range of diseases. Although most infected individuals only develop a chronic inflammation of the stomach, some patients progress to chronic gastritis, duodenal ulceration, or, rarely, cancer. H. pylori is able to send and to receive signals from the gastric epithelium, allowing host and bacteria to become linked in a dynamic equilibrium. Several studies have demonstrated that H. pylori infection induces morphological changes of gastric epithelial cells other than cell proliferation, increase of mitosis and mutations. It has also been demonstrated that H. pylori may predispose to cancer by altering gastric epithelial cell turnover acting specifically on transcription factors. Although H. pylori is able to induce several host responses, it specifically perturbs the delicate balance of those factors that usually help to maintain cell homeostasis. The study of mechanisms of interaction between the bacterium and gastric cells will surely help to prevent the increase and diffusion of malignancies all over the world.

Helicobacter pylori strain-selective induction of matrix metalloproteinase-7 in vitro and within gastric mucosa

BACKGROUND AND AIMS

Helicobacter pylori strains that possess the cag pathogenicity island (cag(+)) augment the risk for distal gastric cancer. Matrix metalloproteinase (MMP)-7, an epithelial cell-derived MMP that is induced by bacterial contact, is overexpressed within human gastric adenocarcinoma specimens and enhances tumor formation in rodents. We determined whether H. pylori alters MMP-7 expression and investigated the molecular pathways required for these events.

METHODS

MMP-7 was detected in human gastric mucosa by immunohistochemistry and in H. pylori/AGS gastric epithelial cell coculture supernatants by Western analysis. AGS cells were cocultured with wild-type H. pylori, or isogenic cagA(-), cagE(-), or vacA(-) mutants, in the absence or presence of inhibitors of nuclear factor kappaB activation, p38, or extracellular signal-regulated kinase (ERK) mitogen-activated protein kinase.

RESULTS

H. pylori cag(+) strains increased MMP-7 expression in AGS cells 5-7-fold, whereas cag(-) isolates had no effect. Inactivation of cagE, but not cagA or vacA, completely attenuated induction of MMP-7, and inhibition of ERK 1/2 decreased MMP-7 production. In vivo, MMP-7 was expressed in gastric epithelial cells in specimens from 80% of cag(+)-colonized persons but in none of the cag(-) or uninfected subjects.

CONCLUSIONS

H. pylori cag(+) strains enhance levels of MMP-7 within inflamed mucosa. In vitro, cag(+) isolates selectively induce MMP-7, and this is dependent on activation of ERK 1/2 by specific components within the cag island. Differential induction of MMP-7 by H. pylori cag(+) isolates may explain in part the augmentation in gastric cancer risk associated with these strains.

Effect of cyclooxygenase-2 inhibition on human Helicobacter pylori gastritis: mechanisms underlying gastrointestinal safety and implications for cancer chemoprevention

Cyclooxygenase (COX)-2 expression and prostaglandin production is increased by Helicobacter pylori infection. Non-selective COX inhibitors reduce prostaglandins and mucosal proliferation in infected mucosa and may reduce gastric cancer risk, but ulceration precludes their use. COX-2 inhibitors cause fewer ulcers and may be chemopreventive. Physiological studies of COX-2 inhibitors in humans with H. pylori infection have not been performed.

AIM

To study the impact of COX-2 specific inhibition on gastric prostaglandin levels, H. pylori gastritis and proliferation.

METHODS

Twenty infected (eight males, 12 females; age 38 +/- 1.8) and six uninfected (four males, two females; age 36 +/- 3.5) healthy volunteers received rofecoxib 25 mg daily for 14 days. Endoscopic biopsies were evaluated for prostaglandin E2 (PGE2) content, gastritis and proliferation.

RESULTS

Before drug therapy, compared to uninfected, H. pylori-infected subjects had significantly higher: (a) gastric mucosal PGE2 (pg/mg tissue) in the gastric body and antrum, (b) H. pylori score in body and antrum and (c) mid-gland proliferation index in antrum and body. The COX-2 inhibitor did not significantly affect PGE2 levels, gastritis scores or proliferation indices in the body or antrum in the H. pylori-positive or -negative subjects.

CONCLUSION

The predominant source of increased gastric PGE2 in H. pylori infection appears to be COX-1-derived. In non-ulcerated H. pylori gastritis, COX-2 inhibition does not affect cellular proliferation. Rofecoxib's lack of effect on gastric prostaglandin levels and proliferation in H. pylori-infected mucosa may explain the absence of an increased ulcer risk among COX-2 inhibitor users with H. pylori infection. The lack of significant effect on intermediate biomarkers raises uncertainty regarding the potential of specific COX-2 inhibitors for chemoprevention of gastric cancer.

Improvement of gastric atrophy after Helicobacter pylori eradication therapy

BACKGROUND

It remains controversial whether gastric atrophy is reversible after Helicobacter pylori eradication therapy.

AIM

To clarify whether gastric atrophy improves after H. pylori eradication therapy using a histologic approach.

METHODS

Subjects were 87 H. pylori infection-cured patients (treatment group) and 29 continuously H. pylori-infected patients (control group). The subjects in the treatment and control groups were followed for 10-49 months (mean, 22 months) and 11-50 months (mean, 22 months), respectively. Biopsy specimens were obtained from the greater curvature of the antrum and corpus at the beginning and end of the observation period; histologic analyses of these specimens were performed for detection of activity, inflammation, atrophy, and intestinal metaplasia. Results were scored without any clinical information according to the Sydney system.

RESULTS

In the treatment group, the histologic score for atrophy was improved in the corpus but not in the antrum. Intestinal metaplasia was not improved in either the antrum or the corpus. There were no significant differences during the follow-up in gastric atrophy and intestinal metaplasia in the control group.

CONCLUSION

Gastric atrophy was improved in the corpus approximately 2 years after H. pylori eradication therapy.

Tumor necrosis factor alpha and apoptosis in Helicobacter pylori related progressive gastric damage: a possible mechanism of immune system involvement in epithelial turnover regulation

Helicobacter pylori (HP) related inflammation is mediated by tumour necrosis factor alpha (TNFalpha), which "in vitro" increases epithelial apoptosis in response to infection. In the early stages of HP gastritis, a raised epithelial apoptosis occurs; this phenomenon becomes less evident with progression towards intestinal metaplasia. Aim of our study was to analyze "in vivo" mucosal TNFalpha in relation to epithelial apoptosis in the progression of HP related histological damage. Antral biopsies from 20 HP positive patients were retrospectively studied: 10 with and 10 without intestinal metaplasia (IM and CG group respectively); samples of 10 dyspeptics with normal HP negative stomach (N) were used as control. The following parameters were evaluated by immunohistochemistry: 85 kDa caspase-cleaved fragment (p85) of human poly (ADP-ribose) polymerase (PARP) labelling index (LI) as marker of apoptosis and TNFalpha LI in stromal cells as marker of inflammatory response. Both epithelial apoptosis and mucosal TNFalpha expression were higher in chronic active gastritis compared to intestinal metaplasia and controls (PARP and TNFalpha LI: CG > IM > N; ANOVA & Student-Neumann-Keuls; p < 0.05 and p < 0.01, respectively). Pearson's coefficient showed a significant correlation between PARP and TNFalpha LI in IM and CG groups. Our data show that mucosal TNFalpha, similarly to what suggested "in vitro", may be related "in vivo" to epithelial apoptosis thus suggesting a possible mechanism for immune system involvement in the control of gastric epithelial turnover.

Mutant p53 expression and apoptotic activity of Helicobacter pylori positive and negative gastritis in correlation with the presence of intestinal metaplasia

BACKGROUND

Mutation of the p53 gene is detectable in most cases of gastric cancer, as it is the most common genetic alteration in human malignancies. It is also well documented that Helicobacter pylori infection plays an important role in gastric carcinogenesis. There is still no clarification, however, concerning how genetic instability influences the homeostasis of gastric epithelium. We have studied the effect of H. pylori infection on apoptosis of the antral epithelium in the presence/absence of intestinal metaplasia and the expression of the p53 oncoprotein. The relationship between these two processes is analysed.

METHODS

Antral biopsies were taken from 36 patients who underwent routine upper endoscopy (17 men, 19 women, mean age 61.0 years). The biopsies were fixed in formalin and embedded in paraffin. Patients were classified into two histological groups: (1) as chronic gastritis without intestinal metaplasia (n = 19), and (2) chronic gastritis with intestinal metaplasia (n = 17). An immunohistochemical method was used to detect the expression of p53 oncoprotein, and the terminal transferase mediated dUTP nick end-labelling (TUNEL) method was used to detect apoptotic cells.

RESULTS

In the absence of intestinal metaplasia, both the apoptotic index (0.0272 +/- 0.011 vs 0.0128 +/- 0.006) and expresssion of p53 (35.55 +/- 31.16 vs 18.33 +/- 19.65) were significantly higher in H. pylori positive cases compared to H. pylori negative cases. In the presence of intestinal metaplasia, p53 expression was further increased (P < 0.05), but apoptosis was similar to that observed in H. pylori negative gastritis without intestinal metaplasia. In the presence of intestinal metaplasia, H. pylori infection did not influence apoptosis (0.013 +/- 0.004 vs 0.011 +/- 0.004), or p53 ratio (70.16 +/- 22.54 vs 68.50 +/- 28.96). In the sequence of gastritis-intestinal metaplasia the two indices show a close negative correlation (P < 0.05).

CONCLUSION

In the absence of intestinal metaplasia H. pylori infection increases both apoptotic activity and expression of p53 oncoprotein in the gastric mucosa. The lack of increased apoptosis with a higher p53 expression in the presence of intestinal metaplasia suggests an increased genetic instability and also may suggest that mutation of the p53 gene is an early step in the multistep process of gastric carcinogenesis.

Change in apoptosis in the gastric surface epithelium and glands after eradication of Helicobacter pylori

BACKGROUND

Change in apoptosis in gastric glands after eradication of Helicobacter pylori has never been reported.

AIMS

The purpose of this paper is to investigate the change in apoptosis in gastric glands after eradication of Heliobacter pylori.

PATIENTS AND METHODS

We studied 23 Heliobacter pylori-positive patients with duodenal and gastric ulcers, who were monitored for 6-12 months after eradication, and eight controls. Biopsies were taken from the antrum and body. Apoptosis was evaluated immunohistochemically using anti-single stranded DNA antibody. Apoptotic index was calculated by counting immunostained cells in surface epithelial and glandular cells.

RESULTS

In the surface epithelium, Apoptotic indexes were significantly higher in patients than in controls. In the upper portion of fundic glands, apoptotic indexes were significantly higher in patients with gastric ulcers (14.2% (9.3, 17.8)) (median (1st quartile, 3rd quartile)) than in controls (8.0% (2.0, 9.0), p < 0.01) and decreased significantly after eradication (3.4% (2.0, 5.3)), p < 0.01). In pyloric glands, apoptotic indexes were no different between patients and controls. In the lower portion of fundic glands, apoptotic indexes were very low, both in patients and in controls.

CONCLUSIONS

Our results showed that apoptosis, not only of surface epithelial cells but also of glandular cells in the upper portion of fundic glands, increased in Heliobacter pylori-positive patients with gastric ulcers and decreased to normal levels after eradication of Heliobacter pylori.

[Genetics and environmental factors in gastric carcinogenesis]

BACKGROUND

Gastric cancer is considered to be the second most common cancer worldwide. Carcinogenesis of the stomach is a multi-stage process. The progression from normal epithelial to tumor cells may involve at least five stages: superficial gastritis, chronic atrophic gastritis, intestinal metaplasia, dysplasia and carcinoma. These sequential changes in the gastric mucosa may occur over a period of many years as a result of exposure to a variety of exogenous and/or endogenous factors which cause genetic alterations. Recent developments in molecular genetics have shown that the accumulation of these multiple genetic alterations, including activation of oncogenes and inactivation of tumor-suppressor genes, results in cancer development. Genetic alterations previously reported in gastric carcinomas include amplifications or mutations of the c-ERBB2, K-RAS, c-MET and TP53. Chromosomal gains were also found in various combinations with chromosomal losses and may be associated with the overexpression of dominant oncogenes contributing to tumor progression.

CONCLUSIONS

These accumulated genetic changes in carcinomas provide evidences for the stepwise mode of gastric carcinogenesis through the accumulation of a series of genetic alterations.

Helicobacter pylori activates the proto-oncogene c-fos through SRE transactivation

Epidemiological studies have demonstrated a strong association between Helicobacter pylori infection and gastric cancer. However, there have been few detailed studies on the mechanism of cellular proliferation by H. pylori. Thus, we examined activation of the proto-oncogene c-fos to elucidate the underlying mechanism of cell proliferation caused by H. pylori. Activation of c-fos was evaluated in human gastric cancer cells (TMK1) by Northern blot and reporter assays with deletion analysis of the c-fos transcriptional control region. c-fos promoter activation and transcription were enhanced when cocultured with cag-positive strains. H. pylori-mediated c-fos promoter activation was inhibited by MEK1/2 inhibitor (U0126). The deletion analysis indicated that serum response element (SRE) was required for the activation of c-fos by H. pylori. In conclusion, c-fos promoter activation and transcription were enhanced through the activation of extracellular signal-regulated kinases (ERK)/mitogen-activated protein kinase (MAPK) cascade in gastric cancer cells when cocultured with H. pylori possessing intact cag PAI. SRE is required for the activation of c-fos by H. pylori. These results suggest a direct involvement of H. pylori infection in cellular proliferation, which may play a role in neoplastic transformation.

Helicobacter pylori strain-specific modulation of gastric mucosal cellular turnover: implications for carcinogenesis

Helicobacter pylori colonization induces inflammation in essentially all hosts, a persistent process that increases the risk of developing distal gastric adenocarcinoma. However, only a small percentage of persons carrying H. pylori develop neoplasia; enhanced risk may be related to differences in expression of specific bacterial products, differences in the host response to the bacteria, or the interaction between host and microbe. H. pylori strains that have the cag pathogenicity island are associated with further increased risk for developing distal gastric cancer; however, host responses to H. pylori, such as altered epithelial cell proliferation and apoptosis, also may be important in lowering the threshold for carcinogenesis. H. pylori cag+ strains selectively enhance proliferation and attenuate apoptosis in human mucosa compared to cag- strains. However, cag+ strains also induce more severe gastritis, suggesting that host inflammatory mediators such as cytokines, prostaglandins, and hormones may modulate H. pylori-induced alterations in cellular turnover. In the Mongolian gerbil model of gastric carcinogenesis, apoptosis increases early and transiently following H. pylori infection, but scores progressively decline despite worsening gastric inflammation. Epithelial cell proliferation peaks later and is significantly related to increased gastrin levels, suggesting that epithelial cell growth in H. pylori-colonized mucosa may be mediated by gastrin-dependent mechanisms. An emerging model invoked by these data is one in which H. pylori cag+ strains, in conjunction with host mediators, enhance gastric epithelial cell proliferation but not apoptosis in vivo. The combination of increased proliferation without a concordant increase in apoptosis may therefore contribute to the heightened retention of mutagenized cells, which over decades may increase the subsequent risk for gastric cancer.

pathogenesis of Helicobacter pylori-induced gastric inflammation

Helicobacter pylori causes persistent inflammation in the human stomach, yet only a minority of persons harbouring this organism develop peptic ulcer disease or gastric malignancy. An important question is why such variation exists among colonized individuals. Recent evidence has demonstrated that H. pylori isolates possess substantial phenotypic and genotypic diversity, which may engender differential host inflammatory responses that influence clinical outcome. For example, H. pylori strains that possess the cag pathogenicity island induce more severe gastritis and augment the risk for developing peptic ulcer disease and distal gastric cancer. An alternative, but not exclusive, hypothesis is that enhanced inflammation and injury is a consequence of an inappropriate host immune response to the chronic presence of H. pylori within the gastric niche. Investigations that precisely delineate the mechanisms responsible for induction of gastritis will ultimately help to define which H. pylori-colonized persons bear the highest risk for subsequent development of clinical disease, and thus, enable physicians to focus eradication therapy.

Activation of peroxisome proliferator-activated receptor gamma suppresses nuclear factor kappa B-mediated apoptosis induced by Helicobacter pylori in gastric epithelial cells

Helicobacter pylori colonization leads to epithelial cell hyperproliferation within inflamed mucosa, but levels of apoptosis vary, suggesting that imbalances between rates of cell production and loss may contribute to differences in gastric cancer risk among infected populations. Peroxisome proliferator-activated receptor gamma (PPARgamma) regulates inflammatory and growth responses of intestinal epithelial cells. We determined whether activation of PPARgamma modified H. pylori-induced apoptosis in gastric epithelial cells. PPARgamma was expressed and functionally active in gastric epithelial cell lines sensitive to H. pylori-induced apoptosis. PPARgamma ligands 15d-PGJ(2) and BRL-49653 significantly attenuated H. pylomicronri-induced apoptosis, effects that could be reversed by co-treatment with a specific PPARgamma antagonist. Cyclopentanone prostaglandins that do not bind and activate PPARgamma had no effects on H. pylori-induced apoptosis. The ability of H. pylori to activate nuclear factor (NF)-kappaB and increase levels of the NF-kappaB target IL-8 was blocked by co-treatment with PPARgamma agonists, and direct inhibition of NF-kappaB also abolished H. pylori-stimulated apoptosis. These results suggest that activation of the PPARgamma pathway attenuates the ability of H. pylori to induce NF-kappaB-mediated apoptosis in gastric epithelial cells. Because PPARgamma regulates a multitude of host responses, activation of this receptor may contribute to varying levels of cellular turnover as well as the diverse pathologic outcomes associated with chronic H. pylori colonization.

Effects of nonsteroidal anti-inflammatory drugs on Helicobacter pylori-infected gastric mucosae of mice: apoptosis, cell proliferation, and inflammatory activity

Helicobacter pylori and nonsteroidal anti-inflammatory drugs (NSAIDs) are two well-known important causative factors of gastric damage. While H. pylori increases apoptosis and the proliferation of gastric epithelial cells and is an important factor in peptic ulcer and gastric cancer, NSAIDs induce cell apoptosis and have antineoplastic effects. We investigated the effects of NSAIDs (a nonselective cyclooxygenase [COX] inhibitor [indomethacin] and a selective COX-2 inhibitor [NS-398]) on the apoptosis and proliferation of gastric epithelial cells and gastric inflammation in H. pylori-infected mice. C57BL/6 mice were sacrificed 8 weeks after H. pylori SS1 inoculation. Indomethacin (2 mg/kg) or NS-398 (10 mg/kg) was administered subcutaneously once daily for 10 days before sacrifice. The following were assessed: gastric inflammatory activity, gastric COX protein expression by Western blotting; gastric prostaglandin E(2) levels by enzyme immunoassay, apoptosis by terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling, and cell proliferation by Ki67 immunostaining. Compared to the controls, H. pylori infection and/or NSAID treatment increased COX-1 and COX-2 protein expression. Gastric prostaglandin E(2) levels, apoptotic index, cell proliferation index, neutrophil activity, and the degree of chronic inflammation were all increased by H. pylori infection, and these effects were significantly decreased by indomethacin treatment. However, NS-398 treatment after H. pylori infection did not induce a significant reduction, although it did result in a tendency to decrease. These results show that NSAIDs can reverse the increased apoptosis and proliferation of epithelial cells and inflammatory activity in the stomachs of H. pylori-infected mice and that, like COX-2 activation, COX-1 induction contributes to the change of gastric mucosal cell turnover and inflammation induced by H. pylori infection.

Helicobacter pylori induces apoptosis in human epithelial gastric cells by stress activated protein kinase pathway

BACKGROUND

The pathway by which Helicobacter pylori induces apoptosis in gastric epithelial cells is not known. The aim of this study was to determine whether H. pylori-induced apoptosis is associated with SAPK/JNK activity in human gastric cancer KATO III cells.

MATERIALS AND METHODS

H. pylori VacA toxin positive strain was incubated with KATO III cells for 0.5, 1, 2 or 24 hours. The SAPK/JNK protein was harvested from the KATO III cell lysate by precipitation with a C-jun fusion protein and its activity was measured by C-jun phosphorylation utilizing transblotting and phosphoserine antibody. Cellular apoptosis was demonstrated by DNA fragmentation. In addition, cell growth in coculture with H. pylori was determined over 72 hours.

RESULTS

H. pylori significantly stimulated SAPK/JNK activity in KATO III cells with a peak at the 0.5 hour time point (3.6-fold vs. control, p <.05), but a return to basal levels by 2 hours. In addition, significant DNA fragmentation was observed after 24 hours in these cells but not in the control KATO III cells. Cell growth was inhibited in a dose dependent fashion in coculture with H. pylori.

CONCLUSION

These results show that H. pylori triggers an increase in apoptosis in KATO III cells as reflected by DNA fragmentation. This effect was preceded and correlated with an increase in SAPK/JNK activity suggesting that the H. pylori-induced apoptosis in human gastric epithelial cells may be mediated by the SAPK/JNK pathway.

p53 expression in the gastric mucosa before and after eradication of Helicobacter pylori

BACKGROUND

Accumulation of p53 has been recognized in the gastric mucosa infected with Helicobacter pylori. We investigated the prevalence of p53-positive cells in the gastric mucosa before and one month after eradication of H. pylori and the relationship between p53 positivity and inflammation and cell proliferation.

METHODS

The subjects included 24 H. pylori-positive patients. They achieved eradication one month after anti-H. pylori therapy. Biopsies were taken from the greater curvatures of the antrum and middle body. H. pylori status was assessed using culture and tissue section (Giemsa stain). Serial sections were used for examination of gastritis (hematoxylin and eosin stain) and for immunostaining of p53, Ki-67 and myeloperoxidase (MPO). p53 index and Ki-67 labeling index (LI) were calculated by counting p53-positive and Ki-67-positive cells in the entire gastric pits longitudinally sectioned and expressing them as a percentage of the total cells in a gastric pit. In the neck regions with and without p53-positive cells, polymorphonuclear leukocytes (PMNs) were counted in the corresponding area (/50 x 50 microm2) of the sections stained both with p53 and MPO.

RESULTS

p53-positive cells decreased significantly after eradication of H. pylori. Before eradication, the number of PMNs was significantly higher in the neck regions with p53-positive cells than in those without.

CONCLUSIONS

In the gastric mucosa infected with H. pylori, p53-positive cells were found in the neck region infiltrated with PMNs. p53 expression decreased significantly one month after eradication of H. pylori.

Comparison of gastritis and gastric epithelial proliferation in Helicobacter heilmannii-infected nude and BALB/c mice

Gastric mucosal hypertrophy/nodular hyperplasia occurs as a consequence of Helicobacter infection in mice and humans. The pathogenesis of this hyperplastic response is not understood. To determine the role of host cellular immunity in gastric mucosal hypertrophy/hyperplasia, 6-8-week-old female euthymic BALB/c (n = 30) or NIH athymic nude (n = 40) mice were inoculated with H. heilmannii. Equal numbers of uninoculated mice of each strain served as controls. Mice from each group were euthanatized at 0.5, 6, 12, and 18 months postinoculation (PI). Lymphoplasmacytic gastritis and lymphoid follicle development were less severe in nude mice than in euthymic mice at <6 months PI. The prevalence of gastritis at 0.5, 6, 12, and 18 months PI was 0%, 17%, 67%, and 88%, respectively, in infected nude mice and 33%, 83%, 71%, and 100%, respectively, in infected BALB/c mice. CD4+ T cells in infected nude mice were evident at > or =6 months PI but were less numerous than in infected BALB/c mice at comparable time intervals. However, numbers of CD4+ T cells increased substantially throughout the experiment in infected BALB/c mice. The prevalence of nodular mucosal hyperplasia at 0.5, 6, 12, and 18 months PI was 0%, 0%, 33%, and 20%, respectively, in infected nude mice and 0%, 33%, 80%, and 80%, respectively, in infected BALB/c mice. Nodular hyperplasia occurred in association with the appearance of chronic lymphoplasmacytic inflammation and CD4+ T cells at 12 and 18 months PI in nude mice. H. heilmannii-associated gastritis and mucosal remodeling is reduced in immunodeficient mouse strains lacking normal CD4+ T cell numbers as compared with the response in immunocompetent mice. Additionally, CD4 immunocompetence is an integral aspect of the mucosal hypertrophy/nodular hyperplasia in experimental H. heilmannii-associated disease of mice.

"Malgun" (clear) cell change of gastric epithelium in chronic Helicobacter pylori gastritis

To characterize the Helicobacter pylori gastritis-associated epithelial change, we analyzed 251 randomly selected gastric biopsies. The "malgun" (clear) cell change of the gastric epithelium was noted in 229 biopsies (91.2%). Malgun cells were characterized by large, pale nuclei with a euchromatin pattern, enlarged nucleoli, and clear cytoplasm. In the proliferative zone, individual malgun cells and small clusters were often in close contact with infiltrating neutrophils, suggesting that they had developed individually in the background of acute foveolitis. Mitotic figures of malgun cells were not infrequent, including atypical ones. In the surface epithelium, most malgun cells were in clusters that were often large enough to occupy wide epithelial segments. With Warthin-Starry triple staining, they were distinguished by the absence of silver impregnation, while other cells showed staining of the heterochromatin. They displayed prominent immunostaining for low molecular weight cytokeratin (No. 8). Most malgun cells were PCNA-positive in both surface and proliferative zones, whereas Ki67-positive cells were found only in the proliferative zone. It was suggested that a population of malgun cells, which were positive for PCNA only, were in the process of active DNA repair. The malgun cell change may represent a "cellular pattern of activation" in a population which had significant DNA damage, but somehow escaped the detection by the apoptosis system. The notion of "damage at the genetic level" was supported by the observation that these cells remained at least for 8 weeks after eradication of the H. pylori infection.

Effect of Helicobacter pylori infection and eradication on gastric epithelial cell proliferation and apoptosis

OBJECTIVES

the effect of Helicobacter pylori infection on gastric epithelial cell proliferation and apoptosis is still controversial. Our aim was to evaluate the effect of H. pylori infection on cell kinetic parameters in normal gastric epithelium, gastritis with/without intestinal metaplasia and gastric cancer.

PATIENTS AND METHODS

antral biopsies were taken from 121 patients (61 women, 60 men, mean age 58.5+/-14.3 years of age) who underwent routine gastroscopy for upper gastrointestinal symptoms. Sections were scored for normal epithelia (n=15), gastritis without intestinal metaplasia (n=74), gastritis with intestinal metaplasia (n=24), and gastric adenocarcinoma (n=8). Fifty-two patients had H. pylori positive gastritis, and success of H. pylori eradication therapy was controlled in 12 cases, all with intestinal metaplasia. To characterize cell proliferation and assess apoptosis, immunohistochemistry [Proliferating Cell Nuclear Antigen (PCNA)], histochemistry [Argyrophil Nucleolar Organizer Regions (AgNOR)], and terminal deoxynucleotidyl transferase (TdT)-mediated deoxyuridinetriphosphate (dUTP) nick end-labeling (TUNEL) were used, respectively.

RESULTS

both cell proliferation and apoptosis is was higher in chronic gastritis when compared with normal epithelia, but neither PCNA LI (54.79+/-19.1 vs. 53.20+/-20.7) nor AgNOR counts (291.43+/-44.3 vs. 277.8+/-57.54) were different in H. pylori positive versus negative chronic gastritis. A significant positive correlation (P<0.05) was found in this group between PCNA and AgNOR techniques. Apoptosis was significantly higher (P<0.05) in H. pylori positive cases only when intestinal metaplasia was not present. Cell proliferation in intestinal metaplasia decreased to the activity of normal epithelium after successful eradication of H. pylori but remained high if eradication therapy failed.

CONCLUSIONS

epithelial cell proliferation does not depend on H. pylori status in chronic gastritis. H. pylori increases apoptosis only in the absence of intestinal metaplasia.

Cell proliferation in type C gastritis affecting the intact stomach

AIMS

Type C gastritis caused by bile reflux has a characteristic appearance, similar to that seen in other forms of chemical gastritis, such as those associated with NSAIDs or alcohol. An increase in mucosal cell proliferation increases the likelihood of a neoplastic clone of epithelial cells emerging, particularly where there is chronic epithelial injury associated with bile reflux. It has been shown previously that type C gastritis is associated with increased cell proliferation in the postsurgical stomach. The aim of this study was to determine cell proliferation in type C gastritis caused by bile reflux affecting the intact stomach.

METHODS

Specimens from 15 patients with a histological diagnosis of type C gastritis on antral biopsy were obtained from the pathology archives between 1994 and 1997. A control group of nine normal antral biopsies was also selected and all underwent MIB-1 immunostaining. The gastric glands were divided into three zones (zone 1, gastric pit; zone 2, isthmus; and zone 3, gland base) and the numbers of positively staining nuclei for 500 epithelial cell nuclei were counted in each zone to determine the percentage labelling index (LI%).

RESULTS

Cell proliferation was significantly higher in all three zones of the gastric glands with type C gastritis compared with controls as follows: zone 1, median LI% in type C gastritis 64.7 (range, 7.8-99.2), controls 4.7 (range, 2.0-11.3); zone 2, median LI% in type C gastritis 94.7 (range, 28.8-98.7), controls 40.2 (range, 23.1-70.3); and zone 3, median LI% in type C gastritis 20.0 (range, 1.3-96.0), controls 2.6 (range, 0.9-8.7).

CONCLUSIONS

Bile reflux is thought to act as a promoter of gastric carcinogenesis in the postsurgical stomach. The same may be true in the intact stomach.

Helicobacter pylori activates mitogen-activated protein kinase cascades and induces expression of the proto-oncogenes c-fos and c-jun

Helicobacter pylori is an etiological agent in the development of mucosa-associated lymphoid tissue lymphoma and gastric adenocarcinoma. Patients infected with H. pylori carry a 3-6-fold increased risk of developing cancer compared with uninfected individuals. H. pylori strains expressing the cytotoxin-associated antigen A (CagA) are more frequently associated with the development of neoplasia than cagA-negative strains. However, the molecular mechanism by which H. pylori causes neoplastic transformation remains unclear. Here we report that exposure of gastric epithelial cells to H. pylori induces activation of the transcription factor activator protein 1. Activation of the proto-oncogenes c-fos and c-jun is strongly induced. We show that H. pylori activates the ERK/MAP kinase cascade, resulting in Elk-1 phosphorylation and increased c-fos transcription. H. pylori strains that do not express CagA or that are mutated in cag genes encoded by the CagI pathogenicity island do not induce activator protein 1, MAP kinase activity, or c-fos or c-jun activation. Proto-oncogene activation may represent a crucial step in the pathomechanism of H. pylori induced neoplasia.

Proliferating cell nuclear antigen (PCNA) immunostaining in Helicobacter pylori infection: impact of eradication

Despite the fact that the association of Helicobacter pylori (H. pylori)with an increased risk of gastric cancer has been well documented, the exact mechanisms of this association have not been fully elucidated. The aim of the present prospective study was to contribute to the exploration of these mechanisms by studying the relationship between H. pylori infection and proliferating cell nuclear antigen (PCNA) immunostaining in endoscopic biopsies in gastric antrum. Furthermore, we examined the impact of H. pylorieradication on this relationship. We studied 28 H. pyloripositive patients and the results were compared with 22 endoscopically and histologically normal H. pylorinegative patients (control group) who were comparable to the H. pyloripositive group for age and sex. In addition all H. pyloripositive patients were examined before and after treatment aiming to eradicate H. pylori. In the H. pylori(+) patients the median PCNA index was 35 (range 8-58) and this was significantly higher than the respective number in the control group [5.5 (2 14), p<0.001]. In patients studied before and after successful eradication of H. pylori(n=10) the corresponding numbers were 35 (8-56) and 7 (4 13) (p<0.01) the latter not being significantly different from the control group of H. pylori(-)patients. On the contrary, in patients without successful H. pylori eradication (n=18) the PCNA indices before and after treatment were similar [35.5 (21-58) vs 31.5 (20-56)]. It is concluded that H. pyloriinfection alters the replication cycle of the gastric mucosa inducing hyperproliferation, which return towards normal after successful H. pylori eradication.

Helicobacter pylori. One bacterium and a broad spectrum of human disease! An overview

Since the historical rediscovery of gastric spiral Helicobacter pylori in the gastric mucosa of patients with chronic gastritis by Warren and Marshall in 1983, peptic ulcer disease has been largely viewed as being of infectious aetiology. Indeed, there is a strong association between the presence of H. pylori and chronic active gastritis in histology. The bacterium can be isolated in not less than 70% of gastric and in over 90% of duodenal ulcer patients. Eradication of the organism has been associated with histologic improvement of gastritis, lower relapse rate and less risk of bleeding from duodenal ulcer. The bacterium possesses several virulence factors enabling it to survive the strong acid milieu inside the stomach and possibly damaging host tissues. The sequence of events by which the bacterium might cause gastric or duodenal ulcer is still not fully elucidated and Koch's postulates have never been fulfilled. In the majority of individuals, H. pylori infection is largely or entirely asymptomatic and there is no convincing data to suggest an increase in the prevalence of peptic ulcer disease among these subjects. An increasingly growing body of literature suggests an association between colonization by H. pylori in the stomach and a risk for developing gastric mucosa-associated lymphoid tissue (MALT), MALT lymphoma, gastric adenocarcinoma and even pancreatic adenocarcinoma. The bacterium has been implicated also in a number of extra-gastrointestinal disorders such as ischaemic heart disease, ischaemic cerebrovascular disease, atherosclerosis, and skin diseases such as rosacea, but a causal role for the bacterium is missing. Eradication of H. pylori thus seems to be a beneficial impact on human health. Various drug regimens are in use to eradicate H. pylori involving the administration of three or four drugs including bismuth compounds, metronidazole, clarithromycin, tetracyclines, amoxycillin, ranitidine, omeprazole for 1-2 weeks. The financial burden, side effects and emergence of drug resistant strains due to an increase in the use in antibiotics for H. pylori eradication therapy need further reconsideration.

Role of apoptosis in Helicobacter pylori-associated gastric mucosal injury

Apoptosis, a programmed cell death, was ignored, just like Helicobacter pylori, only to reappear recently. However, the number of current publications dealing with apoptosis or H. pylori has increased exponentially. Although gastric epithelial apoptosis is a programmed physiological event in the superficial aspect of the mucosa and is important for healthy cell turnover, H. pylori infection reportedly promotes such a cell death sequence. Because apoptosis regulates the cycle of cell turnover in balance with proliferation, dysregulation of apoptosis or proliferation evoked by H. pylori colonization would be linked to the gastric carcinogenesis. In other words, a reduced level of apoptosis could contribute to the generation of gastric cancer. Herein, we review apoptosis as well as its associated pathological events, such as hyperproliferation, in H. pylori-colonized gastric mucosa.

Role of apoptosis in gastric epithelial turnover

Gastric epithelial turnover is a dynamic process. It is characterized by continuous cell proliferation, which is counterbalanced by cell loss. The biological principle that mediates the homeostasis of epithelium is programmed cell death, or apoptosis. Currently, several subtypes of apoptosis are distinguished, which are mediated by different mechanisms. Various subtypes of apoptosis also occur in the gastric epithelium under various conditions. In the normal stomach, apoptosis due to cell isolation (anoikis) mediates the physiological epithelial turnover. Albeit rarely seen in routine histology, approximately 2% of epithelial cells in the normal stomach are apoptotic. In Helicobacter pylori-induced gastritis, apoptosis and epithelial proliferation are moderately increased, with approximately 8% apoptotic epithelial cells. In gastritis, factors such as CD95 ligand or tumor necrosis factor (TNF) alpha act as death factors. They bind to specific receptors, CD95 and TNF-R, which are induced either by other cytokines, such as interferon gamma, or by Helicobacter pylori itself. In addition to CD95, H.pylorican also induce upregulation of CD95 ligand expression. Taken together, the upregulated expression of CD95, and the presence of CD95L in the close proximity to apoptotic gastric epithelial cells suggest a functional role of the CD95-CD95L system in the induction of apoptosis in H.pylori-gastritis. The role of other pathways to apoptosis is currently under study. Apart from being a biological phenomenon, apoptosis in the stomach may also have direct clinical consequences. An extreme example is given in gastric graft-vs.-host disease when epithelial denudement occurs.

Helicobacter pylori alters gastric epithelial cell cycle events and gastrin secretion in Mongolian gerbils

BACKGROUND & AIMS

Human colonization with Helicobacter pylori increases the risk for distal gastric adenocarcinoma, possibly by altering gastric epithelial cell cycle events and/or gastrin secretion. This study aimed to determine whether H. pylori virulence-related characteristics affect apoptosis, proliferation, and gastrin levels in a rodent model of gastric adenocarcinoma.

METHODS

Mongolian gerbils were challenged with H. pylori wild-type or isogenic cagA(-) and vacA(-) mutants, and apoptotic and proliferating cells were identified by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling and proliferating cell nuclear antigen immunohistochemistry, respectively. Serum gastrin levels were determined by radioimmunoassay.

RESULTS

Gastric epithelial cell turnover was no different after infection with the wild-type, cagA(-), or vacA(-) strains. H. pylori infection significantly increased antral apoptosis 2-4 weeks after challenge, before apoptotic indices decreased to baseline. In contrast, antral proliferation rates were significantly higher 16-20 weeks after inoculation, but then decreased by 40 weeks. Antral proliferation was significantly related to serum gastrin levels, whereas antral apoptosis was inversely related to acute inflammation and lymphoid follicles.

CONCLUSIONS

In H. pylori-infected gerbils, enhanced antral apoptosis is an early and transient cell cycle event. Epithelial cell proliferation peaks later and is significantly related to increased gastrin levels, suggesting that epithelial cell growth in H. pylori-colonized mucosa may be mediated by gastrin-dependent mechanisms.

Cell proliferation in the post-surgical stomach, dietary salt, and the effect of H pylori eradication

AIMS

To study the epithelial kinetics of the post-surgical stomach with reference to dietary salt intake and H pylori.

METHODS

Endoscopic biopsies of the antrum/anastomosis and corpus were taken for histology and MIB-1 immunostaining. The labelling index (LI%) was determined in the three zones of the gastric glands (zone 1 = surface + gastric pit; zone 2 = isthmus; zone 3 = gland base) in patients with vagotomy and pyloroplasty (n = 12), gastroenterostomy + vagotomy (n = 4), partial gastrectomy (n = 3), and Billroth I operation (n = 3). Dietary salt was determined by urinary sodium/creatinine ratio. Twelve patients were H pylori positive (10 vagotomy and pyloroplasty; 2 partial gastrectomy) and had a repeat biopsy three months after antihelicobacter treatment (10 were H pylori negative after treatment).

RESULTS

There was no correlation between salt intake and antrum/anastomosis (r = -0.34; p = 0.2) or corpus (r = -0.16; p = 0.2) labelling indices. Gastric mucosal proliferation is increased in the antrum/ anastomosis compared to the corpus in H pylori positive (p = 0.014) but not H pylori negative subjects (p = 0.084). This may reflect the different types of post-surgical stomach in each group. Gastric mucosal proliferation is reduced in antrum/anastomosis (p = 0.002) and corpus (p = 0.016) following H pylori eradication.

CONCLUSIONS

Dietary salt does not influence gastric mucosal proliferation in the post-surgical stomach but H pylori may have a role in gastric stump carcinogenesis.

Gastric cellular turnover and the development of atrophy after 31 years of follow-up: a case-control study

OBJECTIVE

Why only some patients colonized with Helicobacter pylori (H. pylori) develop atrophy, a preneoplastic change, is not known. Because gastric mucosal mass is dependent upon a balance between epithelial proliferation and turnover, we hypothesized that atrophy may develop due to increased apoptosis relative to proliferation.

METHODS

Gastric epithelial apoptosis was measured by terminal deoxyuridine nucleotide nick end labeling (TUNEL) assay and proliferation by Ki-67 immunohistochemistry in gastric corpus biopsies in a unique cohort of patients followed for 31 yr (1952-1983). Sixteen patients who developed atrophy over this time were selected (cases), with two matched controls, who did not develop atrophy, for each. Apoptosis and proliferation were measured in the corpus biopsies taken in 1952.

RESULTS

Cases (N = 16) and controls (N = 32) were well matched for age, sex, initial histology, and severity of H. pylori infection. In the initial (1952) biopsies, 4.3 +/- 1.7 cells (mean +/- SEM) per gland were Ki-67-positive in the cases, compared with 2.1 +/- 0.4 in controls (p = 0.48). 9.2 +/- 2.3 cells per gland were terminal deoxyuridine nucleotide nick end labeling-positive in cases, compared with 6.3 +/- 0.8 in controls (p = 0.29). Proliferation to apoptosis ratios were similar in both groups (cases, 0.38 +/- 0.16; controls 0.39 +/- 0.08, p = 0.37).

CONCLUSIONS

Patients who later developed atrophy, initially had mildly (but not statistically significant) increased gastric epithelial cell proliferation and apoptosis, compared with those patients who did not develop atrophy, suggesting increased cellular turnover in the atrophy group. However, in these patients with gastritis, the ratio of apoptosis to proliferation was not a determinant of risk for development of atrophy decades later.

Monochloramine induced DNA fragmentation in gastric cell line MKN45

Monochloramine (NH2Cl) is known to be one of the virulence factors in Helicobacter pylori-associated gastric mucosal injury. The present study was designed to examine NH2Cl-evoked DNA fragmentation in the gastric epithelial cell line MKN45. NH2Cl was produced by mixing NH3 with sodium hypochlorite (NaClO). MKN45 cells were exposed to NH2Cl, NH3, or NaClO in Hanks' balanced salt solution. DNA cleavage was evaluated quantitatively by photometeric enzyme immunoassay for the in vitro determination of cytoplasmic mono- and oligonucleosomes. Damage to the plasma membrane was assessed by measuring the activity of lactate dehydrogenase in the supernatants. Separately, DNA ladder formation was performed to confirm the incidence of DNA fragmentation. NH2Cl (0.001-0.01 mM) significantly increased the cytoplasmic mono- and oligonucleosomes, suggesting the incidence of DNA cleavage. The DNA ladder was clearly evoked by NH2Cl. NH2Cl induced a DNA fragmentation, one of the important aspects in apoptosis, in the gastric cell line MKN45.

Apoptosis in gastric epithelial cells is induced by Helicobacter pylori and accompanied by increased expression of BAK

Carriage of the bacterium H. pylori in the human stomach is associated with evidence of increased epithelial cell apoptosis. This may be of significance in the etiology of gastritis, peptic ulcers, and neoplasia. The ability of H. pylori to directly induce epithelial apoptosis was examined in vitro by fluorescence and electron microscopy, flow cytometry, and DNA fragmentation ELISA. The induction of apoptosis by H. pylori was time and concentration-dependent and inhibited by preventing direct bacterial-epithelial cell contact. Apoptosis was accompanied by increased expression of Bak, with little change in expression of other Bcl-2 family proteins. The expression of Bak was also increased in gastric biopsies from patients colonized by H. pylori. Thus, H. pylori induces gastric epithelial cell apoptosis, by a Bak-dependent pathway.

Helicobacter pylori cagA+ strains and dissociation of gastric epithelial cell proliferation from apoptosis

BACKGROUND

Infection with Helicobacter pylori induces chronic gastritis in virtually all infected persons, and such gastritis has been associated with an increased risk of developing gastric cancer. This risk is further enhanced with cagA+ (positive for cytotoxin-associated gene A) H. pylori strains and may be a consequence of induced gastric cell proliferation and/or alteration in apoptosis (programmed cell death) in the gastric epithelium.

PURPOSE

To determine whether the H. pylori cagA genotype and another virulence-related characteristic, the vacA (vacuolating cytotoxin A) s1a genotype, differentially affect epithelial cell proliferation, apoptosis, and the histologic parameters of inflammation and injury, we quantitated these characteristics in infected and uninfected persons.

METHODS

Fifty patients underwent upper gastrointestinal endoscopy, and biopsy specimens were taken. Apoptotic cells in the specimens were quantitated after terminal deoxynucleotidyl transferase labeling of DNA fragments with digoxigenin-deoxyuridine triphosphate; epithelial cell proliferation was scored by immunohistochemical analysis of the proliferation-associated antigen Ki-67. Antibodies directed against H. pylori and CagA protein were measured in the serum of patients by means of enzyme-linked immunosorbent assays. Analysis of H. pylori genomic DNA, by use of the polymerase chain reaction, was performed to determine the cagA and vacA genotypes. Acute and chronic inflammation, epithelial cell degeneration, mucin depletion, intestinal metaplasia, glandular atrophy, and vacuolation were each scored in a blinded manner. Reported P values are two-sided.

RESULTS

Persons harboring cagA+ strains (n = 20) had significantly higher gastric epithelial proliferation scores than persons infected with cagA-strains (n = 9) or uninfected persons (n = 21) (P = .025 and P<.001, respectively), but the difference in cell proliferation between the latter two groups was not statistically significant. The number of apoptotic cells per 100 epithelial cells (apoptotic index) in persons infected with cagA+ strains was lower than in persons infected with cagA-strains (P = .05). Apoptotic indices in the cagA+ group were similar to those in the uninfected group (P = .2). Epithelial cell proliferation was significantly correlated with acute gastric inflammation, but only in the cagA+ group (r = .44; P = .006). The cagA+ and vacA s1a genotypes were found to be concordant, confirming the close relationship between these virulence-related genotypes.

CONCLUSIONS

Gastric mucosal proliferation was significantly correlated with the severity of acute gastritis in persons infected with cagA+ vacA s1a strains of H. pylori. This increased proliferation was not accompanied by a parallel increase in apoptosis.

IMPLICATIONS

Increased cell proliferation in the absence of a corresponding increase in apoptosis may explain the heightened risk for gastric carcinoma that is associated with infection by cagA+ vacA s1a strains of H. pylori.

Proliferative activity of gastric epithelium in progressive stages of Helicobacter pylori infection

Helicobacter pylori (HP) infection is the main etiopathogenetic agent responsible for inflammatory and ulcerative changes in gastroduodenal mucosa and the basis for both intestinal and diffuse types of gastric carcinoma. In this latter case, intestinal metaplasia is the intermediary between gastritis and cancer. In this study we describe the proliferative activity of gastric epithelium in the progressive stages of HP infection. The expression of proliferating cell nuclear antigen (PCNA), which has proven to be a reliable method for this evaluation, was used as a marker. The study was performed on endoscopic biopsies of the gastric antrum of 40 patients, who were divided into five groups, eight in each group: normal histology and endoscopy, HP-; histological HP+ gastritis with normal endoscopy; histological HP+ gastritis with endoscopic evidence of chronic erosions; complete and incomplete intestinal metaplasia in a HP+ stomach. PCNA was detected by immunohistochemistry and expressed as labeling index, ie, percentage of positive nuclei either in the whole or upper third of foveolae. Our data show a progressive increase of epithelial proliferation in the successive stages of HP infection ranging from gastritis alone to the development of incomplete intestinal metaplasia, a well-known precancerous condition. The proliferative pattern tended to expand towards the upper foveolar third, which in normal conditions does not represent a site of epithelial renewal. These alterations may be related to the development of neoplastic transformations of gastric epithelium. It is well known that genetic mutations are facilitated in proliferating cells. Therefore, our results indicate that the high epithelial turnover, expressed by PCNA LI, may be an indicator of increased risk of neoplastic changes in long-standing untreated HP+ chronic gastritis.