Helicobacter pylori, neutrophils, interleukins, and gastric epithelial proliferation

The Importance of Th2 Immune Responses in Mediating the Progression of Gastritis-Associated Metaplasia to Gastric Cancer

Gastric cancer is one of the leading causes of cancer deaths worldwide, with chronic gastritis representing the main predisposing factor initiating the cascade of events leading to metaplasia and eventually progressing to cancer. A widely accepted classification distinguishes between autoimmune and environmental atrophic gastritis, mediated, respectively, by T cells promoting the destruction of the oxyntic mucosa, and chronic H. pylori infection, which has also been identified as the major risk factor for gastric cancer. The original dogma posits Th1 immunity as a main causal factor for developing gastritis and metaplasia. Recently, however, it has become evident that Th2 immune responses play a major role in the events causing chronic inflammation leading to tumorigenesis, and in this context, many different cell types and cytokines are involved. In particular, the activity of cytokines, such as IL-33 and IL-13, and cell types, such as mast cells, M2 macrophages and eosinophils, are intertwined in the process, promoting chronic gastritis-dependent and more diffuse metaplasia. Herein, we provide an overview of the critical events driving the pathology of this disease, focusing on the most recent findings regarding the importance of Th2 immunity in gastritis and gastric metaplasia.

Innate immune activation and modulatory factors of Helicobacter pylori towards phagocytic and nonphagocytic cells

Helicobacter pylori is an intriguing obligate host-associated human pathogen with a specific host interaction biology, which has been shaped by thousands of years of host-pathogen coevolution. Molecular mechanisms of interaction of H. pylori with the local immune cells in the human system are less well defined than epithelial cell interactions, although various myeloid cells, including neutrophils and other phagocytes, are locally present or attracted to the sites of infection and interact with H. pylori. We have recently addressed the question of novel bacterial innate immune stimuli, including bacterial cell envelope metabolites, that can activate and modulate cell responses via the H. pylori Cag type IV secretion system. This review article gives an overview of what is currently known about the interaction modes and mechanisms of H. pylori with diverse human cell types, with a focus on bacterial metabolites and cells of the myeloid lineage including phagocytic and antigen-presenting cells.

Sarcocystis camelicanis increases interleukin (IL)-6 expression in one-humped camels (Camelus dromedarius) from Riyadh and Al Qassim, Saudi Arabia

Sarcocystis spp. are intracellular protozoan parasites with an intermediate-definitive host life cycle based on a prey-predator relationship. Sarcocystis infection is common among different vertebrates including humans. The pathogenicity of Sarcocystis spp. is of varied significance including a possible lethal effect for the host. The goal of the present study was to investigate the inflammatory activity of Sarcocystis spp. in different organs of naturally infected camels. The tongue, esophagus, heart, diaphragm, and skeletal muscles were collected from 50 camels, and the tissues assessed for the presence of Sarcocystis spp. by macroscopic examination, light microscopy, and transmission electron microscopy (TEM). Moreover, expression of the interleukin (IL)-6 was analyzed using reverse transcriptase quantitative polymerase chain reaction (qPCR). Microscopic Sarcocystis spp. cysts were found in camels. TEM identified the cysts as Sarcocystis camelicanis (S. camelicanis). Sarcocystis infection increased inflammation by stimulation of IL-6 expression in different organs of the camels, particularly in those from the Al-Qassim region.

Helicobacter pylori Related Diseases and Osteoporotic Fractures (Narrative Review)

Osteoporosis (OP) and osteoporotic fractures (OFs) are common multifactorial and heterogenic disorders of increasing incidence. Helicobacter pylori (H.p.) colonizes the stomach approximately in half of the world's population, causes gastroduodenal diseases and is prevalent in numerous extra-digestive diseases known to be associated with OP/OF. The studies regarding relationship between H.p. infection (HPI) and OP/OFs are inconsistent. The current review summarizes the relevant literature on the potential role of HPI in OP, falls and OFs and highlights the reasons for controversies in the publications. In the first section, after a brief overview of HPI biological features, we analyze the studies evaluating the association of HPI and bone status. The second part includes data on the prevalence of OP/OFs in HPI-induced gastroduodenal diseases (peptic ulcer, chronic/atrophic gastritis and cancer) and the effects of acid-suppressive drugs. In the next section, we discuss the possible contribution of HPI-associated extra-digestive diseases and medications to OP/OF, focusing on conditions affecting both bone homeostasis and predisposing to falls. In the last section, we describe clinical implications of accumulated data on HPI as a co-factor of OP/OF and present a feasible five-step algorithm for OP/OF risk assessment and management in regard to HPI, emphasizing the importance of an integrative (but differentiated) holistic approach. Increased awareness about the consequences of HPI linked to OP/OF can aid early detection and management. Further research on the HPI-OP/OF relationship is needed to close current knowledge gaps and improve clinical management of both OP/OF and HPI-related disorders.

Molecular pathogenesis of lymphomas of mucosa-associated lymphoid tissue--from (auto)antigen driven selection to the activation of NF-κB signaling

Lymphomas of mucosa-associated lymphoid tissue (MALT) are typically present at sites such as the stomach, lung or urinary tract, where lymphoid tissues scatter in mucosa lamina propria, intra- or sub-epithelial cells. The infection of certain pathogens, such as Helicobacter pylori, Chlamydophila psittaci, Borrelia burgdorferi, hepatitis C virus, or certain autoantigens cause these sites to generate a germinal center called the "acquired lymphoid tissue". The molecular pathogenesis of MALT lymphoma is a multi-step process. Receptor signaling, such as the contact stimulation of B cell receptors and CD4 positive T cells mediated by CD40/CD40-ligand and T helper cell type 2 cytokines like interleukin-4, contributes to tumor cell proliferation. A number of genetic alterations have been identified in MALT lymphoma, and among them are important translocations, such as t(11;18)(q21;q21), t(1;14)(p22;q32), t(14;18)(q32;q21) and t(3;14)(p13;q32). Fusion proteins generated by these translocations share the same NF-κB signaling pathway, which is activated by the caspase activation and recruitment domain containing molecules of the membrane associated guanylate kinase family, B cell lymphoma-10 and MALT1 (CBM) protein complex. They act downstream of cell surface receptors, such as B cell receptors, T cell receptors, B cell activating factors and Toll-like receptors, and participate in the biological process of MALT lymphoma. The discovery of therapeutic drugs that exclusively inhibit the antigen receptor signaling pathway will be beneficial for the treatment of B cell lymphomas in the future.

A miRNA-binding site single nucleotide polymorphism in the 3'-UTR region of the NOD2 gene is associated with colorectal cancer

Colorectal cancer (CRC) is one of the common malignancies worldwide. Single nucleotide polymorphisms in miRNA-binding site on gene transcripts are reported to play important role in increased risk of CRC in different population. We performed a case-control study using 88 CRC patients and 88 non-cancer counterparts to evaluate the association between NOD2 rs3135500 polymorphism located at 3' untranslated region of the gene and risk of sporadic CRC. Genotyping of rs3135500 polymorphism was performed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay. We found a significant association of AA genotype with risk of CRC (adjusted OR 3.100, CI 1.621-5.930, p < 0.001). Also, significant difference in physical activity (p = 0.001) between case and control groups was found. We also found that individuals in control group were more aspirin or NSAID user compared to sporadic CRC cases (p = 0.002). In the case group, individuals with GG genotype consumed more aspirin or NSAID compared with AA+AG genotypes (33.3 vs. 9.6 %, adjusted OR 4.71, CI 1.25-17.76, p = 0.02). However, in the control group, individuals with AA+AG genotypes used more aspirin or NSAID compared with GG genotypes (47.2 vs. 11.4 %, adjusted OR 14 %, CI 0.05-0.47, p < 0.001).

CARD15 mutations and colorectal cancer in a South European country

PURPOSE

CARD15 mutations are associated with higher susceptibility to Crohn's disease (CD) and longstanding colonic CD increases the risk of developing colorectal cancer (CRC). The relation between these mutations and sporadic CRC remains controversial. The aim of this study was to assess whether germline and/or somatic CARD15 mutations are risk factors for sporadic CRC in Portugal and whether there are genotype-phenotype correlations in these patients.

METHODS

The three main CARD15 mutations (R702W, G908R and 3020insC) were researched in 112 sporadic CRC patients and 152 healthy subjects.

RESULTS

Overall, CARD15 mutations were found in 18 patients (16.1%) and in 15 controls (9.9%; p = 0.132). Individually, the incidence of R702W was significantly higher in patients than in controls (12.5% vs. 5.3%, p = 0.035), whereas the genotype frequencies for G908R (2.7% vs. 3.3%) and 3020insC (0.9% vs. 1.3%) were not statistically different between the two groups. Entire genotypic agreement was found in patients genotyped for blood and neoplastic DNA. A significantly higher incidence of CARD15 mutations was detected in patients with CRC diagnosed under 60 years old (28.6% vs. 10.4%, p = 0.015) and in female patients (24.4% vs. 10.4%, p = 0.048). No associations were found between CARD15 mutations and family history, symptoms or CRC pathologic characteristics.

CONCLUSIONS

The CARD15 R702W variant might be a predisposing factor to sporadic CRC in Portugal, particularly in patients under 60-years old and in female patients. This susceptibility appears to be linked with germline CARD15 mutations. Nevertheless, we have found no evidence that CARD15 mutations predict the pathologic characteristics of CRC.

Differential effects of NOD2 polymorphisms on colorectal cancer risk: a meta-analysis

INTRODUCTION

Since Kurzawski et al. described an association between the 3020insC NOD2 single nucleotide polymorphism and the risk of colorectal cancer(CRC) in 2004, reports published in the past several years have controversial results regarding the relationship between the development of CRC and NOD2 gene polymorphisms. To clarify the potential role of NOD2 P286S, R702W, G908R, and 3020insC polymorphisms in CRC patients, we have undertaken a systematic review and meta-analysis of published articles.

MATERIALS AND METHODS

Studies reporting on NOD2 polymorphisms and CRC were searched in the PubMed, EMBASE, and the Science Citation Index from the inception of each database to May, 2009. The search strategy included the keywords "CRC", "colon cancer", "rectal cancer", "polymorphism", and "NOD2/CARD15".

RESULT

Eight eligible case-control studies about Caucasians from four countries contributed data on 5,888 subjects (cases: 3,524; controls: 2,364). Compared to the wild genotype, the R702W, G908R, and 3020insC polymorphisms were associated with an increased risk of CRC (odds ratio (OR): 1.59, 1.98, 1.44; 95% confidence interval (CI): 1.09-2.32, 1.14-3.44, 1.13-1.84; P = 0.02, 0.01, 0.003). However, P268S polymorphism did not influence CRC risk (OR: 1.27; CI: 0.32-5.00; P = 0.73).

CONCLUSIONS

These findings indicate that NOD2 R702W, G908R, and 3020insC polymorphisms contribute to CRC susceptibility in Caucasians. Meta-analysis of these polymorphisms in NOD2 gene will help determine their role in CRC carcinogenesis.

NOD2/CARD15 genotype and common gastrointestinal diseases in 43,600 individuals

OBJECTIVES

NOD2/CARD15 is involved in the innate immune response and three polymorphisms in this gene (Arg702Trp rs2066844, Gly908Arg rs2066845 and Leu1007fsinsC rs5743293) have been associated with risk of the rare Crohn's disease. We tested the hypothesis that polymorphisms in NOD2/CARD15 associate with risk of nine common gastrointestinal diseases.

DESIGN AND SETTING

We genotyped 43 596 white individuals from the Danish general population followed for 31 years, during which time 782 developed oesophagitis and reflux, 1395 ulcus ventriculi and duodeni, 1384 gastritis and dyspepsia, 1407 appendicitis, 646 irritable bowel syndrome, 1301 infectious diseases of the gastrointestinal tract, 681 anal fissure, fistula and abscess, 826 gastrointestinal cancer and 161 developed cancer in liver and pancreas.

RESULTS

Some 89% were non-carriers, 11% heterozygotes, 0.15% homozygotes and 0.23% compound heterozygotes. Cumulative incidences differed by genotype for appendicitis (log-rank P = 0.02), anal fissure, fistula and abscess (P = 0.003) and gastrointestinal cancer (P = 0.004), but not for any of the other endpoints. Compared with non-carriers, age and sex adjusted hazard ratios were 2.7 (95%CI 1.4-5.5) for appendicitis amongst compound heterozygotes, 3.2 (1.3-7.8) for anal fissure, fistula and abscess amongst compound heterozygotes, and 3.8 (1.6-9.2) for gastrointestinal cancer amongst homozygotes, whilst other genotypes did not have increased risk. The increased risk of gastrointestinal cancer amongst homozygotes appeared to be similar amongst both men and women and amongst those below or above 60 years, and likely included both upper gastrointestinal cancer and colorectal cancer.

CONCLUSIONS

NOD2/CARD15 polymorphisms are not major risk factors for common gastrointestinal diseases; however, we cannot completely exclude association with appendicitis, anal fissure, fistula and abscess, and gastrointestinal cancer.

NOD2/CARD15 polymorphisms impair innate immunity and increase susceptibility to gastric cancer in an Italian population

In the present case-control study we investigated the potential role of CARD15 R702W, G908R, and 1007fs polymorphisms in Italian gastric cancer patients. The study population consisted of 170 gastric cancer patients and 156 controls. Unconditional regression (odds ratios and 95% confidence interval) was used to investigate the association of the studied polymorphisms with gastric cancer. Higher allele frequencies of R702W and 1007fs polymorphisms were observed in patients with gastric cancer compared with controls (8.53 vs 2.3 and 9.4 vs 0.7, respectively). CARD15 R702W and 1007fs polymorphisms were significantly correlated with gastric cancer incidence (p < 0.0001, p < 0.0001, respectively). No correlation was found upon analyzing the G908R single nucleotide polymorphism (SNP). Our study reports an increased susceptibility to gastric cancer in Italian populations when R702W and 1007fs polymorphisms in the coding region of CARD15 are present. The interaction between NOD-induced proinflammatory cytokines on gastric mucosa and environmental carcinogens could represent one of the mechanisms by which CARD15 polymorphisms increase the susceptibility to gastric cancer. Meta-analyses of these SNPs and further analyses of additional polymorphisms/haplotypes in NOD genes will help determine their role in carcinogenesis.

Antioxidant and Anti-Inflammatory Activities of the PlantAndrographis PaniculataNees

In this study, we explored the antioxidant and anti-inflammatory properties of the medicinal herb Andrographis paniculata using in vitro as well as in vivo systems. Methanolic extract of Andrographis paniculata was found to inhibit formation of oxygen derived free radicals such as superoxide (32%) hydroxyl radicals (80%) lipid peroxidation (80%) and nitric oxide (42.8%) in in vitro system. In vivo studies using BALB/c mice models also showed significant inhibition in PMA induced superoxide (32.4%) and nitric oxide (65.3%) formation. Interestingly we also found that, administration of Andrographis paniculata extract produced complete inhibition of carageenan induced inflammation compared with control models.

Polymorphisms within inflammatory genes and colorectal cancer

Background

Chronic inflammation is a risk factor for colorectal cancer and polymorphisms in the inflammatory genes could modulate the levels of inflammation. We have investigated ten single nucleotide polymorphisms (SNPs) in the following inflammation-related genes: TLR4 (Asp299Gly), CD14 (-260 T>C), MCP1 (-2518 A>G), IL12A (+7506 A>T, +8707 A>G, +9177 T>A, +9508 G>A), NOS2A (+524T>C), TNF (-857C>T), and PTGS1 (V444I) in 377 colorectal (CRC) cancer cases and 326 controls from Barcelona (Spain).

Results

There was no statistically significant association between the SNPs investigated and colorectal cancer risk.

Conclusion

The lack of association may show that the inflammatory genes selected for this study are not involved in the carcinogenic process of colorectum. Alternatively, the negative results may derive from no particular biological effect of the analysed polymorphisms in relation to CRC. Otherwise, the eventual biological effect is so little to go undetected, unless analysing a much larger sample size.

Alteration of gene expression in macroscopically normal colonic mucosa from individuals with a family history of sporadic colon cancer

PURPOSE

We have shown that the expression of several genes associated with human colon cancer is altered in the morphologically normal colonic mucosa (MNCM) of APC(min) mice and humans with colon cancers. To determine whether these alterations also occur in the MNCM of individuals who have not developed colon cancer but are at high risk of doing so, we measured gene expression in the MNCM of individuals with a family history of colon cancer.

METHODS

Expression of 16 genes in the MNCM of 12 individuals with a first-degree relative with sporadic colon cancer and 16 normal controls were measured by quantitative reverse transcription-PCR. All subjects tested had normal colonoscopic examinations. Biopsy samples of MNCM were obtained from the ascending, transverse, descending, and rectosigmoid regions of the colon (2-8 biopsy samples were obtained from each region).

RESULTS

Relative to normal controls, the expression of several genes, including PPAR-gamma, SAA1, and IL-8 were significantly altered in the macroscopically normal rectosigmoid mucosa from individuals with a family history of colon cancer.

CONCLUSIONS

Molecular abnormalities that precede the appearance of adenomatous polyp are present in the MNCM of individuals who have a family history of colon cancer. This observation raises the possibility of screening for individuals who are at an increased risk of developing colon cancer by analysis of gene expression in rectosigmoid biopsy samples. To assess this possibility, prospective studies will be needed to determine whether or not altered gene expression is associated with the subsequent development of adenomatous polyps and/ or colonic carcinomas.

Association between mutations in the CARD15/NOD2 gene and colorectal cancer in a Greek population

Epidemiological observations suggest that cancer arises from chronically inflamed tissues. Inflammatory bowel disease (IBD) is a typical example since patients with longstanding IBD are at increased risk for development of colorectal cancer (CRC). Therefore, genetic factors predisposing to or implicated in the chronic inflammatory process in IBD may simultaneously predispose to CRC. Recently CARD15/NOD2 has been associated with IBD, which further strengthens the notion that the inflammatory response plays a crucial role in this disease. Several mutations have been identified in the CARD15/NOD2 gene, which appear with significantly higher frequency in patients with IBD. In this report, we have examined the frequency of the 3 major mutations R702W, G908R and 3020insC of the CARD2/NOD2 gene in a series of 104 consecutive Greek patients with sporadic colorectal cancer and 100 healthy individuals. The frequency of all the mutations was significantly elevated compared to the control population (R702W, OR=5.00, p=0.023; G908R, OR=2.78, p=0.025; 3020insC, OR=2.44, p=0.017). Patients with advanced stage tumors were more frequently carriers of at least 1 variant in the CARD15/NOD2 gene (p=0.009). Our results suggest that CARD2/NOD2 may be a genetic factor that predispose to sporadic colorectal cancer.

Interferon-gamma cooperates with Helicobacter pylori to induce iNOS-related apoptosis in AGS gastric adenocarcinoma cells

Helicobacter pylori colonizes the human stomach and causes gastric disease. The resulting gastric damage is a multi-step process involving several molecular factors and different target cells. Th1 cytokines released by neutrophils and lymphoid cells that infiltrate gastric mucosa, nitric oxide production and inducible nitric oxide synthase (iNOS) are associated with immune activation and tissue injury. Many other molecular processes such as apoptosis, as well as angiogenic factors and integrins, are involved in H. pylori pathogenesis. We used cancer gastric cells AGS and MKN as experimental models to evaluate apoptotic rates, iNOS gene expression with and without the presence of interferon-gamma (IFN-gamma), placenta growth factor gene expression and alphav modulation. Our results show that AGS cells stimulated with H. pylori underwent apoptosis. Moreover, the addition of IFN-gamma caused a further increase in iNOS gene expression and in the apoptotic rates. We also found early modulation in PlGF and alphav expression, and noted that p53 and bax gene expression was involved in the apoptotic process. Taken together, these findings demonstrate that H. pylori employs a series of mechanisms to avoid the host defense and cause gastric mucosa damage. One H. pylori pathogenic mechanism for causing gastric damage is the induction of iNOS-dependent apoptosis that is strongly enhanced by IFN-gamma. Thus, data obtained indicate that Th1 cytokines such as IFN-gamma, via modulation of iNOS gene expression, may contribute to an increase in the pathogenicity of H. pylori infections.

Detection of serum anti-Helicobacter pylori immunoglobulin G in patients with different digestive malignant tumors

AIM: To investigate the seroprevalence of Helicobacter pylori infection in patients with different digestive malignant tumors.

METHODS: Enzyme linked immunosorbent assay (ELISA) was used to detect serum anti-Helicobacter pylori IgG antibody in 374 patients with different digestive malignant tumors and 310 healthy subjects (normal control group).

RESULTS: The seroprevalence of Helicobacter pylori infection was 61.50% (230/374) and 46.77% (145/310), respectively, in patients with digestive tumors and normal controls (P < 0.05). The seroprevalence was 52.38% (33/63), 86.60% (84/97), 83.14% (84/101), 45.24 (19/42), 51.13% (18/35) and 44.44% (16/36), respectively in patients with carcinomas of esophagus, stomach, duodenum, rectum, colon and liver (P < 0.01). In patients with intestinal and diffuse type gastric cancers, the seroprevalence was 93.75% (60/64) and 72.73% (24/33), respectively (P < 0.05). In patients with gastric antral and cardiac cancers, the seroprevalence was 96.43% (54/56) and 73.17% (30/41), respectively (P < 0.05). In patients with ulcerous and proliferous type duodenal cancers, the seroprevalence of H. pylori infection was 91.04% (61/67) and 52.27% (23/44), respectively (P < 0.05). In patients with duodenal bulb and descending cancers, the seroprevalence was 94.20% (65/69) and 45.20% (19/42), respectively (P < 0.05).

CONCLUSION: H. pylori infection is associated with occurrence and development of gastric and duodenal carcinomas. Furthermore, it is also associated with histological type and locations of gastric and duodenal carcinomas.

Helicobacter pylori modulation of gastric and duodenal mucosal T cell cytokine secretions in children compared with adults

BACKGROUND

In contrast to adults, ulcers are un-common in Helicobacter pylori-infected children. Since immunological determinants influence the outcome of H. pylori infection, we have investigated mucosal T cell responses in H. pylori-infected children and compared them with those of adults and negative controls.

MATERIAL AND METHODS

Mucosal biopsies were obtained from 43 patients undergoing an upper GI endoscopy for dyspeptic symptoms. The concentrations of released cytokines and the density of CD3+, CD25+ and CD69+cells were evaluated by flow cytometry, and the numbers of cytokine-secreting cells were measured by ELISPOT.

RESULTS

The numbers of isolated antral CD3+ lymphocytes were only significantly raised in infected adults compared with noninfected controls (p < 0.05), whereas the proportion of CD3+ cells expressing activation markers (CD25 or CD69) remained low. In the stomach, IFN-gamma concentrations increased in infected children and infected adults compared with controls (p < 0.05), but IFN-gamma concentrations were tenfold lower in children than in adults (p < 0.01). IL-2, IL-4, IL-10 and TNF-alpha concentrations were similar in infected and in uninfected children and adults. In contrast, in the duodenum, IFN-gamma, as well as IL-4 and IL-10 concentrations were only increased in infected children compared with controls (p < 0.05). The concentrations of these cytokines were similar in both groups of adults who, however, like children, displayed a higher number of duodenal IL-4-secreting cells compared to controls (p < 0.05).

CONCLUSION

These results suggest that IFN-gamma secretion in the stomach of H. pylori-infected patients is lower in children than in adults. This could protect children from development of severe gastro-duodenal diseases such as ulcer disease. In addition, infected patients are characterised by a dysregulation of the mucosal cytokine secretion at distance from the infection site.

Depletion of neutrophils in IL-10(-/-) mice delays clearance of gastric Helicobacter infection and decreases the Th1 immune response to Helicobacter

Gastric infection with Helicobacter induces a lymphocyte-rich mucosal inflammation that contains a minor population of neutrophilic granulocytes. The function of neutrophils in the local immune response to gastric Helicobacter infection remains unknown. To investigate this issue, we conducted experiments in neutrophil-depleted control wild-type (wt) and IL-10(-/-) mice infected with Helicobacter felis by gastric lavage. Infection of wt mice elicited a mild, focal gastritis and a Helicobacter-specific Th1 immune response. In wt mice Helicobacter colonization of the stomach was persistent and progressively increased during the 29 days of observation. Infection of IL-10(-/-) mice with H. felis elicited a severe chronic gastritis and a greatly enhanced Helicobacter-specific Th1 immune response, as compared with wt mice. After initial colonization, the IL-0(-/-) mice completely cleared Helicobacter from the stomach by day 8. The gastric inflammation in wt and IL-10(-/-) mice contained modest numbers of neutrophils. The intensity of gastric inflammation and the extent of Helicobacter colonization were similar in control and in neutrophil-depleted wt mice. In contrast, neutrophil depletion of Helicobacter-infected IL-10(-/-) mice decreased the severity of gastritis, modulated the Helicobacter-specific Th1 immune response, and delayed the clearance of bacteria from the stomach. These studies identify a role for neutrophils in the local and systemic immune response to gastric Helicobacter in IL-10(-/-) mice.

Specific entry of Helicobacter pylori into cultured gastric epithelial cells via a zipper-like mechanism

Although Helicobacter pylori has generally been considered an extracellular pathogen, a number of in vitro infection experiments and biopsy examinations have shown that it is capable of occasionally entering mammalian host cells. Here, we characterized this entry process by using AGS cells as a host cell model. In gentamicin protection-invasion assays, the number of H. pylori colonies recovered was lower than that for Salmonella enterica serovar Typhimurium X22, Escherichia coli expressing InvA, and Yersinia enterocolitica YO:9 grown at 25 degrees C but higher than that for Neisseria gonorrhoeae VP1 and Y. enterocolitica YO:9 grown at 37 degrees C. At the ultrastructural level, the entry process was observed to occur via a zipper-like mechanism. Internalized H. pylori was bound in tight LAMP-1-containing vacuoles in close association with condensed filamentous actin and tyrosine phosphorylation signals. Wortmannin, a potent inhibitor of phosphatidylinositol 3-kinase, and calphostin C, an inhibitor of protein kinase C, both inhibited the entry of H. pylori in a sensitive and dose-dependent manner; however, the level of entry was enhanced by sodium vanadate, an inhibitor of tyrosine phosphatases and ATPases. Furthermore, the cytokine tumor necrosis factor alpha antagonized the entry of H. pylori into AGS cells. Collectively, these results demonstrate that the entry of H. pylori into AGS cells occurs via a zipper-like mechanism which involves various host signal transduction events.

Apoptosis in gastric epithelium induced by Helicobacter pylori infection: implications in gastric carcinogenesis

OBJECTIVES

Helicobacter pylori is an identified carcinogen for gastric cancer, however, the underlying mechanisms remain to be defined. In this review, we sought to elucidate the role of apoptosis in gastric carcinogenesis, to determine the influence of H. pylori infection on apoptosis, and finally to provide insights into the mechanisms by which H. pylori may lead to gastric carcinogenesis.

METHODS

A broad-based MEDLINE and Current Contents literature search was performed to identify relevant publications between 1966 and March 2000 addressing H. pylori infection, apoptosis, cell proliferation, gastric carcinoma, oncogenes, and tumor suppressor genes, as well as the products of these genes. Abstracts from recent major conferences that provided adequate additional data were also included.

RESULTS

Apoptotic cells are rare in the glandular neck region (the generative cell zone) of normal gastric mucosa. With progression of atrophic gastritis, the generative cell zone shifts downward and a relatively large number of apoptotic cells occur. In intestinalized glands, both apoptotic cells and proliferative cells are present in deeper portions of the glands, corresponding to the generative zone. A higher frequency of apoptosis has been observed in gastric dysplasia than in coexisting gastric carcinomas, whereas the number of proliferative cells is significantly higher in gastric carcinoma than in dysplasia. Upregulation of oncogene bcl-2 in premalignant lesions and "downregulation" of the gene after malignant change is probably a common event. Accumulation of p53 protein is first detected in dysplasia, although mutation of the pS3 gene may occur in intestinal metaplasia. H. pylori infection induces apoptosis in gastric epithelial cells, which returns to normal after eradication of the infection. Numerous molecules produced by H. pylori including cytotoxin (VacA), lipopolysaccharide, monochloramine, and nitric oxide may directly induce apoptosis. Moreover, H. pylori-stimulated host inflammatory/immune responses lead to release of a large amount of cytokines. Cytokines produced by type 1 T helper cells, such as TNF-alpha and IFN-gamma, markedly potentiate apoptosis. Gastric cell proliferation is significantly higher in patients with H. pylori infection than in normal controls, and eradication of the infection leads to a reduction in cell proliferation. Apoptosis and cell proliferation are also increased in precancerous lesions such as gastric atrophy, intestinal metaplasia, and dysplasia in the presence of H. pylori infection. However, H. pylori-induced apoptosis may no longer be cell cycle-dependent in these lesions because of the occurrence of alterations and mutations of apoptosis-regulating genes, resulting in a loss of balance between apoptosis and cell proliferation.

CONCLUSIONS

It is hypothesized that H. pylori-induced apoptosis may play a key role in gastric carcinogenesis by increasing cell proliferation and/or resulting in gastric atrophy.