Helicobacter pylori Counteracts the Apoptotic Action of Its VacA Toxin by Injecting the CagA Protein into Gastric Epithelial Cells

Infection with Helicobacter pylori is responsible for gastritis and gastroduodenal ulcers but is also a high risk factor for the development of gastric adenocarcinoma and lymphoma. The most pathogenic H. pylori strains (i.e., the so-called type I strains) associate the CagA virulence protein with an active VacA cytotoxin but the rationale for this association is unknown. CagA, directly injected by the bacterium into colonized epithelium via a type IV secretion system, leads to cellular morphological, anti-apoptotic and proinflammatory effects responsible in the long-term (years or decades) for ulcer and cancer. VacA, via pinocytosis and intracellular trafficking, induces epithelial cell apoptosis and vacuolation. Using human gastric epithelial cells in culture transfected with cDNA encoding for either the wild-type 38 kDa C-terminal signaling domain of CagA or its non-tyrosine-phosphorylatable mutant form, we found that, depending on tyrosine-phosphorylation by host kinases, CagA inhibited VacA-induced apoptosis by two complementary mechanisms. Tyrosine-phosphorylated CagA prevented pinocytosed VacA to reach its target intracellular compartments. Unphosphorylated CagA triggered an anti-apoptotic activity blocking VacA-induced apoptosis at the mitochondrial level without affecting the intracellular trafficking of the toxin. Assaying the level of apoptosis of gastric epithelial cells infected with wild-type CagA⁺/VacA⁺ H. pylori or isogenic mutants lacking of either CagA or VacA, we confirmed the results obtained in cells transfected with the CagA C-ter constructions showing that CagA antagonizes VacA-induced apoptosis. VacA toxin plays a role during H. pylori stomach colonization. However, once bacteria have colonized the gastric niche, the apoptotic action of VacA might be detrimental for the survival of H. pylori adherent to the mucosa. CagA association with VacA is thus a novel, highly ingenious microbial strategy to locally protect its ecological niche against a bacterial virulence factor, with however detrimental consequences for the human host.     

Helicobacter pylori Genotypes Associated with Gastric Histo-Pathological Damages in a Moroccan Population

H. pylori persistent infection induces chronic gastritis and is associated with peptic ulcer disease and gastric carcinoma development. The severity of these diseases is related to human’s genetic diversity, H. pylori genetic variability and environmental factors. To identify the prevalence of histo-pathological damages caused by H. pylori infection in Moroccan population, and to determine their association to H. pylori genotypes, a prospective study has been conducted during 3 years on patients attending the gastroenterology department of Hassan II University Hospital (CHU) of Fez, Morocco. A total of 801 Moroccan adults’ patients were recruited; H. pylori was diagnosed and genotyped by PCR in biopsy specimens and histological exam was performed. We found a high rate of glandular atrophy. Chronic inflammation, neutrophil activity and glandular atrophy showed statistically significant association with H. pylori infection. However, intestinal metaplasia was inversely associated to this infection and no association was observed with gastric cancer cases. A statistically significant association was found between intestinal metaplasia and vacAs1 and vac Am1 genotypes in patients aged 50 years and more but not in younger. This last genotype is also associated to gastric cancer. In this study, gastric cancer showed no significant association with H. pylori. Further studies are warranted to determine the role of other etiological agents such as Epstein-Barr virus, human papillomavirus and possibly environmental and dietetic factors in the occurrence of this pathology.     

Helicobacter pylori,HIV and Gastric Hypochlorhydria in the Malawian Population

Background

HIV and Helicobacter pylori are common chronic infections in sub-Saharan Africa. Both conditions can predispose to gastric hypochlorhydria that may be a risk factor for enteric infections and reduced drug absorption. We have investigated to what extent HIV and H. pylori infections are associated with hypochlorhydria in a Malawian cohort of patients undergoing endoscopy.

Methods

104 sequential symptomatic adults referred for gastroscopy at Queen Elizabeth Central Hospital, Blantyre, Malawi, had blood taken for rapid HIV testing and fasting serum gastrin analysis. Gastric fluid was aspirated for pH testing, and gastric biopsies were taken.

Results

After 9/104 HIV-infected patients who were already established on anti-retroviral therapy were excluded, 17/95 (25.0%) were seropositive for untreated HIV, and 68/95 (71.6%) patients were H. pylori positive by histology. Hypochlorhydria (fasting gastric pH>4.0) was present in 55.8% (53/95) of patients. H. pylori infection was significantly associated with hypochlorhydria (OR 2.91, [1.02-7.75], p=0.046). While single infection with HIV was not significantly independently associated with hypochlorhydria. H. pylori and HIV co-infection was more strongly associated with hypochlorhydria (OR 6.25, [1.33-29.43], p=0.020) than either infection alone, suggesting an additive effect of co-infection. HIV infection was associated with higher serum gastrin levels (91.3pM vs. 53.1pM, p=0.040), while H. pylori infection was not (63.1pM vs. 55.1pM, p=0.610). Irrespective of H. pylori and HIV status, most patients (>90%) exhibited pangastritis. Only three patients had histological evidence of gastric atrophy, of which only one was HIV-infected.

Conclusion

H. pylori infection was associated with fasting hypochlorhydria, while HIV was not independently associated. HIV and H. pylori co-infection, however, was more strongly associated with hypochlorhydria than H. pylori infection alone. The mechanism of this apparent additive effect between HIV and H. pylori remains unclear, but appears to be related to chronic pangastritis rather than gastric atrophy, and associated with hypergastrinaemia in HIV-infected individuals.     

N-myc Downstream Regulated Gene 1 (NDRG1) Promotes Metastasis of Human Scirrhous Gastric Cancer Cells through Epithelial Mesenchymal Transition

Our recent study demonstrated that higher expression of N-myc downregulated gene 1 (NDRG1) is closely correlated with poor prognosis in gastric cancer patients. In this study, we asked whether NDRG1 has pivotal roles in malignant progression including metastasis of gastric cancer cells. By gene expression microarray analysis expression of NDRG1 showed the higher increase among a total of 3691 up-regulated genes in a highly metastatic gastric cancer cell line (58As1) than their parental low metastatic counterpart (HSC-58). The highly metastatic cell lines showed decreased expression of E-cadherin, together with enhanced expression of vimentin and Snail. This decreased expression of E-cadherin was restored by Snail knockdown in highly metastatic cell lines. We next established stable NDRG1 knockdown cell lines (As1/Sic50 and As1/Sic54) from the highly metastatic cell line, and both of these cell lines showed enhanced expression of E-cadherin and decreased expression of vimentin and Snail. And also, E-cadherin promoter-driven luciferase activity was found to be increased by NDRG1 knockdown in the highly metastatic cell line. NDRG1 knockdown in gastric cancer cell showed suppressed invasion of cancer cells into surround tissues, suppressed metastasis to the peritoneum and decreased ascites accumulation in mice with significantly improved survival rates. This is the first study to demonstrate that NDRG1 plays its pivotal role in the malignant progression of gastric cancer through epithelial mesenchymal transition.     

Helicobacter pylori Eradication Prevents Metachronous Gastric Neoplasms after Endoscopic Resection of Gastric Dysplasia

Purpose

There is insufficient data about the role of eradication of H. pylori after endoscopic resection (ER) for gastric dysplasia. The aim was to investigate the benefit of H. pylori eradication after ER in patients with gastric dysplasia to prevent metachronous gastric neoplasms.

Materials and Methods

We retrospectively reviewed 1872 patients who underwent ER of gastric dysplasia. We excluded patients with a follow-up period of <2 years or who had not undergone tests for active H. pylori infection. A total of 282 patients were enrolled. The patients were categorized into those without active H. pylori infection (H. pylori-negative group, n = 124), those who successfully underwent H. pylori eradication (eradicated group, n = 122), and those who failed or did not undergo H. pylori eradication (persistent group, n = 36).

Results

Metachronous recurrence was diagnosed in 36 patients, including 19 in the H. pylori-negative group, 10 in the eradicated group, and 7 in the persistent group. The cumulative incidence of metachronous recurrence was significantly lower in the H. pylori-eradicated group in comparison with either of the H. pylori-persistent (non-eradicated or failed) groups (p = 0.039). Similarly, the incidence of metachronous recurrence was significantly lower in the H. pylori-eradicated group compared with the H. pylori-negative group (p = 0.041).

Conclusion

Successful H. pylori eradication may reduce the development of metachronous gastric neoplasms after ER in patients with gastric dysplasia.     

Crosstalk between Helicobacter pylori and Gastric Epithelial Cells Is Impaired by Docosahexaenoic Acid

H. pylori colonizes half of the world''s population leading to gastritis, ulcers and gastric cancer. H. pylori strains resistant to antibiotics are increasing which raises the need for alternative therapeutic approaches. Docosahexaenoic acid (DHA) has been shown to decrease H. pylori growth and its associated-inflammation through mechanisms poorly characterized. We aimed to explore DHA action on H. pylori-mediated inflammation and adhesion to gastric epithelial cells (AGS) and also to identify bacterial structures affected by DHA. H. pylori growth and metabolism was assessed in liquid cultures. Bacterial adhesion to AGS cells was visualized by transmission electron microscopy and quantified by an Enzyme Linked Immunosorbent Assay. Inflammatory proteins were assessed by immunoblotting in infected AGS cells, previously treated with DHA. Bacterial total and outer membrane protein composition was analyzed by 2-dimensional gel electrophoresis. Concentrations of 100 µM of DHA decreased H. pylori growth, whereas concentrations higher than 250 µM irreversibly inhibited bacteria survival. DHA reduced ATP production and adhesion to AGS cells. AGS cells infected with DHA pre-treated H. pylori showed a 3-fold reduction in Interleukin-8 (IL-8) production and a decrease of COX2 and iNOS. 2D electrophoresis analysis revealed that DHA changed the expression of H. pylori outer membrane proteins associated with stress response and metabolism and modified bacterial lipopolysaccharide phenotype. As conclusions our results show that DHA anti-H. pylori effects are associated with changes of bacteria morphology and metabolism, and with alteration of outer membrane proteins composition, that ultimately reduce the adhesion of bacteria and the burden of H. pylori-related inflammation.     

上皮间充质转化促进肿瘤细胞干性获得的研究进展

上皮间充质转化是上皮细胞丢失细胞极性和细胞黏附,而获得间充质细胞迁移和侵袭特性的生物学过程.肿瘤干细胞是存在于肿瘤中具有自我更新和异质性分化能力的一小群细胞,在肿瘤的发生发展过程中起重要的作用.上皮间充质转化(EMT)与肿瘤的转移密切相关,而近几年的研究表明,EMT也可以促进肿瘤细胞获得干细胞的特性,因此使肿瘤治疗更困难,本文对EMT促肿瘤干细胞形成机制及其对临床治疗意义的研究进展作一综述.     

Collagen XV Inhibits Epithelial to Mesenchymal Transition in Pancreatic Adenocarcinoma Cells

Collagen XV (COLXV) is a secreted non-fibrillar collagen found within basement membrane (BM) zones of the extracellular matrix (ECM). Its ability to alter cellular growth in vitro and to reduce tumor burden and increase survival in vivo support a role as a tumor suppressor. Loss of COLXV during the progression of several aggressive cancers precedes basement membrane invasion and metastasis. The resultant lack of COLXV subjacent to the basement membrane and subsequent loss of its interactions with other proteins in this zone may directly impact tumor progression. Here we show that COLXV significantly reduces invasion of pancreatic adenocarcinoma cells through a collagen I (COLI) matrix. Moreover, we demonstrate that epithelial to mesenchymal transition (EMT) in these cells, which is recapitulated in vitro by cell scattering on a COLI substrate, is inhibited by over-expression of COLXV. We identify critical collagen-binding surface receptors on the tumor cells, including the discoidin domain receptor 1 (DDR1) and E-Cadherin (E-Cad), which interact with COLXV and appear to mediate its function. In the presence of COLXV, the intracellular redistribution of E-Cad from the cell periphery, which is associated with COLI-activated EMT, is inhibited and concurrently, DDR1 signaling is suppressed. Furthermore, continuous exposure of the pancreatic adenocarcinoma cells to high levels of COLXV suppresses endogenous levels of N-Cadherin (N-Cad). These data reveal a novel mechanism whereby COLXV can function as a tumor suppressor in the basement membrane zone.     

Streptococcus mitis Induces Conversion of Helicobacter pylori to Coccoid Cells during Co-Culture In Vitro

Helicobacter pylori (H. pylori) is a major gastric pathogen that has been associated with humans for more than 60,000 years. H. pylori causes different gastric diseases including dyspepsia, ulcers and gastric cancers. Disease development depends on several factors including the infecting H. pylori strain, environmental and host factors. Another factor that might influence H. pylori colonization and diseases is the gastric microbiota that was overlooked for long because of the belief that human stomach was a hostile environment that cannot support microbial life. Once established, H. pylori mainly resides in the gastric mucosa and interacts with the resident bacteria. How these interactions impact on H. pylori-caused diseases has been poorly studied in human. In this study, we analyzed the interactions between H. pylori and two bacteria, Streptocccus mitis and Lactobacillus fermentum that are present in the stomach of both healthy and gastric disease human patients. We have found that S. mitis produced and released one or more diffusible factors that induce growth inhibition and coccoid conversion of H. pylori cells. In contrast, both H. pylori and L. fermentum secreted factors that promote survival of S. mitis during the stationary phase of growth. Using a metabolomics approach, we identified compounds that might be responsible for the conversion of H. pylori from spiral to coccoid cells. This study provide evidences that gastric bacteria influences H. pylori physiology and therefore possibly the diseases this bacterium causes.     

幽门螺杆菌细胞毒素相关蛋白A对人胃腺癌上皮AGS细胞蛋白质组的影响

为明确幽门螺杆菌细胞毒素相关蛋白A(CagA)在致病过程中对宿主细胞蛋白质表达的影响及其与CagA磷酸化的相关性,分别用野生型cagA质粒和磷酸化位点突变型cagA质粒转染人胃腺癌上皮AGS细胞,应用表面加强激光解析电离-飞行时间质谱技术,分析细胞蛋白质组的改变。结果表明,在可捕获的400多个蛋白质中,野生型CagA可使AGS细胞质荷比为4229、4714、4728、5129、6546、6657、8162、9084、13803、14021的10个蛋白质表达上调,质荷比为2013、4286、8563、9952、11085、11645的6个蛋白质表达下调。突变型CagA只能使质荷比为4714、4728、6546和6657的蛋白质表达上调。这些结果提示,这16个差异表达蛋白质可能参与了CagA的致病过程,其中质荷比为4714、4728、6546和6657蛋白质表达的改变与CagA的磷酸化作用无关,而其余12个蛋白质表达的改变则都依赖于CagAEPIYA重复序列酪氨酸位点的磷酸化。这些发现为进一步探讨CagA的致病机制提供了实验依据。     

DEC205在幽门螺杆菌感染胃上皮细胞中的表达

目的：探讨幽门螺杆菌及其热休克蛋白60（H．pylori—HSP60）感染与胃上皮细胞表面DEC205受体的关系。方法：分别用H．pylori、H．pylori-HSP60及E．coliLPS刺激胃上皮细胞KATOIII,利用免疫荧光染色技术观察KATOIII细胞表面DEC205蛋白的表达变化,再利用RT—PCR技术,观察细胞中DEC205mRNA对上述抗原刺激后的变化。结果：H．pylori、H．pylori—HSP60及E．coliLPS的刺激明显引起细胞表面DEC205蛋白的表达以及细胞内DEC205mRNA的产生。结论：H．pylori感染与胃上皮细胞表面的胞吞受体DEC205有着密切的关系。     

Helicobacter pylori from Gastric Cancer and Duodenal Ulcer Show Same Phylogeographic Origin in the Andean Region in Colombia

Background

A recent report has shown that the phylogenetic origin of Helicobacter pylori based on multi-locus sequence typing (MLST) was significantly associated with the severity of gastritis in Colombia. However, the potential relationship between phylogenetic origin and clinical outcomes was not examined in that study. If the phylogenetic origin rather than virulence factors were truly associated with clinical outcomes, identifying a population at high risk for gastric cancer in Colombia would be relatively straightforward. In this study, we examined the phylogenetic origins of strains from gastric cancer and duodenal ulcer patients living in Bogota, Colombia.

Methods

We included 35 gastric cancer patients and 31 duodenal ulcer patients, which are considered the variant outcomes. The genotypes of cagA and vacA were determined by polymerase chain reaction. The genealogy of these Colombian strains was analyzed by MLST. Bacterial population structure was analyzed using STRUCTURE software.

Results

H. pylori strains from gastric cancer and duodenal ulcer patients were scattered in the phylogenetic tree; thus, we did not detect any difference in phylogenetic distribution between gastric cancer and duodenal ulcer strains in the hpEurope group in Colombia. Sixty-six strains, with one exception, were classified as hpEurope irrespective of the cagA and vacA genotypes, and type of disease. STRUCTURE analysis revealed that Colombian hpEurope strains have a phylogenetic connection to Spanish strains.

Conclusions

Our study showed that a phylogeographic origin determined by MLST was insufficient for distinguishing between gastric cancer and duodenal ulcer risk among hpEurope strains in the Andean region in Colombia. Our analysis also suggests that hpEurope strains in Colombia were primarily introduced by Spanish immigrants.