幽门螺杆菌慢性感染诱导胃上皮细胞产生凋亡耐受

目的：建立幽门螺杆菌（H.pylori)慢性感染胃上皮细胞模型,并分析H.pylori慢性感染与胃上皮细胞凋亡的关系。方法：首先用H.pylori SS1与人非肿瘤性胃上皮细胞株GES－1共培养16周,建立GES－1模型细胞,然后采用流式细胞术分析这种模型细胞对H.pylori和其它肠道细菌以及抗肿瘤药物凋亡诱导剂的应答。结果：成功获得了H.pylori慢性感染胃上皮细胞模型（GES－1模型细胞）。这种模型细胞不仅对H.pylori诱导的凋亡耐受,而且对其他肠道细菌和一些凋亡诱导剂也是耐受的。结论：幽门螺杆菌慢性感染诱导胃上皮细胞产生凋亡耐受,由此可能增加了胃上皮细胞癌变的危险性。     

Effect of Helicobacter pylori on gastric epithelial cells

The gastrointestinal epithelium has cells with features that make them a powerful line of defense in innate mucosal immunity. Features that allow gastrointestinal epithelial cells to contribute in innate defense include cell barrier integrity, cell turnover, autophagy, and innate immune responses. Helicobacter pylori (H. pylori) is a spiral shape gram negative bacterium that selectively colonizes the gastric epithelium of more than half of the world’s population. The infection invariably becomes persistent due to highly specialized mechanisms that facilitate H. pylori’s avoidance of this initial line of host defense as well as adaptive immune mechanisms. The host response is thus unsuccessful in clearing the infection and as a result becomes established as a persistent infection promoting chronic inflammation. In some individuals the associated inflammation contributes to ulcerogenesis or neoplasia. H. pylori has an array of different strategies to interact intimately with epithelial cells and manipulate their cellular processes and functions. Among the multiple aspects that H. pylori affects in gastric epithelial cells are their distribution of epithelial junctions, DNA damage, apoptosis, proliferation, stimulation of cytokine production, and cell transformation. Some of these processes are initiated as a result of the activation of signaling mechanisms activated on binding of H. pylori to cell surface receptors or via soluble virulence factors that gain access to the epithelium. The multiple responses by the epithelium to the infection contribute to pathogenesis associated with H. pylori.     

Sequence anomalies in the Cag7 gene of the Helicobacter pylori pathogenicity island

The severity of Helicobacter pylori-related disease is correlated with a pathogenicity island (the Cag region of about 26 genes) whose presence is associated with the up-regulation of an IL-8 cytokine inflammatory response in gastric epithelial cells. Statistical analysis of the Cag gene sequences calculated from the complete genome of strain 26695 revealed several unusual features. The Cag7 sequence (1,927 aa) has two repeat regions. Repeat region I runs 317 aa in a form of AAA proximal to the protein N terminal; repeat region II extends 907 aa in the middle of the protein sequence consisting of 74 contiguous segments composed from selections among six consensus sequences and includes 58 regularly distributed cysteine residues with consecutive cysteines mostly 12, 18, or 24 aa apart. This "regular" cysteine arrangement may provide a scaffolding of linker elements stabilized by disulfide bridges. When Cag7 homologues from different strains are compared, differences were found almost exclusively in the repeat regions, resulting from deletion and/or insertion of repeating units. These observations suggest that the anomalous repetitive structure of the sequence plays an important role in the conformation of Cag7 gene product and potentially in the function of the pathogenicity island. Other facets of the Cag7 sequence show significant charge clusters, high multiplet count, and extremes of amino acid usage.     

Helicobacter pylori increases proliferation of gastric epithelial cells.

The direct and indirect effects of helicobacter pylori on cell kinetics of gastric epithelial cell line AGS were investigated by flow cytometric analysis of Ki-67 positive cells and by MTT assay. Flow cytometric analysis of Ki-67 positivity permits detection of cells that are in S-phase, whereas the MTT assay is a colometric measure of the number of viable cells. In the absence of added stimulants, 23.06 (4.88)% mean (SD) of AGS cells were Ki-67 positive. When cells were preincubated in the presence of H pylori, there was a significant increase in Ki-67 positivity (66.20 (7.89)%, p < 0.001). This increase was not seen in cells cultured in the presence of Campylobacter jejuni (24.63 (8.11)% or Escherichia coli (21.66 (9.78)%). Pre-incubation of AGS cells with supernatants from both H pylori and mitogen activated peripheral blood lymphocytes also increased the per cent of cells that were Ki-67 positive (72.93 (8.68) and 69.96 (12.35)%; p, 0.001) respectively. Similar results were also found in MTT assay. These data show that both H pylori directly and the immune/inflammatory response to H pylori indirectly can influence the rate of epithelial cell proliferation, suggesting this bacterium may be an initiating step in gastric carcinogenesis and an important co-carcinogenic factor in H pylori positive subjects.     

Immune responses to Helicobacter pylori infection

Helicobacter pylori(H.pylori)infection is one of the most common infections in human beings worldwide.H.pylori express lipopolysaccharides and flagellin that do not activate efficiently Toll-like receptors and express dedicated effectors,such asγ-glutamyl transpeptidase,vacuolating cytotoxin(vacA),arginase,that actively induce tolerogenic signals.In this perspective,H.pylori can be considered as a commensal bacteria belonging to the stomach microbiota.However,when present in the stomach,H.pylori reduce the overall diversity of the gastric microbiota and promote gastric inflammation by inducing Nod1-dependent pro-inflammatory program and by activating neutrophils through the production of a neutrophil activating protein.The maintenance of a chronic inflammation in the gastric mucosa and the direct action of virulence factors(vacA and cytotoxinassociated gene A)confer pro-carcinogenic activities to H.pylori.Hence,H.pylori cannot be considered as symbiotic bacteria but rather as part of the pathobiont.The development of a H.pylori vaccine will bring health benefits for individuals infected with antibiotic resistant H.pylori strains and population of underdeveloped countries.     

Urease prevents adherence of Helicobacter pylori to Kato III gastric epithelial cells

The role of urease in Helicobacter pylori adherence to and internalization by Kato III cells was investigated. Kato III cells were incubated with wild-type strains (N6 or P1), with isogenic mutants lacking urease (N6ureB::TnKm or P1ureA::TnMax5) or producing the inactive apoprotein (N6ureG::TnKm), and with urease-positive clones recovered after complementation of N6ureB::TnKm with ureAB. Bacteria were stained with the green fluorescent dye PKH2, and the bacteria load of cells was analyzed by flow cytometry. With mutants lacking urease, the bacteria load was considerably increased, in comparison with the corresponding parental strains (P<.001). With clone K2(3), producing larger amounts of urease than N6, a significant reduction of bacteria load was observed, in comparison with the wild type (P<.001). N6ureG::TnKm showed adherence characteristics similar to those of N6. The role of urease in internalization was not clear. Thus, urease significantly inhibits H. pylori adherence to Kato III cells by a mechanism largely independent of enzymatic activity.     

Helicobacter pylori impairs DNA mismatch repair in gastric epithelial cells

BACKGROUND & AIMS: Helicobacter pylori infection is a major gastric cancer risk factor. H. pylori gastritis occurs more frequently in individuals with microsatellite instability-positive than those with microsatellite instability-negative gastric cancers, raising the possibility that H. pylori infection affects DNA mismatch repair (MMR). The aim of this study was to determine the effect of H. pylori on the expression of DNA MMR proteins and RNA in gastric epithelial cells. METHODS: Gastric cancer cell lines were cocultured with H. pylori, bacterial extracts, and Campylobacter jejuni or Escherichia coli. MutS (hMSH2 and hMSH6) and MutL (hMLH1, hPMS2, and hPMS1) DNA MMR protein and RNA levels were determined. RESULTS: All cell lines examined showed decreased levels of MutS and MutL DNA MMR proteins in a dose-dependent manner after coculture with H. pylori strains. The reduction in DNA MMR protein levels was caused by heat-sensitive H. pylori products. The levels of DNA MMR proteins were affected by C. jejuni but not by E. coli. RNA levels of hMSH2 and hMSH6 were also reduced after exposure to H. pylori. CONCLUSIONS: H. pylori infection of gastric epithelial cells leads to a decrease in DNA MMR proteins that is at least in part related to an H. pylori-induced decrease in messenger RNA levels of repair genes. These data suggest that H. pylori infection might lead to a deficiency of DNA MMR in gastric epithelial cells that may increase the risk of mutation accumulation in gastric mucosa cells and the risk of gastric cancer during chronic H. pylori infection.     

Role of serum factors in epithelial cell responses to Helicobacter pylori infection in vitro

BACKGROUND: Gastric epithelial cell lines have been utilized extensively as tools to define aspects of the interactions between Helicobacter pylori and host epithelial cells. Fetal calf serum (FCS) is employed as a growth stimulant, but it is unclear whether this agent may in itself alter host responses. METHODS: Two gastric epithelial cell lines were utilized to ascertain the effects of varying FCS concentration on cellular responses following H. pylori infection. Media containing 0%, 5% or 10% FCS was added to cell lines prior to infection with H. pylori of defined genotype. Cellular interleukin (IL)-8 production was measured as a marker of cellular response. Effects of altered FCS upon cell viability were also determined by trypan blue exclusion. RESULTS: Interleukin-8 production by AGS cells following H. pylori infection was not altered by variation of media FCS concentration. However, KATO-III cells produced greater amounts of IL-8 when media was FCS-free than at 5% or 10% FCS. Although cellular viability was not altered in AGS cells exposed to varied concentrations of FCS, viability was decreased in serum-free KATO-III cells, but not when cells were kept at 5% FCS. CONCLUSIONS: Serum-derived factors alter cellular responses to H. pylori infection in a cell-line-dependent manner and impaired cellular viability may relate to this effect. However, the mechanisms for these observations are unclear and further work is now required to determine the nature of these important interactions.     

幽门螺杆菌感染对胃上皮细胞增殖和凋亡的影响

目的为了探讨幽门螺杆菌感染对胃粘膜上皮细胞动力学的影响。方法应用免疫组织化学和切口末端标记法（ＴＵＮＥＬ），检测了１６例正常胃粘膜者和３１例幽门螺杆菌（Ｈｐ）相关慢性胃炎患者治疗前后胃粘膜上皮细胞增殖细胞核抗原（ＰＣＮＡ）标记指数（ＬＩ％）、细胞凋亡指数（ＡＩ）和表皮生长因子受体（ＥＧＦ－Ｒ）的表达。结果Ｈｐ阳性患者的ＰＣＮＡＬＩ％为１３．９４±１．６４，正常对照组为６．７１±０．９２，差异有非常显著性（Ｐ＜０．０１）；ＥＧＦ－Ｒ表达与ＰＣＮＡＬＩ％呈正相关（ｒ＝０．４４８７，Ｐ＜０．０１）：Ｈｐ阳性患者组的ＡＩ为７．１±１．６，正常对照组为１．３±０．６，差异有非常显著性（Ｐ＜０．０１）；抗Ｈｐ治疗后，２１例Ｈｐ根除者的ＰＣＮＡＬＩ％和细胞ＡＩ分别降至８．２１±１．３２和１．２±０．６，与治疗前相比差异有非常显著性（Ｐ＜０．０１），而１０例Ｈｐ持续阳性者则无明显降低（Ｐ＞０．０５）：ＰＣＮＡＬＩ％、ＥＧＦ－Ｒ表达及细胞ＡＩ与胃粘膜炎症程度无显著相关（Ｐ＞０．０５）。结论上述结果提示，Ｈｐ感Ｈ能引起胃粘膜上皮细胞过度增殖和凋亡。这为Ｈｐ感染胃癌发病中的作用机制提供了一些线索。     

Comparative genomic study of gastric epithelial cells co-cultured with Helicobacter pylori

AIM: To identify genes potentially involved in Helicobacter pylori (H. pylori)-induced gastric carcinogenesis.METHODS: GES-1 cells were co-cultured with H. pylori strains isolated from patients with gastric carcinoma (GC, n = 10) or chronic gastritis (CG, n = 10) for in vitro proliferation and apoptosis assays to identify the most and least virulent strains. These two strains were cagA-genotyped and used for further in vivo carcinogenic virulence assays by infecting Mongolian gerbils for 52 wk, respectively; a broth free of H. pylori was lavaged as control. Genomic profiles of GES-1 cells co-cultured with the most and least virulent strains were determined by microarray analysis. The most differentially expressed genes were further verified using quantitative real-time polymerase chain reaction in GES-1 cells infected with the most and least virulent strains, and by immunohistochemistry in H. pylori positive CG, precancerous diseases, and GC biopsy specimens in an independent experiment.RESULTS: GC-derived H. pylori strains induced a potent proliferative effect in GES-1 cells in co-culture, whereas CG-derived strains did not. The most (from a GC patient) and least (from a CG patient) virulent strains were cagA-positive and negative, respectively. At week 52, CG, atrophy, metaplasia, dysplasia, and GC were observed in 90.0%, 80.0%, 80.0%, 90%, and 60.0%, respectively, of the animals lavaged with the most virulent strain. However, only mild CG was observed in 90% of the animals lavaged with the least virulent strain. On microarray analysis, 800 differentially expressed genes (49 up- and 751 down-regulated), involving those associated with cell cycle regulation, cell apoptosis, cytoskeleton, immune response, and substance and energy metabolisms, were identified in cells co-cultured with the most virulent strain as compared with those co-cultured with the least virulent strain. The six most differentially expressed genes (with a betweenness centrality of 0.1-0.2) were identified among the significant differential gene profile network, including JUN, KRAS, BRCA1, SMAD2, TRAF1, and HDAC6. Quantitative real-time polymerase chain reaction analyses verified that HDAC6 and TRFA1 mRNA expressions were significantly more up-regulated in GES-1 cells co-cultured with the most virulent strain than in those co-cultured with the least virulent strain. Immunohistochemistry of gastric mucosal specimens from H. pylori-positive patients with CG, intestinal metaplasia (IM), dysplasia, and GC showed that moderately positive and strongly positive HDAC6 expression was detected in 21.7% of CG patients, 30.0% of IM patients, 54.5% of dysplasia patients, and 77.8% of GC patients (P < 0.001). The up-regulation of TRAF1 expressions was detected in 34.8%, 53.3%, 72.7%, and 88.9% specimens of CG, IM, dysplasia, and GC, respectively (P < 0.001).CONCLUSION: The overexpression of HDAC6 and TRAF1 in GES-1 cells co-cultured with the GC-derived strain and in H. pylori-positive dysplasia and GC suggests that HDAC6 and TRAF1 may be involved in H. pylori-induced gastric carcinogenesis.     

幽门螺杆菌体外诱导大鼠胃黏膜上皮细胞凋亡

目的:研究幽门螺杆菌(Hpylori)在大鼠胃黏膜上皮诱导细胞凋亡中的作用,并初步探讨其中凋亡相关基因表达的情况,为胃癌发病机制提供依据.方法:Hpylori超声提取液来自SydneySS-1Hpylori菌株.大鼠胃黏膜细胞OUMS-37为永生化细胞,当细胞生长至60%融合时,加入不同浓度的Hpylori超声提取液,同时设置空白,于培养的24-48h收集细胞进行形态观察.Westhernblotting检测P53蛋白表达,Northernblotting检测bax、bcl-2mRNA的表达.结果:细胞经Hpylori作用48h后在高倍镜下观察到细胞核碎裂成大小不等的块状,表现出细胞凋亡如细胞皱缩,胞浆嗜碱性,核染色质固缩致密,核染色质断裂,形成大小不等的胞内核小体,部分细胞核膜消失,核染色质聚集中细胞中央,呈现分裂期的形态学等形态学特征,对照组未出现以上特征性改变.培养细胞经过Hpylori作用后提取DNA,经15g/L琼脂糖凝胶电泳,在紫外线灯下观察呈现不连续的梯状结构电泳条带.培养细胞经过Hpylori作用后,Westhernblotting显示P53蛋白表达随Hpylori超声提取液浓度而升高,Northernblotting显示baxmRNA表达随Hpylori浓度而增加,bcl-2mRNA表达随Hpylori浓度而降低.结论:Hpylori超声提取液可在体外诱导鼠胃黏膜上皮细胞凋亡.其机制可能通过上调野生型P53蛋白和凋亡促进基因baxmRNA表达,并下调凋亡抑制基因bcl-2mRNA表达.提示Hpylori感染可通过干扰胃上皮细胞增殖与凋亡之间的平衡在胃癌病因学中发挥作用.     

Intracellular Helicobacter pylori in gastric epithelial progenitors

Helicobacter pylori is generally viewed as an extracellular pathogen. We have analyzed the tropism of H. pylori clinical isolates in a gnotobiotic transgenic mouse model of human chronic atrophic gastritis, a preneoplastic condition. These mice lack acid-producing parietal cells and have an amplified population of dividing gastric epithelial progenitors (GEPs) that express NeuAc alpha 2,3Gal beta 1,4-glycans recognized by H. pylori adhesins. Scanning confocal and transmission electron microscopic studies of stomachs that had been colonized for 1 month or 1 year revealed intracellular bacterial collections (IBCs) in a small subset of multi- and oligopotential epithelial progenitors. Transmission electron microscopic and multilabel immunohistochemical analyses disclosed bacteria with several morphotypes, including spiral-shaped, in the cytoplasm and endosomes. Several stages in IBC evolution were documented, from a few solitary bacteria to consolidated populations in dividing and nondividing GEPs, to microorganisms traversing breaches in the GEP plasma cell membrane. IBC formation was not a unique feature of H. pylori strains isolated from patients with chronic atrophic gastritis. The notion that adult mammalian epithelial progenitors can function as a repository for H. pylori broadens the view of host habitats available to this and perhaps other pathogens.     

Helicobacter pylori infection and gastric cancer

Gastric cancer remains a major health burden on many societies claiming hundreds of thousands of lives every year. The discovery of Helicobacter pylori has no doubt revolutionised our understanding of this malignancy, which is now regarded as a paradigm for infection-induced chronic inflammation-mediated cancer. In this paper, we discuss the evidence for the association between H. pylori and gastric adenocarcinoma and MALT lymphoma. We also discuss the pathogenesis of these two forms of cancer and the factors that determine their outcome. There is no doubt that the knowledge accumulated over the past two decades will be translated into eventual victory over this killer cancer, largely because we now appreciate that the best way to prevent the cancer is by preventing acquisition of the infection in the first place, or by eradicating the infection in infected subjects. Defining the optimal timing of intervention is going to be the challenge facing us over the next two decades.     

Helicobacter pylori infection and gastric cancer

According to several prospective controlled epidemiologic studies, the positive rate of H. pylori antibody was shown to be higher in the patients with gastric cancer than in the control group. Retrospective studies on the association between gastric cancer and H. pylori have been conducted in a large number of subjects and the results can be classified broadly into two categories, i.e., findings affirming an association and others denying it. Research concerning the association between gastric cancer and H. pylori has achieved great progress over time, leading to the recognition of this relationship by the WHO. One of the greatest concerns is to ascertain whether the final outcome of H. pylori-induced gastritis may lead to gastric cancer. The onset of gastric cancer can be explained as being caused not only by H. pylori infection, but also by a combination of various factors such as food and the environment. However, the possibility that the occurrence of gastric cancer, like the recurrence of peptic ulcer, can be prevented by eradication of H. pylori has also been suggested. Further progress in clinical research is needed to resolve this issue.