幽门螺杆菌改变人肝细胞系HepG2蛋白质表达谱

目的研究H.pylori作用后肝细胞系HepG2蛋白质表达谱的改变,通过对差异蛋白质点的鉴定与分析,以探讨H.pylori对肝细胞的病理作用。方法采用体外肝细胞和H.pylori共培养,应用双向凝胶电泳分离H.pylori处理前后细胞总蛋白,筛选出差异表达的蛋白质点,并进行质谱分析鉴定。结果鉴定出7种表达上调的蛋白质点,包括整合素-β1、蛋白激酶C-α、LIM同源盒蛋白Lhx1、真核翻译起始因子2-β亚单位、PINCH蛋白、MAPK激酶3、Ras相关蛋白Rab-37等。这些蛋白质参与了基因表达调控、细胞免疫、细胞生长、信号传导等众多事件。结论H.pylori可能通过介导这些蛋白质的上调而发挥对HepG2细胞的病理作用。这种蛋白质组的差异分析有助于进一步研究H.pylori与人类肝胆疾病的关系。     

H pylori stimulates proliferation of gastric cancer cells through activating mitogen-activated protein kinase cascade

INTRODUCTION H pylori is an important pathogen associated with gastritis and peptic ulcers[1]. It has also been defined as a carcinogen[2]. The mechanisms of pathogenic and carcinogenic effects of H pylori infection are under intensive investigation. Rese…     

幽门螺杆菌对人肝细胞系HepG2原癌基因c-fos表达的影响

目的　探讨H .pylori对HepG2c-fos基因表达的影响。 方法　将H .pylori与HepG2共同培养 1、3、6、12和2 4h ,采用RT -PCR和Westernblot方法检测不同作用时相细胞的c -fosmRNA和蛋白表达。结果　cgA+ H .pylori作用HepG2后c -fos呈短暂一过性表达升高 ,c -fosmRNA、蛋白质在H .pylori感染后 1h开始增加 ,6h达高峰 ,表达水平分别为对照组的 2 .5倍和 1.6倍 (P <0 .0 1)。 12h开始下降 ,2 4h基本恢复到刺激前水平。而cgA-H .pylori及空肠弯曲菌与HepG2细胞共培养后 ,未见该基因的表达升高。结论　cag+ A H .pylori可诱导HepG2c -fos基因表达升高 ,其在肝癌发生中的作用有待进一步研究。     

脂筏介导的内源性大麻素对HepG2细胞的作用及其机制

目的 研究内源性大麻素(AEA)以脂质为基础的信号途径对肝癌细胞株HepG2的作用机制,探讨AEA在肝癌发生和发展中的作用.方法 免疫荧光检测脂肪酸水解酶、大麻素受体(CB)1和CB2在胎肝细胞株L02和肝癌细胞株HepG2中的定位.以不同浓度的AEA及膜胆固醇耗竭剂甲基-β-环糊精(MCD)处理,分为AEA 10 μmol/L组、AEA 20 μmol/L组、AEA40 μmol/L组,MCD 10 mmol/L+AEA 10 μmol/L组、MCD 10 mmol/L+AEA 20 μmol/L组和MCD 10 mmol/L+AEA 40 μmol/L组,分别孵育L02细胞和HepG2细胞,流式细胞术碘化丙啶单染法检测细胞的坏死率.Western Blot检测L02和HepG2细胞中脂肪酸水解酶、CB1和CB2的蛋白表达及其下游信号通路磷酸化P38促分裂原活化蛋白激酶(p-P38MAPK)和磷酸化c-Jun氨基端激酶(P-JNK)的表达变化.组间均数的比较采用独立样本t检验或单因素方差分析.结果 AEA可有效地导致肝癌细胞坏死,以浓度为AEA 40 μmol/L组达到最大效应,F=108.594,P<0.05,差异有统计学意义.MCD 10mmol/L预孵育后的HepG2细胞坏死率在AEA 10 μmol/L组、AEA 20 μmol/L组和AEA 40 μmol/L组分别为7.83%±2.13%,16.30%±0.94%,43.09%±5.10%,MCD处理前AEA 10 μmol/L组、AEA 20 μmol/L组、AEA 40 μmol/L组分别为13.64%±1.69%、20.28%±0.91%,52.71%±4.29%,处理前后比较,t值分别为3.702,5.274和3.503,P值均<0.05,差异均有统计学意义.同时,AEA能激活HepG2细胞中P38 MAPK和JNK,以AEA 40 μmol/L组作用明显,F值分别为11.908和26.054,P值均<0.05,差异均有统计学意义,MCD作用前p-P38 MAPK和p-JNK/β-肌动蛋白灰度值分别为1.63±0.06,1.60±0.31,MCD作用后p-P38 MAPK/β-肌动蛋白、p-JNK灰度值分别为1.14±0.01、1.17±0.29,作用前后相比,t值分别为2.801和12.829,P值均<0.05,差异均有统计学意义.结论 AEA可以有效地导致HepG2细胞坏死而对L02细胞无影响,AEA激活了HepG2细胞p-P38 MAPK和P-JNK相关信号传导途径,且此过程与脂筏有关.     

East Asian-type Helicobacter pylori cytotoxin-associated gene A protein has a more significant effect on growth of rat gastric mucosal cells than the Western type

BACKGROUND AND AIM: Cytotoxin-associated gene A (CagA) protein from H. pylori was reported to be injected into host gastric epithelial cells via a bacterial type IV secretion system, thereby modifying signal transduction. It is classified into two major subtypes, Western and East Asian. The present study aimed to compare the effects of East Asian-type and Western-type CagA on host cell growth. METHODS: A tetracycline (tet)-off system and cagA genes from Western and East Asian-type H. pylori (NCTC 11637 and F32) were transfected into untransformed rat gastric mucosal (RGM1) cells to establish RGM1-CagA cell lines in which CagA expression could be controlled by tetracycline. These cell lines were used to investigate the effect of CagA protein expression on cell growth with BrdU and water-soluble tetrazolium reagent (WST-8) assays. CagA expression, phosphorylation and extracellular signal-regulated kinase (ERK) activation were examined with immunoprecipitation and Western blotting analysis. RESULTS: 5-Bromo-2'deoxyuridine (BrdU) and WST-8 assays demonstrated significant increases in DNA replication and RGM1 cell growth after CagA protein expression. ERK phosphorylation was enhanced when CagA protein was expressed in RGM1-CagA cells. Moreover, the East Asian-type CagA showed a significantly greater effect on ERK activation and host cell growth than the Western type. PD98059, a mitogen-activated protein kinase kinase (MEK) inhibitor, suppressed ERK phosphorylation and the CagA protein-induced increase in RGM1-CagA cell growth. CONCLUSIONS: CagA protein expression induces an increase in RGM1-CagA cell proliferation via the mitogen-activated protein kinase (MAPK) signal pathway. The East Asian-type CagA showed a significantly greater effect on cell growth than the Western type, suggesting that the East Asian CagA-positive strain may have an important role in pathogenesis.     

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.     

Helicobacter pylori induces up-regulation of the epidermal growth factor receptor in AGS gastric epithelial cells

BACKGROUND: Helicobacter pylori infection increases the risk of gastric carcinogenesis. The aim of the present study was to determine whether H. pylori could up-regulate the expression of the epidermal growth factor receptor (EGFR), a critical gene in the carcinogenic process. METHODS: AGS gastric epithelial cells were infected with cag(+) toxigenic or cag(-) nontoxigenic strains of H. pylori or isogenic mutants. EGFR protein expression was determined by Western blotting and immunofluorescence. EGFR mRNA levels were evaluated using real-time polymerase chain reaction. The signaling pathways leading to EGFR up-regulation were examined using the ERK1/2 inhibitor PD98059, the Src inhibitor pp2, the nuclear factor- kappa B inhibitor caffeic acid phenethyl ester, EGFR neutralizing antibodies, and the EGFR kinase inhibitor AG1478. RESULTS: Infection of AGS cells by H. pylori significantly increased EGFR mRNA and protein levels. We found that this effect was limited to cag(+) H. pylori strains and that mutants with a defective type IV secretion system were unable to cause EGFR up-regulation. Increased EGFR expression was found to be dependent on EGFR receptor transactivation, ERK1/2 phosphorylation, and Src activation. CONCLUSION: Infection of gastric epithelial cells by H. pylori triggers an autocrine loop whereby EGFR transactivation leads to the up-regulation of EGFR expression. This, in turn, may contribute to unrestrained epithelial cell proliferation and carcinogenesis.     

Increased glutathione and mitogen‐activated protein kinase phosphorylation are involved in the induction of doxorubicin resistance in hepatocellular carcinoma cells

Aim: The human hepatocellular carcinoma (HCC) cell line HepG2 can easily acquire resistance to doxorubicin. However, the mechanism of action is unclear. Methods: In the present study, we used confocal microscopy, flow cytometry and other methods to reveal the mechanisms by which HepG2 cells acquire doxorubicin resistance. Results: Our results showed that R‐HepG2 cells, a doxorubicin‐resistant sub‐line of HepG2, exhibited decreased intracellular accumulation of doxorubicin and increased expression of P‐glycoprotein (P‐gp) and multidrug resistance‐associated protein 1 when compared with HepG2 cells. R‐HepG2 cells also harbored higher levels of glutathione and increased expression of glutathione peroxidase. Furthermore, we demonstrated that the phosphorylation of mitogen‐activated protein kinases (p38 and c‐jun‐N‐terminal kinases), IkBα and CREB were increased in R‐HepG2 cells. Specific p38 inhibitor SB203580 decreased P‐gp expression. The multi‐kinase inhibitor sorafenib tosylate also significantly suppressed the phosphorylation of these proteins and inhibited the expression of P‐gp. Conclusion: These findings reveal that the drug resistance could be acquired through mitogen‐activated protein kinase‐dependent upregulation of P‐gp. This mechanism protects R‐HepG2 cells from the anticancer action of doxorubicin.     

cag致病岛的差异及不同激酶抑制剂对幽门螺杆菌诱导胃上皮细胞IL-8分泌的影响

目的：分析中国临床分离的幽门螺杆菌的cag致病岛的差异和不同激酶抑制剂对幽门螺杆菌诱导中国人胃上皮细胞IL-8分泌的影响。方法：在体外分别用中国临床分离的cagA^ cagE^ 、cagA^ cagE^ 、cagA^ cagE^ 、cagA^ cagE^ 的幽门螺杆菌与中国人胃上皮细胞MGC-803共培养,IL-8分泌用ELISA进行检测,比较蛋白激酶A、C、G和蛋白酪氨酸激酶的抑制剂对幽门螺杆菌诱导胃上皮细胞IL-8分泌的影响。结果：cagA^ cagE^ 幽门螺杆菌显增加了胃上皮细胞IL-8的分泌,cagA^ cagE^ 、cagA^ cagE^ 幽门螺杆菌作用次之,而cagA^ cagE^ 幽门螺杆菌不能增加胃上皮细胞IL-8的分泌。蛋白激酶A、C、G的抑制剂不能阻断幽门螺杆菌增加胃上皮细胞IL-8的分泌,而蛋白酪氨酸激酶的抑制剂阻断了幽门螺杆菌增加胃上皮细胞IL-8的分泌。结论：cagA^ cagE^ 幽门螺杆菌显增加了胃上皮细胞IL-8的分泌并且依赖于蛋白酪氨酸激酶的活性。     

辛伐他汀抑制HepG2细胞增殖作用的机制

目的 体外观察辛伐他汀对人肝癌细胞HepG2增殖、细胞周期及细胞周期蛋白依赖激酶抑制因子p21蛋白表达的影响.方法 采用四甲基偶氮唑盐(MTT)法观察辛伐他汀对HepG2细胞增殖的影响,用流式细胞仪检测辛伐他汀对细胞周期的作用,用免疫细胞化学法观察辛伐他汀对细胞周期蛋白依赖激酶抑制因子p2l蛋白表达的影响.对数据进行析因设计与单因素方差分析.结果 体外辛伐他汀可抑制HepG2细胞的增殖(F浓度=1264,P＜0.001 ;F时间=17.466,P＜0.001;F浓度*时间=35.053,P＜0.001).辛伐他汀处理组G0/G1期细胞增多,但细胞凋亡不明显;体外辛伐他汀可增强HepG2细胞周期蛋白依赖激酶抑制因子p21蛋白的表达(F=512.133,P＜0.001).结论 体外辛伐他汀对HepG2细胞增殖有抑制作用,该作用可能与其使细胞生长阻滞于G0/G1期及增强细胞周期蛋白依赖激酶抑制因子p21蛋白表达有关.     

Mutation of cytotoxin-associated gene A affects expressions of antioxidant proteins of Hellcobacter pylori

AIM: To determine if disruption of the cagA gene of Helicobacter pylori ( H pylori) has an effect on the expression of other proteins at proteome level.METHODS: Construction of a cagA knock out mutant Hp27_. cagA ( cagA-) via homologous recombinat ion wi th the wi ld- type st rain Hp27 ( cagA+) as a recipient was performed. The method of sonicat ion-urea-CHAPS-DTT was employed to extract bacterial proteins from both strains. Soluble proteins were analyzed by two-dimensional electrophoresis (2-DE). Images of 2-DE gels were digitalized and analyzed. Only spots that had a statistical significance in differential expression were selected and analyzed by matrix-assisted laser desorption/ionizationtime of flight mass spectrometry (MALDI-TOF-MS). Biological information was used to search protein database and identify the biological function of proteins. RESULTS: The proteome expressions between wild-type strain and isogenic mutant with the cagA gene knocked-out were compared. Five protein spots with high abundance in bacteria proteins of wild-type strains, down-regulated or absently expressed in bacteria proteins of mutants, were identified and analyzed. From a quantitative point of view, the identified proteins are related to the cagA gene and important antioxidant proteins of H pylori, including alkyl hydroperoxide reductase (Ahp), superoxide dismutase (SOD) and modulator of drug activity (Mda66), respectively, suggesting that cagA is important to maintain the normal activity of antioxidative stress and ensure H pylori persistent colonization in the host. CONCLUSION: cagA gene i s relevant to the expressions of antioxidant proteins of H pylori, which may be a novel mechanism involved in H pylori cagA pathogenesis.     

PPARγ pathway activation results in apoptosis and COX－2 inhibition in HepG2 cells

AIM: To investigate whether troglitazone (TGZ), the peroxisome proliferator-activated receptor (PPAR) gamma ligand, can induce apoptosis and inhibit cell proliferation in human liver cancer cell line HepG2 and to explore the molecular mechanisms. METHODS: (3-(4,5)-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT), ((3)H) Thymidine incorporation, Hochest33258 staining, DNA ladder, enzyme-linked immunosorbent assay (ELISA), RT-PCR, Northern and Western blotting analyses were employed to investigate the effect of TGZ on HepG2 cells and related molecular mechanisms.RESULTS: TGZ was found to inhibit the growth of HepG2 cells and to induce apoptosis. During the process, the expression of COX-2 mRNA and protein and Bcl-2 protein was down-regulated, while that of Bax and Bak proteins was up-regulated, and the activity of caspase-3 was elevated. Furthermore, the level of PGE(2) was decreased transiently after 12 h of treatment with 30 microM troglitazone. CONCLUSION: TGZ inhibits cell proliferation and induces apoptosis in HepG2 cells, which may be associated with the activation of caspase-3-like proteases, down-regulation of the expression of COX-2 mRNA and protein, Bcl-2 protein, the elevation of PGE2 levels, and up-regulation of the expressions of Bax and Bak proteins.     

Helicobacter pylori inhibits activity of cdc2 kinase and delays G2/M to G1 progression in gastric adenocarcinoma cell line

BACKGROUND: Helicobacter pylori is a bacterial pathogen strongly associated with ulcer diseases and gastric cancer. The bacterial-induced alteration of cell-cycle control in host cells may play a role in the pathogenetic mechanisms. The aims of this study were to define the effect of H. pylori on the G2/M to G1 transition in a gastric cell line. METHODS: Cultured gastric cells, AGS, were synchronized in the S/early G2 phase and treated with intact H. pylori. The cell-cycle distribution of AGS cells was determined by flow cytometry. The activity of cdc2 kinase, as well as of some parameters that affect the kinase activity, was also examined. RESULTS: H. pylori delays cell-cycle progression at the G2/M phase in AGS cells. The G2/M delay was associated with reduced activity of cdc2 kinase. Both down-regulation of cell-cycle regulators (p34cdc2, cyclin B1 and cdc25C) and decreased association between p34cdc2 and cyclin B1 were found to be associated with the activity of cdc2 kinase abated after the H. pylori infection. In addition, the H. pylori-induced G2/M delay required direct contact between the bacteria and host cells. CONCLUSIONS: H. pylori inhibits G2/M to G1 progression and causes a reduction of cell division in gastric epithelial cells.     

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.     

Helicobacter pylori infection affects the expression of PCNA, p53, c-erbB-2 and Bcl-2 in the human gastric mucosa.

OBJECTIVE: Helicobacter pylori infection has been related to gastric carcinogenesis. This association is based on epidemiological data, pathological changes observed in the gastric mucosa, and chemical products from bacteria that may induce damage of DNA. In the present study we examined gastric endoscopic biopsies from patients with chronic gastritis, with and without H. pylori infection, and surgical biopsies from gastric cancer patients to evaluate whether this bacteria may induce changes in the expression of molecular markers associated with carcinogenesis. PATIENTS AND METHODS: the study involved 57 biopsies from the antral region of the stomach of patients with chronic gastritis and gastric cancer that were analyzed by immunohistochemistry. Molecular markers examined were: PCNA (Proliferating Cell Nuclear Antigen), p53, c-erbB-2, Bcl-2, and p21 H-ras. RESULTS: PCNA content of epithelial cells was significantly higher in H. pylori infected biopsies. Treatment aimed to eradicate H. pylori decreased the level of PCNA-positive cells in the group of patients that became H. pylori-negative as well as in H. pylori-positive patients. Nuclear p53 expression (used here as a surrogate marker for p53 mutation/inactivation) and c-erbB-2 expression were observed only in the group of patients that remained with the bacteria after treatment. A higher bcl-2 expression in lymphoid cells was observed in H. pylori-positive biopsies, and treatment did not change the expression of this protein. No significant expression of p21 H-ras was observed in the studied biopsies. CONCLUSION: this study suggests that H. pylori is involved in the induction of molecular changes that might predispose human gastric mucosa cells to pre-neoplastic and neoplastic events.