幽门螺杆菌对胃上皮细胞间隙连接超微结构的影响(英文)

通过实验和临床观察幽门螺杆菌（Helicobacter pylori）对胃上皮细胞间隙连接超微结构的影响,从细胞间隙连接角度探讨H.pylori致癌机制.将不同H.pylori菌株与BGC-823细胞共培养24h或48h,用原位固定与原位包埋法透射电镜观察细胞间隙连接超微结构变化.对70例胃癌患者,用快速尿素酶试验、碱性品红染色和14C尿素呼气实验检测H.pylori,PCR法检测H.pyloriCagA基因,及透射电镜观察胃上皮细胞间隙连接超微结构变化.结果显示,未加H.pylori组BGC-823细胞可见较多细胞连接及连接复合体,加H.pylori各组细胞的连接数、单位周长连接数与单位周长连接长度均小于未加H.pylori组,而细胞间隙最小宽度大于未加H.pylori组（P〈0.001或P〈0.005）,且CagA＋的NCTCJ99组、临床株GC01组和NCTC11639组细胞连接数、单位周长连接数均小于CagA-的NCTC12908组（P〈0.001或P〈0.05）,NCTCJ99组与临床株GC01组细胞单位周长连接长度短于NCTC12908组（P〈0.001）.胃癌患者H.pylori感染组细胞连接数、单位周长连接数与单位周长连接长度均小于无H.pylori感染组,细胞间隙最小宽度大于无H.pylori感染组（P〈0.001）,且CagA＋H.pylori感染者细胞连接数、单位周长连接数与单位周长连接长度均小于CagA-H.pylori感染者,细胞间隙最小宽度大于CagA-H.pylori感染者.上述结果表明,胃上皮细胞间隙连接改变与H.pylori感染,特别是CagA＋H.pylori感染有关.     

抗VacA+CagA+幽门螺杆菌IgY的抗感染作用研究*

为研究抗VacA⁺CagA⁺幽门螺杆菌(Hp)IgY的抗感染作用,以VacA⁺CagA+Hp为抗原免疫蛋鸡,聚乙二醇法和水稀释法从鸡卵黄中提取抗-VacA⁺CagA⁺Hp-IgY,酶联免疫吸附实验(ELISA)测定IgY抗体效价。建立胃腔感染VacA⁺CagAHp的昆明系小鼠模型,观察抗-VacA⁺CagA⁺     

幽门螺旋菌感染血清学诊断

运用建立起来的酶联免疫吸附试验对80名胃镜确诊胃炎及消化性溃疡患者的血清中抗幽门螺旋菌(Helicobacter pylori)IgG、IgA IgM进行了检测。结果表明,抗H.pylori IgG、IgA都可作为H.pylori感染的指标,但前者敏感性较好(92.0%),后者特异性较高(94.4%);抗H.pyloriIgM升高和降低与H.pylori感染无明显关系。抗H.pylori IgG、IgA水平与H.py     

组蛋白去乙酰化酶3对外周CD4+ T细胞分化的影响

目的 探讨组蛋白去乙酰化酶3（HDAC3）对外周CD4⁺ T细胞分化及功能的调控作用。方法 采用CD4cre酶介导Hdac3杂合基因缺失小鼠（Hdac3^fl/flCD4^cre+/-）及其野生型正常对照小鼠（Hdac3^fl/fl，WT），流式细胞术检测HDAC3缺失对外周CD4⁺和CD8⁺ T细胞比例和数量的影响；在体外佛波酯（PMA）和离子霉素（Ionomycin）刺激条件下，流式细胞术检测HDAC3缺失对CD4⁺ T细胞中IFN-γ、IL-4和IL-17A的表达以及Tfh细胞产生的影响；采用ELISA检测HDAC3缺失对小鼠血清IFN-γ、IL-4和IL-17表达的影响；分选Hdac3^fl/flCD4^cre+/-和WT小鼠外周初始CD4⁺ T细胞，分别在Th1和Th2分化条件下培养，细胞内染色检测HDAC3缺失对Th1、Th2以及Th17相关细胞因子及其特异转录因子表达的影响；采用Microarray检测HDAC3缺失对CD4⁺ T细胞分化亚群相关基因表达的影响；采用链脲佐菌素（STZ）处理小鼠构建I型糖尿病（TIDM）疾病模型，检测HDAC3缺失对T1DM发病的影响。结果 与WT小鼠相比，Hdac3^fl/flCD4^cre+/-小鼠外周CD4⁺和CD8⁺ T细胞的比例和数量显著降低。Hdac3^fl/flCD4^cre+/-小鼠CD4⁺ T细胞及血清中IFN-γ的表达显著降低，而IL-4和IL-17A的表达显著增加，Tfh细胞比例也显著增加；HDAC3缺失抑制体外培养CD4⁺ T细胞向Th1分化但促进其向Th2分化；Microarray检测发现HDAC3缺失导致Th1型细胞谱系基因表达降低，而Th2、Th17以及Tfh细胞谱系基因表达增加；在STZ诱导条件下，HDAC3缺失抑制小鼠T1DM的发生和CD4⁺ T细胞向Th1分化。结论 HDAC3促进外周CD4⁺ T细胞向Th1细胞分化并加重T1DM的发生。     

IL-7和胸腺基质细胞系(MTEC5)诱导胸腺CD3- CD4- CD8- 细胞分化

胸腺细胞发育是细胞因子及胸腺细胞与胸腺基质细胞相互作用的结果.观察了IL-7及小鼠胸腺基质上皮细胞系MTEC5对成年小鼠CD3^- CD4^- CD8^- 胸腺细胞发育的影响.IL-7能促进TN细胞增殖.TN细胞经在IL-7条件下培养后表达CD3-TCR分子,其中20％～40％为TCRγδ⁺,60％～80％为TCRαβ⁺,但保持CD4^- CD8^- .该细胞获得对 Con A、抗CD3mAb及抗TCRmAb进行增殖应答的能力,抗CD28mAb能促进这种增殖应答,证明表达的CD3-TCR分子功能成熟.当在该系统中加入MTEC5,部分TN细胞转变为CD3⁺TCRβ⁺CD4⁺CD8^- 和CD3⁺TCRβ⁺CD4^- CD8⁺SP细胞,表明MTEC5可诱导TN细胞分化为表现型成熟的胸腺细胞.     

表达幽门螺杆菌粘附素保守区的减毒鼠伤寒沙门菌免疫治疗作用的研究

探讨表达幽门螺杆菌（Helicobacter pylori,Hp）粘附素保守区（AB）的减毒鼠伤寒沙门菌X4072（pYA248-AB）的免疫治疗效果,以及可能的免疫治疗机制,以确定X4072（pYA248-AB）在Hp疫苗研制中的应用价值.建立Hp感染小鼠模型,在该模型中评价X4072（pYA248-AB）治疗Hp感染的效果,运用细菌培养法观察Hp根除率及定植量的改变,流式细胞术分析免疫后小鼠脾细胞亚型,IL-2和IL-4细胞依赖株的细胞测活法检测细胞因子,ELISA法检测小鼠血清及肠液中抗AB抗体产生情况.结果表明,免疫治疗后疫苗治疗组根除率为53.3%,显著高于X4072（pYA248）和PBS对照组（P＜0.01）.未根除Hp的小鼠,疫苗治疗组Hp的定植密度明显低于其他两组（P＜0.01）.应用流式细胞仪分析免疫小鼠脾CD4⁺/CD8⁺ T淋巴细胞的比值时,发现疫苗治疗组和鼠伤寒菌对照组的比值均显著高于PBS对照组（P＜0.05）,而疫苗治疗组的比值又显著高于鼠伤寒菌对照组（P＜0.05）.进一步对细胞因子进行分析发现,与PBS对照组相比免疫治疗组和鼠伤寒菌对照组IL-2和IL-4明显升高(P＜0.05).同时,免疫治疗组与鼠伤寒菌对照组相比,IL-4增高明显(P＜0.05).针对AB的抗体测定结果发现,仅在免疫治疗组的小鼠肠液中检测到了IgA抗体.免疫治疗组IgG抗体滴度较其他两组明显升高,第二次加强免疫后2周即上升至1∶10 000.动物实验表明,X4072（pYA248-AB）能根除或显著降低Hp在小鼠胃内的定植,其可能的免疫治疗机制包括提高CD4⁺/CD8⁺比值,诱导Th1和Th2反应以及产生针对AB的特异性抗体.     

CD38基因敲除的淋巴瘤细胞株构建

摘要 目的：构建Luc⁺CD38^-的Raji细胞株,并进行功能的初步验证,为后期探索淋巴瘤细胞CD38位点免疫逃逸现象奠定基础。方法：通过CRISPR-cas9技术和PiggyBac(PB)转座子系统,对Luc⁺Raji细胞的CD38基因位点进行敲除,构建Luc⁺CD38^-Raji细胞株,使用流式细胞术检测与Luc⁺CD38^-Raji细胞株以1：1的比例共孵育CD19 CAR-T和CD38 CAR-T以及未转导的原始T细胞表面活化因子CD69的表达水平,荧光素酶检测法检测上述几组效应细胞对Luc⁺CD38^-Raji细胞株的杀伤效率。结果：成功构建Luc⁺CD38^-Raji细胞,激活实验结果显示,CD19 CAR-T与CD38 CAR-T均可以被Luc⁺Raji细胞激活。而Luc⁺CD38^-Raji19号单克隆细胞由于缺失CD38的表达,仅能够激活CD19 CAR-T。杀伤实验结果显示,两种CAR-T细胞均能够对Luc⁺Raji细胞进行杀伤,而CD38 CAR-T对Luc⁺CD38^-Raji19号单克隆细胞的杀伤效率与原始的T细胞相似。结论：成功构建了Luc⁺CD38^-Raji细胞株,为后期探索淋巴瘤CD38位点免疫逃逸现象奠定基础。     

口服维生素D对实验性脑疟小鼠树突状细胞的影响

维生素D（VD）为固醇类衍生物,除发挥抗佝偻病作用,还具有一定的免疫调节功能。主要研究VD对实验性脑疟小鼠树突状细胞的影响。结果显示,与对照组相比,在伯氏疟原虫（P.bANKA）感染前给予VD,可降低C57BL/6小鼠发生脑型疟疾的风险,存活时间明显延长。VD预处理后,脾脏中髓样树突状细胞（CD11c⁺CD11b⁺）和浆样树突状细胞（CD11c⁺B220⁺）百分率明显降低,CD11c⁺MHCII⁺细胞、CD11c⁺TLR4⁺细胞和CD11c⁺TLR9⁺细胞的百分含量也显著减少。由此提示,预防性口服VD可抑制感染小鼠树突状细胞的数量和功能,对脑型疟疾的发生具有一定预防作用,为新型抗疟药物的研发提供参考。     

研究报告: 实验性自身免疫性葡萄膜炎模型中肝脏免疫系统紊乱的研究

葡萄膜炎是一种反复发作的炎症性疾病,可导致免疫系统功能障碍和多器官损伤．然而,葡萄膜炎是否导致肝功能损害尚不十分清楚．本文通过运用流式分析技术和激光共聚焦成像技术,研究了实验性自身免疫葡萄膜炎模型的肝脏病理和功能变化．结果显示肝损伤可出现在葡萄膜炎的炎症后期并与眼损伤程度相关．并且CD3⁺ CD4⁺ T细胞、CD3^- NK1.1⁺ DX5^- NK细胞、和CD11b⁺ F4/80^- ly6c⁺ 细胞在感染的眼睛和肝脏中增加．将CD3⁺ CD4⁺ T细胞回输给炎症的小鼠后,眼睛和肝脏的病理损伤加重．此外,在炎症的小鼠中可见血管扩张,大量淋巴细胞浸润到炎症的眼和肝脏的血管周围．总之,我们的研究结果提示,肝损伤可以发生在小鼠葡萄膜炎模型中,这种损伤可能与通过外周循环浸润到肝脏的CD3⁺ CD4⁺ T细胞有关．     

肝癌肿瘤干细胞的分离鉴定及差异性小分子RNA筛选

旨在分离并鉴定肝癌肿瘤干细胞,并对其异常表达的microRNA进行了初步筛选。首先利用流式细胞术及免疫荧光技术分别在肝癌细胞系及肝癌组织标本中确认了CD90⁺细胞的存在;随后利用免疫磁珠分选技术从肝癌细胞系MHCC97-H中分离出了CD90⁺细胞,化疗药物耐药性实验表明,CD90⁺细胞具有明显的化疗药物耐受能力;两次裸鼠皮下成瘤性实验也表明CD90⁺细胞具有较强的成瘤能力,而CD90^-细胞不具备成瘤能力。上述实验充分说明:CD90⁺细胞具有肝癌肿瘤干细胞特性。因此利用该细胞模型进行了肝癌肿瘤干细胞CD90⁺细胞和非肝癌肿瘤干细胞CD90^-细胞之间差异表达的microRNA的检测,结果表明,CD90⁺细胞与CD90^-细胞之间共有92个microRNAs的表达存在差异性,其中在CD90⁺细胞中高表达的microRNAs有52个;在CD90^-细胞中高表达的microRNAs有40个。     

Dual roles of CagA protein in Helicobacterpylori-induced chronic gastritis in mice

Cytotoxin-associated gene A (CagA) acts directly on gastric epithelial cells. However, the roles of CagA in host adaptive immunity against Helicobacter pylori (H. pylori) infection are not fully understood. In this study, to investigate the roles of CagA in the development of H. pylori-induced chronic gastritis, we used an adoptive-transfer model in which spleen cells from C57BL/6 mice with or without H. pylori infection were transferred into RAG2^−/− mice, with gastric colonization of either CagA⁺H. pylori or CagA⁻H. pylori. Colonization of CagA⁺H. pylori but not CagA⁻H. pylori in the host gastric mucosa induced severe chronic gastritis in RAG2^−/− mice transferred with spleen cells from H. pylori-uninfected mice. In addition, when CagA⁺H. pylori-primed spleen cells were transferred into RAG2^−/− mice, CD4⁺ T cell infiltration in the host gastric mucosa were observed only in RAG2^−/− mice infected with CagA⁺H. pylori but not CagA⁻H. pylori, suggesting that colonization of CagA⁺H. pylori in the host gastric mucosa is essential for the migration of H. pylori-primed CD4⁺ T cells. On the other hand, transfer of CagA⁻H. pylori-primed spleen cells into CagA⁺H. pylori-infected RAG2^−/− mice induced more severe chronic gastritis with less Foxp3⁺ regulatory T-cell infiltration as compared to transfer of CagA⁺H. pylori-primed spleen cells. In conclusion, CagA in the stomach plays an important role in the migration of H. pylori-primed CD4⁺ T cells in the gastric mucosa, whereas CagA-dependent T-cell priming induces regulatory T-cell differentiation, suggesting dual roles for CagA in the pathophysiology of H. pylori-induced chronic gastritis.     

<Emphasis Type="Italic">PARP-1 Val762Ala</Emphasis> polymorphism,CagA<Superscript>+</Superscript><Emphasis Type="Italic">H. pylori</Emphasis> infection and risk for gastric cancer in Han Chinese population

Introduction PARP-1 plays important role in the BER (base excision repair) and maintenance of genomic integrity. Previous study found the Val762Ala genetic variant in the PARP-1 gene contributed to susceptibility of some cancers and decreased PARP-1 enzyme activity in response to oxidative damage. Helicobacter pylori (H. pylori) infection was thought to be one of the major causes of gastric cancer. In this study, we investigated the association between the PARP-1 Val762Ala polymorphism, CagA⁺ H. pylori infection, and the risk for gastric cancer. Methods This hospital-based, case–control study was performed involving 556 individuals (236 cases with gastric cancer and 320 controls without evidence of neoplasm and gastrointestinal disease) using a PCR-RFLP method. Chi-square test and logistic regression analysis were used to count OR and 95% CI. Results 762Ala/Ala genotype was overrepresented in the cases (16.9%) compared with controls (10.3%), (OR, 1.942; 95% CI, 1.157–3.257, P = 0.011). Multivariate analysis showed that two factors were significantly associated with risk of gastric cancer, including CagA⁺ H. pylori infection (OR, 2.562; 95% CI, 1.174–5.240, P = 0.037), PARP-1 762AA genotype (OR, 1.772; 95% CI, 1.065–3.867; P = 0.042). Stratification analysis indicated that among Cag⁺ H. pylori positive subjects, 762Ala/Ala carriers had higher risk for developing gastric cancer compared with 762Val/Val carrier (OR, 2.337; 95% CI, 1.148–4.758; P = 0.017). Conclusion PARP-1 762Ala/Ala could be a risk factor for gastric cancer in Han Chinese population; PARP-1 762Val/Ala polymorphism and Cag⁺ H. pylori infection jointly contribute to higher risk for gastric cancer.     

Current information on the association of Helicobacter pylori with autophagy and gastric cancer

Helicobacter pylori (H. pylori) is a Gram-negative bacterium and causative agent of gastric cancer. H. pylori induce defective autophagy or inhibit it by means of CagA and vacuolating cytotoxin A (VacA) toxins leading to the gastric cancer induction. Impaired or defective autophagy leads to the accumulation of cytotoxic materials, such as ROS and P62 that lead to increased mutations in the DNA, genome instability, and risk of cancer formation. H. pylori CagA may inhibit autophagy through the c-Met-PI3k/Akt-mTOR signaling pathway. However, VacA induces autophagy by some signaling pathways. In the gastric epithelial cells, VacA is a necessary and sufficient factor for the creation of autophagy. While CagA is a negative regulator of this phenomenon, the elimination of this gene from H. pylori has increased autophagy and the production of inflammatory cytokines is reduced. In gastrointestinal cancers, some of the microRNAs (miRNAs) act as tumor suppressors and some other are oncogenes by regulating various genes expression. H. pylori can also modify autophagy through a mechanism that includes the function of miRNAs. In autophagy, oncogenic miRNAs inhibit activation of some tumor suppressor signaling pathways (e.g., ULK1 complex, Beclin-1 function, and Atg4 messaging), whereas tumor suppressor miRNAs can block the activation of oncogenic signaling pathways. For instance, Beclin-1 is negatively regulated by miRNA-376b (oncogenic miRNA) and miRNA-30a (tumor suppressor miRNA). Similarly, Atg4 by miRNA-376b (oncogenic miRNA) and miRNA-101 (tumor suppressor miRNA). So, this apparent paradox can be explained as that both Beclin-1 and Atg4 play different roles in a particular cell or tissue.     

In vitro assembly of gap junctions

Gap junction structures were assembled in vitro from octyl-β- -glucopyranoside-solubilized components of lens fiber cell membranes. Individual pore structures (connexons), short double-membrane structures, and other amorphous material were evident in the solubilized mixture. Following the removal of the detergent by dialysis, these connexons associated to form single- and double-layered, two-dimensional hexagonal arrays (unit cell size a = B = 8.5 nm). The formation of larger arrays was dependent on the lipid-to-protein ratio and the presence of Mg²⁺ ions. Crystallographic analysis of electron micrographs revealed that lens junctional connexons consisted of six subunits surrounding a stain-filled channel. Upon further detergent treatment, in vitro assembled gap junctions were insoluble and formed three-dimensional stacks while other components were solubilized. SDS-PAGE and mass data from scanning transmission electron microscopy strongly suggest that a 38-kDa polypeptide, which is a processed form of the lens specific gap junction protein MP70, is a major component of the arrays. The in vitro assembly of gap junctions opens new avenues for the structural analysis of gap junctions and for the study of the intermolecular interactions of connexons during junctional assembly.     

Gap junction reductions precede tissue hyperplasia following temperature-upshift in theDrosophila ts-mutantl(3)c43 hs1

Summary The wing discs of the temperature-sensitiveDrosophila mutantl(3)c43 ^hs1 become hyperplastic when larvae are reared at the restrictive temperature of 25° C or above (Martin et al. 1977). We have previously shown that reductions in gap junctions are correlated with the hyperplasia (Ryerse and Nagel 1984a). We report here that reductions in gap junction surface density, number and percent of the lateral plasma membrane area precede the onset of tissue hyperplasia as defined by the gross appearance of tissue overgrowth in the wing pouch and an increase in cell number. Gap junction reductions begin soon after temperature upshift and become significantly different from non-shifted controls by 16 h. Direct cell counts indicate that there is no difference in the total number of cells in experimental vs control discs until after 16 h when the 28° C discs begin to grow rapidly with a cell doubling time of about 6 h as compared with about 13 h for the 20°C controls. The finding that gap junction reductions precede the onset of tissue hyperplasia is consistent with the idea that gap junctions play a regulatory role in growth control and pattern formation and strengthens our hypothesis (Ryerse and Nagel 1984b) that a minimum number and a specific distribution of gap junctions are required for normal development.     

Gap junctions are non-randomly distributed inDrosophila wing discs

Summary The distribution of gap junctions in mature larvalDrosophila melanogaster wing discs was analyzed by means of quantitative electron microscopy. Gap junctions are non-randomly distributed in the proximal-distal disc axis and in the apical-basal cell axis of the epithelium. In the epithelial cells, the surface density, number and length of gap junctions are greatest in the apical cell region and distal disc region. The average gap junction surface density is 0.0572 m^–1 and 2.77% of the lateral cell surface is composed of gap junctions. In the adepithelial cells, the gap junction surface density is 0.0005 m^–1 and 0.06% of the cell surface is composed of gap junctions. No gap junctions were observed between epithelial cells and adepithelial cells. The absolute area of gap junctions was estimated in a proximal-distal strip of cells in the disc and is considerably less in the folded regions of the epithelium compared to the flat notum and wing pouch regions. The results are discussed with respect to pattern formation and growth control in imaginal discs.     

Variability of gene order in different Helicobacter pylori strains contributes to genome diversity

Considerable genomic microdiversity has been reported previously among Helicobacter pylori isolates. We have constructed genome maps of four unrelated H. pylori strains (NCTC11637, NCTC11639, UA802 and UA861) using pulsed-field gel electrophoresis (PFGE) with Notl and Nrul, hybridization with extracted PFGE DNA fragments and probing with 17 gene probes. These strains of H. pylori were compared with a fifth unrelated H. pylori strain NCTC11638 mapped previously. Considerable diversity in gene arrangement was evident among the five H, pylori maps, and no consistent gene clustering was found. The association of only four genes, katA (catalase gene), vacA (vacuo-lating cytotoxin gene), hpaA (a putative adhesin gene), and pfr (bacterial ferritin gene) were generally conserved within approximately the same 25% of the genome; however, the order of these genes also varied. Our study demonstrates that macrodiversity, i.e. variability in gene order, in addition to microdiversity, is a characteristic of the H. pylori genome.     

Increased microRNA-223 in Helicobacter pylori-associated gastric cancer contributed to cancer cell proliferation and migration

Dysregulation of microRNA-223 (miR-223) was associated with gastric cancer (GC), in which Helicobacter pylori (H. pylori) played important roles. However, the mechanism of relationships between miR-223 and H. pylori-associated GC was largely undiscovered. Here, we found the overexpression of miR-223 was related with H. pylori positive infection in vivo and in vitro in GC by relative quantification of qRT-PCR. Upregulated miR-223 was responsible for the poorer prognosis of GC with H. pylori positive, also. The result indicated not only overexpression of miR-223 stimulated the proliferation by CCK-8 assays and colony formation of H. pylori associated GC cells, but also migration and invasion by scratch assay and transwell invasion assays in vitro. Above all, all our data declared H. pylori infection played an important role in developing GC according to overexpression of miR-223, which increased cancer cell proliferation and migration.     

Helicobacter pylori Induces Apoptosis of T- and B-Cell Lines and Translocates Mitochondrial Apoptosis-Inducing Factor to Nucleus

Immune cell apoptosis may play a role in human persistent Helicobacter pylori infection. We planned to study the apoptosis of T and B cells by H. pylori strains. T (Jurkat) and B (Raji) cell lines were co-cultured with cagA-positive H. pylori strains carrying different vacA genotypes (s1a/m1, s1a/m2, and s2/m2). Apoptosis was detected by microscopy, DNA fragmentation assay, and flow cytometry. Apoptosis-inducing factor (AIF) transfer from mitochondria to nucleus was studied by immunoblot analysis. Apoptosis of T and B cells was significantly higher in H. pylori-infected cells than in uninfected controls (s1a/m1 80%, s1a/m2 78%, s2m2 69% vs. control 16% for T cells, P < 0.001; s1 a/m1 78%, s1a/m2 73%, s2m2 62% vs. control 24% for B cells, P < 0.001 by flow cytometry) with no difference among the genotypes. AIF transfer from mitochondria to nucleus was demonstrated in both apoptotic cell lines. Thus, H. pylori induces apoptosis in T- and B-cell lines and translocates AIF. T and B cells deletion through apoptosis may explain the persistence of H. pylori infection; its role in pathogenesis needs further research.     

Induction of cyclooxygenase 2 by Escherichia coli but not Helicobacter pylori lipopolysaccharide in gastric epithelial cells in vitro

Background. Cyclooxygenase 2 (COX‐2) is an inducible enzyme that plays a key role in the synthesis of prostaglandins in response to inflammatory stimuli. It is expressed in the gastric mucosa as part of the response to infection with Helicobacter pylori. The specific interaction between H. pylori and the gastric epithelium that results in COX‐2 expression has not been identified. Methods. In order to investigate the hypothesis that lipopolysaccharide (LPS) from H. pylori plays a role in the induction of cyclooxygenase 2 in the stomach, gastric cell lines MKN‐7 and MKN‐45 were incubated with LPS from either H. pylori NCTC 11637 or Escherichia coli 055:B5. Incubation of cells with live H. pylori NCTC 11637 was also carried out as a positive control. Cells were then analysed for COX‐2 protein and mRNA and prostaglandin E2 synthesis. Results. Cyclooxygenase 2 protein and mRNA expression was induced by E. coli LPS and live H. pylori, but not by H. pylori LPS. Prostaglandin E₂ synthesis increased in a dose‐dependent manner in both cell lines with E. coli but not H. pylori LPS. Conclusions. H. pylori LPS is of low biological activity when compared with E. coli LPS in its ability to induce the expression of cyclooxygenase 2 and synthesis of prostaglandin E₂. This may provide one mechanism by which H. pylori minimizes the inflammatory response in the gastric mucosa, allowing chronic infection.