Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.7.49 (reverse transcriptase)
 31,746 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Active Helicobacter pylori-associated gastritis is characterized by a dense mucosal infiltration with granulocytes. Since H. pylori is noninvasive, secondary signals must induce the accumulation of granulocytes. Interleukin-8 (IL-8) has been shown to play a key role in this event. Using competitive reverse transcriptase-PCR on mRNA from gastric biopsies, we could show a clear correlation between the amount of IL-8 transcripts and the activity of H. pylori gastritis. Due to the inability of the bacterium to invade host cells, the epithelial layer is a potential candidate as an IL-8 source. To study the mechanism of IL-8 induction, established gastric carcinoma epithelial cell lines (AGS and Kato III) and well-defined H. pylori strains were used in a modified in vitro system. The experimental design enabled us to prevent direct contact of bacteria with epithelial cells by use of a filter membrane which did not block secreted bacterial products crossing the membrane. The data clearly showed that the direct contact of the bacterial cell with the epithelial cell is necessary for optimal IL-8 production because not only live bacteria, but also metabolically inactive bacteria, increased IL-8 secretion. Neither purified lipopolysaccharide nor water-soluble protein fractions of H. pylori NCTC 11637 and Tx30a nor the cytotoxin of H. pylori was able to increase IL-8 production significantly by the epithelial cells used. Furthermore, preparations of total membrane and outer membrane proteins of H. pylori were not able to stimulate IL-8 release in vitro. Accumulatively, these results imply that active metabolism is not necessary for stimulation as long as there is an intact membrane aiding the presentation of a stimulating membrane complex or aggregate on the surface of the bacteria. From these results, we conclude that whole bacteria and their direct contact with epithelial cells may be critical for IL-8 induction in vivo.
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PMID:Role of adherence in interleukin-8 induction in Helicobacter pylori-associated gastritis. 928 28

In gastric cancer, altered expression of MUC1, MUC2, MUC5AC, and MUC6 mucin genes has already been described. We show in this report by the means of in situ hybridization, reverse transcriptase-polymerase chain reaction, and transfection assays that MUC5B is also abnormally expressed in gastric carcinomatous tissues and cell lines. We thus undertook to elucidate the molecular mechanisms that regulate the transcription of MUC5B in gastric cancer cells. To this end, high expressing (KATO-III) and low expressing (AGS) gastric cancer cell lines were chosen to study human mucin gene MUC5B expression and promoter activity. Sequencing of the promoter region revealed a distal TATA box located 1 kilobase upstream of the proximal TATA box. Functional activity of the promoter was addressed by using deletion mutants covering 2044 nucleotides upstream of the MUC5B transcription start site. We identified a distal promoter 10 times more active than the proximal promoter in KATO-III cells. In AGS cells, both promoters, much less active, showed the same range of activity. Binding assays allowed us to show that the transcription factor ATF-1 binds to a cis-element present in the distal promoter. Sp1, which binds to both promoters specifically transactivates the proximal promoter. Treatment of transfected cells with PMA, cholera toxin A subunit, and calcium ionophore showed that only PMA led to a substantial activation of the distal promoter. MUC5B 5'-flanking region having a high GC content, influence of methylation on the MUC5B expression was assessed. Our results indicate that repression of MUC5B expression visualized in AGS cells is due in part to the presence of numerous methylated cytosine residues throughout the 5'-flanking region. Altogether these results demonstrate that MUC5B expression in gastric cancer cells is governed by a highly active distal promoter that is up-regulated by protein kinase C and that repression is under the influence of methylation.
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PMID:Aberrant expression of human mucin gene MUC5B in gastric carcinoma and cancer cells. Identification and regulation of a distal promoter. 1127 96

Modifications of mucosal phospholipids have been detected in samples from patients with Helicobacter pylori-positive gastritis. These alterations appear secondary to increased phospholipase A2 activity (PLA2). The cytosolic form of this enzyme (cPLA2), normally involved in cellular signaling and growth, has been implicated in cancer pathogenesis. The aim of this study was to investigate cPLA2 expression and PLA2 activity in the gastric mucosae of patients with and without H. pylori infection. In gastric biopsies from 10 H. pylori-positive patients, cPLA2 levels, levels of mRNA as determined by reverse transcriptase PCR, levels of protein as determined by immunohistochemistry, and total PLA2 activity were higher than in 10 H. pylori-negative gastritis patients. To clarify whether H. pylori had a direct effect on the cellular expression of cPLA2, we studied cPLA2 expression in vitro with different human epithelial cell lines, one from a patient with larynx carcinoma (i.e., HEp-2 cells) and two from patients with gastric adenocarcinoma (i.e., AGS and MKN 28 cells), incubated with different H. pylori strains. The levels of cPLA2, mRNA, and protein expression were unchanged in Hep-2 cells independently of cellular adhesion or invasion of the bacteria. Moreover, no change in cPLA2 protein expression was observed in AGS or MKN 28 cells treated with wild-type H. pylori. In conclusion, our study shows increased cPLA2 expression and PLA2 activity in the gastric mucosae of patients with H. pylori infection and no change in epithelial cell lines exposed to H. pylori.
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PMID:In vivo and in vitro studies of cytosolic phospholipase A2 expression in Helicobacter pylori infection. 1150 Apr 64

Helicobacter pylori (H. pylori) infection leads to gastroduodenal inflammation, peptic ulceration and gastric carcinoma. H. pylori may induce disease-specific gene expression in gastric epithelial cells. cDNA microarray for 352 cancer-related genes was used to identify the genes altered by H. pylori (cagA positive) in gastric epithelial AGS cells. Expressions of the genes identified on the microarray and other genes closely associated with these genes were determined by reverse transcriptase-polymerase chain reaction (RT-PCR). Western blot analysis and cell adhesion assay were performed to confirm the protein levels of the genes and the role of the genes on cell adhesion in H. pylori-infected AGS cells. As a result, the expression of four genes (galectin 1, aldolase A, integrin alpha5, LIM domain only 7 (LMO7)) were up-regulated by H. pylori in AGS cells, determined by cDNA microarray. RT-PCR analysis showed that the genes up-regulated by H. pylori were the genes regulating cell-cell adhesion and cell-extracellular matrix interaction, such as galectin-1 and galectin-3, integrin alpha5, and LIM domain only 7 (LMO7), and cancer-related glycolytic enzyme aldolase A and C. Cell adhesion to extracellular matrix proteins such as poly-L-lysine and fibronectin was mediated by H. pylori-induced expression of integrin alpha5. RT-PCR and Western blot analysis showed that E-cadherin, regulating cell adhesion and contact cell inhibition, was decreased by H. pylori in AGS cells. In conclusion, the increased expression of cell adhesion molecules and decrease in E-cadherin expression by H. pylori might contribute to cell adhesion, invasion and possibly cell proliferation in gastric epithelial cells.
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PMID:Cell adhesion-related gene expression by Helicobacter pylori in gastric epithelial AGS cells. 1275 65

Interaction of nuclear beta-catenin and TCF4 is the end point of canonical Wnt signaling, which is believed to trigger the transcription of multiple cancer-associated genes, including CD44. So far, the combined status of beta-catenin and TCF4 and its relevance for lymph node metastasis and CD44 expression have not been well studied in gastric cancers (GCs). To address these issues, we examined 31 GCs, 17 premalignant tissues, 10 noncancerous gastric mucosae, 17 regional lymph node metastases, and 4 human GC cell lines (MGC803, MGC823, AGS, and HGC-27) using immunohistochemical and immunofluorescence staining, reverse transcriptase polymerase chain reaction, and Western blot analysis. Frequent TCF4 up-regulation and nuclear translocation of beta-catenin were found in both primary and metastatic tumors. Standard CD44 was detected in all gastric tissue samples. The frequency of variant CD44 expression increased in parallel with stepwise gastrocarcinogenesis and tumor spread, but the rates of detection did not match that of nuclear beta-catenin and TCF4, especially in the premalignant and noncancerous samples. The data from the 4 cell lines were in accordance with the in vivo findings in terms of beta-catenin nuclear translocation, TCF4 activation, and CD44 expression. Our results suggest an established Wnt signaling pathway in most GCs, a close correlation of beta-catenin/TCF4-mediated signaling with tumor dissemination, and the unlikelihood of a direct effect of activated Wnt signaling on CD44 expression. The influence of beta-catenin-TCF4 interaction on alternative CD44 splicing was not established. These 3 alterations may be regarded as unfavorable features of GC.
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PMID:Nuclear translocations of beta-catenin and TCF4 in gastric cancers correlate with lymph node metastasis but probably not with CD44 expression. 1631 Nov 23

Our recent studies documented that red ginseng extract (RGE, isolates from steamed and dried Panax ginseng, C.A. Meyer) can inhibit Helicobacter pylori-induced mitogen-activated protein kinase (MAPK) signaling with repressing either nuclear factor (NF)-kappaB-DNA binding activity or releases of IL-8 and COX-2 in gastric epithelial cells (Dig Dis Sci 50:1218-1227, 2005). We extended the experiment to prove whether RGE influences 5-lipoxygenase (5-LOX) pathway, thereby suppressing the biosynthesis of 5(S)-HETE. The 5-LOX enzyme activities were measured by thin layer chromatography using (14)C-labeled arachidonic acid (AA) and quantified by reverse phase-high performance liquid chromatography in human gastric adenocarcinoma (AGS) cells cocultured with H pylori (ATCC 43504 strain) with or without pretreatment of RGE. Western blotting analyses for MAPK signaling and 5-LOX, reverse transcriptase polymerase chain reaction for interleukin-8, and electrophoretic mobility shift assay for NF-kappaB-DNA binding were done, respectively. H pylori infection increased exclusively 5-LOX enzyme activity and RGE inhibited H pylori-stimulated 5-LOX activity, resulting in suppression of 5(S)-HETE generations from AA. RGE inactivated c-jun phosphorylation and repressed redox-sensitive transcriptional activation, led to reduced expression of IL-8 and 5-LOX mRNA in gastric mucosal cells, of which action was very similar to known LOX inhibitor, 200 mumol of geraniin. RGE could be phytoceutical against H pylori infection-associated gastric inflammation through its LOX-inhibiting actions, inhibitory 5-LOX enzyme activity, and attenuating its expression.
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PMID:Inhibitory activities and attenuated expressions of 5-LOX with red ginseng in Helicobacter pylori-infected gastric epithelial cells. 1733 52

Proteinase-activated receptor-2 (PAR-2) belongs to a novel subfamily of G protein-coupled receptors with seven-transmembrane domains. PAR-2 is activated by serine proteases, such as trypsin, mast cell tryptase, and allergic or bacterial proteases. The presence of trypsin has been shown in human stomach. Cyclooxygenase-2 (COX-2) is induced by inflammatory cytokines, growth factors, gastrin, and reactive oxygen species in gastric epithelial cells, which may lead to mutagenesis and subsequent metaplasia, dysplasia, and cancer formation. We investigated whether PAR-2 is activated in H. pylori (HP99)-infected cells, which is related to COX-2 induction in gastric epithelial cells. After treatment of H. pylori to AGS (gastric adenocarcinoma) cells at a bacteria/cell ratio of 100:1, we determine the expression and the activation of PAR-2 and the expression of COX-2. The same experiments were performed in the cells treated with PAR-2 agonist peptide. mRNA and protein expression of PAR-2 and COX-2 were determined by reverse transcriptase-polymerase chain reaction (RT-PCR) and Western blotting. PAR-2 activation was assessed by increase in intracellular calcium level. As a result, H. pylori induced the activation and expression of PAR-2 as well as COX-2 expression. PAR-2 agonist peptide augmented H. pylori-induced COX-2 expression in AGS cells. H. pylori induces COX-2 expression, which is mediated by both activation and expression of PAR-2 in gastric epithelial cells.
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PMID:Role of proteinase-activated receptor-2 on cyclooxygenase-2 expression in H. pylori-infected gastric epithelial cells. 1740 13

Helicobacter pylori infection leads to gastroduodenal inflammation, peptic ulceration, gastric lymphoma and gastric cancer. Certain herbal remedies have been used to treat gastric disease. In this study, we examined the anti-inflammatory effect of San-Huang-Xie-Xin-Tang (SHXT) and its main component baicalin on Helicobacter pylori-infected human gastric epithelial AGS cell. AGS cells were treated with Helicobacter pylori at a bacterium/cell ratio of 300:1. mRNA expression and protein levels were determined by reverse transcriptase-polymerase chain reaction (RT-PCR) analysis and western blot analysis, respectively. Interleukin-8 (IL-8) level and the translocation of nuclear factor kappa B (NF-kappaB) were measured by enzyme-linked immunosorbent assay (ELISA) and enzyme-linked DNA-protein interaction assay (ELDIA), respectively. Nitric oxide production was measured by Griess reagent. We found that SHXT and baicalin inhibited Helicobacter pylori-induced cyclooxygenase-2 (COX-2) enhancement and IkappaBalpha degradation in both mRNA and protein levels. SHXT and baicalin also inhibited Helicobacter pylori-induced inducible nitric oxide synthase (iNOS) and IL-8 mRNA expression, and decreased NO and IL-8 production. Furthermore, SHXT and baicalin inhibited nuclear translocation of p50 subunit of NF-kappaB in Helicobacter pylori-infected AGS cells. Based on the above findings, SHXT and baicalin might exert anti-inflammatory and gastroprotective effects in Helicobacter pylori-induced gastric inflammation.
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PMID:San-Huang-Xie-Xin-Tang inhibits Helicobacter pylori-induced inflammation in human gastric epithelial AGS cells. 1753 3

In recent years, natural dietary agents have drawn a great deal of attention owing to their demonstrated ability to suppress cancer. We aimed to investigate the in-vitro gastric cancer preventive activity of a methanol extract obtained from table olives of Greek origin. Tested were AGS cell proliferation, induction of apoptosis and inhibition of inflammation. AGS stomach cancer cells were cultured at a density of 10 cells/ml. Methanol extract of olive was added to cultures at concentrations of 2.0, 1.6, 1.0, and 0.4 microg phenols/ml. Effect on cellular viability was evaluated via 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and percentages of early and late apoptotic cells were assayed by annexin V-FITC staining on a FACS scan. Interleukin-8 (IL-8) and intercellular adhesion molecule (ICAM)-1 mRNA and protein production were measured by applying reverse transcriptase-PCR and enzyme-linked immunosorbent assay. Olive extract significantly suppressed cell proliferation at 2.0, 1.6, and 1.0 microg phenols/ml. Flow cytometric analysis of Annexin-V labeled cells indicated that 2.0 microg phenols/ml significantly induced apoptosis. Similarly, at 2.0, 1.6, and 1.0 microg phenols/ml a significant decrease of ICAM-1 and IL-8 protein levels was observed. ICAM-1, as well as IL-8, mRNA expression were decreased in the presence of 2.0 microg phenols/ml. Results indicate that the methanol extract from olives, rich in phenolic compounds, exhibits gastric cancer preventive efficacy by limiting cell proliferation, inducing cell death and suppressing inflammation in AGS cells.
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PMID:In-vitro gastric cancer prevention by a polyphenol-rich extract from olives through induction of apoptosis. 1907 62

Although the biologic function of Reg IV is poorly understood, it has been reported that Reg IV is a potent activator of the epidermal growth factor receptor/Akt/AP-1 signaling pathway in colon cancer cells and closely linked with the inhibition of apoptosis. To clarify the role of Reg IV in gastric carcinogenesis and subsequent progression, we examined its expression by immunohistochemistry and in situ hybridization on tissue microarray containing gastric carcinoma, adjacent nonneoplastic mucosa, adenoma, intestinal metaplasia, or gastritis. Gastric carcinoma cell lines (MKN28, AGS, MKN45, KATO-III, and HGC-27) were studied for Reg IV expression by Western blot and reverse transcriptase-polymerase chain reaction followed by sequencing. Frozen samples of gastric carcinoma and adjacent nonneoplastic mucosa were subjected to Western blot, and patient serum, to enzyme-linked immunosorbent assay for Reg IV. Gastric carcinoma cell lines showed different levels of Reg IV mRNA and its encoding protein. The Reg IV protein expression was gradually decreased from intestinal metaplasia, adenoma, and carcinoma to gastritis (P < .05). The positive rate of its mRNA was higher in intestinal metaplasia than carcinoma or nonneoplastic mucosa (P < .05). Elevated serum Reg IV level in gastric carcinoma patients was detected in comparison with that in health individuals (P < .05). Reg IV expression was significantly correlated with the MUC-2 and MUC-5AC expression (P < .05). Among histologic subtypes of the World Health Organization, signet ring cell carcinoma more frequently expressed Reg IV than the others (P < .05), whereas it is the converse for the poorly differentiated group (P < .05). Our study indicated that Reg IV expression experienced up-regulation in gastric intestinal metaplasia and adenoma and then down-regulation with malignant transformation of gastric epithelial cells. It was suggested that Reg IV expression should be considered as a good biomarker for gastric precancerous lesions and was especially related to the histogenic pathway of signet ring cell carcinoma.
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PMID:The role of Reg IV gene and its encoding product in gastric carcinogenesis. 1974 May 14


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