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Background/aims: Junctional adhesion molecules (JAMs) are known as integral constituents of cellular tight junctions. However, the functions of JAMs in cancer tissues are controversial and the function of JAM-A in gastric cancer is unclear. Acordingly, we investigated the function of JAM-A in gastric epithelial and gastric cancer cell proliferation, invasion and apoptosis., Methodology: A normal rat gastric mucosa-derived cell line (RGM1), a rat gastric cancer-like cell line established from RGM1 (RGK1), and a human gastric cancer cell line (NCI-N87) were used in this study. To examine the expression of junctional proteins, immunoblotting and immunofluorescent staining were performed with specific antibodies (JAM-A, claudins, occludin and ZO-1). JAM-A was knocked down by small interfering RNA., Results: RGM1 and RGK1 expressed JAM-A, occludin and ZO-1 but not claudins. RGK1 were significantly more invasive than RGM1. JAM-A knock-down significantly decreased the proliferation and the invasion of RGK1 but not of RGM1. JAM-A knock-down significantly decreased the proliferation of NCI-N87 cells and significantly decreased expression of the anti-apoptotic protein Bcl-xL but not the expression of AKT or Mcl-1., Conclusions: JAM-A promotes proliferation and inhibits apoptosis of gastric cancer, suggesting that it has a pivotal role in gastric cancer progression.

HLE, a human hepatocellular carcinoma cell line was transiently transfected with normal human MnSOD and MnSOD without a mitochondrial targeting signal (MTS). Mitochondrial reactive oxygen species (ROS), lipid peroxidation and apoptosis were examined as a function of time following 18.8 Gy X-ray irradiation. Our results showed that the level of mitochondrial ROS increased and reached a maximum level 2 hours after X-ray irradiation. Authentic MnSOD, but not MnSOD lacking MTS, protected against mitochondrial ROS, lipid peroxidation and apoptosis. In addition, the levels of mitochondrial ROS were consistently found to always correlate with the levels of authentic MnSOD in mitochondria. These results suggest that only when MnSOD is located in mitochondria is it efficient in protecting against cellular injuries by X-ray irradiation and that mitochondria are the critical sites of X-ray-induced cellular oxidative injuries.

Rebamipide, a gastromucosal protective drug, suppresses indomethacin-induced gastropathy in humans and rodents. Effects of rebamipide on gene expression in indomethacin-treated gastric mucosal cells (RGM1) were investigated using high-density oligonucleotide arrays. Indomethacin induced apoptosis in RGM1 cells in a dose-dependent manner. Rebamipide pretreatment significantly reduced indomethacin-induced apoptosis. We used gene expression profiling on high-density oligonucleotide probe arrays to characterize the transcriptional response of RGM1 cells to indomethacin treatment for 6 hr. Of the 8,799 probes examined, 717 (8.1%) were induced (400 probes) or repressed (317 probes) at least 1.5-fold. Among the 158 genes that were induced by indomethacin at least 2.0-fold, four genes that were down-regulated by rebamipide at least 2.0-fold are listed: growth arrest and DNA-damage-inducible 45 alpha (GADD 45 alpha), golgi SNAP receptor complex member 1, iodothyronine deiodinases, and transcription factor 8. Real time-PCR confirmed GADD 45 alpha expression and its inhibition by rebamipide. Inhibition of apoptosis-related genes is possibly important for the cytoprotective effect of rebamipide against indomethacin-induced gastric mucosal cell injury.

Gastric luminal ammonia produced by Helicobacter pylori has been shown to cause gastric mucosal injury. This study was conducted to examine the mechanisms by which gastric luminal ammonia causes apoptosis of gastric epithelial cells. Monolayers of GSM06 cells, developed from murine gastric surface mucous cells, were cultured in the absence or presence of 10-30 mM NH(4)Cl at ambient pH of 5.0, 6.0, and 7.0. In the presence of luminal NH(4)Cl, GSM06 cells showed 1) cell shrinkage and nuclear chromatin condensation, 2) DNA fragmentation into oligonucleosomes, 3) leakage of cytochrome c into cytosolic fraction without affecting bax expression, and 4) increases in activity of caspases-3 and -9. These changes were accentuated when the cells were cultured at pH 7.0. In the absence of NH(4)Cl, none of these changes was detected at any pH examined. These results suggest that gastric luminal ammonia, at concentrations detected in H. pylori-infected subjects, induces apoptosis of gastric epithelial cells by release of cytochrome c from mitochondria, followed by activation of caspases-9 and -3, especially at higher ambient pH.

Aspirin causes gastrotoxicity and damaged epithelial defense via cyclooxygenase inhibition. C-phycocyanin (CPC) and Lycium barbarum polysaccharides (LBP), an active ingredient of Spirulina platensis and wolfberry, respectively, exerted antioxidation, anti-inflammation, and/or immunoregulation. The actions of CPC and/or LBP on gastric damage induced by aspirin were explored in rat gastric mucosal RGM-1 cells. Gastric injury was performed by 21 mM aspirin for 3 h after the pretreatment of CPC and/or LBP (100–500 μg/mL) for 24 h in RGM-1 cells. Proinflammatory, anti-inflammatory, and apoptotic markers were examined by ELISA or gel electrophoresis and Western blotting. Cell viability and interleukin 10 (IL-10) were reduced by aspirin. Increased proinflammatory markers, caspase 3 activity, and Bax protein were observed in RGM-1 cells with aspirin treatment. Aspirin elevated nuclear factor-κB (NF-κB), extracellular signal-regulated kinase (ERK), p38, and c-Jun N-terminal kinase (JNK) activation, while CPC and/or LBP increased IL-10, and attenuated proinflammatory markers, Bax protein, NF-κB, and the activation of ERK and JNK. Therefore, CPC and/or LBP possess anti-inflammation by restraining the activation of the ERK signaling pathway, and LBP decreases apoptosis by suppressing the JNK signaling pathway activation in gastric RGM-1 cells with aspirin-induced epithelial damage. [ABSTRACT FROM AUTHOR]

Background: Gastric hydrochloric acid (HCl) has been regarded as an inciting factor in gastric mucosal injuries and has been reported to induce lipid peroxidation in vitro. However, because HCl is not an oxidant per se, the exact mechanism by which the acid induces lipid peroxidation is unknown. We hypothesized that gastric acid may disrupt mitochondrial transmembrane potential and induce the production of superoxide in mitochondria, which subsequently may induce lipid peroxidation and apoptosis in gastric mucosal cells. Methods: Firstly we treated gastric epithelial RGM1 cells with solutions containing various concentrations of HCl (i.e., of varying pH), and examined cellular injury, lipid peroxidation, and apoptosis with specific fluorescent dyes. Secondly, we performed electron paramagnetic resonance (EPR) spectroscopy of isolated, acid-exposed mitochondria from the cells, using a spin-trapping reagent for superoxide, 5-(2,2-dimethyl-1,3-propoxy cyclophosphoryl)-5-methyl-1-pyrroline N-oxide (CYPMPO). Finally, we established novel RGM1 cells that overexpressed manganese superoxide dismutase (MnSOD), which removes superoxide from mitochondria, and examined the effect of acid treatment on cellular membrane lipid peroxidation. Results: The results indicated that the exposure to acid indeed induced cellular injury, cellular lipid peroxidation, apoptosis, and the demonstration of the exact superoxide spectra on EPR spectroscopy in gastric epithelial cells, and that overexpression of MnSOD decreased superoxide production and prevented cellular lipid peroxidation. Conclusion: These results suggested that gastric acid, like nonsteroidal anti-inflammatory drugs (NSAIDs), induces mitochondrial superoxide production, which induces gastric cellular injury by triggering cellular lipid peroxidation and apoptosis. [ABSTRACT FROM AUTHOR]

Indomethacin is one of non-steroidal anti-inflammatory drugs that are commonly used clinically and often cause gastric mucosal injury as a side effect. Generation of reactive oxygen species (ROS) and activation of apoptotic signaling are involved in the pathogenesis of indomethacin-induced gastric mucosal injury. Thioredoxin-1 (Trx-1) is a small redox-active protein with anti-oxidative activity and redox-regulating functions. The aim of this study was to investigate the protective effect of Trx-1 against indomethacin-induced gastric mucosal injury. Trx-1 transgenic mice displayed less gastric mucosal damage than wild type (WT) C57BL/6 mice after intraperitoneal administration of indomethacin. Administration of recombinant human Trx-1 (rhTrx-1) or transfection of the Trx-1 gene reduced indomethacin-induced cytotoxicity in rat gastric epithelial RGM-1 cells. Pretreatment with rhTrx-1 suppressed indomethacininduced ROS production and downregulation of phosphorylated Akt in RGM-1 cells. Survivin, a member of inhibitors of apoptosis proteins family, was downregulated by indomethacin, which was suppressed in Trx-1 transgenic mice or by administration of rhTrx-1 in RGM-1 cells. Trx-1 inhibits indomethacin-induced apoptotic signaling and gastric ulcer formation, suggesting that it may have a preventive and therapeutic potential against indomethacin-induced gastric injury. [ABSTRACT FROM AUTHOR]

Background and Aim: Gastric cancer is associated not only with Helicobacter pylori ( H. pylori) infection, but also with the intake of a high salt diet. Interleukin-1β (IL-1β) is highly expressed in H. pylori-infected gastric mucosa. The aim of the present study was to determine if hyperosmotic stress induces IL-1β expression in gastric epithelial cells in vitro. Method: Murine gastric epithelial cells, GSM06, were cultured with or without H. pylori (Sydney strain-1) at different osmolarities in the range of 300–450 mOsM. Expressions of IL-1β mRNA and mature IL-1β protein were evaluated by reverse transcription-polymerase chain reaction (RT-PCR) and an IL-1β enzyme-linked immunosorbent assay (ELISA), respectively. IL-1β converting enzyme (ICE) activity was measured by an ICE colorimetric assay. Apoptosis was evaluated by a single stranded-DNA assay. Results: Addition of H. pylori at 300 mosM caused significant increases in IL-1β mRNA, IL-1β protein, ICE activity and apoptosis. Hyperosmotic stress alone also caused upregulation of IL-1β mRNA and IL-1β protein, enhanced ICE activity and accelerated apoptosis. Hyperosmotic stress accentuated the increases in IL-1β mRNA, IL-1β protein, ICE activity and apoptosis induced by H. pylori alone. Enhancement of IL-1β protein release induced by hyperosmotic stress was significantly attenuated by an ICE inhibitor, Z-YVAD-FMK. Conclusions: Hyperosmotic stress enhances the release of bioactive mature IL-1β protein in H. pylori-infected gastric epithelial cells, in part by upregulating IL-1β mRNA expression, and in part by enhancing ICE activity. These results may explain the mechanisms by which chronic intake of a high salt diet increases the risk of gastric cancer among H. pylori-infected human subjects. [ABSTRACT FROM AUTHOR]

Heme is an essential substance for oxygen metabolism. 5-aminolevulinic acid (ALA) is a precursor of heme and accelerates plants, hair and sperm growth. However, ALA is reported to be an oxidative stressor. We previously reported that reactive oxygen species (ROS) enhanced cancer cellular bioactivity such as metastasis and invasion. On the other hand, over-generation of ROS induces apoptotic cell death in normal cells. Thus, ROS caused by ALA may promote cancerous malignancy and give damage to normal cells. In this study, we investigated the different effect of ALA between normal cells and cancer cells using a rat normal gastric epithelial cell line, RGM and its chemically mutated cell line, RGK. 50 μM ALA for 48h induced normal cellular apoptosis, not in cancer cells. In addition, the normal cell death was suppressed by treatment with N-acetylcysteine. Therefore, we concluded that ALA induced ROS and subsequent normal cell specific death via oxidative stress. From this result, administration of ALA for cancer patients may bring getting worse. [ABSTRACT FROM AUTHOR]

Abstract: The molecular mechanisms underlying the posttranslational modification of proteins in gastrointestinal cancer are still unknown. Here, we investigated the role of methylglyoxal modifications in gastrointestinal tumors. Methylglyoxal is a reactive dicarbonyl compound produced from cellular glycolytic intermediates that reacts non-enzymatically with proteins. By using a monoclonal antibody to methylglyoxal-modified proteins, we found that murine heat-shock protein 25 and human heat-shock protein 27 were the major adducted proteins in rat gastric carcinoma mucosal cell line and human colon cancer cell line, respectively. Furthermore, we found that heat-shock protein 27 was modified by methylglyoxal in ascending colon and rectum of patients with cancer. However, methylglyoxal-modified heat-shock protein 25/heat-shock protein 27 was not detected in non cancerous cell lines or in normal subject. Matrix-associated laser desorption/ionization mass spectrometry/mass spectrometry analysis of peptide fragments identified Arg-75, Arg-79, Arg-89, Arg-94, Arg-127, Arg-136, Arg-140, Arg-188, and Lys-123 as methylglyoxal modification sites in heat-shock protein 27 and in phosphorylated heat-shock protein 27. The transfer of methylglyoxal-modified heat-shock protein 27 into rat intestinal epithelial cell line RIE was even more effective in preventing apoptotic cell death than that of native control heat-shock protein 27. Furthermore, methylglyoxal modification of heat-shock protein 27 protected the cells against both the hydrogen peroxide- and cytochrome c-mediated caspase activation, and the hydrogen peroxide-induced production of intracellular reactive oxygen species. The levels of lactate converted from methylglyoxal were increased in carcinoma mucosal cell lines. Our results suggest that posttranslational modification of heat-shock protein 27 by methylglyoxal may have important implications for epithelial cell injury in gastrointestinal cancer. [Copyright &y& Elsevier]