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Major depressive disorder (MDD) is a worldwide concern owing to its negative impact on the quality of life. Gamma-aminobutyric acid (GABA), an essential neurotransmitter in the brain, is important for regulating the enteric nervous system and gut-brain dual communication (gut-brain axis), thus providing gastrointestinal GABA and GABA-related pathways with possible targets for MDD treatment. However, the use of GABA for this disease remains limited due to its poor pharmacokinetic properties, including the low permeability through the blood-brain barrier, and the rapid clearance from the gastrointestinal tract. Since poly(amino acid)s are advantageous for improving the beneficial bioactivities of conventional amino acids, poly(gamma-aminobutyric acid) (poly(GABA)) is a potential candidate for MDD therapy. Nevertheless, the non-water-soluble and non-dispersible characteristics of poly(GABA) render difficulty in administering its conventional forms in vitro/in vivo, thereby hindering its therapeutic applications. Therefore, this study proposes a new design for poly(GABA) in nanoparticle form, which is composed of the amphiphilic diblock copolymers of poly(GABA) and poly(ethylene glycol), providing a suitable formulation for medication applications. Herein, we report on a new orally deliverable poly(GABA)-based nanoparticles (NanoGABA) in aqueous media and their efficacy on mouse depression models. NanoGABA treatment efficiently attenuated depression-like symptoms as evidenced by behavioral tests (forced swimming tests and tail suspension tests) and stress biomarkers (corticosterone). These findings suggest that the newly designed poly(GABA)-based nanoparticles are a promising candidate for the treatment of depression. This research is the first to report the preparation of poly(GABA)-based nanoparticles in aqueous conditions with beneficial physical properties to open the gate for medical and pharmaceutical applications of poly (GABA). It is also a pioneer in using poly(GABA)-based materials for major depressive disorder therapeutics in vivo. Oral administration of NanoGABA attenuates depressive-like symptoms by targeting the enteric nervous system possibly through modulation of the gut-brain axis pathways with negligible toxicity, suggesting that NanoGABA is a promising therapeutic agent for major depressive disorders. Design and strategy of orally administrable NanoGABA for treatment of depression. After oral administration, NanoGABA accumulates in the intestinal mucosa, where it disintegrates and continuously supplies a small amount of GABA, enhancing the gut GABAergic pathway and attenuating stress-induced depressive-like symptoms via the connection of the gut-brain axis. [Display omitted] • Poly(GABA)-based nanoparticles (NanoGABA) were successfully prepared in water. • NanoGABA accumulates in the gastrointestinal tract after oral administration. • Oral administration of NanoGABA attenuates depressives' symptoms in mouse model. • The bioactivity of NanoGABA would relate to GABA release and gut GABAergic pathway. [ABSTRACT FROM AUTHOR]

Aim: Although increased intraluminal pressure in the stomach due to gastric outlet obstruction or functional gastric motor dysfunction, including gastroparesis, may affect gastric mucosal integrity, the direct effect of mechanical pressure on gastric mucosal cells has not yet been fully investigated. The aims of this study were to determine whether exposure to transmural pressure would affect the proliferation of gastric mucosal cells and to elucidate the intracellular signaling pathways involved.Methods: Cellular proliferation and DNA synthesis were evaluated in rat gastric epithelial cells exposed to high transmural pressures. The levels of activation of 3 MAP kinases, ERK, JNK, and p38, were assessed, and the induction of immediate early gene expression was examined. The activation of nuclear factor activator protein-1 (AP-1) was evaluated by an electrophoretic mobility shift assay.Results: Exposure to high transmural pressure significantly increased DNA synthesis within 24 h, with the most marked increase observed after exposure to a pressure of 80 mmHg, and this increase was inhibited by the MEK1 inhibitor PD98059. Early activation of ERK kinase, but not of JNK or p38 kinase, was detected after pressure loading. Early induction of the c-fos and c-myc genes and activation of the AP-1 transcription factor were also demonstrated within 3 h of exposure to 80 mmHg of pressure.Conclusion: Gastric mucosal cell proliferation induced by exposure to high transmural pressure may be related to early activation of ERK, the induction of c-fos and c-myc, and the activation of AP-1. [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]

Background and Aim: Helicobacter pylori ( H. pylori) infection enhances the production of reactive oxygen species and peroxynitrite, thereby resulting in oxidative tissue damage. In this study, we examined the role of peroxiredoxin I (Prx I), a stress-induced antioxidant enzyme, in protecting gastric mucosa from H. pylori-induced gastric mucosal injury. Methods: Wild type (Prx I+/+) and Prx I-deficient type (Prx I–/–) mice were maintained for 2 to 12 months with or without infection of H. pylori, Sydney strain-1. Gastric mucosal expression of Prx I was assessed by immunoblot analysis and immunohistochemistry. The degree of gastritis was evaluated by the updated Sydney system and by mucosal levels of inflammatory cytokines (MIP-2, IL-1β, and TNF-α). Oxidative DNA injury and apoptosis were analyzed by mucosal level of 8-hydroxy-2′-deoxyguanosine, and the number of apoptotic cells stained with a single-stranded DNA antibody, respectively. Results: H. pylori infection upregulated gastric mucosal Prx I expression in the Prx I+/+ but not the Prx I–/– mice. H. pylori infection also induced more severe gastritis and a more prominent increase in MIP level, more marked oxidative DNA injury, and apoptosis in the Prx I–/– than the Prx I+/+ mice. In the absence of H. pylori infection, no changes were demonstrated in gastric mucosa in either the Prx I+/+ or the Prx I−/− mice. Conclusion: These data suggest that H. pylori infection upregulates gastric mucosal Prx I expression, and further, that Prx I plays an important role in gastric mucosal protection against oxidative injury induced by H. pylori infection. [ABSTRACT FROM AUTHOR]

N-methyl- N′-nitro- N-nitrosoguanidine (MNNG) induces gastric cancer in animal models. We established an MNNG-induced mutant of the rat murine RGM-1 gastric epithelial cell line, which we named RGK-1, that could be used as an in vitro model of gastric cancer. This cell line showed signs of neoplasia and transformation, in that it lost contact inhibition and formed tumors in nude mice. The mutant cells also expressed parietal cell-specific H+,K+-adenosine triphosphatase (H+,K+-ATPase), which parent RGM-1 did not. The results suggested that parent RGM-1 cells were gastric progenitor cells. This mutant RGK-1 cell line will contribute to future investigation on gastric carcinogenesis and to the development of other pathophysiologic fields. [ABSTRACT FROM AUTHOR]

Gastric complications of indomethacin involve generation of reactive oxygen species, which induce gastric mucosal injury via lipid peroxidation of cell membranes. Peroxidation by reactive oxygen species alters the amounts of unsaturated fatty acids in the cell membrane and thus affects membrane fluidity. Indomethacin-induced lipid peroxidation can thus be detected by measuring cellular membrane fluidity by the fluorescence polarization (FP) method. The aim of this study was to elucidate the usefulness of the FP method for detecting indomethacin-induced gastric cellular injury in RGM-1 cells. Indomethacin-treated RGM-1 cells were investigated by conventional cytotoxicity assay, fluorometry of diphenyl-1-pyrenylphosphine (DPPP) to detect lipid peroxidation, and FP. The effects of both a radical scavenger and an initiator on membrane fluidity change (MFC) in RGM-1 cells were examined. The sensitivity of FP in detecting cellular injury was compared with those of DPPP fluorometry and conventional cytotoxicity measurements. Indomethacin caused an increase in MFC as determined by FP before cytotoxicity was detected by conventional methods. The increase in MFC was associated with increased membrane phospholipid peroxidation (MPP) but not with a prostaglandin deficiency, and the increases in both MFC and MPP were prevented by vitamin E. The FP method is potentially useful for detecting cellular injury in vitro. [ABSTRACT FROM AUTHOR]

Our previous studies show that Helicobacter pylori ( H. pylori) induces oxidative stress and the expression of proinflammatory cytokines in gastric epithelial cells. H. pylori induces the expression of molecular chaperones and proteins involved in protein-folding machinery as a defense mechanism against cellular stress. The suppressors of cytokine signaling (SOCS) are known as negative regulators of major immune signal pathways. The purpose of this article is to determine whether H. pylori in a Korean isolate (HP99) induces the expression of SOCS in rat gastric mucosal RGM-1 cells as a defense mechanism. As a result, HP99 induced SOCS-3 expression time-dependently in RGM-1 cells. SOCS-1 was not expressed while SOCS-2 expression was not changed by HP99 infection in RGM-1 cells. SOCS-3 might have a defensive role in H. pylori-infected gastric mucosal cells. Further study by manipulating SOCS-3 gene should be performed to investigate the physiological meaning of SOCS-3 induced by H. pylori in gastric mucosal cells. [ABSTRACT FROM AUTHOR]

Proteinase-activated receptor-1 (PAR1), a G protein–coupled receptor (GPCR) for thrombin, can be activated not only by PAR1-activating peptides (PAR1APs) based on the N-terminal cryptic tethered ligand sequence but also by an N-palmitoylated (Pal) peptide, Pal-RCLSSSAVANRSKKSRALF-amide (P1pal-19), based on the intracellular loop 3 of PAR1, designated pepducin, in human platelets or PAR1-transfected cells. The present article evaluated the actions of P1pal-19 and also the shorter peptide, Pal-RCLSSSAVANRS-amide (P1pal-12), known as a possible PAR1 antagonist, in multiple cells/tissues that naturally express PAR1. P1pal-19 as well as a PAR1AP, TFLLR-amide, evoked cytosolic Ca2+ mobilization in cultured human lung epithelial cells (A549) and rat gastric mucosal epithelial cells (RGM1). P1pal-19 and TFLLR-amide, but not a PAR2-activating peptide, SLIGRL-amide, caused delayed prostaglandin E2 formation in RGM1 cells. P1pal-19, like TFLLR-amide, produced endothelial NO-dependent relaxation in rat aorta and epithelial prostanoid-dependent relaxation in mouse bronchus. The P1pal-19-induced relaxation remained constant even after desensitization of PAR1 with TFLLR-amide in either tissue. P1pal-19 failed to mimic the contractile effects of TFLLR-amide in the endothelium-denuded preparations of rat aorta or superior mesenteric artery and the rat gastric longitudinal smooth muscle strips. P1pal-12 partially inhibited the vasorelaxation caused by TFLLR-amide and P1pal-19, but not SLIGRL-amide, in the rat aorta. Our data thus indicate that P1pal-19 is capable of mimicking the effects of PAR1APs in the endothelial and epithelial, but not smooth muscle, cells/tissues, and suggest that P1pal-12 may act as a PAR1 antagonist in the vascular endothelium. [ABSTRACT FROM AUTHOR]

A new digital distortion calibration technique is demonstrated in a 14-bit 20-MS/s pipelined analog-to-digital converter (ADC). Calibration parameters are obtained in a way similar to conventional digital gain calibration. The prototype ADC has been fabricated in a 0.18-µm CMOS process and consumes 33.7 mW at 2.8 V. Using the proposed calibration method, a 15-dB improvement of the third-order harmonic rejection is achieved. The measured SNDR and SFDR are 71.6 and 82.3 dB, respectively. [ABSTRACT FROM AUTHOR]

This paper presents a 14-bit digitally self-calibrated pipelined analog-to-digital converter (ADC) featuring adaptive bias optimization. Adaptive bias optimization controls the bias currents of the amplifiers in the ADC to the minimum amount required, depending on the sampling speed, environment temperature, and power-supply voltage, as well as the variations in chip fabrication. It utilizes information from the digital calibration process and does not require additional analog circuits. The prototype ADC occupies an area of 0.5 × 2.3 mm² in a 0.18-µm dual-gate CMOS technology; with a power supply of 2.8 V, it consumes 19.2, 33.7, 50.5, and 72.8 mW when operating at 10, 20, 30, and 40 MS/s, respectively. The peak differential nonlinearity (DNL) is less than 0.5 least significant bit (LSB) for all the sampling speeds with temperature variation up to 80°C. When operated at 20 MS/s with 1-MHz input, the ADC achieves 72.1-dB SNR and 71.1-dB SNDR. [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]

The article discusses the results of a study concerning the influence of chemotherapeutic agents and cytokines on the expression of 5-fluorouracil-associated enzymes in human colon cancer cell lines. The results indicate the mRNA level of 5-FU-associated enzymes in colon cancer cells was markedly influenced by other chemotherapeutic agents, especially the suppression of DPD, which must then be understood to plan chemotherapeutic options and strategies.

Previous investigations have demonstrated that the cellular signaling induced by hypoxia-reoxygenation is a major pathway contributing to gastric mucosal injury induced by stress, non-steroidal anti-inflammatory drugs, and Helicobacter pylori. The aim of the present study was to perform a gene expression analysis of the gastric mucosal cellular response and to define the protective molecules in hypoxia and reoxygenation using a high-density DNA microarray analysis. Normal rat gastric mucosal (RGM-1) cells were subjected to hypoxia for 2 h, and reoxygenation was initiated by placing the cells in an environment of normoxia for 2, 4, or 8 h. Total RNA was extracted, and differences in the gene expression profiles between the normoxia and hypoxia groups or among the different durations of reoxygenation were investigated using a high-density DNA microarray. HIF-1- and apoptosis-related genes were modulated by hypoxia. Moreover, inflammation-, stress-, and wound- healing-related genes were regulated by reoxygenation following hypoxia. In particular, the expression of heat shock protein-70, amphiregulin and cyclooxygenase-2 were upregulated during reoxygenation following hypoxia, suggesting that these upregulations may play an important role in maintaining cell survival and supporting cell function. Copyright © 2006 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Although hepatocyte growth factor (HGF) can act synergistically or antagonistically with transforming growth factor-ß(TGF-ß) signaling, molecular mechanism of their crosstalk remains unknown. Using antibodies which selectively distinguished receptor-regulated Smads (R-Smads) phosphorylated at linker regions from those at C-terminal regions, we herein showed that either HGF or TGF-ßtreatment of normal stomach-origin cells activated the JNK pathway, thereafter inducing endogenous R-Smads phosphorylation at linker regions. However, the phosphorylation at their C-terminal regions was not induced by HGF treatment. The activated JNK could directly phosphorylate R-Smads in vitro at the same sites that were phosphorylated in response to TGF-ßor HGF in vivo. Thus, the linker regions of R-Smads were the common phosphorylation sites for HGF and TGF-ßsignaling pathways. The phosphorylation induced by simultaneous treatment with HGF and TGF-ßallowed R-Smads to associate with Smad4 and to translocate into the nucleus. JNK pathway involved HGF and TGF-ß-mediated infiltration potency since a JNK inhibitor SP600125 caused the reduction of invasive capacity induced by HGF and TGF-ßsignals. Moreover, a combined treatment with HGF and TGF-ßled to a potent increase in plasminogen activator inhibitor type 1 transcriptional activity through Smad3 phosphorylation at the linker region. In contrast, HGF treatment reduced TGF-ß-dependent activation of p15INK4B promoter, in which Smad3 phosphorylation at the C-terminal region was involved. In conclusion, HGF and TGF-ßtransmit the signals through JNK-mediated R-Smads phosphorylation at linker regions.Oncogene (2004) 23, 7416-7429. doi:10.1038/sj.onc.1207981 Published online 23 August 2004 [ABSTRACT FROM AUTHOR]