RGM1 Cells Research Articles

A novel role for Helicobacter pylori cytotoxin-associated gene A in negative regulation of autophagy in human gastric cells

BackgroundAutophagy plays an important role in carcinogenesis and tumor progression in many cancers, including gastric cancer. Cytotoxin-associated gene A (CagA) is a well-known virulent factor in Helicobacter pylori (H. pylori) infection that plays a critical role in gastric inflammation and gastric cancer development. However, its role in autophagy during these processes remains unclear. Therefore, we aimed to clarify the role of CagA in autophagy in CagA-related inflammation.MethodsWe evaluated the autophagic index of AGS cells infected with wild-type cagA-positive H. pylori (Hp-WT) and cagA-knockout H. pylori (Hp-ΔcagA) and rat gastric mucosal (RGM1) cells transfected with CagA genes. To identify the mechanisms underlying the down regulation of autophagy in AGS cells infected with H. pylori, we evaluated protein and mRNA expression levels of autophagy core proteins using western blotting and quantitative reverse transcription-polymerase chain reaction (RT-PCR). To determine whether autophagy induced the expression of the pro-inflammatory mediator, cyclooxygenase-2 (COX-2), we evaluated COX-2 expression in AGS cells treated with an autophagy inducer and inhibitor and infected with H. pylori. In addition, we evaluated whether COX-2 protein expression in AGS cells influenced beclin-1 (BECN1) expression with si-RNA transfection when infected with H. pylori.ResultsAutophagic flux assay using chloroquine showed that autophagy in AGS cells was significantly suppressed after H. pylori infection. The autophagic index of AGS cells infected with Hp-WT was decreased significantly when compared with that in AGS cells infected with Hp-ΔcagA. The autophagic index of RGM1 cells transfected with CagA was lower, suggesting that CagA inhibits autophagy. In addition, BECN1 expression levels in AGS cells infected with Hp-WT were reduced compared to those in AGS cells infected with Hp-ΔcagA. Furthermore, COX-2 expression in AGS cells infected with H. pylori was controlled in an autophagy-dependent manner. When AGS cells were transfected with small interfering RNA specific for BECN1 and infected with Hp-WT and Hp-ΔcagA, COX-2 was upregulated significantly in cells infected with Hp-ΔcagA.ConclusionsIn conclusion, the H. pylori CagA protein negatively regulated autophagy by downregulating BECN1. CagA-induced autophagy inhibition may be a causative factor in promoting pro-inflammatory mediator production in human gastric epithelial cells.

Freshwater Clam Extract Attenuates Indomethacin-Induced Gastric Damage In Vitro and In Vivo.

Contemporary pharmacological studies have reported that freshwater clam (Corbicula fluminea) can provide a broad spectrum of bioactivities, including antioxidant, anticancer, antihypertensive, hepatoprotective, and hypocholesterolemic effects. The aim of this study was to evaluate the gastroprotective effects of water extract of freshwater clam (WEC) on indomethacin (IND)-induced gastric mucosal cell damage in vitro and gastric ulcer in vivo. The cell viability of rat gastric mucosa RGM-1 cells was markedly decreased by 0.8 mM of IND treatment, and pre-treated with various concentration of WEC significantly restored IND-induced cell damage in a dose-dependent manner. WEC also significantly attenuated the elevated reactive oxygen species (ROS) levels, inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) expression, and nuclear factor-κB (NF-κB) p65 nuclear translocation induced by IND. In the in vivo study, IND caused severe gastric ulcer in Wistar rats, while WEC pretreatment effectively reduced the ulcer area and edema in the submucosa. We found that WEC significantly restored glutathione (GSH) content in gastric mucosa in a dose-dependent manner (p < 0.05). The reduction of prostaglandin E2 (PGE2) caused by IND was also improved with higher doses of WEC administration. Moreover, the overexpression of COX-2, iNOS, and tumor necrosis factor-α (TNF-α) proteins in gastric mucosa was downregulated by administration of WEC. Consequently, WEC can be used as a potential nutritional supplement to improve NSAIDs-caused gastric mucosal lesions.

C-Phycocyanin and Lycium barbarum Polysaccharides Protect against Aspirin-Induced Inflammation and Apoptosis in Gastric RGM-1 Cells

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.

Direct tool for quantitative analysis of cell/object dynamic behavior – metastasis and far beyond

IntroductionThe dynamics and depth of invasion as well as the ability of cancer cells to penetrate the walls of lymphatic or blood vessels represent critical survival-influencing factors in cancer patients. Depending on the cell type and tissue environment, cancer cell invasion differ in terms of motility mechanism and migration modes. Thus, there is the need of effective models allowing not only for single cell invasion potential assessment but also for collective migration and expansive growth evaluation in 3D microenvironment e.g. basement membranes. To meet this task, the specimens should be compared and analyzed in terms of the dynamics of movement and the evolution of the shape. ObjectivesOur main objective was development of the mathematical method that enables fast and credible calculation of parameters of shape and position, namely standard deviations (σX, σY), centroid position (μX, μY) and correlation coefficient ρ, based only on the contour of the aggregate. MethodsIn order to accomplish this goal we measured geometrical properties of aggregates of RGM1 cells seeded in 3D Geltrex basement membrane. Referential microscopic images were taken 24 and 48 h after seeding and cell group dynamics was registered over 8 h periods using time lapse microscopy. ResultsBased on gathered data, we managed to develop and fully test universal numerical tool allowing for estimation of statistical parameters of cell groups and aggregates which then allows for the precise evaluation of their behavior within microenvironment with time. ConclusionWe conclude, that our tool is suitable for any research on the metastatic potential and motility of cancer cells in a given microenvironment, regardless of the migration mechanism, which together with the advanced analysis like cell single-cell transcriptomic, proteomic, and chromatin accessibility data may allow to identify precise targets for anti-cancer therapies, to predict the degree of malignancy of neoplastic lesions as well as it can be useful during architecting therapeutic strategies. Moreover, the developed tool seems to be broadly applicable for assessment of behavioural dynamics of any population.

Sodium sulfite causes gastric mucosal cell death by inducing oxidative stress

Sulfites are commonly used as a preservative and antioxidant additives in the food industry. Sulfites are absorbed by the gastrointestinal tract and distributed essentially to all body tissues. Although sulfites have been believed to be safe food additives, some studies have shown that they exhibit adverse effects in various tissues. In this study, we examined the cytotoxic effect of sodium sulfite (Na2SO3) against rat gastric mucosal cells (RGM1) and further investigated its underlying molecular mechanism. We demonstrated that exposure to Na2SO3 exerts significant cytotoxicity in RGM1 cells through induction of oxidative stress. Exposure of RGM1 cells to Na2SO3 caused a significant formation of protein carbonyls and 8-hydroxy-2'-deoxyguanosine, major oxidative stress markers, with a concomitant accumulation of carbonylated protein-related aggregates. Furthermore, we found that incubation of lysozyme with Na2SO3 evokes protein carbonylation and aggregation via the metal ion-catalyzed free radical formation derived from Na2SO3. Our results suggest that Na2SO3 might lead to gastric tissue injury via induction of oxidative stress by the formation of Na2SO3-related free radicals.

The gastroprotective effect of alpinia officinarum extract on indomethacin-induced topical injuries in RGM-1 Cells: Involvement of H+/K+-ATPase- and mitochondrial-mediated apoptosis

Background: Topical effects are essential mechanisms of nonsteroidal anti-inflammatory drugs (NSAIDs)-induced gastric damage. Our previous study showed that the extract of Alpinia officinarum (AOE) may have some protective effects against the topical effects of indomethacin (INDO). The aim of this study was to elucidate the protective effects and mechanisms of A. officinarum against INDO-induced topical injuries to gastric mucosa. Materials and Methods: 0.5 mM INDO was used to cause topical effects to rat gastric epithelial cells (RGM-1). Meanwhile, AOE (2.5 μg/mL) and galangin (GAL) (0.05 mM) were added, respectively, to explore their protective effects. The cell proliferation, mitochondrial viability, and mitochondrial-mediated apoptosis were assessed by flow cytometry, inverted fluorescence microscope, or microplate reader. Pro- and cleaved-caspase-3 were detected by Western blot method. Results: AOE and GAL could significantly protect INDO-damaged RGM-1 cells by promoting cell proliferation, upregulating mitochondrial viability, inhibiting mitochondrial cytochrome c release into cytoplasm, inhibiting lipid peroxidation and caspase-3 activity, and suppressing H+/K+-ATPase activity. Conclusion: The gastroprotective effects of AOE and GAL were closely associated with suppressing the gastric acid secretion and restraining mitochondrial-mediated apoptosis. These data provided new perceptions into interpreting the underlying mechanisms of gastroprotective effects of A. officinarum and showed a promising clinical use in treating gastric mucosal injury induced by NSAIDs.

Protective effect of rosmarinic acid-rich trichodesma khasianum clarke leaves against ethanol-induced gastric mucosal injury in vitro and in vivo

BackgroundAlthough gastroprotective drugs have been used for peptic ulcer disease prevention and treatment, side effects have been observed. Finding a safe and effective treatment strategy is important. PurposeEdible Trichodesma khasianum (T. khasianum) Clarke leaves are considered to protect against peptic ulcers. However, scientific evidence of this effect of T. khasianum Clarke leaves remains limited. Study design/methodsIn this study, we aimed to evaluate the effect of T. khasianum Clarke leaves on ethanol-induced gastric injury and gut microbiota using RAW 264.7 cells, RGM-1 cells, and BALB/c mice, respectively. ResultThe rosmarinic acid was identified as the major component of T. khasianum Clarke leaves extracted by 80% ethanol (80EETC). The results showed that 80EETC suppressed inflammatory mediator protein levels in LPS-induced RAW 264.7 cells. Additionally, heat shock protein expression, antiapoptotic ability, and wound healing migration capability were increased by 80EETC pretreatment in RGM-1 cells with the ethanol-induced injury. Remarkably, pretreatment with 80EETC (150 mg/kg b.w.) promoted gastric mucosal healing by decreasing oxidative stress, inflammatory response, proapoptotic protein expression, and gastric mucosa damage in ethanol-induced gastric injury in mice. Crucially, no liver or kidney toxicities were observed by 80EETC oral gavage. Moreover, 80EETC increased gut microbiota diversity and short-chain fatty acid production. ConclusionOur results illustrated the remarkable gastroprotective effect by 80EETC treatment in vitro and in vivo. These findings are the first to demonstrate the powerful protective effect of T. khasianum Clarke leaves against gastric mucosal injury development.

Long-Term Helicobacter pylori Infection Switches Gastric Epithelium Reprogramming Towards Cancer Stem Cell-Related Differentiation Program in Hp-Activated Gastric Fibroblast-TGFβ Dependent Manner.

Helicobacter pylori (Hp)-induced inflammatory reaction leads to a persistent disturbance of gastric mucosa and chronic gastritis evidenced by deregulation of tissue self-renewal and local fibrosis with the crucial role of epithelial–mesenchymal transition (EMT) in this process. As we reported before, Hp activated gastric fibroblasts into cells possessing cancer-associated fibroblast properties (CAFs), which secreted factors responsible for EMT process initiation in normal gastric epithelial RGM1 cells. Here, we showed that the long-term incubation of RGM1 cells in the presence of Hp-activated gastric fibroblast (Hp-AGF) secretome induced their shift towards plastic LGR5+/Oct4high/Sox-2high/c-Mychigh/Klf4low phenotype (l.t.EMT+RGM1 cells), while Hp-non-infected gastric fibroblast (GF) secretome prompted a permanent epithelial–myofibroblast transition (EMyoT) of RGM1 cells favoring LGR−/Oct4high/Sox2low/c-Myclow/Klf4high phenotype (l.t.EMT−RGM1 cells). TGFβ1 rich secretome from Hp-reprogrammed fibroblasts prompted phenotypic plasticity and EMT of gastric epithelium, inducing pro-neoplastic expansion of post-EMT cells in the presence of low TGFβR1 and TGFβR2 activity. In turn, TGFβR1 activity along with GF-induced TGFβR2 activation in l.t.EMT−RGM1 cells prompted their stromal phenotype. Collectively, our data show that infected and non-infected gastric fibroblast secretome induces alternative differentiation programs in gastric epithelium at least partially dependent on TGFβ signaling. Hp infection-activated fibroblasts can switch gastric epithelium microevolution towards cancer stem cell-related differentiation program that can potentially initiate gastric neoplasm.

Walnut polyphenol extracts inhibit Helicobacter pylori-induced STAT3Tyr705 phosphorylation through activation of PPAR-γ and SOCS1 induction.

The health beneficial effects of walnut plentiful of n-3 polyunsaturated fatty acid had been attributed to its anti-inflammatory and anti-oxidative properties against various clinical diseases. Since we have published Fat-1 transgenic mice overexpressing 3-desaturase significantly mitigated Helicobacter pylori (H. pylori)-associated gastric pathologies including rejuvenation of chronic atrophic gastritis and prevention of gastric cancer, in this study, we have explored the underlying molecular mechanisms of walnut against H. pylori infection. Fresh walnut polyphenol extracts (WPE) were found to suppress the phosphorylation and nuclear translocation of signal transducer and activator of transcription 3 (STAT3) induced by H. pylori infection in RGM-1 gastric mucosal cells. Notably, H. pylori infection significantly decreased suppressor of cytokine signaling 1 (SOCS1), but WPE induced expression of SOCS1, by which the suppressive effect of walnut extracts on STAT3Tyr705 phosphorylation was not seen in SOCS1 KO cells. WPE induced significantly increased nuclear translocation nuclear translocation of PPAR-γ in RGM1 cells, by which PPAR-γ KO inhibited transcription of SOCS1 and suppressive effect of WPE on p-STAT3Tyr705 was not seen. WPE inhibited the expression of c-Myc and IL-6/IL-6R signaling, which was attenuated in the RGM1 cells harboring SOCS1 specific siRNA. Conclusively, WPE inhibits H. pylori-induced STAT3 phosphorylation in a PPAR-γ and SOCS1-dependent manner.

Total triterpenes from the fruits of Chaenomeles speciosa (Sweet) Nakai protects against indomethacin-induced gastric mucosal injury: involvement of TFF1-mediated EGF/EGFR and apoptotic pathways.

Our previous studies indicated that the triterpenes from the fruits of Chaenomeles speciosa (Sweet) Nakai (TCS) owned effectively therapeutic effects on gastric ulcer patients and animals, but its mechanisms have not been fully understood. The current study was to further investigate its protective effect on indomethacin (IND)-damaged RGM-1 cells and rats, as well as its mechanisms involved. The gastroprotection of TCS was evaluated with IND-induced gastric lesions model in RGM-1 cells and rats. In vitro, the proliferation, migration, mitochondrial viability and apoptosis were assessed. In vivo, ulcer index, ulcer inhibition rate, gastric juice acidity, gastric wall mucus (GWM) and histopathology of gastric mucosa were detected. The gastroprotective effects of TCS through the TFF1-mediated EGF/EGFR and apoptotic pathways were measured by qRT-PCR and Western blot assays. The results demonstrated that TCS had gastroprotective function, which was related to the amelioration in promoting IND-damaged RGM-1 cell proliferation and migration, hoisting gastric juice acidity and GWM, improving ulcer index and ulcer inhibition rate, attenuating the haemorrhage, oedema, epithelial cell loss and inflammatory cell infiltration of gastric mucosa, upregulating PCNA, Bcl-2, Bcl-xl mRNA and TFF1, EGF, p-EGFR, p-Src, pro-caspase-3, pro-caspase-9 protein expressions, mitochondrial viability, mitochondrial cytochrome c concentration and p-EGFR/EGFR, p-Src/Src, Bcl-2/Bax, Bcl-xl/Bad ratioes, downregulating Bax, Bad, Apaf-1 mRNA and cleaved-caspase-3, cleaved-caspase-9, cleaved PARP-1 protein expressions and cytosol cytochrome c concentration. Our present study demonstrated that TCS's gastroprotective effect was closely connected with boosting TFF1 expression, activating TFF1-mediated EGF/EGFR pathway, thus restraining mitochondrial-dependent apoptosis, which provided new insights into interpreting its underlying mechanism and promised to act as a candidate drug to treat gastric mucosal injury.

NSAID-induced injury of gastric epithelial cells is reversible: roles of mitochondria, AMP kinase, NGF, and PGE2.

Nonsteroidal anti-inflammatory drugs (NSAIDs) such as diclofenac (DFN) and indomethacin (INDO) are extensively used worldwide. Their main side effects are injury of the gastrointestinal tract, including erosions, ulcers, and bleeding. Since gastric epithelial cells (GEPCs) are crucial for mucosal defense and are the major target of injury, we examined the extent to which DFN- and INDO-induced GEPC injury can be reversed by nerve growth factor (NGF), 16,16 dimethyl prostaglandin E2 (dmPGE2), and 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR), the pharmacological activator of the metabolic sensor AMP kinase (AMPK). Cultured normal rat gastric mucosal epithelial (RGM1) cells were treated with PBS (control), NGF, dmPGE2, AICAR, and/or NSAID (DFN or INDO) for 1-4 h. We examined cell injury by confocal microscopy, cell death/survival using calcein AM, mitochondrial membrane potential using MitoTracker, and phosphorylation of AMPK by Western blotting. DFN and INDO treatment of RGM1 cells for 2 h decreased mitochondrial membrane potential and cell viability. NGF posttreatment (initiated 1 or 2 h after DFN or INDO) reversed the dissipation of mitochondrial membrane potential and cell injury caused by DFN and INDO and increased cell viability versus cells treated for 4 h with NSAID alone. Pretreatment with dmPGE2 and AICAR significantly protected these cells from DFN- and INDO-induced injury, whereas dmPGE2 and AICAR posttreatment (initiated 1 h after NSAID treatment) reversed cell injury and significantly increased cell viability and rescued the cells from NSAID-induced mitochondrial membrane potential reduction. DFN and INDO induce extensive mitochondrial injury and GEPC death, which can be significantly reversed by NGF, dmPGE2, and AICAR.NEW & NOTEWORTHY This study demonstrated that mitochondria are key targets of diclofenac- and indomethacin-induced injury of gastric epithelial cells and that diclofenac and indomethacin injury can be prevented and, importantly, also reversed by treatment with nerve growth factor, 16,16 dimethyl prostaglandin E2, and 5-aminoimidazole-4-carboxamide ribonucleotide.

Helicobacter pylori‐activated gastric fibroblasts induce epithelial‐mesenchymal transition of gastric epithelial cells in vitro in a TGF‐β‐dependent manner

Colonization of the gastric mucosa with Helicobacter pylori (Hp) leads to the cascade of pathologic events including local inflammation, gastric ulceration, and adenocarcinoma formation. Paracrine loops between tissue cells and Hp contribute to the formation of gastric cancerous loci; however, the specific mechanisms underlying existence of these loops remain unknown. We determined the phenotypic properties of gastric fibroblasts exposed to Hp (cagA+vacA+) infection and their influence on normal epithelial RGM-1 cells. RGM-1 cells were cultured in the media conditioned with Hp-activated gastric fibroblasts. Their morphology and phenotypical changes associated with epithelial-mesenchymal transition (EMT) were assessed by Nomarski and fluorescence microscopy and Western blot analysis. Motility pattern of RGM-1 cells was examined by time-lapse video microscopy and transwell migration assay. The content of TGF-β in Hp-activated fibroblast-conditioned media was determined by ELISA. The supernatant from Hp-activated gastric fibroblasts caused the EMT-like phenotypic diversification of RGM-1 cells. The formation of fibroblastoid cell sub-populations, the disappearance of their collective migration, an increase in transmigration potential with downregulation of E-cadherin and upregulation of N-cadherin proteins, prominent stress fibers, and decreased proliferation were observed. The fibroblast (CAF)-like transition was manifested by increased secretome TGF-β level, α-SMA protein expression, and its incorporation into stress fibers, and the TGF-βR1 kinase inhibitor reduced the rise in Snail, Twist, and E-cadherin mRNA and increased E-cadherin expression induced by CAFs. Gastric fibroblasts which are one of the main targets for Hp infection contribute to the paracrine interactions between Hp, gastric fibroblasts, and epithelial cells. TGF-β secreted by Hp-activated gastric fibroblasts prompting their differentiation toward CAF-like phenotype promotes the EMT-related phenotypic shifts in normal gastric epithelial cell populations. This mechanism may serve as the prerequisite for GC development.

Mitochondria in gastric epithelial cells are the key targets for NSAIDs-induced injury and NGF cytoprotection.

Gastric epithelial cells are important components of mucosal protection and targets of nonsteroidal anti-inflammatory drugs (NSAIDs)-induced injury. Diclofenac (DFN) is one of the most widely used NSAIDs; however, even its short-term use can induce gastric erosions and ulcers. Nerve growth factor (NGF) has been reported to act not only on neuronal cells but also on endothelial cells; however, its action on gastric epithelial cells is unknown. This study was aimed to determine, whether NGF can protect gastric epithelial cells against DFN-induced injury, and to determine the underlying molecular mechanisms with a focus on mitochondria, survivin, and insulin-like growth factor 1 (IGF-1). Cultured normal rat gastric mucosal epithelial cells 1 (RGM1) were treated with phosphate-buffered saline (PBS; control), NGF (100 ng/mL) and/or DFN (0.25-1.00 mM) for 4 hours. We examined: (1) cell injury by confocal microscopy; (2) cell death/survival using Calcein AM live cell tracking dye; (3) mitochondrial structure and membrane potential function using MitoTracker in live cells; and (4) expression of NGF, its receptor - tropomyosin receptor kinase A (TrkA), survivin and IGF-1 by immunostaining. DFN treatment of RGM1 cells for 4 hours caused extensive cell injury, mitochondrial disintegration, reduced cell viability (from 94 ± 3% in controls to 14 ± 4% in 0.5 mM DFN-treated cells; P < 0.001), and expression of survivin and IGF-1. NGF treatment significantly increased survivin and IGF-1 expression by 41% and 75%, respectively versus PBS controls. Pretreatment with NGF before DFN treatment reduced mitochondrial damage and cell death by 73% and 82%, respectively versus treatment with DFN alone (all P < 0.001). This study also showed the presence of high-affinity TrkA receptors in the plasma membrane and mitochondria of RGM1 cells indicating novel actions of NGF.

Protein changes in gastric epithelial cells RGM-1 in response to Helicobacter pylori infection.

Helicobacter pylori-induced inflammation significantly increases the risk of gastric cancer. To investigate the role of H. pylori infection in gastric epithelial cell carcinogenesis, flow cytometry was used to analyze the apoptosis of gastric epithelial cells infected by H. pylori. Next, LTQ MS mass spectrometry (MS) was applied to identify protein changes in gastric epithelial cells infected with H. pylori, and then bioinformatics was adopted to analyze the cellular localization and biological function of differential proteins. LTQ MS/MS successfully identified identified 22 differential proteins successfully, including 20 host-cell proteins and two H. pylori bacterial proteins. Also, human proteins were located in all areas of cells and involved in various cell biological functions. The oncogene proteins p53, p16, and C-erbB-2 proteins in H. pylori-infected RGM-1 cells were remarkably increased from the analysis by Western blot analysis. H. pylori infection of gastric epithelial cells leads to changes in various protein components in the cell, and enhances the expression of oncogene proteins, thereby increasing the possibility of possibility of carcinogenesis of H. pylori infection.

O32 Curcumin induces expression of 15-hydroxyprostaglandin dehydrogenase in normal gastric mucosa RGM-1 cells and mouse stomach in vivo: A potential role of AP-1

Overproduction of prostaglandin E 2 (PGE 2 ) has been reported to be implicated in carcinogenesis. The intracellular level of PGE 2 is regulated not only by its biosynthesis, but also by the degradation process. 15-Hydroxyprostaglandin dehydrogenase (15-PGDH) is the key enzyme that catalyzes the inactivation of PGE 2 . In the present study, we found that curcumin, a yellow coloring agent present in the rhizome of Curcuma longa Linn (Zingiberaceae), induced expression of 15-PGDH at both the protein and mRNA levels in normal rat gastric mucosa cells (RGM-1). By using deletion constructs of the 15-PGDH promoter, we have found that activator protein-1 (AP-1) is the most essential transcription factor responsible for curcumin-induced upregulation of 15-PGDH expression. In addition, oral administration of curcumin increased the expression of 15-PGDH in the mouse stomach. Curcumin enhanced the expression of c-Jun and c-Fos in the nuclear fraction of RGM-1 cells and the mouse stomach in vivo . Knockdown of c- jun , a gene encoding one of the major components of AP-1, suppressed curcumin-induced expression of 15-PGDH. In addition, curcumin increased phosphorylation of ERK1/2 and JNK. Curcumin-induced 15-PGDH expression was abrogated by the pharmacological inhibition of the aforementioned kinases. In contrast, tetrahydrocurcumin which lacks the α , β -unsaturated carbonyl group failed to induce expression of 15-PGDH, suggesting that the electrophilic α , β -unsaturated carbonyl group of curcumin is essential for its induction of 15-PGDH expression in RGM-1 cells. Taken together, our study suggests that curcumin-induced upregulation of 15-PGDH in RGM-1 cells and mouse stomach through activation of AP-1 may contribute to chemopreventive effects of this phytochemical on inflammation-associated gastric carcinogenesis.

Protective Effect of Camellia Oil (Camellia oleifera Abel.) against Ethanol-Induced Acute Oxidative Injury of the Gastric Mucosa in Mice.

Camellia oil, a common edible oil in Taiwan and China, has health effects for the gastrointestinal tract in folk medicine, and it contains abundant unsaturated fatty acids and phytochemicals. However, the preventive effect of camellia oil on ethanol-induced gastric ulcers remains unclear. This study was aimed to evaluate the preventive effect of camellia oil on ethanol-induced gastric injury in vitro and in vivo as well as its mechanisms of action. In an in vitro study, our results showed that pretreatment of RGM-1 cells with camellia oil enhanced the migration ability as well as increased heat shock protein expression and reduced apoptotic protein expression. In animal experiments, mice pretreated with camellia oil effectively showed improved ethanol-induced acute injury of the gastric muscosa and oxidative damage through the enhancement of antioxidant enzyme activities and heat shock protein and PGE2 production, as well as the suppression of lipid peroxidation, apoptosis-related proteins, pro-inflammatory cytokines, and NO production. Histological injury score and hemorrhage score in ethanol-induced gastric mucosal damage dramatically elevated from the control group (0.00 ± 0.0) to 3.40 ± 0.7 and 2.60 ± 0.5, respectively. However, treatments with camellia oil or olive oil (2 mL/kg bw) and lansoprazole (30 mg/kg bw) showed significant decreases in elevation of injury score and hemorrhage score (p < 0.05). Therefore, camellia oil has the potential to ameliorate ethanol-induced acute gastric mucosal injury through the inhibition of inflammation and oxidative stress.

Na+ /H+ exchanger NHE1 and NHE2 have opposite effects on migration velocity in rat gastric surface cells.

Following superficial injury, neighbouring gastric epithelial cells close the wound by rapid cell migration, a process called epithelial restitution. Na+/H+ exchange (NHE) inhibitors interfere with restitution, but the role of the different NHE isoforms expressed in gastric pit cells has remained elusive. The role of the basolaterally expressed NHE1 (Slc9a1) and the presumably apically expressed NHE2 (Slc9a2) in epithelial restitution was investigated in the nontransformed rat gastric surface cell line RGM1. Migration velocity was assessed by loading the cells with the fluorescent dye DiR and following closure of an experimental wound over time. Since RGM1 cells expressed very low NHE2 mRNA and have low transport activity, NHE2 was introduced by lentiviral gene transfer. In medium with pH 7.4, RGM1 cells displayed slow wound healing even in the absence of growth factors and independently of NHE activity. Growth factors accelerated wound healing in a partly NHE1‐dependent fashion. Preincubation with acidic pH 7.1 stimulated restitution in a NHE1‐dependent fashion. When pH 7.1 was maintained during the restitution period, migratory speed was reduced to ∼10% of the speed at pH 7,4, and the residual restitution was further inhibited by NHE1 inhibition. Lentiviral NHE2 expression increased the steady‐state pHi and reduced the restitution velocity after low pH preincubation, which was reversible by pharmacological NHE2 inhibition. The results demonstrate that in RGM1 cells, migratory velocity is increased by NHE1 activation, while NHE2 activity inhibit this process. A differential activation of NHE1 and NHE2 may therefore, play a role in the initiation and completion of the epithelial restitution process.

Mitigated NSAID-induced apoptotic and autophagic cell death with Smad7 overexpression.

Non-steroidal anti-inflammatory drugs damaged gastrointestinal mucosa in cyclooxygenase-dependent and -independent pathway, among which apopototic or autophagic cell death in gastrointestinal cells might be one of key cytotoxic mechanisms responsible for NSAID-induced damages. Therefore, alleviating this cell death after NSAIDs can be a rescuing strategy. In this study, we explored the role of Smad7 on NSAID-induced cytotoxicity in gastric epithelial cells. Using RGM1 cells, we have compared biological changes between mock-transfected and Smad7-overexpressed cells. As results, significantly decreased cytotoxicity accompanied with decreased levels of cleaved caspase-3 and poly (ADP-ribose) polymerase, Bax, and autophagic vesicles concurrent with decreased expressions of autophagy protein 5 and microtubule-associated protein light chain 3B-II were noted in Smad7-overexpressed cells with indomethacin administration compared to mock-transfected cells. Contrast to mitigated apoptotic execution, anti-apoptotic Bcl-2 and Beclin-1 were significantly increased in Smad7-overexpressed cells compared to mock-transfected cells. Smad7 siRNA significantly reversed these protective actions of Smad7 against indomethacin, in which p38 mitogen-activated protein kinase was significantly intervened. Furthermore, indomethacin-induced Smad7 degradation through ubiquitin-proteasome pathway was relevant to increased cytotoxicity, while chloroquine as autophagy inhibitor significantly attenuated indomethacin-induced cytotoxicity through Smad7 preservation via repressed ubiquitination. Conclusively, either genetic overexpression or pharmacological induction of Smad7 significantly attenuated indomethacin-induced gastric cell damages.

Role of Inhibitory Transforming Growth Factor-β Signal Smad7 in Helicobacter pylori-associated Gastric Damage

Transforming growth factor-beta (TGF-β) is a cytokine implicated in the susceptibility, development, and progression of gastrointestinal cancer and certain other neoplasms. In the later stages of cancer, TGF-β not only acts as a bystander of host-immune response, but also contributes to cell growth, invasion, and metastasis. In the current study, we generated gastric mucosal cells that stably express Smad7, and explored the Helicobacter pylori-associated biological changes between mock-transfected and Smad7-transfected RGM1 cells. RGM1 cells stably transfected with Smad7 were infected with H. pylori, and molecular changes in apoptotic markers and inflammatory mediators were examined. Several candidate genes were explored in Smad7-overexpressing cells after H. pylori infection. Overexpression of Smad7 in RGM1 cells significantly increased the H. pylori-induced cytotoxicity compared to mock-transfected cells. Exaggerated increases in inflammatory mediators, cyclooxygenase 2, inducible NO synthase, and augmented apoptosis were noted in Smad7-overexpressing cells, whereas mitigated heme oxygenase 1 was noted in Smad7- overexpressing cells. These phenomena were reversed in cells transfected with Smad7 siRNA. These data suggest that inhibition of Smad7 is a possible target for mitigating H. pylori-associated inflammation.

Nrf2-mediated mucoprotective and anti-inflammatory actions of Artemisia extracts led to attenuate stress related mucosal damages.

The aim of this study was to compare biological actions between isopropanol and ethanol extracts of Artemisia including antioxidant, anti-inflammatory, and cytoprotective actions. Antioxidant activities were evaluated using 2,2-diphenyl-1-picrylhydrazyl (DPPH) method and confocal microscopy on lipopolysaccharide-induced RGM1 cells, cytoprotection effects evaluated by detecting heme oxygenase-1 (HO-1), Nf-E2 related factor2 (Nrf2) and heat shock protein 70 (HSP70), and anti-inflammatory effects investigated by measuring inflammatory mediators. Water immersion restraint stress was imposed to provoke stress related mucosal damages (SRMD) in rats. Isopropanol extracts of Artemisia showed the higher DPPH radical scavenging activity and lesser LPS-induced reactive oxygen species productions and increased HO-1 expression through increased nuclear translocation of Nrf2 transcription factor compared to ethanol extracts. The increased expression of HSP70 and decreased expression of endothelin-1 were only increased with isopropanol extracts. A concentration-dependent inhibition of LPS-induced COX-2 and iNOS even at a rather lower concentration than ethanol extract was achieved with isopropanol extracts. Cytokine protein array revealed Artemisia extracts significantly attenuated the levels of CXCL-1, CXCL-16, and MCP-1. These orchestrated actions led to significant rescue from SRMD. Conclusively, Artemisia extracts imposed significant antioxidant and anti-inflammatory activity against SRMD and isopropanol extracts were superior to ethanol extracts in these beneficiary actions of Artemisia.