Anti-inflammatory effect of two isoforms of COX in H. pylori-induced gastritis in mice: possible involvement of PGE2

Suppression of progesterone by influenza A virus mediates adverse maternal and fetal outcomes in mice

Influenza A virus infection during pregnancy can cause adverse maternal and fetal outcomes but the mechanism responsible remains elusive. Infection of outbred mice with 2009 H1N1 at embryonic day (E) 10 resulted in significant maternal morbidity, placental tissue damage and inflammation, fetal growth restriction, and developmental delays that lasted through weaning. Restriction of pulmonary virus replication was not inhibited during pregnancy, but infected dams had suppressed circulating and placental progesterone (P4) concentrations that were caused by H1N1-induced upregulation of pulmonary cyclooxygenase (COX)-1-, but not COX-2-, dependent synthesis and secretion of prostaglandin (PG) F2α. Treatment with 17-α-hydroxyprogesterone caproate (17-OHPC), a synthetic progestin that is safe to use in pregnancy, ameliorated the adverse maternal and fetal outcomes from H1N1 infection and prevented placental cell death and inflammation. These findings highlight the therapeutic potential of progestin treatments for influenza during pregnancy.IMPORTANCEPregnant individuals are at risk of severe outcomes from both seasonal and pandemic influenza A viruses. Influenza infection during pregnancy is associated with adverse fetal outcomes at birth and adverse consequences for offspring into adulthood. When outbred dams, with semi-allogenic fetuses, were infected with 2009 H1N1, in addition to pulmonary virus replication, lung damage, and inflammation, the placenta showed evidence of transient cell death and inflammation that was mediated by increased activity along the arachidonic acid pathway leading to suppression of circulating progesterone. Placental damage and suppressed progesterone were associated with detrimental effects on perinatal growth and developmental delays in offspring. Treatment of H1N1-infected pregnant mice with 17-OHPC, a synthetic progestin treatment that is safe to use in pregnancy, prevented placental damage and inflammation and adverse fetal outcomes. This novel therapeutic option for the treatment of influenza during pregnancy should be explored clinically.

Suppression of progesterone by influenza A virus mediates adverse maternal and fetal outcomes in mice

Influenza A virus infection during pregnancy can cause adverse maternal and fetal outcomes, but the mechanism responsible remains elusive. Infection of outbred mice with 2009 H1N1 at embryonic day (E) 10 resulted in significant maternal morbidity, placental tissue damage and inflammation, fetal growth restriction, and developmental delays that lasted through weaning. Restriction of pulmonary virus replication was not inhibited during pregnancy, but infected dams had suppressed circulating and placental progesterone (P4) concentrations that were caused by H1N1-induced upregulation of pulmonary cyclooxygenase (COX)-1, but not COX-2-, dependent synthesis and secretion of prostaglandin (PG) F2α. Treatment with 17-α-hydroxyprogesterone caproate (17-OHPC), a synthetic progestin that is safe to use in pregnancy, ameliorated the adverse maternal and fetal outcomes from H1N1 infection and prevented placental cell death and inflammation. These findings highlight the therapeutic potential of progestin treatments for influenza during pregnancy.

Experimental validation for mechanisms of Qizhiweitong particles against Chronic Non-atrophic gastritis based on metabolomics and network pharmacology

Qizhiweitong particles (QZWT), a classic Chinese herbal prescription derived from the Sinisan decoction in Shang Han Za Bing Lun, has definitive clinical efficacy in treating Chronic Non-atrophic Gastritis (CNG) in China. However, its mechanism of action at the metabolic level remains unclear. The aim of this study was to explore the mechanisms of QZWT against CNG based on non-targeted metabolomics combined with network pharmacology and experimentally validated by enzyme linked immunosorbent assays (ELISA). First, CNG model rats were established by free drinking ammonia water combined with starvation and satiety disorder for 12 weeks. Taking gastric tissue as the object, ultra-high performance liquid chromatography tandem mass spectrometry based metabolomics and network pharmacology were conducted to identify the key compounds, core targets and pathways that mediate the effects of QZWT against CNG. Furthermore, the targets from network pharmacology and the metabolites from metabolomics were jointly analyzed to select crucial metabolism pathways by MetaScape. Finally, the key metabolic enzymes and metabolites were experimentally validated by ELISA. The results indicated that there were 29 differential metabolites were identified and considered to be metabolic biomarkers of QZWT in the treatment of CNG. Among them, 8 of the differential metabolites showed a significant reduction in the content of QZWT groups. Arachidonic acid (AA) metabolic and glycerophospholipid (GP) metabolic are the most crucial metabolic pathways for QZWT to treat CNG. QZWT regulated AA and GP metabolism by synergetic reducing the level of AA, Phospholipid acid and Lysophosphatidic acid and inhibiting the enzyme activity of prostaglandin endoperoxide synthase 1 and prostaglandin endoperoxide synthase 2. And a compound-reaction-enzyme-gene network of mechanism for QZWT against CNG was established. In conclusion, this study reveals the complicated mechanisms of QZWT against CNG. Our work presents a novel strategy to identify the potential mechanisms of pharmacological effects derived from a compound prescription of TCM.

The protective effects of rosmarinic acid on ethanol-induced gastritis in male rats: antioxidant defense enhancement

Background and purpose:

Gastritis is one of the most current gastrointestinal disorders worldwide. Alcohol consumption is one of the major factors, which provides gastritis. Rosmarinic acid (RA) is found in many plants and has powerful antioxidant and anti-inflammatory effects. In this study, the protective effect of RA was evaluated on the histopathological indices, antioxidant ability, and prostaglandin E2 (PGE2) secretion in male rats.

Experimental approach:

Forty-two animals were divided into control, ethanol-induced gastritis, and RA groups, 6 each. The protective groups included RA administration before gastritis induction at 50 mg (R-G50), 100 mg (R-G100), 150 mg (R-G150), and 200 mg (R-G200) doses. Gastritis was induced by gavage of 1 mL pure ethanol in fasted animals. After 1 h of gastritis induction, the rats were sacrificed and stomach tissue was removed.

Findings/Results:

Histological evaluation revealed that RA significantly attenuated gastric ulcers, leucocyte infiltration, and hyperemia. It also increased mucosal layer thickness and restored gastric glands. Furthermore, RA decreased malondialdehyde level, increased superoxide dismutase, catalase, and glutathione in the stomach tissue, and raised gastric PGE2 level.

Conclusion and implications:

Our study demonstrated that rosmarinic acid has a notable effect on gastritis protection that could be due to increased antioxidant defense and PGE2 secretion, eventually maintenance of mucosal barrier integrity and gastric glands.

Gene expression patterns of COX-1, COX-2 and iNOS in H. Pylori infected histopathological conditions

BACKGROUND

Research indicates that Helicobacter pylori can inflict severe histological damage through the modulation of host-related genes. The current study investigated the effect of H. pylori genotypes in the outcome of disease, and the expression of anti-apoptotic related genes, COX-1, COX-2, and iNOS genes in benign, pre-malignant, and malignant lesions of gastric carcinogenesis.

MATERIALS AND METHODS

Tissue samples from H. pylori positive patients were graded based on the genotype of the infected H. pylori strain. Expression of COX-1, COX-2 and iNOS was assessed using a combination of real-time PCR and immunohistochemistry.

RESULTS

Gene expression studies confirmed that COX-2 and iNOS expression was highly and selectively induced in epithelium with premalignant changes such as atrophic conditions, metaplasia and dysplasia, suggesting an important role of these genes in the sequence to gastric carcinoma of the intestinal type. Furthermore, the expression of COX-2 and iNOS was also dependent on the genotype of H. pylori and subjects with genotype-1 exhibited significantly higher expressions of COX-2 and iNOS compared to other genotypes. Comparison of the expression levels among infected and uninfected individuals demonstrated significant difference in the expression pattern of COX-2 gene whereas iNOS expression was found only in subjects infected H. pylori (p < 0.001). Immunohistochemical staining showed 1.5619 folds higher propensity of COX-2 and 3.2941 folds higher intensity of iNOS expression in subjects infected with H. pylori genotype 1.

CONCLUSION

The up-regulation of COX-2 and iNOS was associated with the genotype of the H. pylori strain and the presence of certain genotype may greatly affect early events during carcinogenesis.

Impact of Cyclooxygenase-2 1195 G-Carrier Genotype Associated with Intestinal Metaplasia and Endoscopic Findings Based on Kyoto Classification

BACKGROUND/AIMS

We aimed to clarify whether cyclooxygenase-2 (COX-2) and microsomal prostaglandin E synthase-1 (mPGES-1) genotypes were associated with certain histological findings and endoscopical appearances based on Kyoto classification.

METHODS

We enrolled 285 Helicobacter pylori-infected gastritis patients. Genotypes of COX-2 1195, COX-2 1290, mPGES-1, interleukin-1β (IL-1β) 511 and tumour necrosis factor-α (TNF-α) 308 were analyzed. Genotyping was performed by polymerase chain reaction. Endoscopic appearances and histological assessment were determined by using Kyoto classification, operative link on gastritic intestinal metaplasia assessment and the updated Sydney system.

RESULTS

There was a significant (p = 0.027) relationship between the IL-1β 511 C-carrier and histological gastric inflammation in H. pylori-infected gastritis patients. There was a significant (p = 0.009) correlation between the COX-2 1195 G-carrier genotype and histological intestinal metaplasia in the gastric antrum of H. pylori-infected gastritis patients and gastric xanthoma (p = 0.027). The COX-2 1195 G-carrier genotype was also significantly (p = 0.038) associated with the score of endoscopic intestinal metaplasia based on Kyoto classification. The mPGES-1 genotype was significantly (p = 0.002) associated with endoscopic swelling of area.

CONCLUSION

Our results suggest that in Japan, there exists a significant correlation between the COX-2 1195 G-carrier genotype and intestinal metaplasia in histological and endoscopic findings based on Kyoto classification in H. pylori-infected gastric mucosa.

Helicobacter pylori modulates cyclooxygenase-2 and 15-hydroxy prostaglandin dehydrogenase in gastric cancer

Persistent infection with Helicobacter pylori may contribute to the carcinogenesis of gastric cancer through modulating local prostaglandin E₂ (PGE₂) levels. Cyclooxygenase-2 (COX-2) and 15-hydroxy prostaglandin dehydrogenase (15-PGDH) are two key enzymes that regulate PGE₂ synthesis and inactivation, respectively. The present study was designed to investigate the expression of COX-2 and 15-PGDH in gastric cancer specimens (n=66) in comparison to that of control specimens (n=70) and, furthermore, to semi-quantitatively assess the level of COX-2 and 15-PGDH mRNA and protein in tissues with or without H. pylori infection by reverse transcription-polymerase chain reaction and immunohistochemistry, respectively. It was revealed that COX-2 was expressed in almost all gastric cancer specimens infected with H. pylori (32 out of 33 specimens), but it was also expressed in 2/3 gastric cancers without H. pylori infection (22 out of 33 specimens). By contrast, COX-2 was expressed in <1/6 control subjects regardless of H. pylori infection. Furthermore, 15-PGDH was expressed in control samples but significantly downregulated in gastric cancer specimens. H. pylori infection resulted in slight inhibition of 15-PGDH in control subjects, but significant inhibition of 15-PGDH mRNA expression and protein synthesis in the gastric cancer specimens. These findings indicated that COX-2 and 15-PGDH, the two enzymes that regulate PGE₂ levels, were significantly altered in gastric cancer, and that H. pylori may contribute to gastric carcinogenesis through modulating COX-2 and 15-PGDH mRNA expression and protein synthesis.

Toll-like receptor 9 signaling has anti-inflammatory effects on the early phase of Helicobacter pylori-induced gastritis

Helicobacter pylori (H. pylori)-induced immune responses in the gastric mucosa are skewed toward T helper (Th) 1 phenotype, which is characterized by predominant production of tumor necrosis factor (TNF)-α and interferon (IFN)-γ by helper T cells. Toll-like receptors (TLRs) play an essential role in mucosal defense against microbes through the recognition of bacterial molecules. Among the members of the TLR family, TLR9 recognizes bacterial unmethylated CpG DNA sites, and signal transduction of TLR9 induces production of a variety of cytokines, including type-I IFN (IFN-α/β). We investigated the expression and role of TLR9 in H. pylori-induced gastritis in mice. Expression of TLR9 mRNA in the gastric tissue increased after infection with H. pylori. TLR9 was mainly expressed in the macrophages, dendritic cells, and CD3(+) cells in the gastric mucosa. Neutrophil infiltration and the expression levels of TNF-α and IFN-γ mRNA were higher in TLR9 knockout (KO) mice than in wild-type mice at 2 and 4 months after H. pylori inoculation. These differences in inflammatory parameters between H. pylori-infected wild-type and TLR9 KO mice disappeared 6 months after H. pylori inoculation. Expression of interleukin-4 mRNA, typical Th2 cytokine, in the gastric tissue did not differ between H. pylori-infected wild-type and TLR9 KO mice. Expression level of IFN-α/β mRNA in the TLR9 KO mice was lower than that in wild-type mice by 4 months after inoculation. Administration of IFN-α reduced H. pylori infection-induced increase in neutrophil infiltration and the expression levels of TNF-α and IFN-γ mRNA in TLR9 KO mice. Our findings suggest that TLR9 signaling plays important roles in the suppression of H. pylori-induced gastritis in the early phase via downregulation of Th1-type cytokines modulated by IFN-α.

Pathogenesis of NSAID-induced gastric damage: importance of cyclooxygenase inhibition and gastric hypermotility

This article reviews the pathogenic mechanism of non-steroidal anti-inflammatory drug (NSAID)-induced gastric damage, focusing on the relation between cyclooxygenase (COX) inhibition and various functional events. NSAIDs, such as indomethacin, at a dose that inhibits prostaglandin (PG) production, enhance gastric motility, resulting in an increase in mucosal permeability, neutrophil infiltration and oxyradical production, and eventually producing gastric lesions. These lesions are prevented by pretreatment with PGE₂ and antisecretory drugs, and also via an atropine-sensitive mechanism, not related to antisecretory action. Although neither rofecoxib (a selective COX-2 inhibitor) nor SC-560 (a selective COX-1 inhibitor) alone damages the stomach, the combined administration of these drugs provokes gastric lesions. SC-560, but not rofecoxib, decreases prostaglandin E₂ (PGE₂) production and causes gastric hypermotility and an increase in mucosal permeability. COX-2 mRNA is expressed in the stomach after administration of indomethacin and SC-560 but not rofecoxib. The up-regulation of indomethacin-induced COX-2 expression is prevented by atropine at a dose that inhibits gastric hypermotility. In addition, selective COX-2 inhibitors have deleterious influences on the stomach when COX-2 is overexpressed under various conditions, including adrenalectomy, arthritis, and Helicobacter pylori-infection. In summary, gastric hypermotility plays a primary role in the pathogenesis of NSAID-induced gastric damage, and the response, causally related with PG deficiency due to COX-1 inhibition, occurs prior to other pathogenic events such as increased mucosal permeability; and the ulcerogenic properties of NSAIDs require the inhibition of both COX-1 and COX-2, the inhibition of COX-1 upregulates COX-2 expression in association with gastric hypermotility, and PGs produced by COX-2 counteract the deleterious effect of COX-1 inhibition.

Gastritis induced by Helicobacter pylori infection in experimental rats

BACKGROUND

Gastritis, an inflammation of gastric mucosa, may be due to many pathological factors and infection, such as with Helicobacter pylori. The use of experimental models of gastritis is important to evaluate the biochemical changes and study chemotherapeutic intervention. In a previous study we demonstrated an acute gastritis model induced by iodoacetamide.

AIMS

Our objective in this study was to evaluate a new gastritis model induced by H. pylori infection in experimental rats in terms of certain biomarkers in serum and mucosal tissues in addition to histopathological examination.

METHODS

Gastritis was induced in 20 albino Wistar rats by H. pylori isolated from antral biopsy taken from a 49-year-old male patient endoscopically diagnosed as having H. pylori infection. Another ten rats were used as controls. Serum gastrin, pepsinogen I activity, interleukin-6 (IL-6) and gastric mucosal myeloperoxidase (MPO) activity and prostaglandin E(2) (PGE(2)) were measured. Immunostaining for inducible nitric oxide synthase (iNOS), nitrotyrosine and DNA fragmentation were used to further evaluate H. pylori-induced gastritis.

RESULTS

Serum gastrin, IL-6, mucosal MPO activity, and PGE(2) demonstrated significant increases joined with a decreased serum pepsinogen I activity (P < 0.001). Immunohistochemistry demonstrated positive reaction for iNOS, nitrotyrosine and DNA fragmentation.

CONCLUSIONS

Helicobacter pylori-induced gastritis models demonstrated massive oxidative stress and pronounced injury in mucosal tissue. Since our model in rats reflected the clinical picture of H. pylori infection, it can be considered as a consistent model to study chemotherapeutic intervention for this type of gastritis.

Prostaglandin E2 prevents Helicobacter-induced gastric preneoplasia and facilitates persistent infection in a mouse model

BACKGROUND & AIMS

Persistent infection with the human pathogen Helicobacter pylori increases the risk of gastric cancer. In this study, we investigated the role of cyclooxygenase-2 (COX-2) and its main product, prostaglandin E(2) (PGE(2)), in the development of Helicobacter-induced gastritis and gastric cancer precursor lesions.

METHODS

We utilized mouse models of Helicobacter-induced gastric preneoplasia and vaccine-induced protection to study the effects of COX-2 inhibition and PGE(2) treatment on the induction of Helicobacter-specific immune responses and gastric premalignant immunopathology.

RESULTS

COX-2 and PGE(2) are up-regulated upon Helicobacter infection in cultured epithelial cells and in the gastric mucosa of infected mice. Inhibition of COX-2 activity with celecoxib significantly accelerated early preneoplasia; conversely, systemic administration of synthetic PGE(2) prevented development of premalignant pathology and completely reversed preexisting lesions by suppressing interferon-gamma production in the infected stomachs. The protective effect of PGE(2) was accompanied by increased Helicobacter colonization in all models. All in vivo effects were attributed to immunosuppressive effects of PGE(2) on CD4(+) T-helper 1 cells, which fail to migrate, proliferate, and secrete cytokines when exposed to PGE(2) in vitro and in vivo. T-cell inhibition was found to be due to silencing of interleukin-2 gene transcription, and could be overcome by supplementation with recombinant interleukin-2 in vitro and in vivo.

CONCLUSIONS

COX-2-dependent production of PGE(2) has an important immunomodulatory role during Helicobacter infection, preventing excessive local immune responses and the associated immunopathology by inhibiting the effector functions of pathogenic T-helper 1 cells.

Reduction of 15-hydroxyprostaglandin dehydrogenase expression is an independent predictor of poor survival associated with enhanced cell proliferation in gastric adenocarcinoma

Prostaglandin (PG) E(2) promotes gastrointestinal carcinogenesis and tumor progression. We determined the correlations between pattern of expression of 15-hydroxyprostaglandin dehydrogenase (15-PGDH), a catabolic enzyme for biological inactivation of PGE(2), in gastric adenocarcinoma and various clinicopathological factors and patient outcome in an attempt to elucidate its biological significance. In 35 of 71 cases of gastric adenocarcinoma, expression of 15-PGDH protein was reduced in tumor tissues. Multivariate analysis revealed reduction of 15-PGDH expression to be an independent predictor of poor survival. The proportion of Ki67-positive cells in 15-PGDH-negative adenocarcinoma was higher than that in 15-PGDH-positive adenocarcinoma. No differences were found in clinicopathological parameters between patients with cyclooxygenase-2 (COX-2)-positive tumors and those with COX-2 negative tumors. In an in vitro study, use of specific siRNA to silence 15-PGDH or a specific inhibitor of 15-PGDH enhanced cell proliferation in the gastric cancer cell line AGS, which expresses 15-PGDH. These findings suggest that reduction of 15-PGDH is an independent predictor of poor survival associated with enhancement of cell proliferation in gastric adenocarcinoma.

Combination of sulindac and antimicrobial eradication of Helicobacter pylori prevents progression of gastric cancer in hypergastrinemic INS-GAS mice

Helicobacter pylori infection causes severe dysplasia manifested as gastrointestinal intraepithelial neoplasia (GIN) after 28 weeks post-H. pylori infection (WPI) in cancer-prone, hypergastrinemic male INS-GAS mice. We examined the efficacy of the nonsteroidal anti-inflammatory drug sulindac (400 ppm in drinking water) alone, the CCK2/gastrin receptor antagonist YM022 (45 mg/kg/wk) alone, and sulindac or YM022 combined with H. pylori eradication therapy to prevent H. pylori-associated gastric cancer in male INS-GAS mice. Treatments started at 22 WPI, and mice were euthanized at 28 WPI. In uninfected mice, all treatments significantly delayed development of spontaneous GIN (P < 0.05). In H. pylori-infected mice, sulindac alone or YM022 alone had no protective effect on H. pylori-associated GIN. Importantly, sulindac exacerbated the severity of H. pylori-associated gastritis despite decreased gastric prostaglandin E(2) levels. However, sulindac combined with H. pylori antimicrobial eradication reduced the incidence of GIN (P < 0.05), whereas YM022 combined with antimicrobial eradication did not reduce GIN. In infected mice, sulindac or YM022 treatment did not alter gastric expression of the proinflammatory cytokines Ifn-gamma and Tnf-alpha and mucosal cell proliferation. Sulindac or YM022 combined with antimicrobial eradication down-regulated mRNA levels of Ifn-gamma and Tnf-alpha and mucosal cell proliferation (P < 0.05). We conclude that sulindac enhances H. pylori gastritis and may promote inflammation-mediated gastric carcinogenesis. The combination of sulindac and antimicrobial H. pylori eradication was beneficial for reducing proinflammatory cytokine mRNA in the stomach and preventing progression from severe dysplasia to gastric cancer in H. pylori-infected INS-GAS mice.

Long-term use of nonsteroidal anti-inflammatory drugs normalizes the kinetics of gastric epithelial cells in patients with Helicobacter pylori infection via attenuation of gastric mucosal inflammation

BACKGROUND

Helicobacter pylori (H. pylori) is associated with chronic gastritis and gastric carcinogenesis. The effects of nonsteroidal anti-inflammatory drugs (NSAIDs), which exert chemopreventive effects on several cancers, on H. pylori-induced gastritis remain unknown. We investigated the effects of NSAIDs on gastric inflammation and the kinetics of gastric epithelial cells in H. pylori-induced gastritis.

METHODS

Patients with rheumatoid arthritis or osteoarthritis who took NSAIDs for more than 1 month and complained of dyspeptic symptoms were recruited for this study. Patients not on any NSAIDs were included as non-NSAID user controls. All patients underwent diagnostic testing for H. pylori infection, esophagogastroduodenoscopy, and gastric biopsies. Neutrophil infiltration into gastric mucosa, expression of inducible nitric oxide synthase (iNOS), and apoptosis and proliferation of gastric epithelial cells were evaluated by immunohistochemistry. In an in vitro study, the effects of NSAIDs on production of interleukin (IL)-8 induced by H. pylori in a gastric epithelial cell line (AGS) were determined.

RESULTS

Numbers of neutrophils infiltrating the gastric mucosa, iNOS-expressing inflammatory cells and apoptotic cells, and proliferating cells in gastric epithelium were higher in H. pylori-positive groups than H. pylori-negative groups. Among H. pyloripositive groups, these parameters were lower in NSAID users than in non-NSAID users. NSAIDs inhibited the production of IL-8 induced by H. pylori in AGS cells.

CONCLUSIONS

These findings suggest that long-term use of NSAIDs normalizes the kinetics of gastric epithelial cells in patients with H. pylori infection by attenuating gastric mucosal inflammation, which may result in prevention of the gastric carcinogenesis associated with H. pylori infection.

Roles of cyclooxygenase-2 and microsomal prostaglandin E synthase-1 expression and beta-catenin activation in gastric carcinogenesis in N-methyl-N-nitrosourea-treated K19-C2mE transgenic mice

K19-C2mE transgenic (Tg) mice, simultaneously expressing cyclooxygenase-2 (COX-2) and microsomal prostaglandin E synthase-1 (mPGES-1) in the gastric mucosa under the cytokeratin 19 gene promoter, were here treated with N-methyl-N-nitrosourea (MNU) and inoculated with Helicobacter pylori (H. pylori) to investigate gastric carcinogenesis. Wild-type (WT) and Tg mice undergoing MNU treatment frequently developed tumors in the pyloric region (100% and 94.7%, respectively); multiplicity in Tg was higher than that in WT (P < 0.05) with H. pylori infection. Larger pyloric tumors were more frequently observed in Tg than in WT (P < 0.05). In addition, Tg developed fundic tumors, where WT did not. No gastric tumors were observed without MNU treatment. Transcripts of TNF-alpha, iNOS, IL-1beta, and CXCL14 were up-regulated with H. pylori infection in both genotypes and were also increased more in Tg than in WT within H. pylori-inoculated animals. Immunohistochemical analysis demonstrated significantly greater beta-catenin accumulation in pyloric tumors, compared with those in the fundus (P < 0.01) with mutations of exon 3; 18.2% and 31.6% in MNU-alone and MNU + H. pylori-treated WT, whereas 21.4% and 62.5% was observed in the Tg, respectively; the latter significantly higher (P < 0.05), suggesting the role of H. pylori in Wnt activation. In conclusion, K19-C2mE mice promoted gastric cancer in both fundic and pyloric regions. Furthermore beta-catenin activation may play the important role of pyloric carcinogenesis especially in H. pylori-infected Tg. Induction of various inflammatory cytokines in addition to overexpression of COX-2/mPGES-1 could be risk factors of gastric carcinogenesis and may serve as a better gastric carcinogenesis model.

Effects of aspirin on the development of Helicobacter pylori-induced gastric inflammation and heterotopic proliferative glands in Mongolian gerbils

BACKGROUND

Helicobacter pylori infection is a major cause of gastritis and gastric carcinoma. Aspirin has anti-inflammatory and antineoplastic activity. The aim of the present study was to determine the effects of aspirin on H. pylori-induced gastritis and the development of heterotopic proliferative glands.

METHODS

H. pylori strain SS1 was inoculated into the stomachs of Mongolian gerbils. Two weeks after inoculation, the animals were fed with the powder diets containing 0 p.p.m. (n = 10), 150 p.p.m. (n = 10), or 500 p.p.m. (n = 10) aspirin. Mongolian gerbils were killed after 36 weeks of infection. Uninfected Mongolian gerbils (n = 10) were used as controls. Histologic changes, epithelial cell proliferation and apoptosis, and prostaglandin E(2) (PGE(2)) levels of gastric tissue were determined.

RESULTS

H. pylori infection induced gastric inflammation. Administration of aspirin did not change H. pylori-induced gastritis, but alleviated H. pylori-induced hyperplasia and the development of heterotopic proliferative glands. Administration of aspirin accelerated H. pylori-associated apoptosis but decreased H. pylori-associated cell proliferation. In addition, the increased gastric PGE(2) levels due to H. pylori infection were suppressed by treatment with aspirin, especially at the dose of 500 p.p.m.

CONCLUSIONS

Aspirin alleviates H. pylori-induced hyperplasia and the development of heterotopic proliferative glands. Moreover, aspirin increases H. pylori-induced apoptosis. We demonstrated the antineoplastic activities of aspirin in H. pylori-related gastric carcinogenesis.

Helicobacter pylori VacA enhances prostaglandin E2 production through induction of cyclooxygenase 2 expression via a p38 mitogen-activated protein kinase/activating transcription factor 2 cascade in AZ-521 cells

Treatment of AZ-521 cells with Helicobacter pylori VacA increased cyclooxygenase 2 (COX-2) mRNA in a time- and dose-dependent manner. A p38 mitogen-activated protein kinase (MAPK) inhibitor, SB203580, blocked elevation of COX-2 mRNA levels, whereas PD98059, which blocks the Erk1/2 cascade, partially suppressed the increase. Consistent with involvement of p38 MAPK, VacA-induced accumulation of COX-2 mRNA was reduced in AZ-521 cells overexpressing a dominant-negative p38 MAPK (DN-p38). Phosphatidylinositol-specific phospholipase C, which inhibits VacA-induced p38 MAPK activation, blocked VacA-induced COX-2 expression. In parallel with COX-2 expression, VacA increased prostaglandin E(2) (PGE(2)) production, which was inhibited by SB203580 and NS-398, a COX-2 inhibitor. VacA-induced PGE(2) production was markedly attenuated in AZ-521 cells stably expressing DN-p38. VacA increased transcription of a COX-2 promoter reporter gene and activated a COX-2 promoter containing mutated NF-kappaB or NF-interleukin-6 sites but not a mutated cis-acting replication element (CRE) site, suggesting direct involvement of the activating transcription factor 2 (ATF-2)/CREB-binding region in VacA-induced COX-2 promoter activation. The reduction of ATF-2 expression in AZ-521 cells transformed with ATF-2-small interfering RNA duplexes resulted in suppression of COX-2 expression. Thus, VacA enhances PGE(2) production by AZ-521 cells through induction of COX-2 expression via the p38 MAPK/ATF-2 cascade, leading to activation of the CRE site in the COX-2 promoter.

Prostaglandin E2release in gastric antral mucosa of guinea-pigs: basal PGE2release by cyclo-oxygenase 2 and ACh-stimulated PGE2release by cyclo-oxygenase 1

Prostaglandin E(2) (PGE(2)), which is generated by two isoforms of cyclo-oxygenase (COX(1) and COX(2)), is a key mediator in gastric mucosal defense. In the present study, antral mucosa of guinea-pigs was incubated with various agonists or antagonists in a medium, the PGE(2) concentration of which was measured using a PGE(2) EIA kit. Prostaglandin E(2) was released from the antral mucosa spontaneously (basal PGE(2) release) and acetylcholine (ACh, 10 microM) enhanced the PGE(2) release (ACh-stimulated PGE(2) release) was mediated via intracellular Ca(2+) concentration ([Ca(2+)](i)). Arachidonic acid enhanced both forms of PGE(2) release, and a phospholipase A(2) inhibitor (amylcinnamoyl anthranilic acid) and COX inhibitors (acetylsalicylic acid and indomethacin) decreased them. 5-(4-Chlorophenyl)-1-(4-methoxyphenyl)-3-trifluoromethylpyrazol (SC560, 100 nm, a COX(1)-selective inhibitor) inhibited ACh-stimulated PGE(2) release without any decrease in basal PGE(2) release. N-(2-Cyclohexyloxy-4-nitrophenyl) methanesulphonamide (NS398, 20 microM, a COX(2)-selective inhibitor) decreased basal PGE(2) release without any reduction of ACh-stimulated PGE(2) release. However, ionomycin (a Ca(2+) ionophore) increased PGE(2) release from antral mucosa in the presence of SC560 or NS398, suggesting that COX(1) and COX(2) are regulated by [Ca(2+)](i). These findings indicate that COX(1)-containing cells have ACh receptors but COX(2)-containing cells do not. Moreover, in isolated antral epithelial cells, SC560 decreased basal and ACh-stimulated PGE(2) release, but NS398 did not. In conclusion, in antral mucosa, basal PGE(2) release is mainly maintained by COX(2) of non-epithelial cells, and ACh-stimulated PGE(2) release is maintained by COX(1) of epithelial cells.

Increased prostanoid dependency of arterial relaxation in Chlamydia pneumoniae-infected mice

Endothelial dysfunction plays an important role in the development of atherosclerosis. Previous studies have shown that inoculation with Chlamydia pneumoniae contributes to atherosclerotic development in rabbits and hypercholesterolaemic mice and causes endothelial dysfunction in apolipoprotein E-deficient mice. The effect of acute C. pneumoniae infection on endothelial function in normocholesterolaemic C57BL/6J mice was studied by measuring the force of contraction of the descending aorta after noradrenaline stimulation and in response to methacholine-induced relaxation. In addition, the effects of the nitric oxide synthase inhibitor N(omega)-nitro-L-arginine methyl ester (L-NAME) and the cyclooxygenase inhibitor diclofenac on relaxation were assessed. Pre-treatment of the aortas with L-NAME decreased the relaxation response in both the infected and uninfected groups and no significant difference was detected between these groups, whereas diclofenac significantly attenuated the relaxation response only in the infected animals. In conclusion, infection shifted the balance of endothelium-derived relaxing factors from nitric oxide towards vasorelaxing prostanoids in C57BL/6J mice.

Regulated spatial distribution of cyclooxygenases and lipoxygenases in Crohn's ulcer

BACKGROUND AND AIMS

Arachidonic acid metabolism actively participates in the initiation, climaxing, and resolution phases of inflammation, and its close connection with inflammatory bowel diseases has been only recently discovered. We aimed to clarify the role of different arachidonic pathways and the interrelationships between them in Crohn's disease.

METHODS

Seventeen specimens of Crohn's disease dated between 2003/1/1 and 2005/1/1 were collected and underwent immunohistochemical analyses with cylcooxygenase 1, cyclooxygenase 2, 5-lipoxygenase, and 15-lipoxygenase-1 antibodies.

RESULTS

(1) The spatial distribution of the three leading enzymes in arachidonic acid pathway--cyclooxygenase 2, 5-lipoxygenase, and 15-lipoxygenase-1--followed sequential arrangement in Crohn's ulcer: neutrophils highly expressing 5-lipoxygenase were in the utmost surface which bordered the band of cyclooxygenase-2 expression that is located just beneath it, and in the lower layers and below the granulation region were eosinophils carrying 15-lipoxygeanse-1. (2) Cyclooxygenase-2 and 15-Lipoxygenase-1-positive cells formed two barrier-like structures that possibly inhibited neutrophil infiltration.

CONCLUSION

The regulated distribution indicated coordinated interplay between inflammatory cells and parenchymal cells, between arachidonic acid pathways, and between innate and adaptive immunity; and the barrier-like structures indicated protective roles for cyclooxygenase 2 and 15-Lipoxygenase-1 in Crohn's disease.

Rebamipide reduces delay in gastric ulcer healing in cyclooxygenase-2-deficient mice

Rebamipide is an antiulcer drug capable of various actions including the induction of cyclooxygenase-2 (COX-2). In this study, we investigated the effect of rebamipide on gastric ulcer healing in COX-2-deficient mice. Wild-type (N=34) and COX-2-deficient mice (N=28) with gastric ulcers were administered 30 mg/kg of rebamipide or the vehicle. Ulcerous tissues were subjected to measurements of ulcer size, immunohistochemical staining of CD31 (an endothelial cell marker), and mRNA levels. COX-2 deficiency delayed ulcer healing and inhibited angiogenesis and bFGF mRNA expression in the granulation tissue. In wild-type mice, rebamipide accelerated ulcer healing and increased COX-2 mRNA expression. In COX-2-deficient mice, rebamipide prevented delayed ulcer healing and reversed the inhibition in angiogenesis and bFGF mRNA expression. The effect of rebamipide on the enhancement of ulcer healing, angiogenesis, and induction of bFGF expression was more prominent in wild-type mice than in COX-2-deficient mice. In conclusion, rebamipide may accelerate gastric ulcer healing through both COX-2-dependent and COX-2-independent mechanisms.

Gastroduodenal mucosal defense: role of endogenous mediators

PURPOSE OF REVIEW

The remarkable resistance of the mucosal lining of the upper gastrointestinal tract to concentrated gastric acid remains one of the biggest unsolved mysteries of upper gastrointestinal physiology. In the past year, there have been prominent findings regarding prostaglandin subtypes, growth factors, proteinase-activated receptors, peroxisome proliferator-activated receptors, and nitric oxide releasing nonsteroidal antiinflammatory agents.

RECENT FINDINGS

The prostaglandin I receptor subtype is involved with the mucosal acid-sensing neural circuit termed the capsaicin pathway. Proteinase-activated receptors and peroxisome proliferator activated receptor-gamma are important components of host defense against acid injury. Nitric oxide releasing nonsteroidal antiinflammatory agents have potential usefulness in subjects with mucosal injury related to the use of nonsteroidal antiinflammatory agents and may be an important alternative to selective cyclooxygenase-2 inhibitors for patients who need aspirin cotherapy for the prevention of arterial thrombus formation.

SUMMARY

Peptic ulcer disease, although declining in prevalence, appears to be increasing in virulence, perhaps because of the overall aging of the population and improved care in the intensive care unit. Although Helicobacter pylori and nonsteroidal antiinflammatory agents have been identified as key pro-ulcerogenic factors, many ulcers may also result from a deficiency of other, unknown host protective factors. A more detailed understanding of the host factors involved in mucosal protection will thus help identify novel therapeutic targets aimed at the prevention and treatment of upper gastrointestinal tract mucosal injury.

Pathogenesis of Helicobacter pylori infection

Research in the last year has provided new insights into the function of the the cag-associated type IV secretion system and the vacuolating toxin VacA. A quite new aspect was disclosed by the finding that Helicobacter pylori in Mongolian gerbils colonizes a very distinct topology in the gastric mucous layer, obviously providing optimal conditions for long-term survival. Further research activities focused on H. pylori ammonia and metal metabolism as well as on bacterial stress defence mechanisms. Differential expression of approximately 7% of the bacterial genome was found at low pH suggesting that H. pylori has evolved a multitude of acid-adaptive mechanisms. VacA was shown to interrupt phagosome maturation in macrophage cell lines as well as to modulate and interfere with T lymphocyte immunological functions. Gastric mucosa as well as the H. pylori-infected epithelial cell line AGS strongly express IL-8 receptor A and B, which might contribute to the augmentation of the inflammatory response. Accumulating evidence implicates genetic variation in the inflammatory response to H. pylori in the etiology of the increased risk of gastric cancer after H. pylori infection. The chronic imbalance between apoptosis and cell proliferation is the first step of gastric carcinogenesis. In this regard, it was demonstrated that coexpression of two H. pylori proteins, CagA and HspB, in AGS cells, caused an increase in E2F transcription factor, cyclin D3, and phosphorylated retinoblastoma protein. Taken together, we now have a better understanding of the role of different virulence factors of H. pylori. There is still a lot to be learned, but the promising discoveries summarized here, demonstrate that the investigation of the bacterial survival strategies will give novel insights into pathogenesis and disease development.