Implication of gastrin in cyclooxygenase-2 expression in Helicobacter pylori infected gastric ulceration

Changes of Gastric Juice Microenvironment in Patients with Fundic Gland Polyp and Hyperplastic Polyp

INTRODUCTION

The aim of this study was to study the relationship between the formation of gastric fundic gland polyp and gastric hyperplastic polyp (HP) and the changes of gastric juice microenvironment.

METHODS

The proton-pump inhibitor (PPI) applications to patients were recorded. Gastric juices and biopsy polyps were collected for pathological examination, H. pylori tests, biomarkers, and MUC1, MUC2, MUC5AC expression measurement.

RESULTS

Among 34,892 patients, the detection rate of gastric fundic gland polyps was significantly higher than that of gastric HPs (p < 0.01). The incidence rate of gastric fundic gland polyp and gastric HP in PPI users (n = 3,886) was higher than that of non-PPI users (p < 0.01). The occurrence of polyp was positively related to the duration of PPI application and the H. pylori-positive rate. The bile reflux rate between fundic gland polys group (17.61%) and HPs (28.67%) was significantly different (p < 0.01). The levels of gastric juice Gastrin-17, epidermal growth factor (EGF) and MUC2 from patients with gastric fundic gland polyps and gastric HPs were higher than those in the control group (p < 0.01). However, patients with gastric fundic gland polyps and HPs had significantly lower gastric juice PGE2 and MUC5AC (p < 0.01).

CONCLUSION

PPI application, H. pylori infection, and bile reflux are the potential risk factors for formation of fundic gland polyps and HPs. The potential mechanism of polyps' formation can be related to the levels of Gastrin-17, EGF, MUC2, PGE2, and MUC5AC in gastric juice.

Helicobacter pylori infection, gastrin and cyclooxygenase-2 in gastric carcinogenesis

Gastric cancer is one of the most frequent neoplasms and a main cause of death worldwide, especially in China and Japan. Numerous epidemiological, animal and experimental studies support a positive association between chronic Helicobacter pylori (H. pylori) infection and the development of gastric cancer. However, the exact mechanism whereby H. pylori causes gastric carcinogenesis remains unclear. It has been demonstrated that expression of cyclooxygenase-2 (COX-2) is elevated in gastric carcinomas and in their precursor lesions. In this review, we present the latest clinical and experimental evidence showing the role of gastrin and COX-2 in H. pylori-infected patients and their possible association with gastric cancer risk.

Helicobacter pylori induction of the gastrin promoter through GC-rich DNA elements

BACKGROUND

Helicobacter pylori (H. pylori) infection has been linked to the development of chronic gastritis, duodenal ulcer disease, and gastric cancer. Helicobacter pylori- infected patients and animal models develop hypergastrinemia, chronic gastritis, and gastric atrophy. Since gastrin is an important regulator of gastric acid secretion and cell growth, H. pylori regulation of this hormone has been implicated in its pathogenesis.

OBJECTIVES

To investigate the effect of H. pylori on gastrin gene expression in mice and of human bacterial isolates on gastrin mRNA expressed in a human cell line.

METHODS

Gastrin mRNA was measured by qRT-PCR in H. pylori-infected mice. H. pylori were co-cultured with AGS cells to study regulation of human gastrin gene expression. Various MAP kinases were implicated in signal transduction from the bacteria using specific inhibitors. Gastrin reporter constructs and gel shift assays were used to map DNA responsive elements.

RESULTS

In addition to an increase in gastrin mRNA in H. pylori-infected mice, H. pylori induced the endogenous human gastrin gene through MAP kinase-dependent signaling but not NFκB-dependent signaling. Activation of gastrin through MAPK signaling did not require CagA or VacA virulence factors. Transfection studies demonstrated that a GC-rich motif mediated H. pylori-induction of the gastrin promoter and that the motif inducibly binds Sp1 and Sp3 transcription factors.

CONCLUSIONS

Direct contact of live H. pylori bacteria with human cells is sufficient to induce gastrin gene expression.

Acquired hyperplastic gastric polyps after treatment of ulcer

BACKGROUND/PURPOSE

Healing of gastric ulcers requires repair by epithelial migration and proliferation. We have found a small proportion of patients with acquired hyperplastic polyps at the healed ulcer site. The aim of this study was to identify clinical characteristics that might be associated with the development of hyper-plastic polyps at the site of healed gastric ulcers.

METHODS

This was a retrospective review of 86 patients with gastric ulcers from April 2006 to September 2008. After initial endoscopy, the patients were all treated with proton pomp inhibitors, after which a second endoscopy was performed. Demographic data, polyp characteristics (endoscopic and histological), Helicobacter pylori status, and duration of treatment were analyzed.

RESULTS

A total of 24 hyperplastic gastric polyps were found in 18 patients; all at the site of the healed ulcer (20 in the antrum and 4 in the corpus). The mean size of the ulcers prior to treatment was 14.5 +/- 9.1 mm. Hyperplastic gastric polyps were more likely to occur at the site of ulcers larger than 10 mm (odds ratio = 9.57, 95% confidence interval =2.50-36.65). Age, sex, H. pylori status, ulcer location and duration of treatment did not differ significantly between patients with and without polyps.

CONCLUSION

Hyperplastic polyps that develop after healing of gastric ulcers are likely to be extensive mucosal injury. A gastric ulcer larger than 10 mm is associated with a significantly increased risk of hyperplastic polyps.

Gastrin-mediated interleukin-8 and cyclooxygenase-2 gene expression: differential transcriptional and posttranscriptional mechanisms

BACKGROUND & AIMS

Gastrin induces the expression of cyclooxygenase (COX)-2 and interleukin (IL)-8; however, the mechanism(s), especially in gastric epithelial cells, is not well understood. Here, we have determined the intracellular mechanisms mediating gastrin-dependent gene expression.

METHODS

AGS-E human gastric cancer cell line stably expressing cholecystokinin-2 receptor was treated with amidated gastrin-17. Real-time polymerase chain reaction, Western blot, and enzyme-linked immunosorbent assay were performed to determine COX-2 and IL-8 expression and Akt, Erk, and p38 phosphorylation. Gene promoter activity was determined by luciferase assay. Electrophoretic mobility shift assay analysis was performed for nuclear factor kappaB (NF-kappaB) and activator protein-1 activity. RNA stability was determined after actinomycin D treatment. HuR localization was determined by immunocytochemistry.

RESULTS

Gastrin induced COX-2 and IL-8 expression in AGS-E cells, which was inhibited by phosphatidylinositol 3' kinase (PI3K) and p38 inhibitors. Gastrin-mediated Akt activation was observed to be downstream of p38. IL-8 expression was dependent on COX-2-mediated prostaglandin E(2) synthesis. In the presence of an NF-kappaB inhibitor MG132, IL-8 transcription was inhibited, but not that of COX-2. This was confirmed after knockdown of the p65 RelA subunit of NF-kappaB. Further studies showed that COX-2 gene transcription is regulated by activator protein-1. Gastrin increased the stability of both COX-2 and IL-8 messenger RNA (mRNA) in a p38-dependent manner, the half-life increasing from 31 minutes to 8 hours and approximately 4 hours, respectively. Gastrin, through p38 activity, also enhanced HuR expression, nucleocytoplasmic translocation, and enhanced COX-2 mRNA binding.

CONCLUSIONS

Gastrin differentially induces COX-2 and IL-8 expression at the transcriptional and posttranscriptional levels by PI3K and p38 mitogen-activated protein kinase pathways, respectively.

Expression of cyclooxygenase-2 in colorectal adenocarcinoma is associated with p53 accumulation and hdm2 overexpression

Elevated cyclooxygenase-2 (COX-2) expression has been observed in various types of cancer. Induction of COX-2 expression has been reported to increase invasiveness and angiogenesis of tumours. While COX-2 overexpression has been repeatedly proven to promote tumor growth, little is known about what initiates its induction. There has been evidence to suggest that COX-2 expression is normally suppressed by wild-type p53 but not mutant p53, suggesting that loss of p53 function may result in the induction of COX-2 expression. Loss of p53 function is not only caused by gene mutation, but also through the overexpression of its negative regulator, so called human double minute 2 (hdm2). The aim of this study was to examine the correlation between COX-2 overexpression, p53 accumulation and HDM2 overexpression, as indications of p53 anomalies, and their relationship to clinicopathologic features of colorectal adenocarcinoma. Tumor tissues and the adjacent normal mucosa were obtained from 73 colorectal cancer patients who underwent curative resection at Maharaj Nakorn Chiang Mai Hospital. Protein levels of COX-2, p53 and HDM2 were determined by Western blot analysis. No normal colorectal tissues possessed detectable levels of COX-2, p53 or HDM2. In contrast, 38.3% (28 cases), 54.8% (40 cases) and 8.2% (6 cases) of tumour tissues were found to express COX-2, p53 and HDM2, respectively. Interestingly, there was a significantly positive relationship between COX-2 overexpression and p53 accumulation and/or HDM2 overexpression (P=0.007). Higher COX-2 overexpression was observed in p53-accumulated or HDM2 overexpressed-tumours (22/43 cases, 51.1%) in comparison to tumours with no evidence of p53 and HDM2 alterations (6/30 cases, 20%). The results obtained from this study indicate that overexpression of COX-2 is frequently associated with p53 protein accumulation and HDM2 overexpression, therefore the COX-2 overexpression observed in colorectal cancer cells may be partly due to the dysfunction of p53. Although mutation of p53 has been previously reported to be associated with COX-2 induction, to our knowledge, this is the first study to show the relationship between HDM2 overexpression and COX-2 overexpression.

Effect of probiotics and triple eradication therapy on the cyclooxygenase (COX)-2 expression, apoptosis, and functional gastric mucosal impairment in Helicobacter pylori-infected Mongolian gerbils

BACKGROUND

Helicobacter pylori infection in Mongolian gerbils is an established experimental model of gastric carcinogenesis that mimics H. pylori-positive patients developing gastric ulcer and gastric cancer, but the effect of probiotic therapy on functional aspects of this infection remains unknown.

METHODS

We compared the effects of intragastric inoculation of gerbils with H. pylori strain (cagA+ vacA+, 5 x 10(6) colony forming units/ml) with or without triple therapy including omeprazole, amoxicillin, and tinidazol or probiotic bacteria Lacidofil. Histology of glandular mucosa, the viable H. pylori, and density of H. pylori colonization were evaluated. The gastric blood flow was measured by H2-gas clearance method; the plasma gastrin and gastric luminal somatostatin were determined by RIA and expression of cyclooxygenase (COX)-2 and apoptotic Bax and Bcl-2 proteins were evaluated by Western blot.

RESULTS

The gastric H. pylori infection was detected in all animals by histology and H. pylori culture. Basal gastric acid was significantly reduced in H. pylori-infected animals but not in those with triple therapy or Lacidofil. Early lesions were seen already 4 weeks upon H. pylori inoculation and consisted of chronic gastritis and glandular atypia associated with typical regenerative hyperplasia and increased mitotic activity and formation of apoptotic bodies. The H. pylori infection was accompanied by the fall in gastric blood flow, the marked increase in plasma gastrin, the significant fall in gastric somatostatin levels and Bcl-2 protein expression, and the rise in expression of COX-2 and Bax proteins. These mucosal changes were counteracted by the triple therapy and Lacidofil.

CONCLUSIONS

H. pylori infection in gerbils, associated with regenerative hyperplasia of glandular structure, results in the suppression of gastric secretion, overexpression of COX-2, and enhancement in apoptosis and impairment of both, gastric blood flow and gastrin-somatostatin link that were reversed by anti-H. pylori triple therapy and attenuated by probiotics.

Cholecystokinin octapeptide improves cardiac function by activating cholecystokinin octapeptide receptor in endotoxic shock rats

AIM: To explore the effect of sulfated cholecystokinin octapeptide (sCCK-8) on cardiac functions and its receptor mechanism in endotoxic shock (ES) rats.

METHODS: The changes of the mean arterial pressure (MAP), heart rate (HR), the left ventricular pressure (LVP) and the maximal/minimum rate of LVP (±LVdp/dt_max)) were measured by using physiological record instrument in eight groups of rats. The expression of cholecystokinin-A receptor (CCK-AR) and cholecystokinin-B receptor (CCK-BR) mRNA of myocardium in ES rats was examined by reverse transcription polymerase chain reaction (RT-PCR).

RESULTS: (1) Low doses of sCCK-8 (0.4 μg/kg) caused tachycardia (441±27, normal control 391±22 s/min) and slight increase in MAP, LVP and ±LVdp/dt_max (16.96±1.79, 18.21±1.69 and +768.85±31.28/-565.04±27.71 kPa, respectively, all P<0.01), while medium doses (4.0 μg/kg) and high doses of sCCK-8 (40 μg/kg) elicited bradycardia and marked increase in MAP, LVP and ±LVdp/dt_max (17.29±1.63, 19.46±2.57 and +831.46±22.57/-606.08 ±31.32; 17.46±1.08, 19.83±2.91 and +914.52±35.95/-639.15±30.23 kPa, respectively, all P<0.01). Proglumide (1.0 mg/kg), a nonselective antagonist of CCK-receptor (CCK-R), significantly inhibited the pressor effects of sCCK-8 (15.96±1.38, 17.36±0.66 and +748.18±19.29/-512.12±14.39 kPa, respectively, all P<0.01), whilst reversing the bradycardiac responses. (2) High doses of LPS (8 mg/kg) elicited marked decrease in MAP, LVP and ±LVdp/dt_max. (7.16±0.59, 7.6±0.68 and +298.01±25.52/-166.96±19.25 kPa, respectively, all P<0.01). Pretreatment with sCCK-8 (40 μg/kg) could reverse the decline of cardiac functions (10.71±0.45, 11.7±1.26 and +446.04±67.18/-347.90±36.98 kPa, respectively, all P<0.01), while proglumide could cause further decline of cardiac function in ES rats (4.71±0.67, 5.58±1.25 and +226.48±15.84/-142.83±20.23 kPa, respectively, all P<0.01). (3) CCK-A/BR mRNAs were expressed in myocardium of control rats. Gene expression of CCK-AR and CCK-BR significantly increased in myocardium of ES rats. The increase of CCK-AR mRNA induced by LPS began at 0.5 h, peaked at 2 h, kept a high level at 6 h and declined at 12 h, respectively. Similar to CCK-AR mRNA, the expression of CCK-BR mRNA peaked at 2 h and kept a high level at 6 h, but it did not change at the first 0.5 h and was stable at a high level at 12 h.

CONCLUSION: The above results indicate that endogenous and exogenous sCCK-8 may significantly improve cardiac function and intractable hypotension of ES rats, which was likely related to high expression of CCK-A/BR in myocardium induced by LPS.

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Gastrin and EGF synergistically induce cyclooxygenase-2 expression in Swiss 3T3 fibroblasts that express the CCK2 receptor

Over-expression of cyclooxygenase-2 (COX-2) has been demonstrated to be tumorigenic in transgenic mice. Chronic treatment with NSAIDs is chemoprotective for colorectal cancer. Gastrin is a growth factor for gastric mucosa and has been shown to promote proliferation of colorectal cells. Recent studies suggest that COX-2 expression levels could mediate the growth effects of gastrin. Here, we report that gastrin increased PGE2 secretion in Swiss 3T3 cells expressing the CCK2 receptor. Gastrin dose dependently induced COX-2 protein levels in a time dependent manner. COX-2 mRNA levels were rapidly induced by a dose dependent increase in gastrin. Prior treatment of the cells with the CCK2 receptor specific antagonist, L365,260, inhibited gastrin-induced COX-2 protein and mRNA expression. Pretreatment with L364,714, the CCK1 receptor specific antagonist did not block COX-2 induction by gastrin. Inhibition of de novo protein synthesis by cycloheximide did not block COX-2 mRNA induction by gastrin. Also, gastrin-dependent COX-2 expression did not require PKC activity, activation of ERK, or transactivation of EGFR. However, co-stimulation with EGF and gastrin synergistically induced COX-2 protein and mRNA expression and PGE2 secretion. Measurements of COX-2 mRNA stability and COX-2 gene transcription reveal that EGF significantly increased the half-life of COX-2 mRNA with only a slight increase in the COX-2 transcription rate. Conversely, gastrin significantly increased COX-2 gene transcription rates but did not enhance COX-2 mRNA stability.

Functional and morphological aspects of Helicobacter pylori-induced gastric cancer in Mongolian gerbils

BACKGROUND

Helicobacter pylori infection of Mongolian gerbils is an established model of gastric carcinogenesis, but gastric secretory aspects of this carcinogenesis have not been studied.

METHODS

The effects of single intragastric inoculation of gerbils with H. pylori strain (cagA+ vacA+, 5 x 10(6) CFU/ml) or vehicle (saline) were examined at 1, 2, 4, 6, 9, 12 and 30 weeks from inoculation. Gastric morphology, the presence of H. pylori using the rapid urease test, the density of H. pylori and 16S rRNA and the plasma gastrin and somatostatin were determined.

RESULTS

H. pylori was detected in gastric mucosa in all infected animals. Basal gastric acid in gerbils was reduced by about 50% after H. pylori inoculation. Early lesions seen at 4 weeks after H. pylori inoculation consisted of chronic gastritis with thickened mucosal folds, oedema, congestion and mucosal lymphocytic infiltration. Adenomatous hyperplasia with cellular atypia with increased mitotic activity and the formation of apoptotic bodies and visible erosions and ulcerations were observed at 12-30 weeks after inoculation. The atypical gastric glands were situated 'back-to-back', suggesting gastric pre-cancer. The gastric blood flow in H. pylori-infected gerbils was significantly lower than that in the controls. Six- to seven-fold increase in plasma gastrin levels combined with significant fall in gastric somatostatin contents and the intraepithelial neoplasia were noticed in gerbils at all tested periods.

CONCLUSION

H. pylori-infection in gerbils resulted in gastric pre-cancer associated with functional changes, such as suppression of gastric secretion and impairment of both gastric mucosal microcirculation and the gastrin-somatostatin link.

Gastrin stimulates cyclooxygenase-2 expression in intestinal epithelial cells through multiple signaling pathways. Evidence for involvement of ERK5 kinase and transactivation of the epidermal growth factor receptor

Gastrin is a hormone produced by G-cells in the normal gastric antrum. However, colorectal carcinoma cells may aberrantly produce gastrin and exhibit increased expression of cholecystokinin B (CCK-B)/gastrin receptors. Gastrin is trophic for the normal gastric oxyntic mucosa and exerts a growth-promoting action on gastrointestinal malignancy. Thus, gastrin may act as an autocrine/paracrine or endocrine factor in the initiation and progression of colorectal carcinoma. The molecular mechanisms involved have not been elucidated. Hypergastrinemia induced by Helicobacter pylori infection is associated with increased cyclooxygenase-2 (COX-2) expression in gastric and colorectal tissues, suggesting the possibility that gastrin up-regulates COX-2 expression in these tissues; this has not been confirmed. We report here that gastrin significantly increases the expression of COX-2 mRNA and protein, the activity of the COX-2 promoter, and the release of prostaglandin E(2) from a rat intestinal epithelial cell line transfected with the CCK-B receptor. These actions were dependent upon the activation of multiple MAPK signal pathways, including ERK5 kinase; transactivation of the epidermal growth factor receptor; and the increased expression and activities of transcription factors ELK-1, activating transcription factor-2, c-Fos, c-Jun, activator protein-1, and myocyte enhancer factor-2. Thus, our findings identify the signaling pathways coupling the CCK-B receptor with up-regulation of COX-2 expression. This effect may contribute to this hormone-dependent gastrointestinal carcinogenesis, especially in the colon.

Effect of Helicobacter pylori on delay in ulcer healing induced by aspirin in rats

Helicobacter pylori and nonsteroidal anti-inflammatory drugs (NSAIDs) are major pathogenic factors in peptic ulcer disease but whether these two factors exert synergistic or antagonistic effects on ulcer healing has been a subject of controversy. We compared the effect of aspirin alone with that of aspirin combined with H. pylori on gastric acid secretion and healing of acetic acid gastric ulcers in rats. The H. pylori colonization of gastric mucosa was determined by viable H. pylori culture, histology and assessment of bacterial DNA using polymerase chain reaction (PCR). The area of ulcers, gastric blood flow, mucosal generation of prostaglandin E(2) and plasma gastrin levels and expression of cyclooxygenase-1, cyclooxygenase-2 and growth factors was determined. Aspirin delayed significantly the healing of chronic gastric ulcers, decreased the gastric blood flow at the ulcer margin and gastric mucosal prostaglandin E(2) generation being without significant influence on gastric acid output. H. pylori acquisition that produced moderate gastric inflammation at the ulcer margin delayed significantly the healing of gastric ulcers, decreased significantly both the gastric blood flow at the ulcer margin and the gastric secretion while raising significantly the gastric mucosal prostaglandin E(2) generation and plasma gastrin levels. H. pylori infection attenuated the aspirin-induced inhibition of ulcer healing and accompanying fall in the gastric blood flow. Both aspirin and H. pylori up-regulated significantly cyclooxygenase-2 messenger RNA (mRNA) and protein but not that of cyclooxygenase-1 at the ulcer margin. Aspirin reduced significantly the transforming growth factor alpha- and vascular endothelial growth factor mRNAs, but these effects were significantly attenuated by H. pylori. We conclude that H. pylori antagonizes, in part, aspirin-induced delay of ulcer healing due to suppression of acid secretion, the enhancement in prostaglandin E(2) possibly derived from cyclooxygenase-2 and the overexpression of transforming growth factor alpha and vascular endothelial growth factor in the ulcer area.

Impact of Helicobacter pylori and nonsteroidal anti-inflammatory drugs on gastric ulcerogenesis in experimental animals and in humans

Helicobacter pylori (H. pylori) and nonsteroidal anti-inflammatory drugs (NSAID) are the most common pathogens in the gastroduodenal mucosa in animals and humans, but their relationship in ulcerogenesis has been little studied. According to some authors, H. pylori infection in humans does not act synergistically with NSAID on ulcer healing, therefore, there is no need to eradicate the germ. This notion is supported by the finding that the eradication of H. pylori does not affect NSAID-induced gastropathy treated with omeprazole and that H. pylori infection induces a strong cyclooxygenase-2 expression resulting in excessive biosynthesis of gastroprotective prostaglandins, which should in turn counteract NSAID-induced gastropathy and heal the existing ulcer. Other investigators claim that H. pylori infection acts synergistically with NSAID on ulcer development, therefore, H. pylori should be eradicated, particularly at the start of long-term NSAID therapy. Maastricht 2-2000 consensus also recommends eradication prior to NSAID treatment, but this eradication does not appear to accelerate ulcer healing or to prevent the recurrent ulcers in NSAID users. Our studies in almost 6,000 dyspeptic patients undergoing upper endoscopy and [(13)C]-urea breath test (UBT) revealed that about 70% of these patients are H. pylori (+) and about 30.6% of these develop gastroduodenal ulcers. Of these ulcers, over 70% were H. pylori (+) positive, 12% NSAID (+), 8% were both H. pylori (+) and NSAID (+), while 22% ulcers were H. pylori (-) and NSAID (-) or "idiopathic" ulcers. Basically, our results support Hawkey's concept and this also agrees with our findings in the rat model showing that: (1) there is no synergistic interaction between H. pylori infection and NSAID on gastric ulcer development, (2) H. pylori and NSAID are independent risk factors for peptic ulceration, and (3) NSAID therapy in H. pylori positive patients attenuates the ulcer development possibly due to direct inhibitory action of these drugs on H. pylori.