Up-regulation of heparin binding epidermal growth factor-like growth factor and amphiregulin expression in Helicobacter pylori-infected human gastric mucosa

Gastrin: From Physiology to Gastrointestinal Malignancies

Abetted by widespread usage of acid-suppressing proton pump inhibitors (PPIs), the mitogenic actions of the peptide hormone gastrin are being revisited as a recurring theme in various gastrointestinal (GI) malignancies. While pathological gastrin levels are intricately linked to hyperplasia of enterochromaffin-like cells leading to carcinoid development, the signaling effects exerted by gastrin on distinct cell types of the gastric mucosa are more nuanced. Indeed, mounting evidence suggests dichotomous roles for gastrin in both promoting and suppressing tumorigenesis. Here, we review the major upstream mediators of gastrin gene regulation, including inflammation secondary to Helicobacter pylori infection and the use of PPIs. We further explore the molecular biology of gastrin in GI malignancies, with particular emphasis on the regulation of gastrin in neuroendocrine neoplasms. Finally, we highlight tissue-specific transcriptional targets as an avenue for targetable therapeutics.

Amphiregulin Regulates Phagocytosis-Induced Cell Death in Monocytes via EGFR and the Bcl-2 Protein Family

Neonates are extremely susceptible to bacterial infections, and evidences suggest that phagocytosis-induced cell death (PICD) is less frequently triggered in neonatal monocytes than in monocytes from adult donors. An insufficient termination of the inflammatory response, leading to a prolonged survival of neonatal monocytes with ongoing proinflammatory cytokine release, could be associated with the progression of various inflammatory diseases in neonates. Our previous data indicate that amphiregulin (AREG) is increasingly expressed on the cell surface of neonatal monocytes, resulting in remarkably higher soluble AREG levels after proteolytic shedding. In this study, we found that E. coli-infected neonatal monocytes show an increased phosphorylation of ERK, increased expression of Bcl-2 and Bcl-X_L, and reduced levels of cleaved caspase-3 and caspase-9 compared to adult monocytes. In both cell types, additional stimulation with soluble AREG further increased ERK activation and expression of Bcl-2 and Bcl-X_L and reduced levels of cleaved caspase-3 and caspase-9 in an EGFR-dependent manner. These data suggest that reduced PICD of neonatal monocytes could be due to reduced intrinsic apoptosis and that AREG can promote protection against PICD. This reduction of the intrinsic apoptosis pathway in neonatal monocytes could be relevant for severely prolonged inflammatory responses of neonates.

Suppressed Helicobacter pylori-associated gastric tumorigenesis in Fat-1 transgenic mice producing endogenous ω-3 polyunsaturated fatty acids

Dietary approaches to preventing Helicobacter pylori (H. pylori)-associated gastric carcinogenesis are widely accepted because surrounding break-up mechanisms are mandatory for cancer prevention, however, eradication alone has been proven to be insufficient. Among these dietary interventions, omega-3-polyunsaturated-fatty acids (ω-3 PUFAs) are often the first candidate selected. However, there was no trial of fatty acids in preventing H. pylori-associated carcinogenesis and inconclusive results have been reported, likely based on inconsistent dietary administration. In this study, we developed an H. pylori initiated-, high salt diet promoted-gastric tumorigenesis model and conducted a comparison between wild-type (WT) and Fat-1-transgenic (TG)-mice. Gross and pathological lesions in mouse stomachs were evaluated at 16, 24, 32, and 45 weeks after H. pylori infection, and the underlying molecular changes to explain the cancer preventive effects were investigated. Significant changes in: i) ameliorated gastric inflammations at 16 weeks of H. pylori infection, ii) decreased angiogenic growth factors at 24 weeks, iii) attenuated atrophic gastritis and tumorigenesis at 32 weeks, and iv) decreased gastric cancer at 45 weeks were all noted in Fat-1-TG-mice compared to WT-mice. While an increase in the expression of Cyclooxygenase (COX)-2, and reduced expression of the tumor suppressive 15-PGDH were observed in WT-mice throughout the experimental periods, the expression of Hydroxyprostaglandin dehydrogenase (15-PGDH) was preserved in Fat-1-TG-mice. Using a comparative protein array, attenuated expressions of proteins implicated in proliferation and inflammation were observed in Fat-1-TG-mice compared to WT-mice. Conclusively, long-term administration of ω-3 PUFAs can suppress H. pylori-induced gastric tumorigenesis through a dampening of inflammation and reduced proliferation in accordance with afforded rejuvenation.

STAT3: a critical component in the response to Helicobacter pylori infection

STAT3 imparts a profound influence on both the epithelial and immune components of the gastric mucosa, and through regulation of key intracellular signal transduction events, is well placed to control inflammatory and oncogenic outcomes in the context of Helicobacter (H.) pylori infection. Here we review the roles of STAT3 in the host immune response to H. pylori infection, from both gastric mucosal and systemic perspectives, as well as alluding more specifically to STAT3-dependent mechanisms that might be exploited as drug targets.

A unifying working hypothesis for juvenile polyposis syndrome and Ménétrier's disease: specific localization or concomitant occurrence of a separate entity?

BACKGROUND

Juvenile polyposis syndrome with gastric involvement may mimic Ménétrier's disease, which is correlated to transforming growth factor (TGF)α overproduction and PDX1 upregulation in the gastric fundus.

AIM

We report a family with juvenile polyposis syndrome where one member showed typical features of Ménétrier's disease and concomitant Helicobacter pylori infection.

METHODS

We studied a 31-year-old woman belonging to a family with juvenile polyposis syndrome, who exhibited a particular form of hyperplastic gastropathy diagnosed as Ménétrier's disease with Helicobacter pylori infection.

RESULTS

TGFα overexpression and undetectable PDX1 expression were demonstrated in the fundic gastric biopsy specimens. In all affected members of the family we identified a 4-bp deletion in exon 9 of SMAD4 gene, a mutation usually associated with a more virulent form of juvenile polyposis syndrome with a higher incidence of gastric and colonic polyposis.

CONCLUSION

To explain the association of juvenile polyposis syndrome with Ménétrier's disease we hypothesized a new mechanism that involves TGFβ-SMAD4 pathway inactivation and TGFα overexpression related to Helicobacter pylori infection.

Apple polyphenols extract (APE) improves colon damage in a rat model of colitis

BACKGROUND AND AIM

Searching for alternative therapies that are effective, safe and less expensive of those currently used for ulcerative colitis, we investigated the efficacy of a polyphenol extract from apple in rat colitis.

METHODS

Rats with trinitrobenzensulphonic acid-induced colitis were treated daily with rectal administration of apple polyphenols 10(-4) M for 14 days. COX-2, TNF-α, tissue transglutaminase and calpain in colon mucosa samples were assessed by reverse transcription-polymerase chain reaction and western blot analyses. To ascertain the role of tissue transglutaminase in mucosal healing, wounded rat fibroblasts were incubated with cystamine (a tissue transglutaminase activity inhibitor).

RESULTS

Colitis was associated with increased COX-2, TNF-α, calpain, and tissue transglutaminase mRNA. The protein expression of COX-2, TNF-α and calpain was increased whilst tissue transglutaminase was decreased. Apple extract treatment reduced the severity of colitis (p<0.05) and restored all the considered biomarkers at the baseline level. Apple polyphenols reduced the degradation of tissue transglutaminase protein occurring through calpain action. Apple polyphenols-treated wounded fibroblast recovered within 24h showing intense immunoreactivity for tissue transglutaminase.

CONCLUSION

The efficacy of apple extract is mediated by its effects on COX-2 and TNF-α. The unbalance between calpain and tissue transglutaminase may play a role in colonic damage and future therapeutic interventions in ulcerative colitis can target this mechanisms.

Helicobacter pylori CagL activates ADAM17 to induce repression of the gastric H, K-ATPase alpha subunit

BACKGROUND & AIMS

Infection with Helicobacter pylori represses expression of the gastric H, K-adenosine triphosphatase alpha-subunit (HKalpha), which could contribute to transient hypochlorhydria. CagL, a pilus protein component of the H pylori type IV secretion system, binds to the integrin alpha(5)beta1 to mediate translocation of virulence factors into the host cell and initiate signaling. alpha(5)beta1 binds a disintegrin and metalloprotease (ADAM) 17, a metalloenzyme that catalyzes ectodomain shedding of receptor tyrosine kinase ligands. We investigated whether H pylori-induced repression of HKalpha is mediated by CagL activation of ADAM17 and release of heparin-binding epidermal growth factor (HB-EGF).

METHODS

HKalpha promoter and ADAM17 activity were measured in AGS gastric epithelial cells transfected with HKalpha promoter-reporter constructs or ADAM17-specific small interfering RNAs and infected with H pylori. HB-EGF secretion was measured by enzyme-linked immunosorbent assay analysis, and ADAM17 interaction with integrins was investigated by coimmunoprecipitation analyses.

RESULTS

Infection of AGS cells with wild-type H pylori or an H pylori cagL-deficient isogenic mutant that also contained a wild-type version of cagL (P12DeltacagL/cagL) repressed HKalpha promoter-Luc reporter activity and stimulated ADAM17 activity. Both responses were inhibited by point mutations in the nuclear factor-kappaB binding site of HKalpha or by infection with P12DeltacagL. Small interfering RNA-mediated silencing of ADAM17 in AGS cells inhibited the repression of wild-type HKalpha promoter and reduced ADAM17 activity and HB-EGF production, compared to controls. Coimmunoprecipitation studies of AGS lysates showed that wild-type H pylori disrupted ADAM17-alpha5beta1 complexes.

CONCLUSIONS

During acute H pylori infection, CagL dissociates ADAM17 from the integrin alpha(5)beta1 and activates ADAM17-dependent, nuclear factor-kappaB-mediated repression of HKalpha. This might contribute to transient hypochlorhydria in patients with H pylori infection.

Apple polyphenol extracts prevent aspirin-induced damage to the rat gastric mucosa

Aspirin causes gastroduodenal ulcers and complications. Food bioactive compounds could exert beneficial effects in the gastrointestinal tract. We evaluated whether apple polyphenol extract (APE) reduced aspirin-induced injury to the rat gastric mucosa. Rats were treated with APE (10(-4) m catechin equivalent) before oral aspirin (200 mg/kg). Cyclo-oxygenase-2 (COX-2), transforming growth factor-alpha (TGF alpha) and heparin-binding epidermal-growth-factor-like growth factor (HB-EGF) mRNA and protein expression were assessed by RT-PCR and Western blot analysis, respectively; malondialdehyde (MDA) was determined by HPLC; gastric secretion was evaluated in pylorus-ligated rats. APE decreased acute and chronic aspirin injury both macroscopically and microscopically (approximately 50 % decrease in lesion score; P < 0.05). Aspirin up-regulated mRNA and protein expression of COX-2 and HB-EGF, but not of TGF alpha; APE reduced aspirin-induced mRNA and protein over-expression of COX-2 and HB-EGF; aspirin significantly increased gastric MDA and this effect was counteracted by APE pre-treatment. APE did not significantly affect gastric acid secretion. In conclusion, APE reduces aspirin-induced gastric injury independently of acid inhibition. We speculate that APE might be of therapeutic use in the prophylaxis of aspirin-related gastropathy.

ERBBs in the gastrointestinal tract: recent progress and new perspectives

The gastrointestinal epithelium does much more than provide a physical barrier between the intestinal lumen and our internal milieu. It is actively engaged in absorption and secretion of salt and water via ion transporters, exchangers and selective ion channels. It is also a continuously self-renewing epithelium that undergoes ordered growth and differentiation along its vertical axis. From this dual perspective, we will consider the actions of the ERBB family of ligands and receptors in the maintenance of gastrointestinal homeostasis and discuss instances when the actions of this family go awry such as in cancer and Ménétrier's disease.

Vascular endothelial growth factor and cyclooxygenase-2 are overexpressed in ileal pouch-anal anastomosis

PURPOSE

Pathophysiology of pouchitis after ileal pouch-anal anastomosis is controversial because of the potential for development of carcinoma. Cyclooxygenase-2-derived prostaglandins may be involved in the inflammatory process and play a role in the pathogenesis of colon cancer. Vascular endothelial growth factor plays a major role in neoangiogenesis and is overexpressed in a number of gastrointestinal malignancies. The goal of this study was to evaluate the expression of cyclooxygenase-2 and vascular endothelial growth factor and to assess neoangiogenesis and epithelial cell proliferation in patients with ileal pouch-anal anastomosis.

METHODS

Endoscopic biopsies were obtained from 15 patients with ileal pouch-anal anastomosis without pouchitis (10 biopsies from the ileal pouch and 10 from ileal nonpouch mucosa) and from 15 subjects with irritable bowel syndrome (10 biopsies from normal-appearing ileum and rectum). Cyclooxygenase-1, cyclooxygenase-2, and vascular endothelial growth factor messenger ribonucleic acid expression was determined by reverse transcriptase polymerase chain reaction. Cyclooxygenase-2 and vascular endothelial growth factor protein expression was evaluated by Western blot. Cyclooxygenase-2, vascular endothelial growth factor, CD34 (neoangiogenesis marker), and Ki67 (proliferation marker) mucosal localizations were evaluated by immunohistochemistry.

RESULTS

Expression of cyclooxygenase-2 and vascular endothelial growth factor was increased in ileal pouch mucosa compared with ileal nonpouch mucosa, normal ileum, and rectum. Cyclooxygenase-2 and vascular endothelial growth factor immunostaining in ileal pouch mucosa was more intense in the crypt area than in the surface epithelium compared with ileal nonpouch mucosa. CD34 (neoangiogenesis marker) and Ki67 (proliferation marker) expression was increased in ileal pouch mucosa.

CONCLUSIONS

Cyclooxygenase-2 and vascular endothelial growth factor are overexpressed in the ileal pouch mucosa. This is associated with increased proliferative activity and neoangiogenesis. Cyclooxygenase-2 and vascular endothelial growth factor overexpression might play a role in the pathogenesis of pouchitis.

Gene expression profiling in a mouse model of Helicobacter-induced gastric cancer

We have previously reported that a synergistic interaction between hypergastrinemia and Helicobacter felis (H. felis) infection accelerates gastric carcinogenesis in mice, but the precise mechanism for this interaction has not been clarified. Consequently, we undertook an oligonucleotide cDNA microarray study to investigate changes in gene expression in this model system. Male hypergastrinemic transgenic (INS-GAS) mice with 6-months H. felis infection were compared with three different age, strain and gender-matched control groups: (i) INS-GAS mice without H. felis infection; (ii) non-transgenic FVB/N mice with H. felis infection; and (iii) non-transgenic FVB/N mice without H. felis infection. Complementary RNA derived from whole stomach were hybridized to the Affymetrix GeneChip murine U74Av2 array. Among 12 000 cDNA spotted on each chip, 35 cDNA were upregulated and 41 cDNA were downregulated more than twofold in H. felis-infected INS-GAS mice compared with all three control groups. Expression changes were validated in 12 selected genes by northern hybridization and/or quantitative real-time reverse transcription polymerase chain reaction (RT-PCR). Confirmed upregulated genes included Reg I, amphiregulin, MMP-10, MMP-13, claudin-7 and chitinase 3-like 1, while confirmed downregulated genes included H/K-ATPase alpha and beta subunits, intrinsic factor, somatostatin, galectin-2 and apolipoprotein A-I. Immunohistochemical analysis of MMP-10, amphiregulin, H/K-ATPase beta subunit and galectin-2 confirmed these expression changes at the protein level, and MMP-10 was mainly detected in stromal cells of submucosal region, while the other three genes were expressed in gastric epithelial cells. Taken together, gene expression profiling of this mouse model may provide novel insights into Helicobacter-induced gastric carcinogenesis.

H pylori status and angiogenesis factors in human gastric carcinoma

AIM: To investigate H pylori expression in gastric cancer patients in relation to primary tumor angiogenic markers, such as microvessel density (MVD), thymidine phosphorylase (TP), vascular endothelial growth factor receptor-1 (VEGF-R1), p53 and circulating VEGF levels.

METHODS: Angiogenic markers were analyzed immunohistochemically in 56 primary gastric cancers. H pylori cytotoxin (vacA) and the cytotoxin-associated gene (cagA) amplification were evaluated using PCR assay. Serum H pylori IgG antibodies and serum/plasma circulating VEGF levels were detected in 39 and 38 patients by ELISA, respectively.

RESULTS: A total of 69% of patients were positive for circulating IgG antibodies against H pylori. cagA-positive H pylori strains were found in 41% of gastric patients. vacA was found in 50% of patients; s1 strains were more highly expressed among vacA-positive patients. The presence of the s1 strain was significantly associated with cagA (P = 0.0001). MVD was significantly correlated with both tumor VEGF expression (r = 0.361, P = 0.009) and serum VEGF levels (r = -0.347, P = 0.041). Conversely, neither VEGF-R1 expression nor MVD was related to p53 expression. However, H pylori was not related to any angiogenic markers except for the plasma VEGF level (P = 0.026).

CONCLUSION: H pylori antigen is related to higher plasma VEGF levels, but not to angiogenic characteristics. It can be hypothesized that the toxic effects of H pylori on angiogenesis occurs in early preclinical disease phase or in long-lasting aggressive infections, but only when high H pylori IgG levels are persistent.

Vascular endothelial growth factor and neo-angiogenesis in H. pylori gastritis in humans

Host response plays a major role in the pathogenesis of Helicobacter pylori-induced gastroduodenal disease including adenocarcinoma of the distal stomach. Vascular endothelial growth factor (VEGF) is an important modulator of gastric mucosal repair and is overexpressed in gastric cancer. The present study sought to evaluate the expression of VEGF in the gastric mucosa of H. pylori-infected and H. pylori-non-infected dyspeptic patients. Fifteen H. pylori-infected and 15 H. pylori-non-infected dyspeptic patients were studied. Diagnosis of H. pylori infection was based on rapid urease test and histology. VEGF protein expression was assessed by western blotting. VEGF mRNA expression was assessed by RT-PCR. VEGF localization in the gastric mucosa and neo-angiogenesis were determined by immunohistochemistry. VEGF protein and mRNA expression was significantly greater in H. pylori-infected than in non-infected patients. Immunohistochemistry showed that VEGF expression was more intense in the gastric gland compartment of H. pylori-infected mucosa than in the non-infected mucosa. The increase in VEGF expression was associated with a significant increase in neo-angiogenesis as assessed by determination of CD34-positive micro-vessels. H. pylori gastritis is therefore associated with up-regulation of VEGF expression, which parallels the increased formation of blood vessels in the gastric mucosa. It is postulated that increased VEGF expression and neo-angiogenesis may contribute to H. pylori-related gastric carcinogenesis.

Helicobacter pylori and toll-like receptor agonists induce syndecan-4 expression in an NF-kappaB-dependent manner

The syndecans are a family of transmembrane heparan sulfate proteoglycans (HSPG) that have been implicated in a wide variety of biological functions including the regulation of growth factor signaling, adhesion, tumorigenesis, and inflammation. In the current studies, we examined the regulation of syndecan-4 gene expression in gastric epithelial cells and macrophages in response to infection with live Helicobacter pylori and purified toll-like receptor (TLR) agonists. H. pylori, PAM3CSK4 (a TLR2 agonist), and Escherichia coli flagellin (a TLR5 agonist) all induced the rapid expression of syndecan-4 mRNA in MKN45 gastric epithelial cells. Similarly, lipopolysaccharide (LPS) (a TLR4 agonist) also induced the expression of syndecan-4 in macrophages. The H. pylori- and TLR-induced increase in syndecan-4 mRNA was blocked by the proteosome inhibitor MG-132 suggesting a role for nuclear factor kappaB (NF-kappaB) in the regulation of syndecan-4 gene expression. An 895-bp fragment of the human syndecan-4 promoter was cloned upstream of the luciferase reporter. When transfected into MKN45 cells, the activity of this promoter was inducible by H. pylori and TLR agonists. Inducible activity of the syndecan-4 promoter was blocked by cotransfection with a dominant negative IkappaBalpha expression plasmid. Electrophoretic mobility shift assays (EMSA) demonstrated the presence of a highly conserved NF-kappaB-binding site. Mutation of this site within the context of the full-length syndecan-4 promoter resulted in a complete loss of responsiveness to H. pylori and TLR agonists. These results thus demonstrate that the response of the syndecan-4 gene to infectious agents, or their products, is a direct result of NF-kappaB binding to the promoter and induction of de novo transcription.

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Helicobacter pylori gamma-glutamyltranspeptidase upregulates COX-2 and EGF-related peptide expression in human gastric cells

Gastric mucosa responds to Helicobacter pylori-induced cell damage by increasing the expression of COX-2 and EGF-related peptides. We sought to investigate the bacterial virulence factor/s and the host cellular pathways involved in the upregulation of COX-2, HB-EGF and amphiregulin in MKN 28 and AGS gastric mucosal cells. H. pylori strain CCUG 17874 was grown in Brucella broth supplemented with 0.2% (2,6-dimethyl)-beta-cyclodextrins. The soluble proteins released in the culture medium by the bacterium were fractionated by exclusion size and anion exchange chromatography. A single peak retaining the ability to upregulate COX-2 and HB-EGF mRNA and protein expression was obtained. SDS-PAGE analysis of the peak showed two peptides with an apparent molecular weight of 38 and 22 kDa, which were identified by automated Edman degradation analysis as the N-terminal and C-terminal peptides of H. pylori gamma-glutamyltranspeptidase respectively. Acivicin, a selective gamma-glutamyltranspeptidase inhibitor, counteracted H. pylori-induced upregulation of COX-2 and EGF-related peptide mRNA expression. An H. pylori isogenic mutant gamma-glutamyltranspeptidase-deficient strain did not exert any effect on COX-2, HB-EGF and amphiregulin mRNA expression. Blockade of phosphatidylinositol-3 kinase and p38 kinase, but not MAP kinase kinase, inhibited H. pylori gamma-glutamyltranspeptidase-induced upregulation of COX-2 and EGF-related peptide mRNA expression.