Pylori-associated Gastric Diseases Research Articles

Heat Shock Protein: Hard Worker or Bad Offender for Gastric Diseases

Heat shock proteins (HSPs) have core housekeeping functions in the cells where they are built-in components of folding, signal transduction pathways, and quality control functions for which they proofread the structure of proteins and repair misfolded conformers. Helicobacter pylori (H. pylori) infection leads to significant inflammations in the gastric mucosa, which is closely associated with development of either precancerous lesion including chronic atrophic gastritis or gastric cancer in addition to, peptic ulcer disease, and mucosa-associated lymphoid tissue (MALT) lymphoma. Therefore, the association between H. pylori infection and role of HSP has been focused as an important issue because there had been rather conflicting publications showing that HSPs as a good worker for defense against H. pylori infection, whereas HSPs as a bad offender contributing to the progression of H. pylori-associated gastric carcinogenesis in addition to aggravation of gastric inflammation. In this paper regarding proteomic discovery of HSPs related to H. pylori-associated gastric diseases, we introduce several evidences obtained from proteomic analysis dealing with friend or foe role of HSP in H. pylori infection from a cellular level to human diseases. The implication of HSPs in alcoholic or NSAIDs-induced gastritis and the intervening of HSPs in biological changes exemplified with TGF-β signaling, key tumor suppressor growth factors regulating inflammation, immune function, and carcinogenesis were further introduced.

Are Dental Plaque, Poor Oral Hygiene, and Periodontal Disease Associated With Helicobacter pylori Infection?

The microorganism Helicobacter pylori has been closely linked to chronic gastritis, peptic ulcer, gastric cancer, and mucosa-associated lymphoid tissue (MALT) lymphoma. Despite the current treatment regimens that lead to successful management of H. pylori-positive chronic gastritis, the reinfection rate is high. It has been suggested that one of the possible mechanisms of reinfection is the recolonization from dental plaque. The purpose of this study was to determine whether dental plaque, poor oral hygiene, and periodontal disease were risk factors for H. pylori infection. Among the 134 patients, 65 patients who had a positive H. pylori serology or positive rapid urease test or histologic evidence for the presence of H. pylori in antral biopsy specimens were categorized as cases. The remaining 69 patients who were negative for H. pylori serology, the rapid urease test, and histology were controls. It was found that the association of periodontal disease and poor oral hygiene with H. pylori infection was not significant. There was a higher prevalence of H. pylori in the dental plaque of patients with gastric H. pylori infection than in controls, but both groups had a surprisingly high positive urease test for H. pylori in plaque (89% and 71%, respectively). H. pylori in dental plaque is seldom eliminated by H. pylori-eradication therapy, and this may act as a source for future reinfection. Hence, eradication of H. pylori from the dental plaque should be made an important part of comprehensive management of H. pylori-associated gastric diseases.

Plant polyphenols inhibit VacA, a toxin secreted by the gastric pathogen Helicobacter pylori

VacA is a major virulence factor of the widespread stomach-dwelling bacterium Helicobacter pylori. It causes cell vacuolation and tissue damage by forming anion-selective, urea-permeable channels in plasma and endosomal membranes. We report that several flavone derivatives and other polyphenols present in vegetables and plants inhibit ion and urea conduction and cell vacuolation by VacA. Red wine and green tea, which contain many of the compounds in question, also potently inhibit the toxin. These observations suggest that polyphenols or polyphenol derivatives may be useful in the prevention or cure of H. pylori-associated gastric diseases.

Production of IL-12 in gastritis relates to infection with Helicobacter pylori.

Increased production of proinflammatory cytokines, including tumour necrosis factor-alpha (TNF-alpha), IL-1beta, IL-6 and IL-8, has been demonstrated in Helicobacter pylori-associated gastric mucosal inflammation. IL-12, a newly characterized cytokine, is thought to be a key mediator in host responses to bacterial infections. The aim of this study was to investigate differences in cytokine patterns between H. pylori-positive and -negative gastritis and normal mucosa. Secretion of IL-12, TNF-alpha, IL-1beta, IL-6, IL-8 and IL-10 was measured in 176 patients with chronic gastritis in whole biopsy cultures. Gastritis was graded for chronic inflammation or acute inflammatory activity, respectively, according to the Sydney system. Biopsies with similar scores were matched for analysis from H. pylori-infected and non-infected patients. Secretion of IL-12 was significantly increased in H. pylori-associated gastritis in comparison with H. pylori-negative gastritis (P < 0.0001). In contrast, secretion of TNF-alpha, IL-1beta, IL-6, and IL-8 correlated with the degree of inflammation but was not different between H. pylori-positive and -negative patients. Moreover, IL-10 secretion was found to be higher in H. pylori-positive than in H. pylori-negative patients. IL-12 may play a specific role in H. pylori-associated gastric disease, whereas production of the proinflammatory cytokines TNF-alpha, IL-1beta, IL-6 and IL-8 does not seem to be restricted to H. pylori-induced inflammation. The contra-inflammatory cytokine IL-10 may be a contributor to the chronicity of H. pylori-associated gastritis by impairing clearance of the pathogen.

Virulence factors of Helicobacter pylori

To date a number of virulence factors have been identified and characterised from the gastric pathogen Helicobacter pylori. The vacuolating toxin (VacA) is a major determinant of H. pylori-associated gastric disease. In non-polarised cells, VacA alters the endocytic pathway, resulting in the release of acid hydrolases and the reduction of both extracellular ligand degradation and antigen processing. The toxin forms trans-membrane anion-specific channels and reduces the transepithelial electrical resistance of polarized monolayers. Localization of the VacA channels in acidic intracellular compartments causes osmotic swelling which, together with membrane fusion, leads to vacuole formation. The neutrophil-activating protein of H. pylori (HP-NAP) induces the production of oxygen radicals in human neutrophils via a cascade of intracellular activation events which may contribute to the damage of the stomach mucosa. This protein has recently been shown to be an important antigen in the human immune response to H. pylori infection. In addition, mice vaccinated with recombinant HP-NAP were protected against H. pylori challenge. H. pylori strains that are associated with severe tissue damage and inflammation possess the cag pathogenicity island that contains several genes encoding factors involved in the induction of proinflammatory cytokines/chemokines and of a type IV secretion system involved in the delivery of a highly immunogenic protein, CagA, into eukaryotic cells. Recent advances in our understanding of the involvement of VacA, HP-NAP and the CagA/Type IV secretion system in the H. pylori-associated disease process are discussed in this review.

Formation of anion-selective channels in the cell plasma membrane by the toxin VacA of Helicobacter pylori is required for its biological activity.

The vacuolating toxin VacA, a major determinant of Helicobacter pylori-associated gastric diseases, forms anion-selective channels in artificial planar lipid bilayers. Here we show that VacA increases the anion permeability of the HeLa cell plasma membrane and determines membrane depolarization. Electrophysiological and pharmacological approaches indicated that this effect is due to the formation of low-conductance VacA pores in the cell plasma membrane and not to the opening of Ca(2+)- or volume-activated chloride channels. VacA-dependent increase of current conduction both in artificial planar lipid bilayers and in the cellular system was effectively inhibited by the chloride channel blocker 5-nitro-2-(3-phenylpropylamino) benzoic acid (NPPB), while2-[(2-cyclopentenyl-6,7dichloro-2, 3-dihydro-2-methyl-1-oxo-1H-inden-5-yl)oxy]acetic acid (IAA-94) was less effective. NPPB inhibited and partially reversed the vacuolation of HeLa cells and the increase of ion conductivity of polarized Madine Darby canine kidney cell monolayers induced by VacA, while IAA-94 had a weaker effect. We conclude that pore formation by VacA accounts for plasma membrane permeabilization and is required for both cell vacuolation and increase of trans-epithelial conductivity.

Apoptosis in Helicobacter pylori-associated gastric and duodenal ulcer disease is mediated via the Fas antigen pathway.

Increased mucosal apoptosis is seen in H. pylori-infected gastric tissue; however, the precise mechanism by which this organism triggers programmed cell death is poorly understood and is investigated in this study. One pathway for induction of apoptosis is the Fas Ag pathway. Normal gastric and small bowel tissue express low levels of Fas antigen and nondetectable levels of Fas ligand. Consequent to H. pylori infection, there is elevated expression of Fas antigen in mucosal cells concurrent with Fas ligand expressing lymphocytes. This prompted us to investigate the potential role of Fas in mediating H. pylori-related apoptosis. It has been shown that inflammatory cytokines are abundant in H. pylori-infected tissue and that cytokines regulate the expression of Fas Ag in various tissue types. Using cell culture, we examine the role of specific inflammatory cytokines in activating this pathway. This communication presents the first evidence to implicate the Fas pathway in mediating apoptosis in H. pylori-associated gastric and duodenal ulcer disease.

Pathologic changes in the glandular stomach and duodenum in an H. pylori-infected Mongolian gerbil model.

We have established a Helicobacter pylori-infected Mongolian gerbil model following Hirayama's method to investigate gastric diseases associated with H. pylori infection. We orally administered the culture broth of H. pylori ATCC 43504 to 8-week-old male Mongolian gerbils. After this, the gerbils were fed in a vinyl isolator. Subsequently, over the course of 48 weeks some of them were sacrificed for histopathologic examination and H. pylori culture. H. pylori colonization in the glandular stomach was seen in all the infected gerbils but only a few H. pylori were detected histologically. Acute inflammation, immature epithelium, and erosion were observed 2 weeks after H. pylori infection. Chronic inflammation was noted from 4 weeks after H. pylori infection. In addition, we found intestinal metaplasia and gastric ulcers from 12 and 24 weeks, respectively. There was mild to moderate inflammation in the duodenum but no ulcerative lesions or gastric metaplasia were observed. Some histologic findings were similar to those in humans, but inflammation occurred mainly in the deep mucosa and submucosa. This is a good animal model for H. pylori-associated gastric diseases but not for duodenal ulcers or gastric metaplasia. It might be useful for investigating the pathogenesis of H. pylori infection in the stomach.

Effects of cytokines, without and with Helicobacter pylori components, on mucus secretion by cultured gastric epithelial cells.

Cytokines are suspected to play a crucial role in the pathogenesis of Helicobacter pylori-associated gastric diseases. Hence, considerable attention has been paid to the actions of cytokines on gastric cells. We examined the effects of cytokines on mucus secretion by gastric epithelial cells, without or with H. pylori components. Mucus secretion by cultured gastric epithelial cells was assessed as secretion of [3H]glucosamine-prelabeled high-molecular-weight glycoproteins. Interleukin (IL)-1beta and IL-6 significantly stimulated mucus secretion, but other cytokines such as IL-7, IL-8, IL-10, interferon (IFN)-gamma and tumor necrosis factor (TNF)-alpha had no effect. H. pylori lysate caused a decrease in both basal and stimulated secretion of mucus. In addition, IFN-gamma significantly potentiated the lysate-induced reduction of basal and stimulated secretion. Cell viability was not affected by any of treatments. These results indicate that IL-1beta and IL-6 stimulate mucus secretion, while IFN-gamma potentiates H. pylori-decreased secretion by gastric epithelial cells.

The evaluation of tissue kallikrein in Helicobacter pylori-associated gastric ulcer disease

Helicobacter pylori (Hp) associated ulcer disease is a common form of gastric disorder involving mucosal damage and invasion of the mucosa by polymorphic inflammatory cells with concomitant changes in the epithelial cell structure. The bacteria are thought to adhere by specific junction zones to the epithelial cell surface resulting in the degeneration of the mucosal layer. Our study was undertaken to examine the relative status of tissue kallikrein (TK) in antral and fundic biopsies, endoscopically obtained from 10 patients suspected of having gastric disorders. For histological evidence of inflammation the tissue was stained with hematoxylin and eosin and classified as mild, active, chronic and chronic active gastritis. Hp infection was determined by Giemsa staining. For localisation of TK, slide-mounted tissue sections were subjected to PAP and immunofluorescent staining using a goat anti-human TK IgG antibody. The results revealed that in the antral control tissue, removed during partial antractomy, TK was immunovisualised along the luminal border of the deep pyloric glands. The surface epithelia and superficial glands showed no labelling. The fundic control tissue revealed an absence of TK in the superficial and surface epithelial glands, but was positive in the parietal cells. The fundic biopsy specimens showed similar immunoreactivity in these areas. By contrast, in the inflammed pyloric mucosa, there was a shift of TK localisation to the basal part of the glandular cells and there was also expression of TK in the superficial glands that showed histological evidence of regeneration. In the fundic biopsies there was no change observed in the sites of TK localisation (similar to control tissue). It was observed, that even though 8 of the 10 subjects exhibited Hp infection, the inflamed mucosa showed no discernable difference in the staining patterns between the infected and non-infected tissue sections. Our findings suggest an important role for a B1/B2 kinin antagonist in patients with gastritis.

Helicobacter pylori stimulates inducible nitric oxide synthase expression and activity in a murine macrophage cell line

BACKGROUND & AIMS: Helicobacter pylori uniquely colonizes the human stomach and produces gastric mucosal inflammation. High-output nitric oxide production by inducible nitric oxide synthase (iNOS) is associated with immune activation and tissue injury. Because mononuclear cells comprise a major part of the cellular inflammatory response to H. pylori infection, the ability of H. pylori to induce iNOS in macrophages was assessed. METHODS: H. pylori preparations were added to RAW 264.7 murine macrophages, and iNOS expression was assessed by Northern blot analysis, enzyme activity assay, and NO2- release. RESULTS: Both whole H. pylori and French press lysates induced concentration-dependent NO2- production, with peak levels 20-fold above control. These findings were paralleled by marked increases in iNOS messenger RNA and enzyme activity levels. iNOS expression was synergistically increased with interferon gamma, indicating that the H. pylori effect can be amplified by other macrophage-activating factors. Studies of lipopolysaccharide (LPS) content and polymyxin B inhibition of LPS suggested that the H. pylori effect was attributable to both LPS- dependent and -independent mechanisms. CONCLUSIONS: iNOS expression in macrophages is activated by highly stable H. pylori products and may play an important role in the pathogenesis of H. pylori-associated gastric mucosal disease. (Gastroenterology 1996 Dec;111(6):1524-33)

Inhibition of gastric cell proliferation by acetaldehyde.

Helicobacter pylori possesses alcohol dehydrogenase activity and is capable of producing acetaldehyde from ethanol in vitro. Acetaldehyde is a toxic and reactive compound and has been shown to inhibit the proliferation of many different cell lines in vitro. To study the effects of acetaldehyde on the proliferation of gastric epithelial cells in vivo, we employed an immunohistochemical method after labelling proliferating cells with 5'-bromo-2'-deoxyuridine in rats receiving acetaldehyde intragastrically. Chronic (16 weeks) exposure of gastric mucosa to acetaldehyde given to rats in their drinking water in concentrations of 10 or 20 mM resulted in significant (P < 0.05) inhibition of gastric epithelial cell proliferation, expressed as 332 +/- 36, 348 +/- 8, and 695 +/- 15 proliferating cells per ten high-power (x 400) fields in the groups drinking 10 mM acetaldehyde, 20 mM acetaldehyde, and in controls respectively. In an acute study, significant inhibition of proliferation was observed after as few as 4 days of exposure to acetaldehyde, but only when a higher dose (50 mM) of acetaldehyde was given (438 +/- 44 versus 615 +/- 19 in controls, P < 0.05). The inhibition of gastric cell renewal by acetaldehyde may play a role in the pathogenesis of ethanol- and/or H. pylori-associated gastric diseases by inhibiting normal gastric mucosal protection and repair.

Resolution of Helicobacter pylori-associated gastric lymphoproliferative disease in a child

A possible causative association between Helicobacter pylori infection and gastric lymphoproliferative disorders has recently been recognized. The case of a 14-year-old girl who was diagnosed with H. pylori gastritis and associated gastric lymphoproliferative disease of the low-grade mucosa-associated lymphoid tissue type is reported. The patient was treated only for the H. pylori infection (amoxicillin, bismuth, and metronidazole) without any adjuvant chemotherapy or surgery for her lymphoproliferative disorder. This treatment not only resulted in the eradication of the microorganism but also complete resolution of her lymphoproliferative disease. The patient was subsequently followed up for a period of 7 years. There has been no histological recurrence of H. pylori gastritis or gastric lymphoproliferative disease. It is believed that this is the first report to describe a long-term follow-up of an H. pylori-associated gastric lymphoproliferative disorder in a pediatric patient who was exclusively treated for H. pylori infection. The observations in this report suggest that H. pylori-associated low-grade gastric lymphoproliferative disease can be completely cured by eradicating the organism. Therefore, this therapeutic approach, combined with close follow-up, should be the treatment of choice in children with this associated condition before attempting more aggressive treatments, thus potentially avoiding chemotherapy and/or (partial) gastrectomy.

Resolution of Helicobacter pylori-associated gastric lymphoproliferative disease during childhood: A seven year follow-up : [formula omitted]∗, T.W. McKeithan +, J. Hart +, B.S. Kirschner∗, Depts. of ∗Pediatrics and +Pathology, Pritzker School of Medicine, Wyler Children's Hospital, The University of Chicago, Chicago, IL

Resolution of Helicobacter pylori-associated gastric lymphoproliferative disease during childhood: A seven year follow-up : [formula omitted]∗, T.W. McKeithan +, J. Hart +, B.S. Kirschner∗, Depts. of ∗Pediatrics and +Pathology, Pritzker School of Medicine, Wyler Children's Hospital, The University of Chicago, Chicago, IL

Long-Term Consequences ofHelicobacter pyloriEradication

Long-term infection with Helicobacter pylori could potentially lead to asymptomatic chronic gastritis, chronic dyspepsia, duodenal ulcer disease, gastric ulcer disease, or gastric malignancy, including both adenocarcinoma and B-cell lymphoma. Currently, the two most important indications for eradication of this bacterium are proven H. pylori-associated duodenal or gastric ulcer disease. Many studies have shown that successful eradication of H. pylori dramatically reduces the rate of duodenal ulcer relapse, and long-term follow-up data appear to support the claim 'no H. pylori, no gastritis; no gastritis, no ulcer', which follows on from the old, but certainly valid, dictum 'no acid, no ulcer'. Furthermore, absence of relapse parallels the marked improvement in gastric histology (e.g. regression of gastritis). Whether there is concomitant regression of gastric metaplasia in the duodenal bulb is, however, controversial. Despite the rather limited data for H. pylori-associated gastric ulcer, successful eradication of the organism has been equated with cure of peptic ulcer disease. Again, eradication parallels a substantial improvement in gastric histology. Although eradication of H. pylori is not currently recommended in asymptomatic individuals or dyspeptics, it has been well documented in previous studies that successful eradication improves the gastric histology in patients with H. pylori-associated dyspepsia. From these studies, it appears that the disappearance of polymorphs from the inflammatory infiltrate occurs rather rapidly after eradication, although regression of the mononuclear component of the inflammatory reaction is more prolonged.