Mucosal tumor necrosis factor-alpha, interleukin-1 beta, and interleukin-8 production in patients with Helicobacter pylori infection

Stimulation of pepsinogen release from chief cells by Helicobacter pylori: evidence for a role of calcium and calmodulin

To define the mechanisms by which Helicobacter pylori stimulates pepsinogen secretion, the in vitro release of pepsinogen was studied using a preparation of pig chief cell monolayers. Helicobacter pylori induced a time- and concentration-dependent release of pepsinogen into the medium, with about a three-fold increase in pepsinogen secretion over controls found after 45 min of incubation. 3x10(7) H. pylori produced 50% of the maximal response found at a H. pylori count of 2x10(8). The action of H. pylori did not depend on the presence of the vacuolating toxin (vacA) and the cytotoxin-associated protein (cagA). Dibutyryl-cAMP and the phorbol ester 12-O-tetradecanoylphorbol-13-acetate also markedly stimulated pepsinogen secretion and enhanced the stimulatory effect of H. pylori. Helicobacter pylori-stimulated pepsinogen release was inhibited by lanthanum and the calmodulin antagonist W-7, but not by the L-type Ca2+ channel blocker nifedipine, TMB-8, an agent that blocks the release of Ca2+ from intracellular stores, the protein kinase C inhibitor staurosporine and the protein kinase A inhibitor H-8. It is suggested that H. pylori directly stimulates pepsinogen release from gastric chief cells and that this effect is mediated via the calcium/calmodulin messenger branch.

Differential normalization of mucosal interleukin-8 and interleukin-6 activity after Helicobacter pylori eradication

There is differential resolution of mucosal infiltration with neutrophils and mononuclear cells following successful Helicobacter pylori eradication. We investigated the effects of H. pylori eradication on mucosal interleukin-8 (IL-8) and IL-6 activity in relation to the resolution of H. pylori-associated gastritis. Eighty-one duodenal ulcer patients with H. pylori infection received dual- or triple-treatment eradication therapy, and mucosal biopsy specimens obtained at the initial and follow-up endoscopic examinations were cultured in vitro for 24 h. The levels of IL-8 and IL-6 were measured by enzyme-linked immunosorbent assays. In the 42 patients in whom H. pylori eradication failed, there was little change in the numbers of neutrophils and mononuclear cells infiltrating the mucosa and in IL-8 and IL-6 activity. In the 39 patients in whom H. pylori was eradicated, there was normalization both in the numbers of infiltrating neutrophils and in mucosal IL-8 activity, which was evident within 1 month following therapy. In contrast, there was a gradual resolution of mononuclear cell infiltration over a 6-month period, accompanied by a gradual normalization in IL-6 levels. Addition of H. pylori to cultures of mucosal tissues induced a significant increase in IL-8 activity in both uninfected control subjects and patients from whom H. pylori was eradicated. However, this introduction yielded a significant increase in IL-6 activity only in the latter group. This study indicates a dichotomy in the changes of mucosal IL-8 and IL-6 activity after H. pylori eradication. The rapid normalization of IL-8 after H. pylori eradication and the ability of H. pylori cells to stimulate IL-8 in control tissues indicate that IL-8 induction is a part of the innate (nonimmune) responses to this organism. In contrast, the results of experiments analyzing IL-6 activity in cultured mucosal tissues suggest that the gradual resolution of mucosal IL-6 activity and mononuclear infiltration after successful eradication observed in vivo may reflect gradually diminishing residual immune responses against H. pylori.

Helicobacter pylori and functional dyspepsia: a real causal link?

This chapter reviews the evidence for a link between functional dyspepsia and Helicobacter pylori infection from three angles. In the section on pathophysiology, we evaluate how H. pylori could theoretically produce dyspeptic symptoms: many mechanisms can be proposed. In the discussion on epidemiology, we evaluate possible associations between the occurrence of symptoms and infection. Here, many studies claiming a coincidence or chronological sequence of infection and symptoms are criticized because of their poor design. In the section on the improvement of functional dyspepsia by the treatment of H. pylori infection, the conclusion is reached that if such an effect occurs at all--which is unlikely--it is very weak. The controversy on the link between H. pylori infection and functional dyspepsia is presently ongoing. Some authors are still trying to save an elegant concept that once looked so plausible but now has the facts against it.

Infection with Helicobacter pylori expressing the cagA gene is not associated with an increased risk of developing peptic ulcer diseases in Korean patients

BACKGROUND

Helicobacter pylori strains possessing the cagA gene have been postulated to have a disease-specific relationship to peptic ulcer. The purpose of this study was to investigate the relationship between the infection with Helicobacter pylori expressing the cagA gene and the development of peptic ulcer diseases in Korean patients.

METHODS

Genomic DNA and bacterial mRNA in the gastric mucosa were amplified by polymerase chain reaction (PCR) and reverse transcription PCR, using synthetic oligonucleotide primers to cagA genes to compare the prevalence of cagA genes in 35 patients with non-ulcer gastritis and 99 patients with gastric or duodenal ulcer disease (53 and 46, respectively). Two different primer sets for the cagA gene were used. The first primer set amplified a 298-bp region (nucleotides 1751-2048), and the second set amplified a 349-bp region (nucleotides 1228-1249).

RESULTS

The expected 298 and 349-bp PCR amplicons were identified as follows: 1) 32 (91.4%) and 30 (85.7%) of 35 non-ulcer gastritis patients; 2) 5 1 (96.2%) and 50 (94.3%) of 53 benign gastric ulcer patients; and 3) 46 (100.0%) and 40 (87.0%) of 46 duodenal ulcer patients, respectively.

CONCLUSION

These results strongly suggest that the cagA gene will not prove to be a useful marker to distinguish disease-specific H. pylori strains in the development of peptic ulcer diseases in Korean patients.

Gastrointestinal sensory abnormalities in functional dyspepsia

Symptoms of functional dyspepsia, such as epigastric pain, bloating or early satiety and nausea, are non-specific and are likely to arise from different mechanisms. Current evidence suggests the presence of at least two subgroups: patients who respond to a prolonged course of acid suppression and patients who show a significant overlap of symptoms with other functional gastrointestinal disorders such as irritable bowel syndrome. An enhanced sensitivity of visceral afferent pathways with or without associated autonomic dysregulation appears to play an important role in the aetiology of symptoms in the second group. In the absence of visceral hypersensitivity, neither the slowing of gastric emptying nor the presence of chronic gastritis appears to be sufficient to cause symptoms of functional dyspepsia. The mechanisms and aetiology of visceral hypersensitivity are incompletely understood. An alteration in the interplay between vagal and spinal afferents, and the inadequate activation of antinociceptive systems in response to tissue irritation, may play a role in symptom generation.

Delayed healing of chronic gastric ulcer after Helicobacter pylori infection in mice

It has been suggested that there is a close relationship between Helicobacter pylori and the onset or recurrence of gastroduodenal disease. The aim of this study was to examine the effect of H. pylori on the healing of chronic gastric ulcers induced in mice. H. pylori administered to nude mice delayed the healing of experimental acetic acid-induced gastric ulcers. Histological examination showed the occurrence of high densities of H. pylori on the surface of epithelial cells and in the ulcerated area. Repeated administration of amoxicillin (10 mgkg(-1) daily for 5 days) eradicated H. pylori and increased the rate of healing of gastric ulcers in H. pylori-infected mice, but metronidazole, which also eradicated the organisms, did not significantly affect the rate of healing. In conclusion, H. pylori-infection delayed the healing of gastric ulcers induced by the serosal application of acetic acid in mice, possibly by aggravation or prolongation of the mucosal inflammation. Amoxicillin eradicated H. pylori and promoted gastric ulcer healing in mice infected with H. pylori.

Characterization of lymphocytic subsets and cytokine production in gastric biopsy samples from Helicobacter pylori patients

BACKGROUND

This study characterized the phenotypic subsets of isolated gastric lymphocytes and the cellular immune response in cultured gastric biopsy specimens.

METHODS

Endoscopy specimens from 40 Helicobacter pylori-positive and 40 H. pylori-negative patients were studied. a) Isolated gastric lymphocytes were analysed for CD4+, CD8+ T-lymphocyte subsets, activated T cells, and natural killer cells on a fluorescence-activated cell sorter, using monoclonal antibodies. b) The supernatant of cultured gastric biopsy specimens were assayed for interleukin (IL)-2, IL-4, and IL-6 levels.

RESULTS

In H. pylori-positive patients there was (a) a decrease in CD4+/CD8+ T cells, no change in activated T cells, and an increase in natural killer cells, and (b) no change in IL-2 levels and a significant increase in IL-4 and IL-6 levels.

CONCLUSIONS

There is an increase in CD8+ lymphocytes and natural killer cells, and the observed increase in IL-4 and IL-6 might be important in H. pylori-associated gastritis.

Hypotheses on the role of cytokines in peptic ulcer disease

Helicobacter pylori is the cause of chronic type B gastritis and occurs in almost all patients with duodenal ulcers. Infection with H. pylori is characterized by an increased production of several inflammatory cytokines. Increasing evidence suggests a central role of these cytokines in the pathogenesis of H. pylori-associated gastritis and peptic ulcer disease. Cytokines may be crucial in the recruitment and activation of inflammatory cells and in stimulation of gastrin release. In addition to their proinflammatory properties, cytokines may also inhibit the ulcer occurrence by stimulation of prostaglandins and somatostatin release and by direct impairment of acid secretion. The balance of these factors may determine the clinical outcome of H. pylori infection.

Effects of Helicobacter pylori eradication on gastric function indices in functional dyspepsia. A prospective controlled study

BACKGROUND

To date, it is unclear whether Helicobacter pylori infection is associated with disturbances of gastric emptying or acid secretion in patients with functional dyspepsia (FD). Our aim was to investigate whether, in the long run, cure of H. pylori infection significantly influences gastric emptying of solids, acid secretion, and gastrin and pepsinogen I (PGI) release in patients with FD.

METHODS

Thirty-eight consecutive H. pylori-positive patients with FD, whose complaints were scored for severity and frequency on the basis of a validated symptom questionnaire, were initially enrolled in the study. They were randomized to receive an eradicating regimen consisting of omeprazole plus clarithromycin and tinidazole for 1 week or full-dose ranitidine for 3 weeks. In 33 patients (18 H. pylori-cured and 15 with persistent infection) basal and pentagastrin-stimulated acid secretion, fasting and meal-induced gastrin concentrations, fasting serum PGI levels, and gastric emptying of solids were determined before and 6 months after therapy.

RESULTS

In the 18 H. pylori-cured patients meal-induced gastrin and fasting PGI levels were significantly reduced after 6 months as compared with pretreatment values (peak serum gastrin, 76.0 +/- 23.4 versus 111.9+/-37.4 pg/ml; PGI, 57.1+/-23.4 versus 72.9+/-29.1 ng/ml), whereas they remained virtually unchanged in the 15 patients with persistent infection. In contrast, both basal and stimulated acid secretion and gastric emptying time of solids remained unmodified over time in both groups of patients.

CONCLUSIONS

We confirm that also in patients with functional dyspepsia H. pylori eradication in the long run significantly reduces gastrin and PGI release as a result of improvement in the underlying antral gastritis, but this is not accompanied by modifications of gastric emptying of solids or acid secretion.

Proteins encoded by the cag pathogenicity island of Helicobacter pylori are required for NF-kappaB activation

Helicobacter pylori is the etiological agent in the development of chronic gastritis, duodenal ulceration, and gastric adenocarcinoma. The difference in virulence between individual strains is reflected in their ability to induce interleukin-8 (IL-8) secretion from gastric epithelial cells. It has been shown that virulence is associated with the presence of a bacterial gene cluster (a pathogenicity island). We have recently demonstrated that H. pylori-mediated IL-8 secretion requires activation of the transcription factor NF-kappaB. Here, we show that NF-kappaB induction requires six membrane proteins encoded within the pathogenicity island.

Effect of Helicobacter pylori infection on gastric juice pH

BACKGROUND

How Helicobacter pylori infection affects gastric acid secretion is still unclear.

METHODS

Gastric juice pH, ammonia concentration in gastric juice, serum gastrin level, and grade of gastritis in accordance with the Sydney System were determined for patients with gastric ulcer (GU) and duodenal ulcer (DU) before and after treatment with lansoprazole and amoxicillin, and results were compared with those of H. pylori-negative controls.

RESULTS

Scores for H. pylori density, atrophy, metaplasia, and activity of gastritis in the corpus were higher in patients with GU, especially those with proximally located GU, than in those with DU. Gastric juice pH was significantly higher in GU patients than in DU patients and controls. After H. pylori eradication, gastric juice pH and serum gastrin levels in both GU and DU patients were significantly decreased to control levels. In patients without eradication, no significant changes in these factors were observed.

CONCLUSIONS

These findings suggest that H. pylori infection and gastritis in the corpus suppress acid secretion and increase gastric juice pH, resulting in hypergastrinemia, and that eradication of H. pylori normalizes acid secretion and serum gastrin levels.

Aspirin-induced gastritis, like Helicobacter pylori-induced gastritis disinhibits acid secretion in humans: relation to cytokine expression

BACKGROUND

Helicobacter pylori infection contributes to hypergastrinemia and hypersecretion of acid by blocking inhibitory reflex pathways to gastrin and parietal cells normally activated by antral distention. Our aim was to investigate whether a similar blockade of inhibitory responses could be provoked by inducing gastritis with aspirin, thus implicating a common inflammatory component, possibly a proinflammatory cytokine(s).

METHODS

We studied the effects of antral distention on stimulated acid secretion and gastrin release in H. pylori-negative volunteers, before and after 3 days of aspirin therapy (2 g daily). Immediately before the examinations, the severity of gastric mucosal injury was evaluated macroscopically and histologically, and the production of interleukin (IL)-1beta, IL-6, IL-8, tumor necrosis factor (TNF)-alpha, and interferon (IFN)-gamma was determined by immunohistochemistry.

RESULTS

Most subjects had severe gastric injury after aspirin therapy, resulting in a substantially increased production of IL-1beta, IL-6, and IL-8 but not of TNF-alpha and IFN-gamma in the antral mucosa. In these subjects the acid-inhibitory response was abolished or markedly reduced. Conversely, aspirin therapy failed to affect the gastrin release in all subjects studied.

CONCLUSIONS

The disinhibition of acid secretion in response to antral distention is a joint feature of the gastritis induced by aspirin and H. pylori infection, possibly related to the increased production of IL-1beta, IL-6, and IL-8. The H. pylori-related hypergastrinemia apparently has a different background.

The influence of Helicobacter pylori eradication on the gastric mucosal content of epidermal growth factor, transforming growth factor-alpha, and their common receptor

BACKGROUND

The relationship between the expression of epidermal growth factor (EGF) and transforming growth factor-alpha (TGF-alpha) and that of their receptor (EGF-R) in the Helicobacter pylori-infected gastric mucosa has not been completely elucidated. The aim of this study was to examine the interplay between H. pylori colonization and gastric mucosal growth factor content.

METHODS

By means of a solid-phase enzyme-linked immunosorbent assay EGF, TGF-alpha, and EGF-R levels and interleukin-1beta (IL-1beta) content, which is considered a marker of chronic inflammation, were evaluated in the antral mucosa of 24 H. pylori-positive patients before and 8 weeks after eradication therapy.

RESULTS

After therapy H. pylori was eradicated in 19 patients. The eradication was accompanied by a significant decrease in IL-1beta content and an increase in EGF and TGF-alpha levels. On the other hand, in the five patients in whom the bacterium was not eradicated EGF, TGF-alpha, and EGF-R levels were quite similar to those assayed before therapy, whereas IL-1beta content was still high.

CONCLUSIONS

These results suggest that H. pylori exerts an inhibitory effect on the mucosal expression of EGF and TGF-alpha, which are likely involved in the gastric mucosa repair process.

Activation of IL-8 Gene Expression by Helicobacter pylori Is Regulated by Transcription Factor Nuclear Factor-κB in Gastric Epithelial Cells

In vivo, gastric infection with Helicobacter pylori leads to substantial production of the inflammatory cytokines IL-1, IL-6, TNF-α, and IL-8. H. pylori strains that contain the cag pathogenicity island (cag+) and are associated with ulceration and gastric carcinoma induce greater cytokine production than cag− strains. Expression of these cytokines is often regulated by the transcription factor complex, nuclear factor-κB (NF-κB) through κB-binding elements in the enhancer/promoter regions of their genes. We report that more virulent cag+ H. pylori strains induce increased NF-κB-DNA binding activity, which elevates IL-8 expression in AGS gastric epithelial cells. The cag+ H. pylori strains induce significant stimulation of IL-8 promoter-driven reporter activity, while cag− strains do not. Furthermore, mutation of specific genes within the cag island (picA1 and picB) ablates enhanced NF-κB activation and IL-8 transcription. Increased IL-8 expression is inhibited by mutation in either the NF-κB or NF-IL-6 binding element. The cag+ strains, compared with the cag− strains, induce enhanced nuclear localization of a RelA-containing NF-κB binding complex, but no increase in NF-IL-6 binding activity. These studies demonstrate that the ability of different types of H. pylori strains to activate NF-κB correlates with their ability to induce IL-8 transcription and indicate a mechanism for the heightened inflammatory response seen in subjects infected with cag+ H. pylori strains.

Mucosal chemokine activity in Helicobacter pylori infection

We examined secretion, mRNA expression, and histologic localization of interleukin-8 (IL-*) and growth-related gene product-alpha (GRO alpha) in the Helicobacter pylori-infected gastric antral mucosa. Antral biopsies were obtained from an area of endoscopically intact mucosa. Significantly higher levels of IL-8 and GRO alpha were secreted in organ cultures from patients with H. pylori infection, and their elevation was prominent in patients with duodenal ulcer. There was a significant association between these alpha-chemokine levels and histologic grades of activity, inflammation, and H. pylori density. In fresh antral biopsies, IL-8 and GRO alpha mRNA expression was detected more frequently in H. pylori-infected patients compared with those without infection. Immunofluorescence microscopy showed localization of IL-8 and GRO alpha proteins in gastric epithelial cells and infiltrating CD68+ macrophages. In the chemotaxis assay, a significant positive correlation was found between neutrophil migration induced by the organ culture supernatants and their contents of IL-8 and GRO alpha. After H. pylori eradication, a significant decrease was observed in IL-8 and GRO alpha levels detected in organ cultures. In conclusion, mucosal alpha-chemokine activity correlates well with histologic severity of H. pylori-associated antral gastritis and can be used to predict the effects of H. pylori eradication therapy.

Helicobacter pylori, neutrophils, interleukins, and gastric epithelial proliferation

Infection of Helicobacter pylori causes chronic gastritis and plays an important role in the pathogenesis of gastroduodenal ulceration. H. pylori has also been suggested to be involved in the genesis of adenocarcincoma and MALT lymphoma of the stomach. H. pylori infection is associated with increased gastric epithelial proliferation, which can be reversed by a successful eradication of the organism. Although the mechanisms of increased gastric epithelial proliferation is not known, the enhanced epithelial proliferation is important in developing gastric carcinoma. Whether or not H. pylori de nove stimulates gastric epithelial proliferation is controversial, but gastric infection with H. pylori activates a mucosal inflammatory response by consisting of large numbers of polymorphonuclear and mononuclear cells, that also includes expression of various cytokines including interleukin-8. We review the mechanisms of H. pylori in enhanced gastric epithelial cell proliferation and cytokines in patients with H. pylori infection.

In situ expression of cell adhesion molecules in chronic gastritis with Helicobacter pylori infection

Helicobacter pylori infection of the stomach results in acute inflammation followed by chronic inflammation, but the mechanism is unknown. Adhesion molecules such as ICAM-1, Mac-1, and LFA-1 may help regulate interactions of immune cells and inflammatory cells. We used immunohistochemistry to locate these molecules in the gastric mucosa of patients with chronic gastritis arising from H. pylori infection. Biopsy specimens were taken from five H. pylori-negative healthy volunteers and 20 H. pylori-positive patients with chronic gastritis for immunohistochemical studies of adhesion molecules. In the gastric mucosa of patients with H. pylori-associated chronic gastritis, ICAM-1 expression was prominent in most of the vessels and inflammatory cells, such as lymphocytes and granulocytes, in the lamina propria. However, no intraepithelial lymphocytes and surface epithelial cells expressed ICAM-1. Antigen-presenting cells (APCs), such as macrophages, expressed ICAM-1 as well as HLA-DR antigen. LFA-1 and Mac-1 were strongly expressed in these immune and inflammatory cells. The number of vascular endothelial cells positive for P-selectin was also greater in H. pylori-positive mucosa. The expression of these molecules decreased remarkably after successful eradication of H. pylori. In conclusion, ICAM-1 is the predominant form among the cell adhesion molecules that are expressed in response to chronic H. pylori infection. The increased expression of ICAM-1 is linked with massive infiltration of inflammatory cells that express LFA-1 and Mac-1, and also with APCs that express HLA-DR, suggesting that ICAM-1 exerts a key role in immuno-inflammatory responses in gastric mucosa of patients with H. pylori-associated gastritis.

What role does Helicobacter pylori play in dyspepsia and nonulcer dyspepsia? Arguments for and against H. pylori being associated with dyspeptic symptoms

A major role for Helicobacter pylori gastritis in nonulcer dyspepsia (NUD) is controversial. Gastroduodenal dysfunction may be associated with H. pylori infection, but there is little evidence for a causal link with dyspepsia. Population-based studies with appropriate methodology have generally failed to confirm an association between H. pylori and NUD. Furthermore, no definite association between subgroups of NUD (ulcer-like, dysmotility-like, reflux-like, and nonspecific) and H. pylori has been identified however the subgroups have been defined, and no specific symptom pattern characterizes patients with H. pylori infection. Whether H. pylori-induced alterations of gastric physiology can explain NUD remains open to debate while we await the results of more specific experiments. Although acid secretion in response to gastrin-releasing peptide may be increased in a subset of NUD patients who are infected with H. pylori, uninfected patients with NUD have not been assessed and the results require confirmation. Most studies suggest no association between H. pylori and gastroduodenal motor or sensory dysfunction in NUD. Treatment trials have been unconvincing. The trials with bismuth therapy have not been adequately blinded. Furthermore, some studies suggest that H. pylori-negative patients with NUD may respond to bismuth treatment, although the results have not been uniform. Therapies aimed at curing H. pylori infection have produced mixed results, with small positive and negative trials. The trials that have used adequate outcome measures have more often than not been negative. Based on current evidence, H. pylori is not established to be of causal importance in NUD.

Helicobacter pylori genotypes influence serum pepsinogen C levels

BACKGROUND

Infection from Helicobacter pylori significantly influences pepsinogen A (PGA) and C (PGC) levels in serum. Increased PGA and PGC serum levels are observed in H. pylori positive patients, while a significant decrease is observed after eradication. Little is known about the relative role of H. pylori cytotoxic strains in this phenomenon. The aim of our study was to assess the influence of cagA genotype on circulating levels of PGA and PGC.

MATERIALS AND METHODS

We studied 81 consecutive H. pylori positive patients, 64 H. pylori negative patients and 18 healthy controls. H. pylori was evaluated histologically in two antral and two body biopsies (Giemsa and/or Warthin Starry staining). Extracted DNA was then submitted for PCR amplification of both the urease A and cagA genes. A serum obtained from each patient before endoscopy was used for specific radioimmunoassay measurement of PGA and PGC.

RESULTS

The urease A gene was found in all H. pylori positive patients, the cagA gene was detected in 55 H. pylori positive patients and in none of the H. pylori negative patients. PGA and PGC levels were significantly higher in H. pylori positive than in H. pylori negative patients. A significant association was found between cagA and raised serum PGC levels in patients with antral gastritis but not in patients with peptic ulcer. Serum PGA levels were not affected by cagA.

CONCLUSIONS

Our results indicate that cagA positivity may influence the circulating PGC levels, probably because it causes a higher grade of mucosal inflammation.

How does Helicobacter pylori cause mucosal damage? The inflammatory response

The role for Helicobacter pylori in the pathogenesis of disease provides the conundrum that only a subset of subjects infected with H. pylori will ever develop peptic ulcer or gastric cancer. Thus, variation in strain as well as environmental or host factors converge in the gastroduodenal milieu and control the final outcome of infection. The host immune and inflammatory response is emerging as an important element in the pathogenesis of these gastric diseases. The ideal host response provides protection to clear an infection without causing excessive amounts of inflammation that could compromise the integrity and function of host cells. This review will cover four main questions: (1) What are the mucosal immune/inflammatory responses that confer protection without damaging the host? (2) How do the gastric immune responses during infection with H. pylori differ from this ideal scenario? (3) Do these responses contribute to autoimmune-mediated damage to gastric tissue? (4) Can immunomodulation through vaccination enhance protective, nondestructive responses that prevent or treat infection or, at least, attenuate inflammation?

Proposed link between Helicobacter pylori and sudden infant death syndrome

Helicobacter pylori may be linked to sudden infant death syndrome (SIDS) through synthesis of inflammatory cytokines, particularly interleukin-1, which can produce fever, activation of the immune system, and increased deep sleep. A relatively minor respiratory or enteric infection, together with overwrapping and prone sleep position could then induce terminal hypoxemia. Alternatively, H. pylori produces large amounts of urease which, if aspirated in gastric juice, could reach the alveolae, react with plasma urea, and produce ammonia toxicity leading to respiratory arrest. Epidemiological similarities between H. pylori and SIDS are presented along with possible transmission mechanisms for H. pylori which support this hypothesis.

Helicobacter pylori induces proinflammatory cytokines and major histocompatibility complex class II antigen in mouse gastric epithelial cells

Although Helicobacter pylori has been reported to stimulate the release of various cytokines from gastric tissue, it remains unknown whether normal and nontumorous gastric epithelial cells produce these cytokines. Therefore, in this study, we used a normal mouse gastric surface mucous cell line (GSM06) to determine whether gastric epithelial cells produce proinflammatory cytokines in response to H. pylori. The expression of MHC class II antigen was also examined, to investigate whether gastric epithelial cells participate in the immune response to H. pylori. In the study, GSM06 cells were incubated with H. pylori or its lipopolysaccharide (LPS). Proinflammatory cytokines were detected by Northern and Western blot analysis. The expression of MHC class II antigen was examined by fluorescence activated cell sorter (FACS) analysis. Genetic expression of proinflammatory cytokines such as interleukin-1alpha, tumor necrosis factor-alpha, and cytokine-induced neutrophil chemoattractant-2beta was enhanced by both intact and sonicated H. pylori, but not by H. pylori LPS. The expression of MHC class II antigen was induced by H. pylori more strongly than by interferon-gamma. We conclude that H. pylori induces the expression of proinflammatory cytokines and MHC class II antigen in gastric epithelial cells. Gastric epithelial cells may act as antigen-presenting cells and participate in the immune response to H. pylori infection.

Role of adherence in interleukin-8 induction in Helicobacter pylori-associated gastritis

Active Helicobacter pylori-associated gastritis is characterized by a dense mucosal infiltration with granulocytes. Since H. pylori is noninvasive, secondary signals must induce the accumulation of granulocytes. Interleukin-8 (IL-8) has been shown to play a key role in this event. Using competitive reverse transcriptase-PCR on mRNA from gastric biopsies, we could show a clear correlation between the amount of IL-8 transcripts and the activity of H. pylori gastritis. Due to the inability of the bacterium to invade host cells, the epithelial layer is a potential candidate as an IL-8 source. To study the mechanism of IL-8 induction, established gastric carcinoma epithelial cell lines (AGS and Kato III) and well-defined H. pylori strains were used in a modified in vitro system. The experimental design enabled us to prevent direct contact of bacteria with epithelial cells by use of a filter membrane which did not block secreted bacterial products crossing the membrane. The data clearly showed that the direct contact of the bacterial cell with the epithelial cell is necessary for optimal IL-8 production because not only live bacteria, but also metabolically inactive bacteria, increased IL-8 secretion. Neither purified lipopolysaccharide nor water-soluble protein fractions of H. pylori NCTC 11637 and Tx30a nor the cytotoxin of H. pylori was able to increase IL-8 production significantly by the epithelial cells used. Furthermore, preparations of total membrane and outer membrane proteins of H. pylori were not able to stimulate IL-8 release in vitro. Accumulatively, these results imply that active metabolism is not necessary for stimulation as long as there is an intact membrane aiding the presentation of a stimulating membrane complex or aggregate on the surface of the bacteria. From these results, we conclude that whole bacteria and their direct contact with epithelial cells may be critical for IL-8 induction in vivo.

Increased mucosal inflammatory cytokines in children with Helicobacter pylori-associated gastritis

The concentrations of tumour necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6) and IL-1-beta in tissue homogenates of gastric mucosal biopsy specimens, and in gastric juice samples from Helicobacter pylori-positive and -negative children, were determined. The study population comprised 30 children with recurrent abdominal pain attending upper gastrointestinal endoscopy. Of these patients 18 were infected with H. pylori. Cytokine concentrations in gastric biopsy homogenate supernatants and in gastric juice were measured by enzyme-linked immunosorbent assay (ELISA). TNF-alpha levels in gastric juice and in gastric biopsy homogenate supernatants in patients with H. pylori-positive gastritis were found to be significantly higher than those in children without H. pylori infection. IL-6 levels were also higher in H. pylori-infected subjects, but the difference in IL-6 concentrations measured in gastric juice and biopsy homogenate supernatants did not reach statistical significance. IL-1-beta concentrations in both specimens showed no significant difference between the two groups of children. It was suggested that increased levels of inflammatory cytokines, especially TNF-alpha and IL-6 generated locally within the gastric mucosa might be implicated in the pathogenesis of H. pylori-associated gastritis in childhood.

Mucosal interleukin-1 beta production and acid secretion in enlarged fold gastritis

BACKGROUND

We have previously shown that eradication of Helicobacter pylori increases acid secretion in H. pylori-associated enlarged fold gastritis.

AIM

To investigate whether locally produced interleukin-1 beta is possibly involved in the inhibition of acid secretion in H. pylori gastritis.

METHODS

IL-1 beta release from the gastric body mucosa was determined by short-term culture of biopsy specimens in 13 patients with enlarged fold gastritis (all H. pylori-positive), five H. pylori-positive and 10 H. pylori-negative patients without enlarged folds. The acid-inhibitory effect of locally produced IL-1 beta was examined by [14C]-aminopyrine uptake assay using isolated rabbit gastric glands.

RESULTS

IL-1 beta release was significantly greater in patients with enlarged fold gastritis, significantly correlated with both basal and tetragastrin-stimulated acid outputs in the H. pylori-positive patients (r = -0.591 and r = -0.641, respectively; P < 0.01), and significantly decreased with concomitant increases in acid secretions after eradication of H. pylori. [14C]-aminopyrine uptake was inhibited by IL-1 beta in a dose-dependent manner.

CONCLUSIONS

Increased production of IL-1 beta caused by H. pylori infection is possibly involved in the inhibition of acid secretion in enlarged fold gastritis.

Mechanisms involved in Helicobacter pylori-induced interleukin-8 production by a gastric cancer cell line, MKN45

Accumulating evidence suggests an important role of interleukin-8 (IL-8) in Helicobacter pylori infection-associated chronic atrophic gastritis and peptic ulcer. We observed in this study that a gastric cancer-derived cell line, MKN45, produced a massive amount of IL-8 upon coculture with live H. pylori but not with killed H. pylori, H. pylori culture supernatants, or live H. pylori separated by a permeable membrane, indicating that IL-8 production requires a direct contact between the cells and live bacteria. Moreover, the tyrosine kinase inhibitor herbimycin but neither a protein kinase C inhibitor (staurosporine) nor a protein kinase A inhibitor (H89) inhibited IL-8 production by MKN45 cells cocultured with live bacteria, suggesting the involvement of a tyrosine kinase(s) in H. pylori-induced IL-8 production. In addition, coculture of H. pylori induced IL-8 mRNA expression in MKN45 cells and an increase in luciferase activity in cells which were transfected with a luciferase expression vector linked with a 5'-flanking region of the IL-8 gene (bp -133 to +44), indicating that the induction of IL-8 production occurred at the transcriptional level. This region contain three cis elements important for induction of IL-8 gene expression: AP-1 (-126 to -120 bp), NF-IL6 (-94 to -81 bp), and NF-kappaB (-80 to -70 bp) binding sites. Mutation of the NF-kappaB binding site abrogated completely the induction of luciferase activity, whereas that of the AP-1 site partially reduced the induction. However, mutation of the NF-IL6 binding site resulted in no decrease in the induction of luciferase activity. Moreover, specific NF-kappaB complexes were detected in the nuclear proteins extracted from MKN45 cells which were infected with H. pylori. Collectively, these results suggest that H. pylori induced the activation of NF-kappaB as well as AP-1, leading to IL-8 gene transcription.

Helicobacter pylori lipopolysaccharide inhibits acid secretion in pylorus-ligated conscious rats

To examine the effect of Helicobacter pylori lipopolysaccharide on gastric secretion, the present study was carried out using pylorus ligated conscious rats. Intraperitoneal administration of Helicobacter pylori lipopolysaccharide significantly inhibited gastric acid secretion (4 hr) in a dose-dependent manner (0.033-1.0 mg/rat). The Helicobacter pylori lipopolysaccharide (1 mg/rat)-induced acid inhibition was still observed 8 hr after injection. Gastric acid secretion (4 hr) was compared in the rats that had received intraperitoneal administration of 1 mg/rat dose of Helicobacter pylori lipopolysaccharide or saline alone 24 hr before. There was no significant difference in gastric acid secretion between the saline- and H. pylori lipopolysaccharide-treated rats. These results suggest for the first time that H. pylori lipopolysaccharide may inhibit acid production, and this acid inhibition may be long-lasting. It is also demonstrated that this anti-secretory action of H. pylori lipopolysaccharide has a reversible effect on gastric secretion. All these results suggest that H. pylori lipopolysaccharide might be involved in the low acid secretory function seen in patients with acute H. pylori infection.

Cure of Helicobacter pylori infection improves gastric acid secretion in patients with corpus gastritis

BACKGROUND

For more than 30 years it has been known that gastric acid secretion is inversely related to the extent and severity of corpal gastritis. We therefore evaluated the effect of cure of Helicobacter pylori infection on basal and pentagastrin-stimulated acid secretion.

METHODS

Basal acid output (BAO) and maximal acid output (MAO) were assessed in 11 H. pylori-infected dyspeptic patients (8 women and 3 men; mean age, 28 years) before and after successful anti-H. pylori therapy.

RESULTS

The gastritis index was significantly lower after therapy and was associated with an increase in both BAO and MAO after cure of the H. pylori infection (BAO from 0.3 mmol/h and MAO from 4.8 mmol/h to 19 mmol/ h). Basal and stimulated acid concentrations also increased (29.1 +/- 36.6 to 54 +/- 31 mmol/l and 72.5 +/- 46 to 120.1 +/- 30 mmol/l, respectively, for basal and stimulated acid concentrations; P < 0.05 for peak and MAO, P = 0.07 for BAO).

CONCLUSION

Gastric acid secretion increased into the normal range after successful treatment of H. pylori infection, suggesting that gastric function can recover to normal or almost normal after cure of H. pylori infection.

Helicobacter pylori inhibits the secretory activity of gastric parietal cells in patients with chronic gastritis. An ultrastructural study

BACKGROUND

Previous in vitro studies suggested that Helicobacter pylori may inhibit the acid secretion of gastric parietal cells. The aim of this study was to investigate ultrastructurally the influence of H. pylori infection on the gastric parietal cell function in vivo.

METHODS

This study comprised 28 patients with chronic gastritis. Biopsy specimens were taken from the gastric body in all cases and examined by electron microscopy. Gastric parietal cells were counted in each ultrathin section and classified into secretory and non-secretory types. The pH of the gastric juice was also measured in all patients.

RESULTS

The number of parietal cells in the secretory phase was significantly lower in H. pylori-infected (n = 16) patients than in those (n = 12) without H. pylori infection. The intragastric pH was significantly higher in patients with H. pylori-associated gastritis than in those without H. pylori infection. Parietal cells in secretory phase tended to decrease in proportion to the activity of the gastric mucosal inflammation.

CONCLUSIONS

The results of this investigation suggests that H. pylori-associated gastritis is related to a decreased secretory activity of the gastric parietal cells.

T-cell, antibody, and cytokine responses to homologs of the 60-kilodalton heat shock protein in Helicobacter pylori infection

For Helicobacter pylori, the hsp60 heat shock protein encoded by hspB is being considered as a potential candidate for subunit vaccines. We investigated the humoral and cellular responses to H. pylori hsp60 and its cross-reactivity with the homologous Mycobacterium bovis p65 protein and autologous human hsp60 protein. H. pylori-infected persons had significantly higher levels than uninfected persons of serum immunoglobulin G antibodies recognizing H. pylori hsp60, but not M. bovis p65 or human hsp60, as determined by enzyme-linked immunosorbent assay. In contrast, immunoblotting demonstrated cross-reactivity of H. pylori hsp60 with human hsp60. T-cell recognition of H. pylori hsp60 was found in both infected and uninfected subjects, and there was no recognition of human hsp60. T cells from infected and uninfected subjects that had been activated in response to H. pylori hsp60 or M. bovis p65 were phenotypically similar but appeared to secrete different levels of gamma interferon and interleukin-10. These results demonstrate an apparent difference in the epitopes recognized by the T and B cells responding to H. pylori hsp60 in H. pylori-infected persons. In contrast to the T-cell responses, which were highly variable in all subjects and showed no recognition of autologous proteins, a specific B-cell response that may have cross-reactivity to human hsp60 is evident in some infected subjects.

Helicobacter pylori induces an array of pro-inflammatory cytokines in human gastric epithelial cells: quantification of mRNA for interleukin-8, -1 alpha/beta, granulocyte-macrophage colony-stimulating factor, monocyte chemoattractant protein-1 and tumour necrosis factor-alpha

Despite the fact that Helicobacter pylori is known to be non-invasive, mucosal infiltration of inflammatory cells have been observed in the gastric mucosa. The exact pathogenesis of such an inflammatory reaction has not been well defined. We explored the repertoire of cytokine genes expressed in human gastric epithelial cells in response to coculture with H. pylori. After gastric epithelial cells, SNU-5 and KATO III, were infected with H. pylori, expression of several cytokine genes was assessed using quantitative reverse transcription polymerase chain reaction. Interleukin (IL)-8, -1 alpha and -1 beta mRNA were expressed in both gastric epithelial cells throughout the entire infection period. In SNU-5, IL-1 alpha and IL-8 mRNA were expressed at 1 h, reached a peak level at 4 h and then decreased. Interleukin-1 beta mRNA was expressed less frequently than IL-1 alpha, or IL-8 mRNA. In SNU-5 cells, granulocyte-macrophage colony-stimulating factor (GM-CSF), monocyte chemoattractant protein-1 (MCP-1), and tumour necrosis factor-alpha (TNF-alpha) mRNA were expressed at 9 h, but was not expressed in KATO III. Gene expression paralleled the amount of IL-8 protein measured by enzyme-linked immunoabsorbent assay (ELISA). Interleukin-8 mRNA expression was not observed in KATO III cells infected with Campylobacter fetus ssp. fetus, Campylobacter jejuni or Escherichia coli. IL-8 mRNA expression was increased not only in gastric epithelial cells but also in non-gastric cells infected with H. pylori. These results suggest that an inflammatory reaction induced by H. pylori may be initially triggered by an array of pro-inflammatory cytokines expressed by infected gastric epithelial cells.

Promotion of ulcerative duodenitis in young ferrets by oral immunization with Helicobacter mustelae and muramyl dipeptide

BACKGROUND

The purpose of this study was to determine whether oral immunization of ferret kits with a whole-cell sonicate of Helicobacter mustelae lysate (Hml) and the adjuvant muramyl dipeptide (MDP) would reduce the incidence of natural colonization with H. mustelae and the extent of Helicobacter-associated gastritis by enhancing the host mucosal immune response.

MATERIALS AND METHODS

Between the ages of 4 and 11 weeks, 44 ferret kits were gavaged with Hml and various doses of MDP. The extent of gastritis and duodenitis and the immune response to H. mustelae were evaluated.

RESULTS

All kits became colonized naturally with H. mustelae and the majority developed mild to severe gastritis and duodenitis. Kits that received Hml with MDP developed significantly greater inflammation of the gastric antrum and duodenum, as compared to kits vaccinated with Hml alone. Vaccination with Hml and 50 micrograms of MDP was associated with severe lesions in the proximal duodenum characterized by accumulation of mononuclear inflammatory cells, mucosal erosion, and ulceration. Although serum antibody specific for H. mustelae in 4-week-old kits was approximately 50% of adult levels, a finding attributable to passively acquired maternal antibody, both systemic and mucosal antibody levels became depressed over time despite oral vaccination. The humoral immune response was sufficiently low to prevent detection of any significant dose effect of MDP on antibody levels among experimental groups.

CONCLUSIONS

Oral vaccination of young ferrets with Hml and 50 micrograms MDP increased the risk of Helicobacter-associated mucosal ulceration in the proximal duodenum, which was associated with low humoral (but significant cell-mediated) immune responses to H. mustelae. In retrospect, the frequency of vaccination may have suppressed the systemic humoral immune response, thereby promoting mucosal damage by H. mustelae. The 50-microgram dose of MDP enhanced the cell-mediated immune response, which indirectly contributed to development of severe lesions. The increased frequency of mucosal damage associated with this vaccination regimen enhances the value of the ferret model for studying duodenal ulceration secondary to Helicobacter infection.

Analysis of interleukin-8 secretion induced by Helicobacter pylori from the gastric epithelial cell line MKN45: a mechanism independent of the intensity of cytotoxicity

Interleukin (IL)-8, a potent chemoattractant and activator of neutrophils, has been implicated to have a major role in the pathogenesis of gastric mucosal injury by Helicobacter pylori infection. We examined the relationship between cytotoxicity and IL-8 secretion induced by H. pylori. Furthermore, whether the vacuolating cytotoxin of H. pylori mediates IL-8 secretion from gastric epithelial cell lines was examined. Among the inflammatory cytokines, messages for IL-6, IL-8 and transforming growth factor-beta 1 were produced by gastric cancer (MKN45) cells in response to exposure to the cytotoxic strain of H. pylori. MKN45 incubated with the viable cytotoxic strain of H. pylori secreted IL-8. In contrast, the supernatant of neither the cytotoxic nor the non-cytotoxic strain induced IL-8 secretion. There was no correlation between IL-8 secretion and the intensity of cytotoxicity. In conclusion, these findings suggest that IL-8 secretion from MKN45 induced by H. pylori is mediated by factors other than cytotoxicity.

Pathophysiology of Helicobacter pylori-induced gastritis and peptic ulcer disease

Helicobacter pylori causes persistent infection and inflammation in the human stomach, yet only a small fraction of persons harboring this organism develop peptic ulcer disease. An important question is why this variation in infection outcome exists. Recent studies have demonstrated that H pylori isolates possess substantial phenotypic and genotypic diversity that may engender differential host inflammatory responses that influence clinical outcome. Further investigation in this field may help to define which H pylori-infected persons bear the highest risk for subsequent development of peptic ulcer disease, and thus enable physicians to focus eradication therapy.

Consequences of attachment of Helicobacter pylori to gastric cells

Helicobacter pylori, a human pathogen and type 1 carcinogen, causes gastritis, gastric ulcers and gastric cancer. In vivo, H pylori colonizes only gastric surface cells from the antral and fundal regions of the stomach, and heterotopic or metaplastic gastric epithelium present within the esophagus and duodenum. This review summarizes what is known about the association and consequences of attachment between H pylori and gastric cells in vitro, and compares this to the findings demonstrated in vivo. It has been shown that attachment of H pylori to gastric cells results in cup and pedestal formation and cytoskeleton rearrangement similar to that described for enteropathogenic Escherichia coli. Attachment of H pylori induces additional cellular changes in the host cell, including cytokine responses and induction of signal transduction pathways.

Expression of mRNA for interferon-gamma, interleukin-10, and interleukin-12 (p40) in normal gastric mucosa and in mucosa infected with Helicobacter pylori

BACKGROUND

We studied the mRNA expressions of interferon-gamma (IFN-gamma), interleukin-10 (IL-10), and IL-12 in gastric biopsy and blood samples from patients with and without Helicobacter pylori infection, by reverse-transcription polymerase chain reaction (RT-PCR).

METHODS

RT-PCR was performed on total RNA preparations, and the expressed mRNA were semiquantitated on the basis of band intensities on Southern blots.

RESULTS

In gastric mucosa the expression of IFN-gamma and IL-10 was found in most patients with and without H. pylori infection, whereas IL-12 was found in most of the infected ones. The level of IFN-gamma and IL-10 did not differ between groups, whereas the IL-12 level was significantly higher in those with H. pylori infection. In the blood IFN-gamma expression was found in most samples, with higher level in patients with gastritis than in normals. Few blood samples (33%) had IL-12, and none had IL-10.

CONCLUSION

IFN-gamma and IL-10 expressions in healthy mucosa may indicate a biologic role in a healthy state. IL-12 expression in mucosa was related to the presence of bacterial stimulant and therefore resembles proinflammatory cytokines.

Expression of the human cell surface glycoconjugates Lewis x and Lewis y by Helicobacter pylori isolates is related to cagA status

Monoclonal antibodies were used in an enzyme-linked immunosorbent assay for the detection of human Lewis immunodeterminants in the lipopolysaccharide of Helicobacter pylori. In 94 H. pylori isolates, expression of Lewis(x) (Le(x)) and Le(y) was a stable phenotypic marker independent of the growth medium and cell age; 46 (49%) of the isolates expressed both and 34 (36%) of the isolates expressed either Le(x) or Le(y); 14 (15%) were negative for both determinants. Twelve (13%) isolates expressed Le(b), 3 (3%) expressed Le(a), and 2 (2%) expressed sialyl-Le(x). H. pylori isolates positive for both Le(x) and Le(y) were predominantly cagA+ (P < 0.001) and possessed the s1 signal sequence (P < 0.05) and the m1 midregion type (P = 0.033) of vacA. Isogenic mutants of H. pylori CPY3401 were created by interruption of the cagA, picB, or ureA gene. The cagA-ablated strain (but not the picB- and ureA-ablated mutant strains) had significantly (P < 0.01) diminished expression of Le(y) compared with that of the wild-type strain; for all four strains, expression of Le(x) was similar. In conclusion, 89% of H. pylori isolates express Le determinants in their lipopolysaccharide, mimicking human cell surface glycoconjugates. Strong expression of Le(x) and Le(y) by cagA+ isolates could counterbalance their enhanced proinflammatory activities and thereby facilitate persistence.

Helicobacter pylori infection enhances mucosal interleukin-1 beta, interleukin-6, and the soluble receptor of interleukin-2

It is thought that Helicobacter pylori colonization of the gastric mucosa might stimulate the production of several cytokines, which might trigger and maintain the gastric inflammation associated with Helicobacter pylori infection. In the present study we evaluated interleukin-1 beta. interleukin-6, and the soluble receptor of interleukin-2 both in mucosal homogenates and in the sera of Helicobacter pylori-infected (39 cases) and uninfected (40 cases) patients to investigate whether there was any relationship between variations in cytokines and (1) the severity of Helicobacter pylori-associated gastritis or (2) CagA-positive Helicobacter pylori strains. Mucosal, but not serum levels of interleukins-1 and -6 and interleukin-2 receptor were significantly higher in infected than uninfected patients. Serum levels of Helicobacter pylori antibodies were significantly higher in infected than uninfected patients. These levels correlated with mucosal interleukin-1 beta. The degree of antral or body inflammatory grade was higher in infected than in uninfected patients; cytokines levels were higher in patients with high-grade gastritis, most of whom were Helicobacter pylori positive. Patients infected with CagA-positive strains also had higher levels of interleukin-1 beta, but not of interleukin-2 receptor or interleukin-6. In conclusion. Helicobacter pylori infection results in a local increase in interleukins-1 beta and -6 and interleukin-2 receptor associated with high-grade mucosal inflammation. Interleukin-1 beta seems to favor anti-Helicobacter pylori antibody production, and mucosal levels are enhanced mainly in patients infected with cytotoxic Helicobacter pylori strains.

Helicobacter pylori and ulcerogenesis

The dictum "no acid-no ulcer" had, in the past, summarized the thinking concerning the pathogenesis of peptic ulcer disease. It is now recognized that infection with Helicobacter pylori is the major causal factor leading to both duodenal and gastric ulceration. Infection is associated with many of the acid secretory abnormalities that have traditionally characterized peptic ulcer disease; indeed, acid secretory physiology returns to normal following bacterial eradication. Since not all individuals infected with H. pylori develop ulcers, host susceptibility, bacterial virulence, and/or specific environmental factors must determine the response to infection and the ultimate clinical outcome. The relative importance of these factors and their complex interactions remain to be determined. H. pylori infection produces tissue damage indirectly because the organism does not directly invade gastroduodenal tissue. A variety of bacterial enzymes, toxins, and inflammatory mediators produced in response to bacterial colonization challenge the integrity of host mucosal defenses. In a susceptible host, breached defenses render epithelium more vulnerable to acid injury and ulcer development. Eradication of H. pylori leads to rapid ulcer healing and reversal of tissue injury, thereby obviating ulcer recurrence.

Characterization of lymphocytic infiltrates in Helicobacter pylori-associated gastritis

BACKGROUND

This study evaluated the specific subset composition of lymphocytes present in Helicobacter pylori-associated gastritis (HAG), since reports so far have led to inconclusive and conflicting results.

METHODS

Endoscopic biopsy specimens from 56 patients were studied by quantitative immunohistochemistry using monoclonal antibodies against the lymphocyte markers CD3, CD22, CD4, CD8, CD45RO, CD1O3, TCR alpha/beta, and TCR gamma/delta. Lamina propria and intraepithelial compartments were evaluated separately. Grade, activity, and density of bacterial colonisation were assessed histologically and with Warthin-Starry stain.

RESULTS

Evaluation showed a significant increase in CD4+, CD45RO+, TCR alpha/beta+ activated lamina propria lymphocytes in HAG which correlated with grade and activity of gastritis and degree of bacterial colonisation, whereas subsets of intraepithelial lymphocytes did not change significantly. TCR gamma/delta+ T cells were not found to be increased in HAG.

CONCLUSIONS

Selective expansion of CD4+, CD45RO+ memory-type T cells could reflect an antigen-specific and/or chemokine-mediated effect in HAG. Locally produced CC chemokines such as RANTES have been detected in HAG.

Successful eradicating treatment of Helicobacter pylori in patients with chronic gastritis: gastric levels of cytokines, epidermal growth factor and polyamines before and after therapy

In 10 patients with Helicobacter pylori (HP) positive chronic gastritis, gastric mucosal content of interleukin (IL)-1 beta, IL-8, Transforming Growth Factor (TGF)-beta 1, Epidermal Growth Factor (EGF) and Polyamines (putrescine, spermine and spermidine) was evaluated before and after eradicating treatment. Histologically, in all patients eradication of HP was accompanied by a marked reduction of the inflammatory infiltrate. At the same time, at the end of the therapeutical regimen, elevated levels of IL-1 beta, IL-8, TGF-beta 1, putrescine and spermidine/spermine ratio significantly dropped, while EGF mucosal content, significantly increased. Results are discussed in terms of the reciprocal role of inflammatory cytokines, growth factors and polyamines in the evolution of the HP-associated chronic gastritis.

Immune and inflammatory responses to Helicobacter pylori infection

The gastroduodenal response to chronic Helicobacter pylori infection is characterized by the infiltration of plasma cells, lymphocytes, neutrophils and monocytes into the mucosa. Eradication studies have shown that this inflammatory response represents a specific reaction to the presence of H. pylori. As well as stimulating specific local T and B cell responses and a systemic antibody response, H. pylori infection also induces a local pro-inflammatory cytokine response. Interleukin-8 (IL-8), which is expressed and secreted by gastric epithelial cells, may be an important host mediator inducing neutrophil migration and activation. IL-8 mRNA and protein secretion in gastric epithelial cell lines can be up-regulated by the cytokines tumour necrosis factor-alpha and IL-1 and also by type I strains of H. pylori (expressing the vacuolating toxin and cytotoxin-associated protein, CagA). The gastric epithelium thus plays an active role in mucosal defence. Neutrophil activation and the production of reactive oxygen metabolites will be induced directly by bacterial factors and indirectly via host-derived cytokines, products of complement activation and bioactive lipids. Strain variation in the induction of both IL-8 from epithelial cells and the oxidative burst in neutrophils may be an important factor determining the extent of mucosal injury. There is now increasing evidence from both in vivo and in vitro studies that type I strains induce an enhanced inflammatory response and mucosal damage. An understanding of the bacterial mediators of mucosal inflammation is important in elucidating the role of chronic H. pylori infection in the pathogenesis of gastroduodenal disease.

Helicobacter pylori infection and dyspepsia

It has proved remarkably difficult to confirm or refute an association between Helicobacter pylori-induced gastritis and non-ulcer dyspepsia for several reasons. Dyspepsia has not been defined adequately and current definitions include a variety of symptoms that probably reflect a number of underlying pathophysiological processes. Dyspepsia is a symptom complex, rather than a specific disease entity, and cannot be easily identified. There are probably many causes of dyspepsia, and if H. pylori does cause symptoms, it may produce different symptoms in different people. However, little is known about variations in host susceptibility and H. pylori virulence, or their potential effect on symptomatology. In addition, the mechanisms responsible for dyspeptic symptoms are unknown, regardless of whether or not there is concomitant H. pylori-induced inflammation. A possible aetiological role for H. pylori in dyspepsia has been sought in three major types of study. Epidemiology studies have suggested that H. pylori is not a major cause of non-ulcer dyspepsia. However, both dyspepsia and H. pylori are common, and the studies cannot account for many of the variables detailed above. Pathophysiological studies have commonly reported a variety of motor and sensory 'abnormalities' in association with H. pylori, but none has been confirmed or reproduced. In eradication studies, there is continuing debate as to whether dyspeptic symptoms diminish with treatment. This is partly because of the high placebo-response rate and partly because many treatment regimens have not cured the infection. Suppression of bacterial growth may not affect symptoms significantly, if they are due to mucosal inflammation, and symptom resolution may take many weeks or months following cure of H. pylori and the associated gastritis. Recent findings have shown that symptom reduction is more evident 1 year after eradication of H. pylori than after 4 weeks. There is a continuing and urgent need for well-designed studies to assess the long-term effect of H. pylori and its cure on both gastrointestinal function and dyspeptic symptoms.

Expression of cytokine mRNA in gastric mucosa with Helicobacter pylori infection

BACKGROUND

We have studied the cytokine production patterns in gastric mucosal biopsy specimens with and without the Helicobacter pylori infection, using a reverse transcription-polymerase chain reaction (RT-PCR) method capable of detecting low levels of specific mRNA.

METHODS

Total RNA was prepared from biopsy specimens with the acid guanidinium thiocyanate-phenol-chloroform method. cDNA was synthesized by M-MLV RTase and amplified using the oligonucleotide primers specific for interleukin-1 beta (IL-1beta), IL-2, IL-3, IL-4, IL-5, IL-6, IL-7, IL-8, IL-9, IL-10, tumor necrosis factor-alpha (TNF-alpha), interferon-alpha (IFN-alpha), IFN-beta, and IFN-gamma by PCR methods.

RESULTS

Although IL-1 beta and IFN-gamma mRNA were detected in most specimens, IL-2, IL-3, IL-4, IL-5, IL-9, TNF-alpha, and IFN-beta mRNA were not detected at all. The expressions of IL-7 and IL-8 mRNA were significantly higher in H. pylori-positive gastritis than in H. pylori-negative normal controls. There was a significant correlation between the expression of IL-8 mRNA and the severity of gastritis both in the antrum and in the corpus. On the other hand, there was a significant correlation between the expression of IL-7 mRNA and the severity of gastritis only in the corpus.

CONCLUSIONS

These findings suggest that some cytokines, especially IL-7 and IL-8, play some roles in H. pylori-associated gastritis.

Pathogenic mechanisms

Research is asking how H. pylori causes diseases, and also why the same bacteria produces different conditions in different persons. The process involves bacterial factors and the host's response. Some bacterial factors such as urease are produced by all strains of H. pylori. This enzyme may damage the gastric epithelium by practically releasing ammonia. Other bacterial factors such as vacuolating toxin are only produced by some strains, and these strains are more likely to cause ulcers or cancer. The host's response has been studied by physiologists, immunologists, and histologists, but the separation of systems is artificial. For example, physiologists find that H. pylori stops gastric D-cells from expressing somatostatin normally, which impairs reflex inhibition of acid secretion, but the D-cell malfunction is probably due to inflammatory factors. In H. pylori gastritis, the gastric epithelial cells behave like immunocytes and express class II molecules and cytokines such as interleukin-8. The patient's histological response to H. pylori is quite closely related to the disease outcome. Patients who respond by developing gastric atrophy are more likely to get gastric ulcers or stomach cancer, but patients whose gastric corpus remains healthy tend to secrete more acid and develop duodenal ulcers, particularly if they have gastric metaplasia in their duodenum. Studies of disease mechanisms provide a valuable insight into the development of these common diseases, and may enable us to identify at-risk groups who particularly merit eradication therapy.

Interleukin-8 response of gastric epithelial cell lines to Helicobacter pylori stimulation in vitro

Gastric infection with Helicobacter pylori activates a mucosal inflammatory response by mononuclear cells and neutrophils that includes expression of cytokines interleukin-1 beta (IL-1 beta), IL-6, tumor necrosis factor alpha, and IL-8. In this study, we analyzed the IL-8 response of human gastric cancer cell lines (Kato III, AGS, and MKN28) to H. pylori infection in vitro. IL-8 mRNA expression was detected by reverse transcription-PCR amplification of RNA extracted from epithelial cells after incubation with different H. pylori wild-type and mutant strains, and IL-8 secretion was measured by an enzyme-linked immunosorbent assay. Exposure to viable H. pylori induced IL-8 mRNA and protein synthesis in all three gastric cell lines but not in nongastric epithelial cell lines. Heat-killed H. pylori and a crude cytotoxin preparation did not induce significant IL-8 secretion. IL-8 mRNA peaked between 2 and 4 h postinfection, and IL-8 protein production was maximal 24 h postinfection. Exposure of gastric carcinoma cells to other gastrointestinal bacteria, such as Pseudomonas aeruginosa, Campylobacter jejuni, and Escherichia coli, but not Campylobacter fetus, induced IL-8 synthesis. Wild-type strains that expressed the vacuolating cytotoxin (Tox+) and a cytotoxin-associated gene (cagA) product (CagA+) induced significantly more IL-8 than did CagA- Tox- strains. However, there was no decrease in IL-8 induction by isogenic mutants of CagA-, Tox-, or Cag- Tox- strains or by a mutant lacking the urease subunits. These results indicate that exposure to H. pylori and other gram-negative organisms that do not colonize the gastric mucosa induces IL-8 production by gastric carcinoma cells in vitro. Although the CagA+ Tox+ phenotype of H. pylori is associated with enhanced IL-8 production by gastric cell lines, other bacterial constituents are clearly essential.

Stimulation of interleukin-8 production in epithelial cell lines by Helicobacter pylori

Following exposure to Helicobacter pylori cells, epithelial cell lines secreted interleukin-6 (IL-6) and IL-8 but not tumor necrosis factor alpha. Purified IL-6 alone did not stimulate IL-8 production from the cell lines tested, indicating that IL-6 was not an intermediary in IL-8 induction. Enhanced IL-8 secretion occurred in a time- and dose-dependent manner. None of 12 antibiotics tested exhibited a significant effect on IL-8-inducing activity, suggesting that preformed antigens were responsible for stimulating IL-8 secretion in vitro. Live bacterial cells caused the highest level of stimulation. Proteinase-digested and heated (56 or 100 degrees C) cells had significantly reduced stimulatory activities. Purified H. pylori lipopolysaccharide, but not exopolysaccharide, stimulated low-level secretion of IL-8, but only at high concentrations, while a water-extracted H. pylori antigen preparation was strongly stimulatory for HEp-2 cells. No reduction in IL-8-stimulatory activity was observed for H. pylori mutants negative for urease activity, production of a major lipoprotein, and motility. The noncytotoxic strain CCUG 915 stimulated lower IL-8 levels than other isolates. However, the otherwise isogenic cytotoxin-negative mutant 17874 delta vacA (S. H. Phadnis, D. Ilver, L. Janzon, S. Normark, and T. U. Westblom, Infect. Immun. 62:1557-1565, 1994) had the same IL-8-stimulatory ability as the parent strain, suggesting that surface proteins other than the vacuolating cytotoxin are involved in IL-8 stimulation.