Ammonia as an accelerator of tumor necrosis factor alpha-induced apoptosis of gastric epithelial cells in Helicobacter pylori infection

Protective effect of dietary supplementation of Bupleurum falcatum L saikosaponins on ammonia exposure-induced ileum injury in broilers

Ammonia (NH3) at a high concentration has been recognized as a highly poisonous pollutant affecting both air and water quality. NH3, as a stimulus, exerts negative impact on broiler growth and production, but the molecular mechanisms are not clear yet. This study was designed to evaluate the effects of dietary supplementation of Bupleurum falcatum L saikosaponins (SP) on the growth and ileum health status in broilers exposed to NH3. Day-old Arbor Acers broilers (n = 480) were randomly allocated into 1 of 4 treatments. The main factors were dietary SP supplementation (0 or 80 mg/kg of diet) and NH3 challenge (with or without 70 ± 5 ppm NH3). The data of growth, intestinal morphology, and mRNA expression related to ileal function were collected from broilers exposed to NH3 for 7 d. Results showed that NH3 remarkably suppressed growth performance and intestinal development as well as induced biological injuries in the ileum of broilers, resulting from oxidative stress, mucous barrier damage, and immune dysfunction as well as upregulated apoptosis. These negative effects of NH3 were alleviated by the SP supplement. In conclusion, dietary supplementation of SP may be helpful in alleviating the detrimental effects of NH3 on the ileum development in broilers.

Implications of the Human Gut-Brain and Gut-Cancer Axes for Future Nanomedicine

Recent clinical and pathological evidence have implicated the gut microbiota as a nexus for modulating the homeostasis of the human body, impacting conditions from cancer and dementia to obesity and social behavior. The connections between microbiota and human diseases offer numerous opportunities in medicine, most of which have limited or no therapeutic solutions available. In light of this paradigm-setting trend in science, this review aims to provide a comprehensive and timely summary of the mechanistic pathways governing the gut microbiota and their implications for nanomedicines targeting cancer and neurodegenerative diseases. Specifically, we discuss in parallel the beneficial and pathogenic relationship of the gut microbiota along the gut-brain and gut-cancer axes, elaborate on the impact of dysbiosis and the gastrointestinal corona on the efficacy of nanomedicines, and highlight a molecular mimicry that manipulates the universal cross-β backbone of bacterial amyloid to accelerate neurological disorders. This review further offers a forward-looking section on the rational design of cancer and dementia nanomedicines exploiting the gut-brain and gut-cancer axes.

The influence of indigestible protein on broiler digestive tract morphology and caecal protein fermentation metabolites

Indigestible dietary protein fermentation products have been suggested to negatively influence broiler performance due to their impact on health and digestive tract morphology. This study evaluated the digestive tract morphology and caecal protein fermentation metabolites of broiler fed 3 dietary protein levels (24%, 26% and 28%) with low or high indigestible protein (LIP, HIP). Two completely randomized 3 × 2 factorial trials were conducted with protein level (PL) and indigestible protein (IDP) as the main factors. In both trials, birds received six diets (24-LIP, 24-HIP, 26-LIP, 26-HIP, 28-LIP and 28 HIP) formulated with no medication. On day 5, trial 1 birds were vaccinated with Coccivac-B52, while trial 2 received no vaccine. Tissue and caecal samples were collected and caecal contents analysed for fermentation metabolites. Differences were considered significant when p ≤ .05. The LIP treatment caecal content in trial 1 at 14 days had greater histamine, agmatine and cadaverine levels, while HIP diets resulted in increased serotonin, tryptamine and spermidine. Histamine, serotonin and tryptamine at day 28 were not affected by IDP, and ammonia was not affected by treatments at day 14 or day 28. At day 14, HIP birds had lower total short-chain fatty acids, higher caecal pH and heavier pancreas, proventriculus, gizzard, jejunum and ileum weights. The same effects of IDP found in trial 1 were observed for histamine, agmatine, cadaverine, serotonin, tryptamine and spermidine at day 21 in trial 2. Trial 2 had a PL-by-IDP interaction influencing tyramine, spermidine (28-LIP > 24-LIP) and spermine with values increasing with PL for LIP diets and remaining constant for HIP diets. An interaction between PL and IDP was found for ammonia level and was similar to interactions for biogenic amines. In conclusion, dietary PL and IDP influence broiler caecal protein fermentation metabolites and those effects varied with coccidiosis vaccination and rearing environment.

Haptoglobin and C-Reactive Protein-Non-specific Markers for Nursery Conditions in Swine

A quality concept for production in the pork market includes granting a good health status of pigs from birth to slaughter. This concept is a precondition for animal welfare as well as reducing antibiotic usage in farm animals. The demand for fighting bacterial antimicrobial resistance in humans, animals, and in the environment is one driving force for the development of innovative technical solutions to improve husbandry. Maintenance of a good health status in pigs depends on early detection of a disturbance in homeostasis in critical phases of life. This can be measured by non-specific biomarkers as acute phase proteins. In this project, husbandry conditions and health status in nursery pigs were monitored in an autumn and winter nursery period from weaning to the end of nursery in two compartments with 180 pigs each. It was investigated whether a slight modification in indoor climate achieved by a new ammonia sensory technology coupled with the electronic control unit of the forced ventilation system ensuring ammonia levels lower than 5 ± 3 ppm in one compartment led to a better health status in piglets in comparison to the control compartment. In the examined nursery periods in different seasons, ammonia concentrations in the experimental compartment were significantly lower than in the control compartment, thus proving the functionality and efficacy of the technical system. Production parameters as feed conversion rate and average daily weight gain were slightly improved in the experimental compartment without implementing other measures. Multifactorial analysis of variance resulted in a significant influence of season, daily quarter, and compartment on ammonia concentration. The challenge to preserve a high health status of piglets also during suboptimal outside climate in the transitional season was reflected by an increase in the acute-phase proteins haptoglobin (Hp) and C-reactive protein (CRP) in autumn compared to winter. The seasonal influence on concentrations of CRP and Hp superimposed potential influences of the climate modification. New technological concepts to reduce noxious gases and dust in the animal environment as well as emissions, which in parallel guarantee optimal temperatures also during extreme weather conditions, can be evaluated by clinical data in combination with biomarkers.

Relationship between ureB Sequence Diversity, Urease Activity and Genotypic Variations of Different Helicobacter pylori Strains in Patients with Gastric Disorders

Association of the severity of Helicobacter pylori induced diseases with virulence entity of the colonized strains was proven in some studies. Urease has been demonstrated as a potent virulence factor for H. pylori. The main aim of this study was investigation of the relationships of ureB sequence diversity, urease activity and virulence genotypes of different H. pylori strains with histopathological changes of gastric tissue in infected patients suffering from different gastric disorders. Analysis of the virulence genotypes in the isolated strains indicated significant associations between the presence of severe active gastritis and cagA+ (P = 0.039) or cagA/iceA1 genotypes (P = 0.026), and intestinal metaplasia and vacA m1 (P = 0.008) or vacA s1/m2 (P = 0.001) genotypes. Our results showed a 2.4-fold increased risk of peptic ulcer (95% CI: 0.483-11.93), compared with gastritis, in the infected patients who had dupA positive strains; however this association was not statistically significant. The results of urease activity showed a significant mean difference between the isolated strains from patients with PUD and NUD (P = 0.034). This activity was relatively higher among patients with intestinal metaplasia. Also a significant associa-tion was found between the lack of cagA and increased urease activity among the isolated strains (P = 0.036). While the greatest sequencevariation of ureB was detected in a strain from a patient with intestinal metaplasia, the sole determined amino acid change in UreB sequence (Ala201Thr, 30%), showed no influence on urease activity. In conclusion, the supposed role of H. pylori urease to form peptic ulcer and advancing of intestinal metaplasia was postulated in this study. Higher urease activity in the colonizing H. pylori strains that present specific virulence factors was indicated as a risk factor for promotion of histopathological changes of gastric tissue that advance gastric malignancy.

An infrared spectroscopy method to detect ammonia in gastric juice

Ammonia in gastric juice is considered a potential biomarker for Helicobacter pylori infection and as a factor contributing to gastric mucosal injury. High ammonia concentrations are also found in patients with chronic renal failure, peptic ulcer disease, and chronic gastritis. Rapid and specific methods for ammonia detection are urgently required by the medical community. Here we present a method to detect ammonia directly in gastric juice based on Fourier transform infrared spectroscopy. The ammonia dissolved in biological liquid samples as ammonium ion was released in air as a gas by the shifting of the pH equilibrium of the ammonium/ammonia reaction and was detected in line by a Fourier transform infrared spectroscopy system equipped with a gas cell for the quantification. The method developed provided high sensitivity and selectivity in ammonia detection both in pure standard solutions and in a simulated gastric juice matrix over the range of diagnostic concentrations tested. Preliminary analyses were also performed on real gastric juice samples from patients with gastric mucosal injury and with symptoms of H. pylori infection, and the results were in agreement with the clinicopathology information. The whole analysis, performed in less than 10 min, can be directly applied on the sample without extraction procedures and it ensures high specificity of detection because of the ammonia fingerprint absorption bands in the infrared spectrum. This method could be easily used with endoscopy instrumentation to provide information in real time and would enable the endoscopist to improve and integrate gastroscopic examinations.

Proteome changes in the small intestinal mucosa of broilers (Gallus gallus) induced by high concentrations of atmospheric ammonia

Background

Ammonia is a well-known toxicant both existing in atmospheric and aquatic system. So far, most studies of ammonia toxicity focused on mammals or aquatic animals. With the development of poultry industry, ammonia as a main source of contaminant in the air is causing more and more problems on broiler production, especially lower growth rate. The molecular mechanisms that underlie the negative effects of ammonia on the growth and intestine of broilers are yet unclear. We investigated the growth, gut morphology, and mucosal proteome of Arbor Acres broilers (Gallus gallus) exposed to high concentrations of atmospheric ammonia by performing a proteomics approach integrated with traditional methods.

Results

Exposure to ammonia interfered with the development of immune organ and gut villi. Meanwhile, it greatly reduced daily weight gain and feed intake, and enhanced feed conversion ratio. A total of 43 intestinal mucosal proteins were found to be differentially abundant. Up-regulated proteins are related to oxidative phosphorylation and apoptosis. Down-regulated proteins are related to cell structure and growth, transcriptional and translational regulation, immune response, oxidative stress and nutrient metabolism. These results indicated that exposure to ammonia triggered oxidative stress, and interfered with nutrient absorption and immune function in the small intestinal mucosa of broilers.

Conclusions

These findings have important implications for understanding the toxic mechanisms of ammonia on intestine of broilers, which provides new information that can be used for intervention using nutritional strategies in the future.

Electronic supplementary material

The online version of this article (doi:10.1186/s12953-015-0067-4) contains supplementary material, which is available to authorized users.

N-methyl D-aspartate channels link ammonia and epithelial cell death mechanisms in Helicobacter pylori Infection

BACKGROUND & AIMS

Helicobacter pylori infection is a risk factor for gastric cancer. Ammonia/ammonium (A/A) is a cytotoxin generated by H pylori that kills gastric epithelial cells. We investigated whether A/A cytotoxicity occurs by activating N-methyl d-aspartate (NMDA) channels, which results in Ca(2+) permeation and epithelial cell death.

METHODS

Gastric epithelial cells were cultured to confluence and then incubated with A/A and NMDA channel or cell signaling antagonists. Cells were incubated with wild-type H pylori or mutant strains that do not produce A/A. Changes in intracellular Ca(2+) were examined in living cells by confocal microscopy. Biochemical and histochemical techniques were used to examine the relationship between A/A-induced cell death and intracellular levels of Ca(2+).

RESULTS

A/A increased Ca(2+) permeation in gastric epithelial cells; the increase was blocked by NMDA receptor and cell signaling antagonists. Wild-type, but not mutant H pylori, also caused extensive Ca(2+) permeation of gastric epithelial cells, which was blocked when NMDA-receptor expression was repressed. Ca(2+) that entered cells was initially cytoplasmic and activated proteases. Later, the Ca(2+) was sequestered to cytoplasmic vacuoles that are dilatations of the endoplasmic reticulum. Inositol-3-phosphate-dependent release of Ca(2+) from the endoplasmic reticulum and protease activity damaged mitochondria, reduced levels of adenosine triphosphate, and transcriptionally up-regulated cell death effectors. Expression of the NMDA receptor was altered in stomachs of mice infected with H pylori.

CONCLUSIONS

A/A affects gastric epithelial cell viability by allowing excessive Ca(2+) permeation through NMDA channels. NMDA channels might thereby regulate cell survival and death pathways during development of gastric cancers associated with H pylori infection.

Is stomach spontaneously ageing? Pathophysiology of the ageing stomach

During ageing, histological and physiological modifications occur in the stomach leading to a confirmed state of gastric frailty defined by a decreased capacity of tissue repairing after mucosa gastric aggression. The process of intrinsic gastric ageing may play a role in inducing abnormalities of gastric epithelial proliferation against injury but, most of the time, pathophysiological modifications observed in older people are the consequences of chronic insults, such as chronic Helicobacter pylori infection, polymedication, especially Proton-pump inhibitors (PPI) and Non-steroidal Anti-inflammatory Drugs (NSAID), and co morbidities. One of the major clinical consequences of the gastric frailty is the higher vulnerability to the occurrence of peptic ulcer disease during ageing. In this review recent data on gastric changes during ageing, focussing especially on histological modifications and motility disorders are summarized.

Helicobacter pylori infection and oesophageal cancer risk: association studies via evidence-based meta-analyses

AIMS

Infection of Helicobacter pylori, a major cause of various gastric diseases, has been reported to play a role in the process of tumorigenesis and progression of gastric carcinoma. Some studies have been devoted to the relationship between H. pylori infection and oesophageal cancer and have yielded conflicting results. Whether infection of H. pylori is a risk factor for this cancer remains uncertain. In this study we aimed to evaluate the association of H. pylori infection with oesophageal cancer risk.

MATERIALS AND METHODS

The associated literature was acquired through deliberate searching and selected based on the established inclusion criteria for publications, then the extracted data were further analysed by systematic meta-analyses.

RESULTS

In total, 195 articles were identified, of which 12 case-control studies concerning oesophageal cancer were selected. Oesophageal adenocarcinoma risk for H. pylori infection was 0.58-fold (95% confidence interval 0.48-0.70) (Z=5.79, P<0.01) compared with the controls. Oesophageal squamous cell carcinoma risk was 0.80-fold (95% confidence interval 0.45-1.43) (Z=0.75, P>0.05) compared with the controls. Compared with CagA-negative H. pylori, CagA-positive H. pylori markedly decreased oesophageal cancer risk.

CONCLUSION

The pooled data suggest infection of H. pylori as a possible preventive factor for oesophageal adenocarcinoma and failed to suggest a significant association between H. pylori infection and oesophageal squamous cell carcinoma.

Possible association of Helicobacter pylori infection with laryngeal cancer risk: an evidence-based meta-analysis

BACKGROUND

Infection with Helicobacter pylori (H. pylori) is a major cause of various gastric diseases and has been reported to play a role in the process of tumorigenesis and progression of gastric carcinoma. However, whether H. pylori infection increases susceptibilities to other cancers is not fully understood. Several studies have been devoted to the relationship between H. pylori infection and laryngeal cancer risk and have yielded conflicting results. In this study, we aimed to evaluate the possible association of H. pylori infection with laryngeal cancer risk.

METHODS

The associated literature was acquired through deliberate searching and selected based on the established inclusion criteria for publications. Extracted data were further analyzed by a systematic meta-analysis.

RESULTS

A total of 15 papers were identified. Of these, five case-control studies were selected. Laryngeal cancer risk for H. pylori infection was 2.03-fold (95% CI=1.28-3.23) (Z=3.00, p<0.01) compared with the controls.

CONCLUSIONS

The pooled data suggest infection with H. pylori as a possible risk factor for laryngeal cancer.

Current management of Helicobacter pylori infections in the elderly

Helicobacter pylori infection is a chronic gastric gram-negative infection that increases with age worldwide. However, the percentage age of H. pylori-positive elderly patients who are tested and treated for their infection remains very low. It is now demonstrated that H. pylori infection induces a whole cascade of events leading to gastric pathologies, such as peptic ulcer diseases, gastric precancerous lesions and gastric cancer. Recent data also demonstrated that H. pylori chronic infection can play a role in gastric aging, appetite regulation and extradigestive diseases, such as Alzheimer's disease, in the elderly. The diagnosis of H. pylori infection remains difficult to realize in the very old population, and the urea breath test obtains the best performance in this population. 1-week proton pump inhibitor-based triple therapy regimens are highly effective and well tolerated in elderly patients, and antibiotic resistance remains very low. Low compliance is the main factor related to treatment failure in this population.

Infection à Helicobacter pylori chez la personne âgée

PURPOSES

Helicobacter pylori (H. pylori) infection is a chronic gastric Gram-negative infection that increases with age. Acquired in childhood, H. pylori infection may induce a whole cascade of events leading to gastric pathologies such as peptic ulcer diseases, gastric precancerous lesions, and gastric lymphomas (MALT). The characteristics of the diagnosis and the treatment of this infection in geriatrics are thus particularly important to take into account.

MAIN POINTS

1) The incidence of gastric and duodenal ulcers and their bleeding complications is increasing in old-aged populations. Clinical signs such as anorexia and malnutrition are proven to be excellent indications for endoscopic explorations in the elderly. NSAID-use and H. pylori infection were shown to be independent and unrelated risk factors for peptic ulcer and gastroduodenal bleeding in elderly subjects; 2) H. pylori infection diagnosis is difficult to realize in the very old population, and the urea breath test is the test which obtain the best performances in this population.

PERSPECTIVES

Recent work showed the part played by H. pylori chronic infection in gastric aging and in appetite regulation in the elderly. Research tasks should be continued in this field in order to better understand the part played by this chronic infection in gastric aging and in other pathologies (i.e. neurological or cardiovascular diseases) in this population.

Effects of lactobacillus on phosphorylated p38 mitogen-activated protein kinase and apoptosis in SGC-7901 cells treated with lipopolysaccharide of Helicobacter pylori

AIM: To investigate effects of lactobacillus bulgaricus (LBG) on the levels of phosphorylated p38 mitogen-activated protein kinase (P-p38MAPK) and apoptosis index (AI) in gastric cancer cell line SGC-7901 treated with lipopolysaccharide of H. pylori Sydney strain 1 (H. pylori SS1-LPS).

METHODS: Human gastric cancer cell line SGC-7901 was treated with H. pylori SS1-LPS at the concentration of 2.5×10³, 2.5×10⁴, 2.5 ×10⁵ EU/L, respectively, after pretreatment for 1 h with 10 mmol/L SB203580 (blocker of p38MAPK) or 1×10¹³ CFU/L LBG. The level of P-p38MAPK was analyzed by immunocytochemistry after 2 h of H. pylori SS1-LPS treatment. The cell activity was detected by MTT assay after 4、5 and 6 h of treatment, and the apoptosis was measured by flow cytometry at the 6^th hour.

RESULTS: H. pylori SS1-LPS inhibited cell activity (0.164 ± 0.028 vs 0.622 ± 0.068, P < 0.05) and up-regulated the level of P-p38MAPK (79.771 ± 1.424 vs 4.075 ± 0.135, P < 0.01) and AI value (10.000% ± 0.510% vs 4.175% ± 0.206%, P < 0.05) in a dose-dependent manner. The level of P-p38MAPK and AI value in SGC-7901 cells were not significantly different between LBG pretreatment group and the controls, and the cell activity and AI value were not markedly different between SB203580 pretreatment group and the controls.

CONCLUSION: H. pylori SS1-LPS may induce the apoptosis of SGC-7901 cells by activating the phosphorylation of p38MAPK, while LBG can prevent H. pylori SS1-LPS-induced apoptosis of SGC-7901 cells by inhibiting the phosphorylation of p38MAPK.

Comparative proteomic analysis ofHelicobacter pylori strains associated with iron deficiency anemia

Helicobacter pylori is known to cause chronic gastritis, peptic ulcer, and gastric cancer, and has also been linked to iron deficiency anemia (IDA). To determine whether H. pylori clinical isolates correlate with the prevalence of H. pylori-associated IDA, we compared the proteomic profiles of H. pylori strains isolated from antral biopsy specimens of H. pylori-positive patients with or without IDA. Fifteen strains, including eight non-IDA and seven IDA strains, were cultured under iron-rich and iron-depleted conditions and then analyzed for protein expression profiles by 2-DE. The distances between two H. pylori strains were determined on the basis of similarities between their expression patterns of 189 protein spots, and a phylogenetic tree was constructed. The results revealed that the IDA strains formed a cluster separate from that of six non-IDA strains, with two non-IDA strains between the clusters. H. pylori strain 26695 was located in the non-IDA cluster. Protein spots displaying similar expression patterns were clustered, and 18 spots predominantly expressed in IDA strains were identified by MALDI-TOF analysis. These data indicate that the non-IDA and IDA strains can be distinguished by their protein expression profiles, suggesting that the polymorphism of H. pylori strains may be one of the factors determining the occurrence of H. pylori-associated IDA.

Effect of Helicobacter pylori eradication in patients with chronic idiopathic thrombocytopenic purpura-a randomized controlled trial

OBJECTIVE

Eradication of Helicobacter pylori was reported to increase the platelet counts in some H. pylori-positive patients with chronic idiopathic thrombocytopenic purpura (cITP). However, the efficacy of the eradication was quite different according to the previous reports. To determine whether H. pylori infection can contribute to cITP, we performed a randomized controlled trial for the first time. In addition, to investigate the possible pathogenic mechanisms and to predict the platelet response after eradication of H. pylori in each cITP patient, several H. pylori virulence factors, the urease activities of the infected H. pylori strains, and the titers of anti-CagA IgG antibodies were analyzed.

METHODS

Patients with cITP underwent gastroscopy and gastric H. pylori infection was confirmed by culture. H. pylori-positive cITP patients were randomly assigned to either the eradication or the non-eradication group. The eradication group received a standard antibiotic therapy for H. pylori. Response to treatment was defined as complete (CR) if the platelet count was above 150x10(3)/microl and partial (PR) if the platelet count increased by more than 50x10(3)/microl above the pretreatment count. The virulence factors were investigated by PCR and PCR-based direct sequencing. Anti-CagA IgG antibody titer of each patient's serum was measured by ELISA.

RESULTS

Of the 36 ITP patients, 25 (69.4%) were positive for H. pylori and eradication was achieved in 84.6% of these patients. The platelet response was significantly different between the eradication group (46.2%) and the non-eradication group (0%). No significant differences were found in clinical factors between the responders and the nonresponders. H. pylori virulence factors and the urease activity were not associated with the response. The titers of anti-CagA antibodies in the responders were significantly higher than those in the nonresponders (p=0.04).

CONCLUSIONS

H. pylori eradication treatment is a favorable therapeutic option for H. pylori-positive patients with cITP. Moreover, an ELISA titer of serum anti-CagA antibody may be a good predictor of platelet recovery, and immunological reaction between platelet and anti-CagA antibodies may have some relation to the pathogenesis of H. pylori-positive patients with cITP.

The antigenic and catalytically active formamidase of Paracoccidioides brasiliensis: protein characterization, cDNA and gene cloning, heterologous expression and functional analysis of the recombinant protein

Paracoccidioides brasiliensis is a well-characterized pathogen of humans. To identify proteins involved in the fungus-host interaction, P. brasiliensis yeast proteins were separated by liquid isoelectric focusing, and fractions were subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blot analysis. Immunoreactive bands were detected with pooled sera of patients with P. brasiliensis infection. A protein species with a molecular mass of 45 kDa was subsequently purified to homogeneity by preparative gel electrophoresis. The amino acid sequence of four endoproteinase Lys-C-digested peptides indicated that the protein was a formamidase (FMD) (E.C. 3.5.1.49) of P. brasiliensis. The complete cDNA and a genomic clone (Pbfmd) encoding the isolated FMD were isolated. An open reading frame predicted a 415-amino acid protein. The sequence contained each of the peptide sequences obtained from amino acid sequencing. The Pbfmd gene contained five exons interrupted by four introns. Northern and Southern blot analysis suggested that there is one copy of the gene in P. brasiliensis and that it is preferentially expressed in mycelium. The complete coding cDNA was expressed in Escherichia coli to produce a recombinant fusion protein with glutathione S-transferase (GST). The purified recombinant protein was recognized by sera of patients with proven paracoccidioidomycosis and not by sera of healthy individuals. The recombinant 45-kDa protein was shown to be catalytically active; FMD activity was detected in P. brasiliensis yeast and mycelium.

Tumor necrosis factor-α is required for gastritis induced by Helicobacter felis infection in mice

Helicobacter pylori colonizes the gastric mucosa of human and causes chronic gastritis. The previous studies have demonstrated that gamma interferon (IFN-gamma) but not tumor necrosis factor-alpha (TNF-alpha) plays a critical role in pathogenesis of gastritis induced by H. pylori infection. In this study we investigated the induction of gastritis induced by H. felis infection in TNF-alpha-deficient mice, comparing with IFN-gamma-deficient mice. The scores of gastritis and epithelial changes of TNF-alpha-deficient mice and IFN-gamma-deficient mice were significantly lower than that of C57BL/6 mice. Moreover, the degrees of gastritis and epithelial changes of TNF-alpha-deficient mice were rather low compared with that of IFN-gamma-deficient mice. In spleen cell cultures stimulated with heat-killed H. felis, IFN-gamma production by TNF-alpha-deficient mice and TNF-alpha production by IFN-gamma-deficient mice were significantly reduced compared with those in C57BL/6 mice. These results suggested that TNF-alpha is involved in pathogenesis of gastritis induced by H. felis infection as IFN-gamma and that an interaction between TNF-alpha and IFN-gamma might be required in pathogenesis of gastritis induced by Helicobacter infection.

Mechanism of action of low recurrence of gastritis caused by Helicobacter pylori with the type II urease B gene

BACKGROUND

Low recurrence of gastritis is seen in patients infected with Helicobacter pylori carrying the type II urease B gene, compared with H. pylori carrying types I and III. The underlying mechanism has been studied in terms of the urease activity and interleukin (IL)-8 production capacity of different strains of H. pylori.

MATERIALS AND METHODS

Forty-five patients infected with different strains of H. pylori (type I; 15, type II; 15 and type III; 15) were enrolled in the study. H. pylori was isolated from gastric mucosa and cultured in the presence of urea at pH 5.5 to evaluate urease activity. The capacity of different strains of H. pylori to induce IL-8 mRNA and IL-8 from a human gastric cancer cell line and human peripheral blood mononuclear cells was evaluated.

RESULTS

The urease activity of type II H. pylori[523 +/- 228 micro g of ammonia/dl/10(8) colony-forming units (CFU)/ml] was significantly lower than that of type I (1355 +/- 1369 micro g of ammonia/dl/10(8) CFU/ml) and type III (1442 +/- 2229 micro g of ammonia/dl/10(8) CFU/ml) (p <.05). Gastric cancer cells cocultured with type II H. pylori produced lower levels of IL-8 mRNA compared with type I and type III H. pylori. The levels of IL-8 were also significantly lower in cultures induced by type II H. pylori compared with those induced by type I and type III H. pylori. Peripheral blood mononuclear cells also produced lower levels of IL-8 when cocultured with type II compared with type I H. pylori.

CONCLUSIONS

These results indicate that both the lower level of urease activity and the low IL-8-inducing capacity of type II H. pylori might underlie the lower recurrence rate of gastritis caused by type II H. pylori.

Effect of Helicobacter pylori infection on expression of Bcl-2 family members in gastric adenocarcinoma

AIM

To investigate the effect of Helicobacter pylori (H pylori) infection on the expressions of Bcl-2 family members in gastric adenocarcinoma.

METHODS

Gastric adenocarcinoma and resection margin tissues of 95 patients were studied. Semi-quantitative RT-PCR was used to measure Bid, Bax and Bcl-2 mRNA expressions.

RESULTS

Expressions of Bid and Bax in gastric adenocarcinoma tissues without H pylori infection, with cagA- H pylori infection and cagA+ H pylori infection increased significantly in turn (Bid, 0.304, 0.422 and 0.855 respectively, P<0.05; Bax, 0.309, 0.650 and 0.979 respectively, P<0.05). Bcl-2 mRNA levels increased significantly in gastric adenocarcinoma tissues with cagA- H pylori infection and cagA+ H pylori infection, compared with those without H pylori infection (0.696 and 0.849 vs 0.411, P<0.05). Expressions of Bid, Bax and Bcl-2 in resection margin tissues without H pylori infection, with cagA- H pylori infection and cagA+ H pylori infection increased significantly in turn (Bid, 0.377, 0.686 and 0.939 respectively, P<0.05; Bax, 0.353, 0.645 and 1.001 respectively, P<0.05; Bcl-2, 0.371, 0.487 and 0.619 respectively, P<0.05). In H pylori negative specimens, expressions of Bid and Bax correlated negatively with that of Bcl-2 respectively in adenocarcinoma tissues (Bid vs Bcl-2, r=-0.409, P<0.05; Bax vs Bcl-2, r=-0.451, P<0.05). In H pylori positive specimens, expressions of Bid and Bax did not correlate with that of Bcl-2 in adenocarcinoma tissues (Bid vs Bcl-2, r=0.187, P>0.05; Bax vs Bcl-2, r=0.201, P>0.05), but correlated positively with that of Bcl-2 respectively in resection margin tissues (Bid vs Bcl-2, r=0.331, P<0.05; Bax vs Bcl-2, r=0.295, P<0.05).

CONCLUSION

H pylori may enhance Bid, Bax and Bcl-2 mRNA levels and cause deregulation of these apoptosis-associated genes expressions, which may play a role during development of gastric adenocarcinoma induced by H pylori.

Growth phase-dependent response of Helicobacter pylori to iron starvation

Iron is an essential nutrient that is often found in extremely limited available quantities within eukaryotic hosts. Because of this, many pathogenic bacteria have developed regulated networks of genes important for iron uptake and storage. In addition, it has been shown that many bacteria use available iron concentrations as a signal to regulate virulence gene expression. We have utilized DNA microarray technology to identify genes of the human pathogen Helicobacter pylori that are differentially regulated on a growth-inhibiting shift to iron starvation conditions. In addition, the growth phase-dependent expression of these genes was investigated by examining both exponential and stationary growth phase cultures. We identified known iron-regulated genes, as well as a number of genes whose regulation by iron concentration was not previously appreciated. Included in the list of regulated factors were the known virulence genes cagA, vacA, and napA. We examined the effect of iron starvation on the motility of H. pylori and found that exponential- and stationary-phase cultures responded differently to the stress. We further found that while growing cells are rapidly killed by iron starvation, stationary-phase cells show a remarkable ability to survive iron depletion. Finally, bioinformatic analysis of the predicted promoter regions of the differentially regulated genes led to identification of several putative Fur boxes, suggesting a direct role for Fur in iron-dependent regulation of these genes.

Presence of active aliphatic amidases in Helicobacter species able to colonize the stomach

Ammonia production is of great importance for the gastric pathogen Helicobacter pylori as a nitrogen source, as a compound protecting against gastric acidity, and as a cytotoxic molecule. In addition to urease, H. pylori possesses two aliphatic amidases responsible for ammonia production: AmiE, a classical amidase, and AmiF, a new type of formamidase. Both enzymes are part of a regulatory network consisting of nitrogen metabolism enzymes, including urease and arginase. We examined the role of the H. pylori amidases in vivo by testing the gastric colonization of mice with H. pylori SS1 strains carrying mutations in amiE and/or amiF and in coinfection experiments with wild-type and double mutant strains. A new cassette conferring resistance to gentamicin was used in addition to the kanamycin cassette to construct the double mutation in strain SS1. Our data indicate that the amidases are not essential for colonization of mice. The search for amiE and amiF genes in 53 H. pylori strains from different geographic origins indicated the presence of both genes in all these genomes. We tested for the presence of the amiE and amiF genes and for amidase and formamidase activities in eleven Helicobacter species. Among the gastric species, H. acinonychis possessed both amiE and amiF, H. felis carried only amiF, and H. mustelae was devoid of amidases. H. muridarum, which can colonize both mouse intestine and stomach, was the only enterohepatic species to contain amiE. Phylogenetic trees based upon the sequences of H. pylori amiE and amiF genes and their respective homologs from other organisms as well as the amidase gene distribution among Helicobacter species are strongly suggestive of amidase acquisition by horizontal gene transfer. Since amidases are found only in Helicobacter species able to colonize the stomach, their acquisition might be related to selective pressure in this particular gastric environment.

Apoptosis of gastric lymphocytes in Helicobacter pylori-infected rhesus macaques

In vitro studies suggest that H. pylori induces apoptosis in gastric epithelial cells and perhaps in gastric lymphocytes as well. However, the early effects of H. pylori infection on lymphocyte apoptosis have not been examined in experimental animal models, nor have studies been performed using markers specific for T cells and T-cell subsets. Gastric T-cell apoptosis and Fas ligand expression were examined by flow cytometry after experimental infection of rhesus macaques with H. pylori. Infection induced transient apoptosis of gastric CD4+ and CD8+ T-cells, which began as soon as three days after inoculation and declined to baseline within eight weeks. Fas ligand expression showed a similar transient induction, suggesting that it mediates gastric T-cell apoptosis. We propose that transient, Fas-mediated apoptosis in gastric lymphocytes is a compensatory response to the initial T-cell inflammatory response after acute H. pylori infection.

Differential regulation of amidase- and formamidase-mediated ammonia production by the Helicobacter pylori fur repressor

The production of high levels of ammonia allows the human gastric pathogen Helicobacter pylori to survive the acidic conditions in the human stomach. H. pylori produces ammonia through urease-mediated degradation of urea, but it is also able to convert a range of amide substrates into ammonia via its AmiE amidase and AmiF formamidase enzymes. Here data are provided that demonstrate that the iron-responsive regulatory protein Fur directly and indirectly regulates the activity of the two H. pylori amidases. In contrast to other amidase-positive bacteria, amidase and formamidase enzyme activities were not induced by medium supplementation with their respective substrates, acrylamide and formamide. AmiE protein expression and amidase enzyme activity were iron-repressed in H. pylori 26695 but constitutive in the isogenic fur mutant. This regulation was mediated at the transcriptional level via the binding of Fur to the amiE promoter region. In contrast, formamidase enzyme activity was not iron-repressed but was significantly higher in the fur mutant. This effect was not mediated at the transcriptional level, and Fur did not bind to the amiF promoter region. These roles of Fur in regulation of the H. pylori amidases suggest that the H. pylori Fur regulator may have acquired extra functions to compensate for the absence of other regulatory systems.

Effect of Helicobacter pylori on apoptosis and apoptosis related genes in gastric cancer cells

BACKGROUND/AIMS

Helicobacter pylori induces the apoptosis of gastric epithelial cells in vivo and in vitro. However, the molecular mechanism has not been clarified. The aim of this study was to investigate the effect of H pylori on the apoptosis of gastric epithelial cells and the expression of apoptosis related genes in vitro.

METHODS

Human gastric adenocarcinoma SGC-7901 cells were co-cultured with a cytotoxic H pylori strain, NCTC 11637, at various densities ranging from 3.2 x 10(4) to 1.0 x 10(8) colony forming units (CFU)/ml for 48 hours. Apoptosis in gastric cells was determined by transmission electron microscopy, Hoechst 33258 fluorochrome staining, and flow cytometry. The expression of apoptosis related proteins, Bcl-2, Bax, and c-Myc, was measured by an immunohistochemical method, and c-Myc mRNA expression was determined by the reverse transcription-polymerase chain reaction.

RESULTS

Helicobacter pylori induces morphological changes typical of apoptosis. Both fluorochrome staining and flow cytometry showed that the apoptotic index began to increase when H pylori were at a density of > 1.6 x 10(4) CFU/ml, and in a density dependent manner (p < 0.01; one way ANOVA). The expression of the Bax and c-Myc proteins and of c-Myc mRNA was increased, whereas Bcl-2 expression was decreased after co-culture for 48 hours.

CONCLUSIONS

Helicobacter pylori induced apoptosis in gastric epithelial cells is mediated by altered expression of the products of the Bcl-2, Bax, and c-Myc genes.

Direct random insertion mutagenesis of Helicobacter pylori

Random insertion mutagenesis is a widely used technique for the identification of bacterial virulence genes. Most strategies for random mutagenesis involve cloning in Escherichia coli for passage of plasmids or for phenotypic selection. This can result in biased selection due to restriction or instability of the cloned DNA, or toxicity of the encoded products. We therefore created two mutant libraries in the human pathogen Helicobacter pylori using a simple, direct mutagenesis technique, which does not require E. coli as intermediate. H. pylori total DNA was digested, circularized and digested again with a frequently cutting restriction enzyme, and the resulting fragments were ligated to a kanamycin antibiotic resistance cassette. Subsequently, the ligation mixture was transformed into the parental H. pylori strain 1061. Insertion of the kanamycin cassette by double homologous recombination into the genome of H. pylori 1061 resulted in approximately 2500 kanamycin resistant colonies. Heterogeneity of kanamycin cassette insertion was confirmed by Southern blotting. The isolation of two independent H. pylori mutants defective in production of urease from this library underlines the potential of this mutagenesis strategy.

Ammonia prevents glutamate-induced but not low K(+)-induced apoptosis in cerebellar neurons in culture

Cultured rat cerebellar granule neurons are widely used as a model system for studying neuronal apoptosis. Either low K(+) (5 mM) or low concentrations of glutamate (1-10 microM) induce apoptosis in cerebellar neurons in culture. However, the molecular mechanism(s) involved remain unclear. We show that long-term treatment with ammonia prevents glutamate-induced but not low K(+)-induced apoptosis in cerebellar neurons, as assessed by measuring DNA fragmentation and activation of caspase 3. Ammonia prevented glutamate-induced increase of intracellular calcium, depolarization of the inner mitochondrial membrane, release of cytochrome c to the cytosol, activation of caspase 3 and fragmentation of DNA. However, ammonia did not prevent low K(+)-induced activation of caspase 3 and fragmentation of DNA. These results indicate that the initial steps involved in the induction of apoptosis by low K(+) or by glutamate are different and that ammonia prevents glutamate-induced apoptosis by reducing glutamate-induced rise of intracellular Ca(2+), thus avoiding the activation of subsequent events of the apoptotic process.

Role of glutamine and arginase in protection against ammonia-induced cell death in gastric epithelial cells

Ammonia is a cytotoxic factor produced during Helicobacter pylori infection that may reduce the survival of surface epithelial cells. Here we examine whether ammonia kills cells and whether L-glutamine (L-Gln) protects against cell death by stimulating ammonia detoxification pathways. Cell viability and vacuolation were quantified in rat gastric epithelial (RGM1) cells incubated with ammonium chloride at pH 7.4 in the presence or absence of L-Gln. Incubation of RGM1 cells with ammonium chloride caused a dose-dependent increase in cell death and vacuolation, which were both inhibited by L-Gln. We show that RGM1 cells metabolize ammonia to urea via arginase, a process that is stimulated by L-Gln and results in reduced ammonia cytotoxicity. L-Gln also inhibits the uptake and facilitates the extrusion of ammonia from cells. Blockade of glutamine synthetase did not reduce the survival of RGM1 cells, demonstrating that the conversion of L-glutamate and ammonia to L-Gln is not involved in ammonia detoxification. Thus our data support a role for L-Gln and arginase in protection against ammonia-induced cell death in gastric epithelial cells.

Rebamipide prevents delay of acetic acid-induced gastric ulcer healing caused by Helicobacter pylori infection in Mongolian gerbils

In this study, we examined the effect of rebamipide, a mucoprotective drug, on gastric ulcer healing in Mongolian gerbils infected with H. pylori. Male Mongolian gerbils were inoculated with H. pylori or vehicle alone 12 hr after the production of an acetic acid-induced gastric ulcer. On day 5, the gerbils inoculated with H. pylori were divided into three groups and fed rebamipide-containing diet (0.038%, 60 mg/kg, or 0.0038%, 6 mg/kg), or standard laboratory chow. The gerbils inoculated with the vehicle were fed standard laboratory chow throughout the experiment. The gerbils were killed on day 5, 15, or 30 after ulcer production, and removed stomachs were subjected to calculation of ulcer size, culture for H. pylori, and measurement of myeloperoxidase activity, a marker for neutrophil infiltration, in ulcerated tissue. Apoptotic and proliferating cells of gastric epithelium in ulcer margins were detected by the in situ DNA nick end-labeling method and immunohistochemical staining for 5-bromo-2'-deoxyuridine (BrdU), respectively. Rebamipide did not affect colonization levels of H. pylori. Infection with H. pylori did not affect ulcer size by day 5 but significantly delayed ulcer healing by days 15 and 30, accompanied by an increase in the number of apoptotic cells, a decrease in the number of BrdU-positive cells, and an increase in myeloperoxydase activity. Rebamipide prevented delay of ulcer healing and abolished these effects of H. pylori on cell kinetics and neutrophil infiltration. In conclusion, rebamipide may prevent the delay of acetic acid-induced gastric ulcer healing caused by H. pylori through modulating cell kinetics and inhibiting neutrophil infiltration.

Review article: Helicobacter pylori infection from pathogenesis to treatment--a critical reappraisal

The main areas of this review are Helicobacter pylori and disease pathogenesis; the relationship of H. pylori to lower gastrointestinal diseases, liver disease and extra-gastrointestinal conditions; the relationship of H. pylori to gastro-oesophageal reflux disease; infection in the very young and very old; diagnostic techniques; and management of H. pylori infections with particular emphasis on eradication regimens and antibiotic resistance.