Enhanced gastric nitric oxide synthase activity in duodenal ulcer patients

Prophylactic effect of probiotics fortified with Aloe vera pulp nanoemulsion against ethanol-induced gastric ulcer

The purpose of this study was designed to evaluate the protective effect of probiotics fortified with Aloe vera pulp nanoemulsion on ethanol-induced gastric ulcer (GU). Freshly harvested Aloe vera pulp nanoemulsion was prepared and subsequently inoculated with 2% of the activated yogurt starter culture of Streptococcus thermophilus and Lactobacillus delbreukii subsp. bulgaricus (1:1). Chemical composition and physicochemical characterization of yogurt and the Aloe vera pulp nanoemulsion were assessed. GU was induced by ethanol. Rats were randomly assigned into control, GU, and four prophylactic groups including probiotics fortified with Aloe vera pulp nanoemulsion in the percentage of 0%, 10%, 20%, and 30% respectively. Serum levels of paraoxynase (POX) and tissue levels of malondialdehyde (MDA), nitric oxide (NO), and catalase (CAT) activity were assessed. Serum levels of nuclear factor kappa B (NF-κB), interleukin-1beta (IL-1β), matrix metalloproteinase-9 (MMP-9), ceramide, and homocysteine (Hcy) were evaluated. Results indicated that the Aloe vera pulp nanoemulsion was appeared in spherical nano form with droplets diameter around 330 nm. Ethanol induces GU to cause a significant increase in the levels of MDA, NO, NF-κB, IL-1β, MMP-9, Hcy, and ceramide along with a significant decrease in POX and CAT activities compared to the control group (p < 0.05). Pretreatment with different concentrations of probiotics fortified with Aloe vera pulp nanoemulsion with, especially the 30% concentration, significantly reduce the oxidative stress and ameliorate the release of different inflammatory mediators suggesting it as a promising approach in the protection against GU via scavenging superoxide radicals and inhibiting the activation of the inflammatory signaling cascades.

Tissue transglutaminase activity in human gastric mucosa according to Helicobacter pylori infection

IMPACT STATEMENT

Tissue transglutaminase (t-TG) is unique among TG enzymes because of its additional role in several physiological and pathological activities, including inflammation, fibrosis, and wound healing. The presence of t-TG has previously been described in the intestine of human and animal models, yet studies on t-TG activity in human gastric mucosa are missing. Helicobacter pylori infection is the major cause of gastritis and peptic ulcers. For the first time, our results show that t-TG activity was significantly higher in antral specimens of patients with chronic active gastritis associated with H. pylori infection compared to H. pylori negative chronic gastritis and normal antral mucosa. These findings suggest that t-TG has a role in the natural history of human gastritis, which requires further investigation but may be an avenue for new therapeutic options.

Exhaled nitric oxide as a potential marker for detecting non-ulcer dyspepsia and peptic ulcer disease

Nitric oxide (NO) plays a key role in the development of peptic ulcer disease (PUD). Conversely, the gastric pathogen Helicobacter pylori colonizes the human stomach and contributes to the development of non-ulcer dyspepsia (NUD) and PUD. However, the underlying relation between molecular NO in exhaled breath and H. pylori-associated NUD and PUD remains largely unknown. Here, we found that the excretion kinetics of NO profiles in exhaled breath are altered markedly in H. pylori-infected NUD and PUD subjects. In our observations, PUD led to considerably higher enrichments of NO in exhaled breath compared to NUD, thus revealing a potential link between exhaled NO and ulcer and non-ulcer complications. Our findings therefore suggest that molecular NO in exhaled breath could be used as a potential biomarker for non-invasive diagnosis and selective differentiation of NUD from PUD. Our observations also highlight that alterations of NO in the gastric environment can play an important role in the pathogenesis of peptic ulcers and thus may provide a new strategy for precise evolution of the actual disease state without the need for endoscopic biopsy, even after the eradication of H. pylori infection.

Pathomechanisms of Oxidative Stress in Inflammatory Bowel Disease and Potential Antioxidant Therapies

Inflammatory bowel disease (IBD) is a chronic gastrointestinal disease whose incidence has risen worldwide in recent years. Accumulating evidence shows that oxidative stress plays an essential role in the pathogenesis and progression of IBD. This review highlights the generation of reactive oxygen species (ROS) and antioxidant defense mechanisms in the gastrointestinal (GI) tract, the involvement of oxidative stress signaling in the initiation and progression of IBD and its relationships with genetic susceptibility and the mucosal immune response. In addition, potential therapeutic strategies for IBD that target oxidative stress signaling are reviewed and discussed. Though substantial progress has been made in understanding the role of oxidative stress in IBD in humans and experimental animals, the underlying mechanisms are still not well defined. Thus, further studies are needed to validate how oxidative stress signaling is involved in and contributes to the development of IBD.

Supplementation with Angelica keiskei inhibits expression of inflammatory mediators in the gastric mucosa of Helicobacter pylori-infected mice

Oxidative stress is involved in the pathogenesis of Helicobacter pylori-associated gastric ulceration and carcinogenesis. The oxidant-sensitive transcription factor, nuclear factor κ-light-chain-enhancer of activated B cells (NF-κB), regulates expression of inflammatory mediators such as interferon γ (IFN-γ), cyclooxygenase 2 (COX-2), and inducible nitric oxide synthase (iNOS). These inflammatory mediators increased in gastric mucosal tissues from patients infected with H pylori. Angelica keiskei (AK), a green leafy vegetable, is rich in carotenoids and flavonoids and shows antioxidant and anti-inflammatory activities. Therefore, we hypothesized that AK may protect the gastric mucosa of H pylori-infected mice against inflammation. We determined lipid peroxide abundance, myeloperoxidase activity, expression levels of inflammatory mediators (IFN-γ, COX-2, and iNOS), NF-κB-DNA binding activity, and histologic changes in gastric mucosal tissues. The antioxidant N-acetylcysteine served as the positive control treatment. Supplementation with AK suppressed increases in lipid peroxide abundance, myeloperoxidase activity, induction of inflammatory mediators (IFN-γ, COX-2, and iNOS), activation of NF-κB, and degradation of nuclear factor of κ light polypeptide gene enhancer in B-cells inhibitor α in gastric mucosal tissue from H pylori-infected mice. Inhibition of H pylori-induced alterations by AK was similar to that by N-acetylcysteine. Taken together, these results suggest that supplementation with AK may prevent H pylori-induced gastric inflammation by inhibiting NF-κB-mediated induction of inflammatory mediators in the gastric mucosa of patients infected with H pylori.

Pathophysiological Role of Peroxynitrite Induced DNA Damage in Human Diseases: A Special Focus on Poly(ADP-ribose) Polymerase (PARP)

Peroxynitrite is formed in biological systems when nitric oxide and superoxide rapidly interact at near equimolar ratio. Peroxynitrite, though not a free radical by chemical nature, is a powerful oxidant which reacts with proteins, DNA and lipids. These reactions trigger a wide array of cellular responses ranging from subtle modulations of cell signaling to overwhelming oxidative injury, committing cells to necrosis or apoptosis. The present review outlines the various peroxynitrite-induced DNA modifications with special mention to the formation of 8-nitroguanine and 8-oxoguanine as well as the induction of DNA single strand breakage. Low concentrations of peroxynitrite cause apoptotic death, whereas higher concentrations cause necrosis with cellular energetics (ATP and NAD(+)) serving as control between the two modes of cell death. DNA damage induced by peroxynitrite triggers the activation of DNA repair systems. A DNA nick sensing enzyme, poly(ADP-ribose) polymerase-1 (PARP-1) becomes activated upon detecting DNA breakage and it cleaves NAD(+) into nicotinamide and ADP-ribose and polymerizes the latter on nuclear acceptor proteins. Over-activation of PARP induced by peroxynitrite consumes NAD(+) and consequently ATP decreases, culminating in cell dysfunction, apoptosis or necrosis. This mechanism has been implicated in the pathogenesis of various diseases like diabetes, cardiovascular diseases and neurodegenerative diseases. In this review, we have discussed the cytotoxic effects (apoptosis and necrosis) of peroxynitrite in the etiology of the mentioned diseases, focusing on the role of PARP in DNA repair in presence of peroxynitrite.

H2S regulation of nitric oxide metabolism

Nitric oxide (NO) and hydrogen sulfide (H2S) are two major gaseous signaling molecules that regulate diverse physiological functions. Recent publications indicate the regulatory role of H2S on NO metabolism. In this chapter, we discuss the latest findings on H2S-NO interactions through formation of novel chemical derivatives and experimental approaches to study these adducts. This chapter also addresses potential H2S interference on various NO detection techniques, along with precautions for analyzing biological samples from various sources. This information will facilitate critical evaluation and clearer insight into H2S regulation of NO signaling and its influence on various physiological functions.

Oxidative stress: an essential factor in the pathogenesis of gastrointestinal mucosal diseases

Reactive oxygen species (ROS) are generated as by-products of normal cellular metabolic activities. Superoxide dismutase, glutathione peroxidase, and catalase are the enzymes involved in protecting cells from the damaging effects of ROS. ROS are produced in response to ultraviolet radiation, cigarette smoking, alcohol, nonsteroidal anti-inflammatory drugs, ischemia-reperfusion injury, chronic infections, and inflammatory disorders. Disruption of normal cellular homeostasis by redox signaling may result in cardiovascular, neurodegenerative diseases and cancer. ROS are produced within the gastrointestinal (GI) tract, but their roles in pathophysiology and disease pathogenesis have not been well studied. Despite the protective barrier provided by the mucosa, ingested materials and microbial pathogens can induce oxidative injury and GI inflammatory responses involving the epithelium and immune/inflammatory cells. The pathogenesis of various GI diseases including peptic ulcers, gastrointestinal cancers, and inflammatory bowel disease is in part due to oxidative stress. Unraveling the signaling events initiated at the cellular level by oxidative free radicals as well as the physiological responses to such stress is important to better understand disease pathogenesis and to develop new therapies to manage a variety of conditions for which current therapies are not always sufficient.

Nitric oxide as a mediator of inflammation?-You had better believe it

Nitric oxide has enigmatic qualities in inflammation. In order to appreciate the precise contributions of nitric oxide to a pathophysiological process, one must account for enzyme source, coproduction of oxidants and antioxidant defences, time, rate of nitric oxide production, cellular source, peroxynitrite formation and effects on DNA (mutagenesis/apoptosis). We contend that there is ample evidence to consider nitric oxide as a molecular aggressor in inflammation, particularly chronic inflammation. Therapeutic benefit can be achieved by inhibition of inducible nitric oxide synthase and not the donation of additional nitric oxide. Furthermore, there is growing appreciation that nitric oxide and products derived thereof, are critical components linking the increased incidence of cancer in states of chronic inflammation.

Pharmacological and histological effects of Centaurea bruguierana ssp. belangerana on indomethacin-induced peptic ulcer in rats

The species Centaurea bruguierana (DC.) Hand.-Mazz. ssp. belangerana (DC.) Bornm. (CBB) (Asteraceae), known as "Baad-Avard" in Borazjan, Bushehr Province, southern Iran, is used in folk medicine as a hypoglycemic herb in diabetes and as a remedy for peptic ulcer disorders. Total 80% EtOH extract and petroleum ether, CHCl(3), EtOAc, n-BuOH, and remaining fractions obtained by solvent-solvent fractionation of dried aerial flowering parts of the plant were investigated for anti-ulcer activity against indomethacin-induced ulcerogenesis in rats. Anti-ulcer activity was evaluated by measuring the ulcer index (UI) and ulcer inhibition. The UI was significantly reduced in all treated animals. A dramatic decrease in the UI was observed following the administration of total extract (100 mg/kg, p < 0.001) and CHCl(3) fraction (42 mg/kg, ***p < 0.001) in comparison with the control group. The percentage ulcer inhibition with total extract at a dose of 100 mg/kg (97.66%) and CHCl(3) fraction at a dose of 42 mg/kg (96.96%) was found to be higher (p < 0.001) than the reference group (cimetidine 100 mg/kg) (87.08%). The pharmacological and histological results of the present study proved that the aerial flowering parts of CBB possess preventive activity against peptic ulcer, supporting the traditional assertion in southern Iranian folk medicine.

Induction effect of coadministration of soybean isoflavones and sodium nitrite on DNA damage in mouse stomach

We have already found that nitrite-treated isoflavones exhibit genotoxic activities toward Salmonella typhimurium TA 100 and 98 strains (submitted: nitrite-treated genistein). However, we have not demonstrated genotoxic activity induced by simultaneous treatment with isoflavones and NaNO(2)in vivo. In the present study, we examined whether coadministration of isoflavones (such as daidzein and genistein) and NaNO(2) induces DNA damage in the stomach of ICR male mice. Mice were coadministered with isoflavones (1mg/kg body weight) and NaNO(2) (10mg/kg body weight), and dissected to collect tissues at 1, 3, and 6h after administration. We used comet assay combined with repair enzyme formamidopyrimidine-N-glycosylase (FPG) to detect FPG-sensitive sites. An HPLC-ECD system was employed to determine 8-oxo-2'-deoxyguanosine (8-oxodG) in the stomach. In addition, we observed leukocyte infiltration by histopathological investigation, and measured total superoxide dismutase (SOD) in the stomach. We confirmed that oxidative DNA damage in the stomach was significantly increased by coadministration. Total SOD activities were also significantly stimulated by coadministration. However, the induction of inflammation in the stomach was not found. These data suggest that coadministration of isoflavones and NaNO(2) can cause DNA damage in the stomach because of the formation of radicals.

Involvement of Ras and AP-1 in Helicobacter pylori-induced expression of COX-2 and iNOS in gastric epithelial AGS cells

Helicobacter pylori (H. pylori) is an important risk factor for chronic gastritis, peptic ulcer, and gastric cancer. The genetic differences of H. pylori isolates play a role in the clinical outcome of the infection. Inflammatory genes including cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) are involved in H. pylori gastritis. Transcription factor AP-1 is composed of c-Fos and c-Jun and mediates inflammation and carcinogenesis. Ras acts as a regulator for AP-1 activation in various cells. We investigated whether H. pylori in a Korean isolate (HP99), a cagA ( + ), vacA ( + ) strain, induces the expression of c-Fos and c-Jun for AP-1 activation to induce COX-2 and iNOS and whether HP99-induced expressions of COX-2 and iNOS are mediated by Ras and AP-1, determined by the expressions of c-Fos and c-Jun, in gastric epithelial AGS cells, using transfection with mutant genes for Ras (ras N-17) and c-Jun (TAM-67). As a result, HP99 induced the expression of c-Fos and c-Jun and the expressions of COX-2 and iNOS in AGS cells. Transfection with mutant genes for Ras or c-Jun suppressed HP99-induced expressions of COX-2 and iNOS in AGS cells. In conclusion, H. pylori in a Korean isolate induces the expression of COX-2 and iNOS via AP-1 activation, which may be mediated by Ras and the expression of c-Fos and c-Jun in gastric epithelial cells.

Induced nitric oxide synthase as a major player in the oncogenic transformation of inflamed tissue

Nitric oxide (NO) is a free radical that is involved in the inflammatory process and carcinogenesis. There are four nitric oxide synthase enzymes involved in NO production: induced nitric oxide synthase (iNOS), endothelial NO synthase (eNOS), neural NO synthase (nNOS), and mitochondrial NOS. iNOS is an inducible and key enzyme in the inflamed tissue. Recent literatures indicate that NO as well as iNOS and eNOS can modulate cancer-related events including nitro-oxidative stress, apoptosis, cell cycle, angio-genesis, invasion, and metastasis. This chapter focuses on linking NO/iNOS/eNOS to inflammation and carcinogenesis from experimental evidence to potential targets on cancer prevention and treatment.

The bactericidal and morphological effects of peroxynitrite on Helicobacter pylori

Peroxynitrite (ONOO-) is correlated with the pathogenesis of Helicobacter pylori-induced peptic ulcer diseases. We aimed to investigate the time- and concentration-dependent bactericidal and morphological effects of ONOO- on H. pylori. Authentic ONOO- was synthesized as quenched-flow method. A stock culture of H. pylori NCTC 11637 was exposed to different concentrations of ONOO- (0.1-40 micromol/L) or decomposed ONOO- or fresh medium. Samples were taken at 0, 15, 30, 60, and 120 minutes, for the evaluation of viable bacteria and bacterial morphology with gram strain and transmission electron microscopy. Decomposed ONOO- showed no bactericidal activity against H. pylori. ONOO- application caused a decrease in the number of viable bacteria within the first 15 minutes. The significant conversion of H. pylori from spiral form to coccoid form was determined with 10 micromol/L of ONOO-, and higher concentrations caused lysis of the cells. Separation of cell wall, bleb formation, vacuolization, decrease of secretory granules, and lysis of bacteria were the morphological effects of ONOO- on H. pylori. Because the morphology of the bacteria is one of the important factors in virulence; peroxynitrite-related morphological effects might have an impact in the progress of the H. pylori-induced peptic ulcer diseases.

Oxidative stress expression status associated to Helicobacter pylori virulence in gastric diseases

OBJECTIVES

To analyze the status of expression of inflammation markers, antioxidant and oxidant enzymes in biopsies from patients diagnosed with gastritis, gastric ulcer (GU) and gastric cancer (GC) and the Helicobacter pylori virulence from these isolated biopsies in order to evaluate a possible association among these factors.

METHODS

H. pylori genotype from isolated biopsies was performed by PCR. The pattern of expression of inflammation (TNF-alpha, IL-1beta, IL-8, IL-10 and IL-12), oxidant (iNOS and Nox1) and antioxidant markers (MnSOD, GPX and CAT) of biopsies from gastritis, GU, GC and control groups was performed by RT-PCR.

RESULTS

Different from other gastric diseases studied here, gastritis is characterized by an oxidative stress with significant expression of TNF-alpha, IL-8, IL-12, iNOS and Nox and significant absence of MnSOD and GPX expression. Gastritis was the only condition where there was an association between TNF-alpha or IL-8 expression and H. pylori cagA+/vacAs1 genotype. In this case, TNF-alpha expression was about 3 times higher when compared to control subjects.

CONCLUSION

In this study, only gastritis was found to be associated with significant oxidative stress marker expression of TNF-alpha and IL-8 that was also related to H. pylori virulence, suggesting that they are the main oxidant stress markers responsible to trigger an increase in ROS level that contributes to decrease the expression of the MnSOD and GPX.

Myeloperoxidase, xanthine oxidase and superoxide dismutase in the gastric mucosa of Helicobacter pylori positive and negative pediatric patients

The aim of this study was determination and comparison of the levels of myeloperoxidase (MPO), xanthine oxidase (XO), and superoxide dismutase (SOD) in gastric mucosa of children who were infected and noninfected with Helicobacter pylori (HP). The MPO, and XO enzyme activities were detected via kinetic measurement, and the MPO, XO and SOD enzyme protein levels were detected via Western blot, in antral mucosa specimens of 43 patients who underwent upper gastrointestinal endoscopy with various indications. The diagnosis of HP infection was made with a positive rapid urease test and histopathologic detection. MPO activity and enzyme protein levels were measured in 14 [8 HP (+) and 6 HP (-)], and in 9 [5 HP (+) and 4 HP (-)] while XO activity and enzyme protein levels were measured in 16 [10 HP (+) and 6 HP (-)] and in 9 [5 HP (+) and 4 HP (-)] patients, respectively. SOD protein level was detected in 13 [7 HP (+) and 6 HP (-)] patients. Of 43 patients 25 were HP (+) and 18 were HP (-). MPO activities were 75.6 +/- 40.5 and 98.8 +/- 44.1 U/g. protein (p = 0.302) while XO activities were 0.5 +/- 0.3 and 0.4 +/- 0.2 U/g. protein in HP (+) and HP (-) patients, respectively (p = 0.625). Measured enzyme protein levels of MPO, XO and SOD were found statistically indifferent in HP (+) and HP (-) patients (p = 0.327, p = 0.086, and p = 0.775, respectively). The results of this study revealed that, MPO, XO and SOD conditions in gastric mucosa alone were not affected from HP presence. That's why MPO, XO, and SOD may not have important roles in the pathogenesis of HP related gastric disease in children.

Causal role of Helicobacter pylori infection and eradication therapy in gastric carcinogenesis

Many epidemiological reports indicate that Helicobacter pylori (H pylori) infection plays an important role in gastric carcinogenesis. Several genetic and epigenetic alterations contribute to the initiation, promotion, and progression of the cancer cells in a multi-step manner. H pylori is known to induce chronic inflammation in the gastric mucosa. Its products, including superoxides, participate in the DNA damage followed by initiation, and the inflammation-derived cytokines and growth factors contribute to the promotion of gastric carcinogenesis. By eradicating H pylori, gastric inflammation can be cured; the therapy diminishes the levels not only of inflammatory cell infiltration, but also atrophy/intestinal metaplasia in part. A randomized controlled trial revealed that the eradication therapy diminished the gastric cancer prevalence in cases without pre-cancerous conditions. In addition, recent epidemiological studies from Japanese groups demonstrated that the development of gastric cancer, especially of the intestinal type, was decreased by successful eradication therapy, although these were designed in a non-randomized manner. However, it should be mentioned that endoscopic detection is the only way to evaluate the degree of gastric carcinogenesis. We have reported that the endoscopic and histological morphologies could be modified by eradication therapy and it might contribute to the prevalence of gastric cancer development. Considering the biological nature of cancer cell proliferation, it is considered that a sufficiently long-term follow-up would be essential to discuss the anticancer effect of eradication therapy.

H. pylori infection increases levels of exhaled nitrate

BACKGROUND

Helicobacter pylori infection is one of the most common chronic bacterial infections worldwide. Despite the existence of a breath test for the diagnosis of H. pylori infection, no study has described the composition of volatile compounds, especially the levels of nitrate, in the exhaled air of patients with H. pylori infection.

MATERIALS AND METHODS

The volatile compounds in the exhaled air of 14 patients suffering from H. pylori gastritis and 11 controls were analyzed using proton transfer reaction-mass spectrometry. Gastric biopsy was used to establish diagnosis of current H. pylori infection.

RESULTS

Comparing mass spectra between groups, Mass 28 (hydrogen cyanide, HCN) and Mass 64 (hydrogen nitrate, H2NO3) were found to be significantly elevated in patients with H. pylori infection.

CONCLUSIONS

The main result of the present study is that in H. pylori-infected patients, levels of exhaled hydrogen nitrate and hydrogen cyanide are found to be significantly elevated. However, further studies are necessary to find out whether the differences in the detected mass spectrum are specific enough to differentiate patients with H. pylori gastritis from healthy controls.

Expression of inducible nitric oxide synthase is increased in rat Barrett's esophagus induced by duodenal contents reflux

Barrett's esophagus is a premalignant condition of esophageal adenocarcinoma. Inducible nitric oxide synthase (iNOS) is induced by cytokines and can generate locally high concentrations of nitric oxide (NO), whose metabolites can mediate genotoxicity and influence multistage carcinogenesis by causing DNA damage. Therefore, we evaluated the immunolocalization and expression of iNOS in surgically induced rat Barrett's esophagus. Esophagoduodenal anastomosis was performed in rats for inducing reflux of duodenal contents. Rats were killed at postoperative 10, 20, 30 and 40 weeks. We examined histologic changes and iNOS expression in esophagus by immunohistochemistry and reverse transcription-polymerase chain reaction. Eighty six percent of experimental rats showed Barrett's esophagus above esophagoduodenal junction. iNOS immunoreactivity was clearly observed in the epithelial cells of Barrett's esophagus, predominantly at the apical surface of epithelial cells. Cytoplasmic staining was also seen only in atypical Barrett's esophagus. iNOS mRNA was detected only in the lower esophagus of experimental group. In conclusion, this study suggests that iNOS has some roles on Barrett's esophagus formation.

Helicobacter pylori and gastric diseases: a dangerous association

The bacterium Helicobacter pylori is linked to the appearance of several gastric diseases and in particular is associated with a progression to gastric cancer. Thistrun -1 bacterium colonizes the gastric mucosa directly interacting with epithelial cells. It is well known that H. pylori is associated with alterations in the gastric epithelial cell cycle, and apoptosis, higher levels of mononuclear and neutrophilic infiltrates, more severe atrophy and intestinal metaplasia. In last years, two mechanisms that interact with each other or not have been proposed: the hyperproliferation of gastric cells and oxidative damage of stomach mucosa. In particular, cell cycle alterations induce mitogenic signals and proto-oncogene expression that may trigger the development of cancer. Contemporary, H. pylori is able to induce polymorphonuclear and mononuclear cells that produce oxygen free radicals that could cause DNA damage to the adjacent cells leading to cancer development. Due to dangerous infection of this bacterium, the scientific community must point out its attention on the development of detection and prevention strategies.

Chronic gastritis with expression of inducible nitric oxide synthase is associated with high expression of interleukin-6 and hypergastrinaemia

BACKGROUND AND AIMS

High levels of inducible nitric oxide synthase and nitrotyrosine in Helicobacter pylori-infected gastric mucosa may contribute to development of gastric cancer. We investigated the relation between expression of inducible nitric oxide synthase and proinflammatory cytokines in gastric mucosa and serum markers of gastritis.

METHODS

The study included 103 patients with H. pylori infection. We examined levels of interleukin-1beta, interleukin-6 and interleukin-8 by enzyme-linked immunosorbent assay and evaluated expression of inducible nitric oxide synthase and nitrotyrosine by immunohistochemical staining. Furthermore, we assessed serum levels of pepsinogens, gastrin, anti-parietal cell antibody, nitrite and nitrate, as markers of gastritis.

RESULTS

Thirty-seven of 103 (35.6%) gastric mucosa specimens showed simultaneous expression of inducible nitric oxide synthase and nitrotyrosine. In these patients (inducible nitric oxide synthase-positive group), the serum level of gastrin was significantly higher than that of the inducible nitric oxide synthase-negative group (509.5 +/- 141.5 pg/mL vs. 210.0 +/- 227.2 pg/mL; P < 0.01), whereas there were no significant differences in serum levels of pepsinogen, anti-parietal cell antibody, and nitrate and nitrite or in scores of histological gastritis. Interleukin-6 levels were significantly higher in the inducible nitric oxide synthase-positive group than in the inducible nitric oxide synthase-negative group (25.9 +/- 7.0 pg/mg protein vs. 10.6 +/- 4.9 pg/mg protein; P < 0.05).

CONCLUSIONS

Inducible nitric oxide synthase-producing gastritis was correlated with high levels of interleukin-6. Patients with hypergastrinaemia should be carefully followed on a long-term basis to ensure that the development of any malignancy is detected early.

Intramucosal Helicobacter pylori in the human and murine stomach: its relationship to the inflammatory reaction in human Helicobacter pylori gastritis

Intramucosal Helicobacter pylori (H. pylori) has been described in biopsy tissues and culture systems. However, the association of intramucosal H. pylori with histopathologic features has not been evaluated. The purpose of this study is to investigate the relationship between intramucosal H. pylori and inflammatory reactions in H. pylori infection. In 113 randomly selected human gastric biopsies and 20 murine stomachs, which were inoculated with SSI every day for a week, immunohistochemical analysis for intramucosal H. pylori was done and correlated with histologic parameters. Electron microscopic examination was done on murine stomachs. H. pylori infection was present in 104 gastric biopsies and 17 murine stomachs. Intraepithelial immunopositivity for H. pylori was detected in 27 of 104 (26%) biopsies and in 11 of 17 (65%) murine stomachs. Lamina proprial immunopositivity for H. pylori was present in 51 of 104 (48%) biopsies. Neutrophil-associated immunopositivity for H. pylori was observed in 22 of 90 (24%) biopsies with H. pylori chronic active gastritis. Lamina proprial and neutrophil-associated immunopositivity for H. pylori correlated significantly with the density of H. pylori and the grade of acute inflammatory reaction in H. pylori gastritis. Intramucosal location of H. pylori itself or its antigen is closely associated with acute inflammatory reactions and may play an important role in establishing a persistent infection in chronic H. pylori gastritis. Furthermore, lamina proprial and/or neutrophil-associated H. pylori appears to be more important than intraepithelial H. pylori in acute inflammatory reactions of H. pylori gastritis.

Oxidative damage of the gastric mucosa in Helicobacter pylori positive chronic atrophic and nonatrophic gastritis, before and after eradication

BACKGROUND

Helicobacter pylori is the main cause of gastritis and a primary carcinogen. The aim of this study was to assess oxidative damage in mucosal compartments of gastric mucosa in H. pylori positive and negative atrophic and nonatrophic gastritis.

MATERIALS AND METHODS

Five groups of 10 patients each were identified according to H. pylori positive or negative chronic atrophic (Hp-CAG and CAG, respectively) and nonatrophic gastritis (Hp-CG and CG, respectively), and H. pylori negative normal mucosa (controls). Oxidative damage was evaluated by nitrotyrosine immunohistochemistry in the whole mucosa and in each compartment at baseline and at 2 and 12 months after eradication. Types of intestinal metaplasia were classified by histochemistry.

RESULTS

Total nitrotyrosine levels appeared significantly higher in H. pylori positive than in negative patients, and in Hp-CAG than in Hp-CG (p <.001); no differences were found between H. pylori negative gastritis and normal mucosa. Nitrotyrosine were found in foveolae and intestinal metaplasia only in Hp-CAG. At 12 months after H. pylori eradication, total nitrotyrosine levels showed a trend toward a decrease in Hp-CG and decreased significantly in Hp-CAG (p =.002), disappearing from the foveolae (p =.002), but remaining unchanged in intestinal metaplasia. Type I and II of intestinal metaplasia were present with the same prevalence in Hp-CAG and CAG, and did not change after H. pylori eradication.

CONCLUSIONS

Oxidative damage of the gastric mucosa increases from Hp-CG to Hp-CAG, involving the foveolae and intestinal metaplasia. H. pylori eradication induces a complete healing of foveolae but not of intestinal metaplasia, reducing the overall oxidative damage in the mucosa.

Active and inactive gastroesophageal reflux diseases related to Helicobacter pylori therapy

We systematically reviewed the literature on gastroesophageal reflux disease (GERD) related to Helicobacter pylori therapy, and classified the GERD according to various aspects. Preexisting GERD is active GERD before H. pylori therapy, and a substantial proportion of the GERD patients improve after successful H. pylori therapy. If the GERD does not persist or recur after cessation of acid-suppressive therapy combined with H. pylori therapy, it may have been cured (cured GERD). If it recurs, it may have been masked by acid-suppressive therapy and unmasked with cessation of the therapy (pharmacologically masked and unmasked GERD). Newly developed GERD after successful H. pylori therapy is a kind of unmasked GERD arising after cure of infection (de novo unmasked GERD). The possible mechanism of the improvement of cured GERD is normalized hyperacidity associated with an improved cytokine-somatostatin-gastrin system followed by normalized G-cell activity and parietal cell mass. Preexisting GERD is not a reason to avoid eradication therapy. De novo unmasked GERD develops in a substantial proportion of patients with cured infection. The possible mechanism is increased acid exposure in the esophagus due to gastric acid increase, which is caused by a loss of neutralizing effect by ammonia, normalized cytokine-acid suppression and improvement of corpus atrophy. De novo unmasked GERD is important because GERD is recurrent and may induce adenocarcinoma of the esophagus. However, it is expected that cure of infection lowers gastric cancer incidence. Eradication therapy is recommended irrespective of the possibility that de novo unmasked GERD may have a slight increase of the risk of esophageal adenocarcinoma.

Protective effect of dietary nitrate on experimental gastritis in rats

Nitrates have long been considered as harmful dietary components and judged responsible for deleterious effects on human health, leading to stringent regulations concerning their levels in food and water. However, recent studies demonstrate that dietary nitrate may have a major role in human health as a non-immune mechanism for host defence, through its metabolism to NO in the stomach. NO is a versatile molecule and although evidence exists showing that administration of low doses of exogenous NO protects against gastrointestinal inflammation, higher NO doses have been shown to exacerbate injury. So, the effect of an ingestion of nitrates in doses corresponding to a normal diet in human consumers on an experimental gastritis induced by iodoacetamide in rats was investigated. During gastritis one of the following compounds was given orally: water; KNO3; the NO donor sodium nitroprusside; the NO scavenger haemoglobin given with either water or KNO3. N(G)-nitro-l-arginine methyl ester (l-NAME), a non-specific NO synthase inhibitor, was administered with either water, iodoacetamide alone, or combined with KNO3. After killing, the stomach was resected and microscopic damage scores, myeloperoxidase and NO synthase activities were determined. Iodoacetamide-induced gastritis was significantly reduced by KNO3 administration, an effect which was reproduced by sodium nitroprusside and reversed by haemoglobin. l-NAME induced gastric mucosal damage in itself, and KNO3 did not prevent the gastritis induced by iodoacetamide associated with l-NAME. In conclusion, dietary nitrate exerts a protective effect against an experimental gastritis in rats by releasing NO in the stomach but such an effect requires the production of endogenous NO.

Helicobacter pylori stimulates inducible nitric oxide synthase in diverse topographical patterns in various gastroduodenal disorders

Overproduction of nitric oxide by inducible nitric oxide synthase (iNOS) acts cytotoxically and contributes to inflammation. We explored the roles of iNOS in the pathogenesis of Helicobacter pylori-associated diseases. Using reverse-transcribed PCR, we examined topographical patterns of iNOS mRNA expression in the gastroduodenal mucosa in H. pylori-negative controls and H. pylori-positive patients with duodenal ulcer (DU), gastric ulcer (GU), and ulcer-free gastritis. iNOS expression showed topographical variations among the tested disorders. As compared to controls, DU had a significantly higher expression of iNOS mRNA in the duodenum, GU in the antrum and duodenum, and gastritis in the antrum and corpus. H. pylori eradication yielded a significant reduction of iNOS mRNA in the duodenum of DU and in the antrum of GU. Diverse topographical patterns of H. pylori-induced iNOS expression may contribute to mechanisms by which H. pylori elicits different clinical disorders.

Nitric oxide regulates the release of somatostatin from cultured gastric rabbit primary D-cells

BACKGROUND & AIMS

Neuronal nitric oxide synthase (nNOS) is present in gastric D-cells. Mucosal somatostatin is diminished in H. pylori gastritis, where production of nitric oxide (NO) is increased. Therefore, we investigated the role of NO in D-cell function and the effects of prolonged exposure of D-cells to NO.

METHODS

Rabbit gastric D-cells were cultured. Somatostatin-14 was measured after 2 hours to examine the effects of arginine, nitric oxide sythase (NOS) inhibitors, and NO donors. Some cells were preincubated with a slow releasing NO donor for 12 hours. Results are expressed as percentage of total cell content. Nitrate content was measured by chemiluminescent assay.

RESULTS

L-arginine increased somatostatin-14 release in the presence of CCK8 from 4.4% +/- 0.5% to 6.4% +/- 0.4% (P < 0.02), and this was accompanied by NO release from 27 +/- 7 micromol/L to 86 +/- 12 micromol/L (P = 0.001). D-arginine and L-lysine had no effect. NOS inhibitors LNNA, SMT, and 7NI significantly attenuated the stimulatory response to L-arginine. NO donors sodium nitroprusside (SNP), 1 mmol/L, and S-nitroso-N-acetyl-D-L-penicillamine, 0.1 mmol/L, significantly increased basal and cholecystokinin-8 (CCK8) stimulated somatostatin release. Oxyhemoglobin attenuated the effect of SNP but not of L-arginine. Neither cyclic guanosine monophosphate nor guanylate cyclase were involved in the response to NO. However, inhibition of adenosine diphosphate (ADP) ribosyltransferase significantly decreased the response to L-arginine. Preincubation for 12 hours with 150 micromol/L (Z)-1-[(2-aminoethyl)-N-(2-ammonioethyl)amino]diazen-1-ium-1,2-diolate; IP3, inositol triphosphate decreased the 2-hour cellular response to CCK8 and SNP.

CONCLUSIONS

NO regulates rabbit D-cells. Acute exposure stimulates somatostatin mediated by ADP ribosylation, whereas long-term exposure reduces cellular responses to stimuli. The latter pathway may be responsible for the suppression of somatostatin in H. pylori gastritis.

Bleeding duodenal ulcer and association with polymorphism of endothelial constitutive nitric oxide synthase gene

Nitric oxide (NO) exerts both protective and proinflammatory actions in the gastrointestinal tract. Enhanced gastric NO synthase (NOS) activity has been shown in duodenal ulcer patients. Recently, intron-4 polymorphism of the endothelial constitutive (ec) NOS gene has been associated with some pathological conditions. Our aim was to determine the genotype and allele frequencies of the ecNOS4 polymorphism in peptic ulcer patients. The distribution of the polymorphism ecNOS4a/b was studied in 188 ulcer patients and 120 healthy controls, from genomic DNA. Genotypes ab, bb, and aa and allele frequency were similar in both peptic ulcer patients and controls, and no differences were found when patients and controls were analyzed according to the presence of several etiological factors. However, alelle "a" carrier status was associated with decreased risk of bleeding in duodenal ulcer patients (OR = 0.49; 95% CI = 0.25-0.95; P = 0.03). In conclusion, this ecNOS4 polymorphism gene could be related to susceptibility of duodenal ulcer patients to bleeding.

Effect of rebamipide in treatment of Helicobacter pylori-associated duodenal ulcer: attenuation of chemokine expression and nitrosative damage

Production of cytokines along with increased activity of nitric oxide synthase has been implicated as one of the contributing mechanisms of Helicobacter pylori-mediated gastroduodenal diseases. We aimed to evaluate the effect of rebamipide in treating Helicobacter pylori-associated duodenal ulcers in terms of cytokine production and nitrosative damage of the gastric mucosa. In patients with duodenal ulcers, rebamipide or placebo were given randomly after eradication. Mucosal cytokine production was measured by enzyme linked immunoassay, and nitrotyrosine immunoexpression was measured by immunohistochemistry. The inflammatory activity and degree of neutrophil infiltration were graded accordingly. The mucosal production of RANTES, interleukin-8, and TNF-alpha showed a significant decrease after eradication in patients with rebamipide after-treatment. The nitrotyrosine immunoreactivity of gastric epithelium was significantly decreased in the rebamipide group. Rebamipide treatment after eradication resulted in a significant reduction in chemokine production along with nitrotyrosine immunoexpression in Helicobacter pylori-associated duodenal ulcers.

Helicobacter pylori infection increases serum nitrate and nitrite more prominently than serum pepsinogens

BACKGROUND

Helicobacter pylori infection causes chronic gastritis and results in increased serum concentrations of pepsinogens I and II as well as gastrin, while the ratio of pepsinogen I to II (I : II) is decreased. Inducible nitric oxide synthase (iNOS) is induced in H. pylori-associated gastritis and may modulate inflammation. However serum nitrate and nitrite (NOx) concentrations in patients with H. pylori-induced chronic gastritis have not been reported. We examined differences in serum NOx between H. pylori-negative and positive volunteers relative to differences in pepsinogens and gastrin.

MATERIALS AND METHODS

Sera from 80 healthy asymptomatic volunteers younger than 36 years were analyzed for anti-H. pylori antibody, NOx, gastrin and pepsinogens.

RESULTS

In H. pylori antibody-positive subjects serum NOx concentrations were higher than in negative subjects (p < .005). In H. pylori-negative subjects, NOx correlated with pepsinogen II (r = .405, p < .05). In subjects with low pepsinogen I or II, NOx was higher in H. pylori-positive than negative subjects (p < .001). In subjects with high pepsinogen I : II (6 or higher), serum NOx was higher in H. pylori-positive than in negative subjects.

CONCLUSIONS

H. pylori-induced gastritis increases serum NOx concentrations more prominently than those of pepsinogen. In H. pylori-negative subjects, serum correlates with serum pepsinogen II.

Does serum nitrite concentration reflect gastric carcinogenesis in Japanese Helicobacter pylori-infected patients?

This study investigated whether the serum nitrite concentration reflects Helicobacter pylori-induced inflammation and atrophic changes of gastric mucosa. Ninety-seven patients underwent biopsy of both antrum and fundus. Samples were analyzed by the rapid urease test and histopathological examination according to the updated Sydney system. Fasting serum samples from each subject were analyzed for specific IgG Helicobacter pylori antibodies, pepsinogen I and II concentrations, and NO2-/NO3- content. Eleven patients had H. pylori eradicated with proton pump-based triple therapy. There was a strong positive correlation between the Helicobacter pylori density in the gastric mucosa and the serum nitrite concentration, but a negative correlation existed between the atrophic grade of the gastric mucosa and both serum nitrite concentration and Helicobacter pylori density in the gastric mucosa. Serum nitrite concentrations decreased significantly after successful eradication of Helicobacter pylori. Therefore, serum nitrite concentration may be a useful marker for oxidative DNA damage and apoptosis associated with Helicobacter pylori infection.

Nitric oxide in gastrointestinal epithelial cell carcinogenesis: linking inflammation to oncogenesis

Chronic inflammation of gastrointestinal tissues is a well-recognized risk factor for the development of epithelial cell-derived malignancies. Although the inflammatory mediators linking chronic inflammation to carcinogenesis are numerous, current information suggests that nitric oxide (NO) contributes to carcinogenesis during chronic inflammation. Inducible nitric oxide synthase (iNOS), expressed by both macrophages and epithelial cells during inflammation, generates the bioreactive molecule NO. In addition to causing DNA lesions, NO can directly interact with proteins by nitrosylation and nitosation reactions. The consequences of protein damage by NO appear to be procarcinogenic. For example, NO inhibits DNA repair enzymes such as human 8-oxodeoxyguanosine DNA glycosylase 1 and blocks apoptosis via nitrosylation of caspases. These cellular events permit DNA damage to accumulate, which is required for the numerous mutations necessary for development of invasive cancer. NO also promotes cancer progression by functioning as an angiogenesis factor. Strategies to inhibit NO generation during chronic inflammation or to scavenge reactive nitrogen species may prove useful in decreasing the risk of cancer development in chronic inflammatory gastrointestinal diseases.

NF-kappaB, inducible nitric oxide synthase and apoptosis by Helicobacter pylori infection

Oxygen radicals are considered as an important regulator in the pathogenesis of Helicobacter pylori (H. pylori)-induced gastric ulceration and carcinogenesis. Inflammatory genes including inducible nitric oxide synthase (iNOS) may be regulated by oxidant-sensitive transcription factor, nuclear factor-kappaB (NF-kappaB). iNOS induction has been related to gastric apoptosis. We studied the role of NF-kappaB on iNOS expression and apoptosis in H. pylori-stimulated gastric epithelial AGS cells. AGS cells were treated with antisense oligonucleotide (AS ODN) for NF-kappaB subunit p50, an antioxidant enzyme catalase, an inhibitor of NF-kappaB activation pyrrolidine dithiocarbamate (PDTC), iNOS inhibitors N(G)-nitro-L-arginine-methyl ester (L-NAME) and 2-amino-5,6-dihydro-6-methyl-4H-1,3-thiazine (AMT), a peroxynitrite donor SIN-1, and a nitric oxide donor NOC-18 in the presence or absence of H. pylori. H. pylori induced cytotocixity time- and dose-dependently, which occurred with induction in iNOS expression and nitrite production. SIN-1 and NOC-18 induced dose-dependent cytotoxicity in AGS cells. Catalase, PDTC, L-NAME, and AMT prevented H. pylori-induced cytotoxicity and apoptosis. It was related to their inhibition on iNOS expression and nitrite production. The cells treated with AS ODN had low levels of p50 and NF-kappaB and inhibited H. pylori-induced cytotoxicity, apoptosis, iNOS expression, and nitrite production. In conclusion, NF-kappaB plays a novel role in iNOS expression and apoptosis in H. pylori-infected gastric epithelial cells.

Fundal gastritis as a potential cause of reflux oesophagitis

The transient lower oesophageal sphincter relaxations which allow reflux may be due to altered afferent pathways from the fundus. We aimed to determine whether fundal inflammation is the underlying cause. Two endoscopic biopsies were taken from each of the gastric antrum and fundus in 25 asymptomatic controls with a normal endoscopy (median age 54 range 13-83 years), and 33 patients with erosive oesophagitis (median age 52, 11-78 years). No patient had taken acid suppression therapy or antibiotics for at least 1 month. Sections were stained with haematoxylin and eosin and Giemsa stain and examined in a blinded fashion by one pathologist for the presence of gastritis (Sydney classification) and Helicobacter pylori. Chronic gastritis was common in both groups, but was usually mild. In Helicobacter pylori-negative subjects, there was significantly less chronic gastritis in the antrum and the fundus in oesophagitis patients than in controls (p < 0.05). When present, gastric atrophy was usually antral and mild in severity. There was no difference in the incidence of gastric atrophy in patients with oesophagitis compared with controls (24% compared with 40%; p > 0.05). Chronic gastritis is not more common in patients with oesophagitis, and is unlikely to play a part in the pathogenesis of this disease.

Inducible nitric oxide synthase expression in gastroduodenal diseases infected with Helicobacter pylori

BACKGROUND

Nitric oxide (NO) is synthesized enzymatically from L-arginine by NO synthase, which is measured by inducible NO synthase (iNOS). Helicobacter pylori (H. pylori) infection produces a state of chronic immunostimulation in the gastric epithelium. Infection with cagA+ H. pylori has greater degree of gastric inflammation and epithelial cell damage. Therefore, we compared the levels of iNOS in patients with H. pylori infection in relation to cagA status and H. pylori-related disease.

MATERIALS AND METHODS

One hundred and seven patients, including 51 patients with gastric cancer, 12 patients with gastric ulcer, 18 patients with duodenal ulcer and 26 patients with chronic gastritis, were enrolled in this study. Biopsies from the antrum and body were obtained for histologic examination, culture and reverse transcriptionase-PCR (RT-PCR) for detection of iNOS gene expression. The presence of H. pylori was confirmed by Giemsa staining or culture and the gene expression of cagA in H. pylori isolates was confirmed by PCR.

RESULTS

H. pylori infection was detected in 70.1% (75/107) and cagA was detected in 84.8% (28/33). iNOS expression was detected in 49.5% (53/107) and there was no significant difference in iNOS expression according to H. pylori infection nor the cagA status in the gastroduodenal diseases. However, iNOS expression was more frequently detected in gastric cancer than the other H. pylori-related diseases (64.7% vs. 35.7%, p <.05).

CONCLUSION

Although NO was thought be involved in the gastric carcinogenesis, the level of NO production was not related to H. pylori infection or cagA status.

Apoptosis in gastric epithelium induced by Helicobacter pylori infection: implications in gastric carcinogenesis

OBJECTIVES

Helicobacter pylori is an identified carcinogen for gastric cancer, however, the underlying mechanisms remain to be defined. In this review, we sought to elucidate the role of apoptosis in gastric carcinogenesis, to determine the influence of H. pylori infection on apoptosis, and finally to provide insights into the mechanisms by which H. pylori may lead to gastric carcinogenesis.

METHODS

A broad-based MEDLINE and Current Contents literature search was performed to identify relevant publications between 1966 and March 2000 addressing H. pylori infection, apoptosis, cell proliferation, gastric carcinoma, oncogenes, and tumor suppressor genes, as well as the products of these genes. Abstracts from recent major conferences that provided adequate additional data were also included.

RESULTS

Apoptotic cells are rare in the glandular neck region (the generative cell zone) of normal gastric mucosa. With progression of atrophic gastritis, the generative cell zone shifts downward and a relatively large number of apoptotic cells occur. In intestinalized glands, both apoptotic cells and proliferative cells are present in deeper portions of the glands, corresponding to the generative zone. A higher frequency of apoptosis has been observed in gastric dysplasia than in coexisting gastric carcinomas, whereas the number of proliferative cells is significantly higher in gastric carcinoma than in dysplasia. Upregulation of oncogene bcl-2 in premalignant lesions and "downregulation" of the gene after malignant change is probably a common event. Accumulation of p53 protein is first detected in dysplasia, although mutation of the pS3 gene may occur in intestinal metaplasia. H. pylori infection induces apoptosis in gastric epithelial cells, which returns to normal after eradication of the infection. Numerous molecules produced by H. pylori including cytotoxin (VacA), lipopolysaccharide, monochloramine, and nitric oxide may directly induce apoptosis. Moreover, H. pylori-stimulated host inflammatory/immune responses lead to release of a large amount of cytokines. Cytokines produced by type 1 T helper cells, such as TNF-alpha and IFN-gamma, markedly potentiate apoptosis. Gastric cell proliferation is significantly higher in patients with H. pylori infection than in normal controls, and eradication of the infection leads to a reduction in cell proliferation. Apoptosis and cell proliferation are also increased in precancerous lesions such as gastric atrophy, intestinal metaplasia, and dysplasia in the presence of H. pylori infection. However, H. pylori-induced apoptosis may no longer be cell cycle-dependent in these lesions because of the occurrence of alterations and mutations of apoptosis-regulating genes, resulting in a loss of balance between apoptosis and cell proliferation.

CONCLUSIONS

It is hypothesized that H. pylori-induced apoptosis may play a key role in gastric carcinogenesis by increasing cell proliferation and/or resulting in gastric atrophy.

Helicobacter pylori induces apoptosis in gastric epithelial cells through inducible nitric oxide

BACKGROUND

Gastric mucosal injury by Helicobacter pylori has been suggested to be mediated by various cytokines induced by this organism. Nitric oxide (NO) is an important effector molecule involved in immune regulation and defence. To clarify the mechanisms by which H. pylori induces gastric mucosal cell injury, we examined whether H. pylori induces gastric epithelial death via NO production.

METHODS

Cytotoxic and non-cytotoxic strains of H. pylori were used. The death of MKN45 cells caused by H. pylori was examined by the 3-(4,5-dimethyl-thiazole-2yl)-2,5-diphenyl tetrazolium bromide (MTT) assays. Aminoguanidine was used to inhibit inducible nitric oxide synthase (iNOS) activity. Expression of iNOS mRNA was determined by the reverse transcriptase-polymerase chain reaction and the DNA fragmentation analysis was performed by using agarose gel electrophoresis.

RESULTS

The MTT assay revealed that neither viable H. pylori nor other components of the microorganism induced cell death. Both preincubation of MKN45 cells with interferon-gamma for 6 h and coculture with TNF-alpha significantly increased the cytotoxicity of H. pylori. Both cytotoxic and non-cytotoxic strains of H. pylori induced cell death. Expression of iNOS mRNA was observed in MKN45 cells at 6, 8 and 12 h after H. pylori inoculation. The cytotoxicity of H. pylori was inhibited by aminoguanidine and DNA fragmentation analysis showed that H. pylori induced apoptosis.

CONCLUSIONS

These findings suggested that viable H. pylori induces apoptosis of gastric epithelial cells via nitric oxide. Our study indicated that iNOS expression plays an important role in gastric cell injury.

Coexpression of interleukin-8 and inducible nitric oxide synthase in gastric mucosa infected with cagA+ Helicobacter pylori

The cagA-positive Helicobacter pylori strains are thought to be able to induce interleukin-8 expression and to be associated with gastroduodenal diseases. Inducible nitric oxide synthase (iNOS) may be involved in inflammatory pathogenesis. Our aim was to investigate the interrelationships between cagA and the expression of interleukin-8 and iNOS messenger RNAs, and with the type and degree of inflammation in gastric mucosa. In biopsies from 108 Chinese patients, the cagA, 16S rRNA, interleukin-8, and iNOS mRNAs were analyzed using reverse-transcription polymerase chain reaction. Specimens infected with cagA-positive strains had significantly more severe infiltration by mononuclear and polymorphonuclear leukocytes and more frequently expressed interleukin-8 and iNOS mRNAs than those infected with cagA-negative strains. iNOS and interleukin-8 mRNAs were significantly more frequently expressed together in the specimens with moderate or severe inflammation than in those with normal mucosa or mild inflammation. Our data suggest that interleukin-8 and excess nitric oxide play important roles in the pathogenesis of H. pylori-associated gastroduodenal diseases.

Endogenous nitric oxide in the regulation of gastric secretory and motor activity in humans

BACKGROUND

Studies in animals have shown that nitric oxide (NO) affects gastric secretory and motor functions. However, little information is available about the involvement of this substance in the control of gastric secretory and motor activity in man.

METHODS

This study, performed on 18 healthy, Helicobacter pylori-negative volunteers, was designed to evaluate the role of NO in the control of gastric acid secretion and of gastrin and somatostatin release in response to ordinary feeding (group A) and on gastric motor and electrical activity (group B). Gastric acid secretion was determined by means of intragastric pH-metry before and after feeding with a semi-liquid meal. Plasma levels of gastrin and somatostatin were measured using specific radioimmunoassays. Gastric emptying rate was measured using the 13C-acetate breath test, antral motor activity using a manometric catheter and myoelectric activity using cutaneous electrogastrography. Studies were repeated following pre-treatment with NG-monomethyl-L-Arginine (L-NMMA), L-Arginine (L-Arg) or their combination.

RESULTS

L-NMMA delayed the recovery of intragastric pH to the pre-meal value, and suppressed postprandial gastrin release while increasing the plasma somatostatin level. L-Arg did not affect postprandial pH and plasma hormones, but reversed L-NMMA-induced alterations in intragastric pH and in plasma gastrin and somatostatin levels. Both postprandial antral motor activity (motility index) and gastric emptying significantly increased in tests with L-NMMA, but this was not observed when L-NMMA was given in combination with L-Arg or when L-Arg alone was used. The gastric electrical pattern, as measured by cutaneous electrogastrography, was not affected by L-NMMA, L-Arg or their combination.

CONCLUSIONS

(1) Endogenous NO appears to be involved in the regulation of postprandial gastric acid secretion. This effect may be mediated by the changes in release of gastrin and somatostatin. (2) Endogenous NO delays gastric emptying and antral motor activity without affecting gastric myoelectrical activity.

Increased expression of inducible nitric oxide synthase and peroxynitrite in Helicobacter pylori gastric ulcer

The role of nitric oxide in ulcer formation remains unknown. Accordingly, we assessed local expression of inducible nitric oxide synthase (NOS) and nitration of tyrosine as an indicator of peroxynitrite formation in patients with Helicobacter pylori (HP)-associated gastric ulcers compared with HP-negative ulcers. Biopsy specimens were taken from the ulcer margin and from an area remote from the ulcer portion. Inducible NOS, nitrotyrosine, and macrophage immunoreactivity were assessed immunohistochemically using a labeled streptavidin-biotin method. In HP-positive gastric ulcers, inducible NOS and nitrotyrosine immunoreactivity was frequently observed at active ulcer margins, sometimes in surface epithelial cells as well as in the lamina propria. Occasionally, inducible NOS and nitrotyrosine reactivity were found in areas remote from the lesion in cases of HP-positive ulcer and HP-related gastritis. Macrophages accumulated significantly in the margin of HP-positive ulcers. In HP-negative gastric ulcers, inducible NOS and nitrotyrosine immunoreactivity also were frequent at the ulcer margin, but no significant immunoreactivity was observed at a distance. HP eradication caused significant attenuation in inducible NOS and macrophage immunoreactivity. In conclusion, nitric oxide and peroxynitrite formation is increased in HP-infected gastric mucosa, suggesting that HP promotes nitric oxide stress.

Proinflammatory activation of neutrophils and monocytes by Helicobacter pylori in patients with different clinical presentations

Chronic Helicobacter pylori infection is associated with mucosal inflammation. The aim of the present study was to assess human neutrophil and monocyte activation by H. pylori strains obtained from patients with different clinical presentations. Bacterial sonicates from 12 strains were used to stimulate phagocyte upregulation of CD11b/CD18 adherence molecules assessed by fluorescence flow cytometry and oxidative burst responses assessed by chemiluminescence. A dose-dependent activation of CD11b/CD18 adherence molecules was observed with all strains on both neutrophils and monocytes. The activities were similar for strains from patients with duodenal ulceration and for strains from asymptomatic volunteers irrespective of histopathologic grades of the biopsy specimens from the antral mucosa. The neutrophil chemiluminescence response correlated with histopathologic severity. We conclude that upregulation of neutrophil and monocyte adherence molecules by H. pylori sonicates is not associated with clinical presentation of the infection.

Inhibition of lipopolysaccharide-induced inducible nitric oxide (iNOS) mRNA expression and nitric oxide production by higenamine in murine peritoneal macrophages

Nitric oxide synthesized by inducible nitric oxide synthase (iNOS) has been implicated as a mediator of inflammation in rheumatic and autoimmune diseases. The effects of higenamine, a tetrahydroisoquinoline compound, on induction of NOS by bacterial lipopolysaccharide (LPS) were examined in murine peritoneal macrophages. LPS-induced nitrite/nitrate production was markedly inhibited by higenamine which at 0.01 mM, decreased nitrite/nitrate levels by 48.7+/-4.4%. This was comparable to the inhibition of LPS-induced nitrite/nitrate production by tetrandrin (49.51+/-2.02%) at the same concentration. Northern and Western blot analysis of iNOS expression demonstrated that iNOS expression was significantly attenuated following co-incubation of peritoneal macrophages with LPS (10 microg/ml; 18 hrs) and higenamine (0.001, 0.01 mM; 18 hrs). These results suggest that higenamine can inhibit LPS-induced expression of iNOS mRNA in murine peritoneal macrophages. The clinical implications of these findings remain to be established.

Oxidant stress, anti-oxidants, nitric oxide and essential fatty acids in peptic ulcer disease

In patients with duodenal ulcer (DU), the plasma levels of nitrite and lipid peroxides, the anti-oxidant content of red cells and plasma phospholipid fatty acid analysis were performed both before and after healing of the ulcer following treatment with lansoprazole, a proton pump inhibitor. These results showed that during the phase of active DU, the concentrations of antioxidants (superoxide dismutase, SOD, catalase and glutathione peroxidase) in red cells were low where as those of lipid peroxides and nitric oxide were high. Of the fatty acids measured, the concentration of palmitic acid (16:0) was increased during the active ulcer phase whereas those of arachidonic acid, alpha-linolenic acid and docosahexaenoic acid were low. These biochemical abnormalities reverted to normal following healing of the ulcer with lansoprazole. These results coupled with the observation that polyunsaturated fatty acids (PUFAs) can inhibit the growth of Helicobacterpylori and heal the ulcer suggest that free radicals, anti-oxidants, nitric oxide and PUFAs may play a significant role in the pathogenesis of DU. If this is true, it suggests that PUFAs can be exploited as potential anti-peptic ulcer drugs.