Role of Helicobacter pylori infection in gastroduodenal injury and gastric prostaglandin synthesis during long term/low dose aspirin therapy: a prospective placebo-controlled, double-blind randomized trial

OBJECTIVES: Whether gastric infection with Helicobacter pylori increases the risk of gastric mucosal injury during long term/low dose aspirin therapy is unknown. We examined whether H. pylori infection enhances upper GI mucosal damage, assessed endoscopically, in volunteers given low dose aspirin. We studied 61 healthy men and women, 29 with and 32 without active H. pylori infection. METHODS: We treated volunteers for 45 days with a placebo or aspirin (either 81 mg every day or 325 mg every 3 days). Gastroduodenal mucosal damage was then assessed by endoscopy, as was gastric histology and ex vivo gastric mucosal prostaglandin E2 and F2alpha synthesis rates. RESULTS: Erosive disease from low dose aspirin (erosions and/or ulcers) occurred in 50% of H. pylori-infected volunteers and in 16% of their noninfected counterparts (p = 0.02). Aspirin caused a significantly higher average mucosal injury score in the gastric antrum in H. pylori-infected participants than in noninfected subjects (p = 0.03), and two H. pylori-infected subjects developed antral gastric ulcers. Subjects with H. pylori gastritis treated with the placebo had nearly 50% higher gastric mucosal prostaglandin (E2 plus F2alpha) synthesis rates than their noninfected counterparts (108 +/- 6 ng/g/min versus 75 +/- 6 ng/g/min, p < 0.001). Aspirin reduced mucosal prostaglandin synthesis to similar levels in infected and noninfected participants. CONCLUSIONS: Long term/low dose aspirin therapy led to more gastric mucosal damage when H. pylori gastritis was present than when it was absent, despite similar degrees of gastric mucosal prostaglandin depletion.     

Effect of Helicobacter pylori Infection on the Severity of Gastroduodenal Mucosal Injury after the Acute Administration of Naproxen or Aspirin to Normal Volunteers

This study asked whether Helicobactor pylori infection accentuated the severity of NSAID-induced mucosal injury of the stomach or duodenum. We evaluated the severity of acute mucosal injury and H. pylori status in 61 normal volunteers (ages 22-43 yr) receiving naproxen (1000 mg, n = 30) or aspirin (3900 mg, n = 31) daily for 7 days. NSAID-induced gastric and duodenal mucosa each were endoscopically graded separately for hemorrhages and erosions-ulcers on a scale of 0 to 4. H. pylori infection was identified by a sensitive and specific ELISA. Nine of the 30 subjects in the naproxen group and 12 of the 31 subjects in the aspirin group were H. pylori positive (p = NS). There was no statistically significant difference between the frequency of mucosal hemorrhage in those with and those without H. pylori infection (44% compared with 33% for those receiving naproxen and 90% of those receiving ASA, p = NS for each). There were also no differences in the frequency or severity of erosive mucosal injury seen, e.g., acute ulcers were found in 16.5% and 17.5% of infected and uninfected subjects, respectively. We conclude that the presence of H. pylori infection does not influence the degree or type of mucosal damage associated with the acute administration of naproxen or aspirin.     

Helicobacter pylori infection potentiates aspirin induced gastric mucosal injury in Mongolian gerbils

BACKGROUND: Helicobacter pylori infection and non-steroidal anti-inflammatory drugs are two major causes of gastric ulceration but interactions between H pylori and these drugs in gastric mucosal injury are unclear. AIMS: We studied the influence of experimental H pylori infection on gastric mucosal injury induced by aspirin. SUBJECTS: Male Mongolian gerbils free of specific pathogens were used. METHODS: H pylori ATCC43504 culture broth was administered by oral gavage at seven weeks of age. After three weeks, acidified aspirin (400 mg/kg) was administered orally, and three hours later the total area of gastric erosions, myeloperoxidase (MPO) activity (an index of neutrophil accumulation), thiobarbituric acid reactive substances (TBARS, an index of lipid peroxidation), and KC/GRO (a chemoattractive cytokine in rodents) were measured in gastric mucosa. To determine the role of neutrophils in these circumstances, antigerbil neutrophil rabbit serum (ANS) was administered to some animals 18 hours before aspirin. RESULTS: Aspirin caused more extensive haemorrhagic erosions (33.1 (12.3) mm2) associated with greater MPO activity (1887.7 (598.5) microU/mg protein) and TBARS (0.33 (0.14) nmol/mg protein) and KC/GRO concentrations (28.3 (9.5) pg/mg protein) in infected than in uninfected gerbils (13.7 (2.3); 204.0 (68.9); 0.12 (0.06); 3.1 (0.8), respectively) Pretreatment with ANS inhibited the increases in gastric erosions, MPO activity, and TBARS but not KC/GRO concentration. The reduction in aspirin induced mucosal injury by administration of ANS was much greater in H pylori infected animals (65%) than in uninfected animals (31%). CONCLUSIONS: H pylori infection potentiates aspirin induced gastric mucosal injury by mechanisms that include accumulation of activated neutrophils.     

Helicobacter pylori induces apoptosis in mucosal lymphocytes in patients with gastritis

BACKGROUND: Previous studies suggest that Helicobacter pylori (H. pylori) induces apoptosis and compensatory hyperproliferation in gastric epithelial cells possibly explaining the carcinogenic capacity of the bacteria. The aim of this study was to measure the effect of H. pylori on apoptosis of gastric lymphoid cells in view of the development of gastric lymphoma. METHODS: 16 H. pylori-positive and 19 H. pylori-negative individuals were enrolled. Single cell suspensions were prepared from antral biopsies and apoptosis was measured by staining with the TUNEL-assay and the fluorochrome Hoechst 33342. Lymphocyte subsets were simultaneously identified by immunocytochemistry. RESULTS: The apoptotic index of all gastric mucosal cells was significantly higher in H. pylori-positive mucosa compared to negative controls. Additionally, H. pylori-infected patients showed a significant increase in apoptosis of mucosal B-lymphocytes. Apoptosis of T cells and plasma cells was unaffected by H. pylori. CONCLUSION: H. pylori induces apoptosis in mucosal B cells which might be important in the development of gastritis and possibly B-cell lymphoma of the mucosa-associated lymphoid tissue (MALT).     

Irsogladine maleate suppresses indomethacin-induced elevation of proinflammatory cytokines and gastric injury in rats

AIM： To investigate the mucosal protective effect and the mechanisms of action of the anti-ulcer drug irsogladine maleate in gastric injury induced by indomethacin in rats. METHODS： Gastric mucosal injury was induced in male Hos：Donryu rats by oral administration of indomethacin at a dose of 48 mg/kg. One hour before indomethacin treatment, animals were orally pretreated with irsogladine maleate at doses of 1 mg/kg, 3 mg/kg or 10 mg/kg. Four hours after indomethacin administration, the animals were sacrificed and their stomachs were rapidly removed and processed for the evaluation of gastric mucosal damage and the determination of the concentrations of tumor necrosis factor-α （TNF-α）, interleukin-1β （IL-1β）, IL-8 and myeloperoxidase （MPO） in mucosal tissues. RESULTS： Linear hemorrhagic mucosal lesions were observed primarily in the glandular stomach 4 h alter oral administration of indomethacin. Pretreatment with irsogladine maleate markedly reduced the number and severity of these lesions in a dose-dependent manner. The mucosal concentrations of proinflammatory cytokines （TNF-α, IL-1β, and IL-8） and MPO, which indicates the degree of mucosal infiltration by neutrophils, increased concomitantly with the occurrence of gastric injury in the indomethacintreated rats. Pretreatment with irsogladine maleate significantly decreased the levels of these inflammatory factors in gastric tissue elicited by indomethacin.CONCLUSION： The mucosal protective effects afforded by irsogladine maleate on gastric injury induced by indomethacin are mediated by inhibition of mucosal proinflammatory cytokine production and neutrophil infiltration, leading to suppression of mucosal inflammation and subsequent tissue destruction.     

Mucosal in Vitro Permeability in the Intestinal Tract of the Pig,the Rat,and Man: Species- and Region-Related Differences

Background: Excessive upregulation of gastric epithelial cell apoptosis is speculated to be associated with ulcerogenesis in Helicobacter pylori -positive peptic ulcer disease. H. pylori may have an ulcerogenic effect through induction of gastric epithelial cell apoptosis mediated by infiltrating T cells and their soluble products. Methods: The contents of soluble Fas ligand (sFasL) and interferon- &;#110 (IFN- &;#110 ) in organ cultures and the degree of apoptosis and the expression of apoptosis-related proteins in the gastric epithelium were examined using the mucosal tissues obtained from the antrum and the ulcer site in patients with H. pylori -positive gastric ulcer (GU). The molecular mechanisms of gastric epithelial cell apoptosis induced by sFasL and IFN- &;#110 were analyzed using epithelial cell lines, MKN 45 and KATO III. Results: The mucosal tissues of the ulcer site had substantially higher contents of sFasL and IFN- &;#110 in organ cultures regardless of its healing stage in association with increased numbers of apoptotic cells and enhanced expression of proapoptotic proteins Bak and Bax in the surface foveolar epithelium as compared with the antral tissues in patients with H. pylori -positive GU. The addition of sFasL caused increases in cytotoxic cell death and caspase-3 activation in MKN 45 and KATO III cells in which IFN- &;#110 -treated cells had more prominent effects than untreated cells. The expression of Bak in MKN 45 cells increased when they were treated with IFN- &;#110. Conclusions: Upregulation of mucosal sFasL and IFN- &;#110 may be involved in ulcerogenesis in patients with H. pylori- positive GU through induction of gastric epithelial cell apoptosis.     

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.     

幽门螺杆菌iceA1基因地域分布特征

iceA基因是近年来发现的一种幽门螺杆菌(Helicobacter pylori,H.pylori)毒力相关基因.H.pylori与胃黏膜上皮接触后可引起iceA1基因表达上调,该基因与nlaIIIR基因(位于乳糖奈瑟氏菌)具有相似性,其编码的蛋白质产物具有NlaIIIR样限制性核酸内切酶活性.研究表明,iceA1阳性...     

Increase in apoptosis and decrease in ornithine decarboxylase activity of the gastric mucosa in patients with atrophic gastritis and gastric ulcer after successful eradication of Helicobacter pylori

OBJECTIVE: Recent reports have shown that patients infected with Helicobacter pylori (H. pylori) have a higher risk of gastric cancer. However, the mechanism of this increased risk is still unclear. In the gastric mucosa, the size of a continuously renewed population of cells is determined by the rates of cell production and of cell loss. Ornithine decarboxylase (ODC) activity is elevated in various gastrointestinal cancers and serves as a marker of mucosal proliferative activity. Apoptosis occurs throughout the gut and is associated with cell loss. Both cell proliferation and cell loss have important roles in H. pylori-associated gastric carcinogenesis. Therefore, we investigated the effect of H. pylori eradication on ODC activity and apoptosis in the gastric mucosa of patients with atrophic gastritis and gastric ulcers. METHODS: Biopsy specimens of the gastric antrum were obtained at endoscopy from 17 H. pylori-positive gastric ulcers patients and 15 H. pylori-positive gastritis patients before and 4 wk after eradication therapy with amoxicillin, omeprazole, and a new anti-ulcer agent, ecabet sodium, and from 10 gastric ulcer patients in whom ulcer healed but H. pylori was left untreated. ODC activity and induction of apoptosis were determined immunohistochemically. RESULTS: H. pylori was successfully eradicated with the triple therapy in 12 (80%) of 15 gastritis patients and 13 (76%) of 17 gastric ulcer patients. ODC activity was present in the gastric mucosa in 21 (84%) patients before eradication but in only four (16%) patients after successful eradication (p = 0.0005). The apoptotic index increased significantly (p = 0.0006) from 4.2% +/- 0.4% before treatment to 7.4% +/- 0.5% after successful eradication. CONCLUSIONS: Successful eradication of H. pylori decreases mucosal ODC activity and increases apoptosis in the gastric mucosa. These findings indicate that by decreasing mucosal cell proliferation and increasing epithelial cell loss, H. pylori eradication may help decrease the subsequent risk of gastric cancer.     

Water extract of Helicobacter pylori stimulates interleukin-8 secretion by a human gastric epithelial cell line (JR-St) through protein tyrosine phosphorylation

BACKGROUND: Infection by Helicobacter pylori induces cytokine production in gastric mucosal cells. Production of interleukin-8 (IL-8) is known to be markedly increased and is believed to play an important role in gastric mucosal inflammation. The aim of this study was to elucidate the effects of soluble factors of H. pylori on IL-8 production in a gastric epithelial cell line, JR-St. METHODS: JR-St cells were cocultured with a H. pylori water extract, live H. pylori or culture medium supernatant for 24 h, then the IL-8 secreted into the culture medium was assayed. The effects of three different inhibitors; (i) an inhibitor of protein kinase C (PKC); (ii) an inhibitor of PKC and protein kinase A (PKA); and (iii) an inhibitor of protein tyrosine kinase (PTK) were also compared. Specific induction of IL-8 mRNA was also examined. RESULTS: Water extract of H. pylori increased IL-8 secretion 7.72-fold, more than the control. The increase was concentration dependent. Live bacteria, supernatant and water extract significantly stimulated IL-8 secretion. Addition of live bacteria increased IL-8 secretion most strongly, while the effect of water extract was small (22% that of live bacteria). Secretion was not inhibited by the PKC inhibitor staurosporine or the inhibitors of PKA and PKC H7. However, secretion was significantly reduced by the PTK inhibitor herbimycin in a dose-dependent manner. Furthermore, 24 h exposure to water extract increased IL-8 mRNA expression, suggesting water extract increased production of IL-8. CONCLUSIONS: Some soluble factors of H. pylori can stimulate IL-8 production by JR-St cells. Stimulation was not dependent on PKA or PKC but was, at least partially, dependent on protein tyrosine phosphorylation. This suggests that soluble factors of H. pylori can play an important role in mediating the inflammatory response of H. pylori gastritis.     

Sustained increase in the proliferation of rat colonic mucosa during chronic treatment with aspirin

The effects of indomethacin and aspirin on colonic epithelial proliferative activity, colonic prostaglandin synthesis, and colonic mucosal cyclic adenosine 3',5'-monophosphate content were examined. Administration of indomethacin (3 mg/kg.day, s.c.) for 2 wk suppressed ex vivo colonic prostaglandin E2 production by 50% and increased [3H]thymidine incorporation into mucosal DNA in vivo, but induced colonic inflammation. Higher doses of indomethacin were toxic and associated with high mortality. By contrast, administration of aspirin (50 mg/kg.day, s.c.) for 2-20 wk suppressed colonic prostaglandin E2 production by 97% and was unassociated with colonic inflammation or systemic toxicity. Suppression of colonic prostaglandin E2 production was associated with a sustained stimulation of [3H]thymidine incorporation into colonic mucosal deoxyribonucleic acid (2-20 wk) and an increase in the [3H]thymidine labeling index when examined at 20 wk. Basal cyclic adenosine 3',5'-monophosphate content of colonic mucosa was markedly reduced in aspirin-treated rats. Moreover, addition of dimethyl prostaglandin E2 or 8-Br-cyclic adenosine 3',5'-monophosphate suppressed the elevated levels of [3H]thymidine incorporation into mucosal deoxyribonucleic acid in incubated colonic segments from aspirin-treated rats. The results demonstrate that sustained suppression of colonic prostaglandin synthesis by aspirin is associated with a persistent increase in colonic epithelial proliferative activity. They support a role for local colonic prostaglandin synthesis as a negative modulator of epithelial growth, possibly mediated through increases in colonic mucosal cyclic adenosine 3',5'-monophosphate.     

Mucosal expression and luminal release of epidermal and transforming growth factors in patients with duodenal ulcer before and after eradication of Helicobacter pylori.

BACKGROUND: Epidermal growth factor (EGF) and transforming growth factor-alpha (TGF alpha) are potent gastric acid inhibitors and stimuli of mucosal growth and protection but their involvement in Helicobacter pylori associated duodenal ulcer has been little examined. AIM: To assess gastric acid secretion, plasma gastrin concentrations, mucosal content of EGF and TGF alpha, and mucosal expression of these peptides and their receptor (EGFr) as well as salivary and gastric luminal release of EGF under basal conditions and after pentagastrin stimulation in 10 healthy subjects and in 25 H pylori positive patients with duodenal ulcer before and after two weeks of triple anti-H pylori therapy and four weeks after the termination of this therapy. RESULTS: Pentagastrin stimulation caused a significant increase in salivary and gastric release of EGF both in healthy controls and patients with duodenal ulcers but in the patients, the eradication of H pylori resulted in several fold higher gastric luminal (but not salivary) EGF release than before the anti-H pylori therapy. Mucosal contents of immunoreactive EGF and TGF alpha and mucosal expression of EGF, TGF alpha, and EGFr in H pylori positive patients with duodenal ulcer were significantly higher than those in healthy H pylori negative controls and this increase persisted after eradication of H pylori. Basal plasma gastrin was significantly reduced after two weeks of triple therapy and four weeks after the H pylori eradication all ulcers were completely healed. CONCLUSIONS: (1) H pylori infection in patients with duodenal ulcer was accompanied by enhanced plasma gastrin and increased mucosal content and expression of TGF alpha, EGF, and EGFr; (2) H pylori eradication resulted in ulcer healing, reduction in plasma gastrin, and enhancement of gastric (but not salivary) luminal release of EGF, particularly after pentagastrin stimulation; and (3) enhanced mucosal content and expression of TGF alpha, EGF, and EGFr and increased luminal release of EGF may contribute to ulcer healing after eradication of H pylori.     

Effect of Helicobacter pylori eradication on anti-thrombotic dose aspirin-induced gastroduodenal mucosal injury

BACKGROUND: Helicobacter pylori infection and non-steroidal anti-inflammatory drugs are two major causes of gastric injury but the effect of H. pylori eradication on the development of aspirin-induced gastric mucosal injury is unclear. The aim of the present study was to investigate the effect of Helicobacter pylori eradication on gastroduodenal mucosal injury induced by antithrombotic doses of aspirin. METHODS: Patients who had been planned to start on medium-dose aspirin (300 mg) for any kind of indication were included in the study. All subjects underwent upper gastrointestinal endoscopy for determination of H. pylori status and Lanza score. The H. pylori-positive patients were randomized to receive either aspirin + eradication (omeprazole 20 mg b.i.d. and amoxicillin 500 mg q.i.d. for 2 weeks) or aspirin + placebo eradication. Endoscopic reassessment was done 4 months after the onset of aspirin or when symptoms developed. RESULTS: Thirty-two patients (placebo group n = 16, H. pylori-eradicated group n = 16) completed the study and Lanza scores of both groups were similar before treatment. Lanza scores significantly increased in the placebo group (0.69 +/- 0.87 vs 2.25 +/- 1.3, P < 0.0001) and did not change in the H. pylori-eradicated group after aspirin treatment (0.43 +/- 0.72 vs 0.75 +/- 0.93, P > 0.05). CONCLUSION: Helicobacter pylori eradication may prevent medium-dose aspirin-induced gastroduodenal mucosal injury.     

Eradication therapy of Helicobacter pylori directly induces apoptosis in inflammation-related immunocytes in the gastric mucosa--possible mechanism for cure of peptic ulcer disease and MALT lymphoma with a low-grade malignancy

BACKGROUND/AIMS: A possibility that the eradication therapy not only eliminates Helicobacter pylori (H. pylori) but also influences some factors regulating pathological changes in the gastric mucosa should be taken into consideration from some phenomena. Such as non-recurrent cases of peptic ulcer long-term in spite of unsuccessful anti-H. pylori eradication therapy and the effectiveness of eradication therapy for mucosa-associated lymphoid tissue with a low-grade malignancy except stomach. We hypothesized and investigated that antibiotic treatment for elimination of H. pylori might directly affect inflammatory cells to induce apoptosis in them and protect against pathological changes of gastric mucosa. METHODOLOGY: Subjects consisted of twenty-one patients with chronic gastritis. All were H. pylori positive and we investigated the effects of eradication therapy of H. pylori on inflammation-related immunocytes in the gastric mucosa of patients with chronic gastritis caused by H. pylori isolated mononuclear leukocytes which were taken from the patients and were examined for apoptosis-related morphological changes and DNA fragmentation before and after the therapy. Eradication therapy of H. pylori was performed by lansoprazole 30 mg/day, amoxicillin 1500 mg/day and clarithromycin 400 mg/day for one week. RESULTS: After the H. pylori eradication therapy, regardless of its effect on H. pylori status, marked vacuolation and degeneration were observed in mononuclear leukocytes in the gastric mucosa with a concomitant enhancement of nuclear DNA fragmentation. CONCLUSIONS: This observation suggests that H. pylori eradication therapy itself induces apoptosis in mononuclear leukocytes in the gastric mucosa.     

Role of Endothelin-converting Enzyme-1 in the Suppression of Constitutive Nitric Oxide Synthase in Rat Gastric Mucosal Injury by Indomethacin

Background: Disturbances in nitric oxide generation and the release of a vasoactive peptide, endothelin-1 (ET-1), are well recognized early events in pathogenesis of NSAID-induced gastropathy. In this study using phosphoramidon, a potent inhibitor of endothelin-converting enzyme-1 (ECE-1), we investigated the influence of ET-1 on the expression of constitutive (cNOS) and inducible nitric oxide synthase (NOS-2) during gastric mucosal injury caused by indomethacin. Methods: The experiments were conducted with groups of rats pretreated intragastrically with phosphoramidon (10, 20, and 40 mg/kg) or vehicle, followed 30 min later by an intragastric dose of indomethacin (60 mg/kg). The animals were killed 4 h later and their mucosal tissue subjected to macroscopic damage assessment and biochemical measurements. Results: In the absence of phosphoramidon, indomethacin caused extensive multiple hemorrhagic lesions of glandular mucosa, accompanied by a 29.9-fold increase in epithelial cell apoptosis, a 13.3-fold increase in NOS-2 and a 5.5-fold decline in the activity of cNOS, while the mucosal expression of ECE-1 activity increased 4-fold and the level of ET-1 showed a 4.8-fold increase. Pretreatment with phosphoramidon produced dose-dependent reduction in the extent of mucosal damage caused by indomethacin, accompanied by a significant recovery in the expression of cNOS, and a marked decline in ECE-1, epithelial cell apoptosis and the mucosal level of ET-1. Phosphoramidon, however, had no effect on the indomethacin-induced increase in the mucosal expression of NOS-2. Conclusions: The results suggest that suppression of ET-1 generation counters the mucosal drop in cNOS and the extent of gastric mucosal damage caused by indomethacin, but has no effect on the mucosal responses associated with up-regulation of NOS-2 expression. Hence, only cNOS plays a role in the protection of gastric mucosa against damage by NSAIDs.     

Inhibition of Gastric Mucosal Laminin Receptor by Helicobacter pylori Lipopolysaccharide: Effect of Sucralfate

The maintenance of gastric mucosal integrity depends upon the interaction involving specific cell surface receptors with distinct proteins of extracellular matrix, one of which is laminin. We present here evidence that lipopolysaccharide from Helicobacter pylori interferes with laminin binding on the receptor. The laminin receptor was isolated from gastric epithelial cell membrane by the procedure involving membrane solubilization with octylglucoside followed by affinity chromatography on laminin-coupled Sepharose. The receptor protein yielded on SDS-PAGE a single 67 kDa band. After radioiodination, the protein was incorporated into liposomes which displayed specific affinity toward laminin-coated surface. The binding of liposomal receptor to the laminin-coated surface was inhibited by lipopolysaccharide from H. pylori. The inhibitory effect was proportional to the concentration of lipopolysaccharide up to 50 micrograms/ml, at which a 96% decrease in binding occurred. Introduction of sucralfate to the assay system led to the prevention of the inhibitory effect of lipopolysaccharide on the receptor-laminin binding. The effect was dose dependent and, at sucralfate concentration of 45 micrograms/ml, nearly complete restoration in binding was achieved. The results suggest that H. pylori also may be capable of disrupting the gastric mucosal integrity through a similar mechanism in vivo, and that anti-ulcer drug sucralfate counteracts this effect.     

Role of endothelin-converting enzyme-1 in the suppression of constitutive nitric oxide synthase in rat gastric mucosal injury by indomethacin

BACKGROUND: Disturbances in nitric oxide generation and the release of a vasoactive peptide, endothelin-1 (ET-1), are well recognized early events in pathogenesis of NSAID-induced gastropathy. In this study using phosphoramidon, a potent inhibitor of endothelin-converting enzyme-1 (ECE-1), we investigated the influence of ET-1 on the expression of constitutive (cNOS) and inducible nitric oxide synthase (NOS-2) during gastric mucosal injury caused by indomethacin. METHODS: The experiments were conducted with groups of rats pretreated intragastrically with phosphoramidon (10, 20, and 40 mg/kg) or vehicle, followed 30 min later by an intragastric dose of indomethacin (60 mg/kg). The animals were killed 4 h later and their mucosal tissue subjected to macroscopic damage assessment and biochemical measurements. RESULTS: In the absence of phosphoramidon, indomethacin caused extensive multiple hemorrhagic lesions of glandular mucosa, accompanied by a 29.9-fold increase in epithelial cell apoptosis, a 13.3-fold increase in NOS-2 and a 5.5-fold decline in the activity of cNOS, while the mucosal expression of ECE-1 activity increased 4-fold and the level of ET-1 showed a 4.8-fold increase. Pretreatment with phosphoramidon produced dose-dependent reduction in the extent of mucosal damage caused by indomethacin, accompanied by a significant recovery in the expression of cNOS, and a marked decline in ECE-1, epithelial cell apoptosis and the mucosal level of ET-1. Phosphoramidon, however, had no effect on the indomethacin-induced increase in the mucosal expression of NOS-2. CONCLUSIONS: The results suggest that suppression of ET-1 generation counters the mucosal drop in cNOS and the extent of gastric mucosal damage caused by indomethacin, but has no effect on the mucosal responses associated with up-regulation of NOS-2 expression. Hence, only cNOS plays a role in the protection of gastric mucosa against damage by NSAIDs.