Helicobacter pylori augments the acid inhibitory effect of omeprazole on parietal cells and gastric H(+)/K(+)-ATPase

Pathways of Gastric Carcinogenesis, Helicobacter pylori Virulence and Interactions with Antioxidant Systems, Vitamin C and Phytochemicals

Helicobacter pylori is a class one carcinogen which causes chronic atrophic gastritis, gastric intestinal metaplasia, dysplasia and adenocarcinoma. The mechanisms by which H. pylori interacts with other risk and protective factors, particularly vitamin C in gastric carcinogenesis are complex. Gastric carcinogenesis includes metabolic, environmental, epigenetic, genomic, infective, inflammatory and oncogenic pathways. The molecular classification of gastric cancer subtypes has revolutionized the understanding of gastric carcinogenesis. This includes the tumour microenvironment, germline mutations, and the role of Helicobacter pylori bacteria, Epstein Barr virus and epigenetics in somatic mutations. There is evidence that ascorbic acid, phytochemicals and endogenous antioxidant systems can modify the risk of gastric cancer. Gastric juice ascorbate levels depend on dietary intake of ascorbic acid but can also be decreased by H. pylori infection, H. pylori CagA secretion, tobacco smoking, achlorhydria and chronic atrophic gastritis. Ascorbic acid may be protective against gastric cancer by its antioxidant effect in gastric cytoprotection, regenerating active vitamin E and glutathione, inhibiting endogenous N-nitrosation, reducing toxic effects of ingested nitrosodimethylamines and heterocyclic amines, and preventing H. pylori infection. The effectiveness of such cytoprotection is related to H. pylori strain virulence, particularly CagA expression. The role of vitamin C in epigenetic reprogramming in gastric cancer is still evolving. Other factors in conjunction with vitamin C also play a role in gastric carcinogenesis. Eradication of H. pylori may lead to recovery of vitamin C secretion by gastric epithelium and enable regression of premalignant gastric lesions, thereby interrupting the Correa cascade of gastric carcinogenesis.

Progress in research of Helicobacter pylori efflux pumps

The wide use and abuse of antibiotics have led to serious drug resistance of Helicobacter pylori (H. pylori), and strains simultaneously resistant to metronidazole, clarithromycin and amoxicillin have appeared. As a result, the rate of H. pylori eradication declines clinically. The presence of bacterial efflux pumps is an important mechanism responsible for bacterial resistance to most antibiotics, especially multiple drug resistance (MDR). In recent years, much attention has been paid to the research of efflux pumps and their inhibitors to solve the problem of drug resistance of H. pylori. In this paper we will introduce main efflux pumps and efflux pump inhibitors in H. pylori.

Clinical outcome of patients with Helicobacter pylori infection: the bug, the host, or the environment?

It is well established that only a minority of patients with Helicobacter pylori infection develop severe inflammation leading to peptic ulcer or gastric cancer. Recent evidence suggests that the virulence factors of the organism do not seem crucial in the progression of inflammation towards a more severe disease. It seems probable that other host derived and environmental factors are more significant in determining clinical outcome but additional studies are needed to clarify the underlying mechanisms involved in the pathogenesis of infection.

Dynamic functional and ultrastructural changes of gastric parietal cells induced by water immersion-restraint stress in rats

AIM: To investigate the dynamic functional and ultrastructural changes of gastric parietal cells induced by water immersion-restraint stress (WRS) in rats.

METHODS: WRS model of Sprague-Dawley (SD) rats was established. Fifty-six male SD rats were randomly divided into control group, stress group and post-stress group. The stress group was divided into 1, 2 and 4 h stress subgroups. The post-stress group was divided into 24, 48 and 72 h subgroups. The pH value of gastric juice, ulcer index (UI) of gastric mucosa and H⁺, K⁺-ATPase activity of gastric parietal cells were measured. Ultrastructural change of parietal cells was observed under transmission electron microscope (TEM).

RESULTS: The pH value of gastric juice decreased time-dependently in stress group and increased in post-stress group. The H⁺, K⁺-ATPase activity of gastric parietal cells and the UI of gastric mucosa increased time-dependently in stress group and decreased in post-stress group. Compared to control group, the pH value decreased remarkably (P = 0.0001), the UI and H⁺, K⁺-ATPase activity increased significantly (P = 0.0001, P = 0.0174) in 4 h stress subgroup. UI was positively related with stress time (r = 0.9876, P < 0.01) but negatively with pH value (r = -0.8724, P < 0.05). The parietal cells became active in stress group, especially in 4 h stress subgroup, in which plenty of intracellular canalicular and mitochondria were observed under TEM. In post-stress group, the parietal cells recovered to resting state.

CONCOUSION: The acid secretion of parietal cells is consistent with their ultrastructural changes during the development and healing of stress ulcer induced by WRS and the degree of gastric mucosal lesions, suggesting gastric acid play an important role in the development of stress ulcer and is closely related with the recovery of gastric mucosal lesions induced by WRS.

Impact of Helicobacter pylori eradication on the anti-secretory efficacy of lansoprazole in gastroesophageal reflux disease patients

BACKGROUND

Helicobacter pylori eradication was recommended for the prevention of atrophic gastritis in gastroesophageal reflux disease (GERD) patients on long-term omeprazole treatment. It has been also shown that the treatment with proton pump inhibitors produces lower intragastric pH after H. pylori eradication in subjects with peptic ulcer and healthy individuals. The aim of the present study was to test the hypothesis of whether the efficacy of lansoprazole is reduced after the eradication of H. pylori in GERD patients with peptic esophagitis.

METHODS

Eight-hour intragastric pH recordings were performed before and after an 8-day course of lansoprazole (30 mg once daily) in 10 H. pylori-positive male patients with reflux esophagitis and were repeated after the H. pylori eradication. Intragastric acidity was measured by using an antimony electrode placed 10 cm below the cardia.

RESULTS

Baseline median preprandial, post-prandial, total intragastric pH and the percentage of time with pH < 3 were not different before and after H. pylori eradication without lansoprazole treatment. During lansoprazole treatment, median post-prandial intragastric pH was lower (4 vs 2.7; P < 0.05) and the percentage of time with pH < 3 was longer (3.4%vs 41.8%; P < 0.05) after H. pylori eradication. Median total intragastric pH tended to be lower after eradication but no difference was found in preprandial median pH.

CONCLUSIONS

In patients with reflux esophagitis treated with lansoprazole, intragastric pH increased significantly when H. pylori was present, especially in the post-prandial period, whereas baseline pH remained unchanged after H. pylori eradication.

Direct measurement of gastric H+/K+-ATPase activities in patients with or without Helicobacter pylori-associated chronic gastritis

AIM: The role of Helicobacter pylori (H pylori ) infection in gastric acid secretion of patients with chronic gastritis remains controversial. This study was designed to elucidate the effect of H pylori on H⁺/K⁺-ATPase activities in gastric biopsy specimens.

METHODS: Eighty-two patients with chronic gastritis who had undergone upper endoscopy were included in this study. H pylori infection was confirmed by rapid urease test and histology. Gastric H⁺/K⁺-ATPase activities and serum gastrin concentrations were measured by an enzymatic method and radioimmunoassay, respectively. For those patients who received triple therapy for eradicating H pylori, changes in the activity of gastric H⁺/K⁺-ATPase and serum gastrin levels were also measured.

RESULTS: The mean gastric H⁺/K⁺-ATPase activity in H pylori-positive group (42 patients) was slightly higher than that in H pylori-negative group (29 patients) (169.65±52.9 and 161.38±43.85 nmol P_i/(mg·h), respectively, P = 0.301). After eradication of H pylori, the gastric H⁺/K⁺-ATPase activities slightly decreased compared to prior therapy (165.03±59.50 and 158.42±38.93 nmol P_i/(mg·h), respectively, P = 0.805). The mean basal gastrin concentration was slightly higher in H pylori-positive patients than in H pylori-negative patients (87.92±39.65 pg/mL vs 75.04± 42.57 pg/mL, P = 0.228). The gastrin levels fell significantly after the eradication of H pylori. (Before treatment 87.00±30.78 pg/mL, after treatment 64.73±18.96 pg/mL, P = 0.015).

CONCLUSION: Gastric H⁺/K⁺-ATPase activities are not associated with H pylori status in patients with chronic gastritis.

The effects of nocturnal acid breakthrough on Helicobacter pylori eradication

BACKGROUND

The effects of nocturnal gastric acid breakthrough (NAB) on Helicobacter pylori eradication are still unknown in peptic ulcer patients. The purposes of this study were to compare the effect of lansoprazole 30 mg twice a day (bid) to lansoprazole 60 mg once a day (qd) on the prevalence of NAB, and to determine whether NAB affects the eradication of H. pylori in peptic ulcer patients.

METHODS

Experiments were carried out in 67 patients with H. pylori-positive peptic ulcers. They were randomized into two groups, one treated with a combination of lansoprazole 60 mg, clarithromycin 1.0 g, and amoxycillin 2.0 g once a day before breakfast (qd group), and the other, divided doses of the drugs were given before breakfast and dinner (bid group) for 2 weeks.

RESULTS

NAB occurred in 31 patients, 55.2% in qd group, and 39.5% in bid group (p =.226). H. pylori eradication was achieved in 61.3% in NAB positive group and 83.3% in NAB negative group (p =.055). The mean duration of NAB for H. pylori eradication group was 99.3 +/- 22.7 min, and 293.2 +/- 49.8 min for H. pylori persistence group (p <.05). The median intragastric pH of the H. pylori eradication and persistence group was 5.7 +/- 0.2 and 4.2 +/- 0.4, respectively (p <.05).

CONCLUSIONS

Neither the morning dose and the divided dose regimen of lansoprazole affected the intragastric acidity and occurrence of the NAB. NAB did not influence H. pylori eradication in peptic ulcer patients, but the duration of NAB and total intragastric median pH were found to influence the H. pylori eradication.