Inhibition of human gastric cyclic AMP production by Helicobacter pylori protein--possible involvement of mucosal prostaglandin E2

A role for CagA/VacA in Helicobacter pylori inhibition of murine duodenal mucosal bicarbonate secretion

Duodenal mucosal bicarbonate secretion is diminished in patients with Helicobacter pylori (HP)-associated duodenal ulcer disease. We examined whether HP water extracts inhibit murine duodenal mucosal bicarbonate secretion in vitro, and the mechanisms involved. Murine duodenal mucosae were mounted in Ussing chambers. Short-circuit current and bicarbonate secretion was measured. CagA/VacA-positive HP water extract (HPWE+/+) markedly inhibited PGE2-, carbachol-, or the calcium ionophore A23187-stimulated bicarbonate secretion in a dose-dependent manner. While 3-isobutyl-1-methylxanthine-stimulated bicarbonate secretion was not affected by HPWE+/+, HPWE+/+ did diminish forskolin-stimulated bicarbonate secretion. HPWE+/+ markedly diminished PGE2-induced increases in duodenal mucosal cAMP. CagA/VacA of HP decreases Ca2+-mediated bicarbonate secretion downstream of increases in intracellular Ca2+. Dimunition of PGE2-stimulated bicarbonate secretion occurs, in part, by inhibition of adenylate cyclase, which leads to decreased cAMP levels. The ability of virulent HP strains to inhibit duodenal bicarbonate secretion through multiple intracellular pathways likely contributes to the pathogenesis of HP-associated duodenal ulcer disease.

A sensitive, colorimetric, microtitre assay for alcohol dehydrogenase in standard endoscopic gastric biopsies

Traditional assays of alcohol dehydrogenase (ADH) activity in gastric mucosa use spectrophotometry of tissue homogenates, which are based on the reduction of nicotinamide adenine dinucleotide (NAD). We describe a colorimetric method using the coupled reduction of N,N-dimethyl-4-nitrosoaniline. This method has increased sensitivity, allowing activity to readily be determined in standard endoscopic biopsies. Tissue homogenisation has been replaced by an incubation stage, and the method has been optimised for a 96-well plate reader, allowing rapid processing of large numbers of samples. We found that Helicobacter pylori infection and age have a significant effect on gastric ADH activity.

Omeprazole and sucralfate in the treatment of NSAID-induced gastric and duodenal ulcer

AIM

To establish the healing efficacy of two drugs, omeprazole and sucralfate, when given to patients who had developed gastric or duodenal ulcer while undergoing chronic treatment with non-steroidal anti-inflammatory drugs (NSAIDs).

METHODS

Ninety-eight patients with arthritis or arthrosis and NSAID-related gastric or duodenal ulcer were admitted to the endoscopic, single-blind study. They were randomized to receive either omeprazole 20 mg o.m. or sucralfate 2 g b.d. for 4-8 weeks. The patients continued to receive the same NSAID during the trial. Upper gastrointestinal endoscopy was performed at entry and after 4 or 8 weeks.

RESULTS

Eighty-eight patients completed the 4-week study, but only 81 were available for final analysis at 8 weeks. Omeprazole was significantly superior to sucralfate in inducing gastric ulcer healing after both 4 (87 vs. 52%, P = 0.007) and 8 weeks (100 vs. 82%, P = 0.04). No statistically significant difference in duodenal ulcer healing rates emerged between the two groups either at 4 (79 vs. 55%) or 8 weeks (95 vs. 73%). The healing rates in patients with combined gastric and duodenal ulcer were 67 vs. 33% after 4 weeks and 6 7 vs. 6 7% after 8 weeks of treatment. The percentages of asymptomatic patients were similar in the two treatment groups both at 4 (70 vs. 73%) and 8 weeks (70 vs. 75%). H. pylori infection did not influence healing rates, but significantly more H. pylori-positive patients healed with omeprazole.

CONCLUSIONS

The results of this study show that omeprazole is superior to sucralfate in healing NSAID-induced gastroduodenal ulcer in patients who continue to take anti-inflammatory drugs. The good results observed were unrelated to H. pylori status.

Does Helicobacter pylori status affect nonsteroidal anti-inflammatory drug-associated gastroduodenal pathology?

There are two lines of thought regarding the interrelationship between the damaging effects of Helicobacter pylori and those of nonsteroidal anti-inflammatory drugs (NSAIDs) on the gastroduodenal mucosa. First, both pathogenic factors exert a damaging effect on the mucosa, and therefore an additive, or even synergistic, effect occurs, leading to aggravation of mucosal damage. Second, mutual antagonism exists, leading to one of the pathogenic factors actually deriving some protection from the damaging potential of the other. Microscopically, H. pylori- and NSAID-associated gastritis are recognized as two separate entities. Furthermore, pathologically, the mechanisms of mucosal damage of the two factors have important differences; for example, H. pylori increases the synthesis of prostaglandins, whereas NSAIDs inhibit prostaglandin synthesis. The role of H. pylori infection in patients with NSAID-associated peptic ulcers has been addressed recently in two large, randomized, multicenter trials. From these studies, it appears that antisecretory drugs are more effective in H. pylori-positive peptic ulcer patients taking NSAIDs than in H. pylori-negative patients taking these drugs. The studies, however, do not provide any evidence that H. pylori infection reduces the pathogenic effects of NSAIDs. Other studies, however, have shown protection against NSAID-associated gastroduodenal damage in H. pylori-negative patients. Thus, there are no firm conclusions on the role of H. pylori infection in patients with NSAID-associated peptic ulcers. Based on the available data, however, practical considerations and guidelines are listed.

Gastric and duodenal mucosal blood flow in patients receiving non-steroidal anti-inflammatory drugs--influence of age, smoking, ulceration and Helicobacter pylori

Using laser Doppler flowmetry, we measured gastric and duodenal mucosal blood flow in 70 patients who had taken non-steroidal anti-inflammatory drugs (NSAIDs) for longer than 4 weeks, and studied the correlation with demographic factors, ulceration, and Helicobacter pylori. Blood flow was also measured in 17 other subjects not taking any drugs. Measurements were taken from healthy-looking mucosa in the gastric antrum and the first part of the duodenum. Both gastric and duodenal blood flow values were significantly lower in patients taking NSAID than in those who did not. In the NSAID group, the median duodenal mucosal blood flow was 150 perfusion units in smokers (n = 29) compared with 175 in non-smokers (P = 0.024), 123 units in patients with duodenal ulcers (n = 12) compared with 160 in those without duodenal ulcers (P = 0.020), 135 units in patients with H. pylori (n = 30) compared with 168 in patients without H. pylori (P = 0.033), and 118 in smokers infected with H. pylori compared with 175 units in non-smokers not infected with H. pylori (F = 13.4, P = 0.0005). There was no correlation with age. Gastric blood flow was not significantly influenced by any of the above variables. These results suggest that chronic NSAID intake is associated with reduced blood flow in both the stomach and duodenum. However, amongst NSAID patients, duodenal, but not gastric, mucosal blood flow is reduced in smokers, and in those with duodenal ulcers and H. pylori.(ABSTRACT TRUNCATED AT 250 WORDS)