Conceivable mechanisms by which Helicobacter pylori provokes duodenal ulcer disease

Rise and fall of peptic ulceration: A disease of civilization?

Humans and Helicobacter pylori have evolved and adapted over tens of thousands of years. Yet peptic ulcer disease appeared to be rare prior to the 19th century. The prevalence of peptic ulcer disease increased between 1850 and 1900 and culminated in a cohort at high risk that was born at the end of the 19th century. This coincided with the provision of safe water and improvements in sanitation and personal hygiene. One hypothesis for the emergence of peptic ulcer disease focuses on the rate of development of atrophic gastritis induced by H. pylori. The hypothesis developed in this article focuses on delay in the age of acquisition of H. pylori to a time when immune and inflammatory responses to the infection were more mature. Whereas the acquisition of H. pylori in infancy usually resulted in mild pangastritis, hypochlorhydria, and a low risk for peptic ulcer disease, delayed acquisition could cause either more severe pangastritis (predisposing to gastric ulceration) or gastritis largely restricted to the antrum of the stomach (predisposing to duodenal ulceration). The decline in the prevalence of peptic ulcer disease over the past 100 years parallels the decline in the prevalence of H. pylori. The epidemic of ulcer disease in the first half of the 20th century seems likely to be an adverse effect of important public health measures undertaken in the latter half of the 19th century.

Helicobacter pylori infection and duodenal gastric metaplasia in healthy young adults

BACKGROUND/AIMS

Duodenal ulcers occur relatively frequently in adolescents, like in adults, and may relate to Helicobacter pylori infection and duodenal gastric metaplasia (DGM). This study investigated the association between H. pylori infection and DGM in healthy adults aged 20-29.

METHODS

Between 1995 and 2005, endoscopic biopsies of the duodenum, antrum and body were taken from healthy, young volunteers, who were first-year medical students, faculty staff, residents, and research assistants of Gyeongsang National University in Jinju, Korea. Urease tests were performed and the extent of DGM and histopathological grades according to the Updated Sydney System were determined.

RESULTS

In total, 662 subjects were enrolled (429 males and 233 females). The median age was 22.3 years. The overall incidence of DGM was 11.5% but DGM was more frequent in males (15.4%) than in females (4.3%) (p<0.0001). While H. pylori positivity rates changed significantly during the 1995-2005 period (p<0.01), the incidences of DGM did not. DGM was observed in 7.2% and 14.9% of subjects who were and were not colonized with H. pylori, respectively. DGM was also associated with less severe chronic gastritis and the absence of active gastritis in both the antrum and body, and the absence of follicles in the antrum (p<0.05).

CONCLUSIONS

These findings suggested that DGM is not rare in healthy young adults and is unrelated to gastric H. pylori infection.

Increasing gastric juice pH level prior to anti-Helicobacter pylori therapy may be beneficial to the healing of duodenal ulcers

The aim of this study was to observe the efficacy of clarithromycin-based triple therapy for Helicobacter pylori (Hp)-infected duodenal ulcer when combined with different pH levels of gastric juices. A total of 160 patients with Hp-infected duodenal ulcers were randomly allocated into two groups. Patients in the treatment group (n=80) were administered a 20-mg dose of omeprazole twice daily for 1 week and then the treatment and control groups (n=80) received therapy for Hp infection and duodenal ulcers. We observed the ulcer healing stage, the content of anti-Hp IgA in gastric juice and the Hp eradication rate before and after proton pump inhibitor therapy in the two groups. Results revealed that the Hp eradication rate in the treatment group was 93% compared with 81% in the control group, and the difference was statistically significant (P<0.05). The ulcer healing rate in the treatment group was 93%, compared with 70% in the control group (P<0.05). A positive linear correlation was observed between gastric pH and the content of anti-Hp IgA in gastric juice (P<0.05). Increasing gastric pH prior to anti-Hp therapy may be beneficial to the eradication of Hp and for promoting the healing of duodenal ulcers.

Helicobacter pylori vacuolating cytotoxin inhibits duodenal bicarbonate secretion by a histamine-dependent mechanism in mice

BACKGROUND

The pathogenic mechanisms involved in Helicobacter pylori-induced duodenal mucosal injury are incompletely understood. In the present study, we sought to investigate the effect of H. pylori vacuolating cytotoxin (VacA) on duodenal mucosal bicarbonate (HCO3-) secretion.

METHODS

Concentrated bacterial culture supernatants from an H. pylori wild-type strain producing VacA with s1/m1 genotypes (P12) and from an isogenic mutant lacking VacA (P12DeltavacA) were used. HCO3- secretion by murine duodenal mucosa was examined in vitro in Ussing chambers. Duodenal mucosal histamine release was measured using enzyme-linked immunosorbent assay. The expression of histamine H2 receptor was examined by immunohistochemical analysis.

RESULTS

In a dose-dependent manner, the VacA-positive supernatant P12 reduced prostaglandin E2 (PGE2)-stimulated duodenal mucosal HCO3- secretion to a maximum of 49% (P<.0001), whereas P12DeltavacA did not result in significant inhibition (P>.05). Purified VacA had a similar effect. Histamine H2 receptor antagonists attenuated the effect of P12 on PGE2-induced HCO3- secretion. P12 stimulated duodenal histamine release in a dose-dependent manner, and exogenous histamine inhibited PGE2-stimulated duodenal HCO3- secretion. H2 receptor expression was found in duodenal epithelial cells, the enteric nerve plexus, and lymphocytes in Peyer's patch.

CONCLUSIONS

H. pylori VacA inhibits PGE2-stimulated duodenal epithelial HCO3- secretion by a histamine-dependent mechanism. This effect likely contributes to the damaging effect of H. pylori in the duodenal mucosa.

Strong activation of PAR-2 receptors: a common trigger for the development of gastrointestinal adenocarcinomas?

Helicobacter pylori infection is considered to be an important factor in the development of gastric cancer, while duodenogastroesophageal reflux is claimed to be the main cause of development of esophageal adenocarcinoma. A pronounced activation of PAR-2 receptors may be a common denominator in triggering the development of these cancers, and possibly pancreatic and colonic cancers as well. Evidence supporting such a concept is presented.

A new subtype of 3’ region of cagA gene in Helicobacter pylori strains isolated from Zhejiang Province in China

AIM: To isolate the subtypes of 3’ region of cagA gene in Helicobacter pylori (H pylori) strains from Zhejiang Province in China and to investigate their relations to H pylori-associated gastroduodenal diseases.

METHODS: One hundred and thirty-seven H pylori clinical strains were isolated from the gastric mucosa specimens of 74 patients with chronic gastritis, 61 with peptic ulceration, and 2 with gastric cancer. Bacterial genomic DNA was extracted and 3’ region of cagA gene was amplified by polymerase chain reaction (PCR). Subtypes of 3’ region of cagA gene were determined by the size of PCR amplified segments. The sequences of the subtypes were analyzed by PCR-based sequencing.

RESULTS: Of the 137 H pylori isolates from Zhejiang Province, 132 (96.4%) yielded PCR products that could be classified into three groups of subtypes, named as subtypes I, II, and III according to their sizes. The sizes of subtypes I, II, and III were 648-650 bp, 705-707 bp, and 815 bp, respectively. Among the 132 cagA-positive H pylori strains, 123 (93.2%) belonged to the group of subtype I, 6 (4.5%) presented subtype II, 1 (0.8%) was subtype III, and 2 (1.5%) presented subtypes I and III both. The primary structure of subtype I was composed of 3 repeats of R1, 1 repeat of R2 and 1 repeat of R3. Subtype II possessing 4 repeats of R1, 2 repeats of R2 and 1 repeat of R3 was a newly found type of 3’ region of cagA gene which had not been reported before. The primary structure of subtype III consisted of 4 repeats of R1, 1 repeat of R2 and 2 repeats of R3. Comparison of the sequences of subtype I strains with the corresponding sequences deposited in GenBank, showed a similarity of 95.0% (94.0%-96.1%) for nucleotide sequences and 95.9% (94.9%-97.4%) for deduced amino acid sequences. Comparison of the sequences of subtype III strains with the corresponding sequences deposited in GenBank, showed a similarity of 93.9% (90.8%-96.9%) for nucleotide sequences and 93.2% (90.2%-96.2%) for deduced amino acid sequences. Among subtype II strains, the nucleotide and deduced amino acid sequences showed a similarity of 95.2% (94.1%-96.5%) and 96.4% (93.8%-97.9%), respectively. There were no statistical differences in the distribution of subtypes of 3’ region of cagA gene among different H pylori-associated gastroduodenal diseases (χ² = 11.544, P > 0.05).

CONCLUSION: There are three subtypes (I, II, and III) of 3’ region of cagA gene in H pylori strains isolated from Zhejiang Province, and subtypeIis predominant. Subtype II is a newly found subtype of 3’ region of cagA gene. The result of this study does not support the view that the subtypes of 3’ region of cagA gene in H pylori isolated from Zhejiang Province are correlated with the clinical outcomes of H pylori infection.

Genotypes of Helicobacter pylori in patients with peptic ulcer bleeding

AIM: Helicobacter pylori causes chronic gastritis, peptic ulcer, gastric cancer and MALT-lymphoma. Different genotypes of Helicobacter pylori are confirmed from diverse geographic areas. Its association with bleeding peptic ulcer remains controversial. The aim of this study was to investigate the Helicobacter pylori vacA alleles, cagA and iceA in patients with bleeding peptic ulcer.

METHODS: We enrolled patients with bleeding, non-bleeding peptic ulcers and chronic gastritis. Biopsy specimens were obtained from the antrum of the stomach for rapid urease test, bacterial culture and PCR assay. DNA extraction and polymerase chain reaction were used to detect the presence or absence of cagA and to assess the polymorphism of vacA and iceA.

RESULTS: A total of 168 patients (60.4%) (25 patients with chronic gastritis, 26 patients with bleeding gastric ulcer, 51 patients with non-bleeding gastric ulcer, 26 patients with bleeding duodenal ulcer, and 40 patients with non-bleeding duodenal ulcer) were found to have positive PCR results between January 2001 and December 2002. Concerning genotypes, we found cagA (139/278, 50%), vacA s1a (127/278, 45.7%), and ice A1 (125/278, 45%) predominated in all studied patients. In patients with bleeding peptic ulcers, vacA s1a and m1T were fewer than those in patients with non-bleeding peptic ulcers (37/106 vs 69/135, P = 0.017, and 4/106 vs 21/135, P = 0.002).

CONCLUSION: In patients with peptic ulcers, H pylori vacA s1a and m1T prevent bleeding complication.

The changing epidemiology of GERD: geography and Helicobacter pylori

BACKGROUND

Issues have arisen regarding H. pylori infection and GERD that have caused unnecessary confusion among practicing physicians. In the last century GERD became increasingly recognized in the West and it has become evident that the prevalence of GERD is now occurring in many previously underdeveloped countries.

METHODS

This review article fosters understanding of the issues by focusing on the esophageal acid load and the factors that control it. In particular, we discuss the effects of the change in the patterns of gastritis that have occurred naturally as well as after H. pylori eradication and correlate those changes with their effects on the esophageal acid load. We show how it is possible to separate gastroesophageal reflux from gastroesophageal reflux disease based on differences in esophageal acid load. We also describe how the practice of assessing gastroesophageal reflux based on the time the intraesophageal pH is less than 4 resulted in investigators systematically discarding data critical to understanding of the effect of their interventions on esophageal acid load. Testable hypotheses are presented to explain the interactions between H. pylori and GERD and between H. pylori and the changing epidemiology of GERD.

CONCLUSIONS

We propose that the confusion regarding H. pylori and the changing epidemiology of GERD is based on the failure to critically examine the historical evidence in relation to the other H. pylori-related diseases as well as reliance on techniques that are either unable to measure, or systematically discard data critical for understanding effects of various interventions on the esophageal acid load. This has resulted in propagation of erroneous concepts regarding H. pylori and adenocarcinoma of the esophagus and has resulted in some patients being denied appropriate therapy.

Antralization at the edge of proximal gastric ulcers: does Helicobacter pylori infection play a role?

AIM

To determine the prevalence of antralization at the edge of proximal gastric ulcers, and the effect of H. pylori eradication on the mucosal appearances.

METHODS

Biopsies were taken from the antrum, body and the ulcer edge of patients with benign proximal gastric ulcers before and one year after treatment. Gastric mucosa was classified as antral, transitional or body type. H. pylori positive patients received either triple therapy, or omeprazole.

RESULTS

Patients with index ulcers in the incisura, body or fundus (n=116) were analyzed. Antral-type mucosa was more prevalent at the ulcer edge in H. pylori-positive patients than H. pylori-negative patients (93 % vs 60 %, OR=8.95, 95 %CI: 2.47-32.4, P=0.001). At one year, there was a significant reduction in the prevalence of antralization (from 93 % to 61 %, P=0.004) at the ulcer edge in patients with H. pylori being eradicated. However, there was no difference in the prevalence of antralization at the ulcer edge in those with persistent infection.

CONCLUSION

H. pylori infection is associated with antralization at the edge of proximal gastric ulcers, which may be reversible in some patients after eradication of the infection.

Review article: Helicobacter pylori infection in peptic ulcer haemorrhage

In this overview, medical advice for routine clinical practice regarding peptic ulcer haemorrhage (PUH) is given, based on the extensive literature about Helicobacter pylori and the controversial results about the interaction of H. pylori infection and nonsteriodal anti-inflammatory drug (NSAID) use. PUH remains an important emergency situation with an incidence between 32 and 51/100 000 persons per year. There is a high association between H. pylori infection and peptic ulcer disease. The association between H. pylori infection and PUH is less clear, but a strong argument for the aetiological role is the fact that eradication of H. pylori decreases recurrence of bleeding. NSAID use is another important risk factor for PUH. H. pylori infection and NSAID use seem to act independently, although some studies show a synergistic interaction while other studies report that H. pylori is protective against the development of PUH in NSAID users. All patients with PUH should be tested for H. pylori infection, regardless of the use of NSAIDs. Because invasive tests are less sensitive in PUH patients, negative tests in patients with no other risk factors should be confirmed by serology or urea breath test (UBT). Eradication therapy with a proton pump inhibitor or ranitidine bismuth citrate-based triple therapy should be given to all H. pylori-positive patients. Only for nonaspirin-NSAID users does the effect of eradication therapy on the healing of gastric ulcers remain controversial, but currently we also advise eradication of H. pylori in this subgroup. After eradication therapy, acid-suppressant therapy is advised to heal the ulcer. The success of eradication should always be confirmed because of the risk of recurrence of peptic ulcer disease and bleeding in H. pylori-infected patients.