Johanna Höök-Nikanne

Characteristics of Helicobacter pylori alcohol dehydrogenase

BACKGROUND Helicobacter pylori shows alcohol dehydrogenase activity, which in the presence of ethanol leads to in vitro production of acetaldehyde, a toxic and highly reactive substance. The present study was undertaken to further define H. pylori-related ethanol and acetaldehyde metabolism by characterizing H. pylori alcohol dehydrogenase and by determining whether the organism possesses aldehyde dehydrogenase. METHODS Cytosolic alcohol and aldehyde dehydrogenase activities were determined spectrophotometrically. Acetaldehyde produced by cytosol during incubation with ethanol was measured by head space gas chromatography. Isoenzyme pattern was studied using isoelectric focusing. RESULTS Significant alcohol dehydrogenase activity was observed at a neutral pH known to occur in gastric mucus. The Km for ethanol oxidation was approximately 100 mmol/L for the two strains tested. Acetaldehyde was formed already from a low ethanol concentration known to prevail in the stomach endogenously. Isoelectric focusing of the enzyme showed activity bands with pI at 7.1-7.3, a pattern different from that of gastric mucosal alcohol dehydrogenase. 4-methylpyrazole inhibited enzyme activity in a competitive manner and suppressed the growth of the organism during culture. Neither Helicobacter strain studied showed aldehyde dehydrogenase activity and can thus not remove acetaldehyde by that pathway. CONCLUSIONS Acetaldehyde production by H. pylori from exogenous or endogenous ethanol may be a pathogenetic mechanism behind mucosal injury associated with the organism.

Alcohol dehydrogenase mediated acetaldehyde production by Helicobacter pylori — a possible mechanism behind gastric injury

Two standard Helicobacter pylori strains showed significant cytosolic alcohol dehydrogenase activity and produced considerable amounts of acetaldehyde when incubated with an ethanol containing solution in vitro. The alcohol dehydrogenase activity of the Helicobacter pylori strains was almost as high as that found in Klebsiella pneumoniae and far greater than that in Escherichia coli or Campylobacter jejuni. The amount of acetaldehyde produced by cytosol prepared from Helicobacter pylori exceeded that by any of the other bacteria studied. The bacterial production of acetaldehyde--a highly toxic and reactive substance--could be an important factor in the pathogenesis of Helicobacter pylori associated gastric injury and increased risk of gastric cancer.

Acetaldehyde and Ethanol Production by Helicobacter pylori

By virtue of possessing alcohol dehydrogenase activity, cytosol prepared from Helicobacter pylori produces toxic acetaldehyde from ethanol in vitro. To approach the in vivo situation in the stomach, we have now investigation whether intact H. pylori--without addition of exogenous nicotinamide adenine dinucleotide--also forms acetaldehyde. Furthermore, to assess the energy metabolism of H. pylori, we determined whether the alcohol dehydrogenase-catalyzed reaction can run in the opposite direction with ethanol as the end-product and thereby yield energy for the organism. Intact H. pylori formed acetaldehyde already at low ethanol concentrations (at 0.5% ethanol, acetaldehyde, 64 +/- 21 and 75 +/- 9 mumol/l (mean +/- SEM) for strains NCTC 11637 and NCTC 11638, respectively). H. pylori produced ethanol in concentrations that can be significant for the energy metabolism of the organism. Acetaldehyde production by H. pylori may be an important factor in the pathogenesis of gastroduodenal diseases associated with the organism. The primary function of H. pylori alcohol dehydrogenase may, however, be alcoholic fermentation and consequent energy production under microaerobic conditions.

Is Helicobacter pylori Infection Associated with Chronic Urticaria

There have been controversial reports of an elevated prevalence rate of Helicobacter pylori infection in chronic urticaria patients. Furthermore, in some studies remission of chronic urticaria has been reported after eradication of H. pylori. The aim of this investigation was to evaluate the prevalence of H. pylori infection among chronic urticaria patients and to study the effect of eradication therapy on urticaria symptoms. Chronic urticaria patients (n=235) were enrolled and H. pylori status was determined serologically. Thirty-five patients received antimicrobial triple therapy. 25% of the patients were positive for H. pylori. The prevalence of H. pylori infection was not significantly higher among urticaria patients compared with the normal Finnish population in any of the age groups studied. Of the successfully treated patients, 27% showed remission of urticaria. Our data suggest that the prevalence of H. pylori infection is not elevated among chronic urticaria patients and that H. pylori eradication does not appear to influence the course of chronic urticaria.

Colloidal bismuth subcitrate and omeprazole inhibit alcohol dehydrogenase mediated acetaldehyde production by Helicobacter pylori

We have recently shown that Helicobacter pylori possesses marked alcohol dehydrogenase (ADH) activity and is capable--when incubated with an ethanol containing solution in vitro--of producing large amounts of acetaldehyde. In the present study we report that some drugs commonly used for the eradication of H. pylori and for the treatment of gastroduodenal diseases are potent ADH inhibitors and, consequently, effectively prevent bacterial oxidation of ethanol to acetaldehyde. Colloidal bismuth subcitrate (CBS), already at a concentration of 0.01 mM, inhibited H. pylori ADH by 93% at 0.5 M ethanol and decreased oxidation of 22 mM ethanol to acetaldehyde to 82% of control. At concentrations above 5 mM, CBS almost totally inhibited acetaldehyde formation. Omeprazole, a drug also known to suppress growth of H. pylori, also inhibited H. pylori ADH and suppressed bacterial acetaldehyde formation significantly to 69% of control at a drug concentration of 0.1 mM. By contrast, the H2-receptor antagonists ranitidine and famotidine showed only modest effect on bacterial ADH and acetaldehyde production. We suggest that inhibition of bacterial ADH and a consequent suppression of acetaldehyde production from endogenous or exogenous ethanol may be a novel mechanism by which CBS and omeprazole exert their effect both on the growth of H. pylori as well as on H. pylori associated gastric injury.

Effect of Alcohol Consumption on the Risk of Helicobacter pylori Infection

To investigate the effect of alcohol consumption on the risk of Helicobacter pylori infection, standardized questionnaires on drinking habits were used to interview 451 patients, whose H. pylori status was determined both by culture and serology. Reported alcohol consumption did not increase the risk of H. pylori infection (a 1.0 odds ratio, CI95 0.6-1.6). However, when the patients were divided into two age-groups, those under 35 years who reported to use alcohol seemed to have a slightly higher risk of H. pylori infection (a 3.3 odds ratio CI95 0.9-12.2) compared to those over 35 years (a 1.0 odds ratio, CI95 0.5-2.2). This phenomenon did not reach statistical significance. The type of alcohol consumed did not affect the age-adjusted risk of H. pylori infection. If pathologically defined chronic gastritis was found, the risk for H. pylori was high (a 26.7 odds ratio, CI95 12.1-59.0, for those under 35 years, and a 12.8 odds ratio, CI95 6.7-24.3, for those over 35 years of age.

Effect of Bismuth and Nitecapone on Acetaldehyde Production by Helicobacter pylori

BACKGROUND We have recently shown that colloidal bismuth subcitrate inhibits cytosolic alcohol dehydrogenase of Helicobacter pylori as well as acetaldehyde production from excess ethanol. We now extend our studies to bismuth subsalicylate and nitecapone, a novel antiulcer agent. METHODS Cytosol of H. pylori was incubated with 0.1% or 1% ethanol in the presence of different drug concentrations for 2 h, whereafter acetaldehyde formed was analyzed by head space gas chromatography. In addition, we incubated a culture solution containing intact bacteria with the drugs at 1% ethanol. RESULTS Bismuth subsalicylate and nitecapone inhibit acetaldehyde formation from 0.1% ethanol by H. pylori cytosol at drug concentrations theoretically achievable in the stomach after intake of therapeutic doses of these drugs. Furthermore, colloidal bismuth subcitrate, bismuth subsalicylate, and nitecapone also inhibit acetaldehyde production by intact H. pylori, although rather high drug concentrations are required for this to occur. CONCLUSIONS Inhibition of H. pylori acetaldehyde formation may be one of the mechanisms by which bismuth and nitecapone exert their effect in the treatment of H. pylori-related disorders.

Association of alcohol consumption andHelicobacter pylori infection in young adulthood and early middle age among patients with gastric complaints

There is growing evidence thatHelicobacter pylori is responsible for a variety of gastric and duodenal changes which can eventually lead to stomach cancer. Little is known about risk factors forH. pylori infection. We re-analyzed the association of alcohol withH. pylori positivity in 451 conscripts, officers and other military personnel endoscoped due to gastric complaints in the Central Military Hospital of Finland in 1987 and 1988. Serology and culture were done in all patients. Alcohol consumption histories were obtained by use of a self-administered questionnaire. We observed a high odds ratio (OR) ofH. pylori infection among young adults who were heavy alcohol consumers compared to non-drinkers (OR 5.32, 95% confidence interval: 1.09–25.95). There was evidence of a dose response when heavy and moderate drinkers were compared to non-drinkers (Mantel-Haenszel χ2 for trend,p=0.02) in young adulthood. A subgroup of young respondents who reported drinking all classes of alcohol (including hard liquor) showed an even stronger association and more significant dose-response. Multivariate techniques revealed a qualitative interaction of alcohol withH. pylori positivity in different age groups and among old people an inverse association ofH. pylori and alcohol consumption was observed. These findings, if confirmed independently, might have implications for preventing a variety of gastric and duodenal lesions, since they allow identification of high risk groups.There is growing evidence that Helicobacter pylori is responsible for a variety of gastric and duodenal changes which can eventually lead to stomach cancer. Little is known about risk factors for H. pylori infection. We re-analyzed the association of alcohol with H. pylori positivity in 451 conscripts, officers and other military personnel endoscoped due to gastric complaints in the Central Military Hospital of Finland in 1987 and 1988. Serology and culture were done in all patients. Alcohol consumption histories were obtained by use of a self-administered questionnaire. We observed a high odds ratio (OR) of H. pylori infection among young adults who were heavy alcohol consumers compared to non-drinkers (OR 5.32, 95% confidence interval: 1.09-25.95). There was evidence of a dose response when heavy and moderate drinkers were compared to non-drinkers (Mantel-Haenszel chi 2 for trend, p = 0.02) in young adulthood. A subgroup of young respondents who reported drinking all classes of alcohol (including hard liquor) showed an even stronger association and more significant dose-response. Multivariate techniques revealed a qualitative interaction of alcohol with H. pylori positivity in different age groups and among old people an inverse association of H. pylori and alcohol consumption was observed. These findings, if confirmed independently, might have implications for preventing a variety of gastric and duodenal lesions, since they allow identification of high risk groups.

Comparison of Partial 16S rRNA Sequences of Different Helicobacter pylori Strains, Helicobacter mustelae and a Gastric Campylobacter-like Organism (GCLO)

Summary Partial 16S rRNA sequences of seven Helicobacter pylori strains from three different continents were compared. High homogeneity (99.5%–100%) of 16S rRNA between H. pylori strains was demonstrated, when a 397 nucleotides long stretch of RNA was compared. The obtained consensus sequence was practically identical with one of the two published sequences, 99.4% similarity ( Romaniuk et al., J. Bact. 169 , 2137–2141 (1987)), whereas with the other published sequence the identity was lower, 95.8% similarity ( Thompson et al., Int. J. System. Bact. 38 , 190–200 (1988)). Comparison of the consensus H. pylori sequence with the sequence of Helicobacter mustelae , the spiral organism isolated from ferrets, revealed 93.8% similarity. H. mustelae was also compared with published sequences of Wollinella succinogenes , and Campylobacter jejuni . The percentual sequence similarities were 96.0 and 83.7, respectively. A gastric campylobacter-like organism (GCLO, NCTC 11847), isolated from the gastric antrum has been demonstrated to resemble C. jejuni biochemically. By 16S rRNA sequences we demonstrate that the GCLO is in fact a C. jejuni strain.

The Helicobacter felis mouse model in assessing anti-Helicobacter therapies and gastric mucosal prostaglandin E2 levels

BACKGROUND The aims of the present study were to assess the usefulness of the Helicobacter felis mouse model in the evaluation of antimicrobial therapies and the effect of Helicobacter infection on gastric mucosal prostaglandin E2 release. METHODS Barrier-maintained BALB/c mice were infected with H. felis and treated with different antibacterial therapies. H. felis status was determined by bacterial culture, urease test, and bacterial and histologic stainings. Release of prostaglandin E2 from the gastric mucosa was measured by radioimmunoassay. RESULTS All triple-treated mice were cleared of bacteria both 24 h and 1 month after treatment. However, tinidazole alone also resulted in 100% eradication. Monotherapies with erythromycin acistrate, tetracycline, colloidal bismuth subcitrate, and nitecapone failed to eradicate the bacteria. The release of gastric prostaglandin E2 was doubled in the infected mice (554 +/- 39, mean +/- SE) compared with the noninfected mice (270 +/- 35) (p < 0.01). CONCLUSIONS The H. felis mouse model proved satisfactory for assessing both anti-Helicobacter therapies and the prostaglandin E2 release. The reliability of this method was improved when several methods to assess the H. felis status were used in parallel.