Helicobacter pylori urease activity is toxic to human gastric epithelial cells

Smoot, Duane T.; Mobley, Harry L. T.; Chippendale, G. R.; Lewison, J. F.; Resau, James H.

doi:10.1128/iai.58.6.1992-1994.1990

Cited by 193 publications

(66 citation statements)

References 8 publications

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“…In addition to its involvement in colonization, urease is also believed to mediate certain pathogenic processes. The activity of H. pyiori urease has been postulated to affect various aspects of gastric physiology including transepithelial H* ion flow (Hazell and Lee, 1986), the constituency of gastric mucus (Sidebotham and Baron, 1990) and the viability of gastric epitheiiai ceiis (Smoot et aL, 1990). it has been shown that H. pylori urease activity acting in concert with a cytotoxin causes vacuoiation in iHeLa tissue culture cells (Cover et aL, 1991).…”

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confidence: 99%

Cloning, expression and sequencing of Helicobacter felis urease genes

Ferrero

Labigne

1993

Molecular Microbiology

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Urease genes from Helicobacter felis were cloned and expressed in Escherichia coli cells. A genomic bank of Sau3A-digested H. felis chromosomal DNA was created using a cosmid vector. Cosmid clones were screened for urease activity following subculture on a nitrogen-limiting medium. Subcloning of DNA from an urease-positive cosmid clone led to the construction of pILL205 (9.5 kb) which conferred a urease activity of 1.2 +/- 0.5 mumole urea min-1 mg-1 bacterial protein to E. coli HB101 bacteria grown on a nitrogen-limiting medium. Random mutagenesis using a MiniTn3-Km transposable element permitted the identification of three DNA regions on pILL205 which were necessary for the expression of an urease-positive phenotype in E. coli clones. To localize the putative structural genes of H. felis on pILL205, extracts of clones harbouring the mutated copies of the plasmid were analysed by Western blotting with anti-H. felis rabbit serum. One mutant clone did not synthesize the putative UreB subunit of H. felis urease and it was postulated that the transposable element had disrupted the corresponding structural gene. By sequencing the DNA region adjacent to the transposon insertion site two open reading frames, designated ureA and ureB, were identified. The polypeptides encoded by these genes had calculated molecular masses of 26,074 and 61,663 Da, respectively, and shared 73.5% and 88.2% identity with the corresponding gene products of Helicobacter pylori urease.

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confidence: 99%

Cloning, expression and sequencing of Helicobacter felis urease genes

Ferrero

Labigne

1993

Molecular Microbiology

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“…Production of ammonium by urease could result in the back diffusion of hydrogen ions which may increase acidity at the gastric mucosal surface (Hazell and Lee, 1986) or may damage the integrity of the mucosa. It has also been shown that the presence of ammonium potentates cytotoxic effects of H. pylori on cultured human gastric epithelial cells (Smoot et al, 1990;Cover et al, 1991).…”

Section: Oral Diseasesmentioning

confidence: 99%

Oral Microbiology: Environmental cues and gene expression in Porphyromonas gingivalis and Actinobacillus actinomycetemcomitans

Champagne

Simpson

et al. 2000

Oral Diseases

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Microorganisms typically adapt to environmental cues by turning on and off the expression of virulence genes which, in turn, allows for optimal growth and survival within different environmental niches. This adaptation strategy includes sensing and responding to changes in nutrients, pH, temperature, oxygen tension, redox potential, microbial flora, and osmolarity. For a bacterium to adhere to, penetrate, replicate in, and colonize host cells, it is critical that virulence genes are expressed during certain periods of the infection process. Thus, throughout the different stages of an infection, different sets of virulence factors are turned on and off in response to different environmental signals, allowing the bacterium to effectively adapt to its varying niche. In this review, we focus on the regulation of virulence gene expression in two pathogens which have been implicated as major etiological agents in adult and juvenile periodontal diseases: Porphyromonas gingivalis and Actinobacillus actinomycetemcomitans. Understanding the mechanisms of virulence gene expression in response to the local environment of the host will provide crucial information in the development of effective treatments targeted at eradication of these periodontal disease pathogens. Oral Diseases (2000) 6, 351-365

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“…The ammonia released after the hydrolyzation of urea is likely to neutralize the hydrochloric acid. Ammonia may also be directly toxic to the gastric epithelial cells (Smoot et al 1990). Further cell damage may be caused by cytotoxins, one of which has been shown to lead to vacuolization in vitro (Leunk et a/.…”

Section: Pathogenetic Aspectsmentioning

confidence: 99%

Helicobacter pylori and associated gastroduodenal diseases

Rautelin

Kosunen

1991

APMIS

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Helicobacter pylori is a microaerophilic, Gram‐negative, spiral rod, the role of which in different gastric diseases has been investigated worldwide since the beginning of the 1980s. H. pylori has been shown to be the causative agent in active chronic gastritis, and it is regularly found in patients endoscopied for duodenal ulcer. The bacterium is also frequently isolated from persons with gastric ulcer, gastric carcinoma and non‐ulcer dyspepsia. Apart from cultivation of the bacterium, other diagnostic procedures include various staining methods and urease tests of gastric biopsy samples. The application of non‐invasive diagnostic methods, serology and urea breath tests, is rapidly increasing. H. pylori is susceptible to several antimicrobials in vitro, but eradication of the bacterium from the gastric mucosa is not always achieved. The best results until now have been obtained with the combined use of bismuth salts and two antibiotics. In active chronic gastritis and duodenal ulcer patients, eradication of the bacteria has resulted in healing of the disease with permanent decrease of circulating antibodies and negative urease tests. H. pylori has been found worldwide and the infection shows an age‐dependent increase. Man, apparently, is the reservoir of the bacterium, but the exact mechanisms of interhuman transmission are still not defined.

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Helicobacter pylori urease activity is toxic to human gastric epithelial cells

Cited by 193 publications

References 8 publications

Cloning, expression and sequencing of Helicobacter felis urease genes

Cloning, expression and sequencing of Helicobacter felis urease genes

Oral Microbiology: Environmental cues and gene expression in Porphyromonas gingivalis and Actinobacillus actinomycetemcomitans

Helicobacter pylori and associated gastroduodenal diseases

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