Related Experiment Videos
Cutting edge: urease release by Helicobacter pylori stimulates macrophage inducible nitric oxide synthase
Alain P Gobert1, Benjamin D Mersey, Yulan Cheng
1Department of Medicine, Division of Gastroenterology, and Greenebaum Cancer Center, University of Maryland School of Medicine, Baltimore, MD 21201, USA.
Abstract:
Inducible NO synthase (iNOS) expression and production of NO are both up-regulated with Helicobacter pylori infection in vivo and in vitro. We determined whether major pathogenicity proteins released by H. pylori activate iNOS by coculturing macrophages with wild-type or mutant strains deficient in VacA, CagA, picB product, or urease (ureA(-)). When filters were used to separate H. pylori from macrophages, there was a selective and significant decrease in stimulated iNOS mRNA, protein, and NO(2)(-) production with the ureA(-) strain compared with wild-type and other mutants. Similarly, macrophage NO(2)(-) generation was increased by H. pylori protein water extracts of all strains except ureA(-). Recombinant urease stimulated significant increases in macrophage iNOS expression and NO(2)(-) production. Taken together, these findings indicate a new role for the essential H. pylori survival factor, urease, implicating it in NO-dependent mucosal damage and carcinogenesis.
Insights
Helicobacter pylori urease activates inducible NO synthase (iNOS) in macrophages, increasing nitric oxide (NO) production. This suggests urease contributes to H. pylori-induced mucosal damage and cancer.
Area of Science:
- Microbiology
- Immunology
- Gastroenterology
Background:
- Helicobacter pylori infection up-regulates inducible NO synthase (iNOS) and nitric oxide (NO) production.
- The role of specific H. pylori virulence factors in iNOS activation is not fully understood.
Purpose of the Study:
- To investigate whether major Helicobacter pylori pathogenicity proteins activate iNOS in macrophages.
- To determine the specific role of urease in iNOS activation and NO production.
Main Methods:
- Coculturing macrophages with wild-type and mutant H. pylori strains (deficient in VacA, CagA, picB, or urease).
- Separating bacteria from macrophages using filters to assess direct vs. indirect effects.
- Analyzing iNOS mRNA, protein, and NO2- production.
- Stimulating macrophages with recombinant urease and H. pylori protein extracts.
Main Results:
- H. pylori ureA(-) mutant strain significantly reduced iNOS mRNA, protein, and NO2- production compared to wild-type.
- H. pylori protein extracts from all strains except ureA(-) increased macrophage NO2- generation.
- Recombinant urease significantly increased macrophage iNOS expression and NO2- production.
Conclusions:
- Urease, an essential H. pylori survival factor, activates iNOS in macrophages.
- Urease plays a significant role in NO-dependent mucosal damage and carcinogenesis associated with H. pylori infection.