Helicobacter pylori arginase inhibits nitric oxide production by

Helicobacter pylori arginase inhibits nitric oxide production by eukaryotic cells: A strategy for bacterial survival Alain P. Gobert, David J. Mc. Gee, Mahmood Akhtar, George L. Mendz, Jamie C. Newton, Yulan Cheng, Harry L. T. Mobley, and Keith T. Wilson Presented by Mihaela C. Badea-Mic

So, Who Am I? • Gram negative bacteria inside the stomach and duodenum The Helicobacter Foundation

Who discovered me? • 1983 -Campylobacter pyloridis • 1997 - Tomb et al sequenced the HP genome • The Helicobacter Foundation, 2005

Epidemiology • Prevalence (USA) • African-American • Hispanic • Eastern Europeans • UBIQUITOUS • 50% world population • The Helicobacter Foundation, 2005

Pathophysiology • The most common route of H. Pylori infection • Oral to oral • Fecal to oral PS: watch your pets!

Histology The Helicobacter Foundation, 2005

Diagnosis ・ Breath test - Based on the detection of the products of urea The Helicobacter Foundation, 2005

Diagnosis- cont. ・ Esophagogastroduodenoscopy with biopsy ・ H. Pylori fecal antigen ・ H. Pylori serology

Diseases The Helicobacter Foundation, 2005

Diseases- cont. • • Gastric and duodenal ulcers Gastric cancer ( 90%) Non-ulcer dyspepsia Weird syndromes

Treatment • Antidiarrheals – bistmuth • Antibiotics - metronidazole, tetracycline, amoxicilin • Proton pump inhibitors - omeprazole, lansoprazole • H 2 receptor blockers – ranitidine, famotidine

My survival strategies D. S. Merrel et al, 2004

My virulence factors D. M. Monack et al, 2004

Details D. M. Monack et al, 2004

And now…finally the paper • Activated macrophages produce NO using L-arginine as a substrate • H. Pylori arginase competes with NOS 2 for the substrate • H. Pylori converts the substrate to urea and L-ornithine, not NO • roc. F gene encodes arginase • Mutations in roc. F gene helps the NO to kill H. Pylori

Experiment # 1 A • Hypothesis - the activated macrophage production of NO is inhibited by wt H. Pylori at physiologic L-arginine concentrations

Experiment #1 A – cont. Conclusion: -only the wt H. Pylori inhibited NO released - the arginase deficient H. Pylori did not inhibit

Experiment # 1 B • Conclusion: adding more substrate will stop the competitive inhibition between H. pylori and activated macrophages

Experiment # 2 • Hypothesis – H. Pylori wt compete for the same substrate with activated macrophages. This substrate is L-arginine.

Experiment # 2 –cont. Conclusion -the wt H. Pylori uses L-arginine decreasing the macrophage NO production because of the loss of the substrate - the roc. F mutant does not use the L-arginine

Experiment # 3 • Hypothesis – the macrophage production of NO is regulated by the H. Pylori arginase independently of i. NOS expression • Conclusion- both H. Pylori induce i. NOS m. RNA expression

Experiment # 4 • Hypothesis – The bacterial arginase inhibits the release of NO by preformed i. NOS in macrophages.

Experiment # 4 -cont • Conclusion: the wt H. Pylori inhibits macrophage NO production by the preactivated cells

Experiment # 5 • Hypothesis – Only viable H. pylori can inhibit the release of macrophage NO • Conclusion : only live H. Pylori can consume the substrate in order to inhibit the i. NOS

Experiment # 6 • Hypothesis – Inhibition of the host cell NO production is a survival strategy for H. Pylori. • Conclusion – the wt H. Pylori has an increased rate of survival in comparison with roc. F mutant H. Pylori in the presence of macrophages.