Helicobacter pylori arginase inhibits nitric oxide production by eukaryotic cells: A strategy for bacterial survivalAlain P. Gobert, David J. McGee, 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

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Who discovered me?

• 1983-Campylobacter pyloridis

• 1997- Tomb et al sequenced the HP genome

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Epidemiology• Prevalence (USA)• African-American• Hispanic• Eastern Europeans

• UBIQUITOUS• 50% world population

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Pathophysiology

• The most common route of H. Pylori infection• Oral to oral• Fecal to oral

PS: watch your pets!

Histology

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Diagnosis

・ Breath test

- Based on the detection of the products of urea

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Diagnosis- cont.

・ Esophagogastroduodenoscopy with biopsy

・ H. Pylori fecal antigen・ H. Pylori serology

Diseases

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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• H2 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 NOS2 for the substrate• H. Pylori converts the substrate to urea and L-ornithine,

not NO• rocF gene encodes arginase • Mutations in rocF gene helps the NO to kill H. Pylori

Experiment # 1A

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

Experiment #1A – cont.

Conclusion:

-only the wt H. Pylori inhibited NO released

- the arginase deficient H. Pylori did not inhibit

Experiment # 1B

• 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 rocF mutant does not use the L-arginine

Experiment # 3

• Hypothesis – the macrophage production of NO is regulated by the H. Pylori arginase independently of iNOS expression

• Conclusion- both H. Pylori induce iNOS mRNA expression

Experiment # 4

• Hypothesis – The bacterial arginase inhibits the release of NO by preformed iNOS 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 iNOS

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 rocF mutant H. Pylori in the presence of macrophages .

Experiment # 6 A

Experiment # 6B

Conclusion:The rocF mutant H. Pylori survives in the presence of iNOS -/- macrophages.

Summary

• Bacterial arginase evolutionary adaptation survival strategy for H. pylori gastric mucosa protection

Don’t let your kids kiss us!

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Invitation

That is all I had to say…

• The End!