H. pylori remains a major public health problem, since half of the world's population is infected and the associated gastric cancer is the second leading cause of cancer deaths. We have elucidated mechanisms of immune system failure that result in persistence of the organism and sustained oxidative stress that leads to DNA damage. H. pylori induces ornithine decarboxylase (ODC), the rate limiting enzyme for polyamine synthesis, in macrophages. In both in vitro and in vivo models, ODC-derived spermine synthesis results in 1.) apoptosis;and 2.) inhibition of nitric oxide (NO) synthesis, by inhibition of L-arginine (L-Arg)-dependent inducible nitric oxide (NO) synthase (iNOS) protein translation. Inhibition of ODC with oral administration of a- difluoromethylornithine (DFMO) in mice restores L-Arg uptake, macrophage NO production, and cytokine balance, resulting in reduction in both gastritis and H. pylori colonization. H. pylori also up-regulates the enzyme spermine oxidase (SMO), thus generating H2O2, and acting as a novel mechanism for the generation of oxidative stress-associated DNA damage in gastric epithelial cells. We have also discovered another target of H. pylori, heme oxygenase (HO)-1, known for its anti-inflammatory and anti-oxidant properties. We show that H. pylori blocks NO-induced HO-1 in gastric epithelial cells, and this results in unrestrained chemokine synthesis. We hypothesize that H. pylori infection results in failure of antimicrobial and immunoregulatory NO generation and overproduction of polyamines and H2O2, leading to dysregulation of immune responses and survival of gastric epithelial cells with DNA damage. These events lead to persistence of the bacterium, chronic inflammation, and risk for neoplastic transformation.
Our Specific Aims are as follows. 1.) To determine the mechanism of persistence of H. pylori colonization and gastritis due to ODC. We will compare WT and ODC+/-, myeloid-specific ODC-/-, iNOS-/- mice, and appropriate bone marrow chimeras, each ? DFMO, and assess: A.) gastritis and colonization;B.) immune responses;C.) DNA damage and carcinogenesis by comparing WT and ODC mutant x INS-GAS mice, each ? DFMO. 2.) To determine the role of SMO in H. pylori infection, gastritis, and carcinogenesis. We will use SMO-/- mice and assess: A.) colonization, gastritis, advanced lesions, and effects on iNOS;B.) gastric epithelial cell apoptosis and DNA damage;C.) role in carcinogenesis by comparing WT and SMO-/- INS-GAS mice. 3.) To determine the role of HO-1 as a regulator of H. pylori immunopathogenesis and carcinogenesis in vivo by assessing: A.) modulation of HO-1 by polyamines and NO in ODC, SMO, and iNOS KO mice;B.) in mice with normal versus increased NO production and HO-1 expression treated with a pharmacologic inhibitor of HO-1, or in HO-1-/- and epithelial-specific HO-1-/- mice, effects on colonization, gastritis, immune responses, apoptosis, DNA damage, and carcinogenesis. The studies proposed seek new strategies for amelioration or prevention of H. pylori-induced disease by clarifying targets for intervention in the pathogenic immune response that lead to disease persistence and cancer risk.

Public Health Relevance

Helicobacter pylori is a type of bacteria that infects the stomach of half of the world's human population, which can lead to the development of gastric cancer, the second leading cause of cancer death worldwide. In this project we will utilize in vitro and in vivo model systems to assess novel molecular pathways that are altered by H. pylori leading to host responses that fail to eradicate the pathogen, and cause persistent inflammation and DNA damage. The studies proposed seek to define new strategies for amelioration or prevention of H. pylori-induced disease by clarifying targets for intervention in the pathogenic immune response that lead to disease persistence and cancer risk.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
2R01DK053620-11A1
Application #
8205881
Study Section
Special Emphasis Panel (ZRG1-DKUS-C (05))
Program Officer
Hamilton, Frank A
Project Start
1997-09-30
Project End
2015-06-30
Budget Start
2011-09-01
Budget End
2012-06-30
Support Year
11
Fiscal Year
2011
Total Cost
$390,000
Indirect Cost
Name
Vanderbilt University Medical Center
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
004413456
City
Nashville
State
TN
Country
United States
Zip Code
37212
Sierra, Johanna C; Asim, Mohammad; Verriere, Thomas G et al. (2017) Epidermal growth factor receptor inhibition downregulates Helicobacter pylori-induced epithelial inflammatory responses, DNA damage and gastric carcinogenesis. Gut :
Parang, Bobak; Kaz, Andrew M; Barrett, Caitlyn W et al. (2017) BVES regulates c-Myc stability via PP2A and suppresses colitis-induced tumourigenesis. Gut 66:852-862
Hardbower, Dana M; Asim, Mohammad; Luis, Paula B et al. (2017) Ornithine decarboxylase regulates M1 macrophage activation and mucosal inflammation via histone modifications. Proc Natl Acad Sci U S A 114:E751-E760
Gobert, Alain P; Wilson, Keith T (2017) Effect of CO2 on Peroxynitrite-Mediated Bacteria Killing: Response to Tsikas et al. Trends Microbiol 25:602-603
Noto, Jennifer M; Chopra, Abha; Loh, John T et al. (2017) Pan-genomic analyses identify key Helicobacter pylori pathogenic loci modified by carcinogenic host microenvironments. Gut :
Hardbower, D M; Coburn, L A; Asim, M et al. (2017) EGFR-mediated macrophage activation promotes colitis-associated tumorigenesis. Oncogene 36:3807-3819
Gobert, Alain P; Wilson, Keith T (2017) Human and Helicobacter pylori Interactions Determine the Outcome of Gastric Diseases. Curr Top Microbiol Immunol 400:27-52
Mera, Robertino M; Bravo, Luis E; Camargo, M Constanza et al. (2017) Dynamics of Helicobacter pylori infection as a determinant of progression of gastric precancerous lesions: 16-year follow-up of an eradication trial. Gut :
Suarez, Giovanni; Romero-Gallo, Judith; Sierra, Johanna C et al. (2017) Genetic Manipulation of Helicobacter pylori Virulence Function by Host Carcinogenic Phenotypes. Cancer Res 77:2401-2412
Beceiro, S; Radin, J N; Chatuvedi, R et al. (2017) TRPM2 ion channels regulate macrophage polarization and gastric inflammation during Helicobacter pylori infection. Mucosal Immunol 10:493-507

Showing the most recent 10 out of 117 publications