African Americans have a 6-fold higher H. pylori (Hp) infection than the non-Hispanic white population; however, underlying gene(s) for this disparity remain elusive. We discovered that a human TP53 gene variant at amino acid 47 exists predominantly in people of African descent. Macrophages containing the S47 variant are defective in ferroptosis, M2 polarized and show more productive infections by Hp and other bacteria. Macrophage adaptive response is essential for eliminating Hp infection and is suppressed in chronic infections that lead to gastritis. Our collaborator, Dr. Keith Wilson, reported the role of Arg2 activation by Hp in suppressing the macrophage response. Unbiased WT and S47 macrophage proteomics revealed marked differences in Liver X Receptor activation, arginase II activity, inflammation, iron transport and antibacterial defense machinery which regulate immune response and directly affect outcomes of bacterial infections. Although p53 is known to regulate immune response, we are the first to discover the exact genetic variant causing the disparities. We will reverse the Hp infection disparities in African Americans with the S47 SNP by in-depth mechanistic and therapeutic study. Our human studies will give translational relevance to this project. We will test ~500 Hp seropositive African American samples for the prevalence of S47 and other SNPs. Then we will focus on improving macrophage response, Hp clearance and reduce chronic gastric dysplasia in S47 mice using Liver X Receptor (LXR) agonists. We will test if LXR activation improves these outcomes for multiple Hp strains with differing virulence. Moreover, we will generate a genome-wide map of macrophage binding of LXR to ?fine tune? its activity on macrophage activation and eliminate undesired effect of hepatic steatosis. Since Hp is found both extracellularly and within macrophages, specific depletion of immune cells will be used to distinguish the role of macrophages from other tissue environment in H. pylori pathogenesis. These studies will be validated by bone marrow swaps between WT and S47 mice. we will test macrophage regulation and tissue environment for more. We will prioritize and test pathways associated with LXR such as arginase pathway (Arg2, Slc7a2), iron transport (Tfrc, Slc40a1, Fth1) and innate immune proteins (TLR3 and TLR7) as novel therapeutic targets. Lastly, we will test macrophage regulatory factors (NOTCH1 and mTOR), energy metabolism (switching from ox-phos to glycolysis by Metformin) and polyamine pathway (DFMO-polyamine synthesis inhibitor) in fine tuning LXR agonist induced reversal of anti-inflammatory polarization in S47 mice, clearance of Hp infection and reduction of gastric dysplasia. This proposal will a) improve our understanding of the biological mechanism for the disparity in Hp infection in African Americans and b) provide several therapeutic avenues to improve clearance of Hp infection and gastritis. This project is a stepping stone for human studies in personalized medicine to address this health disparity. Hp infection has been deemed of critical importance in the African American minority, by the NIDDK.

Public Health Relevance

African Americans have 6-fold higher prevalence for carrying an H. pylori Infection. We discovered that an African-centric S47 variant of the cancer suppressor gene - TP53 causes macrophages to engage an anti- inflammatory response to bacterial infections. In this proposal, we will describe the mechanism by which the S47 SNP causes disparities in H. pylori infection, test therapeutic avenues with focus on LXR agonists to reverse the macrophage anti-inflammatory phenotype and reduce the disparity in H. pylori infection.

National Institute of Health (NIH)
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Research Project (R01)
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Gastrointestinal Mucosal Pathobiology Study Section (GMPB)
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Perrin, Peter J
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Wistar Institute
United States
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