Impact of nucleotide metabolism on bacterial clearance

Project Summary In my laboratory, we study how host metabolism determines the outcome of infectious diseases, such as during pneumonia. Pneumonia is a brisk inflammatory reaction to airway pathogens that, if not adequately regulated, can predispose to infection by opportunists that exploit airway oxidation to persist, such as Pseudomonas aeruginosa and Staphylococcus aureus, which belong to the feared family of multidrug-resistant ESKAPE pathogens. In response to the oxidative metabolism of airway cells, these organisms activate many mechanisms of virulence that favor their survival in the human lung, such as toxins and biofilms, which exacerbate the damage of the respiratory mucosa. Although it is known how these opportunists exploit airway damage to persist, it remains poorly understood how the host eradicates infections by controlling these pro-oxidant pathways. In the 5 years contemplated for this project, we will address how regulation of oxidative metabolism in airway cells limits bacterial persistence, and how we can use this knowledge to design new therapies to eradicate pulmonary infections by ESKAPE pathogens. Nucleotides, like purines and pyrimidines, are not only used by cells to generate nucleic acids to grow, but also to supervise many physiological processes, such as inflammation. Indeed, in many autoimmune diseases, anti-inflammatory nucleotide signaling is severely impaired, causing tissue oxidation and mucosal damage. These strong anti-inflammatory properties of certain nucleotidic routes are also exploited by tumors to evade host immunity. In order to suppress the activation of anti-tumor leukocytes, malignant cells co-opt both dihydroorotate dehydrogenase (DHODH) and the ecto-nucleotidase CD73, which are two major components of the de novo pathway of pyrimidine synthesis and the purine dephosphorylation route, respectively. While the regulatory roles of DHODH and CD73 are well appreciated in cancer and autoimmune diseases, their activities in other major inflammatory pathologies, like pneumonia, remains unclear. Here, we will progress in the research line of my laboratory by establishing that nucleotide metabolism through both DHODH and CD73 is critical in the protection of the host lung against pneumonia by P. aeruginosa and S. aureus. We will demonstrate that both DHODH and CD73 limit the detrimental oxidative metabolism of airway cells, thus preventing from activation of mechanisms of pathogenesis by ESKAPE opportunists that feed off lung damage to cause disease, like toxin synthesis and biofilms. We will accomplish these goals by performing transcriptomic and metabolomics analyses in the airway of infected both controls and DHODH/CD73-deficient animals, in which we will measure the host and bacterial networks related with oxidative metabolism, host immunity, and pathogen virulence. Thus, in this project, we will establish the impact of nucleotide metabolism in lung health against pulmonary pathogens, which will provide us both a metabolic framework to better understand the pathology of pneumonia and new targets to clear infection produced by these opportunists.