Online

Snyder, Julia Priscilla

Cellular, Molecular and Biomedical Sciences Graduate Program

2022

Ph. D.

Dendritic cells (DCs) are sentinel immune cells capable of directly sensing and responding to pathogens. Upon pathogen recognition, DCs undergo a process of activation that allows them to participate in the proinflammatory response at the site of infection and to initiate the adaptive immune response through antigen presentation to T cells. Because activated DCs serve as the critical link between innate and adaptive immunity, modulating DC activation could be a powerful tool in various clinical contexts such as vaccine design. DC activation is accompanied by widespread changes in metabolism including the rapid upregulation of glycolysis, which is sustained in DCs that express inducible nitric oxide synthase (Nos2, iNOS) due to nitric oxide-mediated inhibition of mitochondrial respiration. Here, we utilize a wild-derived genetically divergent mouse strain PWD/PhJ (PWD) to assess the conservation of nitric oxide-mediated loss of mitochondrial respiration, as this phenomenon has predominantly been studied in DCs from the classic inbred mouse strain C57BL/6J (B6). We report that activated PWD DCs maintain mitochondrial respiration due to highly attenuated Nos2 induction and nitric oxide production, and as a result have a longer post-activation lifespan than B6 DCs. In the field of immunometabolism, nitric oxide production is a key difference between mouse and human DC culture systems. We show that activated PWD DCs phenocopy the restrained nitric oxide production and maintenance of mitochondrial respiration observed in human monocyte derived DCs. To begin genetically mapping the PWD phenotype, we utilize a congenic mouse strain B6.PWD-Chr11.2 (11.2) that carries a PWD-derived portion of chromosome 11 including Nos2 on a B6 genetic background. Activated 11.2 DCs induce higher Nos2 and iNOS expression than PWD DCs but produce nitric oxide at lower levels than B6 DCs. Due to restrained nitric oxide production, 11.2 DCs maintain mitochondrial respiration and survive longer post-activation than B6 DCs but have impaired control of the intracellular pathogen Listeria monocytogenes. We report that in B6 DCs iNOS activity is impacted by competition with arginase for the shared substrate arginine. A future direction of this work is to investigate the contribution of arginase competition and Nos2 coding polymorphisms to strain differences in nitric oxide production. Collectively, these studies demonstrate that nitric oxide-mediated loss of mitochondrial respiration is not a universal feature of murine DCs and establish a genetic model of restrained endogenous nitric oxide production to investigate the role of nitric oxide in regulating metabolism and immune function in activated DCs.