Glycogen pathway intermediate uridine diphosphate glucose alters dendritic cell mitochondrial respiration in a nitric oxide-dependent manner

Abstract

Abstract Dendritic cells (DCs), the professional antigen presenting cells of the immune system, undergo metabolic reprogramming in response to stimulation through Toll-Like Receptors (TLRs). Our lab and others have shown that metabolic reprogramming in DCs is accompanied by increased reliance on glycolytic metabolism through use of glucose and glycogen as fuel. Both metabolites are required by DCs to perform immune functions associated with activation including secretion of cytokines, upregulation of costimulatory molecules, and initiation of the T cell-mediated immune response. While our lab has published that glycogen is required within 4–8 hours after activation, production of nitric oxide (NO) regulates many metabolic processes during the later stages of activation via NO-dependent suppression of mitochondrial respiration. Recent studies have shown that glycogen pathway intermediate uridine diphosphate glucose (UDPG) is continually elevated in inflammatory macrophages past 24 hours of activation. Additionally, UDPG can be exported extracellularly and act as an autocrine signaling molecule to increase proinflammatory gene expression. We tested the hypothesis, that, like inflammatory macrophages, DCs elevate production of UDPG in response to activation and that this metabolite can bolster NO-mediated processes during DC activation. To investigate the role of UDPG in DCs, we characterized DC mitochondrial respiration in response to activation by LPS and the addition of exogenous UDPG. Additionally, we performed functional assays to assess NO production, cytokine secretion, as well as inflammatory gene expression to begin elucidating an axis by which UDPG and NO work together to regulate DC metabolism and immune function. Supported by grants from UVM (COBRE VCIID Funding Support and Pilot Project) and NIH (NIAID 1R21AI135385-01A1)