Recent advances highlight a pivotal role for cellular metabolism in programming immune responses. Here, we demonstrate that cell-autonomous generation of nicotinamide adenine dinucleotide (NAD+) via the kynurenine pathway (KP) regulates macrophage immune function in aging and inflammation. Isotope tracer studies revealed that macrophage NAD+ derives substantially from KP metabolism of tryptophan. Genetic or pharmacological blockade of de novo NAD+ synthesis depleted NAD+, suppressed mitochondrial NAD+-dependent signaling and respiration, and impaired phagocytosis and resolution of inflammation. Innate immune challenge triggered upstream KP activation but paradoxically suppressed cell-autonomous NAD+ synthesis by limiting the conversion of downstream quinolinate to NAD+, a profile recapitulated in aging macrophages. Increasing de novo NAD+ generation in immune-challenged or aged macrophages restored oxidative phosphorylation and homeostatic immune responses. Thus, KP-derived NAD+ operates as a metabolic switch to specify macrophage effector responses. Breakdown of de novo NAD+ synthesis may underlie declining NAD+ levels and rising innate immune dysfunction in aging and age-associated diseases.
CITATION STYLE
Minhas, P. S., Liu, L., Moon, P. K., Joshi, A. U., Dove, C., Mhatre, S., … Andreasson, K. I. (2019). Macrophage de novo NAD+ synthesis specifies immune function in aging and inflammation. Nature Immunology, 20(1), 50–63. https://doi.org/10.1038/s41590-018-0255-3
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