UV-irradiation of skin enhances glycolytic flux in bone marrow-differentiated dendritic cells. Mus musculus

Following UV irradiation of skin, dendritic cells (DCs) differentiating from the bone marrow (BM) of mice have a reduced ability to prime new immune responses; their reduced immunogenicity is maintained for at least 16 weeks in UV-chimeric mice. We hypothesized that different metabolic states underpin changes in DC function. Compared with DCs from the BM of non-irradiated mice, DCs from the BM of UV-irradiated mice produced more lactate and utilized greater amounts of glucose, a profile that was supported by greater glycolytic flux when incubated in low-serum-containing medium. Responses to a mitochondrial stress test were similar suggesting that the DCs from the BM of UV-irradiated mice had not switched from a profile of oxidative phosphorylation, but were imprinted for greater glycolytic responses. After microarray profiling, RT-qPCR confirmation and Ingenuity pathway analysis, greater expression of the enzyme, 3-hydroxyanthranilate 3,4-dioxygenase, was identified as a potential contributor to increased glycolysis by BM-differentiated DCs. This enzyme provides the final step of the biosynthetic pathway from tryptophan to quinolinate, the universal de novo precursor to the pyridine ring of nicotinamide adenine dinucleotide (NAD), and may provide a mechanism to ensure sufficient NAD is available to support enhanced glycolysis. Increased lactate production was also measured for DCs from the BM of 16-week engrafted UV-chimeric mice and suggests long-lasting imprinting of progenitor cells for altered immunometabolism in their progeny cells. This study provides evidence of changes to metabolic states that associate with altered DC function. Overall design: Female C57BL/6J (CD45.2 alloantigen) and B6.SJL-Ptprca (CD45.1 alloantigen) mice were obtained from the Animal Resources Centre (Murdoch, Western Australia). A bank of TL40W/12RS lamps (Philips, Amsterdam, The Netherlands) emitting broadband UVR with 65% UVB (280-320 nm) and peak emission at 313 nm was used. Twenty-four h prior to irradiation, a uniform area of dorsal skin of mice was shaved (8 cm2). To administer UVR, mice were held in perspex compartments which were covered with 0.2 mm polyvinyl chloride plastic to eliminate wavelengths 95% CD11c+ cells (confirmed by flow cytometry) using anti-CD11c magnetic microbeads (Miltenyi Biotec, Bergisch Gladbach, Germany) and autoMACS-Pro (Miltenyi Biotec) separation. Total RNA was extracted from triplicate preparations of BM-differentiated CD11c+ cells. Two sample groups; BM-differentiated DC sample from C57BL/6J mice injected with 2 x 10^6 BM cells from a naïve congenic B6.SJL-Ptprca mouse BM-differentiated DC sample from C57BL/6J mice injected with 2 x 10^6 BM cells from a UV irradiated congenic B6.SJL-Ptprca mouse