Abstract
AbstractCholine is an essential nutrient and in macrophages, mainly supports phosphatidylcholine (PC) synthesis. Cellular uptake and incorporation of choline into PC is critical for LPS-induced macrophage inflammation. Here, we examined choline metabolism in the context of IL-4 polarization of mouse macrophages in vitro and in vivo. Like LPS, IL-4 increased the levels of choline transporter-like protein 1, the rate of choline uptake, and incorporation into PC. Targeted lipidomics analysis revealed higher PC content in IL-4-polarized macrophages, with enrichment in low-saturated species. Pharmacological inhibition of choline metabolism significantly suppressed the transcription of certain hallmark IL-4 genes (Retnla) but not others (Chil3, Mrc1, Arg1). Blocking choline metabolism diminished the expression and secretion of RELMα protein (encoded by Retnla), while also limiting PD-L2 up-regulation and increasing PD-L1 expression. In vivo administration of RSM-932a, a choline kinase inhibitor, caused a dramatic shift in the peritoneal immune cell profile and up-regulated macrophage CD86 and PD-L1, while down-regulating CD206 and PD-L2. Strikingly, blocking choline metabolism lowered RELMα expression in multiple cell-types and tissues in naïve mice as well as mice infected with the helminth pathogens Heligmosomoides polygyrus and Nippostrongylus brasiliensis. There were no changes in pathogen burden or clearance in the two separate helminth models. In contrast, in dextran sulfate sodium-induced colitis, loss of colon length as a marker of inflammation was mitigated by choline metabolism inhibition. These data demonstrate a critical link between choline and macrophage effector functions and suggest that targeting choline metabolism could be leveraged to fine-tune immunopathology.Abstract Figure
Publisher
Cold Spring Harbor Laboratory