Abstract 3047: Extracellular Vesicles Produced By IL4-polarized Human Macrophages Suppress Atherosclerosis By Reprograming Ly6c hi Monocytes

Introduction: Extracellular vesicles (EVs) produced by IL4-polarized macrophages (Mφ) suppress inflammation by communicating microRNA-controlled immunometabolic signaling to recipient immune cells and adipocytes. However, detailed cellular and molecular pathways responsible for these effects remain incompletely understood. Objectives: Examine transcriptional responses sensitive to IL4-polarized Mφ EVs among circulating Ly6C hi monocytes derived from mice with hyperlipidemia. Methods/Approach: EVs were produced by culturing THP1 macrophages with human IL4, and purified using cushioned-density gradient ultracentrifugation. Twenty-week old male LDL-receptor deficient mice fed high-fat diet for 16 weeks were treated to a 6-week course of 3-weekly intraperitoneal infusions of 10e 10 THP1-IL4 EVs or sham. Circulating Ly6C hi monocytes were collected using a cell sorter and RNA was examined using nanoString nCounter inflammatory and metabolic pathway panels. Plasma cytokines were detected with a V-Plex MesoScale assay, while atherosclerosis was assessed by detecting myeloid cell subsets in enzymatically-digested aortae and oil red O positive lesions in the aortic root. Results: THP1-IL4 EVs caused profound transcriptional reprogramming among Ly6C hi monocytes, resulting in reduced signaling pathways controlled by MAPK, PI3K, TLR and inflammasomes. We identified reduced levels of Casp-1, Nlrp1a, as well as Aim2, all recognized to drive atherosclerosis including in JAK2 vf clonal hematopoiesis. Furthermore, THP1-IL4 EVs upregulated metabolic pathways involved in arginine metabolism, IDH1/2 activity, redox stress control, nucleotide salvage, fatty acid oxidation and mitochondrial respiration. In contrast they reduced pathways involved in glucose transport, hypoxia, KEAP-NRF2 pathway and tryptophan metabolism. Control of these pathways in Ly6C hi monocytes contributed to reduced levels of IL-1β, IL-6, IFNγ and TNFα in plasma, as well as CD45 + aortic myeloid cells and oil red O positive aortic lesions. Conclusions: IL4-polarized Mφ EVs suppress atherosclerosis by communicating profound transcriptional reprogramming to Ly6C hi monocytes. Ongoing studies examine their capacity to drive atherosclerosis regression.