Abstract Body: Introduction: ApoE4 is recognized to drive cardiometabolic disease (CMD). We recently uncovered that ApoE regulates microRNA-controlled immunometabolic signaling in macrophages (Mf) that can be communicated via extracellular vesicles (EVs).
Hypothesis: Test whether ApoE4 deregulates microRNA-controlled immunometabolism in Mf and whether this can be communicated via EVs.
Methods: Primary BMDM derived from human ApoE3 & ApoE4 gene-targeted mice were tested for bioenergetic responses with Seahorse. Cellular and mitochondrial fitness, redox stress and lipid levels were detected using flow cytometry, and both small and long RNA transcripts were detected by sequencing. EVs were produced by BMDM and purified using ultracentrifugation. In vitro signaling by Mf EVs was examined in WT mouse BMDM as well as inguinal adipocytes. In vivo signaling by Mf EVs was examined through tri-weekly IP infusions of 10e9 Mf EVs into WT mice fed a HFD diet for 8 weeks. Circulating Ly6Chi monocytes and lipid associated macrophage subtypes (LAMs) in adipose tissue were detected by flow cytometry, and adipose tissue bioenergetic activity was recorded ex vivo.
Results: ApoE4 reprogramed bioenergetic activity in BMDM, augmenting glycolysis while reducing mitochondrial fitness and metabolism. This derived from deregulated microRNA and mRNA involved in immunometabolic activities. Pathways negatively impacted by ApoE4 included glucose uptake and processing, redox stress, accumulation of oxidized neutral lipids and activated inflammatory signaling. Transcriptomic reprograming by ApoE4 also led to reduced OxPHOS, anti-oxidant and inflammatory defense pathways. Deregulation of immunometabolism by ApoE4 led to monocytosis, adipose tissue expansion and inflammation as a consequence of impaired Mf efferocytosis and an imbalance in populations of LAMs. Detrimental effects of ApoE4 extended to Mf EVs that displayed differences in microRNA cargo mirroring parental cells. In vitro, ApoE4 EVs drove glycolytic metabolism and mitochondrial dysfunction in WT BMDM that impaired efferocytosis. They also inhibited the beiging of inguinal adipocytes. In vivo, ApoE4 EVs drove monocytosis, organomegaly and fat accumulation in WT mice. ApoE4 EVs also caused an imbalance in populations of LAMs and contributed to reduced OxPHOS in inguinal adipose tissue.
Conclusions: ApoE4 deregulation of microRNA-controlled Mf immunometabolism reduces efferocytosis that drives CMD, which can be communicated via EVs.