Macrophage PSRC1 attenuates atherosclerosis via extracellular vesicle-mediated MBD2 delivery to induce PCSK9 promoter methylation in hepatocytes

BACKGROUND: Atherosclerotic cardiovascular disease (ASCVD) is driven by dysregulated lipid metabolism and chronic inflammation. However, the mechanisms governing immune-liver crosstalk in this context remain poorly defined. Proline/serine-rich coiled-coil protein 1 (PSRC1) is a known regulator of cholesterol metabolism, but whether macrophage-derived PSRC1 influences hepatic functions via intercellular communication is unknown. METHODS: The relationship between macrophage PSRC1 and hepatic PCSK9 was examined in patients with coronary artery disease and murine models. We employed AAV6-mediated macrophage-specific targeting and whole-body Psrc1⁻/⁻ mice to evaluate cell-type-specific effects. Macrophage-hepatocyte communication was investigated using transwell systems and genetic blockade of EV secretion (sh-Rab27a). The selectivity of EV cargo loading was validated by protease protection assays and TSG101 interaction analysis. In vivo EV tracking (DiI-labeling) and ChIP-qPCR for DNMT recruitment were performed to elucidate the systemic and epigenetic mechanisms. RESULTS: Macrophage PSRC1 expression was significantly reduced in atherosclerotic conditions and inversely correlated with hepatic PCSK9 levels. Macrophage-specific PSRC1 depletion alone was sufficient to recapitulate the systemic hypercholesterolemia and accelerated atherosclerosis observed in whole-body knockout models. PSRC1 was found to interact with TSG101 to promote the selective loading of MBD2 into the EV lumen, a process confirmed by protease protection. These MBD2-enriched EVs were preferentially sequestered by the liver after systemic administration. Mechanistically, transferred MBD2 functioned as an epigenetic scaffold, recruiting DNA methyltransferases (DNMT1/3A) to the PCSK9 promoter to drive CpG hypermethylation and transcriptional repression. In vivo, administration of MBD2-enriched EVs significantly reduced hepatic PCSK9 protein, lowered plasma cholesterol, and enhanced plaque stability in ApoE⁻/⁻ mice. CONCLUSIONS: Our findings uncover a novel macrophage-liver epigenetic axis where macrophage PSRC1 controls systemic cholesterol homeostasis by regulating the EV-mediated delivery of MBD2. This "Reader-recruits-Writer" mechanism provides a refined understanding of immune-metabolic crosstalk and suggests that engineered EV-based MBD2 delivery represents a promising therapeutic strategy for ASCVD.