MiR487a-3p and MiR6855-3p Facilitate Macrophage Pro-inflammatory Polarization and Lipid Accumulation in Atherosclerosis

BACKGROUND: MicroRNAs (miRNAs) regulate macrophage plasticity in atherosclerosis (AS). We tested the hypothesis that miR487a-3p and miR6855-3p accelerate AS by promoting macrophage inflammatory responses and metabolic dysregulation. METHODS: miRNA-seq and mRNA-seq were performed on peripheral monocytes from CAD patients and healthy controls. Macrophages in mouse aortas and human coronary arteries were characterized by flow cytometry and immunostaining. AS was evaluated in PCSK9-overexpressing mice with myeloid-specific deficiency of carboxypeptidase E (CPE) or ribonucleotide reductase subunit M2 (RRM2) fed a high-fat diet. RESULTS: miR487a-3p and miR6855-3p were the top differentially expressed miRNAs in peripheral monocytes from CAD patients versus controls. Both miRNAs were lipid-inducible, with transcription driven by ox-LDL via KLF5 and IRF1, respectively, and were secreted extracellularly. Plasma levels of both miRNAs were elevated in CAD patients, correlated positively with blood lipids and Gensini score, and exhibited diagnostic accuracy (AUC 0.83 each). Both miRNAs were predominantly expressed in coronary plaque macrophages, and their abundance correlated with lesion area. Overexpression of either miRNA promoted macrophage pro-inflammatory polarization, lipid metabolic dysregulation, foam cell formation, and endothelial cell apoptosis, whereas miRNA inhibition attenuated these ox-LDL-induced phenotypes. CPE and RRM2 were identified as direct targets of miR487a-3p and miR6855-3p, respectively, by integrating mRNA-seq and TargetScan predictions, with binding confirmed by dual-luciferase assays and miRNA pulldown. CPE or RRM2 overexpression partially reversed miRNA-induced macrophage dysfunction. Conversely, myeloid-specific deletion of Cpe or Rrm2 exacerbated AS in hypercholesterolemic mice. CONCLUSIONS: miR-487a-3p and miR-6855-3p are promising biomarkers for CAD diagnosis and prognosis. Mechanistically, they drive macrophage inflammation and lipid metabolic disruption, identifying them as potential therapeutic targets. Key Words: microRNA; atherosclerosis; macrophage; inflammation; lipid disorders