Plasminogen as a Ribonucleoprotein: Regulatory small RNA Cargo Modulates Fibrinolysis and Inflammation

Cell-free RNA (cf-RNA) have emerged as critical mediators of intercellular communication and potential regulators of hemostasis. In this study, plasminogen (Plg), the zymogen precursor of plasmin, was demonstrated to function as a secreted ribonucleoprotein that carries regulatory, extracellular small non-coding RNAs (sRNA). Purified human and bovine Plg, isolated via lysine-affinity chromatography, were found to transport 25-60 nucleotide-long sRNAs derived from both host and microbial sources. In vitro studies revealed that Plg accepted sRNA cargo from primary macrophages and bound candidate sRNAs with moderate (µM) affinity. Notably, Plg-sRNA complexes exhibited a distinct RNA profile compared to high-density lipoproteins (HDL), and their compositions were sensitive to hypercholesterolemic conditions. Functionally, removal of sRNA cargo from Plg via RNase digestion significantly increased plasmin enzymatic activity and accelerated clot lysis, while also attenuating Plg-induced pro-inflammatory cytokine expression in both mouse and human macrophages. These findings reveal a dual regulatory role for sRNAs in modulating both the fibrinolytic and immunogenic properties of Plg, offering novel insights into the crosstalk between cf-RNA biology and coagulation pathways. This work positions Plg-sRNA interactions as promising targets for therapeutic intervention in thrombotic and inflammatory diseases.