Systemic Delivery of MicroRNA-181b Inhibits Nuclear Factor-κB Activation, Vascular Inflammation, and Atherosclerosis in Apolipoprotein E-Deficient Mice

Rationale: Activated nuclear factor (NF)-B signaling in the vascular endothelium promotes the initiation and progression of atherosclerosis. Targeting endothelial NF-B may provide a novel strategy to limit chronic inflammation. Objective: To examine the role of microRNA-181b (miR-181b) in endothelial NF-B signaling and effects on atherosclerosis. Methods and Results: MiR-181b expression was reduced in the aortic intima and plasma in apolipoprotein E-deficient mice fed a high-fat diet. Correspondingly, circulating miR-181b in the plasma was markedly reduced in human subjects with coronary artery disease. Systemic delivery of miR-181b resulted in a 2.3-fold overexpression of miR-181b in the aortic intima of apolipoprotein E-deficient mice and suppressed NF-B signaling revealed by bioluminescence imaging and reduced target gene expression in the aortic arch in apolipoprotein E-deficient/NF-B-luciferase transgenic mice. MiR-181b significantly inhibited atherosclerotic lesion formation, proinflammatory gene expression and the influx of lesional macrophages and CD4+ T cells in the vessel wall. Mechanistically, miR-181b inhibited the expression of the target gene importin-3, an effect that reduced NF-B nuclear translocation specifically in the vascular endothelium of lesions, whereas surprisingly leukocyte NF-B signaling was unaffected despite a 7-fold overexpression of miR-181b. Our findings uncover that NF-B nuclear translocation in leukocytes does not involve importin-3, but rather importin-5, which miR-181b does not target, highlighting that inhibition of NF-B signaling in the endothelium is sufficient to mediate miR-181b's protective effects. Conclusions: Systemic delivery of miR-181b inhibits the activation of NF-B and atherosclerosis through cell-specific mechanisms in the vascular endothelium. These findings support the rationale that delivery of miR-181b may provide a novel therapeutic approach to treat chronic inflammatory diseases such as atherosclerosis.