Utilizing Liposomes That Selectively Target Inflamed Endothelium to Upregulate Macrophage-Like Cell ABCA1 Through Endothelial Cell-Derived Exosome-Mediated Processes

Background: Atherosclerosis is caused by lipid accumulation in arterial endothelial cells and intimal cells. Atherosclerosis generally occurs in arteries that exhibit vascular inflammation, thereby making pro-inflammatory arterial endothelial cells a potential target for delivering atheroprotective material. Lipid-laden macrophages and vascular smooth muscle cells that have transdifferentiated into macrophage-like cells from cholesterol accumulation are the two primary intimal cell types that drive atherosclerosis. We have constructed a novel liposome-based therapeutic system (LP-pXMoA5p) that can specifically target inflamed arterial endothelial cells, resulting in endothelial cells that internalize LP-pXMoA5p to express and then package anti-miR-33a-5p into exosomes that are released basolaterally, which may lead to effective transfer of atheroprotective anti-miR-33a-5p to intimal cells. We have previously tested this delivery method with cultured macrophages being the recipient of endothelial-cell-derived exosomes filled with anti-miR-33a-5p, resulting in enhanced macrophage ABCA1-dependent cholesterol efflux. Methods: In this study, we wanted to test whether our LP-pXMoA5p delivery system is successful when utilizing cultured macrophage-like cells as the recipient cells for endothelial-cell-derived exosomes loaded with anti-miR-33a-5p. To test the atheroprotective efficacy of our LP-pXMoA5p delivery method, we measured miR-33a-5p expression, ABCA1 protein expression, and apoAI-mediated cholesterol efflux in recipient macrophage-like cells. Results: In our experiments, we observed that cultured macrophage-like cells incubated with anti-miR-33a-5p-filled exosomes exhibited high levels of cellular anti-miR-33a-5p, which resulted in decreased miR-33a-5p expression. Moreover, inhibition of miR-33a-5p within macrophage-like cells caused enhanced apoAI-mediated cholesterol efflux in these cells, which was likely the result of increased ABCA1 protein expression. Conclusions: Our findings reveal that LP-pXMoA5p appears capable of enhancing ABCA1-dependent cholesterol efflux within cultured macrophage-like cells, with this outcome potentially being due to macrophage-like cells internalizing anti-miR-33a-5p-loaded exosomes which are secreted by pro-inflammatory cultured immortalized mouse aortic endothelial cells (iMAECs), but we acknowledge this may not translate to similar effects in vivo.