SS-31 Modification Inhibits Pro-inflammatory Effect of Macrophages Induced by Superparamagnetic Iron Oxide Nanoparticles

Abstract Superparamagnetic iron oxide nanoparticles (SPION) could induce macrophage polarization into the pro-inflammatory M1-like subtype. The adverse effect is very likely to restrict the diagnostic or therapeutic applications of SPION in the cardiovascular field. To inhibit the pro-inflammatory effect, a mitochondrial targeted antioxidant peptide SS-31 modifying SPION (SPION@SS-31) was constructed. The macrophages (RAW 264.7) were incubated with SPION or SPION@SS-31 at the concentration of 50 µg Fe3O4/mL for 24 hours. Compared to the SPION group, the SPION@SS-31 group demonstrated significantly reduced macrophage damage, evidenced by maintained cell viability, a decrease of early cells apoptosis and reactive oxygen species (ROS) production. Moreover, the pro-inflammatory factor TNF-α and M1-like cell surface markers CD86 and CD80 were significantly down-regulated in the SPION@SS-31 group. Notably, higher levels of anti-inflammatory factors IL-10 and TGF-β and M2-like cell surface marker CD163 were detected in the SPION@SS-31 group by enzyme-linked immunosorbent assay (ELISA) and flow cytometric analysis. Besides, severe disruption of mitochondrial microstructure was observed by transmission electron microscope (TEM) in the SPION group, but less in the SPION@SS-31 group. Co-loading mitochondria-targeted antioxidant peptide SS-31 could significantly mitigate the pro-inflammatory effect of macrophages induced by SPION, indicating that the modification strategy has the potential to promote macrophages M2-like polarization in vitro study.