Macrophage Corpses for Immunoregulation and Targeted Drug Delivery in Treatment of Collagen-induced Arthritis Mice

The role of pro-inflammatory macrophages (M1) in rheumatoid arthritis (RA) is significant, as they produce excessive cytokines. Targeting efferocytosis is a potential manner to repolarize M1 macrophages into pro-resolving M2 phenotype, which restores immune homeostasis by releasing anti-inflammatory mediators. In this study, liquid nitrogen-treated dead macrophages (DM) are employed to act as a dead cell-derived active targeted drug carrier for shikonin (SHK) and induce efferocytosis in M1 macrophages with the enhancement of SHK as an AMP-activated protein kinase (AMPK)-activator. The synergistic activation of AMPK leads to uncoupled protein 2 (UCP2) upregulation and reprograms M1 macrophages into M2 phenotypes by promoting oxidative phosphorylation. In the mouse model of collagen-induced arthritis, the intravenous administration of DM/SHK leads to a consistent transformation of M1 macrophages into the M2 phenotype within the infiltrative synovium. This transformation of macrophages results in the restoration of immune homeostasis in the synovium through an increase in the production of pro-resolving mediators. Additionally, it inhibits synovial proliferation and infiltration and provides protection against erosion of cartilage and bone. In summary, LNT-based DM serves as an active targeting drug carrier to M1 macrophages and also acts synergistically with SHK to target immunometabolism.