Therapeutic attenuation of orbital adipogenesis via M2 macrophage exosomes: A dual inhibition of oxidative stress and autophagy.

BACKGROUND: Pathological adipogenesis of orbital fibroblasts (OFs) is a hallmark of Graves' orbitopathy (GO). While oxidative stress and autophagy are implicated in this process, the role of immune cell-derived exosomes, particularly from M2 macrophages, remains unexplored. We investigated the hypothesis that M2 macrophage-derived exosomes (M2-exo) protect OFs from oxidative stress and inhibit adipogenesis via the PI3K/AKT/FOXO1 signaling pathway. METHODS: M2-exo were isolated from cytokine-induced THP-1 macrophages and characterized by NTA, TEM, and immunoblotting. An oxidative stress model was established in adipogenic-differentiated OFs using H₂O₂. The effects of M2-exo on cell viability, cell cycle, lipid accumulation (Oil Red O), oxidative markers (ROS, MDA, SOD, GSH), and autophagy (LC3-II/I, p62) were assessed. Key findings were validated using the PI3K agonist 740 Y-P and the autophagy inducer rapamycin. RESULTS: M2-exo were successfully internalized by OFs. Under H₂O₂ stress, M2-exo restored cell viability, mitigated G0/G1 phase arrest, and suppressed lipid droplet formation. Mechanistically, M2-exo reduced ROS/MDA levels, elevated SOD/GSH, and inhibited excessive autophagy. They also suppressed H₂O₂-induced activation of the PI3K/AKT pathway and downstream FOXO1 phosphorylation. Crucially, the protective effects of M2-exo were abolished by both 740 Y-P and rapamycin, confirming the involvement of the PI3K/AKT/FOXO1-autophagy axis. CONCLUSION: This study unveils a novel paracrine mechanism whereby M2-exo alleviate oxidative stress and inhibit autophagy in OFs, thereby countering adipogenesis, via modulation of the PI3K/AKT/FOXO1 pathway. Targeting this axis may represent a promising therapeutic strategy for GO.