OP30 Human umbilical cord mesenchymal stem cells derived exosomes alleviate Ulcerative Colitis by inhibiting macrophage ferroptosis via miR-23b-3p/Nrf2 pathway

Abstract Background Human umbilical cord mesenchymal stem cell derived exosomes (HucMSC-Exo) have broad application prospects in treatment of various disease, including ulcerative colitis (UC). Macrophages can trigger intestinal mucosal inflammation thereby participating in the onset and development of UC. As a newly discovered iron-dependent cell death pathway, ferroptosis has also been found accompanied by inflammatory response in recent studies. We speculated that there could be relationship between macrophage ferroptosis and inflammatory response in UC. Furthermore, the role of macrophage ferroptosis in the process of HucMSC-Exo alleviating UC remains undefined. This study aims to explore the therapeutic effect and mechanism of HucMSC-Exo on UC by regulating macrophage ferroptosis. Methods The gene expression of ferroptosis-related proteins was assessed in colon samples from healthy controls and UC patients to explore the relationship between ferroptosis and UC. In vivo, colitis was induced by dextran sulfate sodium in mice. HucMSC-Exo was administered intravenously to estimate its curative effect, and its gut homing was evaluated by animal live imaging analysis. In vitro, HucMSC-Exo were cocultured with ferroptosis inducer RSL3-treated bone marrow-derived macrophages (BMDMs), RAW264.7 cell line, followed by examining the effect of HucMSC-Exo. Transfection of microRNA mimics and gene knockdown were used to confirm the role of miR-23b-3p in HucMSC-Exo regulating of macrophage ferroptosis. Results Compared with healthy individuals, ferroptosis may be involved in the mucosal inflammation of UC patients. HucMSC-Exo were found to successfully target damaged colon tissues in vivo. HucMSC-Exo treatment significantly improved the pathological damage of colon tissue, increased the expression of glutathione peroxidase 4 (GPX4), while markedly decreasing the levels of iron and lipid ROS, and reducing the secretion of interleukin (IL)-1β and IL-6, and then relieved macrophage ferroptosis to alleviate murine colitis. In vitro experiments showed that HucMSC-Exo could be effectively absorbed by macrophages and rescued RSL3-induced ferroptosis, which was consistent with the effect of ferrostatin-1, a ferroptosis-specifific inhibitor. Mechanismly, HucMSC-exo could inhibit macrophage ferroptosis by delivering its highly expressed miR-23b-3p to activate Nrf2 pathway. Additionally, the protection of HucMSC-exo for UC was attenuated by decreasing the expression of miR-23b-3p or inhibiting Nrf2 pathway. Conclusion HucMSC-Exo could activate Nrf2 antioxidant pathway and abrogate macrophage ferroptosis by delivering miR-23b-3p and ultimately ameliorate colitis.