Melatonin promotes skin flap survival by inhibiting ferroptosis

Abstract Background Random skin flaps application is considerably limited by postoperative complications, particularly distal tissue ischemia and necrosis. Melatonin, a molecule with well-documented antioxidant and cytoprotective properties, has shown promise in protecting ischemic tissues. However, its specific role in regulating ferroptosis during ischemic flap injury, as well as its safety and efficacy in primate models (a key step for clinical translation), remains to be systematically validated. In this study, we aimed to promote angiogenesis within flap tissue through exogenous melatonin administration, and to inhibit ferroptosis to mitigate ischemia-reperfusion injury, presenting a novel strategy for enhancing flap survival rates. Methods A random skin flap was constructed in C57BL/6J mice. After melatonin treatment for seven days, the influence of melatonin on the levels of oxidative stress, iron accumulation, and mitochondrial morphology within the skin flap tissue were assessed. We used Transwell migration assays, tube formation assays, flow cytometry and immunofluorescence staining to determine the effects of melatonin in vitro. The ferroptosis inducer erastin was used in combination with melatonin to treat random skin flap mice and Tert-butyl hydroperoxide (TBHP) induced cellular models, And the pathway through which melatonin counteracts iron mutations was explored. Lastly, we conducted experiments using nonhuman primate (NHP) models and analyzed the protective effects of melatonin on ischemic flaps in macaques, highlighting its potential for clinical translation. Results Melatonin ameliorated the survival area of ischemic flaps in mice, enhanced angiogenesis, reduced mitochondrial damage, and also suppressed lipid peroxidation and iron ion accumulation. Melatonin attenuated TBPH-induced cell death, lipid peroxidation, and mitochondrial damage in vitro. Further mechanistic studies revealed that melatonin inhibited ferroptosis, accompanied by nuclear translocation of nuclear factor E2-related factor 2 (Nrf2), and increases the expression of downstream gene (effector) heme oxygenase-1 (HO-1). More importantly, experiments in macaques demonstrated that melatonin could enhance flap viability and angiogenesis, and exhibited good safety profile. Conclusion Melatonin enhanced flap viability in mice and macaques by inhibiting ferroptosis, boosting angiogenesis, and attenuating oxidative stress injury.