Resonance raman studies on manganese porphyrin detection and redox state in endothelial cells: implications for antioxidant cytoprotection

Manganese Porphyrins (MnPs) act as efficient catalytic antioxidants. They can reach mitochondria and confer pharmacological protection in pathologies related to an increase in oxidants formation, particularly peroxynitrite. However, a direct method to evaluate the uptake and redox state of MnPs in living cells has not been developed. In this work by applying Resonance Raman (RR) confocal microscopy, we detected the incorporation into endothelial cells of two potent MnPs-based lipophilic SOD mimics, MnTnBuOE-2-PyP5+ and MnTnHex-2-PyP5+ and confirmed that MnPs are mostly reduced intracellularly. RR assays with isolated mitochondria also revealed the reduction of MnPs by mitochondrial components, supporting their action as redox active compounds in mitochondria. To assess the combined impact of reactivity and bioavailability, we studied the kinetics of MnPs with peroxynitrite and evaluated their cytoprotective capacity. MnPs protected endothelial cells from a nitro-oxidative stress induced by peroxynitrite, preserving mitochondrial function and preventing apoptotosis. These data introduces a novel application of RR spectroscopy for the direct detection of MnPs and their redox state in living cells, helping to rationalize its protective antioxidant mechanisms in biological systems.