Diplacone Isolated from Paulownia tomentosa Mature Fruit Induces Ferroptosis-Mediated Cell Death through Mitochondrial Ca2+ Influx and Mitochondrial Permeability Transition

The recently defined type of cell death Ferroptosis has garnered significant attention as a potential new approach to Cancer treatment owing to its more immunogenic nature when compared with Apoptosis. Ferroptosis is characterized by the depletion of glutathione (GSH)/glutathione peroxidase-4 (GPx4) and iron-dependent lipid peroxidation. Diplacone (DP), a geranylated flavonoid compound found in Paulownia tomentosa fruit, has been identified to have anti-inflammatory and anti-radical activity. In this study, the potential Anticancer activity of DP was explored against A549 human lung Cancer cells. It was found that DP induced a form of cytotoxicity distinct from Apoptosis, which was accompanied by extensive mitochondrial-derived cytoplasmic vacuoles. DP was also shown to increase mitochondrial CA²⁺ influx, Reactive Oxygen Species (ROS) production, and mitochondrial permeability transition (MPT) pore-opening. These changes led to decreases in mitochondrial membrane potential and DP-induced cell death. DP also induced lipid peroxidation and ATF3 expression, which are hallmarks of Ferroptosis. The Ferroptosis inhibitors ferrostatin-1 and liproxstatin-1 were effective in counteracting the DP-mediated ferroptosis-related features. Our results could contribute to the use of DP as a ferroptosis-inducing agent, enabling studies focusing on the relationship between Ferroptosis and the immunogenic cell death of Cancer cells.