Single fluorescent probe reveals glutathione-viscosity crosstalk in the endoplasmic reticulum during ferroptosis and extracellular vesicles in synergistic ferroptosis-apoptosis

Ferroptosis is an iron-dependent cell death triggered by lipid peroxidation accumulation, representing a redox imbalance in cells. The increased knowledge of ferroptosis has led to various potential strategies to develop new cancer therapies, such as synergistic ferroptosis-apoptosis. The endoplasmic reticulum (ER) is the major hub for lipid metabolism in cells and plays a central role in lipid peroxidation. Glutathione (GSH) and viscosity levels in ER are important parameters for intracellular redox homeostasis, which remain unclear in ferroptosis and synergistic ferroptosis-apoptosis. This study developed an ER-targeting fluorescent probe (MMPY) with a dual-emission response to GSH and viscosity. Fluorescent cell imaging using MMPY revealed different GSH-viscosity crosstalk in the ER for the four ferroptosis pathways induced by erastin, RSL3, FIN56, and FINO2. GSH and viscosity changes in the ER during synergistic ferroptosis-apoptosis were also investigated. Interestingly, the new types of extracellular vesicles were observed during the synergistic process, which burdened the ER fragments with different GSH contents.