A triple-targeting fluorescent probe reveals the glutathione and viscosity crosstalk in mitochondria, endoplasmic reticulum, and nucleoli in cells during ferroptosis

Ferroptosis, a recently termed cell death form, is featured by iron accumulation and lipid peroxidation, which plays various roles in physiological and pathological processes such as cancer evolution and therapy. Redox homeostasis profoundly varies in cells during ferroptosis, but many events remain to be explored, especially at the sub-cellular level. Glutathione (GSH) is the most abundant bio-reductant and mainly distributes in mitochondria (Mito), endoplasmic reticulum (ER), and nucleoli (Nuc) except the cytoplasm. The GSH level is intrinsically related to the redox equilibriums in the three organelles. Viscosity is an index of the intracellular micro-environments related to redox homeostasis. The dynamics of the GSH and viscosity levels in organelles are vital to understanding cell ferroptosis but are in a veil due to the lack of the appropriate tools. Here we report a fluorescent probe (FPY) with dual-response to GSH and viscosity, characteristic of the triple-targeting to Mito, ER, and Nuc. We apply FPY in fluorescent imaging of cells during ferroptosis and disclose the GSH-viscosity crosstalk at the sub-cellular level. We discover an abnormal GSH recruitment in Nuc from the cytoplasm in the late stage of ferroptosis.