Organelle-specific analysis of labile Fe(II) during ferroptosis by using a cocktail of various colour organelle-targeted fluorescent probes

Ferroptosis is an emerging type of cell death mode that is dependent on iron. Unfortunately, the detailed analysis of the function of organelle labile Fe(II) in oxidative damage and lethality of the cells has not been demonstrated so far, mainly due to the lack of efficient methods to visualize labile Fe(II) at the targeted organelles. We have recently reported a series of Fe(II)-selective fluorescent probes, i.e., Ac-MtFluNox, Lyso-RhoNox, and ER-SiRhoNox, which can detect Fe(II) specifically in the mitochondria, lysosomes, and endoplasmic reticulum (ER), respectively. These probes demonstrate similar reaction rates and off/on contrasts with various colours and intracellular distributions, enabling simultaneous multi-colour imaging that allows the monitoring of labile Fe(II) levels at each targeted organelle. In this paper, by using a cocktail of these probes, we successfully visualised the aberrant elevation of labile Fe(II) in the lysosomes and ER prior to HT1080 cell death induced by erastin, which is an inducer of ferroptosis.