Imaging changes in the polarity of lipid droplets during NAFLD-Induced ferroptosis via a red-emitting fluorescent probe with a large Stokes shift

Cell death resulting from ferroptosis is a consequence of the accumulation of lipid peroxides that are produced when lipids and reactive oxygen species (ROS) interact. This process is dependent on iron and alters the structure and polarity of lipid droplets (LDs). Unlike reactive fluorescent probes, environment-sensitive fluorescent probes can accurately monitor metabolic activities by sensing the intracellular environment of living organisms. To this end, we developed a polarity-sensitive fluorescent probe LIP-Ser that anchors to LDs and can be used to monitor changes in the polarity of LDs during ferroptosis by in situ imaging. LIP-Ser has a red-emitting (λem = 634 nm) and a large Stokes shift (Δλ = 161 nm in 1,4-dioxane), which avoids it from autofluorescence interference and crosstalk between excitation and emission spectra, thereby preventing low signal-to-noise ratio and severe fluorescence self-quenching during imaging. Additionally, LIP-Ser is used in this study to demonstrate that non-alcoholic fatty liver disease (NAFLD) promotes ferroptosis at the cellular and in vivo levels, and that inhibition of cellular ferroptosis effectively reduces the damage caused by NAFLD to cells and mouse liver tissue.