Revealing mitochondrial microenvironmental changes triggered by ferroptosis regulation

Ferroptosis is a unique form of iron-dependent cell death characterized by dramatic ultrastructural changes in mitochondria. Since mitochondria are intracellular energy factories and binding sites for producing reactive oxygen species, there is increasing evidence that mitochondria are closely related to ferroptosis and play a crucial role in the regulation and execution of ferroptosis. The pH of the mitochondrial microenvironment is an important parameter for cellular physiological activities. Its abnormal fluctuations are commonly thought to be associated with cancers and other diseases. Herein, a surface-enhanced Raman scattering (SERS)-based pH nanosensor with high sensitivity and targeting function was utilized to quantify and monitor mitochondrial pH value. This nanosensor was constructed by gold nanorods (AuNRs) functionalized with pH-responsive molecules (4-mercaptopyridine, MPy) and mitochondrion-targeting peptides (AMMT) that can precisely deliver AuNRs to mitochondria. Super-resolution fluorescence imaging was employed to evidence the mitochondrial targeting feature of this nanosensor. Ferroptosis regulation induces intracellular accumulation of lipid peroxide (LPO) and reactive oxygen species (ROS), which cause changes in the mitochondrial pH. This method reveals that ferroptosis leads to the gradual acidification of the mitochondrial internal environment. The conclusion deduced by this study will be helpful for the evaluation and diagnosis of diseases according to intracellular abnormal microenvironments.