Migratory fluorescent probe for monitoring dynamic changes in lysosomal pH during apoptosis

Abstract

Precise regulation of apoptosis is crucial for maintaining cellular homeostasis. Dysregulation leads to diseases such as neurodegenerative disorders, inflammation, organ failure, and cancer. In the pathological processes of these apoptosis-related diseases, organelle homeostasis undergoes abnormal changes, notably including increased lysosomal pH and decreased mitochondrial membrane potential. Notably, lysosomes serve as pivotal organelles regulating apoptotic signaling. During apoptosis, dynamic changes in lysosomal pH directly participate in the initiation and execution of apoptotic pathways. Therefore, developing tools to monitor lysosomal pH shifts during apoptosis is crucial for elucidating cellular apoptotic mechanisms. This study developed a novel migratory fluorescent probe, KY-OH, based on an intramolecular reversible structural transformation strategy for fluorescence imaging of lysosomal pH changes within cells. Utilizing hydroxyethyl as the recognition moiety, the probe undergoes a reversible intramolecular switch loop under different pH conditions. Fluorescence imaging revealed that under normal cellular conditions, lysosomes maintain an acidic environment. KY-OH targets lysosomes and remains in an open-ring state, emitting red fluorescence. During apoptosis, abnormal pH changes in lysosomes trigger the probe's migration from lysosomes to mitochondria, where it adopts a closed-ring state and emits green fluorescence. Furthermore, KY-OH successfully monitored lysosomal pH shifts during apoptosis induced by hydrogen peroxide, colchicine, and rotenone. Due to pH changes, the probe's migration from lysosomes to mitochondria allowed for visual tracking of intracellular lysosomal pH dynamics. This probe can be used to study the process of abnormal lysosomal pH elevation caused by apoptosis, providing a powerful tool for monitoring the pH regulation mechanism of lysosomes during apoptosis.