Lysosomal peroxynitrite imaging reveals oxidative stress and therapeutic response in osteoarthritis using a fluorogenic probe.

Osteoarthritis (OA) is closely associated with oxidative and nitrosative stress, in which peroxynitrite (ONOO-) contributes to inflammatory damage and cartilage degeneration. Given the involvement of lysosomal dysfunction in OA, lysosomal ONOO- imaging may provide valuable information on disease progression and therapeutic response. Herein, we developed a lysosome-targeted fluorogenic probe, Lys-ONOO, for sensitive ONOO- detection in living systems. Lys-ONOO exhibited a rapid and selective response toward ONOO- with a detection limit of 11.4 nM and enabled imaging of both exogenous and endogenous ONOO-. The probe showed effective lysosomal localization and was successfully applied in cells, zebrafish, and murine OA models. Elevated ONOO- signals were observed in osteoarthritic joints, whereas pharmacological treatment markedly reduced the fluorescence response. These findings demonstrate the potential of Lys-ONOO for lysosomal ONOO- imaging, OA assessment, and therapeutic efficacy evaluation.