Engineering fluorescent NO probes for live-monitoring cellular inflammation and apoptosis

The processes of apoptosis and inflammatory responses, which are defensive strategies used by cells to confront external substances, can give rise to diverse diseases when prolonged or disrupted, such as cancer, Alzheimer's disease, and Parkinson's disease. Here we engineered a live-cell imaging fluorescent probe for nitric oxide (NO) based on naphthalimide and o-phenylenediamine, enabling the sensitive detection of NO in cancer cells and thereby live-monitoring of the doxorubicin-induced apoptosis and lipopolysaccharide-triggered inflammation reactions. Importantly, we found that the level of released NO can sensitively indicate the early stages of both cellular inflammatory responses and apoptotic processes. This suggested that cellular NO in fact behaves as a new class of signaling molecule for inflammatory responses and apoptosis processes, providing a potent tool for live-monitoring cellular physiological reactions.