A mitochondria-targeted fluorescent probe for revealing H₂O₂ elevation modulated by basal HClO in HeLa and A549 cells

Hydrogen peroxide, which is mainly produced in mitochondria, plays deleterious and beneficial roles in cells depending on its localized concentration. Tumor cells have been observed to have increased H₂O₂ levels due to enhanced metabolic activity. Moderately high levels of H₂O₂ are crucial for the growth and survival of tumor cells. Monitoring mitochondrial H₂O₂ is essential for revealing the factors that affect cellular redox balance. In the present work, we have developed a fast responsive fluorescent probe for the detection of H₂O₂ in mitochondria. Hcy-S shows high selectivity, sensitivity and a fast response to H₂O₂, enabling imaging of basal levels of mitochondrial H₂O₂ in tumor cells in 1 min. Hcy-S has been applied to the study of the impact of HClO on H₂O₂ level. The results revealed that endogenous HClO raises the levels of H₂O₂ by inactivating catalase and glutathione peroxidase in HeLa and A549 cells. This study offers a novel insight into the redox balance in tumor cells.