Molecular mechanisms of the killing effects on Ehrlich ascites tumor cells by sono-chemical-activated protoporphyrin Ⅸ

We studied the Ehrlich ascetic tumor (EAT) cell line killing effects by ultrasound activating protoporphyrin Ⅸ (PPⅨ) and its mechamism. The cellular uptake and subcellular localization of protoporphyrin Ⅸ were estimated by fluorescence photometer and laser scanning confocal microscopy (LSCM) respectively. The trypan blue exclusion method was used to analyze the relative viability of EAT cells after ultrasonically activated protoporphyrin Ⅸ. Changes of ultra-microstructure of the treated cells were examined by transmission electron microscopy.Mitochondrial membrane potential(MMP), intracellular reactive oxygen species (ROS) levels, and the level of lipid peroxidation were determined by Rhodamine 123, 2′,7′- dichlorodihydrofluorescin diacetate (DCFH-DA) and thiobarbituric acid reaction method respectively. Results showed that there is a selective uptake and retention of the PPⅨ in tumor cells. CLSM revealed that PPⅨ localize mainly in the mitochondria. In the ultrasound plus PPⅨ group, the survival rate of cells was significantly lower. The ultra-microstructural damage of treated cells was the most remarkable, the loss of mitochondria membrane potential was the most noticeable, levels of ROS and lipid peroxides were remarkably increased. These results indicate that there is significant synergistic killing effect with ultrasound activating PPⅨ. The decreased mitochondria membrane potential and the increased level of lipid peroxidation in the ultrasound plus PPⅨ group may be associated with reactive oxygen species. In summary, reactive oxygen species might be involved in mediating the killing effect of EAT cells in SDT [Acta Zoologica Sinica 54(5): 846– 854, 2008]