Comparison of Accumulation, Subcellular Location, and Sonodynamic Cytotoxicity between Hematoporphyrin and Protoporphyrin IX in L1210 Cells

Abstract

Background: Sonodynamic therapy (SDT) is a promising modality for cancer treatment which requires the synergistic effect of ultrasound and tumor-localized sonosensitizers. Sonodynamic efficacy can be improved through a better understanding of the accumulation and subcellular location of sonosensitizers. Here, a comparison of the accumulation, sublocation, and sonodynamic effect of hematoporphyrin (Hp) and protoporphyrin IX (PpIX) was studied in L1210 cells. Methods: The kinetics of intracellular Hp and PpIX accumulation were detected using a fluorescence spectrophotometer. The subcellular distributions of Hp and PpIX were monitored by laser scanning confocal microscopy. The cytotoxic effects of Hp-mediated SDT (Hp-SDT) and PpIX-mediated SDT (PpIX-SDT) were evaluated by MTT assay. Results: The accumulation of Hp and PpIX presented different kinetic changes depending on the time, and was also concentration- and temperature-dependent. The intracellular PpIX content was much higher than that of Hp under the same conditions; however, there were no obvious differences in terms of their subcellular locations, and both of them mainly accumulated on the mitochondria and the plasma membrane in L1210 cells. PpIX exhibited more potential cytotoxicity than did Hp when they were irradiated with ultrasound under the same experimental conditions. Conclusion: Our results indicate that there were significant differences regarding the intracellular accumulation features between Hp and PpIX. PpIX-SDT produced a more serious cytotoxic effect than did Hp-SDT, which may be due to the higher PpIX uptake in L1210 cells compared to that of Hp at the same concentrations. Additionally, the absorption of Hp and PpIX in L1210 cells might be energy dependent.