Study of the Synergistic Effect on Hepatoma 22 Tumor Cells by Focused Ultrasound Activation of Hematoporphyrin

Abstract

The synergistic effect of ultrasound and drugs on tumor cells is known as sonodynamic therapy (SDT). The purpose of this study was to evaluate the effects of SDT on lipid peroxidation and the activity of antioxidative enzymes in isolated hepatoma 22 (H-22) cells to better understand the bioeffects of SDT. The viability of cells was evaluated by the Trypan blue dye exclusion test. The morphologic changes of H-22 cells were observed by a scanning electron microscope immediately after treatment. The intracellular reactive oxygen species levels were detected by 2',7'-dichlorofluorescein diacetate. Colorimetry and enzymatic chemical methods were used to measure the lipid peroxidation levels and activities of key antioxidant enzymes (ie, superoxide dismutase, selenium-dependent glutathione peroxidase, and catalase) in H-22 tumor cells. Our experiments indicated that the ultrasonically induced cell damage rate was increased with 100-microg/mL hematoporphyrin, whereas no cell damage was observed with hematoporphyrin alone. Generation of reactive oxygen species in cell suspensions after SDT treatment was remarkably higher than in controls. The malondialdehyde content was remarkably enhanced, and antioxidative enzyme activities were obviously decreased compared with controls. This study suggests that oxygen free radicals may play an important role in improving membrane lipid peroxidation and decreasing the activities of key antioxidant enzymes in cells. It was speculated that this biological mechanism might be involved in mediating the killing effect of H-22 cells in SDT.