Hypocrellin B, a natural pigment from a traditional Chinese herb, has been attracting extensive attention. The present study aims to investigate whether
hypocrellin B can enhance cell death induced by ultrasound sonification on
nasopharyngeal carcinoma cells in vitro. The sonodynamic action of
hypocrellin B was investigated on
nasopharyngeal carcinoma cell line CNE2 cells as
tumor model cells. In the experiments, the
hypocrellin B concentration was kept constant at 2.5 microM and the cells were subject to ultrasound exposure for 15 s at an intensity of 0.65 W/cm(2). Cytotoxicity was investigated 24 h after ultrasound sonification. Apoptosis was evaluated using flow cytometry with
annexin V-FITC and
propidium iodine staining and nuclear staining with
Hoechst 33258. Cell ultrastructure morphology was observed using transmission electron microscopy (TEM). No significant dark cytotoxicity of
hypocrellin B in the CNE2 cells was observed at the concentration of 2.5 microM. The cell death rate induced by ultrasound sonification was significantly higher in the presence of
hypocrellin B than in the absence of
hypocrellin B. Flow cytometry showed that ultrasound exposure in the presence of
hypocrellin B significantly increased the early and late apoptotic rate, 18.64% and 22.57%, respectively, compared with the controls. Nuclear condensation was observed in the nuclear staining and swollen mitochondria and more vacuolar and broken cell membrane were found in TEM after the treatment of
hypocrellin B and ultrasound. Our findings demonstrated that the presence of
hypocrellin B significantly enhanced the cytotoxicity of ultrasound radiation in CNE2 cells, suggesting that
hypocrellin B is a novel sonosensitizer and
hypocrellin B-mediated sonodynamic
therapy is a potential therapeutic modality in the management of malignant
tumors.