Involvment of Reactive Oxygen in Sonodynamically Induced Apoptosis by Pyrrolidine Tris-Acid Fullerene

Ultrasound has been widely utilized for medical diagnosis and therapy due to its ability to penetrate deep-seated tissue with less attenuation of energy and minimal undesirable side effects. Functionalized fullerenes, such as pyrrolidine tris-acid fullerene (PTF), have attracted particular attention due to their water solubility and potential application in tumor imaging and therapy as carbon nanomaterials. The present study investigated sonodynamically induced apoptosis using PTF. Cell suspensions were treated with 2-MHz continuous ultrasound in the presence of PTF for 3 min, and apoptosis was assessed by cell morphology using confocal microscopy, fragmentation of DNA and caspase-3 activation. The number of apoptotic cells after sonodynamic exposure (ultrasound and PTF) was significantly higher than after other treatments, such as ultrasound alone and PTF alone. Furthermore, DNA fragmentation, caspase-3 activation, and enhanced 4oxoTEMPO formation were observed in the sonodynamically treated cells. Histidine, a well-known reactive oxygen scavenger, significantly inhibited the sonodynamically induced apoptosis, caspase-3 activation and 4oxoTEMPO formation.The significant inhibition of sonodynamically induced apoptosis, caspase-3 activation, and 4oxoTEMPO formation due to histidine and tryptophan suggests that reactive oxygen species, such as singlet oxygen, are involved in the sonodynamic induction of apoptosis.