Apoptosis induced by sonodynamic treatment by protoporphyrin IX on MDA-MB-231 cells

Sonodynamic therapy (SDT) is a promising modality for cancer treatment, involving the synergistic interaction of ultrasound and some chemical compounds termed as sono-sensitizers. It has been found that SDT can lead to apoptotic cell death because of the induction of direct sonochemical and subsequent redox reactions. However, the detailed mechanisms are not clear. This study was to identify the cytotoxic effects of ultrasound-activated protoporphyrin IX (PpIX) on MDA-MB-231 cells. The fluorescence microscope was used to detect the sub-cellular localization of PpIX. Several distinct sonochemical effects were found after SDT treatment, including the decrease of cell viability, generation of intracellular ROS, the loss of mitochondrial membrane potential. The activation of some special apoptosis-associated proteins [Caspase-9, Caspase-3 and polypeptide poly (ADP-robose) polymerase] was evaluated by western blotting. The results show that PpIX mediated SDT (PpIX-SDT) treatment could obviously inhibit the proliferation of MDA-MB-231 cells, and which was significantly reduced by the pan-Caspase inhibitor z-VAD-fmk and the reactive oxygen species (ROS) scavenger N-acetylcysteine (NAC). Further, SDT induced a conspicuous loss of mitochondrial membrane potential (MMP) and a mass of ROS accumulation in MDA-MB-231 cells at 1 h post-treatment and the SDT-treated cells showed obvious Caspase-3 and Caspase-9 activation, and PARP cleavage at 6 h after treatment. And, the general apoptosis marker-Caspase-3 activation-was also greatly relieved by NAC. These findings primarily indicate a Caspase-depended apoptosis could be induced by PpIX-SDT in MDA-MB-231 cells, and the intracellular ROS was involved during the apoptotic process.     

Sonodynamic effects of protoporphyrin IX disodium salt on Ehrlich ascetic tumor cells

The cytotoxic effect of protoporphyrin IX disodium salt (PPIX) on isolated Ehrlich ascetic tumor (EAT) cells induced by ultrasound exposure was investigated. Tumor cells suspended in air-saturated phosphate buffer solution (PBS, pH 7.2) were exposed to ultrasound at 2.2 MHz for up to 60 s in the presence and absence of PPIX. The viability of cells was determined by a trypan blue exclusion test. The morphological changes of cells in SDT were observed by scanning electron microscope (SEM). And the sub-cellular localization of PPIX in EAT cells was detected by confocal laser scanning microscopy (CLSM). The ultrasonically-induced cell damage increased as PPIX concentration increased, while no cell damage was observed with PPIX alone. CLSM observation revealed that the fluorescence of PPIX and rhodamine 123 (mitochondrial probe) overlapped very well in the cytoplasm. The results indicate that PPIX could enhance the ultrasonically-induced cell damage and mitochondria may play an important role during sonodynamically induced cytotoxicity.     

Proton polarization with p-terphenyl crystal by integrated solid effect on photoexcited triplet state

We have carried out the experiments for polarizing protons in single crystals of p-terphenyl doped with 0.1 mol% pentacene. The experiments have been performed in a magnetic field of 3 kG at room temperature or at 77 K. We obtained the polarization of 1.3% for protons in bulk at room temperature by using a pulsed dye-laser with the wavelength of 590 nm, the average power of 150 mW, and the repetition rate of 50 Hz. The polarization at 77 K reached 18% by irradiation with the dye-laser of 500 mW, 50 Hz and the same wavelength. The polarization of protons was measured by the neutron transmission method also. The result was consistent with that measured by the nuclear magnetic resonance.