Preliminary Study On Apoptosis Induced By 5-Aminolaevulinic Acid-Mediated Sonodynamic Action In Human Malignant Myeloid Cell Lines K562 Cells

Background/Objective: Leukemia is a potentially fatal stem cell cancer that threatens the live and health of children in the world. The incidence of leukemia is about 2.76/10 millions and ranked as the sixth leading cause of cancer deaths in China. Current therapeutic modalities of leukemia are chemotherapy, radiation therapy and bone marrow transplant. However, chemical durg resistance and side-effects on normal cells of adverse reaction, and high cost and zygosity difficulties in bone marrow transplantation are hindering the development of leukemia treatment. Recent studies showed that sonodynamic therapy is a promising candidate in the management of malignant tumors. The present study aims to investigate that apoptosis induced by 5-aminolaevulinic acid (5-ALA)-mediatid sonodynamic action in human leukemia cell line K562 cells.Materials/Methods: The human leukemia cell line K562 cells were chosen in the present study. The cells were randomly divided into four groups: sham irradiation group, 5-ALA alone group, ultrasound irradiation group and 5-ALA-SDT group. For ultrasond exposure, continuous ultrasound energy was emitted from a 1-cm-diameter transducer with the working frequency of 1.7 MHz. The acoustic intensity was calibrated using hydrophone assay. Cytotoxicity was investigated 24 h using the trypan blue exclusion test post ultrasound exposure. Apoptosis was measured using Flow cytometry. Ultrastructural Cell morphology and mitochondrial changes was observed using transmission electron microscopy (TEM).Results: Trypsn blue staining showed that ultrasound radiation at the intensity of 1.35 W/cm2)for ten seconds,the cytotoxicitic rate exceeded 60%. In order to explore sonodynamic action of 5-ALA in K562 cells, we adjusted the intensity of ultrasound radiation to 0.65 W/cm2. The results show that 5-ALA have no significantly dark cytotoxicity in K562 cells at the concentration of 2 mM. Ultrasound radiation alone showed dose-dependent cytotoxicity. In the presence of 5-ALA could significantly enhance the ultrasound-induced cell death (P<0.05). Flow cytometry showed that apoptotic rate of K562 cells induced by 5-ALA-ultrasound increased up to 10.71%. Mitochondria expanding and some vacuoles were found in the ultrasound-treated cells under TEM. After the treatment of ultrasound and 5-ALA together some cells presented typical characteristics of apoptotic cells, such as nuclear condensation and crescent formation were observed. Mitochondria of the cells were damaged more seriously than those treated by ultrasound alone, obvious swollen mitochondria and mitochondria in which cristae were almost perfectly disappeared, and more vacuolar mitochondria were founded. Mitochondrial membrane potential (ΔΨm) was more significantly collapsed when K562 cells were exposed to 2 mM 5-ALA for 4 h and then 0.65 mW/cm2 irradiation of ultrasound than ultrasound radiation alone.Conclusion: 5-ALA significantly enhanced the cytotoxicity of ultrasound radiation in K562 cells. The damage of mitochondria structure and function might be an important cause of cell death in K562 cells induced by the treatment of ultrasound radiation and 5-ALA together. Sonodynamic therapy with 5-ALA maybe is a potential therapeutic modality of leukemia.