title: Cytotoxic effect of protoporphyrin IX to human Leukemia U937 cells under ultrasonic irradiation.
abstract: BACKGROUND
  Sonodynamic therapy (SDT) is an alternative strategy that manages malignancies via the generation of cytotoxic factors during ultrasound-activated sono-sensitive agents. However, the detailed mechanisms are not clear. This study was to identify the cytotoxic effects of ultrasound-activated protoporphyrin IX (PpIX) on U937 cells.
  
  
  METHODS
  Flow cytometry was performed to detect the time course for PpIX uptake in U937 cells. Sub-cellular localization of PpIX in U937 cells was visualized by inverted confocal laser scanning microscope. Following PpIX-mediated SDT treatment, cell viability was evaluated by the 3-(4, 5- dimethylthiazol-2-yl)-2, 5-diphenyltetrazoliumbromide (MTT) assay; nuclear damage was observed under fluorescent microscope; DNA fragmentation and mitochondrial membrane potential disruption were measured by flow cytometry. The role of reactive oxygen species (ROS) in SDT-induced cell death was also evaluated.
  
  
  RESULTS
  We observed that PpIX is mainly localized in the mitochondria, with a maximal uptake within 2 h. Compared with PpIX or ultrasound alone, PpIX plus ultrasound treatment significantly declined cell viability, caused more serious damage of cell morphology, DNA and mitochondria. In the combined treatment group, the intracellular ROS was greatly higher than in other groups; ROS scavenger N-acetylcysteine could effectively rescue the loss of mitochondria membrane potential and cell viability induced by SDT.
  
  
  CONCLUSIONS
  Taken together, these findings primarily indicated that fatal damage could be induced by PpIX-mediated SDT in U937 cells, and the intracellular ROS was involved during this process. © 2014 S. Karger AG, Basel.
authors.affiliation: Key Laboratory of Medicinal Resources and Natural Pharmaceutical Chemistry, Ministry of Education, National Engineering Laboratory for Resource Developing of Endangered Chinese Crude Drugs in Northwest of China, College of Life Sciences, Shaanxi Normal University, Xi'an, China.
authors.forename: Yixiang
authors.initials: Y
authors.lastname: Li
authors.forename: Xiaomin
authors.initials: X
authors.lastname: Su
authors.forename: Xiaobing
authors.initials: X
authors.lastname: Wang
authors.forename: Albert Wingnang
authors.initials: AW
authors.lastname: Leung
authors.forename: Chuanshan
authors.initials: C
authors.lastname: Xu
authors.forename: Pan
authors.initials: P
authors.lastname: Wang
authors.forename: Quanhong
authors.initials: Q
authors.lastname: Liu
mesh_terms: D000111:Acetylcysteine / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D004247:DNA / Q000378:metabolism; D053938:DNA Fragmentation / Q000187:drug effects; D006801:Humans; D007938:Leukemia / Q000378:metabolism / Q000473:pathology; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D008928:Mitochondria / Q000378:metabolism; D011524:Protoporphyrins / Q000633:toxicity*; D017382:Reactive Oxygen Species / Q000378:metabolism; D013010:Sonication; D020298:U937 Cells
chemical_list: D011524:Protoporphyrins; D017382:Reactive Oxygen Species; D004247:DNA; C028025:protoporphyrin IX; D000111:Acetylcysteine