title: Photodynamic action of methylene blue in osteosarcoma cells in vitro.
abstract: BACKGROUND
  Osteosarcoma is a common malignant bone tumor which threatens the life of young people worldwide. To explore alternative strategy for combating osteosarcoma, a light-emitting diode (LED) that activates methylene blue (MB) was used in the present study to investigate cell death of osteosarcoma-derived UMR106 cells.
  
  
  METHODS
  Photocytotoxicity in UMR106 cells was investigated 24h after photodynamic activation of MB using sulforhodamine B (SRB) assay and light microscopy. Apoptosis induction was observed 24h after photodynamic treatment using a confocal laser scanning microscopy (CLSM) with Hoechst 33342 staining. The change in mitochondrial membrane potential (MMP) was analyzed using a flow cytometry with rhodamine 123 staining.
  
  
  RESULTS
  MB under red light irradiation caused a drug-concentration (0-100μM) and light-dose (0-32J/cm(2)) dependent cytotoxicity in UMR106 cells. The SRB assay and light microscopy observed a significant decrease in the number of UMR106 cells attached to the bottom of culture well after LED light-activated MB (100μM, 32J/cm(2)). Nuclear shrinkage, chromatin condensation and fragmentation were found in the treated cells by nuclear staining. In addition, flow cytometry showed that the MMP in UMR106 cells was rapidly reduced by photo-activated MB (100μM, 32J/cm(2)).
  
  
  CONCLUSIONS
  Photodynamic action of MB under LED irradiation could remarkably kill osteosarcoma cells and induce cell apoptosis as well as MMP collapse.
authors.affiliation: School of Chinese Medicine, The Chinese University of Hong Kong, Shatin, Hong Kong; School of Chinese Medicine, Guangzhou University of Chinese Medicine, Guangzhou, Guangdong, China.
authors.forename: Jiemin
authors.initials: J
authors.lastname: Guan
authors.affiliation: School of Chinese Medicine, Guangzhou University of Chinese Medicine, Guangzhou, Guangdong, China. Electronic address: laixp88@126.com.
authors.forename: Xiaoping
authors.initials: X
authors.lastname: Lai
authors.affiliation: School of Chinese Medicine, The Chinese University of Hong Kong, Shatin, Hong Kong.
authors.forename: Xinna
authors.initials: X
authors.lastname: Wang
authors.affiliation: School of Chinese Medicine, The Chinese University of Hong Kong, Shatin, Hong Kong. Electronic address: awnleung@cuhk.edu.hk.
authors.forename: Albert Wingnang
authors.initials: AW
authors.lastname: Leung
authors.affiliation: School of Chinese Medicine, The Chinese University of Hong Kong, Shatin, Hong Kong.
authors.forename: Hongwei
authors.initials: H
authors.lastname: Zhang
authors.affiliation: School of Chinese Medicine, The Chinese University of Hong Kong, Shatin, Hong Kong. Electronic address: xcshan@163.com.
authors.forename: Chuanshan
authors.initials: C
authors.lastname: Xu
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D045744:Cell Line, Tumor; D006801:Humans; D008751:Methylene Blue / Q000494:pharmacology*; D018613:Microscopy, Confocal; D012516:Osteosarcoma / Q000188:drug therapy*; D010778:Photochemotherapy / Q000295:instrumentation / Q000379:methods*; D017319:Photosensitizing Agents / Q000494:pharmacology*
chemical_list: D017319:Photosensitizing Agents; D008751:Methylene Blue
keywords: Apoptosis; Cell death; Methylene blue; Mitochondrial membrane potential; Osteosarcoma cells; Photodynamic action