title: Comparison of pharmacokinetics, intracellular localizations and sonodynamic efficacy of endogenous and exogenous protoporphyrin IX in sarcoma 180 cells.
abstract: OBJECTIVE
  The aim of the present study was to investigate the differences in pharmacokinetics, sub-cellular localizations and sonodynamic efficacy between endogenous and exogenous protoporphyrin IX (endo-PpIX and exo-PpIX) in sarcoma 180 (S180) cells.
  
  
  METHODS
  The 5-aminolevulinic acid (ALA)-derived endo-PpIX and exo-PpIX pharmacokinetic profiles were determined by the fluorescence intensity of cell extracts with a spectrophotometer based on a standard curve. The changes in their sub-cellular localization patterns over a prolonged incubation time were evaluated by laser scanning confocal microscopy. The cytotoxic effects of 5-ALA-mediated sonodynamic therapy (ALA-SDT) and exogenous PpIX-mediated sonodynamic therapy (PpIX-SDT) were also evaluated by the MTT assay.
  
  
  RESULTS
  The exo-PpIX showed dose-dependent pharmacokinetics in which a plateau of intra- and extracellular content was observed 45min after administration. However, the amount of ALA-derived endogenous intracellular PpIX, as well as extracellular PpIX in the same samples, showed linear accumulation with incubation time, which was independent of ALA concentration. Fluorescent imaging revealed that the exo-PpIX mainly accumulated at the plasma membrane in the early stage, whereas the ALA-derived PpIX initially localized in the mitochondria. Cells displayed sonodynamic damage by the synthesized endo-PpIX after addition of 1mM ALA for 12h, but the cytotoxicity induced by the equivalent amount of exo-PpIX was much more significant with increasing ultrasound intensities.
  
  
  CONCLUSIONS
  Our findings suggest that endo- and exo-PpIX in S180 cells differ not only in pharmacokinetics but also in sub-cellular localizations, which may affect their sonodynamic efficacy and mechanisms of inducing cell death.
authors.affiliation: Key Laboratory of Ministry of Education for Medicinal Resources and Natural Pharmaceutical Chemistry, College of Life Sciences, Shaanxi Normal University, Shaanxi, Xi'an, China.
authors.forename: Xiaobing
authors.initials: X
authors.lastname: Wang
authors.forename: Pan
authors.initials: P
authors.lastname: Wang
authors.forename: Wanyan
authors.initials: W
authors.lastname: Tong
authors.forename: Quanhong
authors.initials: Q
authors.lastname: Liu
mesh_terms: D000818:Animals; D002470:Cell Survival; D004867:Equipment Design; D018613:Microscopy, Confocal; D011524:Protoporphyrins / Q000493:pharmacokinetics*; D012510:Sarcoma 180 / Q000378:metabolism / Q000628:therapy*; D013010:Sonication; D013050:Spectrometry, Fluorescence; D014407:Tumor Cells, Cultured; D014464:Ultrasonic Therapy / Q000295:instrumentation / Q000379:methods*
chemical_list: D011524:Protoporphyrins; C028025:protoporphyrin IX