title: In vitro comparison of hypericin and 5-aminolevulinic acid-derived protoporphyrin IX for photodynamic inactivation of medulloblastoma cells.
abstract: BACKGROUND
  Hypericin (HYP) is a naturally occurring photosensitizer. Cellular uptake and photodynamic inactivation after incubation with this photosensitizer have neither been examined in medulloblastoma cells in vitro, nor compared with 5-aminolevulinic acid-derived protoporphyrin IX (5-ALA-derived PpIX).
  
  
  METHODS
  In 3 medulloblastoma cell lines (D283 Med, Daoy, and D341 Med) the time- and concentration-dependent intracellular accumulation of HYP and 5-ALA-derived PpIX was analyzed by fluorescence microscopy (FM) and FACS. Photocytotoxicity was measured after illumination at 595 nm (HYP) and 635 nm (5-ALA-derived PpIX) in D283 Med cells and compared to U373 MG glioma cells.
  
  
  RESULTS
  All medulloblastoma cell lines exhibited concentration- and time-dependent uptake of HYP. Incubation with HYP up to 10 µM resulted in a rapid increase in fluorescence intensity, which peaked between 2 and 4 hours. 5-ALA-derived PpIX accumulation increased in D283 Med cells by 22% over baseline after 5-ALA incubation up to 1.2 mM. Photocytotoxicity of 5-ALA-derived PpIX was higher in D283 Med medulloblastoma compared to U373MG glioma. The LD50 [lethal dose (light dose that is required to reduce cell survival to 50% of control)] of 5-ALA-derived PpIX was 3.8 J/cm(2) in D283 Med cells versus 5.7 J/cm2 in U373MG glioma cells. Photocytotoxicity of HYP in D283 Med cells was determined at 2.5 µM after an incubation time of 2 h and an illumination wavelength of 595 nm. The [Formula: see text] value was 0.47 J/cm(2).
  
  
  CONCLUSIONS
  By its 5-fold increase in fluorescence over autofluorescence levels HYP has excellent properties for tumor visualization in medulloblastomas. The high photocytotoxicity of HYP, compared to 5-ALA-derived PpIX, is convincingly demonstrated by its 8- to 13-fold lower LD50. Therefore HYP might be a promising molecule for intraoperative visualization and photodynamic treatment of medulloblastomas.
authors.affiliation: Department of Neurosurgery, Eberhard Karls University Tübingen, Tübingen, Germany. rainer_ritz@hotmail.com
authors.forename: Rainer
authors.initials: R
authors.lastname: Ritz
authors.forename: Christian
authors.initials: C
authors.lastname: Scheidle
authors.forename: Susan
authors.initials: S
authors.lastname: Noell
authors.forename: Florian
authors.initials: F
authors.lastname: Roser
authors.forename: Martin
authors.initials: M
authors.lastname: Schenk
authors.forename: Klaus
authors.initials: K
authors.lastname: Dietz
authors.forename: Wolfgang S L
authors.initials: WS
authors.lastname: Strauss
mesh_terms: D000622:Aminolevulinic Acid / Q000493:pharmacokinetics / Q000494:pharmacology*; D000873:Anthracenes; D045744:Cell Line, Tumor; D002528:Cerebellar Neoplasms / Q000175:diagnosis / Q000188:drug therapy* / Q000378:metabolism; D006801:Humans; D008527:Medulloblastoma / Q000175:diagnosis / Q000188:drug therapy* / Q000378:metabolism; D008856:Microscopy, Fluorescence; D010569:Perylene / Q000031:analogs & derivatives* / Q000493:pharmacokinetics / Q000494:pharmacology; D010778:Photochemotherapy / Q000379:methods*; D017319:Photosensitizing Agents / Q000493:pharmacokinetics / Q000494:pharmacology*; D011524:Protoporphyrins / Q000493:pharmacokinetics / Q000494:pharmacology*
chemical_list: D000873:Anthracenes; D017319:Photosensitizing Agents; D011524:Protoporphyrins; D010569:Perylene; C004965:hypericin; D000622:Aminolevulinic Acid; C028025:protoporphyrin IX