title: Photodecomposition, photomutagenicity and photocytotoxicity of retinyl palmitate under He-Ne laser photoirradiation and its effects on photodynamic therapy of cancer cells in vitro.
abstract: OBJECTIVE
  Our aim was to study photodecomposition, photomutagenicity and cytotoxicity of retinyl palmitate (RP), a principal storage form of vitamin A in humans and animals, under He-Ne laser photoirradiation. Moreover, the effect of different concentrations and timing protocol of antioxidants on photodynamic therapy (PDT) is contradictory, so the effect of RP (as antioxidant) on the PDT cytotoxicity was studied.
  
  
  METHODS
  Photomutagenicity was tested by Ames test. Photodecomposition was studied by UV-vis spectroscopy. Cytotoxicity was measured with MTT-assay. Moreover, the effect of PDT, using hematoporphyrin derivatives (HpD) as photosensitizer under He-Ne laser irradiation (10 J/cm(2)), was studied on HeLa cells either with or without RP (1-100 μM) which incubated with the cells for short or long incubation period (1 h or 24 h) prior to PDT.
  
  
  RESULTS
  No photodecomposition of RP alone was obseved whereas there is a little photodecomposition of RP only in presence of HpD under irradiation with He-Ne laser. Moreover, no photomutagenicity was observed in Salmonella typhimurium strains under laser irradiation in presence or absence of HpD. RP alone (1-100 μM) significantly decrease the viability of HeLa cells. Laser irradiation of HeLa cells pre-incubated with RP alone for 24 h showed further significant decrease in viability of the cells. While RP incubations for 1 h before PDT had slight effect on the cells, 24 h incubation before PDT enhanced the cytotoxicity of PDT on HeLa cells.
  
  
  CONCLUSIONS
  RP can be used 24 h before PDT to enhance its effects. RP is not mutagenic under irradiation with He-Ne laser.
authors.affiliation: National Institute of Laser Enhanced Science (NILES), Cairo University, Cairo, Egypt. Electronic address: trkali@gmail.com.
authors.forename: Tarek
authors.initials: T
authors.lastname: Ibrahim
authors.affiliation: National Cancer Institute (NCI), Cairo University, Cairo, Egypt.
authors.forename: Mahmoud N El
authors.initials: MNE
authors.lastname: Rouby
authors.affiliation: National Institute of Laser Enhanced Science (NILES), Cairo University, Cairo, Egypt.
authors.forename: El-Sayed A M
authors.initials: EAM
authors.lastname: Al-Sherbini
authors.affiliation: National Institute of Laser Enhanced Science (NILES), Cairo University, Cairo, Egypt.
authors.forename: Amr H El
authors.initials: AHE
authors.lastname: Noury
authors.affiliation: National Institute of Laser Enhanced Science (NILES), Cairo University, Cairo, Egypt.
authors.forename: Mona E
authors.initials: ME
authors.lastname: Morsy
mesh_terms: D002470:Cell Survival / Q000187:drug effects; D002869:Chromosome Aberrations / Q000187:drug effects; D004224:Diterpenes; D004305:Dose-Response Relationship, Drug; D006367:HeLa Cells; D006801:Humans; D053685:Laser Therapy / Q000379:methods; D009374:Neoplasms, Experimental / Q000188:drug therapy* / Q000473:pathology*; D010778:Photochemotherapy / Q000379:methods*; D017319:Photosensitizing Agents / Q000008:administration & dosage / Q000737:chemistry / Q000528:radiation effects; D000084562:Retinyl Esters; D016896:Treatment Outcome; D014801:Vitamin A / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000737:chemistry / Q000528:radiation effects
chemical_list: D004224:Diterpenes; D017319:Photosensitizing Agents; D000084562:Retinyl Esters; D014801:Vitamin A; C014794:retinol palmitate
keywords: Photodecomposition; Photodynamic therapy (PDT); Photomutagenicity; Retinyl palmitate (RP); Vitamin A