title: Differential photodynamic response of cultured cells to methylene blue and toluidine blue: role of dark redox processes.
abstract: Cultured cells treated with equal concentrations of thiazine photosensitizers methylene blue (MB) or toluidine blue (TB) showed a distinct photodynamic lethality, with TB being much more effective, when exposed to red light from a LED source. This effect is accounted for because of the differences in the chemical reduction of MB and TB in the intracellular environment. While TB accumulates as blue granular structures, MB does not give such a localization pattern. However, upon exposure of MB-treated cells to oxidant agents, the dye becomes clearly localized in the cytoplasm as blue granules. We propose that massive reduction of MB to its leuco form inside the cell inhibits most of the photodynamic damage, while no such reduction occurs with TB.
authors.affiliation: Department of Biology, Faculty of Sciences, Autonomous University of Madrid, 28049, Madrid, Spain. alfonso.blazquez@uam.es
authors.forename: Alfonso
authors.initials: A
authors.lastname: Blázquez-Castro
authors.forename: Juan C
authors.initials: JC
authors.lastname: Stockert
authors.forename: Francisco
authors.initials: F
authors.lastname: Sanz-Rodríguez
authors.forename: Alicia
authors.initials: A
authors.lastname: Zamarrón
authors.forename: Angeles
authors.initials: A
authors.lastname: Juarranz
mesh_terms: D000818:Animals; D002460:Cell Line; D002470:Cell Survival; D006367:HeLa Cells; D006801:Humans; D008027:Light; D008751:Methylene Blue / Q000737:chemistry / Q000494:pharmacology*; D051379:Mice; D010084:Oxidation-Reduction; D017319:Photosensitizing Agents / Q000737:chemistry / Q000494:pharmacology*; D014048:Tolonium Chloride / Q000737:chemistry / Q000494:pharmacology*
chemical_list: D017319:Photosensitizing Agents; D014048:Tolonium Chloride; D008751:Methylene Blue