title: Intracellular damage in yeast cells caused by photodynamic treatment with toluidine blue.
abstract: The positively charged photosensitizer toluidine blue (TB) can induce loss of clonogenicity in Kluyveromyces marxianus. Previous studies have revealed that, as a consequence of the localization of this dye at the cell surface, photodynamic action results in extensive damage at the level of the plasma membrane. In this paper, a study is reported on the effect of photodynamic treatment with TB on intracellular enzymes. It is shown that treatment with TB and light resulted in the inhibition of alcohol dehydrogenase, cytochrome c oxidase, glyceraldehyde-3-phosphate dehydrogenase and hexokinase. Photodynamic treatment also lowered the ATP levels. The ATP levels could be partially restored in the presence of glucose but not with ethanol. Toluidine blue binding experiments revealed that photodynamic treatment caused a rapid increase in the amount of cell-associated dye. Moreover, it also appeared that this treatment decreased the binding of TB to the cell surface. It is concluded that TB enters the cell during the first minutes of illumination, whereafter intracellular enzymes are inactivated. The data indicate that photodynamic damage of intracellular sites contributes to the loss of viability.
authors.affiliation: Department of Medical Biochemistry, Sylvius Laboratory, Leiden, The Netherlands.
authors.forename: M
authors.initials: M
authors.lastname: Paardekooper
authors.forename: A W
authors.initials: AW
authors.lastname: De Bruijne
authors.forename: J
authors.initials: J
authors.lastname: Van Steveninck
authors.forename: P J
authors.initials: PJ
authors.lastname: Van den Broek
mesh_terms: D002462:Cell Membrane / Q000187:drug effects / Q000528:radiation effects; D003576:Electron Transport Complex IV / Q000037:antagonists & inhibitors; D005954:Glucosephosphate Dehydrogenase / Q000037:antagonists & inhibitors; D006593:Hexokinase / Q000037:antagonists & inhibitors; D007259:Infrared Rays; D007716:Kluyveromyces / Q000187:drug effects* / Q000201:enzymology / Q000528:radiation effects*; D008954:Models, Biological; D010778:Photochemotherapy; D014048:Tolonium Chloride / Q000494:pharmacology*
chemical_list: D014048:Tolonium Chloride; D005954:Glucosephosphate Dehydrogenase; D003576:Electron Transport Complex IV; D006593:Hexokinase