PHOTODYNAMIC DAMAGE TO HELA-CELL MICROTUBULES INDUCED BY THIAZINE DYES

The aim of this study was to analyze possible alterations of the micro tubule cytoskeleton of cultured cells subjected to photodynamic treatm ents with the thiazine dyes methylene blue or toluidine blue. Indirect immunofluorescence labeling of a-tubulin was performed in HeLa cells after 1 or 18 h of incubation with thiazines followed by red-light irr adiation for 15 min [leading to surviving fractions (SF) of about 65% (SF65) or 1% (SF1), respectively. Untreated control cells showed the n ormal distribution of interphase microtubules, whereas considerable or severe disorganization of the microtubule network was observed after SF65 or SF1 photodynamic treatments, respectively]. A great amount of blebs showing homogeneous fluorescence was also found on the cell surf ace after SF1 treatments. Possible mechanisms responsible for the phot odamage to microtubules induced by thiazine dyes are briefly discussed .