Uptake of tetraphenylporphycene and its photoeffects on actin and cytokeratin elements of HeLa cells

In the present work we have continued our studies in the photobiological properties of the 2,7,12,17-tetraphenylporphycene (TPPo). In particular, the uptake, the subcellular localization and the photoeffects on two cytoskeletal elements (actin, microfilaments and cytokeratin intermediate filaments) of HeLa cells have been analyzed. The uptake kinetics of TPPo, determined by fluorescence spectroscopy, was initially very rapid, reaching saturation at ~6 h of incubation. This porphycene tends to be accumulated mainly in rounded particles distributed throughout the cytoplasm. The morphological comparison of the localization pattern of TPPo and those of acridine orange and rhodamine 123, which are fluorescence markers for lysosomes and mitochondria respectively, allowed us to confirm that this porphycene is mainly accumulated in lysosomal organelles. The results obtained after treatment with TPPo and red light indicated that this compound is very effective in mediating the photodestruction of lysosomes. The photosensitizing effects on the cytoskeletal elements studied depended on both the irradiation time and the elapsed time after treatment. The implications of damage to lysosomes and actin and cytokeratin filaments on the process of cell death is discussed.