Photodynamic effects induced by meso-tetrakis[4-(carboxymethyleneoxy)phenyl]porphyrin on isolated Sarcoma 180 ascites mitochondria

Using mitochondria isolated from Sarcoma 180 ascites tumour in Swiss mice a s a model system, we have evaluated the ability of a novel porphyrin, meso- tetrakis [4- (carboxymethyleneoxy) phenyl] porphyrin (H(2)T4CPP), to induce damage on photosensitization. Oxidative damage to mitochondria, one of the primary and crucial targets of the photodynamic effect, is assessed by mea suring products of lipid peroxidation such as thiobarbituric acid reactive substances (TBARS) and lipid hydroperoxides (LOOH), besides the loss of act ivity of the mitochondrial marker enzyme succinate dehydrogenase ( SDH). An alysis of product formation, the effect of deuteration and selective inhibi tion by scavengers of reactive oxygen species (ROS) show that the damage ob served is due mainly to singlet oxygen (O-1(2)) and to a minor extent to hy droxyl radicals ((OH)-O-.). The O-1(2) generation and triplet lifetime of t his porphyrin have also been estimated. Fluorescence spectroscopy, used to ascertain the binding of this porphyrin to the mitochondrial proteins, show s a rapid association within 0-2 h and a decline thereafter. Confocal micro scopy reveals intracellular localisation of this porphyrin in cells in vitr o. Our overall results suggest that the porphyrin H(2)T4CPP, due to its abi lity to bind to mitochondrial protein components and to generate ROS upon p hotoexcitation, may have potential applications in photodynamic therapy. (C ) 1999 Elsevier Science S.A. All rights reserved.