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.