Mechanisms of mitochondrial photosensitization by the cationic dye, N,N-bis(2-ethyl-1,3-dioxylene)kryptocyanine (EDKC): preferential inactivation of complex I in the electron transport chain (original) (raw)
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Cancer research, 1988
The phototoxicity mechanism of a kryptocyanine dye, N,N'-bis(2-ethyl-1,3-dioxolane)kryptocyanine (EDKC+), has been studied in RBC membranes and isolated mitochondria. Lipophilic, positively charged dyes, such as EDKC+, may be useful as tumor-cell-selective, light-activated cytotoxic agents. Exposure of the RBC membranes to 700-nm light and EDKC+ inhibited membrane acetylcholinesterase and photodecomposed EDKC+ in air-purged but not argon-purged samples. Photoinactivation of acetylcholinesterase was the same in D2O as in H2O and was not quenched by superoxide dismutase. Ascorbate and azide (10 mM) quenched or slightly enhanced, respectively, the inactivation. In argon-purged samples containing methyl viologen, EDKC+ photodecomposed, but acetylcholinesterase activity was unaffected. The mechanism may involve electron transfer to oxygen and subsequent formation of toxic photoproducts from EDKC+. In contrast, exposure of murine mitochondria to EDKC+ and 700-nm light caused inhibitio...
Photochemistry and Photobiology, 1989
A chalcogenapyrylium dye 8b, which is under investigation for the photodynamic therapy of malignant gliomas (brain tumors), was evaluated for inhibition of mitochondrial function both before and after exposure to laser light of 800 nm. Neoplastic and normal cells forced to use mitochondrial substrates were killed by the light-activation of intracellular 8b as well as exposure to classic mitochondrial inhibitors, rotenone and sodium azide. Correspondingly, cells in glucose-rich media showed little decrease in viability due to the photolysis of intracellular 8b or the presence of mitochondrial toxins. The toxicity of 8b without light activation was found to be the same regardless of the cell's energy source. Measurement of cellular ATP generated during treatment also showed the photolysis of intracellular 8b to be more inhibitory towards mitochondrial function than the unactivated parent compound. We conclude that the chalcogenapyrylium dyes localize to the mitochondrion and that photoactivation results in mitochondrial injury.
Mitochondrial toxicity of cationic photosensitizers for photochemotherapy
Cancer research, 1990
The triarylmethane derivative Victoria Blue-BO (VB-BO) and the chalcogenapyrylium (CP) dyes have potential for use in photochemotherapy, because they are taken up by the mitochondria of malignant cells and cause cell death. To clarify the mechanism of cell killing we examined the phototoxic effects of VB-BO and a series of three CP dyes on bioenergetic function in isolated rat liver mitochondria. Without photoirradiation, and irrespective of the respiratory substrate used, each of the compounds tested induced some uncoupling of oxidative phosphorylation. Visible irradiation of VB-BO produced an inhibition of mitochondrial respiration when glutamate plus malate, but not succinate, was used as the respiratory substrate. With photoirradiation VB-BO was also shown to inhibit rotenone-sensitive NADH-cytochrome c reductase activity, but it had no effect on succinate-cytochrome c reductase activity. These data indicate that photoactivation of VB-BO produces selective inhibition of mitochon...
Mitochondrial Toxicity of Cationic Photosensitiziers for Photochemotherapy
Cancer Research
The triarylmethane derivative Victoria Blue-BO (VB-BO) and the chalcogenapyrylium (CP) dyes have potential for use in pholochemolherapy, because they are taken up by the mitochondria of malignant cells and cause cell death. To clarify the mechanism of cell killing we examined the phototoxic effects of VB-BO and a series of three CP dyes on bioenergetic function in isolated rat liver mitochondria. Without photoir radiation, and irrespective of the respiratory substrate used, each of the compounds tested induced some uncoupling of oxidative phosphorylation. Visible irradiation of VB-BO produced an inhibition of mitochondria! respiration when glutamate plus malate, but not succinate, was used as the respiratory substrate. With photoirradiation VB-BO was also shown to inhibit rotenone-sensitive NADH-cytochrome c reducÃ-aseactivity, but it had no effect on succinate-cytochrome c reducÃ-aseactivity. These data indicate that photoactivation of VB-BO produces selective inhibition of mitochondria! respiratory complex I. Photoirradiation of the CP dyes inhibited both complex I and complex II initiated respiratory activity. With photoirradiation, the CP dyes also inhibited both NADH-and succinate-cytochrome c reducÃ-aseactivilies, as well as olher membranebound enzymes, cylochrome c oxidase and succinale dehydrogenase, bul noi Ihe milochondrial malrix enzyme, citrate synthelase, or the cylosolic enzyme, láclaledehydrogenase. a-Tocopherol prolecled bioenergelic aclivilies againsl CP dye photodamage. These results suggesl thai milochondrial pholosensilizalion by CP compounds is medialed by Ihe pro duction of membrane-damaging singlel oxygen which causes nonspecific damage lo membranes and membrane-bound enzymes.
Intramitochondrial dyes allow selective in vitro photolysis of carcinoma cells
Proceedings of the National Academy of Sciences, 1986
Carcinoma cell mitochondria preferentially accumulate and retain certain cationic dyes to a much greater extent than most normal cells. Thus, they can potentially serve as targets for highly selective photochemotherapy. We evaluated 10 rhodamine and cyanine dyes as carcinoma-specific mitochondrial photosensitizers in vitro. The most effective,
Photoactivation enhances the mitochondrial toxicity of the cationic rhodacyanine MKT-077
Cancer research, 1998
In this study, the mitochondrial phototoxicity of the cationic rhodacyanine MKT-077 was investigated by comparing its effects on the inhibition of mitochondrial respiration and the structural integrity of mitochondrial DNA (mtDNA) in the presence and absence of added high-intensity visible light (7.5 J/cm2). Results indicate that photoirradiation significantly enhances the mitochondrial toxicity of MKT-077 at both the biochemical and DNA levels. For example, the concentration of MKT-077 required to achieve one-half maximal inhibition of ADP-stimulated respiration was observed to be 6-fold lower in the presence versus absence of high-intensity light (one-half maximal inhibition at 2.5 versus 15 microg MKT-077/ mg, respectively). In addition, photoirradiation produced a 25-fold increase in inhibition of succinate-cytochrome c reductase activity by MKT-077 (one-half maximal inhibition at 2 versus 50 microg MKT-077/ml, +/-light, respectively) and a 6-fold increase in inhibition of cytoc...
Archives of Biochemistry and Biophysics, 2003
Previously, we demonstrated that mitochondrial NAD(P)H is the primary target of singlet oxygen ( 1 O 2 ) generated by photoactivation of mitochondria-selective rhodamine derivatives. Hence, local NAD(P)H oxidation/fluorescence decrease may be used to reveal the site of intracellular 1 O 2 generation. Therefore, in addition to the previously used tetramethylrhodamine methylester (TMRM), 2 0 ,4 0 ,5 0 ,7 0 -tetrabromorhodamine 123 bromide (TBRB) and rhodamine 123 (Rho 123), we tested here whether mitochondrial NAD(P)H of cultured hepatocytes is directly oxidized upon irradiation of different ''mitochondrial'' photosensitizers (Photofrin; protoporphyrin IX; Al(III) phthalocyanine chloride tetrasulfonic acid; meso-tetra(4-sulfonatophenyl)porphine dihydrochloride; Visudyne). In contrast to TMRM and Rho 123, which directly oxidized NAD(P)H upon irradiation, irradiation of intracellular TBRB and the photochemical drugs only indirectly affected mitochondrial NAD(P)H due to loss of mitochondrial integrity. In line with this result only TMRM and Rho 123 exclusively localized within the mitochondrial matrix. Due to these results it is doubtful whether real mitochondrial photosensitizers actually exist among the photochemical drugs applicable/used for photodynamic therapy. Groot).
Photosensitization of Isolated Rat Liver Mitochondria by Tetra(m-hydroxyphenyl)chlorin
Archives of Biochemistry and Biophysics, 1997
photosensitizer by light of an appropriate wavelength Tetra(m-hydroxyphenyl)chlorin (mTHPC) is used as (for reviews, see 1, 2). The excited singlet photosensia photosensitizer in photodynamic therapy (PDT), a tizer may decay back to its ground state by emitting novel modality for cancer treatment. Since little is fluorescence. This property is useful for tumor localizaknown about mTHPC-mediated damage in vitro, we tion as well as for subcellular localization of the photochose isolated rat liver mitochondria as a model syssensitizer itself. Intersystem crossover of the singlet tem to study its photodynamic effects. Incubation of sensitizer yields a triplet sensitizer, which can undergo isolated mitochondria with mTHPC plus irradiation type I (electron or hydrogen transfer) or type II (energy with light of a wavelength of 652 nm resulted in protransfer to molecular oxygen generating singlet oxytein oxidation and lipid peroxidation, as measured gen) photochemical reactions which result in oxidative by the mitochondrial content of carbonyl groups and damage. Since reactive oxygen species thus generated thiobarbituric acid-reactive substances, respectively. have a short lifetime and diffusion distance-singlet Type I and type II photochemical reactions contribute oxygen is assumed to diffuse less than 0.07 mm in cells to this oxidative damage as shown by the use of scavenbefore it reacts (3)-the localization of photosensitizers gers. Photodynamically treated mitochondria had a determines the sites of damage in the cell. reduced membrane potential, and their Ca 2/ uptake Mitochondria accumulate photosensitizers, are a was impaired. Oxygen consumption of complex I of the respiratory chain was stimulated at a low concentra-sensitive target in porphyrin-mediated PDT (4-6; for tion of mTHPC plus irradiation, but decreased at a review, see 7), and are altered in PDT-resistant cells higher concentrations, whereas oxygen consumption (8). After in vitro treatment with hematoporphyrin deat complex II and IV decreased with all mTHPC conrivative (HpD) plus light mitochondrial enzymes, e.g., centrations offered. No mitochondrial changes were malate dehydrogenase, succinate dehydrogenase, cytoseen with mTHPC in the absence of irradiation. Our chrome c oxidase and the ADP/ATP translocator, are results confirm the sensitivity of mitochondria to PDT inhibited (9-11). and may help to understand the mechanisms by which Tetra(m-hydroxyphenyl)chlorin (mTHPC; Fig. 1) has PDT using mTHPC kills cells. ᭧ 1997 Academic Press been tested as a photosensitizer in vitro (12, 13) and Key Words: photodynamic therapy; photosensitizer; in vivo in mouse models (14, 15). Accumulation of mTHPC; chlorin; mitochondria. mTHPC in tumor and other tissues of mice was investigated by several groups (14, 16, 17). mTHPC is superior Photodynamic therapy (PDT) 3 is a new modality for to its corresponding porphyrin or Photofrin II in PDT cancer treatment which is based on the activation of a because of a stronger light absorption above 600 nm (15, 18). Such light penetrates tissues better than light 1 Financial support by Leica and Avina-Foundation, Switzerland of shorter wavelengths. In contrast to HpD-mediated is gratefully acknowledged.
Bioorganic & Medicinal Chemistry, 2009
Mitochondria are attractive targets in photodynamic therapy. Two conjugates: TPP-Rh (a porphyrin-rhodamine B conjugate) and TPP-AO (a porphyrin-acridine orange conjugate), each possessing a single delocalized lipophilic cation, were designed and synthesized as photosensitizers. Their ability to target the mitochondria for photodynamic therapy was evaluated. The conjugates were synthesized by conjugating a monohydroxy porphyrin (TPP-OH) to rhodamine B (Rh B) and acridine orange base (AO), respectively, via a saturated hydrocarbon linker. To evaluate the efficiency of the conjugates as photosensitizers, their photophysical properties and in vitro photodynamic activities were studied in comparison to those of TPP-OH. Although fluorescence energy transfer (FRET) was observed in the conjugates, they were capable of generating singlet oxygen at rates comparable to TPP-OH. Biologically, exciting results were observed with TPP-Rh, which showed a much higher phototoxicity [IC 50 , 3.95 lM: irradiation of 400-850 nm light (3 mW cm À2 ) for 1 h] than either TPP-OH or Rh B (both, IC 50 , >20 lM) without significant dark toxicity at 20 lM. This improved photodynamic activity might be due to a greater cellular uptake and preferential localization in mitochondria. The cellular uptake of TPP-Rh was 8 and 14 times greater than TPP-OH and Rh B, respectively. In addition, fluorescence imaging studies suggest that TPP-Rh localized more in mitochondria than TPP-OH. On the other hand, TPP-AO showed some dark toxicity at 10 lM and stained both mitochondria and nucleus. Our study suggests that conjugation of photosensitizers to Rh might provide two benefits, higher cellular uptake and mitochondrial localization, which are two important subjects in photodynamic therapy.