SINGLET OXYGEN INVOLVEMENT IN PHOTOHEMOLYSIS SENSITIZED BY MEROCYANINE‐540 and ROSE BENGAL

Valenzeno, Dennis Paul; Trudgen, Julia; Hutzenbuhler, Angela; Milne, Mark

doi:10.1111/j.1751-1097.1987.tb04881.x

Cited by 49 publications

(24 citation statements)

References 43 publications

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“…RB is a water-soluble dye and a localized anionic group on its molecule inhibits it from penetrating into or through the lipid bilayer. Several studies showed that RB is localized in the plasma membrane of mammalian cells [8,[21][22][23], especially on the outer surface of the membrane [23]. Therefore, we assumed that the site of reaction might be limited in the endothelial cells of vessels and that the cochlear dysfunction might be induced by ischemia, but not by direct damage to the hair cells and/or spiral ganglion cells.…”

Section: Discussionmentioning

confidence: 99%

Mechanisms of Photoinduced Cochlear Ischemia in the Guinea Pig

Saitô

Ogawa²,

Inoue

et al. 2001

ORL

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An experimental model of cochlear ischemia using the photosensitization reaction of rose bengal (RB) is reported. Ischemia was induced by the systemic administration of RB solution and localized irradiation of the cochlea with a green light of specific wavelength for RB activation. After the RB solution was administered, the cochlear blood flow was temporarily increased and then decreased, and the latency of wave I of the auditory brainstem response increased and the amplitude of wave I decreased after RB injection and finally wave I disappeared completely. A histological study revealed thrombus formation in the vessels of the irradiated cochlea not only in the stria vascularis and the spiral ligament, but also in the modiolus. L-Histidine, a scavenger of singlet oxygen (¹O₂) and hydroxyl radical (·OH), significantly prolonged cochlear dysfunction, but D-mannitol, a specific scavenger of ·OH did not, suggesting that ¹O₂ has an important role in this reaction.

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Section: Discussionmentioning

confidence: 99%

Mechanisms of Photoinduced Cochlear Ischemia in the Guinea Pig

Saitô

Ogawa²,

Inoue

et al. 2001

ORL

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“…[4][5][6][7][8][9][10] Second-generation merocyanines have not yet been characterized as thoroughly as MC540. However, all available data are consistent with the notion that when used as agents for PDT, all dyes of Günther's series behave like Type II photosensitizers.…”

Section: Introductionmentioning

confidence: 99%

Role of photoproducts in the cytotoxic action of selenomerocyanine-mediated photodynamic therapy

Sieber

Daziano

Sampson

et al. 2005

Optical Methods for Tumor Treatment and Detection: Mechanisms and Techniques in Photodynamic Therapy XIV

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Many Type II photosensitizers are substrates of the singlet oxygen they generate. They are, therefore, converted to photoproducts when exposed to light in the presence of oxygen. While most photoproducts appear to be biologically inert, one of the photoproducts generated by selenomerocyanine photosensitizers is a form of elemental selenium that is surprisingly toxic to tumor cells if allowed to form conjugates with serum albumin or lipoproteins. Albumin and lipoproteins act as delivery vehicles for the cytotoxic entity, exploiting the fact that many tumor cells have an increased capacity to bind and internalize albumin and/or lipoproteins. The cytotoxic mechanism of Se(0)-protein conjugates is not yet fully understood but is obviously quite different from the singlet oxygen-mediated mechanism of merocyanine-mediated photodynamic therapy (PDT). Whereas merocyanine-PDT is directed against the plasma membrane, is more effective at 4 °C than at room temperature, and is inhibited by excess albumin and lipoproteins, selenomerocyanine-derived cytotoxic photoproducts act on intracellular targets, are ineffective at low temperatures, and require albumin or lipoproteins as carrier molecules. The discovery of cytotoxic Se(0)-protein conjugates provides a rare example of photoproducts contributing substantially to the cytotoxic effect of PDT and challenges the widely held notion that elemental selenium is biologically inert.

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“…33 However, the rate decrease observed should not be taken as an argument against a singlet-oxygen mechanism. As discussed by Valenzeno et al 34 the D 2 O effects on photohemolysis using other sensitizers are somewhat variable, ranging from no effect to an enhancement of over 200%. We have shown recently that the binding constant between RBC and InTPP is (2.40 0.05) 10 7 L mol -1 , in aqueous solutions.…”

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confidence: 98%

Type II photooxidation mechanism of biomolecules using chloro (5,10,15,20-Tetraphenylporphyrinato) indium (III) as a photosensitizer

Silva¹,

Ribeiro²,

Rettori³

et al. 2008

J. Braz. Chem. Soc.

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Foi determinado o mecanismo de fotooxidação de albumina de soro bovino (BSA), L-triptofano (Trp) e células vermelhas do sangue (RBC) por cloro (5,10,15,20-tetrafenilporfirinato) de índio(III) (InTPP). A velocidade de fotooxidação de Trp, BSA e RBC por InTPP foi diminuída na presença de NaN 3 . A presença de D 2 O aumentou a velocidade de fotooxidação de Trp e BSA e diminuiu a de RBC. Esta diminuição provavelmente está correlacionada com a redução da constante de associação entre InTPP e RBC na presença de D 2 O. Não foi observada variação significativa na fluorescência das biomoléculas ou sobre a porcentagem de hemólise quando supressores de radicais (ferricianeto, manitol e superóxido dismutase) foram usados. Experimentos usando espectroscopia de ressonância paramagnética (EPR) mostraram que somente o 1 O 2 foi gerado por InTPP. Foi proposto um modelo cinético para a fotooxidação de Trp e BSA. A concordância entre os resultados experimentais e este modelo corrobora a predominância do mecanismo via 1 O 2 na fotooxidação das biomoléculas pelo InTPP.The photooxidation mechanism of bovine serum albumin (BSA), L-tryptophan (Trp) and red blood cells (RBC) by chloro (5,10,15,20-tetraphenylporphyrinato)indium(III) (InTPP) was investigated. The photooxidation rate of Trp, BSA and RBC by InTPP was decreased in the presence of NaN 3 . The presence of D 2 O increases the photooxidation rate of Trp and BSA and decreases that of RBC. This decrease is probably related to a reduction of the binding constant between InTPP and RBC in the presence of D 2 O. No significant change in biomolecule fluorescence or in the percent of hemolysis was observed when radical quenchers (ferricyanide, mannitol and dismutase superoxide) were used. Experiments using electron paramagnetic resonance (EPR) show that only 1 O 2 was generated by InTPP. A mechanistic model based on the preferential oxidation of Trp and BSA by singlet oxygen is proposed. The agreement between the experimental data and the kinetic model gives additional support to the predominance of a mechanism via 1 O 2 in biomolecule photooxidation by InTPP.Keywords: chloro(5,10,15,20-tetraphenylporphyrinato)indium(III), photodynamic therapy, photooxidation mechanism, cancer, erythrocytes IntroductionPhotodynamic therapy (PDT) is a two-step therapeutic modality in which the topical or systemic delivery of photosensitizing drugs is followed by irradiation with visible light, at doses that are not in themselves harmful. 1 For treatment of cancer the photosensitizer is retained preferentially by the tumor and when excited by irradiation generates reactive oxygen species (ROS) that have a cytotoxic effect to the neoplasm. 2 These ROS can be generated by two mechanisms, known as type I and type II. 3,4 In type I the photosensitizer in the excited triplet state can interact directly with the substrate and/or solvent, through an electron transfer reaction or hydrogen transfer, generating radical ions or neutral radicals, which quickly react with oxygen molecules producing ROS such as supero...

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SINGLET OXYGEN INVOLVEMENT IN PHOTOHEMOLYSIS SENSITIZED BY MEROCYANINE‐540 and ROSE BENGAL

Cited by 49 publications

References 43 publications

Mechanisms of Photoinduced Cochlear Ischemia in the Guinea Pig

Mechanisms of Photoinduced Cochlear Ischemia in the Guinea Pig

Role of photoproducts in the cytotoxic action of selenomerocyanine-mediated photodynamic therapy

Type II photooxidation mechanism of biomolecules using chloro (5,10,15,20-Tetraphenylporphyrinato) indium (III) as a photosensitizer

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