Zinc coproporphyrin I derived from meconium has an antitumor effect associated with singlet oxygen generation.

INTRODUCTION: Zinc coproporphyrin I (ZnCP-I) is a photosensitive molecule and a major component of meconium. Here, we examined the effects of ZnCP-I as a potential photosensitizer in photodynamic therapy for tumors. MATERIALS AND METHODS: (1) Aqueous ZnCP-I was irradiated with a pulsed YAG-SHG laser (wavelength: 532 nm)/YAG-SHG dye laser (wavelength: 566 nm). (2) HeLa cells were incubated in 200 mM ZnCP-I, and accumulation of ZnCP-I in HeLa cells was evaluated with ZnCP-I-specific fluorescence over 500 nm. (3) Aqueous ZnCP-I was administered intravenously to HeLa tumor-bearing mice at a dose of 10.2 mg/kg body weight. The tumors were irradiated with a filtered halogen lamp (wavelength: 580 nm) at 100 J/cm(2) 20 min after administration. RESULTS: (1) An intense near-infrared emission spectrum was observed at around 1,270 nm after irradiation. The emission intensity was proportional to the laser power between 10 and 80 mW and was completely inhibited by addition of NaN3, a singlet oxygen scavenger. (2) ZnCP-I-specific fluorescence was detected in the HeLa cell cytoplasm. (3) Irradiated tumors treated with ZnCP-I were mostly necrotized. CONCLUSION: ZnCP-I accumulated in tumor cells, produced singlet oxygen upon irradiation, and necrotized the tumor cells. These results suggest that ZnCP-I may be an effective photosensitizer.

Production of singlet oxygen on irradiation of a photodynamic therapy agent, zinc-coproporphyrin III, with low host toxicity.

Zinc-coproporphyrin III (Zincphyrin) acts efficiently as a photodynamic therapy (PDT) agent in mice, while it shows no tumor cell-killing activity in vitro and has a high LD50 (low toxicity) in mice. It appears to have advantages over other porphyrins as a practical PDT reagent. In order to examine the action mechanism of Zincphyrin in PDT, we evaluated the photochemical characteristics of Zincphyrin by measurement of the near-infrared emission at 1268 nm, which provides direct evidence for formation of 1O2. Intense emission was observed in the presence of Zincphyrin, and was completely inhibited by NaN3, a 1O2 scavenger. Based on a quenching study, the rate constant of the reaction of 1O2 with NaN3 was determined to be 1.5-3.5 M(-1) s(-1), which is close to the reported value (3.8 x 10(8) M(-1) s(-1)). The intensity of the 1O2-specific emission was proportional to both the laser power and the concentration of Zincphyrin. The fluorescence quantum yield of Zincphyrin was 0.004 in phosphate buffer (100 mM, pH 7.4), which indicates that the excited state decays via other pathway(s) faster than through the fluorescence emission pathway. The lifetime of the triplet state of Zincphyrin (210 micros) was relatively long compared to that of other porphyrins, such as hematoporphyrin (Hp) (40 micros), coproporphyrin I (50 gs), or coproporphyrin III (36 gs). These results demonstrate the photodynamic generation of 1O2 by Zincphyrin.

Conformational dynamics and temperature dependence of photoinduced electron transfer within self-assembled coproporphyrin:cytochrome c complexes.

The focus of the present study is to better understand the complex factors influencing intermolecular electron transfer (ET) in biological molecules using a model system involving free-base coproporphyrin (COP) complexed with horse heart cytochrome c (Cc). Coproporphyrin exhibits bathochromic shifts in both the Soret and visible absorption bands in the presence of Cc and an absorption difference titration reveals a 1:1 complex with an association constant of 2.63 +/- 0.05 x 10(5) M(-1). At 20 degrees C, analysis of time-resolved fluorescence data reveals two lifetime components consisting of a discrete lifetime at 15.0 ns (free COP) and a Gaussian distribution of lifetimes centered at 2.8 ns (representing (1)COP --> Cc ET). Temperature-dependent, time-resolved fluorescence data demonstrate a shift in singlet lifetime as well as changes in the distribution width (associated with the complex). By fitting these data to semiclassical Marcus theory, the reorganizational energy (lambda) of the singlet state electron transfer was calculated to be 0.89 eV, consistent with values for other porphyrin/Cc intermolecular ET reactions. Using nanosecond transient absorption spectroscopy the temperature dependences of the forward and thermal back ET originating from triplet state were examined ((3)COP --> Cc ET). Fits of the temperature dependence of the rate constants to semiclassical Marcus theory gave lambda of 0.39 eV and 0.11 eV for the forward and back triplet ET, respectively (k(f) = (7.6 +/- 0.3) x 10(6) s(-1), k(b) = (2.4 +/- 0.3) x 10(5) s(-1)). The differing values of lambda for the forward and back triplet ET demonstrate that these ET reactions do not occur within a static complex. Comparing these results with previous studies of the uroporphyrin:Cc and tetrakis (4-carboxyphenyl)porphyrin:Cc complexes suggests that side-chain flexibility gives rise to the conformational distributions in the (1)COP --> Cc ET whereas differences in overall porphyrin charge regulates gating of the back ET reaction (reduced Cc --> COP(+)).

Singlet oxygen (1 delta g) generation from coproporphyrin in Propionibacterium acnes on irradiation.

Although singlet oxygen has been postulated to be a highly reactive and toxic intermediate, there has been no evidence of considerable generation of singlet oxygen in vivo level except for special cases. In this work, we firstly measured the near-infrared emission spectra corresponding to the O2(1 delta g) --> O2(3 epsilon g-) transition of singlet oxygen of cutaneous Propionibacterium acnes (P. acnes) porphyrin under laser excitation. A comparison of the singlet oxygen production of coproporphyrin, which is produced predominantly from P. acnes, with that of other photosensitizers revealed coproporphyrin to be a highly efficient singlet oxygen generator under ultraviolet light A irradiation on the skin. These results suggest that singlet oxygen can be generated on the skin surface from P. acnes porphyrin under ultraviolet irradiation and induce serious damage to the skin.

Instrumentaçäo de estado sólido para excitaçäo de indicador fosforecente de O2 / Solid state instrumentation for excitation of O2 phosphorescence indicator

Descreve-se a construção e desempenho de um instrumento para excitar o indicador fosforescente de O2, Paládio (Pd) coproporfirina imobilizado em um polímero. A excitação é efetuada via LEDs. Os resultados mostram que é possível a excitação do indicador, entretanto com baixa relação sinal/ruído. Pela utilização das medidas de tempos de vida de fosforescência, concentrações de O2 até 21 por cento podem ser determinadas.

The construction and performance of an instrument to excite the dye Pd coproporphyrin and to measure its phosphorescence lifetimes are described. The instrument employs LEDs as optical source. The results have shown that it is possible the excitation of the dye, although the intensity of the registered signals was very low. By measuring phosphorescence lifetimes concentrations up to 21 % of gaseous oxygen can be determined when the dye is immobilised in a polymer.

[The use of porphyrins for assessing the effect of low doses of ionizing radiation on the human body]. / Ispol'zovanie porfirinov dlia otsenki vliianiia malykh doz ioniziruiushchego izlucheniia na organizm cheloveka.

Data on porphyrin metabolism disturbances under the action of ionizing radiation on the human body are presented. The studies are based on estimating the quantitative content of coproporphyrin in the diurnal urine diuresis of persons irradiated as a result of the Chernobyl accident. The results of examining the population of a number of the zones of close control in Mogilev and Gomel Provinces are considered. Unlike the presumably healthy subjects, many people of this group show a significant decrease of porphyrin excretion with urine. The discovered sensitivity to the action of radiation is individual. A preliminary estimation of the porphyrin test depending on the degree of morphological changes in the gastric mucosa was made during an all-round clinical examination of the irradiated subjects.

Quantitation of hydrogen peroxide formed during UV-visible irradiation of protoporphyrin, coproporphyrin and uroporphyrin.

Free porphyrins are strong photosensitizers. Previously reported findings indicate that the in vitro cell lysis induced by irradiation in the presence of coproporphyrin (CP) and uroporphyrin (UP) is mediated by H2O2 and that induced by irradiation with protoporphyrin (PP) is not mediated by H2O2. In the present study the possible role of H2O2 in the porphyrin photosensitization was investigated by direct measurement of the H2O2 formed during the irradiation of PP, CP and UP. Our results show that the amount of H2O2 formed decreased in the following order: UP, CP, PP. The amounts of H2O2 formed during irradiation of CP and PP were approximately 86% and 38% respectively in comparison to the H2O2 formed during the irradiation of UP. The formation of H2O2 was inhibited by sodium azide, a strong quencher of singlet oxygen. These observations are in good agreement with the previous report that the in vitro photolysis of Ehrlich ascites carcinoma cells by UP and CP, but not that by PP, was inhibited by catalase and clinical findings with patients with erythropoietic protoporphyria (EPP) and porphyria cutanea tarda (PCT). The patients with EPP, where the photosensitivity is due to PP, respond well to beta-carotene while beta-carotene does not protect against the photosensitivity in PCT, in which case the photosensitivity is due to uroporphyrin.

[Fine structure luminescence of etio-, copro- and mesoporphyrin following selective laser excitation]. / Tonkostrukturnaia liuminestsentsiia étio-, kopro- i mezoporfirina pri selektivnom lazernom vozbuzhdenii.

Fluorescence line spectra of etio- and coproporphyrin isomers and mesoporphyrin IX, as well as their ionic forms have been obtained and investigated using a tunable dye laser excitation (T = 4.2 K). Normal vibrational frequencies in the ground electronic state of both the neutral molecules and their ions have been determined. By comparing the line spectra of different porphyrins and their isomers the distinctions have been revealed which may be used for the identification of these compounds in solutions. Changes have been discovered in the coproporphyrin ion spectra in different solvents.