Nanosonosensitizers for Highly Efficient Sonodynamic Cancer Theranostics

Background: Multifunctional nanoplatforms with diagnostic-imaging and targeted therapeutic functionality (theranostics) are of great interest in the field of precision nanomedicine. The emerging sonodynamic therapy (SDT) combined with sonosensitizers under the guidance of photoacoustic (PA) imaging is highly expected to accurately eliminate cancer cells/tissue. Methods: Unique core/shell-structured theranostic FA-HMME-MNPs-PLGA nanoparticles (FHMP NPs, FA: folate, HMME: hematoporphyrin monomethyl ether, MNPs: melanin nanoparticles, PLGA: poly (lactic-co-glycolic) acid) were constructed by the integration of MNPs (for PA imaging) in the core and HMME in the shell for enhanced PA imaging-guided SDT, which were further functionalized with a tumor-targeting ligand, FA. The PA imaging-guided SDT was systematically and successfully demonstrated both in vitro and in vivo. The high biosafety of FHMP NPs was also systematically evaluated. Results: The synthesized FHMP NPs with a broad optical absorption not only possess high PA-imaging contrast enhancement capability but also exhibit significant SDT efficiency. Importantly, such a PLGA based nanoplatform improved light stability of HMME, enhancing sonodynamic performance and facilitated delivery of MNPs to the tumor region. Meanwhile, a combined effect between HMME and MNPs was discovered and verified. Furthermore, a sonosensitizer assisted by ultrasound irradiation engenders reactive oxygen species (ROS)-mediated cytotoxicity toward tumor cells/tissue. Both in vitro cell-level and systematic in vivo xenograft evaluations on tumor-bearing mice demonstrated that the selective killing effect of ROS on tumor cells was assisted by FHMP NPs, which played an active role in the suppression of tumor growth with high biosafety. Conclusion: A theranostic nanoplatform was successfully constructed, achieving PA imaging-guided SDT against breast cancer cells/tissue. More importantly, MNPs and HMME in one platform with combined effect for enhancing PA imaging was demonstrated. This unique theranostic nanoplatform with multiple capabilities paves a new way toward personalized medicine by rational utilization.

Elimination Pathway of Hematoporphyrin from Normal and Tumor-Bearing Rats

Hematoporphyrin orally administered to rats largely precipitates in the stomach thus reaching the various tissues at a very slow rate. Whatever the administration pathway (oral, i.p., i.V.), hematoporphyrin is eliminated in the feces with no apparent chemical modification; the elimination is slower from rats affected by ascites hepatoma than from normal rats owing to the high affinity of tumor cells for the porphyrin.

Time Dependence of Hematoporphyrin Distribution in Selected Tissues of Normal Rats and in Ascites Hepatoma

The distribution of hematoporphyrin was determined in normal rats and in rats bearing ascites hepatoma as a function of time after i.p. injection of 10-20 mg/kg of dye. In both cases, hematoporphyrin displayed a high affinity for the tumor cells. At 20 mg/kg, the maximum difference between the amount of hematoporphyrin accumulated in the tumor and in the liver was obtained at 12 h after injection (tumor/liver ratio = 28). Our results suggest that hematoporphyrin is almost exclusively metabolized in the liver and excreted via the biliary tract, whereas only minor amounts are metabolized in the tumor cells. Moreover, the binding between the porphyrin and tumor cells is competitive with serum protein binding.

Photocytotoxicity of a cyanine dye with two chromophores toward melanoma and normal cells

BACKGROUND

Due to high optical absorption, triplet quantum yield and affinity to biological structures bichromophoric cyanine dyes (BCDs) can be considered promising sensitizers for application in photodynamic therapy (PDT). In this work, we report on the study of the BCD photocytotoxicity toward melanoma and normal cells in comparison with that of commercial photosensitizer Photogem®.

METHODS

The cytotoxic and phototoxic effects were measured by standard tests of cell viability. The drug uptake was obtained by the flow cytometry and optical absorption techniques. The BCD intracellular distribution was obtained by the fluorescence image microscopy using specific organelle markers.

RESULTS

Both drugs demonstrated increased cytotoxicity under irradiation, while in darkness their cytotoxic effect at concentrations lower than 20 μM after 24 h of incubation did not exceed 20%. For 5 h of incubation, BCD photocytotoxicity in relation to melanoma cells reached 100% already at concentrations below 5 μM, while for normal cells the effect did not exceed 70% even for the 20 μM concentration. It is shown that BCD penetrates into the cells and is located predominantly in perinuclear cytoplasmic structures.

CONCLUSIONS

The BCD photosensitizing characteristics appear more adequate for application in PDT than that of the actually applied commercial photosensitizer Photogem®. Higher light absorption by BCD in the near IR region and its preferential localization in mitochondria can explain its high photocytotoxicity.

GENERAL SIGNIFICANCE

BCD can be considered as a new promising photosensitizer class for cancer PDT.

Deciphering the binding modes of hematoporphyrin to bovine serum albumin

Interaction of proteins with small molecules is important in understanding delivery and transport of different therapeutic agents, including drugs. In the present study, we investigated the interaction between hematoporphyrin (HP), the principal component of photosensitizing drug with bovine serum albumin (BSA) in aqueous buffer solution using UV-Vis absorption spectroscopy and fluorescence measurements. The results were further substantiated by molecular docking and molecular dynamics (MD) simulation. Our results revealed that fluorescence of BSA was dominantly quenched by the ground-state complex formation with HP accompanied by the electronic energy transfer (EET) to the later. We experimentally determined the thermodynamic parameters such as deltaG0, deltaH0, and deltaS0 for the HP-BSA system which were -35.5 kJ mole(-1), -56.4 kJ mole(-1) and -0.06 kJ mole(-1) K(-1), respectively. These parameters suggested hydrogen-bonding and Van der Waals forces playing major role in the complexation. This was also supported by the binding energy parameters calculated by molecular docking. Moreover, the experimentally determined deltaG0 nicely correlated with those determined by molecular docking and MD-simulation. Further, computational results clearly showed that the binding of HP with BSA in the subdomains IB and IIA.

The role of p53 in the response of tumor cells to sonodynamic therapy in vitro

p53 plays a pivotal role in apoptosis. In addition, p53 is currently extensively investigated as a promising strategy for highly specific anticancer therapy in chemotherapeutics and photodynamic therapy. However, the role of p53 in the response of tumor cells to sonodynamic therapy treatment is still unclear. In this study, we aim to investigate the activation of p53 in sonodynamic therapy. Three murine tumor models with distinct aggressiveness (S180, H-22 and EAC) were treated with 1.75MHz continuous ultrasound at an acoustic intensity (I(SATA)) of 1.4W for 3min in the presence of 20μg/ml hematoporphyrin. The DNA fragment and nuclear damage were observed by TUNEL and single cell gel electrophoresis. Western blotting and RT-PCR were used to analyze the expression of p53, PUMA, Bax and Fas. Then we checked the translocation of p53 by confocal microscopy. DNA sequencing was used to determine the status of p53 gene in three tumor cell lines. Our results indicated that the level of p53 protein and mRNA increased significantly, and p53 activated the expression of its downstream pro-apoptosis gene PUMA, Bax and Fas in the S180 and H-22 cells. Meanwhile, p53 protein translocated onto mitochondria. In the EAC cells, expression and translocation of p53 was not found; the level of PUMA, Bax and Fas remained unaltered. The S180 cells showed most serious DNA fragment and nuclear damage with 77.43% TDNA; H-22 cells in the middle with 58.85% TDNA; whereas EAC cells appeared less nuclear material lost with just 15.82% TDNA. The results of DNA sequencing showed that the sequences of exons 5-8 of the p53 gene of S180, H-22 and EAC cells were the same with the sequences of wild-type p53 provided by NCBI. These results primarily demonstrated that: (1) p53 was activated to promote SDT-induced apoptosis through extrinsic and intrinsic signaling pathways in the S180 and H-22 cells; (2) cellular responses of different cells to SDT were distinct, the aggressive S180 cells were much more sensitive than H-22, whereas EAC cells were relatively less sensitive. The discrepancy among the cell lines may be due to different activation time of p53 protein.

Intracellular metabolism, subcellular localization and phototoxicity of HMME/HB in ovarian cancer cells

BACKGROUND

Photodynamic therapy (PDT) is considered a promising new strategy for ovarian cancer treatment. As the key component in PDT, photosensitizer metabolism and localization in cancer cells is particularly important.

MATERIALS AND METHODS

The localization of the photosensitizers hematoporphyrin monomethyl ether (HMME) and hypocrellin B (HB) were determined in the ovarian cancer cell lines SKOV3 and NuTu-19 by fluorescence microscopy and laser scanning confocal microscopy(LSCM). A JD801 image analysis system was used to analyze the fluorescence intensity of the photosensitizers in the cells. The phototoxicity of both drugs to the cancer cells was determined by MTT assay.

RESULTS

Both photosensitizers were mainly distributed in the cytoplasm. Drug uptake reached a peak after 4 h incubation with HB and after 3 h incubation with HMME. Within a certain range, the higher the concentration, the stronger the fluorescence became and at 40 μg/ml, the intracellular photosensitizer had reached saturation. Based on these results PDT was applied to SKOV3 cells. All the cells were killed when the photosensizer dose reached 40 μg/ml.

CONCLUSION

PDT is an effective therapy for ovarian cancer cells.

[Role of erythrocyte cytoplasmic structures in changes in the affinity of haemoglobin for oxygen]

Changes in the refractive index of the cytoplasm and the affinity of haemoporphyrin of erythrocyte haemoglobin to oxygen (pH, 2,3-diphosphoglycerate) have been investigated using laser interference microscopy and Raman spectroscopy. It has been established that a decrease in pH and an increase in the content of 2,3-diphosphoglycerate are accompanied by changes in both the form of the cell and the refractive index of the cytoplasm and the affinity of haemoporphyrin of hemoglobin to oxygen. It has been shown that as pH is reduced, the capacity of haemoporphyrin for binding oxygen decreases and as the concentration of 2,3-diphosphoglycerate is increased, the ability of haemoporphyrin for oxygen reabsorption increases.

Towards environmentally and human friendly insect pest control technologies: Photosensitization of leafminer flies Liriomyza bryoniae

Development of new, ecologically safe technologies to control insect pest populations is of great importance. Photoactive compounds usually used for photosensitization might be effective as pesticide agents, with low impact on the environment, being non-toxic and not mutagenic. Phosensitizer accumulates within the insect body and, following exposure to visible light, induces lethal photochemical reactions and death. The aim of this study is to evaluate the possible usage of several photosensitizers (acridine orange, aminolevulinic acid, hematoporphyrin dimethyl ether, methylene blue) as photopesticides to control population of polyphagous plant pest Liriomyza bryoniae (Kaltenbach, 1858) (Diptera, Agromyzidae). Fluorescence measurements of intact cooled insects indicate that insect feeding with bait containing HPde and sugar induces remarkable accumulation of this compound in the body of insect. This accumulation is strongly dependent on sex and feeding duration. The highest HPde amount in the body of insect was detected 16 h after feeding, whereas no significant photosensitizer amount was detected in the same insect following 48 h. Following irradiation with visible light results in fast death of L. bryoniae. Of importance to note that survival of insects after feeding and irradiation depends on sex: female insect died much faster than males.

Heme orientational disorder in human adult hemoglobin reconstituted with a ring fluorinated heme and its functional consequences

A ring fluorinated heme, 13,17-bis(2-carboxylatoethyl)-3,8-diethyl-2-fluoro-7,12,18-trimethyl-porphyrinatoiron(III), has been incorporated into human adult hemoglobin (Hb A). The heme orientational disorder in the individual subunits of the protein has been readily characterized using (19)F NMR and the O(2) binding properties of the protein have been evaluated through the oxygen equilibrium analysis. The equilibrated orientations of hemes in alpha- and beta- subunits of the reconstituted protein were found to be almost completely opposite to each other, and hence were largely different from those of the native and the previously reported reconstituted proteins [T. Jue, G.N. La Mar, Heme orientational heterogeneity in deuterohemin-reconstituted horse and human hemoglobin characterized by proton nuclear magnetic resonance spectroscopy, Biochem. Biophys. Res. Commun. 119 (1984) 640-645]. Despite the large difference in the degree of the heme orientational disorder in the subunits of the proteins, the O(2) affinity and the cooperativity of the protein reconstituted with 2-MF were similar to those of the proteins reconstituted with a series of hemes chemically modified at the heme 3- and 8-positions [K. Kawabe, K. Imaizumi, Z. Yoshida, K. Imai, I. Tyuma, Studies on reconstituted myoglobins and hemoglobins II. Role of the heme side chains in the oxygenation of hemoglobin, J. Biochem. 92 (1982) 1713-1722], whose O(2) affinity and cooperativity were higher and lower, respectively, relative to those of native protein. These results indicated that the heme orientational disorder could exert little effect, if any, on the O(2) affinity properties of Hb A. This finding provides new insights into structure-function relationship of Hb A.

[Photodynamic effect of hematoporphyrin monomethyl ether on ovarian cancer cell line SKOV3]

BACKGROUND & OBJECTIVE

Photodynamic therapy (PDT) is a new treatment choice for ovarian carcinoma. Hematoporphyrin monomethyl ether (HMME) is a novel photosensitive reagent developed in China. This study was to investigate the photodynamic effect of HMME-based PDT on human epithelial ovarian cancer cell line SKOV3.

METHODS

After an incubation with 30 microg/ml HMME for different time, the fluorescent image and intracellular location of HMME in SKOV3 cells were observed under a fluorescent microscope and laser scanning confocal microscope (LSCM). After being treated with different doses (5-50 microg/ml) of HMME and irradiated with different optical doses (1.5-12 J/cm(2)) of laser, the survival rate of SKOV3 cells was measured by MTT assay. Mechanisms of cell death during PDT was determined by Annexin V/PI double staining technique and analyzed by flow cytometry.

RESULTS

Red fluorescence appeared shortly after administration of HMME and localized in cytoplasm; intracellular fluorescence intensity reached the peak after 3 h. High concentrations of HMME alone had cytotoxicity to SKOV3 cells, while laser irradiation alone had no effect on cell survival. Survival rate of SKOV3 cells was gradually decreased along with the increase of HMME concentration and laser dose, but such a trend diminished when HMME concentration reached 40 microg/ml. After treatment of HMME, the dead cells were predominantly necrosis cells.

CONCLUSION

HMME has a photodynamic effect on SKOV3 cells.

Functional validation of the genetic polymorphisms of human ATP-binding cassette (ABC) transporter ABCG2: identification of alleles that are defective in porphyrin transport

The ATP-binding cassette (ABC) transporter ABCG2 has been implicated to play a significant role in the response of patients to medication and/or the risk of diseases. To clarify the possible physiological or pathological relevance of ABCG2 polymorphisms, we have functionally validated single nucleotide polymorphisms (SNP) of ABCG2. In the present study, based on the currently available data on SNPs and acquired mutations, we have created a total of 18 variant forms of ABCG2 (V12M, G51C, Q126stop, Q141K, T153M, Q166E, I206L, F208S, S248P, E334stop, F431L, S441N, R482G, R482T, F489L, F571I, N590Y, and D620N) by site-directed mutagenesis and expressed them in insect cells. Because porphyrins are considered to be endogenous substrates for ABCG2, we have investigated the porphyrin transport activity of those variant forms in vitro. We herein provide evidence that the variants Q126stop, F208S, S248P, E334stop, and S441N are defective in porphyrin transport, whereas F489L exhibited impaired transport, approximately 10% of the activity observed for the wild type. Furthermore, Flp-In-293 cells expressing those variants were photosensitive. Thus, among those genetic polymorphisms of ABCG2, at least the hitherto validated alleles of Q126stop, S441N, and F489L are suggested to be of clinical importance related to the potential risk of porphyria.

Allosteric modulation of myristate and Mn(III)heme binding to human serum albumin. Optical and NMR spectroscopy characterization

Human serum albumin (HSA) is best known for its extraordinary ligand binding capacity. HSA has a high affinity for heme and is responsible for the transport of medium and long chain fatty acids. Here, we report myristate binding to the N and B conformational states of Mn(III)heme-HSA (i.e. at pH 7.0 and 10.0, respectively) as investigated by optical absorbance and NMR spectroscopy. At pH 7.0, Mn(III)heme binds to HSA with lower affinity than Fe(III)heme, and displays a water molecule coordinated to the metal. Myristate binding to a secondary site FAx, allosterically coupled to the heme site, not only increases optical absorbance of Mn(III)heme-bound HSA by a factor of approximately three, but also increases the Mn(III)heme affinity for the fatty acid binding site FA1 by 10-500-fold. Cooperative binding appears to occur at FAx and accessory myristate binding sites. The conformational changes of the Mn(III)heme-HSA tertiary structure allosterically induced by myristate are associated with a noticeable change in both optical absorbance and NMR spectroscopic properties of Mn(III)heme-HSA, allowing the Mn(III)-coordinated water molecule to exchange with the solvent bulk. At pH = 10.0 both myristate affinity for FAx and allosteric modulation of FA1 are reduced, whereas cooperation of accessory sites and FAx is almost unaffected. Moreover, Mn(III)heme binds to HSA with higher affinity than at pH 7.0 even in the absence of myristate, and the metal-coordinated water molecule is displaced. As a whole, these results suggest that FA binding promotes conformational changes reminiscent of N to B state HSA transition, and appear of general significance for a deeper understanding of the allosteric modulation of ligand binding properties of HSA.

Discrimination between two steps in the mitochondrial permeability transition process

It is well known that a lag phase generally elapses between the addition of inducers of the mitochondrial permeability transition and the opening of the pore. To advance our present understanding as regards the significance of this phenomenon, we used experimental approaches which are sensitive to different aspects of the permeability transition process. The pore conformation was sensed by the fluorescence anisotropy changes of hematoporphyrin-labelled mitochondria. Membrane permeabilization was ascertained by following the matrix swelling consequent to external solute equilibration. We show that the anisotropy changes of mitochondria-bound hematoporphyrin precede both membrane depolarization (proton permeation) and matrix swelling (solute permeation), thus sensing a step of the permeability transition process that involves the pore in its closed state. We suggest that the opening of the pore is preceded by a structural remodelling of mitochondrial domains containing hematoporphyrin-near, pore-regulating histidines. Such a perturbation is strongly inhibited at acidic matrix pH and completely blocked by cyclosporin A. In sucrose-based media the opening of the pore can be strongly delayed, as compared to salt-based media, a fact which probably reflects perturbation of mitochondrial membranes by sugar. We conclude that the mitochondrial permeability transition could be described as an at least two-step process which is mainly regulated by conformational changes of the pore components.

[Thermodynamics studies on the reaction characteristics of hemoporphyrin with human serum albumin]

The quenching reaction of hemoporphyrin with human serum albumin (HSA) was studied by using fluorescence spectraand absorption spectra. The formation constants of them were analyzed at different temperature according to Stem-Volmer equation and double-reciprocal equation, which are smaller at high temperature than at low temperature. The binding site was calculated (r = 4.36) by Foster energy transfer mechanism, and the thermodynamic parameters were obtained. H-bond and Van der Waals are two main reactions between HP and HSA.

pH dependent uptake of porphyrin-type photosensitizers by solid tumor cells in vitro is not induced by modification of transmembrane potential

The uptake of HpIX, TPPS2a and mTHPC by WiDr, THX cells and skin fibroblasts at pH 7.4 and 6.8 was compared. In the absence of serum, the uptake of HpIX was higher at lower pH. The difference was significant in WiDr cells (P < 0.01) and skin fibroblasts (P < 0.05). TPPS2a nor mTHPC showed any pH dependent uptake. Lowering the extracellular pH resulted in a significant depolarization (3-8 mV) of the cells. Application of tetraethylammonium chloride did not affect the cellular uptake of any of the photosensitizers. We conclude that the pH dependent uptake of photosensitizers is not mainly related to altered transmembrane potential.

Distribution and subcellular localization of a water-soluble hematoporphyrin–platinum(II) complex in human bladder cancer cells

The water-soluble porphyrin-platinum complex diammine[7,12-bis[1-(polyethyleneglycol-750-monomethylether-1-yl)ethyl]-3,8,13,17-tetramethylporphyrin-2,18-dipropionato]platinum(II) (PEG-HPPt) was studied with respect to cellular accumulation, subcellular localization, behavior in 3D-cell aggregates and degree of DNA platination on the low-differentiated J82 cells, a model of invasive bladder cancer, and UROtsa, a normal urothelial cell line. Accumulation studies with 2D and spheroid cell cultures revealed that the concentration of PEG-HPPt was 1.7-times higher in J82 cancer cells than in UROtsa cells. Despite its high molecular weight, penetration of PEG-HPPt was not restricted to the peripheral cells of the spheroids. Fluorescence microscopic analysis showed that PEG-HPPt was localized in essential cellular targets of photodynamic therapy. DNA platination in J82 and UROtsa cells was higher by PEG-HPPt than by cisplatin, whereas there was no significant difference between the two cell lines.

Interaction of porphyrins with heme proteins--a brief review

Two important porphyrins, protoporphyrin IX and hematoporphyrin IX, derivatives of which form the basis of photosensitization in the photodynamic therapy of cancer treatment, interact with two physiologically important heme proteins hemoglobin and myoglobin. The extent and modality of these interactions vary with the state of aggregation of the two porphyrins. Upon binding with these proteins, both the drugs change the protein conformations and release the heme-bound oxygen from the oxyproteins. At the same time, the peroxidase activities of these proteins are potentiated due to the protein-porphyrin complexation, as is found in case of horseradish peroxidase also. The effect of porphyrins on heme proteins should be given due consideration in elucidating the details of the mechanism of porphyrin actions in therapy.

The antibody-catalyzed water oxidation pathway--a new chemical arm to immune defense?

Antibodies are the classical adaptor molecules of the immune system, linking recognition and killing of foreign pathogens. However, the recent discovery of a new property of the antibody molecule suggests a previously unexplored effector function of the immune system. All immunoglobulins, regardless of source or antigenic specificity, can catalyze the reaction between singlet (1Deltag) oxygen and water to give hydrogen peroxide (H(2)O(2)). Both the chemical and biological aspects of this pathway are being explored and intriguing new insights into how this pathway might have a role in immune defense are emerging.

Tissue Retention and Adverse Reaction after Intravenous Injection of Hematoporphyrin Derivatives in Dogs

We evaluated changes in hematology and chemical profile, and the tissue retention of hematoporphyrin derivative (HpD) following the intravenous injection in dogs. HpD at concentrations of 1, 5, 10, and 15 mg/kg was intravenously injected to 16 dogs (n=4 each) and complete blood count (CBC) and blood chemistry were performed on days 1, 3, 5, and 7 after the injection. To examine tissue retention, HpD (5 mg/kg) was administered to 15 dogs and 3 dogs were euthanized on days 1, 2, 7, 14, and 28 after the injection, respectively, to collect the skin, muscle, small intestine, spleen, kidney and liver as tissue samples. There were no significant changes in CBC and blood chemical profile except for an increase in LDH concentrations in dogs given 10 and 15 mg/kg of HpD at day 3. The levels of HpD retention in the tissues were ranked in the following order: liver > kidney > spleen > intestine > muscle > skin.

pH effects on the cellular uptake of four photosensitizing drugs evaluated for use in photodynamic therapy of cancer

The difference in extracellular pH in malignant as compared to normal healthy tissues has been proposed to contribute to selective uptake of photosensitizers in tumors. Hematoporphyrin IX (HpIX), disulfonated meso-tetraphenylporphine (TPPS(2a)), meso-tetra(3-hydroxyphenyl)porphine (mTHPP) and meso-tetra(3-hydroxyphenyl)chlorin (mTHPC) were chosen to examine the pH dependence of their cellular drug uptake. The study was performed in the pH range 6.5-8.0 and showed that significantly higher amounts of the drug are taken up by T-47D cells at low pH values only in the case of HpIX. The pH value of the incubation medium did not influence the cellular uptake of mTHPP, mTHPC and TPPS(2a) significantly. The present work indicates that tumor selectivity of dyes, which get more lipophilic with decreasing pH value, may be related to the low extracellular pH value.

Structural modifications of the permeability transition pore complex in resealed mitochondria induced by matrix-entrapped disaccharides

Mitochondrial resealing after the opening of the permeability transition (PT) pore was studied in saline- and sugar-based media by following the fluorescence anisotropy changes of mitochondria-bound hematoporphyrin (HP), a probe sensitive to conformational variations of the pore complex [Biochemistry 38 (1999) 9300]. The HP anisotropy changes correlated well with complete mitochondrial resealing in saline media and suggested that the pore complex regained the native structure after closure. Rebuilding of the pore complex structure was also achieved in monosaccharide-based media, thus ruling out a major influence of the swollen state of mitochondria on the reconstitution properties of the pore components. On the contrary, when sucrose or other disaccharides were used as osmotic support, restoration of the native mitochondrial structure, as monitored by HP anisotropy, was not achieved, though the proton barrier of the inner membrane and respiration functions were reestablished. Infrared spectroscopy experiments indicated the occurrence of strong perturbations of the mitochondrial membrane structure after disaccharide entrapment in the matrix space. These data suggest that mitochondria are able to reseal and regain functional activity after opening of the PT pore irrespective of the incubation medium but in sucrose (and other disaccharides) the pore complex adopts a conformation different from that existing before permeabilization. In general, our data indicate that the pore complex can exist in different conformations which are modulated by the nature of the interactions with the medium cosolvents.

Evidence for antibody-catalyzed ozone formation in bacterial killing and inflammation

Recently, we showed that antibodies catalyze the generation of hydrogen peroxide (H2O2) from singlet molecular oxygen (1O2*) and water. Here, we show that this process can lead to efficient killing of bacteria, regardless of the antigen specificity of the antibody. H2O2 production by antibodies alone was found to be not sufficient for bacterial killing. Our studies suggested that the antibody-catalyzed water-oxidation pathway produced an additional molecular species with a chemical signature similar to that of ozone. This species is also generated during the oxidative burst of activated human neutrophils and during inflammation. These observations suggest that alternative pathways may exist for biological killing of bacteria that are mediated by potent oxidants previously unknown to biology.

The effects of singlet oxygen produced by photodynamic action on the mitochondrial permeability transition differ in accordance with the localization of the sensitizer

We have examined whether the effects of singlet oxygen (1O2) produced by photodynamic action on the mitochondrial permeability transition (PT) can be modulated by the localization of photosensitizers in irradiated mitochondria. We have previously shown that oxidation due to 1O2 photogenerated in hematoporphyrin (HP)-loaded mitochondria can prevent opening of the PT pores, likely after degradation of some critical histidines (Salet et al, 1997, J. Biol. Chem. 272, 21938-21943). Equally, in the present study we have irradiated mitochondria in the presence of a structurally different photosensitizer producing 1O2, namely 4,5',8-trimethylpsoralen (TMP). Fluorescence studies show that TMP binds to protein sites which differ from those of HP. In sharp contrast with HP, TMP-driven photodynamic action triggers per se pore opening. Interestingly, this inducing effect is inhibited when TMP-treated mitochondria are irradiated after addition of mersalyl, a specific reagent protecting thiol groups of the inner mitochondrial membrane that are oriented toward the external hydrophilic phase. This fact suggests that 1O2-mediated thiol oxidation is responsible for TMP-photoinduced pore opening. Taken together, these findings suggest that 1O2 can activate or inactivate a cellular function such as mitochondrial PT depending on the site where it is produced in the mitochondrial membrane.

Quantum yield of singlet oxygen production by monomeric and aggregated forms of hematoporphyrin derivative

Hematoporphyrin derivative (HpD) is a complex mixture of monoporphyrinic compounds, including hematoporphyrin, and oligomers containing up to eight porphyrin units. In methanol a sensitizer concentration-independent quantum yield of 0.64 is measured for the HpD-induced production of singlet molecular oxygen O2 (1Delta(g)). This finding is consistent with the dye components remaining unassociated in this solvent. In water pH 7.4 HpD consists of a complex mixture of non-aggregated and self- and cross-aggregated monoporphyrinic and oligomeric species, and the quantum yield of O2 (1Delta(g)) formation decreases significantly with increasing HpD concentration due to the lower quantum yield of aggregates. These variations can be quantitatively described in terms of a monomer-dimer equilibrium, with quantum yields of 0.64 and 0.11, respectively, for monomers and dimers. The yields of unassociated species are identical in methanol and water.

In vitro selection of hematoporphyrin binding DNA aptamers

DNA aptamers that bind to hematoporphyrin IX (HPIX) were isolated using an in vitro selection technique. Most aptamers obtained after the 7th and 10th rounds contained guanine-rich sequences. Binding assay using fluorescence polarization technique and structural analysis by CD spectra revealed that the parallel guanine-quartet structure of the aptamer participates in the recognition of HPIX.

Erythropoietic protoporphyria with severe liver dysfunction and acute pancreatitis

A case of erythropoietic protoporphyria associated with severe hepatic dysfunction and acute pancreatitis is reported. The patient, a 33-year-old man, was admitted to our hospital complaining of upper abdominal pain, nausea, and vomiting of 3 days' duration. Laboratory tests on admission demonstrated liver dysfunction, anemia, and thrombocytopenia. On the third hospital day, the intensity of the upper abdominal pain increased, concomitantly with elevated levels of serum amylase. Ultrasonography and computed tomography scanning revealed a slightly enlarged pancreas. During this episode, he also complained of various neurological symptoms, including reduced mental alertness, weakness of extremities, constipation, profound sweating, and urinary retention. Porphyrin studies demonstrated markedly elevated erythrocyte and fecal protoporphyrin levels. Laparoscopic findings obtained after the attack subsided were compatible with porphyric liver cirrhosis. We therefore concluded that neurologic disorders and acute pancreatitis could develop in patients with erythropoietic protoporphyria with severe liver dysfunction.

Cellular uptake, subcellular localization and photodamaging effect of temoporfin (mTHPC) in nasopharyngeal carcinoma cells: comparison with hematoporphyrin derivative

Temoporfin (meta-tetra (hydroxyphenyl)chlorin; mTHPC) potentiated a 100-fold higher cytotoxic effect than hematoporphyrin derivative (HPD) on two nasopharyngeal carcinoma cell lines (HK1 and CNE2) in terms of the overall photodynamic therapy (PDT) dose. The cellular uptake, evaluated by flow cytometry and spectrophotometry demonstrated that mTHPC exhibited higher uptake ability than HPD. Confocal laser scanning microscopy detection for both the sensitizer and mitochondria probe on the same cell images revealed that both drugs accumulated diffusely in the cytoplasm and that mitochrondria is a target organelle. Photo-activation ruptured the mitochrondria, with more pronounced mitochondrial damage being observed in mTHPC-PDT course. This correlated well with the cell photokilling efficiency of mTHPC.

Changes of the fluidity of mitochondrial membranes induced by the permeability transition

The dynamic properties of protein and lipid regions of mitochondrial membranes during the permeability transition (PT) process were studied by following the anisotropy changes of hematoporphyrin (HP) and 1,6-diphenyl-1,3,5-hexatriene (DPH), respectively. We show that opening of the PT pore is accompanied by a remarkable increase of mitochondrial membrane fluidity which is specifically localized to protein sites, while lipid domains are unaffected. The increased membrane fluidity is not related to the collapse of transmembrane potential that follows the PT, as demonstrated by a comparison between the anisotropy properties of permeabilized mitochondria and impermeable, depolarized organelles. Parameters such as osmotic swelling and temperature, which are shown to affect the mitochondrial membrane dynamics in the absence of permeability transition, cannot alone account for the pore dynamical properties. We suggest that the observed increase in fluidity is mainly due to a conformational change of pore-forming protein(s) during the "assembly" of the PT pore.

Porphyrin-mediated binding to hemoglobin by the HA2 domain of cysteine proteinases (gingipains) and hemagglutinins from the periodontal pathogen Porphyromonas gingivalis

Heme binding and uptake are considered fundamental to the growth and virulence of the gram-negative periodontal pathogen Porphyromonas gingivalis. We therefore examined the potential role of the dominant P. gingivalis cysteine proteinases (gingipains) in the acquisition of heme from the environment. A recombinant hemoglobin-binding domain that is conserved between two predominant gingipains (domain HA2) demonstrated tight binding to hemin (Kd = 16 nM), and binding was inhibited by iron-free protoporphyrin IX (Ki = 2.5 microM). Hemoglobin binding to the gingipains and the recombinant HA2 (rHA2) domain (Kd = 2.1 nM) was also inhibited by protoporphyrin IX (Ki = 10 microM), demonstrating an essential interaction between the HA2 domain and the heme moiety in hemoglobin binding. Binding of rHA2 with either hemin, protoporphyrin IX, or hematoporphyrin was abolished by establishing covalent linkage of the protoporphyrin propionic acid side chains to fixed amines, demonstrating specific and directed binding of rHA2 to these protoporphyrins. A monoclonal antibody which recognizes a peptide epitope within the HA2 domain was employed to demonstrate that HA2-associated hemoglobin-binding activity was expressed and released by P. gingivalis cells in a batch culture, in parallel with proteinase activity. Cysteine proteinases from P. gingivalis appear to be multidomain proteins with functions for hemagglutination, erythrocyte lysis, proteolysis, and heme binding, as demonstrated here. Detailed understanding of the biochemical pathways for heme acquisition in P. gingivalis may allow precise targeting of this critical metabolic aspect for periodontal disease prevention.

Photodynamic action of porphyrin on Ca2+ influx in endoplasmic reticulum: a comparison with mitochondria

We have studied the distribution properties of haematoporphyrin (HP) and protoporphyrin (PP) in mitochondria and endoplasmic reticulum after isolation from rat liver. The photosensitizing efficiency of porphyrin on the Ca2+ influx function of microsomes has been compared with that obtained on Ca2+ uptake in mitochondria. HP and PP are accumulated in microsomes to a greater extent than in mitochondria, both porphyrins binding to membrane protein sites. The Ca2+ influx functions of mitochondria and microsomes, before and after irradiation in the presence of HP or PP, were studied by following the changes in the free Ca2+ concentration in the medium as revealed by the variations in fluorescence intensity of the Ca2+ indicator Calcium Green-1. For the same amount of incorporated porphyrin, the Ca2+ influx function of microsomes is degraded by irradiation more rapidly than that of mitochondria. The protective effect of dithiothreitol suggests that thiol groups in the Ca2+-transporting enzyme are the preferential targets of the photodynamic effect. These results suggest that intracellular Ca2+ movements are altered primarily by the endoplasmic reticulum rather than by mitochondrial damage, in good agreement with other observations made in porphyrin-loaded irradiated cells.

Variations in rat biochemical parameters after buckshot implant

Twenty eight albino Wistar rats were implanted with two 100 mg lead spheres: 14 received the implant in the peritoneum (P) and 14 in the thigh (T). Variations in the activity of delta-aminolevulinic dehydratase (ALAD), of urinary delta-aminolevulinic acid (ALAU), of hematoporphyrins (HP) and of lead blood levels (BPb) were then determined at 30, 60 and 90 days with respect to basal values. Parallel determinations were performed by the same schedule in 7 rats implanted with two glass beads and in 8 sham animals receiving surgical incision alone. Techniques employed for ALAD were Berlin and Schaller; for ALAU, Tomokuni and Ogata; for HP, Piomelli; and for BPb, atomic absorption spectrophotometry. As indicators of lead presence, HP and ALAU proved better, both in P and in T rats. The replacement of lead buckshot for small game hunting by other less toxic elements is recommended.

Studies on the interaction of hematoporphyrin with hemoglobin

Spectrophotometric and spectrofluorimetric studies reveal that an interaction occurs between hemoglobin and hematoporphyrin, a photosensitizing drug used in photodynamic therapy. Two concentration ranges of hematoporphyrin, 0.4-0.9 microM and 1.8-3.6 microM, representing significantly monomeric and aggregated (dimeric) state, respectively, have been used in the binding studies. The binding affinity constant (K) decreases, while the possible number of binding sites (p) increases as the concentration range of the porphyrin is increased. The nature of interaction has been studied by fluorescence quenching titration method under different ionic strengths and temperature conditions. It appears to be predominantly electrostatic and enthalpy-driven in the lower range of porphyrin concentration. However, the interaction follows mostly hydrophobic and entropy-driven modality in the higher concentration range of the ligand. The porphyrin-hemoglobin interaction results in release of oxygen from the protein. The extent of oxygen release depends on the stoichiometric ratio of hematoporphyrin:hemoglobin.

[Effect of ascorbate on the permeation and photosensitizing activity of hematoporphyrin derivative (HPD) in tumor]

OBJECTIVE

To determine the depth of permeation and concentration of HPD in tumor tissue which had been immersed in HPD in the presence and absence of ascorbic acid, and to examine its photosensitizing effect.

METHODS

Solid S-180 sarcoma of 1 cm3 in size was excised from tumor-bearing mice and immersed in HPD (PsD-007) 1 mg/ml normal saline (group I), or HPD (PsD-007) 1 mg/ml plus ascorbic acid 20 mg/ml normal saline (group II) for 1 hr. For comparison, HPD (PsD-007) 10 mg/kg was injected intravenously to mice bearing tumor of similar size and the tumor was excised 24 hr later(group III).

RESULTS

When the tumors were cross-sectioned and UV (370 nm) irradiated, red fluorescence was mainly at the periphery of tumors that had been immersed in HPD whereas the fluorescence was weaker and more evenly distributed in tumors of mice that had received HPD i.v. Similar features were observed under fluorescence microscope in frozen sections of identically treated tumors. The concentration of PsD-007 (microgram/g) and malondialdehyde (nmol/L) in the tumor homogenates was higher in tumors that had been immersed in PsD-007 plus ascorbate than in tumors immersed in PsD-007 alone. Tumors of mice that had received PsD-007 i.v. had the lowest concentration of both PsD-007 and malondialdehyde.

CONCLUSION

Ascorbate facilitates permeation of HPD into tumor and enhances the photo-dynamic effect of HPD.

Diamino acid derivatives of porphyrins penetrate into yeast cells, induce photodamage, but have no mutagenic effect

The yeast Saccharomyces cerevisiae was used as a model eukaryotic organism to study the uptake of diamino acid derivatives of porphyrins and their phototoxicity with particular emphasis on possible mutagenic effects. The water-soluble hematoporphyrin derivatives diarginate (HpD[Arg]2) and 1-arginin di(N-amino acid)-protoporphyrinate used in this study are effective photosensitizers in tumor photodynamic therapy. Depending on the amino acid substituent, the porphyrin derivatives differ in their affinity for yeast cells. It is shown that HpD(Arg)2 and PP(Met)2 (Arg)2 penetrate into the yeast cell and are metabolized. Both compounds sensitize yeast cells to photodamage but have no mutagenic effect on nuclear or mitochondrial genomes.

Participation of reactive oxygen species in phototoxicity induced by quinolone antibacterial agents

To elucidate the mechanism of phototoxicity induced as a side effect by some of the new quinolone antibiotics, we studied sparfloxacin (SPFX), lomefloxacin, enoxacin, ofloxacin, and ciprofloxacin. We first examined the photosensitized formation of reactive oxygen species such as singlet oxygen (1O2) and superoxide anion (O2-) mediated by the new quinolones. Although a large number of studies have been reported, there is no direct evidence that these drugs generate reactive oxygen species. We employed a near-infrared emission spectrometer to detect 1O2-specific emission (1268 nm), and the nitroblue tetrazolium reduction method to detect O2-. All the quinolones investigated in this study were found to produce 1O2. Four drugs, but not SPFX, produced O2-. We also examined photodynamic DNA strand-breaking activity as a possible mechanism to explain the participation of reactive oxygen species in the phototoxicity of the drugs. All the drugs exhibited photodynamic DNA strand-breaking activity. The inhibitory effect of scavengers of reactive oxygen species indicated that the main active species was 1O2. The DNA strand-breaking activity was correlated not with the 1O2-forming ability, but with the affinity of the drugs for DNA. This result may be due to the short lifetime of 1O2. These data suggested that the phototoxicity of the new quinolones was related to DNA damage caused by reactive oxygen species, especially 1O2.

Membrane lipid peroxidation as a mechanism of sonodynamically induced erythrocyte lysis

Sonodynamically induced lipid peroxidation with haematoporphyrin (Hp) was studied using rat erythrocytes. Both suspensions of erythrocyte ghosts and of intact erythrocytes were exposed to ultrasound in the same way in the presence and absence of Hp (80 microM). The lipid peroxidation in erythrocyte ghost membranes was estimated by measuring the amount of reactive substance produced from thiobarbituric acid added immediately after the exposure. Haematoporphyrin multiplied the ultrasonically induced lipid peroxidation by three to five times, while Hp alone showed no peroxidation. A 24-h interval between the exposure and the preparation for measurement did not increase the measured amount of peroxide. In the presence of Hp the estimated peroxidation rate and the rate of erythrocyte lysis correlated quite well for each acoustic condition and for each chemical condition such as the presence or absence of active oxygen scavengers in the suspension. The sonodynamically induced lipid peroxidation with Hp was doubled by deuterium oxide substitution for suspension medium and was significantly reduced by histidine, by sodium azide, and also by nitrogen substitution for saturation gas, whereas superoxide dismutase and mannitol showed no significant inhibitory effect. These results are consistent with a hypothesis that lipid peroxidation in membranes by singlet oxygen is the primary mechanism of sonodynamically induced erythrocyte lysis with Hp.

Separation of lipoproteins, albumin and gamma-globulin by single-step ultracentrifugation of human serum. Application. I: Binding of hematoporphyrin to human serum and to albumin

Previous studies of the serum binding of the photosensitizer hematoporphyrin (Hp) have given widely different results. The serum binding of Hp is therefore further illuminated by experiment and discussion. Ultracentrifugal separation of serum is improved and applied to study the binding of Hp to human serum and HSA. The observed distribution of Hp among the serum proteins is compared with the distribution expected from available association constants for Hp binding with individual proteins. The lipoprotein classes and the two major high density proteins (HDP), albumin and gamma-globulin, were separated in a NaCl-KBr gradient by single spin ultracentrifugation (SW 40; 30,000 rpm). HSA- and HDP-bound Hp were similarly distributed in the centrifuged gradient. Centrifugation of Hp-doped HSA separated the unbound Hp (75%) and the HSA-bound Hp (25%). The present association constant for the Hp-HSA complex (10(3)/M) was much lower than earlier published ones (10(6)/M) found by other techniques. The association of Hp with HDP in serum was much stronger than the association of Hp with the isolated HSA (electrophoretic grade). The estimated ratio of HSA-bound to LDL-bound HP in serum was at least 25 times larger than the experimental value. The percentage of LDL-bound Hp decreased with increasing Hp concentration. The serum binding of Hp is the same as that found previously using another rotor and another salt gradient (70.1 Ti, 70,000 rpm, NaCl-CsCl). LDL has high-affinity-low-capacity binding sites for Hp. HSA is the major HDP protein that binds Hp in human serum. The strength of the HSA-Hp complex may depend on the batch of HSA used and upon the absence/presence of other proteins. Proteins may interact in serum in manners that affect the binding of certain drugs. Neither the type of gradient salt nor the field of gravity affected the serum binding of Hp.

Photosensitizer targeting in photodynamic therapy. II. Conjugates of haematoporphyrin with serum lipoproteins

Conjugates between haematoporphyrin (HP) and human low-density lipoprotein (LDL), human high-density lipoprotein (HDL) and bovine HDL have been prepared, purified and characterized. HP-LDL is aggregated possibly via interparticle apoB protein cross-linking. HP-HDL human and bovine conjugates show different degrees of intraparticle apoA polypeptide cross-linking. Receptor-mediated endocytosis of HP-LDL by NIH 3T3 cells is inferred from the increased uptake observed when LDL receptors are upregulated. HP-LDL uptake into HT29 cells faces competition from unlabelled LDL, albeit at rather high doses. HP-HDL uptake is also inhibited by LDL, suggesting that both lipoprotein conjugates may have cell-surface binding sites in addition to the specific LDL (apoB) receptor. J774.2 macrophages avidly accumulate HP-LDL, retaining most of the fluorescence and some of the protein while degrading the remainder. Oxidized LDL species compete in these processes, with the major effect on protein degradation. Chloroquine has little effect on the fluorescence uptake but inhibits protein degradation (and hence enhances protein accumulation). HP-HDL is also avidly taken up by J774.2 cells, but in the case of the bovine material with a sigmoidal concentration dependence. This is consistent with prior aggregation before the particles can be endocytosed. P388.D1 cells, which appear to be less activated than the J774.2 line, take up less fluorescence and retain and degrade less protein, but still to higher extents than observed for non-phagocytic cells. We conclude that photosensitizer-lipoprotein conjugates can be taken up in large amounts by cells possessing scavenger receptors and/or phagocytic activity, and that this may be a means of targeting photodynamic therapy.

Effects of photodynamic therapy on xenografts of human mesothelioma and rat mammary carcinoma in nude mice

We have examined the effectiveness of photodynamic therapy against R3230AC rat mammary adenocarcinoma and human mesothelioma as xenografts in the same host. The results demonstrate that the xenografted human tumour is significantly more responsive to photodynamic treatment than the rodent mammary tumour. Studies also showed that the mesothelioma xenograft was fluence rate- and fluence-dependent while the rat tumour exposed to the same conditions demonstrated neither of these dependencies. This disparity in response was not attributable to a difference in either whole-tumour uptake or subcellular distribution of the porphyrin photosensitiser. Analysis of the effects of visible irradiation on cytochrome c oxidase activity, measured in mitochondria prepared from tumours borne on hosts injected with photosensitiser, demonstrated that photoradiation-induced enzyme inhibition was significantly greater in mesothelioma than in R3230AC mammary tumour preparations. However, in parallel studies conducted in vitro, when photosensitiser and light were delivered to previously unperturbed mitochondria, rates of enzyme inhibition were not significantly different. Both tumours were established in long-term cell culture. While the uptake of porphyrin photosensitiser was equivalent in both cell lines, the R3230AC cells displayed a significantly greater photosensitivity than the mesothelioma cells. The data presented here demonstrate that the mechanisms that govern response to photodynamic therapy are complex, but in the case of these two xenografted tumours host response to therapy is not likely to play a significant role.

Uptake and distribution of intravenously or intravesically administered photosensitizers in the rat

Photodynamic therapy using i.v. injected porphyrin photosensitizers have been used to treat selected cases of superficial bladder cancer. Since cutaneous photosensitivity, lasting 6-8 weeks, is a well known undesirable side effect of this therapy, we instilled the photosensitizers intravesically in rats and compared the uptake of photosensitizers in different tissues by this route of administration with the uptake after intravenous injection. The intravesical mode of delivery enhanced photosensitizer uptake in the bladder wall, while giving low concentrations in extravesical organs. Intravesical instillation of the photosensitizers may therefore increase their efficacy and reduce phototoxicity as compared with intravenous injection. Comparing the results obtained by two assays, one based on porphyrin fluorescence and the other based on the application of radioactively labelled photosensitizers, it was concluded that the i.v. administration route may result in tissue uptake of significant amounts of aggregated non-fluorescent, supposedly inactive drug, while the intravesical administration led to less uptake of aggregates relative to active drug monomers.

Selective accumulation of endogenously produced porphyrins in a liver metastasis model in rats

The possibility of using the porphyrin precursor 5-aminolevulinic acid to cause selective porphyrin accumulation in tumors was examined. Syngeneic colon carcinomas CC531 were implanted in the livers of Wag/Rij rats. Groups of three to six animals each were given 2 mg/mL of 5-aminolevulinic acid in drinking water from the 8th, 14th, or 17th day after tumor implantation. Two other groups received either 2.5 or 5 mg/kg of Photofrin II (Photomedica Inc., Raritan, NJ) intravenously on day 17. On day 19 the livers were removed and porphyrin concentrations were measured in normal livers and tumors by solvent extraction and high-performance liquid chromatography. Protoporphyrin accumulated progressively in tumors with increasing duration of 5-aminolevulinic acid administration (P = 0.0001), whereas no increase was found in normal livers. After 11 days of 5-aminolevulinic acid administration the porphyrin concentration ratio between tumors and livers was 4:1. In contrast, after Photofrin II administration the concentration was higher in normal livers than in tumors (1:3 ratio, tumor to liver). Enzyme measurements showed a threefold decrease in ferrochelatase activity in tumors compared with livers (P less than 0.001). In conclusion, oral administration of 5-aminolevulinic acid results in progressive accumulation of protoporphyrin in a transplantable colon carcinoma without accumulation in the surrounding liver tissue. This selective accumulation of porphyrins appears to be caused by a relative ferrochelatase deficiency in malignant tissue. 5-Aminolevulinic acid administration may be a suitable approach to photosensitizing liver tumors for photodynamic therapy or to early detection of tumors by fluorescence in ultraviolet light.

Neurovascular effects of reactive oxygen intermediates produced by photoradiation

These experiments examined the effect of reactive oxygen intermediates, produced by laser illumination of the photosensitizer hematoporphyrin derivative, on the accumulation and release of norepinephrine from sympathetic nerve terminals. Using an isolated, spirally cut, superfused caudal artery of the rat, basal overflow of norepinephrine (NE) was significantly increased both during and after generation of reactive oxygen intermediates. Generation of reactive oxygen intermediates increased overflow of NE in vascular preparations in which release of NE had previously been elevated by the continuous superfusion of Krebs' solution, containing high concentrations of potassium (40 mM). Calcium free solutions did not block the overflow of norepinephrine augmented by reactive oxygen intermediates. This increase in overflow was due both to an increase in release of NE and an inhibition of accumulation of NE.

Ultrastructural damage in photosensitized endothelial cells: dependence on hematoporphyrin delivery pathways

The subcellular photodamage to endothelial cells in culture, revealed by transmission electron microscopy, was correlated with discrete delivery pathways of hematoporphyrin (HP). Cell detachment from the extracellular matrix, prominent water influx starting at the outer membrane and formation of blebs followed by cell death were the result of photodynamic damage induced by aqueous HP. Serum-bound HP was internalized by endocytosis and accumulated in lysosomal compartments as located after photosensitization. Obstructed lysosomal membranes, degradation of chromatin and swelling of endoplasmic reticulum were revealed in these cells. Red blood cells (RBCs), preincubated with HP, delivered low amounts of the drug to endothelial cells. The photodamage was limited to the nucleus and nucleolus. The role of photosensitizer delivery pathways in cancer cell damage is discussed.

Effect of mitomycin C on the uptake of photofrin II in a human colon adenocarcinoma cell line

Flow cytometry (FCM) was used to investigate the effect of mitomycin C (MC) on the cellular uptake of Photofrin II (PII) in a cultured human colon adenocarcinoma cell line (WiDr). The surface area of the cells increased as they passed through the cell cycle from G0/G1 to G2/M phase. MC retarded the cells in G2/M phase and enhanced the surface area of the cells. A 1.3-2.3-fold increase in the cell surface area and a 1.3-2.7-fold increase in the cellular uptake of PII in the tumor cells was observed after 2 h-8 h incubation with MC. Within each sample, an almost linear relationship between the intensity of PII fluorescence in the cells and the surface area of the cells was found. However, for the cells incubated with MC the surface area was not the only determinant of PII uptake. Effects of MC on the cell cycle, the cell surface area and the permeability of the cell membrane are suggested as possible reasons for the increase of cellular uptake of PII in the tumor cells.

Distribution of di-sulfonated aluminum phthalocyanine and Photofrin II in living cells: a comparative fluorometric study

Microspectrofluorometric and fluorescence imaging techniques have been employed to study the internalization and intracellular distribution of both Photofrin II, an experimental drug used in photodynamic therapy, and di-sulfonated aluminum phthalocyanine, a very promising photosensitizer. The results obtained by microscopic techniques in living cells have been compared with those obtained in solution on cell extracts. Experimental results indicated that the complexity of the drug-cell interaction can be explained according to the chemico-physical nature of the drugs. In particular, the presence of both monomeric and aggregated fractions, which are supposed to be internalized through different mechanisms, accounts for the intracellular distributions observed for both drugs, depending on the treatment conditions. Equilibria among the drug fractions take place within the cells, resulting in the persistence of the intracellular fluorescence. On the whole, the behavior of the two drugs appears very similar, except for some aspects related to the intracellular distribution, which can be explained in terms of different degree of lipophilicity of the drugs.

Uptake and retention of Photofrin by cultivated human lymphoblastic cells (Reh6): preferential affinity of the cells for a minor component demonstrated by normal phase chromatography

The uptake of Photofrin by the human cultivated lymphoblastic cell line Reh6 was studied using normal phase high performance liquid chromatography (HPLC) techniques. Relative cellular uptake of eight fractions (uptake/amount of component initially present in the incubation solution) was determined. After 4 h of incubation, protoporphyrin and a small fraction (denoted 4) were incorporated to a greater relative extent than the other fractions. Weakly incorporated components (hematoporphyrin and aggregate-like components) were better retained by cells than the hydrophobic monomeric porphyrins (protoporphyrin and hydroxyethylvinyldeuteroporphyrin). Thus, any benefit gained from a higher uptake was mostly cancelled by a fast release--a situation observed for all fractions except for fraction 4, which displayed both high uptake and good cellular retention. This pattern was not modified when Photofrin concentration or serum percentage was changed. Fraction 4 was further resolved using a gradient system on normal silica. A single component appeared to be mostly responsible for the favorable properties presented by fraction 4, i.e. high uptake and retention within cells. This component was found to correspond to a late eluted peak in the typical reverse-phase HPLC profile of Photofrin. These results emphasize the possible role of minor Photofrin components.