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.

HMME combined with green light-emitting diode irradiation results in efficient apoptosis on human tongue squamous cell carcinoma.

Hematoporphyrin monomethyl ether (HMME) is a novel and promising porphyrin-related photosensitizer for photodynamic therapy (PDT). This study aimed to investigate the efficacy and potential mechanism of HMME-PDT under irradiation of green light-emitting diode (LED) with wavelength of 530 ± 20 nm in treating human tongue squamous cell carcinoma Tca8113 cells in vitro. The HMME concentrations were 1.25, 2.5, and 5 µg/ml while the energy densities were 0.6, 1.2, 1.8, 2.4, and 3.0 J/cm(2). MTT assay demonstrated that HMME-PDT significantly inhibited the proliferation of Tca8113 cells, and the cytotoxicity was improved with increased HMME concentration and light intensity. The amount of cells decreased significantly and the morphology of cells changed drastically after HMME-PDT. Flow cytometry analysis revealed that HMME-PDT induced both apoptosis and necrosis, but apoptosis was the main form of cell death. Apoptotic morphology was confirmed by Hoechst 33342 staining. Laser scanning confocal microscopy observation showed that HMME was mainly localized in mitochondria. The production of intracellular reactive oxygen species increased remarkably after PDT treatment, and both sodium azide (the singlet oxygen quencher) and D-mannitol (the hydroxyl radical scavenger) could protect Tca8113 cells from death induced by HMME-PDT. Additionally, the activity of caspase-3 also increased markedly in treated groups, and the cell death could be rescued by a reversible inhibitor (Ac-DEVD-CHO) of caspase-3. These results demonstrated that HMME combined with green LED significantly induced apoptosis of Tca8113 cells, suggesting that HMME-PDT using green LED might be a potential therapeutic strategy for human tongue squamous cell carcinoma.

Binding of hemin, hematoporphyrin, and protoporphyrin with erythroid spectrin: fluorescence and molecular docking studies.

Free heme has toxic effects, for example lipid peroxidation, DNA damage, and protein aggregation. In severe hemolysis, which occurs during pathological states, for example sickle cell disease, ischemia reperfusion, and malaria, levels of free heme increase inside erythrocytes. The purpose of this study was to investigate whether spectrin, the major erythroid cytoskeleton protein, is involved as an acceptor of free heme. We compared the interactions of three heme derivatives, hemin chloride, hematoporphyrin, and protoporphyrin-IX, with dimeric and tetrameric spectrin. The dissociation constants (K d) for binding to spectrin dimer and tetramer were 0.57 and 1.16 µM respectively. Thermodynamic data associated with this binding revealed the binding to be favored by a positive change in entropy. Although molecular docking studies identified the SH3 domain as the unique binding site of these heme derivatives to erythroid spectrin, experimental results indicated a binding stoichiometry of 1 heme attached to both dimeric and tetrameric spectrin, indicating the common self-associating domain to be the unique binding site. We also noticed heme-induced structural changes in the membrane skeletal protein. Erythroid spectrin could thus act as a potential acceptor of heme, particularly relevant under disease conditions.

Potential role of organic anion transporting polypeptide 1B1 (OATP1B1) in the selective hepatic uptake of hematoporphyrin monomethyl ether isomers.

AIM: Hematoporphyrin monomethyl ether (HMME), which consists of equal amounts of isomers HMME-1 and HMME-2, is a novel porphyrin-related drug for photodynamic therapy. This study was aimed to investigate the uptake transporter-mediated selective uptake of HMME into the liver and to identify the major uptake transporter isoforms involved. METHODS: Adult SD rats were intravenously injected with a single dose of HMME (5 mg/kg) with or without rifampicin (an inhibitor of organic anion transporting polypeptides OATP1B1 and OATP1B3, 25 mg/kg). Blood samples were collected, and HMME concentrations were measured using LC-MS/MS. Rat hepatocytes, human hepatocytes and HEK293 cells expressing OATP1B1, OATP1B3, or OATP2B1 were used to investigate the uptake of HMME or individual isomers in vitro. RESULTS: Co-administration of rifampicin significantly increased the exposure of HMME isomers, and decreased the AUC ratio of HMME-1 to HMME-2 from 1.98 to 1.56. The uptake of HMME-2 into human hepatocytes and the HEK293 cells expressing OATP1B1 or OATP2B1 in vitro was 2-7 times greater than that of HMME-1, whereas OATP1B3 mediated a higher HMME-1 uptake. OATP1B1 exhibited a higher affinity for HMME-2 than for HMME-1 (the Km values were 0.63 and 5.61 µmol/L, respectively), which were similar to those in human hepatocytes. By using telmisartan (a non-specific OATP inhibitor) and rifampicin, OATP2B1 was demonstrated to account for <20% of hepatic HMME uptake. CONCLUSION: OATP1B1 is the major transporter involved in the rapid hepatic uptake of HMME, and the greater uptake of HMME-2 by OATP1B1 may lead to a lower exposure of HMME-2 than HMME-1 in humans.

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.

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.

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.

The effect of liposomes' surface electric potential on the uptake of hematoporphyrin.

Hematoporphyrin is being used as a photosensitizer in photodynamic therapy of tumors, as well as of other clinical cases. Many classes of tetrapyrroles, including hematoporphyrin, are partitioning quite easily into the external cytoplasmic membrane as the mechanism of cellular uptake. Several chemical and physical parameters of the membrane were studied for their effect on the extent of porphyrins' partitioning. In this manuscript we report, for the first time, a quantitative analysis of the effect of the membrane's surface electric potential on the partitioning. We prepared liposomes, as membrane models, composed on zwitterionic DMPC lipid, as well as DMPC liposomes that contain a small, varying fraction of negatively charged DMPS and positively charged DOTAP. We found that indeed the surface potential had a very strong effect on the binding constant of HP, which is negatively charged at the physiological pH that was used. The trend in the apparent binding constant can be formulated and fitted with the Gouy-Chapman model of surface potential. We found that the average concentration of HP within the aqueous shell that has a thickness of the Debye layer around the liposome is determining the extent of binding in the law of mass action.

Induction of NKG2D ligands and increased sensitivity of tumor cells to NK cell-mediated cytotoxicity by hematoporphyrin-based photodynamic therapy.

Natural killer (NK) cells are important innate effector cells which can irradicate tumor cells through specific interactions between activating receptors on NK cells and their cognate ligands on cancer cells. Recently, it has been known that induction of activating NKG2D ligands including MHC class I chain-related (MIC) and UL16-binding protein (ULBP) families on tumor cells by various stresses makes them more susceptible to NK cell-mediated cytotoxicity. Therefore, it was investigated whether sublethal dose of hematoporphyrin-based photodynamic therapy (PDT) could up-regulate NKG2D ligands on tumor cells and increase the susceptibility of cancer cells against NK cells. Treatment with sublethal dose of hematoporphyrin-based PDT increased mRNA transcription and surface expression of ULBP1 and ULBP2 genes in SNU-1 human gastric tumor cell line and MICA/B, ULBP1, ULBP2 and ULBP3 genes in SW-900 human lung cancer cell line. These results were followed by increased susceptibility of cancer cells to NK cell-mediated cytotoxicity after sublethal PDT, which was abolished by addition of a blocking NKG2D mAb. Therefore, it could be suggested that the effect of hematoporphyrin-based PDT might be mediated in part by the increased susceptibility to NK cells via induction of NKG2D ligands on tumor cells, which survived after treatment with PDT.

Comparison of accumulation, subcellular location, and sonodynamic cytotoxicity between hematoporphyrin and protoporphyrin IX in L1210 cells.

BACKGROUND: Sonodynamic therapy (SDT) is a promising modality for cancer treatment which requires the synergistic effect of ultrasound and tumor-localized sonosensitizers. Sonodynamic efficacy can be improved through a better understanding of the accumulation and subcellular location of sonosensitizers. Here, a comparison of the accumulation, sublocation, and sonodynamic effect of hematoporphyrin (Hp) and protoporphyrin IX (PpIX) was studied in L1210 cells. METHODS: The kinetics of intracellular Hp and PpIX accumulation were detected using a fluorescence spectrophotometer. The subcellular distributions of Hp and PpIX were monitored by laser scanning confocal microscopy. The cytotoxic effects of Hp-mediated SDT (Hp-SDT) and PpIX-mediated SDT (PpIX-SDT) were evaluated by MTT assay. RESULTS: The accumulation of Hp and PpIX presented different kinetic changes depending on the time, and was also concentration- and temperature-dependent. The intracellular PpIX content was much higher than that of Hp under the same conditions; however, there were no obvious differences in terms of their subcellular locations, and both of them mainly accumulated on the mitochondria and the plasma membrane in L1210 cells. PpIX exhibited more potential cytotoxicity than did Hp when they were irradiated with ultrasound under the same experimental conditions. CONCLUSION: Our results indicate that there were significant differences regarding the intracellular accumulation features between Hp and PpIX. PpIX-SDT produced a more serious cytotoxic effect than did Hp-SDT, which may be due to the higher PpIX uptake in L1210 cells compared to that of Hp at the same concentrations. Additionally, the absorption of Hp and PpIX in L1210 cells might be energy dependent.

[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.

Switch from inhibition to activation of the mitochondrial permeability transition during hematoporphyrin-mediated photooxidative stress. Unmasking pore-regulating external thiols.

We have studied the mitochondrial permeability transition pore (PTP) under oxidizing conditions with mitochondria-bound hematoporphyrin, which generates reactive oxygen species (mainly singlet oxygen, (1)O(2)) upon UV/visible light-irradiation and promotes the photooxidative modification of vicinal targets. We have characterized the PTP-modulating properties of two major critical sites endowed with different degrees of photosensitivity: (i) the most photovulnerable site comprises critical histidines, whose photomodification by vicinal hematoporphyrin causes a drop in reactivity of matrix-exposed (internal), PTP-regulating cysteines thus stabilizing the pore in a closed conformation; (ii) the most photoresistant site coincides with the binding domains of (external) cysteines sensitive to membrane-impermeant reagents, which are easily unmasked when oxidation of internal cysteines is prevented. Photooxidation of external cysteines promoted by vicinal hematoporphyrin reactivates the PTP after the block caused by histidine photodegradation. Thus, hematoporphyrin-mediated photooxidative stress can either inhibit or activate the mitochondrial permeability transition depending on the site of hematoporphyrin localization and on the nature of the substrate; and selective photomodification of different hematoporphyrin-containing pore domains can be achieved by fine regulation of the sensitizer/light doses. These findings shed new light on PTP modulation by oxidative stress.

The binding of analogs of porphyrins and chlorins with elongated side chains to albumin.

In previous studies, we demonstrated that elongation of side chains of several sensitizers endowed them with higher affinity for artificial and natural membranes and caused their deeper localization in membranes. In the present study, we employed eight hematoporphyrin and protoporphyrin analogs and four groups containing three chlorin analogs each, all synthesized with variable numbers of methylenes in their alkyl carboxylic chains. We show that these tetrapyrroles' affinity for bovine serum albumin (BSA) and their localization in the binding site are also modulated by chain lengths. The binding constants of the hematoporphyrins and protoporphyrins to BSA increased as the number of methylenes was increased. The binding of the chlorins depended on the substitution at the meso position opposite to the chains. The quenching of the sensitizers' florescence by external iodide ions decreased as the side chains became longer, indicating to deeper insertion of the molecules into the BSA binding pocket. To corroborate this conclusion, we studied the efficiency of photodamage caused to tryptophan in BSA upon illumination of the bound sensitizers. The efficiency was found to depend on the side-chain lengths of the photosensitizer. We conclude that the protein site that hosts these sensitizers accommodates different analogs at positions that differ slightly from each other. These differences are manifested in the ease of access of iodide from the external aqueous phase, and in the proximity of the photosensitizers to the tryptophan. In the course of this study, we developed the kinetic equations that have to be employed when the sensitizer itself is being destroyed.

Cellular phototoxicity evoked through the inhibition of human ABC transporter ABCG2 by cyclin-dependent kinase inhibitors in vitro.

PURPOSE: The physiological importance of the human ATP-binding cassette (ABC) transporter ABCG2 has been recognized with regard to porphyrin-mediated photosensitivity. Functional impairment owing to inhibition of ABCG2 by drugs or its genetic polymorphisms may lead to the disruption of porphyrin homeostasis, which in turn causes cellular toxicity. MATERIALS AND METHODS: We evaluated the impact on photosensitivity of the inhibition by cyclin-dependent kinase (CDK) inhibitors of ABCG2 function. For this purpose, we established new methods for photosensitivity assays by using Flp-In-293 cells and plasma membrane vesicles prepared from Sf9 insect cells. With the new methods, we subsequently tested CDK inhibitors, i.e., purvalanol A, WHI-P180, bohemine, roscovitine, and olomoucine. RESULTS: Among CDK inhibitors tested, purvalanol A was found to be the most potent inhibitor (IC50=3.5 microM) for ABCG2-mediated hematoporphyrin transport. At a concentration of 2.5 microM, it evoked the photosensitivity of ABCG2-expressing Flp-In-293 cells treated with pheophorbide a. WHI-P180 moderately inhibited ABCG2 function, exhibiting weak phototoxicity. In contrast, the phototoxicity of bohemine, roscovitine, and olomoucine were minimal in our assay system. CONCLUSIONS: It is suggested that the planar structure is an important factor for interactions with the active site of ABCG2. The present study provides a new approach to studying drug-induced phototoxicity in vitro.

Involvement of mitochondria-caspase pathway in Hemoporfin-mediated cell death.

Hemoporfin is a novel second-generation porphyrin-related photosensitizer for ovarian cancer photodynamic treatment (PDT). The purpose of this study was to investigate the molecular mechanisms of Hemoporfin-mediated photocytotoxicity. Human epithelial ovarian cancer cell line 3AO was incubated with different concentrations of Hemoporfin, and phototoxic effects of Hemoporfin on cells were determined using a Cell Viability Analyzer. Apoptosis or necrosis was determined by flow cytometry analysis using the Annexin V-FITC apoptosis kit. Cellular caspase activation was determined using the fluorescent assay kit for caspase-3 and caspase-9. Rhodamine123 was used as a mitochondrial probe and Lucifer Yellow as a lysosomal probe to investigate the intracellular localization of Hemoporfin in 3AO cancer cells. We demonstrated that both high-dose (30 microg mL(-1)) and low-dose (3 microg mL(-1)) Hemoporfin significantly reduced the viability of ovarian cancer cell 3AO with light illumination, and the photocytotoxicity was dose-dependent (P < 0.01). Using a mitochondrial fluorescence probe, we demonstrated a distinct mitochondrial aggregation in 3AO cells with a low concentration of Hemoporfin. Loss of mitochondrial membrane potential was detected as early as 1 h after Hemoporfin-mediated PDT. PDT with low-dose Hemoporfin predominantly induced apoptosis but not necrosis, and both caspase-3 and caspase-9 were activated. Based on our results, mitochondria play an important role in the Hemoporfin-induced apoptosis, and mitochondria membrane potential loss initiated apoptosis via the activation of caspases. Understanding the mechanisms involved in PDT-mediated apoptosis may improve its therapeutic efficacy and facilitate its transition into the clinic.

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.