Destruction of erythroleukemia, myelocytic leukemia and Burkitt lymphoma cells by photoactivated protoporphyrin

Dual function of lectins — new perspectives in targeted photodynamic therapy

Porphyrins and phthalocyanines are photosensitizers (PS) that are used in clinical imaging, detection of cancer cells and are particularly applied in photodynamic therapy (PDT). Many scientists have been focused on the design of different porphyrin compounds. However, similar to other anti-cancer agents, they cannot selectively recognize tumor tissues. Scientists are seeking new methods to overcome this problem and to find appropriate targeted delivery strategies. Plant lectins are especially suitable molecules for such targeting as they preferentially recognize specific antigens on the glycosylated cancer cells. This review will give more detailed information about the dual function of lectins and their interactions with PSs, which is a new perspective in targeted PDT. The implications and potential applications of such studies will also be discussed.

Antibacterial function of herbal extracts on growth, survival and immunoprotection in the black tiger shrimp Penaeus monodon

This study examined the effects of an herbal extract composed of nine herbs i.e Aloe vera, Andrographis pariculata, Annona squamosa, Azadirachta indica, Citrus aurantifolia, Coriandrum sativum, Ocimum sanctum, Ollium cepa and Psidium guajava on growth, survival rate and immunoprotection against pathogenic Vibrio harveyi in the tiger shrimp Penaeus monodon. The petroleum ether, methanol and N-hexen extracts of different herbal plants were selected, processed and thoroughly mixed in equal proportions and added to the shrimp diets at a concentration of 1.0, 2.5 and 5.0 mL kg^-1. After 60 days of feeding, shrimps were challenged with V. harveyi bacteria (1 × 10⁷ cells mL^-1), which were isolated and propagated from the infected shrimps. The shrimps fed on diets with methanolic extraction of 2.5 mL kg^-1 had significantly (P < 0.001) higher survival rate (76%), specific growth rate (4.26 ± 0.11%) and better food conversion ratio (1.5) than the other groups. This study indicates that addition of methanolic herbal extracts of 2.5 mL kg^-1 can positively influence the immune response of tiger shrimp against V. harveyi infection.

G-quadruplex DNA/protoporphyrin IX-based synergistic platform for targeted photodynamic cancer therapy

Photodynamic therapy (PDT) is an emerging technique to induce cancer cell death. However, the tumor specificity, cellular uptake and biodistribution of many photosensitizers urgently need to be improved. In this regard, we show here that the integrated nanoassemblies based on G-quadruplex DNAs (GQDs)/protoporphyrin IX (PPIX) can serve as a synergistic platform for targeted high-performance PDT. In the nanoassemblies, GQDs function as carriers of sensitiser PPIX and confers the system cancer cell targeting ability. After nucleolin-mediated efficient binding and cellular uptake of GQDs/PPIX assemblies, the strong red fluorescence of GQDs/PPIX complex provides a powerful tool for biological imaging. Moreover, the reactive oxygen species (ROS) generated by GQDs/PPIX under light illumination can effectively kill cancer cells. The present approach is simply composed by DNA and photosensitizers, thereby avoiding any complicated and time-consuming covalent modification or chemical labeling procedure.

Comparative kinetics of damage to the plasma and mitochondrial membranes by intra-cellularly synthesized and externally-provided photosensitizers using multi-color FACS

Photodynamic therapy (PDT) of cancer involves inflicting lethal damage to the cells of malignant tumors, primarily by singlet oxygen that is generated following light-absorption in a photosensitizer molecule. Dysfunction of cells is manifested in many ways, including peroxidation of cellular components, membrane rupture, depolarization of electric potentials, termination of mitochondrial activity, onset of apoptosis and necrosis and eventually cell lysis. These events do not necessarily occur in linear fashion and different types of damage to cell components occur, most probably, in parallel. In this report we measured the relative rates of damage to two cellular membranes: the plasma membrane and the mitochondrial membrane. We employed photosensitizers of diverse hydrophobicities and used different incubation procedures, which lead to their different intra-cellular localizations. We monitored the damage that was inflicted on these membranes, by employing optical probes of membrane integrity, in a multi-color FACS experiment. The potentiometric indicator JC-1 monitored the electric cross-membrane potential of the mitochondria and the fluorometric indicator Draq7 monitored the rupture of the plasma membrane. We show that the electric depolarization of the mitochondrial membrane and the damage to the enveloping plasma membrane proceed with different kinetics that reflect the molecular character and intracellular location of the sensitizer: PpIX that is synthesized in the cells from ALA causes rapid mitochondrial damage and very slow damage to the plasma membrane, while externally added PpIX has an opposite effect. The hydrophilic sensitizer HypS4 can be taken up by the cells by different incubation conditions, and these affect its intracellular location, and as a consequence either the plasma membrane or the mitochondria is damaged first. A similar correlation was found for additional extracellularly-provided photosensitizers HP and PpIX.

Lipid composition affects the rate of photosensitized dissipation of cross-membrane diffusion potential on liposomes

Hydrophobic or amphiphilic tetrapyrrole sensitizers are taken up by cells and are usually located in cellular lipid membranes. Singlet oxygen is photogenerated by the sensitizer, and it diffuses in the membrane and causes oxidative damage to membrane components. This damage can occur to membrane lipids and to membrane-localized proteins. Depolarization of the Nernst electric potential on cells' membranes has been observed in cellular photosensitization, but it was not established whether lipid oxidation is a relevant factor leading to abolishing the resting potential of cells' membranes and to their death. In this work, we studied the effect of liposomes' lipid composition on the kinetics of hematoporphyrin-photosensitized dissipation of K(+)-diffusion electric potential that was generated across the membranes. We employed an electrochromic voltage-sensitive spectroscopic probe that possesses a high fluorescence signal response to the potential. We found a correlation between the structure and unsaturation of lipids and the leakage of the membrane, following photosensitization. As the extent of nonconjugated unsaturation of the lipids is increased from 1 to 6 double bonds, the kinetics of depolarization become faster. We also found that the kinetics of depolarization is affected by the percentage of the unsaturated lipids in the liposome: as the fraction of the unsaturated lipids increases, the leakage through the membrane is enhanced. When liposomes are composed of a lipid mixture similar to that of natural membranes and photosensitization is being carried out under usual photodynamic therapy (PDT) conditions, photodamage to the lipids is not likely to cause enhanced permeability of ions through the membrane, which would have been a mechanism that leads to cell death.

Electrically enhanced percutaneous delivery of delta-aminolevulinic acid using electric pulses and a DC potential

Selectivity of photodynamic therapy can be improved with localized photosensitizer delivery, but topical administration is restricted by poor diffusion across the stratum corneum. We used electric pulses to increase transdermal transport of delta-aminolevulinic acid (ALA), a precursor to the photosensitizer protoporphyrin IX (PpIX). ALA-filled electrodes were attached to the surface of excised porcine skin or the dorsal surface of mice. Pulses were administered and, in some in vivo cases, a continuous DC potential (6 V) was concomitantly applied. For in vitro 14C ALA penetration, 10 microm layers parallel to the stratum corneum were assayed by liquid scintillation analysis, and 10 microm cross sections were examined autoradiographically. As the electrical dose (voltage x frequency x pulse width x treatment duration) increased, there was an increase in penetration depth. In vivo delivery was assayed by measuring the fluorescence of PpIX in skin samples. A greater than two-fold enhancement of PpIX production with electroporative delivery was seen versus that obtained with passive delivery. Superimposition of a DC potential resulted in a nearly three-fold enhancement of PpIX production versus passive delivery. Levels were higher than the sum of PpIX detected after pulse-alone and DC-alone delivery. Electroporation and electrophoresis are likely factors in electrically enhanced delivery.

The depth of porphyrin in a membrane and the membrane's physical properties affect the photosensitizing efficiency

Photosensitized biological processes, as applied in photodynamic therapy, are based on light-triggered generation of molecular singlet oxygen by a membrane-residing sensitizer. Most of the sensitizers currently used are hydrophobic or amphiphilic porphyrins and their analogs. The possible activity of the short-lived singlet oxygen is limited to the time it is diffusing in the membrane, before it emerges into the aqueous environment. In this paper we demonstrate the enhancement of the photosensitization process that is obtained by newly synthesized protoporphyrin derivatives, which insert their tetrapyrrole chromophore deeper into the lipid bilayer of liposomes. The insertion was measured by fluorescence quenching by iodide and the photosensitization efficiency was measured with 9,10-dimethylanthracene, a fluorescent chemical target for singlet oxygen. We also show that when the bilayer undergoes a melting phase transition, or when it is fluidized by benzyl alcohol, the sensitization efficiency decreases because of the enhanced diffusion of singlet oxygen. The addition of cholesterol or of dimyristoyl phosphatydilcholine to the bilayer moves the porphyrin deeper into the bilayer; however, the ensuing effect on the sensitization efficiency is different in these two cases. These results could possibly define an additional criterion for the choice and design of hydrophobic, membrane-bound photosensitizers.

Cellular distribution and phototoxicity of benzoporphyrin derivative and Photofrin

Photodynamic therapy (PDT) induces cell-membrane damage and alterations in cancer-cell adhesiveness, an important parameter in cancer metastasis. These alterations result from cell sensitivity to photosensitizers and the distribution of photosensitizers in cells. The efficacy of photosensitizers depends on their close proximity to targets and thus on their pharmacokinetics at the cellular level. We studied the cellular distribution of photosensitizers with a confocal microspectrofluorimeter by analysing the fluorescence emitted by benzoporphyrin derivative-monoacid ring A (BPD-MA) and Photofrin relative to their cell sensitivity. Two cancer cell lines of colonic origin, but with different metastatic properties, were used: PROb (progressive) and REGb (regressive). For BPD-MA (1.75 microg/ml), maximal fluorescence intensity (8,300 cts) was reached after 2 h for PROb and after 1 h (4,900 cts) for REGb. For Photofrin (10 microg/ml), maximal fluorescence intensity (467 cts) was reached after 5 h for PROb and after 3 h (404 cts) for REGb. Intracellular studies revealed stronger cytoplasmic than nuclear fluorescence for both BPD and Photofrin. Both of the sensitizers induced a dose-dependent phototoxicity; LD50 with BPD-MA was 93.3 ng/ml for PROb and 71.1 ng/ml for REGb, under an irradiation of 10 J/cm2. With Photofrin, LD50 was 1,270 ng/ml for PROb and 1,200 ng/ml for REGb under an irradiation of 25 J/cm2. The photosensitizer effect within PROb and REGb cancer cells was assessed by incorporation kinetics and toxicity-phototoxicity tests. The intracellular concentration of the photosensitive agent was one important factor in the effectiveness of PDT, but not the only one contributing to the photodynamic effect. In conclusion, this study showed that there was a clear difference between sensitizer uptake and phototoxicity, even in cancer cells of the same origin. This could induce cell-killing heterogeneity in clinics.

Effects on the mitosis of normal and tumor cells induced by light treatment of different wavelengths

OBJECTIVE

Although the background of laser therapy by means of low level energy and power is still only partially understood, there are nevertheless promising reports from clinical studies concerning pain treatment, the acceleration of wound healing, and the modulation of cell functions. In order to contribute to the understanding of such a phototherapeutic procedure cell experiments were performed.

MATERIALS AND METHODS

The influence of light (lambda = 410, 488, 630, 635, 640, 805, and 1,064 nm and broad band white light) on the proliferation of cells was investigated on skeletal myotubes (C2), normal urothelial cells (HCV29), human squamous carcinoma cells of the gingival mucosa (ZMK1), urothelial carcinoma cells (J82), glioblastoma cells (U373MG), and mamma adenocarcinoma cells (MCF7) in a computer-controlled light treatment chamber. The cellular response was tested by way of the following methods: The rate of mitosis was determined by counting the single cells after Orcein-staining. The proliferation index measurements were based on the BrdU incorporation during the DNA synthesis. Statistics were performed using unpaired Student's t-test procedures, stating P < 0. 05 to be significant and P>0.05 not to be significant.

RESULTS

Twenty-four hours after light treatment, a significant increase in the mitotic rate of J82 and HCV29 cells was determined when illuminated with lambda = 410 nm, lambda = 635 nm and lambda = 805 nm, respectively. C2 cells showed an increase only after lambda = 635 nm illumination. In all three cell lines, a maximum mitotic rate was determined after an irradiation between 4 and 8 J/cm(2), while a reduced mitotic rate was measured at 20 J/cm(2). MCF7, U373MG, and ZMK1 cells showed a slight decrease in the mitotic rate with increasing irradiation independent of the wavelength used. When an irradiation of 20 J/cm(2) was applied, all cell lines showed a slight decrease compared to the controls independent to the wavelength used. White light as well as lambda = 1,064 nm does not affect the mitotic rate in this irradiation range. No significant differences in the effects could be determined when the irradiance changed between 10 and 150 mW/cm(2) at certain irradiation values. The BrdU test did not show any significant alterations with respect to possible light induced processes compared to the controls.

CONCLUSIONS

Dependent upon the irradiation parameter, light of a defined wavelength does affect the mitotic rate of both normal as well as tumor cells. It could be hypothesized that the action spectra of the cellular response indicate the participation of endogenous porphyrins and cytochromes as primary photoreceptors. Taking into account all light induced processes, the term biomodulation should preferably be used.

BPD-MA-mediated photosensitization in vitro and in vivo: cellular adhesion and beta1 integrin expression in ovarian cancer cells

Benzoporphyrin derivative monoacid (BPD-MA) photosensitization was examined for its effects on cellular adhesion of a human ovarian cancer cell line, OVCAR 3, to extracellular matrix (ECM) components. Mild BPD-MA photosensitization (approximately 85% cell survival) of OVCAR 3 transiently decreased adhesion to collagen IV, fibronectin, laminin and vitronectin to a greater extent than could be attributed to cell death. The loss in adhesiveness was accompanied by a loss of beta1 integrin-containing focal adhesion plaques (FAPs), although beta1 subunits were still recognized by monoclonal antibody directed against human beta1 subunits. In vivo BPD-MA photosensitization decreased OVCAR 3 adhesiveness as well. Photosensitized adhesion was reduced in the presence of sodium azide and enhanced in deuterium oxide, suggesting mediation by singlet oxygen. Co-localization studies of BPD-MA and Rhodamine 123 showed that the photosensitizer was largely mitochondrial, but also exhibited extramitochondrial, intracellullar, diffuse cytosolic fluorescence. Taken together, these data show that intracellular damage mediated by BPD-PDT remote from the FAP site can affect cellular-ECM interactions and result in loss of FAP formation. This may have an impact on long-term effects of photodynamic therapy. The topic merits further investigation.

The kinetics of protoporphyrin fluorescence during ALA-PDT in human malignant skin tumors

Fluorescence monitoring during photodynamic therapy (PDT) with the use of topical 5-aminolevulinic acid (ALA) was carried out in patients bearing superficial and nodular basal cell carcinomas (BCC), squamous cell carcinomas (SCC) and Kaposi's sarcomas. A new diagnostic-therapeutic system based on an incoherent CW light source was used for fluorescence spectral measurements and imaging. The results showed that photoirradiation reduced ALA-induced protoporphyrin IX (PP) fluorescence in all tumors. The rate of PP photobleaching in superficial BCC and SCC tumors was significantly higher than in large nodular BCC tumors. The results showed that the differences in kinetics of fluorescence reduction could be attributed to the tumor thickness. One hour after photoirradiation with a light dose of 170 J/cm2 a phenomenon of re-appearance and recovery of PP fluorescence was observed in the large deeply penetrating BCC tumors and Kaposi's sarcoma lesions. In such cases an additional light treatment was performed. The results of the study demonstrated that fluorescence monitoring is very appropriate for the definition of an optimal ALA-PDT clinical protocol.

Biomodulative effects induced by 805 nm laser light irradiation of normal and tumor cells

The influence of light emitted from a diode laser centred at lambda = 805 nm was investigated on murine skeletal myotubes (C2), normal urothelial cells (HCV29), human squamous carcinoma cells of the gingival mucosa (ZMK) and urothelial carcinoma cells (J82) in a computer-controlled irradiation chamber. Cells were treated with varying fluences between 0 and 20 J cm-2. The response was tested by analysis of the mitotic index using single cell counting after Orcein staining and proliferation index based on BrdU incorporation during DNA synthesis. While the mitotic index of C2, HCV29 and J82 cells increased at a fluence of 4 J cm-2, irradiation with fluences of 20 J cm-2 resulted in a slight decrease. ZMK tumor cells showed a decrease of the mitotic index with both fluences. No significant differences could be determined when using irradiances between 10 mW cm-2 and 150 mW cm-2. The BrdU test after irradiation showed no significant effects compared to the controls in each cell line.

Photodynamic therapy decreases cancer colonic cell adhesiveness and metastatic potential

Plasma membrane damage induced in various cell targets by hematoporphyrin (HPD) photodynamic therapy (PDT) could modify cancer cell adhesiveness, an important parameter in cancer metastasis. We investigated the effect of HPD or HPD incubation followed by argon laser light on the adhesiveness of progressive (PROb) or regressive (REGb) cancer cells of the same colonic origin but with a different in vivo metastatic potential. Adhesiveness was studied on plastic or endothelial cell monolayers (ECM). In the absence of treatment, both PROb and REGb cells adhered better on plastic than on ECM. HPD alone or HPD-PDT induced toxicity proportional to the HPD dose. HPD-PDT increased the adhesiveness rate of both cell lines on plastic and decreased it on ECM. HPD-PDT of ECM increased adhesiveness, but only at HPD doses causing at least 50% cell death. With HPD treatment alone or HPD-PDT of culture media, there was no significant decrease in cell adhesiveness to ECM. We also studied the effect of HPD or HPD incubation followed by argon laser light on the metastatic potential of cancer cells, which was decreased for PROb with HPD alone or HPD-PDT. Decreased adhesiveness of colonic cancer cells to ECM after HPD-PDT was thus correlated with decreased metastatic potential. REGb cells did not acquire a progressive phenotype either in vitro or in vivo after HPD-PDT.

Photosensitization of murine tumor, vasculature and skin by 5-aminolevulinic acid-induced porphyrin

The effects of topical and systemic administration of 5-aminolevulinic acid (ALA) were examined in several murine tumor systems with regard to porphyrin accumulation kinetics in tumor, skin and blood, vascular and tumor cell photosensitization and tumor response after light exposure. Marked, transient increases in porphyrin levels were observed in tumor and skin after systemic and topical ALA. Rapid, transient, dose-dependent porphyrin increases were also observed in blood; these were pronounced after systemic ALA injection and mild after topical application. They were highest within 1 h after ALA injection, thereafter declining rapidly. This matched the clearing kinetics of injected exogenous protoporphyrin IX (PpIX). Initially, vascular photosensitivity changed inversely to blood porphyrin levels, increasing gradually up to 5 h post-ALA, as porphyrin was clearing from the bloodstream. This pattern was again matched by injected, exogenous PpIX. After therapeutic tumor treatment vascular disruption of the tumor bed, while observed, was incomplete, especially at the tumor base. Minimal direct tumor cell kill was found at low photodynamic therapy (PDT) doses (250 mg/kg ALA, 135 J/cm2 light). Significant, but limited (< 1 log) direct photodynamic tumor cell kill was obtained when the PDT dose was raised to 500 mg/kg systemic ALA, followed 3 h later by 270 J/cm2, a dose that was however toxic to the animals. The further reduction of clonogenic tumor cells over 24 h following treatment was moderate and probably limited by the incomplete disruption of the vasculature. Tumor responses were highest when light treatment was carried out at the time of highest tumor porphyrin content rather than at the time of highest vascular photosensitivity. Tumor destruction did not reach the tumor base, regardless of treatment conditions.

Modification of the photodynamic action of delta-aminolaevulinic acid (ALA) on rat pancreatoma cells by mitochondrial benzodiazepine receptor ligands

We have shown that addition of exogenous delta-aminolaevulinic acid (ALA) to rat pancreatoma AR4-2J cells in culture leads to the increased production of porphobilinogen (PBG) and the accumulation of photoactive protoporphyrin IX (PPix) in these cells. Exposure to light (lambda > 400 nm) at an intensity of 0.2 mW cm-2 for 8 min resulted in an ALA dose-dependent cytolysis of the cells, with an EC50 of 6.6 +/- 0.7 microM. This cytolytic effect was light intensity dependent, with greater cell destruction after exposure to light at an intensity of 0.47 mW cm-2 than at 0.2 mW cm-2; it was also dependent on the duration of illumination, cell survival decreasing with increasing illumination times. The photodestruction of the AR4-2J cells following exposure to ALA can be attributed to the production of endogenous PPix, a photoactive porphyrin that we have shown to generate singlet oxygen upon illumination, whereas ALA itself does not. Further investigation of the molecular mechanisms underlying the photodynamic action of ALA demonstrated the involvement of the mitochondrial (peripheral) benzodiazepine receptor (MBR), a high-affinity recognition site for dicarboxylic porphyrins, and especially PPix. The centrally acting benzodiazepine compounds clonazepam and flumazenil, which have negligible affinities for the MBR, had no effect on ALA-mediated phototoxicity. In contrast, both the isoquinoline carboxamide PK11195 and the benzodiazepine Ro 5-4864 ligands, displaying a high affinity for the MBR, did affect ALA-mediated phototoxicity, each markedly increasing the EC50 for cell photodestruction and thus exerting a photoprotective effect. It is concluded that the MBR may play an important role in the expression of ALA-mediated PPix phototoxicity and that MBR ligands, by diminishing the actions of endogenous PPix, have the potential to rescue cells from porphyrin-induced photolysis.

Modulation of colonic cancer cell adhesiveness by haematoporphyrin derivative photodynamic therapy

Haematoporphyrin derivative photodynamic therapy (HPD-PDT) induces damage of plasma membranes and other cellular targets. This damage could modify the adhesiveness of cancer cells, which is an important parameter in cancer metastasis. We studied the effect of HPD alone and HPD incubation followed by argon laser light on the adhesiveness of progressive (PROb) or regressive (REGb) cancer cells of the same colonic origin. Adhesiveness was studied on plastic or endothelial cell monolayers (ECMs). In the absence of treatment, both PROb and REGb cells adhered better on plastic than on ECs. HPD alone and HPD-PDT induced toxicity proportional to the HPD dose. HPD-PDT increased the adhesiveness rate of both cell lines on plastic and decreased adhesiveness to ECs. HPD-PDT of ECMs increased adhesiveness but only for HPD doses giving at least 50% cell death. HPD alone and HPD-PDT of culture media led to an insignificant decrease in the cell adhesiveness to ECMs. As cells which are more metastatic are also more adherent, a decreased adhesiveness to ECMs after HPD-PDT suggests that PDT is a safe treatment considering metastasis.

Protoporphyrin biosynthesis in melanoma B16 cells stimulated by 5-aminolevulinic acid and chemical inducers: characterization of photodynamic inactivation

The stimulation of protoporphyrin (PP) biosynthesis in B16 melanoma cells in order to facilitate photodynamic cell killing was studied. Biosynthesis and accumulation of PP in the melanoma cells was increased from 8 to 15 pmol/mg protein by the use of dimethyl-sulfoxide (DMSO), a differentiation-inducer. Treatment of the cells with the porphyrogenic agent allylisopropyl-acetamide (AIA) stimulated an additional PP increase. The most remarkable enhancement of intracellular PP was achieved by the supplementation of 5-aminolevulinic acid (5-ALA) to the growth medium following the addition of DMSO and AIA during the induction phase. The intracellular concentration of PP exceeded 21,950 pmol/mg protein following combined stimulation by DMSO/AIA and 5-ALA. The porphyrins produced in the incubated cells, in serum-depleted medium, consisted of 95% PP; 88% of it was recovered from the cells and only 7% was excreted into the medium. Photosensitization of the B16 melanoma cells containing high PP concentrations was effective even at low light doses. Potassium (K) efflux was the first measurable sign of cell damage determined by X-ray microanalysis (XRMA) following fast liquid-nitrogen fixation. During a 1 min interval, 70% of cellular K was lost. After 5 min illumination, complete cell destruction was detected by scanning electron microscopy (SEM) and XRMA. The photodamaged cells showed influx of Na, Cl and Ca ions accompanying the immediate K losses. Ultrastructural cell damage was manifested by disintegration of the outer membrane. Total cell death of B16 melanoma cells was achieved by chemical induction of endogenous PP and photosensitization.

Collapse of K+ and ionic balance during photodynamic inactivation of leukemic cells, erythrocytes and Staphylococcus aureus

1. The immediate and fast ionic fluxes in Friend erythroleukemic cells (FELC), erythrocytes and Staphylococcus aureus during short intervals of porphyrin mediated photosensitization were determined uniquely by X-ray microanalysis (XRMA) combined with electron microscopy. 2. Photodynamic inactivation of FELC was mediated by either endogenous protoporphyrin induced by 5-amino levulinic acid (5-ALA), or Photofrin-II. We describe the predominant phenomena of > 85% K-loss within 2-10 min of photoactivation. However the accompanied Na inflow and the collapse of the cellular balance of elemental-composition were inconsistent and acted as a function of cell damage. 3. Erythrocytes treated with hematoporphyrin (HP) lost most of their intracellular K yet instantly gained Na. Nevertheless the K/Na molar ratio of the control erythrocytes was nearly 12/1 while after photosensitization and K loss it changed to 1/1. 4. The S. aureus bacteria photosensitized with HP showed entire K-loss as well as marked Na efflux which increased with irradiation time; this was accompanied by the decline of other cell elements. 5. The prevailing K loss in FELC, erythrocytes and bacteria during the first minutes of photosensitization is deduced to be an immediate primary consequence of the photodynamic effect, while other ionic changes are joined in order with the development of cellular damage.

Neonatal exposure to protoporphyrin-activating lighting as a contributing cause of childhood acute lymphocytic leukemia

While being a relatively rare disease, acute lymphocytic leukemia (ALL) is the leading form of cancer in children in the developed world today. ALL sharply peaks in incidence at ages three to four years. In the United States there have been persistent, unexplained increases in incidence of ALL in the past two decades. We hypothesize that exposure to photosensitizing lighting immediately after birth may be a contributing cause of ALL. Fluorescent lamps and other light sources with strong illumination, around 400 nanometers, are protoporphyrin-activating. Activation of protoporphyrin produces superoxides and free radicals that can induce breaks in DNA. In newborn nurseries in the US, the intensity of lighting has increased five- to 10-fold over the past two decades. Thus, protoporphyrin-activating light may be a contributing cause of childhood ALL. Additional retrospective and prospective studies should be undertaken of the relationship between exposure of newborns to protoporphyrin-activating illumination and the development of childhood ALL, along with in vitro studies of the hematologic effects of fluorescent lighting. Protoporphyrin-activating lighting is clearly not the sole determinant of ALL, but it could be a completely preventable cause. Inexpensive plastic filters could reduce these exposures substantially.

Effects of coumarins, haematoporphyrins and acridine orange on the viability and growth of Landshütz ascites tumour cells, in the presence and absence of photoradiation

The effects of haematoporphyrin (Hp), haematoporphyrin derivative (HpD), coumarin, 7-hydroxycoumarin, 4-hydroxycoumarin, amino-methyl-coumarin acetic acid and acridine orange, with and without photoradiation, on Landschutz ascites tumour (LAT) cells were examined. Hp, HpD and acridine orange showed a significant effect on LAT cell viability following photoradiation. However, coumarin or its derivatives had no significant effect on LAT cell viability, with or without photoradiation, over 18 h. Coumarin alone had a significant effect on viability of LAT cells, in vitro, over a period of 9 days. This effect was verified by transplantability studies. Coumarin and 7-hydroxycoumarin both exhibited cytostatic effects on LAT cell growth.

Inactivation of erythrocytic, lymphocytic and myelocytic leukemic cells by photoexcitation of endogenous porphyrins

The photodynamic sensitization of leukemic cells (erythrocytic, myelocytic and lymphocytic) via light activation of endogenous porphyrins is described. Human myelocytic-erythrocytic K562 cells and murine Friend erythroleukemia (FELC) and T-cell lymphoma Eb-Esb cells were stimulated to synthesize and accumulate porphyrins. K562 cells accumulated high amounts of protoporphyrin by stimulation with 5-aminolevulinic acid (ALA) plus sodium butyrate or hemin. For Friend and Eb-Ebs cells ALA was an adequate stimulator. The high-metastatic Esb lymphoma cells accumulated comparatively more porphyrin than the low-metastatic Eb cell line. Maximal porphyrin accumulation produced mortality rates of more than 99% after 10 min of photoactivation of the three leukemic lines. Thymidine incorporation was inhibited by the photodynamic effect depending on porphyrin concentration. These results confirm the photodynamic ability of endogenous porphyrins to inactivate cancer cells of different origins.

The partition and distribution of porphyrins in liposomal membranes. A spectroscopic study

Spectroscopic techniques were employed to establish the first comparative evaluation of the partition of the photosensitizers hematoporphyrin derivative (HPD) and photofrin II (PF-II) into phosphatidylcholine (PC) and PC/cholesterol liposomes. The fluorescence of the dyes was monitored while they were titrated with liposomes, yielding the dyes' effective binding constants to the membranes. The binding constants of HPD and PF-II to PC liposomes are 12.2 +/- 0.3 (mg/ml)-1 and 9.2 +/- 0.8 (mg/ml)-1 and to PC/cholesterol (50% w/w) liposomes they are 6.7 +/- 0.9 (mg/ml)-1 and 8.0 +/- 0.8 (mg/ml)-1, respectively. The vertical distribution of the dyes in the bilayer was determined by quenching their fluorescence with spin-labeled stearic acids. PF-II was found to reside deeper in the membrane than HPD. Cholesterol was found to modulate the distribution of the two dyes to a greater extent then DPPC and DMPC. The modulation mechanism is discussed.

A comparison of the phototoxicity of protoporphyrin, coproporphyrin and uroporphyrin using a cellular system in vitro

The photobiological effects of protoporphyrin (PP), coproporphyrin (CP) and uroporphyrin (UP) were investigated using an in vitro model. Suspensions of Ehrlich ascites carcinoma cells were labelled with 51Cr and irradiated in the presence of a wide range of concentrations of PP, CP and UP. It was found that PP was the most potent photosensitizer in this system; CP was less effective than PP and UP was the least potent. The cell lysis by CP was enhanced by superoxide dismutase (SOD) and inhibited by catalase; the lysis by UP was also inhibited by catalase; on the other hand, the lysis by PP was not affected by SOD or catalase. These indicate that the cell lysis by CP and UP was largely due to hydrogen peroxide produced from superoxide formed during the irradiation. The lysis produced by PP was not mediated by hydrogen peroxide. These differences in the mechanisms of the phototoxicity of the various porphyrins may have relevance in the etiology and treatment of the porphyrias.

Destruction of erythroleukaemic cells by photoactivation of endogenous porphyrins

Selective destruction of Friend erythroleukaemic cells (FELC) was potentiated by stimulation of endogenous porphyrin synthesis followed by light sensitization. Endogenous porphyrin biosynthesis in FELC was induced by supplementation of 5-amino levulinic acid (5-ALA) at a concentration of 5 X 10(-4) M. The main accumulated product, after 4 days culture, was uroporphyrin, while after 8 days culture the cells were loaded with protoporphyrin, up to 1.5 micrograms 10(-7) cells. Photoirradiation of the cells for 2 min, accumulating endogenous porphyrins, induced cardinal deformations and cell disintegration in greater than 95% of the cells, as examined by scanning electron microscopy (SEM). The photodynamic destruction effects were dependent on cultivation time with 5-ALA. Flow cytometry analysis showed an immediate expansion of cell volume subsequent to irradiation, presumably a consequence of water influx. Transmission electron microscopy (TEM) of photosensitized cells after different time intervals of culture in 5-ALA medium, revealed initial damage to mitochondria and water influx into the nuclear envelope, after 2 days. After 3-4 days in culture the water influx phenomenon was pronounced, chromatin condensation took place and slight rupture of the outer membrane was detected. Cells photosensitized after 5-6 days of culture were completely disintegrated leaving a nuclear remnant and an enormously swollen nuclear envelope. The culture time dependence of the process, showed an interrelationship between the photodynamic effect and porphyrin accumulation sites in cellular compartments. The study presents a specific method for erythroleukaemic cell inactivation.

Effects of membrane physical parameters on hematoporphyrin-derivative binding to liposomes: a spectroscopic study

Physical parameters of membrane bilayers were studied for their effect on the binding of hematoporphyrin derivative (Hpd), which is used as a sensitizer in photodynamic therapy of cancerous tissues. The purpose of this study was to clarify which parameters were relevant, under physiological conditions, to the selectivity of Hpd binding to cancer cells. Fluorescence spectroscopy was used to measure the relative partitioning of the dye between the lipid and aqueous media. Increasing the microviscosity of the liposomes' membranes by various bilayer additives results in a strong reduction of Hpd binding, to an extent independent of the specific additive. The effect of temperature near the physiological value as well as the effect of cross membrane potential are small. Surface potential does not affect the binding constant, indicating that the binding species does not carry a net electric charge.

Uptake and localisation of haematoporphyrin derivative in normal rat liver

Fluorescence microscopy and analytical subcellular fractionation were used to investigate the hepatic localisation of haematoporphyrin derivative (HPD) after intraperitoneal administration. HPD was found to rapidly accumulate in the liver and then to slowly decline over 48 hr. Fluorescence microscopy showed that although at early times porphyrins could not be localised to a particular cell type, at 24 hr porphyrins were preferentially localised to the Kupffer cells of the liver. Subcellular fractionation studies indicated that the initial rapid uptake of HPD was to the cytosol. However, at 24 hr, porphyrins appeared to be localised to lysosomes. Lysosomal localisation was confirmed using the selective organelle perturbant, Triton WR 1339. No evidence was found either at the light microscope level or by subcellular fractionation to suggest association of HPD with other organelles. HPLC analysis showed that the porphyrins present in the plasma and in the cytosol and lysosome fractions were mainly the (RS, SR) and (RR, SS) diastereoisomers of haematoporphyrin and the two position isomers 8-(1-hydroxyethyl)-3-vinyldeuteroporphyrin and 3-(1-hydroxyethyl)-8-vinyldeuteroporphyrin. There was no evidence for the involvement of dimers such as dihaematoporphyrin ether.

In vivo biological activity of the components of haematoporphyrin derivative

The in vivo biological activity of various fractions and components of haematoporphyrin derivative (HpD) have been determined by measuring the depth of necrosis of implanted tumours in mice exposed to light after the administration of standard doses of porphyrins dissolved in alkali. In this assay, haematoporphyrin, hydroxyethylvinyldeuteroporphyrin and protoporphyrin are inactive, but the mono- and di-acetates of haematoporphyrin (which are major components of HpD) and acetoxyethylvinyldeuteroporphyrin are active. However, the situation appears to be more complex than this. The normal method for preparing HpD for injection involves an alkali treatment which causes hydrolysis and elimination of the acetoxy functions, and the only recognized products (haematoporphyrin, hydroxyethylvinyldeuteroporphyrin and protoporphyrin) are inactive in the in vivo assay. It is concluded that the active component here is a porphyrin, possibly a dimer or oligomer, which is retained on the column during the normal separation by HPLC. This conclusion is supported by the observations that (i) the crude material obtained from the spent column is active without further alkali treatment, and (ii) activity develops over 30 min, when HpD or the mono- or diacetates of haematoporphyrin are treated with sodium bicarbonate in aqueous DMSO. The advantages of working with a pure substance (e.g. haematoporphyrin diacetate) rather than a mixture (HpD) are stressed.

Phototoxicity of protoporphyrin as related to its subcellular localization in mice livers after short-term feeding with griseofulvin

In mice, feeding with griseofulvin leads to the rapid accumulation of protoporphyrin in liver mitochondria. When liver mitochondria from mice fed with griseofulvin for 2 days are exposed to irradiation (320-400 nm), uncoupling of oxidative phosphorylation followed by inhibition of respiration occurs at light doses above 3-5 kJ/m2. When combined preparations of mitochondria and lysosomes are irradiated, inactivation of enzymes occurs in the following order: succinate dehydrogenase greater than glutamate dehydrogenase greater than acid phosphatase greater than beta-glucuronidase. Qualitatively, the photodamaging effect of endogenously produced protoporphyrin is indistinguishable from that of externally added protoporphyrin. Quantitatively, however, when protoporphyrin is added externally, more protoporphyrin is taken up by lysosomes, and photoinactivation of the lysosomal enzymes is correspondingly more severe. The results are further evidence that porphyrin-induced photodamage is largely determined by the solubility properties of the porphyrins and the target structures [Sandberg & Romslo (1980) Biochim. Biophys. Acta 593, 187-195], and also that protoporphyrin-induced photodamage is essentially similar whether protoporphyrin is generated endogenously or added exogenously.