Effect of photodynamic therapy mediated by hematoporphyrin derivatives on small cell lung cancer H446 cells and bronchial epithelial BEAS-2B cells

To investigate the effects of photodynamic therapy (PDT) mediated by hematoporphyrin derivatives (HPD) on the proliferation of small cell lung cancer H446 cells and bronchial epithelial BEAS-2B cells. H446 cells and BEAS-2B cells were cultured in vitro with different concentrations of HPD(0, 5, 10, 12, 15, 20 μg/mL) for 4 h, and then irradiated with 630 nm laser with different energy densities (0, 25, 50, 75, 100 mW/cm2). Cell viability of H446 cells and BEAS-2B cells were detected by CCK8 assay. The cell apoptosis was observed with Annexin V-FTTC/PI double staining and Hoechst 33258. The RT-PCR examination was applied to detect the transcriptional changes of the mRNA of Bax、Bcl-2, and Caspase-9. The results of CCK8 showed that when the HPD was 15 μg/mL and the laser power density reached 50 mW/cm2, the cell viability was significantly decreased compared with the black control group. Hoechst 33258 staining showed that with the increase of HPD concentration, the cell density was reduced, and apoptotic cells increased. Flow cytometry assay revealed that the apoptotic rates of the HPD-PDT group of H446 cells and BEAS-2B cells were significantly different from those of the blank control group. The RT-PCR examination showed that the expression levels of Bax and Caspase-9 mRNA in the HPD-PDT group were up-regulated, while the expression levels of Bcl-2 mRNA were down-regulated significantly. HPD-PDT can inhibit H446 cells and BEAS-2B cells growth. The mechanism may be related to up-regulating the expression levels of Bax and Caspase-9 mRNA and down-regulating the expression levels of Bcl-2 mRNA.

Light dose effect of photodynamic therapy on growth inhibition and apoptosis induction in non-small cell lung cancer: A study in nude mouse model

BACKGROUND

Photodynamic therapy (PDT) is receiving increasing attention in treating non-small cell lung cancer (NSCLC) worldwide, but in clinical practice, the relationship between treatment effect and PDT light dose in NSCLC remains unclear. Therefore, we aimed to determine the optimal light dose for PDT by exploring molecular biomarkers and evaluating tumor growth data.

METHODS

We applied bioinformatics to identify promising genes and pathways in NSCLC and PDT. Then, the human lung adenocarcinoma cell line A549-bearing BALB/c nude mice were treated with hematoporphyrin derivative (HPD, 3 mg/kg) that is currently used widely for lung cancer treatment in the world even with photosensitization issues. After 48 h, tumor-bearing mice were irradiated superficially at doses of 100, 200, 300, 400, and 500 J/cm2. The tumor growth data and apoptotic molecules were assessed and calculated.

RESULTS

Bioinformatics results indicated that the apoptosis pathway was significantly enriched and caspase 3 was the most promising biomarker on prognosis in NSCLC-PDT. Compared to the untreated group, there was no difference in the relative tumor volume (RTV) of the 100 J/cm2 group, while the RTV of the other treatment groups (200-500 J/cm2) was significantly lower. In the 100 J/cm2 group, there were significant differences in the complete remission (CR, 0 %) and the percentage of tumor growth inhibition rate (TGI%) over 75 % (20 %) compared with the other treatment groups, especially the 300 and 400 J/cm2 groups (CR 70 %; TGI% 90 %). In the 300 and 400 J/cm2 groups, the expression of caspase 3, cleaved-caspase 3, PARP1, and Bax was increased significantly, while Bcl-2 expression was significantly lower.

CONCLUSIONS

Moderate doses of PDT (300 or 400 J/cm2) are more effective than low (100 or 200 J/cm2) or high doses (500 J/cm2) in the A549 tumor-bearing mice model. Since the A549 tumor is more akin to human tumors in pathological behavior, these experimental data may contribute to improving HPD-PDT illumination protocols for favorable clinical outcomes.

The study of effect and mechanism of 630-nm laser on human lung adenocarcinoma cell xenograft model in nude mice mediated by hematoporphyrin derivatives

To investigate the effect and mechanism of 630-nm laser on human lung adenocarcinoma cell xenograft model in nude mice mediated by hematoporphyrin derivatives (HPD) and provide theoretical basis for clinical photodynamic therapy (PDT). Human lung adenocarcinoma cell xenograft model in nude mice was established and randomly divided into four groups: control group, pure photosensitizer group, pure irradiation group, and photodynamic treatment group. The tumor volume growth was compared, and the tumor growth inhibition rate was calculated. HE staining was used for routine pathological observation of tumor sections, and gross conditions of cells, interstitium, and blood vessels in several groups of tumor tissues were observed. TUNEL staining was used to observe and compare the apoptosis induced by photodynamic therapy. Real-time fluorescence quantitative reverse transcription polymerase chain reaction (RT-PCR) was used to detect the expression level of angiogenesis-related factors VEGF, HIF-1α and apoptosis-related factors Bax and Bcl-2 mRNA in the transplanted tumor tissues. Western blot was employed to detect the expression of angiogenesis-related proteins VEGF, HIF-1α and apoptosis-related proteins Bax, Caspase-3, and Bcl-2. Compared with the other three groups, the tumor growth inhibition rate of the photodynamic treatment group was significantly increased and the difference was statistically significant (P < 0.05). HE staining showed that the animal model of lung adenocarcinoma A549 was successfully established. TUNEL staining revealed that more apoptotic cells were found in the photodynamic treatment group, and the apoptosis index was calculated. Compared with the other three groups, the difference was statistically significant (P < 0.05). RT-PCR results showed that compared with the other three groups, the mRNA expressions of VEGF, HIF-1α, and Bcl-2 in the photodynamic treatment group decreased, while the expression of Bax mRNA increased(P < 0.05), and the differences were statistically significant. Western blot results showed that protein expressions of VEGF, HIF-1α, and Bcl-2 decreased in the photodynamic treatment group, while protein expression level of Bax and Caspase-3 increased (P < 0.05), indicating statistically significant differences. The 630-nm laser mediated by hematoporphyrin derivatives can significantly inhibit the growth of human lung adenocarcinoma xenograft tumor in nude mice, the mechanism of which is related to the inhibition of tumor angiogenesis by down-regulating VEGF and HIF-1α gene expression, and the promotion of tumor apoptosis by up-regulating Bax, Caspase-3, and down-regulating Bcl-2 gene expression.

The influence of electroporation on in vitro photodynamic therapy of human breast carcinoma cells

Phototoxicity of drugs used in cancer photodynamic therapy could be augmented by increased accumulation of a photosensitizer in target cells. The intracellular delivery mode that enhances drug transportation could facilitate therapy by reducing the exposure time. Doses of the administered drug and related side effects could be lowered, whilst maintaining the same therapeutic efficiency. Electroporation supports transport of many drugs by creating electric field-induced transient nanopores in the plasma membrane. In this study, the electroporation- assisted transport of a photosensitizer was tested in vitro in human breast carcinoma cell lines: wild-type (MCF-7/WT) and doxorubicin-resistant (MCF-7/DOX). The efficacy of photodynamic therapy alone and in combination with electroporation was evaluated by cell viability with MTT test, using a haematoporphyrin derivative as a model. The data presented show up to 10-fold greater efficacy of the combined method, with very significantly reduced drug exposure times.

Photo-oxidative action in cervix carcinoma cells induced by HPD - mediated photodynamic therapy

Photodynamic therapy leads to oxidative stress through the generation of free radicals. Oxidative stress causes damage to cellular macromolecules such as nucleic acids, proteins and lipids.

AIM

To examine the hematoporphyrin derivative (HpD) - mediated photodynamic effect on cervical adenocarcinoma cell line HeLa.

METHODS

The HpD localization in HeLa cells was analyzed by confocal microscopy with epi-fluorescence system. Lipid peroxidation (LPO) was estimated by measurement of the concentration of malondialdehyde, protein degradation - by modified Ellman's method, superoxide dysmutase (SOD) - using Ransod Kit. The expression of inducible nitric oxide synthase (iNOS) was detected by immunocytochemical staining.

RESULTS

The HpD was distributed all over the cytoplasm with preferential localization in the inner side of the plasma membrane and around the nuclear envelope. The process of photosensitizer distribution was time dependent. PDT-HpD increased the level of malonodialdehyde (MDA), SOD activity and the expression of iNOS in HeLa cells. However, PDT induced the decrease in the level of protein-associated thiol groups.

CONCLUSIONS

Our study showed the important role of PDT-mediated oxidative stress in HeLa cells. HpD-PDT might be alternative and less invasive approach for treatment of patients with cervical cancer resistant for standard chemotherapy and radiotherapy.

[Main factors affecting the effect of photodynamic therapy against human esophageal cancer cells in vitro]

OBJECTIVE

To evaluate the tumor cell-killing effect of photodynamic therapy against human esophageal cancer cells in vitro and identify the main factors affecting the effect.

METHODS

Human esophageal cancer Eca-109 cells were incubated for 24 h in vitro with hematoporphyrin derivative (HpD) and Photofrin at different concentrations prior to exposure to a light energy density of 15 J/cm(2) delivered from a DIOMED 630 PDT system. The cell killing effect was also evaluated for different HpD concentrations combined with 3 light energy densities (10, 30, and 50 J/cm(2)), respectively. The cell survival rate was measured using MTT assay, and fluorescence spectrometry was used to detect the intracellular photosensitizer fluorescence of the tumor cells after incubation with HpD for 4 h.

RESULTS

The cell survival rate after incubation with the two photosensitizers at different concentrations were significantly different, and under the 3 different light energy densities, incubation of the cells with different HpD concentrations also resulted in significantly different cell survival rates (P<0.05). At the 4 low photosensitizer concentrations and with different light energy densities, the cell survival rates were similar (P>0.05), but the 4 higher photosensitizer concentrations resulted in significant difference in the cells survival (P<0.05). Correlation analysis showed that the intracellular photosensitizer concentration was positively correlated to the photosensitizer concentrations in cell incubation (r=0.997).

CONCLUSION

When the light source remains constant, the light energy density, the kinds of photosensitizers and their concentrations are the main factors affecting the Eca-109 cell-killing effect of PDT.

[Hematoporphyrin derivative-mediated photodynamic therapy for human nasopharyngeal carcinoma: a comparative study with CNE2 and C666-1 cell lines in vitro]

OBJECTIVE

To investigate biological effect of hematoporphyrin derivative (HpD) photodynamic therapy (PDT) on in vitro cultured nasopharyngeal carcinoma (NPC) cell lines CNE2 and C666-1.

METHODS

CNE2 and C666-1 cells cultured in vitro were incubated in a medium containing HpD at different concentrations (0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, and 4.0 microg/ml) for 4 h followed by exposure to different light doses (2, 5, 10, and 20 J/cm2) using a diode laser at 630 nm with power density of 20 mW/cm2. After 24 h of incubation with HpD-PDT, the survival rate of CNE2 and C666-1 cells were analyzed by MTT assay.

RESULTS

HpD-PDT produced effective killing of CNE2 and C666-1 cells cultured in vitro, and the killing effects were positively correlated with HpD concentration and the irradiation dose. Exposure of CNE2 and C666-1 cells to irradiation dose of 20 J/cm2 resulted in the IC50 of 0.7 and 1.2 microg/ml, respectively (P<0.01). With the same HpD concentration and irradiation dose, the survival rate of C666-1 cells, however, was significantly higher than that of CNE2 cells (P<0.05).

CONCLUSION

HpD-PDT may result in effective killing of CNE2 and C666-1 cells cultured in vitro, although C666-1 cells are less sensitive to HpD-PDT than CNE2 cells.

Hydrogen Peroxide, Superoxide, and Hydroxyl Radicals are Involved in the Phototoxic Action of Hematoporphyrin Derivative against Tumor Cells

This study was aimed to estimate the participation of reactive oxygen species (ROS), other than singlet oxygen (1O2), in the antitumor effect of photodynamic therapy (PDT) with hematoporphyrin derivative (HPD) as well as to determine the ability of photoexcited HPD to the formation of protein peroxides that currently are regarded as a new form of ROS. Studies were performed on Ehrlich ascites carcinoma (EAC) cells, which were loaded with HPD in phosphate-buffered saline and then irradiated with red light at 630 run in the same buffer. Experiments indicated that H2O2 and oxygen radicals could mediate the tumoricidal action of HPD-PDT; we found that photosensitization of EAC cells with HPD leads to the formation of significant amounts of H2O2, superoxide (O2-.), and hydroxyl (OH.) radicals, which along with 1O2 were involved in photoinactivation of the cells in vitro. Our data showed that in EAC cells subjected to HPD-PDT, the generation H2O2, O2-., and OH. could be largely mediated by: (i) an increase in the activity of xanthine oxidase (XOD), due most probably to the conversion of xanthine dehydrogenase (XDH) to XOD via a Ca2+-dependent proteolytic process as well as oxidation of SH groups in XDH; and (ii) photooxidation of some cellular constituents (proteins). Another interesting finding of our studies is that in tumor cells subjected to HPD-PDT the Fenton-like reactions could play an important role in the generation of OH., and that cell-bound Cu/Zn-superoxide dismutase as well as catalase can protect tumor cells against the phototoxic action of HPD. In addition, we clearly demonstrated the ability of photoexcited HPD to the generation of protein peroxides in tumor cells. Studies suggest that 1O2 is the main agent responsible for the generation of protein peroxides in EAC cells treated with HPD-PDT, although other ROS (H2O2, O2-., and OH.) were also implicated in this process. However, further work is needed to clarify the significance of these peroxides in the antitumor effect of PDT with HPD.

Study of solar photosensitization processes on dermatophytic fungi

The antifungal activity of solar simulator was evaluated in presence of haematoporphyrin derivative (HPD), methylene blue (MB) and toluidine blue O (TBO) as photosensitizers. Seven dermatophytes were used as test fungi. The solar simulator at fluence rate 400 W/m2 for 30 minutes induced marked inhibition for spore germination of the photosensitized fungi. The rate of inhibition varied according to the fungal species and concentration of the photosensitizer. There was an increase in percentage inhibition of spore germination as the concentration of HPD or MB increased. Complete inhibition for spore germination of Trichophyton. verrucosum, T. mentagrophytes, and Miccrosporum canis was induced when these species were pretreated with 10(-3) M of HPD or MB before irradiation. Epidermophyton floccosum, T. rubrum, M. gypseum and T. violaceum were less sensitive to irradiation when pretreated with HPD or MB. On contrary, the maximum reduction in percentage spore germination was induced at the lowest concentration (10(-7) M) of TBO. The tested dermatophytes were mostly capable of producing different enzymes (keratinase, phosphatases, amylase, lipase). The separate application of radiation or photosensitizer was ineffective or exerted slight inhibition on enzyme production. However, the activity of the enzymes was drastically inhibited when the fungi were irradiated after their treatment with photosensitizer. T. verrucosum and T. mentagrophytes were the most sensitive. In a trail to apply a control measure against dermatomycosis using solar simulator radiation, the results revealed that the radiation was successful in curing the MB-photosensitized guinea pigs, artificially infected with T. verrucosum, T. mentagrophytes or M. canis. The percentage of recovery reached 100% in some treatments.

Effects of photodynamic treatment on biological antioxidant systems in rats

Effects of photodynamic treatments on inherent antioxidant metabolites and cellular defence enzymes have been investigated in rats. Wistar rats were grouped into untreated controls, light controls, hematoporphyrin derivative (Hpd) (treated with 5 and 10 mg Hpd/kg body weight and kept in dark) and sets treated with both Hpd and red light (dose 172 and 344 j/m2 ). After 2, 24, 48 and 72 hr of Hpd injection the rats sacrificed, livers quickly excised to analyze Hpd uptake, activities of enzymes like catalase, GSH-Px and antioxidants like GSH, vitamin A, vitamin E and vitamin C. The results showed that the loss of Hpd from liver as a function of post- injection time was non- linear. An increased generation of lipid radicals was observed in the groups treated with 5 mg Hpd and higher dose of light and in groups treated with 10 mg Hpd at both the doses of light. Combination of light and Hpd reduced hepatic GSH content with a concomitant reduction in GSH-Px. At higher doses of Hpd and light, there was a significant reduction in hepatic vitamin A levels. Combination of Hpd and light in all doses reduced vitamin E content in liver. The decreased biological antioxidant contents and GSH-Px may be attributed to their utilization for the scavenging of free radicals generated by Hpd and light in tissues. However, no change in catalase activity and vitamin C content in liver was noted in experimental rats. The results suggest that exposure to higher doses of Hpd with light alters oxidant stress system and TBARS content in rat.

Raman spectroscopic study of microcosmic photodamage of the space structure of DNA sensitized by Yangzhou haematoporphyrin derivative and Photofrin II

After calf thymus DNA has been photodamaged by Yangzhou haematoporphyrin derivative (YHPD) or Photofrin II, the Raman characteristic frequencies and the intensities of the bands assigned to various groups of the components of DNA change considerably. As a result of damage, homogeneous B-form calf thymus DNA becomes a mixture containing: (1) modified B-form DNA, which is shorter than the original because of double-helical DNA scission; (2) single-stranded DNA due to the breakage of some H-bonds and the lack of some bases, etc.

Determination of endogenous porphyrins and the maximal HpD tumor/normal skin ratio in SKH-1 hairless mice by light induced fluorescence spectroscopy

The treatment of skin tumors is an application of photochemotherapy (PCT) which involves an initial administration of a photosensitizer (PS) followed by irradiation with a light beam that causes the PS to produce cytotoxic oxygen species within the tumors. As the PS is also present in normal skin, it is necessary to know how it is distributed between the two tissues. In this study, we have used SKH-1 hairless mice bearing papillomas or carcinomas chemically induced. The biodistribution of hematoporphyrin derivative (HpD) and the tissue autofluorescence measurements were studied by light induced fluorescence spectroscopy. The tumor and normal autofluorescence spectra measured on control mice with papillomas or carcinomas had a very similar shape. However, the principal endogenous porphyrin peak at about 630 nm showed a fluorescence signal amplitude 2 (for papilloma) and 1.5 (for carcinoma)-fold higher than the one found for the normal skin. Moreover, the fluorescence intensity of carcinoma spectrum is 1.4-fold lower than the one of papilloma spectrum at 630 nm. The tissue autofluorescence can be used to distinguish tumor from normal skin and benign from malignant tumor. This difference in fluorescence intensity at 630 nm was directly related to the concentration of endogenous porphyrins in the tumor. Fluorescence intensity ratios between tumor and normal skin were measured 4, 8, 24, 48, 72 and 96 hours after intraperitoneal injection of HpD (5 mg/kg body weight). The best tumor/normal skin ratio was 6.2 for HpD and the time required to reach this ratio was 48 h. HpD showed a moderate selectivity since the ratio was higher than 1 during the four first days. Photodynamic therapy with the same dose of HpD used in this biodistribution study must also be carried out to verify that the maximal tumor/skin ratio corresponds to the maximal efficiency of HpD.

[Studies on purging leukemic cells by photosensitizer PSD-007 laser photoradiation in vitro]

The sensitivity to photosensitization mediated by the hematoporphyrin photosensitizer PSD-007 of acute promyelocytic leukemic cell line (HL-60) was compared with normal human hemopoietic progenitor cells. The results showed that the leukemic cells were more sensitive. After being treated with 10 micrograms.ml-1 PSD-007 followed by 2J.cm-2 copper vapor laser light irradiation, the clonogenic leukemic (HL-60) cells were reduced 98%, but the survival rate of human granulocyte-macrophage colony-forming units (CFU-GM) was 40 +/- 8%. Mixing of normal human marrow cells with leukemic (HL-60) cells (ratio 100:1) did not interfere with elimination of tumor cells. The ultrastructure changes of HL-60 cells treated by laser photoradiation was observed under the trans-electronic microscope. The mitochondria, endoplasmic reticulum and cell membrane were involved. This means that the cell biomembrane is the main target to be attacked. It is considered that PSD-007-laser photoradiation therapy is efficient for killing leukemic cells.

Delayed hyperresistance of endothelial cells to photodynamic inactivation after contact with hemin

Hemin (ferriprotoporphyrin IX), the oxidized prosthetic group of hemoglobin, is a potential source of prooxidant iron in heavily vascularized tumors. We have evaluated hemin's effects on photodynamic inactivation of bovine artery endothelial cells, using a partially purified oligomeric fraction of hematoporphyrin derivative (HPD-A) as the sensitizing agent. Confluent cells in 5% serum/RPMI medium showed a progressive loss of thiazolyl blue (MTT)-detectable viability when irradiated with broadband visible light in the presence of HPD-A. Cells pretreated with desferrioxamine (DFO) were substantially less sensitive to photokilling, implying that non-heme iron plays a role in cytotoxic activity. Hemin (10-20 microM) had remarkably different effects on photokilling, depending on the time interval between adding it to cells and exposing them to photodynamic action. For example, cells were more sensitive when photostressed immediately after 1 h hemin treatment and washing but much more resistant when photostressed 23 h later. Similar responses were observed when cells were challenged with glucose oxidase. Immunoblot analysis following hemin treatment revealed a progressive induction of the heavy (H) subunit of ferritin that paralleled the development of hyperresistance. After incubation with saturating levels of the synthetic iron donor [55Fe]ferric-8-hydroxyquinoline, hemin-stimulated cells contained about four times more immunoprecipitable ferritin 55Fe than controls. This is consistent with the notion that sequestration of toxic iron as a result of induction of H-chain-enriched ferritin is a key factor in hyperresistance. Inflammatory injury in tumor vasculatures could expose endothelial and neoplastic cells to chronic hemoglobin-derived iron. Consequent upregulation of ferritin could impact negatively on the efficacy of photodynamic therapy and other oxidant-based cancer therapies.

Hematoporphyrin derivative or phthalocyanine photosensitized hemolysis of erythrocytes under laser irradiation

The effect of laser irradiation on the photosensitized hemolysis of rabbit erythrocytes was investigated. Two photosensitizers of domestic production were used: Photohem (a hematoporphyrin derivative) and Photosense (sulfonated phthalocyanine aluminium). The hemolysis was activated by laser irradiation in the presence of Photohem or Photosense. The process depended on the irradiation dose, the concentration of the photosensitizers and on the time during which the erythrocytes were incubated with the photosensitizers. Three lasers with wavelengths 520, 632.8 and 850 nm were used. The photosensitized hemolysis of rabbit erythrocytes was found to be inhibited by antioxidants.

Altered expression of interleukin 6 and interleukin 10 as a result of photodynamic therapy in vivo

Photodynamic therapy (PDT), which can effectively destroy malignant tissue, also induces a complex immune response that potentiates antitumor immunity but also inhibits skin contact hypersensitivity (CHS) and prolongs skin graft survival. The underlying mechanisms responsible for these effects are poorly understood but are likely to involve mediation by cytokines. We demonstrate in a BALB/c mouse model that PDT delivered to normal and tumor tissue in vivo causes marked changes in the expression of cytokines interleukin (IL)-6 and IL-10 but not tumor necrosis factor alpha. IL-6 mRNA and protein are strongly enhanced in the PDT-treated EMT6 tumor. PDT also increased IL-6 mRNA in exposed spleen and skin. These data suggest that the general inflammatory response to PDT may be mediated at least in part by IL-6. In addition, IL-6 may modulate the local antitumor immune response. In contrast, IL-10 mRNA in the tumor decreases following PDT. Most importantly, IL-10 is markedly induced in the skin of mice exposed to a PDT regime that strongly inhibits the CHS response, and the kinetics of IL-10 induction coincide with the known kinetics of CHS inhibition. We propose that the enhanced IL-10 expression plays a role in the observed suppression of cell-mediated responses seen following PDT.

Influence of Photofrin on the hematopoietic accessory function of murine peritoneal cells

The porphyrin photochemotherapeutic agent Photofrin stimulates hematopoietic activity within the bone marrow (BM) and spleens of normal mice. We found that the intraperitoneal (i.p.) administration of Photofrin also caused a 3-4 fold increase in peritoneal cell (PC) numbers, particularly cells bearing granulocyte surface antigens. Little granulocyte-macrophage progenitor activity was detectable within the PC population of control and Photofrin-injected mice suggesting that Photofrin had elicited an influx of inflammatory cells into the region. In contrast to cells from control animals, PC obtained 6 h to 168 h after the i.p. injection of Photofrin exhibited a consistently inferior capacity to support the growth of BM colony forming units granulocyte-macrophage (CFU-GM). When PC from control or Photofrin-treated mice were added to the BM culture system in the presence of defined growth factors there was no effect on the number of colonies formed. This finding indicated that negative regulatory elements were not responsible for the reduced hematopoietic accessory activity exhibited by PC from Photofrin-treated mice. Supernatants conditioned by PC from Photofrin-injected mice poorly supported BM CFU-GM growth in vitro and in contrast to PC supernatants prepared from control mice did not contain detectable amounts of granulocyte-macrophage colony stimulating factor (GM-CSF). The cellular changes which occur within the peritoneal cavity represent bystander events not directly related to the hematostimulatory action of Photofrin.

Cellular accumulation and biological activity of hematoporphyrin derivative(L) in comparison with photofrin II

Hematoporphyrin derivative, a drug used in the photodynamic therapy of solid tumours was synthesized in the laboratory and was called Hpd(L). Physico-chemical and biological properties of this drug have been compared with Photofrin II, the commercially available drug. Both Hpd(L) and Photofrin II possess similar properties qualitatively. Quantitatively, Hpd(L) was half as active as Photofrin II in its efficacy in causing photodynamic cytotoxicity or in the optical densities at the absorption peaks. These differences could be due to the differences in the compositions. Hpd(L) is a non-purified complex mixture of a number of porphyrin derivatives whereas Photofrin II is a relatively purer compound consisting of di- and tri-hematoporphyrins linked through ether or ester bonds. In vitro cellular uptake and retention of these drugs has been found to be a passive process not involving energy expenditure. pH and temperature of the incubation media have been found to profoundly influence these processes, while a complex relation seems to exist between physiological state of a cell and accumulation of these photosensitizers.

Cooperative effects of photodynamic treatment of cells in microcolonies

Microcolonies of 2-8 Madison-Darby canine kidney cells (MDCK II) and Chinese hamster lung fibroblasts (V79) cells were incubated with the photosensitizer Photofrin and exposed to light, and the resulting number of dead cells per colony was determined. The distribution of this number was found to be incompatible with the assumption that cells are inactivated independently. The experimental distributions were significantly different from the binomial distribution expected from this assumption, but in accordance with a model in which an inactivated cell can inactivate adjacent cells with a certain probability. These findings are contrary to the common view that damage caused by radiation is limited to the cell in which the primary damage takes place. Our findings clearly indicate some kind of cooperativity between cells treated with Photofrin and light.

Production of lipid-derived free radicals in L1210 murine leukemia cells is an early oxidative event in the photodynamic action of Photofrin

Photofrin photosensitization initiates a sequence of oxidative events that begins with singlet oxygen formation and ultimately leads to cell death. We hypothesize that membrane lipid-derived free radical formation is an early event in this process. In the presence of iron and ascorbate, lipid free radicals are generated during cellular photosensitization of L1210 cells as detected by electron paramagnetic resonance spin-trapping techniques. Tocopherol levels decline in an inverse manner to lipid radical formation. Trypan blue dye exclusion by membranes also decreases inversely to lipid radical formation but at an initially slower rate than alpha-tocopherol depletion. Propidium iodide nuclear staining as an alternative measure of cell integrity was a later event, occurring when alpha-tocopherol levels had fallen by 90%, trypan blue survival had decreased to below 10%, and lipid radical formation was nearing plateau levels. Likewise, the formation of cellular debris did not occur substantially until alpha-tocopherol was virtually exhausted and radical intensity had nearly reached a maximum. These temporal observations suggest the following sequence of events that leads to Photofrin photosensitization-induced cytotoxicity in the presence of iron and ascorbate: (1) singlet oxygen-derived lipid hydroperoxide formation and subsequent radical production; (2) cellular alpha-tocopherol depletion; (3) trypan blue-detectable membrane leakage; (4) nuclear exposure to propidium; (5) cell disintegration. These observations are consistent with membrane lipid-derived free radical formation being an early and perhaps seminal event in photosensitization by Photofrin, which leads to a concatenated series of events terminating in cell destruction.

Differential response of photosensitized young and old human erythrocytes to photodynamic activation

It has recently been proposed that photosensitized erythrocytes may play an important role in the delivery and targeting of agents such as photosensitizers and chemotherapeutics for use in cancer treatment. It has been suggested that loading of photosensitized erythrocytes with chemotherapeutic agents would provide an ideal means of combining both treatment modalities. The recent application of real-time confocal laser scanning microscopy to the study of immediate effects of photodynamic activation on photosensitized erythrocytes has enabled us, in this study, to distinguish between the differential susceptibility of age-density resolved sub-populations of human erythrocytes to photodynamic activation. In this study we demonstrate that younger (low age-density) sub-populations of photosensitized erythrocytes are less susceptible than older (high age-density) sub-populations to photodynamic activation. We also demonstrate that this phenomenon is exhibited by cells photosensitized using hematoporphyrin derivative and rose bengal as photosensitizers. In both cases no significant difference in uptake of photosensitizer by both populations could be observed using absorbance spectrophotometry. The study suggests that age-density resolution of erythrocytes prior to loading and photosensitization might provide a means of enhancing the release of loaded components from the photosensitized system and this would, in turn, enhance the potential use of photosensitized erythrocytes as delivery or targeting systems for use in combination cancer therapies.

The mechanism of Photofrin photobleaching and its consequences for photodynamic dosimetry

We report experimental results that support a theory of self-sensitized singlet oxygen-mediated bleaching of the porphyrin photosensitizer Photofrin. Microelectrode measurements of photodynamic oxygen consumption were made near the surface of individual, Photofrin-sensitized EMT6 spheroids during laser irradiation. The progressive decrease in photochemical oxygen consumption with sustained irradiation is consistent with a theory in which bleaching occurs via self-sensitized singlet oxygen reaction with the photosensitizer ground state. A bleaching model based solely on absorbed optical energy density is inconsistent with the data. Photobleaching has a significant effect on calculated photodynamic dose distributions in 500 microns diameter spheroids. Dose distributions corrected for the effects of bleaching produce a new estimate (12.1 +/- 1.2 mM) for the threshold dose of reacting singlet oxygen in this system.

[In vitro comparison of the photodynamic activity of meso-tetra (m-hydroxyphenyl) chlorin and hematoporphyrin derivative]

Meso-tetra (hydroxyphenyl) chlorin (mTHPC) was evaluated in vitro in HT29 human colon adenocarcinoma cell line and compared with hematoporphyrin derivative (HpD). The incorporation kinetics, evaluated by flow cytometry showed that mTHPC and HpD cellular uptake was related to the incubation time until 12 hours, then a plateau appeared. Cytotoxicity assays were performed using MTT test after photoirradiation at 650 nm for mTHPC and 630 nm for HpD. The photodynamic activity of both photosensitizers was influenced by serum protein of the culture medium and time interval between irradiation and photocytotoxicity test with a maximal activity 24 and 48 hrs after the photoirradiation. In optimized experimental conditions i.e. 2% serum protein- containing culture medium, 24 hr-incubation period, cytotoxicity measured 48 hrs after exposure, 10 J/cm2 light fluence, mTHPC appeared approximately 20-fold more active than HpD with IC50 values of 0.2 micrograms/mL and 4.2 micrograms/mL, respectively.

The effects of electric fields on photosensitized erythrocytes: possible enhancement of photodynamic activation

In this study it has been found that exposure of photosensitized erythrocytes to short, intense electric pulses, resulted in cell lysis. When erythrocytes were photosensitized with increasing concentrations of the photosensitizer, hematoporphyrin derivative (HPD), and subjected to electric pulses in the absence of light, cell lysis increased with increasing photosensitizer concentration. In addition, it has been shown that exposure of photosensitized erythrocytes to electric field pulses of increasing field strength resulted in increased cell lysis. Light activation of photosensitized erythrocytes, pre-treated with electric pulses, also resulted in increased cell lysis. The results presented here suggest that HPD may be activated in the absence of light using electric pulses. We suggest that enhancement of activation by electric field stimulation may find application in increasing the overall efficiency of photodynamic therapy.

Spectroscopic and biological testing of photobleaching of porphyrins in solutions

The photobleaching of protoporhyrin IX (PP IX) and hematoporphyrin derivative (HpD) solutions was followed using three different methods: spectrophotometry, fluorometry and photodynamically induced cytotoxicity. The latter entails photoirradiation of HT29 human colon adenocarcinoma cells in the presence of preirradiated solutions of HpD and PP IX (lambda < or = 415 nm). The highest cytotoxicity was observed in the presence of unirradiated dye and decreased with the time of preirradiation. This decay in photocytotoxicity was further used to determine the porphyrin photobleaching kinetics in solution. For both sensitizers, quantum yields of photobleaching obtained by matching fluorescence were higher than that obtained from absorbance measurements (10 and 11 times for HpD and PP IX, respectively). This difference reflects preferential photobleaching of photolabile monomeric forms compared to aggregated. The highest quantum yield was obtained in the biological test (decay in cytotoxicity) which was 14 times higher for HpD and 30 times higher for PP IX than the quantum yield obtained from absorbance measurements. The absence of correlation between biological and fluorescence measurements has to be taken into account in the in vivo situation. Dark storage of preirradiated sensitizers (37 degrees C, 24 h) completely restored photocytotoxity for PP IX but only partially for HpD, whereas fluorescence patterns were partially restored for both sensitizers.

Strong and prolonged induction of c-jun and c-fos proto-oncogenes by photodynamic therapy

Photodynamic therapy (PDT) is currently under investigation in phase II and III clinical studies for the treatment of tumours in superficial localisations. Thus far, the underlying mechanisms of PDT regarding cellular responses and gene regulation are poorly understood. Photochemically generated singlet oxygen (1O2) is mainly responsible for cytotoxicity induced by PDT. If targeted cells are not disintegrated, photo-oxidative stress leads to transcription and translation of various stress response and cytokine genes. Tumour necrosis factor (TNF) alpha, interleukin (IL) 1 and IL-6 are strongly induced by photodynamic treatment, supporting inflammatory action and immunological anti-tumour responses. To investigate the first steps of gene activation, this study focused on the proto-oncogenes c-jun and c-fos, both coding for the transcription factor activator protein 1 (AP-1), which was found to mediate IL-6 gene expression. We here determine the effects of photodynamic treatment on transcriptional regulation and DNA binding of transcription factor AP-1 in order to understand the modulation of subsequent regulatory steps. Photodynamic treatment of epithelial HeLa cells was performed by incubation with Photofrin and illumination with 630 nm laser light in vitro. Expression of the c-jun and c-fos genes was determined by way of Northern blot analysis, and DNA-binding activity of the transcription factor AP-1 was evaluated by electrophoretic mobility shift assay (EMSA). Photofrin-mediated photosensitisation of HeLa cells resulted in a rapid and dose-dependent induction of both genes but preferential expression of c-jun. Compared with the transient expression of c-jun and c-fos by phorbol ester stimulation, photodynamic treatment led to a prolonged activation pattern of both immediate early genes. Furthermore, mRNA stability studies revealed an increased half-life of c-jun and c-fos transcripts resulting from photosensitisation. Although mRNA accumulation after PDT was stronger and more prolonged compared with phorbol ester stimulation, with regard to AP-1 DNA-binding activity, phorbol ester was more efficient. Surprisingly, in addition to the activation of AP-1 DNA-binding via PDT, photodynamic treatment can decrease AP-1 DNA-binding of other strong inducers, such as the protein kinase C-mediated pathway of phorbol esters and the antioxidant pyrrolidine dithiocarbamate (PDTC). This study demonstrates a strong induction of c-jun and c-fos expression by PDT, with prolonged kinetics and mRNA stabilisation as compared with activation by phorbol esters. Interestingly, this observation is not coincident with an overinduction of AP-1 DNA-binding, hence suggesting that post-translational modifications are dominant regulatory mechanisms after PDT that tightly control AP-1 activity in the nucleus thus limiting the risk of deregulated oncogene expression.

Photodynamic therapy-mediated oxidative stress can induce expression of heat shock proteins

Photodynamic therapy (PDT) is an experimental cancer therapy inducing tumor tissue damage via photosensitizer-mediated oxidative cytotoxicity. A previous report indicates that oxidative stress induced by hydrogen peroxide or menadione activates the heat shock transcription factor in mouse cells but does not result in either increased transcription or translation of heat shock proteins (HSPs). Our study documents that photosensitizer-mediated oxidative stress can activate the heat shock factor as well as increase HSP-70 mRNA and protein levels in mouse RIF-1 cells. The cellular heat shock response after PDT varied for the different photosensitizers being examined. Treatments using either a chlorin (mono-L-aspartyl chlorin-e6)- or purpurin (tin etio-purpurin)-based sensitizer induced HSP-70 expression, whereas identical photosensitization conditions with a porphyrin (Photofrin)-based sensitizer failed to induce a cellular HSP response. These sensitizers, which generate singlet oxygen as the primary oxidant during photosensitization, were used in experiments under isoeffective treatment conditions. HSP-70 expression after photosensitization was associated with the concomitant induction of thermotolerance in PDT-treated cells. Interestingly, reverse transcription-PCR demonstrated that in vivo PDT treatments of RIF-1 tumors induce expression of HSP-70 for all photosensitizers including Photofrin. These results indicate that photosensitizer-generated singlet oxygen exposure can induce in vitro and in vivo HSP-70 expression, and that specific subcellular targets of PDT (which can differ for various sensitizers) are determinants for HSP-70 activation after oxidative stress.

The killing of Helicobacter pylori by low-power laser light in the presence of a photosensitiser

Helicobacter pylori is associated with various gastrointestinal disorders. Lethal photosensitisation was investigated as a possible technique for killing H. pylori which might offer a better alternative to antibiotics. The susceptibility of H. pylori to lethal photosensitisation was determined by mixing suspensions of H. pylori with various photosensitisers and plating out on blood agar before irradiation with low-power laser light. Five sensitisers were studied further by mixing them with H. pylori in a tissue-culture plate and counting survivors after irradiation as a function of laser exposure time, dye concentration and pre-irradiation time. Crystal violet and thionine were ineffective as sensitisers, but zones of inhibition appeared with methylene blue (MB), protoporphyrin IX (PPIX), haematoporphyrin derivative (HPD), toluidine blue O (TBO) and disulphonated aluminium phthalocyanine (S2). Laser light or sensitiser alone did not affect bacterial viability. S2 (100 microg/ml) with a laser light energy density of 16 J/cm2, HPD (10O microg/ml) with 160 J/cm2, MB (100 microg/ml) with 21 J/cm2, PPIX (150 microg/ml) with 320 J/cm2 and TBO (50 microg/ml) with 160 J/cm2 all reduced bacterial viability by >99%. The killing of sensitised H. pylori by laser light offers a new approach to the treatment of localised infections when all colonised areas are accessible to light.

Spectroscopic studies of photobleaching and photoproduct formation of porphyrins used in tumour therapy

The illumination of haematoporphyrin, meso-tetraphenylporphyrin tetrasulphonate and haematoporphyrin derivative in aqueous solution causes two simultaneously occurring processes: photodegradation and the formation of stable photoproducts absorbing in the red spectral region. In the case of haematoporphyrin and its derivatives, these photoproducts have an absorption maximum around 640 nm (photoproduct 640). The former process, which is detected as the bleaching of the porphyrin absorption spectrum as well as a decrease in the fluorescence intensity, is slightly dependent on the solution pH and becomes dominant when the formation of the photoproduct reaches saturation. For the most part, the photodegradation can be explained as the opening of the porphyrin ring, leading to an increase in light absorbance in the UV region. The formation of photoproduct 640 is closely related to the aggregation state of the porphyrins, and shows a distinct dependence on the medium pH. The effectiveness of photoproduct 640 formation strongly increases in neutral and alkaline solutions, whereas the porphyrins are photostable below pH 5. The spectroscopic features of the photoproducts of haematoporphyrin and haematoporphyrin derivative, with absorption bands in the visible region, are similar to those of chlorin and/or porphyrin-chlorin linked systems. On the basis of these spectroscopic studies, it is suggested that photoproduct 640 is a chlorin-type molecule formed predominantly from the aggregates of porphyrins when photo-oxidation and photoreduction are in competition.

Subcellular distribution and photocytotoxicity of aluminium phthalocyanines and haematoporphyrin derivative in cultured human meningioma cells

The photocytotoxicity characteristics of aluminium phthalocyanine chloride (AIPc), aluminium phthalocyanine disulphonate (AlS2Pc), aluminium phthalocyanine tetrasulphonate (AlS4PC) and haematoporphyrin derivative (HpD) were compared using primary cultures of human meningioma cells. Cells were preincubated with the photosensitising agent for 16 h, then illuminated for 15 min with broad band red light (5 OW/cm2). The resultant cytotoxicity was assessed by tetrazolium (MTT) reduction 24 h later. AlPc was found to be 400, 10,000 and 250 times more potent that AlS2Pc, AlS4Pc and HpD, respectively, as an in vitro photosensitizing agent for meningioma cells. The subcellular localisation of AlPc, AlS2Pc, AlS4Pc and HpD in meningioma cells was determined by confocal laser scanning microscopy. None of the agents localized to the nucleus. The distribution of ALPc was quite diffuse through the cytoplasm. In contrast, AlS2Pc and AlS4Pc were localized vesicles suggestive of lysosomes, and HpD in membranous organelles distinct from mitochondria. AlPc and HpD were tested with five different meningioma samples and provided a range of IC50 values from 0.009 to 0.022 OM and from 3.5 to 6.5 OM, respectively. When the MTT assay with AlPc was performed 0, 24, 48 and 72 h after illumination, the mean IC50 values were 0.25, 0.037, 0.019 and 0.012 OM, respectively, indicating that the cytotoxic effect continued to increase up to 72 h. Cells were incubated with AlPc and HpD for different times up to 24 h before exposure to light. AlPc cytotoxicity was half-maximal with an incubation time of 8 h, whereas HpD cytotoxicity was half-maximal with an incubation time of 2 h, implying slower uptake kinetics for AlPc than for HpD. These data indicate unique features of AlPc which suggests its application as a potent, non-toxic photosensitizer in the photodynamic therapy of human meningiomas.

Photodynamic effects on human and chicken erythrocytes studied with microirradiation and confocal laser scanning microscopy

BACKGROUND AND OBJECTIVE

Photodynamic therapy (PDT) of cancers is associated with the destruction of the microvasculature supplying the tumor. The study elucidates the role of red blood cells in PDT-induced vascular injury.

STUDY DESIGN/MATERIALS AND METHODS

Intracellular accumulation of several photosensitizers in human (non-nucleated) and chicken (nucleated) erythrocytes, as well as photodynamic induced hemolysis were studied using 488 nm laser microirradiation (15 microW) and confocal laser scanning fluorescence microscopy.

RESULTS

Cells incubated with anionic hydrophilic compounds TPPS4 and Pd-TPPS4 exhibited no fluorescence before irradiation, but developed strong and sustained fluorescence in the cellular and nuclear membranes following photoinduced membrane damage. In contrast, microirradiation of Photofrin-incubated erythrocytes showed instantaneous fluorescence which decreased due to photodegradation. For the cationic hydrophilic dye methylene blue, significant fluorescence was detected only in the nucleus. Following ALA incubation, large intercellular differences were observed in fluorescence in the red spectral region. Photofrin induced the most efficient hemolysis. Higher radiant exposures were required for lysis of nucleated rather than of non-nucleated red blood cells, except in the case of methylene blue.

CONCLUSION

Laser microbeams were used, for the first time, to study photodynamic cell damage. Erythrocytes were shown to be primary targets in PDT. Damage to red blood cells could be responsible for hemostasis in the vascular bed of a tumor, which was reported by many groups.

Ex-vivo treatment of gastric Helicobacter infection by photodynamic therapy

Attempts to develop PDT for eradication of Helicobacter infection have only been successful in vitro. We have investigated the effect of topical sensitization (except ALA) of Helicobacter mustelae on explanted ferret gastric mucosa using one of five sensitizers (methylene blue (MB), toluidine blue O (TBO), phthalocyanine, haematoporphyrin derivative and 5-aminolavulinic acid), followed by irradiation with an appropriately tuned copper vapour pumped dye laser. A 90% reduction in counts of bacteria sensitized with 0.75 mg TBO kg-1 were seen after irradiation with 200 J cm-2. Concentrations of MB of 0.75 mg kg-1 and 7.5 mg kg-1 were not toxic to H. mustelae, but the further addition of 20 J cm-2 laser light reduced colony counts by more than 99%. MB at a concentration of 75 mg kg-1 exhibited significant dark toxicity towards H. mustelae, but further addition of 20 J cm-2 laser light resulted in near eradication of all colonies. The remaining three compounds were ineffective. Finally, we studied the microscopic fluorescence distribution of MB (7.5 mg kg-1) on ferret gastric mucosa after topical administration. Fluorescence was greatest in the superficial mucosal layer, upon which lies the bacteria. However, from experiments on rats, the energy required to kill the sensitized bacteria was insufficient to damage the underlying mucosa. We conclude that Helicobacter can be killed on host mucosal epithelium following topical administration of MB and subsequent exposure to laser light.

Effect of hematoporphyrin derivative and light on sulfhydryl groups in brain tumour cells

Effect of hematoporphyrin derivative (HpD) and light on sulfhydryl (SH) groups in brain tumor cells was studied. Sulfhydryl groups were measured by 5,5'-dithiobis-(2-nitrobenzoic acid) (DTNB) and a fluorescent probe 3,4-maleimidylphenyl-4-methyl-7-diethylaminocoumarin (CPM). Incubation of cells with HpD in dark resulted in the loss of DTNB as well as CPM reactive SH groups. After 2 hr of incubation DTNB reactive SH groups showed a negligible change while a continuous decrease was observed in CPM reactive SH groups. Cells treated with HpD showed a further degradation of SH groups upon light irradiation. A comparison of cytotoxicity and SH groups under identical conditions showed that blockage of SH groups by HpD binding is not leathal to the cells where as photoinduced cell death was observed on photodegradation of SH groups.

[Photodynamic effect of HPD on DNA functions]

After treatment of the DNA by HPD and light the number of transformants of the M13mp8 DNA obviously decreased during the period of transforming the treated DNA into E coli. Meanwhile some of the mutation sequences appeared in the DNA which recovered from the DNA/HPD/Light transformant. It showed that the wrong replication happened because of the mutated template. Also the in vitro run-off transcription of IL-2R alpha gene was affected by HPD and light. It means that the DNA functions are influenced by the photodynamic effects.

Interaction of photodynamically induced cell killing and dark cytotoxicity of rhodamine 123

Loss of clonogenicity of Chinese hamster ovary (CHO) cells, murine L929 fibroblasts and human bladder carcinoma T24 cells caused by photodynamic treatment (PDT) with hematoporphyrin derivative (HPD) is synergistically enhanced by subsequent incubation with rhodamine 123 in the dark. For CHO and L929 cells this synergistic interaction can be explained by an increased uptake of rhodamine 123 as the result of the photodynamic treatment. With aluminum phthalocyanine (AIPC) as photosensitizer only additive effects were observed in the three cell lines. Incubation in the dark with rhodamine 123, followed by a photodynamic treatment with HPD, resulted in an antagonistic interaction with regard to loss of colony formation. With AIPc the combination of treatments resulted in an additive effect with L929 and T24 cells, whereas with CHO cells a slight antagonistic interaction was observed. An antagonistic effect was also observed in model experiments, treating histidine photodynamically with HPD and measuring oxygen consumption. A possible explanation of these results could be an interaction or complex formation of rhodamine 123 with HPD resulting in a diminished singlet oxygen production. With AIPc this does not take place.

Correlation of distribution of sulphonated aluminium phthalocyanines with their photodynamic effect in tumour and skin of mice bearing CaD2 mammary carcinoma

A chemical extraction assay and fluorescence microscopy incorporating a light-sensitive thermoelectrically cooled charge-coupled device (CCD) camera was used to study the kinetics of uptake, retention and localisation of disulphonated aluminium phthalocyanine (A1PcS2) and tetrasulphonated aluminium phthalocyanine (A1PcS4) at different time intervals after an i.p. injection at a dose of 10 mg kg-1 body weight (b.w.) in tumour and surrounding normal skin and muscle of female C3D2/F1 mice bearing CaD2 mammary carcinoma. Moreover, the photodynamic effect on the tumour and normal skin using sulphonated aluminium phthalocyanines (A1PcS1, A1PcS2, A1pcS4) and Photofrin was compared with respect to dye, dye dose and time interval between dye administration and light exposure. The maximal concentrations of A1PcS2 in the tumour tissue were reached 2-24 h after injection of the dye, while the amounts of A1PcS4 peaked 1-2 h after the dye administration. A1PcS2 was simultaneously localised in the interstitium and in the neoplastic cells of the tumour, whereas A1PcS4 appeared to localise only in the stroma of the tumour. The photodynamic efficiency (light was applied 24 h after dye injection at a dose of 10 mg kg-1 b.w.) of the tumours was found to decrease in the following order: A1PcS2 > A1PcS4 > Photofrin > A1PcS1. Furthermore, photodynamic efficacy was strongly dependent upon dye doses and time intervals between dye administration and light exposure: the higher the dose, the higher the photodynamic efficiency. The most efficient photodynamic therapy (PDT) of the tumour was reached (day 20 tumour-free) when light exposure took place 2 h after injection of A1PcS2 (10 mg kg-1). A dual intratumoral localisation pattern of the dye, as found for A1PcS2, seems desirable to obtain a high photodynamic efficiency. The kinetic patterns of uptake, retention and localisation of A1PcS2 and A1PcS4 are roughly correlated with their photodynamic effect on the tumour and normal skin.

Effect of hematoporphyrin derivative on hematological parameters in rats

Wistar rats were injected with hematoporphyrin derivative (Hpd) intraperitoneally and kept in the dark. Rats were sacrificed 2,24,48 and 72 h after injection. It was observed that Hpd in the dark did not affect the hemoglobin content and number of erythrocytes, while the leukocyte count was increased and blood pH decreased. Blood levels of glucose and lactate were increased significantly. Because the food intake was similar in all the groups, glycogenolysis was suspected to be the source of increased glucose levels in blood. However, a significant increase in the glycogen content of the livers of Hpd-treated rats was observed, which rules out glycogenolysis. Hyperglycemia may result due to a number of reasons such as stimulation of the central nervous pathways innervating the liver and adrenal medulla, excessive glucogenesis in liver from glycogen and noncarbohydrate sources, emotional stress, anesthesia and hormonal effects. The present study rules out hyperglycemia due to anesthesia and glucogenesis in the liver. Maintenance of blood glucose levels is a highly complex mechanism. Further investigations to understand these mechanisms are in progress.

Alterations in erythrocyte band 3 organization induced by the photosensitizer, hematoporphyrin derivative

Photosensitization of erythrocytes in the presence of hematoporphyrin derivative causes cross-linking of membrane proteins. This cross-linking is associated with partial lysis of the cells and an increased susceptibility to heat-induced membrane fragmentation. The effect of photosensitization on the organization of erythrocyte band 3 was monitored using the technique of time-resolved phosphorescence anisotropy. Band 3 rotational diffusion was somewhat restricted upon photooxidation, indicating aggregation of this major integral membrane protein.

Mechanisms for optimising photodynamic therapy: second-generation photosensitisers in combination with mitomycin C

Mechanisms for improving photodynamic therapy (PDT) were investigated in the murine RIF1 tumour using meso-tetrahydroxyphenylchlorin (m-THPC) or bacteriochlorin a (BCA) as photosensitisers and comparing these results with Photofrin-mediated PDT. The 86Rb extraction technique was used to measure changes in perfusion at various times after interstitial PDT. Non-curative combinations of light doses with m-THPC and BCA PDT markedly decreased vascular perfusion. This decrease was more pronounced for both new photosensitisers than for Photofrin. Comparison of tumour perfusion after PDT with tumour response revealed an inverse correlation for all three photosensitisers, but the relationship was less clear for m-THPC and BCA. In vivo/in vitro experiments were performed after Photofrin or m-THPC PDT in order to assess direct tumour kill (immediate plating) vs indirect vascular effects (delayed plating). For both photosensitisers, there was little direct cell killing but clonogenic survival decreased as the interval between treatment and excision increased. When m-THPC PDT was combined with mitomycin C (MMC), light doses could be decreased by a factor of 2 for equal tumour effects. Lower light and m-THPC doses could be used compared with Photofrin PDT in combination with MMC. BCA PDT with MMC did not result in a greater tumour response compared with BCA PDT alone. Reduction in both light and photosensitiser does for effective PDT regimes in combination with MMC offers substantial clinical advantages, since both treatment time and skin photosensitisation will be reduced.

Isolation and photodynamic effects of hematoporphyrin derivative components: a chromatographic analysis of the starting materials

Twenty different fractions of hematoporphyrin derivatives (HpD) and eight fractions of an HpD dimer mixture were isolated utilizing isocratic reversed-phase ion-pair high-performance liquid chromatography. These fractions were characterized by UV-visible and fluorescence spectrophotometry. Fluorescence quantum yields and photokill efficiency for each fraction in PTK2 epithelial cells were obtained. Results indicate that some part of the photoactivity exhibited by HpD may be due to impurities present in the HpD starting material, hematoporphyrin-IX dihydrochloride, depending on its source. It was also found that hematoporphyrin D, a commercial acetylated product formed during synthesis of HpD, contained a higher percentage of monomers than would be expected.

Lack of reciprocity in drug and light dose dependence of photodynamic therapy of pancreatic adenocarcinoma in vitro

Two human pancreatic cell lines, MIA PaCa 2 and Capan 2, were treated by photodynamic therapy in vitro with Photophrin (0.01-25 micrograms/ml; 24 h) and then light (1-50 J/cm2; lambda = 630 nm). The following model was fit to 6 datasets with weighted nonlinear regression: [sequence: see text] The symbols are: E, cell growth; Econ, control growth in the absence of the combination; B, background signal; m, slope parameter; gamma, interaction parameter; D, concentration of Photofrin; L, light dose; F, fraction of Photofrin not photobleached by the light dose; k, k1, k2, bleaching parameters; A, distribution parameter for biexponential bleaching equation. Simple reciprocity of photosensitizer concentration and light dose was not found; compensation for photobleaching was critical. MIA PaCa2 required the monoexponential bleaching factor, whereas Capan 2 required the biexponential bleaching factor. The greater photosensitivity of MIA PaCa2 over Capan 2 can be best explained not by differences in the interaction parameter but rather by differences in the photobleaching pattern and rate. It may be possible to further enhance the selectivity of photodynamic therapy if differences in photobleaching between different cell types can be exploited by adequate dosimetry.

Selective elimination of malignant stem cells using photosensitizers followed by light treatment

The pros and cons of purging of either bone marrow or peripheral blood stem cell preparations for autologous transplantation for cancer has been debated strongly over the past decade. Recent data implicating the role of minimal residual disease in autografted marrow in cancer relapse have renewed interest in this question. There is a considerable body of literature supporting the possibility that photosensitizer molecules in combination with light might provide a therapeutic window permitting selective elimination of malignant stem cells while sparing those of normal lineage. Molecules of this class are known to be taken up more actively by most malignant cells, and intracellular concentrations are critical in their cytotoxic effect when they are activated by light at an appropriate wavelength. The present paper reviews the observations made over the past decade on a variety of photosensitizers and their effects on hemopoietic progenitors.

Photodynamic therapy induces expression of interleukin 6 by activation of AP-1 but not NF-kappa B DNA binding

Inducibility and regulation of the pleiotropic cytokine interleukin 6 (IL-6) upon photodynamic therapy (PDT) was studied in the epithelial cell line HeLa. Photofrin-mediated photosensitization resulted in a rapid and dose-dependent induction of IL-6 mRNA production. Maximal levels were reached after 4 h and had decreased to baseline levels after 24 h. This photochemical induction of IL-6 transcription was followed by a strong secretion of IL-6 protein. In comparison to stimulation by 12-O-tetradecanoylphorbol-13-acetate, the kinetics of IL-6 mRNA and protein synthesis after PDT were delayed, although the maximal amounts of secreted IL-6 protein were comparable. As compared to UV irradiation, on the other hand, PDT-induced IL-6 protein levels were 2- to 10-fold higher and were detectable 4 h earlier. Several potentially relevant regulatory DNA elements of the IL-6 promoter were analyzed by gel retardation assays for PDT-induced protein binding. Interestingly, increased AP-1 DNA binding was detected only at the distal AP-1-specific motif and not at the proximal site, differing in 1 bp. Binding of c-Fos-containing AP-1 heterodimers to the specific motif was up-regulated 30 min after PDT, reaching maximal activity at 4 h. This PDT-induced AP-1 activation was independent from protein kinase C activity. Photosensitization did not induce increased binding at the well-characterized NF-kappa B element, nor at the multiple cytokine- and second messenger-responsive element of the IL-6 promoter. By analyzing the molecular mechanisms of IL-6 up-regulation upon PDT, we provide evidence for regulatory differences compared to UV light, ionizing irradiation, or stimulation by phorbol ester. Furthermore, this study suggests that the "proinflammatory" cytokine IL-6 might be involved in the inflammatory reaction and subsequent immunological antitumor responses.

Decreased expression and function of alpha-2 macroglobulin receptor/low density lipoprotein receptor-related protein in photodynamic therapy-resistant mouse tumor cells

Parental and photodynamic therapy (PDT)-resistant mouse, radiation-induced fibrosarcoma cell lines were evaluated using mRNA differential display in an attempt to identify unique transcripts. We detected one transcript that was consistently present in the parental cells but absent in PDT-resistant cells. The transcript was cloned, sequenced, and identified as alpha-2 macroglobulin receptor/low density lipoprotein receptor-related protein (alpha-2 MR/LRP). Northern and Western immunoblot analysis confirmed that receptor expression was present in the parental cell line but barely detectable in PDT-resistant cells. Functionality of the receptor was evaluated by exposing cells to Pseudomonas exotoxin A. alpha-2 MR/LRP is responsible for Pseudomonas exotoxin A internalization, and only the parental cells exhibited toxin-mediated cytotoxicity. The binding and endocytosis of activated alpha-2 macroglobulin and lipoproteins by alpha-2 MR/LRP are consistent with modulating uptake and localization of photosensitizers. Our results demonstrate that PDT-resistant murine tumor cells exhibit minimal alpha-2 MR/LRP activity and suggest that this receptor plays a role in PDT sensitivity by modulating photosensitizer uptake and/or subcellular localization.

[The DNA damage by photodynamic effects of hematoporphyrin derivatives (HPD)]

Photodynamic effects of HPD has been used for cancer therapy (PDT) successfuly. The biological mechanism of the PDT was studied by using DNA as a target in this work. After treatment of phage M13 DNA with HPD + light the molecule of the DNA kept intact in TE buffer. But the smear bands by puting DNA in 0.1 mol/L NaOH at 90 degrees C and separating with electrophoresis denoted the degradation of DNA at the alkali-labile sites of phosphodiester bond in which the groups of the bases were photooxydized. The primer extension experiment showed the aggregation of DNA template by photooxydation. The DNA sequencing results showed that some of the wrong sequences appeared both at the site of A,G,C,T bases. The mouse Ehrlich ascetes carcinoma cell DNA was treated as above then degraded by Bgl II and BamH I respectively. It was found that the restriction fragments became larger than the controls. It also meant the alteration of the bases of DNA by the photooxydation. So the four bases of A,G,C,T of DNA were altered by photodynamic effects of HPD.

Inhibition of the ATPase activity of P-glycoprotein by porphyrin photosensitization of multidrug-resistant cells in vitro

The effectiveness of photodynamic therapy against P-glycoprotein ATPase activity in multidrug-resistant cells was studied. Chinese hamster ovary AUXB1 (drug-sensitive) and CR1R12 (multidrug-resistant) cell lines were compared with respect to uptake of 14C-polyhematoporphyrin and porphyrin photosensitization. Phototoxicity of Photofrin was similar in both cell lines, and no major differences in uptake or efflux of 14C-polyhematoporphyrin were observed. Porphyrin photosensitization in vitro of CR1R12 cells or isolated plasma membranes from these cells caused inhibition of P-glycoprotein ATPase activity. Application of porphyrin photosensitization at a sublethal level to CR1R12 cells resulted in a small but significant increase in adriamycin-induced cytotoxicity. The hydrophobic "picket-fence" porphyrin, meso-tetrakis-(o-propionamidophenyl)porphyrin, alpha,alpha,alpha,beta-isomer, was more inhibitory toward P-glycoprotein ATPase activity than the two less hydrophobic porphyrins tetraphenylporphine tetrasulfonate and Photofrin.

Photosensitizing efficacy of MTHPC-PDT compared to photofrin-PDT in the RIF1 mouse tumour and normal skin

The new photosensitizer, meso-tetrahydroxyphenylchlorin (mTPHC) was compared with Photofrin in the murine RIF1 tumour and in normal mouse skin. A range of mTHPC or Photofrin doses were given at intervals of 1 hr to 7 days before illumination. mTHPC-PDT resulted in much higher tumour phototoxicity with longer regrowth delays and more cures. The RIF1 tumour could be effectively treated with 30 J cm-1 (interstitial illumination) at 1 day after mTHPC, whereas 4 to 13 times higher light doses were required with Photofrin for an equivalent anti-tumour effect. High doses of mTHPC also caused more skin phototoxicity (superficial illumination) than Photofrin for the 1-day illumination interval. Evaluating both tumour and normal skin photosensitization, the largest therapeutic gain factor (TGF) for mTHPC-PDT was achieved with a low drug dose (0.15 mg kg-1) at 1 day before illumination (TGF = 5.6, relative to Photofrin PDT). The duration of cutaneous photosensitivity for mTHPC was shorter than for Photofrin. The light dose required to produce a desquamation response in 50% of the animals increased more than 20-fold over the period 1 to 7 days after high doses of mTHPC, whereas this light dose only increased by a factor of 2 from 1 to 7 days after Photofrin. The large therapeutic gains seen for mTHPC-mediated PDT compared to Photofrin, plus the rapid fading of skin photosensitization, suggest that mTHPC is a potent photosensitizer suitable for clinical testing.

Studies of porphyrin-containing specimens using an optical spectrometer connected to a confocal scanning laser microscope

A spectrometer has been developed for use with a confocal scanning laser microscope. With this unit, spectral information from a single point or a user-defined region within the microscope specimen can be recorded. A glass prism is used to disperse the spectral components of the recorded light over a linear CCD photodiode array with 256 elements. A regulated cooling unit keeps the detector at 277 K, thereby allowing integration times of up to 60 s. The spectral resolving power, lambda/delta lambda, ranges from 350 at lambda = 400 nm to 100 at lambda = 700 nm. Since the entrance aperture of the spectrometer has the same size as the detector pinhole used during normal confocal scanning, the three-dimensional spatial resolution is equivalent to that of normal confocal scanning. Light from the specimen is deflected to the spectrometer by a solenoid controlled mirror, allowing fast and easy switching between normal confocal scanning and spectrometer readings. With this equipment, studies of rodent liver specimens containing porphyrins have been made. The subcellular localization is of interest for the mechanisms of photodynamic therapy (PDT) of malignant tumours. Spectroscopic detection is necessary to distinguish the porphyrin signal from other fluorescent components in the specimen. Two different substances were administered to the tissue, Photofrin, a haematoporphyrin derivative (HPD) and delta-amino levulinic acid (ALA), a precursor to protoporphyrin IX and haem in the haem cycle. Both are substances under clinical trials for PDT of malignant tumours. Following administration of these compounds to the tissue, the potent photosensitizer and fluorescent compound Photofrin, or protoporphyrin IX, respectively, is accumulated.(ABSTRACT TRUNCATED AT 250 WORDS)

Photodynamic therapy and cancer of the esophagus

Esophageal carcinoma usually is diagnosed at an advanced, incurable stage. In patients with good operative risk, surgery is still considered the ideal treatment. Patients with coexisting major medical conditions in whom resective surgery is precluded may benefit from several therapeutic options, including photodynamic therapy (PDT) with porfimer sodium (Photofrin; manufactured by Lederle Parenterals, Carolina, Puerto Rico, under license from Quadra Logic Technologies, Inc, Vancouver, British Columbia, Canada), dilation, thermal destruction, Nd:YAG laser ablation, injection therapy, and placement of prosthetic tubes. Photodynamic therapy with porfimer sodium is thought to have a direct toxic effect on malignant cells via the production of singlet oxygen, which damages the microvasculature of the tumor and renders it ischemic. The 630 nm wavelength used for clinical PDT exhibits the greatest relative degree of light penetration into tissue, with corresponding activation of retained photosensitizer. The efficacy of PDT with porfimer sodium is closely related to stage of disease. It should be emphasized that PDT has been shown to be potentially curative in patients with early, noninvasive tumors of both squamous and glandular (adenocarcinoma) histologies. Eighty-three patients with esophageal carcinoma were treated using PDT. At presentation, 60% of patients had recurrence following previous radiotherapy or chemotherapy. Patients with less advanced disease had a better response to PDT with regard to relief of dysphagia and prolongation of survival. Photodynamic therapy was found to be more useful than Nd:YAG laser therapy for high, upper third lesions, especially circumferential ones. For tumors larger than 8 cm, PDT was twice as effective as Nd:YAG laser therapy in establishing prolonged lumen patency, especially for adenocarcinomas. Photodynamic therapy appears to have the added advantages of fewer treatments and less pain. The role of PDT in gastrointestinal malignancies continues to evolve.