Mitochondrial photodamage and PDT-induced apoptosis

Oxidative alterations induced in vitro by the photodynamic reaction in doxorubicin-sensitive (LoVo) and -resistant (LoVoDX) colon adenocarcinoma cells

In photodynamic therapy (PDT) a tumor-selective photosensitizer is administered and then activated by exposure to a light source of appropriate wavelength. Multidrug resistance (MDR) is largely caused by the drug efflux from the tumor cell by means of P-glycoprotein, resulting in reduced efficacy of the anticancer therapy. This study deals with photodynamic therapy with Photofrin® (Ph) on colon cancer cell lines (doxorubicin-sensitive and -resistant). The cells were treated with 15 and 30 μg/mL Ph and then irradiated by a light dose of 3 or 6 J/cm2 (632.8 nm). After irradiation the cells were incubated for 0, 3 or 18 h. Crucial factors of oxidative stress (thiobarbituric acid reactive substances [TBARS], protein damage, thiazolyl blue tetrazolium bromide [MTT] assay), changes in cytosolic superoxide dismutase (SOD1) activity after photodynamic reaction (PDR), and the intracellular accumulation of photosensitizers in the cells were examined. Moreover, the expressions of glutathione S-transferase (GST)-pi, a marker protein for photochemical toxicity, and secretory phospholipase A2, a prognostic and diagnostic marker for colon cancers, were determined. After PDR, increases in SOD1 activity and the level of TBARS were observed in both cell lines. The level of protein-associated –SH groups decreased after PDR. Both cell lines demonstrated stronger GST-pi and PLA2 expression after PDR, especially after 18 h of incubation. The increasing level of reactive oxygen species following the oxidation of sulfhydryl cell groups and lipid peroxidation influence the activity of many transporters and enzymes. The changes in SOD1 activity show that photodynamic action generates oxidative stress in treated cells. Our study presents that PDR caused oxidative alterations in both examined colon adenocarcinoma cell lines. However, the MDR cells reacted more slowly and all oxidative changes occurred in the delay.

In vivo anti-tumor activity of photodynamic therapy with intravenous administration of acridine orange, followed by illumination with high-power flash wave light in a mouse osteosarcoma model

In a recent study, we demonstrated that a high-power flash wave light (FWL) from a xenon lamp exerted a stronger cytocidal effect against a mouse osteosarcoma cell line than continuous wave light (CWL) in photodynamic therapy with acridine orange (AO-PDT). Based on our in vitro results, we investigated the in vivo anti-tumor activity of AO-PDT using flash wave light from a xenon lamp in a mouse osteosarcoma model. Mouse osteosarcoma cells (LM8) were injected into the subcutaneous tissue of the back of C3H mice, and tumors that grew to approximately 3 mm in diameter were treated by AO-PDT using FWL. AO was administered by intravenous injection and 2 h later the entire body of the mouse was illuminated with FWL from a xenon lamp. Significant growth inhibition of the tumor xenografts was observed as compared with that in the control group, suggesting that AO-PDT with FWL may be useful in the treatment of osteosarcoma. An immunohistochemical study of the tumors treated by AO-PDT showed that the underlying mechanism of the tumor growth inhibition involved both apoptosis and necrosis. In conclusion, it appears that following the intravenous administration of AO, AO-PDT in combination with FWL exerts strong anti-tumor activity. Inhibitory effects against growth of the primary tumor in human patients with osteosarcoma as well as other musculoskeletal sarcomas were also observed.

Clinical and immunohistochemical assessment of vulval intraepithelial neoplasia following photodynamic therapy using a novel bioadhesive patch-type system loaded with 5-aminolevulinic acid

BACKGROUND

The work in this study appraised photodynamic treatment (PDT) as a treatment method for vulval intraepithelial neoplasia (VIN) using a novel bioadhesive patch to deliver aminolevulinic acid. An analysis of changes in expression of apoptotic and cell cycle proteins (p53, p21, Mdm2, Blc-2, Bax, Ki-67) in response to PDT was evaluated.

METHODS

PDT was performed using non-laser light, either as a one or two-cycle treatment, with clinical and pathological assessment following after 6 weeks. Twenty-three patients with 25 VIN lesions underwent 49 cycles of PDT. Patches were designed to conform to uneven vulval skin and contained 38 mg cm(-2) aminolevulinic acid. Assessment was carried out at 6 weeks post-treatment. Patient-based treatment assessment, along with clinical and pathological changes, were monitored. Immunohistochemical staining was used to elucidate a possible biomolecular basis for induced cellular changes.

RESULTS

Most patients (52%) reported a symptomatic response, with normal pathology restored in 38% of lesions. The patch was easy to apply and remove, causing minimal discomfort. Fluorescence inspection confirmed protoporphyrin accumulation. Pain during implementation of PDT was problematic, necessitating some form of local analgesia. Changes in expression of cell cycle and apoptotic-related proteins suggested involvement of apoptotic pathways. Down regulation of p21 and inverse changes in Bcl-2 and Bax were key findings.

CONCLUSION

Treatment of VIN lesions using a novel bioadhesive patch induced changes in cell cycle and apoptotic proteins in response to PDT with possible utilisation of apoptotic pathways. The efficacy of PDT in treating VIN could be improved by a better understanding of these apoptotic mechanisms, the influence of factors, such as HPV status, and of the need for effective pain management.

Effects of sodium butyrate on cell death induced by photodynamic therapy in U373-MG and D54-MG astrocytoma cell lines

The damage induced by end products of photodynamic therapy (PDT) in astrocytoma tumors leads to cytotoxicity and cell death. Chromatin modifiers such as sodium butyrate (NaB) induce several genes involved in apoptosis, among others. The PDT improvement was evaluated by the measurement of its effectiveness in the treatment of U373-MG and D54-MG astrocytoma cell lines exposed to NaB. Cells exposed to 80 microg mL(-1) of delta-aminolevulinic acid (ALA) as precursor of endogenous photosensitizer (PS), protoporphyrin IX (PpIX), induced 16.67% and 28.9% of mortality in U373-MG and D54-MG, respectively. The mortality increased to 70.62% and 96.7%, respectively, when U373-MG and D54-MG cells were exposed for 24 h to 8 mm NaB prior to ALA-induction. In this condition, re-expression of some genes related to apoptosis in U373-MG, and differentiation in D54-MG were induced. PpIX accumulation was higher than ALA-induction and the acetylation of histone H4 induced by NaB was verified by immunocytochemistry in both cells. It can be concluded that modified chromatin and genes induced by NaB increment the cellular death induced by PDT in astrocytoma cells using PpIX as endogenous PS.

Pulsed diode laser-based singlet oxygen monitor for photodynamic therapy: in vivo studies of tumor-laden rats

Photodynamic therapy (PDT) is a promising cancer treatment that involves optical excitation of photosensitizers that promote oxygen molecules to the metastable O(2)(a(1)Delta) state (singlet oxygen). This species is believed to be responsible for the destruction of cancerous cells during PDT. We describe a fiber optic-coupled, pulsed diode laser-based diagnostic for singlet oxygen. We use both temporal and spectral filtering to enhance the detection of the weak O(2)(a-->X) emission near 1.27 microm. We present data that demonstrate real-time singlet oxygen production in tumor-laden rats with chlorin e6 and 5-aminolevulinic acid-induced protoporphyrin photosensitizers. We also observe a positive correlation between post-PDT treatment regression of the tumors and the relative amount of singlet oxygen measured. These results are promising for the development of the sensor as a real-time dosimeter for PDT.

Targeting of mitochondria by 10-N-alkyl acridine orange analogues: role of alkyl chain length in determining cellular uptake and localization

10-N-Nonyl acridine orange (NAO) is used as a mitochondrial probe because of its high affinity for cardiolipin (CL). Targeting of NAO may also depend on mitochondrial membrane potential. As the nonyl group has been considered essential for targeting, a systematic study of alkyl chain length was undertaken; three analogues (10-methyl-, 10-hexyl-, and 10-hexadecyl-acridine orange) were synthesized and their properties studied in phospholipid monolayers and breast cancer cells. The shortest and longest alkyl chains reduced targeting, whereas the hexyl group was superior to the nonyl group, allowing very clear and specific targeting to mitochondria at concentrations of 20-100 nM, where no evidence of toxicity was apparent. Additional studies in wild-type and cardiolipin-deficient yeast cells suggested that cellular binding was not absolutely dependent upon cardiolipin.

Photodynamic therapy-induced death of HCT 116 cells: Apoptosis with or without Bax expression

Cell death following photodynamic therapy (PDT) with the photosensitizer Pc 4 involves the intrinsic pathway of apoptosis. To evaluate the importance of Bax in apoptosis after PDT, we compared the PDT responses of Bax-proficient (Bax(+/-)) and Bax knock-out (BaxKO) HCT116 human colon cancer cells. PDT induced a slow apoptotic process in HCT Bax(+/-) cells following a long delay in the activation of Bax and release of cytochrome c from mitochondria. Although cytochrome c was not released from mitochondria following PDT in BaxKO cells, an alternative mechanism of caspase-dependent apoptosis with extensive chromatin and DNA degradation was found in these cells. This alternative process was less efficient and slower than the normal apoptotic process observed in Bax(+/-) cells. Early events upon PDT, such as the loss of mitochondrial membrane potential, photodamage to Bcl-2, and activation of p38 MAP kinase, were observed in both HCT116 cell lines. In spite of differences in the efficiency and mode of apoptosis induced by PDT in the Bax(+/-) and BaxKO cells, they were found to be equally sensitive to killing by PDT, as determined by loss of clonogenicity. Thus, for Pc 4-PDT, the commitment to cell death occurs prior to and independent of Bax activation, but the process of cellular disassembly differs in Bax-expressing vs. non-expressing cells.

Mitochondria targeting by guanidine- and biguanidine-porphyrin photosensitizers

We report the syntheses of three new amphiphilic porphyrin derivatives, containing a guanidine, a biguanidine, or an MLS peptide, that were designed to target the cell mitochondria. The guanidine- and biguanidine-porphyrins are poorly soluble in water, forming J-type aggregates in aqueous solutions. On the other hand, the porphyrin-MLS peptide conjugate bearing a low molecular weight PEG spacer is highly water-soluble and does not aggregate in aqueous media. The fluorescence quantum yields determined for all porphyrins were higher at low pH (<6) and the porphyrin-peptide conjugate had the highest quantum yields in aqueous media. All porphyrins showed low dark toxicity toward human carcinoma HEp2 cells, and the guanidine-porphyrin was the most phototoxic (IC 50 = 4.8 microM at 1 J cm (-2)), followed by the biguanidine-porphyrin and the porphyrin-MLS (IC50 = 8.2 microM and 9.8 microM at 1 J cm (-2), respectively). The porphyrin-MLS peptide conjugate accumulated the most within cells of all porphyrins at all times investigated and the biguanidine-porphyrin accumulated the least. Both the guanidine- and biguanidine-porphyrins localized within cell mitochondria and, in addition, were found in the lysosomes and the ER (in the case of the guanidine-porphyrin). In contrast, the porphyrin-MLS peptide conjugate localized mainly within the cell lysosomes.

Photolon™, a chlorin e6 derivative, triggers ROS production and light-dependent cell death via necrosis

Photolon is a photosensitiser with demonstrated potential as an anti-tumour agent. In this study, an in vitro investigation was performed to determine the mechanism of Photolon-induced cell death. Cell killing was observed in a light-dependent manner and light-activated Photolon resulted in a significant production of reactive oxygen species (ROS), which could be blocked by type I ROS scavengers. Inhibition of ROS production using Trolox prevented Photolon-induced cell death. Light-activated Photolon caused no increase in caspase-3/7 activity, but a rapid increase in lactate dehydrogenase (LDH) release suggesting a loss of membrane integrity and subsequent cell death by necrosis. We conclude that the mechanism of Photolon-induced cell death involves the induction of ROS via a type I mechanism, which is ultimately responsible for cell killing by necrosis.

Involvement of both caspase-dependent and -independent pathways in apoptotic induction by hexaminolevulinate-mediated photodynamic therapy in human lymphoma cells

Photodynamic therapy (PDT) is a cancer treatment based on the interaction of a photosensitizer, light and oxygen. PDT with the endogenous photosensitizer, protoporphyrin IX (PpIX) induced by 5-aminolevulinic acid (ALA) or its derivatives is a modification of this treatment modality with successful application in dermatology. However, the mechanism of cell destruction by ALA-PDT has not been elucidated. In this study a human T-cell lymphoma Jurkat cell line was treated with PDT using hexaminolevulinate (HAL, hexylester of ALA). Four hours following treatment nearly 80% of the cells exhibited typical apoptotic features. Mitochondrial pro-apoptotic proteins were evaluated by Western blots in subcellular fractionated samples. PDT caused cytosolic translocation of cytochrome c and nuclear redistribution of apoptosis-inducing factor (AIF), but the release of mitochondrial Smac/DIABLO, Omi/HtrA2 and EndoG was not observed. The release of cytochrome c was followed by the cleavage of caspase-9 and caspase-3 as well as its downstream substrates, together with oligonucleosomal DNA fragmentation. The pan-caspases inhibitor, z-VAD.fmk, prevented oligonucleosomal DNA fragmentation, but failed to inhibit PDT-mediated apoptosis. The apoptotic induction by AIF-mediated caspase-independent pathway was also found after HAL-PDT with large-scale DNA fragmentation in the presence of z-VAD.fmk. These results demonstrate that cytochrome c-mediated caspase-dependent pathway and AIF-induced caspase-independent pathway are simultaneously involved in the apoptotic induction by PDT. When the cytochrome c-induced caspase-dependent pathway is blocked, the cells go into apoptosis via AIF-mediated pathway, clearly demonstrating that the cytochrome c-mediated caspase-dependent pathway is not required for such apoptotic induction. This finding may have an impact on improved PDT effectiveness.

Mono-(l)-aspartylchlorin-e6?

Mono-(L)-aspartylchlorin-e6 (also known as Talaporfin, NPe6, MACE, and most recently LS-11) is a potent sensitizer for photodynamic therapy that is currently undergoing clinical trials. Using a combination of unambiguous partial synthesis from pheophytin-a and methyl pheophorbide-a, NMR spectroscopy, and single crystal X-ray diffraction, the structure of mono-(L)-aspartylchlorin-e6 is definitively shown to be the isomer in which the aspartyl residue is attached at the 15(2)-side chain position. This conclusion is contrary to earlier assumptions, but affirms the conclusions of a study based on NMR spectroscopy; a rationale for the unique formation of the 15(2)-aspartyl derivative is proposed.

Mapping of oxidative stress responses of human tumor cells following photodynamic therapy using hexaminolevulinate

Background

Photodynamic therapy (PDT) involves systemic or topical administration of a lesion-localizing photosensitizer or its precursor, followed by irradiation of visible light to cause singlet oxygen-induced damage to the affected tissue. A number of mechanisms seem to be involved in the protective responses to PDT, including activation of transcription factors, heat shock proteins, antioxidant enzymes and apoptotic pathways.

Results

In this study, we address the effects of a destructive/lethal hexaminolevulinate (HAL) mediated PDT dose on the transcriptome by using transcriptional exon evidence oligo microarrays. Here, we confirm deviations in the steady state expression levels of previously identified early defence response genes and extend this to include unreported PDT inducible gene groups, most notably the metallothioneins and histones. HAL-PDT mediated stress also altered expression of genes encoded by mitochondrial DNA (mtDNA). Further, we report PDT stress induced alternative splicing. Specifically, the ATF3 alternative isoform (deltaZip2) was up-regulated, while the full-length variant was not changed by the treatment. Results were independently verified by two different technological microarray platforms. Good microarray, RT-PCR and Western immunoblotting correlation for selected genes support these findings.

Conclusion

Here, we report new insights into how destructive/lethal PDT alters the transcriptome not only at the transcriptional level but also at post-transcriptional level via alternative splicing.

Photodynamic therapy: update 2006. Part 1: Photochemistry and photobiology

Photodynamic therapy (PDT) is a two-step therapeutic technique in which the topical or systemic delivery of photosensitizing drugs is followed by irradiation with visible light. Activated photosensitizers transfer energy to molecular oxygen, generating reactive oxygen species (ROS). The subsequent oxidation of lipids, amino acids and proteins induces cell necrosis and apoptosis. In addition, ROS indirectly stimulate the transcription and release of inflammatory mediators. The photosensitizers are selective, in that they penetrate and accumulate in tumour cells or in the endothelium of newly formed vessels while generally avoiding the surrounding healthy tissue. The mechanisms of penetration through the cell membrane and the pattern of subcellular localization strongly influence the type of cellular effect. The photobiology and photoimmunology of the haematoporphyrin (Hp) derivative and its purified, lyophilized and concentrated form porfimer sodium have been investigated over the past 30 years. However, interest in PDT in dermatology was not raised until the 1990s with the availability of a simple and effective technique, the topical application of aminolaevulinic acid (ALA) and its methyl ester (methyl aminolaevulinate, MAL) followed by irradiation with broadband red light. At the same time, several new 'second-generation' synthetic sensitizers (e.g. benzoporphyrin derivatives, phthalocyanines, chlorins and porphycenes) became available. These compounds are chemically pure, highly efficient, selective and safe, while offering the advantage that the generalized skin photosensitivity they produce lasts for only a short time. They are currently under clinical evaluation but have not yet been approved for clinical use. This paper provides an overview of the chemistry of the photosensitizers, the photobiology and photoimmunology of the photodynamic reaction as well as the photophysical characteristics of the light sources available for PDT.

Structural and physico-chemical determinants of the interactions of macrocyclic photosensitizers with cells

New therapies have been developed using reactive oxygen species produced by light-activation of photosensitizers (PS). Since the lifetime of these species is extremely short and their diffusion in space is limited, the photo-induced reactions primarily affect the cell organelles labeled by the PS. In addition to the development of molecules with the best optical and photosensitizing properties, considerable research has been done to understand the physico-chemical parameters governing their subcellular localization. In this review, we examine these parameters to establish the structure/efficacy relationships, which allow specific targeting of PS. We examine the effect of subcellular localization on the cellular response to photosensitization processes. We discuss the determinants of subcellular localization, including the hydrophobic/hydrophilic balance, the specific charge effects and the dynamics of PS' transfer through membranes. Specific targeting can also be achieved with molecular structures able to recognize cellular or intracellular receptors, and this is also dealt with in this paper.

Sonodynamic therapy of cancer using a novel porphyrin derivative, DCPH-P-Na(I), which is devoid of photosensitivity

To improve the efficacy of sonodynamic therapy of cancer using photosensitizers, we developed a novel porphyrin derivative designated DCPH-P-Na(I) and investigated its photochemical characteristics and sonotoxicity on tumor cells. DCPH-P-Na(I) exhibited a minimum fluorescent emission by excitation with light, compared with a strong emission from ATX-70, which is known to reveal both photo- and sonotoxicity. According to this observation, when human tumor cells were exposed to light in the presence of DCPH-P-Na(I) in vitro, the least phototoxicity was observed, in contrast to the strong phototoxicity of ATX-70. However, DCPH-P-Na(I) exhibited a potent sonotoxicity on tumor cells by irradiation with ultrasound in vitro. This sonotoxicity was reduced by the addition of L-histidine, but not D-mannitol, thus suggesting that singlet oxygen may be responsible for the sonotoxicity of DCPH-P-Na(I). DCPH-P-Na(I) demonstrated significant sonotoxicity against a variety of cancer cell lines derived from different tissues. In addition, in a mouse xenograft model, a potent growth inhibition of the tumor was observed using sonication after the administration of DCPH-P-Na(I) to the mouse. These results suggest that sonodynamic therapy with DCPH-P-Na(I) may therefore be a useful clinical treatment for cancers located deep in the human body without inducing skin sensitivity, which tends to be a major side-effect of photosensitizers.

Interaction of cationic meso-porphyrins with liposomes, mitochondria and erythrocytes

Two series of cationic porphyrins meso-(3N-methylpyridinium)phenylporphyrin (3P1, 3P2c, 3P2t, 3P3 and 3P4) and meso-(4N-methylpyridinium)phenylporphyrin (4P1, 4P2c, 4P2t, 4P3 and 4P4) were studied to obtain a comprehensive understanding of factors that influence the binding of cationic porphyrins to liposomes and mitochondria, as well as their photodynamic efficiencies in erythrocytes. Binding and photodynamic efficiency were found to be inversely proportional to the number of positively charged groups and directly proportional to n-octanol/water partition coefficients (log P(OW)), except for the cis molecules 3P2c and 4P2c. In the cis molecules, binding and photodynamic efficiency were much higher than expected, indicating that specific interactions not accounted by log P(OW) enhance photodynamic efficiency. The effect of mitochondrial transmembrane electrochemical potentials on cationic porphyrin binding constants was estimated to be as large as 15%, and may be useful to selectively target this organelle when promoting photodynamic therapy to induce apoptosis.

Characteristics of Photocytotoxicity with high peak power pulsed irradiation: Comparison of Photodynamic Therapy with two photosensitizers, Photofrin&#174; and mono-L-aspartyl chlorin e6 on prostate cancer cell in vitro

We proposed novel depth-controlled photodynamic therapy (PDT) by varying pulsed laser irradiation condition. We focus on photocytotoxicity suppression under high peak power pulsed irradiation to apply this phenomenon to surface intact therapy to preserve healthy wall of a hollow organ. The relation between laser irradiation condition and cell lethality of rat prostate cancer cell with PDT using practical photosensitizers, mono-L-aspartyl chlorine e6 (ME2906) and Photofrin&#174; was investigated. We found cell lethality suppression from 63 % to 20 % when the irradiated pulsed peak power density ranged from 0.2 to 1.4 mW/cm²with ME2906 mediated PDT. There was no significant photocytotoxicity suppression in case of Photofrin&#174; mediated PDT. Singlet oxygen luminescence from the two different kinds of photosensitizer solution was measured. The pulse peak power dependence of singlet oxygen luminescence intensity correlated with the photocytotoxicity. We think the photocytotoxicity suppression with high peak power pulsed irradiation with ME2906 might be useful for the therapeutic depth controlled PDT without damage on the surface of a hollow organ.

Mechanisms of cell death in oxidative stress

Reactive oxygen or nitrogen species (ROS/RNS) generated endogenously or in response to environmental stress have long been implicated in tissue injury in the context of a variety of disease states. ROS/RNS can cause cell death by nonphysiological (necrotic) or regulated pathways (apoptotic). The mechanisms by which ROS/RNS cause or regulate apoptosis typically include receptor activation, caspase activation, Bcl-2 family proteins, and mitochondrial dysfunction. Various protein kinase activities, including mitogen-activated protein kinases, protein kinases-B/C, inhibitor-of-I-kappaB kinases, and their corresponding phosphatases modulate the apoptotic program depending on cellular context. Recently, lipid-derived mediators have emerged as potential intermediates in the apoptosis pathway triggered by oxidants. Cell death mechanisms have been studied across a broad spectrum of models of oxidative stress, including H2O2, nitric oxide and derivatives, endotoxin-induced inflammation, photodynamic therapy, ultraviolet-A and ionizing radiations, and cigarette smoke. Additionally ROS generated in the lung and other organs as the result of high oxygen therapy or ischemia/reperfusion can stimulate cell death pathways associated with tissue damage. Cells have evolved numerous survival pathways to counter proapoptotic stimuli, which include activation of stress-related protein responses. Among these, the heme oxygenase-1/carbon monoxide system has emerged as a major intracellular antiapoptotic mechanism.

Protoporphyrin IX Interacts with Wild-type p53 Protein in Vitro and Induces Cell Death of Human Colon Cancer Cells in a p53-dependent and -independent Manner

Photodynamic therapy (PDT) of cancer is an alternative treatment for tumors resistant to chemo- and radiotherapy. It induces cancer cell death mainly through generation of reactive oxygen species by a laser light-activated photosensitizer. It has been suggested that the p53 tumor suppressor protein sensitizes some human cancer cells to PDT. However, there is still no direct evidence for this. We have demonstrated here for the first time that the photosensitizer protoporphyrin IX (PpIX) binds to p53 and disrupts the interaction between p53 tumor suppressor protein and its negative regulator HDM2 in vitro and in cells. Moreover, HCT116 colon cancer cells exhibited a p53-dependent sensitivity to PpIX in a dose-dependent manner, as was demonstrated using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and fluorescence-activated cell sorter (FACS) analysis of cell cycle profiles. We have also observed induction of p53 target pro-apoptotic genes, e.g. puma (p53-up-regulated modulator of apoptosis), and bak in PpIX-treated cells. In addition, p53-independent growth suppression by PpIX was detected in p53-negative cells. PDT treatment (2 J/cm2) of HCT116 cells induced p53-dependent activation of pro-apoptotic gene expression followed by growth suppression and induction of apoptosis.

Tumor suppressor Fhit protein interacts with protoporphyrin IX in vitro and enhances the response of HeLa cells to photodynamic therapy

Fhit, the product of tumor suppressor fragile histidine triad (FHIT) gene, exhibits antitumor activity of still largely unknown cellular background. However, it is believed that Fhit-Ap(3)A or Fhit-AMP complex might act as a second class messenger in cellular signal transduction pathway involved in cell proliferation and apoptosis. We demonstrate here for the first time that the photosensitizer, protoporphyrin IX (which is a natural precursor of heme) binds to Fhit protein and its mutants in the active site in vitro. Furthermore, PpIX inhibits the enzymatic activity of Fhit. Simultaneously, PpIX shows lower binding capacity to mutant Fhit-H96N of highly reduced hydrolase activity. In cell-based assay PpIX induced HeLa cell death in Fhit and Fhit-H96N-dependent manner which was measured by means of MTT assay. Moreover, HeLa cells stably expressing Fhit or mutant Fhit-H96N were more susceptible to protoporphyrin IX-mediated photodynamic therapy (2J/cm(2)) than parental cells.

Synthesis and cellular studies of PEG-functionalized meso-tetraphenylporphyrins

The total syntheses of four PEG-functionalized porphyrins, containing one to four low molecular weight PEG chains linked via amide bonds to the para-phenyl positions of meso-tetraphenylporphyrin, are reported. The hydrophobic character of the PEG-porphyrins decreases with the number of PEG chains linked to the porphyrin ring, while their tendency for aggregation in buffered aqueous solution increases. The porphyrins containing one or two PEG chains accumulated within human HEp2 cells to a much higher extent than those having three or four PEGs at the macrocycle periphery. All PEG-porphyrins were found to be non-toxic in the dark, and only those containing one or two PEG chains were phototoxic (IC(50)=2 microM at 1J/cm(2) light dose). The preferential sites of subcellular localization of the porphyrins containing one or two PEG chains were found to be the mitochondria and endoplasmic reticulum (ER), while those containing three or four PEG chains localize preferentially in the lysosomes.

Intracellular localization and concentration as well as photodynamic effects of benzoporphyrin derivative monoacid ring A in four types of rodent tumor cells

The relative sensitivities of different tumor cells to photodynamic therapy (PDT) with benzoporphyrin derivative monoacid ring A (BPD-MA) were compared in the four tumor cells. A good correlation was observed between the cell survival at 0.1 microg/ml of BPD-MA and sensitizer uptake/10(6) cells (r = -0.99) or the plating efficiency of cells (r = 0.99). At 3 h after the irradiation, a significant difference was observed in the proportion of apoptotic cells among the four tumor cells (p = 0.024). In conclusion, cell responses to PDT depend on the several factors such as the cell line, photosensitizer dose, and fluence.

Photodynamic therapy of cerebral glioma – A review Part I – A biological basis

Photodynamic therapy (PDT) has been investigated extensively in the laboratory for decades, and for over 25 years in the clinical environment, establishing it as a useful adjuvant to standard treatments for many cancers. A combination of both photochemical and photobiological processes occur that lead to the eventual selective destruction of the tumour cells. It is a potentially valuable adjuvant therapy that can be used in conjunction with other conventional therapies for the treatment of cerebral glioma. PDT has undergone extensive laboratory studies and clinical trials with a variety of photosensitizers (PS) and tumour models of cerebral glioma. Many environmental and genetically based factors influence the outcome of the PDT response. The biological basis of PDT is discussed with reference to laboratory and preclinical studies.

Apoptosis induction and mitochondria alteration in human HeLa tumour cells by photoproducts of Rose Bengal acetate

The aim of this work was to investigate the apoptosis induction and mitochondria alteration after photodamage exerted by incubation of HeLa cells with Rose Bengal acetate-derivative (RBAc) followed by irradiation for a total dose of 1.6 J/cm2. This treatment was previously demonstrated to reduce cell viability under mild treatment conditions, suggesting the restoration of the photoactive molecule in particularly sensitive cell sites. Indeed, Rose Bengal (RB) is a very efficient photosensitizer, whose photophysical properties are inactivated by addition of the quencher group acetate. The RBAc behaves as a fluorogenic substrate by entering easily the cells where the original, photoactive molecule is restored by specific esterases. Different intracellular sites of photodamage of RB are present. In particular, fluorescence imaging of Rodamine 123 and JC-1 labelled cells showed altered morphology and loss of potential membrane of mitochondria. MTT and NR assays gave indications of alteration of mitochondrial and lysosomal enzyme activities. These damaged sites were likely responsible for triggering apoptosis. Significant amount of apoptotic cell death (about 40%) was induced after light irradiation followed RBAc incubation as revealed by morphological (modification of cell shape and blebs formation), cytochemical (FITC-Annexin-V positive cells) and nuclear fragmentation assays.

DH-I-180-3–Mediated Photodynamic Therapy: Biodistribution and Tumor Vascular Damage

An important goal of photodynamic therapy (PDT) for treatment of various cancers is to shorten PDT-performing time and simultaneously enhance PDT efficacy. Here, we investigated the nontumor tissue distribution of and the tumor vascular damage caused by a new photosensitizer, DH-I-180-3, in mice with implanted EMT6 mammary tumor cells. In addition, we performed cell-based assays to evaluate the basic antitumor effect of DH-I-180-3/PDT in EMT6 cells. After administration of PDT, the type of cell death was characterized to be apoptosis, and a change in the mitochondrial membrane potential was also observed within minutes. On the other hand, tumor growth was remarkably retarded in vivo in mice that received DH-I-180-3/PDT, compared with mice in the control group, which were exposed to light irradiation alone. Finally, tumors in some mice nearly healed. The antitumor drug reached a maximum concentration approximately 3 h after administration. However, PDT was most effective when there was substantial accumulation of DH-I-180-3 in the tumor vasculature and in healthy tissue. The histological demonstration provided further evidence of tumor vascular damage. On the basis of these findings, we suggest that PDT with the photosensitizer DH-I-180-3 induces vascular damage with blood vessel shutdown, in addition to direct killing of tumor cells, in mice.

Targeted photodynamic therapy

BACKGROUND AND OBJECTIVES

Photodynamic therapy (PDT) is an emerging modality for the treatment of various neoplastic and non-neoplastic pathologies.

STUDY DESIGN/MATERIALS AND METHODS

PDT usually occurs when reactive oxygen species (ROS) generated from light-activated chemicals (photosensitizer, PS) destroy the target. For non-dermatologic applications the PS are delivered systemically and accumulate, at different concentrations, in most organs.

RESULTS AND CONCLUSION

Typically there is a modest enhanced accumulation of the PS in tumor tissues, providing a first level of selectivity. Additional selectivity is provided by the confined illumination of the target area with the appropriate wavelength of light. For the treatment of pathologies in complex anatomical sites, such as in the peritoneal cavity, where restricted illumination is difficult; improved targeting of the PS is necessary to prevent damage to the surrounding healthy tissue. This article will focus on targeted PDT.

Novel Porphyrin Conjugates with a Potent Photodynamic Antitumor Effect: Differential Efficacy of Mono- and Bis-β-cyclodextrin Derivatives In Vitro and In Vivo

In the present study we investigated the photosensitizing properties of two novel mono- and bis-cyclodextrin tetrakis (pentafluorophenyl) porphyrin derivatives in several tumor cell lines and in BALB/c mice bearing subcutaneously transplanted syngeneic mouse mammary carcinoma 4T1. Both studied sensitizers were localized mainly in lysosomes and were found to induce cell death by triggering apoptosis in human leukemic cells HL-60. In 4T1 and other cell lines both apoptotic and necrotic modes of cell death occurred depending on drug and light doses. Mono-cyclodextrin porphyrin derivative P(beta-CD)1 exhibited stronger in vitro phototoxic effect than bis-cyclodextrin derivative P(beta-CD)2. However, in vivo P(beta-CD)2 displayed faster tumor uptake with maximal accumulation 6 h after application, leading to complete and prolonged elimination of subcutaneous tumors within 3 days after irradiation (100 J cm(-2)). In contrast, P(beta-CD)1 uptake was slower (48 h) and the reduction of tumor mass was only transient, reaching the maximum at the 12 h interval when a favorable tumor-to-skin ratio appeared. Thus, P(beta-CD)2 represents a new photosensitizing drug displaying fast and selective tumor uptake, strong antitumor activity and fast elimination from the body.

Photodynamic damages induced by a monocationic porphyrin derivative in a human carcinoma cell line

The photokilling activity of 5-(4-trimethylammoniumphenyl)-10,15,20-tris(2,4,6-trimethoxyphenyl)porphyrin (CP) was evaluated on a Hep-2 human larynx-carcinoma cell line. Cell treatment was carried out with 5 microM CP incorporated into liposomal vesicles. Under violet-blue exciting light, the red fluorescence of CP was mainly detected as a filamentous pattern characteristic of mitochondrial localization. Similar pattern was also observed using rhodamine 123 in Hep-2 cells. No dark cytotoxicity was observed using 5 microM CP concentration and long incubation time (24 h). Using Hoechst-33258 and caspase-3 immunostaining methods, cell cultures treated for 24 h with CP and exposed to light for 7.5 min (27 J/cm2) showed a great amount of apoptotic cells (40%). In contrast, necrotic cells (58%) were observed using the same drug concentration but irradiated for 15 min (54 J/cm2). The results show that CP can induce different mechanisms of cell death depending on irradiation doses in the photodynamic treatments, which makes this agent an interesting sensitizer with potential application in photodynamic tumor therapy.

Methylene blue in photodynamic therapy: From basic mechanisms to clinical applications

Methylene blue (MB) is a molecule that has been playing important roles in microbiology and pharmacology for some time. It has been widely used to stain living organisms, to treat methemoglobinemia, and lately it has been considered as a drug for photodynamic therapy (PDT). In this review, we start from the fundamental photophysical, photochemical and photobiological characteristics of this molecule and evolved to show in vitro and in vivo applications related to PDT. The clinical cases shown include treatments of basal cell carcinoma, Kaposi's Sarcoma, melanoma, virus and fungal infections. We concluded that used together with a recently developed continuous light source (RL50(®)), MB has the potential to treat a variety of cancerous and non-cancerous diseases, with low toxicity and no side effects.

Extracellular pH influences the mode of cell death in human colon adenocarcinoma cells subjected to photodynamic treatment with chlorin p6

Effect of varying extracellular pH on mode of cell death induced by photodynamic action of chlorin p6 was investigated in human colon carcinoma (Colo-205) cells. At an extracellular pH of 7.4, compared to cells treated with chlorin p6 in dark, the photodynamically treated cells showed reduction in mitochondrial membrane potential, an increase in ADP/ATP ratio (1:2) and a large percentage of cells with chromatin condensation. In contrast, when photodynamic treatment and post irradiation incubation was carried out in acidic medium (pH 6.5), total loss of mitochondrial membrane potential, a marked increase in ADP/ATP ratio (1:33) and increased damage to plasma membrane were observed. Further, cells subjected to photodynamic treatment in a medium of pH 7.4 showed twofold increase in caspase-3 activity as compared to photodynamic treatment at pH 6.5. These results suggest that chlorin p6 mediated photodynamic action induces apoptotic cell death when extracellular pH is 7.4 whereas necrosis is more predominant under condition when extracellular pH is 6.5.