Photosensitization of mitochondria. Molecular and cellular aspects

Biochemical and biophysical study of chemopreventive and chemotherapeutic anti-tumor potential of some Egyptian plant extracts

the present study the was done to evaluate chemopreventive and chemotherapeutic anti-tumor potential of some Egyptian plant extract (moringa, graviola, ginger garden cress and artemisinin) against 7,12-dimethylbenz(a)anthracene (DMBA)-induced mammary carcinogenesis in Swiss albino mice. chemopreventive and chemotherapeutic evaluation was assessed by monitoring the tumor incidence and tumor volume as well as by analyzing the status of (a) biochemical markers (maspin, survivin, livin, caveolin-1, osteopontin and Fucosyltransferase 4 gene expressions), oxidative stress related profile including; total antioxidant capacity (TAC), glutathione reductase (GR) activity, glutathione-s-transferase (GST) activity assay, superoxide dismutase (SOD) activity, catalase (CAT) activity and lipid peroxidation (MDA), renal and hepatic toxicity markers (urea, creatinine, alanine transaminase (alt) activity, aspartate aminotransferase (ast) activity, alkaline phosphatase (ALP) Activity and γ-Glutamyltransferase (GGT) activity also study of (b) biophysical markers (trace and heavy metals (lead (Pb), cadmium (Cd), chromium (Cr), nickel (Ni), iron (Fe), selenium (Se), copper (Cu) and zinc (Zn)), dielectric properties and body water distribution) finally (c) histopathological examination oral administration of increasing dose of moringa, graviola, ginger garden cress and artemisinin extracts, respectively significantly prevented the tumor incidence and tumor volume as well as brought back the status of the above mentioned biochemical and biophysical variables. Histopathological changes also confirmed the formation of tumor tubules and neovascularization after the treatment. Overall, these results suggest that treatment with moringa, graviola, ginger garden cress and artemisinin extracts provided antioxidant defense with strong chemopreventive and chemotherapeutic activity against DMBA-induced mammary tumors.

Polar extracts from the berry-like fruits of Hypericum androsaemum L. as a promising ingredient in skin care formulations

ETHNOPHARMACOLOGICAL RELEVANCE

The top flowering aerial parts of the Hypericum species are traditionally used to prepare ointments to heal cuts and burns. Sometimes even the fruits are used for these purposes. Hypericum androsaemum L., commonly known as tutsan or shrubby St. John's Wort, is a Mediterranean medicinal plant which has been traditionally used to prepare an ointment for treating cuts and wounds.

AIM OF THE STUDY

To evaluate the extracts obtained from H. androsaemum red berries as functional ingredients for skin care formulations.

MATERIALS AND METHODS

The methanolic extract was obtained by Soxhlet extraction while the aqueous extract was prepared by decoction; their composition was determined by HPLC analysis. Their biological activities were measured in terms of proliferation and migration of human fibroblasts, inhibition of collagenase activity, and immunomodulatory effects on human peripheral blood mononuclear cells (PBMCs). In addition, we evaluated their photostability by UV spectroscopy and their protective effects against APPH-induced hemolysis in red blood cells (RBC).

RESULTS

The polar extracts contained significant amounts of shikimic (108,143.7-115,901.3mg/kg) and chlorogenic acids (45,781.1-57,002.7mg/kg). The main components of these extracts made an important contribution to a significant increase in human fibroblast migration. Both extracts were also active as collagenase inhibitors, with the aqueous one showing a greater inhibitory capacity (IC₅₀ value of 88.1µg/mL), similar to that of chlorogenic acid. The kinetic parameters determined for the enzymatic reaction revealed for both aqueous extract and chlorogenic acid an uncompetitive mechanism of inhibition. The methanolic extract showed important effects on PBMCs by modulating IL-6. Both extracts proved to be photostable in the UVA/B range and protected RBC against peroxidation at low concentrations.

CONCLUSIONS

H. androsaemum red berries were proven to contain phytochemicals that improve skin regeneration, hence potentially employable in skin care formulations.

Mitochondrial reactive oxygen species (ROS) and ROS-induced ROS release

Byproducts of normal mitochondrial metabolism and homeostasis include the buildup of potentially damaging levels of reactive oxygen species (ROS), Ca(2+), etc., which must be normalized. Evidence suggests that brief mitochondrial permeability transition pore (mPTP) openings play an important physiological role maintaining healthy mitochondria homeostasis. Adaptive and maladaptive responses to redox stress may involve mitochondrial channels such as mPTP and inner membrane anion channel (IMAC). Their activation causes intra- and intermitochondrial redox-environment changes leading to ROS release. This regenerative cycle of mitochondrial ROS formation and release was named ROS-induced ROS release (RIRR). Brief, reversible mPTP opening-associated ROS release apparently constitutes an adaptive housekeeping function by the timely release from mitochondria of accumulated potentially toxic levels of ROS (and Ca(2+)). At higher ROS levels, longer mPTP openings may release a ROS burst leading to destruction of mitochondria, and if propagated from mitochondrion to mitochondrion, of the cell itself. The destructive function of RIRR may serve a physiological role by removal of unwanted cells or damaged mitochondria, or cause the pathological elimination of vital and essential mitochondria and cells. The adaptive release of sufficient ROS into the vicinity of mitochondria may also activate local pools of redox-sensitive enzymes involved in protective signaling pathways that limit ischemic damage to mitochondria and cells in that area. Maladaptive mPTP- or IMAC-related RIRR may also be playing a role in aging. Because the mechanism of mitochondrial RIRR highlights the central role of mitochondria-formed ROS, we discuss all of the known ROS-producing sites (shown in vitro) and their relevance to the mitochondrial ROS production in vivo.

Theoretical investigation of the absorption spectra and singlet-triplet energy gap of positively charged tetraphenylporphyrins as potential photodynamic therapy photosensitizers

DFT and TD-DFT calculations have been performed on a series of positively charged tetraphenylporphyrins with the aim to check whether these compounds can be used as photosensitizers in photodynamic therapy (PDT). Absorption spectra and singlet-triplet energy gaps have been computed by using the BP86, PBE0, and ωB97XD exchange-correlation functionals. Polarizable continuum model (PCM) has been used to take into account solvent effects. A careful analysis has been made on the Q-band, localized in the near-red visible region of the spectrum, since it plays a fundamental role in the drug design of new photodynamic therapy photosensitizers. Our results show that all the examined molecules have an adsorption band that falls in the so-called therapeutic window and possess a singlet-triplet energy gap able to promote the excitation of molecular oxygen from its ground triplet to the excited singlet state. The use of the ωB97XD exchange correlation functional, which accounts for dispersion interactions, allows calculating excitation energy values close to the experimental values.

Oxidative stress in the in vivo DMBA rat model of breast cancer: suppression by a voltage-gated sodium channel inhibitor (RS100642)

Breast cancer (BCa) was induced in vivo in female rats with 7,12-dimethylbenz(a)anthracene (DMBA). Two main questions were addressed. Firstly, would the carcinogenesis be accompanied by oxidative stress as signalled by superoxide dismutase, glutathione peroxidase, malondialdehyde and total nitrate? Secondly, would treating the rats additionally with a blocker of voltage-gated sodium channel (VGSC) activity, shown previously to promote BCa progression, affect the oxidative responses? The DMBA-induced increases in the antioxidant systems were completely blocked by the VGSC inhibitor RS100642, which also significantly prolonged the lifespan. We conclude that VGSC inhibition in vivo can significantly protect against oxidative stress and improve survival from tumour burden.

Mechanisms of resistance to photodynamic therapy

Photodynamic therapy (PDT) involves the administration of a photosensitizer (PS) followed by illumination with visible light, leading to generation of reactive oxygen species. The mechanisms of resistance to PDT ascribed to the PS may be shared with the general mechanisms of drug resistance, and are related to altered drug uptake and efflux rates or altered intracellular trafficking. As a second step, an increased inactivation of oxygen reactive species is also associated to PDT resistance via antioxidant detoxifying enzymes and activation of heat shock proteins. Induction of stress response genes also occurs after PDT, resulting in modulation of proliferation, cell detachment and inducing survival pathways among other multiple extracellular signalling events. In addition, an increased repair of induced damage to proteins, membranes and occasionally to DNA may happen. PDT-induced tissue hypoxia as a result of vascular damage and photochemical oxygen consumption may also contribute to the appearance of resistant cells. The structure of the PS is believed to be a key point in the development of resistance, being probably related to its particular subcellular localization. Although most of the features have already been described for chemoresistance, in many cases, no cross-resistance between PDT and chemotherapy has been reported. These findings are in line with the enhancement of PDT efficacy by combination with chemotherapy. The study of cross resistance in cells with developed resistance against a particular PS challenged against other PS is also highly complex and comprises different mechanisms. In this review we will classify the different features observed in PDT resistance, leading to a comparison with the mechanisms most commonly found in chemo resistant cells.

Vicente MG, Luguya R, Norton J, Fronczek FR, Smith KM. Effect of overall charge and charge distribution on cellular uptake, distribution and phototoxicity of cationic porphyrins in HEp2 cells

Five cationic porphyrins bearing one to four -N(CH(3))(3)(+) groups linked to the p-phenyl positions of 5,10,15,20-tetraphenylporphyrin (TPP) were synthesized in order to study the effect of overall charge and its distribution on the cellular uptake, phototoxicity and intracellular localization using human carcinoma HEp2 cells. The di-cationic porphyrins DADP-o and DADP-a accumulated the most within cells and preferentially localize within vesicular compartments and in mitochondria. Of these two only DADP-a was phototoxic to the cells (IC(50)=3 microM at 1 J/cm(2)). The mono-cationic porphyrin MAP was found to be the most phototoxic of the series, and it localized mainly in lipid membranes, including the plasma membrane, ER, mitochondria, and Golgi. Both the tri-cationic porphyrin TRAP and the tetra-cationic porphyrin TEAP localized subcellularly mainly in the mitochondria, but of the two only TEAP showed moderate phototoxicity (IC(50)=8 microM at 1 J/cm(2)). Our results suggest that MAP is the most promising PDT photosensitizer, and that both DADP-o and TRAP might find application as transport vehicles for therapeutics into cells.

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.

Photodynamic therapy for pancreatic cancer

OBJECTIVES

This study examined the status of photodynamic therapy (PDT) in the treatment of cancers of the pancreas.

METHODS

Original and review articles, editorials, and case reports published primarily in English and listed in Medline/ISI up to October 2006 or identified by a manual search have been reviewed in an attempt to provide a comprehensive overview of the mechanisms of PDT action and clinical application of PDT in the treatment of pancreatic cancers.

RESULTS

Photodynamic therapy represents a novel treatment of pancreatic malignancy; it produces local necrosis of tissue with light after administration of a photosensitizing agent. Evidences from in vivo and in vitro results have shown that PDT significantly decreases pancreatic cancer cell growth, destroys pancreatic carcinoma, and prolongs the survival of patients with unresectable pancreatic malignancy, and also show that PDT has disadvantages and limitations for the treatment of pancreatic cancer.

CONCLUSIONS

Photodynamic therapy can be an effective treatment of patients with pancreatic cancer, but more extensive preclinical and clinical trials are needed for further improvement in the clinical application of PDT, especially in avoidance of complications during PDT.

Mitochondrial reactive oxygen species and nitric oxide-mediated cancer cell apoptosis in 2-butylamino-2-demethoxyhypocrellin B photodynamic treatment

Photodynamic therapy (PDT) is a novel and promising cancer treatment which employs a combination of a photosensitizing chemical and visible light to induce apoptosis in cancer cells. Singlet oxygen has been recognized as the main origin of oxidative stress in PDT. However, the precise mechanism of PDT-induced apoptosis is not well characterized, especially the dualistic role of nitric oxide (NO). To dissect the apoptosis pathways triggered by PDT, the intracellular free radicals in MCF-7 cells were investigated by examining a novel photosensitizer 2-butylamino-2-demethoxyhypocrellin B (2-BA-2-DMHB)-mediated PDT. It was found that exposure of the cells to 2-BA-2-DMHB and irradiation resulted in a significant increase of intracellular ROS in minutes, and then followed by cytoplasmic free calcium enhancement, mitochondrial nitric oxide synthase (mtNOS) activation, cytochrome c release, and apoptotic death. Scavengers of singlet oxygen or NO could attenuate PDT-induced cell viability loss, nucleus morphology changes, cytochrome c release, mitochondria swelling, and apo-apoptosis gene p53 and p21 mRNA levels. The results suggested that both ROS and NO played important roles in the apoptosis-induced by PDT.

Restorative effect of Kalpaamruthaa, an indigenous preparation, on oxidative damage in mammary gland mitochondrial fraction in experimental mammary carcinoma

Cancer prevention and treatment using phytochemicals have attracted increased interest. Recent studies have shown that Semecarpus anacardium Linn nut milk extract (SA), a promising antioxidant and anticancer drug, exerts its anticancer effect through reducing or quenching reactive oxygen species under different conditions. The present study examined whether Phyllanthus emblica Linn fruit, rich in vitamin C content synergistically in combination can enhance both the antioxidant and anticancer activity of S. anacardium nut milk extract in 7, 12-dimethyl benz[a]anthracene (DMBA)-induced experimental mammary carcinoma in rat model. Female Sprague Dawley rats of 180 +/- 10 g were categorized into six groups. Three groups were administered DMBA (25mg/rat, orally) dissolved in olive oil to induce mammary carcinoma. One of these groups received Kalpaamruthaa (KA) (300 mg/kg b.wt, orally) and other group received SA (200mg/kg b.wt, orally) for 14 days after 90 days of DMBA induction. A vehicle treated control and drug control groups were also included. The mitochondrial fraction of untreated DMBA-induced mammary gland showed 2.61-fold increase in lipid peroxidation level and abnormal changes in the activities/levels of mitochondrial enzymic (superoxide dismutase, glutathione peroxidase and glutathione reductase) and non-enzymic (glutathione, vitamin C and vitamin E) antioxidants were observed. DMBA treated rats also showed decline in the activities of mitochondrial enzymes such as succinate dehydrogenase, malate dehydrogenase, alpha-ketoglutarate dehydrogenase and isocitrate dehydrogenase. In contrast, rats treated with Kalpaamruthaa showed normal lipid peroxide level and antioxidant defenses. The results of the present study highlight the improved antioxidant property of KA than sole treatment of S. anacardium nut milk extract.

Alterations in mitochondrial and apoptosis-regulating gene expression in photodynamic therapy-resistant variants of HT29 colon carcinoma cells

Photodynamic therapy (PDT) is a novel cancer therapy inducing irreversible photodamage to tumor tissue via photosensitizer-mediated oxidative cytotoxicity. The cellular and molecular responses associated with PDT are only partially understood. We have reported previously the generation of several photosensitizer-specific PDT-resistant cell variants of HT29 human colon adenocarcinoma cells by selecting cells from sequential PDT treatment using different photosensitizers. In this report, we describe the use of messenger RNA (mRNA) differential display to identify genes that were differentially expressed in the parental HT29 cells compared with their resistant variants. In comparison with parental HT29 cells, mRNA expression was increased in the PDT-resistant cell variants for BNIP3, estrogen receptor-binding fragment-associated gene 9, Myh-1c, cytoplasmic dynein light chain 1, small membrane protein I and differential dependent protein. In contrast, expression in the PDT-resistant variants was downregulated for NNX3, human HepG2 3' region Mbol complementary DNA, glutamate dehydrogenase, hepatoma-derived growth factor and the mitochondrial genes coding for 16S ribosomal RNA (rRNA) and nicotinamide adenine dinucleotide (NADH) dehydrogenase subunit 4. The reduction for mitochondrial 16S rRNA in the PDT-resistant variants was confirmed by Northern blotting, and the elevated expression of the proapoptotic BNIP3 in the PDT-resistant variants was confirmed by Northern and Western blotting analysis. We also examined the expression of some additional apoptosis-regulating genes using Western blotting. We show an increased expression of Bcl-2 and heat shock protein 27 and a downregulation of Bax in the PDT-resistant variants. In addition, the mutant p53 levels in the parental HT29 cells were reduced substantially in the PDT-resistant variants. We suggest that the altered expression in several mitochondrial and apoptosis-regulating genes contributes to PDT resistance.

Antioxidant activities of phenolic acids on ultraviolet radiation-induced erythrocyte and low density lipoprotein oxidation

The exposure of mammalian cells to UV light induces various deleterious responses. Some of the major harmful effects are DNA damage, cell membrane peroxidation, systemic immune suppression, and aging acceleration. Reactive oxygen species and free radicals are believed to be largely responsible for some of the deleterious effects of UV upon cells. Typical administration of antioxidants has recently proved to represent a successful strategy for protecting the cells against UV-mediated oxidative damage. The objective of this study was to investigate the inhibitory effect of phenolic acids (caffeic acid, ferulic acid, gallic acid, and protocatechuic acid) on oxidative damage in human erythrocytes and low-density lipoprotein (LDL) induced by UVB radiation. The results revealed that the thiobarbituric acids reactive substances induced by UVB were decreased from 2.78 to 0.12-0.89 nmol MDA/mg protein in erythrocyte ghost and from 0.72 to 0.14-0.43 nmol MDA/mg protein in LDL by the addition of phenolic acids (100 muM). Caffeic acid, ferulic acid, and gallic acid exhibited over 85 and 60% inhibitory effect toward UVB-induced oxidation in erythrocytes and LDL, respectively. Phenolic acids, especially gallic acid, could maintain the normal glutathione levels and glutathione peroxidase activity in hemolysate from erythrocytes that were exposed to UVB radiation in comparison with untreated control. The results indicate that the antioxidant activities of caffeic acid and ferulic acid play a potential role in protection against UVB oxidative damage to human erythrocytes and LDL.

Radioprotective property of the ethanolic extract of Piper betel Leaf

The radioprotective activity of Piper betel ethanolic extract (PE) has been studied using rat liver mitochondria and pBR 322 plasmid DNA as two model in vitro systems. The extract effectively prevented gamma-ray induced lipid peroxidation as assessed by measuring thiobarbituric acid reactive substrates, lipid hydroperoxide and conjugated diene. Likewise, it prevented radiation-induced DNA strand breaks in a concentration dependent manner. The radioprotective activity of PE could be attributed to its hydroxyl and superoxide radicals scavenging property along with its lymphoproliferative activity. The radical scavenging capacity of PE was primarily due to its constituent phenolics, which were isolated and identified as chevibetol and allyl pyrocatechol.

Effect of Treating Induced Mitochondrial Damage on Embryonic Development and Epigenesis

Germinal vesicle transplantation (GVT) has been proposed as a possible treatment to correct age-related oocyte aneuploidy caused by dysfunctional ooplasm. How healthy ooplasm regulates normal meiosis and subsequent development has yet to be elucidated, but impaired mitochondrial metabolism may be attributable to incomplete segregation of the oocyte chromosomes. In the present study, after ooplasmic mitochondrial damage by photoirradiating chloromethyl-X-rosamine, examination of the oocyte nuclei's ability to survive after transfer into healthy ooplasts was performed. To assess their fertilizability and potential for development, GVT oocytes were fertilized by intracytoplasmic sperm injection (ICSI) and transferred to foster mice. Condition of the offspring at birth was assessed, and epigenetic analysis was performed. Photosensitization consistently inhibited oocyte maturation. However, after GVT of photosensitized nuclei into healthy ooplasts, 67.2% were reconstituted, and 76.2% of these matured normally, with an overall rate of 51.2%, much higher than that (6.0%) in the mitochondrially injured oocytes. After ICSI, 65.8% (52/79) of GVT oocytes were fertilized normally, and 21.1% (11/52) eventually reached the blastocyst stage. The transfer of 132 two-cell GVT embryos into the oviducts of pseudopregnant females resulted in 17 apparently healthy live offspring. For some key developmental genes, a high level of expression was identified in the GVT and "rescue"-derived fetal adnexa. Thus, one can induce in oocyte mitochondria a photosensitization-based type of damage, which consistently inhibits GV breakdown, meiotic spindle formation, chromosomal segregation, and polar body extrusion. Germinal vesicle transplanted and rescued oocytes were able to undergo maturation, fertilization, and embryonic cleavage and, ultimately, to develop to term. This approach may provide a model with which to study the age-related ooplasmic dysfunction seen in human oocytes.

Inhibition of photohemolysis induced by m-chloroperbenzoic acid by metal complexes with SOD-mimetic activity

Red blood cells (RBCs) are probably the most common target through the damaging action of reactive oxygen species on the cells. The photohemolysis activity of m-chloroperbenzoic acid (CPBA) was concentration- and exposure time-dependent. Twenty minutes photo exposure time and 200 microm of CPBA concentration were optimum to study the effect of generated superoxide (O2-) and hydroxyl (*OH) radicals on RBCs. RBCs lysis photosensitized by CPBA was investigated in the presence of [(VL2O)(VL2H2O)]Cl6, [MnL2O]2Cl42H2O, [FeL2Cl2]Cl H2O, [CoL2Cl2]4H2O or [ZnL2Cl2]H2O respectively, where L is 2-methylaminopyridine, with SOD-mimetic activities with the aim of ascertaining their protective activity towards the photo induced cell damage. The decrease of photolytic activity caused by these complexes was concentration-dependent and the maximum percentage of protective activity was 75, 70, 68, 57 or 24% for [(VL2O)(VL2H2O)]Cl6, [MnL2O]2Cl4 2H2O, [FeL2Cl2]Cl H2O, [CoL2Cl2]4H2O or [ZnL2Cl2]H2O complex respectively, against the cell irradiated without addition of metal complexes. The comparison between the decrease of photolytic activity caused by these complexes and their SOD-mimetic activity of these metal complexes showed an appreciable correlation.

Preparation and biological evaluation of the new chlorin photosensitizer T3,4BCPC for detection and treatment of tumors

The new water-soluble photosensitizer 5,10,15,20-tetrakis[3,4-bis(carboxymethyleneoxy)phenyl]chlorin (T3,4BCPC) has been prepared, characterized and labeled with 99mTc radionuclide. The radiotracer was evaluated for tissue distribution in Wistar rats. Accumulation of administrated activities in the liver, kidney, bladder and large intestine at 4 h post-injection indicated that the labeled ligand was largely eliminated through the renal and partly through the hepatobiliary system. In vivo biodistribution studies of the labeled compound were carried out in rodent and murine tumor models in comparison with other tumor-seeking radiopharmaceuticals such as 99mTc(V)-dimercaptosuccinic acid (DMSA), 201thallous chloride (TlCl) and 99mTc-citrate using a gamma camera computer system. In N-nitrosomethylurea (NMU)-induced rat mammary tumors, the labeled ligand showed a five-fold tumor to muscle (T/M) ratio compared to 99mTc(V)-DMSA (3-fold) and 201TlCl (3-fold). In the case of C(3)H/J virus-induced spontaneous mammary tumors, the differences were not marked. However, in the transplanted rat C(6)-glioma, the T/M ratio of the labeled compound was appreciably higher (four-fold) than that noted with 99mTc(V)-DMSA (two-fold), 201TlCl (three-fold) and 99mTc-citrate (more than three-fold). These findings suggest that the radiolabeled T3,4BCPC may have potential for the detection of cancer. In order to ascertain the efficacy of the compound for photodynamic therapy applications, a preclinical PDT study was carried out in fibrosarcoma-bearing mice after injecting 5.0 mg/kg body weight of the T3,4BCPC. A laser dose of 20 mW for 60 s resulted in 80% destruction of tumors. These data suggest that this molecule could be useful for PDT of cancer. The labeled agent could also be useful in monitoring the progression/regression of tumors before, during, and after chemotherapy, radiation therapy or PDT.

Induction of Hsp60 by Photofrin-mediated photodynamic therapy

Photodynamic therapy (PDT) invokes a number of cellular responses. Other studies have shown that PDT induces transcription and translation of heat shock proteins (Hsps). The expression of mitochondrial heat shock protein, Hsp60, was measured following in vitro Photofrin-mediated PDT in the colon cancer cell line HT29 and its PDT-induced resistant variant HT29-P14 as well as the radiation-induced fibrosarcoma cells RIF-1 and its PDT-induced resistant variant, RIF-8A. Basal levels of Hsp60 were found to be similar in the two murine cell lines. In the human model, the resistant HT29-P14 cell line showed a small increase in basal levels relative to its parental population. Incubation with Photofrin (PII) alone or photosensitization caused a significant increase in Hsp60 levels in all cell lines as determined by flow cytometry. A dose-dependent and temporal relationship for PDT response was observed, maximum levels were detected 6-8 h post PDT, at which time, Hsp60 induction was found to be significantly greater in the two resistant variants. Induction in the RIF cells was also found to be greater after incubation with PII alone at the highest doses tested. These results indicate that the presence of PII and the subsequent oxidative stress of PDT can induce Hsp60 and implicated it as a common factor that may contribute to the resistance observed in the induced resistant cells.

Photodynamic therapy and the alimentary tract

Photodynamic therapy offers the possibility of relatively selective tumour necrosis and normal tissue healing. It has many potential applications but as yet no clear role. Articles, editorials and case reports published primarily in English and listed in Medline/ISI up to April 2000 or identified by a manual search have been reviewed in an attempt to provide a comprehensive overview of the use of photodynamic therapy in the alimentary tract. It is concluded that photodynamic therapy can be an effective treatment for superficial pre-malignant mucosal lesions and early cancers, especially in diffuse disease. Suitable patients include those wishing to avoid surgery, high risk subjects or those in whom other forms of treatment have failed. Superiority over other methods of ablation has not so far been demonstrated. Cheaper and more effective photosensitizers and improved techniques of light delivery are likely to increase the application of photodynamic therapy.

In vitro induction of PDT resistance in HT29, HT1376 and SK-N-MC cells by various photosensitizers

Our approach to examine the mechanism(s) of action for photodynamic therapy (PDT) has been via the generation of PDT-resistant cell lines. In this study we used three human cell lines, namely, human colon adenocarcinoma (HT29), human bladder carcinoma and human neuroblastoma. The three photosensitizers used were Photofrin, Nile Blue A and aluminum phthalocyanine tetrasulfonate. The protocol for inducing resistance consisted of repeated in vitro photodynamic treatments with a photosensitizer to the 1-10%-survival level followed by regrowth of single surviving colonies. Varying degrees of resistance were observed. The three induced variants of the HT29 cell line were the most extensively studied. Their ratios of increased survival at the LD90 level range between 1.5- and 2.62-fold more resistant.

Investigation of cross-resistance to a range of photosensitizers, hyperthermia and UV light in two radiation-induced fibrosarcoma cell strains resistant to photodynamic therapy in vitro

Two distinct photodynamic therapy-resistant variants of the murine radiation-induced fibrosarcoma (RIF) cell line have been isolated. One strain displayed relative resistance over the parental RIF-1 strain to treatment with the porphyrin-based compound, polyhaematoporphyrin (PHP), whereas the other strain displayed relative resistance over the RIF-1 strain to treatment using the cationic zinc (II) pyridinium-substituted phthalocyanine (PPC). The PHP-resistant strain did not display cross-resistance to PPC-mediated treatment, and vice versa. In both PDT-resistant strains, the increased resistance could not be attributed to altered cellular growth rate, antioxidant capacity or intracellular sensitizer localization. The PHP-resistant strain displayed resistance to treatment with both short (1 h) and extended (16 h) sensitizer incubation periods, which may indicate that in this strain, the resistance has arisen through an alteration in a membrane component. Conversely, the PPC-resistant strain only displayed increased resistance over the parental cells to treatment involving the short drug incubation, which is likely to reflect the existence of a threshold effect caused by the alteration of an individual cellular target. Each resistant strain has been compared to the parental strain in terms of cellular sensitivity to treatment with a range of other photosensitizers, hyperthermia, UV light and the anticancer agent cis-diamminedichloroplatinum. The PHP-resistant strain exhibited crossresistance to photosensitization treatment using exogenously added protoporphyrin IX, and also to treatment with the anionic phthalocyanine sensitizers, zinc (II) tetrasulfonated phthalocyanine and zinc (II) tetraglycine-substituted phthalocyanine. The PPC-resistant strain did not display cross-resistance to any of the treatment strategies employed in this investigation. The results of this investigation indicate that there are at least two distinct mechanisms of PDT resistance in RIF cells, and that the mechanism of PHP resistance may, to some extent depend, upon the physical nature of the sensitizer molecule.

Implications of the generation of reactive oxygen species by photoactivated calcein for mitochondrial studies

Calcein is a fluorescent probe that is widely used in studies of cell viability and mitochondrial function by microscopy fluorescence imaging. It was found to have a strong photosensitizing action that prevalently involves the generation of reactive oxygen species (ROS). The photooxidation properties of calcein in solution were studied in the presence of histidine and tryptophan as oxidizable substrates. The photodegradation of histidine was mainly mediated by singlet oxygen (1O2), as shown by the inhibitory effect of sodium azide, a specific 1O2 scavenger. On the other hand, mixed photosensitization mechanisms were present when tryptophan was used as the target of the calcein-stimulated photoprocess. In addition to 1O2, hydroxyl radicals and hydrogen peroxide were involved as reactive species, as shown by using mannitol and catalase as scavengers. The calcein-photosensitized alterations of mitochondria as a potential source of artifacts in confocal microscopy studies of cells were considered. Irradiation of isolated mitochondria with visible light (500-600 nm) in the presence of calcein induced opening of the permeability transition (PT) pore. The extent of the mitochondrial membrane photodamage, however, was modulated by the nature of the calcein environment. Thus, pore opening was triggered at short irradiation times and low dye concentrations when calcein was dissolved in the bulk medium. On the contrary, calcein concentrated in the matrix space was rather inefficient as photosensitizer even at concentrations 10 times higher than those present in the external medium.

In vitro and in vivo photosensitizing capabilities of 5-ALA versus photofrin in vascular endothelial cells

BACKGROUND AND OBJECTIVE

The objective of the present study was to evaluate the feasibility of photodynamic therapy (PDT) for complicated hemangiomas. The photosensitizing activities of 5-aminolevulinic acid (5-ALA) and Photofrin were evaluated in vitro with human dermal microvascular endothelial cells (MEC) and in vivo with the chicken cox comb.

STUDY DESIGN/MATERIALS AND METHODS

The in vitro absorption and photosensitizing activities of 5-ALA and Photofrin were examined in a MEC culture system. The percentages of MEC killed by different drug concentrations at a wavelength of 630 nm were measured by either live/dead or lactate dehydrogenase-released assays. Similarly, the in vivo biological activities of 5-ALA and Photofrin exposed to different total light dosages at 630 nm were studied by determining the amount of necrosis produced in chicken combs.

RESULTS

MEC incubated with 5-ALA at a concentration of 35 microg/ml and exposed to laser light at 630 nm at a power density of 100 mW/cm2 showed a 50% cell kill. MEC incubated with Photofrin at a concentration of 3.5 microg/ml and exposed to laser light at 630 nm at a power density of 100 mW/cm2 showed a 50% cell kill. Chicken combs that received 200 mg/kg of 5-ALA exposed to laser light at 630 nm at a power density of 100 mW/cm2 had an injury depth of 362.5+/-27.6 microm at histologic examination. Combs exposed to a power density of 100 or 120 mW/cm2 showed injury depths of 732.5+/-29.1 and 792.5+/-36.0 microm, respectively. Chicken combs that received 2.5 mg/kg of Photofrin exposed to laser light at 630 nm at a power density of 80 mW/cm2 had an injury depth of 535.6+/-22.3 microm at histologic examination. Combs exposed to a power density of 100 or 120 mW/cm2 showed injury depths of 795.8+/-32.5 and 805.2+/-49.1 microm, respectively.

CONCLUSION

Both 5-ALA and Photofrin have the capability to destroy MEC in vitro and vasculature in vivo. However, Photofrin achieved a higher degree of cell kill and tissue destruction at lower drug concentrations and at lower power densities.

Nicotinamide (vitamin B3) as an effective antioxidant against oxidative damage in rat brain mitochondria

Nicotinamide (vitamin B3) an endogenous metabolite, showed significant inhibition of oxidative damage induced by reactive oxygen species (ROS) generated by ascorbate-Fe2+ and photosensitization systems in rat brain mitochondria. It protected against both protein oxidation and lipid peroxidation, at millimolar concentrations. Inhibition was more pronounced against oxidation of proteins than peroxidation of lipids. Chemically related endogenous compounds, tryptophan and isonicotinic acid, showed comparable inhibitory properties. The protective effect observed, at biologically relevant concentrations, with nicotinamide was more than that of the endogenous antioxidants ascorbic acid and alpha-tocopherol. Hence our studies suggest that nicotinamide (vitamin B3) can be considered as a potent antioxidant capable of protecting the cellular membranes in brain, which is highly susceptible to prooxidants, against oxidative damage induced by ROS.

Serum albumin-lipid membrane interaction influencing the uptake of porphyrins

It is frequently observed in pharmaceutical practice that entrapped substances are lost rapidly when liposomes are used as carriers to introduce substances into cells. The reason for the loss is the interaction of serum components with liposomes. To elucidate the mechanism of this phenomenon the partition of mesoporphyrin (MP) was systematically studied in model systems composed of various lipids and human serum albumin (HSA). As surface charge is an important factor in the interaction, neutral (1, 2-dimyristoyl-sn-glycero-3-phosphatidylcoline, DMPC) and negatively charged (1,2-dimyristoyl-sn-glycero-3-phosphatidylcoline/1, 2-dimyristoyl-sn-glycero-3-phosphatidylglycerol, DMPC/DMPG = 19/1 w/w) lipids were compared. The liposome/apomyoglobin system was the negative control. The size distribution of sonicated samples was carefully analyzed by dynamic light scattering. Constants of association of MP to the proteins and to the liposomes were determined: K(p,1) = (2.5 +/- 0.7) x 10(7) M(-1), K(p,2) = (1.0 +/- 0.7) x 10(8) M(-1), K(L,1) = (1.3 +/- 0.3) x 10(5) M(-1), and K(L,2) = (3.2 +/- 0.6) x 10(4) M(-1) for HSA, apomyoglobin, DMPC, and DMPC/DMPG liposomes, respectively. These data were used to evaluate the partition experiments. The transfer of MP from the liposomes to the proteins was followed by fluorescence spectroscopy. In the case of apomyoglobin, the experimental points could be interpreted by ruling out the protein-liposome interaction. In the case of HSA, the efflux of MP from the liposomes was strongly inhibited above a critical HSA concentration range for negatively charged vesicles. This effect was interpreted as the result of HSA coat formation on the liposome surface. This direct interaction is significant for small liposomes. The interpretation is fully supported by differential scanning calorimetry experiments.

Mitochondria and cell death. Mechanistic aspects and methodological issues

Mitochondria are involved in cell death for reasons that go beyond ATP supply. A recent advance has been the discovery that mitochondria contain and release proteins that are involved in the apoptotic cascade, like cytochrome c and apoptosis inducing factor. The involvement of mitochondria in cell death, and its being cause or consequence, remain issues that are extremely complex to address in situ. The response of mitochondria may critically depend on the type of stimulus, on its intensity, and on the specific mitochondrial function that has been primarily perturbed. On the other hand, the outcome also depends on the integration of mitochondrial responses that cannot be dissected easily. Here, we try to identify the mechanistic aspects of mitochondrial involvement in cell death as can be derived from our current understanding of mitochondrial physiology, with special emphasis on the permeability transition and its consequences (like onset of swelling, cytochrome c release and respiratory inhibition); and to critically evaluate methods that are widely used to monitor mitochondrial function in situ.

Chloromethyl-X-rosamine (MitoTracker Red) photosensitises mitochondria and induces apoptosis in intact human cells

We report that chloromethyl-X-rosamine (MitoTracker Red), a mitochondrion-selective fluorescent probe, has a strong photosensitising action. Photoirradiation of intact cells loaded with chloromethyl-X-rosamine induces depolarisation of the inner mitochondrial membrane and swelling of mitochondria, subsequently resulting in apoptosis. We have studied human osteosarcoma 143B TK-(rho+) cells and the derived (rho)0 206 cell line devoid of mitochondrial DNA. Colony formation tests revealed that chloromethyl-X-rosamine itself has no toxicity to either cell line in the concentration range 100–250 nM (unless photoirradiated). Chloromethyl-X-rosamine has potent phototoxicity such that almost quantitative cell killing was achieved at light doses of >2 J/cm2. These photodamaged cells initially showed swollen degenerative mitochondria and, later, uptake of propidium iodide in their apoptotic nuclei was observed. When cells were loaded with chloromethyl-X-rosamine (100 nM) and imaged by laser scanning confocal microscopy, photoirradiation by the laser beam under routine scanning conditions was sufficient to induce mitochondrial damage in both cell lines. This was evidenced by a rapid decrease of fluorescence intensity of co-loaded rhodamine 123 (indicative of mitochondrial depolarisation). Globular swelling of mitochondria took place within 15 minutes, imaged by the residual fluorescence of chloromethyl-X-rosamine itself, which also markedly decreased in intensity after imaging. Mitochondrial membrane depolarisation of cells loaded with chloromethyl-X-rosamine after photoirradiation using a measured dose of visible light was independently confirmed in 143B TK- and (rho)0 206 cells, by the significant decrease in uptake into cells of [3H]methyltriphenylphosphonium ions. Photoactivation of chloromethyl-X-rosamine in 143B TK-(rho+) cells, whose mitochondria had previously been loaded with calcein, caused rapid release of the mitochondrially entrapped calcein into the cytosol and nucleus. This major change in permeability of the mitochondrial inner membrane could not be prevented by cyclosporin A. Immunohistochemical study of cytochrome c revealed its diffuse redistribution into the cytoplasm in chloromethyl-X-rosamine-loaded cells after irradiation, as opposed to its specific mitochondrial localisation in non-irradiated cells. As a photosensitiser specifically targeted to mitochondria, and also a reporter of membrane potential and morphology, chloromethyl-X-rosamine may provide versatile new applications in studies of mitochondrial roles in cell death.

Photodynamic effects induced by meso-tetrakis[4-(carboxymethyleneoxy)phenyl] porphyrin on isolated Sarcoma 180 ascites mitochondria

Using mitochondria isolated from Sarcoma 180 ascites tumour in Swiss mice as a model system, we have evaluated the ability of a novel porphyrin, meso-tetrakis[4-(carboxymethyleneoxy)phenyl]porphyrin (H2T4CPP), to induce damage on photosensitization. Oxidative damage to mitochondria, one of the primary and crucial targets of the photodynamic effect, is assessed by measuring products of lipid peroxidation such as thiobarbituric acid reactive substances (TBARS) and lipid hydroperoxides (LOOH), besides the loss of activity of the mitochondrial marker enzyme succinate dehydrogenase (SDH). Analysis of product formation, the effect of deuteration and selective inhibition by scavengers of reactive oxygen species (ROS) show that the damage observed is due mainly to singlet oxygen (1O2) and to a minor extent to hydroxyl radicals (.OH). The 1O2 generation and triplet lifetime of this porphyrin have also been estimated. Fluorescence spectroscopy, used to ascertain the binding of this porphyrin to the mitochondrial proteins, shows a rapid association within 0-2 h and a decline thereafter. Confocal microscopy reveals intracellular localisation of this porphyrin in cells in vitro. Our overall results suggest that the porphyrin H2T4CPP, due to its ability to bind to mitochondrial protein components and to generate ROS upon photoexcitation, may have potential applications in photodynamic therapy.

Endogenous porphyrin accumulation and photosensitization in the yeast Saccharomyces cerevisiae in the presence of 2,2'-dipyridyl

The chelator 2,2'-dipyridyl (0.2 mM) induces a remarkable increase of protoporphyrin IX concentration as well as of its Zn-containing complex in the yeast Saccharomyces cerevisiae. Endogenous porphyrin accumulation results in five- to six-fold cell sensitization to visible light (400-600 nm). Mitochondria isolated from the cells grown in the presence of 2,2'-dipyridyl accumulate protoporphyrin IX and Zn-protoporphyrin IX, while plasma membranes besides that exhibit porphyrin-type fluorescence at 670-675 nm in chloroform extract. The protoporphyrin IX content increases more than four-fold in mitochondria and two-fold in plasma membranes isolated from chelator-treated cells. The relative contribution of subcellular structure photodestruction to photoinduced cell inactivation is discussed.

Effects of photodynamic action on respiration in nonphosphorylating mitochondria

We have studied the effects of singlet oxygen produced by photodynamic action on respiration in nonphosphorylating mitochondria (state 4). Isolated rat liver mitochondria were incubated with 3 microM hematoporphyrin and irradiated at 365 nm with a fluence rate of 25 W/m2. After short durations of irradiation, state 4 respiration with beta-hydroxybutyrate as substrate increases while respiration with succinate is negligibly affected. When mitochondria have been uncoupled with carbonylcyanide-p-trifluoromethoxyphenyl hydrazone before irradiation, no change occurs in beta-hydroxybutyrate-driven respiration, while succinate-driven respiration strongly decreases. Stimulation of state 4 NADH respiration cannot be explained by slippage of the NADH ubiquinone oxidoreductase because the stoichiometry of the redox pump was found insensitive to photodynamic action. In the light of the metabolite theory for linear enzymatic chains applied to state 4 respiration (Brand et al., Biochem. J. 255, 535-539, 1988), these results suggest that stimulation of NADH respiration is simply due to an increase of membrane leaks which occurs after irradiation. In the case of succinate-driven respiration, a strong inhibition of succinate dehydrogenase activity has been demonstrated after irradiation. It can be suggested that this inhibition introduces a negative control coefficient over state 4 respiration, counterbalancing the effects due to leakage.

Delta-aminolevulinic acid-mediated photosensitization of prostate cell lines: implication for photodynamic therapy of prostate cancer

BACKGROUND

Delta-aminolevulinic acid (ALA)-mediated photodynamic therapy (PDT) is currently being investigated for the treatment of prostate diseases. In this study, we evaluate 1) the in vitro production of protoporphyrin IX (PPIX) (the active photosensitizing agent of ALA-mediated PDT) by two different prostate cancer cell lines (LNCaP and PC-3) and a benign, modified, prostatic cell line (TP-2), and 2) the extent of PDT-induced cell injury, as determined by electron microscopy (EM) and cell survival.

METHODS

The cell lines were assigned into four treatment groups: group 1, control, no ALA and no light irradiation; group 2, dark control, ALA only; group 3, light control, radiation only; and group 4, PDT, ALA followed by irradiation (630 nm, 3 joules/cm2). The experiments were performed in triplicate. ALA concentration was 50 microg/ml of media in all instances.

RESULTS

Following incubation with ALA, PPIX production was significantly increased in the three cell lines studied, and more notably in the PC-3 cell line. Compared to controls, EM and cell survival studies demonstrated significant mitochondrial damage and decreased survival, respectively, in the cells treated with PDT. This was also more evident in the PC-3 cell line.

CONCLUSIONS

Our results demonstrate that prostate cells differ in their response to ALA-mediated PDT. This response appears to depend on the intracellular production of PPIX and the cell type, i.e., on the functional and structural characteristics of the cell mitochondria. In addition, our results suggest that PDT might be effective at killing prostate cancer cells.

Time-course of hypericin phototoxicity and effect on mitochondrial energies in EMT6 mouse mammary carcinoma cells

Photoactivated hypericin produces singlet oxygen and superoxide anion radical; however, the intracellular events contributing to toxicity are unknown. Clonogenic assays of oxygen-dependent hypericin phototoxicity to EMT6 cells have previously shown that 0.5 microM hypericin + 1.5 J cm(-2) fluorescent light is non-toxic and that 1.0 microM hypericin + 1.5 J cm(-2) fluorescent light produces LD40 toxicity. Intracellular events leading to toxicity were revealed at these doses. Lactate dehydrogenase leakage was elevated for both 0.5 microM and 1.0 microM hypericin + light immediately following irradiation. While values eventually returned to control levels for 0.5 microM hypericin + light, leakage increased over time for 1.0 microM hypericin indicating reversible and irreversible toxicity, respectively. Increases in lipid and protein oxidation were measured immediately following irradiation; however, these parameters return to control levels within 0.5 h for both doses. Both total cellular ATP levels and cellular respiration were depressed by approximately 50% of control values for 1.0 microM hypericin + light. These values were unchanged for 0.5 microM hypericin + light. Along with previously reported data demonstrating that light-activated hypericin can inhibit mitochondial succinoxidase in beef heart mitochondria in vitro, these data support oxidative stress-initiated mitochondrial damage as a key target in hypericin phototoxicity.

Pilot in vitro toxicity study of 5-ALA and Photofrin in microvascular endothelial cell cultures

Complicated hemangiomas are unique problems in which intervention with the proper laser can be an ideal solution. In this study we evaluated the toxicity of 5-Aminolevulinic acid (5-ALA) and Photofrin using in vitro models. The in vitro toxicity of 5-ALA and Photofrin was examined in a microvascular endothelial cell (MEC) culture system. The measurement of the percentage of MEC killed by various drug concentration using fluorescence viability assay. MEC incubated with 5-ALA at various concentrations for evaluation of dark toxicity showed less than a 50% cell kill. A comparison of different intervals of subcultured MEC showed that the early subculture (3 days after primary culture) is more vulnerable than later subculture (7 days after). Cells treated with Photofrin at various concentrations exhibited less than 50% cell kill (dark toxicity). The comparison of different intervals of subculture (3 days and 7 days after primary culture) showed a result similar to that of 5-ALA. All controls showed 0% cell kill. In conclusion, both 5-ALA and Photofrin are capable of destroying human microvascular endothelial cells in vitro. Drug concentrations and the power density for photodynamic therapy should be considered and will be included in our subsequent studies.