Hypericin phototoxicity induces different modes of cell death in melanoma and human skin cells

A combination of photodynamic therapy and chemotherapy displays a differential cytotoxic effect on human metastatic melanoma cells

BACKGROUND

Cutaneous melanoma represents the most lethal form of skin cancer and remains refractory to current therapies. Failure of treatment has been attributed to the over-expression of ABC transporters which efflux the drugs, below their cytotoxic threshold within cells. Therefore, this study set to investigate; the efficacy of a combinatorial approach comprising chemotherapy (Dacarbazine) and photodynamic therapy (PDT) to overcome resistance in pigmented and unpigmented metastatic melanoma and potentially identify resistant mechanisms.

METHODS

The cytotoxic effect of the chemotherapy, PDT and combination therapy treatment (Dacarbazine+PDT) was determined using a cell viability XTT assay. Thereafter, melanoma cells morphology, self-renewal capacity and ABCG2 protein expression, were determined using fluorescence microscopy, clonogenic assay, western blot and flow cytometry. All results were analyzed by t-test and ANOVA, followed by individual comparisons with post-tests.

RESULTS

This study describes possible synergism of PDT+DTIC in reducing melanoma cell viability in vitro. At 24h post-treatment, only the unpigmented melanomas were sensitive to DTIC treatment (20-25% death at 1.25mM). At 48h, a lethal dose of 50% was reached in these cells in contrast to the pigmented melanoma (20% at 48h). The same trend was observed with the combination therapy (DTIC+PDT) at both time points. Furthermore, complete morphological disruption could be observed upon PDT only and PDT+DTIC treatments. Moreover, PDT and DTIC+PDT suppressed the self-renewal capacity of both melanoma cell lines. No significant differences in ABCG2 protein expression was found at 24h post-treatment.

CONCLUSION

Overall, these results suggest that human melanomas remain heterogeneous in their phenotypes. Moreover, in our metastatic melanoma cells, ABCG2 transporters did not seem to be involved in resistance to therapies. Significantly though, a combinatorial approach of PDT and chemotherapy significantly decreases the self-renewal capacity of metastatic melanoma cells and could be a suggested adjunctive approach to post-resection treatment regimes.

Differential diagnosis of gallstones by using hypericin as a fluorescent optical imaging agent

AIM: To explore the feasibility of using hypericin as an optical imaging probe with affinity for cholesterol for differential fluorescent detection of human gallstones.

METHODS: Cholesterol, mixed and pigment stones from cholecystectomy patients were incubated with hypericin or solvent. After 72 h, the stones were analysed for fluorescence (365 nm) and treated with 2-propanol/dimethyl sulfoxide for high performance liquid chromatography (HPLC) analysis. Rats with virtual gallbladder containing human cholesterol, mixed or pigment gallstones (VGHG) received 5 mg/kg hypericin or solvent and VGHG rats with cholesterol stones were given different hypericin doses (5-15 mg/kg). Twelve hours later, the stones were analysed at 365 nm. Biliary excretion and metabolites of hypericin were assessed in common bile duct (CBD) cannulated rats for 9 h using fluorospectrometry, HPLC and matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry (MALDI-TOF MS).

RESULTS: Homogeneous high fluorescence was seen on cholesterol stones either pre-incubated with hypericin or extracted from VGHG rats receiving hypericin. Mixed stones showed a dotted fluorescent pattern, whereas pigment and solvent-treated ones lacked fluorescence. HPLC showed 7.68, 6.65 and 0.08 × 10^-3 M of cholesterol in extracts from cholesterol, mixed, and pigment gallstones, respectively. Hypericin accounted for 2.0, 0.5 and 0.2 × 10^-6 M in that order. On cholesterol stones from VGHG rats receiving different hypericin doses, a positive correlation was observed between dose and fluorescence. In the bile from CBD-cannulated rats, fluorescence represented 20% of the injected dose with two peaks in 9 h. HPLC analysis revealed that hypericin conjugates reached 60% of the peak area. By MALDI-TOF MS, hypericin-glucuronide was detected.

CONCLUSION: This study proves the potential use of hypericin for differential fluorescent detection of human gallstones regarding their chemical composition.

Time course of apoptosis induced by photodynamic therapy with PsD007 in LT12 acute myeloid leukemia cells

Apoptosis is one of the major mechanisms of photodynamic therapy (PDT) that leads to tumor degradation. Apoptosis-related genes and proteins function in a certain order and timing in the complex network of apoptosis. To further understanding of the apoptotic mechanism of PDT, this research examined the time course of apoptosis from PsD007 (a second-generation photosensitizer developed in China) induced PDT on the rat acute myeloid leukemia cell line LT12. MTT was used to detect the temporal dynamic of PDT killing effects and identified the "apoptotic window" of 2-24 h. Apoptosis showed a basal peak at 2 h, and the duration of apoptosis depended on PDT dose, which disappeared quickly at low concentrations but lasted to higher levels to 6 or 12 h at high concentrations as detected by flow cytometry. High-content imaging confirmed these results. An 84-gene apoptosis PCR array identified 15 genes with an expression level change of over twofold at 6 h post-PDT. Nine apoptosis-related genes showed changes in expression at 2-12 h after PDT. TNF family genes TNF and FASLG showed a maximal change of 3.47- and 4.42-fold from baseline. Key apoptosis proteins such as activated caspases showed strong up-regulation after PDT, with the expression peaks of cleaved caspase-7, caspase-9 and PARP at 4-6 h, and cleaved caspase-3 delayed to 6-12 h. Our findings help clarify the time course of apoptosis events in response to PDT treatment in a leukemia cell line and may help contribute to the clinical application of PDT in leukemia treatment.

Hypericin-photodynamic therapy induces human umbilical vein endothelial cell apoptosis

The conventional photosensitizers used in photodynamic therapy (PDT), such as haematoporphyrin (HP), have not yet reached satisfactory therapeutic effects on port-wine stains (PWSs), due largely to the long-term dark toxicity. Previously we have showed that hypericin exhibited potent photocytotoxic effects on Roman chicken cockscomb model of PWSs. However, the molecular mechanism of hypericin-mediated photocytotoxicity remains unclear. In this study, we employed human umbilical vein endothelial cells (HUVECs) to investigate the hypericin-photolytic mechanism. Our study showed that hypericin-PDT induced reactive oxygen species (ROS), resulting in cell killings and an activation of the inflammatory response. Importantly, we have also discovered that photoactivated hypericin induced apoptosis by activating the mitochondrial caspase pathway and inhibiting the activation of the vascular endothelial growth factor-A (VEGF-A)-mediated PI3K/Akt pathway. Notably, we found that hypericin exhibited a more potent photocytotoxic effect than HP, and largely addressed the inconvenience issue associated with the use of HP. Thereby, hypericin may be a better alternative to HP in treating PWSs.

Development of a novel formulation with hypericin to treat cutaneous leishmaniasis based on photodynamic therapy in in vitro and in vivo studies

An evaluation of the leishmanicidal activity in vitro and in vivo of hypericin, an expanded-spectrum photosensitizer found in Hypericum perforatum, is presented. Hypericin was evaluated against intracellular amastigotes in vitro of Leishmania (Viannia) panamensis. A topical formulation containing 0.5% hypericin was developed and assayed in vivo in a hamster model of cutaneous leishmaniasis. Results demonstrate that hypericin induces a significant antiamastigote effect in vitro against L. panamensis by decreasing the number of parasites inside infected cells. The topical formulation of 0.5% hypericin allows healing of L. panamensis-induced lesions upon a topical application of 40 mg/day plus visible-light irradiation (5 J/cm(2), 15 min), twice a week for 3 weeks.

Differential susceptibility of primary cultured human skin cells to hypericin PDT in an in vitro model

Skin cancer is the most common cancer worldwide, and its incidence rate in South Africa is increasing. Photodynamic therapy (PDT) has been shown to be an effective treatment modality, through topical administration, for treatment of non-melanoma skin cancers. Our group investigates hypericin-induced PDT (HYP-PDT) for the treatment of both non-melanoma and melanoma skin cancers. However, a prerequisite for effective cancer treatments is efficient and selective targeting of the tumoral cells with minimal collateral damage to the surrounding normal cells, as it is well established that cancer therapies have bystander effects on normal cells in the body, often causing undesirable side effects. The aim of this study was to investigate the cellular and molecular effects of HYP-PDT on normal primary human keratinocytes (Kc), melanocytes (Mc) and fibroblasts (Fb) in an in vitro tissue culture model which represented both the epidermal and dermal cellular compartments of human skin. Cell viability analysis revealed a differential cytotoxic response to a range of HYP-PDT doses in all the human skin cell types, showing that Fb (LD50=1.75μM) were the most susceptible to HYP-PDT, followed by Mc (LD50=3.5μM) and Kc (LD50>4μM HYP-PDT) These results correlated with the morphological analysis which displayed distinct morphological changes in Fb and Mc, 24h post treatment with non-lethal (1μM) and lethal (3μM) doses of HYP-PDT, but the highest HYP-PDT doses had no effect on Kc morphology. Fluorescent microscopy displayed cytoplasmic localization of HYP in all the 3 skin cell types and additionally, HYP was excluded from the nuclei in all the cell types. Intracellular ROS levels measured in Fb at 3μM HYP-PDT, displayed a significant 3.8 fold (p<0.05) increase in ROS, but no significant difference in ROS levels occurred in Mc or Kc. Furthermore, 64% (p<0.005) early apoptotic Fb and 20% (p<0.05) early apoptotic Mc were evident; using fluorescence activated cell sorting (FACS), 24h post 3μM HYP-PDT. These results depict a differential response to HYP-PDT by different human skin cells thus highlighting the efficacy and indeed, the potential bystander effect of if administered in vivo. This study contributes toward our knowledge of the cellular response of the epidermis to photodynamic therapies and will possibly enhance the efficacy of future photobiological treatments.

Melanoma resistance to photodynamic therapy: new insights

Melanoma is the most dangerous form of skin cancer, with a steeply rising incidence and a poor prognosis in its advanced stages. Melanoma is highly resistant to traditional chemotherapy and radiotherapy, although modern targeted therapies such as BRAF inhibitors are showing some promise. Photodynamic therapy (PDT, the combination of photosensitizing dyes and visible light) has been tested in the treatment of melanoma with some promising results, but melanoma is generally considered to be resistant to it. Optical interference by the highly-pigmented melanin, the antioxidant effect of melanin, the sequestration of photosensitizers inside melanosomes, defects in apoptotic pathways, and the efflux of photosensitizers by ATP-binding cassette transporters have all been implicated in melanoma resistance to PDT. Approaches to overcoming melanoma resistance to PDT include: the discovery of highly active photosensitizers absorbing in the 700-800-nm near infrared spectral region; interventions that can temporarily reduce the amount or pigmentation of the melanin; compounds that can reverse apoptotic defects or inhibit drug-efflux of photosensitizers; and immunotherapy approaches that can take advantage of the ability of PDT to activate the host immune system against the tumor being treated.

Development of a multifunctional luciferase reporters system for assessing endoplasmic reticulum-targeting photosensitive compounds

Photodynamic therapy (PDT) is a recently developed antitumor modality utilizing the generation of reactive oxygen species (ROS), through light irradiation of photosensitizers (PSs) localized in tumor. Interference with proper functioning of endoplasmic reticulum (ER) by ER-targeting PDT is a newly proposed strategy to achieve tumor cell death. The aim of this study is to establish a multifunctional model to screen and assess ER-targeting PSs based on luciferase reporters system. Upregulation of GRP78 is a biomarker for the onset of ER stress. CHOP is a key initiating player in ER stress-induced cell death. Here, the most sensitive fragments of GRP78 and CHOP promoters responding to ER-targeting PDT were mapped and cloned into pGL3-basic vector, forming -702/GRP78-Luc and -443/CHOP-Luc construct, respectively. We demonstrated that -702/GRP78-Luc expression can be used to indicate the ER-targeting of PSs, meanwhile estimate the ROS level induced by low-dose ER-targeting PDT. Moreover, the luciferase signaling of -443/CHOP-Luc showed highly consistence with apoptosis rate caused by ER-targeting PDT, suggesting that -443/CHOP-Luc can evaluate the antitumor properties of PSs. Hypericin, Foscan® and methylene blue were applied to verify the sensitivity and reliability of our model. These results proved that GRP78-CHOP model may be suitable to screen ER-targeting photosensitive compounds with lower cost and higher sensitivity than traditional ways.

Review of natural compounds for potential skin cancer treatment

Most anti-cancer drugs are derived from natural resources such as marine, microbial and botanical sources. Cutaneous malignant melanoma is the most aggressive form of skin cancer, with a high mortality rate. Various treatments for malignant melanoma are available, but due to the development of multi-drug resistance, current or emerging chemotherapies have a relatively low success rates. This emphasizes the importance of discovering new compounds that are both safe and effective against melanoma. In vitro testing of melanoma cell lines and murine melanoma models offers the opportunity for identifying mechanisms of action of plant derived compounds and extracts. Common anti-melanoma effects of natural compounds include potentiating apoptosis, inhibiting cell proliferation and inhibiting metastasis. There are different mechanisms and pathways responsible for anti-melanoma actions of medicinal compounds such as promotion of caspase activity, inhibition of angiogenesis and inhibition of the effects of tumor promoting proteins such as PI3-K, Bcl-2, STAT3 and MMPs. This review thus aims at providing an overview of anti-cancer compounds, derived from natural sources, that are currently used in cancer chemotherapies, or that have been reported to show anti-melanoma, or anti-skin cancer activities. Phytochemicals that are discussed in this review include flavonoids, carotenoids, terpenoids, vitamins, sulforaphane, some polyphenols and crude plant extracts.

St John's Wort (Hypericum perforatum L.) photomedicine: hypericin-photodynamic therapy induces metastatic melanoma cell death

Hypericin, an extract from St John's Wort (Hypericum perforatum L.), is a promising photosensitizer in the context of clinical photodynamic therapy due to its excellent photosensitizing properties and tumoritropic characteristics. Hypericin-PDT induced cytotoxicity elicits tumor cell death by various mechanisms including apoptosis, necrosis and autophagy-related cell death. However, limited reports on the efficacy of this photomedicine for the treatment of melanoma have been published. Melanoma is a highly aggressive tumor due to its metastasizing potential and resistance to conventional cancer therapies. The aim of this study was to investigate the response mechanisms of melanoma cells to hypericin-PDT in an in vitro tissue culture model. Hypericin was taken up by all melanoma cells and partially co-localized to the endoplasmic reticulum, mitochondria, lysosomes and melanosomes, but not the nucleus. Light activation of hypericin induced a rapid, extensive modification of the tubular mitochondrial network into a beaded appearance, loss of structural details of the endoplasmic reticulum and concomitant loss of hypericin co-localization. Surprisingly the opposite was found for lysosomal-related organelles, suggesting that the melanoma cells may be using these intracellular organelles for hypericin-PDT resistance. In line with this speculation we found an increase in cellular granularity, suggesting an increase in pigmentation levels in response to hypericin-PDT. Pigmentation in melanoma is related to a melanocyte-specific organelle, the melanosome, which has recently been implicated in drug trapping, chemotherapy and hypericin-PDT resistance. However, hypericin-PDT was effective in killing both unpigmented (A375 and 501mel) and pigmented (UCT Mel-1) melanoma cells by specific mechanisms involving the externalization of phosphatidylserines, cell shrinkage and loss of cell membrane integrity. In addition, this treatment resulted in extrinsic (A375) and intrinsic (UCT Mel-1) caspase-dependent apoptotic modes of cell death, as well as a caspase-independent apoptotic mode that did not involve apoptosis-inducing factor (501 mel). Further research is needed to shed more light on these mechanisms.

Photo-induced processes in collagen-hypericin system revealed by fluorescence spectroscopy and multiphoton microscopy

Collagen is the main structural protein and the key determinant of mechanical and functional properties of tissues and organs. Proper balance between synthesis and degradation of collagen molecules is critical for maintaining normal physiological functions. In addition, collagen influences tumor development and drug delivery, which makes it a potential cancer therapy target. Using second harmonic generation, two-photon excited fluorescence microscopy, and spectrofluorimetry, we show that the natural pigment hypericin induces photosensitized destruction of collagen-based tissues. We demonstrate that hypericin-mediated processes in collagen fibers are irreversible and may be used for the treatment of cancer and collagen-related disorders.

Investigation of the phototoxicity and cytotoxicity of naproxen, a non-steroidal anti-inflammatory drug, in human fibroblasts

Non-steroidal anti-inflammatory drugs (NSAID) are widely used in the treatment of pain and inflammation associated with several diseases. Naproxen, 2-(6-methoxy-2-naphthyl) propionic acid (NAP), belongs to this pharmacological class and appears to be associated with a high incidence of both photoallergic and phototoxic reactions. In this study, using human fibroblasts, we examined the biological effects of NAP photosensitization induced by UVA, the predominant UV component of sunlight reaching the Earth's surface. We showed that NAP or UVA alone have no cytotoxic effects at the concentrations and doses used in this study. The same result was observed when cells were pre-incubated with NAP but irradiated without NAP. In marked contrast, exposure of cells in the presence of NAP led to a drastic reduction of cell viability. These results suggest that the phototoxicity is mainly due to irradiation of extracellular NAP that damages cell membranes. Moreover, we showed that NAP itself led to a low but reproducible production of reactive oxygen species (ROS), to protein modifications by lipid peroxidation-derived aldehydes, to p38 phosphorylation and to the slowing-down of DNA replication, while UVA treatment alone showed no effects. NAP photosensitization with UVA led to protein S-glutathionylation, oxidation of the proliferating cell nuclear antigen (PCNA), oxidation of cellular tryptophan, phosphorylation of Chk1 and inhibition of DNA replication. However, using small interfering RNA to down regulate Chk1 expression in cells, we showed that Chk1 is not required to slow the S-phase down. Nevertheless, inhibition of Chk1, but not of p38, sensitized the cells to the phototoxic effects of NAP. Collectively, our data suggest that the interaction of NAP with the cells triggers oxidative damage and a replication stress, which are exacerbated by UVA radiation. As oxidative and replication stress-induced genome instability are important factors in aging and tumor predisposition, it is of interest to evaluate the consequence of a non-steroidal anti-inflammatory drug, like naproxen, on genomic instability.

Phototoxicity of herbal plants and herbal products

Plants are used by humans in daily life in many different ways, including as food, herbal medicines, and cosmetics. Unfortunately, many natural plants and their chemical constituents are photocytotoxic and photogenotoxic, and these phototoxic phytochemicals are widely present in many different plant families. To date, information concerning the phototoxicity and photogenotoxicity of many plants and their chemical constituents is limited. In this review, we discuss phototoxic plants and their major phototoxic constituents; routes of human exposure; phototoxicity of these plants and their constituents; general mechanisms of phototoxicity of plants and phototoxic components; and several representative phototoxic plants and their photoactive chemical constituents.

Photodynamic therapeutic activity of indocyanine green entrapped in polymeric nanoparticles

BACKGROUND

Photodynamic therapy (PDT) is a therapeutic modality involving the use of a photosensitizer agent activated by light of appropriate wavelength to selectively destroy tumor cells. Indocyanine green (ICG) is a promising photosensitive agent for PDT of tumor cells. The main disadvantage of using ICG in PDT is the instability of ICG in aqueous solutions. Encapsulating ICG dye in a biocompatible matrix based on PEBBLE technology showed an improvement of aqueous stability comparing with free ICG dye. The main objective of this study is to investigate the photodynamic effect of ICG-ormosil PEBBLEs on two different cell lines: human breast adenocarcinoma cells (MCF-7) and hepatocellular carcinoma cells (HepG2).

METHODS

ICG-embedded ormosil PEBBLEs were synthesized based on a sol-gel process, and characterized by transmission electron microscopy and other fluorescence tests. The cell viability was evaluated by MTT and trypan blue assays. Apoptosis, necrosis, and DNA damage (comet assay), were evaluated by fluorescence microscopic tests.

RESULTS

The results declared that ICG-ormosil PEBBLEs and free ICG both have the same cytotoxic and phototoxic effect on MCF-7 and HepG2 cell lines, where the apoptotic mode of cell death is preferentially occurred in case of PDT using ICG-ormosil PEBBLEs. Both ICG and ICG-ormosil PEBBLEs induced DNA damage after laser exposure. These results would suggest that entrapping ICG in Polymeric nanoparticles forming ICG-ormosil PEBBLEs improve the aqueous stability of the photosensitizer and in the same time retain its photodynamic activity, suggesting that it is preferred to use ICG-ormosil PEBBLEs instead of free ICG dye.

Laser light activation of a second-generation photosensitiser and its use as a potential photomodulatory agent in skin rejuvenation

Photodynamic rejuvenation therapy (PDRT) is a growing field in cosmetic dermatology. In this study, different sources of light (a yellow laser, a red laser and ultraviolet A (UVA) lamps) were used to activate a second-generation photosensitiser, hypericin. Uptake of hypericin was monitored over 24 h and efficacy of PDRT was assessed using cell viability and reactive oxygen species (ROS) quantification assays. In addition, we show for the first time, a quantifiable assay for ROS production in human dermal fibroblasts incubated with hypericin and exposed to yellow laser light or UVA lamps. Furthermore, we optimised a protocol with regard to hypericin concentration and irradiation parameters using the XTT cell viability kit. This study showed that this photosensitiser, hypericin, was taken up by the cells in a concentration-dependent manner over 24 h with cell saturation occurring after approximately 16 h. The uptake seemed to be localised to the cell cytoplasm with no hypericin appearing in the nucleus. The levels of ROS increased in the cell when irradiated with the yellow laser (561 nm) however, it did not increase further with the addition of hypericin. Hypericin and UVA showed a significant increase in the amount of ROS produced. The results also show that cell viability is not affected by low power light (2 mW) from the yellow laser irrespective of the dose used. However, an increase to 10 mW power with 5 J/cm(2) light dose, resulted in a significant drop (p < 0.05) in cell viability at both 0.5 (77.53 ± 9.67 %) and 1 μM (48.51 ± 13.27 %) hypericin concentrations. In contrast, a 20 % increase in cell viability was seen with 1 J/cm(2) and 20 mW and 0.25 μM hypericin. Overall, this study highlights an optimised protocol for hypericin-induced photorejuvenative therapy using laser light and proposes that parameters of 0.25 μM hypericin as a photosensitiser activated via a dosage of 1 J/cm(2) yellow laser light produces an effective in vitro outcome to be considered as an important contribution towards optimising PDRT.

Photodynamic therapy-induced killing is enhanced in depigmented metastatic melanoma cells

The resistance of pigmented human melanomas over their unpigmented counterparts to a number of therapies has suggested that the presence of intracellular melanin plays a role in rendering these cells less susceptible to cell death, probably through the ability of this pigment to act as an intracellular antioxidant, thus neutralizing chemotherapeutic-induced ROS (reactive oxygen species). PDT (photodynamic therapy) was recently suggested as an attractive, adjunctive therapy owing to its cellular specificity and limited side effects. In the present study, we propose that first depigmenting melanomas with a reversible TYR (tyrosinase) inhibitor such as PTU (phenylthiourea) increases their susceptibility to HYP-PDT (hypericin-mediated PDT). Pigmented [UCT Mel-1 (University of Cape Town melanoma cell line 1)] and unpigmented (A375) melanomas were first characterized with respect to their TYR activities and melanin quantities and then treated with a TYR inhibitor for 48 h. Cell viability assays after treatment with 3 μM HYP-PDT showed a significant increase in cell death in depigmented melanomas compared with untreated melanomas that returned to the level of untreated melanoma cells on removing the TYR inhibitor. The present study supports the hypothesis that combining the inhibition of melanogenesis with PDT should be explored as a valid therapeutic target for the management of advanced melanoma.

Many stimuli pull the necrotic trigger, an overview

The lab of Jürg Tschopp was the first to report on the crucial role of receptor-interacting protein kinase 1 (RIPK1) in caspase-independent cell death. Because of this pioneer finding, regulated necrosis and in particular RIPK1/RIPK3 kinase-mediated necrosis, referred to as necroptosis, has become an intensively studied form of regulated cell death. Although necrosis was identified initially as a backup cell death program when apoptosis is blocked, it is now recognized as a cellular defense mechanism against viral infections and as being critically involved in ischemia-reperfusion damage. The observation that RIPK3 ablation rescues embryonic lethality in mice deficient in caspase-8 or Fas-associated-protein-via-a-death-domain demonstrates the crucial role of this apoptotic platform in the negative control of necroptosis during development. Here, we review and discuss commonalities and differences of the increasing list of inducers of regulated necrosis ranging from cytokines, pathogen-associated molecular patterns, to several forms of physicochemical cellular stress. Since the discovery of the crucial role of RIPK1 and RIPK3 in necroptosis, these kinases have become potential therapeutic targets. The availability of new pharmacological inhibitors and transgenic models will allow us to further document the important role of this form of cell death in degenerative, inflammatory and infectious diseases.

Growth inhibition of malignant glioblastoma by DING protein

Malignant gliomas are a highly aggressive type of brain tumor with extremely poor prognosis. These tumors are highly invasive and are often surgically incurable and resistant to chemotherapeutics and radiotherapy. Thus, novel therapies that target pathways involved in growth and survival of the tumor cells are required for the treatment of this class of brain tumors. Previous studies revealed that epidermal growth factor receptor and extracellular-signal-regulated kinases (ERKs), which are involved in the induction of cell proliferation, are activated in the most aggressive type of glioma, i.e. glioblastoma multiforme (GBM). In fact, GBMs with increased levels of ERK activity exhibit a more aggressive phenotype than the others with moderate ERK activity, pointing to the importance of ERK and its kinase activity in the development and progression of these tumors. In this study, we have evaluated the effect of p38SJ, a novel member of the DING family of proteins, derived from Hypericum perforatum calluses, on the growth of malignant glioma cell lines, T98G and U-87MG by focusing on cell cycle and signaling pathways controlled by phosphorylation of various regulatory proteins including ERK. p38SJ, which exhibits profound phosphatase activity, shows the capacity to affect the phosphorylation status of several important kinases modulating signaling pathways, and cell growth and proliferation. Our results demonstrate that p38SJ reduces glioma cell viability and arrests cell cycle progression at G0/G1. The observed growth inhibitory effect of p38SJ is likely mediated by the downregulation of several cell cycle gatekeeper proteins, including cyclin E, Cdc2, and E2F-1. These results suggest that p38SJ may serve as a potential candidate for development of a therapeutic agent for the direct treatment of malignant gliomas and/or as a potential radiosensitizer.

The in vitro PDT efficacy of a novel metallophthalocyanine (MPc) derivative and established 5-ALA photosensitizing dyes against human metastatic melanoma cells

BACKGROUND AND OBJECTIVE

Numerous worldwide clinical trials have shown that photodynamic therapy (PDT) represents an effective and safe modality for various skin disorders, but little research has been done in terms of its effect on malignant melanomas (MM). Thus, the aim of this study was to compare the effect of both established porphyrin photosensitizer 5-aminolevulinic acid (5-ALA) and novel metallophthalocyanine (MPc) photosensitizer on human metastatic skin cells which produce a MM.

MATERIALS AND METHODS

The cellular responses following PDT were assessed using changes in cell morphology, cell viability, cytotoxicity, apoptosis, and proliferation.

RESULTS

Findings reported that in vitro human MM cell line A375 (EACC no: 88113005) are highly sensitive to growth inhibition and apoptosis induction by the cytotoxic side-effects induced by MPc and 5-ALA photosensitizing treatments post-laser irradiation at 680 and 636 nm, respectively. The decrease of cell viability accompanied by an increased cytotoxicity and apoptotic and necrotic levels, with a time-dependant decrease in cellular proliferation was found to be far more significant for MPc-treated cells than 5-ALA-treated cells, since MPc was applied in far lower concentrations and exhibited far less photoxicity to control cells.

CONCLUSION

Hence, novel MPc proved to be the better photosensitizing dye for metastatic melanoma tumor destruction in combination with laser irradiation and is a particularly attractive photosensitizer since it exhibits so many ideal properties of a photosensitizing agent, thus further research of this possible anticancer agent could contribute to its potential application in PDT cancer treatment of MMs.

Chitosan-coated triangular silver nanoparticles as a novel class of biocompatible, highly effective photothermal transducers for in vitro cancer cell therapy

One of the relevant directions that nanotechnology is taking nowadays is connected with nanomedicine and specifically related to the use of light and nanoparticles in early diagnosis and effective therapeutics of cancer. Noble-metal nanoparticles can act under laser irradiation as effective photothermal transducers for triggering localized hyperthermia of tumors. In this work we report the performance of newly synthesized chitosan-coated silver nanotriangles (Chit-AgNTs) with strong resonances in near-infrared (NIR) to operate as photothermal agents against a line of human non-small lung cancer cells (NCI-H460). The hyperthermia experiments were conducted by excitation of nanoparticles-loaded cells at 800 nm wavelength from a Ti:Sapphire laser. We found that the rate of cell mortality in the presence of Chit-AgNTs is higher than in the presence of thiolated poly(ethylene) glycol capped gold nanorods (PEG-AuNRs) - a common hyperthermia agent used as reference-, while no destructive effects were noticed on the control sample (cells without nanoparticles) under identical irradiation conditions. Additionally, we conducted cytotoxicity assays and found Chit-AgNTs to be efficiently uptaken by the cells while exhibiting good biocompatibility for healthy human embryonic cells (HEK), which is essential for any in vivo applications. Our results reveal a novel class of biocompatible plasmonic nanoparticles with high potential to be implemented as effective phototherapeutic agents in the battle against cancer.

Solvatochromic and fluorescence behavior of sulfisoxazole

The Fluorescence spectroscopic and solvatochromic behavior of Sulfisoxazole, a sulfa drug with antimicrobial activities, in various pure solvents of different polarity and hydrogen bonding capability is reported. The fluorescence emission spectrum of sulfisoxazole was found to be solvent polarity dependent, where a notable red shift in emission maximum was observed with increasing solvent polarity as well as hydrogen bonding capability. The effects of the latter two solvent parameters were quantitatively investigated using the methods of Lippert-Mataga and solvatochromic comparison method (SCM) that is based on the Kamlet-Taft equation. Particularly, the Lippert-Mataga method was applied to estimate the dipole moment of the excited state (μ(e)) upon plotting Stokes shift versus solvent polarizability (Δf), where a value of 11.54 Debye was obtained. On the other hand, applying the multiple regression analysis to the SCM method revealed that solvent polarizability (π*) and hydrogen-bond donor capability (α) approximately equally stabilize sulfisoxazole in the excited state with minor destabilization contribution by the hydrogen-bond acceptor capability (β). These findings revealed that the excited state of sulfisoxazole is stabilized by polar solvents, indicating that this drug molecules exhibit larger dipole moment in the excited state than in the ground state, which in turn implies that a potential intramolecular charge transfer (ICT) occurs after excitation.

Combating melanoma: the use of photodynamic therapy as a novel, adjuvant therapeutic tool

Metastatic malignant melanoma remains one of the most dreaded skin cancers worldwide. Numerous factors contribute to its resistance to hosts of treatment regimes and despite significant scientific advances over the last decade in the field of chemotherapeutics and melanocytic targets, there still remains the need for improved therapeutic modalities. Photodynamic therapy, a minimally invasive therapeutic modality has been shown to be effective in a number of oncologic and non-oncologic conditions. Using second-generation stable, lipophilic photosensitizers with optimised wavelengths, PDT may be a promising tool for adjuvant therapy in combating melanoma. Potential targets for PDT in melanoma eradication include cell proliferation inhibition, activation of cell death and reduction in pro-survival autophagy and a decrease in the cellular melanocytic antioxidant system. This review highlights the current knowledge with respect to these characteristics and suggests that PDT be considered as a good candidate for adjuvant treatment in post-resected malignant metastatic melanoma. Furthermore, it suggests that primary consideration must be given to organelle-specific destruction in melanoma specifically targeting the melanosomes - the one organelle that is specific to cells of the melanocytic lineage that houses the toxic compound, melanin. We believe that using this combined knowledge may eventually lead to an effective therapeutic tool to combat this highly intractable disease.

Hypericins as potential leads for new therapeutics

70 years have passed since the first isolation of the naphthodianthrones hypericin and pseudohypericin from Hypericum perforatum L. Today, they continue to be one of the most promising group of polyphenols, as they fascinate with their physical, chemical and important biological properties which derive from their unique chemical structure. Hypericins and their derivatives have been extensively studied mainly for their antitumor, antiviral and antidepressant properties. Notably, hypericin is one of the most potent naturally occurring photodynamic agents. It is able to generate the superoxide anion and a high quantum yield of singlet oxygen that are considered to be primarily responsible for its biological effects. The prooxidant photodynamic properties of hypericin have been exploited for the photodynamic therapy of cancer (PDT), as hypericin, in combination with light, very effectively induces apoptosis and/or necrosis of cancer cells. The mechanism by which these activities are expressed continues to be a main topic of discussion, but according to scientific data, different modes of action (generation of ROS & singlet oxygen species, antiangiogenesis, immune responces) and multiple molecular pathways (intrinsic/extrinsic apoptotic pathway, ERK inhibition) possibly interrelating are implicated. The aim of this review is to analyse the most recent advances (from 2005 and thereof) in the chemistry and biological activities (in vitro and in vivo) of the pure naphthodianthrones, hypericin and pseudohypericin from H. perforatum. Extracts from H. perforatum were not considered, nor pharmakokinetic or clinical data. Computerised literature searches were performed using the Medline (PubMed), ChemSciFinder and Scirus Library databases. No language restrictions were imposed.

Melanomas display increased cytoprotection to hypericin-mediated cytotoxicity through the induction of autophagy

Photodynamic therapy (PDT) as a regime for melanoma is of limited success due to factors such as the efficacy of the photosensitizer used, penetration depth and the presence of pigment. We characterised a pigmented and an unpigmented melanoma cell line with respect to their phenotypes. Cell viability was assessed after exposure to hypericin, a UVA-activated photosensitizer. Exposure to 3 microM activated hypericin induced a cytoprotective (autophagic) response from both cell lines. However, the pigmented cells accumulated a large amount of glycogen in their cytoplasm. We hypothesise that the treatment induces an initial cytoprotective response through autophagy, but with increased stress results in a different mode of cell death in pigmented melanoma cells from unpigmented cells. These results indicate that hypericin-PDT could be an adjuvant therapy for melanoma.

Photodynamic therapy (PDT): a short review on cellular mechanisms and cancer research applications for PDT

Photodynamic therapy (PDT) has been used for many years, but it is only now becoming widely accepted and utilized. Originally it was developed as a tumor therapy and some of its most successful applications are for non-malignant diseases. This article provides a broad review of different parameters used and mechanisms instituted in PDT such as photosensitizers (PS), photochemistry and photophysics, cellular localization, cellular signaling, cell metabolism and modes of cell death that operate on a cellular level, as well as photosensitizer pharmacokinetics, biodistribution, tumor localization and modes of tumor destruction. These specific cellular mechanisms are most commonly applied in PDT and for the most part are often researched and exploited. If the combination of these specific parameters and mechanisms can be optimized within PDT it could possibly be used as a suitable alternative for the treatment and management of specific cancers.