Ascorbic acid suppresses cell death in rat DS-sarcoma cancer cells induced by 5-aminolevulinic acid-based photodynamic therapy

Photosensitive Chitosan-Based Injectable Hydrogel Chemically Cross-Linked by Perylene Bisimide Dopamine with Robust Antioxidant and Cytotoxicity Enhancer Properties for In Vitro Photodynamic Therapy of Breast Cancer

Here, we report the fabrication of an antioxidant photosensitizing hydrogel system based on chitosan (CS-Cy/PBI-DOPA) covalently cross-linked with perylene bisimide dopamine (PBI-DOPA) as a photosensitizer. The severe insolubility and low tumor selectivity limitations of perylene were overcome by conjugation with dopamine and then to the chitosan hydrogel. The mechanical and rheological study of CS-Cy/PBI-DOPA photodynamic antioxidant hydrogels illustrated interconnected microporous morphologies with high elasticity, swelling ability, and suitable shear-thinning behavior. Bio-friendly properties, such as biodegradability and biocompatibility, excellent singlet oxygen production abilities, and antioxidant properties were also delivered. The antioxidant effects of the hydrogels control the physiological levels of reactive oxygen species (ROS) generated by photochemical reactions in photodynamic therapy (PDT), which are responsible for oxidative damage to tumor cells while protecting normal cells and tissues from ROS damage, including blood and endothelial cells. In vitro, PDT tests of hydrogels were conducted on two human breast cancer cell lines, MDA-MB-231 and MCF-7. These hydrogels offered more than 90% cell viability in the dark and good photocytotoxicity performance with 53 and 43% cell death for MCF-7 and MDA-MB-231 cells, which confirmed their promising potential for cancer therapeutic applications.

Influence of Ascorbic Acid as a Growth and Differentiation Factor on Dental Stem Cells Used in Regenerative Endodontic Therapies

BACKGROUND

Vitamin C is one of the major extracellular nonenzymatic antioxidants involved in the biosynthesis of collagen. It promotes the growth of fibroblasts, wound healing processes, and enhances the survival and differentiation of osteoblasts. The potential effects of ascorbic acid on human dental pulp cells (DPC) and the cells of the apical papilla (CAP) used in actual regenerative endodontic procedures remain largely unknown. In this study, we investigated the possible employment of ascorbic acid in the differentiation and regenerative therapies of DPC and CAP.

METHODS

Nine extracted human wisdom teeth were selected for this study. Subpopulations of stem cells within DPC and CAP were sorted with the mesenchymal stem cell marker STRO-1, followed by treatments with different concentrations (0 mM, 0.1 mM, 0.5 mM, and 1.0 mM) of ascorbic acid (AA), RT-PCR, and Western blot analysis.

RESULTS

FACS analysis revealed the presence of cell subpopulations characterized by a strong expression of mesenchymal stem cell marker STRO-1 and dental stem cell markers CD105, CD44, CD146, CD90, and CD29. Treatment of the cells with defined amounts of AA revealed a markedly increased expression of proliferation marker Ki-67, especially in the concentration range between 0.1 mM and 0.5 mM. Further investigations demonstrated that treatment with AA led to significantly increased expression of common stem cell markers OCT4, Nanog, and Sox2. The most potent proliferative and expressional effects of AA were observed in the concentration of 0.1 mM.

CONCLUSIONS

AA might be a novel and potent growth promoter of human dental cells. Increasing the properties of human dental pulp cells and the cells of the apical papilla using AA could be a useful factor for further clinical developments of regenerative endodontic procedures.

The oxidative stress, mitochondrial pathway apoptosis, and the antagonistic effects of chrysophanol in SH-SY5Y cells via DTPP-induced photodynamic therapy

BACKGROUND

To investigate the susceptibility of SH-SY5Y cells to DTPP-based photodynamic therapy (PDT) and the antagonistic effects of chrysophanol (Chr) on PDT.

METHODS

PDT photocytotoxicity to cells was quantified and determined by exposing increasing concentrations of DTPP between 2.5 to 20 μg/mL to radiation with energy densities of 1.2-9.6 J/cm² at 630-nm wavelength. Sodium azide (SA, NaN₃) and d-mannitol (DM) were employed to study the reaction type of PDT. The photodynamic stress after PDT was assessed by superoxide dismutase (SOD), malondialdehyde (MDA), and total antioxidative capacity (T-AOC) assays. The apoptosis pathway of SH-SY5Y cells after PDT was studied by the determination of JC-1 and caspase-9/Caspase-3 concentrations. MTT and double fluorescence staining assays were applied to study the effect of Chr on cell survival and apoptosis rate in PDT, respectively. PI was used to detect the effect of Chr on cell membrane integrity after DTPP-PDT treatment.

RESULTS

The dose-dependent killing effect of high DTPP concentrations and irradiation doses were identified. Cell apoptosis is mediated by a mitochondrial pathway with a total apoptosis rate of 33.8% at 10 μg/mL of DTPP after irradiation with 2.4 J/cm². Oxidative stress was produced by ROS in PDT and non-reversible cell oxidative damage appeared due to the cells' modulation of the oxidative stress balance during the PDT response. Chr had a- effect on ROS capture and an inhibitory effect on the PDT-induced destruction of cell membranes.

CONCLUSIONS

SH-SY5Y cells were susceptible to DTPP-PDT, resulting in a mitochondrial apoptosis pathway. There is an antagonistic effect of Chr on PDT in SH-SY5Y neuroblastoma cells.

Assessment of natural antioxidants' effect on PDT cytotoxicity through fluorescence microscopy image analysis

BACKGROUND AND OBJECTIVES

Photodynamic therapy (PDT) is a cancer treatment modality mediated by reactive oxygen species (ROS). However, the intracellular antioxidant defense system antagonizes PDT-generated ROS, impeding PDT efficacy. This study aimed to evaluate the enhancement of PDT cytotoxicity by its combination with natural antioxidants in pro-oxidant concentrations.

METHODS

A rich natural antioxidant mixture originating from Pinus halepensis bark extract was studied for its potential to enhance the efficacy of m-tetrahydroxyphenylchlorin (m-THPC)-PDT on LNCaP prostate cancer cells, in vitro. Various P. halepensis concentrations, at two different incubation times, were used in combination with m-THPC-PDT. Assessment of cellular viability and intracellular ROS levels evaluated the treatments' outcome. A novel method was developed for the assessment of the intracellular ROS levels, based on image analysis and data extraction from fluorescence microscopy images.

RESULTS

P. halepensis bark extract increased the intracellular ROS levels in a concentration-dependent but not in an incubation-dependent manner. The higher concentrations used (≥50 μg/ml) reduced cellular viability even by 50%. One hour pretreatment with 30 μg/ml P. halepensis before m-THPC-PDT exceeded the levels of cellular death by approximately 15%.

CONCLUSIONS

The results provided evidence of the cytotoxic effect of P. halepensis bark extract on LNCaP cells, showing the potential of P. halepensis to be used as an anticancer agent in prostate cancer treatment. The results also provided evidence of enhancement of m-THPC-PDT by P. halepensis bark extract showed the potential to be used as a supplementary agent to improve prostate cancer PDT treatment.

Photodynamic therapy for cancer: Role of natural products

Photodynamic therapy (PDT) is a promising modality for the treatment of cancer. PDT involves administering a photosensitizing dye, i.e. photosensitizer, that selectively accumulates in tumors, and shining a light source on the lesion with a wavelength matching the absorption spectrum of the photosensitizer, that exerts a cytotoxic effect after excitation. The reactive oxygen species produced during PDT are responsible for the oxidation of biomolecules, which in turn cause cell death and the necrosis of malignant tissue. PDT is a multi-factorial process that generally involves apoptotic death of the tumor cells, degeneration of the tumor vasculature, stimulation of anti-tumor immune response, and induction of inflammatory reactions in the illuminated lesion. Numerous compounds with photosensitizing activity have been introduced commercially. Although many papers have been published with regard to PDT in the last decade, there has been relatively little focus on natural medicinal plant extracts and compounds derived therefrom. Herbal plants and their extracts are natural substances, and in comparison with synthetic chemicals are considered "green". This review focuses on the different mechanisms of PDT and discusses the role of various plant extracts and natural compounds either alone or in combination for carrying out PDT on different types of cancers.

Bis(3,5-diiodo-2,4,6-trihydroxyphenyl)squaraine photodynamic therapy disrupts redox homeostasis and induce mitochondria-mediated apoptosis in human breast cancer cells

Photodynamic therapy (PDT) is a clinically established and highly evolving treatment modality for cancer. PDT utilizes a light responsive drug called photosensitizer that selectively destroys tumor cells upon light irradiation. Squaraines are a class of dyes possessing all favorable characteristics of a photosensitizer and have been considered to be a potent candidate for next generation PDT. In this study we chose an iodo derivative of squaraine called diiodo-squaraine (bis(3, 5-diiodo-2,4,6-trihydroxyphenyl)squaraine) which has been reported for its tumor specificity but least studied for its cellular and molecular functions. Our studies revealed that the iodo derivative of squaraine possess maximum photodynamic activity in human breast cancer cells MDA- MB- 231 and had very little cytotoxicity in normal breast cells MCF-10A. We analyzed its pro and anti-apoptotic events initiated by oxidative stress exploring a proteomic approach and delineated other critical molecular pathways and key proteins involved in regulating the complex network of cellular response upon PDT. Our study showed that, diiodo- squaraines predominantly accumulate in mitochondria and induce mitochondria-mediated apoptosis. Our study also reveals the novel mechanistic role of diiodo-squaraines to induce oxidative stress there by activating both protective and death inducing pathways post PDT.

Carbon Dots with Intrinsic Theranostic Properties for Bioimaging, Red-Light-Triggered Photodynamic/Photothermal Simultaneous Therapy In Vitro and In Vivo

Cancer nanotheranostics combining therapeutic and imaging functions within a single nanoplatform are extremely important for nanomedicine. In this study, carbon dots (C-dots) with intrinsic theranostic properties are prepared by using polythiophene benzoic acid as carbon source. The obtained C-dots absorb light in the range of 400-700 nm and emit bright fluorescence in the red region (peaking from 640 to 680 nm at different excitations). More importantly, the obtained C-dots exhibit dual photodynamic and photothermal effects under 635 nm laser irradiation with a singlet oxygen ((1)O2) generating efficiency of 27% and high photothermal conversion efficiency of 36.2%. These unique properties enable C-dots to act as a red-light-triggered theranostic agent for imaging-guided photodynamic-photothermal simultaneous therapy in vitro and in vivo within the therapeutic window (600-1000 nm).

Peroxidase-like activity of Fe3O4@carbon nanoparticles enhances ascorbic acid-induced oxidative stress and selective damage to PC-3 prostate cancer cells

Ascorbic acid (AA) is capable of inhibiting cancer cell growth by perturbing the normal redox state of cells and causing toxic effects through the generation of abundant reactive-oxygen species (ROS). However, the clinical utility of AA at a tolerable dosage is plagued by a relatively low in vivo efficacy. This study describes the development of a peroxidase-like composite nanoparticle for use in an AA-mediated therapeutic strategy. On the basis of a high-throughput, one-pot solvothermal approach, Fe3O4@C nanoparticles (NPs) were synthesized and then modified with folic acid (FA) on the surface. Particular focus is concentrated on the assessment of peroxidase-like catalytic activity by a chromogenic reaction in the presence of H2O2. The carbon shell of Fe3O4@C NPs contains partially graphitized carbon and thus facilitates electron transfer in the catalytic decomposition of H2O2, leading to the production of highly reactive hydroxyl radicals. Along with magnetic responsiveness and receptor-binding specificity, the intrinsic peroxidase-like catalytic activity of Fe3O4@C-FA NPs pronouncedly promotes AA-induced oxidative stress in cancer cells and optimizes the ROS-mediated antineoplastic efficacy of exogenous AA. In vitro experiments using human prostate cancer PC-3 cells demonstrate that Fe3O4@C-FA NPs serve as a peroxidase mimic to create hydroxyl radicals from endogenous H2O2 that is yielded in response to exogenous AA via an oxidative stress process. The usage of a dual agent leads to the enhanced cytotoxicity of PC-3 cells, and, because of the synergistic effect of NPs, the administrated dosage of AA is reduced markedly. However, because normal cells (HEK 293T cells) appear to have a higher capacity to cope with additionally generated ROS than cancer cells, the NP-AA combination shows little damage in this case, proving that selective killing of cancer cells could be achieved owing to preferential accumulation of ROS in cancer cells. A possible ROS-mediated mechanism is discussed to elucidate the pharmaceutical profile of the NP-AA agent. In general, this foundational study reveals that the peroxidase-like nanomaterials are applicable for modulating oxidative stress for the selective treatment of cancer cells by generating a high level of endogenous ROS.

Advance in photosensitizers and light delivery for photodynamic therapy

The brief history of photodynamic therapy (PDT) research has been focused on photosensitizers (PSs) and light delivery was introduced recently. The appropriate PSs were developed from the first generation PS Photofrin (QLT) to the second (chlorins or bacteriochlorins derivatives) and third (conjugated PSs on carrier) generations PSs to overcome undesired disadvantages, and to increase selective tumor accumulation and excellent targeting. For the synthesis of new chlorin PSs chlorophyll a is isolated from natural plants or algae, and converted to methyl pheophorbide a (MPa) as an important starting material for further synthesis. MPa has various active functional groups easily modified for the preparation of different kinds of PSs, such as methyl pyropheophorbide a, purpurin-18, purpurinimide, and chlorin e6 derivatives. Combination therapy, such as chemotherapy and photothermal therapy with PDT, is shortly described here. Advanced light delivery system is shown to establish successful clinical applications of PDT. Phtodynamic efficiency of the PSs with light delivery was investigated in vitro and/or in vivo.

Combined effects of singlet oxygen and hydroxyl radical in photodynamic therapy with photostable bacteriochlorins: evidence from intracellular fluorescence and increased photodynamic efficacy in vitro

Sulfonamides of halogenated bacteriochlorins bearing Cl or F substituents in the ortho positions of the phenyl rings have adequate properties for photodynamic therapy, including strong absorption in the near-infrared (λ(max) ≈ 750 nm, ε ≈ 10(5) M(-1) cm(-1)), controlled photodecomposition, large cellular uptake, intracellular localization in the endoplasmic reticulum, low cytotoxicity, and high phototoxicity against A549 and S91 cells. The roles of type I and type II photochemical processes are assessed by singlet oxygen luminescence and intracellular hydroxyl radical detection. Phototoxicity of halogenated sulfonamide bacteriochlorins does not correlate with singlet oxygen quantum yields and must be mediated both by electron transfer (superoxide ion, hydroxyl radicals) and by energy transfer (singlet oxygen). The photodynamic efficacy is enhanced when cellular death is induced by both singlet oxygen and hydroxyl radicals.

Photodynamic therapy of cancer: an update

Photodynamic therapy (PDT) is a clinically approved, minimally invasive therapeutic procedure that can exert a selective cytotoxic activity toward malignant cells. The procedure involves administration of a photosensitizing agent followed by irradiation at a wavelength corresponding to an absorbance band of the sensitizer. In the presence of oxygen, a series of events lead to direct tumor cell death, damage to the microvasculature, and induction of a local inflammatory reaction. Clinical studies revealed that PDT can be curative, particularly in early stage tumors. It can prolong survival in patients with inoperable cancers and significantly improve quality of life. Minimal normal tissue toxicity, negligible systemic effects, greatly reduced long-term morbidity, lack of intrinsic or acquired resistance mechanisms, and excellent cosmetic as well as organ function-sparing effects of this treatment make it a valuable therapeutic option for combination treatments. With a number of recent technological improvements, PDT has the potential to become integrated into the mainstream of cancer treatment.

Enhancing photodynamyc therapy efficacy by combination therapy: dated, current and oncoming strategies

Combination therapy is a common practice in many medical disciplines. It is defined as the use of more than one drug to treat the same disease. Sometimes this expression describes the simultaneous use of therapeutic approaches that target different cellular/molecular pathways, increasing the chances of killing the diseased cell. This short review is concerned with therapeutic combinations in which PDT (Photodynamyc Therapy) is the core therapeutic partner. Besides the description of the principal methods used to assess the efficacy attained by combinations in respect to monotherapy, this review describes experimental results in which PDT was combined with conventional drugs in different experimental conditions. This inventory is far from exhaustive, as the number of photosensitizers used in combination with different drugs is very large. Reports cited in this work have been selected because considered representative. The combinations we have reviewed include the association of PDT with anti-oxidants, chemotherapeutics, drugs targeting topoisomerases I and II, antimetabolites and others. Some paragraphs are dedicated to PDT and immuno-modulation, others to associations of PDT with angiogenesis inhibitors, receptor inhibitors, radiotherapy and more. Finally, a look is dedicated to combinations involving the use of natural compounds and, as new entries, drugs that act as proteasome inhibitors.

The outcome of 5-ALA-mediated photodynamic treatment in melanoma cells is influenced by vitamin C and heme oxygenase-1

Photodynamic therapy (PDT) is an important clinical approach for cancer treatment. It involves the administration of a photosensitizer, followed by its activation with light and induction of cell death. The underlying mechanism is an increased production of reactive oxygen species (ROS) leading to oxidative stress, which is followed by cell death. However, effectiveness of PDT is limited due to an initiation of endogenous rescue response systems like heme oxygenase-1 (HO-1) in tumor cells. In recent years, consuming of antioxidant supplements has become widespread, but the effect of exogenously applied antioxidants on cancer therapy outcome remains unclear. Thus, this study was aimed to investigate if exogenous antioxidants might decrease ROS-induced cytotoxicity in photodynamic treatment. Lycopene, β-carotene, vitamin C, N-acetylcysteine, trolox, and N-tert-butyl-α-phenylnitrone in different doses were administered to human melanoma cells prior exposure to photodynamic treatment. Supplementation with vitamin C resulted in a significant decrease of the cell death rate, whereas the other tested antioxidants had no effect on cell viability and oxidative stress markers. The simultaneous application of vitamin C with the HO-1 activity inhibitor zinc protoporphyrine IX (ZnPPIX) caused a considerable decrease of photodynamic treatment-induced cytotoxicity compared to ZnPPIX alone. It can be summarized that exogenously applied antioxidants do not have a leading role in the protective response against photodynamic treatment. However, further studies are necessary to investigate more antioxidants and other substances, which might affect the outcome of photodynamic treatment in cancer therapy.

Antioxidant activity of mangostin in cell-free system and its effect on K562 leukemia cell line in photodynamic therapy

Mangostin (MAG), a kind of xanthone widely used in diet and medicine, has antioxidant, anti-inflammatory, antimicrobial, and anticancer activities. On account of its antioxidant activity, MAG might protect cancer cells from free radical damage in photodynamic therapy (PDT) during which reactive oxygen species production was stimulated leading to irreversible tumor cell injury. In this study, the antioxidant activity of MAG was investigated and the influence of MAG on K562 cells in 5-aminolevulinic acid (ALA)-based PDT is demonstrated. The results showed that MAG could scavenge hydroxyl radical, superoxide anion, and hydrogen peroxide and inhibit the formation of malondialdehyde (MDA), but increase the amounts of singlet oxygen in cell-free systems. MAG inhibits cell proliferation and enhances cell apoptosis, lipid peroxidation, and DNA damage in ALA-PDT on K562 cells. NaN3, a singlet oxygen quencher, suppresses the MAG-induced cell apoptosis, lipid peroxidation, and DNA damage. In conclusion, MAG enhances the PDT-induced cytotoxicity in K562 cells and singlet oxygen was involved in this process. These results implied that the effect of antioxidants on PDT might be determined by its sensitization ability to singlet oxygen.

Cytoprotective role of mitogen-activated protein kinase phosphatase-1 in light-damaged human retinal pigment epithelial cells

The role of the mitogen-activated protein (MAP) kinase phosphatases (MKPs) in light-damaged cells is unclear. Therefore we investigated the involvement of MKP-1 in the regulation of apoptosis and cell survival mediated by MAP kinase pathways in light-damaged human retinal pigment epithelial cells (ARPE-19). Light dose-dependent changes in the expression of MKP-1 and in the phosphorylation status of the MAP kinases, c-Jun-N-terminal kinase (JNK) and p38 were demonstrated. Low light doses up to 2 J cm(-2) led to an upregulation of MKP-1 which resulted in the prevention of cell death by inactivating JNK kinase. However, higher light doses (> or =3 J cm(-2)) significantly reduced MKP-1 protein expression and subsequently led to an increased JNK kinase activity followed by a significant increase in cell death. JNK kinase inactivation by the JNK inhibitor SP600125 significantly reduced light-induced cell death, suggesting that the cytoprotective properties of MKP-1 are mediated mainly by the JNK MAP kinase pathway. Physiological concentrations of ascorbic acid or taurine were seen to prevent apoptosis and cell death in light-damaged ARPE-19 cells by reducing oxidative stress within cells, thus maintaining MKP-1 at high levels, leading to an inactivation of the JNK kinase pathway which resulted in an increased cell viability.

Mitochondrial reactive oxygen species inactivate neuronal nicotinic acetylcholine receptors and induce long-term depression of fast nicotinic synaptic transmission

Neuronal nicotinic acetylcholine receptors (nAChRs), ligand-gated ion channels implicated in a variety of cognitive, motor, and sensory behaviours, are targeted to compartments rich in mitochondria, particularly postsynaptic domains and presynaptic terminals, exposing these receptors to reactive oxygen species (ROS) generated by oxidative phosphorylation. In addition, these receptors can become exposed to ROS during the progression of certain neurodegenerative diseases. Because ROS are known to modify several membrane proteins, including some types of ion channels, it raises the question of whether elevations in cytosolic ROS alter the function of nAChRs. To address this, we elevated ROS in cultured sympathetic neurons, directly by perfusing neurons intracellularly with ROS, indirectly by blocking the mitochondrial electron transport chain, or noninvasively by transient NGF removal; we then simultaneously measured changes in cytosolic ROS levels and whole-cell ACh-evoked currents. In addition, we elevated cytosolic ROS in postganglionic neurons in intact ganglia and measured changes in nerve-evoked EPSPs. Our experiments indicate that mild elevations in cytosolic ROS, including that produced by transient interruption of NGF signaling, induce a use-dependent, long-lasting rundown of ACh-evoked currents on cultured sympathetic neurons and a long-lasting depression of fast nerve-evoked EPSPs. We show that these effects of cytosolic ROS are specific to nAChRs on neurons and do not cause rundown of ACh-evoked currents on muscle. Our results demonstrate that elevations in cytosolic ROS inactivate neuronal nAChRs in a use-dependent manner and suggest that mild oxidative stress impairs mechanisms mediated by cholinergic nicotinic signaling at neuronal-neuronal synapses.

Technology insight: Photodynamic therapy for cholangiocarcinoma

Cholangiocarcinoma is, in most cases, rapidly fatal. Curative resection can only be offered to approximately 10% of patients. Even after seemingly curative resection, recurrence frequently occurs. Adjuvant chemotherapy and/or radiotherapy do not reduce the recurrence rate after resection. In the palliative setting, endoscopic or percutaneous biliary drainage is performed to relieve jaundice; however, poor results have been obtained in patients with tumors involving the intrahepatic bile ducts. Biliary drainage alleviates jaundice, but there is no evidence that it prolongs life. Palliative chemotherapy and/or radiotherapy have not been proven to prolong life and relieve jaundice. Photodynamic therapy (PDT) is a relatively new local, minimally invasive procedure that can be used to treat cholangiocarcinoma. PDT uses the physical properties of light-absorbing molecules, so-called photosensitizers, which accumulate within proliferating cells. Activation of the photosensitizer by a non-thermal laser leads to selective photochemical destruction of tumors. In a randomized trial of patients with nonresectable cholangiocarcinoma, PDT prolonged survival time, improved cholestasis and quality of life considerably, and had a favorable side-effect profile. A second randomized trial confirmed the beneficial effect of PDT. For the time being, PDT is recommended for patients with nonresectable disease. The role of PDT before and after surgical resection needs to be assessed.