Effects of the oxygenation level on formation of different reactive oxygen species during photodynamic therapy

Singlet Oxygen Photophysics: From Liquid Solvents to Mammalian Cells

Molecular oxygen, O2, has long provided a cornerstone for studies in chemistry, physics, and biology. Although the triplet ground state, O2(X3Σg-), has garnered much attention, the lowest excited electronic state, O2(a1Δg), commonly called singlet oxygen, has attracted appreciable interest, principally because of its unique chemical reactivity in systems ranging from the Earth's atmosphere to biological cells. Because O2(a1Δg) can be produced and deactivated in processes that involve light, the photophysics of O2(a1Δg) are equally important. Moreover, pathways for O2(a1Δg) deactivation that regenerate O2(X3Σg-), which address fundamental principles unto themselves, kinetically compete with the chemical reactions of O2(a1Δg) and, thus, have practical significance. Due to technological advances (e.g., lasers, optical detectors, microscopes), data acquired in the past ∼20 years have increased our understanding of O2(a1Δg) photophysics appreciably and facilitated both spatial and temporal control over the behavior of O2(a1Δg). One goal of this Review is to summarize recent developments that have broad ramifications, focusing on systems in which oxygen forms a contact complex with an organic molecule M (e.g., a liquid solvent). An important concept is the role played by the M+•O2-• charge-transfer state in both the formation and deactivation of O2(a1Δg).

Development of targeted photodynamic therapy drugs by combining a zinc phthalocyanine sensitizer with TSPO or EGFR binding groups: the impact of the number of targeting agents on biological activity

Drug-targeted delivery has become a top priority in the world of medicine in order to develop more efficient therapeutic agents. This is important as a critical underlying problem in cancer therapy stems from the inability to deliver active therapeutic substances directly to tumor cells without causing collateral damage. In this work, zinc(II) phthalocyanine (ZnPc) was selected as a sensitizer and was linked to different targeting agents, which would be recognized by overexpressed proteins in cancer cells. As targeting agents, we first selected the two ligands (DAA1106, PK11195) of the translocator protein (TSPO) and then Erlotinib a binding group of the ATP domain of tyrosine kinase in epidermal growth factor (EGFR). ZnPc was connected via an ethylene glycol chain to either one (n = 1) or four (n = 4) targeting agents. The biological activity of these conjugates ZnPc(ligand)n was investigated on MDA-MB-231 breast human cancer cells and human hepatoma HepG2 cells, first in the dark (cytotoxicity) and then under irradiation (photodynamic therapy). The dark cytotoxicity was extremely low (IC50 ≥ 50 μM) for all of these compounds, which is a required criterion for further photodynamic application. After irradiation at 650 nm, only the conjugates bearing one targeting ligand such as ZnPc-[DAA1106]1, ZnPc-[PK11195]1, and ZnPc-[Erlo]1 showed photodynamic activity, while those linked to 4 targeting agents were inactive. Importantly, fluorescence imaging microscopy showed the colocalization of ZnPc-[DAA1106]1, ZnPc-[PK11195]1 and ZnPc-[erlo]1, at mitochondria, a result that justifies the observed photodynamic activity of these conjugates. This study first shows the impact of the number and the mode of organization of targeting agents on the ability of the sensitizer to cross the cell membrane. When zinc(II) phthalocyanine carries a single targeting agent, a significant photodynamic activity on MDA-MB-231 breast human cancer cells was measured and localization at the mitochondria was demonstrated by fluorescence imaging, thus proving the potential of the sensitizer linked to a targeting agent to improve selectivity. Another important conclusion from this study for the design of future effective PDT drugs using multivalence effects is to control the arrangement of the targeting agents in order to design molecules that will be able to pass the cell membrane barriers.

Photodynamic therapy (PDT) as adjuvant treatment to brachytherapy for amelanotic choroidal melanoma

PURPOSE

To evaluate the effect of photodynamic therapy (PDT) as adjuvant treatment, after brachytherapy, in posterior amelanotic choroidal melanomas.

METHODS

Six patients with posterior amelanotic choroidal melanoma underwent brachytherapy treatment. Tumour response was assessed by fundus examination, fundus photography and A-B scan ultrasonography. The residual tumours were treated with adjuvant PDT performed with infusion of verteporfin intravenously at 6 mg/m2 body surface area. Five minutes after infusion, a 689 nm laser was applied with a light dose of 100 J/cm2 over an interval of 166 s.

RESULTS

At a median follow-up after brachytherapy of 17.5 months (IQR 16.2-22.5, range 5-42 months), tumours showed a partial reduction of tumour thickness (22.5% as compared to baseline value) and persistent low internal reflectivity at A-B scan ultrasonography. Supplementary photodynamic treatment resulted in complete resolution of the lesion with marked decrease of elevation . Mean decrease in thickness after PDT was 49.9% with respect to previous brachytherapy treatment 22.5% (p = 0.007). The results was achieved within a median period of 4 months (range 2-4 months) after PDT, and there has been no recurrence after a median follow-up of 84.7 months ± 18.7 (range 59 to 107 months).

CONCLUSION

Combined treatment of brachytherapy and adjuvant PDT in amelanotic uveal melanoma seems to be favourable with regard to complete and rapid tumour regression.

Effect of Combined Perftoran and Indocyanine Green-Photodynamic Therapy on HypoxamiRs and OncomiRs in Lung Cancer Cells

Indocyanine green (ICG) is a nontoxic registered photosensitizer used as a diagnostic tool and for photodynamic therapy (PDT). Hypoxia is one the main factors affecting PDT efficacy. Perfluorodecalin emulsion (Perftoran®) is a known oxygen carrier. This study investigated the effect of Perftoran® on ICG/PDT efficacy in presence and absence of Perftoran® via evaluation of phototoxicity by MTT; hypoxia estimation by pimonidazole, HIF-1α/β by ELISA, and 17 miRNAs (tumor suppressors, oncomiRs, and hypoxamiRs) were analyzed by qPCR. Compared to ICG/PDT, Perftoran®/ICG/PDT led to higher photocytotoxicity, inhibited pimonidazole hypoxia adducts, inhibited HIF-1α/β concentrations, induced the expression of tumor-suppressing miRNAs let-7b/d/f/g, and strongly inhibited the pro-hypoxia miRNA let-7i. Additionally, Perftoran®/ICG/PDT suppressed the expression of the oncomiRs miR-155, miR-30c, and miR-181a and the hypoxamiRs miR-210 and miR-21 compared to ICG/PDT. In conclusion, Perftoran® induced the phototoxicity of ICG/PDT and inhibited ICG/PDT-hypoxia via suppressing HIF-α/β, miR-210, miR-21, let-7i, miR-15a, miR-30c, and miR-181a and by inducing the expression of let-7d/f and miR-15b.

Normalizing Tumor Vasculature to Reduce Hypoxia, Enhance Perfusion, and Optimize Therapy Uptake

Simple Summary

In order for solid tumors to grow, they need to develop new blood vessels in order to support their increasing metabolic requirements. To facilitate the novel vessel formation, the tumor initiates an aggressive pro-angiogenic program. As a result of the aggressive angiogenesis, blood vessels form very rapidly and are often malformed and dysfunctional. There is a reduction in perfusion to the tumor, and often the tumors exhibit significant areas of tumor hypoxia. This review paper discusses the pro-tumorigenic environment induced by tumor hypoxia and how this can be targeted through normalization of the tumor vasculature. Here, we review tumor angiogenesis, the development of a hypoxic phenotype, and how this contributes to sustained tumorigenesis and resistance to therapy. We further discuss the potential of vascular normalization to reduce tumor hypoxia and facilitate uptake and efficacy of a variety of therapies.

Abstract

A basic requirement of tumorigenesis is the development of a vascular network to support the metabolic requirements of tumor growth and metastasis. Tumor vascular formation is regulated by a balance between promoters and inhibitors of angiogenesis. Typically, the pro-angiogenic environment created by the tumor is extremely aggressive, resulting in the rapid vessel formation with abnormal, dysfunctional morphology. The altered morphology and function of tumor blood and lymphatic vessels has numerous implications including poor perfusion, tissue hypoxia, and reduced therapy uptake. Targeting tumor angiogenesis as a therapeutic approach has been pursued in a host of different cancers. Although some preclinical success was seen, there has been a general lack of clinical success with traditional anti-angiogenic therapeutics as single agents. Typically, following anti-angiogenic therapy, there is remodeling of the tumor microenvironment and widespread tumor hypoxia, which is associated with development of therapy resistance. A more comprehensive understanding of the biology of tumor angiogenesis and insights into new clinical approaches, including combinations with immunotherapy, are needed to advance vascular targeting as a therapeutic area.

Evaluating the mechanisms of action and subcellular localization of ruthenium(II)-based photosensitizers

The identification of ruthenium(II) polypyridyl complexes as photosensitizers in photodynamic therapy (PDT) for the treatment of cancer is progressing rapidly. Due to their favorable photophysical and photochemical properties, Ru(II)-based photosensitizers have absorption in the visible spectrum, can be irradiated via one- and two-photon excitation within the PDT window, and yield potent oxygen-dependent and/or oxygen-independent photobiological activities. Herein, we present a current overview of the mechanisms of action and subcellular localization of Ru(II)-based photosensitizers in the treatment of cancer. These photosensitizers are highlighted from a medicinal chemistry and chemical biology perspective. However, although this field is burgeoning, challenges and limitations remain in the photosensitization strategies and clinical translation.

Photosensitization With Supramolecular Arrays for Enhanced Antimicrobial Photodynamic Treatments

Microbial infections represent a silent threat to health that has worsened in recent decades due to microbial resistance to multiple drugs, preventing the fight against infectious diseases. Therefore, the current postantibiotic era forces the search for new microbial control strategies. In this regard, antimicrobial photodynamic therapy (aPDT) using supramolecular arrays with photosensitizing capabilities showed successful emerging applications. This exciting field makes it possible to combine applied aspects of molecular photochemistry and supramolecular chemistry, together with the development of nano- and biomaterials for the design of multifunctional or "smart" supramolecular photosensitizers (SPS). This minireview aims to collect the concepts of the photosensitization process and supramolecular chemistry applied to the development of efficient applications of aPDT, with a brief discussion of the most recent literature in the field.

A Supramolecular Photosensitizer System Based on Nano-Cu/ZIF-8 Capped with Water-Soluble Pillar[6]arene and Methylene Blue Host-Guest Complexations

Photodynamic therapy (PDT) as a safe, non-invasive modality for cancer therapy, in which the low oxygen and high glutathione in the tumor microenvironment reduces therapeutic efficiency. In order to overcome these problems, we prepared a supramolecular photosensitive system of O₂-Cu/ZIF-8@ZIF-8@WP6-MB (OCZWM), which was loaded with oxygen to increase the oxygen concentration in the tumor microenvironment, and the Cu²⁺ in the system reacted with glutathione (GSH) to reduce the GSH concentration to generate Cu⁺. It is worth noting that the generated Cu⁺ can produce the Fenton reaction, thus realizing the combination therapy of PDT and chemodynamic therapy (CDT) to achieve the purpose of significantly improving the anti-cancer efficiency.

Photophysical Properties of Protoporphyrin IX, Pyropheophorbide-a and Photofrin® in Different Conditions

Photodynamic therapy (PDT) is an innovative treatment of malignant or diseased tissues. The effectiveness of PDT depends on light dosimetry, oxygen availability, and properties of the photosensitizer (PS). Depending on the medium, photophysical properties of the PS can change leading to increase or decrease in fluorescence emission and formation of reactive oxygen species (ROS) especially singlet oxygen (¹O₂). In this study, the influence of solvent polarity, viscosity, concentration, temperature, and pH medium on the photophysical properties of protoporphyrin IX, pyropheophorbide-a, and Photofrin^® were investigated by UV-visible absorption, fluorescence emission, singlet oxygen emission, and time-resolved fluorescence spectroscopies.

Fighting Hypoxia to Improve PDT

Photodynamic therapy (PDT) has drawn great interest in recent years mainly due to its low side effects and few drug resistances. Nevertheless, one of the issues of PDT is the need for oxygen to induce a photodynamic effect. Tumours often have low oxygen concentrations, related to the abnormal structure of the microvessels leading to an ineffective blood distribution. Moreover, PDT consumes O2. In order to improve the oxygenation of tumour or decrease hypoxia, different strategies are developed and are described in this review: 1) The use of O2 vehicle; 2) the modification of the tumour microenvironment (TME); 3) combining other therapies with PDT; 4) hypoxia-independent PDT; 5) hypoxia-dependent PDT and 6) fractional PDT.

Therapeutic enhancement of a cytotoxic agent using photochemical internalisation in 3D compressed collagen constructs of ovarian cancer

Photochemical internalisation (PCI) is a method for enhancing delivery of drugs to their intracellular target sites of action. In this study we investigated the efficacy of PCI using a porphyrin photosensitiser and a cytotoxic agent on spheroid and non-spheroid compressed collagen 3D constructs of ovarian cancer versus conventional 2D culture. The therapeutic responses of two human carcinoma cell lines (SKOV3 and HEY) were compared using a range of assays including optical imaging. The treatment was shown to be effective in non-spheroid constructs of both cell lines causing a significant and synergistic reduction in cell viability measured at 48 or 96 h post-illumination. In the larger spheroid constructs, PCI was still effective but required higher saporin and photosensitiser doses. Moreover, in contrast to the 2D and non-spheroid experiments, where comparable efficacy was found for the two cell lines, HEY spheroid constructs were found to be more susceptible to PCI and a lower dose of saporin could be used. PCI treatment was observed to induce death principally by apoptosis in the 3D constructs compared to the mostly necrotic cell death caused by PDT. At low oxygen levels (1%) both PDT and PCI were significantly less effective in the constructs. STATEMENT OF SIGNIFICANCE: Assessment of new drugs or delivery systems for cancer therapy prior to conducting in vivo studies often relies on the use of conventional 2D cell culture, however 3D cancer constructs can provide more physiologically relevant information owing to their 3D architecture and the presence of an extracellular matrix. This study investigates the efficacy of Photochemical Internalisation mediated drug delivery in 3D constructs. In 3D cultures, both oxygen and drug delivery to the cells are limited by diffusion through the extracellular matrix unlike 2D models, and in our model we have used compressed collagen constructs where the density of collagen mimics physiological values. These 3D constructs are therefore well suited to studying drug delivery using PCI. Our study highlights the potential of these constructs for identifying differences in therapeutic response to PCI of two ovarian carcinoma lines.

Photobiomodulation of extracellular matrix enzymes in human nucleus pulposus cells as a potential treatment for intervertebral disk degeneration

Intervertebral disc (IVD) degeneration is associated with imbalances between catabolic and anabolic responses, regulated by extracellular matrix (ECM)-modifying enzymes such as matrix metalloproteinases (MMPs) and their endogenous tissue inhibitors of metalloproteinases (TIMPs). Potential contributing factors, such as interleukin (IL)-1β and tumor necrosis factor (TNF)-α, derived from infiltrated, activated macrophages within IVD tissues, can trigger abnormal production of ECM-modifying enzymes and progression of IVD degeneration. Novel therapies for regulating ECM-modifying enzymes can prevent or ameliorate IVD degeneration. Photobiomodulation (PBM), known to regulate wound repair, exhibits regenerative potential by modulating biological molecules. This study examined the effects of PBM, administered at various wavelengths (630, 525, and 465 nm) and energy densities (16, 32, and 64 J/cm²), on the production of ECM-modifying enzymes in replicated degenerative IVD. Our results showed that PBM selectively inhibited the production of ECM-modifying enzymes in a dose- and wavelength-dependent manner, suggesting that it could be a novel tool for treating symptomatic IVD degeneration.

WST11 Vascular Targeted Photodynamic Therapy Effect Monitoring by Multispectral Optoacoustic Tomography (MSOT) in Mice

Objective: Monitoring emerging vascular-targeted photodynamic therapy (VTP) and understanding the time-dynamics of treatment effects remains challenging. We interrogated whether handheld multispectral optoacoustic tomography (MSOT) could noninvasively monitor the effect of VTP using WST11, a vascular-acting photosensitizer, on tumor tissues over time using a renal cell cancer mouse model. We also investigated whether MSOT illumination can induce VTP, to implement a single-modality theranostic approach. Materials and Methods: Eight BalB/c mice were subcutaneously implanted with murine renal adenocarcinoma cells (RENCA) on the flank. Three weeks later VTP was performed (10 min continuous illumination at 753 nm following intravenous infusion using WST11 or saline as control. Handheld MSOT images were collected prior to VTP administration and subsequently thereafter over the course of the first hour, at 24 and 48 h. Data collected were unmixed for blood oxygen saturation in tissue (SO₂) based on the spectral signatures of deoxy- and oxygenated hemoglobin. Changes in oxygen saturation over time, relative to baseline, were examined by paired t-test for statistical significance (p < 0.05). In-vivo findings were corroborated by histological analyses of the tumor tissue. Results: MSOT is shown to prominently resolve changes in oxygen saturation in tumors within the first 20 min post WST11-VTP treatment. Within the first hour post-treatment, SO₂ decreased by more than 60% over baseline (p < 0.05), whereas it remained unchanged (p > 0.1) in the sham-treated group. Moreover, unlike in the control group, SO₂ in treated tumors further decreased over the course of 24 to 48 h post-treatment, concomitant with the propagation of profound central tumor necrosis present in histological analysis. We further show that pulsed MSOT illumination can activate WST11 as efficiently as the continuous wave irradiation employed for treatment. Conclusion: Handheld MSOT non-invasively monitored WST11-VTP effects based on the SO₂ signal and detected blood saturation changes within the first 20 min post-treatment. MSOT may potentially serve as a means for both VTP induction and real-time VTP monitoring in a theranostic approach.

Chlorophyll a in cyclodextrin supramolecular complexes as a natural photosensitizer for photodynamic therapy (PDT) applications

Chlorophyll a (Chl a), an amphipathic porphyrin, was employed as natural photosensitizer for photodynamic therapy applications. Due to its lacking solubility in water and high tendency to aggregate, Chl a was included into different modified cyclodextrins (CDs) to form stable water-soluble supramolecular complexes. To achieve this aim, 2-Hydroxypropyl-β-cyclodextrin (2-HP-β-CD), 2-Hydroxypropyl-γ-cyclodextrin (2-HP-γ-CD), Heptakis(2,6-di-o-methyl)-β-cyclodextrin (DIMEB) and Heptakis(2,3,6-tri-o-methyl)-β-cyclodextrin (TRIMEB) were used. The chemical physical properties of Chl a/CD complexes in cellular medium were studied by means of UV-Vis absorption spectroscopy. Results demonstrated the good aptitude of 2-HP-γ-CD, and more particularly of 2-HP-β-CD, to solubilize the Chl a in cell culture medium in monomeric and photoactive form. Then, Chl a/2-HP-β-CD and Chl a/2-HP-γ-CD complexes were evaluated in vitro on human colorectal adenocarcinoma HT-29 cell line, and cytotoxicity and intracellular localization were respectively assessed. Further tests, such as phototoxicity, ROS generation, intracellular localization and mechanism of cell death were then focused exclusively on Chl a/2-HP-β-CD system. This complex exhibited no dark toxicity and a high phototoxicity toward HT-29 cells inducing cell death via necrotic mechanism. Therefore, it is possible to affirm that Chl a/2-HP-β-CD supramolecular complex could be a promising and potential formulation for applications in photodynamic therapy.

Porphyrin photosensitizers in photodynamic therapy and its applications

In 1841, the extraction of hematoporphyrin from dried blood by removing iron marked the birth of the photosensitizer. The last twenty years has witnessed extensive research in the application of photodynamic therapy (PDT) in tumor-bearing (or other diseases) animal models and patients. The period has seen development of photosensitizers from the first to the third generation, and their evolution from simple to more complex entities. This review focuses on porphyrin photosensitizers and their effect on tumors, mediated via several pathways involved in cell necrosis, apoptosis or autophagic cell death, and the preventive and therapeutic application of PDT against atherosclerosis.

On the in vivo photochemical rate parameters for PDT reactive oxygen species modeling

Photosensitizer photochemical parameters are crucial data in accurate dosimetry for photodynamic therapy (PDT) based on photochemical modeling. Progress has been made in the last few decades in determining the photochemical properties of commonly used photosensitizers (PS), but mostly in solution or in vitro. Recent developments allow for the estimation of some of these photochemical parameters in vivo. This review will cover the currently available in vivo photochemical properties of photosensitizers as well as the techniques for measuring those parameters. Furthermore, photochemical parameters that are independent of environmental factors or are universal for different photosensitizers will be examined. Most photosensitizers discussed in this review are of the type II (singlet oxygen) photooxidation category, although type I photosensitizers that involve other reactive oxygen species (ROS) will be discussed as well. The compilation of these parameters will be essential for ROS modeling of PDT.

Oncologic Photodynamic Therapy: Basic Principles, Current Clinical Status and Future Directions

Photodynamic therapy (PDT) is a clinically approved cancer therapy, based on a photochemical reaction between a light activatable molecule or photosensitizer, light, and molecular oxygen. When these three harmless components are present together, reactive oxygen species are formed. These can directly damage cells and/or vasculature, and induce inflammatory and immune responses. PDT is a two-stage procedure, which starts with photosensitizer administration followed by a locally directed light exposure, with the aim of confined tumor destruction. Since its regulatory approval, over 30 years ago, PDT has been the subject of numerous studies and has proven to be an effective form of cancer therapy. This review provides an overview of the clinical trials conducted over the last 10 years, illustrating how PDT is applied in the clinic today. Furthermore, examples from ongoing clinical trials and the most recent preclinical studies are presented, to show the directions, in which PDT is headed, in the near and distant future. Despite the clinical success reported, PDT is still currently underutilized in the clinic. We also discuss the factors that hamper the exploration of this effective therapy and what should be changed to render it a more effective and more widely available option for patients.

The hydroxypyridinone iron chelator CP94 increases methyl-aminolevulinate-based photodynamic cell killing by increasing the generation of reactive oxygen species

Methyl-aminolevulinate-based photodynamic therapy (MAL-PDT) is utilised clinically for the treatment of non-melanoma skin cancers and pre-cancers and the hydroxypyridinone iron chelator, CP94, has successfully been demonstrated to increase MAL-PDT efficacy in an initial clinical pilot study. However, the biochemical and photochemical processes leading to CP94-enhanced photodynamic cell death, beyond the well-documented increases in accumulation of the photosensitiser protoporphyrin IX (PpIX), have not yet been fully elucidated. This investigation demonstrated that MAL-based photodynamic cell killing of cultured human squamous carcinoma cells (A431) occurred in a predominantly necrotic manner following the generation of singlet oxygen and ROS. Augmenting MAL-based photodynamic cell killing with CP94 co-treatment resulted in increased PpIX accumulation, MitoSOX-detectable ROS generation (probably of mitochondrial origin) and necrotic cell death, but did not affect singlet oxygen generation. We also report (to our knowledge, for the first time) the detection of intracellular PpIX-generated singlet oxygen in whole cells via electron paramagnetic resonance spectroscopy in conjunction with a spin trap.

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Augmentation of MAL-based photodynamic cell killing with CP94 increases necrosis.

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CP94 augmentation increases generation of ROS, likely to be mitochondria-localised.

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PpIX-generated ¹O₂ was detected in whole cells by EPR spectroscopy.

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Photodynamic cell killing was dependent primarily on ¹O₂.

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Superoxide/other ROS also contributed to the efficacy of photodynamic cell killing.

Multiple sequential light and laser sources to activate aminolevulinic acid for rosacea

BACKGROUND AND AIMS

The use of multiple, sequential light and laser sources for topical ALA activation in photodynamic therapy (PDT) of rosacea has been largely absent from the literature. The aim of this study was to evaluate ALA-PDT for rosacea using blue light sequentially with red light, pulsed-dye laser (PDL), and/or intense pulsed light (IPL).

PATIENTS/METHODS

Thirty patients (39 treatments) were enrolled in this retrospective, single-center study. Treatment groups included blue light + PDL, blue light + IPL, blue light + PDL + IPL, or blue light + red light + PDL + IPL. Patient-reported outcome measures (incidence of adverse events, improvement in rosacea, and improvement in overall skin quality) were obtained via a telephone questionnaire and graded on a 4-point scale.

RESULTS

There was no statistically significant difference in patient-reported rosacea or overall skin quality improvement. Apart from decreased peeling following blue light + IPL compared to blue light + PDL (P = 0.041) and blue light + IPL + PDL (P = 0.005), there were no other statistically significant differences in postprocedure adverse events.

CONCLUSIONS

The use of multiple, sequential light and laser sources with ALA-PDT for rosacea, while well tolerated, did not lead to statistically significant improvements in patient-reported efficacy. Although this retrospective study is limited by a small sample size with disparate patient numbers between groups and no physician-evaluated outcome criteria, it does demonstrate that multiple light sources with PDT can be safely used in a single session.

Multiple sequential light and laser sources to activate aminolevulinic acid in the treatment of photodamage: A retrospective study

INTRODUCTION

The aim of this study was to retrospectively evaluate photodynamic therapy (PDT) with aminolevulinic acid (ALA) for cutaneous photorejuvenation using blue light sequentially with red light, pulsed-dye laser (PDL), and/or intense pulsed light (IPL).

MATERIALS AND METHODS

Ninety-six patients (121 treatments) had photodamage treated with field-directed ALA-PDT from 2001 to 2010 in this single-center study. Treatments were performed with blue light + PDL, blue light + IPL, blue light + PDL + IPL, or blue light + red light + PDL + IPL. Outcome measures were obtained via telephone questionnaire and graded on a four-point scale.

RESULTS

There were no significant differences in patient-reported improvement in photodamage, overall skin quality, and postprocedure adverse events between treatment arms. However, number of patients in the blue light + red light + PDL + IPL group was markedly smaller (n = 2) than that in the other groups (n = 14-46).

DISCUSSION

Although results showed a trend toward greater efficacy with similar tolerability using multiple, sequential light and laser sources with ALA-PDT for photorejuvenation, the potential for recall bias and widely disparate number of patients between treatment groups and follow-up times between patients severely limit this retrospective study. Nevertheless, despite these major statistical flaws, the results may provide valuable information regarding the safety of multiple modalities with PDT of photodamage in a single session.

Promotion of Proapoptotic Signals by Lysosomal Photodamage: Mechanistic Aspects and Influence of Autophagy

Prior studies demonstrated that a low level (LD10-15 ) of lysosomal photodamage can sensitize cells to the apoptotic death that results from subsequent mitochondrial photodamage. We have proposed that this process occurs via a calpain-catalyzed cleavage of the autophagy-associated protein ATG5 to form a proapoptotic fragment. In this report, we provide evidence for the postulated ATG5 cleavage and show that the sequential photodynamic therapy (PDT) protocol can also partly overcome the adverse effect of hypoxia on the initiation of apoptosis. While autophagy can offer cytoprotection after mitochondrial photodamage, this does not appear to apply when lysosomes are the target. This may account for the ability of very low PDT doses directed at lysosomes to evoke ATG5 cleavage. The resulting proapoptotic effect overcomes intrinsic cytoprotection from mitochondrial photodamage along with a further stimulation of phototoxicity.

Synthesis and characterization of photodynamic activity of an iodinated Chlorin p6copper complex

A novel iodinated copper complex of Chlorinp₆that acts as type I photosensitizer and capable of inducing phototoxicity in cancer cells under hypoxia.

Fluorescence characteristics and lifetime images of photosensitizers of talaporfin sodium and sodium pheophorbide a in normal and cancer cells

Fluorescence spectra and fluorescence lifetime images of talaporfin sodium and sodium-pheophorbide a, which can be regarded as photosensitizers for photodynamic therapy, were measured in normal and cancer cells. The reduction of the fluorescence intensity by photoirradiation was observed for both photosensitizers in both cells, but the quenching rate was much faster in cancer cells than in normal cells. These results are explained in terms of the excessive generation of reactive oxygen species via photoexcitation of these photosensitizers in cancer cells. The fluorescence lifetimes of both photosensitizers in cancer cells are different from those in normal cells, which originates from the different intracellular environments around the photosensitizers between normal and cancer cells.

Synthesis, spectroscopic, and in vitro investigations of 2,6-diiodo-BODIPYs with PDT and bioimaging applications

A series of five mono-styryl and their corresponding symmetric di-styryl-2,6-diiodo-BODIPYs containing indolyl, pyrrolyl, thienyl or tri(ethylene glycol)phenyl groups were synthesized using Knoevenagel condensations. The yields for the condensation reactions were improved up to 40% using microwave irradiation (90°C for 1h at 400W) due to lower decomposition of BODIPYs upon prolonged heating. The spectroscopic, structural (including the X-ray of a di-styryl-2,6-diiodo-BODIPY) and in vitro properties of the BODIPYs were investigated. The extension of π-conjugation through the 3,5-dimethyls of the known phototoxic 2,6-diiodo-BODIPY 1 produced bathochromic shifts in the absorption and emission spectra, in the order of 63-125nm for the mono-styryl- and 128-220nm for the di-styryl-BODIPYs in DMSO. The largest red-shifts were observed for the indolyl-containing BODIPYs while the largest fluorescence quantum yields were observed for the tri(ethyleneglycol)phenylstyryl-BODIPYs. Among this series, only the mono-styryl-BODIPYs were phototoxic (IC50=2-15μM at 1.5J/cm(2)), and were observed to localize preferentially in the cell ER and mitochondria. On the other hand, the di-styryl-BODIPYs were found to have low or no phototoxicity (IC50>100μM at 1.5J/cm(2)). Among this series of compounds BODIPY 2a shows the most promise for application as photosensitizer in PDT.

Apoptosis and associated phenomena as a determinants of the efficacy of photodynamic therapy

Failure of neoplastic cells to respond to conventional chemotherapy is usually associated with factors that limit access of drugs to subcellular sites, differences in cell-cycle kinetics or mutations leading to loss of drug-activation pathways or other processes that govern response factors. For PDT, efficacy depends mainly on selective uptake of photosensitizers by neoplastic cells, oxygenation levels, the suitable direction of irradiation and the availability of pathways to cell death that are highly conserved among mammalian cell types. While it is possible to engineer PDT-resistant cell types, current evidence suggests that the major obstacles to cancer control relate to drug, light and oxygen distribution. This review discusses some of the factors that can govern PDT-induced cell death.

An efficient gold nanocarrier for combined chemo-photodynamic therapy on tumour cells

A multimodal Au@mSiO₂ nanocarrier in which AuNPs act as PDT-assistor cores and mesoporous silica shells as supporters to load two drugs.

Efficient photothermal therapy of brain cancer through porphyrin functionalized graphene oxide

High photothermal therapy efficiency is achieved by using an 808 nm laser to irradiate 87-MG cells co-cultured with porphyrin functionalized graphene oxide.

Enhanced efficacy of photodynamic therapy via a sequential targeting protocol

This study was designed to examine determinants of the discovery that low-dose lysosomal photodamage (lyso-PDT) could potentiate the efficacy of subsequent low-dose mitochondrial photodamage (mito-PDT). The chlorin NPe6 and the benzoporphyrin derivative (BPD) were used to separately target lysosomes and mitochondria, respectively, in murine hepatoma cells. Lyso-PDT (LD(5) conditions) followed by mito-PDT (LD(15) conditions) enhanced the loss of the mitochondrial membrane potential, activation of procaspases-3/7 and photokilling. Reversing the sequence was less effective. The optimal sequence did not enhance reactive oxygen species formation above that obtained with low-dose mito-PDT. In contrast, alkalinization of lysosomes with bafilomycin also enhanced low-dose mito-PDT photokilling, but via a different pathway. This involves redistribution of iron from lysosomes to mitochondria leading to enhanced hydroxyl radical formation, effects not observed after the sequential procedure. Moreover, Ru360, an inhibitor of mitochondrial calcium and iron uptake, partially suppressed the ability of bafilomycin to enhance mito-PDT photokilling without affecting the enhanced efficacy of the sequential protocol. We conclude that sequential PDT protocol promotes PDT efficacy by a process not involving iron translocation, but via promotion of the pro-apoptotic signal that derives from mitochondrial photodamage.