Showing papers in "Photochemistry and Photobiology in 2012"
TL;DR: The survey focuses on recent aspects of photochemical reactions to cellular DNA that are implicated through the predominant formation of mostly bipyrimidine photoproducts in deleterious effects of human exposure to sunlight.
Abstract: The survey focuses on recent aspects of photochemical reactions to cellular DNA that are implicated through the predominant formation of mostly bipyrimidine photoproducts in deleterious effects of human exposure to sunlight. Recent developments in analytical methods have allowed accurate and quantitative measurements of the main DNA photoproducts in cells and human skin. Highly mutagenic CC and CT bipyrimidine photoproducts, including cyclobutane pyrimidine dimers and pyrimidine (6-4) pyrimidone photoproducts (6-4PPs) are generated in low yields with respect to TT and TC photoproducts. Another striking finding deals with the formation of Dewar valence isomers, the third class of bipyrimidine photoproducts that is accounted for by UVA-mediated isomerization of initially UVB generated 6-4PPs. Cyclobutadithymine (T T) has been unambiguously shown to be involved in the genotoxicity of UVA radiation. Thus, T T is formed in UVA-irradiated cellular DNA according to a direct excitation mechanism with a higher efficiency than oxidatively generated DNA damage that arises mostly through the Type II photosensitization mechanism. C C and C T are repaired at rates intermediate between those of T T and 6-4TT. Evidence has been also provided for the occurrence of photosensitized reactions mediated by exogenous agents that act either in an independent way or through photodynamic effects.
252 citations
TL;DR: A review of studies published to date on antifungal applications of PDT, with special focus on yeast, and aims to raise awareness of this area of research, which has the potential to make a significant impact in future treatment of fungal infections.
Abstract: The growing resistance against antifungal drugs has renewed the search for alternative treatment modalities, and antimicrobial photodynamic therapy (PDT) seems to be a potential candidate. Preliminary findings have demonstrated that dermatophytes and yeasts can be effectively sensitized in vitro and in vivo by administering photosensitizers (PSs) belonging to four chemical groups: phenothiazine dyes, porphyrins and phthalocyanines, as well as aminolevulinic acid, which, while not a PS in itself, is effectively metabolized into protoporphyrin IX. Besides efficacy, PDT has shown other benefits. First, the sensitizers used are highly selective, i.e., fungi can be killed at combinations of drug and light doses much lower than that needed for a similar effect on keratinocytes. Second, all investigated PSs lack genotoxic and mutagenic activity. Finally, the hazard of selection of drug resistant fungal strains has been rarely reported. We review the studies published to date on antifungal applications of PDT, with special focus on yeast, and aim to raise awareness of this area of research, which has the potential to make a significant impact in future treatment of fungal infections.
150 citations
TL;DR: Cerium‐doped Titanium dioxide (TiO2) nanoparticles are prepared by sol‐gel method, making it efficient for visible light photocatalysis, and cerium doping decreases the effective band gap of TiO2 and increases the Urbach energy levels.
Abstract: Cerium-doped Titanium dioxide (TiO(2)) nanoparticles are prepared by sol-gel method. Doping shifts the UV absorption edge of TiO(2) to the visible region, making it efficient for visible light photocatalysis. Incorporation of cerium decreases the effective band gap of TiO(2) and increases the Urbach energy levels. At the dopant concentrations of 0.015 and 0.025 mol the luminescence intensity increases compared to undoped TiO(2); however, the luminescence is quenched at 0.035 mol. Quenching of luminescence indicates efficient separation of charge carriers. Undoped TiO(2) is showing poor performance in the photocatalytic degradation of methyl orange under visible light. However, on cerium doping its photoactivity is increased, and is drastically enhanced at 0.035 mol of cerium. Further increase in Ce(3+) doping level to 0.045 mol results in the reduction of the photodegradation of the dye. On UV irradiation, entire samples show good photocatalytic activity up to 30 min, but their efficiency decreases when irradiation time is increased to 45 min. Irradiation for longer time results in negative charging of the TiO(2) surface with migrating electrons. The negatively charged surface repels the OH(-) ion and O(2) molecule from adsorbing on its surface thus decreasing the availability of hydroxyl and superoxide radical for dye degradation.
125 citations
TL;DR: The different antimicrobial PDT strategies are discussed and the need for highly informative and comprehensive discovery approaches is highlighted.
Abstract: Conventional antimicrobial strategies have become increasingly ineffective due to the emergence of multidrug resistance among pathogenic microorganisms. The need to overcome these deficiencies has triggered the exploration of alternative treatments and unconventional approaches towards controlling microbial infections. Photodynamic therapy (PDT) was originally established as an anticancer modality and is currently used in the treatment of age-related macular degeneration. The concept of photodynamic inactivation requires cell exposure to light energy, typically wavelengths in the visible region that causes the excitation of photosensitizer molecules either exogenous or endogenous, which results in the production of reactive oxygen species (ROS). ROS produce cell inactivation and death through modification of intracellular components. The versatile characteristics of PDT prompted its investigation as an anti-infective discovery platform. Advances in understanding of microbial physiology have shed light on a series of pathways, and phenotypes that serve as putative targets for antimicrobial drug discovery. Investigations of these phenotypic elements in concert with PDT have been reported focused on multidrug efflux systems, biofilms, virulence and pathogenesis determinants. In many instances the results are promising but only preliminary and require further investigation. This review discusses the different antimicrobial PDT strategies and highlights the need for highly informative and comprehensive discovery approaches.
108 citations
TL;DR: The present study highlighted the importance of inherent cell membrane permeabilizing effect of chitosan and increased cell/biofilm uptake of conjugated photosensitizer to produce significant antibiofilm efficacy during photodynamic therapy.
Abstract: The complex nature of bacterial cell membrane and structure of biofilm has challenged the efficacy of antimicrobial photodynamic therapy. This study was aimed to synthesize a polycationic chitosan-conjugated rose bengal (CSRB) photosensitizer and test its antibiofilm efficacy on Enterococcus faecalis (gram positive) and Pseudomonas aeruginosa (gram negative) using photodynamic therapy. During experiments, CSRB was tested along with an anionic photosensitizer rose bengal (RB) and a cationic photosensitizer methylene blue (MB) for uptake and killing efficacy on 7-day-old E. faecalis and P. aeruginosa biofilms. Microbiological culture based analysis was used to analyze the cell viability, while laser scanning confocal microscopy (LSCM) was used to examine the structure of biofilm. The synthesized CSRB showed absorbance spectrum similar to the RB. The concentration of CSRB uptaken by both the bacterial biofilms was significantly higher than that of RB and MB (P < 0.05). Photoactivation resulted in significantly higher elimination of both bacterial biofilms sensitized with CSRB than RB and MB. The structure of biofilm under LSCM was found to be disrupted following CSRB treatment. The present study highlighted the importance of inherent cell membrane permeabilizing effect of chitosan and increased cell/biofilm uptake of conjugated photosensitizer to produce significant antibiofilm efficacy during photodynamic therapy.
100 citations
TL;DR: CA and FA provided protective effects on UVA‐mediated MMP‐1 induction in HaCaT cells possibly through restoration of antioxidant defense system at the cellular and molecular level.
Abstract: Ultraviolet A (UVA) plays a vital role in the pathogenesis of premature skin aging through keratinocyte cytotoxicity and degradation of collagen, a main component of the extracellular matrix providing structural support. Oxidative stress caused by UVA irradiation can mediate induction of matrix metalloprotease-1 (MMP-1), a major enzyme responsible for collagen damage. Protection against UV-mediated disturbance of antioxidant defense system has been proposed as a possible mechanism by which botanical compounds slow down skin aging process. This study therefore aimed to assess inhibitory effects of caffeic acid (CA) and ferulic acid (FA), powerful plant-based phenolic antioxidants, on UVA-induced cytotoxicity and MMP-1 activity and mRNA level through modulation of antioxidant defense mechanism in immortalized human keratinocyte (HaCaT) cells. Pretreatment of the cells with CA or FA prior to UVA irradiation inhibited cytotoxicity, induction of MMP-1 activity and mRNA and oxidant formation. Moreover, CA and FA were able to up-regulate glutathione (GSH) content, γ-glutamate cysteine ligase (γ-GCL) mRNA as well as activities and mRNA expression of catalase and glutathione peroxidase (GPx) in irradiated cells. In conclusion, CA and FA provided protective effects on UVA-mediated MMP-1 induction in HaCaT cells possibly through restoration of antioxidant defense system at the cellular and molecular level.
97 citations
TL;DR: This article provides a concise review of the current understanding of the effects of the nonionizing solar radiation, at cellular and molecular levels, on human skin pigmentation.
Abstract: The term barrier function as applied to human skin often connotes the physical properties of this organ that provides protection from its surrounding environment. This term does not generally include skin pigmentation. However, skin pigmentation, which is the result of melanin produced in melanocytes residing in the basal layer of the skin and exported to the keratinocytes in the upper layers, serves equally important protective function. Indeed, changes in skin pigmentation are often the most readily recognized indicators of exposure of skin to damaging agents, especially to natural and artificial radiation in the environment. Several recent studies have shed new light on (1) the mechanisms involved in selective effects of subcomponents of UV radiation on human skin pigmentation and (2) the interactive influences between keratinocytes and melanocytes, acting as "epidermal melanin unit," that manifest as changes in skin pigmentation in response to exposure to various forms of radiation. This article provides a concise review of our current understanding of the effects of the nonionizing solar radiation, at cellular and molecular levels, on human skin pigmentation.
95 citations
TL;DR: Research into alternative materials such as CNC‐Por may lead to their application in hospitals and healthcare‐related industries wherein novel materials with the capability of reducing the rates of transmission of a wide range of bacteria, particularly antibiotic resistant strains, are desired.
Abstract: Towards our overall objectives of developing potent antimicrobial materials to combat the escalating threat to human health posed by the transmission of surface-adhering pathogenic bacteria, we have investigated the photobactericidal activity of cellulose nanocrystals that have been modified with a porphyrin-derived photosensitizer (PS). The ability of these previously synthesized porphyrin-cellulose-nanocrystals (CNC-Por (1)) to mediate bacterial photodynamic inactivation was investigated as a function of bacterial strain, incubation time and illumination time. Despite forming an insoluble suspension, CNC-Por (1) showed excellent efficacy toward the photodynamic inactivation of Acinetobacter baumannii, multidrug-resistant Acinetobacter baumannii (MDRAB) and methicillin-resistant Staphylococcus aureus (MRSA), with the best results achieving 5-6 log units reduction in colony forming units (CFUs) upon illumination with visible light (400-700 nm; 118 J cm(-2)). CNC-Por (1) mediated the inactivation of Pseudomonas aeruginosa, although at reduced activity (2-3 log units reduction). Confocal laser scanning microscopy of CNC-Por (1) after incubation with A. baumannii or S. aureus suggested a lack of internalization of the PS. Research into alternative materials such as CNC-Por (1) may lead to their application in hospitals and healthcare-related industries wherein novel materials with the capability of reducing the rates of transmission of a wide range of bacteria, particularly antibiotic resistant strains, are desired.
93 citations
TL;DR: The ability of keratinocytes to produce a wide repertoire of proinflammatory cytokines can influence the immune response locally as well as systematically, and alter the host response to photodamaged cells.
Abstract: Although keratinocytes are relatively resistant to ultraviolet radiation (UVR) induced damage, repeated UVR exposure result in accumulated DNA mutations that can lead to epidermal malignancies. Keratinocytes play a central role in elaborating innate responses that lead to inflammation and influence the generation of adaptive immune responses in skin. Apart from the minor cellular constituents of the epidermis, specifically Langerhans cells and melanocytes, keratinocytes are the major source of cytokines. UVR exposure stimulates keratinocytes to secrete abundant pro-inflammatory IL-1-family proteins, IL-1α, IL-1β, IL-18, and IL-33. Normal skin contains only low levels of inactive precursor forms of IL-1β and IL-18, which require caspase 1-mediated proteolysis for their maturation and secretion. However, caspase-1 activation is not constitutive, but dependents on the UV-induced formation of an active inflammasome complex. IL-1 family cytokines can induce a secondary cascade of mediators and cytokines from keratinocytes and other cells resulting in wide range of innate processes including infiltration of inflammatory leukocytes, induction of immunosuppression, DNA repair or apoptosis. Thus, the ability of keratinocytes to produce a wide repertoire of proinflammatory cytokines can influence the immune response locally as well as systematically, and alter the host response to photodamaged cells. We will highlight differential roles played by each IL-1 family molecule generated by UV-damaged keratinocytes, and reveal their complementary influences in modulating acute inflammatory and immunological events that follow cutaneous UV exposure.
89 citations
TL;DR: Evaluating the photostability of E‐RSV‐loaded supramolecular structures and the skin penetration profile of chemically and physically stable nanoestructured formulations found liposomes were the particles capable of maintaining E‐ RSV concentration for the longest time, while liposome reduced in size showing low physical stability under UVA radiation.
Abstract: It is desirable and challenging to prevent E-resveratrol (E-RSV) from photoisomerizing to its Z-configuration to preserve its biological and pharmacological activities. The aim of this research was to evaluate the photostability of E-RSV-loaded supramolecular structures and the skin penetration profile of chemically and physically stable nanoestructured formulations. Different supramolecular structures were developed to act as carriers for E-RSV, that is, liposomes, polymeric lipid-core nanocapsules and nanospheres and solid lipid nanoparticles. The degrees of photostability of these formulations were compared with that of an ethanolic solution of E-RSV. The skin penetration profiles of the stable formulations were obtained using vertical diffusion cells (protected from light and under UVA radiation) with porcine skin as the membrane, followed by tape stripping and separation of the viable epidermis and dermis in a heated water bath. Photoisomerization was significantly delayed by the association of resveratrol with the nanocarriers independently of the supramolecular structure. Liposomes were the particles capable of maintaining E-RSV concentration for the longest time. On the other hand, E-RSV-loaded liposomes reduced in size showing low physical stability under UVA radiation. In the dark, the skin penetration profiles were very similar, but under UVA radiation the E-RSV-loaded nanocarriers showed increasing amounts in the total epidermis.
87 citations
TL;DR: Investigation of the photochemopreventive effects of PFE after multiple UVB irradiations shows that PFE consumption afforded protection to mouse skin against the adverse effects of UVB radiation by modulating UVB‐induced signaling pathways.
Abstract: There is considerable interest in the identification of natural agents capable of affording protection to skin from the adverse effects of solar ultraviolet B (UVB) radiation. Pomegranate (Punica granatum L.) fruit possesses as strong antioxidant, anti-inflammatory and antiproliferative properties. Recently, we have shown that oral feeding of pomegranate fruit extract (PFE) to mice afforded substantial protection from the adverse effects of single UVB radiation via modulation in early biomarkers of photocarcinogenesis. This study was designed to investigate the photochemopreventive effects of PFE (0.2%, wt/vol) after multiple UVB irradiations (180 mJ cm(-2), on alternative day, for a total of seven treatments) to the skin of SKH-1 hairless mice. Oral feeding of PFE to SKH-1 mice inhibited UVB-induced epidermal hyperplasia, infiltration of leukocytes, protein oxidation and lipid peroxidation. Immunoblot analysis demonstrated that oral feeding of PFE to mice inhibited UVB-induced (1) nuclear translocation and phosphorylation of nuclear factor kappa B/p65, (2) phosphorylation and degradation of IκBα, (3) activation of IKKα/ΙΚΚβ and (4) phosphorylation of mitogen-activated protein kinase proteins and c-Jun. PFE consumption also inhibited UVB-induced protein expression of (1) COX-2 and iNOS, (2) PCNA and cyclin D1 and (3) matrix metalloproteinases-2,-3 and -9 in mouse skin. Taken together, these data show that PFE consumption afforded protection to mouse skin against the adverse effects of UVB radiation by modulating UVB-induced signaling pathways.
TL;DR: The combination of hypericin and light irradiation could induce significant killing of Gram positive methicillin‐sensitive and ‐resistant S. aureus cells but was not effective on Gram negative E. coli cells; the difference was caused by different cell wall/membrane structures that directly affected cellular uptake ofhypericin.
Abstract: The aim of this study was to determine the photodynamic antimicrobial effect of hypericin on clinically isolated Staphylococcus aureus and Escherichia coli cells. Bacterial cells (10(8) cells per mL) were incubated with hypericin (0-40 μM) for 30 min and followed by light irradiation of 600-800 nm at 5-30 J cm(-2). Cell survival was determined by colony counting, cellular hypericin uptake examined by flow cytometer, and cell membrane damage examined by scanning electron microscopy and leakage assay. The effectiveness of hypericin-mediated photodynamic killing was strongly affected by cellular structure and photosensitizer uptake. The combination of hypericin and light irradiation could induce significant killing of Gram positive methicillin-sensitive and -resistant S. aureus cells (>6 log reduction), but was not effective on Gram negative E. coli cells (<0.2 log reduction). The difference was caused by different cell wall/membrane structures that directly affected cellular uptake of hypericin.
TL;DR: The downregulation of the photochemical machinery, which was expressed as dynamic photoinhibition, and the rapid induction of soluble phlorotannins triggered by UV radiation minimized the effects of oxidative stress and maintained the operation of photochemical processes during short‐term thermal stress.
Abstract: Rapid adjustments of the photosynthetic machinery and efficient antioxidant mechanisms to scavenge harmful ROS are physiologic adaptions exhibited by intertidal seaweeds to persist in temperate regions. This study examines short-term (3 h) responses of three large kelps from the cold-temperate coast of Chile, normally adapted to water temperatures <16°C, but exposed abruptly to simultaneous high temperatures and UV radiation during low tide in summer. The kelps were exposed in the laboratory to three temperatures (10, 20 and 28°C) with and without UV radiation, and photochemical reactions, concentration of phlorotannins and antioxidant activity were examined. The exposure to elevated temperature (slightly exacerbated by the presence of UV radiation) decreased photochemical processes (measured as fluorescence kinetics) in the three studied species and increased lipid peroxidation in two of them. The concentration of total soluble phlorotannins was variable and correlated with the antioxidant activity in the presence of UV radiation. Insoluble phlorotannins did not change during the exposure. In all, the downregulation of the photochemical machinery, which was expressed as dynamic photoinhibition, and the rapid induction of soluble phlorotannins triggered by UV radiation minimized the effects of oxidative stress and maintained the operation of photochemical processes during short-term thermal stress.
TL;DR: The antimicrobial activity of ER/CS nanoparticles was significantly higher than ER in free form and the particle size and incubation time of the nanoparticles also appeared to be important factors affecting their PDI activity against S. mutans and C. albicans.
Abstract: The growing resistance to antibiotics has rendered antimicrobial photodynamic inactivation (PDI) an attractive alternative treatment modality for infectious diseases. Chitosan (CS) was shown to further potentiate the PDI effect of photosensitizers and was therefore used in this study to investigate its ability to potentiate the activity of erythrosine (ER) against bacteria and yeast. CS nanoparticles loaded with ER were prepared by ionic gelation method and tested for their PDI efficacy on planktonic cells and biofilms of Streptococcus mutans, Pseudomonas aeruginosa and Candida albicans. The nanoparticles were characterized for their size, polydispersity index and zeta potential. No toxicity was observed when planktonic cells and biofilms were treated with the nanoparticles in the dark. However, when the cells were exposed to light irradiation after treatment with free ER or ER/CS nanoparticles, a significant phototoxicity was observed. The antimicrobial activity of ER/CS nanoparticles was significantly higher than ER in free form. The particle size and incubation time of the nanoparticles also appeared to be important factors affecting their PDI activity against S. mutans and C. albicans.
TL;DR: Investigation of the sensitivity of the significant foodborne pathogen Listeria monocytogenes to selected wavelengths of visible light demonstrates that exposure to wavelength region 400–450 nm, at sufficiently high dose levels (750 J cm−2), induced complete inactivation of a 5 log10 population.
Abstract: The antimicrobial properties of light is an area of increasing interest. This paper investigates the sensitivity of the significant foodborne pathogen Listeria monocytogenes to selected wavelengths of visible-light. Results demonstrate exposure to wavelengths region 400–450nm, at sufficiently high dose levels (750Jcm2), induced complete inactivation of a 5-log10 population. Exposure to wavelengths longer than 450nm did not cause significant inactivation. Analysis of 10nm bandwidths between 400 and 450nm confirmed 405(±5)nm light to be most effective for inactivation of L. monocytogenes, with a lesser bactericidal effect also evident at other wavelengths between 400 and 440nm. Identification of the optimum bactericidal wavelength enabled comparison of inactivation using 405(±5)nm filtered light and a 405nm LED array (14nm FWHM). Results demonstrate similar inactivation kinetics, indicating that the applied dose of 405-nm light is the important factor. Use of the 405nm LED array for inactivation of L. monocytogenes and other Listeria species resulted in similar kinetics, with up to 5-log10 reductions with a dose of 185Jcm2. Comparative data for the 405nm light inactivation of L. monocytogenes and other important foodborne pathogens, Escherichia coli, Salmonella enteritidis and Shigella sonnei, is also presented, with L. monocytogenes showing higher susceptibility to inactivation through 405nm light exposure.
TL;DR: The mechanisms of all‐trans‐RAL clearance in photoreceptor cells by sequential enzymatic reactions, the visual (retinoid) cycle, and potential molecular pathways of retinal photodamage are discussed.
Abstract: Accumulation of all-trans-retinal (all-trans-RAL), reactive vitamin A aldehyde, is one of the key factors in initiating retinal photodamage. This photodamage is characterized by progressive retinal cell death evoked by light exposure in both an acute and chronic fashion. Photoactivated rhodopsin releases all-trans-RAL, which is subsequently transported by ATP-binding cassette transporter 4 and reduced to all-trans-retinol by all-trans-retinol dehydrogenases located in photoreceptor cells. Any interruptions in the clearing of all-trans-RAL in the photoreceptors can cause an accumulation of this reactive aldehyde and its toxic condensation products. This accumulation may result in the manifestation of retinal dystrophy including human retinal degenerative diseases such as Stargardt's disease and age-related macular degeneration. Herein, we discuss the mechanisms of all-trans-RAL clearance in photoreceptor cells by sequential enzymatic reactions, the visual (retinoid) cycle, and potential molecular pathways of retinal photodamage. We also review recent imaging technologies to monitor retinal health status as well as novel therapeutic strategies preventing all-trans-RAL-associated retinal photodamage.
TL;DR: In the in vivo study, aPDT was able to reduce bacterial load in burn wounds, delay bacteremia and keep the bacterial levels in blood 2–3 logs lower compared with an untreated group, suggesting that a PDT may also be a novel prophylactic treatment in the care of burned patients.
Abstract: Pseudomonas aeruginosa is considered one of the most important pathogens that represent life-threatening risk in nosocomial environments, mainly in patients with severe burns. Antimicrobial photodynamic therapy (aPDT) has been effective to kill bacteria. The purpose of this study was to develop a burn wound and bloodstream infection model and verify aPDT effects on it. In vitro, we tested two wavelengths (blue and red LEDs) on a clinical isolate of P. aeruginosa strain with resistance to multiple
TL;DR: It is demonstrated that production of 1O2 is achieved in living cells from PS‐free 1270 nm laser excitation of molecular oxygen, and the quantity produced is sufficient to induce an oxidative stress leading to cell death.
Abstract: Singlet oxygen ((1)O(2)) is an electronic state of molecular oxygen which plays a major role in many chemical and biological photo-oxidation processes. It has a high chemical reactivity which is commonly harnessed for therapeutic issues. Indeed, (1)O(2) is believed to be the major cytotoxic agent in photodynamic therapy. In this treatment of cancer, (1)O(2) is created, among other reactive species, by an indirect transfer of energy from light to molecular oxygen via excitation of a photosensitizer (PS). This PS is believed to be necessary to obtain an efficient (1)O(2) production. In this paper, we demonstrate that production of (1)O(2) is achieved in living cells from PS-free 1270 nm laser excitation of molecular oxygen. The quantity of (1)O(2) produced in this way is sufficient to induce an oxidative stress leading to cell death. Other effects such as thermal stress are discriminated and we conclude that cell death is only due to (1)O(2) creation. This new simplified scheme of (1)O(2) activation can be seen as a breakthrough for phototherapies of malignant diseases and/or as a noninvasive possibility to generate reactive oxygen species in a tightly controlled manner.
TL;DR: The results show that extensive channelrhodopsin diversity exists even within the same genus, Chlamydomonas, and the redshifted spectra and the lack of fast inactivation in CaChR1‐ and CyChR2‐generated currents are features desirable for optogenetics applications.
Abstract: Channelrhodopsins act as photoreceptors for control of motility behavior in flagellates and are widely used as genetically targeted tools to optically manipulate the membrane potential of specific cell populations ("optogenetics"). The first two channelrhodopsins were obtained from the model organism Chlamydomonas reinhardtii (CrChR1 and CrChR2). By homology cloning we identified three new channelrhodopsin sequences from the same genus, CaChR1, CyChR1 and CraChR2, from C. augustae, C. yellowstonensis and C. raudensis, respectively. CaChR1 and CyChR1 were functionally expressed in HEK293 cells, where they acted as light-gated ion channels similar to CrChR1. However, both, which are similar to each other, differed from CrChR1 in current kinetics, inactivation, light intensity dependence, spectral sensitivity and dependence on the external pH. These results show that extensive channelrhodopsin diversity exists even within the same genus, Chlamydomonas. The maximal spectral sensitivity of CaChR1 was at 520 nm at pH 7.4, about 40 nm redshifted as compared to that of CrChR1 under the same conditions. CaChR1 was successfully expressed in Pichia pastoris and exhibited an absorption spectrum identical to the action spectrum of CaChR1-generated photocurrents. The redshifted spectra and the lack of fast inactivation in CaChR1- and CyChR1-generated currents are features desirable for optogenetics applications.
TL;DR: The study highlights the modes of interaction of photosensitizer‐loaded nanovesicles in serum to predict optimal drug delivery and behavior in vivo in preclinical models, as well as the novel application of NTA to assess the destruction of liposomes.
Abstract: mTHPC is a non polar photosensitizer used in photodynamic therapy. To improve its solubility and pharmacokinetic properties, liposomes were proposed as drug carriers. Binding of liposomal mTHPC to serum proteins and stability of drug carriers in serum are of major importance for PDT efficacy; however, neither was reported before. We studied drug binding to human serum proteins using size-exclusion chromatography. Liposomes destruction in human serum was measured by nanoparticle tracking analysis (NTA). Inclusion of mTHPC into conventional (Foslip(®)) and PEGylated (Fospeg(®)) liposomes does not affect equilibrium serum protein binding compared with solvent-based mTHPC. At short incubation times the redistribution of mTHPC from Foslip(®) and Fospeg(®) proceeds by both drug release and liposomes destruction. At longer incubation times, the drug redistributes only by release. The release of mTHPC from PEGylated vesicles is delayed compared with conventional liposomes, alongside with greatly decreased liposomes destruction. Thus, for long-circulation times the pharmacokinetic behavior of Fospeg(®) could be influenced by a combination of protein- and liposome-bound drug. The study highlights the modes of interaction of photosensitizer-loaded nanovesicles in serum to predict optimal drug delivery and behavior in vivo in preclinical models, as well as the novel application of NTA to assess the destruction of liposomes.
TL;DR: Assessment of exposure of normal human epidermal keratinocytes (NHEK) to UVA or UVB radiation finds that exposure of NHEK to UVB, but not UVA, phosphorylates JNK1/2 at Th183/Tyr185, STAT3 at Ser727, AKT at Ser473 and increases c‐Fos expression, whereas exposure to U VA, butNot UVB
Abstract: Ultraviolet (UV) radiation from the solar spectrum is a major etiological factor for many cutaneous pathologies including cancer. By understanding changes in cell signaling pathways induced by UVA and UVB, novel strategies for prevention and treatment of UV-related pathologies could be developed. However, much of the information in the literature from various laboratories cannot cross talk because of difficulties associated with the use of ill-defined light sources and physiologically irrelevant light dosimetry. Herein, we have assessed the effect of exposure of normal human epidermal keratinocytes (NHEK) to UVA (2 and 4 J cm(-2)) or UVB (20 and 40 mJ cm(-2)) radiation. Employing western blot analysis, we found that exposure of NHEK to UVB, but not UVA, phosphorylates JNK1/2 at Th(183)/Tyr(185), STAT3 at Ser(727) , AKT at Ser(473) and increases c-Fos expression, whereas exposure to UVA, but not UVB, phosphorylates AKT at Thr(308). UVB as well as UVA exposure leads to increased phosphorylation of (1) ERK1/2 at Th(202)/Tyr(204); (2) p38 at Th(180)/Tyr(204); (3) STAT3 at Tyr(705); (4) mTOR at Thr(2448); and (v) p70S6k at Thr(421) /Ser(424); enhanced expression of PI3K (p85) and c-jun; and nuclear translocation of NFκB proteins. These findings could be considered as a beginning for understanding the differential effects of UVA and UVB in the human skin and may have implications both with respect to risk assessment from exposure to solar UV radiation, and to target interventions against signaling events mediated by UVA and UVB.
TL;DR: It is suggested that PDT using TB or MB can preserve host neutrophils while exerting a significant therapeutic effect on in vivo localized microbial infection.
Abstract: Photodynamic therapy (PDT) for localized microbial infections exerts its therapeutic effect both by direct bacterial killing and also by the bactericidal effects of host neutrophils stimulated by PDT. Therefore, PDT-induced damage to neutrophils must be minimized, while direct photoinactivation of bacteria is maintained to maximize the therapeutic efficacy of antimicrobial PDT in vivo. However, there has been no study in which the cytocidal effect of PDT on neutrophils was investigated. In this study, the cytocidal effects of PDT on neutrophils were evaluated using different antimicrobial photosensitizers to find suitable candidate photosensitizers for antimicrobial PDT. PDT on murine peripheral-blood neutrophils was performed in vitro using each photosensitizer at a concentration that exerted a maximum bactericidal effect on methicillin-resistant Staphylococcus aureus, and morphological alteration and viability of neutrophils were studied. Most neutrophils were viable (>80%) after PDT using toluidine blue-O (TB) or methylene blue (MB), while neutrophils showed morphological change and their viabilities were decreased (<70%) after PDT using other photosensitizers (erythrosine B, rose bengal, crystal violet, Photofrin, new methylene blue and Laserphyrin). These results suggest that PDT using TB or MB can preserve host neutrophils while exerting a significant therapeutic effect on in vivo localized microbial infection.
TL;DR: Results showed that 670 nm light pretreatment ameliorates the light‐induced alterations in the expression of Müller‐cell specific markers for structure, stress, metabolism and inflammation, suggesting that 670'nm light preconditioning may promote neuroprotective effects in the retina from light‐ induced damage, possibly through pathways regulating the roles of Müllers cells in maintaining retinal homeostasis.
Abstract: Glial cells play an important role in the maintenance of normal structure and function of the neural components of the central nervous system. The Muller cells are one of the macroglial elements in the retina and their wide-ranging roles are responsible for the protection and proper functioning of the photoreceptors. In the present study, we aimed to test the effects of pretreatment with 670 nm red light on Muller cells in the light-induced model of retinal degeneration. Adult Sprague-Dawley albino rats were treated with 670 nm red light, from an LED source prior to exposure to bright (1000 lux) continuous light for 24 h. Muller cell-specific markers were used to assess structural and functional changes in this cell type 1 week after contact with damaging light. Changes in gene (Edn2, LIF, TNF-α) and protein (S100β, Vimentin, LIF, iNOS, GS, Cyclin-D1) levels and localization were evaluated using RT-qPCR, and immunohistochemistry. Our results showed that 670 nm light pretreatment ameliorates the light-induced alterations in the expression of Muller-cell specific markers for structure, stress, metabolism and inflammation. This suggests that 670 nm light preconditioning may promote neuroprotective effects in the retina from light-induced damage, possibly through pathways regulating the roles of Muller cells in maintaining retinal homeostasis.
TL;DR: The characterization of the mechanism of visible light‐induced oxy radicals formation by TiO2 nanoparticles could contribute to its use as a sterilization agent.
Abstract: Photoexcited TiO(2) has been found to generate reactive oxygen species, yet the precise mechanism and chemical nature of the generated oxy species especially regarding the different crystal phases remain to be elucidated. Visible light-induced reactions of a suspension of titanium dioxide (TiO(2)) in water were investigated using electron paramagnetic resonance (EPR) coupled with the spin-trapping technique. Increased levels of both hydroxyl (˙OH) and superoxide anion (˙O(2)(-)) radicals were detected in TiO(2) rutile and anatase nanoparticles (50 nm). The intensity of signals assigned to the ˙OH and ˙O(2)(-) radicals was larger for the anatase phase than that originating from rutile. Moreover, illumination with visible (nonUV) light enhanced ˙O(2)(-) formation in the rutile phase. Singlet oxygen was not detected in water suspension of TiO(2) neither in rutile nor in anatase nanoparticles, but irradiation of the rutile phase with visible light revealed a signal, which could be attributed to singlet oxygen formation. The blue part of visible spectrum (400-500 nm) was found to be responsible for the light-induced ROS in TiO(2) nanoparticles. The characterization of the mechanism of visible light-induced oxy radicals formation by TiO(2) nanoparticles could contribute to its use as a sterilization agent.
TL;DR: In conclusion, laser therapy, especially at a wavelength of 808 nm, stimulated angiogenesis and reduced the formation of fibrosis in an experimental model of OA.
Abstract: The aim of the present study was to analyze the influence of low-level laser radiation at wavelengths of 660 and 808 nm in an experimental model of osteoarthritis (OA). The sample was composed of 36 male adult Wistar rats divided into three groups (G1, G2 and G3). For the induction of cartilage injury, three injections of 4% papain and 10 μL of a cysteine solution were performed at right knee of the hind leg. Two weeks after the last injection, group G1 was treated with InGaAlP (660 nm, 100 mW, 3.57 W cm−2, 40 s) and G2 was treated with AsGaAl (808 nm, 100 mW, 3.57 W cm−2, 40 s) both with energy of 4 J. There were significant differences in the type of squamous epithelium between days 7 and 14 in G2 (P < 0.05) and on day 14 between G1 and G2 (P < 0.05). Moreover, statistically significant differences were found in the formation of new blood vessels between G1 and G3 on days 7 and 21 as well as between G2 and G3 on day 21. The formation of fibrotic tissue was greater in G3 (P < 0.05). In conclusion, laser therapy, especially at a wavelength of 808 nm, stimulated angiogenesis and reduced the formation of fibrosis in an experimental model of OA.
TL;DR: BSO, singly or in combination with other antioxidant inhibitors, significantly potentiated PDT cytotoxicity, corresponding with increased ROS levels and apoptosis and facilitates future in vivo studies.
Abstract: Photodynamic therapy (PDT) is an increasingly popular anticancer treatment that uses photosensitizer, light and tissue oxygen to generate cytotoxic reactive oxygen species (ROS) within illuminated cells. Acting to counteract ROS-mediated damage are various cellular antioxidant pathways. In this study, we combined PDT with specific antioxidant inhibitors to potentiate PDT cytotoxicity in MCF-7 cancer cells. We used disulphonated aluminium phthalocyanine photosensitizer plus various combinations of the antioxidant inhibitors: diethyl-dithiocarbamate (DDC, a Cu/Zn-SOD inhibitor), 2-methoxyestradiol (2-ME, a Mn-SOD inhibitor), l-buthionine sulfoximine (BSO, a glutathione synthesis inhibitor) and 3-amino-1,2,4-triazole (3-AT, a catalase inhibitor). BSO, singly or in combination with other antioxidant inhibitors, significantly potentiated PDT cytotoxicity, corresponding with increased ROS levels and apoptosis. The greatest potentiation of cell death over PDT alone was seen when cells were preincubated for 24 h with 300 μM BSO plus 10 mM 3-AT (1.62-fold potentiation) or 300 μM BSO plus 1 μM 2-ME (1.52-fold), or with a combination of all four inhibitors (300 μM BSO, 10 mM 3-AT, 1 μM 2-ME and 10 μM DDC: 1.4-fold). As many of these inhibitors have already been clinically tested, this work facilitates future in vivo studies.
TL;DR: An accidental exposure of two health‐care workers to ultraviolet radiation produced by a germicidal lamp in a hospital pharmacy and the results of risk assessment by occupational exposure to germicidal lamps are presented.
Abstract: Ultraviolet radiation is known to cause both benefits and harmful effects on humans. The adverse effects mainly involve two target organs, skin and eye, and can be further divided into short- and long-term effects. The present case report describes an accidental exposure of two health-care workers to ultraviolet radiation produced by a germicidal lamp in a hospital pharmacy. The germicidal lamp presented a spectrum with an intense UV-C component as well as a modest UV-B contribution. Overexposure to UV-C radiation was over 100 times as large as the ICNIRP exposure limits. A few hours after the exposure, the two subjects reported symptoms of acute UV injury and both of them continued having significant clinical signs for over 2 years. In this study, we describe acute and potentially irreversible effects caused by high UV exposure. In addition, we present the results of risk assessment by occupational exposure to germicidal lamps.
TL;DR: The synthesis of three new tetra‐ and octa‐thio‐pyridinium phthalocyanine derivatives is described, which generates high amounts of singlet oxygen, does not aggregate in PBS and is highly fluorescent, which makes it an effective PS and a promising fluorescent labeling.
Abstract: This study describes the synthesis of three new tetra- and octa-thio-pyridinium phthalocyanine derivatives. PSs 3a and 4a were prepared from the tetramerization of phthalonitriles 1 and 2, respectively, whereas PS 5 was prepared from the nucleophilic substitution of the 8 beta fluor atoms of hexadecafluorophthalocyaninatozinc(II) by mercaptopyridine, followed by cationization. The recombinant bioluminescent Escherichia coli strain was used to assess, in real time, the photoinactivation efficiency of these cationic phthalocyanines, under white and red light. The cellular localization and uptake were also determined to assess the potential of the new phthalocyanines as antibacterial agents. Derivative 3a was the most effective PS, causing a 5 logs reduction in bioluminescence after 30 min of irradiation under white or red lights. The photoinactivation efficiency of the phthalocyanine 4a was similar (5 logs reduction in bioluminescence) to that of 3a when irradiated with white light, but the efficiency of inactivation was reduced (2.1 logs reduction in bioluminescence) under red light. The tetra-substituted phthalocyanine 3a also generates high amounts of singlet oxygen, does not aggregate in PBS and is highly fluorescent, which makes it an effective PS and a promising fluorescent labeling.
TL;DR: Evaluating the in vitro fungicidal effect of hypericin PDT on various Candida spp.
Abstract: Hypericin is a natural photosensitizer considered for the new generation of photodynamic therapy (PDT) drugs. The aim of this study was to evaluate the in vitro fungicidal effect of hypericin PDT on various Candida spp., assessing its photocytotoxicity to keratinocytes (HaCaT) and dermal fibroblasts (hNDF) to determine possible side effects. A 3 log fungicidal effect was observed at 0.5 McFarland for two Candida albicans strains, Candida parapsilosis and Candida krusei with hypericin concentrations of 0.625, 1.25, 2.5 and 40 μm, respectively, at a fluence of 18 J cm(-2) (LED lamp emitting at 602 ± 10 nm). To obtain a 6 log reduction, significantly higher hypericin concentrations and light doses were needed (C. albicans 5 μM, C. parapsilosis 320 μM and C. krusei 320 μM; light dose 37 J cm(-2)). Keratinocytes and fibroblasts can be preserved by keeping the hypericin concentration below 1 μm and the light dose below 37 J cm(-2). C. albicans appears to be suitable for treatment with hypericin PDT without significant damage to cutaneous cells.
TL;DR: Some of the lesions that are known to be generated from UVA irradiation of DNA 6‐TG are described and how this photochemical damage might contribute to the toxic effect of thiopurine/UVA treatment on cultured cells and to the high risk of skin cancer in thiopirine‐treated patients are discussed.
Abstract: Thiopurines are prescribed frequently as medication for cancer and for inflammatory disorders. One of them, azathioprine, has been the immunosuppressant of choice for organ transplant recipients for many years. Thiopurine use is associated with elevated sun sensitivity and skin cancer risk. Skin sensitization is selective for UVA. 6-TG integrates into DNA and unlike the canonical DNA bases, it is a strong UVA chromophore with an absorbance maximum at 342 nm. DNA 6-TG is a photosensitizer and a source of reactive oxygen species. Reactive oxygen that is generated from the photochemical activation of DNA 6-TG causes extensive damage to DNA and proteins. This damage is mutagenic and extremely toxic to cultured human cells. Here we describe some of the lesions that are known to be generated from UVA irradiation of DNA 6-TG. We discuss how this photochemical damage might contribute to the toxic effect of thiopurine/UVA treatment on cultured cells and to the high risk of skin cancer in thiopurine-treated patients.