Phototoxic and photoallergic skin reactions

Indirect action of sun together with different exogenous agents (systemic medications and topically applied compounds) sometimes may result in phototoxicic and photoallergic reactions. Drug-induced photosensitivity reactions refer to the development of cutaneous disease as a result of the combined effects of a drug and light (mostly spectrum within the UVA and visible light range or UVB range). The aim of the review was to show the prominent features of phototoxic and photoallergic reactions, which occur in sun-exposed areas, including face, neck, hands and forearms. Phototoxic reactions are significantly more common than photoallergic reactions and mostly resemble to exaggerated sunburn. Photoallergic reactions appear only in a minority of individuals and resemble allergic contact dermatitis on sun-exposed areas, although sometimes may extend into covered areas. Generally, the physical examination and a positive patient's history of photosensitivity reactions on substances are of great importance for the diagnostics. The treatment of these reactions includes identification and avoidance of offending agent and application of anti-inflammatory dressings, ointments and corticosteroids.     

Occupational skin diseases caused by solar radiation

UV radiation is present in sunlight and can be emitted from numerous artificial sources. Outdoor workers are exposed to sunlight in a wide variety of occupations like sailors, fishers, construction workers, farmers, and other. Presented are the skin diseases caused by sunlight exposure. They may be of little medical importance such as stigmata or create problems like photoaging, skin carcinoma, melanoma, phototoxic and photoallergic reactions. Shown are briefly data on skin cancer in the Rijeka region in outdoor occupations, the legislation and necessity for prevention. Psoriatic patients need particular caution because they are exposed to UVR, tars, and immunosuppressive drugs during the treatment.     

Chlorpromazine oligomer is a potentially active substance that inhibits human D-amino acid oxidase, product of a susceptibility gene for schizophrenia

D-amino acid oxidase (DAO), a potential risk factor for schizophrenia, has been proposed to be involved in the decreased glutamatergic neurotransmission in schizophrenia. Here we show the inhibitory effect of an antipsychotic drug, chlorpromazine, on human DAO, which is consistent with previous reports using porcine DAO, although human DAO was inhibited to a lesser degree (K(i) = 0.7 mM) than porcine DAO. Since chlorpromazine is known to induce phototoxic or photoallergic reactions and also to be transformed into various metabolites, we examined the effects of white light-irradiated chlorpromazine on the enzymatic activity. Analytical methods including high-resolution mass spectrometry revealed that irradiation triggered the oligomerization of chlorpromazine molecules. The oligomerized chlorpromazine showed a mixed type inhibition with inhibition constants of low micromolar range, indicative of enhanced inhibition. Taken together, these results suggest that oligomerized chlorpromazine could act as an active substance that might contribute to the therapeutic effects of this drug.     

Chlorpromazine oligomer is a potentially active substance that inhibits human D-amino acid oxidase,product of a susceptibility gene for schizophrenia

D-Amino acid oxidase (DAO), a potential risk factor for schizophrenia, has been proposed to be involved in the decreased glutamatergic neurotransmission in schizophrenia. Here we show the inhibitory effect of an antipsychotic drug, chlorpromazine, on human DAO, which is consistent with previous reports using porcine DAO, although human DAO was inhibited to a lesser degree (K_i = 0.7 mM) than porcine DAO. Since chlorpromazine is known to induce phototoxic or photoallergic reactions and also to be transformed into various metabolites, we examined the effects of white light-irradiated chlorpromazine on the enzymatic activity. Analytical methods including high-resolution mass spectrometry revealed that irradiation triggered the oligomerization of chlorpromazine molecules. The oligomerized chlorpromazine showed a mixed type inhibition with inhibition constants of low micromolar range, indicative of enhanced inhibition. Taken together, these results suggest that oligomerized chlorpromazine could act as an active substance that might contribute to the therapeutic effects of this drug.     

氟喹诺酮类药物的光化学性质及其光敏毒性机理

氟喹诺酮类药物(fluoroquinolones,FQs)是目前得到广泛应用的广谱、高效的合成抗菌素。本文通过对FQs光化学研究进展的介绍,详述了具有代表性的FQs的光物理、光化学性质及光化学反应途径,以及其对生物分子的光敏损伤机理等。FQs具有较高的三重激发态产额,其激发态能够发生多种光化学反应,此类反应极易受到溶剂性质和某些盐类的影响,其光敏毒性与其分子结构有着密切的联系,尤其受8位取代基的影响非常大。对该类药物光化学性质和光敏毒性机理的研究,将会对此类药物的合理使用和新一代药物的研发提供很好的理论依据。     

Scattering of exciting light by live cells in fluorescence confocal imaging: phototoxic effects and relevance for FRAP studies

As exciting light in a scanning confocal microscope encounters a cell and its subcellular components, it is refracted and scattered. A question arises as to what proportion of the exciting light is scattered by subcellular structures and whether cells in the vicinity of the imaged area, i.e., cells that are not directly illuminated by the laser beam, can be affected by either an exposure to scattered light and ensuing phototoxic reactions, or by the products of photoactivated reactions diffusing out of the directly illuminated area. We have designed a technique, which allows us to detect subtle cell photodamage and estimate the extent and range of phototoxic effects inflicted by interaction between scattered exciting light and fluorescent probes in the vicinity of the illuminated area. The technique is based on detecting an increased influx of acridine orange into photodamaged cells, which is manifested by a change of color. We demonstrate that phototoxic effects can be exerted not only on the illuminated cell, but also on fluorescently labeled neighboring cells. The damage inflicted on neighbors is due to exposure to light scattered by the imaged (i.e., directly illuminated) cell, but not phototoxic products diffusing out of the directly illuminated area. When light encounters a cell nucleus, scattering is so intense that photodamage can be inflicted even on fluorescently labeled cells located within a radius of approximately 90 microm, i.e., several cell diameters away. This range of scattering is comparable with that caused by the glass bead resting on a coverslip (up to 120 microm). The intense scattering of exciting light imposes limits on FRAP, FLIP, and other techniques employing high intensity laser beams.     

The role of suppressor cells in the induction of murine photoallergic contact dermatitis and in its suppression by prior UVB irradiation

Induction in mice of marked photoallergic contact dermatitis (PCD) to 3,3',4',5-tetrachlorosalicylanilide (TCSA) with UVA (320 to 400 nm) radiation requires pretreatment with cyclophosphamide (CY). Attempts to induce photoallergic contact dermatitis without CY result in only a small degree of sensitivity, accompanied by significant net splenic suppressor cell activity. These suppressor cells are antigen specific, inhibit the induction but not the elicitation of photoallergic contact dermatitis to TCSA, and are T lymphocytes. Exposure of mice to UVB (280 to 320 nm) radiation at a site distant from that of sensitization, before CY administration and sensitization, inhibits the development of photoallergic contact dermatitis. This is analogous to the suppression of allergic contact dermatitis (ACD) observed in mice after exposure to UVB radiation; such suppression is accompanied by the formation of antigen-specific splenic suppressor cells. However, in contrast to the findings with allergic contact dermatitis, splenic suppressor cells are not detected in mice that are treated with UVB radiation before CY administration and sensitization to TCSA. This is presumably because CY prevents their formation. This provides evidence that UVB-irradiated mice have a second form of anergy that is not mediated by suppressor cells.     

Influence of light on plant allelochemicals: A synergistic defense in higher plants

Plant phototoxins are broad-spectrum biocides which adversely affect an array of potential plant enemies, including among others disease-causing pathogens, nematodes, insect herbivores, and competing plant species. Thus far, plants which contain these broad-spectrum allelochemicals have been found to occur in open habitats (i.e., in full sunlight) where a defensive mechanism mediated by light would seem to operate most effectively. The levels of available light in shaded environments, although considerably lower than full sun (1–10% of full sun), are equivalent to the intensities of light used to kill phototoxin-treated insects in laboratory studies. This suggests that phototoxic reactions might mediate important organismal interactions in shaded environments as well. In this study, more than 230 Costa Rican rainforest plants were bioassayed for phototoxic metabolites in an effort to ascertain their prevalence among plants growing in moderate to extreme shade. Microbial bioassays, employing Bacillus cereus (a gram positive bacterium), Escherichia coli (a gram negative bacterium), and Saccharomyces cerevisiae (a yeast) were used to rapidly and sensitively indicate phototoxic action and potential for insecticidal action. Tissue extracts from 12 plant families tested positive for phototoxins. This is the first report of phototoxins occurring in eight of those families (Acanthaceae, Campanulaceae, Gesnariaceae, Loganiaceae, Malpigaceae, Phytolaccaceae, Piperaceae, and Sapotaceae). The presence of phototoxins in rainforest plants suggests that phototoxic plant allelochemicals may function as important defenses in low-light, as well as high-light, environments.     

In vitro photochemical and phototoxicological characterization of major constituents in St. John's Wort (Hypericum perforatum) extracts

Extracts from St. John's Wort (SJW: Hypericum perforatum) have been used for the treatment of mild-to-moderate depression. In spite of the high therapeutic potential, orally administered SJW sometimes causes phototoxic skin responses. As such, the present study aimed to clarify the phototoxic mechanisms and to identify the major phototoxins of SJW extract. Photobiochemical properties of SJW extract and 19 known constituents were characterized with focus on generation of reactive oxygen species (ROS), lipid peroxidation, and DNA photocleavage, which are indicative of photosensitive, photoirritant, and photogenotoxic potentials, respectively. ROS assay revealed the photoreactivity of SJW extract and some SJW ingredients as evidenced by type I and/or II photochemical reactions under light exposure. Not all the ROS-generating constituents caused photosensitized peroxidation of linoleic acid and photodynamic cleavage of plasmid DNA, and only hypericin, pseudohypericin, and hyperforin exhibited in vitro photoirritant potential. Concomitant UV exposure of quercitrin, an SJW component with potent UV/Vis absorption, with hyperforin resulted in significant attenuation of photodynamic generation of singlet oxygen from hyperforin, but not with hypericin. In conclusion, our results suggested that hypericin, pseudohypericin, and hyperforin might be responsible for the in vitro phototoxic effects of SJW extract.     

Role of flavonoids in controlling the phototoxicity of Hypericum perforatum extracts.

Hypericum perforatum extracts are used mainly as oral antidepressants. Depending on source the extracts contain various amounts of phenylpropanes, flavonol derivates, biflavones, proathocyanidines, xanthones, phloroglucinoles, some amino acids, naphtodianthrones (hypericines) and essential oil constituents. The therapeutic use of Hypericum perforatum extracts however is limited by their phototoxic potential. It was the aim of the present study to investigate the phototoxic potential of 3 Hypericum perforatum extracts from different sources as well as some of its main constituents. In order to systematically study the phototoxic potential we established a modified neutral red assay utilizing an immortalized human keratinocyte cell line (HaCaT cells) as substrate and UVA irradiation. This modified neutral red assay was found to be a simple and reliable method for detecting phototoxic effects of reference agents and plant extracts. The validity of this method was demonstrated with known phototoxic compounds like chloropromazine and psoralenes like 5-MOP. Hypericum perforatum extracts demonstrated cytotoxicity and photocytotoxicity in a dose and UVA-dose dependent manner. Hypericine itself also evoked severe phototoxic effects and was thus identified as the main phototoxic constituent. Among the tested flavonoids quercitrin was found to be cytotoxic, while rutin unexpectedly demonstrated phototoxicity whereas quercitrin was effective to control the phototoxic activity of Hypericum perforatum extracts.     

Tryptophan as an endogenous photosensitizer to elicit harmful effects of ultraviolet B.

Owing to stratospheric ozone depletion (SOD) the natural flux of ultraviolet B (UVB) radiation (290-320 nm) is likely to increase on the earth surface. In our efforts to identify endogenous chromophores which may absorb significantly in the UVB range and subsequently induce phototoxic reactions, we have observed that tryptophan (Trp) was quite photoreactive under UVB. It enhanced considerably the oxygen-dependent photooxidation of tyrosine (Tyr) to dopachrome, a precursor of melanin. Our data suggest that UVB-sensitized Trp produces singlet oxygen (1O2) and superoxide radicals (O2-.), and these reactive forms of oxygen may contribute to membrane-, cytoplasm- and DNA-damaging effects. In the event of an increasing SOD level, other UVB chromophores may also exhibit similar phototoxic properties to lead to a definitive imbalance between cell life, injury and death.     

Possible Reasons for Differences in Phototoxic Potential of 5 Quinolone Antibacterial Agents: Generation of Toxic Oxygen

The reason for the differences in phototoxic potential between the 5 quinolone antibacterial agents lomefloxacin, enoxacin, ciprofloxacin, ofloxacin and DR-3355 (the s-isomer of ofloxacin) in mice was investigated. Superoxide anion, hydrogen peroxide (H₂O₂), and bleaching of p-nitrosodimethylaniline (B-NDMA) were detected in quinolone solutions during irradiation with ultraviolet-A (UVA). Apparent levels of H₂O₂ and the B-NDMA per mole of quinolone paralleled the phototoxic potentials in the mice. The N-NDMA induced by quinolones and UVA was inhibited partially by treatment with D-mannitol and dimethylsulfoxide, and also with diethylenetriamine-pentaaceticacid (DTPA), suggesting that Haber-Weiss and Fenton reactions occurred. UVA concentration-dependently increased the level of the B-NDMA in H₂O₂ solution and the swelling in the ear pretreated by intra-auricular injection of H₂O₂. Both augmentations were inhibited by DTPA or DMSO. The swelling induced by the 5 quinolones and UVA was completely inhibited by pretreatment with dimethylsulfoxide. Oxygen consumption was detectable during the photodegradation, and increased with time. These results showed that the phototoxic potentials of the 5 quinolones were probably related to the amounts of toxic oxygens generated in the target cells during irradiation.     

Reliable Screening of Dye Phototoxicity by Using a Caenorhabditis elegans Fast Bioassay

Phototoxicity consists in the capability of certain innocuous molecules to become toxic when subjected to suitable illumination. In order to discover new photoactive drugs or characterize phototoxic pollutants, it would be advantageous to use simple biological tests of phototoxicy. In this work, we present a pilot screening of 37 dyes to test for phototoxic effects in the roundworm Caenorhabditis elegans. Populations of this nematode were treated with different dyes, and subsequently exposed to 30 min of white light. Behavioral outcomes were quantified by recording the global motility using an infrared tracking device (WMicrotracker). Of the tested compounds, 17 dyes were classified as photoactive, being phloxine B, primuline, eosin Y, acridine orange and rose Bengal the most phototoxic. To assess photoactivity after uptake, compounds were retested after washing them out of the medium before light irradiation. Dye uptake into the worms was also analyzed by staining or fluorescence. All the positive drugs were incorporated by animals and produced phototoxic effects after washing. We also tested the stress response being triggered by the treatments through reporter strains. Endoplasmic reticulum stress response (hsp-4::GFP strain) was activated by 22% of phototoxic dyes, and mitochondrial stress response (hsp-6::GFP strain) was induced by 16% of phototoxic dyes. These results point to a phototoxic perturbation of the protein functionality and an oxidative stress similar to that reported in cell cultures. Our work shows for the first time the feasibility of C. elegans for running phototoxic screenings and underscores its application on photoactive drugs and environmental pollutants assessment.     

系统性光变态反应检测动物模型的建立

目的建立稳定、完善的系统性光变态反应检测的动物模型。方法以对氨基苯磺酰胺（SN）作为光敏剂,经腹腔注射与灌胃两种途径对小鼠和豚鼠进行给药,通过UVA加UVB光照诱导以及只用UVA光照激发后,于4h、24h、48h和72h分别测量小鼠耳厚度及观察豚鼠皮肤红斑反应。结果24h、48h和72h时,小鼠出现耳肿胀反应,豚鼠出现皮肤红斑反应。结论口服、腹腔注射SN,均可产生光变态反应,成功建立系统性光变态反应检测的动物模型。     

Photoreactivity of indirubin derivatives

Twenty-nine analogs of indirubin, an isomer of indigo, have been synthesized to optimize its promising kinase inhibitory scaffold. These compounds being also pigmented, have been tested for their photoreactivity. Absorption maxima were between 485 nm and 560 nm. Addition of fetal calf serum induced fluorescence and time dependent absorption modifications. Appropriate illumination induced Reactive Oxygen Species (ROS) production for nineteen compounds out of twenty-nine. The relationship between fluorescence and ROS production is discussed. Six compounds showed an important toxicity on F98 cells, a murine glioma cell line. Three of these were found to be also phototoxic, as four other non-toxic compounds. All but one phototoxic compounds were detected as ROS producers by in vitro tests. Photoreactivity assessment is important to anticipate adverse reactions for compounds that might be clinically developed. The experimental assay was found to be the only way to evaluate the photoreactivity of this family of compounds since no predictive criteria on structures could be found. Combining the vascular tumor growth inhibition induced by kinase inhibitors with the massive local blood flow arrest following photodynamic treatment may be an efficient anti-cancer strategy. These data could orientate further syntheses of either non-photoreactive compounds or compounds displaying both kinase inhibitory activity and strong phototoxicity.     

UV-mediated antibiotic activity of some compositae species

Roots, leaves, and flowers of 80 species of Compositae were tested for phototoxic activity against Candida albicans. Many genera showed activity, especially in the roots. No active genera were found in the tribe Cichorieae. Phototoxic compounds were isolated from Chrysanthemum leucanthemum florets and Cirsium arvense roots. Chemotaxonomic evidence plus preliminary chemical data suggests that the compounds are polyacetylenic in nature. Unlike other phototoxic compounds, these are inactive against human skin.     

The light-dependent cytotoxicity of benzo[a]pyrene: effect on human erythrocytes, Escherichia coli cells, and Haemophilus influenzae transforming DNA

In vitro, the photodynamic compound benzo[a]pyrene (BAP) generates singlet oxygen efficiently when irradiated in organic solvents. It also photogenerates superoxide anion radical in water and can act as a photoreducing agent in the absence of oxygen. In vivo, the hemolysis of human erythrocytes, the inactivation of Escherichia coli cells representing a series of strains differing in excision repair and catalase proficiency, and the inactivation of Haemophilus influenzae transforming DNA activity were used to characterize the phototoxicity of BAP in the presence of near-UV light (290-400 nm). The results are consistent with BAP behaving as a photosensitizer that generates both superoxide and singlet oxygen, and that damages chiefly membranes. DNA does not seem to be a major target in the phototoxic reactions investigated.     

Zn phthalocyanines loaded into liposomes: Characterization and enhanced performance of photodynamic activity on glioblastoma cells

Photodynamic therapy (PDT) is considered a promising strategy for cancer treatment. PDT utilizes light in combination with a photosensitizer (PS) to induce several phototoxic reactions. Phthalocyanines (Pcs), a second generation of photosensitizers, have been studied in several cancer models. Among these, Pcs, have become of interest for the treatment of glioblastomas which are one of the most common and aggressive forms of tumors of the central nervous system. Due to the lipophilic nature of Pcs and their limited solubility in water, Pcs can be loaded in liposomes. In this work, we characterized liposomes of ZnPc and TAZnPc and their effectiveness to photoinactivate glioblastoma cells, was evaluated. Both Pcs show an increase in their photosensitizing activity when they were administrated in Dipalmitoylphosphatidylcholine-cholesterol liposomes compared to Pcs administrated in dimethylformamide.     

Contrasting action of flavonoids on phototoxic effects induced in human skin fibroblasts by UVA alone or UVA plus cyamemazine, a phototoxic neuroleptic.

The potential protective effects of the flavanol catechin, the flavonol quercetin, the flavones, luteolin and rutin, and the isoflavones, genistein and daidzein, against the photo-oxidative stress induced by ultraviolet A radiation (UVA) and by phototoxic reactions resulting from the interaction of UVA with drugs and chemicals, has been assessed with cultured human skin fibroblasts. Lipid peroxidation and cell death have been chosen as model photobiological damage induced by UVA alone or photosensitized by cyamemazine (CMZ) and its photoproduct possessing phototoxic properties. Contrasting effects of flavonoids are observed. The flavanol, the flavonol and the flavones may protect against lipid peroxidation and cell death induced by 30 J cm(-2) of UVA alone or CMZ plus 10 J cm(-2) UVA. On the other hand, an amplification of the photodamage may be observed with isoflavones. A concentration-dependence study demonstrates that among the protective flavonoids, quercetin is the most efficient. The very effective protection brought by quercetin may result from its ability to scavenge reactive oxygen species produced by the photo-oxidative stress. However, the modification of membrane properties and the alteration of the lysosomal function by quercetin may not be neglected in these protective effects. The amplification of the photodamage by isoflavones is in sharp contrast with previous literature data demonstrating photoprotection by genistein. As a consequence, it may be concluded that an eventual antioxidant action of genistein may strongly depend on cells and photosensitizers. Furthermore such contrasting pro-versus anti-oxidant effects have to be taken into account when using flavonoid mixtures of plant extracts.     

Evaluation of chemically-induced phototoxicity to aquatic organism using Paramecium as a model

Phototoxicity evaluation using Paramecium aurelia as a model revealed that 4 out of 21 pesticides produced lethal toxicity to cells. Four commonly used synthetic dyes (bromophenol blue, rose bengal, benzanthrone and methylene blue) also exhibited toxicity. Well known phototoxic agents like hematoporphyrin, riboflavin, and anthracene produced positive phototoxic response. Psoralen, a DNA cross-linking agent, also produced phototoxicity to the cells. The results clearly demonstrate that the synergistic action of chemical agents and sunlight produce lethal effects to aquatic organism.