Phototoxic reaction to xanthene dyes induced by visible light

Visible light. Part I: Properties and cutaneous effects of visible light

Approximately 50% of the sunlight reaching the Earth's surface is visible light (400-700 nm). Other sources of visible light include lasers, light-emitting diodes, and flash lamps. Photons from visible light are absorbed by photoreceptive chromophores (e.g., melanin, heme, and opsins), altering skin function by activating and imparting energy to chromophores. Additionally, visible light can penetrate the full thickness of the skin and induce pigmentation and erythema. Clinically, lasers and light devices are used to treat skin conditions by utilizing specific wavelengths and treatment parameters. Red and blue light from light-emitting diodes and intense pulsed light have been studied as antimicrobial and anti-inflammatory treatments for acne. Pulsed dye lasers are used to treat vascular lesions in adults and infants. Further research is necessary to determine the functional significance of visible light on skin health without confounding the influence of ultraviolet and infrared wavelengths.

Glyceryl Tristearate-Based Lipid Microparticles Loaded with the Tattoo Colorant, Acid Red 87: Colorant Retention Capacity in Excised Porcine Skin

BACKGROUND

With the increasing diffusion of tattooing, the photolability of tattoo inks has become a critical issue, as available data indicated that several tattoo colorants are unstable under sunlight, generating potentially toxic photodegradation products. Therefore, it is desirable to enhance the photostability of coloring agents contained in tattoo inks.

AIMS

Lipid microparticles (LMs) highly loaded with Acid Red 87 (C.I. 45380), a colorant used in tattoo inks, were evaluated for their effect on the colorant photoinstability. In addition, the capacity of the LMs to retain the incorporated C.I. 45380 colorant after their intradermal administration in excised porcine skin was investigated.

METHODS

LMs loaded with C.I. 45380 were prepared using glyceryl tristearate as the lipidic material and phosphatidylcholine as the surfactant. Non-encapsulated C.I. 45380 or the colorant-loaded LMs were irradiated with a solar simulator for photodecomposition studies or introduced in the excised porcine skin mounted in Franz diffusion cells for stability evaluation in the dermal tissue.

RESULTS AND CONCLUSION

The colorant content of the microparticles was 17.7%, and their size ranged from 25 to 170 μm. The light-induced degradation of C.I. 45380 was significantly decreased by its incorporation in the LMs from 20.2 ± 5.8% to 1.9 ± 2.1%. Moreover, after intradermal injection of free or microencapsulated C.I. 45380 in the excised pig skin, the LMs reduced by 93.7% (from 24.6 to 1.5%) the quantity of the colorant diffused and hence lost in the Franz cell receptor fluid. Hence, the LM carrier efficiently retained the entrapped C.I. 45380 following incubation in the dermal region of the isolated porcine skin, which is in favor of a long-lasting tattoo. Based on these data, the incorporation of C.I. 45380 in the LMs could represent a potentially useful strategy to reduce the photodecomposition of the tattoo colorant and its harmful interactions with the skin tissue.

Incorporation in Lipid Microparticles of Acid Red 87, a Colorant Used in Tattoo Inks: Effect on Photodegradation Under Simulated Sunlight and Laser Radiation

Tattoo colorants decompose under solar radiation and when exposed to laser light for their removal, leading to the accumulation in the dermis of toxic products. Aim of this study was to develop lipid microparticles (LMs) loaded with the colorant, Acid Red 87 (C.I. 45380) used in tattoo inks, and to investigate the effect of this system on the photostability of the colorant under simulated sunlight or laser irradiation. LMs loaded with C.I. 45380 were prepared by melt emulsification using tristearin and phosphatidylcholine as excipients. They were characterized by optical microscopy, laser diffraction, X-ray diffraction and release studies. Free C.I. 45380 and the colorant-loaded LMs were irradiated with a solar simulator or a Q-switched laser. Irradiation with a solar simulator demonstrated that photodecomposition of C.I. 45380 was markedly reduced by incorporation of the dye in the LMs, from 20.5 ± 4.6% to 1.3 ± 1.8%. Conversely, the laser-induced degradation of the colorant (30.1 ± 6.6%) was not significantly influenced by encapsulation in the LMs (the encapsulated C.I. 45380 loss was 27.4 ± 5.5%). Incorporation of C.I. 45380 in lipid microparticles enhances the photostability under sunlight of tattoo inks containing this colorant, without affecting its laser-induced degradation and hence laser removal efficiency.

Environmental Basis of Autoimmunity

The three common themes that underlie the induction and perpetuation of autoimmunity are genetic predisposition, environmental factors, and immune regulation. Environmental factors have gained much attention for their role in triggering autoimmunity, with increasing evidence of their influence as demonstrated by epidemiological studies, laboratory research, and animal studies. Environmental factors known to trigger and perpetuate autoimmunity include infections, gut microbiota, as well as physical and environmental agents. To address these issues, we will review major potential mechanisms that underlie autoimmunity including molecular mimicry, epitope spreading, bystander activation, polyclonal activation of B and T cells, infections, and autoinflammatory activation of innate immunity. The association of the gut microbiota on autoimmunity will be particularly highlighted by their interaction with pharmaceutical agents that may lead to organ-specific autoimmunity. Nonetheless, and we will emphasize this point, the precise mechanism of environmental influence on disease pathogenesis remains elusive.

In vitro cytotoxicity and phototoxicity study of cosmetics colorants

The aim of the work was early identification of preventable risk factors connected with the consumers usage of products of everyday use, such as cosmetics, toys and children products, and other materials intended for contact with human skin. The risk factor is represented by substances with irritation potential and subsequent possible sensitisation, resulting in negative impact on human physical and psychical health with social and societal consequences. The legislation for cosmetics, chemical substances and other products requires for hazard identification the application of alternative toxicological methods in vitro without the use of animals. For this reason we used a battery of alternative assays in vitro, based on cell cultures. Progressive methods of molecular biology, based on fluorimetry and fluorescence, were employed for identification of early morphological and functional changes on cellular level. Four colorants frequently used in cosmetics (P-WS Caramel, Chlorophyllin, Unicert Red K 7054-J and Unicert Red K 7008-J) were tested on cell line NIH3T3 (mouse fibroblast cell) and 3T3 Balb/c with/without UV irradiation (dose 5 J cm(-2)). Fluorescence methods for the study of cell damage using fluorescence probes offer results for the evaluation of cytotoxicity and cell viability of adherent cells. We detected intracellular production of ROS investigated by molecular probe CM-H(2)DCFDA, which is primarily sensitive to the increased production of hydrogen peroxide or its downstream products. Toxic effects on the cellular level were identified by viability tests using Neutral Red uptake and MTT assay, where the live cells reduce yellow soluble 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) to insoluble formazan crystals. The reaction was investigated on mitochondrial membrane of living cells and the type of cell death was determined using Apoptosis detection kit. Cytotoxicity tests revealed health risks of using Chlorophyllin and Unicert Red K 7054-J.

The choice of chromogen and reliability of contact rhinoscopy in the irradiated nasopharynx

A cross-sectional randomised single blind study was conducted to assess how concentrations of chromogen (vital stain) and the characteristics of the assessors affect the assessment of contact rhinoscopy. Twenty-eight patients who had undergone external radiotherapy for nasopharyngeal carcinoma were assessed by contact rhinoscopy using 0.5 per cent and 1 per cent methylene blue stain on opposite sides of the nasopharynx. Three independent observers assessed the visual clarity of the 45 contact endoscopic images showing squamous metaplasia according to a visual analogue scale. The intraclass correlation coefficients were 0.916 to 0.957 and 0.839 to 0.964 for intra-observer reliability of assessors in the groups of 0.5 per cent and 1 per cent stains, respectively. The intraclass correlation coefficients for inter-observer reliability of assessors were 0.884 and 0.885 in the groups of 0.5 per cent and 1 per cent stains, respectively. The mean scores of clarity of the cellular details were statistically higher in the group of 1 per cent stain among all assessors. These results showed that the assessment of squamous metaplasia by contact endoscopy is highly reliable irrespective of the clinical experience and knowledge of histopathology of the assessors. One per cent methylene blue should be the vital stain of choice in contact endoscopy.

In vivo real-time diagnosis of nasopharyngeal carcinoma in situ by contact rhinoscopy

BACKGROUND

Nasopharyngeal dysplasia or nasopharyngeal carcinoma in situ (NPCIS) lesions have rarely been reported. Timely diagnosis of the preinvasive lesion may improve prognosis. Contact endoscopy has been documented to accurately differentiate normal cells of the nasopharynx from malignant cells and allows a real-time diagnosis of primary and recurrent nasopharyngeal carcinoma (NPC) in a clinical setting. However, the role of contact endoscopy in the diagnosis of NPCIS is unknown.

METHODS

The superficial cells of the nasopharynx in a patient with NPCIS were examined in vivo under local anaesthesia by use of a contact rhinoscope. The contact endoscopic findings were correlated with the histologic findings of the biopsy.

RESULTS

The atypical cells of the lesion were magnified and visualized under contact endoscopy. Histopathologic analysis of the biopsied tissue confirmed the presence of NPCIS staining positively for Epstein-Barr virus (EBV)-encoded RNA (EBER). No cell-free EBV DNA was detected in the sera of the patient.

CONCLUSIONS

Contact endoscopy can accurately identify the atypical cells of a tiny preinvasive lesion in the nasopharynx in a clinical setting, which may not be evident in routine imaging examination.

Quantitation of cutaneous inflammation induced by reactive species generated by UV-visible irradiation of rose bengal

The present studies were undertaken to quantitate the initial inflammatory response produced by the photo-generated reactive species in rabbit skin. Rose bengal (RB), a photosensitizer dye, was injected into the skin sites at various concentrations and exposed to UV-visible light for 30-120 min. The increase in vascular permeability and the accumulation of PMNs were investigated using 125I-labeled albumin and 51Cr-labeled PMNs. RB at a concentration of 1 nmol with 120-min exposure to light enhanced vascular permeability by 3.7 times and accumulation of PMNs by 3.3 times. As low as 0.01 nmol of RB produced discernible effects. beta-Carotene (0.1 nmole) inhibited the inflammatory response by 75-100%, suggesting that the reactive species involved in this response was predominantly singlet oxygen. The increase in vascular permeability was inhibited by 48-70% by 25 micrograms of chlorpheniramine maleate. It is therefore suggested that histamine plays a major role in the initial vascular response. The studies demonstrate that this rabbit model is suitable for the quantitation of photoinduced inflammatory response which is not observable by gross anatomic procedures.

Evaluation of drug phototoxicity by photosensitization of Trichophyton mentagrophytes

Long wave ultraviolet radiation to suspensions of T. mentagrophytes, in the presence of photosensitizing chemicals, resulted in death of the fungus as measured by loss in colony-forming ability. Photosensitization could be demonstrated, with appropriate exposures and concentrations, with chlorpromazine, promethazine, perphenazine, anthracene, sulphanilamide, trimethylpsoralen, tolbutamide, tetrachlorosalicylanilide, and tribromosalicylanilide. No phototoxicity was detected with demethylchlortetracycline and thiazides. The present system seems to be simple, reproducible, and sensitive as an in vitro screening test for the photosensitizing potential of chemicals.

Identification of topical photosensitizing agents in humans

A method is described for the detection of topical photosensitizers in humans. Test agents were applied to the untanned midback under an occlusive dressing for 6 hr and then exposed to broad-spectrum radiation containing UV-A and visible wavelengths from a Xenon arc source. Well-known topical photosensitizers were readily identified. It was found that with certain poorly-penetrating substances, such as water-soluble dyes, applications to scarified skin were necessary to reveal phototoxic activity. In addition, these dyes were activated by wavelengths in the visible region of the spectrum.