Phototoxicity Test Research Articles

Combination of retinyl palmitate and UV-filters: Phototoxic risk assessment based on photostability and in vitro and in vivo phototoxicity assays

This study aimed to assess the phototoxic potential of combined UV-filters and retinyl palmitate (RP) in the presence or not of bemotrizinol (BMTZ), employing photostability and in vitro and in vivo phototoxicity assays. The formulations tested contained octocrylene (OCT), octyl methoxycinnamate (OMC), benzophenone-3 (BZP-3) and RP (photostable) or octocrylene (OCT), octyl methoxycinnamate (OMC), avobenzone (AVO) and RP (less photostable). Both formulations were supplemented with bemotrizinol. Photostability was evaluated by exposing, or not, formulations spread on a glass plate to UVA/UVB irradiation. The resulting products were quantified by HPLC analysis. In vitro phototoxicity of UV-filters and combinations were evaluated using 3T3 viable monolayer fibroblast cultures submitted, or not, to irradiation according to OECD TG 432. In vivo photoallergy and photoxicity were assessed by clinical studies (photopatch test). Photostability assays showed that UV-filter bemotrizinol was a better photostabilizer for RP/benzophenone-3 than for RP/avobenzone. The in vitro phototoxicity of the combination RP/avobenzone was reduced by bemotrizinol. Clinical studies did not indicate phototoxic or photoallergenic potentials in all formulations tested. It is concluded that the 3T3 NRU phototoxicity test may be considered a supplementary assay in formulation developments, since it can detect chemically unstable and potentially phototoxic combinations. However, extrapolation of in vitro positive results to human photopatch tests may be performed only to a limited extent.

Intravitreal administration of known phototoxicants in the rabbit fails to produce phototoxicity: implications for phototoxicity testing of intravitreally administered small molecule therapeutics

Context: Intravitreal (ITV) dosing has become a clinically important route of administration for the treatment of uveitis, endophthalmitis, retinal vein occlusion, diabetic macular edema and age-related macular degeneration. Despite this, there are no validated non-clinical models of phototoxicity for ITV products.Objective: The objective of this study was to develop an ITV rabbit model of phototoxicity for use in assessing the photosafety of small molecules therapeutics.Materials and methods: Dutch Belted rabbits were intravitreally injected bilaterally with four known phototoxicants: 8-methoxypsoralen, lomefloxacin, doxycycline and stannsoporfrin. Triescence®, a non-phototoxic triamcinolone acetonide steroid formulation designed for ITV administration, was used as a negative control. One eye was then irradiated with solar-simulated ultraviolet radiation for 30 min, 1 h after dosing, while the other eye was occluded, serving as a non-irradiated control.Results: Despite the direct administration of known phototoxicants into the vitreous, no evidence of ocular phototoxicity was observed in any dose group. Direct (non-phototoxic) retinal toxicity was observed in the doxycycline dose group only.Conclusion: These data suggest that the posterior segment of the rabbit eye is protected against phototoxicity by anatomical and/or physiological mechanisms, and is not a useful model for the assessment of phototoxicity of intravitreally administered molecules.

A case study of in vitro phototoxicity testing under Regulation 1107/2009: Implications for agrochemical risk assessment

A case study of in vitro phototoxicity testing under Regulation 1107/2009: Implications for agrochemical risk assessment

Comparison of in vitro and in vivo phototoxicity tests with S-(-)-10,11-dihydroxyfarnesic acid methyl ester produced by Beauveria bassiana KACC46831.

Beauveria bassiana is a fungi that is well-known for demonstrating a resistance to environmental change. To confirm whether S-(-)-10,11-dihydroxyfarnesic acid methyl ester (DHFAME) produced by Beauveria bassiana KACC46831 causes phototoxicity when used for cosmetic purposes due to its anti-tyrosinase activity, we conducted in vitro and in vivo phototoxicity tests. There were no significant changes or damage observed in the compound-treated group with regards to skin phototoxicity, while 8-methoxypsoralen, which served as a positive control, induced toxic effects. The in vitro 3T3 neutral red uptake assay, an alternative assessment, was used for further confirmation of the phototoxicity. The results showed that DHFAME did not exhibit phototoxicity at the designated concentrations, with or without UV irradiation in the 3T3 cells. These results indicated that the methyl ester produced by Beauveria bassiana KACC46831 does not induce phototoxicity in the skin. Therefore, the results of the present study indicate that DHFAME shows potential for use as a cosmetic ingredient that does not cause skin phototoxicity.

Integrated Preclinical Photosafety Testing Strategy for Systemically Applied Pharmaceuticals

Phototoxic properties of systemically applied pharmaceuticals may be the cause of serious adverse drug reactions. Therefore, a reliable preclinical photosafety assessment strategy, combining in vitro and in vivo approaches in a quantitative manner, is important and has not been described so far. Here, we report the establishment of an optimized modified murine local lymph node assay (LLNA), adapted for phototoxicity assessment of systemically applied compounds, as well as the test results for 34 drug candidates in this in vivo photo-LLNA. The drug candidates were selected based on their ability to absorb ultraviolet/visible light and the photo irritation factors (PIFs) determined in the well-established in vitro 3T3 neutral red uptake phototoxicity test. An in vivo phototoxic potential was identified for 13 of these drug candidates. The use of multiple dose levels in the described murine in vivo phototoxicity studies enabled the establishment of no- and/or lowest-observed-adverse-effect levels (NOAELs/LOAELs), also supporting human photosafety assessment. An in vitro-in vivo correlation demonstrated that a drug candidate classified as "phototoxic" in vitro is not necessarily phototoxic in vivo. However, the probability for a drug candidate to cause phototoxicity in vivo clearly correlated with the magnitude of the phototoxicity identified in vitro.

Standardized UV–vis spectra as the foundation for a threshold-based, integrated photosafety evaluation

Phototoxicity is a relatively common phenomenon and is an adverse effect of some systemic drugs. The fundamental initial step of photochemical reactivity is absorption of a photon; however, little guidance has been provided thus far regarding how ultraviolet–visible (UV–vis) light absorption spectra may be used to inform testing strategies for investigational drugs. Here we report the results of an inter-laboratory study comparing the data from harmonized UV–vis light absorption spectra obtained in methanol with data from the in vitro 3T3 Neutral Red Uptake Phototoxicity Test. Six pharmaceutical companies submitted data according to predefined quality criteria for 76 compounds covering a wide range of chemical classes showing a diverse but “positive”-enhanced distribution of photo irritation factors (22%: PIF<2, 12%: PIF 2–5, 66%: PIF>5). For compounds being formally positive (PIF value above 5) the lowest reported molar extinction coefficient (MEC) was 1700Lmol−1cm−1 in methanol. However, the majority of these formally positive compounds showed MEC values being significantly higher (up to almost 40,000Lmol−1cm−1).In conclusion, an MEC value of 1000Lmol−1cm−1 may represent a reasonable and pragmatic threshold warranting further experimental photosafety evaluation.

Non-animal photosafety assessment approaches for cosmetics based on the photochemical and photobiochemical properties

The main purpose of the present study was to establish a non-animal photosafety assessment approach for cosmetics using in vitro photochemical and photobiochemical screening systems. Fifty-one cosmetics, pharmaceutics and other chemicals were selected as model chemicals on the basis of animal and/or clinical photosafety information. The model chemicals were assessed in terms of photochemical properties by UV/VIS spectral analysis, reactive oxygen species (ROS) assay and 3T3 neutral red uptake phototoxicity testing (3T3 NRU PT). Most phototoxins exhibited potent UV/VIS absorption with molar extinction coefficients of over 1000M−1cm−1, although false-negative prediction occurred for 2 cosmetic phototoxins owing to weak UV/VIS absorption. Among all the cosmetic ingredients, ca. 42% of tested chemicals were non-testable in the ROS assay because of low water solubility; thereby, micellar ROS (mROS) assay using a solubilizing surfactant was employed for follow-up screening. Upon combination use of ROS and mROS assays, the individual specificity was 88.2%, and the positive and negative predictivities were estimated to be 94.4% and 100%, respectively. In the 3T3 NRU PT, 3 cosmetics and 4 drugs were incorrectly predicted not to be phototoxic, although some of them were typical photoallergens. Thus, these in vitro screening systems individually provide false predictions; however, a systematic tiered approach using these assays could provide reliable photosafety assessment without any false-negatives. The combined use of in vitro assays might enable simple and fast non-animal photosafety evaluation of cosmetic ingredients.

Evaluation of the efficiency of monopolar and bipolar BDD electrodes for electrochemical oxidation of anthraquinone textile synthetic effluent for reuse

The efficiency of the electrochemical degradation of synthetic wastewater containing an anthraquinone dye has been comparatively studied in two electrolytic cells with a synthetic boron-doped diamond (Si/BDD) as an anode. The first is an individual cell (Cell 1) with monopolar electrode BDD and the second (Cell 2) has two bipolar electrodes BDD self-polarized. The bulk electrolysis was performed at the same initial operating conditions in order to quantify the influence of the initial pH and current density on dye discoloration and global mineralization removal. The current efficiency and the consumption energy were also evaluated. When the same solutions have been comparatively treated with the two cells, a quite good mineralization is found in Cell 2. This result supposed more fraction of the applied current is used for the electrocombustion reaction on Cell 2 if compared to Cell 1 and small amount rest for the side reaction of oxygen evolution. The HPLC analyses confirmed this hypothesis and showed that the concentration trend of intermediates (sulfanilic acid, phthalate acid and salicylic acid) with electrolysis time was different on two cells. Phototoxicity tests show that the electrochemical oxidation with BDD electrodes could be useful as a pretreatment technique for reducing hazardous wastewater toxicity.

Alternative in vitro phototoxicity test using reconstructed skin model, KeraSkin®

The photochemistry of two structure-related fluoroquinolones (FQs), antofloxacin (ANT) and levofloxacin (LEV), was studied in aqueous solution using stable and transient methods. The properties for energy transfer and electron transfer of these two FQs were also studied. The transient absorption spectra of FQs were observed, and transient species were assigned. The LEV triplet state (3LEV⁎) spectra (λmax = 610 nm) were determined, whereas the transient absorption of ANT could not be observed. The decay rate constant of 3LEV⁎ via unimolecular attenuation, self-quenching, and quenching by oxygen was 3.2 × 105 s− 1, 6.72 × 108 M− 1 s− 1, and 1.01 × 109 M− 1 s− 1, respectively. A reasonable diagram showing the decay of 1FQs* consisting of various substituents at the C-5 position was proposed. The phototoxicity of LEV and ANT was investigated and compared. Insertion of an amino group at the C-5 position made ANT relatively photostable and non-phototoxic compared with LEV.

Antagonizing Effects and Mechanisms of Afzelin against UVB-Induced Cell Damage

Ultraviolet (UV) radiation induces DNA damage, oxidative stress, and inflammatory processes in human keratinocytes, resulting in skin inflammation, photoaging, and photocarcinogenesis. Adequate protection of skin against the harmful effects of UV irradiation is essential. Therefore, in this study, we investigated the protective effects of afzelin, one of the flavonoids, against UV irradiation in human keratinocytes and epidermal equivalent models. Spectrophotometric measurements revealed that the afzelin extinction maxima were in the UVB and UVA range, and UV transmission below 376 nm was <10%, indicating UV-absorbing activity of afzelin. In the phototoxicity assay using the 3T3 NRU phototoxicity test (3T3-NRU-PT), afzelin presented a tendency to no phototoxic potential. In addition, in order to investigate cellular functions of afzelin itself, cells were treated with afzelin after UVB irradiation. In human keratinocyte, afzelin effectively inhibited the UVB-mediated increase in lipid peroxidation and the formation of cyclobutane pyrimidine dimers. Afzelin also inhibited UVB-induced cell death in human keratinocytes by inhibiting intrinsic apoptotic signaling. Furthermore, afzelin showed inhibitory effects on UVB-induced release of pro-inflammatory mediators such as interleukin-6, tumor necrosis factor-α, and prostaglandin-E2 in human keratinocytes by interfering with the p38 kinase pathway. Using an epidermal equivalent model exposed to UVB radiation, anti-apoptotic activity of afzelin was also confirmed together with a photoprotective effect at the morphological level. Taken together, our results suggest that afzelin has several cellular activities such as DNA-protective, antioxidant, and anti-inflammatory as well as UV-absorbing activity and may protect human skin from UVB-induced damage by a combination of UV-absorbing and cellular activities.

Effect of the size and surface charge of silica nanoparticles on cutaneous toxicity

Silica nanoparticles (NPs) are widely applied in many fields, such as chemical industry, medicine, cosmetics, and agriculture. However, the hazardous effects of silica NPs exposure are not completely understood. In this study, the two different sizes (20 nm and 100 nm) and different charges (negatively charged [NC] and weakly negatively charged [WNC]) of silica NPs were used. The present study investigated the cytotoxicity and reactive oxygen species (ROS) generation of silica NPs on keratinocytes. The phototoxicity test of silica NPs was performed on skin fibroblast cells. In addition, skin irritation and skin sensitization of silica NPs were studied on HSEM and mouse skin, respectively. The cell viability of NC 20 nm silica NPs was decreased. However, there are no cytotoxicity for NC 100 nm silica NPs and WNC silica NPs (20 and 100 nm). The results for silica NPs-induced ROS generation are consistent with the cytotoxicity test by silica NPs. Further, NC and WNC silica NPs induced no phototoxicity, acute cutaneous irritation, or skin sensitization. These results suggested that silica NPs-induced ROS generation was the determinant of cytotoxicity. This study showed that the smaller size (20 nm) of silica NPs had more toxicity than the larger size (100 nm) of silica NPs for NC silica NPs. Moreover, we observed an effect of surface charge in cytotoxicity and ROS generation, by showing that the NC silica NPs (20 nm) had more toxic than the WNC silica NPs (20 nm). These findings suggested that the surface charge of silica NPs might be the important parameter for silica NPs-induced toxicity. Further study is needed to assess the effect of surface modification of nanotoxicity.

Photosafety assessments on pirfenidone: Photochemical, photobiological, and pharmacokinetic characterization

Pirfenidone (PFD), an idiopathic pulmonary fibrosis drug, has phototoxic risk in clinical use, although its detailed mechanisms for the phototoxicity have never been fully elucidated. In the present study, the photochemical properties and in vitro phototoxicity of PFD were evaluated with a focus on ultraviolet absorption, reactive oxygen species (ROS) generation, photodynamic lipid peroxidation, and DNA photocleavage. To clarify the in vivo phototoxic behavior of PFD, photoirritation and pharmacokinetic characteristics were also assessed in rats after its oral administration. There was marked generation of singlet oxygen and superoxide from PFD upon exposure to simulated sunlight, suggesting its high photoreactivity and phototoxic potential. Photobiochemical studies demonstrated the potent in vitro photoirritation of PFD, but not its photogenotoxic risk. Pharmacokinetic profiling and in vivo phototoxicity testing on PFD at a dose of 160mg/kg suggested that highly concentrated PFD in the skin might cause phototoxic skin reactions in rats, whereas PFD at 30mg/kg was far less phototoxic, possibly due to the limited skin deposition. From these findings, a high dose of orally administered PFD might cause phototoxic skin responses, possibly via a ROS-mediated photoirritant pathway.

Evaluation of acute skin irritation and phototoxicity by aqueous and ethanol fractions of Angelica keiskei

In this study, to assess whether aqueous and ethanol fractions of Angelica keiskei induce acute skin irritation and phototoxicity, acute skin irritancy and phototoxicity tests were performed. The skin of rabbits or guinea pigs was treated with these fractions (100 mg/dose) and whether the animals sustained significant skin damage was determined. The data demonstrated that the aqueous and ethanol fractions of Angelica keiskei did not induce acute toxicity in the skin of the animals, as assessed by anatomical and pathological observations. The results from the present study suggest that these aqueous and ethanol fractions of Angelica keiskei have promising potential uses as cosmetic ingredients that do not induce significant levels of skin irritation or phototoxicity.

Skin phototoxicity of cosmetic formulations containing photounstable and photostable UV-filters and vitamin A palmitate

The aim of this study was to evaluate the in vitro skin phototoxicity of cosmetic formulations containing photounstable and photostable UV-filters and vitamin A palmitate, assessed by two in vitro techniques: 3T3 Neutral Red Uptake Phototoxicity Test and Human 3-D Skin Model In Vitro Phototoxicity Test. For this, four different formulations containing vitamin A palmitate and different UV-filters combinations, two of them considered photostable and two of them considered photounstable, were prepared. Solutions of each UV-filter and vitamin under study and solutions of four different combinations under study were also prepared. The phototoxicity was assessed in vitro by the 3T3 NRU phototoxicity test (3T3-NRU-PT) and subsequently in a phototoxicity test on reconstructed human skin model (H3D-PT). Avobenzone presented a pronounced phototoxicity and vitamin A presented a tendency to a weak phototoxic potential. A synergistic effect of vitamin A palmitate on the phototoxicity of combinations containing avobenzone was observed. H3D-PT results did not confirm the positive 3T3-NRU-PT results. However, despite the four formulations studied did not present any acute phototoxicity potential, the combination 2 containing octyl methoxycinnamate (OMC), avobenzone (AVB) and 4-methylbenzilidene camphor (MBC) presented an indication of phototoxicity that should be better investigated in terms of the frequency of photoallergic or chronic phototoxicity in humans, once these tests are scientifically validated only to detect phototoxic potential with the aim of preventing phototoxic reactions in the general population, and positive results cannot predict the exact incidence of phototoxic reactions in humans.

The 3T3 neutral red uptake phototoxicity test: Practical experience and implications for phototoxicity testing – The report of an ECVAM–EFPIA workshop

This is the report from the “ECVAM–EFPIA workshop on 3T3 NRU Phototoxicity Test: Practical Experience and Implications for Phototoxicity Testing”, jointly organized by ECVAM and EFPIA and held on the 25–27 October 2010 in Somma Lombardo, Italy.The European Centre for the Validation of Alternative Methods (ECVAM) was established in 1991 within the European Commission Joint Research, based on a Communication from the European Commission (1991). The main objective of ECVAM is to promote the scientific and regulatory acceptance of alternative methods which are of importance to the biosciences and which reduce, refine and replace the use of laboratory animals.The European Federation of Pharmaceuticals Industries and Association (EFPIA) represent the pharmaceutical industry operating in Europe. Through its direct membership of 31 national associations and 40 leading pharmaceutical companies, EFPIA is the voice on the EU scene of 2200 companies committed to researching, developing and bringing to patients new medicines that improve health and the quality of life around the world.The workshop, co-chaired by Joachim Kreysa (ECVAM) and Phil Wilcox (GSK, EFPIA) involved thirty-five experts from academia, regulatory authorities and industry, invited to contribute with their experiences in the field of phototoxicology.The main objectives of the workshop were: – to present ‘in use’ experience of the pharmaceutical industry with the 3T3 Neutral Red Uptake Phototoxicity Test (3T3 NRU-PT), – to discuss why it differs from the results in the original validation exercise, – to discuss technical issues and consider ways to improve the usability of the 3T3 NRU-PT for (non-topical) pharmaceuticals, e.g., by modifying the threshold of chemical light absorption to trigger photo-toxicological testing, and by modifying technical aspects of the assay, or adjusting the criteria used to classify a positive response.During the workshop, the assay methodology was reviewed by comparing the OECD Test Guideline (TG 432) with the protocols used in testing laboratories, data from EFPIA and JPMA ‘surveys’ were presented and possible reasons for the outcomes were discussed. Experts from cosmetics and pharmaceutical industries reported on their experience with the 3T3 NRU-PT and evidence was presented for phototoxic clinical symptoms that could be linked to certain relevant molecules. Brainstorming sessions discussed if the 3T3 NRU-PT needed to be improved and whether alternatives to the 3T3 NRU-PT exist. Finally, the viewpoint from EU and US regulators was presented. In the final session, the conclusions of the meeting were summarized, with action points.It was concluded that the 3T3 NRU-PT identifies phototoxicological hazards with a 100% sensitivity, and thus is accepted as the tier one test that correctly identifies the absence of phototoxic potential. Consequently, positive results in the 3T3 NRU-PT often do not translate into a clinical phototoxicity risk. Possible ways to improve the practical use of this assay include: (i) adaptation of changed UV/vis-absorption criteria as a means to reduce the number of materials tested, (ii) reduction of the highest concentration to be tested, and (iii) consideration of modifying the threshold criteria for the prediction of a positive call in the test.

A new in vitro protocol for assessing phototoxic effects of xenobiotics on human keratinocytes

Routine protocols of phototoxicity tests are based on cultured mouse fibroblasts, mainly because these cells are robust and easy to culture in vitro. However, in a real-life situation, phototoxic reactions take place primarily in the epidermis, comprised of keratinocytes – cells which differ substantially from fibroblasts with regard to structure and function. Therefore, keratinocyte cultures seem more appropriate for the phototoxicity testing of xenobiotics, such as cosmetic ingredients or drugs. Aim: To design and implement a test protocol for in vitro assessment of phototoxic properties of xenobiotics in normal human keratinocytes. Material and methods: As a starting point, we applied the EU-approved protocol for testing phototoxicity in mouse fibroblast cultures (3T3 Neutral Red Uptake Phototoxicity Assay, DB-ALM No. 78). The protocol was modified and adjusted in a series of experiments to the specific demands of cultured normal human keratinocytes. After obtaining a stable growth of keratinocytes in microcultures, the cells were exposed for 1 hour to model agents with phototoxic properties known from clinical observations: chlorpromazine, 8-methoxypsoralen, chloroquine, promethazine, etofenamate, ketoprofen, doxycycline, lymecycline, and isotretinoin in a series of concentrations of 0, 1, 3, 11, 33, and 100 μg/ml. Subsequently, the cultures were exposed to the cumulative dose of 5 J/cm2 of artificial sunlight using the EU-recommended solar simulator. The survival of keratinocytes was assessed by their uptake of neutral red (NR) dye. Results: Using the proposed test protocol, we were able to achieve stable growth of normal adult human keratinocytes in vitro. In the absence of phototoxic agents, no effects of light on cell viability were noticeable up to the dose of 10 J/cm2. The proposed system was capable of demonstrating phototoxicity of model phototoxic xenobiotics selected for the tests, which was in line with the clinical experience regarding phototoxic effects of these agents in humans. Conclusions: We have developed an in vitro protocol for assessment of the phototoxic potential of xenobiotics in normal human keratinocytes. Its functionality and reliability has been confirmed by tests results with known phototoxic agents. Although more difficult to culture than mouse fibroblasts, and therefore neglected in routine phototoxicity testing, human keratinocytes seem more appropriate for predicting in vitro phototoxic effects of xenobiotics in human skin, as phototoxic processes predominantly involve the epidermis which consists of keratinocytes.

Miniature swine model of phototoxicity testing

This study determined the threshold doses for 'solar erythema' and for phototoxic responses to 8-methoxypsoralen (8-MOP) in white skin Hanford and grey skin Yucatan miniature swine. For threshold erythema determinations, the UVR exposures included both UVA (315-400 nm) and UVB (290-315 nm) radiation by positioning one fluorescent 'sunlamp' among 10 'PUVA' lamps. With this configuration the UVR exposures ranged from 0.5-2.8 times the 'instrumental MED' (MEDi) for Hanford and from 1.0-5.6 times the MEDi for Yucatan. For phototoxicity determinations (i.e., with and without topically-applied graduated concentrations of 8-MOP), the UVB component was minimized by extinguishing the sunlamp, thus permitting higher UVA exposures. The Hanford had the lower UV erythema dose threshold (1.0-1.4 times the MEDi) and the erythema that developed was readily observable. The exposure doses for the phototoxicity test were 5 J/cm(2) of UVA in 35 minutes or 10 J/cm(2) in 70 minutes. The phototoxic (vascular) response to 8-MOP was observed in the two highest concentrations (0.01% and 0.1%) in Hanford pigs, in a dose-related manner. Microscopic evidence of a dose-related response was also observed as the concentration of 8-MOP increased. This verified that the Hanford miniature swine is the preferable strain for phototoxic effects. In contrast, UVR exposure of the Yucatan pig skin produced tanning rather than erythema, confirming that the Yucatan is the more appropriate strain for studying the melanization response. Thus, Hanford and Yucatan miniature swine have cutaneous photobiological responses that reflect their respective strain differences.

Photosensitizing Properties of Actarit, an Antirheumatic Drug

The photobiological properties of 4-acetylaminophenylacetic acid (Actarit, ACT, MS-932, CAS 18699-02-0) were studied using in vitro phototoxicity assays: photohemolysis, photoperoxidation of linoleic acid and Candida sp phototoxicity test. ACT reduced nitro blue tetrazolium (NBT) when irradiated with lambda > or = 300 nm in deoxygenated aqueous buffer solution (pH 7.4). The photohemolysis rate and photoperoxidation of linoleic acid were inhibited significantly by reduced glutathione. ACT was phototoxic to Candida sp. The isolation and identification of the photodegradation products of ACT in phosphate buffered saline solution (pH 7.4) and methanol were studied under aerobic conditions. Four compounds were identified and two of them isolated and characterized by spectroscopic methods. A photodecarboxylation with the participation of oxygen via a type I mechanism was proposed for the photodegradation of ACT which undergoes direct electron transfer from the excited state of ACT carboxylate and homolytic rupture of the alpha-carbon bond. A photodynamic mechanism involving radicals and electron transfer reactions was suggested for the observed in vitro phototoxicity.

The Impact of Salt Water Soaks on Biophysical and Molecular Parameters in Psoriatic Epidermis Equivalents

Background/Aims: The exact mechanisms of action of balneophototherapy are incompletely understood. We aimed to investigate the effect of salt water soaks on ultraviolet (UV) transmission and the expression of molecular parameters of psoriasis. Methods: We studied UV transmission and the expression of antimicrobial peptides and skin-derived antileukoproteinase (SKALP/elafin) in psoriatic epidermis equivalents which were pretreated with tap water and differently concentrated salt water solutions. Moreover, we performed in vivo phototoxicity tests in healthy subjects. Results: Highly concentrated salt water soaks significantly increase UV transmission through psoriatic epidermis equivalents, in particular within the wavelength range of 305– 360 nm. In vivo tests revealed increased photosensitivity following highly concentrated salt water baths. A significant decrease in human β-defensin-2 (hBD-2) and SKALP/elafin is observed after highly concentrated NaCl soaks. Conclusion: An increase in UV transmission following highly concentrated salt water soaks likely causes enhanced UV gain within the viable epidermis. Moreover, our data indicate that salt water soaks seem to influence the protein profiles of hBD-2 and SKALP/elafin.

In vitro evaluation of betamethasone esters for phototoxic potential

The phototoxicity of Betamethasone valerate and betamethasone dipropionate has been investigated on irradiation in the wavelength range of 300–400 nm, using some basic in vitro phototoxicity tests. Both esters cause photohemolysis of mouse red blood cells and photoperoxidation of linoleic acid. The photoproducts of both esters have also been found to be phototoxic. The toxicity of these photoproducts increases with further irradiation; however, they exhibit toxicity, even in the dark. The efficient inhibition of photohemolysis by the well-known free radical scavengers, such as butylhydroxyanisole and reduced glutathione, and minor inhibition by singlet-oxygen quenchers, such as sodium azide, suggests that cellular damage is mainly mediated by free radicals whereas singlet oxygen plays a minor role.