PhotoSENSIL-18 assay development: Enhancing the safety testing of cosmetic raw materials and finished products to support the in vitro photosensitization assessment?

Although photosensitization remains a major toxicological endpoint for the safety assessment of cosmetic products and their raw materials, there is no validated in vitro method available for the evaluation of this adverse effect so far. Given that previous studies have proposed that the Interleukine-18 (IL-18) plays a key role in keratinocyte-driven pro-inflammatory responses specific of the skin sensitization process, we hypothesize that IL-18 might be used as a specific biomarker for in vitro photosensitization assessment. The aim of the present study was the set-up of a new in vitro assay using IL-18 as a biomarker for the identification of photosensitizers in a reconstructed human epidermis (RHE) model. EpiCS™ RHE were incubated with a set of 16 known sensitising / phototoxic / photosensitizing substances and exposed to ultra-violet (UV) irradiation. Then, the cell viability was analysed by MTT assay, while the IL-18 secretion was quantified by ELISA. Preliminary assays have shown that 1 h of incubation followed by a recovery period of 23 h induced the highest IL-18 production in response to UV exposure. This protocol was used to test 16 substances and a ratio of IL-18 production (UV+/UV- ratio) was then generated. Our data shows that the cut-off of 1.5 (UV+/UV- ratio) is the most predictive model among the tested conditions, being capable of identifying true positive photosensitizers (8 of 9) with a good prediction in comparison with in vivo data. In a nutshell, our data suggests that the PhotoSENSIL-18 is a promising in vitro method for identification of photosensitizing substances. Although further studies are necessary to optimize the model, we foresee that the PhotoSENSIL-18 assay can be used in the context of an Integrative Approach to Testing and Assessment (IATA) of chemicals.

Phenylene Bis-Diphenyltriazine (TriAsorB), a new sunfilter protecting the skin against both UVB + UVA and blue light radiations.

Sunlight induces actinic keratosis, skin cancers and photoaging. Photoprotection is thus a major issue in public health to prevent the harmful effects of solar ultraviolet (UV) radiations. Recent data have shown that the visible (VIS) and infrared (IR) radiations can lead to skin damage by oxidative stress, suggesting that a balanced protection across the entire spectrum of sunlight is necessary to prevent cutaneous alterations. In this context, we developed a new generation of sunfilter called Phenylene Bis-Diphenyltriazine or TriAsorB (CAS N°55514-22-2). The aim of the present study was to assess the photoprotective efficacy of TriAsorB from UV to IR light. Spectrophotometric assays were performed to measure absorption and reflectance of TriAsorB in the different spectral ranges of sunlight: UV, VIS including blue light or high energy visible (HEV) and IR. DNA damage was evaluated using reconstructed human epidermis (RHE): 8-hydroxy-2'-deoxyguanosine (8OHdG) in response to HEV exposure, pyrimidine dimers (CPDs) and (6-4) photoproducts following solar-simulated radiation (SSR). TriAsorB is a broad spectrum UVB + UVA filter including long UVA. Interestingly, it also absorbs VIS radiations, especially in the HEV region. These radiations are also reflected. Protection in the IR spectral range is weak. Furthermore, the sunfilter specifically protects the skin against the oxidative lesions 8OHdG induced by HEV and prevents SSR-induced DNA damage. Thus, TriAsorB is an innovative sunfilter that might be used in sun care products for skin photoprotection from UV to VIS radiations. Finally, it prevents sunlight genotoxicity and protected the skin against solar radiations, especially blue light.

Stepwise approach of development of dermo-cosmetic products in healthy and atopic dermatitis paediatric population: safety evaluation, clinical development and postmarket surveillance.

BACKGROUND/OBJECTIVES: Paediatric skin, considered sensitive, and infant skin, more susceptible to percutaneous toxicity, require specially formulated cosmetic products. As recently shown, early use of emollients in infants "at risk" of developing atopic dermatitis has shown controversial results in reducing the incidence of atopic dermatitis. Development of dermo-cosmetic products for this specific population should especially ensure tolerance and safety. In absence of good clinical practice guideline, we propose here a stepwise approach for the development of paediatric cosmetic skincare products. METHODS: Our stepwise methodology for cosmetics aimed at paediatrics, starts with in vitro assessment of product's ingredients safety, followed by preclinical and clinical evaluations of the final product, including sequentially: (1) Repeated Open Application Test (ROAT), (2) Human Repeated Insult Patch Test (HRIPT), (3) In-use dermatological and ophthalmological tolerance studies (sequentially in 3a: healthy adults, 3b: healthy paediatric subjects and finally 3c: paediatric patients). We also describe the integrated cosmetovigilance-toxicological surveillance during the clinical development phase and postmarketing. RESULTS: As illustrated with one dermo-cosmetic product intended to be used as a preventative/maintenance treatment for atopic dermatitis in paediatric population, we show that using this stepwise methodology to test a product reduces potential risks of irritation and contact dermatitis in this sensitive population. CONCLUSION: Standardized ethical stepwise development approach is needed to ensure the commercialization of safe and well-tolerated dermo-cosmetics for paediatrics. The approach described here could potentially serve as guidance for evaluation of new paediatric cosmetic products.

Influence of the container on the consumption of cosmetic products.

The container, also known as primary package or inner package, could be defined as the packaging designed to come into direct contact with the cosmetic product. To author's knowledge, no study was available regarding the effect of the primary package on the consumption of cosmetic products. The aim of the study was to assess the impact of the container on the consumption of three cosmetic products widely used, i.e. shampoo, shower gel and emollient cream. The three products were contained in a tube with a flip top cap and in a bottle with a pump. The study was conducted on 221 French adults: 108 women and 113 men. Results showed that the consumption of each cosmetic product was slightly higher when the product was packaged in tube with a flip top cap than in bottle with a pump. The difference of consumption could vary from 5 % to 23 % when calculated with mean values. This information could be interesting for safety evaluators, safety agencies and commercial services of cosmetic manufacturers.

Probabilistic exposure assessment of sun care products.

The aim of this study has been to assess the consumption and the exposure to 6 types of sun care products: sunscreen cream, sunscreen milk, sunscreen spray, sunscreen stick, moisturizing cream with SPF and after-sun milk. Consumption data were obtained from 75 clinical safety studies conducted on 3001 subjects: 371 children aged 3-9, 149 children aged 10-14 and 2481 adults aged more than 15. Exposure was assessed using a probabilistic method. Strength of the study include stratification of consumption and exposure data according to sex and age, as well as other important points such as the galenic form, the site of application and the value of the sun protection factor.

Exposure assessment of family cosmetic products dedicated to babies, children and adults.

Very few consumption and exposure data is available for family cosmetic products. The aim of the present study was to assess the consumption and the exposure to family cosmetic products used by babies, children and adults. 10 categories of products were studied: shampoo, shower gel, solid soap, cleansing lotion, emollient foam, emollient bath, cream, milk, balm and lip balm. Consumption data were obtained from 2994 participants (789 babies aged 0-3 years, 837 children aged 4-12 years and 1368 adults aged more than 18 years) included in 87 clinical safety studies. Exposure was performed using a probabilistic method. The implementation of consumption and exposure assessment by age has strengthened this work, as consumption and mainly exposure differences were shown. In fact, babies were always the most exposed to family products, followed by children and adults. These original data will be useful for safety assessors and safety agencies in order to protect consumers.

Preliminary performance data of the RHE/IL-18 assay performed on SkinEthic™ RHE for the identification of contact sensitizers.

OBJECTIVE: The purpose of this study was to evaluate the performances of the RHE/IL-18 assay using the SkinEthic™ RHE model for the identification of contact sensitizers. METHODS: A set of 18 substances and mixtures was tested on this epidermal model, following the RHE/IL-18 protocol. The final results of the assay were obtained following 5 interpretation schemes, to determine the optimal prediction model for this assay with this specific test system. The data were analysed with a special focus on the basal level of IL-18 release and on the performance obtained with respect to three different gold standards: LLNA, HRIPT and an integrated reference, constructed from all available results. RESULTS: No important differences were found in the performance levels depending on the three gold standards. The performances obtained with the SkinEthic™ RHE model support that this model may be considered as an alternative to different reconstructed epidermis models (EpiDERM™ , EpiCS™ and VUMC-EE) for the performance of RHE/IL-18 assays. CONCLUSION: The prediction model to be used was refined, and more substances have to be tested in order to gather enough data for this evaluation and to determine the right criteria applicable for this assay using the SkinEthic™ RHE test system.

Fragility of epidermis in newborns, children and adolescents.

Within their first days of life, newborns' skin undergoes various adaptation processes needed to accommodate the transition from the wet uterine environment to the dry atmosphere. The skin of newborns and infants is considered as a physiological fragile skin, a skin with lower resistance to aggressions. Fragile skin is divided into four categories up to its origin: physiological fragile skin (age, location), pathological fragile skin (acute and chronic), circumstantial fragile skin (due to environmental extrinsic factors or intrinsic factors such as stress) and iatrogenic fragile skin. Extensive research of the past 10 years have proven evidence that at birth albeit showing a nearly perfect appearance, newborn skin is structurally and functionally immature compared to adult skin undergoing a physiological maturation process after birth at least throughout the first year of life. This article is an overview of all known data about fragility of epidermis in 'fragile populations': newborns, children and adolescents. It includes the recent pathological, pathophysiological and clinical data about fragility of epidermis in various dermatological diseases, such as atopic dermatitis, acne, rosacea, contact dermatitis, irritative dermatitis and focus on UV protection.

The superoxide dismutase mimetic MnTBAP prevents Fas-induced acute liver failure in the mouse.

BACKGROUND & AIMS: Acute liver failure (ALF) of viral origin results from massive hepatocyte apoptosis induced by the interaction between Fas expressed on hepatocytes and Fas ligand on activated T lymphocytes. Because Fas-induced apoptosis of hepatocytes involves mitochondrial damages and potential reactive oxygen species (ROS) overproduction, we investigated whether manganese III tetrakis (5,10,15,20 benzoic acid) (MnTBAP), a nonpeptidyl mimic of superoxide dismutase (SOD), can inhibit Fas-induced ALF. METHODS: An agonist anti-Fas monoclonal antibody was used to induce hepatocyte apoptosis in vitro and ALF in vivo. RESULTS: Preventive and curative treatments by MnTBAP significantly increased survival rates and significantly reduced aspartate aminotransferase levels and parenchymal lesions. ROS generation was suggested by those beneficial effects and significant increases in SOD and Gpx activities after anti-Fas injection. Flow cytometry of isolated hepatocytes incubated with anti-Fas monoclonal antibody showed that ROS production was associated with the collapse of transmembrane potential and loss of cardiolipin content. After injection of anti-Fas monoclonal antibody, mitochondrial Bcl-2 was decreased, cytochrome c released, and caspase-3 activated. Mitochondrial alterations and their consequences were abrogated by MnTBAP. CONCLUSIONS: ROS are key executioners in Fas-induced hepatocyte apoptosis. This finding explains why a nonpeptidyl mimic of SOD can cure ALF in a model of viral hepatitis, pointing out the potential interest of this molecule in humans.

Detoxification of reactive oxygen species by a nonpeptidyl mimic of superoxide dismutase cures acetaminophen-induced acute liver failure in the mouse.

Drug-induced acute liver failure (ALF) is a devastating and often fatal disease mainly caused by poisoning by acetaminophen (APAP). The toxic metabolite, N-acetyl-p-benzoquinone-imine (NAPQI), that leads to gluthatione depletion has been suspected to be the main effector of hepatocyte apoptosis during APAP-induced ALF. We have investigated whether reactive oxygen species (ROS) also play a role in APAP-induced ALF, and whether manganese III tetrakis (5,10,15,20 benzoic acid) (MnTBAP), a mimic of superoxide dismutase (SOD) with catalase-like activity, can treat the disease in mice. The effects of MnTBAP were tested on APAP-intoxicated mice and on isolated hepatocytes incubated with APAP. MnTBAP preventively and curatively administered significantly improved survival times, and dramatically reduced serum transaminase activity levels and parenchymal lesions in APAP-intoxicated mice. Whereas pretreatment with N-acetyl-L-cysteine (NAC) prevented ALF in a dose-dependent manner, the molecule was ineffective when curatively administered. The significant increase in glutathione peroxidase (Gpx) activity following APAP administration, and the beneficial effects of MnTBAP suggested that ROS were produced during APAP-induced ALF. A direct evidence of ROS generation was provided by flow cytometry of isolated hepatocytes incubated with APAP. In vitro, ROS production was associated with mitochondrial damage characterized by the collapse of transmembrane potential and the loss of cardiolipin content. In livers of intoxicated mice, ALF was associated with cytochrome c release that led to the activation of caspases-9 and -3. The capacity of MnTBAP to abrogate all those alterations suggests that ROS play a role in APAP-induced apoptosis of hepatocytes, and explains the beneficial effects of MnTBAP, which could be of interest in APAP-induced ALF in humans.

Protective effect of thioredoxin upon NO-mediated cell injury in THP1 monocytic human cells.

Although NO has been postulated to play important roles in host defences, it is potentially damaging for exposed cells, including for the macrophages producing the NO. Thus a network of radical acceptors and enzymes is thought to play an important redox-buffering role to protect cells against NO-mediated injury. We examined the properties of the redox systems superoxide dismutase (SOD)/catalase, glutathione (GSH) and thioredoxin (Trx), in regulating the viability of two human monocytic cell lines (THP1 and U937) exposed to the NO-generating compound diethylene triamine-nitric oxide (DETA-NO). We observed that NO-induced cytotoxic effects were time- and dose-dependent towards the two cell lines. After vitamin-induced differentiation in vitro with retinoic acid (RA) and 1,25-dihydroxy vitamin D(3) (VD), termed RA/VD, we observed that THP1 RA/VD cells became more resistant to NO-mediated cytotoxicity whereas the susceptibility of U937 cells was not modified. Using Western blotting and reverse-transcriptase PCR methods, we observed that gene transcription and protein expression of Trx and thioredoxin reductase were significantly increased upon RA/VD treatment and differentiation in THP1 cells. By contrast, SOD/catalase and GSH redox state remained unmodified. Finally, a stable transfectant THP1 line overexpressing Trx was found to be more resistant than THP1 control cells that were untransfected or transfected with an empty plasmid, when exposed to DETA-NO in vitro. In conclusion, we observed an inverse correlation between cell susceptibility to NO damaging effects and Trx expression, suggesting that the Trx system may have important preventative capacities towards NO-mediated cellular injury in monocytic macrophage cells.