In vivo method for evaluating sunscreen protection against high-energy visible light

BACKGROUND

Overexposure to sunlight can have many harmful biological effects on the skin, leading to skin cancer and photoaging. As ultraviolet (UV) radiation has been identified as a cause of DNA damage and oxidative stress in the skin, the photoprotection provided by sunscreens is evaluated through their ability to filter UV light, using the sun protection factor (SPF). However, recent data have shown that high-energy visible (HEV) light can also cause biological skin damage.

OBJECTIVES

To develop a new in vivo method for evaluating the protection provided by sunscreens across a broad range of wavelengths, including the HEV band, based on multispectral image analysis.

METHODS

This study evaluated the absorption properties of six commercially available sunscreens (five SPF 50+ products containing organic UV filters, and one product containing the wide spectrum filter, phenylene bis-diphenyltriazine [TriAsorB™]) and of a control product containing no filter. Multispectral images were acquired from the skin on the forearms of healthy volunteers, before and after application of the test products. Images taken with LEDs emitting light at wavelengths ranging from UV to infrared were used to generate light reflectance maps for each product. The levels of absorbance of light in the UV and visible bands were then calculated.

RESULTS

The product containing the wide spectrum filter exhibited significantly higher absorbance over the HEV band (380-450 nm) than the control product and the other commercial sunscreens. All the sunscreens tested showed the same level of absorbance at 365 nm (UVA).

CONCLUSIONS

Multispectral imaging provides a simple and reliable in vivo method for assessing the real-world protection provided by sunscreens against all forms of photo-induced skin damage, including that induced by HEV radiation.

Formulation of a new broad-spectrum UVB + UVA and blue light SPF50+ sunscreen containing Phenylene Bis-Diphenyltriazine (TriAsorB), an innovative sun filter with unique optical properties

Accumulating evidence from numerous comprehensive studies has demonstrated that blue light, in particular high-energy visible light, can exert a range of harmful effects on skin cells. These forms of radiation are now known to be able to trigger oxidation reactions, DNA damage, erythema and pigmentary changes, and may also be associated with photoaging. Sunscreens protecting the skin from only ultraviolet (UV)-B and UVA rays can therefore no longer be regarded as sufficient to help prevent skin damage from sunlight, and products containing filters that can provide broad-spectrum photoprotection are required. To meet this need, a new sunscreen formulation that provides photoprotection against solar radiation with wavelengths ranging from UV to visible light has been developed, using an innovative organic sun filter with unique optical properties: phenylene bis diphenyltriazine (TriAsorB™). This article outlines the development and characteristics of this innovative filter and describes new key results from studies performed to assess the effectiveness and safety of the filter and the new sunscreen product. The studies conducted so far demonstrate that the filter has a good human and environmental safety profile. In addition, the sunscreen, which contains TriAsorB in combination with three other UV filters to offer broad-spectrum sun protection with a high sun protection factor (SPF50⁺ ), appears to effectively prevent multiple forms of cellular photodamage, in particular blue light-induced oxidatively generated DNA lesions. Overall, the available data indicate that regular use of the TriAsorB-containing sunscreen could help prevent solar radiation-induced skin damage and the development of signs of premature skin aging, as well as photodermatoses caused or exacerbated by visible light.

Activités immunomodulatrice, anti-inflammatoire, antiprurigineuse et tolérogénique induites par I-modulia ® , un extrait issu de culture d’ Aquaphilus dolomiae , dans les modèles pharmacologiques de dermatite atopique

Atopic dermatitis (AD) is an inflammatory and pruritic dermatosis of multifactorial origin. Topical steroids are the first line treatment for severe AD however alternatives treatment are increasingly needed. A biological concentrate was elaborated from culture of an Avène aquatic microflora isolate namely Aquaphilus dolomiae. Numerous extracts were evaluated in relevant AD in vitro models with human keratinocytes. Among these extracts, a particular one I-modulia^® was found to be remarkable in terms of pharmacological activities: innate immunity modulating by agonizing Toll like receptor (TLR)2, TLR4 and TLR5, induction of anti-microbial peptides, inhibition of cytokines characteristics of T helper (Th)1, Th2 and Th17 responses, inhibition of Protease-activated-receptor (PAR) 2 and Thymic-stromal-lymphopoeitin (TSLP) both being known to be upregulated in pruritus. Additionally, when human dendritic cells (DC) were stimulated in vitro by Staphylococcus aureus secretomes from AD children lesions, I-modulia^® was capable to induce IL-10 secretion to activate regular T lymphocytes and rendered DC tolerogenic. I-modulia^®, extract of biotech origin incorporated in emollient, displays anti-inflammatory, anti-pruritus activities, restores homeostasis immune and ameliorates AD in young infant.

Stabilization of microtubules restores barrier function after cytokine-induced defects in reconstructed human epidermis

BACKGROUND

A variety of human skin disorders is characterized by defects in the epidermal barrier, leading to dehydration, itchiness, and rashes. Previously published literature suggests that microtubule stabilization at the cortex of differentiating keratinocytes is necessary for the formation of the epidermal barrier.

OBJECTIVES

We tested whether stabilization of microtubules with paclitaxel or epothilone B can repair barrier defects that were experimentally induced in three-dimensional culture models of epidermis.

METHODS

We established two models of defective epidermis in vitro, using three-dimensional cultures of primary human keratinocytes on filter supports: immature reconstructed human epidermis (RHE), and RHE that was compromised by treatment with inflammatory cytokines, the latter mimicking defects seen in atopic dermatitis.

RESULTS

Both paclitaxel and epothilone B promoted keratinocyte differentiation, accumulation of junctional proteins at the cell cortex, and the early appearance of lamellar bodies in immature RHE, whereas destabilization of microtubules by nocodazole had the reverse effect. Moreover, stabilization of microtubules rescued the barrier after cytokine treatment. The rescued barrier function correlated with the restoration of filaggrin and loricrin protein levels, the cortical accumulation of junctional proteins (E-cadherin, β-catenin, and claudin-1), and with the secretion of lamellar bodies.

CONCLUSIONS

Our data suggest that the microtubule network is important for the formation of the epidermis, and that stabilization of microtubules promotes barrier formation. Microtubule stabilization may support regeneration of damaged skin, by restoring or improving the barrier.

Visualization of dendritic cells' responses in atopic dermatitis: Preventing effect of emollient

Atopic dermatitis (AD) is a chronic and multifactorial inflammatory skin disease involving various dendritic cells such as epidermal Langerhans cells (LC) and inflammatory dendritic epidermal cells (IDECs). Most of the clinical studies was performed on isolated cells, and thus, it would be useful to characterize directly on the human epidermal tissue the first cellular events occurred during the AD. The suction blister method was used to obtain whole epidermis samples and interstitial cutaneous fluids. Employing multiphoton microscopy, we analyzed the early dynamic behavior of inflammatory cells using Dermatophagoides pteronyssinus atopy patch test (Derp-APT) and evaluated the effects of emollient pre-application. Derp-APT application provoked rapid and strong infiltration of IDECs, and proliferation and activation of LC in the AD subjects' epidermis. Moreover, emollient pre-application strengthened the defective skin barrier and had positive effects on inflammatory cells' behavior, characterized by the complete inhibition of IDEC influx and the presence of immature LC.

Aquaphilus dolomiae extract counteracts the effects of cutaneous S. aureus secretome isolated from atopic children on CD4+ T cell activation

CONTEXT

Skin microbiota takes part in the control of cutaneous inflammation. In skin diseases such as atopic dermatitis (AD) cutaneous dysbiosis and the emergence of Staphylococcus aureus contribute to the pathophysiology of the disease. New therapeutic approaches consist in topical application of natural products able to counteract S. aureus effects through activation of resident immune cells producing anti-inflammatory cytokines such as IL-10.

OBJECTIVE

This study investigates the potential immunosuppressive properties of Aquaphilus dolomiae (Neisseriaceae), a flagellated bacterium contained in Avène Thermal Spring Water used in hydrotherapy treatments of AD patients.

MATERIALS AND METHODS

An aqueous protein extract of Aquaphilus dolomiae (ADE, 60 μg/mL) was added to human monocyte-derived dendritic cells (moDC) for 24 h. Expression of HLA-DR, CD86 and CD83 was evaluated by flow cytometry and released cytokines (IL-10, IL-12) by cytometry bead array assay. The proliferation of allogeneic CFSE-labelled CD4⁺T cells stimulated with ADE-conditioned moDC and S. aureus secretome was analysed by flow cytometry.

RESULTS

MoDC exposed to ADE expressed lower levels of HLA-DR and CD86 than untreated cells, no CD83 and secreted barely detectable IL-12 but high amounts of IL-10 (N = 12, p < 0.0002). The proliferative effect of S. aureus secretome on CD4⁺T cells was reduced (p < 0.001) in the presence of ADE-moDC.

CONCLUSION

ADE counteracted the mitogenic effect of a S. aureus secretome on CD4⁺T cells. Owing to the role of S. aureus colonization in driving inflammation in AD the immunosuppressive property of the ADE might be useful to reduce disease severity.

Effects of a New Emollient-Based Treatment on Skin Microflora Balance and Barrier Function in Children with Mild Atopic Dermatitis

BACKGROUND/OBJECTIVES

The use of emollients is widely recommended for the management of atopic dermatitis (AD), especially between flares. An imbalance of skin microflora is suspected of playing a key role in exacerbations of AD. Our aim was to evaluate the effect of a new emollient balm on clinical parameters (SCORing Atopic Dermatitis [SCORAD], xerosis, pruritus), skin barrier function (transepidermal water loss and loricrin, filaggrin, corneodesmosin, and involucrin expression], skin microflora biodiversity, and Staphylococcus aureus and Staphylococcus epidermidis balance in children with mild AD.

METHODS

Fifty-four children (1-4 yrs old) were enrolled in this randomized, controlled study. Subjects applied a hygiene product and the emollient balm (emollient group, n = 28) or the hygiene product only (control group, n = 26) twice a day for 28 days.

RESULTS

We found improvement in favor of the emollient group in SCORAD (p < 0.001), pruritus (p = 0.06), and xerosis (p = 0.06) after 28 days of application. Moreover, transepidermal water loss decreased in the emollient group by 34% (p = 0.06) and involucrin expression by 37% (p = 0.001) at day 28 from baseline in association with improvement in barrier function, whereas other barrier-specific proteins did not vary. S. aureus increased significantly in the control group only (6.5 times, p = 0.01), whereas S. epidermidis remained stable in both groups. The Shannon index (H' = 2.3) did not vary with treatment in either group.

CONCLUSION

Twice-daily application of a new emollient balm in children with mild AD protected the skin from S. aureus proliferation and preserved microflora biodiversity.

Skin absorption and metabolism of a new vitamin E prodrug, δ-tocopherol-glucoside: in vitro evaluation in human skin models

The aim of this study was to investigate the cutaneous penetration and metabolism of the new vitamin E prodrug delta-tocopherol glucoside (delta-TG), as compared to those of common vitamin E acetate, in vitro, both in reconstituted human epidermis and in viable human skin. Better diffusion was observed with alpha-tocopherol acetate (alpha-TAc) than with delta-tocopherol glucoside in both skin models, at 0.1% and 0.05% in a myritol solution; however, no metabolism was detected with alpha-tocopherol acetate. In all conditions tested (two skin models, two concentrations, three test times, and compartmental analysis) the delta-tocopherol glucoside was metabolized into free tocopherol. In the reconstituted human epidermis, after 18 h, over 90% of the delta-tocopherol glucoside was bioconverted. In the viable human skin, the extent of metabolism was about 20%, with 0.12 and 0.10 microg/cm2 of delta-tocopherol glucoside in the stratum corneum and epidermis, respectively. After topical application, the delta-tocopherol glucoside had a considerable reservoir effect, associated with gradual delivery of free tocopherol. The use of this gluco-conjugated vitamin E at a low concentration shows the capability of the skin to metabolize the prodrug in a slow and prolonged manner, making this gluco-conjugated vitamin E an excellent candidate for continuous reinforcement of antioxidants in the skin.

Human epidermis is a novel site of phospholipase B expression

Phospholipase B (PLB) is an enzyme that displays both phospholipase A(2) and lysophospholipase activities. Analysis of human epidermis homogenates indicated the presence of a 97 kDa PLB protein, as well as a phospholipase A(2) activity, both being enriched in the soluble fraction. Immunolabelling and in situ hybridization experiments showed that this enzyme is expressed in the different layers of epidermis with an accumulation at the dermo-epidermis junction. RT-PCR data indicated that PLB is specifically expressed in natural and reconstructed epidermis. By 3'-RACE-PCR and screening of human genome databases, we obtained a 3600 bp cDNA coding for human PLB highly homologous to already described intestinal brush border PLBs. These data led us to conclude that the soluble PLB corresponds to a proteolytic cleavage of the membrane anchored protein. Altogether, our results provide the first characterization of human PLB which should play an important role in epidermal barrier function.

Variability of enzyme markers during clinical regression of atopic dermatitis

Skin surface enzyme activities were found to be significantly different in healthy and in skin with atopic dermatitis and, following appropriate treatment, a close correlation was observed between the clinical staging of the atopic dermatitis and the levels of the assayed marker enzymes. Samples were taken, by stripping with simple adhesive tapes, from a group of subjects on cure in a spa. The corneocytes were recovered from the first layers of the stratum corneum. Aqueous extracts of the strips were tested for their activity on chromophoric substrates which allow fluorescence spectrometry to be used to assay the trypsin-like, acid-phosphatase-like and phospholipase-A2-like activities. We show that the restoration of return to activities close to those of healthy subjects is related to the general condition of the patients, who showed a clearly improved SCORAD. Recovery of the trypsin-like activity and attenuation of the phospholipase-like activity, paralleled the regression of the dermatitis as assessed by a decrease in clinically evaluated parameters of xerosis and inflammation.