Impact of cigarette smoke on physical-chemical and molecular proprieties of human skin in an ex vivo model.

BACKGROUND: This is a study about the skin ageing exposome, focusing on the effect of cigarette smoke. Human living skin explants (HSE) were exposed to cigarette smoke (CS) of two cigarettes for 2 hours using a custom-made exposure chamber, the Pollubox® . Effects on the surface physico-chemistry and molecular properties of the skin were analyzed and reported for the first time. BASIC PROCEDURES: To this end, transcriptomic study followed by immunohistochemistry, MDA (Malondialdehyde Dosage), and surface physio-chemistry data: surface free energy determination, TEWL (Trans Epidermal Water Loss), skin pH and FT-IR (Fourier Transform-Infrared) spectroscopy of the explant were collected from untreated and treated HSE. MAIN FINDINGS: Results showed a decrease of the total surface free energy of the treated HSE. This decrease reflected higher interactions with polar compounds from the environment and consequently a decrease of the surface hydrophobicity. Additionally, an increase of TEWL and skin pH was observed after treatment. The transcriptomic analysis showed downregulation of mitochondrial genes (PON2-NDUFA4L2-ATP1A1-ALDH2-PRODH) combined with an increase of MDA in CS-treated HSE. CONCLUSIONS: CS-induced oxidation of lipids at HSE surface alters the skin barrier: interactions with polar products are enhanced and the lipid chain packing at the surface is modified. Consequently, skin permeability could increase which correlated with repression of CA9 and AQP1 genes. Beside activation of AHR-NRF2 pathway in CS-exposed HSE, our results suggested that mitochondrial functions were strongly impacted and oxidized lipids failed to be eliminated promoting skin barrier alteration. A mitophagy activity was suggested through the confirmation of PINK1 accumulation in the epidermis by immunostaining.

Design of a Lipid-Coated Polymeric Material Mimic Human Skin Surface Properties: a Performing Tool to Evaluate Skin Interaction with Topical Products.

An original nonbiological skin model (NBSM) has been developed to mimSic skin surface properties. This skin model presents several improvements when compared to existing ones: it has a topography identical to that of in vivo skin and a lipid composition close to that of the skin face. This imparts to the model surface a physicochemistry similar to in vivo skin. The concept and design of the skin model are presented, followed by an instrumental characterization performed using 3D microscopy, attenuated total reflectance-Fourier transformed infrared spectroscopy, and contact angle measurements. Surface free energy components are calculated for the NBSM using the Van Oss approach and compared to ex vivo experiments performed on human living skin explants. A comparison was made with the commercial skin model VITRO-SKIN, this latter being a reference in terms of the NBSM. The effect of several emollients on skin physicochemistry was investigated in vivo and on both nonbiological models. The study focused on several emollients and oils, including silicones and esters, and three emulsions (oil-in-water or water-in-oil). The results obtained confirm the high reliability of the developed model as it shows a skin-like surface behavior. This very interesting tool shows promising results concerning the study of the residual film present after product application or to study skin/product interactions.

Squalene Oxidation Induced by Urban Pollutants: Impact on Skin Surface Physico-Chemistry.

The effect of urban pollutants on skin properties has been revealed through several epidemiological studies. However, comprehension of involved mechanisms remains undetermined. In addition, the impact of such stressors on skin surface properties, especially skin physico-chemistry, has not been investigated. Consequently, the present study aims to develop a new aging protocol able to highlight the impact of selected urban pollutants on a model sebaceous lipid: the squalene. Its quality has been followed during aging using LC-MS analysis. Results showed that the quality of the control solution containing only squalene remains stable during 45 days, whereas the quality of the solution containing squalene mixed with pollutants appears greatly altered, especially in the presence of heavy metals: a large amount of oxidation compounds was evidenced due to oxidation and dehydrogenation mechanisms. In addition, a physicochemical study was performed using a validated nonbiological skin model able to mimic skin physico-chemistry. Surface free energy components were calculated using contact angle measurements according to the Van Oss model. The application of degraded squalene significantly increased skin hydrophilic and monopolar behavior compared to the application of control squalene. Those modifications are essentially explained by the nature of squalene oxidation products. It must be noted from this study that squalene oxidation due to pollutants or due to high temperature did not lead to the same physicochemical consequences neither to the same oxidation products, as shown by thermal analysis. This study gives original and precious information to explain alterations induced by pollutants on skin surface properties, especially skin chemistry and physico-chemistry.

Skin surface physico-chemistry: Characteristics, methods of measurement, influencing factors and future developments.

Physico-chemical properties such as surface free energy, polarity or hydrophobicity of solid surfaces have been largely studied in literature because they are involved in many physical phenomena: adhesion, friction, wetting … Nowadays, the study of biointerfaces is of great interest for the medical, the pharmaceutical or the cosmetic field but also for material design researches, especially for the development of biomimetic surfaces. The present paper focuses on a particular biointerface, namely skin, which is the most extended organ of the human body. The different ways for the study of skin physico-chemistry are first reviewed, followed by their practical uses, from pharmaceutical to cosmetic science. Those properties depict the ways skin interacts with topical products, its lipid composition but also its hydration state. In addition, this article aims to present recent approaches using original model materials in order to mimic human skin; indeed, in vivo experiments are often limited by the inter and intra individual variability, the safety regulation and above all the time and the cost of such studies. Finally, further data clearly highlight the importance of skin surface properties for dermatological and pharmaceutical researches.

Prediction of residual film perception of cosmetic products using an instrumental method and non-biological surfaces: The example of stickiness after skin application.

Prediction of sensory texture attributes using instrumental measurements is a very important challenge for cosmetic industry because in vivo sensory studies are expensive, time consuming and limited by the safety issue of applied products. The aim of this work is to investigate how residual sensory properties of cosmetic products can be predicted without using a panel of assessors, focusing on the residual film attribute "Stickiness". 10 cosmetic products with different galenics have been selected and evaluated in vivo using a classical sensory protocol, developed according to the Spectrum™ Descriptive Analysis method. In addition to this study, products were evaluated after their application on non-biological skin models in order to compare perceptions onto in vivo skin and artificial surfaces. Results obtained show that in vivo perceptions can be compared with the ones on artificial surfaces meaning that residual film stickiness is similar between in vivo skin and non-biological skin models. An instrumental protocol using a texture analyzer has been set up to evaluate residual film adhesiveness. This protocol has been tested and validated in vivo (r²adjusted = 0.90; RPD = 3.07) before being optimized on a selected non-biological skin model Bioskin® (Beaulax, Co. Ltd. Tokyo, Japan) owning good correlation with in vivo perceptions. Established model shows excellent predictive ability with a r²adjusted of 0.94 and a RPD of 3.38, as highlighted by the 4 steps cross-validation performed. It proves that physical stimulus responsible for cosmetic film stickiness can be instrumentally measured on both in vivo skin and artificial skin.

Organocatalytic atroposelective formal Diels-Alder desymmetrization of N-arylmaleimides.

The atroposelective desymmetrization of N-arylmaleimides was realized by means of a primary amine catalyzed Diels-Alder reaction of enones. The chiral axis as new element of chirality is generated under the remote control of the catalyst that selectively drives the formal Diels-Alder reaction through an exclusive stereochemical outcome.