Effect of Ultraviolet Radiation and Benzo[a]pyrene Co-Exposure on Skin Biology: Autophagy as a Potential Target.

The skin is the outermost protective barrier of the human body. Its role is to protect against different physical, chemical, biological and environmental stressors. The vast majority of studies have focused on investigating the effects of single environmental stressors on skin homeostasis and the induction of several skin disorders, such as cancer or ageing. On the other hand, much fewer studies have explored the consequences of the co-exposure of skin cells to two or more stressors simultaneously, which is much more realistic. In the present study, we investigated, using mass-spectrometry-based proteomic analysis, the dysregulated biological functions in skin explants after their co-exposure to ultraviolet radiation (UV) and benzo[a]pyrene (BaP). We observed that several biological processes were dysregulated, among which autophagy appeared to be significantly downregulated. Furthermore, immunohistochemistry analysis was carried out to validate the downregulation of the autophagy process further. Altogether, the output of this study provides an insight into the biological responses of skin to combined exposure to UV + BaP and highlights autophagy as a potential target that might be considered in the future as a novel candidate for pharmacological intervention under such stress conditions.

A Harungana madagascariensis extract with retinol-like properties: Gene upregulations and protein expressions in human fibroblasts and skin explants.

OBJECTIVE: Because they limit, even reverse, age-induced skin alterations, retinoids became a staple in cosmetology. However, their use can result in undesired secondary effects and there is a demand for natural sources of compounds with retinoid-like effects. A preliminary screening identified a Harungana madagascariensis plant extract (HME) as possibly inducing genes stimulated by retinol. We analysed its effect on gene and protein expression, comparing it to retinoids. METHODS: Gene expression was analysed by real-time qPCR on RNA from isolated fibroblasts subjected to retinol or the plant extract for 6, 48 or 96 h. Skin markers were quantified in fibroblasts cultured with retinol or extract containing medium, and UV-aged skin explants subjected to topical applications of creams containing retinol, retinaldehyde or HME. RESULTS: Real-time qPCR shows that the extract induced all RARs and RXRs, even RXRγ that was not induced by retinol. Eighty-eight per cent of the 25 early retinoid reaction genes induced by a concentration of retinol are induced by the extract. In fibroblasts, only the extract increased collagen III labelling, while collagen I and fibronectin labelling are increased by retinol and the extract, with higher levels for the extract. When topically applied to UV-aged skin explants, only the cream containing the HME led to increased labelling of CRABP1 in the epidermis. CRABP2 and Ki67 are induced by all three creams and no effect was detected on RXRs. In the dermisthe extract containing cream increased CRABP2, total collagen, procollagen I and collagen I while creams with retinol or retinaldehyde only affected some of these proteins. CONCLUSIONS: The HME induces an overall retinol-like gene induction profile in isolated fibroblasts and retinoid-like stimulation of protein synthesis in both isolated fibroblasts and photoaged skin explants.

OBJECTIFS: Limitant, voire inversant les altérations cutanées induites par l'âge, les rétinoïdes sont devenus incontournables en cosmétologie. Cependant, leur application topique peut entraîner des effets secondaires indésirables et il existe une demande pour des composés naturels ayant des effets similaires à ceux des rétinoïdes. Un screening préliminaire nous avait permis d'identifier un extrait de la plante Harungana madagascariensis (HME) comme pouvant induire des gènes stimulés par le rétinol. Nous avons donc analysé son effet sur l'expression de gènes et de protéines induits par les rétinoïdes et comparé les résultats à ceux obtenus en présence de rétinoïdes. MÉTHODES: L'expression de gènes a été analysée par qPCR en temps réel réalisée sur l'ARN de fibroblastes isolés soumis au rétinol ou à l'extrait végétal pendant 6, 48 ou 96 heures. Différentes protéines cutanées ont été quantifiés dans des fibroblastes cultivés en présence de rétinol ou d'un milieu contenant l'extrait. Des quantifications ont également été faites sur des explants de peau vieillie par les UV et soumis à des applications topiques de crèmes contenant du rétinol, du rétinaldéhyde ou le HME. RESULTATS: La qPCR en temps réel montre que l'extrait induit tous les gènes RARs et RXRs, même RXRγ qui n'était pas induit par le rétinol. Quatre-vingt-huit pour cent des 25 gènes impliqués dans la réaction précoce aux rétinoïdes induits par une concentration de rétinol ont été induits par l'extrait. Dans les fibroblastes, seul l'extrait a augmenté le marquage du collagène III, tandis que le marquage du collagène I et de la fibronectine a été augmenté par le rétinol et l'extrait, avec des niveaux plus élevés pour l'extrait. En application topique sur des explants de peau vieillie par les UV, seule la crème contenant le HME a entraîné une augmentation du marquage de CRABP1 dans l'épiderme. CRABP2 et Ki67 ont été induits par les trois crèmes et aucun effet n'a été détecté sur les RXRs. Dans le derme, la crème contenant l'extrait a augmenté CRABP2, le collagène total, le procollagène I et le collagène I, tandis que les crèmes contenant du rétinol ou du rétinaldéhyde n'ont affecté que certaines de ces protéines. CONCLUSIONS: Chez les fibroblastes isolés, le HME induit un profil d'induction génique globalement similaire à celui du rétinol. Chez les fibroblastes isolés et des explants de peau photo-vieillie, il entraine une stimulation de la synthèse protéique similaire à celle des rétinoïdes.

Influence of the environmental relative humidity on the inflammatory response of skin model after exposure to various environmental pollutants.

The skin is an essential barrier, protecting the body against the environment and its numerous pollutants. Several environmental pollutants are known to affect the skin, inducing premature aging through mechanisms including oxidative stress, inflammation, and impairment of skin functions. Even climate conditions can impact the skin. Therefore, using a Reconstructed Human Epidermis (RHE), we tested the effect of two samples of fine particulate matters (PM0.3-2.5 - one metals-rich sample and the other organic compounds-rich), two Volatile Organic Compounds mixtures (VOCs - from a solvent-based paint and a water-based paint) and Tobacco Smoke (TS). All pollutants affected cellular functionality, but to a lesser extent for the water-based paint VOC. This effect was enhanced when RHE were preconditioned for 2 h by a semi-dry airflow (45% relative humidity) before pollutants application, compared to preconditioning by a humid airflow (90% relative humidity). In the absence of preconditioning, IL-1α, IL-6, IL-8, and RANTES were almost systematically induced by pollutants. When RHE were preconditioned by a semi-dry or humid airflow before being subjected to pollutants, the increase of IL-1α, IL-8, and RANTES falls into two groups. Similarly to RHE not treated with pollutants, RHE treated with VOCs after preconditioning by a semi-dry airflow showed increased IL-1α, IL-8, and RANTES release. On the contrary, RHE treated with PM or TS after preconditioning by a semi-dry airflow show a lower increase in IL-1α, IL-8, and RANTES compared to preconditioning by a humid airflow. The effect of real environmental relative humidity conditions of the air, combined with acute exposure to various environmental pollutants, seemed to relate mainly to structural changes of the skin, determining the outcome of the inflammatory response depending on the physicochemical characteristics of pollutants.

Human skin responses to environmental pollutants: A review of current scientific models.

Whatever the exposure route, chemical, physical and biological pollutants modify the whole organism response, leading to nerve, cardiac, respiratory, reproductive, and skin system pathologies. Skin acts as a barrier for preventing pollutant modifications. This review aims to present the available scientific models, which help investigate the impact of pollution on the skin. The research question was "Which experimental models illustrate the impact of pollution on the skin in humans?" The review covered a period of 10 years following a PECO statement on in vitro, ex vivo, in vivo and in silico models. Of 582 retrieved articles, 118 articles were eligible. In oral and inhalation routes, dermal exposure had an important impact at both local and systemic levels. Healthy skin models included primary cells, cell lines, co-cultures, reconstructed human epidermis, and skin explants. In silico models estimated skin exposure and permeability. All pollutants affected the skin by altering elasticity, thickness, the structure of epidermal barrier strength, and dermal extracellular integrity. Some specific models concerned wound healing or the skin aging process. Underlying mechanisms were an exacerbated inflammatory skin reaction with the modulation of several cytokines and oxidative stress responses, ending with apoptosis. Pathological skin models revealed the consequences of environmental pollutants on psoriasis, atopic dermatitis, and tumour development. Finally, scientific models were used for evaluating the safety and efficacy of potential skin formulations in preventing the skin aging process or skin irritation after repeated contact. The review gives an overview of scientific skin models used to assess the effects of pollutants. Chemical and physical pollutants were mainly represented while biological contaminants were little studied. In future developments, cell hypoxia and microbiota models may be considered as more representative of clinical situations. Models considering humidity and temperature variations may reflect the impact of these changes.

An in vitro model to evaluate the impact of environmental fine particles (PM0.3-2.5) on skin damage.

Exposure to airborne particulate matter (PM) has significant effects on human health mainly leading to cardio-respiratory diseases. However very few data are available regarding the impact of PM on the skin, so to better understand the impact of fine particle (PM0.3-2.5) on both inflammatory response and epidermal structure, we exposed a reconstructed human epidermis (RHE) to several doses of PM collected in Cotonou (Benin, West Africa). After 24 h of exposure, inflammatory response, histological observations, and gene expression related to oxidative stress, antioxidant defense and structural damages were determined. No PM-linked changes in tissue morphology or membrane integrity were observable. PM was however cytotoxic in a dose dependent manner. An inflammatory response appeared as shown by the increase in IL-1α and IL-8 cytokine productions. PM also induced oxidative stress, leading to an increase in 4-HNE immunostaining and to the up-regulation of HMOX1, MT1G and MT1E. Finally, PM had a negative impact on fundamental skin functions such as tissue anchorage, cell differentiation, cornification / skin desquamation and apoptosis. Our data show that airborne fine particles have an adverse effect on skin integrity, most probably leading to accelerated ageing.

In vitro model adapted to the study of skin ageing induced by air pollution.

More than a barrier against environmental agents, skin reflects individual health and is a visible sign of ageing with the progressive loss of skin integrity. In order to evaluate the consequences of an environmental complex mixture, with tobacco smoke (TS) as model, on cellular and morphological changes, a 3D skin model was used. Morphologically, tissue integrity was intact after one TS-exposure while the superficial layers were drastically reduced after two TS-exposures. However, TS modified epidermal organisation at the molecular level after just one exposure. A decrease in loricrin protein staining was showed in the epidermis, while production of inflammatory cytokines (IL-8, IL-1α, IL-18) and metalloproteinase (MMP-1, MMP-3) were stimulated. Oxidative stress was also illustrated with an increase in 4-HNE protein staining. Moreover, terminal differentiation, cell-cell junction and anchorage gene expression was down-regulated in our model after one TS-exposure. In conclusion, tobacco smoke impacted the fundamental functions of skin, namely tissue anchorage, cornification and skin desquamation. Oxidative stress resulted in skin ageing. The tissue was even reactive with the inflammatory pathways, after one TS-exposure. The 3D-RHE model is appropriate for evaluating the impact of environmental pollutants on skin ageing.