Background: Skin is exposed to ultraviolet radiation (UV) and air pollution and recent works demonstrated these factors have additive effects in the disturbance of skin homeostasis. Nuclear factor erythroid 2-related factor 2 (Nrf2) and aryl hydrocarbon receptor (AHR) appears appropriate targets in the management of combined environmental stressors. The protective effects of Silymarin (SM), an antioxidant and anti-inflammatory complex of flavonoids, were evaluated. Methods: Reactive oxygen species (ROS) and interleukin 1-alpha (IL-1a) were quantified in UV+urban dust stressed reconstructed human epidermis (RHE) treated with SM. Gene expression study was conducted on targets related to AHR and Nrf2. SM agonistic activity on cannabinoid receptor type 2 (CB2R) was evaluated on mast cells. Clinical study quantified the performance of SM and cannabidiol (CBD), in skin exposed to solar radiation and air pollution. Results: SM decreased morphological alterations, ROS and IL-1a in UV+urban dust stressed RHE. AHR and Nrf2 related genes were upregulated that control antioxidant effector and barrier function. Interleukin 8 gene expression was decreased. Clinical study confirmed SM to improve homogeneity and perceived well-being of urban skins exposed to UV, outperforming CBD. SM activated CB2R and release of β-endorphin from mast cells. Conclusions: SM provides protection of skin from oxidative stress and inflammation caused by two major factors of exposome and appears mediated by AHR-Nrf2. SM activation of CB2R opens a new understanding of SM anti-inflammatory properties.

Stretch marks are far from being exclusively appearing on pregnant women and appear whenever the body experience a rapid growth. Into the dermis, collagen fibres are altered associated with a loss of orientation and the elastic network is disrupted leading to a fibrotic organisation. This results to epidermal tearing which produce skin lesions. Centella asiatica is a well-known medicinal plants rich in triterpenic actives molecules and traditionally used to treat wounds and help skin repair. The aim of this study was to evaluate Centella asiatica extract as a natural way to solve stretch marks concern and understand its mechanism of action. We have first evaluated the fibroblast’s proliferation based on scratch assay model and their genes expression by RT-qPCR. At the ex vivo level, elastin fibres were quantified by immunofluorescence. Collagen fibre’s orientation and their occupation of the dermis were analysed after Sirius red staining and specific software analysis. We have proven that Centella asiatica has stimulated fibroblasts proliferation, reduced extracellular matrix degradation and fibrosis. On stretch marked skin explant, Centella asiatica increased the occupation of collagen fibres and elastin production. Based on the mechanisms behind the formation of stretch marks, Centella asiatica restores dermis network by optimising fibres organisation for a visible skin remodelling effect.

Background: Hyaluronic acid (HA) is well known in the cosmetic industry for its hydrating properties linked to its interaction with keratin in the stratum corneum. Hair is also mainly composed of keratin, but no evidence of penetration and interaction of HA in hair had yet been established. Herein, we examined, with appropriate methods, this penetration and interaction. Methods: Confocal Raman Spectroscopy was used to track HA penetration in hair fibers. Human hair was UV-irradiated, or not, before washing with a number of different shampoo formulations. Low-molecular weight hyaluronic acid, high-molecular weight HA, and an optimized blend of low- and high-molecular weight HA, were used. The benefits of HA for cosmetic application were then evaluated at the ex vivo level. Results: Raman analysis of non-irradiated samples revealed that the HA blend penetrated the hair cortex 5.9 times more than the placebo and with irradiated samples, a 1.8-fold increase in penetration was observed. Whatever the irradiation status, penetration of this optimal HA blend was significantly greater than that of the other two active substances. Compared to the placebo, the HA blend significantly decreased spontaneous frizzing by 11%, repaired the hair by increasing the elastic modulus and the break force, and increased the water content in the hair shafts. Conclusion: Confocal Raman Spectroscopy can be considered as a powerful, non-invasive technique to investigate the penetration of active ingredients into the hair.