Soybean extract showed modulation of retinoic acid-related gene expression of skin and photo-protective effects in keratinocytes

Synopsis Soy extracts are well known as medicinal and nutritional ingredients, and exhibit benefits towards human skin including depigmenting or anti‐ageing effects. Despite the wrinkle decreasing effects of retinoids on skin as an anti‐ageing ingredient, retinoid application can causes photo‐sensitive responses such as skin irritation. Thus, their daytime usage is not recommended. The aim of this study is the investigation into the activities of soybean extract as an anti‐ageing ingredient and their comparison to retinoids in this respect. Soybean extract decreased the relative ratio of MMP‐1/TIMP‐1 mRNA to the same degree as retinoic acid in normal human fibroblasts. It also affected mRNA levels of HAS2 and CRABP2 in normal human keratinocytes. Furthermore, we investigated its effect on mRNA expression of histidase, an enzyme that converts histidine into urocanic acid, the main UV light absorption factor of the stratum corneum. Unlike the complete inhibition of histidase exhibited by the mRNA expression of retinoic acid, the effect of soybean extract on histidase gene expression was weaker in normal human keratinocytes. Also, soybean extract pretreatment inhibited UVB‐induced cyclobutane pyrimidine dimer formation dose‐dependently in normal human keratinocytes. In this study, we found that soybean extract modulated retinoic acid‐related genes and showed photo‐protective effects. Our findings suggest that soybean extract could be an anti‐ageing ingredient that can be safely used under the sunlight. Résumé Les extraits de soja sont bien connus comme ingrédients médicinaux et nutritionnels, et possèdentdes activités sur la peau humaine, y compris des effets dépigmentants ou anti‐vieillissement. En dépit des effets anti‐rides des rétinoïdes, leur application peut provoquer des réponses photo‐sensibles tels que les irritations de la peau. Ainsi, leur utilisation quotidienne n'est pasrecommandée. Le but de cette étude est l'évaluationdes activités de l'extrait de soja en tant qu'ingrédient anti‐âge, et sa comparaison aux rétinoïdes à cet égard. L'extrait de sojadiminue la proportion relative des ARNm MMP‐1/TIMP‐1 au même degré que l'acide rétinoïque dansdes fibroblastes humains normaux. Il affecte également les niveaux d'ARNm de HAS2 et CRABP2 dans leskératinocytes humains. En outre, nous avons étudié son effet sur l'expression de l'ARNm dehistidase, une enzyme qui convertit l'histidine en acide urocanique, le principalfacteur d'absorption de la lumière UV de