Oleic acid-induced interleukin-36γ: A possible link between facial skin redness and sebum.

BACKGROUND: Redness of the facial skin is an important cosmetic concern. Although qualitative and quantitative modifications of sebum on the skin surface are major pathogenic factors of chronic inflammatory skin conditions, the relationship between skin redness, sebum, and mild inflammation on the cheeks of healthy subjects remains elusive. AIMS: We aimed to explore the correlation between cheek redness and sebum and inflammatory cytokines in the stratum corneum (SC) of healthy subjects. We also examined the effects of representative sebum lipids on the gene expression of inflammatory cytokines in cultured keratinocytes. PATIENTS/METHODS: This study included 198 healthy participants. Skin sebum was analyzed using flow injection analysis, and skin redness was assessed using a spectrophotometer. Inflammatory cytokines in tape-stripped SC were measured using enzyme-linked immunosorbent assay. RESULTS: Cheek redness parameters positively correlated with the amount of skin sebum and the proportion of monounsaturated free fatty acids (C16:1 and C18:1) in the sebum. They also positively correlated with the interleukin (IL)-36γ/IL-37 ratio in the SC. Among the representative sebum lipids examined, oleic acid (C18:1, cis-9) dose- and time-dependently regulated the mRNA expression of IL-36γ and IL-37 in cultured keratinocytes, and this effect was attenuated by the N-methyl-D-aspartate (NMDA)-type glutamate receptor antagonist, MK801. CONCLUSIONS: Skin surface sebum may be related to cheek redness in healthy subjects, and oleic acid-induced IL-36γ through NMDA-type glutamate receptors may be a link between them. Our study provides a possible skincare strategy for mitigating unfavorable increase in skin redness by targeting the facial skin sebum, particularly oleic acid.

Wearable Artificial Fingers With Skin Vibration and Multi-Axis Force Sensors.

Tactile sensations are based on stimulation elicited on the skin through mechanical interactions between the skin and an object. Hence, it is important to consider skin properties as well as objects. In this article, we aim to develop wearable artificial fingers for quantitative evaluations reflecting individual differences in human fingers. In a previous study, a wearable skin vibration sensor was attached to artificial fingers and it was demonstrated that the skin vibrations differed according to the dimension of surface ridge and the artificial finger is useful for roughness evaluation. This article improved the artificial finger to measure the contact force and friction in addition to the skin vibration. A small three-axis force sensor was embedded into the base of the finger, and normal and friction forces were estimated via a multi-regression method. Furthermore, artificial fingers with different hardness were prepared and six different textures were used to investigate tactile evaluation. Experimental results showed that the artificial fingers could measure normal and friction forces along with the skin vibration and were useful to evaluate textures. Resulting distributions of the vibration intensity and friction coefficient were different for the soft and hard artificial fingers, indicating the complex influence of skin properties on tactile sensations.