Applied Cosmetic Science and Technology Applied Cosmetic Science and Technology

The relationship between mental stress and skin disorders is well known, with cortisol as a contributing factor. Cortisol, a hormone vital for maintaining bodily homeostasis, may have different effects on the skin depending on whether its levels are temporarily elevated due to circadian rhythms or transient stress, or continuously elevated due to chronic stress. To understand the link between mental stress and skin disorders, it is crucial to assess the impact of cortisol on the skin under various stress states. However, it remains unclear whether the skin damage from chronic stress is driven by sustained high cortisol levels or by frequent fluctuations in cortisol. This study investigated the effect of cortisol on the ability of normal human epidermal keratinocytes to form tight junctions by varying cortisol exposure frequency. The results showed that transepithelial electrical resistance and claudin expression were reduced in cells continuously treated with cortisol, compared to those transiently treated with cortisol before differentiation induction. This difference was attributed to variations in the messenger RNA expression levels of 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1), which converts inactive cortisone to active cortisol, and 11β-HSD2, which converts cortisol to cortisone between the 2 cell types, suggesting that the adverse effects of cortisol may be amplified in cells continuously exposed to cortisol due to increased expression of 11β-HSD1. Furthermore, we also established for the first time that Ganoderma lucidum (reishi mushroom) extract acts as an inhibitor of cortisone-to-cortisol metabolism, and alongside its component ganoderic acid A, mitigates the negative effects of continuous cortisol treatment on tight junction formation. Therefore, G. lucidum extract is anticipated to improve the decline in skin barrier function associated with chronic stress.