Effects on skin of Stichopus japonicus viscera extracts detected with saponin including Holothurin A: Down-regulation of melanin synthesis and up-regulation of neocollagenesis mediated by ERK signaling pathway.

ETHNOPHARMACOLOGICAL RELEVANCE: Stichopus japonicus (sea cucumber), edible traditional food in Asia, and its extracts are renowned for their wound healing, pain relieving, and cosmetic effects in traditional medicine. Holothurins, toxins isolated from sea cucumber, are thought to be active components for their beneficial effects. However, researchers have yet to outline specific mechanisms thereof.

AIM OF THE STUDY: The present study was designed to evaluate the anti-melanogenic and anti-wrinkle properties of S. japonicus viscera extracts (VF) on the skin via in vitro and ex vivo experiments and to assess the anti-aging effects of S. japonicus viscera extracts in relation to known wound healing and cosmetic processes.

MATERIALS AND METHODS: The viscera of live S. japonicus specimens were freeze dried and ground into a powder. Aqueous extracts were subsequently prepared from the concentrated powder using a water extraction method. To investigate the inhibitory effects of VF on melanogenesis, mushroom tyrosinase activity assay and melanin assay were performed on Melan-A cells. To further delineate the anti-melanogenic properties of VF, western blot analysis for tyrosinase, TRP-1, TRP-2, MITF, and ERK was conducted. Changes in collagen synthesis in human dermal fibroblast (HDF) were evaluated via CCK-8 assay and immunocytochemistry to determine the anti-wrinkle effects of VF. Finally, anti-aging properties were examined in a human skin equivalent ex vivo model.

RESULTS: In Melan-A cells, VF treatment reduced melanin contents in a concentration-dependent manner. The anti-melanogenic effects of VF appeared to be due to enzymatic inhibition of tyrosinase. In CCK-8 assay, VF also significantly increased the viability of HDFs in a concentration-dependent manner. Immunoblot analysis revealed phosphorylation of ERK in HDFs treated with VF. In a human skin equivalent ex vivo model (Neoderm®-ED), VF treatment at a concentration of 50 μg/ml enhanced collagen type IV and Ki-67 expression and downregulated MMP-9 expression.

CONCLUSION: This study demonstrated that aqueous extracts from S. japonicus viscera are effective whitening and anti-aging agents that stimulate ERK signaling to inhibit melanin synthesis and promote collagen synthesis.