The effect of natural ceramide whose main component is galactosylceramide, on skin barrier function

Tami Igarashi (Rosette Co., Ltd.), Masamitsu Ichihashi (Doshisha University), Masayuki Yagi (Rosette Co., Ltd.)

Sphingolipids play an essential role in the maintenance and formation of the skin barrier function and water-retention. Horse-derived ceramide (HC), whose main component is galactosylceramide, increased ceramide levels and decreased trans-epidermal water loss (TEWL) in human epidermal cultured skin models. HC also changed the mRNA expression level of ceramide metabolism–related genes in human keratinocytes.

1. Introduction
Sphingolipids like ceramides and glycosphingolipids are known to play an essential role in the moisturizing function and barrier function of the epidermis. HC, whose main component is galactosylceramide, has been shown to be effective for improving the skin condition and moisture in clinical trials targeting atopic dermatitis patients using compound fomulations [1]. However, few studies have examined the mechanisms of action involved. Therefore, we examined the effect of HC on epidermal barrier function and its mechanism in normal human epidermal keratinocytes (NHEKs) and reconstructed human epidermis equivalents (RHEEs).

2. Materials and Methods
NHEKs were cultured for 48 hours with or without HC, and mRNA levels were measured at the end of treatment. RHEEs were then cultured with or without HC. And the barrier function was evaluated by measuring TEWL, and ceramide levels were measured using high-performance thin-layer chromatography.

3. Results and Discussion
HC treatment significantly increased the mRNA expression of β-glucocerebrosidase, sphingomyelinase, sphingomyelin synthase-2, ceramide synthase-3, dihydroceramide desaturase-1, transglutaminase, and profilaggrin in NHEKs. Additionally, application of HC in RHEEs significantly improved TEWL and increased ceramide levels. These results suggest that the application of HC to the skin may contribute to improving skin moisture and barrier function by increasing ceramides and natural moisturizing factor (NMF) , and enhancing the structure of cornified envelopes.

4. References
[1] Bito, T., et al., Skin Research 3, 236-242 (2004)