Increasing effect of ceramides in skin by topical application of sphingosine

Introduction and objective : Ceramidase metabolizes ceramide and generates sphingoid and fatty acid. Alkaline ceramidase has been involved in reduction of the ceramide level in atopic dermatitis or in aged dry skin. We hypothesized that the ceramide content can be increased by inhibition of the ceramidase activity. In this study, we aimed to examine the effect of alkaline ceramidase inhibitor on the amount of the ceramide in mice skin and in three-dimensional cultured epidermis model. Material and methods : 4-Nitrobenzo-2-oxa-1,3-diazole-labeled ceramide was used as a substrate and was incubated with skin homogenate at 37?C for 1 or 10 h. Fluorescent-labeled fatty acid, enzymatic reaction product was detected by fluorescence high performance liquid chromatography to determine the alkaline ceramidase activity. The ceramide content was quantitatively analyzed by high performance thin layer chromatography. Results : 50% Inhibitory concentration of sphingosine for alkaline ceramidase in mice skin and three-dimensional cultured epidermis model was >70-fold lower than the corresponding oleoylethanolamide. Ceramide [AS] and ceramide [AP] contents of sphingosine-applied group of mice stratum corneum were significantly higher than in the normal group. Compared with the normal group, ceramide [NDS] in three-dimensional cultured epidermis model was also significantly increased in sphingosine-applied group. Conclusion : This study demonstrated that sphingosine inhibited alkaline ceramidase in mice skin and three-dimensional cultured epidermis model and ceramide contents was increased by application of sphingosine. These results suggest that sphingosine was beneficial compound to increase skin ceramide, though sphingosine may also be affected by another pathway.OAT （Open Access Text）. open-access articl