Altered Levels of Sphingosine and Sphinganine in Psoriatic Epidermis

Background: Ceramides are the main lipid component of the stratum corneum and are a structurally heterogeneous and complex group of sphingolipids of which sphingoid bases are the basic structural constituents. Altered levels of sphingoid bases have been reported in skin conditions that involve dryness and barrier disruption, including atopic dermatitis. Objective: The purpose of this study was to investigate the altered levels of sphingoid bases in psoriatic epidermis and their relationship with the clinical severity of the psoriasis. Methods: Samples from the lesional and non-lesional epidermis were obtained from eight psoriasis patients. Levels of sphingosine and sphinganine were analyzed by high-performance liquid chromatography. The expression of ceramide synthase and ceramidase proteins, which are related to sphingosine and sphinganine metabolism, were measured using Western blot analysis. Results: Levels of sphingosine and sphinganine in the lesional epidermis were significantly higher than those in the non-lesional epidermis. Although there was no altered ceramide synthase and ceramidase, there was a highly significant positive correlation between the % change of ceramidase, the degradative enzyme of ceramide into sphingosine, and the Psoriasis Area Severity Index (PASI) score. Conclusion: The levels of sphingosine and sphinganine were significantly increased in psoriatic epidermis and the % change of ceramidase was positively correlated with the clinical severity of psoriasis.