Alteration to the Skin Ceramide Profile Following Broad-Spectrum UV Exposure

The epidermal stratum corneum (SC) lipid matrix, principally consisting of an equimolar ratio of ceramides, free fatty acids, and cholesterol, plays a crucial role in maintaining proper skin barrier function. Conditions which impair barrier integrity, such as in atopic dermatitis, correlate with the alternation of key ceramide subclasses and reduced chain length of acyl moieties. However, there is limited knowledge about the impact of unprotected repeat sun exposure on the skin lipid composition, especially ceramide profiles. This study investigated the effects of ultraviolet (UV) radiation on the ceramide profile using both an ex vivo skin and a clinical model. Lipidomic analysis of UV-exposed skin showed shifts to the composition of ceramide subclasses essential in repairing and strengthening the SC barrier (including CER1[E0S], CER3[NPI, and CER6[AP1) and reduced very long -chain acyl moieties. Gene expression analysis and immunohistochemical staining of key enzymes (aSMase, DES1, CerS5, CerS3) suggested that lipid alterations can be attributed to changes within the ceramide biosynthesis process. Topical application of ceramide-containing suncare products help maintain SC-essential ceramide subclasses and proper ceramide chain length, demonstrating the importance of proper photoprotection to maintain healthy skin barrier and ceramide quality during daily sun exposure.