Skin Care Alters Endogenous Stratum Corneum Ceramide Profile

Atopic dermatitis is characterized by immunological hypersensitivity to allergen substances, as well as clinical symptoms of severe skin inflammation and dryness, with impairments of barrier function and water-holding capacity recognized in the stratum corneum of affected individuals. When stratum corneum functions are impaired, dermatitis symptoms are likely to recur in atopic skin, with strong itching and stinging on the skin reducing quality of life (QOL) of affected individuals. Therefore, the Atopic Dermatitis Treatment Guidelines^*3 recommend daily skin care to reduce skin symptoms and maintain remission by normalization of stratum corneum functions.

The stratum corneum ceramide level is also known to be decreased in non-lesional sites of skin in atopic dermatitis patients,^*4 one of the causes of stratum corneum function decline seen in atopic skin. In addition, the stratum corneum ceramide profile of atopic skin shifts from that of healthy skin.^*5 However, little is known about the relationship between changes in stratum corneum ceramide profile and stratum corneum function in atopic dermatitis.

Thus, the influence of changes in stratum corneum functions on endogenous ceramide profile was investigated in atopic dermatitis patients.

This study was performed with atopic dermatitis patients diagnosed by a dermatologist as not requiring medical treatment (N=38) following provision of informed consent. The study volunteers treated their skin twice a day with a test lotion for 4 weeks. During that period, they did not use medical treatment drugs or other skin care products, except for the test lotion.

Stratum corneum samples were collected from the volunteers using a tape-stripping method before and after 4 weeks of treatments with the test lotion. Synthetic pseudo-ceramide and endogenous ceramides in the stratum corneum were examined using normal phase liquid chromatography-electrospray ionized (NPLC-ESI) mass spectrometry. Stratum corneum water content was determined by skin conductance measurements.

The endogenous stratum corneum ceramide profile showed a shift after 4 weeks of daily treatments with the test lotion. In particular, ceramide [NH] and [NP] levels were increased, and ceramide [NS] and [AS] levels were decreased at the end of the treatment period (Figure 2a). Furthermore, lengthening of the ceramide [NS] carbon chain was also observed (Figure 2b). These results indicated that the endogenous ceramide profile characteristic of atopic skin shifted to that seen in healthy skin.^*5

The level of synthetic pseudo ceramide showing penetration and accumulation in the stratum corneum after 4 weeks of treatment with the test lotion was found to be significantly correlated with stratum corneum water content (Figure 3a).

In addition, the level of synthetic pseudo-ceramide showing penetration and accumulation in the stratum corneum was negatively correlated with the amount of endogenous ceramide [NS] (Figure 3b), while it was positively correlated with the average carbon chain length of ceramide [NS] (Figure 3c).

Interesting results were obtained in this study showing that daily treatment with a skin care lotion containing synthetic pseudo-ceramide changed the endogenous ceramide profile of individuals with atopic dermatitis to that of healthy skin as well as penetration of synthetic pseudo-ceramide into the stratum corneum.

Kao plans to use knowledge gained in this study, considered to be important for skin care in patients with atopic dermatitis, for future skin research investigations.

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