Effect of Th2 cytokines on ceramide subclasses based on a model of reconstructed human epidermis.

Atopic dermatitis (AD) is associated with chronic inflammation and an altered skin barrier. Lipids of the stratum corneum of AD patients are known to differ substantially in composition from those of healthy subjects. A reconstructed human epidermis (RHE) model has been developed in vitro in order to mimic the characteristics of AD. In this study, using this model, we compared lipid profile modifications between control RHE and RHE treated with Th2 cytokines in order to mimic AD. We focused particularly on the lipid profile of the ceramide subclasses: non-hydroxy sphingosine (NS) and esterified ω-hydroxy sphingosine (EOS), which have been reported to be clearly modified in atopic skin. RHE lipids were extracted and analysed using high-performance liquid chromatography coupled to high-resolution mass spectrometry. The following lipid profile changes were observed in Th2-cytokine-treated RHE: (i) an increase in ceramide NS composed of an unsaturated fatty acid chain; (ii) an increase in saturated ceramide NS with small total carbon content (≤40 carbon atoms), whereas NS with a higher total carbon content (≥42 carbon atoms) was decreased; and (iii) a decrease in ceramide EOS. These results are in accordance with reported lipid profiles of human atopic skin in vivo. Moreover, the in vitro model represents a useful tool to better understand the pathogenesis of AD which may be used for future screening of new effective treatments.