The lipid alterations in the stratum corneum of dogs with atopic dermatitis are alleviated by topical application of a sphingolipid-containing emulsion

Background. Atopic dermatitis (AD) results from an altered skin barrier associated with defects in the lipid composition of the skin. Dogs with AD present similar clinical symptoms to humans, and may be a useful model for investigations into AD. Aim. To analyse the changes occurring in the lipids of the stratum corneum (SC) of dogs with AE after 3 weeks of topical treatment with an emulsion containing ceramides, free fatty acids (FFAs) and cholesterol (skin lipid complex; SLC). Methods. Nonlesional SC was collected by tape stripping from control and treated areas. Free and protein-bound lipids were purified, and the various classes were isolated by column chromatography, analysed by thin-layer chromatography and assayed. Results. Ceramides, FFA and cholesterol were all found to be lower in the skin of untreated dogs with AD than in normal dogs, and the topical treatment resulted in significantly increased values for ceramides. Conversely, only trace amounts of glucosylceramides were present in normal SC, but a high concentration (27 mu g per mg protein) was detected in canine atopic SC, which disappeared after treatment with SLC. There was a heterogeneous distribution of all of the lipids in the different layers of canine atopic SC, which was more pronounced for protein-bound than for free lipids. Following topical treatment, the protein-bound lipid content normalized. Conclusions. Topical treatment with SLC resulted in a significant improvement of the lipid biosynthesis of keratinocytes in atopic dogs, thereby potentially enabling the formation of a tighter epidermal barrier.