The lipid alterations in the stratum corneum of dogs with atopic dermatitis are alleviated by topical application of a sphingolipid-containing emulsion I. Popa, N. Remoue, B. Osta, D. Pin,* H. Gatto,† M. Haftek and J. Portoukalian Laboratory of Dermatological Research, University of Lyon-I, Lyon, France; *University of Lyon, VetAgro Sup, Marcy l’Etoile, France; and †Virbac Laboratories, Carros, France doi:10.1111/j.1365-2230.2011.04313.x Summary 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 cera- mides, 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 lg 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. Introduction Atopic dermatitis (AD) is a skin disease commonly seen in children, and is characterized by inflammatory lesions resulting from an impaired skin barrier, which shows high transepidermal water loss. 1,2 The clinical features of AD are very similar in dogs and humans. 3 Several studies have found an altered lipid composition in the atopic stratum corneum (SC), with a reduced ceramide content identified in both humans 4–7 and dogs. 8,9 A study of the protein-bound ceramides in human AD 10 showed a clear reduction in the quantity of these ceramides compared with normal skin. We recently showed that canine SC has a pattern of free and protein-bound ceramides that is very similar to that of humans. 11 In a further study, 12 we collected canine SC by tape stripping, and carried out a detailed analysis of the free and protein-bound lipids of the SC of normal dogs and dogs with AD. Compared with the normal canine SC, there was a downward trend for free lipids in atopic SC and a highly significant reduction of protein-bound (FAs) and ceramides. More- over, the atopic canine SC contained large amounts of Correspondence: Dr Iuliana Popa, UMR CNRS 8612, University of Paris XI School of Pharmacy, 92290 Cha ˆ tenay-Malabry, France E-mail: iuliana.popa@u-psud.fr Conflict of interest: none declared. Accepted for publication 17 October 2011 Experimental dermatology • Original article CED Clinical and Experimental Dermatology Ó The Author(s) CED Ó 2012 British Association of Dermatologists • Clinical and Experimental Dermatology 1