1. The Epidermal Barrier Catriona Curtis BVM&S MRCVS Field Technical Advisor Virbac UK

3. Programme Introduction Structure Function Therapy

4. General Skin Functions Enclosing barrier Environmental protection Temperature regulation Reservoir of fats, minerals, electrolytes, water, vitamins, fat, carbohydrates, proteins, and other materials Immunoregulation Pigmentation Antimicrobial action through the superficial lipid film Vitamin D production Adnexa production Motion and shape (through pliability and flexibility) Scott, Miller & Griffin - Muller & Kirk ’s Small Animal Dermatology 6th edition - 2001

5. Structure

6. The Epidermal Barrier

7. Emulsion ‘percolates’ between columns of squames, providing ‘mortar’ to strengthen the epidermis as well as providing the all important barrier effect

8. The Skin Barrier Squames = “bricksIntercellular lipid = “mortar”

9. Key Barrier Features Barrier to allergen, microbial and pathogen penetration Prevents trans-epidermal water loss (TEWL)  A healthy stratum corneum has a high water content  Ensures elasticity and pliability of the skin Impaired in specific skin disease proceses  ATOPY  KERATOSEBBORHEAIC DISORDERS Inflammatory responses can further impair epidermal differentiation and hence barrier function Area of on going research in human and veterinary dermatology  Marked similarities between human stratum corneum and canine stratum corneum  Human dermatologists using dogs as models for research

10. Lamellar Lipid Composition Composition  ~50 % Ceramides 1,3 and 6  ~25 % Cholesterol  ~10-20 % Essential fatty acids They are produced by lamellar bodies in the stratum granulosum and spinosum The lipids are then extruded from the lamellar bodies into the inter- corneocyte space Concurrent enzymatic release transforms the polar lipids into nonpolar lipids (hydrophobic)  Ensuring that they are organised into multi-lamellar bilayers

12. Ceramide Composition Ceramides are complex sphingolipids They are formed from the amide linkage of a sphingoid base with a variety of non hydroxylated, α-hydroxylated and ώ-hydroxylated fatty acids 9 ceramides have been identified in the human stratum corneum Ceramides 1, 3 and 6 are now known to be present in the canine lipid surface emulsion Canine stratum corneum ceramide composition similar to the human stratum corneum  Same sphingoid base  Coupled to non hydroxylated and hydroxylated fatty acids

13. Ceramide Structure Amide Bond The hydrophobic chain is formed when the ceramide joins with cholesterol and free fatty acids These hydrophobic chains construct lipid bilayers This dramatically reduces the permeability to water and solutes

14. Ceramide 1 Composition Fatty acids attached to ceramides predominatly saturated An exception is Linoleic acid, which is an essential component of ceramide 1 Ceramide 1 is critical to barrier function Cholesterol is recognised important to cell to cell cohesion and hence alterations in metabolism can affect desquamation.

16. What Happens When Things Go Wrong?? Disruption of barrier function can allow;  Allergen and pathogen penetration  Trans epidermal water loss  Increased permeability Now recognised as a primary disorder with some skin disease’s  Defective lipid lamellae present (Inman et al 2003; Piekutowska et al 2008)  Exhibit an irregular alignment and structure in comparison to normal Abormal lipid expression within the stratum corneum  Reduced free lipid protein bound fatty acids and ceramides with atopic dogs  Larger amounts of glucosylceramides in atopic dogs

17. Defects Electron microscopic observations of the stratum corneum intercellular lipids in normal and atopic dogs (1) Courtesy of: T. Olivry, NC State University, USA.

18. Cytokine Cascade It has been recognised that the compromised epidermal barrier will facilitate penetration of antigens, pathogens and non specific irritants This is turn can stimulate a cytokine cascade which is initiated in the stratum granulosum The ensuing immunological cascade can further compromise the barrier

19. Repairing The Barrier Combination of systemic and topical treatment Options  Direct repair (Allerderm® spot –on)  Oral fatty acid supplementation  Therapy aiming at stopping the cytokine cascade  Therapy aimed at normalising epidermal turnover Management of primary and secondary skin disease

20. Conclusion Extensively studied in human and veterinary dermatology Epidermal barrier is the main defence barrier of the skin It is critical in reducing allergen penetration Marked similarities between human epidermal barrier structure and canine epidermal barrier Deficits and abnormalities in ceramides and fatty acids contribute to the alterations in barrier function Skin disease further compromises barrier function

21. Please email any questions to catriona.curtis@virbac.co.uk

22. References Berardesca E, Barbareschi M, Veraldi S, Pimpinelli N. Evaluation of efficacy of a skin lipid mixture in patients with irritant contact dermatitis, allergic contact dermatitis or atopic dermatitis: a multi-center study. Contact Dermatitis 2001;45:280-285. Campbell KL, Kirkwood AR. Effect of topical oils on transepidermal water loss in dogs with seborrhea sicca. In: Ihrke PJ, Mason IS, White SD (Eds). Advances in Veterinary Dermatology vol. 2, Oxford, Pergamon Press, 1993; p157-162 Chamlin SL, Kao J, Frieden IJ, Sheu MY, Fowler AJ, Fluhr JW, Williams ML, Elias PM. Ceramide-dominant barrier repair lipids alleviate childhood atopic dermatitis: changes in barrier function provide a sensitive indicator of disease activity. J Am Acad Dermatol 2002;47:198-208. Coderch L, Lopez O, de la Maza A, Parra JL. Ceramides and skin function. Am J Clin Dermatol 2003;4: 107-129. Di Nardo A, Sugino K, Wertz P et al. Sodium lauryl sulfate (SLS) induced irritant contact dermatitis: a correlation study between ceramides and in vivo parameters of irritation. Contact Dermatitis 1996;35:86-91. Di Nardo A, Wertz P, Giannetti A, Seidenari S. Ceramide and cholesterol composition of the skin of patients with atopic dermatitis. Acta Derm Venereol 1998;78:27-30. Downing DT. Lipid and protein structures in the permeability barrier of mammalian epidermis. J Lipid Res 1992;33:301-313.

23. References Elias PM, Feingold KR. Does the tail wag the dog? Role of the barrier in the pathogenesis of inflammatory dermatoses and therapeutic implications. Arch Dermatol 2001;137:1079-1081. Elias PM, Hatano Y, Williams ML. Basis for the barrier abnormality in atopic dermatitis: outside-inside-outside pathogenic mechanisms. J Allergy Clin Immunol 2008;121:1337-1343. Fartasch M. Epidermal barrier in disorders of the skin. Microsc Res Tech 1997;38:361-372. Hightower K, Marsella R, Creary E, Dutcher P. Evaluation of trans-epidermal water loss in canine atopic dermatitis: a pilot study in beagle dogs sensitized to houst dust mites. 23 rd Proceedings of the NAVDF Congress 2008, Denver, Colorado, p183. Inman AO, Olivry T, Dunston SM, Monteiro-Riviere NA, Gatto H. Electron Microscopic observations of stratum corneum intercellular lipids in normal and atopic dogs. Vet Pathol 2001;38:720-723. Jungersted JM, Hellgren LI, Jemec GB, Agner T. Lipids and skin barrier function--a clinical perspective. Contact Dermatitis 2008;58:255-62. Kwochka KW. The structure and function of epidermal lipids. Vet Dermatol 1993;4: 151-159 Lavrijsen APM, Bouwstra JA, Gooris GS et al. Reduced skin barrier function parallels abnormal stratum corneum lipid organisation in patients with lamellar ichthyosis. J Invest Dermatol 1995;105:619-624.

24. References Macheleidt O, Kaiser HW, Sandhoff K. Deficiency of epidermal protein-bound omega-hydroxyceramides in atopic dermatitis. J Invest Dermatol 2002;119:166-173. Madison KC. Barrier function of the skin: “La raison d’être” of the epidermis. J Invest Dermatol 2003;121:231-241. Mao-Quiang M, Feingold KR, Thornfeldt CR et al. Optimization of physiological lipid mixtures for barrier repair. J Invest Dermatol 1996;106:1096-1101. Mason IS, Lloyd DH. 1993. Scanning electron microscopical studies of the living epidermis and stratum corneum in dogs. In: Ihrke PJ, Mason IS, White SD (Eds.), Advances in Veterinary Dermatology Vol. 2. Pergamon Press, Oxford, 1993, p131-139. Olivry T, DeBoer DJ, Griffin CE. The ACVD task force on canine atopic dermatitis : forewords and lexicon. Veterinary Immunology and Immunopathology 2001;81:143-146. Piekutowska A, Pin D, Rème CA, Gatto H, Haftek M. Effects of a topically applied preparation of epidermal lipids on the stratum corneum barrier of atopic dogs. J Comp Path 2008;138: 197-203. Pin D, Popa I, Piekutowska, Chapman J, Gatto H, Haftek M, Portoukalian J. Biochemical analysis of epidermal lipids in normal and atopic dogs, before and after administration of an oral omega-6/omega-3 fatty acid supplement (Megaderm®). Vet Dermatol 2008;19 (Suppl. 1):68.

25. References Popa I, Thuy LH, Colsch B, Pin D, Gatto H, Haftek M et al. Analysis of free and protein-bound ceramides by tape stripping of stratum corneum from dogs. Arch Dermatol Res. 2010 Nov;302(9):639-644. Popa I, Remoue N, Hoang LT, Pin D, Gatto H, Haftek M et al. Atopic dermatitis in dogs is associated with a high heterogeneity in the distribution of protein-bound lipids within the stratum corneum. Arch Dermatol Res. (2011, in press). Scott DW, Miller WH, Griffin CE (Eds.). Structure and function of the skin. In: Small Animal Dermatology, 6th Edition. WB Saunders Company, Philadelphia, 2001, p 1-70. Segiguchi M, Ikeno K, Iwasaki T. Ceramides in keratin layer of normal and atopic dogs. Proceedings 18 th AAVD-ACVD Congress 2003, Monterey, p235. Sugarman JL. The epidermal barrier in atopic dermatitis. Semin Cutan Med Surg 2008;27:108-14. Wertz PW. Lipids and barrier function of the skin. Acta Dermatol Venereol 2000;208:7-11. Yamamoto A, Serizawa S, Ito M, et al. Stratum corneum lipid abnormalities in atopic dermatitis. Arch Dermatol Res 1991;238:219-223. Virbac UK. Allerderm Product Profile 2010