Stratum Corneum Lipids and Filaggrin
Stratum corneum, the most upper layer of the skin, plays a key role for the skin barrier function. The stratum corneum mainly consists of corneocytes and lipids. The lipids are divided into ceramides, cholesterol, and free fatty acids. The synthesis of th
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Stratum Corneum Lipids and Filaggrin Jakob Mutanu Jungersted
Contents 3.1 Introduction .....................................................
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3.2 The Lipids: What They Are Influenced by and Their Regulation .................................
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3.3 Atopic Dermatitis from a Lipid and Filaggrin Perspective ...............................
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3.4 pH and Filaggrin .............................................
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3.5 Where to Go from Here ..................................
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References .................................................................
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Stratum corneum, the most upper layer of the skin, is crucial to skin barrier functions. The major components of the stratum corneum are corneocytes and lipids. The lipids surround the corneocytes and are arranged in lipid bilayers, historically described as a brick wall, with the bricks being the annucleated corneocytes and the mortar being the lipids [1]. Accordingly, no substance can pass through the skin without first passing through the stratum corneum lipids [1, 2]. This chapter focuses on the stratum corneum lipids, in particular on the influence of filaggrin on the lipids and its possible role in lipid synthesis through influencing pH.
3.2
J.M. Jungersted, MD, PhD Department of Dermatology, Roskilde Hospital, Køgevej 7-13, Roskilde 4000, Denmark e-mail: [email protected]
Introduction
The Lipids: What They Are Influenced by and Their Regulation
The lipids are mainly composed of three different classes: ceramides, free fatty acids, and cholesterol. The ceramides are further subdivided into 12 subclasses (ceramides 1–12) and, more recently, also according to chain length [3–5]. The synthesis of the lipids takes place in the stratum granulosum, and through lamellar body exocytosis, the lipids are delivered to the stratum corneum [6]. Regulation of the synthesis is linked in a symphony of enzymes, calcium gradient, and pH, which is not fully understood, as yet. Lipid levels in the stratum corneum are related to
J.P. Thyssen, H. Maibach (eds.), Filaggrin, DOI 10.1007/978-3-642-54379-1_3, © Springer-Verlag Berlin Heidelberg 2014
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J.M. Jungersted
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anatomical location and are influenced by environmental factors, such as season and UV exposure. For example, in winter, decreasing levels of ceramides are found on the face compared with more protected areas of the skin [7]. Topical skin treatments also influence stratum corneum lipid levels. Moisturisers, topical corticosteroids, and topical calcineurin inhibitors have been investigated regarding their effect on up- or downregulation of the lipids. Although data are not uniform, it has been shown for moisturisers that the mRNA expression of enzymes involved in lipid synthesis is up- or downregulated according to the ingredients [8, 9]. However, since the moisturisers tested all contained multiple ingredients, the precise influence of each ingredient is unknown. For topical corticosteroids, one group has shown that their use leads to inconsistency in the lipid bilayers [10], which is interpr
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