Molecular Mechanism of Skin Permeability Barrier Formation by Ceramides

Abstract

Ceramides are abundantly present in the stratum corneum of the epidermis on the body surface and play a crucial role in the formation of the skin barrier, which protects against infection and prevents water loss. Human stratum corneum contains a variety of ceramides, with 23 classes and over 1,500 species. Ceramides are classified into free ceramides and protein-bound ceramides, which are components of the multilayered lipid structures (lipid lamellae) present between corneocytes and the corneocyte lipid envelope, respectively. Free ceramides are further classified into non-acylated ceramides and acylceramides. Protein-bound ceramides and acylceramides are especially important for skin barrier formation, and mutations in genes involved in their synthesis cause congenital ichthyosis. This review presents the latest findings on the molecular mechanisms underlying ceramide diversity, the roles of individual ceramide classes in skin barrier formation, and their relationships to skin diseases.

graphical abstract