Dear Colleagues,

Sphingolipids in the skin play a crucial role in skin health and diseases. The most abundant sphingolipids in the skin are ceramides, which are found in great numbers, especially in the most upper stratum corneum layers. Since stratum corneum ceramides have a water-holding function and serve as a percutaneous permeability barrier by forming a multi-lamellar structure between the stratum corneum layers, their deficiency provokes skin diseases characterized by dry and barrier-disrupted skin, which include diseases, such as Niemann–Pick and Gaucher, as well as atopic dermatitis associated with the genetic defects of sphingomyelinase and beta-glucocerebrosidase, and the abnormal expression of sphingomyelin deacylase, recently identified as a beta-subunit of acid ceramidase. Acid ceramidase hydrolyzes the sphingolipid and ceramide into sphingosine and free fatty acids, in order to act as a rheostat that controls the levels of ceramide, sphingosine (a potent antimicrobial agent for St. Aureus) and sphingosine-1-phosphate (acting as an intracellular signaling factor) in cells and/or extracellular spaces. Farber disease is a genetic disorder resulting from a deficiency of acid ceramidase. Despite the many discovered mechanisms involved in the role of sphingolipids, there are stilll several unresolved mechanisms. For instance, how is sphingomyelin deacylase generated from acid ceramidase, which leads to a ceramide deficiency in atopic dermatitis? What is a precise role of acid ceramidase in skin cancers? How does a potent signaling factor such as sphingosine-1-phosphate contribute to skin health and diseases? Most importantly, what are biological factors or chemicals used to ameliorate ceramide or sphingosine deficiencies, as well as regulate sphingosine-1-phosphate levels in the intracellular space? This Special Issue, entitled “The Role of Sphingolipids in Skin Health and Diseases”, aims to provide a summary of these emerging fields, with an emphasis on novel evidence in the biological function of sphingolipids, and novel results on the pathophysiological molecular mechanisms of sphingolipids-associated skin diseases, especially atopic dermatitis and xerosis. This Special Issue will collate original research articles, as well as full reviews, including perspectives from the field on the current understanding of molecular mechanisms involved in atopic dermatitis and other sphingolipids-associated skin diseases. Manuscripts on the molecular mechanisms of new anti-atopic agents, the introduction of ideas for new skin anti-atopic agents, and new techniques for measuring the level of atopic dermatitis severity are all welcome.

Prof. Dr. Genji Imokawa
Guest Editor

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• sphingolipids
• ceramides
• atopic dermatitis
• skin health and diseases