title: Epidermal ceramidase activity regulates epidermal desquamation via stratum corneum acidification.
abstract: The acidic pH of the outer surface of the mammalian skin plays several important roles in the epidermal barrier function. The 2 endogenous pathways that are currently known to elicit this acidic pH are the generation of free fatty acids from phospholipids and the exchange of protons for sodium ions by non-energy-dependent sodium-proton exchangers. In this study, we propose a third endogenous pathway, i.e. epidermal ceramidase activity, generating free fatty acids from ceramides. By topical application of N-oleylethanolamine, a well-known ceramidase inhibitor, we could demonstrate a significant increase in the stratum corneum pH and a corresponding decrease in the epidermal free fatty acid content. Moreover, we could show that the resulting change in the apparent skin pH also provoked a delay in early barrier recovery and an increased epidermal desquamation, corresponding to earlier observations made for the already known endogenous mechanisms.
authors.affiliation: Department of Toxicology, Dermatocosmetology and Pharmacognosy, Vrije Universiteit Brussel, Brussels, Belgium. evi.houben@telenet.be
authors.forename: E
authors.initials: E
authors.lastname: Houben
authors.forename: J P
authors.initials: JP
authors.lastname: Hachem
authors.forename: K
authors.initials: K
authors.lastname: De Paepe
authors.forename: V
authors.initials: V
authors.lastname: Rogiers
mesh_terms: D000287:Administration, Topical; D000581:Amidohydrolases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000818:Animals; D055572:Ceramidases; D003896:Desmosomes / Q000502:physiology; D063388:Endocannabinoids; D004817:Epidermis / Q000378:metabolism / Q000502:physiology* / Q000648:ultrastructure; D004983:Ethanolamines / Q000494:pharmacology; D005230:Fatty Acids, Nonesterified / Q000096:biosynthesis; D006706:Homeostasis; D006863:Hydrogen-Ion Concentration; D008297:Male; D051379:Mice; D008812:Mice, Hairless; D009829:Oleic Acids; D010539:Permeability; D012697:Serine Endopeptidases / Q000378:metabolism
chemical_list: D063388:Endocannabinoids; D004983:Ethanolamines; D005230:Fatty Acids, Nonesterified; D009829:Oleic Acids; C033595:N-oleoylethanolamine; D012697:Serine Endopeptidases; D000581:Amidohydrolases; D055572:Ceramidases