Characterization of overall ceramide species in human stratum corneum

Abstract

Ceramides (CERs) in human stratum corneum (SC) play physicochemical roles in determining barrier and waterholding functions of the skin, and specific species might be closely related to the regulation of keratinization, together with other CER-related lipids. Structures of those diverse CER species, however, have not been comprehensively revealed. The aim of this study was to characterize overall CER species in the SC. First, we constructed 3D multi-mass chromatograms of the overall CER species, based on normalphase liquid chromatography (NPLC) connected to electrospray ionization-mass spectrometry (ESI-MS) using a gradient elution system and a postcolumn addition of a volatile saltcontaining polar solvent. The CERs targeted from the 3D chromatograms were structurally analyzed using NPLC-ESItandem mass spectrometry (MS/MS), which resulted in the identification of 342 CER species in the inner forearm SC. This led to the discovery of a new CER class consisting of ahydroxy fatty acid and dihydrosphingosine moieties, in addition to the 10 classes generally known. The results also revealed that those CERs contain long-chain (more than C 18 )-containing sphingoids and a great number of isobaric species. These novel results will contribute not only to physiochemical research on CERs in the SC but also to lipidomics approaches to CERs in the skin.-Masukawa, Y

The physical chemistry of the stratum corneum lipids

“…The ceramide molecules consist of fatty acids amide linked to sphingoid bases. Fifteen ceramide subclasses have been identified so far in the extracellular space of SC [28][29][30]. The ceramide molecules have different headgroup architectures, all of them considerably smaller and less polar than those of the lipids in a typical phospholipid membrane.…”

“…Both the ceramides and the fatty acids of the SC have unusually long hydrocarbon chains with a broad distribution of lengths [29,30,[35][36][37]. The variety of chain lengths and headgroup structures results in the existence of over 400 different ceramide species [29,30,38]. Most common for the ceramides are lengths of [24][25][26] [37], whereas most common for the fatty acids are lengths of 22-26 carbon atoms [39].…”

“…The different classes of ceramides molecules can participate in different inter-and intramolecular interactions with the other lipid molecules and thus make distinct contributions to the organization and the structural integrity of the lipid matrix [31][32][33][34][35]. Both the ceramides and the fatty acids of the SC have unusually long hydrocarbon chains with a broad distribution of lengths [29,30,[35][36][37]. The variety of chain lengths and headgroup structures results in the existence of over 400 different ceramide species [29,30,38].…”

Phase behavior of selected artificial lipids

“…The general structure of these essential natural products consists on the one hand of a sphingosin (minor amounts of sphinganin were found), phytosphingosine and 6-hydroxysphingosine and on the other hand of fatty acids bound via amide bond to the nitrogen atom of the sphingobases (for a summary see [53]). The most outstanding structures are the ceramides EOS (4) and EOP.…”

Self-Improvement of Keratinocyte Differentiation Defects During Skin Maturation in ABCA12-Deficient Harlequin Ichthyosis Model Mice

“…9 Briefly, lipid analysis was done independently on three Abca12 Ϫ/Ϫ neonates, two wild-type as controls, and two mature Abca12 Ϫ/Ϫ skins 3 months after skin grafting and two mature wild-type skins 3 months after transplantation as control. We separated the epidermis from whole skin specimens of control and Abca12 Ϫ/Ϫ mice by incubation in sterile water at 60°C for 1 minute and homogenized in 0.8 ml of PBS.…”