Abstract
Ceramides (CERs) in human stratum corneum (SC) play physicochemical roles in determining barrier and water-holding 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 normal-phase liquid chromatography (NPLC) connected to electrospray ionization-mass spectrometry (ESI-MS) using a gradient elution system and a postcolumn addition of a volatile salt-containing polar solvent. The CERs targeted from the 3D chromatograms were structurally analyzed using NPLC-ESI-tandem 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 alpha-hydroxy 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.
Highlights
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
Human hair CERs are more complex than are those in human cells/tissues, because hair contains 4 classes, and the predominant class, CERs consisting of nonhydroxy fatty acid and dihydrosphingosine moieties, Abbreviations: CER, ceramide; ESI-MS, electrospray ionization-mass spectrometry; MS/MS, tandem mass spectrometry; normalphase liquid chromatography (NPLC), normal-phase liquid chromatography; SC, stratum corneum; TIC, total ion chromatogram
Normal-phase liquid chromatography (NPLC) connected to electrospray ionization-mass spectrometry (ESI-MS) was optimized for comprehensive profiling of diverse CERs in the SC, and overall CER species were visualized as 3D multi-mass chromatograms, followed by the structural analysis of the targeted peaks in the 3D chromatograms by NPLC-ESI-tandem mass spectrometry (MS/MS)
Summary
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. 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. Normal-phase liquid chromatography (NPLC) connected to electrospray ionization-mass spectrometry (ESI-MS) was optimized for comprehensive profiling of diverse CERs in the SC, and overall CER species were visualized as 3D multi-mass chromatograms, followed by the structural analysis of the targeted peaks in the 3D chromatograms by NPLC-ESI-tandem mass spectrometry (MS/MS) Such analysis has uncovered a new CER class consisting of a-hydroxy fatty acid and dihydrosphingosine moieties. We describe the results of identification of CERs in the SC, which are as many as 342 species
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