Role of Omega-Hydroxy Ceramides in Epidermis: Biosynthesis, Barrier Integrity and Analyzing Method

Abstract

Attached to the outer surface of the corneocyte lipid envelope (CLE), omega-hydroxy ceramides (ω-OH-Cer) link to involucrin and function as lipid components of the stratum corneum (SC). The integrity of the skin barrier is highly dependent on the lipid components of SC, especially on ω-OH-Cer. Synthetic ω-OH-Cer supplementation has been utilized in clinical practice for epidermal barrier injury and related surgeries. However, the mechanism discussion and analyzing methods are not keeping pace with its clinical application. Though mass spectrometry (MS) is the primary choice for biomolecular analysis, method modifications for ω-OH-Cer identification are lacking in progress. Therefore, finding conclusions on ω-OH-Cer biological function, as well as on its identification, means it is vital to remind further researchers of how the following work should be done. This review summarizes the important role of ω-OH-Cer in epidermal barrier functions and the forming mechanism of ω-OH-Cer. Recent identification methods for ω-OH-Cer are also discussed, which could provide new inspirations for study on both ω-OH-Cer and skin care development.

Comparison between ammonium formate and ammonium fluoride in the analysis of stratum corneum lipids by reversed phase chromatography coupled with high resolution mass spectrometry

“…O-Acylceramides play a significant role in skin homeostasis, ensuring the formation and stabilization of lipid organization in the lipid lamellae 6 . In SC, O -ceramides mainly bear ester-linked linoleic acid (LA) 9 . Because of that, linoleoxy-acylceramides were inspected upon extraction of the LA carboxylate anion [M − H] − (m/z 279.233) at a CE of 40 eV from the SC sample 26 .…”

“…FAs can be non-hydroxy (N), α-hydroxy (A), ω-hydroxy (O), esterified ω-hydroxy (EO). When a CER contains a FA hydroxylated at the ω position of the carbon chain, it can be additionally esterified to another FA forming O-acylceramides or it can be combined with proteins forming protein-bound CERs 8 , 9 . β-hydroxy (B) FAs occur rarely 5 , 7 .…”

JAK/STAT Inhibition Normalizes Lipid Composition in 3D Human Epidermal Equivalents Challenged with Th2 Cytokines

“…Nevertheless, CerNP species with 38 to 44 carbon atoms increased after Th2 cytokine treatment, as expected due to the significant upregulation of DEGS2. Ceramides bearing linoleic acid ester bound to omega hydroxylated long-chain FAs have been characterized in the epidermis (EOS, EODS, EOP, EOH) [38]. Several acylceramides showed a decrease in Th2-HEEs, which was recovered with tofacitinib, but significance was not reached.…”

Considering Phytosphingosine-Based Ceramide Formulations for Atopic Skin Care

“…CER nomenclature is based on different combinations and arrangements of the fatty acyl chains/FAs and SBs (Figure 2A,B). In mammals, including humans [35], the SB that contains a polar head group and a non-polar tail group may exist in five types: (1) sphingosine (S), ( 2) phytosphingosine (P), (3) 6-hydroxysphingosine (H), ( 4) dihydrosphingosine (DS), or (5) 4,14-sphingadiene (SD) [3,6,18,[43][44][45][46][47] (Figure 2B). The fatty acyl chain/FA moieties may exist in four types: (1) non-hydroxy fatty acyl chain (N), (2) α-hydroxy fatty acyl chain (A), (3) ω-hydroxy fatty acyl chain (O), or (4) esterified ω-hydroxy fatty acyl chain (EO) [3,6,18,[43][44][45][46][47] (Figure 2B).…”

“…In mammals, including humans [35], the SB that contains a polar head group and a non-polar tail group may exist in five types: (1) sphingosine (S), ( 2) phytosphingosine (P), (3) 6-hydroxysphingosine (H), ( 4) dihydrosphingosine (DS), or (5) 4,14-sphingadiene (SD) [3,6,18,[43][44][45][46][47] (Figure 2B). The fatty acyl chain/FA moieties may exist in four types: (1) non-hydroxy fatty acyl chain (N), (2) α-hydroxy fatty acyl chain (A), (3) ω-hydroxy fatty acyl chain (O), or (4) esterified ω-hydroxy fatty acyl chain (EO) [3,6,18,[43][44][45][46][47] (Figure 2B). Therefore, the final CER molecule is designated by a shorthand nomenclature, CER [XY], where the first letter "X" indicates the fatty acyl chain, and the second letter "Y" designates the SB; for example, CER[EOP] (orange-shaded box) stands for CER (esterified ω-hydroxy fatty acyl phytosphingosine); CER[NP] (orange-shaded box) stands for CER (non-hydroxy fatty acyl phytosphingosine); and CER[AP] (orange-shaded box) stands for CER (α-hydroxy fatty acyl phytosphingosine) [6,18,22,45,46,48] (Figure 2B).…”