Effects of ()- and ()-α-Hydroxylation of Acyl Chains in Sphingosine, Dihydrosphingosine, and Phytosphingosine Ceramides on Phase Behavior and Permeability of Skin Lipid Models. Kováčik Andrej,Pullmannová Petra,Opálka Lukáš,Šilarová Michaela,Maixner Jaroslav,Vávrová Kateřina International journal of molecular sciences Ceramides (Cers) with α-hydroxylated acyl chains comprise about a third of all extractable skin Cers and are required for permeability barrier homeostasis. We have probed here the effects of Cer hydroxylation on their behavior in lipid models comprising the major SC lipids, Cer/free fatty acids (C -C )/cholesterol, and a minor component, cholesteryl sulfate. Namely, Cers with ()-α-hydroxy lignoceroyl chains attached to sphingosine (Cer AS), dihydrosphingosine (Cer AdS), and phytosphingosine (Cer AP) were compared to their unnatural ()-diastereomers and to Cers with non-hydroxylated lignoceroyl chains attached to sphingosine (Cer NS), dihydrosphingosine (Cer NdS), and phytosphingosine (Cer NP). By comparing several biophysical parameters (lamellar organization by X-ray diffraction, chain order, lateral packing, phase transitions, and lipid mixing by infrared spectroscopy using deuterated lipids) and the permeabilities of these models (water loss and two permeability markers), we conclude that there is no general or common consequence of Cer α-hydroxylation. Instead, we found a rich mix of effects, highly dependent on the sphingoid base chain, configuration at the α-carbon, and permeability marker used. We found that the model membranes with unnatural Cer ()-AS have fewer orthorhombically packed lipid chains than those based on the ()-diastereomer. In addition, physiological ()-configuration decreases the permeability of membranes, with Cer ()-AdS to theophylline, and increases the lipid chain order in model systems with natural Cer ()-AP. Thus, each Cer subclass makes a distinct contribution to the structural organization and function of the skin lipid barrier. 10.3390/ijms22147468

Stratum corneum ceramide profiles in vitro, ex vivo, and in vivo: characterization of the α-hydroxy double esterified ceramides. Analytical and bioanalytical chemistry The presence of a new ceramide subclass, the 1-O-acyl omega-linoleoyloxy ceramides [1-O-E (EO) Cer], has been previously highlighted in reconstructed human epidermis (RHE). These ceramides are double esterified on two positions. The first is the 1-O position of the sphingoid base moiety with a long to very long chain of acyl residues (1-O-E), and the second is the position of the ω-hydroxyl group of the fatty acid moiety with linoleic acid (EO). Considering its chemical structure and hydrophobicity, this subclass can contribute to the skin barrier. Thus, it is important to determine whether this subclass is also present in native human stratum corneum (SC). This work compares ceramide structures of this novel subclass between RHE (in vitro) and two sources of human SC (in vivo and ex vivo) using normal-phase high-performance liquid chromatography coupled to high-resolution mass spectrometry (NP-HPLC/HR-MS). The results confirm the presence of this double esterified ceramide subclass [1-O-E (EO) Cer] in human SC. The molecular profile obtained from the RHE was very close to that found in the human SC (in vivo and ex vivo). In addition, thanks to the targeted MS/MS analysis, a new ceramide subclass was discovered and characterized in the three studied samples. We propose to name it [A-1-O-E (EO) Cer] because in these ceramides species, the fatty acid-esterified with the sphingoid base on the 1-O position-is hydroxylated on the α position. These results highlight the potential of both the analytical method and the characterization approach employed in this study. 10.1007/s00216-022-04011-9

Barrier Capability of Skin Lipid Models: Effect of Ceramides and Free Fatty Acid Composition. Uche Lorretta E,Gooris Gerrit S,Bouwstra Joke A,Beddoes Charlotte M Langmuir : the ACS journal of surfaces and colloids The skin is an effective barrier that prevents the influx of harmful substances from the environment and the efflux of body fluid. This barrier function is ascribed to the intercellular lipids present in the outermost layer of the skin referred to as the stratum corneum (SC). These lipids are composed mainly of ceramides (CERs), cholesterol, and free fatty acids (FFAs). Alterations in the SC lipid composition and barrier function impairment occur in several skin diseases including atopic dermatitis (AD). As the etiology of AD is multifactorial, establishing the relationship between the changes in SC lipid composition and barrier function impairment in the patients remains a challenge. Here, we employed model membrane systems to investigate the contribution of various anomalies in the SC CER and FFA composition observed in AD patients' skin to the barrier dysfunction. Using ethyl--aminobenzoate permeation and transepidermal water loss values as markers for barrier function, we determined that the alterations in SC lipid composition contribute to the impaired barrier function in AD patients. By the use of biophysical techniques, we established that the largest reduction in barrier capability was observed in the model with an increased fraction of short-chain FFAs, evident by the decrease in chain packing density. Modulations in the CER subclass composition impacted the lamellar organization while having a smaller effect on the barrier function. These findings provide evidence that AD therapies normalizing the FFA composition are at least as important as normalizing CER composition. 10.1021/acs.langmuir.9b03029