Effects of Ceramide and Dihydroceramide Stereochemistry at C-3 on the Phase Behavior and Permeability of Skin Lipid Membranes

Abstract

Ceramides (Cer) are key components of the skin permeability barrier. Sphingosine-based CerNS and dihydrosphingosine-based CerNdS (dihydroCer) have two chiral centers; however, the importance of the correct stereochemistry in the skin barrier Cer is unknown. We investigated the role of the configuration at C-3 of CerNS and CerNdS in the organization and permeability of model skin lipid membranes. Unnatural l-threo-CerNS and l-threo-CerNdS with 24-C acyl chains were synthesized and, along with their natural d-erythro-isomers, incorporated into membranes composed of major stratum corneum lipids (Cer, free fatty acids, cholesterol, and cholesteryl sulfate). The membrane microstructure was investigated by X-ray powder diffraction and infrared spectroscopy, including deuterated free fatty acids. Inversion of the C-3 configuration in CerNS and CerNdS increased phase transition temperatures, had no significant effects on lamellar phases, but also decreased the proportion of orthorhombic packing and decreased lipid mixing in the model membranes. These changes in membrane organization resulted in membrane permeabilities that ranged from unchanged to 5-fold higher (depending on the permeability markers, namely, water loss, electrical impedance, flux of theophylline, and flux of indomethacin) compared to membranes with natural CerNS/NdS isomers. Thus, the physiological d-erythro stereochemistry of skin Cer and dihydroCer appears to be essential for their correct barrier function.

Behavior of 1-Deoxy-, 3-Deoxy- and N-Methyl-Ceramides in Skin Barrier Lipid Models

“…2A and Supporting Table S1). The d of this short lamellar phase (SLP) is consistent with those found in analogous SC lipid models containing LIG 8 or a mixture of free fatty acids with C16-C24 chain lengths 9,22,23 . In addition, a separated Chol phase with d (001) = 3.41 nm was found.…”

“…However, the detail molecular arrangement of MLP is unknown. In contrast to 3-deoxy-Cer, a change of C-3 stereochemistry in Cer (from D-erythro-lignoceroyl sphingosine to its L-threo-isomer) did not affect the lamellar periodicity in the SC lipid models but diminished the Cer mixing with fatty acids and reduced the water permeability barrier of such lipid systems 23 . Thus, the removal of C-3 hydroxyl in Cer was apparently less detrimental for its mixing with fatty acids and the ability to create a water barrier than incorrect stereochemistry at this position.…”

“…The raw scattered intensities without normalization are shown as a function of the scattering vector Q [nm −1 ]. The data were evaluated using the software package X'Pert Data Viewer (PANalytical B.V., Almelo, Netherlands) as described previously 9,23 .…”

Enantiomers of phospholipids and cholesterol: A key to decipher lipid‐lipid interplay in membrane

“…Fourier transform infrared spectroscopy experiments also provided the melting temperature by the observation of the temperature‐dependent wavenumber change of methylene symmetric stretching vibrations from the all‐trans conformer observed at less than 2850 cm ‐1 . Results revealed that the melting temperatures of L‐ threo Cer (C24:0) and L‐ threo dihydroCer (73°C and 81°C) are higher than those of their natural products (57 and 71°C), which are observed in a skin barrier mimicking lipid mixture together with Cho and sulfoCho …”

“…49 Results revealed that the melting temperatures of L-threo Cer (C24:0) and L-threo dihydroCer (73 C and 81 C) are higher than those of their natural products (57 and 71 C), which are observed in a skin barrier mimicking lipid mixture together with Cho and sulfoCho. 50 Unlike these diastereomers, it is difficult to discriminate between D-erythro and L-erythro sphingosines using spectroscopic methods as they are enantiomers. A recent study, however, revealed that it is possible to discriminate between all of the possible stereoisomers of sphingosines by vibrational circular dichroism (VCD).…”