Probing the role of ceramide hydroxylation in skin barrier lipid models by 2 H solid-state NMR spectroscopy and X-ray powder diffraction

• Published in: Biochimica et biophysica acta. Biomembranes 2018-05, Vol.1860 (5), p.1162
• Main Authors: Kováčik, Andrej, Vogel, Alexander, Adler, Juliane, Pullmannová, Petra, Vávrová, Kateřina, Huster, Daniel
• Format: Article
• Language: English
• Subjects: Cell Membrane Permeability; Ceramides - chemistry; Ceramides - metabolism; Cholesterol - chemistry; Deuterium - chemistry; Humans; Hydroxylation - physiology; Lipid Bilayers - chemistry; Lipid Bilayers - metabolism; Magnetic Resonance Spectroscopy - methods; Models, Biological; Powder Diffraction - methods; Skin - chemistry; Skin - metabolism; Skin Temperature - physiology; Temperature; X-Rays
• ISSN: 0005-2736

In this work, we studied model stratum corneum lipid mixtures composed of the hydroxylated skin ceramides N-lignoceroyl 6-hydroxysphingosine (Cer[NH]) and α-hydroxylignoceroyl phytosphingosine (Cer[AP]). Two model skin lipid mixtures of the composition Cer[NH] or Cer[AP], N-lignoceroyl sphingosine (Cer[NS]), lignoceric acid (C24:0) and cholesterol in a 0.5:0.5:1:1 molar ratio were compared. Model membranes were investigated by differential scanning calorimetry and H solid-state NMR spectroscopy at temperatures from 25 °C to 80 °C. Each component of the model mixture was specifically deuterated for selective detection by H NMR. Thus, the exact phase composition of the mixture at varying temperatures could be quantified. Moreover, using X-ray powder diffraction we investigated the lamellar phase formation. From the solid-state NMR and DSC studies, we found that both hydroxylated Cer[NH] and Cer[AP] exhibit a similar phase behavior. At physiological skin temperature of 32 °C, the lipids form a crystalline (orthorhombic) phase. With increasing temperature, most of the lipids become fluid and form a liquid-crystalline phase, which converts to the isotropic phase at higher temperatures (65-80 °C). Interestingly, lignoceric acid in the Cer[NH]-containing mixture has a tendency to form two types of fluid phases at 65 °C. This tendency was also observed in Cer[AP]-containing membranes at 80 °C. While Cer[AP]-containing lipid models formed a short periodicity phase featuring a repeat spacing of d = 5.4 nm, in the Cer[NH]-based model skin lipid membranes, the formation of unusual long periodicity phase with a repeat spacing of d = 10.7 nm was observed.