The Role of the Trans Double Bond in Skin Barrier Sphingolipids: Permeability and Infrared Spectroscopic Study of Model Ceramide and Dihydroceramide Membranes

Abstract

Dihydroceramides (dCer) are members of the sphingolipid family that lack the C4 trans double bond in their sphingoid backbone. In addition to being precursors of ceramides (Cer) and phytoceramides, dCer have also been found in the extracellular lipid membranes of the epidermal barrier, the stratum corneum. However, their role in barrier homeostasis is not known. We studied how the lack of the trans double bond in dCer compared to Cer influences the permeability, lipid chain order, and packing of multilamellar membranes composed of the major skin barrier lipids: (d)Cer, fatty acids, cholesterol, and cholesteryl sulfate. The permeability of the membranes with long-chain dCer was measured using various markers and was either comparable to or only slightly greater than (by up to 35%, not significant) that of the Cer membranes. The dCer were less sensitive to acyl chain shortening than Cer (the short dCer membranes were up to 6-fold less permeable that the corresponding short Cer membranes). Infrared spectroscopy showed that long dCer mixed less with fatty acids but formed more thermally stable ordered domains than Cer. The key parameter explaining the differences in permeability in the short dCer and Cer was the proportion of the orthorhombic phase. Our results suggest that the presence of the trans double bond in Cer is not crucial for the permeability of skin lipid membranes and that dCer may be underappreciated members of the stratum corneum lipid barrier that increase its heterogeneity.

Effects of (R)- and (S)-α-Hydroxylation of Acyl Chains in Sphingosine, Dihydrosphingosine, and Phytosphingosine Ceramides on Phase Behavior and Permeability of Skin Lipid Models

“…Lipid mixtures with Cer NdS disordered at a higher temperature than those with Cer NS, consistent with the higher melting point of Cer NdS over Cer NS and previous results describing the formation of more thermally stable ordered domains of Cer NdS than Cer NS [ 8 , 17 , 38 ]. α-Hydroxylation of Cer NdS increased the lipid chain order at low temperatures and increased the main transition temperatures without any marked differences between ( R ) and ( S ) isomers ( Figure 3 E–G).…”

“…The behavior of skin-identical Cers with very long non-hydroxylated acyl chains has been widely explored in model biological membranes. The absence of a trans -double bond in Cer precursors, dihydroceramides, that form approximately 12% of Cers in healthy SC [ 7 ] did not affect the permeability of skin lipid models [ 8 ]. The shortening of the acyl or sphingoid chain in canonical sphingosine-based Cers decreased their barrier properties [ 9 , 10 ].…”

Probing the Role of the Ceramide Acyl Chain Length and Sphingosine Unsaturation in Model Skin Barrier Lipid Mixtures by 2H Solid-State NMR Spectroscopy

“…8−10 However, a direct comparison suggested that the presence of the trans double bond in Cer is not essential to their barrier function: the permeability of model SC lipid membranes containing nonhydroxy acyl species of dihydroCer (Cer[NDS24] 11 ) or Cer (Cer[NS24]) was either comparable or only slightly greater in the membranes containing Cer[NDS24]. 12 The barrier properties of sphingolipids are also markedly influenced by their acyl chain length. According to the Cer synthase involved in their formation, the Cer acyls vary from long (13−19 carbons) to very long (20−26 carbons) to ultralong (>28 carbons).…”

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

“…We have previously reported that the both acyl 12 and sphingosine chains shortening 13 , saturation of trans-double bond 71 , hydroxylations in C-4 8,72 or C-6 position 9,10 have different effects on the phase behavior and permeabilities of model skin lipid mixtures. Here we focused on the essential molecular features common to all Cer subclasses, hydroxyls at C-1 and C-3 and amide bond.…”