Bilayer Structure and Lipid Dynamics in a Model Stratum Corneum with Oleic Acid

Abstract

The stratum corneum is the uppermost layer of the skin and acts as a barrier to keep out contaminants and retain moisture. Understanding the molecular structure and behavior of this layer will provide guidance for optimizing its biological function. In this study we use a model mixture comprised of equimolar portions of ceramide NS (24:0), lignoceric acid, and cholesterol to model the effect of the addition of small amounts of oleic acid to the bilayer at 300 and 340 K. Five systems at each temperature have been simulated with concentrations between 0 and 0.1 mol % oleic acid. Our major finding is that subdiffusive behavior over the 200 ns time scale is evident in systems at 340 K, with cholesterol diffusion being enhanced with increased oleic acid. Importantly, cholesterol and other species diffuse faster when radial densities indicate nearest neighbors include more cholesterol. We also find that, with the addition of oleic acid, the bilayer midplane and interfacial densities are reduced and there is a 3% decrease in total thickness occurring mostly near the hydrophilic interface at 300 K with reduced overall density at 340 K. Increased interdigitation occurs independent of oleic acid with a temperature increase. Slight ordering of the long non-hydroxy fatty acid of the ceramide occurs near the hydrophilic interface as a function of the oleic acid concentration, but no significant impact on hydrogen bonding is seen in the chosen oleic acid concentrations.

Localization of Cholesterol and Fatty Acid in a Model Lipid Membrane: A Neutron Diffraction Approach

“…Therefore, both arrangements are, in principle, still possible. The experimental results we obtained using synthetic lipid materials are in accordance with the theoretical simulation studies of SC lipid mixtures where it was shown that CER NS shows significant interdigitation at the center of the unit cell, and with the CHOL headgroups located close to the water-lipid interface (51,52).…”

Effect of monoglycerides and fatty acids on a ceramide bilayer

“…However, the frequency of water permeation events was found to double, indicating some OA-induced permeability enhancement. Recently Hoopes et al 43 studied the effect of OA on the mixed 1 : 1 : 1 CER2-CHOL-FA skin lipid bilayer at the OA concentrations up to 0.1 mol% and T = 300 and 340 K. Similar to the OA-DPPC study discussed above, 42 no significant changes in the properties of the skin lipid bilayer upon addition of OA were observed. Addition of a small amount of OA leads to slight enhancement in the diffusion of cholesterol, the fastest species in this gel-like mixture, which in turn increases the diffusion of ceramide and fatty acid.…”

Eccrine Sweat Duct Occlusion by Staphylococcal-Derived Biofilms: An Unexpected Signature Finding of Eczema in Dermatologic Diseases

“…It is important here to note that our belief is not that eczema is borne solely from the occlusion of sweat ducts by staphylococcalderived biofilm, but as elucidated in our previous work, that eczema develops secondary to a "double-hit phenomenon. " [25] In atopic dermatitis, the first hit is a genetic one-in the form of filaggrin (or other gene) deficiency. It is the biofilm-occluded sweat ducts that constitute an environmental second hit which in turn permits activation of disease.…”

“…Specifically, these disruptive factors are as follows: granules in granular parakeratosis, fungi in tinea pedis, and yeast organisms (especially Malassezia oleosa) in adultonset Seborrheic dermatitis. It has been reported that certain Malassezia species produce oleic acid, a molecule that, in experimental models, has been shown to alter the properties of the Stratum corneum [25]. Thus, in these diseases, the genetic hit is replaced by another environmental hit that results in a similar defect in the Stratum corneum.…”