Water Increases the Fluidity of Intercellular Membranes of Stratum Corneum: Correlation with Water Permeability, Elastic, and Electrical Resistance Properties

Abstract

We used the spin label electron spin resonance technique to monitor the hydration effect on the molecular dynamics of lipids at C-5, C-12, and C-16 positions of the alkyl chain. Increase in water content of neonatal rat SC leads to an increase in membrane fluidity, especially in the region near the membrane-water interface. The effect is less pronounced deeper inside the hydrophobic core. The reorientational correlation time at the C-16 position of hydrocarbon chains showed a higher change up to approximately 18% (w/w) of water content. This behavior was accompanied by an exponential decay both in elastic modulus and electrical resistance with water content. On the contrary, the segmental motion at C-5 and C-12 positions of the chain and the permeability constant increased in the range of around 18% w/w) up to the fully hydrated condition (58 +/- 7%). Our results give a better characterization of the fluidity of SC and show that it is the principal parameter involved in the mechanism of the permeability of different compounds through skin.

Analysis of Electron Spin Resonance Spectra of Alkyl Spin Labels in Excised Guinea Pig Dorsal Skin, Its Stratum Corneum, Delipidized Skin and Stratum Corneum Model Lipid Liposomes.

“…However, there have been few studies on the dependence of the interaction of the spin labels with the membrane components and their localization in the membrane on their chemical structure and electrical charge. As previously reported in human stratum corneum, 7,8) 5-NS in the stratum corneum of guinea pig dorsal skin showed a typical spectrum, which indicated the presence of the spin label in gel state lipid lamella. Intercellular lipid lamella in stratum corneum is known to have a highly ordered structure and to work as an effective barrier to penetration of chemical substances.…”

“…This is consistent with the previous findings in human stratum corneum. 7,8) Order parameter of 5-NS in the stratum corneum was slightly larger than that in the stratum corneum model lipid liposomes (Table 1). As previously reported, 5) the spectrum of the same spin label in the original excised skin (Fig.…”

“…Fatty acid spin labels such as 5-doxylstearic acid (5-NS) have been reported to be present in the lipid lamella in human stratum corneum. 7,8) On the other hand, our recent analysis on the ESR spectra of a long-chain quaternary ammonium spin label 4-(N,N-dimethyl-N-pentadecyl)ammonium-2,2,6,6-tetramethylpiperidine-1-oxyl (CAT-15) in excised guinea pig dorsal skin, has suggested that the spin label is mainly present by binding to stratum corneum proteins. 6) These results suggested the possibility that the localization of the spin labels may be different depending on their electric charge and their chemical structure.…”

Electron paramagnetic resonance (EPR) spectral components of spin-labeled lipids in saturated phospholipid bilayers: effect of cholesterol

“…Several spin labels have previously been examined by EPR spectroscopy to study the lipid dynamics of stratum corneum, in a bid to understand why skin permeability is reduced by dehydration of this membrane. 23,24 Upon decreasing the hydration level of stratum corneum, a gradual decrease in motional dynamics was detected and, most importantly, upon dehydration the population of the second spectral component for various spin labels was diminished, tending to disappear in response to total dehydration of the stratum corneum. Similar results have been observed for phospholipid vesicles (data not shown).…”

Lipid composition and molecular interactions change with depth in the avian stratum corneum to regulate cutaneous water loss

“…It is thought that water molecules permeate through lamellae by inserting between hydrophilic lipid headgroups to increase spacing between lipid molecules (Golden et al, 1986;Alonso et al, 1996). This increase in intermolecular distance disrupts the normal trans configuration of the hydrophobic alkyl chains of the lipids and causes some carbon-carbon bonds to rotate approximately 120 deg to create gauche defects in the alkyl chains.…”