Cholesterol sulfate and calcium affect stratum corneum lipid organization over a wide temperature range

Abstract

The main diffusion barrier for drugs penetrating through the skin is located in the intercellular lipid matrix in the upper layer of the skin, the stratum corneum (SC). The main lipid classes in the SC are ceramides (CER), free fatty acids (FFA) and cholesterol (CHOL). The lipids in SC are organized into two lamellar phases with periodicities of approximately 13 and 6 nm, respectively. Similar lipid organization has been found with equimolar CHOL:CER:FFA mixtures in SAXD studies performed at room temperature. However, one may conclude that the phase behavior of the mixtures is similar to that in SC only when the lipid organization of the lipid mixtures resembles that in SC over a wide temperature range. Therefore, in the present study, the organization of the lipid mixtures has been studied in a temperature range between 20 ؇ and 95 ؇ C. From these experiments it appeared that at elevated temperatures in equimolar CHOL:CER:FFA mixtures a new prominent 4.3 nm phase is formed between 35-55 ؇ C, which is absent or only weakly formed in intact human and pig SC, respectively. As it has been suggested that gradients of pH and cholesterol sulfate exist in the SC and that Ca 2 ؉ is present only in the lowest SC layers, the effect of pH, cholesterol sulfate, and Ca 2 ؉ on the lipid phase behavior has been investigated with lipid mixtures. Both an increase in pH from 5 (pH at the skin surface) to 7.4 (pH at the SC-stratum granulosum interface) and the presence of cholesterol sulfate promote the formation of the 13 nm lamellar phase. Furthermore, cholesterol sulfate reduces the amount of CHOL that is present in crystalline domains, causes a shift in the formation of the 4.3 nm phase to higher temperatures, and makes this phase less prominent at higher temperatures.The finding that Ca 2 ؉ counteracts the effects of cholesterol sulfate indicates the importance of a proper balance of minor SC components for appropriate SC lipid organization. In addition, when the findings are extrapolated to the in vivo situation, it seems that cholesterol sulfate is required to dissolve cholesterol in the lamellar phases and to stabilize SC lipid organization. Therefore, a drop in cholesterol sulfate content in the superficial layers of the SC is expected to destabilize the lipid lamellar phases, which might facilitate the desquamation process. -Bouwstra, J. A., G. S. Gooris, F. E. R. Dubbelaar, and M. Ponec. Cholesterol sulfate and calcium affect stratum corneum lipid organization over a wide temperature range.

Phase Behavior of Stratum Corneum Lipid Mixtures Based on Human Ceramides: The Role of Natural and Synthetic Ceramide 1

“…(ii) In X-linked ichthyosis skin a substantial increase in cholesterol sulfate level has been observed (Elias et al, 1984). In a previous study with pigCER it was shown that an increased level of cholesterol sulfate promotes the formation of a¯uid phase (Bouwstra et al, 1998a;Bouwstra et al, 1999). For this reason the elevated levels of cholesterol sulfate in X-linked ichthyosis skin are expected to promote the formation of a¯uid phase and possibly also to disturb the formation of the LPP.…”

Phase behavior of lipid mixtures based on human ceramides: coexistence of crystalline and liquid phases

“…Previous studies (13,14,16) and the present study reveal that in CHOL:CER mixtures prepared with both pig and human CER the following similarities in phase behavior have been observed: a) In CHOL:CER mixtures the LPP is formed, demonstrating the formation of the same lamellar phases as present in intact SC; b) the phase behavior of CHOL:CER mixtures is not sensitive to changes in the CHOL:CER molar ratio over a wide range; c) in CHOL:CER mixtures hexagonal lateral packing is present. Addition of long chain FFA induces a transition from hexagonal to orthorhombic lateral packing; d) the presence of cholesterol sulfate increases the solubility of CHOL in CHOL: CER:FFA mixtures; and e) in mixtures prepared with HCER lacking HCER1 the formation of the LPP is strongly reduced, as observed with pigCER mixtures.…”

“…This phase was less prominent or even absent in intact SC. From the experiments performed with mixtures prepared from pigCER it became clear that the fraction of lipids forming this phase at elevated temperatures decreased when at room temperature the amount of phase-separated CHOL was reduced (16). Such a situation can also be achieved by addition of cholesterol sulfate.…”

“…It has been observed that addition of cholesterol sulfate to CHOL:pigCER:FFA mixtures induced the formation of liquid lateral packing and increased the solubility of CHOL in the lamellar phases. Furthermore, cholesterol sulfate promoted the formation of the 13 nm lamellar phase (14,16). The presence of calcium counteracted the effect of cholesterol sulfate.…”

pH Directly Regulates Epidermal Permeability Barrier Homeostasis, and Stratum Corneum Integrity/Cohesion

“…An acidic pH is critical for barrier homeostasis, in part because two key lipid-processing enzymes, b-glucocerebrosidase (bGlcCer' ase) and acidic sphingomyelinase, which generate a family of ceramides from glucosylceramide and sphingomyelin precursors, respectively (Uchida et al, 2002), exhibit low pH optima (Vaccaro et al, 1985;Holleran et al, 1993;Jensen et al, 1999;Schmuth et al, 2000). It has also been proposed that an acidic pH directly impacts lipidl ipid interactions in the SC extracellular lamellar bilayers (Bouwstra et al, 1999). Together, these mechanisms appear to regulate the competence of the extracellular lamellar bilayer system.…”