Bouwstra J, Pilgram G, Gooris G, Koerten H, Ponec M
Leiden/Amsterdam Center for Drug Research, University of Leiden-Amsterdam, Leiden, The Netherlands.
Skin Pharmacol Appl Skin Physiol. 2001;14 Suppl 1:52-62. doi: 10.1159/000056391.
In the superficial layer of the skin, the stratum corneum (SC), the lipids form two crystalline lamellar phases with periodicities of 6.4 and 13.4 nm (long-periodicity phase). The main lipid classes in SC are ceramides, free fatty acids and cholesterol. Studies with mixtures prepared with isolated ceramides revealed that cholesterol and ceramides are very important for the formation of the lamellar phases, and the presence of ceramide 1 is crucial for the formation of the long-periodicity phase. This observation and the broad-narrow-broad sequence of lipid layers in the 13.4-nm phase led us to propose a molecular model for this phase. This consists of one narrow central lipid layer with fluid domains on both sides of a broad layer with a crystalline structure. This model is referred to as 'the sandwich model'. While the presence of free fatty acids does not substantially affect the lipid lamellar organization, it is crucial for the formation of the orthorhombic sublattice, since the addition of free fatty acids to cholesterol/ceramide mixtures results in transition from a hexagonal to a crystalline lipid phase. Studies examining lipid organization in SC derived from dry or lamellar X-linked ichthyosis skin revealed that in native tissue the role of ceramide 1 and free fatty acids is similar to that observed with mixtures prepared with isolated SC lipids. From this we conclude that the results obtained with lipid mixtures can be used to predict the SC lipid organization in native tissue.
在皮肤的表层即角质层（SC）中，脂质形成两个具有6.4纳米和13.4纳米周期的结晶层状相（长周期相）。角质层中的主要脂质类别为神经酰胺、游离脂肪酸和胆固醇。对用分离出的神经酰胺制备的混合物进行的研究表明，胆固醇和神经酰胺对层状相的形成非常重要，而神经酰胺1的存在对长周期相的形成至关重要。这一观察结果以及13.4纳米相中脂质层的宽窄宽序列促使我们提出了该相的分子模型。该模型由一个狭窄的中央脂质层和两侧具有晶体结构的宽层上的流体域组成。这个模型被称为“三明治模型”。虽然游离脂肪酸的存在不会实质性地影响脂质层状组织，但它对正交亚晶格的形成至关重要，因为向胆固醇/神经酰胺混合物中添加游离脂肪酸会导致从六方相转变为结晶脂质相。对来自干性或层状X连锁鱼鳞病皮肤的角质层中脂质组织的研究表明，在天然组织中，神经酰胺1和游离脂肪酸的作用与用分离出的角质层脂质制备的混合物中观察到的作用相似。由此我们得出结论，用脂质混合物获得的结果可用于预测天然组织中的角质层脂质组织。
