The hydrocarbon-chain packing structure of intercellular lipids in the stratum corneum (SC) is critical to the skin’s barrier function. We previously found that formation of V-shaped ceramide reduces the barrier function of skin. There are few agents, apart from ceramides and fatty acids that can improve the orthorhombic packing (Orth) ratio of the intercellular lipid packing structure. In this study, we investigated agents that directly increase the Orth ratio. We selected an intercellular lipid model consisting of ceramide, cholesterol, and palmitic acid and performed differential scanning calorimetry. We focused on natural moisturizing factor components in the SC, and therefore investigated amino acids and their derivatives. The results of our intercellular lipid model-based study indicate that N-acetyl-L-hydroxyproline (AHYP), remarkably, maintains the lamellar structure. We verified the effect of AHYP on the lamellar structure and hydrocarbon chain packing structure of intercellular lipids using time-resolved X-ray diffraction measurements of human SC. We also determined the direct physicochemical effects of AHYP on the Orth ratio of the hydrocarbon-chain packing structure. Hence, the results of our human SC study suggest that AHYP preserves skin barrier function by maintaining the hydrocarbon-chain packing structure of intercellular lipids via electrostatic repulsion. These findings will facilitate the development of skincare formulation that can maintain the skin’s barrier function.

角质层 (SC) 中细胞间脂质的烃链堆积结构对皮肤的屏障功能至关重要。我们之前发现V形神经酰胺的形成会降低皮肤的屏障功能。除了神经酰胺和脂肪酸之外，很少有药剂可以改善细胞间脂质堆积结构的正交堆积（Orth）比率。在这项研究中，我们调查了直接增加 Orth 比率的代理。我们选择了一个由神经酰胺、胆固醇和棕榈酸组成的细胞间脂质模型，并进行了差示扫描量热法。我们专注于 SC 中的天然保湿因子成分，因此研究了氨基酸及其衍生物。我们基于细胞间脂质模型的研究结果表明N-乙酰-L-羟脯氨酸（AHYP），显着地，保持层状结构。我们使用人 SC 的时间分辨 X 射线衍射测量验证了 AHYP 对细胞间脂质的层状结构和烃链堆积结构的影响。我们还确定了 AHYP 对烃链堆积结构的 Orth 比的直接物理化学影响。因此，我们人类 SC 研究的结果表明，AHYP通过静电排斥维持细胞间脂质的烃链堆积结构来保护皮肤屏障功能。这些发现将有助于开发可以保持皮肤屏障功能的护肤配方。