Purpose

The tear film lipid layer (TFLL) covers the tear film, stabilizing it and providing a protective barrier against the environment. The TFLL is divided into polar and non-polar sublayers, but the interplay between lipid classes in these sublayers and the structure-function relationship of the TFLL remains poorly characterized. This study aims to provide insight into TFLL function by elucidating the interactions between polar and non-polar TFLL lipids at the molecular level.

Methods

Mixed films of polar O-acyl-ω-hydroxy fatty acids (OAHFA) or phospholipids and non-polar cholesteryl esters (CE) were used as a model of the TFLL. The organization of the films was studied by using a combination of Brewster angle and fluorescence microscopy in a Langmuir trough system. In addition, the evaporation resistance of the lipid films was evaluated.

Results

Phospholipids and OAHFAs induced the formation of a stable multilamellar CE film. The formation of this film was driven by the interdigitation of acyl chains between the monolayer of polar lipids and the CE multilayer lamellae. Surprisingly, the multilayer structure was destabilized by both low and high concentrations of polar lipids. In addition, the CE multilayer was no more effective in resisting the evaporation of water than a polar lipid monolayer.

Conclusions

Formation of multilamellar films by major tear film lipids suggest that the TFLL may have a similar structure. Moreover, in contrast to the current understanding, polar TFLL lipids may not mainly act by stabilizing the non-polar TFLL sublayer, but through a direct evaporation resistant effect.

中文翻译：

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极性脂质与胆固醇酯多层的相互作用阐明了泪膜脂质层的结构。

目的

泪膜脂质层（TFLL）覆盖在泪膜上，使其稳定并提供保护环境的屏障。TFLL分为极性子层和非极性子层，但是这些子层中的脂质类别之间的相互作用以及TFLL的结构-功能关系仍然很差。这项研究旨在通过阐明分子水平上极性和非极性TFLL脂质之间的相互作用来提供TFLL功能的见解。

方法

极性O-酰基-ω-羟基脂肪酸（OAHFA）或磷脂与非极性胆固醇酯（CE）的混合膜用作TFLL的模型。通过使用布鲁斯特角和荧光显微镜在Langmuir槽系统中的组合研究了膜的组织。另外，评价脂质膜的耐蒸发性。

结果

磷脂和OAHFA诱导形成稳定的多层CE膜。该膜的形成是由极性脂质的单层和CE多层片层之间的酰基链相互交叉驱动的。令人惊讶的是，多层结构由于极性脂质的低浓度和高浓度而不稳定。另外，CE多层膜在抵抗水蒸发方面没有比极性脂质单层膜更有效。

结论

主要泪液膜脂质形成的多层膜表明TFLL可能具有相似的结构。而且，与当前的理解相反，极性TFLL脂质可能主要不是通过稳定非极性TFLL亚层来起作用，而是通过直接的抗蒸发作用来起作用。