Department Life Sciences and Biotechnology, University of Ferrara, Ferrara, Italy.
Department of Dermatology, Medical University of Vienna, Christian Doppler Laboratory for Biotechnology of Skin Aging, Vienna, Austria.
Arch Biochem Biophys. 2019 May 15;666:1-7. doi: 10.1016/j.abb.2019.03.005. Epub 2019 Mar 13.
The main functions of the skin are to protect against environmental insults and prevent water loss, which are performed by the complex lipid- and protein matrix present in the outermost layers of the epithelium. The lipidome of these outer layers is mainly composed of ceramides, fatty acids, and cholesterol, which regulates keratinocyte differentiation and skin barrier function. SR-B1 is a multifunctional scavenger receptor that is best known for facilitating uptake of cholesterol from HDL particles in the liver, but it is also expressed in the skin.
To determine the role of SR-B1 in keratinocyte differentiation.
We investigated the relationship between SR-B1 and keratinocyte differentiation using a physiologically relevant model, organotypic skin equivalents (SEs), wherein SR-B1 was knocked down via siRNA transfection. To assess effects of SR-B1 knockdown on keratinocyte differentiation, we performed hematoxylin/eosin staining, RT-PCR, western blotting, and immunohistochemistry. We also examined the effect of SR-B1 knockdown on lipid production by performing Oil Red O staining and thin layer chromatography.
SR-B1 knockdown resulted in decreased lipid levels in SEs, specifically ceramides, and in decreased transcript levels of LDLR, PPAR-α and PPAR-γ, which are factors involved in regulating ceramide synthesis. In addition, filaggrin levels increased in SR-B1 KD tissues, but neither keratin 14 nor keratin 10 were affected.
We conclude that one of the main functions of SR-B1 in the skin is to regulate ceramide levels and thereby maintain the barrier function of the skin, resulting in the protection of cutaneous tissues from outdoor insults.
皮肤的主要功能是防止环境侵害和防止水分流失，这是由上皮细胞最外层的复杂脂质和蛋白质基质来完成的。这些外层的脂质体主要由神经酰胺、脂肪酸和胆固醇组成，它们调节角质形成细胞的分化和皮肤屏障功能。SR-B1 是一种多功能的清道夫受体，它最著名的功能是促进肝脏从 HDL 颗粒中摄取胆固醇，但它也在皮肤中表达。
确定 SR-B1 在角质形成细胞分化中的作用。
我们使用生理相关的模型，即器官型皮肤等效物（SEs），通过 siRNA 转染来研究 SR-B1 与角质形成细胞分化之间的关系，从而敲低 SR-B1。为了评估 SR-B1 敲低对角质形成细胞分化的影响，我们进行了苏木精/伊红染色、RT-PCR、western blot 和免疫组织化学。我们还通过油红 O 染色和薄层色谱法检查了 SR-B1 敲低对脂质产生的影响。
SR-B1 敲低导致 SE 中的脂质水平降低，特别是神经酰胺水平降低，并且 LDLR、PPAR-α 和 PPAR-γ 的转录水平降低，这些因子参与调节神经酰胺合成。此外，在 SR-B1 KD 组织中，丝聚合蛋白水平增加，但角蛋白 14 和角蛋白 10 不受影响。
我们得出结论，SR-B1 在皮肤中的主要功能之一是调节神经酰胺水平，从而维持皮肤的屏障功能，从而保护皮肤组织免受外界侵害。
