Ono Sachiko, Egawa Gyohei, Kabashima Kenji
Department of Dermatology, Kyoto University Graduate School of Medicine, 54 Shogoin-Kawahara, Sakyo, Kyoto, 606-8507 Japan.
Singapore Immunology Network (SIgN) and Institute of Medical Biology, Agency for Science, Technology and Research (ASTAR), Biopolis, Singapore.
Inflamm Regen. 2017 Jul 10;37:11. doi: 10.1186/s41232-017-0042-9. eCollection 2017.
Regulation of blood vessel permeability is essential for the homeostasis of peripheral tissues. This regulation controls the trafficking of plasma contents, including water, vitamins, ions, hormones, cytokines, amyloids, lipoproteins, carrier proteins, and immunoglobulins. The properties of blood vessels vary among tissues based on their structural differences: continuous, fenestrated, or sinusoidal. These three types of blood vessels have different charge and size barrier properties. The anionic luminal glycocalyx layer on endothelial cells establishes the "charge barrier" that repels the attachment of negatively charged blood cells and plasma molecules. In contrast, the "size barrier" of blood vessels largely relies on the interendothelial junctions (IEJs) between endothelial cells, which define the paracellular permeability. As in most peripheral tissues, blood capillaries in the skin are composed of continuous and/or fenestrated blood vessels that have relatively tighter IEJs compared to those in the internal organs. Small vesicles in the capillary endothelium were discovered in the 1950s, and studies have since confirmed that blood endothelial cells transport the plasma contents by endocytosis and subsequent transcytosis and exocytosis-this process is called transcellular permeability. The permeability of blood vessels is highly variable as a result of intrinsic and extrinsic factors. It is significantly elevated upon tissue inflammations as a result of disabled IEJs and increased paracellular permeability due to inflammatory mediators. An increase in transcellular permeability during inflammation has also been postulated. Here, we provide an overview of the general properties of vascular permeability based on our recent observations of murine skin inflammation models, and we discuss its physiological significance in peripheral homeostasis.
血管通透性的调节对于外周组织的稳态至关重要。这种调节控制着血浆成分的运输，包括水、维生素、离子、激素、细胞因子、淀粉样蛋白、脂蛋白、载体蛋白和免疫球蛋白。血管的特性因组织的结构差异而有所不同：连续型、有孔型或窦状型。这三种类型的血管具有不同的电荷和大小屏障特性。内皮细胞上的阴离子腔面糖萼层建立了“电荷屏障”，可排斥带负电荷的血细胞和血浆分子的附着。相比之下，血管的“大小屏障”很大程度上依赖于内皮细胞之间的内皮间连接（IEJ），其决定了细胞旁通透性。与大多数外周组织一样，皮肤中的毛细血管由连续型和/或有孔型血管组成，与内脏器官中的血管相比，其IEJ相对更紧密。毛细血管内皮中的小泡于20世纪50年代被发现，此后的研究证实，血液内皮细胞通过内吞作用以及随后的转胞吞作用和胞吐作用来运输血浆成分——这个过程称为跨细胞通透性。由于内在和外在因素，血管的通透性变化很大。在组织炎症期间，由于IEJ功能障碍和炎症介质导致的细胞旁通透性增加，血管通透性会显著升高。炎症期间跨细胞通透性的增加也已被推测。在此，我们基于对小鼠皮肤炎症模型的最新观察，概述血管通透性的一般特性，并讨论其在外周稳态中的生理意义。
