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血脑屏障是一个可扩散屏障,位于血液与中枢神经系统(CNS)神经组织之间,只允许水和小分子的脂溶性物质凭借浓度梯度自由扩散,是由脑毛细血管内皮细胞(BMECs)及细胞间紧密连接、基底膜、周细胞、星形胶质细胞脚板和极狭小的细胞外隙共同组成的一个细胞复合体。正常血脑屏障具有高度选择性,能防止毒素及其他有害物质进入脑实质内,对维持CNS内环境的稳态起着重要的作用。该结构损伤必将导致脑内微环境变化,从而引起脑神经细胞功能、代谢与结构的改变。Brightmann等提出血管内皮细胞之间的紧密连接是形成血脑屏障的关键因素,与其他器官毛细血管内皮细胞不同的是:BMECs膜上无窗孔,细胞间有紧密连接,缺少收缩性蛋白,吞饮小泡很少,细胞内含有丰富的酶系统,并且内皮细胞膜表面有负电荷,生理情况下只允许气体分子及分子量小于400～600Da的脂溶性小分子通过。
The blood-brain barrier is a diffusible barrier located between the blood and the nervous system of the central nervous system (CNS), allowing only water- and small-molecule lipophilic substances to freely diffuse through concentration gradients and is composed of brain capillary endothelial cells (BMECs) and A tight junction between cells, the basement membrane, pericytes, astrocytes and extremely small extracellular matrix composed of a cell complex. Normal blood-brain barrier is highly selective, to prevent toxins and other harmful substances into the brain parenchyma, to maintain the CNS homeostasis plays an important role. The structural damage will inevitably lead to changes in the brain microenvironment, causing brain nerve cell function, metabolism and structural changes. Brightmann et al. Proposed that the close connection between vascular endothelial cells is the key factor in the formation of the blood-brain barrier. Unlike the other organ capillary endothelial cells, BMECs are membrane-free, have tight intercellular connections, lack of contractile proteins, Drink small vesicles rarely, the cells are rich in enzyme system, and the endothelial cell membrane surface has a negative charge, under physiological conditions allows only gas molecules and molecular weight less than 400 ~ 600Da fat-soluble small molecules through.