Shanghai Key Laboratory of Compound Chinese Medicines, The Ministry of Education (MOE), Key Laboratory for Standardization of Chinese Medicines, Institute of Chinese Materia Medica, Shanghai University of Traditional Chinese Medicine, Shanghai 201203, China.
Shanghai Key Laboratory of Compound Chinese Medicines, The Ministry of Education (MOE), Key Laboratory for Standardization of Chinese Medicines, Institute of Chinese Materia Medica, Shanghai University of Traditional Chinese Medicine, Shanghai 201203, China.
Toxicol Appl Pharmacol. 2018 Feb 1;340:58-66. doi: 10.1016/j.taap.2017.12.019. Epub 2017 Dec 30.
Endothelial cells of cerebral microvessels are one of the components of blood-brain-barrier (BBB), which are connected by tight junctions (TJs). BBB disruption in cerebral diseases such as ischemic stroke, Alzhemer's disease, multiple sclerosis and traumatic brain injury is implicated to exacerbate the disease progression. Astragaloside IV (ASIV) isolated from Astragalus membranaceus prevents BBB breakdown in rodents induced with cerebral edema and experimental autoimmune encephalomyelitis. However, its underlying molecular mechanism has not been elucidated yet. In present study, ASIV was found to prevent the leakage of BBB in LPS-induced mice, which was accompanied with increased zo-1 and occludin but reduced VCAM-1 in brain microvessels. Similarly, in brain endothelial cell line bEnd.3 cells, ASIV mitigated the increased permeability induced by LPS, as evidenced by increased TEER and reduced sodium fluorescein extravasation. ASIV also enhanced the expression of TJ proteins such as zo-1, occludin and claudin-5 in LPS stimulated bEnd.3 cells. Meanwhile, it inhibited the inflammatory responses and prevented the monocyte adhesion onto bEnd.3 cells upon LPS stimulation. Further study disclosed that ASIV could alleviate ROS level and activate Nrf2 antioxidant pathway in bEnd.3 cells. When Nrf2 was silenced, the protective effect of ASIV was abolished. In brain microvessels of LPS-induced mice, ASIV also enhanced the expression of Nrf2 antioxidant pathway related proteins. Collectively, our results demonstrated that ASIV protected the integrity of BBB in LPS-induced mice, the mechanism of which might be mediated via activating Nrf2 signaling pathway. The findings suggested that ASIV might be a potential neuroprotective drug acting on BBB.
脑微血管内皮细胞是血脑屏障 (BBB) 的组成部分之一，它们通过紧密连接 (TJ) 连接。脑缺血性中风、阿尔茨海默病、多发性硬化症和创伤性脑损伤等疾病中 BBB 的破坏被认为会加剧疾病的进展。从黄芪中分离得到的黄芪甲苷 IV (ASIV) 可防止脑水肿和实验性自身免疫性脑脊髓炎诱导的啮齿动物 BBB 破裂。然而，其潜在的分子机制尚未阐明。本研究发现 ASIV 可防止 LPS 诱导的小鼠 BBB 渗漏，同时增加脑微血管中的 zo-1 和 occludin，但减少 VCAM-1。同样，在脑内皮细胞系 bEnd.3 细胞中，ASIV 减轻了 LPS 诱导的通透性增加，表现为 TEER 增加和钠荧光素渗出减少。ASIV 还增强了 LPS 刺激的 bEnd.3 细胞中 TJ 蛋白如 zo-1、occludin 和 claudin-5 的表达。同时，它抑制了炎症反应，并防止了 LPS 刺激时单核细胞黏附到 bEnd.3 细胞上。进一步研究表明，ASIV 可减轻 bEnd.3 细胞中的 ROS 水平并激活 Nrf2 抗氧化途径。当 Nrf2 被沉默时，ASIV 的保护作用被消除。在 LPS 诱导的小鼠脑微血管中，ASIV 还增强了 Nrf2 抗氧化途径相关蛋白的表达。总之，我们的研究结果表明，ASIV 可保护 LPS 诱导的小鼠 BBB 的完整性，其机制可能是通过激活 Nrf2 信号通路介导的。这些发现表明，ASIV 可能是一种潜在的作用于 BBB 的神经保护药物。
