Department of Pathology, Medical School, University of Michigan, Ann Arbor, MI 48109, USA.
Department of Neurosurgery, Medical School, University of Michigan, Ann Arbor, MI 48109, USA; Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI 48109, USA.
Neurobiol Dis. 2019 Jun;126:105-116. doi: 10.1016/j.nbd.2018.09.006. Epub 2018 Sep 6.
Accumulating evidence suggest that cerebral microvascular disease increases with advancing age and is associated with lacunar stroke, leukoaraiosis, vascular dementia and Alzheimer disease. Increased blood brain barrier (BBB) permeability/leakage takes "center stage" in ongoing age-related vascular/brain parenchymal injury. Although significant effort has been made in defining the gene mutations and risk factors involved in microvascular alterations in vascular dementia and Alzheimer disease, the intra- and intercellular pathogenic mechanisms responsible for vascular hyperpermeability are still largely unknown. The present study aimed to reveal the ongoing senescence process in brain endothelial cells and its effect on BBB integrity in healthy/non-disease conditions. An analysis of BBB integrity during the life span of C56Bl6 mice (young, 2-6 months; middle-aged, 6-12, months; old, 16-22 months) showed increased BBB permeability for different molecular sized tracers (sodium fluorescein, inulin and 20 kDa dextran) in aged mice which was accompanied by modifications in tight junction (TJ) complex organization, manifested as altered TJ protein expression (particularly claudin-5). A gene screening analysis of aging associated markers in brain microvessels isolated from "aged" mice (C56Bl6, 18-20 months) and human brain samples showed a significant decline in sirtuin-1 expression (Sirt1; ~2.8-fold) confirmed at mRNA and protein levels and by activation assay. Experiments in Sirt1 transgenic mice and brain endothelial cell-specific Sirt1 knockout mice indicated that Sirt1 affects BBB integrity, with loss increasing permeability. Similarly, in vitro, overexpressing Sirt1 or increasing Sirt1 activity with an agonist (Sirt1720) protected against senescence-induced brain endothelial barrier hyperpermeability, stabilized claudin-5/ZO-1 interactions and rescued claudin-5 expression. These findings reveal a novel role of Sirt1 in modulating aging-associated BBB persistent leakage.
越来越多的证据表明，脑微血管疾病随着年龄的增长而增加，与腔隙性卒中、脑白质病变、血管性痴呆和阿尔茨海默病有关。血脑屏障（BBB）通透性/渗漏增加“占据中心舞台”，与年龄相关的血管/脑实质损伤有关。尽管在定义血管性痴呆和阿尔茨海默病中小血管改变相关的基因突变和危险因素方面已经做出了巨大努力，但导致血管通透性增加的细胞内和细胞间致病机制在很大程度上仍不清楚。本研究旨在揭示脑内皮细胞衰老过程及其对健康/非疾病状态下 BBB 完整性的影响。分析 C56Bl6 小鼠（年轻，2-6 个月；中年，6-12 个月；老年，16-22 个月）寿命期间 BBB 完整性，发现老年小鼠对不同分子大小示踪剂（荧光素钠、菊粉和 20 kDa 葡聚糖）的 BBB 通透性增加，这伴随着紧密连接（TJ）复合体组织的改变，表现为 TJ 蛋白表达改变（特别是 Claudin-5）。从“衰老”小鼠（C56Bl6，18-20 个月）和人脑样本中分离的脑微血管老化相关标志物的基因筛选分析显示，Sirtuin-1 表达（Sirt1；~2.8 倍）显著下降，在 mRNA 和蛋白水平以及激活试验中得到证实。Sirt1 转基因小鼠和脑内皮细胞特异性 Sirt1 敲除小鼠的实验表明，Sirt1 影响 BBB 完整性，缺失会增加通透性。同样，在体外，过表达 Sirt1 或用激动剂（Sirt1720）增加 Sirt1 活性可防止衰老诱导的脑内皮屏障通透性增加，稳定 Claudin-5/ZO-1 相互作用并挽救 Claudin-5 表达。这些发现揭示了 Sirt1 在调节与衰老相关的 BBB 持续渗漏中的新作用。
